The role of thromboxane A2 [TxA2] in liver injury in mice

Screening of polysaccharides from the differently processed products of Angelica sinensis with the best liver protection effect on chicken and the intervention mechanism study based on tandem mass tag proteomics and multiple reaction monitoring approach

The incidence of colibacillosis in poultry is on the rise, significantly affecting the chicken industry. Ceftiofur sodium (CS) is frequently employed to treat this disease, resulting in lipopolysaccharide (LPS) buildup. Processing plays a vital role in traditional Chinese veterinary medicine. The potential intervention in liver injury by polysaccharides from the differently processed products of Angelica sinensis (PDPPAS) induced by combined CS and LPS remains unclear. This study aims to investigate the protective effect of PDPPAS on chicken liver injury caused by CS combined with LPS buildup and further identify the polysaccharides with the highest hepatoprotective activity in chickens. Furthermore, the study elucidates polysaccharides' intervention mechanism using tandem mass tag (TMT) proteomics and multiple reaction monitoring (MRM) methods. A total of 190 1-day-old layer chickens were randomly assigned into 12 groups, of which 14 chickens were in the control group and 16 in other groups, for a 10-day trial. The screening results showed that charred A. sinensis polysaccharide (CASP) had the most effective and the best hepatoprotective effect at 48 h. TMT proteomics and MRM validation results demonstrated that the intervention mechanism of the CASP high-dose (CASPH) intervention group was closely related to the protein expressions of FCER2, TBXAS1, CD34, AGXT, GCAT, COX7A2L, and CYP2AC1. Conclusively, the intervention mechanism of CASPH had multitarget, multicenter regulatory features.

The impact of subchronic ozone exposure on serum metabolome and the mechanisms of abnormal bile acid and arachidonic acid metabolisms in the liver

Ambient ozone (O₃) pollution can induce respiratory and cardiovascular toxicity. However, its impact on the metabolome and the underlying mechanisms remain unclear. This study first investigated the serum metabolite changes in rats exposed to 0.5 ppm O₃ for 3 months using untargeted metabolomic approach. Results showed chronic ozone exposure significantly altered the serum levels of 34 metabolites with potential increased risk of digestive, respiratory and cardiovascular disease. Moreover, bile acid synthesis and secretion, and arachidonic acid (AA) metabolism became the most prominent affected metabolic pathways after O₃ exposure. Further studies on the mechanisms found that the elevated serum toxic bile acid was not due to the increased biosynthesis in the liver, but the reduced reuptake from the portal vein to hepatocytes owing to repressed Ntcp and Oatp1a1, and the decreased bile acid efflux in hepatocytes as a results of inhibited Bsep, Ostalpha and Ostbeta. Meanwhile, decreased expressions of detoxification enzyme of SULT2A1 and the important regulators of FXR, PXR and HNF4α also contributed to the abnormal bile acids. In addition, O₃ promoted the conversion of AA into thromboxane A2 (TXA2) and 20-hydroxyarachidonic acid (20-HETE) in the liver by up-regulation of Fads2, Cyp4a and Tbxas1 which resulting in decreased AA and linoleic acid (LA), and increased thromboxane B2 (TXB2) and 20-HETE in the serum. Furthermore, apparent hepatic chronic inflammation, fibrosis and abnormal function were found in ozone-exposed rats. These results indicated chronic ozone exposure could alter serum metabolites by interfering their metabolism in the liver, and inducing liver injury to aggravate metabolic disorders.

Dietary EPA+DHA Mitigate Hepatic Toxicity and Modify the Oxylipin Profile in an Animal Model of Colorectal Cancer Treated with Chemotherapy

Irinotecan (CPT-11) and 5-fluorouracil (5-FU) are commonly used to treat metastatic colorectal cancer, but chemotherapy-associated steatosis/steatohepatitis (CASSH) frequently accompanies their use. The objective of this study was to determine effect of CPT-11+5-FU on liver toxicity, liver oxylipins, and cytokines, and to explore whether these alterations could be modified by dietary eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) in the form of fish oil (EPA+DHA). Tumor-bearing animals were administered CPT-11+5-FU and maintained on a control diet or a diet containing EPA+DHA (2.3 g/100 g). Livers were collected one week after chemotherapy for the analysis of oxylipins, cytokines, and markers of liver pathology (oxidized glutathione, GSSH; 4-hydroxynonenal, 4-HNE, and type-I collagen fiber). Dietary EPA+DHA prevented the chemotherapy-induced increases in liver GSSH (p < 0.011) and 4-HNE (p < 0.006). Compared with the tumor-bearing animals, ten oxylipins were altered (three/ten n-6 oxylipins were elevated while seven/ten n-3 oxylipins were reduced) following chemotherapy. Reductions in the n-3 fatty-acid-derived oxylipins that were evident following chemotherapy were restored by dietary EPA+DHA. Liver TNF-α, IL-6 and IL-10 were elevated (p < 0.05) following chemotherapy; dietary EPA+DHA reduced IL-6 (p = 0.09) and eotaxin (p = 0.007) levels. Chemotherapy-induced liver injury results in distinct alterations in oxylipins and cytokines, and dietary EPA+DHA attenuates these pathophysiological effects.

