Hydroxyfasudil-mediated inhibition of ROCK1 and ROCK2 improves kidney function in rat renal acute ischemia-reperfusion injury

CircHECTD1 promoted MIRI-associated inflammation via inhibiting miR-138-5p and upregulating ROCK2

Myocardial ischemia-reperfusion injury (MIRI) was often observed after surgeries, causing a lot of suffering to patients. Inflammation and apoptosis were critical determinants during MIRI. We conveyed experiments to reveal the regulatory functions of circHECTD1 in MIRI development. The Rat MIRI model was established and determined by 2,3,5-triphenyl tetrazolium chloride (TTC) staining. We analyzed cell apoptosis using TUNEL and flow cytometry. Proteins expression was evaluated by western blot. The RNA level was determined by qRT-PCR. Secreted inflammatory factors were analyzed by ELISA assay. To predict the interaction sequences on circHECTD1, miR-138-5p, and ROCK2, bioinformatics analysis was performed. Dual-luciferase assay was used to confirm these interaction sequences. CircHECTD1 and ROCK2 were upregulated in the rat MIRI model, while miR-138-5p was decreased. CircHECTD1 knockdown alleviated H/R-induced inflammation in H9c2 cells. Direct interaction and regulation of circHECTD1/miR-138-5p and miR-138-5p/ROCK2 were confirmed by dual-luciferase assay. CircHECTD1 promoted H/R-induced inflammation and cell apoptosis by inhibiting miR-138-5p. miR-138-5p alleviated H/R-induced inflammation, while ectopic ROCK2 antagonized such effect of miR-138-5p. Our research suggested that the circHECTD1-modulated miR-138-5p suppressing is responsible for ROCK2 activation during H/R-induced inflammatory response, providing a novel insight into MIRI-associated inflammation.

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

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

Pericyte-mediated constriction of renal capillaries evokes no-reflow and kidney injury following ischaemia

Acute kidney injury is common, with ~13 million cases and 1.7 million deaths/year worldwide. A major cause is renal ischaemia, typically following cardiac surgery, renal transplant or severe haemorrhage. We examined the cause of the sustained reduction in renal blood flow ('no-reflow'), which exacerbates kidney injury even after an initial cause of compromised blood supply is removed. Adult male Sprague-Dawley rats, or NG2-dsRed male mice were used in this study. After 60 min kidney ischaemia and 30-60 min reperfusion, renal blood flow remained reduced, especially in the medulla, and kidney tubule damage was detected as Kim-1 expression. Constriction of the medullary descending vasa recta and cortical peritubular capillaries occurred near pericyte somata, and led to capillary blockages, yet glomerular arterioles and perfusion were unaffected, implying that the long-lasting decrease of renal blood flow contributing to kidney damage was generated by pericytes. Blocking Rho kinase to decrease pericyte contractility from the start of reperfusion increased the post-ischaemic diameter of the descending vasa recta capillaries at pericytes, reduced the percentage of capillaries that remained blocked, increased medullary blood flow and reduced kidney injury. Thus, post-ischaemic renal no-reflow, contributing to acute kidney injury, reflects pericytes constricting the descending vasa recta and peritubular capillaries. Pericytes are therefore an important therapeutic target for treating acute kidney injury.

Role of actin cytoskeleton in podocytes

The selectivity of the glomerular filter is established by physical, chemical, and signaling interplay among its three core constituents: glomerular endothelial cells, the glomerular basement membrane, and podocytes. Functional impairment or injury of any of these three components can lead to proteinuria. Podocytes are injured in many forms of human and experimental glomerular disease, including minimal change disease, focal segmental glomerulosclerosis, and diabetes mellitus. One of the earliest signs of podocyte injury is loss of their distinct structure, which is driven by dysregulated dynamics of the actin cytoskeleton. The status of the actin cytoskeleton in podocytes depends on a set of actin binding proteins, nucleators and inhibitors of actin polymerization, and regulatory GTPases. Mutations that alter protein function in each category have been implicated in glomerular diseases in humans and animal models. In addition, a growing body of studies suggest that pharmacological modifications of the actin cytoskeleton have the potential to become novel therapeutics for podocyte-dependent chronic kidney diseases. This review presents an overview of the essential proteins that establish actin cytoskeleton in podocytes and studies demonstrating the feasibility of drugging actin cytoskeleton in kidney diseases.

