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A novel role of myeloperoxidase in the induction of endoplasmic reticulum (ER) stress
Heme oxygenase-1 (Hmox1) degrades heme and regulates whole body and cellular iron homeostasis. There is increasing evidence that enhanced Hmox1 expression protects against cardiovascular diseases via multiple biological effects, the precise underlying mechanisms of which remain unknown. Using a global transcriptional approach in yeast, we discovered that the yeast homolog of Hmox1 (i.e., Hmx1) regulates the transcription of COQ7. COQ7 encodes a mitochondrial non-heme di-iron carboxylate monooxygenase required for the biosynthesis of coenzyme Q (CoQ). In addition to COQ7 and COQ7 protein, Hmx1 deficiency also decreased the expression of other genes required for CoQ synthesis, resulting in a significant decrease in the cellular content of CoQ. This was associated with significant decreases in mitochondrial membrane -• potential, respiration and O2 concentration. Overexpression of COQ7, HMX1 or human Hmox1 rescued this phenotype. Similar to yeast cells, mouse embryonic and skin fibroblasts from Hmox1-/- mice had significantly decreased CoQ, O2-• and respiration compared with the corresponding cells from wild-type animals. As Hmox1 is a downstream target of HIF1 and mitochondrial O2• /H2O2 is implicated in hypoxia-mediated stabilization of HIF1a and resulting metabolic reprogramming, we assessed the role of Hmox1 in a mouse model of hind limb ischemia. We observed that a deficiency of Hmox1 in bone marrow cells alone was sufficient for a complete lack of neovascularization, whereas it could not fully explain the amputations caused by the ischemia. Additional experiments with skin fibroblasts revealed that Hmox1-deficient cells failed to respond to hypoxia by increasing O2-• and anaerobic glucose utilization. Furthermore, Hmox1-deficient cells had a decreased ability to respond to hypoxia by HIF1a stabilization. Our results, for the first time, suggest that Hmox1 also acts upstream of HIF1, possibly via mitochondrial CoQ and resulting reactive oxygen species-mediated stabilization of HIF1a. This novel activity of Hmox1 could help explain its cardiovascular protective activities. Keywords: Heme oxygenase-1, Coenzyme Q, Mitochondrial reactive oxygen species, Ischemia/hypoxia doi:10.1016/j.freeradbiomed.2012.08.559 Cardiovascular, Disorders II 3:
Metabolic
&
Environmental
Diabetes has become a great problem in the world. A number of literatures described that the diabetics have higher infection risk than do the healthy. The difference between healthy human plasma proteins (HPP) and type II diabetes plasma proteins (TPP) on free radical 2,2diphenyl-1-picrylhydrazyl (DPPH) scavenging potential of polyphenols was investigated. Blood-derived serum was obtained using blood from 3 type II diabetes and healthy adult volunteers. The DPPH free radical scavenging potential of polyphenolsin the absence and presence of TPP and HPP were measured. Taking advantage of a new chemiluminescence assay involving DPPH free radical, we have found that plasma proteins masked the antioxidant potential of polyphenols. Compared with HPP, TPP obviously weaken the masking effect on the antioxidant capacity of polyphenols, which usually caused by the polyphenolplasma protein interaction. Using fluorescence spectroscopy we have showed that TPP showed about 1-10 times lower affinities with polyphenols than HPP. TPP showed lower binding affinities for polyphenols in blood than that of HPP, which results in releasing more free polyphenols. The corresponding consequence of this action is increasing free polyphenols in blood, which causes polyphenols expose to free radicals in blood. Therefore, polyphenols in diabetics' blood are tend to be oxidized and can not be efficiently delivered to other tissues, which reduces the beneficial impact of polyphenols. It has been suggested that the oxidantscavenging ability of blood is most probably a result of the synergistic effects exerted by the free circulating antioxidants, antioxidant-protein complexes, blood cells coated with antioxidants, and so on. The further research on assessing why glycated plasma proteins are able to cause a big difference on oxidant-scavenging potential of polyphenols, which could help in changing the way such polyphenols are used in the treatment of diabetes. Acknowledgments: Shanghai Rising-Star Program (11QA1404700), Shanghai "Chen Guang" project (09CG46). Keywords: Diabetes, Free Radical polyphenol-plasma proteins interaction
