Klotho has dual protective effects on cisplatin-induced acute kidney injury

Thymoquinone Nanoparticles (TQ-NPs) in Kidney Toxicity Induced by Ehrlich Ascites Carcinoma (EAC): An In Vivo Study

Background

Cisplatin (Cis) is potent chemotherapy used to treating already many different types of cancer; however, it is found to correlate with nephrotoxicity and other adverse health consequences. Thymoquinone (TQ) is an antioxidant and anti-inflammatory molecule that may defend against the consequences of different chemotherapies. Thymoquinone uses, although, are negatively impacted by its weak solubility and inadequate biological availability.

Objectives

This investigation examined the efficacy of a new nanoparticle (NP) absorbing TQ in an Ehrlich Ascites Carcinoma (EAC) mice model to address its low solubility, enhance its bioavailability, and protect against Cis-induced nephrotoxicity.

Methods

Following 4 treatment groups were included in this research: (1) control, (2) EAC, (3) EAC + Cis + Thymoquinone nanoparticle (TQ-NP) treated, and (4) EAC + Cis-treated.

Results

The study revealed that TQ-NP was efficacious in avoiding Cis-induced kidney problems in EAC mice, as well as restoring kidney function and pathology. Thymoquinone nanoparticle considerably reduced Cis-induced oxidative damage in renal tissue by augmenting antioxidant levels. According to tumor weight and histological investigation results, TQ-NP did not impair Cis's anticancer efficacy.

Conclusion

Thymoquinone nanoparticle might be used as a potential drug along with Cis anticancer therapy to reduce nephrotoxicity and other side effects while maintaining Cis anticancer properties.

Klotho as an Early Marker of Acute Kidney Injury Following Cardiac Surgery: A Systematic Review

Acute kidney injury is a common complication following cardiac surgery (CSA-AKI). Serum creatinine levels require a minimum of 24-48 h to indicate renal injury. Nevertheless, early diagnosis remains critical for improving patient outcomes. A PRISMA-compliant systematic review of the PubMed and CENTRAL databases was performed to assess the role of Klotho as a predictive biomarker for CSA-AKI (end-of-search date: 17 February 2024). An evidence quality assessment of the four included studies was performed with the Newcastle-Ottawa scale. Among the 234 patients studied, 119 (50.8%) developed CSA-AKI postoperatively. Serum Klotho levels above 120 U/L immediately postoperatively correlated with an area under the curve (AUC) of 0.806 and 90% sensitivity. Additionally, a postoperative serum creatinine to Klotho ratio above 0.695 showed 94.7% sensitivity and 87.5% specificity, with an AUC of 92.4%, maintaining its prognostic validity for up to three days. Urinary Klotho immunoreactivity was better maintained in samples obtained via direct catheterization rather than indwelling catheter collection bags. Storage at -80 °C was necessary for delayed testing. Optimal timing for both serum and urine Klotho measurements was from the end of cardiopulmonary bypass to the time of the first ICU lab tests. In conclusion, Klotho could be a promising biomarker for the early diagnosis of CSA-AKI. Standardization of measurement protocols and larger studies are needed to validate these findings.

C-terminal fragment of fibroblast growth factor 23 improves heart function in murine models of high intact fibroblast growth factor 23

Cardiovascular disease (CVD) is the major cause of death in chronic kidney disease (CKD) and is associated with high circulating fibroblast growth factor (FGF)23 levels. It is unresolved whether high circulating FGF23 is a mere biomarker or pathogenically contributes to cardiomyopathy. It is also unknown whether the C-terminal FGF23 peptide (cFGF23), a natural FGF23 antagonist proteolyzed from intact FGF23 (iFGF23), retards CKD progression and improves cardiomyopathy. We addressed these questions in three murine models with high endogenous FGF23 and cardiomyopathy. First, we examined wild-type (WT) mice with CKD induced by unilateral ischemia-reperfusion and contralateral nephrectomy followed by a high-phosphate diet. These mice were continuously treated with intraperitoneal implanted osmotic minipumps containing either iFGF23 protein to further escalate FGF23 bioactivity, cFGF23 peptide to block FGF23 signaling, vehicle, or scrambled peptide as negative controls. Exogenous iFGF23 protein given to CKD mice exacerbated pathological cardiac remodeling and CKD progression, whereas cFGF23 treatment improved heart and kidney function, attenuated fibrosis, and increased circulating soluble Klotho. WT mice without renal insult placed on a high-phosphate diet and homozygous Klotho hypomorphic mice, both of whom develop moderate CKD and clear cardiomyopathy, were treated with cFGF23 or vehicle. Mice treated with cFGF23 in both models had improved heart and kidney function and histopathology. Taken together, these data indicate high endogenous iFGF23 is not just a mere biomarker but pathogenically deleterious in CKD and cardiomyopathy. Furthermore, attenuation of FGF23 bioactivity by cFGF23 peptide is a promising therapeutic strategy to protect the kidney and heart from high FGF23 activity.NEW & NOTEWORTHY There is a strong correlation between cardiovascular morbidity and high circulating fibroblast growth factor 23 (FGF23) levels, but causality was never proven. We used a murine chronic kidney disease (CKD) model to show that intact FGF23 (iFGF23) is pathogenic and contributes to both CKD progression and cardiomyopathy. Blockade of FGF23 signaling with a natural proteolytic product of iFGF23, C-terminal FGF23, alleviated kidney and cardiac histology, and function in three separate murine models of high endogenous FGF23.

Comprehensive Overview of Innovative Strategies in Preventing Renal Ischemia-reperfusion Injury: Insights from Bibliometric and In silico Analyses

BACKGROUND

Ischemia-reperfusion Injury (IRI) is a complex pathophysiological process with severe consequences, including irreversible loss of renal function. Various intraoperative prevention methods have been proposed to mitigate the harmful effects of warm ischemia and kidney reperfusion.

AIM

This comprehensive analysis provides an overview of pharmacological agents and intraoperative methods for preventing and treating renal IRI.

METHODS

Our analysis revealed that eplerenone exhibited the highest binding affinity to crucial targets, including Aldehyde Dehydrogenase (AD), Estrogen Receptor (ER), Klotho protein, Mineralocorticoid Receptor (MR), and Toll-like Receptor 4 (TLR4). This finding indicates eplerenone's potential as a potent preventive agent against IRI, surpassing other available therapeutics like Benzodioxole, Hydrocortisone, Indoles, Nicotinamide adenine dinucleotide, and Niacinamide. In preventing kidney IRI, our comprehensive analysis emphasizes the significance of eplerenone due to its strong binding affinity to key targets involved in the pathogenesis of IRI.

RESULTS

This finding positions eplerenone as a promising candidate for further clinical investigation and consideration for future clinical practice.

CONCLUSION

The insights provided in this analysis will assist clinicians and researchers in selecting effective preventive approaches for renal IRI in surgical settings, potentially improving patient outcomes.

Exogenous Klotho Extends Survival in COVID-19 Model Mice

A striking feature of COVID-19 disease is the broad spectrum of risk factors associated with case severity, as well as the diversity of clinical manifestations. While no central agent has been able to explain the pathogenesis of SARS-CoV-2 infection, the factors that most robustly correlate with severity are risk factors linked to aging. Low serum levels of Klotho, an anti-aging protein, strongly correlate with the pathogenesis of the same risk factors and manifestations of conditions similar to those expressed in severe COVID-19 cases. The current manuscript presents original research on the effects of the exogenous application of Klotho, an anti-aging protein, in COVID-19 model mice. Klotho supplementation resulted in a statistically significant survival benefit in parametric and non-parametric models. Further research is required to elucidate the mechanistic role Klotho plays in COVID-19 pathogenesis as well as the possible modulation SARS-CoV-2 may have on the biological aging process.

Is there a role in acute kidney injury for FGF23 and Klotho?

Cardio-renal syndrome is a clinical condition that has recently been well defined. In acute kidney disease, this interaction might trigger chronic processes determining the onset of cardiovascular events and the progression of chronic kidney disease. Moreover, the high mortality rate of acute kidney injury (AKI) is also linked to the fact that this condition is often complicated by dysfunctions of other organs such as lungs or heart, or is associated with septic episodes. In this context the role and the potential link between bone, heart and kidney is becoming an important topic of research. The aim of this review is to describe the cardiac alterations in the presence of AKI (cardiorenal syndrome type 3) and explore how bone can interact with heart and kidney in determining and influencing the trend of AKI in the short and long term. The main anomalies of mineral metabolism in patients with AKI will be reported, with specific reference to the alterations of fibroblast growth factor 23 and Klotho as a link between the bone-kidney-heart axis.

α-Klotho: An Early Risk-Predictive Biomarker for Acute Kidney Injury in Patients with Acute Myocardial Infarction

Background

Acute kidney injury (AKI) was a common and serious complication in patients with acute myocardial infarction (AMI). Novel biomarkers and therapies were deficient and imperative for AKI's early diagnosis and therapy after AMI. α-Klotho was considered as an early biomarker and potential therapy for AKI recently. Previous studies reported that the expression of α-Klotho was decreased in AKI rodents, and supplement of α-Klotho alleviated kidney injury. Nevertheless, its effect has not been studied in patients presenting with AMI.

