Hepatotoxicity of ethanol: protective effect of calcium channel blockers in isolated hepatocytes

Calcium influx and spermatogenesis in the testis and liver enzyme activities in the zebrafish are rapidly modulated by the calcium content of the water

This study investigated the effects of varying environmental Ca²⁺ concentrations on the influx of Ca²⁺ to the testis, testicular morphology, and liver enzymes in the zebrafish. Adult zebrafish (Danio rerio) were held in water containing low (0.02 mM), control (0. 7 mM) or high (2 mM) Ca²⁺ concentrations for 12 h. Testes were then incubated in vitro with 0.1 μCi/mL ⁴⁵Ca²⁺ to measure Ca²⁺ influx at 30 and 60 min and qualitative and quantitative testicular histological analyses were conducted. In addition, activity of alanine aminotransferase (ALT), aspartate aminotransferase (AST) and gamma-glutamyl transpeptidase (GGT), enzymes that indicate tissue damage, were evaluated in the liver. The testes from zebrafish exposed in vivo to low (0.02 mM) and high (2 mM) Ca²⁺ content water had a higher Ca²⁺ influx than the control group after 30 min of incubation, and at 60 min (high Ca²⁺ group only). There were morphological changes in the testes from the low and high Ca²⁺ groups including spermatozoa distributed in dense agglomerates and apoptotic cells. Furthermore, zebrafish exposed to high Ca²⁺ containing water had an increased density of haploid cells (spermatids and spermatozoa). In addition, both low and high Ca²⁺ water affected liver function by increasing ALT and GGT activities. Collectively, these studies show that alterations in calcium homeostasis in the testis, stimulation of the spermatogenic wave and hepatic injury were rapid responses to changes in the concentration of Ca²⁺ in the water.

Sitagliptin-Dependent Differences in the Intensity of Oxidative Stress in Rat Livers Subjected to Ischemia and Reperfusion

Purpose

Ischemia/reperfusion (IR) is the main cause of liver damage after transplantation. We evaluated the effect of sitagliptin (STG) on oxidative stress parameters in the rat liver under IR.

Methods

Rats were treated with STG (5 mg/kg) (S and SIR) or saline solution (C and CIR). Livers from CIR and SIR were subjected to ischemia (60 min) and reperfusion (24 h). During reperfusion, aminotransferases (ALT and AST) were determined in blood samples. Thiobarbituric acid reactive substances (TBARS), superoxide dismutase (SOD), catalase (CAT), paraoxonase-1 (PON1), glutathione peroxidase (GPx), and the mRNA expression of SOD1 were determined in liver homogenates after reperfusion. Different regions of livers were also histologically evaluated.

Results

The PON1 activity was higher, and the TBARS level was lower in SIR than in CIR. There was an inverse relationship between TBARS and PON1 levels in the whole cohort. The GPx activity was lower in ischemic than in nonischemic groups regardless of the STG treatment. In SIR, the SOD1 activity was higher compared to that in CIR. In S, the expression of SOD1 mRNA was the highest of all examined groups and positively correlated with the SOD1 activity in the whole animal cohort. During IR aminotransferases, the activity in the drug-treated group was lower in all examined points of time. In drug-treated groups, the percentage of steatosis was higher than that in nontreated groups regardless of IR.

Conclusions

The protective effect of STG on the rat liver, especially its antioxidant properties, was revealed under IR conditions.

Age-related differences in function and structure of rat livers subjected to ischemia/reperfusion

INTRODUCTION

Liver function is affected during ischemia/reperfusion (IR). The current state of knowledge about liver aging processes during IR is incomplete. We evaluated the effects of aging on liver structure and function under IR conditions.

MATERIAL AND METHODS

Animals were divided into control (C-2) and ischemia/reperfusion (IR-2) groups of young rats (2-4 months old) and C-12 and IR-12 groups of old rats (12-14 months old). The livers from IR-2 and IR-12 groups were subjected to partial ischemia (60 min), followed by global reperfusion (4 h). Blood samples were obtained during reperfusion (0, 30 and 240 min) to estimate the activity of aminotransferases (ALT, AST). After IR, tumor necrosis factor-α (TNF-α), interleukin-1b (IL-1b), malondialdehyde (MDA), and superoxide dismutase (SOD) were determined in liver homogenates.

