Immunolocalization of inducible nitric oxide synthase in synovium and cartilage in rheumatoid arthritis and osteoarthritis

Nitric oxide has been implicated as a mediator of inflammatory arthritis, and recent work has shown that pro-inflammatory cytokines stimulate NO production in vitro by activation of the inducible nitric oxide synthase (iNOS) pathway. In order to identify the cellular sources of NO production within the joint, we have used immunohistochemical techniques to study the distribution of iNOS in synovium and cartilage from normal and diseased joints. iNOS was most strongly expressed in the synovial lining layer, subsynovium, vascular smooth muscle and chondrocytes from patients with rheumatoid arthritis (RA). Analysis of serial sections, coupled with double immunofluorescent staining, showed that the CD68+ macrophages in the synovial lining layer and, to a lesser extent, fibroblasts were the predominant source of iNOS within synovium, whereas T cells, B cells and neutrophils were negative. A similar pattern of iNOS staining was seen in osteoarthritis, but fewer cells were iNOS positive and the intensity of staining, particularly in cartilage, was much weaker than in RA. In contrast, no evidence of iNOS was detected in non- inflammatory synovium or in cartilage derived from normal joints (fractured neck of femur). In conclusion, these data support the hypothesis that synovium and cartilage are important sources of increased NO production in patients with inflammatory arthritis. Localization of iNOS at these sites within the inflamed joint raises the possibility that increased local production of NO may contribute to the pathogenesis of inflammatory arthritis by increasing synovial blood flow and by modulating cellular function within synovium and articular cartilage.      

Expression of microsomal prostaglandin E synthase 1 in rheumatoid arthritis synovium

OBJECTIVE: Microsomal prostaglandin E synthase 1 (mPGES-1) catalyzes the formation of PGE(2) from cyclooxygenase-derived PGH(2). Microsomal PGES-1 is induced by proinflammatory cytokines and is strongly linked to conditions that result in high PGE(2) biosynthesis. PGE(2) contributes to the pathogenesis of rheumatoid arthritis (RA), acting as a mediator of inflammation and promoting bone destruction. Induction of mPGES-1 in rheumatoid synoviocytes by proinflammatory cytokines has been demonstrated in vitro, indicating an important role in RA pathogenesis. Recent studies using mPGES-1-deficient mice demonstrated the importance of this gene in chronic inflammation. The aim of this study was to investigate the expression and localization of mPGES-1 in synovial biopsy specimens obtained from patients with RA. METHODS: Synovial tissue samples from 24 patients with RA were obtained, and immunohistologic analysis was performed using polyclonal antibodies against mPGES-1. Double immunofluorescence staining was performed with antibodies to CD3, CD19, CD20, CD68, CD163, and prolyl 4-hydroxylase. RESULTS: Intracellular mPGES-1 staining was observed in synovial membranes from all of the RA patients studied. Specifically, strong expression of mPGES-1 was detected in synovial lining cells. In sublining mononuclear and fibroblast-like cells, the extent of mPGES-1 staining was less than that in the synovial lining cells. In some patients, positive staining was observed in endothelial cells. With the double immunofluorescence technique, mPGES-1 production was detected in synovial macrophages and fibroblasts, while mPGES-1 expression was not observed in lymphocytes. CONCLUSION: The demonstration of mPGES-1 expression in synovial tissues from patients with RA suggests a role for mPGES-1 in the RA disease process. Microsomal PGES-1 might be a potential new target for treatment strategies to control PGE(2) synthesis in patients with RA, without the systemic side effects associated with cyclooxygenase inhibitors.     

Expression and regulation of endothelial nitric oxide synthase

Endothelium-derived nitric oxide (NO) is a key determinant of blood pressure homeostasis and platelet aggregation and is synthesized by the endothelial isoform of nitric oxide synthase (eNOS). In the vascular wall, eNOS is activated by diverse cell-surface receptors and by increases in blood flow, and the consequent generation of NO leads to vascular smooth-muscle relaxation. Endothelium-dependent vasorelaxation is deranged in a variety of disease states, including hypertension, diabetes, and atherosclerosis, but the roles of eNOS in endothelial dysfunction remain to be clearly defined. The past several years have witnessed important advances in understanding the molecular and cellular biology of eNOS regulation. In endothelial cells, eNOS undergoes a complex series of covalent modifications, including myristoylation, palmitoylation, and phosphorylation. Palmitoylation of eNOS dynamically targets the enzyme to distinct domains of the endothelial plasma membrane termed caveolae; caveolae may serve as sites for the sequestration of signal-transducing proteins and are themselves subject to dynamic regulation by ligands and lipids. Originally thought to be expressed only in endothelial cells, eNOS is now known to be expressed in a variety of tissues, including blood platelets, cardiac myocytes, and brain hippocampus. Paradigms established in endothelial cells for the molecular regulation and subcellular targeting of eNOS are being extended to the investigation of eNOS expressed in nonendothelial tissues. This review summarizes recent advances in understanding the molecular regulation of eNOS and the other NOS isoforms and identifies important parallels between eNOS and other cell-signaling molecules. ? 1997, Elsevier Science Inc. (Trends Cardiovasc Med 1997;7:28-37).     

