Protective Effects of Diallyl Sulfide against Thioacetamide-Induced Toxicity: A Possible Role of Cytochrome P450 2E1

Autophagy blockage and lysosomal dysfunction are involved in diallyl sulfide-induced inhibition of malignant growth in hepatocellular carcinoma cells

Diallyl sulfide (DAS), as a major component of garlic extracts, has been shown to inhibit growth of hepatocellular carcinoma cells (HCC), but the underlying mechanism is still elusive. In this study, we aimed to explore the involvement of autophagy in DAS-induced growth inhibition of HepG2 and Huh7 hepatocellular carcinoma cells. We studied growth of DAS-treated HepG2 and Huh7 cells using the MTS and clonogenic assays. Autophagic flux was examined by immunofluorescence and confocal microscopy. The expression levels of autophagy-related proteins AMPK, mTOR, p62, LC3-II, LAMP1, and cathepsin D in the HepG2 and Huh7 cells treated with DAS as well as the tumors formed by HepG2 cells in the nude mice in the presence or absence of DAS were examined using western blotting and immunohistochemistry analysis. We found that DAS treatment induced activation of AMPK/mTOR, and accumulation of LC3-II and p62 both in vivo and in vitro. DAS inhibited autophagic flux through blocking the fusion of autophagosomes with lysosomes. Furthermore, DAS induced an increase in lysosomal pH and inhibition of Cathepsin D maturation. Co-treatment with an autophagy inhibitor (Chloroquine, CQ) further enhanced the growth inhibitory activity of DAS in HCC cells. Thus, our findings indicate that autophagy is involved in DAS-mediated growth inhibition of HCC cells both in vitro and in vivo.

Estrogen receptor-α36 is involved in diallyl sulfide-induced inhibition of malignant growth of HepG2 and Huh7 hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is a highly malignant disease that currently lacks effective treatment. Epidemiological studies have suggested the preventive role of raw garlic intake in different tumors, such as HCC. Although diallyl sulfide (DAS), the main component of garlic extracts, has been reported to inhibit the growth of HCC cells, the underlying mechanism remains elusive. This study aimed to investigate the inhibitory effect of DAS on the growth of HepG2 and Huh7 hepatocellular carcinoma cells and its underlying mechanism. HepG2 and Huh7 cells were treated with DAS and nude mice were intrahepatically injected with human HCC HepG2 cells and maintained with or without DAS administration for 28 days. MTS and clonogenic assays revealed that DAS inhibited the growth and clonogenicity of HepG2 and Huh7 hepatocellular carcinoma cells. Furthermore, DAS inhibited the growth of xenograft tumors accompanied by a decreased rate of pathological karyomitosis as observed by H&E staining. The expression levels of estrogen receptor-α36 (ER-α36) and epidermal growth factor receptor (EGFR) in HepG2 and Huh7 cells and in xenograft tumors derived from HepG2 cells after DAS treatment were detected by immunohistochemistry and western blotting. We found that DAS disrupted the positive regulatory loop between ER-α36 and EGFR, and decreased the phosphorylation of AKT at Ser 473 both in vivo and in vitro. DAS also induced cell apoptosis, as evidenced by Hoechst and TUNEL staining. Western blotting revealed activation of caspase3, increased BAX and decreased Bcl-2 expression. However, the ER-α36 expression knockdown attenuated DAS-induced ERK and AKT phosphorylation in HCC cells. DAS was also able to inhibit ER-α36-mediated activation of the MAPK/ERK signaling induced by estrogen. Thus, our results indicate that ER-α36 signaling is involved in DAS-induced inhibition of HCC cell growth both in vitro and in vivo.

