Apoptosis in hepatic pathophysiology

Role of Glycogen Synthase Kinase-3 in Interferon-γ-Mediated Immune Hepatitis

Glycogen synthase kinase-3 (GSK-3), a serine/threonine kinase, is a vital glycogen synthase regulator controlling glycogen synthesis, glucose metabolism, and insulin signaling. GSK-3 is widely expressed in different types of cells, and its abundant roles in cellular bioregulation have been speculated. Abnormal GSK-3 activation and inactivation may affect its original bioactivity. Moreover, active and inactive GSK-3 can regulate several cytosolic factors and modulate their diverse cellular functional roles. Studies in experimental liver disease models have illustrated the possible pathological role of GSK-3 in facilitating acute hepatic injury. Pharmacologically targeting GSK-3 is therefore suggested as a therapeutic strategy for liver protection. Furthermore, while the signaling transduction of GSK-3 facilitates proinflammatory interferon (IFN)-γ in vitro and in vivo, the blockade of GSK-3 can be protective, as shown by an IFN-γ-induced immune hepatitis model. In this study, we explored the possible regulation of GSK-3 and the potential relevance of GSK-3 blockade in IFN-γ-mediated immune hepatitis.

Targeting programmed cell death in metabolic dysfunction-associated fatty liver disease (MAFLD): a promising new therapy

Most currently recommended therapies for metabolic dysfunction-associated fatty liver disease (MAFLD) involve diet control and exercise therapy. We searched PubMed and compiled the most recent research into possible forms of programmed cell death in MAFLD, including apoptosis, necroptosis, autophagy, pyroptosis and ferroptosis. Here, we summarize the state of knowledge on the signaling mechanisms for each type and, based on their characteristics, discuss how they might be relevant in MAFLD-related pathological mechanisms. Although significant challenges exist in the translation of fundamental science into clinical therapy, this review should provide a theoretical basis for innovative MAFLD clinical treatment plans that target programmed cell death.

Effects of apoptosis on liver aging

As an irreversible and perennial process, aging is accompanied by functional and morphological declines in organs. Generally, aging liver exhibits a decline in volume and hepatic blood flow. Even with a preeminent regenerative capacity to restore its functions after liver cell loss, its biosynthesis and metabolism abilities decline, and these are difficult to restore to previous standards. Apoptosis is a programmed death process via intrinsic and extrinsic pathways, in which Bcl-2 family proteins and apoptosis-related genes, such as p21 and p53, are involved. Apoptosis inflicts both favorable and adverse influences on liver aging. Apoptosis eliminates transformed abnormal cells but promotes age-related liver diseases, such as nonalcoholic fatty liver disease, liver fibrosis, cirrhosis, and liver cancer. We summarize the roles of apoptosis in liver aging and age-related liver diseases.

Correlation between vitamin D levels and apoptosis in geriatric patients infected with hepatitis C virus genotype 4

Background

Vitamin D levels play a pivotal role in most biological processes and differ according to age. A deficiency of vitamin D in chronic hepatitis C (CHC) patients has been shown to be linked with the severity of liver fibrosis, but little is known about the mechanism of this association.

Objective

In this study, we evaluate the potential interrelation between vitamin D levels, oxidative stress, and apoptosis, based on liver fibrosis in geriatric patients infected with hepatitis C virus (HCV) genotype 4.

Subjects and methods

A total of 120 adult individuals aged 30–68 years were recruited in this study. Of these, 20 healthy subjects (15 men and five women) with a mean age of 48.3±6.1 years were selected as controls, and 100 patients with a mean age of 47.8±4.9 years with chronic HCV (CHC) who had undergone liver biopsy (80 men and 20 women) were included in this study. Based on liver radiographic (computed tomography, magnetic resonance imaging) and histological Metavir system analyses, the CHC patients were classified into three groups: asymptomatic CHC carriers (n=30), fibrosis (n=25), and cirrhosis (n=45). HCV RNA, HCV genotypes, inflammatory cytokines AFP and TNFα, 25-hydroxyvitamin D (25[OH]D) levels, apoptotic markers single-stranded DNA (ssDNA) and soluble Fas (sFas), and oxidative stress markers nitric oxide (NO) and total antioxidant capacity (TAC) were estimated by using molecular, immunoassay, and colorimetric techniques.

