Serum TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosis-inducing ligand (TRAIL) levels of patients with bipolar disorder in manic episode, in remission and healthy controls

Author’s Accepted Manuscript Serum TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosis-inducing ligand (TRAIL) levels of patients with bipolar disorder in manic episode, in remission and healthy controls Merve Cingi Yirün, Onur Yirün, Kübranur Ünal, Rabia Nazik Yüksel, Neslihan Altunsoy, Elif Tatlidil Yaylaci, Makbule Çiğdem Aydemir, Erol Göka

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S0165-1781(16)30438-3 http://dx.doi.org/10.1016/j.psychres.2017.07.067 PSY10701

To appear in: Psychiatry Research Received date: 14 March 2016 Revised date: 27 July 2017 Accepted date: 29 July 2017 Cite this article as: Merve Cingi Yirün, Onur Yirün, Kübranur Ünal, Rabia Nazik Yüksel, Neslihan Altunsoy, Elif Tatlidil Yaylaci, Makbule Çiğdem Aydemir and Erol Göka, Serum TNF-related weak inducer of apoptosis (TWEAK) and TNFrelated apoptosis-inducing ligand (TRAIL) levels of patients with bipolar disorder in manic episode, in remission and healthy controls, Psychiatry Research, http://dx.doi.org/10.1016/j.psychres.2017.07.067 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting galley proof before it is published in its final citable form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.

Serum TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosisinducing ligand (TRAIL) levels of patients with bipolar disorder in manic episode, in remission and healthy controls Merve CİNGİ YİRÜNa1*, Onur YİRÜNa1, Kübranur ÜNALb, Rabia Nazik YÜKSELa, Neslihan ALTUNSOYa2, Elif TATLIDİL YAYLACIa, Makbule Çiğdem AYDEMİRa, Erol GÖKAa a

Ankara Numune Education and Research Hospital Psychiatry Department, Ankara,

TURKEY b

Ankara Numune Education and Research Hospital Biochemistry Department, Ankara,

TURKEY

Merve CİNGİ YİRÜN: [email protected] Onur YİRÜN: [email protected] Kübranur ÜNAL: [email protected] Rabia Nazik YÜKSEL: [email protected] Neslihan ALTUNSOY: [email protected] Elif TATLIDİL YAYLACI: [email protected] Makbule Çiğdem AYDEMİR: [email protected] Erol GÖKA: [email protected] *

Corresponding Author. Merve CİNGİ YİRÜN. Postal Address: Bartın Devlet Hastanesi

Psikiyatri Polikliniği Merkez/Bartın (Phone: 0090 3787620). GSM: 0090 536 345 65 95. email: [email protected]

Present and permanent work address: Bartın State Hospital Psychiatry Department, Bartın, TURKEY 2 Present and permanent work address: Boylam Psychiatry Hospital, Ankara, TURKEY 1

Abstract TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosis-inducing ligand (TRAIL) are members of TNF superfamily, which has various roles in immunologic and inflammatory reactions in the organism. Pathophysiology in bipolar disorder is still under investigation and altered serum levels of cytokines are often encountered. Aim of this study is to detect serum TWEAK and TRAIL levels of patients with bipolar disorder and healthy controls. For this purpose, 55 patients with bipolar disorder -27 manic episode (ME), 28 remission (RE) and 29 healthy controls (HC) were included. TWEAK levels of ME and RE groups were significantly lower than HC. TWEAK levels of bipolar patients (BP) were also lower than HC. TRAIL levels of ME, RE, HC groups and BP, HC groups were statistically similar. In our knowledge, this is the first study concerning about TWEAK and TRAIL levels in bipolar disorder and our results pointed that TWEAK-related immune response might be impaired in bipolar disorder, but our study fails to eradicate the confounders such as medication, smoking and body mass index. Studies having larger samples and limited confounders are needed to be able to evaluate these changes better and detect possible alterations about TRAIL and other TNF superfamily members.

Keywords: Affective disorder; Cytokine; Inflammation; Tumor Necrosis Factor

1. Introduction Bipolar disorder is a complex psychiatric condition characterized by episodes of elevated, depressed, or mixed mood. Despite the disorder’s certain debilitating properties, its etiological mechanisms remain poorly defined (Alloy et al., 2005; Kupfer, 2005; Quraishi and Frangou, 2002). Along with several theories and possible factors, the role of inflammatory processes has long been investigated in the pathophysiology of the disorder (Berk et al., 2011; Kim et al., 2007). On the one hand, the macrophage–T lymphocyte theory, originally hypothesized for the pathophysiology of schizophrenia and later extended to bipolar disorder, holds that chronically activated immune system response by macrophages and T lymphocytes destabilizes central nervous system functions, thereby causing susceptibility to various stressors and mood dysregulations (Smith and Maes, 1995). On the other hand, the microglial hypothesis maintains that microglia activation and proinflammatory cytokines negatively influence the neuroprotective system and trigger mood symptoms (Rajkowska, 2000; Schroeter et al., 2011). In parallel to these hypotheses, many patients with bipolar disorder have demonstrated altered levels of peripheral members of immune system and inflammatory processes (Modabbernia et al., 2013). Cytokines, which regulate the connection between the peripheral immune and central nervous systems (Tian et al., 2014), have shown altered levels in patients with bipolar disorder compared to individuals without the disorder (Modabbernia et al., 2013). Furthermore, changes in the immune system have been associated with the severity of bipolar disorder (Goldstein et al., 2009) and mood episodes involved in the condition (Brietzke et al., 2009), as well as responses to medication (Goldstein et al., 2009). Members of the tumor necrosis factor (TNF) superfamily—19 ligands and 29 receptors in particular—play various roles in the immune response to and pathogenesis of certain autoimmune disorders (Aggarwal et al., 2012; Kumar et al., 2013). TNF-alpha, as a member of the TNF superfamily and major proinflammatory cytokine, plays a crucial role in innate and adaptive immunity, cell proliferation, and apoptotic processes (Popa et al., 2007). Research on inflammatory changes in bipolar disorder has often focused on TNF-alpha levels

(Brietzke et al., 2009; Guloksuz et al., 2010; O’Brien et al., 2006; Ortiz–Domínguez et al., 2007), and some studies (Brietzke et al., 2009; Kim et al., 2007; O’Brien et al., 2006; Ortiz– Domínguez et al., 2007) have reported increased levels of proinflammatory cytokines such as TNF-alpha, interleukin-6, and interleukin-8 in patients with manic episodes (ME), thereby suggesting that mania could be a proinflammatory state. Increments of TNF-alpha and interleukin-6 levels have also been detected during the depressive episodes of patients with bipolar disorder (O’Brien et al., 2006; Ortiz–Domínguez et al., 2007). Kim et al. (2007) observed the normalization of increased interleukin-6 levels in patients with ME following a 6-week-long mood-stabilizing treatment, albeit not with TNFalpha levels, which remained high despite the treatment. The authors accordingly concluded that TNF-alpha could be a trait marker of bipolar disorder, given its persistently high levels following treatment for acute symptoms. In their meta-analysis, Munkholm et al. (2013) reported that patients with bipolar disorder had higher levels of TNF-alpha than healthy controls (HCs). By contrast, Guloksuz et al. (2010) detected similar cytokine levels for medication-free euthymic patients with bipolar disorder and HCs, as well as significantly higher TNF-alpha and interleukin-4 levels in patients with bipolar disorder receiving lithium monotherapy than in both medication-free patients and HCs. As such, the authors pointed out the possible effects of lithium on cytokine levels. In another study on mood-stabilizing drugs and cytokines, the authors revealed that altered cytokine levels of patients with ME returned to levels similar to those of HCs after 8 weeks of treatment (Kim et al., 2004). TNF-related weak inducer of apoptosis (TWEAK), a recently discovered TNF superfamily ligand, works with its only known signaling receptor, fibroblast growth factor inducible 14 (Fn14), and mediates immune response against tissue injury (Burkly et al. 2011). By balancing TNF activity by suppressing the production of proinflammatory cytokines such as interferon gamma and interleukin-12, TWEAK participates in attenuating transitions from innate to adaptive immunity (Maecker et al., 2005). Serum TWEAK levels were previously studied in patients with schizophrenia, another important psychiatric disorder, the pathophysiological factors of which might include changes in inflammatory and immune responses (Tatlidil Yaylacı et al., 2015). TNF-related apoptosis-inducing ligand (TRAIL) is another TNF superfamily ligand, which can trigger the extrinsic apoptotic pathway. It also participates in tumor suppression and immune cell homeostasis (Levandowski et al., 2014).

