Prostacyclin analogue (OP-2507) induces delayed ex vivo neutrophil apoptosis and attenuates reperfusion-induced hepatic microcirculatory derangement in rats

Molecular Mechanisms for Regulation of Neutrophil Apoptosis under Normal and Pathological Conditions

Neutrophils are one of the main cells of innate immunity that perform a key effector and regulatory function in the development of the human inflammatory response. Apoptotic forms of neutrophils are important for regulating the intensity of inflammation and restoring tissue homeostasis. This review summarizes current data on the molecular mechanisms of modulation of neutrophil apoptosis by the main regulatory factors of the inflammatory response-cytokines, integrins, and structural components of bacteria. Disturbances in neutrophil apoptosis under stress are also considered, molecular markers of changes in neutrophil lifespan associated with various diseases and pathological conditions are presented, and data on pharmacological agents for modulating apoptosis as potential therapeutics are also discussed.

Directly acting drugs prostacyclin or nitroglycerine and endothelin receptor blocker bosentan improve cell engraftment in rodent liver

To optimize strategies for liver-directed cell therapy, prevention of initial transplanted cell losses is particularly important for subsequent liver repopulation. After cell transplantation in hepatic sinusoids, perturbations in hepatic microcirculation along with changes in various liver cell types are among the earliest changes. Therefore, for advancing further concepts in cell engraftment we studied vascular and related events in the liver after transplanting syngeneic hepatocytes into dipeptidyl peptidase IV-deficient rats. We treated rats with vascular drugs to define whether deleterious cell transplantation-induced events could be controlled followed by improvements in transplanted cell engraftment and proliferation. We found cell transplantation altered liver gene expression related to vessel tone, inflammation, cell adhesion, thrombosis, or tissue damage/remodeling. This was due to hepatic ischemia, endothelial injury, and activation of neutrophils, Kupffer cells, and hepatic stellate cells. Treatment of rats before cell transplantation with the angiotensin converting enzyme blocker, lisinopril, or angiotensin II receptor blocker, losartan, did not improve cell engraftment. By contrast, direct-acting nitroglycerine or prostacyclin improved cell engraftment and also kinetics of liver repopulation. These drugs lowered hepatic ischemia and inflammation, whereas pretreatment of rats with the dual endothelin-1 receptor blocker, bosentan, improved cell engraftment independently of hepatic ischemia or inflammation, without improving liver repopulation. However, incubation of hepatocytes with bosentan protected cells from cytokine toxicity in vitro and produced superior cell engraftment and proliferation in vivo.

CONCLUSION

Cell transplantation-induced changes in hepatic microcirculation contributed to transplanted cell clearances from liver. Vascular drugs, such as nitroglycerine, prostacyclin, and bosentan, offer opportunities for improving cell therapy results through superior cell engraftment and liver repopulation. Ongoing clinical use of these drugs will permit rapid translation of the findings in people.

Hepatic ischaemia-reperfusion injury from bench to bedside

BACKGROUND

Vascular occlusion to prevent haemorrhage during liver resection causes ischaemia-reperfusion (IR) injury. Insights into the mechanisms of IR injury gathered from experimental models have contributed to the development of therapeutic approaches, some of which have already been tested in randomized clinical trials.

METHODS

The review was based on a PubMed search using the terms 'ischemia AND hepatectomy', 'ischemia AND liver', 'hepatectomy AND drug treatment', 'liver AND intermittent clamping' and 'liver AND ischemic preconditioning'; only randomized controlled trials (RCTs) were included.

RESULTS

Twelve RCTs reported on ischaemic preconditioning and intermittent clamping. Both strategies seem to confer protection and allow extension of ischaemia time. Fourteen RCTs evaluating pharmacological interventions, including antioxidants, anti-inflammatory drugs, vasodilators, pharmacological preconditioning and glucose infusion, were identified.

CONCLUSION

Several strategies to prevent hepatic IR have been developed, but few have been incorporated into clinical practice. Although some pharmacological strategies showed promising results with improved clinical outcome there is not sufficient evidence to recommend them.