Polycystin-1 regulates ARHGAP35-dependent centrosomal RhoA activation and ROCK signaling

Mutations in PKD1 (encoding for polycystin-1 [PC1]) are found in 80%–85% of patients with autosomal dominant polycystic kidney disease (ADPKD). We tested the hypothesis that changes in actin dynamics result from PKD1 mutations through dysregulation of compartmentalized centrosomal RhoA signaling mediated by specific RhoGAP (ARHGAP) proteins resulting in the complex cellular cystic phenotype. Initial studies revealed that the actin cytoskeleton was highly disorganized in cystic cells derived from patients with PKD1 and was associated with an increase in total and centrosomal active RhoA and ROCK signaling. Using cilia length as a phenotypic readout for centrosomal RhoA activity, we identified ARHGAP5, -29, and -35 as essential regulators of ciliation in normal human renal tubular cells. Importantly, a specific decrease in centrosomal ARHGAP35 was observed in PKD1-null cells using a centrosome-targeted proximity ligation assay and by dual immunofluorescence labeling. Finally, the ROCK inhibitor hydroxyfasudil reduced cyst expansion in both human PKD1 3D cyst assays and an inducible Pkd1 mouse model. In summary, we report a potentially novel interaction between PC1 and ARHGAP35 in the regulation of centrosomal RhoA activation and ROCK signaling. Targeting the RhoA/ROCK pathway inhibited cyst formation in vitro and in vivo, indicating its relevance to ADPKD pathogenesis and for developing new therapies to inhibit cyst initiation.

Polycystin-1, the major protein mutated in autosomal dominant polycystic kidney disease, activates centrosomal RhoA activity via interaction with the Rho-GAP protein ARHGAP35, resulting in shorter cilia.

Effect of melatonin on torsion and reperfusion induced pathogenesis of rat uterus

We investigated the use of melatonin to improve fertility and reduce uterine damage caused by torsion of the uterus in pregnant rats. We used 35 pregnant rats at gestational age 18 days. The animals were randomized into five groups. Group 1 was anesthetized only. Group 2 was subjected to experimental uterine torsion of 360° and the torsion was corrected after 6 h. Group 3 was subjected to uterine torsion of 360°, the torsion was corrected after 6 h and melatonin was administered at the time of correction. Group 4 rats were subjected to 360º uterine torsion and melatonin was administered 6 h later at the time of correction. Group 5 was administered melatonin followed by uterine torsion of 360 degrees followed by correction of torsion 6 h later. Samples were obtained from the uterine horns on the day 1 postpartum. We used Bax, Bcl-2 and caspase 3 staining to measure apoptosis in the uterine tissues. The mRNA levels of Rho-associated, coiled-coil containing protein kinases 1 (ROCK1), homeobox D10 (Hox4 HoxD10), TLR4, NFκB1, caveolin 1 (Cav1) heat shock protein 90 alpha (cytosolic), class B member 1 (Hsp90ab1) and glyceraldehyde-3-phosphate dehydrogenase (GAPDH) were determined using quantitative real-time polymerase chain reaction analysis (qRT-PCR). Bax, Bcl-2 and caspase 3 were detected using immunohistochemistry. No difference was observed among groups with respect to abortion, neonatal mortality or congenital abnormalities. Compared to the control group, the mRNA levels of Rock1, Hox4, TLR4, NFκB1, Cav1 and Hsp90 genes were decreased significantly in the study groups; the decrease was greater in groups 3 and 4, which were treated with melatonin. The greatest amount of Bax staining was found in group 1 and the least amount of Bcl-2 staining was found in groups 4 and 5; the greatest amount of caspase 3 staining was found in group 2. Our findings indicate that melatonin reduced uterine torsion related tissue damage and that its application during torsion was more effective than application following removal of torsion.

Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells

Reactivation of Notch signaling in kidneys of animal models and patients with chronic kidney disease (CKD) has been shown to contribute to epithelial injury and fibrosis development. Here, we investigated the mechanisms of Notch-induced injury in renal epithelial cells. We performed genome-wide transcriptome analysis to identify Notch target genes using an in vitro system of cultured tubular epithelial cells expressing the intracellular domain of Notch1. One of the top downregulated genes was Disabled-2 ( Dab2). With the use of Drosophila nephrocytes as a model system, we found that Dab (the Drosophila homolog of Dab2) knockdown resulted in a significant filtration defect, indicating that loss of Dab2 plays a functional role in kidney disease development. We showed that Dab2 expression in cultured tubular epithelial cells is involved in endocytic regulation and that it also protects cells from TGF-β-induced epithelial-to-mesenchymal transition. In vivo correlation studies indicated its additional role in renal ischemia-induced injury. Together, these data suggest that Dab2 plays a versatile role in the kidney and may impact on acute and CKDs.-Schütte-Nütgen, K., Edeling, M., Mendl, G., Krahn, M. P., Edemir, B., Weide, T., Kremerskothen, J., Michgehl, U., Pavenstädt, H. Getting a Notch closer to renal dysfunction: activated Notch suppresses expression of the adaptor protein Disabled-2 in tubular epithelial cells.

