Prevention of kidney ischemia/reperfusion-induced functional injury, MAPK and MAPK kinase activation, and inflammation by remote transient ureteral obstruction

Protective effects of adipose-derived stem cells against testicular injury induced after ischemia-reperfusion by regulating autophagy

The damaged organ may experience severe pathological alterations as a result of tissue ischemia-reperfusion (I/R). The study of stem cell-based repair therapies is actively being conducted, and the outcomes and therapeutic potential of these cells are both promising. Autophagy checks protein homeostasis by breaking down huge damaged proteins or organelles. The study's objective was to assess how ADSCs impact the autophagic process after testicular ischemia/reperfusion. In our investigation, 30 male rats were divided into five groups: control, ADSC, ischemia, I/R, and I/R + ADSC (n = 6). Hematoxylin-eosin (HE) was used to stain the testes, and histological changes were assessed. The immunoexpression of androgen receptor (AR), Beclin1, protein light chain 3B (LC3B), and p62 were examined. The seminiferous epithelium in the testis from the ischemia and I/R groups revealed significant degeneration with disorganized morphology, damaged spermatogenic cells, and interstitial space congestion, according to HE stain results. Johnsen's score were significantly better in I/R + ADSC group than in ischemia and I/R groups. We demonstrated that in rat testes from the I/R groups, immunostaining of Beclin 1 (p = 0.042) and LC3B (p = 0.011) were raised, and p62 (p = 0.047) and AR (p = 0.049) were decreased. Ischemia and I/R promoted testicular autophagy, therefore we can conclude that ADSCs prevent excessive autophagy. Additionally, these results show that the use of ADSCs cures testicular injury and dysfunction associated with I/R injury in rats even a little.

Kidney ischemia/reperfusion injury causes cholangiocytes primary cilia disruption and abnormal bile secretion

BACKGROUND

Acute kidney injury (AKI) causes distant liver injury, to date, which causes poor outcomes of patients with AKI. Many studies have been performed to overcome AKI-associated liver injury. However, those studies have mainly focused on hepatocytes, and AKI-induced liver injury still remains a clinical problem. Here, we investigated the implication of cholangiocytes and their primary cilia which are critical in final bile secretion. Cholangiocyte, a lining cell of bile ducts, are the only liver epithelial cell containing primary cilium (a microtubule-based cell surface signal-sensing organelle).

METHODS

Cystathione γ-lyase (CSE, a transsulfuration enzyme) deficient and wild-type mice were subjected to kidney ischemia followed by reperfusion (KIR). Some mice were administered with N-acetyl-cysteine (NAC).

RESULTS

KIR damaged hepatocytes and cholagiocytes, disrupted cholangiocytes primary cilia, released the disrupted ciliary fragments into the bile, and caused abnormal bile secretion. Glutathione (GSH) and H2S levels in the livers were significantly reduced by KIR, resulting in increased the ratio oxidized GSH to total GSH, and oxidation of tissue and bile. CSE and cystathione β-synthase (CBS) expression were lowered in the liver after KIR. NAC administration increased total GSH and H2S levels in the liver and attenuated KIR-induced liver injuries. In contrast, Cse deletion caused the reduction of total GSH levels and worsened KIR-induced liver injuries, including primary cilia damage and abnormal bile secretion.

CONCLUSIONS

These results indicate that KIR causes cholangiocyte damage, cholangiocytes primary cilia disruption, and abnormal bile secretion through reduced antioxidative ability of the liver.

Targeting Aquaporin-5 by Phosphodiesterase 4 Inhibition Offers New Therapeutic Opportunities for Ovarian Ischemia Reperfusion Injury in Rats

This study aimed to examine the effect of Phosphodiesterase 4 (PDE4) inhibition on Aquaporin-5 (AQP5) and its potential cell signaling pathway in the ovarian ischemia reperfusion (OIR) model. Thirty adult female rats were divided into five groups: Group 1; Control: Sham operation, Group 2; OIR that 3 hour ischemia followed by 3 hour reperfusion, Group 3; OIR + Rolipram 1 mg/kg, Group 4; OIR + Rolipram 3 mg/kg, Group 5; OIR + Rolipram 5 mg/kg. Rolipram was administered intraperitoneally to the rats in groups 3-4 and 5 at determined doses 30 minutes before reperfusion. From ovary tissue; Tumor necrosis factor-a (TNF-α), Cyclic adenosine monophosphate (cAMP), Nuclear factor kappa (NF-κB), Interleukin-6 (IL-6), Phosphodiesterase 4D (PDE4D), Mitogen-activated protein kinase (MAPK) and AQP5 levels were measured by ELISA. We also measured the level of AQP5 in ovary tissue by real-time reverse-transcription polymerase chain reaction (RT-PCR). In the OIR groups; TNF-α, NF-κB, IL-6, MAPK inflammatory levels increased, and cAMP and AQP5 levels decreased, which improved with the administration of rolipram doses. Also histopathological results showed damaged ovarian tissue after OIR, while rolipram administration decrased tissue damage in a dose dependent manner. We propose that the protective effect of PDE4 inhibition in OIR may be regulated by AQP5 and its potential cell signaling pathway and may be a new target in OIR therapy. However, clinical studies are needed to appraise these data in humans.

Pathophysiology of Red Blood Cell Trapping in Ischemic Acute Kidney Injury

Red blood cell (RBC) trapping describes the accumulation of RBCs in the microvasculature of the kidney outer medulla that occurs following ischemic acute kidney injury (AKI). Despite its prominence in human kidneys following AKI, as well as evidence from experimental models demonstrating that the severity of RBC trapping is directly correlated with renal recovery, to date, RBC trapping has not been a primary focus in understanding the pathogenesis of ischemic kidney injury. New evidence from rodent models suggests that RBC trapping is responsible for much of the tubular injury occurring in the initial hours after kidney reperfusion from ischemia. This early injury appears to result from RBC cytotoxicity and closely reflects the injury profile observed in human kidneys, including sloughing of the medullary tubules and the formation of heme casts in the distal tubules. In this review, we discuss what is currently known about RBC trapping. We conclude that RBC trapping is likely avoidable. The primary causes of RBC trapping are thought to include rheologic alterations, blood coagulation, tubular cell swelling, and increased vascular permeability; however, new data indicate that a mismatch in blood flow between the cortex and medulla where medullary perfusion is maintained during cortical ischemia is also likely critical. The mechanism(s) by which RBC trapping contributes to renal functional decline require more investigation. We propose a renewed focus on the mechanisms mediating RBC trapping, and RBC trapping-associated injury is likely to provide important knowledge for improving AKI outcomes. © 2024 American Physiological Society. Compr Physiol 14:5325-5343, 2024.

Hyocholic acid retards renal fibrosis by regulating lipid metabolism and inflammatory response in a sheep model

The kidneys are vital organs that regulate metabolic homeostasis in the body, filter waste products from the blood, and remove extrahepatic bile acids. We previously found that the dietary supplementation of hyocholic acid alleviated the sheep body lipid deposition and decreased kidney weight. This study evaluated hyocholic acid's (HCA) roles and mechanisms on lipid metabolism and anti-inflammatory function in the kidney under a high-energy diet. Histomicrograph showing the apparent improvement by HCA by attenuating structural damage. The HCA treatment reduced the renal accumulation of cholesterol. Bile acid receptors such as LXR and FXR were activated at the protein level. HCA significantly altered several genes related to immune response (NF-κB, IL-6, and MCP1) and fibrosis (TGF-β, Col1α1, and α-SMA). These significant changes correlated with renal lipid accumulation. The KEGG pathways including non-alcoholic fatty liver disease, insulin resistance, TNF signaling pathway, and Th17 cell differentiation were enriched and NF-κB, IL-6, and TGF-β were identified as the core interconnected genes. This study revealed that HCA plays an efficient role in alleviating kidney lipids accumulation and inflammatory response through crucial genes such as FXR, LXR, HMGCR, NF-κB, IL-6, MCP1, and TGF-β, and expand our understanding of HCA's role in kidney function. In conclusion, HCA mitigated kidney fibrosis, lipid metabolism disorders and immune responses induced by a high-energy diet by regulating a potential LXR/SREBP2/TGF-β-NF-κB signaling pathway.

