Native macrophages genetically modified to express heme oxygenase 1 protect rat liver transplants from ischemia/reperfusion injury

Donor graft METTL3 gene transfer ameliorates rat liver transplantation ischemia-reperfusion injury by enhancing HO-1 expression in an m6A-dependent manner

Ischemia-reperfusion injury (IRI) is one of the most common complications in liver transplantation. METTL3 regulates inflammation and various cellular stress responses via modulating RNA m6A modification level. Here, the study aimed to investigate the role and mechanism of METTL3 in IRI after rat orthotopic liver transplantation. Firstly, m6A dot blot assay showed that total RNA m6A modification level in grafts was down-regulated, which echoed with the downregulation of METTL3. Furthermore, METTL3 pretreatment in donor significantly reduced liver grafts necrosis formation, apoptosis, improved liver function and depressed the proinflammatory cytokine/chemokine expression. Mechanistically, western blot and immunohistochemical showed that METTL3 inhibited apoptosis via upregulating HO-1. Moreover, MeRIP-qPCR assay revealed that METTL3 promoted HO-1 expression in an m6A-dependent manner. Additionally, METTL3 alleviated primary hepatocytes apoptosis by upregulating HO-1 under hypoxia/reoxygenation condition. Taken together, these results demonstrated that METTL3 exerted a cytoprotective role against IRI via inducing HO-1 in an m6A-dependent manner.

Bracteanolide A abrogates oxidative stress-induced cellular damage and protects against hepatic ischemia and reperfusion injury in rats

Liver diseases, including viral hepatitis, liver cirrhosis, and liver cancer, mostly remain silent until the late stages and pose a continuing threat to millions of people worldwide. Liver transplantation is the most appropriate solution in the case of liver failure, but it is associated with hepatic ischemia and reperfusion (I/R) injury which severely reduces the prognosis of the patients. In order to ameliorate I/R injury, we investigated the potential of bracteanolide A, from the herb Tradescantia albiflora Kunth in protecting the liver from I/R injury. We first determined the protective effect of bracteanolide A against oxidative stress and DNA damage using HepG2 hepatocyte cell line and then assessed the levels of inflammatory cytokines and antioxidant proteins in response to hepatic insult using an animal model of hepatic I/R injury. The results showed bracteanolide A greatly enhanced cell survival and decreased reactive oxygen species (ROS) production under H2O2 induction. It also upregulated the expression of nuclear factor (erythroid-derived 2)-like2 (Nrf2) and its downstream cytoprotective proteins NAD(P)H quinone oxidoreductase 1 (NQO1) and heme oxygenase-1 (HO-1). Bracteanolide A effectively reduced the severity of liver lesions in I/R-injured rats revealed by histological analysis and significantly decreased the levels of alanine transaminase (ALT), aspartate transaminase (AST), cyclooxygenase-2, and inflammatory cytokines interleukin (IL)-1β and tumor necrosis factor (TNF)-α. Bracteanolide A preconditioning effectively protected the liver from I/R damage in the animal model, and this easily applied procedure may provide a new means to ameliorate hepatic I/R injury during liver surgeries.

Heme oxygenase-1: Equally important in allogeneic hematopoietic stem cell transplantation and organ transplantation?

The intracellular enzyme heme oxygenase-1 (HO-1) is responsible for the degradation of cell-free (cf) heme. Cfheme, released upon cell damage and cell death from hemoglobin, mitochondria and myoglobin, functions as a powerful damage-associated molecular pattern (DAMP). Indeed, cfheme plays a role in a myriad of diseases characterized by (systemic) inflammation, and its rapid degradation by HO-1 is pivotal to maintain homeostasis. In the past decade, HO-1 has been extensively studied for its potential protective role in different transplantation settings, including allogeneic hematopoietic stem cell transplantation (HSCT), solid organ transplantation and pancreatic islet transplantation. These studies have shown that HO-1 can be induced by a wide range of molecules, and that induction of HO-1 has the potential to significantly reduce the incidence and severity of transplantation-related complications such as graft-versus-host disease (GvHD) and ischemia/reperfusion injury (IRI). As such, further investigation into the use of HO-1-inducing agents in human transplantation settings to facilitate the potential use of these agents in the clinic is warranted. In this review, we summarize the literature of the past 10 years on the role of HO-1 in allogeneic HSCT, solid organ transplantation (focusing on kidney and liver) and pancreatic islet transplantation. Furthermore, we provide a hypothesis about the way that HO-1 is able to provide protection against acute GvHD after allogeneic HSCT. A total of 48 research articles and 17 review articles were included in this review.

