Bidirectional Regulation Of Chronic Stress On Alcohol Central Actions And Its Mechanism

Part I Effects of chronic stress on alcohol central inhibition action Objective: Alcohol is widely used as self-medication and provides transient relief from depressive symptoms.The presence of major depression increases risk of alcohol addiction and acute alcohol intoxication.However,the effect of chronic stress on alcohol intoxication remains unknown.Ethonal is the main component of alcohol.Here we explore the effects of chronic stress on ethonal intoxication.Methods: Chronic social defeat stress(CSDS)and chronic unpredictable mild stress(CUMS)were used to induce depressive-like behavior in mice;Sucrose preference test(SPT),tail suspension test(TST),novelty-suppressed feeding test(NSFT)and social interaction(SI)were used to confirm the depressive-like behavior induced by chronic stress in C57BL/6J mice;LORR was used to investigate the effect of chronic stress on alcohol induced sedation,temperature detection was used to explore the effect of chronic stress on alcohol induced hypothermia and rotarod test was used to evaluate the effect of chronic stress on alcohol induced ataxia.Results:(1)CUMS induced depressive-like behaviors in C57BL/6J mice to investigate the role of chronic stress in alcohol intoxication: CUMS significantly increased the duration of alcohol(4.0 g/kg)induced LORR(Control: 54.1 ± 3.8 min;CUMS: 69.3 ± 5.1 min;P < 0.01 vs Control);Compared with control(-2.1 ± 0.2 ℃),CUMS exposure significantly potentiated alcohol(3.0g/kg)induced hypothermia(-2.8 ± 0.2 ℃,P < 0.05 vs Control);CUMS also potentiated alcohol(1.75 g/kg)induced ataxia(Control:-20.9 ± 4.2 sec;CUMS:-39.8 ± 6.2 sec,P < 0.05 vs Control);(2)CSDS induced depressive-like behavior to investigate the role of chronic stress in alcohol intoxication: compared with control(37.8 ± 4.1 min),CSDS(62.3 ± 5.0 min,P < 0.001 vs Control)increased the duration of LORR;CSDS exposure significantly potentiated alcohol induced hypothermia(Control:-1.2 ± 0.2 ℃,CSDS:-2.0 ± 0.2 ℃,P < 0.01 vs Control);CSDS potentiated alcohol induced ataxia(Control:-25.1 ± 3.1 sec,CUMS:-44.2 ± 5.6 sec,P < 0.01 vs Control).Conclusion: Chronic stress potentiates central inhibition actions of alcohol,both CUMS and CSDS aggravate acute intoxicating actions of alcohol,including increasing the duration of LORR,decreasing core temperature and potentiating alcohol-induced ataxia.Part II Effects of chronic stress on alcohol-induced antidepressant-like behaviors Objective: Increased reports demonstrate that NMDAR(N-methyl-D-aspartate receptor)blockers act as rapid antidepressants.Ethonal is the allostic blocker of NMDAR and previous report show that alcohol elicits antidepressants behavior in C57BL/6 mice.It remains unvein the effects of alcohol on chronic stress induced depressive-like behavior.This part mainly explored the antidepressant effects of ethonal and its metabolistic product acetaldehyde in both normal C57 BL/6J mice and mice under chronic stress.Methods: Forced swimming test(FST)and TST were used to evaluate the antidepressants effects on C57BL/6J mice.CSDS was used to induce depressive-like behavior.Social interaction test was used to evaluate the effect of ethonal and acetaldehyde on CSDS mice.Results:(1)Ethonal(2.5 g/kg)reduced the immobility time of C57BL/6J mice in FST(NS: 110.2 ± 5.6 sec;2.5 g/kg: 88.5 ± 2.9 sec,P < 0.01 vs NS)and TST(NS: 146.1 ± 6.5 sec;2.5 g/kg: 118.5 ± 8.0 sec,P < 0.01 vs NS);(2)Ethonal(2.5 g/kg)had no effect