Diazepam binding inhibitor and total cholesterol plasma levels in cirrhosis and hepatocellular carcinoma

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.

Influence of cholesterol on cancer progression and therapy

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Abnormality in blood cholesterol level is significantly correlated with risk of different cancers.

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Majority of tumor tissue from cancer patient exhibits overexpression of LDLR and ACAT for supporting rapid cancer cell proliferation.

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Alteration of the cholesterol metabolism in cancer cells hampers therapeutic response.

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Targeting cholesterol metabolism for treatment of cancer with other conventional chemotherapeutic drugs appears to be beneficial.

Cholesterol is a fundamental molecule necessary for the maintenance of cell structure and is vital to various normal biological functions. It is a key factor in lifestyle-related diseases including obesity, diabetes, cardiovascular disease, and cancer. Owing to its altered serum chemistry status under pathological states, it is now being investigated to unravel the mechanism by which it triggers various health complications. Numerous clinical studies in cancer patients indicate an alteration in blood cholesterol level (either decreased or increased) in comparison to normal healthy individuals. This article elaborates on our understanding as to how cholesterol is being hijacked in the malignancy for the development, survival, stemness, progression, and metastasis of cancerous cells. Also, it provides a glimpse of how cholesterol derived entities, alters the signaling pathway towards their advantage. Moreover, deregulation of the cholesterol metabolism pathway has been often reported to hamper various treatment strategies in different cancer. In this context, attempts have been made to bring forth its relevance in being targeted, in pre-clinical and clinical studies for various treatment modalities. Thus, understanding the role of cholesterol and deciphering associated molecular mechanisms in cancer progression and therapy are of relevance towards improvement in the management of various cancers.

Evaluation of TSPO PET Ligands [18F]VUIIS1009A and [18F]VUIIS1009B: Tracers for Cancer Imaging

PURPOSE

Positron emission tomography (PET) ligands targeting translocator protein (TSPO) are potential imaging diagnostics of cancer. In this study, we report two novel, high-affinity TSPO PET ligands that are 5,7 regioisomers, [¹⁸F]VUIIS1009A ([¹⁸F]3A) and [¹⁸F]VUIIS1009B ([¹⁸F]3B), and their initial in vitro and in vivo evaluation in healthy mice and glioma-bearing rats.

PROCEDURES

VUIIS1009A/B was synthesized and confirmed by X-ray crystallography. Interactions between TSPO binding pocket and novel ligands were evaluated and compared with contemporary TSPO ligands using 2D ¹H-¹⁵N heteronuclear single quantum coherence (HSQC) spectroscopy. In vivo biodistribution of [¹⁸F]VUIIS1009A and [¹⁸F]VUIIS1009B was carried out in healthy mice with and without radioligand displacement. Dynamic PET imaging data were acquired simultaneously with [¹⁸F]VUIIS1009A/B injections in glioma-bearing rats, with binding reversibility and specificity evaluated by radioligand displacement. In vivo radiometabolite analysis was performed using radio-TLC, and quantitative analysis of PET data was performed using metabolite-corrected arterial input functions. Imaging was validated with histology and immunohistochemistry.

RESULTS

Both VUIIS1009A (3A) and VUIIS1009B (3B) were found to exhibit exceptional binding affinity to TSPO, with observed IC₅₀ values against PK11195 approximately 500-fold lower than DPA-714. However, HSQC NMR suggested that VUIIS1009A and VUIIS1009B share a common binding pocket within mammalian TSPO (mTSPO) as DPA-714 and to a lesser extent, PK11195. [¹⁸F]VUIIS1009A ([¹⁸F]3A) and [¹⁸F]VUIIS1009B ([¹⁸F]3B) exhibited similar biodistribution in healthy mice. In rats bearing C6 gliomas, both [¹⁸F]VUIIS1009A and [¹⁸F]VUIIS1009B exhibited greater binding potential (k ₃/k ₄)in tumor tissue compared to [¹⁸F]DPA-714. Interestingly, [¹⁸F]VUIIS1009B exhibited significantly greater tumor uptake (V _T) than [¹⁸F]VUIIS1009A, which was attributed primarily to greater plasma-to-tumor extraction efficiency.

