Late administration of COX-2 inhibitors minimize hepatic necrosis in chloroform induced liver injury

Drug-induced liver injury: Interactions between drug properties and host factors

Idiosyncratic drug-induced liver injury (DILI) is a common cause for drug withdrawal from the market and although infrequent, DILI can result in serious clinical outcomes including acute liver failure and the need for liver transplantation. Eliminating the iatrogenic "harm" caused by a therapeutic intent is a priority in patient care. However, identifying culprit drugs and individuals at risk for DILI remains challenging. Apart from genetic factors predisposing individuals at risk, the role of the drugs' physicochemical and toxicological properties and their interactions with host and environmental factors need to be considered. The influence of these factors on mechanisms involved in DILI is multi-layered. In this review, we summarize current knowledge on 1) drug properties associated with hepatotoxicity, 2) host factors considered to modify an individuals' risk for DILI and clinical phenotypes, and 3) drug-host interactions. We aim at clarifying knowledge gaps needed to be filled in as to improve risk stratification in patient care. We therefore broadly discuss relevant areas of future research. Emerging insight will stimulate new investigational approaches to facilitate the discovery of clinical DILI risk modifiers in the context of disease complexity and associated interactions with drug properties, and hence will be able to move towards safety personalized medicine.

Nonselective inhibition of prostaglandin-endoperoxide synthases by naproxen ameliorates acute or chronic liver injury in animals

The rising prevalence of hepatic injury due to toxins, metabolites, viruses, etc., necessitates development of further mechanisms for protecting the liver and for treating acute or chronic liver diseases. To examine whether inhibition of inflammation is directed by cyclo-oxygenase pathways, we performed animal studies with naproxen, which inhibits prostaglandin-endoperoxide synthases 1 and 2 and is in extensive clinical use. We administered carbon tetrachloride to induce acute liver injury and ligated the common bile duct to induce chronic liver injury in adult rats. These experimental manipulations produced abnormalities in liver tests, tissue necrosis, compensatory hepatocyte or biliary proliferation, and onset of fibrosis, particularly after bile duct ligation. After carbon tetrachloride-induced acute injury, naproxen decreased liver test abnormalities, tissue necrosis and compensatory hepatocellular proliferation. After bile duct ligation-induced chronic injury, naproxen decreased liver test abnormalities, tissue injury and compensatory biliary hyperplasia. Moreover, after bile duct ligation, naproxen-treated rats showed more periductular oval liver cells, which have been classified as hepatic progenitor cells. In naproxen-treated rats, we found greater expression in hepatic stellate cells and mononuclear cells of cytoprotective factors, such as vascular endothelial growth factor. The ability of naproxen to induce expression of vascular endothelial growth factor was verified in cell culture studies with CFSC-8B clone of rat hepatic stellate cells. Whereas assays for carbon tetrachloride toxicity using cultured primary hepatocytes established that naproxen was not directly cytoprotective, we found conditioned medium containing vascular endothelial growth factor from naproxen-treated CFSC-8B cells protected hepatocytes from carbon tetrachloride toxicity. Therefore, naproxen was capable of ameliorating toxic liver injury, which involved naproxen-induced release of physiological cytoprotective factors in nonparenchymal liver cells. Such drug-induced release of endogenous cytoprotectants will advance therapeutic development for hepatic injury.

Monoacylglycerol lipase controls endocannabinoid and eicosanoid signaling and hepatic injury in mice

BACKGROUND & AIMS

The endocannabinoid and eicosanoid lipid signaling pathways have important roles in inflammatory syndromes. Monoacylglycerol lipase (MAGL) links these pathways, hydrolyzing the endocannabinoid 2-arachidonoylglycerol to generate the arachidonic acid precursor pool for prostaglandin production. We investigated whether blocking MAGL protects against inflammation and damage from hepatic ischemia/reperfusion (I/R) and other insults.

