Small Interfering RNA Targeting RelB Protects Against Renal Ischemia-reperfusion Injury

Potential of oligonucleotide- and protein/peptide-based therapeutics in the management of toxicant/stressor-induced diseases

Exposure to toxicants/stressors has been linked to the development of many human diseases. They could affect various cellular components, such as DNA, proteins, lipids, and non-coding RNAs (ncRNA), thereby triggering various cellular pathways, particularly oxidative stress, inflammatory responses, and apoptosis, which can contribute to pathophysiological states. Accordingly, modulation of these pathways has been the focus of numerous investigations for managing related diseases. The involvement of various ncRNAs, such as small interfering RNA (siRNA), microRNAs (miRNA), and long non-coding RNAs (lncRNA), as well as various proteins and peptides in mediating these pathways, provides many target sites for pharmaceutical intervention. In this regard, various oligonucleotide- and protein/peptide-based therapies have been developed to treat toxicity-induced diseases, which have shown promising results in vitro and in vivo. This comprehensive review provides information about various aspects of toxicity-related diseases including their causing factors, main underlying mechanisms and intermediates, and their roles in pathophysiological states. Particularly, it highlights the principles and mechanisms of oligonucleotide- and protein/peptide-based therapies in the treatment of toxicity-related diseases. Furthermore, various issues of oligonucleotides and proteins/peptides for clinical usage and potential solutions are discussed.

Liraglutide abrogates nephrotoxic effects of chemotherapies

Acute kidney injury (AKI) is a common clinical complication. Cisplatin (Cis) is an effective chemotherapeutic drug; however, its acute nephrotoxicity often limits its application. The role of liraglutide (Lir), an agonist of the glucagon-like peptide-1 receptor (GLP-1R), has recently attracted increasing attention beyond glycemic regulation. This study showed that Lir significantly ameliorated Cis-induced kidney dysfunction and renal damage. However, this renoprotective effect was partially abolished in GLP-1R knockout (GLP-1R^-/-) mice. Furthermore, we synthesized Lir metabolites, GLP-1 (9-37) and GLP-1 (28-37), and found that they also exerted reno-protective effects that were not impaired in GLP-1R^-/- mice. We also demonstrated that Lir and its metabolites reduced cisplatin-induced apoptosis in human renal tubular epithelial cells (HK-2). After silencing GLP-1R expression in HK-2 cells with small interfering ribose nucleic acid (siRNA), the protective effect of Lir on HK-2 cells was inhibited, while the protective effects of GLP-1 (9-37) and GLP-1 (28-37) were not affected. Additionally, we demonstrated that Lir and its metabolites inhibited Cis-induced high-mobility group box 1 (HMGB1) nuclear-cytoplasmic translocation and release, and reduced inflammatory cytokines and HMGB1 receptor expression. The exogenous use of recombinant HMGB1 (rHMGB1) dramatically weakened the protective effects of Lir and its metabolites. In conclusion, our study shows that Lir significantly attenuated Cis-induced AKI through GLP-1R dependent and independent pathways, mediated by inhibiting nuclear-cytoplasmic translocation and release of HMGB1. Lir and its metabolites may be effective drugs for treating cisplatin-induced nephrotoxicity.

Kidney Allograft Fibrosis: Diagnostic and Therapeutic Strategies

Interstitial fibrosis with tubule atrophy (IF/TA) is the response to virtually any sustained kidney injury and correlates inversely with kidney function and allograft survival. IF/TA is driven by various pathways that include hypoxia, renin-angiotensin-aldosterone system, transforming growth factor (TGF)-β signaling, cellular rejection, inflammation and others. In this review we will focus on key pathways in the progress of renal fibrosis, diagnosis and therapy of allograft fibrosis. This review discusses the role and origin of myofibroblasts as matrix producing cells and therapeutic targets in renal fibrosis with a particular focus on renal allografts. We summarize current trends to use multi-omic approaches to identify new biomarkers for IF/TA detection and to predict allograft survival. Furthermore, we review current imaging strategies that might help to identify and follow-up IF/TA complementary or as alternative to invasive biopsies. We further discuss current clinical trials and therapeutic strategies to treat kidney fibrosis.Supplemental Visual Abstract; http://links.lww.com/TP/C141.

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.

TRAF3 Modulation: Novel Mechanism for the Anti-inflammatory Effects of the Vitamin D Receptor Agonist Paricalcitol in Renal Disease

BACKGROUND

CKD leads to vitamin D deficiency. Treatment with vitamin D receptor agonists (VDRAs) may have nephroprotective and anti-inflammatory actions, but their mechanisms of action are poorly understood.

METHODS

Modulation of the noncanonical NF-κB2 pathway and its component TNF receptor-associated factor 3 (TRAF3) by the VDRA paricalcitol was studied in PBMCs from patients with ESKD, cytokine-stimulated cells, and preclinical kidney injury models.

