No abstract

This study was aimed at evaluating, on a limited number of benzopyran compounds, whether the insertion of an electron-rich spirocyclic substituent at the C4 carbon of the benzopyran molecular nucleus may improve the cardioprotective properties against ischemia. Some of the new compounds (1b, 2b, and 4b) exhibited interesting anti-ischemic properties without affecting significantly the blood pressure parameters.

Many activators of K(ATP) channels exhibit cardioprotective effects, mainly mediated by channels expressed on mitochondria (mito-K(ATP)). Previous results showed anti-ischemic effects of the spiro-cyclic derivative A, on isolated rat hearts. In this work this molecule was more extensively studied and diazoxide was used as reference mito-K(ATP) opener. The studies were performed on an in vivo rat model of myocardial infarct and on heart-derived H9c2 cells exposed to an anoxic environment. The mechanism of action was further investigated on isolated rat heart mitochondria. In the model of myocardial infarct compound A and diazoxide produced significant cardioprotective effects, antagonised by the selective mito-K(ATP) blocker 5-hydroxydecanoic acid (5-HD). Compound A, like diazoxide, produced modest and non-significant hypotensive responses, while the hyperglycaemic effects of diazoxide were not observed for the new compound. Protective effects of compound A and diazoxide were also recorded in H9c2 cells and again were inhibited by 5-HD. Compound A and diazoxide caused swelling of cardiac mitochondria, in agreement with the profile of mito-K(ATP) openers. Both compounds evoked concentration-dependent Ca2+-release from Ca2+-preloaded mitochondria, prevented mitochondrial Ca2+-uptake and caused mitochondrial membrane depolarisation. These effects were antagonised by ATP, the endogenous K(ATP) inhibitor. In conclusion, compound A exhibits a promising profile of an anti-ischemic agent, with a mechanism likely to be linked to the activation of mito-K(ATP) channels, and, because of its chemical characteristics such as structural rigidity and chirality due to the spiro-cyclic moiety, represents an interesting template for development of analogues further improved in activity and selectivity.

In a preliminary work, we reported two NO-sartans, possessing the characteristics of an AT(1) antagonist and a "slow NO donor", obtained by adding NO-donor side chains to losartan 1. The NO release from an NO-sartan should be modulated in order to strengthen the antihypertensive activity of the native drug and to ensure additional effects, such as the antiplatelet and anti-ischemic ones. To obtain a collection of prototypical NO-sartans, showing different rates of NO release, new NO-donor moieties have been linked to 1 or its active metabolite 2 (EXP 3174). Almost all the synthesized compounds exhibited both AT(1)-antagonist and NO-mediated vasorelaxing properties, with a wide range of NO-releasing rates. Further pharmacological investigation on compound 4a showed that it possessed antihypertensive and cardiac antihypertrophic effects similar to those of the reference AT(1)-blocking or ACE-inhibiting drugs. Furthermore, the additional anti-ischemic cardio-protective properties and antiplatelet effects of 4a have been preliminarily investigated.

The aim of this work was to develop lead pharmacodynamic hybrids, NO-sartans, possessing the characteristics of a typical AT1-antagonist and of a "slow NO donor", by adding NO-donor side chains to losartan. These new compounds, 2a and 2b, displayed vasorelaxing effects, due to the release of NO, and antagonized the vasocontractile effects of angiotensin II, with potency values similar to that of losartan. In vivo, the antihypertensive effects of 2a were similar to those of losartan and captopril.