Early renal ischemia, with or without reperfusion, activates NFkappaB and increases TNF-alpha bioactivity in the kidney

Kidney toxicology of a novel compound Lithium Bis(trifluoromethanesulfonyl)imide (LiTFSI, ie. HQ-115) used in energy applications: An epigenetic perspective

Exposure to emerging energy-based environmental contaminants such as lithium bis(trifluoromethanesulfonyl)imide (LiTFSI, trade name HQ-115), poses a significant threat to human health, yet its impact on kidney function and epigenetic regulation remains poorly understood. Here, we investigated the effects of LiTFSI exposure on kidney-related biochemical indicators, renal injuries, and epigenetic alterations in male CD-1 mice under both 14-day and 30-day exposure durations. Our study revealed that LiTFSI exposure led to changes in kidney-related markers, notably affecting serum bicarbonate levels, while relative kidney weight remained unaffected. Histological analysis revealed tubule dilation, inflammation, and loss of kidney structure in LiTFSI-exposed mice, alongside dysregulated expression of genes associated with inflammation, renal function, and uric acid metabolism. Epigenetic analysis further identified widespread DNA methylation changes in the two exposure regimes. Functional analysis revealed that differentially methylated regions are implicated in cell apoptosis and cancer-related pathways and are enriched with development-related transcription factor binding motifs, suggesting a potential mechanism of action underlying exposure induced kidney damage. These findings underscore the intricate interplay between environmental exposures, epigenetic modulation, and kidney health, emphasizing the need for additional research to unravel precise mechanisms and develop targeted interventions to mitigate the adverse effects of LiTFSI and exposure of similar clean energy compounds on human health.

Tumor necrosis factor-alpha blockade suppresses BK polyomavirus replication

Purpose

BK Polyomavirus (BKPyV) infection manifests as renal inflammation and can cause kidney damage. Tumor necrosis factor-α (TNF-α) is increased in renal inflammation and injury. The aim of this study was to investigate the effect of TNF-α blockade on BKPyV infection.

Methods

Urine specimens from 22 patients with BKPyV-associated nephropathy (BKPyVN) and 35 non-BKPyVN kidney transplant recipients were analyzed.

Results

We demonstrated increased urinary levels of TNF-α and its receptors, TNFR1 and TNFR2, in BKPyVN patients. Treating BKPyV-infected human proximal tubular cells (HRPTECs) with TNF-α stimulated the expression of large T antigen and viral capsid protein-1 mRNA and proteins and BKPyV promoter activity. Knockdown of TNFR1 or TNFR2 expression caused a reduction in TNF-α-stimulated viral replication. NF-κB activation induced by overexpression of constitutively active IKK2 significantly increased viral replication and the activity of the BKPyV promoter containing an NF-κB binding site. The addition of a NF-κB inhibitor on BKPyV-infected cells suppressed viral replication. Blockade of TNF-α functionality by etanercept reduced BKPyV-stimulated expression of TNF-α, interleukin-1β (IL-1β), IL-6 and IL-8 and suppressed TNF-α-stimulated viral replication. In cultured HRPTECs and THP-1 cells, BKPyV infection led to increased expression of TNF-α, interleukin-1 β (IL-1β), IL-6 and TNFR1 and TNFR2 but the stimulated magnitude was far less than that induced by poly(I:C). This may suggest that BKPyV-mediated autocrine effect is not a major source of TNFα.

Conclusion

TNF-α stimulates BKPyV replication and inhibition of its signal cascade or functionality attenuates its stimulatory effect. Our study provides a therapeutic anti-BKPyV target.

Maslinic Acid Attenuates Ischemia/Reperfusion-Induced Acute Kidney Injury by Suppressing Inflammation and Apoptosis Through Inhibiting NF-κB and MAPK Signaling Pathway

Inflammation and apoptosis are the major contributors to the mechanisms of acute kidney injury (AKI) due to renal ischemia-reperfusion injury (IRI). Maslinic acid (MA), a pentacyclic triterpene acid mostly found in dietary plants, the current study was to demonstrate the renoprotective effect of MA on IRI-induced AKI, and to investigate the role of inflammation and apoptosis-related signaling pathways as a molecular mechanism. C57BL/6J mice were subjected to IRI for 72 h, and MA was daily administered by intraperitoneal injection during this period. In parallel, rat renal proximal tubule cells (NRK52E) were prophylactically treated with MA and then exposed to hydrogen peroxide (H₂O₂). MA treatment significantly inhibited the mRNA expression of interleukin (IL-1β), tumor necrosis factor-α (TGF-α), monocyte chemoattractant protein-1 (MCP-1), and intercellular adhesion molecule-1(ICAM-1). Also, MA reduced the expression of Bax/Bcl2 ratio and cleaved caspase-3. In NRK52 cells, MA inhibited the IκBα degradation, blocked NF-κB/p65 phosphorylation, and nuclear translocation. The phosphorylation of ERK, JNK, and p38 was attenuated by MA in IRI-induced kidney injury and H₂O₂-stimulated NRK52 cells. The expression levels of IL-1β, MCP-1, and ICAM-1 were upregulated in H₂O₂-stimulated NRK52E cells, which was attenuated by NF-κB inhibitor. H₂O₂ treatment increased the Bax/Bcl2 ratio and cleaved caspase-3 in NRK52E cells, which was counteracted by MAPK inhibitors. Together, our data demonstrate that MA suppresses IR-induced AKI injury through NF-κB and MAPK signaling pathways and that MA is a promising agent in the treatment of kidney diseases.

Synthesis, Characterization, and In Vivo Study of Some Novel 3,4,5-Trimethoxybenzylidene-hydrazinecarbothioamides and Thiadiazoles as Anti-Apoptotic Caspase-3 Inhibitors

The present study aims to discover novel derivatives as antiapoptotic agents and their protective effects against renal ischemia/reperfusion. Therefore, a series of new thiadiazole analogues 2a–g was designed and synthesized through cyclization of the corresponding opened hydrazinecarbothioamides 1a–g, followed by confirmation of the structure via spectroscopic tools (NMR, IR and mass spectra) and elemental analyses. The antiapoptotic activity showed alongside decreasing of tissue damage induced by I/R in the kidneys of rats using N-acetylcysteine (NAC) as an antiapoptotic reference. Most of the cyclized thiadiazoles are better antiapoptotic agents than their corresponding opened precursors. Particularly, compounds 2c and 2g were the most active antiapoptotic compounds with significant biomarkers. A preliminary mechanistic study was performed through caspase-3 inhibition. Compound 2c was selected along with its corresponding opened precursor 1c. An assay of cytochrome C revealed that there is an attenuation of cytochrome C level of about 5.5-fold, which was better than 1c with a level of 4.1-fold. In caspases-3, 8 and 9 assays, compound 2c showed more potency and selectivity toward caspase-3 and 9 compared with 1c. The renal histopathological investigation indicated normal renal tissue for most of the compounds, especially 2c and 2g, relative to the control. Finally, a molecular docking study was conducted at the caspase-3 active site to suggest possible binding modes.

The Fetal-Maternal Immune Interface in Uterus Transplantation

Uterus transplants (UTxs) have been performed worldwide. Overall frequencies have been low, but globally initiated UTx programs are expected to increase clinical implementation. The uterus constitutes a unique immunological environment with specific features of tissue renewal and a receptive endometrium. Decidual immune cells facilitate embryo implantation and placenta development. Although UTx adds to the complexity of immunity during pregnancy and transplantation, the procedure provides a unique clinical and experimental model. We posit that understanding the distinct immunological properties at the interface of the transplanted uterus, the fetus and maternal circulation might provide valuable novel insights while improving outcomes for UTx. Here, we discuss immunological challenges and opportunities of UTx affecting mother, pregnancy and healthy livebirths.

Inhibition of BRD4 Reduces Neutrophil Activation and Adhesion to the Vascular Endothelium Following Ischemia Reperfusion Injury

Renal ischemia reperfusion injury (IRI) is associated with inflammation, including neutrophil infiltration that exacerbates the initial ischemic insult. The molecular pathways involved are poorly characterized and there is currently no treatment. We performed an in silico analysis demonstrating changes in NFκB-mediated gene expression in early renal IRI. We then evaluated NFκB-blockade with a BRD4 inhibitor on neutrophil adhesion to endothelial cells in vitro, and tested BRD4 inhibition in an in vivo IRI model. BRD4 inhibition attenuated neutrophil adhesion to activated endothelial cells. In vivo, IRI led to increased expression of cytokines and adhesion molecules at 6 h post-IRI with sustained up-regulated expression to 48 h post-IRI. These effects were attenuated, in part, with BRD4 inhibition. Absolute neutrophil counts increased significantly in the bone marrow, blood, and kidney 24 h post-IRI. Activated neutrophils increased in the blood and kidney at 6 h post-IRI and remained elevated in the kidney until 48 h post-IRI. BRD4 inhibition reduced both total and activated neutrophil counts in the kidney. IRI-induced tubular injury correlated with neutrophil accumulation and was reduced by BRD4 inhibition. In summary, BRD4 inhibition has important systemic and renal effects on neutrophils, and these effects are associated with reduced renal injury.

