Endotoxin is angiogenic

The formation of new blood vessels, angiogenesis, is an important event in inflammation, wound healing and tumour growth. Mediators produced by various cells when exposed to endotoxin include cytokines (tumour necrosis factor, interleukins 1 and 6, and basic fibroblast growth factor) which, it has been suggested, stimulate angiogenesis. The angiogenic effect of endotoxin (lipopolysaccharide, LPS) was studied in rats using the quantitative mesenteric window assay. Adult rats were injected intraperitoneally with Escherichia coli LPS (5 pg/ml-20,000 ng/ml) twice daily for 4.5 consecutive days and were sacrificed 14 days after the start of this treatment. An angiogenic response was observed at concentrations of > 2 ng/ml in a dose-dependent manner. No inflammatory cellular exudate was seen in the test tissue at the time of angiogenesis analysis. Suppressed body-weight gain, a marker of the systemic effect of LPS in the rat, was significant only at the highest dose tested. The data suggest that endotoxin-mediated neovascularization could be a component of inflammation and wound healing.