Methods

A total of 155 consecutive diagnosed with AMI at emergency department whose eGFR >60 ml/min ∗ 1.73 m2 were enrolled in this prospective observational cohort study which conducted between May 2016 and April 2019 in Peking University People's Hospital. AKI was defined according to the KDIGO criteria in 2012. At admission, the clinical data of patients were collected and serum α-Klotho was tested by ELISA. The relationship between α-Klotho, serum creatinine, eGFR, systolic pressure, BNP, LVEF, and Hgb of AKI were analyzed and their discrimination performances were compared. The association variables were calculated (adjusted odds ratio) with a confidence interval (CI) of 95% by binary logistic regression. And, we followed up the incidence of CKD and rehospitalization after patients' discharge in one year. Our study was approved by the ethics committee (no. 2016PHB042-01).

Results

AKI incidence was 17.4% (27/155) during hospitalization. Compared to patients without AKI, the AKI group had obviously higher mortality and was more female and had higher incidence of chronic kidney disease, worse cardiac function, more cardiac complications, larger doses of diuretics, and less use of angiotensin-converting enzyme inhibitors/angiotensin receptor blocker. By contrary to previous animal experiments, we found serum α-Klotho levels were increased significantly in AKI patients (740.2 ± 306.8 vs. 419.0 ± 272.6 pg/mL, p < 0.001). And, the areas under the receiver operating curves indicated serum α-Klotho levels had a superior discriminative power for predicting AKI after AMI compared with other risk factors (0.792, 95% CI, 0.706-0.878, p < 0.001). Meanwhile, logistic regression model indicates extensive anterior myocardial infarction, Killip classification ≥2 grade, α-Klotho ≥516.9 pg/mL, eGFR (decrease per 10 ml/min ∗ 1.73 m2), Hgb, and nonuse of ACEI/ARB were the risk factors of AKI after AMI. Moreover, one-year follow-up presented AMI patients developed CKD had higher α-Klotho levels (739.7 ± 315.2 vs. 443.8 ± 292.5 pg/mL, p = 0.001), but no significant difference in rehospitalization. And, patients with α-Klotho ≥516.9 pg/ml was 6.699 times more likely to develop CKD than those with α-Klotho <516.9 pg/ml (relative risk 6.699, 95% CI 1.631-27.519, p = 0.007).

Conclusion

Compared with traditional cardiac and renal biomarkers, serum α-Klotho could be a more appropriate predict biomarker for AKI after AMI in patients' eGFR >60 ml/min ∗ 1.73 m2. Higher α-Klotho levels are related to the development of AKI during hospitalization and suggest a higher prevalence of CKD after discharge. By contrary to animal experiments, whether the increased expression of α-Klotho could be a protective factor secreted by AKI after AMI, is remained to be further studied.

Role of Transcription Factor EB in Mitochondrial Dysfunction of Cisplatin-Induced Acute Kidney Injury

Cisplatin, a widely used anticancer agent, can cause nephrotoxicity, including both acute kidney injury (AKI) and chronic kidney diseases, by accumulating in renal tubular epithelial cells (TECs). Mitochondrial pathology plays an important role in the pathogenesis of AKI. Based on the regulatory role of transcription factor EB (TFEB) in mitochondria, we investigated whether TFEB is involved in cisplatin-induced TEC damage. The results show that the expression of TFEB decreased in a concentration-dependent manner in both mouse kidney tissue and HK-2 cells when treated with cisplatin. A knockdown of TFEB aggravated cisplatin-induced renal TEC injury, which was partially reversed by TFEB overexpression in HK-2 cells. It was further observed that the TFEB knockdown also exacerbated cisplatin-induced mitochondrial damage in vitro, and included the depolarization of membrane potential, mitochondrial fragmentation and swelling, and the production of reactive oxygen species. In contrast, TFEB overexpression alleviated cisplatin-induced mitochondrial damage in TECs. These findings suggest that decreased TFEB expression may be a key mechanism of mitochondrial dysfunction in cisplatin-induced AKI, and that upregulation of TFEB has the potential to act as a therapeutic target to alleviate mitochondrial dysfunction and cisplatin-induced TEC injury. This study is important for developing therapeutic strategies to manipulate mitochondria through TFEB to delay AKI progression.

Klotho, Oxidative Stress, and Mitochondrial Damage in Kidney Disease

Reducing oxidative stress stands at the center of a prevention and control strategy for mitigating cellular senescence and aging. Kidney disease is characterized by a premature aging syndrome, and to find a modulator targeting against oxidative stress, mitochondrial dysfunction, and cellular senescence in kidney cells could be of great significance to prevent and control the progression of this disease. This review focuses on the pathogenic mechanisms related to the appearance of oxidative stress damage and mitochondrial dysfunction in kidney disease. In this scenario, the anti-aging Klotho protein plays a crucial role by modulating signaling pathways involving the manganese-containing superoxide dismutase (Mn-SOD) and the transcription factors FoxO and Nrf2, known antioxidant systems, and other known mitochondrial function regulators, such as mitochondrial uncoupling protein 1 (UCP1), B-cell lymphoma-2 (BCL-2), Wnt/β-catenin, peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC-1 alpha), transcription factor EB, (TFEB), and peroxisome proliferator-activated receptor gamma (PPAR-gamma). Therefore, Klotho is postulated as a very promising new target for future therapeutic strategies against oxidative stress, mitochondria abnormalities, and cellular senescence in kidney disease patients.

Klotho's impact on diabetic nephropathy and its emerging connection to diabetic retinopathy

Diabetic nephropathy (DN) is the leading cause of end-stage renal disease worldwide and is a significant burden on healthcare systems. α-klotho (klotho) is a protein known for its anti-aging properties and has been shown to delay the onset of age-related diseases. Soluble klotho is produced by cleavage of the full-length transmembrane protein by a disintegrin and metalloproteases, and it exerts various physiological effects by circulating throughout the body. In type 2 diabetes and its complications DN, a significant decrease in klotho expression has been observed. This reduction in klotho levels may indicate the progression of DN and suggest that klotho may be involved in multiple pathological mechanisms that contribute to the onset and development of DN. This article examines the potential of soluble klotho as a therapeutic agent for DN, with a focus on its ability to impact multiple pathways. These pathways include anti-inflammatory and oxidative stress, anti-fibrotic, endothelial protection, prevention of vascular calcification, regulation of metabolism, maintenance of calcium and phosphate homeostasis, and regulation of cell fate through modulation of autophagy, apoptosis, and pyroptosis pathways. Diabetic retinopathy shares similar pathological mechanisms with DN, and targeting klotho may offer new insights into the prevention and treatment of both conditions. Finally, this review assesses the potential of various drugs used in clinical practice to modulate klotho levels through different mechanisms and their potential to improve DN by impacting klotho levels.

Platinum-based drug-induced depletion of amino acids in the kidneys and liver

Cisplatin (cis-diamminedichloroplatinum II; CDDP) is a widely used cytostatic agent; however, it tends to promote kidney and liver disease, which are a major signs of drug-induced toxicity. Platinum compounds are often presented as alternative therapeutics and subsequently easily dispersed in the environment as contaminants. Due to the major roles of the liver and kidneys in removing toxic materials from the human body, we performed a comparative study of the amino acid profiles in chicken liver and kidneys before and after the application of CDDP and platinum nanoparticles (PtNPs-10 and PtNPs-40). The treatment of the liver with the selected drugs affected different amino acids; however, Leu and Arg were decreased after all treatments. The treatment of the kidneys with CDDP mostly affected Val; PtNPs-10 decreased Val, Ile and Thr; and PtNPs-40 affected only Pro. In addition, we tested the same drugs on two healthy cell lines, HaCaT and HEK-293, and ultimately explored the amino acid profiles in relation to the tricarboxylic acid cycle (TCA) and methionine cycle, which revealed that in both cell lines, there was a general increase in amino acid concentrations associated with changes in the concentrations of the metabolites of these cycles.

The Role of Alterations in Alpha-Klotho and FGF-23 in Kidney Transplantation and Kidney Donation

Cardiovascular disease and mineral bone disorders are major contributors to morbidity and mortality among patients with chronic kidney disease and often persist after renal transplantation. Ongoing hormonal imbalances after kidney transplant (KT) are associated with loss of graft function and poor outcomes. Fibroblast growth factor 23 (FGF-23) and its co-receptor, α-Klotho, are key factors in the underlying mechanisms that integrate accelerated atherosclerosis, vascular calcification, mineral disorders, and osteodystrophy. On the other hand, kidney donation is also associated with endocrine and metabolic adaptations that include transient increases in circulating FGF-23 and decreases in α-Klotho levels. However, the long-term impact of these alterations and their clinical relevance have not yet been determined. This manuscript aims to review and summarize current data on the role of FGF-23 and α-Klotho in the endocrine response to KT and living kidney donation, and importantly, underscore specific areas of research that may enhance diagnostics and therapeutics in the growing population of KT recipients and kidney donors.

Epigenetic restoration of endogenous Klotho expression alleviates acute kidney injury-diabetes comorbidity

AIMS

The present study aimed at exploring the mechanisms behind Klotho regulation in hyperglycemia augmented AKI. In addition, epigenetic ways to restore the Klotho expression in AKI-diabetes comorbidity have been evaluated.

