Ginsenoside-Rg1 protects podocytes from complement mediated injury

Downregulation of TRPC6 regulates ERK1/2 to prevent sublytic C5b‑9 complement complex‑induced podocyte injury through activating autophagy

Idiopathic membranous nephropathy (IMN) is a common glomerular disease, in which 50-60% of patients can progress to end-stage renal disease within 10-20 years, seriously endangering human health. Podocyte injury is the direct cause of IMN. Sublytic C5b-9 complement complex induces damage in podocytes' structure and function. In sublytic C5b-9 treated podocytes, the expression of canonical transient receptor potential 6 (TRPC6) is increased. However, the specific mechanism of TRPC6 in sublytic C5b-9 treated podocytes is unclear. The present study aimed to reveal the effect and mechanism of TRPC6 on sublytic C5b-9-induced podocytes. Normal human serum was stimulated using zymosan to form C5b-9. A lactate dehydrogenase release assay was used to examine C5b-9 cytotoxicity in podocytes. The RNA and protein expression levels were analyzed using reverse transcription-quantitative PCR, western blotting and immunofluorescent assay, respectively. Cell Counting Kit-8 assay and flow cytometry were carried out to test the viability and apoptosis of podocytes, respectively. Transmission electron microscopy was used to observe autophagic vacuole. F-actin was tested through phalloidin staining. Sublytic C5b-9 was deposited and TRPC6 expression was boosted in podocytes stimulated through zymosan activation serum. Knockdown of TRPC6 raised the viability and reduced the apoptosis rate of sublytic C5b-9-induced podocytes. Meanwhile, transfection of small-interfering (si)TRPC6 facilitated autophagy progression and enhanced the activation of cathepsin B/L in sublytic C5b-9-induced podocytes. The phosphorylation level of ERK1/2 was receded in siTRPC6 and sublytic C5b-9 co-treated podocytes. Moreover, the addition of the ERK1/2 activator partially reversed the effect of TRPC6 inhibition on sublytic C5b-9-induced podocytes. TRPC6 knockdown reduced the damage of sublytic C5b-9 to podocytes by weakening the ERK1/2 phosphorylation level to activate autophagy. These results indicated that targeting TRPC6 reduced the injury of sublytic C5b-9 on podocytes.

Ginsenoside Rg1 attenuates LPS-induced chronic renal injury by inhibiting NOX4-NLRP3 signaling in mice

Chronic renal injury (CRI) is a common pathological damage in chronic renal disease, and the therapeutic options for preventing its progression are limited at present. Ginsenoside Rg1 (Rg1) is reported to have a protective effect on renal injury by improving oxidative stress and inflammation. Lipopolysaccharide (LPS) plays important roles in inducing inflammatory and high-dose LPS is often used to perform acute renal injury. However, little is known about the effect of low-dose LPS on CRI, and the protective effect of Rg1 against chronic LPS-induced CRI. Here, we reported the protective effect and mechanism of Rg1 against LPS-induced CRI in mice. In this study, the results demonstrated that low-dose LPS (0.25 mg/kg) exposure for 14 days significantly induced renal function impairment and renal injury and fibrosis. Meanwhile, LPS exposure significantly increased reactive oxygen species (ROS) generation, NADPH oxidase 4 (NOX4) and NLRP3 inflammasome expression in renal cortex. However, treatment with Rg1, tempol (a superoxide dismutase mimetic), and apocynin (a NOX inhibitor) significantly improved renal function impairment and renal fibrosis, and significantly decreased the levels of TGF-β, IL-1β, KIM-1, β-Gal, and collagen IV in the kidneys. And Rg1 treatment also significantly reduced ROS generation and inhibited the activation of NOX4 and NLRP3 inflammasome. Overall, these results suggest that Rg1 treatment can ameliorate LPS-induced chronic kidney injury and renal fibrosis, the mechanisms may be involved in reducing NOX2-mediated oxidative stress and inhibiting NLRP1 inflammasome.