Organ-Protective Effects and the Underlying Mechanism of Dexmedetomidine

Dexmedetomidine (DEX) is a highly selective α2 adrenergic receptor (α2AR) agonist currently used in clinical settings. Because DEX has dose-dependent advantages of sedation, analgesia, antianxiety, inhibition of sympathetic nervous system activity, cardiovascular stabilization, and significant reduction of postoperative delirium and agitation, but does not produce respiratory depression and agitation, it is widely used in clinical anesthesia and ICU departments. In recent years, much clinical study and basic research has confirmed that DEX has a protective effect on a variety of organs, including the nervous system, heart, lungs, kidneys, liver, and small intestine. It acts by reducing the inflammatory response in these organs, activating antiapoptotic signaling pathways which protect cells from damage. Therefore, based on wide clinical application and safety, DEX may become a promising clinical multiorgan protection drug in the future. In this article, we review the physiological effects related to organ protection in α2AR agonists along with the organ-protective effects and mechanisms of DEX to understand their combined application value.

Protective effect of dapsone against renal ischemia-reperfusion injury in rat

Background: Ischemia/reperfusion can cause injury to tissues and compromise functionality of organs due to inflammatory processes. Significantly, development of these effects in kidney tissue has been a challenging issue that leads to acute renal injury. In this study, anti-inflammatory, anti-oxidative, and protective features of dapsone on kidney ischemia/reperfusion injury were investigated.Material and methods: Renal ischemia was induced in rats by bilateral renal arteries clamping for 45 min followed by 24 h reperfusion phase. The effects of different doses of dapsone (1, 3, 10 mg/kg) on ischemia/reperfusion injury in kidney tissue were investigated by targeting BUN, Creatinine, LDH, MDA, MPO, IL-1β, TNF-α, and NFκB. In addition histopathological examination was performed by H&E staining method.Results and discussion: Comparing the findings of this study showed significant reduction in BUN and LDH in 10 mg/kg dapsone received groups, and Cr, MDA, and MPO in 3 mg/kg dapsone received groups. The serum level of TNF-α was significantly decreased with both doses of 3 and 10 mg/kg dapsone. The same results were observed in the serum level of IL-1β and NFκB. Besides, remarkable improvement in histological damages was also observed with dapsone treatment.Conclusion: These results support the hypothesis that the positive effects of dapsone on the renal ischemia/reperfusion injury are mediated by modulating inflammatory cascades.

Dexmedetomidine Preconditioning Protects Rats from Renal Ischemia-Reperfusion Injury Accompanied with Biphasic Changes of Nuclear Factor-Kappa B Signaling

Acute kidney injury (AKI) is one of the most common and troublesome perioperative complications. Dexmedetomidine (DEX) is a potent α2-adrenoceptor (α2-AR) agonist with anti-inflammatory and renoprotective effects. In this study, a rat renal ischemia–reperfusion injury (IRI) model was induced. At 24 h after reperfusion, the IRI-induced damage and the renoprotection of DEX preconditioning were confirmed both biochemically and histologically. Changes in nuclear factor-kappa B (NF-κB), as well as its downstream anti-inflammatory factor A20 and proinflammatory factor tumor necrosis factor-α (TNF-α), were detected. Atipamezole, a nonselective antagonist, was then added 5 min before the administration of DEX to further analyze DEX's effects on NF-κB, and another anti-inflammatory medicine, methylprednisolone, was used in comparison with DEX, to further analyze DEX's effects on NF-κB. Different concentrations of DEX (0 nM, 0.1 nM, 1 nM, 10 nM, 100 nM, 1 μM, and 10 μM) were applied to preincubated human renal tubular epithelial cell line (HK-2) cells in vitro. After anoxia and reoxygenation, the MTT (3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) tetrazolium assay and enzyme-linked immunosorbent assay (ELISA) were performed to evaluate the levels of NF-κB downstream anti-inflammatory cytokines. The results showed that, unlike methylprednisolone, DEX preconditioning led to a time-dependent biphasic change (first activation then inhibition) of NF-κB in the rat renal IRI models that were given 25 μg/kg i.p. It was accompanied by a similarly biphasic change of TNF-α and an early and persistent upregulation of A20. In vitro, DEX's cellular protection showed a concentration-dependent biphasic change which was protective within the range of 0 to 100 nM but became opposite when concentrations are greater than 1 μM. The changes in the A20 and NF-κB messenger RNA (mRNA) levels were consistent with the renoprotective ability of DEX. In other words, DEX preconditioning protected the rats from renal IRI via regulation biphasic change of NF-κB signaling.

Back signaling of HLA class I molecules and T/NK cell receptor ligands in epithelial cells reflects the rejection-specific microenvironment in renal allograft biopsies

The role of endothelial cells in the pathophysiology of antibody-mediated rejection after renal transplantation has been widely investigated. We expand this scenario to the impact of epithelial cells on the microenvironment during rejection. Primary proximal tubular epithelial cells were stimulated via HLA class I, CD155 and CD166 based on their potential signal-transducing capacity to mediate back signaling after encounter with either T/NK cells or donor-specific antibodies. Upon crosslinking of these ligands with mAbs, PTEC secreted IL-6, CXCL1,8,10, CCL2, and sICAM-1. These proteins were also released by PTEC as consequence of a direct interaction with T/NK cells. Downmodulation of the receptor CD226 on effector cells confirmed the involvement of this receptor/ligand pair in back signaling. In vivo, CD155 and CD166 expression was detectable in proximal and distal tubuli of renal transplant biopsies, respectively. The composition of the protein microenvironment in these biopsies showed a substantial overlap with the PTEC response. Cluster and principal component analyses of the microenvironment separated unsuspicious from rejection biopsies and, furthermore, ABMR, TCMR, and borderline rejection. In conclusion, our results provide evidence that epithelial cells may contribute to the rejection process and pave the way to a better understanding of the pathomechanisms of kidney allograft rejection.

Peptidyl arginine deiminase-4 exacerbates ischemic AKI by finding NEMO

Peptidyl arginine deiminase-4 (PAD4) catalyzes the conversion of peptidylarginine residues to peptidylcitrulline. We have previously shown that kidney ischemia-reperfusion (I/R) injury increases renal proximal tubular PAD4 expression and activity. Furthermore, kidney PAD4 plays a critical role in ischemic acute kidney injury (AKI) by promoting renal tubular inflammation, neutrophil infiltration, and NF-κB activation. However, the mechanisms of PAD4-mediated renal tubular inflammation and NF-κB activation after I/R remain unclear. Here, we show that recombinant PAD4 preferentially citrullinates recombinant IKKγ [also called NF-κB essential modulator (NEMO)] over recombinant IKKα or IKKβ. Consistent with this finding, PAD4 citrullinated renal proximal tubular cell IKKγ and promoted NF-κB activation via IκBα phosphorylation in vitro. NEMO inhibition with a selective NEMO-binding peptide attenuated PAD4-mediated proinflammatory cytokine mRNA induction in HK-2 cells. Moreover, NEMO inhibition did not affect proximal tubular cell survival, proliferation, or apoptosis, unlike global NF-κB inhibition. In vivo, NEMO-binding peptide treatment protected against ischemic AKI. Finally, NEMO-binding peptide attenuated recombinant PAD4-mediated exacerbation of ischemic AKI, renal tubular inflammation, and apoptosis. Taken together, our results show that PAD4 exacerbates ischemic AKI and inflammation by promoting renal tubular NF-κB activity and inflammation via NEMO citrullination. Targeting NEMO activation may serve as a potential therapy for this devastating clinical problem.

Podocyte NF-κB is dispensable for the pathogenesis of renal ischemia-reperfusion injury

Podocytes play a central role in the formation of the glomerular filtration barrier in the kidney, and their dysfunction has been shown to result in multiple proteinuric kidney diseases. In this study, we sought to determine whether NF-κB, a proinflammatory signaling, within podocytes was involved in renal ischemia-reperfusion (I/R) injury. Podocyte-specific IκBΔN transgenic (Pod-IκBΔN) mice, in which NF-κB was inhibited specifically in podocytes, were generated by the Cre-loxP technology, and their phenotype was compared with control mice after bilateral renal ischemia. The effect of systemic administration of a NF-κB inhibitor, pyrrolidinedithiocarbamate (PDTC), on renal I/R injury was also examined. Pod-IκBΔN mice were phenotypically normal before surgery. Following renal I/R injury, serum concentrations of urea nitrogen and creatinine were elevated in both Pod-IκBΔN and control mice to a similar extent, whereas PDTC treatment attenuated the elevation of these parameters. Renal histological damage in I/R-injured Pod-IκBΔN mice was also similar to I/R-injured control mice, although it was improved by PDTC treatment. Moreover, I/R induced accumulation of inflammatory cells, such as neutrophils and macrophages, was reduced by PDTC treatment, but not by podocyte-specific NF-κB inhibition. These results provide evidence that the NF-κB activity in podocytes does not contribute to the pathogenesis of renal I/R injury.

