Rv2346c enhances mycobacterial survival within macrophages by inhibiting TNF-α and IL-6 production via the p38/miRNA/NF-κB pathway

Abstract

The intracellular survival of Mycobacterium tuberculosis (Mtb) has a central role in the pathogenesis of tuberculosis. Mtb Rv2346c is a member of 6-kDa early secreted antigenic target family of proteins, which are known to inhibit the host immune responses to promote bacillary persistence in macrophages. However, the mechanism through which Rv2346c participates in Mtb pathogenesis is unclear. In the present study, recombinant Rv2346c protein was synthesized and used to treat Bacillus Calmette–Guérin (BCG)-infected macrophages. The results showed that Rv2346c inhibited the proliferation of BCG-infected macrophages and enhanced the survival of BCG in macrophages. Tumor necrosis factor-α (TNF-α) and interleukin (IL)-6 were upregulated during BCG infection but downregulated by Rv2346c. Additional experiments showed that nuclear transcription factor-κB (NF-κB) in BCG-infected macrophages induced the production of TNF-α and IL-6. In addition, miR-155 and miR-99b had a suppressive effect on NF-κB, and the expression of these miRNAs was promoted by p38. Furthermore, Rv2346c was shown to decrease the activation of NF-κB, whereas it enhanced the phosphorylation of p38 and the expression of miR-155 and miR-99b. The function of Rv2346c was also verified in Mtb-infected mice. The results showed that Rv2346c increased the observed bacterial load and lung injury and downregulated TNF-α and IL-6 in vivo. Overall, our results reveal that Rv2346c enhances mycobacterial survival in macrophages via inhibiting the production of TNF-α and IL-6 in a p38/miRNA/NF-κB pathway-dependent manner, suggesting that Rv2346c acts as a crucial virulence factor in Mtb infection and has potential use as a target for anti-tuberculosis therapy.

Unraveling the Role of MicroRNAs in Mycobacterium tuberculosis Infection and Disease: Advances and Pitfalls

“…3F) (85). In this same showed an increase in miR-155 levels (102), as well as the human monocytic leukemia cell line (U937 cells) infected with BCG, where the upregulation was further enhanced by stimulating with Rv2346c, a putative ESAT-6-like protein of M. tuberculosis (103).…”

Machine Learning Algorithms Evaluate Immune Response to Novel Mycobacterium tuberculosis Antigens for Diagnosis of Tuberculosis

“…We also included the recently discovered in vivo -expressed antigens (Rv2346/47c, Rv2431c, Rv3614/15c, Rv3865) that have not been studied extensively in humans, but are believed to be important virulence factors ( Commandeur et al., 2013 ). Rv2346 and Rv2347c are ESAT-6 like proteins and associated with downregulation of IL-6 and TNF-α enabling survival of bacteria inside macrophages ( Malen et al., 2007 ; Yao et al., 2018 ). Rv2431c is a prolin-glutamic acid family protein, and its function is yet to be understood ( Malen et al., 2007 ).…”

The Roles of Host Noncoding RNAs in Mycobacterium tuberculosis Infection

“…The experiment proved that in A20-deficient macrophages, the production of proinflammatory factors (TNF-α, IL-1β) was increased and M. tuberculosis survival was attenuated ( 22 ). In infected macrophages, experiments confirmed that Rv2346c, an ESAT-6-like protein, which augmented the phosphorylation of P38, simultaneously upregulates miR-155 and miR-99b, which reduced the production of TNF-α and IL-6 by inhibiting the activation of NF-κB, thereby facilitates intracellular M. tuberculosis survival ( 23 ).…”