Genetic or pharmacologic inhibition of EGFR ameliorates sepsis-induced AKI

Despite recent studies have demonstrated that the EGF receptor (EGFR) activation provided a renoprotective role during ischemic and folic acid-induced AKI, the role and regulation mechanism of EGFR in septic AKI remains unclear. Here, gefitinib, a highly selective EGFR inhibitor, abrogated LPS-induced phosphorylation of EGFR, ERK1/2, and STAT3 as well as expression of COX, eNOS, and proinflammatory cytokines in HK-2 cells. In addition, c-Src is an upstream of EGFR signaling pathway and mediates LPS-induced EGFR transactivation. In vivo, either gefitinib or genetic approaches (Wave-2 mutant mice, which have reduced EGFR tyrosine kinase activity) protected against LPS or cecal ligation and puncture (CLP) induced AKI respectively. Interestingly, the beneficial effects of gefitinib or genetic approaches were accompanied by the dephosphorylation of EGFR, ERK1/2, and STAT3, the down regulation of expression of COX, eNOS, macrophage infiltration, proinflammatory cytokines production and the renal cell apoptosis. Furthermore, mRNA array results indicated that gene families involved in cell death, inflammation, proliferation and signal transduction were down regulated in Wave-2 (Wa-2) mice. Take together, these data suggest that EGFR may mediate renal injury by promoting production of inflammatory factors and cell apoptosis. Inhibition of EGFR may have therapeutic potential for AKI during endotoxemia.

HIV-1 Tat Regulates Occludin and Aβ Transfer Receptor Expression in Brain Endothelial Cells via Rho/ROCK Signaling Pathway

HIV-1 transactivator protein (Tat) has been shown to play an important role in HIV-associated neurocognitive disorders. The aim of the present study was to evaluate the relationship between occludin and amyloid-beta (Aβ) transfer receptors in human cerebral microvascular endothelial cells (hCMEC/D3) in the context of HIV-1-related pathology. The protein expressions of occludin, receptor for advanced glycation end products (RAGE), and low-density lipoprotein receptor-related protein 1 (LRP1) in hCMEC/D3 cells were examined using western blotting and immunofluorescent staining. The mRNA levels of occludin, RAGE, and LRP1 were measured using quantitative real-time polymerase chain reaction. HIV-1 Tat at 1 µg/mL and the Rho inhibitor hydroxyfasudil (HF) at 30 µmol/L, with 24 h exposure, had no significant effect on hCMEC/D3 cell viability. Treatment with HIV-1 Tat protein decreased mRNA and protein levels of occludin and LRP1 and upregulated the expression of RAGE; however, these effects were attenuated by HF. These data suggest that the Rho/ROCK signaling pathway is involved in HIV-1 Tat-mediated changes in occludin, RAGE, and LRP1 in hCMEC/D3 cells. HF may have a beneficial influence by protecting the integrity of the blood-brain barrier and the expression of Aβ transfer receptors.

Transcription Factor Sp1 Promotes the Expression of Porcine ROCK1 Gene

Rho-associated, coiled-coil containing protein kinase 1 (ROCK1) gene plays a crucial role in maintaining genomic stability, tumorigenesis and myogenesis. However, little is known about the regulatory elements governing the transcription of porcine ROCK1 gene. In the current study, the transcription start site (TSS) was identified by 5'-RACE, and was found to differ from the predicted one. The region in ROCK1 promoter which is critical for promoter activity was investigated via progressive deletions. Site-directed mutagenesis indicated that the region from -604 to -554 bp contains responsive elements for Sp1. Subsequent experiments showed that ROCK1 promoter activity is enhanced by Sp1 in a dose-dependent manner, whereas treatment with specific siRNA repressed ROCK1 promoter activity. Electrophoretic mobility shift assay (EMSA), DNA pull down and chromatin immunoprecipitation (ChIP) assays revealed Sp1 can bind to this region. qRT-PCR and Western blotting research followed by overexpression or inhibition of Sp1 indicate that Sp1 can affect endogenous ROCK1 expression at both mRNA and protein levels. Overexpression of Sp1 can promote the expression of myogenic differentiation 1(MyoD), myogenin (MyoG), myosin heavy chain (MyHC). Taken together, we conclude that Sp1 positively regulates ROCK1 transcription by directly binding to the ROCK1 promoter region (from -604 to -532 bp) and may affect the process of myogenesis.

