Pathologic role of stressed-induced glucocorticoids in drug-induced liver injury in mice

Embryonic dexamethasone exposure exacerbates hepatic steatosis and APAP-mediated liver injury in zebrafish

Dexamethasone (DXMS), a synthetic glucocorticoid, is known for its pharmacological effects on anti-inflammation, stress response enhancement and immune suppression, and has been widely used to treat potential premature delivery and related diseases. However, emerging evidence has shown that prenatal DXMS exposure leads to increased susceptibility to multiple diseases. In the present study, we used zebrafish as a model to study the effects of embryonic DXMS exposure on liver development and disease. We discovered that embryonic DXMS exposure upregulated the levels of total cholesterol and triglycerides in the liver, increased the glycolysis process and ultimately caused hepatic steatosis in zebrafish larvae. Furthermore, DXMS exposure exacerbated hepatic steatosis in a zebrafish model of fatty liver disease. In addition, we showed that embryonic DXMS exposure worsened liver injury induced by paracetamol (N-acetyl-p-aminophenol, APAP), increased the infiltration of macrophages and neutrophils, and promoted the expression of inflammatory factors, leading to impeded liver regeneration. Taken together, our results provide new evidence that embryonic DXMS exposure exacerbates hepatic steatosis by activating glycolytic pathway, aggravates APAP-induced liver damage and impeded regeneration under a persistent inflammation, calling attention to DXMS administration during pregnancy with probable clinical implications for offspring.

The role of corticosterone in nevirapine-induced idiosyncratic drug-induced liver injury

Nevirapine, an antiretroviral used in the treatment of HIV, is associated with idiosyncratic drug-induced liver injury (IDILI), a potentially life-threatening adverse drug reaction. Its usage has decreased due to this concern, but it is still widely used in lower-resource settings. In general, the mechanisms underlying idiosyncratic drug reactions (IDRs) are poorly understood, but evidence indicates that most are immune-mediated. There is very limited understanding of the early immune response following administration of drugs associated with IDRs, which likely occurs due to reactive metabolite formation. In this work, we aimed to characterize the links between covalent binding of nevirapine, the development of an early immune response, and the subsequent liver injury using a mouse model. We describe initial attempts to characterize an early immune response to nevirapine followed by the discovery that nevirapine induced the release of corticosterone. Corticosterone release was partially associated with the degree of drug covalent binding in the liver but was also likely mediated by additional mechanisms at higher drug doses. Transcriptomic analysis confirmed metabolic activation, glucocorticoid signaling, and decreased immune activation; GDF-15 also warrants further investigation as part of the immune response to nevirapine. Finally, glucocorticoid blockade preceding the first dose of nevirapine attenuated nevirapine-induced liver injury at 3 weeks, suggesting that acute glucocorticoid signaling is harmful in the context of nevirapine-induced liver injury. This work demonstrates that nevirapine induces acute corticosterone release, which contributes to delayed-onset liver injury. It also has implications for screening drug candidates for IDILI risk and preventing nevirapine-induced IDILI.

Sodium Pentaborate Prevents Acetaminophen-Induced Hepatorenal Injury by Suppressing Oxidative Stress, Lipid Peroxidation, Apoptosis, and Inflammatory Cytokines in Rats

Acetaminophen (N-acetyl-p-aminophenol, APAP, or paracetamol) is one of the drugs that may be damaging to the kidneys and liver when used in excess. In this context, it is vital to treat these side effects on the liver and kidneys with various antioxidants. Diseases have been treated using herbal and mineral remedies since ancient times. The mineral boron, found in rocks and water, is a crucial ingredient with multiple positive biological effects. The primary objective of this research is to determine whether or not boron has a protective effect against the toxicity generated by APAP in rats. Male Sprague-Dawley rats were pretreated orally with boron-source sodium pentaborate (B50 and B100 mg/kg) for 6 days by gastric gavage in order to counteract the toxicity caused by a single dose of APAP (1g/kg). APAP increased lipid peroxidation as well as serum BUN, creatinine concentrations, and serum activities of AST, ALP, and ALT by consuming GSH in liver and kidney tissues. In addition, the activity of antioxidative enzymes, including SOD, CAT, and GPx, was diminished. Inflammatory indicators such as TNF-α, IL-1β, and IL-33 were elevated in conjunction with APAP toxicity. In kidney and liver tissues, APAP dramatically increased the activity of caspase-3 and triggered apoptosis. Sodium pentaborate therapy on a short-term basis reduced biochemical levels despite these effects of APAP. This study showed that boron protects rats from the harmful effects of APAP by acting as an anti-inflammatory, antioxidant, and anti-apoptotic agent.

