In vitro and in vivo induction of ochratoxin A exposure-related micronucleus formation in rat proximal tubular epithelial cells and expression profiling of chromosomal instability-related genes

Ochratoxin A (OTA) is a renal carcinogen in rats, and repeated administration induces karyomegaly in proximal tubular epithelial cells (PTECs) of the outer stripe of the outer medulla (OSOM) before inducing proliferative lesions. To investigate whether OTA induces micronuclei (MN) in PTECs, we performed an in vitro MN assay using rat renal NRK-52E PTECs after treatment for ≤21 days, and an in vivo OSOM MN assay in rats treated with OTA, other renal carcinogens, or non-carcinogenic renal toxicants for 4 or 13 weeks. The in vitro assay revealed an increased frequency of micronucleated cells from the acceptable dose level for cell viability, even after 21 days of treatment. The in vivo assay also revealed a dose- and treatment period-dependent increase in PTECs with γ-H2AX+ MN. OTA-specific gene expression profiling by OSOM RNA sequencing after week 13 revealed the altered expression of genes related to microtubule-kinetochore binding, the kinesin superfamily, centriole assembly, DNA damage repair, and cell cycle regulation. MN formation was also observed with other renal carcinogens that induce karyomegaly similarly to OTA. These results imply that γ-H2AX+ MN formation by OTA treatment is related to the induction of chromosomal instability accompanying karyomegaly formation before proliferative lesions form, providing a new insight into the carcinogenic mechanism that may be relevant to humans.

An orally deliverable ornithine-based self-assembling polymer nanomedicine ameliorates hyperammonemia in acetaminophen-induced acute liver injury

l-Ornithine (Orn) is a core amino acid responsible for ammonia detoxification in the body via the hepatic urea cycle. Clinical studies in Orn therapy have focused on interventions for hyperammonemia-associated diseases, such as hepatic encephalopathy (HE), a life-threatening neurological symptom affecting more than 80% of patients with liver cirrhosis. However, its low molecular weight (LMW) causes Orn to diffuse nonspecifically and be rapidly eliminated from the body after oral administration, resulting in unfavorable therapeutic efficacy. Hence, Orn is constantly supplied by intravenous infusion in many clinical settings; however, this treatment inevitably decreases patient compliance and limits its application in long-term management. To improve the performance of Orn, we designed self-assembling polyOrn-based nanoparticles for oral administration through ring-opening polymerization of Orn-N-carboxy anhydride initiated with amino-ended poly(ethylene glycol), followed by acylation of free amino groups in the main chain of the polyOrn segment. The obtained amphiphilic block copolymers, poly(ethylene glycol)-block-polyOrn(acyl) (PEG-block-POrn(acyl)), enabled the formation of stable nanoparticles (NanoOrn(acyl)) in aqueous media. We employed the isobutyryl (iBu) group for acyl derivatization in this study (NanoOrn(iBu)). In the healthy mice, daily oral administration of NanoOrn(iBu) for one week did not induce any abnormalities. In the mice exhibiting acetaminophen (APAP)-induced acute liver injury, oral pretreatment with NanoOrn(iBu) effectively reduced systemic ammonia and transaminases levels compared to the LMW Orn and untreated groups. The results suggest that the application of NanoOrn(iBu) is of significant clinical value with the feasibility of oral delivery and improvement in APAP-induced hepatic pathogenesis. STATEMENT OF SIGNIFICANCE: Liver injury is often accompanied by hyperammonemia, a life-threatening condition characterized by elevated blood ammonia levels. Current clinical treatments for reducing ammonia typically entail the invasive approach of intravenous infusion, involving the administration of l-ornithine (Orn) or a combination of Orn and L-aspartate. This method is employed due to the poor pharmacokinetics associated with these compounds. In our pursuit of enhancing therapy, we have developed an orally administrable nanomedicine based on Orn-based self-assembling nanoparticle (NanoOrn(iBu)), which provides sustained Orn supply to the injured liver. Oral administration of NanoOrn(iBu) to healthy mice did not cause any toxic effects. In a mouse model of acetaminophen-induced acute liver injury, oral administration of NanoOrn(iBu) surpassed Orn in reducing systemic ammonia levels and liver damage, thereby establishing NanoOrn(iBu) as a safe and effective therapeutic option.

Absence of Increased Susceptibility to Acetaminophen-Induced Liver Injury in a Diet-Induced NAFLD Mouse Model

Nonalcoholic fatty liver disease (NAFLD) is a common chronic liver disease and its influence on drug-induced liver injury (DILI) is not fully understood. We investigated whether NAFLD can influence acetaminophen (APAP [N-acetyl-p-aminophenol])-induced hepatotoxicity in a diet-induced obese (DIO) mouse model of NAFLD. The male C57BL/6NTac DIO mice, fed a high-fat diet for more than 12 weeks, developed obesity, hyperinsulinemia, impaired glucose tolerance, and hepatomegaly with hepatic steatosis, similar to human NAFLD. In the acute toxicity study after a single dose of APAP (150 mg/kg), compared with control lean mice, the DIO mice had decreased serum transaminase levels and less severe hepatocellular injury. The DIO mice also had altered expression of genes related to APAP metabolism. Chronic APAP exposure for 26 weeks did not predispose the DIO mice with NAFLD to more severe hepatotoxicity compared with the lean mice. These results suggested that the C57BL/6NTac DIO mouse model appears to be more tolerant to APAP-induced hepatotoxicity than lean mice, potentially related to altered xenobiotic metabolizing capacity in the fatty liver. Further mechanistic studies with APAP and other drugs in NAFLD animal models are necessary to investigate the mechanism of altered susceptibility to intrinsic DILI in some human NAFLD patients.