Diallyl sulfide-induced attenuation of n-hexane-induced peripheral nerve impairment is associated with metabolic inhibition of n-hexane

Chronic exposure to n-hexane could induced serious peripheral nerve impairments. It has been well documented that the metabolic activation from n-hexane to 2,5-hexanedione (2,5-HD) is vital in the pathogenesis. Diallyl sulfide (DAS) is an extract of garlic and able to block the bioactivation of xenobiotic. The current study was designed to investigate whether DAS can attenuate n-hexane induced neuropathy. Male Wistar rats were pretreated with DAS (50 or 100 mg/kg.bw) and then n-hexane (3 g/kg.bw) for 7 weeks. Behavioral performance, biomarker measurement and toxicokinetic studies were performed. Enzymatic methods and western blotting analyses were also conducted to investigate the hepatic phase I enzymes (including cytochrome P450(CYP)2E1, CYP1A1 and CYP2B1) and phase II enzymes (including glutathione S transferase theta 1 (GSTT1) and NA(D)PH dehydrogenase quinone 1 (NQO1)). The results showed that DAS improved the behavioral performance while reducing the toxic metabolite: 2,5-HD and pyrrole adducts. Besides, DAS reduced the expression of CYP2E1 with a proportional decrease in activity, which largely decreased the bioactivation of n-hexane in vivo. The results suggested that DAS decreased the toxic metabolites of n-hexane to attenuate n-hexane-induced peripheral neuropathy.

Modulatory effect of Prosopis juliflora leaves on hepatic fibrogenic and fibrolytic alterations induced in rats by thioacetamide

This study investigated the antifibrotic effect of Prosopis juliflora leaves crude methanolic extract (PJEL) against thioacetamide (TAA)-induced liver fibrosis. The phytochemical analysis of PJEL was performed via HPLC/MS in association with evaluating its free radical scavenging and cytotoxic activities. The antifibrotic activity of PJEL was assessed by dividing Wistar rats into 8 groups: normal control, PJEL1-administered rats (2 mg/ Kg b.w.), PJEL2-administered rats (4 mg/ Kg b.w.), PJEL3-administered rats (8 mg/Kg b.w.), TAA-induced hepatic fibrosis, TTA + PJEL1, TAA + PJEL2, and TAA + PJEL3. Results indicated that PJEL crude methanolic extract is rich in polyphenolic compounds and alkaloids. PJEL exerted free radical scavenging activity with IC₅₀ of 123.5 μg/mL and cytotoxic activity against a well-differentiated hepatocellular cell line (IC₅₀ = 11.1 μg/mL). PJEL at a dose of 4 mg/Kg b.w. ameliorated serum ALT activity and improved serum albumin level and hepatic hydroxyproline content in association with a reduction in the fibrosis stage. PJEL elevated hepatic tumor necrosis factor-α and interleukin-6 contents with less necrosis grade. PJEL post-therapy ameliorated the relative expression of Bcl-2, Col1A1, Mmp-9, and Mmp-2 genes in liver. CONCLUSION: PJEL possesses a good therapeutic activity against TAA-induced liver fibrosis via enhancing extracellular matrix removal and stimulating hepatic regeneration to decrease hepatic necrosis.

The anti-inflammatory and anti-fibrotic effects of tadalafil in thioacetamide-induced liver fibrosis in rats

Liver fibrosis is a health concern that leads to organ failure mediated via production of inflammatory cytokines and fibrotic biomarkers. This study aimed to explore the protective effect of tadalafil, a phosphodiesterase-5 inhibitor, against thioacetamide (TAA)-induced liver fibrosis. Fibrosis was induced by administration of TAA (200 mg/kg, i.p.) twice weekly for 6 weeks. Serum transaminases activities, liver inflammatory cytokines, fibrotic biomarkers, and liver histopathology were assessed. TAA induced marked histopathological changes in liver tissues coupled with elevations in serum transaminases activities. Furthermore, hepatic content of nitric oxide and tumor necrosis factor-alpha, interleukin-6, and interleukin-1 beta were elevated, together with a reduction of interleukin-10 in the liver. In addition, TAA increased hepatic contents of transforming growth factor-beta, hydroxyproline, alpha-smooth muscle actin, and gene expression of collagen-1. Pretreatment with tadalafil protected against TAA-induced liver fibrosis, in a dose-dependent manner, as proved by the alleviation of inflammatory and fibrotic biomarkers. The effects of tadalafil were comparable with that of silymarin, a natural antioxidant, and could be assigned to its anti-inflammatory and anti-fibrotic properties.

