Crosstalk between protective autophagy and NF-κB signal in high glucose-induced podocytes

Autophagy in peritoneal fibrosis

Peritoneal dialysis (PD) is a widely accepted renal replacement therapy for patients with end-stage renal disease (ESRD). Morphological and functional changes occur in the peritoneal membranes (PMs) of patients undergoing long-term PD. Peritoneal fibrosis (PF) is a common PD-related complication that ultimately leads to PM injury and peritoneal ultrafiltration failure. Autophagy is a cellular process of "self-eating" wherein damaged organelles, protein aggregates, and pathogenic microbes are degraded to maintain intracellular environment homeostasis and cell survival. Growing evidence shows that autophagy is involved in fibrosis progression, including renal fibrosis and hepatic fibrosis, in various organs. Multiple risk factors, including high-glucose peritoneal dialysis solution (HGPDS), stimulate the activation of autophagy, which participates in PF progression, in human peritoneal mesothelial cells (HPMCs). Nevertheless, the underlying roles and mechanisms of autophagy in PF progression remain unclear. In this review, we discuss the key roles and potential mechanisms of autophagy in PF to offer novel perspectives on future therapy strategies for PF and their limitations.

The Mechanism of Hyperglycemia-Induced Renal Cell Injury in Diabetic Nephropathy Disease: An Update

Diabetic Nephropathy (DN) is a serious complication of type I and II diabetes. It develops from the initial microproteinuria to end-stage renal failure. The main initiator for DN is chronic hyperglycemia. Hyperglycemia (HG) can stimulate the resident and non-resident renal cells to produce humoral mediators and cytokines that can lead to functional and phenotypic changes in renal cells and tissues, interference with cell growth, interacting proteins, advanced glycation end products (AGEs), etc., ultimately resulting in glomerular and tubular damage and the onset of kidney disease. Therefore, poor blood glucose control is a particularly important risk factor for the development of DN. In this paper, the types and mechanisms of DN cell damage are classified and summarized by reviewing the related literature concerning the effect of hyperglycemia on the development of DN. At the cellular level, we summarize the mechanisms and effects of renal damage by hyperglycemia. This is expected to provide therapeutic ideas and inspiration for further studies on the treatment of patients with DN.

Nuclear factor-kappaB mediates the survival of rat kidney cells after cadmium exposure via promoting autophagy and inhibiting apoptosis

Cadmium (Cd) is a heavy metal pollutant in the environment, and the kidney is one of the target organs after Cd exposure. Previous studies have shown that apoptosis and autophagy disorders are the main mechanisms of Cd-induced nephrotoxicity in rats. As a transcription factor that balances cell survival and death, nuclear factor-kappaB (NF-κB) protein plays dual regulatory effects on apoptosis and autophagy in multiple renal diseases. However, the regulatory mechanisms of NF-κB in Cd-induced kidney injury remain unclear. Therefore, the normal rat kidney cell line (NRK-52E cells) was applied to investigate the above questions in this study. Here, we found that Cd promotes the nuclear translocation and activation of NF-κB in a concentration-dependent manner, and activated NF-κB mediates NRK-52E cells survival after Cd exposure. Next, our study elaborated the mechanisms of NF-κB in antagonizing Cd-induced renal cytotoxicity. Inhibition of NF-κB by inhibitor BAY 11-7082 (BAY) and NF-κB p65 siRNA (siNF-κB p65) exacerbate Cd-induced apoptosis and autophagy inhibition, and then aggravate Cd-induced NRK-52E cells injury. Activation of NF-κB by activator phorbol-12-myristate-13-acetate (PMA) alleviates Cd-induced apoptosis and autophagy inhibition, and then attenuates Cd-induced NRK-52E cells injury. In conclusion, Cd exposure promotes the activation of NF-κB, and activated NF-κB mediates the survival of NRK-52E cells after Cd exposure via promoting autophagy and inhibiting apoptosis.

