Insights in the mechanism underlying the protective effect of α-lipoic acid against acetaminophen-hepatotoxicity

The Impact of Drugs on Hydrogen Sulfide Homeostasis in Mammals

Mammalian cells and tissues have the capacity to generate hydrogen sulfide gas (H₂S) via catabolic routes involving cysteine metabolism. H₂S acts on cell signaling cascades that are necessary in many biochemical and physiological roles important in the heart, brain, liver, kidney, urogenital tract, and cardiovascular and immune systems of mammals. Diminished levels of this molecule are observed in several pathophysiological conditions including heart disease, diabetes, obesity, and immune function. Interestingly, in the last two decades, it has become apparent that some commonly prescribed pharmacological drugs can impact the expression and activities of enzymes responsible for hydrogen sulfide production in cells and tissues. Therefore, the current review provides an overview of the studies that catalogue key drugs and their impact on hydrogen sulfide production in mammals.

The Effect of β-Carotene, Tocopherols and Ascorbic Acid as Anti-Oxidant Molecules on Human and Animal In Vitro/In Vivo Studies: A Review of Research Design and Analytical Techniques Used

Prolonged elevated oxidative stress (OS) possesses negative effect on cell structure and functioning, and is associated with the development of numerous disorders. Naturally occurred anti-oxidant compounds reduce the oxidative stress in living organisms. In this review, antioxidant properties of β-carotene, tocopherols and ascorbic acid are presented based on in vitro, in vivo and populational studies. Firstly, environmental factors contributing to the OS occurrence and intracellular sources of Reactive Oxygen Species (ROS) generation, as well as ROS-mediated cellular structure degradation, are introduced. Secondly, enzymatic and non-enzymatic mechanism of anti-oxidant defence against OS development, is presented. Furthermore, ROS-preventing mechanisms and effectiveness of β-carotene, tocopherols and ascorbic acid as anti-oxidants are summarized, based on studies where different ROS-generating (oxidizing) agents are used. Oxidative stress biomarkers, as indicators on OS level and prevention by anti-oxidant supplementation, are presented with a focus on the methods (spectrophotometric, fluorometric, chromatographic, immuno-enzymatic) of their detection. Finally, the application of Raman spectroscopy and imaging as a tool for monitoring the effect of anti-oxidant (β-carotene, ascorbic acid) on cell structure and metabolism, is proposed. Literature data gathered suggest that β-carotene, tocopherols and ascorbic acid possess potential to mitigate oxidative stress in various biological systems. Moreover, Raman spectroscopy and imaging can be a valuable technique to study the effect of oxidative stress and anti-oxidant molecules in cell studies.

Mechanics Insights of Alpha-Lipoic Acid against Cardiovascular Diseases during COVID-19 Infection

Coronavirus disease 2019 (COVID-19) was first reported in Wuhan, China, in late December 2019. Since then, COVID-19 has spread rapidly worldwide and was declared a global pandemic on 20 March 2020. Cardiovascular complications are rapidly emerging as a major peril in COVID-19 in addition to respiratory disease. The mechanisms underlying the excessive effect of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection on patients with cardiovascular comorbidities remain only partly understood. SARS-CoV-2 infection is caused by binding of the viral surface spike (S) protein to the human angiotensin-converting enzyme 2 (ACE2), followed by the activation of the S protein by transmembrane protease serine 2 (TMPRSS2). ACE2 is expressed in the lung (mainly in type II alveolar cells), heart, blood vessels, small intestine, etc., and appears to be the predominant portal to the cellular entry of the virus. Based on current information, most people infected with SARS-CoV-2 virus have a good prognosis, while a few patients reach critical condition, especially the elderly and those with chronic underlying diseases. The "cytokine storm" observed in patients with severe COVID-19 contributes to the destruction of the endothelium, leading to "acute respiratory distress syndrome" (ARDS), multiorgan failure, and death. At the origin of the general proinflammatory state may be the SARS-CoV-2-mediated redox status in endothelial cells via the upregulation of ACE/Ang II/AT1 receptors pathway or the increased mitochondrial reactive oxygen species (mtROS) production. Furthermore, this vicious circle between oxidative stress (OS) and inflammation induces endothelial dysfunction, endothelial senescence, high risk of thrombosis and coagulopathy. The microvascular dysfunction and the formation of microthrombi in a way differentiate the SARS-CoV-2 infection from the other respiratory diseases and bring it closer to cardiovascular diseases like myocardial infarction and stroke. Due the role played by OS in the evolution of viral infection and in the development of COVID-19 complications, the use of antioxidants as adjuvant therapy seems appropriate in this new pathology. Alpha-lipoic acid (ALA) could be a promising candidate that, through its wide tissue distribution and versatile antioxidant properties, interferes with several signaling pathways. Thus, ALA improves endothelial function by restoring the endothelial nitric oxide synthase activity and presents an anti-inflammatory effect dependent or independent of its antioxidant properties. By improving mitochondrial function, it can sustain the tissues' homeostasis in critical situation and by enhancing the reduced glutathione it could indirectly strengthen the immune system. This complex analysis could open a new therapeutic perspective for ALA in COVID-19 infection.

