Ernesto Cano

Pyridazines. Part XXIX: synthesis and platelet aggregation inhibition activity of 5-substituted-6-phenyl-3(2H)-pyridazinones. Novel aspects of their biological actions.

A series of 6-phenyl-3(2H)-pyridazinones with a diverse range of substituents in the 5-position have been prepared and evaluated in the search for new antiplatelet agents. A significant dependence of the substituent on the inhibitory effect has been observed. The pharmacological study of these compounds confirms that modification of the chemical group at position 5 of the 6-phenyl-3(2H)-pyridazinone system influences both variations in the antiplatelet activity and the mechanism of action.

AM1 theoretical study, synthesis and biological evaluation of some benzofuran analogues of anti-inflammatory arylalkanoic acids

Using the semi-empirical quantum-mechanical method AM1, the molecular geometries of the arylalkanoic acids, indomethacin, naproxen and ibuprofen, were optimized and their frontier orbital charge distributions evaluated. Then, these molecular parameters were compared in order to identify structure-activity relationships and, on the basis of these, four benzofuran-3-acetic acids were designed as potential non-steroidal anti-inflammatory agents, and rapidly synthesized by a novel and easily generalized route. Notwithstanding the structural similarities between the synthesized compounds and the anti-inflammatory arylalkanoic acids, these compounds did not appreciably inhibit human platelet cyclooxygenase in vitro.

Pyridazines. Part 28: 5-Alkylidene-6-phenyl-3(2H)-pyridazinones, a New Family of Platelet Aggregation Inhibitors §

The synthesis and anti-platelet activity of several 5-alkylidene-6-phenyl-3(2H)-pyridazinones are described. The most active compounds are those that contain oxygenated functions (COOR, COMe) on the alkylidene fragment (6a, 6b and 6c).

In Vitro Effects of Resveratrol on the Viability and Infectivity of the Microsporidian Encephalitozoon cuniculi

ABSTRACT Microsporidians of the genus Encephalitozoon are an important cause of disease in immunocompromised patients, and there are currently no completely effective treatments. The present study investigated the viability and infectivity of spores of Encephalitozoon cuniculi that had been exposed to resveratrol (RESV), a natural phytoalexin found in grapes and red wine. RESV at 50 μM showed significant sporicidal activity, and at 10 to 50 μM it reduced the capacity of the spores to infect dog kidney epithelial cells of the MDCK line. At 10 μM RESV also significantly inhibited intracellular development of the parasite, without affecting host cell viability. These results suggest that RESV may be useful in the treatment of Encephalitozoon infections.

Parallel regulation by olanzapine of the patterns of expression of 5-HT2A and D3 receptors in rat central nervous system and blood cells.

Patterns of protein expression can be used to identify biomarkers of disease, prognosis or treatment response. Peripheral 5-HT2A and D3 receptors have been proposed as protein markers in schizophrenia. We investigated the possible parallel regulation of these candidate biomarkers in central nervous system (CNS) and peripheral blood cells by a comparative study of the effects of antipsychotic treatment on the expression of the receptors in both systems in rats. Acute (24 and 48 h) and subchronic (16 days) treatment of rats with olanzapine induced a significant decrease in 5-HT2A receptor density both in frontal cortex (Bmax=76.2%, 83.0% and 46.0% of control after 24 h, 48 h and 16 days of treatment, respectively; P<0.01) and blood platelets (Bmax approximately 55% of control at all times measured; P<0.01), without any changes in receptor affinity. Furthermore, olanzapine induced redistribution in 5-HT2A-like immunoreactivity and time-dependent remodelling of synaptic circuits involved in the activity of pyramidal and GABAergic neurons in frontoparietal motor cortex of treated rats, as assessed by immunohistochemical studies. D3 receptor mRNA levels increased significantly by 52.5% (P<0.01) and 21.1% (P<0.05) in nucleus accumbens, and by 53.4% (P<0.05) and 91.7% (P<0.01) in lymphocytes, after acute (24 h and 48 h) treatment with olanzapine, returning to levels similar to control after subchronic treatment (16 days). In conclusion, we observed in rats after olanzapine treatment: (1) parallelism in the regulation of 5-HT2A receptors in frontal cortex and in blood platelets; (2) parallelism in the regulation of D3 mRNA levels in nucleus accumbens and lymphocytes. These results endorse the interest in future studies aimed at validating these receptors as candidate biomarkers in schizophrenia.