Scavenging,
doi:10.1016/j.freeradbiomed.2012.08.560
Diabetes Can Diminish Benefits of Free Radical Scav enging Potential of Polyphenols in Blood
Cardiovascular, Disorders II 4:
J.B. Xiao*1, Y.X. Xie2, H. Cao2, X.Q. Chen2 1 College of Life & Environment Science, Shanghai Normal University, China, 2College of Chemistry and Chemical Engineering, Central South University, China
A novel role of myeloperoxidase in the induction of endoplasmic reticulum (ER) stress
Metabolic
&
Environmental
A. Forsman Quigley1, F.A. Summers1, T.J. Barrett1 ,2, C.A. Bursill1 ,2, C.L. Hawkins*1 ,2
S67
1
Heart Research Institute, Australia, 2University of Sydney, Australia Endoplasmic reticulum (ER) stress results from the cellular accumulation of unfolded or misfolded proteins. ER stress triggers a signalling cascade termed the unfolded protein response (UPR), in an attempt to restore ER homeostasis. However, prolonged ER stress leads to cell damage and the induction of apoptosis; this is increasingly recognised to contribute to the development of diseases, including atherosclerosis. Although ER stress is a hallmark of advanced lesions, the mechanisms responsible for the induction of the UPR in atherosclerosis are not well defined. In this study, we show that hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN) produced by myeloperoxidase (MPO), may induce activation of the UPR, resulting in elevated expression of the effector protein CHOP (C/EBP-homologous protein). This may be a pathway to UPR activation in lesions, owing to the compelling evidence for a role of MPO in the development of atherosclerosis. The UPR consists of 3 signalling pathways, pancreatic ER kinase-like ER kinase (PERK), activating transcription factor 6 (ATF6) and inositol-requiring enzyme 1 (IRE1). Exposure of human coronary artery endothelial cells (HCAEC) and macrophages to the MPO-derived oxidants HOCl and HOSCN, resulted in increased phosphorylation of eIF2a, and expression of the transcription factor ATF4, which characterise activation of the PERK pathway. Importantly, increased expression of the UPR effector protein CHOP, which has been linked to lesion destabilisation, was seen in both cell types on treatment with HOCl and HOSCN. Data from proteomic studies using the thiol-specific probe 5iodoacetamidofluorescein, suggest that the activation of the UPR may be triggered by MPO oxidant targeting of various ER resident proteins, including protein disulphide isomerase (PDI), GRP78 and calreticulin, which may compromise protein folding. The induction of ER stress and activation of the UPR, may be a novel pathway by which MPO-derived oxidants promote the development of clinically-relevant lesions in atherosclerosis. Keywords: Myeloperoxidase, Atherosclerosis, ER stress, Protein oxidation doi:10.1016/j.freeradbiomed.2012.08.561
Cardiovascular, Disorders II 5:
Metabolic
&
Environmental
Myeloperoxidase levels and cellular stress response after explosive-type of moderate resistance training in the elderly
S68
R.M. Beltran Valls1, I. Dimauro1, A. Brunelli1, P. Caserotti2, A. Parisi1, D. Caporossi*1 1 DepartmentUniversity of Rome "Foro Italico", Italy, 2 University of Southern Denmark, Denmark Oxidative stress likely plays a role in inactivity-induced biological aging. While endurance training proved to reduce the systemic level of oxidative stress, little is known on the effect of resistance exercise on biomarkers of aging. Therefore, the aim of the study was to analyse the effects of explosive type of moderate resistance exercise (EMRT) on muscle power, cardiovascular fitness, and peripheral markers of oxidative stress and cell stress response in older adults. 