The protective potential of alpha lipoic acid on amiodarone-induced pulmonary fibrosis and hepatic injury in rats

Amiodarone (AMD) is a widely used antiarrhythmic drug prescribed to treat cardiac tachyarrhythmias; however, AMD has been reported to provoke pulmonary fibrosis (PF) and hepatotoxicity. This study aimed to investigate the influence of alpha lipoic acid (ALA) on AMD-induced PF and hepatotoxicity in male Wistar rats. AMD administration resulted in elevated lung contents of hydroxyproline (Hyp), malondialdehyde (MDA), and increased serum levels of transforming growth factor beta-1 (TGF-β1), interferon-γ (IFN-γ), alanine amino transaminase (ALT), aspartate amino transaminase (AST), total cholesterol (TC), and glucose. On the other side, lung content of glutathione reduced (GSH) and serum levels of total anti-oxidant capacity (TAC) were significantly decreased. Histopathologically, AMD caused PF, produced a mild hepatic injury, and increased expression of alpha smooth muscle actin (α-SMA). Treatment with ALA produced a significant reversal of the oxidative stress, fibrosis, and inflammation parameters with reductions in α-SMA expressions, leading to amelioration of histopathological lesions. ALA might provide supportive therapy in AMD-receiving cardiovascular patients.

The combination of N-acetylcysteine and cyclosporin A reduces acetaminophen-induced hepatotoxicity in mice

Acetaminophen (APAP)-induced hepatotoxicity is the most common cause of acute liver failure in worldwide. N-acetyl cysteine (NAC) is used as the APAP antidote. Cyclosporin A (CsA) is suppressed mitochondrial damage by binding cyclophilin, a mitochondrial pore transport component. The study aimed to evaluate the effects of NAC, CsA, and NAC+CsA treatments on APAP-induced hepatotoxicity in mice. Mice were randomly divided into five groups (n = 6). 400 mg/kg/ip/single dose APAP, 1200 mg/kg/i.p/single dose NAC and 50 mg/kg/i.p/single dose CsA were performed. Light and electron microscopic alterations were investigated in liver samples. Levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) and liver glutathione (GSH) were analyzed. 3-nitrotyrosine and cytochrome c immunoreactivities were evaluated in liver tissue. Here, we found that APAP leads to histopathological and ultrastructural changes in mice liver. Also, APAP increased cytochrome c and 3-nitrotyrosine immunopositive staining. Besides, a significant decrease in liver GSH and an increase in serum AST and ALT levels were detected in the APAP group. Interestingly, NAC+CsA treatment improved histological alterations, cytochrome c, and 3-nitrotyrosine immunoreactivities and liver GSH, serum AST/ALT levels caused by APAP. We suggest that the combination of NAC and CsA reduces acetaminophen-induced hepatotoxicity in mice.

