Epigallocatechin-3-gallate protects kidneys from ischemia reperfusion injury by HO-1 upregulation and inhibition of macrophage infiltration

Nrf2/HO-1 as a therapeutic target in renal fibrosis

Chronic kidney disease (CKD) is one of the most prevalent chronic diseases and affects between 10 and 14 % of the world's population. The World Health Organization estimates that by 2040, the disease will be fifth in prevalence. End-stage CKD is characterized by renal fibrosis, which can eventually lead to kidney failure and death. Renal fibrosis develops due to multiple injuries and involves oxidative stress and inflammation. In the human body, nuclear factor erythroid 2-related factor 2 (Nrf2) plays an important role in the expression of antioxidant, anti-inflammatory, and cytoprotective genes, which prevents oxidative stress and inflammation damage. Heme oxygenase (HO-1) is an inducible homolog influenced by heme products and after exposure to cellular stress inducers such as oxidants, inflammatory chemokines/cytokines, and tissue damage as an outcome or downstream of Nrf2 activation. HO-1 is known for its antioxidative properties, which play an important role in regulating oxidative stress. In renal diseases-induced tissue fibrosis and xenobiotics-induced renal fibrosis, Nrf2/HO-1 has been targeted with promising results. This review summarizes these studies and highlights the interesting bioactive compounds that may assist in attenuating renal fibrosis mediated by HO-1 activation. In conclusion, Nrf2/HO-1 signal activation could have a renoprotective effect strategy against CKD caused by oxidative stress, inflammation, and consequent renal fibrosis.

Epigallocatechin-3-gallate in combination with corticosteroids mitigates heat stress-induced acute kidney injury through modulating heat shock protein 70 and toll-like receptor 4-dependent pathways

Recently, recurrent heat stress (HS) and dehydration have been exhibited to give rise to kidney disease epidemic in hot regions. The current study was carried out to estimate a possible renoprotective effect of dexamethasone (Dexa) and epigallocatechin-3-gallate (EGCG) as a heat shock protein (HSP)-70 inhibitor on HS-induced nephropathy. In total, five groups of rats were used: control group, HS group (exposed to heat for 40 min), Dexa+HS group (rats were injected with Dexa i.p.15 mg/kg/day for 3 days followed by HS), EGCG+HS group (rats received EGCG 100 mg/kg/day, orally, for 7 days followed by HS), and EGCG+ Dexa +HS group (rats received EGCG 100 mg/kg/day, orally, for 7 days and injected Dexa as described along the last 3 days followed by HS). Kidney sections were stained with H&E and scored for tubular injury. A marked increase in creatinine, urea, malondialdehyde (MDA), monocyte chemoattractant protein (MCP)-1, HSP-70, nuclear factor kappa B (NF-κB), toll-like receptor 4 (TLR-4) and Caspase-3 expression was observed after HS induction (p < 0.001). Treatment with EGCG combined with Dexa notably reduced tubular injury, MCP-1, HSP-70, NF-κB, and TLR-4 levels (p < 0.001). Moreover, it increased IL-10, antioxidant capacity and Bcl-2 expression levels in the kidney (p < 0.001). This renoprotective impact might be attributed to anti-inflammatory, antioxidant, and anti-apoptotic mechanisms besides interfering with TLR-4-mediated NF-κB activation pathway.

Antifibrotic Agents for the Management of CKD: A Review

Kidney fibrosis is a hallmark of chronic kidney disease (CKD) and a potential therapeutic target. However, there are conceptual and practical challenges to directly targeting kidney fibrosis. Whether fibrosis is mainly a cause or a consequence of CKD progression has been disputed. It is unclear whether specifically targeting fibrosis is feasible in clinical practice because most drugs that decrease fibrosis in preclinical models target additional and often multiple pathogenic pathways (eg, renin-angiotensin-aldosterone system blockade). Moreover, tools to assess whole-kidney fibrosis in routine clinical practice are lacking. Pirfenidone, a drug used for idiopathic pulmonary fibrosis, is undergoing a phase 2 trial for kidney fibrosis. Other drugs in use or being tested for idiopathic pulmonary fibrosis (eg, nintedanib, PRM-151, epigallocatechin gallate) are also potential candidates to treat kidney fibrosis. Novel therapeutic approaches may include antagomirs (eg, lademirsen) or drugs targeting interleukin 11 or NKD2 (WNT signaling pathway inhibitor). Reversing the dysfunctional tubular cell metabolism that leads to kidney fibrosis offers additional therapeutic opportunities. However, any future drug targeting fibrosis of the kidneys should demonstrate added benefit to a standard of care that combines renin-angiotensin system with mineralocorticoid receptor (eg, finerenone) blockade or with sodium/glucose cotransporter 2 inhibitors.

Ethnobotanical, pharmacological, phytochemical, and clinical investigations on Moroccan medicinal plants traditionally used for the management of renal dysfunctions

ETHNOPHARMACOLOGICAL RELEVANCE

Renal disease is a significant public health concern that affects people all over the world. The main limitations of conventional therapy are the adverse reaction on human health and the expensive cost of drugs. Indeed, it is necessary to develop new therapeutic strategies that are less expensive and have fewer side effects. As a consequence of their natural compounds, medicinal plants can be used as an alternative therapy to cure various ailments including kidney diseases.

OBJECTIVE

of the study: This review paper has two principal goals: (1) to inventory and describe the plants and their ancestral use by Moroccan society to cure renal problems, (2) to link traditional use with scientific confirmations (preclinical and clinical).

METHODS

To analyze pharmacological effects, phytochemical, and clinical trials of plants, selected for renal therapy, a bibliographical search was undertaken by examining ethnobotanical investigations conducted in Morocco between 1991 and 2019 and consulting peer-reviewed papers from all over the world.