CONCLUSIONS

The novel PET ligand [¹⁸F]VUIIS1009B exhibits promising characteristics for imaging glioma; its superiority over [¹⁸F]VUIIS1009A, a regioisomer, appears to be primarily due to improved plasma extraction efficiency. Continued evaluation of [¹⁸F]VUIIS1009B as a high-affinity TSPO PET ligand for precision medicine appears warranted.

Metabolomic and transcriptomic profiling of hepatocellular carcinomas in Hras12V transgenic mice

Activation of the Ras/MAPK pathway is prevalently involved in the occurrence and development of hepatocellular carcinoma (HCC). However, its effects on the deregulated cellular metabolic processes involved in HCC in vivo remain unknown. In this study, a mouse model of HCC induced by hepatocyte-specific expression of the Hras12V oncogene was investigated using an integrative analysis of metabolomics and transcriptomics data. Consistent with the phenotype of abundant lipid droplets in HCC, the lipid biosynthesis in HCC was significantly enhanced by (1) a sufficient supply of acetyl-CoA from enhanced glycolysis and citrate shuttle activity; (2) a sufficient supply of NADPH from enhanced pentose phosphate pathway (PPP) activity; (3) upregulation of key enzymes associated with lipid biosynthesis; and (4) downregulation of key enzymes associated with bile acid biosynthesis. In addition, glutathione (GSH) was significantly elevated, which may result from a sufficient supply of 5-oxoproline and L-glutamate as well as an enhanced reduction in the process of GSSG being turned into GSH by NADPH. The high level of GSH along with elevated Bcl2 and Ucp2 expression may contribute to a normal level of reactive oxygen species (ROS) in HCC. In conclusion, our results suggest that the lipid metabolism, glycolysis, PPP, tricarboxylic acid (TCA) cycle, citrate shuttle activity, bile acid synthesis, and redox homeostasis in the HCC induced by ras oncogene are significantly perturbed, and these altered metabolic processes may play crucial roles in the carcinogenesis, development, and pathological characteristics of HCC.

Long-chain acyl-CoA esters in metabolism and signaling: Role of acyl-CoA binding proteins

Long-chain fatty acyl-CoA esters are key intermediates in numerous lipid metabolic pathways, and recognized as important cellular signaling molecules. The intracellular flux and regulatory properties of acyl-CoA esters have been proposed to be coordinated by acyl-CoA-binding domain containing proteins (ACBDs). The ACBDs, which comprise a highly conserved multigene family of intracellular lipid-binding proteins, are found in all eukaryotes and ubiquitously expressed in all metazoan tissues, with distinct expression patterns for individual ACBDs. The ACBDs are involved in numerous intracellular processes including fatty acid-, glycerolipid- and glycerophospholipid biosynthesis, β-oxidation, cellular differentiation and proliferation as well as in the regulation of numerous enzyme activities. Little is known about the specific roles of the ACBDs in the regulation of these processes, however, recent studies have gained further insights into their in vivo functions and provided further evidence for ACBD-specific functions in cellular signaling and lipid metabolic pathways. This review summarizes the structural and functional properties of the various ACBDs, with special emphasis on the function of ACBD1, commonly known as ACBP.

Overexpression of PGC‑1α enhances cell proliferation and tumorigenesis of HEK293 cells through the upregulation of Sp1 and Acyl-CoA binding protein

