Cytochrome P450 dysregulations in thioacetamide-induced liver cirrhosis in rats and the counteracting effects of hepatoprotective agents

Decoding the Role of CYP450 Enzymes in Metabolism and Disease: A Comprehensive Review

Cytochrome P450 (CYP450) is a group of enzymes that play an essential role in Phase I metabolism, with 57 functional genes classified into 18 families in the human genome, of which the CYP1, CYP2, and CYP3 families are prominent. Beyond drug metabolism, CYP enzymes metabolize endogenous compounds such as lipids, proteins, and hormones to maintain physiological homeostasis. Thus, dysregulation of CYP450 enzymes can lead to different endocrine disorders. Moreover, CYP450 enzymes significantly contribute to fatty acid metabolism, cholesterol synthesis, and bile acid biosynthesis, impacting cellular physiology and disease pathogenesis. Their diverse functions emphasize their therapeutic potential in managing hypercholesterolemia and neurodegenerative diseases. Additionally, CYP450 enzymes are implicated in the onset and development of illnesses such as cancer, influencing chemotherapy outcomes. Assessment of CYP450 enzyme expression and activity aids in evaluating liver health state and differentiating between liver diseases, guiding therapeutic decisions, and optimizing drug efficacy. Understanding the roles of CYP450 enzymes and the clinical effect of their genetic polymorphisms is crucial for developing personalized therapeutic strategies and enhancing drug responses in diverse patient populations.

Effects of chronic cirrhosis induced by intraperitoneal thioacetamide injection on the protein content and Michaelis-Menten kinetics of cytochrome P450 enzymes in the rat liver microsomes

Chronic intraperitoneal injection of thioacetamide (TAA) in rats has been used as an animal model of human cirrhosis to study the effects of the disease on drug metabolism. However, TAA inhibits P450 enzymes directly and independently of cirrhosis. We investigated the effects of chronic cirrhosis in rats, induced by 10 weeks of intraperitoneal TAA, on the P450 enzymes after a 10-day washout period to eliminate TAA. Liver histology and serum biomarkers of hepatic function confirmed cirrhosis in all animals. Microsomal total P450 content, P450 reductase activity and ethoxycoumarin O-deethylase activity, a general marker of P450 activity, were significantly reduced by 30%-50% in cirrhotic animals. Additionally, the protein content and Michaelis-Menten kinetics of the activities of CYP2D, CYP2E1 and CYP3A were investigated. Whereas cirrhosis reduced the microsomal protein contents of CYP2D and CYP3A by 70% and 30%, respectively, the protein contents of CYP2E1 were not affected. However, the activities of all the tested isoenzymes were substantially lower in the cirrhotic livers. It is concluded that the TAA model of cirrhosis that incorporates a 10-day washout period after intraperitoneal injection of the chemical to rats produces isoenzyme-selective reductions in the P450 proteins or activities, which are independent of the direct inhibitory effects of TAA.

Hepatoprotective Effect of Opuntia robusta Fruit Biocomponents in a Rat Model of Thioacetamide-Induced Liver Fibrosis

Liver fibrosis is a chronic disease associated with oxidative stress that has a great impact on the population mortality. Due to their antioxidant capacity, we evaluated the protective effect of Opuntia robusta fruit (Or) on liver fibrosis. A nutraceutical characterization of Or was performed and a model of fibrosis was induced with thioacetamide (TAA) in Wistar rats. Aminotransferases, reduced glutathione (GSH) and histopathology were evaluated. Or contained 436.5 ± 57 mg of Betacyanins equivalents/L., 793 mg of catechin equivalents (CAE)/100 g for flavonoids, 1118 mg of gallic acid equivalents (GAE)/100 g for total phenols, 141.14 mg/100 g for vitamin C and 429.9 μg/100 g for vitamin E. The antioxidant capacity of Or was: 2.27 mmol of Trolox® equivalents (TE)/L (DPPH), 62.2 ± 5.0 μmol TE/g (ABTS•+), 80.2 ± 11.7 μmol TE/g (FRAP), 247.9 ± 15.6 µmol TE/g (AAPH) and 15.0% of H2O2 elimination. An increase (p < 0.05) of aminotransferases and a decrease (p < 0.05) of hepatic GSH was observed in the TAA group compared to the control and the concomitant groups. Histopathology showed changes in the normal architecture of the liver treated with TAA compared to the concomitant treatments. Or contains bioactive components with antioxidant capacity, which can reduce fibrotic liver damage.