RESULTS

Approximately 290 plant species, spanning 81 families and 218 genera have been reported as being utilized by Moroccans to manage renal illness. The most frequently mentioned species in Morocco were Herniaria hirsuta subsp. cinerea (DC.), Petroselinum crispum (Mill.) Fuss and Rosmarinus officinalis L. The leaves were the most frequently used plant parts, followed by the whole plant. Decoction and infusion were the most popular methods of preparation. A record of 71 plant species was studied in vitro and/or in vivo for their therapeutic efficacy against kidney disorders, including 10 plants attempting to make it to the clinical stage. Twenty compounds obtained from 15 plants have been studied for the treatment of kidney diseases.

CONCLUSION

Medicinal herbs could be a credible alternative therapy for renal illness. However, additional controlled trials are required to confirm their efficiency in patients with kidney failure. Overall, this work could be used as a database for future exploration.

Polyphenols and Their Metabolites in Renal Diseases: An Overview

Kidney diseases constitute a worldwide public health problem, contributing to morbidity and mortality. The present study aimed to provide an overview of the published data regarding the potential beneficial effects of polyphenols on major kidney diseases, namely acute kidney injury, chronic kidney disease, diabetic nephropathy, renal cancer, and drug-induced nephrotoxicity. This study consists of a bibliographical review including in vitro and in vivo studies dealing with the effects of individual compounds. An analysis of the polyphenol metabolome in human urine was also conducted to estimate those compounds that are most likely to be responsible for the kidney protective effects of polyphenols. The biological effects of polyphenols can be highly attributed to the modulation of specific signaling cascades including those involved in oxidative stress responses, anti-inflammation processes, and apoptosis. There is increasing evidence that polyphenols afford great potential in renal disease protection. However, this evidence (especially when in vitro studies are involved) should be considered with caution before its clinical translation, particularly due to the unfavorable pharmacokinetics and extensive metabolization that polyphenols undergo in the human body. Future research should consider polyphenols and their metabolites that indeed reach kidney tissues.

Potential Effects of Delphinidin-3-O-Sambubioside and Cyanidin-3-O-Sambubioside of Hibiscus sabdariffa L. on Ruminant Meat and Milk Quality

Simple Summary

Hibiscus sabdariffa (HS) calyxes are widely used as nutraceutical supplements in humans; however, stalks, leaves, and seeds are considered as agriculture by-products. Including HS by-products in animal feeding could reduce economic costs and environmental problems, and due to their bioactive compounds, could even improve the quality of meat and milk. However, although HS antioxidants have not been tested enough in ruminants, comparison with other by-products rich in polyphenols allows for hypothesizing on the potential effects of including HS by-products and calyxes in nutrition, animal performance, and meat and milk quality. Antioxidants of HS might affect ruminal fiber degradability, fermentation patterns, fatty acids biohydrogenation (BH), and reduce the methane emissions. After antioxidants cross into the bloodstream and deposit into ruminants’ milk and meat, they increase the quality of fatty acids, the antioxidant activity, and the shelf-life stability of dairy products and meat, which leads to positive effects in consumers’ health. In other animals, the specific anthocyanins of HS have improved blood pressure, which leads to positive clinical and chemicals effects, and those could affect some productive variables in ruminants. The HS by-products rich in polyphenols and anthocyanins can improve fatty acid quality and reduce the oxidative effects on the color, odor, and flavor of milk products and meat.

Abstract

The objective was to review the potential effects of adding anthocyanin delphinidin-3-O-sambubioside (DOS) and cyanidin-3-O-sambubioside (COS) of HS in animal diets. One hundred and four scientific articles published before 2021 in clinics, pharmacology, nutrition, and animal production were included. The grains/concentrate, metabolic exigency, and caloric stress contribute to increasing the reactive oxygen species (ROS). COS and DOS have antioxidant, antibacterial, antiviral, and anthelmintic activities. In the rumen, anthocyanin might obtain interactions and/or synergisms with substrates, microorganisms, and enzymes which could affect the fiber degradability and decrease potential methane (CH₄) emissions; since anthocyanin interferes with ruminal fatty acids biohydrogenation (BH), they can increase the n-3 and n-6 polyunsaturated fatty acids (PUFA), linoleic acid (LA), and conjugated linoleic acid (CLA) in milk and meat, as well as improving their quality. Anthocyanins reduce plasma oxidation and can be deposited in milk and meat, increasing antioxidant activities. Therefore, the reduction of the oxidation of fats and proteins improves shelf-life. Although studies in ruminants are required, COS and DOS act as inhibitors of the angiotensin-converting enzyme (ACEi) and rennin expression, regulating the homeostatic control and possibly the milk yield and body weight. By-products of HS contain polyphenols as calyces with positive effects on the average daily gain and fat meat quality.

Epigallocatechin-3-gallate Alleviates Vanadium-Induced Reduction of Antioxidant Capacity via Keap1-Nrf2-sMaf Pathway in the Liver, Kidney, and Ovary of Laying Hens

This study evaluated the effect of epigallocatechin-3-gallate (EGCG) alleviating the reduction of antioxidant capacity induced by dietary vanadium (V) in the liver, kidney, and ovary of laying hens. Furthermore, Kelch-like ECH-associated protein 1(Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2)-small Maf proteins (sMaf) pathway was explored to reveal the molecular mechanism. A total of 768 40-week-old Hyline-Brown laying hens were randomly allocated to 4 groups with 8 pens per group and 24 hens per pen. The experimental groups were as follows: control (basal diet); V15, control + 15 mg/kg V; EGCG150, control + 150 mg/kg EGCG; V15 + EGCG150, V15 + 150 mg/kg EGCG. Our results revealed that dietary EGCG supplementation completely alleviated the V-induced reductions of hen-day egg production, average egg weight, Haugh unit, albumen height, eggshell strength, and eggshell thickness. Dietary EGCG supplementation completely prevented the V-induced reductions of serum follicle-stimulating hormone and luteinizing hormone levels. Besides, dietary EGCG supplementation reversed the V-induced increments of alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), creatinine (Cr), and uric acid (UA). In addition, dietary EGCG supplementation partially alleviated the V-induced reductions of the enzyme activities and gene expressions of superoxidative dismutase (SOD), catalase (CAT), glutathione reductase (GR), and glutathione peroxidase (GSH-Px). Furthermore, dietary EGCG supplementation partially alleviated the V-induced reductions of Nrf2 and sMaf gene expressions, and the increments of Keap1 gene expression. In summary, EGCG partially alleviated V-induced reduction of antioxidant capacity through Keap1-Nrf2-sMaf pathway in the liver, kidney, and ovary of laying hens.