Results

Approximately 30% of the study population (n=30) were diagnosed as asymptomatic CHC carriers, and 70% of the study population (n=70) had severe fibrosis; these were classified into fibrosis and cirrhosis. There was a significant reduction in 25(OH)D levels and TAC activity, along with an increase in levels of NO, AFP, TNFα, ssDNA, and sFas in fibrosis and cirrhosis subjects compared with those of asymptomatic CHC carriers and health controls. The deficiency in 25(OH)D levels correlated positively with sFas, ssDNA, AFP, TNFα, NO, and TAC, and negatively with age, sex, liver function, body mass index, homeostatic model assessment – insulin resistance, HCV RNA, and viral load. Significant intercorrelation was reported between serum 25(OH)D concentrations and apoptotic and oxidative markers, which suggested progression of liver pathogenesis and fibrogenesis via oxidative and apoptotic mechanisms.

Conclusion

The data showed that vitamin D status was significantly correlated with pathogenesis and fibrogenesis of the liver in geriatric patients infected with HCV genotype 4. The deficiency in 25(OH)D levels was shown to have a pivotal role in the pathogenesis of liver via apoptotic, oxidative stress, and inflammatory mechanistic pathways. The data point to adequate vitamin D levels being recommended for a good response to treatment strategies, especially in older CHC patients.

Apigenin, a dietary flavonoid, inhibits proliferation of human bladder cancer T-24 cells via blocking cell cycle progression and inducing apoptosis

BACKGROUND

Apigenin is a nontoxic dietary flavonoid, and it may have chemopreventive and therapeutic potential as an anti-inflammatory, antioxidant, and anti-cancer agent. However, its role in bladder cancer remains poorly understood. The aim of this study was to investigate the anti-proliferative activity of apigenin in human bladder cancer T-24 cells.

METHODS AND RESULTS

Apigenin inhibited T-24 cell proliferation in a dose-dependent manner. We demonstrated that apigenin-induced early and mid-apoptotic cell could be identified by Annexnin V-Alexa Fluor 488/PI apoptosis detection and TUNEL assay. Moreover, using a JC-1 staining assay, we found that apigenin may induce the loss of the mitochondrial membrane potential. By performing flow cytometry and Western blotting, apigenin-mediated subG1 phase acculmulation was also associated with an increase in the phospho-p53, p53, p21, and p27 levels, and with a decrease in the Cyclin A, Cyclin B1, Cyclin E, CDK2, Cdc2, and Cdc25C levels, thereby blocking cell cycle progression. ELISA showed that the subG1 phase acculmulation was due to the increase in the p53, p21, and p27 levels. In addition, apigenin increased the Bax, Bad, and Bak levels, but reduced the Bcl-xL, Bcl-2, and Mcl-1 levels, and subsequently triggered the mitochondrial apoptotic pathway (release of cytochrome c and activation of caspase-9, caspase-3, caspase-7, and PARP). Further analysis demonstrated that apigenin increased the ROS levels and depleted GSH in T-24 cells at 12 h.

CONCLUSIONS

The results suggested that apigenin inhibits T-24 cells proliferation via blocking cell cycle progression and inducing apoptosis. In addition, we discovered a potential anticancer activity of apigenin against T-24 cells.

Toxicological evaluation of methanol leaves extract of Vernonia bipontini Vatke in blood, liver and kidney tissues of mice

BACKGROUND

Various medicinal plants have been studied using modern scientific approaches. These plants have a variety of properties and various biological components that can be used to treat various diseases. However, harmful effects of plants are common clinical occurrence.

OBJECTIVE

This study was designed to investigate toxicological assessment of acute and chronic methanol leaf extract of Vernonia bipontini Vatke (V.bipontini V) on blood, liver and kidney tissues of mice.

METHODS

Lethal dose (LD) at which 50% of experimental mice died and long term toxicity of methanolic leaf extract of V. bipontini V were determined. Some hematological and biochemical parameters were evaluated. Then, liver and kidney tissues of each animal were taken and processed for light microscopy.