Hepatoprotective and therapeutic effects of resveratrol: A focus on anti-inflammatory and anti- oxidative activities

Being the most essential organ in the body, the liver performs critical functions. Hepatic disorders, such as alcoholic liver disease, hepatic steatosis, liver fibrosis, non-alcoholic fatty liver disease, hepatocellular carcinoma and hepatic failure, have an impact on the biochemical and physiological functions of the body. The main representative of the flavonoid subgroup of flavones, Resveratrol (RES), exhibits suitable pharmacological activities for treating various liver diseases, such as fatty hepatitis, liver steatosis, liver cancer and liver fibrosis. According to various studies, grapes and red wine are good sources of RES. RES has various health properties; it is anti-inflammatory, anti-apoptotic, anti-oxidative and hepatoprotective against several hepatic diseases and hepatoxicity. Therefore, we performed a thorough research and created a summary of the distinct targets of RES in various stages of liver diseases. We concluded that RES inhibited liver inflammation essentially by causing a significant decrease in the expression of various pro-inflammatory cytokines like TNF-α, IL-1α, IL-1β, and IL-6. It also inhibits the transcription factor nuclear NF-κB that brings about the inflammatory cascade. RES also inhibits the PI3K/Akt/mTOR pathway to induce apoptosis. Additionally, it reduces oxidative stress in hepatic tissue by markedly reducing MDA and NO contents, and significantly increasing the levels of CAT, SOD and reduced GSH, in addition to AST and ALT, against toxic chemicals like CC14, As2O3 and TTA. Due to its anti-oxidant, anti-inflammatory and anti-fibrotic properties, RES reduces liver injury markers. RES is safe natural antioxidant that provides pharmacological rectification of the hepatoxicity of toxic chemicals.

Effect of Uncaria rhynchophylla against Thioacetamide-Induced Acute Liver Injury in Rat

Both oxidative stress (OS) and inflammation are two fundamental pathological processes of acute liver injury (ALI). The current work is to investigate the effect and possible mechanism of Uncaria rhynchophylla (UR) on thioacetamide- (TAA-) induced ALI in rats. UR (100 and 200 mg/kg) was orally administrated with TAA (200 mg/kg of bodyweight, intraperitoneal injection) for 3 consecutive days. ALI was confirmed using histological examination and the factors associated with OS and liver function activity measured in serum. Moreover, expressions of inflammation and collagen-related proteins were measured by the Western blot analysis. Myeloperoxidase (MPO), which mediates OS in the ALI control group, was manifested by a significant rise compared with the normal group. UR significantly reduced AST, ALT, and ammonia levels in serum. The nuclear factor-κB (NF-κB) activation induced by TAA led to increase both inflammatory mediators and cytokines. Whereas, UR administration remarkably suppressed such an overexpression. UR supplementation improved matrix metalloproteinases (MMPs) such as MMP-1, -2, and -8. In contrast, tissue inhibitors of metalloproteinases- (TIMP-) 1 level increased significantly by UR treatment. In addition, the histopathological analysis showed that the liver tissue lesions were improved obviously by UR treatment. UR may ameliorate the effects of TAA-induced ALI in rats by suppressing both OS through MPO activation and proinflammatory factors through NF-κB activation. In conclusion, UR exhibited a potent hepatoprotective effect on ALI through the suppression of OS.

Sidr honey abrogates the oxidative stress and downregulates the hyaluronic acid concentration and gene expression of TGF-β1 and COL1a1 in rat model of thioacetamide-induced hepatic fibrosis

Liver fibrosis is a major health concern, which might progress to cirrhosis. To date, treatment trials rely mainly on the removal of the causative factor. The current study investigated the potential ameliorative role of sidr honey on thioacetamide (TAA)-induced liver fibrosis in rats. Forty-eight Wistar albino rats were equally allocated into four groups: control; sidr honey (5g/kg body weight (BW), orally); TAA (200 mg/kg BW, IP three times weekly/15 weeks); and sidr honey plus TAA at the same dose and administration rout. Rats co-treated with sidr honey plus TAA revealed significant reduction in hepatic malondialdehyde, hyaluronic acid (HA), alanine aminotransferase, aspartate aminotransferase, alkaline phosphatase, gamma glutamyl transferase, direct bilirubin, and hepatic mRNA expression of transforming growth factor (TGF)-β1 and collagen type I alpha 1 chain (COL1a1) compared to TAA-exposed rats. In addition, the hepatoprotective potential of sidr honey was indicated via improvement of histopathologic picture of hepatocytes and upregulation of total antioxidant capacity, reduced glutathione, catalase, glutathione peroxidase, superoxide dismutase, total protein, and albumin compared to TAA-treated rats. In conclusion, daily administration of sidr honey (5 g/kg BW) is a promising natural antioxidant and fibrosuppressive agent that could ameliorate liver fibrosis via downregulation of fibrosis genes including TGF-β1 and COL1a1 and HA and via enhancement of antioxidant system.