RESULTS

At all points of reperfusion, an increase in aminotransferase activity levels in the ischemic groups was observed; mainly between IR-12 and C-12 rats. The concentration of TNF-α was significantly higher in young animals (in non-ischemic groups: p = 0.09, in ischemic groups: p = 0.05). Under IR conditions, the concentration of IL-1b dropped (p = 0.05). The concentration of MDA was significantly higher in mature animals (in non-ischemic groups: p = 0.09, in ischemic groups: p = 0.05). In ischemic groups an increase in necrosis rate was observed regardless of age. Rats in the IR-12 group showed the most pronounced changes in hepatic architecture, including increased micro- and macrosteatosis and parenchymal cell destruction.

CONCLUSIONS

The function and structure of mature livers slightly deteriorate with age and these differences are more noticeable under IR conditions.

Influence of ezetimibe on selected parameters of oxidative stress in rat liver subjected to ischemia/reperfusion

INTRODUCTION

Ischemia/reperfusion (I/R) is considered to be one of the main causes of liver damage after transplantation. The authors evaluated the effect of ezetimibe on selected oxidative stress parameters in ischemic/reperfused (I/R) rat liver.

MATERIAL AND METHODS

Rats were administered ezetimibe (5 mg/kg) (groups E and E-I/R) or saline solution (groups C and C-I/R) intragastrically for 21 days. Livers of animals in groups C-I/R and E-I/R were subjected to 60 min of partial ischemia (left lateral and median lobes) followed by 4 h of reperfusion. Alanine and asparagine aminotransferase (ALT, AST) activity was determined in blood before I/R and during reperfusion (at 15 and 240 min). After the reperfusion period, malondialdehyde (MDA), superoxide dismutase (SOD), glutathione (GSH) and glutathione peroxidase (GPx) were determined in liver homogenates using colorimetric methods.

RESULTS

Ezetimibe caused a significant increase in GSH level in groups subjected to I/R (E-I/R (99.91 ±9.01) vs. C-I/R (90.51 ±8.87), p < 0.05). Additionally, under I/R the decrease of GPx activity in the drug-treated group was lower compared to the non-treated group (E-I/R (3.88 ±1.11) vs. E (5.31 ±1.83), p = 0.076). Neither ezetimibe nor I/R affected SOD or MDA levels. I/R produced a significant increase in aminotransferase levels (ALT240-0: C-I/R (42.23 ±43.56) vs. C (9.75 ±11.09), and E-I/R (39.85 ±26.53) vs. E (4.38 ±1.36), p < 0.05 in both cases; AST 240-0: E-I/R (53.87 ±17.23) vs. E (24.10 ±9.66), p < 0.05) but no effect of ezetimibe on those enzymes was found.

CONCLUSIONS

Ezetimibe demonstrates antioxidant properties in rat livers subjected to I/R. However, neither a hepatoprotective nor a hepatotoxic effect of ezetimibe was demonstrated, regardless of I/R.

Establishment of a methodology for investigating protectants against ethanol-induced hepatotoxicity

Ethanol-induced liver injury has been extensively reported in clinic, but still lacks an efficient in vitro platform for investigating its hepatotoxicity and protectants. This study aimed to establish a methodology on the culture conditions regarding the sealability against evaporation of ethanol, culture medium and 2D/3D culture of hepatocytes. Based on the experimental findings, it was indicated that the ethanol evaporation from culture plates was a severe problem reducing its toxicity in hepatocyte. According to the detected ethanol toxic response marked by reduced cell viability, 3D cultured hepatocytes in gel entrapment were suggested to be better than 2D hepatocyte in monolayer, but the cultures in either William's Medium E or DMEM exhibited comparable sensitivity to ethanol toxicity. Subsequently, 3D cultured hepatocytes with Parafilm sealing were systematically illustrated to well reflect the ethanol-induced lipid accumulation, reactive oxygen species/malondialdehyde generation, glutathione depletion and cytochrome 2E1 induction. Finally, such hepatocyte models were proposed as a platform for screening of herbal component against ethanol hepatotoxicity. Nano-silibinin, for the first time, found to perform significant protection against ethanol-induced hepatotoxicity while silibinin in normal particles could not inhibit such toxicity. This protection of nano-silibinin might relate to its improved bioavailability compared to normal insoluble silibinin and could act as an anti-oxidative and anti-steatosis agent against ethanol-induced hepatotoxicity.