RESULTS

In PBMCs isolated from patients with ESKD, TRAF3 protein levels were lower than in healthy controls. This finding was associated with evidence of noncanonical NF-κB2 activation and a proinflammatory state. However, PBMCs from patients with ESKD treated with paricalcitol did not exhibit these features. Experiments in cultured cells confirmed the link between TRAF3 and NF-κB2/inflammation. Decreased TRAF3 ubiquitination in K48-linked chains and cIAP1-TRAF3 interaction mediated the mechanisms of paricalcitol action.TRAF3 overexpression by CRISPR/Cas9 technology mimicked VDRA's effects. In a preclinical model of kidney injury, paricalcitol inhibited renal NF-κB2 activation and decreased renal inflammation. In VDR knockout mice with renal injury, paricalcitol prevented TRAF3 downregulation and NF-κB2-dependent gene upregulation, suggesting a VDR-independent anti-inflammatory effect of paricalcitol.

CONCLUSIONS

These data suggest the anti-inflammatory actions of paricalcitol depend on TRAF3 modulation and subsequent inhibition of the noncanonical NF-κB2 pathway, identifying a novel mechanism for VDRA's effects. Circulating TRAF3 levels could be a biomarker of renal damage associated with the inflammatory state.

RNA interference therapeutics in organ transplantation: The dawn of a new era

RNA interference (RNAi) is a natural process through which double-stranded RNA molecules can silence the gene carrying the same code as the particular RNA of interest. In 2006, the discovery of RNAi was awarded the Nobel Prize in Medicine and its success has accumulated since. Gene silencing through RNAi has been used successfully in a broad range of diseases, and, more recently, this technique has gained interest in the field of organ transplantation. Here, genes related to ischemia-reperfusion injury (IRI) or graft rejection may be silenced to improve organ quality after transplantation. Several strategies have been used to deliver siRNA, and pretransplant machine perfusion presents a unique opportunity to deliver siRNA to the target organ during ex situ preservation. In this review, the potential of RNAi in the field of organ transplantation will be discussed. A brief overview on the discovery of RNAi, its mechanism, and limitations are included. In addition, studies using RNAi to target genes related to IRI in liver, kidney, lung, and heart transplantation are discussed.

Genetic Engineering of the Kidney to Permanently Silence MHC Transcripts During ex vivo Organ Perfusion

Organ gene therapy represents a promising tool to correct diseases or improve graft survival after transplantation. Polymorphic variation of the major histocompatibility complex (MHC) antigens remains a major obstacle to long-term graft survival after transplantation. Previously, we demonstrated that MHC-silenced cells are protected against allogeneic immune responses. We also showed the feasibility to silence MHC in the lung. Here, we aimed at the genetic engineering of the kidney toward permanent silencing of MHC antigens in a rat model. We constructed a sub-normothermic ex vivo perfusion system to deliver lentiviral vectors encoding shRNAs targeting β2-microglobulin and the class II transactivator to the kidney. In addition, the vector contained the sequence for a secreted nanoluciferase. After kidney transplantation (ktx), we detected bioluminescence in the plasma and urine of recipients of an engineered kidney during the 6 weeks of post-transplant monitoring, indicating a stable transgene expression. Remarkably, transcript levels of β2-microglobulin and the class II transactivator were decreased by 70% in kidneys expressing specific shRNAs. Kidney genetic modification did not cause additional cell death compared to control kidneys after machine perfusion. Nevertheless, cytokine secretion signatures were altered during perfusion with lentiviral vectors as revealed by an increase in the secretion of IL-10, MIP-1α, MIP-2, IP-10, and EGF and a decrease in the levels of IL-12, IL-17, MCP-1, and IFN-γ. Biodistribution assays indicate that the localization of the vector was restricted to the graft. This study shows the potential to generate immunologically invisible kidneys showing great promise to support graft survival after transplantation and may contribute to reduce the burden of immunosuppression.

