Nox2 is a mediator of ischemia reperfusion injury

Synthetic Bilirubin-Based Nanomedicine Protects Against Renal Ischemia/Reperfusion Injury Through Antioxidant and Immune-Modulating Activity

Renal ischemia/reperfusion injury (IRI) is a common form of acute kidney injury. The basic mechanism underlying renal IRI is acute inflammation, where oxidative stress plays an important role. Although bilirubin exhibits potent reactive oxygen species (ROS)-scavenging properties, its clinical application is hindered by problems associated with solubility, stability, and toxicity. In this study, BX-001N, a synthetic polyethylene glycol-conjugated bilirubin 3α nanoparticle is developed and assessed its renoprotective effects in renal IRI. Intravenous administration of BX-001N led to increase uptake in the kidneys with minimal migration to the brain after IRI. Peri-IRI BX-001N administration improves renal function and attenuates renal tissue injury and tubular apoptosis to a greater extent than free bilirubin on day 1 after IRI. BX-001N suppressed renal infiltration of inflammatory cells and reduced expression of TNF-α and MCP-1. Furthermore, BX-001N increases renal tubular regeneration on day 3 and suppresses renal fibrosis on day 28. BX-001N decreases the renal expressions of dihydroethidium, malondialdehyde, and nitrotyrosine after IRI. In conclusion, BX-001N, the first Good Manufacturing Practice-grade synthetic bilirubin-based nanomedicine attenuates acute renal injury and chronic fibrosis by suppressing ROS generation and inflammation after IRI. It shows adequate safety profiles and holds promise as a new therapy for renal IRI.

Nox4 is involved in acute kidney injury associated to intravascular hemolysis

Massive intravascular hemolysis occurs not unfrequently in many clinical conditions. Breakdown of erythrocytes promotes the accumulation of heme-derivates in the kidney, increasing oxidative stress and cell death, thus promoting acute kidney injury (AKI). NADPH oxidase 4 (Nox4) is a major source of reactive oxygen species (ROS) in the kidney, however it is unknown the role of Nox4 in hemolysis and whether inhibition of this enzyme may protect from heme-mediated injury. To answer these questions, we elicited intravascular hemolysis in wild type and Nox4 knockout mice. We also evaluated whether nephrotoxic effects of heme may be reduced by using Nox4 siRNA and pharmacologic inhibition with GKT137831, a Nox4 inhibitor, both in vivo and in cultured renal cells. Our results showed that induction of massive hemolysis elicited AKI characterized by loss of renal function, morphological alterations of the tubular epithelium and podocytes, oxidative stress, inflammation, mitochondrial dysfunction, blockade of autophagy and cell death. These pathological effects were significantly prevented in Nox4-deficient mice and in animals treated with GKT137831. In vitro studies showed that Nox4 disruption by specific siRNAs or Nox4 inhibitors declined heme-mediated ROS production and cell death. Our data identify Nox4 as a key enzyme involved in intravascular hemolysis-induced AKI. Thus, Nox4 inhibition may be a potential therapeutic approach to prevent renal damage in patients with severe hemolytic crisis.

Protective effects of pioglitazone in renal ischemia-reperfusion injury (RIRI): focus on oxidative stress and inflammation

BACKGROUND

Renal ischemia-reperfusion injury (RIRI) is a critical phenomenon that compromises renal function and is the most serious health concern related to acute kidney injury (AKI). Pioglitazone (Pio) is a known agonist of peroxisome proliferator-activated receptor-gamma (PPAR-γ). PPAR-γ is a nuclear receptor that regulates genes involved in inflammation, metabolism, and cellular differentiation. Activation of PPAR-γ is associated with antiinflammatory and antioxidant effects, which are relevant to the pathophysiology of RIRI. This study aimed to investigate the protective effects of Pio in RIRI, focusing on oxidative stress and inflammation.

METHODS

We conducted a comprehensive literature search using electronic databases, including PubMed, ScienceDirect, Web of Science, Scopus, and Google Scholar.

RESULTS

The results of this study demonstrated that Pio has antioxidant, anti-inflammatory, and anti-apoptotic activities that counteract the consequences of RIRI. The study also discussed the underlying mechanisms, including the modulation of various pathways such as TNF-α, NF-κB signaling systems, STAT3 pathway, KIM-1 and NGAL pathways, AMPK phosphorylation, and autophagy flux. Additionally, the study presented a summary of various animal studies that support the potential protective effects of Pio in RIRI.

CONCLUSION

Our findings suggest that Pio could protect the kidneys from RIRI by improving antioxidant capacity and decreasing inflammation. Therefore, these findings support the potential of Pio as a therapeutic strategy for preventing RIRI in different clinical conditions.

Inhibition of both NOX and TNF-α exerts substantial renoprotective effects in renal ischemia reperfusion injury rat model

BACKGROUND AND AIMS

Acute kidney injury (AKI) due to renal ischemia-reperfusion injury (RIRI) is associated with high morbidity and mortality, with no renoprotective drug available. Previous research focused on single drug targets, yet this approach has not reached translational success. Given the complexity of this condition, we aimed to identify a disease module and apply a multitarget network pharmacology approach.

METHODS

Identification of a disease module with potential drug targets was performed utilizing Disease Module Detection algorithm using NADPH oxidases (NOXs) as seeds. We then assessed the protective effect of a multitarget network pharmacology targeting the identified module in a rat model of RIRI. Rats were divided into five groups; sham, RIRI, and RIRI treated with setanaxib (NOX inhibitor, 10 mg/kg), etanercept (TNF-α inhibitor, 10 mg/kg), and setanaxib and etanercept (5 mg/kg each). Kidney functions, histopathological changes and oxidative stress markers (MDA and reduced GSH) were assessed. Immunohistochemistry of inflammatory (TNF-α, NF-κB) apoptotic (cCasp-3, Bax/Bcl 2), fibrotic (α-SMA) and proteolysis (MMP-9) markers was performed.

RESULTS

Our in-silico analysis yielded a disease module with TNF receptor 1 (TNFR1A) as the closest target to both NOX1 and NOX2. Targeting this module by a low-dose combination of setanaxib, and etanercept, resulted in a synergistic effect and ameliorated ischemic AKI in rats. This was evidenced by improved kidney function and reduced expression of inflammatory, apoptotic, proteolytic and fibrotic markers.

CONCLUSIONS

Our findings show that applying a multitarget network pharmacology approach allows synergistic renoprotective effect in ischemic AKI and might pave the way towards translational success.

