Preservation of Ca2+ spark activity in MitoQ treated long term hypoxic newborn lambs

Abstract

Before birth, the pulmonary vasculature is relatively constricted and has reduced blood flow. The vasculature dilates with birth, and blood flow and oxygenation increase. Pulmonary arterial dilation during birth is related to activation of large conductance potassium channels and Ca2+ spark events through activation of ryanodine receptors (RyR) on the sarcoplasmic reticulum. This coupled mechanism is driven by activation of L-type Ca2+ channels, which stimulate RyRs. Long-term maternal hypoxia increases oxidative stress in neonatal pulmonary arteries, which may arise from the mitochondria. There is also disruption of Ca2+ sparks and pulmonary hypertension in newborn lambs. Long-term MitoQ usage, an antioxidant that targets the mitochondria, can reduce oxidative stress levels and improve vascular function due to hypoxic stress. We hypothesize that hypoxia induced reactive oxygen species generated through disruption of mitochondrial function dysregulates Ca2+ spark activity, underlying functional problems due to long term hypoxic stress. This study aims to analyze and understand whether MitoQ treatment can recover Ca2+ spark activity. To address this hypothesis, pulmonary arterial myocytes of control (N=11 normoxic, 2 hypoxic) and MitoQ treated newborn sheep (N=2 normoxic, 5 hypoxic) were examined in the presence and absence of membrane depolarization with 30 mM potassium (30K). The intracellular Ca2+ was recorded in the myocytes of isolated pulmonary arteries that were loaded with Fluo-4 using line-scan techniques on a confocal microscope. Ca2+ spark activity was analyzed using automated customized software (Sparklab). In comparison to our previously published work, the basal spark activity was generally high in both normoxic and hypoxic groups, but the MitoQ normoxic group had lower activity. MitoQ treatment did not modify Ca2+ spark activity in any group. Use of the newly designed automated detection software may underlie differences as compared to our published work. The lack of an effect of MitoQ on spark activity parallels the ineffectiveness of acute antioxidant treatment in our other pilot studies on fetal pulmonary arteries. Overall, additional studies are required to resolve the discrepancies between our current and previous work. NIH R01HL155295 and R01HL149608, NSF Grant MRI-DBI 0923559 and the Loma Linda University School of Medicine This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.