Abstract-The role of nitric oxide (NO) in the brain in the control of blood pressure and the sympathetic nervous system is debated. This study examined the effect of overexpression of endothelial NO synthase (eNOS) in the nucleus tractus solitarii (NTS) on blood pressure in conscious rats. Adenovirus vectors encoding either eNOS (AdeNOS) or ␤-galactosidase were transfected into the NTS in vivo. In the AdeNOS-treated rats, the local expression of eNOS in the NTS was confirmed by immunohistochemical staining and Western blot analysis for the eNOS protein and by increased production of nitrite/nitrate in the NTS measured by in vivo microdialysis. Blood pressure and heart rate, monitored by the use of a radiotelemetry system in a conscious state, were significantly decreased in the AdeNOS-treated group at day 5 to day 10 after the gene transfer. Urinary norepinephrine excretion also was decreased at day 7 after the gene transfer in the AdeNOS-treated group. Our results indicate that overexpression of eNOS in the NTS decreases blood pressure, heart rate, and sympathetic nerve activity in conscious rats. (Hypertension. 2000;36:1023-1028.)Key Words: genes Ⅲ nitric oxide Ⅲ brain Ⅲ sympathetic nervous system T here is considerable evidence that nitric oxide (NO) in the brain affects sympathetic nerve activity and modulates blood pressure and heart rate. [1][2][3][4][5][6] Studies that used immunohistochemistry for neuronal NO synthase (nNOS), nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase staining, have demonstrated the presence of nNOS at a high concentration in the regions of the brain stem, such as the nucleus tractus solitarii (NTS) and the ventrolateral medulla (VLM), which plays an important role in regulation of sympathetic nerve activity. 7,8 However, conflicting results have been obtained with regard to the effect of NO in the regulation of blood pressure and sympathetic nerve activity. Several studies have demonstrated that unilateral microinjection of the NOS inhibitor N G -monomethyl-L-arginine (L-NMMA) into the NTS produced the pressor effect, 1,2 and L-arginine, the precursor of NO, decreased blood pressure, heart rate, and renal sympathetic nerve activity. 2 On the contrary, the other study has shown that the microinjection of N -nitro-L-arginine methyl ester (L-NAME), another NOS inhibitor, into the NTS decreased blood pressure, heart rate, and renal sympathetic nerve activity, 3 and the NO donor Et 2 N[N(O)NO]Na (NOC 18) increased those variables. 3 Similarly, conflicting results have also been reported as regard to the effects of NO in the rostral VLM. 2,4,5 However, all of these studies were performed in anesthetized animals and examined only acute effects of NO or NOS inhibitors. Long-term effects of increased NO production in these regions on the regulation of blood pressure and sympathetic nerve activity in conscious animals remain to be clarified.Replicant-deficient recombinant adenovirus is now widely used for gene transfer into the brain as well as into the blood vessel. 9 -12 Of...

Rapid regrowth or recurrent growth of occult cancer cells are often observed after esophagectomy or postoperative complications. In order to clarify the mechanism of such oncological circumstances, we focused on neutrophil elastase (NE), which degrades a broad spectrum of extracellular matrix and cell surface proteins. In the present study, we demonstrated that NE stimulated the growth of all of the five esophageal cell lines (TE-1, -7, -8, -12 and -13) by MTT assay and promoted cell invasion by cell migration assay. Protransforming growth factor-• (pro-TGF-•) from the cell membrane was released to the culture medium as a mature form after treatment with 5 μg/ml NE, and it reached the maximum level of 153% compared to the control values at 15 min of treatment in TE-13 cells. The phosphorylation of epidermal growth factor receptor (EGFR) rapidly occurs after treatment with NE and triggered the extracellular signalregulated kinases 1 and 2 (ERK) signaling pathway. Moreover, NE induced release of platelet-derived growth factor-AA (PDGF-AA), PDGF-BB and vascular endothelial growth factor (VEGF) to 141.9, 227.7, and 171.6% of the control values, respectively. A specific NE inhibitor, sivelestat, significantly inhibited the NE-induced cell proliferation, cell invasion and subsequently inhibited the signal transduction pathway. Furthermore, sivelestat significantly inhibited NE-induced release of TGF-•, PDGF-AA, PDGF-BB and VEGF in the medium in TE-13 esophageal carcinoma cells. These results strongly indicate that NE released from activated neutrophils stimulates the growth and progression of esophageal cancer cells by releasing the growth factors on the cell surface and that sivelestat, a specific NE inhibitor, blocks these processes. Furthermore, we postulate that postoperative administration of sivelestat might be useful as a new molecular-targeting cancer therapy as well as for the treatment of postoperative respiratory complications.

