Cryptotanshinone inhibits hypoxia/reoxygenation-induced oxidative stress and apoptosis in renal tubular epithelial cells

Cryptotanshinone (CTS), an active component extracted from the root of Salvia miltiorrhiza Bunge , was reported to attenuate hepatic ischemia/reperfusion (I/R) injury. However, its protective effect against renal I/R injury remains unclear. In this study, the role of CTS in renal I/R injury in vitro and its possible mechanism were investigated. Our results showed that CTS improved cell viability in HK-2 cells exposed to hypoxia/reoxygenation (H/R). CTS also inhibited the H/R-mediated production of reactive oxygen species, as well as increased the activities of superoxide dismutase and catalase in H/R-stimulated HK-2 cells. In addition, CTS dramatically attenuated the induction of bax expression and caspase-3 activity and alleviated the reduction of bcl-2 expression in HK-2 cells cultured with H/R. Furthermore, CTS activated the levels of p-PI3K and p-Akt in H/R-injured HK-2 cells; meanwhile, the renal protective activity of CTS was inhibited by the inhibitor of the (phosphatidylinositol 3 kinase/protein kinase B) PI3K/Akt pathway (LY294002). These findings indicate that CTS can ameliorate renal I/R injury in vitro partly through regulating the PI3K/Akt pathway.     

METTL14-regulated PI3K/Akt signaling pathway via PTEN affects HDAC5-mediated epithelial–mesenchymal transition of renal tubular cells in diabetic kidney disease

Histone deacetylase 5 (HDAC5) belongs to class II HDAC subfamily and is reported to be increased in the kidneys of diabetic patients and animals. However, little is known about its function and the exact mechanism in diabetic kidney disease (DKD). Here, we found that HDAC5 was located in renal glomeruli and tubular cells, and significantly upregulated in diabetic mice and UUO mice, especially in renal tubular cells and interstitium. Knockdown of HDAC5 ameliorated high glucose-induced epithelial–mesenchymal transition (EMT) of HK2 cells, indicated in the increased E-cadherin and decreased α-SMA, via the downregulation of TGF-β1. Furthermore, HDAC5 expression was regulated by PI3K/Akt signaling pathway and inhibition of PI3K/Akt pathway by LY294002 treatment or Akt phosphorylation mutation reduced HDAC5 and TGF-β1 expression in vitro high glucose-cultured HK2 cells. Again, high glucose stimulation downregulated total m6A RNA methylation level of HK2 cells. Then, m6A demethylase inhibitor MA2 treatment decreased Akt phosphorylation, HDAC5, and TGF-β1 expression in high glucose-cultured HK2 cells. In addition, m6A modification-associated methylase METTL3 and METTL14 were decreased by high glucose at the levels of mRNA and protein. METTL14 not METTL3 overexpression led to PI3K/Akt pathway inactivation in high glucose-treated HK2 cells by enhancing PTEN, followed by HDAC5 and TGF-β1 expression downregulation. Finally, in vivo HDACs inhibitor TSA treatment alleviated extracellular matrix accumulation in kidneys of diabetic mice, accompanied with HDAC5, TGF-β1, and α-SMA expression downregulation. These above data suggest that METTL14-regulated PI3K/Akt signaling pathway via PTEN affected HDAC5-mediated EMT of renal tubular cells in diabetic kidney disease.Subject terms: Epithelial-mesenchymal transition, Insulin signalling, Diabetes complications     

TLR2 protects cisplatin-induced acute kidney injury associated with autophagy via PI3K/Akt signaling pathway

