Dynamic changes of post-ischemic hepatic microcirculation improved by a pre-treatment of phosphodiesterase-3 inhibitor, milrinone

Olprinone, a Selective Phosphodiesterase III Inhibitor, Has Protective Effects in a Septic Rat Model after Partial Hepatectomy and Primary Rat Hepatocyte

Olprinone (OLP) is a selective inhibitor of phosphodiesterase III and is used clinically in patients with heart failure and those undergoing cardiac surgery; however, little is known about the effects of OLP on hepatoprotection. The purpose of this study aimed to determine whether OLP has protective effects in in vivo and in vitro rat models of endotoxin-induced liver injury after hepatectomy and to clarify the mechanisms of action of OLP. In the in vivo model, rats underwent 70% partial hepatectomy and lipopolysaccharide treatment (PH/LPS). OLP administration increased survival by 85.7% and decreased tumor necrosis factor-α, C-X-C motif chemokine ligand 1, and inducible nitric oxide synthase (iNOS) mRNA expression in the livers of rats treated with PH/LPS. OLP also suppressed nuclear translocation and/or DNA binding ability of nuclear factor kappa B (NF-κB). Pathological liver damage induced by PH/LPS was alleviated and neutrophil infiltration was reduced by OLP. Primary cultured rat hepatocytes treated with the pro-inflammatory cytokine interleukin-1β (IL-1β) were used as a model of in vitro liver injury. Co-treatment with OLP inhibited dose-dependently IL-1β-stimulated iNOS induction and NF-κB activation. Our results demonstrate that OLP may partially inhibit the induction of several inflammatory mediators through the suppression of NF-κB and thus prevent liver injury induced by endotoxin after liver resection.

Milrinone is better choice for controlled low central venous pressure during hepatectomy: A randomized, controlled trial comparing with nitroglycerin

BACKGROUND

To explore the feasibility and effectiveness of controlled low central venous pressure(CLCVP)induced by milrinone during hepatectomy, and its influence on perioperative hemodynamics, blood loss and patients' recovery, comparing with the traditional method by nitroglycerin.

METHODS

52 patients who underwent elective open hepatectomy were enrolled in the study and randomly divided into two groups: milrinone (M) group and nitroglycerin (NG) group. Milrinone was infused with the rate of 0.5 μg/kg/min in group M, while nitroglycerin was given 0.2-0.5 μg/kg/min in group NG to maintain CVP≤ 5 mmHg during liver resection. The demographic variables, data of the operative procedure and intraoperative hemodynamics were recorded. The postoperative recovery profiles and pre- and post-operative haematological markers of vital organs were also collected and compared.

RESULTS

1. The blood loss of group M, no matter during liver resection or in the whole procedure, was both less than that of group NG (P < 0.05), so did the hemoglobin detected by blood gas analysis (P < 0.05). Meanwhile, time of hepatectomy and hepatic hilum occlusion were shorter in group M (P < 0.05). 2. Compared with the NG group, cardiac index (CI) and stroke volume index (SVR) were higher in group M in the operation. The norepinephrine dosage necessary in the operation was of no difference in two groups (P > 0.05). 3. Drainage indwelling time and postoperative hospital stay of group M were shorter than that of group NG (P < 0.05). Most of the blood biomarkers increased on postoperative day (POD)-1, and returned to the preoperative level on POD-7 without inter-group difference (P > 0.05). Brain natriuretic peptide precursor (Pro-BNP) in group M was higher than NG group on POD-1 (P < 0.05), and the statistical difference disappeared on POD-7.

CONCLUSION

Milrinone can effectively maintain a controlled low central venous pressure during hepatectomy. Compared with nitroglycerin, milrinone can reduce the amount of blood loss, with the benefit of better manifestation of hemodynamics and enhanced postoperative recovery.