RESULTS

Almost all mice treated with 800mg/kg methanol leaf extract of V. bipontini V showed swellings on the left part of abdominal region related to location of spleen, mild diarrhea and enlargement of spleen. The LD50 of the methanol leaf extract of V. bipontini V was 2130.6±1.5mg/kg. Treatment with 800mg/kg body weight of methanol leaf extract significantly decreased body, liver and kidney weights, red blood cells (RBC), haemoglobin (Hgb), mean cell haemoglobin (Mch), Mchc, platelet and significantly increased serum aspartate transferance (AST), vatanine tranferance(ALT) and alkaline phosphate (ALP) levels while 400mg/kg dose had no effect on these parameters. The reduced organ weights did not correlate with loss of body weight at 800mg/kg of methanol leaf extract of the plant. Light microscope observations of liver tissue of mice treated with 800mg/kg of the methanol leaf extract revealed dilated sinusoids, nuclear enlargement, lots of bi-nucleation of hepatocytes, peripheral cramped chromatin, shrinkages (single cell death) of hepatocytes, fragmentation of hepatocytes while no histopathological changes were observed in liver and kidney of mice treated at 400mg/kg. Kidney tissue sections of mice did not show significant histopathological changes at 400mg/kg. However, at 800mg/kg kidney sections showed increased cellularity of glomerulus, urinary space obliteration and enlarged macula densa.

CONCLUSION

This study suggests that the methanol leaf extract may have been phytotoxic to liver that resulted in a rise in serum AST, ALT and ALP levels.

Combined effects of an antioxidant and caspase inhibitor on the reversal of hepatic fibrosis in rats

We sought to determine the hepatic fibrosis-reversal effects upon simultaneous administration of lithospermate B (LAB), an anti-oxidant, and nivocasan, a caspase inhibitor, to rats compared with each compound alone. Liver fibrosis was induced in Sprague-Dawley rats by thioacetamide (TAA). Rats were treated with TAA and then given LAB and (or) nivocasan. Fibrotic areas were evaluated quantitatively by computerized morphometry. Apoptosis was assessed using a TUNEL assay, and immunohistochemical staining for malondialdehyde (MDA) and 4-hydroxy-2-nonenal (4HNE) was performed to assess oxidative stress levels. Real-time quantitative PCR was used to quantify expression of fibrosis-related genes. The degree of hepatic fibrosis was significantly reduced in rats treated with LAB and nivocasan compared to either treatment alone (P < 0.001). Treatment with each compound significantly decreased expression of fibrosis-related genes, such as type I collagen α1 (col1α1), α-SMA and TGF-β1 (P < 0.05). Co-treatment with LAB and nivocasan further reduced col1α1 expression compared to treatment with either compound. A TUNEL assay revealed that hepatocyte apoptosis was significantly decreased in the group treated with nivocasan compared to other groups (P < 0.01). Immunohistochemistry showed a decrease in MDA and 4HNE, reflecting amelioration of oxidative stress, when LAB or LAB+nivocasan was administered compared to nivocasan alone (P < 0.01). Nivocasan was found to inhibit caspase-1, -3, -7, -9 and gliotoxin-induced death of rat-derived hepatic stellate cells was inhibited by nivocasan administration without overexpression of α-SMA.

CONCLUSIONS

Co-incidental administration of LAB and nivocasan suppressed oxidative stress and apoptosis, resulting in enhanced reversal of hepatic fibrosis in rat.

Apoptosis and clinical severity in patients with psoriasis and HCV infection

BACKGROUND

It has been proposed that hepatitis C virus (HCV) antigens are involved in the pathogenesis of psoriasis and may contribute to severity of the disease. Increased expression of the apoptosis-regulating proteins p53 and tTG and decreased levels of bcl-2 in the keratinocytes of the skin of psoriatic patients have been reported.

AIM

This study aims to identify the serum levels of apoptosis-regulating proteins in patients with psoriasis and without HCV infection and to study the relation between clinical severity of psoriasis and the presence of HCV infection.

MATERIALS AND METHODS

Disease severity was assessed by psoriasis area severity index score (PASI) of 90 patients with psoriasis grouped as mild (n = 30), moderate (n = 30) and severe (n = 30); 20 healthy individuals were used as controls. All groups were subjected for complete history taking, clinical examination, and tests for liver function and HCV infection. The serum levels of apoptosis related proteins: p53, tTG and bcl-2 were estimated by enzyme linked immune sorbent assay (ELISA).

