Saige M. Mitchell

Background: Alternating hemiplegia of childhood (AHC) is a rare disorder with both neurologic and cardiac manifestations. The ATP1A3-D801N variant is associated with a pathologically short QT interval and risk of ventricular arrhythmia following bradycardia; however, the mechanism of this remains unknown. We investigated the relationship between heart rate (HR), QT, and QTc, hypothesizing that individuals with ATP1A3-D801N have abnormal, impaired shortening of QT and QTc at lower HR leading to arrhythmia predisposition. Methods: We performed a retrospective observational study of individuals who underwent clinical evaluation, Holter monitoring, and genetic testing for AHC at Duke University Hospitals. We also compiled a group of healthy individuals as a control cohort. A larger, worldwide cohort of individuals with ATP1A3 -related phenotypes was compiled to investigate sinus node dysfunction. Linear regression analysis was then performed. Results: The cohort consisted of 44 individuals with ATP1A3 -related phenotypes with 81 Holter recordings (52.27% female; mean age at first Holter 8.04 years, range 0.58 – 33 years), compared to 36 healthy individuals with 57 Holter recordings (52.78% female; mean age at first Holter 9.84 years, range 0.08 – 38 years). Individuals with ATP1A3-D801N had reduced prolongation of QT at lower HR, manifest as a significantly lower slope for HR vs QT compared to healthy (PATP1A3 -related phenotypes and baseline QTc 4 seconds. Conclusions: Individuals with the ATP1A3-D801N variant exhibit paradoxical shortening of QT and QTc at lower HR, which contributes to an increased risk of arrhythmias during bradycardia. This is exacerbated by an underlying risk of sinus node dysfunction. Clinical Perspective: What is Known: Individuals with ATP1A3-D801N have a short baseline QTc. Two individuals with AHC experienced ventricular fibrillation following bradycardia. What the Study Adds: The QT and QTc shorten to a greater extent at lower heart rate in individuals with ATP1A3-D801N than in healthy individuals. Individuals with ATP1A3 -related phenotypes and QTc ATP1A3 -related phenotypes, with a relatively greater prevalence in those with ATP1A3-D801N.

In this work, for the first time, we designed derivatives of beta-D-glucosyloxy-3-hydroxy-trans-stiblene-2-carboxylic acid (GHS), by conjugating GHS with tumor targeting peptides RPARPAR and GGKRPAR to target over-expressed receptors in tumor cells. The sequences RPARPAR and GGKRPAR are known to target the neuropilin1 (NRP1) receptor due to the C-terminal Arg domain; however, their effectiveness has never been examined with other commonly over-expressed receptors in tumor cells, particularly of chronic lymphocytic leukemia that include integrin α1β1 and CD22. By conjugating these peptides with GHS, which is known for its inherent anti-cancer properties, the goal is to further enhance tumor cell targeting by developing compounds that can target multiple receptors. The physicochemical properties of the conjugates and individual peptides were analyzed using Turbomole and COSMOthermX20 in order to determine their hydrogen bond accepting and donating capabilities. The web server POCASA was used in order to determine the surface cavities and binding pockets of the three receptors. To explore the binding affinities, we conducted molecular docking studies with the peptides and the conjugates with each of the receptors. After molecular docking, the complexes were analyzed using Protein–Ligand Interaction Profiler to determine the types of interactions involved. Molecular dynamics simulation studies were conducted to explore the stability of the receptor-ligand complexes. Our results indicated that in most cases the conjugates showed higher binding and stability with the receptors. Additionally, highly stable complexes of conjugates were obtained with CD22, NRP1 and in most cases with the integrin α1β1 receptor as well. The binding energies were calculated for each of the receptor ligand complexes through trajectory analysis using MMGBSA studies. SwissADME studies revealed that the compounds showed low GI absorption and were not found to be CYP inhibitors and had bioavailability score that would allow them to be considered as potential drug candidates. Overall, our results for the first time show that the designed conjugates can target multiple over-expressed receptors in tumor cells and may be potentially developed as future therapeutics for targeting tumor cells. Graphical abstract