Macrophage Polarization and Liver Ischemia-Reperfusion Injury

Ischemia-reperfusion injury refers to organ damage caused by the previous insufficient supply of oxygen and nutrients and the involvement of metabolic by-products after blood flow is restored. Liver ischemia-reperfusion injury (IRI) has become a hot research in recent years, because it occurs in many clinical scenarios. After the introduction of liver transplantation and vascular control techniques in liver surgery, liver ischemia-reperfusion injury is considered to be an important factor affecting postoperative mortality and morbidity. As the largest immune organ in the human body, liver contain a lot of immune cells such as resident macrophages (Kupffer cells), dendritic cells, natural killer cells, and natural killer T cells which play a key role in ischemia-reperfusion injury. Among those, macrophage-mediated excessive inflammatory response is considered to be an important factor in liver ischemia-reperfusion injury. The prominent feature of liver injury is an increase in the number of macrophages in liver due to the infiltration of blood monocytes and differentiation into monocyte-derived macrophages. Liver macrophages can be divided into M1 macrophages which can promote inflammation progress and M2 macrophages that inhibit inflammation progress according to their different phenotypes and functions. Both of them can regulate liver aseptic inflammation, and play an important role in triggering, maintaining, and improving liver ischemia-reperfusion injury. This review summarizes studies of macrophage polarization on liver ischemia-reperfusion injury in recent years, to provide potential ideas for translation application in future clinical management.

Heme Oxygenase-1 in Gastrointestinal Tract Health and Disease

Heme oxygenase 1 (HO-1) is the rate-limiting enzyme of heme oxidative degradation, generating carbon monoxide (CO), free iron, and biliverdin. HO-1, a stress inducible enzyme, is considered as an anti-oxidative and cytoprotective agent. As many studies suggest, HO-1 is highly expressed in the gastrointestinal tract where it is involved in the response to inflammatory processes, which may lead to several diseases such as pancreatitis, diabetes, fatty liver disease, inflammatory bowel disease, and cancer. In this review, we highlight the pivotal role of HO-1 and its downstream effectors in the development of disorders and their beneficial effects on the maintenance of the gastrointestinal tract health. We also examine clinical trials involving the therapeutic targets derived from HO-1 system for the most common diseases of the digestive system.

Heme Oxygenase-1 in liver transplant ischemia-reperfusion injury: From bench-to-bedside

Hepatic ischemia-reperfusion injury (IRI), a major risk factor for early allograft dysfunction (EAD) and acute or chronic graft rejection, contributes to donor organ shortage for life-saving orthotopic liver transplantation (OLT). The graft injury caused by local ischemia (warm and/or cold) leads to parenchymal cell death and release of danger-associated molecular patterns (DAMPs), followed by reperfusion-triggered production of reactive oxygen species (ROS), activation of inflammatory cells, hepatocellular damage and ultimate organ failure. Heme oxygenase 1 (HO-1), a heat shock protein-32 induced under IR-stress, is an essential component of the cytoprotective mechanism in stressed livers. HO-1 regulates anti-inflammatory responses and may be crucial in the pathogenesis of chronic diseases, such as arteriosclerosis, hypertension, diabetes and steatosis. An emerging area of study is macrophage-derived HO-1 and its pivotal intrahepatic homeostatic function played in IRI-OLT. Indeed, ectopic hepatic HO-1 overexpression activates intracellular SIRT1/autophagy axis to serve as a key cellular self-defense mechanism in both mouse and human OLT recipients. Recent translational studies in rodents and human liver transplant patients provide novel insights into HO-1 mediated cytoprotection against sterile hepatic inflammation. In this review, we summarize the current bench-to-bedside knowledge on HO-1 molecular signaling and discuss their future therapeutic potential to mitigate IRI in OLT.

