Nephrin loss is reduced by grape seed proanthocyanidins in the experimental diabetic nephropathy rat model

Proanthocyanidins alleviate Henoch-Schönlein purpura by mitigating inflammation and oxidative stress through regulation of the TLR4/MyD88/NF-κB pathway

OBJECTIVE

Investigate Proanthocyanidins (PCs) efficacy and mechanisms in treating Henoch-Schönlein purpura (HSP)-like rat models, focusing on inflammatory and oxidative stress (OS) responses.

METHODS

An HSP-like rat model was established using ovalbumin (OVA) injection, leading to symptoms mimicking HSP. The study measured inflammatory markers (IL-4, IL-17, TNF-α), OS markers (MDA, SOD, CAT), and assessed the TLR4/MyD88/NF-κB signaling pathway's involvement via histopathological and immunofluorescence analyses.

RESULTS

PCs treatment significantly improved HSP-like symptoms, reduced inflammatory cell infiltration, and decreased IgA deposition in renal mesangial areas. Serum analyses revealed that PCs effectively lowered IL-4, IL-17, TNF-α, and MDA levels while increasing SOD and CAT levels (p < 0.05). Crucially, PCs also downregulated TLR4, MyD88, and NF-κB expressions, highlighting the blockage of the TLR4-mediated signaling pathway as a key mechanism.

CONCLUSION

PCs show promising therapeutic effects in HSP-like rats by mitigating inflammatory responses and oxidative damage, primarily through inhibiting the TLR4/MyD88/NF-κB pathway. These findings suggest PCs as a potential treatment avenue for HSP, warranting further investigation.

Mechanistic role of Syzygium cumini (L.) Skeels in glycation induced diabetic nephropathy via RAGE-NF-κB pathway and extracellular proteins modifications: A molecular approach

ETHNOPHARMACOLOGY RELEVANCE

Syzygium cumini (L.) Skeels (SC), an ancient medicinal plant, is used as a complementary and alternative medicine for treating diabetes mellitus and its associated complications, such as diabetic nephropathy (DN). Phytochemicals present in SC homeopathic formulations possess anti-glycemic, anti-glycation, anti-inflammatory, and antioxidant properties. Additionally, the non-enzymatic formation of advanced glycation end products (AGEs) increases during hyperglycemia in diabetes. AGEs interaction with their receptor of AGEs (RAGE) promotes inflammation via Nuclear Factor-κB (NF-κB) and the accumulation of Extracellular Matrix (ECM) proteins, contributing to the renal dysfunction in DN. However, the molecular mechanism through which SC formulations interact with the AGEs-RAGE-NF-κB pathway has not yet been investigated.

AIM

This study aims to examine the impact of SC formulations on the RAGE-NF-κB pathway and ECM protein modifications in glycation-induced DN using a molecular approach.

MATERIALS AND METHODS

Human serum albumin (10 mg/ml) was glycated with MGO (55 mM) in the presence of SC formulations - Mother tincture (MT), 30C, 200C for 7 days. Glycated samples were added to renal cells (HEK 293) for 24 h. Subsequently, cellular gene and protein expressions of RAGE, NF-κB, vascular endothelial growth factor (VEGF), interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), collagen IV (Col IV), and fibronectin were determined using RT-qPCR and Western blot analysis. The immunofluorescence, luciferase assay, and chromatin immunoprecipitation techniques were employed to gain insights into glycation-induced NF-κB nuclear translocation, transcriptional activity, and its effect on RAGE promoter activity in SC-treated cells.

RESULTS

SC formulations significantly downregulated glycation-induced elevated levels of RAGE and NF-κB. Mechanistically, SC formulations prevented NF-κB nuclear translocation, transcriptional activity, and RAGE promoter activity. Also, SC formulations significantly attenuated glycation-enhanced expressions of inflammatory cytokines (IL-6, TNF-α, and VEGF) and ECM proteins (Col IV and fibronectin).

CONCLUSION

Our findings enlighten the molecular mechanism of SC in DN by targeting the AGEs-RAGE-NF-κB signaling pathway, inflammatory responses, and ECM accumulation. Hence, the study validates the protective role of SC formulations and signifies its novel potential for treating DN.