MAP3K kinases and kidney injury

Mitogen-activated protein kinases (MAP kinases) are functionally connected kinases that regulate key cellular process involved in kidney disease such as all survival, death, differentiation and proliferation. The typical MAP kinase module is composed by a cascade of three kinases: a MAP kinase kinase kinase (MAP3K) that phosphorylates and activates a MAP kinase kinase (MAP2K) which phosphorylates a MAP kinase (MAPK). While the role of MAPKs such as ERK, p38 and JNK has been well characterized in experimental kidney injury, much less is known about the apical kinases in the cascade, the MAP3Ks. There are 24 characterized MAP3K (MAP3K1 to MAP3K21 plus RAF1, BRAF and ARAF). We now review current knowledge on the involvement of MAP3K in non-malignant kidney disease and the therapeutic tools available. There is in vivo interventional evidence clearly supporting a role for MAP3K5 (ASK1) and MAP3K14 (NIK) in the pathogenesis of experimental kidney disease. Indeed, the ASK1 inhibitor Selonsertib has undergone clinical trials for diabetic kidney disease. Additionally, although MAP3K7 (MEKK7, TAK1) is required for kidney development, acutely targeting MAP3K7 protected from acute and chronic kidney injury; and targeting MAP3K8 (TPL2/Cot) protected from acute kidney injury. By contrast MAP3K15 (ASK3) may protect from hypertension and BRAF inhibitors in clinical use may induced acute kidney injury and nephrotic syndrome. Given their role as upstream regulators of intracellular signaling, MAP3K are potential therapeutic targets in kidney injury, as demonstrated for some of them. However, the role of most MAP3K in kidney disease remains unexplored.

Gene Silencing With siRNA (RNA Interference): A New Therapeutic Option During Ex Vivo Machine Liver Perfusion Preservation

RNA interference (RNAi) is a natural process of posttranscriptional gene regulation that has raised a lot of attention culminating with the Nobel Prize in Medicine in 2006. RNAi-based therapeutics have been tested in experimental transplantation to reduce ischemia/reperfusion injury (IRI) with success. Modulation of genes of the innate immune system, as well as apoptotic genes, and those involved in the nuclear factor kappa B pathways can reduce liver injury in rodent liver pedicle clamping and transplantation models of IRI. However, in vivo use of RNAi faces limitations regarding the method of administration, uptake, selectivity, and stability. Machine perfusion preservation, a more recent alternative approach for liver preservation showing superior results to static cold preservation, could be used as a platform for gene interference therapeutics. Our group was the first to demonstrate uptake of small interfering RNA (siRNA) during liver machine preservation under both normothermic and hypothermic perfusion. Administering siRNA in the perfusion solution during ex vivo machine preservation has several advantages, including more efficient delivery, lower doses and cost-saving, and none/fewer side effects to other organs. Recently, the first RNAi drug was approved by the US Food and Drug Administration for clinical use, opening a new avenue for new drugs with different clinical applications. RNAi has the potential to have transformational therapeutic applications in several areas of medicine including transplantation. We believe that machine preservation offers great potential to be the ideal delivery method of siRNA to the liver graft, and future studies should be initiated to improve the clinical applicability of RNAi in solid organ transplantation.

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.

Down-regulation of nuclear HMGB1 reduces ischemia-induced HMGB1 translocation and release and protects against liver ischemia-reperfusion injury

Hepatocyte-specific HMGB1 deletion has been found to worsen the injury and inflammation in liver ischemia-reperfusion injury (IRI), highlighting a role for intracellular HMGB1 in cellular protection. Down-regulation of nuclear HMGB1 by small interfering RNA (siRNA) might not only decrease its injurious extracellular role by reducing its release but also serve to maintain its beneficial intracellular role, thus protecting against IRI. We established a non-lethal liver IRI model in mice via segmental hepatic warm ischemia for 1 h and reperfusion for 6 h. HMGB1-siRNA achieved a reduction of ~60–70% in the nuclear HMGB1 expression in the liver at 48 h post-treatment. Knockdown of nuclear HMGB1 expression dramatically reduced both the degree of nuclear-cytoplasmic translocation of HMGB1 during hepatic ischemia and of HMGB1 release after hepatic reperfusion, resulting in significant preservation of liver function and a marked reduction in pathological damage. Also, HMGB1-siRNA pretreatment markedly inhibited the increases in hepatic expression of TLR4, TLR2, RAGE, TNF-α, IL-1β, IL-6, MCP-1, iNOS, and COX-2 seen in control mice after hepatic reperfusion. We demonstrated for the first time that down-regulation of nuclear HMGB1 reduces ischemia-induced HMGB1 release and protects against liver IRI, which is helpful for better understanding the role of HMGB1 in organ IRI.

