Is rat liver affected by non-alcoholic steatosis more susceptible to the acute toxic effect of thioacetamide?

Jiang-Zhi granules decrease sensitivity to low-dose CCl4 induced liver injury in NAFLD rats through reducing endoplasmic reticulum stress

Background

Non-alcoholic fatty liver disease (NAFLD) may increase the sensitivity to liver injury caused by stimulants such as drugs and poisons. The traditional Chinese medicine (TCM) Jiang-Zhi Granule (JZG) has been proven effective for improving liver function, reducing hepatic fat accumulation and inflammation in NAFLD. The purpose of this study is to evaluate the effect of JZG on the susceptibility of NAFLD rats to liver injury and to identify the relevant mechanism.

Methods

Forty wistar rats were randomly divided into five groups, normal group, normal+CCl₄ group, high-fat diet (HFD) group, HFD + CCl₄ group, and HFD + CCl₄ + JZG group. NAFLD were established with HFD for 8 weeks. Then Low-dose CCl₄ was given intraperitoneally to induce liver injury in NAFLD rats for 48 h. From the 5th week of HFD, intragastric administration of JZG was simultaneously given to the rats in the HFD + CCl₄ + JZG group. At the end of the experiment, liver histological pathology, serum transaminase, lipid in liver and blood, as well as hepatic expression levels of endoplasmic reticulum stress (ERS) related molecules were evaluated.

Results

NAFLD rat model was established by eight-week HFD feeding, exhibiting elevated levels of hepatic lipid, blood lipid, serum transaminase and significantly increased expression of ERS related molecules including glucose regulating protein 78 (GRP78), protein kinase RNA-like endoplasmic reticulum kinase (PERK), eukaryotic translation initiation factor 2α (EIF2α), and nuclear factor-kappa B (NFκB) in liver tissues. After injection of CCl₄ in NAFLD rats, elevated serum transaminases, severe inflammation and focal necrosis were observed in liver tissue, but no obvious change was found in the rats of normal group. JZG reduced hepatic inflammation, hepatic necrosis, hepatic lipid, blood transaminases and blood lipids in HFD + CCl₄ rats. ERS related molecules were significantly elevated by low-dose CCl₄ in NAFLD rats, and were down-regulated by JZG.

Conclusion

The sensitivity to CCl₄-induced liver injury is increased in NAFLD rats, which could be improved by JZG. The pharmacological mechanism may involve the regulation of ERS signaling pathway by JZG.

M1-/M2-macrophage polarization in pseudolobules consisting of adipohilin-rich hepatocytes in thioacetamide (TAA)-induced rat hepatic cirrhosis

INTRODUCTION

Liver steatosis is the most frequent liver disease and may further develop into non-alcoholic steatohepatitis (NASH), liver cirrhosis, and finally hepatocellular carcinoma. Adipophilin (Adp) is localized on lipid droplet membrane in cytoplasm, and its increased expression is related to development of steatosis and NASH. The relationship between M1-/M2-macrophage polarization and Adp-rich hepatocyte-consisting pseudolobules (PLs) was investigated in thioacetamide (TAA)-induced rat cirrhosis.

MATERIALS AND METHOD

F344 rats were injected twice weekly with TAA (100mg/kg bodyweight) and sacrificed at post-first injection (PFI) weeks 5, 10, 15, 20, 25 and 32. Macrophage immunophenotypes and Adp-containing hepatocytes were analyzed by single immunolabeling. Adp and M1-/M2-related factors were analyzed by real -time RT-PCR.

RESULTS

PLs consisting exclusively of Adp-containing hepatocytes (Adp-positive) and PLs consisting of few Adp-containing hepatocytes (Adp-negative) were clearly distinguishable at PFI week 20 onwards. The numbers of M1-macrophages (reacting to CD68 and Iba1) and M2- macrophages (reacting to CD163, CD204 and Gal-3) were considerably greater in Adp-positive PLs. Expressions for both M1 (TNF-α, MCP-1, and Iba1)- and M2 (IL-4, TGF-β1, Gal-3, and Hsp25)-related factors were markedly higher in Adp-positive PLs at PFI week 25. Interestingly, MHC class II-positive macrophages/dendritic cells were increased in Adp-positive clusters/foci at the early stages at PFI weeks 5 and 10, and the level was gradually decreased thereafter.

