Hypoxia-Inducible Factor Activation Protects the Kidney from Gentamicin-Induced Acute Injury

Gentamicin nephrotoxicity is one of the most common causes of acute kidney injury (AKI). Hypoxia-inducible factor (HIF) is effective in protecting the kidney from ischemic and toxic injury. Increased expression of HIF-1α mRNA has been reported in rats with gentamicin-induced renal injury. We hypothesizd that we could study the role of HIF in gentamicin-induced AKI by modulating HIF activity. In this study, we investigated whether HIF activation had protective effects on gentamicin-induced renal tubule cell injury. Gentamicin-induced AKI was established in male Sprague-Dawley rats. Cobalt was continuously infused into the rats to activate HIF. HK-2 cells were pre-treated with cobalt or dimethyloxalylglycine (DMOG) to activate HIF and were then exposed to gentamicin. Cobalt or DMOG significantly increased HIF-1α expression in rat kidneys and HK-2 cells. In HK-2 cells, HIF inhibited gentamicin-induced reactive oxygen species (ROS) formation. HIF also protected these cells from apoptosis by reducing caspase-3 activity and the amount of cleaved caspase-3, and -9 proteins. Increased expression of HIF-1α reduced the number of gentamicin-induced apoptotic cells in rat kidneys and HK-2 cells. HIF activation improved the creatinine clearance and proteinuria in gentamicin-induced AKI. HIF activation also ameliorated the extent of histologic injury and reduced macrophage infiltration into the tubulointerstitium. In gentamicin-induced AKI, the activation of HIF by cobalt or DMOG attenuated renal dysfunction, proteinuria, and structural damage through a reduction of oxidative stress, inflammation, and apoptosis in renal tubular epithelial cells.     

Matrix metalloproteinase-10 protects against acute kidney injury by augmenting epidermal growth factor receptor signaling

Matrix metalloproteinase-10 (MMP-10) is a zinc-dependent endopeptidase involved in regulating a wide range of biologic processes, such as apoptosis, cell proliferation, and tissue remodeling. However, the role of MMP-10 in the pathogenesis of acute kidney injury (AKI) is unknown. In this study, we show that MMP-10 was upregulated in the kidneys and predominantly localized in the tubular epithelium in various models of AKI induced by ischemia/reperfusion (IR) or cisplatin. Overexpression of exogenous MMP-10 ameliorated AKI, manifested by decreased serum creatinine, blood urea nitrogen, tubular injury and apoptosis, and increased tubular regeneration. Conversely, knockdown of endogenous MMP-10 expression aggravated kidney injury. Interestingly, alleviation of AKI by MMP-10 in vivo was associated with the activation of epidermal growth factor receptor (EGFR) and its downstream AKT and extracellular signal-regulated kinase-1 and 2 (ERK1/2) signaling. Blockade of EGFR signaling by erlotinib abolished the MMP-10-mediated renal protection after AKI. In vitro, MMP-10 potentiated EGFR activation and protected kidney tubular cells against apoptosis induced by hypoxia/reoxygenation or cisplatin. MMP-10 was colocalized with heparin-binding EGF-like growth factor (HB-EGF) in vivo and activated it by a process of proteolytical cleavage in vitro. These studies identify HB-EGF as a previously unrecognized substrate of MMP-10. Our findings also underscore that MMP-10 can protect against AKI by augmenting EGFR signaling, leading to promotion of tubular cell survival and proliferation after injury.Subject terms: Apoptosis, Cell growth     

ERK-mediated suppression of cilia in cisplatin-induced tubular cell apoptosis and acute kidney injury

