Improvement of recipient survival after small size graft liver transplantation in rats with preischemic manipulation or administering antisense against nuclear factor-kappaB

Exosome-based delivery of super-repressor IκBα ameliorates kidney ischemia-reperfusion injury

Ischemia-reperfusion injury is a major cause of acute kidney injury. Recent studies on the pathophysiology of ischemia-reperfusion-induced acute kidney injury showed that immunologic responses significantly affect kidney ischemia-reperfusion injury and repair. Nuclear factor (NF)-ĸB signaling, which controls cytokine production and cell survival, is significantly involved in ischemia-reperfusion-induced acute kidney injury, and its inhibition can ameliorate ischemic acute kidney injury. Using EXPLOR, a novel, optogenetically engineered exosome technology, we successfully delivered the exosomal super-repressor inhibitor of NF-ĸB (Exo-srIĸB) into B6 wild type mice before/after kidney ischemia-reperfusion surgery, and compared outcomes with those of a control exosome (Exo-Naïve)-injected group. Exo-srIĸB treatment resulted in lower levels of serum blood urea nitrogen, creatinine, and neutrophil gelatinase-associated lipocalin in post-ischemic mice than in the Exo-Naïve treatment group. Systemic delivery of Exo-srIĸB decreased NF-ĸB activity in post-ischemic kidneys and reduced apoptosis. Post-ischemic kidneys showed decreased gene expression of pro-inflammatory cytokines and adhesion molecules with Exo-srIĸB treatment as compared with the control. Intravital imaging confirmed the uptake of exosomes in neutrophils and macrophages. Exo-srIĸB treatment also significantly affected post-ischemic kidney immune cell populations, lowering neutrophil, monocyte/macrophage, and T cell frequencies than those in the control. Thus, modulation of NF-ĸB signaling through exosomal delivery can be used as a novel therapeutic method for ischemia-reperfusion-induced acute kidney injury.

Wnt agonist stimulates liver regeneration after small-for-size liver transplantation in rats

AIM

Liver regeneration is inhibited in small-for-size grafts, which plays a role in the failure of partial liver grafts after transplantation. The Wnt/β-catenin signaling pathway plays a critical role in liver development, regeneration and homeostasis. In this study, we investigated whether pharmacological activation of Wnt signaling improves liver regeneration after small-for-size liver transplantation.

METHODS

The livers of male Sprague-Dawley rats were reduced to approximately 50% and 30% of their original sizes and transplanted. A Wnt agonist (2-amino-4-[3,4-[methylenedioxy]benzylamino]-6-[3-methoxyphenyl] pyrimidine], 5 mg/kg bodyweight) or an equal volume of vehicle was administrated i.p. into the donor 1 h before the transplantation. Tissue and blood samples were collected at various times after transplantation, and a survival study was performed.

RESULTS

Hepatic expression of active β-catenin and its downstream target gene Axin2 were decreased in 30% of liver grafts after transplantation while the Wnt agonist increased their expression similar to the 50% liver grafts. The Wnt agonist reversed inhibition of cyclin D1 expression and adenosine triphosphate production in the 30% liver grafts compared with the 50% grafts. The Wnt agonist also attenuated hepatocellular injury and increased the hepatocyte proliferation response, liver regeneration rate and survival after transplantation of the 30% liver graft.

CONCLUSION

Activation of Wnt/β-catenin signaling in liver grafts by pharmacological pretreatment can accelerate regeneration in a partial liver transplant model.

SOD mimetic improves the function, growth, and survival of small-size liver grafts after transplantation in rats

BACKGROUND

Small-for-size syndrome (SFSS) may occur when graft volume is less than 45% of the standard liver volume, and it manifests as retarded growth and failure of the grafts and more mortality. However, its pathogenesis is poorly understood, and few effective interventions have been attempted.

AIMS

The present study aimed to delineate the critical role of oxidant stress in SFSS and protective effects of a superoxide dismutase mimetic, Mn(III)tetrakis(4-benzoic acid)porphyrin chloride (MnTBAP), on graft function, growth, and survival in the recipient rats.

