Tunicamycin-Induced Alterations in the Vasorelaxant Response in Organ-Cultured Superior Mesenteric Arteries of Rats

Abstract

In cellular events, endoplasmic reticulum (ER) stress has an important role in the development of various diseases including cardiovascular diseases. Tunicamycin, an inhibitor of N-linked glycosylation, is known to be an inducer of ER stress. However, the extent to which tunicamycin affects the vasorelaxant function is not completely understood. Thus, we investigated the effect of tunicamycin on relaxations induced by various vasorelaxant agents, including acetylcholine (ACh; endothelium-dependent vasodilator), sodium nitroprusside (SNP; endothelium-independent vasodilator), isoprenaline (ISO; beta-adrenoceptor agonist), forskolin ( Key words endoplasmic reticulum stress; mesenteric artery; relaxation; tunicamycin Organelle dysfunction, including endoplasmic reticulum (ER) stress, has an important role in the development of various diseases, such as cancer, and neuronal, metabolic, and cardiovascular diseases.1-10) ER stress is caused by various conditions, including glucose deprivation or glucose overload, calcium depletion or overload, hypoxia or oxidative stress, fatty acid overload, protein aggregation, and exposure to chemicals, such as tunicamycin or thapsigargin. 10,11) Recent evidence has shown a relationship between ER stress and vascular function in various disease states. 8,11,12) For instance, inhibition of ER stress could decrease blood pressure, aortic apoptosis, and fibrosis, and normalize vascular dysfunction in the aorta and mesenteric resistance artery of angiotensin II (Ang II)-treated hypertensive animals. 13,14) Spitler et al. found that increased ER stress was present in the aorta of spontaneously hypertensive rats (SHR) and that the suppression of ER stress reduced acetylcholine (ACh)-induced endothelium-dependent contraction in the aorta of SHR.15) Moreover, we recently suggested that a relationship existed between ER stress and renal arterial function in type 2 diabetic rats.16) Therefore, ER stress is a key intracellular event in the pathogenesis of vascular dysfunction and is an important target against such vasculopathies. However, the direct linkage between ER stress and vascular function especially vasorelaxation, remains unclear.Tunicamycin, an antibiotic, is known to inhibit N-linked glycosylation.17,18) Moreover, tunicamycin is also a major ER stress inducer in vitro and in vivo. 13,14,[19][20][21] In vivo treatment with tunicamycin for several weeks reduced ACh-induced endothelium-dependent relaxation in large and small arteries. 13,14) Moreover, in vitro acute treatment with tunicamycin (for 1 h) impaired insulin-mediated vasomotor activity, such as by causing contraction but no relaxation in the aorta through endothelin-1 (ET-1) release. 22) However, there are no reports regarding the in vitro effect of short-term treatment with tunicamycin on relaxations induced by various types of mechanisms in the superior mesenteric artery of rats.The aim of this study was to investigate the effect of short-term tunicamycin treatment on vasorelaxant responses induced by various vasodilator...

Effect of Equol on Vasocontractions in Rat Carotid Arteries Treated with High Insulin

“…The present study used organ culture techniques to investigate the direct associations among equol, insulin, and vascular function without the influence of complicated factors from other organs. [26][27][28][29][30][31] After prolonged treatment with equol and high insulin, each carotid arterial ring was mounted in an organ bath system where equol and insulin were completely removed. Thus, alterations of vascular function are resulted from prolonged but not acute effects.…”

“…Organ Culture Procedure and Vascular Function Study The organ culture procedures and measurements of vascular functions were as performed according to our previous studies. [26][27][28]30,32) Briefly, common carotid artery was isolated from a rat anesthetized with isoflurane and euthanized by exsanguination. The carotid artery was cleaned of adhering fat and connective tissue, cut into rings under sterile conditions, and placed in the medium consisted of low-glucose (5.5 mmol/L) Dulbecco's modified Eagle's medium (DMEM) (Gibco BRL, Grand Island, NY, U.S.A.) supplemented with 1% fetal bovine serum (Biological Industries, Kibbutz Beit Haemek, Israel) and 1% penicillin/streptomycin (Gibco BRL).…”

“…Following incubation under these three conditions at 37°C for 23 ± 1 h, vascular function was assessed by our previously-established organ bath technique. [26][27][28]30,32,[36][37][38] Subsequently, the rings were mounted into the organ bath system. After stabilization, the rings were exposed to an 80 mM high-K + solution and washed with modified Krebs-Henseleit solution [KHS; comprising (in mM) 118.0 NaCl, 4.7 KCl, 25.0 NaHCO 3 , 1.8 CaCl 2 , 1.2 NaH 2 PO 4 , 1.2 MgSO 4 , and 11.0 glucose].…”

“…In organ culture, conditions are easily manipulated and vascular function resulting from treatment incubation may be assessed purely without complicated interactions among other factors, such as neurohumoral substances and other cells. [26][27][28][29][30][31]…”

Augmented Contractility to Noradrenaline in Femoral Arteries from the Otsuka Long-Evans Tokushima Fatty Rat, a Model of Type 2 Diabetes

“…1C)-induced contractions were similar between OLETF and LETO groups. aline-Induced Contraction in Femoral Artery Since NO and/or prostanoids play important roles in the control of vascular tone on stimulation with endogenous contractile ligands, 25,29,30) we performed measurements of concentrationresponse curve for noradrenaline in the presence of L-NNA (an inhibitor of NOS, 10 −4 M) (Fig. 1D), indomethacin (an inhibitor of COX, 10 −5 M) (Fig.…”