17β-Estradiol protects against acetaminophen-overdose-induced acute oxidative hepatic damage and increases the survival rate in mice

Growth Hormone Accelerates Recovery From Acetaminophen-Induced Murine Liver Injury

Background and Aims

Acetaminophen (APAP) overdose is the leading cause of acute liver failure, with one available treatment, N-acetyl cysteine (NAC). Yet, NAC effectiveness diminishes about ten hours after APAP overdose, urging for therapeutic alternatives. This study addresses this need by deciphering a mechanism of sexual dimorphism in APAP-induced liver injury, and leveraging it to accelerate liver recovery via growth hormone (GH) treatment. GH secretory patterns, pulsatile in males and near-continuous in females, determine the sex bias in many liver metabolic functions. Here, we aim to establish GH as a novel therapy to treat APAP hepatotoxicity.

Approach and Results

Our results demonstrate sex-dependent APAP toxicity, with females showing reduced liver cell death and faster recovery than males. Single-cell RNA sequencing analyses reveal that female hepatocytes have significantly greater levels of GH receptor expression and GH pathway activation compared to males. In harnessing this female-specific advantage, we demonstrate that a single injection of recombinant human GH protein accelerates liver recovery, promotes survival in males following sub-lethal dose of APAP, and is superior to standard-of-care NAC. Alternatively, slow-release delivery of human GH via the safe nonintegrative lipid nanoparticle-encapsulated nucleoside-modified mRNA (mRNA-LNP), a technology validated by widely used COVID-19 vaccines, rescues males from APAP-induced death that otherwise occurred in control mRNA-LNP-treated mice.

Conclusions

Our study demonstrates a sexually dimorphic liver repair advantage in females following APAP overdose, leveraged by establishing GH as an alternative treatment, delivered either as recombinant protein or mRNA-LNP, to potentially prevent liver failure and liver transplant in APAP-overdosed patients.

Effects of 5α-dihydrotestosterone on the modulation of monocyte/macrophage response to Staphylococcus aureus: an in vitro study

BACKGROUND

Staphylococcus aureus (S. aureus) is a pathogen responsible for a wide range of clinical manifestations and potentially fatal conditions. There is a paucity of information on the influence of androgens in the immune response to S. aureus infection. In this study, we evaluated the influence of the hormone 5α-dihydrotestosterone (DHT) on mouse peritoneal macrophages (MPMs) and human peripheral blood monocytes (HPBMs) induced by S. aureus.

METHODS

An in vitro model of MPMs from BALB/c sham males, orchiectomised (OQX) males, and females was used. Cells were inoculated with 10 μL of S. aureus, phage-type 80 or sterile saline (control) for 6 h. The MPMs of OQX males and females were pre-treated with 100 μL of 10^-2 M DHT for 24 h before inoculation with S. aureus. The concentration of the cytokines TNF-α, IL-1α, IL-6, IL-8, and IL-10; total nitrites (NO^-2); and hydrogen peroxide (H₂O₂) were measured in the supernatant of MPM cultures. In addition, the toll-like receptor 2 (TLR2) and nuclear factor kappa B (NF-kB) genes that are involved in immune responses were analysed. For the in vitro model of HPBMs, nine men and nine women of childbearing age were selected and HPBMs were isolated from samples of the volunteers' peripheral blood. In women, blood was collected during the periovulatory period. The HPBMs were inoculated with S. aureus for 6 h and the supernatant was collected for the analysis of cytokines TNF-α, IL-6, IL-12; and GM-CSF, NO^-2, and H₂O₂. The HPBMs were then removed for the analysis of 84 genes involved in the host's response to bacterial infections by RT-PCR array. GraphPad was used for statistical analysis with a p value < 0.05.

RESULTS

Our data demonstrated that MPMs from sham males inoculated with S. aureus displayed higher concentrations of inflammatory cytokines and lower concentrations of IL-10, NO^-2, and H₂O₂ when compared with MPMs from OQX males and females. A similar result was observed in the HPBMs of men when compared with those of women. Previous treatment with DHT in women HPBMs increased the production of pro-inflammatory cytokines and decreased the levels of IL-10, NO^-2, and H₂O₂. The analysis of gene expression showed that DHT increased the activity of the TLR2 and NF-kB pathways in both MPMs and HPBMs.

