Protection of transplant-induced hepatic ischemia/reperfusion injury with carbon monoxide via MEK/ERK1/2 pathway downregulation

Low dose of carbon monoxide intraperitoneal injection provides potent protection against GalN/LPS-induced acute liver injury in mice

Carbon monoxide (CO) is an important effector-signaling molecule involved in various pathophysiological processes. Here we investigated the protective effects of exogenous CO in a murine model of acute liver damage induced by d-galactosamine (GalN) and lipopolysaccharide (LPS). Exogenous CO gas was administered to mice via intraperitoneal injection (first at a dose of 15 ml kg(-1) and then, 6 h later, 8 ml kg(-1)), which caused a significant elevation of blood carboxyhemoglobin levels of up to 12-14% for more than 12 h. GalN/LPS were given to induce acute liver damage in mice 30 min prior to CO exposure. This showed that GalN/LPS induced severe liver injury in mice, whereas CO injection remarkably improved the survival rate of mice and led to attenuated hepatocellular damage. CO exhibited anti-oxidative capabilities by inhibiting hepatic malondialdehyde contents and restoring superoxide dismutase and glutathione, as well as by reducing inducible NOS/NO production. The anti-apoptotic and anti-inflammatory effects of CO were substantial, characterized by a notable inhibition of hepatocyte apoptosis and a reduction of pro-inflammatory cytokines in mice. Our findings thus supported the hypothesis that exogenous CO provides protective effects against acute liver damage in mice, mainly dependent on its anti-oxidative, anti-inflammatory and anti-apoptotic properties.

Inhalation of carbon monoxide reduces skeletal muscle injury after hind limb ischemia-reperfusion injury in mice

BACKGROUND

The purpose of this study was to determine if inhaled carbon monoxide (CO) can ameliorate skeletal muscle injury, modulate endogenous heme oxygenase-1 expression, and improve indexes of tissue integrity and inflammation after hind limb ischemia reperfusion.

METHODS

C57BL6 mice inhaling CO (250 ppm) or room air were subjected to 1.5 hours of ischemia followed by limb reperfusion for either 3 or 6 hours (total treatment time, 4.5 or 7.5 h). After the initial period of reperfusion, all mice breathed only room air until 24 hours after the onset of ischemia. Mice were killed at either the end of CO treatment or at 24 hours' reperfusion. Skeletal muscle was subjected to histologic and biochemical analysis.

RESULTS

CO treatment for 7.5 hours protected skeletal muscle from histologic and structural evidence of skeletal muscle injury. Serum and tissue cytokines were reduced significantly (P < .05) in mice treated with CO for 7.5 hours. Tubulin, heme oxygenase, and adenosine triphosphate levels were higher in CO-treated mice.

CONCLUSIONS

Inhaled CO protected muscle from structural injury and energy depletion after ischemia reperfusion.

HepaCAM induces G1 phase arrest and promotes c-Myc degradation in human renal cell carcinoma

Hepatocyte cell adhesion molecule (hepaCAM) encodes a generally inactive phosphorylated glycoprotein which mediates cancer cell proliferation, migration, and differentiation. We have reported that hepaCAM is down-regulated in renal cell carcinoma (RCC) and takes responsibility of cell growth inhibition. However, the precise mechanisms of hepaCAM inhibits cell growth is still unknown. In this study, we demonstrated that re-expression of hepaCAM can cause an accumulation in G0/G1 phase in 786-0 cells. This reaction was accompanied by a substantial reduction of c-Myc expression through using an ectopic hepaCAM expression system. Furthermore, we found a comparable decrease in proliferation and G0/G1 accumulation of 786-0 and RC-2 cells after treatment with a small molecule c-Myc inhibitor, 10058-F4. This indicated that the down regulation of c-Myc was an essential process in controlling growth inhibitory actions of hepaCAM. Nevertheless, re-expression of hepaCAM results in apparent reduction of c-Myc protein with no corresponding reduction of c-Myc mRNA. This suggests that this reaction might take place at a post-transcriptional level rather than transcriptional one. Consistent with these findings, hepaCAM decreased c-Myc stability by increasing the proportion of c-Myc phosphorylation on T58 which can be abrogated by a proteasomal inhibitor (MG132). Thus, our research implies that the decrease in c-Myc protein expression, resulting from ectopic expression of hepaCAM, may contribute to the inhibition of proliferation in these cells.

Preconditioning donor liver with Nodosin perfusion lessens rat ischemia reperfusion injury via heme oxygenase-1 upregulation

BACKGROUND AND AIM

Ischemia reperfusion injury (IRI) remains a major cause of graft injury, dysfunction and even failure post-transplantation. Heme oxygenase 1 (HO-1) has been found to be an attractive target for anti-inflammatory therapies and a potential candidate responsible for cell injury. The objective of this study was to investigate whether preconditioning the donor liver with Nodosin perfusion upregulates HO-1 and then lessens IRI in rat models.

METHODS

Wistar rats were divided into four groups: experimental group, control group, positive control group and negative control group in which the donor liver was preconditioned with Nodosin, lactated ringer's solution, cobalt protoporphyrin and zinc protoporphyrin perfusion, respectively. We measured HO-1 expression and enzyme activity in rat livers of each group ex vivo at 0, 1 and 2 h after perfusion. At 1 h after perfusion, donor livers of Wistar rats were transplanted into Sprague-Dawley rats orthotopically. Serum transaminase levels, degree of cell apoptosis and Suzuki's score were used to assess ischemia/reperfusion injury in recipients at 24 h after transplantation.

