The inner lining of such tissues as blood vessels and airways is called the endothelium. The endothelium regulates blood vessel relaxation and airway volume by control of smooth muscle tone. This tone is regulated by nitric oxide (NO,) which is produced from arginine by the nitric oxide synthase (NOS) enzyme.
Arginase enzyme inhibits NOS by competing for the use of their raw material, arginine. Arginase enzyme has an advantage when there is tetrahydorbiopterin (BH4) deficiency or arginine deficiency. Arginase is a target for treating cardiovascular disease. Arginase inhibition increases NO production. It should be part of therapy for arteriosclerosis. A chemical, piceatannol-3′-O-beta-D-glucopyranoside (PG,) inhibits arginase activity. The increased NO is beneficial to the heart, atherogenesis, aging, erectile dysfunction and sickle cell disease.
Rhubarb (Rheum undulatum) is an Asian plant which contains stilbenes (emodin, chrysophanol, physcion, resveratrol, rhapontigenin, rhaponticin, and piceatanno,) which cause blood vessel relaxation. The authors studied PG and found it had strong inhibitory effects on arginase. The increased amount of NO produced with PG treatment was due to the increase amount of arginine available for NOS with inhibition of the NOS competitor, arginase.
In mice, treatment of aorta tissue with PG decreased the production of reactive oxygen species (ROS.) PG and resveratrol have both shown strong radical scavenging activity and lipoxygenase inhibition activity.
CONCLUSION: PG from rhubarb is an arginase inhibitor and should be useful to humans for the treatment of all types of vascular problems and cardiovascular disease.
NOTE: Read more about arginase inhibitors for endothelial dysfunction.
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