Nitric oxide synthase and hypertension

Nitric oxide, the metabolic product of L-arginine by the enzyme nitric oxide synthase, plays a pivotal role in the regulation of vascular homeostasis. Its complex interaction with the autocrine and paracrine systems, particularly angiotensin II, modulates vasoconstriction and vasodilatation as well as the architectural remodeling of the vascular bed. The major vascular hormones known to be involved are angiotensin II and endothelin-1. Upregulation of endothelin-1, a potent molecule, appears to be a consequence of the nitric oxide-angiotensin II imbalance that contributes to end-organ injury. Increased oxidative stress, common to different diseases including diabetes mellitus and hypertension, is also a determinant player in the interaction between angiotensin II and nitric oxide. The influence of a relative malfunction of the nitric oxide system on the vascular tone and vascular structure, and the effects of hypertension on this system, are discussed.     

Infantile hypertrophic pyloric stenosis: a review of 222 cases

The results of 222 cases of hypertrophic pyloric stenosis operated on at the Princess Margaret Hospital for Children in Perth, from 1979 to 1984, have been reviewed. There were no deaths, but there was a 7% incidence of wound infection and a 72% incidence of postoperative vomiting. Staphylococcus Aureus was cultured from 62% of the infected wounds. Prophylaxis against Staphylococcus Aureus infection and delayed introduction of feeding are suggested.     

不同月龄大鼠阴茎组织一氧化氮合成酶活性测定及生理意义

应用离子交换层析法测定正常大鼠小脑、心脏及阴茎海绵体组织中ＮＯＳ活性，同法比较了２、１２和２４月龄大鼠阴茎海绵体组织的ＮＯＳ活性。结果显示：大鼠阴茎海绵体组织中ＮＯＳ活性水平达到小脑组织的７１．４％，是心脏组织的２．２倍，提示ＮＯＳ活性与阴茎勃起有密切关系。老龄大鼠与低月龄大鼠相比，阴茎组织中ＮＯＳ活性明显降低（２月龄对１２月龄，Ｐ＜０．０５；１２月龄，Ｐ＜０．０１），提示ＮＯＳ活性降低可能是阳萎     

Nitric oxide synthase as a marker in colorectal carcinoma.

Elevated inducible nitric oxide synthase (iNOS) activity has been found in 60 per cent of colon adenomas and 20 to 50 per cent of adenocarcinomas. We postulated that high levels of iNOS may increase the invasive and metastatic potential of colon carcinoma and could be indicative of survival potential. Data were reviewed for 52 patients with colorectal carcinoma diagnosed in 1991 and 1992. Specimens were stained for iNOS and catalogued as low-activity staining (LAS) or high-activity staining (HAS) on the basis of visual evaluation by three pathologists. Thirty patients were LAS and 22 HAS. Age, sex, preoperative carcinoembryonic antigen, tumor and nodal status, and American Joint Committee on Cancer staging were not different between groups. Forty-six per cent of the HAS group remained alive after 5 years versus 71 per cent in the LAS group. Survival was significantly lower and metastatic status significantly higher in the HAS group. Results indicated that iNOS activity may be a prognostic indicator of long-term survival potential after treatment for colon cancer. In addition results suggested that metastasis was greater in colon carcinoma specimens that maintain an activated iNOS and that these cells clinically react more aggressively. Conclusions are tempered by the fact that results were based on a limited sample size.     