Intervention of NF-Κb Signaling Pathway and Preventing Post-Operative Cognitive Dysfunction as Well as Neuronal Apoptosis

Background:

The Postoperative cognitive dysfunction (POCD) model was constructed by resection of the left hepatic lobe in aged mice to determine the behavioral effects of the POCD model in aged mice and the relationship between NF-κB and POCD in apoptosis and autophagy. Provide a theoretical basis for POCD prevention and treatment.

Methods:

This study was carried out in Ningbo No. 6 Hospital, Zhejiang, China, from Jun 2019 to Dec 2020. The POCD model was constructed after resection of the left extrahepatic lobe in aged mice and randomly divided into 6 groups: sham operation group, operation group (normal saline control group, solvent group, YC-1 group, PDTC group and 3-MA group). Related indicators of behavioral changes, neuronal inflammatory responses, apoptosis, and autophagy were examined.

Results:

The escape latency of the aged mice in the surgical group was significantly prolonged at three time points compared with the control group, and the number of insertions decreased significantly. Microglia are activated and the inflammatory response is increased, whereas PDTC has an inhibitory effect. It was demonstrated that apoptosis and necrosis of neurons can be induced by the NF-κb pathway, and autophagy can be promoted, whereas autophagy occurs before apoptosis.

Conclusion:

Activation of NF-κb pathway in neurons after POCD causes neuronal apoptosis and autophagy, and cognitive impairment occurs. PDTC, a NF-κb pathway inhibitor, can effectively reduce neuronal apoptosis induced by secondary brain injury after POCD. Necrosis, to protect the brain tissue.

Morin hydrate inhibits atherosclerosis and LPS-induced endothelial cells inflammatory responses by modulating the NFκB signaling-mediated autophagy

Atherosclerosis (AS) is a chronic inflammatory disease involving blood vessels. Inflammation affects different cells and increases the expression of adhesion molecules. Morin hydrate (MO) is a naturally occurring bioflavonoid with anti-inflammatory and anti-oxidant effects. Although the exact mechanism has not been fully elucidated, MO possibly influences autophagy pathways in immunity and inflammation. In this study, MO showed the potential to inhibit atherosclerotic and promote vascular endothelial autophagy in apolipoprotein E (ApoE)-/- mice with a high-fat diet. Then, we aimed to explore the anti-inflammatory effects of MO in human umbilical vein endothelial cells (HUVECs) and its relationship with autophagy. We found that MO inhibited lipopolysaccharide (LPS)-induced monocyte adhesion and the expression of intercellular adhesion molecule-1 (ICAM-1), vascular cell adhesion molecule-1 (VCAM-1), cyclooxygenase-2 (COX-2), and matrix metallopeptidase 9 (MMP-9) in HUVECs. Moreover, MO reduced the expression of tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) by inhibiting the phosphatidylinositol-3-kinase (PI3K)/protein kinase B (Akt)/nuclear factor kappa B (NFκB) signaling pathway. MO induced autophagy by inhibiting the NFκB signaling pathway in normal HUVECs and LPS-stimulated HUVECs. When autophagy was inhibited by 3-methyladenine (3-MA) or small interfering RNA (siRNA), the anti-inflammatory effect of MO was reduced. In conclusion, MO inhibits atherosclerosis in ApoE-/- mice and LPS-induced inflammatory responses by inhibiting the activation of the PI3K/Akt1/NFκB signaling pathway in a NFκB signaling-mediated autophagy way.

Yishen capsule promotes podocyte autophagy through regulating SIRT1/NF-κB signaling pathway to improve diabetic nephropathy

