KCNQ1 p.D446E Variant as a Risk Allele for Arrhythmogenic Phenotypes: Electrophysiological Characterization Reveals a Complex Phenotype Affecting the Slow Delayed Rectifier Potassium Current (IKs) Voltage Dependence by Causing a Hyperpolarizing Shift and a Lack of Response to Protein Kinase A Activation.

Genetic testing is crucial in inherited arrhythmogenic channelopathies; however, the clinical interpretation of genetic variants remains challenging. Incomplete penetrance, oligogenic, polygenic or multifactorial forms of channelopathies further complicate variant interpretation. We identified the KCNQ1/p.D446E variant in 2/63 patients with long QT syndrome, 30-fold more frequent than in public databases. We thus characterized the biophysical phenotypes of wildtype and mutant IKs co-expressing these alleles with the ß-subunit minK in HEK293 cells. KCNQ1 p.446E homozygosity significantly shifted IKs voltage dependence to hyperpolarizing potentials in basal conditions (gain of function) but failed to shift voltage dependence to hyperpolarizing potentials (loss of function) in the presence of 8Br-cAMP, a protein kinase A activator. Basal IKs activation kinetics did not differ among genotypes, but in response to 8Br-cAMP, IKs 446 E/E (homozygous) activation kinetics were slower at the most positive potentials. Protein modeling predicted a slower transition of the 446E Kv7.1 tetrameric channel to the stabilized open state. In conclusion, biophysical and modelling evidence shows that the KCNQ1 p.D446E variant has complex functional consequences including both gain and loss of function, suggesting a contribution to the pathogenesis of arrhythmogenic phenotypes as a functional risk allele.

Hepatic mir-122-3p, mir-140-5p and mir-148b-5p expressions are correlated with cytokeratin-18 serum levels in MAFLD.

INTRODUCTION AND OBJECTIVES: Metabolic-associated fatty liver disease (MAFLD) is defined by steatosis in more than 5% of hepatocytes without other liver diseases. Patients with this disease can progress to multiple stages like liver fibrosis, cirrhosis, and hepatocellular carcinoma. miRNAs are single-stranded molecules that regulate metabolic homeostasis; their differential expression postulates them as potential circulating biomarkers for MAFLD. Previous research reported that hsa-miR-140-5p, hsa-miR-148-5p, and hsa-miR-122-3p have a differential expression in patients with MAFLD. This study aimed to investigate the correlation between liver hsa-miR-140-5p, hsa-miR-148-5p, and hsa-miR-122-3p and serum biomarkers CK-18, APOB, IL-6, IL-32, and TNF-α in patients with MAFLD compared with control patients. MATERIALS AND METHODS: A cross-sectional study was carried out with 16 patients of both sexes, aged between 18-60 years, to determine the association between the levels of hsa-miR-140-5p, hsa-miR-148-5p, and hsa-miR-122-3p with MAFLD in liver biopsies of patients who underwent laparoscopic cholecystectomy. RESULTS: Twelve patients presented MAFLD, four without hepatic steatosis. Circulating levels of CK-18 showed a significant difference in patients with MAFLD, and a strong correlation was found between hsa-miR-122-3p, hsa-miR-140-5p, and hsa-miR-148b-5p versus the CAP value. CONCLUSION: There is a correlation between elevated tissue expression of hsa-miR-122-3p, hsa-miR-140-5p, and hsa-miR-148b-3p with plasma levels of CK-18 in patients with simple steatosis compared with patients without the disease.

Inflammasome Genes Polymorphisms and Susceptibility to Gout. Is There a Link?