RESULTS

Ex vivo, donor liver preconditioning with Nodosin perfusion induced HO-1 expression and enzyme activity significantly, compared with the control group (P < 0.05). In vivo, serum transaminase levels, cell apoptosis degree and Suzuki's score of representative recipients in the Nodosin group were lower than that in the control group (P < 0.05). Preconditioning with Nodosin perfusion induced HO-1 protein mainly in Kupffer cells.

CONCLUSIONS

This study suggests that preconditioning with Nodosin perfusion provides a potential protective effect through inducing HO-1 expression to attenuate ischemia/reperfusion injury in liver transplantation.

Carbon monoxide: an unusual drug

The highly toxic gas carbon monoxide (CO) displays many physiological roles in several organs and tissues. Although many diseases, including cancer, hematological diseases, hypertension, heart failure, inflammation, sepsis, neurodegeneration, and sleep disorders, have been linked to abnormal endogenous CO metabolism and functions, CO administration has therapeutic potential in inflammation, sepsis, lung injury, cardiovascular diseases, transplantation, and cancer. Here, insights into the CO-based therapy, characterized by the induction or gene transfer of heme oxygenase-1 and either gas or CO-releasing molecule administration, are reviewed.

Contributions of heme oxygenase-1 in postconditioning-protected ischemia-reperfusion injury in rat liver transplantation

BACKGROUND

Heme oxygenase-1 (HO-1), an oxidative stress-response gene up-regulated by various physiological and exogenous stimuli, has cytoprotective activities. Ischemic postconditioning (Postcon) can protect an organ from ischemia-reperfusion (I/R) injury. In the present study, we investigated the potential contributions of HO-1 to Postcon-dependent protection against I/R injury in rat liver transplantation models.

MATERIALS AND METHODS

Adult male Sprague-Dawley rats were randomly divided into four groups: sham group with laparotomy for liver exposure; I/R group with 24-hour cold ischemia of the donor liver; Postcon group with the same treatment as the I/R group plus ischemic Postcon; and zinc protoporphyrin (ZnPP HO-1 inhibitor) + Postcon group treated the same as the Postcon cohort with donors pretreated using ZnPP 24 hours before the I/R injury. We measured liver tissue and peripheral blood samples collected at 6 hours after reperfusion and serum transaminase levels, histopathology, liver tissue malondialdehyde (MDA) content, superoxide dismutase (SOD) activity and HO-1 expression in the liver.

RESULTS

Postcon significantly diminished the elevation of serum transaminases levels after I/R injury when compared with I/R and ZnPP+Postcon groups. Postcon treated rats showed significantly lower MDA production and higher SOD activity. HO-1 was induced in rat livers exposed to Postcon; its levels were obviously overexpressed after 6 hours in Postcon rats. Inhibiting the expression of HO-1, negated the protective effects of Postcon.

CONCLUSIONS

Induction of HO-1 in the Postcon condition played a protective role against hepatic I/R injury and enhanced the early antioxidative activity. The protective effects of Postcon were significantly associated with greater intrahepatic HO-1 expression.

Efficacy of a phosphorodiamidate morpholino oligomer antisense compound in the inhibition of corneal transplant rejection in a rat cornea transplant model

PURPOSE

The cornea is one of the most commonly transplanted tissues. The morpholino-oligomer antisense compound AVI-5126 suppresses expression of proto-oncogene c-myc, a key factor in transplant rejection. AVI-5126 was evaluated in a rat cornea transplant model.

METHODS

Donor corneas obtained from August x Copenhagen Irish rats were stored in Optisol™ containing 1.0 or 0.5 mg/mL AVI-5126 or Optisol alone for 24 h before transplant. Recipient Lewis rats were treated topically 3x/d with TobraDex™ and with 1.0 or 0.5 mg/mL of AVI-5126 or saline with daily monitoring for rejection using a modified McDonald-Shadduck Slit Lamp Scale. Using the high-performance liquid chromatography technique, the stability of AVI-5126 (0.5 mg/mL) in Optisol was evaluated for 30 days. AVI-5126 corneal transport was measured using Ussing chamber mounted rabbit corneas. The potential ocular toxicity of AVI-5126 (0.5 mg/mL) was evaluated after 8 days of 3x/d topical application in rats and in-vitro by incubation of human corneas for 8 days.

RESULTS

Cornea storage in Optisol containing 1.0 mg/mL AVI-5126 plus post-transplant topical tid AVI-5126 (1.0 mg/mL) application significantly increased graft survival (7.0±1.6 days) versus 5.0±0.8 days for Optisol alone storage plus post-transplant topical tid saline application (P<0.001). After 30 days of storage, no significant degradation of AVI-5126 in Optisol was noted by high-performance liquid chromatography analysis. After 24 h, 5 μg/mL (1% of total dose) crossed the corneas mounted in Ussing chambers. Neither extended topical application of AVI-5126 to rats nor incubation of human corneas in AVI-5126 decreased endothelial cell density.

