- Email: [email protected]
Indomethacin reverts sleep disorders produced by ozone exposure in rats
Toxicology 191 (2003) 89 /96 www.elsevier.com/locate/toxicol
Indomethacin reverts sleep disorders produced by ozone exposure in rats Carmen Rubio, Carlos Paz * Departamento de Neurofisiologı´a, Instituto Nacional de Neurologı´a y Neurocirugı´a M.V.S., Insurgentes Sur 3877, Mexico 14269 D.F., Mexico Received 21 October 2002; received in revised form 28 March 2003; accepted 8 May 2003
Abstract Ozone (O3) exposure causes pulmonary biochemical changes both in humans and experimental animals, inducing the release of inflammatory mediators such as cytokines and eicosanoids. Some of these reaction products have been characterized as endogenous sleep-promoting substances and have been implicated in the development of sleepiness in patients with inflammatory disease. Furthermore, sleep alterations are known to occur in O3-exposed humans and experimental animals. In order to test the probable involvement of such inflammatory mediators in O3-induced sleep disorders, we blocked prostaglandin synthesis administrating the cyclooxygenase inhibitor indomethacin (IM) and compared conventional electrographic sleep parameters in rats under four different experimental conditions: treatment with IM alone, O3-exposure, pre-treatment with IM plus O3 exposure, and control conditions. We found that O3 exposure increased slow wave sleep (SWS) and decreased rapid eye movement sleep (REMs) significantly, while IM pretreatment reduced these O3-induced sleep disorders. IM treatment alone did not affect sleep. These findings strongly support a role for inflammatory mediators in O3 exposure-induced neurological alterations. # 2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Ozone; Sleep; Inflammation; Indomethacin; Cytokines; Eicosanoids
1. Introduction Ozone (O3) is the main photochemical oxidant found in polluted urban areas. Being a gas, toxicity studies have focused on the functional and morphological effects of O3 in the lungs of humans and laboratory animals. Exposure to more than 0.12 ppm O3 is known to decrease forced vital capacity * Corresponding author. Fax: /52-5-606-3032. E-mail address: [email protected] (C. Paz).
and forced expiratory volume expelled in the 1st second (Kinney et al., 1989; Specktor et al., 1988). O3-induced airway damage is morphologically characterized by dysplasia and metaplasia (Hiroshima et al., 1987; Wilson et al., 1984). However, the most remarkable effect of O3 exposure (0.4 ppm) in humans is a pulmonary inflammatory response characterized by increased concentrations of soluble mediators such as interleukins (ILs), prostaglandins (PGs) and tumor necrosis factor-a (TNF-a) (Devlin et al., 1996).
0300-483X/03/$ - see front matter # 2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/S0300-483X(03)00245-2
90
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
Some extrapulmonary effects have been described in addition to the vast number of descriptions of lung impairment in O3-exposed humans and experimental animals. Impaired mental performance, complaints of fatigue, headache and sleepiness are some of the neurological symptoms reported by O3-exposed individuals (Hackney et al., 1977; Lategola et al., 1980). Electrographic studies demonstrated that exposure to 0.2 /1.2 ppm O3 significantly decreases rapid eye movement sleep (REMs) and increases slow wave sleep (SWS) in rats (Arito et al., 1992; Paz and Huitro´nRese´ndiz, 1996) and cats (Paz and Bazan-Perkins, 1992). Moreover, O3-exposed rats showed significant changes in sleep-related neurotransmitters (Cottet-Emard et al., 1997; Gonzalez-Pin˜a and Paz, 1997). Because it is highly reactive, O3 is totally destroyed in the lung tissue. Its pathological effects beyond the pulmonary system remain to be elucidated. Certain O3-reaction products known to cross the blood /gas barrier in experimental animals might be involved in the pathogenesis of these extrapulmonary effects. Plasma concentrations of PGs-F2 and -E2 were found to be increased in rats exposed to 4.0 ppm O3 for up to 8 h (Giri et al., 1980). PGs are involved in regulation of physiological sleep /wake cycles (Koyama and Hayaishi, 1994; Matsumura et al., 1989a,b; Moussard et al., 1994). To explore the possible involvement of inflammatory reaction products in O3-induced sleep disorders, we blocked arachidonic acid metabolism and PG synthesis by administering the cyclooxygenase inhibitor indomethacin (IM), and analyzed a 24 h electrographic study in rats exposed to O3.
2. Materials and methods Ten adult male Wistar rats weighting 280 /300 g were anaesthetized (Ketamine, 100 mg/kg, i.p.) and placed on a stereotaxic apparatus. After exposing the vertex of the skull, bipolar electrodes were implanted on the sensorimotor cortex to record the electrocorticogram (ECG), and on the ocular orbit to record eye movements (EOG). Other electrodes were fixed to the neck muscles
through a cut over the nape of the neck to record the electromyogram (EMG). All electrodes were made of stainless steel Teflon-coated wire (0.005 in. diameter) with uncoated tips. A screw implanted in the skull served as an indifferent source of reference. The external electrode tips were attached to pins and fixed to a rectangular male plug, which was secured to the skull with dental acrylic. Skin cuts were sutured and 200 000 U penicillin G potassium was administered to each rat. After 1 week of recovery, the plugs were connected to a polygraph (Grass S88) by means of flexible cables, allowing the rat to move freely in a hermetic chamber (30 /22 /22 cm) fitted with two tubes: one to add filtered air and the other for draining and inner air analysis. Rats were habituated to these laboratory conditions during 3 days under 12-h light:12-h darkness cycles, at 249/ 1 8C and with free access to food and water. Once habituated, rats received an intramuscular injection of vehicle alone (20% ethanol and 4% sodium bicarbonate dissolved in saline solution). A 24 h control polygraphic recording was obtained 1 h after the injection. Thereafter, the rats were connected as described above, every week, to obtain additional 24 h recordings under three different experimental conditions: (a) IM injection (10 mg/kg) 1 h before initiating sleep recordings with no O3 exposure; (b) vehicle injection 1 h before the 24 h sleep recording, adding 1.0 ppm O3 to the filtered air; and (c) pre-treatment with IM (10 mg/kg) and 24 h exposure to 1.0 ppm O3. Ozone was added to the filtered air with a P15 Triozon generator, and O3 concentrations were measured using a 1008-PC Dasibi UV light photometric analyzer. The vigilance states of the rat were visually analyzed and defined according to the following electrophysiological criteria: wakefulness (W) characterized by ECG disynchronization and presence of accentuated muscle tone during movements; SWS characterized by the presence of sleep spindles, slow waves with voltage higher than 75 mV and decreased EMG voltage; REMs characterized by ECG disynchronization, rapid eye movements and absence of voltage in the EMG succeeding SWS periods. Total time spent in W,
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
SWS, and REMs during 24 h, as well as in an hourly step analysis was compared under control, IM injection, O3 exposure, and IM plus O3 experimental conditions. Besides, duration, number and onset latency of the vigilance stage periods were compared during the light and dark conditions. Results were analyzed by an ANOVA conducted as a block design with factorial treatment combinations considering IM treatment, O3 exposure, and time of recording as factors. Subsequent comparisons within conditions were made using a Tukey test. The accepted nominal levels of significance was P B/0.01.
