Aortic Smooth Muscle Relaxants KMUP-3 and KMUP-4, Two Nitrophenylpiperazine Derivatives of Xanthine, Display cGMP-Enhancing Activity

Abstract

The cellular mechanisms of vasorelaxant effects of newly synthesized KMUP-3 and KMUP-4 were investigated in rat aortic smooth muscle (RASM). KMUP-3 (7-[2-[4-(4-nitrobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine) and KMUP-4 (7-[2-[4-(2-nitrobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine) elicited concentration-dependent relaxation of endothelium-intact and denuded RASM precontracted with phenylephrine. Relaxant responses were also produced by the PDE inhibitors theophylline, milrinone, rolipram, and zaprinast (1 nM-100 microM). The relaxant responses of KMUP-3 and KMUP-4 were reduced by endothelium removal and by the presence of the NOS inhibitor L-NAME (100 microM), the sGC inhibitor ODQ (1 microM), the adenylyl cyclase (AC) inhibitor SQ 22536 (100 microM), and the prostaglandin inhibitor indomethacin (10 microM). Additionally, the vasorelaxations of both agents were also attenuated by pretreatment with the nonselective K+ channel blocker TEA (10 mM), the KATP channel blocker glibenclamide (1 microM), the voltage-dependent K+ (KV) channel blocker 4-AP (100 microM), and Ca(2+)-dependent K+ (KCa) channel blockers apamin (1 microM) and charybdotoxin (ChTX, 0.1 microM). In addition, elevated extracellular K+ (80 mM) interferes with KMUP-3- and KMUP-4-induced vasorelaxations. Preincubation with both agents (1 microM) significantly enhanced the dilator responses of isoproterenol and SNP. KMUP-3 and KMUP-4 inhibited PDE activities and increased cAMP and cGMP levels in primary culture of RASM that were inhibited by SQ 22536 and ODQ, respectively. In cultured HUVECs, KMUP-3 and KMUP-4 (0.1 microM), more potent than YC-1, significantly increased the expression of eNOS protein. In summary, KMUP-3 and KMUP-4 induce aortic relaxations through both endothelium-dependent and -independent mechanisms. Mechanisms of vasorelaxation induced by both compounds involve multiple processes, such as accumulation of cyclic nucleotides partly as a result of PDE inhibition, K-channel activation, and indomethacin-sensitive endothelium function.

KMUP‐3 attenuates ventricular remodelling after myocardial infarction through eNOS enhancement and restoration of MMP‐9/TIMP‐1 balance

“…Recently, longterm administration of KATP channel activators has also been shown to attenuate the ventricular remodelling after MI (Lee et al, 2008). A xanthinebased vasorelaxant synthesized in our laboratory, 7 -[2-[4-(4-Nitrobenzene ) -piperazinyl ] ethyl]-1,3-dimethylxanthine (KMUP-3), has been demonstrated to elevate cyclic nucleotide levels, inhibit phosphodiesterase and affect KATP channel opening (Wu et al, 2005;. In previous studies, KMUP-3 induced aortic smooth muscle relaxation through a KATP channel-dependent pathway.…”

“…In previous studies, KMUP-3 induced aortic smooth muscle relaxation through a KATP channel-dependent pathway. The vasorelaxant effect of KMUP-3 was attenuated by the KATP channel blocker glibenclamide and elevated extracellular K + levels (80 mM) (Wu et al, 2005;Lin et al, 2006). KMUP-1, an analogue of KMUP-3, has been shown to have a cardioprotective effect in hypertensive rats, reducing cardiac hypertrophy and fibrosis (Wu et al, 2001;Yeh et al, 2010).…”

“…KMUP-1, an analogue of KMUP-3, has been shown to have a cardioprotective effect in hypertensive rats, reducing cardiac hypertrophy and fibrosis (Wu et al, 2001;Yeh et al, 2010). KMUP-3, a more potent phosphodiesterase inhibitor than KMUP-1, also has the ability to enhance endothelial nitric oxide synthase (eNOS), as demonstrated in human umbilical vein endothelial cells (HUVECs) (Wu et al, 2005;Lin et al, 2006). By releasing the chemical mediator nitric oxide (NO), eNOS is involved in a variety of inflammatory responses.…”

A Xanthine-Based Epithelium-Dependent Airway Relaxant KMUP-3 (7-[2-[4-(4-Nitrobenzene)piperazinyl]ethyl]-1,3-dimethylxanthine) Increases Respiratory Performance and Protects against Tumor Necrosis Factor-α-Induced Tracheal Contraction, Involving Nitric Oxide Release and Expression of cGMP and Protein Kinase G

“…Evidence indicates that KMUP-3-induced relaxation was sensitive to various K ϩ channel blockers. Therefore, it is likely that KMUP-3-induced relaxation is partly mediated by NO-induced effects, including stimulating K ϩ efflux resulting in hyperpolarization (Wu et al, 2005) and thereafter accumulation of cGMP leading to the expression of PKG and reduction of Ca 2ϩ influx. KMUP-3-induced TSM relaxation was significantly reduced by pretreatment with ODQ.…”

“…To create a more hopeful xanthine-based tracheal smooth muscle (TSM) relaxant, KMUP-3 ( Fig. 1) was synthesized (Wu et al, 2005) and investigated regarding its mechanism of TSM-relaxing activity and the benefits of its intratracheal administration. In routine clinical practice, in addition to corticosteroids and ␤ 2 -adrenoreceptor agonist inhalants, however, no xanthine derivatives are inhaled for the treatment of bronchocontraction or airway inflammation.…”