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Abstract Inflammation is the result of a complex network of cellular and molecular interactions and mechanisms that facilitate immune protection against intrinsic and extrinsic stimuli, particularly pathogens, to maintain homeostasis and promote tissue healing. However, dysregulation in the immune system elicits excess/abnormal inflammation resulting in unintended tissue damage and causes major inflammatory diseases including asthma, chronic obstructive pulmonary disease, atherosclerosis, inflammatory bowel diseases, sarcoidosis and rheumatoid arthritis. It is now widely accepted that both endoplasmic reticulum (ER) stress and inflammasomes play critical roles in activating inflammatory signalling cascades. Notably, evidence is mounting for the involvement of ER stress in exacerbating inflammasome‐induced inflammatory cascades, which may provide a new axis for therapeutic targeting in a range of inflammatory disorders. Here, we comprehensively review the roles, mechanisms and interactions of both ER stress and inflammasomes, as well as their interconnected relationships in inflammatory signalling cascades. We also discuss novel therapeutic strategies that are being developed to treat ER stress‐ and inflammasome‐related inflammatory disorders.

IntroductionThe RNA-binding protein AU-rich-element factor-1 (AUF-1) participates to posttranscriptional regulation of genes involved in inflammation and cellular senescence, two pathogenic mechanisms of chronic obstructive pulmonary disease (COPD). Decreased AUF-1 expression was described in bronchiolar epithelium of COPD patients versus controls and in vitro cytokine- and cigarette smoke-challenged human airway epithelial cells, prompting the identification of epithelial AUF-1-targeted transcripts and function, and investigation on the mechanism of its loss.ResultsRNA immunoprecipitation-sequencing (RIP-Seq) identified, in the human airway epithelial cell line BEAS-2B, 494 AUF-1-bound mRNAs enriched in their 3’-untranslated regions for a Guanine-Cytosine (GC)-rich binding motif. AUF-1 association with selected transcripts and with a synthetic GC-rich motif were validated by biotin pulldown. AUF-1-targets’ steady-state levels were equally affected by partial or near-total AUF-1 loss induced by cytomix (TNFα/IL1β/IFNγ/10 nM each) and siRNA, respectively, with differential transcript decay rates. Cytomix-mediated decrease in AUF-1 levels in BEAS-2B and primary human small-airways epithelium (HSAEC) was replicated by treatment with the senescence- inducer compound etoposide and associated with readouts of cell-cycle arrest, increase in lysosomal damage and senescence-associated secretory phenotype (SASP) factors, and with AUF-1 transfer in extracellular vesicles, detected by transmission electron microscopy and immunoblotting. Extensive in-silico and genome ontology analysis found, consistent with AUF-1 functions, enriched RIP-Seq-derived AUF-1-targets in COPD-related pathways involved in inflammation, senescence, gene regulation and also in the public SASP proteome atlas; AUF-1 target signature was also significantly represented in multiple transcriptomic COPD databases generated from primary HSAEC, from lung tissue and from single-cell RNA-sequencing, displaying a predominant downregulation of expression.DiscussionLoss of intracellular AUF-1 may alter posttranscriptional regulation of targets particularly relevant for protection of genomic integrity and gene regulation, thus concurring to airway epithelial inflammatory responses related to oxidative stress and accelerated aging. Exosomal-associated AUF-1 may in turn preserve bound RNA targets and sustain their function, participating to spreading of inflammation and senescence to neighbouring cells.

Abstract Background Both the six gene signature (6GS: CPA3, DNASE1L3, CLC, IL1B, ALPL, and CXCR2) and T‐helper 2 signature (TH2S: CLCA1, SERPINB2, and POSTN) are proposed as biomarkers in the identification of inflammatory phenotypes of asthma in induced sputum and epithelial brushings, respectively. The aim of this study was to explore patterns of gene expression of known signatures, 6GS and TH2S in endobronchial biopsies. Methods This was an exploratory cross‐sectional study of gene expression in endobronchial biopsies of 55 adults with asthma and 9 healthy controls (HC). The expression of the 6GS and TH2S was determined by quantitative polymerase chain reaction. Correlations with clinical and cellular characteristics were performed, and receiver operating characteristic was utilized to assess signatures' ability to predict asthma from HC and inflammatory phenotypes. Results Gene expression of DNASE1L3 (P = .045) was upregulated in asthma compared with HC, and IL1B (P = .017) was upregulated in neutrophilic asthma compared with non‐neutrophilic asthma. In asthma, the expression of CPA3 was negatively associated with ICS daily dose (r = −.339; P = .011), IL1B expression was positively associated with bronchial lavage fluid (BLF) total cell count (r = .340; P = .013) and both CLC and POSTN expression were associated with lymphocytes percentage in BLF (r = −.355, P = .009; r = −.300, P = .025, respectively). Both 6GS (area under curve [AUC] = 86.3%; P = .017) and TH2S (AUC = 72.7%; P = .037) could significantly predict asthma from HC. In addition, 6GS can identify neutrophilic (AUC = 93.2%; P = .005) and TH2S identifies eosinophilic (AUC = 62.7%; P = .033) asthma. Conclusions and Clinical Relevance There was increased expression of DNASE1L3 in asthma and IL1B in neutrophilic asthma. These results show similar upregulated patterns of expression in two genes of the 6GS in endobronchial biopsies, previously identified in sputum. The upregulation of DNASE1L3 and IL1B suggests that common mechanisms may be at play throughout the airway.

Abstract Objective Chronic obstructive pulmonary disease (COPD) is a progressive disease that causes significant mortality and morbidity worldwide and is primarily caused by the inhalation of cigarette smoke (CS). Lack of effective treatments for COPD means there is an urgent need to identify new therapeutic strategies for the underlying mechanisms of pathogenesis. Tristetraprolin (TTP) encoded by the Zfp36 gene is an anti‐inflammatory protein that induces mRNA decay, especially of transcripts encoding inflammatory cytokines, including those implicated in COPD. Methods Here, we identify a novel protective role for TTP in CS‐induced experimental COPD using Zfp36aa/aa mice, a genetically modified mouse strain in which endogenous TTP cannot be phosphorylated, rendering it constitutively active as an mRNA‐destabilising factor. TTP wild‐type (Zfp36+/+) and Zfp36aa/aa active C57BL/6J mice were exposed to CS for four days or eight weeks, and the impact on acute inflammatory responses or chronic features of COPD, respectively, was assessed. Results After four days of CS exposure, Zfp36aa/aa mice had reduced numbers of airway neutrophils and lymphocytes and mRNA expression levels of cytokines compared to wild‐type controls. After eight weeks, Zfp36aa/aa mice had reduced pulmonary inflammation, airway remodelling and emphysema‐like alveolar enlargement, and lung function was improved. We then used pharmacological treatments in vivo (protein phosphatase 2A activator, AAL(S), and the proteasome inhibitor, bortezomib) to promote the activation and stabilisation of TTP and show that hallmark features of CS‐induced experimental COPD were ameliorated. Conclusion Collectively, our study provides the first evidence for the therapeutic potential of inducing TTP as a treatment for COPD.