Despite recent evidence of incrementalism in proinflammatory cytokines and the alteration of peripheral levels of TNF superfamily members in bipolar disorder, to our knowledge TWEAK and TRAIL have never been investigated. In response, our study aims to detect levels of TWEAK and TRAIL in patients with bipolar disorder and thereby contribute to existing evidence about immune processes and bipolar disorder. Based on available data about inflammatory changes in bipolar disorder, we hypothesized that TWEAK levels would be lower in patients with bipolar disorder, given TWEAK’s suppressive effects on proinflammatory mechanisms, and that TRAIL levels would be greater, given its possible inflammation-stimulating properties.

2. Methods 2.1. Sample Our study’s sample consisted of 55 patients with bipolar disorder, who were grouped as either having ME or being in remission (RE). The RE group included 28 euthymic outpatients who applied to Ankara Numune Education and Research Hospital Psychiatry Department Outpatient Clinic during June–December 2014 and met Diagnostic and Statistical Manual of Mental Disorders, Fifth Edition (DSM-5) criteria for bipolar disorder I. By contrast, the ME group included 27 patients currently hospitalized in the psychiatry ward of the same hospital with a diagnosis of bipolar disorder manic episode, also according to DSM-5 criteria. Last, 29 healthy individuals, who were working as hospital staff and had no prior psychiatric history or ongoing complaints, formed the HC group. For the entire sample, inclusion criteria were an age between 18 and 65 years and no history of dementia or cognitive deterioration; exclusion criteria were any past or present chronic inflammatory disease, cardiovascular disease, diabetes mellitus, hypertension, obesity, alcohol or drug dependence, additional psychiatric disorder, or mental retardation, as well as any history of anti-inflammatory medication in the past 8 weeks. Two psychiatrists interviewed patients following the Structured Clinical Interview for DSM 5 Disorders, Clinical Version, to confirm ME diagnoses of members of the ME group (n = 27), to acknowledge that patients in the RE group (n = 28) did not meet DSM-5 criteria for any bipolar disorder episode (i.e., depressive, mixed, manic, or hypomanic) in the past 6 months,

and that HC group members (n = 29) showed no evidence of any present or previous psychiatric disease. The Hamilton Depression Rating Scale (HAM-D) and Young Mania Rating Scale (YMRS) were also used to support the diagnoses of RE (i.e., HAM-D score <7 or YMRS score <4) and ME (i.e., YMRS score >20). Our study was approved by the ethics committee of the Ankara Numune Education and Research Hospital. After a detailed explanation of study procedures, all participants provided their written informed consent.

2.2. Instruments 2.2.1. Hamilton Depression Rating Scale (HAM-D) Designed by Hamilton (1960), the original version of the HAM-D contains 17 items, each scored from 0 to 4 for a maximum total score of 53. Decades later, Williams (1988) developed the Structured Interview for HAM-D-21 as another version of the HAM-D that improved its interrater reliability. The Turkish version of the scale was found to be valid and reliable (Akdemir et al. 2001). In our study, patients were evaluated with the 17-item version. 2.2.2 Young Mania Rating Scale YMRS is an 11-item diagnostic questionnaire used to measure the severity of ME. Each item measures five degrees of severity; seven items are answered by using a five-point Likert-type scale, while four items are answered by using a 9-point Likert-type scale. The Turkish version of the scale was found to be both valid and reliable (Karadağ et al. 2002). 2.3. Biochemical analysis Blood samples of patients and HCs were collected during 8:00–9:00 am following at least 8 h of fasting. After obtained, samples were kept at room temperature for 20 min to optimize coagulation, centrifuged at 4.000 g for 10 minutes, and their sera separated. Samples were transferred to polypropylene tubes and stored at -80°C; 24 h prior to analysis, they were stored at 2°C to 8°C.

TWEAK concentrations were determined by using the eBioscience Instant ELISA kit (Ref:BMS2006, Lot:106510036), whereas TRAIL concentrations were determined by using the Bioscience Instant ELISA kit (Ref: BMS2004, Lot:106300013), both according to the manufacturer’s procedures. Both plasma TWEAK and TRAIL levels were recorded in pg/mL. 2.4. Statistical analysis For discrete and continuous variables, descriptive statistics (mean, standard deviation, standard error, and percentile) were given. In addition, the homogeneity of the variances, which is one of the prerequisites of parametric tests, was checked through the Levene test. The assumption of normality was tested via the Shapiro-Wilk test. To compare the differences between the two groups, Student’s t-test was used when the parametric test prerequisites were fulfilled, and the Mann-Whitney U test was used when such prerequisites were not fulfilled. To compare the differences between three and more groups, one-way analysis of variance was used when the parametric test prerequisites were fulfilled, and the Kruskal-Wallis test was used when such prerequisites were not fulfilled. The Bonferroni correction method, which is a multiple comparison test, was used to evaluate the significant results concerning three and more groups. Age-adjusted covariance Analysis (General Linear Model [GLM]) for TWEAK and TRAIL parameters.

Chi-square test was used for

determining the relationships between two discrete variables. When the expected sources were less than 25%, values were determined through the Monte Carlo Simulation Method in order to include such sources in analysis. The data were evaluated via SPPS 20 (IBM Corp. Released 2011. IBM SPSS Statistics for Windows, Version 20.0. Armonk, NY: IBM Corp.). p<0.05 and p<0.01 were considered as significance levels. 3. Results There were 27 patients (14 males, 13 females) in the ME group, 28 (14 males, 14 females) in the RE group, and 29 (14 males, 15 females) in the HC group, with mean ages of 34.4 ± 13.3, 38.7 ± 9.1, and 32.3 ± 8.4 years, respectively. An evaluation of the groups by age revealed a statistically significant difference (p = .035) (Kruskal-Wallis test, d f= 5

=8,927), and

additional comparisons revealed that the ME and RE groups were not statistically different (p = .41), as were the ME and HC groups (p = .86), whereas the RE group was significantly

older than the HC group (p = .02). As Table 1 shows, all three groups were not statistically different in terms of their male-to-female ratio (p = .965). Number of previous episodes was significantly higher in the RE group than in the ME group (p = .006), whereas illness duration was not significantly different between ME and RE groups (p = .073) (Table 1). Along with an analysis of all three groups, all participants in both experimental groups (BP group) were evaluated against the HC group, whose mean ages were 36.6 ± 11.5 and 32.3 ± 8.4 years, respectively. The two groups were not statistically significantly different in terms of age (p = .061) and sex (p = .818), as shown in Table 2. All patients with bipolar disorder participating in our study were on mood-stabilizing medication. Forty-five patients (25 in ME and 20 in RE groups) were using valproate sodium, as well as 9 patients (1 in ME and 8 in RE groups) using lithium and 1 patient (in ME group) using carbamazepine. All data on TWEAK and TRAIL levels have statistically evaluated according to sex as the following sections report, because some of the previous studies regarding TWEAK molecule have also examined the relationship between sex-TWEAK level (Tatlidil Yaylaci et al.).

