Isoaspartate, carbamoyl phosphate synthase-1, and carbonic anhydrase-III as biomarkers of liver injury

Tissue damage, antioxidant capacity, transcriptional and metabolic regulation of red drum Sciaenops ocellatus in response to nanoplastics exposure and subsequent recovery

Nanoplastics are recognized as emerging contaminants that can cause severe toxicity to marine fishes. However, limited researches were focusing on the toxic effects of nanoplastics on marine fish, especially the post-exposure resilience. In this study, red drum (Sciaenops ocellatus) were exposed to 5 mg/L polystyrene nanoplastics (100 nm, PS-NPs) for a 7-day exposure experiment, and a 14-day recovery experiment that followed. The aim was to evaluate the dynamic alterations in hepatic and branchial tissue damage, hepatic antioxidant capacity, as well as hepatic transcriptional and metabolic regulation in the red drum during exposure and post-exposure to PS-NPs. Histopathological observation found that PS-NPs primarily triggered hepatic lipid droplets and branchial epithelial liftings, a phenomenon persistently discernible up to the 14 days of recovery. Although antioxidant capacity partially recovered during recovery periods, PS-NPs resulted in a sustained reduction in hepatic antioxidant activity, causing oxidative damage throughout the entire exposure and recovery phases, as evidenced by decreased total superoxide dismutase activities and increased malondialdehyde content. At the transcriptional and metabolic level, PS-NPs primarily induced lipid metabolism disorders, DNA damage, biofilm disruption, and mitochondrial dysfunction. In the gene-metabolite correlation interaction network, numerous CcO (cytochrome c oxidase) family genes and lipid metabolites were identified as key regulatory genes and metabolites in detoxification processes. Among them, the red drum possesses one additional CcO6B in comparison to human and zebrafish, which potentially contributes to its enhanced capacity for maintaining a stable and positive regulatory function in detoxification. This study revealed that nanoplastics cause severe biotoxicity to red drum, which may be detrimental to the survival of wild populations and affect the economics of farmed populations.

Carbonic anhydrase 3 increases during liver adipogenesis even in pre-obesity, and its inhibitors reduce liver adipose accumulation

The abnormal lipid metabolism in the liver that occurs after high caloric intake is the main cause of nonalcoholic fatty liver disease (NAFLD). Differences between samples from healthy livers and livers from individuals with NAFLD indicate that changes in liver function occur during disease progression. Here, we examined changes in protein expression in a fatty liver model in the early stages of obesity to identify potential alterations in function. The proteins expressed in the liver tissue of pre‐obese rats were separated via SDS/PAGE and stained with Coomassie brilliant blue‐G250. Peptide mass fingerprinting indicated an increase in the expression of carbonic anhydrase 3 (CA3) relative to controls. Western blotting analysis confirmed the increase in CA3 expression, even in an early fat‐accumulation state in which excessive weight gain had not yet occurred. In human hepatoma HepG2 cells, fat accumulation induced with oleic acid also resulted in increased CA3 expression. When the cells were in a state of fat accumulation, treating them with the CA3 inhibitors acetazolamide (ACTZ) or 6‐ethoxyzolamide (ETZ) suppressed fat accumulation, but only ETZ somewhat reduced the fat‐induced upregulation of CA3 expression. Expression of CA3 was therefore upregulated in response to the consumption of a high‐fat diet, even in the absence of an increase in body weight. The suppression of CA3 activity by ACTZ or ETZ reduced fat accumulation in hepatocytes, suggesting that CA3 is involved in the development of fatty liver.

Squalene Epoxidase Induces Nonalcoholic Steatohepatitis Via Binding to Carbonic Anhydrase III and is a Therapeutic Target

BACKGROUNDS & AIMS

Squalene epoxidase (SQLE) is the rate-limiting enzyme for cholesterol biosynthesis. We elucidated the functional significance, molecular mechanisms, and clinical impact of SQLE in nonalcoholic steatohepatitis (NASH).

