title: Chronic intermittent ethanol induced axon and myelin degeneration is attenuated by calpain inhibition.
abstract: Chronic alcohol consumption causes multifaceted damage to the central nervous system (CNS), underlying mechanisms of which are gradually being unraveled. In our previous studies, activation of calpain, a calcium-activated neutral protease has been found to cause detrimental alterations in spinal motor neurons following ethanol (EtOH) exposure in vitro. However, it is not known whether calpain plays a pivotal role in chronic EtOH exposure-induced structural damage to CNS in vivo. To test the possible involvement of calpain in EtOH-associated neurodegenerative mechanisms the present investigation was conducted in a well-established mouse model of alcohol dependence - chronic intermittent EtOH (CIE) exposure and withdrawal. Our studies indicated significant loss of axonal proteins (neurofilament light and heavy, 50-60%), myelin proteins (myelin basic protein, 20-40% proteolipid protein, 25%) and enzyme (2', 3'-cyclic-nucleotide 3'-phosphodiesterase, 21-55%) following CIE in multiple regions of brain including hippocampus, corpus callosum, cerebellum, and importantly in spinal cord. These CIE-induced deleterious effects escalated after withdrawal in each CNS region tested. Increased expression and activity of calpain along with enhanced ratio of active calpain to calpastatin (sole endogenous inhibitor) was observed after withdrawal compared to EtOH exposure. Pharmacological inhibition of calpain with calpeptin (25 μg/kg) prior to each EtOH vapor inhalation significantly attenuated damage to axons and myelin as demonstrated by immuno-profiles of axonal and myelin proteins, and Luxol Fast Blue staining. Calpain inhibition significantly protected the ultrastructural integrity of axons and myelin compared to control as confirmed by electron microscopy. Together, these findings confirm CIE exposure and withdrawal induced structural alterations in axons and myelin, predominantly after withdrawal and corroborate calpain inhibition as a potential protective strategy against EtOH associated CNS degeneration.
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, MSC 606, Charleston, SC, USA. Electronic address: samanta@musc.edu.
authors.forename: Supriti
authors.initials: S
authors.lastname: Samantaray
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, MSC 606, Charleston, SC, USA. Electronic address: vknaryan@yahoo.com.
authors.forename: Varduhi H
authors.initials: VH
authors.lastname: Knaryan
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, MSC 606, Charleston, SC, USA. Electronic address: kspatel1990@gmail.com.
authors.forename: Kaushal S
authors.initials: KS
authors.lastname: Patel
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA; Charleston Alcohol Research Center, Department of Psychiatry and Behavioral Sciences, Charleston, SC, USA. Electronic address: mulholl@musc.edu.
authors.forename: Patrick J
authors.initials: PJ
authors.lastname: Mulholland
authors.affiliation: Department of Neurosciences, Medical University of South Carolina, Charleston, SC, USA; Charleston Alcohol Research Center, Department of Psychiatry and Behavioral Sciences, Charleston, SC, USA; Department of Veterans Affairs, Ralph H. Johnson Medical Center, Charleston, SC, USA. Electronic address: beckerh@musc.edu.
authors.forename: Howard C
authors.initials: HC
authors.lastname: Becker
authors.affiliation: Department of Neurology and Neurosurgery, Medical University of South Carolina, MSC 606, Charleston, SC, USA; Department of Veterans Affairs, Ralph H. Johnson Medical Center, Charleston, SC, USA. Electronic address: baniknl@musc.edu.
authors.forename: Naren L
authors.initials: NL
authors.lastname: Banik
mesh_terms: D000280:Administration, Inhalation; D000437:Alcoholism / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D000818:Animals; D001369:Axons / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D001921:Brain / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D002154:Calpain / Q000037:antagonists & inhibitors / Q000378:metabolism; D002492:Central Nervous System Depressants / Q000008:administration & dosage / Q000097:blood / Q000633:toxicity; D004151:Dipeptides / Q000494:pharmacology*; D004195:Disease Models, Animal; D000431:Ethanol / Q000008:administration & dosage / Q000097:blood / Q000633:toxicity; D006023:Glycoproteins / Q000494:pharmacology*; D008297:Male; D008810:Mice, Inbred C57BL; D009186:Myelin Sheath / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D009410:Nerve Degeneration / Q000188:drug therapy* / Q000473:pathology / Q000503:physiopathology; D018696:Neuroprotective Agents / Q000494:pharmacology*; D013116:Spinal Cord / Q000187:drug effects / Q000378:metabolism / Q000648:ultrastructure; D013375:Substance Withdrawal Syndrome / Q000188:drug therapy / Q000473:pathology / Q000503:physiopathology
chemical_list: D002492:Central Nervous System Depressants; D004151:Dipeptides; D006023:Glycoproteins; D018696:Neuroprotective Agents; C039304:calpain inhibitors; C071482:calpeptin; D000431:Ethanol; D002154:Calpain
keywords: Axonal degeneration; Calpain; Calpastatin; Ethanol withdrawal; Myelin proteins and enzyme; Neurofilament proteins