Diabetic nephropathy (DN) is a common complication of diabetes. Yishen capsule, composed of Chinese herbs, improves the clinical outcome in DN patients. However, its therapeutic potential and underlying mechanisms require further elucidation. Hence, our study aimed to investigate the underlying mechanisms and therapeutic potential of Yishen capsule in DN. Streptozotocin-induced DN rats were treated with Yishen capsules (1.25 g/kg/day) for 8 weeks. Then, blood glucose and urine protein levels were measured. Hematoxylin and eosin staining and western blot assays were used to examine the histologic changes and gene expression, respectively, in kidney samples. Mouse podocytes were treated with rat serum containing Yishen capsule and transmission electron microscopy was used to examine autophagosome formation. Cell counting kit-8 assay was performed to examine cell proliferation. Western blot and reverse transcription-quantitative polymerase chain reaction (RT-qPCR) analyses were conducted to detect changes in gene expression. The localization of SIRT1 was examined in the podocytes using immunocytofluorescence assay. We found that Yishen capsule relieved pathological changes, decreased urine protein, increased SIRT1, LC3-II, and Beclin-1 expression, and reduced acetylated NF-κB p65 expression in vivo. In addition, rat serum containing Yishen capsule showed improved podocyte proliferation, promoted the mRNA and protein levels of LC3-II and Beclin-1, and induced nuclear translocation of SIRT1. Furthermore, it increased SIRT1 expression and decreased mRNA level of NF-κB in the serum. SIRT1 inhibitor increased the mRNA level of NF-κB. Our data suggests that Yishen capsule improves DN by promoting podocyte autophagy via the SIRT1/NF-κB pathway.

SIRT1 suppresses cellular senescence and inflammatory cytokine release in human dermal fibroblasts by promoting the deacetylation of NF-κB and activating autophagy

Skin aging is a complex process and involves extrinsic and intrinsic processes with distinct characteristics. Understanding skin aging requires knowledge of the senescence of human dermal fibroblasts (HDFs) and the biological mechanisms involved in this process. However, the molecular mechanism responsible for the aging of HDFs is still not clear. Therefore, we investigated mechanisms of autophagy, inflammation, and cellular senescence by Western blotting, immunofluorescence, real-time PCR, and senescence-associated β-galactosidase (SA-β-gal) staining in senescent HDFs. We found SRT1720 inhibited the inductions of inflammatory cytokines and cellular senescence by deacetylating acetyl-NF-κB levels and enhancing levels of autophagy-associated proteins and SIRT1 in senescent HDFs. However, the NF-κB activator prostratin attenuated signals associated with autophagy, such as those of LC3-II and Beclin-1, but increased inflammatory cytokine levels and cellular senescence. Notably, the expression levels of SIRT1 and autophagy-associated proteins were higher in aged mice administered SRT1720 than in old mice, and SRT1720 also decreased levels of acetyl-NF-κB, inflammatory cytokines, and senescence markers, which was in accord with in vitro results. These findings support that SRT1720 acts as an anti-aging agent and inhibits the inductions of inflammatory cytokines and senescence by regulating the SIRT1/acetyl-NF-κB signaling pathway and activating autophagy in senescent HDFs.

Ginsenoside Rg1 Alleviates Podocyte Injury Induced by Hyperlipidemia via Targeting the mTOR/NF-κB/NLRP3 Axis

Background

Podocyte injury plays an important role in diabetic nephropathy (DN). The aim of this study was to determine the potential therapeutic effects of the ginsenoside Rg1 on hyperlipidemia-stressed podocytes and elucidate the underlying mechanisms.

Methods

In vitro and in vivo models of DN were established as previously described, and the expression levels of relevant markers were analyzed by Western blotting, real-time Polymerase Chain Reaction (PCR), immunofluorescence, and immunohistochemistry.

Results

Ginsenoside Rg1 alleviated pyroptosis in podocytes cultured under hyperlipidemic conditions, as well as in the renal tissues of diabetic rats, and downregulated the mammalian target of rapamycin (mTOR)/NF-κB pathway. In addition, Rg1 also inhibited hyperlipidemia-induced NLRP3 inflammasome in the podocytes, which was abrogated by the mTOR activator L-leucine (LEU). The antipyroptotic effects of Rg1 manifested as improved renal function in the DN rats.

Conclusion

Ginsenoside Rg1 protects podocytes from hyperlipidemia-induced damage by inhibiting pyroptosis through the mTOR/NF-κB/NLRP3 axis, indicating a potential therapeutic function in DN.