CONCLUSIONS

We found that DHT acts as an inflammatory modulator in the monocyte/macrophage response induced by S. aureus and females exhibit a better immune defence response against this pathogen.

Enhanced therapeutic efficacy of a novel self-micellizing nanoformulation-loading fisetin against acetaminophen-induced liver injury

Aim: To evaluate the feasibility of using dipotassium glycyrrhizinate (DG) as a nanocarrier-loading fisetin (FIT) with strengthened treatment efficacies against liver injury induced by acetaminophen overdose. Methods: DG-FIT was prepared, and its efficacy against liver injury induced by acetaminophen overdose was evaluated. Results: DG-FIT was successfully fabricated with excellent physicochemical properties. DG-FIT could be easily dissolved in water to form a clear micelle solution with high FIT encapsulation efficiency. FIT in DG-FIT exhibited a dramatically improved aqueous solubility. DG-FIT improved intestinal permeation. Regarding in vivo efficacies, DG-FIT exhibited significant effect against acetaminophen overdose by suppressing oxidative stress and proinflammatory cytokines involved. Conclusion: DG-FIT formulation possibly represents a promising method for strengthening the efficacy of FIT against acetaminophen-induced liver injury.

Estrogen receptor agonists protect against acetaminophen-induced hepatorenal toxicity in rats

AIMS

Acetaminophen-induced hepatorenal toxicity varies among sexes with controversial results among species. The aim was to compare the impact of sex and ovarian hormones on hepatorenal toxicity and to elucidate protective effects of estrogen and estrogen receptor (ER) agonists.

MAIN METHODS

Under anesthesia, female rats underwent ovariectomy (OVX) or sham-OVX. Starting at postsurgical 40th day, OVX-rats received subcutaneously (each, 1 mg/kg/day) 17β-estradiol (E₂), ERβ-agonist (DPN) or ERα-agonist (PPT) for 10 days, while male and sham-OVX rats received vehicle for 10 days. Then, rats received either acetaminophen (3 g/kg) or saline by orogastric gavage and were decapitated at 24th h. Blood samples were obtained to measure serum ALT, AST, BUN, creatinine levels. Liver and kidney samples were obtained for histopathologic examination and for analyzing levels of luminol- and lucigenin-chemiluminescence, glutathione and myeloperoxidase activity.

KEY FINDINGS

Compared to their control groups, levels of AST, ALT, BUN, creatinine, hepatic and renal myeloperoxidase activity and chemiluminescence levels were increased, and hepatic glutathione level was decreased in acetaminophen-administered male groups, while ALT and hepatic chemiluminescence levels were not elevated in sham-OVX-rats. Both ER-agonists and E₂ reduced BUN, creatinine and reversed all oxidative parameters in renal tissues of OVX-rats. Additionally, ERα-agonist reversed all hepatic injury parameters, while ERβ-agonist elevated hepatic glutathione level.

SIGNIFICANCE

Acetaminophen toxicity in female rats presented with a more preserved hepatic function, while renal toxicity was not influenced by sex or by the lack of ovarian hormones. Pretreatment with estrogen or ER agonists, via their antioxidant actions, provided protective effects on acetaminophen-induced hepatorenal toxicity.

Identifying drug-target interactions based on graph convolutional network and deep neural network

Identification of new drug-target interactions (DTIs) is an important but a time-consuming and costly step in drug discovery. In recent years, to mitigate these drawbacks, researchers have sought to identify DTIs using computational approaches. However, most existing methods construct drug networks and target networks separately, and then predict novel DTIs based on known associations between the drugs and targets without accounting for associations between drug-protein pairs (DPPs). To incorporate the associations between DPPs into DTI modeling, we built a DPP network based on multiple drugs and proteins in which DPPs are the nodes and the associations between DPPs are the edges of the network. We then propose a novel learning-based framework, 'graph convolutional network (GCN)-DTI', for DTI identification. The model first uses a graph convolutional network to learn the features for each DPP. Second, using the feature representation as an input, it uses a deep neural network to predict the final label. The results of our analysis show that the proposed framework outperforms some state-of-the-art approaches by a large margin.

