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Valproic acid attenuates microgliosis in injured spinal cord and purinergic P2X 4 receptor expression in activated microglia
Author(s) -
Lu WenHsin,
Wang ChihYen,
Chen PoSee,
Wang JingWen,
Chuang DeMaw,
Yang ChungShi,
Tzeng ShunFen
Publication year - 2013
Publication title -
journal of neuroscience research
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.72
H-Index - 160
eISSN - 1097-4547
pISSN - 0360-4012
DOI - 10.1002/jnr.23200
Subject(s) - purinergic receptor , spinal cord , microglia , pharmacology , trichostatin a , hindlimb , nociception , medicine , downregulation and upregulation , receptor , chemistry , anesthesia , endocrinology , neuroscience , histone deacetylase , inflammation , biology , biochemistry , gene , histone
Peripheral injection with a high dose of valproic acid (VPA), a histone deacetylase (HDAC) inhibitor, into animals with mild or moderate spinal cord injury (SCI) for 1 week can reduce spinal cord tissue loss and promote hindlimb locomotor recovery. A purinergic adenosine triphosphate (ATP) receptor subtype, P2X 4 receptor (P2X 4 R), has been considered as a potential target to diminish SCI‐associated inflammatory responses. In this study, using a minipump‐based infusion system, we found that intraspinal infusion with VPA for 3 days into injured spinal cord significantly improved hindlimb locomotion of rats with severe SCI induced by a 10‐g NYU impactor dropping from the height of 50 mm onto the spinal T9/10 segment. The neuronal fibers in the injured spinal cord tissues were significantly preserved in VPA‐treated rats compared with those observed in vehicle‐treated animals. Moreover, the accumulation of microglia/macrophages and astrocytes in the injured spinal cord was attenuated in the animal group receiving VPA infusion. VPA also significantly reduced P2X 4 R expression post‐SCI. Furthermore, in vitro study indicated that VPA, but not the other HDAC inhibitors, sodium butyrate and trichostatin A (TSA), caused downregulation of P2X 4 R in microglia activated with lipopolysaccharide (LPS). Moreover, p38 mitogen‐activated protein kinase (MAPK)‐triggered signaling was involved in the effect of VPA on the inhibition of P2X 4 R gene expression. In addition to the findings from others, our results also provide important evidence to show the inhibitory effect of VPA on P2X 4 R expression in activated microglia, which may contribute to reduction of SCI‐induced gliosis and subsequently preservation of spinal cord tissues. © 2013 Wiley Periodicals, Inc.