Thioacetamide-induced Hepatocellular Necrosis Is Attenuated in Diet-induced Obese Mice

Spatial Transcriptomics Reveals the Transcriptomic Signatures in a Mouse Model of Pediatric Metabolic Dysfunction-Associated Steatohepatitis

Metabolic dysfunction-associated steatohepatitis (MASH) is considered the progressive form of metabolic dysfunction-associated steatotic liver disease, which is the leading cause of chronic liver disease in children. However, the pathogenesis of pediatric MASH remains poorly understood because of the lack of animal models. In this study, a mouse model of pediatric MASH was developed and its hepatic transcriptomic profile was characterized using spatial transcriptomics technology. C57BL/6J mice were fed a Western diet (WD) along with weekly injections of carbon tetrachloride (CCl4) from the age of 3 weeks and lasting up to 8 weeks. After 5 weeks of feeding, WD + CCl4-treated mice showed significant liver injury without the development of insulin resistance. Histologically, WD + CCl4 induced key features of type 2 MASH, the most common type observed in children, characterized by liver steatosis, portal inflammation, and portal fibrosis. Spatial transcriptomics analysis of liver tissues indicated that cluster 0 in the mouse from the WD + CCl4 group was enriched in pathways associated with lipid metabolism. Further investigation revealed that cytochrome p450 2E1 was the top marker gene of cluster 0, and its expression was increased in the periportal area of mice from the WD + CCl4 group. These findings suggest that this mouse model of pediatric MASH mirrors the histologic features of human MASH, and the up-regulation of cytochrome p450 2E1 may be linked to the disease pathogenesis.

Unveiling thioacetamide-induced toxicity: Multi-organ damage and omitted bone toxicity

Thioacetamide (TAA), a widely employed hepatotoxic substance, has gained significant traction in the induction of liver failure disease models. Upon administration of TAA to experimental animals, the production of potent oxidative derivatives ensues, culminating in the activation of oxidative stress and subsequent infliction of severe damage upon multiple organs via dissemination through the bloodstream. This review summarized the various organ damages and corresponding mechanistic explanations observed in previous studies using TAA in toxicological animal experiments. The principal pathological consequences arising from TAA exposure encompass oxidative stress, inflammation, lipid peroxidation, fibrosis, apoptosis induction, DNA damage, and osteoclast formation. Recent in vivo and in vitro studies on TAA bone toxicity have confirmed that long-term high-dose use of TAA not only induces liver damage in experimental animals but also accompanies bone damage, which was neglected for a long time. By using TAA to model diseases in experimental animals and controlling TAA dosage, duration of use, and animal exposure environment, we can induce various organ injury models. It should be noted that TAA-induced injuries have a time-dependent effect. Finally, in our daily lives, especially for researchers, we should take precautions to minimize TAA exposure and reduce the probability of related organ injuries.

Molecular mechanisms in thioacetamide-induced acute and chronic liver injury models

Thioacetamide (TAA) undergoes bioactivation in the liver by the CYP450 2E1 enzyme, resulting in the formation of TAA-S-oxide and TAA-S-dioxide. TAA-S-dioxide induces oxidative stress via lipid peroxidation of the hepatocellular membrane. A single TAA dose (50-300 mg/kg) administration initiates hepatocellular necrosis around the pericentral region after its covalent binding to macromolecules in the liver. Intermittent TAA administration (150-300 mg/kg, weekly thrice, for 11-16 weeks) activates transforming growth factor (TGF)-β/smad3 downstream signaling in injured hepatocytes, causing hepatic stellate cells (HSCs) to acquire myofibroblast like phenotype. The activated HSCs synthesize a variety of extracellular matrix, leading to liver fibrosis, cirrhosis, and portal hypertension. The TAA induced liver injury varies depending on the animal model, dosage, frequency, and routes of administration. However, TAA induces hepatotoxicity in a reproducible manner, and it is an ideal model to evaluate the antioxidant, cytoprotective, and antifibrotic compounds in experimental animals.