Effects of curcumin on ethanol-induced hepatocyte necrosis and apoptosis: implication of lipid peroxidation and cytochrome c

Ethanol-induced hepatocyte necrosis and apoptosis are valid in vitro models to investigate the modulatory effects of hepatoprotective/toxic agents such as curcumin. In this study, suspension and monolayer cultures of isolated rat hepatocytes were used. Levels of trypan blue uptake, reduced glutathione, and lipid peroxidation were quantified. Chromatin condensation, caspase-3 activity, and cytochrome c extramitochondrial translocation were also evaluated. Results revealed that curcumin did not protect against either ethanol-induced necrosis or glutathione depletion. Neither did curcumin reduce caspase-3 activation nor chromatin condensation. In contrast, curcumin induced glutathione depletion, caspase-3 activation, necrosis, and apoptosis. Fortunately, all tested curcumin concentrations (1 microM-10 mM) diminished the ethanol-induced lipid peroxidation. In addition, 1 microM curcumin decreased cytochrome c translocation in hepatocyte monolayers. In conclusion, low concentrations of curcumin may protect hepatocytes by reducing lipid peroxidation and cytochrome c release. Conversely, higher concentrations provoke glutathione depletion, caspase-3 activation, and hepatocytotoxicity.

Effect of chronic ethanol exposure on the hepatotoxicity of ecstasy in mice: an ex vivo study

3,4-Methylenedioxymethamphetamine (MDMA) is frequently consumed at "rave" parties by polydrug users that usually take this drug in association with ethanol. In addition, many young people are repeatedly exposed to ethanol, which likely leads to tolerance phenomena. Both compounds are metabolized in the liver, with formation of hepatotoxic metabolites, which gives high relevance to the evaluation of their putative toxicological interaction. Therefore, the aim of this study was to evaluate the toxicity induced by 0.8 and 1.6 mM MDMA to freshly isolated hepatocytes obtained from ethanol-treated mice whose tap drinking water was replaced by a 5% ethanol solution for 1 week and, afterwards, by a 12% ethanol solution for 8 weeks (ethanol group) comparatively to non-treated animals (non-ethanol group). The hepatocytes were incubated under normothermic and hyperthermic conditions in order to simulate in vitro the hyperthermic response induced in vivo by MDMA, a condition that has been recognized as a life-threatening effect associated with MDMA exposure and implicated in its hepatotoxicity. Six mice treated under the same protocol as the ethanol group were used for histological analysis, and compared to non-ethanol-treated animals. The pre-treatment of mice with ethanol caused a significant decrease in the hepatocytes yield in the isolation procedure comparatively to the non-ethanol group, which can be explained by an increase in collagen deposition along the hepatic parenchyma as observed in the histological analysis. The initial cell viability of hepatocytes suspensions was similar between ethanol and non-ethanol groups. However, the ethanol group showed a higher GSH oxidation rate, which was enhanced under hyperthermia. Additionally, a concentration-dependent MDMA-induced loss of cell viability and ATP depletion was observed for both groups, at 41 degrees C. In conclusion, the repeated treatment with ethanol seems to increase the vulnerability of freshly isolated mice hepatocytes towards pro-oxidant conditions, as ascertained by the increase in collagen deposition, lower hepatocyte yield and decreased glutathione levels. However, MDMA toxicity to the isolated hepatocytes was independent of ethanol pre-treatment, while significantly dependent on incubation temperature.

Pathobiology of alcoholic pancreatitis

This paper provides a summary of the effects of alcohol abuse on the pathobiologic responses that occur during acute and chronic pancreatitis considering both the human disease and animal/tissue models. The effects are multiple and include ones on cell death leading to necrosis; on inflammation resulting in a sensitized response to pancreatic stress; and fibrosis through effects of ethanol on pancreatic stellate cells and the plasminogen system. Although the effects of alcohol are multiple and complex, it is likely that a combination of a few key effects on these pathobiologic responses drive the increased sensitivity of the pancreas to acute pancreatitis with pancreatic stress and the promotion of chronic pancreatitis with pancreatic injury occurring during acute pancreatitis.