Systemic Mutation of Ncf1 Ameliorates Obstruction-Induced Renal Fibrosis While Macrophage-Rescued NCF1 Further Alleviates Renal Fibrosis

Aims: NCF1, a subunit of the NADPH oxidase 2 (NOX2), first described the expression in neutrophils and macrophages and participated in the pathogenesis from various systems. However, there are controversial findings on the role of NCF1 in different kinds of kidney diseases. In this study, we aim to pinpoint the specific role of NCF1 in the progression of renal fibrosis induced by obstruction. Results: In this study, NCF1 expression was upregulated in kidney biopsies of chronic kidney disease patients. The expression level of all subunits of the NOX2 complex was also significantly increased in the unilateral ureteral obstruction (UUO) kidney. Then, we used wild-type mice and Ncf1 mutant mice (Ncf1m1j mice) to perform UUO-induced renal fibrosis. Results demonstrated that Ncf1m1j mice exhibited mild renal fibrosis but increased macrophages count and CD11b+Ly6Chi macrophage proportion. Next, we compared the renal fibrosis degree between Ncf1m1j mice and Ncf1 macrophage-rescued mice (Ncf1m1j.Ncf1Tg-CD68 mice). We found that rescuing NCF1 expression in macrophages further alleviated renal fibrosis and decreased macrophage infiltration in the UUO kidney. In addition, flow cytometry data showed fewer CD11b+Ly6Chi macrophages in the kidney of the Ncf1m1j.Ncf1Tg-CD68 group than the Ncf1m1j group. Innovation: We first used the Ncf1m1j mice and Ncf1m1j.Ncf1Tg-CD68 mice to detect the role of NCF1 in the pathological process of renal fibrosis induced by obstruction. Also, we found that NCF1 expressed in different cell types exerts opposing effects on obstructive nephropathy. Conclusion: Taken together, our findings support that systemic mutation of Ncf1 ameliorates renal fibrosis induced by obstruction, and rescuing NCF1 in macrophages further alleviates renal fibrosis.

Deletion of NADPH oxidase 2 attenuates cisplatin-induced acute kidney injury through reducing ROS-induced proximal tubular cell injury and inflammation

Backgrounds

Cisplatin is a commonly used chemotherapeutic agent in cancer treatment. However, its high nephrotoxicity limits its therapeutic application and efficacy. Cisplatin induces nephrotoxicity mainly through oxidative stress and inflammation. Reactive oxygen species (ROS) in the kidneys mainly arise from nicotinamide adenine dinucleotide phosphate (NADPH) oxidases 2 (NOX2), which is highly upregulated during ischemia-reperfusion injury and diabetes mellitus. However, its role in cisplatin-induced acute kidney injury (AKI) remains unknown.

Methods

A 8-10-week-old NOX2 gene-knockout and wild-type mice were injected with 25 mg/kg cisplatin intraperitoneally for experiments.

Results

We investigated the role of NOX2 in cisplatin-induced AKI and found that NOX2-mediated ROS production is a key inflammatory mediator of proximal tubular cell injury in cisplatin-induced AKI. NOX2 gene-knockout alleviated cisplatin-induced renal function decline, tubular injury score, kidney injury molecule-1(Kim-1) expression, and interleukin (IL)-6 and IL-1α levels with a reduction of ROS production. Moreover, in cisplatin-induced AKI, intercellular adhesion molecule 1 (ICAM-1) and the chemoattractant CXC ligand 1 (CXCL1) were highly expressed in association with neutrophil infiltration, which were all attenuated by deletion of NOX2.

Conclusion

These data indicate that NOX2 aggravates cisplatin nephrotoxicity by promoting ROS-mediated tissue injury and neutrophil infiltration. Thus, appropriate targeting of NOX2/ROS pathway may minimize the risk of cisplatin-induced kidney injury in patients receiving cancer therapy.

Novel role of macrophage TXNIP-mediated CYLD-NRF2-OASL1 axis in stress-induced liver inflammation and cell death

Background & Aims

The stimulator of interferon genes (STING)/TANK-binding kinase 1 (TBK1) pathway is vital in mediating innate immune and inflammatory responses during oxidative/endoplasmic reticulum (ER) stress. However, it remains unknown whether macrophage thioredoxin-interacting protein (TXNIP) may regulate TBK1 function and cell death pathways during oxidative/ER stress.

Methods

A mouse model of hepatic ischaemia/reperfusion injury (IRI), the primary hepatocytes, and bone marrow-derived macrophages were used in the myeloid-specific TXNIP knockout (TXNIPM-KO) and TXNIP-proficient (TXNIPFL/FL) mice.

Results

The TXNIPM-KO mice were resistant to ischaemia/reperfusion (IR) stress-induced liver damage with reduced serum alanine aminotransferase (ALT)/aspartate aminotransferase (AST) levels, macrophage/neutrophil infiltration, and pro-inflammatory mediators compared with the TXNIPFL/FL controls. IR stress increased TXNIP, p-STING, and p-TBK1 expression in ischaemic livers. However, TXNIPM-KO inhibited STING, TBK1, interferon regulatory factor 3 (IRF3), and NF-κB activation with interferon-β (IFN-β) expression. Interestingly, TXNIPM-KO augmented nuclear factor (erythroid-derived 2)-like 2 (NRF2) activity, increased antioxidant gene expression, and reduced macrophage reactive oxygen species (ROS) production and hepatic apoptosis/necroptosis in IR-stressed livers. Mechanistically, macrophage TXNIP deficiency promoted cylindromatosis (CYLD), which colocalised and interacted with NADPH oxidase 4 (NOX4) to enhance NRF2 activity by deubiquitinating NOX4. Disruption of macrophage NRF2 or its target gene 2',5' oligoadenylate synthetase-like 1 (OASL1) enhanced Ras GTPase-activating protein-binding protein 1 (G3BP1) and TBK1-mediated inflammatory response. Notably, macrophage OASL1 deficiency induced hepatocyte apoptotic peptidase activating factor 1 (APAF1), cytochrome c, and caspase-9 activation, leading to increased caspase-3-initiated apoptosis and receptor-interacting serine/threonine-protein kinase 3 (RIPK3)-mediated necroptosis.

Conclusions

Macrophage TXNIP deficiency enhances CYLD activity and activates the NRF2-OASL1 signalling, controlling IR stress-induced liver injury. The target gene OASL1 regulated by NRF2 is crucial for modulating STING-mediated TBK1 activation and Apaf1/cytochrome c/caspase-9-triggered apoptotic/necroptotic cell death pathway. Our findings underscore a novel role of macrophage TXNIP-mediated CYLD-NRF2-OASL1 axis in stress-induced liver inflammation and cell death, implying the potential therapeutic targets in liver inflammatory diseases.

Lay summary

Liver inflammation and injury induced by ischaemia and reperfusion (the absence of blood flow to the liver tissue followed by the resupply of blood) is a significant cause of hepatic dysfunction and failure following liver transplantation, resection, and haemorrhagic shock. Herein, we uncover an underlying mechanism that contributes to liver inflammation and cell death in this setting and could be a therapeutic target in stress-induced liver inflammatory injury.

