Depolarization-induced suppression of excitation in murine autaptic hippocampal neurones

Depolarization-induced suppression of excitation and inhibition (DSE and DSI) appear to be important forms of short-term retrograde neuronal plasticity involving endocannabinoids (eCB) and the activation of presynaptic cannabinoid CB1 receptors. We report here that CB1-dependent DSE can be elicited from autaptic cultures of excitatory mouse hippocampal neurones. DSE in autaptic cultures is both more robust and elicited with a more physiologically relevant stimulus than has been thus far reported for conventional hippocampal cultures. An additional requirement for autaptic DSE is filled internal calcium stores. Pharmacological experiments favour a role for 2-arachidonyl glycerol (2-AG) rather than arachidonyl ethanolamide (AEA) or noladin ether as the relevant endocannabinoid to elicit DSE. In particular, the latter two compounds fail to reversibly inhibit EPSCs, a quality inconsistent with the role of bona fide eCB mediating DSE. Δ⁹-Tetrahydrocannabinol (Δ⁹-THC) fails to inhibit EPSCs, yet readily occludes both DSE and EPSC inhibition by a synthetic CB1 agonist, WIN 55212-2. With long-term exposure (∼18 h), Δ⁹-THC also desensitizes CB1 receptors. Lastly, a functional endocannabinoid transporter is necessary for the expression of DSE.     

Profiling the proteomic inflammatory state of human astrocytes using DIA mass spectrometry

Background

Astrocytes are the most abundant cells in the central nervous system and are responsible for a wide range of functions critical to normal neuronal development, synapse formation, blood-brain barrier regulation, and brain homeostasis. They are also actively involved in initiating and perpetuating neuroinflammatory responses. However, information about their proteomic phenotypes under inflammation is currently limited.

Method

Data-independent acquisition mass spectrometry was applied to extensively characterize the profile of more than 4000 proteins in immortalized human fetal astrocytes under distinct inflammatory conditions induced by TNF, IL-1β, and LPS, while multiplex immunoassay-based screening was used to quantify a wide range of cytokines released under these inflammatory conditions. Then, immunocytochemistry and western blotting were used to verify the activation of canonical and non-canonical NF-κB upon exposure to the different stimuli. Finally, an in vitro model of the blood-brain barrier consisting of a co-culture of primary human brain microvascular endothelial cells and primary human astrocytes was used to verify the inflammatory response of astrocytes upon LPS exposure in a more complex in vitro system.

Results

We reported on a set of 186 proteins whose levels were significantly modulated by TNF, IL-1β, and LPS. These three stimuli induced proteome perturbations, which led to an increased abundance of key inflammatory proteins involved in antigen presentation and non-canonical NF-κB pathways. TNF and IL-1β, but not LPS, also activated the canonical NF-κB pathway, which in turn led to an extensive inflammatory response and dysregulation of cytoskeletal and adhesion proteins. In addition, TNF and LPS, but not IL-1β, increased the abundance of several interferon-stimulated gene products. Finally, TNF and IL-1β similarly upregulated the secretion of several cytokines and chemokines, whereas LPS only induced a moderate increase in IL-8, IFN-γ, and IL-1β secretion. Upregulation of proteins associated with type I IFN and non-canonical NF-κB signaling was also observed in primary astrocytes co-cultured with primary brain microvascular endothelial cells exposed to LPS.

Conclusions

The present study provides comprehensive information about the proteomic phenotypes of human astrocytes upon exposure to inflammatory stimuli both in monoculture and in co-culture with human brain microvascular endothelial cells.

     

Na(+)-current expression in rat hippocampal astrocytes in vitro: alterations during development