Acetaminophen-Induced Hepatotoxicity in Obesity and Nonalcoholic Fatty Liver Disease: A Critical Review

The epidemic of obesity, type 2 diabetes and nonalcoholic liver disease (NAFLD) favors drug consumption, which augments the risk of adverse events including liver injury. For more than 30 years, a series of experimental and clinical investigations reported or suggested that the common pain reliever acetaminophen (APAP) could be more hepatotoxic in obesity and related metabolic diseases, at least after an overdose. Nonetheless, several investigations did not reproduce these data. This discrepancy might come from the extent of obesity and steatosis, accumulation of specific lipid species, mitochondrial dysfunction and diabetes-related parameters such as ketonemia and hyperglycemia. Among these factors, some of them seem pivotal for the induction of cytochrome P450 2E1 (CYP2E1), which favors the conversion of APAP to the toxic metabolite N-acetyl-p-benzoquinone imine (NAPQI). In contrast, other factors might explain why obesity and NAFLD are not always associated with more frequent or more severe APAP-induced acute hepatotoxicity, such as increased volume of distribution in the body, higher hepatic glucuronidation and reduced CYP3A4 activity. Accordingly, the occurrence and outcome of APAP-induced liver injury in an obese individual with NAFLD would depend on a delicate balance between metabolic factors that augment the generation of NAPQI and others that can mitigate hepatotoxicity.

Caveolin-1 attenuates acetaminophen aggravated lipid accumulation in alcoholic fatty liver by activating mitophagy via the Pink-1/Parkin pathway

Alcoholic fatty liver (AFL) is a disease characterized by the abnormal structure and dysfunction of hepatocytes caused by long-term, excessive drinking. Acetaminophen (APAP) is a commonly used painkiller, but it can aggravate lipid deposition in the liver and cause liver injury when used in fatty liver disease. Here, we investigated the effect of caveolin-1 (CAV-1), an intracellular stent protein, on the pathogenesis of APAP aggravated lipid deposition in AFL mice. This study shows that lipid accumulation was more severe in APAP groups than in alcohol-treated mice. The CAV-1 stent-like domain (CSD, 82-101 amino acids of caveolin-1), used to upregulate CAV-1 expression, could reduce lipid accumulation and activate autophagy in AFL mice treated with APAP. The levels of CAV-1 and autophagy-related proteins (LC3-II/I and Beclin-1) had decreased, whereas SREBP-1c had increased in A/O (alcohol and oleic acid) and APAP-co-treated L02 cells. CAV-1 small interfering RNA and CAV1-overexpressing plasmid were separately transfected into A/O and APAP co-treated L02 cells. When CAV-1 was downregulated, the levels of Pink-1, Parkin, and autophagy-related proteins (LC3-II/I and Beclin-1) were decreased, whereas SREBP-1c was increased. The opposite trend was observed when CAV-1 was overexpressed. The results show that CAV-1 reduced lipid accumulation in L02 cells and activated Pink-1/Parkin-related mitophagy. This study highlights the positive role of CAV-1 in APAP-increased lipid accumulation under the AFL status and provides a new understanding of the function of CAV-1 in the liver through mitophagy associated with the Pink-1/Parkin pathway.

Zucker Lean Rats With Hepatic Steatosis Recapitulate Asymptomatic Metabolic Syndrome and Exhibit Greater Sensitivity to Drug-Induced Liver Injury Compared With Standard Nonclinical Sprague-Dawley Rat Model

Fatty liver disease is a potential risk factor for drug-induced liver injury (DILI). Despite advances in nonclinical in vitro and in vivo models to assess liver injury during drug development, the pharmaceutical industry is still plagued by idiosyncratic DILI. Here, we tested the hypothesis that certain features of asymptomatic metabolic syndrome (namely hepatic steatosis) increase the risk for DILI in certain phenotypes of the human population. Comparison of the Zucker Lean (ZL) and Zucker Fatty rats fed a high fat diet (HFD) revealed that HFD-fed ZL rats developed mild hepatic steatosis with compensatory hyperinsulinemia without increases in liver enzymes. We then challenged steatotic HFD-fed ZL rats and Sprague-Dawley (SD) rats fed normal chow, a nonclinical model widely used in the pharmaceutical industry, with acetaminophen overdose to induce liver injury. Observations in HFD-fed ZL rats included increased liver injury enzymes and greater incidence and severity of hepatic necrosis compared with similarly treated SD rats. The HFD-fed ZL rats also had disproportionately higher hepatic drug accumulation, which was linked with abnormal hepatocellular efflux transporter distribution. Here, we identify ZL rats with HFD-induced hepatic steatosis as a more sensitive nonclinical in vivo test system for modeling DILI compared with SD rats fed normal chow.