Inhibitory effects of fasudil on renal interstitial fibrosis induced by unilateral ureteral obstruction

Renal fibrosis is the major cause of chronic kidney disease, and the Rho/Rho-associated coiled-coil kinase (ROCK) signaling cascade is involved in the renal fibrotic processes. Several studies have reported that ROCK inhibitors attenuate renal fibrosis. However, the mechanism of this process remains to be fully elucidated. The present study assessed the inhibitory effect of fasudil, a ROCK inhibitor using immunohistochemistry, reverse transcription-quantitative polymerase chain reaction and western blot analyses, in vivo and in vitro, to elucidate the mechanisms underlying renal interstitial fibrosis. In mice induced with unilateral ureteral obstruction (UUO), collagen accumulation, the expression of fibrosis-associated genes and the content of hydroxyproline in the kidney increased 3, 7, and 14 days following UUO. Fasudil attenuated the histological changes, and the production of collagen and extracellular matrix in the UUO kidney. The expression of α-smooth muscle actin (α-SMA) and the transforming growth factor-β (TGFβ)-Smad signaling pathway, and macrophage infiltration were suppressed by fasudil in the kidneys of the UUO mice. The present study also evaluated the role of intrinsic renal cells and infiltrated macrophages using NRK-52E, NRK-49F and RAW264.7 cells. The mRNA and protein expression levels of collagen I and α-SMA increased in the NRK-52E and NRK-49F cells stimulated by TGF-β1. Hydroxyfasudil, a bioactive metabolite of fasudil, attenuated the increase in the mRNA and protein expression levles of α-SMA in the two cell types. However, the reduction in the mRNA expression of collagen I was observed in the NRK-49F cells only. Hydroxyfasudil decreased the mRNA expression of monocyte chemoattractant protein-1 (MCP-1) induced by TGF-β1 in the NRK-52E cells, but not in the NRK-49F cells. In the RAW264.7 cells, the mRNA expression levels of MCP-1, interleukin (IL)-1β, IL-6 and tumor necrosis factor α were increased significantly following lipopolysaccharide stimulation, and were not suppressed by hydroxyfasudil. These data suggested that the inhibition of ROCK activity by fasudil suppressed the transformation of renal intrinsic cells into the myofibroblast cells, and attenuated the infiltration of macrophages, without inhibiting the expression or the activation of cytokine/chemokines, in the progression of renal interstitial fibrosis.

Endothelial Krüppel-Like Factor 4 Mediates the Protective Effect of Statins against Ischemic AKI

Endothelial cells participate in the pathophysiology of ischemic AKI by increasing the expression of cell adhesion molecules and by recruiting inflammatory cells. We previously showed that endothelial Krüppel-like factor 4 (Klf4) regulates vascular cell adhesion molecule 1 (Vcam1) expression and neointimal formation after carotid injury. In this study, we determined whether endothelial Klf4 is involved in ischemic AKI using endothelial Klf4 conditional knockout (Klf4 cKO) mice generated by breeding Tek-Cre mice and Klf4 floxed mice. Klf4 cKO mice were phenotypically normal before surgery. However, after renal ischemia-reperfusion injury, Klf4 cKO mice exhibited elevated serum levels of urea nitrogen and creatinine and aggravated renal histology compared with those of Klf4 floxed controls. Moreover, Klf4 cKO mice exhibited enhanced accumulation of neutrophils and lymphocytes and elevated expression of cell adhesion molecules, including Vcam1 and Icam1, in injured kidneys. Notably, statins ameliorated renal ischemia-reperfusion injury in control mice but not in Klf4 cKO mice. Mechanistic analyses in cultured endothelial cells revealed that statins increased KLF4 expression and that KLF4 mediated the suppressive effect of statins on TNF-α-induced VCAM1 expression by reducing NF-κB binding to the VCAM1 promoter. These results provide evidence that endothelial Klf4 is renoprotective and mediates statin-induced protection against ischemic AKI by regulating the expression of cell adhesion molecules and concomitant recruitment of inflammatory cells.

