Selective Antagonists of the Bronchiolar Epithelial NF-κB-Bromodomain-Containing Protein 4 Pathway in Viral-Induced Airway Inflammation

Abstract

SUMMARY The mechanisms how the mammalian airway detects invading viral pathogens to trigger protective innate neutrophilic inflammation are incompletely understood. We observe that innate activation of the NFκB/RelA transcription factor indirectly activates atypical BRD4 histone acetyltransferase (HAT) activity, RNA Polymerase II (Pol II) phosphorylation, and secretion of neutrophilic chemokines. To study this pathway in vivo, we develop a conditional knockout of RelA in the distal airway epithelial cell; these animals have reduced mucosal BRD4/Pol II activation and neutrophilic inflammation to viral patterns. To further understand the role of BRD4 in vivo, two potent, highly selective small-molecule BRD4 inhibitors were developed. These well-tolerated inhibitors disrupt BRD4 complex with Pol II and histones, completely blocking inducible epithelial chemokine production and neutrophilia. We conclude RelA-BRD4 signaling in distal tracheobronchiolar epithelial cells mediates acute inflammation in response to luminal viral patterns. These potent BRD4 antagonists are versatile pharmacological tools for investigating BRD4 functions in vivo.

The NFκB subunit RELA is a master transcriptional regulator of the committed epithelial-mesenchymal transition in airway epithelial cells

“…A 20-nucleotide seed sequence in exon 4 of the RELA gene was used to introduce a stop codon that induces nonsensemediated RNA decay. RELA Ϫ/Ϫ hSAECs lack detectable RELA mRNA and protein (34,57).…”

RSV Reprograms the CDK9•BRD4 Chromatin Remodeling Complex to Couple Innate Inflammation to Airway Remodeling

“…To study the role of nonciliated small airway cells on RSV-induced inflammation in vivo, we developed an inducible NFκB/RelA knockout mouse, where RelA could be deleted in small airway epithelial cells [47,48]. Mice depleted of RelA in the Scgb1a1 progenitor-derived population have significantly reduced chemokine response, leukocytic inflammation, and airway obstruction in response to experimental RSV infection [37].…”

“…Mice depleted of RelA in the Scgb1a1 progenitor-derived population have significantly reduced chemokine response, leukocytic inflammation, and airway obstruction in response to experimental RSV infection [37]. Interestingly, TLR3-driven inflammation is also mediated by the same epithelial cell population [48]. In a manner similar to the findings with RSV infection, mice depleted of RelA in the Scgb1a1 + progenitor cells respond to luminal TLR3 agonist with reduced epithelial-dependent chemokine expression, neutrophilia, airway hyperreactivity, and remodeling.…”

“…The essential functional role of CDK9•BRD4 in RSV-induced IIR has been demonstrated by disruption of P-TEFb recruitment by RelA Ser 276 site mutation [52], siRNA-mediated silencing of CDK9 and BRD4 [24,52,53,61], and small-molecule inhibition of CKD9 and BRD4 [34,48,53]. Consequently, CDK9•BRD4 are molecules receiving significant attention as a target for pharmacological manipulation of viral and allergen-inducible mucosal inflammation [48,[62][63][64][65][66].…”

Bromodomain‐containing protein 4 inhibition alleviates matrix degradation by enhancing autophagy and suppressing NLRP3 inflammasome activity in NP cells

“…LINC00969, a long noncoding RNA, also influences NLRP3 inflammation activation by regulating miR‐335‐3p (Yu, Hao, Xu, Zhu, & Cai, 2018). BRD4 plays essential roles in many diseases, such as virus‐induced airway inflammation and spinal cord injury (Rudman et al, 2018; Tian et al, 2018). However, there are no reports on the relationship between BRD4 and NLRP3 inflammasome‐mediated pyroptosis.…”