Nitric oxide synthase inhibition negates bombesin-induced gastroprotection

BACKGROUND: Bombesin prevents gastric injury primarily by the release of endogenous gastrin. Gastroprotection by exogenous gastrin is negated by nitric oxide synthase inhibition, which implicates a role for nitric oxide as a protective mediator. Because both endothelial and inducible isoforms of this enzyme can play a role in mucosal defense, this study was done to examine the contrasting effects of 2 nitric oxide synthase inhibitors on bombesin-induced gastroprotection. METHODS: Rats were given subcutaneous saline or bombesin (10-100 microg/kg) 30 minutes before they received a 1-mL orogastric bolus of acidified ethanol (150 mmol/L of hydrochloric acid/50% ethanol) and rats were killed 5 minutes later for assessment of macroscopic injury (mm(2)). Gastric mucosal blood flow was measured by laser Doppler. Endothelial, neural, and inducible nitric oxide synthase were assessed by using Western immunoblot. RESULTS: Bombesin decreased gastric mucosal damage, and dose-dependently increased blood flow when compared with saline-treated rats. Endothelial but not neural or inducible nitric oxide synthase immunoreactivity was increased by bombesin. In additional studies, intraperitoneal administration of N(G)-nitro-l-arginine methyl ester (l-NAME, 5-10 mg/kg), a nonselective nitric oxide synthase inhibitor, negated bombesin-induced gastroprotection and hyperemia, whereas the selective inducible inhibitor aminoguanidine (45 mg/kg) did not. Subcutaneous (SC) l-arginine (300 mg/kg), but not d-arginine, abolished the effects of l-NAME. CONCLUSIONS: Taken together, these data suggest that nitric oxide produced by the endothelial isoform of nitric oxide synthase plays an important role in mediating the gastroprotective and hyperemic actions associated with bombesin.     

Genomic variants in the coding region of neuronal nitric oxide synthase (NOS1) in infantile hypertrophic pyloric stenosis

Background

Infantile hypertrophic pyloric stenosis (IHPS) is a common childhood pathology affecting 1 to 5:1000 newborns, with a genetic background suggested by familial occurrence. Neuronal nitric oxide synthase (NOS1) is a candidate gene owing to its role in the relaxation of smooth musculature and the association of the −84g>a variant of NOS1 with IHPS.

Methods

We investigated NOS1 through sequencing of the complete NOS1 coding region in DNA from 43 patients with IHPS compared the genotype frequencies to 47 controls using the Cochran-Armitage trend or Fisher exact tests.

Results

We found 19 polymorphisms in the coding region of NOS1. The variants c.3827-42_3827-43 del_insTA and c.+276 c>t were more frequent in IHPS with statistically significant exact P values (P = .010 and P = .039, respectively) yet failed to show significance after Bonferroni adjustment for multiple testing. We have also found a marginally significant occurrence of the variants c.−460A (P = .065) and c.2823+15G (P = .076). There was a significant correlation between the variants c.2706C>T ? c.2823+15A>G, (r² = 1.00) and c.3258 C>T ? c.3235+31A>G (r² = 1.00).

Conclusions

We conclude that NOS1 variants are present in patients with IHPS yet show no significant statistical association with the IHPS phenotype, suggesting at best an adjuvant role for NOS1 in IHPS.     

一氧化氮供体及一氧化氮合酶抑制剂与动脉疾病

自血管内皮衍生舒张因子(endothelium-derived relaxing factor,EDRF)的化学本质被证实是NO以来[1],学者们对NO进行了大量的研究,证实NO在许多疾病的病理生理过程中具有重要功能.在血管系统研究方面,以往主要集中在NO的减少与冠心病、高血压相关的研究以及较新的冠脉PTA术后再狭窄的基因治疗的研究等方面,而对NO在动脉扩张病及周围动脉硬化闭塞症的作用的研究较少.本文仅就NO供体和抑制剂在动脉瘤及周围动脉硬化闭塞症中的作用及应用的研究进展作一综述.     

一氧化氮供体及一氧化氮合酶抑制剂与动脉疾病

自血管内皮衍生舒张因子 (ｅｎｄｏｔｈｅｌｉｕｍ ｄｅｒｉｖｅｄｒｅｌａｘｉｎｇｆａｃｔｏｒ,ＥＤＲＦ)的化学本质被证实是ＮＯ以来[1] ,学者们对ＮＯ进行了大量的研究 ,证实ＮＯ在许多疾病的病理生理过程中具有重要功能。在血管系统研究方面 ,以往主要集中在ＮＯ的减少与冠心病、高血压相关的研究以及较新的冠脉ＰＴＡ术后再狭窄的基因治疗的研究等方面 ,而对ＮＯ在动脉扩张病及周围动脉硬化闭塞症的作用的研究较少。本文仅就ＮＯ供体和抑制剂在动脉瘤及周围动脉硬化闭塞症中的作用及应用的研究进展作一综述。1　ＮＯ生物学简介1.1　Ｎ…     