Hepatoprotective Actions of Ascorbic Acid, Alpha Lipoic Acid and Silymarin or Their Combination Against Acetaminophen-Induced Hepatotoxicity in Rats

Background and objectives: Ascorbic acid, alpha lipoic acid (ALA) and silymarin are well-known antioxidants that have hepatoprotective effects. This study aims to investigate the effects of these three compounds combined with attenuating drug-induced oxidative stress and cellular damage, taking acetaminophen (APAP)-induced toxicity in rats as a model both in vivo and in vitro. Materials and Methods: Freshly cultured primary rat hepatocytes were treated with ascorbic acid, ALA, silymarin and their combination, both with and without the addition of APAP to evaluate their in vitro impact on cell proliferation and mitochondrial activity. In vivo study was performed on rats supplemented with the test compounds or their combination for one week followed by two toxic doses of APAP. Results: Selected liver function tests and oxidative stress markers including superoxide dismutase (SOD), malondialdehyde (MDA) and oxidized glutathione (GSSG) were detected. The in vivo results showed that all three pretreatment compounds and their combination prevented elevation of SOD and GSSG serum levels indicating a diminished burden of oxidative stress. Moreover, ascorbic acid, ALA and silymarin in combination reduced serum levels of liver enzymes; however, silymarin markedly maintained levels of all parameters to normal ranges. Silymarin either alone or combined with ascorbic acid and ALA protected cultured rat hepatocytes and increased cellular metabolic activity. The subjected agents were capable of significantly inhibiting the presence of oxidative stress induced by APAP toxicity and the best result for protection was seen with the use of silymarin. Conclusions: The measured liver function tests may suggest an augmented hepatoprotection of the combination preparation than when compared individually.

Thymoquinone Attenuates Acetaminophen Overdose-Induced Acute Liver Injury and Inflammation Via Regulation of JNK and AMPK Signaling Pathway

Thymoquinone (TQ) is a main aromatic component of Nigella sativa L. seeds or Agastache rugosa (Fisch. & C.A.Mey.) Kuntze. The protective mechanism of TQ against acute liver injury induced by acetaminophen (APAP), however, remains unclear. We aimed to investigated the hepato-protective mechanism of TQ on the development of APAP-induced acute liver injury. Male kunming mice were pretreated with TQ or N-acetylcysteine (NAC) before a single APAP injection. Human Chang liver cells were incubated with TQ, SP600125 or AICAR in presence of APAP for 24 h. TQ pretreatment reduced levels of serum aminotransferases and increased hepatic glutathione and glutathione peroxidase activities via inhibiting CYP2E1 expression. TQ inhibited JNK, ERK and P38 phosphorylation induced by APAP. Meanwhile, TQ inhibited PI3K/mTOR signaling activation and activated AMPK phosphorylation. Moreover, TQ prevented APAP-induced hepatocytes apoptosis regulated by Bcl-2 and Bax. Furthermore, TQ inhibited STAT3 phosphorylation on APAP-induced acute liver injury. In addition, TQ significantly inhibited P2X7R protein expression and IL-1 β release. APAP-enhanced JNK phosphorylation and APAP-suppressed AMPK phosphorylation were also observed in Chang liver cells, and these changes were recovered by pretreatment with TQ, SP600125 and AICAR. Our findings suggest that TQ may actively prevent APAP-induced acute liver injury, and the effect may be mediated by JNK and AMPK signaling pathways.

The effects of colostrum on some biochemical parameters in the experimental intoxication of rats with paracetamol

In the current study, the possible prophylactic and therapeutic effects of colostrum (COL) on acute organ injury caused by paracetamol (PAR) in rats were evaluated. Within the scope of this study, a 2-month-old male (150-200 g) 70 Wistar Albino rat was used and a total of seven groups were designed. The first group (CNT) was maintained for control purposes. The second group (COL-1) was given COL for 1 day, at a dose of 500 mg/kg at 6-h intervals, and blood and tissue sampling was performed at 24 h. The third group (COL-7) received COL for 7 days, at a dose of 500 mg/kg at 6-h intervals on day 1 and at a daily dose of 500 mg/kg on the following days, and blood and tissue samples were taken at the end of seventh day. The fourth group (PAR-1) was administered with PAR at a dose of 1.0 g/kg bw and was blood and tissue sampled at 24 h. The fifth group (PAR-7) received PAR at a dose of 1.0 g/kg bw on day 1 and was blood and tissue was removed at the end of day 7. The sixth group (PAR+COL-1) was administered with a combination of PAR (1 g/kg bw) and COL (500 mg/kg at 6-h intervals), and blood and tissue samples were collected at 24 h. The seventh group (PAR+COL-7) received 1.0 g/kg bw of PAR on day 1 and was given COL throughout the 7-day study period (at a dose of 500 mg/kg at 6-h intervals on day 1 and at a daily dose of 500 mg/kg on the following days). In the seventh group, blood and tissue samples were taken at the end of seventh day. Alkaline phosphatase (ALP), alanine aminotransferase (ALT), aspartate aminotransferase (AST), blood urea nitrogen (BUN), glucose, creatinine, triglyceride, total bilirubin, total protein and albumin levels/activities were analysed in the serum samples. The malondialdehyde (MDA), nitric oxide (NO), superoxide dismutase (SOD), catalase (CAT) and glutathione peroxidase (GSH-Px) levels/activities, known as oxidative stress parameters, were assayed for tissue homogenates and blood (erythrocytes/plasma); in addition, enzyme activities of GSH S-transferase (GST), cytochrome P4502E1 (CYP2E1), NADH-cytochrome b5 reductase (CYTB5), glucose-6-phosphate dehydrogenase (G6PD), NADPH-cytochrome P450 C reductase (CYTC) and glutathione (GSH) levels/activities defined as drug metabolising parameters were measured in liver homogenates. In result, it was determined that PAR caused significant alterations in some biochemical and lipid peroxidation parameters and the activities/levels of drug metabolising parameters in the liver and that COL normalised some of these parameters and reduced PAR-induced tissue damage.