1. With the use of whole-cell patch-clamp recording. Na(+)-current expression was studied in hippocampal astrocytes in vitro, individually identified by filling with Lucifer yellow (LY) and staining for glial fibrillary acidic protein (GFAP) and vimentin. 2. The proportion of astrocytes that express Na+ currents in rat hippocampal cultures changes during development in vitro and decreases from approximately 75% at day 1 to approximately 30% after 10 days in culture. 3. The sodium currents expressed in astrocytes can be differentiated into two types on the basis of kinetics. At early times in culture the time course of Na+ currents is fast in both onset and decay with an average decay time constant of 1.27 ms, whereas after 6 days Na+ currents become comparatively slow and decayed with an average time constant of 1.86 ms. 4. As with the time-course of Na+ currents, the two age groups of astrocytes (i.e., days 1-5 and day 6 and older) differ with respect to their steady-state inactivation characteristics. Early after plating and up to day 5, the midpoint of the steady-state inactivation curve is close to -60 mV, as also observed in hippocampal neurons of various ages; in contrast, after 6 days in culture the curve is shifted by approximately 25 mV toward more hyperpolarized potentials with a midpoint close to -85 mV. 5. In contrast to h infinity-curves, current-voltage (I-V) curves of Na(+)-current activation were identical in all astrocytes studied and did not change with time in culture. 6. In astrocytes expressing Na+ currents, current densities (average of 35 pA/pF on day 1) decreased throughout the first 5 days and were almost abolished around days 4 and 5 in culture. Beginning on day 6, however, current densities increased again and maintained a steady level (average of 14 pA/pF) for the duration of the time period in culture (20 days). This biphasic time course closely correlates with the time course of changes in Na(+)-current kinetics and steady-state inactivation. 7. These data suggest that Na+ currents in cultured hippocampal astrocytes show characteristic changes with increasing time in culture. During the first 4-5 days in culture, hippocampal astrocytes display Na+ currents with properties similar to those of hippocampal neurons. Our data further suggest that Na+ currents with distinctive, "glial-type" characteristics are only expressed in hippocampal astrocytes after 6 days in culture.     

Diagnosis and classification of drug-induced autoimmunity (DIA)

Since sulfadiazine associated lupus-like symptoms were first described in 1945, certain drugs have been reported to interfere with the immune system and induce a series of autoimmune diseases (named drug-induced autoimmunity, DIA), exemplified by systemic lupus erythematosus (SLE). Among the drugs, procainamide and hydralazine are considered to be associated with the highest risk for developing lupus, while quinidine has a moderate risk, and all other drugs have low or very low risk. More recently, drug-induced lupus has been associated with the use of newer biological modulators, such as tumor necrosis factor (TNF)-alpha inhibitors and cytokines. In addition to lupus, other major autoimmune diseases, including vasculitis and arthritis, have also been associated with drugs. Because resolution of symptoms generally occurs after cessation of the offending drugs, early diagnosis is crucial for treatment strategy and improvement of prognosis. Unfortunately, it is difficult to establish standardized criteria for DIA diagnosis. Diagnosis of DIA requires identification of a temporal relationship between drug administration and the onset of symptoms, but the relative risk with respect to dose and duration for each drug has rarely been determined. DIA is affected by multiple genetic and environmental factors, leading to difficulties in establishing a list of global clinical features that are characteristic of most or all DIA patients. Moreover, the distinction between authentic DIA and unmasking of a latent autoimmune disease also poses challenges. In this review, we summarize the highly variable clinical features and laboratory findings of DIA, with an emphasis on the diagnostic criteria.     

Depolarization-induced release of folates from slices of rat cerebellum

Potassium (55 mM)-induced depolarization of slices of adult rat cerebellum caused substantial release of endogenous folate from the tissue. Stimulated release reached approximately 300% of the control unstimulated efflux, and was partially (65%) dependent on the presence of Ca²⁺ in the depolarizing medium. These results support the idea that folates might function as neuromodulators in the mammalian central nervous system.     

亚低温对缺氧缺血新生大鼠海马星形胶质细胞增殖和凋亡的影响

目的观察亚低温对新生大鼠海马星形胶质细胞增殖和凋亡的影响,以探讨亚低温对缺氧缺血脑损伤保护作用的机制。方法①体外实验：取3日龄大鼠海马脑片,培养至第4天用氧糖剥夺法制备标本,于33℃（亚低温组）和37℃培养48h（常温组）;对照组脑片不进行氧糖剥夺处理,37℃培养7d。采用免疫荧光染色方法观察培养脑片星形胶质细胞的活化和增殖。②体内实验：取7日龄大鼠,分手术组和假手术组。手术组永久性结扎左侧颈总动脉,然后置于含8%O2＋92%N2中缺氧2h,制备缺氧缺血模型,分为手术亚低温亚组和手术常温亚组。假手术组仅分离左侧颈总动脉,不结扎,不予缺氧处理,分为假手术常温亚组和假手术亚低温亚组。各组于术后3和7d处死取材,采用免疫荧光染色方法检测海马星形胶质细胞的活化、增殖和凋亡。结果①体外实验：氧糖剥夺后3d常温组较对照组胶质纤维酸性蛋白（GFAP）阳性细胞数量明显增多;亚低温组与常温组比较,GFAP阳性细胞数量明显减少。②体内实验：术后3和7d亚低温组GFAP阳性细胞数量较常温组显著降低,较常温对照组和亚低温对照组显著增高。GFAP与caspase-3免疫荧光双标记结果显示,术后3d常温组海马区84.5%GFAP阳性细胞表达caspase-3,亚低温组仅32.3%GFAP阳性细胞表达caspase-3,差异有统计学意义。结论亚低温能减轻新生大鼠缺氧缺血后海马星形胶质细胞的活化增殖和凋亡。     

