The effect of AL0671, a novel potassium channel opener, on potassium current in rat aortic smooth muscle cells

Paracrine role for periadventitial adipose tissue in the regulation of arterial tone

Recent studies propose a paracrine role for periadventitial adipose tissue in the regulation of vascular tone. This regulation depends on the anatomical integrity of the periadventitial adipose tissue and involves adipocyte-derived relaxing factor (ADRF). Although the nature of ADRF is largely unknown, it is released by periadventitial adipocytes and induces vasorelaxation by opening K+ channels in the plasma membrane of smooth muscle cells. Alterations in the paracrine role of periadventitial adipose tissue might have a role in vascular dysfunction in hypertension and metabolic disease. Therefore, understanding alterations in ADRF release and the K+ channels involved will help further our understanding of the increased cardiovascular risk and development of chronic vascular disease in obesity. Furthermore, ADRF and perhaps its putative targets might represent exciting new targets for the development of drugs to treat cardiovascular disorders.

Visceral Periadventitial Adipose Tissue Regulates Arterial Tone of Mesenteric Arteries

Periadventitial adipose tissue produces vasoactive substances that influence vascular contraction. Earlier studies addressed this issue in aorta, a vessel that does not contribute to peripheral vascular resistance. We tested the hypothesis that periadventitial adipose tissue modulates contraction of smaller arteries more relevant to blood pressure regulation. We studied mesenteric artery rings surrounded by periadventitial adipose tissue from adult male Sprague-Dawley rats. The contractile response to serotonin, phenylephrine, and endothelin I was markedly reduced in intact vessels compared with vessels without periadventitial fat. The contractile response to U46619 or depolarizing high K + -containing solutions (60 mmol/L) was similar in vessels with and without periadventitial fat. The K + channel opener cromakalim induced relaxation of vessels precontracted by serotonin but not by U46619 or high K + -containing solutions (60 mmol/L), suggesting that K + channels are involved. The intracellular membrane potential of smooth muscle cells was more hyperpolarized in intact vessels than in vessels without periadventitial fat. Both the anticontractile effect and membrane hyperpolarization of periadventitial fat were abolished by inhibition of delayed-rectifier K + (K v ) channels with 4-aminopyridine (2 mmol/L) or 3,4-diaminopyridine (1 mmol/L). Blocking other K + channels with glibenclamide (3 μmol/L), apamin (1 μmol/L), iberiotoxin (100 nmol/L), tetraethylammonium ions (1 mmol/L), tetrapentylammonium ions (10 μmol/L), or Ba 2+ (3 μmol/L) had no effect. Longitudinal removal of half the perivascular tissue reduced the anticontractile effect of fat by almost 50%, whereas removal of the endothelium had no effect. We suggest that visceral periadventitial adipose tissue controls mesenteric arterial tone by inducing vasorelaxation via K v channel activation in vascular smooth muscle cells.

AL0671, a new potassium channel opener, inhibits nonenzymatic glycation of protein and LDL oxidation

1. The effects of AL0671, a novel potassium channel opener, on protein glycation and low-density lipoprotein (LDL) oxidation were tested. 2. AL0671 dose-dependently inhibited both fluorescence development of bovine serum albumin and cross-linking of lysozyme. These inhibitory effects for glycation were no less potent than aminoguanidine. 3. AL0671 dose-dependently inhibited both increase in negative charge and apo B-100 fragmentation during incubation of LDL with Cu2+. In addition, AL0671 significantly decreased the LDL degradation in rat peritoneal macrophages. 4. Neither pinacidil nor levcromakalim inhibited protein glycation and LDL oxidation. 5. Antioxidant properties of AL0671 might be due to its potent electron-donating ability, and this agent is expected to be useful for hypertensive diabetes.