The phosphoinositide-3 kinase γ–Akt pathway mediates renal tubular injury in cisplatin nephrotoxicity

Piracetam mitigates nephrotoxicity induced by cisplatin via the AMPK-mediated PI3K/Akt and MAPK/JNK/ERK signaling pathways

AIMS

Cisplatin (CDDP) is commonly employed as an antineoplastic agent, but its use is significantly limited by the occurrence of dose-dependent nephrotoxicity, the detailed mechanisms of which remain unclear. This research is aimed to explore the molecular mechanisms of Piracetam (PIR)'s protective effects on nephrotoxicity resulting from CDDP exposure and to elucidate the mechanisms responsible for these effects.

MAIN METHODS

PIR was given in dosages of 100 and 300 mg/kg body weight for a duration of 15 days; concurrently, on the last day, a single 10 mg/kg dose of CDDP was delivered via intraperitoneal injection. Forty-eight hours post-CDDP injection, the animals were sacrificed to assess nephrotoxicity. Blood samples and renal tissues were taken for biochemical and histopathological investigations. Serum creatinine and blood urea nitrogen (BUN) were measured. AMP-activated protein kinase (AMPK), caspase-9 and nuclear factor kappa b p65 (NF-κB p65) were assessed by immunohistochemistry method. Enzyme-linked immunosorbent assay (ELISA) analysis was employed to determine cytochrome c (Cyt. c), Bcl-2-associated X-protein (BAX), caspase-3, nuclear factor erythroid 2-related factor 2 (Nrf2), Heme oxygenase-1 (HO-1), superoxide dismutase (SOD), tumor necrosis factor alpha (TNF-α), myeloperoxidase (MPO), and interleukin-1β (IL-1β) levels in renal tissue homogenates. The mRNA levels of tumor protein P53 (TP53), phosphatidylinositol-3 kinase (PI3K), protein kinase B (Akt), p38 mitogen-activated protein kinase (p38 MAPK), extracellular signal-regulated kinases (ERK), and c-Jun N-terminal kinases (JNK) were tested by quantitative real-time polymerase chain reaction (qRT-PCR). Additionally, histopathological evaluations of the renal tissues and the binding affinity of PIR to AMPK by molecular docking were also performed.

KEY FINDINGS

Pre-treatment with PIR enhanced renal function markers such as urea and creatinine, mitigated histological damage, and diminished inflammatory cell presence in renal tubules. PIR demonstrated antioxidant effects by reestablishing the equilibrium between pro-oxidants and antioxidants such as MPO, HO-1, Nrf2, as well as SOD. Furthermore, PIR inhibited the inflammatory pathways through the MAPK/NF-κB pathway. Additionally, PIR counteracted the CDDP-induced decline in PI3K/Akt activity and hindered caspase-dependent apoptotic processes.

SIGNIFICANCE

In summary, PIR appears to be an effective therapeutic strategy for reducing CDDP-induced nephrotoxicity, attributed to its antioxidant, anti-inflammatory, and antiapoptotic mechanisms. Consequently, PIR may serve as a complementary treatment alongside CDDP to alleviate nephrotoxicity associated with CDDP.

Global burden of anticancer drug-induced acute kidney injury and tubulointerstitial nephritis from 1967 to 2023

This study aims to figure out the worldwide prevalence of anticancer therapy-associated acute kidney injury (AKI) and tubulointerstitial nephritis (TIN) and the relative risk of each cancer drug. We conducted an analysis of VigiBase, the World Health Organization pharmacovigilance database, 1967-2023 via disproportionate Bayesian reporting method. We further categorized the anticancer drugs into four groups: cytotoxic therapy, hormone therapy, immunotherapy, and targeted therapy. Reporting odds ratio (ROR) and information component (IC) compares observed and expected values to investigate the associations of each category of anticancer drugs with AKI and TIN. We identified 32,722 and 2056 reports (male, n = 17,829 and 1,293) of anticancer therapy-associated AKI and TIN, respectively, among 4,592,036 reports of all-drug caused AKI and TIN. There has been a significant increase in reports since 2010, primarily due to increased reports of targeted therapy and immunotherapy. Immunotherapy exhibited a significant association with both AKI (ROR: 8.92; IC0.25: 3.06) and TIN (21.74; 4.24), followed by cytotoxic therapy (7.14; 2.68), targeted therapy (5.83; 2.40), and hormone therapy (2.59; 1.24) for AKI, and by cytotoxic therapy (2.60; 1.21) and targeted therapy (1.54; 0.61) for TIN. AKI and TIN were more prevalent among individuals under 45 years of age, with a female preponderance for AKI and males for TIN. These events were reported in close temporal relationship after initiation of the respective drug (16.53 days for AKI and 27.97 days for TIN), and exhibited a high fatality rate, with 23.6% for AKI and 16.3% for TIN. These findings underscore that kidney-related adverse drug reactions are of prognostic significance and strategies to mitigate such side effects are required to optimize anticancer therapy.

Degradation-controlled tissue extracellular sponge for rapid hemostasis and wound repair after kidney injury

Patients diagnosed with T1a cancer undergo partial nephrectomy to remove the tumors. In the process of removing the tumors, loss of kidney volume is inevitable, and current surgical methods focus solely on hemostasis and wound closure. Here, we developed an implantable form of decellularized extracellular matrix sponge to target both hemostasis and wound healing at the lesion site. A porous form of kidney decellularized matrix was achieved by fabricating a chemically cross-linked cryogel followed by lyophilization. The prepared kidney decellularized extracellular matrix sponge (kdES) was then characterized for features relevant to a hemostasis as well as a biocompatible and degradable biomaterial. Finally, histological evaluations were made after implantation in rat kidney incision model. Both gelatin sponge and kdES displayed excellent hemocompatibility and biocompatibility. However, after a 4-week observation period, kdES exhibited more favorable wound healing results at the lesion site. This suggests a promising potential for kdES as a supportive material in facilitating wound closure during partial nephrectomy surgery. KdES not only achieved rapid hemostasis for managing renal hemorrhage that is comparable to commercial hemostatic sponges, but also demonstrated superior wound healing outcomes.

Toxicological effects of microplastics in renal ischemia-reperfusion injury

The widespread presence of microplastics (MPs) in the environment poses a significant threat to biological survival and human health. However, our understanding of the toxic effects of MPs on the kidneys remains limited. This study aimed to investigate the underlying mechanism of the toxic effects of MPs on the kidneys using an ischemia-reperfusion (IR) mouse model. Four-week-old ICR mice were exposed to 0.5 μm MPs for 12 weeks prior to IR injury. The results showed that MPs exposure could aggravate the IR-induced damage to renal tubules and glomeruli. Although there were no significant changes in blood urea nitrogen and serum creatinine levels 7 days after IR, MPs treatment resulted in a slight increase in both parameters. In addition, the expression levels of inflammatory factors (MCP-1 and IL-6) at the mRNA level, as well as macrophage markers (CD68 and F4/80), were significantly higher in the MPs + IR group than in the Sham group after IR. Furthermore, MPs exposure exacerbated IR-induced renal fibrosis. Importantly, the expression of pyroptosis-related genes, including NLRP3, ASC, GSDMD, cleaved caspase-1, and IL-18, was significantly upregulated by MPs, indicating that MPs exacerbate pyroptosis in the context of renal IR. In conclusion, our findings suggest that MPs exposure can aggravate renal IR-induced pyroptosis by activating NLRP3-GSDMD signaling.