In kidneys, each tubular epithelial cell contains a primary cilium that protrudes from the apical surface. Ciliary dysfunction was recently linked to acute kidney injury (AKI) following renal ischemia–reperfusion. Whether ciliary regulation is a general pathogenic mechanism in AKI remains unclear. Moreover, the ciliary change during AKI and its underlying mechanism are largely unknown. Here we examined the change of primary cilium and its role in tubular cell apoptosis and AKI induced by cisplatin, a chemotherapy agent with notable nephrotoxicity. In cultured human proximal tubular HK-2 epithelial cells, cilia became shorter during cisplatin treatment, followed by apoptosis. Knockdown of Kif3a or Polaris (cilia maintenance proteins) reduced cilia and increased apoptosis during cisplatin treatment. We further subcloned HK-2 cells and found that the clones with shorter cilia were more sensitive to cisplatin-induced apoptosis. Mechanistically, cilia-suppressed cells showed hyperphosphorylation or activation of ERK. Inhibition of ERK by U0126 preserved cilia during cisplatin treatment and protected against apoptosis in HK-2 cells. In C57BL/6 mice, U0126 prevented the loss of cilia from proximal tubules during cisplatin treatment and protected against AKI. U0126 up-regulated Polaris, but not Kif3a, in kidney tissues. It is suggested that ciliary regulation by ERK plays a role in cisplatin-induced tubular apoptosis and AKI.     

Artesunate relieves acute kidney injury through inhibiting macrophagic Mincle-mediated necroptosis and inflammation to tubular epithelial cell

Artesunate is a widely used derivative of artemisinin for malaria. Recent researches have shown that artesunate has a significant anti-inflammatory effect on many diseases. However, its effect on acute kidney injury with a significant inflammatory response is not clear. In this study, we established a cisplatin-induced AKI mouse model and a co-culture system of BMDM and tubular epithelial cells (mTEC) to verify the renoprotective and anti-inflammatory effects of artesunate on AKI, and explored the underlying mechanism. We found that artesunate strongly down-regulated the serum creatinine and BUN levels in AKI mice, reduced the necroptosis of tubular cells and down-regulated the expression of the tubular injury molecule Tim-1. On the other hand, artesunate strongly inhibited the mRNA expression of inflammatory cytokines (IL-1β, IL-6 and TNF-α), protein levels of inflammatory signals (iNOS and NF-κB) and necroptosis signals (RIPK1, RIPK3 and MLKL) in kidney of AKI mouse. Notably, the co-culture system proved that Mincle in macrophage can aggravate the inflammation and necroptosis of mTEC induced by LPS, and artesunate suppressed the expression of Mincle in macrophage of kidney in AKI mouse. Overexpression of Mincle in BMDM restored the damage and necroptosis inhibited by artesunate in mTEC, indicating Mincle in macrophage is the target of artesunate to protect tubule cells in AKI. Our findings demonstrated that artesunate can significantly improve renal function in AKI, which may be related to the inhibition of Mincle-mediated macrophage inflammation, thereby reducing the damage and necroptosis to tubular cells that provide new option for the treatment of AKI.     

p53 induces miR-199a-3p to suppress mechanistic target of rapamycin activation in cisplatin-induced acute kidney injury

How p53 participates in acute kidney injury (AKI) progress and what are the underlying mechanisms remain illusive. For this issue, it is important to probe into the role of p53 in cisplatin-induced AKI. We find that p53 was upregulated in cisplatin-induced AKI, yet, pifithrin-α inhibites the p53 expression to attenuated renal injury and cell apoptosis both in vivo cisplatin-induced AKI mice and in vitro HK-2 human renal tubular epithelial cells. To knock down p53 by siRNA significantly decreased the miRNA, miR-199a-3p, expression in HK-2 cells. Blockade of miR-199a-3p significantly reduced cisplatin-induced cell apoptosis and inhibited caspase-3 activity. Mechanistically, we identified that miR-199a-3p directly bound to mechanistic target of rapamycin (mTOR) 3′-untranslated region and overexpressed miR-199a-3p reduce the expression and phosphorylation of mTOR. Furthermore, we demonstrated that p53 inhibited mTOR activation through activating miR-199a-3p. In conclusion, our findings reveal that p53, upregulating the expression of miR-199a-3p affects the progress of cisplatin-induced AKI, which might provide a promising therapeutic target of AKI.     

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.     

Renoprotective effect of paricalcitol via a modulation of the TLR4-NF-κB pathway in ischemia/reperfusion-induced acute kidney injury

Background

The pathophysiology of ischemic acute kidney injury (AKI) is thought to include a complex interplay between vascular endothelial cell dysfunction, inflammation, and tubular cell damage. Several lines of evidence suggest a potential anti-inflammatory effect of vitamin D in various kidney injury models. In this study, we investigated the effect of paricalcitol, a synthetic vitamin D analog, on renal inflammation in a mouse model of ischemia/reperfusion (I/R) induced acute kidney injury (AKI).