on CSDS induced depressive-like behaviors;(3)Acetaldehyde(100 mg/kg)reduced the immobility time of C57BL/6J mice in TST(NS: 148.6 ± 3.4 sec;100 mg/kg: 111.5 ± 8.8 sec);(4)Acetaldehyde(170 mg/kg)significantly reversed CSDS induced social avoidance post 30 min(NS: 121.2 ± 7.0%;ACD: 142.2 ± 7.2%;CSDS+NS: 74.0 ± 5.7%;CSDS+AC: 107.8 ± 7.0%)and 24 h(NS: 184.7 ± 19.2%;ACD: 166.9 ± 17.0%;CSDS+NS: 59.2 ± 12.4%;CSDS+ACD: 186.8 ± 24.4%).Conclusion: Ethonal(2.5 g/kg)and acetaldehyde(100 mg/kg)exhibite antidepressants-like behaviors in C57BL/6J.Ethonal(2.5 g/kg)have no effect on CSDS mice while acetaldehyde(100 mg/kg)reverses the depressive-like behaviors induced by CSDS.These findings indicate that the antidepressants effect of ethonal is attenuated under chronic stress,while the metabolic products acetaldehyde remains effective.Part III Mechanism of bidirectional regulation effects of chronic stress on alcohol central actions Objective: ADH(alcohol dehydrogenase)is response for the peripheral metabolism of ethanol while catalase is the key enzyme to oxidize ethanol into acetaldehyde in brain.Acetaldehyde is futher converted to acetic acid by ALDH(acetaldehyde dehydrogenase).The ability of alcohol metabolism to acetaldehyde under chronic stress is still unveiled.Here we investigate how alcohol metabolism enzymes involved in bidirectional regulation effects of chronic stress on alcohol central actions.Methods: q RT-PCR(quantitative real-time PCR)and Western blotting were used to analyze the m RNA and protein level of ADH-1,Catalase,ALDH-2 and Nrf2 in the liver or hippocampus of CSDS and CUMS mice.Activity Colorimetric Assay Kits were used to detect the activities of ADH-1,catalase and ALDH-2 in the liver or hippocampus of CSDS and CUMS mice.Results:(1)ALDH-2 m RNA was significantly downregulated in liver of CUMS and CSDS mice(Control: 100 ± 9.2%;CSDS: 55.8 ± 5.8%,P < 0.001 vs Control;Control: 100 ± 5.8%;CUMS: 58.1 ± 9.0%,P < 0.001 vs Control).There was no difference between stress mice and control in the ALDH-2 protein level and activity in liver.The expression and activity of ADH-1 in CSDS mice and CUMS mice had no difference with control mice;(2)Both CUMS and CSDS significantly down-regulated the m RNA level of Catalase in hippocampus of mice(Control: 100 ± 3.8%;CUMS: 84.1 ± 4.7%,P < 0.05 vs Control;Control: 100 ± 2.6%,CSDS: 84.8 ± 4.1%,P < 0.01 vs Control)without affecting the m RNA level of ALDH-2 in hippocampus;(3)The nuclear level of Nrf2 protein was decreased in hippocampus of CUMS mice(Control:100 ± 2.7%;CUMS:82.73 ± 4.2%,P < 0.01 vs Control).Consistently,the activity of catalase was reduced to 66.5 ± 5.5% in the hippocampus of CUMS mice compared with control(P < 0.05 vs Control);(4)Both sodium azide(10 mg/kg)and 3-AT(1 g/kg)potentiated alcohol intoxication in C57BL/6J mice.Sodium azide and 3-AT lengthened the LORR duration(NS: 31.3 ± 1.2 min;Sodium azide: 44.3 ± 2.1 min;3-AT: 53.9 ± 4.5 min);Both sodium azide and 3-AT significantly potentiated alcohol-induced hypothermia(NS:-2.3 ± 0.1 ℃;Sodium azide:-3.0 ± 0.1 ℃;3-AT:-3.3 ± 0.1 ℃);The Catalase inhibitors also aggravated alcohol-induced ataxia.(NS:-26.1 ± 3.2 sec;Sodium azide: 52.9 ± 5.1 sec;3-AT:-44.5 ± 3.5 sec).Conclusion: Chronic stress reduces central rather than peripheral alcohol metabolism.Nrf2-Catalase pathway is involved in the mechanism of regulation of chronic stress on alcohol central inhibition actions.Upregulation of Nrf2-Catalase pathway reverses the regulation of CUMS on alcohol central inhibition.