RESULTS

There was a statistically significant (P < 0.001) correlation between clinical severity of psoriasis and presence of HCV antibodies and HCV-mRNA. In addition, significantly (P < 0.001) raised serum p53 and tTG, and reduced bcl-2 were observed among HCV-positive patients as compared to HCV-negative patients and control patients.

CONCLUSION

These results conclude that clinical severity of psoriasis is affected by the presence of HCV antibodies and overexpression of apoptotic related proteins. In addition, altered serum levels of apoptosis-regulating proteins could be useful prognostic markers and therapeutic targets of psoriatic disease.

Hepatoprotective effects of reynosin against thioacetamide-induced apoptosis in primary hepatocytes and mouse liver

The aim of this study was to identify the hepatoprotective effects of reynosin, sesquiterpenes from the leaves of Laurus nobilis, against thioacetamide (TAA)-induced apoptosis in primary hepatocyte cultures and an in vivo mouse model. Rat hepatocytes were isolated and pretreated with 0.13, 0.64, or 3.22 μM reynosin and then exposed to 100 mM TAA. Reynosin treatment significantly inhibited TAA-induced apoptosis and hepatocellular DNA damage in primary rat hepatocytes. We observed an increase in levels of antiapoptotic Bcl-2, Bcl-XL mRNA and a decrease in levels of proapoptotic Bax mRNA following reynosin treatment of hepatocytes. Apoptosis in BALB/c mice was induced with intra-peritoneal injection of 200 mg/kg TAA for 2 weeks every other day. Then reynosin (5 mg/kg) and TAA were intragastrically given for 3 weeks every other day. Aspartate aminotransferase and alanine aminotransferase levels in the blood of mice were decreased in the reynosin administration group. Bcl-2 and Bcl-XL mRNA levels were increased, and the Bax mRNA level was decreased in reynosin-treated mice. Thus, reynosin inhibited TAA-induced apoptosis in primary hepatocytes and an in vivo mouse model.

Expression of apoptosis regulatory markers in the skin of advanced hepatitis-C virus liver patients

BACKGROUND

Hepatitis-C virus (HCV) infection is considered a major worldwide public health problem with a global prevalence. Maintenance of skin homeostasis requires a delicate balance between proliferation, differentiation, and apoptosis. Meanwhile, it is unclear if there is an altered keratinocyte proliferation/apoptosis balance in advanced liver disease with HCV infection.

AIM

This work aimed to evaluate the epidermal thickness and changes in the expression of apoptosis regulatory markers as well as apoptotic index in skin samples of advanced HCV liver patients compared to normal controls.

MATERIALS AND METHODS

Twenty biopsies were taken from apparently normal skin of advanced HCV liver disease patients, as well as five healthy control subjects. These specimens were used for histometric epidermal measurement, immunohistochemical staining of apoptosis regulatory proteins (Bax, Fas, p53, Caspase-3, Bcl-2, Bcl-xL) as well as the TUNEL technique for detection of apoptotic cells.

RESULTS

The mean epidermal thickness was significantly lower than the control group (P=0.000). There were significant overexpression of pro-apoptotic markers (Bax, Fas, P53, and Caspase-3) in patients (P=0.03, 0.03, 0.003, 0.003 respectively), with increased apoptotic index in HCV liver patients (P=0.002) when compared to normal controls. On the other hand, no statistically significant difference were encountered in the expression of antiapoptotic markers (Bcl-2, Bcl-xL) in HCV patients when compared to normal controls (P=0.5, 0.9, respectively).

CONCLUSION

These findings suggest that an alteration in the proliferation/apoptosis balance is present in the skin of HCV liver patients.