3. Results Total wakefulness time recorded over a 24 h period was not significantly affected during control, IM injection, O3 exposure, and IM plus O3 experimental conditions. However, total time spent in SWS during O3 exposure was significantly longer when compared with the lack of O3 condition (F /34.9, df /1935, P B/0.001). The specific effect of O3 condition was confirmed when no significant differences were found between with and without IM condition (F /0.2, df /1935, NS), as well as when O3 and IM interaction were compared (F /5.7, df /1935, NS). On the other hand, time spent in REMs under O3 exposure was significantly shorter when compared with the lack of O3 condition (F / 220.7, df /1935, P B/0.001). Time spent in REMs also showed significant differences between with and without IM condition (F /42.6, df / 1935, P B/0.001), as well as during the O3 and IM interaction (F /24.6, df /1935, P B/0.001). However, only the O3 without IM condition was significantly shorter than the other three conditions using the Tukey test (P B/0.001). Interestingly, IM plus O3 condition became significantly greater than the O3 without IM condition (P B/ 0.001) Fig. 1. Both IM and O3-exposed conditions did not significantly change the latency and duration of SWS episodes during light and dark periods as compared with the other conditions. However, the number of SWS episodes during the light period
91
Fig. 1. Duration (min) of wakefulness (W), SWS and REMs assessed on 24 h polygraphic recordings in ten rats under control (C), indomethacin (IM), ozone (O3), and indomethacin plus ozone (IM/O3) experimental conditions. Bars and vertical lines indicates mean9/S.E.M., respectively.
increased significantly when rats were treated with IM. Furthermore, O3-exposure significantly delayed REMs onset latency and decreased the number and duration of REMs episodes during the light and dark periods (Table 1). Treatment by time interactions was evaluated comparing SWS duration each hour under control, IM, O3, and IM plus O3 experimental conditions. We found that the time spent in SWS changed significantly along the 24-h study (F / 10.0, df /23 935, P B/0.001). This finding could be attributed to the natural variations along the light and dark periods because no significant changes along the time were found in those interactions where the IM and O3 were included as factors (F /1.4, df /23 935, NS and F /0.6, df /23 935, NS, respectively). Also, the time spent in REMs changed significantly along the study (F /8.1, df /23 935, P B/0.001). Moreover, during this sleep condition time and O3 interaction also showed significant differences (F /2.8, df / 23 935, P B/0.001). Some significant differences were found comparing O3 without IM to O3 with IM using the Tukey test (P B/0.001) Fig. 2.
4. Discussion Among the extrapulmonary effects of O3 exposure, those affecting the central nervous system are particularly relevant. O3 exposure has been
92
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
Table 1 Effect of IM and O3 exposure on SWS and REMs episodes
SWS Onset latency (min) SWS light period (min) SWS dark period (min) SWS episodes, light period SWS episodes, dark period REMs onset latency (min) REMs episodes, light period REMs episodes, dark period REMs light period (min) REMs dark period (min)
Control
IM
O3
IM/O3
26.19/3.56 7.89/0.53 5.49/0.24 45.39/2.39 48.59/1.52 66.69/4.76 28.49/2.73 37.59/2.05 1.99/0.06 1.39/0.08
25.39/2.18 5.759/0.37 4.69/0.19 64.29/4.64 66.09/3.70a 59.49/4.45 30.61.43 36.39/2.20 1.99/0.11 1.49/0.08
15.99/1.38 8.39/0.93 6.59/0.53 53.49/5.37 54.29/7.45 98.59/6.99b 16.89/1.90b 17.19/1.64b 1.29/0.13c 1.09/0.12c
19.89/2.63 8.59/0.77 5.69/0.52 48.79/3.98 58.19/2.35 64.09/4.13 30.39/1.53 31.79/1.04 1.59/0.15 1.19/0.04
Values are expressed as mean9/S.E.M. Statistically significant was stressed by a one-way analysis of variance followed by a Tukey test (P B/0.00 1). (a) Compared with control; (b) compared with control, IM and IM/O3; (c) compared with control and IM.
found to induce significant disturbances in several sleep-related neurotransmitters in rats (CottetEmard et al., 1997; Gonzalez-Pin˜a and Paz, 1997), as well as to increase SWS and decrease REMs (Arito et al., 1992; Huitro´n-Rese´ndiz et al., 1994; Paz and Bazan-Perkins, 1992). Our data confirm the latter findings. However, because O3 is too reactive to penetrate far into the lung tissue, it is unlikely that O3 itself is responsible for such extrapulmonary effects. Several lines of evidence strongly suggest that O3 exposure effects may be mediated by the inflammatory response. Firstly, O3-induced biochemical changes observed in pulmonary lining cells are indicative of inflammation. Secondly, inhaled oxidants interact with the epithelial lining fluid resulting in a cascade of ozonation products. The presence of O3-derived free radicals in the lungs of exposed rats has been demonstrated by electron paramagnetic resonance (Kennedy et al., 1992). These free radicals catalyze cyclooxygenasemediated arachidonic acid oxidation inducing PG synthesis (Liu and Li, 1995; Shimizu and Wolfe, 1990). Moreover, cellular damage and physiological changes can further increase plasma and tissue PG concentrations by inhibiting the activity of PG inactivators (PG dehydrogenase and PG reductase) (Nakano and Prancan, 1973). Bronchoalveolar lavage fluid analyzes have revealed the presence of different inflammatory mediators derived from O3 exposure. PG-E2, IL-6 and IL-8 levels were found to be significantly
increased in 0.4 ppm O3-exposed humans (Devlin et al., 1996; Selzer et al., 1986). Increased IL-1 and TNF-a concentrations were found in rats exposed to 0.1 /2.0 ppm O3 (Cohen et al., 2001; Pendino et al., 1994); and increased PG-E2 and PG-F2 concentrations were found in rats after 2 and 8 h of O3 exposure (Giri et al., 1980). In addition, the O3induced inflammatory response characterized by macrophage adherence to epithelial cells was attenuated by the administration of IL-1 and TNF-a antibodies (Pearson and Bhalla, 1997). Some inflammatory products such as PGs and ILs have been characterized as endogenous sleeppromoting substances (Borbe´ly and Tobler, 1989). The potent sleep-inducing effect of PG-D2 has been demonstrated in laboratory animals by intravenous administration (Laychock et al., 1979) and by injection into the preoptic/anterior hypothalamic area (Hayaishi, 1991; Koyama and Hayaishi, 1994; Moussard et al., 1994). On the other hand, the effect of PG-E2 on sleep /wake activity varies in different brain regions. When administered into the third ventricle, PG-E2 decreases both SWS and REMs, and increases wakefulness and brain temperature (Matsumura et al., 1989a,b). However, when administered to the posterior hypothalamus, PG-E2 decreases the total duration of SWS and increases W without altering the brain temperature (Onoe et al., 1992). Prostaglandin plasma concentrations are increased in rats exposed to high O3 concentrations (4 ppm) (Giri et al., 1980), and circulating PGs are
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
93
Fig. 2. Duration (min) of SWS and REMs assessed every hour throughout one 12-h light:12-h darkness cycle. Control data are represented as filled circles while experimental data as open circles in each of the following conditions: (A) IM treatment; (B) ozone treatment; and (C) IM plus O3 treatment. The horizontal black bars on the X axis represent the dark phase of the circadian cycle. Vertical lines on circles represent the S.E.M.