Alpha lipoic acid intoxicatıon: An adult

INTRODUCTION

Alpha lipoic acid (ALA) is a potent antioxidant used to treat a variety of disorders. Although ALA is considered a very safe supplement and intoxication is very rare, acute high-dose ingestions can cause mortality. In this report, we discuss a very rare case of ALA intoxication to increase awareness of this issue.

CASE REPORT

A 22-year-old female was referred to our emergency department with ALA intoxication after ingesting a total of 18g of ALA with a suicidal intention. The patient was found in an altered mental state and confused. During the physical examination, the patient's Glasgow Coma Scale was 13 (E4M6V3); however, she was neither alert nor oriented. Vital signs revealed a mildly decreased blood pressure, tachycardia, and an increased respiratory rate. Cranial nerve examination was normal except a horizontal gaze nystagmus. Laboratory testing showed a decompensated metabolic acidosis. T wave inversions were seen in the electrocardiography (EKG). The patient was treated with supportive treatment and discharged within three days of intensive care unit (ICU) admission.

CONCLUSION

ALA is a very common supplement that is easily accessible worldwide. Although ALA intoxication is very rare, it is sometimes seen after accidental or suicidal acute ingestion. Neurologic effects, metabolic acidosis, and t wave inversions in the EKG are observed when this acute poisoning occurs. Supportive treatment should be the main therapy.

The impact of α-Lipoic acid on cell viability and expression of nephrin and ZNF580 in normal human podocytes

Human podocytes (hPC) are essential for maintaining normal kidney function and dysfunction or loss of hPC play a pivotal role in the manifestation and progression of chronic kidney diseases including diabetic nephropathy. Previously, α-Lipoic acid (α-LA), a licensed drug for treatment of diabetic neuropathy, was shown to exhibit protective effects on diabetic nephropathy in vivo. However, the effect of α-LA on hPC under non-diabetic conditions is unknown. Therefore, we analyzed the impact of α-LA on cell viability and expression of nephrin and zinc finger protein 580 (ZNF580) in normal hPC in vitro. Protein analyses were done via Western blot techniques. Cell viability was determined using a functional assay. hPC viability was dynamically modulated via α-LA stimulation in a concentration-dependent manner. This was associated with reduced nephrin and ZNF580 expression and increased nephrin phosphorylation in normal hPC. Moreover, α-LA reduced nephrin and ZNF580 protein expression via 'kappa-light-chain-enhancer' of activated B-cells (NF-κB) inhibition. These data demonstrate that low α-LA had no negative influence on hPC viability, whereas, high α-LA concentrations induced cytotoxic effects on normal hPC and reduced nephrin and ZNF580 expression via NF-κB inhibition. These data provide first novel information about potential cytotoxic effects of α-LA on hPC under non-diabetic conditions.

