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In this paper, the in vitro microsomal hepatic metabolism of the antiasthmatic prototype LASSBio-448 and the structural identification of its major phase I metabolites were described. Incubation with pooled rat liver microsomes converted LASSBio-448 to the following major metabolites: O-demethyl-LASSBio-448 (M1) and 3,4-dihydroxyphenyl- LASSBio-448 (M2). These metabolites were formed by the dealkylation step of 3,4-dimethoxyphenyl and 1,3- benzodioxole subunits, respectively, in agreement with the in silico prediction using MetaSite Program. The development of a reproducible analytical methodology for the major metabolites by using HPLC-MS showed that both reactions require NADPH generating system and appeared to be catalyzed by cytochrome P450 (CYP). The identification of which isoenzyme was involved in the oxidative metabolism of LASSBio-448 was carried out by pre-incubations with the selective inhibitors sulfaphenazole (CYP2C9), quinidine (CYP2D6), furafylline (CYP1A2), p-nitrophenol (CYP2E1), ticlopidine (CYP2C19) and ketoconazole (CYP3A4). CYP1A2, CYP2C19 and CYP3A4 were demonstrated to be involved in the oxidative biotransformation of LASSBio-448.

In this study, we examined the effects of LASSBio-965 (N-[2-(3,4-dimethoxyphenyl) ethyl]-benzenesulfonamide), a compound designed as a simplified structure of a non-selective phosphodiesterase 4 inhibitor, on vascular smooth muscle in vitro as well as in a rat model of monocrotaline (MCT)-induced pulmonary arterial hypertension. LASSBio-965 (50 mg/kg) treatment caused a significant decrease in right systolic ventricular pressure (32.47 ± 3.09 mmHg) compared to the MCT-vehicle group (51.88 ± 3.23 mmHg; P0.05) and in the ratio of right ventricular weight to left ventricular weight plus septum (0.42 ± 0.03 g compared to 0.59 ± 0.06 g, respectively; MCT-vehicle group; P0.05). LASSBio-965 induced a concentration-dependent relaxation of rat aortic rings, which was decreased by mechanical removal of the endothelium. Milrinone, rolipram, and sildenafil reduced the maximum relaxation (100%) to 22.4 ± 5.8, 69.5 ± 5.6 and 80.1 ± 10.7%, respectively (P0.05). Maximum relaxation responses of aortic and pulmonary artery rings were decreased in the MCT-vehicle group (54.80 ± 5.69 and 35.87 ± 4.78, respectively) compared to the control (91.51 ± 4.79 and 54.32 ± 2.39, respectively) but improved with LASSBio-965 treatment (50mg/kg; 88.43 ± 4.54 and 59.36 ± 4.83, respectively). These results indicate that LASSBio-965 can attenuate the pulmonary arterial hypertension in an animal model most likely through the nonselective inhibition of phosphodiesterases 3, 4, and 5.