Methods

Paricalcitol was administered via intraperitoneal (IP) injection at 24 h before ischemia, and then I/R was performed through bilateral clamping of the renal pedicles. Twenty-four hours after I/R, mice were sacrificed for the evaluation of injury and inflammation. Additionally, an in vitro experiment using HK-2 cells was also performed to examine the direct effect of paricalcitol on tubular cells.

Results

Pre-treatment with paricalcitol attenuated functional deterioration and histological damage in I/R induced AKI, and significantly decreased tissue neutrophil and macrophage infiltration and the levels of chemokines, the pro-inflammatory cytokine interleukin-6 (IL-6), and monocyte chemoattractant protein-1 (MCP-1). It also decreased IR-induced upregulation of Toll-like receptor 4 (TLR4), and nuclear translocation of p65 subunit of NF-κB. Results from the in vitro study showed pre-treatment with paricalcitol suppressed the TNF-α-induced depletion of cytosolic IκB in HK-2 cells.

Conclusion

These results demonstrate that pre-treatment with paricalcitol has a renoprotective effect in ischemic AKI, possibly by suppressing TLR4-NF-κB mediated inflammation.     

Fatty acid-binding protein 4 is a therapeutic target for septic acute kidney injury by regulating inflammatory response and cell apoptosis

Sepsis is a systemic inflammatory state in response to infection, and concomitant acute kidney injury (AKI) significantly increases morbidity and mortality. Growing evidence suggests that fatty acid-binding protein 4 (FABP4) is critically involved in kidney diseases, while its role in septic AKI remains unknown. Here, FABP4 was mainly upregulated in renal tubular epithelial cells (RTECs) following cecal ligation and puncture (CLP)- or lipopolysaccharide (LPS)-induced septic AKI. FABP4 inhibition by genetic deletion or BMS309403 treatment both attenuated kidney dysfunction and pathological injury in CLP- or LPS-treated mice. Notably, RTEC-specific deletion of FABP4 also showed similar renoprotective effects. Moreover, FABP4 inhibition alleviated inflammation and apoptosis in CLP-injured kidneys and LPS-stimulated mouse tubular epithelial cells. Mechanistically, TLR4 blockage improved sepsis-induced kidney injury, as well as suppressed c-Jun phosphorylation and FABP4 expression, where c-Jun knockdown also inhibited LPS-stimulated FABP4 level. Meanwhile, FABP4 inhibition reduced the elevated phosphorylated c-Jun, while the levels of TLR4 and MyD88 were uninfluenced. Collectively, the increased FABP4 in RTECs is dependent on TLR4/c-Jun signaling activation and contributes to kidney injury, by forming a positive feedback loop with c-Jun to aggravate inflammation and apoptosis in septic AKI. Thus, FABP4 may be a therapeutic target for septic AKI.Subject terms: Acute kidney injury, Chronic kidney disease

Upregulation of tubular FABP4 in septic AKI is dependent on TLR4/c-Jun signaling activation, and FABP4 mediates sepsis-induced RTEC injury, likely by forming a positive feedback loop with c-Jun to aggravate inflammation and apoptosis.     

Mesenchymal-like progenitors derived from human embryonic stem cells promote recovery from acute kidney injury via paracrine actions

