Activation pattern of mitogen-activated protein kinases in early phase of different size liver isografts in rats

Effects of SP600125 and hypothermic machine perfusion on livers donated after cardiac death in a pig allograft transplantation model

BACKGROUND

Hypothermic machine perfusion (HMP) improves the quality of donor livers for transplantation, both in animal models and in clinical practice. Treatment with SP600125, an inhibitor of c-Jun N-terminal kinase (JNK), can suppress the JNK signaling pathway to alleviate donor liver ischemia-reperfusion injury (IRI). We performed the present study with the objective of exploring the protective effects exerted by a combination of HMP and SP600125 on liver xenograft viability for donation after cardiac death (DCD) in a porcine model.

METHODS

54 adult BAMA mini-pigs were randomly assigned to 5 groups, including sham, cold storage for 4 h (CS 4 h), CS 4 h + SP600125, CS 2 h + HMP 2 h, and CS 2 h + HMP 2 h + SP600125 groups. Donor livers in the CS 4 h and CS 4 h + SP600125 groups were conventionally cold preserved for 4 h, whereas donor livers in the CS 2 h + HMP 2 h and CS 2 h + HMP 2 h + SP600125 groups were cold preserved for 2 h and then treated with HMP for 2 h. The preservation and perfusion solutions contained SP600125 (20 µM). Follow-up was conducted for 5 days after liver transplantation to compare the surgical outcomes by means of serological examination, pathological results, and survival rate.

RESULTS

The most satisfactory outcome after liver transplantation was observed in the CS 2 h + HMP 2 h + SP600125 group, which presented with minimal damage of donor livers during 5 days' follow-up. Additionally, serological examination, pathological results, and survival rate concurred in showing better results in the CS 2 h + HMP 2 h ± SP600125 group than in the CS 4 h ± SP600125 group.

CONCLUSION

HMP in combination with SP600125 has hepatoprotective properties and improves the quality and viability of porcine livers collected after DCD, thus improving prognosis after liver transplantation.

Mitogen Activated Protein Kinases in Steatotic and Non-Steatotic Livers Submitted to Ischemia-Reperfusion

We analyzed the participation of mitogen-activated protein kinases (MAPKs), namely p38, JNK and ERK 1/2 in steatotic and non-steatotic livers undergoing ischemia-reperfusion (I-R), an unresolved problem in clinical practice. Hepatic steatosis is a major risk factor in liver surgery because these types of liver tolerate poorly to I-R injury. Also, a further increase in the prevalence of steatosis in liver surgery is to be expected. The possible therapies based on MAPK regulation aimed at reducing hepatic I-R injury will be discussed. Moreover, we reviewed the relevance of MAPK in ischemic preconditioning (PC) and evaluated whether MAPK regulators could mimic its benefits. Clinical studies indicated that this surgical strategy could be appropriate for liver surgery in both steatotic and non-steatotic livers undergoing I-R. The data presented herein suggest that further investigations are required to elucidate more extensively the mechanisms by which these kinases work in hepatic I-R. Also, further researchers based in the development of drugs that regulate MAPKs selectively are required before such approaches can be translated into clinical liver surgery.

Bilirubin rinse of the graft ameliorates ischemia reperfusion injury in heart transplantation

Ischemia and reperfusion contribute to substantial organ damage in transplantation. Clinically feasible measures for the prevention thereof are scarce. We tested whether rinsing rodent hearts with the antioxidant bilirubin ameliorates ischemia reperfusion injury (IRI). Left ventricular end-diastolic pressure (LVEDP), left ventricular developed pressure (LVDevP), rate per pressure product (RPP), coronary flow, maximum (+dP/dt) and minimum (-dP/dt) rate of contraction were analyzed in Lewis rat hearts rinsed with bilirubin prior to reperfusion on a Langendorff apparatus after 12 h of cold ischemia. In vivo, isogenic C57Bl/6 mouse hearts rinsed with bilirubin were transplanted after 12 h of cold ischemia. Cardiac function and apoptosis were assessed 24 h after reperfusion. Heart lysates recovered 15 min after reperfusion were probed for the total and the phosphorylated forms of extracellular signal-related protein kinases (ERK), JNK, p38-MAPK, and Akt. In isolated perfused hearts, bilirubin rinse resulted in significantly lower LVEDP and improved LVDevP, RPP, coronary flow, +dP/dt and -dP/dt. In vivo, after reperfusion, all mitogen-activated protein kinases (MAPKs) were suppressed significantly by bilirubin pretreatment. Bilirubin rinse improved cardiac scores (3.4 ± 0.5 vs. 2.0 ± 1.0 in controls, P < 0.05) and significantly suppressed apoptosis. Ex vivo administration of bilirubin to heart grafts prior reperfusion ameliorates IRI and provides a simple and effective tool to ameliorate outcome in heart transplantation.