Metabonomics Study on the hepatoprotective effect mechanism of polysaccharides from different processed products of Angelica Sinensis on the layer chickens based on UPLC-Q/TOF-MS/MS, multivariate statistical analysis and conjoint analysis

Chicken colibacillosis is one of the most severe diseases in the poultry industry. Ceftiofur sodium (CS) is often used to treat it in clinical practice and lipopolysaccharide (LPS) accumulates in the chicken's body. Previous experimental studies found that CS combined with LPS could induce liver injury in layer chickens, and polysaccharides from charred Angelica sinensis(CASP) had a better hepatoprotective effect than polysaccharides from unprocessed Angelica sinensis(UASP). However, the intervention mechanism was unclear. Thus, UPLC–Q/TOF–MS/MS‐based metabonomics and transcriptomics were used in this study to clarify the hepatoprotective effect mechanism of CASP and UASP in layer chickens. Transcriptomics and enzyme‐linked immunosorbent assay were used for biological verification of some critical mutual metabolic pathways screened with metabonomics. The comprehensive analysis results showed that in a layer chicken liver injury model built with LPS and CS, 12 critical metabolic pathways were disturbed, involving 10 important differential metabolites. The hepatoprotective effect mechanism of CASP is related to the arachidonic acid metabolism and mTOR signaling pathways, involving nine important differential metabolites. In contrast, the hepatoprotective effect mechanism of UASP is related to the arachidonic acid metabolism pathway, involving six important differential metabolites.

Synthesis, Stability, and Biological Studies of Fluorinated Analogues of Thromboxane A2

Platelet activation results in the generation of thromboxane A₂ (TxA₂), which promotes thrombus formation by further amplifying platelet function, as well as causing vasoconstriction. Due to its role in thrombus formation and cardiovascular disease, its production is the target of antiplatelet drugs such as aspirin. However, the study of TxA₂-stimulated cellular function has been limited by its instability (t _1/2 = 32 s, pH = 7.4). Although more stable analogues such as U46619 and difluorinated 10,10-F₂-TxA₂ have been prepared, we targeted a closer mimic to TxA₂ itself, monofluorinated 10-F-TxA₂, since the number of fluorine atoms can affect function. Key steps in the synthesis of F-TxA₂ included α-fluorination of a lactone bearing a β-alkoxy group, and a novel synthesis of the strained acetal. F-TxA₂ was found to be 10⁵ more stable than TxA₂, and surprisingly was only slightly less stable than F₂-TxA₂. Preliminary biological studies showed that F-TxA₂ has similar potency as TxA₂ toward inducing platelet aggregation but was superior to F₂-TxA₂ in activating integrin α_IIbβ₃.

Influence of various diet regimens on deterioration of hepatic function and hematological parameters following carbon tetrachloride: a potential protective role of natural honey

The objective was to assess the effects of commercial regular diet as control, total food restriction with honey, commercial regular diet with dextrose, or total food restriction with dextrose, on blood variables after carbon tetrachloride (CCl4) administration. Sprague Dawley albino rats were divided into four groups, 10 rats each; Group 1 rats were on commercial regular diet, Group 2 rats were on commercial regular diet with 50% dextrose, Group 3 rats were on total food restriction with 50% dextrose, and Group 4 rats were on total food restriction with 50% honey. Rats in all the groups were i.m. administered CCL4 (2.4 mL kg b. wt.-1). Blood tests including ALT, AST, serum albumin, serum protein, BUN, blood glucose (BG), hemoglobin (Hb), and white blood cell (WBC) were performed before CCl4 administration and repeated after 48 and 96 h of post-injection. In Group 1, CCl4 caused significant elevation in AST and ALT, and decrease in BS, WBC, and BUN; lower elevation in AST and ALT at 48 h and decreased AST and ALT at 96 h were obtained when dextrose was added to commercial regular diet (Group 2). Using dextrose alone (Group 3), though there was significant elevation of AST and ALT and decrease in BUN and WBC as compared to baseline values, significant decrease in ALT, AST, and BUN as compared to control was obtained. During absolute honey feeding (Group 4), elevation in AST and ALT obtained, following CCl4 administration was significantly less than the values obtained in all other groups; with lower elevation in AST and ALT as compared to baseline values. Honey increased serum albumin, serum protein, BG, and caused lower reduction in Hb. Conclusively, exclusive honey feeding (50% concentration) significantly modifies and ameliorates biochemical and hematological changes obtained after CCl4 injection.

