The ProS Peptide of Porcine Cathelicidins Is an Active Component of Swine Concentrated Animal Feeding Operations (CAFOs) Dust that Mobilizes Calcium and Stimulates Proliferation in Human Airway Smooth Muscle Cells

Abstract

Components in the dust from swine concentrated animal feeding operations (CAFOs) can induce inflammatory lung disease with features of chronic obstructive lung disease. An aqueous hogbarn dust extract (HDE) induces pro‐inflammatory responses in both airway cells in culture and in mouse airways in vivo, thus providing a starting point for identifying the dust molecules that are involved. Proteomics analysis of an EGF receptor‐activating peak from gel filtration of HDE revealed multiple fragments from the ProS peptide precursor of a subset of porcine anti‐bacterial cathelicidins. Antibodies against ProS confirmed its presence in HDE. The full‐length ProS peptide, without the N‐terminal signal peptide and the C‐terminal anti‐bacterial peptide, stimulated proliferation of human airway smooth muscle (HASM) cells assessed as [3H]thymidine incorporation. Stimulation was concentration‐dependent, with a maximal stimulation of 2‐ to 3‐fold, greater than that with EGF and somewhat less than with the G protein‐coupled receptor (GPCR) mitogen lysophosphatidic acid (LPA). ProS stimulation was blocked by the EGF receptor inhibitor AG1478 and the phospholipase C inhibitor U73122, but not by the Gq inhibitor YM‐254890 or the matrix metalloprotease inhibitor GM6001. ProS also stimulated a concentration‐dependent increase in intracellular calcium that was not blocked by AG1478 but was blocked by U73122 and by the Gq inhibitor YM‐254890. These data indicate that ProS is likely to be a novel Gq‐coupled GPCR agonist that mobilizes calcium in HASM cells via Gq activation but stimulates HASM cell proliferation through a Gq‐independent pathway involving EGF receptor activation. Whether and how the phospholipase C‐dependent calcium response may be related to the phospholipase C‐dependent proliferation response remains to be established. Further studies are in progress to identify the specific receptor and signaling pathways involved. The simultaneous formation of both an anti‐bacterial peptide to fight infection and the ProS peptide to activate EGF receptors to initiate cell proliferation and repair suggests a unique dual role for the cathelicidin precursor protein.Support or Funding InformationFunded by NIOSH 1RO1‐0H008539‐09 to DJR and UNMC Institutional Funds to MLT