Distribution of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the rat brain

In the first of two papers dealing with the distribution of glial fibrillary acidic protein-(GFAP)-immunoreactive elements in the rat brain, the localization of immunostaining in the forebrain is systematically described. While the limbic cortex was found to contain intensely stained, evenly distributed astrocytes, the neocortex showed clearly stratified GFAP-staining, with substantially less immunoreactivity occurring in the middle layers than in the areas close to the brain surface or the white matter. A remarkably regular staining pattern was observed in the hippocampus and dentate gyrus. The striatum remained unstained in sharp contrast to the pallidum. In the diencephalon, the main thalamic nuclei were poor in GFAP-labelled elements in contrast to the internuclear border zones. In the hypothalamus, nuclei were conspicuous by their GFAP-staining. A consistent differential staining pattern was obtained in the epithalamic structures. The observed distributional pattern of diencephalic GFAP-immunoreactivity is thought to be due to different regional proliferation of the embryonic neuroepithelium of the diencephalon. The uneven distribution of GFAP-immunoreactivity in the forebrain is explained on a mainly developmental basis.     

Distribution of glial fibrillary acidic protein (GFAP)-immunoreactive astrocytes in the rat brain

Summary The topographical mapping of glial fibrillary acidic protein (GFAP)-immunoreactivity was performed in coronal serial sections of the rat mesencephalon, rhombencephalon and spinal cord. Relative to a background of poor or moderate overall staining of the mesencephalon, the interpeduncular nucleus, substantia nigra and the periaqueductal grey matter were prominent by their intense GFAP-immunoreactivity. The pons and particularly the medulla contained more GFAP-labelled elements compared with the mesencephalon. The spinal trigeminal nucleus and Rolando substance were distinguished by their intense staining. Large fibre tracts were usually poor in immunoreactive GFAP. In a concluding discussion, findings relevant to the GFAP-mapping of the whole rat CNS are evaluated with regard to possible reasons underlying the observed differential distribution of GFAP-immunoreactivity.     

Contribution of epoxyeicosatrienoic acids to the hypoxia-induced activation of Ca-activated K channel current in cultured rat hippocampal astrocytes

Brief hypoxia differentially regulates the activities of Ca²⁺-activated K⁺ channels (K_Ca) in a variety of cell types. We investigated the effects of hypoxia (<2% O₂) on K_Ca channel currents and on the activities of cytochrome P450 2C11 epoxygenase (CYP epoxygenase) in cultured rat hippocampal astrocytes. Exposure of astrocytes to hypoxia enhanced macroscopic outward K_Ca current, increased the open state probability (NPo) of 71 pS and 161 pS single-channel K_Ca currents in cell-attached patches, but failed to increase the NPo of both the 71 pS and 161 pS K_Ca channel currents recorded from excised inside-out patches. The hypoxia-induced enhancement of macroscopic K_Ca current was attenuated by pretreatment with tetraethylammonium (TEA, 1 mM) or during recording using low-Ca²⁺ external bath solution. Exposure of astrocytes to hypoxia was associated with generation of superoxide as detected by staining of cells with the intracellular superoxide detection probe hydroethidine (HE), attenuation of the hypoxia-induced activation of unitary K_Ca channel currents by superoxide dismutation with tempol, and as quantitated by high-pressure liquid chromatography/fluorescence assay using HE as a probe. In cultured astrocytes in which endogenous CYP epoxygenase activity has been inhibited with either miconazole or N-methylsulfonyl-6-(2-propargyloxyphenyl) hexanamide (MSPPOH) hypoxia failed to increase the NPo of both the 71 pS and 161 pS K_Ca currents and generation of superoxide. Hypoxia increased the level of P450 epoxygenase protein and production of epoxyeicosatrienoic acids (EETs) from cultured astrocytes, as determined by immunohistochemical staining and LC/MS analysis, respectively. Exogenous 11,12-EET increased the NPo of both the 71 pS and 161 pS K_Ca single-channel currents only in cell-attached but not in excised inside-out patches of cultured astrocytes. These findings indicate that hypoxia enhances the activities of two types of unitary K_Ca currents in astrocytes by a mechanism that appears to involve CYP epoxygenase-dependent generation of superoxide and increased production or release of EETs.     