The roles of aerobic exercise training and suppression IL-6 gene expression by RNA interference in the development of insulin resistance

OBJECTIVE

To demonstrate the hypothesis that aerobic exercise training inhibits the development of insulin resistance through IL-6 and probe into the possible molecular mechanism about it.

METHODS

Rats were raised with high-fat diets for 8 weeks to develop insulin resistance, and glucose infusion rates (GIRs) were determined by hyperinsulinemic-euglycemic clamping to confirm the development of insulin resistance. Aerobic exercise training (the speed and duration time in the first week were respectively 16 m/min and 50 min, and speed increased 1m/min and duration time increased 5 min every week following it) and/or IL-6shRNA plasmid injection (rats received IL-6shRNA injection via the tail vein every two weeks) were adopted during the development of insulin resistance. The serum IL-6, leptin, adiponectin, fasting blood glucose, fasting serum insulin, GIR, IL-6 gene expression levels, p-p38 in various tissues and p-STAT3/t-STAT3 ratio in the liver were measured.

RESULTS

Rats fed with high-fat diets for 8 weeks were developed insulin resistance and the IL-6mRNA levels of IL-6shRNA injection groups in various tissues were significantly lower than those of control group (P<0.05), respectively. The development of insulin resistance in exercise rats significantly decreased, however, compared with that, the GIR of exercise rats injected by IL-6shRNA was lower (P<0.05). The IL-6mRNA levels were highest in the fat tissue and lowest in the skeletal muscles in all the rats. The serum adiponectin levels decreased (P<0.05) following the development of insulin resistance, and it increased (P<0.05) when the rats were intervened by aerobic exercise training for 8 weeks at the same time. However, there were not significant differences when serum leptin concentrations were compared (P>0.05). The p-p38 significantly increased in the rats fed with high-fat diets, however, p-p38 of the exercise high-fat diets rats in the liver and fat tissues significantly decreased than that (P<0.05). The changes of p-p38 in exercise rats injected by IL-6shRNA were irregular. The activation of STAT3 in the liver significantly increased (P<0.05) following the development of insulin resistance, and it decreased (P<0.05) when the rats were intervened by aerobic exercise training for 8 weeks at the same time, and the gene silencing of IL-6 did not have effects on the activation of STAT3 in the liver (P>0.05).

CONCLUSIONS

In conclusion, aerobic exercise training prevented the development of insulin resistance through IL-6 to a certain degree. The gene expression and secretion of IL-6 could inhibit the development of insulin resistance. The mechanism of the effects were possibly related with elevating the levels of serum adiponectin, and/or inhibiting the activation of STAT3 in the liver and p38MAPK in the skeletal muscles, liver and fat tissues.

Cardiotrophin-1 reduces ischemia/reperfusion injury during liver transplant

BACKGROUND

Orthotopic liver transplantation (OLT) is currently the elective treatment for advanced liver cirrhosis and acute liver failure. Ischemia/reperfusion damage may jeopardize graft function during the postoperative period. Cardiotrophin-1 (CT-1) has demonstrated cytoprotective properties in different experimental models of liver injury. There is no evidence to demonstrate its potential use in the prevention of the ischemia/reperfusion injury that occurs during OLT. The present study is the first report to show that the administration of CT-1 to donors would benefit the outcome of OLT.

MATERIALS AND METHODS

We tested the cytoprotective effect of CT-1 administered to the donor prior to OLT in an experimental pig model. Hemodynamic changes, hepatic histology, cell death parameters, activation of cell signaling pathways, oxidative and nitrosative stress, and animal survival were analyzed.

RESULTS

Our data showed that CT-1 administration to donors increased animal survival, improved cardiac and respiratory functions, and reduced hepatocellular injury as well as oxidative and nitrosative stress. These beneficial effects, related to the activation of AKT, ERK, and STAT3, reduced caspase-3 activity and diminished IL-1β and TNF-α expression together with IL-6 upregulation in liver tissue.

