Downregulation of hepatic cytochrome P-450 isoforms and PPAR-gamma: their role in hepatic injury and proinflammatory responses in a double-hit model of hemorrhage and sepsis

Antioxidant, anti-inflammatory and hepatoprotective activities of Terminalia bellirica and its bioactive component ellagic acid against diclofenac induced oxidative stress and hepatotoxicity

Long term usage and overdose of diclofenac (DCF), an anti-inflammatory drug is known to cause oxidative stress and liver injury. The present study reports the antioxidant, anti-inflammatory and hepatoprotective activities of Terminalia bellirica (Tb) fruit aqueous and ethyl acetate extracts and its bioactive compound ellagic acid (EA) against DCF-induced toxicity. in vitro antioxidant activities were measured by ABTS and FRAP assays while anti‐inflammatory activity was assessed by the albumin denaturation method. The adverse effects of DCF and hepatoprotective potential of Tb extracts and EA were assessed in serum and liver tissue of rats after oral administration for 21 days. Silymarin was used as standard hepatoprptective agent for comparison. Hepatic markers analyzed in serum included ALP, GPT, GOT, LDH, γ-glutamyl transferase, total protein, creatinine, and uric acid while superoxide dismutase (SOD) and catalase (CAT) were analyzed in liver tissue. The EA exhibited superior ABTS radical scavenging, FRAP, and anti-inflammatory activities as compared to fruit extracts. DCF treatment led to rise in the levels of most of the serum hepatic markers with decline in total serum protein as well as SOD and CAT in liver tissue. The supplementation of extracts, EA and silymarin in DCF treated rats significantly reduced the adverse effects of DCF on serum and tissue markers. Histopathology of the liver indicated that extracts and EA significantly decreased the degree of liver fibrosis. The hepatoprotective ability of EA was comparable to the silymarin but activity of Tb fruit extracts was little lower. Among fruit extracts ethyl acetate extract exhibited better activity than aqueous extract. The results revealed that ellagic acid and T. bellirica fruit extracts have potential to mitigate oxidative stress and hepatotoxicity produced by long term use of diclofenac.

Eicosanoids derived from cytochrome P450 pathway of arachidonic acid and inflammatory shock

Sepsis is a life-threatening organ dysfunction caused by a dysregulated host response to infection. Septic shock, the most common form of vasodilatory shock, is a subset of sepsis in which circulatory and cellular/metabolic abnormalities are severe enough to increase mortality. Inflammatory shock constitutes the hallmark of sepsis, but also a final common pathway of any form of severe long-term tissue hypoperfusion. The pathogenesis of inflammatory shock seems to be due to circulating substances released by pathogens (e.g., bacterial endotoxins) and host immuno-inflammatory responses (e.g., changes in the production of histamine, bradykinin, serotonin, nitric oxide [NO], reactive nitrogen and oxygen species, and arachidonic acid [AA]-derived eicosanoids mainly through NO synthase, cyclooxygenase, and cytochrome P450 [CYP] pathways, and proinflammatory cytokine formation). Therefore, refractory hypotension to vasoconstrictors with end-organ hypoperfusion is a life threatening feature of inflammatory shock. This review summarizes the current knowledge regarding the role of eicosanoids derived from CYP pathway of AA in animal models of inflammatory shock syndromes with an emphasis on septic shock in addition to potential therapeutic strategies targeting specific CYP isoforms responsible for proinflammatory/anti-inflammatory mediator production.

In vivo investigation on the chronic hepatotoxicity induced by sertraline

Although sertraline is widely prescribed as relatively safe antidepressant drug, hepatic toxicity was reported in some patients with sertraline treatment. The present study was conducted to investigate the morphometric, hepatotoxicity, and change in gene expression of drug metabolizing enzymes. Male healthy adult rabbits (Oryctolagus cuniculus) ranging from 1050 to 1100 g were exposed to oral daily doses of sertraline (0, 1, 2, 4, 8 mg/kg) for 9 weeks. The animals were subjected to morphometric, hepatohistological, histochemical and quantitative real-time polymerase chain reaction analyses. Sertraline chronic exposure induced morphometric changes and provoked histological and histochemical alterations including: hepatocytes hydropic degeneration, necrosis, nuclear alteration, sinusoidal dilation, bile duct hyperplasia, inflammatory cells infiltration, portal vessel congestion, Kupffer cells hyperplasia, portal fibrosis and glycogen depletion. In addition, the gene expression of drug and arachidonic acid metabolizing enzymes were reduced significantly (p value <0.05). The most affected genes were cyp4a12, ephx2, cyp2d9 and cyp1a2, demonstrating 5 folds or more down-regulation. These findings suggest that chronic sertraline treatment induced toxic histological alterations in the hepatic tissues and reduced the gene expression of drug metabolizing enzymes. Patients on chronic sertraline treatment may be on risk of hepatotoxicity with reduced capacity to metabolize drugs and fatty acids.