HSF2BP protects against acute liver injury by regulating HSF2/HSP70/MAPK signaling in mice

Heat shock proteins (HSPs) depletion and protein misfolding are important causes of hepatocyte death and liver regeneration disorder in liver injury. HSF2BP, as its name implies, is a binding protein of HSF2, but the specific role of HSF2BP in heat shock response (HSR) remains unknown. The aim of this study is to identify the role of HSF2BP in HSR and acute liver injury. In this study, we found that HSF2BP expression increased significantly within 24 h after APAP administration, and the trend was highly consistent with that of HSP70. hsf2bp-KO and hsf2bp-TG mouse models demonstrated HSF2BP reduced hepatocyte death, ameliorated inflammation, and improved liver function in APAP- or D-GalN/LPS- induced liver injury. Meanwhile, a significant increase of the survival rate was observed in hsf2bp-TG mice after APAP administration. Further studies showed that HSF2BP upregulated the expression of HSF2 and HSP70 and inhibited the activation of Jnk1/2 and P38 MAPK. Additionally, HSP70 siRNA pretreatment abolished the effect of HSF2BP on the MAPK pathway in APAP-treated hepatocytes. The results reveal that HSF2BP is a protective factor in acute liver injury, and the HSF2BP/HSP70/MAPK regulatory axis is crucial for the pathogenesis of liver injury. HSF2BP is a potential therapeutic target for liver injury.

Short-term control of diet affects cisplatin-induced acute kidney injury through modulation of mitochondrial dynamics and mitochondrial GSH

Obesity affects acute kidney injury (AKI) induced by various clinical settings, including transplantation and cisplatin-cancer therapy. However, the effect of short-term food intake change remains to be defined. Here, we investigated the effects of short-term high-fat diet intake and food restriction on cisplatin-induced AKI. Mice were fed either a high-fat diet (HFD) or a low-fat diet (LFD) for 11 days or were not fed for 40 hh (fasting), before cisplatin administration. Cisplatin-induced functional and structural damages to kidneys in both HFD- and LFD-fed mice, with greater damages in HFD-fed mice than LFD-fed mice. HFD decreased mitochondrial total glutathione (tGSH) level, along with increases in the plasma and kidney cholesterol levels. Cisplatin caused the increase of kidney cholesterol levels and oxidative stress, along with the decrease of mitochondrial tGSH levels. In addition, cisplatin-induced mitochondrial damage and apoptosis of tubular cells in both HFD- and LFD-fed mice. An increase of Fis1 (mitochondria fission 1 protein), whereas a decrease of Opa1 (mitochondria fusion 1 protein) occurred by cisplatin. These cisplatin effects were greater in HFD-fed mice than in LFD-fed mice. Administration of mitochondria-specific antioxidant treatment during HFD feeding inhibited these cisplatin-induced changes. Fasting for 40 h also significantly reduced the cisplatin-induced changes mentioned above. These data demonstrate that short-term HFD intake worsens cisplatin-induced oxidative stress by the reduction of mitochondrial tGSH, resulting in increased cisplatin-induced nephrotoxicity. These data newly indicate that the control of calorie intake, even for a short period, affects kidney susceptibility to injury. Although most studies described the effects of a long-term high-fat diet on the kidneys, in this study, we found that even if a high-fat diet was consumed for a short-term, physiological changes and mitochondria tGSH decrease in the kidneys, and consequently increased cisplatin-nephrotoxic susceptibility. These data suggest the association of calorie intake with kidney susceptibility to cisplatin.

Sustained local inhibition of thrombin preserves renal microarchitecture and function after onset of acute kidney injury

Acute kidney injury (AKI) management remains mainly supportive as no specific therapeutic agents directed at singular signaling pathways have succeeded in clinical trials. Here, we report that inhibition of thrombin-driven clotting and inflammatory signaling with use of locally-acting thrombin-targeted perfluorocarbon nanoparticles (PFC NP) protects renal vasculature and broadly modulates diverse inflammatory processes that cause renal ischemia reperfusion injury. Each PFC NP was complexed with ~13,650 copies of the direct thrombin inhibitor, PPACK (proline-phenylalanine-arginine-chloromethyl-ketone). Mice treated after the onset of AKI with PPACK PFC NP exhibited downregulated VCAM-1, ICAM-1, PGD2 prostanoid, M-CSF, IL-6, and mast cell infiltrates. Microvascular architecture, tubular basement membranes, and brush border components were better preserved. Non-reperfusion was reduced as indicated by reduced red blood cell trapping and non-heme iron. Kidney function and tubular necrosis improved at 24 hours versus the untreated control group, suggesting a benefit for dual inhibition of thrombosis and inflammation by PPACK PFC NP.

Dissecting the Involvement of Ras GTPases in Kidney Fibrosis

Many different regulatory mechanisms of renal fibrosis are known to date, and those related to transforming growth factor-β1 (TGF-β1)-induced signaling have been studied in greater depth. However, in recent years, other signaling pathways have been identified, which contribute to the regulation of these pathological processes. Several studies by our team and others have revealed the involvement of small Ras GTPases in the regulation of the cellular processes that occur in renal fibrosis, such as the activation and proliferation of myofibroblasts or the accumulation of extracellular matrix (ECM) proteins. Intracellular signaling mediated by TGF-β1 and Ras GTPases are closely related, and this interaction also occurs during the development of renal fibrosis. In this review, we update the available in vitro and in vivo knowledge on the role of Ras and its main effectors, such as Erk and Akt, in the cellular mechanisms that occur during the regulation of kidney fibrosis (ECM synthesis, accumulation and activation of myofibroblasts, apoptosis and survival of tubular epithelial cells), as well as the therapeutic strategies for targeting the Ras pathway to intervene on the development of renal fibrosis.

Reduction of Renal Preservation/Reperfusion Injury by Controlled Hyperthermia During Ex Vivo Machine Perfusion

The possible reno-protective effect of a controlled brief heat-shock treatment during isolated ex vivo machine perfusion of donor grafts prior to reperfusion should be investigated in a primary in vitro study. Porcine kidneys (n = 14) were retrieved after 20 minutes of cardiac standstill of the donor and subjected to 20 hours of static cold storage in University of Wisconsin solution. Prior to reperfusion, kidneys were subjected to 2 hours of reconditioning machine perfusion with gradual increase in perfusion temperature up to 35°C. In half of the kidneys (n = 7), a brief hyperthermic impulse (10 minutes perfusion at 42°C) was implemented in the machine perfusion period. Functional recovery of the grafts was observed upon normothermic reperfusion in vitro. Hyperthermic treatment resulted in a 50% increase of heat shock protein (HSP) 70 and HSP 27 mRNA and was accompanied by ~ 50% improvement of tubular re-absorption of sodium and glucose upon reperfusion, compared with the controls. Furthermore, renal loss of aspartate aminotransferase was significantly reduced to one-third of the controls as was urinary protein loss, evaluated by the albumin to creatinine ratio. It is concluded that ex vivo heat-shock treatment seems to be an easily implementable and promising option to enhance renal self-defense machinery against reperfusion injury after preservation that merits further investigation in preclinical models.

