Activation of the JAK/STAT pathway in vascular smooth muscle by serotonin.

Serotonin (5-hydroxytryptamine, 5-HT) is a vasoconstrictor and mitogen whose levels are elevated in diabetes. Previous studies have shown the presence of 5-HT2A, 5-HT2B, and 5-HT1B receptors in vascular smooth muscle cells (VSMCs). There are currently no data regarding 5-HT2B and 5-HT1B receptor activation of the JAK/STAT pathway in VSMCs and resultant potential alterations in 5-HT signaling in diabetes. Therefore, we tested the hypothesis that 5-HT differentially activates the JAK/STAT pathway in VSMCs under conditions of normal (5 mM) and high (25 mM) glucose. Treatment of rat VSMCs with 5-HT (10(-6) M) resulted in time-dependent activation ( approximately 2-fold) of JAK2, JAK1, and STAT1, but not STAT3 (maximal at 5 min, returned to baseline by 30 min). The 5-HT2B receptor agonist BW723C86 and the 5-HT1B receptor agonist CGS12066A (10(-9)-10(-5) M, 5-min stimulation) did not activate the JAK/STAT pathway. Treatment with the 5-HT2A receptor antagonist ketanserin (10 nM) inhibited JAK2 activation by 5-HT. Treatment of streptozotocin-induced diabetic rats with ketanserin (5 mg.kg-1.day-1) reduced activation of JAK2 and STAT1 but not STAT3 in endothelium-denuded thoracic aorta in vivo. 5-HT (10(-6) M) treatment resulted in increased cell proliferation and increased DNA synthesis, which were inhibited by the JAK2 inhibitor AG490. Further studies with apocynin, diphenyleneiodonium chloride, catalase, and virally transfected superoxide dismutase had no effect at either glucose concentration on activation of the JAK/STAT pathway by 5-HT. Therefore, we conclude that 5-HT activates JAK2, JAK1, and STAT1 via the 5-HT2A receptors in a reactive oxygen species-independent manner under both normal and high glucose conditions.

Arterial expression of 5-HT2B and 5-HT1B receptors during development of DOCA-salt hypertension.

BACKGROUND: 5-hydroxytryptamine (5-HT)2B and 5-HT1B receptors are upregulated in arteries from hypertensive DOCA-salt rats and directly by mineralocorticoids. We hypothesized that increased 5-HT2B and 5-HT1B receptor density and contractile function would precede increased blood pressure in DOCA-high salt rats. We performed DOCA-salt time course (days 1, 3, 5 and 7) studies using treatment groups of: DOCA-high salt, DOCA-low salt, Sham and Sham-high salt rats. RESULTS: In isolated-tissue baths, DOCA-high salt aorta contracted to the 5-HT2B receptor agonist BW723C86 on day 1; Sham aorta did not contract. The 5-HT1B receptor agonist CP93129 had no effect in arteries from any group. On days 3, 5 and 7 CP93129 and BW723C86 contracted DOCA-high salt and Sham-high salt aorta; Sham and DOCA-low salt aorta did not respond. Western analysis of DOCA-high salt aortic homogenates revealed increased 5-HT2B receptor levels by day 3; 5-HT1B receptor density was unchanged. Aortic homogenates from the other groups showed unchanged 5-HT2B and 5-HT1B receptor levels. CONCLUSION: These data suggest that functional changes of 5-HT2B but not 5-HT1B receptors may play a role in the development of DOCA-salt hypertension.

Upregulation of arterial serotonin 1B and 2B receptors in deoxycorticosterone acetate-salt hypertension.

Previous studies have established a role for 5-hydroxytryptamine (5-HT)(2B) and 5-HT(1B) receptors in mediating enhanced contraction to serotonin (5-HT) in arteries from hypertensive deoxycorticosterone acetate (DOCA)-salt rats. To determine whether the observed increase in responsiveness was due to upregulation of 5-HT receptors, we used Western analysis to measure 5-HT(1B) and 5-HT(2B) receptor protein density. In endothelium-denuded aortas from hypertensive DOCA-salt rats (mean systolic blood pressure 192 +/- 6 mm Hg), 5-HT(1B) and 5-HT(2B) receptor proteins were upregulated approximately 2-fold compared with the response in the aortas of sham-operated control rats (mean systolic blood pressure 119 +/- 2 mm Hg). Contraction to 5-HT(2B) receptor agonists was also enhanced in arteries from Wistar-Furth rats given DOCA and salt. This strain is relatively resistant to the hypertensive effects of DOCA and salt treatment. A common factor between the model of DOCA-salt hypertension and the DOCA-salt--treated Wistar-Furth rats is the presence of mineralocorticoids. Therefore, we tested the hypothesis that mineralocorticoids can upregulate 5-HT(1B) and 5-HT(2B) receptors. Aortas from normal Sprague-Dawley rats were incubated with aldosterone (100 nmol/L) for 8, 12, 24, and 48 hours. The expression of 5-HT(2B) and 5-HT(1B) receptor proteins was significantly increased (approximately 2- fold over vehicle treatment) by 8 hours. 5-HT(2B) and 5-HT(1B) receptors were upregulated by aldosterone in a concentration-dependent manner, and incubation with spironolactone (10 micromol/L) blocked this upregulation. These data support the conclusion that the increased expression of 5-HT(1B) and 5-HT(2B) receptors observed in arteries from DOCA-salt rats may be partially due to mineralocorticoids acting via the mineralocorticoid receptor to modulate gene expression.