Alterations in the gene expression of drug and arachidonic acid-metabolizing Cyp450 in the livers of controlled and uncontrolled insulin-dependent diabetic mice

BACKGROUND

Diabetic patients have lower capacity to metabolize drugs in comparison to normal people. Therefore, the present study aimed to investigate the alterations in gene expression of drug and arachidonic acid metabolizing cytochrome p450s (cyp450s) in the livers of controlled (CDM) and uncontrolled (UDM) insulin-dependent diabetic mice.

METHODS

Balb/c mice were treated with single dose of streptozocin (240 mg/kg) to induce diabetes and compared with control group, which was treated with citric buffer (pH =4.5). After 3 days, the blood glucose level was measured to confirm the induction of diabetes. Normalization of blood glucose level in diabetic mice was achieved after 0.1 mL/kg Mixtard® insulin therapy for more 5 days. Then, the mice livers were isolated to extract RNA and convert it to cDNA. The gene expression of 14 genes, which play a major role in drug and arachidonic acid metabolism, were measured using quantitative real-time polymerase chain reaction technique.

RESULTS

It was found that the gene expression was downregulated (ANOVA test, P-value <0.05) in the livers of UDM mice. The most downregulated genes were cyp4a12, cyp1a2, and slc22a1 with more than 10-fold reduction. The livers of CDM mice showed significantly (P-value <0.05) higher levels of mRNA than UDM mice, but still lower than the non-diabetic mice.

CONCLUSION

This study concluded that hepatic gene expression of drug metabolizing and arachidonic acid- cyp450 enzymes is reduced in insulin-dependent diabetic mice, which can explain, at least in part, the variation in drug and fatty acid metabolism between normal and diabetic patients.

OXYGEN MITIGATES THE INFLAMMATORY RESPONSE IN A MODEL OF HEMORRHAGE AND ZYMOSAN-INDUCED INFLAMMATION

Sequential insults (hits) may change the inflammatory reaction that develops in response to separate single hits (e.g., injury, infection); however, their effects on the long-term clinical outcome are still only partially elucidated. Double-hit models are typically severe and fatal. We characterized in C57BL/6 mice a moderate double-hit model of hemorrhage (35%-40% of total blood volume) and resuscitation, followed by peritoneal injection of zymosan A that induced local and systemic inflammation with 58% mortality. This model allowed exploration of the inflammatory response over time in the surviving mice. We show that after 2 days, mice subjected to the double-hit model had elevated proinflammatory systemic and local peritoneal cytokine response (interleukin [IL]-1β, tumor necrosis factor-α, IL-6) and moderately elevated anti-inflammatory cytokines (IL-10, transforming growth factor-β), compared with the single-hit and sham mice. However, this dynamically changed, and by day 7, proinflammatory cytokines were reduced, and anti-inflammatory cytokines were markedly (P < 0.05) elevated in the double-hit group. Mice in the double-hit group that inhaled 100% oxygen intermittently for 6 h every day exhibited markedly reduced serum proinflammatory cytokines as early as day 2 (P < 0.05), inhibited macrophage infiltration into the peritoneum (by 13-fold; P < 0.05), and substantially increased survival rates of 85% (P = 0.00144). Oxygen mitigates the inflammatory response and exerts a beneficial effect on survival in a double-hit model of hemorrhage and zymosan-induced inflammation.

