Lee, YB Du, S Rhim, H Lee, EB Markelonis, GJ Oh, TH 2024-01-21T14:04:58Z 2024-01-21T14:04:58Z 2021-09-05 2000-05-12 0006-8993 https://pubs.kist.re.kr/handle/201004/141382 In higher vertebrates, reactive gliosis resulting from injury to the central nervous system (CNS) is characterized by a rapid increase in immunoreactivity (IR) to glial fibrillary acidic protein (GFAP). Little is known about the extracellular signals that initiate the increase in GFAP-IR following CNS injury. We demonstrated recently [T.H. Oh, G.J. Markelonis, J.R. Von Visger, B. Balk, M.T. Shipley, Acidic pH rapidly increases immunoreactivity of glial fibrillary acidic protein in cultured astrocytes, Glia 13 (1995) 319-322] that a rapid increase in GFAP-IR can be evoked in mature astrocyte cultures by exposing the cells to an acidic medium. We investigated the intracellular pathway(s) involved in initiating increased GFAP-IR, a hallmark of reactive astrocytes. The increase in GFAP-IR produced by exposure to acidic medium was blocked by pretreatment with nickel ions, by such blockers of L-type calcium channels as nifedipine, verapamil and diltiazem, by calpain inhibitor I, or by the intracellular calcium chelator, BAPTA-AM. At physiological pH, treatment with the calcium ionophore, A23187, resulted in increased GFAP-LR which could be blocked by pretreatment with calpain inhibitor I. Astrocytes exposed to low pH exhibited a marked increase in a GFAP fragment with a molecular weight of 48 kDa. In astrocytes exposed to acidic medium, cr-fodrin, a selective endogenous substrate of calpain, was also found to be hydrolyzed producing fragments with molecular weights of 120-158 kDa. As anticipated, pretreatment with calpain inhibitor I prevented the proteolytic degradation of both GFAP and oc-fodrin in these samples. These results suggest that the initial increase in GFAP-IR after CNS injury appears to be linked to Ca++ influx, and is mediated further by a proteolytic process that seemingly involves the activation of the calcium-dependent protease, calpain I. (C) 2000 Elsevier Science BN. All rights reserved. English ELSEVIER SCIENCE BV SPINAL-CORD INJURY EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS MESSENGER-RNA CULTURED ASTROCYTES NEURONAL-ACTIVITY INDUCED SEIZURES ALPHA-FODRIN CATHEPSIN-B STAB WOUNDS RAT-BRAIN Rapid increase in immunoreactivity to GFAP in astrocytes in vitro induced by acidic pH is mediated by calcium influx and calpain I Article 10.1016/S0006-8993(00)02180-6 1 BRAIN RESEARCH, v.864, no.2, pp.220 - 229 BRAIN RESEARCH 864 2 220 229 scie scopus 000087003000007 2-s2.0-0034640450 Neurosciences Neurosciences & Neurology Article SPINAL-CORD INJURY EXPERIMENTAL AUTOIMMUNE ENCEPHALOMYELITIS MESSENGER-RNA CULTURED ASTROCYTES NEURONAL-ACTIVITY INDUCED SEIZURES ALPHA-FODRIN CATHEPSIN-B STAB WOUNDS RAT-BRAIN reactive astrocytes Ca+2 channel blockers calpain I activation calpain inhibitor I intracellular Ca+2 chelator Ca+2 ionophore alpha-fodrin degradation GFAP proteolysis