Nephroprotective Activity of Papaloquelite (Porophyllum ruderale) in Thioacetamide-Induced Injury Model

Acute kidney injury and impaired kidney function is associated with reduced survival and increased morbidity. Porophyllum ruderale is an edible plant endemic to Mexico used in Mexican traditional medicine. The aim of this study was to evaluate the nephroprotective effect of a hydroalcoholic extract (MeOH:water 70:30, v/v) from the aerial parts of P. ruderale (HEPr). Firstly, in vitro the antioxidant and anti-inflammatory activity of HEPr was determined; after the in vivo nephroprotective activity of HEPr was evaluated using a thioacetamide-induced injury model in rats. HEPr showed a slight effect on LPS-NO production in macrophages (15% INO at 40 µg/mL) and high antioxidant activity in the ferric reducing antioxidant power (FRAP) test, followed by the activity on DPPH and ABTS radicals test (69.04, 63.06 and 32.96% of inhibition, respectively). In addition, values of kidney injury biomarkers in urine (urobilinogen, hemoglobin, bilirubin, ketones, glucose, protein, pH, nitrites, leukocytes, specific gravity, and the microalbumin/creatinine) and serum (creatinine, urea, and urea nitrogen) of rats treated with HEPr were maintained in normal ranges. Finally, 5-O-caffeoylquinic, 4-O-caffeoylquinic and ferulic acids; as well as 3-O-quercetin glucoside and 3-O-kaempferol glucoside were identified by HPLC as major components of HEPr. In conclusion, Porophyllum ruderale constitutes a source of compounds for the treatment of acute kidney injury.

Nonalcoholic Fatty Liver Disease Is a Susceptibility Factor for Perchloroethylene-Induced Liver Effects in Mice

Nonalcoholic fatty liver disease (NAFLD) is the most prevalent pathological liver condition in developed countries. NAFLD results in severe alterations in liver function, including xenobiotic metabolism. Perchloroethylene (PERC) is a ubiquitous environmental pollutant, a known hepatotoxicant in rodents, and a probable human carcinogen. It is known that PERC disposition and metabolism are affected by NAFLD in mice; here, we examined how NAFLD changes PERC-associated liver effects. Male C57Bl6/J mice were fed a low-fat diet (LFD), high-fat diet (HFD), or methionine/folate/choline-deficient diet (MCD) to model a healthy liver, or mild and severe forms of NAFLD, respectively. After 8 weeks on diets, mice were orally administered PERC (300 mg/kg/day) or vehicle (5% aqueous Alkamuls-EL620) for 5 days. PERC-induced liver effects were exacerbated in both NAFLD groups. PERC exposure was associated with up-regulation of genes involved in xenobiotic, lipid, and glutathione metabolism, and down-regulation of the complement and coagulation cascades, regardless of the diet. Interestingly, HFD-fed mice, not MCD-fed mice, were generally more sensitive to PERC-induced liver effects. This was indicated by histopathology and transcriptional responses, where induction of genes associated with cell cycle and inflammation were prominent. Liver effects positively correlated with diet-specific differences in liver concentrations of PERC. We conclude that NAFLD alters the toxicodynamics of PERC and that NAFLD is a susceptibility factor that should be considered in future risk management decisions for PERC and other chlorinated solvents.

Mice in the early stage of liver steatosis caused by a high fat diet are resistant to thioacetamide-induced hepatotoxicity and oxidative stress

Lipogenesis is stimulated in the liver by an unfolded protein response (UPR) to endoplasmic reticulum stress under a variety of pathological conditions and results in the accumulation of lipids in hepatocytes. Assuming that UPR is a protective mechanism against stress, we hypothesized that the accumulated lipids might have a beneficial function. We prepared mice with fatty livers by feeding two types of high-calorie diets; a lard-rich high-calorie diet (LHD) or a menhaden oil-containing high-calorie diet (MHD), for two weeks and treated them, as well as control diet (CD)-fed mice, with thioacetamide (TAA), a liver toxicant. When a lethal dose (500mg/kg) of TAA was administered, the LHD-fed mice and the MHD-fed mice survived longer than those fed with CD. The accumulated lipids appeared to be associated with protecting the liver against TAA toxicity (200mg/kg). Consistently, lipid-loaded Hepa 1-6 cells showed a partial resistance to hydrogen peroxide toxicity compared to those cultured in conventional media. In conclusion, while sustained steatosis impairs liver function and leads to hazardous conditions, lipids that transiently accumulate as the result of UPR or other stimuli may exert a beneficial function in the liver at least partly through scavenging reactive oxygen species.

A high-fat diet temporarily renders Sod1-deficient mice resistant to an oxidative insult