METHODS

We analyzed the effects of hepatic I/R in mice given the selective MAGL inhibitor JZL184, in Mgll(-/-) mice, fatty acid amide hydrolase(-/-) mice, and in cannabinoid receptor type 1(-/-) (CB1-/-) and cannabinoid receptor type 2(-/-) (CB2-/-). Liver tissues were collected and analyzed, along with cultured hepatocytes and Kupffer cells. We measured endocannabinoids, eicosanoids, and markers of inflammation, oxidative stress, and cell death using molecular biology, biochemistry, and mass spectrometry analyses.

RESULTS

Wild-type mice given JZL184 and Mgll(-/-) mice were protected from hepatic I/R injury by a mechanism that involved increased endocannabinoid signaling via CB2 and reduced production of eicosanoids in the liver. JZL184 suppressed the inflammation and oxidative stress that mediate hepatic I/R injury. Hepatocytes were the major source of hepatic MAGL activity and endocannabinoid and eicosanoid production. JZL184 also protected from induction of liver injury by D-(+)-galactosamine and lipopolysaccharides or CCl4.

CONCLUSIONS

MAGL modulates hepatic injury via endocannabinoid and eicosanoid signaling; blockade of this pathway protects mice from liver injury. MAGL inhibitors might be developed to treat conditions that expose the liver to oxidative stress and inflammatory damage.

Polyploidization without mitosis improves in vivo liver transduction with lentiviral vectors

Lentiviral vectors are efficient gene delivery vehicles for therapeutic and research applications. In contrast to oncoretroviral vectors, they are able to infect most nonproliferating cells. In the liver, induction of cell proliferation dramatically improved hepatocyte transduction using all types of retroviral vectors. However, the precise relationship between hepatocyte division and transduction efficiency has not been determined yet. Here we compared gene transfer efficiency in the liver after in vivo injection of recombinant lentiviral or Moloney murine leukemia viral (MoMuLV) vectors in hepatectomized rats treated or not with retrorsine, an alkaloid that blocks hepatocyte division and induces megalocytosis. Partial hepatectomy alone resulted in a similar increase in hepatocyte transduction using either vector. In retrorsine-treated and partially hepatectomized rats, transduction with MoMuLV vectors dropped dramatically. In contrast, we observed that retrorsine treatment combined with partial hepatectomy increased lentiviral transduction to higher levels than hepatectomy alone. Analysis of nuclear ploidy in single cells showed that a high level of transduction was associated with polyploidization. In conclusion, endoreplication could be exploited to improve the efficiency of liver-directed lentiviral gene therapy.

A low-power electronic nose signal-processing chip for a portable artificial olfaction system

The bulkiness of current electronic nose (E-Nose) systems severely limits their portability. This study designed and fabricated an E-Nose signal-processing chip by using TSMC 0.18-μ m 1P6M complementary metal-oxide semiconductor technology to overcome the need to connect the device to a personal computer, which has traditionally been a major stumbling block in reducing the size of E-Nose systems. The proposed chip is based on a conductive polymer sensor array chip composed of multiwalled carbon nanotubes. The signal-processing chip comprises an interface circuit, an analog-to-digital converter, a memory module, and a microprocessor embedded with a pattern-recognition algorithm. Experimental results have verified the functionality of the proposed system, in which the E-Nose signal-processing chip successfully classified three odors, carbon tetrachloride (CCl4), chloroform (CHCl3), and 2-Butanone (MEK), demonstrating its potential for portable applications. The power consumption of this signal-processing chip was maintained at a very low 2.81 mW using a 1.8-V power supply, making it highly suitable for integration as an electronic nose system-on-chip.

Macrophages and tissue injury: agents of defense or destruction?

