miR‐18a promotes Mycobacterial survival in macrophages via inhibiting autophagy by down‐regulation of ATM

Abstract

Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is one of leading causes of global deaths. This study aimed to explore the role of miR‐18a in RAW264.7 cells response to Mtb infection. Exosomes derived from Mtb‐infected cells were isolated and further validated by size, transmission electron microscopy and Western blot. RT‐PCR was utilized to measure miR‐18a expression. Cell viability and ultrastructure were examined by CFU counting, CCK‐8 and electron microscope, respectively. Potential target genes of miR‐18a were predicted with bioinformatics and further confirmed using RT‐PCR, Western blot and laser confocal microscope analysis, respectively. LC3, AMPK and mTOR were measured using Western blot. We found that miR‐18a was induced both in Mtb‐infected RAW264.7 cells and its derived exosomes compared with the controls. In addition, up‐regulation of miR‐18a promoted intracellular Mtb survival, attenuated cell viability and reduced LC3‐II level, while its down‐regulation had the opposite effect. miR‐18a overexpression suppressed level of ATM, one possible target of miR‐18a, while its underexpression enhanced ATM. We also found that inhibition of ATM induced LC3‐II decrease in Mtb‐infected cells and could reverse the increase of LC3‐II caused by inhibition of miR‐18a. Moreover, down‐regulation of miR‐18a increased p‐AMPK level while reduction of ATM could reverse the change. Taken together, our results suggest that miR‐18a is up‐regulated in macrophages response to Mtb infection, and it promotes intracellular Mtb survival through repressing autophagic process by down‐regulation of ATM pathway. This provides new thought for TB pathogenesis, diagnosis and treatment.

Emerging Role of Exosomes in Tuberculosis: From Immunity Regulations to Vaccine and Immunotherapy

“…RNA sequencing provides a powerful strategy to explore the miRNA in exosomes from MTB-infected macrophages and plasma from tuberculosis patients, which are predicted to be closely linked with the metabolism and energy production-related pathways ( 53 , 61 ). MiR-18a, a type of miRNA also found in exosomes, is upregulated to promote mycobacterial survival in MTB-infected macrophages by inhibiting the autophagy pathways ( 62 ). In MTB infection, individual miRNA alternation might induce cellular function changing as miRNA could regulate gene expression post-transcriptionally.…”

Regulatory Mechanisms of Autophagy-Targeted Antimicrobial Therapeutics Against Mycobacterial Infection

“…In addition, Mtb pathogens can epigenetically control host autophagy pathway through regulation of microRNAs (miRNAs) to favor mycobacterial replication in the host cells during infection ( Batista et al., 2020 ; Ruiz-Tagle et al., 2020 ; Silwal et al., 2020 ). The miRNAs that are associated with pathogenesis of Mtb infection include miR-33/miR-33* ( Ouimet et al., 2016 ), miR-889 ( Chen et al., 2020 ), miR-18a ( Yuan et al., 2020 ), and miR-125a ( Kim et al., 2015 ), all of which are increased by Mtb infection; whereas others such as miR-26a ( Sahu et al., 2017 ) and miR-17-5p ( Kumar et al., 2016 ), both of which are decreased by Mtb infection. Numerous miRNAs that are involved in the regulation of autophagy in terms of host-pathogen interaction during Mtb infection have been extensively discussed elsewhere ( Kim J. K. et al., 2017 ; Sabir et al., 2018 ; Yang and Ge, 2018 ; Silwal et al., 2020 ; Sinigaglia et al., 2020 ) and are not the focus of this Review.…”

“…Mtb infection increases miR-18a expression to suppress the autophagy; and miR-18a inhibition increases AMPK phosphorylation and promotes autophagy, resulting in suppression of intracellular Mtb survival ( Yuan et al., 2020 ). Mtb induction of miR33/33* supports intracellular bacterial replication by inhibiting the autophagic flux via repression of AMPK-dependent activation of forkhead box O (FOXO) 3 and TFEB ( Ouimet et al., 2016 ).…”

Extracellular RNAs in Bacterial Infections: From Emerging Key Players on Host-Pathogen Interactions to Exploitable Biomarkers and Therapeutic Targets

“…Some of these exosome-delivered miRNAs seem to immunomodulate the inflammatory response, however, their specific role in host vesicles derived from bacterially infected host cells is not completely understood. For instance, higher levels of miR-18a, a miRNA that promotes the intracellular Mycobacterium tuberculosis survival by counteracting autophagy, were detected in macrophages infected by M. tuberculosis and in their derived exosomes [ 52 ]. However, the miR-18a impact in exosome-receiving cells remains unclear.…”