Mitogen-Activated Protein Kinase 14 Promotes AKI

An improved understanding of pathogenic pathways in AKI may identify novel therapeutic approaches. Previously, we conducted unbiased liquid chromatography-tandem mass spectrometry-based protein expression profiling of the renal proteome in mice with acute folate nephropathy. Here, analysis of the dataset identified enrichment of pathways involving NFκB in the kidney cortex, and a targeted data mining approach identified components of the noncanonical NFκB pathway, including the upstream kinase mitogen-activated protein kinase kinase kinase 14 (MAP3K14), the NFκB DNA binding heterodimer RelB/NFκB2, and proteins involved in NFκB2 p100 ubiquitination and proteasomal processing to p52, as upregulated. Immunohistochemistry localized MAP3K14 expression to tubular cells in acute folate nephropathy and human AKI. In vivo, kidney expression levels of NFκB2 p100 and p52 increased rapidly after folic acid injection, as did DNA binding of RelB and NFκB2, detected in nuclei isolated from the kidneys. Compared with wild-type mice, MAP3K14 activity-deficient aly/aly (MAP3K14^aly/aly) mice had less kidney dysfunction, inflammation, and apoptosis in acute folate nephropathy and less kidney dysfunction and a lower mortality rate in cisplatin-induced AKI. The exchange of bone marrow between wild-type and MAP3K14^aly/aly mice did not affect the survival rate of either group after folic acid injection. In cultured tubular cells, MAP3K14 small interfering RNA targeting decreased inflammation and cell death. Additionally, cell culture and in vivo studies identified the chemokines MCP-1, RANTES, and CXCL10 as MAP3K14 targets in tubular cells. In conclusion, MAP3K14 promotes kidney injury through promotion of inflammation and cell death and is a promising novel therapeutic target.

Tubular Epithelial NF-κB Activity Regulates Ischemic AKI

NF-κB is a key regulator of innate and adaptive immunity and is implicated in the pathogenesis of AKI. The cell type-specific functions of NF-κB in the kidney are unknown; however, the pathway serves distinct functions in immune and tissue parenchymal cells. We analyzed tubular epithelial-specific NF-κB signaling in a mouse model of ischemia-reperfusion injury (IRI)-induced AKI. NF-κB reporter activity and nuclear localization of phosphorylated NF-κB subunit p65 analyses in mice revealed that IRI induced widespread NF-κB activation in renal tubular epithelia and in interstitial cells that peaked 2-3 days after injury. To genetically antagonize tubular epithelial NF-κB activity, we generated mice expressing the human NF-κB super-repressor IκBαΔN in renal proximal, distal, and collecting duct epithelial cells. Compared with control mice, these mice exhibited improved renal function, reduced tubular apoptosis, and attenuated neutrophil and macrophage infiltration after IRI-induced AKI. Furthermore, tubular NF-κB-dependent gene expression profiles revealed temporally distinct functional gene clusters for apoptosis, chemotaxis, and morphogenesis. Primary proximal tubular cells isolated from IκBαΔN-expressing mice and exposed to hypoxia-mimetic agent cobalt chloride exhibited less apoptosis and expressed lower levels of chemokines than cells from control mice did. Our results indicate that postischemic NF-κB activation in renal tubular epithelia aggravates tubular injury and exacerbates a maladaptive inflammatory response.

Heat shock protein 90 inhibition abrogates TLR4-mediated NF-κB activity and reduces renal ischemia-reperfusion injury

Renal ischemia-reperfusion injury (IRI) is a common cause of acute kidney injury. Toll-like receptor 4 (TLR4) mediates sterile inflammation following renal IRI. Heat shock protein 90 (Hsp90) inhibition is a potential strategy to reduce IRI, and AT13387 is a novel Hsp90 inhibitor with low toxicity. This study assessed if pre-treatment with AT13387 could reduce renal IRI and established if the mechanism of protection involved a reduction in inflammatory signalling. Mice were pre-treated with AT13387 prior to renal IRI. 24 h later, renal function was determined by serum creatinine, kidney damage by tubular necrosis score, renal TLR4 expression by PCR and inflammation by cytokine array. In vitro, human embryonic kidney cells were co-transfected to express TLR4 and a secreted alkaline phosphatase NF-κB reporter. Cells were pre-treated with AT13387 and exposed to endotoxin-free hyaluronan to stimulate sterile TLR4-specific NF-κB inflammatory activation. Following renal IRI, AT13387 significantly reduced serum creatinine, tubular necrosis, TLR4 expression and NF-κB-dependent chemokines. In vitro, AT13387-treatment resulted in breakdown of IκB kinase, which abolished TLR4-mediated NF-κB activation by hyaluronan. AT13387 is a new agent with translational potential that reduces renal IRI. The mechanism of protection may involve breakdown of IκB kinase and repression of TLR4-mediated NF-κB inflammatory activity.

siRNA technology in kidney transplantation: current status and future potential

Kidney transplantation is one of the most common transplantation operations in the world, accounting for up to 50 % of all transplantation surgeries. To curtail the damage to transplanted organs that is caused by ischemia-reperfusion injury and the recipient's immune system, small interfering RNA (siRNA) technology is being explored. Importantly, the kidney as a whole is a preferential site for non-specific systemic delivery of siRNA. To date, most attempts at siRNA-based therapy for transplantation-related conditions have remained at the in vitro stage, with only a few of them being advanced into animal models. Hydrodynamic intravenous injection of naked or carrier-bound siRNAs is currently the most common route for delivery of therapeutic constructs. To our knowledge, no systematic screens for siRNA targets most relevant for kidney transplantation have been attempted so far. A majority of researchers have arrived at one or another target of interest by analyzing current literature that dissects pathological processes taking place in transplanted organs. A majority of the genes that make up the list of 53 siRNA targets that have been tested in transplantation-related models so far belong to either apoptosis- or immune rejection-centered networks. There is an opportunity for therapeutic siRNA combinations that may be delivered within the same delivery vector or injected at the same time and, by targeting more than one pathway, or by hitting the same pathways within two different key points, will augment the effects of each other.

