Evaluation of Acute Toxicity of Novel Selective ETA-Receptor Antagonists that Control Preterm Birth in a Mouse Model
Ralph Stephani and Sandra E. Reznik, Department of Pharmaceutical Sciences, College of Pharmacy and Health Sciences, Nicole S. Olgun, Student, and Hardik J. Patel, Graduate, College of Pharmacy and Health Sciences
Preterm birth (PTB), for which the single most common cause is intrauterine infection, is defined as any birth occurring before the completion of 37 weeks gestation and is a leading cause of perinatal morbidity and death. Endothelin-1 (ET-1) is a potent vasoconstrictor peptide that is both regulated by inflammatory cytokines and also capable of increasing myometrial smooth muscle tone. We have synthesized a novel series of 1-3-6-trisubstituted-2-carboxy-quinol-4-one’s that act as selective Endothelin-A receptor antagonists (ETA-RA) in vitro. Our overlying hypothesis is that these compounds will control inflammation-associated PTB in vivo without having significant toxic effect. Several different analogues of our compound are tested for an effect on PTB. Briefly, C57Bl/6 mice at gestational day (E) 15.5 are injected intraperitoneally (i.p.) with lipopolysaccharide (LPS) and then treated with the compound being tested. Control mice are injected with LPS and then treated with vehicle. In addition, the LD50 of the compound is determined by the “Acute Toxic Class” method with slight modifications as per OECD 423 guidelines. Neurotoxicity is evaluated further with the rotorod test. Our results show that these novel compounds have a significant effect on the number of pups prematurely delivered (P<0.001). Furthermore, the estimated LD50 range for the prototype is 200-15000 mg/kg and for the n-propyl analogue (results not shown) is 200-1000mg/kg, which, for both, is several fold higher than the therapeutic dose range. Rotorod tests confirm that the n-propyl analogue causes neurotoxicity at doses several fold higher than therapeutic doses. Finally, organs were taken from mice receiving the n-propyl analogue for tissue histology in order to assess organ specific toxicity. We conclude that the novel ETA-RA’s control PTB at doses that do not have significant toxic effect. These results may impact a very important clinical problem for which there is currently no satisfactory therapy.