Transcription factor Nrf2 is protective during ischemic and nephrotoxic acute kidney injury in mice

Potential role of molecular hydrogen therapy on oxidative stress and redox signaling in chronic kidney disease

Oxidative stress plays a key role in chronic kidney disease (CKD) development and progression, inducing kidney cell damage, inflammation, and fibrosis. However, effective therapeutic interventions to slow down CKD advancement are currently lacking. The multifaceted pharmacological effects of molecular hydrogen (H2) have made it a promising therapeutic avenue. H2 is capable of capturing harmful •OH and ONOO- while maintaining the crucial reactive oxygen species (ROS) involved in cellular signaling. The NRF2-KEAP1 system, which manages cell redox balance, could be used to treat CKD. H2 activates this pathway, fortifying antioxidant defenses and scavenging ROS to counteract oxidative stress. H2 can improve NRF2 signaling by using the Wnt/β-catenin pathway and indirectly activate NRF2-KEAP1 in mitochondria. Additionally, H2 modulates NF-κB activity by regulating cellular redox status, inhibiting MAPK pathways, and maintaining Trx levels. Treatment with H2 also attenuates HIF signaling by neutralizing ROS while indirectly bolstering HIF-1α function. Furthermore, H2 affects FOXO factors and enhances the activity of antioxidant enzymes. Despite the encouraging results of bench studies, clinical trials are still limited and require further investigation. The focus of this review is on hydrogen's role in treating renal diseases, with a specific focus on oxidative stress and redox signaling regulation, and it discusses its potential clinical applications.

Farnesol prevents chlorpyrifos nephrotoxicity by modulating inflammatory mediators, Nrf2 and FXR and attenuating oxidative stress

Chlorpyrifos (CPF) is a broad-spectrum insecticide widely employed in agricultural field for pest control. Exposure to CPF is associated with serious effects to the main organs, including kidneys. Significant evidence denotes that oxidative stress (OS) and inflammation are implicated in CPF toxicity. This study aimed to evaluate the potential of farnesol (FAR) to modulate inflammatory mediators and farnesoid-X-receptor (FXR) and Nrf2 in a rat model of CPF nephrotoxicity. CPF and FAR were orally supplemented for 28 days and blood and kidney samples were collected for investigations. CPF administration elevated blood creatinine and urea, kidney MDA and NO, and upregulated NF-κB p65, IL-1β, TNF-α, iNOS, and caspase-3. In addition, CPF upregulated kidney Keap1, and decreased GSH, antioxidant enzymes, and Nrf2, FXR, HO-1 and NQO-1. FAR ameliorated creatinine and urea, prevented histopathological alterations, decreased MDA and NO, and enhanced antioxidants in CPF-administered rats. FAR modulated NF-κB p65, iNOS, TNF-α, IL-1β, caspase-3, Keap1, HO-1, NQO-1, Nrf2 and FXR. In silico investigations revealed the binding affinity of FAR towards Keap1 and FXR, as well as NF-κB, caspase-3, iNOS, and HO-1. In conclusion, FAR prevents CPF-induced kidney injury by attenuating OS, inflammation, and apoptosis, effects associated with modulation of FXR, Nrf2/HO-1 signaling and antioxidants.

Dose-dependent renoprotective effect of vanillic acid on methotrexate-induced nephrotoxicity via its anti-apoptosis, antioxidant, and anti-inflammatory properties

Methotrexate-induced nephrotoxicity is a medical emergency which is associated with a variety of side effects. Vanillic acid (VA), as an antioxidant, removes free radical oxygen to protect cell defense. Therefore, this study investigated VA's beneficial effects on nephrotoxicity induced by methotrexate through its anti-apoptosis, antioxidant, and anti-inflammatory properties. Our study included five groups of male Wistar rats (n = 8): sham, MTX (Methotrexate) group: rats receiving methotrexate (20 mg/kg, intraperitoneally) on Day 2. Moreover, the remaining groups consisted of animals that received vanillic acid (25, 50, and 100 mg/kg, orally for seven days) plus MTX on the 2nd day. The rats were deeply anesthetized on the eighth day to obtain blood and renal tissue samples. The results showed that MTX can increase blood urea nitrogen and creatinine. However, VA (50 and 100 mg/kg) improved renal function as approved by histological findings. Compared with MTX-treated rats, VA enhanced the contents of total antioxidant capacity (TAC) and reduced renal malondialdehyde (MDA). Moreover, VA reduced mRNA expressions of caspase-3 and Bcl-2-associated x protein (Bax) and caused mRNA overexpression of the renal B-cell lymphoma-2 (Bcl-2), and Nrf-2 (Nuclear factor erythroid 2-related factor 2) compared to the MTX group. Also, VA administration significantly reduced inflammatory agents. Overall, VA protects the kidneys against methotrexate-induced nephrotoxicity via anti-apoptosis, antioxidant, and anti-inflammatory properties. Our results revealed that the most effective dose of VA was 100 mg/kg.

Novel Insight into the Effect of Probiotics in the Regulation of the Most Important Pathways Involved in the Pathogenesis of Type 2 Diabetes Mellitus

Type 2 diabetes mellitus (T2DM) is considered one of the most common disorders worldwide. Although several treatment modalities have been developed, the existing interventions have not yielded the desired results. Therefore, researchers have focused on finding treatment choices with low toxicity and few adverse effects that could control T2DM efficiently. Various types of research on the role of gut microbiota in developing T2DM and its related complications have led to the growing interest in probiotic supplementation. Several properties make these organisms unique in terms of human health, including their low cost, high reliability, and good safety profile. Emerging evidence has demonstrated that three of the most important signaling pathways, including nuclear factor kappa B (NF-κB), phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), and nuclear factor erythroid 2-related factor 2 (Nrf2), which involved in the pathogenesis of T2DM, play key functions in the effects of probiotics on this disease. Hence, we will focus on the clinical applications of probiotics in the management of T2DM. Then, we will also discuss the roles of the involvement of various probiotics in the regulation of the most important signaling pathways (NF-κB, PI3K/Akt, and Nrf2) involved in the pathogenesis of T2DM.

Multi-Omic Analysis Reveals Genetic Determinants and Therapeutic Targets of Chronic Kidney Disease and Kidney Function

Chronic kidney disease (CKD) presents a significant global health challenge, characterized by complex pathophysiology. This study utilized a multi-omic approach, integrating genomic data from the CKDGen consortium alongside transcriptomic, metabolomic, and proteomic data to elucidate the genetic underpinnings and identify therapeutic targets for CKD and kidney function. We employed a range of analytical methods including cross-tissue transcriptome-wide association studies (TWASs), Mendelian randomization (MR), summary-based MR (SMR), and molecular docking. These analyses collectively identified 146 cross-tissue genetic associations with CKD and kidney function. Key Golgi apparatus-related genes (GARGs) and 41 potential drug targets were highlighted, with MAP3K11 emerging as a significant gene from the TWAS and MR data, underscoring its potential as a therapeutic target. Capsaicin displayed promising drug-target interactions in molecular docking analyses. Additionally, metabolome- and proteome-wide MR (PWMR) analyses revealed 33 unique metabolites and critical inflammatory proteins such as FGF5 that are significantly linked to and colocalized with CKD and kidney function. These insights deepen our understanding of CKD pathogenesis and highlight novel targets for treatment and prevention.

G protein-coupled estrogen receptor selective agonist, G1, improves the molecular and biochemical markers in a cisplatin mouse model of CKD

Multiple cycles of cisplatin result in a permanent loss of kidney function with severe and life-limited chronic kidney disease (CKD) after successful cisplatin therapy. Recently, studies have showed that the activation of G-protein coupled estrogen receptor (GPER) could protect against kidney disease. This study aimed to test the potential of the G1 compound, a GPER selective agonist, to prevent CKD development after cisplatin therapy. Male C57BL/6 mice were exposed to 2 cycles of 2.5 mg/kg cisplatin in a regimen miming clinical exposure (1 injection daily for 5 days, followed by a 16-day recovery period between cycles). G1 (50 or 100 μg/kg) was administered daily for 6 weeks. G1 dose-dependently improved kidney function biomarkers (serum creatinine, creatinine clearance, and protein excretion) and histopathological changes compared to the cisplatin-treated group. Collagen 3 expression was dose-dependently decreased in G1-treated groups that was parallel to the reduction of fibrosis in Masson's trichrome-stained sections. G1 administration also increased total antioxidant capacity (TAC) and nuclear factor erythroid 2-related factor 2 (Nrf2) and reduced the level of malondialdehyde and the proinflammatory cytokine, tumor necrosis factor-α. In addition, G1 downregulated the expression of inflammasome NLRP3 and nuclear factor kappa B p65 (NF-κB p65) in a dose-dependent manner. In conclusion, these data suggest that G1 could be a new therapeutic tool for CKD prevention post cisplatin therapy. These effects might be mediated through the activation of Nrf2 and the inhibition of NF-κB/NLRP3 signaling.

Selenium protects against Pb-induced renal oxidative injury in weaning rats and human renal tubular epithelial cells through activating NRF2

BACKGROUND

Lead (Pb) poisoning posing a crucial health risk, especially among children, causing devastating damage not only to brain development, but also to kidney function. Thus, an urgent need persists to identify highly effective, safe, and low-toxicity drugs for the treatment of Pb poisoning. The present study focused on exploring the protective effects of Se on Pb-induced nephrotoxicity in weaning rats and human renal tubular epithelial cells, and investigated the possible mechanisms.