Recipient HO-1 inducibility is essential for posttransplant hepatic HO-1 expression and graft protection: From bench-to-bedside

By documenting potent antioxidative and anti-inflammatory functions, preclinical studies encourage heme oxygenase-1 (HO-1)-inducing regimens in clinical orthotopic liver transplantation (OLT). We aimed to determine the importance of recipient-derived HO-1 in murine and human OLTs. Hepatic biopsies from 51 OLT patients were screened for HO-1 expression (Western blots) prior to put-in (basal) and post reperfusion (stressed) and correlated with the hepatocellular function. In parallel, livers from HO-1 proficient mice (WT; C57/BL6), subjected to ex vivo cold storage (18 hour), were transplanted to syngeneic myeloid HO-1 deficient (mHO-1 KO) or FLOX (control) hosts, and sampled postreperfusion (6 hour). In human OLT, posttransplant but not pretransplant HO-1 expression correlated negatively with ALT levels (P = .0178). High posttransplant but not pretransplant HO-1 expression trended with improved OLT survival. Compared with controls, livers transplanted into mHO-1 KO recipient mice had decreased HO-1 levels, exacerbated hepatic damage/frequency of TUNEL+ cells, increased mRNA levels coding for TNFα/CXCL1/CXCL2/CXCL10, higher frequency of Ly6G+/4HN+ neutrophils; and enhanced MPO activity. Peritoneal neutrophils from mHO-1 KO mice exhibited higher CellRox+ ratio and increased TNFα/CXCL1/CXCL2/CXCL10 expression. By demonstrating the importance of posttransplant recipient HO-1 phenotype in hepatic macrophage/neutrophil regulation and function, this translational study identifies recipient HO-1 inducibility as a novel biomarker of ischemic stress resistance in OLT.

Myeloid HO-1 modulates macrophage polarization and protects against ischemia-reperfusion injury

Macrophages polarize into heterogeneous proinflammatory M1 and antiinflammatory M2 subtypes. Heme oxygenase 1 (HO-1) protects against inflammatory processes such as ischemia-reperfusion injury (IRI), organ transplantation, and atherosclerosis. To test our hypothesis that HO-1 regulates macrophage polarization and protects against IRI, we generated myeloid-specific HO-1-knockout (mHO-1-KO) and -transgenic (mHO-1-Tg) mice, with deletion or overexpression of HO-1, in various macrophage populations. Bone marrow-derived macrophages (BMDMs) from mHO-1-KO mice, treated with M1-inducing LPS or M2-inducing IL-4, exhibited increased mRNA expression of M1 (CXCL10, IL-1β, MCP1) and decreased expression of M2 (Arg1 and CD163) markers as compared with controls, while BMDMs from mHO-1-Tg mice displayed the opposite. A similar pattern was observed in the hepatic M1/M2 expression profile in a mouse model of liver IRI. mHO-1-KO mice displayed increased hepatocellular damage, serum AST/ALT levels, Suzuki's histological score of liver IRI, and neutrophil and macrophage infiltration, while mHO-1-Tg mice exhibited the opposite. In human liver transplant biopsies, subjects with higher HO-1 levels showed lower expression of M1 markers together with decreased hepatocellular damage and improved outcomes. In conclusion, myeloid HO-1 expression modulates macrophage polarization, and protects against liver IRI, at least in part by favoring an M2 phenotype.

Dual Effect of Hepatic Macrophages on Liver Ischemia and Reperfusion Injury during Liver Transplantation

Ischemia-reperfusion injury (IRI) is a major complication in liver transplantation (LT) and it is closely related to the recovery of grafts' function. Researches has verified that both innate and adaptive immune system are involved in the development of IRI and Kupffer cell (KC), the resident macrophages in the liver, play a pivotal role both in triggering and sustaining the sterile inflammation. Damage-associated molecular patterns (DAMPs), released by the initial dead cell because of the ischemia insult, firstly activate the KC through pattern recognition receptors (PRRs) such as toll-like receptors. Activated KCs is the dominant players in the IRI as it can secret various pro-inflammatory cytokines to exacerbate the injury and recruit other types of immune cells from the circulation. On the other hand, KCs can also serve in a contrary way to ameliorate IRI by upregulating the anti-inflammatory factors. Moreover, new standpoint has been put forward that KCs and macrophages from the circulation may function in different way to influence the inflammation. Managements towards KCs are expected to be the effective way to improve the IRI.

