Influence of celecoxib on the vasodilating properties of human mesenteric arteries constricted with endothelin-1

Abstract

The mitogenic and vasoconstrictive properties of the vascular system are attributed to endothelin-1 (ET-1). ET-1 serum concentration increases in a number of pathological conditions, particularly in those associated with blood vessel constriction. ET-1 is also associated with the underlying pathomechanisms of primary pulmonary hypertension, arterial hypertension and eclampsia. The aim of this study was to compare the vasodilating properties of selected phosphodiesterase (PDE) inhibitors and celecoxib in human mesenteric arteries constricted with ET-1, and investigate the role of the endothelium in relaxation. Perfused human mesenteric arteries were collected and stored under the same conditions as organs for transplantation. The mesenteric arteries (with and without the endothelium) were constricted by the addition of ET-1 and treated with one of the following: sildenafil (PDE5 inhibitor), zaprinast (PDE5 and 6 inhibitor), rolipram (PDE4 inhibitor) and celecoxib [cyclooxygenase-2 (COX-2) inhibitor]. Based on the observed changes of the perfusion pressure, concentration response curves (CRCs) were prepared for the respective inhibitors and the EC₅₀ (concentration causing an effect equal to half of the maximum effect), pD₂ (negative common logarithm of EC₅₀) and relative potency (RP) were calculated. The results suggested that all the inhibitors triggered a concentration-dependent decrease in the perfusion pressure in isolated human superior mesenteric arteries with endothelium constricted by the addition of ET-1. In the arteries without endothelium, CRCs for celecoxib and rolipram were shifted to the right without a significant decrease in the maximum dilating effect. Moreover, CRCs for sildenafil and zaprinast were shifted to the right with a simultaneous significant decrease in the maximum dilating effect and with an increased inclination angle in reference to the concentration axis. In the presence of the endothelium, all of the evaluated PDE inhibitors, as well as celecoxib, reduced the reactivity of the mesenteric arteries caused by ET-1. Sildenafil indicated the lowest efficacy in the presence of the endothelium, but showed a higher potency compared to that of the other compounds. Removing the endothelium significantly reduced the vasodilating efficacy of PDE5 and 6 inhibitors and a statistically significant influence on the vasodilating efficacy of PDE4 inhibitor and celecoxib was observed. The high vasorelaxing efficacy of celecoxib at the background of the PDE inhibitors was observed, not only in the presence, but also in the absence of the endothelium and may be evidence for the relaxation induced by this COX-2 inhibitor in the cAMP- and cGMP-dependent pathways.

Keywords: celecoxib; constriction; endothelin-1; endothelium; phosphodiesterase inhibitors.

Figure 1

CRCs for celecoxib, zaprinast, sildenaphil and rolipram. The study was performed on human mesenteric arteries (with endothelium) contracted by ET-1. All the inhibitors triggered a concentration-dependent decrease in perfusion pressure in the mesenteric arteries. Points marked on the CRC present the mean relaxation effect in % and SE (n=12 arteries per group). Graphs were approximated to sigmoidal curve. CRC, concentration response curves; ET-1, endothelin-1; SE, standard error; Emax, maximal response produced by the drug.

Figure 2

CRCs for celecoxib, zaprinast, sildenafil and rolipram. The study was performed on human mesenteric arteries (without endothelium) contracted by ET-1. Points marked on the CRC present the mean relaxation effect in % and SE (n=12 arteries per group). Graphs were approximated to the sigmoidal curve. CRCs, concentration response curves; ET-1, endothelium; SE, standard error.

Figure 3

Em and RP of celecoxib, sildenafil, rolipram and zaprinast for human mesenteric arteries, with and without the endothelium constricted by ET-1. Results are based on the data from Table I. Em, maximum effect; RP, relative potency.