CONCLUSIONS

Graft rejection was significantly delayed after pretransplantation storage of graft corneas in Optisol containing AVI-5126 followed by topical application of AVI-5126 post-transplantation. AVI-5126 was well tolerated, stable, and effectively penetrated the cornea.

Carbon monoxide induces hypothermia tolerance in Kupffer cells and attenuates liver ischemia/reperfusion injury in rats

Ischemia/reperfusion (I/R) injury in liver grafts, which is initiated by cold preservation and is augmented by reperfusion, is a major problem that complicates graft quality, posttransplant patient care, and outcomes of liver transplantation (LT). Kupffer cells (KCs) play important roles in I/R injury; however, little is known about their changes during cold preservation. We examined whether a pretreatment with carbon monoxide (CO), a cytoprotective product of heme degradation, could influence KC activity during cold storage and protect liver grafts against LT-induced I/R injury. In vitro, primary rat KCs were stimulated for 24 hours under hypothermic conditions (4°C, 20% O(2)), with lipopolysaccharide, or under hypoxic conditions (37°C, 5% O(2)) with or without a CO pretreatment. When rat KCs were exposed to hypothermic conditions, they produced reactive oxygen species (ROS), but they did not produce tumor necrosis factor α (TNF-α) or nitric oxide. The preincubation of KCs with CO up-regulated heat shock protein 70 (HSP70) and inhibited ROS generation. When liver grafts from donor rats exposed to CO (250 ppm) for 24 hours were transplanted after 18 hours of cold preservation in University of Wisconsin solution, HSP70 expression increased in these grafts versus control grafts, and serum aspartate aminotransferase and alanine aminotransferase levels as well as necrotic areas and inflammatory infiltrates were significantly reduced after LT. CO-pretreated liver grafts showed less up-regulation of TNF-α and inducible nitric oxide synthase messenger RNA (mRNA) and reduced expression of proapoptotic B cell lymphoma 2-associated X protein mRNA, cleaved caspase-3, and poly(adenosine diphosphate ribose) polymerase. In conclusion, the pretreatment of donors with CO ameliorates LT-associated I/R injury with increased hepatic HSP70 expression, particularly in the KC population.

Carbon monoxide inhibits apoptosis during cold storage and protects kidney grafts donated after cardiac death

Ischemia/reperfusion (I/R) injury remains as a serious deleterious factor in kidney transplantation (KTx). We hypothesized that carbon monoxide (CO), an endogenous potent cytoprotective molecule, inhibits hypothermia-induced apoptosis of kidney grafts. Using the rat KTx model mimicking the conditions of donation after cardiac death (DCD) as well as nontransplantable human kidney grafts, this study examined effects of CO in preservation solution in improving the quality of marginal kidney grafts. After cardiac cessation, rat kidneys underwent 40 min warm ischemia (WI) and 24 h cold storage (CS) in control UW or UW containing CO (CO-UW). At the end of CS, kidney grafts in control UW markedly increased mitochondrial porin release into the cytosol and resulted in increased cleaved caspase-3 and PARP expression. In contrast, grafts in CO-UW had significantly reduced mitochondrial breakdown and caspase pathway activation. After KTx, recipient survival significantly improved with CO-UW with less TUNEL(+) cells and reduced mRNA upregulation for proinflammatory mediators (IL-6, TNF-α, iNOS). Furthermore, when nontransplantable human kidney grafts were stored in CO-UW for 24 h, graft PARP expression, TUNEL(+) cells, and proinflammatory mediators were less than those in control UW. CO in UW inhibited hypothermia-induced apoptosis and significantly improved kidney graft function and outcomes of KTx.

Use of carbon monoxide in minimizing ischemia/reperfusion injury in transplantation

Although carbon monoxide (CO) is known to be toxic because of its ability to interfere with oxygen delivery at high concentrations, mammalian cells endogenously generate CO primarily via the catalysis of heme by heme oxygenases. Recent findings have indicated that heme oxygenases and generation of CO serve as a key mechanism to maintain the integrity of the physiological function of organs and supported the development of a new paradigm that CO, at low concentrations, functions as a signaling molecule in the body and exerts significant cytoprotection. Consequently, exogenously delivered CO has been shown to mediate potent protection in various injury models through its anti-inflammatory, vasodilating, and antiapoptotic functions. Ischemia/reperfusion (I/R) injury associated with organ transplantation is one of the major deleterious factors limiting the success of transplantation. Ischemia/reperfusion injury is a complex cascade of interconnected events involving cell damage, apoptosis, vigorous inflammatory responses, microcirculation disturbance, and thrombogenesis. Carbon monoxide has a great potential in minimizing I/R injury. This review will provide an overview of the basic physiology of CO, preclinical studies examining efficacy of CO in I/R injury models, and possible protective mechanisms. Carbon monoxide could be developed to be a valuable therapeutic molecule in minimizing I/R injury in transplantation.

Elevated activation of ERK1 and ERK2 accompany enhanced liver injury following alcohol binge in chronically ethanol-fed rats

BACKGROUND

Binge drinking after chronic ethanol consumption is one of the important factors contributing to the progression of steatosis to steatohepatitis. The molecular mechanisms of this effect remain poorly understood. We have therefore examined in rats the effect of single and repeat ethanol binge superimposed on chronic ethanol intake on liver injury, activation of mitogen-activated protein kinases (MAPKs), and gene expression.