TAK-242 treatment ameliorates liver ischemia/reperfusion injury by inhibiting TLR4 signaling pathway in a swine model of Maastricht-category-III cardiac death

OBJECTIVES

This study aims to test the effects of TAK-242 on liver transplant viability in a model of swine Maastricht-category-III cardiac death.

METHODS

A swine DCD Maastricht-III model of cardiac death was established, and TAK-242 was administered prior to the induction of cardiac death. The protein and mRNA level of TLR4 signaling pathway molecules and cytokines that are important in mediating immune and inflammatory responses were assessed at different time points following the induction of cardiac death.

RESULTS

After induction of cardiac death, both the mRNA and protein levels of key molecules (TLR4, TRAF6, NF-ϰB, ICAM-1, MCP-1 and MPO), TNF-α and IL-6 increased significantly. Infusion of TAK-242 1h before induction of cardiac death blocked the increase of immune and inflammatory response molecules. However, the increase of TLR4 level was not affected by infusion of TAK-242. Histology study showed that infusion of TAK-242 protect liver tissue from damage during cardiac death.

CONCLUSIONS

These results indicates that TLR4 signaling pathway may contribute to ischemia/reperfusion injury in the liver grafts, and blocking TLR4 pathway with TAk-242 may reduce TLR4-mediated tissue damage.

Endoplasmic reticulum stress of Kupffer cells involved in the conversion of natural regulatory T cells to Th17 cells in liver ischemia-reperfusion injury

BACKGROUND AND AIM

Our previous studies have shown that regulatory T cells (Tregs) are reduced and Th17 cells are elevated in liver insults. Recent studies have indicated the critical role of endoplasmic reticulum (ER) stress of Kupffer cells (KCs) in evoking liver inflammation following reperfusion. The objective of this study was to investigate the role of ER stress of KCs in the conversion of Tregs to Th17 cells and the effect on liver ischemia-reperfusion injury.

METHODS

The partial warm liver ischemia-reperfusion injury mouse model was adopted. ER stress of KCs and the frequency of Tregs and Th17 cells following reperfusion were analyzed. Apart from depletion and adoptive transfer of KCs, KCs were isolated from ischemic lobes and co-cultured with Tregs to study the effect of KCs on Tregs and Th17 cells.

RESULTS

It was found that KCs induced ER stress, decreased natural Tregs (nTregs), and increased Th17 cells after reperfusion. Depletion of KCs modulated the reduction of nTregs and elevation of Th17 cells. Co-culture with stressed KCs led to the reduction in nTregs and elevation of Th17 cells. This effect was suppressed by anti-interleukin-6. Adoptive transfer of these stressed KCs resulted in the reduction in nTregs and elevation of Th17 cells and caused liver injury.

CONCLUSION

Endoplasmic reticulum stress of KCs contributed to the conversion of nTregs to Th17 cells due to interleukin-6, resulting in the worsening of liver insult.

Kupffer Cell Transplantation in Mice for Elucidating Monocyte/Macrophage Biology and for Potential in Cell or Gene Therapy

Kupffer cells (KC) play major roles in immunity and tissue injury or repair. Because recapitulation of KC biology and function within liver will allow superior insights into their functional repertoire, we studied the efficacy of the cell transplantation approach for this purpose. Mouse KC were isolated from donor livers, characterized, and transplanted into syngeneic recipients. To promote cell engraftment through impairments in native KC, recipients were preconditioned with gadolinium chloride. The targeting, fate, and functionality of transplanted cells were evaluated. The findings indicated that transplanted KC engrafted and survived in recipient livers throughout the study period of 3 months. Transplanted KC expressed macrophage functions, including phagocytosis and cytokine expression, with or without genetic modifications using lentiviral vectors. This permitted studies of whether transplanted KC could affect outcomes in the context of acetaminophen hepatotoxicity or hepatic ischemia-reperfusion injury. Transplanted KC exerted beneficial effects in these injury settings. The benefits resulted from cytoprotective factors including vascular endothelial growth factor. In conclusion, transplanted adult KC were successfully targeted and engrafted in the liver with retention of innate immune and tissue repair functions over the long term. This will provide excellent opportunities to address critical aspects in the biogenesis, fate, and function of KC within their native liver microenvironment and to develop the cell and gene therapy potential of KC transplantation.

