Repeated Systemic Escherichia coli Infection Enhances Anti-oxidant Response in Hypercholesterolemic Mice Inducing Cardiovascular Inflammation

Abstract

It has been well established that diet high in cholesterol and saturated fatty acids could significantly elevate plasma cholesterol levels and also increase the risk of cardiovascular diseases. We hypothesize that repeated systemic Escherichia coli (E. coli) in conjunction with hypercholesterolemia, leads to development of oxidative stress that may affect the development and progression of inflammatory CVD. Swiss albino mice (4 weeks old) were randomly assigned to high cholesterol diet (HCD) or normal laboratory diet (NLD) groups. At 10 weeks of age, mice were inoculated intravenously with E. coli or vehicle for 24 weeks. Serum cholesterol, low density lipoprotein, C reactive protein levels, blood glucose level and selective antioxidant enzymes throughout the systemic infection period in murine aorta, heart and liver during hypercholesterolemia, were examined. Serum cholesterol levels were elevated in HCD-fed mice, compared to NLD. The blood colony forming units (CFU) of E. coli suggested persistence of systemic infection. The antioxidant enzyme levels were elevated in E. coli infected groups as compared to controls. The myeloperoxidase content of aortic tissue was significantly higher in all groups infected with E. coli. Our study suggests that during hypercholesterolemia, repeated systemic E. coli infection induces an endogenous antioxidant response that serves to modulate vascular inflammation leading to cardiovascular diseases.