Carbon monoxide potently prevents ischemia-induced high-mobility group box 1 translocation and release and protects against lethal renal ischemia-reperfusion injury

High-mobility group box 1 (HMGB1) is a chromatin-binding nuclear molecule that has potent proinflammatory effects once released by damaged cells. In some disease models, carbon monoxide (CO) exhibits anti-inflammatory and protective properties. Here, we investigated whether the protective effect of CO on renal ischemia-reperfusion injury is associated with the inhibition of HMGB1 translocation and release. A renal ischemia-reperfusion injury model was established with a 100% mortality rate in untreated mice. Pretreatment with the CO-releasing molecule-2 (CORM-2) resulted in 100% survival, maximal preservation of renal function, a marked reduction in pathological damage, and blunted upregulation of TLR4, RAGE, TNF-α, IL-1β, IL-6, and MCP1 mRNA. Interestingly, CORM-2 pretreatment almost completely inhibited ischemia-induced HMGB1 nucleocytoplasmic shuttling and release. This inhibition was associated with a decrease in nuclear histone acetyltransferase activity. Indeed, CORM-2 pretreatment inhibited the acetylation and release of HMGB1 during hypoxic culture of primary mouse renal tubular epithelia cells in vitro. Using the same renal ischemia-reperfusion injury model, neutralization of HMGB1 was protective, and administration of exogenous HMGB1 largely reversed the protective effect of CORM-2 on kidney ischemia-reperfusion injury. Thus, CORM-2-delivered CO protects against lethal renal ischemia-reperfusion injury. This protection is correlated with the prevention of HMGB1 nuclear-cytoplasmic translocation and release.

Powerful protection against renal ischemia reperfusion injury by T cell-specific NF-κB inhibition

BACKGROUND

NF-κB plays a key role in ischemia reperfusion injury (IRI). Systemic inhibition of NF-κB by various methods has been proven to ameliorate IRI. However, NF-κB is also responsible for tissue protection against IRI. Systemic NF-κB inhibition may not be the optimal way for preventing IRI because of its complex roles. T cells are essential in mediating IRI. NF-κB is an important molecule during T cell activation. It is not clear the effect of T cell-specific NF-κB inhibition on IRI. We aimed to study the effect of T cell-specific NF-κB inhibition on renal IRI in IκBαΔN-Tg mice. We also compared the different effects between T cell-specific and systemic NF-κB inhibition on IRI.

METHODS

Renal IRI was induced by left renal pedicle clamping for 60 or 80 min in wild-type, ursolic acid-treated or IκBαΔN-Tg mice. Renal function, histologic examination and overall survival after lethal IRI was evaluated in each group.

RESULTS

Serum creatinine, BUN, and pathologic damage were all reduced in IκBαDN-Tg mice and ursolic acid-treated mice than those in the control group. All the above indexes were improved better in IκBαDN-Tg mice than those in ursolic acid-treated mice. The survival rate of IκBαDN-Tg mice was higher than that of ursolic acid-treated mice after lethal kidney ischemia reperfusion injury. Immunohistochemistry showed a significant reduced CD4+ T cells and neutrophil infiltration in IκBαDN-Tg mice.

CONCLUSION

T cell-specific NF-κB inhibition provides powerful protective effect against renal IRI.

The effect of mTOR-inhibition on NF-κB activity in kidney ischemia-reperfusion injury in mice

