Protective Effects of Thalidomide on High-Glucose-Induced Podocyte Injury through In Vitro Modulation of Macrophage M1/M2 Differentiation

Objective. It has been shown that podocyte injury represents an important pathological basis that contributes to proteinuria and eventually leads to kidney failure. High glucose (HG) activates macrophage polarization, further exacerbating HG-induced podocyte injury. Our previous study on diabetic nephropathy rats indicated that thalidomide (Tha) has renoprotective properties. The present study explored the effects of Tha on mRNA and protein expressions of inducible nitric oxide synthase (iNOS), tumor necrosis factor- (TNF-)alpha, mannose receptor (CD206), and arginase- (Arg-) 1 in HG-activated macrophages. iNOS and TNF-alpha are established as markers of classically activated macrophage (M1). CD206 and Arg-1 are regarded as markers of alternatively activated macrophages (M2). During the experiment, the supernatants of (HG)-treated and (Tha)-treated macrophages, designated as (HG) MS and (Tha) MS, were simultaneously collected and processed. TNF-alpha and interleukin- (IL-) 1 beta levels as well as protein expressions of nephrin and podocin in HG, (HG) MS, and (Tha) MS-cultured podocytes were evaluated. The results showed that compared to the 11.1 mM normal glucose (NG), the 33.3 mM HG-cultured RAW 264.7 cells exhibited upregulated iNOS and TNF-alpha mRNAs and protein expressions, and downregulated CD206 and Arg-1 expressions significantly (p<0.05). Tha 200 mu g/ml suppressed iNOS and TNF-alpha, and promoted CD206 and Arg-1 expressions significantly compared to the HG group (p<0.05). Furthermore, (HG) MS-treated podocytes showed an increase in TNF-alpha and IL-1 beta levels and a downregulation in nephrin and podocin expression significantly compared to NG-treated and HG-treated podocytes (p<0.05). The (Tha 200 mu g/ml) MS group exhibited a decrease in TNF-alpha and IL-1 beta level, and an upregulation in nephrin and podocin expressions significantly compared to the (HG) MS group (p<0.05). Our research confirmed that HG-activated macrophage differentiation aggravates HG-induced podocyte injuryin vitroand the protective effects of Tha might be related to its actions on TNF-alpha and IL-1 beta levels via its modulation on M1/M2 differentiation.