Flucytosine and Amphotericin B Coadministration Induces Dose-Related Renal Injury

Invasive fungal infections remain an important clinical problem, and despite recent approaches, they bring high morbidity and mortality. Combination therapies are the most effective; however, adverse effects need to be considered. In this study, we aimed to evaluate the nephrotoxicity induced by combined therapy of flucytosine (FL) and amphotericin B (AMF) at 3 different doses administered to mice for 14 days: 300 μg/kg AMF+50 mg/kg FL; 600 μg/kg AMF+100 mg/kg FL; 900 μg/kg AMF+150 mg/kg FL. Antifungal coadministration triggered nuclear translocation of NF-κB and upregulated nuclear factor kappa-light-chain-enhancer of activated B cells subunit p65 (NF-κB p65) messenger RNA mRNA level in dose-dependent manner. The immunopositivity of tumor necrosis factor-α and interleukin-6 (IL-6), together with IL-6 gene expression, increased both in tubular and glomerular cells. Amphotericin B–flucytosine cotreatment increased significantly the number of terminal deoxy-nucleotidyl transferase (TdT)-mediated dUTP nick end-labeling positive nuclei. Apoptotic cells in renal tubuli were confirmed by electron microscopy. Histopathological analysis revealed collagen accumulation at the glomerular level. Collagen was also evidenced in the glomeruli at the dose of 900 μg/kg AMF+150mg/kg FL by Masson-Goldner trichrome staining and electron microscopy. Moreover, antifungal cotherapy induced upregulation of transforming growth factor beta 1 (TGF-β1) gene expression in a dose-dependent manner. Inflammation and epithelial tubular apoptosis are associated with TGF-β1 activation and initiation of the early stage of glomerular fibrosis at higher doses, leading to tubule–interstitial fibrosis.

Allicin ameliorates kidney function and urinary bladder sensitivity in cyclosporine A-treated rats

Cyclosporine-A (CsA) is an immunosuppressive drug which has been used to prevent rejection after organ transplantation and to treat certain autoimmune diseases. However, its therapeutic use is limited by nephrotoxicity. In this study, the modulator effect of allicin on the oxidative nephrotoxicity of CsA in rats was investigated. Furthermore, the effect of allicin on CsA-induced hypersensitivity of urinary bladder rings to acetylcholine (ACh) was estimated. Rats were divided into three groups, control, CsA (15 mg/kg, subcutaneously), and CsA/allicin (50 mg/kg, orally). At the end of the study, all rats were killed and then blood, urine samples, and kidneys were taken. CsA administration caused a severe nephrotoxicity which was evidenced by elevated kidney/body weight ratio, serum creatinine (Cr), blood urea nitrogen, lactate dehydrogenase, and urinary protein with a concomitant reduction in serum albumin and Cr clearance as compared with control. A significant increase in renal contents of malondialdehyde, myeloperoxidase, and tumor necrosis factor-alpha with a significant decrease in renal reduced glutathione, superoxide dismutase activities, and nitric oxide (NOx) content was detected upon CsA administration. Exposure to CsA increased the sensitivity of isolated urinary bladder rings to ACh. Histological analysis revealed that CsA caused tubular necrosis and moderate diffuse tubular atrophy. Allicin protected kidney tissue against the oxidative damage and the nephrotoxic effect of CsA and significantly reduced the responses of isolated bladder rings to ACh. Our study indicates that allicin administration has the potential to protect against CsA-induced renal injury by reducing oxidative stress and inflammation and restoring NOx level.

Desflurane preconditioning protects human umbilical vein endothelial cells against anoxia/reoxygenation by upregulating NLRP12 and inhibiting non-canonical nuclear factor-κB signaling

Volatile anesthetics modulate endothelial cell apoptosis and inhibit nuclear factor-κB (NF-κB) signaling. In this study, we aimed to assess whether desflurane preconditioning protects human umbilical vein endothelial cells (HUVECs) agaist anoxia/reoxygenation (A/R) injury. HUVECs were pre-conditioned with desflurane (1.0 MAC) for 30 min, followed by a 15-min washout, then exposed to 60 min anoxia and 60 min reoxygenation (A/R), and incubated with 10 ng/ml tumor necrosis factor (TNF)-α for 60 min. HUVEC viability and apoptosis were measured by MTT assay and annexin V staining, and immunoblot analysis was used to measure the levels of Smac and cellular inhibitor of apoptosis 1 (cIAP1). NF-κB activation was assessed using the NF-κB signaling pathway real‑time PCR array, and the levels of NF-κB inducing kinase (NIK), p52, IκB kinase (IKK)α, p100, RelB and NLR family, pyrin domain containing 12 (NLRP12) were assessed by immunoblot analysis. Desflurane preconditioning attenuated the effects of A/R and/or A/R plus TNF-α on cell viability, decreasing the levels of Smac and enhancing the levels of of cIAP1 (P<0.05). Preconditioning with desflurane also enhanced the mRNA levels of interleukin (IL)-10 and NLRP12 in the cells exposed to A/R by 2.40- and 2.16‑fold, respectively. The HUVECs exposed to A/R had greater levels of NIK and p100 and reduced levels of p52 and IKKα. Desflurance preconditioning further increased p100 levels, decreased the level of NIK, further decreased p52 levels and further reduced IKKα levels. A/R in combination with TNF-α increased the NIK, IKKα, p100 and RelB levels, and this increase was significantly attenuated by desflurance preconditioning (all P<0.05). Desflurane preconditioning enhanced HUVEC survival and protected the cells against A/R injury, and our results suggested that this process involved the upregulation of NLRP12 and the inhibition of non-canonical NF-κB signaling.

Slit2-Robo signaling in inflammation and kidney injury

Acute kidney injury is an increasingly common global health problem and is associated with severe morbidity and mortality. In addition to facing high mortality rates, the survivors of acute kidney injury are at increased risk of developing chronic kidney disease and end-stage renal disease. Renal ischemia-reperfusion injury (IRI) is the most common cause of acute kidney injury, and results from impaired delivery of oxygen and nutrients to the kidney. Massive leukocyte influx into the post-ischemic kidney is one of the hallmarks of IRI. The recruited leukocytes exacerbate tissue damage and, if uncontrolled, initiate the progressive changes that lead to renal fibrosis and chronic kidney disease. Early on, recruitment and activation of platelets promotes microthrombosis in the injured kidney, further exacerbating kidney damage. The diversity, complexity, and multiplicity of pathways involved in leukocyte recruitment and platelet activation make it extremely challenging to control these processes, and past efforts have met with limited success in human trials. A generalized strategy to inhibit infiltration of inflammatory leukocytes and platelets, thereby reducing inflammation and injury, may prove to be more beneficial. In this review, we summarize recent findings demonstrating that the neuronal guidance cues, Slit and Roundabout (Robo), prevent the migration of multiple leukocyte subsets towards diverse inflammatory chemoattractants, and have potent anti-platelet functions in vitro and in vivo. These properties uniquely position Slit2 as a novel therapeutic that could be used to prevent acute kidney injury associated with IRI.

The role of tumor necrosis factor alpha in regulating the expression of Tamm-Horsfall Protein (uromodulin) in thick ascending limbs during kidney injury

BACKGROUND

Tamm-Horsfall Protein (THP) is a glycoprotein expressed exclusively by cells of the thick ascending loop (TAL) of Henle. THP has a protective role in acute kidney injury (AKI), and its expression is downregulated in the early stages of injury. Tumor necrosis factor alpha (TNFα) is a cytokine endogenously expressed by the TAL and is also induced by AKI. Therefore, we hypothesized that TNFα is a key regulator of THP expression.

METHODS

We used a mouse model of AKI (ischemia-reperfusion injury, IRI) and a cell culture system of a TAL cell line (MKTAL).

RESULTS

We show that TNFα is upregulated by TAL cells early after AKI in vivo. The expression of THP and its transcription factor Hepatocyte nuclear factor 1β (HNF1β) were concomitantly decreased at the peak of injury. Furthermore, recombinant TNFα inhibits significantly, and in a dose-dependent manner, the expression of THP, but not HNF1β in MKTAL cells. Interestingly, neither TNFα neutralization nor genetic deletion of TNFα increased THP or HNF levels after injury in vivo.

CONCLUSION

Our data suggest that TNFα can inhibit the expression of THP in TAL cells via an HNF1β-independent mechanism, but the downregulation of THP expression in the early AKI does not depend on TNFα. We propose that TNFα regulates THP expression in a homeostatic setting, but the impact of TNFα on THP during kidney injury is superseded by other factors that could inhibit HNF1β-mediated expression of THP.