Impact of Rho-Kinase Inhibitor Hydroxyfasudil in Protamine Sulphate Induced Cystitis Rat Bladder

OBJECTIVES

The objective of the present study was to evaluate anti-inflammatory effects of hydroxyfasudil in a protamine sulfate (PS) induced cystitis rat model. Additionally, we investigated prevention of bladder overactivity (BO), and tissue damage in these experiments.

METHODS

Animals were divided into four groups. In Groups 1 and 2, chemical induced cystitis model was created by administrating intravesical PS with PE50 catheter by the transurethral route. In Group 1, Rho-kinase inhibitor hydroxyfasudil was administered intaperitoneally, and in Group 2, subjects were administered a corresponding volume of saline in the same way. In Group 3, vehicle was administered intravesically and hydroxyfasudil was administrated intraperitoneally. Group 4 was a control Group, and the vehicle was administered intravesically and intraperitoneally. Micturition frequencies were recorded. Biochemical analyses were performed for oxidative stress, and pathological evaluations were investigated. In vitro contractions of bladder tissue strips were measured in tissue-bath.

RESULTS

There were significantly lower Lipid peroxidase levels and higher levels of Glutathione in Group 1 than Group 2 (P = 0.016, P = 0.001, respectively). There was generally more inflammation in Group 2 than the other groups as determined by microscopy. There were significantly higher frequencies of micturition, lower volume, and mean voided maximum urine output after PS administration in Groups 1 and 2. In vitro contraction responses of bladder strips to potassium chloride and acetylcholine were statistically higher in Group 2 than Groups 1 and 3.

CONCLUSIONS

Significant reduction of inflammation by affecting the anti-oxidant defense systems was provided by hydroxyfasudil. Decreased in vitro responses to contractions of bladder smooth muscle strips were obtained. Hydroxyfasudil may be a potential new therapeutic option for inflammation and BO, in rat bladder.

Renal Function Trajectories and Clinical Outcomes in Acute Heart Failure

Background—

Prior studies have demonstrated adverse risk associated with baseline and worsening renal function in acute heart failure, but none has modeled the trajectories of change in renal function and their impact on outcomes.

Methods and Results—

We used linear mixed models of serial measurements of blood urea nitrogen and creatinine to describe trajectories of renal function in 1962 patients with acute heart failure and renal dysfunction enrolled in the Placebo-Controlled Randomized Study of the Selective A 1 Adenosine Receptor Antagonist Rolofylline for Patients Hospitalized with Acute Decompensated Heart Failure and Volume Overload to Assess Treatment Effect on Congestion and Renal Function study. We assessed risk of 180-day mortality and 60-day cardiovascular or renal readmission and used Cox regression to determine association between renal trajectories and outcomes. Compared with patients alive at 180 days, patients who died were older, had lower blood pressure and ejection fraction, and higher creatinine levels at baseline. On average for the entire cohort, creatinine rose from days 1 to 3 and increased further after discharge, with the trajectory dependent on the day of discharge. Blood urea nitrogen, creatinine, and the rate of change in creatinine from baseline were the strongest independent predictors of 180-day mortality and 60-day readmission, whereas the rate of change of blood urea nitrogen from baseline was not predictive of outcomes. Baseline blood urea nitrogen >35 mg/dL and increase in creatinine >0.1 mg/dL per day increased the risk of mortality, whereas stable or decreasing creatinine was associated with reduced risk.

Conclusions—

Patients with acute heart failure and renal dysfunction demonstrate variable rise and fall in renal indices during and immediately after hospitalization. Risk of morbidity and mortality can be predicted based on baseline renal function and creatinine trajectory during the first 7 days.

Clinical Trial Registration—

URL: http://www.clinicaltrials.gov . Unique identifiers: NCT00328692 and NCT00354458.

Histological study on effect of mesenchymal stem cell therapy on experimental renal injury induced by ischemia/reperfusion in male albino rat

BACKGROUND AND OBJECTIVES

Acute kidney injury (AKI) represents a major clinical problem with high mortality and limited treatment protocols. This study was planned to evaluate the therapeutic effectiveness of bone marrow - derived mesenchymal stem cells (BM-MSCs) in a rat model of ischemia/reperfusion (I/R) AKI.