Circulating Biomarkers and their Possible Role in Pathogenesis of Chronic Hepatitis B and C Viral Infections

The present study evaluated the plausible role of circulating biomarkers in immune pathogenesis of chronic hepatitis considered a priority in clinical hepatology. Total viral load of chronic hepatitis B virus (HBV) and hepatitis C virus (HCV) patients was quantified and correlation studies were performed with circulating levels of Th1/Th2 cytokines; C reactive protein and circulating nucleosomes; glutathione reductase (GR) and superoxide dismutase. To our knowledge, the study is first among its kind that validates strong positive correlation of viral load with IL-4, IL-6, GR in HBV and IL-6, IL-10, GR in HCV infections. Although, multi-centric studies including large cohorts are required for translating our findings to clinical practice, however, role of these biomarkers with potential diagnostic or prognostic significance might be helpful in clinical assessment of high-risk individuals, thereby, designing interventional strategies, towards development of personalized medicare. The results of our study also offer valuable insights of immune signaling mediators engaged in development of hepatocellular carcinoma.

Preconditioning with L-alanyl-glutamine reduces hepatic ischemia-reperfusion injury in rats

PURPOSE: To evaluate the effects of pre-conditioning with L-alanyl- glutamine (L-Ala-Gln) in rats subjected to total hepatic ischemia. METHODS: Thirty Wistar rats, average weight 300g, were randomly assigned to 3 groups (n=10): G-1 - Saline, G-2- L-Ala-Gln, G-3-control (Sham). G-1 and G-3 groups were treated with saline 2.0 ml or L-Ala-Gln (0.75mg/Kg) intraperitoneally (ip) respectively, 2 hours before laparotomy. Anesthetized rats were subjected to laparotomy and total hepatic ischemia (30 minutes) induced by by clamping of portal triad. Control group underwent peritoneal puncture, two hours before the sham operation (laparotomy only). At the end of ischemia (G1 and G2), the liver was reperfused for 60 minutes. Following reperfusion blood samples were collected for evaluation of alanine aminotransferase (ALT) and lactate dehydrogenase (LDH) levels. Liver (medium lobe) was removed for immunohistochemistry study with antibody for Caspase-3. RESULTS: It was found a significant decrease (p<0.05) of ALT levels (270.6 +40.8 vs 83.3 +5.5 - p <0.05), LDH (2079.0 +262.4 vs. 206.6 +16.2 - p <0.05) and Caspase-3 expression (6.72 +1.35 vs. 2.19 +1.14, p <0.05) in rats subjected to I / R, comparing the group treated with L-Ala -Gln with G-2. Also, the ALT level was significantly lower (P<0.05) in G-1 and G-2 groups than in G-3 (control group). CONCLUSION: L-Ala-Gln preconditioning in rats submitted to hepatic I/R significantly reduces ALT, LDH and Caspase-3 expression, suggesting hepatic protection.

Reactive oxygen species-mediated kinase activation by dihydrotanshinone in tanshinones-induced apoptosis in HepG2 cells

The role of reactive oxygen species (ROS) and p38 mitogen-activated protein kinases (MAPK) in tanshinones-induced apoptosis was investigated in HepG2 cells in this study. The major tanshinones (cryptotanshinone, dihydrotanshinone, tanshinone I, tanshinone IIA), isolated from Salvia miltiorrhiza, inhibit cell growth and induce caspase-dependent apoptosis concentration-dependently, with dihydrotanshinone being the most potent. All four tanshinones were found to induce ROS generation, but only dihydrotanshinone can induce activation of p38 MAPK. The p38 MAPK activation by dihydrotanshinone was inhibited by N-acetyl cysteine pretreatment. It is thus concluded that ROS-mediated p38 MAPK activation plays a vital role in dihydrotanshinone-induced apoptosis in HepG2 cells.

Changes in FADD levels, distribution, and phosphorylation in TNFalpha-induced apoptosis in hepatocytes is caspase-3, caspase-8 and BID dependent

FADD/MORT1 (The adaptor protein of Fas Associate Death Domain/Mediator of Receptor Induced Toxicity) is essential for signal transduction of death receptor signaling. We have previously shown that FADD is significantly up-regulated in TNFalpha/ActD induced apoptosis. Over-expression of FADD also induces death of lung cancer cells and primary hepatocytes. We hypothesize that the increase in detectable FADD levels require the proximal steps in apoptotic signaling and speculated that FADD would be redistributed in cells destined to undergo apoptosis. We show that monomeric non-phosphorylated FADD is up-regulated in hepatocytes treated with TNFalpha/ActD and that it accumulates in the cytoplasm. Nuclear phosphorylated FADD decreases with TNFalpha/ActD treatment. Dimeric FADD in the cytoplasm remains constant with TNFalpha/ActD. The change in FADD levels and distribution was dependent on caspase-3, caspase-8 activity and the presence of BID. Thus, changes in FADD levels and distribution are downstream of caspase activation and mitochondria changes that are initiated by the formation of the DISC complex. Changes in FADD levels and distribution may represent a novel feed-forward mechanism to propagate apoptosis signaling in hepatocytes.