Outcome using selective hemihepatic vascular occlusion and Pringle maneuver for hepatic resection of liver cavernous hemangioma

Background

Though accumulated evidence proved the advantages of laparoscopic hepatectomy, bleeding still remains the most important challenge in clinical practice. Our study aimed to compare the outcomes of Pringle maneuver (PM) and selective hemihepatic vascular occlusion (SHVO) surgeries for patients with liver cavernous hemangioma (LCH).

Methods

The SHVO (n = 26; mean age, 42) and PM (n = 78; mean age, 43) surgeries were performed in 104 LCH patients from January 2006 to January 2015. The intraoperative (bleeding, arterial pressure, oxyhemoglobin saturation, etc.) and postoperative parameters (anal exhaust time, complications, blood cell numbers, etc.) were measured and compared between the two groups. Liver function of all these patients was detected by blood test at 1-day preoperation, and at 1, 3, and 5 days postoperation.

Results

Both of the two surgeries were successfully performed without any mortality. The intraoperative systolic arterial pressure and pulse in PM group were much higher than that in SHVO group (P < 0.01). The postoperative liver function parameters such as alanine transaminase (ALT), aspartate transaminase (AST), and total bilirubin (TBIL) increased much more in the PM group than that in the SHVO group compared with preoperation results (P < 0.05). However, there were no statistical differences in intraoperative bleeding, blood transfusion, hepatic inflow occlusion time, oxygen saturation occlusion, anal exhaust time and incidence of complications between the two groups (P > 0.05).

Conclusions

SHVO is safer with less ischemia reperfusion injury than PM surgery for hemangioma resection on patients with LCH.

Protective effects against hepatic ischemia-reperfusion injury after rat orthotopic liver transplantation because of BCL-2 overexpression

This study aims to investigate the protective effects and mechanism of recombinant adenovirus Ad.VSG-hBCL-2 towards ischemia/reperfusion injury in rat liver graft. Recombinant adenovirus Ad.VSG-hBCL-2 was injected into the donor rat liver of the experiment group through the portal vein, the laparotomy was performed for liver 36 h later, and the liver was save in lactated Ringer's solution at 4°C for 4 h, "two-cuff method" was used to perform the orthotopic liver transplantation. The bile secretion situations of two groups were observed 6 h after the portal vein reflow; the recipient rats were killed to detect the plasma levels of AST, ALT and LDH. And the expressions of Bcl-2 and TNF-α in liver tissue, and TUNEL assay was used to detect the apoptosis of liver tissue cells, electron microscopy was used to observe the changes of subcellular structures of liver tissue. 6 h after the surgery, the immunohistochemistry and Western Blot test showed that the Bcl-2 expression in the liver of the experiment group significantly increased than the control group, the bile secretion increased, the levels of AST, ALT and LDH were significantly lower, and the TNF-α expression increased significantly. The changes of cellular morphology of the experiment group were milder, and the apoptotic index was significantly lower than the control group. The portal vein-transfected recombinant adenovirus Ad.VSG-hBCL-2 could be effectively expressed in rat liver, and the high expressed Bcl-2 could reduce the ischemia/reperfusion injury in the transplanted liver.

Prospective study of the safety and efficacy of intermittent inflow occlusion (Pringle maneuver) in living donor left hepatectomy

AIM

The impact of intermittent inflow occlusion (Pringle maneuver) in living donor hepatectomy on the outcome of both the donor and the recipient is unknown. The aim of this study is to elucidate the safety and efficacy of Pringle maneuver in living donor hepatectomy.

METHODS

Twenty consecutive cases of living donors who underwent left hepatectomy were prospectively divided into two groups, with (Group A, n = 10) or without (Group B, n = 10) the Pringle maneuver during hepatectomy. Intraoperative blood loss, postoperative liver functions in the donors and recipient outcome were reviewed.

RESULTS

Median blood loss was significantly less in group A than in group B. Median alanine aminotransferase was significantly higher on postoperative day 1 in group A than in group B, but the difference was not significant at 7 days after surgery. Eight of 10 recipients in each group survived with good graft function with a median follow-up period of 20 months in group A and 19 months in group B.

CONCLUSION

The Pringle maneuver was safely applied in living donor hepatectomy, but the only benefit was the reduction of blood loss during the donor surgery, and no positive impact on the recipient outcome.

