MicroRNA expression profiling of peripheral blood mononuclear cells associated with syphilis.

BACKGROUND: Treponema pallidum (T. pallidum) infection evokes significant immune responses, resulting in tissue damage. The immune mechanism underlying T. pallidum infection is still unclear, although microRNAs (miRNAs) have been shown to influence immune cell function and, consequently, the generation of antibody responses during other microbe infections. However, these mechanisms are unknown for T. pallidum. METHODS: In this study, we performed a comprehensive analysis of differentially expressed miRNAs in healthy individuals, untreated patients with syphilis, patients in the serofast state, and serologically cured patients. miRNAs were profiled from the peripheral blood of patients obtained at the time of serological diagnosis. Then, both the target sequence analysis of these different miRNAs and pathway analysis were performed to identify important immune and cell signaling pathways. Quantitative reverse transcription-polymerase chain reaction (RT-PCR) was performed for microRNA analysis. RESULTS: A total of 74 differentially regulated miRNAs were identified. Following RT-qPCR confirmation, three miRNAs (hsa-miR-195-5p, hsa-miR-223-3p, hsa-miR-589-3p) showed significant differences in the serofast and serologically cured states (P < 0.05). One miRNA (hsa-miR-195-5p) showed significant differences between untreated patients and healthy individuals. CONCLUSIONS: This is the first study of miRNA expression differences in peripheral blood mononuclear cells (PBMCs) in different stages of T. pallium infection. Our study suggests that the combination of three miRNAs has great potential to serve as a non-invasive biomarker of T. pallium infections, which will facilitate better diagnosis and treatment of T. pallium infections.

MicroRNA-101-3p Downregulates TLR2 Expression, Leading to Reduction in Cytokine Production by Treponema pallidum-Stimulated Macrophages.

Treponema pallidum (Tp) infection-induced immune responses can cause tissue damage. However, the underlying mechanism by which Tp infection induces immune response is unclear. Recent studies suggest a regulatory role of microRNAs in host immunity. We assessed whether microRNAs also have a regulatory role in immune response to Tp infection in vitro. Our results showed that microRNA-101-3p (miR-101-3p) levels were significantly higher in peripheral blood mononuclear cells of patients with primary syphilis and those in the serofast state, whereas toll-like receptor (TLR) 2 levels were higher in patients with syphilis than in healthy controls. In vitro, stimulation of THP-1 cells with Tp increased miR-101-3p expression. Moreover, miR-101-3p reduced expression levels of TLR2 mRNA and protein in THP-1 cells via binding to the 3' untranslated region of TLR2. Likewise, miR-101-3p inhibited production of inflammatory cytokines, including IL-1ß, IL-6, tumor necrosis factor-α, and IL-12, in Tp-stimulated macrophages. IL-1ß and IL-6 mRNA expression levels were reduced by transfection of macrophages with a TLR2-specific small interfering RNA. Conversely, overexpression of TLR2 upregulated cytokine expression. Patients with secondary syphilis exhibited the highest levels of plasma IL-6, which were negatively correlated with miR-101-3p. In conclusion, Tp infection upregulates miR-101-3p expression, which in turn inhibits the TLR2 signaling pathway, leading to reduced cytokine production.