Co-culture of Hepatocytes and Kupffer Cells as an In Vitro Model of Inflammation and Drug-Induced Hepatotoxicity

Immune-mediated drug-induced hepatotoxicity is often unrecognized as a potential mode of action due to the lack of appropriate in vitro models. We have established an in vitro rat donor-matched hepatocyte and Kupffer cell co-culture (HKCC) model to study immune-related responses to drug exposure. Optimal cell culture conditions were identified for the maintenance of co-cultures based on cell longevity, monolayer integrity, and cytokine response after lipopolysaccharide (LPS) exposure. Hepatocyte monocultures and HKCCs were then used to test a subset of compounds associated with hepatotoxic effects with or without LPS. Cytokine levels and metabolic activity (cytochrome P450 3A [Cyp3A]) were measured after a 48-h exposure to monitor endotoxin-induced changes in acute phase and functional end points. LPS-activated HKCCs, but not hepatocyte monocultures, treated with trovafloxacin or acetaminophen, compounds associated with immune-mediated hepatotoxicity, showed LPS-dependent decreases in interleukin-6 production with concomitant increases in Cyp3A activity. Differential endotoxin- and model-dependent alterations were observed in cytokine profiles and Cyp3A activity levels that corresponded to specific compounds. These results indicate the utility of the HKCC model system to discern compound-specific effects that may lead to enhanced or mitigate hepatocellular injury due to innate or adaptive immune responses.

Dietary fish oil reduces systemic inflammation and ameliorates sepsis-induced liver injury by up-regulating the peroxisome proliferator-activated receptor gamma-mediated pathway in septic mice

This study investigated the effect of dietary fish oil on systemic inflammation and hepatic injury in mice with polymicrobial sepsis. Male ICR mice were assigned to a control group (C, n=30) and a fish oil group (FO, n=30). Mice in the C group were fed a semi-purified diet with 10% soybean oil, and those in the FO group were fed a fish oil diet (2.5% fish oil+7.5% soybean oil; w/w). Three weeks later, sepsis was induced by cecal ligation and puncture (CLP), and mice were sacrificed at 0, 6 and 24 h after CLP, respectively. Results showed that compared with C group, the FO group had lower plasma levels of tumor necrosis factor (TNF)-α, interleukin (IL)-6, IL-10, and nitrite at 6 and 24 h after CLP. Also, peritoneal lavage fluid concentrations of TNF-α and prostaglandin (PG) E2 were significantly lower at 24 h in the FO than in the C group. The FO group had lower myeloperoxidase activities at 6 h after CLP in various organs. Plasma aminotransferase and alanine aminotransferase activities revealed significantly decreased in the FO group. The DNA-binding activity of peroxisome proliferators-activated receptor gamma (PPARγ) and mRNA expression of I kappaB alpha (IκBα) were up-regulated while nuclear factor (NF)-κB p65 DNA-binding activity, inducible nitric oxide synthase protein expression and the concentration of nitrotyrosine were significantly decreased in the FO group in liver after CLP. These results indicate that dietary fish oil administration may attenuate systemic inflammation and up-regulate hepatic PPARγ DNA-binding activity, which may consequently have ameliorated liver injury in these septic mice.

Organotypic liver culture models: meeting current challenges in toxicity testing

Prediction of chemical-induced hepatotoxicity in humans from in vitro data continues to be a significant challenge for the pharmaceutical and chemical industries. Generally, conventional in vitro hepatic model systems (i.e. 2-D static monocultures of primary or immortalized hepatocytes) are limited by their inability to maintain histotypic and phenotypic characteristics over time in culture, including stable expression of clearance and bioactivation pathways, as well as complex adaptive responses to chemical exposure. These systems are less than ideal for longer-term toxicity evaluations and elucidation of key cellular and molecular events involved in primary and secondary adaptation to chemical exposure, or for identification of important mediators of inflammation, proliferation and apoptosis. Progress in implementing a more effective strategy for in vitro-in vivo extrapolation and human risk assessment depends on significant advances in tissue culture technology and increasing their level of biological complexity. This article describes the current and ongoing need for more relevant, organotypic in vitro surrogate systems of human liver and recent efforts to recreate the multicellular architecture and hemodynamic properties of the liver using novel culture platforms. As these systems become more widely used for chemical and drug toxicity testing, there will be a corresponding need to establish standardized testing conditions, endpoint analyses and acceptance criteria. In the future, a balanced approach between sample throughput and biological relevance should provide better in vitro tools that are complementary with animal testing and assist in conducting more predictive human risk assessment.