Regeneration of glutathione by α-lipoic acid via Nrf2/ARE signaling pathway alleviates cadmium-induced HepG2 cell toxicity

Alpha-lipoic acid (α-LA) is an important antioxidant that is capable of regenerating other antioxidants, such as glutathione (GSH). However, the underlying molecular mechanism by which α-LA regenerates GSH remains poorly understood. The current study aimed to investigate whether α-LA regenerates GSH by activation of Nrf2 to alleviate cadmium-induced cytotoxicity in HepG2 cells. In the present study, we found that cadmium induced cell death by depletion of GSH through inactivation of Nrf2. Addition of α-LA to cadmium-treated cells reactivated Nrf2 and regenerated GSH through elevating the Nrf2-downstream genes γ-glutamate-cysteine ligase (γ-GCL) and GR, both of which are key enzymes for GSH synthesis. However, blocking Nrf2 with brusatol in the cells co-treated with α-LA and cadmium reduced the mRNA and the protein levels of γ-GCL and GR, thus suppressed GSH regeneration by α-LA. Our results indicated that α-LA activated Nrf2 signaling pathway, which upregulated the transcription of the enzymes for GSH synthesis and therefore GSH contents to alleviate cadmium-induced cytotoxicity in HepG2 cells.

Autism genes are selectively targeted by environmental pollutants including pesticides, heavy metals, bisphenol A, phthalates and many others in food, cosmetics or household products

The increasing incidence of autism suggests a major environmental influence. Epidemiology has implicated many candidates and genetics many susceptibility genes. Gene/environment interactions in autism were analysed using 206 autism susceptibility genes (ASG's) from the Autworks database to interrogate ∼1 million chemical/gene interactions in the comparative toxicogenomics database. Any bias towards ASG's was statistically determined for each chemical. Many suspect compounds identified in epidemiology, including tetrachlorodibenzodioxin, pesticides, particulate matter, benzo(a)pyrene, heavy metals, valproate, acetaminophen, SSRI's, cocaine, bisphenol A, phthalates, polyhalogenated biphenyls, flame retardants, diesel constituents, terbutaline and oxytocin, inter alia showed a significant degree of bias towards ASG's, as did relevant endogenous agents (retinoids, sex steroids, thyroxine, melatonin, folate, dopamine, serotonin). Numerous other suspected endocrine disruptors (over 100) selectively targeted ASG's including paraquat, atrazine and other pesticides not yet studied in autism and many compounds used in food, cosmetics or household products, including tretinoin, soy phytoestrogens, aspartame, titanium dioxide and sodium fluoride. Autism polymorphisms influence the sensitivity to some of these chemicals and these same genes play an important role in barrier function and control of respiratory cilia sweeping particulate matter from the airways. Pesticides, heavy metals and pollutants also disrupt barrier and/or ciliary function, which is regulated by sex steroids and by bitter/sweet taste receptors. Further epidemiological studies and neurodevelopmental and behavioural research is warranted to determine the relevance of large number of suspect candidates whose addition to the environment, household, food and cosmetics might be fuelling the autism epidemic in a gene-dependent manner.

Role of food-derived antioxidant agents against acetaminophen-induced hepatotoxicity

Context Acetaminophen (APAP), also known as paracetamol and N-acetyl p-aminophenol, is one of the most frequently used drugs for analgesic and antipyretic purposes on a worldwide basis. It is safe and effective at recommended doses but has the potential for causing hepatotoxicity and acute liver failure (ALF) with overdose. To solve this problem, different strategies have been developed, including the use of compounds isolated from food, which have been studied to characterize their efficacy as natural dietary antioxidants. Objective The objective of this study is to show the beneficial effects of a variety of natural compounds and their use against acetaminophen-induced hepatotoxicity. Methods PubMed database was reviewed to compile data about natural compounds with hepatoprotective effects against APAP toxicity. Results and conclusion As a result, the health-promoting properties of 13 different food-derived compounds with protective effect against APAP-induced hepatotoxicity were described as well as the mechanisms involved in hepatoprotection.

