Inhibition of acyl-CoA binding protein (ACBP) by means of a GABAARγ2-derived peptide

Acyl-CoA binding protein (ACBP) encoded by diazepam binding inhibitor (DBI) is an extracellular inhibitor of autophagy acting on the gamma-aminobutyric acid A receptor (GABAAR) γ2 subunit (GABAARγ2). Here, we show that lipoanabolic diets cause an upregulation of GABAARγ2 protein in liver hepatocytes but not in other major organs. ACBP/DBI inhibition by systemically injected antibodies has been demonstrated to mediate anorexigenic and organ-protective, autophagy-dependent effects. Here, we set out to develop a new strategy for developing ACBP/DBI antagonists. For this, we built a molecular model of the interaction of ACBP/DBI with peptides derived from GABAARγ2. We then validated the interaction between recombinant and native ACBP/DBI protein and a GABAARγ2-derived eicosapeptide (but not its F77I mutant) by pull down experiments or surface plasmon resonance. The GABAARγ2-derived eicosapeptide inhibited the metabolic activation of hepatocytes by recombinant ACBP/DBI protein in vitro. Moreover, the GABAARγ2-derived eicosapeptide (but not its F77I-mutated control) blocked appetite stimulation by recombinant ACBP/DBI in vivo, induced autophagy in the liver, and protected mice against the hepatotoxin concanavalin A. We conclude that peptidomimetics disrupting the interaction between ACBP/DBI and GABAARγ2 might be used as ACBP/DBI antagonists. This strategy might lead to the future development of clinically relevant small molecules of the ACBP/DBI system.

Targeted Analysis of Glycerophospholipids and Mono-, Di-, or Tri-Acylglycerides in Liver Cancer

The metabolic rearrangements of hepatic metabolism associated with liver cancer are still incompletely understood. There is an ongoing need to identify novel and more efficient diagnostic biomarkers and therapeutic targets based on the metabolic mechanisms of these diseases. In comparison to traditional diagnostic biomarkers, metabolomics is a comprehensive technique for discovering chemical signatures for liver cancer screening, prediction, and earlier diagnosis. Lipids are a large and diverse group of complex biomolecules that are at the heart of liver physiology and play an important role in the development and progression of cancer. In this chapter, we described two detailed protocols for targeted lipids analysis: glycerophospholipids and mono, di, tri-acylglycerides, both by Flow Injection Analysis (FIA) HPLC coupled to a SelexIon/QTRAP 6500+ system. These approaches provide a targeted lipidomic metabolomic signature of dissimilar metabolic disorders affecting liver cancers.

Orthotopic Model of Hepatocellular Carcinoma in Mice

Orthotopic models of hepatocellular carcinoma (HCC) consist in the implantation of tumor cells into the liver by direct intrahepatic injection. In this model, tumorigenesis is triggered within the hepatic microenvironment, thus mimicking the metastatic behavior of HCC. Herein, we detail a surgically mediated methodology that allows the reproducible and effective induction of liver-sessile tumors in mice. We enumerate the steps to be followed before and after the surgical procedure, including HCC cell preparation, the quantity of cancer cells to be injected, presurgical preparation of the mice, and finally, postoperative care. The surgical procedure involves laparotomy to expose the liver, injection of cells into the left-lateral hepatic lobe, and closure of the incision with sutures followed by wound clips. We also provide information concerning the subsequent tumor growth follow-up, as well as the application of bioluminescence imaging to monitor tumor development.

Isolation of Primary Mouse Hepatocytes and Non-Parenchymal Cells from a Liver with Precancerous Lesions

In the early stages of liver carcinogenesis, rare hepatocytes and cholangiocytes are transformed into preneoplastic cells, which can progressively acquire a neoplastic phenotype, favored by the failure of natural antitumor immunosurveillance. The detailed study of both hepatic parenchymal (e.g., hepatocytes) and non-parenchymal cells (NPCs), such as immune cells, could help understand the cellular microenvironment surrounding these pre-cancerous and neoplastic lesions.Cultures of primary hepatocytes are of interest in various biomedical research disciplines, serving as an ex vivo model for liver physiology. Obtaining high viability and yield of primary mouse hepatocytes and other liver cell populations is technically challenging, thus limiting their use. In the first section of the current chapter, we introduce a protocol based on the two-step collagenase perfusion technique (by inferior vena cava) to isolate hepatocytes and, to a lower extent, NPCs and detailed the different considerations to take into account for a successful perfusion. The liver is washed by perfusion, hepatocytes are dissociated with collagenase, and different cell populations are separated by centrifugation. Various techniques have been described for the isolation of healthy and malignant hepatocytes; however, the viability and purity of the isolated cells is frequently not satisfactory. Here, we significantly optimized this protocol to reach improved yield and viability of the hepatocytes and concomitantly obtain preserved NPC populations of the liver.Within NPCs, tissue-resident or recruited immune cells are essential actors regulating hepatocarcinogenesis. However, simultaneous isolation of hepatic leukocytes together with other cell types generally yields low immune cell numbers hindering downstream application with these cells. In the second section of this chapter, as opposed to the first section primarily aiming to isolate hepatocytes, we present a tissue dissociation protocol adapted to efficiently recover leukocytes from non-perfused bulk (pre-)cancerous livers. This protocol has been optimized to be operator-friendly and fast compared to other liver processing methods, allowing easy simultaneous sample processing to retrieve hepatic (tumor-infiltrating) immune cells.