Molecular Biology of Apoptosis in Ischemia and Reperfusion

This study reviews the current understanding of the mechanisms that mediate the complex processes involved in apoptosis secondary to ischemia and reperfusion (I/R) and is not intended as a complete literature review of apoptosis. Several biochemical reactions trigger a cascade of events, which activate caspases. These caspases exert their effect through downstream proteolysis until the final effector caspases mediate the nuclear features characteristic of apoptosis, DNA fragmentation and condensation. Within the context of ischemia, the hypoxic environment initiates the expression of several genes involved in inflammation, the immune response, and apoptosis. Many of these same genes are activated during reperfusion injury in response to radical oxygen species generation. It is plausible that inhibition of specific apoptotic pathways via inactivation or downregulation of those genes responsible for the initiation of inflammation, immune response, and apoptosis may provide promising molecular targets for ameliorating reperfusion injury in I/R-related processes. Such inhibitory mechanisms are discussed in this review. Important targets in I/R-related pathologies include the brain during stroke, the heart during myocardial infarction, and the organs during harvesting and/or storage for transplantation. In addition, we present data from our ongoing research of specific signal transduction-related elements and their role in ischemia/reperfusion injury. These data address the potential therapeutic application of anti-inflammatory and anti-ischemic compounds in the prevention of I/R damage.

A role for IL-18 in human neutrophil apoptosis

Decreased neutrophil apoptosis is associated with persistent inflammation, the severity of which correlates with serum IL-18 levels. IL-18 receptors as well as Toll-like receptors, including Toll-like receptor 4, a receptor for LPS, possess a highly conserved intracellular domain called "Toll-IL-1R domain" and activate overlapping signaling pathways. Here, we show that IL-18 modulates neutrophil apoptosis and compare its mechanism of action with LPS. We found that both IL-18 and LPS decreased neutrophil apoptosis in a similar dose- and time-dependent fashion. However, pretreatment with the phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002 increased apoptosis more effectively in IL-18- than in LPS-stimulated cells, whereas the ERK inhibitor PD98059 had the same effect in both. In contrast, the p38 mitogen-activated protein kinase (MAPK) inhibitor SB203580 had no influence on apoptosis at all. Neutrophils constitutively expressed mRNA for IL-18 receptor beta, but little or no receptor alpha, both of which increased during coculture with either IL-18 or LPS in a time- and dose-dependent manner. Of the Bcl-2 family, antiapoptotic A1/Bfl-1 tended to increase on IL-18 and LPS stimulation, but was further increased despite increased apoptosis in the presence of MAPK inhibitors. Thus, human neutrophils can express mRNA for IL-18 receptors alpha and beta, and IL-18, like LPS, inhibits neutrophil apoptosis by activating PI3K and ERK pathways but not p38MAPK. However, PI3K may play more important role(s) in IL-18- than in LPS-induced inhibition of apoptosis. Mitogen-activated protein kinases seem to mediate antiapoptotic signals through factors other than Bcl-2 gene family expression.

Epoprostenol improves mucosal tissue oxygen tension in an acute endotoxemic pig model

The objective of the present study was to determine the effects of increasing dosages of continuously infused epoprostenol (PGI), a prostacyclin analog, on intestinal oxygen supply and jejunal mucosal tissue oxygen tension in an acute endotoxic pig model. Jejunal mucosal tissue PO2, oxygen saturation of jejunal microvascular hemoglobin, and gut microvascular blood flow were investigated. Systemic hemodynamic variables, mesenteric-venous and systemic acid base and blood gas variables, and lactate measurements were recorded. Measurements were performed at baseline, after Escherichia coli LPS administration, and at 20-min intervals during incremental PGI infusion (n = 8; 25, 50, 100, and 200microg x kg x h, respectively); or infusion of an equal amount of isotonic sodium chloride solution (n = 7). LPS infusion led to a significant decrease in mucosal tissue oxygen tension and microvascular hemoglobin oxygen saturation. Epoprostenol infusion led to a significant, dose-dependent increase in cardiac index and systemic oxygen delivery. Mucosal tissue oxygen tension and microvascular hemoglobin oxygen saturation increased after PGI administration and even returned to more-than-baseline values. Continuously infused PGI increased intestinal hemoglobin oxygen saturation and mucosal tissue oxygen tension in a dose-dependent manner mainly due to an increase in villus blood flow in this acute endotoxic pig model.

Omega 3 - Omega 6: What is right for the liver?

Linoleic and alpha-linolenic acids are the fatty acids designated as "essential" since they are not synthesized by mammalian cells and must be provided in the diet. The recent dietary shift towards the consumption of n-6 (omega-6) at the expense of n-3 (omega-3) polyunsaturated fatty acids (PUFAs) is thought to be a primary cause of many diseases related to the Western diet. The body converts linoleic acid to arachidonic acid and derives eicosapentaenoic acid from alpha-linolenic acid. Ideally the effects of these fatty acids and their eicosanoid derivatives are tailored to the specific biological needs of the body. The balance between n-3 and n-6 PUFAs is essential for metabolism and maintenance of the functions of both classes. The availability of n-3 long chain PUFAs plays a major role in regulating both fat accumulation and its elimination by the liver. Derangement of hepatic n-6:n-3 PUFA ratio impacts on the histological pattern of fatty liver through modulation of the amount of intrahepatic lipids. Moreover, the influence of PUFAs and their eicosanoid products on hepatic microcirculation and ischemia/reperfusion injury has been demonstrated in many studies. This concise review article will focus on the role of PUFAs and eicosanoids in hepatic steatosis, microcirculation and ischemia/reperfusion injury.