Role of nicotinamide (vitamin B3) in acetaminophen-induced changes in rat liver: Nicotinamide effect in acetaminophen-damged liver

Acetaminophen is a widely used analgesic and antipyretic agent, which is safe at therapeutic doses. However, overdoses of acetaminophen induce severe oxidative stress, which leads to acute liver failure. Nicotinamide has proven effective in ameliorating many pathological conditions that occur due to oxidative stress. This study verifies the prophylactic and therapeutic effects of nicotinamide against the hepatic pathophysiological and ultrastructural alterations induced by acetaminophen. Wistar rats intoxicated with an acute overdose of acetaminophen (5g/kg b.wt) were given a single dose of nicotinamide (500mg/kg b.wt) either before or after intoxication. Acetaminophen caused significant elevation in the liver functions and lipid peroxidation marker, and decline in the activities of the hepatic antioxidant enzymes. This oxidative injury was associated with hepatic centrilobular necrosis, hemorrage, vacuolar degeneration, lipid accumulation and mitochondrial alterations. Treating intoxicated rats with nicotinamide (500mg/kg) significantly ameliorated acetaminophen-induced biochemical changes and pathological injuries. However, administering the same dose of nicotinamide to healthy animals or prior to acetaminophen-intoxication induced hepatotoxicity. Caution should be taken when administering high doses of NAM because of its possible hepatotoxicity. Considering the wide use of nicotinamide, there is an important need for monitoring nicotinamide tolerance, safety and efficacy in healthy and diseased subjects.

Curcumin prevents paracetamol-induced liver mitochondrial alterations

OBJECTIVE

In the present study was evaluated if curcumin is able to attenuate paracetamol (PCM)-induced mitochondrial alterations in liver of mice.

METHODS

Mice (n = 5-6/group) received curcumin (35, 50 or 100 mg/kg bw) 90 min before PCM injection (350 mg/kg bw). Plasma activity of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) was measured; histological analyses were done; and measurement of mitochondrial oxygen consumption, mitochondrial membrane potential, ATP synthesis, aconitase activity and activity of respiratory complexes was carried out.

KEY FINDINGS

Curcumin prevented in a dose-dependent manner PCM-induced liver damage. Curcumin (100 mg/kg) attenuated PCM-induced liver histological damage (damaged hepatocytes from 28.3 ± 7.7 to 8.3 ± 0.7%) and increment in plasma ALT (from 2300 ± 150 to 690 ± 28 U/l) and AST (from 1603 ± 43 to 379 ± 22 U/l) activity. Moreover, curcumin attenuated the decrease in oxygen consumption using either succinate or malate/glutamate as substrates (evaluated by state 3, respiratory control ratio, uncoupled respiration and adenosine diphosphate/oxygen ratio), in membrane potential, in ATP synthesis, in aconitase activity and in the activity of respiratory complexes I, III and IV.

CONCLUSIONS

These results indicate that the protective effect of curcumin in PCM-induced hepatotoxicity is associated with attenuation of mitochondrial dysfunction.

Current and future directions in the treatment and prevention of drug-induced liver injury: a systematic review

While the pace of discovery of new agents, mechanisms and risk factors involved in drug-induced liver injury (DILI) remains brisk, advances in the treatment of acute DILI seems slow by comparison. In general, the key to treating suspected DILI is to stop using the drug prior to developing irreversible liver failure. However, predicting when to stop is an inexact science, and commonly used ALT monitoring is an ineffective strategy outside of clinical trials. The only specific antidote for acute DILI remains N-acetylcysteine (NAC) for acetaminophen poisoning, although NAC is proving to be beneficial in some cases of non-acetaminophen DILI in adults. Corticosteroids can be effective for DILI associated with autoimmune or systemic hypersensitivity features. Ursodeoxycholic acid, silymarin and glycyrrhizin have been used to treat DILI for decades, but success remains anecdotal. Bile acid washout regimens using cholestyramine appear to be more evidenced based, in particular for leflunomide toxicity. For drug-induced acute liver failure, the use of liver support systems is still investigational in the United States and emergency liver transplant remains limited by its availability. Primary prevention appears to be the key to avoiding DILI and the need for acute treatment. Pharmacogenomics, including human leukocyte antigen genotyping and the discovery of specific DILI biomarkers offers significant promise for the future. This article describes and summarizes the numerous and diverse treatment and prevention modalities that are currently available to manage DILI.