Biomarker Identification in Liver Cancers Using Desorption Electrospray Ionization Mass Spectrometry (DESI-MS) Imaging: An Approach for Spatially Resolved Metabolomics

Liver cancers are characterized by interindividual and intratumoral heterogeneity, which makes early diagnosis and the development of therapies challenging. Desorption electrospray ionization mass spectrometry (DESI-MS) imaging is a potent and sensitive MS ionization technique for direct, unaltered 2D and 3D imaging of metabolites in complex biological samples. Indeed, DESI gently desorbs and ionizes analyte molecules from the sample surface using an electrospray source of highly charged aqueous spray droplets in ambient conditions. DESI-MS imaging of biological samples allows untargeted analysis and characterization of metabolites in liver cancers to identify new biomarkers of malignancy. In this chapter, we described a detailed protocol using liver cancer samples collected and stored for histopathology examination, either as frozen or as formalin-fixed, paraffin-embedded specimens. Such hepatocellular carcinoma samples can be subjected to DESI-MS analyses, illustrating the capacity of spatially resolved metabolomics to distinguish malignant lesions from adjacent normal liver tissue.

A Mouse Model of Non-Alcoholic Steatohepatitis and Hepatocellular Carcinoma Induced by Western Diet and Carbon Tetrachloride

Non-alcoholic steatohepatitis (NASH) is a severe form of non-alcoholic fatty liver disease (NAFLD). Obesity is a known risk factor of NASH, which, in turn, increases the risk of developing cirrhosis (liver scarring) and hepatocellular carcinoma (HCC). In addition to being a potentially life-threatening condition, public health concerns surrounding NASH are amplified by the lack of FDA-approved treatments. Although various preclinical models reflecting both the histopathology and the pathophysiological progression of human NASH exist, most of these models are diet-based and require 6-13 months for NASH symptom manifestation. Here, we describe a simple and rapid-progression model of NASH and NASH-driven HCC in mice. Mice received a western diet equivalent (WD; i.e., a high-fat, high-fructose, and high-cholesterol diet), high-sugar water (23.1 g/L fructose and 18.9 g/L glucose), and weekly intraperitoneal injections of carbon tetrachloride (CCl4) at a dose of 0.2 μL/g of body weight. The resulting phenotype, consisting in liver fibrosis and HCC, appeared within 24 weeks of diet/treatment initiation and presented similar histological and transcriptomic features as human NASH and NASH-driven HCC, thereby supporting the adequacy of this preclinical model for the development and evaluation of drugs that can prevent or reverse these diseases.

A Mouse Model of Hepatocellular Carcinoma Induced by Streptozotocin and High-Fat Diet

Hepatocellular carcinoma (HCC) is the most common type of liver cancer and the second most common cause of cancer-related death. HCC is associated to chronic diseases such as viral hepatitis, alcoholic, and non-alcoholic fatty liver disease (NAFLD), diabetes mellitus, and obesity, among others. Although pre-clinical models have been investigated to mimic the transition from NAFLD to HCC, they do not accurately reproduce the phenotypic evolution from simple steatosis to steatohepatitis, fibrosis/cirrhosis, and HCC. Hence, these models have failed to demonstrate the influence of diabetes on hepatic carcinogenesis. Here, we report a novel mouse model of HCC triggered by fast-developing diabetes and NAFLD. The first step consists in a single intraperitoneal injection of a low dose of streptozotocin into neonatal C57BL/6J mice to induce type 2 diabetes. In a second step, mice are fed with high-fat diet to accelerate the development of simple steatosis. Continuous high-fat diet exacerbates hepatic fat deposition with increased lobular inflammation (by activation of foam cell-like macrophages) and fibrosis (by activating hepatic stellate cells), two representative pathological traits of steatohepatitis/fibrosis. After 20 weeks, all mice developed multiple HCCs. This model of hepatic carcinogenesis triggered by diabetes mellitus and NAFLD offers the advantage of being rapid and accurately recapitulates the pathogenesis of human HCC without the need of administering hepatic carcinogens.

3,4-dimethoxychalcone induces autophagy and reduces neointimal hyperplasia and aortic lesions in mouse models of atherosclerosis

Autophagy inducers can prevent cardiovascular aging and age-associated diseases including atherosclerosis. Therefore, we hypothesized that autophagy-inducing compounds that act on atherosclerosis-relevant cells might have a protective role in the development of atherosclerosis. Here we identified 3,4-dimethoxychalcone (3,4-DC) as an inducer of autophagy in several cell lines from endothelial, myocardial and myeloid/macrophagic origin, as demonstrated by the aggregation of the autophagosome marker GFP-LC3 in the cytoplasm of cells, as well as the downregulation of its nuclear pool indicative of autophagic flux. In this respect, 3,4-DC showed a broader autophagy-inducing activity than another chalcone (4,4- dimethoxychalcone), spermidine and triethylene tetramine. Thus, we characterized the potential antiatherogenic activity of 3,4-DC in two different mouse models, namely, (i) neointima formation with smooth muscle expansion of vein segments grafted to the carotid artery and (ii) genetically predisposed ApoE-/- mice fed an atherogenic diet. In the vein graft model, local application of 3,4-DC was able to maintain the lumen of vessels and to reduce neointima lesions. In the diet-induced model, intraperitoneal injections of 3,4-DC significantly reduced the number of atherosclerotic lesions in the aorta. In conclusion, 3,4-DC stands out as an autophagy inducer with potent antiatherogenic activity.