CONCLUSIONS

M1-/M2-macrophages may simultaneously participate in the pathogenesis of steatosis in TAA-induced cirrhosis through M1- and M2-related factors. MHC class II cells may be responsible for steatosis at early stages, suggesting different functions from the above M1-/M2-macropahges.

The effect of D-galactosamine on lean and steatotic rat hepatocytes in primary culture

The aim of our work was to compare the effect of D-galactosamine (GalN) on primary cultures of lean and steatotic rat hepatocytes isolated from intact and fatty liver, respectively. GalN caused more severe injury to steatotic hepatocytes than to lean cells as documented by lactate dehydrogenase leakage. Necrotic mode of cell death strongly prevails over apoptosis since we did not observe any significant increase in activities of caspase 3, 8 and 9 in any group of hepatocytes treated with GalN. Reactive oxygen species (ROS) formation and lipid peroxidation were elevated in a dose-dependent manner by GalN and were significantly more pronounced in fatty hepatocytes. A decrease in the percentage of hepatocytes with energized mitochondria was observed from 30 mM and 10 mM GalN in lean and steatotic hepatocytes, respectively. Our results undoubtedly indicate that steatotic hepatocytes exert higher sensitivity to the toxic effect of GalN. This sensitivity may be caused by more intensive GalN-induced ROS production and lipid peroxidation and by higher susceptibility of mitochondria to loss of mitochondrial membrane potential in steatotic hepatocytes. In our experimental arrangement, apoptosis does not seem to participate considerably on hepatotoxic action of GalN in either group of hepatocytes.

The Effect of Oleic and Palmitic Acid on Induction of Steatosis and Cytotoxicity on Rat Hepatocytes in Primary Culture

In vitro models serve as a tool for studies of steatosis. Palmitic and oleic acids can induce steatosis in cultured hepatocytes. The aim of our study was to verify steatogenic and cytotoxic effects of palmitic acid (PA), oleic acid (OA) and their combinations as well as their impact on functional capacity of rat primary hepatocytes. Hepatocytes were exposed to OA or PA (0.125-2 mmol/l) or their combination at ratios of 3:1, 2:1 or 1:1 at the final concentrations of 0.5-1 mmol/l. Both OA and PA caused a dose-dependent increase in triacylglycerol content in hepatocytes. PA was more steatogenic at 0.25 and 0.5 mmol/l while OA at 0.75 and 1 mmol/l. PA exhibited a dose-dependent cytotoxic effect associated with ROS production, present markers of apoptosis and necrosis and a decrease in albumin production. OA induced a damage of the cytoplasmic membrane from 1 mM concentration. Mixture of OA and PA induced lower cytotoxicity with less weakened functional capacity than did PA alone. Extent of steatosis was comparable to that after exposure to OA alone. In conclusion, OA or combination of OA with PA is more suitable for simulation of simple steatosis than PA alone.

Pathways involved in acetaminophen hepatotoxicity with specific targets for inhibition/downregulation

Insights on molecular/immunological mechanisms involve in APAP hepatotoxicity and pave way for researchers/clinicians/pharma bodies to identify novel biomarkers, effective bioactive candidates and fruitful therapy against APAP hepatotoxicity.

The effect of tert-butyl hydroperoxide-induced oxidative stress on lean and steatotic rat hepatocytes in vitro

Oxidative stress and mitochondrial dysfunction play an important role in the pathogenesis of nonalcoholic fatty liver disease and toxic liver injury. The present study was designed to evaluate the effect of exogenous inducer of oxidative stress (tert-butyl hydroperoxide, tBHP) on nonfatty and steatotic hepatocytes isolated from the liver of rats fed by standard and high-fat diet, respectively. In control steatotic hepatocytes, we found higher generation of ROS, increased lipoperoxidation, an altered redox state of glutathione, and decreased ADP-stimulated respiration using NADH-linked substrates, as compared to intact lean hepatocytes. Fatty hepatocytes exposed to tBHP exert more severe damage, lower reduced glutathione to total glutathione ratio, and higher formation of ROS and production of malondialdehyde and are more susceptible to tBHP-induced decrease in mitochondrial membrane potential. Respiratory control ratio of complex I was significantly reduced by tBHP in both lean and steatotic hepatocytes, but reduction in NADH-dependent state 3 respiration was more severe in fatty cells. In summary, our results collectively indicate that steatotic rat hepatocytes occur under conditions of enhanced oxidative stress and are more sensitive to the exogenous source of oxidative injury. This confirms the hypothesis of steatosis being the first hit sensitizing hepatocytes to further damage.