Glibenclamide protects against thioacetamide-induced hepatic damage in Wistar rat: investigation on NLRP3, MMP-2, and stellate cell activation

Glibenclamide (GLB), most widely used in the treatment of type II diabetes mellitus, inhibits K⁺_ATP channel in pancreatic-β cells and releases insulin, while thioacetamide (TAA) is a well-known hepatotoxicant and most recommended for the induction of acute and chronic liver disease. The purpose of this study was to evaluate the hepatoprotective potential of GLB against TAA-induced hepatic damage in Wistar rats. TAA (200 mg/kg, ip, twice weekly) and GLB (1.25, 2.5, and 5 mg/kg/day, po) were administered for 6 consecutive weeks. Different biochemical, DNA damage, histopathological, TEM, immunohistochemical, and western blotting parameters were evaluated. GLB treatment has no effects on the TAA-induced significant decrease in body and liver weights. TAA treatment significantly increased liver index and treatment with GLB has no effect the same. TAA treatment altered the liver morphology, whereas treatment with GLB normalized the alteration in morphology. Further, significant increase in oxidative stress, apoptosis, and DNA damage was found in TAA-treated animals and GLB treatment significantly reduced these effects. TAA-induced plasma transaminases and serum ALP levels were significantly restored by GLB. Furthermore, histopathological findings showed the presence of lymphocyte infiltration, collagen deposition, bridging fibrosis, degeneration of portal triad, and necrosis in TAA-treated animals and GLB intervention significantly reduced the same. TEM images revealed that GLB significantly normalized the hepatic stellate cell morphology as well as restored the number of lipid droplets. GLB treatment significantly downregulated the expressions of TGF-β1, α-SMA, NLRP3, ASC, caspase-1, and IL-1β, and upregulated MMP-2 and catalase against TAA-induced liver damage. The outcomes of the present study confirmed that GLB ameliorated the liver damage induced by TAA.

Hepatic damage exacerbates cisplatin-induced acute kidney injury in Sprague-Dawley rats

The objective of this study was to elucidate the effect of hepatic damage on cisplatin (CDDP)-induced acute kidney injury (AKI). Thioacetamide (TAA, 150 mg/kg), a hepatotoxicant, was intraperitoneally (i.p.) injected to male Sprague-Dawley rats for 3 d prior to CDDP (5 mg/kg, i.p.) injection. All animals were sacrificed 5 d after CDDP treatment, and urine or blood was obtained to measure various parameters. No significant changes in serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) activity were observed after CDDP treatment. However, pretreatment with TAA significantly elevated ALT and AST activity. Serum blood urea nitrogen and creatinine levels significantly increased in CDDP-treated group compared to control. In addition, urinary excretion of novel protein-based biomarkers such as neutrophil gelatinase-associated lipocalin, vascular endothelial growth factor, kidney injury molecule-1, and tissue inhibitor of metalloproteinase-1 rose markedly in the CDDP-treated group. In particular, pretreatment with TAA markedly elevated CDDP-induced urinary excretion of protein-based nephrotoxic biomarkers compared with CDDP alone. Hematoxylin and eosin staining demonstrated that pretreatment with TAA following CDDP injection led to more severe tubular damage and apoptosis in rats compared with CDDP alone. Antioxidant status was significantly reduced in kidneys following pretreatment with TAA prior to CDDP. These findings indicate that liver injury enhanced the vulnerability of kidney to CDDP-induced AKI and this phenomenon may be associated with severe apoptotic damage.

Diallyl Sulfide: Potential Use in Novel Therapeutic Interventions in Alcohol, Drugs, and Disease Mediated Cellular Toxicity by Targeting Cytochrome P450 2E1