able to cross the blood /brain barrier (Bito et al., 1976). However, high plasma prostaglandin levels are unlikely the cause of O3-induced sleep disturbances because PGs are metabolized very rapidly (only 31% of the total amount induced by lung shock remained after 5 min) (Giri et al., 1980). ILs can also cross the blood /brain barrier (Banks et al., 1995). However, unlike PGs, these cytokines induce NF-kB synthesis at the cerebral
microvasculature activating the transcription of target genes such as the one encoding cyclooxygenase, and thus initiate local prostaglandin synthesis (Rivest, 1999; Stitt, 1990). Specifically IL-1b-induced PG-E2 is mediated by type I and II IL-1 receptors (Mirtella et al., 1995). In addition, IL-1b has been found to increase PG-E2 release in several other brain areas (Komaki et al., 1992). Furthermore, ILs are also involved in sleep
94
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
regulation not only by inducing PGs synthesis in the brain, but also by a direct effect in response to infection (Krueger et al., 1995). Specifically, IL-1 and TNF-a infused in the lateral ventricles enhanced SWS and reduced REMs without affecting body temperature (Borbe´ly and Tobler, 1989). Cyclooxygenase inhibitors such as glucocorticoids and non-steroid anti-inflammatory drugs (aspirin, naproxene and IM) inhibit PG and IL synthesis (Naito et al., 1988; Terao et al., 1995). Moreover, dexamethasone inhibits PG and IL expression in rats exposed to 3.0 ppm O3 (Haddad et al., 1996), while pre-treatment with IM reduced pulmonary edema produced by 4.0 ppm O3 exposure in rats (Giri et al., 1975). Considering that sleep disorders could be due to an inflammatory response, in the present study we used high concentrations of O3 (1.0 ppm) in order to stress the anti-inflammatory effects of IM. We found that IM significantly reduced the sleep disorders induced by O3 exposure. Although sleepiness is a known complaint of subjects exposed to high levels of atmospheric O3 (Hackney et al., 1977; Lategola et al., 1980), we cannot directly extrapolate our results to humans because of the large species differences. The total duration of all vigilance states did not differ in IM treatment and control conditions at any time, although REMs was significantly higher when rats were treated with IM only 7 h after the injection. Because sleep reduction has been reported to occur in rats during the first hour after handling and IM administration (5 /10 mg/kg) (Naito et al., 1988), we were careful to initiate our analysis after this period. SWS was similar under both experimental conditions throughout the entire 24 h study period (Fig. 2A). The IM dose used was low to avoid toxic reactions such as hypothermia (Scales and Kluger, 1987). Consequently, the above REMs increase was not considered as a side effect of an IM toxic reaction. O3 exposure increases the concentration of various neurotransmitters (NE, DA, 5-HT) in different brain regions (Cottet-Emard et al., 1997; Gonzalez-Pin˜a and Paz, 1997). The same effect was observed after the direct administration of IL-1b into the anterior hypothalamus (Shintani et al., 1993). Such findings in addition to our
observation that O3-induced sleep disorders can be reverted with IM treatment, strongly suggest that an inflammatory mechanism could be responsible for these extrapulmonary effects of O3 exposure. IM inhibits PG synthesis in both the lung and brain, and thus the eventual PG depletion in the brain might be responsible for reverting O3induced sleep disorders.
Acknowledgements The authors wish to thank Francisco Gutie´rrez for his technical assistance, and Dr Teresa Villarreal for reviewing the manuscript.
References Arito, H., Uchiyama, J., Yokoyama, E., 1992. Acute effects of ozone on EEG activity, sleep /wakefulness and heart rate in rats. Ind. Health 30, 23 /34. Banks, W.A., Kastin, A.L., Broadwell, R.D., 1995. Passage of cytokines across the blood /brain barrier. Neuroimmunomodulation 2, 241 /248. Bito, L.Z., Davson, H., Hollingworth, J.R., 1976. Facilitated transport of prostaglandines across the blood /cerebrospinal fluid and blood barriers. J. Physiol. 256, 273 /285. Borbe´ly, A.A., Tobler, I., 1989. Endogenous sleep-promoting substances and sleep regulation. Physiol. Rev. 69, 605 /670. Cohen, M.D., Sisco, M., Li, Y., Zelikoff, J.T., Schlesinger, R.B., 2001. Ozone-induced modulation of cell-mediated immune responses in the lungs. Toxicol. Appl. Pharmacol. 171, 71 /84. Cottet-Emard, J.M., Dalmaz, Y., Pequignot, J., Peyrin, L., Pequignot, J.M., 1997. Long-term exposure to ozone alters peripheral and central catecholamine activity in rats. Pflu¨gers Arch. Eur. J. Physiol. 433, 744 /749. Devlin, R.B., McDonnell, W.F., Becker, S., Madden, M.C., McGee, M.P., Perez, R., Hatch, G., House, D.E., Koren, H.S., 1996. Time-dependent changes of inflammatory mediators in the lungs of humans exposed to 0.4 ppm ozone for 2 hr: a comparison of mediators found in bronchoalveolar lavage fluid 1 and 18 hr after exposure. Toxicol. Appl. Pharmacol. 138, 176 /185. Giri, S.N., Benson, J., Siegel, D.M., Rice, S.A., Schiedt, M., 1975. Effects of pretreatment with anti-inflammatory drugs on ozone-induced lung damage in rats. Proc. Soc. Exp. Biol. Med. 150, 810 /814. Giri, S.N., Hollinger, M.A., Schiedt, M.J., 1980. The effects of ozone and paraquat on PGF2 and PGE2 levels in plasma and combine pleural effusion and lung lavage of rats. Environ. Res. 21, 467 /476.
