Human Airway Smooth Muscle Cells Express Eotaxin in Response to Signaling following Mast Cell Contact

Abstract

Background: Asthma is a chronic inflammatory disease of the airways. Mast-cell (MC)-derived cytokines may mediate both airway inflammation and remodeling. It has also been shown that airway smooth muscle cells (ASMC) can be a source of proinflammatory cytokines. In the human airways, MC-ASMC cell interactions may have pivotal effects on modulating inflammation. Objectives: We wanted to know whether the production of eotaxin, an important proinflammatory cytokine, through a cell-to-cell contact mechanism of human ASMC activation by MC was mediated by p38 MAPK. Methods: We cocultured normal humanASMC with a human MC line (HMC-1) and assayed for the production of eotaxin. Results: When cultured together, human ASMC and HMC-1 contact induced eotaxin secretion. Separation of HMC-1 and human ASMC by a porous membrane inhibited this induction. Coculturing of human ASMC with HMC-1 induced increased expression of eotaxin gene mRNA. HMC-1-derived cellular membranes caused an increase in eotaxin production in human ASMC. Activation of p38 MAPK was also seen in cocultures by Western blot, whereas eotaxin production in cocultures was significantly inhibited by the p38 inhibitor SB203580. Conclusion: These novel studies reveal the importance of cell-to-cell interactions in the complex milieu of airway inflammation.

Secreted Factors from Human Mast Cells Trigger Inflammatory Cytokine Production by Human Airway Smooth Muscle Cells

“…These results are in accordance with an earlier study that showed enhanced eotaxin release after co-culture of hASM cells and HMC-1 cells [13]. The actions of HMCα-derived CM were examined in parallel studies.…”

“…CM derived from resting HMCα cells also triggered IL-8 and IL-6 production from hASM cells, but to a lesser extent than direct cell-cell contact. This observation emphasizes the importance, under resting conditions, of cell-cell contact for cell stimulation, as was shown previously using HMC-1 cells [13]. However, antigen-stimulated HMCα cell-derived CM had an effect similar to that of direct cell-cell contact, demonstrating a dominant role for a soluble factor released from the antigen-stimulated HMCα cells.…”

“…MAPK pathways have been well studied in relation to their regulation of cytokine production in hASM cells [13,38,39,40,41,42]. We examined whether treatment of hASM cells with HMCα CM affected the activation of ERK1/2 and p38 MAPK .…”

“…hASM cells co-cultured with mast cells, or mast cell-derived membranes, showed elevated eotaxin production, which was greater when cells were in direct contact [13]. …”

“…In contrast to earlier studies [13,31], the HMCα cell line, generated by stable transfection of HMC-1 cells with the α-subunit of human FcεRI (HMCα cells) [32], was utilized throughout to also permit investigation of IgE-dependent activation of the mast cells.…”