ABSTRACT Background: The inflammatory response in gout disease is induced by the activation of NLR family pyrin domain-containing 3 (NLPR3) signaling pathway mediated by IL-1β release. Objective: The objective of the study was to determine the association between single nucleotide polymorphisms (SNPs) within NLRP3 inflammasome genes and gout susceptibility. Methods: Mexican patients with gout from the National Rehabilitation Institute and General Hospital of Mexico were enrolled. A healthy control group was also included. We analyzed the frequency and allelic distribution of eight SNPs from seven different genes within the NLRP3 inflammasome signaling pathway: TLR4 rs2149356, CD14 rs2569190, NLRP3 rs3806268, NLRP3 rs10754558, CARD8 rs2043211, IL-1β rs1143623, P2RX7 rs3751142, and PPARGC1B rs45520937 SNPs. Results: We found that the SNP rs45520937 of PPARGC1B was associated with the risk of developing gout when it was analyzed using the dominant model (Odds ratio [OR] = 2.30; 95% confidence interval [CI]: 1.09-4.86; p = 0.030), and it is proposed that the adaptor molecule CD14 rs2569190 polymorphism could be associated with a lower risk of gout under an additive model (OR= 0.41;95% CI: 0.16-1.05; p = 0.064). No significant associations were identified for the remaining SNPs. Conclusion: Our findings suggest that the PPARGC1B rs45520937 SNP is associated with gout susceptibility.

Inflammasome genes polymorphisms and susceptibility to gout. Is there a link?

Background: The inflammatory response in gout disease is induced by the activation of NLR family pyrin domain-containing 3 (NLPR3) signaling pathway mediated by IL-1ß release. Objective: The objective of the study was to determine the association between single nucleotide polymorphisms (SNPs) within NLRP3 inflammasome genes and gout susceptibility. Methods: Mexican patients with gout from the National Rehabilitation Institute and General Hospital of Mexico were enrolled. A healthy control group was also included. We analyzed the frequency and allelic distribution of eight SNPs from seven different genes within the NLRP3 inflammasome signaling pathway: TLR4 rs2149356, CD14 rs2569190, NLRP3 rs3806268, NLRP3 rs10754558, CARD8 rs2043211, IL-1ß rs1143623, P2RX7 rs3751142, and PPARGC1B rs45520937 SNPs. Results: We found that the SNP rs45520937 of PPARGC1B was associated with the risk of developing gout when it was analyzed using the dominant model (Odds ratio [OR] = 2.30; 95% confidence interval [CI]: 1.09-4.86; p = 0.030), and it is proposed that the adaptor molecule CD14 rs2569190 polymorphism could be associated with a lower risk of gout under an additive model (OR= 0.41;95% CI: 0.16-1.05; p = 0.064). No significant associations were identified for the remaining SNPs. Conclusion: Our findings suggest that the PPARGC1B rs45520937 SNP is associated with gout susceptibility.

Genome-Wide Association Study Identifies a Functional SIDT2 Variant Associated With HDL-C (High-Density Lipoprotein Cholesterol) Levels and Premature Coronary Artery Disease.

Objective: Low HDL-C (high-density lipoprotein cholesterol) is the most frequent dyslipidemia in Mexicans, but few studies have examined the underlying genetic basis. Our purpose was to identify genetic variants associated with HDL-C levels and cardiovascular risk in the Mexican population. Approach and Results: A genome-wide association studies for HDL-C levels in 2335 Mexicans, identified four loci associated with genome-wide significance: CETP, ABCA1, LIPC, and SIDT2. The SIDT2 missense Val636Ile variant was associated with HDL-C levels and was replicated in 3 independent cohorts (P=5.9×10−18 in the conjoint analysis). The SIDT2/Val636Ile variant is more frequent in Native American and derived populations than in other ethnic groups. This variant was also associated with increased ApoA1 and glycerophospholipid serum levels, decreased LDL-C (low-density lipoprotein cholesterol) and ApoB levels, and a lower risk of premature CAD. Because SIDT2 was previously identified as a protein involved in sterol transport, we tested whether the SIDT2/Ile636 protein affected this function using an in vitro site-directed mutagenesis approach. The SIDT2/Ile636 protein showed increased uptake of the cholesterol analog dehydroergosterol, suggesting this variant affects function. Finally, liver transcriptome data from humans and the Hybrid Mouse Diversity Panel are consistent with the involvement of SIDT2 in lipid and lipoprotein metabolism. Conclusions: This is the first genome-wide association study for HDL-C levels seeking associations with coronary artery disease in the Mexican population. Our findings provide new insight into the genetic architecture of HDL-C and highlight SIDT2 as a new player in cholesterol and lipoprotein metabolism in humans.

