nitroarginine and Hyperplasia

The selective 5-HT(2A) receptor antagonist sarpogrelate has been clinically used for treatment in atherosclerotic diseases. However, it remains unknown whether administration of sarpogrelate inhibits intimal hyperplasia seen in autologous vein grafts. Therefore, we sought to clarify this question using an experimental rabbit vein graft model.. Male rabbits were divided into two groups: a control group and a sarpogrelate-treated group. The jugular vein was interposed in the carotid artery in reversed fashion for 4 weeks and intimal hyperplasia of the grafted vein was measured (n = 8, in each group). Acetylcholine (ACh)-induced endothelium-dependent relaxation was tested by precontraction with prostaglandin F(2alpha) (PGF(2alpha), 5 muM) (n = 5, in each). endothelial nitric oxide synthase (eNOS) protein expression and superoxide production of these veins were also assessed.. The suppression of intimal hyperplasia was significantly greater in the sarpogrelate-treated group than in the control group. ACh induced an endothelium-dependent relaxation in the sarpogrelate-treated group (but not in the control group). In endothelium-intact strips from the sarpogrelate-treated group, the nitric oxide (NO) synthase inhibitor nitroarginine enhanced the PGF(2alpha)-induced contraction and blocked the ACh-induced relaxation. Immunoreactive eNOS protein expression was similar between the two groups but superoxide production (estimated from ethidium fluorescence) in endothelial cells was significantly smaller in the sarpogrelate-treated group.. The present results indicate that in vivo blockade of 5-HT(2A) receptors leads to an inhibition of intimal hyperplasia in rabbit vein graft. It is suggested that an increased function of endothelium-derived NO through a reduction in endothelial superoxide production may be a possible underlying mechanism for this. These novel findings support the clinical usefulness of sarpogrelate for preventing intimal hyperplasia in vein graft after bypass grafting.

Topics: Acetylcholine; Administration, Oral; Animals; Carotid Arteries; Cell Proliferation; Endothelium, Vascular; Enzyme Inhibitors; Hyperplasia; Jugular Veins; Male; Models, Animal; Nitric Oxide; Nitric Oxide Synthase Type III; Nitroarginine; Rabbits; Receptor, Serotonin, 5-HT2A; Serotonin 5-HT2 Receptor Antagonists; Serotonin Antagonists; Succinates; Superoxides; Tunica Intima; Vasodilation; Vasodilator Agents

Extensive proliferation and migration of smooth muscle cells (SMCs) contribute to development of fibromuscular intimal hyperplasia in response to balloon catheter-induced injury of the left carotid artery in Fischer 344 rats. The purpose of the present study was to test the hypothesis that endogenously generated nitric oxide (NO) and prostaglandins act synergistically to limit the extent of neointimal hyperplasia.. The left carotid artery of Fischer 344 rats was injured with a 2F balloon catheter. The following treatment was initiated 24 hours before arterial injury, and was continued for 2 weeks: N-nitro-l-arginine (L-NA; 10 mg/kg/d, in drinking water), indomethacin (1.5 mg/kg/d per gavage), and L-NA (10 mg/kg/d) plus indomethacin (1.5 mg/kg/d). After application of an overdose of pentobarbital animals were formalin-fixed. Subsequently, paraffin-embedded cross sections of the uninjured and injured carotid arteries were analyzed morphometrically. SMC proliferation was determined by incorporation of 5-bromo-2'-deoxyuridine.. Two weeks after injury, L-NA caused a 1.29-fold +/- 0.29-fold (mean +/- SD; n = 14; P <.05) increase in the intima-media ratio, compared with control animals, whereas indomethacin had no effect. Combined treatment with L-NA plus indomethacin further increased intima-media ratio (1.65-fold +/- 0.5-fold over control; n = 14; P <.05). SMC proliferation in the neointima of rats treated with L-NA and L-NA plus indomethacin was elevated. Furthermore, neointimal cell density (nuclei per square millimeter) was reduced after combined inhibition of cyclooxygenases and NO synthases.. The present results of pharmacologic NO synthase and cyclooxygenase inhibition suggest that NO and prostaglandins are part of an endogenous growth inhibitory mechanism that synergistically suppresses intimal thickening.. The role of cyclooxygenase-1 (COX1) and cyclooxygenase-2 (COX2) during vascular recurrent stenosis and atherosclerosis is not clear yet. In particular, the effects of selective COX2 inhibitors on the frequency of cardiovascular events is still controversial. It is shown here in rats that the application of a non-selective COX inhibitor does not affect arterial stenosis. However, the concurrent inhibition of endogenous nitric oxide generation and COX1 or COX2 causes overshooting neointimal hyperplasia. These results suggest that increased vascular stenosis can result from administration of drugs that pharmacologically block 2 or more inhibitory pathways that normally counterbalance the effect of promotors of neointimal hyperplasia.

