The influence of treatment-resistance on the serotonin 2A receptor in unipolar melancholic depression

Introduction

Major depression is one of the most common mental diseases, and quite a number of patients are resistant to several psychopharmacological interventions, even when applying current treatment guidelines. To date, it remains unclear as to how the serotonergic system is implicated in treatment-resistance found in melancholically depressed patients.

Objectives & aims

In this study, we examined the involvement of post-synaptic 5-HT2A receptors in the pathophysiology of treatment resistance in major depression with 123I-5-I-R91150 SPECT, focusing on the frontal cortex and hippocampus.

Method

15 unipolar antidepressant naïve (ADN) patients and 15 treatment-resistant depressed (TRD) patients, all of the melancholic subtype, matched for age and gender were studied. All subjects were antidepressant free when they underwent a static 123I-5-I-R91150 SPECT scan.

Results

Compared to ADN patients, TRD patients displayed significantly less 5-HT2A receptor binding index (BI) in the dorsal regions of the prefrontal cortex and in the anterior cingulate cortex. No hippocampal 5-HT2A receptor BI differences were observed.

Conclusions

Our results suggest that when confronted with treatment resistance in melancholic depression the 5-HT2A receptors in the DPFC-ACC axis are significantly more down-regulated when compared to depressed ADN patients. This might to some extent explain the observed continued cognitive problems and might reflect the long-term serotonin depletion with reduced neurogenesis in treatment resistant patients.

Inhibition of all-TRANS-retinoic acid metabolism by R116010 induces antitumour activity

All-trans-retinoic acid is a potent inhibitor of cell proliferation and inducer of differentiation. However, the clinical use of all-trans-retinoic acid in the treatment of cancer is significantly hampered by its toxicity and the prompt emergence of resistance, believed to be caused by increased all-trans-retinoic acid metabolism. Inhibitors of all-trans-retinoic acid metabolism may therefore prove valuable in the treatment of cancer. In this study, we characterize R116010 as a new anticancer drug that is a potent inhibitor of all-trans-retinoic acid metabolism. In vitro, R116010 potently inhibits all-trans-retinoic acid metabolism in intact T47D cells with an IC(50)-value of 8.7 nM. In addition, R116010 is a selective inhibitor as indicated by its inhibition profile for several other cytochrome P450-mediated reactions. In T47D cell proliferation assays, R116010 by itself has no effect on cell proliferation. However, in combination with all-trans-retinoic acid, R116010 enhances the all-trans-retinoic acid-mediated antiproliferative activity in a concentration-dependent manner. In vivo, the growth of murine oestrogen-independent TA3-Ha mammary tumours is significantly inhibited by R116010 at doses as low as 0.16 mg kg(-1). In conclusion, R116010 is a highly potent and selective inhibitor of all-trans-retinoic acid metabolism, which is able to enhance the biological activity of all-trans-retinoic acid, thereby exhibiting antitumour activity. R116010 represents a novel and promising anticancer drug with an unique mechanism of action.

The pore of the leaf cavity of Azolla species: teat cell differentiation and cell wall projections

The differentiation of the specialized secretory teat cells of the leaf cavity pore of Azolla species was investigated at the ultrastructural level with emphasis on their peculiar cell wall projections. The results indicated that the projections are formed as soon as the teat cells complete their differentiation and that their production is principally associated with changes in endoplasmic reticulum profiles. The number of projections increases with the teat cell age and is stimulated under salt and P deficiency stresses. Salt stress also promotes their emergence on Azolla species that under normal conditions do not produce projections. Cytochemical tests on different Azolla species showed that the projection composition is almost identical: proteins, acidic polysaccharides, and pectin are always detected. This study revealed that Azolla teat cell projections differ fundamentally from other types of hitherto described cell wall projections that are considered as remnant structures from cell separation. In contrast, in Azolla teat cells projections are actively produced and compounds are excreted by an exocytotic mechanism. The possible role of the projections in the symbiosis of Azolla spp. with Anabaena azollae is discussed.