Heme oxygenase-1 dysregulation in the brain: implications for HIV-associated neurocognitive disorders

Heme oxygenase-1 (HO-1) is a highly inducible and ubiquitous cellular enzyme that subserves cytoprotective responses to toxic insults, including inflammation and oxidative stress. In neurodegenerative diseases such as Alzheimer’s disease, Parkinson’s disease and multiple sclerosis, HO-1 expression is increased, presumably reflecting an endogenous neuroprotective response against ongoing cellular injury. In contrast, we have found that in human immunodeficiency virus (HIV) infection of the brain, which is also associated with inflammation, oxidative stress and neurodegeneration, HO-1 expression is decreased, likely reflecting a unique role for HO-1 deficiency in neurodegeneration pathways activated by HIV infection. We have also shown that HO-1 expression is significantly suppressed by HIV replication in cultured macrophages which represent the primary cellular reservoir for HIV in the brain. HO-1 deficiency is associated with release of neurotoxic levels of glutamate from both HIV-infected and immune-activated macrophages; this glutamate-mediated neurotoxicity is suppressed by pharmacological induction of HO-1 expression in the macrophages. Thus, HO-1 induction could be a therapeutic strategy for neuroprotection against HIV infection and other neuroinflammatory brain diseases. Here, we review various stimuli and signaling pathways regulating HO-1 expression in macrophages, which could promote neuronal survival through HO-1-modulation of endogenous antioxidant and immune modulatory pathways, thus limiting the oxidative stress that can promote HIV disease progression in the CNS. The use of pharmacological inducers of endogenous HO-1 expression as potential adjunctive neuroprotective therapeutics in HIV infection is also discussed.

A novel in situ model of liver cold ischemia-reperfusion in rats

BACKGROUND

Orthotopic liver transplantation (OLT) is being used for studying cold ischemia reperfusion (I/R)-induced injury in experimental animals, but the technique is complicated and it does not accurately reflect the pathophysiology. Here, we report a novel model, termed "in situ liver cold ischemia (ISLCI)", in Wistar rats.

METHODS

ISLCI was achieved in rats by establishing a portal-jugular shunt and a cannula shunt in inferior vena cava, and the liver was continuously perfused with lactate Ringer's solution at a speed of 150 mL/h through the portal vein for 60 min. Portal venous pressure, serum levels of total bilirubin, alkaline phosphatase, alanine aminotransferase and γ-glutamyl transpeptidase (GGT), and hepatic histopathology were examined, and compared with rats undergoing OLT, in which the donor liver was subjected to a 60 min cold ischemia.

RESULTS

Livers from ISLCI and OLT rats showed histopathologic changes characteristic of I/R-induced injury when examined on days 1 and 7, with complete recovery 14 d after reperfusion. Compared with OLT rats, ISLCI rats had significantly lower levels of portal venous pressure 1 and 10 min after porta hepatis clamping. They suffered a milder degree of I/R-induced hepatic injury, reflected by significantly lower levels of GGT, alanine aminotransferase, and alkaline phosphatase on day 1, and a significant lower level of GGT and a lower histopathologic score on day 7 after reperfusion.

CONCLUSIONS

Our preliminary results indicate that the ISLCI model is reliable and technically easier, and is superior to OLT for studying cold I/R injury.

Lesional accumulation of heme oxygenase-1+ microglia/macrophages in rat traumatic brain injury

Heme oxygenase-1 (HO-1) is an inducible rate-limiting enzyme for heme degradation. Here, we studied the HO-1 expression in an open-skull weight-drop-induced traumatic brain injury, with a focus on the early phase, most amenable to therapy. In normal rat brains of our study, HO-1 cells were rarely observed. Significant parenchymal accumulation of HO-1 non-neuron cells was observed 18 h post-traumatic brain injury and increased continuously during the investigating time. We also observed that the accumulated HO-1 non-neuron cells were mainly distributed in the perilesional areas and showed activated microglia/macrophage phenotypes with ramified or amoeboid morphologic characteristics. Further double-labeling experiments showed that most HO-1 non-neuron cells coexpressed CD68 and CD163, but not glial fibrillary acid protein. Our data suggest that HO-1 expression defines a subtype of activated microglia/macrophages involved in the early processes following traumatic brain injury.