Effect of melatonin and nifedipine on some antioxidant enzymes and different energy fuels in the blood and brain of global ischemic rats

The brain normally derives most of its energy from the aerobic oxidation of glucose and therefore it must be nourished with a rich supply of both glucose and oxygen. Interference with the blood supply, such as in ischemia, could shift the brain to search for another source of energy and to spare its own glucose. Ischemia results not only in energy fuel disturbance, but also in free radical formation and Ca(2+) homeostasis disruption. Therefore, our investigations studied the influence of ischemia on energy fuels, on some natural free radical scavengers, and the relationship between the changes of these parameters in brain and blood. Each of these was also studied under the influence of melatonin, a well-known free radical scavenger, and nifedipine, a Ca(2+)-channel blocker and antioxidant, during ischemia followed by reperfusion (I/R). Adult male Wistar rats were subjected to global ischemia by occlusion of the two carotid arteries for 1 hr (group I), followed by reperfusion for another hour in group II. Drugs were injected after ischemia (group I), and before or after reperfusion onset in the second group. Two series of animals were used. In the first series the effect of the two drugs on the activity of superoxide dismutase (SOD), glutathione reductase (GR), and lactate dehydrogenase (LDH) was investigated in the cytosolic fraction of four brain areas, viz., cortex (CC), thalamus/hypothalamus (T/TH), midbrain (MB) and medulla, pons and cerebellum (MPC). Moreover, the level of both SOD and GR in the erythocytes of these rats was also estimated. In the second series, we studied the effect of each drug on the content of glucose and beta-hydroxybutyrate (beta-HB) in whole brain, in addition to the plasma levels of glucose, beta-HB and lactate. The results showed that (i), ischemia elevated the brain levels of LDH and beta-HB, as well as the plasma level of glucose, beta-HB, lactate and erythocytic GR. Conversely, it lowered glucose, SOD and GR levels in the brain; (ii), reperfusion reversed the ischemic effect on all the previously altered parameters except for plasma levels of lactate and glucose; (iii), melatonin (10 mg/kg, i.p) and nifedipine (1.5 mg/kg, i.p), restored the energy fuel levels in the brain of ischemic and I/R rats, as well as the ischemic effect on the erythocyte activities of SOD and GR. Furthermore, both drugs reversed I/R effect on the cytosolic activities of the antioxidant enzymes. We conclude that melatonin and nifedipine are both neuroprotective with improvement in the antioxidant system and energy fuels.

Role of the cellular redox state in modulating acute ethanol toxicity in isolated hepatocytes

OBJECTIVES

To propose a mechanism for ethanol induced hepatocytotoxicity.

DESIGN AND METHODS

Hepatocytotoxicity was determined at various concentrations of oxygen and agents involved in NADH metabolism.

RESULTS

At 1% O2, hepatocytes were nearly 8-fold more susceptible to ethanol than at 95% O2 (carbogen). Cytotoxicity at 1% O2 was enhanced in the presence of glycolytic substrates that generate NADH (e.g., sorbitol or xylitol), and prevented by glycolytic substrates that reoxidise NADH (e.g., fructose or dihydroxyacetone). Susceptibility to ethanol correlated with the cytosolic redox state (lactate; pyruvate ratio). Cytotoxicity also correlated with reactive oxygen species (ROS) formation. Cytotoxicity was averted by ROS scavengers or the ferric chelator desferoxamine but was increased by hydroxylamine, a catalase inhibitor, or by prior glutathione depletion. Ethanol induced cytotoxicity was also decreased by inhibitors of alcohol/aldehyde dehydrogenases or CYP2E1, an alcohol inducible cytochrome P450.

CONCLUSIONS

A cytotoxic mechanism was proposed where the sustained increase in NADH levels, resulting from ethanol metabolism, maintains CYP2E1 in a more reduced state that increases ROS formation.