Delayed neutrophil apoptosis attenuated by melatonin in human acute pancreatitis

OBJECTIVES

This study evaluated the expression of neutrophil apoptosis and the effects of melatonin at different concentrations on delayed neutrophil apoptosis in different severities of acute pancreatitis in patients.

METHODS

The study population was comprised of 10 patients with severe acute pancreatitis (SAP) and 10 with mild acute pancreatitis (MAP). A total of 10 mL of blood was drawn 24 hours after the onset of the clinical disease for isolation and incubation of the human neutrophils with 4 different concentrations of melatonin. Neutrophil apoptosis activity, CD18 expression, and respiratory burst activity were assessed with flow cytometry 12 hours after incubation. Another group of neutrophils from a healthy control group was used (n = 6) for comparison.

RESULTS

Neutrophil apoptosis in patients with SAP is delayed compared with that of patients with MAP. Neutrophils from patients with SAP or MAP are functionally activated. Melatonin at concentrations of 10(-8), 10(-7), or 10(-6) M reverses the delayed process and enhances apoptosis activity in neutrophils in patients with MAP. Melatonin at concentrations of 10(-7) and 10(-6) M reverses the delayed process and increases apoptosis activity in neutrophils in patients with SAP. Neutrophils from patients with SAP and MAP showed significantly increased CD18 expression and respiratory burst activity. Melatonin at concentrations of 10(-7) or 10(-6) M reverses CD18 expression and respiratory burst activity in neutrophils in patients with SAP.

CONCLUSIONS

This study highlights the importance of neutrophil apoptosis in patients with SAP and raises the possibility of a therapeutic strategy. Study data show that melatonin promotes neutrophil apoptosis in human acute pancreatitis.

Iloprost: an adjunctive approach to chronic viral hepatitis treatment

Chronic viral liver disease may evolve to cirrhosis. The medical treatment to slow down this passage is based on anti-viral and anti-fibrotic properties of interferon. Recently, we evidenced significant increase of portal vein flow velocity and volume after a prostacyclin analog (iloprost) infusion in subjects without and with chronic viral hepatitis. On the basis of these results and considering both the pathophysiology of viral liver disease and the mechanism of action of iloprost in portal microcirculation, we hypothesize that it may be of some efficacy in chronic liver disease ameliorating the portal hemodynamics and producing an anti-oxidant liver effect.

Role of mitochondria in cell apoptosis during hepatic ischemia-reperfusion injury and protective effect of ischemic postconditioning

AIM: To investigate the role of mitochondria in cell apoptosis during hepatic ischemia-reperfusion injury and protective effect of ischemic postconditioning (IPC).

METHODS: A rat model of acute hepatic ischemia-reperfusion was established, 24 healthy male Wistar rats were randomly divided into sham-operated group, ischemia-reperfusion group (IR) and IPC group. IPC was achieved by several brief pre-reperfusions followed by a persistent reperfusion. Concentration of malondialdehyde (MDA) and activity of several antioxidant enzymes in hepatic tissue were measured respectively. Apoptotic cells were detected by TdT-mediated dUTP-biotin nick end labeling (TUNEL) and expression of Bcl-2 protein was measured by immunohistochemical techniques. Moreover, mitochondrial ultrastructure and parameters of morphology of the above groups were observed by electron microscope.

RESULTS: Compared with IR group, the concentration of MDA and the hepatocellular apoptotic index in IPC group was significantly reduced (P < 0.05), while the activity of antioxidant enzymes and OD value of Bcl-2 protein were markedly enhanced (P < 0.05). Moreover, the injury of mitochondrial ultrastructure in IPC group was also obviously relieved.

CONCLUSION: IPC can depress the synthesis of oxygen free radicals to protect the mitochondrial ultrastructure and increase the expression of Bcl-2 protein that lies across the mitochondrial membrane. Consequently, IPC can reduce hepatocellular apoptosis after reperfusion and has a protective effect on hepatic ischemia-reperfusion injury.