Patients with nonalcoholic fatty liver disease may subsequently develop nonalcoholic steatohepatitis after suffering from a second insult, such as oxidative stress. Aim of this study was to investigate the pathogenesis of the liver injury caused when lipids accumulate under conditions of intrinsic oxidative stress using mice that are deficient in superoxide dismutase 1 (SOD1) and the leptin receptor (Lepr). We established Sod1^-/-::Lepr^db/db mice and carried out analyses of four groups of genetically modified mice, namely, wild type, Sod1^-/-, Lepr^db/db and Sod1^-/-::Lepr^db/db mice. Mice with defects in the SOD1 or Lepr gene are vulnerable to developing fatty livers, even when fed a normal diet. Feeding a high-fat diet (HFD) caused an increase in the number of lipid droplets in the liver to different extents in each genotypic mouse. an HFD caused the accelerated death of db/db mice, but contradictory to our expectations, the death rates for the Sod1-deficient mice were decreased by feeding HFD. Consistent with the improved probability of survival, liver damage was significantly ameliorated by feeding an HFD compared to a normal diet in the mice with an Sod1-deficient background. Oxidative stress markers, hyperoxidized peroxiredoxin and lipid peroxidation products, were decreased somewhat in Sod1^-/- mice by feeding HFD. We conclude that lipids reacted with reactive oxygen species and eliminated them in the livers of the young mice, which resulted in the alleviation of oxidative stress, but in advanced age oxidized products accumulated, leading to the aggravation of the liver injury and an increase in fatality rate.

Hepatic glutathione contributes to attenuation of thioacetamide-induced hepatic necrosis due to suppression of oxidative stress in diet-induced obese mice

We previously reported that hepatic necrosis induced by thioacetamide (TA), a hepatotoxicant, was attenuated in mice fed a high-fat diet (HFD mice) in comparison with mice fed a normal rodent diet (ND mice). In this study, we focused on investigation of the mechanism of the attenuation. Hepatic content of thiobarbituric acid reactive substances (TBARS), an oxidative stress marker, significantly increased in ND mice at 24 and 48 hr after TA administration in comparison to that in vehicle-treated ND mice. At these time points, severe hepatic necrosis was observed in ND mice. Treatment with an established antioxidant, butylated hydroxyanisole, attenuated the TA-induced hepatic necrosis in ND mice. In contrast, in HFD mice, hepatic TBARS content did not increase, and hepatic necrosis was attenuated in comparison with ND mice at 24 and 48 hr after TA dosing. Metabolomics analysis regarding hepatic glutathione, a biological antioxidant, revealed decreased glutathione and changes in the amount of glutathione metabolism-related metabolites, such as increased ophtalmate and decreased cysteine, and this indicated activation of glutathione synthesis and usage in HFD mice. Finally, after treatment with L-buthionine-S,R-sulfoxinine, an inhibitor of glutathione synthesis, TA-induced hepatic necrosis was enhanced and hepatic TBARS contents increased after TA dosing in HFD mice. These results suggested that activated synthesis and usage of hepatic GSH, which suppresses hepatic oxidative stress, is one of the factors that attenuate TA-induced hepatic necrosis in HFD mice.

Evidence that the capacity of nongenotoxic carcinogens to induce oxidative stress is subject to marked variability

Many drugs and environmental chemicals which are not directly mutagenic have the capacity to increase the incidence of tumors in the liver and other tissues. For this reason, such compounds are known as nongenotoxic carcinogens. The mechanisms underlying their effects remain unclear; however, their capacity to induce oxidative stress is considered to be a critical step in the carcinogenic process, although the evidence that this is actually the case remains equivocal and sparse. We have exploited a novel heme oxygenase-1 reporter mouse to evaluate the capacity of nongenotoxic carcinogens with different mechanisms of action to induce oxidative stress in the liver in vivo. When these compounds were administered at doses reported to cause liver tumors, marked differences in activation of the reporter were observed. 1,4-Dichlorobenzene and nafenopin were strong inducers of oxidative stress, whereas phenobarbital, piperonyl butoxide, cyproterone acetate, and WY14,643 were, at best, only very weak inducers. In the case of phenobarbital and thioacetamide, the number of LacZ-positive hepatocytes increased with time, and for the latter also with dose. The data obtained demonstrate that although some nongenotoxic carcinogens can induce oxidative stress, it is not a dominant feature of the response to these compounds. Therefore in contrast to the current models, these data suggest that oxidative stress is not a key determinant in the mechanism of nongenotoxic carcinogenesis but may contribute to the effects in a compound-specific manner.

Human mesenchymal stromal cell lysates as a novel strategy to recover liver function

AIM

It is unknown if the beneficial effects of mesenchymal stromal cells (MSC) transplantation into the liver are dependent on their anchorage and differentiation into hepatocytes or rather the result of the release of stem cell intracellular content with hepatoprotector properties.

MATERIALS & METHODS

The effects of intact MSC transplantation were compared with the infusion of MSC lysates in an experimental rat model of acute liver failure.

RESULTS

A more powerful hepatoprotective and antiapoptotic effect was obtained after infusion of MSC lysates than intact MSC. Changes in IL-6 levels and miRNAs might explain the beneficial effects of MSC lysates.

CONCLUSION

Infusion of MSC lysates show a better hepatoprotective effect than the transplantation of intact MSC.