MAIN METHODS

Bilateral ischemia-reperfusion injury (IRI) and chemical hypoxia-reperfusion injury (HRI) were developed in diabetic rats and, NRK52E cells under high glucose conditions respectively, to mimic the AKI condition. Plasma, urine, tubular lysate of the kidney and NRK52E cell lysate were used for biochemical, ELISA, histology, immunoblotting, RT-PCR and RNA interference studies.

KEY FINDINGS

Hyperglycemia significantly aggravated IRI/HRI induced AKI as evidenced by biochemical and histological results. We also observed a significant increase in expressions of kidney specific histone deacetylases (HDACs), apoptotic and inflammatory proteins, and decrease in levels of endogenous Klotho, H3K9Ac and H3K27Ac proteins in hyperglycemic IRI/HRI groups.

SIGNIFICANCE

Diabetes comorbidity exaggerates AKI, where endogenous Klotho loss could be a potential connecting link. However, kidney-specific HDACs inhibition showed reno-protection via restoring the endogenous Klotho loss and thus prevention of inflammation and apoptosis, which could prove to be a potential therapeutic strategy against diabetes-AKI comorbidity.

In vivo evidence for therapeutic applications of beclin 1 to promote recovery and inhibit fibrosis after acute kidney injury

Autophagy regulator beclin 1 activity determines the severity of kidney damage induced by ischemia reperfusion injury, but its role in kidney recovery and fibrosis are unknown and its therapeutic potentials have not been tested. Here, we explored beclin 1 effects on kidney fibrosis in three models of acute kidney injury (AKI)-ischemia reperfusion injury, cisplatin kidney toxicity, and unilateral ureteric obstruction in mouse strains with three levels of beclin 1 function: normal (wild type), low (heterozygous global deletion of beclin 1, Becn1^+/-), and high beclin 1 activity (knockin gain-of-function mutant Becn1, Becn1^FA). Fourteen days after AKI induction, heterozygous mice had more, but knockin mice had less kidney fibrosis than wild-type mice did. One day after ischemia reperfusion injury, heterozygous pan-kidney tubular Becn1 null mice had more severe kidney damage than homozygous distal tubular Becn1 null mice did, which was similar to the wild-type mice, implying that proximal tubular beclin 1 protects the kidney against ischemia reperfusion injury. By 14 days, both pan-kidney heterozygous Becn1 null and distal tubular homozygous Becn1 null mice had poorer kidney recovery than wild-type mice did. Injection of beclin 1 peptides increased cell proliferation in kidney tubules in normal mice. Beclin 1 peptides injection either before or after (2-5 days) ischemia reperfusion injury protected the kidney from injury and suppressed kidney fibrosis. Thus, both endogenous beclin 1 protein expression in kidney tubules and exogenous beclin 1 peptides are kidney protective via attenuation of acute kidney damage, promotion of cell proliferation, and inhibition of kidney fibrosis, consequently improving kidney recovery post-AKI. Hence, exogenous beclin 1 peptide may be a potential new therapy for AKI.

Administration of α-Klotho Does Not Rescue Renal Anemia in Mice

Renal anemia is a common complication in chronic kidney disease (CKD), associated with decreased production of erythropoietin (EPO) due to loss of kidney function, and subsequent decreased red blood cell (RBC) production. However, many other factors play a critical role in the development of renal anemia, such as iron deficiency, inflammation, and elevated fibroblast growth factor 23 (FGF23) levels. We previously reported that inhibition of FGF23 signaling rescues anemia in mice with CKD. In the present study we sought to investigate whether α-Klotho deficiency present in CKD also contributes to the development of renal anemia. To address this, we administered α-Klotho to mice with CKD induced by an adenine-rich diet. Mice were sacrificed 24 h after α-Klotho injection, and blood and organs were collected immediately post-mortem. Our data show that α-Klotho administration had no beneficial effect in mice with CKD-associated anemia as it did not increase RBC numbers and hemoglobin levels, and it did not stimulate EPO secretion. Moreover, α-Klotho did not improve iron deficiency and inflammation in CKD as it had no effect on iron levels or inflammatory markers. Interestingly, Klotho supplementation significantly reduced the number of erythroid progenitors in the bone marrow and downregulated renal Epo and Hif2α mRNA in mice fed control diet resulting in reduced circulating EPO levels in these mice. In addition, Klotho significantly decreased intestinal absorption of iron in control mice leading to reduced serum iron and transferrin saturation levels. Our findings demonstrate that α-Klotho does not have a direct role in renal anemia and that FGF23 suppresses erythropoiesis in CKD via a Klotho-independent mechanism. However, in physiological conditions α-Klotho appears to have an inhibitory effect on erythropoiesis and iron regulation.

Klotho and Mesenchymal Stem Cells: A Review on Cell and Gene Therapy for Chronic Kidney Disease and Acute Kidney Disease

Chronic kidney disease (CKD) and acute kidney injury (AKI) are public health problems, and their prevalence rates have increased with the aging of the population. They are associated with the presence of comorbidities, in particular diabetes mellitus and hypertension, resulting in a high financial burden for the health system. Studies have indicated Klotho as a promising therapeutic approach for these conditions. Klotho reduces inflammation, oxidative stress and fibrosis and counter-regulates the renin-angiotensin-aldosterone system. In CKD and AKI, Klotho expression is downregulated from early stages and correlates with disease progression. Therefore, the restoration of its levels, through exogenous or endogenous pathways, has renoprotective effects. An important strategy for administering Klotho is through mesenchymal stem cells (MSCs). In summary, this review comprises in vitro and in vivo studies on the therapeutic potential of Klotho for the treatment of CKD and AKI through the administration of MSCs.

Klotho overexpression protects against renal aging along with suppression of transforming growth factor-β1 signaling pathways

Klotho is an antiaging protein reported to suppress transforming growth factor-β1 (TGF-β1) signaling. Aging kidneys are characterized by interstitial fibrosis, accumulation of cell cycle-arrested cells, and increased levels of oxidative stress. TGF-β1 signaling is involved in these processes. In this study, we investigated whether klotho overexpression improves these features in the kidneys of aging mice and examined the inhibitory effect of klotho on signaling molecules related to transforming growth of TGF-β1. Klotho transgenic (KLTG) and wild-type (WT) mice were used, and 8-wk-old and 24-mo-old mice were defined as young and aging, respectively. We found that klotho expression was decreased in aging WT mice, but it was maintained in aging KLTG mice. Klotho overexpression improved the survival of 24-mo-old mice. Although the serum Ca²⁺ level was significantly lower in aging KLTG mice than in aging WT mice, the serum phosphate level did not differ between these mice. Klotho overexpression attenuated the increases in blood pressure, serum blood urea nitrogen level, and serum creatinine level in aging mice. Interstitial fibrosis, accumulation of cell cycle-arrested cells, and oxidative stress did not differ between young KLTG and WT mice, but they were significantly suppressed in aging KLTG mice compared with aging WT mice. Furthermore, the expression of TGF-β1-related signaling molecules was increased in aging WT mice, whereas it was inhibited in aging KLTG mice. These data suggest that klotho overexpression protects against kidney aging along with suppression of TGF-β1 signaling pathways.NEW & NOTEWORTHY Klotho is considered as an antiaging protein, and its overexpression may be a candidate therapy for protection against kidney damage with advanced aging. Although multiple factors are involved in the aging process, we showed that klotho overexpression inhibited interstitial fibrosis, accumulation of cell cycle-arrested cells, and increased levels of oxidative stress in the kidneys of aging mice, suppressing transforming growth factor-β1-related signaling pathways. The present data showed that klotho overexpression protects against age-associated kidney damage.

Klotho as Potential Autophagy Regulator and Therapeutic Target

The protein Klotho can significantly delay aging, so it has attracted widespread attention. Abnormal downregulation of Klotho has been detected in several aging-related diseases, such as Alzheimer’s disease, kidney injury, cancer, chronic obstructive pulmonary disease (COPD), vascular disease, muscular dystrophy and diabetes. Conversely, many exogenous and endogenous factors, several drugs, lifestyle changes and genetic manipulations were reported to exert therapeutic effects through increasing Klotho expression. In recent years, Klotho has been identified as a potential autophagy regulator. How Klotho may contribute to reversing the effects of aging and disease became clearer when it was linked to autophagy, the process in which eukaryotic cells clear away dysfunctional proteins and damaged organelles: the abovementioned diseases involve abnormal autophagy. Interestingly, growing evidence indicates that Klotho plays a dual role as inducer or inhibitor of autophagy in different physiological or pathological conditions through its influence on IGF-1/PI3K/Akt/mTOR signaling pathway, Beclin 1 expression and activity, as well as aldosterone level, which can help restore autophagy to beneficial levels. The present review examines the role of Klotho in regulating autophagy in Alzheimer’s disease, kidney injury, cancer, COPD, vascular disease, muscular dystrophy and diabetes. Targeting Klotho may provide a new perspective for preventing and treating aging-related diseases.