METHODS

Rats were chronically treated with ethanol in liquid diet for 4 weeks followed by single ethanol binge (5 gm/kg body weight) or 3 similar repeated doses of ethanol. Serum alcohol and alanine amino transferase (ALT) levels were determined by enzymatic methods. Steatosis was assessed by histology and hepatic triglycerides. Activation of MAPK, 90S ribosomal kinase (RSK), and caspase 3 were evaluated by Western blot. Levels of mRNA for tumor necrosis factor alpha (TNFα), early growth response-1 (egr-1), and plasminogen activator inhibitor-1 (PAI-1) were measured by real-time qRT-PCR.

RESULTS

Chronic ethanol treatment resulted in mild steatosis and necrosis, whereas chronic ethanol followed by binge group exhibited marked steatosis and significant increase in necrosis. Chronic binge group also showed significant increase (compared with chronic ethanol alone) in the phosphorylation of extracellular regulated kinase 1 (ERK1), ERK2, and RSK. Phosphorylation of c-Jun N-terminal kinase (JNK) and p38 MAPK did not increase by the binge. Ethanol binge, after chronic ethanol intake, caused increase in mRNA for egr-1 and PAI-1, but not TNFα.

CONCLUSIONS

Chronic ethanol exposure increases the susceptibility of rat liver to increased injury by 1 or 3 repeat binge. Among other alterations, the activated levels of ERK1, and more so ERK2, were remarkably amplified by binge suggesting a role of these isotypes in the binge amplification of the injury. In contrast, p38 MAPK and JNK1/2 activities were not amplified. These binge-induced changes were also reflected in the increases in the RNA levels for egr-1 and PAI-1. This study offers chronic followed by repeat binge as a model for the study of progression of liver injury by ethanol and highlights the involvement of ERK1 and ERK2 isotypes in the amplification of liver injury by binge ethanol.

Carbon monoxide liberated from carbon monoxide-releasing molecule exerts an anti-inflammatory effect on dextran sulfate sodium-induced colitis in mice

BACKGROUND

Endogenous carbon monoxide (CO) is one of the three products of heme degradation by heme oxygenase-1 (HO-1) and exerts novel anti-inflammatory and anti-apoptotic effects as a gaseous second messenger. The purpose of this investigation was to determine whether exogenous CO could modulate intestinal inflammation.

METHODS

Acute colitis was induced with 2% DSS in male C57BL/6 mice. CO-releasing molecule-2 (CORM-2; tricarbonyldichlororuthenium(II) dimer) was intraperitoneally administered twice daily and the disease activity index (DAI) was determined. We measured tissue-associated myeloperoxidase (MPO) activity as an index of neutrophil infiltration, and the production of keratinocyte chemoattractant (KC) and tumor necrosis factor-α (TNF-α) protein in the intestinal mucosa. In an in-vitro study, young adult mouse colonic epithelial (YAMC) cells were incubated with TNF-α, and KC mRNA/protein expression and nuclear translocation of nuclear factor-kappa B (NF-κB) were measured with or without CORM-2 treatment.

RESULTS

After DSS administration, DAI score increased in a time-dependent manner, and this increase was ameliorated by CORM-2 treatment. Increases in MPO activity and in the production of KC and TNF-α after DSS administration were significantly inhibited by CORM-2. TNF-α-induced KC production in YAMC cells was also inhibited by CORM-2 treatment. Further, nuclear translocation of NF-κB in YAMC cells was inhibited by CORM-2.

CONCLUSION

CORM-liberated CO significantly inhibited inflammatory response in murine colitis by inhibition of cytokine production in the colonic epithelium. These results suggest that CO could become a new therapeutic molecule for inflammatory bowel disease.

Organ Preservation: Current Concepts and New Strategies for the Next Decade

SUMMARY: Organ transplantation has developed over the past 50 years to reach the sophisticated and integrated clinical service of today through several advances in science. One of the most important of these has been the ability to apply organ preservation protocols to deliver donor organs of high quality, via a network of organ exchange to match the most suitable recipient patient to the best available organ, capable of rapid resumption of life-sustaining function in the recipient patient. This has only been possible by amassing a good understanding of the potential effects of hypoxic injury on donated organs, and how to prevent these by applying organ preservation. This review sets out the history of organ preservation, how applications of hypothermia have become central to the process, and what the current status is for the range of solid organs commonly transplanted. The science of organ preservation is constantly being updated with new knowledge and ideas, and the review also discusses what innovations are coming close to clinical reality to meet the growing demands for high quality organs in transplantation over the next few years.

