Inhibition of Akt/mTOR/p70S6K Signaling Activity With Huangkui Capsule Alleviates the Early Glomerular Pathological Changes in Diabetic Nephropathy

Abstract

Huangkui capsule (HKC), a Chinese modern patent medicine extracted from Abelmoschus manihot (L.) medic, has been widely applied to clinical therapy in the early diabetic nephropathy (DN) patients. However, it remains elusive whether HKC can ameliorate the inchoate glomerular injuries in hyperglycemia. Recently the activation of phosphatidylinositol-3-kinase (PI3K)/serine-threonine kinase (Akt)/mammalian target of rapamycin (mTOR) signaling and its downstream regulator, 70-kDa ribosomal protein S6 kinase (p70S6K), play important roles in the early glomerular pathological changes of DN including glomerular hypertrophy, glomerular basement membrane (GBM) thickening and mild mesangial expansion. This study thereby aimed to clarify therapeutic effects of HKC during the initial phase of DN and its underlying mechanisms. Fifteen rats were randomly divided into 3 groups: the normal group, the model group and the HKC group. The early DN model rats were induced by unilateral nephrectomy combined with intraperitoneal injection of streptozotocin, and administered with either HKC suspension or vehicle after modeling and for a period of 4 weeks. Changes in the incipient glomerular lesions-related parameters in urine and blood were analyzed. Kidneys were isolated for histomorphometry, immunohistochemistry, immunofluorescence and Western blotting (WB) at sacrifice. In vitro, murine mesangial cells (MCs) were used to investigate inhibitory actions of hyperoside (HYP), a bioactive component of HKC, on cellular hypertrophy-associated signaling pathway by WB, compared with rapamycin (RAP). For the early DN model rats, HKC ameliorated micro-urinary albumin, body weight and serum albumin, but had no significant effects on renal function and liver enzymes; HKC improved renal shape, kidney weight and kidney hypertrophy index; HKC attenuated glomerular hypertrophy, GBM thickening and mild mesangial expansion; HKC inhibited the phosphorylation of Akt, mTOR and p70S6K, and the protein over-expression of transforming growth factor-β1 in kidneys. In vitro, the phosphorylation of PI3K, Akt, mTOR and p70S6K in MCs induced by high-glucose was abrogated by treatment of HYP or RAP. On the whole, this study further demonstrated HKC safely and efficiently alleviates the early glomerular pathological changes of DN, likely by inhibiting Akt/mTOR/p70S6K signaling activity in vivo and in vitro, and provided the first evidence that HKC directly contributes to the prevention of the early DN.

Total Flavones of Abelmoschus manihot Remodels Gut Microbiota and Inhibits Microinflammation in Chronic Renal Failure Progression by Targeting Autophagy-Mediated Macrophage Polarization

“…One capsule of HKC contains 0.5 g of AM and 34 mg of TFA. Our previous animal experiment revealed that a 2 g/kg/day dose of HKC, which contains a 136 mg/kg/day dose of TFA, can significantly attenuate renal fibrosis (Wu et al, 2018). Thus, the rats in the TFA group received a TFA suspension at a dosage of 136 mg/kg/day.…”

Astragaloside IV ameliorates high glucose‑induced renal tubular epithelial‑mesenchymal transition by blocking mTORC1/p70S6K signaling in HK‑2 cells

“…The incidence of DM has been increasing worldwide and as a secondary complication, DN is one of the most significant causes of end-stage renal disease (29,30). In China (31) and the United States (32), ~16 and 26% of patients with DN develop end-stage renal disease, respectively; thus, effective and safe treatment strategies to delay the progression of DN are urgently required in the clinic (21). However, little progress has been made in the treatment of patients with DN (33).…”

“…However, only mTORC1 is sensitive to rapamycin inhibition, and controls cell proliferation and growth via the phosphorylation of certain downstream targets, such as ribosomal protein S6 kinase β-1 (p70S6K) (20). Aberrant activation of the mTORC1/p70S6K pathway has been reported to be involved in the pathogenesis of DN (21). Furthermore, mTORC1/p70S6K signaling may mediate renal tubular EMT during DN (19).…”

Traditional Uses, Chemical Constituents, Biological Properties, Clinical Settings, and Toxicities of Abelmoschus manihot L.: A Comprehensive Review

“…for 28 days) dramatically reduced urinary microalbumin levels, increased body weight and serum albumin levels, improved renal morphology and kidney weight, reduced the kidney hypertrophy index, alleviated glomerular hypertrophy, decreased the expression of α-smooth muscle actin and proliferating nuclear cell antigen, and decreased thickening of the glomerular basement membrane. The mechanism explored demonstrated that HKC downregulated the protein expression of p-p70S6K, p-mammalian target of rapamycin (mTOR), TGF-β1, and p-Akt by repressing the phosphoinositide-3-kinase (PI3K)/Akt/mTOR/p70S6K signaling pathway in the kidneys of rats in a model of early DN ( Wu et al., 2018 ). In agreement with the results of the in vivo study, hyperoside, which is a bioactive component of HKC, at concentrations of 5 and 15 µg/mL significantly downregulated the protein expression of p-Akt, p-mTOR, p-PI3K, and p-p70S6K in murine mesangial cells induced by high glucose levels in vitro ( Wu et al., 2018 ), which suggested that HKC safely and efficiently alleviates early pathological changes in the glomeruli in DN by inhibiting the PI3K/Akt/mTOR/p70S6K signaling pathway in vivo and in vitro and provides reliable evidence of the prevention of early DN.…”