Acyl coenzyme A binding protein (ACBP): An aging- and disease-relevant "autophagy checkpoint"

Acyl coenzyme A binding protein (ACBP), also known as diazepam-binding inhibitor (DBI), is a phylogenetically ancient protein present in some eubacteria and the entire eukaryotic radiation. In several eukaryotic phyla, ACBP/DBI transcends its intracellular function in fatty acid metabolism because it can be released into the extracellular space. This ACBP/DBI secretion usually occurs in response to nutrient scarcity through an autophagy-dependent pathway. ACBP/DBI and its peptide fragments then act on a range of distinct receptors that diverge among phyla, namely metabotropic G protein-coupled receptor in yeast (and likely in the mammalian central nervous system), a histidine receptor kinase in slime molds, and ionotropic gamma-aminobutyric acid (GABA)A receptors in mammals. Genetic or antibody-mediated inhibition of ACBP/DBI orthologs interferes with nutrient stress-induced adaptations such as sporulation or increased food intake in multiple species, as it enhances lifespan or healthspan in yeast, plant leaves, nematodes, and multiple mouse models. These lifespan and healthspan-extending effects of ACBP/DBI suppression are coupled to the induction of autophagy. Altogether, it appears that neutralization of extracellular ACBP/DBI results in "autophagy checkpoint inhibition" to unleash the anti-aging potential of autophagy. Of note, in humans, ACBP/DBI levels increase in various tissues, as well as in the plasma, in the context of aging, obesity, uncontrolled infection or cardiovascular, inflammatory, neurodegenerative, and malignant diseases.

Protein regulator of cytokinesis 1: a potential oncogenic driver

Protein regulator of cytokinesis 1 (PRC1) is involved in cytokinesis. Growing evidence suggests the association of PRC1 with multiple cancers. Here, we unveil that, in 28 cancer types, PRC1 is higher expressed in tumor tissues than in non-malignant tissues. Overexpression of PRC1 indicates unfavorable prognostic value, especially in ACC, LGG, KIRP, LICH, LUAD, MESO, PAAD, SARC and UCEC, while methylation of the PRC1 gene at sites associated with its inactivation has a favorable prognostic value in ACC, KIRP, LUAD, MESO, KIRP and LGG. Differentially expressed genes (DEGs) associated with high (> median) PRC1 expression contribute to key signaling pathways related with cell cycle, DNA damage and repair, EMT, cell migration, invasion and cell proliferation in most cancer types. More specifically, the DEGs involved in RAS/RAF/MAPK, PI3K/AKT, WNT, NOTCH, TGF-β, integrin, EMT process, focal adhesion, RHO GTPase-related pathway or microtubule cytoskeleton regulation are upregulated when PRC1 expression is above median, as confirmed for most cancers. Most importantly, high expression of PRC1 appears to be associated with an overabundance of poor-prognosis TH2 cells. Furthermore, positive correlations of PRC1 and some immune checkpoint genes (CD274, CTLA4, HAVCR2, LAG3, PDCD1, PDCD1LG2, TIGIT, and CD86) were observed in several cancers, especially BLCA, BRCA, KIRC, LUAD, LIHC, PRAD and THCA. These findings plead in favor of further studies validating the diagnostic and prognostic impact of PRC1 as well as the elaboration of pharmacological strategies for targeting PRC1.

Full-Spectrum CARS Microscopy of Cells and Tissues with Ultrashort White-Light Continuum Pulses

Coherent anti-Stokes Raman scattering (CARS) microscopy is an emerging nonlinear vibrational imaging technique that delivers label-free chemical maps of cells and tissues. In narrowband CARS, two spatiotemporally superimposed picosecond pulses, pump and Stokes, illuminate the sample to interrogate a single vibrational mode. Broadband CARS (BCARS) combines narrowband pump pulses with broadband Stokes pulses to record broad vibrational spectra. Despite recent technological advancements, BCARS microscopes still struggle to image biological samples over the entire Raman-active region (400-3100 cm^-1). Here, we demonstrate a robust BCARS platform that answers this need. Our system is based on a femtosecond ytterbium laser at a 1035 nm wavelength and a 2 MHz repetition rate, which delivers high-energy pulses used to produce broadband Stokes pulses by white-light continuum generation in a bulk YAG crystal. Combining such pulses, pre-compressed to sub-20 fs duration, with narrowband pump pulses, we generate a CARS signal with a high (<9 cm^-1) spectral resolution in the whole Raman-active window, exploiting both the two-color and three-color excitation mechanisms. Aided by an innovative post-processing pipeline, our microscope allows us to perform high-speed (≈1 ms pixel dwell time) imaging over a large field of view, identifying the main chemical compounds in cancer cells and discriminating tumorous from healthy regions in liver slices of mouse models, paving the way for applications in histopathological settings.