METHODS

We performed studies with hepatocyte-specific Sqle overexpression transgenic (Sqle tg) mice and mice given high-fat high-cholesterol (HFHC) or methionine- and choline-deficient (MCD) diet to induce NASH. SQLE downstream target carbonic anhydrase III (CA3) was identified using co-immunoprecipitation and Western Blot. Some mice were given SQLE inhibitor (terbinafine) and CA3 inhibitor (acetazolamide) to study the therapeutic effects in NASH. Human samples (N = 217) including 65 steatoses, 80 NASH, and 72 healthy controls were analyzed for SQLE levels in liver tissue and in serum.

RESULTS

SQLE is highly up-regulated in human NASH and mouse models of NASH. Sqle tg mice triggered spontaneous insulin resistance, hepatic steatosis, liver injury, and accelerated HFHC or MCD diet-induced NASH development. Mechanistically, SQLE tg mice caused hepatic cholesterol accumulation, thereby triggering proinflammatory nuclear factor-κB signaling and steatohepatitis. SQLE directly bound to CA3, which induced sterol regulatory element-binding protein 1C activation, acetyl-CoA carboxylase, fatty acid synthase, and stearoyl-CoA desaturase1 expression and de novo hepatic lipogenesis. Combined targeting SQLE (terbinafine) and CA3 (acetazolamide) synergistically ameliorated NASH in mice with superior efficacy to either drug alone. Serum SQLE with CA3 could distinguish patients with NASH from steatosis and healthy controls (area under the receiver operating characteristic curve, 0.815; 95% confidence interval, 0.758-0.871).

CONCLUSIONS

SQLE drives the initiation and progression of NASH through inducing cholesterol biosynthesis, and SQLE/CA3 axis-mediated lipogenesis. Combined targeting of SQLE and CA3 confers therapeutic benefit in NASH. Serum SQLE and CA3 are novel biomarkers for the noninvasive diagnosis of patients with NASH.

Proteomics evaluation of enniatins acute toxicity in rat liver

Enniatins (ENs) are emerging mycotoxins produced by Fusarium fungi which are cytotoxic also at low concentrations due to its ionophoric properties. The aim of this study was to evaluate the hepatic toxicity of ENs exposure at different concentrations in Wistar rats through a proteomic approach. Animals were intoxicated by oral gavage with medium (EN A 256, ENA1 353, ENB 540, ENB1 296 μg/mL) and high concentrations (ENA 513, ENA1 706, ENB 1021, ENB1 593 μg/mL) of an ENs mixture and sacrificed after 8 h. Protein extraction was performed using powdered liver. Peptides were analyzed using a liquid chromatography coupled with a quadrupole time-of-flight mass spectrometer. Proteins were filtered by abundance using Mass Professional Profiler software (Agilent Technologies) and 57 were differentially expressed when compared to the control. In terms of abundance, the liver biomarker Carboamoyl-phosphate synthase showed the highest levels in all conditions employed while actin-1 had the lowest. Bioinformatic analysis using DAVID platform reported acetylation, nucleotide phosphate-binding region:NAD and catalytic activity as the most represented terms. Furthermore, metabolism was the most significant and enriched pathway in Reactome overrepresentation. In conclusion, ENs acute exposure caused protein expression changes related to major cellular processes in rats, hinting its involvement in liver disturbance.

[Full transcriptome analysis of gene expression in liver of mice in a comparative study of quercetin efficiency on two obesity models]

BACKGROUND

Quercetin (Q; 3,3',4',5,7 - pentahydroxyflavone) can help alleviate the pathological effects of nutritional obesity and metabolic syndrome when taken as part of products for special dietary needs and food supplements. The mechanisms of action of Q at the genetic level are not well understood.

AIMS

To study gene expression in liver tissue of mice with alimentary and genetically determined obesity upon intake of Q with diet.

MATERIALS AND METHODS

During 46 days of the experiment on 32 male C57Bl/6J mice fed a diet with an excess of fat and fructose and 24 male genetically obese db/db mice the effect of Q in dose of 25 or 100 mg/kg of body weight was studied on differential expression of 39430 genes in mice livers by full transcriptome profiling on microchip according to the Agilent One-Color Microarray-Based Gene Expression Analysis Low Input Quick Amp Labeling protocol (version 6.8). To identify metabolic pathways (KEGGs) that were targets of Q exposure, transcriptomic data were analyzed using bioinformatics methods in an "R" environment.

