Autophagy Is an Innate Mechanism Associated with Leprosy Polarization

PLoS Pathog. 2017 Jan 5;13(1):e1006103. doi: 10.1371/journal.ppat.1006103. eCollection 2017 Jan.

Abstract

Leprosy is a chronic infectious disease that may present different clinical forms according to the immune response of the host. Levels of IFN-γ are significantly raised in paucibacillary tuberculoid (T-lep) when compared with multibacillary lepromatous (L-lep) patients. IFN-γ primes macrophages for inflammatory activation and induces the autophagy antimicrobial mechanism. The involvement of autophagy in the immune response against Mycobacterium leprae remains unexplored. Here, we demonstrated by different autophagic assays that LC3-positive autophagosomes were predominantly observed in T-lep when compared with L-lep lesions and skin-derived macrophages. Accumulation of the autophagic receptors SQSTM1/p62 and NBR1, expression of lysosomal antimicrobial peptides and colocalization analysis of autolysosomes revealed an impairment of the autophagic flux in L-lep cells, which was restored by IFN-γ or rapamycin treatment. Autophagy PCR array gene-expression analysis revealed a significantly upregulation of autophagy genes (BECN1, GPSM3, ATG14, APOL1, and TPR) in T-lep cells. Furthermore, an upregulation of autophagy genes (TPR, GFI1B and GNAI3) as well as LC3 levels was observed in cells of L-lep patients that developed type 1 reaction (T1R) episodes, an acute inflammatory condition associated with increased IFN-γ levels. Finally, we observed increased BCL2 expression in L-lep cells that could be responsible for the blockage of BECN1-mediated autophagy. In addition, in vitro studies demonstrated that dead, but not live M. leprae can induce autophagy in primary and lineage human monocytes, and that live mycobacteria can reduce the autophagy activation triggered by dead mycobacteria, suggesting that M. leprae may hamper the autophagic machinery as an immune escape mechanism. Together, these results indicate that autophagy is an important innate mechanism associated with the M. leprae control in skin macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Autophagy / physiology*
  • Blotting, Western
  • Enzyme-Linked Immunosorbent Assay
  • Female
  • Fluorescent Antibody Technique
  • Humans
  • Immunohistochemistry
  • Interferon-gamma / immunology
  • Leprosy / immunology*
  • Leprosy / pathology
  • Macrophages / immunology
  • Male
  • Microscopy, Electron, Transmission
  • Middle Aged
  • Mycobacterium leprae / immunology
  • Polymerase Chain Reaction
  • Skin / immunology
  • Skin / microbiology*
  • Skin / pathology
  • Transcriptome
  • Young Adult

Substances

  • Interferon-gamma

Grants and funding

The study was financed by grants from Conselho Nacional de Desenvolvimento Científico e Tecnológico/CNPq (www.cnpq.br) 311488/2009-9 and 311489/2009-9 to ROP; and Fundação Carlos Chagas Filho de Amparo à Pesquisa do Estado do Rio de Janeiro/FAPERJ (www.faperj.br) 203675 to ROP. ENS and ROP are research fellows of the Brazilian National Council for Scientific and Technological Development – CNPq. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.