Hepatoprotective effect of polyphenols in rats with experimental thioacetamide-induced toxic liver pathology

Non-alcoholic fatty liver disease is associated with a number of disorders (diabetes, obesity, cardiovascular diseases), and can also be induced by drugs or toxic compounds. Recently the important branch of medicine is the search for effective means of prevention and treatment of fatty hepatosis. Our work was aimed to study the effect of some biologically active natural polyphenols (resveratrol and pinosylvin stilbenes as well as dihydromyricetin dihydroflavonol) on the function and histologic features of the liver. In the experimental model of thioacetamide-induced toxic hepaptitis, the male rats of the Wistar line daily received the effective doses of polyphenols intragastically by gavage together with 0.05% thioacetamide added to drinking water. All studied polyphenols contributed to stabilization of rat weight and a two-fold significant (p < 0.05) decrease in the level of direct bilirubin in the blood serum of animals treated with thioacetamide. Histological analysis of the liver confirmed a decrease in inflammation and hemorrhage in animals treated with polyphenols amid continued administration of thioacetamide for 30 days. Based on the data obtained, it can be concluded that the natural polyphenols which belong to the classes of dihydroflavonols (dihydromyricetin) and stilbenes (resveratrol and pinosylvin) have a positive effect on liver function in the experimental model of toxic hepatosis. The studied polyphenols can be considered as potential hepatoprotective drugs used as a part of the liver diseases complex therapy.

Amelioration of hepatic function, oxidative stress, and histopathologic damages by Cassia fistula L. fraction in thioacetamide-induced liver toxicity

Cassia fistula L. (Caesalpinioideae) is a highly admirable medicinal plant and is traditionally recommended for the treatment of rheumatism, liver disorders, jaundice, and other inflammatory diseases. This study was designed to investigate the hepatoprotective properties of ethyl acetate fraction from C. fistula leaves in an animal model. Treatment with thioacetamide significantly elevated the level of serum glutamic-oxaloacetic transaminase (1.75-fold), alkaline phosphatase (4.07-fold), and total bilirubin (2.29-fold) as compared to the control. It was found that pretreatment of fraction followed by consecutive 2 days thioacetamide reduced the conversion of thioacetamide carcinogen to its reactive metabolites by phase I enzymes and increased the level of detoxification phase II along with antioxidative enzymes. The histopathological studies revealed the hepatoprotective nature of the fraction in restoring the normal architecture of thioacetamide-intoxicated damaged liver. The fraction showed downregulation in the expression level of p-PI3K, p-Akt, and p-mTOR pointing towards its chemopreventive potential. The HPLC analysis of the fraction had shown the dominance of three phenolic compounds namely, catechin, epicatechin, and chlorogenic acid. The above studies comprising histopathological, immunohistochemical, and hepatic enzymes are strong indicative of the potential protective ability of ethyl acetate fraction phytoconstituents against thioacetamide-induced toxicity. Graphical abstract.

Protective Effects of Nutria Bile against Thioacetamide-Induced Liver Injury in Mice

Several eradication programs have been developed and executed to curb alien invasive species that tend to damage the ecological environments they colonize; however, only few studies have evaluated the utilization of carcasses of these species after eradication. Nutria (Myocastor coypus) is an invasive rodent species targeted by eradication programs in many countries. We noted that nutria produce large amounts of ursodeoxycholic acid (UDCA) in their bile. UDCA is a unique component responsible for the anti-inflammatory and hepatoprotective effects exerted by bear bile. Therefore, we sought to examine the medicinal utility of nutria carcasses by investigating the hepatoprotective effect of their bile in mice. C57BL/6 mice were injected with thioacetamide (TAA), which induced liver damage by increasing Kupffer cell infiltration. Administration of nutria bile reduced hepatic inflammation, improved hepatic function, and increased the levels of senescence marker protein 30 (an indicator of hepatocyte viability). Our results show that nutria bile exerts protective effects against TAA-induced liver injury in mice, suggesting that nutria carcasses may be used for the treatment of liver injuries.