Topics: Angioplasty, Balloon; Animals; Carotid Arteries; Carotid Artery Injuries; Cyclooxygenase Inhibitors; Enzyme Inhibitors; Hyperplasia; Indomethacin; Male; Models, Animal; Nitric Oxide Synthase; Nitroarginine; Rats; Rats, Inbred F344; Tunica Intima

We compared the effects of NO donors and cGMP analogues on the growth of aortic smooth muscle cells (SMCs) derived from newborn, adult (aged 3 months), and old (aged 2 years) rats. We found that the NO donor S-nitroso-N-acetylpenicillamine failed to block DNA synthesis in SMCs from old rats but was effective in SMCs from newborn and adult rats. However, cGMP analogues were inhibitory in all 3 SMC types. We demonstrated that in SMCs from old rats, NO was unable to increase the concentration of intracellular cGMP, suggesting that either cGMP synthesis was defective or cGMP degradation was enhanced. Western blot analysis revealed that SMCs from old rats do not express the beta subunit of soluble guanylyl cyclase. To confirm the importance of this observation in vivo, we balloon-injured the carotid arteries of adult and old rats. Whereas soluble guanylyl cyclase was expressed at the same level in the media of injured vessels and uninjured vessels of both groups, its expression in the intimas of old rats was reduced by 70% compared with intimas from adult animals. Furthermore, N(omega)-nitro-L-arginine, an inhibitor of NO synthesis, enhanced the intimal thickening in injured vessels in adult rats but not in old rats. We conclude that the loss of NO responsiveness in aged rats is due to the lack of the beta subunit of soluble guanylyl cyclase, and we speculate that this defect contributes to the enhanced intimal thickening in response to injury in old animals.

Topics: Aging; Angioplasty, Balloon; Animals; Aorta; Carotid Artery Injuries; Cells, Cultured; Cyclic GMP; Cyclic GMP-Dependent Protein Kinases; DNA; Enzyme Inhibitors; Guanylate Cyclase; Hyperplasia; Male; Muscle, Smooth, Vascular; Nitric Oxide; Nitric Oxide Donors; Nitroarginine; Penicillamine; Protein Kinases; Rats; Rats, Inbred F344; Signal Transduction; Solubility; Tunica Intima

Bladder outlet obstruction (BOO) is associated with altered bladder structure and function. Endothelin-1 (ET-1) has mitogenic and potent contractile properties. There are two ET receptors: ET(A) and ET(B). Nitric oxide synthase (NOS) is the enzyme responsible for the synthesis of nitric oxide (NO) which is involved in smooth muscle relaxation. We investigated whether there are any changes in the density of ET-receptors and NOS in the detrusor and bladder neck in a rabbit model of BOO. Partial BOO was induced in adult male New Zealand White rabbits. Sham operated age-matched rabbits acted as controls. After six weeks the urinary bladders were excised and detrusor and bladder neck sections incubated with radioligands for ET-1, ET(A) and ET(B) receptors and with [3H]-1-NOARG (a ligand for NOS). NADPH histochemistry was also performed. BOO bladder weights were significantly increased (P = 0.002). ET-1 binding and ETA receptor binding sites were significantly increased in the BOO detrusor smooth muscle (P = 0.04, P = 0.03 respectively) and urothelium (P = 0.002, P = 0.02 respectively). ET(B) receptor binding sites were also significantly increased in the BOO detrusor smooth muscle (P = 0.04). However, there was no change in the BOO bladder neck. NOS was significantly decreased in the detrusor smooth muscle (P = 0.003) and urothelium (P = 0.0002). In the bladder neck NOS was also significantly reduced in the urothelium (P = 0.003). NADPH staining was decreased in the detrusor and bladder neck. The up-regulation of ET receptors along with the down-regulation of NOS in the detrusor may contribute to the symptoms associated with BOO. Since ET-1 has a mitogenic role, especially via its ETA receptors, the increase in ETA receptors may also be involved in detrusor hyperplasia and hypertrophy in BOO. ET antagonists may therefore have a role in the treatment of patients with BOO.

Topics: Animals; Autoradiography; Binding Sites; Disease Models, Animal; Down-Regulation; Endothelin-1; Humans; Hyperplasia; Hypertrophy; Male; Muscle, Smooth; NADPH Dehydrogenase; Nitric Oxide Synthase; Nitric Oxide Synthase Type III; Nitroarginine; Prostatic Hyperplasia; Rabbits; Receptor, Endothelin A; Receptor, Endothelin B; Receptors, Endothelin; Up-Regulation; Urinary Bladder Neck Obstruction