Peroxisome proliferator-activated receptor γ coactivator-1α (PGC‑1α), a coactivator interacting with multiple transcription factors, regulates several metabolic processes. Although recent studies have focused on the role of PGC‑1α in cancer, the underlying molecular mechanism has not been clarified. Therefore, we evaluated the role of PGC‑1α in cell proliferation and tumorigenesis using human embryonic kidney (HEK)293 cells and colorectal cancer cells. We established stable HEK293 cell lines expressing PGC‑1α and examined cell proliferation, anchorage-independent growth, and oncogenic potential compared to parental HEK293 cells. To identify the molecular PGC‑1α targets for increased cell proliferation and tumorigenesis, the GeneFishing™ DEG (differentially expressed genes) screening system was used. Western blot analysis and immunofluorescence staining were performed for a regulated gene product to confirm the results. Forced expression of PGC‑1α in HEK293 cells promoted cell proliferation and anchorage-independent growth in soft agar. In addition, HEK293 cells that highly expressed PGC‑1α showed enhanced tumor formation when subcutaneously injected into the bilateral flanks of immunodeficient mice. The results of the GeneFishing DEG screening system identified one upregulated gene (Acyl-CoA binding protein; ACBP). Real-time RT-PCR, western blot analysis, and immunofluorescence staining showed that ACBP was markedly increased in HEK293 cells stably overexpressing PGC‑1α (PGC‑1α-HEK293 cells) compared to those expressing an empty vector. In PGC‑1α, ACBP, and specificity protein 1 (Sp1) siRNA knockdown experiments in PGC‑1α-HEK293 and SNU-C4 cells, we also observed inhibition of cell proliferation, reduced expression of antioxidant enzymes, and increased H2O2-induced reactive oxygen species production and apoptosis. These findings suggest that PGC‑1α may promote cell proliferation and tumorigenesis through upregulation of ACBP. We provide evidence that increased Sp1 expression might contribute to enhanced ACBP expression by PGC‑1α. The current results also suggest that PGC‑1α, whose expression is related to enhanced cell proliferation and tumorigenesis, may be a good candidate molecular target for cancer therapy.

Identification of gene co-expression clusters in liver tissues from multiple porcine populations with high and low backfat androstenone phenotype

Background

Boar taint is principally caused by accumulation of androstenone and skatole in adipose tissues. Studies have shown high heritability estimates for androstenone whereas skatole production is mainly dependent on nutritional factors. Androstenone is a lipophilic steroid mainly metabolized in liver. Majority of the studies on hepatic androstenone metabolism focus only on a single breed and very few studies account for population similarities/differences in gene expression patterns. In this work, we concentrated on population similarities in gene expression to identify the common genes involved in hepatic androstenone metabolism of multiple pig populations. Based on androstenone measurements, publicly available gene expression datasets from three porcine populations were compiled into either low or high androstenone dataset. Gene expression correlation coefficients from these datasets were converted to rank ratios and joint probabilities of these rank ratios were used to generate dataset specific co-expression clusters. Finally, these networks were clustered using a graph clustering technique.

Results

Cluster analysis identified a number of statistically significant co-expression clusters in the dataset. Further enrichment analysis of these clusters showed that one of the clusters from low androstenone dataset was highly enriched for xenobiotic, drug, cholesterol and lipid metabolism and cytochrome P450 associated metabolism of drugs and xenobiotics. Literature references revealed that a number of genes in this cluster were involved in phase I and phase II metabolism. Physical and functional similarity assessment showed that the members of this cluster were dispersed across multiple clusters in high androstenone dataset, possibly indicating a weak co-expression of these genes in high androstenone dataset.

Conclusions

Based on these results we hypothesize that majority of the genes in this cluster forms a signature co-expression cluster in low androstenone dataset in our experiment and that majority of the members of this cluster might be responsible for hepatic androstenone metabolism across all the three populations used in our study. We propose these results as a background work towards understanding breed similarities in hepatic androstenone metabolism. Additional large scale experiments using data from multiple porcine breeds are necessary to validate these findings.

Electronic supplementary material

The online version of this article (doi:10.1186/s12863-014-0158-8) contains supplementary material, which is available to authorized users.

Preclinical imaging evaluation of novel TSPO-PET ligand 2-(5,7-Diethyl-2-(4-(2-[(18)F]fluoroethoxy)phenyl)pyrazolo[1,5-a]pyrimidin-3-yl)-N,N-diethylacetamide ([ (18)F]VUIIS1008) in glioma

PURPOSE

Translocator protein (TSPO) concentrations are elevated in glioma, suggesting a role for TSPO positron emission tomography (PET) imaging in this setting. In preclinical PET studies, we evaluated a novel, high-affinity TSPO PET ligand, [(18)F]VUIIS1008, in healthy mice and glioma-bearing rats.

PROCEDURES

Dynamic PET data were acquired simultaneously with [(18)F]VUIIS1008 injection, with binding reversibility and specificity evaluated in vivo by non-radioactive ligand displacement or blocking. Compartmental analysis of PET data was performed using metabolite-corrected arterial input functions. Imaging was validated with histology and immunohistochemistry.