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96 Gonzalez-Pin˜a, R., Paz, C., 1997. Brain monoamine changes in rats after short periods of ozone exposure. Neurochem. Res. 22, 63 /66. Hackney, J.D., Linn, W.S., Karuza, S.K., Buckley, R.D., Bates, D.V., Hazucha, M.L., Pengelly, L.D., Silverman, F., 1977. Effects of ozone exposure in Canadians and southern Californians. Arch. Environ. Health 32, 110 /116. Haddad, E.B., Salmon, M., Koto, H., Barnes, P.J., Adcock, I., Chung, K.F., 1996. Ozone induction of cytokine-induced neutrophil chemoattractant (CINC) and nuclear factor-kB in rat lung: inhibition of corticosteroids. FEBS Lett. 379, 265 /268. Hayaishi, O., 1991. Molecular mechanisms of sleep /wake regulation: roles of prostaglandines D2 and E2. FASEB J. 5, 2575 /2581. Hiroshima, K., Kohno, T., Owada, H., Hayashi, Y., 1987. A morphological study of the effects of ozone on rat lung. I. Short-term exposure. Exp. Mol. Pathol. 47, 327 /345. Huitro´n-Rese´ndiz, S., Custodio-Ramirez, V., Escalante-Membrillo, C., Gonzalez-Pin˜a, R., Paz, C., 1994. Sleep alterations and brain regional changes of serotonin and its metabolite in rats exposed to ozone. Neurosci. Lett. 177, 119 /122. Kennedy, C.H., Hatch, G.E., Slade, R., Mason, R.P., 1992. Application of the EPR spintrapping technique to the detection of radicals produced in vivo during inhalation exposure of rats to ozone. Toxicol. Appl. Pharmacol. 114, 41 /46. Kinney, P.L., Ware, J.H., Spengler, J.D., Dockery, D.W., Speizer, F.E., Ferris, B.G., 1989. Short-term pulmonary function change in association with ozone levels. Am. Rev. Respir. Dis. 139, 56 /61. Komaki, G., Arimura, A., Koves, K., 1992. Effect of intravenous injection of IL-1b on PGE2 levels in several brain areas as determined by microdialysis. Am. J. Physiol. 262, 246 / 251. Koyama, Y., Hayaishi, O., 1994. Modulation by prostaglandins of activity of sleep-related neurons in the preoptic/anterior hypothalamic areas in rats. Brain Res. Bull. 33, 367 /372. Krueger, J.M., Takahashi, S., Kapas, L., Bredow, S., Roky, R., Fang, J., Floyd, R., Renegar, K.B., Guha-Thakurta, N., Novitsky, S., Obal, F., 1995. Cytokines in sleep regulation. Adv. Neuroimmunol. 5, 171 /188. Lategola, M.T., Melton, C.E., Higgins, E., 1980. Effects of ozone on symptoms and cardiopulmonary function in a flight attendant surrogate population. Aviat. Space Environ. Med. 51, 237 /246. Laychock, S.G., Johnson, D.N., Hats, L.S., 1979. PGD2 effects on rodent behavior and EEG patterns in cats. Pharmacol. Biochem. Behav. 12, 747 /754. Liu, D., Li, L., 1995. Prostaglandin F2a rises in response to hydroxyl radical generated in vivo. Free Radic. Biol. Med. 18, 571 /576. Matsumura, H., Honda, K., Choi, W.S., Inoue´, S., Sakai, T., Hayaishi, O., 1989a. Evidence that brain prostaglandin E2 is involved in physiological sleep /wake regulation in rats. Proc. Natl. Acad. Sci. USA 86, 5666 /5669.
95
Matsumura, H., Honda, K., Goh, Y., Ueno, R., Sakai, T., Inoue, S., Hayaishi, O., 1989b. Awaking effect of prostaglandin E2 in freely moving rats. Brain Res. 481, 242 /249. Mirtella, A., Tringali, G., Guerriero, G., Ghiara, P., Parente, L., Preziosi, P., Navarra, P., 1995. Evidence that the interleukin-1b-induced prostaglandin E2 release from rat hypothalamus is mediated by type I and type II interleukin1 receptors. J. Neuroimmunol. 61, 171 /177. Moussard, C., Alber, D., Mozer, J.L., Henry, J.C., 1994. Effects of chronic REM sleep deprivation on pituitary, hypothalamus and hippocampus PGE2 and PGD2 biosynthesis in the mouse. Prostaglandins Leukotrienes Essent. Fatty Acids 51, 369 /372. Nakano, J., Prancan, A.V., 1973. Metabolic degradation of prostaglandin E1 in the lung and kidney of rats in endotoxin shock. Proc. Soc. Exp. Biol. Med. 144, 506 /508. Naito, K., Osama, H., Ueno, R., Hayaishi, O., Honda, K., Inoue, S., 1988. Suppression of sleep by prostaglandin synthesis inhibitors in unrestrained rats. Brain Res. 453, 329 /336. Onoe, H., Watanabe, Y., Ono, K., Koyama, Y., Hayaishi, O., 1992. Prostaglandin E2 exerts an awaking effect in the posterior hypothalamus at a site distinct from that mediating its febrile action in the anterior hypothalamus. J. Neurosci. 12, 2715 /2725. Paz, C., Bazan-Perkins, B., 1992. Sleep /wake disorganization in cats exposed to ozone. Neurosci. Lett. 140, 270 /272. Paz, C., Huitro´n-Rese´ndiz, S., 1996. The effects of ozone exposure on the sleep /wake cycle and serotonin contents in the pons of the rat. Neurosci. Lett. 204, 49 /52. Pearson, A.C., Bhalla, D.K., 1997. Effects of ozone on macrophage adhesion in vitro and epithelial and inflammatory response in vivo: the role of cytokines. J. Toxicol. Environ. Health 50, 143 /157. Pendino, K.J., Shuler, R.L., Laskin, J.D., Laskin, D.L., 1994. Enhanced production of interleukin-1 tumor necrosis factor-a, and fibronectin by rats lung phagocytes following inhalation of a pulmonary irritant. Am. J. Respir. Cell. Mol. Biol. 11, 279 /286. Rivest, S., 1999. What is the cellular source of prostaglandins in the brain in response to systemic inflammation? Facts and controversies. Mol. Psychiatry 4, 500 /507. Scales, W.E., Kluger, M.J., 1987. Effect of antipyretic drugs on circadian rhythm in body temperature. Am. J. Physiol. 253, 306 /313. Selzer, J., Bigby, B.G., Stulborg, M., Holzman, M.J., Nadel, J.A., Ueki, I.F., Leikauf, G.D., Goetzel, E.J., Boushey, H.A., 1986. Ozone induced change in bronchial reactivity to methacholine and airway inflammation in humans. J. Appl. Physiol. 60, 1321 /1326. Shimizu, T., Wolfe, L.S., 1990. Arachidonic acid cascade and signal transduction. J. Neurochem. 55, 1 /15. Shintani, F., Kanba, S., Nakaki, T., Nibuya, M., Kinoshita, N., Suzuki, E., Yagy, G., Kato, R., Asai, M., 1993. Interleukin1b augments release of noradrenaline, dopamine, and serotonin in the rat anterior hypothalamus. J. Neurosci. 13, 3574 /3581.
96
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
Specktor, D.A., Lippmann, M., Thurston, G.D., Lioy, P.J., Steko, J., O’Connor, G., Garshick, E., Speizer, F.E., Hayes, C., 1988. Effects of ambient ozone on respiratory function in healthy adults exercising outdoors. Am. Rev. Respir. Dis. 138, 821 /828. Stitt, J.T., 1990. Passage of immunomodulators across the blood /brain barrier. Yale J. Biol. Med. 63, 121 / 131.
Terao, A., Kitamura, H., Asano, A., Kobayashi, M., Saito, M., 1995. Roles of prostaglandins D2 and E2 in interleukin-1induced activation of norepinephrine turnover in the brain and peripheral organs of rat. J. Neurochem. 65, 2742 /2747. Wilson, D.W., Plopper, C.G., Dungworth, D.L., 1984. The response of the macaque tracheobronchial epithelium to acute ozone injury. A qualitative ultrastructural and autoradiographic study. Am. J. Pathol. 116, 193 /206.
