Expression of IL-17 and its gene promoter methylation status are associated with the progression of chronic hepatitis B virus infection

Abstract

To explore interleukin-17 (IL-17) and its epigenetic regulation during the progression of chronic hepatitis B virus (HBV) infection.A total of 162 patients with chronic HBV infection, including 75 with chronic hepatitis B (CHB), 54 with hepatitis B-associated liver cirrhosis and 33 with hepatitis B-associated hepatocellular carcinoma (HBV-HCC), were enrolled in this study. Thirty healthy adults of the same ethnicity were enrolled in the control group. Whole venous blood was obtained from the patients and normal controls (n = 30). Clinical and laboratory parameters were assessed, and we performed enzyme-linked immunosorbent assay and quantitative real-time PCR to measure the serum levels and relative mRNA expression of IL-17, respectively. IL-17 promoter methylation in peripheral blood mononuclear cells was assessed by methylation-specific PCR. We analyzed the serum and mRNA levels of IL-17 and IL-17 promoter methylation in the 4 groups as well as the effect of methylation on serum IL-17 levels. Correlations between the IL-17 promoter methylation status and clinical parameters were analyzed by Spearman correlation analysis.Compared to the normal control group, the patient groups exhibited significantly higher serum and relative mRNA levels of IL-17. The methylation distribution among the patients was significantly lower than that among the normal controls (P < .05), with the HBV-HCC group showing the lowest IL-17 gene methylation frequency. The average IL-17 promoter CG methylation level was negatively correlated with IL-17 mRNA expression (r = -0.39, P = .03), and negative correlations between IL-17 promoter methylation and prothrombin time activity (r = -0.585, P = .035), alanine aminotransferase (r = -0.522, P < .01), aspartate aminotransferase (r = -0.315, P < .05), and the model for end-stage liver disease score (r = -0.461, P < .05) were observed. IL-17 serum levels in the methylated-promoter groups were significantly lower than those in the unmethylated-promoter groups.IL-17 expression and promoter methylation were associated with chronic HBV infection progression, especially in the HBV-HCC group. The IL-17 promoter status may help clinicians initiate the correct treatment strategy at the CHB stage.

Figure 1

Comparison of serum IL-17 levels among the different hepatitis B virus infection progression groups and healthy controls. Notes: All data are summarized as the mean and standard deviations. P < .05 was considered statistically significant. P > .05, CHB group versus HBV-LC group; P < .05 CHB group, HBV-LC group, HBV-HCC group versus control. CHB = chronic hepatitis B, HBV-HCC = hepatitis B-associated hepatocellular carcinoma, HBV-LC = hepatitis B-associated liver cirrhosis, HC = healthy controls.

Figure 2

Comparison of IL-17 mRNA levels in PBMCs among different hepatitis B virus infection progression groups and healthy controls. Notes: All data are summarized as the mean and standard deviations. P < .05 was considered statistically significant. IL-17 mRNA expression was analyzed by Gel-pro analyzer software. Mean ± s. P > .05, CHB group versus HBV-LC group; P < .05 CHB group, HBV-LC group, HBV-HCC group versus control. CHB = chronic hepatitis B, HBV-HCC = hepatitis B-associated hepatocellular carcinoma, HBV-LC = hepatitis B-associated liver cirrhosis, HC = healthy controls, PBMCs = peripheral blood mononuclear cells.

Figure 3

IL-17 promoter methylation frequency among different hepatitis B virus infection progression groups and healthy controls. Notes: All data are summarized as the mean and standard deviations. P < .05 was considered statistically significant. P > .05, CHB group versus HBV-LC group; P < .05 CHB group, HBV-LC group, HBV-HCC group v control. CHB = chronic hepatitis B, HBV-HCC = hepatitis B-associated hepatocellular carcinoma, HBV-LC = hepatitis B-associated liver cirrhosis, HC = healthy controls.

Figure 4

Analysis of the correlation between IL-17 expression level and the level of IL-17 promoter methylation in patients and normal controls. Notes: N = 84, r = −0.39, P = .03.

Figure 5

Serum IL-17 levels in methylated DNA groups and unmethylated DNA groups. Notes: All data are summarized as the mean and standard deviations. P < .05 was considered statistically significant. Significant difference (P < .05, methylated vs unmethylated). CHB = chronic hepatitis B, HBV-HCC = hepatitis B-associated hepatocellular carcinoma, HBV-LC = hepatitis B-associated liver cirrhosis, HC = healthy controls.