Pretreatment with a Phosphodiesterase-3 Inhibitor, Milrinone, Reduces Hepatic Ischemia-Reperfusion Injury, Minimizing Pericentral Zone-Based Liver and Small Intestinal Injury in Rats

BACKGROUND Severe pericentral zone (zone 3)-based liver injury (LI) may become intractable, with allograft dysfunction after liver transplantation. The phosphodiesterase-3 inhibitor, milrinone, has been reported to attenuate hepatic ischemia-reperfusion injury (IRI). This study clarified how hepatic IRI involved zone 3-based LI, in which zone milrinone was effective, and whether milrinone could improve small intestinal injury (SII) with hepatic IRI. MATERIAL AND METHODS Rats were divided into sham, ischemia-reperfusion (IR), or IR+milrinone groups (n=13 per group). Milrinone was administered intraportally via intrasplenic injection, and whole hepatic ischemia was induced for 30 min. Five hours after reperfusion, serum chemistry and histopathological findings were compared. Expression of CD34 for the detection of altered sinusoidal endothelium as sinusoidal capillarization and cleaved caspase-3 as an apoptosis marker were analyzed via immunohistochemistry. Survival rates were examined after 45 min of whole hepatic ischemia. RESULTS Serum aspartate aminotransferase and direct bilirubin levels were significantly decreased in the IR+milrinone group compared with those of the IR group. The degree of LI, sinusoidal capillarization and apoptosis at zone 3 in the IR group was significantly increased compared with those at the periportal zone (zone 1). These findings at zone 3 in the IR group were improved in the IR+milrinone group. SII with villus congestion and apoptosis in the IR group was significantly attenuated in the IR+milrinone group. The 7-day survival rate was significantly elevated in the IR+milrinone group as compared with that of the IR group. CONCLUSIONS A hepatic IRI model caused zone 3-based LI and SII, which were attenuated by intraportal administration of milrinone.

Milrinone-Induced Pharmacological Preconditioning in Cardioprotection: Hints for a Role of Mitochondrial Mechanisms

The activation of mitochondrial calcium-sensitive potassium (mBK_Ca) channels is crucially involved in cardioprotection induced by preconditioning. For milrinone (Mil)-induced preconditioning, the involvement of mBK_Ca-channels and further mitochondrial signaling is unknown. We hypothesize that (1) Mil-induced preconditioning is concentration-dependent and (2) that the activation of mBK_Ca-channels, release of reactive oxygen species (ROS), and the mitochondrial permeability transition pore (mPTP) could be involved. Isolated hearts of male Wistar rats were perfused with Krebs-Henseleit buffer and underwent 33 min of ischemia followed by 60 min of reperfusion. For determination of a concentration-dependent effect of Mil, hearts were perfused with different concentrations of Mil (0.3–10 µM) over 10 min before ischemia. In a second set of experiments, in addition to controls, hearts were pretreated with the lowest protective concentration of 1 µM Mil either alone or combined with the mBK_Ca-channel blocker paxilline (Pax + Mil), or paxilline alone (Pax). In additional groups, Mil was administered with and without the ROS scavenger N-2-mercaptopropionylglycine (MPG + Mil, MPG) or the mPTP inhibitor cyclosporine A (MPG + Mil + CsA, CsA + Mil), respectively. Infarct sizes were determined by triphenyltetrazolium chloride (TTC) staining. The lowest and most cardioprotective concentration was 1 µM Mil (Mil 1: 32 ± 6%; p < 0.05 vs. Con: 63 ± 8% and Mil 0.3: 49 ± 6%). Pax and MPG blocked the infarct size reduction of Mil (Pax + Mil: 53 ± 6%, MPG + Mil: 59 ± 7%; p < 0.05 vs. Mil: 34 ± 6%) without having an effect on infarct size when administered alone (Pax: 53 ± 7%, MPG: 58 ± 5%; ns vs. Con). The combined administration of CsA completely restored the MPG-inhibited cardioprotection of Mil (MPG + Mil + CsA: 35 ± 7%, p < 0.05 vs. MPG + Mil). Milrinone concentration-dependently induces preconditioning. Cardioprotection is mediated by the activation of mBK_Ca-channels, release of ROS and mPTP inhibition.

