PDE4 and PDE5 regulate cyclic nucleotides relaxing effects in human umbilical arteries

Abstract

Cyclic nucleotides (cAMP and cGMP) are the main second messengers linked to vasodilatation. They are synthesized by cyclases and degraded by different types of phosphodiesterases (PDE). The effect of PDE inhibition and cyclases stimulation on 5-hydroxytryptamine (5-HT; 1 microM) and histamine (10 microM) contracted arteries was analysed. Stimulation of guanylate cyclase or adenylate cyclase relaxed the histamine- and 5-HT-induced contractions indicating that intracellular increase of cyclic nucleotides leads to vasodilatation of the human umbilical artery. We investigated the role of different PDE families in the regulation of this effect. The presence of the different PDE types in human umbilical artery smooth muscle was analysed by RT-PCR and the expression of PDE1B, PDE3A, PDE3B, PDE4C, PDE4D and PDE5A was detected. The unspecific PDE inhibitor 3-isobutyl-1-methylxanthine (IBMX; 50 microM) relaxed histamine-contracted human umbilical artery on 47.4+/-7.2%. This effect seems to be due to PDE4 and PDE5 inhibition because among the selective PDE inhibitors used only the PDE4 inhibitor (rolipram; 1 microM) and the PDE5 inhibitors (dipyridamole and T0156; 3 microM and 1 microM respectively) induced significant relaxation (39.0+/-8.7, 30.4+/-6.0 and 36.3+/-2.8 respectively). IBMX, dipyridamole and T0156 produced similar relaxation on 5-HT-induced contraction. After forskolin, the addition of IBMX or rolipram increased the effect of the adenylate cyclase stimulator and almost completely relaxed the human umbilical artery contracted by histamine (92.5+/-4.9 and 90.9+/-4.7 respectively), suggesting a main role of PDE4. The data obtained with 5-HT contracted arteries confirmed this, because only rolipram and IBMX significantly increased the forskolin vasodilator effect. The administration of dipyridamole and T0156 after sodium nitroprusside (SNP) induced a significant increase of the SNP relaxant effect on histamine-contracted arteries, but PDE1 and PDE3 inhibition did not increase the effect of the guanylate cyclase stimulator. Similar effects were obtained in 5-HT contracted arteries, the SNP induced relaxation was increased by the PDE5 inhibition, but not by PDE1 or PDE3 inhibition. In summary, our results demonstrate that: 1) the increase of cAMP and/or cGMP levels induces relaxation of the human umbilical vascular smooth muscle; 2) four families of PDE are expressed in this smooth muscle: PDE1, PDE3, PDE4 and PDE5; 3) between these families, PDE4 and PDE5 are the key enzymes involved in the regulation of the relaxation associated to cAMP and cGMP, respectively.

Effect of Sildenafil on Neuropathic Pain and Hemodynamics in Rats

“…Moreover, phosphodiesterase 5 activity seemed to be relevant to cGMP-linked vasodilatation 19. It is, therefore, possible that phosphodiesterase 5 inhibitor may have significant effect on hemodynamics.…”

“…Also, cGMP plays important role in the regulation of vascular tone,18 and it has recently been reported that phosphodiesterase 5 is the key enzyme involved in the regulation of the cGMP-associated vascular relaxation 19. Therefore, hemodynamic change due to vasodilating effect of phosphodiesterase 5 inhibitor is expected.…”

How is the human umbilical artery regulated?

“…The main difference between this artery and the systemic vessels is the lack of nerve fibers, and since it is a local physiological regulation of muscle contraction and relaxation, it is independent of nerve regulation. The vascular tonus of HUA depends entirely on vasoactive substances released locally or existing in the circulation, such as serotonin (5‐HT), histamine (His) and thromboxane, and of some ions such as calcium (Ca 2+ ) and potassium (K + ) . So, the HUA tonus is modulated by endocrine and paracrine mechanisms that regulate the contractile response of SMC .…”

Stimulation of Neural Stem Cell Proliferation by Inhibition of Phosphodiesterase 5

“…Treatment with T0156 (1  μ M [37]) significantly increased the incorporation of EdU (140.7 ± 11.9% of the control, P < 0.05; Figure 1(a)), when compared to control cultures (no treatment). Both sildenafil and zaprinast increased EdU incorporation, in comparison to untreated cultures, as follows: sildenafil (1  μ M, 137.4 ± 7.0%, P < 0.05; 10  μ M, 120.8 ± 10.4%, P > 0.05; 50  μ M, 141.3 ± 12.6%, P < 0.01; Figure 1(b)) and zaprinast (10  μ M, 125.6 ± 7.8%, P < 0.01; 50  μ M, 118.1 ± 5.6%, P > 0.05; Figure 1(c)).…”