Prevention of the Lachnum polysaccharide and its selenium derivatives on cisplatin-induced acute kidney injury in mice

To investigate the renal protective effects of the polysaccharide LEP-1a and derivatives of selenium (SeLEP-1a) from Lachnum YM38, cisplatin (CP) was used to establish an acute kidney model. LEP-1a and SeLEP-1a could effectively reverse the decrease in renal index and improved renal oxidative stress. LEP-1a and SeLEP-1a significantly reduced the contents of the inflammatory cytokines. They could inhibit the release of cyclooxygenase 2 (COX-2) and nitric oxide synthase (iNOS) and increase the expression of nuclear factor erythroid 2-related factor 2 (Nrf2) and hemeoxygenase-1 (HO-1). At the same time, the PCR results indicated that SeLEP-1a could significantly inhibit the mRNA expression levels of toll-like receptor 4 (TLR4), nuclear factor-kB (NF-κB) p65 and inhibitor of kappa B-alpha (IκBα). Western blot analysis showed that LEP-1a and SeLEP-1a significantly downregulated the expression levels of Bcl-2-associated X protein (Bax) and cleaved caspase-3 and upregulated phosphatidylinositol 3-kinase (p-PI3K), protein kinase B (p-Akt) and B-cell lymphoma 2 (Bcl-2) protein expression levels in the kidney. LEP-1a and SeLEP-1a could improve CP-induced acute kidney injury by regulating the oxidative stress response, NF-κB-mediated inflammation and the PI3K/Akt-mediated apoptosis signalling pathway.

Unveiling the mechanisms of nephrotoxicity caused by nephrotoxic compounds using toxicological network analysis

Billions of people worldwide have experienced irreversible kidney injuries, which is mainly attributed to the complexity of drug-induced nephrotoxicity. Consequently, there is an urgent need for uncovering the mechanisms of nephrotoxicity caused by compounds. In the present study, a network-based methodology was applied to explore the mechanisms of nephrotoxicity induced by specific compounds. Initially, a total of 42 nephrotoxic compounds and 60 kinds of syndromes associated with nephrotoxicity were collected from public resources. Afterward, network localization and separation algorithms were used to map the targets of compounds and diseases into the human interactome. By doing so, 199 statistically significant nephrotoxic networks displaying the interaction between compound targets and disease genes were obtained, which played pivotal roles in compounds-induced nephrotoxicity. Subsequently, enrichment analysis pinpointed core Gene Ontology and Kyoto Encyclopedia of Genes and Genomes pathways that highlight commonalities in nephrotoxicity induced by nephrotoxic compounds. It was found that nephrotoxic compounds primarily induce nephrotoxicity by mediating the advanced glycosylation end products-receptor for advanced glycosylation end products signaling pathway in diabetic complications, human cytomegalovirus infection, lipid and atherosclerosis, Kaposi sarcoma-associated herpesvirus infection, apoptosis, and the phosphatidylinositol 3-kinase-Akt pathways. These results provide valuable insights for preventing drug-induced nephrotoxicity. Furthermore, the approaches we used are also helpful in conducting research on other kinds of toxicities.

Revealing the biological mechanism of acupuncture in alleviating excessive inflammatory responses and organ damage in sepsis: a systematic review

Sepsis is a systemic inflammation caused by a maladjusted host response to infection. In severe cases, it can cause multiple organ dysfunction syndrome (MODS) and even endanger life. Acupuncture is widely accepted and applied in the treatment of sepsis, and breakthroughs have been made regarding its mechanism of action in recent years. In this review, we systematically discuss the current clinical applications of acupuncture in the treatment of sepsis and focus on the mechanisms of acupuncture in animal models of systemic inflammation. In clinical research, acupuncture can not only effectively inhibit excessive inflammatory reactions but also improve the immunosuppressive state of patients with sepsis, thus maintaining immune homeostasis. Mechanistically, a change in the acupoint microenvironment is the initial response link for acupuncture to take effect, whereas PROKR2 neurons, high-threshold thin nerve fibres, cannabinoid CB2 receptor (CB2R) activation, and Ca2+ influx are the key material bases. The cholinergic anti-inflammatory pathway of the vagus nervous system, the adrenal dopamine anti-inflammatory pathway, and the sympathetic nervous system are key to the transmission of acupuncture information and the inhibition of systemic inflammation. In MODS, acupuncture protects against septic organ damage by inhibiting excessive inflammatory reactions, resisting oxidative stress, protecting mitochondrial function, and reducing apoptosis and tissue or organ damage.

Potential therapeutic effects of Chinese meteria medica in mitigating drug-induced acute kidney injury

Drug-induced acute kidney injury (DI-AKI) is one of the leading causes of kidney injury, is associated with high mortality and morbidity, and limits the clinical use of certain therapeutic or diagnostic agents, such as antineoplastic drugs, antibiotics, immunosuppressants, non-steroidal anti-inflammatory drugs, and contrast media. In recent years, numerous studies have shown that many Chinese meteria medica, metabolites derived from botanical drugs, and Chinese medicinal formulas confer protective effects against DI-AKI by targeting a variety of cellular or molecular mechanisms, such as oxidative stress, inflammatory, cell necrosis, apoptosis, and autophagy. This review summarizes the research status of common DI-AKI with Chinese meteria medica interventions, including cisplatin, gentamicin, contrast agents, methotrexate, and acetaminophen. At the same time, this review introduces the metabolites with application prospects represented by ginseng saponins, tetramethylpyrazine, panax notoginseng saponins, and curcumin. Overall, this review provides a reference for the development of promising nephroprotectants.

Akt1 is involved in renal fibrosis and tubular apoptosis in a murine model of acute kidney injury-to-chronic kidney disease transition

Maladaptive repair after acute kidney injury (AKI) can predispose patients to chronic kidney disease (CKD). However, the molecular mechanism underlying the AKI-to-CKD transition remains unclear. The Akt signaling pathway has been reported to be involved in the pathological processes of both AKI and CKD. In this study, we investigated the role of Akt1 in a murine model of the AKI-to-CKD transition. Wild-type (WT) and Akt1^-/- mice were subjected to unilateral ischemia-reperfusion injury (UIRI), with their kidneys harvested after two days and two, four, and six weeks after UIRI. The dynamic changes in tubulointerstitial fibrosis, markers of tubular epithelial-mesenchymal transition (EMT), and tubular apoptosis were investigated. Akt1 of the three Akt isoforms was activated during the AKI-to-CKD transition. After UIRI, tubulointerstitial fibrosis and tubular EMT were significantly increased in WT mice, but were attenuated in Akt1^-/- mice. The expression of the transforming growth factor (TGF)-β1/Smad was increased in both WT and Akt1^-/- mice, but was not different between the two groups. The levels of phosphorylated glycogen synthase kinase (GSK)-3β, Snail, and β-catenin in the Akt1^-/- mice were lower than those in the WT mice. The number of apoptotic tubular cells and the expression of cleaved caspase-3/Bax were both lower in Akt1^-/- mice than in WT mice. Genetic deletion of Akt1 was associated with attenuation of tubulointerstitial fibrosis, tubular EMT, and tubular apoptosis during the AKI-to-CKD transition. These findings were associated with TGF-β1/Akt1/GSK-3β/(Snail and β-catenin) signaling independent of TGF-β1/Smad signaling. Thus, Akt1 signaling could serve as a potential therapeutic target for inhibiting the AKI-to-CKD transition.

Melatonin protects against methotrexate hepatotoxicity in young rats: Impact of PI3K/Akt/mTOR signaling

With the improvement in children's acute lymphoblastic leukemia (ALL) care, the survival rate in children ALL has improved much. Methotrexate (MTX) plays an essential role in the success of children's ALL treatment. Since hepatotoxicity is commonly reported in individuals treated with intravenous or oral MTX, our study further examined the hepatic effect following intrathecal MTX treatment, which is an essential treatment for leukemia patients. Specifically, we examined the pathogenesis of MTX hepatotoxicity in young rats and explored the impact of melatonin treatment in protection against MTX hepatotoxicity. Successfully, we found that melatonin was able to protect against MTX hepatotoxicity.

Therapeutic effect and underlying mechanism of Shenkang injection against cisplatin-induced acute kidney injury in mice

ETHNOPHARMACOLOGICAL RELEVANCE

Shenkang injection (SKI), a Chinese patent medicine injection, has been approved for the treatment of chronic kidney disease (CKD) due to its definite clinical therapeutic efficacy. However, the effect and associated underlying mechanism of Shenkang injection against cisplatin (CDDP)-induced acute kidney injury (AKI) has not yet been well elucidated.

