title: Induction of group IVC phospholipase A2 in allergic asthma: transcriptional regulation by TNFα in bronchoepithelial cells.
abstract: Airway inflammation in allergen-induced asthma is associated with eicosanoid release. These bioactive lipids exhibit anti- and pro-inflammatory activities with relevance to pulmonary pathophysiology. We hypothesized that sensitization/challenge using an extract from the ubiquitous fungus Aspergillus fumigatus in a mouse model of allergic asthma would result in altered phospholipase gene expression, thus modulating the downstream eicosanoid pathway. We observed the most significant induction in the group IVC PLA2 (phospholipase A2) [also known as cPLA2γ (cytosolic PLA2γ) or PLA2G4C]. Our results infer that A. fumigatus extract can induce cPLA2γ levels directly in eosinophils, whereas induction in lung epithelial cells is most likely to be a consequence of TNFα (tumour necrosis factor α) secretion by A. fumigatus-activated macrophages. The mechanism of TNFα-dependent induction of cPLA2γ gene expression was elucidated through a combination of promoter deletions, ChIP (chromatin immunoprecipitation) and overexpression studies in human bronchoepithelial cells, leading to the identification of functionally relevant CRE (cAMP-response element), NF-κB (nuclear factor κB) and E-box promoter elements. ChIP analysis demonstrated that RNA polymerase II, ATF-2 (activating transcription factor 2)-c-Jun, p65-p65 and USF (upstream stimulating factor) 1-USF2 complexes are recruited to the cPLA2γ enhancer/promoter in response to TNFα, with overexpression and dominant-negative studies implying a strong level of co-operation and interplay between these factors. Overall, our results link cytokine-mediated alterations in cPLA2γ gene expression with allergic asthma and outline a complex regulatory mechanism.
authors.affiliation: Department of Neuroscience, College of Medicine, University of Florida, Gainesville, FL 32610, USA.
authors.forename: Justin S
authors.initials: JS
authors.lastname: Bickford
authors.forename: Kimberly J
authors.initials: KJ
authors.lastname: Newsom
authors.forename: John-David
authors.initials: JD
authors.lastname: Herlihy
authors.forename: Christian
authors.initials: C
authors.lastname: Mueller
authors.forename: Benjamin
authors.initials: B
authors.lastname: Keeler
authors.forename: Xiaolei
authors.initials: X
authors.lastname: Qiu
authors.forename: Jewell N
authors.initials: JN
authors.lastname: Walters
authors.forename: Nan
authors.initials: N
authors.lastname: Su
authors.forename: Shannon M
authors.initials: SM
authors.lastname: Wallet
authors.forename: Terence R
authors.initials: TR
authors.lastname: Flotte
authors.forename: Harry S
authors.initials: HS
authors.lastname: Nick
mesh_terms: D051698:Activating Transcription Factor 2 / Q000378:metabolism; D000818:Animals; D001232:Aspergillus fumigatus / Q000276:immunology*; D001249:Asthma / Q000235:genetics* / Q000276:immunology; D002460:Cell Line; D004790:Enzyme Induction; D005786:Gene Expression Regulation / Q000187:drug effects; D054513:Group IV Phospholipases A2 / Q000096:biosynthesis*; D006801:Humans; D008168:Lung / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D014157:Transcription Factors / Q000096:biosynthesis; D014409:Tumor Necrosis Factor-alpha / Q000494:pharmacology* / Q000502:physiology
chemical_list: C497105:ATF2 protein, human; D051698:Activating Transcription Factor 2; D014157:Transcription Factors; D014409:Tumor Necrosis Factor-alpha; C472331:PLA2G4C protein, human; D054513:Group IV Phospholipases A2