thromboxane-a2 and Fatty-Liver

Mast cells are important cells of the immune system and are recognized as participants in the pathogenesis of atherosclerosis. In this study, we evaluated the role of mast cells on the progression of atherosclerosis and hepatic steatosis using the apolipoprotein E-deficient (ApoE(-/-)) and ApoE(-/-)/mast cell-deficient (Kit(W-sh/W-sh)) mouse models maintained on a high-fat diet. The en face analyses of aortas showed a marked reduction in plaque coverage in ApoE(-/-)/Kit(W-sh/W-sh) compared with ApoE(-/-) after a 6-mo regimen with no significant change noted after 3 mo. Quantification of intima/media thickness on hematoxylin and eosin-stained histological cross sections of the aortic arch revealed no significant difference between ApoE(-/-) and ApoE(-/-)/Kit(W-sh/W-sh) mice. The high-fat regimen did not induce atherosclerosis in either Kit(W-sh/W-sh) or wild-type mice. Mast cells with indications of degranulation were seen only in the aortic walls and heart of ApoE(-/-) mice. Compared with ApoE(-/-) mice, the serum levels of total cholesterol, low-density lipoprotein and high-density lipoprotein were decreased by 50% in ApoE(-/-)/Kit(W-sh/W-sh) mice, whereas no appreciable differences were noted in serum levels of triglycerides or very low density lipoprotein. ApoE(-/-)/Kit(W-sh/W-sh) mice developed significantly less hepatic steatosis than ApoE(-/-) mice after the 3-mo regimen. The analysis of Th1/Th2/Th17 cytokine profile in the sera revealed significant reduction of interleukin (IL)-6 and IL-10 in ApoE(-/-)/Kit(W-sh/W-sh) mice compared with ApoE(-/-) mice. The assessment of systemic generation of thromboxane A(2) (TXA(2)) and prostaglandin I(2) (PGI(2)) revealed significant decrease in the production of PGI(2) in ApoE(-/-)/Kit(W-sh/W-sh) mice with no change in TXA(2). The decrease in PGI(2) production was found to be associated with reduced levels of cyclooxygenase-2 mRNA in the aortic tissues. A significant reduction in T-lymphocytes and macrophages was noted in the atheromas of the ApoE(-/-)/Kit(W-sh/W-sh) mice. These results demonstrate the direct involvement of mast cells in the progression of atherosclerosis and hepatic steatosis.

Topics: Animals; Aorta; Apolipoproteins E; Atherosclerosis; Carotid Intima-Media Thickness; Cytokines; Diet, High-Fat; Disease Models, Animal; Disease Progression; Epoprostenol; Fatty Liver; Macrophages; Male; Mast Cells; Mice; Mice, Knockout; Plaque, Atherosclerotic; T-Lymphocytes; Thromboxane A2

Cirrhotic portal hypertension is characterized by increased hepatic oxidative stress, AA (arachidonic acid)-derived TXA(2) (thromboxane A(2)) release and exaggerated hepatic response to the α-adrenergic agonist MTX (methoxamine). Besides promoting hepatic fibrosis, the role of hyperleptinaemia in the modulation of vascular response in NASH (non-alcoholic steatohepatitis) rat livers remains unknown. The aim of the present study was to explore the possible links between hyperleptinaemia and the disarrangement in the hepatic microcirculation. NASH-cirrhosis with hyperleptinaemia was induced in lean rats by feeding with an HF/MCD (high-fat/methionine-choline-deficient) diet. Portal haemodynamics, various substances, protein and mRNA expression and PUFA (polyunsaturated fatty acid) composition were measured. Finally, the effects of leptin pre-infusion on TXA(2) release and concentration-PPP (portal perfusion pressure) curves in response to MTX were evaluated by simultaneously pre-treatment with the Kupffer cell inactivators GdCl(3) (gadolinium chloride) or EC (encapsulated clodronate), the TXS (TXA(2) synthase) inhibitor furegrelate, the TP receptor (TXA(2) receptor) antagonist SQ29548 and the dual TXS/TP receptor antagonist BM567. In HF/MCD+leptin-lean rats, cirrhosis-induced PPP and MTX hyper-responsiveness were associated with increased hepatic TXA(2) production, TBARS (thiobarbituric acid-reacting substances) levels and the AA (arachidonic acid)/n-3 PUFA ratio, and up-regulation of hepatic leptin, FAS (fatty acid synthase), NADPH oxidase subunits, TXS, TP receptor, TGFβ(1) (transforming growth factor β(1)) proteins and mRNAs. Pre-infusion of leptin significantly enhanced MTX-stimulated PPP elevation and TXA(2) release, which were attenuated by GdCl(3) and EC pre-treatment. Concomitantly pre-incubation with BM567, but not furegrelate or SQ29548, significantly abolished the leptin-enhanced MTX-stimulated increase in PPP in NASH-cirrhotic rats. Hyperleptinaemia plays an important role in hyper-responsiveness to MTX in NASH-cirrhotic rat livers with portal hypertension. The leptin-enhanced MTX-stimulated increase in PPP is mediated by increased oxidative stress and Kupffer-cell-activated AA-derived TXA(2) release in NASH-cirrhotic rats.