Huang-lian-jie-du-tang, a traditional Chinese medicine prescription, induces cell-cycle arrest and apoptosis in human liver cancer cells in vitro and in vivo

BACKGROUND AND AIM

Huang-lian-jie-du-tang (HLJDT; Japanese name, oren-gedoku-to) is a traditional Chinese medicine prescription known to possess anti-inflammatory activity. Our study reports here for the first time the anticancer effect of HLJDT in two human liver cancer cell lines, Hep G2 and PLC/PRF/5.

METHODS

Inhibition of cell proliferation by HLJDT was measured by sodium 3'-(1-(phenylamino-carbonyl)-3,4-tetrazolium)-bis(4-methoxy-6-nitro) benzene-sulfonic acid hydrate (XTT) assay. Clonogenic assay was used to elucidate the possible differences in long-term effects of HLJDT on human liver cancer cells. Cell cycle distribution was determined by flow cytometry. Apoptosis was detected using electrophoresis and terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate nick endlabeling (TUNEL) assay. Protein expressions were determined by immunoblot assay. The activity of nuclear factor-kappa B (NF-kappaB) was determined by Trans-AM ELISA kit. In vivo tumor activity was assessed by xenograft study.

RESULTS

HLJDT significantly increased the expression of inactivated phospho-Cdc2 and phospho-Cdc25C, and decreased the levels of cyclin A, cyclin B1, Cdc2, and Cdc25C, thereby contributing to cell-cycle arrest. HLJDT increased the expression of Bax and Bak, but decreased the level of Bcl-2 and Bcl-XL, and subsequently triggered the mitochondrial apoptotic pathway. In addition, HLJDT also inhibited cell-survival signaling by enhancing the amount of IkappaBalpha in the cytoplasm, reducing the level and activity of NF-kappaB in the nucleus, and subsequently attenuating the expression of Bcl-XL in Hep G2 and PLC/PRF/5 cells(.) The inhibitory effect mediated by HLJDT on cell growth was also demonstrated in a nude mouse model, in which the liver cancer cells induced tumor xenograft shrank considerably following treatment with HLJDT.

CONCLUSIONS

Taken together, these results suggest a potential anticancer effect of HLJDT against human liver cancer cells.

Apoptosis of hepatic stellate cells in carbon tetrachloride induced acute liver injury of the rat: analysis of isolated hepatic stellate cells

BACKGROUND/AIMS

Analysis of isolated hepatic stellate cells (HSCs) from the injured liver may provide direct information on HSC apoptosis. However, it has not been established whether apoptotic HSCs would be isolated using the usual density gradient centrifugation method. The aim of this study was to observe the serial pattern of proliferation and apoptosis in isolated HSCs in comparison with that of liver tissue sections in CCl4 induced acute liver injury.

METHODS

Male Sprague-Dawley rats were treated with a single intraperitoneal injection of carbon tetrachloride (CCl4) and were killed at various time points after the treatment.

RESULTS

HSC proliferation showed a maximal increase at 32 h after CCl4 injection. Apoptosis of HSC, examined by quantitative analysis of annexin-V-fluorescein isothiocyanate (FITC)staining, showed the maximal increase at 64 h. Apoptosis of HSC in liver tissue sections examined by counting desmin and Tdt-mediated-dUTP biotin nick end labeling (TUNEL) double staining cells, peaked at 64 h. The number of TUNEL positive HSCs in liver tissue sections correlated significantly with annexin-V-FITC binding of isolated HSC.

CONCLUSIONS

Studying apoptosis using apoptotic HSCs isolated by a usual density gradient centrifugation method from injured tissue sections would be feasible since it correlated with in vivo apoptosis of HSC.