Background aimsThe engraftment of mesenchymal stem cells (MSCs) is reported to promote recovery of renal function in animal models of acute kidney injury (AKI). However, it is unknown whether mesenchymal-like progenitors (MPs) derived from human embryonic stem cells (hESCs) can mediate similar therapeutic effects. We investigated the responses of recipient renal tissue to engraftment of hESC-MPs and underlying mechanisms of these effects.MethodsWe measured blood urea nitrogen and creatinine levels of AKI mice with hESC-MPs transplantation and control mice. We performed renal morphology analysis by immunohistochemistry and electron microscopy to confirm the renoprotective effects of engrafted hESC-MPs. Proliferation, apoptosis and gene expression of tubular cells were also monitored by immunohistochemistry and real-time quantitative polymerase chain reaction to investigate the mechanisms that occurred.ResultsAfter transplantation of hESC-MPs into mice with cisplatin-induced AKI, improvements in renal function and recovery from tubular epithelial cell injury were observed. Engrafted hESC-MPs were localized to areas of injured kidney 5 days after cisplatin induction, where they promoted tubular cell proliferation and decreased kidney cell apoptosis. The beneficial effect was further confirmed by the capability of the engrafted cells to up-regulate renal gene expression of anti-inflammatory cytokines and pro-survival cytokines. Meanwhile, infusion of these cells reduced renal gene expression of pro-inflammatory cytokines and monocyte chemotactic protein-1, a chemokine that stimulates monocyte and macrophage infiltration.ConclusionsOur results show that infused hESC-MPs may promote recovery from AKI by regulating related cytokines.     

VEGF-modified human embryonic mesenchymal stem cell implantation enhances protection against cisplatin-induced acute kidney injury

The implantation of mesenchymal stem cells (MSC) has been reported as a new technique to restore renal tubular structure and improve renal function in acute kidney injury (AKI). Vascular endothelial growth factor (VEGF) plays an important role in the renoprotective function of MSC. Whether upregulation of VEGF by a combination of MSC and VEGF gene transfer could enhance the protective effect of MSC in AKI is not clear. We investigated the effects of VEGF-modified human embryonic MSC (VEGF-hMSC) in healing cisplatin-injured renal tubular epithelial cells (TCMK-1) with a coculture system. We found that TCMK-1 viability declined 3 days after cisplatin pretreatment and that coculture with VEGF-hMSC enhanced cell protection via mitogenic and antiapoptotic actions. In addition, administration of VEGF-hMSC in a nude mouse model of cisplatin-induced kidney injury offered better protective effects on renal function, tubular structure, and survival as represented by increased cell proliferation, decreased cellular apoptosis, and improved peritubular capillary density. These data suggest that VEGF-modified hMSC implantation could provide advanced benefits in the protection against AKI by increasing antiapoptosis effects and improving microcirculation and cell proliferation.     

Gypenoside XLIX protects against acute kidney injury by suppressing IGFBP7/IGF1R-mediated programmed cell death and inflammation

BackgroundAcute kidney injury (AKI), characterised by excessive inflammatory cell recruitment and programmed cell death, has a high morbidity and mortality; however, effective and specific therapies for AKI are still lacking.ObjectiveThis study aimed to evaluate the renoprotective effects of gypenoside XLIX (Gyp XLIX) in AKI.MethodsThe protective effects of Gyp XLIX were tested in two AKI mouse models established using male C57BL/6 mice (aged 6–8 weeks) by a single intraperitoneal injection of cisplatin (20 mg/kg) or renal ischemia-reperfusion for 40 min. Gyp XLIX was administered intraperitoneally before cisplatin administration or renal ischemia-reperfusion. Renal function, tubular injury, renal inflammation and programmed cell death were evaluated. In addition, the renoprotective effects of Gyp XLIX were also evaluated in cisplatin- or hypoxia-treated tubular epithelial cells. The mechanisms underlying these effects were then explored using RNA sequencing.ResultsIn vivo, Gyp XLIX substantially suppressed the increase in serum creatinine and blood urea nitrogen levels. Moreover, tubular damage was alleviated by Gyp XLIX as shown by periodic acid-Schiff staining, electron microscopy and molecular analysis of KIM-1. Consistently, we found that Gyp XLIX suppressed renal necroptosis though the RIPK1/RIPK3/MLKL pathway. The anti-inflammatory and antinecroptotic effects were further confirmed in vitro. Mechanistically, RNA sequencing showed that Gyp XLIX markedly suppressed the levels of IGF binding protein 7 (IGFBP7). Co-immunoprecipitation and western blot analysis further showed that Gyp XLIX reduced the binding of IGFBP7 to IGF1 receptor (IGF1R). Additionally, picropodophyllin, an inhibitor of IGF1R, abrogated the therapeutic effects of Gyp XLIX on cisplatin-induced renal cell injury; this finding indicated that Gyp XLIX may function by activating IGF1R-mediated downstream signalling Additionally, we also detected the metabolic distribution of Gyp XLIX after injection; Gyp XLIX had a high concentration in the kidney and exhibited a long retention time. These findings may shed light on the application of Gyp XLIX for AKI treatment clinically.ConclusionGyp XLIX may serve as a potential therapeutic agent for AKI treatment via IGFBP7/ IGF1R-dependent mechanisms.     