The role of heme oxygenase and carbon monoxide in inflammatory bowel disease

Inflammatory bowel disease (IBD), including ulcerative colitis (UC) and Crohn's disease, is a chronic and recurrent inflammatory disorder of the intestinal tract. Since the precise pathogenesis of IBD remains unclear, it is important to investigate the pathogenesis of IBD and to evaluate new anti-inflammatory strategies. Recent evidence suggests that heme oxygenase-1 (HO-1) plays a critical protective role during the development of intestinal inflammation. In fact, it has been demonstrated that the activation of HO-1 may act as an endogenous defensive mechanism to reduce inflammation and tissue injury in various animal intestinal injury models induced by ischemia-reperfusion, indomethacin, lipopolysaccharide-associated sepsis, trinitrobenzene sulfonic acid or dextran sulfate sodium. In addition, carbon monoxide (CO) derived from HO-1 has been shown to be involved in the regulation of intestinal inflammation. Furthermore, administration of a low concentration of exogenous CO has a protective effect against intestinal inflammation. These data suggest that HO-1 and CO may be novel therapeutic molecules for patients with gastrointestinal inflammatory diseases. In this review, we present what is currently known regarding the role of HO-1 and CO in intestinal inflammation.

Immunoregulatory properties of heme oxygenase-1

Heme oxygenase-1 (HO-1) is one of the three isoforms of the heme oxygenase enzyme that catabolyzes the degradation of heme into biliverdin with the production of free iron and CO. HO-1 is induced by its substrate and by other stimuli, including agents involved in oxidative stress and proinflammatory cytokines as well as several anti-inflammatory stimuli. A growing body of evidence points toward the capacity of this molecule to inhibit immune reactions and the pivotal role of HO-1 in inflammatory diseases. We will first review the physiological role of HO-1 as determined by the analysis of HO-1-deficient individuals. This will be followed by an examination of the effect of HO-1 within immunopathological contexts such as immune disorders (autoimmunity and allergy) or infections. A section will be devoted to the use of an HO-1 inducer as an immunosuppressive molecule in transplantation. Finally, we will review the molecular basis of HO-1 actions on different immune cells.

Insulin like growth factor-1 increases fatty liver preservation in IGL-1 solution

AIM

To investigate the benefits of insulin like growth factor-1 (IGF-1) supplementation to serum-free institut georges lopez-1 (IGL-1) solution to protect fatty liver against cold ischemia reperfusion injury.

METHODS

Steatotic livers were preserved for 24 h in IGL-1 solution supplemented with or without IGF-1 and then perfused "ex vivo" for 2 h at 37degrees C. We examined the effects of IGF-1 on hepatic damage and function (transaminases, percentage of sulfobromophthalein clearance in bile and vascular resistance). We also studied other factors associated with the poor tolerance of fatty livers to cold ischemia reperfusion injury such as mitochondrial damage, oxidative stress, nitric oxide, tumor necrosis factor-α (TNF-α) and mitogen-activated protein kinases.

RESULTS

Steatotic livers preserved in IGL-1 solution supplemented with IGF-1 showed lower transaminase levels, increased bile clearance and a reduction in vascular resistance when compared to those preserved in IGL-1 solution alone. These benefits are mediated by activation of AKT and constitutive endothelial nitric oxide synthase (eNOS), as well as the inhibition of inflammatory cytokines such as TNF-α. Mitochondrial damage and oxidative stress were also prevented.

CONCLUSION

IGL-1 enrichment with IGF-1 increased fatty liver graft preservation through AKT and eNOS activation, and prevented TNF-α release during normothermic reperfusion.

Inhalation of carbon monoxide ameliorates TNBS-induced colitis in mice through the inhibition of TNF-α expression

BACKGROUND

Carbon monoxide (CO), long considered a toxic gas, has recently been shown to mediate anti-inflammatory effects in various animal models. The aim of this study was to investigate whether the inhalation of CO ameliorated 2,4,6-trinitrobenzine sulfonic acid (TNBS)-induced colitis in mice.

METHODS

The CO treatment group was exposed to CO gas at a concentration of 200 ppm in a closed cage starting on the day when TNBS was administered and throughout the remaining study period. The distal colon was removed, and ulcerative lesions were subsequently evaluated with macroscopic damage scores. Furthermore, thiobarbituric acid (TBA)-reactive substances and tissue-associated myeloperoxidase (MPO) activity in colonic mucosa were measured as indices of lipid peroxidation and neutrophil infiltration. The expressions of TNF-α in colonic mucosa were also measured by enzyme-linked immunosorbent assay. In additional experiments in vitro, CD4(+) T cells isolated from the spleen were stimulated with anti-CD3/CD28 Ab, and the cells and supernatants were collected and evaluated for TNF-α expression.

RESULTS

The increased colonic damage after TNBS administration was significantly inhibited by the treatment with CO. Furthermore, CO significantly inhibited the increases in TBA-reactive substances, MPO activity and TNF-α production in colonic mucosa after the induction of TNBS colitis. In CD4(+) T cells isolated from mice treated with CO inhalation, the production of TNF-α was significantly inhibited.

CONCLUSIONS

The inhalation of CO protected mice from developing intestinal inflammation. Based on these data, the beneficial effects of CO in a murine colitis model may be attributed to its anti-inflammatory properties.

Differential changes in MAP kinases, histone modifications, and liver injury in rats acutely treated with ethanol

BACKGROUND

Acute ethanol is known to affect cells and organs but the underlying molecular mechanisms are poorly explored. Recent developments highlight the potential importance of mitogen-activated protein kinases, MAPKs (i.e., ERK1/2, p38, and JNK1/2) signaling, and histone modifications (i.e., acetylation, methylation, and phosphorylation) in the actions of ethanol in hepatocytes. We have therefore investigated significance of these molecular steps in vivo using a model in which rats were acutely administered ethanol intraperitoneally (IP).