Indomethacin reverts sleep disorders produced by ozone exposure in rats Carmen Rubio, Carlos Paz * Departamento de Neurofisiologı´a, Instituto Nacional de Neurologı´a y Neurocirugı´a M.V.S., Insurgentes Sur 3877, Mexico 14269 D.F., Mexico Received 21 October 2002; received in revised form 28 March 2003; accepted 8 May 2003
Abstract Ozone (O3) exposure causes pulmonary biochemical changes both in humans and experimental animals, inducing the release of inflammatory mediators such as cytokines and eicosanoids. Some of these reaction products have been characterized as endogenous sleep-promoting substances and have been implicated in the development of sleepiness in patients with inflammatory disease. Furthermore, sleep alterations are known to occur in O3-exposed humans and experimental animals. In order to test the probable involvement of such inflammatory mediators in O3-induced sleep disorders, we blocked prostaglandin synthesis administrating the cyclooxygenase inhibitor indomethacin (IM) and compared conventional electrographic sleep parameters in rats under four different experimental conditions: treatment with IM alone, O3-exposure, pre-treatment with IM plus O3 exposure, and control conditions. We found that O3 exposure increased slow wave sleep (SWS) and decreased rapid eye movement sleep (REMs) significantly, while IM pretreatment reduced these O3-induced sleep disorders. IM treatment alone did not affect sleep. These findings strongly support a role for inflammatory mediators in O3 exposure-induced neurological alterations. # 2003 Elsevier Ireland Ltd. All rights reserved. Keywords: Ozone; Sleep; Inflammation; Indomethacin; Cytokines; Eicosanoids
1. Introduction Ozone (O3) is the main photochemical oxidant found in polluted urban areas. Being a gas, toxicity studies have focused on the functional and morphological effects of O3 in the lungs of humans and laboratory animals. Exposure to more than 0.12 ppm O3 is known to decrease forced vital capacity * Corresponding author. Fax: /52-5-606-3032. E-mail address: [email protected] (C. Paz).
and forced expiratory volume expelled in the 1st second (Kinney et al., 1989; Specktor et al., 1988). O3-induced airway damage is morphologically characterized by dysplasia and metaplasia (Hiroshima et al., 1987; Wilson et al., 1984). However, the most remarkable effect of O3 exposure (0.4 ppm) in humans is a pulmonary inflammatory response characterized by increased concentrations of soluble mediators such as interleukins (ILs), prostaglandins (PGs) and tumor necrosis factor-a (TNF-a) (Devlin et al., 1996).
0300-483X/03/$ - see front matter # 2003 Elsevier Ireland Ltd. All rights reserved. doi:10.1016/S0300-483X(03)00245-2
90
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
Some extrapulmonary effects have been described in addition to the vast number of descriptions of lung impairment in O3-exposed humans and experimental animals. Impaired mental performance, complaints of fatigue, headache and sleepiness are some of the neurological symptoms reported by O3-exposed individuals (Hackney et al., 1977; Lategola et al., 1980). Electrographic studies demonstrated that exposure to 0.2 /1.2 ppm O3 significantly decreases rapid eye movement sleep (REMs) and increases slow wave sleep (SWS) in rats (Arito et al., 1992; Paz and Huitro´nRese´ndiz, 1996) and cats (Paz and Bazan-Perkins, 1992). Moreover, O3-exposed rats showed significant changes in sleep-related neurotransmitters (Cottet-Emard et al., 1997; Gonzalez-Pin˜a and Paz, 1997). Because it is highly reactive, O3 is totally destroyed in the lung tissue. Its pathological effects beyond the pulmonary system remain to be elucidated. Certain O3-reaction products known to cross the blood /gas barrier in experimental animals might be involved in the pathogenesis of these extrapulmonary effects. Plasma concentrations of PGs-F2 and -E2 were found to be increased in rats exposed to 4.0 ppm O3 for up to 8 h (Giri et al., 1980). PGs are involved in regulation of physiological sleep /wake cycles (Koyama and Hayaishi, 1994; Matsumura et al., 1989a,b; Moussard et al., 1994). To explore the possible involvement of inflammatory reaction products in O3-induced sleep disorders, we blocked arachidonic acid metabolism and PG synthesis by administering the cyclooxygenase inhibitor indomethacin (IM), and analyzed a 24 h electrographic study in rats exposed to O3.
2. Materials and methods Ten adult male Wistar rats weighting 280 /300 g were anaesthetized (Ketamine, 100 mg/kg, i.p.) and placed on a stereotaxic apparatus. After exposing the vertex of the skull, bipolar electrodes were implanted on the sensorimotor cortex to record the electrocorticogram (ECG), and on the ocular orbit to record eye movements (EOG). Other electrodes were fixed to the neck muscles
through a cut over the nape of the neck to record the electromyogram (EMG). All electrodes were made of stainless steel Teflon-coated wire (0.005 in. diameter) with uncoated tips. A screw implanted in the skull served as an indifferent source of reference. The external electrode tips were attached to pins and fixed to a rectangular male plug, which was secured to the skull with dental acrylic. Skin cuts were sutured and 200 000 U penicillin G potassium was administered to each rat. After 1 week of recovery, the plugs were connected to a polygraph (Grass S88) by means of flexible cables, allowing the rat to move freely in a hermetic chamber (30 /22 /22 cm) fitted with two tubes: one to add filtered air and the other for draining and inner air analysis. Rats were habituated to these laboratory conditions during 3 days under 12-h light:12-h darkness cycles, at 249/ 1 8C and with free access to food and water. Once habituated, rats received an intramuscular injection of vehicle alone (20% ethanol and 4% sodium bicarbonate dissolved in saline solution). A 24 h control polygraphic recording was obtained 1 h after the injection. Thereafter, the rats were connected as described above, every week, to obtain additional 24 h recordings under three different experimental conditions: (a) IM injection (10 mg/kg) 1 h before initiating sleep recordings with no O3 exposure; (b) vehicle injection 1 h before the 24 h sleep recording, adding 1.0 ppm O3 to the filtered air; and (c) pre-treatment with IM (10 mg/kg) and 24 h exposure to 1.0 ppm O3. Ozone was added to the filtered air with a P15 Triozon generator, and O3 concentrations were measured using a 1008-PC Dasibi UV light photometric analyzer. The vigilance states of the rat were visually analyzed and defined according to the following electrophysiological criteria: wakefulness (W) characterized by ECG disynchronization and presence of accentuated muscle tone during movements; SWS characterized by the presence of sleep spindles, slow waves with voltage higher than 75 mV and decreased EMG voltage; REMs characterized by ECG disynchronization, rapid eye movements and absence of voltage in the EMG succeeding SWS periods. Total time spent in W,
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
SWS, and REMs during 24 h, as well as in an hourly step analysis was compared under control, IM injection, O3 exposure, and IM plus O3 experimental conditions. Besides, duration, number and onset latency of the vigilance stage periods were compared during the light and dark conditions. Results were analyzed by an ANOVA conducted as a block design with factorial treatment combinations considering IM treatment, O3 exposure, and time of recording as factors. Subsequent comparisons within conditions were made using a Tukey test. The accepted nominal levels of significance was P B/0.01.
