Diabetic kidney disease (DKD) is the leading cause of chronic kidney disease with limited treatment options. Currently, blockade of the renin-angiotensin system is the main therapy to delay the progression of DKD and provide partial renal protection. However, the majority of diabetic patients who take angiotensin-converting enzyme inhibitors (ACEi) or angiotensin receptor blockers (ARBs) will develop end-stage renal disease. Therefore, more effective treatments for DKD patients need to be developed.
In China, traditional herbal medicines are widely used in the treatment of diabetes and its complications. Among them, Fructus Arctii (Niubangzi) is widely used to treat DKD patients alone or in combination with other herbs. Clinical observational studies have shown that Fructus Arctii can significantly reduce severity of proteinuria in patients with DKD. However, the underlying mechanism of its renal protection remains unclear. Arctigenin (ATG), the main component of Fructus Arctii, has various cellular effects in vitro, including anti-proliferative effects in cancer cells and anti-inflammatory and antioxidant effects in various cell types, and has also been confirmed in vivo AMPK can be activated both internally and externally. However, the molecular mechanism by which ATG exerts these effects remains unclear.
The team of Dr. Yifei Zhong at Longhua Hospital, Shanghai University of Traditional Chinese Medicine, revealed that ATG protects podocyte injury caused by high glucose by activating PP2A, dephosphorylating NF-κB and DBN1, thereby alleviating inflammation, increasing podocyte adhesion, and proved the mechanism that ATG achieves renal protection by activating PP2A. thus established PP2A as a potential target for DKD progression. For the first time, the study found PP2A agonists from effective traditional Chinese medicines for the treatment of DKD, and confirmed that ATG can increase its activity by regulating the structure of PP2A subunits, which is also a noval type of PP2A agonist. At the same time, this study opens up a new way for Chinese medicine research to find potential targets of diseases through effective Chinese medicine components.
This is a collaboration work between Longhua Hospital and Icahn School of Medicine at Mount Sinai, New York.
Summary of the manuscript
Title: Arctigenin attenuates diabetic kidney disease through the activation of PP2A in podocytes
Abstract:
Arctigenin (ATG) is a major component of Fructus Arctii, a traditional herbal remedy that reduced proteinuria in diabetic patients. However, whether ATG specifically provides renoprotection in DKD is not known. Here we report that ATG administration is sufficient to attenuate proteinuria and podocyte injury in mouse models of diabetes. Transcriptomic analysis of diabetic mouse glomeruli showed that cell adhesion and inflammation are two key pathways affected by ATG treatment, and mass spectrometry analysis identified protein phosphatase 2 A (PP2A) as one of the top ATG-interacting proteins in renal cells. Enhanced PP2A activity by ATG reduces p65 NF-κB-mediated inflammatory response and high glucoseinduced migration in cultured podocytes via interaction with Drebrin-1. Importantly,
podocyte-specific Pp2a deletion in mice exacerbates DKD injury and abrogates the ATGmediated renoprotection. Collectively, our results demonstrate a renoprotective mechanism of ATG via PP2A activation and establish PP2A as a potential target for DKD progression.
ATG treatment mitigates proteinuria and glomerular injury in diabetic eNOS−/− mice. a Diabetes was induced in 8-week old eNOS−/− mice with streptozotocin (+STZ). Vehicle-injected mice were used as nondiabetic controls (−STZ). Mice were treated with arctigenin (ATG) or vehicle by oral gavage daily at 40 mg/kg body weight for 8 weeks, starting at 10 weeks post diabetes induction. All mice were killed at 18 weeks post diabetes induction. b Analysis of urinary albumin-to-creatinine ratio (UACR), n = 6 per group. c Representative images of periodic acid–Schiff (PAS)-stained kidneys. Scale bar, 20 μm. d Quantification of the glomerular area and mesangial area fraction in diabetic and control eNOS−/− mice, n = 6 per group. ****P < 0.0001 when compared with nondiabetic controls, ####P < 0.0001 when compared with vehicle-treated diabetic eNOS−/− mice by two-way ANOVA with Tukey’s post hoc analysis. The data are represented as mean ± SD. Source data are provided as a Source Data file.
ATG binds to PP2A to enhance its activity. Drug Affinity Responsive Target Stability (DARTS) assay was performed to test the direct binding of ATG to PP2A in renal cells. a HEK293T cell lysates were pre-incubated with various concentrations of ATG as indicated at 25 °C for 1 h prior to digestion with pronase (0 or 1:1000 dilution) for 20 min. Lysates were then probed for PP2A expression, with GAPDH as a loading control. b Surface Plasmon Resonance (SPR) assay with Biacore showing the steady-state fit of binding between ATG and PP2A. c PP2A activity in HEK293T cells treated with various ATG concentrations as indicated for 2 h. Total PP2A activity is expressed as a relative fold change to no ATG treatment. n = 3 experiments. *P < 0.05 and ***P < 0.001 when compared with control by one-way ANOVA with Tukey’s post hoc analysis. d PP2A activity in conditionally immortalized human podocytes exposed to normal glucose and high mannitol (NG; 5 mM glucose and 25 mM mannitol) or high glucose (HG; 30 mM glucose) conditions for 24 h prior to treatment with ATG (10 μM) or vehicle for 2 h. Total PP2A activity is expressed as a relative fold change to NG vehicle control. ***P < 0.001 compared wqith vehicle control; n = 3. e PP2A activity in isolated glomeruli of control and diabetic eNOS−/− mice. Total PP2A activity is expressed as a relative fold change to vehicle-treated nondiabetic control. n = 3 per group. **P < 0.01 and ***P < 0.001 compared with vehicle control; #P < 0.05 compared wqith vehicle-treated control mice. f PP2A activity in isolated glomeruli of db/m and db/db mice. Total PP2A activity is expressed as a relative fold change to vehicle-treated db/m mice. n = 5 per group. *P < 0.05 and ***P < 0.001 compared with respective vehicle control; #P < 0.05 compared with vehicle-treated db/m mice by two-way ANOVA with Tukey’s post hoc analysis. *P < 0.05 and ***P < 0.001 when compared with control by two-way ANOVA with Tukey’s post hoc analysis. The data are represented as mean ± SD. g Computational prediction of ATG binding to PP2A crystal structure. Docking values for ATG for the binding using the virtual screening: Value S = −8.7414; E configuration = 3.2185; E place = -51.5684; E score1 = −8.7414.
References:
1. Yifei Zhong, Kyung Lee, Yueyi Deng, Yueming Ma, Yiping Chen, Xueling Li, Chengguo Wei, Shumin Yang, Tianming Wang, Nicholas J Wong, Alecia N Muwonge, Evren U Azeloglu, Weijia Zhang, Bhaskar Das, John Cijiang He, Ruijie Liu. Arctigenin attenuates diabetic kidney disease through the activation of PP2A in podocytes.Nat Commun. 2019 Oct 4;10(1):4523.
2. http://www.sh.chinanews.com.cn/yljk/2019-10-15/64550.shtml (in Chinese)
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