CONCLUSIONS

The administration of CT-1 to donors reduced ischemia/reperfusion injury and improved survival in an experimental pig model of OLT.

Decreased expression of hepatic signaling phosphoproteins after laparoscopic and hand-assisted surgery in a porcine model

OBJECTIVE

Minimally-invasive surgery (MIS) is associated with a decreased activation of both systemic and peritoneal immunity compared with the open technique. However, hepatic response to laparoscopic (LAP) and hand-assisted laparoscopic (HAL) surgery has not been defined well. We postulated that both LAP and HAL approaches are associated with a diminished activation of hepatic inflammatory signaling pathways compared with the traditional open surgery.

MATERIALS AND METHODS

Eighteen pigs underwent a transabdominal nephrectomy via Open, HAL, or LAP approach. Liver samples were obtained 24 h postoperatively and spot frozen. Frozen tissue samples were then homogenized and the nuclear pellets were separated and stored. Nuclear extracts were analyzed for activation of three nuclear signaling phosphoproteins: nuclear factor-kappaB (NFκB)-p65, heat-shock protein 27 (HSP27), and p38 mitogen-activated protein kinases (p38MAPK) using a standard Bioplex technique. Statistical comparison was performed using ANOVA and Student's t-test.

RESULTS

The average expression of HSP27 was significantly higher in the Open versus either the LAP or the HAL groups (P = 0.028 and P = 0.039). The average expression of NFκB-p65 was significantly higher in the Open versus either the LAP or the HAL groups (P = 0.032 and P = 0.049). The average expression of p38MAPK was significantly higher in the Open versus either the LAP or the HAL groups (P = 0.007 and P = 0.036). There was no significant difference in the expressions of HSP27 and NFκB-p65 between LAP and HAL groups (P = 0.38 and P = 0.20), however, detection of p38MAPK generated statistical difference between these two groups (P = 0.018).

CONCLUSION

Hand-assisted laparoscopic surgery has been widely accepted as an effective alternative to traditional laparoscopic procedures. We demonstrated that both laparoscopic and hand-assisted approaches resulted in blunted hepatic stress manifested by diminished expression of hepatic HSP27, NFκB, and p38-MAPK. In addition, the hand-assisted approach was equal to the laparoscopic approach in two of the three phosphoproteins studied. It appears that the use of hand-assisted techniques did not abrogate immunologic benefits of pure laparoscopy. Overall, in addition to the clinical benefits of minimal access, both hand-assisted and pure laparoscopic techniques may also confer an immunologic advantage over laparotomy.

Role of hepatic stellate cells on graft injury after small-for-size liver transplantation

BACKGROUND AND AIM

Small-for-size grafts are prone to mechanical injury and a series of chemical injuries that are related to hemodynamic force. Hepatic stellate cells activate and trans-differentiate into contractile myofibroblast-like cells during liver injury. However, the role of hepatic stellate cells on sinusoidal microcirculation is unknown with small-for-size grafts.

METHODS

Thirty-five percent of small-for-size liver transplantation was performed with rats as donors and recipients. Endothelin-1 levels as well as hepatic stellate cells activation-related protein expression, endothelin-1 receptors, and ultrastructural changes were examined. The cellular localizations of two types of endothelin-1 receptors were detected. Furthermore, liver function and sinusoidal microcirculation were analyzed using two different selective antagonists of endothelin-1 receptor.

RESULTS

Intragraft expression of hepatic stellate cells activation-related protein such as desmin, crystallin-B and smooth muscle α-actin was upregulated as well as serum endothelin-1 levels and intragraft expression of the two endothelin receptors. The antagonist to endothelin-1 A receptor not to the endothelin-1 B receptor could attenuate microcirculatory disturbance and improve liver function.

CONCLUSIONS

Small-for-size liver transplantation displayed increased hepatic stellate cells activation and high level of endothelin-1 binding to upregulation of endothelin-1 A receptor on hepatic stellate cells, which contracted hepatic sinusoid inducing graft injury manifested as reduction of sinusoidal perfusion rate and elevation of sinusoidal blood flow.