Investigating the Opposing Effect of Two Different Green Tea Supplements on Oxidative Stress, Mitochondrial Function and Cell Viability in HepG2 Cells

Green tea extract (GTE) improves exercise outcomes and reduces obesity. However, case studies indicate contradictory physiology regarding liver function and toxicity. We studied the effect of two different decaffeinated GTE (dGTE) products, from a non-commercial (dGTE1) and commercial (dGTE2) supplier, on hepatocyte function using the human cell model, HepG2. dGTE1 was protective against hydrogen peroxide (H₂O₂)-induced apoptosis and cell death by attenuating oxidative stress pathways. Conversely, dGTE2 increased cellular and mitochondrial oxidative stress and apoptosis. A bioavailability study with dGTE showed the major catechin in GTE, EGCG, reached 0.263 µg·ml^-1. In vitro, at this concentration, EGCG mimicked the protective effect of dGTE1. GC/MS analysis identified steric acid and higher levels of palmitic acid in dGTE2 versus dGTE1 supplements. We demonstrate the significant biological differences between two GTE supplements which may have potential implications for manufacturers and consumers to be aware of the biological effects of supplementation.

Naturally Derived Heme-Oxygenase 1 Inducers and Their Therapeutic Application to Immune-Mediated Diseases

Heme oxygenase (HO) is the primary antioxidant enzyme involved in heme group degradation. A variety of stimuli triggers the expression of the inducible HO-1 isoform, which is modulated by its substrate and cellular stressors. A major anti-inflammatory role has been assigned to the HO-1 activity. Therefore, in recent years HO-1 induction has been employed as an approach to treating several disorders displaying some immune alterations components, such as exacerbated inflammation or self-reactivity. Many natural compounds have shown to be effective inductors of HO-1 without cytotoxic effects; among them, most are chemicals present in plants used as food, flavoring, and medicine. Here we discuss some naturally derived compounds involved in HO-1 induction, their impact in the immune response modulation, and the beneficial effect in diverse autoimmune disorders. We conclude that the use of some compounds from natural sources able to induce HO-1 is an attractive lifestyle toward promoting human health. This review opens a new outlook on the investigation of naturally derived HO-1 inducers, mainly concerning autoimmunity.

Preventive Effects of Grape Extract on Ischemia/Reperfusion-Induced Acute Kidney Injury in Mice

Since grape extract (GE) contains oligomeric proanthocyanidins and numerous polyphenols, dietary GE supplements may exert protective effects against various diseases. The present study investigated the pharmacological effects of GE derived from Chardonnay in vitro and in vivo. GE (100 µg/mL) completely inhibited tumor necrosis factor-α-induced endothelin-1, monocyte chemoattractant protein-1, interleukin-1β, and intercellular adhesion molecule-1 gene expression in cultured endothelial cells. GE also strongly stimulated the phosphatidylinositol 3-kinase (PI3K)/Akt/endothelial nitric oxide synthase (eNOS) pathway. In the in vivo study, the effects of GE on ischemic acute kidney injury (AKI) were examined using male C57bl/6J wild-type and eNOS^-/- mice. Right nephrectomized mice were exposed to 45 min of ischemia in the left kidney and this was followed by reperfusion. Although renal functional parameters in AKI mice significantly increased 48 h after reperfusion, the administration of GE (0.1 and 1 mg/kg, intravenous (i.v.)) 5 min before ischemia dose-dependently improved post-ischemic renal dysfunction in wild-type mice. Renal histopathological studies on AKI mice revealed tubular necrosis, proteinaceous casts in tubuli, and medullary congestion. The administration of GE ameliorated this damage in wild-type mice, but not in eNOS^-/- mice. Furthermore, GE significantly restored decreases in the renal nitric oxide metabolite content due to ischemia in wild-type mice, but not in eNOS^-/- mice. Thus, eNOS is closely involved in the renoprotective effects of GE, strongly suggesting that GE supplements are useful as a prophylactic treatment for the development of ischemic AKI.

Inflammation and Oxidative Stress in Chronic Kidney Disease-Potential Therapeutic Role of Minerals, Vitamins and Plant-Derived Metabolites

Chronic kidney disease (CKD) is a debilitating pathology with various causal factors, culminating in end stage renal disease (ESRD) requiring dialysis or kidney transplantation. The progression of CKD is closely associated with systemic inflammation and oxidative stress, which are responsible for the manifestation of numerous complications such as malnutrition, atherosclerosis, coronary artery calcification, heart failure, anemia and mineral and bone disorders, as well as enhanced cardiovascular mortality. In addition to conventional therapy with anti-inflammatory and antioxidative agents, growing evidence has indicated that certain minerals, vitamins and plant-derived metabolites exhibit beneficial effects in these disturbances. In the current work, we review the anti-inflammatory and antioxidant properties of various agents which could be of potential benefit in CKD/ESRD. However, the related studies were limited due to small sample sizes and short-term follow-up in many trials. Therefore, studies of several anti-inflammatory and antioxidant agents with long-term follow-ups are necessary.

Protective Effects of Ozone Oxidative Postconditioning on Long-term Injury After Renal Ischemia/Reperfusion in Rat

BACKGROUND

Renal ischemia/reperfusion (I/R) injury can cause serious kidney damage (eg, acute aortic injury, chronic fibrosis). Some postconditioning treatments have been reported to protect from I/R effects. However, their mechanisms remain unclear. Here, we focused on potential protective effects of ozone on tubulointerstitial fibrosis after renal I/R injury in rats.