New platelet aggregation inhibitors based on pyridazinone moiety.

New series of pyridazinone derivatives (4, 5 and 6) were synthesized in good yields following a synthetic strategy based on singlet oxygen oxidation of alkyl furans, in which a suitable β(α)-substituted γ-hydroxybutenolide (10 or 11) or a bicyclic lactone (12 or 13) was the key intermediate. The synthesized compounds were tested in vitro as antiplatelet agents and some of them (compounds 4b, 4d and 5b) exhibited potent inhibitory effects on collagen-induced platelet aggregation with IC50 values in the low μM range. Studies performed with the most active compound of these series (4b) demonstrated its lack of activity as inhibitor of platelet aggregation induced by other agonists as thrombin, ionomycin or U-46619 suggesting a selective action on the biochemical mechanisms triggered by collagen in the platelets.

Calpain controls the balance between protein tyrosine kinase and tyrosine phosphatase activities during platelet activation

Protein phosphorylation was studied during platelet stimulation in two ranges of ionized [Ca2+]. At ionized [Ca2+]i≤1 μM, proteins were phosphorylated. At ionized [Ca2+]i≥4 μM, phosphoproteins disappeared. Protein dephosphorylation was prevented by the combined action of calpeptin and phosphatase inhibitors. Protein tyrosine phosphatase activity was stimulated regardless of the ionized [Ca2+]i level. Protein tyrosine kinase activity was stimulated at ionized [Ca2+]i≤1 μM, whereas at ionized [Ca2+]i≥4 μM, no protein tyrosine kinase activity was observed except in the presence of calpeptin. Thus, the massive tyrosine phosphoprotein disappearance observed at a high ionized [Ca2+]i resulted not only in protein tyrosine phosphatase activation, but also in calpain‐induced protein tyrosine kinase inactivation.

Discovery and Preliminary SAR of 5-Arylidene-2,2-Dimethyl-1,3-Dioxane- 4,6-Diones as Platelet Aggregation Inhibitors

We herein document the discovery of 5-arylidene-2,2-dimethyl-1,3-dioxane-4,6-diones as a novel family of platelet aggregation inhibitors. The preliminary optimization study enabled us to establish the most salient features of the structure-activity relationships in this series as well as to identify novel derivatives that are upto 60 times more potent than the hit structure 1 and slightly superior to the reference drug Milrinone.

In-vitro platelet responses to arachidonic acid in the rat

Using both the turbidimetric and the conductive methods to study aggregation of platelets, we found that arachidonic acid stimulated rat washed platelets in a dose‐dependent manner (40 μM‐0.5mM).

Synthesis and vasorelaxant and antiplatelet activities of a new series of (4-Benzylphthalazin-1-ylamino)alcohol derivatives

A new series of phthalazine derivatives was synthesized by reaction of phthalic anhydride and different substituted phenylacetic acids to yield the benzyliden-3H-isobenzofuran-1-one intermediates 2a–d. Treatment of them with hydrazine afforded 4-benzyl-2H-phthalazin-1-one derivatives 3a–d, which were substituted with the corresponding aminoalkylalcohol to obtain the (4-benzylphthalazin-1-ylamino)alcohol derivatives 4a–h. In general, these phthalazine derivatives relaxed the contractions produced by phenylephrine both in intact or endothelium-denuded aortic rings. In addition, platelet aggregation induced by thrombin was also inhibited by compounds 4c and 4g.