Increased Hydrogen Peroxide After Traumatic Brain Injury Disrupts Phosphatidylinositol 4,5‐Bisphosphate Metabolism Causing Impaired Inward Rectifier Potassium Channel Function
Authors: Sackheim Adrian M. , Villalba Nuria , Bonev Adrian , Nelson Mark , Freeman Kalev 
Published: June 2021

Severe trauma, including traumatic brain injury (TBI), can result in several deleterious outcomes including coagulopathy, multi‐organ failure and death. We previously showed that TBI in rodents causes uncoupling of mesenteric artery (MA) nitric oxide production, resulting in excessive reactive oxygen species (ROS) generation and impaired endothelial‐dependent vasodilation. The inward‐rectifier potassium channel (KIR) is an essential component of agonist‐ and flow‐induced vasodilation and signal transduction in mesenteric arteries (MAs); however, its function following trauma has not been assessed. Phosphatidylinositol 4,5‐bisphosphate (PIP2) is a membrane phospholipid which is required for normal KIR channel function in MAs. We hypothesized that oxidative stress, specifically hydrogen peroxide (H2O2), was driving down PIP2 levels, causing KIR channelopathies. We studied male rats 24 hours after fluid percussion TBI, compared to controls. Plasma oxidative‐reduction potential (ORP), an indicator of oxidative stress, was significantly elevated in TBI rats compared to controls. In TBI but not control plasma, catalase application significantly reduced the ORP signal to control values, suggesting that H2O2 contributes to global oxidative stress following TBI. We then measured KIR currents in isolated endothelial cells (ECs) from MAs, using the whole‐cell patch‐clamp technique from control and TBI rats. KIR channel currents were significantly diminished in ECs from TBI rats compared to controls. KIR currents in ECs from TBI MAs were rescued with the addition of PIP2 to the pipette solution when compared to untreated TBI cells, and showed no difference from their control, treated counterparts, implying depletion of PIP2 following TBI is a contributing factor to KIR channel dysfunction. Next, diameter responses of arteries using pressure myography were measured. In control arteries, increasing concentrations of extracellular potassium from 6 to 10 mM K+ caused dilations; concentrations between 14 to 60 mM K+ caused constrictions. Dilations to 10 mM K+ were significantly reduced following TBI, consistent with an impaired KIR channel response. Next, basal KIR function was assessed using the KIR and KIR2.1 antagonists BaCl2 (100 μM) and ML 133 (20 μM). Following TBI, arteries constricted significantly less to both BaCl2 and ML 133. Furthermore, dilations to 10 mM K+ and constrictions to ML 133 were restored in TBI arteries in the presence of catalase. Lastly, To further quantify cellular pathology following TBI, the metabolomic phenotype was measured by liquid chromatography‐mass spectrometry (LC‐MS) in plasma obtained from control and TBI rats. Rats exhibited a profound metabolopathy following TBI; within the lipidome: arachidonate metabolism, glycerophospholipid synthesis, and fatty acid mobilization were significantly altered. These data suggest H2O2 production serves an antagonistic role on KIR channel function through changes in second messenger and lipid signaling pathways in the mesenteric circulation following TBI.Support or Funding InformationThis work was supported by the Totman Medical Research Trust and the National Institute of Health (K08‐GM‐098795 and UM1‐HL‐120877).This abstract is from the Experimental Biology 2018 Meeting. There is no full text article associated with this abstract published in The FASEB Journal.