Downregulation of TIMP2 attenuates sepsis-induced AKI through the NF-κb pathway

Acute kidney injury (AKI) is a frequent complication of sepsis and contributes to increased morbidity and mortality. Urinary tissue inhibitor of metalloproteinases-2 (TIMP2) has been recently recognized as an early biomarker to predict AKI in critically ill patients. However, the biological functions of TIMP2 remain largely unknown. In this study, we investigated the role of TIMP2 in mediating inflammation and tubular cell apoptosis in AKI. In kidney tissue taken from mice exposed to cecal ligation and puncture (CLP) and in human kidney 2 (HK-2) cells exposed to lipopolysaccharide (LPS) in culture, TIMP2 expression was significantly upregulated. The expression of TIMP2 in the kidney tissue correlated with the severity of AKI in vivo. In cultured HK-2 cells, LPS challenge markedly induced cytokine release, and recombinant cytokines promoted TIMP2 expression and apoptosis. However, TIMP2 silencing ameliorated LPS-induced cytokine release, apoptosis, and cell injury. We further found that the effects of downregulation of TIMP2 on a suppression of release of inflammatory cytokines were mediated by p-P65. Stable, kidney-specific TIMP2 knockdown mice were transduced by injecting the TIMP2 knockdown lentiviral vector into kidney parenchyma. TIMP2 silencing ameliorated CLP-induced proinflammatory cytokines, kidney dysfunction as measured by serum creatinine level, and histopathological changes. Downregulation of TIMP2 showed renoprotective effects on endotoxin-induced AKI, which was associated with the anti-inflammatory activity through inhibition of the nuclear factor (NF)-κB pathway. Collectively, our results indicate that TIMP2 plays an important role in mediating sepsis-induced AKI through regulation of NF-κB. These findings reveal the pathogenic role of TIMP2 in AKI and suggest a novel target for the treatment of AKI.     

IGFBP7 regulates sepsis-induced acute kidney injury through ERK1/2 signaling

IGFBP7 as an early biomarker has been used to identify patients at risk of developing acute kidney injury (AKI). Nevertheless, its role in AKI remains obscure. The aim of our study is to determine the role and mechanism of IGFBP7 in lipopolysaccharide (LPS)-induced HK-2 cells in vitro and on sepsis-induced AKI by cecal ligation and puncture (CLP) in vivo. Here, we identified that IGFBP7 expression was increased in patients with AKI and HK-2 cells with LPS (1, 2, and 5 μg/mL) induction. HK-2 cells with LPS induction showed cell cycle arrest at G1-G0 phases and cell apoptosis and activated ERK1/2 parallel with the changes in the proteins belonging to the ERK1/2 pathway, including Cyclin D1, P21, Bax, and Bcl-2, which were inhibited by the IGFBP7 knockdown. Moreover, IGFBP7 overexpression significantly induced cell cycle arrest at G1-G0 phases and cell apoptosis of HK-2 cells, which were inhibited by PD98509, an ERK1/2 signaling inhibitor. IGFBP7 knockdown effectively alleviated the severity of the renal injury, evidenced by decreases in the urinary levels of creatinine, blood urea nitrogen, and albumin, cell apoptosis, and activation of ERK1/2 signaling in CLP mice. Taken together, our findings indicate that IGFBP7 regulates sepsis-induced AKI through ERK1/2 signaling.     