Decreased hepatic peroxisome proliferator-activated receptor-γ contributes to increased sensitivity to endotoxin in obstructive jaundice

AIM: To investigate the role of hepatic peroxisome proliferator-activated receptor-γ (PPAR-γ) in increased susceptibility to endotoxin-induced toxicity in rats with bile duct ligation during endotoxemia.

METHODS: Male Sprague-Dawley rats were subjected to bile duct ligation (BDL). Sham-operated animals served as controls. DNA binding were determined by polymerase chain reaction, Western blotting analysis, and electrophoretic mobility shift assay, respectively. BDL and sham-operated rats received a non-lethal dose of intraperitoneal lipopolysaccharide (LPS) injection (3 mg/kg, i.p.). Additionally, the potential beneficial effects of the PPAR-γ agonist rosiglitazone were determined in BDL and sham-operated rats treated with a non-lethal dose of LPS. Survival was assessed in BDL rats treated with a non-lethal dose of LPS and in sham-operated rats treated at a lethal dose of LPS (6 mg/kg, i.p.).

RESULTS: PPAR-γ activity in rats undergoing BDL was significantly lower than in the sham-controls. Hepatic PPAR-γ gene expression was downregulated at both the mRNA and protein levels. In a parallel group, serum levels of pro-inflammatory cytokines were nearly undetectable in the sham-operated rats. When challenged with a non-lethal dose of LPS (3 mg/kg), the BDL rats had approximately a 2.4-fold increase in serum IL-6, a 2.7 fold increase in serum TNF-α, 2.2-fold increase in serum IL-1 and 4.2-fold increase in serum ALT. The survival rate was significantly lower as compared with that in sham-operated group. Additionally, rosiglitazone significantly reduced the concentration of TNF-α, IL-1β, IL-6 and ALT in sham-operated rats, but not in BDL rats, in response to LPS (3 mg/kg). Also, the survival was improved by rosiglitazone in sham-operated rats challenged with a lethal dose of LPS, but not in BDL rats, even with a non-lethal dose of LPS (3 mg/kg).

CONCLUSION: Obstructive jaundice downregulates hepatic PPAR-γ expression, which in turn may contribute to hypersensitivity towards endotoxin.

Protective effects of asiaticoside on septic lung injury in mice

Asiaticoside (AS), a major triterpenoid saponin component isolated from Centella asiatica, has been described to exhibit antioxidant and anti-inflammatory activities. The present study aimed to determine the protective effects and the underlying mechanisms of AS on septic lung injury induced by cecal ligation and puncture (CLP). Mice were pretreated with the AS (45 mg/kg) or AS as well as GW9662 at 1h before CLP, the survival, lung injury, inflammatory mediators and signaling molecules, and Peroxisome proliferator-activated receptor-γ (PPAR-γ) were determined 24 h after CLP. The results showed that AS significantly decreased CLP-induced the mortality, lung pathological damage, the infiltration of mononuclear, polymorphonuclear (PMN) leucocytes and total proteins. Moreover, AS inhibited CLP-induced the activation of mitogen-activated protein kinases (MAPKs) and nuclear factor-κB (NF-κB), the expression of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) protein in lung tissues, and the production of serum tumor necrosis factor (TNF-α) and interleukin-6 (IL-6). Interestingly, the expression of PPAR-γ protein in lung tissue was up-regulated by AS. Furthermore, GW9662 (the inhibitor of PPAR-γ) significantly reversed these beneficial effects of AS in septic mice. These findings suggest that AS could effectively protect from septic lung injury induced by CLP and the underlying mechanisms might be related to up-regulation of PPAR-γ expression to some extent, which inhibits MAPKs and NF-κB pathway.

