New Pathogenic Concepts and Therapeutic Approaches to Oxidative Stress in Chronic Kidney Disease

The role of mitochondrial dysfunction in kidney injury and disease

Mitochondria are the main sites of aerobic respiration in the cell and mainly provide energy for the organism, and play key roles in adenosine triphosphate (ATP) synthesis, metabolic regulation, and cell differentiation and death. Mitochondrial dysfunction has been identified as a contributing factor to a variety of diseases. The kidney is rich in mitochondria to meet energy needs, and stable mitochondrial structure and function are essential for normal kidney function. Recently, many studies have shown a link between mitochondrial dysfunction and kidney disease, maintaining mitochondrial homeostasis has become an important target for kidney therapy. In this review, we integrate the role of mitochondrial dysfunction in different kidney diseases, and specifically elaborate the mechanism of mitochondrial reactive oxygen species (mtROS), autophagy and ferroptosis involved in the occurrence and development of kidney diseases, providing insights for improved treatment of kidney diseases.

Pathophysiological concepts and screening of cardiovascular disease in dialysis patients

Dialysis patients experience 10-20 times higher cardiovascular mortality than the general population. The high burden of both conventional and nontraditional risk factors attributable to loss of renal function can explain higher rates of cardiovascular disease (CVD) morbidity and death among dialysis patients. As renal function declines, uremic toxins accumulate in the blood and disrupt cell function, causing cardiovascular damage. Hemodialysis patients have many cardiovascular complications, including sudden cardiac death. Peritoneal dialysis puts dialysis patients with end-stage renal disease at increased risk of CVD complications and emergency hospitalization. The current standard of care in this population is based on observational data, which has a high potential for bias due to the paucity of dedicated randomized clinical trials. Furthermore, guidelines lack specific guidelines for these patients, often inferring them from non-dialysis patient trials. A crucial step in the prevention and treatment of CVD would be to gain better knowledge of the influence of these predisposing risk factors. This review highlights the current evidence regarding the influence of advanced chronic disease on the cardiovascular system in patients undergoing renal dialysis.

Arabic gum ameliorates systemic modulation in Alloxan monohydrate-induced diabetic rats

Medicinal plants are considered an alternative therapy for diabetes mellitus as they regulate glucose levels. Moreover, a variety of plants offer a rich source of bioactive compounds that have potent pharmacological effects without any negative side effects. The present study aimed to clarify the effects of Arabic gum/Gum Acacia (GA) on the biochemical, histopathological, and immunohistochemical changes observed in diabetic rats. Further, the anti-inflammatory activity of GA in response to diabetes, through inflammatory mediators analysis. Male rats were divided into four groups: untreated control, diabetic, Arabic gum-treated, and Arabic gum-treated diabetic rats. Diabetes was induced using alloxan. Animals were sacrificed after 7 and 21 days of treatment with Arabic gum. Body weight, blood and pancreas tissue samples were collected for analysis. Alloxan injection significantly decreased body weight, increased glucose levels, decreased insulin levels, and caused depletion of islets of Langerhans and β-cell damage in the pancreas. Arabic gum treatment of diabetic rats significantly increased body weight, decreased serum glucose levels, increased insulin levels, exerts anti-inflammatory effect, and improved the pancreas tissue structure. Arabic gum has beneficial pharmacological effects in diabetic rats; therefore, it might be employed as diabetic therapy to reduce the hyperglycemic damage and may be applicable for many autoimmune and inflammatory diseases treatment. Further, the new bioactive substances, such as medications made from plants, have larger safety margins, and can be used for a longer period of time.

Renoprotective potentials of small molecule natural products targeting mitochondrial dysfunction

Kidney diseases, including acute kidney injury (AKI) and chronic kidney disease (CKD), have become critical clinical, socioeconomic, and public health concerns worldwide. The kidney requires a lot of energy, and mitochondria act as the central organelle for the proper functioning of the kidney. Mitochondrial dysfunction has been associated with the pathogenesis of AKI and CKD. Natural products and their structural analogs have been sought as an alternative therapeutic strategy despite the challenges in drug discovery. Many studies have shown that small-molecule natural products can improve renal function and ameliorate kidney disease progression. This review summarizes the nephroprotective effects of small-molecule natural products, such as berberine, betulinic acid, celastrol, curcumin, salidroside, polydatin, and resveratrol. Treatment with small-molecule natural products was shown to attenuate renal oxidative stress and mitochondrial DNA (mtDNA) damage and restore mitochondrial biogenesis and dynamics in the kidneys against various injury stimuli. Therefore, small-molecule natural products should be recognized as multi-target therapeutics and promising drugs to prevent kidney diseases, particularly those with mitochondrial dysfunction.