Development and Application of an UHPLC-MS/MS Method for Comparative Pharmacokinetic Study of Eight Major Bioactive Components from Yin Chen Hao Tang in Normal and Acute Liver Injured Rats

Yin Chen Hao Tang (YCHT) is one of the most famous hepatoprotective herbal formulas in China, but its pharmacokinetic investigation in model rats has been rarely conducted. In this study, the hepatic injury model was caused by intraperitoneal injections of carbon tetrachloride (CCl₄), and YCHT was orally administered to the model and normal rats. An ultrahigh performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) method was established to analyze the plasma pharmacokinetics of eight major bioactive ingredients from YCHT in both the normal and liver injured rats. The calibration curves presented good linearity (r > 0.9981) in the concentration range. The relative standard deviation (RSD%) of inter- and intraday precision was within 9.55%, and the accuracy (RE%) ranged from -10.72% to 2.46%. The extraction recovery, matrix effect, and stability were demonstrated to be within acceptable ranges. The lower limit of detection (LLOD) and lower limit of quantitation (LLOQ) were around 0.1 ng/mL and 0.5 ng/mL, respectively, which were much lower than those in other related researches. Results reveal that there are significant differences in the pharmacokinetics of scoparone, geniposide, rhein, aloe-emodin, physcion, and chrysophanol in hepatic injured rats as compared to those in control except for scopoletin and emodin. Our experimental results provide a meaningful reference for the clinical dosage of YCHT in treating liver disorders, and the improvement of LLOD and LLOQ can also broaden the range of our method's application, which is very suitable for quantitating these eight compounds with low levels.

Nucleos(t)ide Analogs Do Not Independently Influence Hepatic Fibrosis and Portal Hypertension beyond Viral Suppression in CBDL-Induced Cirrhotic Rat

Chronic hepatitis is the major cause of liver cirrhosis and portal hypertension. Several factors affect portal pressure, including liver fibrosis, splanchnic vasodilatation, and pathologic angiogenesis. Nucleos(t)ide analogs (NUCs), the oral antiviral agents, effectively attenuate chronic hepatitis B-related liver cirrhosis and portal hypertension via viral suppression and alleviation of hepatitis. On the other hand, NUCs affect tumor necrosis factor (TNF)-α, vascular endothelial growth factor (VEGF), and nitric oxide, which participate in fibrogenesis, vasodilatation, and angiogenesis. However, whether NUCs independently influence liver fibrosis and portal hypertension beyond viral suppression is unknown. This study thus aimed to evaluate the influences of three frequently used NUCs in rats with nonviral cirrhosis. Male Sprague-Dawley rats received common bile duct ligation (CBDL) to induce cholestatic cirrhosis and portal hypertension. The rats were randomly allocated into four groups, treated by mouth with lamivudine (30 mg/kg per day), entecavir (0.09 mg/kg per day), tenofovir (50 mg/kg per day), or distilled water (vehicle control) from the 15th day after CBDL. On the 29th day, liver cirrhosis- and portal hypertension-related parameters were evaluated. The results showed that chronic NUCs treatment did not affect hemodynamic parameters, plasma TNF-α concentration, and hepatic fibrogenesis protein expressions in rats with nonviral cirrhosis. Though the mesenteric VEGF receptor 2 phosphorylation was downregulated in NUCs-treated groups, the splanchnic angiogenesis was not influenced. In conclusion, lamivudine, entecavir, and tenofovir had no additional effects on liver cirrhosis and portal hypertension in rats with nonviral cirrhosis.