Characterisation of forkhead box protein A3 as a key transcription factor for hepatocyte regeneration

Background & Aims

Liver regeneration is vital for the recovery of liver function after injury, yet the underlying mechanism remains to be elucidated. Forkhead box protein A3 (FOXA3), a member of the forkhead box family, plays important roles in endoplasmic reticulum stress sensing, and lipid and glucose homoeostasis, yet its functions in liver regeneration are unknown.

Methods

Here, we explored whether Foxa3 regulates liver regeneration via acute and chronic liver injury mice models. We further characterised the molecular mechanism by chromatin immunoprecipitation sequencing and rescue experiments in vivo and in vitro. Then, we assessed the impact of Foxa3 pharmacological activation on progression and termination of liver regeneration. Finally, we confirmed the Foxa3-Cebpb axis in human liver samples.

Results

Foxa3 is dominantly expressed in hepatocytes and cholangiocytes and is induced upon partial hepatectomy (PH) or carbon tetrachloride (CCl4) administration. Foxa3 deficiency in mice decreased cyclin gene levels and delayed liver regeneration after PH, or acute or chronic i.p. CCl4 injection. Conversely, hepatocyte-specific Foxa3 overexpression accelerated hepatocytes proliferation and attenuated liver damage in an CCl4-induced acute model. Mechanistically, Foxa3 directly regulates Cebpb transcription, which is involved in hepatocyte division and apoptosis both in vivo and in vitro. Of note, Cebpb overexpression in livers of Foxa3-deficient mice rescued their defects in cell proliferation and regeneration upon CCl4 treatment. In addition, pharmacological induction of Foxa3 via cardamonin speeded up hepatocyte proliferation after PH, without interfering with liver regeneration termination. Finally, Cebpb and Ki67 levels had a positive correlation with Foxa3 expression in human chronic disease livers.

Conclusions

These data characterise Foxa3 as a vital regulator of liver regeneration, which may represent an essential factor to maintain liver mass after liver injury by governing Cebpb transcription.

Impact and Implications

Liver regeneration is vital for the recovery of liver function after chemical insults or hepatectomy, yet the underlying mechanism remains to be elucidated. Herein, via in vitro and in vivo models and analysis, we demonstrated that Forkhead box protein A3 (FOXA3), a Forkhead box family member, maintained normal liver regeneration progression by governing Cebpb transcription and proposed cardamonin as a lead compound to induce Foxa3 and accelerate liver repair, which signified that FOXA3 may be a potential therapeutic target for further preclinical study on treating liver injury.

Arylacetamide deacetylase knockout mice are sensitive to ketoconazole-induced hepatotoxicity and adrenal insufficiency

Orally administered ketoconazole may rarely induce liver injury and adrenal insufficiency. A metabolite formed by arylacetamide deacetylase (AADAC)-mediated hydrolysis has been observed in cellulo studies, and it is relevant to ketoconazole-induced cytotoxicity. This study tried to examine the significance of AADAC in ketoconazole-induced toxicity in vivo using Aadac knockout mice. Oral administration of 150 mg/kg ketoconazole resulted in the area under the plasma concentration-time curve values of ketoconazole and N-deacetylketoconazole, a hydrolyzed metabolite of ketoconazole, in Aadac knockout mice being significantly higher and lower than those in wild-type mice, respectively. With the administration of ketoconazole (300 mg/kg/day) for 7 days, Aadac knockout mice showed higher mortality (100%) than wild-type mice (42.9%), and they also showed significantly higher plasma alanine transaminase and lower corticosterone levels, thus representing liver injury and steroidogenesis inhibition, respectively. It was suggested that a higher plasma ketoconazole concentration likely accounts for the inhibition of the synthesis of corticosterone, which has anti-inflammatory effects, in the adrenal gland in Aadac KO mice. In Aadac knockout mice, hepatic mRNA levels of immune- and inflammation-related factors were increased by the administration of 300 mg/kg ketoconazole, and the increase was restored by the replenishment of corticosterone (40 mg/kg, s.c.) along with recoveries of plasma alanine transaminase levels. In conclusion, Aadac defects exacerbate ketoconazole-induced liver injury by inhibiting glucocorticoid synthesis and enhancing the inflammatory response. This in vivo study revealed that the hydrolysis of ketoconazole by AADAC can mitigate ketoconazole-induced toxicities.