Simvastatin protects against acetaminophen-induced liver injury in mice

The present study aimed to investigate the effect of simvastatin on acetaminophen (APAP) hepatotoxicity in a mouse model. Male C57BL/6 mice were allocated into the following groups: control, APAP, APAP+SIM10, APAP+SIM20, APAP+SIM100 and APAP+SIM200 groups. The mice in the APAP group were treated with saline intraperitoneally (i.p.) 72 h before and 24 h or 72 h after APAP challenge (i.p., 400 mg/kg of APAP). The simvastatin-treated groups were treated with different doses of simvastatin i.p. (10, 20, 100 and 200 mg/kg/day) as in the APAP group. After 24 h or 72 h of APAP challenge, blood and liver samples were collected to detect hepatic injury and liver regeneration. The results showed that low doses of simvastatin (10 and 20 mg/kg) could significantly reverse the histological change and decrease hepatic injury. Simvastatin also reduced the serum cytokine levels and transcriptional levels of tumor necrosis factor-α and interleukin-6 in the liver. The malonyldialdehyde and myeloperoxidase levels significantly decreased in the simvastatin treatment groups compared with the APAP group. Simvastatin restored the decrease in superoxide dismutase, catalase, glutathione and glutathione peroxidase activities induced by APAP hepatotoxicity. In addition, simvastatin inhibited hepatic C/EBP-homologous protein expression and hepatocyte apoptosis. However, simvastatin had no effect on liver regeneration after APAP hepatotoxicity. Moreover, high doses could aggravate APAP-induced liver injury. In conclusion, low doses of simvastatin had a significant therapeutic effect in APAP-induced liver injury by inhibiting oxidative stress, inflammation and apoptosis. However, high doses of simvastatin had adverse hepatotoxicity.

Glucocorticoids, Sex Hormones, and Immunity

Glucocorticoid hormones regulate essential body functions in mammals, control cell metabolism, growth, differentiation, and apoptosis. Importantly, they are potent suppressors of inflammation, and multiple immune-modulatory mechanisms involving leukocyte apoptosis, differentiation, and cytokine production have been described. Due to their potent anti-inflammatory and immune-suppressive activity, synthetic glucocorticoids (GCs) are the most prescribed drugs used for treatment of autoimmune and inflammatory diseases. It is long been noted that males and females exhibit differences in the prevalence in several autoimmune diseases (AD). This can be due to the role of sexual hormones in regulation of the immune responses, acting through their endogenous nuclear receptors to mediate gene expression and generate unique gender-specific cellular environments. Given the fact that GCs are the primary physiological anti-inflammatory hormones, and that sex hormones may also exert immune-modulatory functions, the link between GCs and sex hormones may exist. Understanding the nature of this possible crosstalk is important to unravel the reason of sexual disparity in AD and to carefully prescribe these drugs for the treatment of inflammatory diseases. In this review, we discuss similarities and differences between the effects of sex hormones and GCs on the immune system, to highlight possible axes of functional interaction.

Glutathione peroxidase 3 is a protective factor against acetaminophen‑induced hepatotoxicity in vivo and in vitro

Acetaminophen (APAP) is a widely available antipyretic and analgesic; however, overdose of the drug inflicts severe damage to the liver. It is well established that the hepatotoxicity of APAP is initiated by formation of a reactive metabolite, N-acetyl-p-benzoquinone imine (NAPQI), which can be detoxified by conjugation with reduced glutathione (GSH), a typical antioxidant. We recently found that the blood mRNA expression level of glutathione peroxidase 3 (Gpx3), which catalyzes the oxidation of GSH, is associated with the extent of APAP-induced hepatotoxicity in mice. The present study was carried out to determine the in vivo and in vitro role of GPx3 in APAP-induced hepatotoxicity. In in vivo experiments, oral administration of APAP to mice induced liver injury. Such liver injury was greater in males than in females, although no gender difference in the plasma concentration of APAP was found. Female mice had a 2-fold higher expression of Gpx3 mRNA and higher plasma GPx activity than male mice. 17β-estradiol, a major female hormone, decreased APAP-induced hepatotoxicity and increased both the expression of blood Gpx3 mRNA and plasma GPx activity, suggesting that the cytoprotective action of this hormone is mediated by the increase in GPx3. To further clarify the role of GPx3 in APAP-induced hepatotoxicity, we evaluated the effect of a change in cellular GPx3 expression resulting from transfection of either siRNA-GPx3 or a GPx3 expression vector on NAPQI-induced cellular injury (as assessed by a tetrazolium assay) in in vitro experiments using heterogeneous cultured human cell lines (Huh-7 or K562). NAPQI-induced cell death was reduced by increased GPx3 and was enhanced by decreased GPx3. These results suggest that GPx3 is an important factor for inhibition of APAP-induced hepatotoxicity both in vivo and in vitro. To our knowledge, this is the first report to show a hepatoprotective role of cellular GPx3 against APAP-induced liver damage.