Kidney ischemia-reperfusion injury (IRI) is associated with a robust inflammatory response, which is regulated by nuclear factor-kappaB (NF-κB), mainly its heterodimeric form p65/p50. Considering immunomodulatory properties of mammalian target of rapamycin (mTOR) inhibitors, the effect of everolimus on NF-κB activation in kidney IRI was determined in this study. IRI was induced in C57/BL6 mice by clamping both renal pedicles for 45 minutes. Application of everolimus (0.25 mg/kg bw subcutaneously daily) was started one day before IRI induction. Both everolimus-treated and nontreated mice were sacrificed at several times starting at 30 minutes and finishing on day 7 after IRI induction. The NF-κB activity, proinflammatory cytokines IL-1β, TNF-α, and anti-inflammatory cytokine IL-10 production were determined in kidneys. Compared with nontreated animals, everolimus-treated animals showed significantly increased TNF-α (2741.6 ± 201.72 pg/mg; 1925 ± 185.81 pg/mg, P < .05) and IL-1β (11.47 ± 1.2 pg/mg; 4.3 ± 0.13 pg/mg, P < .01) production on day 2 after IRI induction accompanied by significantly greater NF-κB/DNA binding activity and p65 nuclear expression (P < .01). Two hours after IRI induction, everolimus-treated animals showed significantly increased IL-1β mRNA expression (P < .05) followed by increased IL-1β protein concentrations when compared with nontreated animals measured 6 hours after IRI induction (11.71 ± 1.5 pg/mg; 7.5 ± 1.11 pg/mg, P < .01). Both experimental groups showed increased NF-κB/DNA binding activity at 7 days after IRI induction. Significantly increased nuclear p65 expression was measured in nontreated animals (P < .01), whereas everolimus-treated hosts showed significantly increased nuclear RelB expression (P < .01). These data suggested that everolimus potentiated innate immunity in the early phase of IRI, stimulating the production of NF-κB-driven proinflammatory cytokines such as TNF-α and IL-1β. The NF-κB activity was potentiated under m-TOR inhibition during kidney IRI, implicating a possible beneficial role of alternative NF-κB activation during the repair phase.

TWEAK/Fn14 and Non-Canonical NF-kappaB Signaling in Kidney Disease

The incidence of acute kidney injury (AKI) and chronic kidney disease (CKD) is increasing. However, there is no effective therapy for AKI and current approaches only slow down, but do not prevent progression of CKD. TWEAK is a TNF superfamily cytokine. A solid base of preclinical data suggests a role of therapies targeting the TWEAK or its receptor Fn14 in AKI and CKD. In particular TWEAK/Fn14 targeting may preserve renal function and decrease cell death, inflammation, proteinuria, and fibrosis in mouse animal models. Furthermore there is clinical evidence for a role of TWEAK in human kidney injury including increased tissue and/or urinary levels of TWEAK and parenchymal renal cell expression of the receptor Fn14. In this regard, clinical trials of TWEAK targeting are ongoing in lupus nephritis. Nuclear factor-kappa B (NF-κB) activation plays a key role in TWEAK-elicited inflammatory responses. Activation of the non-canonical NF-κB pathway is a critical difference between TWEAK and TNF. TWEAK activation of the non-canonical NF-κB pathways promotes inflammatory responses in tubular cells. However, there is an incomplete understanding of the role of non-canonical NF-κB activation in kidney disease and on its contribution to TWEAK actions in vivo.

Novel signalling mechanisms and targets in renal ischaemia and reperfusion injury

Acute kidney injury (AKI) induced by ischaemia and reperfusion (I/R) injury is a common and severe clinical problem. Vascular dysfunction, immune system activation and tubular epithelial cell injury contribute to functional and structural deterioration. The search for novel therapeutic interventions for I/R-induced AKI is a dynamic area of experimental research. Pharmacological targeting of injury mediators and corresponding intracellular signalling in endothelial cells, inflammatory cells and the injured tubular epithelium could provide new opportunities yet may also pose great translational challenge. Here, we focus on signalling mediators, their receptors and intracellular signalling pathways which bear potential to abrogate cellular processes involved in the pathogenesis of I/R-induced AKI. Sphingosine 1 phosphate (S1P) and its respective receptors, cytochrome P450 (CYP450)-dependent vasoactive eicosanoids, NF-κB- and protein kinase-C (PKC)-related pathways are representatives of such 'druggable' pleiotropic targets. For example, pharmacological agents targeting S1P and PKC isoforms are already in clinical use for treatment for autoimmune diseases and were previously subject of clinical trials in kidney transplantation where I/R-induced AKI occurs as a common complication. We summarize recent in vitro and in vivo experimental studies using pharmacological and genomic targeting and highlight some of the challenges to clinical application of these advances.

Prevention of renal ischemia-reperfusion injury by short hairpin RNA of endothelin A receptor in a rat model

