Altered stiffness in coronary arteries and effect of pirfenidone on endothelium-dependent vasodilatation in type 2 diabetic (db/db) mice

Background: In order to improve the diagnosis and treatment of cardiovascular disease, there is a great needfor a better understanding of the patho-physiological mechanisms of heart disease. Both endothelial celldysfunction and vessel stiffness is associated with worsening of the prognosis in patients with cardiovasculardiseases. This project investigated the relationship between development of dysfunction in endothelial celllayer and the development of vessel stiffness and the vascular effects of the antifibrotic drug, perfinidone.Methods: In this study the left anterior descending coronary arteries (LAD) from diabetic db/db mice andnormoglycaemic (db+/db) mice were investigated using in vitro methods. The structural and mechanicalparameters of the coronary arteries from db/db mice were analyzed under passive conditions using a pressuremyograph system. The functional responses of the coronary arteries and aorta segments were mounted inmicrovascular myographs for isometric tension recordings.Results: The mechanical parameters indicated an increased vascular elasticity in the arteries from the 15-weekold male db/db mice and the structural parameters suggest that the arteries undergo compensatedhypotrophy. The structural and mechanical parameters of the arteries from 13-week old, female mice showquite an opposite tendency. In these arteries, the incremental distensibility is decreased indicating a more rigidvascular wall. Furthermore, the vessel and lumen diameters were reduced while the wall thickness wasincreased. These changes suggest an inward hypertrophic remodelling. Pirfenidone induced relaxations ofU46619-contracted LAD, and these relaxations were attenuated by high extracellular potassium and by a nitricoxide (NO)-synthase inhibitor, L-NOARG. In contrast to a blocker of KV1.3 channels, a blocker of KV7 channels,XE991 inhibited perfinidone relaxations. In aorta acetylcholine relaxation was impaired in segments from bothmale db/db mice and restored in the presence of pirfenidone or a selective opener of KV7 channels, flupirtine,while there was no additional effect by combining the compounds or effect of pirfenidone on flupirtinerelaxation.Conclusion: The present findings suggest that there is not a general relation of the presence of endothelialdysfunction to altered stiffness in diabetic mice, although further testing is required to address whether thereis a local relation. The antifibrotic drug perfinidone restored endothelium-dependent vasodilatation probablyby a mechanism lowering smooth muscle membrane potential in aorta from diabetic animals.