RESULTS

[(18)F]VUIIS1008 exhibited rapid uptake in TSPO-rich organs. PET ligand uptake was displaceable with non-radioactive VUIIS1008 or PBR06 in mice. Tumor accumulation of [(18)F]VUIIS1008 was blocked by pretreatment with VUIIS1008 in rats. [(18)F]VUIIS1008 exhibited improved tumor-to-background ratio and higher binding potential in tumors compared to a structurally similar pyrazolopyrimidine TSPO ligand, [(18)F]DPA-714.

CONCLUSIONS

The PET ligand [(18)F]VUIIS1008 exhibits promising characteristics as a tracer for imaging glioma. Further translational studies appear warranted.

Reduced fasting plasma levels of diazepam-binding inhibitor in adolescents with anorexia nervosa

OBJECTIVE

Altered expression and/or function, both peripherally and centrally, of various neuropeptides is involved in the neurophysiology of anorexia nervosa (AN). Diazepam-binding inhibitor (DBI) is an interesting peptide for understanding this crosstalk. The aim of this work was to assess fasting plasma levels of DBI and leptin in patients with AN.

METHOD

Twenty-four AN adolescents were recruited together with 10 age-comparable healthy controls. Neuropeptide determinations were performed on plasma samples by enzyme-linked immunosorbent assays. Patients with AN were further characterized for the presence of a depressive state or anxiety by using, respectively, the Children's Depression Inventory or the State-Trait Anxiety Inventory form Y.

RESULTS

Levels of both plasma DBI and leptin were reduced in patients with AN (∼40 and ∼70%, respectively). DBI levels displayed a tendency to increase in the presence of a depressive state, although not with anxiety, whereas leptin levels correlated exclusively with body mass index.

DISCUSSION

These data further extend our knowledge of neuropeptide dysfunction in AN, and plasma DBI may represent a marker for this disease, in particular considering its correlation with comorbid mood disorders.

Differential gene expression in mouse primary hepatocytes exposed to the peroxisome proliferator-activated receptor alpha agonists

Background

Fibrates are a unique hypolipidemic drugs that lower plasma triglyceride and cholesterol levels through their action as peroxisome proliferator-activated receptor alpha (PPARα) agonists. The activation of PPARα leads to a cascade of events that result in the pharmacological (hypolipidemic) and adverse (carcinogenic) effects in rodent liver.

Results

To understand the molecular mechanisms responsible for the pleiotropic effects of PPARα agonists, we treated mouse primary hepatocytes with three PPARα agonists (bezafibrate, fenofibrate, and WY-14,643) at multiple concentrations (0, 10, 30, and 100 μM) for 24 hours. When primary hepatocytes were exposed to these agents, transactivation of PPARα was elevated as measured by luciferase assay. Global gene expression profiles in response to PPARα agonists were obtained by microarray analysis. Among differentially expressed genes (DEGs), there were 4, 8, and 21 genes commonly regulated by bezafibrate, fenofibrate, and WY-14,643 treatments across 3 doses, respectively, in a dose-dependent manner. Treatments with 100 μM of bezafibrate, fenofibrate, and WY-14,643 resulted in 151, 149, and 145 genes altered, respectively. Among them, 121 genes were commonly regulated by at least two drugs. Many genes are involved in fatty acid metabolism including oxidative reaction. Some of the gene changes were associated with production of reactive oxygen species, cell proliferation of peroxisomes, and hepatic disorders. In addition, 11 genes related to the development of liver cancer were observed.

Conclusion

Our results suggest that treatment of PPARα agonists results in the production of oxidative stress and increased peroxisome proliferation, thus providing a better understanding of mechanisms underlying PPARα agonist-induced hepatic disorders and hepatocarcinomas.

Peripheral benzodiazepine receptor ligands induce apoptosis and cell cycle arrest in human hepatocellular carcinoma cells and enhance chemosensitivity to paclitaxel, docetaxel, doxorubicin and the Bcl-2 inhibitor HA14-1

BACKGROUND/AIMS

Hepatocellular carcinoma (HCC) is one of the most common causes of cancer deaths worldwide. Thus, novel therapies are urgently needed. A promising approach is the use of peripheral benzodiazepine receptor (PBR) ligands which inhibit the proliferation of various tumors.