Lower susceptibility of female mice to acetaminophen hepatotoxicity: Role of mitochondrial glutathione, oxidant stress and c-jun N-terminal kinase

Acetaminophen (APAP) overdose causes severe hepatotoxicity in animals and humans. However, the mechanisms underlying the gender differences in susceptibility to APAP overdose in mice have not been clarified. In our study, APAP (300mg/kg) caused severe liver injury in male mice but 69-77% lower injury in females. No gender difference in metabolic activation of APAP was found. Hepatic glutathione (GSH) was rapidly depleted in both genders, while GSH recovery in female mice was 2.6 fold higher in the mitochondria at 4h, and 2.5 and 3.3 fold higher in the total liver at 4h and 6h, respectively. This faster recovery of GSH, which correlated with greater induction of glutamate-cysteine ligase, attenuated mitochondrial oxidative stress in female mice, as suggested by a lower GSSG/GSH ratio at 6h (3.8% in males vs. 1.4% in females) and minimal centrilobular nitrotyrosine staining. While c-jun N-terminal kinase (JNK) activation was similar at 2 and 4h post-APAP, it was 3.1 fold lower at 6h in female mice. However, female mice were still protected by the JNK inhibitor SP600125. 17β-Estradiol pretreatment moderately decreased liver injury and oxidative stress in male mice without affecting GSH recovery.

CONCLUSION

The lower susceptibility of female mice is achieved by the improved detoxification of reactive oxygen due to accelerated recovery of mitochondrial GSH levels, which attenuates late JNK activation and liver injury. However, even the reduced injury in female mice was still dependent on JNK. While 17β-estradiol partially protects male mice, it does not affect hepatic GSH recovery.

Is nuclear factor erythroid 2-related factor 2 responsible for sex differences in susceptibility to acetaminophen-induced hepatotoxicity in mice?

Nuclear factor erythroid 2-related factor 2 (Nrf2) is a transcription factor that positively regulates the expression and activity of cytoprotective genes during periods of oxidative stress. It has previously been shown that some Nrf2 genes are more highly expressed in livers of female than male mice. This could explain previously reported sex-related differences in susceptibility to acetaminophen (APAP) hepatotoxicity in mice, where females show greater resistance to APAP hepatotoxicity. Here, we examined, for the first time, differences in mRNA and protein expression for Nrf2 and a battery of Nrf2-dependent genes in naïve wild-type (WT) and overnight-fasted WT and Nrf2-null male and female mice following APAP treatment. Alanine aminotransferase (ALT) activity was measured as an indicator of hepatotoxicity. Hepatic mRNA and protein levels were measured by quantitative polymerase chain reaction and western blotting, respectively. Contrary to expectations, basal Nrf2 mRNA and protein expression were significantly lower in livers of naïve female than male mice. Although mRNA and/or protein expression of quinone oxidoreductase 1 and multidrug resistance-associated protein 4 was more pronounced in livers of female than male mice under some of the conditions examined, no higher global expression of Nrf2-dependent genes was detected in female mice. Furthermore, ALT activity was significantly elevated in overnight-fasted WT and Nrf2-null male mice following APAP treatment, but no increases in ALT were observed in either genotype of female mice. These results indicate that factors other than Nrf2 are responsible for the lower susceptibility of female mice to APAP hepatotoxicity.