Alpha-lipoic acid treatment of acetaminophen-induced rat liver damage

Acetaminophen (paracetamol) is a well-tolerated analgesic and antipyretic drug when used at therapeutic doses. Overdoses, however, cause oxidative stress, which leads to acute liver failure. Alpha lipoic acid is an antioxidant that has proven effective for ameliorating many pathological conditions caused by oxidative stress. We evaluated the effect of alpha lipoic acid on the histological and histochemical alterations of liver caused by an acute overdose of acetaminophen in rats. Livers of acetaminophen-intoxicated rats were congested and showed centrilobular necrosis, vacuolar degeneration and inflammatory cell infiltration. Necrotic hepatocytes lost most of their carbohydrates, lipids and structural proteins. Liver sections from rats pre-treated with lipoic acid showed fewer pathological changes; the hepatocytes appeared moderately vacuolated with moderate staining of carbohydrates and proteins. Nevertheless, alpha lipoic acid at the dose we used did not protect the liver fully from acetaminophen-induced acute toxicity.

Essential role of Nrf2 in the protective effect of lipoic acid against lipoapoptosis in hepatocytes

Excess of saturated free fatty acids, such as palmitic acid (PA), in hepatocytes has been implicated in nonalcoholic fatty liver disease. α-Lipoic acid (LA) is an antioxidant that protects against oxidative stress conditions. We have investigated the effects of LA in the early activation of oxidative and endoplasmic reticulum stress, lipid accumulation, and Nrf2-mediated antioxidant defenses in hepatocytes treated with PA or in rats fed a high-fat diet. In primary human hepatocytes, a lipotoxic concentration of PA triggered endoplasmic reticulum stress, induced the apoptotic transcription factor CHOP, and increased the percentage of apoptotic cells. Cotreatment with LA prevented these effects. Similar results were found in mouse hepatocytes in which LA attenuated PA-mediated activation of caspase 3 and reduced lipid accumulation by decreasing PA uptake and increasing fatty acid oxidation and lipophagy, thereby preventing lipoapoptosis. Moreover, LA augmented the proliferation capacity of hepatocytes after PA challenge. Antioxidant effects of LA ameliorated reactive oxygen species production and endoplasmic reticulum stress and protected against mitochondrial apoptosis in hepatocytes treated with PA. Cotreatment with PA and LA induced an early nuclear translocation of Nrf2 and activated antioxidant enzymes, whereas reduction of Nrf2 by siRNA abolished the benefit of LA on PA-induced lipoapoptosis. Importantly, posttreatment with LA reversed the established damage induced by PA in hepatocytes, as well as preventing obesity-induced oxidative stress and lipoapoptosis in rat liver. In conclusion, our work has revealed that in hepatocytes, Nrf2 is an essential early player in the rescue of oxidative stress by LA leading to protection against PA-mediated lipoapoptosis.

Apoptotic events induced by high glucose in human hepatoma HepG2 cells involve endoplasmic reticulum stress and MAPK's activation

To investigate whether endoplasmic reticulum (ER) stress participates in the induction of apoptosis in HepG2 cells exposed to high glucose and explore its probable mechanism. A series of experiments were performed following HepG2 cells treated with different concentrations of glucose for 48 h. The apoptosis was detected by means of Hoechst staining and flow cytometry. Caspase-3 activity assay was performed by measuring the pNA (p-nitroaniline) to indirectly reveal the catalytic activity of caspase-3. The expression levels of apoptosis-, ER stress-associated proteins and MAPKs were analyzed by western blot. To further characterize the molecular mechanisms, the effects of antioxidant alpha-lipoic acid (ALA) and specific inhibitors for JNK and p38 (SP600125 and SB203580, respectively) were examined by Hoechst staining, immunofluorescence, and western blot. After HepG2 cells were incubated with high glucose for 48 h, both Hoechst staining and flow cytometry analyses unveiled the apoptosis of HepG2 cells. Caspase-3 activity assay revealed that the activity of caspase-3 was enhanced. Western blot showed an enhancement of pro-caspase-9 degradation, a reduction of Bcl-2/Bax ratio, a decrease in GRP78 expression, and increases in CHOP and p47/phox levels. In addition, western blot analysis presented that phosphorylation of p38 and JNK was triggered and that the expression of ASK1 was elevated. In the case of the contributions of oxidative stress and the MAPK signaling pathways, all ALA, SP600125 and SB203580 were able to largely rescue high glucose-induced apoptosis. High glucose induced the apoptosis in HepG2 cells through the activation of ASK1-p38/JNK pathway mediated by ER stress and oxidative stress.