3.1. TWEAK analysis TWEAK levels significantly differed among the ME, RE, and HC groups (p < .001) (F = 9.304; df = 2;81), as Table 1 also shows. Further analysis showed that TWEAK levels of both the ME and RE groups were lower than those in the HC group —p < .001 and p < .001, respectively—whereas those of the ME and RE groups were not significantly different (p = .368). Similar results were obtained as a result of age-adjusted covariance analysis (GLM), as Table 1 also shows (F = 6.744; df = 3;80). Similar results emerged in comparisons by gender, which showed that both males and females in the ME, RE, and HC groups differed significantly in terms of TWEAK levels (p = .001 for males (Kruskal-Wallis test, df = 2 Wallis test, df = 2

=14.663) and p = .006 for females (Kruskal-

=10.572)) (Table 3). Further comparisons revealed that TWEAK levels

(analysis of covariance) in the ME and RE group were lower than those in the HC group,

whereas those in the ME and RE groups were not statistically different for both males and females (F = 8.210; df = 3;43) (males: p = .001, p = .001, and p = .781, respectively; females (F = 6.544; df = 3;40): p = .005, p = .009, and p = .193, respectively). Similar results were obtained because of age-adjusted covariance analysis (GLM), as Table 3 also shows. As Table 2 illustrates, the BP group exhibited significantly lower TWEAK levels than the HC group (p < .000). The TWEAK levels of males in the BP group were lower than those of males in the HC group (p < .001), and female patients in the BP group had lower TWEAK levels than those in the HC group (p = .002), as Table 4 shows. No significant correlation was detected between TWEAK levels and illness duration, episode number, and YMRS scores for either BP group (p = .083 r = -0.236; p = .177 r = -0.185; p = .291 r = 0.145); or ME (p = .056 r = -0.372; p = .275 r = -0.218; p = .568 r = -0.115) and RE group (p = .873 r = -0.032; p = .967 r = 0.008; p = .193 r = 0.254) individually. We used correlation analysis to determine the relationship between age and TWEAK levels, which showed a weak negative correlation (p = .023 r = -0.248). Further analysis of age’s confounding effect on TWEAK levels revealed that the age-adjusted TWEAK levels of the BP group remained significantly lower than those in the HC group (p < .001, r = 0.180). The ME, RE, and HC groups continued to differ significantly in terms of age-adjusted TWEAK levels (p = .001, r = 0.172). Both ME and RE groups were significantly lower than the HC group (p < .001 r = 0.296; p = .011 r = 0.141 ), yet statistically similar to each other (p = .665 r = -0.022), in terms of TWEAK levels.

3.1.1 TWEAK values and medication Patients using valproate sodium (n = 45), who formed most of the BP group, showed significantly lower TWEAK levels than those in the HC group (p < .001). Patients using lithium (n = 9) also showed lower TWEAK levels than those in the HC group (p < .014), yet had a notably small sample size. No significant difference was detected between patients using valproate sodium and those using lithium in terms of TWEAK levels (p = .917).

3.2. TRAIL analysis No statistically significant difference among the ME, RE, and HC group emerged in terms of TRAIL levels (p = .829) (F = 1.620; df = 2;81), as Table 1 shows. Similar results were obtained as a result of age-adjusted covariance analysis (GLM), as Table 1 also shows (F = 1.161; df = 3;80). The TRAIL levels of male members of the ME, RE, and HC groups were not statistically different (p = .719), and no significant difference surfaced between the serum TRAIL levels of female members of the ME, RE, and HC groups (p = .996), as depicted in Table 3. Similar results were obtained as a result of age-adjusted covariance analysis (GLM), as Table 3 also shows. BP and HC groups were also not statistically different in terms of TRAIL levels (p = .570) (Table 2). The TRAIL levels of male patients in the BP group were not statistically different from those of males in the HC group (p = .554) along with females in the BP group, who had TRAIL results not statistically differing from those of females in the HC group (p = .804), as Table 4 shows. No significant correlation was detected between TRAIL levels and illness duration, episode number, or YMRS score for the BP group (p = .974 r = 0.004; p = .459 r = -0.103; p = .604 r = 0.072) or the ME group (r = .841 r = -0.040; p = .952 r = 0.012; p = .456 r = 0.150) and RE group individually (p = .447 r = 0.153; p = .343 r = -0.190; p = .316 r = 0.2). There was not any significant correlation between age and TRAIL levels of participants (p = .841 r = 0.023); and the age-adjusted TRAIL levels of participants were still not statistically different in comparisons of the BP and HC groups (p = .119 r = 0.012), as well as among the ME, RE, and HC groups p = .233 r = 0.006)

3.2.1 TRAIL values and medication Last, no significant difference emerged among participants using valproate sodium (n = 45), participants using lithium (n = 9), and the HC group in terms of TRAIL levels (p = .688 df = 2).

4. Discussion In several studies, the role of immune and inflammatory mechanisms in bipolar disorder has been investigated by detecting levels of various cytokines. Such studies have routinely focused on the major cytokine TNF-alpha, whose related blood levels were shown to differ significantly in patients with bipolar disorder and healthy individuals (Brietzke and Kapczinski 2008). Although differences have generally been encountered, findings concerning TNF-alpha in patients with bipolar disorder remain inconsistent (Barbosa et al. 2011; Brietzke et al. 2009; Kim et al. 2007; Kunz et al. 2011). As relatively new members of TNF superfamily, TWEAK and TRAIL affect organisms in a multifunctional way, depending on cell type and current conditions, in terms of differentiation, proliferation, migration, angiogenesis, and apoptosis (Chicheportiche et al. 1997). Given their comparatively recent discovery, TWEAK and TRAIL, unlike other cytokines, have received focus in only two prior studies with psychiatric samples (Tatlidil Yaylaci et al. 2015; Levandowski et al. 2014). TWEAK expression in tissues increases substantially in cases of acute injury, inflammatory disease, and cancer, all of which are characterized with the infiltration of inflammatory cells or the activation of resident innate immune cell types, if not both (Zimmermann et al. 2011). Anti-TWEAK antibodies have been shown to improve serum biomarkers of rheumatoid arthritis and yield positive outcomes on mice with nephrotoxic acute nephritis (Wisniacki et al. 2013; Xia et al. 2012). To the best of our knowledge, our study is the first to detect TWEAK levels in patients with bipolar disorder. Our results showed significantly lower TWEAK levels in patients in either the ME or RE group compared to those in the HC group. ME and RE group members were also similar in terms of serum TWEAK levels. In light of these findings, we suggest that TWEAK-related immune response in bipolar disorder might be impaired, and this impairment seems not to be related to presence of a ME. The comparison of all patients with bipolar disorder independent of their current mood status and HCs supports that conclusion, given significantly lower TWEAK levels in the BP than in the HC group, as well as contributes to mounting evidence on inflammatory system alterations in bipolar disorder

