Destruction of microsomal calcium pump activity: a possible secondary mechanism in BrCCl3 and CCl4 liver cell injury

Vitamin D3-induced hypercalcemia increases carbon tetrachloride-induced hepatotoxicity through elevated oxidative stress in mice

The aim of this study was to determine whether calcium potentiates acute carbon tetrachloride (CCl₄) -induced toxicity. Elevated calcium levels were induced in mice by pre-treatment with cholecalciferol (vitamin D3; V.D3), a compound that has previously been shown to induce hypercalcemia in human and animal models. As seen previously, mice injected with CCl₄ exhibited increased plasma levels of alanine aminotransferase, aspartate aminotransferase, and creatinine; transient body weight loss; and increased lipid peroxidation along with decreased total antioxidant power, glutathione, ATP, and NADPH. Pre-treatment of these animals with V.D3 caused further elevation of the values of these liver functional markers without altering kidney functional markers; continued weight loss; a lower lethal threshold dose of CCl₄; and enhanced effects on lipid peroxidation and total antioxidant power. In contrast, exposure to V.D3 alone had no effect on plasma markers of liver or kidney damage or on total antioxidant power or lipid peroxidation. The potentiating effect of V.D3 was positively correlated with elevation of hepatic calcium levels. Furthermore, direct injection of CaCl₂ also enhanced CCl₄-induced hepatic injury. Since CaCl₂ induced hypercalcemia transiently (within 3 h of injection), our results suggest that calcium enhances the CCl₄-induced hepatotoxicity at an early stage via potentiation of oxidative stress.

Kampo formula "Hochu-ekki-to" suppressed carbon tetrachloride-induced hepatotoxicity in mice

OBJECTIVE

The aim of this study was to investigate whether pretreatment with the Japanese herbal medicine "Hochu-ekki-to" (TJ-41) has an ameliorative effect on carbon tetrachloride (CCl4)-induced hepatotoxicity through anorexia prevention.

METHODS

Twenty-four hours before CCl4 injection, TJ-41 or saline solution was intraperitoneally administered. Furthermore, 24 h after TJ-41 injection, mice were intraperitoneally administered 1.6 g/kg CCl4 or olive oil. Moreover, 24 h after CCl4/olive oil injection, mice from each group were euthanized and bled for plasma analysis.

RESULTS

Mice injected with CCl4 exhibited severe anorexia. Moreover, CCl4 increased the plasma levels of hepatic injury markers (i.e., alanine aminotransferase and aspartate aminotransferase) as well as lipid peroxidation and hepatic Ca levels. Pretreatment with TJ-41 recovered the CCl4-induced anorexia and plasma levels of the hepatic injury markers. Moreover, CCl4-induced lipid peroxidation and hepatic Ca levels decreased upon TJ-41 pretreatment. In addition, hepatic metallothionein levels in the TJ-41 + CCl4-treated group were decreased by >50 % compared with the levels in the TJ-41-treated group, implying that metallothionein was consumed by CCl4-induced radicals.

CONCLUSION

Our results suggest that TJ-41 attenuates CCl4-induced hepatotoxicity, presumably by the induction of metallothionein, which in turn scavenges radicals induced by CCl4 exposure.

Calcium-deficient diet attenuates carbon tetrachloride-induced hepatotoxicity in mice through suppression of lipid peroxidation and inflammatory response

The aim of this study is to investigate whether a Ca-deficient diet has an attenuating effect on carbon tetrachloride (CCl4)-induced hepatotoxicity. Four-week-old male ddY mice were fed a Ca-deficient diet for 4 weeks as a part of the experimental protocol. While hypocalcemia was observed, there was no significant change in body weight. The CCl4-exposed hypocalcemic mice exhibited a significant decrease in alanine aminotransferase and aspartate aminotransferase activities at both 6 h and 24 h even though markers of renal function remained unchanged. Moreover, lipid peroxidation was impaired and total antioxidant power was partially recovered in the liver. Studies conducted in parallel with the biochemical analysis revealed that hepatic histopathological damage was attenuated 24 h post CCl4 injection in hypocalcemic mice fed the Ca-deficient diet. Finally, this diet impaired CCl4-induced inflammatory responses. Although upregulation of Ca concentration is a known indicator of terminal progression to cell death in the liver, these results suggest that Ca is also involved in other phases of CCl4-induced hepatotoxicity, via regulation of oxidative stress and inflammatory responses.