The past several years have seen the accumulation of evidence demonstrating that tissue injury induced by diverse toxicants is due not only to their direct effects on target tissues but also indirectly to the actions of resident and infiltrating macrophages. These cells release an array of mediators with cytotoxic, pro- and anti-inflammatory, angiogenic, fibrogenic, and mitogenic activity, which function to fight infections, limit tissue injury, and promote wound healing. However, following exposure to toxicants, macrophages can become hyperresponsive, resulting in uncontrolled or dysregulated release of mediators that exacerbate acute tissue injury and/or promote the development of chronic diseases such as fibrosis and cancer. Evidence suggests that the diverse activity of macrophages is mediated by distinct subpopulations that develop in response to signals within their microenvironment. Understanding the precise roles of these different macrophage populations in the pathogenic response to toxicants is key to designing effective treatments for minimizing tissue damage and chronic disease and for facilitating wound repair.

Hypertonic sodium pyruvate solution is more effective than Ringer's ethyl pyruvate in the treatment of hemorrhagic shock

Hypertonic sodium pyruvate (HSP), as well as ethyl pyruvate solutions, has been proposed as resuscitative fluids in the treatment of hemorrhagic shock (HS) because of their anti-inflammatory and antioxidant properties. The effectiveness of one pyruvate preparation over the other in the treatment of HS has not been evaluated. The authors aimed to compare two pyruvate solutions for resuscitation and their mechanisms of action in rats during HS. The effects of infusion of low-volume HSP were compared against high-volume Ringer's ethyl pyruvate on hemodynamic parameters, inflammatory cascade, and regulation of stress and apoptosis-related proteins in the liver. Sprague-Dawley rats were either treated as sham animals or subjected to computer-controlled arterial hemorrhage (40 mmHg) for 60 min followed by resuscitation with isotonic sodium chloride solution, hypertonic saline, Ringer's lactate solution, Ringer's ethyl pyruvate, or HSP for 60 min. Animals were continuously monitored for hemodynamic and biochemical parameters in blood. At the end of the experiment, animals were killed, and liver samples were taken for the evaluation of inflammatory and anti-inflammatory markers and mediators of oxidative stress, liver injury, and expression of apoptotic signaling proteins. In comparison with Ringer's ethyl pyruvate, HSP administration after hemorrhage reduced liver injury, which was associated with increased levels of serum and tissue inflammatory cytokines, inflammatory mediators such as NOS and cyclooxygenase 2, lipid peroxidation, and higher hepatocellular adenosine triphosphate. Cellular apoptotic events related to the activation of caspase-3 and poly(ADP-ribose)polymerase cleavage were also decreased by sodium pyruvate. Resuscitation with small-volume HSP offers significant protection against inflammatory and oxidative stress and in preventing liver injury compared with large-volume Ringer's ethyl pyruvate.

Co-medications that modulate liver injury and repair influence clinical outcome of acetaminophen-associated liver injury

BACKGROUND & AIMS

Acetaminophen-induced liver injury is the most common cause of acute liver failure in the United States; it occurs inadvertently in approximately half of all cases. Concomitant use of other medications might impact susceptibility to acetaminophen hepatotoxicity. We investigated its association with administration of drugs that have been shown to modulate liver injury and/or repair in preclinical studies.

METHODS

We analyzed data from 6386 cases of acetaminophen-associated liver injury that were defined in the FDA database of reported adverse events. Data reported in the severe adverse event categories of "died" or "life-threatening" (defined as "fatal" cases, n = 2512) were compared with those of "non-fatal" cases (n = 3874). Potential associations between fatality and concomitant use of 9 drug classes were assessed using multiple logistic regression analyses after adjusting for other variables.

RESULTS

Among female subjects, concomitant use of statins, fibrates or nonsteroidal anti-inflammatory drugs was associated with decreased likelihood of fatality, whereas ethanol use was associated with increased likelihood. Among male subjects, concomitant use of statins was associated with decreased likelihood of fatality, whereas concomitant use of sympathetic stimulants or ethanol was associated with increased likelihood. Concomitant use of angiotensin converting enzyme inhibitors or angiotensin receptor II antagonists was associated with decreased likelihood of fatality among younger subjects.