Toll-like receptors (TLRs), which are essential components of the innate immune response, play an important role in acute kidney injury (AKI). Toll-like receptor 2 (TLR2) is constitutively expressed in tubular epithelial cells of the kidney and participates in cisplatin-induced AKI. The autophagy is a dynamic catabolic process that maintains intracellular homeostasis, which is involved in the pathogenesis of AKI. Recent studies demonstrate that PI3K/Akt signaling pathway regulates autophagy in response to various stimuli. Therefore, we propose that cisplatin might activate TLR2, which subsequently phosphorylates PI3K/Akt, leading to enhanced autophagy of renal tubular epithelial cells and protecting cisplatin-induced AKI. We found that TLR2 expression was significantly increased in the kidney after the cisplatin treatment. TLR2-deficient mice exacerbated renal injury in cisplatin-induced AKI, with higher serum creatinine and blood urea nitrogen, more severe morphological injury compared with that of wild-type mice. In vitro, we found that inhibition of TLR2 reduced tubular epithelial cell autophagy after the cisplatin treatment. Mechanistically, TLR2 inhibited autophagy via activating PI3K/Akt signaling pathway in renal tubular epithelial cells after the cisplatin treatment. Take together, these results suggest that TLR2 may protect cisplatin-induced AKI by activating autophagy via PI3K/Akt signaling pathway.     

Sulodexide attenuates endoplasmic reticulum stress induced by myocardial ischaemia/reperfusion by activating the PI3K/Akt pathway

Acute myocardial ischaemia/reperfusion (MI/R) injury causes severe arrhythmias with a high rate of lethality. Extensive research focus on endoplasmic reticulum (ER) stress and its dysfunction which leads to cardiac injury in MI/R Our study evaluated the effects of sulodexide (SDX) on MI/R by establishing MI/R mice models and in vitro oxidative stress models in H9C2 cells. We found that SDX decreases cardiac injury during ischaemia reperfusion and decreased myocardial apoptosis and infarct area, which was paralleled by increased superoxide dismutase and reduced malondialdehyde in mice plasm, increased Bcl‐2 expression, decreased BAX expression in a mouse model of MI/R. In vitro, SDX exerted a protective effect by the suppression of the ER stress which induced by tert‐butyl hydroperoxide (TBHP) treatment. Both of the in vivo and in vitro effects were involved in the phosphatidylinositol 3‐kinase (PI3K)/Akt signalling pathway. Inhibition of PI3K/Akt pathway by specific inhibitor, LY294002, partially reduced the protective effect of SDX. In short, our results suggested that the cardioprotective role of SDX was related to the suppression of ER stress in mice MI/R models and TBHP‐induced H9C2 cell injury which was through the PI3K/Akt signalling pathway.     

Penehyclidine hydrochloride protects against anoxia/reoxygenation injury in cardiomyocytes through ATP‐sensitive potassium channels,and the Akt/GSK‐3β and Akt/mTOR signaling pathways

Penehyclidine hydrochloride (PHC) can protect against myocardial ischemia/reperfusion (I/R) injury. However, the possible mechanisms of PHC in anoxia/reoxygenation (A/R)‐induced injury in H9c2 cells remain unclear. In the present study, H9c2 cells were pretreated with PI3K/Akt inhibitor LY294002, ATP‐sensitive K⁺ (KATP) channel blocker 5‐hydroxydecanoate (5‐HD), PHC, or KATP channel opener diazoxide (DZ) before subjecting to A/R injury. Cell viability and cell apoptosis were determined by cell counting kit‐8 assay and annexin V/PI assay, respectively. Myocardial injury was evaluated by measuring creatine kinase (CK) and lactate dehydrogenase (LDH) activities. Intracellular Ca²⁺ levels, reactive oxygen species (ROS) generation, mitochondrial membrane potential (ΔΨ_m), and mitochondrial permeability transition pore (mPTP) were measured. The levels of cytoplasmic/mitochondrial cytochrome c (Cyt‐C), Bax, Bcl‐2, cleaved caspase‐3, KATP channel subunits (Kir6.2 and SUR2A), and the members of the Akt/GSK‐3β and Akt/mTOR signaling pathways were determined by western blotting. We found that PHC preconditioning alleviated A/R‐induced cell injury by increasing cell viability, reducing CK and LDH activities, and inhibiting cell apoptosis. In addition, PHC preconditioning ameliorated intracellular Ca²⁺ overload and ROS production, accompanied by inhibition of both mPTP opening and Cyt‐C release into cytoplasm, and maintenance of ΔΨ_m. Moreover, PHC preconditioning activated mitochondrial KATP channels, and modulated the Akt/GSK‐3β and Akt/mTOR signaling pathways. Similar effects were observed upon treatment with DZ. Pretreatment with LY294002 or 5‐HD blocked the beneficial effects of PHC. These results suggest that the protective effects of PHC preconditioning on A/R injury may be related to mitochondrial KATP channels, as well as the Akt/GSK‐3β and Akt/mTOR signaling pathways.     