METHODS

Adult male rats were randomly divided into 4 groups with (1) sham-without I/R; (2) I/R-by clamping renal pedicle for 45 minutes; (3) I/R with ozone oxidative postconditioning (OzoneOP) following a 10-day reperfusion; and (4) I/R with oxygen oxidative postconditioning (OxygenOP) following a 10-day reperfusion. The kidneys were collected at 2 time points post I/R 10 days (at early phase) and 12 weeks (at late phase) and then analyzed for renal function, tissue fibrosis, and serum creatinine and urea nitrogen levels by staining and colorimetric methods. Additionally, expression levels of related fibrotic factors, such as α-smooth muscle actin, transforming growth factor β1, and phospho-Smad2, were assayed by immunochemistry staining.

RESULTS

OzoneOP treatment downregulated the α-smooth muscle actin, transforming growth factor β1, and phospho-Smad 2 protein expression in rats subjected to I/R at 10 days and 12 weeks. Moreover, it improved renal dysfunction and attenuated the patchy tubulointerstitial fibrosis.

CONCLUSION

Ourdata indicate that I/R-induced renal damage might cause severe tubulointerstitial fibrosis at the late phase, and OzoneOP treatment may inhibit this fibrotic development.

Protective Effect of Epigallocatechin Gallate in Ischemia-Reperfusion Injury of Rat Skeletal Muscle

BACKGROUND

Reactive oxygen species-induced cell injury has been considered to be one of the main etiologic factors in ischemia-reperfusion injury (IRI). As a potential antioxidant agent, epigallocatechin gallate (EGCG) was examined in skeletal muscle of the rats after IRI with or without treatment.

MATERIALS AND METHODS

Tourniquet application applied to the rats' hind limbs was selected as the appropriate IRI method. Animals were randomly distributed to one of the following groups: (1) sham control + SF (saline) (10 mg/kg/i.p.) (SC-SF), (2) IRI (4 + 2 h) + SF (10 mg/kg/i.p.) (IRI-SF), (3) IRI and EGCG (25 mg/kg/i.p.) (IRI-EG25), and (4) IRI and EGCG (50 mg/kg/i.p) (IRI-EG50). In another set of experiments with identical groups, the only difference was that the reperfusion period was 24 h. A number of different parameters relating to the damage seen in the skeletal muscles, lungs, kidneys, and liver and particular cytokines were measured by proper analytical methods.

RESULTS

In comparison with the SC-SF group, IRI (4 + 2 h) induced an increase in the total oxidative status of skeletal muscle (10.17 ± 0.61 versus 15.74 ± 1.10) and blood creatine phosphokinase (CPK) (669.88 ± 50.23 versus 7202.38 ± 766.13) and lactate dehydrogenase levels (686.00 ± 67.48 versus 1343.00 ± 113.01). Although 25 mg/kg EGCG could not reverse these parameters to their normal levels, the higher dose of EGCG, that is, 50 mg/kg, was sufficient to prevent the increases seen in total oxidative status (8.55 ± 0.85) and CPK levels (4741.63 ± 339.40). In addition, reduced total antioxidant status of skeletal muscle in the IRI-SF group (0.50 ± 0.06) was elevated by the administration of EGCG (50 mg/kg) (0.85 ± 0.04). Regarding remote organ injury, only alanine transaminase (ALT) and aspartate transaminase (AST) levels were found to be increased, showing a slight damage in liver tissue. However, neither dose of EGCG was able to prevent this deleterious effect. As for cytokines (interleukin-1β, IL-6, IL-8, tumor necrosis factor-α, and monocyte chemotactic protein-1), there were no differences between the study groups. In regard to long-term IRI (i.e., 4 + 24 h), statistically significantly elevated parameters in the IRI-SF group were as follows: CPK, lactate dehydrogenase, creatinine (Cr), and blood urea nitrogen. On the other hand, none of them were influenced by either dose of EGCG. According to the results, EGCG demonstrates a considerable protective effect toward IRI (4 + 2 h) of skeletal muscle.

CONCLUSIONS

Although oxidative stress seems to play a significant role both in the pathogenesis of IRI and in the mechanism of action of EGCG, there is no evidence that inflammatory cytokines are, at least in our model, crucial mediators regarding the former events.

Exenatide Reduces Graft Injury in a Rat Transplantation Model Using Kidneys Donated after Cardiac Death

Besides being used in the therapy of type 2 diabetes, exenatide reduces cerebral ischemia-reperfusion (I/R) injury. We evaluated the potential effects of exenatide on inhibition of apoptosis in kidney grafts donated after cardiac death and on reduction of I/R injury after kidney transplantation (KTx) in a rat model. We used a rat syngeneic KTx model with kidney grafts obtained after cardiac death, and apoptosis was detected in the graft before KTx. Graft function, rat survival, morphologic examination, and activation of inflammatory molecules were analyzed after KTx. By the end of the cold storage, exenatide pretreatment donors had significantly reduced caspase pathway activation, terminal deoxynucleotidyl transferase dUTP nick-end labeling--positive cells, release of mitochondrial porin proteins into the cytosol, and expression of cleaved caspase-3 and poly (ADP-ribose) polymerase in kidney grafts. Exenatide pretreatment improved renal function survival rate with lower scores of acute tubular necrosis, infiltrating macrophages, and interstitial fibrosis as well as reduced messenger RNA expression of inflammatory mediators (tumor necrosis factor α, interleukin-6, interleukin-1β, and intercellular adhesion molecule-1) after KTx. Our study showed that exenatide reduced I/R injury in kidneys donated after cardiac death in a rat transplantation model and improved recipient survival and graft function.

The protective effect of epigallocatechin 3-gallate on mouse pancreatic islets via the Nrf2 pathway

PURPOSE

Epigallocatechin 3-gallate (EGCG), a green tea polyphenol, has been shown to have anti-oxidant and anti-inflammatory effects in vitro and in vivo. The aim of this study was to investigate the effects and mechanism of EGCG on isolated pancreatic islets as pre-conditioning for pancreatic islet transplantation.