Endothelial Dysfunction, Inflammation and Coronary Artery Disease: Potential Biomarkers and Promising Therapeutical Approaches.

Coronary artery disease (CAD) and its complications are the leading cause of death worldwide. Inflammatory activation and dysfunction of the endothelium are key events in the development and pathophysiology of atherosclerosis and are associated with an elevated risk of cardiovascular events. There is great interest to further understand the pathophysiologic mechanisms underlying endothelial dysfunction and atherosclerosis progression, and to identify novel biomarkers and therapeutic strategies to prevent endothelial dysfunction, atherosclerosis and to reduce the risk of developing CAD and its complications. The use of liquid biopsies and new molecular biology techniques have allowed the identification of a growing list of molecular and cellular markers of endothelial dysfunction, which have provided insight on the molecular basis of atherosclerosis and are potential biomarkers and therapeutic targets for the prevention and or treatment of atherosclerosis and CAD. This review describes recent information on normal vascular endothelium function, as well as traditional and novel potential biomarkers of endothelial dysfunction and inflammation, and pharmacological and non-pharmacological therapeutic strategies aimed to protect the endothelium or reverse endothelial damage, as a preventive treatment for CAD and related complications.

Compound Heterozygous KCNQ1 Mutations Causing Recessive Romano-Ward Syndrome: Functional Characterization by Mutant Co-expression.

Next Generation Sequencing has identified many KCNQ1 genetic variants associated with type 1 long QT or Romano-Ward syndrome, most frequently inherited in an autosomal dominant fashion, although recessive forms have been reported. Particularly in the case of missense variants, functional studies of mutants are of aid to establish variant pathogenicity and to understand the mechanistic basis of disease. Two compound heterozygous KCNQ1 mutations (p.A300T and p.P535T) were previously found in a child who suffered sudden death. To provide further insight into the clinical significance and basis for pathogenicity of these variants, different combinations of wildtype, A300T and P535T alleles were co-expressed with the accessory ß-subunit minK in HEK293 cells, to analyze colocalization with the plasma membrane and some biophysical phenotypes of homo and heterotetrameric channels using the patch-clamp technique. A300T homotetrameric channels showed left-shifted activation V1/2 as previously observed in Xenopus oocytes, decreased maximum conductance density, slow rise-time300ms, and a characteristic use-dependent response. A300T slow rise-time300ms and use-dependent response behaved as dominant biophysical traits for all allele combinations. The P535T variant significantly decreased maximum conductance density and Kv7.1-minK-plasma membrane colocalization. P535T/A300T heterotetrameric channels showed decreased colocalization with plasma membrane, slow rise-time300ms and the A300T characteristic use-dependent response. While A300T left shifted activation voltage dependence behaved as a recessive trait when co-expressed with WT alleles, it was dominant when co-expressed with P535T alleles. Conclusions: The combination of P535T/A300T channel biophysical properties is compatible with recessive Romano Ward syndrome. Further analysis of other biophysical traits may identify other mechanisms involved in the pathophysiology of this disease.

The Role of the ATP-Binding Cassette A1 (ABCA1) in Human Disease.