戊四氮慢性致痫大鼠海马星形胶质细胞的激活

目的：研究慢性癫痫大鼠点燃时海马星形胶质细胞的激活情况。方法：采用免疫组化和双重免疫荧光标记法观察戊四氮慢性癫痫大鼠点燃后海马NF-kBp65和胶质原纤维酸性蛋白(glial fibrillary acidic protein,GFAP)的变化。结果：癫痫发作1 h,CA1区出现NF-kBp65-IR阳性细胞,4 h胶质细胞p65-IR维持在高水平,并持续至发作后12 h;发作1 h,CA1区GFAP-IR开始增强,4～8 h观察到明显浓染和突起增多的GFAP-IR阳性细胞,并持续至24 h;GFAP/p65一IR阳性细胞发作后1 h可观察到,4 h达最高峰,24 h恢复至对照组水平。结论：戊四氮致痫大鼠点燃时,星形胶质细胞的这种早期而持续的激活提示该细胞在慢性癫痫的复发中可能起到重要作用。     

柴胡皂苷a抑制PTZ诱导的小鼠海马星形胶质细胞活化

目的:探讨柴胡皂苷a(SSa)对戊四氮(PTZ)诱导的小鼠海马星形胶质细胞活化的抑制作用。方法:分离培养小鼠海马星形胶质细胞,将细胞随机分为对照组、PTZ组、PTZ+0.625 mg/L SSa组和PTZ+1.25 mg/L SSa组。通过免疫荧光染色检测胶质细胞原纤维酸性蛋白(GFAP)的表达来鉴定细胞;用MTT检测评估细胞活力;用流式细胞术检测各组细胞的周期变化;ELISA法检测各组细胞中GFAP和间隙连接蛋白43(Cx43)的表达水平;流式细胞术和Hoechst 33258染色检测各组细胞的凋亡情况。结果:体外原代培养的星形胶质细胞贴壁生长,细胞突起明显。免疫荧光显示星形胶质细胞呈GFAP阳性表达。与对照组比较,PTZ组细胞活力和G_2/M期细胞百分比显著增加(P0.05),GFAP和Cx43的表达水平也显著上调(P0.05);与PTZ组比较,PTZ+0.625 mg/L SSa组和PTZ+1.25 mg/L SSa组细胞活力和G_2/M期细胞百分比均明显下降,GFAP和Cx43的表达水平也降低,但细胞凋亡水平显著增加(P0.05)。结论:SSa能够显著抑制PTZ诱导的海马星形胶质细胞活化,抑制细胞增殖并诱导凋亡。     

低氧预适应上调大鼠海马神经元和星形胶质细胞在急性缺氧时的葡萄糖转运蛋白的活性和基因表达

目的 研究低氧预适应对海马神经元和星形胶质细胞在急性缺氧暴露时的葡萄糖转运蛋白的活性和基因表达的影响。方法 培养大鼠海马神经元和星形胶质细胞,每天间歇暴露于低氧混合气体（1% O2、10% CO2、89% N2）20min,连续6d。最后1次低氧暴露24h后,将细胞暴露于无氧混合气体（10% CO2、90% N2）6h,然后立即检测[3H]-2-脱氧葡萄糖（2-DG）的摄取率、GLUT1和GLUT3的mRNA水平及神经元的存活率。结果 低氧预适应上调急性缺氧时神经元和星形胶质细胞的2-DG吸收率、星形胶质细胞GLUT1 mRNA的表达及神经元GLUT1和GLUT3 mRNA的表达,提高神经元存活率,这一作用可被细胞松弛素B消除。结论 低氧预适应上调海马神经元和星形胶质细胞在急性缺氧时的葡萄糖摄取率和葡萄糖转运蛋白的基因表达。     

Heterosynaptic expression of depolarization-induced suppression of inhibition (DSI) in rat hippocampal cultures

