Allen, P. D. | Search bioRxiv

bioRxiv2020

A novel saline-soluble, rapidly-metabolized RyR1 inhibitor rescues volatile anesthesia-induced death and environmental heat stroke in a mouse model relevant to malignant hyperthermia

Mutations in the type 1 ryanodine receptor (RyR1), a Ca2+ release channel in skeletal muscle, hyperactivate the channel to cause malignant hyperthermia (MH) and are implicated in severe heat stroke. Dantrolene, the only approved drug for MH, has the disadvantages of having very poor water solubility and long plasma half-life. We show here that a novel RyR1-selective inhibitor, 6,7-(methylenedioxy)-1-octyl-4-quinolone-3-carboxylic acid (Compound 1, Cpd1), effectively prevents and treats MH and heat stroke in several mouse models relevant to MH. Cpd1 reduced resting intracellular Ca2+, inhibited halothane- and isoflurane-induced Ca2+ release, suppressed caffeine-induced contracture in skeletal muscle, reduced sarcolemmal cation influx, and prevented or reversed the fulminant MH crisis induced by isoflurane anesthesia and rescued animals from heat stroke caused by environmental heat stress. Notably, Cpd1 has great advantages of better water solubility and rapid clearance in vivo over dantrolene. Cpd1 has the potential to be a promising new candidate for effective treatment of patients carrying RyR1 mutations.

pharmacology and toxicology↗

bioRxiv2020

MgrA regulates interaction of Staphylococcus aureus with mucin

BackgroundTo defend the lungs, mucus adheres to bacterial cells and facilitates their removal by ciliary transport. Our goals were to measure the affinity of mucus for the respiratory pathogen Staphylococcus aureus and identify bacterial genes that regulate this interaction. MethodsS. aureus was added to pig tracheas to determine whether it binds mucus or epithelial cells. To quantify its affinity for mucus, we developed a competition assay in microtiter plates. Mucin was added over a dose range as an inhibitor of bacterial attachment. We then examined how transcriptional regulator MgrA and cell wall transpeptidase sortase (SrtA) affect bacterial interaction with mucin. ResultsIn pig tracheas, S. aureus bound mucus strands from submucosal glands more than epithelial cells. In microtiter plate assays, {Delta}srtA failed to attach even in the absence of mucin. Mucin blocked wild type S. aureus attachment in a dose-dependent manner. Higher concentrations were needed to inhibit binding of {Delta}mgrA. Co-deletion of ebh and sraP, which encode surface proteins repressed by MgrA, suppressed the {Delta}mgrA binding phenotype. No differences between {Delta}mgrA and wild type were observed when methylcellulose or heparin sulfate were substituted for mucin, indicating specificity. ConclusionsMucin decreases attachment of S. aureus to plastic, consistent with its physiologic role in host defense. S. aureus deficient in MgrA has decreased affinity for mucin. Ebh and SraP, which are normally repressed by MgrA, may function as inhibitors of attachment to mucin. These data show that specific bacterial factors may regulate the interaction of S. aureus with mucus.

microbiology↗