Differential expression and significance of CD4+CD25+Foxp3+regulatory T cell in liver of arsenic-exposed rats / 中华地方病学杂志

ABSTRACT

Objective To observe the differential expression level of CD4+CD25+Foxp3+regulatory T cells (Treg) in liver of arsenic-exposed rats, explore the regulatory mechanisms on immunological of hepatic injury induced by arsenic, and provide a basis for prevention and treatment of the disease. Methods Thirty-two healthy Wistar rats were selected and randomly divided into control,low,medium and high arsenic dose groups by weight,8 rats per group. Rats in control group were given oral gavage of deionized water, while the other groups were given oral gavage doses of 2.00 g/L sodium arsenite(NaAsO2) according to their body weight for 6 days every week, the concentrations were 1.25, 2.50 and 5.00 ml/kg. After 4 months, liver tissue samples of rats were collected, the content of arsenic in liver was detected by inductively coupled plasma mass spectrometry (ICP-MS);the expression of Treg cells in liver was detected by immunohistochemistry; enzyme-linked immunosorbent assay (ELISA) was applied to detect the levels of interloukin-10 (IL-10),transforming growth factor beta 1 (TGF-β1), IL-6, IL-17 and IL-2. Results Compared with the control group [28.57 (17.64 - 35.64)μg/g], the content of arsenic in liver in low,medium and high arsenic exposed groups[M(P25-P75)638.30(527.91-802.58),591.64(513.82-723.16),792.55 (695.93 - 1 074.41) μg/g] increased, the differences were statistically significant(P < 0.05). Compared with low arsenic group, the content of arsenic in liver in high arsenic group increased, the difference was statistically significant (P < 0.05). Numerical density on area (NA) of positive Treg cells in medium,high arsenic exposed groups [(2.25 ± 0.50),(4.00 ± 2.16)A/cm2]was higher than that of the control group[(0.60 ± 0.54)A/cm2,P<0.05];NA of positive Treg cells in high arsenic exposed group was higher than that of the low arsenic exposed group[(1.50 ± 0.58) A/cm2, P < 0.05]. The expressions of the IL-10 in low, medium and high arsenic exposed groups [(5.58 ± 1.70), (6.78 ± 1.09),(7.18 ± 0.53)μg/L]were higher than that of the control group[(2.32 ± 0.83) μg/L,P<0.05];compared with low arsenic group, the expression of IL-10 in high arsenic group increased (P < 0.05); compared with control group [(1.46 ± 0.65) μg/L], the expression of TGF-β1 in high arsenic exposed group increased[(9.06 ± 3.60)μg/L, P<0.05];compared with control group [(2.33 ± 0.66)μg/L], the expression of IL-6 in high arsenic exposed group increased [(5.03 ± 1.39) μg/L, P < 0.05], compared with low arsenic exposed group [(2.46 ± 1.71) μg/L], the expressions of IL-6 in high arsenic exposed group increased, the difference was statistically significant (P < 0.05);the expression of IL-17 among control, low, medium and high arsenic exposed groups[(4.87 ± 1.64),(7.50 ± 2.74), (6.21 ± 1.47),(7.23 ± 2.68)μg/L]were not statistically significant (F = 1.429, P > 0.05); compared with control group [(16.30 ± 3.98) μg/L], the expression of IL-2 in high arsenic exposed group decreased[(9.93 ± 2.65) μg/L, P <0.05]. The content of arsenic in liver was positively correlated with the expression of IL-10, TGF-β1, IL-17, IL-6 (rs=0.696,0.463,0.632,0.502,P<0.05),and negatively correlated with the expression of IL-2(rs=-0.522,P<0.05). Conclusion With increasing of arsenic exposure level, the content of arsenic in liver and the expression of CD4+CD25+Foxp3+Treg have increased,the cytokines are secreted abnormally,liver immunological micro environment is disordered,immune tolerance is formed,and immune clearance is inhibited,which may play an important role in the occur and development of immunological liver damage induced by arsenic in rat.