Activation of store-operated calcium entry in airway smooth muscle cells: insight from a mathematical model.

Intracellular Ca(2+) dynamics of airway smooth muscle cells (ASMC) mediate ASMC contraction and proliferation, and thus play a key role in airway hyper-responsiveness (AHR) and remodelling in asthma. We evaluate the importance of store-operated Ca(2+) entry (SOCE) in these Ca(2+) dynamics by constructing a mathematical model of ASMC Ca(2+) signaling based on experimental data from lung slices. The model confirms that SOCE is elicited upon sufficient Ca(2+) depletion of the sarcoplasmic reticulum (SR), while receptor-operated [Ca(2+) entry (ROCE) is inhibited in such conditions. It also shows that SOCE can sustain agonist-induced Ca(2+) oscillations in the absence of other [Ca(2+) influx. SOCE up-regulation may thus contribute to AHR by increasing the Ca(2+) oscillation frequency that in turn regulates ASMC contraction. The model also provides an explanation for the failure of the SERCA pump blocker CPA to clamp the cytosolic Ca(2+) of ASMC in lung slices, by showing that CPA is unable to maintain the SR empty of Ca(2+). This prediction is confirmed by experimental data from mouse lung slices, and strongly suggests that CPA only partially inhibits SERCA in ASMC.