AIM OF THE STUDY

This study aims to investigate the therapeutic effect and associated underlying mechanism of Shenkang injection against CDDP-induced AKI.

MATERIALS AND METHODS

We established a CDDP-induced AKI mouse model to evaluate renal function by biochemical markers measurement and to observe histopathological alterations by haemotoxylin and eosin (HE)-staining sections of renal. In addition, the distribution of representative components of SKI in the kidneys of mice was evaluated by liquid chromatography tandem mass spectrometry (LC-MS/MS). Furthermore, the degree of oxidative stress and inflammation were assessed by detecting the levels of inflammatory cytokines and oxidants, while the related mechanisms were elucidated by network pharmacology.

RESULTS

CDDP could induce excessive inflammation and severe injury to the kidneys of mice. However, SKI significantly ameliorated the kidney damages and improved the renal function by reducing the levels of renal function markers (SCr, BUN and urine protein), and inhibiting the production of inflammatory cytokines IL-34, IL-6 and TNF-α. SKI repaired oxidative balance through up-regulation of antioxidants SOD and GSH and down-regulated oxidants MDA. Moreover, 4 components from SKI were detected in the kidney by LC-MS/MS quantification. In addition, pharmacology network indicated the PI3K/AKT, TNF, MAPK, and p53 were the possible signaling pathways for the therapeutic effect of SKI against CDDP-induced AKI, which were related to inflammation, oxidative stress and apoptosis.

CONCLUSION

In the present study, we for the first time demonstrated that SKI alleviates CDDP-induced nephrotoxicity by antioxidant and anti-inflammation via regulating PI3K/AKT, MAPK, TNF, and p53 signaling pathways. The study may provide a scientific rationale for the clinical indication of SKI.

Integrative analysis of renal microRNA and mRNA to identify hub genes and pivotal pathways associated with cyclosporine-induced acute kidney injury in mice

Cyclosporine (CsA) is an immunosuppressive agent that often causes acute kidney injury (AKI) in children. The specific mechanisms underlying CsA-induced AKI are currently unknown. This study used an integrated network analysis of microRNA (miRNA) and mRNA expression profiles, biochemical and pathological analyses to further investigate these potential mechanisms of CsA-induced AKI. Small RNA sequence analysis identified 25 differentially expressed miRNAs, RNA sequencing analysis identified 4,109 differentially expressed mRNAs. We obtained a total of 4,367 target genes from the 25 differentially expressed miRNAs based on three algorithms, including the Mirdb, Mirtarbase, and TargetScan. 971 target genes overlapped between the 4,367 target genes and 4,109 differentially expressed mRNAs were identified for further bioinformatics analysis. Finally, 30 hub genes and two main modules were recognized. Functional enrichment analysis of 30 hub genes indicated that inflammation and epithelial-mesenchymal transition (EMT) related genes were mainly concentrated together. Pathway analysis revealed that the PI3K-Akt signaling pathway plays an integral role in CsA-induced AKI. Network analysis identified 3 important miRNAs, mmu-miR-17b-5p, mmu-miR-19b-3p, and mmu-mir-423-5p that may further promote the development of inflammatory responses and EMT by mediating a complex network of factors. Our research provides a clearer understanding the molecular mechanism of this specific drug-induced AKI by CsA use, which is useful for discovering potential targets for gene therapies, and drug development in CsA-induced AKI.

Knockout of Zeb2 ameliorates progression of renal tubulointerstitial fibrosis in a mouse model of renal ischemia-reperfusion injury

BACKGROUND

Zeb2, a zinc finger E-box-binding homeobox transcription factor, regulates transforming growth factor (TGF)-β signaling pathway. However, its role in the pathogenesis of acute kidney injury (AKI) and AKI to chronic kidney disease (CKD) transition is unclear.

METHODS

We evaluated Zeb2 function in a bilateral renal ischemia-reperfusion injury (IRI)-induced AKI model using proximal tubule-specific Zeb2 conditional knockout (Zeb2-cKO) and wild-type (WT) mice, and in renal biopsy samples.

RESULTS

In Zeb2-cKO mice, the levels of plasma creatinine and blood urea nitrogen post-IRI were significantly lower than that in WT mice. Immunohistological analysis revealed mild tubular injury, reduced neutrophil infiltration, less fibrotic changes, and reduced expression of fibrotic proteins (collagen type IV, α-smooth muscle actin [α-SMA], fibronectin, and connective tissue growth factor [CTGF]), at 3-14 days post-IRI. Zeb2 expression was upregulated in proximal tubular cells post-IRI in WT mice. Zeb2 siRNA transfection reduced TGF-β stimulated mRNA and protein expression of collagen type IV, α-SMA, fibronectin, and CTGF in cultured renal tubular cells. Patients with AKI to CKD transition exhibited high Zeb2 expression in renal tubules, as revealed by renal biopsy. Hypoxia and CoCl2-treatment upregulated Zeb2 promoter activity and mRNA and protein expression in cultured renal tubular epithelial cells, suggesting a regulatory role for hypoxia.

CONCLUSIONS

Zeb2 was upregulated in renal tissues in both mice and humans with AKI. Zeb2 regulates fibrotic pathways in the pathogenesis of AKI and AKI to CKD transition. Therefore, inhibition of Zeb2 could be a potential therapeutic strategy for AKI.

Acute kidney injury promotes development of papillary renal cell adenoma and carcinoma from renal progenitor cells

Acute tissue injury causes DNA damage and repair processes involving increased cell mitosis and polyploidization, leading to cell function alterations that may potentially drive cancer development. Here, we show that acute kidney injury (AKI) increased the risk for papillary renal cell carcinoma (pRCC) development and tumor relapse in humans as confirmed by data collected from several single-center and multicentric studies. Lineage tracing of tubular epithelial cells (TECs) after AKI induction and long-term follow-up in mice showed time-dependent onset of clonal papillary tumors in an adenoma-carcinoma sequence. Among AKI-related pathways, NOTCH1 overexpression in human pRCC associated with worse outcome and was specific for type 2 pRCC. Mice overexpressing NOTCH1 in TECs developed papillary adenomas and type 2 pRCCs, and AKI accelerated this process. Lineage tracing in mice identified single renal progenitors as the cell of origin of papillary tumors. Single-cell RNA sequencing showed that human renal progenitor transcriptome showed similarities to PT1, the putative cell of origin of human pRCC. Furthermore, NOTCH1 overexpression in cultured human renal progenitor cells induced tumor-like 3D growth. Thus, AKI can drive tumorigenesis from local tissue progenitor cells. In particular, we find that AKI promotes the development of pRCC from single progenitors through a classical adenoma-carcinoma sequence.

Telmisartan Exacerbates Cisplatin-Induced Nephrotoxicity in a Mouse Model

Cisplatin (CDDP; cis-diamine dichloroplatinum)-induced nephrotoxicity is the main reason for dose limitations, which can reduce the efficacy of cancer treatment. Lower blood pressure and administration of renin angiotensin system (RAS) inhibitors have been reported as factors that exacerbate CDDP-induced nephrotoxicity; however, the detailed mechanisms remain unknown and the results of previous studies are conflicting. In this study, we examined the influence of various hypotensive drugs, including RAS inhibitors and calcium channel blockers, on CDDP-induced nephrotoxicity in BALB/c mice. The mice were divided into nine groups: (1) CDDP group (15 mg/kg CDDP), (2) AML group (5 mg/kg amlodipine), (3) ENA group (2.5 mg/kg enalapril), (4) telmisartan (TEL) group (10 mg/kg telmisartan), (5) LOS group (10 mg/kg losartan), (6) CDDP + AML group, (7) CDDP + ENA group, (8) CDDP + TEL group, and (9) CDDP + LOS group. Nephrotoxicity was evaluated by measuring serum creatinine (CRE) and blood urea nitrogen (BUN) levels. In addition, the kidney sections were stained with Masson's trichrome and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling (TUNEL) to assess the renal fibrosis area and apoptotic area. Serum CRE and BUN levels were increased in the CDDP + ENA, CDDP + LOS, and CDDP + TEL groups compared to those in the CDDP alone group, and the CDDP + AML group showed an increasing trend. However, there was no correlation between ∆CRE or ∆BUN levels and ∆ systolic blood pressure. The CDDP + TEL group showed a significant increase in the renal fibrosis area. These results suggest that exacerbation of CDDP-induced nephrotoxicity is not correlated with systolic blood pressure but is associated with administration of RAS inhibitors, particularly TEL.