Nrf2 Activation in Chronic Kidney Disease: Promises and Pitfalls

The nuclear factor erythroid 2-related factor 2 (Nrf2) protects the cell against oxidative damage. The Nrf2 system comprises a complex network that functions to ensure adequate responses to redox perturbations, but also metabolic demands and cellular stresses. It must be kept within a physiologic activity range. Oxidative stress and alterations in Nrf2-system activity are central for chronic-kidney-disease (CKD) progression and CKD-related morbidity. Activation of the Nrf2 system in CKD is in multiple ways related to inflammation, kidney fibrosis, and mitochondrial and metabolic effects. In human CKD, both endogenous Nrf2 activation and repression exist. The state of the Nrf2 system varies with the cause of kidney disease, comorbidities, stage of CKD, and severity of uremic toxin accumulation and inflammation. An earlier CKD stage, rapid progression of kidney disease, and inflammatory processes are associated with more robust Nrf2-system activation. Advanced CKD is associated with stronger Nrf2-system repression. Nrf2 activation is related to oxidative stress and moderate uremic toxin and nuclear factor kappa B (NF-κB) elevations. Nrf2 repression relates to high uremic toxin and NF-κB concentrations, and may be related to Kelch-like ECH-associated protein 1 (Keap1)-independent Nrf2 degradation. Furthermore, we review the effects of pharmacological Nrf2 activation by bardoxolone methyl, curcumin, and resveratrol in human CKD and outline strategies for how to adapt future Nrf2-targeted therapies to the requirements of patients with CKD.

Involvement of Inflammasome Components in Kidney Disease

Inflammasomes are multiprotein complexes with an important role in the innate immune response. Canonical activation of inflammasomes results in caspase-1 activation and maturation of cytokines interleukin-1β and -18. These cytokines can elicit their effects through receptor activation, both locally within a certain tissue and systemically. Animal models of kidney diseases have shown inflammasome involvement in inflammation, pyroptosis and fibrosis. In particular, the inflammasome component nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) and related canonical mechanisms have been investigated. However, it has become increasingly clear that other inflammasome components are also of importance in kidney disease. Moreover, it is becoming obvious that the range of molecular interaction partners of inflammasome components in kidney diseases is wide. This review provides insights into these current areas of research, with special emphasis on the interaction of inflammasome components and redox signalling, endoplasmic reticulum stress, and mitochondrial function. We present our findings separately for acute kidney injury and chronic kidney disease. As we strictly divided the results into preclinical and clinical data, this review enables comparison of results from those complementary research specialities. However, it also reveals that knowledge gaps exist, especially in clinical acute kidney injury inflammasome research. Furthermore, patient comorbidities and treatments seem important drivers of inflammasome component alterations in human kidney disease.

Prospects for Protective Potential of Moringa oleifera against Kidney Diseases

Kidney diseases are regarded as one of the major public health issues in the world. The objectives of this study were: (i) to investigate the causative factors involved in kidney disease and the therapeutic aspects of Moringa oleifera, as well as (ii) the effectiveness of M. oleifera in the anti-inflammation and antioxidant processes of the kidney while minimizing all potential side effects. In addition, we proposed a hypothesis to improve M. oleifera based drug development. This study was updated by searching the key words M. oleifera on kidney diseases and M. oleifera on oxidative stress, inflammation, and fibrosis in online research databases such as PubMed and Google Scholar. The following validation checking and scrutiny analysis of the recently published articles were used to explore this study. The recent existing research has found that M. oleifera has a plethora of health benefits. Individual medicinal properties of M. oleifera leaf extract, seed powder, stem extract, and the whole extract (ethanol/methanol) can up-increase the activity of antioxidant enzymes like superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH), while decreasing the activity of inflammatory cytokines such as TNF-α, IL-1β, IL-6, and COX-2. In our study, we have investigated the properties of this plant against kidney diseases based on existing knowledge with an updated review of literature. Considering the effectiveness of M. oleifera, this study would be useful for further research into the pharmacological potential and therapeutic insights of M. oleifera, as well as prospects of Moringa-based effective medicine development for human benefits.

An update of genetics, co-morbidities and management of hyperuricaemia

Hyperuricaemia (HU) caused by disorders of purine metabolism is a metabolic disease. A number of epidemiological reports have confirmed that HU is correlated with multiple disorders, such as chronic kidney diseases, cardiovascular disease and gout. Recent studies showed that the expression and functional changes of uric acid transporters, including URAT1, GLUT9 and ABCG2, were associated with HU. Moreover, a large number of genome-wide association studies have shown that these transporters' dysfunction leads to HU. In this review, we describe the recent progress of aetiology and related transporters of HU, and we also summarise the common co-morbidities possible mechanisms, as well as the potential pharmacological and non-pharmacological treatment methods for HU, aiming to provide new ideas for the treatment of HU.

Mitochondrial Targeting of Herbal Medicine in Chronic Kidney Disease

Chronic kidney disease (CKD) is a common progressive disease that is typically characterized by the permanent loss of nephrons and an eventual decline in glomerular filtration rate. CKD increases mortality and has a significant impact on the quality of life and the economy, which is becoming a major public health issue worldwide. Since current conventional-medicine treatment options for CKD are not satisfactory, many patients seek complementary and alternative medicine treatments including Traditional Chinese Medicine. Herbal medicine is often used to relieve symptoms of renal diseases in the clinic. The kidney is abundant in the number of mitochondria, which provide enough energy for renal function and metabolism. In recent years, a vital role for mitochondrial dysfunction has been suggested in CKD. Mitochondria have become a new target for the treatment of diseases. A growing number of studies have demonstrated herbal medicine could restore mitochondrial function and alleviate renal injury both in vivo and in vitro. In this review, we sum up the therapeutic effect of herbal medicine in CKD via targeting mitochondrial function. This implies future strategies in preventing CKD.