Lysosomal dysfunction-induced autophagic stress in diabetic kidney disease

The catabolic process that delivers cytoplasmic constituents to the lysosome for degradation, known as autophagy, is thought to act as a cytoprotective mechanism in response to stress or as a pathogenic process contributing towards cell death. Animal and human studies have shown that autophagy is substantially dysregulated in renal cells in diabetes, suggesting that activating autophagy could be a therapeutic intervention. However, under prolonged hyperglycaemia with impaired lysosome function, increased autophagy induction that exceeds the degradative capacity in cells could contribute toward autophagic stress or even the stagnation of autophagy, leading to renal cytotoxicity. Since lysosomal function is likely key to linking the dual cytoprotective and cytotoxic actions of autophagy, it is important to develop novel pharmacological agents that improve lysosomal function and restore autophagic flux. In this review, we first provide an overview of the autophagic-lysosomal pathway, particularly focusing on stages of lysosomal degradation during autophagy. Then, we discuss the role of adaptive autophagy and autophagic stress based on lysosomal function. More importantly, we focus on the role of autophagic stress induced by lysosomal dysfunction according to the pathogenic factors (including high glucose, advanced glycation end products (AGEs), urinary protein, excessive reactive oxygen species (ROS) and lipid overload) in diabetic kidney disease (DKD), respectively. Finally, therapeutic possibilities aimed at lysosomal restoration in DKD are introduced.

Astragaloside IV inhibits glucose-induced epithelial-mesenchymal transition of podocytes through autophagy enhancement via the SIRT-NF-κB p65 axis

Both autophagy and podocyte epithelial-mesenchymal transition (EMT) are critical factors in glomerular diseases that involve proteinuria and fibrosis. Here, we sought to determine whether plant-derived saponin astragaloside IV (AS-IV) was able to reverse renal fibrosis and improve renal function through regulation of autophagy and podocyte EMT. Cultured immortalized mouse podocytes and KK-Ay mice models of diabetes were exposed to AS-IV. Western blotting, real-time PCR, immunofluorescence and histochemistry were used to analyze markers of autophagy and podocyte EMT. We observed that AS-IV inhibited glucose-induced podocyte EMT and enhanced autophagy by decreasing NF-κB subunit p65 acetylation as well as increasing Sirtuin1 (SIRT1) expression. Treatment of the cells and animal models with a SIRT1 inhibitor EX527 was able to reverse these effects. The SIRT1 activator SRT1720 was also found to decrease p65 acetylation and enhance autophagy in glucose-induced podocyte EMT. Additionally, further treatment with autophagy inhibitor 3-methyladenine was able to reverse the effects of AS-IV on podocyte EMT, while the autophagy activator rapamycin or the NF-κB pathway inhibitor ammonium pyrrolidinedithiocarbamate (PDTC) were able to reverse glucose-induced podocyte EMT. Notably, both renal fibrosis and renal function in diabetic KK-Ay mice were improved after treatment with AS-IV. These findings support AS-IV as a renoprotective agent that likely exerts its effects on podocyte EMT through modulation of the SIRT1-NF-κB pathway and autophagy activation. Further studies are required to clarify the role of AS-IV as a potential therapeutic agent in glomerular diseases.

Astragaloside IV represses high glucose-induced mesangial cells activation by enhancing autophagy via SIRT1 deacetylation of NF-κB p65 subunit

Aim

Mesangial cell (MC) activation plays an important role in many glomerular diseases associated with renal fibrosis, including diabetic kidney disease (DKD). The aim of this study was to determine whether Astragaloside IV (AS-IV) modulated MC activation in DKD via autophagy by specifically regulating the autophagy inducer sirtuin 1 (SIRT1).

Methods

Cultured MCs and diabetic KK-Ay mice were treated with AS-IV, and the markers and regulatory mediators of autophagy were analyzed using Western blotting, real-time PCR, ELISA and IF.

Results

AS-IV inhibited MC activation and enhanced autophagy in hyperglycemic conditions by increasing SIRT1 expression and decreasing NF-κB p65 acetylation. In addition, the SIRT1 activator SRT1720 enhanced autophagy and decreased p65 acetylation during hyperglycemia-induced MC activation. Opposite effects were seen with the SIRT1 inhibitor EX527. Furthermore, the ameliorative effect of AS-IV on MCs was abolished by the autophagy inhibitor 3-MA, while the autophagy activator rapamycin restored hyperglycemia-induced MC activation. Finally, AS-IV improved renal function and fibrosis in the diabetic KK-Ay mice.