A Novel Formulation of Cisplatin with γ-Polyglutamic Acid and Chitosan Reduces Its Adverse Renal Effects: An In Vitro and In Vivo Animal Study

Cisplatin (cis-diamminedichloroplatinum (II); CDDP) is a key chemotherapeutic agent but causes renal damage and other off-target effects. Here, we describe the pharmacological and biochemical characteristics of a novel formulation of CDDP complexed with γ-polyglutamic acid (γ-PGA) and chitosan (CS), γ-PGA/CDDP-CS, developed by complexing CDDP with γ-PGA, then adding CS (15 kDa; 10 mol%/γ-PGA). We analyzed tumor cytotoxicity in vitro, as well as blood kinetics, acute toxicity, and antitumor efficacy in vivo in BALB/cAJcl mice. γ-PGA/CDDP-CS showed pH-dependent release in vitro over 12 days (9.1% CDDP released at pH 7.4; 49.9% at pH 5.5). It showed in vitro cytotoxicity in a dose-dependent manner similar to that of uncomplexed CDDP. In a mesothelioma-bearing mouse model, a 15 mg/kg dose of CDDP inhibited tumor growth regardless of the type of formulation, complexed or uncomplexed; however, all mice in the uncomplexed CDDP group died within 13 days. γ-PGA/CDDP-CS was as effective as free CDDP in vivo but much less toxic.

Arbutin attenuates LPS-induced acute kidney injury by inhibiting inflammation and apoptosis via the PI3K/Akt/Nrf2 pathway

BACKGROUND

Arbutin (Ar) has anti-oxidative and anti-inflammatory activities. However, the effects of Ar on lipopolysaccharide (LPS)-induced acute kidney injury (AKI) are not clear.

PURPOSE

This study aimed to investigate the effects of Ar on LPS-induced AKI in rats.

METHODS

The possible data regarding the effects of Ar on AKI were collected by network pharmacology research. Histological changes in the kidney and the levels of blood urea nitrogen, serum creatinine, and kidney injury molecule 1 were measured to assess the effects of Ar on renal function in LPS-induced AKI. The levels of inflammatory were detected by live small-animal imaging, cytometric bead array and enzyme linked immunosorbent assay. The levels of reactive oxygen species and apoptosis of primary kidney cells were detected by flow cytometry. The oxidative stress-related markers were detected by the cuvette assay. The TLR4/NF-κB and PI3K/Akt/Nrf2 levels and apoptosis were detected by Western blot analysis. The effects of GDC-0068 (GDC, Akt inhibitor) on Ar interposed on LPS-induced NRK-52e cell apoptosis were investigated by flow cytometry.

RESULTS

The data collected by network pharmacology suggested that Ar might inhibit AKI by exerting an anti-inflammatory effect and regulating the Akt signaling pathway. The experimental results showed that Ar markedly improved renal function, and attenuated inflammation and cell apoptosis via regulating PI3K/Akt/Nrf2 pathway following LPS challenge in vivo, which blocked by GDC effectively in vitro.

CONCLUSION

In a word, this study demonstrated that Ar attenuated LPS-induced AKI by inhibiting inflammation and apoptosis via the PI3K/Akt/Nrf2 pathway.

α-Mangostin, a Dietary Xanthone, Exerts Protective Effects on Cisplatin-Induced Renal Injury via PI3K/Akt and JNK Signaling Pathways in HEK293 Cells

Previous report has confirmed the beneficial effects of α-mangostin (α-MG), a major and representative xanthone distributed in mangosteen (Garcinia mangostana) on the cisplatin-induced rat model. However, the molecular mechanisms related to its renoprotection have not been elucidated exhaustively. The present study investigated the protective effect of α-MG against cisplatin-induced cytotoxicity in the human embryonic kidney (HEK293) cell model. In this study, α-MG prevented cisplatin-induced cell death, accompanied with the decreased levels of malondialdehyde and increased glutathione content. Particularly, α-MG significantly suppressed the overproduction of reactive oxygen species (ROS), restored the activation of phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt), and downregulated the c-JUN N-terminal kinase (JNK) pathways following cisplatin challenge. Subsequently, the cleavage of caspases and poly-ADP-ribose polymerase (PARP) implicating ROS-mediated apoptosis pathways induced by cisplatin was effectively inhibited by α-MG. In conclusion, our findings provided a rationale for the development of α-MG to attenuate cisplatin-induced nephrotoxicity.

Canagliflozin reduces cisplatin uptake and activates Akt to protect against cisplatin-induced nephrotoxicity

Cisplatin is a widely used chemotherapy drug with notorious nephrotoxicity. Na⁺-glucose cotransporter 2 inhibitors are a class of novel antidiabetic agents that may have other effects in the kidneys besides blood glucose control. In the present study, we demonstrated that canagliflozin significantly attenuates cisplatin-induced nephropathy in C57BL/6 mice and suppresses cisplatin induced renal proximal tubular cell apoptosis in vitro. The protective effect of canagliflozin was associated with inhibition of p53, p38 and JNK activation. Mechanistically, canagliflozin partially reduced cisplatin uptake by kidney tissues in mice and renal tubular cells in culture. In addition, canagliflozin enhanced the activation of Akt and inhibited the mitochondrial pathway of apoptosis during cisplatin treatment. The protective effect of canagliflozin was diminished by the phosphatidylinositol 3-kinase/Akt inhibitor LY294002. Notably, canagliflozin did not affect the chemotherapeutic efficacy of cisplatin in A549 and HCT116 cancer cell lines. These results suggest a new application of canagliflozin for renoprotection in cisplatin chemotherapy. Canagliflozin may protect kidneys by reducing cisplatin uptake and activating cell survival pathways.

Dexmedetomidine alleviates cisplatin‑induced acute kidney injury by attenuating endoplasmic reticulum stress‑induced apoptosis via the α2AR/PI3K/AKT pathway

Cisplatin (CP) is an effective antineoplastic agent; however, CP-induced acute kidney injury (AKI) seriously affects the prognosis of patients with cancer. Endoplasmic reticulum (ER) stress (ERS)-induced apoptosis serves a pivotal role in the pathogenesis of CP-induced AKI. Dexmedetomidine (Dex), a potent α₂ adrenergic agonist, has been reported to exert protective effects against AKI. However, the protective effects of Dex against CP-induced AKI and the potential molecular mechanisms remain unknown. In the present study, male Sprague-Dawley rats were divided into four groups (n=10/group), as follows: Control group; CP group, rats received an intraperitoneal (i.p.) injection of 5 mg/kg CP; Dex + CP group, rats received an i.p. injection of 25 µg/kg Dex immediately after CP treatment; and Dex + CP + atipamezole (Atip) group, rats received an i.p. injection of 250 µg/kg Atip, an α₂ adrenoreceptor (α₂AR) antagonist, and then received the same treatment as the Dex + CP group. Rats were anesthetized and sacrificed 96 h after CP injection. Subsequently, serum blood urea nitrogen (BUN) and serum creatinine (Scr) were analyzed, and kidney samples were collected for analyses. Pathological changes were examined using hematoxylin and eosin staining, and protein expression levels were assessed using western blotting and immunohistochemical staining. In addition, apoptosis was examined using a terminal deoxynucleotidyl transferase dUTP nick-end labeling assay. The present results suggested that Dex protected against CP-induced AKI by attenuating histological changes in the kidney, serum BUN and Scr production. Furthermore, the expression levels of 78-kDa glucose-regulated protein, C/EBP homologous protein and caspase-12, and the apoptotic rate in the kidney were decreased following Dex treatment. In addition, the expression levels of phosphorylated (p)-PI3K and p-AKT in the Dex + CP group were significantly increased. Conversely, the renoprotective effects of Dex were attenuated following the addition of Atip. In conclusion, Dex may alleviate CP-induced AKI by attenuating ERS-induced apoptosis, at least in part, via the α₂AR/PI3K/AKT signaling pathway.