Cardio-, hepato- and pneumoprotective effects of autophagy checkpoint inhibition by targeting DBI/ACBP

DBI/ACBP (diazepam binding inhibitor, also known as acyl coenzyme A binding protein), acts as a paracrine inhibitor of macroautophagy/autophagy. We characterized a monoclonal antibody neutralizing mouse DBI/ACBP (a-DBI) for its cytoprotective effects on several organs (heart, liver and lung) that were damaged by surgical procedures (ligation of coronary and hepatic arteries or bile duct ligation), a variety of different toxins (acetaminophen, bleomycin, carbon tetrachloride or concanavalin A) or a methionine/choline-deficient diet (MCD). In all these models of organ damage, a-DBI prevents cell loss, inflammation and fibrosis through pathways that are blocked by pharmacological or genetic inhibition of autophagy. The hepatoprotective effects of a-DBI against MCD are mimicked by three alternative strategies to block DBI/ACBP signaling, in particular (i) induction of DBI/ACBP-specific autoantibodies, (ii) tamoxifen-inducible knockout of the Dbi gene, and (iii) a point mutation in Gabrg2 (gamma-aminobutyric acid A receptor, subunit gamma 2; Gabrg2F77I) that abolishes binding of DBI/ACBP. We conclude that a-DBI-mediated neutralization of extracellular DBI/ACBP mediates potent autophagy-dependent organ protection by on-target effects, hence unraveling a novel and potentially useful strategy for autophagy enhancement. "Autophagy checkpoint inhibition" can be achieved by targeting DBI/ACBP.

Involvement of Bcl-2 Family Proteins in Tetraploidization-Related Senescence

The B-cell lymphoma 2 (Bcl-2) family of proteins is the main regulator of apoptosis. However, multiple emerging evidence has revealed that Bcl-2 family proteins are also involved in cellular senescence. On the one hand, the different expression of these proteins determines the entry into senescence. On the other hand, entry into senescence modulates the expression of these proteins, generally conferring resistance to apoptosis. With some exceptions, senescent cells are characterized by the upregulation of antiapoptotic proteins and downregulation of proapoptotic proteins. Under physiological conditions, freshly formed tetraploid cells die by apoptosis due to the tetraploidy checkpoint. However, suppression of Bcl-2 associated x protein (Bax), as well as overexpression of Bcl-2, favors the appearance and survival of tetraploid cells. Furthermore, it is noteworthy that our laboratory has shown that the joint absence of Bax and Bcl-2 antagonist/killer (Bak) favors the entry into senescence of tetraploid cells. Certain microtubule inhibitory chemotherapies, such as taxanes and vinca alkaloids, induce the generation of tetraploid cells. Moreover, the combined use of inhibitors of antiapoptotic proteins of the Bcl-2 family with microtubule inhibitors increases their efficacy. In this review, we aim to shed light on the involvement of the Bcl-2 family of proteins in the senescence program activated after tetraploidization and the possibility of using this knowledge to create a new therapeutic strategy targeting cancer cells.

High plasma concentrations of acyl-coenzyme A binding protein (ACBP) predispose to cardiovascular disease: Evidence for a phylogenetically conserved proaging function of ACBP

Autophagy defects accelerate aging, while stimulation of autophagy decelerates aging. Acyl-coenzyme A binding protein (ACBP), which is encoded by a diazepam-binding inhibitor (DBI), acts as an extracellular feedback regulator of autophagy. As shown here, knockout of the gene coding for the yeast orthologue of ACBP/DBI (ACB1) improves chronological aging, and this effect is reversed by knockout of essential autophagy genes (ATG5, ATG7) but less so by knockout of an essential mitophagy gene (ATG32). In humans, ACBP/DBI levels independently correlate with body mass index (BMI) as well as with chronological age. In still-healthy individuals, we find that high ACBP/DBI levels correlate with future cardiovascular events (such as heart surgery, myocardial infarction, and stroke), an association that is independent of BMI and chronological age, suggesting that ACBP/DBI is indeed a biomarker of "biological" aging. Concurringly, ACBP/DBI plasma concentrations correlate with established cardiovascular risk factors (fasting glucose levels, systolic blood pressure, total free cholesterol, triglycerides), but are inversely correlated with atheroprotective high-density lipoprotein (HDL). In mice, neutralization of ACBP/DBI through a monoclonal antibody attenuates anthracycline-induced cardiotoxicity, which is a model of accelerated heart aging. In conclusion, plasma elevation of ACBP/DBI constitutes a novel biomarker of chronological aging and facets of biological aging with a prognostic value in cardiovascular disease.