METHODS

Forty weaning rats were randomly divided into four groups in vivo: control, Pb-exposed, Pb+Se and Se. Serum creatinine (Cr), urea nitrogen (BUN) and hematoxylin and eosin (H&E) staining were performed to evaluate renal function. The activities of antioxidant enzymes in the kidney tissue were determined. In vitro experiments were performed using human renal tubular epithelial cells (HK-2 cells). The cytotoxicity of Pb and Se was detected by 3-(4,5-dimethylthiazol-2yl)-2, 5-diphenyltetrazolium bromide (MTT) assay. Inverted fluorescence microscope was used to investigate cell morphological changes and the fluorescence intensity of reactive oxygen species (ROS). The oxidative stress parameters were measured by a multi-detection reader. Nuclear factor-erythroid-2-related factor (NRF2) signaling pathways were measured by Western blot and reverse transcription polymerase chain reaction (RT-PCR) in HK-2 cells.

RESULTS

We found that Se alleviated Pb-induced kidney injury by relieving oxidative stress and reducing the inflammatory index. Se significantly increased the activity of the antioxidant enzymes glutathione (GSH), superoxide dismutase (SOD) and catalase (CAT), whereas it decreased the excessive release of malondialdehyde (MDA) in the kidneys of weaning rats and HK-2 cells. Additionally, Se enhanced the antioxidant defense systems via activating the NRF2 transcription factor, thereby promoting the to downstream expression of heme oxygenase 1. Furthermore, genes encoding glutamate-cysteine ligase synthetase catalytic (GCLC), glutamate-cysteine ligase synthetase modifier (GCLM) and NADPH quinone oxidoreductase 1 (NQO1), downstream targets of NRF2, formed a positive feedback loop with NRF2 during oxidative stress responses. The MTT assay results revealed a significant decrease in cell viability with Se treatment, and the cytoprotective role of Se was blocked upon knockdown of NRF2 by small interfering RNA (siRNA). MDA activity results also showed that NRF2 knockdown inhibited the NRF2-dependent transcriptional activity of Se.

CONCLUSIONS

Our findings demonstrate that Se ameliorated Pb-induced nephrotoxicity by reducing oxidative stress both in vivo and in vitro. The molecular mechanism underlying Se's action in Pb-induced kidney injury is related to the activation of the NRF2 transcription factor and the activity of antioxidant enzymes, ultimately suppressing ROS accumulation.

Agrimol B alleviates cisplatin-induced acute kidney injury by activating the Sirt1/Nrf2 signaling pathway in mice

Cisplatin (CDDP) is a widely used chemotherapeutic agent that has remarkable antineoplastic effects. However, CDDP can cause severe acute kidney injury (AKI), which limits its clinical application. Agrimol B is the main active ingredient found in Agrimonia pilosa Ledeb and has a variety of pharmacological activities. The effect of agrimol B on CDDP-induced renal toxicity has not been determined. To investigate whether agrimol B has a protective effect against CDDP-induced AKI, we first identify Sirtuin 1 (Sirt1) as a critical target protein of agrimol B in regulating AKI through network pharmacology analysis. Subsequently, the AKI mouse model is induced by administering a single dose of CDDP via intraperitoneal injection. By detecting the serum urea nitrogen and creatinine levels, as well as the histopathological changes, we confirm that agrimol B effectively reduces CDDP-induced AKI. In addition, treatment with agrimol B counteracts the increase in renal malondialdehyde level and the decrease in superoxide dismutase (SOD), catalase and glutathione levels induced by CDDP. Moreover, western blot results reveal that agrimol B upregulates the expressions of Sirt1, SOD2, nuclear factor erythroid2-related factor 2, and downstream molecules, including heme oxygenase 1 and NAD(P)H quinone dehydrogenase 1. However, administration of the Sirt1 inhibitor EX527 abolishes the effects of agrimol B. Finally, we establish a tumor-bearing mouse model and find that agrimol B has a synergistic antitumor effect with CDDP. Overall, agrimol B attenuates CDDP-induced AKI by activating the Sirt1/Nrf2 signaling pathway to counteract oxidative stress, suggesting that this compound is a potential therapeutic agent for the treatment of CDDP-induced AKI.

Activation of the Nrf2/ARE signaling pathway ameliorates hyperlipidemia-induced renal tubular epithelial cell injury by inhibiting mtROS-mediated NLRP3 inflammasome activation

Dyslipidemia is the most prevalent independent risk factor for patients with chronic kidney disease (CKD). Lipid-induced NLRP3 inflammasome activation in kidney-resident cells exacerbates renal injury by causing sterile inflammation. Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that modulates the cellular redox balance; however, the exact role of Nrf2 signaling and its regulation of the NLRP3 inflammasome in hyperlipidemia-induced kidney injury are poorly understood. In this study, we demonstrated that activation of the mtROS-NLRP3 inflammasome pathway is a critical contributor to renal tubular epithelial cell (RTEC) apoptosis under hyperlipidemia. In addition, the Nrf2/ARE signaling pathway is activated in renal tubular epithelial cells under hyperlipidemia conditions both in vivo and in vitro, and Nrf2 silencing accelerated palmitic acid (PA)-induced mtROS production, mitochondrial injury, and NLRP3 inflammasome activation. However, the activation of Nrf2 with tBHQ ameliorated mtROS production, mitochondrial injury, NLRP3 inflammasome activation, and cell apoptosis in PA-induced HK-2 cells and in the kidneys of HFD-induced obese rats. Furthermore, mechanistic studies showed that the potential mechanism of Nrf2-induced NLRP3 inflammasome inhibition involved reducing mtROS generation. Taken together, our results demonstrate that the Nrf2/ARE signaling pathway attenuates hyperlipidemia-induced renal injury through its antioxidative and anti-inflammatory effects through the downregulation of mtROS-mediated NLRP3 inflammasome activation.

Sexually dimorphic renal expression of Klotho is directed by a kidney-specific distal enhancer responsive to HNF1b

Transcription enhancers are genomic sequences regulating common and tissue-specific genes and their disruption can contribute to human disease development and progression. Klotho, a sexually dimorphic gene specifically expressed in kidney, is well-linked to kidney dysfunction and its deletion from the mouse genome leads to premature aging and death. However, the sexually dimorphic regulation of Klotho is not understood. Here, we characterize two candidate Klotho enhancers using H3K27ac epigenetic marks and transcription factor binding and investigate their functions, individually and combined, through CRISPR-Cas9 genome engineering. We discovered that only the distal (E1), but not the proximal (E2) candidate region constitutes a functional enhancer, with the double deletion not causing Klotho expression to further decrease. E1 activity is dependent on HNF1b transcription factor binding site within the enhancer. Further, E1 controls the sexual dimorphism of Klotho as evidenced by qPCR and RNA-seq. Despite the sharp reduction of Klotho mRNA, unlike germline Klotho knockouts, mutant mice presented normal phenotype, including weight, lifespan, and serum biochemistry. Lastly, only males lacking E1 display more prominent acute, but not chronic kidney injury responses, indicating a remarkable range of potential adaptation to isolated Klotho loss, especially in female E1 knockouts, retaining renoprotection despite over 80% Klotho reduction.

NRF2 in kidney physiology and disease

The role of NRF2 in kidney biology has received considerable interest over the past decade. NRF2 transcriptionally controls genes responsible for cellular protection against oxidative and electrophilic stress and has anti-inflammatory functions. NRF2 is expressed throughout the kidney and plays a role in salt and water handling. In disease, animal studies show that NRF2 protects against tubulointerstitial damage and reduces interstitial fibrosis and tubular atrophy, and may slow progression of polycystic kidney disease. However, the role of NRF2 in proteinuric glomerular diseases is controversial. Although the NRF2 inducer, bardoxolone methyl (CDDO-Me), increases glomerular filtration rate in humans, it has not been shown to slow disease progression in diabetic kidney disease and Alport syndrome. Furthermore, bardoxolone methyl was associated with negative effects on fluid retention, proteinuria, and blood pressure. Several animal studies replicate findings of worsened proteinuria and a more rapid progression of kidney disease, although considerable controversy exists. It is clear that further study is needed to better understand the effects of NRF2 in the kidney. This review summarizes the available data to clarify the promise and risks associated with targeting NRF2 activity in the kidney.

Oxidative stress and the role of redox signalling in chronic kidney disease

Chronic kidney disease (CKD) is a major public health concern, underscoring a need to identify pathogenic mechanisms and potential therapeutic targets. Reactive oxygen species (ROS) are derivatives of oxygen molecules that are generated during aerobic metabolism and are involved in a variety of cellular functions that are governed by redox conditions. Low levels of ROS are required for diverse processes, including intracellular signal transduction, metabolism, immune and hypoxic responses, and transcriptional regulation. However, excess ROS can be pathological, and contribute to the development and progression of chronic diseases. Despite evidence linking elevated levels of ROS to CKD development and progression, the use of low-molecular-weight antioxidants to remove ROS has not been successful in preventing or slowing disease progression. More recent advances have enabled evaluation of the molecular interactions between specific ROS and their targets in redox signalling pathways. Such studies may pave the way for the development of sophisticated treatments that allow the selective control of specific ROS-mediated signalling pathways.

Aging-related NOX4-Nrf2 redox imbalance increases susceptibility to cisplatin-induced acute kidney injury by regulating mitophagy

BACKGROUND

During aging, excessive ROS production in the kidneys leads to redox imbalance, which contributes to oxidative damage and impaired organ homeostasis. However, whether and how aging-related NOX4-Nrf2 redox imbalance increases susceptibility to cisplatin-induced acute kidney injury remain largely unknown.

METHODS

In this study, we used cisplatin-challenged aging mouse models and senescent HK-2 cells to investigate the effects and mechanisms of aging on susceptibility to cisplatin-induced acute kidney injury.