Protective effects of relaxin against cisplatin-induced nephrotoxicity in rats

BACKGROUND

Cisplatin (CDDP)-induced acute kidney injury (AKI) involves pro-inflammatory responses, apoptosis of renal tubular epithelial cells and vascular damage. AKI increases the risk of chronic kidney disease. Relaxin (RLX) has anti-apoptotic and anti-fibrosis properties. The aim of this study was to investigate the effects of RLX on CDDP-induced nephrotoxicity.

METHODS

We investigated the mitigating effects of RLX based on the etiopathology of AKI induced by CDDP, and also the anti-fibrotic effect of RLX on renal fibrosis after AKI. In the short-term experiments, rats were divided into the control group, CDDP group, and CDDP+RLX group. In the latter group, RLX was infused for 5 or 14 days using an implanted osmotic minipump. CDDP was injected intraperitoneally (6 mg/kg) after RLX or saline infusion. At 5 and 14 days post-CDDP, the kidneys were removed for analysis. The effect of RLX on renal fibrosis after AKI was evaluated at 6 weeks post-CDDP.

RESULTS

In short-term experiments, CDDP transiently increased plasma creatinine and blood urea nitrogen with peaks at day 5, and RLX prevented such rises. Semiquantitative analysis of the histological lesions indicated marked structural damage and apoptotic cells in the CDDP group, with the lesions being reduced by RLX treatment. Overexpression of Bax, interleukin-6 and tumor necrosis factor-α observed in the kidneys of the CDDP group was reduced in the CDDP+RLX group. In the long-term experiments, RLX significantly reduced renal fibrosis compared with the CDDP group.

CONCLUSIONS

The results suggested that RLX provided protection against CDDP-induced AKI and subsequent fibrosis by reducing apoptosis and inflammation.

AKI associated with cardiac surgery

Approximately 18% of patients undergoing cardiac surgery experience AKI (on the basis of modern standardized definitions of AKI), and approximately 2%-6% will require hemodialysis. The development of AKI after cardiac surgery portends poor short- and long-term prognoses, with those developing RIFLE failure or AKI Network stage III having an almost 2-fold increase in the risk of death. AKI is caused by a variety of factors, including nephrotoxins, hypoxia, mechanical trauma, inflammation, cardiopulmonary bypass, and hemodynamic instability, and it may be affected by the clinician's choice of fluids and vasoactive agents as well as the transfusion strategy used. The risk of AKI may be ameliorated by avoidance of nephrotoxins, achievement of adequate glucose control preoperatively, and use of goal-directed therapy hemodynamic strategies. Remote ischemic preconditioning is an exciting future strategy, but more work is needed before widespread implementation. Unfortunately, there are no pharmacologic agents known to reduce the risk of AKI or treat established AKI.

Nuclear factor-κB activation inhibitor attenuates ischemia reperfusion injury and inhibits Hmgb1 expression

OBJECTIVE AND DESIGN

To investigate the effects of nuclear factor-κB activation inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) on cardiac ischemia reperfusion injury in a transplantation model.

METHODS

Hearts of C57BL/6 mice were flushed and stored in cold Bretschneider solution for 8 h and then transplanted into syngeneic recipient. Some mice were administrated intraperitoneally with DHMEQ (8 mg/kg) 1 h before reperfusion. For inhibition of Hmgb1, mice were treated with glycyrrhizin at 250 mg/kg prior to reperfusion.

RESULTS

DHMEQ decreased cardiomyocyte apoptosis and recruitment of neutrophils and macrophages. Troponin T (TnT) production on 24 h after myocardial IR injury was reduced by DHMEQ treatment. Cardiac output at 60 mmHg of afterload pressure was significantly increased in hearts with DHMEQ treatment (IR+DHMEQ: 58.6 ± 5.75 ml/min; IR: 25.9 ± 4.1 ml/min; P < 0.05). Furthermore, DHMEQ suppressed high mobility group protein (Hmgb1) expression. And the Caspase 3 activity, the number of TUNEL-positive cardiomyocytes and infiltrated neutrophil in cardiac allograft were markedly decreased with Hmgb1 inhibitor treatment.

CONCLUSIONS

Nuclear factor-κB activation inhibitor DHMEQ attenuates ischemia reperfusion injury in a cardiac transplantation model and it may be a suitable agent for the protection of the cardiac against ischemia reperfusion injury.

Intravenous pretreatment with emulsified isoflurane preconditioning protects kidneys against ischemia/reperfusion injury in rats

Background

Emulsified isoflurane (EIso) is a novel intravenous general anesthetic, which can provide rapid anesthetic induction and recovery. EIso preconditioning could attenuate heart, lung and liver ischemia/reperfusion (I/R) injury. We tested the hypothesis that intravenous pretreatment with EIso would protect kidneys against I/R injury by inhibiting systemic inflammatory responses and improving renal antioxidative ability.

Methods

Rats were randomly divided into these six groups: sham, I/R, intralipid, 1, 2 or 4 ml/kg EIso. Rats were subjected to 45 min left renal pedicle occlusion followed by 3 h reperfusion after right nephrectomy. Rat were treated with intravenous 8% EIso with 1, 2 or 4 ml/kg, or 30% intralipid with 2 ml/kg for 30 min before ischemia, respectively. After reperfusion, renal functional parameters, serum mediator concentrations and markers of oxidative stress in kidney tissues were determined, and renal histopathological analysis were performed.

Results

Serum creatinine, blood urea nitrogen, cystatin c, tumor necrosis factor-α, interleukin-6, and interleukin-10 concentrations were significantly increased after renal I/R as compared to the sham group. So was renal tissue MDA content and histological scores, but renal tissue SOD activity was decreased. Additionally, severe morphological damages were observed in these study groups. In contrast, 2 or 4 ml/kg EIso reduced serum creatinine, blood urea nitrogen, cystatin c, tumor necrosis factor-α, and interleukin-6 levels, decreased renal tissue MDA content and histological scores, increased serum interleukin-10 level and tissue SOD activity as compared to the I/R, intralipid and 1 ml/kg EIso groups. Renal morphological damages were alleviated after pretreatment of 2 or 4 ml/kg EIso.

Conclusions

Intravenous EIso produces preconditioning against renal I/R injury in rats, which might be mediated by attenuating inflammation and increasing antioxidation ability.

Effect of a novel nuclear factor-κB activation inhibitor on renal ischemia-reperfusion injury

BACKGROUND

In kidney transplantation, the relationship between prolonged warm or cold ischemic storage of kidneys and a higher incidence of delayed graft function is previously known, and delayed graft function has been known to aggravate poor long-term graft survival. We investigated the effect of a novel nuclear factor-κB activation inhibitor, dehydroxymethylepoxyquinomicin (DHMEQ), on renal ischemia-reperfusion (I/R) injury.

METHODS

DHMEQ was administered to Lewis rats once just before renal artery clamping (DHMEQ pretreatment group), and the effect on I/R injury was investigated.

RESULTS

In the DHMEQ pretreatment group, the 24-hr urine volume on days 1 to 3 after I/R was significantly larger, and the protein concentration of the urine on days 2 to 7 was significantly smaller than in the untreated group. The serum creatinine level was significantly improved, and significantly lower levels of the inflammatory cells and inflammatory cytokines were present in the kidneys on day 1. The relative ratio of nuclear to cytoplasmic nuclear factor-κB and oxidative stress of kidney tissue on day 1 were significantly decreased.

CONCLUSIONS

Treatment with DHMEQ before renal artery clamping may therefore be useful for renal I/R injury and application to renal transplantation is expected.

Relaxin protects against renal ischemia-reperfusion injury

Relaxin, a pregnancy hormone, has antiapoptotic and anti-inflammatory properties. The aim of this study was to determine the effects of relaxin on ischemia-reperfusion (IR)-induced acute kidney injury. Male rats underwent unilateral nephrectomy and contralateral renal IR (45 min of renal pedicle clamping). Rats were divided into three groups: 1) sham group, 2) IR group, and 3) IR-RLX group (rats treated with relaxin before ischemia). In this group, relaxin was infused at 500 ng/h via subcutaneous osmotic minipump for 24 h beginning 2 h before renal ischemia. At 24 h after reperfusion, renal function was assessed and kidneys were removed for analysis. There was no significant difference in blood pressure among the three groups. IR increased plasma levels of creatinine and urea nitrogen, and relaxin provided protection against the increases in these two parameters. Relaxin significantly decreased plasma TNF-α levels and renal TNF receptor 1 mRNA expression, compared with the IR group. Semiquantitative assessment of the histological lesions showed marked structural damage in IR rats compared with the IR-RLX rats. RLX significantly reduced apoptotic cell counts compared with the IR group. Overexpression of caspase-3 observed in the IR kidneys was reduced in the IR-RLX group. The results demonstrated that relaxin provided protection against IR-induced renal injury by reducing apoptosis and inflammation.

