Up-regulation Of The Expression Of Melanopsin In CRS Mice And Cultured Retina Cells Treated With Hydrocortisone

Objective:Intrinsically photosensitive retinal ganglion cells (ipRGCs) play a critical role in the regulation of circadian rhythms and sleep. Additionally, recent studies highlight a possible role of ipRGCs in the regulation of emotion and cognitive functions. Melanopsin, a membrane protein expressed in ipRGCs, is hypothesized to correlate with depression. To investigate the mechanism of the potential relationship between circadian rhythm disorder and the occurrence of depression, we take the clock gene melanopsin as the basic starting point to study the change of expression of melanopsin in the depression model, aims to study the possible mechanism of depression and further to provide new ideas for the treatment of depression.Methods:In this study, Forty healthy adult C57 mice were randomly divided into chronic restraint stress (CRS) group and control group, each group were 20 mice, CRS group were subjected to 6 hrs daily restraint stress for 21 consecutive days. Then Sucrose preference test and forced swimming test were conducted to confirm the depression like behavior in mice. We investigated a alteration in melanopsin expression of mice by Western Blotting analysis, immunofluorescence. In addition,we cultured RGC cells and treated them with 1μM hydrocortisone for seven days, then Western Blotting was used to detect the change of melanopsin expression.Results:After 21 days of The CRS, Sucrose Preference Test and forced swimming results showed that our model of depression is successful, immunofluorescence results showed Melanopsin were distributed in a small part of the cell bodies and dendrites and axons of ipRGCs, dendritic branches were anastomosed and formed a network structure. Our results showed that CRS mice had an significantly increased expression of melanopsin. In addition, we found melanopsin expressions in hydrocortisone treatments were also increased compared with the controls (p<0.05).Conclusion:These findings demonstrate that both Chronic restraint stress and hydrocortisone treatments can up-regulates melanopsin protein expression in mice, and this change may be concerned with hydrocortisone. It is suggested that down-regulating melanopsin protein expression could be therapeutic idea.