AUTHOR=Haidar Omar , O’Neill Nathanael , Staunton Caroline A. , Bavan Selvan , O’Brien Fiona , Zouggari Sarah , Sharif Umar , Mobasheri Ali , Kumagai Kosuke , Barrett-Jolley Richard 

TITLE=Pro-inflammatory Cytokines Drive Deregulation of Potassium Channel Expression in Primary Synovial Fibroblasts

JOURNAL=Frontiers in Physiology

VOLUME=11

YEAR=2020

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2020.00226

DOI=10.3389/fphys.2020.00226

ISSN=1664-042X

ABSTRACT=<p>The synovium secretes synovial fluid, but is also richly innervated with nociceptors and acts as a gateway between avascular joint tissues and the circulatory system. Resident fibroblast-like synoviocytes’ (FLS) calcium-activated potassium channels (<italic>K</italic><sub>Ca</sub>) change in activity in arthritis models and this correlates with FLS <italic>activation</italic>.</p><sec><title>Objective</title><p>To investigate this activation in an <italic>in vitro</italic> model of inflammatory arthritis; 72 h treatment with cytokines TNFα and IL1β.</p></sec><sec><title>Methods</title><p>FLS cells were isolated from rat synovial membranes. We analyzed global changes in FLS mRNA by RNA-sequencing, then focused on FLS ion channel genes and the corresponding FLS electrophysiological phenotype and finally modeling data with ingenuity pathway analysis (IPA) and MATLAB.</p></sec><sec><title>Results</title><p>IPA showed significant activation of inflammatory, osteoarthritic and calcium signaling canonical pathways by cytokines, and we identified ∼200 channel gene transcripts. The large <italic>K</italic><sub>Ca</sub> (BK) channel consists of the pore forming Kcnma1 together with β-subunits. Following cytokine treatment, a significant increase in Kcnma1 RNA abundance was detected by qPCR and changes in several ion channels were detected by RNA-sequencing, including a loss of BK channel β-subunit expression Kcnmb1/2 and an increase in Kcnmb3. In electrophysiological experiments, there was a decrease in over-all current density at 20 mV without change in chord conductance at this potential.</p></sec><sec><title>Conclusion</title><p>TNFα and IL1β treatment of FLS <italic>in vitro</italic> recapitulated several common features of inflammatory arthritis at the transcriptomic level, including increase in Kcnma1 and Kcnmb3 gene expression.</p></sec>