Meprin-β activity modulates the β-catalytic subunit of protein kinase A in ischemia-reperfusion-induced acute kidney injury

Meprin metalloproteases have been implicated in the progression of kidney injury. Previous work from our group has shown that meprins proteolytically process the catalytic subunit of protein kinase A (PKA-C), resulting in decreased PKA-C kinase activity. The goal of the present study was to determine the PKA-C isoforms impacted by meprin-β and whether meprin-β expression affects downstream mediators of the PKA signaling pathway in ischemia-reperfusion (IR)-induced kidney injury. IR was induced in 12-wk-old male wild-type (WT) and meprin-β knockout (βKO) mice. Madin-Darby canine kidney cells transfected with meprin-β cDNA were also subjected to 2 h of hypoxia. Western blot analysis was used to evaluate levels of total PKA-C, PKA-Cα, PKA-Cβ, phosphorylated (p-)PKA-C, and p-ERK1/2. Meprin-β expression enhanced kidney injury as indicated by levels of neutrophil gelatinase-associated lipocalin and cystatin C. IR-associated decreases were observed in levels of p-PKA-C in kidney tissue from WT mice but not βKO mice, suggesting that meprin-β expression/activity is responsible for the in vivo reduction in kinase activity. Significant increases in levels of PKA-Cβ were observed in kidney lysates for WT mice but not βKO mice at 6 h post-IR. Proximal tubule PKA-Cβ increases in WT but not βKO kidneys were demonstrated by fluorescent microscopy. Furthermore, IR-induced injury was associated with significant increases in p-ERK levels for both genotypes. The present data demonstrate that meprin-β enhances IR-induced kidney injury in part by modulating mediators of the PKA-Cβ signaling pathway.

Edaravone Ameliorates Renal Warm Ischemia-Reperfusion Injury by Downregulating Endoplasmic Reticulum Stress in a Rat Resuscitation Model

Background

This study was conducted to explore whether the effect of edaravone (5-methyl-2-phenyl-2,4-dihydro-3H-pyrazol3-one, EDR) can ameliorate renal warm ischemia-reperfusion injury (IRI) by modulating endoplasmic reticulum stress (ERS) and its downstream effector after cardiac arrest (CA) and cardiopulmonary resuscitation (CPR) in a rat model.

Methods

The rats (n=10) experienced anaesthesia and intubation followed by no CA inducement were defined as the Sham group. Transoesophageal alternating current stimulation was employed to establish 8 min of CA followed by conventional CPR for a resuscitation model. The rats with successful restoration of spontaneous circulation (ROSC) randomly received EDR (3 mg/kg, EDR group, n=10) or equal volume normal saline solution (the NS group, n=10). At 24 hr after ROSC, serum creatinine (SCR), blood urea nitrogen (BUN) levels, and cystatin-C (Cys-C) levels were determined and the protein level of glucose-regulated protein (GRP78), C/EBP homologous protein (CHOP), extracellular signal-regulated kinase (ERK), phosphorylated extracellular signal-regulated kinase 1/2 (p-ERK1/2), Bax/Bcl-2, and caspase-3 were detected by Western blot method.

Results

At 24 hrs after ROSC, SCR, BUN and Cys-C were obviously increased and the proteins expression, including GRP78, CHOP and p-ERK1/2, cleaved-caspase 3 Bax/Bcl-2 ratio, were significantly upregulated in the NS group compared with the Sham group (p<0.05). The remarkable improvement of these adverse outcomes was observed in the EDR group (p<0.05).

Conclusion

In conclusion, we found that EDR ameliorates renal warm IRI by downregulating ERS and its downstream effectors in a rat AKI model evoked by CA/CPR. These data may provide evidence for future therapeutic benefits of EDR against AKI induced by CA/CPR.

Gcm1 is involved in cell proliferation and fibrosis during kidney regeneration after ischemia-reperfusion injury

In acute kidney injury (AKI), the S3 segment of the proximal tubule is particularly damaged, as it is most vulnerable to ischemia. However, this region is also involved in renal tubular regeneration. To deeply understand the mechanism of the repair process after ischemic injury in AKI, we focused on glial cells missing 1 (Gcm1), which is one of the genes expressed in the S3 segment. Gcm1 is essential for the development of the placenta, and Gcm1 knockout (KO) is embryonically lethal. Thus, the function of Gcm1 in the kidney has not been analyzed yet. We analyzed the function of Gcm1 in the kidney by specifically knocking out Gcm1 in the kidney. We created an ischemia-reperfusion injury (IRI) model to observe the repair process after AKI. We found that Gcm1 expression was transiently increased during the recovery phase of IRI. In Gcm1 conditional KO mice, during the recovery phase of IRI, tubular cell proliferation reduced and transforming growth factor-β1 expression was downregulated resulting in a reduction in fibrosis. In vitro, Gcm1 overexpression promoted cell proliferation and upregulated TGF-β1 expression. These findings indicate that Gcm1 is involved in the mechanisms of fibrosis and cell proliferation after ischemic injury of the kidney.

Circulating miR-21, miR-210 and miR-146a as potential biomarkers to differentiate acute tubular necrosis from hepatorenal syndrome in patients with liver cirrhosis: a pilot study

BACKGROUND

Acute kidney injury (AKI) in cirrhotic patients may be functional (hepatorenal syndrome [HRS]) or structural (acute tubular necrosis [ATN]). The differentiation between these two conditions remains challenging; no definite biomarker with a clear cutoff value had been declared. miRNAs seem to be attractive innovative biomarkers to identify the nature of kidney injury in cirrhotic patients. This study aimed to investigate the possibility of using miR-21, miR-210 and miR-146a as differentiating markers between HRS and ATN.

METHODS

This pilot case control study included 50 patients with liver cirrhosis; 25 with HRS and another 25 with ATN beside 30 healthy controls. Real-time qPCR was used to measure the circulating miRNA tested.

RESULTS

Higher levels of miR-21 were observed in both ATN and HRS vs. controls with statistically significant difference between ATN and HRS. The means were 9.466±3.21 in ATN, 2.670±1.387 in HRS and 1.090±0.586 in controls. miR-146a and miR-210 were both significantly lower in ATN and HRS compared to controls with statistically significant differences between ATN and HRS. The means of miR-210 were 1.020±0.643, 1.640±0.605 and 3.0±0.532 in ATN, HRS and controls, respectively. The means of miR-146a were 2.543±1.929, 4.98±1.353 and 6.553±0.426 in ATN, HRS and controls, respectively. ROC analyses proved that the three studied mi-RNAs can be used as differentiating biomarkers between ATN and HRS with the best performance observed with mi-21 achieving specificity and sensitivity equal 96%.

CONCLUSIONS

miR-21, miR-210 and miR-146a may be candidate differentiating markers between HRS and ATN in cirrhotic patients.

Schizonepeta tenuifolia inhibits collagen stimulated platelet function via suppressing MAPK and Akt signaling

The prevalence of cardiovascular diseases (CVDs) is increasing at a rapid pace in developed countries, and CVDs are the leading cause of morbidity and mortality. Natural products and ethnomedicine have been shown to reduce the risk of CVDs. Schizonepeta (S.) tenuifolia is a medicinal plant widely used in China, Korea, and Japan and is known to exhibit anti-inflammatory, antioxidant, and immunomodulatory activities. We hypothesized that given herbal plant exhibit pharmacological activities against CVDs, we specifically explored its effects on platelet function. Platelet aggregation was evaluated using standard light transmission aggregometry. Intracellular calcium mobilization was assessed using Fura-2/AM, and granule secretion (ATP release) was measured in a luminometer. Fibrinogen binding to integrin αⅡbβ3, was assessed using flow cytometry. Phosphorylation of mitogen-activated protein kinase (MAPK) signaling molecules and activation of the protein kinase B (Akt) was assessed using Western blot assays. S. tenuifolia, extract potently and significantly inhibited platelet aggregation, calcium mobilization, granule secretion, and fibrinogen binding to integrin αⅡbβ3. Moreover, all extracts significantly inhibited MAPK and Akt phosphorylation. S. tenuifolia extract inhibited platelet aggregation and granule secretion, and attenuated collagen mediated GPVI downstream signaling, indicating the potential therapeutic effects of these plant extracts on the cardiovascular system and platelet function. We suggest that S. tenuifolia extract may be a potent candidate to treat platelet-related CVDs and to be used as an antiplatelet and antithrombotic agent.