Study on the clinical efficacy of specific phosphodiesterase inhibitor in patients with pulmonary hypertension due to left heart disease

Pulmonary hypertension due to left heart disease (PH-LHD) is caused by left ventricular (LV) systolic and/or diastolic dysfunction and left heart valve disease. LV diseases lead to left ventricular filling pressure increases, pulmonary venous obstruction and pulmonary venous pressure increases, and thus to secondary PH. Exercise tolerance is lower and fatality rates are higher in patients with PH-LHD than those in subjects with normal pulmonary arterial pressure. In spite of the progress in the study of the mechanisms of PH-LHD in recent years, no specific treatment is currently available. The efficacy and safety of targeted therapies for pulmonary arterial hypertension remain to be fully established. In the present study, PH-LHD patients were treated with milrinone injection. It was concluded that milrinone significantly reduces pulmonary artery systolic pressure (PASP) in patients with PH-LHD, and significantly improves the cardiac structure, cardiac function and biochemical indexes. PASP was significantly correlated with the left atrial diameter, LV end diastolic diameter, LV ejection fraction, tricuspid annular plane systolic excursion, right ventricular fractional area change, N-terminal pro-B-type natriuretic peptide and hypersensitive C-reactive protein.

Limb remote ischemic conditioning of the recipient protects the liver in a rat model of arterialized orthotopic liver transplantation

Background

Ischemic-reperfusion (IR) injury still represents a major concern in clinical transplantation, especially in the era of extreme organ shortage and extended criteria donor organs. In the present study we aimed to investigate the hepatoprotective effects of remote ischemic conditioning (RIC) in a rat model of arterialized orthotopic liver transplantation (OLT).

Methods

Male Lewis rats were used (n = 144 / 72 OLT cases; 240–340g) as donors and recipients. Livers were flushed and stored in 4°C HTK-solution for 8h before implantation. Recipients were randomly allocated into three experimental groups: RIC 1, RIC 2, Control. In RIC 1, RIC 2 groups, RIC was applied in the recipient before hepatectomy or after reperfusion (4x5-5min IR via clamping the infrarenal aorta), respectively. Animals were sacrificed at 1, 3, 24, 168h post-reperfusion (n = 6 recipient/group/time point). Hepatocellular injury, graft circulation, serum cytokines, tissue redox-stress and adenosine-triphosphate (ATP) levels have been assessed. Additional markers were analyzed, using Western blotting and reverse-transcription polymerase chain reaction.

Results

RIC 1 group showed significantly (p<0.05) improved portal venous and microcirculation flow as well as velocity. RIC has significantly reduced tissue injury according to the serum levels of transaminases and results of histopathological evaluation. Reduced TUNEL-staining (p<0.01 RIC 1–2 vs. Control) and elevated pBAD/BAD ratio was detected in the RIC groups (p<0.01 RIC 1 vs. Control). Supporting findings were obtained from measurements of serum IL-10 as well as tissue malondialdehyde and ATP levels. Hemoxygenase-1 (HO-1) mRNA-expression was significantly higher in RIC 1 compared to Control (p<0.05 RIC 1 vs. Control).

Conclusion

These results suggest that RIC might confer potent protection against the detrimental effects of IR injury including tissue damage, apoptosis, graft circulation, inflammation, tissue energetic status in OLT. HO-1 overexpression might play an orchestrating role in RIC mediated organ protection. An earlier intervention (RIC 1 protocol) was more effective than remote conditioning after graft reperfusion.

Milrinone attenuates arteriolar vasoconstriction and capillary perfusion deficits on endotoxemic hamsters

Background and Objective

Apart from its inotropic property, milrinone has vasodilator, anti-inflammatory and antithrombotic effects that could assist in the reversal of septic microcirculatory changes. This paper investigates the effects of milrinone on endotoxemia-related microcirculatory changes and compares them to those observed with the use of norepinephrine.

