PGL I expression in live bacteria allows activation of a CD206/PPARγ cross-talk that may contribute to successful Mycobacterium leprae colonization of peripheral nerves

PLoS Pathog. 2018 Jul 6;14(7):e1007151. doi: 10.1371/journal.ppat.1007151. eCollection 2018 Jul.

Abstract

Mycobacterium leprae, an obligate intracellular bacillus, infects Schwann cells (SCs), leading to peripheral nerve damage, the most severe leprosy symptom. In the present study, we revisited the involvement of phenolic glycolipid I (PGL I), an abundant, private, surface M. leprae molecule, in M. leprae-SC interaction by using a recombinant strain of M. bovis BCG engineered to express this glycolipid. We demonstrate that PGL I is essential for bacterial adhesion and SC internalization. We also show that live mycobacterium-producing PGL I induces the expression of the endocytic mannose receptor (MR/CD206) in infected cells in a peroxisome proliferator-activated receptor gamma (PPARγ)-dependent manner. Of note, blocking mannose recognition decreased bacterial entry and survival, pointing to a role for this alternative recognition pathway in bacterial pathogenesis in the nerve. Moreover, an active crosstalk between CD206 and the nuclear receptor PPARγ was detected that led to the induction of lipid droplets (LDs) formation and prostaglandin E2 (PGE2), previously described as fundamental players in bacterial pathogenesis. Finally, this pathway was shown to induce IL-8 secretion. Altogether, our study provides evidence that the entry of live M. leprae through PGL I recognition modulates the SC phenotype, favoring intracellular bacterial persistence with the concomitant secretion of inflammatory mediators that may ultimately be involved in neuroinflammation.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Antigens, Bacterial / metabolism*
  • Glycolipids / metabolism*
  • Humans
  • Lectins, C-Type / metabolism*
  • Leprosy / metabolism*
  • Mannose Receptor
  • Mannose-Binding Lectins / metabolism*
  • Mycobacterium leprae / metabolism
  • PPAR gamma / metabolism*
  • Receptor Cross-Talk / physiology
  • Receptors, Cell Surface / metabolism*
  • Schwann Cells / virology*

Substances

  • Antigens, Bacterial
  • Glycolipids
  • Lectins, C-Type
  • Mannose Receptor
  • Mannose-Binding Lectins
  • PPAR gamma
  • Receptors, Cell Surface
  • phenolic glycolipid I, Mycobacterium leprae

Grants and funding

This work was funded by the Brazilian National Council for Scientific Research (CNPq) (individual grant number 310634/2013-0 to MCVP). CCDA was a recipient of a doctoral fellowship awarded by PEC-PG/CAPES. New York Community Trust. The Heiser Program for Research in Leprosy. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.