Cholesterol homeostasis is essential in normal physiology of all cells. One of several proteins involved in cholesterol homeostasis is the ATP-binding cassette transporter A1 (ABCA1), a transmembrane protein widely expressed in many tissues. One of its main functions is the efflux of intracellular free cholesterol and phospholipids across the plasma membrane to combine with apolipoproteins, mainly apolipoprotein A-I (Apo A-I), forming nascent high-density lipoprotein-cholesterol (HDL-C) particles, the first step of reverse cholesterol transport (RCT). In addition, ABCA1 regulates cholesterol and phospholipid content in the plasma membrane affecting lipid rafts, microparticle (MP) formation and cell signaling. Thus, it is not surprising that impaired ABCA1 function and altered cholesterol homeostasis may affect many different organs and is involved in the pathophysiology of a broad array of diseases. This review describes evidence obtained from animal models, human studies and genetic variation explaining how ABCA1 is involved in dyslipidemia, coronary heart disease (CHD), type 2 diabetes (T2D), thrombosis, neurological disorders, age-related macular degeneration (AMD), glaucoma, viral infections and in cancer progression.

Clinical Spectrum of SCN5A Channelopathy in Children with Primary Electrical Disease and Structurally Normal Hearts.

Sodium voltage-gated channel α subunit 5 (SCN5A)-mutations may cause an array of arrhythmogenic syndromes most frequently as an autosomal dominant trait, with incomplete penetrance, variable expressivity and male predominance. In the present study, we retrospectively describe a group of Mexican patients with SCN5A-disease causing variants in whom the onset of symptoms occurred in the pediatric age range. The study included 17 patients with clinical diagnosis of primary electrical disease, at least one SCN5A pathogenic or likely pathogenic mutation and age of onset <18 years, and all available first- and second-degree relatives. Fifteen patients (88.2%) were male, and sixteen independent variants were found (twelve missense, three truncating and one complex inframe deletion/insertion). The frequency of compound heterozygosity was remarkably high (3/17, 17.6%), with early childhood onset and severe disease. Overall, 70.6% of pediatric patients presented with overlap syndrome, 11.8% with isolated sick sinus syndrome, 11.8% with isolated Brugada syndrome (BrS) and 5.9% with isolated type 3 long QT syndrome (LQTS). A total of 24/45 SCN5A mutation carriers were affected (overall penetrance 53.3%), and penetrance was higher in males (63.3%, 19 affected/30 mutation carriers) than in females (33.3%, 5 affected/15 carriers). In conclusion, pediatric patients with SCNA-disease causing variants presented mainly as overlap syndrome, with predominant loss-of-function phenotypes of sick sinus syndrome (SSS), progressive cardiac conduction disease (PCCD) and ventricular arrhythmias.

Non-alcoholic fatty liver disease and microRNAs expression, how it affects the development and progression of the disease.

The obesity pandemic that affects the global population generates one of the most unfavorable microenvironmental conditions in the hepatocyte, which triggers the metabolic hepatopathy known as non-alcoholic fatty liver; its annual rates increase in its prevalence and does not seem to improve in the future. The international consortia, LITMUS by the European Union and NIMBLE by the United States of America, have started a race for the development of hepatic steatosis and steatohepatitis reliable biomarkers to have an adequate diagnosis. MicroRNAs have been proposed as diagnostic and prognostic biomarkers involved in adaptation to changes in the liver microenvironment, which could improve clinical intervention strategies in patients with hepatic steatosis.

Genomic study of dilated cardiomyopathy in a group of Mexican patients using site-directed next generation sequencing.