RESULTS

In vivo, we found that cisplatin stimulation caused more severe renal damage, oxidative stress, mitochondrial dysfunction and mitophagy impairment in aging mice than in young mice. Moreover, Nrf2 deficiency aggravated cisplatin-induced acute kidney injury by exacerbating NOX4-Nrf2 redox imbalance and defective mitophagy. In vitro experiments on D-gal-treated human renal tubular epithelial cells (HK-2) demonstrated that senescent renal epithelial cells exhibited increased susceptibility to cisplatin-induced apoptosis, NOX4-Nrf2 redox imbalance-mediated oxidative stress and defective mitophagy. Mechanistically, we found that knockdown of Nrf2 in HK2 cells resulted in increased ROS and aggravated mitophagy impairment, whereas these effects were reversed in NOX4-knockdown cells.

CONCLUSION

The present study indicates that NOX4-Nrf2 redox imbalance is critical for mitophagy deficiency in aged renal tubular epithelial cells and is a therapeutic target for alleviating cisplatin-induced acute kidney injury in elderly patients.

Oxidative Stress Induced by Lipotoxicity and Renal Hypoxia in Diabetic Kidney Disease and Possible Therapeutic Interventions: Targeting the Lipid Metabolism and Hypoxia

Oxidative stress, a hallmark pathophysiological feature in diabetic kidney disease (DKD), arises from the intricate interplay between pro-oxidants and anti-oxidants. While hyperglycemia has been well established as a key contributor, lipotoxicity emerges as a significant instigator of oxidative stress. Lipotoxicity encompasses the accumulation of lipid intermediates, culminating in cellular dysfunction and cell death. However, the mechanisms underlying lipotoxic kidney injury in DKD still require further investigation. The key role of cell metabolism in the maintenance of cell viability and integrity in the kidney is of paramount importance to maintain proper renal function. Recently, dysfunction in energy metabolism, resulting from an imbalance in oxygen levels in the diabetic condition, may be the primary pathophysiologic pathway driving DKD. Therefore, we aim to shed light on the pivotal role of oxidative stress related to lipotoxicity and renal hypoxia in the initiation and progression of DKD. Multifaceted mechanisms underlying lipotoxicity, including oxidative stress with mitochondrial dysfunction, endoplasmic reticulum stress activated by the unfolded protein response pathway, pro-inflammation, and impaired autophagy, are delineated here. Also, we explore potential therapeutic interventions for DKD, targeting lipotoxicity- and hypoxia-induced oxidative stress. These interventions focus on ameliorating the molecular pathways of lipid accumulation within the kidney and enhancing renal metabolism in the face of lipid overload or ameliorating subsequent oxidative stress. This review highlights the significance of lipotoxicity, renal hypoxia-induced oxidative stress, and its potential for therapeutic intervention in DKD.

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.

Superiority of systemic bleomycin to intradermal HOCl for the study of interstitial lung disease

Systemic sclerosis (SSc) is an autoimmune disease characterized by vasculopathy, immune dysregulation, and multi-organ fibrosis. Interstitial lung disease (ILD) is a complication of SSc and a leading cause of SSc-death. The administration of hypochlorous acid (HOCl) intradermally in the mouse (HOCl-SSc) purportedly shows several features typical of SSc. We studied the model by injecting BALB/c mice daily intradermally with HOCl for 6-weeks, an exposure reported to induce lung fibrosis. On day 42, the skinfold thickness and the dermal thickness were two and three times larger respectively in the HOCl group compared to controls. HOCl treatment did not result in histological features of pulmonary fibrosis nor significant changes in lung compliance. Automated image analysis of HOCl mice lungs stained with picrosirius red did not show increased collagen deposition. HOCl injections did not increase pulmonary mRNA expression of pro-fibrotic genes nor induced the production of serum advanced oxidation protein products and anti-topoisomerase 1 antibodies. Immune cells in bronchoalveolar lavage fluid (BALF) and whole lung digests were not increased in HOCl-treated animals. Since lung fibrosis is proposed to be triggered by oxidative stress, we injected HOCl to Nrf2-/- mice, a mouse deficient in many antioxidant proteins. Lung compliance, histology, and BALF leukocyte numbers were comparable between Nrf2-/- mice and wild-type controls. We conclude that the HOCl-SSc model does not manifest SSc-lung disease.

CDDO-Me ameliorates podocyte injury through anti-oxidative stress and regulation of actin cytoskeleton in adriamycin nephropathy

Podocyte injury is the common initiating event in focal segmental glomerulosclerosis (FSGS). Oxidative stress and inflammation mediate podocyte injury in FSGS. NRF2 pathway regulates the constitutive and inducible transcription of various genes that encode antioxidant proteins and anti-inflammatory proteins and have pivotal roles in the defense against cellular oxidative stress. In this study, we used adriamycin-induced nephropathy (ADR) in mice as a model of FSGS to confirm that CDDO-Me treatment ameliorated adriamycin-induced kidney damage by improving renal function and kidney histology. CDDO-Me inhibited the level of oxidative stress, inflammation, and apoptosis in adriamycin-induced podocyte injury by activating NRF2 pathway in vivo and in vitro. Furthermore, CDDO-Me stabled the cytoskeleton by regulating NRF2/srGAP2a pathway. Together, these findings show that by activating NRF2 pathway, CDDO-Me could be a therapeutic strategy to prevent the adverse effects of adriamycin-induced podocyte injury.

MiR-132-3p activation aggravates renal ischemia-reperfusion injury by targeting Sirt1/PGC1alpha axis

The pathogenesis of renal ischemic diseases remains unclear. In this study, we demonstrate the induction of microRNA-132-3p (miR-132-3p) in ischemic acute kidney injury (AKI) and cultured renal tubular cells under oxidative stress. miR-132-3p mimic increased apoptosis in renal tubular cells and enhanced ischemic AKI in mice, whereas miR-132-3p inhibition offered protective effects. We analyzed miR-132-3p target genes through bioinformatic analysis and Sirt1 was predicted as the target gene of miR-132-3p. Luciferase microRNA target reporter assay further verified Sirt1 as a direct target of miR-132-3p. In cultured tubular cells and mouse kidneys, IRI and H2O2 treatment repressed Sirt1 and PGC-1α/NRF2/HO-1 expression, whereas anti-miR-132-3p preserved Sirt1 and PGC-1α/NRF2/HO-1 expression. In renal tubular, Sirt1 inhibitor suppressed PGC1-1α/NRF2/HO-1 expression and aggravated tubular apoptosis. Together, the results suggest that miR-132-3p induction aggravates ischemic AKI and oxidative stress by repressing Sirt1 expression, and miR-132-3p inhibition offers renal protection and may be a potential therapeutic target.

Emerging significance and therapeutic targets of ferroptosis: a potential avenue for human kidney diseases

Kidney diseases remain one of the leading causes of human death and have placed a heavy burden on the medical system. Regulated cell death contributes to the pathology of a plethora of renal diseases. Recently, with in-depth studies into kidney diseases and cell death, a new iron-dependent cell death modality, known as ferroptosis, has been identified and has attracted considerable attention among researchers in the pathogenesis of kidney diseases and therapeutics to treat them. The majority of studies suggest that ferroptosis plays an important role in the pathologies of multiple kidney diseases, such as acute kidney injury (AKI), chronic kidney disease, and renal cell carcinoma. In this review, we summarize recently identified regulatory molecular mechanisms of ferroptosis, discuss ferroptosis pathways and mechanisms of action in various kidney diseases, and describe the protective effect of ferroptosis inhibitors against kidney diseases, especially AKI. By summarizing the prominent roles of ferroptosis in different kidney diseases and the progress made in studying ferroptosis, we provide new directions and strategies for future research on kidney diseases. In summary, ferroptotic factors are potential targets for therapeutic intervention to alleviate different kidney diseases, and targeting them may lead to new treatments for patients with kidney diseases.

Redox Regulation of Nrf2 in Cisplatin-Induced Kidney Injury

Cisplatin, a potent chemotherapeutic agent, is marred by severe nephrotoxicity that is governed by mechanisms involving oxidative stress, inflammation, and apoptosis pathways. The transcription factor Nrf2, pivotal in cellular defense against oxidative stress and inflammation, is the master regulator of the antioxidant response, upregulating antioxidants and cytoprotective genes under oxidative stress. This review discusses the mechanisms underlying chemotherapy-induced kidney injury, focusing on the role of Nrf2 in cancer therapy and its redox regulation in cisplatin-induced kidney injury. We also explore Nrf2's signaling pathways, post-translational modifications, and its involvement in autophagy, as well as examine redox-based strategies for modulating Nrf2 in cisplatin-induced kidney injury while considering the limitations and potential off-target effects of Nrf2 modulation. Understanding the redox regulation of Nrf2 in cisplatin-induced kidney injury holds significant promise for developing novel therapeutic interventions. This knowledge could provide valuable insights into potential strategies for mitigating the nephrotoxicity associated with cisplatin, ultimately enhancing the safety and efficacy of cancer treatment.

Phytocompounds from Amazonian Plant Species against Acute Kidney Injury: Potential Nephroprotective Effects

There are several Amazonian plant species with potential pharmacological validation for the treatment of acute kidney injury, a condition in which the kidneys are unable to adequately filter the blood, resulting in the accumulation of toxins and waste in the body. Scientific production on plant compounds capable of preventing or attenuating acute kidney injury-caused by several factors, including ischemia, toxins, and inflammation-has shown promising results in animal models of acute kidney injury and some preliminary studies in humans. Despite the popular use of Amazonian plant species for kidney disorders, further pharmacological studies are needed to identify active compounds and subsequently conduct more complex preclinical trials. This article is a brief review of phytocompounds with potential nephroprotective effects against acute kidney injury (AKI). The classes of Amazonian plant compounds with significant biological activity most evident in the consulted literature were alkaloids, flavonoids, tannins, steroids, and terpenoids. An expressive phytochemical and pharmacological relevance of the studied species was identified, although with insufficiently explored potential, mainly in the face of AKI, a clinical condition with high morbidity and mortality.