METHODS

Small size graft liver transplantation (SSGLT) was performed to determine the survival, graft injury, and growth. MnTBAP was administered in SSGLT recipients (SSGLT+MnTBAP).

RESULTS

Serum alanine aminotransferase levels were sustained higher in SSGLT recipients, which were correlated with an increased apoptotic cell count and hepatocellular necrosis in liver sections. Malondialdehyde content, gene expression of tumor necrosis factor α and interleukin 1β, and DNA binding activity of nuclear factor-κB in the grafts were increased significantly in SSGLT recipients compared with sham-operated controls. Both phosphorylated p38 mitogen-activated protein kinase and nuclear c-Jun were increased in SSGLT. All these changes were strikingly reversed by the administration of MnTBAP, with an increase in serum superoxide dismutase activity. Moreover, in situ bromodeoxyuridine incorporation demonstrated that graft regeneration was much more profound in the SSGLT+MnTBAP group than in the SSGLT group. Finally, the survival of recipients with MnTBAP treatments was significantly improved.

CONCLUSIONS

Enhanced oxidant stress with activation of the p38/c-Jun/nuclear factor-κB signaling pathway contributes to SFSS-associated graft failure, retarded graft growth, and poor survival. MnTBAP effectively reversed the pathologic changes in SFSS-associated graft failure.

miRNA regulation of liver growth after 50% partial hepatectomy and small size grafts in rats

BACKGROUND

The molecular mechanisms underlying the growth of small size grafts and the remaining livers are poorly understood. MicroRNAs (miRNAs) negatively modulate expression of genes that are involved in cellular function and metabolism. The aim of this study is to identify critical miRNA species that modulate the growth of small grafts and the remaining livers after partial hepatectomy (PH).

METHODS

Small size graft liver transplantation was performed in rats. Liver tissue was harvested after transplant or PH for the determination of miRNA expression profile, and the data were confirmed by quantitative reverse-transcriptase polymerase chain reaction. The genes involved in cell cycle and proliferation were analyzed by quantitative reverse-transcriptase polymerase chain reaction and immunohistochemical staining.

RESULTS

Compared with control liver, miR_122a, Let_7b, and miR_26a were reduced by more than 90% in 45% volume grafts. In the remaining livers after 50% PH, 30 miRNAs were down-regulated by more than 50%, and among them, miR_22a, miR_26a, miR_30b, Let_7f, and Let_7g were markedly decreased. A negative correlation existed between down-regulated miRNAs and highly up-regulated genes involved in cell cycle and proliferation in the remaining livers. Moreover, overexpression of miR_26a markedly down-regulated cyclin E2 protein levels and significantly decreased proliferation of HepG2 cells.

CONCLUSION

Down-regulated miRNAs play a pivotal role in promoting the growth of small size grafts and the remaining livers. The negative correlation between down-regulated miRNAs and up-regulated genes suggests that these specific miRNAs participate in the modulation of a growth response in both living donors and small size graft recipients.

Carbon monoxide-releasing molecule-2 (CORM-2) attenuates acute hepatic ischemia reperfusion injury in rats

Background

Hepatic ischemia-reperfusion injury (I/Ri) is a serious complication occurring during liver surgery that may lead to liver failure. Hepatic I/Ri induces formation of reactive oxygen species, hepatocyte apoptosis, and release of pro-inflammatory cytokines, which together causes liver damage and organ dysfunction. A potential strategy to alleviate hepatic I/Ri is to exploit the potent anti-inflammatory and cytoprotective effects of carbon monoxide (CO) by application of so-called CO-releasing molecules (CORMs). Here, we assessed whether CO released from CORM-2 protects against hepatic I/Ri in a rat model.

