Abstract

Background: Patients undergoing hemodialysis (HD) have a greater prevalence of aortic valve calcification and aortic valve stenosis (AS). High prevalence and rapid progression of AS have been reported in patients undergoing HD. However, the precise mechanism of the relationship between HD treatment and rapid development of AS is still unknown. Several findings suggest a pivotal role for oxidative stress in the progression and acceleration of atherosclerosis in patients undergoing HD. A considerable number of human diseases have an inflammatory component, and a key mediator of immune activation and inflammation is inducible nitric oxide synthase (iNOS). Overexpressed iNOS has been implicated in numerous pathogenetic processes, including coronary plaque destabilization. To elucidate the role of iNOS in the aortic valve of patients with AS, we studied its presence in aortic valve specimens from patients with AS undergoing HD. Methods: We enrolled 32 patients undergoing HD and 42 patients not undergoing HD who had severe AS and underwent AVR. Valve samples were analyzed immunohistochemically with antibodies against macrophages, microvessels, iNOS and 4-hydroxy-2-nonenal (4-HNE), an index of lipid peroxidation. Immunoreactivity was quantified with computer-aided polarimetry. Double immunostaining was also performed to identify cell types that stained positive for iNOS. Results: Quantitative analysis demonstrated that macrophage-, iNOS-, and 4-HNE-positive areas, as well as the number of microvessels, were significantly higher in patients with AS undergoing HD (macrophages, P <0.001; microvessels, P <0.05; 4-HNE, P <0.05; iNOS , P <0.001). iNOS-positive areas were positively correlated with 4-HNE-positive areas (R=0.71, P <0.0001). Double immunostaining for both iNOS and macrophages identified iNOS-positive cells as macrophages. Conclusions: These findings indicate that accumulation of iNOS in macrophages may increase oxidative stress and contribute to the rapid progression of AS in patients undergoing HD.