Tubular Apoptosis Research Articles

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

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

#5658 TUBULE-SPECIFIC CYCLIN-DEPENDENT KINASE 12 KNOCKDOWN POTENTIATES KIDNEY INJURY THROUGH TRANSCRIPTIONAL ELONGATION DEFECTS

Abstract Background and Aims Direct tubular injury caused by several medications, especially chemotherapeutic drugs, is a common cause of AKI. Inhibition or loss of cyclin-dependent kinase 12 (CDK12) triggers a transcriptional elongation defect that results in deficiencies in DNA damage repair, producing genomic instability in a variety of cancers. Notably, 10-25% of individuals developed AKI after treatment with a CDK12 inhibitor, and the potential mechanism is not well understood. Method Here, we established a cisplatin-induced AKI mouse model with CDK12 knockdown mice and created stable in vitro models with CDK12 knockdown tubular epithelial cells. Cisplatin nephrotoxicity was induced by intraperitoneal injection of cisplatin (20 mg/kg). After 2 days following cisplatin treatment, blood and kidney tissues were harvested. Renal function and histology were evaluated. DDR, tubular apoptosis, cell proliferation were evaluated by immunofluorescence assays, real-time PCR, flow cytometer and western blot analysis. Notably, we performed single-molecule real-time sequencing (SMRT), a long-read sequencing platform, to identify the formation of novel transcripts involved in the above events. Results We found that CDK12 was downregulated in the renal tubular epithelial cells in both patients with AKI and murine AKI models. Moreover, tubular cell-specific knockdown of CDK12 in mice enhanced cisplatin-induced AKI through promotion of genome instability, apoptosis, and proliferative inhibition, whereas CDK12 overexpression protected against AKI. Using the single molecule real-time (SMRT) platform on the kidneys of CDK12RTEC+/− mice, we found that CDK12 knockdown targeted Fgf1 and Cast through transcriptional elongation defects, thereby enhancing genome instability and apoptosis. Conclusion These data demonstrated that CDK12 knockdown could potentiate the development of AKI by altering the transcriptional elongation defect of the Fgf1 and Cast genes, and more attention should be given to patients treated with CDK12 inhibitors to prevent AKI.

The Interplay between Immune and Metabolic Pathways in Kidney Disease

Kidney disease is a significant health problem worldwide, affecting an estimated 10% of the global population. Kidney disease encompasses a diverse group of disorders that vary in their underlying pathophysiology, clinical presentation, and outcomes. These disorders include acute kidney injury (AKI), chronic kidney disease (CKD), glomerulonephritis, nephrotic syndrome, polycystic kidney disease, diabetic kidney disease, and many others. Despite their distinct etiologies, these disorders share a common feature of immune system dysregulation and metabolic disturbances. The immune system and metabolic pathways are intimately connected and interact to modulate the pathogenesis of kidney diseases. The dysregulation of immune responses in kidney diseases includes a complex interplay between various immune cell types, including resident and infiltrating immune cells, cytokines, chemokines, and complement factors. These immune factors can trigger and perpetuate kidney inflammation, causing renal tissue injury and progressive fibrosis. In addition, metabolic pathways play critical roles in the pathogenesis of kidney diseases, including glucose and lipid metabolism, oxidative stress, mitochondrial dysfunction, and altered nutrient sensing. Dysregulation of these metabolic pathways contributes to the progression of kidney disease by inducing renal tubular injury, apoptosis, and fibrosis. Recent studies have provided insights into the intricate interplay between immune and metabolic pathways in kidney diseases, revealing novel therapeutic targets for the prevention and treatment of kidney diseases. Potential therapeutic strategies include modulating immune responses through targeting key immune factors or inhibiting pro-inflammatory signaling pathways, improving mitochondrial function, and targeting nutrient-sensing pathways, such as mTOR, AMPK, and SIRT1. This review highlights the importance of the interplay between immune and metabolic pathways in kidney diseases and the potential therapeutic implications of targeting these pathways.

