Inflammasomes activation in alveolar macrophages and peripheral blood mononuclear cells in fibrotic Interstitial Lung Diseases

Abstract

Idiopathic pulmonary fibrosis(IPF) is characterized by complex pathogenetic mechanisms. Alterations in the lung microbiome in IPF have been reported and correlated with disease progression and host transcriptomic changes.NOD-like receptors are cytosolic receptors of the innate immune system. Sensing of sterile and microbial stimuli lead to the formation of Inflammasomes, responsible for the cleavage of IL-1b, a pro-inflammatory and fibrotic cytokine. Aim was to study the basal levels and potential activation of NLRP3 and NLRC4 inflammasomes in alveolar macrophages (AMs) and peripheral blood leukocytes (PBMCs) in IPF, other fibrotic lung diseases(fILDs) and controls. PBMCs and AMs, obtained from blood and BAL from healthy volunteers and patients with lung fibrosis were primed with LPS, followed by NLRP3 inflammasome specific stimuli, ATP and double stranded DNA (dsDNA) transfection, while NLRC4 inflammasome was stimulated by Flagellin transfection. Activation was measured by IL-1b secretion. Our preliminary data in PBMCs suggest that in IPF, IL-1b secretion upon NLRP3 stimulation is similar between groups, while flagellin did not activate NLRC4 in IPF and fILDs in contrast to controls. IL-1b secretion was similar between the groups in un-stimulated AMs. Upon stimulation with ATP or dsDNA, NLRP3 activation was highest in fILDs, followed by IPF relative to controls. NLRC4 activation in AMs tended to be higher in IPF and fILDs. Our preliminary data in AMs suggest that NLRP3 is hyper-responsive in fibrotic ILDs, following bacterial insults and may provide insight in the pathogenesis of acute exacerbations after bacterial infections in fibrotic Lung Diseases.