Non-alcoholic fatty liver disease fibrosis score predicts hematological toxicity of chemotherapy including irinotecan for colorectal cancer

Liver dysfunction that may affect drug metabolism is a major concern in patients treated with chemotherapy. Thus, assessment of the degree of liver dysfunction is crucial for predicting the adverse events of chemotherapy. The non-alcoholic fatty liver disease fibrosis score (NFS) is a non-invasive clinical scoring system constructed from routine clinical and laboratory variables. The aim of this study was to evaluate whether NFS was useful for predicting the adverse events of chemotherapy including irinotecan (CPT-11) for colorectal cancer. Between January, 2007 and May, 2013, a total of 87 patients with unresectable/recurrent colorectal cancer who received first-line chemotherapy including CPT-11 were reviewed. Demographic variables, including pretreatment NFS, were retrospectively collected from medical records. The primary outcome was the association between pretreatment NFS and adverse events, such as hematological and non-hematological toxicity, of chemotherapy including CPT-11. The median pretreatment NFS was 1.302 (range, 5.158-2.620). Pretreatment NFS was an independent risk factor for hematological toxicity in a multivariate analysis (coefficient=0.932, 95% CI: 0.083-1.781; P=0.031). Receiver operating characteristic curve analysis identified 0.347 as the optimal cut-off value associated with hematological toxicity. Using this cut-off, high NFS was found to be a significant risk factor for hematological toxicity (coefficient=2.019, 95% CI: 0.239-3.798, P=0.026), but not for non-hematological toxicity (P=0.546). Therefore, based on these results, NFS appears to be a significant predictor of hematological adverse events in chemotherapy including CPT-11 for colorectal cancer and it is a non-invasive, useful tool that may be used for determining regimens or doses of chemotherapy including CPT-11.

Isochlorogenic acid A affects P450 and UGT enzymes in vitro and in vivo

Isochlorogenic acid A (ICQA), which has anti-inflammatory, hepatoprotective, and antiviral properties, is commonly presented in fruits, vegetables, coffee, plant-based food products, and herbal medicines. These herbal medicines are usually used in combination with other medicines in the clinic. However, little is known about the regulatory effects of ICQA on drug-metabolizing enzymes and the herb-drug interactions. In the present study, we evaluated the inhibitory potentials of ICQA on CYP1A2, CYP2C9, CYP2C19, CYP3A4, CYP2D6, and CYP2E1 in vitro based on a cocktail approach. The P450 and UGT activities in mice treated with ICQA for a prolonged period were also determined. Our results demonstrated that ICQA exhibited a weak inhibitory effect on CYP2C9 in human liver microsomes with IC₅₀ being 57.25 μmol·L^-1 and Ki being 26.77 μmol·L^-1. In addition, ICQA inhibited UGT1A6 activity by 25%, in the mice treated with ICQA (i.p.) at 30 mg·kg^-1 for 14 d, compared with the control group. Moreover, ICQA showed no mechanism-based inhibition on CYP2C9 or UGT1A6. In conclusion, our results further confirm a safe use of ICQA in clinical practice.

Resveratrol mitigates hepatic injury in rats by regulating oxidative stress, nuclear factor-kappa B, and apoptosis

Resveratrol is a naturally occurring polyphenol, possesses several pharmacological activities including anticancer, antioxidant, antidiabetic, antinociceptive, and antiasthmatic activity. Little is known about its hepatoprotective action mechanisms. This study was conceived to explore the possible protective mechanisms of resveratrol compared with the hepatoprotective silymarin in thioacetamide (TAA)-induced hepatic injury in rats. Thirty-two rats were equally divided into four groups; normal control (i), TAA (100 mg/kg) (ii), TAA + silymarin (50 mg/kg) (iii), and TAA + resveratrol (10 mg/kg) (iv). Liver function and histopathology, pro-inflammatory cytokines, oxidative stress, and apoptotic markers were examined. Data were analyzed using ANOVA test followed by Tukey post hoc test. Compared to TAA-intoxicated group, resveratrol mitigated liver damage, and inflammation as noted by less inflammatory infiltration, hydropic degeneration with decreased levels of tumor necrosis factor-alpha, interleukin-6, and interferon-gamma by 78.83, 18.12, and 64.49%, respectively. Furthermore, it reduced (P < 0.05) alanine and aspartate aminotransferases by 36.64 and 48.09%, respectively, restored hepatic glutathione content and normalized superoxide dismutase and malondialdehyde levels. While it inhibited nuclear factor-kappa B, cytochrome 2E1, and enhanced apoptosis of necrotic hepatocytes via increasing caspase-3 activity. Our findings indicated that the potential hepatoprotective mechanisms of resveratrol are associated with inhibition of inflammation, enhancing the apoptosis of necrotic hepatocytes, and suppression of oxidative stress.