Role of APE1/Ref-1 in hydrogen peroxide-induced apoptosis in human renal HK-2 cells.

Apurinic/apyrimidinic endonuclease 1/redox factor-1 (APE1/Ref-1) is a multipotent protein that plays essential roles in cellular responses to oxidative stress. To examine the role of APE1/Ref-1 in ischemia-reperfusion (I/R) injuries and hydrogen peroxide (H2O2)-induced renal tubular apoptosis, we studied male C57BL6 mice and human proximal tubular epithelial (HK-2) cells treated with H2O2 at different concentrations. The colocalization of APE1/Ref-1 in the proximal tubule, distal tubule, thick ascending limb, and collecting duct was observed with confocal microscopy. The overexpression of APE1/Ref-1 with knockdown cell lines using an APE1/Ref-1-specific DNA or small interfering RNA (siRNA) was used for the apoptosis assay. The promotor activity of nuclear factor kappa B (NF-κB) was assessed and electrophoretic mobility shift assay was conducted. APE1/Ref-1 was predominantly localized to the renal tubule nucleus. In renal I/R injuries, the levels of APE1/Ref-1 protein were increased compared with those in kidneys subjected to sham operations. The overexpression of APE1/Ref-1 in HK-2 cells enhanced the Bax/Bcl-2 ratio as a marker of apoptosis. Conversely, the suppression of APE1/Ref-1 expression by siRNA in 1-mM H2O2-treated HK-2 cells decreased the Bax/Bcl-2 ratio, the phosphorylation of extracellular signal-regulated kinase (ERK) 1/2, p38, c-Jun N-terminal kinase (JNK) 1/2, and NF-κB. In HK-2 cells, the promoter activity of NF-κB increased following H2O2 exposure, and this effect was further enhanced by APE1/Ref-1 transfection. The inhibition of APE1/Ref-1 with siRNA attenuated H2O2-induced apoptosis through the modulation of mitogen-activated protein kinase pathways mediated by ERK, JNK, and p38 and the nuclear activation of NF-κB and proapoptotic factors.

Regulatory roles of SP-A and exosomes in pneumonia-induced acute lung and kidney injuries.

Pneumonia-induced sepsis can cause multiple organ dysfunction including acute lung and kidney injury (ALI and AKI). Surfactant protein A (SP-A), a critical innate immune molecule, is expressed in the lung and kidney. Extracellular vesicles like exosomes are involved in the processes of pathophysiology. Here we tested one hypothesis that SP-A regulates pneumonia-induced AKI through the modulation of exosomes and cell death. Wild-type (WT), SP-A knockout (KO), and humanized SP-A transgenic (hTG, lung-specific SP-A expression) mice were used in this study. After intratracheal infection with Pseudomonas aeruginosa, KO mice showed increased mortality, higher injury scores, more severe inflammation in the lung and kidney, and increased serum TNF-α, IL-1β, and IL-6 levels compared to WT and hTG mice. Infected hTG mice exhibited similar lung injury but more severe kidney injury than infected WT mice. Increased renal tubular apoptosis and pyroptosis in the kidney of KO mice were found when compared with WT and hTG mice. We found that serum exosomes from septic mice cause ALI and AKI through mediating apoptosis and proptosis when mice were injected intravenously. Furthermore, primary proximal tubular epithelial cells isolated from KO mice showed more sensitivity than those from WT mice after exposure to septic serum exosomes. Collectively, SP-A attenuates pneumonia-induced ALI and AKI by regulating inflammation, apoptosis and pyroptosis; serum exosomes are important mediators in the pathogenesis of AKI.

Fenofibrate Attenuates Renal Tubular Cell Apoptosis by Up-Regulating MCAD in Diabetic Kidney Disease.

