Early apoptosis of monocytes contributes to the pathogenesis of systemic inflammatory response and of bacterial translocation in an experimental model of multiple trauma

Summary The objective of this study was to investigate the occurrence of apoptosis of monocytes in an experimental model of multiple trauma and its probable correlation to bacterial translocation. Thirty‐two rabbits were applied in three groups: A, controls; B, myotomy of the right femur; and C, myotomy and fracture of the right femur. Blood was sampled for the estimation of endotoxins [lipopolysaccharide (LPS)], tumour necrosis factor (TNF)‐α, malondialdehyde (MDA) and isolation of peripheral blood mononuclear cells (PBMCs). PBMCs, derived after centrifugation over Ficoll, were incubated in flasks and apoptosis of non‐adherent lymphocytes and adherent monocytes was estimated after staining for Annexin‐V and flow cytometry. TNF‐α of supernatants of cultured monocytes was also determined. Tissue segments were cultured after death. Median survival of groups A, B and C was > 14, > 14 and 9·00 days, respectively. Apoptosis of lymphocytes in group C was higher than group A at 2, 4 and 48 h and of monocytes in group C higher than group A at 2 and 4 hours. LPS in group C was higher than group A at 2, 4 and 48 h. Apoptosis of lymphocytes and monocytes was correlated positively with serum TNF‐α and negatively with TNF‐α of monocyte supernatants. Cultures of organ segments of group A were sterile. Pseudomonas aeruginosa was isolated from liver, lung and spleen in five animals in group B (45·45%) and in six in group C (54·54%). Early apoptosis of blood monocytes supervened after multiple trauma; the phenomenon was accompanied by apoptosis of blood lymphocytes and subsequent bacterial translocation.