Lipopolysaccharide (LPS)-induced autophagy is involved in the restriction of Escherichia coliin peritoneal mesothelial cells

Abstract

BackgroundHost cell autophagy is implicated in the control of intracellular pathogen. Escherichia coli (E.coli) is the most common organism caused single-germ enterobacterial peritonitis during peritoneal dialysis. In this study, we investigated autophagy of peritoneal mesothelial cells and its role in defense against E.coli.ResultsAutophagy in human peritoneal mesothelial cell line (HMrSV5) was induced by lipopolysaccharide (LPS) in a dose-dependent and time-dependent way, which was demonstrated by increased expression of Beclin-1 and light chain 3 (LC3)-II, the accumulation of punctate green fluorescent protein-LC3, and a higher number of monodansylcadaverine-labeled autophagic vacuoles. After incubation of HMrSV5 cells with E.coli following LPS stimulation, both the intracellular bactericidal activity and the co-localization of E.coli (K12-strain) with autophagosomes were enhanced. Conversely, blockade of autophagy with 3-methyladenine, wortmannin or Beclin-1 small-interfering RNA (siRNA) led to a significant reduction in autophagy-associated protein expression, attenuation of intracellular bactericidal activity, and reduced co-localization of E.coli with monodansylcadaverine-labeled autophagosomes. In addition, treatment of HMrSV5 cells with LPS caused a dose-dependent and time-dependent increase in Toll-like receptor 4 (TLR4) expression. Both knockdown of TLR4 with siRNA and pharmacological inhibition of TLR4 with Polymyxin B significantly decreased LPS-induced autophagy. Furthermore, TLR4 siRNA attenuated remarkably LPS-induced intracellular bactericidal activity.ConclusionsOur findings demonstrated for the first time that LPS-induced autophagy in peritoneal mesothelial cells could enhance the intracellular bactericidal activity and the co-localization of E.coli with autophagosomes. The activation of TLR4 signaling was involved in this process. These results indicate that LPS-induced autophagy may be a cell-autonomous defense mechanism triggered in peritoneal mesothelial cells in response to E.coli infection.

Toll/IL-1 domain-containing adaptor inducing IFN-β (TRIF) mediates innate immune responses in murine peritoneal mesothelial cells through TLR3 and TLR4 stimulation

“…The role of TLR4 is somewhat controversial. Colmont et al demonstrated that TLR4 was not expressed in primary cultured human PMCs and LPS also did not induce any inflammatory molecules tested [11], whereas it was strongly expressed in a cell line (HMrSV5 cells) and LPSinduced autophagy was dependent on TLR4 in the cells [16,17]. Bacterial and viral peritonitis can occur in patients with intestinal perforation or undergoing continuous ambulatory peritoneal dialysis (CAPD) [18,19].…”

Vitamin C Mitigates Oxidative Stress and Tumor Necrosis Factor-Alpha in Severe Community-Acquired Pneumonia and LPS-Induced Macrophages

“…LPS-induced autophagy is involved in the restriction of Escherichia coli in peritoneal mesothelial cells [26]. To determine whether LPS induces autophagy, MH-S cells were transfected with RFP-LC3 plasmids or GFP-LC3 plasmid.…”

Variants of Porphyromonas gingivalis lipopolysaccharide alter lipidation of autophagic protein, microtubule‐associated protein 1 light chain 3, LC3

“…Such large autophagosomal structures were not seen upon serum starvation of the Saos‐2 cells suggesting signaling specificity in assembly of these structures with LPS 1690 . Similarly, very large autophagic structures, termed mega‐phagosomes, have been observed with coxsackievirus B3 infection (Kemball et al ., ), as well as E. coli LPS‐induced autophagy and subsequent infection (Wang et al ., ). In the case of coxsackievirus B3 infection, these large vacuoles are non‐degradative so providing the virus with a replicative niche.…”