Upregulation of NADPH Oxidase 2 Contributes to Renal Fibrosis in Mice: An Experimental Model of Nephronophthisis

<b><i>Background:</i></b> DBA/2FG-<i>pcy</i> (<i>pcy</i>) mice harbor a homozygous <i>Nphp3</i> missense mutation and develop nephronophthisis with renal interstitial fibrosis. Previous studies have shown that aberrant oxygen homeostasis contributes to the renal pathology in <i>pcy</i> mice, but the underlying molecular mechanism remains largely unknown. <b><i>Methods:</i></b> <i>pcy</i> mice and a control strain, DBA/2N (DBA) mice, were used. Renal levels of 62 mRNAs involved in oxygen homeostasis were investigated by real-time PCR, and the resulting data were used for extraction of pathological pathways. On the basis of the genes found to be upregulated and pathway analysis, further studies were performed using immunoblotting, immunohistochemistry, and pharmacological intervention. <b><i>Results:</i></b> In comparison with DBA mice, the levels of 18 mRNAs were altered by &#x3e;2-fold in <i>pcy</i> mice. Pathway analysis extracted molecular pathways related to oxidative stress, inflammation, and cell adhesion. As the levels of mRNAs relevant to the NADPH oxidase 2 (NOX2) pathway were prominently (4 genes &#x3e;5-fold) increased in <i>pcy</i> mice, we further analyzed the molecules related to this pathway. A time course study suggested that the pathway was gradually activated in <i>pcy</i> mice from at least 5 weeks of age. Immunohistochemistry study revealed that NOX2 protein was colocalized with a macrophage marker protein in the renal interstitium. Moreover, treatment of <i>pcy</i> mice with apocynin, an inhibitor of the NOX2 pathway, ameliorated the renal fibrosis. <b><i>Conclusion:</i></b> Our findings suggest that the activation of the NOX2 pathway, possibly mediated by macrophage infiltration, plays a pivotal role in progressive renal fibrosis in <i>pcy</i> mice.

Renal Tubular Epithelial TRPA1 Acts as An Oxidative Stress Sensor to Mediate Ischemia-Reperfusion-Induced Kidney Injury through MAPKs/NF-κB Signaling

Oxidative stress and inflammation play important roles in the pathophysiology of acute kidney injury (AKI). Transient receptor potential ankyrin 1 (TRPA1) is a Ca2+-permeable ion channel that is sensitive to reactive oxygen species (ROS). The role of TRPA1 in AKI remains unclear. In this study, we used human and animal studies to assess the role of renal TRPA1 in AKI and to explore the regulatory mechanism of renal TRPA1 in inflammation via in vitro experiments. TRPA1 expression increased in the renal tubular epithelia of patients with AKI. The severity of tubular injury correlated well with tubular TRPA1 or 8-hydroxy-2'-deoxyguanosine expression. In an animal model, renal ischemia-reperfusion injury (IR) increased tubular TRPA1 expression in wild-type (WT) mice. Trpa1^-/- mice displayed less IR-induced tubular injury, oxidative stress, inflammation, and dysfunction in kidneys compared with WT mice. In the in vitro model, TRPA1 expression increased in renal tubular cells under hypoxia-reoxygenation injury (H/R) conditions. We demonstrated that H/R evoked a ROS-dependent TRPA1 activation, which elevated intracellular Ca²⁺ level, increased NADPH oxidase activity, activated MAPK/NF-κB signaling, and increased IL-8. Renal tubular TRPA1 may serve as an oxidative stress sensor and a crucial regulator in the activation of signaling pathways and promote the subsequent transcriptional regulation of IL-8. These actions might be evident in mice with IR or patients with AKI.

Ameliorative effect of umbelliferone in remote organ injury induced by renal ischemia-reperfusion in rats

We evaluated the ameliorative role of umbelliferone in kidney, heart, and lung damage induced by renal ischemia/reperfusion (I/R) injury in rats. Umbelliferone was given orally to rats 60 min before ischemia. Ischemia was induced for 50 min and then reperfusion for 3 hr. The antioxidant enzymes, myeloperoxidase (MPO) activity, malondialdehyde (MDA) content, and cytokine levels in the kidney, heart, and lung were measured by ELISA. Moreover, histopathological changes were monitored. Renal I/R-induced oxidative stress in the organs by decreasing antioxidant enzymes. However, umbelliferone pretreatment enhanced superoxide dismutase (SOD) and glutathione (GSH), levels, reduced MDA and MPO levels. Renal I/R increased in tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6) levels, and histopathological changes but these effects were inhibited with umbelliferone pretreatment. Furthermore, umbelliferone increased in nitric oxide synthase (eNOS) level under ischemia conditions. Our results indicated that pretreatment of umbelliferone-ameliorated damages in remote organ induced by renal I/R through suppressing oxidative stress and modulating inflammatory responses. PRACTICAL APPLICATIONS: kidney, heart, and lung damages induced by renal I/R in rats was alleviated by umbelliferone. The oral treatment of umbelliferone markedly reversed the oxidative stress, inflammation, and histopathological changes by increasing in the levels of SOD, GSH, and eNOS, decreasing in the levels of MDA, MPO, TNF-α, and IL-6 in distant organ injury induced by renal I/R. This study firstly revealed that umbelliferone has potent antioxidant and anti-inflammatory activity in the remote organ damages caused by renal I/R. Consequently, umbelliferone may be an alternative therapeutic agent for treating renal I/R-induced damages.

Bruton's tyrosine kinase inhibition attenuates oxidative stress in systemic immune cells and renal compartment during sepsis-induced acute kidney injury in mice

Sepsis is a life-threatening condition which affects multiple organs including the kidney. Sepsis-induced acute kidney injury (AKI) is a major health burden throughout the globe. Pathogenesis of sepsis-induced AKI is complex; however, it involves both innate and adaptive immune cells such as B cells, T cells, dendritic cells (DCs), macrophages, and neutrophils. Bruton's tyrosine kinase (BTK) is reportedly involved in inflammatory and oxidative signaling in different immune cells, however its contribution with respect to sepsis-induced AKI has not been delineated. This study attempted to investigate the role of BTK and its inhibition on oxidizing enzymes NADPH oxidase (NOX-2) and inducible nitric oxide synthase (iNOS) in DCs, neutrophils, and B cells during AKI. Our data reveal that BTK is activated in DCs, neutrophils, and B cells which causes an increase in AKI associated biochemical markers such as serum creatinine/blood urea nitrogen, renal myeloperoxidase activity, and histopathological disturbances in renal tubular structures. Activation of BTK causes upregulation of NOX-2/iNOS/nitrotyrosine in these immune cells and kidney. Treatment with BTK inhibitor, Ibrutinib causes attenuation in AKI associated dysfunction in biochemical parameters (serum creatinine/blood urea nitrogen, renal myeloperoxidase activity) and oxidative stress in immune cells and kidney (iNOS/NOX2/lipid peroxides/nitrotyrosine/protein carbonyls). In summary, the current investigation reveals a compelling role of BTK signaling in sepsis-induced AKI which is evident from amelioration of AKI associated renal dysfunction after its inhibition.

NOX1 Inhibition Attenuates Kidney Ischemia-Reperfusion Injury via Inhibition of ROS-Mediated ERK Signaling

The protective effects of nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) 1 inhibition against kidney ischemia-reperfusion injury (IRI) remain uncertain. The bilateral kidney pedicles of C57BL/6 mice were clamped for 30 min to induce IRI. Madin–Darby Canine Kidney (MDCK) cells were incubated with H₂O₂ (1.4 mM) for 1 h to induce oxidative stress. ML171, a selective NOX1 inhibitor, and siRNA against NOX1 were treated to inhibit NOX1. NOX expression, oxidative stress, apoptosis assay, and mitogen-activated protein kinase (MAPK) pathway were evaluated. The kidney function deteriorated and the production of reactive oxygen species (ROS), including intracellular H₂O₂ production, increased due to IRI, whereas IRI-mediated kidney dysfunction and ROS generation were significantly attenuated by ML171. H₂O₂ evoked the changes in oxidative stress enzymes such as SOD2 and GPX in MDCK cells, which was mitigated by ML171. Treatment with ML171 and transfection with siRNA against NOX1 decreased the upregulation of NOX1 and NOX4 induced by H₂O₂ in MDCK cells. ML171 decreased caspase-3 activity, the Bcl-2/Bax ratio, and TUNEL-positive tubule cells in IRI mice and H₂O₂-treated MDCK cells. Among the MAPK pathways, ML171 affected ERK signaling by ERK phosphorylation in kidney tissues and tubular cells. NOX1-selective inhibition attenuated kidney IRI via inhibition of ROS-mediated ERK signaling.