METHODS

The pancreatic islets were divided into two groups: an islet culture medium group (control) and an islet culture medium with EGCG (100 µM) group. We investigated the islet viability, Nrf2 expression, reactive oxygen species (ROS) production, and heme oxygenase-1 (HO-1) mRNA. Five hundred islet equivalents after 12 h of culture for the EGCG 100 µM and control group were transplanted under the kidney capsule of streptozotocin-induced diabetic ICR mice.

RESULTS

The cell viability and insulin secretion ability in the EGCG group were preserved, and the nuclear translocation of Nrf2 was increased in the EGCG group (p < 0.01). While the HO-1 mRNA levels were also higher in the EGCG group than in the control group (p < 0.05), the ROS production was lower (p < 0.01). An in vivo functional assessment showed that the blood glucose level had decreased in the EGCG group after transplantation (p < 0.01).

CONCLUSION

EGCG protects the viability and function of islets by suppressing ROS production via the Nrf2 pathway.

Protective Effects of Epigallocatechin-3-Gallate from Green Tea in Various Kidney Diseases

Kidney diseases are common health problems worldwide. Various etiologies (e.g., diabetes, hypertension, drug-induced nephrotoxicity, infection, cancers) can affect renal function and ultimately lead to development of chronic kidney disease (CKD) and end-stage renal disease (ESRD). The global rise in number of CKD/ESRD patients during recent years has led to tremendous concern to look for effective strategies to prevent or slow progression of CKD and ESRD. Natural compounds derived from herbs or medicinal plants have gained wide attention for scientific scrutiny to achieve such goals. One of such natural compounds that has been extensively investigated is epigallocatechin-3-gallate (EGCG), a major polyphenol found in the tea plant (Camellia sinensis). A growing body of recent evidence has shown that EGCG may be a promising therapeutic or protective agent in various kidney diseases. This article thus highlights recent progress in medical research on beneficial effects of EGCG against a broad spectrum of kidney diseases, including acute kidney injury, cisplatin-induced nephrotoxicity, kidney stone disease, glomerulonephritis, lupus nephritis, renal cell carcinoma, diabetic nephropathy, CKD, and renal fibrosis. The renoprotective mechanisms are also detailed. Finally, future perspectives of medical research on EGCG and its potential use in clinical practice for treatment and prevention of kidney diseases are discussed.

Aged (Black) versus Raw Garlic against Ischemia/Reperfusion-Induced Cardiac Complications

Recent evidence from studies suggests that aged black garlic also has an effect on health. The major aim of the present study is to compare the effect of raw and aged black garlic on postischemic cardiac recovery. Male Sprague Dawley rats were randomly divided into three groups. Animals of the first group were fed with raw garlic, animals of the second group received aged black garlic, while the third group served as vehicle-treated controls. Upon conclusion of the treatment, isolated hearts were undertaken to ischemia/reperfusion. Heart function and infarct size were measured and the level of HO-1 and iNOS were studied. Superior postischemic cardiac function and reduced infarct size in both garlic treated groups compared to the drug-free control group, indicated cardioprotective effects. However, no significant differences between the garlic treated groups were observed. Western blot analysis revealed that raw garlic enhanced the level of HO-1 before ischemia, while in ischemic samples, we found elevated HO-1 expression in both garlic treated groups. The level of iNOS was the same before ischemia in all groups, however, a markedly reduced iNOS level in ischemic/reperfused hearts originating from control and raw garlic treated animals was observed. Samples from aged black garlic treated animals demonstrated that the level of iNOS was not significantly reduced after ischemia/reperfusion. Taken together these results indicate that not only raw but also aged black garlic possess a cardioprotective effect.

Naturally Occurring Compounds: New Potential Weapons against Oxidative Stress in Chronic Kidney Disease

Oxidative stress is a well-described imbalance between the production of reactive oxygen species (ROS) and the antioxidant defense system of cells and tissues. The overproduction of free radicals damages all components of the cell (proteins, lipids, nucleic acids) and modifies their physiological functions. As widely described, this condition is a biochemical hallmark of chronic kidney disease (CKD) and may dramatically influence the progression of renal impairment and the onset/development of major systemic comorbidities including cardiovascular diseases. This state is exacerbated by exposure of the body to uremic toxins and dialysis, a treatment that, although necessary to ensure patients' survival, exposes cells to non-physiological contact with extracorporeal circuits and membranes with consequent mitochondrial and anti-redox cellular system alterations. Therefore, it is undeniable that counteracting oxidative stress machinery is a major pharmacological target in medicine/nephrology. As a consequence, in recent years several new naturally occurring compounds, administered alone or integrated with classical therapies and an appropriate lifestyle, have been proposed as therapeutic tools for CKD patients. In this paper, we reviewed the recent literature regarding the "pioneering" in vivo testing of these agents and their inclusion in small clinical trials performed in patients affected by CKD.

Heat shock proteins and kidney disease: perspectives of HSP therapy

Heat shock proteins (HSPs) mediate a diverse range of cellular functions, prominently including folding and regulatory processes of cellular repair. A major property of these remarkable proteins, dependent on intracellular or extracellular location, is their capacity for immunoregulation that optimizes immune activity while avoiding hyperactivated inflammation. In this review, recent investigations are described, which examine roles of HSPs in protection of kidney tissue from various traumatic influences and demonstrate their potential for clinical management of nephritic disease. The HSP70 class is particularly attractive in this respect due to its multiple protective effects. The review also summarizes current understanding of HSP bioactivity in the pathophysiology of various kidney diseases, including acute kidney injury, diabetic nephropathy, chronic glomerulonephritis, and lupus nephritis-along with other promising strategies for their remediation, such as DNA vaccination.

