Protective effects of p-coumaric acid against acetaminophen-induced hepatotoxicity in mice.

Acetaminophen (N-acetyl-p-aminophenol, AAP) is an effective analgesic and antipyretic drug with minimal toxicity when used at therapeutic doses. However, AAP overdose is the most common cause of drug-induced acute liver failure and one of the main causes of morbidity and mortality. p-Coumaric acid (PCA) is the most abundant isomer of hydroxycinnamic acid in nature, and it can be widely found in fruits, vegetables, and plants products. PCA has strong antioxidant activity and exhibits protective effects in numerous disease models associated with reactive oxygen species (ROS) generation. In this study, we investigated the protective effects of PCA on AAP-induced hepatotoxicity and the underlying mechanisms using an in vivo model. We found that PCA ameliorates AAP-induced hepatotoxicity as well as the reduced serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity. Furthermore, we observed that PCA suppressed hepatic apoptosis via ROS-mediated DNA damage responses and inflammation by modulating the mitogen-activated protein kinase (MAPK) signaling axis in an ROS-dependent manner. These findings indicate that the administration of PCA protects against AAP-induced hepatotoxicity, suggesting it could be a novel therapeutic strategy for AAP-induced liver injury.

Inhibition of Glycogen Synthase Kinase 3 Accelerated Liver Regeneration after Acetaminophen-Induced Hepatotoxicity in Mice.

Overdose of acetaminophen (APAP) is the leading cause of acute liver failure (ALF) in the United States. Timely initiation of compensatory liver regeneration after APAP hepatotoxicity is critical for final recovery, but the mechanisms of liver regeneration after APAP-induced ALF have not been extensively explored yet. Previous studies from our laboratory have demonstrated that activation of ß-catenin signaling after APAP overdose is associated with timely liver regeneration. Herein, we investigated the role of glycogen synthase kinase 3 (GSK3) in liver regeneration after APAP hepatotoxicity using a pharmacological inhibition strategy in mice. Treatment with specific GSK3 inhibitor (L803-mts), starting from 4 hours after 600 mg/kg dose of APAP, resulted in early initiation of liver regeneration in a dose-dependent manner, without modifying the peak regenerative response. Acceleration of liver regeneration was not secondary to alteration of APAP-induced hepatotoxicity, which remained unchanged after GSK3 inhibition. Early cell cycle initiation in hepatocytes after GSK3 inhibition was because of rapid induction of cyclin D1 and phosphorylation of retinoblastoma protein. This was associated with increased activation of ß-catenin signaling after GSK3 inhibition. Taken together, our study has revealed a novel role of GSK3 in liver regeneration after APAP overdose and identified GSK3 as a potential therapeutic target to improve liver regeneration after APAP-induced ALF.

Dual Role of Epidermal Growth Factor Receptor in Liver Injury and Regeneration after Acetaminophen Overdose in Mice.

Epidermal growth factor receptor (EGFR) plays a crucial role in hepatocyte proliferation. Its role in acetaminophen (APAP)-mediated hepatotoxicity and subsequent liver regeneration is completely unknown. Role of EGFR after APAP-overdose in mice was studied using pharmacological inhibition strategy. Rapid, sustained and dose-dependent activation of EGFR was noted after APAP-treatment in mice, which was triggered by glutathione depletion. EGFR-activation was also observed in primary human hepatocytes after APAP-treatment, preceding elevation of toxicity markers. Treatment of mice with an EGFR-inhibitor (EGFRi), Canertinib, 1h post-APAP resulted in robust inhibition of EGFR-activation and a striking reduction in APAP-induced liver injury. Metabolic activation of APAP, formation of APAP-protein adducts, APAP-mediated JNK-activation and its mitochondrial translocation were not altered by EGFRi. Interestingly, EGFR rapidly translocated to mitochondria after APAP-treatment. EGFRi-treatment abolished mitochondrial EGFR activity, prevented APAP-mediated mitochondrial dysfunction/oxidative-stress and release of endonucleases from mitochondria, which are responsible for DNA-damage/necrosis. Treatment with N-acetylcysteine (NAC), 4h post-APAP in mice did not show any protection but treatment of EGFRi in combination with NAC showed decrease in liver injury. Finally, delayed treatment with EGFRi, 12-h post-APAP, did not alter peak injury but caused impairment of liver regeneration resulting in sustained injury and decreased survival after APAP overdose in mice. Impairment of regeneration was due to inhibition of cyclinD1 induction and cell cycle arrest. Our study has revealed a new dual role of EGFR both in initiation of APAP-injury and in stimulation of subsequent compensatory regeneration after APAP-overdose.

Effect of Prolonged Iodine Overdose on Type 2 Iodothyronine Deiodinase Ubiquitination-Related Enzymes in the Rat Pituitary.