Corticosterone-mediated microglia activation affects dendritic spine plasticity and motor learning functions in minimal hepatic encephalopathy

Minimal hepatic encephalopathy (MHE) is characterized as cognitive deficits including memory and learning dysfunctions after liver injuries or hepatic diseases. Our understandings of neurological mechanisms of MHE-associated cognitive syndromes, however, are far from complete. In the current study we generated a mouse MHE model by repetitive administrations of thioacetamide (TAA), which induced hyperammonemia plus elevated proinflammatory cytokines in both the general circulation and motor cortex. MHE mice presented prominent motor learning deficits, which were associated with excess dendritic spine pruning in the motor cortex under 2-photon in vivo microscopy. The pharmaceutical blockade of glucocorticoid receptor or suppression of its biosynthesis further rescued motor learning deficits and synaptic protein loss. Moreover, MHE mice presented microglial activation, which can be alleviated after glucocorticoid pathway inhibition. In sum, our data demonstrates corticosterone-induced microglial activation, synaptic over-pruning and motor learning impairments in MHE, providing new insights for MHE pathogenesis and potential targets of clinical interventions.

Selective Glucocorticoid Receptor Modulators (SGRMs) Delay Castrate-Resistant Prostate Cancer Growth

Increased glucocorticoid receptor (GR) expression and activity following androgen blockade can contribute to castration-resistant prostate cancer (CRPC) progression. Therefore, we hypothesized that GR antagonism will have therapeutic benefit in CRPC. However, the FDA-approved nonselective, steroidal GR antagonist, mifepristone, lacks GR specificity, reducing its therapeutic potential. Here, we report that two novel nonsteroidal and highly selective GR modulators (SGRM), CORT118335 and CORT108297, have the ability to block GR activity in prostate cancer and slow CRPC progression. In contrast to mifepristone, these novel SGRMs did not affect androgen receptor (AR) signaling, but potently inhibited GR transcriptional activity. Importantly, SGRMs decreased GR-mediated tumor cell viability following AR blockade. In vivo, SGRMs significantly inhibited CRPC progression in high GR-expressing, but not in low GR-expressing xenograft models. Transcriptome analysis following AR blockade and GR activation revealed that these SGRMs block GR-mediated proliferative gene expression pathways. Furthermore, GR-regulated proliferation-associated genes AKAP12, FKBP5, SGK1, CEBPD, and ZBTB16 are inhibited by CORT108297 treatment in vivo Together, these data suggest that GR-selective nonsteroidal SGRMs potently inhibit GR activity and prostate cancer growth despite AR pathway inhibition, demonstrating the therapeutic potential of SGRMs in GR-expressing CRPC. Mol Cancer Ther; 16(8); 1680-92. ©2017 AACR.

Simultaneous Assessment of the Efficacy and Toxicity of Marine Mollusc-Derived Brominated Indoles in an In Vivo Model for Early Stage Colon Cancer

The acute apoptotic response to genotoxic carcinogens animal model has been extensively used to assess the ability of drugs and natural products like dietary components to promote apoptosis in the colon and protect against colorectal cancer (CRC). This work aimed to use this model to identify the main chemopreventative agent in extracts from an Australian mollusc Dicathais orbita, while simultaneously providing information on their potential in vivo toxicity. After 2 weeks of daily oral gavage with bioactive extracts and purified brominated indoles, mice were injected with the chemical carcinogen azoxymethane (AOM; 10 mg/kg) and then killed 6 hours later. Efficacy was evaluated using immunohistochemical and hematoxylin staining, and toxicity was assessed via hematology, blood biochemistry, and liver histopathology. Comparison of saline- and AOM-injected controls revealed that potential toxic side effects can be interpreted from blood biochemistry and hematology using this short-term model, although AOM negatively affected the ability to detect histopathological effects in the liver. Purified 6-bromoisatin was identified as the main cancer preventive agent in the Muricidae extract, significantly enhancing apoptosis and reducing cell proliferation in the colonic crypts at 0.05 mg/g. There was no evidence of liver toxicity associated with 6-bromoisatin, whereas 0.1 mg/g of the brominated indole tyrindoleninone led to elevated aspartate aminotransferase levels and a reduction in red blood cells. As tyrindoleninone is converted to 6-bromoisatin by oxidation, this information will assist in the optimization and quality control of a chemopreventative nutraceutical from Muricidae. In conclusion, preliminary data on in vivo safety can be simultaneously collected when testing the efficacy of new natural products, such as 6-bromoisatin from Muricidae molluscs for early stage prevention of colon cancer.