Depolarization-induced suppression of inhibition (DSI) is a transient suppression of the inhibitory synaptic transmission, observed in the hippocampus and the cerebellum, upon postsynaptic depolarization. Using rat hippocampal cultures, we examined whether DSI is confined to the inhibitory synapses on the depolarized neuron or, if DSI can spread to those on neighboring non-depolarized neurons. Whole-cell recordings were performed in 108 neuronal pairs with the following synaptic responses. Stimulation of one neuron evoked the inhibitory autaptic currents (IACs) recurrently in that neuron and also elicited the inhibitory postsynaptic currents (IPSCs) orthodromically in the other neuron. In 38 of 108 pairs, the postsynaptic depolarization caused transient suppression of IPSCs (homosynaptic DSI). In 11 of the 38 pairs exhibiting the homosynaptic DSI, the depolarization also induced suppression of IACs (heterosynaptic DSI). The heterosynaptic DSI, like the homosynaptic DSI, depended on depolarizing pulse duration and was blocked by a phorbol ester. These results suggest that DSI can spread to the synapses on a neighboring non-depolarized neuron in rat hippocampal cultures.     

Adenosine induces expression of glial cell line-derived neurotrophic factor (GDNF) in primary rat astrocytes

Adenosine, which accumulates rapidly during ischemia due to the breakdown of ATP, has beneficial effects in many tissues. We examined whether adenosine induces the production of glial cell line-derived neurotrophic factor (GDNF) in cultured astrocytes. We evaluated GDNF mRNA expression and GDNF production in astrocytes cultured with adenosine and the adenosine selective receptor agonists 5-(N-ethylcarboxamido) adenosine (NECA), N(6)-cyclopentyladenosine (CPA) and 2-p-(2-carboxyethyl) phenethylamino-5'-N-ethylcarboxamindo-adenosine hydrochloride (CGS 21680). Moreover, we examined the possibility that the expression of GDNF is regulated differently in cultured astrocytes from the stroke-prone spontaneously hypertensive rat (SHRSP) than in those from Wistar Kyoto rats (WKY). In this study, we confirmed that adenosine and the selective A(2B) adenosine receptor agonist NECA induced the expression of GDNF in cultured astrocytes. The A(2B) receptor antagonist alloxazine was able to inhibit the increase in extracellular GDNF produced by adenosine. Furthermore, the amounts of GDNF produced were significantly reduced in astrocytes of the adenosine-treated SHRSP compared with those of WKY. These results indicate that adenosine induces the expression of GDNF, and adenosine A(2B) receptors participate in the regulation of GDNF levels in astrocytes. This expression was attenuated in astrocytes of SHRSP compared with those of WKY.     

Activity-dependent decrease of excitability in rat hippocampal neurons through increases in I(h)

Hippocampal long-term potentiation (LTP) induced by theta-burst pairing of Schaffer collateral inputs and postsynaptic firing is associated with localized increases in synaptic strength and dendritic excitability. Using the same protocol, we now demonstrate a decrease in cellular excitability that was blocked by the h-channel blocker ZD7288. This decrease was also induced by postsynaptic theta-burst firing alone, yet it was blocked by NMDA receptor antagonists, postsynaptic Ca2+ chelation, low concentrations of tetrodotoxin, omega-conotoxin MVIIC, calcium/calmodulin-dependent protein kinase II (CaMKII) inhibitors and a protein synthesis inhibitor. Increasing network activity with high extracellular K+ caused a similar reduction of cellular excitability and an increase in h-channel HCN1 protein. We propose that backpropagating action potentials open glutamate-bound NMDA receptors, resulting in an increase in I(h) and a decrease in overall excitability. The occurrence of such a reduction in cellular excitability in parallel with synaptic potentiation would be a negative feedback mechanism to normalize neuronal output firing and thus promote network stability.     