Protective effect of arbutin against cyclophosphamide-induced oxidative stress, inflammation, and hepatotoxicity via Nrf2/HO-1 pathway in rats

Cyclophosphamide (CP) is a potent anticancer drug widely employed in chemotherapy against various types of cancer. However, CP leads to toxicity to non-targeted organs, including the liver and this limits its clinical use. This study explored the role of arbutin (ARB) against CP-mediated oxidative and inflammatory reactions and hepatotoxicity. Rats were administered ARB (25 and 50 mg/kg) for 14 days and CP (150 mg/kg). CP triggered liver tissue injury with marked increase in serum AST, ALT, ALP, and bilirubin, and hepatic malondialdehyde (MDA) and nitric oxide (NO) coupled with diminution of GSH, SOD, catalase, and GPx. Liver NF-kB p65, NOS, IL-6, TNF-α, Bax and caspase-3 were upregulated by CP injection and IL-10 and Bcl-2 were decreased. ARB prevented liver injury, suppressed MDA, NO, NF-kB p65, inflammatory markers, Bax and caspase-3 in CP-treated rats. ARB restored antioxidants, IL-10 and Bcl-2, and enhanced Nrf2 and hemeoxygenase-1 (HO) both gene and protein in the liver of rats. In conclusion, these results pinpointed the protective role of ARB on oxidative and inflammatory reactions, apoptosis, and hepatotoxicity in rats. This hepatoprotective activity was linked to the ability of ARB to modulate Nrf2/HO-1 pathway.

T Cell Nrf2/Keap1 Gene Editing Using CRISPR/Cas9 and Experimental Kidney Ischemia-Reperfusion Injury

Aims: T cells play pathophysiologic roles in kidney ischemia-reperfusion injury (IRI), and the nuclear factor erythroid 2-related factor 2/kelch-like ECH-associated protein 1 (Nrf2/Keap1) pathway regulates T cell responses. We hypothesized that clustered regularly interspaced short palindromic repeats (CRISPR)/CRISPR-associated protein 9 (Cas9)-mediated Keap1-knockout (KO) augments Nrf2 antioxidant potential of CD4+ T cells, and that Keap1-KO CD4+ T cell immunotherapy protects from kidney IRI. Results: CD4+ T cell Keap1-KO resulted in significant increase of Nrf2 target genes NAD(P)H quinone dehydrogenase 1, heme oxygenase 1, glutamate-cysteine ligase catalytic subunit, and glutamate-cysteine ligase modifier subunit. Keap1-KO cells displayed no signs of exhaustion, and had significantly lower levels of interleukin 2 (IL2) and IL6 in normoxic conditions, but increased interferon gamma in hypoxic conditions in vitro. In vivo, adoptive transfer of Keap1-KO CD4+ T cells before IRI improved kidney function in T cell-deficient nu/nu mice compared with mice receiving unedited control CD4+ T cells. Keap1-KO CD4+ T cells isolated from recipient kidneys 24 h post IR were less activated compared with unedited CD4+ T cells, isolated from control kidneys. Innovation: Editing Nrf2/Keap1 pathway in murine T cells using CRISPR/Cas9 is an innovative and promising immunotherapy approach for kidney IRI and possibly other solid organ IRI. Conclusion: CRISPR/Cas9-mediated Keap1-KO increased Nrf2-regulated antioxidant gene expression in murine CD4+ T cells, modified responses to in vitro hypoxia and in vivo kidney IRI. Gene editing targeting the Nrf2/Keap1 pathway in T cells is a promising approach for immune-mediated kidney diseases.

Immune Checkpoint Molecule TIGIT Regulates Kidney T Cell Functions and Contributes to AKI

SIGNIFICANCE STATEMENT

T cells mediate pathogenic and reparative processes during AKI, but the exact mechanisms regulating kidney T cell functions are unclear. This study identified upregulation of the novel immune checkpoint molecule, TIGIT, on mouse and human kidney T cells after AKI. TIGIT-expressing kidney T cells produced proinflammatory cytokines and had effector (EM) and central memory (CM) phenotypes. TIGIT-deficient mice had protection from both ischemic and nephrotoxic AKI. Single-cell RNA sequencing led to the discovery of possible downstream targets of TIGIT. TIGIT mediates AKI pathophysiology, is a promising novel target for AKI therapy, and is being increasingly studied in human cancer therapy trials.

BACKGROUND

T cells play pathogenic and reparative roles during AKI. However, mechanisms regulating T cell responses are relatively unknown. We investigated the roles of the novel immune checkpoint molecule T cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif domains (TIGIT) in kidney T cells and AKI outcomes.

METHODS

TIGIT expression and functional effects were evaluated in mouse kidney T cells using RNA sequencing (RNA-Seq) and flow cytometry. TIGIT effect on AKI outcomes was studied with TIGIT knockout (TIGIT-KO) mice in ischemia reperfusion (IR) and cisplatin AKI models. Human kidney T cells from nephrectomy samples and single cell RNA sequencing (scRNA-Seq) data from the Kidney Precision Medicine Project were used to assess TIGIT's role in humans.

RESULTS

RNA-Seq and flow cytometry analysis of mouse kidney CD4+ T cells revealed increased expression of TIGIT after IR injury. Ischemic injury also increased TIGIT expression in human kidney T cells, and TIGIT expression was restricted to T/natural killer cell subsets in patients with AKI. TIGIT-expressing kidney T cells in wild type (WT) mice had an effector/central memory phenotype and proinflammatory profile at baseline and post-IR. Kidney regulatory T cells were predominantly TIGIT+ and significantly reduced post-IR. TIGIT-KO mice had significantly reduced kidney injury after IR and nephrotoxic injury compared with WT mice. scRNA-Seq analysis showed enrichment of genes related to oxidative phosphorylation and mTORC1 signaling in Th17 cells from TIGIT-KO mice.

CONCLUSIONS

TIGIT expression increases in mouse and human kidney T cells during AKI, worsens AKI outcomes, and is a novel therapeutic target for AKI.

Betulinic acid protects against cardiotoxicity of the organophosphorus pesticide chlorpyrifos by suppressing oxidative stress, inflammation, and apoptosis in rats

The widespread application of organophosphorus (OP) pesticides can affect the environment as well as the animal and human health. Chlorpyrifos (CPF) is a broad-spectrum OP pesticide used in agriculture and can cause several toxic effects in which oxidative stresses and inflammation play a key role. This study aimed to evaluate the protective activity of betulinic acid (BA), an antioxidant and anti-inflammatory pentacyclic triterpene, against CPF cardiotoxicity in rats. The rats were divided into four groups. CPF (10 mg/kg) and BA (25 mg/kg) were orally administered for 28 days, and blood and heart samples were collected. CPF-administered rats showed an increase in serum cardiac troponin I (cTnI), creatine kinase (CK)-MB, and lactate dehydrogenase (LDH), accompanied with multiple myocardial tissue alterations. Lipid peroxidation (LPO), nitric oxide (NO), nuclear factor-kappaB (NF-κB), interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α were increased, and antioxidant were decrease in CPF-administered rats. BA ameliorated cardiac function markers and tissue injury, decreased LPO, NO, NF-κB, and proinflammatory cytokines, and increased antioxidants. In addition, BA decreased proapoptosis markers, and increased B-cell lymphoma (Bcl)-2, IL-10, Nrf2, and HO-1 in the heart of CPF-treated rats. In conclusion, BA protected against cardiotoxicity in CPF-administered rats by mitigating oxidative stress, inflammation, and apoptosis, and enhanced Nrf2 and antioxidants.

Insights into the Molecular Mechanisms of NRF2 in Kidney Injury and Diseases

Redox is a constant phenomenon in organisms. From the signaling pathway transduction to the oxidative stress during the inflammation and disease process, all are related to reduction-oxidation (redox). Nuclear factor erythroid 2-related factor 2 (NRF2) is a transcription factor targeting many antioxidant genes. In non-stressed conditions, NRF2 maintains the hemostasis of redox with housekeeping work. It expresses constitutively with basal activity, maintained by Kelch-like-ECH-associated protein 1 (KEAP1)-associated ubiquitination and degradation. When encountering stress, it can be up-regulated by several mechanisms to exert its anti-oxidative ability in diseases or inflammatory processes to protect tissues and organs from further damage. From acute kidney injury to chronic kidney diseases, such as diabetic nephropathy or glomerular disease, many results of studies have suggested that, as a master of regulating redox, NRF2 is a therapeutic option. It was not until the early termination of the clinical phase 3 trial of diabetic nephropathy due to heart failure as an unexpected side effect that we renewed our understanding of NRF2. NRF2 is not just a simple antioxidant capacity but has pleiotropic activities, harmful or helpful, depending on the conditions and backgrounds.

Ellagic acid ameliorates aging-induced renal oxidative damage through upregulating SIRT1 and NRF2

BACKGROUND

Aging is associated with impaired renal function and structural alterations. Oxidative stress plays a vital role in renal senescence and damage. Sirtuin 1 (SIRT1) is thought to protect cells from oxidative stress through nuclear factor erythroid 2-related factor 2 (NRF2). Ellagic acid (EA), a natural antioxidant, has been demonstrated to have renoprotective roles in vitro and in vivo. This study investigated if SIRT1 and NRF2 mediate the protective effects of EA in aged kidneys.