BACKGROUND: Dilated cardiomyopathy (DCM) is a major cause of nonischemic heart failure and death in young adults. Next generation sequencing (NGS) has become part of the diagnostic workup in idiopathic and familial DCM. More than 50 DCM genes have been identified, revealing great molecular heterogeneity and variable diagnostic yield. Interpretation of variant pathogenicity is challenging particularly in underrepresented populations, as pathogenic variant databases include studies mainly from European/Caucasian populations. To date, no studies on genomic diagnosis of DCM have been conducted in Mexico. METHODS: We recruited 55 unrelated DCM patients, 22 familial (F-DCM), and 33 idiopathic (I-DCM), and performed site-directed NGS seeking causal mutations. Diagnostic yield was defined as the proportion of individuals with at least one pathogenic (P) or likely pathogenic (LP) variant in DCM genes. RESULTS: Overall diagnostic yield was 47.3%, and higher in F-DCM (63.6%) than in I-DCM (36.4%, p = 0.047). Overall, NGS disclosed 41 variants of clinical interest (61.0% novel), 27 were classified as P/LP and 14 of unknown clinical significance. Of P/LP variants, 10 were A-band region TTN truncating variants, five were found in DSP (18.5%), five in MYH7 (18.5%), two in LMNA (7.4%), and one in RBM20, ABCC9, FKTN, ACTA1, and TNNT2. NGS findings suggested autosomal recessive inheritance in three families, two with DSP loss of function mutations in affected individuals. The increasing number of mutation reports in DCM, increasing knowledge on the functional consequences of mutations, mutational hotspots and functional domains of DCM-related proteins, the recent refinement ACMG/ClinGen Guidelines, and co-segregation analysis in DCM families helped increase the diagnostic yield. CONCLUSION: This is the first NGS study performed in a group of Mexican DCM patients, contributing to understand the mutational spectrum and complexity of DCM molecular diagnosis.

The fibrogenic process and the unleashing of acute-on-chronic liver failure.

Acute-on-chronic liver failure (ACLF) is a life-threatening condition characterized by a rapid deterioration of previously well-compensated chronic liver diseases. One of the main obstacles in ACLF is the lack of knowledge of the pathogenesis and specific broad-spectrum treatments. An excessive systemic inflammatory response has been proposed to explain the pathogenesis of ACLF; this hypothesis involves stellate cells, which are implicated in many liver homeostatic functions that include vitamin A storage, regulation of sinusoidal blood flow, local inflammation, maintenance of the hepatocyte phenotype and extracellular matrix remodeling. However, when there is damage to the liver, these cells are the main target of the inflammatory stimulus, as a result, the secretion of the extracellular matrix is altered. Activated hepatic stellate cells raise the survival of neutrophils by the stimulation of granulocytes colonies and macrophages, which exacerbates liver inflammation and promotes damage to hepatocytes. Elevation of pathogen-associated molecular patterns is related to liver damage by different pathophysiological mechanisms of decompensation, showing ballooning degeneration and cell death with a predominance of cholestatic infection. Moreover, patients with ACLF present a marked elevation of C-reactive protein together with an elevation of the leukocyte count. Chronic liver disease is a complex pathological state with a heterogeneous pathophysiology in which genetic factors of the host and external triggers interact and culminate in hepatic insufficiency. The better understanding of such interactions should lead to a better comprehension of the disease and to the discovery of new treatment targets that will make acute decompensations preventable and even decrease mortality.

Impact of cadmium toxicity on cartilage loss in a 3D in vitro model.

Osteoarthritis (OA) is the gradual loss of articular cartilage and decrease in subchondral space. One of the risk factors Exposure to cadmium (Cd) through tobacco smoke has been identified as a major OA risk factor. There are no reports addressing the role of Cd in OA progression at the molecular level. Our findings revealed that Cd can promote the activation of metalloproteinases (MMP1, MMP3, MMP9 y MMP13), affecting the expression of COL2A1 and ACAN, and decreasing the presence of glycosaminoglycans and proteoglycans through an inflammatory response related to IL-1ß y a IL-6, as well as oxidative by producing ROS like O2-• and H2O2. In conclusion, our findings suggest a cytotoxic role of Cd in the articular cartilage, which could affect OA development.

Cholesterol burden in the liver induces mitochondrial dynamic changes and resistance to apoptosis.

