Th1/Th2 cytokine imbalance and the growth of cancer in S180 cancer-loaded rats under restriction stress / 中国组织工程研究

ABSTRACT

BACKGROUND: Restriction is a reliable means in the study of psychological stress, and restriction stress can suppress cellular immunity of T lymphocytes through hypothalamus-pituitary-adrenal axis.OBJECTIVE: To investigate the changes of Th1/Th2 balance due to restriction stress in cancer-loaded rats and the growth of cancer so as to explore the effect of psychological stress on cancer cells.DESIGN:Case control study based on experimental animal as subjects.SETTING: Teaching and Research Department of Microbiology and Immunology of Beijing University of Traditional Chinese Medical.MATERIALS This study was carried out in the Immunology Laboratory of Beijing Traditional Chinese Medical University. Kunming rats of 6-8weeks old were selected. They were raised for 3 days before experiment to adapt to the environment and numbered according to their weight. Rats with the highest and lowest body weight were excluded, and the rest were randomly divided into 4 groups of 16 rats (8 male rats and 8 female rats)weighing 18 to 20 g.METHODS: S180 cancer cells were collected at 7 days of celiac subculture and rinsed with normal saline before made into cell suspensions of 1×1010 L-1 with RPMI 1640 medium. Rats were given subcutaneous injection of 0.2 mL cell suspension at the right axilla in cancer group and cancer-combined restriction group. Meanwhile, the same dosage of normal saline was used instead in normal control group and pure restriction group in the same way. After injection, movements of rats in pure restriction group and cancer-combined restriction group were restricted in specially-made tubes for 8 hours a day. Ten days later rats were killed to remove the tumor and thymus which were then weighed for calculating the thymus index. MTT colorimetry and mitogen-activated immunoblast method were used to examine the proliferation of spleen T lymphocytes and the production of Thl-type cytokines, such as interleukin-2(IL-2), interferon-γ (IFN-γ); meanwhile,ELISA technique was used to detect the level of serum Th2-type cytokines,such as interleukin-4(IL-4) and interleukin-10(IL-10).MAIN OUTCOME MEASURES: Primary outcomes: effect of restriction stress on T lymphocyte' production of IL-2 and interferon-γ, and on IL-4and IL-10 as well as the effect in promoting the cancer growth in cancer-loaded rats. Secondary outcomes: effect of restriction stress on T-lymphocyte proliferation and thymus index.RESULTS: Restriction stress significantly increased the cancer weight and decreased thymus index and the proliferation of spleen T lymphocytes. Meanwhile, IL-2 and IFN-γ produced by spleen cells also decreased, with serum IL-4 and IL-10 level obviously increased in cancer-loaded rats.CONCLUSION:The cellular immunity of cancer-loaded rats was obviously suppressed due to restriction stress, which was presented by decreased Thl-type cytokine production and increased Th2-type cytokine production,resulting in Thl/Th2 cytokine imbalance towards Th2. It may be the important mechanism of its promoting effect on the growth of cancer.