Complement induces podocyte pyroptosis in membranous nephropathy by mediating mitochondrial dysfunction

Podocyte damage mediated by in situ complement activation in the glomeruli is a key factor in the pathogenesis of membranous nephropathy (MN), but the molecular mechanism has not been fully elucidated. Pyroptosis is a special type of programmed cell death, mediate inflammatory response and induce tissue injury. However, it is not clear whether pyroptosis is involved in the development and progression of MN. Here, we report that pyroptosis plays an important role in promoting podocyte injury in MN. We first observed the occurrence of pyroptosis in the kidneys of MN patients and validated that complement stimulation triggered pyroptosis in podocytes and that inhibiting pyroptosis reversed complement-induced podocyte damage in vitro. In addition, stimulation of complement caused mitochondrial depolarization and reactive oxygen species (ROS) production in podocytes, and inhibition of ROS reversed complement-induced pyroptosis in podocytes. Interestingly, inhibition of pyroptosis in turn partially alleviated these effects. Furthermore, we also found the involvement of pyroptosis in the kidneys of passive Heymann nephritis (PHN) rats, and inhibitors of pyroptosis-related molecules relieved PHN-induced kidney damage in vivo. Our findings demonstrate that pyroptosis plays a critical role in complement-induced podocyte damage in MN and mitochondrial dysfunction is an important mechanism underlying this process. It provides new insight that pyroptosis may serve as a novel therapeutic target for MN treatment in future studies.

The promising therapeutic potentials of ginsenosides mediated through p38 MAPK signaling inhibition

The p38 mitogen-activated protein kinases (p38 MAPK) is a 38kD polypeptide recognized as the target for many potential anti-inflammatory agents. Accumulating evidence indicates that p38 MAPK could perform many roles in human disease pathophysiology. Therefore, great therapeutic benefits can be attained from p38 MAPK inhibitors. Ginseng is an exceptionally valued medicinal plant of the family Araliaceae (Panax genus). Recently, several studies targeted the therapeutic effects of purified individual ginsenoside, the most significant active ingredient of ginseng, and studied its particular molecular mechanism(s) of action rather than whole-plant extracts. Interestingly, several ginsenosides: ginsenosides compound K, F1, Rb1, Rb3, Rc, Rd, Re, Rf, Rg1, Rg2, Rg3, Rg5, Rh1, Rh2, Ro, notoginsenoside R1, and protopanaxadiol have shown to possess great therapeutic potentials mediated by their ability to downregulate p38 MAPK signaling in different cell lines and experimental animal models. Our review compiles the research findings of various ginsenosides as potent anti-inflammatory agents, highlighting the crucial role of p38 MAPK suppression in their pharmacological actions. In addition, in silico studies were conducted to explore the probable binding of these ginsenosides to p38 MAPK. The results obtained proposed p38 MAPK involvement in the beneficial pharmacological activities of ginsenosides in different ailments.

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p38 MAPK plays many roles in human disease pathophysiology. Therefore, great therapeutic benefits can be attained from p38 MAPK inhibitors.

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Several ginsenosides showed to possess great therapeutic potentials mediated by its ability to downregulate p38 MAPK signaling.

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in silico ​studies were conducted to explore the binding of these ginsenosides to p38 MAPK and evidenced the promising their inhibitory effect.

The Ginsenoside Rg1 Rescues Mitochondrial Disorders in Aristolochic Acid-Induced Nephropathic Mice

