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Phosphatidylinositol 3-kinase-? controls endoplasmic reticulum membrane fluidity and permeability in fungus-induced allergic inflammation in mice.

ABSTRACT: BACKGROUND AND PURPOSE:Phosphatidylinositol 3-kinase (PI3K), especially PI3K-?, and endoplasmic reticulum (ER) stress play important roles in refractory asthma induced by the fungus Aspergillus fumigatus through mechanisms that are not well understood. Here we have investigated these mechanisms, using BEAS-2B human bronchial epithelial cells and a mouse model of A. fumigatus-induced allergic lung inflammation. EXPERIMENTAL APPROACH:A selective PI3K-? inhibitor, IC87114, and an ER folding chaperone, 4-phenylbutyric acid (4-PBA), were applied to a model of A. fumigatus-induced asthma in female C57BL/6 mice. The therapeutic potential of IC87114 and 4-PBA was assessed in relevant primary cell, tissue, and disease models, using immunohistochemistry, western blotting and assessment of ER redox state and membrane fluidity. KEY RESULTS:Treatment with IC87114 or 4-PBA alleviated pulmonary inflammation and airway remodelling and reduced ER stress and inflammation-associated intra-ER hyperoxidation, disrupting protein disulfide isomerase (PDI) chaperone activity. IC87114 and 4-PBA also reversed changes in ER membrane fluidity and permeability and the resultant mitochondrial hyperactivation (i.e., Ca2+ accumulation) under hyperoxidation, thereby restoring the physiological state of the ER and mitochondria. These compounds also abolished mitochondria-associated ER membrane (MAM) formation caused by the physical contact between these subcellular organelles. CONCLUSION AND IMPLICATIONS:PI3K-? and ER stress mediate A. fumigatus-induced allergic lung inflammation by altering the ER redox state, PDI chaperone function, and ER membrane fluidity and permeability and by amplifying ER signalling to mitochondria through MAM formation. Thus, therapeutic strategies that target the PI3K-?-ER stress axis could be an effective treatment for allergic asthma caused by fungi.

SUBMITTER: Lee HY

PROVIDER: S-EPMC7060358 | biostudies-literature | 2020 Apr

REPOSITORIES: biostudies-literature

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Phosphatidylinositol 3-kinase-δ controls endoplasmic reticulum membrane fluidity and permeability in fungus-induced allergic inflammation in mice.

Lee Hwa-Young HY Lee Geum-Hwa GH Kim Hyung-Ryong HR Lee Yong-Chul YC Chae Han-Jung HJ

British journal of pharmacology 20200127 7

<h4>Background and purpose</h4>Phosphatidylinositol 3-kinase (PI3K), especially PI3K-δ, and endoplasmic reticulum (ER) stress play important roles in refractory asthma induced by the fungus Aspergillus fumigatus through mechanisms that are not well understood. Here we have investigated these mechanisms, using BEAS-2B human bronchial epithelial cells and a mouse model of A. fumigatus-induced allergic lung inflammation.<h4>Experimental approach</h4>A selective PI3K-δ inhibitor, IC87114, and an ER ...[more]

PMID: 31713846

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Project description:Dysregulated phosphatidylinositol (PI) signaling has been implicated in human gastrointestinal (GI) malignancies and inflammatory states, underlining the need to study pathophysiological roles of PI in an in vivo genetic model. Here, we study the significance of PI in GI pathophysiology using the zebrafish mutant cdipt(hi559), which lacks PI synthesis, and unravel a crucial role of PI in intestinal mucosal integrity and inflammation. The cdipt(hi559) mutants exhibit abnormal villous architecture and disorganized proliferation of intestinal epithelial cells (IECs), with pathologies reminiscent of inflammatory bowel disease (IBD), including apoptosis of goblet cells, abnormal mucosecretion, bacterial overgrowth and leukocyte infiltration. The mutant IECs exhibit vacuolation, microvillus atrophy and impaired proliferation. The cdipt(hi559) gene expression profile shows enrichment of acute phase response signaling, and the endoplasmic reticulum (ER) stress factors hspa5 and xbp1 are robustly activated in the mutant GI tissue. Temporal electron micrographic analyses reveal that PI-deficient IECs undergo sequential ER-Golgi disruption, mitochondrial depletion, macroautophagy and cell death, consistent with chronic ER-stress-mediated cytopathology. Furthermore, pharmacological induction of ER stress by inhibiting protein glycosylation or PI synthase inhibition in leukocyte-specific reporter lines replicates the cdipt(hi559) inflammatory phenotype, suggesting a fundamental role of PI metabolism and ER stress in mucosal inflammation. Antibiotics and anti-inflammatory drugs resolved the inflammation, but not the autophagic necroapoptosis of IECs, suggesting that bacterial overgrowth can exacerbate ER stress pathology, whereas persistent ER stress is sufficient to trigger inflammation. Interestingly, the intestinal phenotype was partially alleviated by chemical chaperones, suggesting their therapeutic potential. Using zebrafish genetic and pharmacological models, this study demonstrates a newly identified link between intracellular PI signaling and ER-stress-mediated mucosal inflammation. The zebrafish cdipt mutants provide a powerful tool for dissecting the fundamental mechanisms of ER-stress-mediated human GI diseases and a platform to develop molecularly targeted therapies.

Dataset Information

Phosphatidylinositol 3-kinase-? controls endoplasmic reticulum membrane fluidity and permeability in fungus-induced allergic inflammation in mice.

Publications

Phosphatidylinositol 3-kinase-δ controls endoplasmic reticulum membrane fluidity and permeability in fungus-induced allergic inflammation in mice.

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