METHODS

Ethanol was administered IP (3.5 gm/kg body weight) to 12-week-old male Sprague-Dawley rats. Liver was subsequently removed at 1 and 4 hours. Serum was used for alcohol and ALT assays. At the time of the removal of liver, small portions of each liver were formalin-fixed and stained with hematoxylin and eosin (H&E) and used for light microscopy. Western blot analysis was carried out with specific primary antibodies for various parameters.

RESULTS

There were clear differences at 1 and 4 hours in blood ethanol, ALT, steatosis, and cleaved caspase 3. Apoptosis at 1 hour was followed by necrosis at 4 hours. Acute alcohol elicited a marked increase in the phosphorylation of ERK1/2 and moderate increases in the phosphorylation of p38 MAPK and JNK. Temporally different phosphorylation of histone H3 at ser-10 and ser-28 occurred and acetylation of histone H3 at lys 9 increased progressively.

CONCLUSIONS

There were distinct differences in the behavior of the activation of the 3 MAP kinases and histone modifications after acute short exposure of liver to ethanol in vivo. Although all 3 MAPKs were rapidly activated at 1 hour, the necrosis, occurring at 4 hours, correlated to sustained activation of ERK1/2. Transient activation of p38 is associated with rapid phosphorylation of histone H3, whereas prolonged activation of ERK1/2 is correlated to persistent histone H3 acetylation.

Carbon monoxide liberated from CO-releasing molecule (CORM-2) attenuates ischemia/reperfusion (I/R)-induced inflammation in the small intestine

CORM-released CO has been shown to be beneficial in resolution of acute inflammation. The acute phase of intestinal ischemia-reperfusion (I/R) injury is characterized by oxidative stress-related inflammation and leukocyte recruitment. In this study, we assessed the effects and potential mechanisms of CORM-2-released CO in modulation of inflammatory response in the small intestine following I/R-challenge. To this end mice (C57Bl/6) small intestine were challenged with ischemia by occluding superior mesenteric artery (SMA) for 45 min. CORM-2 (8 mg/kg; i.v.) was administered immediately before SMA occlusion. Sham operated mice were injected with vehicle (0.25% DMSO). Inflammatory response in the small intestine (jejunum) was assessed 4 h following reperfusion by measuring tissue levels of TNF-alpha protein (ELISA), adhesion molecules E-selectin and ICAM-1 (Western blot), NF-kappaB activation (EMSA), along with PMN tissue accumulation (MPO assay) and leukocyte rolling/adhesion in the microcirculation of jejunum (intravital microscopy). The obtained results indicate that tissue levels of TNF-alpha, E-selectin and ICAM-1 protein expression, activation of NF-kappaB, and subsequent accumulation of PMN were elevated in I/R-challenged jejunum. The above changes were significantly attenuated in CORM-2-treated mice. Taken together these findings indicate that CORM-2-released CO confers anti-inflammatory effects by interfering with NF-kappaB activation and subsequent up-regulation of vascular pro-adhesive phenotype in I/R-challenged small intestine.

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.

The protective role of pregnane X receptor in lipopolysaccharide/D-galactosamine-induced acute liver injury

The pregnane X receptor (PXR) is a nuclear receptor transcription factor regulating drug-metabolizing enzymes and transporters that facilitate xenobiotic and endobiotic detoxification. Recent studies show that PXR is important in abrogating intestinal tissue damage. This study examines the role of PXR in lipopolysaccharide (LPS)/D-galactosamine (GalN)-induced acute liver injury using wild-type and PXR-null mice. LPS/GalN-treated PXR-null mice had greater increases of alanine transaminase (ALT), hepatocyte apoptosis, necrosis, and hemorrhagic liver injury than wild-type mice. LPS/GalN-mediated phosphorylation of JNK1/2 and ERK1/2 was differentially regulated in wild-type and PXR-null mice. Importantly, LPS/GalN-induced hepatic Stat3 survival signaling was impaired and early activation of Jak2 was delayed in PXR-null mice. Expression levels of pro-survival proteins Bcl-xL and heme oxygenase-1 (HO-1), which are downstream of Stat3, were substantially lower in PXR-null than wild-type mouse livers after LPS/GalN treatment. Autophagy is also involved in LPS/GalN-induced liver injury. Lack of PXR resulted in a significant reduction of LC3B-I, -II as well as Beclin-1 protein levels after LPS/GalN treatment. In addition, PXR is implicated in hepatocytes homeostasis. Taken together, PXR is a critical hepatoprotective factor. Increases of LPS/GalN-induced hepatocyte apoptosis and liver injury in PXR-null mice are due to deregulated mitogen-activated protein (MAP) kinase activation as well as delayed Jak2/Stat3 activation, which lead to a compromise in defense mechanisms that involve Bcl-xL-, HO-1, and autophagy-mediated pathways.