Matrix metalloproteinase 2 in reduced-size liver transplantation: beyond the matrix

We studied the contribution of matrix metalloproteinase 2 (MMP2) and matrix metalloproteinase 9 (MMP9) to the beneficial effects of preconditioning (PC) in reduced-size orthotopic liver transplantation (ROLT). We also examined the role of c-Jun N-terminal kinase (JNK) and whether it regulates MMP2 in these conditions. Animals were subjected to ROLT with or without PC and pharmacological modulation, and liver tissue samples were then analyzed. We found that MMP2, but notMMP9, is involved in the beneficial effects of PC in ROLT. MMP2 reduced hepatic injury and enhanced liver regeneration. Moreover, inhibition of MMP2 in PC reduced animal survival after transplantation. JNK inhibition in the PC group decreased hepatic injury and enhanced liver regeneration. Furthermore, JNK upregulated MMP2 in PC. In addition, we showed that Tissue inhibitors of matrix metalloproteinases 2 (TIMP2) was also upregulated in PC and that JNK modulation also altered its levels in ROLT and PC. Our results open up new possibilities for therapeutic treatments to reduce I/R injury and increase liver regeneration after ROLT, which are the main limitations in living-donor transplantation.

Sinusoidal microcirculatory changes after small-for-size liver transplantation in rats

Small-for-size graft injury is characterized by portal venous hypertension and loss of intracellular homeostasis early after transplant. The long-term alteration of sinusoidal microcirculatory hemodynamic state remains unknown. A syngeneic rat orthotopic liver transplantation model was developed using small-for-size grafts (35% of recipient liver weight) or whole grafts (100% of recipient liver weight). Graft survival, portal pressure, liver function, hepatocellular apoptosis as well as morphological changes (by light microscopy and electron microscopy) were assessed. Sinusoidal microcirculatory hemodynamics was examined by intravital fluorescence microscopy. Although portal hypertension lasted only for 1 h after performance of small-for-size liver transplantation, a sustained microcirculatory disturbance was accompanied by dramatic reduction of sinusoidal perfusion rate, elevation of sinusoidal diameter as well as increase in the number of apoptotic hepatocytes during the first 7 days. These resulted in lower survival rate (50% vs. 100%, P = 0.012), higher level of liver function, and more severe morphological changes, which could induce small-for-size syndrome. In conclusion, persistent microcirculatory hemodynamic derangement during the first 7 days after reperfusion as well as transient portal hypertension is significant manifestation after small-for-size liver transplantation. Long-term microcirculation disturbance displayed as decrease of sinusoidal reperfusion area and increase of spread in functional liver mass seems to be the key factor for graft injuries.

The cytoprotective effects of addition of activated protein C into preservation solution on small-for-size grafts in rats

Small-for-size liver grafts are a serious obstacle for partial orthotopic liver transplantation. Activated protein C (APC), a potent anticoagulant serine protease, is known to have cell-protective properties due to its anti-inflammatory and antiapoptotic activities. This study was designed to examine the cytoprotective effects of a preservation solution containing APC on small-for-size liver grafts, with special attention paid to ischemia-reperfusion injury and shear stress in rats. APC exerted cytoprotective effects, as evidenced by (1) increased 7-day graft survival; (2) decreased initial portal pressure and improved hepatic microcirculation; (3) decreased levels of aminotransferase and improved histological features of hepatic ischemia-reperfusion injury; (4) suppressed infiltration of neutrophils and monocytes/macrophages; (5) reduced hepatic expression of tumor necrosis factor alpha and interleukin 6; (6) decreased serum levels of hyaluronic acid, which indicated attenuation of sinusoidal endothelial cell injury; (7) increased hepatic levels of nitric oxide via up-regulated hepatic endothelial nitric oxide synthesis expression together with down-regulated hepatic inducible nitric oxide synthase expression; (8) decreased hepatic levels of endothelin 1; and (9) reduced hepatocellular apoptosis by down-regulated caspase-8 and caspase-3 activities. These results suggest that a preservation solution containing APC is a potential novel and safe product for small-for-size liver transplantation, alleviating graft injury via anti-inflammatory and antiapoptotic effects and vasorelaxing conditions.

Hepatic regenerative response in small-sized liver isografts in the rat

BACKGROUND

To investigate hepatic regenerative response and associated mechanisms in different-size liver grafts in the rat.