(Brietzke et al. 2009; Cetin et al. 2012; Lee et al. 2013; O’Brien et al. 2006; Ortiz– Domínguez et al, 2007; Stertz et al. 2013). At the same time, our results indicated no difference in TWEAK levels between ME and euthymia, which contradicts some previous studies on other cytokines. Fiedorowicz et al. (2015) reported higher TNF-alpha, interleukin-6, and interleukin-8 levels in patients with mania and depression than both euthymic patients and HCs. Furthermore, Munkholm et al. (2013) reported increased TNF-alpha and soluble tumor necrosis factor receptor 1 levels in patients with ME compared with those with euthymia. Earlier, Brietzke et al. (2009) found similar TNF-alpha, interleukin 2, and interleukin 6 levels in patients with euthymia and HCs, yet pointed out that interleukin 4 levels of euthymic patients were statistically different from those of HCs. Similar to our results, Guloksuz et al. (2010) reported increased TNF-alpha and interleukin-4 levels in euthymic patients on lithium treatment compared with HCs, yet no significant difference between medication-free euthymic patients and HCs in terms of cytokine levels. Ortiz–Domínguez et al. (2007) moreover found increased levels of TNFalpha during both manic and depressive episodes compared to HCs, yet did not include any euthymic patients in their study. Furthermore, in their meta-analysis, Modabbernia et al. (2013) observed higher TNF-alpha levels in patients with ME than in euthymic patients, though that difference lost significance after adjusting for multiple comparisons. Among more recent studies, Barbosa et al. (2014) found higher interleukin-33 levels in both patients with ME and those with euthymia than HCs. Barbosa et al. (2013) also detected higher TNF-alpha levels in euthymic patients with bipolar disorder than in HCs, as well as an increased activation of mitogen-activated protein kinase and nuclear factor kappa B pathways in patients with bipolar disorder, and thus concluded that bipolar disorder can be a proinflammatory state. Among our results, decreased TWEAK levels suggest the existence of a proinflammatory tendency in patients with bipolar disorder, because TWEAK is a molecule that balances TNF activity by suppressing proinflammatory cytokine production, including that of interferon-gamma and interleukin-12 (Maecker et al. 2005). In turn, decreased TWEAK levels could mitigate the suppression and increase the production of proinflammatory cytokines, which would thereby contribute to the proinflammatory tendency.

Although data regarding cytokine changes during episodes show considerable contradictions, recent studies tend to report relatively normalized TNF-alpha levels during euthymic mood in comparison with those during manic state, as mentioned previously. Our results revealed decreased TWEAK levels for patients in both the ME and RE groups, which could derive from a higher number of previous mood episodes in the RE group. More episodes in history might be leading to more persistent alterations in TWEAK-related inflammatory processes, even though we did not find any statistically significant correlation between previous episode number and TWEAK levels. Because this study is the first to address TWEAK levels, it can be also hypothesized that TWEAK might be a steadier molecule in bipolar disorder, or else one whose normalization is delayed. Prospective standardized studies with larger sample sizes, however, could offer a clearer view on the subject. Our statistical analysis of results regarding mean ages showed that participants in the ME, RE, and HC groups were dissimilarly aged and that patients in the RE group were significantly older than members of the HC group. Furthermore, members of the BP and HC groups were found not to be statistically different in terms of age, albeit to only a slightly statistically significant degree (p = .06). To understand the possible effect of age on our results, we performed correlation analysis and thereby detected a weak negative correlation between age and TWEAK levels. This finding was not only inconsistent with findings of former studies (Bielecki et al. 2009; Chorianopoulos et al. 2010), but moreover indicated that though a weak determinant, age might have contributed to the statistically significant decrease of TWEAK levels in individuals with bipolar disorder. However, further analysis including adjustments for age differences revealed that age-adjusted TWEAK levels of the BP group were significantly lower than those in the HC group. The ME, RE, and HC groups also differed significantly in terms of age-adjusted TWEAK levels. Together, those data confirm that though age can be a confounding factor, significantly different results in TWEAK levels in bipolar disorder are not directly related to between-group age differences, which ranks among the major findings of our work. We evaluated the TWEAK results of male and female participants separately, to ultimately show that, for both sexes, the ME and RE groups’ results were less than those of the HC group, which in turn were less than those of the BP group. Therefore, the alteration of

TWEAK-related inflammatory processes in patients with bipolar disorder was not found to be related to sex. Although the effects of mood-stabilizing medication on inflammatory processes have long been examined, the mechanisms remain unclear. Nevertheless, lithium has been thought to have immunomodulatory effects (Brietzke and Kapczinski 2008), and previous studies found that effective lithium treatment significantly decreased plasma in acute-phase proteins, which were markers of inflammatory response (Maes et al. 1997; Sluzewska et al. 1997). In a more recent study, Guloksuz et al. (2010) detected higher TNF-alpha levels in euthymic patients with bipolar disorder who had undergone lithium treatment for at least 8 weeks than in HCs, as well as similar TNF-alpha levels between HCs and euthymic patients with bipolar disorder who had not taken medication for at least 4 weeks. They concluded that higher TNF-alpha levels stemmed from the effects of lithium, not the influence of bipolar disorder on the immune system. Earlier, Himmerich et al. (2005) reported increased TNF-alpha levels after 4 weeks of treatment with both lithium and carbamazepine. However, in 2007, Kim et al. reported that patients with ME had higher levels of interleukin6 and TNF-α in the blood than did HCs, as well as that the interleukin-6 levels of those patients returned to baseline after 6 weeks of mood-stabilizing treatment. By contrast, TNF-α levels remained high. Pointing out that mood-stabilizing medication exerted no effect on TNF levels, the authors therefore discussed the possibility that TNF levels showed more persistent change and that interleukin-6 levels tended to indicate a manic state. Along with previous studies that found no correlation between medication use and cytokine levels (Barbosa et al. 2012, 2011; Tsai et al. 2012, 2001), other research has demonstrated significant correlations between medication use and individual cytokine parameters (Guloksuz et al. 2010; Hope et al. 2011; Kim et al. 2004, 2002). Along these lines, a major limitation of our study was its inability to exclude potential inflammation-related effects of mood-stabilizing medication on TWEAK levels. Although our results showed that patients using valproate sodium or lithium had lower TWEAK levels than HCs, such levels might have been influenced by mood-stabilizing medication or persist despite the medication. Because it is impossible to confirm either of those hypotheses with our findings, however, our failure to exclude patients’ use of medication constitutes a clear weakness of our study. Interestingly, our findings nevertheless showed significantly similar TWEAK levels between

