Expression of Nitric Oxide Synthase and Endothelin-1 in Human Uterine Artery from Full-Term Pregnancies

The aim of this study was to determine the roles of ET-1 and NO on uterine blood flow in pregnancy. Uterine arteries were isolated from 17 nonpregnant and 12 pregnant women. Nonpregnant group included patients with median age of 48.6+/-2.3 years who underwent hysterectomy, because of myoma. Pregnant group included patients with median age of 31.3+/-1.4 years undergoing cesarean delivery. ET-1 and ET-2 induced concentration-dependent contraction in isolated nonpregnant and pregnant uterine arteries. The contractile response and maximal contraction were increased in pregnant uterine arteries. In nonpregnant uterine arteries, there was no contraction in response to ET-3, whereas pregnancy induced concentration-dependent contraction by ET-3. Tissue nitrite/nitrate level and immunohistochemical staining of eNOS and iNOS were increased in pregnant uterine arteries, compared with nonpregnant uterine arteries. In addition, the expressions of eNOS and iNOS mRNA were significantly increased in pregnancy. Moreover, contractions by ET isopeptides, including ET-1, were enhanced, and immunohistochemical staining of ET-1 and ET-1 mRNA expression was increased in pregnant uterine arteries. These results suggest that NO production by increased NOS activity, especially eNOS activity, is related to placental and uterine blood flow. Furthermore, ET-1 appears to play a pathophysiological role in pregnant complications such as hypertension.

Characterization of ETB Receptor-mediated Relaxation in Precontracted Mesenteric Artery from Streptozotocin-induced Diabetic Rats

Diabetes mellitus is associated with vascular complications, including an impairment of vascular function and alterations in the reactivity of blood vessels to vasoactive substances in various vasculature. In the present study, the authors have observed endothelin-B (ETB) receptor agonist-induced relaxation in precontracted mesenteric arterial segments from streptozotocin (STZ) -induced diabetic rats, which was not shown from control rats or in other arterial segments from diabetic rats. Accordingly, the goal of this study was to investigate in what way STZ-induced diabetes altered reactivity of the mesenteric arterial bed and to examine the causal relaxation, if any, between this ETB receptor-mediated relaxation and endothelial paracrine function, especially nitric oxide (NO) production. The relaxation induced by ETB agonists was not observed in mesenteric arteries without endothelium. The relaxation to ETB agonists was completely abolished by pretreatment with BQ788, but not by BQ610. N omega-nitro-L-arginine methyl ester and soluble guanylate cyclase inhibitors, methylene blue or LY83583 significantly attenuated the relaxant responses to ETB agonists, respectively. When the expression of eNOS and iNOS was evaluated on agarose gel stained with ethidium bromide, the expression of eNOS mRNA in diabetic rats was significantly decreased, but the expression of iNOS was increased compared with control rats. Furthermore, the iNOS-like immunostaining was densely detected in the endothelium and slightly in the arterial smooth muscle of diabetic rats, but not in control rats. These observations suggest that ETB receptor may not play a role in maintaining mesenteric vascular tone in normal situation. However, the alterations in ETB receptor sensitivity were found in diabetic rats and lead to the ETB agonist-induced vasorelaxation, which is closely related to NO production. In the state of increased vascular resistance of diabetic mesenteric vascular bed, enhanced NO production by activation of iNOS could lead to compensatory vasorelaxation to modulate adequate perfusion pressure to splanchnic area.

Conditioned Medium from Dying Smooth Muscle Cell Induced Apoptotic Death

In this study, the authors investigated whether death of vascular smooth muscle cell (VSMC) had a pathological pertinence. Conditioned media obtained from rat aorta smooth muscle cell (SMC) that were induced death by expressing FADD in the absence of tetracycline (FADD-SMC) triggered death of normal SMC. DNA fragmentation and caspase-3 activation were observed in dying SMC by conditioned media. FADD-SMC showed transcriptional activation of tumor necrosis factor (TNF)-alpha. Conditioned medium contained TNF-alpha, indicating secretion of the cytokine from dying FADD-SMC. It was investigated if secreted TNF-alpha was functional. Conditioned medium activated ERK and p38 MAPK pathways and induced MMP-9 expression, whereas depletion of the cytokine with its soluble receptor (sTNFR) remarkably inhibited induction of MMP-9 by conditioned medium. These findings suggest that TNF-alpha in conditioned medium seems to be active. Then, contribution of TNF-alpha on death-inducing activity of conditioned medium was examined. Depletion of TNF-alpha with soluble TNF-alpha receptor decreased the death activity of conditioned medium by 35%, suggesting that TNF-alpha play a partial role in the death activity. Boiling of medium almost completely abolished the death-inducing activity, suggesting that other heat labile death inducing proteins existed in conditioned medium. Taken together, these results indicate that SMC undergoing death could contribute to inflammation by expressing inflammatory cytokines and pathological complications by inducing death of neighboring cells.