Circ_0023404 sponges miR-136 to induce HK-2 cells injury triggered by hypoxia/reoxygenation via up-regulating IL-6R

The significance of circular RNAs (circRNAs) is reported in various kidney diseases including acute kidney injury (AKI). Specific circRNAs have the capacity to function as novel indicators of AKI. Circ_0023404 exhibits an important role in several diseases. Nevertheless, the detailed biological role of circ_0023404 in AKI remains poorly known. The present study aimed to investigate the effect of circ_0023404 on renal ischaemia/reperfusion (I/R) injury in vitro. Here, we evaluated the function of circ_0023404 in HK-2 cells in response to hypoxia/reoxygenation (H/R). We established a cell AKI model induced by H/R in HK-2 cells. We found circ_0023404 was significantly increased in AKI. Then, we found loss of circ_0023404 increased cell growth, repressed apoptosis, reduced inflammatory factors secretion and oxidative stress generation in vitro. Besides, circ_0023404 sponged miR-136. miR-136 overturned the effects of circ_0023404 on HK-2 cell injury. We assumed IL-6 receptor (IL-6R) as a target of miR-136 and IL-6R was activated by circ_0023404 via sponging miR-136. In conclusion, we revealed circ_0023404 contributed to HK-2 cells injury stimulated by H/R via sponging miR-136 and activating IL-6R.     

Exosomes from human-bone-marrow-derived mesenchymal stem cells protect against renal ischemia/reperfusion injury via transferring miR-199a-3p

Renal ischemia/reperfusion (I/R) injury is the main reason for acute kidney injury (AKI) and is closely related to high morbidity and mortality. In this study, we found that exosomes from human-bone-marrow-derived mesenchymal stem cells (hBMSC-Exos) play a protective role in hypoxia/reoxygenation (H/R) injury. hBMSC-Exos were enriched in miR-199a-3p, and hBMSC-Exo treatment increased the expression level of miR-199a-3p in renal cells. We further explored the function of miR-199a-3p on H/R injury. miR-199a-3p was knocked down in hBMSCs with a miR-199a-3p inhibitor. HK-2 cells cocultured with miR-199a-3p-knockdown hBMSCs were more susceptible to H/R injury and showed more apoptosis than those cocultured with hBMSCs or miR-199a-3p-overexpressing hBMSCs. Meanwhile, we found that HK-2 cells exposed to H/R treatment incubated with hBMSC-Exos decreased semaphorin 3A (Sema3A) and activated the protein kinase B (AKT) and extracellular-signal-regulated kinase (ERK) pathways. However, HK-2 cells cocultured with miR-199a-3p-knockdown hBMSCs restored Sema3A expression and blocked the activation of the AKT and ERK pathways. Moreover, knocking down Sema3A could reactivate the AKT and ERK pathways suppressed by a miR-199a-3p inhibitor. In vivo, we injected hBMSC-Exos into mice suffering from I/R injury; this treatment induced functional recovery and histologic protection and reduced cleaved caspase-3 and Sema3A expression levels, as shown by immunohistochemistry. On the whole, this study demonstrated an antiapoptotic effect of hBMSC-Exos, which protected against I/R injury, via delivering miR-199a-3p to renal cells, downregulating Sema3A expression and thereby activating the AKT and ERK pathways. These findings reveal a novel mechanism of AKI treated with hBMSC-Exos and provide a therapeutic method for kidney diseases.     

miR-191 secreted by platelet-derived microvesicles induced apoptosis of renal tubular epithelial cells and participated in renal ischemia-reperfusion injury via inhibiting CBS

In this study, we aimed to reveal the role of miR-191 in apoptosis of renal tubular epithelial cells and in the involvement of renal ischemia-reperfusion injury. Renal transplantation rat model was established. miR-191 and Cystathionine-β-synthase (CBS) were measured by qRT-PCR and Western blot. The regulation of miR-191 on CBS was detected by luciferase reporter assay. We found miR-191 expression in platelets and platelet microvesicles (P-MVs) of patients and model rats was significantly upregulated than that of health and normal rats. Also, mRNA and protein levels of CBS in renal tissues of patients were significantly downregulated than that of health and normal rats. We also found that P-MVs could transfer miR-191 to HK-2 cells. Luciferase reporter assay showed that CBS was a direct target of miR-191. In addition, we proved that P-MVs-secreted miR-191 inhibited CBS expression in HK-2 cells, and P-MVs-secreted miR-191 promoted HK-2 cell apoptosis via CBS. Finally, we verified the trends of CBS expressions, HK-2 cell apoptosis and apoptosis-related proteins in vivo were similar as the trends in vitro. Therefore, CBS was a direct target of miR-191, and miR-191 could transfer to HK-2 cells via P-MVs to decrease the expression of CBS, thus to promote cell apoptosis and renal IR injury.     