patients using valproate sodium and those using lithium, which therefore contributes to evidence of different mood-stabilizing drugs in terms of inflammation-related actions. To the best of our knowledge, TWEAK has been investigated in only two studies with psychiatric samples. Most recently, after examining TWEAK status in patients with schizophrenia, Tatlidil Yaylaci et al. (2015) detected no statistically significant difference between those patients and HCs, yet nevertheless observed quantitatively lower TWEAK levels in the patient group. Similar to our results of ME and RE intergroup comparisons, Tatlidil Yaylaci et al. (2015) reported no significant difference between patients with acute episodes and those in remission. In the other study with a psychiatric sample, Levandowski et al. (2014) investigated TWEAK and TRAIL levels in patients with crack cocaine dependency to demonstrate lower TWEAK and higher TNF-alpha levels patients with such dependency coupled with early life stress than in patients without early life stress and HCs. They also reported that TWEAK negatively correlated with severity of childhood maltreatment and depression. TRAIL is a type II transmembrane protein that triggers apoptosis in cellular mechanisms (Cheng et al. 2014). Given its apoptosis-promoting specialization, TRAIL exhibits potential antitumor activities and is thus used in clinical trials for cancer therapy (Stuckey and Shah 2013). Its potentially protective effect on the cardiovascular system, however, remains under investigation (Di Bartolo et al. 2011). Despite various multisystematic activities, to our knowledge, only one study has been conducted concerning TRAIL levels in a psychiatric sample: the aforementioned work by Levandowski et al. (2014). Thus, our study is the first to investigate TRAIL levels in bipolar disorder, even if our results showed no significant differences among ME, RE, and HC groups in terms of those levels. This lack of difference persisted in our subsequent analysis that compared participants in the BP and HC groups, and TRAIL levels were statistically similar in both male and female participants as well. Similar to our results, the study by Levandowski et al. (2014) showed no significant difference between the TRAIL levels of patients with crack cocaine dependency with early life stress, patients with such dependency but without early life stress, and HCs. Although our results showed no changes in TRAIL status among patients with bipolar disorder, our small sample size likely influenced those results.

Another factor that could have swayed our findings regarding TRAIL levels was the presence of mood-stabilizing medication, which was previously investigated for possible inflammation-related actions (Ichiyama et al. 2000; Nemeth et al. 2002). As mentioned earlier, both lithium and valproate sodium have normalizing effects on some cytokines. More specifically, lithium is known to reduce acute-phase proteins (Maes et al. 1997; Sluzewska et al. 1997) and have immunomodulatory effects. Kim et al. (2007) reported that interleukin-6 levels normalized and TNF-alpha maintained high levels after 6 weeks of randomized moodstabilizing treatment with lithium, valproate sodium, or both. By contrast, other studies have reported that mood stabilizers can increase TNF-alpha levels (Guloksuz et al. 2010; Himmerich et al. 2005). Although the mechanism remains unclear, recent studies have shown a relationship between mood-stabilizing medication and cytokine levels, which suggests that medication could have contributed to our detecting similar TRAIL results between patients and HCs. As suggested above, our study has certain limitations. First, our small sample size might have obscured a possible alteration in TWEAK levels between episodes of bipolar disorder and the TRAIL levels of all patients. Second, as detailed earlier, the presence of mood-stabilizing medication, previously shown to relate to inflammatory processes, was not excluded from our sample. Third, recruiting HCs not matched for age or sex resulted in a statistically significant age difference between the RE and HC groups, and the statistical similarity of age between BP and HC groups with a marginally significant p value revealed that age might have affected our results, despite obtaining similar results after age-related adjustments. Fourth, we did not screen out other potential confounding factors that might affect the inflammatory system, including smoking, body mass index, physical activity, and alcohol consumption. For example, nicotine consumption has been shown to alter cytokine levels (Haack et al. 1999; McCrea et al. 1994; Tappia et al. 1995; Tollerud et al. 1994), and though two recent studies (Chorianopoulos et al., 2010; Koçak et al., 2012) focusing on TWEAK did not report a relationship between smoking status and TWEAK levels, all findings about TWEAK and nicotine consumption remain highly premature. As such, smoking status could possibly be a confounding factor. Furthermore, visceral obesity has previously been reported to relate to the overproduction of proinflammatory cytokines (Esposito et al. 2003), whereas other clinical variables—alcohol consumption, physical activity, and blood pressure—have been related to altered cytokine levels (Chae et al. 2001; Imhof et al. 2001; Pischon et al. 2003). In

response to our failure to screen and standardize those factors, future studies should form larger sample sizes and impose a more detailed control of confounders and standardization in the use of medication.

5. Conclusion This is the first study concerning both TWEAK and TRAIL levels in bipolar disorder. Our results showed significantly decreased TWEAK levels in ME and RE patients, with reference to HCs, and no significant difference between ME and RE. Further, TWEAK levels of all patients with bipolar disorder were encountered to be significantly lower, in comparison with HC group. No significant difference was detected between participants with bipolar disorder and HCs in terms of TRAIL levels. As a limitation, our study fails to eradicate some confounders such as medication use, smoking, body mass index, or alcohol consumption, which can have potential effects on inflammatory markers.

Conflict of interest The authors declare no conflict of interest.

References Aggarwal, B.B., Gupta, S.C., Kim, J.H., 2012. Historical perspectives on tumor necrosis factor and its superfamily: 25 years later, a golden journey. Blood. doi:10.1182/blood-201104-325225 Akdemir, A., Türkçapar, M.H., Örsel, S.D., Demirergi, N., Dag, I., Özbay, M.H., 2001. Reliability and validity of the Turkish version of the Hamilton Depression Rating Scale. Compr. Psychiatry 42, 161–165. doi:10.1053/comp.2001.19756 Alloy, L.B., Abramson, L.Y., Urosevic, S., Walshaw, P.D., Nusslock, R., Neeren, A.M., 2005. The psychosocial context of bipolar disorder: Environmental, cognitive, and developmental risk factors. Clin. Psychol. Rev. doi:10.1016/j.cpr.2005.06.006 Barbosa, I.G., Huguet, R.B., Mendonça, V.A., Sousa, L.P., Neves, F.S., Bauer, M.E., Teixeira, A.L., 2011. Increased plasma levels of soluble TNF receptor i in patients with bipolar disorder. Eur. Arch. Psychiatry Clin. Neurosci. 261, 139–143. doi:10.1007/s00406010-0116-z Barbosa, I.G., Morato, I.B., De Miranda, A.S., Bauer, M.E., Soares, J.C., Teixeira, A.L., 2014. A preliminary report of increased plasma levels of IL-33 in bipolar disorder: Further evidence

of

pro-inflammatory

status.

J.

Affect.

Disord.

157,

1–4.

doi:10.1016/j.jad.2013.12.042 Barbosa, I.G., Nogueira, C.R.C., Rocha, N.P., Queiroz, A.L.L., Vago, J.P., Tavares, L.P., Assis, F., Fagundes, C.T., Huguet, R.B., Bauer, M.E., Teixeira, A.L., De Sousa, L.P., 2013. Altered intracellular signaling cascades in peripheral blood mononuclear cells from BD patients. J. Psychiatr. Res. 47, 1949–1954. doi:10.1016/j.jpsychires.2013.08.019 Barbosa, I.G., Rocha, N.P., Huguet, R.B., Ferreira, R.A., Salgado, J.V., Carvalho, L.A., Pariante, C.M., Teixeira, A.L., 2012. Executive dysfunction in euthymic bipolar disorder patients and its association with plasma biomarkers. J. Affect. Disord. 137, 151–155. doi:10.1016/j.jad.2011.12.034 Berk, M., Kapczinski, F., Andreazza, A.C., Dean, O.M., Giorlando, F., Maes, M., Yucel, M., Gama, C.S., Dodd, S., Dean, B., Magalhaes, P.V.S., Amminger, P., McGorry, P., Malhi,

