Icariin is a cGMP-specific PDE5 inhibitor with IC50 of 0.432 μM, 167-fold selective for PDE5 than PDE4 and exhibits multiple biological properties, including anti-inflammatory, neuroregulatory and neuroprotective activities. It is a major constituent of flavonoids from the Chinese medicinal herb Epimedium brevicornum..
Icariin is a flavonol glycoside. It inhibits PDE5 and PDE4 activities with IC50s of 432 nM and 73.50 μM, respectively. Icariin also is a PPARα activator[3]. Icariin was injected in a dose of 50 mg/kg, and significantly reduced paw swelling in carrageenan-injected animals. It also ameliorated carrageenan-induced paw histopathological alterations. Icariin significantly increased paw enzymatic and non-enzymatic antioxidants. It decreased paw lipid peroxidation. Icariin decreased paw levels of inflammatory cytokines and NF-kB[4]. Icariin can prevent the production of amyloid β (1-42) and inhibit the expression of amyloid precursor protein (APP) and β-site APP cleaving enzyme 1 (BACE-1) in animal models of Alzheimer's disease (AD). Icariin also prevents the neurotoxicity induced by hydrogen peroxide (H2O2), endoplasmic reticulum (ER) stress, ibotenic acid, and homocysteine[5]. Icariin selectively inhibited proliferation and triggered apoptosis in breast cancer cells in a concentration- and time-dependent manner, but exhibited little cytotoxicity in normal breast cells. Moreover, icariin induced cell apoptosis via a mitochondria-mediated pathway, as indicated by the upregulated ratio of Bax/Bcl-2 and reactive oxygen species induction. Importantly, icariin impaired the activation of the NF-κB/EMT pathway, as evidenced by upregulation of SIRT6, resulting in inhibition of migration and invasion of breast cancer cells[6]. Icariin protects BMSCs (bone marrow-derived mesenchymal stem cells) against OGD (oxygen, glucose and serum deprivation)-induced apoptosis by inhibiting ERs-mediated (ER Stress) autophagy via MAPK signaling pathway[7].
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