Chronic exposure to aristolochic acid (AA) leads to renal interstitial fibrosis and nephropathy. In this study, we aimed to investigate the renoprotective effects of Panax ginseng extract (GE) and ginsenoside saponin (GS) on AA-induced nephropathy (AAN) in mice. Eighty female C3H/He mice were randomly divided into eight groups, including normal; AA (3 μg/mL for 56 days); AA with GE (125, 250, or 500 mg/kg/d for 14 days); and AA with important GE ingredients, Rg₁, Rb₁, or Rd (5 mg/kg/d for 14 days). Compared with the AA group, renal injuries were significantly decreased in the GE (250 mg/kg/d), Rb₁, and Rg₁ treatment groups. Rg₁ exhibited the best renoprotection among all GS-treated groups. There were 24 peaks significantly altered among normal, AA, and AA + Rg₁ groups, and four mitochondrial proteins were identified, including acyl-CoA synthetase medium-chain family member 2, upregulated during skeletal muscle growth 5 (Usmg5), mitochondrial aconitase 2 (ACO2), and cytochrome c oxidase subunit Va preprotein (COX5a). We demonstrated for the first time that the AAN mechanism and renoprotective effects of Rg₁ are associated with expression of mitochondrial proteins, especially ACO2, Usmg5, and COX5a.

Advances of the experimental models of idiopathic membranous nephropathy (Review)

Idiopathic membranous nephropathy (IMN) is one of the main types of chronic kidney disease in adults and one of the most common causes of end-stage renal disease. In recent years, the morbidity of IMN among primary glomerular diseases has markedly increased, while the pathogenesis of the disease remains unclear. To address this, a number of experimental models, including Heymann nephritis, anti-thrombospondin type-1 domain-containing 7A antibody-induced IMN, cationic bovine serum albumin, anti-human podocyte antibodies and zymosan-activated serum-induced C5b-9, have been established. This review comprehensively summarized the available animal and cell models for IMN. The limitations and advantages of the current models were discussed and two improved models were introduced to facilitate the selection of an appropriate model for further studies on IMN.

Ginsenoside Rg1 ameliorates glomerular fibrosis during kidney aging by inhibiting NOX4 and NLRP3 inflammasome activation in SAMP8 mice

Aging is closely related to the progress of renal fibrosis, which eventually results in renal dysfunction. Ginsenoside Rg1 (Rg1) has been reported to have an extensive anti-aging effect. However, the role and mechanism of Rg1 in aging-related renal fibrosis remain unclear. The present study aimed to evaluate the protective effect and mechanism of Rg1 in renal fibrosis during kidney aging in a model of SAMP8 mice. Taking SAMR1 mice as the control group, SAMP8 mice were administered Apocynin (50 mg/kg), Tempol (50 mg/kg), or Rg1 (5, 10 mg/kg) intragastrically for 9 weeks as treatment groups. The results showed that the elevated levels of blood urea nitrogen, serum creatinine and senescence-associated β-galactosidase (β-Gal) were markedly decreased, the glomerular mesangial proliferation was significantly alleviated and the increased levels of collagen IV and TGF-β1 were significantly downregulated by Rg1 in SAMP8 mice. In addition, the generation of ROS and the expression of NADHP oxidase 4 (NOX4) in the renal cortex were significantly reduced by Rg1 treatment. The expression levels of NLRP3 inflammasome-related proteins and the inflammation-related cytokine IL-1β were also inhibited by Rg1 treatment in the SAMP8 mice. These results suggested that Rg1 could delay kidney aging and inhibit aging-related glomerular fibrosis by reducing NOX4-derived ROS generation and downregulating NLRP3 inflammasome expression.

Ginsenoside Rg1 Protects against Oxidative Stress-induced Neuronal Apoptosis through Myosin IIA-actin Related Cytoskeletal Reorganization

