GHK Cu may Prevent Oxidative Stress in Skin by Regulating Copper and Modifying Expression of Numerous Antioxidant Genes Organic Nitrate Therapy, Nitrate Tolerance, and Nitrate Induced Endothelial Dysfunction: Emphasis on Redox Biology and Oxidative Stress Andreas Daiber, Thomas Mnzel, 2015 Frontiers Exploring the beneficial effects of GHK Cu on an experimental model of colitis and the underlying mechanisms Not too big. Not too small. Because of their intermediate size, macrocyclic peptides combine the potency and precise targeting of an antibody or biologic therapy with the stability and ease of administration of a Nitrite reverses nitroglycerin tolerance via repletion of a nitrodilator activated nitric oxide store in vascular smooth muscle cells ScienceDirect