Materials and Methods

After skinfold chamber implantation procedures and endotoxemia induction by intravenous Escherichia coli lipopolysaccharide administration (2 mg.kg-1), male golden Syrian hamsters were treated with two regimens of intravenous milrinone (0.25 or 0.5 μg.kg-1.min-1). Intravital microscopy of skinfold chamber preparations allowed quantitative analysis of microvascular variables. Macro-hemodynamic, biochemical, and hematological parameters and survival rate were also analyzed. Endotoxemic non-treated animals, endotoxemic animals treated with norepinephrine (0.2 μg.kg-1.min-1), and non-endotoxemic hamsters served as controls.

Results

Milrinone (0.5 μg.kg-1.min-1) was effective in reducing lipopolysaccharide-induced arteriolar vasoconstriction, capillary perfusion deficits, and inflammatory response, and in increasing survival. Norepinephrine treated animals showed the best mean arterial pressure levels but the worst functional capillary density values among all endotoxemic groups.

Conclusion

Our data suggests that milrinone yielded protective effects on endotoxemic animals’ microcirculation, showed anti-inflammatory properties, and improved survival. Norepinephrine did not recruit the microcirculation nor demonstrated anti-inflammatory effects.

Hepatoprotective effect by pretreatment with olprinone in a swine partial hepatectomy model

Excessive portal flow to a small remnant liver or small-for-size graft is a primary factor of small-for-size syndrome. We demonstrated that olprinone (OLP), a phosphodiesterase III inhibitor, had a hepatoprotective effect in a rat extended hepatectomy model and a small-for-size liver transplantation model through a modification of the portal venous pressure (PVP). To identify the appropriate dose and duration of treatment for clinical applications, we conducted experiments with a swine partial hepatectomy model. Twenty microminipigs were divided into 4 groups that received the following treatments: (A) saline (control group), (B) OLP at 0.3 μg/kg/minute (preoperative and postoperative administration), (C) OLP at 0.1 μg/kg/minute (preoperative administration), and (D) OLP at 0.3 μg/kg/minute (preoperative administration). The pigs underwent 70% partial hepatectomy. Hemodynamic changes, including changes in PVP, were examined. Liver biopsy was performed 1 and 3 hours after hepatectomy. Blood samples were collected until postoperative day 7 (POD7). In comparison with group A, PVP elevations, periportal edema, and sinusoidal hemorrhaging were attenuated after left Glisson's ligation in groups C and D. Pretreatment with OLP in groups C and D preserved the microstructure of sinusoids and improved the prothrombin activity 1 and 3 hours after hepatectomy. These animals showed better recovery of the remnant liver volume and the plasma disappearance rate of indocyanine green on POD7. In contrast, group B showed exacerbation of liver damage. Measurements of the serum OLP concentration showed that 10 ng/mL OLP was appropriate for a hepatoprotective effect. In conclusion, pretreatment with OLP shows hepatoprotective effects in a swine partial hepatectomy model. OLP may have the potential to ameliorate patients' outcomes after hepatectomy or liver transplantation.

Effect of milrinone on the inflammatory response and NF-kB activation in renal ischemia-reperfusion injury in mice

BACKGROUND

Milrinone increases intracellular adenosine 3',5'-cyclic monophosphate concentration and enhances vascular relaxation. Nuclear factor-kappa B (NF-kB) plays a key role in inflammatory responses during ischemia-reperfusion (I/R) injury. We aimed to investigate the effect of milrinone on the inflammatory responses and NF-kB activation in renal I/R injury in mice.

METHODS

Thirty C57BL/6 mice were allocated into 3 groups. In group S (n = 10), only right nephrectomy was done. In group C (n = 10), the left kidney was subjected to 30 min of ischemia after right nephrectomy. In group M (n = 10), milrinone (5 µg/kg) was administered before ischemia. After 24 hours of reperfusion, the serum creatinine was measured, kidney samples were obtained for histology, and expressions of NF-kB and proinflammatory cytokines were analyzed.