Coenzyme Q10 supplementation improves metabolic parameters, liver function and mitochondrial respiration in rats with high doses of atorvastatin and a cholesterol-rich diet

Background

The aim of this study was to evaluate the actions of coenzyme Q₁₀ (CoQ₁₀) on rats with a cholesterol-rich diet (HD) and high doses of atorvastatin (ATV, 0.2, 0.56 or 1.42 mg/day).

Methods

Two experiments were done, the first one without coenzyme Q₁₀ supplementation. On the second experiment all groups received coenzyme Q₁₀ 0.57 mg/day as supplement. After a 6-week treatment animals were sacrificed, blood and liver were analyzed and liver mitochondria were isolated and its oxygen consumption was evaluated in state 3 (phosphorylating state) and state 4 (resting state) in order to calculate the respiratory control (RC).

Results

HD increased serum and hepatic cholesterol levels in rats with or without CoQ₁₀. ATV reduced these values but CoQ₁₀ improved even more serum and liver cholesterol. Triacylglycerols (TAG) were also lower in blood and liver of rats with ATV + CoQ₁₀. HDL-C decreased in HD rats. Treatment with ATV maintained HDL-C levels. However, these values were lower in HD + CoQ₁₀ compared to control diet (CD) + CoQ₁₀. RC was lessened in liver mitochondria of HD. The administration of ATV increased RC. All groups supplemented with CoQ₁₀ showed an increment in RC. In conclusion, the combined administration of ATV and CoQ₁₀ improved biochemical parameters, liver function and mitochondrial respiration in hypercholesterolemic rats.

Conclusions

Our results suggest a potential beneficial effect of CoQ₁₀ supplementation in hypercholesterolemic rats that also receive atorvastatin. This beneficial effect of CoQ₁₀ must be combined with statin treatment in patient with high levels of cholesterol.

Decreased translation of Dio3 mRNA is associated with drug-induced hepatotoxicity

Recent work has demonstrated the importance of post-transcriptional gene regulation in toxic responses. In the present study, we used two rat models to investigate mRNA translation in the liver following xenobiotic-induced toxicity. By combining polysome profiling with genomic methodologies, we were able to assess global changes in hepatic mRNA translation. Dio3 (iodothyronine deiodinase type III) was identified as a gene that exhibited specific translational repression and had a functional role in a number of relevant canonical pathways. Western blot analysis indicated that this repression led to reduced D3 (the protein expressed by Dio3) levels, enhanced over time and with increased dose. Using Northern blotting techniques and qRT-PCR (quantitative reverse transcription–PCR), we confirmed further that there was no reduction in Dio3 mRNA, suggesting that translational repression of Dio3 is an important determinant of the reduced D3 protein expression following liver damage. Finally, we show that drug-induced hepatotoxicity appears to cause localized disruptions in thyroid hormone levels in the liver and plasma. We suggest that this leads to reduced translation of Dio3 mRNA, which results in decreased D3 production. It may therefore be possible that this is an important mechanism by which the liver can, upon early signs of damage, act rapidly to maintain its own energy equilibrium, thereby avoiding global disruption of the hypothalamic–pituitary–thyroid axis.

Steatotic rat hepatocytes in primary culture are more susceptible to the acute toxic effect of acetaminophen

Acetaminophen (APAP) overdose is the most common cause of acute liver failure in humans. Non-alcoholic fatty liver disease is the most frequent chronic liver disease in developed countries. The aim of our work was to compare the effect of APAP on intact rat hepatocytes and hepatocytes isolated from steatotic liver in primary cultures. Male Wistar rats were fed with standard diet (10 % energy from fat) and high-fat diet (71 % energy from fat) for 6 weeks and then hepatocytes were isolated. After cell attachment, APAP (1; 2.5; 3.75 and 5 mM) was added to culture media (William's E medium) and hepatocytes were cultured for up to 24 hours. APAP caused more severe dose-dependent damage of steatotic hepatocytes as documented by increased release of lactate dehydrogenase (LDH) and LDH leakage, decreased activity of cellular dehydrogenases (WST-1 test) and reduced albumin production. Intact steatotic hepatocytes contained lower amount of reduced glutathione (GSH). Treatment with APAP (1 and 2.5 mmol/l) caused more pronounced decrease in GSH in steatotic hepatocytes. ROS (reactive oxygen species) formation after 24-hour incubation was significantly higher in fatty hepatocytes using APAP at concentration of 3.75 and 5 mmol/l. Interleukin 6 (IL-6) production was elevated in 2.5 mM APAP-treated nonsteatotic and steatotic hepatocyte cultures at 8 hours, compared to appropriate controls. In conclusions, our results indicate that steatotic hepatocytes exert higher sensitivity to the toxic action of APAP. This sensitivity may be caused by lower content of GSH in intact steatotic hepatocytes and by more pronounced APAP-induced decrease in intracellular concentration of GSH.