Oxidative stress-induced cytoskeletal dysfunction of neurons has been implicated as a crucial cause of cell apoptosis or death in the central nervous system (CNS) diseases, such as neurodegenerative and psychiatric diseases. The application of neuroprotectants rescuing the neurons from cytoskeletal damage and apoptosis can be a potential treatment for these CNS diseases. Ginsenoside Rg1 (Rg1), one of the major active components of ginseng, has been reported possessing notable neuroprotective activities. However, there is rare report about its effect on cytoskeleton and its undergoing mechanism. The current study is to reveal the regulatory effects of Rg1 on cytoskeletal and morphological lesion in oxidative stress-induced neuronal apoptosis. The results demonstrated that pre-treatment with Rg1 (0.1-10 μM) attenuated hydrogen peroxide (H₂O₂)-induced neuronal apoptosis and oxidative stress through reducing the intracellular reactive oxygen species (ROS) production and methane dicarboxylic aldehyde (MDA) level. The Rg1 treatment also abolished H₂O₂-induced morphological changes, including cell rounding, membrane blebbing, neurite retraction and nuclei condensation, which were generated by myosin IIA-actin interaction. These effects were mediated via the down-regulation of caspase-3, ROCK1 (Rho-associated kinase1) activation and myosin light chain (MLC, Ser-19) phosphorylation. Furthermore, inhibiting myosin II activity with blebbistatin partly blocked the neuroprotective effects of Rg1. The computer-aided homology modelling revealed that Rg1 preferentially positioned in the actin binding cleft of myosin IIA and might block the binding of myosin IIA to actin filaments. Accordingly, the neuroprotective mechanism of Rg1 is related to the activity that inhibits myosin IIA-actin interaction and the caspase-3/ROCK1/MLC signaling pathway. These findings put some insights into the unique neuroprotective properties of Rg1 associated with the regulation of myosin IIA-actin cytoskeletal structure under oxidative stress and provide experimental evidence for Rg1 in CNS diseases.

Mechanism of ginsenoside Rg1 renal protection in a mouse model of d-galactose-induced subacute damage

Context Ginseng is a widely used herbal medicine in China but its mechanism of action remains unclear. Objective The objectives of this work were to study the protective effect of ginsenoside Rg1 on subacute murine renal damage induced by d-galactose and its mechanism. Materials and methods C57BL/6J mice were injected with 120 mg/kg/d (sc) d-galactose for 1 week, followed by a combined treatment of Rg1 20 mg/kg/d (ip) and 120 mg/kg/d d-galactose (sc) for 5 weeks. Mice were injected with the 0.9% saline 0.2 mL/d (sc) and 120 mg/kg/d d-galactose (sc) for 6 weeks in the control group and the d-galactose group, respectively. After 6 weeks, urea, creatinine, uric acid, cystatin (Cys-C), senescence-associated β-galactosidase (SA-β-gal) staining positive kidney cells, superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), malondialdehyde (MDA), glycation end products (AGEs) and 8-hydroxy-2 deoxyguanosine (8-OH-dG) were measured. Results Treatment with Rg1 ameliorated kidney function and aging state (urea from 17.19 ± 1.09 to 15.77 ± 1.22 mmol·L (-) (1), creatinine from 29.40 ± 5.72 to 22.60 ± 3.97 μmol·L (-) (1), uric acid from 86.80 ± 5.97 to 72.80 ± 10.61 μmol·L (-) (1), Cys-C from 0.23 ± 0.03 to 0.18 ± 0.05 mg·L (-) (1), ROD of SA-β-gal from 56.32 ± 10.48 to 26.78 ± 7.34, SOD from 150.22 ± 19.07 to 190.56 ± 15.83 U·(mg·prot) (-1), MDA from 9.28 ± 1.59 to 3.17 ± 0.82 nmol·(mg·prot) (-1), GSH-PX from 15.68 ± 2.11 to 20.32 ± 2.96 U·(mg·prot) (-1) as well as regulated glomerulus morphology (glomerulus diameter from 775.77 ± 18.41 to 695.04 ± 14.61 μm, renal capsule width from 39.56 ± 3.51 to 31.42 ± 2.70 μm, glomerulus basement membrane from 206.03 ± 16.22 to 157.27 ± 15.70 nm, podocyte slit from 55.21 ± 8.55 to 37.63 ± 6.65 nm). Conclusions Ginsenoside Rg1 can antagonise d-galactose subacute renal damage in mice and this may occur due to alleviating oxidative stress injury.