Renal and non-renal response of ABC and SLC transporters in chronic kidney disease

INTRODUCTION

The solute carrier (SLC) and the ATP-binding cassette (ABC) transporter superfamilies play essential roles in the disposition of small molecules (endogenous metabolites, uremic toxins, drugs) in the blood, kidney, liver, intestine, and other organs. In chronic kidney disease (CKD), the loss of renal function is associated with altered function of remote organs. As renal function declines, many molecules accumulate in the plasma. Many studies now support the view that ABC and SLC transporters as well as drug metabolizing enzymes (DMEs) in renal and non-renal tissues are directly or indirectly affected by the presence of various types of uremic toxins, including those derived from the gut microbiome; this can lead to aberrant inter-organ communication.

AREAS COVERED

Here, the expression, localization and/or function of various SLC and ABC transporters as well as DMEs in the kidney and other organs are discussed in the context of CKD and systemic pathophysiology.

EXPERT OPINION

According to the Remote Sensing and Signaling Theory (RSST), a transporter and DME-centric network that optimizes local and systemic metabolism maintains homeostasis in the steady state and resets homeostasis following perturbations due to renal dysfunction. The implications of this view for pharmacotherapy of CKD are also discussed.

Pleiotropic Effects of Eugenol: The Good, the Bad, and the Unknown

Phytocompounds and medicinal herbs were used in traditional ancient medicine and are nowadays increasingly screened in both experimental and clinical settings due to their beneficial effects in several major pathologies. Similar to the drug industry, phytotherapy is interested in using nanobased delivery systems to view the identification and characterization of the cellular and molecular therapeutic targets of plant components. Eugenol, the major phenolic constituent of clove essential oil, is a particularly versatile phytochemical with a vast range of therapeutic properties, among which the anti-inflammatory, antioxidant, and anticarcinogenic effects have been systematically addressed. In the past decade, with the emerging understanding of the role of mitochondria as critical organelles in the pathophysiology of noncommunicable diseases, research regarding the role of phytochemicals as modulators of bioenergetics and metabolism is on a rise. Here, we present a brief overview of the major pharmacological properties of eugenol, with special emphasis on its applications in dental medicine, and provide preliminary data regarding its effects, alone, and included in polyurethane nanostructures, on mitochondrial bioenergetics, and glycolysis in human HaCaT keratinocytes.

Systematic review of the nuclear factor erythroid 2-related factor 2 (NRF2) system in human chronic kidney disease: alterations, interventions, and relation to morbidity

BACKGROUND

NRF2 and its effectors NAD(P)H:quinoneoxidoreductase 1 (NQO1) and heme oxygenase 1 (HO-1) are of interest in kidney disease. We therefore reviewed studies about their status in patients with chronic kidney disease (CKD).

METHODS

We undertook systematic searches of PubMed and EMBASE databases. Alterations of NRF2, NQO1 and HO-1 in CKD, their responses to interventions and their relation to clinically relevant parameters were reported.

RESULTS

We identified 1373 articles, of which 32 studies met the inclusion criteria. NRF2 levels were decreased in the majority of analyses of CKD patients. Half of the analyses showed a similar or increased NQO1 level vs. control, whereas NQO1 was decreased in half of the analyses. Most of the studies reported either an increased or similar HO-1 level in CKD patients compared to controls. For patients with CKD stages 1-4, studies reported positive correlations to markers of kidney disease severity. Also, positive associations of NQO1/HO-1 levels to inflammation and comorbidities were reported. One third of the studies showed discordant changes between gene expression and protein level of NRF2 system components. Two thirds of intervention studies (50% dietary, such as using resistant starch) reported an increase of NRF2, NQO1, or HO-1.

CONCLUSIONS

In patients with CKD, NRF2 expression was downregulated, while NQO1 and HO-1 showed varying alterations related to inflammation, comorbidities, and severity of kidney damage. Interventions that increased NRF2 system components were described, but their effectiveness and clinical relevance require further clinical studies of high quality. Research on gene expression together with protein analyses is indispensable to understand NRF2 system alterations in CKD.

A nano based approach to alleviate cisplatin induced nephrotoxicity

BACKGROUND AND OBJECTIVE

Cisplatin, an effective drug against cancer, commonly induces nephrotoxicity; limiting its therapeutic efficacy and application. In this study, Cisplatin NanoComposite (Cis NC) was formulated successfully from irradiated chitosan coated Cisplatin and MgO nanoparticles (CHIT/Cis/MgO NPs) to promote cisplatin release in a more sustained manner to improve therapeutic efficacy via the reduction of its nephrotoxicity. To compare the relative induced renal toxicity of cisplatin with Cisplatin NanoComposite, histological and biochemical mechanisms underlying nephrotoxicity were investigated.

METHODS

Thirty rats were equally separated to three groups, first group received saline injections and adjusted as the control group, the second group was injected intra-peritoneal with cisplatin 0.64 mg/kg b. wt./day for 6 weeks, the third group was injected intra-peritoneal with Cis NC 5.75 mg/kg b. wt. daily for 6 weeks.

RESULTS

Cisplatin-induced renal functional impairment and histopathological damages in the kidney; also, cisplatin disrupted the balance of the redox system in renal tissue, stimulated the inflammatory reactions in the kidney via triggering signal transducer and activator of transcription-1 (STAT1) dependent pathways. Moreover, Cisplatin-induced activation of mammalian target of rapamycin mTOR and inactivation of AMPK/PI3K/Akt signal pathway, and was coupled with induction of p53 activity and the executioner caspase3 to induce apoptotic renal cell death. On the other hand, Cis NC exerted a minimal stimulatory effect on apoptotic and inflammatory signal cascade with negligible renal functional and morphological alterations.