Paradoxical implication of BAX/BAK in the persistence of tetraploid cells

Pro-apoptotic multi-domain proteins of the BCL2 family such as BAX and BAK are well known for their important role in the induction of mitochondrial outer membrane permeabilization (MOMP), which is the rate-limiting step of the intrinsic pathway of apoptosis. Human or mouse cells lacking both BAX and BAK (due to a double knockout, DKO) are notoriously resistant to MOMP and cell death induction. Here we report the surprising finding that BAX/BAK DKO cells proliferate less than control cells expressing both BAX and BAK (or either BAX or BAK) when they are driven into tetraploidy by transient exposure to the microtubule inhibitor nocodazole. Mechanistically, in contrast to their BAX/BAK-sufficient controls, tetraploid DKO cells activate a senescent program, as indicated by the overexpression of several cyclin-dependent kinase inhibitors and the activation of β-galactosidase. Moreover, DKO cells manifest alterations in ionomycin-mobilizable endoplasmic reticulum (ER) Ca2+ stores and store-operated Ca2+ entry that are affected by tetraploidization. DKO cells manifested reduced expression of endogenous sarcoplasmic/endoplasmic reticulum Ca2+ ATPase 2a (Serca2a) and transfection-enforced reintroduction of Serca2a, or reintroduction of an ER-targeted variant of BAK into DKO cells reestablished the same pattern of Ca2+ fluxes as observed in BAX/BAK-sufficient control cells. Serca2a reexpression and ER-targeted BAK also abolished the tetraploidy-induced senescence of DKO cells, placing ER Ca2+ fluxes downstream of the regulation of senescence by BAX/BAK. In conclusion, it appears that BAX/BAK prevent the induction of a tetraploidization-associated senescence program. Speculatively, this may contribute to the low incidence of cancers in BAX/BAK DKO mice and explain why human cancers rarely lose the expression of both BAX and BAK.

Effects of acyl-coenzyme A binding protein (ACBP)/diazepam-binding inhibitor (DBI) on body mass index

In mice, the plasma concentrations of the appetite-stimulatory and autophagy-inhibitory factor acyl-coenzyme A binding protein (ACBP, also called diazepam-binding inhibitor, DBI) acutely increase in response to starvation, but also do so upon chronic overnutrition leading to obesity. Here, we show that knockout of Acbp/Dbi in adipose tissue is sufficient to prevent high-fat diet-induced weight gain in mice. We investigated ACBP/DBI plasma concentrations in several patient cohorts to discover a similar dual pattern of regulation. In relatively healthy subjects, ACBP/DBI concentrations independently correlated with body mass index (BMI) and age. The association between ACBP/DBI and BMI was lost in subjects that underwent major weight gain in the subsequent 3-9 years, as well as in advanced cancer patients. Voluntary fasting, undernutrition in the context of advanced cancer, as well as chemotherapy were associated with an increase in circulating ACBP/DBI levels. Altogether, these results support the conclusion that ACBP/DBI may play an important role in body mass homeostasis as well as in its failure.

Antibody-mediated neutralization of ACBP/DBI has anorexigenic and lipolytic effects

We recently identified acyl coenzyme A-binding protein (ACBP)/diazepam binding inhibitor (DBI) as a novel 'hunger factor': a protein that is upregulated in human or murine obesity and that, if administered to mice, causes hyperphagy, adipogenesis and obesity. Conversely, neutralization of ACBP/DBI by systemic injection of neutralizing monoclonal antibodies or autoantibodies produced after auto-immunization against ACBP/DBI has anorexigenic and lipolytic effects. Thus, neutralization of ACBP/DBI results in reduced food intake subsequent to the activation of anorexigenic neurons and the inactivation of orexigenic neurons in the hypothalamus. Moreover, ACBP/DBI neutralization results into enhanced triglyceride lipolysis in white fat, a surge in free fatty acids in the plasma, enhanced incorporation of glycerol-derived carbon atoms into glucose, as well as an increase in β-oxidation, resulting in a net reduction of fat mass. Importantly, ACBP/DBI neutralization also stimulated an increase in autophagy in various organs, suggesting that it might mediate anti-ageing effects.

Protective Role of Hepatocyte Cyclooxygenase-2 Expression Against Liver Ischemia-Reperfusion Injury in Mice

Liver ischemia and reperfusion injury (IRI) remains a serious clinical problem affecting liver transplantation outcomes. IRI causes up to 10% of early organ failure and predisposes to chronic rejection. Cyclooxygenase-2 (COX-2) is involved in different liver diseases, but the significance of COX-2 in IRI is a matter of controversy. This study was designed to elucidate the role of COX-2 induction in hepatocytes against liver IRI. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were subjected to IRI. hCOX-2-Tg mice exhibited lower grades of necrosis and inflammation than Wt mice, in part by reduced hepatic recruitment and infiltration of neutrophils, with a concomitant decrease in serum levels of proinflammatory cytokines. Moreover, hCOX-2-Tg mice showed a significant attenuation of the IRI-induced increase in oxidative stress and hepatic apoptosis, an increase in autophagic flux, and a decrease in endoplasmic reticulum stress compared to Wt mice. Interestingly, ischemic preconditioning of Wt mice resembles the beneficial effects observed in hCOX-2-Tg mice against IRI due to a preconditioning-derived increase in endogenous COX-2, which is mainly localized in hepatocytes. Furthermore, measurement of prostaglandin E₂ (PGE₂ ) levels in plasma from patients who underwent liver transplantation revealed a significantly positive correlation of PGE₂ levels and graft function and an inverse correlation with the time of ischemia. Conclusion: These data support the view of a protective effect of hepatic COX-2 induction and the consequent rise of derived prostaglandins against IRI.

