Mycobacterium tuberculosis-induced apoptotic neutrophils trigger a pro-inflammatory response in macrophages through release of heat shock protein 72, acting in synergy with the bacteria

Microbes Infect. 2008 Mar;10(3):233-40. doi: 10.1016/j.micinf.2007.11.007. Epub 2007 Nov 29.

Abstract

Mycobacterium tuberculosis (Mtb) survive inside macrophages by manipulating microbicidal functions such as phago-lysosome fusion, production of reactive oxygen species and nitric oxide, and by rendering macrophages non-responsive to IFN-gamma. Mtb-infected lung tissue does however not only contain macrophages, but also significant numbers of infiltrating polymorphonuclear neutrophils (PMN). These are able to phagocytose and kill ingested Mtb, but are short-lived cells that constantly need to be removed from tissues to avoid tissue damage. Phagocytosis of aged or UV-induced apoptotic PMN by macrophages induce an anti-inflammatory response in macrophages. However, in the present study, we show that engulfment of Mtb-induced apoptotic PMN by macrophages initiates secretion of TNF-alpha from the macrophages, reflecting a pro-inflammatory response. Moreover, Mtb-induced apoptotic PMN up-regulate heat shock proteins 60 and 72 (Hsp60, Hsp72) intracellularly and also release Hsp72 extracellularly. We found that both recombinant Hsp72 and released Hsp72 enhanced the pro-inflammatory response to both Mtb-induced apoptotic PMN and Mtb. This stimulatory effect of the supernatant was abrogated by depleting the Hsp72 with immunoprecipitation. These findings indicate that released Hsp72 from Mtb-infected PMN can trigger macrophage activation during the early stage of Mtb infections, thereby creating a link between innate and adaptive immunity.

Publication types

  • Research Support, N.I.H., Extramural

MeSH terms

  • Apoptosis*
  • Cells, Cultured
  • HSP72 Heat-Shock Proteins / immunology*
  • HSP72 Heat-Shock Proteins / metabolism
  • Humans
  • Leukocytes, Mononuclear
  • Macrophage Activation
  • Macrophages / immunology*
  • Mycobacterium tuberculosis / immunology*
  • Neutrophils / physiology*
  • Tuberculosis / immunology*

Substances

  • HSP72 Heat-Shock Proteins