Role of thromboxane derived from COX-1 and -2 in hepatic microcirculatory dysfunction during endotoxemia in mice

Although thromboxanes (TXs), whose synthesis is regulated by cyclooxygenase (COX), have been suggested to promote inflammation in the liver, little is known about the role of TXA(2) in leukocyte endothelial interaction during endotoxemia. The present study was conducted to investigate the role of TXA(2) as well as that of COX in lipopolysaccharide (LPS)-induced hepatic microcirculatory dysfunction in male C57Bl/6 mice. We observed during in vivo fluorescence microscopic study that LPS caused significant accumulation of leukocytes adhering to the hepatic microvessels and non-perfused sinusoids. Levels of serum alanine transaminase (ALT) and tumor necrosis factor alpha (TNF alpha) also increased. LPS raised the TXB(2) level in the perfusate from isolated perfused liver. A TXA(2) synthase inhibitor, OKY-046, and a TXA(2) receptor antagonist, S-1452, reduced LPS-induced hepatic microcirculatory dysfunction by inhibiting TNF alpha production. OKY-046 suppressed the expression of an intercellular adhesion molecule (ICAM)-1 in an LPS-treated liver. In thromboxane prostanoid receptor-knockout mice, hepatic responses to LPS were minimized in comparison with those in their wild-type counterparts. In addition, a selective COX-1 inhibitor, SC-560, a selective COX-2 inhibitor, NS-398, and indomethacin significantly attenuated hepatic responses to LPS including microcirculatory dysfunction and release of ALT and TNF alpha. The effects of the COX inhibitors on hepatic responses to LPS exhibited results similar to those obtained with TXA(2) synthase inhibitor, and TXA(2) receptor antagonist. In conclusion, these results suggest that TXA(2) is involved in LPS-induced hepatic microcirculatory dysfunction partly through the release of TNF alpha, and that TXA(2) derived from COX-1 and COX-2 could be responsible for the microcirculatory dysfunction during endotoxemia.

Analysis of gene expression in carbon tetrachloride-treated rat livers using a novel bioarray technology

The present study successfully utilizes a new ADME Rat Expression Bioarray, containing 1040 metabolism- and toxicology-linked genes, to monitor gene expression from the livers of rats treated with carbon tetrachloride (CCl(4)). Histopathological analysis, hierarchical clustering methods, and gene expression profiling are compared between the control and CCl(4)-treated animals. A total of 44 transcripts were found to be altered in response to the hepatotoxin, 19 of which were upregulated and 25 were downregulated. Some of these gene expression changes were expected and concurred with previously published data while others were novel findings.

Intravenous and Intrapulmonary Administration of Honey Solution to Healthy Sheep: Effects on Blood Sugar, Renal and Liver Function Tests, Bone Marrow Function, Lipid Profile, and Carbon Tetrachloride-Induced Liver Injury

