Antithrombotic nipecotamide increases cyclic AMP levels and inhibits protein phosphorylation in human platelets

Investigation of platelet aggregation inhibitory activity by phenyl amides and esters of piperidinecarboxylic acids

A series of anilides and phenyl esters of piperidine-3-carboxylic acid (nipecotic acid) were synthesized and tested for the ability to inhibit aggregation of human platelet rich-plasma triggered by adenosine 5'-diphosphate (ADP) and adrenaline. As a rule, amides were about two times more active than the corresponding esters, and derivatives bearing substituents at the para position of the phenyl ring were significantly more active than the meta-substituted ones. Among the tested compounds, 4-hexyloxyanilide of nipecotic acid (18a) was found to be the most active one, its IC(50) value being close to that of the most active bis-3-carbamoylpiperidines reported in literature (ca. 40 micro M) and aspirin (ca. 60 microM) in ADP- and adrenaline-induced aggregation, respectively. Compared with the isomeric 4-hexyloxyanilides of piperidine-2-carboxylic (pipecolinic) and piperidine-4-carboxylic (isonipecotic) acids, compound 18a showed higher activity, and a Hansch-type quantitative structure-activity relationship (QSAR) study highlighted lipophilicity and increase in electron density of the phenyl ring as the properties which mainly increase the antiplatelet activity (r(2)=0.74, q(2)=0.64). The interaction of nipecotoyl anilides with phosphatidylinositol, a major component of the inner layer of the platelet membranes, was investigated by means of flexible docking calculation methods to give an account of a key event underlying their biological action.

New carbamoylpiperidines as human platelet aggregation inhibitors

A series of 3-carbamoylpiperidines (nipecotamides) are designed, synthesized and tested for their inhibitory action against adenosine diphosphate (ADP)-induced aggregation of human platelets. A structure-activity analysis of the bis(nipecotamido)aralkane type showed that a substituent on the piperidine ring should preferably be an amide and that the electronegativity of the carbonyl oxygen and the orientation of the amide group affected activities. Based on the knowledge of factors influencing platelet activation and aggregation, a nitric ester moiety which could release nitric oxide (NO) in situ, is incorporated into the nipecotamide structure. These compounds exhibit increased activity compared to those having no -ONO2 function. They also show stereoselectivity, with the meso isomer being approximately twice as potent as the synthetic diastereomeric mixture. Replacement of the -ONO2 function with hydroxyl, ester or alkyl groups considerably diminishes aggregation-inhibitory potential. Nipecotamides are shown here to inhibit the basal and collagen-induced rise in platelet inositol trisphosphate (IP3) levels, as well as phosphoinositide turnover. A comprehensive mechanism of action is proposed taking earlier results into consideration.

Effect of PP1D-1, a synthetic antiplatelet compound, on rabbit platelets

The antiplatelet mechanism of a synthetic compound, 2-chloro-3-methoxycarbonylpropionamido-1,4-naphthoquinone (PP1D-1), was studied by employing washed rabbit platelets in vitro. PP1D-1 concentration-dependently inhibited thrombin (0.1 U/ml)-, platelet-activating factor (2 ng/ml)-, collagen (10 microg/ml)-, arachidonic acid (100 microM)- and U46619 (1 microM)-induced aggregation and ATP release in washed rabbit platelets. The IC50 values of PP1D-1 for aggregation induced by the above inducers are 17.9+/-1.7, 9.8+/-1.1, 3.9+/-0.4, 1.8+/-0.3 and 1.7+/-0.3 microM, respectively. PP1D-1 did not affect platelet thromboxane B2 or prostaglandin D2 formation induced by arachidonic acid, indicating that it did not affect cyclooxygenase and thromboxane synthase activities. PP1D-1 significantly inhibited the formation of inositol 1,4,5-trisphosphate caused by these five platelet stimulators. Moreover, PP1D-1 inhibited the increase in intracellular calcium concentration induced by these agents. On the contrary, PP1D-1 did not inhibit thapsigargin-elevated intracellular calcium concentration in indomethacin-pretreated platelets, indicating it did not influence the effect of thapsigargin. According to these data, PP1D-1 exerts antiplatelet effects mainly by inhibiting phosphoinositide turnover.

Antiplatelet effects of R,S-(meso)-alpha, alpha'-bis[3-(N,N-diethylcarbamoyl) piperidino]-p-xylene ex vivo in the dog and in vivo in the mouse

1. The nipecotamide alpha,alpha'-bis[3-(N,N-diethylcarbamoyl)piperidino]-p-xylene (A-1) is a platelet aggregation inhibitor. The meso diastereomer A-1c is superior in potency and duration to the synthetic diastereomeric mixture consisting of the R,R-, S,S-, and R,S- (meso) isomers in inhibiting collagen-induced platelet aggregation ex vivo in the dog. 2. A-1c also is more potent and longer acting than A-1 in protecting mice from collagen+epinephrine-induced thromboembolic death. 3. The mechanism of antiplatelet action of this compound appears to be related to its ability to prevent agonist-induced inhibition of platelet cyclic adenosine monophosphate (cAMP) levels.