CONCLUSIONS

Concomitant use of medications that have been shown in preclinical studies to modulate liver injury and/or repair influenced acetaminophen hepatotoxicity. Drugs that reduce injury or increase repair are protective, whereas those that exacerbate injury or reduce repair are detrimental.

Role of mammalian cytosolic molybdenum Fe-S flavin hydroxylases in hepatic injury

The study was designed to investigate the role of molybdenum iron-sulfur flavin hydroxylases in the pathogenesis of liver injuries induced by structurally and mechanistically diverse hepatotoxicants. While carbon tetrachloride (CCl4), thioacetamide (TAA) and chloroform (CHCl3) inflict liver damage by producing free radicals, acetaminophen (AAP) and bromobenzene (BB) exert their effects by severe glutathione depletion. Appropriate doses of these compounds were administered to induce liver injury in rats. The activities of the Mo-Fe-S flavin hydroxylases were measured and correlated with the biochemical markers of hepatic injury. The activity levels of the anti-oxidative enzymes and glutathione redox cycling enzymes were also determined. The treatment of rats with the hepatotoxins that inflict liver injury by generating free radicals (CCl4, TAA, CHCl3) had elevated activity levels of hepatic Mo-Fe-S flavin hydroxylases (p<0.05). Specific inhibition of these hydroxylases by their common inhibitor, sodium tungstate, suppresses biochemical and oxidative stress markers of hepatic tissue damage. On the contrary, Mo-Fe-S flavin hydroxylases did not show any change in animals receiving AAP and BB. Correspondingly, sodium tungstate could not attenuate damage in AAP and BB treated groups of rats. The study concludes that Mo-Fe-S hydroxylases contribute to the hepatic injury inflicted by free radical generating agents and does not play any role in hepatic injury produced by glutathione depleting agents. The study has implication in understanding human liver diseases caused by a variety of agents, and to investigate the efficacy of the inhibitors of Mo-Fe-S flavin hydroxylases as potential therapeutic agents.

Diverse cellular localizations of secretory phospholipase A2 enzymes in several human tissues

The secretory phospholipase A2 (sPLA2) family in mammals contains more than 10 enzymes. In this study, we examined by immunohistochemistry the localization of six sPLA2s (IIA, IID, IIE, IIF, V and X) in human heart, kidney, liver and stomach. In normal hearts, sPLA2-IIA was detected in coronary vascular smooth muscle cells (VSMC) and sPLA2-V in cardiomyocytes beneath the endocardium. In infarcted hearts, expression of these two enzymes was markedly increased in damaged cardiomyocytes, and expression of sPLA2-IID and-IIE, which was undetectable in normal hearts, was elevated in damaged cardiomyocytes and VSMC, respectively. In infarcted kidneys, sPLA2-IIA and-V were markedly induced in the uriniferous tubular epithelium. In livers affected by viral hepatitis, sPLA2-IIA and-V were expressed in hepatocytes with fatty degeneration. In the gastric glands exhibiting intestinal metaplasia, sPLA2-IIA was localized in the glandular base, sPLA2-IID and-V in the glandular body epithelium, sPLA2-IIE and-IIF in goblet cells in the foveolar epithelium, and sPLA2-X in both glandular body epithelial cells and foveolar epithelial goblet cells. In the gastric submucosal tissues, sPLA2-IIA and-IIE were located in VSMC and sPLA2-V was in the interstitial fibroblasts. In addition, sPLA2-IIA,-IIE,-IIF and-X were highly expressed in gastric signet ring cell carcinoma. Thus, individual sPLA2s exhibit unique cellular localizations in each tissue, suggesting their distinct roles in pathophysiology.