Safety of intravenous (i.v.) or intrapulmonary administration of different concentrations of honey and their effects on blood sugar, renal and liver function tests, bone marrow function, lipid profile, and carbon tetrachloride (CCl(4))-induced liver damage were studied. Healthy sheep of either sex, 6-8 months old, were assigned randomly into the following groups: sheep received i.v. infusion of 5% honey in normal saline at 10-day intervals for 50 days and were compared with sheep that received 5% dextrose; sheep received higher doses of honey (50 g of honey) by i.v. infusion daily for 10 days; sheep received four higher doses of honey (80 g each dose) for 2 weeks; sheep received subcutaneous injection of CCl(4) after four doses of i.v. infusion of 80 g of honey, and estimations of serum gamma-glutamyl transpeptidase (SGGT), serum glutamic oxaloacetic transaminase (SGOT), and serum glutamate pyruvate transaminase (SGPT) were performed daily for 10 days postinjection; sheep received i.v. infusion of 40 g of honey, and blood sugar estimation was performed for 3 h at 30-min intervals after infusion and compared with sheep that received 5% dextrose; sheep received rapid i.v. injection of 40% honey or 40% dextrose, and blood sugar was estimated before and after injection; sheep received various concentrations of honey in distilled water (0.5 mL/1.5 mL, 0.75 mL/1.75 mL and 1.2 mL/2.2 mL), and blood sugar estimation was performed before and after inhalation. Results showed that i.v. or intrapulmonary administration of honey did not cause any adverse effect. Intravenous delivery of honey by slow infusion caused improvement of renal and hepatic function, bone marrow function, and lipid profile. It reduced SGOT, SGPT, triglyceride, cholesterol, blood urea nitrogen, and blood sugar and elevated serum protein, serum albumin, hemoglobin, white blood cell, and neutrophil percentage. Similar results were obtained with the use of higher doses of honey. CCl(4) caused mild elevation of SGPT and SGGT and lowering of SGOT in sheep that received repeated i.v. administration of honey before administration of CCl(4), whereas in control sheep CCl(4) caused significant elevation of all the liver enzymes. Intravenous infusion of 40 g of honey caused elevation of blood sugar for 90 min postinfusion, whereas it decreased blood sugar at 2 and 3 h postinfusion as compared with fasting blood sugar. Dextrose caused significant elevation of blood sugar at all time intervals. Similar results were obtained with the use of 10% dextrose or 80 g of honey. Addition of honey to dextrose caused less hyperglycemia as compared with dextrose alone. Acute injection of 20 mL of 40% dextrose significantly elevated blood sugar for 3 h postinjection, whereas little elevation in blood sugar was obtained after injection of 40% honey; the difference between honey and dextrose was significant. Inhalation of honey caused significant lowering of blood sugar during and after inhalation as compared with fasting blood sugar and water inhalation. The effect was greater with a higher concentration of inhaled honey. It might be concluded that slow i.v. infusion or rapid i.v. injection of honey in different concentrations was safe and could lower blood sugar and improve renal, hepatic, and bone marrow functions and lipid profile. Intravenous honey had a hepatoprotective effect against CCl(4)-induced liver injury. Inhaled honey was safe and reduced blood sugar significantly.

The influence of carbon tetrachloride-induced liver damage on the inflammatory reaction elicited by carrageenan and its treatment with diclofenac

The effect of impaired hepatic function on the development of the inflammatory process as well as on treatment with diclofenac was investigated. Carbon tetrachloride was used to induce liver injury and the elevation of serum transaminases was taken as evidence for impaired hepatic function. The carrageenan-induced rat hind paw oedema and the granuloma pouch were chosen as models of inflammation. The results of the study revealed that: (1) The intensity of inflammation in both models was markedly attenuated in CCl4-treated animals. (2) Serum total proteins were decreased in liver-injured animals particularly in acute experiments. (3) In liver-injured groups diclofenac showed more pronounced anti-inflammatory activity in chronic experiments, but not in acute ones. (4) Neither CCl4 nor diclofenac affected the levels of histamine and serotonin in the granuloma pouch exudate. The level of prostaglandins was decreased in CCl4 and in diclofenac-treated animals. At the same time, the leukotriene content was elevated. The mechanism by which CCl4 induced liver injury attenuates inflammatory response to carrageenan is not entirely understood. Its effect on protein metabolism and extravasation as well as on PG synthesis could play a possible role. Decreased drug metabolism may be, at least in part, responsible for the enhanced response of diclofenac in the cases of liver-injured animals. Dose adjustment of the drug in case of hepatic impairment might be necessary.

Eicosanoid profile and evidence for endotoxin tolerance in chronic ethanol-fed rats

The present study evaluated the role of endotoxin, prostaglandin E2 (PGE2), leukotriene B4 (LTB4) and thromboxane B2 in alcoholic liver injury. Animals (4-5 per group per time period) were fed ethanol and either saturated fat (SE group) or corn oil (CE group) and sacrificed at various time intervals: 1, 2, and 4 weeks. Non parenchymal cells (NPC) were isolated and the spontaneous and LPS-stimulated production of eicosanoids was evaluated. In addition, severity of pathology, plasma levels of endotoxin, TXB2, LTB4 and PGE2 were compared in the two groups. The severity of fatty, liver, necrosis and inflammation was significantly greater in the CE group compared to the SE group after 1 month. Plasma endotoxin levels were significantly higher in the CE group vs. SE group at all time periods studied. PGE2 levels in NPCS and plasma were in general higher in the SE group. LTB4 levels in NPCS declined with time in the SE group; in contrast the levels rose in the CE group. There was no difference in LTB4 levels in plasma between the two groups. TXB2 levels in plasma and NPCS were significantly higher in the CE group at all times. The pattern of LPS-stimulated eicosanoid production by NPC in the two groups (SE and CE) suggested the development of endotoxin tolerance in the CE group. However, an additional modulatory effect of ethanol was also suggested by our findings.