METHODS AND RESULTS

This study was carried out on thirty adult male albino rats. Animals were divided equally into three groups. Group I (control sham-operated group) (n=10), were subdivided equally into two subgroups; Ia and Ib. The experimental group (n=20) were all subjected to I/R injury by clamping both renal pedicles for 40 minutes. Half of the I/R animals did not receive MSC therapy (group II) [non-MSC treated group]. The other half of the I/R animals received single intravenous injection of PKH26 labelled BM-MSCs immediately after removal of the clamps and visual confirmation of reflow (group III) [MSC treated group]. Animals were sacrificed 24 hrs (subgroups IIa & IIIa) and 72 hrs (subgroups IIb & IIIb) after intervention. Serological measurements included serum urea and creatinine. Kidney specimens were processed for H&E, PAS and PCNA. Mean % of renal corpuscles with affected glomeruli, mean % of affected tubules, mean area % of PAS-positive reaction and mean area % of PCNA immunoreactivity were measured by histomorphometric studies and statistically compared. MSCs-treated group exhibited protection against renal injury serologically and histologically.

CONCLUSIONS

Results of the present study suggest a potential reno-protective capacity of MSCs which could be of considerable therapeutic promise for cell-based management of clinical AKI.

Donor simvastatin treatment prevents ischemia-reperfusion and acute kidney injury by preserving microvascular barrier function

Ischemia-reperfusion injury (IRI) after kidney transplantation may result in delayed graft function. We used rat renal artery clamping and transplantation models to investigate cholesterol-independent effects of clinically relevant single-dose peroral simvastatin treatment 2 h before renal ischemia on microvascular injury. The expression of HMG-CoA reductase was abundant in glomerular and peritubular microvasculature of normal kidneys. In renal artery clamping model with 30-min warm ischemia, simvastatin treatment prevented peritubular microvascular permeability and perfusion disturbances, glomerular barrier disruption, tubular dysfunction and acute kidney injury. In fully MHC-mismatched kidney allografts with 16-h cold and 1-h warm ischemia, donor simvastatin treatment increased the expression of flow-regulated transcription factor KLF2 and vasculoprotective eNOS and HO-1, and preserved glomerular and peritubular capillary barrier integrity during preservation. In vitro EC Weibel-Palade body exocytosis assays showed that simvastatin inhibited ischemia-induced release of vasoactive angiopoietin-2 and endothelin-1. After reperfusion, donor simvastatin treatment prevented microvascular permeability, danger-associated ligand hyaluronan induction, tubulointerstitial injury marker Kim-1 immunoreactivity and serum creatinine and NGAL levels, and activation of innate and adaptive immune responses. In conclusion, donor simvastatin treatment prevented renal microvascular dysfunction and IRI with beneficial effects on adaptive immune and early fibroproliferative responses. Further studies may determine potential benefits in clinical cadaveric kidney transplantation.

Transcriptome analysis of renal ischemia/reperfusion injury and its modulation by ischemic pre-conditioning or hemin treatment

Ischemia/reperfusion injury (IRI) is a leading cause of acute renal failure. The definition of the molecular mechanisms involved in renal IRI and counter protection promoted by ischemic pre-conditioning (IPC) or Hemin treatment is an important milestone that needs to be accomplished in this research area. We examined, through an oligonucleotide microarray protocol, the renal differential transcriptome profiles of mice submitted to IRI, IPC and Hemin treatment. After identifying the profiles of differentially expressed genes observed for each comparison, we carried out functional enrichment analysis to reveal transcripts putatively involved in potential relevant biological processes and signaling pathways. The most relevant processes found in these comparisons were stress, apoptosis, cell differentiation, angiogenesis, focal adhesion, ECM-receptor interaction, ion transport, angiogenesis, mitosis and cell cycle, inflammatory response, olfactory transduction and regulation of actin cytoskeleton. In addition, the most important overrepresented pathways were MAPK, ErbB, JAK/STAT, Toll and Nod like receptors, Angiotensin II, Arachidonic acid metabolism, Wnt and coagulation cascade. Also, new insights were gained about the underlying protection mechanisms against renal IRI promoted by IPC and Hemin treatment. Venn diagram analysis allowed us to uncover common and exclusively differentially expressed genes between these two protective maneuvers, underscoring potential common and exclusive biological functions regulated in each case. In summary, IPC exclusively regulated the expression of genes belonging to stress, protein modification and apoptosis, highlighting the role of IPC in controlling exacerbated stress response. Treatment with the Hmox1 inducer Hemin, in turn, exclusively regulated the expression of genes associated with cell differentiation, metabolic pathways, cell cycle, mitosis, development, regulation of actin cytoskeleton and arachidonic acid metabolism, suggesting a pleiotropic effect for Hemin. These findings improve the biological understanding of how the kidney behaves after IRI. They also illustrate some possible underlying molecular mechanisms involved in kidney protection observed with IPC or Hemin treatment maneuvers.