Sasa veitchii extract protects against carbon tetrachloride-induced hepatic fibrosis in mice

BACKGROUND

The current study aimed to investigate the hepatoprotective effects of Sasa veitchii extract (SE) on carbon tetrachloride (CCl₄)-induced liver fibrosis in mice.

METHODS

Male C57BL/6J mice were intraperitoneally injected with CCl₄ dissolved in olive oil (1 g/kg) twice per week for 8 weeks. SE (0.1 mL) was administered orally once per day throughout the study, and body weight was measured weekly. Seventy-two hours after the final CCl₄ injection, mice were euthanized and plasma samples were collected. The liver and kidneys were collected and weighed.

RESULTS

CCl₄ administration increased liver weight, decreased body weight, elevated plasma alanine aminotransferase, and aspartate aminotransferase and increased liver oxidative stress (malondialdehyde and glutathione). These increases were attenuated by SE treatment. Overexpression of tumor necrosis factor-α was also reversed following SE treatment. Furthermore, CCl₄-induced increases in α-smooth muscle actin, a marker for hepatic fibrosis, were attenuated in mice treated with SE. Moreover, SE inhibited CCl₄-induced nuclear translocation of hepatic nuclear factor kappa B (NF-κB) p65 and phosphorylation of mitogen-activated protein kinase (MAPK).

CONCLUSION

These results suggested that SE prevented CCl₄-induced hepatic fibrosis by inhibiting the MAPK and NF-κB signaling pathways.

Gintonin modulates platelet function and inhibits thrombus formation via impaired glycoprotein VI signaling

Panax ginseng (P. ginseng), one of the most valuable medicinal plants, is known for its healing and immunobooster properties and has been widely used in folk medicine against cardiovascular diseases, including stroke and heart attack. In this study, we explored the anti-platelet activity of gintonin (a recently discovered non-saponin fraction of ginseng) against agonist-induced platelet activation. In vitro effects of gintonin on agonist-induced human and rat platelet aggregation, granule secretion, integrin α_IIbβ₃ activation, and intracellular calcium ion ([Ca²⁺]_i) mobilization were examined. Western blot analysis and immunoprecipitation techniques were used to estimate the expression of mitogen-activated protein kinases (MAPKs) and phosphatidylinositol 3-kinase (PI3K)/protein kinase B (Akt) and interaction of glycoprotein VI (GPVI) signaling pathway molecules such as Src family kinases (SFK), tyrosine kinase Syk, and PLCγ2. In vivo effects were studied using acute pulmonary thromboembolism model in mice. Gintonin remarkably inhibited collagen-induced platelet aggregation and suppressed granule secretion, [Ca²⁺]_i mobilization, and fibrinogen binding to integrin α_IIbβ₃ in a dose-dependent manner and clot retraction. Gintonin attenuated the activation of MAPK molecules and PI3K/Akt pathway. It also inhibited SFK, Syk, and PLCγ2 activation and protected mice from thrombosis. Gintonin inhibited agonist-induced platelet activation and thrombus formation through impairment in GPVI signaling molecules, including activation of SFK, Syk, PLCγ2, MAPK, and PI3K/Akt; suggesting its therapeutic potential against platelet related CVD.

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

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

Heat shock proteins and kidney disease: perspectives of HSP therapy

Heat shock proteins (HSPs) mediate a diverse range of cellular functions, prominently including folding and regulatory processes of cellular repair. A major property of these remarkable proteins, dependent on intracellular or extracellular location, is their capacity for immunoregulation that optimizes immune activity while avoiding hyperactivated inflammation. In this review, recent investigations are described, which examine roles of HSPs in protection of kidney tissue from various traumatic influences and demonstrate their potential for clinical management of nephritic disease. The HSP70 class is particularly attractive in this respect due to its multiple protective effects. The review also summarizes current understanding of HSP bioactivity in the pathophysiology of various kidney diseases, including acute kidney injury, diabetic nephropathy, chronic glomerulonephritis, and lupus nephritis-along with other promising strategies for their remediation, such as DNA vaccination.

Peroxiredoxin 6 overexpression attenuates lipopolysaccharide-induced acute kidney injury

Peroxiredoxin 6 (PRDX6) is a member of the PRDX family of antioxidant enzymes and correlated with inflammatory response. Therefore, we investigated the role of PRDX6 during lipopolysaccharide (LPS)-induced acute kidney injury. Both 3 months aged PRDX6-overexpressing transgenic mice (PRDX6 mice) and wild type (WT) mice had acute renal injury induced by intraperitoneal injection of LPS (10 mg/kg)., PRDX6 mice showed decreased mortality and renal injury following LPS challenge compared to WT mice. Furthermore, infiltration of macrophages, T-cells and neutrophils, and the number of apoptotic cells were more decreased by LPS treatment in PRDX6 mice than in WT mice. Because LPS induces reactive oxygen species (ROS) production which induces inflammation through c-Jun N-terminal Kinase (JNK) and p38 MAPK activation, we investigated ROS concentration and MAPK signaling pathway in the kidney of PRDX6 mice. As expected, LPS-induced oxidative stress was attenuated, and p38 MAPK and JNK activation was decreased in the kidney of PRDX6 mice. Inhibitory effect of PRDX6 on LPS-induced apoptosis and MAPK activation in the primary renal proximal tubular cells were overcome by treatment with PRDX6 inhibitor or hydrogen peroxide. These results suggest that PRDX6 overexpression inactivates p38 MAPK and JNK pathway through decrease LPS-induced ROS concentration in the kidney, resulting in inhibition of renal apoptosis and leukocyte infiltration and led to attenuation of LPS-induced acute kidney injury.

Age and Surgical Complexity impact on Renoprotection by Remote Ischemic Preconditioning during Adult Cardiac Surgery: A Meta analysis

We aimed to conduct an up-to-date meta-analysis to comprehensively assess the renoprotective effect of remote ischemic preconditioning (RIPC) in patients undergoing adult cardiac surgery. 21 randomized controlled trials (RCTs) with a total of 6302 patients were selected and identified. Compared with controls, RIPC significantly reduced the incidence of acute kidney injury (AKI) [odds ratio (OR) = 0.79; P = 0.02; I² = 38%], and in particular, AKI stage I (OR = 0.65; P = 0.01; I² = 55%). RIPC significantly shortened mechanical ventilation (MV) duration [weighted mean difference (WMD) = −0.79 hours; P = 0.002; I² = 53%), and reduced intensive care unit (ICU) stay (WMD = −0.23 days; P = 0.07; I² = 96%). Univariate meta-regression analyses showed that the major sources of heterogeneity for AKI stage I were age (coefficient = 0.06; P = 0.01; adjusted R2 = 0.86) and proportion of complex surgery (coefficient = 0.02; P = 0.03; adjusted R2 = 0.81). Subsequent multivariate regression and subgroup analyses also confirmed these results. The present meta-analysis suggests that RIPC reduces the incidence of AKI in adults undergoing cardiac surgery and this benefit was more pronounced in younger patients undergoing non-complex cardiac surgery. RIPC may also shorten MV duration and ICU stay. Future RCTs tailored for those most likely to benefit from RIPC warrants further investigation.