Endothelin A receptor (ETaR) is a key molecule involved in a variety of biological events such as vessel contraction and inflammatory response in ischemia-reperfusion (I/R) injury. RNA interference using short hairpin RNA (shRNA) is a powerful tool to silence gene expression. Here, the effect of ETaR shRNA on I/R injury in rats was studied. A more effective shRNA sequence out of two constructed into plasmid vectors was selected using the A-10 cell line, and was then applied to a rat model. Twenty-eight male Sprague-Dawley rats were randomized into four groups: Sham, shRNA, vector and phosphate-buffered saline (PBS). Renal I/R injury was induced by clamping the left renal pedicle for one hour followed by reperfusion for 24 h. ETaR shRNA (100 μg) plasmid was administered by renal vein injection 48 h before clamping. The expression of both ETaR mRNA and protein was lowered by ETaR shRNA treatment compared with that in the vector and PBS groups; serum creatinine and blood urea nitrogen were significantly decreased; the semi-quantitative score of renal structural damage was improved; the mRNA level of endothelin 1 (ET-1), tumor necrosis factor-α (TNF-α), interleukin 6 (IL-6), macrophage inflammatory protein 2 (MIP-2) and monocyte chemoattractant protein 1 (MCP-1) was reduced, but nitric oxide (NO) production in kidney tissues was increased (P < 0.05). In conclusion, ETaR shRNA partially silenced ETaR expression in I/R injury kidneys, reduced the mRNA level of ET-1, inflammatory mediators including TNF-α, IL-6, MIP-2 and MCP-1, increased NO production, and ultimately improved renal function and structure.

Nuclear protein 1 promotes pancreatic cancer development and protects cells from stress by inhibiting apoptosis

Pancreatic ductal adenocarcinoma (PDAC) has the lowest survival rate of all cancers and shows remarkable resistance to cell stress. Nuclear protein 1 (Nupr1), which mediates stress response in the pancreas, is frequently upregulated in pancreatic cancer. Here, we report that Nupr1 plays an essential role in pancreatic tumorigenesis. In a mouse model of pancreatic cancer with constitutively expressed oncogenic Kras(G12D), we found that loss of Nupr1 protected from the development of pancreatic intraepithelial neoplasias (PanINs). Further, in cultured pancreatic cells, nutrient deprivation activated Nupr1 expression, which we found to be required for cell survival. We found that Nupr1 protected cells from stress-induced death by inhibiting apoptosis through a pathway dependent on transcription factor RelB and immediate early response 3 (IER3). NUPR1, RELB, and IER3 proteins were coexpressed in mouse PanINs from Kras(G12D)-expressing pancreas. Moreover, pancreas-specific deletion of Relb in a Kras(G12D) background resulted in delayed in PanIN development associated with a lack of IER3 expression. Thus, efficient PanIN formation was dependent on the expression of Nupr1 and Relb, with likely involvement of IER3. Finally, in patients with PDAC, expression of NUPR1, RELB, and IER3 was significantly correlated with a poor prognosis. Cumulatively, these results reveal a NUPR1/RELB/IER3 stress-related pathway that is required for oncogenic Kras(G12D)-dependent transformation of the pancreas.

Hepatocyte growth factor preferentially activates the anti-inflammatory arm of NF-κB signaling to induce A20 and protect renal proximal tubular epithelial cells from inflammation

Inflammation induces the NF-κB dependent protein A20 in human renal proximal tubular epithelial cells (RPTEC), which secondarily contains inflammation by shutting down NF-κB activation. We surmised that inducing A20 without engaging the pro-inflammatory arm of NF-κB could improve outcomes in kidney disease. We showed that hepatocyte growth factor (HGF) increases A20 mRNA and protein levels in RPTEC without causing inflammation. Upregulation of A20 by HGF was NF-κB/RelA dependent as it was abolished by overexpressing IκBα or silencing p65/RelA. Unlike TNFα, HGF caused minimal IκBα and p65/RelA phosphorylation, with moderate IκBα degradation. Upstream, HGF led to robust and sustained AKT activation, which was required for p65 phosphorylation and A20 upregulation. While HGF treatment of RPTEC significantly increased A20 mRNA, it failed to induce NF-κB dependent, pro-inflammatory MCP-1, VCAM-1, and ICAM-1 mRNA. This indicates that HGF preferentially upregulates protective (A20) over pro-inflammatory NF-κB dependent genes. Upregulation of A20 supported the anti-inflammatory effects of HGF in RPTEC. HGF pretreatment significantly attenuated TNFα-mediated increase of ICAM-1, a finding partially reversed by silencing A20. In conclusion, this is the first demonstration that HGF activates an AKT-p65/RelA pathway to preferentially induce A20 but not inflammatory molecules. This could be highly desirable in acute and chronic renal injury where A20-based anti-inflammatory therapies are beneficial.

