Biochanin A, a Phytoestrogenic Isoflavone with Selective Inhibition of Phosphodiesterase 4, Suppresses Ovalbumin-Induced Airway Hyperresponsiveness

Figure 7

Mechanisms involved in the action of Biochanin A. Biochanin A selectively inhibits phosphodiesterase (PDE)4 activity resulting in an increase in cAMP, activating cAMP dependent protein kinase (PKA) and increasing calcium extrusion from the intracellular space and uptake to sarcoplasmic reticula (SR). Biochanin A largely decreased the concentration of intracellular calcium ([Ca²⁺]_i) resulting in trachobronchial smooth muscle relaxation. The increase in cAMP also had anti-inflammatory and immunoregulatory effects. AC, adenylate cyclase; Th, T-helper cells; Ig, immunoglobulin; IL, interleukin; TNF-𝛼, tumor necrosis factor-𝛼. Up and down arrows indicate increases and decreases, respectively.