Expression of inducible and endothelial nitric oxide synthases in pouchitis

To study the induction of nitric oxide synthase (NOS) in different forms of pouchitis, we divided patients in five groups: 1) ulcerative colitis, no pouch; 2) no-pouchitis; 3) chronic asymptomatic pouchitis; 4) chronic active pouchitis; and 5) acute pouchitis. Ileal biopsies were scored for NOS-2 (inducible) and NOS-3 (endothelial) immunoreactivity and acute inflammation. In group 1, most specimens lacked NOS-2 immunoreactivity. In group 2, some specimens showed NOS-2 immunoreactive epithelium. In group 3, areas of NOS-2-immunoreactive epithelium were consistently observed in most specimens. In groups 4 and 5, most specimens showed moderate-to-extensive epithelial NOS-2 staining. NOS-2 immunoreactivity scores of groups 1-5 were 0.25 +/- 0.16, 0.67 +/- 0.19, 1.19 +/- 0.40, 2.0 +/- 0.23, and 2.18 +/- 0.12, respectively. Corresponding acute inflammation scores were 0, 0.53 + 0.17, 1.00 +/- 0.33, 1.80 +/- 0.20, and 1.64 +/- 0.15. NOS-2 score correlated with acute inflammation score (p < 0.0001), indicating that NOS-2 induction correlates with both the clinical degree of pouchitis and the severity of acute inflammation. NOS-3 immunoreactivity increased in all pouchitis groups.     

Expression of inducible nitric oxide synthase in human gastric cancer

INTRODUCTIONInduciblenitricoxidesynthase(iNOS)isanenzymethatcatalyzestheformationofnitric0xide(N0)fromL-arginine.iNOSexpressionandactivityresultsintheproduction0fhighlevelsofNO[1].ThegenerationofphysiologicallevelsofNOisimp0rtantformucosalfunctionanditalsoexertsacytoprotectiveeffectonthegastr0intestinalmucosa.However,increasediNOSexpressionhasbeenobservedinpatientswithchronicinflammatorydiseasesofthegastr0intestinaltract,suchasulcerativec0litis[2'3],andgastritis['Jandithasbeenspecul…     

Localization of inducible nitric oxide synthase and endothelial constitutive nitric oxide synthase in airway mucosa of toluene diisocyanate-induced asthma.

Endogenous exhaled nitric oxide (NO) is increased in asthma patients, especially in the exacerbated state. To evaluate the role of NO in airway mucosa of toluene diisocyanate (TDI)-induced asthma in relation to clinical and immunologic findings, 20 TDI-induced asthma patients were enrolled and classified into two groups: 9 newly diagnosed patients (group I) and 11 patients having persistent asthma symptoms for > 5 years despite work withdrawal (group II). Immunohistocytochemistry was applied to compare the expression of endothelial constitutive NOS (c-NOS) and induced NOS (i-NOS) in airway mucosa of both groups. They were observed in four areas: epithelium (EP), smooth muscle (SM), vascular endothelium (VE), and mucous gland (MG). The intensity of expression was graded on a scale of one to four and mean values were presented from blind readings observed by two experts. Serum-specific immunoglobulin E (IgE) and immunoglobulin G (IgG) antibodies to TDI-human serum albumin conjugate were measured by enzyme-linked immunosorbent assay. e-NOS was found most frequently in VE (5/6 [83.3] versus 7/10 [70%]) followed by MG, EP, and SM in both groups, i-NOS was found most frequently in EP (7/9 [77.8%] versus 7/11 [63.6%]), followed by MG, VE, and SM in both groups. The intensities of i-NOS and c-NOS of MG were significantly higher in group I than in group II (p < 0.05) with no significant differences in other areas (p > 0.05, respectively). There were no significant correlations between i-NOS or c-NOS expression and exposure or asthma symptom duration (p > 0.05). No associations were found between i-NOS or c-NOS expression and the presence of specific IgE or IgG to TDI-human serum albumin conjugate (p > 0.05, respectively). In conclusion, i-NOS and c-NOS expressions were noted in EP, SM, VE, and MG in airway mucosa of TDI-induced asthma patients, which may contribute to airway inflammation.     

Development of lyme arthritis in mice deficient in inducible nitric oxide synthase

Nitric oxide (NO) is a powerful antimicrobial agent and an important regulatory molecule of the innate immune response. To determine if NO has a role in experimental Lyme disease, arthritis-resistant DBA/2J and arthritis-susceptible C3H/HeJ mice were bred to be genetically deficient for inducible NO synthase (iNOS). Following footpad injection of Borrelia burgdorferi, arthritis was similar between iNOS-deficient and control animals regardless of their genetic background. Histologic examination and arthritis severity scores of ankles revealed no differences in arthritis development between iNOS-deficient and control animals. Despite being deficient in a key antimicrobial agent, iNOS-deficient mice had tissue levels of B. burgdorferi similar to those in control mice. Thus, NO does not have a critical role in susceptibility to Lyme arthritis through tissue damage via an overexuberant inflammatory response, nor is it required in resistance through the clearance of spirochetes from tissues.     