Role of eicosanoids in experimental alcoholic liver disease

Based on our previous observations that linoleic acid is an important dietary requirement for the development of liver injury in the intragastric feeding rat model for alcoholic liver disease, we postulated that the conversion of linoleic acid to arachidonic acid and various eicosanoids could be important in the pathogenesis of liver injury. We showed that liver nonparenchymal cell production of thromboxane B2 and leukotriene B4 was higher in rats fed corn oil and ethanol (liver injury model) than in animals fed saturated fat and ethanol (no liver injury). In contrast, prostaglandin E2 levels were lower in the former group. The best correlate of pathologic changes was the plasma level of thromboxane B2. The importance of thromboxanes in alcoholic liver injury is further suggested by the fact that inhibition of thromboxane production is accompanied by amelioration of liver injury.

Liver cytoprotection by prostaglandins

During the last decade intensive work on the relationships between the liver and the arachidonic acid cascade has greatly expanded our knowledge of this area of research. The liver has emerged as the major organ participating in the degradation and elimination of arachidonate products of systemic origin. The synthesis in the liver of arachidonate products derived from the cyclooxygenase, lipoxygenase and cytochrome P450 system pathways has been demonstrated. The participation of leukotriene B4 and cysteinyl-leukotrienes as mediators of liver damage and the possible therapeutic usefulness of prostaglandins (PGs) in acute liver injury has attracted the interest of clinicians. This article reviews the essential features regarding the role of arachidonate metabolites in liver disease and specially focuses on the cytoprotective effects on the liver displayed by PGE2, PGE1, PGI2 and synthetic PG analogs in experimental models of liver damage induced by ischemia-reperfusion injury, carbon tetrachloride, bacterial lipopolysaccharide and viral hepatitis and on the possible mechanisms underlying liver cytoprotection in these experimental models. The therapeutic usefulness of PGs in clinical practice is critically analyzed on the basis of available evidence in patients with fulminant hepatic failure and primary graft nonfunction following liver transplantation.

Protective effects of E3330, a novel quinone derivative, on galactosamine/tumor necrosis factor-alpha-induced hepatitis in mice

Oral pretreatment with E3330, a novel quinone derivative, attenuated liver injury induced with tumor necrosis factor-alpha in galactosamine-sensitized mice. Tumor necrosis factor-alpha is known to induce inflammatory mediators such as leukotrienes and prostanoids. An in vitro study showed that E3330 inhibited the generation of leukotriene B4 and thromboxane B2, but enhanced prostaglandin E2 generation from rat peritoneal exudate cells stimulated with the Ca(2+)-ionophore, A23187. These findings suggest that the protective effect of E3330 on galactosamine/tumor necrosis factor-alpha hepatitis is due at least in part to its inhibition of the generation of leukotrienes. The inhibition of thromboxane B2 generation or the enhancement of prostaglandin E2 generation by E3330 may also contribute to its hepatoprotective effect.

Phospholipase A2 activation and cell injury in isolated rat hepatocytes exposed to bromotrichloromethane, chloroform, and 1,1-dichloroethylene as compared to effects of carbon tetrachloride

It was found that the four toxigenic agents, CCl4, CHCl3, CBrCl3, and 1,1-dichloroethylene (vinylidene chloride) all share the property of activating phospholipase A2 (PLA2) of isolated hepatocytes in suspension, as determined over a 60- or 120-min time period. In all cases, PLA2 activation, measured as the appearance of lysophosphatidylethanolamine, preceded the release of lactic dehydrogenase during incubation of the cells at 37 degrees C. It is concluded that for these halogenated hydrocarbons phospholipase A2 activation may be part of the chain of causality leading from initial bioactivation to ultimate cell death.

Prevention of Ca(2+)-induced or thromboxane B2-induced hepatocyte plasma membrane bleb formation by thromboxane receptor antagonists

Isolated hepatocytes incubated in the presence of either Ca2+ ionophore A23187 or thromboxane B2 develop many plasma membrane blebs which are a characteristic feature of toxic or ischaemic cell injury. When hepatocytes are incubated in the presence of both Ca2+ ionophore A23187 and any one of three thromboxane receptor antagonists (SK and F 88046, B.M. 13505, B.M. 13177), bleb formation is strongly inhibited. Hepatocytes incubated in the presence of both thromboxane B2 and any one of the three thromboxane receptor antagonists are also well protected from the formation of blebs. Treatment of isolated hepatocytes with Ca2+ ionophore A23187 is known to stimulate the production of thromboxanes. The data presented are consistent with thromboxane B2 acting as an intermediary in a proposed mechanism of cell injury and death in which elevated cytosolic free Ca2+ levels activate phospholipase A2 and the arachidonate cascade.