bFGF attenuates endoplasmic reticulum stress and mitochondrial injury on myocardial ischaemia/reperfusion via activation of PI3K/Akt/ERK1/2 pathway

Extensive research focused on finding effective strategies to prevent or improve recovery from myocardial ischaemia/reperfusion (I/R) injury. Basic fibroblast growth factor (bFGF) has been shown to have therapeutic potential in some heart disorders, including ischaemic injury. In this study, we demonstrate that bFGF administration can inhibit the endoplasmic reticulum (ER) stress and mitochondrial dysfunction induced in the heart in a mouse model of I/R injury. In vitro, bFGF exerts a protective effect by inhibiting the ER stress response and mitochondrial dysfunction proteins that are induced by tert‐Butyl hydroperoxide (TBHP) treatment. Both of these in vivo and in vitro effects are related to the activation of two downstream signalling pathways, PI3K/Akt and ERK1/2. Inhibition of these PI3K/Akt and ERK1/2 pathways by specific inhibitors, LY294002 and PD98059, partially reduces the protective effect of bFGF. Taken together, our results indicate that the cardioprotective role of bFGF involves the suppression of ER stress and mitochondrial dysfunction in ischaemic oxidative damage models and oxidative stress‐induced H9C2 cell injury; furthermore, these effects underlie the activation of the PI3K/Akt and ERK1/2 signalling pathways.     

Effects of astragalus polysaccharide on apoptosis of myocardial microvascular endothelial cells in rats undergoing hypoxia/reoxygenation by mediation of the PI3K/Akt/eNOS signaling pathway

The study explores the effect of astragalus polysaccharide (APS) mediating P13K/Akt/eNOS signaling pathway on apoptosis of myocardial microvascular endothelial cells (MMECs) in hypoxia/reoxygenation (H/R). MMECs were classified into blank, H/R, H/R + 25 mg/L APS, H/R + 50 mg/L APS, H/R + 100 mg/L APS, H/R + LY, and HR + 100 mg/L APS + LY groups. Cell viability was detected using MTT assay and apoptotic cell morphological changes by Hoechst staining. NO content, cell cycle and apoptosis, PI3K/Akt/eNOS signaling pathway proteins were detected using nitrate reductase assay, flow cytometry and Western blotting. An increased cell survival rate, NO content and expression of PI3K/Akt/eNOS signaling pathway associated proteins, and a decreased apoptosis rate was observed in the H/R + 50 mg/L APS and H/R + 100 mg/L APS groups compared with the H/R and H/R + 25 mg/L APS groups. Compared with the H/R + 50 mg/L APS group, the apoptosis rate decreased, whereas the cell survival rate, NO content and expression of PI3K/Akt/eNOS signaling pathway associated proteins increased in the H/R + 100 mg/L APS group. The H/R + LY and HR + 100 mg/L APS + LY groups followed opposite trends. In comparison to the HR + 100 mg/L APS group, the apoptosis rate in the H/R + LY and HR + 100 mg/L APS + LY groups increased, and the cell survival rate, NO content and expression of PI3K/Akt/eNOS signaling pathway associated proteins decreased. Collectively, APS improves the damage caused by H/P by mediating PI3K/Akt/eNOS signaling pathway.     

