Lupus nephritis (LN) leads to chronic kidney disease (CKD) through progressive fibrosis. Mycophenolate inhibits inosine monophosphate dehydrogenase and is a standard treatment for LN. The mammalian or mechanistic target of rapamycin (mTOR) pathway is activated in LN. Rapamycin inhibits mTOR and is effective in preventing kidney transplant rejection, with the additional merits of reduced incidence of malignancies and viral infections. The effect of mycophenolate or rapamycin on kidney fibrosis in LN has not been investigated. We investigated the effects of mycophenolate and rapamycin in New Zealand Black and White first generation (NZB/W F1) murine LN and human mesangial cells (HMCs), focusing on mechanisms leading to kidney fibrosis. Treatment of mice with mycophenolate or rapamycin improved nephritis manifestations, decreased anti-double stranded (ds) DNA antibody titer and reduced immunoglobulin G (IgG) deposition in the kidney. Both mycophenolate and rapamycin, especially the latter, decreased glomerular mTOR Ser 2448 phosphorylation. Renal histology in untreated mice showed mesangial proliferation and progressive glomerulosclerosis with tubular atrophy, and increased expression of transforming growth factor β1 (TGF-β1), monocyte chemoattractant protein-1 (MCP-1), α-smooth muscle actin (α-SMA), fibronectin (FN) and collagen. Both mycophenolate and rapamycin ameliorated the histopathological changes. Results from in vitro experiments showed that both mycophenolate and rapamycin decreased mesangial cell proliferation and their binding with anti-dsDNA antibodies. Mycophenolate and rapamycin also down-regulated mTOR and extracellular signal-regulated kinase (ERK) phosphorylation and inhibited fibrotic responses in mesangial cells that were induced by anti-dsDNA antibodies or TGF-β1. Our findings suggest that, in addition to immunosuppression, mycophenolate and rapamycin may reduce fibrosis in LN, which has important implications in preventing CKD in patients with LN.

Diabetic kidney disease (DKD) is among the most common complications of diabetes mellitus (DM), and remains the leading cause of end-stage renal diseases (ESRDs) in developed countries, with no definitive therapy yet available. It is imperative to decipher the exact mechanisms underlying DKD and identify novel therapeutic targets. Burgeoning evidence indicates that long non-coding RNAs (lncRNAs) are essential for diverse biological processes. However, their roles and the mechanisms of action remain to be defined in disease conditions like diabetes and DKD. The pathogenesis of DKD is twofold, so is the principle of treatments. As the underlying disease, diabetes per se is the root cause of DKD and thus a primary focus of therapy. Meanwhile, aberrant molecular signaling in kidney parenchymal cells and inflammatory cells may directly contribute to DKD. Evidence suggests that a number of lncRNAs are centrally involved in development and progression of DKD either via direct pathogenic roles or as indirect mediators of some nephropathic pathways, like TGF-β1, NF-κB, STAT3 and GSK-3β signaling. Some lncRNAs are thus likely to serve as biomarkers for early diagnosis or prognosis of DKD or as therapeutic targets for slowing progression or even inducing regression of established DKD. Here, we elaborated the latest evidence in support of lncRNAs as a key player in DKD. In an attempt to strengthen our understanding of the pathogenesis of DKD, and to envisage novel therapeutic strategies based on targeting lncRNAs, we also delineated the potential mechanisms of action as well as the efficacy of targeting lncRNA in preclinical models of DKD.

