Background and purpose: KMUP-1 is known to increase cGMP, enhance endothelial nitric oxide synthase (eNOS) and suppress Rho kinase (ROCK) expression in smooth muscle. Here, we investigated the mechanism of action of KMUP-1 on acute and chronic pulmonary artery hypertension (PAH) in rats. Experimental approach: We measured pulmonary vascular contractility, wall thickening, eNOS immunostaining, expressions of ROCK II, RhoA activation, myosin phosphatase target subunit 1 (MYPT1) phosphorylation, eNOS, soluble guanylyl cyclase (sGC), protein kinase G (PKG) and phosphodiesterase 5A (PDE-5A), blood oxygenation and cGMP/cAMP, and right ventricular hypertrophy (RVH) in rats. Key results: In rings of intact pulmonary artery (PA), KMUP-1 relaxed the vasoconstriction induced by phenylephrine (10 mM) or the thromboxane A2-mimetic U46619 (0.5 mM). In endothelium-denuded PA rings, this relaxation was reduced. In acute PAH induced by U46619 (2.5 mg·kg -1 ·min -1 , 30 min), KMUP-1 relaxed vasoconstriction by enhancing levels of eNOS, sGC and PKG, suppressing those of PDE-5A, RhoA/ROCK II activation and MYPT1 phosphorylation, and restoring oxygenation in blood and cGMP/cAMP in plasma. Incubating smooth muscle cells from PA (PASMCs) with KMUP-1 inhibited thapsigargin-induced Ca 2+ efflux and angiotensin II-induced Ca 2+ influx. In chronic PAH model induced by monocrotaline, KMUP-1 increased eNOS and reduced RhoA/ROCK II activation/expression, PA wall thickening, eNOS immunostaining and RVH. KMUP-1 and sildenafil did not inhibit monocrotaline-induced PDE-5A expression. Conclusion and implications: KMUP-1 decreased PAH by enhancing NO synthesis by eNOS, with consequent cGMPdependent inhibition of RhoA/ROCK II and Ca 2+ desensitization in PASMCs. KMUP-1 has the potential to reduce vascular resistance, remodelling and RVH in PAH.

BackgroundKMUP-1 is a xanthine derivative with inhibitory activities on the phosphodiesterase (PDE) 3,4 and 5 isoenzymes to suppress the degradation of cyclic AMP and cyclic GMP. However, the effects of KMUP-1 on osteoclast differentiation are still unclear. In this study, we investigated whether KMUP-1 inhibits osteoclastogenesis induced by RANKL in RAW 264.7 cells and bone loss induced by ovariectomy in mice, and the underlying mechanisms.Principal Findings In vitro, KMUP-1 inhibited RANKL-induced TRAP activity, the formation of multinucleated osteoclasts and resorption-pit formation. It also inhibited key mediators of osteoclastogenesis including IL-1β, IL-6, TNF-α and HMGB1. In addition, KMUP-1 inhibited RANKL-induced activation of signaling molecules (Akt, MAPKs, calcium and NF-κB), mRNA expression of osteoclastogensis-associated genes (TRAP, MMP-9, Fra-1, and cathepsin K) and transcription factors (c-Fos and NFATc1). Furthermore, most inhibitory effects of KMUP-1 on RANKL-mediated signal activations were reversed by a protein kinase A inhibitor (H89) and a protein kinase G inhibitor (KT5823). In vivo, KMUP-1 prevented loss of bone mineral content, preserved serum alkaline phosphate and reduced serum osteocalcin in ovariectomized mice.ConclusionsKMUP-1 inhibits RANKL-induced osteoclastogenesis in vitro and protects against ovariectomy-induced bone loss in vivo. These effects are mediated, at least in part, by cAMP and cGMP pathways. Therefore, KMUP-1 may have a role in pharmacologic therapy of osteoporosis.

1 7-[2-[4-(2-chlorophenyl)piperazinyl]ethyl]-1,3-dimethylxanthine (KMUP-1) produces tracheal relaxation, intracellular accumulation of cyclic nucleotides, inhibition of phosphodiesterases (PDEs) and activation of K þ channels. 2 KMUP-1 (0.01-100 mM) induced concentration-dependent relaxation responses in guinea-pig epithelium-intact trachea precontracted with carbachol. Relaxation responses were also elicited by the PDE inhibitors theophylline, 3-isobutyl-1-methylxanthine (IBMX), milrinone, rolipram and zaprinast (100 mM), and a K ATP channel opener, levcromakalim. 3 Tracheal relaxation induced by KMUP-1 was attenuated by epithelium removal and by pretreatment with inhibitors of soluble guanylate cyclase (sGC) (1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), 1 mM), nitric oxide synthase (N o -nitro-L-arginine methyl ester, 100 mM), K þ channels (tetraethylammonium, 10 mM), K ATP channels (glibenclamide, 1 mM), voltage-dependent K þ channels (4-aminopyridine, 100 mM) and Ca 2 þ -dependent K þ channels (charybdotoxin, 0.1 mM or apamin, 1 mM). 4 Both KMUP-1 (10 mM) and theophylline nonselectively and slightly inhibited the enzyme activity of PDE3, 4 and 5, suggesting that they are able to inhibit the metabolism of adenosine 3 0 ,5 0 -cyclic monophosphate (cyclic AMP) and guanosine 3 0 ,5 0 -cyclic monophosphate (cyclic GMP). Likewise, the effects of IBMX were also measured and its IC 50 values for PDE3, 4 and 5 were 6.571.2, 26.373.9 and 31.775.3 mM, respectively. 5 KMUP-1 (0.01-10 mM) augmented intracellular cyclic AMP and cyclic GMP levels in guinea-pig cultured tracheal smooth muscle cells. These increases in cyclic AMP and cyclic GMP were abolished in the presence of an adenylate cyclase inhibitor SQ 22536 (100 mM) and an sGC inhibitor ODQ (10 mM), respectively. 6 KMUP-1 (10 mM) increased the expression of protein kinase A (PKA RI ) and protein kinase G (PKG 1a1b ) in a time-dependent manner, but this was only significant for PKG after 9 h. 7 Intratracheal administration of tumour necrosis factor-a (TNF-a, 0.01 mg kg À1 ) induced bronchoconstriction and exhibited a time-dependent increase in lung resistance (R L ) and decrease in dynamic lung compliance (C dyn ). KMUP-1 (1.0 mg kg À1 ), injected intravenously for 10 min before the intratracheal TNF-a, reversed these changes in R L and C dyn . 8 These data indicate that KMUP-1 activates sGC, produces relaxation that was partly dependent on an intact epithelium, inhibits PDEs and increases intracellular cyclic AMP and cyclic GMP, which then increases PKA and PKG, leading to the opening of K þ channels and resulting tracheal relaxation.

