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Heat shock protein 27 inhibits apoptosis in human neutrophils
1Department of Surgery, University of Massachusetts Medical School, Worcester, Massachusetts, 01655, USA.
Background:
Prolonged neutrophil(PMN) survival has been implicated in tissue injury following sepsis. A variety of bacterial products have been identified which inhibit PMN apoptosis including lipopolysaccharide(LPS). Extracellular heat shock proteins(Hsp) have recently been identified as potent regulatory signals for the innate immune system during the inflammatory response. We hypothesized that Hsp 27 can affect PMN phenotype with respect to apoptosis and cytokine profile.
Materials And Methods:
PMN were isolated from the peripheral blood of healthy human volunteers by red blood cell sedimentation and gradient centrifugation. Cells were placed in media and cultured for 18 h with and without recombinant human Hsp 27 at various concentrations. In parallel experiments, PMN were stimulated with LPS, a known inhibitor of PMN apoptosis, for comparison. Apoptosis was quantified using annexin V and propidium iodide staining with flow cytometric analysis. Culture supernatants were assayed for secretion of TNF-alpha, IL-10, and IL-12.
Results:
Hsp 27 significantly inhibits PMN apoptosis [control; 81.8 +/- 3.6%, vs Hsp 27, 60.4 +/- 4.1% p < 0.05]. The reduction is similar to that signaled by LPS, alone. Together their effect is not synergistic. The Hsp 27 response is dose-dependent. Hsp 27 does not induce secretion of TNF-alpha, IL-10, or IL-12, whereas LPS does signal IL-12 and TNF-alpha secretion.
Conclusion:
These data demonstrate that exogenous Hsp 27 may play a role in neutrophil-mediated tissue injury during trauma and sepsis via its ability to inhibit neutrophil apoptosis. However, Hsp 27 does not significantly alter neutrophil phenotype with respect to cytokine production profile.
Insights
Heat shock protein 27 (Hsp 27) inhibits neutrophil apoptosis, prolonging their survival and potentially contributing to tissue injury in sepsis. Hsp 27 does not significantly alter neutrophil cytokine profiles.
Area of Science:
- Immunology
- Cell Biology
- Inflammation Research
Background:
- Prolonged neutrophil survival is linked to tissue injury in sepsis.
- Bacterial products like lipopolysaccharide (LPS) inhibit neutrophil apoptosis.
- Extracellular heat shock proteins (Hsps) are emerging signals in innate immunity.
Purpose of the Study:
- To investigate the effect of Hsp 27 on neutrophil (PMN) apoptosis.
- To determine if Hsp 27 influences PMN cytokine secretion profile.
Main Methods:
- Human neutrophils were isolated and cultured with recombinant Hsp 27 or LPS.
- Apoptosis was measured using annexin V and propidium iodide staining via flow cytometry.
- Cytokine secretion (TNF-alpha, IL-10, IL-12) was analyzed in culture supernatants.
Main Results:
- Hsp 27 significantly inhibited PMN apoptosis in a dose-dependent manner.
- The anti-apoptotic effect of Hsp 27 was comparable to LPS but not synergistic.
- Hsp 27 did not induce secretion of TNF-alpha, IL-10, or IL-12, unlike LPS.
Conclusions:
- Exogenous Hsp 27 may contribute to neutrophil-mediated tissue injury by inhibiting apoptosis.
- Hsp 27 does not significantly alter the neutrophil cytokine production profile.