Effects of chronic stress-induced depression on survival and immune function of tumor-bearing rats

Objective To investigate the effects of stress-induced depression on the survival and the immune function of tumor-bearing(rats.) Methods Forty-eight female SD rats((170~180 g)) were randomly divided into four(groups:) Group A(walker 256 sarcoma cells inoculation only),Group B(stress after tumor cells inoculation),Group C(stress before tumor cells inoculation) and Group D(stress before and after tumor cell inoculation).Survival time of the rats after tumor cell inoculation was observed;the T lymphocyte subsets(CD4~+,CD8~+,CD4~+/CD8~+) and the serum cortisol levels of animals were examined.Results Compared with Group A,the survival time in Group D decreased significantly(P0.05),however,there were no significant differences among the other groups(P0.05).Compared with Group A,the CD4~+ level of Group D decreased significantly(P0.05).Moreover,the CD4~+ level of Group D was significantly lower than that of Group B and Group C(P0.05).There were no significant differences in the CD8~+level among four groups.Compared with Group A,the ratio of CD4~+/CD8~+ in Group B,C and D decreased significantly(P0.05).Additionally,the ratio of CD4~+/CD8~+ in Group D was significantly lower than that in Group B and Group C(P0.05).Compared with Group A,the concentration of serum cortisol in Group B,C,D increased significantly(P0.05).Furthermore,the concentration of serum cortisol in Group D was significantly higher than that in Group B and Group C(P0.05).Conclusions Stress-induced depression can significantly shorten the survival time of the tumor-bearing rats.One possible mechanism is the dysfunction of the immune system caused by the disturbance of the T lymphocyte subsets and the rise of serum cortisol.