Cisplatin decreases HOXA13 and alphaVBeta3 integrin levels in the uterus

OBJECTIVE

To examine the effects of cisplatin on uterine histology and implantation molecules and the possible protective role of recombinant Klotho administration on uterine histology and uterine receptivity in mice exposed to cisplatin.

MATERIALS AND METHODS

This study was conducted using thirty-two adult female mice assigned to four groups with 8 mice in each group. Saline was given to the 1st group, cisplatin to the 2nd group, recombinant mouse Klotho to the 3rd group and recombinant mouse Klotho plus cisplatin to the 4th group. Uterine tissues were examined for damage histologically and immunobiologically for the uterine receptivity markers HOXA13 and alphaVBeta3 integrin.

RESULTS

Apoptosis, degeneration, decrease in uterine thickness and uterine absence of gland scores were higher in the cisplatin group (3rd group) compared to the saline group (1st group) (cisplatin vs. saline p < 0.0001 for all parameters). In the recombinant Klotho plus cisplatin group (4th group), scores of apoptosis, degeneration, reduction in uterine thickness and uterine absence of gland were lower than the group receiving only cisplatin (cisplatin plus recombinant Klotho vs cisplatin, p = 0.006 for apoptosis; p = 0.017 for degeneration; p = 0.011 for the reduction in uterine thickness; p = 0.002 for the absence of gland). However, HOXA13 and alphaVBeta3 integrin staining levels were not different between the cisplatin group (group 3) and the cisplatin plus recombinant Klotho group (group 4) (p = 0.980 and p = 0.762, respectively.) CONCLUSION: Cisplatin has adverse effects on the uterus. Administration of recombinant Klotho was found to attenuate the cisplatin-induced damage but failed to preserve levels of the implantation molecules HOXA13 and alphaVbeta3. Further studies examining the effect of cisplatin toxicity using other implantation markers along with functional studies are needed.

A Decreased Level of Soluble Klotho Can Predict Cardiovascular Death in No or Mild Abdominal Aortic Calcification Hemodialysis Patients

Background: Soluble Klotho plays an important role in cardiovascular disease and death in chronic kidney disease (CKD). We assessed the relationship between serum soluble Klotho (sKL) level and outcome in MHD patients.

Methods: Soluble Klotho was detected by ELISA. Cox regression analysis and Kaplan-Meier analysis showed the relationship between sKL and cardiovascular disease (CVD) mortality in maintenance hemodialysis (MHD) patients.

Results: There were 45 cases (35.2%) of all-cause death and 36 cases (28.1%) of CVD mortality. Multivariate linear regression analysis showed that Log[iPTH] (γ = −0.224, P = 0.015) was an independent predictor of sKL level. Cox regression showed that lower sKL was associated with higher CVD mortality rate [OR = 0.401, 95% CI (0.183–0.867), P = 0.022]. Kaplan-Meier analysis showed that the CVD mortality rate increased significantly in patients with low sKL (P = 0.006). Compared with high sKL patients, low sKL patients with no or mild vascular calcification [aortic calcification score (AACs) ≤ 4] had no significant difference in all-cause mortality rate. The CVD mortality rate was significantly lower in high sKL patients (P = 0.004) than in those with low sKL. In the severe calcification group (AACs ≥ 5), all-cause and CVD mortality rates were similar between different sKL groups (P = 0.706 and 0.488, respectively). The area under the receiver-operating characteristic curve (AUC) of soluble Klotho for predicting the CVD in MHD patients with AACs ≤ 4 was 0.796 (0.647–0.946, P = 0.017), sensitivity was 0.921, and specificity was 0.50 for a cutoff value of 307.69 pg/ml.

Conclusions: Lower sKL was associated with higher CVD mortality rate. Lower sKL concentration in MHD patients with no or mild calcification can predict CVD mortality.

αKlotho protein has therapeutic activity in contrast-induced acute kidney injury by limiting NLRP3 inflammasome-mediated pyroptosis and promoting autophagy

Contrast-induced acute kidney injury (CI-AKI) is a main cause of hospital-acquired renal failure. Nevertheless, limited measures have been shown to be effective for the treatment of CI-AKI. Here, we demonstrated that αKlotho, which is highly expressed in kidney, has therapeutic activity in CI-AKI. Our data showed that αKlotho expression levels were decreased both in the kidney and serum of CI-AKI mice. Administration of αKlotho protein protected the kidney and HK-2 cells against contrast-induced injury. Mechanistically, αKlotho reduced contrast-induced renal tubular cells pyroptosis by limiting NLRP3 inflammasome activation. Meanwhile, αKlotho up-regulated autophagy via inhibiting the AKT/mTOR pathway and decreased mitochondrial ROS level. Inhibition of autophagy blunted the suppression effect of αKlotho on NLRP3 inflammasome activation and cell pyroptosis in contrast-treated HK-2 cells. Taken together, our data suggest that αKlotho protein protects against CI-AKI through inhibiting NLRP3 inflammasome-mediated pyroptosis, which is likely by promoting autophagy. αKlotho may be a promising therapeutic strategy for CI-AKI.

The effects of recombinant klotho in cisplatin-induced ovarian failure in mice

AIM

To investigate whether recombinant klotho given concomitantly with cisplatin is effective in preventing cisplatin-induced ovarian damage.

METHODS

Thirty-two adult female mice were divided into four groups. Saline was given to the first group, cisplatin to the second group, recombinant mouse klotho to the third group, and recombinant mouse klotho + cisplatin to the fourth group. The removed ovarian tissues were examined and groups were compared histologically and immunohistochemical examination for antimullerian hormone (AMH), superoxide dismutase (SOD) and catalase expression were done. Glutathione peroxidase (GPx) and glutathione reductase (GR) activities were measured by ELISA.

RESULTS

Ovarian tissue weight, primary and secondary follicle counts were higher in cisplatin + recombinant klotho group compared to cisplatin group in our study (respectively p < 0.0001, p < 0.0001, and p = 0.010). Injury scores (stromal congestion, edema and infiltration, follicular degeneration scores and edema in corpus luteum scores) were similar between cisplatin and cisplatin + recombinant klotho groups (all p > 0.05). AMH staining intensities were similar between cisplatin and cisplatin + recombinant klotho groups (p = 0.925). There was no difference between the groups in terms of SOD, GPx, and GR (p > 0.05).

CONCLUSIONS

The recombinant klotho administered before cisplatin could partially protect the ovarian tissue from cisplatin-induced ovarian damage considering that there was no difference in histologic injury score parameters, AMH staining intensity and oxidative stress markers between cisplatin and cisplatin plus klotho groups except that klotho preserved follicules to some extent. The antioxidant mechanism of action of klotho may not be the primary protection mechanism in cisplatin induced ovarian injury.

Klotho in Clinical Nephrology: Diagnostic and Therapeutic Implications

αKlotho (called Klotho here) is a membrane protein that serves as the coreceptor for the circulating hormone fibroblast growth factor 23 (FGF23). Klotho is also cleaved and released as a circulating substance originating primarily from the kidney and exerts a myriad of housekeeping functions in just about every organ. The vital role of Klotho is shown by the multiorgan failure with genetic deletion in rodents, with certain features reminiscent of human disease. The most common causes of systemic Klotho deficiency are AKI and CKD. Preclinical data on Klotho biology have advanced considerably and demonstrated its potential diagnostic and therapeutic value; however, multiple knowledge gaps exist in the regulation of Klotho expression, release, and metabolism; its target organs; and mechanisms of action. In the translational and clinical fronts, progress has been more modest. Nonetheless, Klotho has potential clinical applications in the diagnosis of AKI and CKD, in prognosis of progression and extrarenal complications, and finally, as replacement therapy for systemic Klotho deficiency. The overall effect of Klotho in clinical nephrology requires further technical advances and additional large prospective human studies.

Klotho ameliorates diabetic nephropathy via LKB1-AMPK-PGC1α-mediated renal mitochondrial protection

Diabetic nephropathy (DN) is associated with renal mitochondrial injury and decreased renal klotho expression. Klotho is known as an aging suppressor, and mitochondrial dysfunction is the hallmark of aging. Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1α) is a master regulator of mitochondrial biogenesis, and adenosine monophosphate-activated protein kinase (AMPK) is known as a guardian of mitochondria. Here, we report that recombinant soluble klotho protein (rKL) protects against DN in db/db mice via PGC1α-AMPK-mediated mitochondrial recovery in the kidney. We injected rKL into db/db and db/m mice for 8 weeks and collected the serum and kidney tissue. We treated murine renal tubular cells with rKL in vitro, with and without exposure to 30 mM high glucose (HG). rKL treatment ameliorated major disorders from diabetes, such as obesity, hyperglycemia, and intrarenal reactive oxygen species (ROS) generation, in db/db mice. rKL also diminished albuminuria, recovered renal proximal tubular mitochondria, increased renal p-AMPK and PGC1α, and down-regulated mTOR/TGF-β in db/db mice. In S1 mouse proximal tubular cells, rKL treatment ameliorated HG-mediated cellular and mitochondrial damage and enhanced oxidative phosphorylation, with an increase in PGC1α-AMPK-induced mitochondrial recovery. Our data suggest that klotho exerts a mitochondrial protective effect in diabetic kidney disease by inducing AMPK-PGC1α expression.