Nitric oxide synthase is expressed in experimental malignant glioma and influences tumour blood flow

Summary The distribution and function of nitric oxide synthase (NOS) was studied in the rodent C6 implantation glioma model. Using a histochemical stain for NADPH diaphorase, which colocalises with NOS, morphological studies revealed non homogenous staining of the constituent tumour cells and the neoplastic endothelium. Immunocytochemical staining for macrophages (ED1, ED2) showed dense positivity at the tumour brain interface with more patchy positivity within the tumour mass. This finding suggests that both macrophages, which are known to produce large amounts of NO, and the C6 cells contribute to the NADPH diaphorase positivity. Administration of the NOS inhibitor N^g-nitro-L-argine methyl ester (L-NAME) significantly reduced both tumour (40%) and contralateral local cerebral blood flow (20%) compared to control animals. These findings demonstrate that (i) NOS is present in experimental malignant glioma; (ii) NO mediated mechanisms contribute to tumour blood vessel dilatation and blood flow regulation; and (iii) using this model there is a significant differential sensitivity of the tumour and brain parenchymal vascular beds to a NOS inhibitor. Further investigations are required to determine the potential therapeutic and biological relevance of these findings and the relative contributions of tumour cells, neoplastic endothelium and reactive macrophages to NO mechanisms in gliomas.Presented at the 2nd Meeting of the British Neurosurgical Research Group, Newcastle, March 1995     

Nitric oxide synthase is downregulated, while haem oxygenase is increased, in patients with septic shock

Background. The vasodilatation characteristic of human septicshock is conventionally attributed to increased nitric oxideproduction, primarily by extrapolation of animal and human invitro studies. There are no conclusive studies of human disease,and the cellular source of nitric oxide in human sepsis is notknown. Haem oxygenase is upregulated by oxidative stress, butlittle is known about haem oxygenase expression in human sepsis.Haem oxygenase may modulate nitric oxide production, and mayalso have a direct effect on vascular tone. Methods. Mesenteric arterial smooth muscle (ASM) (obtained duringlaparotomy) and peripheral blood mononuclear cells (PBMCs) wereobtained from patients with early septic shock and from controlpatients. mRNA levels were determined by real-time RT-PCR. Results. mRNA for inducible and endothelial nitric oxide synthasewas reduced in both ASM and PBMCs from septic patients. In contrast,inducible haem oxygenase mRNA was increased in sepsis in bothcell types. Conclusions. These results suggest that, rather than being induced,the enzymes which produce nitric oxide are reduced at this timepoint in human septic shock. Thus many of the in vitro modelsof sepsis studied to date may not fully replicate human disease.The increase in haem oxygenase expression confirms that thesecells have been subjected to oxidative stress in sepsis. Theactivity of induced haem oxygenase may limit nitric oxide production,while possibly causing vasodilation through production of carbonmonoxide.     

Nitric oxide synthase gene transfer for erectile dysfunction in a rat model

OBJECTIVE: To determine whether over-expression of nitric oxide synthase (NOS) in the corpus cavernosum of the penis improves erectile function, as NO is an important transmitter for genitourinary tract function, mediating smooth muscle relaxation and being essential for penile erection. MATERIALS AND METHODS: The inducible form of the enzyme NOS (iNOS) was introduced into the corpus cavernosum of adult Sprague-Dawley rats (250-300 g) by injecting a solution of plasmid, adenovirus or adenovirus-transduced myoblast cells (adeno-myoblasts). Plasmid, adenovirus and adeno-myoblasts encoding the expression of the beta-galactosidase reporter gene were also injected into rats. RESULTS: Throughout the corpora cavernosum there was expression of beta-galactosidase after injecting each of the three solutions. Maximum staining was greatest for adeno-myoblast, then adenovirus and then plasmid. The mean (sd) basal intracavernosal pressure (ICP) of iNOS-treated animals (adenovirus and adeno-myoblast) increased to 55 (23) cmH2O, compared with naive animals with a basal ICP of 5 (6) cmH2O (P = 0.001). Stimulating the cavernosal nerve (15 Hz, 1.5 ms, 10-40 V, 1 min) resulted in a doubling of the ICP (adenovirus and adeno-myoblast) from the basal level of the iNOS-treated animals. Direct in situ measurement of NO showed the release of 1-1.3 micro mol/L in the adeno-myoblast penis. CONCLUSION: Myoblast-mediated gene therapy was more successful for delivering iNOS into the corpus cavernosum than direct adenovirus injection or plasmid transfection. Surprisingly, implanting muscle cells into the penis is not only feasible but also beneficial. Gene therapy for NOS may open new avenues of treatment for erectile dysfunction. Control of NOS expression would be necessary to prevent priapism.     