Tanshinone IIA pretreatment attenuates ischemia/reperfusion-induced renal injury

Tanshinone IIA is a chemical compound extracted from the root of traditional Chinese herb Salvia miltiorrhiza Bunge. Tanshinone IIA has been suggested to possess anti-inflammatory activity and antioxidizing capability. Recently, accumulating results have indicated the antitumor activity of tanshinone IIA; thus, it has attracted increasing attention. In addition, tanshinone IIA has been indicated to attenuate ischemia/reperfusion induced renal injury (I/RIRI); however, little is known regarding the underlying mechanisms involved in this process. In the present study an I/RIRI rat model was used to analyze the effects of tanshinone IIA on myeloperoxidase (MPO), TNF-α and IL-6 activities using ELISA kits. Furthermore, macrophage migration inhibitory factor (MIF), cleaved caspase-3, B-cell lymphoma 2 (Bcl-2) and p38 mitogen-activated protein kinase (MAPK) protein expression levels were evaluated using western blot analysis. The results indicated that tanshinone IIA protected renal function in I/RIRI rats. ELISA demonstrated that tanshinone IIA significantly reduced MIF, TNF-α and IL-6 activities in I/RIRI rats. Western blot analysis showed that tanshinone IIA significantly suppressed MIF, cleaved caspase-3 and p38 MAPK protein expression levels in I/RIRI rats. The present results suggest that tanshinone IIA pretreatment attenuates I/RIRI via the downregulation of MPO expression, inflammation, MIF, cleaved caspase-3 and p38 MAPK.

Carnosic acid attenuates unilateral ureteral obstruction-induced kidney fibrosis via inhibition of Akt-mediated Nox4 expression

Fibrosis represents a common pathway to end-stage renal disease. Transforming growth factor-β (TGF-β) plays a critical role in the progression of kidney fibrosis. In the present study, we explored the effect of carnosic acid (CA) against TGF-β-induced fibroblast activation in vitro and unilateral ureteral obstruction (UUO)-induced kidney fibrosis in vivo. CA attenuated TGF-β-induced up-regulation of profibrogenic proteins, α-smooth muscle actin (α-SMA), collagen I (COLI), fibronectin (FN), and plasminogen activator inhibitor-1 (PAI-1) in kidney fibroblast cells (NRK-49F). CA inhibited TGF-β-induced hydrogen peroxide generation via inhibition of NADPH oxidase 4 (Nox4) expressions. In mice, CA-administration markedly mitigated the UUO-induced interstitial extension, collagen deposition, superoxide anion formation, hydrogen peroxide production, and lipid peroxidation. In addition, CA significantly attenuated the expression of α-SMA, COLI, FN, PAI-1, and Nox4 in UUO-induced kidneys. These results indicated that CA attenuated oxidative stress via inhibition of Nox4 expression in TGF-β-stimulated fibroblasts and UUO operated-kidneys, suggesting that CA may be useful for the treatment of fibrosis-related diseases.

Renoprotection by remote ischemic conditioning during elective coronary revascularization: A systematic review and meta-analysis of randomized controlled trials

BACKGROUND

Remote ischemic conditioning (RIC) has been recognized an emerging non-invasive approach for preventing acute kidney injury (AKI) in patients undergoing either elective coronary artery bypass graft (CABG) surgery or percutaneous coronary intervention (PCI). On the other hand, accumulating evidence has indicated the involving role of pre-CABG contrast usage for coronary angiography in post-surgery AKI risk. Along with the shortening time delay of CABG after coronary angiography, and the prevalent hybrid coronary revascularization (HCR), the AKI prevention by RIC has faced challenges following coronary revascuralization.

METHODS

Randomized controlled trials (RCTs) were searched from Pubmed, EMBase, and Cochrane library (until May 2016). The primary outcome was postoperative AKI. The second outcomes were included the requirement for renal replacement therapy (RRT), and in-hospital or 30-day mortality.

RESULTS

Twenty eligible RCTs (CABG, 3357 patients; PCI, 1501 patients) were selected. RIC significantly halved the incidence of AKI following PCI when compared with controls [n=1501; odds ratio (OR)=0.51; 95% CI, 0.32 to 0.82; P=0.006; I(2)=29.6%]. However, RIC did not affect the incidence of AKI following CABG (n=1850; OR=0.94; 95% CI, 0.73 to 1.19; P=0.586; I(2)=12.4%). The requirement for RRT and in-hospital mortality was not affected by RIC in CABG (n=2049, OR=1.04, P=0.87; n=1920, OR=0.89, P=0.7; respectively).

CONCLUSIONS

Our meta-analysis suggests that RIC for preventing AKI following CABG has faced with challenges in terms of AKI, the requirement for RRT, and mortality. However, RIC shows a renoprotective benefit for PCI. Hence, our findings may infer the preserved renal effects of RIC in CABG with preconditioning before the coronary angiography, or in HCR.

Unilateral nephrectomy elongates primary cilia in the remaining kidney via reactive oxygen species

The length of primary cilia is associated with normal cell and organ function. In the kidney, the change of functional cilia length/mass is associated with various diseases such as ischemia/reperfusion injury, polycystic kidney disease, and congenital solitary kidney. Here, we investigate whether renal mass reduction affects primary cilia length and function. To induce renal mass reduction, mice were subjected to unilateral nephrectomy (UNx). UNx increased kidney weight and superoxide formation in the remaining kidney. Primary cilia were elongated in proximal tubule cells, collecting duct cells and parietal cells of the remaining kidney. Mn(III) Tetrakis (1-methyl-4-pyridyl) porphyrin (MnTMPyP), an antioxidant, reduced superoxide formation in UNx-mice and prevented the elongation of primary cilia. UNx increased the expression of phosphorylated ERK, p21, and exocyst complex members Sec8 and Sec10, in the remaining kidney, and these increases were prevented by MnTMPyP. In MDCK, a kidney tubular epithelial cell line, cells, low concentrations of H2O2 treatment elongated primary cilia. This H2O2-induced elongation of primary cilia was also prevented by MnTMPyP treatment. Taken together, these data demonstrate that kidney compensation, induced by a reduction of renal mass, results in primary cilia elongation, and this elongation is associated with an increased production of reactive oxygen species (ROS).

Elevation of miR-21, through targeting MKK3, may be involved in ischemia pretreatment protection from ischemia-reperfusion induced kidney injury

BACKGROUND

Ischemia-reperfusion (IR) causes acute kidney injury (AKI), and ischemia pretreatment may exert protection. Mitogen-activated protein kinase kinase 3 (MKK3), which is involved in the signal transduction pathway in IR-induced injury, is a potential target of miR-21. We aimed to verify the targeting regulation of miR-21 on MKK3 and to explore the effects of miR-21-mediated MKK3 expression changes in AKI.

METHODS

Vectors containing the MKK3 3'UTR and mutated MKK3-3U-M were constructed and co-transfected with nonsense miR, miR-21-5p mimics or inhibitor in HEK293 cells. Gene expressions were detected by dual luciferase reporter assay. The effects of miR-21 on mRNA and protein of MKK3 were investigated in HK-2 cells. Male C57BL/6J mice were treated with ischemic preconditioning (IPC) and IR. Kidney functions were assessed through monitoring serum creatinine (Scr) and blood urea nitrogen (BUN). Pathological changes were observed and scored with histological samples of kidney. Expression levels of miR-21, MKK3, interleukin (IL)-6, tumor necrosis factor (TNF)-α before and after IPC and IR were examined by real-time polymerase chain reaction and/or immunohistochemistry.

RESULTS

miR-21 regulated the expression of MKK3 via 3'UTR. Following IR, MKK3, IL-6 and TNF-α levels were increased. Scr, BUN and pathological injuries were aggravated, and miR-21 expression was increased. IPC increased miR-21 levels ahead of IR and inhibited the increases in MKK3, IL-6 and TNF-α levels and the aggravation of Scr, BUN and pathological injuries.

CONCLUSIONS

miR-21 targets MKK3 in vivo and in vitro, inhibiting the downstream factors IL-6 and TNF-α. Therefore, miR-21 might be involved in protection of IPC against IR of the kidney.

