Fuad Fares

Peripheral-type benzodiazepine receptors in the regulation of proliferation of MCF-7 human breast carcinoma cell line

Peripheral-type benzodiazepine receptors (PBR) have been implicated in cell proliferation. The aim of the present study was to test the effect of the PBR ligands PK 11195 and Ro 5-4864 and the central-type benzodiazepine receptor ligand clonazepam on breast carcinoma cell proliferation, using [3H] thymidine incorporation. We then carried out a study to identify where the PBR-specific ligands Ro 5-4864 and PK 11195 act in the cell cycle, using flow cytometric analysis. We found PBR expression in the malignant breast cancer tumors, representing various levels of estrogen and/or progesterone receptors, as well as in the MCF-7 breast carcinoma cell line. PK 11195 and Ro 5-4864 inhibited cell proliferation at concentrations of 10(-5) to 10(-4) M, while clonazepam (the central-type benzodiazepine receptor-specific ligand) had no effect. In this same concentration range, PK 11195 and Ro 5-4864, in contrast to clonazepam, induced an accumulation of MCF-7 cells in both the G0-G1 and G2-M phases of the cell cycle. The present study demonstrates that PBR ligands play a role in regulating cell proliferation in the human breast carcinoma cell line MCF-7.

Modulatory action of benzodiazepines on human term placental steroidogenesis in vitro

Peripheral benzodiazepine (BZ) binding sites (PBzS) were characterized on placental explant membranes. [3H]PK 11195, an isoquinoline carboxamide derivative, which is a ligand specific for PBzS, labeled these sites with an equilibrium dissociation constant of 2.1 nM; the maximal number of binding sites was 396 fmol/mg protein. The effect of various BZ ligands and PK 11195 on the secretion of progesterone (P4) and estradiol-17 beta (E2) from human term placental explants was studied. Exposure of placental explants to low doses (10(-8) M) of Ro 5-4864, a BZ ligand which binds with high affinity to PBzS, caused a significant (P less than 0.05) increase in the secretion of P4 and E2 into the media (2.4- and 1.4-fold, respectively). On the other hand, high doses (10(-5) M) of Ro 5-4864 caused a significant (P less than 0.05) decrease in the secretion of P4 and E2 into the media. Also, exposure of explants to diazepam (10(-7) M) and PK 11195 (10(-6) M) caused a significant increase in P4 and E2 secretion into the media. In contrast, clonazepam, a BZ ligand specific for the central-type receptors, had no effect on the secretion of either steroid. The combination of diazepam (10(-7) M) or Ro 5-4864 (10(-8) M) with PK 11195 (10(-6) M) did not enhance the stimulatory effects obtained with each agent alone. The effects exerted by Ro 5-4864, PK 11195, and diazepam may be mediated via PBzS.

Characterization of peripheral benzodiazepine binding sites in human term placenta

Peripheral benzodiazepine binding sites were characterized in human term placental membranes using [3H]PK 11195, which is a ligand specific for peripheral benzodiazepine binding sites. Binding of [3H]PK 11195 to human term placental membranes was found to be saturable. Scatchard analysis revealed a single population of binding sites (r = 0.98). Equilibrium dissociation constant (KD) was 2.1 +/- 0.3 nM, and density of binding sites (Bmax) was 920 +/- 105 fmol/mg protein. The KD value calculated from kinetic experiments was 3.6 +/- 0.2 nM. The ability of various drugs to displace [3H]PK 11195 from human term placental binding sites was tested: the inhibition constants (KI) for PK 11195, Ro 5-4864, and diazepam were 2.9, 11.8, and 177 nM, respectively, whereas clonazepam, methyl-beta-carboline-3-carboxylate, Ro 15-1788, chlordiazepoxide, atropine, and estradiol were inefficient in displacing [3H]PK 11195 (KI greater than 10(-5) M).

Gonadotropin- and estrogen-induced increase of peripheral-type benzodiazepine binding sites in the hypophyseal-genital axis of rats

Peripheral-type benzodiazepine binding sites (PBS) were demonstrated in the cell membranes of various organs (ovary, uterus, oviduct, pituitary and kidney) of mature and immature female rats by using the PBS-specific ligand [3H]PK 11195. The equilibrium dissociation constants of [3H]PK 11195 for PBS in mature rats ranged from 3 to 4 nM. The specific binding of [3H]PK 11195 (2 nM) in the hypophyseal-genital axis of immature (19-27 days old) female rats was found to be significantly increased in the ovary and uterus, concurrently with the increase in age. Administration of pregnant mare serum gonadotropin or diethylstilbestrol to immature rats increased the density of PBS in the ovary and uterus 2- to 3-fold but no change was found in the kidney. The affinity of [3H]PK 11195 to these tissues did not change following hormonal treatment. These results suggest that gonadotropin and estrogen are involved in the induction of PBS in the organs of the hypophyseal-genital axis in female rats.

Food deprivation modulates γ-aminobutyric acid receptors and peripheral benzodiazepine binding sites in rats

The effect of 5 days of food deprivation followed by 5 days of refeeding on gamma-aminobutyric acid (GABA) receptors, central benzodiazepine receptors (CBR), and peripheral benzodiazepine binding sites (PBzS) was studied in female Sprague-Dawley rats. Starvation induced a decrease in the density of PBzS in peripheral organs: adrenal (35%; P less than 0.001), kidney (33%; P less than 0.01), and heart (34%; P less than 0.001). Restoration of [3H]PK 11195 binding to normal values was observed in all three organs after 5 days of refeeding. The density of PBzS in the ovary, pituitary, and hypothalamus was not affected by starvation. Food deprivation resulted in a 35% decrease in cerebellar GABA receptors (P less than 0.01), while CBR in the hypothalamus and cerebral cortex remained unaltered. The changes in PBzS observed in the heart and kidney may be related to the long-term metabolic stress associated with starvation and to the functional changes occurring in these organs. The down-regulation of the adrenal PBzS is attributable to the suppressive effect of hypercortisolemia on pituitary ACTH release. The reduction in cerebellar GABA receptors may be an adaptive response to food deprivation stress and may be relevant to the proaggressive effect of hunger.