Conclusion

AS-IV ameliorated renal function and morphology by inducing autophagy and inhibiting MC activation through the SIRT1-NF-κB pathway, indicating a potential therapeutic role of AS-IV in glomerular diseases.

Advanced glycation end-products suppress autophagic flux in podocytes by activating mammalian target of rapamycin and inhibiting nuclear translocation of transcription factor EB

Insufficient autophagy in podocytes is related to podocyte injury in diabetic nephropathy (DN). Advanced glycation end‐products (AGEs) are major factors of podocyte injury in DN. However, the role and mechanism of AGEs in autophagic dysfunction remain unknown. We investigated autophagic flux in AGE‐stimulated cultured podocytes using multiple assays: western blotting, reverse transcription–quantitative PCR, immunofluorescence staining, and electron microscopy. We also utilized chloroquine and a fluorescent probe to monitor the formation and turnover of autophagosomes. Mice of the db/db strain were used to model diabetes mellitus (DM) with high levels of AGEs. To mimic DM with normal levels of AGEs as a control, we treated db/db mice with pyridoxamine to block AGE formation. AGEs impaired autophagic flux in the cultured podocytes. Compared with db/db mice with normal AGEs but high glucose levels, db/db mice with high AGEs and high glucose levels exhibited lower autophagic activity. Aberrant autophagic flux was related to hyperactive mammalian target of rapamycin (mTOR), a major suppressor of autophagy. Pharmacologic inhibition of mTOR activity restored impaired autophagy. AGEs inhibited the nuclear translocation and activity of the pro‐autophagic transcription factor EB (TFEB) and thus suppressed transcription of its several autophagic target genes. Conversely, TFEB overexpression prevented AGE‐induced autophagy insufficiency. Attenuating mTOR activity recovered TFEB nuclear translocation under AGE stimulation. Co‐immunoprecipitation assays further demonstrated the interaction between mTOR and TFEB in AGE‐stimulated podocytes and in glomeruli from db/db mice. In conclusion, AGEs play a crucial part in suppressing podocyte autophagy under DM conditions. AGEs inhibited the formation and turnover of autophagosomes in podocytes by activating mTOR and inhibiting the nuclear translocation of TFEB. © 2018 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of Pathological Society of Great Britain and Ireland.

Effect of 1,25(OH)2D3 on high glucose‑induced autophagy inhibition in peritoneum

High glucose (HG) may damage the structure and function of the peritoneal membrane, and is considered to be one of the most important factors that leads to peritoneal fibrosis and ultrafiltration failure. Recently, 1,25(OH)2D3, the active form of vitamin D, was demonstrated to protect against epithelial‑mesenchymal transition and fibrosis in peritoneal mesothelium and other organs. Accumulating evidence has suggested that autophagy serves a protective role in certain diseases by regulating cell survival. The present study examined whether 1,25(OH)2D3 has an effect on autophagy in peritoneal mesothelial cells. The protein level of Beclin, anti‑ubiquitin‑binding protein p62 (p62), microtubule‑associated proteins 1A/1B light chain 3B (LC3-II), mechanistic target of rapamycin (mTOR) and phosphorylated mTOR were evaluated by western blot analysis. Autophagosomes were detected under transmission electron microscopy. It was revealed that exposure to HG inhibited autophagy in peritoneal mesothelial cells. However, 1,25(OH)2D3 alleviated autophagy inhibition induced by HG in human peritoneal mesothelial cells, which activated expression of autophagy‑associated genes encoding Beclin‑1 and LC3-II downregulated the expression of p62 via mTOR signaling pathway. In a mouse model of HG‑treated peritoneal mesothelium, autophagy inhibition was observed in peritoneum, 1,25(OH)2D3 attenuated HG‑induced autophagy inhibition in peritoneal mesothelium via the mTOR signaling pathway. These findings suggested that 1,25(OH)2D3 may be a potential therapy for peritoneal injury.