Liver graft exposure to carbon monoxide during cold storage protects sinusoidal endothelial cells and ameliorates reperfusion injury in rats

Hepatic ischemia/reperfusion (I/R) injury significantly influences short-term and long-term outcomes after liver transplantation (LTx). The critical step initiating the injury is known to include sinusoidal endothelial cell (SEC) alteration during the cold preservation period. As carbon monoxide (CO) has potent cytoprotective functions on vascular endothelial cells, this study examined if CO treatment of excised liver grafts during cold storage could protect SECs and ameliorate hepatic I/R injury. Rat liver grafts were preserved in University of Wisconsin (UW) solution containing 5% CO (CO-UW solution) for 18 to 24 hours and were transplanted into syngeneic Lewis rats. After 18 hours of cold preservation, SEC damage was evident with propidium iodide (PI) nuclear staining on SECs, and the frequency of PI(+) SECs was significantly lower in grafts stored in CO-UW solution versus those stored in control UW solution. SEC protection with CO was associated with decreased intercellular cell adhesion molecule translocation and less matrix metalloproteinase release during cold preservation. After LTx with 18 hours of cold preservation, serum alanine aminotransferase levels and hepatic necrosis were significantly less in the CO-UW group than in the control UW group. With 24 hours of cold storage, 35% (7/20) survived with control UW solution, whereas the survival with CO-UW solution improved to 80% (8/10). These beneficial effects of CO-UW solution were associated with a significant reduction of neutrophil extravasation, down-regulation of hepatic messenger RNA for tumor necrosis factor alpha and intercellular cell adhesion molecule 1, and less hepatic extracellular signal-regulated kinase activation. Liver grafts from Kupffer cell-depleted donors or pseudogerm-free donors showed less SEC death during cold preservation, and CO-UW solution further reduced SEC death. In conclusion, CO delivery to excised liver grafts during cold preservation efficiently ameliorates SEC damage and hepatic I/R injury.

Protective effects of a carbon monoxide-releasing molecule (CORM-3) during hepatic cold preservation

There is increasing evidence that carbon monoxide (CO), a signaling molecule generated during the degradation of heme by heme oxygenase-1 (HO-1) in biological systems, has a variety of cytoprotective actions, including anti-hypoxic effects at low temperatures. However, during liver cold preservation, a direct effect needs to be established. Here, we designed a study to analyze the role of CO, delivered via a carbon monoxide-releasing molecule (CO-RM) in the maintenance of liver function, and integrity in rats during cold ischemia/reperfusion (CI/R) injury. We used an isolated normothermic perfused liver system (INPL) following a clinically relevant model of ex vivo 48 h cold ischemia stored in a modified University of Wisconsin (UW) solution, to determine the specific effects of CO in a rat model. CO was generated from 50 microM tricarbonylchloro ruthenium-glycinato (CORM-3), a water-soluble transition metal carbonyl that exerts pharmacological activities via the liberation of controlled amounts of CO in biological systems. The physiological effects of CORM-3 were confirmed by the parallel use of a specific inactive compound (iCORM-3), which does not liberate CO in the cellular environment. CORM-3 addition was found to prevent the injury caused by cold storage by improving significantly the perfusion flow during reperfusion (by almost 90%), and by decreasing the intrahepatic resistance (by 88%) when compared with livers cold preserved in UW alone. Also, CORM-3 supplementation preserved good metabolic capacity as indicated by hepatic oxygen consumption, glycogen content, and release of lactate dehydrogenase. Liver histology was also partially preserved by CORM-3 treatment.

CONCLUSIONS

These findings suggest that CO-RM could be utilized as adjuvant therapeutics in UW solutions to limit the injury sustained by donor livers during cold storage prior to transplantation, as has been similarly proposed for the heart, and kidney.

Bench-to-bedside review: Carbon monoxide--from mitochondrial poisoning to therapeutic use

Carbon monoxide (CO) is generated during incomplete combustion of carbon-containing compounds and leads to acute and chronic toxicity in animals and humans depending on the concentration and exposure time. In addition to exogenous sources, CO is also produced endogenously by the activity of heme oxygenases (HOs) and the physiological significance of HO-derived CO has only recently emerged. CO exerts vasoactive, anti-proliferative, anti-oxidant, anti-inflammatory and anti-apoptotic effects and contributes substantially to the important role of the inducible isoform HO-1 as a mediator of tissue protection and host defense. Exogenous application of low doses of gaseous CO might provide a powerful tool to protect organs and tissues under various stress conditions. Experimental evidence strongly suggests a beneficial effect under pathophysiological conditions such as organ transplantation, ischemia/reperfusion, inflammation, sepsis, or shock states. The cellular and molecular mechanisms mediating CO effects are only partially characterized. So far, only a few studies in humans are available, which, however, do not support the promising results observed in experimental studies. The protective effects of exogenous CO may strongly depend on the pathological condition, the mode, time point and duration of application, the administered concentration, and on the target tissue and cell. Differences in bioavailability of endogenous CO production and exogenous CO supplementation might also provide an explanation for the lack of protective effects observed in some experimental and clinical studies. Further randomized, controlled clinical studies are needed to clarify whether exogenous application of CO may turn into a safe and effective preventive and therapeutic strategy to treat pathophysiological conditions associated with inflammatory or oxidative stress.