Uric acid induced epithelial−mesenchymal transition of renal tubular cells through PI3K/p-Akt signaling pathway

The phenotypic changes of tubular epithelial cell are hallmark features of renal diseases caused by abnormal uric acid levels. We hereby intend to investigate whether PI3K/p-Akt signaling plays a role in uric-acid induced epithelial−mesenchymal transition process. The normal rat kidney cell line (NRK-52E) was used as a proximal tubular cell model in this study. NRK-52E cells were exposed to different concentrations of uric acid, or PI3K inhibitor LY294002, or both, respectively. The effects of uric acid on cell morphology were examined by phase contrast microscopy, while molecular alternations were assessed by western blot analysis and immunofluorescence staining. We found that uric acid induced visible morphological alterations in NRK-52E cells accompanied by increased expression of α-smooth muscle actin and reduced expression of E-cadherin. Moreover, phosphorylation of Akt protein was obviously increased, whereas Akt level remained stable. Furthermore, the above effects were abolished when PI3K/p-Akt pathway was blocked by the PI3K inhibitor. These findings demonstrated that high uric acid could induce phenotypic transition of cultured renal tubular cells, which was probably via activating PI3K/p-Akt signaling pathway.     

Salidroside suppressing LPS‐induced myocardial injury by inhibiting ROS‐mediated PI3K/Akt/mTOR pathway in vitro and in vivo

The purpose of the present study was to investigate the effect of salidroside (Sal) on myocardial injury in lipopolysaccharide (LPS)‐induced endotoxemic in vitro and in vivo. SD rats were randomly divided into five groups: control group, LPS group (15 mg/kg), LPS plus dexamethasone (2 mg/kg), LPS plus Sal groups with different Sal doses (20, 40 mg/kg). Hemodynamic measurement and haematoxylin and eosin staining were performed. Serum levels of creatine kinase (CK), lactate dehydrogenase, the activities of the antioxidant enzymes catalase (CAT), superoxide dismutase (SOD), glutathione peroxidase (GSH‐px), glutathione, tumour necrosis factor‐α (TNF‐α), interleukin‐6 (IL‐6), and interleukin‐1β (IL‐1β) were measured after the rats were killed. iNOS, COX‐2, NF‐κB and PI3K/Akt/mTOR pathway proteins were detected by Western blot. In vitro, we evaluated the protective effect of Sal on rat embryonic heart‐derived myogenic cell line H9c2 induced by LPS. Reactive oxygen species (ROS) in H9c2 cells was measured by flow cytometry, and the activities of the antioxidant enzymes CAT, SOD, GSH‐px, glutathione‐S‐transferase, TNF‐α, IL‐6 and IL‐1β in cellular supernatant were measured. PI3K/Akt/mTOR signalling was examined by Western blot. As a result, Sal significantly attenuated the above indices. In addition, Sal exerts pronounced cardioprotective effect in rats subjected to LPS possibly through inhibiting the iNOS, COX‐2, NF‐κB and PI3K/Akt/mTOR pathway in vivo. Furthermore, the pharmacological effect of Sal associated with the ROS‐mediated PI3K/Akt/mTOR pathway was proved by the use of ROS scavenger, N‐acetyl‐l ‐cysteine, in LPS‐stimulated H9C2 cells. Our results indicated that Sal could be a potential therapeutic agent for the treatment of cardiovascular disease.     

Gastrin-releasing peptide receptor gene silencing inhibits the development of the epithelial–mesenchymal transition and formation of a calcium oxalate crystal in renal tubular epithelial cells in mice with kidney stones via the PI3K/Akt signaling pathway