BTB and CNC homolog 1 (Bach1) deficiency ameliorates TNBS colitis in mice: role of M2 macrophages and heme oxygenase-1

BACKGROUND

BTB and CNC homolog 1 (Bach1) is a transcriptional repressor of heme oxygenase-1 (HO-1), which plays an important role in the protection of cells and tissues against acute and chronic inflammation. However, the role of Bach1 in the gastrointestinal mucosal defense system remains little understood. HO-1 supports the suppression of experimental colitis and localizes mainly in macrophages in colonic mucosa. This study was undertaken to elucidate the Bach1/HO-1 system's effects on the pathogenesis of experimental colitis.

METHODS

This study used C57BL/6 (wild-type) and homozygous Bach1-deficient C57BL/6 mice in which colonic damage was induced by the administration of an enema of 2,4,6-trinitrobenzene sulfonic acid (TNBS). Subsequently, they were evaluated macroscopically, histologically, and biochemically. Peritoneal macrophages from the respective mice were isolated and analyzed. Then, wild-type mice were injected with peritoneal macrophages from the respective mice. Acute colitis was induced similarly.

RESULTS

TNBS-induced colitis was inhibited in Bach1-deficient mice. TNBS administration increased the expression of HO-1 messenger RNA and protein in colonic mucosa in Bach1-deficient mice. The expression of HO-1 mainly localized in F4/80-immunopositive and CD11b-immunopositive macrophages. Isolated peritoneal macrophages from Bach1-deficient mice highly expressed HO-1 and also manifested M2 macrophage markers, such as Arginase-1, Fizz-1, Ym1, and MRC1. Furthermore, TNBS-induced colitis was inhibited by the transfer of Bach1-deficient macrophages into wild-type mice.

CONCLUSIONS

Deficiency of Bach1 ameliorated TNBS-induced colitis. Bach1-deficient macrophages played a key role in protection against colitis. Targeting of this mechanism is applicable to cell therapy for human inflammatory bowel disease.

Tauroursodeoxycholic acid affects PPARγ and TLR4 in Steatotic liver transplantation

Numerous steatotic livers are discarded for transplantation because of their poor tolerance to ischemia-reperfusion (I/R). We examined whether tauroursodeoxycholic acid (TUDCA), a known inhibitor of endoplasmic reticulum (ER) stress, protects steatotic and nonsteatotic liver grafts preserved during 6 h in University of Wisconsin (UW) solution and transplanted. The protective mechanisms of TUDCA were also examined. Neither unfolded protein response (UPR) induction nor ER stress was evidenced in steatotic and nonsteatotic liver grafts after 6 h in UW preservation solution. TUDCA only protected steatotic livers grafts and did so through a mechanism independent of ER stress. It reduced proliferator-activated receptor-γ (PPARγ) and damage. When PPARγ was activated, TUDCA did not reduce damage. TUDCA, which inhibited PPARγ, and the PPARγ antagonist treatment up-regulated toll-like receptor 4 (TLR4), specifically the TIR domain-containing adaptor inducing IFNβ (TRIF) pathway. TLR4 agonist treatment reduced damage in steatotic liver grafts. When TLR4 action was inhibited, PPARγ antagonists did not protect steatotic liver grafts. In conclusion, TUDCA reduced PPARγ and this in turn up-regulated the TLR4 pathway, thus protecting steatotic liver grafts. TLR4 activating-based strategies could reduce the inherent risk of steatotic liver failure after transplantation.

Liver-protecting effects of omega-3 fish oil lipid emulsion in liver transplantation

AIM: To investigate the liver-protecting effect of parenteral nutrition (PN) support with omega-3 fatty acids in a randomized controlled clinical trial.

METHODS: Sixty-six patients with the diagnosis of end-stage liver disease or hepatic cellular carcinoma were admitted to the Affiliated Drum Tower Hospital, Nanjing University, China for orthotopic liver transplantation. The patients were randomly divided into two groups: PN group (n = 33) and polyunsaturated fatty acid (PUFA) group (n = 33). All patients received isocaloric and isonitrogenous PN for seven days after surgery, and in PUFA group omega-3 fish oil lipid emulsion replaced part of the standard lipid emulsion. Liver function was tested on days 2 and 9 after surgery. Pathological examination was performed after reperfusion of the donor liver and on day 9. Clinical outcome was assessed based on the post-transplant investigations, including: (1) post-transplant mechanical ventilation; (2) total hospital stay; (3) infectious morbidities; (4) acute and chronic rejection; and (5) mortality (intensive care unit mortality, hospital mortality, 28-d mortality, and survival at a one-year post-transplant surveillance period).

