Proteases derived from fish species and king crab display variations in the stimulation of inflammatory signalling pathways

Introduction: Serine proteases are widely distributed in nature and found in all kingdoms of cellular life as well as in many viral genomes. Our previous research has demonstrated that production workers in the seafood industry inhale aerosols containing trypsin and other serine proteases. Protease activated receptors (PARs) are important signalling mediators in airways transmitting protease activity into increased production of inflammatory agents in presence as well as in absence of allergic sensitization.  

Objectives: The objective of this study was to increase the understanding of the role of serine proteases, protease activated receptors (PAR-2) and downstream signalling pathways in airway reactivity towards fish and king crabs. Specifically, we wished to compare king crab trypsin and fish trypsins regarding capacity of activating PAR-2 and intracellular signal pathways.  

Methods: Human airway epithelial cells (A549) were exposed to purified seafood trypsins. The amount of secreted IL-8 was determined by an enzyme-linked immunosorbent assay. Induction of NF-kB-mediated transcription was demonstrated by a luciferase reporter gene assay. The involvement of the protease-activated receptor 2 (PAR-2) was investigated by the use of PAR-2 siRNA.   Results: Dose-dependent stimulation of IL-8 and NF-kB gene transcription was demonstrated for both salmon, sardine and king crab trypsins. The stimulation of IL-8 secretion and NF-kB- gene transcription were mediated at least partly through activation of PAR-2, as demonstrated by reduced response after transfection with PAR-2 siRNA. Fish and king crab trypsins display individual differences in PAR-2-activating capability and transformation of the NF-kB signal to secretion of IL-8.    

Conclusion: Our data demonstrate that trypsins purified from salmon, sardine and king crab stimulate the excretion of inflammatory cytokines from cultured airway epithelial cells and display individual differences in PAR-2 activating capability and inflammatory signal transformation.