Methods

Forty male Wistar rats were randomly assigned into four groups (n = 10). Sham group underwent a sham operation and received saline. I/R group underwent hepatic I/R procedure by partial clamping of portal structures to the left and median lobes with a microvascular clip for 60 minutes, yielding ~70% hepatic ischemia and subsequently received saline. CORM-2 group underwent the same procedure and received 8 mg/kg of CORM-2 at time of reperfusion. iCORM-2 group underwent the same procedure and received iCORM-2 (8 mg/kg), which does not release CO. Therapeutic effects of CORM-2 on hepatic I/Ri was assessed by measuring serum damage markers AST and ALT, liver histology score, TUNEL-scoring of apoptotic cells, NFkB-activity in nuclear liver extracts, serum levels of pro-inflammatory cytokines TNF-α and IL-6, and hepatic neutrophil infiltration.

Results

A single systemic infusion with CORM-2 protected the liver from I/Ri as evidenced by a reduction in serum AST/ALT levels and an improved liver histology score. Treatment with CORM-2 also up-regulated expression of the anti-apoptotic protein Bcl-2, down-regulated caspase-3 activation, and significantly reduced the levels of apoptosis after I/Ri. Furthermore, treatment with CORM-2 significantly inhibited the activity of the pro-inflammatory transcription factor NF-κB as measured in nuclear extracts of liver homogenates. Moreover, CORM-2 treatment resulted in reduced serum levels of pro-inflammatory cytokines TNF-α and IL-6 and down-regulation of the adhesion molecule ICAM-1 in the endothelial cells of liver. In line with these findings, CORM-2 treatment reduced the accumulation of neutrophils in the liver upon I/Ri. Similar treatment with an inactive variant of CORM-2 (iCORM-2) did not have any beneficial effect on the extent of liver I/Ri.

Conclusions

CORM-2 treatment at the time of reperfusion had several distinct beneficial effects on severity of hepatic I/Ri that may be of therapeutic value for the prevention of tissue damage as a result of I/Ri during hepatic surgery.

Searching for NF-kappaB-based treatments of ischemia reperfusion injury

When a tissue becomes ischemic, a host of changes occur at the cellular level that lead to a shift in transcriptional activity of many inflammatory and cytoprotective compounds, a process which is extensively controlled through a family of transcription factors known as nuclear factor kappa-B (NF-kappaB). This shift in activity paradoxically results in both a cytoprotective effect at the cellular level and upon reperfusion, a generally destructive inflammatory response, a phenomenon referred to as ischemia reperfusion (IR) injury. To date, a number of methods of modifying the activity of NF-kappaB through either physiologic or pharmacologic manipulation have been developed and studied in animal models of IR injury and in some cases in human clinical trials. Nearly every method of NF-kappaB antagonism has demonstrated a discrete protective effect allowing investigators to reduce myocardial infarct sizes by 60% and cerebral infarct sizes by 57% relative to untreated control animals. The problem of IR injury is all too common and represents a discrete threat not only to the tissues directly involved in the ischemic event, but also to distal sites as well as is seen in the evolution of acute respiratory distress and severe inflammatory response syndromes. In the course of this review, the nature of NF-kappaB and its involvement in IR injury is examined along with the efficacy of the various NF-kappaB-based investigational treatment developed to date.

Inhibition of TNF-alpha reduces transplant arteriosclerosis in a murine aortic transplant model

Experimental and clinical data provide evidence that TNF-alpha contributes to acute and chronic allograft rejection. In this study, we explored the effect of TNF-alpha blockade using the chimeric monoclonal antibody infliximab on the development of transplant arterisoclerosis in a fully mismatched aortic allograft model. Post-transplant treatment of CBA (H2(k)) recipients with 250 mug infliximab (cumulative dose 1.25 mg) reduced luminal occlusion of C57Bl/6 (H2(b)) aortic grafts on day 30 from 77 +/- 5% in untreated controls to 52 +/- 6%. Increasing the dose of anti-TNF-alpha antibody had no further beneficial effect. Treatment with human control immunoglobulin had no effect on intima proliferation. Under TNF-alpha blockade, ICAM-1 and PDGF mRNA expression within the grafts was strongly reduced, whereas iNOS expression was enhanced. The data show that TNF-alpha blockade using infliximab can reduce the development of transplant arteriosclerosis in fully mismatched murine aortic grafts.