METHODS

Male Wistar rats were divided into three groups including young (4 months), old, and old + EA (25 months). Young and old groups received EA solvent, while the old + EA group was treated with EA (30 mg/kg) by gavage for 30 days. Then, the level of renal oxidative stress, SIRT1 and NRF2 expression, kidney function parameters, and histopathological indices were measured.

RESULTS

Treatment with EA significantly increased the level of antioxidant enzymes and reduced malondialdehyde concentration (P < 0.01). Moreover, EA administration remarkably upregulated mRNA and protein levels of SIRT1 and NRF2 as well as deacetylated NRF2 protein (P < 0.05). Additionally, EA treated rats improved kidney function and histopathological scores (P < 0.05).

CONCLUSIONS

These findings suggest that ellagic acid exerts protective effects on aged kidneys by activating SIRT1 and NRF2 signaling.

Flavonoids of Haloxylon salicornicum (Rimth) prevent cisplatin-induced acute kidney injury by modulating oxidative stress, inflammation, Nrf2, and SIRT1

Cisplatin (CIS) is an effective chemotherapeutic drug used for the treatment of many types of cancers, but its use is associated with adverse effects. Nephrotoxicity is a serious side effect of CIS and limits its therapeutic utility. Haloxylon salicornicum is a desert shrub used traditionally in the treatment of inflammatory disorders, but neither its flavonoid content nor its protective efficacy against CIS nephrotoxicity has been investigated. In this study, seven flavonoids were isolated from H. salicornicum methanolic extract (HSE) and showed in silico binding affinity with NF-κB, Keap1, and SIRT1. The protective effect of HSE against CIS nephrotoxicity was investigated. Rats received HSE (100, 200, and 400 mg/kg) for 14 days followed by a single injection of CIS. The drug increased Kim-1, BUN, and creatinine and caused multiple histopathological changes. CIS-administered rats showed an increase in renal ROS, MDA, NO, TNF-α, IL-1β, and NF-κB p65. HSE prevented tissue injury, and diminished ROS, NF-κB, and inflammatory mediators. HSE enhanced antioxidants and Bcl-2 and downregulated pro-apoptosis markers. These effects were associated with downregulation of Keap1 and microRNA-34a, and upregulation of SIRT1 and Nrf2/HO-1 signaling. In conclusion, H. salicornicum is rich in flavonoids, and its extract prevented oxidative stress, inflammation, and kidney injury, and modulated Nrf2/HO-1 and SIRT1 signaling in CIS-treated rats.

Methyl eugenol protects the kidney from oxidative damage in mice by blocking the Nrf2 nuclear export signal through activation of the AMPK/GSK3β axis

Disrupted redox homeostasis contributes to renal ischemia-reperfusion (IR) injury. Abundant natural products can activate nuclear factor erythroid-2-related factor 2 (Nrf2), thereby providing therapeutic benefits. Methyl eugenol (ME), an analog of the phenolic compound eugenol, has the ability to induce Nrf2 activity. In this study, we investigated the protective effects of ME against renal oxidative damage in vivo and in vitro. An IR-induced acute kidney injury (AKI) model was established in mice. ME (20 mg·kg-1·d-1, i.p.) was administered to mice on 5 consecutive days before IR surgery. We showed that ME administration significantly attenuated renal destruction, improved the survival rate, reduced excessive oxidative stress and inhibited mitochondrial lesions in AKI mice. We further demonstrated that ME administration significantly enhanced Nrf2 activity and increased the expression of downstream antioxidative molecules. Similar results were observed in vitro in hypoxia/reoxygenation (HR)-exposed proximal tubule epithelial cells following pretreatment with ME (40 μmol·L-1). In both renal oxidative damage models, ME induced Nrf2 nuclear retention in tubular cells. Using specific inhibitors (CC and DIF-3) and molecular docking, we demonstrated that ME bound to the binding pocket of AMPK with high affinity and activated the AMPK/GSK3β axis, which in turn blocked the Nrf2 nuclear export signal. In addition, ME alleviated the development of renal fibrosis induced by nonfatal IR, which is frequently encountered in the clinic. In conclusion, we demonstrate that ME modulates the AMPK/GSK3β axis to regulate the cytoplasmic-nuclear translocation of Nrf2, resulting in Nrf2 nuclear retention and thereby enhancing antioxidant target gene transcription that protects the kidney from oxidative damage.

Assessment of cancer-related signaling pathways in responses to polystyrene nanoplastics via a kidney-testis microfluidic platform (KTP)

As a new type of environmental pollutants, micro/nano plastics (MPs/NPs) derived from plastic products are commonly contact in daily life and lead to some serious health issues. The toxicity effects of MPs/NPs on the human body have aroused wide concerns. Although MPs/NPs have been reported to be transmitted into the kidney and reproductive organs, the molecular mechanisms of MPs/NPs toxicity remain unclear due to the lack of a physiologically relevant organ-organ linking platform in vitro. Here, we present a kidney-testis microfluidic platform (KTP) with NPs exposure that enables the communication of kidney and testis chambers and reproduces endothelium-linked chambers to simulate the state in vivo. The function of KTP was assessed by cell counting kit (CCK-8), tight junction protein claudin-2 and glucose consumption. Results revealed that MPs/NPs entered the kidney and testis via endocytosis. Immunofluorescence and ELISA analysis were performed on KTP at 200 μg/mL PS-NP to identify the dysregulated proteins on cancer-related signaling pathways, including the MAPK signaling pathway (RTK, RAS, ERK, JNK, P38, NRF2, TNF-α, and TNF-α-R) and the PI3K-AKT signaling pathway (PI3K, AKT, MDM2, P53, and ΒΑD). This multi-organ platform (KTP) contributes to clarifying cancer pathways triggered by MPs/NPs exposure and provides a promising method for assessing diseases induced by environmental pollutants.

Rosmarinic acid mitigates chlorpyrifos-induced oxidative stress, inflammation, and kidney injury in rats by modulating SIRT1 and Nrf2/HO-1 signaling

Chlorpyrifos (CPF) is a widely used broad-spectrum pesticide with multi-organ toxic effects. Oxidative stress was found to play a role in the deleterious effects of CPF, including nephrotoxicity. This study investigated the protective effect of the antioxidant polyphenol rosmarinic acid (RA) against CPF-induced kidney injury, with an emphasis on oxidative injury, inflammation, SIRT1, and Nrf2/HO-1 signaling. Rats received 10 mg/kg CPF and 25, 50, and 100 mg/kg RA orally for 28 days, and the samples were collected for analysis. CPF increased serum urea and creatinine and kidney Kim-1 and caused several histopathological alterations. ROS, MDA, NO, NF-κB p65, TNF-α, and IL-1β were elevated in the kidney of CPF-intoxicated rats. RA ameliorated kidney function markers, prevented tissue injury, suppressed ROS, MDA, and NO, and downregulated NF-κB p65, TNF-α, and IL-1β in CPF-intoxicated rats in a dose-dependent manner. RA decreased Bax, caspase-3, oxidative DNA damage, and Keap1, boosted antioxidant enzymes and Bcl-2, and upregulated Nrf2, HO-1, and SIRT1 in CPF-administered rats. Molecular docking simulation revealed the binding affinity of RA toward NF-κB, Keap1, HO-1, and SIRT1. In conclusion, RA prevented CPF nephrotoxicity by attenuating oxidative stress, inflammation, and apoptosis and upregulating SIRT1 and Nrf2/HO-1 signaling.

Network pharmacology and experimental validation to elucidate the pharmacological mechanisms of Bushen Huashi decoction against kidney stones

INTRODUCTION

Kidney stone disease (KS) is a complicated disease with an increasing global incidence. It was shown that Bushen Huashi decoction (BSHS) is a classic Chinese medicine formula that has therapeutic benefits for patients with KS. However, its pharmacological profile and mechanism of action are yet to be elucidated.

METHODS

The present study used a network pharmacology approach to characterize the mechanism by which BSHS affects KS. Compounds were retrieved from corresponding databases, and active compounds were selected based on their oral bioavailability (≥30) and drug-likeness index (≥0.18). BSHS potential proteins were obtained from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database, whereas KS potential genes were obtained from GeneCards and OMIM, TTD, and DisGeNET. Gene ontology and pathway enrichment analysis were used to determine potential pathways associated with genes. The ingredients of BSHS extract were identified by the ultra-high-performance liquid chromatography coupled with quadrupole orbitrap mass spectrometry (UHPLC-Q/Orbitrap MS). The network pharmacology analyses predicted the potential underlying action mechanisms of BSHS on KS, which were further validated experimentally in the rat model of calcium oxalate kidney stones.

RESULTS

Our study found that BSHS reduced renal crystal deposition and improved renal function in ethylene glycol(EG)+ammonium chloride(AC)-induced rats, and also reversed oxidative stress levels and inhibited renal tubular epithelial cell apoptosis in rats. BSHS upregulated protein and mRNA expression of E2, ESR1, ESR2, BCL2, NRF2, and HO-1 in EG+AC-induced rat kidney while downregulating BAX protein and mRNA expression, consistent with the network pharmacology results.

DISCUSSION

This study provides evidence that BSHS plays a critical role in anti-KS via regulation of E2/ESR1/2, NRF2/HO-1, and BCL2/BAX signaling pathways, indicating that BSHS is a candidate herbal drug for further investigation in treating KS.

