Apical dehydration impairs the cystic fibrosis airway epithelium barrier via a β1-integrin/YAP1 pathway

Defective hydration of airway surface mucosa is associated with lung infection in cystic fibrosis (CF), partly caused by disruption of the epithelial barrier integrity. Although rehydration of the CF airway surface liquid (ASL) alleviates epithelium vulnerability to infection by junctional protein expression, the mechanisms linking ASL to barrier integrity are unknown. We show here the strong degradation of YAP1 and TAZ proteins in well-polarized CF human airway epithelial cells (HAECs), a process that was prevented by ASL rehydration. Conditional silencing of YAP1 in rehydrated CF HAECs indicated that YAP1 expression was necessary for the maintenance of junctional complexes. A higher plasma membrane tension in CF HAECs reduced endocytosis, concurrent with the maintenance of active β1-integrin ectopically located at the apical membrane. Pharmacological inhibition of β1-integrin accumulation restored YAP1 expression in CF HAECs. These results indicate that dehydration of the CF ASL affects epithelial plasma membrane tension, resulting in ectopic activation of a β1-integrin/YAP1 signaling pathway associated with degradation of junctional proteins.

Akt-driven TGF-β and DKK1 Secretion Impairs F508del CF Airway Epithelium Polarity

Epithelial polarity is fundamental in maintaining barrier integrity and tissue protection. In cystic fibrosis (CF), apicobasal polarity of the airway epithelium is altered, resulting in increased apical fibronectin deposition and enhanced susceptibility to bacterial infections. Here, we evaluated the effect of highly effective modulator treatment (HEMT) on fibronectin apical deposition and investigated the intracellular mechanisms triggering the defect in polarity of the CF airway epithelium. To this end, primary cultures of CF (F508del variant) human airway epithelial cells (HAECs) and a HAEC line, Calu-3, knocked-down (KD) for CFTR (CFTR KD) were compared to control counterparts, grown at an air-liquid interface (ALI). We show that CFTR mutation in primary HAECs and CFTR KD cells promote the overexpression and over-secretion of TGF-β1 and DKK1 when cultured at ALI. These dynamic changes result in hyperactivation of the TGF-β pathway and inhibition of the Wnt pathway through degradation of β-catenin leading to imbalanced proliferation and polarization. The abnormal interplay between TGF-β and Wnt signaling pathways is reinforced by aberrant Akt signaling. Pharmacological manipulation of TGF-β, Wnt, and Akt pathways restored polarization of the F508del CF epithelium, a correction that was not achieved by HEMT. Our data shed new insights into the signaling pathways that fine-tune apicobasal polarization in primary airway epithelial cells and may provide an explanation to the mitigated efficacy of HEMT on lung infection in people with CF.

Oscillatory shear stress augments endothelial pannexin1 by inhibiting macro-autophagy

Funding Acknowledgements

Type of funding sources: None.

Introduction

Atherosclerotic lesions preferentially develop in arterial regions exposed to disturbed blood flow, which are characterized by a dysfunctional proinflammatory endothelial cell (EC) phenotype. ECs release ATP in response to changes in wall shear stress (WSS), which subsequently regulates the inflammatory response. ATP can be released from cells in a controlled manner through Pannexin1 (Panx1) channels.

Objective

To study the expression of Panx1 in response to WSS and its role in the endothelium.

Methods

Human ECs (HUVECs or EA.hy926) were exposed to physiological high laminar shear stress (HLSS) and atheroprone oscillatory shear stress (OSS) for 48h using an orbital shaker. Panx1 transcript and protein levels were determined by qPCR and Western blot, respectively. mRNA was extracted for RNAseq. WSS-modifying casts were placed for 1 week around the carotid artery of mice and Panx1 expression was analyzed en face. Carotid WSS-modifying casts were also placed in Tie2CreTgPanx1fl/flApoE-/- and Panx1fl/flApoE-/- mice followed by 9 weeks high fat diet. CD68+ cells were quantified in OSS-induced atherosclerotic lesions.