Non-alcoholic fatty liver disease (NAFLD) encompasses a broad spectrum of histopathological changes ranging from non-inflammatory intracellular fat deposition to non-alcoholic steatohepatitis (NASH), which may progress into hepatic fibrosis, cirrhosis, or hepatocellular carcinoma. Recent data suggest that impaired hepatic cholesterol homeostasis and its accumulation are relevant to the pathogenesis of NAFLD/NASH. Despite a vital physiological function of cholesterol, mitochondrial dysfunction is an important consequence of dietary-induced hypercholesterolemia and was, subsequently, linked to many pathophysiological conditions. The aim in the current study was to evaluate the morphological and molecular changes of cholesterol overload in mouse liver and particularly, in mitochondria, induced by a high-cholesterol (HC) diet for one month. Histopathological studies revealed microvesicular hepatic steatosis and significantly elevated levels of liver cholesterol and triglycerides leading to impaired liver synthesis. Further, high levels of oxidative stress could be determined in liver tissue as well as primary hepatocyte culture. Transcriptomic changes induced by the HC diet involved disruption in key pathways related to cell death and oxidative stress as well as upregulation of genes related to glutathione homeostasis. Impaired liver function could be associated with a decrease in mitochondrial membrane potential and ATP content and significant alterations in mitochondrial dynamics. We demonstrate that cholesterol overload in the liver leads to mitochondrial changes which may render damaged hepatocytes proliferative and resistant to cell death whereby perpetuating liver damage.

Cadmium exposure exacerbates hyperlipidemia in cholesterol-overloaded hepatocytes via autophagy dysregulation.

Metabolic factors are the major risk of non-alcoholic fatty liver disease, although other factors may contribute steatosis. Cadmium exposure produces histopathological and molecular changes in liver, which are consistent with steatosis. In the present study, we describe the effect of low cadmium acute treatment on hepatocytes obtained from mice fed with a high cholesterol diet. Our data suggest that hepatocytes with cholesterol overload promote an adaptive response against cadmium-induced acute toxicity by up-regulating anti-apoptotic proteins, managing ROS overproduction, increasing GSH synthesis and MT-II content to avoid protein oxidation. Cadmium treatment increases lipid content in cholesterol-fed mice hepatocytes because of an impaired autophagy process. Our data suggest an essential function of macroautophagy in the regulation of lipid storage induced by Cd on hepatocytes, that implies that alterations in this pathway may be a mechanism that aggravates hepatic steatosis.

Liver Cholesterol Overload Aggravates Obstructive Cholestasis by Inducing Oxidative Stress and Premature Death in Mice.

Nonalcoholic steatohepatitis is one of the leading causes of liver disease. Dietary factors determine the clinical presentation of steatohepatitis and can influence the progression of related diseases. Cholesterol has emerged as a critical player in the disease and hence consumption of cholesterol-enriched diets can lead to a progressive form of the disease. The aim was to investigate the impact of liver cholesterol overload on the progression of the obstructive cholestasis in mice subjected to bile duct ligation surgery. Mice were fed with a high cholesterol diet for two days and then were subjected to surgery procedure; histological, biochemical, and molecular analyses were conducted to address the effect of cholesterol in liver damage. Mice under the diet were more susceptible to damage. Results show that cholesterol fed mice exhibited increased apoptosis and oxidative stress as well as reduction in cell proliferation. Mortality following surgery was higher in HC fed mice. Liver cholesterol impairs the repair of liver during obstructive cholestasis and aggravates the disease with early fatal consequences; these effects were strongly associated with oxidative stress.

Hepatocyte Growth Factor Reduces Free Cholesterol-Mediated Lipotoxicity in Primary Hepatocytes by Countering Oxidative Stress.