Diabetic kidney disease (DKD) is a major diabetic microvascular complication. Fatty acid-induced lipotoxicity and apoptosis were associated with the exacerbation of DKD. However, the association of lipotoxicity with renal tubular apoptosis and the effects of fenofibrate on DKD are not fully understood. Eight-week-old db/db mice were given fenofibrate or saline by gavage for 8 weeks. Human kidney proximal tubular epithelial (HK2) cells stimulated with palmitic acid (PA) and high glucose (HG) were used as a model of lipid metabolism disorders. Apoptosis was assessed with or without fenofibrate. The AMP-activated protein kinase (AMPK) activator 5-aminoimidazole-4-carboxamide ribonucleotide (AICAR) and AMPK inhibitor Compound C were used to determine the involvement of AMPK and Medium-chain acyl-CoA dehydrogenase (MCAD) in the regulation of lipid accumulation by fenofibrate. MCAD silencingwasachievedbysmall interfering RNA (siRNA)transfection. Fenofibrate reduced triglyceride (TG) content and lipid accumulation in DKD. Importantly, renalfunction and tubularcellapoptosis weresignificantlyimproved by fenofibrate. Fenofibrate reduced apoptosis, accompanied by increased activation of the AMPK/FOXA2/MCAD pathway. MCAD silencing resulted in apoptosis and lipid accumulation despite fenofibrate treatment. Fenofibrate improves lipid accumulation and apoptosis through the AMPK/FOXA2/MCAD pathway. MCAD may be a potential therapeutic target of DKD, and the use of fenofibrate as a treatment for DKD warrants further study.

Diminazene aceturate exacerbates renal fibrosis after unilateral ureteral obstruction in female mice.

Diminazene aceturate (DIZE), an angiotensin-converting enzyme 2 (ACE2) activator, exerts anti-inflammatory and antifibrotic effects in a variety of human chronic diseases. However, the role of DIZE in kidney fibrosis and the underlying mechanism remain unclear. Therefore, we investigated the effects of DIZE on the progression of renal fibrosis after unilateral ureteral obstruction (UUO), a well-established model of chronic kidney disease. C57BL/6 female or male mice were subjected to right UUO. Mice received 15 mg/kg DIZE or vehicle (saline) daily. On the 7th day after UUO, kidneys were collected for analysis of renal fibrosis (α-smooth muscle actin, phosphorylated SMAD3, transforming growth factor (TGF)-β, Masson's trichrome, and Sirius red staining), inflammation (macrophage infiltration, proinflammatory cytokines/ chemokines), apoptosis/necrotic cell death (TUNEL and periodic acid-Schiff staining), and ACE2 activity and messenger RNA (mRNA) expression. Treatment with DIZE exacerbated renal fibrosis by upregulating the profibrotic TGF-β/SMAD3 pathway, proinflammatory cytokine/chemokines (interleukin [IL]-1β, monocyte chemoattractant protein-1, IL-6, and macrophage inflammatory protein-2) levels, M2 macrophage accumulation (CD206, IL-4, IL-10, and CX3CL1), and apoptotic/necrotic cell death in the obstructed kidneys of female mice but not male mice. However, DIZE treatment had no effect on ACE2 activity or mRNA expression. DIZE exacerbates UUO-induced renal fibrosis by aggravating tubular damage, apoptosis, and inflammation through independent of angiotensin (1-7), angiotensin II levels, and ACE2 expression/activity, rather than protecting against renal fibrosis after UUO. DIZE also has powerful effects on recruiting macrophages, including the M2-polarized subtype, in female UUO mice.

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.