The functional gamma-secretase inhibitor prevents production of amyloid beta 1-34 in human and murine cell lines

The amyloid precursor protein (APP) undergoes two consecutive cleavages by different proteases, beta-secretase and gamma-secretase, leading to the release of an amyloidogenic 4 kDa fragment called amyloid beta (Abeta). Combining immunoprecipitation and mass spectrometry, we characterized soluble Abeta in cultured cell media of mouse neuroblastoma N2a cells and double hAPP/hBACE-1 transfected HEK293. The major Abeta isoforms detected were Abeta11-34, Abeta1-34, Abeta11-40 and Abeta1-40. In this study, we demonstrate that overexpression of human beta-secretase (BACE-1) in HEK293 cells resulted in predominant Abeta cleavage at position Glu(11) rather than Asp(1), as well as increased production of Abeta(x)-34, but not Abeta(x)-40. Incubation of cells with a specific gamma-secretase inhibitor suggests that cleavage of APP at Leu(34) could be mediated by gamma-secretase itself or by a gamma-secretase dependent process.

R115866 inhibits all-trans-retinoic acid metabolism and exerts retinoidal effects in rodents

All-trans-retinoic acid (RA) regulates epithelial differentiation and growth through activation of specific nuclear RA receptors (RARs). Because high-rate metabolism largely impairs the biological efficacy of RA, we have sought for compounds capable of inhibiting the metabolic breakdown of the retinoid. This study identifies R115866 as a novel inhibitor of the cytochrome P450 (CYP)-mediated metabolism of RA. In vitro, nanomolar concentrations of R115866 inhibited the conversion of RA by CYP26, a RA-inducible RA metabolizing enzyme. In vivo, oral administration of R115866 (2.5 mg/kg) to rats induced marked and transient increases of endogenous RA levels in plasma, skin, fat, kidney, and testis. Consistent with its ability to enhance endogenous RA content in tissues, R115866 was found to exert retinoidal activities. Like RA, the title compound: 1) inhibited vaginal keratinization in estrogen-stimulated rats; 2) induced epidermal hyperplasia in mouse ear skin; 3) transformed mouse tail epidermis from a para- to an orthokeratotic skin type; and 4) up-regulated the CYP26 mRNA expression in rat liver. Furthermore, we found that the keratinization-suppressive and CYP26-inducing activities of R115866 could be reversed by concomitant administration of the RAR antagonist, AGN193109. Our data characterize R115866 as a potent, orally active inhibitor of RA metabolism, capable of enhancing RA levels and displaying retinoidal actions. These activities are reversed by RAR antagonism, supporting the idea that the actions of R115866 result from increased availability of endogenous RA and improved RAR triggering.

Accumulation of 3-ketosteroids induced by itraconazole in azole-resistant clinical Candida albicans isolates

The effects of itraconazole on ergosterol biosynthesis were investigated in a series of 16 matched clinical Candida albicans isolates which had been previously analyzed for mechanisms of resistance to azoles (D. Sanglard, K. Kuchler, F. Ischer, J. L. Pagani, M. Monod, and J. Bille, Antimicrob. Agents Chemother., 39:2378-2386, 1995). Under control conditions, all isolates contained ergosterol as the predominant sterol, except two strains (C48 and C56). In isolates C48 and C56, both less susceptible to azoles than their parent, C43, substantial concentrations (20 to 30%) of 14alpha-methyl-ergosta-8,24(28)-diene-3beta,6alpha-dio l (3, 6-diol) were found. Itraconazole treatment of C43 resulted in a dose-dependent inhibition of ergosterol biosynthesis (50% inhibitory concentration, 2 nM) and accumulation of 3,6-diol (up to 60% of the total sterols) together with eburicol, lanosterol, obtusifoliol, 14alpha-methyl-ergosta-5,7,22,24(28)-tetraene-3betaol, and 14alpha-methyl-fecosterol. In strains C48 and C56, no further increase of 3,6-diol was observed after exposure to itraconazole. Ergosterol synthesis was less sensitive to itraconazole inhibition, as was expected for these azole-resistant isolates which overexpress ATP-binding cassette transporter genes CDR1 and CDR2. In addition to 3,6-diol, substantial amounts of obtusifolione were found after exposure to itraconazole. This toxic 3-ketosteroid was demonstrated previously to accumulate after itraconazole treatment in Cryptococcus neoformans and Histoplasma capsulatum but has not been reported in Candida isolates. Accumulation of obtusifolione correlated with nearly complete growth inhibition in these azole-resistant strains compared to that found in the susceptible parent strain, although the onset of growth inhibition only occurred at higher concentrations of itraconazole. ERG25 and ERG26 are the only genes assigned to the 4-demethylation process, of which the 3-ketoreductase is part. To verify whether mutations in these ERG25 genes contributed to obtusifolione accumulation, their nucleotide sequences were determined in all three related isolates. No mutations in ERG25 alleles of isolates C48 and C56 were found, suggesting that this gene is not involved in obtusifolione accumulation. The molecular basis for the accumulation of this sterol in these two strains remains to be established.

