Proteolytic destruction of functional proteins by phagocytes in human peritonitis

Background Besides phagocyte-derived oxidative autoaggression, proteolytic destruction of functional proteins in the peritoneal cavity may also be inv olved in the pathomechanism of secondary peritonitis. To evaluate the patte rn of proteolysis, 43 patients undergoing initial operation for acute perit onitis (n = 30) or scheduled abdominal lavages (Etappenlavage) for resoluti on of persistent peritonitis (n = 13) and 16 surgical patients with abdomin al exudation without peritonitis were enrolled in our study. Materials and methods Thirty blood samples and purulent exudates were taken simultaneously in each peritonitis group at the surgical interventions. Si xteen clear exudates were obtained li om patients with post-operative non-i nfectious irritations. The following parameters were measured: (a) elastase (from neutrophils) and cathepsin B (from monocytes/ macrophages); (b) alph a(1)-proteinase inhibitor (alpha(1)PI) and overall cysteine proteinase inhi bitor capacity; and (c) opsonic activity and degradation products of fibrin ogen, complement C3 and immunoglobulin IgG. Results Circulating levels of phagocyte proteinases and of alpha(1)PI were significantly elevated, whereas antigen concentrations and opsonic activity of C3 and IgG were slightly reduced in peritonitis patients compared to he althy volunteers. No degradation products were detectable in patients' bloo d. Discharge of phagocyte proteinases was even more pronounced in both type s of peritonitis exudates. Although most of the elastase was complexed with alpha(1)PI, active elastase and its specific fibrinogen split product was found along with significantly reduced inhibitory capacity for elastase and cysteine proteinases. Local opsonic activity was dramatically diminished b ecause of proteolytic degradation of C3 and IgG. Despite some phagocyte pro teinase release, no destruction of functional proteins was seen in clear ex udates. Conclusions Higher values of extracellularly released phagocyte proteinases concomitant with lower opsonin activity in exudates from patients with per sistent peritonitis can be taken as a further hint of the involvement of lo cal proteolysis-induced pathomechanisms in the development of lethal multip le organ failure, which occurred more frequently in patients with persisten t peritonitis (54%) than in those with acute peritonitis (27%).