Soy protein diet inhibits zymosan induced monocyte migration

Atherosclerosis has been recognized as a chronic inflammatory disease. Recently, we showed reduced atherosclerotic lesions in a hyperlipidemic mouse model fed isoflavone‐free soy protein diet (SPI − ) compared to casein (CAS)‐fed mice, despite unchanged serum lipid levels. However, the molecular mechanisms contributing to the atheroprotective effect of soy‐based diets are not clear. We hypothesize that soy protein/peptides (SPI − ) exert their protective effect by inhibiting monocyte migration. To address this hypothesis, a zymosan‐induced acute peritonitis inflammation model in apoE−/− mouse was developed. Dose response studies showed zymosan at 100 μg/mouse is sufficient to induce inflammatory cell migration including neutrophils and monocytes. ELISA analyses showed levels of MCP‐1, IP‐10, IL‐6, and TNF‐α were high in peritoneal exudates in zymosan‐injected mice. Further, quantitative RT‐PCR analyses showed expression of inflammatory cytokine (TNF‐α, IL‐6) and chemokines (MCP‐1, Gro, MCP‐1 and IP‐10) were upregulated in peritoneal exudates cells in zymosan‐injected mice. Interestingly, dietary SPI − inhibited zymosan‐induced recruitment of inflammatory cells and chemokines and cytokine expression. These findings suggest that the atheroprotective effect of isoflavone free soy diet is mediated, in part, by blocking inflammatory cell migration associated with atherosclerosis. USDA‐CRIS‐6251‐5100002‐06S.