Between 1% and 15% of people are globally affected by kidney stones, and this disease has become more common since the 1970s. Therefore, this study aims to investigate the effects of gastrin-releasing peptide receptor (GRPR) gene silencing via the PI3K/Akt signaling pathway on the development of the epithelial–mesenchymal transition (EMT) and formation of a calcium oxalate crystal in renal tubular epithelial cells (TECs) of kidney stones. A total of 70 clean and healthy C57BL/6J mice were assigned into the normal ( n = 10) and kidney stones groups ( n = 60). The underlying regulatory mechanisms of GRPR were analyzed in concert with the treatment of shGRPR-1, LY294002, and shGRPR-1 + LY294002 in TECs isolated from mice with kidney stones. A series of experiments were conducted for the measurement of urinary oxalate and urinary calcium, the renal calcium salt deposition, the positive rate of GRPR, the expressions of renal TECs related genes and calcium oxalate regulation related genes, and the growth of calcium crystals induced by cells. After treatment of shGRPR-1 and shGRPR-1 + LY294002, levels of urinary oxalate and urinary calcium in the serum, as well as positive rate of GRPR, became relatively low, levels of E-cadherin enhanced, whereas levels of Akt, PI3K, GRPR, extents of PI3K and Akt phosphorylation, α-SMA, Vimentin and FSP-1, OPN, MCP-1, and CD44 decreased and a number of crystals reduced. Taken together, we conclude that GRPR gene silencing suppresses the development of the EMT and formation of the calcium oxalate crystal in renal TECs of kidney stones through the inactivation of the PI3K/Akt signaling pathway.     

IL‐17A‐producing T cells exacerbate fine particulate matter‐induced lung inflammation and fibrosis by inhibiting PI3K/Akt/mTOR‐mediated autophagy

Fine particulate matter (PM2.5) is the primary air pollutant that is able to induce airway injury. Compelling evidence has shown the involvement of IL‐17A in lung injury, while its contribution to PM2.5‐induced lung injury remains largely unknown. Here, we probed into the possible role of IL‐17A in mouse models of PM2.5‐induced lung injury. Mice were instilled with PM2.5 to construct a lung injury model. Flow cytometry was carried out to isolate γδT and Th17 cells. ELISA was adopted to detect the expression of inflammatory factors in the supernatant of lavage fluid. Primary bronchial epithelial cells (mBECs) were extracted, and the expression of TGF signalling pathway‐, autophagy‐ and PI3K/Akt/mTOR signalling pathway‐related proteins in mBECs was detected by immunofluorescence assay and Western blot analysis. The mitochondrial function was also evaluated. PM2.5 aggravated the inflammatory response through enhancing the secretion of IL‐17A by γδT/Th17 cells. Meanwhile, PM2.5 activated the TGF signalling pathway and induced EMT progression in bronchial epithelial cells, thereby contributing to pulmonary fibrosis. Besides, PM2.5 suppressed autophagy of bronchial epithelial cells by up‐regulating IL‐17A, which in turn activated the PI3K/Akt/mTOR signalling pathway. Furthermore, IL‐17A impaired the energy metabolism of airway epithelial cells in the PM2.5‐induced models. This study suggested that PM2.5 could inhibit autophagy of bronchial epithelial cells and promote pulmonary inflammation and fibrosis by inducing the secretion of IL‐17A in γδT and Th17 cells and regulating the PI3K/Akt/mTOR signalling pathway.     

Circular RNA YAP1 acts as the sponge of microRNA‐21‐5p to secure HK‐2 cells from ischaemia/reperfusion‐induced injury

Circular RNA YAP1 (circYAP1) was reported to participate in progression of gastric cancer. However, the role of circYAP1 in acute kidney injury (AKI) remains obscure. We attempted to examine the effects of circYAP1 on ischaemia/reperfusion‐stimulated renal injury. AKI model was established by treating HK‐2 cells in ischaemia/reperfusion (I/R) environment. CircYAP1 expression in blood of AKI patients and I/R‐treated HK‐2 cells was evaluated via RT‐qPCR. CCK‐8, flow cytometry, ELISA and ROS assay were executed to test the impact of circYAP1 on cell viability, apoptosis, inflammatory cytokines and ROS generation. Bioinformatic analysis was executed to explore miRNA targets. The relativity between circYAP1 and miR‐21‐5p was verified by RT‐qPCR and luciferase assay. The functions of miR‐21‐5p in I/R‐triggered injury were reassessed. PI3K/AKT/mTOR pathway was detected by Western blot. Down‐regulated circYAP1 was observed in AKI blood samples and I/R‐treated HK‐2 cells. CircYAP1 overexpression expedited cell growth and weakened secretion of inflammatory factors and ROS generation in I/R‐disposed cells. Besides, we found circYAP1 could sponge to miR‐21‐5p. Interestingly, miR‐21‐5p overexpression overturned the repressive effects of circYAP1 on cell injury. Moreover, PI3K/AKT/mTOR pathway was activated by circYAP1 via inhibiting miR‐21‐5p. We demonstrated that circYAP1 activated PI3K/AKT/mTOR pathway and secured HK‐2 cells from I/R injury via sponging miR‐21‐5p.     