Effect of acetaminophen exposure in Oncorhynchus mykiss gills and liver: detoxification mechanisms, oxidative defence system and peroxidative damage

The increasing presence of pharmaceutical drugs in nature is cause of concern due to the occurrence of oxidative stress in non-target species. Acetaminophen is widely used in human medicine as an analgesic and antipyretic drug, and it is one of the most sold non-prescription drugs. The present study aimed to assess the toxic effects of acetaminophen (APAP) in Oncorhynchus mykiss following acute and chronic exposures in realistic levels. In order to evaluate the APAP effects in the rainbow trout, gills and liver were analyzed with biochemical biomarkers, such as catalase (CAT), total and selenium-dependent glutathione peroxidase (GPx), glutathione reductase (GRed) and glutathione-S-transferases (GSTs) activity and also lipid peroxidation levels (TBARS). The results obtained in all tests indicate that a significant response of oxidative stress was established, along with the increase of APAP concentrations. The establishment of an oxidative stress scenario occurred with the involvement of all tested biomarkers, sustaining a generalized set of pro-oxidative effects elicited by APAP. Additionally, the occurrence of oxidative damage strongly suggests the impairment of the antioxidant defense mechanism of O. mykiss. It is important to note that the occurrence of oxidative deleterious effects and peroxidative damages occurred for concentrations similar to those already reported for several freshwater ecosystems. The importance of these assumptions is further discussed under the scope of ecological relevance of the assessment of effects caused by pharmaceuticals in non-target organisms.

Increased total scavenger capacity in rats fed corticosterone and cortisol on lipid-rich diet

BACKGROUND

In our earlier studies both corticosterone and cortisol had antioxidant effect in vitro.

OBJECTIVES

Our aim was to clarify whether corticosterone and cortisol oral administration results in beneficial antioxidant changes in Sprague-Dawley adult male rats in vivo.

METHODS

Experimental animals were fed a lipid rich diet and treated with corticosterone or cortisol in the drinking fluid. Control group was fed only lipid rich diet with untreated drinking water. The untreated group was feda normal diet with untreated water. Total scavenger capacity (TSC) was measured before and after 4 weeks of treatment in blood samples using a chemiluminometric assay.

RESULTS

Both corticosterone and cortisol treatment caused increased TSC. The control group and the untreated group showed no significant changes in TSC.

CONCLUSION

Our results support the hypothesis that corticosterone and cortisol administration can improve the antioxidant status not only in vitro but also in vivo.

The effect of certain steroid hormones on the expression of genes involved in the metabolism of free radicals

Steroid hormones influence the antioxidant processes of cells. However, the molecular mechanism of this effect is not fully clear. Our aim was to examine how steroid hormones affect the expression of certain genes that play a role in antioxidant processes. Blood was taken from ten healthy volunteers. Neutrophil granulocytes were separated and treated either with 17-β-estradiol, progesterone, testosterone, or cortisol. Whole RNA was isolated and reverse transcription was carried out in treated and control groups. Relative quantification was performed with SYBR Green assay and gene-specific oligonucleotides. We found that the expression of Mn-superoxide dismutase was significantly increased by 17-β-estradiol and testosterone, myeloperoxidase expression was significantly elevated by cortisol and progesterone, and the expression of NADPH oxidase was significantly decreased by progesterone. We conclude that the antioxidant effect of steroid hormones is in part carried out through transcriptional regulation of certain enzymes. Subsequent studies are required in order to examine the non-genomic, membrane receptor mediated effect of steroids on antioxidant processes.