Bisindolylmaleimide alkaloid BMA-155Cl induces autophagy and apoptosis in human hepatocarcinoma HepG-2 cells through the NF-κB p65 pathway

Bisindolylmaleimides, a series of derivatives of a PKC inhibitor staurosporine, exhibit potential as anti-cancer drugs and have received considerable attention in clinical trials. This study aims to investigate the effects of a bisindolylmaleimide alkaloid 155Cl (BMA-155Cl) with a novel structure on autophagy and apoptosis in human hepatocarcinoma HepG-2 cells in vitro and in vivo. The cell poliferation was assessed with a MTT assay. Autophagy was evaluated by MDC staining and TEM analysis. Apoptosis was investigated using Annexin V-FITC/PI and DAPI staining. The antitumor effects were further evaluated in nude mice bearing HepG-2 xenografts, which received BMA-155Cl (10, 20 mg/kg, ip) for 18 days. Autophagy- and apoptosis-associated proteins and their mRNA levels were examined with Western blotting, immunohistochemistry, and RT-PCR. BMA-155Cl (2.5-20 μmol/L) inhibited the growth of HepG-2 cells with IC₅₀ values of 16.62±1.34, 12.21±0.83, and 8.44±1.82 μmol/L at 24, 48, and 72 h, respectively. Furthermore, BMA-155Cl (5-20 μmol/L) dose-dependently induced autophagy and apoptosis in HepG-2 cells. The formation of autophagic vacuoles was induced by BMA-155Cl (10 μmol/L) at approximately 6 h and peaked at approximately 15 h. Pretreatment with 3-MA potentiated BMA-155Cl-mediated apoptotic cell death. This compound dose-dependently increased the mRNA and protein levels of Beclin-1, NF-κB p65, p53, and Bax, but decreased the expression of IκB and Bcl-2. Pretreatment with BAY 11-7082, a specific inhibitor of NF-κB p65, blocked BMA-155Cl-induced expression of autophagy- and apoptosis-associated proteins. BMA-155Cl administration effectively suppressed the growth of HepG-2 xenografts in vivo, and increased the protein expression levels of LC3B, Beclin-1, NF-κB p65, and Bax in vivo. We conclude that the NF-κB p65 pathway is involved in BMA-155Cl-triggered autophagy, followed by apoptosis in HepG-2 cells in vitro and in vivo. Hence, BMA-155Cl could be a promising pro-apoptotic candidate for developing as a novel anti-cancer drug.

Sirtuin 6 modulates hypoxia-induced autophagy in nasal polyp fibroblasts via inhibition of glycolysis

BACKGROUND

To elucidate the interaction between hypoxia-induced autophagy and glycolysis in nasal polyp fibroblasts, and the regulatory role of Sirtuin 6 (SIRT6) in the pathogenesis of nasal polyp.

OBJECTIVE

Through examining the expressions of lactate dehydrogenase (LDH), microtubule-associated protein II light chain 3 (LC3II) (an autophagy marker), and production of lactate under hypoxia, the interaction between autophagy and glycolysis was investigated. The role of SIRT6 on the hypoxia-induced autophagy and glycolysis was also examined.

METHODS

Nasal polyp specimens were used to examine the expressions of hypoxia-inducible factor (HIF) 1α, LDH, and LC3II by Western blot analysis, and primary cultures of nasal polyp fibroblasts were established from resected nasal polyps to measure hypoxia-induced LDH and LC3II expression by Western blot analysis and lactate production by colorimetry. Forced expression of SIRT6 with a lentiviral-based technique was used to evaluate its suppressive effect on autophagy and glycolysis. Immunohistochemical staining was performed to detect the expressions of SIRT6, LDH, and beclin (another autophagy marker) in nasal polyps.

RESULTS

Expression of HIF-1α, LDH, and an autophagy marker, LC3II, are increased in nasal polyp specimens, and forced expression of SIRT6 in nasal polyp fibroblasts inhibited LDH expression, lactate production under hypoxia, and SIRT6. An immunohistochemistry study of nasal polyp showed that SIRT6 expression was reduced and LDH and beclin were enhanced.

