The expression of miR-122 in the liver of rats infected with Clonorchis sinensis and its correlation with inflammatory cytokines / 中华地方病学杂志

ABSTRACT

Objective:To observe the expression changes of microRNA(miR)-122 in liver tissue of rats infected with Clonorchis sinensis and its correlation with expression level of inflammatory cytokines. Methods:Totally 24 SPF grade Wistar male rats were selected and randomly divided into a control group (100 μl physiological saline gavage), a 4-week infection group (100 Clonorchis sinensis metacercariae gavage), and an 8-week infection group (100 Clonorchis sinensis metacercariae gavage) based on body weight (100-120 g) using a random number table method, with 8 rats in each group. Starting from the third week of infection, rat feces were collected and directly smeared with physiological saline for identification of Wistar rat animal models infected with Clonorchis sinensis. After 4 and 8 weeks of infection, the rats in the 4- and 8-week infection groups were euthanized, while 4 rats in the control group were euthanized, respectively. The heart blood and left lobe liver tissue and serum samples were collected from each group of rats. Using hematoxylin-eosin (HE) staining to observe liver pathological damage under the light microscope, real-time fluorescence quantitative PCR to detect the expression level of miR-122 in liver tissue, and Luminex 200 liquid suspension chip to detect the expression levels of serum inflammatory cytokines [tumor necrosis factor-α(TNF-α), interleukin-1β(IL-1β), interleukin-6 (IL-6)]. The correlation between miR-122 and inflammatory cytokines was analyzed using Pearson correlation. Results:Under the light microscope, the morphology of hepatocytes in control group was normal, and no inflammatory cell infiltration was observed. There was inflammatory cells such as lymphocyte, eosinophil and other inflammatory cell infiltration around the portal area in the 4-week infection group. The hepatocytes of the 8-week infected rats were arranged in a disordered manner, with varying degrees of swelling, loose and lightly stained cytoplasm, and some hepatocytes showed watery degeneration; additionally, bile duct dilation and thickening of the bile duct wall were observed in the liver tissue. There were statistically significant differences of liver miR-122 (1.00 ± 0.32, 2.57 ± 0.60, 3.63 ± 1.63), serum TNF-α [(0.14 ± 0.06), (0.43 ± 0.09), (0.61 ± 0.10) ng/ml], and IL-6 expression levels [(0.03 ± 0.01), (1.06 ± 0.24), (1.48 ± 0.33) ng/ml] in control group, 4- and 8-week infection groups ( F = 13.36, 69.99, 82.23, P < 0.001). There was no statistically significant difference in expression level of IL-1β between different groups ( F = 2.15, P = 0.141). The Pearson correlation analysis showed that the expression level of miR-122 was positively correlated with the expression levels of inflammatory cytokines TNF-α and IL-6 ( r = 0.67, 0.80, P < 0.001). Conclusion:Clonorchis sinensis infection can increase the expression of miR-122 in the host liver tissue, and the miR-122 is closely related to the expression levels of inflammatory cytokines TNF-α and IL-6.