Preventive Effects of a Natural Anti-Inflammatory Agent, Astragaloside IV, on Ischemic Acute Kidney Injury in Rats

This study investigated the anti-inflammatory effects of astragaloside IV(AS-IV) on ischemia/reperfusion (IR) induced acute kidney injury (AKI) in rats. Experimental model of ischemic AKI was induced in rats by bilateral renal artery clamp for 45 min followed by reperfusion of 12 h and 24 h, respectively. AS-IV was orally administered once a day to rats at 10 and 20 mg·kg⁻¹·d⁻¹ for 7 days prior to ischemia. AS-IV pretreatment significantly decreased serum urea, creatinine, and cystatin C levels at 12 h and 24 h of reperfusion in AKI rats. AS-IV pretreatment also ameliorated tubular damage and suppressed the phosphorylation of p65 subunit of NF-κB in AKI rats. Moreover, NF-κB and MPO activity as well as serum and tissue levels of TNF-α, MCP-1, and ICAM-1 were elevated in AKI rats. All of these abnormalities were prevented by AS-IV. Furthermore, AS-IV downregulated the mRNA expression of NF-κB, TNF-α, MCP-1, and ICAM-1 in AKI rats. These results suggest that AS-IV might be developed as a novel therapeutic approach to prevent ischemic AKI through inhibition of NF-κB mediated inflammatory genes expression.

Desflurane preconditioning induces oscillation of NF-κB in human umbilical vein endothelial cells

Background

Nuclear factor kappa B (NF-κB) has been implicated in anesthetic preconditioning (APC) induced protection against anoxia and reoxygenation (A/R) injury. The authors hypothesized that desflurane preconditioning would induce NF-κB oscillation and prevent endothelial cells apoptosis.

Methods

A human umbilical vein endothelial cells (HUVECs) A/R injury model was used. A 30 minute desflurane treatment was initiated before anoxia. NF-κB inhibitor BAY11-7082 was administered in some experiments before desflurane preconditioning. Cells apoptosis was analyzed by flow cytometry using annexin V–fluorescein isothiocyanate staining and cell viability was evaluated by modified tertrozalium salt (MTT) assay. The cellular superoxide dismutases (SOD) activitiy were tested by water-soluble tetrazolium salt (WST-1) assay. NF-κB p65 subunit nuclear translocation was detected by immunofluorescence staining. Expression of inhibitor of NF-κB-α (IκBα), NF-κB p65 and cellular inhibitor of apoptosis 1 (c-IAP1), B-cell leukemia/lymphoma 2 (Bcl-2), cysteine containing aspartate specific protease 3 (caspases-3) and second mitochondrial-derived activator of caspase (SMAC/DIABLO) were determined by western blot.

Results

Desflurane preconditioning caused phosphorylation and nuclear translocation of NF-κB before anoxia, on the contrary, induced the synthesis of IκBα and inhibition of NF-κB after reoxygenation. Desflurane preconditioning up-regulated the expression of c-IAP1 and Bcl-2, blocked the cleavage of caspase-3 and reduced SMAC release, and decreased the cell death of HUVECs after A/R. The protective effect was abolished by BAY11-7082 administered before desflurane.

Conclusions

The results demonstrated that desflurane activated NF-κB during the preconditioning period and inhibited excessive activation of NF-κB in reperfusion. And the oscillation of NF-κB induced by desflurane preconditioning finally up-regulated antiapoptotic proteins expression and protected endothelial cells against A/R.

Mineralocorticoid receptor blockade reduced oxidative stress in renal transplant recipients: a double-blind, randomized pilot study

BACKGROUND

Previous experimental studies from our laboratory have demonstrated that aldosterone plays a central role in renal ischemic processes. This study was designed to evaluate the effect of mineralocorticoid receptor blockade in renal transplant recipients from living donors.

METHODS

20 adult kidney transplant recipients from living donors were included in a double-blind, randomized, placebo-controlled clinical pilot study that compared spironolactone and placebo. Placebo or spironolactone (25 mg) was administered 1 day before and 3 days posttransplantation. Renal function and urinary kidney injury molecule-1, interleukin-18, and heat shock protein 72 as well as urinary hydrogen peroxide (H2O2) levels were quantified.

RESULTS

No significant differences were seen between the groups studied regarding age, gender, indication for kidney transplantation, residual renal function, renal replacement therapy, or warm and cold ischemia periods. In contrast, spironolactone administration significantly reduced the oxidative stress assessed by the urinary H2O2 excretion, in spite of no differences in renal function or reduction in tubular injury biomarkers.

CONCLUSIONS

The findings of this exploratory study strongly suggest that aldosterone promotes oxidative stress and that the administration of spironolactone reduces the production of urinary H2O2 as a result of lesser formation of surrogate reactive oxygen species secondary to the ischemia-reperfusion phenomenon.

Sildenafil protects against nitric oxide deficiency-related nephrotoxicity in cyclosporine A treated rats

Cyclosporine A (CsA) is the most widely used immunosuppressant in organ transplant surgery and in treatment of autoimmune disease. Nevertheless, animal and clinical studies have demonstrated that nephrotoxicity is the major adverse effect limiting the prolonged CsA therapeutic use. The present study aimed to investigate possible protective effect of sildenafil, a phoshodiestrase-5 inhibitor, on CsA-induced nephrotoxicity and various mechanism(s) underlies this effect. Male Wistar rats were administered CsA (20 mg/kg/day, s.c.) for 21 days alone or in combination with sildenafil (5 mg/kg/day, p.o.). Sildenafil exhibited nephroprotective effects as evidenced by significant decrease in serum creatinine and urea levels, spot urine albumin-creatinine ratio, as well as renal level of malondialdehyde, with a concurrent increase in renal levels of reduced glutathione and nitric oxide along with catalase activity compared to CsA-treated rats. [corrected]. Additionally, immunohistochemical analysis demonstrated that sildenafil treatment markedly reduced inducible nitric oxide synthase, tumor necrosis factor-alpha, and caspase-3 expressions, while expression of endothelial nitric oxide synthase was prominently enhanced. The protective effects of sildenafil were confirmed by renal histopathological examination. Pretreatment with l-nitro-arginine methyl ester (10 mg/kg/day, i.p.), a non-selective nitric oxide synthase inhibitor, reversed the protection afforded by sildenafil. Taken together, the current study highlighted the renoprotective effects of sildenafil against CsA-induced nephrotoxicity in rats, which might be mediated, in part, through nitric oxide pathway as well as antioxidant, anti-inflammatory, and anti-apoptotic activities.

Palmitoylethanolamide reduces early renal dysfunction and injury caused by experimental ischemia and reperfusion in mice

This study was designed to assess a protective effect of palmitoylethanolamide (PEA) in the development of inflammation after ischemia-reperfusion injury of the kidney. Moreover, to suggest a possible mechanism, renal ischemia-reperfusion was performed in mice with targeted disruption of peroxisome proliferator-activated receptor α (PPAR-α) gene (PPAR-αKO) to explain whether the observed PEA effect was dependent on PPAR-α pathway. Peroxisome proliferator-activated receptor-αKO and littermate wild-type controls (PPAR-αWT) were subjected to bilateral renal artery occlusion (30 min) and reperfusion (6 h) and received PEA (10 mg/kg i.p.) 15 min before release of clamps. Serum and urinary indicators of renal dysfunction and tubular and reperfusion injury were measured, specifically serum urea, creatinine, aspartate aminotransferase and γ-glutamyl transferase, and creatinine clearance. In addition, renal sections were used for histological scoring of renal injury and for immunologic evidence of nitrotyrosine formation, poly[adenosine diphosphate-ribose] (PAR), and adhesion molecules expression. The oxidative stress-sensitive nuclear factor κB signaling pathway was also investigated by Western blot analysis. Kidney myeloperoxidase activity and malondialdehyde levels were measured for assessment of polymorphonuclear leukocyte cell infiltration and lipid peroxidation, respectively. Apoptotic mechanisms were also investigated. Moreover, the infiltration and activation of mast cells were explored. In vivo, PEA administration during ischemia significantly reduced the increase in (i) creatinine, γ-glutamyl transferase, aspartate aminotransferase; (ii) nuclear translocation of nuclear factor κB p65; (iii) kidney myeloperoxidase activity and malondialdehyde levels; (iv) nitrotyrosine, PAR, and adhesion molecules expression; (v) the infiltration and activation of mast cells; and (vi) apoptosis. Our results clearly demonstrate that PEA significantly attenuated the degree of renal dysfunction, injury, and inflammation caused by ischemia-reperfusion injury. Moreover, the positive effects of PEA were at least in part dependent on PPAR-α pathway.