Cholesterol overload in the liver has shown toxic effects by inducing the aggravation of nonalcoholic fatty liver disease to steatohepatitis and sensitizing to damage. Although the mechanism of damage is complex, it has been demonstrated that oxidative stress plays a prominent role in the process. In addition, we have proved that hepatocyte growth factor induces an antioxidant response in hepatic cells; in the present work we aimed to figure out the protective effect of this growth factor in hepatocytes overloaded with free cholesterol. Hepatocytes from mice fed with a high-cholesterol diet were treated or not with HGF, reactive oxygen species present in cholesterol overloaded hepatocytes significantly decreased, and this effect was particularly associated with the increase in glutathione and related enzymes, such as γ-gamma glutamyl cysteine synthetase, GSH peroxidase, and GSH-S-transferase. Our data clearly indicate that HGF displays an antioxidant response by inducing the glutathione-related protection system.

Free fatty acids enhance the oxidative damage induced by ethanol metabolism in an in vitro model.

In recent years, there has been a growing interest to explore the responsiveness to injury in steatotic hepatocyte. VL-17A cells, which express ADH and Cyp2E1 overloaded with free fatty acids (1 mM of oleic and palmitic acid 2:1) showed an increased oxidative damaged after 24 h free fatty acids treatment when exposed to ethanol (100 mM) for 48 h as a second injury. An increment in reactive oxygen species, determined by DCFH-DA, protein oxidation, and apoptosis were observed although an increase in main antioxidant proteins such as superoxide dismutase 1 and glutathione peroxidase were observed, but failed in gamma-glutamylcysteine synthetase, suggesting a decreased capacity of synthesis of glutathione compared with cells treated only with free fatty acids or ethanol. The increased oxidative stress and toxicity in lipid overloaded VL-17A cells subjected to ethanol exposure were accompanied by increases in Cyp2E1 protein expression. Our data show that lipid loaded in an in vitro model, VL-17A cells, is more susceptible to cell damage and oxidative stress when treated with ethanol.

Acetaldehyde targets superoxide dismutase 2 in liver cancer cells inducing transient enzyme impairment and a rapid transcriptional recovery.

Alcohol is undoubtedly, the main toxic agent that people consume by recreation and the abuse is associated with liver damage, mainly by the overproduction of reactive oxygen species and the toxic effects of its first metabolite acetaldehyde. It is known that acetaldehyde targets mitochondria inducing redox imbalance and oxidative stress. Mitochondrial superoxide dismutase transforms superoxide radical into hydrogen peroxide, which in addition, is transformed in water by other enzymes. In the present study we demonstrate that acetaldehyde transiently impairs SOD2 activity in HepG2 cells, the decrease in the enzyme activity was associated to a reduction in the protein content, which was rapidly recovered, to basal values, by synthesis de novo in a mechanism mediated by NF-κB and PKC. The SOD2 impairment was not associated with adduct formation. The recovery on SOD2 activity in HepG2 cells can represent survival advantage for cancer cells, the results shown that SOD2 could be considered a therapeutic target in liver cancer.

Biphasic regulation of the NADPH oxidase by HGF/c-Met signaling pathway in primary mouse hepatocytes.

Redox signaling is emerging as an essential mechanism in the regulation of biological activities of the cell. The HGF/c-Met signaling pathway has been implicated as a key regulator of the cellular redox homeostasis and oxidative stress. We previously demonstrated that genetic deletion of c-Met in hepatocytes disrupts redox homeostasis by a mechanism involving NADPH oxidase. Here, we were focused to address the mechanism of NADPH oxidase regulation by HGF/c-Met signaling in primary mouse hepatocytes and its relevance. HGF induced a biphasic mechanism of NADPH oxidase regulation. The first phase employed the rapid increase in production of ROS as signaling effectors to activate the Nrf2-mediated protective response resulting in up-regulation of the antioxidant proteins, such as NAD(P)H quinone oxidoreductase and γ-glutamylcysteine synthetase. The second phase operated under a prolonged HGF exposure, caused a suppression of the NADPH oxidase components, including NOX2, NOX4, p22 and p67, and was able to abrogate the TGFß-induced ROS production and improve cell viability. In conclusion, HGF/c-Met induces a Nrf2-mediated protective response by a double mechanism driven by NADPH oxidase.