Honokiol Protects the Kidney from Renal Ischemia and Reperfusion Injury by Upregulating the Glutathione Biosynthetic Enzymes

Glutathione (GSH) is an endogenous antioxidant found in plants, animals, fungi, and some microorganisms that protects cells by neutralizing hydrogen peroxide. Honokiol, an active ingredient of Magnolia officinalis, is known for antioxidant, anti-inflammatory, and anti-bacterial properties. We investigated the protective mechanism of honokiol through regulating cellular GSH in renal proximal tubules against acute kidney injury (AKI). First, we measured cellular GSH levels and correlated them with the expression of GSH biosynthetic enzymes after honokiol treatment in human kidney-2 (HK-2) cells. Second, we used pharmacological inhibitors or siRNA-mediated gene silencing approach to determine the signaling pathway induced by honokiol. Third, the protective effect of honokiol via de novo GSH biosynthesis was investigated in renal ischemia-reperfusion (IR) mice. Honokiol significantly increased cellular GSH levels by upregulating the subunits of glutamate-cysteine ligase (Gcl)—Gclc and Gclm. These increases were mediated by activation of nuclear factor erythroid 2-related factor 2, via PI3K/Akt and protein kinase C signaling. Consistently, honokiol treatment reduced the plasma creatinine, tubular cell death, neutrophil infiltration and lipid peroxidation in IR mice and the effect was correlated with upregulation of Gclc and Gclm. Conclusively, honokiol may benefit to patients with AKI by increasing antioxidant GSH via transcriptional activation of the biosynthetic enzymes.

Empagliflozin attenuates acute kidney injury after myocardial infarction in diabetic rats

Acute kidney injury (AKI) predicts poor prognosis in patients with acute myocardial infarction (MI) and diabetes mellitus (DM) is an independent risk factor of AKI. Recent clinical studies have shown the beneficial effects of sodium-glucose cotransporter 2 (SGLT2) inhibitors on cardiovascular and renal outcomes in patients with DM. We recently reported that canagliflozin normalized susceptibility of diabetic rats to AKI after acute MI via β-hydroxybutyrate-mediated suppression of NOX expression. Here we examined whether the same renoprotective effect is shared by empagliflozin. Serum creatinine levels were not changed by MI induced by coronary artery occlusion in LETO, non-diabetic control rats, and OLETF, obese type 2 diabetic rats. However, immunohistochemistry revealed that MI increased renal expression of NGAL and KIM-1, early markers of tubular injury, by 3.2-fold and 2.6-fold, respectively, in OLETF. These increases in injury markers were not observed in LETO. Pretreatment with empagliflozin of OLETF for 2 weeks improved hyperglycemia, increased blood β-hydroxybutyrate level, and suppressed MI-induced expression of NGAL and KIM-1. Empagliflozin suppressed upregulation of NOX2 and NOX4 in the kidney of OLETF. Taken together with the results of our previous study, it was concluded that treatment with the SGLT2 inhibitor protects the diabetic kidney from MI-induced AKI.

Influence of Different Partial Pressures of Oxygen During Continuous Hypothermic Machine Perfusion in a Pig Kidney Ischemia-reperfusion Autotransplant Model

BACKGROUND

The optimal perfusate partial pressure of oxygen (PO2) during hypothermic machine perfusion (HMP) is unknown. The aims of the study were to determine the functional, metabolic, structural, and flow dynamic effects of low and high perfusate PO2 during continuous HMP in a pig kidney ischemia-reperfusion autotransplant model.

METHODS

The left kidneys of a ±40 kg pigs were exposed to 30 minutes of warm ischemia and randomized to receive 22-hour HMP with either low perfusate PO2 (30% oxygen, low oxygenated HMP [HMPO2]) (n = 8) or high perfusate PO2 (90% oxygen, HMPO2high) (n = 8), before autotransplantation. Kidneys stored in 22-hour standard HMP (n = 6) and 22-hour static cold storage (n = 6) conditions served as controls. The follow-up after autotransplantation was 13 days.

RESULTS

High PO2 resulted in a 3- and 10-fold increase in perfusate PO2 compared with low HMPO2 and standard HMP, respectively. Both HMPO2 groups were associated with superior graft recovery compared with the control groups. Oxygenation was associated with a more rapid and sustained decrease in renal resistance. While there was no difference in functional outcomes between both HMPO2 groups, there were clear metabolic differences with an inverse correlation between oxygen provision and the concentration of major central metabolites in the perfusion fluid but no differences were observed by oxidative stress and metabolic evaluation on preimplantation biopsies.

CONCLUSIONS

While this animal study does not demonstrate any advantages for early graft function for high perfusate PO2, compared with low perfusate PO2, perfusate metabolic profile analysis suggests that aerobic mechanism is better supported under high perfusate PO2 conditions.

Gene knockout of the Na+-glucose cotransporter SGLT2 in a murine model of acute kidney injury induced by ischemia-reperfusion

In the early proximal tubule, Na⁺-glucose cotransporter 2 (SGLT2) mediates the bulk of renal glucose reabsorption. Gene deletion in mice (Sglt2^-/-) was used to determine the role of SGLT2 in acute kidney injury induced by bilateral ischemia-reperfusion (IR). In Sglt2^-/- and littermate wild-type mice, plasma creatinine increased similarly on day 1 after IR. This was associated with an equal increase in both genotypes in the urinary kidney injury molecule-1-to-creatinine ratio, a tubular injury marker, and similarly reduced urine osmolality and increased plasma osmolality, indicating impaired urine concentration. In both IR groups, FITC-sinistrin glomerular filtration rate was equally reduced on day 14, and plasma creatinine was similarly and incompletely restored on day 23. In Sglt2^-/- mice subjected to IR, fractional urinary glucose excretion was increased on day 1 but reduced and associated with normal renal Na⁺-glucose cotransporter 1 (Sglt1) mRNA expression on day 23, suggesting temporary SGLT1 suppression. In wild-type mice subjected to IR, renal Sglt1 mRNA was likewise normal on day 23, whereas Sglt2 mRNA was reduced by 57%. In both genotypes, IR equally reduced urine osmolality and renal mRNA expression of the Na⁺-K⁺-2Cl^- cotransporter and renin on day 23, suggesting thick ascending limb dysfunction, and similarly increased renal mRNA expression of markers of injury, inflammation, oxidative stress, and fibrosis (kidney injury molecule-1, neutrophil gelatinase-associated lipocalin, monocyte chemoattractant protein-1, transforming growth factor-β1, NADPH oxidase-2, and collagen type 1). This was associated with equal increases in kidney histological damage scores and similar degree of capillary loss in both genotypes. The data indicate that genetic deletion of SGLT2 did not protect the kidneys in the initial injury phase or the subsequent recovery phase in a mouse model of IR-induced acute kidney injury.