Ginkgo Biloba Extract Alleviates Methotrexate-Induced Renal Injury: New Impact on PI3K/Akt/mTOR Signaling and MALAT1 Expression

Renal injury induced by the chemotherapeutic agent methotrexate (MTX) is a serious adverse effect that has limited its use in the treatment of various clinical conditions. The antioxidant activity of Ginkgo biloba extract (GB) was reported to mitigate renal injury induced by MTX. Our research was conducted to examine the nephroprotective role of GB versus MTX-induced renal injury for the first time through its impact on the regulation of phosphatidylinositol 3-kinase/protein kinase B/ mammalian target of rapamycin (PI3K/Akt/mTOR) signaling together with the renal level of TGF-β mRNA and long non-coding RNA-metastasis-associated lung adenocarcinoma transcript-1 (MALAT1) expression. A group of adult rats was intraperitoneally (ip) injected with MTX 20 mg/kg as a single dose to induce kidney injury (MTX group). The other group of rats was orally administered with GB 60 mg/kg every day for 10 days (GB+ MTX group). The MTX increased the serum creatinine and urea levels, renal TGF-β mRNA and MALAT1 expression, in addition to dysregulation of the PI3K/Akt/mTOR signaling when compared with normal control rats that received saline only (NC group). Moreover, renal damage was reported histopathologically in the MTX group. The GB ameliorated the renal injury induced by MTX and reversed the changes of these biochemical analyses. The involvement of PI3K/Akt/mTOR signaling and downregulation of TGF-β mRNA and MALAT1 renal expressions were firstly reported in the nephroprotective molecular mechanism of GB versus MTX-induced renal injury.

Platycodon grandiflorum Saponins Ameliorate Cisplatin-Induced Acute Nephrotoxicity through the NF-κB-Mediated Inflammation and PI3K/Akt/Apoptosis Signaling Pathways

Although cisplatin is a potent chemotherapeutic agent against cancers, its clinical application is seriously limited by its severe side effects of nephrotoxicity. Previous studies reported that saponins isolated from the roots of Platycodon grandiflorum (PGS) exerted protective effects in various animal models of renal injury, with no confirmation on cisplatin-induced injury. This study was designed to investigate the protective effect of PGS (15 and 30 mg/kg) on cisplatin-induced kidney injury in mice. The levels of serum creatinine (CRE) and blood urea nitrogen (BUN), and renal histopathology demonstrated the protective effect of PGS against cisplatin-induced kidney injury. PGS exerted anti-inflammation effects via suppressing nuclear factor-kappa B (NF-κB) activation and alleviating the cisplatin-induced increase in inducible nitric oxide synthase (iNOS), cyclooxygenase-2 (COX-2), tumor necrosis factor-α (TNF-α), and interleukin-1β (IL-1β) in kidney tissues. The expressions of phosphorylation of phosphatidylinositol 3-kinase/protein kinase B and its downstream apoptotic factors, such as Bcl-2 and caspase families were regulated by PGS in a dose-dependent manner. In conclusion, PGS exerted kidney protection effects against cisplatin-induced kidney injury by inhibiting the activation of NF-κB and regulating PI3K/Akt/apoptosis signaling pathways in mice.

Cisplatin-Induced Rodent Model of Kidney Injury: Characteristics and Challenges

Cisplatin is an antitumor drug used in the treatment of a wide variety of malignancies. However, its primary dose-limiting side effect is kidney injury, which is a major clinical concern. To help understand mechanisms involved in the development of kidney injury, cisplatin rodent model has been developed. Given the complex pathogenesis of kidney injury, which involves both local events in the kidney and interconnected and interdependent systemic effects in the body, cisplatin rodent model is indispensable in the investigation of underlying mechanisms and potential treatment strategies of both acute and chronic kidney injury. Cisplatin rodent model is well appreciated and widely used model due to its simplicity. It has many similarities to human cisplatin nephrotoxicity, which are mentioned in the paper. In spite of its simplicity and wide applicability, there are also traps that need to be taken into account when using cisplatin model. The present paper is aimed at giving a concise insight into the complex characteristics of cisplatin rodent model and heterogeneity of cisplatin dosage regimens as well as outlining factors that can severely influence the outcome of the model and the study. Challenges for future research are also mentioned.

Nutritionally Available Selenocysteine Derivative Antagonizes Cisplatin-Induced Toxicity in Renal Epithelial Cells through Inhibition of Reactive Oxygen Species-Mediated Signaling Pathways

Discovery of nutritionally available agents that could antagonize cisplatin-induced nephrotoxicity is of great significance and clinical application potential. 3,3'-Diselenodipropionic acid (DSePA) is a seleno-amino acid derivative that exhibits strong antioxidant activity. Therefore, this study aimed to examine the protective effects of DSePA on cisplatin-induced renal epithelial cells damage as well as the molecular mechanisms. The results revealed that DSePA effectively inhibited cell apoptosis induced by cisplatin through suppressing the caspase activation and poly(ADP-ribose) polymerase cleavage. In addition, DSePA blocked the cisplatin-induced mitochondrial dysfunction, as evidenced by the loss of mitochondrial membrane potential and reduction of mitochondrial mass. The results of western blot analysis showed that DSePA reversed the expression level of Bcl-2 family proteins altered by cisplatin. The cisplatin-activated AKT pathway was also modulated by DSePA. Moreover, these results indicate that DSePA could protect HK-2 cells from cisplatin-induced toxicity in renal epithelial cells by inhibiting intracellular reactive oxygen species-mediated apoptosis while showing an unobvious effect on its anticancer efficacy. Taken together, this study demonstrates that selenocysteine could be further developed as novel nutritionally available agents to antagonize cisplatin-induced nephrotoxicity during cancer therapy.

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.

Hyperhomocysteinemia Exacerbates Cisplatin-induced Acute Kidney Injury

Hyperhomocysteinemia (HHcy) has been linked to several clinical manifestations including chronic kidney disease. However, it is not known whether HHcy has a role in the development of acute kidney injury (AKI). In the present study, we reported that HHcy mice developed more severe renal injury after cisplatin injection and ischemia-reperfusion injury shown as more severe renal tubular damage and higher serum creatinine. In response to cisplatin, HHcy mice showed more prevalent tubular cell apoptosis and decreased tubular cell proliferation. Mechanistically, a heightened ER stress and a reduced Akt activity were observed in kidney tissues of HHcy mice after cisplatin injection. Stimulating cultured NRK-52E cells with Hcy significantly increased the fraction of cells in G2/M phase and cell apoptosis together with decreased Akt kinase activity. Akt agonist IGF-1 rescued HHcy-induced cell cycle arrest and cell apoptosis. In conclusion, the present study provides evidence that HHcy increases the sensitivity and severity of AKI.

Reduction in Renal Ischemia-Reperfusion Injury in Mice by a Phosphoinositide 3-Kinase p110gamma-Specific Inhibitor

BACKGROUND

Although renal ischemia-reperfusion injury (IRI) can cause delayed graft function, a targeted therapy is not yet available. Because phosphoinositide 3-kinases (PI3K) p110γ and p110δ play important roles in immune cell migration and function, we investigated the effects of PI3K p110γ- and p110δ-specific inhibitors in a murine renal IRI model.

METHODS

Renal function was assessed by serum creatine and hematoxylin-eosin staining. Immune cell migration was assessed by flow cytometry and an in vitro cell migration assay using Transwell plates. Gene expression analysis and a multiplex cytokine/chemokine assay were performed to find cytokines/chemokines whose expression was upregulated in renal IRI and affected by p110γ-specific inhibitor.