Disruption of tumor necrosis factor alpha receptor 1 signaling accelerates NAFLD progression in mice upon a high-fat diet

Obesity is accompanied by a low-grade inflammation state, characterized by increased proinflammatory cytokines levels such as tumor necrosis factor alpha (TNFα) and interleukin-1 beta (IL-1β). In this regard, there exists a lack of studies in hepatic tissue about the role of TNFα receptor 1 (TNFR1) in the context of obesity and insulin resistance during the progression of nonalcoholic fatty liver disease (NAFLD). The aim of this work was to evaluate the effects of high-caloric feeding (HFD) (40% fat, for 16 weeks) on liver inflammation-induced apoptosis, insulin resistance, hepatic lipid accumulation and its progression toward nonalcoholic steatohepatitis (NASH) in TNFR1 knock-out and wild-type mice. Mechanisms involved in HFD-derived IL-1β release and impairment of insulin signaling are still unknown, so we determined whether IL-1β affects liver insulin sensitivity and apoptosis through TNFα receptor 1 (TNFR1)-dependent pathways. We showed that knocking out TNFR1 induces an enhanced IL-1β plasmatic release upon HFD feed. This was correlated with higher hepatic and epididymal white adipose tissue mRNA levels. In vivo and in vitro assays confirmed an impairment in hepatic insulin signaling, in part due to IL-1β-induced decrease of AKT activation and diminution of IRS1 levels, followed by an increase in inflammation, macrophage (resident and recruited) accumulation, hepatocyte apoptotic process and finally hepatic damage. In addition, TNFR1 KO mice displayed higher levels of pro-fibrogenic markers. TNFR1 signaling disruption upon an HFD leads to an accelerated progression from simple steatosis to a more severe phenotype with many NASH features, pointing out a key role of TNFR1 in NAFLD progression.

PGE2 induces apoptosis of hepatic stellate cells and attenuates liver fibrosis in mice by downregulating miR-23a-5p and miR-28a-5p

MicroRNAs (miRNAs), small noncoding RNAs modulating messenger RNA (mRNA) and protein expression, have emerged as key regulatory molecules in chronic liver diseases, whose end stage is hepatic fibrosis, a major global health burden. Pharmacological strategies for prevention or treatment of hepatic fibrosis are still limited, what makes it necessary to establish a better understanding of the molecular mechanisms underlying its pathogenesis. In this context, we have recently shown that cyclooxygenase-2 (COX-2) expression in hepatocytes restricts activation of hepatic stellate cells (HSCs), a pivotal event in the initiation and progression of hepatic fibrosis. Here, we evaluated the role of COX-2 in the regulation of a specific set of miRNAs on a mouse model of CCl₄ and bile duct ligation (BDL)-induced liver fibrosis. Our results provide evidence that COX-2 represses miR-23a-5p and miR-28-5p expression in HSC. The decrease of miR-23a-5p and miR-28-5p expression promotes protection against fibrosis by decreasing the levels of pro-fibrogenic markers α-SMA and COL1A1 and increasing apoptosis of HSC. Moreover, we demonstrate that serum levels of miR-28-5p are decreased in patients with chronic liver disease. These results suggest a protective effect exerted by COX-2-derived prostanoids in the process of hepatofibrogenesis.

Benznidazole, the trypanocidal drug used for Chagas disease, induces hepatic NRF2 activation and attenuates the inflammatory response in a murine model of sepsis

Molecular mechanisms on sepsis progression are linked to the imbalance between reactive oxygen species (ROS) production and cellular antioxidant capacity. Previous studies demonstrated that benznidazole (BZL), known for its antiparasitic action on Trypanosoma cruzi, has immunomodulatory effects, increasing survival in C57BL/6 mice in a model of polymicrobial sepsis induced by cecal ligation and puncture (CLP). The mechanism by which BZL inhibits inflammatory response in sepsis is poorly understood. Also, our group recently reported that BZL is able to activate the nuclear factor erytroide-derived 2-Like 2 (NRF2) in vitro. The aim of the present work was to delineate the beneficial role of BZL during sepsis, analyzing its effects on the cellular redox status and the possible link to the innate immunity receptor TLR4. Specifically, we analyzed the effect of BZL on Nrf2 regulation and TLR4 expression in liver of mice 24hours post-CLP. BZL was able to induce NRF2 nuclear protein localization in CLP mice. Also, we found that protein kinase C (PKC) is involved in the NRF2 nuclear accumulation and induction of its target genes. In addition, BZL prompted a reduction in hepatic CLP-induced TLR4 protein membrane localization, evidencing its immunomodulatory effects. Together, our results demonstrate that BZL induces hepatic NRF2 activation with the concomitant increase in the antioxidant defenses, and the attenuation of inflammatory response, in part, by inhibiting TLR4 expression in a murine model of sepsis.

