Reticuloendothelial failure in chronic intra-abdominal sepsis: the role of opsonic fibronectin

Fibronectin blocks p38 and jnk activation by cyclic strain in Caco-2 cells

Diverse repetitive forces deform the intestinal epithelium and basement membrane. Such repetitive deformation induces intestinal epithelial proliferation, differentiation, and intracellular signaling. Although at least some deformation-induced signals probably involve integrins, the matrix-dependence of these signals is poorly understood. We compared rapid strain activation of p38 and jnk in human Caco-2 intestinal epithelial cells cultured on collagen I, collagen IV, laminin, and tissue fibronectin. These signals were inhibited in cells on a fibronectin substrate, but activated by strain on collagens and laminin. Furthermore, adding 300 microg/ml plasma fibronectin (approximately the concentration found in plasma) to the culture medium inhibited strain activation of p38 and jnk in cells cultured on collagen. Since tissue and plasma fibronectin levels vary in acute or chronic inflammatory or infectious conditions, these results suggest that tissue or plasma fibronectin may modulate the intestinal epithelial response to repetitive deformation.

Effect of acute starvation on plasma fibronectin response to sepsis

There is evidence that undernutrition may contribute to the reduction in plasma fibronectin concentration and the depression of the reticuloendothelial (RE) system associated with severe sepsis. We have investigated the effects of fasting, surgical trauma and sepsis on plasma fibronectin concentrations and RE function. In experiment 1, plasma fibronectin was measured in rabbits (n = 14) before and 48 h after fasting. In experiment 2, sepsis was induced by devascularization of the appendix in animals on a normal diet (sepsis group, n = 7). A third group of animals underwent only a laparotomy (laparotomy only group, n = 7). Plasma fibronectin concentrations and the blood clearance and organ distribution of 99mtechnetium tin colloid (TTC) were measured 24 h after operation. Compared with pooled reference plasma, fasting in experiment 1 resulted in a reduction in mean(s.e.m.) plasma fibronectin concentration from 98(1.5) per cent to 86(3.7) per cent (T = 2, P less than 0.005). Mean(s.e.m.) plasma fibronectin concentration was raised in the sepsis group to 117(4.6) per cent, compared with 97(2.5) per cent in the laparotomy only group (U = 5, P less than 0.02), but there was no such increase in the fasting and sepsis group. There was a delay in the blood clearance and reduced hepatic uptake of TTC in both sepsis groups. The dissociation between fibronectin concentrations and RE function in animal models of sepsis casts doubt on the importance of fibronectin in RE function.