Expression of cell surface receptors and oxidative metabolism modulation in the clinical continuum of sepsis.

BACKGROUND: Infection control depends on adequate microbe recognition and cell activation, yet inflammatory response may lead to organ dysfunction in sepsis. The aims of this study were to evaluate cell activation in the context of sepsis and its correlation with organ dysfunction. METHODS: A total of 41 patients were prospectively enrolled: 14 with sepsis, 12 with severe sepsis and 15 with septic shock. A total of 17 healthy volunteers were included as a control group. Patients were admitted to the Intensive Care Units and Emergency Rooms of Hospital Sao Paulo (Federal University of Sao Paulo) and Hospital Santa Marcelina, Sao Paulo, Brazil. Toll-like receptor (TLR)2, TLR4, CD11b, CD11c and CD66b expression on neutrophil surfaces and oxidative metabolism measured by non-fluorescent dichlorofluorescein (DCFH) oxidation in neutrophils and monocytes, using whole blood, were evaluated using flow cytometry. Organ dysfunction was measured using the sepsis-associated organ failure assessment (SOFA) score. RESULTS: TLR2 expression on neutrophils was found to be downregulated in septic shock patients compared to healthy volunteers (p = 0.05). No differences were found in CD11b and CD11c expression. CD66b expression was increased in the patient group compared to the control group (p = 0.01). Neutrophil and monocyte oxidative burst was increased in septic patients compared to the control group at baseline and after stimulation with phorbol myristate acetate (PMA), formyl-methionyl-leucyl-phenylalanine (fMLP), lipopolysaccharide (LPS) and Staphylococcus aureus (p < 0.001 and p < 0.01, respectively, for neutrophils and monocytes in all tested conditions). A strong correlation was observed between neutrophil and monocyte oxidative metabolism. A SOFA score of 7 discriminated patients between survivors and non-survivors (area under the curve for reactive oxygen species (ROS) was 0.78; p = 0.02). ROS generation in patients with sepsis and septic shock with SOFA scores > 7 was higher than in patients with SOFA scores < 7, both in neutrophils and monocytes. However, oxidative burst in patients with sepsis was as high as in septic shock. CONCLUSION: Surface receptors expression on neutrophils may be modulated across the continuum of sepsis, and enhanced or decreased expression may be found depending on the receptor considered. ROS generation is upregulated both in neutrophils and monocytes in septic patients, and it is differently modulated depending on the stage of the disease and the stimuli used.

Lipopolysaccharide-cell interaction and induced cellular activation in whole blood of septic patients.

We used biotinylated LPS (LPSb) and flow cytometry to study LPS-monocyte interaction and LPS-induced cellular activation in whole blood from septic patients (SP). Expression of surface activation markers was evaluated on monocytes (HLA-DR) and T lymphocytes (CD69 and CD95), and intracellular TNF-alpha on monocytes. Saturating curve and kinetics of LPSb detection on monocytes were similar in SP and healthy volunteers (HV). LPSb bound to monocytes was detected after 5 min of incubation in both groups, with a more pronounced decay in SP. Monocytes from SP had a lower expression of HLA-DR as compared to HV, both constitutive and upon LPS stimulation. The proportion of monocytes producing TNF-alpha after LPS stimulus was higher in HV than SP (mean +/- SD = 25.2 +/- 14.2% and 2.2 +/- 2.6%, respectively, P < 0.001). LPS-induced CD69 on T CD8+ and CD8- lymphocytes was similar for patients and controls. Expression of CD95 on T lymphocytes was higher in SP as compared to HV on T CD8+ cells (GMFI, mean +/- SD = 22.3 +/- 14.6 and 8.6 +/- 5.0, respectively, P = 0.01) and CD8- cells (GMFI, mean +/- SD = 28.3 +/- 7.7 and 14 +/- 4.3 respectively, P < 0.001). Thus, monocytes and lymphocytes seem to respond differently to LPS in septic patients. Monocyte hyporesponsiveness appears not to be related to a decreased binding capacity of LPS, but rather to an impaired signal transduction.