Evaluating the role of polysaccharide extracted from Pleurotus columbinus on cisplatin-induced oxidative renal injury

This research aimed to examine the antioxidant polysaccharide activity (PsPc-3) derived from Pleurotus columbinus (P. columbinus) on oxidative renal injury (ORI) induced by cisplatin (CP). The principal components of crude polysaccharide were assessed. We studied the preventive impact of polysaccharide on cisplatin-induced renal damage in this study. For 21 days, we employed the CP-induced ORI rat model and divided the rats into four groups: control, CP alone, polysaccharide post CP (100 mg/kg) orally, and CP + polysaccharide (pre and post). The chemical characterization of the polysaccharide fraction PsPc-3 stated that protein was not present. PsPc-3 contained 7.2% uronic acid as assessed as 0% sulfate. PsPc-3 hydrolysate structured of Galacturonic:Glucose:Xylose and their molar proportions were 1:4:5, respectively. The average molecular weight (Mw) and molecular mass (Mn) per molecule of PsPc-3 were 5.49 × 104 g/mol and Mn of 4.95 × 104 g/mol respectively. DPPH radical scavenging activity was demonstrated by the polysaccharide of 65.21–95.51% at 10 mg/ml with IC50 less than 10 mg/ml. CP increased serum urea to 92.0 mg/dl and creatinine up to 1.0 mg/dl, with a concurrent decrease in the levels of total protein to 4.0 mg/dl. Besides, Also, CP-induced ORI raised levels of malondialdehyde (MDA), alkaline phosphatase (ALP), and renal hormones (renin and aldosterone), with a decline in antioxidants compared to control rats. In addition, in the presence of CP, interleukin-6 (IL-6) and tumour necrosis factor-alpha (TNF-alpha) levels increased. PsPc-3 decreased these changes dramatically. PsPc-3 improves pathological renal damage caused by CP and decreases tubular apoptosis measured by DNA ladder formation and cleaved caspase- 3. These findings showed that PsPc-3 isolated from P. columbinus protects and inhibits tubular apoptosis in cisplatin-induced ORI. Furthermore, PsPc-3 has no influence on the anticancer efficacy of CP in rats. Thus, PsPc-3 derived from P. columbinus might provide a novel therapy method for cisplatin-induced nephrotoxicity.

Radioprotective effects of dexmedetomidine on X-ray-induced testicular damage.

Approximately 70% of cancer patients require radiotherapy. However, despite its effectiveness in the treatment of cancer, radiotherapy can also affect and damage surrounding healthy tissues in addition to tumorous tissues. Since testicular tissues are highly radiosensitive, radiotherapy can cause impairments in spermatogenesis leading to infertility. The purpose of this study was to examine the potential radio-protective effect of dexmedetomidine (Dex), an α2-adrenoceptor agonist, on oxidative stress and apoptosis in testicular tissues caused by x-irradiation in rats. Thirty male Sprague-Dawley rats were allocated into three groups of ten (n=10): control, irradiation (IR), and IR + Dex groups. The IR group was exposed to a single dose of 2 Gy IR. The IR+Dex group was given a single intraperitoneal (i.p.) dose of 100 µg/kg Dex before IR. The control group received a single dose of saline solution i.p. Testicular tissues removed 24 hours after IR were subjected to histochemical, biochemical, and immunohistochemical analysis. IR resulted in increased malondialdehyde (MDA) activity and significant changes in testis tissues. However, the application of Dex elevated glutathione levels by preventing MDA formation. In addition, Dex decreased tubular epithelial apoptosis via elevated Cleaved Caspase-3 expressions. Dex exhibited a radio-protective effect against lipid peroxidation and apoptosis caused by IR.

Direct targeting of sEH with alisol B alleviated the apoptosis, inflammation, and oxidative stress in cisplatin-induced acute kidney injury.