1 KMUP-1 (1, 3, 5 mg kg 71 , i.v.), a xanthine derivative, produced dose-dependent sustained hypotensive and short-acting bradycardiac eects in anaesthetized rats. This hypotensive eect was inhibited by pretreatment with glibenclamide (5 mg kg 71 , i.v.). 2 In endothelium-intact or denuded aortic rings preconstricted with phenylephrine, KMUP-1 caused a concentration-dependent relaxation. This relaxation was reduced by endothelium removal, the presence of NOS inhibitor L-NAME (100 mM) and sGC inhibitors methylene blue (10 mM) and ODQ (1 mM). 3 The vasorelaxant eects of KMUP-1 was attenuated by pretreatment with various K + channel blockers TEA (10 mM), glibenclamide (1 mM), 4-AP (100 mM), apamin (1 mM) and charybdotoxin (ChTX, 0.1 mM). 4 Increased extracellular potassium levels (30 ± 80 mM) caused a concentration-related reduction of KMUP-1-induced vasorelaxations. Preincubation with KMUP-1 (1, 10, 100 nM) increased the AChinduced maximal vasorelaxations mediated by endogenous NO release, and enhanced the potency of exogenous NO-donor SNP. 5 The vasorelaxant responses of KMUP-1 (0.01, 0.05, 0.1 mM) together with a PDE inhibitor IBMX (0.5 mM) had an additive action. Additionally, KMUP-1 (100 mM) aected cyclic GMP metabolism since it inhibited the activity of PDE in human platelets. 6 KMUP-1 induced a dose-related increase in intracellular cyclic GMP levels in rat A10 vascular smooth muscle (VSM) cells, but not cyclic AMP. The increase in cyclic GMP content of KMUP-1 (0.1 ± 100 mM) was almost completely abolished in the presence of methylene blue (10 mM), ODQ (10 mM), and L-NAME (100 mM). 7 In conclusion, these results indicate that KMUP-1 possesses the following merits: (1) stimulation of NO/sGC/cyclic GMP pathway and subsequent elevation of cyclic GMP, (2) K + channels opening, and (3) inhibition of PDE or cyclic GMP breakdown. Increased cyclic GMP display a prominent role in KMUP-1-induced VSM relaxations.

Background and purpose:To determine whether KMUP-1, a novel xanthine-based derivative, attenuates isoprenaline (ISO)-induced cardiac hypertrophy in rats, and if so, whether the anti-hypertrophic effect is mediated by the nitric oxide (NO) pathway. Experimental approach: In vivo, cardiac hypertrophy was induced by injection of ISO (5 mg·kg , s.c.) for 10 days in Wistar rats. In the treatment group, KMUP-1 was administered 1 h before ISO. After 10 days, effects of KMUP-1 on survival, cardiac hypertrophy and fibrosis, the NO/guanosine 3′5′-cyclic monophosphate (cGMP)/protein kinase G (PKG) and hypertrophy signalling pathways [calcineurin A and extracellular signal-regulated kinase (ERK)1/2] were examined. To investigate the role of nitric oxide synthase (NOS) in the effects of KMUP-1, a NOS inhibitor, N w -nitro-L-arginine (L-NNA) was co-administered with KMUP-1. In vitro, anti-hypertrophic effects of KMUP-1 were studied in ISO-induced hypertrophic neonatal rat cardiomyocytes. Key results:In vivo, KMUP-1 pretreatment attenuated the cardiac hypertrophy and fibrosis and improved the survival of ISO-treated rats. Plasma NOx (nitrite and nitrate) and cardiac endothelial NOS, cGMP and PKG were all increased by KMUP-1. The activation of hypertrophic signalling by calcineurin A and ERK1/2 in ISO-treated rats was also attenuated by KMUP-1. All these effects of KMUP-1 were inhibited by simultaneous administration of L-NNA. Similarly, in vitro, KMUP-1 attenuated hypertrophic responses and signalling induced by ISO in neonatal rat cardiomyocytes. Conclusions and implications: KMUP-1 attenuates the cardiac hypertrophy in rats induced by administration of ISO. These effects are mediated, at least in part, by NOS activation. This novel agent, which targets the NO/cGMP pathway, has a potential role in the prevention of cardiac hypertrophy.