Cyclooxygenase-2 expression in hepatocytes attenuates non-alcoholic steatohepatitis and liver fibrosis in mice

Cyclooxygenase-2 (COX-2) is involved in different liver diseases but little is known about the significance of COX-2 in the development and progression of non-alcoholic steatohepatitis (NASH). This study was designed to elucidate the role of COX-2 expression in hepatocytes in the pathogenesis of steatohepatitis and hepatic fibrosis. In the present work, hepatocyte-specific COX-2 transgenic mice (hCOX-2-Tg) and their wild-type (Wt) littermates were either fed methionine-and-choline deficient (MCD) diet to establish an experimental non-alcoholic steatohepatitis (NASH) model or injected with carbon tetrachloride (CCl4) to induce liver fibrosis. In our animal model, hCOX-2-Tg mice fed MCD diet showed lower grades of steatosis, ballooning and inflammation than Wt mice, in part by reduced recruitment and infiltration of hepatic macrophages, with a corresponding decrease in serum levels of pro-inflammatory cytokines. Furthermore, hCOX-2-Tg mice showed a significant attenuation of the MCD diet-induced increase in oxidative stress and hepatic apoptosis observed in Wt mice. Even more, hCOX-2-Tg mice treated with CCl4 had significantly lower stages of fibrosis and less hepatic content of collagen, hydroxyproline and pro-fibrogenic markers than Wt controls. Collectively, our data indicates that constitutive hepatocyte COX-2 expression ameliorates NASH and liver fibrosis development in mice by reducing inflammation, oxidative stress and apoptosis and by modulating activation of hepatic stellate cells, respectively, suggesting a possible protective role for COX-2 induction in NASH/NAFLD progression.

Alternative Splicing of Neuronal Differentiation Factor TRF2 Regulated by HNRNPH1/H2

During neuronal differentiation, use of an alternative splice site on the rat telomere repeat-binding factor 2 (TRF2) mRNA generates a short TRF2 protein isoform (TRF2-S) capable of derepressing neuronal genes. However, the RNA-binding proteins (RBPs) controlling this splicing event are unknown. Here, using affinity pull-down analysis, we identified heterogeneous nuclear ribonucleoproteins H1 and H2(HNRNPH) as RBPs specifically capable of interacting with the spliced RNA segment (exon 7) of Trf2 pre-mRNA. HNRNPH proteins prevent the production of the short isoform of Trf2 mRNA, as HNRNPH silencing selectively elevates TRF2-S levels. Accordingly, HNRNPH levels decline while TRF2-S levels increase during neuronal differentiation. In addition, CRISPR/Cas9-mediated deletion of hnRNPH2 selectively accelerates the NGF-triggered differentiation of rat pheochromocytoma cells into neurons. In sum, HNRNPH is a splicing regulator of Trf2 pre-mRNA that prevents the expression of TRF2-S, a factor implicated in neuronal differentiation.

Regulation of MicroRNA 183 by Cyclooxygenase 2 in Liver Is DEAD-Box Helicase p68 (DDX5) Dependent: Role in Insulin Signaling

Cyclooxygenase (COX) catalyzes the first step in prostanoid biosynthesis and exists as two isoforms. COX-1 is a constitutive enzyme involved in physiological processes, whereas COX-2 is induced by a variety of stimuli. MicroRNAs (miRNAs) are noncoding RNAs that function as key posttranscriptional regulators of gene expression. Although it is known that COX-2 expression is regulated by miRNAs, there are no data regarding COX-2 involvement in miRNA regulation. Considering our previous results showing that COX-2 expression in hepatocytes protects against insulin resistance, we evaluated the role of COX-2 in the regulation of a specific set of miRNAs implicated in insulin signaling in liver cells. Our results provide evidence of the molecular basis for a novel function of COX-2 in miRNA processing. COX-2 represses miRNA 23b (miR-23b), miR-146b, and miR-183 expression in liver cells by increasing the level of DEAD-box helicase p68 (DDX5) through phosphatidylinositol 3-kinase (PI3K)/p300 signaling and by modulating the enzymatic function of the Drosha (RNase type III) complex through its physical association with DDX5. The decrease of miR-183 expression promotes protection against insulin resistance by increasing insulin receptor substrate 1 (IRS1) levels. These results indicate that the modulation of miRNA processing by COX-2 is a key event in insulin signaling in liver and has potential clinical implications for the management of various hepatic dysfunctions.

Hepatic cyclooxygenase-2 expression protects against diet-induced steatosis, obesity, and insulin resistance

Accumulation evidence links obesity-induced inflammation as an important contributor to the development of insulin resistance, which plays a key role in the pathophysiology of obesity-related diseases such as type 2 diabetes and nonalcoholic fatty liver disease. Cyclooxygenase (COX)-1 and -2 catalyze the first step in prostanoid biosynthesis. Because adult hepatocytes fail to induce COX-2 expression regardless of the proinflammatory stimuli used, we have evaluated whether this lack of expression under mild proinflammatory conditions might constitute a permissive condition for the onset of insulin resistance. Our results show that constitutive expression of human COX-2 (hCOX-2) in hepatocytes protects against adiposity, inflammation, and, hence, insulin resistance induced by a high-fat diet, as demonstrated by decreased hepatic steatosis, adiposity, plasmatic and hepatic triglycerides and free fatty acids, increased adiponectin-to-leptin ratio, and decreased levels of proinflammatory cytokines, together with an enhancement of insulin sensitivity and glucose tolerance. Furthermore, hCOX-2 transgenic mice exhibited increased whole-body energy expenditure due in part by induction of thermogenesis and fatty acid oxidation. The analysis of hepatic insulin signaling revealed an increase in insulin receptor-mediated Akt phosphorylation in hCOX-2 transgenic mice. In conclusion, our results point to COX-2 as a potential therapeutic target against obesity-associated metabolic dysfunction.