CONCLUSION

We postulated that Cis NC may be a valued possible drug to decrease the cytotoxicity of cisplatin thus reserves the renal function and structure.

Dietary total antioxidant capacity and its association with anthropometric, biochemical, and functional parameters in chronic kidney disease patients on hemodialysis

ABSTRACT Objective To investigate the association of dietary total antioxidant capacity with anthropometric, functional, and biochemical parameters in chronic kidney disease patients on hemodialysis. Methods This is a cross-sectional study of hemodialysis patients in Western Bahia. A structured questionnaire, three 24-hour dietary recalls, anthropometric measurements and clinical and biochemical records were used for data collection. Dietary total antioxidant capacity was estimated using 24-hour dietary recalls data. A database of ferric reducing antioxidant power values for foods was used to evaluate the dietary total antioxidant capacity. Multiple linear regression was applied to assess the relationship between dietary total antioxidant capacity and anthropometric, functional, and biochemical parameters. Results A total of 97 patients were evaluated, of which 57.7% were men and 57.7% were aged between 36 and 59 years. After adjusting for gender, education level, and socioeconomic level, inverse associations were found between dietary total antioxidant capacity and body mass index (p=0.008). Handgrip strength (p=0.037) and serum albumin concentration (p=0.047) were positively associated with dietary total antioxidant capacity. Conclusion High dietary total antioxidant capacity is associated with low body mass index, high handgrip strength, and high serum albumin concentration in chronic kidney disease patients undergoing hemodialysis.

Implications of Oxidative Stress and Potential Role of Mitochondrial Dysfunction in COVID-19: Therapeutic Effects of Vitamin D

Due to its high degree of contagiousness and like almost no other virus, SARS-CoV-2 has put the health of the world population on alert. COVID-19 can provoke an acute inflammatory process and uncontrolled oxidative stress, which predisposes one to respiratory syndrome, and in the worst case, death. Recent evidence suggests the mechanistic role of mitochondria and vitamin D in the development of COVID-19. Indeed, mitochondrial dynamics contribute to the maintenance of cellular homeostasis, and its uncoupling involves pathological situations. SARS-CoV-2 infection is associated with altered mitochondrial dynamics with consequent oxidative stress, pro-inflammatory state, cytokine production, and cell death. Furthermore, vitamin D deficiency seems to be associated with increased COVID-19 risk. In contrast, vitamin D can normalize mitochondrial dynamics, which would improve oxidative stress, pro-inflammatory state, and cytokine production. Furthermore, vitamin D reduces renin–angiotensin–aldosterone system activation and, consequently, decreases ROS generation and improves the prognosis of SARS-CoV-2 infection. Thus, the purpose of this review is to deepen the knowledge about the role of mitochondria and vitamin D directly involved in the regulation of oxidative stress and the inflammatory state in SARS-CoV-2 infection. As future prospects, evidence suggests enhancing the vitamin D levels of the world population, especially of those individuals with additional risk factors that predispose to the lethal consequences of SARS-CoV-2 infection.

Temporal Alterations in Mitochondrial β-Oxidation and Oxidative Stress Aggravate Chronic Kidney Disease Development in 5/6 Nephrectomy Induced Renal Damage

Five-sixths nephrectomy (5/6Nx) model is widely used for studying the mechanisms involved in chronic kidney disease (CKD) progression, a kidney pathology that has increased dramatically in recent years. Mitochondrial impairment is a key mechanism that aggravates CKD progression; however, the information on mitochondrial bioenergetics and redox alterations along a time course in a 5/6Nx model is still limited and in some cases contradictory. Therefore, we performed for the first time a time-course study of mitochondrial alterations by high-resolution respirometry in the 5/6Nx model. Our results show a decrease in mitochondrial β-oxidation at early times, as well as a permanent impairment in adenosine triphosphate (ATP) production in CI-linked respiration, a permanent oxidative state in mitochondria and decoupling of these organelles. These pathological alterations are linked to the early decrease in complex I and ATP synthase activities and to the further decrease in complex III activity. Therefore, our results may suggest that mitochondrial bioenergetics impairment is an early event in renal damage, whose persistence in time aggravates CKD development in the 5/6Nx model.

The sweet side of dark chocolate for chronic kidney disease patients

Chocolate is a widely appreciated foodstuff with historical appreciation as a food from the gods. In addition to its highly palatable taste, it is a rich source of (poly)phenolics, which have several proposed salutogenic effects, including neuroprotective anti-inflammatory, anti-oxidant and cardioprotective capabilities. Despite the known benefits of this ancient foodstuff, there is a paucity of information on the effects of chocolate in the context of chronic kidney disease (CKD). This review focusses on the potential salutogenic contribution of chocolate intake, to mitigate inflammatory and oxidative burden in CKD, its potential, for cardiovascular protection and on the maintenance of diversity in gut microbiota, as well as clinical perspectives, on regular chocolate intake by CKD patients.

Heme-Oxygenase and Kidney Transplantation: A Potential for Target Therapy?