Nitric oxide synthase activity in the human urogenital tract

Nitric oxide (NO) has been suggested as a non-adrenergic non-cholinergic neurotransmitter in the urogenital tract and has previously been shown to have a smooth muscle relaxing effect in the urogenital organs both in various animals and in humans. It has been shown that NO is a mediator of the erection and the dilatation of the bladder neck and urethra. The aim of the study was to analyse nitric oxide synthase (NOS) activity in the human urogenital tract. NOS activity was measured by the conversion of l-[U-¹⁴C] arginine to l-[U-¹⁴C] citrulline. In the upper urinary tract there was Ca²⁺-dependent NOS activity in the renal pelvis, but no significant NOS activity could be found in the ureter. In the lower urinary tract we found high Ca²⁺-dependent NOS activity in the urethra, intermediate activity in the bladder neck and comparatively low activity in the detrusor muscle. In the male genital tract the testis and epididymis had no significant NOS activity. The vas deferens, prostate, seminal vesicle and corpus cavernosum were found to have high levels of Ca²⁺-dependent NOS activity. Ca²⁺-independent NOS activity was not obtained in the urogenital tract. Our results correspond well with previous functional studies indicating NO to be an important nerve-induced mediator of erection and in the micturition reflex, but also suggest that NO may be involved in several other functions in the human urogenital tract.     

Nitric oxide synthase expression after human brain contusion

OBJECTIVE: Nitric oxide is a universal mediator of biological effects in the brain, and it has been implicated in the pathophysiological processes of traumatic brain injury. Experimental studies have indicated posttraumatic up-regulation of the three different isoforms of nitric oxide synthase (NOS) (i.e., inducible NOS [iNOS], endothelial NOS, and neuronal NOS) after brain trauma. This study was undertaken to investigate the cellular sources and tissue compartments of nitric oxide produced by human patients undergoing surgical treatment for contusional brain injuries. METHODS: Contused brain tissue specimens from eight consecutive patients who underwent surgical treatment for brain contusions 3 hours to 5 days after trauma were evaluated in immunohistochemical analyses. Double-staining assays were used to define which cells produced the different isoforms. RESULTS: Increases in iNOS-positive cells were detectable within 6 hours after trauma, with a peak at 8 to 23 hours. Expression of iNOS after trauma was detected in neurons, macrophages, neutrophils, astrocytes, and oligodendrocytes. The cellular sources of iNOS differed at different times after trauma. No detectable difference in the expression of the neuronal or endothelial isoforms was observed for trauma patients, compared with control subjects. CONCLUSION: iNOS expression was up-regulated in a time-dependent manner in human brain tissue obtained from patients undergoing surgical treatment for contusional trauma. Our human data largely parallel experimental findings in rats, indicating that such trauma models are relevant for experimental studies and treatment trials.     

Nitric oxide synthase isoforms during fracture healing.