Systemic protection through remote ischemic preconditioning is spread by platelet-dependent signaling in mice

Remote ischemic preconditioning (RIPC), the repetitive transient mechanical obstruction of vessels at a limb remote to the operative site, is a novel strategy to mitigate distant organ injury associated with surgery. In the clinic, RIPC has demonstrated efficacy in protecting various organs against ischemia reperfusion (IR), but a common mechanism underlying the systemic protection has not been identified. Here, we reasoned that protection may rely on adaptive physiological responses toward local stress, as is incurred through RIPC. Standardized mouse models of partial hepatic IR and of RIPC to the femoral vascular bundle were applied. The roles of platelets, peripheral serotonin, and circulating vascular endothelial growth factor (Vegf) were studied in thrombocytopenic mice, Tph1(-) (/) (-) mice, and through neutralizing antibodies, respectively. Models of interleukin-10 (Il10) and matrix metalloproteinase 8 (Mmp8) deficiency were used to assess downstream effectors of organ protection. The protection against hepatic IR through RIPC was dependent on platelet-derived serotonin. Downstream of serotonin, systemic protection was spread through up-regulation of circulating Vegf. Both RIPC and serotonin-Vegf induced differential gene expression in target organs, with Il10 and Mmp8 displaying consistent up-regulation across all organs investigated. Concerted inhibition of both molecules abolished the protective effects of RIPC. RIPC was able to mitigate pancreatitis, indicating that it can protect beyond ischemic insults.

CONCLUSIONS

We have identified a platelet-serotonin-Vegf-Il10/Mmp8 axis that mediates the protective effects of RIPC. The systemic action, the conservation of RIPC effects among mice and humans, and the protection beyond ischemic insults suggest that the platelet-dependent axis has evolved as a preemptive response to local stress, priming the body against impending harm.

Angiotensin II removes kidney resistance conferred by ischemic preconditioning

Ischemic preconditioning (IPC) by ischemia/reperfusion (I/R) renders resistance to the kidney. Strong IPC triggers kidney fibrosis, which is involved in angiotensin II (AngII) and its type 1 receptor (AT1R) signaling. Here, we investigated the role of AngII/AT1R signal pathway in the resistance of IPC kidneys to subsequent I/R injury. IPC of kidneys was generated by 30 minutes of bilateral renal ischemia and 8 days of reperfusion. Sham-operation was performed to generate control (non-IPC) mice. To examine the roles of AngII and AT1R in IPC kidneys to subsequent I/R, IPC kidneys were subjected to either 30 minutes of bilateral kidney ischemia or sham-operation following treatment with AngII, losartan (AT1R blocker), or AngII plus losartan. IPC kidneys showed fibrotic changes, decreased AngII, and increased AT1R expression. I/R dramatically increased plasma creatinine concentrations in non-IPC mice, but not in IPC mice. AngII treatment in IPC mice resulted in enhanced morphological damage, oxidative stress, and inflammatory responses, with functional impairment, whereas losartan treatment reversed these effects. However, AngII treatment in non-IPC mice did not change I/R-induced injury. AngII abolished the resistance of IPC kidneys to subsequent I/R via the enhancement of oxidative stress and inflammatory responses, suggesting that the AngII/AT1R signaling pathway is associated with outcome in injury-experienced kidney.

G-protein βγ subunit dimers modulate kidney repair after ischemia-reperfusion injury in rats

Heterotrimeric G-proteins play a crucial role in the control of renal epithelial cell function during homeostasis and in response to injury. In this report, G-protein βγ subunit (Gβγ) dimer activity was evaluated during the process of tubular repair after renal ischemia-reperfusion injury (IRI) in male Sprague Dawley rats. Rats were treated with a small molecule inhibitor of Gβγ activity, gallein (30 or 100 mg/kg), 1 hour after reperfusion and every 24 hours for 3 additional days. After IRI, renal dysfunction was prolonged after the high-dose gallein treatment in comparison with vehicle treatment during the 7-day recovery period. Renal tubular repair in the outer medulla 7 days after IRI was significantly (P < 0.001) attenuated after treatment with high-dose gallein (100 mg/kg) in comparison with low-dose gallein (30 mg/kg), or the vehicle and fluorescein control groups. Gallein treatment significantly reduced (P < 0.05) the number of proliferating cell nuclear antigen-positive tubular epithelial cells at 24 hours after the ischemia-reperfusion phase in vivo. In vitro application of gallein on normal rat kidney (NRK-52E) proximal tubule cells significantly reduced (P < 0.05) S-phase cell cycle entry compared with vehicle-treated cells as determined by 5'-bromo-2'-deoxyuridine incorporation. Taken together, these data suggest that Gβγ signaling contributes to the maintenance and repair of renal tubular epithelium and may be a novel therapeutic target for the development of drugs to treat acute kidney injury.

Regulator of G protein signaling 2 (RGS2) deficiency accelerates the progression of kidney fibrosis

The regulator of G protein signaling 2 (RGS2) is a potent negative regulator of Gq protein signals including the angiotensin II (AngII)/AngII receptor signal, which plays a critical role in the progression of fibrosis. However, the role of RGS2 on the progression of kidney fibrosis has not been assessed. Here, we investigated the role of RGS2 in kidney fibrosis induced by unilateral ureteral obstruction (UUO) in mice. UUO resulted in increased expression of RGS2 mRNA and protein in the kidney along with increases of AngII and its type 1 receptor (AT1R) signaling and fibrosis. Furthermore, UUO increased the levels of F4/80, Ly6G, myeloperoxidase, and CXCR4 in the kidneys. RGS2 deficiency significantly enhanced these changes in the kidney. RGS2 deletion in the bone marrow-derived cells by transplanting the bone marrow of RGS2 knock-out mice into wild type mice enhanced UUO-induced kidney fibrosis. Overexpression of RGS2 in HEK293 cells, a human embryonic kidney cell line, and RAW264.7 cells, a monocyte/macrophage line, inhibited the AngII-induced activation of ERK and increase of CXCR4 expression. These findings provide the first evidence that RGS2 negatively regulates the progression of kidney fibrosis following UUO, likely by suppressing fibrogenic and inflammatory responses through the inhibition of AngII/AT1R signaling.

Mice with an absent stress response are protected against ischemic renal injury

Inducible heat shock proteins (HSP), regulated by heat shock factor-1 (HSF-1), protect against renal cell injury in vitro. To determine whether HSPs ameliorate ischemic renal injury in vivo, HSF-1functional knock-out mice (HSF-KO) were compared with wild-type mice following bilateral ischemic renal injury. Following injury, the kidneys of wild-type mice had the expected induction of HSP70 and HSP25; a response absent in the kidneys of HSF-KO mice. Baseline serum creatinine was equivalent between strains. Serum creatinines at 24 hours reflow in HSF-KO mice were significantly lower than in the wild-type. Histology showed similar tubule injury in both strains after ischemic renal injury but increased medullary vascular congestion in wild-type compared with HSF-KO mice. Flow-cytometry of mononuclear cells isolated from kidneys showed no difference between strains in the number of CD4⁺ and CD8⁺ T cells in sham operated animals. At 1 hour of reflow, CD4⁺ and CD8⁺ cells were doubled in the kidneys of wild type but not HSF-KO mice. Foxp3⁺ T regulatory cells were significantly more abundant in the kidneys of sham-operated HSF-KO than wild-type mice. Suppression of CD25⁺Foxp3⁺ cells in HSF-KO kidneys with the anti-CD25 antibody PC61 reversed the protection against ischemic renal injury. Thus, HSF-KO mice are protected from ischemic renal injury by a mechanism that depends on an increase in the T regulatory cells in the kidney associated with altered T cell infiltration early in reflow. Hence, stress response activation may contribute to early injury by facilitating T cell infiltration into ischemic kidney.