Protective effect of ginsenosides Rk3 and Rh4 on cisplatin-induced acute kidney injury in vitro and in vivo

BACKGROUND

Nephrotoxicity is the major side effect in cisplatin chemotherapy. Previously, we reported that the ginsenosides Rk3 and Rh4 reduced cisplatin toxicity on porcine renal proximal epithelial tubular cells (LLC-PK1). Here, we aimed to evaluate the protective effect of ginsenosides Rk3 and Rh4 on kidney function and elucidate their antioxidant effect using in vitro and in vivo models of cisplatin-induced acute renal failure.

METHODS

An enriched mixture of ginsenosides Rk3 and Rh4 (KG-KH; 49.3% and 43.1%, respectively) was purified from sun ginseng (heat processed Panax ginseng). Cytotoxicity was induced by treatment of 20μM cisplatin to LLC-PK1 cells and rat model of acute renal failure was generated by single intraperitoneal injection of 5 mg/kg cisplatin. Protective effects were assessed by determining cell viability, reactive oxygen species generation, blood urea nitrogen, serum creatinine, antioxidant enzyme activity, and histopathological examination.

RESULTS

The in vitro assay demonstrated that KG-KH (50 μg/mL) significantly increased cell viability (4.6-fold), superoxide dismutase activity (2.8-fold), and glutathione reductase activity (1.5-fold), but reduced reactive oxygen species generation (56%) compared to cisplatin control cells. KG-KH (6 mg/kg, per os) also significantly inhibited renal edema (87% kidney index) and dysfunction (71.4% blood urea nitrogen, 67.4% creatinine) compared to cisplatin control rats. Of note, KG-KH significantly recovered the kidney levels of catalase (1.2-fold) and superoxide dismutase (1.5-fold).

CONCLUSION

Considering the oxidative injury as an early trigger of cisplatin nephrotoxicity, our findings suggest that ginsenosides Rk3 and Rh4 protect the kidney from cisplatin-induced oxidative injury and help to recover renal function by restoring intrinsic antioxidant defenses.

Autophagy protects podocytes from sublytic complement induced injury

Podocyte injury induced by sublytic complement attack is the main feature of membranous nephropathy (MN). This study aimed at investigating the impact of sublytic complement attack-related autophagy on podocyte injury in vitro. Here, we show that sublytic complement attack enhances MPC5 podocyte autophagy in vitro. Inhibition of autophagy by treatment with 3-methyladenine (3-MA) significantly increased sublytic complement attack-induced changes in the injury-related morphology, stress fiber, and podocyte apoptosis, but decreased the survival and adhesion of MPC5 podocytes. In contrast, promotion of autophagy by treatment with rapamycin mitigated sublytic complement attack-induced changes in the injury-related morphology, stress fiber, and podocyte apoptosis, but increased the survival and adhesion of MPC5 podocytes. These data suggest that autophagy may protect podocytes from sublytic complement attack-induced injury in vitro.

Tongxinluo Protects against Hypertensive Kidney Injury in Spontaneously-Hypertensive Rats by Inhibiting Oxidative Stress and Activating Forkhead Box O1 Signaling