Differences in early acetaminophen hepatotoxicity between obese ob/ob and db/db mice

Clinical investigations suggest that hepatotoxicity after acetaminophen (APAP) overdose could be more severe in the context of obesity and nonalcoholic fatty liver disease. The pre-existence of fat accumulation and CYP2E1 induction could be major mechanisms accounting for such hepatic susceptibility. To explore this issue, experiments were performed in obese diabetic ob/ob and db/db mice. Preliminary investigations performed in male and female wild-type, ob/ob, and db/db mice showed a selective increase in hepatic CYP2E1 activity in female db/db mice. However, liver triglycerides in these animals were significantly lower compared with ob/ob mice. Next, APAP (500 mg/kg) was administered in female wild-type, ob/ob, and db/db mice, and investigations were carried out 0.5, 2, 4, and 8 h after APAP intoxication. Liver injury 8 h after APAP intoxication was higher in db/db mice, as assessed by plasma transaminases, liver histology, and terminal deoxynucleotidyl transferase-mediated dUTP nick-end labeling assay. In db/db mice, however, the extent of hepatic glutathione depletion, levels of APAP-protein adducts, c-Jun N-terminal kinase activation, changes in gene expression, and mitochondrial DNA levels were not greater compared with the other genotypes. Furthermore, in the db/db genotype plasma lactate and β-hydroxybutyrate were not specifically altered, whereas the plasma levels of APAP-glucuronide were intermediary between wild-type and ob/ob mice. Thus, early APAP-induced hepatotoxicity was greater in db/db than ob/ob mice, despite less severe fatty liver and similar basal levels of transaminases. Hepatic CYP2E1 induction could have an important pathogenic role when APAP-induced liver injury occurs in the context of obesity and related metabolic disorders.

Dangfei liganning capsules attenuate the susceptibility of rat nonalcoholic fatty liver to carbon tetrachloride toxicity

OBJECTIVE

To test whether nonalcoholic hepatic steatosis sensitizes carbon tetrachloride (CCl4)-induced liver injury, and to assess the therapeutic effect of Chinese medicine extracts of Dangfei Liganning capsules and their potential underlying mechanisms.

METHODS

Male Wistar rats were fed a high-fat diet to induce nonalcoholic fatty liver disease (NAFLD) or a normal diet (N). Eight weeks later, a nonlethal dose of CCl4 was applied intraperitoneally. From the start, HF-CCl4 rats were administered daily Dangyao extracts (D), Dangfei Liganning capsules (DF), or Diammonium Glycyrrhizinate (G) intragastrically. Rats were sacrificed 48 h after CCl4 administration. In addition to serum biochemistry, liver histopathology was observed using hematoxylin-eosin (HE) and oil red O staining, and hepatic levels of triglyceride (TG), malondialdehyde (MDA), glutathione (GSH), superoxide dismutase (SOD), caspase-3 activation and cytochrome P450 (CYP2E1) expression were assessed.

RESULTS

There was almost no response to the nonlethal dose of CCl4 in the N control group. However, the HF group demonstrated massive steatosis, and elevated levels of serum ALT and AST, liver MDA, CYP2E1, and caspase-3 activation, whereas the levels of GSH and SOD were significantly decreased. All indexes assessed were dramatically worse in the HF-CCl4 group compared to the HF group, in addition to the more severe steatosis, hepatocyte ballooning, and inflammatory infiltration apparent in the centrilobular area. The medicines we tested affected the pathological changes in HF-CCl4 rats to differing degrees: DF and G led to improvements in all of the above examined indexes, including an obvious improvement in histopathology, and DF improved serum ALT and MDA levels more markedly than G, whereas D extracts produced only mild liver injury attenuation.

CONCLUSION

Liver with NAFLD is more sensitive to hepatotoxicity; furthermore, the disrupted balance of oxidative stress and anti-oxidant defense contributes to the underlying mechanisms. Dangfei Liganning capsules potentially decrease this toxic susceptibility and alleviate liver injury in non-alcoholic fatty liver.