NOX2 is involved in CB2-mediated protection against lung ischemia-reperfusion injury in mice

Lung ischemia-reperfusion injury (LIRI) can occur in many clinical scenarios. Activation of the cannabinoid 2 (CB2) receptor limits tissue injury in some ischemia-reperfusion (I/R) models. However, whether and how CB2 receptor activation alleviates lung injury induced by I/R remain unclear. In this study, we sought to determine whether JWH133, a selective CB2 receptor agonist, could alleviate lung injury induced by I/R and to examine the role of NOX2 in this process. Here, an I/R model was established using male C57BL/6 mice, by blocking the left pulmonary hilum for 1 h, followed by reperfusion for 2 h. Results showed that pretreatment with JWH133 significantly attenuated I/R-induced lung injury (decreased lung injury scores and wet-to-dry weight ratio and increased oxygenation index), alleviated oxidative stress (increased superoxide dismutase (SOD), and decreased Malondialdehyde (MDA) levels). It also significantly increased CB2 receptor mRNA expression and protein levels and significantly reduced NOX2 mRNA and protein expression. Further, the CB2 receptor antagonist AM630 eliminated these effects mediated by JWH133. Pretreatment with the NOX2 inhibitor, gp91 ds-tat, reduced NOX2 expression, but did not affect CB2 receptor expression and failed to alleviate lung injury and oxidative stress after additional JWH133 treatment. Our study suggests that CB2 receptor activation alleviates LIRI by inhibiting oxidative stress and that NOX2 is involved in CB2-mediated protection against LIRI in mice.

Microcystin exposure worsens nonalcoholic fatty liver disease associated ectopic glomerular toxicity via NOX-2-MIR21 axis

NAFLD often results in cardiovascular, intestinal and renal complications. Previous reports from our laboratory highlighted NAFLD induced ectopic inflammatory manifestations in the kidney that gave rise to glomerular inflammation. Extending our studies, we hypothesized that existing inflammatory conditions in NAFLD could make the kidneys more susceptible to environmental toxicity. Our results showed that exposure of Microcystin-LR (MC) in NAFLD mice caused a marked increase in cellular scarring with a concomitant increase in mesangial cell activation as observed by increased α-SMA in the extracellular matrix surrounding the glomeruli. Renal tissue surrounding the glomeruli also showed increased NOX2 activation as shown by greater co-localization of p47 Phox and its membrane component gp91Phox both in the mesangial cell and surrounding tissue. Mechanistically, mesangial cells incubated with apocynin, nitrone spin trap DMPO and miR21 inhibitor showed significantly decreased α-SMA, miR21 levels and proinflammatory cytokine release in the supernatant. In parallel, mice lacking miR21, known to be activated by NOX2, when exposed to MC in NAFLD showed decreased mesangial cell activation. Strikingly, phenyl boronic acid incubated cells that were exposed to MC showed significantly decreased mesangial cell activation showing that peroxynitrite might be the major reactive species involved in mediation of the activation process, release of proinflammatory micro RNAs and cytokines that are crucial for renal toxicity. Thus, in conclusion, MC exposure causes NOX2 activation that leads to mesangial cell activation and toxicity via release of peroxynitrite that also represses PTEN by the upregulation of miR21 thus amplifying the toxicity.

Aldosterone promotes renal interstitial fibrosis via the AIF‑1/AKT/mTOR signaling pathway

A number of studies have shown that aldosterone serves an important role in promoting renal interstitial fibrosis, although the specific mechanism remains to be elucidated. A previous study revealed that the fibrotic effect of aldosterone was associated with the expression of allograft inflammatory factor 1 (AIF‑1) in RAW264.7 macrophage cells, in a time‑ and concentration‑dependent manner. However, the exact mechanism through which aldosterone promotes renal interstitial fibrosis remains unknown. In the present study, the effects of aldosterone on renal inflammatory cell infiltration, collagen deposition and the expression levels of AIF‑1, phosphatidylinositol 3‑kinase (PI3K), AKT serine/threonine kinase (AKT), mammalian target of rapamycin (mTOR), the oxidative stress factor NADPH oxidase 2 (NOX2) and nuclear transcription factor erythroid‑related factor 2 (Nrf2) were assessed in normal rats, rats treated with aldosterone, rats treated with aldosterone and spironolactone and those treated with spironolactone only (used as the control). The effect of aldosterone on these factors was also investigated in the renal interstitium of unilateral ureteral obstruction (UUO) rats. Additionally, the AIF‑1 gene was overexpressed and knocked down in macrophage RAW264.7 cells, and the effects of aldosterone on PI3K, AKT, mTOR, NOX2 and Nrf2 were subsequently investigated. The results showed that aldosterone promoted inflammatory cell infiltration, collagen deposition and the expression of AIF‑1, PI3K, AKT, mTOR and NOX2, but inhibited the expression of Nrf2. In the UUO rats, aldosterone also promoted renal interstitial inflammatory cell infiltration, collagen deposition and the expression of AIF‑1, NOX2, PI3K, AKT and mTOR, whereas the expression of Nrf2 was downregulated by aldosterone compared with that in the UUO‑only group; the influence of aldosterone was counteracted by spironolactone in the normal and UUO rats. In vitro, aldosterone upregulated the expression levels of AKT, mTOR, NOX2 and Nrf2 in RAW264.7 cells compared with those in untreated cells. Suppressing the expression of AIF‑1 inhibited the effects of aldosterone, whereas the overexpression of AIF‑1 enhanced these effects in RAW264.7 cells. These findings indicated that aldosterone promoted renal interstitial fibrosis by upregulating the expression of AIF‑1 and that the specific mechanism may involve AKT/mTOR and oxidative stress signaling.

NADPH oxidase 4 mediates TGF-β1/Smad signaling pathway induced acute kidney injury in hypoxia

Hypoxia is an important cause of acute kidney injury (AKI) in various conditions because kidneys are one of the most susceptible organs to hypoxia. In this study, we investigated whether nicotinamide adenine dinucleotide 3-phosphate (NADPH) oxidase 4 (Nox4) plays a role in hypoxia induced AKI in a cellular and animal model. Expression of Nox4 in cultured human renal proximal tubular epithelial cells (HK-2) was significantly increased by hypoxic stimulation. TGF-β1 was endogenously secreted by hypoxic HK-2 cells. SB4315432 (a TGF-β1 receptor I inhibitor) significantly inhibited Nox4 expression in HK-2 cells through the Smad-dependent cell signaling pathway. Silencing of Nox4 using Nox4 siRNA and pharmacologic inhibition with GKT137831 (a specific Nox1/4 inhibitor) reduced the production of ROS and attenuated the apoptotic pathway. In addition, knockdown of Nox4 increased cell survival in hypoxic HK-2 cells and pretreatment with GKT137831 reproduce these results. This study demonstrates that hypoxia induces HK-2 cell apoptosis through a signaling pathway involving TGF-β1 via Smad pathway induction of Nox4-dependent ROS generation. In an ischemia/reperfusion rat model, pretreatment of GKT137831 attenuated ischemia/reperfusion induced acute kidney injury as indicated by preserved kidney function, attenuated renal structural damage and reduced apoptotic cells. Therapies targeting Nox4 may be effective against hypoxia-induced AKI.