RESULTS

In group C, the serum creatinine concentration was markedly elevated, compared with group S. Creatinine concentration in group M was also elevated, but it was significantly lower than that in group C. Histologic evidence of renal damage was severe in group C, but it was improved in group M. In groups C and M, expression of NF-kB, tumor necrosis factor-α (TNF-α), intercellular adhesion molecule-1 (ICAM-1), monocyte chemoattractant protein-1 (MCP-1) and macrophage inflammatory protein-2 (MIP-2) mRNA increased significantly compared with group S (P < 0.05). But group M showed a lower expression of NF-kB, TNF-α, ICAM-1, MCP-1 and MIP-2 mRNA than group C (P < 0.05).

CONCLUSIONS

Milrinone treatment attenuates the renal inflammatory response and activation of NF-kB, resulting in improvement of renal function and tissue injury.

Anti-inflammatory effects of selected drugs on activated neonatal and adult neutrophils

AIM

In view of the central role of granulocytic neutrophils in the context of inflammatory reactions, the present study focuses on anti-inflammatory effects of drugs on activated neutrophils in neonates and adults.

METHODS

Sixteen blood samples of neonates and adults were investigated in a prospective study. Loss of deformability, morphological changes, and increases in neutrophil elastase were determined as measures of neutrophil activation due to incubation with the pro-inflammatory cytokine interleukin-8. For inhibition experiments, the blood samples were also incubated with the phosphodiesterase inhibitors milrinone and piclamilast, the protease inhibitor urinastatin, ketamine, protein C concentrate, and the nitric oxide donor FK 409. Changes in deformability were investigated with a cell transit analyzer, morphological changes by microscopic observation, and the extent of neutrophil elastase release with an enzyme immunoassay.

RESULTS

The drugs milrinone, piclamilast, urinastatin, ketamine, protein C concentrate and FK 409 showed deactivating effects on activated neutrophils in recommended clinical doses. They improved deformability as well as reduced pseudopod formation and the release of neutrophil elastase. The effects on neutrophils did not differ between neonates and adults despite their functional differences.

CONCLUSION

We conclude that these drugs may reduce the inflammatory response and improve microcirculation in neonates and adults during inflammation.

How to protect liver graft with nitric oxide

Organ preservation and ischemia reperfusion injury associated with liver transplantation play an important role in the induction of graft injury. One of the earliest events associated with the reperfusion injury is endothelial cell dysfunction. It is generally accepted that endothelial nitric oxide synthase (e-NOS) is cell-protective by mediating vasodilatation, whereas inducible nitric oxide synthase mediates liver graft injury after transplantation. We conducted a critical review of the literature evaluating the potential applications of regulating and promoting e-NOS activity in liver preservation and transplantation, showing the most current evidence to support the concept that enhanced bioavailability of NO derived from e-NOS is detrimental to ameliorate graft liver preservation, as well as preventing subsequent graft reperfusion injury. This review deals mainly with the beneficial effects of promoting “endogenous” pathways for NO generation, via e-NOS inducer drugs in cold preservation solution, surgical strategies such as ischemic preconditioning, and alternative “exogenous” pathways that focus on the enrichment of cold storage liquid with NO donors. Finally, we also provide a basic bench-to-bed side summary of the liver physiology and cell signalling mechanisms that account for explaining the e-NOS protective effects in liver preservation and transplantation.

Olprinone attenuates excessive shear stress through up-regulation of endothelial nitric oxide synthase in a rat excessive hepatectomy model

After extended hepatectomy, excessive shear stress in the remnant liver causes postoperative liver failure. Olprinone (OLP), a selective phosphodiesterase inhibitor, has been reported to improve microcirculation and attenuate inflammation. The aim of this study was to investigate the effects of OLP on shear stress in rats with an excessive hepatectomy (EHx) model. In this study, EHx comprised 90% hepatectomy with ligation of the left and right Glisson's sheaths in Lewis rats. OLP or saline was intraperitoneally administered with an osmotic pump 48 hours before EHx. To evaluate the shear stress, we measured the portal vein (PV) pressure. We also assessed sinusoidal endothelial cell injury by immunohistochemistry and electron microscopy. Furthermore, we assessed apoptosis in the liver with the terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick-end labeling method. Treatment with OLP up-regulated hepatic endothelial nitric oxide synthase (eNOS) expression. The increase in the PV pressure due to Glisson's sheath ligation was attenuated in OLP-treated rats during a 30-minute period after ligation. Treatment with OLP preserved sinusoidal endothelial cells and reduced apoptosis in the remnant liver. The probability of survival in the OLP-treated rats was significantly better than that in the controls (33.3% versus 13.3%). Furthermore, the postoperative eNOS activity in the OLP-treated rats was higher than that in the controls. The administration of Nω-nitro-l-arginine methyl ester to OLP-treated rats eliminated the effects of OLP on PV pressure and survival after EHx. Therefore, we concluded that OLP attenuates excessive shear stress through the up-regulation of eNOS and improves the survival rate after EHx.

