Enhanced Transcription of Contractile 5‐Hydroxytryptamine 2A Receptors via Extracellular Signal‐Regulated Kinase 1/2 after Organ Culture of Rat Mesenteric Artery

Abstract

5-Hydroxytryptamine (5-HT) has been found to elicit enhanced contractile effects in some vascular disorders. The present study was designed to examine if vascular 5-HT 2A receptors are up-regulated during organ culture and if the extracellular signal-regulated protein kinase 1/2 (ERK1/2) pathways are involved. Compared with fresh rat mesenteric artery ring segments, the contractile responses to 5-HT were significantly increased in the segments cultured for 6, 24 or 48 hr (PϽ0.05, PϽ0.01, PϽ0.01, respectively). The 5-HT-induced contraction occurred via 5-HT 2A receptors, since the selective 5-HT 2A antagonist ketanserin blocked the 5-HT-induced contraction in the fresh segments with a pA 2 value 9.5 (slope was 0.98 with 95% confidence intervals from 0.8 to 1.1). A similar result was obtained in the segments cultured for 24 hr with a pA 2 value of 9.43 (slopeΩ0.91 and 95% confidence intervals between 0.45 to 2.3). In addition, the enhanced 5-HT 2A receptor contraction occurred with a significant increase of 5-HT 2A receptor mRNA (PϽ0.05). Organ culture of the mesenteric artery was found to activate ERK1/2 already within 1 and 3 hr. It is likely that the ERK1/2 pathways were involved as a initial switch, since the selective ERK1/2 pathway inhibitor SB386023 abolished both up-regulation of 5-HT 2A mRNA transcription and the enhanced contractile response to 5-HT. These data reveal a role of ERK1/2 in upregulation of 5-HT 2A receptors and suggest a possibility to inhibit the enhanced responses to 5-HT by inhibition of the ERK1/2 pathway.There is increased vascular responsiveness to some contractile agonists in vascular disease which may be associated with enhanced receptor expression. 5-Hydroxytryptamine (5-HT), a G-protein-coupled receptor ligand, has been reported to be involved in the pathogenesis of hypertension (Banes & Watts 2003), acute myocardial infarction (Coto et al. 2003) and subarachnoid haemorrhage (HansenSchwartz et al. 2003a). The main source of circulating 5-HT is the platelets (Elliott et al. 2003). Activation of platelets results in local release of 5-HT that interacts with the vascular endothelium and smooth muscle cells (Tasaki et al. 2003). In addition, 5-HT is a central neuromediator but it is not restricted to the central nervous system, and it can be stored in and released from so-called paraneurons and blood platelets (Verge & Calas 2000). In fresh arteries, 5-HT acts on the endothelium to induce a small relaxation (Hansen-Schwartz et al. 2003b;Saini et al. 2004). In vascular disease such as atherosclerotic lesions, stroke and acute myocardial infarction, the endothelium is generally considered damaged, dependent on the degree of underlying pathology. Thus isolated arteries from experimental subarachnoid haemorrhage (Hansen-Schwartz et al. 2003a). ii) Vascular contraction induced by 5-HT in the rat is primarily mediated by 5-HT 2A receptors (Gul et al. 2003). iii) 5-HT 2A receptormediated contraction occurs in part via activation of mitogen-activated protein kinase and specifically ...

Vascular endothelin ETB receptor-mediated contraction requires phosphorylation of ERK1/2 proteins

“…In the present study, we focused on the role of MAPK and intracellular calcium to understand the process of contraction induced via endothelin ET B receptors in rat mesenteric artery and demonstrated that activation of MAPK ERK1/2 is required for the contraction. This is supported by previous findings that contraction induced via G-protein-coupled receptors 5-HT 2A receptors in rat mesenteric artery requires ERK1/2 activities (Cao et al, 2005). Nifedipine, a selective calcium channel blocker markedly reduced sarafotoxin 6c-induced contraction.…”

“…The mechanisms responsible for the upregulation of endothelin ET B receptors involves gene transcription and include activation of protein kinase and mitogen-activated protein kinase (MAPK) pathways consist of ERK1/2 (Uddman et al, 2003). It has been observed that of MAPK and down stream transcriptional factors regulate the gene expression of G-protein-coupled receptors, such as endothelin ET B , 5-hydroxytryptamine (5-HT) 2A and bradykinin B 1 and B 2 receptors in response to extracellular stimuli (Cao et al, 2005, Zhang et al, 2004and Zhang et al, 2005. Typically, these events induce a contractile phenotype (Moller et al, 2002).…”

The enhanced endothelin-1-induced contraction in cultured coronary arteries from mature female pigs is not antagonized by 17β-estradiol

“…Organ culture has also been shown to enhance the contractile response to the selective ET B receptor agonist, sarafotoxin S6c, while having no effect on the prostaglandin F 2α and interleukin-1β contraction in the human temporal artery (White et al, 1999). Cao et al (2005) has also demonstrated an organ culture induced increase in the contractile response to 5-hydroxytryptamine in the rat mesenteric artery. Previously, using pigs 6-9 months old, we found a T max to 3 × 10 −7 M ET-1 of 121 ± 8% and 227 ± 20% of the maximum response to 80 mM KCl in fresh and organ cultured rings, respectively (Hill et al, 2000).…”

Altered ATP-sensitive potassium channels may underscore obesity-triggered increase in blood pressure1

“…Pinacidil-induced relaxation responses in aortas and mesenteric arteries The responses of the arterial segments to pinacidil were measured with a myograph system [10,11] . Briefly, the fresh vessels were then cut into 1 or 2 mm-long cylindrical segments.…”