Significant Reduction of Murine Renal Ischemia-Reperfusion Cell Death Using the Immediate-Acting PrC-210 Reactive Oxygen Species Scavenger

Background.

Ischemia-reperfusion (IR) injury remains a significant problem for all solid organ transplants; thus, an important unmet need in transplantation is the prevention of IR injury. PrC-210 has demonstrated superior prevention of reactive oxygen species damage in several preclinical studies as a free radical scavenger. Here, we describe its profound efficacy in suppressing IR injury in a murine model of kidney IR injury.

Methods.

C57/B6 mice underwent laparotomy with the left renal pedicle occluded for 30 minutes to induce IR injury. Right nephrectomy was performed at the time of surgery. Mice received a single systemic dose of the PrC-210, PrC-211, or PrC-252 aminothiols 20 minutes before IR injury. Twenty-four hours following IR injury, blood and kidney tissue were collected for analysis. Kidney caspase-3 level (a marker of cell death), direct histological analysis of kidneys, and serum blood urea nitrogen (BUN) were measured in animals to assess reactive oxygen species scavenger protective efficacies.

Results.

A single systemic PrC-210 dose 20 minutes before IR injury resulted in significant reductions in (1) IR-induced kidney caspase level (P < 0.0001); caspase was reduced to levels not significantly different than control caspase levels seen in unperturbed kidneys, (2) IR-induced renal tubular injury scores (P < 0.0001); brush border loss and tubular dilation were markedly reduced, and (3) serum BUN compared with control IR injury kidneys (P < 0.0001). The ranked protective efficacies of PrC-210 > PrC-211 >> PrC-252 paralleled previous radioprotection studies of the molecules.

Conclusions.

A single PrC-210 dose, minutes before the IR insult, profoundly reduced caspase, renal tubular injury, and serum BUN in mice exposed to standard kidney IR injury. These findings support further development of the PrC-210 molecule to suppress or prevent IR injury in organ transplant and other IR injury settings.

Is Aberrant Reno-Renal Reflex Control of Blood Pressure a Contributor to Chronic Intermittent Hypoxia-Induced Hypertension?

Renal sensory nerves are important in the regulation of body fluid and electrolyte homeostasis, and blood pressure. Activation of renal mechanoreceptor afferents triggers a negative feedback reno-renal reflex that leads to the inhibition of sympathetic nervous outflow. Conversely, activation of renal chemoreceptor afferents elicits reflex sympathoexcitation. Dysregulation of reno-renal reflexes by suppression of the inhibitory reflex and/or activation of the excitatory reflex impairs blood pressure control, predisposing to hypertension. Obstructive sleep apnoea syndrome (OSAS) is causally related to hypertension. Renal denervation in patients with OSAS or in experimental models of chronic intermittent hypoxia (CIH), a cardinal feature of OSAS due to recurrent apnoeas (pauses in breathing), results in a decrease in circulating norepinephrine levels and attenuation of hypertension. The mechanism of the beneficial effect of renal denervation on blood pressure control in models of CIH and OSAS is not fully understood, since renal denervation interrupts renal afferent signaling to the brain and sympathetic efferent signals to the kidneys. Herein, we consider the currently proposed mechanisms involved in the development of hypertension in CIH disease models with a focus on oxidative and inflammatory mediators in the kidneys and their potential influence on renal afferent control of blood pressure, with wider consideration of the evidence available from a variety of hypertension models. We draw focus to the potential contribution of aberrant renal afferent signaling in the development, maintenance and progression of high blood pressure, which may have relevance to CIH-induced hypertension.

Pretreatment with Cholecalciferol Alleviates Renal Cellular Stress Response during Ischemia/Reperfusion-Induced Acute Kidney Injury

Background

Cellular stress is involved in ischemia/reperfusion- (I/R-) induced acute kidney injury (AKI). This study is aimed at investigating the effects of pretreatment with cholecalciferol on renal oxidative stress and endoplasmic reticulum (ER) stress during I/R-induced AKI.

Methods

I/R-induced AKI was established by cross-clamping renal pedicles for 90 minutes and then reperfusion. In the Chol + I/R group, mice were orally administered with three doses of cholecalciferol (25 μg/kg) at 1, 24, and 48 h before ischemia. Renal cellular stress and kidney injury were measured at different time points after reperfusion.

Results

I/R-induced AKI was alleviated in mice pretreated with cholecalciferol. In addition, I/R-induced renal cell apoptosis, as determined by TUNEL, was suppressed by cholecalciferol. Additional experiment showed that I/R-induced upregulation of renal GRP78 and CHOP was inhibited by cholecalciferol. I/R-induced renal IRE1α and eIF2α phosphorylation was attenuated by cholecalciferol. Moreover, I/R-induced renal GSH depletion, lipid peroxidation, and protein nitration were blocked in mice pretreated with cholecalciferol. I/R-induced upregulation of renal NADPH oxidases, such as p47phox, gp91phox, and nox4, was inhibited by cholecalciferol. I/R-induced upregulation of heme oxygenase- (HO-) 1, gshpx and gshrd, was attenuated in mice pretreated with cholecalciferol.

Conclusions

Pretreatment with cholecalciferol protects against I/R-induced AKI partially through suppressing renal cellular stress response.

Reactive Oxygen Species Related Noncoding RNAs as Regulators of Cardiovascular Diseases

Reactive oxygen species (ROS) are a class of reactive molecules that have been implicated in a variety of cardiovascular diseases, accompanied by disorder of multiple signaling events. As cardiomyocytes maintain abundant of mitochondria, which supply the major source of endogenous ROS, oxidative damage to mitochondria often drives apoptotic cell death and initiates cardiac pathology. In recent years, non-coding RNAs (ncRNAs) have received much attention to uncover their roles in regulating gene expression during those pathological events in the heart, such as myocardial infarction, cardiac hypertrophy, and heart failure. Emerging evidences have highlighted that different ROS levels in response to diverse cardiac stresses result in differential expression of ncRNAs, subsequently altering the expression of pathogenetic genes. However, the knowledge about the ncRNA-linked ROS regulatory mechanisms in cardiac pathologies is still largely unexplored. In this review, we summarize the connections that exist among ROS, ncRNAs, and cardiac diseases to understand the interactions among the molecular entities underlying cardiac pathological events in the hopes of guiding novel therapies for heart diseases in the future.