Acute kidney injury (AKI) is a pathological condition characterized by a rapid decrease in glomerular filtration rate and nitrogenous waste accumulation during hemodynamic regulation. Alisol B, from Alisma orientale, displays anti-tumor, anti-complement, and anti-inflammatory effects. However, its effect and action mechanism on AKI is still unclear. Herein, alisol B significantly attenuated cisplatin (Cis)-induced renal tubular apoptosis through decreasing expressions levels of cleaved-caspase 3 and cleaved-PARP and the ratio of Bax/Bcl-2 depended on the p53 pathway. Alisol B also alleviated Cis-induced inflammatory response (e.g. the increase of ICAM-1, MCP-1, COX-2, iNOS, IL-6, and TNF-α) and oxidative stress (e.g. the decrease of SOD and GSH, the decrease of HO-1, GCLC, GCLM, and NQO-1) through the NF-κB and Nrf2 pathways. In a target fishing experiment, alisol B bound to soluble epoxide hydrolase (sEH) as a direct cellular target through the hydrogen bond with Gln384, which was further supported by inhibition kinetics and surface plasmon resonance (equilibrium dissociation constant, K D = 1.32 μM). Notably, alisol B enhanced levels of epoxyeicosatrienoic acids and decreased levels of dihydroxyeicosatrienoic acids, indicating that alisol B reduced the sEH activity in vivo. In addition, sEH genetic deletion alleviated Cis-induced AKI and abolished the protective effect of alisol B in Cis-induced AKI as well. These findings indicated that alisol B targeted sEH to alleviate Cis-induced AKI via GSK3β-mediated p53, NF-κB, and Nrf2 signaling pathways and could be used as a potential therapeutic agent in the treatment of AKI.

The Protective Role of Strong Antioxidant Astaxanthin on Burn Wound and Burn-Induced Early Acute Kidney Injury through Abilities to Relieve Oxidative Stress and Inhibit Apoptosis by Modulating Mitochondrial-Apoptotic Pathways

Summary: Burns are skin damage caused by heat trauma or cold trauma (frost bite). Causes include fire, hot water, electricity, chemicals, radiation, and cold (frostbite). This damage may involve subcutaneous tissue. Burn injuries are associated with high incidence and prevalence, high risk of morbidity and mortality, resource-intensive, and costly. One of the most common complications in burn patients is acute kidney injury (AKI). The mechanism of early AKI after burn injury is multifactorial, and previous studies have mainly focused on oxidative stress injury, tubular apoptosis, and systemic or local inflammation. Previous results (from our group and others) suggested that ROS-induced oxidative stress damage and apoptosis play an important role in the development of early AKI due to burn injury, and that 24 h after burn injury are useful for observing changes in burn injury. It shows that it provides an important timeframe. Kidney function and levels of oxidative stress and apoptosis. Astaxanthin (ATX) is a naturally occurring carotenoid that is readily obtained from marine organisms and stronger antioxidant effects than other carotenoids. Given the critical role of oxidative stress and secondary renal inflammation in severe burn-induced early AKI, a protective role of ATX through its anti-inflammatory effects and potential mechanisms of action in early post-burn AKI is reasonable.

PARK7 is induced to protect against endotoxic acute kidney injury by suppressing NF-κB.

Sepsis is a leading cause of acute kidney injury (AKI), and the pathogenesis of septic AKI remains largely unclear. Parkinson disease protein 7 (PARK7) is a protein of multiple functions that was recently implicated in septic AKI, but the underlying mechanism is unknown. In the present study, we determined the role of PARK7 in septic AKI and further explored the underlying mechanism in lipopolysaccharide (LPS)-induced endotoxic models. PARK7 was induced both in vivo and in vitro following LPS treatment. Compared with wild-type (WT) mice, Park7-deficient mice experienced aggravated kidney tissue damage and dysfunction, and enhanced tubular apoptosis and inflammation following LPS treatment. Consistently, LPS-induced apoptosis and inflammation in renal tubular cells in vitro were exacerbated by Park7 knockdown, whereas they were alleviated by PARK7 overexpression. Mechanistically, silencing Park7 facilitated nuclear translocation and phosphorylation of p65 (a key component of the nuclear factor kappa B [NF-κB] complex) during LPS treatment, whereas PARK7 overexpression partially prevented these changes. Moreover, we detected PARK7 interaction with p65 in the cytoplasm in renal tubular cells, which was enhanced by LPS treatment. Collectively, these findings suggest that PARK7 is induced to protect against septic AKI through suppressing NF-κB signaling.

