Pharmacological inhibition of autophagy by 3-MA attenuates hyperuricemic nephropathy

Abstract

Autophagy has been identified as a cellular process of bulk degradation of cytoplasmic components and its persistent activation is critically involved in the renal damage induced by ureteral obstruction. However, the role and underlying mechanisms of autophagy in hyperuricemic nephropathy (HN) remain unknown. In the present study, we observed that inhibition of autophagy by 3-methyladenine (3-MA) abolished uric acid-induced differentiation of renal fibroblasts to myofibroblasts and activation of transforming growth factor-β1 (TGF-β1), epidermal growth factor receptor (EGFR), and Wnt signaling pathways in cultured renal interstitial fibroblasts. Treatment with 3-MA also abrogated the development of HN in vivo as evidenced by improving renal function, preserving renal tissue architecture, reducing the number of autophagic vacuoles, and decreasing microalbuminuria. Moreover, 3-MA was effective in attenuating renal deposition of extracellular matrix (ECM) proteins and expression of α-smooth muscle actin (α-SMA) and reducing renal epithelial cells arrested at the G2/M phase of cell cycle. Injury to the kidney resulted in increased expression of TGF-β1 and TGFβ receptor I, phosphorylation of Smad3 and TGF-β-activated kinase 1 (TAK1), and activation of multiple cell signaling pathways associated with renal fibrogenesis, including Wnt, Notch, EGFR, and nuclear factor-κB (NF-κB). 3-MA treatment remarkably inhibited all these responses. In addition, 3-MA effectively suppressed infiltration of macrophages and lymphocytes as well as release of multiple profibrogenic cytokines/chemokines in the injured kidney. Collectively, these findings indicate that hyperuricemia-induced autophagy is critically involved in the activation of renal fibroblasts and development of renal fibrosis and suggest that inhibition of autophagy may represent a potential therapeutic strategy for HN.

Relationship between serum uric acid and clustering of cardiovascular disease risk factors and renal disorders among Shanghai population: a multicentre and cross-sectional study

“…It was demonstrated that 70% of urate eliminated occurs in the kidneys, and decreased eGFR would result in elevated levels of SUA 48. However, UA could induce oxidative stress, trigger activation of RAAS and inflammation, cause endothelial dysfunction, and thus subsequently lead to the decline in eGFR 35 49 50. The persistently high level of SUA predicts the high risk of developing CKD 51.…”

Delayed treatment with an autophagy inhibitor 3-MA alleviates the progression of hyperuricemic nephropathy

“…Epidemiological studies show that increased serum uric acid often precedes the deterioration of chronic kidney disease (CKD) 3 . Moreover, basic studies demonstrate that chronic uric acid injury to the kidney is sufficient to trigger renal tubular damage, interstitial fibrosis, glomerulosclerosis and urate crystal deposition, leading to hyperuricemic nephrology (HN) 1,4,5 . Therefore, further exploration of the mechanism leading to hyperuricemic nephrology will aid in the development of new strategy for treatment of HN.…”

“…Tubulointerstitial fibrosis is thought to be the primary pathogenesis for progressive HN [4][5][6] . Diseased proximal tubules act as a driving force for interstitial fibrosis through activation of autocrine and paracrine signals.…”

“…The disequilibrium of ECM modificators such as matrix metalloproteinases (MMPs) will affect depostion of ECM 15,16 . In addition, both hyperuricemia and tubule-secreted cytokines can activate STAT3 and NF-κB-signaling pathways, and induce the infiltration of macrophage and lymphocyte to the injured kidney, leading to aggravation of tubulointerstitial fibrosis 4,5 .…”

Targeting Autophagy in Breast Cancer

“…Common autophagy-inhibiting molecules could be categorized into four groups according to their mode of action: (1) Repressors of autophagosome formation, class III PI3K inhibitors, e.g., 3-methyladenine (3-MA), Wortmannin, LY294002, SAR405 and Viridiol that block the formation of autophagosome. (2) Repressors of lysosomal acidification: Lysosomotropic agents, such as Cloroquine (CQ), Hydroxychloroquine (HCQ), Lys0569, and Monensin prevent acidification of lysosomes and thus inhibit degradation of the cargo in the autophagosomes; (3) Inhibitors of autophagosome-lysosome fusion: Vacuolar-ATPase inhibitors, Bafilomycin and Concanamycin variants that interfere with the fusion of autophagosomes with lysosomes; (4) Silencers of transcription of autophagy-related genes: it has been demonstrated, indeed, that by means of siRNA-or miRNA-mediated silencing strategies, knockdown of autophagy-related genes can be achieved with subsequent inhibition of autophagic activity [74][75][76][77][78][79].…”