Effect of olprinone, a phosphodiesterase III inhibitor, on hepatic ischemia-reperfusion injury in rats

I/R injury is the main cause for hepatic dysfunction and failure after liver transplantation and liver resection. Therefore, reduction of I/R injury is the most important goal to improve the outcome of these procedures. Olprinone is a newly developed selective phosphodiesterase III inhibitor, which has been reported to ameliorate renal I/R injury in rats. However, no clear evidence for the actions of olprinone on inflammatory response after hepatic I/R injury has been disclosed thus far. Our study was designed to evaluate the action of olprinone on the hepatic I/R injury in rats. Olprinone increased the cyclic adenosine monophosphate level in injured liver tissue and ameliorated the liver injury after hepatic I/R. Moreover, olprinone suppressed the activation of p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and nuclear factor-kappaB, cytokine production (TNF-alpha, IL-6, and cytokine-induced neutrophil chemoattractant factor 1), and intercellular adhesion molecule 1 expression in liver after hepatic I/R. These observations suggest that olprinone protects liver against I/R injury via the elevation of cyclic adenosine monophosphate level and suppression of intercellular adhesion molecule 1 expression and cytokine production (TNF-alpha, IL-6, and cytokine-induced neutrophil chemoattractant factor 1), possibly by interfering with the signaling pathways of p38 mitogen-activated protein kinase, c-Jun N-terminal kinase, and nuclear factor-kappaB in rats.

Low central venous pressure with milrinone during living donor hepatectomy

Maintaining a low central venous pressure (CVP) has been frequently used in liver resections to reduce blood loss. However, decreased preload carries potential risks such as hemodynamic instability. We hypothesized that a low CVP with milrinone would provide a better surgical environment and hemodynamic stability during living donor hepatectomy. Thirty-eight healthy adult liver donors were randomized to receive either milrinone (milrinone group, n = 19) or normal saline (control group, n = 19) infusion during liver resection. The surgical field was assessed using a four-point scale. Intraoperative vital signs, blood loss, the use of vasopressors and diuretics and postoperative laboratory data were compared between groups. The milrinone group showed a superior surgical field (p < 0.001) and less blood loss (142 +/- 129 mL vs. 378 +/- 167 mL, p < 0.001). Vital signs were well maintained in both groups but the milrinone group required smaller amounts of vasopressors and less-frequent diuretics to maintain a low CVP. The milrinone group also showed a more rapid recovery pattern after surgery. Milrinone-induced low CVP improves the surgical field with less blood loss during living donor hepatectomy and also has favorable effects on intraoperative hemodynamics and postoperative recovery.

The hepatic microcirculation: mechanistic contributions and therapeutic targets in liver injury and repair

