Figure 9From: Hesperetin-7,3'-O-dimethylether selectively inhibits phosphodiesterase 4 and effectively suppresses ovalbumin-induced airway hyperresponsiveness with a high therapeutic ratioMechanisms of action of HDME. HDME selectively inhibits PDE4 activities and results in an increase in cAMP, which activates cAMP-dependent protein kinase (PKA) and increases calcium extrusion from the intracellular space and uptake to sarcoplasmic reticula (SR). Therefore, HDME largely decreases the concentration of intracellular calcium ([Ca2+]i) and results in bronchodilatation. The increase in cAMP also has anti-inflammatory and immunoregulatory effects. AC, adenylate cyclase; Th, T-helper cells; Ig, immunoglobulin; IL, interleukin; IFN, interferon; TNF, tumor necrosis factor. Up and down arrows respectively indicate increases and decreases.Back to article page