Results

We found that Panx1 expression was increased in carotid regions exposed to OSS as compared to HLSS regions. These results were confirmed in vitro in HUVECs. In silico analysis of the promotor of Panx1 revealed binding sites for the WSS-sensitive transcription factors NF-kB and CREB. NF-kB and CREB mRNA levels were similar under OSS and HLSS, however NF-kB activation (phospho-NF-kB) was detected in ECs under OSS. Surprisingly, Panx1 mRNA level was not affected under these conditions, suggesting that the increased Panx1 protein observed under OSS may be due to decreased Panx1 degradation rather than to increased synthesis of the protein. Unbiased analysis of differential gene expression in ECs exposed to HLSS or OSS revealed 320 up-regulated and 353 down-regulated genes under OSS. Down-regulated genes included proteins involved in macro-autophagy. Inhibition of macro-autophagy in ECs by exposure to chloroquine for 6h increased the expression of glycosylated Panx1, suggestive for more Panx1 channels at the plasma membrane under these conditions. Finally, we observed that atherosclerotic lesions in OSS regions of Tie2CreTgPanx1fl/flApoE-/- mice contained more CD68+ cells than Panx1fl/flApoE-/- controls.

Conclusion

Endothelial Panx1 expression is upregulated in response to OSS. Absence of OSS effects on NF-kB, CREB and Panx1 mRNA revealed that the upregulation of Panx1 protein is not due to transcriptional effects of OSS. Expression of genes involved in the macro-autophagic process were down-regulated under OSS, and chemical inhibition of macro-autophagy augmented the plasma membranous form of Panx1. OSS-induced decrease in autophagic flux may enhance ATP release through Panx1 channels, thereby counterbalancing leukocyte recruitment in atherosclerosis.

Vav3 Mediates Pseudomonas aeruginosa Adhesion to the Cystic Fibrosis Airway Epithelium

Pseudomonas aeruginosa (Pa) represents the leading cause of airway infection in cystic fibrosis (CF). Early airways colonization can be explained by enhanced adhesion of Pa to the respiratory epithelium. RNA sequencing (RNA-seq) on fully differentiated primary cultures of airway epithelial cells from CF and non-CF donors predict that VAV3, β1 INTEGRIN, and FIBRONECTIN genes are significantly enriched in CF. Indeed, Vav3 is apically overexpressed in CF, associates with active β1 integrin luminally exposed, and increases fibronectin deposition. These luminal microdomains, rich in fibronectin and β1 integrin and regulated by Vav3, mediate the increased Pa adhesion to the CF epithelium. Interestingly, Vav3 inhibition normalizes the CF-dependent fibronectin and β1-integrin ectopic expression, improves the CF epithelial integrity, and prevents the enhanced Pa trapping to the CF epithelium. Through its capacity to promote a luminal complex with active β1 integrin and fibronectin that favors bacteria trapping, Vav3 may represent a new target in CF.

Steroid receptors in carcinoma of the breast. Results of immunocytochemical and biochemical determination and their effects on short-term prognosis

A group of 241 nonpretreated breast carcinomas was studied for estrogen receptor (ER) and progesterone receptor (PR) content by both immunocytochemistry (ICC) and biochemical analysis (dextran-coated charcoal [DCC]). While the tumors were judged to be ER positive in 67.6% and PR positive in 65.6% by ICC, DCC analysis showed positive results in 77.6% for both ER and PR. There was only a moderate correlation between the semiquantitative results of ER and PR ICC and the corresponding values for DCC receptor determination. Among tumors shown to be steroid receptor positive by ICC, a majority showed a wide spectrum of staining intensity, from negative to intensely positive (type C staining pattern, ER 87.7%, PR 73.4%). Less frequently, carcinomas showing uniform, intense staining of all epithelial tumor cells were observed (type A staining pattern, ER 11.7%, PR 18.4%). Finally, only very few tumors had both clearly negative and distinctly positive cells (type B staining pattern, ER 0.6%, PR 8.2%). On analyzing the relationship between the expression of steroid receptors (ICC and DCC) and the prognostic factors axillary node status, tumor size, tumor histology, grade and patient age, only a significant correlation between patient age and ER (ICC, r = .46; DCC, r = .43), a weakly significant negative correlation between node involvement and ER, and a weakly significant negative correlation between tumor grade and ER (ICC only) as well as between tumor grade and PR were found. Among all patients, the recurrence-free interval was significantly longer in patients with ER- or PR-positive carcinomas (ICC and DCC).(ABSTRACT TRUNCATED AT 250 WORDS)