microRNA-18a upregulates the regulatory immune function in patients with chronic hepatitis B through the PPARα/γ signaling pathway

Objective To investigate the effect of microRNA-18 a(miRNA-18 a) on the regulatory immune function in patients withchronic hepatitis B(CHB) through the PPARα/γ signaling pathway.Methods A total of 98 CHB patients and 96 patients without hepatitisB, who were treated in Air Force Special Medical Center(formerly known as General Air Force Hospital, PLA) from April 2017 to October2018, were enrolled as experimental group and control group, respectively. There were no significant differences in age and sex between thetwo groups(P> 0. 05). RT-PCR was used to measure the relative mRNA expression of miRNA-18 a in serum; flow cytometry was usedto measure the expression of miRNA-18 a in peripheral blood mononuclear cells(PBMCs); ELISA was used to observe the effect of miRNA-18 a on the frequency of CD4+CD25+regulatory T(Treg) cells; Western blot was used to measure the expression of proteins associatedwith the PPARα/γ signaling pathway. PBMCs were further divided into si-miRNA-18 a inhibitor group(transfected with si-miRNA-18 a inhibitor) and si-miRNA-18 a normal control group(transfected with si-miRNA-18 a plasmid); flow cytometry was used to investi-gate the effect of miRNA-18 a inhibition on the frequency of CD4+CD25+Treg cells, and Western blot was used to measure the expressionof proteins associated with the PPARα/γ signaling pathway. Thet-test was used for comparison of normally distributed continuous data between two groups, and a Pearson correlation analysis was performed to investigate the correlation between miRNA-18 a expression and pro-teins associated with the PPARα/γ signaling pathway.Results Compared with the control group, the experimental group had significantlyupregulated mRNA expression of miRNA-18 a in serum and liver tissue(t= 9. 634 and 9. 863, bothP< 0. 01). The experimental grouphad a significantly higher frequency of CD4+CD25+Treg cells than the control group(t =9.854,P< 0. 01). Compared with the controlgroup, the experimental group had significantly upregulated levels of interferon-γ and interlukin-9(t =8. 235 and 8. 382, bothP<0. 05). Compared with the control group, the experimental group had significantly upregulated expression of PPARα and PPARγ （t =4. 229 and 3. 545, bothP< 0. 05). Compared with the si-miRNA-18 a normal control group, the si-miRNA-18 a inhibitor group had a signifi-cantly lower percentage of peripheral blood CD4+CD25+Treg cells among CD4+T cells(t =3.968,P< 0. 01). Compared with the si-miRNA-18 a normal control group, the si-miRNA-18 a inhibitor group had significantly lower expression of PPARα and PPARγ （t =5. 023 and 4. 983, bothP< 0. 05). miRNA-18 a was positively correlated with the protein expression of PPARα and PPARγ in thePPARα/γ signaling pathway(r= 0. 701 and 0. 682, bothP< 0. 05).Conclusion miRNA-18 a may affect the regulatory immune functionin CHB patients by activating the PPARα/γ signaling pathway and thus upregulate the frequency of cell surface factors and cytokine secretionlevels associated with immune function.