METHODS

Rat models of different-size-graft liver transplantation (whole, 50%-size, or 30%-size) were established, with a sham operation group serving as a control. Portal pressure, graft injury, interleukin 6 (IL-6), signal transducer and activator of transcription (Stat3), mitogen-activated protein kinase (MAPK), cyclin D1, and proliferating cell nuclear antigen (PCNA) were all assessed.

RESULTS

The portal pressure was significantly higher and hepatic injury more severe in the smaller sized groups than in the whole graft group, especially in the 30%-size grafts. Hepatic IL-6 and tumor necrosis factor-alpha (TNF-alpha) levels in the two smaller sized groups were significantly higher than in the whole graft group, while IL-6 levels appeared to be negatively associated with graft sizes. Downstream markers of IL-6, Stat3 and MAPK phosphorylation, cyclin D1, and PCNA expression were also markedly increased in the small-sized grafts compared with the whole grafts, and appeared to positively correlate with early measurements of portal pressure and subsequent hepatic injury.

CONCLUSION

Vigorous hepatic regeneration in small-for-size liver grafts may be associated with highly activated IL-6/Stat3 and MAPK signaling, which may in turn correlate with graft size, portal pressure, and hepatic injury.

Therapeutic targets in liver transplantation: angiotensin II in nonsteatotic grafts and angiotensin-(1-7) in steatotic grafts

Numerous steatotic livers are discarded as unsuitable for transplantation because of their poor tolerance of ischemia-reperfusion(I/R). The injurious effects of angiotensin (Ang)-II and the benefits of Ang-(1-7) in various pathologies are well documented. We examined the generation of Ang II and Ang-(1-7) in steatotic and nonsteatotic liver grafts from Zucker rats following transplantation. We also studied in both liver grafts the effects of Ang-II receptors antagonists and Ang-(1-7) receptor antagonists on hepatic I/R damage associated with transplantation. Nonsteatotic grafts showed higher Ang II levels than steatotic grafts, whereas steatotic grafts showed higher Ang-(1-7) levels than nonsteatotic grafts. Ang II receptor antagonists protected only nonsteatotic grafts against damage, whereas Ang-(1-7) receptor antagonists were effective only in steatotic grafts. The protection conferred by Ang II receptor antagonists in nonsteatotic grafts was associated with ERK 1/2 overexpression, whereas the beneficial effects of Ang-(1-7) receptor antagonists in steatotic grafts may be mediated by NO inhibition. Our results show that Ang II receptor antagonists are effective only in nonsteatotic liver transplantation and point to a novel therapeutic target in liver transplantation based on Ang-(1-7), which is specific for steatotic liver grafts.

Overexpression of myocyte enhancer factor 2 and histone hyperacetylation in hepatocellular carcinoma

PURPOSE

It has been indicated that activated hepatic stellate cells (HSCs) play key roles on the pathogenesis of hepatocellular carcinoma (HCC). The purpose of the study was to investigate the potential mechanism in it.

METHODS

Activation of HSCs, the expression of myocyte enhancer factor 2 (MEF2), class II histone deacetylases (II HDACs) and histone acetylation were analyzed in specimens of primary HCCs, cirrhotic and normal livers. Activated HSCs were identified using anti-a-smooth muscle actin (a-SMA) by Immunohistochemistry (IHC). The levels of expression of MEF2A, MEF2C and II HDACs mRNA and protein were measured by real time quantitative PCR and western blot (WB). Histone acetylation was assessed using anti-acetyl-histone H3, -H4 by WB and IHC. A P value < 0.05 was considered statistically significant.

RESULTS

A-SMA positive activated HSCs were more prominent in HCCs and cirrhotic livers than in normal livers, accompanied by marked expression of MEF2A and MEF2C. The expression of MEF2A, MEF2C and II HDACs, both mRNA and protein, were much more enhanced in HCCs than those in cirrhotic and normal livers (P < 0.05). Histone H3 and H4 were hyperacetylated in HCCs compared with those in cirrhotic and normal livers (P < 0.05). The correlation coefficients between the expression of MEF2 and II HDACs, acetyl-histones were all beyond 0.5.

CONCLUSIONS

These data showed a potential molecular mechanism that activated HSCs participate in the pathogenesis of HCCs by overexpression of MEF2 and its consequent impact on histone hyperacetylation. Further investigations aimed at interfering MEF2 expression are needed.