Cytoplasmic mitochondrial dsRNA in pediatric Sjogren's syndrome

点击翻译按钮获取中文摘要

ABSTRACT Through our multidisciplinary clinical and research collaboration, we have recently discovered a rare cohort of children and adolescents who fulfill the Sjögren’s syndrome (SS) diagnostic criteria (pediatric SS, PSS). As autoimmune SS typically affects elderly females, whether PSS is a unique disease entity or a mere reflection of an early stage of SS is completely unknown. PSS is commonly misdiagnosed as infectious recurrent parotitis (RP), since glandular swelling and pain without a viral/bacterial infection occurs more frequently in PSS than in SS. The overall goal of this application is to characterize the pathology of robust target tissue inflammation in PSS with RP. Our recent, preliminary discovery by RNA-sequencing of SS monocytes revealed aberrant expression of mitochondrial-dsRNA (mtdsRNA) regulators such as SUV3 (ATP-dependent RNA helicase, suppressor of variegation 3), along with the type I IFN signature and a tendency of M1 polarization-associated genes. Consistently, SUV3 gene expression was downregulated in PSS monocytes, detected by RT-qPCR, and knockdown of SUV3 by shRNA transfection led to massive accumulation of mtdsRNA in a cell line. More interestingly, cytoplasmic accumulation of particulate dsRNA was detected in PSS and SS monocytes, which prompted us to ask fundamental questions regarding the nature of the detected dsRNA and its potential impact on monocytes and subsequent immune dysregulation in PSS. To address these questions, we propose our central hypothesis that aberrant mtdsRNA degradation by altered RNA helicase expression and activity elicits amplified priming sensitivity of PSS monocytes by mimicking a viral infection. Our two Specific Aims are: Aim 1. To characterize the nature of cytoplasmic dsRNA involving SUV3 in monocytes of PSS. We hypothesize that cytoplasmic accumulation of mtdsRNA by aberrant mtdsRNA degradation triggers type I IFN production in monocytes of PSS. Cytoplasmic dsRNA transfer and mitochondrial genome depletion will be applied to identify potential mitochondriopathies involving SUV3, which will be complemented by RNA-sequencing of purified monocytes. Aim2. To determine the impact of dsRNA- positive monocytes on macrophage polarization and regulatory T cell (Treg) conversion. We hypothesize that dsRNA and type I IFN signature in PSS monocytes confer propensity toward intensified M1polarization impacting T reg plasticity. Various in vitro assays, such as co-culture experiments and functional assays, will be carried out in parallel with scRNA-seq of PMBC and paired biopsy specimens to profile cellular communications between macrophage and Tregs in the target tissue, which we hypothesize to be influenced by cytoplasmic dsRNA in PSS monocytes. To our knowledge, this is the first study to delineate the properties and impact of cytoplasmic mtdsRNA on monocyte dysregulation and robust inflammation in RP, as well as the first investigation of PSS pathogenesis in the field. Our novel hypothesis involving mtRNA helicases will provide a new opportunity to fill the current knowledge gap.