Electroacupuncture Pretreatment at Zusanli (ST36) Ameliorates Hepatic Ischemia/Reperfusion Injury in Mice by Reducing Oxidative Stress via Activating Vagus Nerve-Dependent Nrf2 Pathway

Background and Purpose

Current pharmacological approaches to prevent hepatic ischemia/reperfusion injury (IRI) are limited. To mitigate hepatic injury, more research is needed to improve the understanding of hepatic IRI. Depending on traditional Chinese medicine (TCM) theory, acupuncture therapy has been used for the treatment of ischemic diseases with good efficacy. However, the efficacy and mechanism of acupuncture for hepatic IRI are still unclear.

Methods

Blood provided to the left and middle lobe of mice livers was blocked with a non-invasive clamp and then the clamps were removed for reperfusion to establish a liver IRI model. Quantitative proteomics approach was used to evaluate the impact of EA pretreatment on liver tissue proteome in the IRI group. Serum biochemistry was used to detect liver injury, inflammation, and oxidative stress levels. H&E staining and TUNEL staining were used to detect hepatocyte injury and apoptosis. Immunohistochemistry and ELISA were used to detect the degree of inflammatory cell infiltration and the level of inflammation. The anti-inflammatory and antioxidant capacities were detected by Quantitative RT-PCR and Western blotting.

Results

We found that EA at Zusanli (ST36) has a protective effect on hepatic IRI in mice by alleviating oxidative stress, hepatocyte death, and inflammation response. Nuclear factor E2-related factor 2 (Nrf2) as a crucial target was regulated by EA and was then successfully validated. The Nrf2 inhibitor ML385 and cervical vagotomy eliminated the protective effect in the EA treatment group.

Conclusion

This study firstly demonstrated that EA pretreatment at ST36 significantly ameliorates hepatic IRI in mice by inhibiting oxidative stress via activating the Nrf2 signal pathway, which was vagus nerve-dependent.

Taxifolin Prevents Cisplatin Nephrotoxicity by Modulating Nrf2/HO-1 Pathway and Mitigating Oxidative Stress and Inflammation in Mice

Cisplatin (CIS) is an effective chemotherapeutic agent used in the treatment of several malignancies. The clinical use of CIS is associated with adverse effects, including acute kidney injury (AKI). Oxidative stress and inflammation are key events in the development of CIS-induced AKI. This study investigated the protective effect of taxifolin (TAX), a bioactive flavonoid with promising health-promoting properties, on CIS-induced nephrotoxicity in mice. TAX was orally given to mice for 10 days and a single dose of CIS was injected at day 7. Serum blood urea nitrogen (BUN) and creatinine were elevated, and multiple histopathological alterations were observed in the kidney of CIS-administered mice. CIS increased renal malondialdehyde (MDA), nitric oxide (NO), nuclear factor-kappaB (NF-κB) p65, tumor necrosis factor (TNF)-α, and interleukin (IL)-1β, and decreased cellular antioxidants in mice. TAX remarkably prevented kidney injury, ameliorated serum BUN and creatinine, and renal MDA, NO, NF-κB p65, and pro-inflammatory cytokines, and boosted antioxidant defenses in CIS-administered mice. TAX downregulated Bax and caspase-3, and upregulated Bcl-2. These effects were associated with upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) expression and heme oxygenase (HO)-1 activity in CIS-administered mice. In conclusion, TAX prevented CIS-induced AKI by mitigating tissue injury, oxidative stress, inflammation, and cell death. The protective efficacy of TAX was associated with the upregulation of Nrf2/HO-1 signaling.

Oxidant- induced preconditioning: A pharmacologic approach for triggering renal 'self defense'

Acute kidney injury (AKI) is a common event, occurring in ~5% and ~35% of hospitalized and ICU patients, respectively. The development of AKI portends an increased risk of morbidity, mortality, prolonged hospitalization, and subsequent development of chronic kidney disease (CKD). Given these facts, a multitude of experimental studies have addressed potential methods for inducing AKI prevention in high-risk patients. However, successful clinical translation of promising experimental data has remained elusive. Over the past decade, our laboratory has focused on developing a method for safely triggering AKI protection by inducing "kidney preconditioning" in mice by the intravenous administration of a combination of Fe sucrose (FeS) + tin protoporphyrin (SnPP). These agents induce mild, but short lived, 'oxidant stress' which synergistically activate a number of kidney 'self-defense' pathways (e.g., Nrf2, ferritin, IL-10). Within 18-24 h of Fe/SnPP administration, marked protection against diverse forms of experimental toxic and ischemic AKI results. FeS/SnPP-mediated reductions in kidney injury can also indirectly decrease injury in other organs by mitigating the so called "organ cross talk" phenomenon. Given these promising experimental data, three phase 1b clinical trials were undertaken in healthy subjects and patients with stage 3 or 4 CKD. These studies demonstrated that FeS/SnPP were well tolerated and that they up-regulated the cytoprotective Nrf2, ferritin, and IL-10 pathways. Two subsequent phase 2 trials, conducted in patients undergoing 'on-pump' cardiovascular surgery or in patients hospitalized with COVID 19, confirmed FeS/SnPP safety. Furthermore, interim data analyses revealed statistically significant improvements in several clinical parameters. The goals of this review are to: (i) briefly discuss the historical background of renal "preconditioning"; (ii) present the experimental data that support the concept of FeS/SnPP- induced organ protection; and (iii) discuss the initial results of clinical trials that suggest the potential clinical utility of an 'oxidant preconditioning' strategy.

Suppression of NRF2 Activity by HIF-1α Promotes Fibrosis after Ischemic Acute Kidney Injury

Acute kidney injury (AKI) is a rapid decline in renal function and can occur after ischemia/reperfusion injury (IRI) to the tubular epithelia. The nuclear factor erythroid-2-related factor 2 (NRF2) pathway protects against AKI and AKI-to-chronic kidney disease (CKD) progression, but we previously demonstrated that severe IRI maladaptively reduced NRF2 activity in mice. To understand the mechanism of this response, we subjected C57BL/6J mice to unilateral kidney IRI with ischemia times that were titrated to induce mild to severe injury. Mild IRI increased NRF2 activity and was associated with renal recovery, whereas severe IRI decreased NRF2 activity and led to progressive CKD. Due to these effects of ischemia, we tested the hypothesis that hypoxia-inducible factor-1α (HIF-1α) mediates NRF2 activity. To mimic mild and severe ischemia, we activated HIF-1α in HK-2 cells in nutrient-replete or nutrient-deficient conditions. HIF-1α activation in nutrient-replete conditions enhanced NRF2 nuclear localization and activity. However, in nutrient-deficient conditions, HIF-1α activation suppressed NRF2 nuclear localization and activity. Nuclear localization was rescued with HIF-1α siRNA knockdown. Our results suggest that severe ischemic AKI leads to HIF-1α-mediated suppression of NRF2, leading to AKI-to-CKD progression.

Activation of the Nrf2/ARE signaling pathway protects against palmitic acid-induced renal tubular epithelial cell injury by ameliorating mitochondrial reactive oxygen species-mediated mitochondrial dysfunction

Chronic kidney disease (CKD) is often accompanied by dyslipidemia, and abnormal lipid metabolism in proximal tubule cells is considered closely related to the dysfunction of proximal tubule cells and eventually leads to accelerated kidney damage. Nuclear factor E2-related factor 2 (Nrf2), known as a redox-sensitive transcription factor, is responsible for regulating cellular redox homeostasis. However, the exact role of Nrf2 in dyslipidemia-induced dysfunction of proximal tubule cells is still not fully elucidated. In the present study, we showed that palmitic acid (PA) induced mitochondrial damage, excessive mitochondrial reactive oxygen species (ROS) (mtROS) generation, and cell injury in HK-2 cells. We further found that mtROS generation was involved in PA-induced mitochondrial dysfunction, cytoskeletal damage, and cell apoptosis in HK-2 cells. In addition, we demonstrated that the Nrf2/ARE signaling pathway was activated in PA-induced HK-2 cells and that silencing Nrf2 dramatically aggravated PA-induced mtROS production, mitochondrial damage, cytoskeletal damage and cell apoptosis in HK-2 cells. However, the mitochondrial antioxidant MitoTEMPOL effectively eliminated these negative effects of Nrf2 silencing in HK-2 cells under PA stimulation. Moreover, activation of the Nrf2/ARE signaling pathway with tBHQ attenuated renal injury, significantly reduced mtROS generation, and improved mitochondrial function in rats with HFD-induced obesity. Taken together, these results suggest that the Nrf2/ARE-mediated antioxidant response plays a protective role in hyperlipidemia-induced renal injury by ameliorating mtROS-mediated mitochondrial dysfunction and that enhancing Nrf2 antioxidant signaling provides a potential therapeutic strategy for kidney injury in CKD with hyperlipidemia.

Endoplasmic reticulum stress contributes to cisplatin-induced chronic kidney disease via the PERK-PKCδ pathway

BACKGROUND

Cisplatin is an effective chemotherapeutic drug, but it may induce both acute and chronic kidney problems. The pathogenesis of chronic kidney disease (CKD) associated with cisplatin chemotherapy remains largely unclear.

METHODS

Mice and renal tubular cells were subjected to repeated low-dose cisplatin (RLDC) treatment to induce CKD and related pathological changes. The roles of endoplasmic reticulum (ER) stress, PERK, and protein kinase C-δ (PKCδ) were determined using pharmacological inhibitors and genetic manipulation.