METHODS

PBR expression both in human HCC cell lines and in tumor specimens of HCC patients was analyzed by RT-PCR and immunostaining. To evaluate PBR ligands for the treatment of HCC, we tested their effects on human HCC cells.

RESULTS

PBR was localized to the mitochondria both of HCC cell lines and tumor tissues of HCC patients. In contrast, normal liver did not express PBR. PBR ligands inhibited the proliferation of HCC cell lines by inducing apoptosis and cell cycle arrest. Apoptosis was characterized by a breakdown of the mitochondrial membrane potential, caspase-3 activation and nuclear degradation. Furthermore, pro-apoptotic Bax was overexpressed while anti-apoptotic Bcl-2 and Bcl-X(L) were suppressed. Cell cycle was arrested both at the G1/S- and G2/M-checkpoints. Synergistic anti-neoplastic effects were obtained by a combination of PBR ligands with cytostatic drugs (paclitaxel, docetaxel, doxorubicin), or with an experimental Bcl-2 inhibitor.

CONCLUSIONS

This is the first report on the induction of apoptosis and cell cycle arrest by PBR ligands in HCC cells. Moreover, PBR ligands sensitized HCC cells to taxans and doxorubicin.

Functional characterization and expression of PBR in rat gastric mucosa: stimulation of chloride secretion by PBR ligands

Previous studies have demonstrated that gastric mucosa contained high levels of the polypeptide diazepam binding inhibitor, the endogenous ligand of the peripheral-type benzodiazepine receptor (PBR). However, the expression and function of this receptor protein in these tissues have not been investigated. Immunohistochemistry identified an intense PBR immunoreactivity in the mucous and parietal cells of rat gastric fundus and in the mucous cells of antrum. Immunoelectron microscopy revealed the mitochondrial localization of PBR in these cells. Binding of isoquinoline PK 11195 and benzodiazepine Ro5-4864 to gastric membranes showed that fundus had more PBR-binding sites than antrum, displaying higher affinity for PK 11195 than Ro5-4864. In a Ussing chamber, PK 11195 and Ro5-4864 increased short-circuit current (I(sc)) in fundic and antral mucosa in a concentration-dependent manner in the presence of GABA(A) and central benzodiazepine receptor (CBR) blockers. This increase in I(sc) was abolished after external Cl(-) substitution and was sensitive to chloride channels or transporter inhibitors. PK 11195-induced chloride secretion was also 1) sensitive to verapamil and extracellular calcium depletion, 2) blocked by thapsigargin and intracellular calcium depletion, and 3) abolished by the mitochondrial pore transition complex inhibitor cyclosporine A. PK 11195 had no direct effect on H(+) secretion, indicating that it stimulates a component of Cl(-) secretion independent of acid secretion in fundic mucosa. These data demonstrate that mucous and parietal cells of the gastric mucosa express mitochondrial PBR functionally coupled to Ca(2+)-dependent Cl(-) secretion, possibly involved in the gastric mucosa protection.

Increased expression of peripheral benzodiazepine receptors and diazepam binding inhibitor in human tumors sited in the liver

The peripheral benzodiazepine receptor system triggers intracellular metabolic events and has been associated with cell proliferation. Its endogenous ligand, the diazepam binding inhibitor, contributes to steroidogenesis by promoting cholesterol delivery to the inner mitochondrial membrane. The present study was undertaken to verify whether this system is altered in tumors sited in the liver. Peripheral benzodiazepine receptors and diazepam binding inhibitor were studied using immunocytochemistry and in situ hybridization in 9 human tumors sited in the liver, in liver hyperplasia, cirrhotic nodular regeneration, intestinal adenocarcinoma and in surrounding non-tumoral tissue. Immunocytochemical staining and in situ hybridization demonstrated that peripheral benzodiazepine receptors and diazepam binding inhibitor were more prominently expressed in neoplastic cells than in non-tumoral tissue. They were present in the same cells, suggesting that diazepam binding inhibitor may act in an intracrine manner in these cells. Higher peripheral benzodiazepine receptors and diazepam binding inhibitor expression in tumor cells suggest an implication of this system in the metabolism of neoplastic cells. Furthermore the evaluation of peripheral benzodiazepine receptor and diazepam binding inhibitor expression might be useful in evaluating malignancy and in diagnostic approaches of tumors in liver tissue.