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Gastrointestinal and hepatic toxicity of selective and non-selective cyclooxygenase-2 inhibitors in pregnant and non-pregnant rats

The aim of the study was to evaluate the toxicity of non-selective (tolmetin, ibuprofen and piroxicam) and selective (DFU) cyclooxygenase-2 inhibitors on pregnant and non-pregnant rats. The drugs were administered orally once (DFU, piroxicam) or three times (tolmetin, ibuprofen) a day from days 8 through 21 of gestation experiment in three doses. The initial dose was similar to the human antiinflammatory one and set as 8.5 mg/kg (tolmetin, ibuprofen), 0.3 mg/kg (piroxicam) and 0.2 mg/kg (DFU). The middle dose was increased 10 times and the highest one 100 times the initial dose. The highest dose for ibuprofen was set at 200mg/kg due to high mortality. On gestation/experimental day 21 animals were sacrificed, blood was collected and abdominal organs were taken for pathological examination. Activity of alanine and asparate aminotransferases and levels of total protein and urea were determined. Stomach, small and large intestines, and liver were grossly and histologically examined. Dose-dependent mortality, signs of gastrointestinal toxicity, and significant changes of biochemical parameters were found in groups exposed to non-selective COX inhibitors in both pregnant and non-pregnant rats. Mild regressive structural hepatic changes were observed. Significant decrease of protein level in non-pregnant rats treated with high DFU dose, and occasionally observed gastrointestinal changes were the only changes noted in groups exposed to the selective COX-2 inhibitor. Tolerability of non-selective COX inhibitors was lower in both pregnant and non-pregnant groups when compared with DFU. Insignificant mortality and histological changes were noted between pregnant and non-pregnant groups.

Drug-induced liver disease in 2003

Drug-induced liver disease remains an important topic of concern for all prescribers as well as drug manufacturers. The withdrawal of troglitazone (Rezulin) and bromfenac (Duract) a few years ago remains fresh in the minds of regulatory authorities as well as clinicians and researchers who are focusing renewed attention on ways to better understand mechanisms of injury to predict and avert serious drug-induced liver disease in the future from drugs under development as well as existing agents known to cause liver injury. As in past years, this review describes new and first-time reports of various aspects of drug-induced liver disease for several classes of compounds, including herbal products (such as kava kava), reviews the risk factors seen with antiretroviral and antituberculosis agents among others. It provides a sampling of experimental hepatoprotection studies that may hold the key to treatment and prevention of drug-induced liver disease in the future and discusses the ongoing approaches to be taken to restrict the availability of acetaminophen that have proved successful in reducing the number of overdoses, deaths, and liver transplantations from this drug in the United Kingdom. Given the fact that acetaminophen is the single most important cause of acute liver failure here and abroad, such efforts to limit its use seem appropriate for other nations as well.

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Cellular prostaglandin E2 production by membrane-bound prostaglandin E synthase-2 via both cyclooxygenases-1 and -2

Current evidence suggests that two forms of prostaglandin (PG) E synthase (PGES), cytosolic PGES and membrane-bound PGES (mPGES) -1, preferentially lie downstream of cyclooxygenase (COX) -1 and -2, respectively, in the PGE2 biosynthetic pathway. In this study, we examined the expression and functional aspects of the third PGES enzyme, mPGES-2, in mammalian cells and tissues. mPGES-2 was synthesized as a Golgi membrane-associated protein, and spontaneous cleavage of the N-terminal hydrophobic domain led to the formation of a truncated mature protein that was distributed in the cytosol with a trend to be enriched in the perinuclear region. In several cell lines, mPGES-2 promoted PGE2 production via both COX-1 and COX-2 in the immediate and delayed responses with modest COX-2 preference. In contrast to the marked inducibility of mPGES-1, mPGES-2 was constitutively expressed in various cells and tissues and was not increased appreciably during tissue inflammation or damage. Interestingly, a considerable elevation of mPGES-2 expression was observed in human colorectal cancer. Collectively, mPGES-2 is a unique PGES that can be coupled with both COXs and may play a role in the production of the PGE2 involved in both tissue homeostasis and disease.