Serum Cystatin C, Klotho, and Neutrophil Gelatinase-Associated Lipocalin in the Risk Prediction of Acute Kidney Injury after Acute Myocardial Infarction

BACKGROUND

Patients with acute myocardial infarction (AMI) are at high risk for acute kidney injury (AKI). Novel biomarkers that can predict AKI after AMI may facilitate immediate interventions. Recently, cystatin C, neutrophil gelatinase-associated lipocalin (NGAL), and klotho have been established as novel AKI biomarkers. However, their effects have not been studied in patients presenting with AMI. In this study, we will measure the serum levels of these three biomarkers to find reliable biomarkers for early diagnosis of AKI in AMI patients.

METHODS

This prospective observational cohort study was conducted between May 2016 and November 2017. A total of 285 consecutive patients with AMI were enrolled. The study was approved by the institutional review board of Peking University People's Hospital (No. 2016PHB 042-01). AKI was defined according to the KDIGO criteria in 2012. At admission, the clinical data of patients was collected and serum levels of several AKI biomarkers, including cystatin C, NGAL, and klotho, were measured by ELISA. The relationship between biomarker levels of AKI were analyzed and their discrimination performances were compared.

RESULTS

AKI incidence was 17.5% (50/285) during hospitalization. Compared to patients without AKI, the AKI group had higher mortality (20.0% vs. 0.4%, p < 0.001) and tended to be older, had higher incidence of chronic kidney disease, severe cardiac function, more cardiac complications, larger doses of diuretics, and less use of angiotensin-converting enzyme inhibitors/angiotensin receptor blocker and statins. Moreover, AKI patients experienced an increase in serum cystatin C (3,709.2 ± 2,281.5 vs. 1,918.5 ± 1,140.6 ng/mL, p < 0.001), NGAL (118.0 ± 70.3 vs. 91.8 ± 52.3 ng/mL, p = 0.003), and klotho (742.2 ± 497.4 vs. 470.3 ± 257.2 pg/mL, p <0.001). Furthermore, the areas under the receiver operating curves demonstrated that serum cystatin C levels at admission had modest discriminative powers for predicting AKI after AMI compared with serum creatinine (0.899, 95% CI, 0.855-0.944 vs. 0.734, 95% CI, 0.649-0.819, p <0.001). There was no difference between the discrimination performances of serum creatinine, NGAL, and klotho.

CONCLUSION

Elevated cystatin C levels are associated with AKI in patients with AMI. This study provides reliable evidence that cystatin C levels may be superior to serum creatinine for predicting AKI after AMI at admission.

Dietary vitamin D interacts with high phosphate-induced cardiac remodeling in rats with normal renal function

BACKGROUND

Vitamin D (VD) and phosphate (Pi) load are considered as contributors to cardiovascular disease in chronic kidney disease and the general population, but interactive effects of VD and Pi intake on the heart are not clearly illustrated.

METHODS

We fed normal male rats with three levels of dietary VD (100, 1100 or 5000 IU/kg chow) and Pi (0.2, 0.6 or 1.6%) (3X3 design) for 8 weeks and examined renal and cardiac function and histology.

RESULTS

High dietary Pi decreased plasma and renal Klotho and plasma 25-hydroxyvitamin D, and increased plasma Pi, fibroblast growth factor 23 and parathyroid hormone without affecting renal function, while low Pi increased plasma and renal Klotho. Both low and high VD diets enhanced high Pi-reduced Klotho expression. Low dietary VD reduced-plasma Klotho was rescued by a low Pi diet. High dietary Pi reduced-cardiac ejection fraction was not modified by a low or high VD diet, but the dietary VD effects on cardiac pathologic changes were more complex. High dietary Pi-induced cardiac hypertrophy was attenuated by a low VD and exacerbated by a high VD diet. In contrast, high dietary Pi -induced cardiac fibrosis was magnified by a low VD and attenuated by a high VD diet.

CONCLUSIONS

High Pi diet induces hypertrophy and fibrosis in left ventricles, a low VD diet accelerates high Pi-induced fibrosis, and a high VD diet exacerbated high Pi -induced hypertrophy. Therefore, cardiac phosphotoxicity is exacerbated by either high or low dietary VD in rats with normal kidney function.

Fibroblast Growth Factor 23 and αKlotho in Acute Kidney Injury: Current Status in Diagnostic and Therapeutic Applications

Fibroblast growth factor (FGF) 23 and αKlotho are circulating mineral regulatory substances that also have a very diverse range of actions. Acute kidney injury (AKI) is a state of high FGF23 and low αKlotho. Clinical association data for FGF23 are strong, but the basic pathobiology of FGF23 in AKI is rather sparse. Conversely, preclinical data supporting a pathogenic role of αKlotho in AKI are strong, but the human data are still being generated. This pair of substances can potentially serve as diagnostic and prognostic biomarkers. FGF23 blockade and αKlotho restoration can have prophylactic and therapeutic utility in AKI. The literature to date is briefly reviewed in this article.

High Phosphate Induces and Klotho Attenuates Kidney Epithelial Senescence and Fibrosis

Cellular senescence is an irreversible cell growth arrest and is associated with aging and age-related diseases. High plasma phosphate (Pi) and deficiency of Klotho contribute to aging and kidney fibrosis, a pathological feature in the aging kidney and chronic kidney disease. This study examined the interactive role of Pi and Klotho in kidney senescence and fibrosis. Homozygous Klotho hypomorphic mice had high plasma Pi, undetectable Klotho in plasma and kidney, high senescence with massive collagen accumulation in kidney tubules, and fibrin deposits in peritubular capillaries. To examine the Pi effect on kidney senescence, a high (2%) Pi diet was given to wild-type mice. One week of high dietary Pi mildly increased plasma Pi, and upregulated kidney p16/p21 expression, but did not significantly decrease Klotho. Two weeks of high Pi intake led to increase in plasminogen activator inhibitor (PAI)-1, and decrease in kidney Klotho, but still without detectable increase in kidney fibrosis. More prolonged dietary Pi for 12 weeks exacerbated kidney senescence and fibrosis; more so in heterozygous Klotho hypomorphic mice compared to wild-type mice, and in mice with chronic kidney disease (CKD) on high Pi diet compared to CKD mice fed a normal Pi diet. In cultured kidney tubular cells, high Pi directly induced cellular senescence, injury and epithelial-mesenchymal transition, and enhanced H₂O₂-induced cellular senescence and injury, which were abrogated by Klotho. Fucoidan, a bioactive molecule with multiple biologic functions including senescence inhibition, blunted Pi-induced cellular senescence, oxidation, injury, epithelial-mesenchymal transition, and senescence-associated secretary phenotype. In conclusion, high Pi activates senescence through distinct but interconnected mechanisms: upregulating p16/p21 (early), and elevating plasminogen activator inhibitor-1 and downregulating Klotho (late). Klotho may be a promising agent to attenuate senescence and ameliorate age-associated, and Pi-induced kidney degeneration such as kidney fibrosis.

Serum Klotho in Living Kidney Donors and Kidney Transplant Recipients: A Meta-Analysis

α-Klotho is a known anti-aging protein that exerts diverse physiological effects, including phosphate homeostasis. Klotho expression occurs predominantly in the kidney and is significantly decreased in patients with chronic kidney disease. However, changes in serum klotho levels and impacts of klotho on outcomes among kidney transplant (KTx) recipients and kidney donors remain unclear. A literature search was conducted using MEDLINE, EMBASE, and Cochrane Database from inception through October 2019 to identify studies evaluating serum klotho levels and impacts of klotho on outcomes among KTx recipients and kidney donors. Study results were pooled and analyzed utilizing a random-effects model. Ten cohort studies with a total of 431 KTx recipients and 5 cohort studies with a total of 108 living kidney donors and were identified. After KTx, recipients had a significant increase in serum klotho levels (at 4 to 13 months post-KTx) with a mean difference (MD) of 243.11 pg/mL (three studies; 95% CI 67.41 to 418.81 pg/mL). Although KTx recipients had a lower serum klotho level with a MD of = -234.50 pg/mL (five studies; 95% CI -444.84 to -24.16 pg/mL) compared to healthy unmatched volunteers, one study demonstrated comparable klotho levels between KTx recipients and eGFR-matched controls. Among kidney donors, there was a significant decrease in serum klotho levels post-nephrectomy (day 3 to day 5) with a mean difference (MD) of -232.24 pg/mL (three studies; 95% CI -299.41 to -165.07 pg/mL). At one year following kidney donation, serum klotho levels remained lower than baseline before nephrectomy with a MD of = -110.80 pg/mL (two studies; 95% CI 166.35 to 55.24 pg/mL). Compared to healthy volunteers, living kidney donors had lower serum klotho levels with a MD of = -92.41 pg/mL (two studies; 95% CI -180.53 to -4.29 pg/mL). There is a significant reduction in serum klotho levels after living kidney donation and an increase in serum klotho levels after KTx. Future prospective studies are needed to assess the impact of changes in klotho on clinical outcomes in KTx recipients and living kidney donors.