Pre- and postischemic pulsed acoustic cellular expression conditioning modulates expression of inflammation factors in cremaster ischemia/reperfusion injury model

Pulsed acoustic cellular expression (PACE) is a treatment that applies focused acoustic shock waves to promote tissue healing. The aim of this study was to assess the effect of PACE treatment on inflammatory responses in a cremaster muscle ischemia/reperfusion injury model. Seventeen cremaster muscle flaps were evaluated in four groups: nonischemic controls (n = 5), 5-hour ischemia controls (n = 4), preischemic (5-hour) PACE conditioning (n = 4), and postischemic (5-hour) PACE conditioning (n = 4). The expression of proinflammatory cytokines (TNFα, IL-6, IL-1α, IL-1β, GM-CSF) and chemokines (CCL3, CCL4, CXCL4) was assessed using TaqMan® real-time PCR. Expression of ELAM-1, VCAM-1, and ICAM-1 was assessed by immunostaining. Preischemic PACE conditioning upregulated expression of IL-6, CCL3, CCL4, and CXCL4, and downregulated expression of TNFα, GM-CSF, and IL-1α. Postischemic PACE conditioning significantly decreased expression of all evaluated genes. Pre- and postischemic PACE conditioning decreased expression of ELAM-1 and ICAM-1. Results of the study indicate that application of PACE conditioning may have a beneficial effect on the recovery of tissues subjected to the ischemia/reperfusion injury. Postischemic PACE conditioning revealed anti-inflammatory effect as confirmed by decreased expression of inflammatory cytokines, chemokines, and cell adhesion molecules (ELAM-1 and ICAM-1) that are responsible for leukocyte recruitment into ischemic tissues. Hence, PACE therapy may be used effectively in clinical practice as a convenient therapeutic strategy to protect tissues against ischemia/reperfusion related injury after microsurgical procedures of free tissue transfers.

Spironolactone prevents chronic kidney disease caused by ischemic acute kidney injury

Acute kidney injury (AKI) has been recognized as a risk factor for the development of chronic kidney disease (CKD). Aldosterone has a critical role in promoting renal injury induced by ischemia. Here, we evaluated whether spironolactone administered before or after AKI caused by ischemia protects against CKD. In the first set of experiments, Wistar rats underwent a sham operation without or with prior spironolactone treatment, or underwent 45 minutes of bilateral renal ischemia without or with spironolactone treatment before ischemia and assessed over 270 days. The second set of rats received low (20 mg/kg) or high (80 mg/kg) doses of spironolactone at three different times after the sham operation or bilateral renal ischemia and were assessed after 90 days. Untreated animals developed CKD following ischemia-induced AKI as characterized by a progressive increase in proteinuria, renal dysfunction, podocyte injury, glomerular hypertrophy, and focal sclerosis. This was associated with increased oxidative stress, an upregulation of tumor growth factor (TGF)-β, followed by upregulation of the TGF-β downstream effectors phospho-Smad3, collagen I, fibronectin, and proinflammatory cytokines. Treatment with spironolactone either before or after ischemia prevented subsequent CKD by avoiding the activation of fibrotic and inflammatory pathways. Thus, spironolactone may be a promising treatment for the prevention of AKI-induced CKD.

Amelioration of renal ischaemia-reperfusion injury by liposomal delivery of curcumin to renal tubular epithelial and antigen-presenting cells

BACKGROUND AND PURPOSE

Renal ischaemia-reperfusion (IR) injury is an inevitable consequence of renal transplantation, causing significant graft injury, increasing the risk of rejection and contributing to poor long-term graft outcome. Renal injury is mediated by cytokine and chemokine synthesis, inflammation and oxidative stress resulting from activation of the NF-κB pathway.

EXPERIMENTAL APPROACH

We utilized liposomal incorporation of a potent inhibitor of the NF-κB pathway, curcumin, to target delivery to renal tubular epithelial and antigen-presenting cells. Liposomes containing curcumin were administered before bilateral renal ischaemia in C57/B6 mice, with subsequent reperfusion. Renal function was assessed from plasma levels of urea and creatinine, 4 and 24 h after reperfusion. Renal tissue was examined for NF-κB activity and oxidative stress (histology, immunostaining) and for apoptosis (TUNEL). Cytokines and chemokines were measured by RT-PCR and Western blotting.

KEY RESULTS

Liposomal curcumin significantly improved serum creatinine, reduced histological injury and cellular apoptosis and lowered Toll-like receptor-4, heat shock protein-70 and TNF-α mRNA expression. Liposomal curcumin also reduced neutrophil infiltration and diminished inflammatory chemokine expression. Curcumin liposomes reduced intracellular superoxide generation and increased superoxide dismutase levels, decreased inducible NOS mRNA expression and 3-nitrotyrosine staining consistent with limitations in nitrosative stress and inhibited renal tubular mRNA and protein expression of thioredoxin-interacting protein. These actions of curcumin were mediated by inhibition of NF-κB, MAPK and phospho-S6 ribosomal protein.

CONCLUSIONS AND IMPLICATIONS

Liposomal delivery of curcumin promoted effective, targeted delivery of this non-toxic compound that provided cytoprotection via anti-inflammatory and multiple antioxidant mechanisms following renal IR injury.

A1 adenosine receptor allosteric enhancer PD-81723 protects against renal ischemia-reperfusion injury

Activation of A(1) adenosine receptors (ARs) protects against renal ischemia-reperfusion (I/R) injury by reducing necrosis, apoptosis, and inflammation. However, extrarenal side effects (bradycardia, hypotension, and sedation) may limit A(1)AR agonist therapy for ischemic acute kidney injury. Here, we hypothesized that an allosteric enhancer for A(1)AR (PD-81723) protects against renal I/R injury without the undesirable side effects of systemic A(1)AR activation by potentiating the cytoprotective effects of renal adenosine generated locally by ischemia. Pretreatment with PD-81723 produced dose-dependent protection against renal I/R injury in A(1)AR wild-type mice but not in A(1)AR-deficient mice. Significant reductions in renal tubular necrosis, neutrophil infiltration, and inflammation as well as tubular apoptosis were observed in A(1)AR wild-type mice treated with PD-81723. Furthermore, PD-81723 decreased apoptotic cell death in human proximal tubule (HK-2) cells in culture, which was attenuated by a specific A(1)AR antagonist (8-cyclopentyl-1,3-dipropylxanthine). Mechanistically, PD-81723 induced sphingosine kinase (SK)1 mRNA and protein expression in HK-2 cells and in the mouse kidney. Supporting a critical role of SK1 in A(1)AR allosteric enhancer-mediated renal protection against renal I/R injury, PD-81723 failed to protect SK1-deficient mice against renal I/R injury. Finally, proximal tubule sphingosine-1-phosphate type 1 receptors (S1P(1)Rs) are critical for PD-81723-induced renal protection, as mice selectively deficient in renal proximal tubule S1P(1)Rs (S1P(1)R(flox/flox) PEPCK(Cre/-) mice) were not protected against renal I/R injury with PD-81723 treatment. Taken together, our experiments demonstrate potent renal protection with PD-81723 against I/R injury by reducing necrosis, inflammation, and apoptosis through the induction of renal tubular SK1 and activation of proximal tubule S1P(1)Rs. Our findings imply that selectively enhancing A(1)AR activation by locally produced renal adenosine may be a clinically useful therapeutic option to attenuate ischemic acute kidney injury without systemic side effects.

Ischaemic/reperfusion injury: Role of infliximab

Ischaemia/reperfusion (I/R) injury is an underlying complex interrelated patho-physiological process which effects the outcome of many clinical situations, in particular transplantation. Tumor necrosis factor (TNF)-α is a pleiotropic inflammatory cytokine; a trimeric protein encoded within the major histocompatibility complex which plays a pivotal role in this disease process. This review is based at looking into an update, particularly the new insights in the mechanisms of action of TNF antagonist such as infliximab. Infliximab may thus play a dual role in the field of transplantation where it might not only down regulate the I/R injury, it may also have a beneficial role in the reduction of acute rejection.

