Alternative pre-mRNA splicing of Toll-like receptor signaling components in peripheral blood mononuclear cells from patients with ARDS

Abstract

A key physiological feature of acute respiratory distress syndrome (ARDS) is inflammation. Toll-like receptor (TLR) signaling is required to combat the infection that underlies many ARDS cases but also contributes to pathological inflammation. Several TLR signaling pathway genes encoding positive effectors of inflammation also produce alternatively spliced mRNAs encoding negative regulators of inflammation. An imbalance between these isoforms could contribute to pathological inflammation and disease severity. To determine whether splicing in TLR pathways is altered in patients with ARDS, we monitored alternative splicing of and, two genes that function in multiple TLR pathways. The and genes produce long proinflammatory mRNAs (MyD88 and IRAK1) and shorter anti-inflammatory mRNAs (MyD88 and IRAK1c). We quantified mRNA encoding inflammatory cytokines and and isoforms in peripheral blood mononuclear cells (PBMCs) from 104 patients with ARDS and 30 healthy control subjects. We found that pre-mRNA splicing is altered in patients with ARDS in a proinflammatory direction. We also observed altered isoform levels in a second critically ill patient cohort, suggesting that these changes may not be unique to ARDS. Early in ARDS, PBMC IRAK1c levels were associated with patient survival. Despite the similarities in and alternative splicing observed in previous in vitro studies, there were differences in how and alternative splicing was altered in patients with ARDS. We conclude that pre-mRNA splicing of TLR signaling genes is altered in patients with ARDS, and further investigation of altered splicing may lead to novel prognostic and therapeutic approaches.

Inflammation Drives Alternative First Exon usage to Regulate Immune Genes including a Novel Iron Regulated Isoform of Aim2

“…Alternative splicing within the immune system can affect the type and magnitude of the inflammatory response, such as the production of a soluble form of TLR4 that is expressed upon LPS, which leads to inhibition of TNFα and NFκB serving as a negative feedback mechanism (19,20). Additionally, this mechanism has been characterized within signaling molecules (21,22), including TBK1 (23) and MyD88 (24), that produce the alternative RNA splice forms, TBK1s and MyD88s respectively, which function to limit the extent of the proinflammatory response. Alternative splicing can also result in the production of inflammatory signaling molecules, such as TRIF (25) and the proteins in the NFκB family (9) with altered activity or stability.…”

Inflammation-Induced Alternative Pre-mRNA Splicing in Mouse Alveolar Macrophages

“…For example, alternative pre-mRNA splicing can result in production of inflammatory signaling molecules with altered activity or stability (Cadalbert et al 2010;Han et al 2010;Phan et al 2006;Wells et al 2006). Additionally, some genes that encode positive effectors of inflammatory signaling can also produce alternate pre-mRNA splice forms that encode negative regulators of signaling (Blumhagen et al 2017;De Arras and Alper 2013;Deng et al 2008;Gray et al 2010;Hardy and O'Neill 2004;Iwami et al 2000;Janssens et al 2002;Koop et al 2011;Palsson-McDermott et al 2009;Rao et al 2005;Rosenstiel et al 2006), thus mediating a negative feedback loop to limit the extent of the inflammatory response. In a similar fashion, alternative pre-mRNA splicing has been shown to alter cellular metabolism (Clower et al 2010;Yang and Lu 2013;Satoh et al 2015).…”

NF-κB mediates lipopolysaccharide-induced alternative pre-mRNA splicing of MyD88 in mouse macrophages

“…Several studies have reported an association of MyD88 isoform levels with inflammatory disease. MyD88-L but not MyD88-S is increased in PBMCs from patients with two different inflammatory lung diseases (acute respiratory distress syndrome and interstitial lung disease with an acute exacerbation) (11). The increase in MyD88-L without a corresponding alteration in MyD88-S could contribute to the inflammatory milieu in these patients.…”

“…Mouse studies were approved by the National Jewish Health Animal Care and Use Committee (IACUC). [8][9][10][11][12] week old mice of both sexes were obtained from the Jackson Laboratories (Bar Harbor, ME). These mice included C57BL/6J (stock #000664), TLR4 knockout mice (stock #029015), and TRIF knockout mice (stock # 005037).…”

“…More than 256 different mRNA isoforms encompassing receptors, adaptors, and downstream effectors have been identified in the TLR signaling pathway; many of these different isoforms encode proteins with differing functions (10). In particular, while the canonical mRNAs in this signaling pathway usually encode activators of signaling, many TLR pathway genes also produce alternative mRNA splice forms that encode dominant negative inhibitors of the signaling pathway (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21). Production of many of these negatively acting alternative splice forms is induced by LPS and/or other TLR agonists (11)(12)(13)(14)(15)(16)(17)(18)(19)(20)(21); thus, induction of this alternative splicing constitutes a negative feedback loop that terminates persistent inflammatory signaling.…”