Antioxidant and protective effect of Stachys pilifera Benth against nephrotoxicity induced by cisplatin in rats

The aim of current study was to assess the antioxidant and renoprotective effects of Stachys pilifera Benth (S.P.B.) hydroalcoholic extract on nephrotoxicity induced with cisplatin (CP). Adult rats with bodyweight of 180-220 g were divided into five groups (n = 7) treated as follows: group 1, control; group 2, CP; group 3, pretreatment with S.P.B. before CP; group 4, posttreatment with S.P.B. after CP; and, group 5, S.P.B. extract. A single dose of CP (7 mg/kg) was intraperitoneally injected on the fifth day and hydroalcoholic extract of S.P.B. (500 mg kg^-1  day^-1 ) was orally administered. The levels of oxidative stress markers, biochemical tests, and histopathological staining were assayed in serum and renal tissue. Also, the chemical composition of S.P.B. extract was determined by GC-MS analysis. The main compositions of S.P.B. extract identified by GC-MS analysis, were hexadeca-2,6,10,14-tetraen-1-ol, 3,7,11,16-tetramethyl (24.77%), thymol (14.1%), and linolenic acid (13.4%). In groups treated and pretreated with S.P.B., blood urea nitrogen, creatinine, malondialdehyde, and nitric oxide metabolite in serum as well as malondialdehyde and protein carbonyl content of kidney tissues were significantly decreased in comparison to CP group; in contrast, total thiol group showed a significant increase in treated group as compared to CP group. Furthermore, histological investigation indicated that treatment with S.P.B. improved renal damages induced by CP. The current study showed that S.P.B. hydroalcoholic extract improved the biochemical parameters and kidney function as well as restored antioxidant activity in CP-induced nephrotoxicity. However, it needs more investigations to define the mechanism of S.P.B. action. PRACTICAL APPLICATIONS: In different regions of Iran, Stachys is demonstrated by 34 species, out of which 13 are endemic, one of these endemic species is Stachys pilifera Benth (S.P.B.). The oil of S.P.B. is mainly consisted of cis-chrysanthenyl acetate, cis-chrysanthenol, spathulenol, β-caryophyllene, linalool, and terpinen-4-ol. Moreover, phytochemical studies have shown the presence of compounds such as diterpenes, phenylethanoid glycosides, saponins, terpenoides, and flavonoids in Stachys species. The aerial parts of S.P.B. are consumed as herbal tea to treat several disorders, for example, infections, asthma, and rheumatoid arthritis in Iranian folk medicine. The aim of current study was to evaluate the antioxidant and protective effects of S.P.B. hydroalcoholic extract on nephrotoxicity induced with cisplatin (CP). The current study showed that S.P.B. hydroalcoholic extract improved the biochemical parameters and kidney function as well as restored antioxidant activity in CP-induced nephrotoxicity. However, it needs more researches to define the mechanism of S.P.B. action.

Beclin 1/Bcl-2 complex-dependent autophagy activity modulates renal susceptibility to ischemia-reperfusion injury and mediates renoprotection by Klotho

Klotho- and beclin 1-driven autophagy extends life. We examined the role of beclin 1 in modifying acute kidney injury (AKI) and whether beclin 1 mediates Klotho's known renoprotective action in AKI. AKI was induced by ischemia-reperfusion injury in mice with different levels of autophagy activity by genetic manipulation: wild-type (WT) mice with normal beclin 1 expression and function, mice with normal beclin 1 levels but high activity through knockin of gain-of-function mutant beclin 1 (Becn1F121A), mice with low beclin 1 levels and activity caused by heterozygous global deletion of beclin 1 (Becn1+/-), or mice with extremely low beclin 1 activity from knockin of the mutant constitutively active beclin 1 inhibitor Bcl-2 (Bcl2AAA). Klotho was increased by transgenic overexpression (Tg-Kl) or recombinant Klotho protein administration. After ischemia-reperfusion injury, Becn1F121A mice (high autophagy) had milder AKI and Becn1+/- and Bcl2AAA mice (low autophagy) had more severe AKI than WT mice. Tg-Kl mice had milder AKI, but its renoprotection was partially attenuated in Becn1+/-;Tg-Kl mice and was significantly reduced, although not completely abolished, in Bcl2AAA;Tg-Kl mice. Recombinant Klotho protein conferred more renoprotection from AKI in WT mice than in Becn1+/- or Bcl2AAA mice. Klotho reduced beclin 1/Bcl-2 protein complexes and increased autophagy activity, but this effect was less prominent in mice or cells with Bcl2AAA. Transfected Bcl2AAA or Becn1F123A decreased or increased autophagy activity and rendered cells more susceptible or more resistant to oxidative cytotoxicity, respectively. In conclusion, beclin 1 confers renoprotection by activating autophagy. Klotho protects the kidney partially via disruption of beclin 1/Bcl-2 interactions and enhancement of autophagy activity.

Urinary Extracellular Vesicles Carrying Klotho Improve the Recovery of Renal Function in an Acute Tubular Injury Model

Acute kidney injury, defined by a rapid deterioration of renal function, is a common complication in hospitalized patients. Among the recent therapeutic options, the use of extracellular vesicles (EVs) is considered a promising strategy. Here we propose a possible therapeutic use of renal-derived EVs isolated from normal urine (urine-derived EVs [uEVs]) in a murine model of acute injury generated by glycerol injection. uEVs accelerated renal recovery, stimulating tubular cell proliferation, reducing the expression of inflammatory and injury markers, and restoring endogenous Klotho loss. When intravenously injected, labeled uEVs localized within injured kidneys and transferred their microRNA cargo. Moreover, uEVs contained the reno-protective Klotho molecule. Murine uEVs derived from Klotho null mice lost the reno-protective effect observed using murine EVs from wild-type mice. This was regained when Klotho-negative murine uEVs were reconstituted with recombinant Klotho. Similarly, ineffective fibroblast EVs acquired reno-protection when engineered with human recombinant Klotho. Our results reveal a novel potential use of uEVs as a new therapeutic strategy for acute kidney injury, highlighting the presence and role of the reno-protective factor Klotho.

αKlotho-FGF23 interactions and their role in kidney disease: a molecular insight

Following the serendipitous discovery of the ageing suppressor, αKlotho (αKl), several decades ago, a growing body of evidence has defined a pivotal role for its various forms in multiple aspects of vertebrate physiology and pathology. The transmembrane form of αKl serves as a co-receptor for the osteocyte-derived mineral regulator, fibroblast growth factor (FGF)23, principally in the renal tubules. However, compelling data also suggest that circulating soluble forms of αKl, derived from the same source, may have independent homeostatic functions either as a hormone, glycan-cleaving enzyme or lectin. Chronic kidney disease (CKD) is of particular interest as disruption of the FGF23-αKl axis is an early and common feature of disease manifesting in markedly deficient αKl expression, but FGF23 excess. Here we critically discuss recent findings in αKl biology that conflict with the view that soluble αKl has substantive functions independent of FGF23 signalling. Although the issue of whether soluble αKl can act without FGF23 has yet to be resolved, we explore the potential significance of these contrary findings in the context of CKD and highlight how this endocrine pathway represents a promising target for novel anti-ageing therapeutics.

Neferine Attenuates Acute Kidney Injury by Inhibiting NF-κB Signaling and Upregulating Klotho Expression

Purpose: Morbidity associated with and mortality from acute kidney injury (AKI) is gradually increasing, and no efficient drug is available. We explored whether neferine, a bisbenzylisoquinoline alkaloid, attenuated AKI, and the possible mechanisms in play in vivo and in vitro.

Methods: We induced AKI using ischemia-reperfusion (I/R) or lipopolysaccharide (LPS) in vivo. C57 BL/6 male mice were randomized into two groups each containing four subgroups: control, neferine, I/R or LPS, and I/R or LPS + neferine. Mice were sacrificed 24 h after AKI induction and kidneys and sera were collected. NRK-52E cells were exposed to hypoxia/reoxygenation (H/R) or LPS in vitro.

Results: Neferine pretreatment significantly alleviated kidney functional loss and pathological damage. In the AKI mouse models induced by I/R or LPS, neferine inhibited the infiltration of inflammatory cells, including granulocytes and macrophages. Both in vivo and in vitro, neferine attenuated apoptosis, suppressed inflammatory cytokine production, decreased degradation of IκB-α, and inhibited nuclear translocation of NF-κB. Furthermore, it also upregulated Klotho expression in AKI.

Conclusion: Neferine mitigated renal injury in AKI models, perhaps by suppressing the activation of NF-κB and upregulating the expression of Klotho.

Performance of soluble Klotho assays in clinical samples of kidney disease

Background

Soluble Klotho has multiple systemic salutary effects. In animals, both acute and chronic kidney disease models display systemic Klotho deficiency. As such, there is considerable interest in investigating soluble Klotho as a biomarker in patients with different types and severity of kidney diseases. Unfortunately, there remains uncertainty regarding the best method to measure soluble Klotho in human serum samples.

Methods

Using human serum samples obtained from several clinical cohorts with a wide range of kidney function, we measured soluble Klotho using a commercial enzyme-linked immunosorbent assay (ELISA) as well as with an immunoprecipitation-immunoblot (IP-IB) assay utilizing a synthetic antibody with high affinity and specificity for Klotho. Recovery of spiking with a known amount of exogenous Klotho was tested. A subset of samples was analyzed with and without the addition of a protease inhibitor cocktail at the time of collection or after the first freeze-thaw cycle to determine if these maneuvers influenced performance.