Kidney transplantation is a well-established therapy for patients with end-stage renal disease. While a significant improvement of short-term results has been achieved in the short-term, similar results were not reported in the long-term. Heme-oxygenase (HO) is the rate-limiting enzyme in heme catabolism, converting heme to iron, carbon monoxide, and biliverdin. Heme-oxygenase overexpression may be observed in all phases of transplant processes, including brain death, recipient management, and acute and chronic rejection. HO induction has been proved to provide a significant reduction of inflammatory response and a reduction of ischemia and reperfusion injury in organ transplantation, as well as providing a reduction of incidence of acute rejection. In this review, we will summarize data on HO and kidney transplantation, suggesting possible clinical applications in the near future to improve the long-term outcomes.

(-)-Epigallocatechin-3-gallate (EGCG) attenuates salt-induced hypertension and renal injury in Dahl salt-sensitive rats

Epigallocatechin-3-gallate (EGCG), a main active catechin in green tea, was reported to attenuate renal injury and hypertension. However, its effects on salt-induced hypertension and renal injury remain unclear. In the present study, we explored its effects on hypertension and renal damage in Dahl rats with salt-sensitive hypertension. We found that EGCG could lower blood pressure after 6 weeks of oral administration, reduce 24 h urine protein levels and decrease creatinine clearance, and attenuate renal fibrosis, indicating that it could attenuate hypertension by protecting against renal damage. Furthermore, we studied the renal protective mechanisms of EGCG, revealing that it could lower malondialdehyde levels, reduce the numbers of infiltrated macrophages and T cells, and induce the apoptosis of NRK-49F cells. Considering that the 67 kD laminin receptor (67LR) binds to EGCG, its role in EGCG-induced fibroblast apoptosis was also investigated. The results showed that an anti-67LR antibody partially abrogated the apoptosis-inducing effects of EGCG on NRK-49F cells. In summary, EGCG may attenuate renal damage and salt-sensitive hypertension via exerting anti-oxidant, anti-inflammatory, and apoptosis-inducing effects on fibroblasts; the last effect is partially mediated by 67LR, suggesting that EGCG represents a potential strategy for treating salt-sensitive hypertension.

Mitochondrial DNA: A New Predictor of Diabetic Kidney Disease

Diabetic kidney disease (DKD) is a common cause of end-stage renal disease, and diagnosis and treatment in time can help delay its progress. At present, there are more and more studies on the pathogenesis of DKD; mitochondrial dysfunction plays an important role in DKD. The occurrence and development of DKD is closely related to epigenetic changes and the interaction between mtDNA, ROS, inflammatory factors, and endothelial damage, which continuously aggravates kidney. The change of mtDNA is both the cause of DKD and the result of DKD. It is of great significance to incorporate the change of mtDNA into the monitoring of patients with diabetes. Existing evidence indicates that changes in mtDNA copy number in blood and urine reflect mitochondrial dysfunction and the severity of DKD. However, large-scale, long-term follow-up clinical trials are still needed to determine the threshold range. By the time, mitochondrial-targeted antioxidants will become a new method for the treatment of DKD and other diabetic complications; mtDNA also can be a therapeutic target for them.

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.

Cardiovascular disease in dialysis patients

Cardiovascular disease (CVD) is a highly common complication and the first cause of death in patients with end-stage renal disease (ESRD) on haemodialysis (HD). In this population, mortality due to CVD is 20 times higher than in the general population and the majority of maintenance HD patients have CVD. This is likely due to ventricular hypertrophy as well as non-traditional risk factors, such as chronic volume overload, anaemia, inflammation, oxidative stress, chronic kidney disease–mineral bone disorder and other aspects of the ‘uraemic milieu’. Better understanding the impact of these numerous factors on CVD would be an important step for prevention and treatment. In this review we focus non-traditional CVD risk factors in HD patients.

Antioxidant supplements as a novel mean for blocking recurrent heat stress-induced kidney damage following rehydration with fructose-containing beverages

Recently repeated heat stress and dehydration have been reported to cause oxidative stress and kidney damage that is enhanced by rehydrating with fructose solutions. We hypothesized that antioxidants might provide a novel way to prevent kidney damage. To test this hypothesis, mild heat stress was induced by exposing rats to 37 °C during 1 h in a closed chamber. The supplementation with water-soluble antioxidants (Antiox), ascorbic acid 1% plus N-acetyl cysteine 600 mg/L was done either in the 10% fructose 2 h rehydration fluid immediately after heat stress (Fructose 10% + Antiox), and/or in the tap water (Water + Antiox) for the remainder of the day, or in both fluids. After 4 weeks, control rats exposed to heat with fructose rehydration developed impaired renal function, tubular injury, intrarenal oxidative stress, a reduction in Nrf2-Keap1 antioxidant pathway, stimulation of vasopressin and the intrarenal polyol-fructokinase pathway. In contrast, dosing the antioxidants in the tap water (i.e., before the heat exposure and rehydration with fructose) preserved renal function, prevented renal tubule dysfunction and avoided the increase in systemic blood pressure. These effects were likely due to the amplification of the antioxidant defenses through increased Nrf2 nuclear translocation stimulated by the antioxidants and by the prevention of polyol fructokinase pathway overactivation. More studies to understand the mechanisms implicated in this pathology are warranted as there is recent evidence that they may be operating in humans as well.

