Mitochondrial membrane potential and apoptosis peripheral blood monocytes in severe human sepsis

Reduced mitochondrial membrane potential (Delta psim), which is considered as an initial and irreversible step towards apoptosis, as well as cell death regulating proteins, such as Fas, Hsp70, or Bcl-2, may play an important role in sepsis. We studied the relationship between sepsis severity and peripheral blood monocyte Delta psim, cell death (necrosis and apoptosis), soluble Fas ligand, Hsp70, and Bcl-2 expression over time in 18 patients with sepsis, and compared these data with those of a group of 17 healthy control subjects. All measurements were performed within 3 d of the onset of severe sepsis (T1), then 7 to 10 d later (T2), and finally at hospital discharge (T3). Delta psim was expressed as the percent monocytes with altered Delta psim (%Delta psim). Patients with sepsis had greater %Delta psim at T1 and T2 but not at T3 (14.6 +/- 2.6% and 15.9 +/- 2%, respectively, versus control 6.6 +/- 0.2%, p < 0.01). Septic patients exhibited greater cell death in their monocytes and had greater Hsp70 expression only at T1. Bcl-2 levels were similar in septic and control subjects. Comparing survivors with non-survivors of sepsis, nonsurvivors had a greater %Delta psim at T1 (26.4 +/- 5.3% versus 10.1 +/- 2.7%, p < 0.01) and a significant decrease in Bcl-2 expression, whereas no difference was found in Hsp70 levels. These results indicate that mitochondrial dysfunction and subsequent cell death occur in severe sepsis and suggest that %Delta psim is a marker of severity in human sepsis.