Protective role of AMP-activated protein kinase-evoked autophagy on an in vitro model of ischemia/reperfusion-induced renal tubular cell injury

Ischemia/reperfusion (I/R) injury is a common cause of injury to target organs such as brain, heart, and kidneys. Renal injury from I/R, which may occur in renal transplantation, surgery, trauma, or sepsis, is known to be an important cause of acute kidney injury. The detailed molecular mechanism of renal I/R injury is still not fully clear. Here, we investigate the role of AMP-activated protein kinase (AMPK)-evoked autophagy in the renal proximal tubular cell death in an in vitro I/R injury model. To mimic in vivo renal I/R injury, LLC-PK1 cells, a renal tubular cell line derived from pig kidney, were treated with antimycin A and 2-deoxyglucose to mimic ischemia injury followed by reperfusion with growth medium. This I/R injury model markedly induced apoptosis and autophagy in LLC-PK1 cells in a time-dependent manner. Autophagy inhibitor 3-methyladenine (3MA) significantly enhanced I/R injury-induced apoptosis. I/R could also up-regulate the phosphorylation of AMPK and down-regulate the phosphorylation of mammalian target of rapamycin (mTOR). Cells transfected with small hairpin RNA (shRNA) for AMPK significantly increased the phosphorylation of mTOR as well as decreased the induction of autophagy followed by enhancing cell apoptosis during I/R. Moreover, the mTOR inhibitor RAD001 significantly enhanced autophagy and attenuated cell apoptosis during I/R. Taken together, these findings suggest that autophagy induction protects renal tubular cell injury via an AMPK-regulated mTOR pathway in an in vitro I/R injury model. AMPK-evoked autophagy may be as a potential target for therapeutic intervention in I/R renal injury.

Expression of phosphorylated extracellular signal-regulated kinase in rat kidneys exposed to high +Gz

Exposure to high gravitational acceleration forces acting along the body axis from the head to the feet (+Gz) severely reduces blood flow to the visceral organs, including the kidneys. Extracellular signal-regulated kinase (ERK) figures predominantly in mediating kidney cell responses to a wide variety of stress-related stimuli. Though previous studies have shown the activation of ERK in some experimental models, the regulation of ERK associated with +Gz exposure has not yet been investigated. The aim of this study was to examine the effect of high +Gz exposure on ERK activation in the kidneys. Using a small animal centrifuge, eight male Sprague-Dawley rats were exposed to +10Gz or +13Gz three times for 3 minutes each. The bilateral kidneys were obtained from each rat, and the expression levels of phosphorylated ERK (p-ERK) were evaluated using immunohistochemistry. In the control group, the collecting duct epithelium displayed faint cytoplasmic staining with no nuclear staining of p-ERK. By contrast, rats exposed to +10Gz showed strong nuclear staining intensity for p-ERK. In the renal papilla, the epithelial cells of collecting ducts and thin segments of the loop of Henle exhibited strong nuclear immunoreactivity for p-ERK. Rats exposed to +13Gz also showed the same staining intensity and distribution of p-ERK expression as that of rats exposed to +10Gz. This study is the first to describe +Gz exposure-induced alteration in the expression of p-ERK in the kidneys. Our finding suggests that high +Gz exposure leads to the activation of ERK in the renal papilla.

Chronic epithelial kidney injury molecule-1 expression causes murine kidney fibrosis

Acute kidney injury predisposes patients to the development of both chronic kidney disease and end-stage renal failure, but the molecular details underlying this important clinical association remain obscure. We report that kidney injury molecule-1 (KIM-1), an epithelial phosphatidylserine receptor expressed transiently after acute injury and chronically in fibrotic renal disease, promotes kidney fibrosis. Conditional expression of KIM-1 in renal epithelial cells (Kim1(RECtg)) in the absence of an injury stimulus resulted in focal epithelial vacuolization at birth, but otherwise normal tubule histology and kidney function. By 4 weeks of age, Kim1(RECtg) mice developed spontaneous and progressive interstitial kidney inflammation with fibrosis, leading to renal failure with anemia, proteinuria, hyperphosphatemia, hypertension, cardiac hypertrophy, and death, analogous to progressive kidney disease in humans. Kim1(RECtg) kidneys had elevated expression of proinflammatory monocyte chemotactic protein-1 (MCP-1) at early time points. Heterologous expression of KIM-1 in an immortalized proximal tubule cell line triggered MCP-1 secretion and increased MCP-1-dependent macrophage chemotaxis. In mice expressing a mutant, truncated KIM-1 polypeptide, experimental kidney fibrosis was ameliorated with reduced levels of MCP-1, consistent with a profibrotic role for native KIM-1. Thus, sustained KIM-1 expression promotes kidney fibrosis and provides a link between acute and recurrent injury with progressive chronic kidney disease.

Vitamin E modulates apoptosis and c-jun N-terminal kinase activation in ovarian torsion-detorsion injury

The aim of this study was to evaluate the role of vitamin E in follicular degeneration and to assess histopathological and biochemical changes following ischemia-reperfusion (IR) injury in rat ovaries. Twenty-eight Wistar albino rats were randomly divided into four groups: sham, 4h torsion, 24h detorsion, and a vitamin E group. Thirty minutes before detorsion, a single dose of 200mg/kg vitamin E was administered intraperitoneally. The ovarian histology score was determined, serum levels of malondialdehyde (MDA) and myeloperoxidase (MPO) were measured. The apoptosis of granulosa cells and the phospho-c-jun N-terminal kinase (p-JNK) and phospho-p38 (p-p38) immunoreactivities of these cells were determined. MDA and MPO levels were significantly increased in the torsion and detorsion groups. Hemorrhage, edema, and congestion were also apparent in these groups. In addition, the apoptotic index and the immunoreactivity of p-JNK were highest in the detorsion group, which also showed marked follicular degeneration. However, p-p38 activity was not affected by torsion-detorsion (TD) induction. Vitamin E ameliorated TD-induced histological alterations. It also decreased serum levels of MDA and MPO, reduced the activity of p-JNK in the ovaries, and reduced numbers of apoptotic follicular cells. In conclusion, these data indicate that vitamin E attenuated ovarian follicular degeneration by inhibiting the immunoreactivity of p-JNK and reducing the apoptosis of granulosa cells.

Two independent pathways of regulated necrosis mediate ischemia-reperfusion injury

Regulated necrosis (RN) may result from cyclophilin (Cyp)D-mediated mitochondrial permeability transition (MPT) and receptor-interacting protein kinase (RIPK)1-mediated necroptosis, but it is currently unclear whether there is one common pathway in which CypD and RIPK1 act in or whether separate RN pathways exist. Here, we demonstrate that necroptosis in ischemia-reperfusion injury (IRI) in mice occurs as primary organ damage, independent of the immune system, and that mice deficient for RIPK3, the essential downstream partner of RIPK1 in necroptosis, are protected from IRI. Protection of RIPK3-knockout mice was significantly stronger than of CypD-deficient mice. Mechanistically, in vivo analysis of cisplatin-induced acute kidney injury and hyperacute TNF-shock models in mice suggested the distinctness of CypD-mediated MPT from RIPK1/RIPK3-mediated necroptosis. We, therefore, generated CypD-RIPK3 double-deficient mice that are viable and fertile without an overt phenotype and that survived prolonged IRI, which was lethal to each single knockout. Combined application of the RIPK1 inhibitor necrostatin-1 and the MPT inhibitor sanglifehrin A confirmed the results with mutant mice. The data demonstrate the pathophysiological coexistence and corelevance of two separate pathways of RN in IRI and suggest that combination therapy targeting distinct RN pathways can be beneficial in the treatment of ischemic injury.