CONCLUSION

Analysis of these data indicated that hypoxia may contribute to the formation of nasal polyp by promoting autophagy in nasal polyp fibroblasts. Through the antiglycolytic activity of SIRT6, the autophagy was suppressed, which was beneficial to nasal polyp formation. Modulation of glucose metabolism through SIRT6-based strategy may possess therapeutic potential for nasal polyposis in the future.

Metformin modulates apoptosis and cell signaling of human podocytes under high glucose conditions

Diabetic nephropathy, which is associated with loss of human (h) podocytes (PC), is a major complication in diabetes mellitus. High-glucose modulates AMP-activated protein kinase (AMPK) signaling and cell apoptosis. Metformin has been demonstrated to reduce apoptosis and albuminuria in type 2 diabetes. Here, we examined the effect of metformin on cell apoptosis and on pro-/anti-apoptotic signaling in hPC. Expression analyses were done by real-time polymerase chain reaction and western blotting. Moreover, a functional apoptosis assay was performed in hPC. Determination of kinase activation by phosphorylation was done via immunodetection analyses and digital quantification. We found that hPC express organic cation transporter 1 which is the major uptake transporter of metformin. High-glucose reduced AMPK phosphorylation and induced mammalian target of rapamycin (mTOR) activation in podocytes, which was abolished and reversed by pre-treatment with metformin. Furthermore, metformin reduced high-glucose-induced podocytes apoptosis in a concentration-dependent manner. In summary, metformin exhibits an anti-apoptotic impact on podocytes under high-glucose conditions via activation of AMPK and inhibition of mTOR signaling. These data support a beneficial effect of metformin in diabetic nephropathy.

Triptolide Inhibited Cytotoxicity of Differentiated PC12 Cells Induced by Amyloid-Beta₂₅₋₃₅ via the Autophagy Pathway

Evidence shows that an abnormal deposition of amyloid beta-peptide_25–35 (Aβ_25–35) was the primary cause of the pathogenesis of Alzheimer’s disease (AD). And the elimination of Aβ_25–35 is considered an important target for the treatment of AD. Triptolide (TP), isolated from Tripterygium wilfordii Hook.f. (TWHF), has been shown to possess a broad spectrum of biological profiles, including neurotrophic and neuroprotective effects. In our study investigating the effect and potential mechanism of triptolide on cytotoxicity of differentiated rat pheochromocytoma cell line (the PC12 cell line is often used as a neuronal developmental model) induced by Amyloid-Beta_25–35 (Aβ_25–35), we used 3-(4, 5-dimethylthiazol-2-yl)-2, 5- diphenyltetrazolium bromide (MTT) assay, flow cytometry, Western blot, and acridine orange staining to detect whether triptolide could inhibit Aβ_25–35–induced cell apoptosis. We focused on the potential role of the autophagy pathway in Aβ_25–35-treated differentiated PC12 cells. Our experiments show that cell viability is significantly decreased, and the apoptosis increased in Aβ_25–35-treated differentiated PC12 cells. Meanwhile, Aβ_25–35 treatment increased the expression of microtubule-associated protein light chain 3 II (LC3 II), which indicates an activation of autophagy. However, triptolide could protect differentiated PC12 cells against Aβ_25–35-induced cytotoxicity and attenuate Aβ_25–35-induced differentiated PC12 cell apoptosis. Triptolide could also suppress the level of autophagy. In order to assess the effect of autophagy on the protective effects of triptolide in differentiated PC12 cells treated with Aβ_25–35, we used 3-Methyladenine (3-MA, an autophagy inhibitor) and rapamycin (an autophagy activator). MTT assay showed that 3-MA elevated cell viability compared with the Aβ_25–35-treated group and rapamycin inhibits the protection of triptolide. These results suggest that triptolide will repair the neurological damage in AD caused by deposition of Aβ_25–35 via the autophagy pathway, all of which may provide an exciting view of the potential application of triptolide or TWHF as a future research for AD.