Rho-kinase inhibition prevents proteinuria in immune-complex-mediated antipodocyte nephritis

Podocyte foot process retraction is a hallmark of proteinuric glomerulonephritis. Cytoskeletal rearrangement causes a redistribution of slit membrane proteins from the glomerular filtration barrier towards the cell body. However, the underlying signaling mechanisms are presently unknown. Recently, we have developed a new experimental model of immune-mediated podocyte injury in mice, the antipodocyte nephritis (APN). Podocytes were targeted with a polyclonal antipodocyte antibody causing massive proteinuria around day 10. Rho-kinases play a central role in the organization of the actin cytoskeleton of podocytes. We therefore investigated whether inhibition of Rho-kinases would prevent podocyte disruption. C57/BL6 mice received antipodocyte serum with or without daily treatment with the specific Rho-kinase inhibitor HA-1077 (5 mg/kg). Immunoblot analysis demonstrated activation of Rho-kinase in glomeruli of antipodocyte serum-treated mice, which was prevented by HA-1077. Increased Rho-kinase activity was localized to podocytes in APN mice by immunostainings against the phosphorylated forms of Rho-kinase substrates. Rho-kinase inhibition significantly reduced podocyte loss from the glomerular tuft. Periodic acid staining demonstrated less podocyte hypertrophy in Rho-kinase-inhibited APN mice, despite similar amounts of immune complex deposition. Electron microscopy revealed reduced foot process effacement compared with untreated APN mice. Internalization of the podocyte slit membrane proteins nephrin and synaptopodin was prevented by Rho-kinase inhibition. Functionally, Rho-kinase inhibition significantly reduced proteinuria without influencing blood pressure. In rats with passive Heymann nephritis and human kidney biopsies from patients with membranous nephropathy, Rho-kinase was activated in podocytes. Together, these data suggest that increased Rho-kinase activity in the podocyte may be a mechanism for in vivo podocyte foot process retraction.

The role of SDF-1-CXCR4/CXCR7 axis in the therapeutic effects of hypoxia-preconditioned mesenchymal stem cells for renal ischemia/reperfusion injury

In vitro hypoxic preconditioning (HP) of mesenchymal stem cells (MSCs) could ameliorate their viability and tissue repair capabilities after transplantation into the injured tissue through yet undefined mechanisms. There is also experimental evidence that HP enhances the expression of both stromal-derived factor-1 (SDF-1) receptors, CXCR4 and CXCR7, which are involved in migration and survival of MSCs in vitro, but little is known about their role in the in vivo therapeutic effectiveness of MSCs in renal ischemia/reperfusion (I/R) injury. Here, we evaluated the role of SDF-1-CXCR4/CXCR7 pathway in regulating chemotaxis, viability and paracrine actions of HP-MSCs in vitro and in vivo. Compared with normoxic preconditioning (NP), HP not only improved MSC chemotaxis and viability but also stimulated secretion of proangiogenic and mitogenic factors. Importantly, both CXCR4 and CXCR7 were required for the production of paracrine factors by HP-MSCs though the former was only responsible for chemotaxis while the latter was for viability. SDF-1α expression was upregulated in postischemic kidneys. After 24 h systemical administration following I/R, HP-MSCs but not NP-MSCs were selectively recruited to ischemic kidneys and this improved recruitment was abolished by neutralization of CXCR4, but not CXCR7. Furthermore, the increased recruitment of HP-MSCs was associated with enhanced functional recovery, accelerated mitogenic response, and reduced apoptotic cell death. In addition, neutralization of either CXCR4 or CXCR7 impaired the improved therapeutic potential of HP-MSCs. These results advance our knowledge about SDF-1-CXCR4/CXCR7 axis as an attractive target pathway for improving the beneficial effects of MSC-based therapies for renal I/R.