3. Results Total wakefulness time recorded over a 24 h period was not significantly affected during control, IM injection, O3 exposure, and IM plus O3 experimental conditions. However, total time spent in SWS during O3 exposure was significantly longer when compared with the lack of O3 condition (F /34.9, df /1935, P B/0.001). The specific effect of O3 condition was confirmed when no significant differences were found between with and without IM condition (F /0.2, df /1935, NS), as well as when O3 and IM interaction were compared (F /5.7, df /1935, NS). On the other hand, time spent in REMs under O3 exposure was significantly shorter when compared with the lack of O3 condition (F / 220.7, df /1935, P B/0.001). Time spent in REMs also showed significant differences between with and without IM condition (F /42.6, df / 1935, P B/0.001), as well as during the O3 and IM interaction (F /24.6, df /1935, P B/0.001). However, only the O3 without IM condition was significantly shorter than the other three conditions using the Tukey test (P B/0.001). Interestingly, IM plus O3 condition became significantly greater than the O3 without IM condition (P B/ 0.001) Fig. 1. Both IM and O3-exposed conditions did not significantly change the latency and duration of SWS episodes during light and dark periods as compared with the other conditions. However, the number of SWS episodes during the light period
91
Fig. 1. Duration (min) of wakefulness (W), SWS and REMs assessed on 24 h polygraphic recordings in ten rats under control (C), indomethacin (IM), ozone (O3), and indomethacin plus ozone (IM/O3) experimental conditions. Bars and vertical lines indicates mean9/S.E.M., respectively.
increased significantly when rats were treated with IM. Furthermore, O3-exposure significantly delayed REMs onset latency and decreased the number and duration of REMs episodes during the light and dark periods (Table 1). Treatment by time interactions was evaluated comparing SWS duration each hour under control, IM, O3, and IM plus O3 experimental conditions. We found that the time spent in SWS changed significantly along the 24-h study (F / 10.0, df /23 935, P B/0.001). This finding could be attributed to the natural variations along the light and dark periods because no significant changes along the time were found in those interactions where the IM and O3 were included as factors (F /1.4, df /23 935, NS and F /0.6, df /23 935, NS, respectively). Also, the time spent in REMs changed significantly along the study (F /8.1, df /23 935, P B/0.001). Moreover, during this sleep condition time and O3 interaction also showed significant differences (F /2.8, df / 23 935, P B/0.001). Some significant differences were found comparing O3 without IM to O3 with IM using the Tukey test (P B/0.001) Fig. 2.
4. Discussion Among the extrapulmonary effects of O3 exposure, those affecting the central nervous system are particularly relevant. O3 exposure has been
92
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
Table 1 Effect of IM and O3 exposure on SWS and REMs episodes
SWS Onset latency (min) SWS light period (min) SWS dark period (min) SWS episodes, light period SWS episodes, dark period REMs onset latency (min) REMs episodes, light period REMs episodes, dark period REMs light period (min) REMs dark period (min)
Control
IM
O3
IM/O3
26.19/3.56 7.89/0.53 5.49/0.24 45.39/2.39 48.59/1.52 66.69/4.76 28.49/2.73 37.59/2.05 1.99/0.06 1.39/0.08
25.39/2.18 5.759/0.37 4.69/0.19 64.29/4.64 66.09/3.70a 59.49/4.45 30.61.43 36.39/2.20 1.99/0.11 1.49/0.08
15.99/1.38 8.39/0.93 6.59/0.53 53.49/5.37 54.29/7.45 98.59/6.99b 16.89/1.90b 17.19/1.64b 1.29/0.13c 1.09/0.12c
19.89/2.63 8.59/0.77 5.69/0.52 48.79/3.98 58.19/2.35 64.09/4.13 30.39/1.53 31.79/1.04 1.59/0.15 1.19/0.04
Values are expressed as mean9/S.E.M. Statistically significant was stressed by a one-way analysis of variance followed by a Tukey test (P B/0.00 1). (a) Compared with control; (b) compared with control, IM and IM/O3; (c) compared with control and IM.
found to induce significant disturbances in several sleep-related neurotransmitters in rats (CottetEmard et al., 1997; Gonzalez-Pin˜a and Paz, 1997), as well as to increase SWS and decrease REMs (Arito et al., 1992; Huitro´n-Rese´ndiz et al., 1994; Paz and Bazan-Perkins, 1992). Our data confirm the latter findings. However, because O3 is too reactive to penetrate far into the lung tissue, it is unlikely that O3 itself is responsible for such extrapulmonary effects. Several lines of evidence strongly suggest that O3 exposure effects may be mediated by the inflammatory response. Firstly, O3-induced biochemical changes observed in pulmonary lining cells are indicative of inflammation. Secondly, inhaled oxidants interact with the epithelial lining fluid resulting in a cascade of ozonation products. The presence of O3-derived free radicals in the lungs of exposed rats has been demonstrated by electron paramagnetic resonance (Kennedy et al., 1992). These free radicals catalyze cyclooxygenasemediated arachidonic acid oxidation inducing PG synthesis (Liu and Li, 1995; Shimizu and Wolfe, 1990). Moreover, cellular damage and physiological changes can further increase plasma and tissue PG concentrations by inhibiting the activity of PG inactivators (PG dehydrogenase and PG reductase) (Nakano and Prancan, 1973). Bronchoalveolar lavage fluid analyzes have revealed the presence of different inflammatory mediators derived from O3 exposure. PG-E2, IL-6 and IL-8 levels were found to be significantly
increased in 0.4 ppm O3-exposed humans (Devlin et al., 1996; Selzer et al., 1986). Increased IL-1 and TNF-a concentrations were found in rats exposed to 0.1 /2.0 ppm O3 (Cohen et al., 2001; Pendino et al., 1994); and increased PG-E2 and PG-F2 concentrations were found in rats after 2 and 8 h of O3 exposure (Giri et al., 1980). In addition, the O3induced inflammatory response characterized by macrophage adherence to epithelial cells was attenuated by the administration of IL-1 and TNF-a antibodies (Pearson and Bhalla, 1997). Some inflammatory products such as PGs and ILs have been characterized as endogenous sleeppromoting substances (Borbe´ly and Tobler, 1989). The potent sleep-inducing effect of PG-D2 has been demonstrated in laboratory animals by intravenous administration (Laychock et al., 1979) and by injection into the preoptic/anterior hypothalamic area (Hayaishi, 1991; Koyama and Hayaishi, 1994; Moussard et al., 1994). On the other hand, the effect of PG-E2 on sleep /wake activity varies in different brain regions. When administered into the third ventricle, PG-E2 decreases both SWS and REMs, and increases wakefulness and brain temperature (Matsumura et al., 1989a,b). However, when administered to the posterior hypothalamus, PG-E2 decreases the total duration of SWS and increases W without altering the brain temperature (Onoe et al., 1992). Prostaglandin plasma concentrations are increased in rats exposed to high O3 concentrations (4 ppm) (Giri et al., 1980), and circulating PGs are
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
93
Fig. 2. Duration (min) of SWS and REMs assessed every hour throughout one 12-h light:12-h darkness cycle. Control data are represented as filled circles while experimental data as open circles in each of the following conditions: (A) IM treatment; (B) ozone treatment; and (C) IM plus O3 treatment. The horizontal black bars on the X axis represent the dark phase of the circadian cycle. Vertical lines on circles represent the S.E.M.