γ‐secretase inhibitor DAPT mitigates cisplatin‐induced acute kidney injury by suppressing Notch1 signaling

Organ toxicity, including kidney injury, limits the use of cisplatin for the treatment of multiple human cancers. Hence, interventions to alleviate cisplatin‐induced nephropathy are of benefit to cancer patients. Recent studies have demonstrated that pharmacological inhibition of the Notch signaling pathway enhances cisplatin efficacy against several cancer cells. However, whether augmentation of the anti‐cancer effect of cisplatin by Notch inhibition comes at the cost of increased kidney injury is unclear. We show here that treatment of mice with cisplatin resulted in a significant increase in Notch ligand Delta‐like 1 (Dll1) and Notch1 intracellular domain (N1ICD) protein expression levels in the kidneys. N‐[N‐(3,5‐difluorophenacetyl)‐L‐alanyl]‐S‐phenylglycine t‐butyl ester (DAPT), a γ‐secretase inhibitor reversed cisplatin‐induced increase in renal N1ICD expression and plasma or urinary levels of predictive biomarkers of acute kidney injury (AKI). DAPT also mitigated cisplatin‐induced tubular injury and reduction in glomerular filtration rate. Real‐time multiphoton microscopy revealed marked necrosis and peritubular vascular dysfunction in the kidneys of cisplatin‐treated mice which were abrogated by DAPT. Cisplatin‐induced Dll1/Notch1 signaling was recapitulated in a human proximal tubule epithelial cell line (HK‐2). siRNA‐mediated Dll1 knockdown and DAPT attenuated cisplatin‐induced Notch1 cleavage and cytotoxicity in HK‐2 cells. These data suggest that Dll1‐mediated Notch1 signaling contributes to cisplatin‐induced AKI. Hence, the Notch signaling pathway could be a potential therapeutic target to alleviate renal complications associated with cisplatin chemotherapy.     

Protective effect of N-acetylcysteine (NAC) on renal ischemia/reperfusion injury through Nrf2 signaling pathway

Abstract

The aim of this study was to investigate whether N-acetylcysteine (NAC), a known antioxidant, can protect kidney against ischemic injury through regulating Nrf2 signaling pathway. The expression of Nrf2, HO-1 and cleaved caspase 3 were analyzed by Western blot analysis. Apoptosis of renal tubular epithelial cells was assessed by the TUNEL method. Malondialdehyde (MDA) levels were measured by the thiobarbituric acid reaction. Blood serum creatinine and blood urea nitrogen levels were measured with an Olympus automatic multi-analyzer. We found that NAC significantly increased Nrf2 and downstream HO-1 expression. Furthermore, NAC significantly decreased cleaved caspase 3, p53 and renal epithelial tubular cell apoptosis. In addition, NAC reduced the MDA level. These findings suggest that the protective action of NAC on ischemia renal injury is associated closely with Nrf2 signaling pathway.     

