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=Volume 11 - 2020

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=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 (KCa) change in activity in arthritis models and this correlates with FLS activation.  
Objective: To investigate this activation in an in vitro model of inflammatory arthritis; 72hr treatment with cytokines TNF and IL1.  
Methods: FLS cells were isolated from rat synovial membranes.  We analysed global changes in FLS mRNA by RNA-sequencing and then focused on FLS ion channels genes and corresponding FLS electrophysiological phenotype, finally modelling data with Ingenuity Pathway Analysis (IPA) and MATLAB. 
Results:  IPA showed significant activation of inflammatory, osteoarthritic and calcium signalling canonical pathways by cytokines, and we identified ~200 channel gene transcripts.  The large KCa (BK) channel consists of the pore forming Kcnma1 together with -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 -subunit expression Kcnmb1/2 and increase in Kcnmb3.  In electrophysiological experiments, there was a decrease in over-all current density at 20mV without change in chord conductance at this potential. 
Conclusion: TNF and IL1 treatment of FLS in vitro recapitulated several common features of inflammatory arthritis at the transcriptomic level, including increase in Kcnma1 and Kcnmb3 gene expression.