Appetizing rancidity of apoptotic cells for macrophages: oxidation, externalization, and recognition of phosphatidylserine

Programmed cell death (apoptosis) functions as a mechanism to eliminate unwanted or irreparably damaged cells ultimately leading to their orderly phagocytosis in the absence of calamitous inflammatory responses. Recent studies have demonstrated that the generation of free radical intermediates and subsequent oxidative stress are implicated as part of the apoptotic execution process. Oxidative stress may simply be an unavoidable yet trivial byproduct of the apoptotic machinery; alternatively, intermediates or products of oxidative stress may act as essential signals for the execution of the apoptotic program. This review is focused on the specific role of oxidative stress in apoptotic signaling, which is realized via phosphatidylserine-dependent pathways leading to recognition of apoptotic cells and their effective clearance. In particular, the mechanisms involved in selective phosphatidylserine oxidation in the plasma membrane during apoptosis and its association with disturbances of phospholipid asymmetry leading to phosphatidylserine externalization and recognition by macrophage receptors are at the center of our discussion. The putative importance of this oxidative phosphatidylserine signaling in lung physiology and disease are also discussed.

COX-2 inhibits Fas-mediated apoptosis in cholangiocarcinoma cells

Fas expression has been shown to negatively regulate the progression of cholangiocarcinoma cells in xenografts. However, many human cholangiocarcinomas express Fas, suggesting these cancers have developed mechanisms to inhibit Fas-mediated apoptosis. Cyclooxygenase-2 (COX-2), which generates prostanoids, is expressed by many cholangiocarcinomas. Therefore, our aim was to determine whether COX-2 expression inhibits death receptor--mediated apoptosis in KMBC cells, a cholangiocarcinoma cell line. These cells express messenger RNA for the death receptors Fas, tumor necrosis factor receptor 1 (TNF-R1), death receptor 4 (DR4), and DR5. Agonists for these death receptors, CH-11, TNF-alpha, and TRAIL all induced apoptosis. However, COX-2, whether induced by proinflammatory cytokines or transient transfection, only significantly inhibited Fas-mediated apoptosis. The COX-2 inhibitor NS-398 restored Fas-mediated apoptosis in COX-2 transfected cells. Prostaglandin E2 reduced apoptosis and mitochondrial depolarization after treatment with the Fas agonist CH-11. Of a variety of antiapoptotic proteins examined, COX-2/prostaglandin E2 only increased expression of Mcl-1, an antiapoptotic member of the Bcl-2 family. In conclusion, these data suggest that prostanoid generation by COX-2 specifically inhibits Fas-mediated apoptosis, likely by up-regulating Mcl-1 expression. Pharmacologic inhibition of COX-2 may be useful in augmenting Fas-mediated apoptosis of cholangiocarcinoma cells.

Molecular aspects of hepatic carcinogenesis

Exogenous agents correlated with hepatocellular carcinoma (HCC) have been identified and well characterized. These agents, including the different viruses that cause chronic hepatitis and cirrhosis, can lead to regenerative nodules and dysplastic nodules/adenomatous hyperplasia. These conditions associated with several molecular alterations of hepatocyte ultimately culminate in hepatocellular carcinoma. Recently, there has been a great progress in the identification of somatic and germinative mutations that may be correlated with the development of HCC, justifying a review on the subject. Hence, the factors involved in the process of hepatic carcinogenesis, such as infection by the hepatitis B and C viruses, with a special focus in the molecular alterations described in recent years are discussed herein, pointing out areas potentially relevant for clinical development.

[Apoptosis as a mechanism of tissue injury in hepatobiliary diseases]

BACKGROUND

Cell death by apoptosis is a fundamental biologic process involved in many physiologic and pathophysiologic processes in the liver.

OBJECTIVE

To review the process of apoptosis, its cellular mechanisms, its regulation by external factors, and its role in pathophysiologic process and specific diseases of the liver.

CONCLUSION

An understanding of the cellular mechanisms of apoptosis and their dysregulation during pathophysiologic disturbances will help in understanding human liver diseases. The modulation of apoptosis may lead to novel therapeutic strategies for the treatment of a wide range of liver diseases.