able to cross the blood /brain barrier (Bito et al., 1976). However, high plasma prostaglandin levels are unlikely the cause of O3-induced sleep disturbances because PGs are metabolized very rapidly (only 31% of the total amount induced by lung shock remained after 5 min) (Giri et al., 1980). ILs can also cross the blood /brain barrier (Banks et al., 1995). However, unlike PGs, these cytokines induce NF-kB synthesis at the cerebral
microvasculature activating the transcription of target genes such as the one encoding cyclooxygenase, and thus initiate local prostaglandin synthesis (Rivest, 1999; Stitt, 1990). Specifically IL-1b-induced PG-E2 is mediated by type I and II IL-1 receptors (Mirtella et al., 1995). In addition, IL-1b has been found to increase PG-E2 release in several other brain areas (Komaki et al., 1992). Furthermore, ILs are also involved in sleep
94
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
regulation not only by inducing PGs synthesis in the brain, but also by a direct effect in response to infection (Krueger et al., 1995). Specifically, IL-1 and TNF-a infused in the lateral ventricles enhanced SWS and reduced REMs without affecting body temperature (Borbe´ly and Tobler, 1989). Cyclooxygenase inhibitors such as glucocorticoids and non-steroid anti-inflammatory drugs (aspirin, naproxene and IM) inhibit PG and IL synthesis (Naito et al., 1988; Terao et al., 1995). Moreover, dexamethasone inhibits PG and IL expression in rats exposed to 3.0 ppm O3 (Haddad et al., 1996), while pre-treatment with IM reduced pulmonary edema produced by 4.0 ppm O3 exposure in rats (Giri et al., 1975). Considering that sleep disorders could be due to an inflammatory response, in the present study we used high concentrations of O3 (1.0 ppm) in order to stress the anti-inflammatory effects of IM. We found that IM significantly reduced the sleep disorders induced by O3 exposure. Although sleepiness is a known complaint of subjects exposed to high levels of atmospheric O3 (Hackney et al., 1977; Lategola et al., 1980), we cannot directly extrapolate our results to humans because of the large species differences. The total duration of all vigilance states did not differ in IM treatment and control conditions at any time, although REMs was significantly higher when rats were treated with IM only 7 h after the injection. Because sleep reduction has been reported to occur in rats during the first hour after handling and IM administration (5 /10 mg/kg) (Naito et al., 1988), we were careful to initiate our analysis after this period. SWS was similar under both experimental conditions throughout the entire 24 h study period (Fig. 2A). The IM dose used was low to avoid toxic reactions such as hypothermia (Scales and Kluger, 1987). Consequently, the above REMs increase was not considered as a side effect of an IM toxic reaction. O3 exposure increases the concentration of various neurotransmitters (NE, DA, 5-HT) in different brain regions (Cottet-Emard et al., 1997; Gonzalez-Pin˜a and Paz, 1997). The same effect was observed after the direct administration of IL-1b into the anterior hypothalamus (Shintani et al., 1993). Such findings in addition to our
observation that O3-induced sleep disorders can be reverted with IM treatment, strongly suggest that an inflammatory mechanism could be responsible for these extrapulmonary effects of O3 exposure. IM inhibits PG synthesis in both the lung and brain, and thus the eventual PG depletion in the brain might be responsible for reverting O3induced sleep disorders.
Acknowledgements The authors wish to thank Francisco Gutie´rrez for his technical assistance, and Dr Teresa Villarreal for reviewing the manuscript.
References Arito, H., Uchiyama, J., Yokoyama, E., 1992. Acute effects of ozone on EEG activity, sleep /wakefulness and heart rate in rats. Ind. Health 30, 23 /34. Banks, W.A., Kastin, A.L., Broadwell, R.D., 1995. Passage of cytokines across the blood /brain barrier. Neuroimmunomodulation 2, 241 /248. Bito, L.Z., Davson, H., Hollingworth, J.R., 1976. Facilitated transport of prostaglandines across the blood /cerebrospinal fluid and blood barriers. J. Physiol. 256, 273 /285. Borbe´ly, A.A., Tobler, I., 1989. Endogenous sleep-promoting substances and sleep regulation. Physiol. Rev. 69, 605 /670. Cohen, M.D., Sisco, M., Li, Y., Zelikoff, J.T., Schlesinger, R.B., 2001. Ozone-induced modulation of cell-mediated immune responses in the lungs. Toxicol. Appl. Pharmacol. 171, 71 /84. Cottet-Emard, J.M., Dalmaz, Y., Pequignot, J., Peyrin, L., Pequignot, J.M., 1997. Long-term exposure to ozone alters peripheral and central catecholamine activity in rats. Pflu¨gers Arch. Eur. J. Physiol. 433, 744 /749. Devlin, R.B., McDonnell, W.F., Becker, S., Madden, M.C., McGee, M.P., Perez, R., Hatch, G., House, D.E., Koren, H.S., 1996. Time-dependent changes of inflammatory mediators in the lungs of humans exposed to 0.4 ppm ozone for 2 hr: a comparison of mediators found in bronchoalveolar lavage fluid 1 and 18 hr after exposure. Toxicol. Appl. Pharmacol. 138, 176 /185. Giri, S.N., Benson, J., Siegel, D.M., Rice, S.A., Schiedt, M., 1975. Effects of pretreatment with anti-inflammatory drugs on ozone-induced lung damage in rats. Proc. Soc. Exp. Biol. Med. 150, 810 /814. Giri, S.N., Hollinger, M.A., Schiedt, M.J., 1980. The effects of ozone and paraquat on PGF2 and PGE2 levels in plasma and combine pleural effusion and lung lavage of rats. Environ. Res. 21, 467 /476.