Activation of GR but not PXR by dexamethasone attenuated acetaminophen hepatotoxicities via Fgf21 induction

Glucocorticoid receptor (GR) signaling is indispensable for cell growth and development, and plays important roles in drug metabolism. Fibroblast growth factor (Fgf) 21, an important regulator of glucose, lipid, and energy metabolism, plays a cytoprotective role by attenuating toxicities induced by chemicals such as dioxins, acetaminophen (APAP), and alcohols. The present study investigates the impact of dexamethasone (DEX)-activated GR on Fgf21 expression and how it affects the progression of APAP-induced hepatotoxicity. Our results showed that DEX dose/concentration- and time-dependently increased Fgf21 mRNA and protein expression in mouse liver as well as cultured mouse and human hepatoma cells. By using PXR-null mouse model, we demonstrated that DEX induced Fgf21 expression by a PXR-independent mechanism. In cultured mouse and human hepatoma cells, inhibition of GR signaling, by RU486 (Mifepristone) or GR silencing using GR-specific siRNA, attenuated DEX-induced Fgf21 expression. In addition, DEX increased luciferase reporter activity driven by the 3.0-kb mouse and human Fgf21/FGF21 gene promoter. Further, ChIP-qPCR assays demonstrated that DEX increased the binding of GR to the specific cis-regulatory elements located in the 3.0-kb mouse and human Fgf21/FGF21 gene promoter. Pretreatment of 2mg/kg DEX ameliorated APAP-induced liver injury in wild-type but not Fgf21-null mice. In conclusion, via GR activation, DEX induced Fgf21 expression in mouse liver and human hepatoma cells.

Immune mechanisms in acetaminophen-induced acute liver failure

An overdose of acetaminophen (N-acetyl-p-aminophenol, APAP), also termed paracetamol, can cause severe liver damage, ultimately leading to acute liver failure (ALF) with the need of liver transplantation. APAP is rapidly taken up from the intestine and metabolized in hepatocytes. A small fraction of the metabolized APAP forms cytotoxic mitochondrial protein adducts, leading to hepatocyte necrosis. The course of disease is not only critically influenced by dose of APAP and the initial hepatocyte damage, but also by the inflammatory response following acetaminophen-induced liver injury (AILI). As revealed by mouse models of AILI and corresponding translational studies in ALF patients, necrotic hepatocytes release danger-associated-molecular patterns (DAMPs), which are recognized by resident hepatic macrophages, Kupffer cell (KC), and neutrophils, leading to the activation of these cells. Activated hepatic macrophages release various proinflammatory cytokines, such as TNF-α or IL-1β, as well as chemokines (e.g., CCL2) thereby further enhancing inflammation and increasing the influx of immune cells, like bone-marrow derived monocytes and neutrophils. Monocytes are mainly recruited via their receptor CCR2 and aggravate inflammation. Infiltrating monocytes, however, can mature into monocyte-derived macrophages (MoMF), which are, in cooperation with neutrophils, also involved in the resolution of inflammation. Besides macrophages and neutrophils, distinct lymphocyte populations, especially γδ T cells, are also linked to the inflammatory response following an APAP overdose. Natural killer (NK), natural killer T (NKT) and T cells possibly further perpetuate inflammation in AILI. Understanding the complex interplay of immune cell subsets in experimental models and defining their functional involvement in disease progression is essential to identify novel therapeutic targets for human disease.

Optimization of stress response through the nuclear receptor-mediated cortisol signalling network

It is an accepted paradigm that extended stress predisposes an individual to pathophysiology. However, the biological adaptations to minimize this risk are poorly understood. Using a computational model based upon realistic kinetic parameters we are able to reproduce the interaction of the stress hormone cortisol with its two nuclear receptors, the high-affinity glucocorticoid receptor and the low-affinity pregnane X-receptor. We demonstrate that regulatory signals between these two nuclear receptors are necessary to optimize the body's response to stress episodes, attenuating both the magnitude and duration of the biological response. In addition, we predict that the activation of pregnane X-receptor by multiple, low-affinity endobiotic ligands is necessary for the significant pregnane X-receptor-mediated transcriptional response observed following stress episodes. This integration allows responses mediated through both the high and low-affinity nuclear receptors, which we predict is an important strategy to minimize the risk of disease from chronic stress.