The complex functions of the liver in biosynthesis, metabolism, clearance, and host defense are tightly dependent on an adequate microcirculation. To guarantee hepatic homeostasis, this requires not only a sufficient nutritive perfusion and oxygen supply, but also a balanced vasomotor control and an appropriate cell-cell communication. Deteriorations of the hepatic homeostasis, as observed in ischemia/reperfusion, cold preservation and transplantation, septic organ failure, and hepatic resection-induced hyperperfusion, are associated with a high morbidity and mortality. During the last two decades, experimental studies have demonstrated that microcirculatory disorders are determinants for organ failure in these disease states. Disorders include 1) a dysregulation of the vasomotor control with a deterioration of the endothelin-nitric oxide balance, an arterial and sinusoidal constriction, and a shutdown of the microcirculation as well as 2) an overwhelming inflammatory response with microvascular leukocyte accumulation, platelet adherence, and Kupffer cell activation. Within the sequelae of events, proinflammatory mediators, such as reactive oxygen species and tumor necrosis factor-alpha, are the key players, causing the microvascular dysfunction and perfusion failure. This review covers the morphological and functional characterization of the hepatic microcirculation, the mechanistic contributions in surgical disease states, and the therapeutic targets to attenuate tissue injury and organ dysfunction. It also indicates future directions to translate the knowledge achieved from experimental studies into clinical practice. By this, the use of the recently introduced techniques to monitor the hepatic microcirculation in humans, such as near-infrared spectroscopy or orthogonal polarized spectral imaging, may allow an early initiation of treatment, which should benefit the final outcome of these critically ill patients.

cAMP-GEF cytoprotection by Src tyrosine kinase activation of phosphoinositide-3-kinase p110 beta/alpha in rat hepatocytes

Cyclic AMP protects against hepatocyte apoptosis by a protein kinase A-independent cAMP-GEF/phosphoinositide-3-kinase (PI3K)/Akt signaling pathway. However, the signaling pathway coupling cAMP-GEF with PI3K is unknown. The aim of this study was to investigate the role of Src tyrosine kinases (Src-TYK) and PI3K-p110 isoforms in this pathway. Studies were done in rat hepatocytes using the hydrophobic bile acid glycochenodeoxycholic acid (GCDC) to induce apoptosis. cAMP-binding guanine nucleotide exchange factors (cAMP-GEFs) were selectively activated by using 4-(4-chloro-phenylthio)-2'-O-methyladenosine-3'-5'-cyclic monophosphate (CPT-2-Me-cAMP), which sequentially phosphorylated Src-TYK (within 1 min) followed by Akt (within 5 min). The Src inhibitors PP2 and SU6656 inhibited basal and CPT-2-Me-cAMP-mediated Src and Akt phosphorylation. These inhibitors had no effect on CPT-2-Me-cAMP-mediated activation of Rap GTPases. CPT-2-Me-cAMP induced transient Src dependent autophosphorylation of the epidermal growth factor receptor (EGFR). Inhibition of the EGFR with AG 1478 partially inhibited the ability of CPT-2-Me to phosphorylate Akt. Whereas PP2 completely abolished the protective effect of CPT-2-Me-cAMP in GCDC induced apoptosis, AG 1478 partially inhibited the cytoprotective effect. CPT-2-Me-cAMP treatment resulted in Src-dependent activation of the p110 beta and alpha subunits of PI3K, but only the latter was sensitive to inhibition with AG 1478. In conclusion, activation of cAMP-GEFs results in phosphorylation of Src-TYK and Akt and activation of the p110 beta/alpha subunits of PI3K. Maximal cAMP-GEF-mediated Akt phosphorylation as well as protection from bile acid-induced apoptosis requires activation of Src-TYK and the EGFR. These studies support the existence of two pathways: cAMP-GEF/Rap/Src/PI3Kbeta/Akt and cAMP-GEF/Rap/Src/EGFR/PI3Kalpha/Akt, both of which are necessary for maximal cytoprotective effect of cAMP-GEFs in hepatocytes.

Implication of protein kinase A for a hepato-protective mechanism of milrinone pretreatment

BACKGROUND

We have previously reported that an increase of adenosine 3',5'-cyclic monophosphate (cAMP) in liver tissue after an administration of milrinone, a phosphodiesterase-3 inhibitor attenuates hepatic warm ischemia-reperfusion injury. The aim of this study was to determine whether cAMP-dependent protein kinase (protein kinase A) activation was involved in the milrinone-induced hepatoprotective effect on an ischemia-reperfusion injury in an in vivo model.