G.S., 2011. Pathways underlying neuroprogression in bipolar disorder: Focus on inflammation, oxidative stress and neurotrophic factors. Neurosci. Biobehav. Rev. doi:10.1016/j.neubiorev.2010.10.001 Bielecki, M., Kowal, K., Lapinska, A., Chwiecko, J., Skowronski, J., Sierakowski, S., Chyczewski, L., Kowal-Bielecka, O., 2009. Diminished production of TWEAK by the peripheral blood mononuclear cells is associated with vascular involvement in patients with systemic sclerosis. Folia Histochem. Cytobiol. 47, 465–9. doi:10.2478/v10042-009-0103-2 Brietzke, E., Kapczinski, F., 2008. TNF-alpha as a molecular target in bipolar disorder. Prog. Neuropsychopharmacol. Biol. Psychiatry 32, 1355–61. doi:10.1016/j.pnpbp.2008.01.006 Brietzke, E., Stertz, L., Fernandes, B.S., Kauer-Sant’Anna, M., Mascarenhas, M., Escosteguy Vargas, A., Chies, J.A., Kapczinski, F., 2009. Comparison of cytokine levels in depressed, manic and euthymic patients with bipolar disorder. J. Affect. Disord. 116, 214–217. doi:10.1016/j.jad.2008.12.001 Burkly, L.C., Michaelson, J.S., Zheng, T.S., 2011. TWEAK/Fn14 pathway: An immunological switch for shaping tissue responses. Immunol. Rev. doi:10.1111/j.1600065X.2011.01054.x Cetin, T., Guloksuz, S., Cetin, E.A., Gazioglu, S.B., Deniz, G., Oral, E.T., van Os, J., 2012. Plasma concentrations of soluble cytokine receptors in euthymic bipolar patients with and without subsyndromal symptoms. BMC Psychiatry 12, 158. doi:10.1186/1471-244X-12-158 Chae, C.U., Lee, R.T., Rifai, N., Ridker, P.M., 2001. Blood pressure and inflammation in apparently healthy men. Hypertension 38, 399–403. doi:10.1161/01.HYP.38.3.399 Cheng, W., Zhao, Y., Wang, S., Jiang, F., 2014. Tumor necrosis factor-related apoptosisinducing ligand in vascular inflammation and atherosclerosis: A protector or culprit? Vascul. Pharmacol. doi:10.1016/j.vph.2014.10.004 Chicheportiche, Y., Bourdon, P.R., Xu, H., Hsu, Y.M., Scott, H., Hession, C., Garcia, I., Browning, J.L., 1997. TWEAK, a new secreted ligand in the tumor necrosis factor family that weakly induces apoptosis. J. Biol. Chem. 272, 32401–32410. doi:10.1074/jbc.272.51.32401

Chorianopoulos, E., Jarr, K., Steen, H., Giannitsis, E., Frey, N., Katus, H.A., 2010. Soluble TWEAK is markedly upregulated in patients with ST-elevation myocardial infarction and related

to

an

adverse

short-term

outcome.

Atherosclerosis

211,

322–326.

doi:http://dx.doi.org/10.1016/j.atherosclerosis.2010.02.016 Di Bartolo, B.A., Chan, J., Bennett, M.R., Cartland, S., Bao, S., Tuch, B.E., Kavurma, M.M., 2011. TNF-related apoptosis-inducing ligand (TRAIL) protects against diabetes and atherosclerosis in Apoe -/- mice. Diabetologia 54, 3157–3167. doi:10.1007/s00125-0112308-0 Esposito, K., Pontillo, A., Di Palo, C., Giugliano, G., Masella, M., Marfella, R., Giugliano, D., 2003. Effect of weight loss and lifestyle changes on vascular inflammatory markers in obese women: a randomized trial. JAMA J. Am. Med. Assoc. 289, 1799–804. doi:10.1001/jama.289.14.1799 Fiedorowicz, J.G., Prossin, A.R., Johnson, C.P., Christensen, G.E., Magnotta, V.A., Wemmie, J.A., 2015. Peripheral inflammation during abnormal mood states in bipolar i disorder. J. Affect. Disord. 187, 172–178. doi:10.1016/j.jad.2015.08.036 Goldstein, B.I., Kemp, D.E., Soczynska, J.K., McIntyre, R.S., 2009. Inflammation and the phenomenology, pathophysiology, comorbidity, and treatment of bipolar disorder: a systematic

review

of

the

literature.

J

Clin

Psychiatry

70,

1078–1090.

doi:10.4088/JCP.08r04505 Guloksuz, S., Aktas Cetin, E., Cetin, T., Deniz, G., Oral, E.T., Nutt, D.J., 2010. Cytokine levels

in

euthymic

bipolar

patients.

J.

Affect.

Disord.

126,

458–462.

doi:10.1016/j.jad.2010.04.027 Haack, M., Hinze-Selch, D., Fenzel, T., Kraus, T., Kühn, M., Schuld, A., Pollmächer, T., 1999. Plasma levels of cytokines and soluble cytokine receptors in psychiatric patients upon hospital admission: Effects of confounding factors and diagnosis. J. Psychiatr. Res. 33, 407– 418. doi:10.1016/S0022-3956(99)00021-7 Himmerich, H., Koethe, D., Schuld, A., Yassouridis, A., Pollmächer, T., 2005. Plasma levels of leptin and endogenous immune modulators during treatment with carbamazepine or

lithium. Psychopharmacology (Berl). 179, 447–451. doi:10.1007/s00213-004-2038-9 Hope, S., Dieset, I., Agartz, I., Steen, N.E., Ueland, T., Melle, I., Aukrust, P., Andreassen, O.A., 2011. Affective symptoms are associated with markers of inflammation and immune activation in bipolar disorders but not in schizophrenia. J. Psychiatr. Res. 45, 1608–1616. doi:10.1016/j.jpsychires.2011.08.003 Ichiyama, T., Okada, K., Lipton, J.M., Matsubara, T., Hayashi, T., Furukawa, S., 2000. Sodium valproate inhibits production of TNF-alpha and IL-6 and activation of NF-kappaB. Brain Res. 857, 246–251. doi:10.1016/S0006-8993(99)02439-7 Imhof, A., Froehlich, M., Brenner, H., Boeing, H., Pepys, M., Koenig, W., 2001. Effect of alcohol consumption on systemic markers of inflammation. Lancet 357, 763–767. doi:10.1016/S0140-6736(00)04170-2 Karadağ, F., Oral, T., Yalçin, F.A., Erten, E., 2002. Reliability and validity of Turkish translation of Young Mania Rating Scale. Turk Psikiyatri Derg. 13, 107–114. Kim, Y.K., Jung, H.G., Myint, A.M., Kim, H., Park, S.H., 2007. Imbalance between proinflammatory and anti-inflammatory cytokines in bipolar disorder. J. Affect. Disord. 104, 91– 95. doi:10.1016/j.jad.2007.02.018 Kim, Y.K., Myint, A.M., Lee, B.H., Han, C.S., Lee, S.W., Leonard, B.E., Steinbusch, H.W.M., 2004. T-helper types 1, 2, and 3 cytokine interactions in symptomatic manic patients. Psychiatry Res. 129, 267–272. doi:10.1016/j.psychres.2004.08.005 Kim, Y.-K., Suh, I.-B., Kim, H., Han, C.-S., Lim, C.-S., Choi, S.-H., Licinio, J., 2002. The plasma levels of interleukin-12 in schizophrenia, major depression, and bipolar mania: effects of psychotropic drugs. Mol. Psychiatry 7, 1107–1114. doi:10.1038/sj.mp.4001084 Koçak, E., Köklü, S., Başar, O., Yilmaz, F.M., Ciftçi, A., Kaya, C., Cesur, S., Demirci, S., Akbal, E., Taş, A., 2012. Evaluation of serum TWEAK concentration in patients with acute pancreatitis. Scand J Clin Lab Invest. 72, 192–6. doi:10.3109/00365513.2011.629678 Kumar, A., Abbas, W., Herbein, G., 2013. TNF and TNF receptor superfamily members in HIV

infection:

New

cellular

targets

for

therapy?