RESULTS

The PI3K p110γ-specific inhibitor, but not p110δ-specific inhibitor, significantly reduced serum creatine levels and acute tubular necrosis. These were accompanied by reduced infiltration of B cells and reduced expression of CXCL9, a CXCR3 ligand, suggesting that p110γ plays an important role in B-cell migration toward injured kidneys. An in vitro cell migration assay revealed for the first time that B-cell migration to injured kidney cells and to CXCL9 requires p110γ.

CONCLUSIONS

p110γ-specific inhibitor ameliorates renal IRI by reducing necrosis and immune cell migration. This inhibitor may have the potential to reduce renal graft failure caused by renal IRI.

Electroacupuncture Ameliorates Acute Renal Injury in Lipopolysaccharide-Stimulated Rabbits via Induction of HO-1 through the PI3K/Akt/Nrf2 Pathways

Electroacupuncture at select acupoints have been verified to protect against organ dysfunctions during endotoxic shock. And, heme oxygenase (HO)-1 as a phase II enzyme and antioxidant contributed to the protection of kidney in septic shock rats. The phosphatidylinositol 3-kinase (PI3K)-Akt pathway mediated the activation of NF-E2 related factor-2 (Nrf2), which was involved in HO-1 induction. To understand the efficacy of electroacupuncture stimulation in ameliorating acute kidney injury (AKI) through the PI3K/Akt/Nrf2 pathway and subsequent HO-1 upregulation, a dose of LPS 5mg/kg was administered intravenously to replicate the rabbit model of AKI induced by endotoxic shock. Electroacupuncture pretreatment was handled bilaterally at Zusanli and Neiguan acupoints for five consecutive days while sham electroacupuncture at non-acupoints as control. Results displayed that electroacupuncture stimulation significantly alleviated the morphologic renal damage, attenuated renal tubular apoptosis, suppressed the elevated biochemical indicators of AKI caused by LPS, enhanced the expressions of phospho-Akt, HO-1protein, Nrf2 total and nucleoprotein, and highlighted the proportions of Nrf2 nucleoprotein as a parallel. Furthermore, partial protective effects of elecroacupuncture were counteracted by preconditioning with wortmannin (the selective PI3K inhibitor), indicating a direct involvement of PI3K/Akt pathway. Inconsistently, wortmannin pretreatment made little difference to the expressions of HO-1, Nrf2 nucleoprotein and total protein, which indicated that PI3K/Akt may be not the only pathway responsible for electroacupuncture-afforded protection against LPS-induced AKI. These findings provide new insights into the potential future clinical applications of electroacupuncture for AKI induced by endotoxic shock instead of traditional remedies.

An in vitro investigation into the role of bone marrow‑derived mesenchymal stem cells in the control of disc degeneration

Excessive apoptosis and high expression levels of interleukin-1β (IL-1β) in disc cells have been reported to serve important roles in intervertebral disc degeneration (IVDD). Previous studies investigating mesenchymal stem cells (MSCs) have indicated potential for their use in the treatment of IVDD. However, the therapeutic potential and anti-apoptotic ability of MSCs remains to be fully elucidated. The present study aimed to establish an in vitro model for bone marrow-derived MSC (BMSC) therapy by investigating the anti-apoptotic effects, in addition to the migration of BMSCs to nucleus pulposus (NP) cells stimulated by IL-1β. A co-culture system of BMSCs and NP cells was founded. Following inflammatory stimulation, the NP cells exhibited increased indexes for inflammation-induced degeneration. The degenerative and apoptotic indexes were significantly reduced when NP cells were co-cultured with BMSCs. Compared with the indirect co-culture group, the direct co-culture group exhibited an improved capacity for anti-apoptosis. In addition, IL-1β-stimulated NP cells attracted and mediated the migration of BMSCs. Mitochondrial transfer from BMSCs to NP cells by tunneling nanotubes was also observed. In conclusion, the anti-apoptosis and the migration, in addition to mitochondrial transfer associated with BMSC treatments in IVDD, were investigated in vitro in the present study. The interaction between stimulated NP cells and BMSCs is likely involved in to simulating the in vivo process of stem cell-mediated repair.

Epidermal growth factor receptor inhibition with erlotinib partially prevents cisplatin-induced nephrotoxicity in rats

The effects of blocking the epidermal growth factor receptor (EGFR) in acute kidney injury (AKI) are controversial. Here we investigated the renoprotective effect of erlotinib, a selective tyrosine kinase inhibitor that can block EGFR activity, on cisplatin (CP)-induced AKI. Groups of animals were given either erlotinib or vehicle from one day before up to Day 3 following induction of CP-nephrotoxicity (CP-N). In addition, we analyzed the effects of erlotinib on signaling pathways involved in CP-N by using human renal proximal tubular cells (HK-2). Compared to controls, rats treated with erlotinib exhibited significant improvement of renal function and attenuation of tubulointerstitial injury, and reduced the number of apoptotic and proliferating cells. Erlotinib-treated rats had a significant reduction of renal cortical mRNA for profibrogenic genes. The Bax/Bcl-2 mRNA and protein ratios were significantly reduced by erlotinib treatment. In vitro, we observed that erlotinib significantly reduced the phosphorylation of MEK1 and Akt, processes that were induced by CP in HK-2. Taken together, these data indicate that erlotinib has renoprotective properties that are likely mediated through decreases in the apoptosis and proliferation of tubular cells, effects that reflect inhibition of downstream signaling pathways of EGFR. These results suggest that erlotinib may be useful for preventing AKI in patients receiving CP chemotherapy.

Extracellular nucleotides from dying cells act as molecular signals to promote wound repair in renal tubular injury

Acute kidney injury (AKI) often correlates with poor prognosis and is followed by various severe unfavorable systemic outcomes. It is important to understand the pathophysiology of AKI for the development of novel therapeutic approaches toward promoting renal regeneration after injury. Recent studies have indicated that AKI-induced tubular cell death plays an active role in the onset of tissue regeneration; however, the mechanisms underlying renal tubular repair after injury have yet to be understood. In the present study, we explored molecules that might serve as "danger" signals in mediating tubular regeneration. Kidneys of rats systemically administered the nephrotoxicant cisplatin (to induce AKI) exhibited massive cell proliferation. The proportion of proliferating cells in the total cell distribution was highest in the outer stripe of the outer medulla coincided with where the tubular damage was the most severe in this study. This finding suggests that soluble factors may have been released from damaged cells to stimulate the proliferation of neighboring tubular epithelial cells. In elucidating the mechanism of dying cell-to-surviving cell communication using normal rat kidney NRK-52E epithelial cells, we found a significant increase in ATP levels in supernatants of these cells after the induction of cell death using ultraviolet irradiation. Furthermore, treatment of conditioned supernatants with apyrase or suramin, which inhibits purinergic signaling, resulted in significant decreases in cell proliferation and migration activities. These results demonstrate a novel role for extracellular nucleotides, probably as danger signals in aggravating tubular regeneration after AKI.

5-Aminolevulinic acid protects against cisplatin-induced nephrotoxicity without compromising the anticancer efficiency of cisplatin in rats in vitro and in vivo

Background/Aims

Nephrotoxicity is a frequent and major limitation in cisplatin (CDDP)-based chemotherapy. 5-Aminolevulinic acid (ALA) is widely distributed in animal cells, and it is a precursor of tetrapyrole compounds such as heme that is fundamentally important in aerobic energy metabolism. The aim of this study is to evaluate the protective role of ALA in CDDP-induced acute kidney injury (AKI).

Method

We used CDDP-induced AKI rat model and cultured renal tubular cells (NRK-52E). We divided four groups of rats: control, CDDP only, CDDP + ALA(post);(ALA 10 mg/kg + Fe in drinking water) after CDDP, CDDP + ALA(pre & post).