Reduction of oxidative stress during recovery accelerates normalization of primary cilia length that is altered after ischemic injury in murine kidneys

The primary cilium is a microtubule-based nonmotile organelle that extends from the surface of cells, including renal tubular cells. Here, we investigated the alteration of primary cilium length during epithelial cell injury and repair, following ischemia/reperfusion (I/R) insult, and the role of reactive oxygen species in this alteration. Thirty minutes of bilateral renal ischemia induced severe renal tubular cell damage and an increase of plasma creatinine (PCr) concentration. Between 8 and 16 days following the ischemia, the increased PCr returned to normal range, although without complete histological restoration. Compared with the primary cilium length in normal kidney tubule cells, the length was shortened 4 h and 1 day following ischemia, increased over normal 8 days after ischemia, and then returned to near normal 16 days following ischemia. In the urine of I/R-subjected mice, acetylated tubulin was detected. The cilium length of proliferating cells was shorter than that in nonproliferating cells. Mature cells had shorter cilia than differentiating cells. Treatment with Mn(III) tetrakis(1-methyl-4-pyridyl) porphyrin (MnTMPyP), an antioxidant, during the recovery of damaged kidneys accelerated normalization of cilia length concomitant with a decrease of oxidative stress and morphological recovery in the kidney. In the Madin-Darby canine kidney (MDCK) cells, H2O2 treatment caused released ciliary fragment into medium, and MnTMPyP inhibited the deciliation. The ERK inhibitor U0126 inhibited elongation of cilia in normal and MDCK cells recovering from H2O2 stress. Taken together, our results suggest that primary cilia length reflects cell proliferation and the length of primary cilium is regulated, at least, in part, by reactive oxygen species through ERK.

Defect in Runx2 gene accelerates ureteral obstruction-induced kidney fibrosis via increased TGF-β signaling pathway

Runt-related transcription factor 2 (Runx2) plays an important role in bone formation and de novo synthesis of proteins, including type 1 collagen. Runx2 has a potent effect on signaling of transforming growth factor (TGF)-β and vice versa, implicating its significant role in fibrosis. Chronic renal failure comprises fibrosis, characterized as an increase in TGF-β signaling, and expression of α-smooth muscle actin (α-SMA), and extracellular matrix proteins. Here, we evaluated the role of Runx2 in ureteral obstruction (UO)-induced kidney fibrosis using mice whose Runx2 gene expression is genetically down-regulated. UO caused tubular atrophy and dilation, expansion of interstitium, and increased expression of collagens and α-SMA with a concomitant decrease in expression of Runx2. Deficiency of Runx2 gene (Runx2(+/-) mice) showed higher expression of collagens and α-SMA in the kidney following UO compared to wild type (Runx2(+/+)) mice. UO-induced activation of TGF-β signaling was higher in the Runx2(+/-) kidney than Runx2(+/+) kidney, suggesting an inhibitory effect of Runx2 on TGF-β signaling in kidney fibrosis. Besides, overexpression of the Runx2 gene using an adenoviral vector in kidney tubule cells resulted in attenuated TGF-β-induced Smad3 phosphorylation and expressions of α-SMA and collagen I. Furthermore, Runx2 gene deficient mouse embryonic fibroblasts induced greater activation of Smad3 and expression of α-SMA in response to TGF-β. Collectively, Runx2 plays a protective role in UO-induced kidney fibrosis by inhibition of TGF-β signaling, suggesting Runx2 as a novel target for protection against fibrosis-related diseases such as chronic renal failure.

Phosphoenolpyruvate, a glycolytic intermediate, as a cytoprotectant and antioxidant in ex-vivo cold-preserved mouse liver: a potential application for organ preservation

OBJECTIVES

The aim of this study was to examine the effect of phosphoenolpyruvate (PEP), a glycolytic intermediate, on organ damage during cold preservation of liver.

METHODS

An ex-vivo mouse liver cold-preservation model and an in-vitro liver injury model induced by hydrogen peroxide in HepG2 cells were leveraged.

KEY FINDINGS

PEP attenuated the elevation of aminotransferases and lactate dehydrogenase leakage during organ preservation, histological changes and changes in oxidative stress parameters (measured as thiobarbituric acid reactive substance and glutathione content) induced by 72 h of cold preservation of the liver. The effects were comparable with the University of Wisconsin solution, a gold standard organ preservation agent. The decrease in ATP content in liver during the cold preservation was attenuated by PEP treatment. PEP prevented the cellular injury and increases in intracellular reactive oxygen species in HepG2 cells. In addition, PEP scavenged hydroxyl radicals, but had no effect on superoxide anion as evaluated by an electron paramagnetic resonance spin-trapping technique.

CONCLUSIONS

PEP significantly attenuated the injury, oxidative stress and ATP depletion in liver during cold preservation. The antioxidative potential of PEP was confirmed by in-vitro examination. We suggest that PEP acts as a glycolytic intermediate and antioxidant, and is particularly useful as an organ preservation agent in clinical transplantation.

The role of heat shock protein 90 in modulating ischemia-reperfusion injury in the kidney

INTRODUCTION

Kidney transplantation is the gold standard treatment for end-stage renal disease. Ischemia-reperfusion injury (IRI) is an unavoidable consequence of the transplantation procedure and is responsible for delayed graft function and poorer long-term outcomes.

AREAS COVERED

Pharmacological induction of heat shock protein (Hsp) expression is an emerging pre-conditioning strategy aimed at reducing IRI following renal transplantation. Hsp90 inhibition up-regulates protective Hsps (especially Hsp70) and potentially down-regulates NF-κB by disruption of the IκB kinase (IKK) complex. However, the clinical application of Hsp90 inhibitors is currently limited by their toxicity profile and the exact mechanism of protection conferred is unknown. Toll-like receptor 4 (TLR4) is a further regulator of NF-κB and recent studies suggest TLR4 plays a dominant role in mediating kidney damage following IRI. The full interaction of Hsps with TLRs is yet to be delineated and whether TLR4 signalling can be targeted by Hsp90 inhibition in IRI remains uncertain.

EXPERT OPINION

Pharmacological pre-conditioning by Hsp90 inhibition involves direct treatment to the kidney donor and/or organ, which aims to reduce injury prior to the onset of ischemia. The major challenges going forward are to establish the exact mechanism of protection offered by these drugs and the investgiation of less toxic analogues that could be safely translated into human studies.

Phosphoenolpyruvic acid, an intermediary metabolite of glycolysis, as a potential cytoprotectant and anti-oxidant in HeLa cells

This study examined the cytoprotective and anti-oxidative properties of phosphoenolpyruvic acid (PEP), a glycolysis metabolite with a high-energy phosphate group. PEP (0.1-10 mM) significantly attenuated the decrease in cell viability induced by hydrogen peroxide (H(2)O(2)) in HeLa cells in a dose-dependent manner. PEP also inhibited the decrease in calcein-acetomethoxy-stained cells and the increase in propidium iodide-stained cells that were induced by H(2)O(2). The H(2)O(2)-stimulated increase in intracellular reactive oxygen species was significantly reduced by PEP. PEP also demonstrated scavenging potential against hydroxyl radicals, as assessed by the electron paramagnetic resonance method. In addition, PEP demonstrated scavenging potential against the 1,1-diphenyl-2-picrylhydrazyl radical, a representative artificial radical, although the potential is very weak. PEP (10 mM) slightly inhibited the decrease in cellular ATP content induced by H(2)O(2), but did not show any effects at low doses (0.1, 1 mM). PEP (0.1-10 mM) also attenuated the cell injury but not the decrease in intracellular ATP content, induced by 2-deoxy-D-glucose, a glycolysis inhibitor. These results indicate that PEP exerts cytoprotective effects and has anti-oxidative potential, although the precise cytoprotective mechanisms are not fully elucidated. We suggest that PEP is a functional carbohydrate metabolite with cytoprotective and anti-oxidative activity, and is potentially useful as a therapeutic agent against diseases that involve the oxidative stress.