17β-estradiol induces hyperresponsiveness in guinea pig airway smooth muscle by inhibiting the plasma membrane Ca2+-ATPase

High serum estrogen concentrations are associated with asthma development and severity, suggesting a link between estradiol and airway hyperresponsiveness (AHR). 17β-estradiol (E2) has non-genomic effects via Ca²⁺ regulatory mechanisms; however, its effect on the plasma membrane Ca²⁺-ATPases (PMCA1 and 4) and sarcoplasmic reticulum Ca²⁺-ATPase (SERCA) is unknown. Hence, in the present study, we aim to demonstrate if E2 favors AHR by increasing intracellular Ca²⁺ concentrations in guinea pig airway smooth muscle (ASM) through a mechanism involving Ca²⁺-ATPases.

In guinea pig ASM, Ca²⁺ microfluorometry, muscle contraction, and Western blot were evaluated. Then, we performed molecular docking analysis between the estrogens and Ca²⁺ ATPases.

In tracheal rings, E2 produced AHR to carbachol. In guinea pig myocytes, acute exposure to physiological levels of E2 modified the transient Ca²⁺ peak induced by caffeine to a Ca²⁺ plateau. The incubation with PMCA inhibitors (lanthanum and carboxyeosin, CE) partially reversed the E2-induced sustained plateau in the caffeine response. In contrast, cyclopiazonic acid (SERCA inhibitor), U-0126 (an inhibitor of ERK 1/2), and choline chloride did not modify the Ca²⁺ plateau produced by E2. The mitochondrial uniporter activity and the capacitative Ca²⁺ entry were unaffected by E2. In guinea pig ASM, Western blot analysis demonstrated PMCA1 and PMCA4 expression. The results from the docking modeling demonstrate that E2 binds to both plasma membrane ATPases. In guinea pig tracheal smooth muscle, inhibiting the PMCA with CE, induced hyperresponsiveness to carbachol. 17β-estradiol produces hyperresponsiveness by inhibiting the PMCA in the ASM and could be one of the mechanisms responsible for the increase in asthmatic crisis in women.