Mcl-1 correlates with reduced apoptosis in neutrophils from patients with sepsis.

BACKGROUND

Reduction of PMN apoptosis during sepsis contributes to the pathogenesis of multiple organ failure. Differential expression of Bcl-2 proteins, which participate in apoptosis regulation, may be responsible for the dysbalanced apoptosis seen in neutrophils from septic patients. In this study, expression of Mcl-1, Bid, Bcl-2, and Bax were investigated in septic neutrophils.

STUDY DESIGN

PMN (1 x 10(6)/mL) from septic patients (n = 16) or healthy volunteers (n = 10) were incubated with either lipopolysaccharide (1 microg/mL), agonistic CD95 antibody (100 ng/mL), or medium for 16 hours. Apoptosis was quantified in FACS after propidium iodine staining. Mcl-1, Bid, Bcl-2, and Bax mRNA expression was detected by reverse transcriptase-polymerase chain reaction and protein determined by Western blot analysis.

RESULTS

Spontaneous apoptosis was significantly reduced in PMN from septic patients (28.8% versus 64.0% in controls). Mcl-1 protein levels decreased in patients after 16 hours but remained stable in controls. Mcl-1 mRNA was found in freshly isolated PMN from controls and patients but remained elevated only in patients. Bid protein level decreased significantly in control PMN undergoing apoptosis but differences were less prominent in septic patients. Bid mRNA was detected only in freshly isolated PMN. No Bcl-2 mRNA or protein was detected in neutrophils from patients or controls, and detectable Bax protein and mRNA levels remained unchanged in all samples.

CONCLUSIONS

Alterations of Bid and Mcl-1 protein in neutrophils may reflect the level of apoptosis. The upregulation of Mcl-1 mRNA in patients with sepsis suggests an active role for Mcl-1 in regulation of apoptosis during sepsis; Bax remains unchanged.