Diallyl sulfide (DAS) and other organosulfur compounds are chief constituents of garlic. These compounds have many health benefits, as they are very efficient in detoxifying natural agents. Therefore, these compounds may be useful for prevention/treatment of cancers. However, DAS has shown appreciable allergic reactions and toxicity, as they can also affect normal cells. Thus their use as in the prevention and treatment of cancer is limited. DAS is a selective inhibitor of cytochrome P450 2E1 (CYP2E1), which is known to metabolize many xenobiotics including alcohol and analgesic drugs in the liver. CYP2E1-mediated alcohol/drug metabolism produce reactive oxygen species and reactive metabolites, which damage DNA, protein, and lipid membranes, subsequently causing liver damage. Several groups have shown that DAS is not only capable of inhibiting alcohol- and drug-mediated cellular toxicities, but also HIV protein- and diabetes-mediated toxicities by selectively inhibiting CYP2E1 in various cell types. However, due to known DAS toxicities, its use as a treatment modality for alcohol/drug- and HIV/diabetes-mediated toxicity have only limited clinical relevance. Therefore, effort is being made to generate DAS analogs, which are potent and selective inhibitor of CYP2E1 and poor substrate of CYP2E1. This review summarizes current advances in the field of DAS, its anticancer properties, role as a CYP2E1 inhibitor, preventing agent of cellular toxicities from alcohol, analgesic drugs, xenobiotics, as well as, from diseases like HIV and diabetes. Finally, this review also provides insights toward developing novel DAS analogues for chemical intervention of many disease conditions by targeting CYP2E1 enzyme.

Pharmacokinetic Interaction of Chrysin with Caffeine in Rats

Pharmacokinetic interaction of chrysin, a flavone present in honey, propolis and herbs, with caffeine was investigated in male Sprague-Dawley rats. Because chrysin inhibited CYP1A-selective ethoxyresorufin O-deethylase and methoxyresorufin O-demethylase activities in enriched rat liver microsomes, the pharmacokinetics of caffeine, a CYP 1A substrate, was studied following an intragastric administration with 100 mg/kg chrysin. In addition to the oral bioavailability of chrysin, its phase 2 metabolites, chrysin sulfate and chrysin glucuronide, were determined in rat plasma. As results, the pharmacokinetic parameters for caffeine and its three metabolites (i.e., paraxanthine, theobromine and theophylline) were not changed following chrysin treatment in vivo, despite of its inhibitory effect on CYP 1A in vitro. The bioavailability of chrysin was found to be almost zero, because chrysin was rapidly metabolized to its sulfate and glucuronide conjugates in rats. Taken together, it was concluded that the little interaction of chrysin with caffeine might be resulted from the rapid metabolism of chrysin to its phase 2 metabolites which would not have inhibitory effects on CYP enzymes responsible for caffeine metabolism.

Diallyl Sulfide and Its Role in Chronic Diseases Prevention

Diallyl sulfide (C₆H₁₀S, DAS) is one of the novel natural organosulfur compounds, which is mostly obtained from the genus Allium plants. Numerous studies have revealed several unique properties of DAS in terms of its health-promoting effects. DAS has proved to be anticancer, antimicrobial, anti-angiogenic, and immunomodulatory like unique functions as demonstrated by the multiple investigations. Diallyl sulfide can also impede oxidative stress and chronic inflammation as suggested by the literature. Studies also explored that DAS could thwart the development of chronic diseases like cancer, neuronal, cardiovascular disease through modulating mechanistic pathways involved in pathogenesis. In this book chapter, we have attempted to give the comprehensive view on DAS about the physiochemical and biological properties, and its preventive role in chronic diseases with a mechanistic overview.

Effects of baicalin on oral pharmacokinetics of caffeine in rats

Scutellaria baicalensis is one of the most widely used herbal medicines in East Asia. Because baicalein and baicalin are major components of this herb, it is important to understand the effects of these compounds on drug metabolizing enzymes, such as cytochrome P450 (CYP), for evaluating herb-drug interaction. The effects of baicalin and baicalein on activities of ethoxyresorufin O-deethylase (EROD), methoxyresorufin O-demethylase (MROD), benzyloxyresorufin O-debenzylase (BROD), p-nitrophenol hydroxylase and erythromycin N-demethylase were assessed in rat liver microsomes in the present study. In addition, the pharmacokinetics of caffeine and its three metabolites (i.e., paraxanthine, theobromine and theophylline) in baicalin-treated rats were compared with untreated control. As results, EROD, MROD and BROD activities were inhibited by both baicalin and baicalein. However, there were no significant differences in the pharmacokinetic parameters of oral caffeine and its three metabolites between control and baicalin-treated rats. When the plasma concentration of baicalin was determined, the maximum concentration of baicalin was below the estimated IC₅₀ values observed in vitro. In conclusion, baicalin had no effects on the pharmacokinetics of caffeine and its metabolites in vivo, following single oral administration in rats.