RESULTS

ER stress was induced by RLDC in kidney tubular cells in both in vivo and in vitro models. ER stress inhibitors given immediately after RLDC attenuated kidney dysfunction, tubular atrophy, kidney fibrosis, and inflammation in mice. In cultured renal proximal tubular cells, inhibitors of ER stress or its signaling kinase PERK also suppressed RLDC-induced fibrotic changes and the expression of inflammatory cytokines. Interestingly, RLDC-induced PKCδ activation, which was blocked by ER stress or PERK inhibitors, suggesting PKCδ may act downstream of PERK. Indeed, suppression of PKCδ with a kinase-dead PKCδ (PKCδ-KD) or Pkcδ-shRNA attenuated RLDC-induced fibrotic and inflammatory changes. Moreover, the expression of active PKCδ-catalytic fragment (PKCδ-CF) diminished the beneficial effects of PERK inhibitor in RLDC-treated cells. Co-immunoprecipitation assay further suggested PERK binding to PKCδ.

CONCLUSION

These results indicate that ER stress contributes to chronic kidney pathologies following cisplatin chemotherapy via the PERK-PKCδ pathway.

Salvianolate ameliorates renal tubular injury through the Keap1/Nrf2/ARE pathway in mouse kidney ischemia-reperfusion injury

ETHNOPHARMACOLOGICAL RELEVANCE

Acute kidney injury (AKI) is a common clinical disease characterized by rapid loss of renal function. Salvianolate is a prescribed Chinese medicine derived from traditional Chinese medicine Salvia miltiorrhiza bunge that possesses many pharmacological effects, the active components extracted from Salvia miltiorrhiza bunge have been proved to protect ischemia-reperfusion (I/R)-AKI.

AIM OF THE STUDY

This study aims to validate the therapeutic effect of SAL on I/R-AKI, and explore its potential pharmacological mechanism.

MATERIALS AND METHODS

Mice were pretreated with/without salvianolate (10, 30, and 90 mg/kg) before renal ischemia-reperfusion operation. Serum creatinine, BUN, and H&E staining were performed to evaluate renal function. Immunofluorescence analysis was conducted to measure renal tubular injury including inflammatory factors and peroxide level. Apoptosis of the kidney tissues was determined by TUNEL assay. Keap1-Nrf2-ARE and apoptosis signaling pathways were measured by Western blot, RT-PCR, and YO-PRO-1 staining in kidneys or NRK52E cells.

RESULTS

Pretreatment with SAL effectively alleviated renal function and ameliorated epithelial tubular injury, oxidative stress, and inflammatory response. Furthermore, the mechanistic study demonstrated that the SAL exerts anti-apoptotic effects through activation of the Keap1-Nrf2-ARE signaling pathway in renal tubular cells.

CONCLUSION

These findings indicate the therapeutic benefit of salvianolate in the protection of renal injury from ischemia-reperfusion, and strengthen the evidence for the AKI treatment strategy by the anti-oxidative stress response, suggesting that SAL may be a potential agent for the treatment of AKI.

Protective effect of Rhein against vancomycin-induced nephrotoxicity through regulating renal transporters and Nrf2 pathway

Vancomycin (VCM)'s nephrotoxicity limits its application and therapeutic efficiency. The aim of this study was to determine the protective effect of rhein against VCM-induced nephrotoxicity (VIN). VIN models were established in rats and NRK-52E cells. Rhein up-regulated the expressions of renal organic anion transporter (Oat) 1, Oat3, organic cation transporter 2 (Oct2), multidrug resistance-associated protein 2 (Mrp2), mammal multidrug and toxin extrusion proteins 1 (Mate 1) and P-glycoprotein (P-gp) to facilitate the efflux of plasma creatinine, blood urea nitrogen (BUN), and plasma indoxyl sulfate. Rhein increased the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) to regulate the expression of Mrp2, P-gp, and Mate 1. The increased level of superoxide dismutase (SOD), decreased level of malondialdehyde (MDA) and reduced number of apoptosis cells were observed after treatment of rhein. Rhein decreased the number of apoptosis cells as well as increased the expression of B-cell lymphoma-2 (Bcl-2) and decreased expressions of Bcl-2-like protein 4 (Bax). ML385, as a typical inhibitor of Nrf2, reversed the protective effects of rhein in cells. Rhein oriented itself in the site of Keap1, inhibiting the Keap1-Nrf2 interaction. Rhein ameliorated VIN mainly through regulating the expressions of renal transporters and acting on Nrf2 pathway.

Bisdemethoxycurcumin Attenuated Renal Injury via Activation of Keap1/Nrf2 Pathway in High-Fat Diet-Fed Mice

Bisdemethoxycurcumin (BDMC), a principal and active component of edible turmeric, was previously found to have beneficial effects on metabolic diseases. Chronic kidney disease (CKD) may benefit from its potential therapeutic use. Using a high-fat diet (HFD)-fed mouse model, we examined the effects of BDMC on renal injury and tried to determine how its associated mechanism works. A number of metabolic disorders are significantly improved by BDMC, including obesity, hyperglycemia, hyperinsulinemia, hyperlipidemia and inflammation. Further research on renal histopathology and function showed that BDMC could repair renal pathological changes and enhance renal function. Moreover, decreased serum malondialdehyde (MDA), elevated superoxide dismutase (SOD) activity, and the inhibition of renal reactive oxygen species (ROS) overproduction revealed the alleviation of oxidative stress after BDMC administration. In addition, renal Kelch-like ECH-associated protein 1/nuclear factor erythroid 2-related factor 2 (Keap1/Nrf2) pathway was activated in BDMC-treated mice. In conclusion, these findings demonstrated BDMC as a potential therapy for HFD-induced CKD via the activation of the Keap1/Nrf2 pathway.

Macrophage nuclear factor erythroid 2-related factor 2 deficiency promotes innate immune activation by tissue inhibitor of metalloproteinase 3-mediated RhoA/ROCK pathway in the ischemic liver

BACKGROUND AND AIMS

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a master regulator of reactive oxygen species (ROS) and inflammation and has been implicated in both human and murine inflammatory disease models. We aimed to characterize the roles of macrophage-specific Nrf2 in liver ischemia/reperfusion injury (IRI).

APPROACH AND RESULTS

First, macrophage Nrf2 expression and liver injury in patients undergoing OLT or ischemia-related hepatectomy were analyzed. Subsequently, we created a myeloid-specific Nrf2-knockout (Nrf2M-KO ) strain to study the function and mechanism of macrophage Nrf2 in a murine liver IRI model. In human specimens, macrophage Nrf2 expression was significantly increased in liver tissues after transplantation or hepatectomy. Interestingly, lower Nrf2 expressions correlated with more severe liver injury postoperatively. In a mouse model, we found Nrf2M-KO mice showed worse hepatocellular damage than Nrf2-proficient controls based on serum biochemistry, pathology, ROS, and inflammation. In vitro, Nrf2 deficiency promoted innate immune activation and migration in macrophages on toll-like receptor (TLR) 4 stimulation. Microarray profiling showed Nrf2 deletion caused markedly lower transcriptional levels of tissue inhibitor of metalloproteinase 3 (Timp3). ChIP-seq, PCR, and luciferase reporter assay further demonstrated Nrf2 bound to the promoter region of Timp3. Moreover, a disintegrin and metalloproteinase (ADAM) 10/ROCK1 was specifically increased in Nrf2-deficient macrophages. Increasing Timp3 expression effectively inhibited ADAM10/ROCK1 expression and rescued the Nrf2M-KO -mediated inflammatory response on TLR4 stimulation in vitro. Importantly, Timp3 overexpression, recombinant Timp3 protein, or ROCK1 knockdown rescued Nrf2M-KO -related liver IRI by inhibiting macrophage activation.

CONCLUSIONS

In conclusion, macrophage Nrf2 mediates innate proinflammatory responses, attenuates liver IRI by binding to Timp3, and inhibits the RhoA/ROCK pathway, which provides a therapeutic target for clinical organ IRI.

Formononetin Ameliorates Renal Dysfunction, Oxidative Stress, Inflammation, and Apoptosis and Upregulates Nrf2/HO-1 Signaling in a Rat Model of Gentamicin-Induced Nephrotoxicity

Gentamicin (GEN) is a bactericidal aminoglycoside known to cause nephrotoxicity. Formononetin (FN) is a potent flavonoid that exhibits numerous promising pharmacological activities. In this study, we have assessed the nephroprotective efficacy of FN against GEN-induced renal injury in rats. Rats were orally administered with FN (60 mg/kg/day, for 2 weeks) and were co-treated with intraperitoneal (i.p.) injection of GEN (100 mg/kg/day) during the days 8–14. GEN-treated rats demonstrated increased urea and creatinine levels in serum associated with marked histopathological changes in the kidney. Malondialdehyde (MDA) and protein carbonyl contents were elevated, whereas glutathione concentration and catalase and superoxide dismutase activities were lowered in GEN-administered rats. The FN largely prevented tissue damage, attenuated renal function, reduced MDA and protein carbonyl, and enhanced antioxidant capacity in the kidney of GEN-administrated animals. The kidney of GEN-treated rats demonstrated elevated Bax and caspase-3 protein expression, accompanied by lowered Bcl-2 protein expression, an effect that FN attenuated. Moreover, FN treatment caused upregulation of nuclear factor erythroid 2-related factor 2 (Nrf2) and heme oxygenase 1 (HO-1) expression in renal tissue of GEN-intoxicated animals. Collectively, FN protects against GEN-caused renal damage via exhibiting antioxidant, anti-inflammatory, and antiapoptotic activities and augmenting Nrf2 signaling, suggesting FN as a promising agent for preventing drug-induced organ damage.

