Author(s)

Jan Laudenbach^1,2,3, Yu Wang^1,4, Beibei Xing^1,5, Silvia Schwarz^1,5, Yinfang Xu^1,5, Quanbao Gu¹, Wolfgang Schwarz^1,2,3,5*

¹Shanghai Research Center for Acupuncture & Meridians, Shanghai, China.
²Max-Planck-Institute for Biophysics and Institute for Biophysics, Frankfurt am Main, Germany.
³Institute for Biophysics, Goethe University, Frankfurt am Main, Germany.
⁴Shanghai Research Institute of Acupuncture & Moxibustion and Meridian, Shanghai, China.
⁵Shanghai Key Laboratory for Acupuncture Mechanism and Acupoint Function, Shanghai, China.

The Na⁺/Ca²⁺ exchanger plays an important role in regulation of airway smooth muscle contraction by regulating intracellular calcium, and is a potential target for treatment of asthma. To test modulation of exchanger activity, we used Xenopus oocytes as model system. Na⁺/Ca²⁺ exchanger was expressed in the cells by microinjection of cRNA of the exchanger isoform NCX₁. The activity of NCX₁ was determined as Ni²⁺-sensitive current under voltage clamp in low Cl^– medium and in the presence of the Cl^–-channel inhibitor niflumic acid. Only this composition of solution allowed determining NCX₁-mediated current with sufficient accuracy. Among a few tested Chinese herbal drugs, glycyrrhizic acid turned out to be a potent inhibitor of NCX₁ with an apparent IC₅₀ value of 40 μM. Previous work had revealed elevated cyclophylin A concentration in serum of asthmatic rats after receiving acupuncture treatment. Extracellular incubation of the oocytes in cyclophylin A for one day led to significant inhibition with an apparent IC₅₀ value of about 1 μM. We suggest that effects of acupuncture and application of glycyrrhizic acid as an active constituent of Chinese medicine for treatment of asthma symptoms may partially be attributed to inhibition of the reversed mode of NCX₁ and that these compounds may stimulate the search for new anti-asthmatic drugs.

Sodium-Calcium Exchanger, Asthma, Voltage Clamp, Glycyrrhizic Acid, Cyclophylin A

Laudenbach, J. , Wang, Y. , Xing, B. , Schwarz, S. , Xu, Y. , Gu, Q. and Schwarz, W. (2017) Inhibition of the Na⁺/Ca²⁺ Exchanger NCX₁ Expressed in Xenopus Oocyte by Glycyrrhizic Acid and Cyclophylin A. Journal of Biosciences and Medicines, 5, 128-141. doi: 10.4236/jbm.2017.53014.