Results

The IP-IB assay was superior to the ELISA at recovery of exogenous Klotho (81-115% versus 60-81%) across the spectrum of kidney function. Klotho measurements by IP-IB were highly correlated with estimated glomerular filtration rate (eGFR) (R = 0.80, P < 0.001) in comparison with the commercial ELISA, which exhibited minimal correlation with eGFR (R = 0.18, P = 0.12). Use of a protease inhibitor cocktail neither improved nor impaired performance of the IP-IB assay; however, subsequent freeze-thaw cycle resulted in a significant reduction in Klotho recovery and dissipated the correlation between Klotho levels and eGFR. With the ELISA, the use of protease inhibitor cocktail resulted in an increase in intrasubject variability.

Conclusions

The IP-IB assay is preferable to the commercial ELISA to measure soluble Klotho concentrations in never-thawed serum samples of humans with varying severity of kidney disease. However, due to the labor-intensive nature of the IP-IB assay, further research is needed to secure an assay suitable for high-throughput work.

Fibroblast Growth Factor 23 and Klotho in AKI

Acute kidney injury (AKI) is associated with many of the same mineral metabolite abnormalities that are observed in chronic kidney disease. These include increased circulating levels of the osteocyte-derived, vitamin D-regulating hormone, fibroblast growth factor 23 (FGF23), and decreased renal expression of klotho, the co-receptor for FGF23. Recent data have indicated that increased FGF23 and decreased klotho levels in the blood and urine could serve as novel predictive biomarkers of incident AKI, or as novel prognostic biomarkers of adverse outcomes in patients with established AKI. In addition, because FGF23 and klotho exert numerous classic as well as off-target effects on a variety of organ systems, targeting their dysregulation in AKI may represent a unique opportunity for therapeutic intervention. We review the pathophysiology, kinetics, and regulation of FGF23 and klotho in animal and human studies of AKI, and we discuss the challenges and opportunities involved in targeting FGF23 and klotho therapeutically.

Recombinant α-Klotho Protein Alleviated Acute Cardiorenal Injury in a Mouse Model of Lipopolysaccharide-Induced Septic Cardiorenal Syndrome Type 5

Background and Aims

Klotho is an aging-suppressor gene mainly expressed in the renal tubules. The klotho gene encodes the α-klotho protein, which has many functions. Previous studies have found that α-klotho protein has a cardiorenal protective function. α-Klotho deficiency renders the kidney more susceptible to injury and results in cardiovascular calcification and left ventricular hypertrophy in chronic kidney disease. However, the role of α-klotho in acute heart injury and acute kidney injury with sepsis remains unknown. This study aimed to investigate the effects and mechanisms of α-klotho in septic cardiorenal injury.

Methods

Male 8-week-old C57BL/6 mice were randomly assigned to the control group, lipopolysaccharide (LPS; 10 mg/kg) group, LPS (10 mg/kg)+α-klotho (0.01 mg/kg) group, and LPS (10 mg/kg)+α-klotho (0.02 mg/kg) group. Recombinant α-klotho was intraperitoneally injected an hour before LPS injection. Mice were euthanized at 24 h after LPS injection. The serum troponin, brain natriuretic peptide (BNP), neutrophil gelatinase-associated lipocalin (NGAL), and creatinine levels were measured in all groups at 24 h. Biomarkers of mice heart apoptosis, inflammation, oxidative stress, and endoplasmic reticulum stress, such as caspase-3, interleukin 1 (IL-1), reactive oxygen species (ROS), and glucose-regulated protein 78 (GRP78), were also measured.

Results

α-Klotho was mainly expressed in mice kidneys and was undetectable in the control mice hearts. α-Klotho substantially decreased after LPS injection. In the LPS group, the serum troponin levels significantly increased as early as 6 h (p < 0.05) after LPS injection, while the BNP, NGAL, and creatinine levels significantly increased at 24 h (p < 0.05). Pretreatment with α-klotho significantly ameliorated acute cardiorenal injury. In the LPS+α-klotho (0.01 mg/kg) group, the levels of apoptosis, inflammation, and oxidative stress were decreased, while the level of endoplasmic reticulum stress was elevated.

Conclusions

α-Klotho significantly alleviates acute cardiorenal injury in LPS-induced septic cardiorenal injury due to the inhibition of apoptosis, inflammation, and oxidation, as well as the regulation of endoplasmic reticulum stress levels.

Urine Klotho Is Lower in Critically Ill Patients With Versus Without Acute Kidney Injury and Associates With Major Adverse Kidney Events

Supplemental Digital Content is available in the text.

Klotho and fibroblast growth factor-23 were recently postulated as candidate biomarkers and/or therapeutic targets in acute kidney injury. We examined whether urine Klotho and serum intact fibroblast growth factor-23 levels were differentially and independently associated with major adverse kidney events in critically ill patients with and without acute kidney injury.

Melatonin attenuates cisplatin-induced acute kidney injury in rats via induction of anti-aging protein, Klotho

This study investigated the protective effects of melatonin (MT) against cisplatin (CP)-induced acute kidney injury in rats as well as its possible mechanism of action associated with anti-aging protein Klotho. The following four experimental groups were evaluated: vehicle control, CP (7 mg/kg), CP&MT20 (20 mg/kg/day), and CP&MT40 (40 mg/kg/day). The concomitant administration of MT significantly ameliorated CP-induced acute kidney injury in rats, as evidenced by increased kidney weight, increased serum levels of blood urea nitrogen and creatinine, and increased incidence of histopathological alterations with renal tubular cell apoptosis. In addition, MT treatment protected kidney tissue against oxidative damages and significantly upregulated the expression level of Klotho decreased by CP treatment, resulting in reduced phosphorylation of protein kinase B (AKT) and forkhead box O (FOXO) as well as reduced expression levels of B-cell lymphoma 2-associated X protein (Bax) and caspase-3. MT not only partially regulated oxidative stress via AKT/FOXO signaling, but also reduced apoptosis caused by CP by inhibiting the Bax/caspase-3 pathway. Our results indicated that MT could prevent acute kidney injury induced by CP in rats, presumably through upregulating the expression of Klotho, resulting in elevated anti-oxidant and anti-apoptotic properties.

Evaluation of Cisplatin Efficacy on HepG2 and E. coli Cells under Acidic Conditions

Background: Cisplatin (Cispt) is a common anticancer drug for the treatment of several malignancies, including hepatocarcinoma. However, this drug suffers from instability in aqueous solutions. The study aimed to evaluate cisplatin efficacy on HepG2 and E. coli cells under an acidic condition. Methods: Acidic Cispt was prepared via incubation in acidic condition (pH=2) for a month duration. The chemical structure of the acidic Cispt was evaluated by using Fourier Transform Infrared Spectroscopy (FTIR) method. The cytotoxicity of the standard and acidic Cispt were then determined by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) and minimum inhibitory concentration (MIC) assays on HepG2 and E. coli cells, respectively. Results: After preparing of acidic Cispt, its chemical structure was determined by FTIR method. In addition, cytotoxicity effects of Cispt in the standard and acidic forms were calculated 58 ± 2.9 and 65 ± 3.25 μM, respectively. MIC results also confirmed the results of MTT assay. MIC results for the standard and acidic Cispt were estimated 9.5 ± 0.47 and 9.8 ± 0.49 μM, respectively. Conclusion: Preparing Cispt in acidic condition not only did not degrade the drug, but also kept the potency of the drug approximately equal to parent drug. Regarding the instability issues of Cispt, keeping Cispt in acidic condition could be a promising approach to preserve its efficacy.

Genetic Variations and Cisplatin Nephrotoxicity: A Systematic Review

Background: Nephrotoxicity is a notable adverse effect in cisplatin treated patients characterized by tubular injury and/or increased serum creatinine (SCr) with incidence varying from 20 to 70%. Pharmacogenomics has been shown to identify strongly predictive genetic markers to help determine which patients are more likely to experience, for example, a serious adverse drug reaction or receive optimal benefit through enhanced efficacy. Genetic variations have been reported to influence the risk of cisplatin nephrotoxicity; however, a comprehensive overview is lacking. Methods: A systematic review was performed using Pubmed, Embase and Web of Science on clinical studies that used cisplatin-based chemotherapy as treatment, had available genotyping data, and evaluated nephrotoxicity as an outcome. The quality of reporting was assessed using the STrengthening the REporting of Genetic Association Studies (STREGA) checklist. Results: Twenty-eight eligible studies were included; all were candidate gene studies. Over 300 SNPs across 135 genes were studied; 29 SNPs in 14 genes were significantly associated with cisplatin-induced nephrotoxicity. A variation in SLC22A2 rs316019, a gene involved in platinum uptake by the kidney, was associated with different measures of nephrotoxicity in four independent studies. Further, variants of ERCC1 (rs11615 and rs3212986) and ERCC2 (rs13181), two genes involved in DNA repair, were found to be positively associated with increased risks of nephrotoxicity in two independent studies. Conclusion: Three genes consistently associated with cisplatin-induced nephrotoxicity. Further research is needed to assess the biological mechanism and the clinical value of modifying treatment based on SLCC22A2 and ERCC1/2 genotypes.

