title: Calpastatin overexpression limits calpain-mediated proteolysis and behavioral deficits following traumatic brain injury.
abstract: Traumatic brain injury (TBI) results in abrupt, initial cell damage leading to delayed neuronal death. The calcium-activated proteases, calpains, are known to contribute to this secondary neurodegenerative cascade. Although the specific inhibitor of calpains, calpastatin, is present within neurons, normal levels of calpastatin are unable to fully prevent the damaging proteolytic activity of calpains after injury. In this study, increased calpastatin expression was achieved using transgenic mice that overexpress the human calpastatin (hCAST) construct under control of a calcium-calmodulin-dependent kinase II α promoter. Naïve hCAST transgenic mice exhibited enhanced neuronal calpastatin expression and significantly reduced protease activity. Acute calpain-mediated spectrin proteolysis in the cortex and hippocampus induced by controlled cortical impact brain injury was significantly attenuated in calpastatin overexpressing mice. Aspects of posttraumatic motor and cognitive behavioral deficits were also lessened in hCAST transgenic mice compared to their wildtype littermates. However, volumetric analyses of neocortical contusion revealed no histological neuroprotection at either acute or long-term time points. Partial hippocampal neuroprotection observed at a moderate injury severity was lost after severe TBI. This study underscores the effectiveness of calpastatin overexpression in reducing calpain-mediated proteolysis and behavioral impairment after TBI, supporting the therapeutic potential for calpain inhibition. In addition, the reduction in spectrin proteolysis without accompanied neocortical neuroprotection suggests the involvement of other factors that are critical for neuronal survival after contusion brain injury.
authors.affiliation: Spinal Cord and Brain Injury Research Center, University of Kentucky, B416 Biomedical and Biological Sciences Research Building, 741 South Limestone Street, Lexington, KY 40536-0509, USA. kmscho6@uky.edu
authors.forename: Kathleen M
authors.initials: KM
authors.lastname: Schoch
authors.forename: Heather N
authors.initials: HN
authors.lastname: Evans
authors.forename: Jennifer M
authors.initials: JM
authors.lastname: Brelsfoard
authors.forename: Sindhu K
authors.initials: SK
authors.lastname: Madathil
authors.forename: Jiro
authors.initials: J
authors.lastname: Takano
authors.forename: Takaomi C
authors.initials: TC
authors.lastname: Saido
authors.forename: Kathryn E
authors.initials: KE
authors.lastname: Saatman
mesh_terms: D000818:Animals; D001930:Brain Injuries / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D002135:Calcium-Binding Proteins / Q000096:biosynthesis* / Q000235:genetics; D002154:Calpain / Q000037:antagonists & inhibitors / Q000502:physiology*; D005786:Gene Expression Regulation; D006624:Hippocampus / Q000378:metabolism / Q000473:pathology; D006801:Humans; D018782:Maze Learning / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D008822:Mice, Transgenic; D019579:Neocortex / Q000378:metabolism / Q000473:pathology; D059748:Proteolysis
chemical_list: D002135:Calcium-Binding Proteins; C033668:calpastatin; D002154:Calpain