Antiplatelet pyrazolopyridines derivatives: pharmacological, biochemical and toxicological characterization.

Platelet aggregation is one of the main events involved in vascular thrombus formation. Recently, N'-substituted-phenylmethylene-3-methyl-1,6-diphenyl-1H-pyrazolo[3,4-b]pyridine-4-carbohydrazides were described as antiplatelet derivatives. In this work, we explore the properties of these antiplatelet agents through a series of pharmacological, biochemical and toxicological studies. The antiplatelet activity of each derivative was confirmed as 3a, 3b and 3 h significantly inhibited human platelet aggregation induced by arachidonic acid, with no detectable effect on clotting factors or healthy erythrocytes. Importantly, mice treated with derivative 3a showed a higher survival rate at an in vivo model of pulmonary thromboembolism with a lower bleeding risk in comparison to aspirin. The in silico studies pointed a series of structural parameters related to thromboxane synthase (TXS) inhibition by 3a, which was confirmed by tracking plasma levels of PGE2 and TXB2 through an in vitro enzyme immunoassay. Derivative 3a showed selective TXS inhibition allied with low bleeding risk and increased animal survival, revealing the derivative as a promising candidate for treatment of cardiovascular diseases.

Antinociceptive, anti-inflammatory and antipyretic effects of 1.5-diphenyl-1H-Pyrazole-3-carbohydrazide, a new heterocyclic pyrazole derivative.

AIMS: Heterocyclic pyrazole derivative has been described for the treatment of pain and inflammatory diseases. This study evaluated the in vivo, antinociceptive, anti-inflammatory and antipyretic effects of 1.5-diphenyl-1H-Pyrazole-3-carbohydrazide (1.5-DHP) and the in vivo or in vitro mechanism of action. MAIN METHODS: Acetic acid-induced writhing, hot-plate and formalin-induced nociception tests were used to evaluate the antinociceptive effect, while the rota-rod test was used to assess the motor activity. Croton oil-induced ear edema and carrageenan-induced peritonitis tests were used to investigate the anti-inflammatory effect of 1.5-DHP. The antipyretic effect was assessed using the LPS-induced fever model. The mechanism of action was evaluated by PGE2 and TNF-α measurement and cyclooxygenase inhibition assay. KEY FINDINGS: Oral administration (p.o.) of 1.5-DHP (1, 3, 10 mg/kg) caused a dose-related inhibition of the acetic acid-induced writhing, however the highest dose was not effective on the hot-plate and rota-rod. In the formalin-induced nociception, 1.5-DHP (10mg/kg, p.o.) inhibited only the late phase of nociception. This same dose of 1.5-DHP also reduced the croton oil-induced ear edema. 1.5-DHP (3, 10, 30 mg/kg, p.o.) produced a dose-related reduction of leukocyte migration on the carrageenan-induced peritonitis. 1.5-DHP (60 mg/kg, p.o.) reduced the fever and the increase of PGE2 concentration in the cerebrospinal fluid induced by LPS. 1.5-DHP inhibited both COXs in vitro. Finally, 1.5-DHP (10 mg/kg, p.o.) reduced the TNF-α concentration in peritoneal exudates after carrageenan injection. SIGNIFICANCE: These results indicate that 1.5-DHP produces anti-inflammatory, antinociceptive and antipyretic effects by PGE2 synthesis reduction through COX-1/COX-2 inhibition and by TNF-α synthesis/release inhibition.