Molecular Mechanisms of Epigallocatechin-3-Gallate for Prevention of Chronic Kidney Disease and Renal Fibrosis: Preclinical Evidence

Chronic kidney disease (CKD) is a common public health problem worldwide characterized by gradual decline of renal function over months/years accompanied by renal fibrosis and failure in tissue wound healing after sustained injury. Patients with CKD frequently present with profound signs/symptoms that require medical treatment, mostly culminating in hemodialysis and renal transplantation. To prevent CKD more efficiently, there is an urgent need for better understanding of the pathogenic mechanisms and molecular pathways of the disease pathogenesis and progression, and for developing novel therapeutic targets. Recently, several lines of evidence have shown that epigallocatechin-3-gallate (EGCG), an abundant phytochemical polyphenol derived from Camellia sinensis, might be a promising bioactive compound for prevention of CKD development/progression. This review summarizes current knowledge of molecular mechanisms underlying renoprotective roles of EGCG in CKD based on available preclinical evidence (from both in vitro and in vivo animal studies), particularly its antioxidant property through preservation of mitochondrial function and activation of Nrf2 (nuclear factor erythroid 2-related factor 2)/HO-1 (heme oxygenase-1) signaling, anti-inflammatory activity, and protective effect against epithelial mesenchymal transition. Finally, future perspectives, challenges, and concerns regarding its clinical use in CKD and renal fibrosis are discussed.

Ginsenoside Rb3 provides protective effects against cisplatin-induced nephrotoxicity via regulation of AMPK-/mTOR-mediated autophagy and inhibition of apoptosis in vitro and in vivo

Objectives

Based on previous reports that ginsenosides have been shown to exert better preventive effects on cisplatin‐induced kidney injury, the present work aims to evaluate the protective effects of ginsenoside Rb3 (G‐Rb3) on cisplatin‐induced renal damage and underlying mechanisms in vivo and in vitro.

Materials and methods

The protective effect of G‐Rb3 on cisplatin‐induced acute renal failure in ICR mouse model and HEK293 cell model was investigated, and the underlying possible mechanisms were also explored. For animal experiment, renal function, kidney histology, inflammation, oxidative stress, relative protein molecules involved in apoptosis and autophagy signalling pathways were assessed. In addition, rapamycin (a specific inhibitor of mTOR), compound C (a specific inhibitor of AMPK) and acetylcysteine (NAC, a specific ROS scavenger) were employed to testify the effects of AMPK/mTOR signal pathway on the protective effects of G‐Rb3 in HEK293 cells.

Results

Pre‐treatment with G‐Rb3 at doses of 10 and 20 mg/kg for ten days significantly reversed the increases in serum creatinine (CRE), blood urea nitrogen (BUN) and malondialdehyde (MDA), and decrease in glutathione (GSH) content and superoxide dismutase (SOD) activity. Histopathological examination further revealed that G‐Rb3 inhibited cisplatin‐induced nephrotoxicity. G‐Rb3 diminished cisplatin‐induced increase in protein expression levels of p62, Atg3, Atg5 and Atg7, and decrease in protein expression level of p‐mTOR and the ratio of LC3‐I/LC3‐II, indicating that G‐Rb3 suppressed cisplatin‐induced activation of autophagy. Inhibition of autophagy induced inactivation of apoptosis, which suggested that autophagy played an adverse effect on cisplatin‐evoked renal damage. Further, we found that G‐Rb3 might potentially modulate the expressions of AMPK‐related signal pathways.

Conclusions

These findings clearly suggested that G‐Rb3‐mediated alleviation of cisplatin‐induced nephrotoxicity was in part due to regulation of AMPK‐/mTOR‐mediated autophagy and inhibition of apoptosis in vitro and in vivo.

Berberine Protects Glomerular Podocytes via Inhibiting Drp1-Mediated Mitochondrial Fission and Dysfunction

Elevated levels of plasma free fatty acid (FFA) and disturbed mitochondrial dynamics play crucial roles in the pathogenesis of diabetic kidney disease (DKD). However, the mechanisms by which FFA leads to mitochondrial damage in glomerular podocytes of DKD and the effects of Berberine (BBR) on podocytes are not fully understood.

Methods: Using the db/db diabetic mice model and cultured mouse podocytes, we investigated the molecular mechanism of FFA-induced disturbance of mitochondrial dynamics in podocytes and testified the effects of BBR on regulating mitochondrial dysfunction, podocyte apoptosis and glomerulopathy in the progression of DKD.

Results: Intragastric administration of BBR for 8 weeks in db/db mice significantly reversed glucose and lipid metabolism disorders, podocyte damage, basement membrane thickening, mesangial expansion and glomerulosclerosis. BBR strongly inhibited podocyte apoptosis, increased reactive oxygen species (ROS) generation, mitochondrial fragmentation and dysfunction both in vivo and in vitro. Mechanistically, BBR could stabilize mitochondrial morphology in podocytes via abolishing palmitic acid (PA)-induced activation of dynamin-related protein 1 (Drp1).

Conclusions: Our study demonstrated for the first time that BBR may have a previously unrecognized role in protecting glomerulus and podocytes via positively regulating Drp1-mediated mitochondrial dynamics. It might serve as a novel therapeutic drug for the treatment of DKD.

