Importance of Mast Cell Prss31/Transmembrane Tryptase/Tryptase-{gamma} in Lung Function and Experimental Chronic Obstructive Pulmonary Disease and Colitis [Immunology]

May 12th, 2014 by Hansbro, P. M., Hamilton, M. J., Fricker, M., Gellatly, S. L., Jarnicki, A. G., Zheng, D., Frei, S. M., Wong, G. W., Hamadi, S., Zhou, S., Foster, P. M., Krilis, S. A., Stevens, R. L.

Protease serine member S31 (Prss31)/transmembrane tryptase/tryptase γ is a unique mast cell (MC)-restricted protease of unknown function retained on the outer leaflet of the plasma membrane when MCs are activated. We determined the nucleotide sequences of the Prss31 gene in different mouse strains, and then used a Cre/loxP homologous recombination approach to create a novel Prss31 / C57BL/6 mouse line. The resulting animals exhibited no obvious developmental abnormality, contained normal numbers of granulated MCs in their tissues, and did not compensate for their loss of the membrane tryptase by increasing their expression of other granule proteases. When Prss31-null MCs were activated with calcium ionophore or by their high-affinity IgE receptors, they degranulated in a pattern similar to that of WT MCs. Prss31 null mice had increased baseline airway reactivity to methacholine, but reduced experimental chronic obstructive pulmonary disease (COPD) and colitis, thereby indicating both beneficial and adverse functional roles for the tryptase. In a cigarette smoke induced model of COPD, WT mice had more pulmonary macrophages, higher histopathology scores, and more collagen in their small airways than similarly treated Prss31-null mice. In a dextran sodium sulfate-induced colitis model, WT mice lost more weight, had higher histopathology scores, and contained more Cxcl1 and IL-6 mRNA in their colons than similarly treated Prss31-null mice. The accumulated data raise the possibility that inhibitors of this membrane tryptase may provide additional therapeutic benefit in the treatment of humans with these MC-dependent inflammatory disorders.
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