MATERIALS AND METHODS

Male Lewis rats were allocated into 3 groups. In Group M, milrinone was administrated before ischemia; in Group I, a protein kinase A inhibitor, adenosine 3',5'-cyclic monophosphorothioate, 8-bromo-, Rp-isomer, sodium salt (Rp-8-Br-cAMPS), was injected prior to the administration of milrinone; and in Group C, the control group, there was no pretreatment. After pretreatment, all rats were exposed to a 45-min total hepatic inflow occlusion.

RESULTS

After milrinone administration, liver cAMP concentrations and protein kinase A activity ratios were elevated. They protected the liver from ischemia-reperfusion injury. Rp-8-Br-cAMPS suppressed protein kinase A activation without affecting cAMP elevating responses to milrinone. Compared with Group C, hepatocellular necrosis, neutrophil infiltration, and congestion were ameliorated, and serum tumor necrosis factor-alpha, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase levels were significantly suppressed in Group M. Rp-8-Br-cAMPS canceled this effect, showing histological damages in Group I as severe as in Group C. The levels of tumor necrosis factor-alpha, aspartate aminotransferase, alanine aminotransferase, and lactate dehydrogenase were the same in Groups C and I.

CONCLUSIONS

Activation of protein kinase A might play an important role in the mechanism of milrinone-induced ischemic tolerance in the liver.

Preservation of non-heart-beating donor livers in extracorporeal liver perfusion and histidine-trytophan-ketoglutarate solution

AIM: To compare the preservation of non-heart-beating donor (NHBD) livers in cold histidine-trytophan-ketoglutarate (HTK) solution and extracorporeal liver perfusion (ECLP).

METHODS: Livers harvested from health pigs were stored for 10 h in cold HTK solution (group A, n = 4) or perfused with oxygenated autologous blood at body temperature (group B, n = 4). Both groups were then tested on the circuit for 4 h. Bile production, hemodynamic parameters, hepatocyte markers and reperfusion injury of extracorporeal livers were tested in each group. Liver tissues from each group were examined at the end of reperfusion.

RESULTS: At 1, 2, 3 and 4 h after reperfusion, bile production, hemodynamic parameters, hepatocyte markers and reperfusion injury of livers in group A were statistically different from those in group B (P < 0.05 or P < 0.01).

CONCLUSION: ECLP is better than HTK solution to preserve NHBD livers. ECLP can assess the graft viability before liver transplantation.

Effects of amrinone in an experimental model of hepatic ischemia-reperfusion injury

BACKGROUND

During some surgical interventions, temporary occlusion of the hepatic blood supply may cause ischemia-reperfusion (IR) injury. Recent studies suggest that type 3 phosphodiesterase inhibitors may have a beneficial effect on liver IR injury. The aim of this study was to investigate whether amrinone, a type 3 phosphodiesterase inhibitor, could have a protective effect on liver having experimental liver IR injury.

MATERIALS AND METHODS

Sixty Wistar albino rats were randomly divided into three groups. The IR and amrinone groups were subjected to 1 h total hepatic ischemia, followed by 2 h of reperfusion. The sham group underwent midline laparotomy only. Amrinone 10 microg/kg/min was infused to the amrinone group during the 3 h of the IR period. Histopathological examination, biochemical liver function, and liver adenosine triphosphate concentration after reperfusion and survival rate on the seventh day after the IR insult were recorded.

RESULTS

Serum aspartate aminotransferase, alanine aminotransferase, lactic dehydrogenase levels, and histological damage scores in the amrinone and IR groups were significantly higher compared with the sham group (P < 0.01). However, all of these values were significantly lower in the amrinone group than in the IR group (P < 0.05). Liver adenosine triphosphate levels and the rat survival rate in the amrinone and IR groups were significantly lower than those in the sham group (P < 0.01). However, these values were significantly higher in the amrinone group compared to those in the IR group (P < 0.01).

CONCLUSIONS

These results suggest that amrinone plays a significant role in the protection of liver against IR injury and that this treatment may be a novel pharmacological agent for safe and efficient liver surgery.