Intraparenchymal injection of bone marrow mesenchymal stem cells reduces kidney fibrosis after ischemia-reperfusion in cyclosporine-immunosuppressed rats

Ischemia-reperfusion and immunosuppressive therapy are a major cause of progressive renal failure after kidney transplantation. Recent studies have shown that administration of bone marrow mesenchymal stem cells (MSCs) improves kidney functional recovery in the acute phase of post ischemia-reperfusion injury. In the present study, we used an original model of renal ischemia-reperfusion in immunosuppressed rats (NIRC) to investigate the effects of bone marrow MSCs on progression of chronic renal failure and the mechanisms potentially involved. Left renal ischemia-reperfusion (IR) was induced in unilateral nephrectomized Lewis rats. After IR, rats were treated daily with cyclosporine (10 mg/kg SC) for 28 days. MSCs were injected into the kidney at day 7 after IR. At day 28 after IR, kidneys were removed for histomorphological, biochemical, and gene expression analysis. The effect of conditioned media from MSCs on epithelial-mesenchymal transition was studied in vitro on HK2 cells. Our results show that, as compared to untreated NIRC rats, rats treated by intrarenal injection of MSCs 7 days after IR displayed improvement in renal function, reduction of interstitial fibrosis, and decrease in chronic tubule injury. These effects were associated with a decrease in interstitial α-SMA accumulation and MMP2 activity, markers of fibroblast/fibroblast-like cell activation, and renal remodeling, respectively. Finally, experiments in vitro showed that MSC-conditioned medium prevented epithelial-mesenchymal transition induced by TGF-β in HK2 cells. In conclusion, our results show that, in immunosuppressed animals, a single intrarenal administration of MSCs reduced renal fibrosis and promoted the recovery of renal function.

Donor preconditioning with rabbit anti-rat thymocyte immunoglobulin ameliorates ischemia reperfusion injury in rat kidney transplantation

A major concern in transplantation is the preservation of organ function. Ischemia time and microcirculatory disturbance of the organ cannot be avoided and may result in ischemia reperfusion injury (IRI), increasing the risk of delayed graft function (DGF) and acute and chronic rejection. Anti-thymocyte immunoglobulin (rATG) is a polyclonal antibody preparation with multiple effects when administered to recipients. Our objective has been to evaluate whether the administration of rATG to kidney donors instead of recipients, in an experimental model of syngeneic rat transplantation, ameliorates IRI and facilitates immediate graft function recovery. Urea and creatinine levels and necrosis severity scores were significantly lower in kidneys from donors that had received rATG (urea: control: 211±8mg/dl vs. treatment: 110±15mg/dl, p<0.001; creatinine: control: 4.6±0.24mg/dl vs. treatment: 2.6±0.22mg/dl, p<0.001; necrosis severity scores: control: 2.3 vs. treatment: 1.6, p<0.05). TUNEL staining showed 80±13 positive cells in control group and 9±3 (p<0.001) in treatment group. In situ expression of proinflammatory cytokines TNF-α, IL-6, IL-21 and TGF-β1 was reduced in rATG group (p<0.01); the same was observed for KIM-1 and caspase 8 (p<0.001). Cytoprotective genes Bcl2 and HO-1 were upregulated in situ in treatment group (p<0.001). In situ expression of IL-17, caspase 9, IL-23a, CxCl3 and ICAM1 showed no difference between groups (p>0.05). Findings suggest ATG administered to donors may ameliorate the IRI process in kidney transplantation, expressed by lower necrosis and apoptosis scores and the improvement of renal function, which may be explained through the diminished in situ expression of inflammatory mediators.

Effects of thyroid hormone analogue and a leukotrienes pathway-blocker on renal ischemia/reperfusion injury in mice

BACKGROUND

Acute renal failure (ARF) is an important clinical problem with a high mortality and morbidity. One of the primary causes of ARF is ischemia/reperfusion (I/R). Inflammatory process and oxidative stress are thought to be the major mechanisms causing I/R. MK-886 is a potent inhibitor of leukotrienes biosynthesis which may have anti-inflammatory and antioxidant effects through inhibition of polymorphonuclear leukocytes (PMNs) infiltration into renal tissues. 3, 5-diiodothyropropionic acid (DITPA) have evidences of improving effects on I/R in heart through modulation of cellular signaling in response to ischemic stress. The objective of present study was to assess the effects of MK-886 and DITPA on renal I/R injury.

METHODS

A total of 24 Adult males of Swiss albino mice were randomized to four groups: I/R group (n = 6), mice underwent 30 minute bilateral renal ischemia and 48 hr reperfusion. Sham group (n = 6), mice underwent same anesthetic and surgical procedures except for ischemia induction. MK-886-treated group: (n = 6), I/R + MK-886 (6 mg/kg) by intraperitoneal injection. DITPA-treated group: (n = 6), I/R + DITPA (3.75 mg/kg) by intraperitoneal injection.After the end of reperfusion phase mice were sacrificed, blood samples were collected directly from the heart for determination of serum TNF-a, IL-6, urea and Creatinine. Both kidney were excised, the right one homogenized for oxidative stress parameters (MDA and GSH) measurements and the left kidney fixed in formalin for histological examination.

RESULTS

Serum TNF-α, IL-6, urea and Creatinine, kidney MDA levels and scores of histopathological changes were significantly (P < 0.05) elevated in I/R group as compared with that of sham group. Kidney GSH level was significantly (P < 0.05) decreased in I/R group as compared with that of sham group. MK-886 treated group has significantly (P < 0.05) lowered levels of all study parameters except for GSH level which was significantly (P < 0.05) higher as compared with that of I/R group. DITPA caused non-significant (P > 0.05) changes in levels of all study parameters as compared with that of I/R group.

CONCLUSION

The results of the present study show that MK-886 significantly ameliorated kidney damage that resulted from I/R. For DITPA, as its administration might not be successful, administration using a different protocol may give different effects on I/R.

Type I interferon pathway mediates renal ischemia/reperfusion injury

BACKGROUND

Ischemia/reperfusion (I/R) injury is a common cause of acute renal failure after kidney transplantation. This study was designed to analyze the role of type I interferon (IFN) signaling downstream of Toll-like receptor 2/Toll-like receptor 4 activation in the mechanism of I/R-triggered kidney damage.

METHODS

Local warm ischemia was induced in groups wild-type (WT) and type I IFN receptor (IFNAR)-/- mice (C57BL/6) by clamping both kidney pedicles for 45 min. Mice were killed at 5/24/72 hr after reperfusion for serum and kidney sampling.

RESULTS

At 5 hr, serum creatinine and blood urea nitrogen levels were markedly reduced in IFNAR-/- mice as compared with WT. By 24 hr after reperfusion, both serum creatinine/blood urea nitrogen in WT increased further, whereas those in IFNAR-/- mice remained comparable with sham controls. Histological analyses showed significantly higher percentage of tubules in the outer medulla displaying cell necrosis, loss of the brush border, cast formation and tubular dilatation in WT mice, as compared with IFNAR-/-. Immunohistology revealed increased neutrophil and macrophage infiltration in the outer medulla in WT mice. The expression of proinflammatory tumor necrosis factor-α, interleukin-1, interleukin-6, and CXCL-2 was markedly reduced selectively in IFNAR-/- mice. Finally, terminal deoxynucleotide transferase-mediated dUTP nick-end labeling analysis showed significantly decreased frequency of apoptotic tubular epithelial cells in IFNAR-deficient mice, as compared with WT.

CONCLUSION

This is the first report, which documents the key role of type I IFN signaling in the mechanism of kidney I/R injury. Type I IFN may thus serve as a novel target for the therapy against renal I/R injury.

Low birth weight increases susceptibility to renal injury in a rat model of mild ischemia-reperfusion

Renal injury due to ischemia-reperfusion (I/R) is the major cause of acute kidney injury. Whether enhanced susceptibility to renal injury due to I/R can be programmed during fetal life is unknown. Epidemiological studies indicate that low birth weight (LBW) individuals are more susceptible to renal injury than normal birth weight (NBW) individuals. Thus, the aim of this study was to test the hypothesis that LBW is associated with an increased susceptibility to renal injury induced by mild renal I/R (15-min ischemia). Systemic and renal hemodynamic parameters were determined in NBW and LBW adult male rats after mild renal I/R; renal superoxide production and tubular injury were also assessed. A subgroup was pretreated with tempol, a superoxide dismutase mimetic, initiated 15 min before ischemia. Mild renal I/R did not alter renal hemodynamic parameters, induce tubular injury, or induce superoxide production in NBW rats. However, renal hemodynamic parameters declined, superoxide production increased, and histological indicators of tubular injury were present following mild renal I/R in LBW rats. Acute treatment with tempol prevented these alterations in LBW rats subjected to mild renal I/R. Thus, these findings suggest that adverse conditions during fetal life can compromise the renal response to subtle insults leading to an increased susceptibility to renal injury, suggesting that LBW individuals may be an "at risk" population for renal disease. Additionally, the outcome of tempol treatment proposes a possible mechanistic pathway involved in mediating enhanced susceptibility to renal injury programmed during fetal life.

