Bell’s Palsy Was Associated With TRPV2 Downregulation Of Schwann Cell By Cold Stress

Objective:In this study,we investigated the effects of cold stress on secreted proteins such as TRPV2 in Schwann cells and their relationship with Bell’s palsy.Methods:Schwann cells were cultured at different temperatures(37℃,30℃,37-30℃ for 1h,2h,and 4h)for 8 hours.Transmission electron microscopy(TEM)was used to observe the effect of cold stimulation on the morphology of Schwann cells.CCK8 assay was used to analyze the effect of cold stress on Schwann cell proliferation.Flow cytometry was employed to assess the repercussions of cold stress on Schwann cell cycle and apoptosis.ELISA,RT-q PCR,and Western blotting were then employed to detect the effects of cold stress on TRPV2,NCAM,and NGF secreted by Schwann cells.A rat model of Bell’s palsy was established by lying on its side and blowing air on its face for 8 h with an electric fan.Following euthanasia,the heads of the rats were cut and subjected to HE staining.To investigate the impact of cold stress on TRPV2,NCAM and NGF in the facial nerve of rats,tissue immunofluorescence staining(IF)was employed.Results:The results of TEM showed that the tight junctions between Schwann cells were weakened after 8 h of cold stress.The intercellular space was significantly widened and enlarged,the rough endoplasmic reticulum was fragmented and scattered,and the granules on the membrane were lost to varying degrees.CCK8 and flow cytometry results showed that cold stress may arrest Schwann cells in S phase and keep Schwann cells in cold dormancy by inhibiting Schwann cell proliferation and apoptosis.Results from ELISA,RT-q PCR,and Western blotting demonstrated that cold stress hindered the secretion of TRPV2,NCAM,and NGF proteins in Schwann cells in rats.HE findings indicated that the nerve fiber envelope was fractured and the usual uninterrupted structure of axons and myelin sheath was disrupted under cold stress.Immunofluorescence showed that the expression of TRPV2,NCAM,and NGF in the cold stress group was significantly lower than in the control group.Conclusions:The drastic alteration in temperature can lead to a decrease in Schwann cell viability,the weakening of tight connections between cells,and the deterioration and fragmentation of the rough endoplasmic reticulum in the cytoplasm.The expression of bioactive molecules TRPV2,NCAM and NGF was down-regulated.The imbalance of Schwann cell homeostasis under stress may be one of the reasons that cause neuronal signal transduction block and lead to the occurrence and development of peripheral facial paralysis.