Cisplatin and AKI: an ongoing battle with new perspectives-a narrative review.

Acute kidney injury (AKI) is a growing global health problem with increased mortality and morbidity. Cisplatin is achemotherapy drug first introduced in 1978, and since then, it became one of the most widely used and successful anti-cancer medication. However, there are risks associated with cisplatin administration, such as nephrotoxicity. Mechanisms of nephrotoxicity include proximal tubular injury, DNA damage, apoptosis, inflammation, oxidative stress, and vascular injury. Although various protocols are being used in clinical practice in nephrotoxicity prevention due to cisplatin, there are no clear guidelines regarding this approach. Most recommendations include hydration and avoiding additional nephrotoxic drugs. To prevent nephrotoxicity, future perspectives could rely on natural products, such as flavonoids or saponins or pharmacological products, such as aprepitant, but data are scarce in this direction. Repetitive administration of cisplatin could cause subclinical kidney injury, which over time, leads to chronic kidney disease (CKD). Therefore, more studies are needed to determine possible ways to prevent nephrotoxicity and avoid the burden of CKD worldwide.

The Uremic Toxin Homocysteine Exacerbates the Brain Inflammation Induced by Renal Ischemia-Reperfusion in Mice.

Homocysteine (Hcy), a homologue of cysteine, is biosynthesized during methionine metabolism. Elevated plasma Hcy is associated with glomerular injury and considered as a risk factor for renal dysfunction, predicting incident chronic kidney disease. Hcy promotes oxidative stress, inflammation, and endothelial dysfunction. Acute kidney injury (AKI) is defined as a sudden decline in renal function and is important clinically due to the high mortality rate in AKI patients with multiple organs failure, including the brain. However, the cytotoxic role of Hcy on the brain following AKI is not directly shown. In this study, C57BL/6 mice were subjected to renal ischemia reperfusion (IR), one of the causes of AKI, and treated with vehicle or Hcy (0.2 mg/kg) to analyse the brain inflammation. IR mice showed a significant induction in plasma creatinine and Hcy levels, associated with tubular injury and neutrophil infiltration, and upregulation of pro-inflammatory cytokines and tubular apoptosis. Hcy treatment aggravated these renal damage and dysfunction by regulating cyclooxygenase-2 (COX-2), inhibitor of κB phosphorylation, and heme oxygenase-1. Consistently, Hcy treatment significantly increased expression of pro-inflammatory cytokines, glial fibrillary acidic protein, and COX-2 in the prefrontal cortex of IR mice. We conclude that Hcy treatment aggravated the renal dysfunction and enhanced IR-induced inflammatory cytokines and astrocyte activation in the brain. We propose that lowering plasma Hcy levels may attenuate neurological dysfunction found in patients with AKI.

Perilla frutescens L. alleviates trimethylamine N-oxide-induced apoptosis in the renal tubule by regulating ASK1-JNK phosphorylation.

Trimethylamine N-oxide (TMAO) is associated with overall mortality in patients with chronic kidney disease (CKD). Previous findings suggest that P. frutescens (L.) can alleviate renal injury, but its effects and mechanisms underlying alleviation of TMAO-induced kidney damage remain unclear. In this study, a TMAO injury model, in vivo and in vitro, was established to clarify the effects and mechanisms of P. frutescens in alleviating TMAO-induced kidney injury. The results show that TMAO (60 mM/L) can induce the activation of apoptosis signal-regulating kinase 1 (ASK1)-c-Jun N-terminal kinase (JNK), thus aggravating downstream cell apoptosis in vitro. The study also found that P. frutescens aqueous extract (PFAE) (5mg/mL) can inhibit TMAO-induced apoptosis by downregulating ASK1-JNK phosphorylation. In the in vivo experiments, it was demonstrated that TMAO can increase the levels of blood urea nitrogen and cystatin C, aggravating renal tubular epithelial apoptosis. The results also show that PFAE can reduce TMAO-induced renal damage by inhibiting ASK1-JNK phosphorylation in vivo. Our findings confirmed that P. frutescens can alleviate TMAO-induced renal tubule apoptosis by regulating ASK1-JNK phosphorylation, indicating that P. frutescens may be an effective treatment for alleviating TMAO damage in CKD.