Cytokines induce small intestine and liver injury after renal ischemia or nephrectomy

Patients with acute kidney injury (AKI) frequently suffer from extra-renal complications including hepatic dysfunction and systemic inflammation. We aimed to determine the mechanisms of AKI-induced hepatic dysfunction and systemic inflammation. Mice subjected to AKI (renal ischemia reperfusion (IR) or nephrectomy) rapidly developed acute hepatic dysfunction and suffered significantly worse hepatic IR injury. After AKI, rapid peri-portal hepatocyte necrosis, vacuolization, neutrophil infiltration and pro-inflammatory mRNA upregulation were observed suggesting an intestinal source of hepatic injury. Small intestine histology after AKI showed profound villous lacteal capillary endothelial apoptosis, disruption of vascular permeability and epithelial necrosis. After ischemic or non-ischemic AKI, plasma TNF-α, IL-17A and IL-6 increased significantly. Small intestine appears to be the source of IL-17A, as IL-17A levels were higher in the portal circulation and small intestine compared with the levels measured from the systemic circulation and liver. Wild-type mice treated with neutralizing antibodies against TNF-α, IL-17A or IL-6 or mice deficient in TNF-α, IL-17A, IL-17A receptor or IL-6 were protected against hepatic and small intestine injury because of ischemic or non-ischemic AKI. For the first time, we implicate the increased release of IL-17A from small intestine together with induction of TNF-α and IL-6 as a cause of small intestine and liver injury after ischemic or non-ischemic AKI. Modulation of the inflammatory response and cytokine release in the small intestine after AKI may have important therapeutic implications in reducing complications arising from AKI.

MnTMPyP, a superoxide dismutase/catalase mimetic, decreases inflammatory indices in ischemic acute kidney injury

OBJECTIVE

This study investigates the effect of a superoxide dismutase mimetic, MnTMPyP, on pro- and anti-inflammatory cytokines in acute renal ischemia-reperfusion (IR).

MATERIALS AND TREATMENT

Male Sprague-Dawley rats underwent bilateral clamping of the renal arteries for 45 min followed by 1, 4, or 24 h of reperfusion. A subset of animals was treated with MnTMPyP (5 mg/kg, i.p.) or saline. Porcine proximal tubular epithelial cells were ATP-depleted for 4 h followed by recovery for 2 h.

METHODS

Cytokines were analyzed by ELISA, and ED1(+) macrophages and CD8(+) T lymphocytes by immunohistochemistry. Statistical analysis was performed using ANOVA.

RESULTS

MnTMPyP attenuated the IR-mediated increase in serum creatinine and circulating levels of interleukin (IL)-2 following 24 h of reperfusion. Furthermore, treatment attenuated increases in tissue levels of tumor necrosis factor (TNF)-α, IL-2, IL-4, and IL-13. MnTMPyP partially prevented the IR-induced infiltration of ED1(+) macrophages and CD8(+) T lymphocytes in the kidney. ATP depletion-recovery of porcine proximal tubular epithelial cells resulted in decreased IL-6 and IL-10 levels, and MnTMPyP partially restored these cytokines.

CONCLUSIONS

These results show that MnTMPyP is partially effective in reducing inflammation associated with renal IR and that reactive oxygen species play a role in modulating both pro- and anti-inflammatory pathways in acute kidney injury.

The antioxidant role of oral administration of garlic oil on renal ischemia-reperfusion injury

AIM

In this study we examined the effect of oral application of garlic form [garlic oil (GO)] on rats after renal ischemia-reperfusion (I/R) injury.

MATERIALS AND METHODS

Forty male Wistar albino rats were divided into four groups: control, sham-operated, I/R, and I/R+GO. GO was diluted in water and administered by oral intubation three times each week for 6 weeks. All rats except sham-operated underwent 45 min of bilateral renal ischemia followed by 6 hr of reperfusion. Blood samples and kidney tissues were harvested from the rats, and then rats were killed. Serum urea, creatinine, and cystatin C levels were determined. Total antioxidant capacity (TAC), catalase (CAT), total oxidant status (TOS), oxidative stress index (OSI), myeloperoxidase (MPO), nitrite oxide (NO), and protein carbonyl (PC) levels in kidney tissue and blood were measured. In addition, kidney tissue histopathology was evaluated.

RESULTS

The serum urea, creatinine, and cystatin C levels were significantly higher in I/R group compared to I/R+GO group (p<0.01). The serum and tissue antioxidant markers (TAC, CAT) were significantly lower in I/R group than I/R+GO group (p<0.01). The serum oxidant markers (TOS, MPO, NO, and PC) were significantly higher in I/R group than I/R+GO group (p<0.01). Also oral application of GO was effective in decreasing of tubular necrosis score.

CONCLUSION

Based on the present data, we conclude that increased antioxidants and decreased oxidants modulated by oral application of GO attenuated the renal I/R injury.

Protective effects of Nigella sativa against ischemia-reperfusion injury of kidneys

BACKGROUND

Ischemia-reperfusion, commonly seen in the fields of trauma surgery and renal transplantation, is a major cause of acute kidney injury and is associated with significant morbidity and mortality. The protective effects of Nigella sativa against ischemia-perfusion damage to various organs have been previously documented. However, its protective effects on kidney tissue against ischemia-reperfusion injury are unclear. In this study, we aimed to examine the effect of Nigella sativa in modulating inflammation and apoptosis after renal I/R injury.

MATERIALS AND METHODS

Thirty male Wistar-albino rats were divided into three groups: sham-operated, ischemia-reperfusion, and ischemia-reperfusion + Nigella sativa. Rats in the third group were given Nigella sativa 6 h prior to ischemia-reperfusion and at the beginning of reperfusion. All rats except those in the sham-operated group underwent 45 min of bilateral renal ischemia followed by 45 min of reperfusion. Blood samples and liver tissues were harvested from the rats, and then rats were sacrificed. Serum urea and creatinine levels were determined. Total antioxidant capacity (TAC), catalase (CAT), total oxidant status (TOS), oxidative stress index (OSI), and myeloperoxidase (MPO) in kidney tissue and blood were measured. Kidney tissue histopathology was also evaluated. Results. Nigella sativa was effective in reducing serum urea and creatinine levels as well as decreasing the tubular necrosis score. Nigella sativa treatment significantly reduced OSI and TOS levels and increased TAC levels in both kidney tissue and blood.

CONCLUSION

The observed differences seem to demonstrate the protective effect of Nigella sativa against renal I/R injury in rat kidneys.

Effects of metalloproteinase inhibition in a murine model of renal ischemia-reperfusion injury

Ischemia-reperfusion injury (IRI) is a leading cause of acute tubular necrosis (ATN) and delayed graft function in transplanted organs. Up-regulation of matrix metalloproteinases (MMPs) propagates the microinflammatory response that drives IRI. This study sought to determine the specific effects of Marimastat (Vernalis, BB-2516), a broad spectrum MMP and TNF-alpha-converting enzyme inhibitor, on IRI-induced ATN. Mice were pretreated with Marimastat or methylcellulose vehicle for 4 d before surgery. Renal pedicles were bilaterally occluded for 30 min and allowed to reperfuse for 24 h. Baseline creatinine levels were consistent between experimental groups; however, post-IRI creatinine levels were 4-fold higher in control mice (p < 0.0001). The mean difference between the post-IRI histology grades of Marimastat-treated and control kidneys was 1.57 (p = 0.003), demonstrating more severe damage to control kidneys. Post-IRI mean (+/-SEM) MMP-2 activity rose from baseline levels in control mice (3.62 +/- 0.99); however, pretreated mice presented only a slight increase in mean MMP-2 activity (1.57 +/- 0.72) (p < 0.001). In conclusion, these data demonstrate that MMP inhibition is associated with a reduction of IRI in a murine model.

Selective intrarenal human A1 adenosine receptor overexpression reduces acute liver and kidney injury after hepatic ischemia reperfusion in mice

Acute kidney injury (AKI) is frequent after liver ischemia reperfusion (IR) can potentiate liver injury and is often complicated by subsequent multiorgan dysfunction syndrome. AKI because of liver IR is characterized by early renal endothelial cell apoptosis and impaired vascular integrity with subsequent neutrophil infiltration, proximal tubule necrosis/inflammation, and filamentous (F) actin disintegration. We tested whether selective renal overexpression of human A(1) adenosine receptors (huA(1)AR) protects against both liver and kidney injury sustained after liver IR. Mice were subjected to liver IR or to sham surgery 48 h after unilateral intrarenal injection of lentivirus encoding enhanced green fluorescent protein (EGFP) or EGFP-huA(1)AR. Intrarenal lentiviral gene delivery caused a robust transgene expression in the injected kidney without significant expression in the contralateral kidney or in the liver. Mice injected with EGFP-huA(1)AR lentivirus were protected against hepatic IR-induced liver and kidney injury with reduced necrosis, inflammation, and apoptosis, and better preserved F-actin and vascular permeability compared with mice injected with EGFP lentivirus. Importantly, we show that removing the EGFP-huA(1)AR lentivirus-injected kidney before hepatic ischemia abolished both renal and hepatic protection after liver IR showing that the overexpression of huA(1)AR in the injected kidney has a crucial role in protecting the kidney and liver after liver IR. Therefore, our findings show that protecting the kidney reduces liver IR injury and selective overexpression of cytoprotective A(1)ARs in the kidney leads to protection of both liver and kidney after hepatic IR.