7-Hydroxycoumarin protects against cisplatin-induced acute kidney injury by inhibiting necroptosis and promoting Sox9-mediated tubular epithelial cell proliferation

Background7-Hydroxycoumarin (7-HC), also known as umbelliferon, is commonly found in Chinese herbs (e.g. Eucommiae Cortex, Prunellae Spica, Radix Angelicae Biseratae). Previous laboratory studies have indicated that 7-HC has anti-inflammatory, anti-oxidative, and anti-tumor effects. Cisplatin is a widely used chemotherapeutic agent for cancer. Nephrotoxicity is one of the limiting side effects of cisplatin use.PurposeThis study aimed to evaluate the renoprotective effect of 7-HC in a cisplatin-induced acute kidney injury (AKI) mouse model.MethodsAKI was induced in male C57BL/6 mice (aged 6–8 weeks) by a single intraperitoneal injection of cisplatin at 20 mg/kg. The mice received 7-HC at 30, 60, and 90 mg/kg intraperitoneally before or after cisplatin administration. Renal function, necroptosis, and cell proliferation were measured. Mechanisms underlying the reno-protective effect of 7-HC were explored in renal tubular epithelial cells treated with or without cisplatin.ResultsIn-vivo experiments showed that 7-HC significantly improved the loss in kidney function induced by cisplatin, as indicated by lower levels of serum creatinine and blood urea nitrogen, in AKI mice. Consistent herewith, cisplatin-induced tubular damage was alleviated by 7-HC as shown by morphological (periodic acid–Schiff staining) and kidney injury marker (KIM-1) analyses. We found that 7-HC suppressed renal necroptosis via the RIPK1/RIPK3/MLKL pathway and accelerated renal repair as evidenced by the upregulation of cyclin D1 in cisplatin-induced nephropathy. In-vitro experiments showed that knockdown of Sox9 attenuated the suppressive effect of 7-HC on KIM-1 and reversed the stimulatory effect of 7-HC on cyclin D1 expression in cisplatin-treated HK-2 cells, indicating that 7-HC may protect against AKI via a Sox9-dependent mechanism.Conclusion7-HC inhibits cisplatin-induced AKI by suppressing RIPK1/RIPK3/MLKL-mediated necroptosis and promoting Sox9-mediated tubular epithelial cell proliferation. 7-HC may serve as a preventive and therapeutic agent for AKI.     

Heme oxygenase-1 induction contributes to renoprotection by G-CSF during rhabdomyolysis-associated acute kidney injury

Granulocyte colony-stimulating factor (G-CSF) is renoprotective during acute kidney injury (AKI) induced by ischemia and cisplatin nephrotoxicity; however, the underlying mechanism is not entirely clear. Rhabdomyolysis is another important clinical cause of AKI, due to the release of nephrotoxins (e.g., heme) from disrupted muscles. The current study has determined the effects of G-CSF on rhabdomyolysis-associated AKI using in vivo and in vitro models. In C57BL/6 mice, intramuscular injection of glycerol induced AKI, which was partially prevented by G-CSF pretreatment. Consistently, glycerol-induced renal tissue damage was ameliorated by G-CSF. In addition, animal survival following the glycerol injection was improved from ～30 to ～70% by G-CSF. In cultured renal tubular cells, hemin-induced apoptosis was also suppressed by G-CSF. Interestingly, G-CSF induced heme oxygenase-1 (HO-1, a critical enzyme for heme/hemin degradation and detoxification) in both cultured tubular cells and mouse kidneys. Blockade of HO-1 with protoporphyrin IX zinc(II) (ZnPP) could largely diminish the protective effects of G-CSF. Together, these results demonstrated the renoprotective effects of G-CSF in rhabdomyolysis-associated AKI. Notably, G-CSF may directly protect against tubular cell injury under the disease condition by inducing HO-1.