The flavonoid-rich fraction from rhizomes of Smilax glabra Roxb. ameliorates renal oxidative stress and inflammation in uric acid nephropathy rats through promoting uric acid excretion

Uric acid metabolic disorder is considered to be the main pathogenesis of uric acid nephropathy (UN). Smilax glabra Roxb. is a traditional Chinese herb which has been used in the treatment of gout, but the mechanism was unclear. In this study, we investigated the protective effects of the flavonoid-rich fraction from rhizomes of Smilax glabra Roxb. (SGF) on uric acid nephropathy rats and its underlying mechanisms of promoting uric acid excretion. Sprague Dawley (SD) rats were induced by high purine diet (yeast pellets + adenine) for 5 weeks. Rats were orally treated with SGF or allopurinol daily. The biochemical parameters and enzymes in different treated rats were determined by commercial kits. Kidney pathology was visualized using optical microscopy and electron microscopy. Renal inflammatory factors were detected by ELISA. Renal fibrosis factors and uric acid transporters were analyzed by real time RT-PCR and western blot. The results showed that SGF significantly improved kidney function. Histopathologic examination revealed that urate-induced renal damage was markedly reversed by SGF. Meanwhile, SGF treatment was also found to significantly inhibit renal oxidative stress. SGF treatment obviously suppressed the inflammatory factors of interleukin-6 (IL-6), tumor necrosis factor alpha (TNF-α), interleukin-1β (IL-1β), cyclooxygenase-2 (COX-2) and the profibrotic factors of basic fibroblast growth factor (bFGF), transforming growth factor-β₁ (TGF-β₁) expression in UN rats. Moreover, SGF either significantly inhibited uric acid production or promoted uric acid excretion in UN rats. The mechanism of SGF promoting uric acid excretion was related to its increase of ATP-binding cassette transporter G2 (ABCG2), organic anion transporter 1 (OAT1), organic anion transporters 2 (OCT2) and organic cation/carnitine transporters 2 (OCTN2) expression. In conclusion, SGF could ameliorate renal oxidative stress and inflammation in UN rats through promoting uric acid excretion.

Serum heat shock protein 27 levels predict cardiac mortality in hemodialysis patients

Background

Decreased heat shock protein 27 (HSP27) participates in many processes that are involved in cardiovascular (CV) disease. The objective of the study was to evaluate if HSP27 level was predictive of mortality as well as to evaluate factors associated with HSP27 level in a group of patients treated with HD.

Methods

Enrolled to the study were 202 HD patients. Clinical data, biochemical, echocardiographic, and carotid atherosclerosis parameters were evaluated. Patients were splited into groups on the basis of the cut-off lower and higher 50th percentile of serum HSP27 levels, and were followed-up for 28.68 ± 6.12 months.

Results

No significant difference was observed between serum HSP27 levels in patients and controls. Low HSP27 patients were older, had higher left ventricular mass index, lower ejection fraction, higher prevalence of diabetes, myocardial infarction and carotid atherosclerosis, higher C-reactive protein level, and worse oxidant/antioxidant status. The multiple regression analysis identified that HSP27 levels were independently, negatively associated with serum oxidized LDL and the number of carotid plaques. Using the Kaplan–Meier analysis it was shown that the cumulative incidences of both CV and sudden cardiac death (SCD) mortality were higher in low HSP27 group in comparison with high serum HSP27 group. A multivariate Cox analysis showed that HSP27 level is an independent and strong predictor of CV as well as SCD mortality.

Conclusions

Low serum HSP27 level is independently associated with both CV and SCD mortality but not with all-cause mortality. Low serum HSP27 level is associated with carotid atherosclerosis and oxidative stress.

Bioactive food and exercise in chronic kidney disease: Targeting the mitochondria

Chronic kidney disease (CKD), which affects 10%-15% of the population, associates with a range of complications-such as cardiovascular disease, frailty, infections, muscle and bone disorders and premature ageing-that could be related to alterations of mitochondrial number, distribution, structure and function. As mitochondrial biogenesis, bioenergetics and the dynamic mitochondrial networks directly or indirectly regulate numerous intra- and extracellular functions, the mitochondria have emerged as an important target for interventions aiming at preventing or improving the treatment of complications in CKD. In this review, we discuss the possible role of bioactive food compounds and exercise in the modulation of the disturbed mitochondrial function in a uraemic milieu.

Enhanced oral bioavailability of EGCG using pH-sensitive polymeric nanoparticles: characterization and in vivo investigation on nephrotic syndrome rats

Objective

Chronic kidney disease (CKD) is characterized by progressive loss of renal functions. At present, there are only limited therapeutic strategies to slow down the progress of CKD and there is an urgent need to develop new therapeutic strategies to treat CKD patients. Numerous research evidence supports the potential role of EGCG in the renal protection of CKD. However, the clinical use is still limited due to the poor oral bioavailability. The aim of this study was to develop pH-sensitive polymeric nanoparticles of EGCG to improve this deficiency.

Materials and methods

EGCG-loaded nanoparticles (EGCG NPs) were prepared by an improved emulsion evaporation method. The formulation prepared was in spherical with uniform sizes, high encapsulation efficiencies and drug loading. The therapeutic efficacy of EGCG NPs on chronic kidney disease was investigated on model of rat Nephrotic syndrome by measuring urinary protein excretion and kidney pathology score.

Results

The mean particle size was found to be 91.3±0.8 nm and the encapsulation efficiency% and drug loading% of the formulation were 80.8%±1.6% and 6.3%±1.4%, respectively. The powder X-ray diffraction and differential scanning calorimetry of EGCG NPs showed that EGCG existed in amorphous form in NPs. The release of EGCG from NPs exhibited the lower burst release at pH 1.2 (<10%) and with the increase of pH value, the release of EGCG also gradually increased. During the observation period (24 hours), the total release amount was almost 68%. EGCG NPs could significantly modify the pharmacokinetic profile and increase the bioavailability of EGCG by more than 2.4-fold in comparison with the EGCG powder group. At the end of the fourth and sixth week, proteinuria excretion of nephrotic syndrome rats treated with EGCG NPs was significantly lower than those treated with EGCG powder, and kidney pathology scores in EGCG NPs treated rats were also significantly lower than EGCG powder treated rats.