Glucocorticoid receptor antagonism as a novel therapy for triple-negative breast cancer

PURPOSE

Triple-negative breast cancer (TNBC) accounts for 10% to 20% of newly diagnosed invasive breast cancer. Finding effective targets for chemotherapy-resistant TNBC has proven difficult in part because of TNBC's molecular heterogeneity. We have previously reported that likely because of the antiapoptotic activity of glucocorticoid receptor (GR) in estrogen receptor (ER)-negative breast epithelial and cancer cells, high GR expression/activity in early-stage TNBC significantly correlates with chemotherapy resistance and increased recurrence. We hypothesized that pretreatment with mifepristone, a GR antagonist, would potentiate the efficacy of chemotherapy in GR+ TNBCs by inhibiting the antiapoptotic signaling pathways of GR and increasing the cytotoxic efficiency of chemotherapy.

EXPERIMENTAL DESIGN

TNBC cell apoptosis was examined in the context of physiologic glucocorticoid concentrations, chemotherapy, and/or pharmacologic concentrations of mifepristone. We used high-throughput live microscopy with continuous recording to measure apoptotic cells stained with a fluorescent dye and Western blot analysis to detect caspase-3 and PARP cleavage. The effect of mifepristone on GR-mediated gene expression was also measured. TNBC xenograft studies were performed in female severe combined immunodeficient (SCID) mice and tumors were measured following treatment with vehicle, paclitaxel, or mifepristone/paclitaxel.

RESULTS

We found that although mifepristone treatment alone had no significant effect on TNBC cell viability or clonogenicity in the absence of chemotherapy, the addition of mifepristone to dexamethasone/paclitaxel treatment significantly increased cytotoxicity and caspase-3/PARP cleavage. Mifepristone also antagonized GR-induced SGK1 and MKP1/DUSP1 gene expression while significantly augmenting paclitaxel-induced GR+ MDA-MB-231 xenograft tumor shrinkage in vivo.

CONCLUSIONS

These results suggest that mifepristone pretreatment could be a useful strategy for increasing tumor cell apoptosis in chemotherapy-resistant GR+ TNBC.

Mapping acute systemic effects of inhaled particulate matter and ozone: multiorgan gene expression and glucocorticoid activity

Recent epidemiological studies have demonstrated associations between air pollution and adverse effects that extend beyond respiratory and cardiovascular disease, including low birth weight, appendicitis, stroke, and neurological/neurobehavioural outcomes (e.g., neurodegenerative disease, cognitive decline, depression, and suicide). To gain insight into mechanisms underlying such effects, we mapped gene profiles in the lungs, heart, liver, kidney, spleen, cerebral hemisphere, and pituitary of male Fischer-344 rats immediately and 24h after a 4-h exposure by inhalation to particulate matter (0, 5, and 50mg/m³ EHC-93 urban particles) and ozone (0, 0.4, and 0.8 ppm). Pollutant exposure provoked differential expression of genes involved in a number of pathways, including antioxidant response, xenobiotic metabolism, inflammatory signalling, and endothelial dysfunction. The mRNA profiles, while exhibiting some interorgan and pollutant-specific differences, were remarkably similar across organs for a set of genes, including increased expression of redox/glucocorticoid-sensitive genes and decreased expression of inflammatory genes, suggesting a possible hormonal effect. Pollutant exposure increased plasma levels of adrenocorticotropic hormone and the glucocorticoid corticosterone, confirming activation of the hypothalamic-pituitary-adrenal axis, and there was a corresponding increase in markers of glucocorticoid activity. Although effects were transient and presumably represent an adaptive response to acute exposure in these healthy animals, chronic activation and inappropriate regulation of the hypothalamic-pituitary-adrenal axis are associated with adverse neurobehavioral, metabolic, immune, developmental, and cardiovascular effects. The experimental data are consistent with epidemiological associations of air pollutants with extrapulmonary health outcomes and suggest a mechanism through which such health effects may be induced.

