Background  

We have demonstrated that macrophages/microglia were activated during post-ischemic inflammation in a mouse model of ischemic retinal neovascularization, and that the angiogenesis induced by tumor necrosis factor- (TNF-) appeared to be modulated through such angiogenic factors as interleukin-8 (IL-8), vascular endothelial growth factor (VEGF), and basic fibroblast growth factor (bFGF) in microvascular endothelial cells. We have extended these studies, and investigated whether TNF- is localized in macrophages/microglia in the mouse model of retinal neovascularization, and whether TNF- can induce angiogenic factors in retinal glial cells.

Methods  

C57BL/6 J pups were placed in a 75% oxygen environment on postnatal day 7 (P7) for 5 days and then returned to room air. The co-localization of TNF- with macrophages/microglia in the ischemic retina was examined by fluorescent immunohistochemistry. Bovine retinal glial cells were isolated for Northern blot analysis to quantify the expression levels of monocyte chemotactic protein-1 (MCP-1), IL-8, bFGF, and VEGF.

Results  

Double staining of retinas revealed that the TNF- expression level was enhanced in macrophages/microglia 4 days after the hypoxia. Cellular mRNA levels of MCP-1, IL-8, and bFGF, but not VEGF, were increased after treating retinal glial cells with TNF- (100 U/ml).

Conclusions  

The results indicate that TNF- is produced by activated macrophages/microglia and may participate in retinal neovascularization during post-ischemic inflammation through the induction of potent angiogenic factors in an autocrine or paracrine manner.