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Rational A disintegrin and metalloproteinase 33 (ADAM33) was discovered in 2002 as an asthma susceptibility gene. Genetic associations have been made between ADAM33 polymorphisms and asthma disease severity, bronchial hyperresponsivenss (BHR) and rate of lung function decline in both adults and children. A soluble, catalytically active form of the protein (sADAM33) has been identified in the bronchoalveolar lavage fluid of patients, levels of which correlate with disease severity (Lee JY et al, AJRCCM 2006). To study the role sADAM33, a lung specific, doxycycline (Dox) inducible, transgenic mouse, expressing the human pro and metalloproteinase domains of the full-length protein was generated (Ccsp-rtTA/Otet-ADAM33-Pro-MP). Induction of sADAM33, followed by house dust mite (HDM) sensitisation and challenge, resulted in increased BHR and airway inflammation (Davies ER et al, JCI-Insight 2016). The mechanisms by which ADAM33 promotes this susceptibility are unclear. The aim of this work is to identify pathways that are augmented by the induction of sADAM33, which promote increased sensitivity to allergen. Methods RNA samples from whole lung of adult mice, where sADAM33 had been induced for 4 or 8 weeks, were analysed by next generation RNA sequencing. Identified genes were confirmed across experimental time points (72 hour, 7 day, 4 and 8 weeks on Dox) in wider sample cohorts of Ccsp-rtTA/Otet-ADAM33-Pro-MP and control mice through RTqPCR. Results The predominant signal from the RNAseq output was for modulation of immune response genes at 4 weeks of sADAM33 expression (GO:0006955 Immune response: 31 genes, 58.49% coverage, FDR p value=7.09 E-22). Genes associated with an immune activation signature (Ccl5, Irgm1, Gm12250, Gzmb, Ncr1) were validated at least one time point. By 8 weeks of sADAM33 expression genes associated with negative regulation of the response were also validated (Ido1, Cd274). Conclusion Induction of sADAM33 in murine lungs, without allergic sensitisation, augmented underlying immune processes in this transgenic mouse model, which may contribute to increased susceptibility to allergic airway inflammation and BHR when challenged with allergen. Further work is required to delineate how sADAM33 affects immune cell populations and their behaviour in the lung. |