Interpreting Stress Responses during Routine Toxicity Studies

Stress often occurs during toxicity studies. The perception of sensory stimuli as stressful primarily results in catecholamine release and activation of the hypothalamic–pituitary–adrenal (HPA) axis to increase serum glucocorticoid concentrations. Downstream effects of these neuroendocrine signals may include decreased total body weights or body weight gain; food consumption and activity; altered organ weights (e.g., thymus, spleen, adrenal); lymphocyte depletion in thymus and spleen; altered circulating leukocyte counts (e.g., increased neutrophils with decreased lymphocytes and eosinophils); and altered reproductive functions. Typically, only some of these findings occur in a given study. Stress responses should be interpreted as secondary (indirect) rather than primary (direct) test article–related findings. Determining whether effects are the result of stress requires a weight-of-evidence approach. The evaluation and interpretation of routinely collected data (standard in-life, clinical pathology, and anatomic pathology endpoints) are appropriate and generally sufficient to assess whether or not changes are secondary to stress. The impact of possible stress-induced effects on data interpretation can partially be mitigated by toxicity study designs that use appropriate control groups (e.g., cohorts treated with vehicle and subjected to the same procedures as those dosed with test article), housing that minimizes isolation and offers environmental enrichment, and experimental procedures that minimize stress and sampling and analytical bias.

This article is a comprehensive overview of the biological aspects of the stress response, beginning with a Summary (Section 1) and an Introduction (Section 2) that describes the historical and conventional methods used to characterize acute and chronic stress responses. These sections are followed by reviews of the primary systems and parameters that regulate and/or are influenced by stress, with an emphasis on parameters evaluated in toxicity studies: In-life Procedures (Section 3), Nervous System (Section 4), Endocrine System (Section 5), Reproductive System (Section 6), Clinical Pathology (Section 7), and Immune System (Section 8). The paper concludes (Section 9) with a brief discussion on Minimizing Stress-Related Effects (9.1.), and a final section explaining why Parameters routinely measured are appropriate for assessing the role of stress in toxicology studies (9.2.).

Endogenous interleukin-4 regulates glutathione synthesis following acetaminophen-induced liver injury in mice

In a recent study, we reported that interleukin (IL)-4 had a protective role against acetaminophen (APAP)-induced liver injury (AILI), although the mechanism of protection was unclear. Here, we carried out more detailed investigations and have shown that one way IL-4 may control the severity of AILI is by regulating glutathione (GSH) synthesis. In the present studies, the protective role of IL-4 in AILI was established definitively by showing that C57BL/6J mice made deficient in IL-4 genetically (IL-4(-/-)) or by depletion with an antibody, were more susceptible to AILI than mice not depleted of IL-4. The increased susceptibility of IL-4(-/-) mice was not due to elevated levels of hepatic APAP-protein adducts but was associated with a prolonged reduction in hepatic GSH that was attributed to decreased gene expression of γ-glutamylcysteine ligase (γ-GCL). Moreover, administration of recombinant IL-4 to IL-4(-/-) mice postacetaminophen treatment diminished the severity of liver injury and increased γ-GCL and GSH levels. We also report that the prolonged reduction of GSH in APAP-treated IL-4(-/-) mice appeared to contribute toward increased liver injury by causing a sustained activation of c-Jun-N-terminal kinase (JNK) since levels of phosphorylated JNK remained significantly higher in the IL-4(-/-) mice up to 24 h after APAP treatment. Overall, these results show for the first time that IL-4 has a role in regulating the synthesis of GSH in the liver under conditions of cellular stress. This mechanism appears to be responsible at least in part for the protective role of IL-4 against AILI in mice and may have a similar role not only in AILI in humans but also in pathologies of the liver caused by other drugs and etiologies.