Hormonal regulation of peripheral benzodiazepine binding sites in female rat adrenal gland and kidney.

The effect of hypophysectomy and hormonal replacement on the density of peripheral benzodiazepine binding sites (PBS) in rat adrenal gland and kidney was studied. In the adrenal gland, hypophysectomy caused a significant decrease of 3-fold in PBS density. In the kidney, in contrast, hypophysectomy did not affect PBS density. In the adrenal gland, adrenocorticotropic hormone (ACTH) administered to hypophysectomized rats caused a significant increase of more than 5-fold in PBS density compared to untreated hypophysectomized rats, and of more than 1.6-fold compared to intact rats. In contrast, the hormones pregnant mare serum gonadotropin (PMSG), diethylstilbestrol (DES), and hydrocortisone (HC), administered to hypophysectomized rats, failed to restore PBS density in the adrenal gland. In the kidney, HC administered to hypophysectomized rats caused an increase of 1.4-fold in PBS density compared to untreated hypophysectomized and intact rats. In contrast, the hormones ACTH, PMSG, and DES, administered to hypophysectomized rats, did not affect PBS density in the kidney. None of the hormones tested altered the equilibrium dissociation constant of PBS in either the adrenal gland or the kidney. These findings indicate that PBS density in rat adrenal gland and kidney is hormonally modulated.

Growth hormone (GH) retardation of muscle damage due to immobilization in old rats. Possible intervention with a new long-acting recombinant GH.

Four weeks immobilization of the right leg of aged rats (26 months old) caused a marked 31% and 27% reduction of muscle mass of the plantaris and soleus muscles, respectively. In animals treated with 0.6 mg/kg body weight of growth hormone (GH), the reduction of weight of the above muscles was only 14.7 and 16.1%, respectively. Biochemical studies of the level of acid phosphatase as a marker of muscle catabolism showed a significant increase of this enzyme in the immobilized muscles. GH treatment had a positive effect in curtailing the increase due to immobilization. Studies on muscle protein oxidation used as another measure of damage in immobilized animals, showed a 400% increase in protein carbonyls in plantaris muscles. GH administration reduced this value significantly. One major issue hampering the clinical use of human GH (hGH) is its short half-life in vivo (14 min). In a previous work it was possible to enhance the in vivo longevity of other hormones such as follicle-stimulating hormone (FSH) and human chorionic gonadotropin (hCG) by fusing carboxyl-terminal peptide (CTP) of the hCG gene to the above hormones. The CTP has four serine-linked oligosaccharides, which have been shown to be important in maintaining the longer half-lives of these hormones. With the above rationale of using the CTP as a general target to increase the potency of bioactive hormones, we have now fused the CTP with hGH. This has provided us with a new successfully constructed recombinant hGH, which is currently being tested for its biological potency and for possible use in aging animals.

Paternal isodisomy of chromosome 7 with cystic fibrosis and overgrowth

We have diagnosed a boy with cystic fibrosis (CF) due to paternal UPD presenting with overweight and developmental delay, not typical features to CF patients. Two previously reported patients with paternal UPD(7) did not present overgrowth. The discrepancy between the phenotype of this boy and the other two patients raises the question of imprinted genes or homozygotization of a disease‐causing gene in paternal UPD7.

Ontogenetic development of peripheral benzodiazepine binding sites in rat brain, heart and lung

In rats, the brain exhibits negligible ontogenetic changes, while a steady marked increase in the density of peripheral benzodiazepine binding sites (PBS) has been demonstrated in the heart and lungs, reaching maximal levels at 31 days after birth. It may be that PBS play a role in the cellular proliferation of these peripheral organs. The present findings are consistent with current evidence of a relationship between these binding sites and mitochondrial function.

The potential efficacy of 3,3'-diindolylmethane in prevention of prostate cancer development.

The objective of this study was to examine the efficacy of 3,3′-diindolylmethane (DIM) in prevention of prostate cancer tumor development in an animal model. Mouse prostate cancer cells (TRAMP-C2, 2×10−6) were injected subcutaneously into three groups of C57BL/6 mice (10 mice in each group). Two groups were treated earlier with DIM; 2 or 10 mg/kg each, and an additional control group was injected with medium. Animals were treated for five more weeks until sacrificed. Tumor sizes were measured biweekly. At the end of the experiment, mice were sacrificed, and tumors were excised, weighed, measured and tested using immunohistochemical studies. In addition blood samples were collected for biochemical analysis. The results indicated that DIM significantly reduced tumor development in treated animals when compared with controls. Tumors developed in 80% of controls and 40% and 60% of animals treated with 10 or 2 mg/kg of DIM, respectively. Moreover, tumors that developed in treated animals were significantly (P<0.001) smaller than in controls. Additionally, our results indicated that DIM has no effect on animal weight or liver and kidney functions. These results indicated that the DIM agent is not toxic and has an in-vivo preventive effect against the development of prostate cancer in a mouse model.