EDHF: new therapeutic targets?

Besides cyclooxygenase and NO-synthase, another distinct endothelial pathway, endothelium-dependent hyperpolarization (EDHF), is involved in the relaxation of the vascular smooth muscle cells. EDHF has been demonstrated unequivocally in various blood vessels from different species, including human, and is likely to play an important role in cardiovascular physiology. This alternative pathway involves the activation of two populations of endothelial potassium channels, the small conductance and intermediate conductance calcium-activated potassium channels (SK(Ca) and IK(Ca), respectively). EDHF-mediated responses are clearly altered in various pathological conditions (ageing, hypertension, atherosclerosis, hypercholesterolemia, heart failure, ischemia-reperfusion, angioplasty, eclampsia, diabetes, sepsis). Therapeutic or adjutant interventions (angiotensin converting enzyme inhibitors, antagonist of the angiotensin receptor, estrogen, omega-3 polyunsaturated fatty acids, polyphenol derivatives, potassium and/or calcium intake) can restore these responses, suggesting that the improvement of the EDHF pathway contributes to the observed beneficial effect of these various substances. However, the improvement or restoration of EDHF responses has not been, yet, the direct purpose of any pharmaceutical effort. Activating endothelial IK(Ca) and/or SK(Ca) or increasing their expression as well as improving myo-endothelial communication, for instance by increasing the expression of connexin(s), could become interesting therapeutic targets.