Hepatoprotective Activity of BV-7310, a Proprietary Herbal Formulation of Phyllanthus niruri, Tephrosia purpurea, Boerhavia diffusa, and Andrographis paniculata, in Alcohol-Induced HepG2 Cells and Alcohol plus a Haloalkane, CCl4, Induced Liver Damage in Rats

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Abstract

Excessive alcohol consumption is a worldwide threat with severe morbidity and mortality. Other than abstinence, there is still no FDA-approved drug for alcoholic liver disease (ALD). Liver is the primary site of ethanol metabolism and hence gets the most damage from excessive drinking. It triggers multiple signalling events including inflammation, leading to an array of hepatic lesions like steatosis, hepatitis, fibrosis, and cirrhosis. Similarly, when medications or xenobiotic compounds are ingested orally, the liver gets the highest exposure of those metabolites, which in turn can cause severe liver toxicity. BV-7310 is a standardized mixture of four Ayurvedic plants, namely, Phyllanthus niruri, Tephrosia purpurea, Boerhavia diffusa, and Andrographis paniculata. In different systems of traditional medicine, each of these plants has been known to have use in gastrointestinal disorders. We wanted to assess the combined effect of these plant extracts on alcohol-induced liver damage. First, we investigated the hepatoprotective activity of BV-7310 against alcohol-induced toxicity in human liver HepG2 cells. Ethanol treatment (120 mM for 48 hours) significantly showed toxicity (around 42%) in these cells, and coincubation with BV-7310 prevented ethanol-induced cell death in a dose-dependent manner. Interestingly, the formulation BV-7310 showed synergistic activity than any individual extract tested in this assay. BV-7310 also showed potent antioxidant activity in 2,2-diphenyl-1-picryl-hydrazyl (DPPH) assay. Next, we induced hepatitis in Sprague–Dawley (SD) rats using repeated alcohol (40%) dosing, and carbon tetrachloride (CCl ₄) 24 hours before termination. Both oral doses of BV-7310 (250 and 500 mg/kg body weight) protected the alcohol-induced body weight loss and significantly improved the elevated levels of liver enzymes compared to the vehicle treated group. Thus, BV-7310 prevents alcohol-induced toxicity in both in-vitro and in-vivo models and could be beneficial for the treatment of ALD or other conditions, which may cause liver toxicity.

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Hepatotoxicity and mechanism of action of haloalkanes: carbon tetrachloride as a toxicological model.

Lutz Weber, Meinrad Boll, Andreas Stampfl (2003)