Result

CDDP increased Cr up to 6.5 mg/dl, BUN up to 230 mg/dl, and ALA significantly reduced these changes. ALA ameliorates CDDP-induced morphological renal damages, and reduced tubular apoptosis evaluated by TUNEL staining and cleaved caspase 3. Protein and mRNA levels of ATP5α, complex(COX) IV, UCP2, PGC-1α in renal tissue were significantly decreased by CDDP, and ALA ameliorates reduction of these enzymes. In contrast, Heme Oxigenase (HO)-1 level is induced by CDDP treatment, and ALA treatment further up-regulates HO-1 levels. In NRK-52E cells, the CDDP-induced reduction of protein and mRNA levels of mitochondrial enzymes was significantly recovered by ALA + Fe. CDDP-induced apoptosis were ameliorated by ALA + Fe treatment. Furthermore, we evaluated the size of transplantated bladder carcinoma to the rat skin, and ALA did not change the anti cancer effects of CDDP.

Conclusion

These data suggested that the protective role of ALA in cisplatin-induced AKI is via protection of mitochondrial viability and prevents tubular apoptosis. Also there are no significant effects of ALA on anticancer efficiency of CDDP in rats. Thus, ALA has the potential to prevent CDDP nephrotoxicity without compromising its anticancer efficacy.

Met activation is required for early cytoprotection after ischemic kidney injury

Renal proximal tubule epithelial cells express high levels of the hepatocyte growth factor receptor Met, and both the receptor and ligand are upregulated after ischemic injury. Activation of the Met receptor after hepatocyte growth factor stimulation in vitro promotes activities involved in kidney repair, including cell survival, migration, and proliferation. However, characterizing the in vivo role of these signaling events in proximal tubule responses to kidney injury has been difficult because global Met knockout results in embryonic lethality due to placental and liver abnormalities. Here, we used γGT-Cre to knockout Met receptor expression selectively in the proximal tubules of mice (γGT-Cre;Met(fl/fl)). The kidneys of these mice developed normally, but exhibited increased initial tubular injury, tubular cell apoptosis, and serum creatinine after ischemia/reperfusion compared with γGT-Cre;Met(+/+) kidneys. These changes in γGT-Cre;Met(fl/fl) mice correlated with a selective reduction in PI3K/Akt activation in response to injury and subsequent decreases in inhibitory phosphorylation of the proapoptotic factor Bad and activating phosphorylation of the ribosomal regulatory protein p70-S6 kinase. Moreover, tubular cell proliferation after ischemia/reperfusion was delayed in γGT-Cre;Met(fl/fl) mice. In conclusion, this study identifies Met-dependent phosphoinositide 3-kinase activation in proximal tubules as a critical determinant of initial tubular cell survival and reparative proliferation after ischemic injury.

Sustained activation of EGFR triggers renal fibrogenesis after acute kidney injury

Severe acute kidney injury (AKI) is frequently accompanied by maladaptive repair and renal fibrogenesis; however, the molecular mechanisms that mediate these acute and chronic consequences of AKI remain poorly understood. In this study, we examined the role of epidermal growth factor receptor (EGFR) in these processes using waved-2 (Wa-2) mice, which have reduced EGFR activity, and their wild-type (WT) littermates after renal ischemia. Renal EGFR phosphorylation was induced within 2 days after ischemia, increased over time, and remained elevated at 28 days in WT mice, but this was diminished in Wa-2 mice. At the early stage of postischemia (2 days), Wa-2 mice developed more severe acute renal tubular damage with less reparative responses as indicated by enhanced tubular cell apoptosis, and reduced dedifferentiation and proliferation as compared to WT animals. At the late stage of postischemia (28 days), Wa-2 mice exhibited a less severe renal interstitial fibrosis as shown by reduced activation/proliferation of renal myofibroblasts and decreased deposition of extracellular matrix proteins. EGFR activation also contributed to cell cycle arrest at the G2/M phase, a cellular event associated with production of profibrogenetic factors, in the injured kidney. Collectively, these results indicate that severe AKI results in sustained activation of EGFR, which is required for reparative response of renal tubular cells initially, but eventually leads to fibrogenesis.

Transient receptor potential vanilloid 1 (TRPV1), TRPV4, and the kidney

Recent preclinical data indicate that activators of transient receptor potential channels of the vanilloid receptor subtype 1 (TRPV1) may improve the outcome of ischaemic acute kidney injury (AKI). The underlying mechanisms are unclear, but may involve TRPV1 channels in dorsal root ganglion neurones that innervate the kidney. Recent data identified TRPV4, together with TRPV1, to serve as major calcium influx channels in endothelial cells. In these cells, gating of individual TRPV4 channels within a four-channel cluster provides elementary calcium influx (calcium sparklets) to open calcium-activated potassium channels and promote vasodilation. The TRPV receptors can also form heteromers that exhibit unique conductance and gating properties, further increasing their spatio-functional diversity. This review summarizes data on electrophysiological properties of TRPV1/4 and their modulation by endogenous channel agonists such as 20-HETE, phospholipase C and phosphatidylinositide 3-kinase (PI3 kinase). We review important roles of TRPV1 and TRPV4 in kidney physiology and renal ischaemia reperfusion injury; further studies are warranted to address renoprotective mechanism of vanilloid receptors in ischaemic AKI including the role of the capsaicin receptor TRPV1 in primary sensory nerves and/or endothelium. Particular attention should be paid to understand the kidneys' ability to respond to ischaemic stimuli after catheter-based renal denervation therapy in man, whereas the discovery of novel pharmacological TRPV modulators may be a successful strategy for better treatment of acute or chronic kidney failure.

HuR inhibits apoptosis by amplifying Akt signaling through a positive feedback loop

Human antigen R (HuR) is a post-transcriptional regulator of gene expression that plays a key role in stabilizing mRNAs during cellular stress, leading to enhanced survival. HuR expression is tightly regulated through multiple transcription and post-transcriptional controls. Although HuR is known to stabilize a subset of mRNAs involved in cell survival, its role in the survival pathway of PI3-kinase/Akt signaling is unclear. Here, we show that in renal proximal tubule cells, HuR performs a central role in cell survival by amplifying Akt signaling in a positive feedback loop. Key to this feedback loop is HuR-mediated stabilization of mRNA encoding Grb10, an adaptor protein whose expression is critical for Akt activation. Stimulation of Akt by interaction with Grb10 then activates NF-κB, which further enhances HuR mRNA and protein expression. This feedback loop is active in unstressed cells, but its effects are increased during stress. Therefore, this study demonstrates a central role for HuR in Akt signaling and reveals a mechanism by which modest changes in HuR levels below or above normal may be amplified, potentially resulting in cell death or cellular transformation.

EGFR activity is required for renal tubular cell dedifferentiation and proliferation in a murine model of folic acid-induced acute kidney injury

Proliferation of dedifferentiated intrinsic renal tubular cells has been recognized to be the major cellular event that contributes to renal repair after acute kidney injury (AKI). However, the underlying mechanism that initiates renal tubular dedifferentiation in vivo remains unexplored. Here we investigated whether epidermal growth factor receptor (EGFR) mediates this process in a murine model of folic acid (FA)-induced AKI using waved-2 mice that have reduced tyrosine kinase activity of EGFR and gefitinib, a specific EGFR inhibitor. Administration of FA for 48 h induced EGFR phosphorylation in the kidney of wild-type mice, but this was inhibited in waved-2 mice and wild-type mice given gefitinib. Compared with wild-type mice, waved-2 mice and wild-type mice treated with gefitinib had increased renal dysfunction, histologic damage, and tubular cell apoptosis after FA administration. PAX2, a dedifferentiation marker, and proliferating cell nuclear antigen, a proliferating marker, were highly expressed in renal tubular cells in wild-type mice; however, their expression was largely inhibited in the kidney of waved-2 mice. Inhibition of EGFR with gefitinib also blocked FA-induced expression of these two proteins in wild-type mice. Moreover, FA exposure resulted in phosphorylation of AKT, a downstream signaling molecule of the phosphatidylinositol 3-kinases pathway associated with renal epithelial proliferation in wild-type mice, and its phosphorylation was totally suppressed in waved-2 mice and wild-type mice given gefitinib. Taken together, these results suggest that EGFR activation is essential for initiation of renal tubular cell dedifferentiation and proliferation after AKI.