The arginine methyltransferase PRMT5 regulates CIITA-dependent MHC II transcription

Class II major histocompatibility complex (MHC II) dependent antigen presentation serves as a key step in mammalian adaptive immunity and host defense. In antigen presenting cells (e.g., macrophages), MHC II transcription can be activated by interferon gamma (IFN-γ) and mediated by class II transactivator (CIITA). The underlying epigenetic mechanism, however, is not completely understood. Here we report that following IFN-γ stimulation, symmetrically dimethylated histone H3 arginine 2 (H3R2Me2s) accumulated on the MHC II promoter along with CIITA. IFN-γ augmented expression, nuclear translocation, and promoter binding of the protein arginine methyltransferase PRMT5 in macrophages. Over-expression of PRMT5 potentiated IFN-γ induced activation of MHC II transcription in an enzyme activity-dependent manner. In contrast, PRMT5 silencing or inhibition of PRMT5 activity by methylthioadenosine (MTA) suppressed MHC II transactivation by IFN-γ. CIITA interacted with and recruited PRMT5 to the MHC II promoter and mediated the synergy between PRMT5 and ASH2/WDR5 to activate MHC II transcription. PRMT5 expression was down-regulated in senescent and H2O2-treated macrophages rendering ineffectual induction of MHC II transcription by IFN-γ. Taken together, our data reveal a pathophysiologically relevant role for PRMT5 in MHC II transactivation in macrophages.

Targeting HO-1 by Epigallocatechin-3-Gallate Reduces Contrast-Induced Renal Injury via Anti-Oxidative Stress and Anti-Inflammation Pathways

Both oxidative stress and inflammation are involved in the pathogenesis of contrast-induced nephropathy (CIN). Epigallocatechin-3-gallate (EGCG), a purified catechin from green tea, has antioxidant and anti-inflammatory effects. However, it is unknown whether or not EGCG is effective in treating CIN. Our present study found that intravenous administration of EGCG, either before or just after the establishment of CIN, had a protective effect, determined by normalization of serum creatinine and blood urea nitrogen levels, improvement in renal histopathological scoring and alleviation of apoptosis, accompanied by decreased oxidative stress and inflammation. Because EGCG is a potent inducer of the antioxidant heme oxygenase-1 (HO-1), we studied HO-1 signaling in CIN. HO-1 levels were increased in CIN; treatment with EGCG further increased HO-1 levels, accompanied by an increase in Nrf2, a regulator of antioxidant proteins. Interestingly, blockade of HO-1 with protoporphyrin IX zinc(II) (ZnPP) prevented the protective effect of EGCG on CIN. ZnPP also blocked the ability of EGCG to increase the activity of an antioxidant (superoxide dismutase), and decrease markers of oxidative stress (myeloperoxidase and malondialdehyde) and inflammation (myeloperoxidase and IL-1β), indicating that HO-1 is the upstream molecule that regulates the EGCG-mediated protection. To determine further the role of HO-1 on the EGCG-mediated inhibition of inflammation, we studied the effect of EGCG on the NLRP3 inflammasome, an upstream signaling of IL-1β. EGCG down-regulated NLRP3 expression, which was blocked by ZnPP, indicating that HO-1 links EGCG with NLRP3. Therefore, EGCG, via up-regulation of HO-1, protects against CIN by amelioration of oxidative stress and inflammation.

Protective effect of epigallocatechin gallate, a major constituent of green tea, against renal ischemia-reperfusion injury in rats

BACKGROUND

Renal ischemia-reperfusion (I/R) injury plays an important role in the acute kidney injury. The pathogenetic mechanisms potential I/R injury is involved in apoptosis and inflammation. Epigallocatechin gallate (EGCG), a major constituent of green tea, has been shown to have anti-inflammatory and anti-apoptotic activities. This study aimed to explore the underlying effects and mechanisms of EGCG on renal I/R injury in a rat model.

MATERIALS AND METHODS

We induced renal I/R injury in SD rats by clamping the left renal artery for 45 min followed by 24-h reperfusion, along with a contralateral nephrectomy. We randomly allocated 30 rats to three groups (n = 10): sham group, IRI group, and EGCG group. We preconditioned rats intraperitoneally with EGCG (50 mg/kg) or vehicle (50 mg/kg) 45 min before inducing renal ischemia. We collected serum and kidneys at 24 h after reperfusion. Renal function and histologic damage were assessed. We also determined markers of inflammation and apoptosis in kidneys or serum.

RESULTS

EGCG pretreatment can significantly reduce renal dysfunction, histologic change and the expression of tumor necrosis factor-α, IL-1β, IL-6, Bax and cleavage caspase 3 induced by I/R injury and increase the expression of Bax and caspase 3. Moreover, EGCG pretreatment can further induce the activation of p38 mitogen-activated protein kinase in kidney, with no influence on the expression of p38.

CONCLUSIONS

EGCG treatment can decrease renal ischemia-reperfusion injury by suppressing inflammation and cell apoptosis. Thus, EGCG may represent a potential strategy to reduce renal I/R injury.

Epigallocatechin-3-gallate reduces tubular cell apoptosis in mice with ureteral obstruction

BACKGROUND

Tubular cell apoptosis plays a crucial role in different kinds of renal diseases. Epigallocatechin-3-gallate (EGCG), a polyphenol extracted from green tea, has been shown to inhibit renal fibrosis in unilateral ureteral obstruction (UUO) mice, but its role in preventing tubular cell apoptosis and the underlying signaling mechanisms still remains unclear.

MATERIALS AND METHODS

Mice subjected to UUO were intraperitoneally administered EGCG (5 mg/kg) for 14 d. Normal rat kidney proximal tubular epithelial cell line NRK-52E was induced by transforming growth factor β1 (TGF-β1). Periodic acid-schiff and Masson's trichrome staining was used for histologic study. TUNEL, Hoechst staining, and flow cytometry analysis were used to measure the apoptotic status of tubular cells. Western blotting was used to determine the expression of apoptotic-associated proteins and mitogen-activated protein kinase pathway proteins.