The use of many halogenated alkanes such as carbon tetrachloride (CCl4), chloroform (CHCl3) or iodoform (CHI3), has been banned or severely restricted because of their distinct toxicity. Yet CCl4 continues to provide an important service today as a model substance to elucidate the mechanisms of action of hepatotoxic effects such as fatty degeneration, fibrosis, hepatocellular death, and carcinogenicity. In a matter of dose,exposure time, presence of potentiating agents, or age of the affected organism, regeneration can take place and lead to full recovery from liver damage. CCl4 is activated by cytochrome (CYP)2E1, CYP2B1 or CYP2B2, and possibly CYP3A, to form the trichloromethyl radical, CCl3*. This radical can bind to cellular molecules (nucleic acid, protein, lipid), impairing crucial cellular processes such as lipid metabolism, with the potential outcome of fatty degeneration (steatosis). Adduct formation between CCl3* and DNA is thought to function as initiator of hepatic cancer. This radical can also react with oxygen to form the trichloromethylperoxy radical CCl3OO*, a highly reactive species. CCl3OO* initiates the chain reaction of lipid peroxidation, which attacks and destroys polyunsaturated fatty acids, in particular those associated with phospholipids. This affects the permeabilities of mitochondrial, endoplasmic reticulum, and plasma membranes, resulting in the loss of cellular calcium sequestration and homeostasis, which can contribute heavily to subsequent cell damage. Among the degradation products of fatty acids are reactive aldehydes, especially 4-hydroxynonenal, which bind easily to functional groups of proteins and inhibit important enzyme activities. CCl4 intoxication also leads to hypomethylation of cellular components; in the case of RNA the outcome is thought to be inhibition of protein synthesis, in the case of phospholipids it plays a role in the inhibition of lipoprotein secretion. None of these processes per se is considered the ultimate cause of CCl4-induced cell death; it is by cooperation that they achieve a fatal outcome, provided the toxicant acts in a high single dose, or over longer periods of time at low doses. At the molecular level CCl4 activates tumor necrosis factor (TNF)alpha, nitric oxide (NO), and transforming growth factors (TGF)-alpha and -beta in the cell, processes that appear to direct the cell primarily toward (self-)destruction or fibrosis. TNFalpha pushes toward apoptosis, whereas the TGFs appear to direct toward fibrosis. Interleukin (IL)-6, although induced by TNFalpha, has a clearly antiapoptotic effect, and IL-10 also counteracts TNFalpha action. Thus, both interleukins have the potential to initiate recovery of the CCl4-damaged hepatocyte. Several of the above-mentioned toxication processes can be specifically interrupted with the use of antioxidants and mitogens, respectively, by restoring cellular methylation, or by preserving calcium sequestration. Chemicals that induce cytochromes that metabolize CCl4, or delay tissue regeneration when co-administered with CCl4 will potentiate its toxicity thoroughly, while appropriate CYP450 inhibitors will alleviate much of the toxicity. Oxygen partial pressure can also direct the course of CCl4 hepatotoxicity. Pressures between 5 and 35 mmHg favor lipid peroxidation, whereas absence of oxygen, as well as a partial pressure above 100 mmHg, both prevent lipid peroxidation entirely. Consequently, the location of CCl4-induced damage mirrors the oxygen gradient across the liver lobule. Mixed halogenated methanes and ethanes, found as so-called disinfection byproducts at low concentration in drinking water, elicit symptoms of toxicity very similar to carbon tetrachloride, including carcinogenicity.

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Milk thistle (Silybum marianum ): A concise overview on its chemistry, pharmacological, and nutraceutical uses in liver diseases

Ludovico Abenavoli, Angelo Izzo, Nataša Milić … (2018)

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Postulated carbon tetrachloride mode of action: a review.

Mary K Manibusan, Marc Odin, David A Eastmond (2015)

Under the 2005 U.S. EPA Guidelines for Carcinogen Risk Assessment (1), evaluations of carcinogens rely on mode of action data to better inform dose response assessments. A reassessment of carbon tetrachloride, a model hepatotoxicant and carcinogen, provides an opportunity to incorporate into the assessment biologically relevant mode of action data on its carcinogenesis. Mechanistic studies provide evidence that metabolism of carbon tetrachloride via CYP2E1 to highly reactive free radical metabolites plays a critical role in the postulated mode of action. The primary metabolites, trichloromethyl and trichloromethyl peroxy free radicals, are highly reactive and are capable of covalently binding locally to cellular macromolecules, with preference for fatty acids from membrane phospholipids. The free radicals initiate lipid peroxidation by attacking polyunsaturated fatty acids in membranes, setting off a free radical chain reaction sequence. Lipid peroxidation is known to cause membrane disruption, resulting in the loss of membrane integrity and leakage of microsomal enzymes. By-products of lipid peroxidation include reactive aldehydes that can form protein and DNA adducts and may contribute to hepatotoxicity and carcinogenicity, respectively. Natural antioxidants, including glutathione, are capable of quenching the lipid peroxidation reaction. When glutathione and other antioxidants are depleted, however, opportunities for lipid peroxidation are enhanced. Weakened cellular membranes allow sufficient leakage of calcium into the cytosol to disrupt intracellular calcium homeostasis. High calcium levels in the cytosol activate calcium-dependent proteases and phospholipases that further increase the breakdown of the membranes. Similarly, the increase in intracellular calcium can activate endonucleases that can cause chromosomal damage and also contribute to cell death. Sustained cell regeneration and proliferation following cell death may increase the likelihood of unrepaired spontaneous, lipid peroxidation- or endonuclease-derived mutations that can lead to cancer. Based on this body of scientific evidence, doses that do not cause sustained cytotoxicity and regenerative cell proliferation would subsequently be protective of liver tumors if this is the primary mode of action. To fulfill the mode of action framework, additional research may be necessary to determine alternative mode(s) of action for liver tumors formed via carbon tetrachloride exposure.