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Direct activation of human peritoneal mesothelial cells by heat-killed microorganisms
P Kinnaert1, J P De Wilde, B Bournonville
1Laboratoire Pluridisciplinaire de Recherches Expérimentales Biomédicales, Université Libre de Bruxelles, Belgium.
Objective:
The aim of the study was to determine if human peritoneal mesothelial cells (HPMCs) can be activated directly by bacterial products contained in preparations of heat-killed Escherichia coli and staphylococci.
Summary Background Data:
It has been shown recently that cytokine-activated HPMCs produce the inflammatory mediators, interleukin-1, interleukin-6, interleukin-8, and macrophage chemotactic protein-1. Studies concerning the effects of bacterial products on HPMCs are scarce and have not yielded conclusive results.
Methods:
Growth-arrested HPMC monolayers were prepared from cell suspensions obtained by enzymatic disaggregation of small pieces of omentum. They were incubated for 24 hours with heat-killed E. coli (ATCC 25922), heat-killed staphylococci (ATCC 25933), or E. coli lipopolysaccharide, and the release of various cytokines in the culture media was measured by radioimmunoassays or enzyme-linked immunosorbent assays. Results were expressed as mean +/- standard error of the mean in picograms per milliliter of supernatant and analyzed with the Wilcoxon test; p values of less than 0.05 were considered significant.
Results:
Baseline production of interleukin-6, interleukin-8, the chemokine "regulated upon activation, normal T cell expressed and secreted" (RANTES), and macrophage chemotactic protein-1 varied widely from one omental preparation to the other. E. coli increased the release of these mediators: from 1206 +/- 316 pg/mL to 8480 +/- 2189 pg/mL for interleukin-6, from 285 +/- 58 pg/mL to 3164 +/- 1053 pg/mL for interleukin-8, from 7 +/- 5 pg/mL to 684 +/- 264 pg/mL for RANTES, and from 2212 +/- 346 pg/mL to 7726 +/- 1473 pg/mL for macrophage chemotactic protein-1. Heat-killed staphylococci did not alter significantly the production of RANTES or macrophage chemotactic protein-1 but increased the production of the two other cytokines from 1325 +/- 389 pg/mL to 2206 +/- 523 pg/mL for interleukin-6 and from 318 +/- 70 pg/mL to 819 +/- 265 pg/mL for interleukin-8.
Conclusions:
The authors' results show that HPMCs are able to react to a direct stimulation with heat-killed microbes. They suggest that HPMCs, as well as resident macrophages, participate actively in the initiation and possibly in the modulation of intraperitonen inflammatory reactions.
Insights
Human peritoneal mesothelial cells (HPMCs) activate in response to heat-killed bacteria like E. coli and staphylococci. This suggests HPMCs play a role in initiating and modulating inflammatory responses within the peritoneum.
Area of Science:
- Immunology
- Cell Biology
- Microbiology
Background:
- Human peritoneal mesothelial cells (HPMCs) are known to produce inflammatory mediators when activated by cytokines.
- Limited research exists on the direct effects of bacterial products on HPMCs, with inconclusive findings.
Purpose of the Study:
- To investigate the direct activation of HPMCs by bacterial components from heat-killed Escherichia coli and staphylococci.
- To determine the release of specific cytokines and chemokines following direct bacterial stimulation.
Main Methods:
- HPMCs were isolated from omentum and cultured.
- Monolayers were incubated with heat-killed E. coli, heat-killed staphylococci, or E. coli lipopolysaccharide.
- Cytokine and chemokine release (IL-6, IL-8, RANTES, MCP-1) was measured using immunoassays.
Main Results:
- E. coli significantly increased the release of IL-6, IL-8, RANTES, and MCP-1.
- Heat-killed staphylococci significantly increased IL-6 and IL-8 release.
- Staphylococci did not significantly affect RANTES or MCP-1 production.
Conclusions:
- HPMCs demonstrate a direct response to stimulation by heat-killed microbes.
- HPMCs, alongside macrophages, actively contribute to the initiation and modulation of intraperitoneal inflammation.