PPAR gamma agonist, pioglitazone, rescues liver damage induced by renal ischemia/reperfusion injury

Remote organ damage is the major cause of death in patients with acute kidney injury (AKI) due to renal ischemia reperfusion (IR). Liver is one of the vital organs which are profoundly affected by AKI. The present study aims to investigate the role of peroxisome proliferator activator receptor gamma (PPARγ) in liver damage induced by IR injury in rats. Renal IR was induced by right nephrectomy, occlusion of left renal pedicle for 45 min to induce ischemia, and then reperfusion for 6 or 24 h. The PPARγ agonist, pioglitazone, was given orally for 7 days before renal IR procedure. Animals receiving pioglitazone showed improvement in renal and hepatic functions when compared to IR groups. Renal IR increased renal, hepatic and serum levels of tumor necrosis factor-α (TNF-α) and induced apoptotic cell death in liver. These effects were diminished with pioglitazone. In addition, pioglitazone reduced renal IR-induced oxidative stress in liver. Pioglitazone reduced malondialdehyde (MDA) content and NADPH oxidase mRNA expression and induced further increase in nuclear factor erythroid 2-related factor 2 (Nrf2) expression when compared to IR groups. Furthermore, pioglitazone increased the expression of PPARγ target genes such as renal and hepatic PPARγ1 (Pparg1), hepatic hemoxygenase-1 (Hmox1), and hepatic thioredoxin (TRx). Histological profiles for kidney and liver were also ameliorated with pioglitazone. Hence, PPARγ is a potential target to protect liver in patients with renal IR injury.

Oxidative Stress and Arterial Dysfunction in Peripheral Artery Disease

Peripheral artery disease (PAD) is an atherosclerotic disease characterized by a narrowing of the arteries in the lower extremities. Disease manifestations are the result of more than just reduced blood flow, and include endothelial dysfunction, arterial stiffness, and inflammation. Growing evidence suggests that these factors lead to functional impairment and decline in PAD patients. Oxidative stress also plays an important role in the disease, and a growing amount of data suggest a link between arterial dysfunction and oxidative stress. In this review, we present the current evidence for the involvement of endothelial dysfunction, arterial stiffness, and inflammation in the pathophysiology of PAD. We also discuss the links between these factors and oxidative stress, with a focus on nicotinamide adenine dinucleotide phosphate (NADPH) oxidase 2 (NOX2)-derived reactive oxygen species (ROS) and decreased nitric oxide (NO) bioavailability. Finally, the potential therapeutic role of NOX2 antioxidants for improving arterial function and functional status in PAD patients is explored.

Oxidant Signaling Mediated by Nox2 in Neutrophils Promotes Regenerative Myelopoiesis and Tissue Recovery following Ischemic Damage

Ischemic tissue damage activates hematopoietic stem and progenitor cells (HSPCs) in the bone marrow (BM)-generating myeloid cells, and persistent HSPC activity may drive chronic inflammation and impair tissue recovery. Although increased reactive oxygen species in the BM regulate HSPC functions, their roles in myelopoiesis of activated HSPCs and subsequent tissue recovery during ischemic damage are not well understood. In this paper, we report that deletion of Nox2 NADPH oxidase in mice results in persistent elevations in BM HSPC activity and levels of inflammatory monocytes/macrophages in BM and ischemic tissue in a model of hindlimb ischemia. Ischemic tissue damage induces oxidants in BM such as elevations of hydrogen peroxide and oxidized phospholipids, which activate redox-sensitive Lyn kinase in a Nox2-dependent manner. Moreover, during tissue recovery after ischemic injury, this Nox2-ROS-Lyn kinase axis is induced by Nox2 in neutrophils that home to the BM, which inhibits HSPC activity and inflammatory monocyte generation and promotes tissue regeneration after ischemic damage. Thus, oxidant signaling in the BM mediated by Nox2 in neutrophils regulates myelopoiesis of HSPCs to promote regeneration of damaged tissue.

Sirt6 deficiency results in progression of glomerular injury in the kidney

Aging is associated with an increased incidence and prevalence of renal glomerular diseases. Sirtuin (Sirt) 6, a nicotinamide adenine dinucleotide (NAD)-dependent histone deacetylase, has been shown to protect against multiple age-associated phenotypes; however it is unknown whether Sirt6 has a direct pathophysiologic role in the kidney. In the present study, we demonstrate that Sirt6 is expressed in the kidney and aging Sirt6-deficient mice exhibit renal hypertrophy with glomerular enlargement. Sirt6 deletion induces podocyte injury, including decreases in slit diaphragm proteins, foot process effacement, and cellular loss, resulting in proteinuria. Knockdown of Sirt6 in cultured primary murine podocytes induces shape changes with loss of process formation and cell apoptosis. Moreover, Sirt6 deficiency results in progressive renal inflammation and fibrosis. Collectively, these data provide compelling evidence that Sirt6 is important for podocyte homeostasis and maintenance of glomerular function, and warrant further investigation into the role of Sirt6 in age-associated kidney dysfunction.

A Comparative Study of the Predictive Values of Urinary Acute Kidney Injury Markers Angiogenin and Kidney Injury Molecule 1 for the Outcomes of Kidney Allografts

Supplemental digital content is available in the text.

Background

Whether injury-related molecules in urines of individuals with ischemia-reperfusion injury (IRI) are independent predictors of graft outcomes and provide additional information compared with usual risk factors remains to be established.

Methods

We explored a cohort of 244 kidney transplant recipients who systematically had a urine collection 10 days after transplantation. The injury-related markers kidney injury molecule-1 (KIM-1) and angiogenin (ANG) levels in urines were measured. We determined the prognostic values of these markers on graft outcomes.

Results

Urinary KIM-1 and ANG concentrations were strongly correlated to each other and were significantly and independently associated with cold ischemia time, delayed graft function, and plasma creatinine 10 days after transplantation, indicating that these markers reflect the severity of IRI. However, urinary ANG and KIM-1 were not predictive of histological changes on protocol biopsies performed 3 and 12 months after transplantation. Finally, urinary ANG and urinary KIM-1 were not associated with graft survival.

Conclusions

Together, our results indicate that, in a cohort of 244 kidney transplant recipients, urinary ANG and KIM-1 levels in a single measurement 10 days after transplantation reflect the severity of IRI after kidney transplantation, but are neither independent predictors of renal function, histological changes and graft survival.

Role of Intrinsic (Graft) Versus Extrinsic (Host) Factors in the Growth of Transplanted Organs Following Allogeneic and Xenogeneic Transplantation

In our studies of life-supporting α-1,3-galactocyltransferase knockout (GalT-KO) pig-to-baboon kidneys, we found that some recipients developed increased serum creatinine with growth of the grafts, without histological or immunological evidence of rejection. We hypothesized that the rapid growth of orthotopic pig grafts in smaller baboon recipients may have led to deterioration of organ function. To test this hypothesis for both kidneys and lungs, we assessed whether the growth of outbred (Yorkshire) organ transplants in miniature swine was regulated by intrinsic (graft) or extrinsic (host environment) factors. Yorkshire kidneys exhibited persistent growth in miniature swine, reaching 3.7 times their initial volume over 3 mo versus 1.2 times for miniature swine kidneys over the same time period. Similar rapid early growth of lung allografts was observed and, in this case, led to organ dysfunction. For xenograft kidneys, a review of our results suggests that there is a threshold for kidney graft volume of 25 cm³ /kg of recipient body weight at which cortical ischemia is induced in transplanted GalT-KO kidneys in baboons. These results suggest that intrinsic factors are responsible, at least in part, for growth of donor organs and that this property should be taken into consideration for growth-curve-mismatched transplants, especially for life-supporting organs transplanted into a limited recipient space.