The high glucose-induced stimulation of B1R and B2R expression via CB(1)R activation is involved in rat podocyte apoptosis

AIMS

We examined renal kallikrein-kinin system (KKS) apoptosis and its related signaling pathway in rat podocytes. In addition, we studied the relationship of cannabinoid receptor 1 (CB(1)R) with high glucose and BK receptors.

MAIN METHODS

Cell viability was determined by an MTT assay and apoptosis by DNA fragmentation assay, while gene expression was investigated by RT-PCR. Protein expression was analyzed by Western blot analysis. A chemical inhibitor or siRNA transfection was used to inhibit B1R, B2R, and CB(1)R signaling.

KEY FINDINGS

High glucose (25 mM) treatment decreased cell viability and increased DNA fragmentation. High glucose-induced DNA fragmentation and PARP and caspase-3 activations were blocked by both [des-Arg(10)]-HOE 140 (a B1R antagonist) and HOE 140 (a B2R antagonist). High glucose also increased Akt phosphorylation, ER stress-related protein expression, and NF-κB/I-κB phosphorylation in podocytes, which was blocked by both [des-Arg(10)]-HOE 140 and HOE 140. In addition, B1R and B2R siRNA transfections prevented high glucose-induced Akt and NF-κB activations in rat podocytes. Moreover, AM251 (a CB(1)R antagonist) treatment and CB(1)R siRNA transfection blocked the high glucose-induced stimulation of BK receptor expression, Akt activation, and NF-κB activation.

SIGNIFICANCE

Our study suggests that hyperglycemia induces apoptosis via the stimulation of B1R and B2R expression through CB(1)R activation in rat podocytes in vitro, which is associated with the development of diabetic nephropathy.

DAP5 ameliorates cisplatin-induced apoptosis of renal tubular cells

BACKGROUND

Nephrotoxicity of cisplatin limits its clinical application. Cisplatin-induced acute renal tubular epithelial cell apoptosis is one of the major mechanisms of cisplatin nephrotoxicity. Here, the role and regulation of death-associated protein 5 (DAP5) in cisplatin-induced tubular cell apoptosis were investigated.

METHODS

After upregulation of DAP5 expression by plasmid transfection and downregulation of DAP5 expression by small interfering RNA in human kidney tubular epithelial cell line (HKC) cells, the degree of cell apoptosis was assessed by flow cytometric analysis. The expression of Bax and Bcl-2 proteins was detected by Western blot analysis. The relationship between the PI3K/Akt/mTOR signaling pathway and DAP5 was also evaluated.

RESULTS

During cisplatin-induced apoptosis in HKC cells, DAP5 underwent proteolytic fragmentation, yielding an 86-kDa species, DAP5/p86. Overexpression of DAP5/p97 and DAP5/p86 increased the translation of Bcl-2 and reduced the extent of cisplatin-induced apoptosis. Knockdown of DAP5 expression using small interfering RNA decreased the translation of Bcl-2 and increased the degree of apoptosis. Neither manipulation affected the expression of Bax. DAP5 expression was positively regulated by the PI3K/Akt/mTOR signaling pathway.

CONCLUSION

Collectively, the results from the present study revealed a new role for DAP5 in cisplatin-induced apoptosis: DAP5/p97 and DAP5/p86 enhanced the translation of the anti-apoptotic protein Bcl-2 and inhibited cisplatin-induced apoptosis. The PI3K/Akt/mTOR signaling pathway may positively regulate the expression of DAP5.

Transforming growth factor-β induces vascular endothelial growth factor-C expression leading to lymphangiogenesis in rat unilateral ureteral obstruction

Inflammation is recognized as an important contributor to lymphangiogenesis; however, in tubulointerstitial lesions in human chronic kidney diseases, this process is better correlated with the presence of myofibroblasts rather than macrophages. As little is known about the interaction between lymphangiogenesis and renal fibrosis, we utilized the rat unilateral ureteral obstruction model to analyze inflammation, fibrosis, lymphangiogenesis, and growth factor expression. Additionally, we determined the relationship between vascular endothelial growth factor-C (VEGF-C), an inducer of lymphangiogenesis, and the profibrotic factor, transforming growth factor-β1 (TGF-β1). The expression of both TGF-β1 and VEGF-C was detected in tubular epithelial and mononuclear cells, and gradually increased, peaking 14 days after ureteral obstruction. The kinetics and localization of VEGF-C were similar to those of TGF-β1, and the expression of these growth factors and lymphangiogenesis were linked with the progression of fibrosis. VEGF-C expression was upregulated by TGF-β1 in cultured proximal tubular epithelial cells, collecting duct cells, and macrophages. Both in vitro and in vivo, the induction of VEGF-C along with the overall appearance of lymphatics in vivo was specifically suppressed by the TGF-β type I receptor inhibitor LY364947. Thus, TGF-β1 induces VEGF-C expression, which leads to lymphangiogenesis.

Human amniotic fluid stem cell preconditioning improves their regenerative potential

Human amniotic fluid stem (hAFS) cells, a novel class of broadly multipotent stem cells that share characteristics of both embryonic and adult stem cells, have been regarded as promising candidate for cell therapy. Taking advantage by the well-established murine model of acute kidney injury (AKI), we studied the proregenerative effect of hAFS cells in immunodeficient mice injected with the nephrotoxic drug cisplatin. Infusion of hAFS cells in cisplatin mice improved renal function and limited tubular damage, although not to control level, and prolonged animal survival. Human AFS cells engrafted injured kidney predominantly in peritubular region without acquiring tubular epithelial markers. Human AFS cells exerted antiapoptotic effect, activated Akt, and stimulated proliferation of tubular cells possibly via local release of factors, including interleukin-6, vascular endothelial growth factor, and stromal cell-derived factor-1, which we documented in vitro to be produced by hAFS cells. The therapeutic potential of hAFS cells was enhanced by cell pretreatment with glial cell line-derived neurotrophic factor (GDNF), which markedly ameliorated renal function and tubular injury by increasing stem cell homing to the tubulointerstitial compartment. By in vitro studies, GDNF increased hAFS cell production of growth factors, motility, and expression of receptors involved in cell homing and survival. These findings indicate that hAFS cells can promote functional recovery and contribute to renal regeneration in AKI mice via local production of mitogenic and prosurvival factors. The effects of hAFS cells can be remarkably enhanced by GDNF preconditioning.

Inhibition of PKCδ reduces cisplatin-induced nephrotoxicity without blocking chemotherapeutic efficacy in mouse models of cancer

Cisplatin is a widely used cancer therapy drug that unfortunately has major side effects in normal tissues, notably nephrotoxicity in kidneys. Despite intensive research, the mechanism of cisplatin-induced nephrotoxicity remains unclear, and renoprotective approaches during cisplatin-based chemotherapy are lacking. Here we have identified PKCδ as a critical regulator of cisplatin nephrotoxicity, which can be effectively targeted for renoprotection during chemotherapy. We showed that early during cisplatin nephrotoxicity, Src interacted with, phosphorylated, and activated PKCδ in mouse kidney lysates. After activation, PKCδ regulated MAPKs, but not p53, to induce renal cell apoptosis. Thus, inhibition of PKCδ pharmacologically or genetically attenuated kidney cell apoptosis and tissue damage, preserving renal function during cisplatin treatment. Conversely, inhibition of PKCδ enhanced cisplatin-induced cell death in multiple cancer cell lines and, remarkably, enhanced the chemotherapeutic effects of cisplatin in several xenograft and syngeneic mouse tumor models while protecting kidneys from nephrotoxicity. Together these results demonstrate a role of PKCδ in cisplatin nephrotoxicity and support targeting PKCδ as an effective strategy for renoprotection during cisplatin-based cancer therapy.