Targeted gene silencing of TLR4 using liposomal nanoparticles for preventing liver ischemia reperfusion injury

RNAi-based therapy is a promising strategy for the prevention of ischemia-reperfusion injury (IRI). However, systemic administration of small interfering RNA (siRNA) may cause globally nonspecific targeting of all tissues, which impedes clinical use. Here we report a hepatocyte-specific delivery system for the treatment of liver IRI, using galactose-conjugated liposome nanoparticles (Gal-LipoNP). Heptocyte-specific targeting was validated by selective in vivo delivery as observed by increased Gal-LipoNP accumulation and gene silencing in the liver. Gal-LipoNP TLR4 siRNA treatment resulted in a significant decrease of serum alanine transferase (ALT) and aspartate transaminase (AST) in a hepatic IRI model. Histopathology displayed an overall reduction of the injury area in the Gal-LipoNP TLR4 siRNA treated mice. Additionally, neutrophil accumulation and lipid peroxidase-mediated tissue injury, detected by MPO, MDA and ROS respectively, were attenuated after Gal-LipoNP TLR4 siRNA treatment. Moreover, therapeutic effects of Gal-LipoNP TLR4 siRNA were associated with suppression of the inflammatory cytokines IL-1 and TNF-α. Taken together, this study is the first demonstration of liver IRI treatment using liver-specific siRNA delivery.

Small interfering RNA targeting IKKβ prevents renal ischemia-reperfusion injury in rats

The transcription factor NF-κB has been found critical to the pathogenesis of renal ischemia-reperfusion injury, which is a major cause of acute kidney injury (AKI). Activation of NF-κB is dependent upon the activation of the specific inhibitory κB kinase (IKK) subunit IKKβ. Here, we investigate whether small interfering RNA (siRNA) targeting IKKβ protects rats from renal ischemia- reperfusion injury in vivo. Renal ischemia-reperfusion injury was induced by clamping the renal artery for 45 min. Rats were treated before ischemia with IKKβ siRNA or scrambled siRNA, administered by renal artery injection. Treated animals were evaluated for renal IKKβ protein and mRNA expression, blood biochemistry, tissue histopathology, NF-κB/DNA binding activity, and expression of two downstream inflammatory cytokines, neutrophil gelatinase-associated lipocalin (NGAL) and IL-18. A local injection of IKKβ siRNA resulted in inhibition of renal IKKβ gene expression, NF-κB/DNA binding activity, and expression of NGAL and IL-18. Rats pretreated with IKKβ siRNA had significantly less blood urea nitrogen and serum creatinine levels and less renal tubular damage scores. Consequently, our data confirm that targeted silencing of IKKβ using siRNA substantially diminishes kidney injury and inflammation following ischemia-reperfusion.

RNA interference for improving the outcome of islet transplantation

Islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still not common because a large number of transplanted islets get damaged by multiple challenges including instant blood mediated inflammatory reaction, hypoxia/reperfusion injury, inflammatory cytokines, and immune rejection. RNA interference (RNAi) is a novel strategy to selectively degrade target mRNA. The use of RNAi technologies to downregulate the expression of harmful genes has the potential to improve the outcome of islet transplantation. The aim of this review is to gain a thorough understanding of biological obstacles to islet transplantation and discuss how to overcome these barriers using different RNAi technologies. This eventually will help improve islet survival and function post transplantation. Chemically synthesized small interferring RNA (siRNA), vector based short hairpin RNA (shRNA), and their critical design elements (such as sequences, promoters, and backbone) are discussed. The application of combinatorial RNAi in islet transplantation is also discussed. Last but not the least, several delivery strategies for enhanced gene silencing are discussed, including chemical modification of siRNA, complex formation, bioconjugation, and viral vectors.

Neutralization of the extracellular HMGB1 released by ischaemic damaged renal cells protects against renal ischaemia-reperfusion injury

BACKGROUND

Graft quality, comprised of ischaemia-reperfusion injury (IRI) and surgical manipulation, is one of the major factors influencing transplant rejection. High-mobility group box 1 (HMGB1), a known activator of innate immunity, has been associated with tissue-generated immunological 'danger' signals; however, its role in renal IRI is not clear.

METHODS

Renal IRI was induced by clamping the left renal pedicle for 60 min in uninephrectomized BALB/c mice. Rabbit anti-mouse HMGB1 antibody was given intraperitoneally 24 h and 30 min before renal ischaemia. Renal HMGB1 expression was assessed by immunohistochemistry and western blot. The therapeutic effect of HMGB1 neutralizing antibody on IRI was evaluated in terms of renal function, histological and immunopathologic examination and terminal deoxynucleotidyl transferase-mediated uridine triphosphate nick end labelling assays.

RESULTS

Ischaemia alone was associated with release of HMGB1, which after reperfusion appeared to induce localization of HMGB1 to renal tubules, peritubular capillaries and glomeruli where the renal cells might be more susceptible to ischaemic insult. Administration of blocking antibody to HMGB1 was associated with reduction in tubular apoptosis and inflammation (TNF-α expression) in situ and in vivo with preservation of renal function.

CONCLUSIONS

These data suggest that released HMGB1 by ischaemic renal parenchyma cells may act as an essential early mediator in delayed inflammatory response during IRI, and targeting HMGB1 may represent a potential approach in the prevention of clinical IRI associated with kidney transplantation.