Cytoprotective and Antioxidant Effects of Steen Solution on Human Lung Spheroids and Human Endothelial Cells

Respiratory diseases represent a major healthcare burden worldwide. Lung transplantation (LTx) is the "gold standard" for end-stage patients, strongly limited by shortage of available/suitable donor lungs. Normothermic ex vivo lung perfusion (EVLP) has significantly increased the number of lungs suitable for transplantation. Steen solution is used for EVLP, but the mechanisms involved in its beneficial properties remain to be clarified. We investigated the effects of Steen solution in an in vitro protocol of cold starvation and normothermic recovery on human lung spheroids, named pneumospheres (PSs), containing epithelial/basal cells, and on endothelial human umbilical vein endothelial cells (HUVEC). Steen solution significantly preserved the viability of PSs, reduced reactive oxygen species (ROS) release by PSs and HUVECs, decreased NADPH-oxidase (NOX) activity in PSs, and reduced inflammatory cytokines expression levels in HUVECs. Steen solution was able to specifically reduce NADPH oxidase 2 (NOX2) isoform activation, particularly in PSs, as detected by soluble-NOX2 peptide and p47-phosphorylation. Interestingly, a specific NOX2 inhibitor could partly mimic the pro-survival effect of Steen on PSs. We provide the first evidence that Steen solution can preserve lung epithelial/progenitor cells viability partially through NOX2 downregulation, and exert antioxidant effects on parenchymal cells, with consequent ROS reduction. These results suggest that NOX2 inhibition might be an additional strategy to reduce cellular damage during LTx procedures.

Nox2 and Cyclosporine-Induced Renal Hypoxia

BACKGROUND

We hypothesized that nicotinamide adenosine diphosphate oxidase 2 (Nox2) plays an important role in cyclosporine A (CsA)-induced chronic hypoxia.

METHODS

We tested this hypothesis in Fisher 344 rats, C57BL/6 J wild type and Nox2-/- mice, and in liver transplant recipients with chronic CsA nephrotoxicity. We used noninvasive molecular imaging (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging) and molecular diagnostic tools to assess intrarenal oxygenation and perfusion, and the molecular phenotype of CsA nephrotoxicity.

RESULTS

We observed that chemical and genetic inhibition of Nox2 in rats and mice resulted in the prevention of CsA-induced hypoxia independent of regional perfusion (blood oxygen level-dependent magnetic resonance imaging and dynamic contrast-enhanced magnetic resonance imaging, pimonidazole, HIF-1α). Nicotinamide adenosine diphosphate oxidase 2 knockout was also associated with decreased oxidative stress (Nox2, HIF-1α, hydrogen peroxide, hydroxynonenal), and fibrogenesis (α-smooth muscle actin, picrosirius red, trichrome, vimentin). The molecular signature of chronic CsA nephrotoxicity using transcriptomic analyses demonstrated significant changes in 40 genes involved in injury repair, metabolism, and oxidative stress in Nox2-/- mice. Immunohistochemical analyses of kidney biopsies from liver transplant recipients with chronic CsA nephrotoxicity showed significantly greater Nox2, α-smooth muscle actin and picrosirius levels compared with controls.

CONCLUSIONS

These studies suggest that Nox2 is a modulator of CsA-induced hypoxia upstream of HIF-1α and define the molecular characteristics that could be used for the diagnosis and monitoring of chronic calcineurin inhibitor nephrotoxicity.

Progression of Interstitial Fibrosis during the First Year after Deceased Donor Kidney Transplantation among Patients with and without Delayed Graft Function

BACKGROUND AND OBJECTIVES

Delayed graft function is a form of AKI resulting from ischemia-reperfusion injury. Our aim was to study the effect of delayed graft function on the progression of interstitial fibrosis after deceased donor kidney transplantation.

DESIGN, SETTING, PARTICIPANTS, & MEASUREMENTS

Our study is a retrospective study of all patients transplanted at our center between July of 2003 and September of 2014 using a kidney from a deceased donor. The primary outcome was the progression of interstitial fibrosis on serial protocol biopsies done during the first year post-transplant. We analyzed the distribution of the change in the Banff interstitial fibrosis (ci) score between the delayed graft function and nondelayed graft function groups for all of the paired biopsies done at time 0 and 12 months post-transplant (Δfibrosis). We also performed a linear mixed model analyzing the difference in the slopes for the progression of mean Banff ci score for all of the biopsies done at time 0 and 1, 4, and 12 months post-transplant.

RESULTS

There were 343 (36.7%) in the delayed graft function group and 591 in the control group. The biopsy rates for the delayed graft function and nondelayed graft function groups at time 0 were 65.3% (n=224) and 67.0% (n=396), respectively, and at 12 months, they were 64.4% (n=221) and 68.4% (n=404), respectively. Paired biopsies were available for 155 in the delayed graft function group and 283 in the control group. In a risk-adjusted model, Banff ci score >0 on the time 0 biopsy had a higher odds of delayed graft function (odds ratio, 1.70; 95% confidence interval, 1.03 to 2.82). The distribution of the Δfibrosis between 0 and 12 months was similar in delayed graft function and control groups (P=0.91). The slopes representing the progression of fibrosis were also similar between the groups (P=0.66).

CONCLUSIONS

Donor-derived fibrosis may increase the odds of delayed graft function; however, delayed graft function does not seem to increase the progression of fibrosis during the first year after transplantation.

Nitro-oleic acid ameliorates oxygen and glucose deprivation/re-oxygenation triggered oxidative stress in renal tubular cells via activation of Nrf2 and suppression of NADPH oxidase

Nitroalkene derivative of oleic acid (OA-NO₂), due to its ability to mediate revisable Michael addition, has been demonstrated to have various biological properties and become a therapeutic agent in various diseases. Though its antioxidant properties have been reported in different models of acute kidney injury (AKI), the mechanism by which OA-NO₂ attenuates intracellular oxidative stress is not well investigated. Here, we elucidated the anti-oxidative mechanism of OA-NO₂ in an in vitro model of renal ischemia/reperfusion (I/R) injury. Human tubular epithelial cells were subjected to oxygen and glucose deprivation/re-oxygenation (OGD/R) injury. Pretreatment with OA-NO₂ (1.25 μM, 45 min) attenuated OGD/R triggered reactive oxygen species (ROS) generation and subsequent mitochondrial membrane potential disruption. This action was mediated via up-regulating endogenous antioxidant defense components including superoxide dismutase (SOD1), heme oxygenase 1 (HO-1), and γ-glutamyl cysteine ligase modulatory subunits (GCLM). Moreover, subcellular fractionation analyses demonstrated that OA-NO₂ promoted nuclear translocation of nuclear factor-E2- related factor-2 (Nrf2) and Nrf2 siRNA partially abrogated these protective effects. In addition, OA-NO₂ inhibited NADPH oxidase activation and NADPH oxidase 4 (NOX4), NADPH oxidase 2 (NOX2) and p22^phox up-regulation after OGD/R injury, which was not relevant to Nrf2. These results contribute to clarify that the mechanism of OA-NO₂ reno-protection involves both inhibition of NADPH oxidase activity and induction of SOD1, Nrf2-dependent HO-1, and GCLM.