Effects and mechanism of miR-23b on glucose-mediated epithelial-to-mesenchymal transition in diabetic nephropathy

MicroRNAs (miRNAs) play important roles in epithelial-to-mesenchymal transition (EMT). Moreover, hyperglycaemia induces damage to renal tubular epithelial cells, which may lead to EMT in diabetic nephropathy. However, the effects of miRNAs on EMT in diabetic nephropathy are poorly understood. In the present study, we found that the level of microRNA-23b (miR-23b) was significantly decreased in high glucose (HG)-induced human kidney proximal tubular epithelial cells (HK2) and in kidney tissues of db/db mice. Overexpression of miR-23b attenuated HG-induced EMT, whereas knockdown of miR-23b induced normal glucose (NG)-mediated EMT in HK2 cells. Mechanistically, miR-23b suppressed EMT in diabetic nephropathy by targeting high mobility group A2 (HMGA2), thereby repressing PI3K-AKT signalling pathway activation. Additionally, HMGA2 knockdown or inhibition of the PI3K-AKT signalling pathway with LY294002 mimicked the effects of miR-23b overexpression on HG-mediated EMT, whereas HMGA2 overexpression or activation of the PI3K-AKT signalling pathway with BpV prevented the effects of miR-23b on HG-mediated EMT. We also confirmed that overexpression of miR-23b alleviated EMT, decreased the expression levels of EMT-related genes, ameliorated renal morphology, glycogen accumulation, fibrotic responses and improved renal functions in db/db mice. Taken together, we showed for the first time that miR-23b acts as a suppressor of EMT in diabetic nephropathy through repressing PI3K-AKT signalling pathway activation by targeting HMGA2, which maybe a potential therapeutic target for diabetes-induced renal dysfunction.     

Improved Mitochondrial Function Underlies the Protective Effect of Pirfenidone against Tubulointerstitial Fibrosis in 5/6 Nephrectomized Rats

Dysfunctional mitochondria participate in the progression of chronic kidney disease (CKD). Pirfenidone is a newly identified anti-fibrotic drug. However, its mechanism remains unclear. Mitochondrial dysfunction is an early event that occurs prior to the onset of renal fibrosis. In this context, we investigated the protective effect of pirfenidone on mitochondria and its relevance to apoptosis and oxidative stress in renal proximal tubular cells. A remnant kidney rat model was established. Human renal proximal tubular epithelial cells (HK2) using rotenone, a mitochondrial respiratory chain complex Ι inhibitor were further investigated in vitro to examine the mitochondrial protective effect of pirfenidone. Pirfenidone protected mitochondrial structures and functions by stabilizing the mitochondrial membrane potential, maintaining ATP production and improving the mitochondrial DNA (mtDNA) copy number. Pirfenidone decreased tubular cell apoptosis by inhibiting the mitochondrial apoptotic signaling pathway. Pirfenidone also reduced oxidative stress by enhancing manganese superoxide dismutase (Mn-SOD) and inhibiting intracellular reactive oxygen species (ROS) generation, which suggested that the anti-oxidant effects occurred at least partially via the mitochondrial pathway. Pirfenidone may be effective prior to the onset of renal fibrosis because this drug exerts its anti-fibrotic effect by protection of mitochondria in renal proximal tubular cells.     

Acute treatment with relaxin protects the kidney against ischaemia/reperfusion injury

Although recent preclinical and clinical studies have demonstrated that recombinant human relaxin (rhRLX) may have important therapeutic potential in acute heart failure and chronic kidney diseases, the effects of acute rhRLX administration against renal ischaemia/reperfusion (I/R) injury have never been investigated. Using a rat model of 1‐hr bilateral renal artery occlusion followed by 6‐hr reperfusion, we investigated the effects of rhRLX (5 μg/Kg i.v.) given both at the beginning and after 3 hrs of reperfusion. Acute rhRLX administration attenuated the functional renal injury (increase in serum urea and creatinine), glomerular dysfunction (decrease in creatinine clearance) and tubular dysfunction (increase in urinary excretion of N‐acetyl‐β‐glucosaminidase) evoked by renal I/R. These beneficial effects were accompanied by a significant reduction in local lipid peroxidation, free radical‐induced DNA damage and increase in the expression/activity of the endogenous antioxidant enzymes Mn‐ and CuZn‐superoxide dismutases (SOD). Furthermore, rhRLX administration attenuated the increase in leucocyte activation, as suggested by inhibition of myeloperoxidase activity, intercellular‐adhesion‐molecule‐1 expression, interleukin (IL)‐1β, IL‐18 and tumour necrosis factor‐α production as well as increase in IL‐10 production. Interestingly, the reduced oxidative stress status and neutrophil activation here reported were associated with rhRLX‐induced activation of endothelial nitric oxide synthase and up‐regulation of inducible nitric oxide synthase, possibly secondary to activation of Akt and the extracellular signal‐regulated protein kinase (ERK) 1/2, respectively. Thus, we report herein that rhRLX protects the kidney against I/R injury by a mechanism that involves changes in nitric oxide signalling pathway.     