Regulation of 15-hydroxyprostaglandin dehydrogenase expression in hepatocellular carcinoma

Cyclooxygenase-2 (COX-2), a rate limiting step in arachidonic acid cascade, plays a key role in the biosynthesis of prostaglandin E2 (PGE2) upon inflammatory stimuli, growth factors, hormones and other cellular stresses. Overproduction of PGE2 stimulates proliferation of various cancer cells, confers resistance to apoptosis and favors metastasis and angiogenesis. The steady-state level of PGE2 is maintained by interplay between the biosynthetic pathway including COX and PGE2 synthases and the catabolic pathways involving nicotinamide adenine dinucleotide (NAD(+))-dependent 15-hydroxyprostaglandin dehydrogenase (15-PGDH). 15-PGDH is a crucial enzyme responsible for the biological inactivation of PGE2. Adult hepatocytes fail to induce COX-2 expression regardless of the pro-inflammatory factors used. COX-2 is induced in hepatocytes after partial hepatectomy (PH), in animal models of cirrhosis, in human hepatoma cell lines, in human HCC and after HBV and HCV infection. However, no data are available regarding 15-PGDH expression in HCC. Our results show that 15-PGDH is downregulated in human hepatoma cells with a high COX-2 expression, in chemical and genetic murine models of HCC and in human HCC biopsies. Moreover, 15-PGDH expression is suppressed by EGF (epidermal growth factor) and HGF (hepatocyte growth factor) mainly involving PI3K (phosphatidylinositol-3-kinase), ERK (extracellular signal-regulated kinase) and p38MAPK (mitogen-activated protein kinase) activation. Conversely, ectopic expression of 15-PGDH induces apoptosis in hepatoma cells and decreases the growth of hepatoma cells in nude mice whereas the silencing of 15-PGDH increases the tumor formation. These data suggest a potential therapeutic application of 15-PGDH in HCC.

EGF promotes neuroendocrine-like differentiation of prostate cancer cells in the presence of LY294002 through increased ErbB2 expression independent of the phosphatidylinositol 3-kinase-AKT pathway

An increased neuroendocrine (NE) cell population in prostate cancer is associated with more aggressive disease and recurrence after androgen-deprivation therapy, although the mechanism responsible is unknown. In this study, we report that the treatment of LNCaP cells with epidermal growth factor (EGF) in the presence of LY294002, an inhibitor of the phosphoinositol 3'-kinase (PI3K)-AKT pathway, induced an increase of levels and activity of ErbB2. Under these conditions, we also observed cell survival and NE differentiation. When we treated with wortmannin, another PI3K inhibitor, or we knocked down PI3K or AKT isoforms in the presence of EGF, ErbB2 up-regulation was not observed, suggesting that the increase of ErbB2 induced by EGF plus LY294002 is not mediated by the PI3K-Akt pathway. Other targets of LY294002 were also discounted. We also show that ErbB2 up-regulation is directly involved in neuroendocine differentiation but not in cell survival as ErbB2 levels increased in parallel with NE differentiation marker levels, whereas ErbB2 knockdown reduced them; other NE differentiation inducers also increased the ErbB2 levels and the immunohistochemical analysis of prostate cancer samples showed colocalization of ErbB2 and chromogranin A. We found that, in LNCaP cells, EGF in combination with LY294002 increased ErbB2 levels by a PI3K/AKT-independent mechanism and that this increase was associated with the acquisition of a NE phenotype. These results suggest that is worth reconsidering ErbB2 as a drug target in prostate cancer and this should be kept in mind when designing new clinical schedules for the treatment of this disease.

Cyclooxygenase-2 is a target of microRNA-16 in human hepatoma cells

Cyclooxygenase-2 (COX-2) expression has been detected in human hepatoma cell lines and in human hepatocellular carcinoma (HCC); however, the contribution of COX-2 to the development of HCC remains controversial. COX-2 expression is higher in the non-tumoral tissue and inversely correlates with the differentiation grade of the tumor. COX-2 expression depends on the interplay between different cellular pathways involving both transcriptional and post-transcriptional regulation. The aim of this work was to assess whether COX-2 could be regulated by microRNAs in human hepatoma cell lines and in human HCC specimens since these molecules contribute to the regulation of genes implicated in cell growth and differentiation. Our results show that miR-16 silences COX-2 expression in hepatoma cells by two mechanisms: a) by binding directly to the microRNA response element (MRE) in the COX-2 3'-UTR promoting translational suppression of COX-2 mRNA; b) by decreasing the levels of the RNA-binding protein Human Antigen R (HuR). Furthermore, ectopic expression of miR-16 inhibits cell proliferation, promotes cell apoptosis and suppresses the ability of hepatoma cells to develop tumors in nude mice, partially through targeting COX-2. Moreover a reduced miR-16 expression tends to correlate to high levels of COX-2 protein in liver from patients affected by HCC. Our data show an important role for miR-16 as a post-transcriptional regulator of COX-2 in HCC and suggest the potential therapeutic application of miR-16 in those HCC with a high COX-2 expression.