We have shown previously that nitric oxide (NO) has regulatory effects on fracture healing. Our aim here was to investigate the temporal expression patterns of the three NO synthase (NOS) isoforms that are responsible for the generation of NO by semiquantitative competitive polymerase chain reaction (PCR) and immunoblot analysis after femoral fractures in rats. We found that 4 days after fracture, there were increases in the levels of messenger RNA (mRNA) for all three NOS isoforms, with peaks for the inducible NOS (iNOS; 35-fold increase, p < 0.05) at day 4, the endothelial NOS (eNOS; 5-fold increase, p < 0.05) at day 7, and the neuronal NOS (bNOS; 16-fold increase, p < 0.05) at day 21. At a protein level, the time course expression of NOS isoforms was consistent with the results of those at the mRNA level. In addition, we have previously reported a 2.5-fold increase in NOS activity detected by [3H]arginine to [3H]citrulline conversion at day 15 compared with that at day 4 after fracture. The findings that the expression of NOS isoforms during fracture healing is type specific and time dependent are important and may have clinical applications in the regulation of bone repair by NOS inhibitors or stimulators at different stages after injury.     

Nitric oxide synthase in acute alteration of nitric oxide levels after subarachnoid hemorrhage

OBJECTIVE: Subarachnoid hemorrhage (SAH) is associated with acute decreases and subsequent recovery of cerebral nitric oxide (NO) levels, but the mechanisms of these alterations are not known. In this study, we measured NO synthase (NOS) protein and kinetics to determine its involvement in the alterations of cerebral NO levels after SAH. METHODS: The endovascular rat model of SAH was used. The number of NOS-1 (neuronal) and NOS-2 (inducible)-positive cells (0-96 h) was determined by counting immunoreactive cells in 8-microm cryostat sections. The tissue content of active NOS and its kinetic parameters were studied with an enzymatic l-citrulline assay. RESULTS: The number of NOS-1-positive cells increased between 1 and 3 hours after SAH, decreased to and below control values at 6 and 72 hours after SAH, and increased to control values 96 hours after SAH. The number of NOS-2-positive cells increased 1 hour after SAH, decreased to control values at 24 hours, and increased above control values 96 hours after SAH. The Michaelis-Menten kinetic parameters (V(max), K(m), slope) of NOS remained unchanged at 10 and 90 minutes after SAH. CONCLUSION: NOS-1 and -2 proteins undergo a triphasic alteration after SAH, whereas the amount of active NOS and its kinetic parameters remain unchanged during the first 90 minutes after SAH. Depletion of NOS is not involved in the acute alterations of cerebral NO levels after SAH.     

Nitric oxide synthase isoform expression in a porcine model of granulation tissue formation

BACKGROUND: This study was designed to determine whether the nitric oxide (NO) pathway is involved in wound granulation tissue formation. METHODS: A section of the pig abdominal wall (excluding the skin) was excised, creating an incisional hernia. The resulting defect was repaired with silicone sheeting in a manner that mimics a temporary abdominal wall closure. During the 14-day experimental period, porcine omentum adhered to the peritoneal edges of the defect and a highly vascularized granulation tissue formed on both sides of the sheeting. Granulation tissue thickness and wound fluid volume were monitored by ultrasonography and epigastric artery flow velocity was monitored by color Doppler flow analysis at days 2, 4, 7, 9, 11, and 14. Fluid was serially harvested from the wound compartment at days 2, 4, 7, 9, 11, and 14 for nitrite/ nitrate (NOx) analysis. Finally, granulation tissue was harvested at day 14 for immunohistochemical and molecular analyses. RESULTS: There was a significant increase in granulation tissue thickness and wound fluid volume during the 14-day study period. Blood flow to the wound increased significantly by day 4 and returned toward baseline by day 14. Wound fluid NOx levels significantly increased from days 7 to 11 and then decreased to near baseline values by day 14. Wound fluid arginine levels significantly decreased when compared with peritoneal fluid and plasma levels at day 14, while wound fluid ornithine levels significantly increased. Immunohistochemical analysis of granulation tissue at day 14 revealed nitric oxide synthase (NOS) 2 was present in the majority of the cells in the granulation tissue. NOS 3 was expressed in endothelial cells only, and NOS 1 expression was not observed in the granulation tissue. CONCLUSIONS: This study suggests that NO, NOS 2, and arginine may play critical roles in granulation tissue formation and wound healing. Arginase and NOS 2 may compete for available arginine as a substrate, thereby limiting later NO production in favor of sustained ornithine synthesis.