Role of direct cytotoxic effects of NSAIDs in the induction of gastric lesions

A major clinical problem encountered with the use of non-steroidal anti-inflammatory drugs (NSAIDs), is gastrointestinal complications. We previously reported that NSAIDs induce both necrosis and apoptosis in vitro. We here examined the cyclooxygenase (COX) dependency of this cytotoxic effect of NSAIDs and its involvement in NSAID-induced gastric lesions. Necrosis and apoptosis by NSAIDs was observed with all selective COX-2 inhibitors except rofecoxib and was not inhibited by exogenously added prostaglandin E2, suggesting that cytotoxicity of NSAIDs seems to be independent of the inhibition of COX. Intravenously administered indomethacin, which completely inhibited COX activity at gastric mucosa, did not produce gastric lesions. Orally administered selective COX-2 inhibitors, which did not inhibit COX at gastric mucosa, also did not produce gastric lesions. Interestingly, a combination of the oral administration of each of all selective COX-2 inhibitors except rofecoxib with the intravenous administration of indomethacin clearly produced gastric lesions. These results suggest that in addition to COX inhibition by NSAIDs, direct cytotoxicity of NSAIDs may be involved in NSAID-induced gastric lesions.

Altered neutrophil apoptosis activity is reversed by melatonin in liver ischemia-reperfusion

Delayed neutrophil apoptosis has been implicated as the mechanism of the systemic inflammatory response. Herein, we examined the effect of melatonin on the neutrophil apoptosis in ischemia and reperfusion of the human liver. We studied seven patients receiving elective hepatectomy for liver tumor and ten patients receiving laparoscopic cholecystectomy for gallstones. Ten milli liters of blood was drawn isolation and incubation of the human neutrophils. Neutrophil apoptosis activity and CD18 expression and respiratory burst activity were assessed flow cytometrically. Another group of neutrophils included those from the patients receiving hepatectomy and isolated and incubated with melatonin. Neutrophil apoptosis is delayed from patients after hepatectomy or laparoscopic cholecystectomy when compared with that of the preoperative state. The decrease in the apoptosis activity is more severe in patients receiving hepatectomy as compared with those receiving laparoscopic cholecystectomy. Neutrophils from patients receiving hepatectomy or laparoscopic cholecystectomy are functionally activated. Melatonin can reverse the delayed process and enhance the apoptosis activity in neutrophils from patients receiving hepatectomy. This study demonstrates that melatonin enhances neutrophil apoptosis in patients receiving hepatectomy involving ischemia and reperfusion of the human liver.

Fas-mediated neutrophil apoptosis and associated A1 protein expression during systemic inflammation are regulated independently of both tumor necrosis factor receptors

TNFR-1 (p55) and Fas share a death domain which is critical for apoptosis signaling whereas TNFR-p55 and TNFR-2 (p75) can activate NF-kappaB leading to anti-apoptotic proteins expression such as A1. The purpose of this study was to elucidate the role(s) of TNFR-p55 and TNFR-p75 in Fas-mediated neutrophil apoptosis and A1 expression in a mouse model of endotoxemia. Gene knockout (KO) (p55-/-, p75-/-, p55(-/-)/p75(-/-)) or wild type (WT) mice were injected i.p. with saline or LPS (4 microg/g) followed by collecting peripheral blood after 24 h. Neutrophil apoptosis was assessed by propidium iodide staining using two-color flow cytometry with granulocyte-specific Gr1-FITC after 6-h whole blood culture with or without Fas agonist Jo2 (300 ng/ml) in the presence or absence of cycloheximide (CHX, 30 microg/ml). Membrane-associated receptors (Fas, TNFR-p55 and TNFR-p75) and cytoplasmic A1 expression of freshly isolated neutrophils were assessed by one-color flow cytometry and western blotting respectively. Compared with the group-WT/Sal, Jo2 induced apoptosis only in the presence of CHX (J+C). J+C-induced apoptosis was significantly lower in the group-p55(-/-)/Sal and p55(-/-)/p75(-/-)/Sal but not in the group-p75(-/-)/Sal. J+C-induced apoptosis was inhibited similarly in all the LPS-injected WT and KO mice. Strong A1 expression was also induced similarly in all the LPS-injected WT and KO mice. Fas and TNFR-p55 expression was normal and TNFR-p75 was significantly increased in all the LPS-injected WT and KO mice although absence of the appropriate surface receptors was confirmed in the KO mice. We conclude that p55 normally plays a proapoptotic role, but p75 appears to play a minimal role in Fas-mediated neutrophil apoptosis. During endotoxin-induced systemic inflammation, both TNFR-p55 and TNFR-p75 appear to be of minimal importance for modulation of Fas-mediated apoptosis and associated A1 protein expression despite normal Fas/TNFR-p55 and increased TNFR-p75 expression in neutrophils.