Role of GLCCI1 in inhibiting PI3K-induced NLRP3 inflammasome activation in asthma.

Abstract

Background: Glucocorticoid-induced transcript 1 (GLCCI1) has been reported to be associated with the efficiency of inhaled glucocorticoids in patients with asthma. This study aimed to investigate the role of GLCCI1 in the regulation of nucleotide-binding oligomerization domain (NOD)-like receptor (NLR) family pyrin domain-containing 3 (NLRP3) by the phosphatidylinositol 3-kinase (PI3K) pathway in the pathogenesis of allergic asthma.

Methods: The expression levels of genes encoding GLCCI1, NLRP3 inflammasome components, and PI3K pathway-related indicators were detected in cells isolated from induced sputum from patients with asthma and healthy controls. Next, we induced asthma in wild-type C57BL/6 mice and Glcci1 knockout (Glcci1 ^-/-) mice by injecting them with ovalbumin (OVA) and treated the asthmatic mice with a PI3K pathway inhibitor (LY294002) or left them untreated. We also performed adoptive transfer of macrophages into the mice and assessed lung inflammation, as well as GLCCI1, PI3K pathway component, and NLRP3 inflammasome component expression levels. Finally, primary bone marrow-derived macrophages (BMDMs) from wild-type and Glcci1 ^-/- mice were treated with OVA, either in the presence or absence of LY294002 and the NLRP3 inhibitor (MCC950), to validate our findings.

Results: The mRNA level of Glcci1 in induced sputum cells from asthmatic patients was lower compared to that of healthy controls. Additionally, Glcci1 mRNA expression correlated negatively with NLRP3 inflammasome indicators and the PI3K pathway components, as well as with IL-1β expression in induced sputum macrophages. In vivo, Glcci1 ^-/- asthmatic mice showed elevated levels of airway inflammation and NLRP3 inflammasome activation compared to wild-type asthmatic mice. Surprisingly, the efficacy of LY294002 in reducing lung tissue inflammation and NLRP3 inflammasome activity in wild-type asthmatic mice was attenuated by Glcci1 knockout. LY294002 enhanced GLCCI1 levels in macrophages within the lung tissue of wild-type asthmatic mice. Moreover, LY294002 did not inhibit lung inflammation in wild-type asthmatic mice depleted of macrophages that had received adoptive transfer of Glcci1 ^-/- BMDMs. In vitro experiments further illustrated that LY294002 suppressed NLRP3 activation by upregulating GLCCI1 expression in BMDMs. The introduction of MCC950 led to a marked decrease in NLRP3 and apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) protein levels, but did not affect the expression levels of GLCCI1 or the phospho-protein kinase B (p-AKT)/AKT ratio.

Conclusions: GLCCI1 deficiency promotes asthma inflammation through PI3K-induced NLRP3 inflammasome activation.