Oxidized low-density lipoprotein enhances intimal thickening and alters vascular reactivity

Oxidized low density lipoprotein (oxLDL) is present in atherosclerotic lesions and has been implicated in the etiopathogenesis of atherosclerosis mainly based on in vitro studies. In view of the lack of data on the activity of oxLDL in vivo, we decided to study its effects in the rabbit by local application at the level of the vascular wall. Intimal thickening was evoked by the placement of a silicone collar around the carotid arteries during 2 weeks. The collar was connected to an osmotic minipump containing human oxLDL (7 micrograms h-1), LDL (7 micrograms h-1) or phosphate-buffered saline. Collar placement resulted in a thickening of the intima thereby increasing the thickness from 5 +/- 1 to 26 +/- 5 microns with the appearance of alpha-actine positive smooth muscle cells. Perivascular infusion of LDL or oxLDL significantly enhanced the intima, containing large amounts of T-lymphocytes, collagen and smooth muscle cells. The placement of the collar and the infusion of oxLDL during 14 days resulted in an increased sensitivity to serotonin and a decreased sensitivity to acetylcholine. The maximal relaxation to acetylcholine was reduced by 50% whereas the endothelium-independent relaxation to nitroglycerin were not affected. These results show for the first time that the local application of oxLDL in vivo promotes intimal thickening and impairs the endothelium-dependent relaxations thereby supporting the suggestion that oxLDL plays an important role in the morphological and functional changes present in atherosclerotic blood vessels.

Induction of the oxidative catabolism of retinoid acid in MCF-7 cells

Cytochrome P450-dependent oxidation is a pathway for all-trans-retinoic acid (all-trans-RA) catabolism. Induction of this catabolic pathway was studied in MCF-7 breast cancer cells. MCF-7 cells showed low constitutive all-trans-RA catabolism. Concentration-dependent induction was obtained by preincubation of the cells with all-trans-RA (10(-9) to 10(-6) M). Onset of induction was fast, being detectable within 60 min, with maximal induction (45-fold) obtained after 16 h. Enzymatic characterization of induced all-trans-RA catabolism showed an estimated Km value (Michaelis-Menten constant) of 0.33 microM and a Vmax value (maximal velocity of an enzyme-catalysed reaction) of 54.5 fmol polar all-trans-RA metabolites 10(6) cells(-1) h(-1). These kinetic parameters represent the overall formation of polar metabolites from all-trans-RA. Induction of all-trans-RA catabolism was also obtained with other retinoids, CH55 >> 13-cis-RA = all-trans-RA > 9-cis-RA > 4-keto-all-trans-RA > 4-keto-13-cis-RA > retinol. The potency of the retinoids to induce all-trans-RA catabolism was correlated to their retinoic acid receptor affinity (Crettaz et al, 1990; Repa et al, 1990; Sani et al, 1990). Induction of all-trans-RA catabolism was inhibited by actinomycin D. Furthermore, all-trans-RA did not increase cytosolic retinoic acid-binding protein (CRABP) mRNA levels. These data suggest that induction of all-trans-RA catabolism in MCF-7 cells is a retinoic acid receptor-mediated gene transcriptional event. Induced all-trans-RA catabolism was inhibited by various retinoids with decreasing potency in the order: all-trans-RA > 4-keto-all-trans-RA > 13-cis-RA > 9-cis-RA > 4-keto-13-cis-RA > retinol > CH55. The antitumoral compound liarozole-fumarate inhibited all-trans-RA catabolism with a potency similar to that of all-trans-RA.

