Figure 4.

Formaldehyde-treated human bronchial epithelial (HBE) cells have little effect on agonist-induced [Ca²⁺]_i or MYPT1 phosphorylation in HASM cells. Air–liquid interface–differentiated HBE cells were exposed to formaldehyde and co-incubated with HASM cells for 24 hours. Agonist-induced [Ca²⁺]_i and phosphorylation status of myosin light chain (MLC) and MYPT1 were determined in the HASM cells. Co-culture of HASM cells with formaldehyde-treated HBE cells had little effect on (A) histamine- or (B) thrombin-induced [Ca²⁺]_i in the HASM cells (left panels, baseline-corrected fluorescence intensity; right panels, AUCs of the traces; mean ± SEM, n = 3 donors, 60 cells/experimental condition). (C) There were marginal elevations in the baseline phosphorylation of MLC and MYPT1 in the HASM cells cocultured with formaldehyde-treated HBE cells (immune blot representative of five experiments). (D) At the baseline (without carbachol), phosphorylated MLC levels trended toward an increase in HASM cells cocultured with formaldehyde-treated HBE cells, although the increase was not statistically significant (mean ± SEM; n = 5 donors). (E) At baseline, phosphorylated MYPT1 levels were marginally elevated in HASM cells upon coculture with formaldehyde-treated HBE cells, without statistical significance (mean ± SEM; n = 5 donors).