Impaired liver regeneration with humoral and genetic disturbances in urinary trypsin inhibitor-deficient mice

BACKGROUND/AIMS

Urinary trypsin inhibitor (UTI) is an innate anti-inflammatory regulator. It can block the release of inflammatory factors, prevent the cascade reaction of cytokines and inhibit excessive activation of leukocytes. Liver regeneration (LR) is a dynamic molecular phenomenon without inflammation. Many cytokines, including tumour necrosis factor-alpha (TNF-alpha) and interleukin-6 (IL-6), have been implicated in regulating LR. However, the role of UTI in LR is totally unknown. The aim of this study was to elucidate the role of UTI in LR using genetically UTI-deficient mice.

METHODS

We performed 68% hepatectomy, comparing UTI (-/-) and UTI (+/+) mice. Recovery of liver weight was recorded and we calculated labelling indices after 5-bromo-2'-deoxyuridine (BrdU) immunohistochemistry. A DNA microarray was used to examine gene expression followed by real-time polymerase chain reaction. Serum IL-6, IL-10, monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-1beta (MIP-1beta) were measured.

RESULTS

LR in UTI (-/-) mice was delayed at 36 h after hepatectomy, at which time the DNA profile was different. One hundred and fourteen genes were upregulated and 100 genes were downregulated in UTI (-/-) mice at 36 h after hepatectomy among the 21, 977 mRNAs examined. Furthermore, serum IL-6, IL-10, MCP-1 and MIP-1beta levels at 36 h after hepatectomy in the UTI (-/-) mice were significantly higher than in the UTI (+/+) mice.

CONCLUSION

UTI appears to important cytokine and chemokine regulation in normal liver regeneration.

Inhibition of Kupffer cell-mediated early proinflammatory response with carbon monoxide in transplant-induced hepatic ischemia/reperfusion injury in rats

Proinflammatory responses play critical roles in hepatic ischemia/reperfusion (I/R) injury associating with liver transplantation (LTx), and carbon monoxide (CO) can effectively down-regulate them. Using wild-type (WT) to enhanced green fluorescent protein (EGFP)-transgenic rat LTx with 18-hour cold preservation in University of Wisconsin solution, this study analyzed the relative contribution of donor and host cells during early posttransplantation period and elucidated the mechanism of hepatic protection by CO. CO inhibited hepatic I/R injury and reduced peak alanine aminotransferase levels at 24 hours and hepatic necrosis at 48 hours. Abundant EGFP(+) host cells were found in untreated WT liver grafts at 1 hour and included nucleated CD45(+) leukocytes (myeloid, T, B, and natural killer cells) and EGFP(+) platelet-like depositions in the sinusoids. However, reverse transcription polymerase chain reaction (RT-PCR) analysis of isolated graft nonparenchymal cells (NPCs) revealed that I/R injury-induced proinflammatory mediators [for example, tumor necrosis factor alpha (TNF-alpha), interleukin-6 (IL-6), and inducible nitric oxide synthase (iNOS)] were not up-regulated in purified CD45(+) cells of donor or host origin. Instead, TNF-alpha and IL-6 messenger RNA (mRNA) elevation was exclusively seen in isolated CD68(+) cells, whereas iNOS mRNA up-regulation was seen in hepatocytes. Nearly all CD68(+) cells at 1 hour after LTx were EGFP(-) donor Kupffer cells, and CO efficiently inhibited TNF-alpha and IL-6 up-regulation in the CD68(+) Kupffer cell fraction. When graft Kupffer cells were inactivated with gadolinium chloride, activation of inflammatory mediators in liver grafts was significantly inhibited. Furthermore, in vitro rat primary Kupffer cell culture also showed significant down-regulation of lipopolysaccharide (LPS)-induced inflammatory responses by CO.

CONCLUSION

These results indicate that CO ameliorates hepatic I/R injury by down-regulating graft Kupffer cells in early postreperfusion period. The study also suggests that different cell populations play diverse roles by up-regulating distinctive sets of mediators in the acute phase of hepatic I/R injury.

Natural heme oxygenase-1 inducers in hepatobiliary function

Many physiological effects of natural antioxidants, their extracts or their major active components, have been reported in recent decades. Most of these compounds are characterized by a phenolic structure, similar to that of alpha-tocopherol, and present antioxidant properties that have been demonstrated both in vitro and in vivo. Polyphenols may increase the capacity of endogenous antioxidant defences and modulate the cellular redox state. Changes in the cellular redox state may have wide-ranging consequences for cellular growth and differentiation. The majority of in vitro and in vivo studies conducted so far have attributed the protective effect of bioactive polyphenols to their chemical reactivity toward free radicals and their capacity to prevent the oxidation of important intracellular components. However, in recent years a possible novel aspect in the mode of action of these compounds has been suggested; that is, the ultimate stimulation of the heme oxygenase-1 (HO-1) pathway is likely to account for the established and powerful antioxidant/anti-inflammatory properties of these polyphenols. The products of the HO-catalyzed reaction, particularly carbon monoxide (CO) and biliverdin/bilirubin have been shown to exert protective effects in several organs against oxidative and other noxious stimuli. In this context, it is interesting to note that induction of HO-1 expression by means of natural compounds contributes to protection against liver damage in various experimental models. The focus of this review is on the significance of targeted induction of HO-1 as a potential therapeutic strategy to protect the liver against various stressors in several pathological conditions.