Transforming growth factor-β1 hyperexpression in African American end-stage renal disease patients

End-stage renal disease (ESRD) is more frequent in African Americans (blacks) compared to Caucasian Americans (whites). Identification of remediable causes of the increased prevalence has the potential to reduce the excess burden of ESRD. Because renal fibrosis is a correlate of progressive renal failure and a dominant feature of ESRD, and because transforming growth factor-beta(1) (TGF-beta(1)) can induce fibrosis and renal insufficiency, we explored the hypothesis that TGF-beta(1) hyperexpression is more frequent in black ESRD patients compared to white ESRD patients. Our postulate was tested by determining circulating levels of TGF-beta(1) protein in the sera of 56 black and 42 white ESRD patients treated by chronic hemodialysis. A solid-phase sandwich enzyme-linked immunosorbent assay, specific for TGF-beta(1), was used to quantify TGF-beta(1) levels in the ESRD cohort. Additional cytokines implicated in tissue repair/remodeling, interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-alpha), were also measured. Our investigation demonstrated a significantly higher concentration of TGF-beta(1) protein but not that of IL-6 or TNF-alpha in blacks compared to whites. Our observation that TGF-beta(1) is hyperexpressed in black ESRD patients suggests a mechanism for the increased prevalence of renal failure (since TGF-beta(1) hyperexpression can result in renal insufficiency in experimental models) among the black population.