RESULTS

Differences were revealed in the nature of Q supplementation action in animals with dietary induced and genetically determined obesity on a number of key metabolic pathways, including the metabolism of lipids and steroids (Saa3, Cidec, Scd1, Apoa4, Acss2, Fabp5, Car3, Acacb, Insig2 genes), amino acids and nitrogen bases (Ngef, Gls2), carbohydrates (G6pdx, Pdk4), regulation of cell growth, apoptosis and proliferation (Btg3, Cgref1, Fst, Nrep Tuba8), neurotransmission (Grin2d, Camk2b), immune system reactions (CD14i, Jchain, Ifi27l2b).

CONCLUSIONS

The data obtained help to explain the ambiguous effectiveness of Q, like other polyphenols, in the dietary treatment of various forms of obesity in humans, as well as to form a set of sensitive biomarkers that allow us to elucidate the effectiveness of minor biologically active food substances in preclinical trials of new means of metabolic correction of obesity and metabolic syndrome.

Gene expression profiling in the hippocampus of adolescent rats after chronic alcohol administration

In South Korea, the average age of onset of alcohol drinking is 13.3 years and half of adolescents drink alcohol more than once a month; 8.45% of the Korean adolescent population become future high-risk alcohol drinkers. Chronic alcohol abuse causes physical and psychiatric health problems such as alcohol addiction, liver disease, stroke and cognitive impairments. This study aimed to investigate the effect of alcohol on gene expression and their function in the hippocampus of adolescent rats. After chronic alcohol administration in male (control, n = 6; alcohol, n = 6) Sprague-Dawley rats for 6 weeks, we analysed up- or down-regulated genes using RNA-sequencing technology. We found 83 genes more than 1.5-fold up- or down-regulated in the alcohol-treated group. Among them, genes (Dnai1, Cfap206 and Dnah1) associated with cilium movement were up-regulated in the alcohol-treated group. Mlf1, related to cell cycle arrest, was also up-regulated in the alcohol-treated group. On the other hand, genes (Smad3 and Plk5) involved in negative regulation of cell proliferation were down-regulated in the hippocampus by chronic alcohol administration. In addition, expression levels of genes associated with oxidative stress (Krt8 and Car3) and migration (Vim) were changed by chronic alcohol administration. These results pave a path for a better understanding of the neuromolecular mechanisms mediated by chronic alcohol exposure in the hippocampus of adolescents and negative pathology due to chronic alcohol abuse.

Transgenic expression of carbonic anhydrase III in cardiac muscle demonstrates a mechanism to tolerate acidosis

Carbonic anhydrase III (CAIII) is abundant in liver, adipocytes, and skeletal muscles, but not heart. A cytosolic enzyme that catalyzes conversions between CO₂ and HCO3- in the regulation of intracellular pH, its physiological role in myocytes is not fully understood. Mouse skeletal muscles lacking CAIII showed lower intracellular pH during fatigue, suggesting its function in stress tolerance. We created transgenic mice expressing CAIII in cardiomyocytes that lack endogenous CAIII. The transgenic mice showed normal cardiac development and life span under nonstress conditions. Studies of ex vivo working hearts under normal and acidotic conditions demonstrated that the transgenic and wild-type mouse hearts had similar pumping functions under normal pH. At acidotic pH, however, CAIII transgenic mouse hearts showed significantly less decrease in cardiac function than that of wild-type control as shown by higher ventricular pressure development, systolic and diastolic velocities, and stroke volume via elongating the time of diastolic ejection. In addition to the effect of introducing CAIII into cardiomyocytes on maintaining homeostasis to counter acidotic stress, the results demonstrate the role of carbonic anhydrases in maintaining intracellular pH in muscle cells as a potential mechanism to treat heart failure.

Carbonic anhydrases as disease markers

INTRODUCTION

The physiologic importance of fast CO₂/HCO₃^- interconversion in various tissues requires the presence of carbonic anhydrase (CA, EC 4.2.1.1). Fourteen CA isozymes are present in humans, all of them being used as biomarkers.