5-Methyltetrahydrofolate Attenuates Oxidative Stress and Improves Kidney Function in Acute Kidney Injury through Activation of Nrf2 and Antioxidant Defense

Oxidative stress is a major mediator of adverse outcomes in acute kidney injury (AKI). Deficiency of micronutrients, such as folate, is common in AKI. Our previous study reported that AKI impaired kidney reabsorption of folate and decreased plasma folate level in rats. The present study investigated the effect of 5-methyltetrahydrofolate (5-MTHF), a biologically active form of folate/folic acid, on AKI-impaired kidney function and oxidative stress. Sprague-Dawley rats developed AKI after kidney ischemia (45 min) and reperfusion (24 h). Injection of 5-MTHF (3 µg/kg body weight) improved kidney function and attenuated oxidative stress with a restoration of glutathione and a reduction of lipid peroxidation in the kidney. Injection of 5-MTHF activated transcription factor Nrf2 and increased the expression of glutathione synthesizing enzymes, superoxide dismutase-1 and heme oxygenase-1 in the kidney. Simulated ischemia-reperfusion through hypoxia-reoxygenation increased oxidative stress in proximal tubular cells. Incubation of cells with 5-MTHF alleviated cell injury and increased antioxidant enzyme expression and intracellular glutathione levels. Inhibition of Nrf2 expression through siRNA transfection abolished the effect of 5-MTHF against oxidative stress. These results suggest that low-dose folic acid can improve kidney function through activation of Nrf2 and restoration of antioxidant defence. Micronutrient supplements may improve clinical outcomes in AKI.

Mitochondrial ROS, ER Stress, and Nrf2 Crosstalk in the Regulation of Mitochondrial Apoptosis Induced by Arsenite

Long-term ingestion of arsenicals, a heterogeneous group of toxic compounds, has been associated with a wide spectrum of human pathologies, which include various malignancies. Although their mechanism of toxicity remains largely unknown, it is generally believed that arsenicals mainly produce their effects via direct binding to protein thiols and ROS formation in different subcellular compartments. The generality of these mechanisms most probably accounts for the different effects mediated by different forms of the metalloid in a variety of cells and tissues. In order to learn more about the molecular mechanisms of cyto- and genotoxicity, there is a need to focus on specific arsenic compounds under tightly controlled conditions. This review focuses on the mechanisms regulating the mitochondrial formation of ROS after exposure to low concentrations of a specific arsenic compound, NaAsO₂, and their crosstalk with the nuclear factor (erythroid-2 related) factor 2 antioxidant signaling and the endoplasmic reticulum stress response.

Regulation of Mitochondrial Homeostasis and Nrf2 in Kidney Disease: Timing Is Critical

Abnormal regulation of mitochondrial homeostasis plays a critical role in the progression of renal disease. Recent studies have shown that activation of nuclear factor erythroid 2-related factor 2 (Nrf2) has time-dependent protective effects, which can be explained by the differing regulation of mitochondrial homeostasis during the various stages of kidney disease. In this review, we summarize the mechanisms whereby mitochondrial homeostasis is regulated and the nature of the dysregulation of mitochondrial homeostasis in renal disease. In addition, we summarize the dual roles of Nrf2 in kidney disease by discussing the studies that have shown the importance of the timing of its activation in the regulation of mitochondrial homeostasis. This should provide a theoretical basis for therapeutic strategies aimed at activating Nrf2 in kidney disease.

Oxidative Stress and Ischemia/Reperfusion Injury in Kidney Transplantation: Focus on Ferroptosis, Mitophagy and New Antioxidants

Although there has been technical and pharmacological progress in kidney transplant medicine, some patients may experience acute post-transplant complications. Among the mechanisms involved in these conditions, ischemia/reperfusion (I/R) injury may have a primary pathophysiological role since it is one of the leading causes of delayed graft function (DGF), a slow recovery of the renal function with the need for dialysis (generally during the first week after transplantation). DGF has a significant social and economic impact as it is associated with prolonged hospitalization and the development of severe complications (including acute rejection). During I/R injury, oxidative stress plays a major role activating several pathways including ferroptosis, an iron-driven cell death characterized by iron accumulation and excessive lipid peroxidation, and mitophagy, a selective degradation of damaged mitochondria by autophagy. Ferroptosis may contribute to the renal damage, while mitophagy can have a protective role by reducing the release of reactive oxygen species from dysfunctional mitochondria. Deep comprehension of both pathways may offer the possibility of identifying new early diagnostic noninvasive biomarkers of DGF and introducing new clinically employable pharmacological strategies. In this review we summarize all relevant knowledge in this field and discuss current antioxidant pharmacological strategies that could represent, in the next future, potential treatments for I/R injury.

The Protective Role of Celastrol in Renal Ischemia-Reperfusion Injury by Activating Nrf2/HO-1, PI3K/AKT Signaling Pathways, Modulating NF-κb Signaling Pathways, and Inhibiting ERK Phosphorylation

Celastrol, a natural triterpenoid derived from Tripterygium wilfordii, possesses numerous biological effects. We investigated celastrol's antioxidant potential through nuclear factor erythroid 2-related factor 2 (Nrf2)/heme oxygenase 1 (HO-1) and its effect on phosphoinositide 3-kinase (PI3K)/protein kinase B (AKT) signaling, nuclear factor-kappa B (NF-κB) pathways, and extracellular signal-regulated kinase (ERK) activation in kidney ischemia-reperfusion injury (IRI) rat model. Rats were given celastrol 2 mg/kg orally for 1 week before subjection to renal ischemia-reperfusion surgery. Kidney functions, renal MDA, and reduced glutathione were determined; also, renal levels of ERK1/2, HO-1, PI3K, IL-6, TNF-α, IκBα, NF-κB/p65, and cleaved caspase-3 were measured. In addition, gene expression of kidney injury molecule-1 (KIM-1), Nrf-2, and AKT were determined. Celastrol pretreatment attenuated oxidative stress and increased Nrf2 gene expression and HO-1 level. Also, it activated the PI3K/AKT signaling pathway and decreased the p-ERK:t- ERK ratio and NFκBp65 level, with a remarkable decrease in inflammatory cytokines and cleaved caspase-3 levels compared with those in renal IRI rats. Conclusively, celastrol showed a reno-protective potential against renal IRI by suppressing oxidative stress through enhancing the Nrf2/HO-1 pathway, augmenting cell survival PI3K/AKT signaling pathways, and reducing inflammation by inhibiting NF-κB activation.

Using Collagen Peptides From the Skin of Monkfish (Lophius litulon) to Ameliorate Kidney Damage in High-Fat Diet Fed Mice by Regulating the Nrf2 Pathway and NLRP3 Signaling

Background

Oxidative stress and inflammation play important roles in high-fat diet (HFD) induced kidney damage. Previous studies show that the collagen extracted from the skin of monkfish (Lophius litulon) with pepsin (pepsin-solubilized collagen, PSC) exhibits good biological activities. This study investigates the protective effect of PSCP against chronic kidney injury in HFD-fed mice.

Methods

Pepsin-solubilized collagen was further hydrolyzed into collagen peptides, and the compound with the best 2,2-diphenyl-1-picrylhydrazyl (DPPH) clearance rate was named pepsin-solubilized collagen peptide (PSCP). A group of mice were fed an HFD for 4 weeks, and then for another 6 weeks PSCP was added to their diet at the amount of either 100 or 200 mg/kg.

Results

Pepsin-solubilized collagen peptide treatment (200 mg/kg) reduced the mice's serum levels of uric acid (UA), creatinine (CRE), and blood urea nitrogen (BUN) by 27, 20, and 37%, respectively. This treatment also remarkably improved renal histopathology. Moreover, the activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) were increased by 96, 52, and 74%, respectively, and decreased the malondialdehyde (MDA) level by 36%. Additionally, PSCP activated the Nrf2 pathway and inhibited NLRP3 signaling to significantly reduce the levels of inflammatory cytokines IL-1β, IL-6, and TNF-α.

Conclusions

Our results indicate that compound PSCP has the potential to prevent or control chronic kidney damage.

Empagliflozin Enhances Autophagy, Mitochondrial Biogenesis, and Antioxidant Defense and Ameliorates Renal Ischemia/Reperfusion in Nondiabetic Rats

Background. Recent meta-analyses have shown that sodium-glucose cotransporter 2 (SGLT-2) inhibitors alleviate chronic kidney disease and acute kidney injury in diabetic patients. In this study, we aimed to investigate the effect of empagliflozin on renal ischemia/reperfusion (I/R) in nondiabetic rats and find the possible mechanisms. Experimental Approach. Eighteen male Wistar rats were randomly divided into three groups, including healthy control, ischemic control, and empagliflozin-treated group. Thirty minutes of bilateral renal ischemia was induced by clamping the renal hilum. Forty-eight hours after reopening the clamps, rats’ blood samples and tissue specimens were collected. Empagliflozin 10 mg/kg was administered by gavage, 2 hours before ischemia and 24 hours after the first dose. Results. I/R injury led to a significant rise in serum creatinine and blood urea nitrogen which was significantly decreased after treatment with empagliflozin. Empagliflozin also alleviated tubulointerstitial and glomerular damage and significantly decreased tissue histology scores. Empagliflozin decreased the increased levels of malondialdehyde, interleukin 1β, and tumor necrosis factor α. SGLT2 inhibition increased the decreased expression of nuclear factor erythroid 2-related factor 2 and PPARG coactivator 1 alpha that conduct antioxidant defense and mitochondrial biogenesis, respectively. Furthermore, empagliflozin markedly increased LC3-II/LC3-I and bcl2/bax ratios, showing its beneficial effect on activation of autophagy and inhibition of apoptosis. Despite its effects on diabetic nephropathy, empagliflozin did not activate the Sestrin2/AMP-activated protein kinase pathway in this study. Conclusion. Empagliflozin improved renal I/R injury in nondiabetic rats in this study by promoting autophagy and mitochondrial biogenesis and attenuation of oxidative stress, inflammation, and apoptosis.