Contribution of volume overload to progression of cardiovascular disease in a rat model of chronic kidney disease

Volume overload is a common phenomenon in patients with chronic kidney disease that is associated with cardiovascular risk factors. However, its contribution to the development of adverse cardiovascular outcomes in those patients is not fully understood. Thus, the present work investigated the effect of salt-induced volume overload on cardiac functions and geometry in a rat model of chronic kidney disease. Thirty adult male Sprague-Dawley rats were randomly divided. One set of animals received a sham operation, while another set of animals underwent uninephrectomy. Rats were then fed either a normal-salt (0.4%) or high-salt (8.0%) diet for 6 weeks. The salt-loaded, uninephrectomized rats were treated with indapamide (3 mg·kg^-1·day^-1, orally) for 6 weeks. We found that uninephrectomized rats subjected to a high-salt diet (8.0%) for 6 weeks presented with hypertension, proteinuria, decreased renal Klotho expression, and deterioration in cardiac hemodynamics and histology. Echocardiography to assess cardiac function showed that ejection fraction and fractional shortening were positively correlated with relative renal Klotho expression. In conclusion, salt-induced volume overload in a rat model of chronic kidney disease has an adverse cardiovascular outcome and is associated with inflammatory activation and decrease in renal Klotho expression.

Cisplatin nephrotoxicity as a model of chronic kidney disease

Cisplatin (CP)-induced nephrotoxicity is widely accepted as a model for acute kidney injury (AKI). Although cisplatin-induced chronic kidney disease (CKD) in rodent has been reported, the role of phosphate in the cisplatin-induced CKD progression is not described. In this study, we gave a single peritoneal injection of CP followed by high (2%) phosphate diet for 20 weeks. High dose CP (20 mg/Kg) led to high mortality; whereas a lower dose (10 mg/Kg) resulted in a full spectrum of AKI with tubular necrosis, azotemia, and 0% mortality 7 days after CP injection. After consuming a high phosphate diet, mice developed CKD characterized by low creatinine clearance, interstitial fibrosis, hyperphosphatemia, high plasma PTH and FGF23, low plasma 1,25(OH)₂ Vitamin D₃ and αKlotho, and classic uremic cardiovasculopathy. The CP model was robust in demonstrating the effect of aging, sexual dimorphism, and dietary phosphate on AKI and also AKI-to-CKD progression. Finally, we used the CP-high phosphate model to examine previously validated methods of genetically manipulated high αKlotho and therapy using exogenous soluble αKlotho protein supplementation. In this CP CKD model, αKlotho mitigated CKD progression, improved mineral homeostasis, and ameliorated cardiovascular disease. Taken together, CP and high phosphate nephrotoxicity is a reproducible and technically very simple model for the study of AKI, AKI-to-CKD progression, extrarenal complications of CKD, and for evaluation of therapeutic efficacy.

Necrostatin-1 Attenuates Cisplatin-Induced Nephrotoxicity Through Suppression of Apoptosis and Oxidative Stress and Retains Klotho Expression

Aim: Cisplatin is an effective chemotherapeutic drug, but the application in clinical is greatly limited by its nephrotoxicity. Necrostatin-1 (Nec-1), an inhibitor of RIP1 kinase, has been reported to inhibit RIP-mediated necroptosis. The aim of this study is to detect the protective effects of Nec-1 on the nephrotoxicity of cisplatin and to investigate its renoprotection mechanism. Methods: 8-week-old male C57BL/6 mice were randomly assigned into four groups: Control, Nec-1, Cisplatin, and Cisplatin+Nec-1. Mice were treated with cisplatin with or without Nec-1 pre-treatment. Renal function, histological changes, necroptosis, and apoptotic markers were investigated. NFκB pathway related proteins, proinflammatory cytokines, oxidative stress markers, renal Klotho, and autophagy-related proteins levels were also examined. Results: Renal function and histological data displayed that the treatment with Nec-1 significantly attenuates cisplatin-induced renal damage. The expression of RIPK1/RIPK3/MLKL were significantly enhanced in cisplatin group as compared to the control group (p < 0.05) and was significantly reduced by pre-treatment of Nec-1 (p < 0.05). The level of stress and apoptosis-related protein, including p-JNK, p-c-Jun, p-p38, Bax/Bcl-2 ratio, and caspase-3 showed the similar trend. Pre-treatment with Nec-1 inhibit NFκB signaling, reduced proinflammatory cytokines and oxidative stress, up-regulated renal Klotho, and autophagy-related proteins levels. Conclusion: Our results suggest that Nec-1 could be a potential therapeutic drug against the cisplatin-induced nephrotoxicity through its anti-necroptosis, anti-apoptotic, anti-inflammatory anti-oxidant and retain Klotho expression and activate autophagy effects in the kidney.

In Vivo Target Gene Activation via CRISPR/Cas9-Mediated Trans-epigenetic Modulation

Current genome-editing systems generally rely on inducing DNA double-strand breaks (DSBs). This may limit their utility in clinical therapies, as unwanted mutations caused by DSBs can have deleterious effects. CRISPR/Cas9 system has recently been repurposed to enable target gene activation, allowing regulation of endogenous gene expression without creating DSBs. However, in vivo implementation of this gain-of-function system has proven difficult. Here, we report a robust system for in vivo activation of endogenous target genes through trans-epigenetic remodeling. The system relies on recruitment of Cas9 and transcriptional activation complexes to target loci by modified single guide RNAs. As proof-of-concept, we used this technology to treat mouse models of diabetes, muscular dystrophy, and acute kidney disease. Results demonstrate that CRISPR/Cas9-mediated target gene activation can be achieved in vivo, leading to measurable phenotypes and amelioration of disease symptoms. This establishes new avenues for developing targeted epigenetic therapies against human diseases. VIDEO ABSTRACT.

Effects of erythropoietin receptor activity on angiogenesis, tubular injury, and fibrosis in acute kidney injury: a "U-shaped" relationship

The erythropoietin receptor (EpoR) is widely expressed but its renoprotective action is unexplored. To examine the role of EpoR in vivo in the kidney, we induced acute kidney injury (AKI) by ischemia-reperfusion in mice with different EpoR bioactivities in the kidney. EpoR bioactivity was reduced by knockin of wild-type human EpoR, which is hypofunctional relative to murine EpoR, and a renal tubule-specific EpoR knockout. These mice had lower EPO/EpoR activity and lower autophagy flux in renal tubules. Upon AKI induction, they exhibited worse renal function and structural damage, more apoptosis at the acute stage (<7 days), and slower recovery with more tubulointerstitial fibrosis at the subacute stage (14 days). In contrast, mice with hyperactive EpoR signaling from knockin of a constitutively active human EpoR had higher autophagic flux, milder kidney damage, and better renal function at the acute stage but, surprisingly, worse tubulointerstitial fibrosis and renal function at the subacute stage. Either excess or deficient EpoR activity in the kidney was associated with abnormal peritubular capillaries and tubular hypoxia, creating a "U-shaped" relationship. The direct effects of EpoR on tubular cells were confirmed in vitro by a hydrogen peroxide model using primary cultured proximal tubule cells with different EpoR activities. In summary, normal erythropoietin (EPO)/EpoR signaling in renal tubules provides defense against renal tubular injury maintains the autophagy-apoptosis balance and peritubular capillary integrity. High and low EPO/EpoR bioactivities both lead to vascular defect, and high EpoR activity overides the tubular protective effects in AKI recovery.

Anti-aging factor, serum alpha-Klotho, as a marker of acute physiological stress, and a predictor of ICU mortality, in patients with septic shock

PURPOSE

Genetic deletions decreasing serum alpha-Klotho (alpha-KL) have been associated with rapid aging, multi-organ failure and increased mortality in experimental sepsis. We hypothesized that lower alpha-KL obtained at the onset of septic shock correlates with higher mortality.

MATERIALS AND METHODS

Prospective cohort of 104 adult patients with septic shock. Alpha-KL was measured via ELISA on serum collected on the day of enrollment (within 72h from the onset of shock). Relationship between alpha-KL and clinical outcome measures was evaluated in uni- and multi-variable models.

RESULTS

Median (IQR) alpha-KL was 816 (1020.4) pg/mL and demonstrated a bimodal distribution with two distinct populations, Cohort A [n=97, median alpha-KL 789.3 (767.1)] and Cohort B [n=7, median alpha-KL 4365.1(1374.4), >1.5 IQR greater than Cohort A]. Within Cohort A, ICU non-survivors had significantly higher serum alpha-KL compared to survivors as well as significantly higher APACHE II and SOFA scores, rates of mechanical ventilation, and serum BUN, creatinine, calcium, phosphorus and lactate (all p≤0.05). Serum alpha-KL≥1005, the highest tertile, was an independent predictor of ICU mortality when controlling for co-variates (p=0.028, 95% CI 1.143-11.136).

CONCLUSIONS

Elevated serum alpha-KL in patients with septic shock is independently associated with higher mortality. Further studies are needed to corroborate these findings.