21 men and female (72±3 yrs) participated to the study: 13 subjects followed low frequency short duration (2days/week, 12weeks) EMRT and 8 subjects were control group. Training included lower and upper body exercises performed at 10 RM, concentric and eccentric phases of the movement at maximal intentional acceleration and moderate speed, respectively. Cardiovascular fitness (ECG, hearth rate, blood pressure) was assessed by maximal graded exercise stress test (GXT). Countermovement jump (CMJ) and 4 training devices with load at 70% of the 1RM recorded at baseline (FreePower, Sensorize) were used for muscle power evaluation. HSP70 and HSP27 expression in PBMC was analyzed by western blot. Serum myeloperoxidase (MPO) was quantified by ELISA assay. As expected, training significantly increased maximum GXT load (16%, p <0.05) without affecting heart rate and blood pressure recorded at the same relative work intensity. Peak power was enhanced in leg curl, leg extension, chest press, low row and in the CMJ (2030%, p<0.05). HSP70 and HSP27 decreased significantly after training (15% & 11% respectively, p<0.05). The MPO levels decreased after EMRT, with no significant difference (p=0.06). Our findings show that EMRT improves endurance capacity and muscle power in elderly. The reduced basal levels of HSP and the tendency to decrease of MPO may indicate an adaptation to the exercise stimuli during training attributable to the reduction of physiological stressor/s and/or higher tolerance to them. Keywords: aging, resistance exercise, myeloperoxidase doi:10.1016/j.freeradbiomed.2012.08.562
Metabolic
&
Environmental
Diabetes has become a great problem in the world. A number of literatures described that the diabetics have higher infection risk than do the healthy. The difference between healthy human plasma proteins (HPP) and type II diabetes plasma proteins (TPP) on free radical 2,2diphenyl-1-picrylhydrazyl (DPPH) scavenging potential of polyphenols was investigated. Blood-derived serum was obtained using blood from 3 type II diabetes and healthy adult volunteers. The DPPH free radical scavenging potential of polyphenolsin the absence and presence of TPP and HPP were measured. Taking advantage of a new chemiluminescence assay involving DPPH free radical, we have found that plasma proteins masked the antioxidant potential of polyphenols. Compared with HPP, TPP obviously weaken the masking effect on the antioxidant capacity of polyphenols, which usually caused by the polyphenolplasma protein interaction. Using fluorescence spectroscopy we have showed that TPP showed about 1-10 times lower affinities with polyphenols than HPP. TPP showed lower binding affinities for polyphenols in blood than that of HPP, which results in releasing more free polyphenols. The corresponding consequence of this action is increasing free polyphenols in blood, which causes polyphenols expose to free radicals in blood. Therefore, polyphenols in diabetics' blood are tend to be oxidized and can not be efficiently delivered to other tissues, which reduces the beneficial impact of polyphenols. It has been suggested that the oxidantscavenging ability of blood is most probably a result of the synergistic effects exerted by the free circulating antioxidants, antioxidant-protein complexes, blood cells coated with antioxidants, and so on. The further research on assessing why glycated plasma proteins are able to cause a big difference on oxidant-scavenging potential of polyphenols, which could help in changing the way such polyphenols are used in the treatment of diabetes. Acknowledgments: Shanghai Rising-Star Program (11QA1404700), Shanghai "Chen Guang" project (09CG46). Keywords: Diabetes, Free Radical polyphenol-plasma proteins interaction
Scavenging,
doi:10.1016/j.freeradbiomed.2012.08.560
Diabetes Can Diminish Benefits of Free Radical Scav enging Potential of Polyphenols in Blood
Cardiovascular, Disorders II 4:
J.B. Xiao*1, Y.X. Xie2, H. Cao2, X.Q. Chen2 1 College of Life & Environment Science, Shanghai Normal University, China, 2College of Chemistry and Chemical Engineering, Central South University, China
A novel role of myeloperoxidase in the induction of endoplasmic reticulum (ER) stress
Metabolic
&
Environmental
A. Forsman Quigley1, F.A. Summers1, T.J. Barrett1 ,2, C.A. Bursill1 ,2, C.L. Hawkins*1 ,2
S67
1
