Neutrophils and reactive oxygen intermediates mediate glucan-induced pulmonary granuloma formation through the local induction of monocyte chemoattractant protein-1.

Monocyte chemoattractant protein-1 (MCP-1), which is required for full development of glucan-induced granulomas, in the rat, is expressed in the walls of blood vessels at sites of glucan embolization. Early (1 hour) vessel wall expression of MCP-1 is temporally and anatomically linked to the transient accumulation of neutrophils, even though these cells are not present within definitive lesions. To ascertain the potential pathophysiologic role of neutrophils in glucan-induced granuloma formation, rats were neutrophil-depleted using specific antiserum. There was a marked reduction in mean granuloma size and number in neutrophil-depleted animals when compared with neutrophil-sufficient controls. To determine potential mechanisms through which neutrophils may participate in granuloma formation, the antioxidant enzymes superoxide dismutase and catalase were administered to neutrophil-sufficient animals that had received glucan. Superoxide dismutase treatment did not reduce granuloma formation, whereas catalase treatment resulted in decreased granuloma size, suggesting that H2O2 plays an important role in this process. The local expression of MCP-1 mRNA and protein, as determined by in situ hybridization and immunohistochemical analysis, respectively, was decreased in both neutrophil-depleted and catalase-treated animals but not in superoxide dismutase-treated rats. Quiescent human umbilical vein endothelial cells incubated with either H2O2 or activated neutrophils secreted MCP-1. These data indicate that neutrophils and H2O2 are required for both full granuloma development and early blood vessel wall-associated MCP-1 expression after glucan infusion. These in vivo data, coupled with in vitro data that indicate that both catalase-sensitive reagent H2O2 and neutrophil-derived reactive oxygen intermediates (ie, H2O2) can induce MCP-1 secretion by human umbilical vein endothelial cells, support the hypothesis that neutrophils and neutrophil-derived products (H2O2) influence granuloma formation through induction of local MCP-1 expression.

The membrane attack complex of complement induces interleukin-8 and monocyte chemoattractant protein-1 secretion from human umbilical vein endothelial cells.

Cell surface assembly of the membrane attack complex (MAC) of complement occurs in a variety of pathophysiological settings. Depending upon the density and size distribution of pores formed by the MAC and the functional integrity of membrane regulators of complement activation, the MAC can either cause direct cell lysis or transduce cell activation. We have examined the functional capacity of sublytic concentrations of MAC to induce the secretion of specific alpha- and beta-chemokines from human umbilical vein endothelial cells (HUVECs). Endothelial cell activation by the MAC has particular relevance to complement-dependent inflammatory processes including ischemia-reperfusion injury and acute lung injury. Assembly of sublytic concentrations of the MAC on HUVECs resulted in the sequential secretion of both neutrophil and monocyte chemotactic activities. Analysis of conditioned medium from MAC-bearing HUVECs revealed that the neutrophil chemotactic activity was largely attributable to interleukin (IL)-8, whereas the monocyte chemotactic activity, which was detected later (peak at 8 hours versus 4 hours), was largely attributable to MCP-1. This temporal pattern of MAC-induced secretion of IL-8 and MCP-1 was confirmed using IL-8- and MCP-1-specific enzyme-linked immunosorbent assays. Northern hybridization analysis of HUVECs revealed that MAC deposition was accompanied by an increase in IL-8 and MCP-1 mRNA levels. These data indicate that assembly of sublytic concentrations of the MAC on HUVECs can induce the sequential secretion of both neutrophil and monocyte chemotactic activities and that the former is largely attributable to IL-8 whereas the latter is largely attributable to MCP-1.

Factors influencing the efficacy of light cured materials for earmoulds.

This work was undertaken to investigate two systems for producing light-cured earmoulds, in order to evaluate the factors which influence the efficacy of such procedures. It was shown that there were variations in light intensity in the light boxes, and that the depth and age of gel in which curing takes place was important. Degree of cure of the materials was assessed by hardness measurements for hard materials and resistance to tearing for hard materials. Light-cured technology has great potential for the rapid production of earmoulds.