α-Hemolysin of uropathogenic E. coli regulates NLRP3 inflammasome activation and mitochondrial dysfunction in THP-1 macrophages

Sci Rep. 2020 Jul 28;10(1):12653. doi: 10.1038/s41598-020-69501-1.

Abstract

Hemolysin expressing UPEC strains have been associated with severe advanced kidney pathologies, such as cystitis and pyelonephritis, which are associated with an inflammatory response. Macrophages play an important role in regulating an inflammatory response during a urinary tract infection. We have studied the role of purified recombinant α-hemolysin in inducing inflammatory responses and cell death in macrophages. Acylation at lysine residues through HlyC is known to activate proHlyA into a fully functional pore-forming toxin, HlyA. It was observed that active α-hemolysin (HlyA) induced cleavage of caspase-1 leading to the maturation of IL-1β, while inactive α-hemolysin (proHlyA) failed to do so in THP-1 derived macrophages. HlyA also promotes deubiquitination, oligomerization, and activation of the NLRP3 inflammasome, which was found to be dependent on potassium efflux. We have also observed the co-localization of NLRP3 within mitochondria during HlyA stimulations. Moreover, blocking of potassium efflux improved the mitochondrial health in addition to a decreased inflammatory response. Our study demonstrates that HlyA stimulation caused perturbance in potassium homeostasis, which led to the mitochondrial dysfunction followed by an acute inflammatory response, resulting in cell death. However, the repletion of intracellular potassium stores could avoid HlyA induced macrophage cell death. The findings of this study will help to understand the mechanism of α-hemolysin induced inflammatory response and cell death.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acylation
  • Cell Death
  • Escherichia coli Infections / drug therapy
  • Escherichia coli Infections / immunology*
  • Escherichia coli Infections / microbiology
  • Escherichia coli Proteins / pharmacology*
  • Hemolysin Proteins / pharmacology*
  • Humans
  • Inflammasomes / drug effects
  • Inflammasomes / physiology*
  • Inflammation / drug therapy
  • Inflammation / immunology
  • Inflammation / microbiology
  • Macrophages / immunology
  • Macrophages / metabolism
  • Macrophages / microbiology
  • Macrophages / pathology
  • Mitochondria / drug effects
  • Mitochondria / immunology
  • Mitochondria / metabolism
  • Mitochondria / pathology*
  • NLR Family, Pyrin Domain-Containing 3 Protein / genetics
  • NLR Family, Pyrin Domain-Containing 3 Protein / metabolism*
  • Potassium / metabolism
  • Uropathogenic Escherichia coli / drug effects
  • Uropathogenic Escherichia coli / immunology*
  • Uropathogenic Escherichia coli / metabolism

Substances

  • Escherichia coli Proteins
  • Hemolysin Proteins
  • Inflammasomes
  • NLR Family, Pyrin Domain-Containing 3 Protein
  • Potassium