AREAS COVERED

A great number of patents and articles were focused on the use of CA isozymes as biomarkers for various diseases and syndromes in the recent years, in an ascending trend over the last decade. The review highlights the most important studies related with each isozyme and covers the most recent patent literature.

EXPERT OPINION

The CAs biomarker research area expanded significantly in recent years, shifting from the predominant use of CA IX and CA XII in cancer diagnostic, staging, and prognosis towards a wider use of CA isozymes as disease biomarkers. CA isozymes are currently used either alone, in tandem with other CA isozymes and/or in combination with other proteins for the detection, staging, and prognosis of a huge repertoire of human dysfunctions and diseases, ranging from mild transformation of the normal tissues to extreme shifts in tissue organization and function. The techniques used for their detection/quantitation and the state-of-the-art in each clinical application are presented through relevant clinical examples and corresponding statistical data.

Carbamoyl phosphate synthetase 1 (CPS1) as a prognostic marker in chronic hepatitis C infection

This study aims to assess the value of carbamoyl phosphate synthetase 1 (CPS1), as a non-invasive serum marker, for the evolution of chronic HCV infection and hepatic fibrosis. Seventy-two patients with HCV positive serum RNA and 15 health volunteers were enrolled in this study. Out of 72 patients, 10 patients had decompensated liver with ascites. Quantitative analysis of CPS1 was performed in the harvested sera and corresponding liver biopsies using ELISA and immunohistochemistry techniques respectively. Also, mitochondrial count using electron microscopy, urea analysis and conventional liver tests were done. Patients were grouped into (F1 + F2) and (F3 + F4) representing stages of moderate and severe fibrosis respectively. Tissue and serum CPS1 (s.CPS1) correlated significantly in moderate and severe fibrosis. Patients with severe fibrosis showed significantly higher levels of s.CPS1 (p-value ≤ 0.05) and significantly lower mitochondrial counts (p-value = 0.0065) than those with moderate fibrosis. S.urea positively correlated with s.CPS1 only in the decompensated group, at which s.urea reached maximal levels. In conclusion, s.CPS1 is a potential non-invasive marker for the assessment of severity and progression of HCV in relation to mitochondrial dysfunction. Also, increased s.urea with the progression of the disease is mainly due to a concurrent renal malfunction, which needs further investigation.

The Loss of α- and β-Tubulin Proteins Are a Pathological Hallmark of Chronic Alcohol Consumption and Natural Brain Ageing

Repetitive excessive alcohol intoxication leads to neuronal damage and brain shrinkage. We examined cytoskeletal protein expression in human post-mortem tissue from Brodmann's area 9 of the prefrontal cortex (PFC). Brain samples from 44 individuals were divided into equal groups of 11 control, 11 alcoholic, 11 non-alcoholic suicides, and 11 suicide alcoholics matched for age, sex, and post-mortem delay. Tissue from alcoholic cohorts displayed significantly reduced expression of α- and β-tubulins, and increased levels of acetylated α-tubulin. Protein levels of histone deacetylase-6 (HDAC6), and the microtubule-associated proteins MAP-2 and MAP-tau were reduced in alcoholic cohorts, although for MAPs this was not significant. Tubulin gene expressions increased in alcoholic cohorts but not significantly. Brains from rats administered alcohol for 4 weeks also displayed significantly reduced tubulin protein levels and increased α-tubulin acetylation. PFC tissue from control subjects had reduced tubulin protein expression that was most notable from the sixth to the eighth decade of life. Collectively, loss of neuronal tubulin proteins are a hallmark of both chronic alcohol consumption and natural brain ageing. The reduction of cytosolic tubulin proteins could contribute to the brain volumetric losses reported for alcoholic patients and the elderly.