Conclusion

The results of pharmacodynamics showed that compared with EGCG powder treatment group, EGCG NPs treatment group had better efficacy and reduce kidney damage.

Mitochondrial bioenergetics, redox state, dynamics and turnover alterations in renal mass reduction models of chronic kidney diseases and their possible implications in the progression of this illness

Nowadays, chronic kidney disease (CKD) is considered a worldwide public health problem. CKD is a term used to describe a set of pathologies that structurally and functionally affect the kidney, it is mostly characterized by the progressive loss of kidney function. Current therapeutic approaches are insufficient to avoid the development of this disease, which highlights the necessity of developing new strategies to reverse or at least delay CKD progression. Kidney is highly dependent on mitochondrial homeostasis and function, consequently, the idea that mitochondrial pathologies could play a pivotal role in the genesis and development of kidney diseases has risen. Although many research groups have recently published studies of mitochondrial function in acute kidney disease models, the existing information about CKD is still limited, especially in renal mass reduction (RMR) models. This paper focuses on reviewing current experimental information about the bioenergetics, dynamics (fission and fusion processes), turnover (mitophagy and biogenesis) and redox mitochondrial alterations in RMR, to discuss and integrate the mitochondrial changes triggered by nephron loss, as well as its relationship with loss of kidney function in CKD, in these models. Understanding these mechanisms would allow us to design new therapies that target these mitochondrial alterations.

Critical Shear Stress is Associated with Diabetic Kidney Disease in Patients with Type 2 Diabetes

Critical shear stress (CSS, mPa) is an index of red blood cell (RBC) aggregability, defined as the minimal shear stress required to disperse RBC aggregates. This study aimed to investigate the association between CSS and the risk of diabetic kidney disease (DKD). A total of 421 (mean age, 58.1 ± 11.5 years; male, 250) individuals with T2DM were enrolled and divided into three groups according to CSS level. CSS was measured using a transient microfluidic technique. DKD was defined as a glomerular filtration rate (GFR) <60 ml/min/1.73 m2 or a urine albumin-to-creatinine ratio (uACR) ≥30 mg/g. CSS was significantly higher in patients with DKD than in those without (317.43 ± 125.11 vs 385.22 ± 182.89, p < 0.001). Compared to the lowest CSS tertile, the highest CSS tertile was independently associated with the risk of DKD after adjusting for age, sex, duration of diabetes, presence of hypertension and haemoglobin. The cut-off value of CSS for DKD was approximately 310 mPa. These results suggest that haemorheologic changes may contribute to DKD, and further prospective studies are warranted to determine the role of CSS as a DKD screening tool.

Cytochrome P450-2E1 is involved in aging-related kidney damage in mice through increased nitroxidative stress

The aim of this study was to investigate the role of cytochrome P450-2E1 (CYP2E1) in aging-dependent kidney damage since it is poorly understood. Young (7 weeks) and aged female (16-17 months old) wild-type (WT) and Cyp2e1-null mice were used. Kidney histology showed that aged WT mice exhibited typical signs of kidney aging such as cell vacuolation, inflammatory cell infiltration, cellular apoptosis, glomerulonephropathy, and fibrosis, along with significantly elevated levels of renal TNF-α and serum creatinine than all other groups. Furthermore, the highest levels of renal hydrogen peroxide, protein carbonylation and nitration were observed in aged WT mice. These increases in the aged WT mice were accompanied by increased levels of iNOS and mitochondrial nitroxidative stress through altered amounts and activities of the mitochondrial complex proteins and significantly reduced levels of the antioxidant glutathione (GSH). In contrast, the aged Cyp2e1-null mice exhibited significantly higher antioxidant capacity with elevated heme oxygenase-1 and catalase activities compared to all other groups, while maintaining normal GSH levels with significantly less mitochondrial nitroxidative stress compared to the aged WT mice. Thus, CYP2E1 is important in causing aging-related kidney damage most likely through increasing nitroxidative stress and that CYP2E1 could be a potential target in preventing aging-related kidney diseases.

The Green Tea Polyphenol(-)-epigallocatechin-3-gallate and its beneficial roles in chronic kidney disease

Chronic kidney disease (CKD), a condition that affects around 10% of the population, has become a significant public health concern. Current therapeutic strategies to slow down the progression of CKD remain limited. Thus, it is urgent to develop new strategies to manage the patients with CKD. Work within the past decade has improved our understanding of the mechanisms contributing to CKD. In particular, oxidative stress as well as inflammation appears to play a pivotal role in CKD progression. ()-Epigallocatechin-3-gallate (EGCG), the major catechin of green tea extract, is known as a powerful antioxidant and reactive oxygen species scavenger. Various studies have shown EGCG has a potential role in chronic kidney disease models. It is suggested that EGCG modulates cellular and molecular mechanisms via inflammation-related NF-кB and Nrf2 signaling pathway, as well as apoptosis-related ER stress pathway and mitochondrial pathway. Therefore, based on these studies, this review attempts to present a recent state of our knowledge and understanding of mechanisms of its role on the process of CKD, with the aim of providing some clues for the future optimization of EGCG in renal diseases.