The regulatory role of a novel miRNA, miR-378 , was determined in the development of fibrosis through repression of the MAPK1 pathway, miR-378 and fibrotic gene expression was examined in streptozotocin (STZ)-induced diabetic mice at 18 weeks or in unilateral ureteral obstruction (UUO) mice at 7 days. miR-378 transfection of proximal tubular epithelial cells, NRK52E and mesangial cells was assessed with/without endogenous miR-378 knockdown using the locked nucleic acid (LNA) inhibitor. NRK52E cells were co-transfected with the mothers against decapentaplegic homolog 3 (SMAD3) CAGA reporter and miR-378 in the presence of transforming growth factor-β (TGF-β1) was assessed. Quantitative polymerase chain reaction (qPCR) showed a significant reduction in miR-378 ( P <0.05) corresponding with up-regulated type I collagen, type IV collagen and α-smooth muscle actin (SMA) in kidneys of STZ or UUO mice, compared with controls. TGF-β1 significantly increased mRNA expression of type I collagen ( P <0.05), type IV collagen ( P <0.05) and α-SMA ( P <0.05) in NRK52E cells, which was significantly reduced ( P <0.05) following miR-378 transfection and reversed following addition of the LNA inhibitor of endogenous miR-378 . Overexpression of miR-378 inhibited mesangial cell expansion and proliferation in response to TGF-β1, with LNA– miR-378 transfection reversing this protective effect, associated with cell morphological alterations. The protective function of MAPK1 on miR-378 was shown in kidney cells treated with the MAPK1 inhibitor, selumetinib, which inhibited mesangial cell hypertrophy in response to TGF-β1. Taken together, these results suggest that miR-378 acts via regulation of the MAPK1 pathway. These studies demonstrate the protective function of MAPK1, regulated by miR-378 , in the induction of kidney cell fibrosis and mesangial hypertrophy.

The molecular mechanisms of endothelin (ET)-dependent activation of extracellular signal-regulated kinase (ERK)and p38 mitogen-activated protein (MAP) kinase were studied in rat and human renal glomerular mesangial cells. ET-1 induced a rapid and transient activation of Ras in renal mesangial cells, which was dependent upon the formation of the Shc/Grb2/Sos1 signalling complex and resulted in transient ERK activation. We have observed that Pyk2, a calcium-dependent cytoplasmic tyrosine kinase, was expressed in human renal mesangial cells and was tyrosine phosphorylated after ET-1 treatment. ET-1-induced activation of p38 MAPK pathway (but not ERK pathway) was inhibited in human and in rat glomerular mesangial cells expressing dominant-negative form of Pyk2, suggesting the engagement of Pyk2 in ET-1-mediated activation of p38 MAP kinase cascade. Contractive responsiveness of renal mesangial cells was shown to depend on activation of the p38 MAP kinases. Thus, p38 MAP kinase stimulation could perhaps partially account for ET-1 contractive properties, whereas ET-1-induced cell proliferation occurs primarily via Ras-dependent activation of the ERK.

1. This study examined the influence of H 2 O 2 , interleukin-6 and platelet-derived growth factor on the proliferation of rat mesangial cells. Mesangial cells were exposed to either a single pulse or three daily pulses of H 2 O 2 (10 −8 -10 −4 mol/l), alone or in combination with interleukin-6 (5 ng/ml) and/or platelet-derived growth factor (10 ng/ml). Proliferation was assessed after 24 h and 72 h of incubation using [ 3 H]thymidine incorporation and cell counts. 2. Although one pulse of H 2 O 2 had no significant effect on mesangial cell proliferation, three daily pulses of 10 −6 mol/l H 2 O 2 resulted in a significant increase in [ 3 H]thymidine incorporation of 31 (52.6, 10.3)% (median and 75th-25th interquartile range) ( P <0.001). Both interleukin-6 and platelet-derived growth factor were also mitogenic to mesangial cells, [ 3 H]thymidine incorporation increasing by 19 (36.7, −6.7)% ( P <0.05) and 53.5 (107, 21.9)% ( P <0.001), respectively. The mitogenic effect of interleukin-6 was enhanced by 10 −6 mol/l H 2 O 2 [49.9 (77.7, 12.3)%] ( P <0.01), whereas the addition of 10 −6 mol/l H 2 O 2 to platelet-derived growth factor resulted in a summated increase in [ 3 H]thymidine incorporation of 82.7 (113, 57.4)% ( P <0.001). Incubation with all three substances simultaneously resulted in down-regulation of growth compared with H 2 O 2 plus platelet-derived growth factor by 55.4 (77.7, 103)% ( P <0.05). 3. These findings suggest that reactive oxygen species may play a major role in determining the mesangial cell proliferation that occurs in certain forms of glomerulonephritis, acting either alone or in combination with other growth factors.