Liver apoptosis is age dependent and is reduced by activation of peroxisome proliferator-activated receptor-gamma in hemorrhagic shock

A clinical observation in pediatric and adult intensive care units is that the incidence of multiple organ failure in pediatric trauma victims is lower than in adult patients. However, the molecular mechanisms are not yet defined. Recent experimental studies have shown that the nuclear peroxisome proliferator-activated receptor-gamma (PPARgamma) modulates the inflammatory process. In this study, we hypothesized that severity of liver injury may be age dependent and PPARgamma activation may provide beneficial effects. Hemorrhagic shock was induced in anesthetized young (3-5 mo old) and mature male Wistar rats (11-13 mo old) by withdrawing blood to a mean arterial blood pressure of 50 mmHg. After 3 h, rats were rapidly resuscitated with shed blood. Animals were euthanized 3 h after resuscitation. In mature rats, liver injury appeared more pronounced compared with young rats and was characterized by marked hepatocyte apoptosis, extravasation of erythrocytes, and accumulation of neutrophils. The ratio between the antiapoptotic protein Bcl-2 and the proapoptotic protein BAX was lower, whereas activity of caspase-3, the executioner of apoptosis, was higher in liver of mature rats compared with young rats. Plasma alanine aminotransferase levels were not different between the two age groups. This heightened liver apoptosis was associated with a significant downregulation of PPARgamma DNA binding in mature rats compared with young rats. Treatment with the PPARgamma ligand ciglitazone significantly reduced liver apoptosis in mature rats. Our data suggest that liver injury after severe hemorrhage is age dependent and PPARgamma activation is a novel hepatoprotective mechanism.

Lung injury after hemorrhage is age dependent: role of peroxisome proliferator-activated receptor gamma

OBJECTIVE

The incidence of multiple organ failure in pediatric trauma victims is lower than in the adult population. However, the molecular mechanisms are not yet defined. We investigated whether the pathophysiologic characteristics of hemorrhage-induced lung injury may be age dependent and may be regulated by the peroxisome proliferator-activated receptor gamma (PPARgamma).

DESIGN

Prospective, laboratory investigation that used an established rodent model of hemorrhagic shock.

SETTING

University hospital laboratory.

SUBJECTS

Young (n = 67; 3-5 months old) and mature (n = 66; 11-13 months old) male rats.

INTERVENTIONS

Hemorrhagic shock was induced in young and mature rats by withdrawing blood to a mean arterial blood pressure of 50 mm Hg. After 3 hours, rats were rapidly resuscitated by infusing the shed blood and killed 3 hours thereafter.

MEASUREMENTS AND MAIN RESULTS

In young rats, lung injury was characterized by accumulation of red cells and neutrophils at the end of the resuscitation period; on Western blot analysis, lung expression of intercellular adhesion molecule-1 was increased. In contrast, the severity of lung injury was more pronounced in mature rats. Lung myeloperoxidase activity and expression of constitutive and inducible intercellular adhesion molecule-1 was significantly higher in mature rats compared with young rats. Mature rats also had higher plasma levels of cytokines and chemokines compared with young rats. This heightened inflammation was associated with higher degree of activation of nuclear factor-kappaB and down-regulation of PPARgamma and heat shock factor-1 in the lung of mature rats compared with young rats. Treatment with the PPARgamma ligand, the cyclopentenone prostaglandin 15-deoxy-Delta-prostaglandin J2, ameliorated lung injury in young, but not in mature animals.

CONCLUSIONS

Lung injury after severe hemorrhage is age dependent and may be secondary to a diverse regulation of PPARgamma.

Activation of endoplasmic reticulum stress response following trauma-hemorrhage

Hemorrhagic trauma leads to organ dysfunction, sepsis and death. There is abnormal production of proinflammatory cytokines by Kupffer cells, tissue hypoxia and liver injury following trauma-hemorrhage. The physiological conditions consequent to trauma-hemorrhage are consistent with factors necessary to initiate endoplasmic reticulum (ER) stress and unfolded protein response. However, the contribution of ER stress to apoptosis and liver injury after trauma-hemorrhage is not known. In the present study ER stress was investigated in mice that underwent trauma-hemorrhage or sham operation. Expressions of endoplasmic reticulum stress proteins Bip, ATF6, PERK, IRE1alpha, and PDI were significantly elevated in the liver after trauma-hemorrhage compared to the controls. The ER stress associated proapoptotic transcription factor CHOP protein expression was also significantly elevated in trauma-hemorrhage group. Consistent with this, enhanced DNA fragmentation was observed, confirming apoptosis, in the liver following trauma-hemorrhage. These results demonstrate the initiation of ER stress and its role in apoptosis and liver injury, subsequent to hemorrhagic trauma.