The Neuroprotective Effect Of Inhibition Of TRPV1 In Experimental Traumatic Brain Injury And The Study Of Its Mechanism

Objective:Transient receptor potential vanilloid 1?TRPV1?is a non-selective cation channel with high permeability to calcium(Ca²⁺),which can be activated by diverse stimuli,including cell swelling,hyposmolality,high temperature?>43°C?,low pH?<6.0?,and endogenous or synthetic ligands.Recent studies have shown that the expression of TRPV1 is increased in the model of ischemia stroke and inhibiting TRPV1 has neuroprotective effects on the pathological process of cerebral ischemia,its mechanism is still unclear,however.Furthermore,the role of inhibiting TRPV1 to protect against brain damage after traumatic brain injury?TBI?remains unclear.Therefore,we investigated the effects of TRPV1 inhibition on the neurological function deficit and blood-brain barrier?BBB?destruction in a mouse model of TBI,and explored its potential molecular biological mechanism.Methods:In this study,adult male C57BL/6 mice underwent controlled cortical impact injury?CCI?and received capsazepine?1?mol/kg body weight,twice daily,intraperitoneally?,the specific inhibitor of TRPV1,until sacrifice.The modified neurological severity score?mNSS?,rotarod test,and Morris water maze test were used to assess the neurological deficits,motor function,and learning and memory ability of mice.The brain edema lesion was assessed based on the T2-weighted images of head magnetic resonance imaging.The water content in brain tissues was measured by the wet-dry method.The BBB permeability was evaluated by detecting extravasation of Evans Blue,expression of tight junction proteins ZO-1 and occludin.Apoptotic cells in the brain tissue sections were detected by the terminal deoxynucleotidyl transferase mediated dUTP nick end labeling?TUNEL?assay.We explored its mechanisms in vitro using human neuroblastoma SH-SY5Y cells and mouse brain microvascular endothelial?bEnd.3?cells after stretch injury?SI?.We detected the effects of inhibiting TRPV1 on the apoptosis induced by SI in SH-SY5Y cells and bEnd.3 cells by flow cytometry.And its effects on modulating mitogen-activated protein kinases?MAPKs?and apoptosis-related proteins were detected by Westen blot analysis.Results:Compared with the vehicle-treated group,CPZ-mediated inhibition of TRPV1can significantly improve the neurobehavioral competency and learning and memory ability of the mice,and reduce the volume of brain edema lesion and the water content of the ipsilateral cortical tissues,and attenuate disruption of the BBB and the apoptosis induced by TBI in brain tissues.The results of flow cytometry suggest that CPZ-mediated inhibition of TRPV1 reduces the apoptosis induced by SI in SH-SY5Y cells and bEnd.3cells,which were consistent with the in vivo data obtained from the apoptosis assay of injured brain tissue using TUNEL staining.Westen blot analyses revealed that inhibition of TRPV1 decreased the expression of pro-apoptotic proteins and increased the expression of anti-apoptotic proteins in SH-SY5Y cells and bEnd.3 cells after SI;and it attenuates SI-induced activation of c-Jun N-terminal kinase?JNK?and p38 MAPKs.Conclusions:Our study demonstrated that inhibition of TRPV1 by CPZ promoted neurological function recovery,and improved learning and memory ability,and reduced disruption of the BBB and brain edema in mice after TBI,and those were mediated,at least in part,by protecting brain neurons and endothelial cells.The anti-apoptosis effects of CPZ-mediated inhibition of TRPV1 may act by modulating the JNK and p38 MAPK signaling pathways,which in turn regulates the mitochondrial apoptosis pathway.Taken together,we conclude that TRPV1 plays an important role in the pathophysiology of TBI and that TRPV1 inhibition may be a new target for pharmacotherapeutic intervention to protect against brain damage and promote neurological function recovery after TBI.