Abstract 243: Roles of TNF alpha and MCP-1 in Type II Diabetes-induced Endothelial Dysfunction
Tumor necrosis factor alpha (TNF) is reported to underlie a component of vascular inflammation and ensuing endothelial dysfunction in diabetes, but the role of inflammatory cells in these events is unknown. Because TNF reportedly induces monocyte chemoattractant protein-1 (MCP-1) expression, we hypothesized that the interaction between TNF and MCP-1 contributes to the evolution of vascular inflammation in diabetes. To test this hypothesis, expression of TNF and MCP-1, and formation of nitrotyrosine (N-Tyr, an indicator of peroxynitrite production) were determined in isolated coronary arterioles (50–100um) from genetically modified mice with Type II diabetes (Leprdb) and the lean control heterozygotes (m Leprdb). Protein and mRNA expression of TNF, protein expression of MCP-1, and presence of N-Tyr were significantly increased in arterioles from Leprdb mice compared to those from m Leprdb. Immunofluorescence double labeling revealed the prominent localization of MCP-1 to endothelium (Von Willebrand factor) of arterioles and venules. MCP-1 also co-localized with macrophages (CD68) in the heart tissue. To determine if MCP-1 may be key to the vascular inflammation and ensuing endothelial dysfunction, we administered anti-MCP-1 (10 μg/day, 3 days, i.p., n=4; to block MCP-1 signaling) in the mice and then determined endothelial dilation in isolated, cannulated pressurized (60 cmH2O) arterioles. Anti-MCP-1 restored dilation to acetylcholine in Leprdb mice by 35±2% (P<0.05 vs Leprdb mice without treatment, 9.8±4%) but did not affect dilation in m Leprdb mice. To establish interactions between TNF and MCP-1, we administered anti-TNF (72hr treatment; 0.625mg/kg, i.p.) to block TNF signaling and determined effects on MCP-1 and oxidative stress. After anti-TNF administration, expression of MCP-1 was decreased and numbers of MCP-1 positive cells were markedly reduced in Leprdb mice. Moreover, anti-TNF prevented the formation of N-Tyr in Leprdb mice. These findings demonstrate that the endothelial dysfunction occurring in type II diabetes is the result of the effects of the inflammatory cytokine TNF and TNF related signaling, including the expression of MCP-1, which also furthers the oxidative stress.