Hypertension is an independent risk factor for the progression of chronic renal failure, and oxidative stress plays a critical role in hypertensive renal damage. Forkbox O1(FoxO1) signaling protects cells against oxidative stress and may be a useful target for treating oxidative stress-induced hypertension. Tongxinluo is a traditional Chinese medicine with cardioprotective and renoprotective functions. Therefore, this study aimed to determine the effects of Tongxinluo in hypertensive renal damage in spontaneously hypertensive rats(SHRs)and elucidate the possible involvement of oxidative stress and FoxO1 signaling in its molecular mechanisms. SHRs treated with Tongxinluo for 12 weeks showed a reduction in systolic blood pressure. In addition to increasing creatinine clearance, Tongxinluo decreased urinary albumin excretion, oxidative stress injury markers including malondialdehyde and protein carbonyls, and expression of nicotinamide adenine dinucleotide phosphate oxidase subunits and its activity in SHR kidneys. While decreasing phosphorylation of FoxO1, Tongxinluo also inhibited the phosphorylation of extracellular signal-regulated kinase1/2 and p38 and enhanced manganese superoxide dismutase and catalase activities in SHR kidneys. Furthermore, histology revealed attenuation of glomerulosclerosis and renal podocyte injury, while Tongxinluo decreased the expression of α-smooth muscle actin, extracellular matrixprotein, transforming growth factor β1 and small mothers against decapentaplegic homolog 3,and improved tubulointerstitial fibrosis in SHR kidneys. Finally, Tongxinluo inhibited inflammatory cell infiltration as well as expression of tumor necrosis factor-α and interleukin-6. In conclusion, Tongxinluo protected SHRs against hypertension-induced renal injury by exerting antioxidant, antifibrotic, and anti-inflammatory activities. Moreover, the underlying mechanisms of these effects may involve inhibition of oxidative stress and functional activation of FoxO1 signaling.

Effect of Tongxinluo on Nephrin Expression via Inhibition of Notch1/Snail Pathway in Diabetic Rats

Podocyte injury is an important mechanism of diabetic nephropathy (DN). Accumulating evidence suggests that nephrin expression is decreased in podocyte in DN. Moreover, it has been demonstrated that tongxinluo (TXL) can ameliorate renal structure disruption and dysfunction in DN. However, the effect of TXL on podocyte injury in DN and its molecular mechanism is unclear. In order to explore the effect of TXL on podocyte injury and its molecular mechanism in DN, our in vivo and in vitro studies were performed. Our results showed that TXL increased nephrin expression in diabetic rats and in high glucose cultured podocyte. Meanwhile, TXL decreased ICN1 (the intracellular domain of notch), HES1, and snail expression in podocyte in vivo and in vitro. More importantly, we found that TXL protected podocyte from injury in DN. The results demonstrated that TXL inhibited the activation of notch1/snail pathway and increased nephrin expression, which may be a mechanism of protecting effect on podocyte injury in DN.

Ginsenoside Rg1 protects mouse podocytes from aldosterone-induced injury in vitro

AIM

Aldosterone is elevated in many diseases such as hypertension, diabetic nephropathy and chronic kidney disease, etc. The aim of this study was to investigate the effects of aldosterone on intracellular ROS production and autophagy in podocytes in vitro, and to explore the possibility of ginsenoside Rg1 (Rg1) being used for protecting podocytes from aldosterone-induced injury.

METHODS

MPC5 mouse podocyte cells were tested. Autophagosome and autophagic vacuole formation were examined under confocal microscopy with MDC and acridine orange staining, respectively. ROS were detected with flow cytometry. Malondialdehyde content and superoxide dismutase (T-SOD) activity were measured using commercial kits. The expression of LC3-II, beclin-1, SOD2 and catalase was measured by Western blotting.

RESULTS

Treatment with aldosterone (10 nmol/L) significantly increased ROS generation and the expression of SOD2 and catalase in MPC5 cells. Furthermore, treatment with aldosterone significantly increased the conversion of LC3-I to LC3-II, beclin-1 expression and autophagosome formation. Co-treatment with rapamycin (1 ng/mL) or chloroquine (10 μmol/L) further increased aldosterone-induced autophagosome formation. Co-treatment with Rg1 (80 ng/mL) effectively relieved oxidative stress and increased T-SOD activity at the early stage and subsequently decreased autophagy in aldosterone-treated podocytes. Co-treatment with 3-MA (4 mmol/L) or NAC (50 mmol/L) exerted similar effects against aldosterone-induced autophagy in podocytes.

CONCLUSION

Aldosterone enhances ROS generation and promotes autophagy in podocytes in vitro. Ginsenoside-Rg1 effectively relieves aldosterone-induced oxidative stress, thereby indirectly inhibiting aldosterone-induced podocyte autophagy.