Antidepressants are cytotoxic to rat primary blood brain barrier endothelial cells at high therapeutic concentrations

Antidepressants are commonly employed for the treatment of major depressive disorders and other psychiatric conditions. We investigated the relatively acute cytotoxic effects of three commonly prescribed antidepressants: fluoxetine, sertraline, and clomipramine on rat primary blood brain barrier endothelial cells over a concentration range of 0.1-100μM. At therapeutic concentrations (0.1μM) no significant cytotoxicity was observed after 4, 24, or 48h. At high therapeutic to overdose concentrations (1-100μM), antidepressants reduced cell viability in proportion to their concentration and exposure duration. At 1μM, antidepressants significantly reduced mitochondrial membrane potential. At drug concentrations producing ~50% inhibition of cell viability, all drugs significantly reduced cellular oxygen consumption rates, activities of mitochondrial complexes I and III, and triggered a significant increase of lactate production. Fluoxetine (6.5μM) and clomipramine (5.5μM) also significantly lowered transcellular transport of albumin. The mechanism of cellular cytotoxicity was evaluated and at high concentrations all drugs significantly increased the production of reactive oxygen species, and significantly increased the activity of the pro-apoptotic caspases-3, 8, and 9. Comet assays revealed that all drugs were genotoxic. Pre-incubation of cells with glutathione significantly ameliorated antidepressant-induced cytotoxicity, indicating the potential benefit of treatment of overdosed patients with antioxidants.

Carbonic anhydrase III (Car3) is not required for fatty acid synthesis and does not protect against high-fat diet induced obesity in mice

Carbonic anhydrases are a family of enzymes that catalyze the reversible condensation of water and carbon dioxide to carbonic acid, which spontaneously dissociates to bicarbonate. Carbonic anhydrase III (Car3) is nutritionally regulated at both the mRNA and protein level. It is highly enriched in tissues that synthesize and/or store fat: liver, white adipose tissue, brown adipose tissue, and skeletal muscle. Previous characterization of Car3 knockout mice focused on mice fed standard diets, not high-fat diets that significantly alter the tissues that highly express Car3. We observed lower protein levels of Car3 in high-fat diet fed mice treated with niclosamide, a drug published to improve fatty liver symptoms in mice. However, it is unknown if Car3 is simply a biomarker reflecting lipid accumulation or whether it has a functional role in regulating lipid metabolism. We focused our in vitro studies toward metabolic pathways that require bicarbonate. To further determine the role of Car3 in metabolism, we measured de novo fatty acid synthesis with in vitro radiolabeled experiments and examined metabolic biomarkers in Car3 knockout and wild type mice fed high-fat diet. Specifically, we analyzed body weight, body composition, metabolic rate, insulin resistance, serum and tissue triglycerides. Our results indicate that Car3 is not required for de novo lipogenesis, and Car3 knockout mice fed high-fat diet do not have significant differences in responses to various diets to wild type mice.

Identification of consensus biomarkers for predicting non-genotoxic hepatocarcinogens

The assessment of non-genotoxic hepatocarcinogens (NGHCs) is currently relying on two-year rodent bioassays. Toxicogenomics biomarkers provide a potential alternative method for the prioritization of NGHCs that could be useful for risk assessment. However, previous studies using inconsistently classified chemicals as the training set and a single microarray dataset concluded no consensus biomarkers. In this study, 4 consensus biomarkers of A2m, Ca3, Cxcl1, and Cyp8b1 were identified from four large-scale microarray datasets of the one-day single maximum tolerated dose and a large set of chemicals without inconsistent classifications. Machine learning techniques were subsequently applied to develop prediction models for NGHCs. The final bagging decision tree models were constructed with an average AUC performance of 0.803 for an independent test. A set of 16 chemicals with controversial classifications were reclassified according to the consensus biomarkers. The developed prediction models and identified consensus biomarkers are expected to be potential alternative methods for prioritization of NGHCs for further experimental validation.

Aberrant post-translational protein modifications in the pathogenesis of alcohol-induced liver injury

It is likely that the majority of proteins will undergo post-translational modification, be it enzymatic or non-enzymatic. These modified protein(s) regulate activity, localization and interaction with other cellular molecules thereby maintaining cellular hemostasis. Alcohol exposure significantly alters several of these post-translational modifications leading to impairments of many essential physiological processes. Here, we present new insights into novel modifications following ethanol exposure and their role in the initiation and progression of liver injury. This critical review condenses the proceedings of a symposium at the European Society for the Biomedical Research on Alcoholism Meeting held September 12-15, 2015, in Valencia, Spain.