Airway Ciliary Beating Affected by the Dose-Dependent [Ca] Increase in Down Syndrome Mice, Ts1Rhr.

In Ts1Rhr, a Down syndrome model mouse, the airway ciliary beatings are impaired; that is, decreases in ciliary beat frequency (CBF) and ciliary bend angle (CBA, an index of ciliary beat amplitude)). A resumption to two copies of the gene on the Ts1Rhr trisomic segment (Ts1Rhr:) rescues the decreases in CBF and CBA that occur in Ts1Rhr. In airway cilia, upon stimulation with procaterol (a β-agonist), the CBF increase is slower over the time course than the CBA increase because of cAMP degradation by Ca/calmodulin-dependent phosphodiesterase 1 (PDE1) existing in the metabolon regulating CBF. In Ts1Rhr, procaterol-stimulated CBF increase was much slower over the time course than in the wild-type mouse (Wt) or Ts1Rhr:. However, in the presence of 8MmIBMX (8-methoxymethyl isobutylmethyl xanthine, an inhibitor of PDE1) or calmidazolium (an inhibitor of calmodulin), in both Wt and Ts1Rhr, procaterol stimulates CBF and CBA increases over a similar time course. Measurements of cAMP revealed that the cAMP contents were lower in Ts1Rhr than in Wt or in Ts1Rhr:, suggesting the activation of PDE1A that is present in Ts1Rhr airway cilia. Measurements of the intracellular Ca concentration ([Ca]) in airway ciliary cells revealed that temperature (increasing from 25 to 37 °C) or 4αPDD (a selective transient receptor potential vanilloid 4 (TRPV4) agonist) stimulates a larger [Ca] increase in Ts1Rhr than in Wt or Ts1Rhr:. In airway ciliary cells of Ts1Rhr, -dose dependent activation of TRPV4 appears to induce an increase in the basal [Ca]. In early embryonic day mice, a basal [Ca] increased by PCP4 expressed may affect axonemal regulatory complexes regulated by the Ca-signal in Ts1Rhr, leading to a decrease in the basal CBF and CBA of airway cilia.