Investigation of the effect of gallic acid on the dexamethasone induced immunesuppression in rats

Dexamethasone is an anti-inflammatory and immunosuppressive drug and is also used experimentally for immunosuppression. Levamisole is a synthetic compound of the imidazothiazole class with immunomodulatory activity. Gallic acid, one of the flavonoids in oak bark, blackberry, chestnut, grape, pomegranate, tea leaves, especially propolis, is known to contain antioxidant, anti-inflammatory, antimicrobial and anticancer effects. In this study, we investigated the effect of gallic acid on the improvement of immune system parameters in rats immunosuppressed with dexamethasone. In addition, the immunomodulatory effect of gallic acid was compared with levamisole. In the study, 70 7-8 week old male Spraque-Dawley rats were used. The rats were divided into 6 groups as Control group (n=15), Dexamethasone group (n=15), Dexamethasone-Gallic acid group (n=10), Dexamethasone-Levamisole group (n=10), Gallic acid group (n=10), Levamisole group (n=10). In the 19-day study, rats were decapitated as 10 animals on the 5th day, 10 animals on the 7th day, 20 animals on the 12th day, 10 animals on the 14th day and 20 animals at the end of the 19th day. Hemograms were performed in blood samples taken from the rats. In the serum samples obtained, IGM, IGG, IGA, CRP, CD4, CD8, TNF-α, IL1B, IL2, IL6, IL10 and IL12 levels were determined by Enzyme-Linked ImmunoSorbent Assay (ELISA) test. In addition, thymus, liver and spleen tissues were obtained, weighed and immunohistochemistry was performed. On the 7th day of the study, WBC, TNF-α, IL6, CRP, CD4, CD8, IGM, IGG, IGA levels and liver and spleen weights decreased; PLT, NE, MO and thymus weights increased in the D+G group compared to the control group. On day 14, WBC, LY, TNF-α, IL6, thymus diameter and thymus, liver and spleen weights decreased; NE, MO, IL1B, CD8 and IGG levels increased. Compared to the dexamethasone group, TNF-α, IL6, CRP, CD4, IGM and IGG levels decreased and LY, thymus diameter and weight increased in the D+G group on day 7. On day 14, RBC, LY, MO, TNF-α, thymus and liver weight decreased, while NE, CRP, CD8, IGM, IGG and IGA levels increased. The findings suggest that gallic acid has an immunomodulatory effect on the suppressed immune system.