Mediators

Inflamm.

doi:10.1155/2013/484378 Kunz, M., Ceresér, K.M., Goi, P.D., Fries, G.R., Teixeira, A.L., Fernandes, B.S., Belmontede-Abreu, P.S., Kauer-Sant’Anna, M., Kapczinski, F., Gama, C.S., 2011. Serum levels of IL6, IL-10 and TNF-α in patients with bipolar disorder and schizophrenia: differences in proand anti-inflammatory balance. Rev. Bras. Psiquiatr. 33, 268–74. doi:10.1590/S151644462011000300010 Kupfer, D.J., 2005. The increasing medical burden in bipolar disorder. JAMA 293, 2528– 2530. doi:10.1001/jama.293.20.2528 Lee, S.-Y., Chen, S.-L., Chang, Y.-H., Chen, P.S., Huang, S.-Y., Tzeng, N.-S., Wang, Y.-S., Wang, L.-J., Lee, I.H., Wang, T.-Y., Yeh, T.L., Yang, Y.K., Hong, J.-S., Lu, R.-B., 2013. Inflammation’s Association with Metabolic Profiles before and after a Twelve-Week Clinical Trial in Drug-Naïve Patients with Bipolar II Disorder. PLoS One 8, e66847. doi:10.1371/journal.pone.0066847 Levandowski, M.L., Viola, T.W., Wearick-Silva, L.E., Wieck, A., Tractenberg, S.G., Brietzke, E., Bauer, M.E., Teixeira, A.L., Grassi-Oliveira, R., 2014. Early life stress and tumor necrosis factor superfamily in crack cocaine withdrawal. J. Psychiatr. Res. 53, 180– 186. doi:10.1016/j.jpsychires.2014.02.017 Maecker, H., Varfolomeev, E., Kischkel, F., Lawrence, D., LeBlanc, H., Lee, W., Hurst, S., Danilenko, D., Li, J., Filvaroff, E., Yang, B., Daniel, D., Ashkenazi, A., 2005. TWEAK attenuates the transition from innate to adaptive immunity. Cell 123, 931–944. doi:10.1016/j.cell.2005.09.022 Maes, M., Delange, J., Ranjan, R., Meltzer, H.Y., Desnyder, R., Cooremans, W., Scharpe, S., 1997. Acute phase proteins in schizophrenia, mania and major depression: Modulation by psychotropic drugs. Psychiatry Res. 66, 1–11. doi:10.1016/S0165-1781(96)02915-0 McCrea, K.A., Ensor, J.E., Nall, K., Bleecker, E.R., Hasday, J.D., 1994. Altered cytokine regulation in the lungs of cigarette smokers. Am. J. Respir. Crit. Care Med. 150, 696–703. doi:10.1164/ajrccm.150.3.8087340 Modabbernia, A., Taslimi, S., Brietzke, E., Ashrafi, M., 2013. Cytokine alterations in bipolar

disorder:

A

meta-analysis

of

30

studies.

Biol.

Psychiatry

74,

15–25.

doi:10.1016/j.biopsych.2013.01.007 Munkholm, K., Brauner, J.V., Kessing, L.V., Vinberg, M., 2013. Cytokines in bipolar disorder vs. healthy control subjects: A systematic review and meta-analysis. J. Psychiatr. Res. doi:10.1016/j.jpsychires.2013.05.018 Nemeth, Z.H., Deitch, E.A., Szabo, C., Fekete, Z., Hauser, C.J., Hasko, G., 2002. Lithium induces NF-kappa B activation and interleukin-8 production in human intestinal epithelial cells. J. Biol. Chem. 277, 7713–7719. doi:10.1074/jbc.M109711200\rM109711200 [pii] O’Brien, S.M., Scully, P., Scott, L. V., Dinan, T.G., 2006. Cytokine profiles in bipolar affective disorder: Focus on acutely ill patients. J. Affect. Disord. 90, 263–267. doi:10.1016/j.jad.2005.11.015 Ortiz-Dominguez, A., Hernandez, M.E., Berlanga, C., Gutierrez-Mora, D., Moreno, J., Heinze, G., Pavon, L., 2007. Immune variations in bipolar disorder: Phasic differences. Bipolar Disord. 9, 596–602. doi:10.1111/j.1399-5618.2007.00493.x Pischon, T., Hankinson, S.E., Hotamisligil, G.S., Rifai, N., Rimm, E.B., 2003. Leisure-time physical activity and reduced plasma levels of obesity-related inflammatory markers. Obes. Res. 11, 1055–1064. doi:10.1038/oby.2003.145 Popa, C., Netea, M.G., van Riel, P.L.C.M., van der Meer, J.W.M., Stalenhoef, A.F.H., 2007. The role of TNF-alpha in chronic inflammatory conditions, intermediary metabolism, and cardiovascular risk. J. Lipid Res. 48, 751–762. doi:10.1194/jlr.R600021-JLR200 Quraishi, S., Frangou, S., 2002. Neuropsychology of bipolar disorder: A review. J. Affect. Disord. 72, 209–226. doi:10.1016/S0165-0327(02)00091-5 Rajkowska, G., 2000. Postmortem studies in mood disorders indicate altered numbers of neurons and glial cells, in: Biological Psychiatry. pp. 766–777. doi:10.1016/S00063223(00)00950-1 Schroeter, M.L., Steiner, J., Mueller, K., 2011. Glial pathology is modified by age in mood disorders - A systematic meta-analysis of serum S100B in vivo studies. J. Affect. Disord.

doi:10.1016/j.jad.2010.11.008 Sluzewska, A., Sobieska, M., Rybakowski, J.K., 1997. Changes in acute-phase proteins during lithium potentiation of antidepressants in refractory depression. Neuropsychobiology 35, 123–127. doi:10.1159/000119332 Smith, R.S., Maes, M., 1995. The macrophage-T-lymphocyte theory of schizophrenia: Additional evidence. Med. Hypotheses 45, 135–141. doi:10.1016/0306-9877(95)90062-4 Stertz, L., Magalhães, P.V.S., Kapczinski, F., 2013. Is bipolar disorder an inflammatory condition? The relevance of microglial activation. Curr. Opin. Psychiatry 26, 19–26. doi:10.1097/YCO.0b013e32835aa4b4 Stuckey, D.W., Shah, K., 2013. TRAIL on trial: Preclinical advances in cancer therapy. Trends Mol. Med. doi:10.1016/j.molmed.2013.08.007 Tappia, P.S., Troughton, K.L., Langley-Evans, S.C., Grimble, R.F., 1995. Cigarette smoking influences cytokine production and antioxidant defences. Clin. Sci. (Lond). 88, 485–9. doi:10.1042/cs0880485 Tatlidil Yaylaci, E., Yuksel, R.N., Unal, K., Altunsoy, N., Cingi, M., Yalcin Sahiner, Safak, Aydemir, M. Cigdem, Goka, E., 2015. TNF-related weak inducer of apoptosis (TWEAK) levels in schizophrenia. Psychiatry Res. 229, 755–759. doi:10.1016/j.psychres.2015.08.006 Tian, L., Tan, Y., Chen, D., Lv, M., Tan, S., Soares, J.C., Zhang, X.Y., 2014. Reduced serum TNF alpha level in chronic schizophrenia patients with or without tardive dyskinesia. Prog. Neuro-Psychopharmacology Biol. Psychiatry 54, 259–264. doi:10.1016/j.pnpbp.2014.06.012 Tollerud, D.J., Kurman, C.C., Nelson, D.L., Brown, L.M., Maloney, E.M., Blattner, W.A., 1994. Racial variation in serum-soluble interleukin-2 receptor levels: a population-based study of healthy smokers and nonsmokers. Clin Immunol Immunopathol 70, 274–279. doi:S0090122984710403 [pii] Tsai, S.Y., Chung, K.H., Wu, J.Y., Kuo, C.J., Lee, H.C., Huang, S.H., 2012. Inflammatory markers and their relationships with leptin and insulin from acute mania to full remission in bipolar disorder. J. Affect. Disord. 136, 110–116. doi:10.1016/j.jad.2011.08.022