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96 Gonzalez-Pin˜a, R., Paz, C., 1997. Brain monoamine changes in rats after short periods of ozone exposure. Neurochem. Res. 22, 63 /66. Hackney, J.D., Linn, W.S., Karuza, S.K., Buckley, R.D., Bates, D.V., Hazucha, M.L., Pengelly, L.D., Silverman, F., 1977. Effects of ozone exposure in Canadians and southern Californians. Arch. Environ. Health 32, 110 /116. Haddad, E.B., Salmon, M., Koto, H., Barnes, P.J., Adcock, I., Chung, K.F., 1996. Ozone induction of cytokine-induced neutrophil chemoattractant (CINC) and nuclear factor-kB in rat lung: inhibition of corticosteroids. FEBS Lett. 379, 265 /268. Hayaishi, O., 1991. Molecular mechanisms of sleep /wake regulation: roles of prostaglandines D2 and E2. FASEB J. 5, 2575 /2581. Hiroshima, K., Kohno, T., Owada, H., Hayashi, Y., 1987. A morphological study of the effects of ozone on rat lung. I. Short-term exposure. Exp. Mol. Pathol. 47, 327 /345. Huitro´n-Rese´ndiz, S., Custodio-Ramirez, V., Escalante-Membrillo, C., Gonzalez-Pin˜a, R., Paz, C., 1994. Sleep alterations and brain regional changes of serotonin and its metabolite in rats exposed to ozone. Neurosci. Lett. 177, 119 /122. Kennedy, C.H., Hatch, G.E., Slade, R., Mason, R.P., 1992. Application of the EPR spintrapping technique to the detection of radicals produced in vivo during inhalation exposure of rats to ozone. Toxicol. Appl. Pharmacol. 114, 41 /46. Kinney, P.L., Ware, J.H., Spengler, J.D., Dockery, D.W., Speizer, F.E., Ferris, B.G., 1989. Short-term pulmonary function change in association with ozone levels. Am. Rev. Respir. Dis. 139, 56 /61. Komaki, G., Arimura, A., Koves, K., 1992. Effect of intravenous injection of IL-1b on PGE2 levels in several brain areas as determined by microdialysis. Am. J. Physiol. 262, 246 / 251. Koyama, Y., Hayaishi, O., 1994. Modulation by prostaglandins of activity of sleep-related neurons in the preoptic/anterior hypothalamic areas in rats. Brain Res. Bull. 33, 367 /372. Krueger, J.M., Takahashi, S., Kapas, L., Bredow, S., Roky, R., Fang, J., Floyd, R., Renegar, K.B., Guha-Thakurta, N., Novitsky, S., Obal, F., 1995. Cytokines in sleep regulation. Adv. Neuroimmunol. 5, 171 /188. Lategola, M.T., Melton, C.E., Higgins, E., 1980. Effects of ozone on symptoms and cardiopulmonary function in a flight attendant surrogate population. Aviat. Space Environ. Med. 51, 237 /246. Laychock, S.G., Johnson, D.N., Hats, L.S., 1979. PGD2 effects on rodent behavior and EEG patterns in cats. Pharmacol. Biochem. Behav. 12, 747 /754. Liu, D., Li, L., 1995. Prostaglandin F2a rises in response to hydroxyl radical generated in vivo. Free Radic. Biol. Med. 18, 571 /576. Matsumura, H., Honda, K., Choi, W.S., Inoue´, S., Sakai, T., Hayaishi, O., 1989a. Evidence that brain prostaglandin E2 is involved in physiological sleep /wake regulation in rats. Proc. Natl. Acad. Sci. USA 86, 5666 /5669.
95
Matsumura, H., Honda, K., Goh, Y., Ueno, R., Sakai, T., Inoue, S., Hayaishi, O., 1989b. Awaking effect of prostaglandin E2 in freely moving rats. Brain Res. 481, 242 /249. Mirtella, A., Tringali, G., Guerriero, G., Ghiara, P., Parente, L., Preziosi, P., Navarra, P., 1995. Evidence that the interleukin-1b-induced prostaglandin E2 release from rat hypothalamus is mediated by type I and type II interleukin1 receptors. J. Neuroimmunol. 61, 171 /177. Moussard, C., Alber, D., Mozer, J.L., Henry, J.C., 1994. Effects of chronic REM sleep deprivation on pituitary, hypothalamus and hippocampus PGE2 and PGD2 biosynthesis in the mouse. Prostaglandins Leukotrienes Essent. Fatty Acids 51, 369 /372. Nakano, J., Prancan, A.V., 1973. Metabolic degradation of prostaglandin E1 in the lung and kidney of rats in endotoxin shock. Proc. Soc. Exp. Biol. Med. 144, 506 /508. Naito, K., Osama, H., Ueno, R., Hayaishi, O., Honda, K., Inoue, S., 1988. Suppression of sleep by prostaglandin synthesis inhibitors in unrestrained rats. Brain Res. 453, 329 /336. Onoe, H., Watanabe, Y., Ono, K., Koyama, Y., Hayaishi, O., 1992. Prostaglandin E2 exerts an awaking effect in the posterior hypothalamus at a site distinct from that mediating its febrile action in the anterior hypothalamus. J. Neurosci. 12, 2715 /2725. Paz, C., Bazan-Perkins, B., 1992. Sleep /wake disorganization in cats exposed to ozone. Neurosci. Lett. 140, 270 /272. Paz, C., Huitro´n-Rese´ndiz, S., 1996. The effects of ozone exposure on the sleep /wake cycle and serotonin contents in the pons of the rat. Neurosci. Lett. 204, 49 /52. Pearson, A.C., Bhalla, D.K., 1997. Effects of ozone on macrophage adhesion in vitro and epithelial and inflammatory response in vivo: the role of cytokines. J. Toxicol. Environ. Health 50, 143 /157. Pendino, K.J., Shuler, R.L., Laskin, J.D., Laskin, D.L., 1994. Enhanced production of interleukin-1 tumor necrosis factor-a, and fibronectin by rats lung phagocytes following inhalation of a pulmonary irritant. Am. J. Respir. Cell. Mol. Biol. 11, 279 /286. Rivest, S., 1999. What is the cellular source of prostaglandins in the brain in response to systemic inflammation? Facts and controversies. Mol. Psychiatry 4, 500 /507. Scales, W.E., Kluger, M.J., 1987. Effect of antipyretic drugs on circadian rhythm in body temperature. Am. J. Physiol. 253, 306 /313. Selzer, J., Bigby, B.G., Stulborg, M., Holzman, M.J., Nadel, J.A., Ueki, I.F., Leikauf, G.D., Goetzel, E.J., Boushey, H.A., 1986. Ozone induced change in bronchial reactivity to methacholine and airway inflammation in humans. J. Appl. Physiol. 60, 1321 /1326. Shimizu, T., Wolfe, L.S., 1990. Arachidonic acid cascade and signal transduction. J. Neurochem. 55, 1 /15. Shintani, F., Kanba, S., Nakaki, T., Nibuya, M., Kinoshita, N., Suzuki, E., Yagy, G., Kato, R., Asai, M., 1993. Interleukin1b augments release of noradrenaline, dopamine, and serotonin in the rat anterior hypothalamus. J. Neurosci. 13, 3574 /3581.
96
C. Rubio, C. Paz / Toxicology 191 (2003) 89 /96
Specktor, D.A., Lippmann, M., Thurston, G.D., Lioy, P.J., Steko, J., O’Connor, G., Garshick, E., Speizer, F.E., Hayes, C., 1988. Effects of ambient ozone on respiratory function in healthy adults exercising outdoors. Am. Rev. Respir. Dis. 138, 821 /828. Stitt, J.T., 1990. Passage of immunomodulators across the blood /brain barrier. Yale J. Biol. Med. 63, 121 / 131.
Terao, A., Kitamura, H., Asano, A., Kobayashi, M., Saito, M., 1995. Roles of prostaglandins D2 and E2 in interleukin-1induced activation of norepinephrine turnover in the brain and peripheral organs of rat. J. Neurochem. 65, 2742 /2747. Wilson, D.W., Plopper, C.G., Dungworth, D.L., 1984. The response of the macaque tracheobronchial epithelium to acute ozone injury. A qualitative ultrastructural and autoradiographic study. Am. J. Pathol. 116, 193 /206.