216 - Validating vascular KATP channel inhibitors as novel therapeutics to treat patent ductus arteriosus

Poster Number: 216
Publication Number: 216.220

Elaine L. Shelton, Vanderbilt University Medical Center, Nashville, TN, United States; Claire Sorenson, Monroe Carell Jr. Children's Hospital at Vanderbilt, Nashville, TN, United States; Anet Sanchez, Florida International University Herbert Wertheim College of Medicine, Miami, FL, United States; Paywand Baghal, Vanderbilt University, Nashville, TN, United States; Jerod Denton, Vanderbilt University School of Medicine, Nashville, TN, United States

Background: All current drugs used to treat patent ductus arteriosus (PDA) target the prostaglandin pathway and have worrisome off target effects. We have identified APT-gated potassium (KATP) channels as promising drug targets for new PDA therapeutics. While KATP channels are present in many tissues, the vascular-specific isoform (Kir6.1/Sur2b) is highly enriched in the ductus arteriosus (DA). The non-specific KATP channel inhibitor, glibenclamide, is effective at promoting DA constriction in vitro and in vivo, but is not an ideal therapy given the potential for off target effects. 

Objective: The goal of this study is to identify compounds that specifically inhibit Kir6.1/Sur2b KATP channels and modulate DA tone. We hypothesize that novel vascular-specific KATP channel inhibitors will promote DA closure, while avoiding the pitfalls of currently available PDA drugs.

Design/Methods: A high throughput screen (HTS) identified compounds that specifically inhibit Kir6.1/Sur2b channels. Pressure myography assays were used to assess the ability of novel Kir6.1/Sur2b inhibitors to induce DA constriction in vessels isolated from term- (e19) and preterm- (e15) gestation fetal mice. Myography studies were also used to evaluate the effects of KATP inhibitors on O2-induced ductus constriction. For in vivo studies, newborn mouse pups were given intraperitoneal injections of KAPT channel modulators and the extent of ductus closure was assessed by comparing DA lumen diameter to that of the adjacent main pulmonary artery. For some studies, mouse pups were placed in a hypoxia chamber to evaluate the ability of KATP inhibitors to promote DA closure under low oxygen conditions. Data were analyzed by t-test or ANOVA as appropriate.

Results: The HTS identified hit compounds that specifically inhibit the Kir6.1/Sur2b channel isoform, but have no effect on other KATP channel isoforms. Of the compounds we have evaluated thus far, some are able to induce DA constriction in a dose-dependent manner. Interestingly, some compounds can also make preterm vessels more sensitive to O2. Furthermore, placing newborn mouse pups in a hypoxic environment delays ductus closure and decreases pup survival. However, injecting pups with KATP inhibitors prior to placing them in the hypoxia chamber induces DA closure and significantly improves survival. Conclusion(s): KATP channels are enriched in the DA and regulate vessel tone. We have identified novel Kir6.1/Sur2b inhibitors that promote DA closure and increase the vessel's sensitivity to oxygen-induced vasoconstriction, thereby making them promising alternatives to currently available PDA therapies.