Brucella Downregulates Tumor Necrosis Factor-α to Promote Intracellular Survival via Omp25 Regulation of Different MicroRNAs in Porcine and Murine Macrophages

Abstract

Brucella spp. impedes the production of pro-inflammatory cytokines by its outer membrane protein Omp25 in order to promote survival and immune evasion. However, how Omp25 regulates tumor necrosis factor (TNF-α) expression in different mammalian macrophages remains unclear. In this study, we investigated the potential mechanisms by which Omp25 regulates TNF-α expression and found that Omp25-deficient mutant of B. suis exhibited an enhanced TNF-α expression compared with wild-type (WT) B. suis, whereas ectopic expression of Omp25 suppressed LPS-induced TNF-α production at both protein and mRNA levels in porcine alveolar macrophages (PAMs) and murine macrophage RAW264.7 cells. We observed that Omp25 protein as well as WT B. suis upregulated miR-146a, -181a, -181b, and -301a-3p and downregulated TRAF6 and IRAK1 in both PAMs and RAW264.7 cells, but separately upregulates miR-130a-3p in PAMs and miR-351-5p in RAW264.7. The upregulation of miR-146a or miR-351-5p attenuated TNF-α transcription by targeting TRAF6 and IRAK1 at the 3′ untranslated region (UTR), resulting in inhibition of NF-kB pathway, while upregulation of miR-130a-3p, -181a, or -301a-3p correlated temporally with decreased TNF-α by targeting its 3′UTR in PAMs or RAW264.7 cells. In contrast, inhibition of miR-130a-3p, -146a, -181a, and -301a-3p attenuated the inhibitory effects of Omp25 on LPS-induced TNF-α in PAMs, while inhibition of miR-146a, -181a, -301a-3p, and -351-5p attenuated the inhibitory effects of Omp25 in RAW264.7, resulting in an increased TNF-α production and decreased intracellular bacteria in both cells. Taken together, our results demonstrate that Brucella downregulates TNF-α to promote intracellular survival via Omp25 regulation of different microRNAs in porcine and murine macrophages.

miR-181a-5p Regulates TNF-α and miR-21a-5p Influences Gualynate-Binding Protein 5 and IL-10 Expression in Macrophages Affecting Host Control of Brucella abortus Infection

“…mmu-miR-181a-5p was reported to be important in the regulation of NF-κB activation and TNF-α production ( 28 ). More recently, Luo et al ( 29 ) have demonstrated that Brucella suis upregulated miR-181a that correlated with decreased TNF-α in Raw264.7 macrophage cell line. To further investigate whether miR-181a-5p can influence TNF-α expression in BMDMs during B. abortus infection, we transfected macrophages with the specific mimic or inhibitor for mmu-miR-181a-5p before infection.…”

“…We carried out further functional analysis using mmu-miR-181a-5p and mmu-miR-21a-5p. Recently, Luo et al ( 29 ) have identified that B. suis upregulates miR-146a, miR-181a, miR-181b, and miR-301a-3p leading to reduced TNF-α expression in Raw264.7 cells. In addition, according to Dan et al ( 40 ), stability of TNF-α mRNA was influenced by miR-181a-5p.…”

Outer Membrane Vesicles From Brucella melitensis Modulate Immune Response and Induce Cytoskeleton Rearrangement in Peripheral Blood Mononuclear Cells

“…TNFα is an important cytokine in Th1 immune responses to eliminate intracellular pathogens. Lou et al (2018) showed TNFα down-regulation on the expression of miRNAs induced by cells of B. suis and B. suis Omp25 protein in porcine and murine macrophages. Other Brucella antigens such as the Lon protease, phosphoglyceromutase, and dihydrodipicolinate reductase induce TNFα production (Park et al, 2013;Li et al, 2018).…”

Dendritic cells and Brucella spp. interaction: the sentinel host and the stealthy pathogen

“…TNFα is essential for DC maturation; in a previous report, B. suis Omp25 impaired TNFα production on THP-1 monocytes (Jubier-Maurin et al 2001). Recently, it was demonstrated that B. suis Omp25 dysregulates microRNA expression on porcine alveolar and murine macrophages, leading to the inhibition of NF-κB signaling and TNFα suppression (Billard et al 2007b;Luo et al 2018). The decrease in inflammatory cytokines and the poor T cell stimulation of Brucellainfected GM-DCs avert the induction of a Th1 immune response, which is essential for eradicating intracellular bacteria (Billard et al 2007b).…”