Heart Research Institute, Australia, 2University of Sydney, Australia Endoplasmic reticulum (ER) stress results from the cellular accumulation of unfolded or misfolded proteins. ER stress triggers a signalling cascade termed the unfolded protein response (UPR), in an attempt to restore ER homeostasis. However, prolonged ER stress leads to cell damage and the induction of apoptosis; this is increasingly recognised to contribute to the development of diseases, including atherosclerosis. Although ER stress is a hallmark of advanced lesions, the mechanisms responsible for the induction of the UPR in atherosclerosis are not well defined. In this study, we show that hypochlorous acid (HOCl) and hypothiocyanous acid (HOSCN) produced by myeloperoxidase (MPO), may induce activation of the UPR, resulting in elevated expression of the effector protein CHOP (C/EBP-homologous protein). This may be a pathway to UPR activation in lesions, owing to the compelling evidence for a role of MPO in the development of atherosclerosis. The UPR consists of 3 signalling pathways, pancreatic ER kinase-like ER kinase (PERK), activating transcription factor 6 (ATF6) and inositol-requiring enzyme 1 (IRE1). Exposure of human coronary artery endothelial cells (HCAEC) and macrophages to the MPO-derived oxidants HOCl and HOSCN, resulted in increased phosphorylation of eIF2a, and expression of the transcription factor ATF4, which characterise activation of the PERK pathway. Importantly, increased expression of the UPR effector protein CHOP, which has been linked to lesion destabilisation, was seen in both cell types on treatment with HOCl and HOSCN. Data from proteomic studies using the thiol-specific probe 5iodoacetamidofluorescein, suggest that the activation of the UPR may be triggered by MPO oxidant targeting of various ER resident proteins, including protein disulphide isomerase (PDI), GRP78 and calreticulin, which may compromise protein folding. The induction of ER stress and activation of the UPR, may be a novel pathway by which MPO-derived oxidants promote the development of clinically-relevant lesions in atherosclerosis. Keywords: Myeloperoxidase, Atherosclerosis, ER stress, Protein oxidation doi:10.1016/j.freeradbiomed.2012.08.561
Cardiovascular, Disorders II 5:
Metabolic
&
Environmental
Myeloperoxidase levels and cellular stress response after explosive-type of moderate resistance training in the elderly
S68
R.M. Beltran Valls1, I. Dimauro1, A. Brunelli1, P. Caserotti2, A. Parisi1, D. Caporossi*1 1 DepartmentUniversity of Rome "Foro Italico", Italy, 2 University of Southern Denmark, Denmark Oxidative stress likely plays a role in inactivity-induced biological aging. While endurance training proved to reduce the systemic level of oxidative stress, little is known on the effect of resistance exercise on biomarkers of aging. Therefore, the aim of the study was to analyse the effects of explosive type of moderate resistance exercise (EMRT) on muscle power, cardiovascular fitness, and peripheral markers of oxidative stress and cell stress response in older adults. 21 men and female (72±3 yrs) participated to the study: 13 subjects followed low frequency short duration (2days/week, 12weeks) EMRT and 8 subjects were control group. Training included lower and upper body exercises performed at 10 RM, concentric and eccentric phases of the movement at maximal intentional acceleration and moderate speed, respectively. Cardiovascular fitness (ECG, hearth rate, blood pressure) was assessed by maximal graded exercise stress test (GXT). Countermovement jump (CMJ) and 4 training devices with load at 70% of the 1RM recorded at baseline (FreePower, Sensorize) were used for muscle power evaluation. HSP70 and HSP27 expression in PBMC was analyzed by western blot. Serum myeloperoxidase (MPO) was quantified by ELISA assay. As expected, training significantly increased maximum GXT load (16%, p <0.05) without affecting heart rate and blood pressure recorded at the same relative work intensity. Peak power was enhanced in leg curl, leg extension, chest press, low row and in the CMJ (2030%, p<0.05). HSP70 and HSP27 decreased significantly after training (15% & 11% respectively, p<0.05). The MPO levels decreased after EMRT, with no significant difference (p=0.06). Our findings show that EMRT improves endurance capacity and muscle power in elderly. The reduced basal levels of HSP and the tendency to decrease of MPO may indicate an adaptation to the exercise stimuli during training attributable to the reduction of physiological stressor/s and/or higher tolerance to them. Keywords: aging, resistance exercise, myeloperoxidase doi:10.1016/j.freeradbiomed.2012.08.562