Airway relaxation mechanisms and structural basis of osthole for improving lung function in asthma.

Overuse of ß2-adrenoceptor agonist bronchodilators evokes receptor desensitization, decreased efficacy, and an increased risk of death in asthma patients. Bronchodilators that do not target ß2-adrenoceptors represent a critical unmet need for asthma management. Here, we characterize the utility of osthole, a coumarin derived from a traditional Chinese medicine, in preclinical models of asthma. In mouse precision-cut lung slices, osthole relaxed preconstricted airways, irrespective of ß2-adrenoceptor desensitization. Osthole administered in murine asthma models attenuated airway hyperresponsiveness, a hallmark of asthma. Osthole inhibited phosphodiesterase 4D (PDE4D) activity to amplify autocrine prostaglandin E2 signaling in airway smooth muscle cells that eventually triggered cAMP/PKA-dependent relaxation of airways. The crystal structure of the PDE4D complexed with osthole revealed that osthole bound to the catalytic site to prevent cAMP binding and hydrolysis. Together, our studies elucidate a specific molecular target and mechanism by which osthole induces airway relaxation. Identification of osthole binding sites on PDE4D will guide further development of bronchodilators that are not subject to tachyphylaxis and would thus avoid ß2-adrenoceptor agonist resistance.

[Effects of lead and selenium on telomere binding protein Rap1p, telomerase and telomeric DNA in Saccharomyces cerevisiae].

The effects on S.cerevisiae telomere binding protein Rap1p, telomerase and telomeric DNA by the lead (Pb), the selenium (Se) and Pb + Se were tested respectively in this study. Compared with the control S.cerevisiae after 100 gene rations, the mean telomere length shortened, Rap1p concentration was significantly lower and the secondary structure of Rap1p was disturbed, the telomerase activity was reduced in Pb treated cells. In Se treated cells, telomere length was significantly longer, and telomerase activity expressed higher. The concentration and secondary structure of Rap1p were similar to that of the control. Further more, the viability of Pb treated cells were significantly reduced while cells undergone other three treatments were similar and normal. These results suggest that Pb could damage Rap1p, reduce telomerase activity, resulting in the telomer length shortening and cell death. On the other hand, Se could protect and repair the damage in Rap1p and telomere caused by Pb to some extent.