Endotoxin inhibits heat shock protein 70 (HSP70) expression in peripheral blood mononuclear cells of patients with severe sepsis

Objective:To investigate the ex vivo endotoxin-inducible heat shock protein 70 (HSP70) expression in the peripheral blood mononuclear cells (PBMC) of patients with severe sepsis in order to assess the capacity of this potenti ally protective response during systemic inflammation. Design: Prospective observational study in consecutive patients with severe sepsis and healthy blood donors. Setting: Surgical intensive care unit in a university hospital. Patients and Participants: Eleven patients with the diagnosis of severe sep sis, one patient who had recovered from severe sepsis and 13 healthy blood donors. Interventions: None. Measurements and results: We studied the inducibility of HSP70 expression i n the PBMC of patients with severe sepsis and healthy blood donors ex vivo. Human whole blood was incubated with variable lipopolysaccharide (LPS from Salmonella minnesota Re 595) concentrations (0; 0.1; 10; 100 ng/ml) for di fferent periods of time (0.5; 2; 4; 10 h). The PBMC were separated by Ficol l density gradient and then disrupted by hypotonic lysis. HSP70 was measure d by means of enzyme-linked immunosorbent assay (ELISA). Mit found a LPS do se- and time-dependent inhibition of ex vivo HSP70 expression in the PBMC o f both patients with severe sepsis and healthy individuals. However, the le vels of HSP70 expression in patients were significantly lower compared to t hose of healthy individuals at all LPS concentrations and incubation times. On average, HSP70 expression in the PBMC of healthy controls was 2.8 (rang e 1.2-3.9) times higher than in patients. HSP70 expression was inducible by thermal heat shock in the PBMC of both patients and healthy individuals. Conclusions: Endotoxin inhibits HSP70 expression in PBMC ex vivo. In vivo, the suppression of HSP70 expression induced by endotoxin and high levels of proinflammatory cytokines may contribute to the cellular dysfunction of im munocompetent cells concerning antigen presentation, phagocytosis and antib ody production associated with decreased resistance to infectious insults d uring severe sepsis.