Mechanism of exacerbative effect of progesterone on drug-induced liver injury

Drug-induced liver injury (DILI) is a major safety concern in drug development and clinical drug therapy. However, the underlying mechanism of DILI is little known. It is generally believed that women exhibit worse outcomes from DILI than men. Recently, we found that pretreatment of mice with estradiol attenuated halothane (HAL)-induced liver injury, whereas pretreatment with progesterone exacerbated it in female mice. To investigate the mechanism of sex difference of DILI, we focused on progesterone in this study. We found the exacerbating effect of progesterone in thioacetamide (TA), α-naphthylisothiocyanate, and dicloxacillin-induced liver injury only in female mice. Higher number of myeloperoxidase-positive mononuclear cells infiltrated into the liver and increased levels of Chemokine (C-X-C motif) ligand 1 and 2 (CXCL1 and CXCL2) and intercellular adhesion molecule-1 in the liver were observed. Interestingly, CXCL1 was slightly increased by progesterone pretreatment alone. Progesterone pretreatment increased the extracellular signal-regulated kinase (ERK) phosphorylation in HAL-induced liver injury. Pretreatment with U0126 (ERK inhibitor) significantly suppressed the exacerbating effect of progesterone and the expression of inflammatory mediators. In addition, pretreatment with gadolinium chloride (GdCl(3): inhibitor of Kupffer cells) significantly suppressed the exacerbating effect of progesterone pretreatment and the expression of inflammatory mediators. Moreover, posttreatment of RU486 (progesterone receptor antagonist) 1 h after the HAL or TA administration ameliorated the HAL- or TA-induced liver injury, respectively, in female mice. In conclusion, progesterone exacerbated the immune-mediated hepatotoxic responses in DILI via Kupffer cells and ERK pathway. The inhibition of progesterone receptor and decrease of the immune response may have important therapeutic implications in DILI.

Activation of MDL-1 (CLEC5A) on immature myeloid cells triggers lethal shock in mice

Systemic inflammatory response syndrome (SIRS) is a potentially lethal condition, as it can progress to shock, multi-organ failure, and death. It can be triggered by infection, tissue damage, or hemorrhage. The role of tissue injury in the progression from SIRS to shock is incompletely understood. Here, we show that treatment of mice with concanavalin A (ConA) to induce liver injury triggered a G-CSF-dependent hepatic infiltration of CD11b+Gr-1+Ly6G+Ly6C+ immature myeloid cells that expressed the orphan receptor myeloid DAP12-associated lectin-1 (MDL-1; also known as CLEC5A). Activation of MDL-1 using dengue virus or an agonist MDL-1-specific antibody in the ConA-treated mice resulted in shock. The MDL-1+ cells were pathogenic, and in vivo depletion of MDL-1+ cells provided protection. Triggering MDL-1 on these cells induced production of NO and TNF-α, which were found to be elevated in the serum of treated mice and required for MDL-1-induced shock. Surprisingly, MDL-1-induced NO and TNF-α production required eNOS but not iNOS. Activation of DAP12, DAP10, Syk, PI3K, and Akt was critical for MDL-1-induced shock. In addition, Akt physically interacted with and activated eNOS. Therefore, triggering of MDL-1 on immature myeloid cells and production of NO and TNF-α may play a critical role in the pathogenesis of shock. Targeting the MDL-1/Syk/PI3K/Akt/eNOS pathway represents a potential new therapeutic strategy to prevent the progression of SIRS to shock.

Natural killer cells mediate severe liver injury in a murine model of halothane hepatitis

Severe halothane (HAL)-induced hepatotoxicity occurs in one in 6000-30,000 patients by an unknown mechanism. Female sex is a risk factor in humans and rodents. We tested the hypothesis that a sex difference in natural killer (NK) cell activity contributes to HAL-induced liver injury. HAL (15 mmol/kg, ip) treatment resulted in severe liver injury by 12 h in female, wild-type BALB/cJ mice, and the magnitude of liver injury varied with stage of the estrous cycle. Ovariectomized (OVX) mice developed only mild liver injury. Plasma interferon-gamma (IFN-γ) was elevated 10-fold in HAL-treated females compared with similarly treated male mice or with OVX female mice. IFN-γ knockout mice were resistant to severe HAL-induced liver injury. The deactivation of NK cells with anti-asialo GM1 treatment attenuated liver injury and the increase in plasma IFN-γ compared with immunoglobulin G-treated control mice. Mice with a mutated form of perforin, a protein involved in granule-mediated cytotoxicity, were protected from severe liver injury. Furthermore, HAL increased the activity of NK cells in vivo, as indicated by increased surface expression of CD69, an early activation marker. In response to HAL, NK cell receptor ligands on the surface of hepatocytes were expressed in a manner that can activate NK cells. These results confirm the sexual dimorphic hepatotoxic response to HAL in mice and suggest that IFN-γ and NK cells have essential roles in the development of severe HAL-induced hepatotoxicity.