Tsai, S.Y.M., Yang, Y.Y., Kuo, C.J., Chen, C.C., Leu, S.J.C., 2001. Effects of symptomatic severity on elevation of plasma soluble interleukin-2 receptor in bipolar mania. J. Affect. Disord. 64, 185–193. doi:10.1016/S0165-0327(00)00252-4 Williams, J.B., 1988. A structured interview guide for the Hamilton Depression Rating Scale. Arch. Gen. Psychiatry 45, 742–747. doi:10.1001/archpsyc.1988.01800320058007 Wisniacki, N., Amaravadi, L., Galluppi, G.R., Zheng, T.S., Zhang, R., Kong, J., Burkly, L.C., 2013. Safety, tolerability, pharmacokinetics, and pharmacodynamics of anti-TWEAK monoclonal antibody in patients with rheumatoid arthritis. Clin. Ther. 35, 1137–1149. doi:10.1016/j.clinthera.2013.06.008 Xia, Y., Campbell, S.R., Broder, A., Herlitz, L., Abadi, M., Wu, P., Michaelson, J.S., Burkly, L.C., Putterman, C., 2012. Inhibition of the TWEAK/Fn14 pathway attenuates renal disease in

nephrotoxic

serum

nephritis.

Clin.

Immunol.

145,

108–121.

doi:10.1016/j.clim.2012.08.008 Zimmermann, M., Koreck, A., Meyer, N., Basinski, T., Meiler, F., Simone, B., Woehrl, S., Moritz, K., Eiwegger, T., Schmid-Grendelmeier, P., Kemeny, L., Akdis, C.A., 2011. TNFlike weak inducer of apoptosis (TWEAK) and TNF-α cooperate in the induction of keratinocyte apoptosis. J. Allergy Clin. Immunol. 127. doi:10.1016/j.jaci.2010.11.005

SERUM TWEAK LEVELS 400

SERUM TRAIL LEVELS

Mean

300

200

100

0 Healthy Controls

Manic Episode

Remission

PARTICIPANTS

Figure 1. Mean TWEAK and TRAIL results of ME, RE and HC groups

Table 1. Demographical and clinical features and serum TWEAK and TRAIL levels of manic episode (ME). remission (RE) and healthy control (HC) groups M: Male F:Female ME RE HC p Pairwise (n=27) (n=28) (n=29) Comparison a* Age 34.4 ± 13.3 38.7±9.1 32.3±8.4 0.035 ME-REd ME-HCd b M/F ratio 14/13 14/14 14/15 0.965 lllness duration (years) Number of previous episodes YMRS

11.7±12.2

15.4±10

0.073c

4.6±6.3

8.1±8.8

0.006c**

29.5±7.1

0.7±0.8

TWEAK

255.0±58.7

261.7±114.5

344.3±77.5

0.001 a**

TWEAKe

254.2±16.6

265.9±16.7

341.1±16.3

0.001 f**

TRAIL

26.7±16.6

32.4±32.4

42.9±45.5

0.829 a

TRAIL h

26.5±6.5

33.1±6.7

42.3±6.5

0.233

a

ME-HCd RE-HCd ME-HCg RE-HCg

f

p value determined by Kruskal-Wallis test p value determined by Chi-Square test c p value determined by Mann-Whitney U test d p value determined by Bonferroni e Covariates appearing in the model are evaluated at the following values: Age = 35.1 f p value determined by Analysis of Covariance (ANCOVA) test g p value determined by Bonferroni-Dunn h Covariates appearing in the model are evaluated at the following values: Age = 35.2 *p<0.05 **p<0.01 b

Table 2. Demographical and clinical features and serum TWEAK and TRAIL levels of bipolar patients (BP) and healthy control (HC) groups M: Male F:Female BP HC p (n=55) (n=29) Age 36.6±11.5 32.3±8.4 0.061 c 14/15

0.818 b

258.4±90.7

344.3±77.5

0.001 c**

29.5±25.7

49.9±45.5

0.570 c

M/F ratio

28/27

Illness duration (years) Number of previous episodes YMRS

13.6±11.2

TWEAK TRAIL

6.4±7.8 14.8±15.3

b

p value determined by Chi-Square test p value determined by Mann-Whitney U test **p<0.01 Table 3. Serum TWEAK and TRAIL levels of manic episode (ME). remission (RE) and healthy control (HC) groups according to gender ME RE HC p Pairwise Comparison c

TWEAK

239.1±62.8

250.7±57.8

335.6±67.1

0.001 a**

TRAIL

25.9±15.0

34.9±38.4

43.9±45.2

0.719 a

TWEAK

234.1±15.8

260.7±17.0

331.4±16.3

0.001 d**

TRAIL

23.6±9.0

39.6±10.1

41.9±9.3

0.318 d

TWEAK

274.9±48.4

272.3±154.6

349.4±90.1

0.006 a**

TRAIL

27.7±19.0

30.2±27.0

41.9±47.5

0.996 a

Female f

TWEAK

277.1±31.7

273.6±29.2

349.5±28.6

0.001d**

Female g

TRAIL

27.1±9.9

29.8±9.2

42.8±9.3

0.473 d

Male

Male b

Female

a

p value determined by Kruskal-Wallis test Covariates appearing in the model are evaluated at the following values: Age = 34.6 c p value determined by Bonferroni d p value determined by Analysis of Covariance (ANCOVA) test e p value determined by Bonferroni-Dunn f Covariates appearing in the model are evaluated at the following values: Age = 35.6 g Covariates appearing in the model are evaluated at the following values: Age = 35.7 **p<0.01 b

ME-HCc RE-HCc ME-HCe RE-HCe ME-HCc RE-HCc ME-HCe RE-HCe

Table 4. Serum TWEAK and TRAIL levels of bipolar patients (BP) and healthy control (HC) groups according to gender BP HC p Male

Female

c

TWEAK

244.1±59.6

335.6±67.1

0.001 c

TRAIL

30.7±28.5

43.9±45.2

0.554 c

TWEAK

273.3±113.8

352.5±87.6

0.002 c

TRAIL

28.4±23.0

41.9±47.5

0.804 c

p value determined by Mann-Whitney U test

Highlights 

TNF-related weak inducer of apoptosis (TWEAK) and TNF-related apoptosisinducing ligand (TRAIL) are members of TNF superfamily.



Cytokine levels alter in bipolar disorder.



This is the first study concerning TWEAK and TRAIL in bipolar disorder.



TWEAK was found to be decreased in bipolar patients both for manic episode and remission.