Involvement of Extracellular Signal-Regulated Kinase 5 in Kinin B1 Receptor Upregulation in Isolated Human Umbilical Veins.

The upregulated kinin B1 receptors exert a pivotal role in modulating inflammatory processes. In isolated human umbilical veins (HUVs), kinin B1 receptor is upregulated as a function of in vitro incubation time and proinflammatory stimuli. The aim of this study was to evaluate, using functional and biochemical methods, the involvement of extracellular signal-regulated kinase 5 (ERK5), p38 mitogen-activated protein kinase (MAPK), c-Jun N-terminal kinase (JNK), and extracellular signal-regulated kinase 1/2 (ERK1/2) on the kinin B1 receptor upregulation process in HUV. Real-time polymerase chain reaction analysis revealed for the first time that kinin B1 receptor mRNA expression closely parallels the functional sensitization to kinin B1 receptor selective agonist des-Arg(10)-kallidin (DAKD) in HUV. Moreover, the selective inhibition of ERK5, p38 MAPK, and JNK, but not ERK1/2, produced a dose-dependent rightward shift of the concentration-response curves to DAKD after 5-hour incubation and a reduction in kinin B1 receptor mRNA expression. Biochemical analyses showed that ERK5, p38 MAPK, and JNK phosphorylation is maximal during the first 2 hours postisolation, followed by a significant reduction in the last 3 hours. None of the treatments modified the responses to serotonin, an unrelated agonist, suggesting a specific effect on kinin B1 receptor upregulation. The present work provides for the first time pharmacologic evidence indicating that ERK5 plays a significant role on kinin B1 receptor upregulation. Furthermore, we confirm the relevance of p38 MAPK and JNK as well as the lack of effect of ERK1/2 in this process. This study may contribute to a better understanding of MAPK involvement in inflammatory and immunologic diseases.

Endothelial angiotensin-converting enzyme and neutral endopeptidase in isolated human umbilical vein: an effective bradykinin inactivation pathway.

Kinins are metabolized by metallopeptidases present in different tissues. The aim of this study was to evaluate, employing functional studies in isolated human umbilical vein, the possible participation of angiotensin-converting enzyme, neutral endopeptidase and aminopeptidase P as an inactivation pathway of bradykinin, as well as assess if the endothelial layer is involved in this process. Concentration-response curves to bradykinin were constructed after 120 min incubation period on human umbilical vein rings with and without endothelium and enzymatic inhibitors were applied 30 min before construction of concentration-response curves. The presence of endothelium was confirmed by histological studies. Bradykinin-induced contractile responses were potentiated in human umbilical vein without endothelium when compared to intact tissues. Application of captopril 1 µM (angiotensin-converting enzyme inhibitor) or phosphoramidon 10 µM (neutral endopeptidase inhibitor) induced a leftward shift of bradykinin-elicited responses in human umbilical vein with endothelium while no effect was observed in tissues denuded of endothelium under the same treatment. Exposure to apstatin 10 µM (aminopeptidase P inhibitor) did not potentiate bradykinin-induced effects in intact human umbilical vein. When angiotensin-converting enzyme and neutral endopeptidase were concomitantly inhibited, there was a higher potentiation of bradykinin-elicited responses compared to the effects observed under individual inhibition of either enzyme. Moreover, concentration-response curves to FR190997, a non-peptidic bradykinin B(2) receptor agonist, were not modified under dual enzymatic inhibition. In conclusion, our results demonstrate for the first time the functional relevance of angiotensin-converting enzyme and neutral endopeptidase, localized on the endothelial layer, acting concurrently as a bradykinin inactivating pathway in isolated human umbilical vein.