Topics: Analysis of Variance; Animals; Arachidonic Acid; Benzofurans; Choline; Clodronic Acid; Diet, High-Fat; DNA Primers; Fatty Acids, Unsaturated; Fatty Liver; Gadolinium; Hemodynamics; Hypertension, Portal; Insulin Resistance; Kupffer Cells; Leptin; Methionine; Methoxamine; Microcirculation; Non-alcoholic Fatty Liver Disease; Oxidative Stress; Rats; Receptors, Thromboxane A2, Prostaglandin H2; RNA, Messenger; Sulfonylurea Compounds; Thiobarbituric Acid Reactive Substances; Thromboxane A2

Chemical composition of hepatic lipids is an evolving player in steatotic liver ischemia/reperfusion (I/R) injury. Thromboxane A(2) (TXA(2)) is a vasoactive pro-inflammatory lipid mediator derived from arachidonic acid (AA), an omega-6 fatty acid (Ω-6 FA). Reduced tolerance of the macrosteatotic liver to I/R may be related to increased TXA(2) synthesis due to the predominance of Ω-6 FAs.. TXA(2) levels elicited by I/R in ob/ob and wild type mice were assessed by ELISA. Ob/ob mice were fed Ω-3 FAs enriched diet to reduce hepatic synthesis of AA and TXA(2) or treated with selective TXA(2) receptor blocker before I/R.. I/R triggered significantly higher hepatic TXA(2) production in ob/ob than wild type animals. Compared with ob/ob mice on regular diet, Ω-3 FAs supplementation markedly reduced hepatic AA levels before ischemia and consistently blunted hepatic TXA(2) synthesis after reperfusion. Sinusoidal perfusion and hepatocellular damage were significantly ameliorated despite downregulation of heme oxygenase-1. Hepatic transcript and protein levels of IL-1β and neutrophil recruitment were significantly diminished after reperfusion. Moreover, TXA(2) receptor blockage conferred similar protection without modification of the histological pattern of steatosis. A stronger protection was achieved in the steatotic compared with lean animals.. Enhanced I/R injury in the macrosteatotic liver is explained, at least partially, by TXA(2) mediated microcirculatory failure rather than size-related mechanical compression of the sinusoids by lipid droplets. TXA(2) blockage may be a simple strategy to include steatotic organs and overcome the shortage of donor organs for liver transplantation.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Arachidonic Acid; Fatty Acids, Omega-3; Fatty Liver; Lipid Metabolism; Lipids; Liver; Macrophage Activation; Male; Mice; Mice, Inbred C57BL; Mice, Obese; Microcirculation; Neutrophil Activation; Oxidative Stress; Receptors, Thromboxane A2, Prostaglandin H2; Reperfusion Injury; Thromboxane A2

To investigate the dynamic changes of plasma levels of prostacycline (PGI2) and thromboxane A2 (TXA2) and their relationship with the severity of hepatic injury in rats with nonalcoholic fatty liver disease (NAFLD).. We established a NAFLD model, with a fat-rich diet consisting of 10% lard oil + 2% cholesterol, which was given to Sprague-Dawley rats (n=48) for a period of 8, 12, 16 and 24 weeks. The other rats were fed standard diets and were used as normal controls (n=24). At sacrifice, liver pathology scores were evaluated and plasma levels of PGI2, its stable metabolic product 6-keto-PGF1 alpha and TXA2, and TXB2 were determined by radioimmunoassay.. Simple fatty livers were observed in the model group at 8 weeks. From 12 weeks to 24 weeks, the livers gradually progressed from simple steatohepatitis to liver fibrosis. Plasma levels of TXB2 in the model group increased higher than in the control group after 8 weeks [(52.4+/-3.15) ng/L vs (41.1+/-1.45) ng/L] and continued to increase over time, with the highest levels at 24 weeks [(117.7+/-7.47) ng/L]. A strong positive correlation (r=0.537) was seen between plasma TXB2 levels and the severity of liver injury. Plasma 6-keto-PGF1 alpha concentrations decreased in the model group in comparison with the control group after 8 weeks [(31.1+/-1.62) ng/L vs (36.5+/-1.68) ng/L] and continued to decrease over time, with the lowest concentrations at 24 weeks [(3.4+/-2.43) ng/L t=3.77]. A negative correlation was shown between the 6-keto-PGF1 alpha level and the severity of the liver injury.. A rat model of NAFLD was established successfully by feeding a fat-rich diet for 24 weeks. In this model, the imbalance of plasma PGI2 and TXA2 levels (increased TXB2 and decreased 6-keto-PGF1 alpha levels) may play a role in the pathogenesis of experimental NAFLD.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Epoprostenol; Fatty Liver; Liver; Male; Rats; Rats, Sprague-Dawley; Thromboxane A2; Thromboxane B2