Sphingosine kinase-1 (SphK-1) regulates Mycobacterium smegmatis infection in macrophages

PLoS One. 2010 May 17;5(5):e10657. doi: 10.1371/journal.pone.0010657.

Abstract

Sphingosine kinase-1 is known to mediate Mycobacterium smegmatis induced inflammatory responses in macrophages, but its role in controlling infection has not been reported to date. We aimed to unravel the significance of SphK-1 in controlling M. smegmatis infection in RAW 264.7 macrophages. Our results demonstrated for the first time that selective inhibition of SphK-1 by either D, L threo dihydrosphingosine (DHS; a competitive inhibitor of Sphk-1) or Sphk-1 siRNA rendered RAW macrophages sensitive to M. smegmatis infection. This was due to the reduction in the expression of iNOs, p38, pp-38, late phagosomal marker, LAMP-2 and stabilization of the RelA (pp-65) subunit of NF-kappaB. This led to a reduction in the generation of NO and secretion of TNF-alpha in infected macrophages. Congruently, overexpression of SphK-1 conferred resistance in macrophages to infection which was due to enhancement in the generation of NO and expression of iNOs, pp38 and LAMP-2. In addition, our results also unraveled a novel regulation of p38MAPK by SphK-1 during M. smegmatis infection and generation of NO in macrophages. Enhanced NO generation and expression of iNOs in SphK-1++ infected macrophages demonstrated their M-1(bright) phenotype of these macrophages. These findings thus suggested a novel antimycobacterial role of SphK-1 in macrophages.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Lipopolysaccharides / pharmacology
  • Lysophospholipids / biosynthesis
  • Macrophages / drug effects
  • Macrophages / enzymology*
  • Macrophages / metabolism
  • Macrophages / microbiology*
  • Mice
  • Mice, Inbred C57BL
  • Mycobacterium Infections, Nontuberculous / enzymology*
  • Mycobacterium Infections, Nontuberculous / microbiology
  • Mycobacterium Infections, Nontuberculous / pathology*
  • Mycobacterium smegmatis / drug effects
  • Mycobacterium smegmatis / physiology*
  • Nitric Oxide / biosynthesis
  • Phosphotransferases (Alcohol Group Acceptor) / metabolism*
  • Reproducibility of Results
  • Sphingosine / analogs & derivatives
  • Sphingosine / biosynthesis
  • Tumor Necrosis Factor-alpha / metabolism
  • p38 Mitogen-Activated Protein Kinases / metabolism

Substances

  • Lipopolysaccharides
  • Lysophospholipids
  • Tumor Necrosis Factor-alpha
  • sphingosine 1-phosphate
  • Nitric Oxide
  • Phosphotransferases (Alcohol Group Acceptor)
  • sphingosine kinase
  • p38 Mitogen-Activated Protein Kinases
  • Sphingosine