In this study, we examine the role of NO located in the rostral ventrolateral medulla (RVLM) in the control of blood pressure and the activity of the sympathetic nervous system. To determine the effect of an increase in NO production in the RVLM on blood pressure in conscious rats, adenovirus vectors encoding either endothelial NO synthase (AdeNOS) or β-galactosidase (Adβgal) were transfected into the bilateral RVLM. The local expression of endothelial NO synthase (eNOS) protein in the RVLM was confirmed by immunohistochemical staining for the eNOS protein and by Western blot analysis. Mean arterial blood pressure (MAP) and heart rate, which were monitored using a radio-telemetry system, were significantly decreased in the AdeNOS-treated group from day 5 to day 10 after the gene transfer. Urinary norepinephrine excretion was decreased on day 7 after the gene transfer in the AdeNOS-treated group. Microinjection of either N G -monomethyl- l -arginine (L-NMMA) or bicuculine, a γ-amino butyric acid (GABA) receptor antagonist, into the RVLM at day 7 after the gene transfer increased MAP to significantly greater levels in the AdeNOS-treated group. However, microinjection of kynurenic acid into the RVLM on day 7 after the gene transfer did not alter MAP levels in either group. GABA and glutamate levels in the RVLM, when measured by in vivo microdialysis, were significantly increased in the AdeNOS-treated group. These results suggest that the increase in NO production caused by the overexpression of eNOS in the bilateral RVLM decreases blood pressure, heart rate, and sympathetic nerve activity in conscious rats. Furthermore, these responses may be mediated by an increased release of GABA in the RVLM.

Abstract-Activation of the sympathetic nervous system and renin-angiotensin system has been suggested to contribute to the hypertension caused by chronic nitric oxide synthase inhibition. The aim of the present study was to determine whether angiotensin within the nucleus tractus solitarii (NTS) plays a role in activation of the sympathetic nervous system in this model. Rats were treated with N -nitro-L-arginine methyl ester (L-NAME, 100 mg ⅐ kg Ϫ1 ⅐ d Ϫ1 in drinking water) for 2 weeks. Experiments were performed on anesthetized rats with denervated arterial and cardiopulmonary baroreceptors. Arterial pressure, heart rate, and renal sympathetic nerve activity (RSNA) were measured. Microinjection of an angiotensin II type 1 (AT 1 ) receptor antagonist (CV11974) or an angiotensin II type 2 (AT 2 ) receptor antagonist (PD123319) into the depressor region within the NTS (identified by prior injection of L-glutamate) was performed. Microinjection of CV11974, but not of PD123319, produced greater decreases in arterial pressure, heart rate, and RSNA in L-NAME-treated rats than in control rats. The administration of hexamethonium resulted in a larger fall in arterial pressure in L-NAME-treated rats than in control rats. The ACE mRNA level in the brain stem was greater in L-NAME-treated rats than in control rats. These results suggest that increased sympathetic nerve activity plays a role in hypertension caused by chronic nitric oxide synthase inhibition and that activation of the renin-angiotensin system in the NTS is involved at least in part in this increased sympathetic nerve activity via AT 1 receptors. (Hypertension. 2000;36:259-263.) Key Words: nitric oxide Ⅲ sympathetic nervous system Ⅲ brain Ⅲ angiotensin Ⅲ blood pressure Ⅲ heart rate I t is well established that pharmacological inhibition of nitric oxide (NO) synthesis produces acute and chronic hypertension in many animal species, 1,2 but the underlying mechanisms that mediate this hypertension are not fully understood. Although this hypertension was initially attributed solely to the inhibition of endothelial NO synthase (eNOS), numerous studies have demonstrated that the inhibition of neuronal NO may also play a role. [3][4][5][6][7] The administration of an NOS inhibitor, such as N G -monomethyl-Larginine (L-NMMA) or N -nitro-L-arginine methyl ester (L-NAME), into the central nervous system evokes acute increases in both arterial pressure and sympathetic nerve activity. 8,9 These results have been interpreted to suggest that neuronal NO plays roles in the signal transduction pathways involved in the tonic inhibition of sympathetic vasoconstrictor outflow from the brain stem. The removal of this inhibition by NOS inhibitors is postulated to activate the sympathetic nervous system and thereby result in hypertension.Several investigators have demonstrated a great effect of sympathectomy or ganglionic blockade on L-NAME-induced hypertension, suggesting that the sympathetic nervous system is involved primarily in the maintenance, rather than the initiation, of L...

Nitric oxide (NO) in the nucleus tractus solitarii (NTS) plays an important role in regulating sympathetic nerve activity. The aims of this study were to determine whether the activation of N-methyl-D-aspartate (NMDA) receptors in the NTS facilitates the release of L-glutamate (Glu) via NO production, and, if so, to determine whether this mechanism is involved in the depressor and bradycardic responses evoked by NMDA. We measured the production of NO in the NTS as NO2- and NO3- (NO(x)) or Glu levels by in vivo microdialysis before, during, and after infusion of NMDA in anesthetized rats. We also examined effects of N(omega)-nitro-L-arginine methyl ester (L-NAME) on the changes in these levels. NMDA elicited depressor and bradycardic responses and increased the levels of NO(x) and Glu. L-NAME abolished the increases in the levels of NO(x) and Glu and attenuated cardiovascular responses evoked by NMDA. These results suggest that NMDA receptor activation in the NTS induces Glu release through NO synthesis and that Glu released via NO enhances depressor and bradycardic responses.