Protection by ascorbic acid against oxidative injury of isolated hepatocytes

1. The ability of ascorbic acid to protect from prooxidant-induced toxic injury was investigated in isolated, intact rat hepatocytes, whose ascorbic acid content had been restored by means of exogenous supplementation. 2. Ascorbate-supplemented and ascorbate-non-supplemented cells in suspension were treated with a series of different prooxidants (allyl alcohol, diethyl maleate, carbon tetrachloride, menadione), and the development of lipid peroxidation and cell injury was evaluated. 3. With allyl alcohol and diethyl maleate, ascorbic acid was able to protect cells from both lipid peroxidation and cell injury. The same protection was offered by ascorbate also in hepatocytes obtained from vitamin E-deficient animals. 4. With carbon tetrachloride, ascorbate supplementation did not affect the initial steps of lipid peroxidation, but nevertheless provided a marked protection against lipid peroxidation and cell injury at later times of incubation. The protection was unaffected by the vitamin E content of cells. 5. With menadione, a toxin which does not induce lipid peroxidation, ascorbic acid did not protect cells against injury. 6. It is concluded that ascorbic acid can act as an efficient antioxidant in isolated rat liver cells, with protection against cell injury. The antioxidant effect appears primarily to involve membrane lipids, and can be independent from the cellular content of vitamin E, thus suggesting that ascorbic acid can play a direct and independent role in the intact cell, in addition to its synergistic interaction with vitamin E described in other models.

Calcium staining by the glyoxal-bis-(2-hydroxyanil)-method in the livers of rats treated with CCl4, diltiazem, and with both agents together

We studied the histochemistry of Ca in livers treated with CCl4, diltiazem (one of the Ca antagonists), and both agents together to determine whether hepatocytes or other parts of the liver lesions show Ca staining and whether the grade or location of Ca in these injuries varies. For Ca staining, cryostat sections were treated by the glyoxal-bis-(2-hydroxyanil) (GBHA)-method using O.C.T. imbedding compound instead of paraffin. Diltiazem-treated rats showed Ca granules in the bile canaliculi around the terminal hepatic veins and Kupffer cells 6 h after intragastric injection. Rats treated with CCl4 showed fine red granules in the cytoplasm of the hepatocytes around the terminal hepatic veins as soon as 5 min mildly and 2 h moderately after intraperitoneal injection. Hepatocytes around the terminal hepatic veins showed positive Ca granules 6 to 30 h after intragastric injection of CCl4. Hepatocytes stained by Ca showed acidophilic degeneration and coagulative necrosis. The hepatocytes of rats treated with both diltiazem and CCl4 revealed fewer Ca granules than those treated with CCl4 alone. In summary, Ca was stained by the GBHA method from the early stage of liver injury by CCl4 and was closely involved in acidophilic degeneration and coagulative necrosis of hepatocytes. The Ca staining in liver cells in CCl4-treated rats was decreased by diltiazem.

Lipid peroxidation and mechanisms of toxicity

Aerobic organisms by definition require oxygen, and the importance of iron in aerobic respiration has long been recognized, but despite their beneficial roles, these elements can pose a real threat to the organism. During oxygen reduction, reactive species such as O2-. and H2O2 are formed readily. Iron can combine with these species, or with molecular oxygen itself, to generate free radicals which will attack the polyunsaturated fatty acids of membrane lipids. This oxidative deterioration of membrane lipids is known as lipid peroxidation. To protect itself against this form of attack, the organism possesses several types of defense mechanisms. Under normal conditions, these defenses appear to offer adequate protection for cell membranes, but the possibility exists that certain foreign compounds may interfere with or even overwhelm these defenses, and herein could lie a general mechanism of toxicity. This possible cause of toxicity is discussed in relation to other suggested causes.