Analysis of the oxidative catabolism of retinoic acid in rat Dunning R3327G prostate tumors

We studied the enzymatic characteristics of the oxidative catabolism of retinoic acid (RA) and its inhibition by liarozole-fumarate in homogenates of rat Dunning R3327G prostate tumors. Homogenates of rat liver were used as reference material. Both tumor and liver homogenates were able to catabolize retinoic acid. HPLC analysis revealed only very polar metabolites in tumors, while in the liver both metabolites with intermediate polarity and more polar metabolites were found. Kinetic analysis of retinoic acid catabolism showed a K(m) of 1.7 +/- 0.7 microM and a Vmax of 4.2 +/- 4.4 pmol polar RA metabolites/mg protein/hr for Dunning G tumor homogenates. In liver homogenates a K(m) value of 4.3 +/- 0.5 microM and a Vmax value of 290 +/- 120 pmol polar RA metabolites/mg protein/hr were obtained. Liarozole-fumarate inhibited retinoic acid catabolism in Dunning tumors and liver with IC50 values of 0.26 +/- 0.16 microM and 0.14 +/- 0.05, respectively. The results suggest that rat Dunning R3327G tumors are able to metabolize retinoic acid in a manner similar to that found in rat liver but with a lower metabolizing capacity.

Genetic diversity and phylogeny analysis of Anabaena azollae based on RFLPs detected in Azolla-Anabaena azollae DNA complexes using nif gene probes

The cyanobacterium Anabaena has both symbiotic and free-living forms. The genetic diversity of Anabaena strains symbiotically associated with the aquatic fern Azolla and the evolutionary relationships among these symbionts were evaluated by means of RFLP (restriction fragment length polymorphism) experiments. Three DNA fragments corresponding to nif genes were cloned from the free-living cyanobacterium Anabaena PCC 7120 and used as probes. A mixture of Azolla, Anabaena and bacterial DNA was extracted from Azolla fronds and digested with two restriction enzymes. Single-copy RFLP signals were detected with two of the probes in all Azolla Anabaena examined. Multiple-copy RFLP signals were obtained from the third probe which corresponded to a part of the nif N gene. A total of 46 probe/enzyme combinations were scored as present or absent and used to calculate pairwise Nei's genetic distances among symbiotic Anaebaena strains. Phylogenetic trees summarizing phenetic and cladistic relationships among strains were generated according to three different evolutionary scenarios: parsimony, UPGMA and neighbour joining. All trees revealed identical phylogenetic relationships. Principal component analysis was also used to evaluate genetic similarities and revealed three groups: group one contains the cyanobacteria associated with plants from the Azolla section, group two contains those associated with plants from the pinnata species and group three contains those associated with plants from the nilotica species. The same groups had already been identified earlier in a random amplified polymorphic DNA (RAPD) analysis of Azolla-Anbaena DNA complexes, suggesting that the present Azolla taxonomy should be revised. We now suggest a taxonomy of Anabaena azollae that is parallel to such a revised Azolla taxonomy. An Azolla chloroplast DNA sequence derived from Oryza sativa was also used as an RFLP probe on Azolla DNA to confirm the presence of plant DNA in the total genomic DNA extracted from ferns with or without the symbiont. Our results also suggest that total DNA extracted from the Azolla-Anabaena complexes includes both plant and symbiont DNA and can be used equally well for RFLP analysis of host plant or symbiotic cyanobacteria.

Liarozole fumarate inhibits the metabolism of 4-keto-all-trans-retinoic acid

The metabolism of 4-keto-all-trans-retinoic-acid (4-keto-RA), a biologically active oxygenated metabolite of all-trans-retinoic (RA), has been examined. In vitro, incubation of [14C]4-keto-RA with hamster liver microsomes in the presence of NADPH produced two major radioactive metabolites which were more polar than the parent compound. Following isolation, appropriate derivatization and analysis by GC-MS, these compounds were tentatively identified as 2-hydroxy- and 3-hydroxy-4-ketoretinoic acid. Formation of both hydroxy-keto derivatives was suppressed by the imidazole-containing P450 inhibitor liarozole fumarate (IC50, 1.3 microM). In vitro, an i.v. injection of 4-keto-RA (20 micrograms) into rats was followed by rapid disappearance of the retinoid from plasma with a half-life of 7 min. Pretreatment with liarozole fumarate (40 mg/kg, -60 min) reduced the elimination rate of 4-keto-RA: it prolonged the plasma half-life of the retinoid to 12 min, without affecting its distribution volume. These results indicate the important role of the P450 enzyme system in the metabolism of 4-keto-RA both in vitro and in vivo. The inhibitory effect of liarozole fumarate on this metabolic process may contribute to the reported retinoid-mimetic activity of this drug.