Interleukin 24 promotes cell death in renal epithelial cells and is associated with acute renal injury

Ischemia-reperfusion injury is a major cause of acute kidney injury. Many cytokines are involved in the pathogenesis of renal ischemia-reperfusion injury. IL24 is a member of the IL10 family and has gained importance because of its apoptosis-inducing effects in tumor disease besides its immunoregulative function. Littles is known about the role of IL24 in kidney disease. Using a mouse model, we found that IL24 is upregulated in the kidney after renal ischemia-reperfusion injury and that tubular epithelial cells and infiltrating inflammatory cells are the source of IL24. Mice lacking IL24 are protected from renal injury and inflammation. Cell culture studies showed that IL24 induces apoptosis in renal tubular epithelial cells, which is accompanied by an increased endoplasmatic reticulum stress response. Moreover, IL24 induces robust expression of endogenous IL24 in tubular cells, fostering ER-stress and apoptosis. In kidney transplant recipients with delayed graft function and patients at high risk to develop acute kidney injury after cardiac surgery IL24 is upregulated in the kidney and serum. Taken together, IL24 can serve as a biomarker, plays an important mechanistic role involving both extracellular and intracellular targets, and is a promising therapeutic target in patients at risk of or with ischemia-induced acute kidney injury.

Methotrexate-Induced Alteration of Renal Aquaporins 1 and 2, Oxidative Stress and Tubular Apoptosis Can Be Attenuated by Omega-3 Fatty Acids Supplementation

Methotrexate (MTX) is a potent anti-cancer drug, commonly associated with nephrotoxicity via the induction of oxidative stress and apoptosis with alteration of renal water channel proteins, namely aquaporins (AQPs). Omega-3 long-chain polyunsaturated fatty acids (LC-PUFA) have shown cytoprotective effects through their anti-oxidant and antiapoptotic activities. The present study aims for the first time to explore the role of LC-PUFA against MTX-induced nephrotoxicity. Rats were divided into the following groups: saline control, LC-PUFA control, MTX, MTX + LC-PUFA (150 mg/kg), or MTX + LC-PUFA (300 mg/kg). Then, H&E staining and immunohistochemical staining for the anti-apoptosis marker B-cell lymphoma 2 (BCL-2), the apoptosis marker BCL2-Associated X Protein (BAX), the proinflammatory marker Nuclear factor kappa B (NF-kB), AQPs 1 and 2 were performed in kidney sections with an assessment of renal oxidative stress. The MTX caused a renal histopathological alteration, upregulated renal BAX and NF-kB, downregulated Bcl-2 and AQP1, altered the distribution of AQP2, and caused oxidative stress. The LC-PUFA attenuated the pathological changes and decreased renal BAX and NF-kB, increased BCL-2 and AQP1, restored the normal distribution of AQP2, and decreased the oxidative stress. Therefore, LC-PUFA is a good adjuvant to MTX to prevent its adverse effects on kidneys through its antiapoptotic, antioxidant, and anti-inflammatory effect and its role in the restoration of the expression of AQPs 1 and 2.

The α7 nicotinic acetylcholine receptor agonist PNU-282987 ameliorates sepsis-induced acute kidney injury through CD4+CD25+ regulatory T cells in rats.