RESULTS: On days 2 and 9 after operation, a significant decrease of alanine aminotransferase (299.16 U/L ± 189.17 U/L vs 246.16 U/L ± 175.21 U/L, P = 0.024) and prothrombin time (5.64 s ± 2.06 s vs 2.54 s ± 1.15 s, P = 0.035) was seen in PUFA group compared with PN group. The pathological results showed that omega-3 fatty acid supplement improved the injury of hepatic cells. Compared with PN group, there was a significant decrease of post-transplant hospital stay in PUFA group (18.7 d ± 4.0 d vs 20.6 d ± 4.6 d, P = 0.041). Complications of infection occurred in 6 cases of PN group (2 cases of pneumonia, 3 cases of intra-abdominal abscess and 1 case of urinary tract infection), and in 3 cases of PUFA group (2 cases of pneumonia and 1 case of intra-abdominal abscess). No acute or chronic rejection and hospital mortality were found in both groups. The one-year mortality in PN group was 9.1% (3/33), one died of pulmonary infection, one died of severe intra-hepatic cholangitis and hepatic dysfunction and the other died of hepatic cell carcinoma recurrence. Only one patient in PUFA group (1/33, 3.1%) died of biliary complication and hepatic dysfunction during follow-up.

CONCLUSION: Post-transplant parenteral nutritional support combined with omega-3 fatty acids can significantly improve the liver injury, reduce the infectious morbidities, and shorten the post-transplant hospital stay.

A technique of recipient portal venoplasty and cuff insertion for portal revascularization in orthotopic rat liver transplantation

BACKGROUND

In addition to suprahepatic vena cava anastomosis in two-cuff rat liver transplantation, recipient portal vein revascularization is one of the most difficult procedures that must be performed, especially for beginners.

MATERIALS AND METHODS

A total of 43 cases of liver transplantation were performed. Rats in Group 1 and Group 2 were subjected to transplant procedures that used the conventional and portal venoplasty techniques, respectively. The portal vein anastomosis duration, anhepatic phase length, portal vein surgical complications, and 1 wk post-transplant survival rates were recorded for each group.

RESULTS

The portal revascularization duration was statistically significantly less for Group 2 versus Group 1 (1.50 ± 0.61 min and 4.32 ± 0.67 min, respectively, P < 0.05). The anhepatic phase length of Groups 1 and 2 were 21.79 ± 1.27 min and 18.55 ± 1.47 min, respectively (P < 0.05). No significant differences between the groups were observed in relation to either portal vein surgery complications or 1-week survival rates.

CONCLUSIONS

The recipient portal venoplasty and cuff insertion technique is a safe and fast alternative surgical option for portal revascularization in two-cuff rat liver transplantations performed by a single trainee.

Liver graft injury induced by ischemia and reperfusion secondary to retrograde reperfusion

AIM: To evaluate the influence of retrograde reperfusion on ischemia/reperfusion injury in a rat model of liver transplantation.

METHODS: Thirty-six male Sprague-Dawley rats undergoing orthoptic liver transplantation were divided into three groups (n = 12 for each group): group 1, antegrade reperfusion via the portal vein; group 2, antegrade reperfusion simultaneously via the portal vein and hepatic artery; group 3: retrograde reperfusion via the vena cava. Serum parameters were determined 1, 6 and 24 h after operation. Liver samples were taken for histological assessment. Cell apoptotic index was determined.

RESULTS: Rats of group 3 showed significantly lower serum level of aspartate aminotransferase compared to groups 1 and 2 (968.4 U/L ± 221.5 U/L vs 1 801.6 U/L ± 324.5 U/L, 2 564.1 U/L ± 410.3 U/L, P = 0.003, 0.000). Serum level of aspartate aminotransferase was significantly lower in group 1 than in group 2. The liver of rats of group 3 showed significantly less leukocytic infiltrates compared to groups 1 and group 2. The apoptotic index was lower in group 3 than in group 1 and 2.

CONCLUSION: Retrograde reperfusion leads to a lower level of ischemia/reperfusion injury than antegrade reperfusion in rats undergoing liver transplantation.