Isolating single primary rat hippocampal neurons & astrocytes on ultra-thin patterned parylene-C/silicon dioxide substrates

We report here the patterning of primary rat neurons and astrocytes from the postnatal hippocampus on ultra-thin parylene-C deposited on a silicon dioxide substrate, following observations of neuronal, astrocytic and nuclear coverage on strips of different lengths, widths and thicknesses. Neuronal and glial growth was characterized 'on', 'adjacent to' and 'away from' the parylene strips. In addition, the article reports how the same material combination can be used to isolate single cells along thin tracks of parylene-C. This is demonstrated with a series of high magnification images of the experimental observations for varying parylene strip widths and thicknesses. Thus, the findings demonstrate the possibility to culture cells on ultra-thin layers of parylene-C and localize single cells on thin strips. Such work is of interest and significance to the Neuroengineering and Multi-Electrode Array (MEA) communities, as it provides an alternative insulating material in the fabrication of embedded micro-electrodes, which can be used to facilitate single cell stimulation and recording in capacitive coupling mode.     

NMDA receptor-dependent high-frequency network oscillations (100-300 Hz) in rat hippocampal slices

High-frequency oscillations (HFOs or ripples, >or=100 Hz) appear to be important expressions of cortical circuits, characterizing physiological and pathological functional states. Synaptic and non-synaptic mechanisms are involved in their generation. This study shows that spontaneous N-methyl-D-aspartate receptor (NMDAR) mediated potentials, recorded in dorsal and ventral hippocampal slices perfused with magnesium-free medium and antagonists of non-NMDARs and GABA receptors were associated with high-frequency oscillations (100-300 Hz), recorded in all hippocampal subregions. Both CA3 and CA1 regions displayed HFOs at the range of 180-300 Hz with oscillations in CA3 being significantly faster than in CA1 (232+/-22 Hz, n=64 slices versus 206+/-18 Hz, n=24, P<0.001). Moreover, in most of the slices (39/63) the CA1 network oscillated also at a lower frequency (121.8+/-2.45 Hz). Simultaneous recordings showed that activity was most often initiated in CA3 region; however, dentate gyrus and CA1 were potential sites of generation as well. The incidence of spontaneous events was significantly higher in ventral than in dorsal slices (20+/-1.6/min versus 5.4+/-0.3/min, P<0.001). The competitive and non-competitive NMDAR antagonists, d-AP5 (50 microM) and MK 801 (50 microM), respectively abolished spontaneous activity. The gap-junction blocker carbenoxolone significantly suppressed spontaneous activity in a concentration-dependent manner. These data indicate that synaptic transmission provided by solely NMDARs can sustain the generation of high-frequency network oscillations, which display distinct characteristics in CA3 and CA1 subregions.     

Acrylonitrile-induced oxidative DNA damage in rat astrocytes

Chronic administration of acrylonitrile results in a dose-related increase in astrocytomas in rat brain, but the mechanism of acrylonitrile carcinogenicity is not fully understood. The potential of acrylonitrile or its metabolites to induce direct DNA damage as a mechanism for acrylonitrile carcinogenicity has been questioned, and recent studies indicate that the mechanism involves the induction of oxidative stress in rat brain. The present study examined the ability of acrylonitrile to induce DNA damage in the DI TNC1 rat astrocyte cell line using the alkaline Comet assay. Oxidized DNA damage also was evaluated using formamidopyrimidine DNA glycosylase treatment in the modified Comet assay. No increase in direct DNA damage was seen in astrocytes exposed to sublethal concentrations of acrylonitrile (0-1.0 mM) for 24 hr. However, acrylonitrile treatment resulted in a concentration-related increase in oxidative DNA damage after 24 hr. Antioxidant supplementation in the culture media (alpha-tocopherol, (-)-epigallocathechin-3 gallate, or trolox) reduced acrylonitrile-induced oxidative DNA damage. Depletion of glutathione using 0.1 mM DL-buthionine-[S,R]-sulfoximine increased acrylonitrile-induced oxidative DNA damage (22-46%), while cotreatment of acrylonitrile with 2.5 mM L-2-oxothiazolidine-4-carboxylic acid, a precursor for glutathione biosynthesis, significantly reduced acrylonitrile-induced oxidative DNA damage (7-47%). Cotreatment of acrylonitrile with 0.5 mM 1-aminobenzotriazole, a suicidal inhibitor of cytochrome P450, prevented the oxidative DNA damage produced by acrylonitrile. Cyanide (0.1-0.5 mM) increased oxidative DNA damage (44-160%) in astrocytes. These studies demonstrate that while acrylonitrile does not directly damage astrocyte DNA, it does increase oxidative DNA damage. The oxidative DNA damage following acrylonitrile exposure appears to arise mainly through the P450 metabolic pathway; moreover, glutathione depletion may contribute to the induction of oxidative DNA damage by acrylonitrile.