TGF-β1/Smad Signalling in Proliferative Glomerulonephritis Associated with Autoimmune Diseases

Glomerulonephritis is a common cause of chronic kidney disease, which has emerged as a major cause of end-stage renal disease. Autoimmune diseases, such as Systemic Lupus Erythematosus (SLE) and ANCA-associated vasculitis (AAV) are often associated with proliferative glomerulonephritis. Transforming growth factor-β1 (TGF-β1) is a cytokine with pleiotropic effects in chronic renal diseases, based on in vivo and in vitro studies. The Smad-dependent signalling pathway plays an important role in the regulation of renal fibrosis (excessive production of extracellular matrix [ECM]) and inflammation. However, clinical trials targeting TGF-β1 have presented disappointing results, suggesting that the downstream signalling is quite complex. The diversity of the effects may associate with the interactions between TGF-β1 signalling and other downstream signalling, as well as the different cellular responses, which TGF-β1 promotes. Recently, macrophage chemoattract and epigenetic effects have also been identified as new mechanisms, wherefore TGF-β1/Smad signalling mediates renal injury. This review provides an overview of the role of TGF-β1/Smad signalling pathway from in vivo and in vitro studies in the pathogenesis of glomerulonephritis and particularly in proliferative glomerulonephritis, which is associated with autoimmune diseases.