RESULTS

EGCG significantly attenuated tubular injury and renal tubulointerstitial fibrosis in the obstructed kidneys of UUO mice. In addition, EGCG prevented UUO and TGF-β1-induced tubular apoptosis in a dose-dependent manner. In parallel, protein expression of B-clell lymphoma-2 (Bcl-2) was upregulated and protein expressions of Bcl-2 accosiated X protein (Bax), cleaved caspase 3, and cleaved poly ADP-ribose polymerase (PARP) were downregulated by EGCG. Furthermore, UUO and TGF-β1-stimulated phosphorylation of mitogen-activated protein kinase was inhibited by EGCG.

CONCLUSIONS

EGCG effectively reduces tubular cell apoptosis induced by UUO and may have potential as a clinical treatment in patients with chronic kidney disease.

Epigallocatechin-3-gallate attenuates unilateral ureteral obstruction-induced renal interstitial fibrosis in mice

The severity of tubulointerstitial fibrosis is regarded as an important determinant of renal prognosis. Therapeutic strategies targeting tubulointerstitial fibrosis have been considered to have potential in the treatment of chronic kidney disease. This study aims to evaluate the protective effects of (-)-epigallocatechin-3-gallate (EGCG), a green tea polyphenol, against renal interstitial fibrosis in mice. EGCG was administrated intraperitoneally for 14 days in a mouse model of unilateral ureteral obstruction (UUO). The results of our histological examination showed that EGCG alleviated glomerular and tubular injury and attenuated renal interstitial fibrosis in UUO mice. Furthermore, the inflammatory responses induced by UUO were inhibited, as represented by decreased macrophage infiltration and inflammatory cytokine production. Additionally, the expression of type I and III collagen in the kidney were reduced by EGCG, which indicated an inhibition of extracellular matrix accumulation. EGCG also caused an up-regulation in α-smooth muscle actin expression and a down-regulation in E-cadherin expression, indicating the inhibition of epithelial-to-mesenchymal transition. These changes were found to be in parallel with the decreased level of TGF-β1 and phosphorylated Smad. In conclusion, the present study demonstrates that EGCG could attenuate renal interstitial fibrosis in UUO mice, and this renoprotective effect might be associated with its effects of inflammatory responses alleviation and TGF-β/Smad signaling pathway inhibition.

Epigallocatechin gallate attenuates proliferation and oxidative stress in human vascular smooth muscle cells induced by interleukin-1β via heme oxygenase-1

Proliferation of vascular smooth muscle cells (VSMCs) triggered by inflammatory stimuli and oxidative stress contributes importantly to atherogenesis. The association of green tea consumption with cardiovascular protection has been well documented in epidemiological observations, however, the underlying mechanisms remain unclear. This study aimed to elucidate the effects of the most active green tea catechin derivative, (−)-epigallocatechin-3-gallate (EGCG), in human aortic smooth muscle cells (HASMCs), focusing particularly on the role of a potent anti-inflammatory and antioxidative enzyme heme oxygenase-1 (HO-1). We found that pretreatment of EGCG dose- and time-dependently induced HO-1 protein levels in HASMCs. EGCG inhibited interleukin- (IL-)1β-induced HASMC proliferation and oxidative stress in a dose-dependent manner. The HO-1 inducer CoPPIX decreased IL-1β-induced cell proliferation, whereas the HO-1 enzyme inhibitor ZnPPIX significantly reversed EGCG-caused growth inhibition in IL-1β-treated HASMCs. At the molecular level, EGCG treatment significantly activated nuclear factor erythroid-2-related factor (Nrf2) transcription activities. These results suggest that EGCG might serve as a complementary and alternative medicine in the treatment of these pathologies by inducing HO-1 expression and subsequently decreasing VSMC proliferation.

Suppression of renal TRPM7 may alleviate kidney injury in the renal transplantation

PURPOSE

The aim of this study was to investigate the effect of renal cortex transient receptor potential melastatin 7 (TRPM7) suppression on renal ischemia reperfusion injury induced by transplantation in mice.

METHODS

M7shRNA was used to decrease the expression of TRPM7 in NRK-52e cells. The mice were subjected to renal intra-parenchymal injection with lentivirus containing M7shRNA to produce hypo-expression of TRPM7 in renal cortex. Cell hypoxia mode and syngeneic renal transplantation in vivo were established. Then the effects of M7shRNA were measured by fluorescent probe for reactive oxygen species (ROS), intracellular calcium and magnesium; Western blot was applied for p38-MAPKs and Bax expression in cell studies. In vivo studies, mice were killed 24 h, 48 h, 72 h, 7 days and 21 days, respectively, after transplantation and the kidneys were dissected. Serum creatinine was measured, and the H&E, Masson's trichrome staining, TUNEL, Kim-1 and α-smooth muscle actin were used to evaluate pathological change.

RESULTS

In cell model of hypoxia, the level of ROS in NRK-52e-M7shRNA was significantly lower than that in both NRK-52e and NRK-52e control cells, while the activation of p38-MAPKs was limited. In renal transplanted mice, renal function of M7shRNA group was conspicuously better than PBS- and vector-control-treated group. The histological examination showed that renal tubule injury and interstitial fibrosis were lower in M7shRNA-treated group compared with PBS and vector-control group.

CONCLUSIONS

Suppression of renal cortex TRPM7 could alleviate kidney injury induced by transplantation in mice. The mechanism may involve reducing the early stage of ischemia reperfusion injury by inhibition of intracellular Ca(2+), Mg(2+) and ROS.