Optimizing diabetic kidney disease animal models: Insights from a meta-analytic approach

Diabetic kidney disease (DKD) is a prevalent complication of diabetes, often leading to end-stage renal disease. Animal models have been widely used to study the pathogenesis of DKD and evaluate potential therapies. However, current animal models often fail to fully capture the pathological characteristics of renal injury observed in clinical patients with DKD. Additionally, modeling DKD is often a time-consuming, costly, and labor-intensive process. The current review aims to summarize modeling strategies in the establishment of DKD animal models by utilizing meta-analysis related methods and to aid in the optimization of these models for future research. A total of 1215 articles were retrieved with the keywords of "diabetic kidney disease" and "animal experiment" in the past 10 years. Following screening, 84 articles were selected for inclusion in the meta-analysis. Review manager 5.4.1 was employed to analyze the changes in blood glucose, glycosylated hemoglobin, total cholesterol, triglyceride, serum creatinine, blood urea nitrogen, and urinary albumin excretion rate in each model. Renal lesions shown in different models that were not suitable to be included in the meta-analysis were also extensively discussed. The above analysis suggested that combining various stimuli or introducing additional renal injuries to current models would be a promising avenue to overcome existing challenges and limitations. In conclusion, our review article provides an in-depth analysis of the limitations in current DKD animal models and proposes strategies for improving the accuracy and reliability of these models that will inspire future research efforts in the DKD research field.

Therapeutic Potential of Extracts from Macaranga tanarius (MTE) in Diabetic Nephropathy

Diabetic nephropathy is a complication of diabetes that leads to end-stage kidney disease and is a major health burden worldwide. Prenylflavonoid compounds extracted from Macaranga tanarius (MTE) exhibit anti-inflammation, anti-oxidant, and anti-bacterial properties. However, the effects of these compounds on diabetic nephropathy remain unclear. The effects of MTE on diabetic nephropathy were investigated in vitro by using mouse renal mesangial cells and in vivo by using a db/db knockout mouse model. No overt alteration in proliferation was observed in mouse renal mesangial cells treated with 0-1 μg/mL MTE. Western blot analysis indicated that MTE dose-dependently attenuated the expression of fibronectin, α-smooth muscle actin, and collagen IV. Administration of MTE ameliorated renal albumin loss in db/db mice. Immunohistochemical staining revealed that MTE mitigated diabetes-induced fibronectin and collagen IV expression. Periodic acid-Schiff (PAS) and trichrome staining also showed that administration of MTE reduced the renal fibrosis phenomenon. MTE significantly ameliorated diabetes-induced nephropathy.

Grape seed proanthocyanidin extract targets p66Shc to regulate mitochondrial biogenesis and dynamics in diabetic kidney disease

Mitochondrial biogenesis and dynamics are associated with renal mitochondrial dysfunction and the pathophysiological development of diabetic kidney disease (DKD). Decreased p66Shc expression prevents DKD progression by significantly regulating mitochondrial function. Grape seed proanthocyanidin extract (GSPE) is a potential therapeutic medicine for multiple kinds of diseases. The effect of GSPE on the mitochondrial function and p66Shc in DKD has not been elucidated. Hence, we decided to identify p66Shc as a therapeutic target candidate to probe whether GSPE has a renal protective effect in DKD and explored the underlying mechanisms.

METHODS

In vivo, rats were intraperitoneally injected with streptozotocin (STZ) and treated with GSPE. Biochemical changes, mitochondrial morphology, the ultrastructure of nephrons, and protein expression of mitochondrial biogenesis (SIRT1, PGC-1α, NRF1, TFAM) and dynamics (DRP1, MFN1) were determined. In vitro, HK-2 cells were transfected with p66Shc and treated with GSPE to evaluate changes in cell apoptosis, reactive oxygen species (ROS), mitochondrial quality, the protein expression.

RESULTS

In vivo, GSPE significantly improved the renal function of rats, with less proteinuria and a lower apoptosis rate in the injured renal tissue. Besides, GSPE treatment increased SIRT1, PGC-1α, NRF1, TFAM, and MFN1 expression, decreased p66Shc and DRP1 expression. In vitro, overexpression of p66Shc decreased the resistance of HK-2 cells to high glucose toxicity, as shown by increased apoptosis and ROS production, decreased mitochondrial quality and mitochondrial biogenesis, and disturbed mitochondrial dynamic homeostasis, ultimately leading to mitochondrial dysfunction. While GSPE treatment reduced p66Shc expression and reversed these changes.

CONCLUSION

GSPE can maintain the balance between mitochondrial biogenesis and dynamics by negatively regulating p66Shc expression.

A natural products solution to diabetic nephropathy therapy

Diabetic nephropathy is one of the most common complications in diabetes. It has been shown to be the leading cause of end-stage renal disease. However, due to their complex pathological mechanisms, effective therapeutic drugs other than angiotensin-converting enzyme inhibitors (ACEIs) and angiotensin receptor blockers (ARBs), which have been used for 20 years, have not been developed so far. Recent studies have shown that diabetic nephropathy is characterized by multiple signalling pathways and multiple targets, including inflammation, apoptosis, pyroptosis, autophagy, oxidative stress, endoplasmic reticulum stress and their interactions. It definitely exacerbates the difficulty of therapy, but at the same time it also brings out the chance for natural products treatment. In the most recent two decades, a large number of natural products have displayed their potential in preclinical studies and a few compounds are under invetigation in clinical trials. Hence, many compounds targeting these singals have been emerged as a comprehensive blueprint for treating strategy of diabetic nephropathy. This review focuses on the cellular and molecular mechanisms of natural prouducts that alleviate this condition, including preclinical studies and clinical trials, which will provide new insights into the treatment of diabetic nephropathy and suggest novel ideas for new drug development.