The purpose of this study is to determine the effect of prolonged iodine overdose on type 2 iodothyronine deiodinase (D2) ubiquitination-related enzymes. Male Wistar rats were fed different doses of iodine and were then euthanized at the 4, 8, 12, or 24 weeks (4w, 8w, 12w, or 24w) after iodine administration. Urinary iodine concentration (UIC), thyroid-stimulating hormone (TSH), total thyroxine (TT4), and total triiodothyronine (TT3) were determined. Real-time quantitative RT-PCR and Western blot were used to measure mRNA and protein expression levels of pituitary D2 as well as two D2-specific ubiquitin ligases [WD repeat and SOCS box-containing protein 1 (WSB-1), membrane-associated ring finger (C3HC4) 6 (MARCH6 or TEB4)] and two D2-specific deubiquitinating enzymes [ubiquitin-specific peptidase 20 (USP20) and ubiquitin-specific peptidase 33 (USP33)]. The mRNA and protein expression levels of USP19, a TEB4-specific deubiquitinating enzyme, were also measured. Prolonged high iodine intake significantly increased TSH expression. At 12w, TSH was 1.57-, 1.44-, and 2.11-fold of NI group in 6HI, 10HI, and 50HI groups, respectively. At 24w, TSH had increased to 2.11-fold in the 50HI group. The pituitary D2 protein level decreased at 12w and 24w; though the mRNA level did not change. Prolonged iodine intake increased mRNA and protein expression levels of pituitary WSB-1 and TEB4. High iodine intake had no discernible effects on USP20. Temporary increases in USP33 and USP19 mRNA levels were observed. The enzymes related to D2 ubiquitination change with prolonged high iodine intake. Increased D2 ubiquitination suppresses the activity of D2, causing a decrease in negative feedback of the hypothalamic-pituitary-thyroid axis.

Increased densities of nitric oxide synthase expressing neurons in the temporal cortex and the hypothalamic paraventricular nucleus of polytoxicomanic heroin overdose victims: possible implications for heroin neurotoxicity.

Heroin is one of the most dangerous drugs of abuse, which may exert various neurotoxic actions on the brain (such as gray matter loss, neuronal apoptosis, mitochondrial dysfunction, synaptic defects, depression of adult neurogenensis, as well as development of spongiform leucoencephalopathy). Some of these toxic effects are probably mediated by the gas nitric oxide (NO). We studied by morphometric analysis the numerical density of neurons expressing neuronal nitric oxide synthase (nNOS) in cortical and hypothalamic areas of eight heroin overdose victims and nine matched controls. Heroin addicts showed significantly increased numerical densities of nNOS immunoreactive cells in the right temporal cortex and the left paraventricular nucleus. Remarkably, in heroin abusers, but not in controls, we observed not only immunostained interneurons, but also cortical pyramidal cells. Given that increased cellular expression of nNOS was accompanied by elevated NO generation in brains of heroin addicts, these elevated levels of NO might have contributed to some of the known toxic effects of heroin (for example, reduced adult neurogenesis, mitochondrial pathology or disturbances in synaptic functioning).

The role of the glutathione S-transferase genes GSTT1, GSTM1, and GSTP1 in acetaminophen-poisoned patients.

The aim of this study was to assess if genetic variants in the glutathione-S-transferase genes GST-T1, M1, and P1 reflect risk factors in acetaminophen (APAP)-poisoned patients assessed by investigation of the relation to prothrombin time (PT), which is a sensitive marker of survival in these patients. A total of 104 APAP-poisoned patients were genotyped for deletion polymorphisms in the GSTT1 and GSTM1 genes and for the GSTP1 Ile105Val polymorphism. We found a borderline association (p = 0.05) between the GSTT1 homozygous deletion genotype and high trough PT (a marker of prognosis in APAP poisoning) compared to carrying two functioning copies of the gene. No significant association was found between any of the GSTM1 and GSTP1 genotypes and PT. The frequency of GSTP1 Val/Val genotypes was significantly lower in the patients than in the background population (p = 0.047). The results suggest that the GSTT1 homozygous deletion genotype may be associated with a better prognosis after APAP poisoning and that carriers of the GSTP1 homozygous variant genotype may have a decreased risk of being APAP poisoned.

[Plasma and urine catecholamines in a 7-day survival of parathion poisoning]. / Plasma- und Urin-Katecholamine bei einer 7 Tage überlebten Parathion-Intoxikation.

During the intensive medical treatment of a finally fatal parathion poisoning (survival time 7 days) with shock symptoms (lung and kidney) the kinetic profiles of both plasma and urinary catecholamines were taken up. In addition the parathion concentrations of the same plasma samples were measured. There could have been found plasma catecholamine profiles exhibiting peak concentrations in the initial phase, followed by a period of 4 days without any detectable plasma epinephrine and finally an extreme elevation of both catecholamines in the last period before death. The excretion patterns confirmed the plasma results. Imaginable pathophysiological mechanisms in consideration of the shock induced renal insufficiency are discussed. The question is raised whether the kinetics of plasma catecholamines may be a possible marker for the prognosis of organophosphate poisoning.