The Xanthine Derivative KMUP-1 Attenuates Serotonin-Induced Vasoconstriction and K⁺-Channel Inhibitory Activity via the PKC Pathway in Pulmonary Arteries

Abstract

Serotonin (5-hydroxytryptamine, 5-HT) is a potent pulmonary vasoconstrictor that promotes pulmonary artery smooth muscle cell (PASMC) proliferation. 5-HT-induced K+ channel inhibition increases [Ca2+]i in PASMCs, which is a major trigger for pulmonary vasoconstriction and development of pulmonary arterial hypertension (PAH). This study investigated whether KMUP-1 reduces pulmonary vasoconstriction in isolated pulmonary arteries (PAs) and attenuates 5-HT-inhibited K+ channel activities in PASMCs. In endothelium-denuded PA rings, KMUP-1 (1 μM) dose-dependently reduced 5-HT (100 μM) mediated contractile responses. Responses to KMUP-1 were reversed by K+ channel inhibitors (TEA, 10 mM, 4-aminopyridine, 5 mM, and paxilline, 10 μM). In primary PASMCs, KMUP-1 also dose-dependently restored 5-HT-inhibited voltage-gated K+-channel (Kv1.5 and Kv2.1) and large-conductance Ca2+-activated K+-channel (BKCa) proteins, as confirmed by immunofluorescent staining. Furthermore, 5-HT (10 μM)-inhibited Kv1.5 protein was unaffected by the PKA inhibitor KT5720 (1 μM) and the PKC activator PMA (1 μM), but these effects were reversed by KMUP-1 (1 μM), 8-Br-cAMP (100 μM), chelerythrine (1 μM), and KMUP-1 combined with a PKA/PKC activator or inhibitor. Notably, KMUP-1 reversed 5-HT-inhibited Kv1.5 protein and this response was significantly attenuated by co-incubation with the PKC activator PMA, suggesting that 5-HT-mediated PKC signaling can be modulated by KMUP-1. In conclusion, KMUP-1 ameliorates 5-HT-induced vasoconstriction and K+-channel inhibition through the PKC pathway, which could be valuable to prevent the development of PAH.

Xanthine scaffold: scope and potential in drug development

“…Till date four KMUP derivatives (KMUP-1 ( 11 ) (7-[2-[4-(2-chlorophenyl) piperazinyl]ethyl]-1,3-dimethylxanthine), KMUP-2 ( 12 ) (7-[2-[4-(2-methoxy) piperazinyl]ethyl]-1,3-dimethylxanthine), KMUP-3 ( 13 ) (7-[2-[4-(4-nitro) piperazinyl]ethyl]-1,3-dimethylxanthine) and KMUP-4 ( 14 ) (7-[2-[4-(2-nitro) piperazinyl]ethyl]-1,3-dimethylxanthine) are reported with their therapeutic activities. KMUP derivatives, act as inhibitor for PDE3, PDE4 and PDE5 thus maintaining the level of second messengers which in turn activate protein kinase A (PKA), protein kinases G (PKG) and K + channels which results tracheal smooth muscle relaxation [ 19 , 112 , 113 ]. KMUP-1 and KMUP-3 acts as eNOS/cGMP-enhancer which increases the level of nitric oxide (NO), gaseous second messenger, through endothelium nitric-oxide synthase (eNOS) [ 109 , 114 , 115 ].…”

“…There are increasing evidence that xanthine derivatives such as caffeine, theophylline, pentoxifylline, KMUP-1, etc show anti-inflammatory effect [19] . Anti-inflammatory responses of these derivatives are the result of their non-selective phosphodiesterase inhibition and/or their non-selective adenosine receptor antagonist properties.…”

“…PDE inhibition and/or adenosine antagonist role of xanthine derivatives leads to increase in cAMP concentration, activation of protein kinase A, inhibition of tumor necrosis factor (TNF-α) and leukotriene synthesis. With inhibition of leukotrienes synthesis, inflammation reduces [ 19 , 31 ]. Leukotrienes increase inflammation by raising leukocyte infiltration, phagocyte microbial ingestion, and generation of pro-inflammatory cytokines such as IL-5, TNFα, and macrophage inflammatory protein-1β [31] .…”

“…This has helped in exploring the significance of these derivatives in various therapeutics applications such as adenosine receptor antagonists, inducers of histone deacetylase activity, antitumor drugs, anti asthmatic drug, psycho-stimulant drug etc [ 10 , 11 , 12 , 13 , 14 ]. The wider pharmaceutical applications of natural xanthine derivatives has prompted medicinal chemist or pharmaceutical companies to go for certain changes over lead molecule to develop more specific compounds using synthesis methodologies [ 15 , 16 , 17 , 18 , 19 ]. In drug development process, one of the major challenges is deciding the lead molecule which would act as a scaffold to provide avenue for achieving molecular diversity.…”

Design and synthesis of five‐membered heterocyclic derivatives of istradefylline with comparable pharmacological activity

“…This has aided in the investigation of the use of these compounds in a variety of therapeutic applications, including adenosine receptor antagonists, histone deacetylase activity inducers, anticancer medications, anti-asthmatic pharmaceuticals, psychostimulant drugs, and so on ( Van der Walt & Terre'Blanche, 2015). Natural xanthine derivatives' broader therapeutic possibilities have motivated medicinal chemists or pharmaceutical corporations to make alterations to the lead molecule in order to generate more specific molecules employing synthesis procedures (Dai et al, 2015).…”