Oxidative Stress and NRF2/KEAP1/ARE Pathway in Diabetic Kidney Disease (DKD): New Perspectives

Diabetes mellitus (DM) is one of the most debilitating chronic diseases worldwide, with increased prevalence and incidence. In addition to its macrovascular damage, through its microvascular complications, such as Diabetic Kidney Disease (DKD), DM further compounds the quality of life of these patients. Considering DKD is the main cause of end-stage renal disease (ESRD) in developed countries, extensive research is currently investigating the matrix of DKD pathophysiology. Hyperglycemia, inflammation and oxidative stress (OS) are the main mechanisms behind this disease. By generating pro-inflammatory factors (e.g., IL-1,6,18, TNF-α, TGF-β, NF-κB, MCP-1, VCAM-1, ICAM-1) and the activation of diverse pathways (e.g., PKC, ROCK, AGE/RAGE, JAK-STAT), they promote a pro-oxidant state with impairment of the antioxidant system (NRF2/KEAP1/ARE pathway) and, finally, alterations in the renal filtration unit. Hitherto, a wide spectrum of pre-clinical and clinical studies shows the beneficial use of NRF2-inducing strategies, such as NRF2 activators (e.g., Bardoxolone methyl, Curcumin, Sulforaphane and their analogues), and other natural compounds with antioxidant properties in DKD treatment. However, limitations regarding the lack of larger clinical trials, solubility or delivery hamper their implementation for clinical use. Therefore, in this review, we will discuss DKD mechanisms, especially oxidative stress (OS) and NRF2/KEAP1/ARE involvement, while highlighting the potential of therapeutic approaches that target DKD via OS.

Flavonoids on diabetic nephropathy: advances and therapeutic opportunities

With the advances in biomedical technologies, natural products have attracted substantial public attention in the area of drug discovery. Flavonoids are a class of active natural products with a wide range of pharmacological effects that are used for the treatment of several diseases, in particular chronic metabolic diseases. Diabetic nephropathy is a complication of diabetes with a particularly complicated pathological mechanism that affects at least 30% of diabetic patients and represents a great burden on public health. A large number of studies have shown that flavonoids can alleviate diabetic nephropathy. This review systematically summarizes the use of common flavonoids for the treatment of diabetic nephropathy. We found that flavonoids play a therapeutic role in diabetic nephropathy mainly by regulating oxidative stress and inflammation. Nrf-2/GSH, ROS production, HO-1, TGF-β1 and AGEs/RAGE are involved in the process of oxidative stress regulation. Quercetin, apigenin, baicalin, luteolin, hesperidin, genistein, proanthocyanidin and eriodictyol were found to be capable of alleviating oxidative stress related to the aforementioned factors. Regarding inflammatory responses, IL-1, IL-6β, TNF-α, SIRT1, NF-κB, and TGF-β1/smad are thought to be essential. Quercetin, kaempferol, myricetin, rutin, genistein, proanthocyanidin and eriodictyol were confirmed to influence the above targets. As a result, flavonoids promote podocyte autophagy and inhibit the overactivity of RAAS by suppressing the upstream oxidative stress and inflammatory pathways, ultimately alleviating DN. The above results indicate that flavonoids are promising drugs for the treatment of diabetic nephropathy. However, due to deficiencies in the effect of flavonoids on metabolic processes and their lack of structural stability in the body, further research is required to address these issues.

Protective Effects of Grape Seed Proanthocyanidins on the Kidneys of Diabetic Rats through the Nrf2 Signalling Pathway

Background

Diabetic nephropathy (DN) is the most common cause of end-stage renal failure. Grape seed proanthocyanidin extract (GSPE) is a powerful antioxidant that is believed to protect the kidney through antioxidant action. However, the underlying mechanism of GSPE protection against DN remains unclear.

Objective

To explore if GSPE can improve DN by activating nuclear factor erythroid 2-related factor 2 (Nrf2) antioxidant response element signalling and to clarify its possible mechanism. Materials and methods. Ten healthy Sprague-Dawley rats were randomly selected as controls. Rats with streptozotocin-induced diabetes were randomly divided into three groups (10 animals/group): type 2 diabetes mellitus (T2DM) group (untreated), L-GSPE group (treated with 125-mg/kg/day GSPE for 8 weeks), and H-GSPE group (treated with 250 mg/kg/day GSPE for 8 weeks).