Dynorphin activation of kappa opioid receptor protects against epilepsy and seizure-induced brain injury via PI3K/Akt/Nrf2/HO-1 pathway

Dynorphins act as endogenous anticonvulsants via activation of kappa opioid receptor (KOR). However, the mechanism underlying the anticonvulsant role remains elusive. This study aims to investigate whether the potential protection of KOR activation by dynorphin against epilepsy was associated with the regulation of PI3K/Akt/Nrf2/HO-1 pathway. Here, a pilocarpine-induced rat model of epilepsy and Mg²⁺-free-induced epileptiform hippocampal neurons were established. Decreased prodynorphin (PDYN) expression, suppressed PI3K/Akt pathway, and activated Nrf2/HO-1 pathway were observed in rat epileptiform hippocampal tissues and in vitro neurons. Furthermore, dynorphin activation of KOR alleviated in vitro seizure-like neuron injury via activation of PI3K/Akt/Nrf2/HO-1 pathway. Further in vivo investigation revealed that PDYN overexpression by intra-hippocampus injection of PDYN-overexpressing lentiviruses decreased hippocampal neuronal apoptosis and serum levels of inflammatory cytokines and malondialdehyde (MDA) content, and increased serum superoxide dismutase (SOD) level, in pilocarpine-induced epileptic rats. The protection of PDYN in vivo was associated with the activation of PI3K/Akt/Nrf2/HO-1 pathway. In conclusion, dynorphin activation of KOR protects against epilepsy and seizure-induced brain injury, which is associated with activation of the PI3K/Akt/Nrf2/HO-1 pathway.     

Glaucocalyxin B protects against oxygen-glucose-deprivation/reperfusion-induced neuronal injury in PC-12 cells

Oxidative stress has been implicated in the development of cerebral ischemia/reperfusion (I/R) injury. Glaucocalyxin B (GLB), one of five ent-kauranoid diterpenoids, was reported to possess neuroprotective activity. However, the effect of GLB on oxygen-glucose-deprivation/reperfusion (OGD/R)-induced cell injury in PC-12 cells has not been explored. PC-12 cells was treated with various concentrations of GLB (0, 2.5, 5 and 10 μM), and cell viability was detected using the MTT assay. PC-12 cells were pretreated with the indicated concentration of GLB (2.5-10 μM, 2 hours pretreatment), and were maintained under OGD for 3 hours, followed by 24 hours of reoxygenation. Cell viability was assessed using the MTT assay. The levels of superoxide dismutase, malondialdehyde, and glutathione peroxidase were detected using commercially available ELISA Kits. Intracellular reactive oxygen species level was measured using the fluorescent probe 2′,7′-dichlorofluorescein diacetate. The levels of Bcl-2, Bax, p-Akt, Akt, p-mTOR, mTOR were detected using Western blot. Our results revealed that GLB significantly protected PC12 cells against OGD/R-induced cell injury. In addition, GLB efficiently inhibited oxidative stress and cell apoptosis in OGD/R-stimulated PC-12 cells. Mechanistic studies revealed that pretreatment with GLB could induce the activation of Akt/mTOR signaling pathway resulting in protection of OGD-treated PC12 cells. In conclusion, our data indicate for the first time that GLB protects against OGD/R-induced neuronal injury in PC-12 cells. The mechanism of the protective effect of GLB is partially associated with activation of the Akt/mTOR signaling pathway. Thus, GLB may be a potential agent for protection against cerebral I/R injury.