Preexisting diabetes mellitus had no effect on the no-observed-adverse-effect-level of acetaminophen in rats

Information on the safety of chemical substances in patients with various preexisting conditions remains limited. Acetaminophen was added to the basal diet at 0, 80, 253, 800, 2530, or 8000 ppm and administered to type 2 diabetes mellitus rats (GK/Jcl) and the control male rats (Wistar) for 13 weeks. Both strains treated with 8000 ppm acetaminophen (561.4 and 567.7 mg/kg body weight/day, GK/Jcl and Wistar rats, respectively) showed decreased levels of red blood cell counts, blood urea nitrogen, creatinine, and total bilirubin compared to those of non-treated rats. Treatment with 8000 ppm of acetaminophen reduced the blood glucose and hemoglobin A1c levels of GK/Jcl rats. An increase in the relative weights of the kidneys and liver, and a decrease in the weight of the salivary glands were observed in both GK/Jcl and Wistar rats treated with 8000 ppm acetaminophen relative to those of non-treated control rats. Microscopically, both strains treated with 2530 (174.3 and 164.2 mg/kg body weight/day, GK/Jcl and Wistar rats, respectively) or 8000 ppm acetaminophen showed hepatocellular hypertrophy and degenerative lesions in the salivary glands, whereas similar lesions were not observed in non-treated rats. In conclusion, the no-observed-adverse-effect-level of acetaminophen was 800 ppm in both diabetic and control rats.

Evaluation of the In Vitro Damage Caused by Lipid Factors on Stem Cells from a Female Rat Model of Type 2 Diabetes/Obesity and Stress Urinary Incontinence

Human stem cell therapy for type 2 diabetes/obesity (T2D/O) complications is performed with stem cell autografts, exposed to the noxious T2D/O milieu, often with suboptimal results. We showed in the Obese Zucker (OZ) rat model of T2D/O that when their muscle-derived stem cells (MDSC) were from long-term T2D/O male rats, their repair efficacy for erectile dysfunction was impaired and were imprinted with abnormal gene- and miR-global transcriptional signatures (GTS). The damage was reproduced in vitro by short-term exposure of normal MDSC to dyslipidemic serum, causing altered miR-GTS, fat infiltration, apoptosis, impaired scratch healing, and myostatin overexpression. Similar in vitro alterations occurred with their normal counterparts (ZF4-SC) from the T2D/O rat model for female stress urinary incontinence, and with ZL4-SC from non-T2D/O lean female rats. In the current work we studied the in vitro effects of cholesterol and Na palmitate as lipid factors on ZF4-SC and ZL4-SC. A damage partially resembling the one caused by the female dyslipidemic serum was found, but differing between both lipid factors, so that each one appears to contribute specifically to the stem cell damaging effects of dyslipidemic serum in vitro and T2D/O in vivo, irrespective of gender. These results also confirm the miR-GTS biomarker value for MDSC damage.

Acetaminophen aggravates fat accumulation in NAFLD by inhibiting autophagy via the AMPK/mTOR pathway

Non-alcoholic fatty liver disease (NAFLD) is the most common chronic liver disease which affects millions of people worldwide. Acetaminophen (APAP) overdose is the leading cause of acute liver failure. In this study, APAP (50, 100, 200 mg/kg) were employed on mice fed with a high-fat diet, and APAP (2, 4, 8 mM) were cultured with L02 cells in the presence of alcohol and oleic acid. APAP treatment significantly aggravated hepatic lipid accumulation, increased the serum levels of triglyceride (TG), alanine aminotransferase (ALT) and aspartate aminotransferase (AST), and increased hepatic lipid accumulation in H&E and Oil red O staining results. Transmission electron microscopy (TEM) found fewer number of autophagosomes in APAP (100 mg/kg) treated group. Immunohistochemistry analysis showed the intensity of hepatic mTOR was increased and AMPK was decreased in 200 mg/kg APAP treated group. Western blot analysis showed APAP treatment decreased the levels of LC3-Ⅱ, Beclin1 and AMPK, while increased the levels of mTOR and SREBP-1c, respectively. In vitro study showed APAP treatment obviously increased TG activities in cell supernatant, and Oil red O staining had the same results. Western blot analysis demonstrated APAP treatment decreased the levels of LC3-Ⅱ, Beclin1 and AMPK, increased the levels of mTOR and SREBP-1c, but rapamycin treatment significantly reversed these effects of APAP. In conclusion, therapeutic dosages of APAP aggravates fat accumulation in NAFLD, the potential mechanism might be involved in inhibiting autophagy associated with the AMPK/mTOR pathway, and patients with NAFLD should use a lower dose of APAP.