Results

Renal histopathological results indicated limited pathological damage in GSPE-treated groups. Compared with the T2DM group, the H-GSPE group had significantly reduced kidney weight and renal index. Similarly, the levels of fasting blood glucose, serum creatinine, blood urea nitrogen, uric acid, urinary albumin, and renal malondialdehyde (p < 0.05) were also significantly decreased. In addition, GSPE significantly increased the levels of superoxide dismutase, total antioxidative capability, and glutathione (p < 0.05) as well as the protein levels of Nrf2, HO-1, glutathione S-transferase, and NAD (P)H quinone oxidoreductase 1 (p < 0.05).

Conclusion

The results indicate that GSPE reduced renal damage in rats with diabetes by activating the Nrf2 signalling pathway, which consequently increased the antioxidant capacity of the tissue. Therefore, GSPE is a potential natural agent for the treatment of diabetic nephropathy.

Renal protective effect of pinitol in experimental diabetes

Pinitol is a natural antidiabetic agent shown to prevent or ameliorate metabolic and overall vascular and neural function. In the present study we have evaluated the potential benefits of pinitol on renal function of streptozotocin (STZ)-induced diabetic rats. Both euglycemic or 8-week or 16-week diabetic rats were treated with either saline (1 ml/kg/12h; p.o) or pinitol (20 mg/kg/12h; p.o). The renal function was evaluated by using metabolic cages, renal hemodynamic and tubular parameters measurements. Histological examination and evaluation of the protein expression of renal markers such as nephrin, TGFβ and pERK were also performed. Pinitol decreased by 50% the increased urinary albumin/creatinine ratio in both 8-week and 16 week diabetic rats. In addition, the glomerular volume of 16-week rats increased by 55% and this increase was blunted by pinitol. Remarkably, pressure-natriuresis was completely blunted in both 8 and 16-week diabetic rats but this impairment was prevented by pinitol in both treatment regimens. Pinitol ameliorated renal lesions and also prevented the decrease in nephrin expression and the increase of pERK and TGFβ expression in both diabetic groups. Natriuresis due to high renal perfusion pressure increased 7-fold in control animals but was blocked in 16-week diabetic rats and remarkably pinitol partially restored pressure natriuresis (3-fold increase in sodium excretion during pressure natriuresis). Pinitol prevents and ameliorates albuminuria, glomerular expansion, impairment of pressure-natriuresis, renal structural alterations and changes of renal markers and has the potential to be tested for the prevention of diabetic kidney disease.

Saxagliptin attenuates glomerular podocyte injury by increasing the expression of renal nephrin and podocin in type 2 diabetic rats

AIMS

To observe the effects of saxagliptin on the expression of mitogen-activated protein kinase 38 (p38MAPK), nephrin and podocin in renal tissue in type 2 diabetic (T2DM) rats, and to explore the possible mechanism of its renal protection.

METHODS

Forty-eight male Sprague-Dawley rats were used for the study and divided into four different groups: normal controls (Group NC), DM controls (Group DM), DM + glibenclamide (Group Su) and DM + saxagliptin (Group Sa). The day drug administration started was defined as week 0. After 12 weeks, hemoglobin A1c (HbA1c), total cholesterol (TC), triglyceride (TG), urea nitrogen (BUN) and creatinine (Cr) in serum were detected, simultaneously albumin and creatinine in urine were measured, respectively, and then urinary albumin/creatinine ratio (UACR) was calculated. The pathological morphology of kidney tissue in different groups was observed, and the expression of nephrin and podocin mRNA and protein in kidney tissue were detected.

RESULTS

(1) After 12 weeks, FBG and HbA1c in Group Su and Group Sa were significantly lower than those in Group DM (both P < 0.05), while there was no significant difference between Group Su and Group Sa. TC, TG and UACR in Group Sa were significantly decreased than those in Group DM. (2) When compared with Group DM, the kidney weight/body weight ratios, the average width of glomerular basement membrane and foot process fusion ratio were all improved in Group Sa after 12 weeks. (3) The expression of p38MAPK mRNA and protein was significantly decreased, while nephrin and podocin mRNA and protein were significantly higher in Group Sa than those in Group DM after 12 weeks. (4) A significant negative correlation was detected between p38MAPK mRNA and nephrin (r = - 0.421, P = 0.009) and podocin mRNA (r = - 0.570, P = 0.000), respectively.

CONCLUSIONS

Saxagliptin can reduce urinary albumin excretion and exert renal protective effect, especially on podocytes in T2DM rats. The mechanism may be related to its inhibition of renal p38MAPK signaling pathway and the increase in the expression of nephrin and podocin in renal tissue, which is independent of its hypoglycemic effect.