Genetic diversity and phylogeny analysis of Azolla based on DNA amplification by arbitrary primers

The polymerase chain reaction was used to amplify random sequences of DNA from 25 accessions of Azolla to evaluate the usefulness of this technique for identification and phylogenetic analysis of this aquatic fern. Accessions were selected to represent all known species within the genus Azolla and to encompass the world-wide distribution of the fern. Primers of 10 nucleotides with 70% G + C content were used to generate randomly amplified polymorphic DNA from the symbiotic Azolla-Anabaena complex. Twenty-two primers were used and each primer gave 4-10 bands of different molecular weights for each accession. Bands were scored as present or absent for each accession and variation among accessions was quantified using Nei's genetic distances. A dendrogram summarizing phenetic relationships among the 25 accessions was generated using the unweighted pair-group method with arithmetic mean. Principal component analysis was also used to evaluate genetic similarities. Three distinct groups were identified: group 1 contains five species, group 2 contains the pinnata species, and group 3 contains the nilotica species. The analysis demonstrates that the major groups of Azolla species can be easily distinguished from one an other and, in addition, that closely related accessions within species can be identified. We further found that using 10 primers, a phylogeny that is essentially the same as that derived from 22 primers can be constructed. Our results suggest that total DNA extracted from the Azolla-Anabaena symbionts is useful for classification and phylogenetic studies of Azolla.

[Phyllodes type of atypical prostatic hyperplasia]

The author describes one case of phyllodes type of atypical prostatic hyperplasia. This is a benign prostatic lesion characterised by atypical epithelial hyperplasia and pleomorphism of the stromal elements. There is a resemblance with cystosarcoma phyllodes of the female breast. There have been described only a few cases of such atypical hyperplasia.

Mechanism of complement-induced stimulation of prostacyclin production by isolated rabbit peritoneum

The interaction between the complement system and prostaglandin synthesis has not thoroughly been explored, although both mediators are known to be involved in inflammatory reactions and endotoxic shock. When rabbit peritoneum, a rich source of prostacyclin forming activity was incubated in serum in which the complement system was activated (CVF, LPS, zymosan), the tissue produced significantly more PGI2, when compared with appropriate controls, indicating that by activation of the complement, factors were generated that stimulated PGI2 biosynthesis. Further results indicated that tryptic cleavage products of complement factor C3 and C5 also led to the appearance of PGI2 releasing principles with a molecular weight of about 7000-11000. The stimulation of PGI2 biosynthesis was explained by enhanced release of AA, and not due to increased activity of cyclo-oxygenase or PGI2 synthetase. Our results suggest that complement-derived products may promote the supply of prostaglandins at the site of inflammation.

Arachidonic acid metabolism by cultured mesothelial cells. Different transformations of exogenously added and endogenously

The capacity of cultured mesothelial cells to produce prostaglandins from both exogenous an endogenous arachidonic acid has been investigated. Incubations with labelled [1-14C]arachidonic acid and [1-14C]prostaglandin endoperoxide H2 indicated the formation of prostacyclin and prostaglandin E2. Evaluation of the transformation of endogenously released arachidonic acid, however, could only confirm the production of prostacyclin.

Quantitative determination of 6-Oxo-PGF1 alpha in biological fluids by gas chromatography mass spectrometry

A selected ion monitoring method for the determination of 6-oxo-PGF1 alpha, the stable end-product of prostacyclin, in biological fluids has been developed. In this method, biosynthetically prepared [2H6]-6-oxo-PGF1 alpha is used as internal standard. The method involves extraction, thin-layer chromatography purification and derivatization into the methyl ester, methoxime, trimethylsilyl ether derivatives by carrying out the methoximation first. Quantitative gas chromatographic mass spectrometric analysis is performed in the electron impact mode by monitoring the [M - (TMSOH + CH3O)]+ fragment ions. The use of this method in the measurement of 6-oxo-PGF1 alpha in serous fluids and in incubation media of serous tissues is described.