S56 ZFP36L1 and ZFP36L2 deficiency contribute to steroid refractoriness and epithelial remodelling in severe asthma. (11th November 2022) - Rynne, J
Abstract : Background: Asthma is the most common chronic inflammatory disease of the airways. Patients with severe asthma (SA) show poor response to steroid treatment and can be now treated by biologics if eosinophilic. The underlying mechanisms of SA, however, remain poorly understood. Most omics approaches assess changes at the mRNA (transcription) or protein levels, overlooking that not all mRNAs translate into proteins. mRNA-to-protein levels correlate poorly due to post-transcriptional regulation, undertaken by microRNAs and RNA binding proteins (RBPs). There are more RBPs than transcription factors; however, their role in SA and steroid responsiveness remains largely unknown. Methods: Frac-seq (subcellular fractionation and RNA-sequencing) to investigate transcriptional and post-transcriptional mRNA expression, qPCR, siRNA modulation and RNA immunoprecipitation (RIP). Results: The RBPs ZFP36L1 and ZFP36L2 are dysregulated in SA bronchial epithelial cells (BECs) and modulate corticosteroid responses. We employed Frac-seq in primary BECs depleted of L1 and L2 (mimicking SA) vs control and stimulated with dexamethasone. We compared the effects of dexamethasone on gene expression in different subcellular compartments: 'total' (current 'transcriptomics'), 'monosomes' (mRNAs poorly translated) and 'polyribosomes' (mRNAs heavily translated). Dexamethasone modulated mRNA expression distinctively on these three subcellular compartments; thus steroids modulate both mRNA transcription and translation. RIP demonstrated that ZFP36L1/L2 bind to their mRNA targets in a steroid-dependent manner. ZFP36L1/L2 and steroids altered the expression of mRNAs encoding structural proteins, hinting at these RBPS as modulators of epithelial structural changes and steroid poor responsiveness. Conclusions: ZFP36L1/L2 are novel modulators of steroid effects in epithelium and may potentially contribute to steroid refractoriness. Please refer to page A210 for declarations of interest related to this abstract.