Reno-protective effects of epigallocatechingallate in a small piglet model of extracorporeal circulation

Cardiopulmonary bypass still often is a necessary tool in cardiac surgery in particular in the correction of congenital heart defects in small infants. Nevertheless, among the complications linked to extracorporeal circulation (ECC) with cardiopulmonary bypass (CPB) in both infants and adults one of the most serious problems is renal impairment. Since this might be caused by ischemia/reperfusion injury and accumulation of free radicals, we used (-)-epigallocatechin-3-gallate (EGCG), a derivate from green tea, which is known to possess antioxidant, antiapoptotic and NO-scavenging properties in order to find out whether EGCG may protect the kidney. 23 four-week-old Angler Sattelschwein-piglets (8-15 kg) were divided into three groups: control-group (n=7), ECC-group (n=10), EGCG-group (n=6). The ECC- and EGCG-group were thoracotomized and underwent CPB for 120 min followed by a 90-min recovery-time. The EGCG-group received 10 mg/kg EGCG before and after CPB. Histology revealed that CPB led to widening of Bowman's capsule, and to vacuolization of proximal tubular cells (p<0.05) which could be prevented by EGCG (p<0.05). Using immunohistology, we found significant nuclear translocation of hypoxia-inducible-factor-1-alpha (HIF-1-alpha) and increased nitrotyrosine formation in the ECC-group. Both were significantly (p<0.05) inhibited by EGCG. ECC-induced loss of energy-rich phosphates was prevented by EGCG. In blood samples we found that CPB resulted in increases in creatinine and urea (in serum) and led to loss of total protein (p<0.05), which all was not present in EGCG-treated animals. We conclude that CPB causes damage in the kidney which can be attenuated by EGCG.

Beneficial effects of (-)-epigallocatechin gallate on ischemia-reperfusion testicular injury in rats

BACKGROUND/PURPOSE

The purpose of the study was to determine the effect of (-)-epigallocatechin gallate (EGCG) on testicular ischemia-reperfusion injury in rats.

METHODS

Forty male Wistar rats were assigned to 5 groups. A sham operation was performed on the animals in group 1. In group 2, after 4 hours of unilateral testicular ischemia, 4 hours of testicular reperfusion was performed with EGCG administered 1 hour before reperfusion. In group 3, the same surgical procedure as in group 2 was performed, but without EGCG. Serum superoxide dismutase activity, creatine kinase, and lactate dehydrogenase were then measured in blood samples from groups 1 to 3. In group 4, after 4 hours of unilateral testicular ischemia, testicular reperfusion was performed. In group 5, the same procedure as in group 4 was performed, but with EGCG administered 1 hour before reperfusion. For groups 4 and 5, bilateral orchiectomy was performed for histologic examination 4 weeks after reperfusion was started.

RESULTS

Serum superoxide dismutase activity was significantly higher in group 2 than in group 3. The ratios of bilateral testicular weight, mean seminiferous tubule diameter, and germinal epithelial cell thickness were significantly higher in group 5 than in group 4.

CONCLUSIONS

Therapy with EGCG before reperfusion might exert protective effects via antioxidant activities in a rat experimental model of testicular ischemia-reperfusion injury.

Suramin alleviates glomerular injury and inflammation in the remnant kidney

BACKGROUND

Recently, we demonstrated that suramin, a compound that inhibits the interaction of multiple cytokines/growth factors with their receptors, inhibits activation and proliferation of renal interstitial fibroblasts, and attenuates the development of renal interstitial fibrosis in the murine model of unilateral ureteral obstruction (UUO). However, it remains unclear whether suramin can alleviate glomerular and vascular lesions, which are not typical pathological changes in the UUO model. So we tested the efficacy of suramin in the remnant kidney after 5/6 nephrectomy, a model characterized by the slow development of glomerulosclerosis, vascular sclerosis, tubulointerstitial fibrosis and renal inflammation, mimicking human disease.

METHODS/FINDINGS

5/6 of normal renal mass was surgically ablated in male rats. On the second week after surgery, rats were randomly divided into suramin treatment and non-treatment groups. Suramin was given at 10 mg/kg once per week for two weeks. In the remnant kidney of mice receiving suramin, glomerulosclerosis and vascular sclerosis as well as inflammation were ameliorated. Suramin also attenuated tubular expression of two chemokines, monocyte chemoattractant protein-1 and regulated upon expression normal T cell expressed and secreted (RANTES). After renal mass ablation, several intracellular molecules associated with renal fibrosis, including NF-kappaB p65, Smad-3, signal transducer and activator of transcription-3 and extracellular regulated kinase 1/2, are phosphorylated; suramin treatment inhibited their phosphorylation. Futhermore, suramin abolished renal ablation-induced phosphorylation of epidermal growth factor receptor and platelet derived growth factor receptor, two receptors that mediate renal fibrosis.

CONCLUSIONS AND SIGNIFICANCE

These findings suggest that suramin attenuates glomerular and vascular injury and reduces inflammatory responses by suppression of multiple growth factor receptor-mediated profibrotic signaling pathways. Therefore, suramin may be a useful drug in preventing the fibrosis and sclerosis that characterizes progression of chronic kidney disease.

Role of haeme oxygenase-1 in resolution of oxidative stress-related pathologies: focus on cardiovascular, lung, neurological and kidney disorders

The present review examines the role of the cytoprotective enzyme haeme oxygenase-1 (HO-1) in adaptive responses to inflammatory disease and explores strategies for its clinical use, with particular emphasis on use of therapeutic use of the enzyme using phytochemical inducers of HO-1 such as extracts of Ginkgo biloba, curcumin, and flavonoids extracted from seeds of the sour cherry (Prunus cerasus). This laboratory has identified strategies by which combinations of dietary phytochemicals may be configured to synergistically strengthen immunoregulatory mechanisms that normally prevent inflammation from leading to disease. A major focus of this research initiative has been HO-1, which is capable of substantially reducing oxidative stress by several mechanisms. HO-1 metabolizes haeme that accumulates in tissues because of red blood cell turnover. Two products of this degradation - carbon monoxide (CO) and bilirubin - have potent capacity for reducing oxidative stress and for counteracting its effects. A description will be provided of how HO-1 products maintain healthy tissue function and remediate oxidative tissue damage. This will be explored in four major organ systems, including the cardiovascular system, the lungs, the central nervous system and the kidneys. Particular focus will be given to the physiological coordination of cardiovascular functions mediated by CO produced by HO-1 and to nitric oxide (NO), a gaseous second messenger expressed by nitric oxide synthetase. A major unifying theme of the present review is an exploration of the potential use of dietary phytochemical formulations as tools for the clinical application of HO-1 in therapeutic reduction of oxidative stressors, with resultant improved treatment of inflammatory pathologies.