The ameliorative effects of α7 nicotinic acetylcholine receptor (α7nAChR) agonists have been demonstrated in acute kidney injury (AKI) caused by multiple stimulations. However, the ameliorative effect of α7nAChR on sepsis-induced acute kidney injury (SAKI) in the cecal ligation and puncture (CLP) model is unclear. Previous studies have demonstrated that α7nAChR is highly expressed on the surface of CD4+CD25+ regulatory T cells (Tregs). However, the role of Tregs in SAKI is unclear. We hypothesized that Tregs might play a role in the ameliorative effect of α7nAChR on SAKI. Hence, in this study, we determined the effects of PNU-282987 (a selective α7nAchR agonist) on SAKI and evaluated whether PNU-282987 would attenuate SAKI via regulating Tregs. Our study showed that immediate administration of PNU-282987 after CLP surgery in rats improved renal function, reduced levels of systemic inflammatory factors (tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6), etc.), inflammatory cell infiltration and tubular apoptosis in renal tissues, and increased forkhead/winged helix transcription factor p3 (Foxp3) and cytotoxic T-lymphocyte-associated protein 4 (CTLA-4) expression indicating activated Tregs. Moreover, in in vitro experiments, isolated Tregs co-cultured with PNU-282987 also displayed enhanced expression of CTLA-4 and Foxp3. Furthermore, Tregs were co-cultured with PNU-282987 for 24 hours and then reinfused into rats through the tail vein immediately after CLP surgery, and a significant renal protective effect was observed 24 hours postoperatively. These results demonstrate that PNU-282987 exerts its renal protective effects on SAKI through activation of Tregs.

Histone methyltransferase MLL1 drives renal tubular cell apoptosis by p53-dependent repression of E-cadherin during cisplatin-induced acute kidney injury

Mixed lineage leukemia 1 (MLL1) is a histone H3 lysine 4 (H3K4) methyltransferase that interacts with WD repeat domain 5 (WDR5) to regulate cell survival, proliferation, and senescence. The role of MLL1 in the pathogenesis of acute kidney injury (AKI) is unknown. In this study, we demonstrate that MLL1, WDR5, and trimethylated H3K4 (H3K4me3) were upregulated in renal tubular cells of cisplatin-induced AKI in mice, along with increased phosphorylation of p53 and decreased expression of E-cadherin. Administration of MM102, a selective MLL1/WDR5 complex inhibitor, improved renal function and attenuated tubular injury and apoptosis, while repressing MLL1, WDR5, and H3K4me3, dephosphorylating p53 and preserving E-cadherin. In cultured mouse renal proximal tubular cells (RPTCs) exposed to cisplatin, treatment with MM102 or transfection with siRNAs for either MLL1 or WDR5 also inhibited apoptosis and p53 phosphorylation while preserving E-cadherin expression; p53 inhibition with Pifithrin-α lowered cisplatin-induced apoptosis without affecting expression of MLL1, WDR5, and H3K4me3. Interestingly, silencing of E-cadherin offset MM102’s cytoprotective effects, but had no effect on p53 phosphorylation. These findings suggest that MLL1/WDR5 activates p53, which, in turn, represses E-cadherin, leading to apoptosis during cisplatin-induced AKI. Further studies showed that MM102 effectively inhibited cisplatin-triggered DNA damage response (DDR), as indicated by dephosphorylation of ataxia telangiectasia mutated (ATM) and ATM and Rad-3 related (ATR) proteins, dephosphorylation of checkpoint kinase 1 and 2 (Chk1 and Chk2); depression of γ-H2AX; and restrained cell cycle arrest, as evidenced by decreased expression of p21 and phospho-histone H3 at serine 10 in vitro and in vivo. Overall, we identify MLL1 as a novel DDR regulator that drives cisplatin-induced RPTC apoptosis and AKI by modulating the MLL1/WDR5-/ATR/ATM-Chk-p53-E-cadherin axis. Targeting the MLL1/WDR5 complex may have a therapeutic potential for the treatment of AKI.