Novel protective mechanisms for S-adenosyl-L-methionine against acetaminophen hepatotoxicity: improvement of key antioxidant enzymatic function

Acetaminophen (APAP) overdose leads to severe hepatotoxicity, increased oxidative stress and mitochondrial dysfunction. S-adenosyl-L-methionine (SAMe) protects against APAP toxicity at a mmol/kg equivalent dose to N-acetylcysteine (NAC). SAMe acts as a principle biological methyl donor and participates in polyamine synthesis which increase cell growth and has a role in mitochondrial protection. The purpose of the current study tested the hypothesis that SAMe protects against APAP toxicity by maintaining critical antioxidant enzymes and markers of oxidative stress. Male C57Bl/6 mice were treated with vehicle (Veh; water 15 ml/kg, ip), SAMe (1.25 mmol/kg, ip), APAP (250 mg/kg, ip), and SAMe+APAP (SAMe given 1 h following APAP). Liver was collected 2 and 4 h following APAP administration; mitochondrial swelling as well as hepatic catalase, glutathione peroxidase (GPx), glutathione reductase, and both Mn- and Cu/Zn-superoxide dismutase (SOD) enzyme activity were evaluated. Mitochondrial protein carbonyl, 3-nitrotyrosine cytochrome c leakage were analyzed by Western blot. SAMe significantly increased SOD, GPx, and glutathione reductase activity at 4 h following APAP overdose. SAMe greatly reduced markers of oxidative stress and cytochrome C leakage following APAP overdose. Our studies also demonstrate that a 1.25 mmol/kg dose of SAMe does not inhibit CYP 2E1 enzyme activity. The current study identifies a plausible mechanism for the decreased oxidative stress observed when SAMe is given following APAP.

Fully biodegradable and cationic poly(amino oxalate) particles for the treatment of acetaminophen-induced acute liver failure

Acute inflammatory diseases are one of major causes of death in the world and there is great need for developing drug delivery systems that can target drugs to macrophages and enhance their therapeutic efficacy. Poly(amino oxalate) (PAOX) is a new family of fully biodegradable polymer that possesses tertiary amine groups in its backbone and has rapid hydrolytic degradation. In this study, we developed PAOX particles as drug delivery systems for treating acute liver failure (ALF) by taking the advantages of the natural propensity of particulate drug delivery systems to localize to the mononuclear phagocyte system, particularly to liver macrophages. PAOX particles showed a fast drug release kinetics and excellent biocompatibility in vitro and in vivo. A majority of PAOX particles were accumulated in liver, providing a rational strategy for effective treatment of ALF. A mouse model of acetaminophen (APAP)-induced ALF was used to evaluate the potential of PAOX particles using pentoxifylline (PTX) as a model drug. Treatment of PTX-loaded PAOX particles significantly reduced the activity of alanine transaminase (ALT) and inhibited hepatic cell damages in APAP-intoxicated mice. The high therapeutic efficacy of PTX-loaded PAOX particles for ALF treatment may be attributed to the unique properties of PAOX particles, which can target passively liver, stimulate cellular uptake and trigger a colloid osmotic disruption of the phagosome to release encapsulated PTX into the cytosol. Taken together, we believe that PAOX particles are a promising drug delivery candidate for the treatment of acute inflammatory diseases.

Osteopontin is involved in estrogen-mediated protection against diethylnitrosamine-induced liver injury in mice

Diethylnitrosamine (DEN) is a potent hepatotoxin and hepatocarcinogen in animals and possible in humans. Estrogen has been reported to play a protective role against DEN exposure. Osteopontin (OPN), a downstream molecular of estrogen, plays a role in many pathophysiological processes. In this study, we evaluate the role of OPN in estrogen-mediated hepatoprotection in DEN-treated mice. DEN was administrated intraperitoneally to C57BL/6 and OPN(-/-) mice. Compared to male mice, female mice exhibited significantly higher hepatic OPN expression with less liver damage 48 h after DEN treatment. Interestingly, enhanced OPN expression was predominantly detected in hepatocytes after DEN treatment. OPN deficiency enhanced the susceptibility to DEN, which was more apparent in females than males. Estrogen-mediated protection against DEN in males was abrogated by OPN deficiency. The protective activities of estrogen could be mimicked by exogenous OPN. Consistent with liver injury, oxidative stress in liver was enhanced with OPN depletion. OPN reduced DEN-induced oxidative stress likely through inhibition of CYP2A5 expression. In conclusion, we demonstrate that OPN may be involved in estrogen-mediated hepatoprotection in DEN-induced liver injury through enhancement of hepatocyte survival and inhibition of DEN biotransformation. Our findings may provide new insight into gender differences in chemical-induced liver injury and related diseases.

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.