Mechanism-based inhibitory and peroxisome proliferator-activated receptor α-dependent modulating effects of silybin on principal hepatic drug-metabolizing enzymes

Silybin, a major pharmacologically active compound in silymarin, has been widely used in combination with other prescriptions in the clinic to treat hepatitis and a host of other diseases. Previous studies suggested that silybin is a potential inhibitor of multiple drug-metabolizing enzymes (DMEs); however, the in vitro to in vivo translation and the mechanisms involved remain established. The aim of this study was to provide a mechanistic understanding of the regulatory effects of silybin on principal DMEs. Silybin (50 or 150 mg/kg/d) was administered to mice for a consecutive 14 days. The plasma and hepatic exposure of silybin were detected; the mRNA, protein levels, and enzyme activities of principal DMEs were determined. The results demonstrated that the enzyme activities of CYP1A2, CYP2C, CYP3A11, and UGT1A1 were significantly repressed, whereas little alteration of the mRNA and protein levels was observed. Silybin inhibits these DMEs in a mechanism-based and/or substrate-competitive manner. More importantly, silybin was found to be a weak agonist of peroxisome proliferator-activated receptor (PPAR)α, as evidenced from the molecular docking, reporter gene assay, and the targeting gene expression analysis. However, silybin could significantly compromise the activation of PPARα by fenofibrate, characterized with significantly repressed expression of PPARα targeting genes, including L-FABP, ACOX1, and UGT1A6. This study suggests that silybin, despite its low bioavailability, may inhibit enzyme activities of multiple DMEs in a mechanism-based mode, and more importantly, may confer significant drug-drug interaction with PPARα agonists via the repression of PPARα activation in a competitive mode.

Thioacetamide-induced liver injury: protective role of genistein

This study aimed to investigate the possible protective effects of genistein (GEN), a phytoestrogen, on the liver injury induced in rats by thioacetamide (TTA; 200.0 mg·(kg body mass)(-1); administered 3 times a week by intraperitoneal injection). GEN (0.5, 1.0, or 2.0 mg·(kg body mass)(-1); by subcutaneous injection) was concurrently administered on a daily basis for 8 weeks, and its effects were evaluated 24 h after the administration of the last dose. The results from this study revealed that TTA-induced liver injury was associated with massive changes in the serum levels of liver biomarkers, oxidative stress markers, and liver inflammatory cytokines. Treatment of TAA-induced liver injury in rats with GEN decreased the elevated serum levels of aspartate aminotransferase, alanine aminotransferase, and total and direct bilirubin, and increased the serum level of albumin. GEN also restored the liver levels of malondialdehyde and reduced glutathione, as well as tumor necrosis factor-alpha, interleukin-6, and their modulator nuclear factor kappa-light-chain-enhancer of activated B cells. From our results, it can be concluded that GEN attenuates the liver injury-induced in rats with TAA, and this hepatoprotective role is attributed to its anti-inflammatory and antioxidant properties.

Reversing effects of lignans on CCl4-induced hepatic CYP450 down regulation by attenuating oxidative stress

Oxidative stress has been proved to be a critical reason of regulating CYP450s under hepatic injury status. The study was aimed to investigate the effect of pretreatment of schisandra lignan extracts (SLE) and dimethyl diphenyl bicarboxylate (DDB) on expressions and activities of the main liver P450 isoenzymes in CCl4 induced liver injury rats and their anti-oxidative effects on both CCl4 induced liver injury rats and a CCl4 induced HepG2 cell injury model. Acute experimental liver injury induced by CCl4 caused drastically decreasing activities of the main liver P450 isoenzymes such as CYP1A2, CYP2C6, CYP2E1 and CYP3A2, as well as their protein expressions. Pretreatment of SLE (500 mg/kg) and DDB (200 mg/kg) twice a day for three days significantly decreased the losses of activities of CYP1A2, CYP2C6, CYP2E1 and CYP3A2. Similar results were observed in protein expressions. In addition, in the CCl4 induced HepG2 cells injury model and the CYP3A activity level correlated well with ROS level in several ingredients of SLE treated groups, especially in γ-schisandrin group. These results indicated that the reversion of P450 after SLE/DDB treatment were, on one hand, due to hepatoprotective effects of these lignans on livers; on the other hand, due to their regulation of P450 through anti-oxidative effect and γ-schisandrin might be the most powerful ingredient of SLE. Also, there might be potential interactions between SLE or DDB and co-administered medicines and it is necessary to adjust the dosage of co-administrated medicines in clinical medication of liver disease.

Reversing effects of silybin on TAA-induced hepatic CYP3A dysfunction through PXR regulation

AIM

Silybin (SB), a major constituent of the milk thistle, has been used to treat several liver disorders. However, liver diseases were always accompanied by CYP450 dysfunction. This study was designed to explore the relationship between the hepatoprotective effect and CYP3A regulation of SB during thioacetamide (TAA)-induced rat liver injury.

METHODS

Serum biochemical analysis and histopathological study were taken to evaluate the hepatoprotectinve effect of SB. α-SMA were detected by immunohistochemical analysis and cytokine release in rat liver was determined by ELISA assay. CYP3A and PXR expression were determined by RT-PCR and Western blot analysis, and CYP3A activity was based on the midazolam 4-hydroxylation reaction. Also, siRNA transfection was induced in HepG2 cells to evaluate the effect of PXR on cytotoxicity and CYP3A4 dysregulation caused by TAA.

RESULTS

SB showed powerful hepatoprotective effects, and anti-inflammatory and anti-fibrosis effects, and reversed the loss of CYP3A and PXR in TAA-injured rat liver, and decreased PXR translocation into the cell nucleus. PXR silencing weakened the effect of SB on cytoprotection and CYP3A regulation.

CONCLUSIONS

PXR was a very important factor of CYP3A regulation and might be the target of SB in TAA-induced liver disease. Also, because of the potential interactions of SB and co-administered medicines, it might be necessary to adjust the dosage in the clinical medication of liver disease.

Advances in development of large animal models of liver fibrosis and cirrhosis

Liver fibrogenesis refers to a dynamic process involving complex cellular and molecular mechanisms, resulting in the chronic activation of tissue repair mechanisms and reiterated liver tissue injury. Regardless of the etiology, hepatic fibrosis is a characteristic feature of chronic liver disease. Advanced liver fibrosis results in cirrhosis, portal hypertension, and eventually hepatic cancer and liver failure. Liver fibrosis represents a significant health problem worldwide, and no acceptable therapy exists. Blocking of liver fibrosis formation has become a key problem in the therapy of chronic liver disease. Animal models of liver fibrosis and cirrhosis have been applied to study the occurrence of liver fibrosis and evaluate the potential and possibility of anti-fibrosis treatments for several decades. This article reviews recent advances in the development of large animal models (e.g., rabbits, dogs, monkeys, and pigs) of liver fibrosis and cirrhosis.

Covalent modification of lipids and proteins in rat hepatocytes and in vitro by thioacetamide metabolites

Thioacetamide (TA) is a well-known hepatotoxin in rats. Acute doses cause centrilobular necrosis and hyperbilirubinemia while chronic administration leads to biliary hyperplasia and cholangiocarcinoma. Its acute toxicity requires its oxidation to a stable S-oxide (TASO) that is oxidized further to a highly reactive S,S-dioxide (TASO(2)). To explore possible parallels among the metabolism, covalent binding, and toxicity of TA and thiobenzamide (TB), we exposed freshly isolated rat hepatocytes to [(14)C]-TASO or [(13)C(2)D(3)]-TASO. TLC analysis of the cellular lipids showed a single major spot of radioactivity that mass spectral analysis showed to consist of N-acetimidoyl PE lipids having the same side chain composition as the PE fraction from untreated cells; no carbons or hydrogens from TASO were incorporated into the fatty acyl chains. Many cellular proteins contained N-acetyl- or N-acetimidoyl lysine residues in a 3:1 ratio (details to be reported separately). We also oxidized TASO with hydrogen peroxide in the presence of dipalmitoyl phosphatidylenthanolamine (DPPE) or lysozyme. Lysozyme was covalently modified at five of its six lysine side chains; only acetamide-type adducts were formed. DPPE in liposomes also gave only amide-type adducts, even when the reaction was carried out in tetrahydrofuran with only 10% water added. The exclusive formation of N-acetimidoyl PE in hepatocytes means that the concentration or activity of water must be extremely low in the region where TASO(2) is formed, whereas at least some of the TASO(2) can hydrolyze to acetylsulfinic acid before it reacts with cellular proteins. The requirement for two sequential oxidations to produce a reactive metabolite is unusual, but it is even more unusual that a reactive metabolite would react with water to form a new compound that retains a high degree of chemical reactivity toward biological nucleophiles. The possible contribution of lipid modification to the hepatotoxicity of TA/TASO remains to be determined.