The functional variants of endothelial nitric oxide synthase gene associated with rheumatoid arthritis in Turkish adults

This study aimed to investigate whether functional variants of endothelial nitric oxide synthase (eNOS) gene play any role in rheumatoid arthritis (RA) ethiopathogenesis and treatment in the Turkish population. Because, eNOS variants are responsible for alteration of the NO level in plasma, by reducing/increasing the endothelial NO synthesis. In the study, two eNOS gene variants (G894T and intron 4 VNTR A/B) were examined at extracted DNAs from 65 peripheral blood cell of RA patients. For the control, blood samples obtained from 70 healthy persons were studied. Genotyping of molecular variants was performed by PCR-RFLP and/or PCR technique. The data obtained was compared in itself and response to therapy. We found that “TT genotypic frequency” for the G894T variant was significantly associated with RA with an overall risk of 8.3-fold (p 0.029). No association was identified between intron 4 VNTR A/B variant and RA. At the 6 months, the mean visual analog scale (VAS), health assessment questionnaire (HAQ), and disease activity score for 28 joints (DAS 28) improvement was not significant among groups. Improvement in DAS was significantly better in anti-TNF treatment than disease-modifying antirheumatic drugs (DMARD) treatment treated subgroup. We report for the first time that variants in the eNOS “TT” genotype might be contributed to the increased risk of RA in the Turkish population. These results imply that functional variants of eNOS gene might have an effect on RA patients and response to anti-TNF treatment. In addition, the results suggest that eNOS variants might be associated and affect host susceptibility and/or response to treatment in Turkish RA patients.     

Luminal nitric oxide and epithelial expression of inducible and endothelial nitric oxide synthase in collagenous and lymphocytic colitis

BACKGROUND: Colonic nitric oxide (NO) production in collagenous colitis (CC) has been studied in a small number of patients and found increased. The cellular source of NO is believed to be the colonic epithelial cells. The aim of this study was to investigate colonic NO levels in patients with CC and lymphocytic colitis (LC), to compare with the histopathological status and with the clinical activity, and to assess the epithelial expression of inducible and endothelial nitric oxide synthase (iNOS and eNOS). METHODS: We included 19 patients with CC, 8 patients with LC and 15 controls. During colonoscopy, luminal gas was sampled and NO levels were measured using the chemiluminescence technique. Mucosal biopsies were obtained for routine histopathologic examination and immunohistochemical studies of iNOS and eNOS. Clinical activity, as measured by the mean frequency of daily bowel movements during the week prior to colonoscopy, was assessed. RESULTS: Luminal NO levels, median (25-75 percentiles), in the patients with CC and LC were greatly increased compared to the controls, 1673 (145-8143) parts per billion (ppb) and 1838 (1065-2694) ppb versus 28 (20-46) ppb (P < 0.005, both). A positive association was seen between NO levels and histopathological status as well as clinical activity. Strong expression of iNOS was seen in the surface epithelium in 5 of 6 patients with CC and in 2 of 5 patients with LC. CONCLUSIONS: The fact that luminal NO levels are related to histopathological status and correlate with clinical activity indicates that NO is involved in the pathophysiology of CC and LC. The epithelial cells are the most likely source of luminal NO.     

Discrepant effects of inducible nitric oxide synthase modulation on systemic and splanchnic endothelial nitric oxide synthase activity and expression in cirrhotic rats

BACKGROUND: Arterial vasodilatation, which is a major factor in the pathogenesis of the hyperkinetic circulatory state and portal hypertension in cirrhosis, is due to arterial nitric oxide (NO) overproduction secondary to endothelial NO synthase (eNOS) and inducible NOS (iNOS) upregulation. However, in cirrhosis, the respective roles of eNOS and iNOS isoforms in NO overproduction are still unknown and the effect of iNOS modulation on eNOS activity and expression has not been evaluated in the systemic or splanchnic vessels. The aim of this study was to evaluate the effects of modulating aortic and superior mesenteric arteries (SMA) iNOS on arterial eNOS activity and expression in rats with cirrhosis. METHODS: eNOS and iNOS protein expression and eNOS activity (assessed by its phosphorylation at serine 1177) were measured in the aortas and SMA in untreated and treated cirrhotic rats with lipopolysaccharide (LPS), N-iminoethyl-L-lysine (L-NIL), a selective iNOS inhibitor, and LPS plus L-NIL. RESULTS: LPS administration significantly increased eNOS and iNOS protein expression and eNOS activity in the aortas of both sham-operated and cirrhotic rats. However, in SMA, LPS administration induced a decrease in eNOS protein expression and activity and an increase in iNOS protein expression. CONCLUSION: The results of this study may explain the worsening of the hyperdynamic state in cirrhosis during septic shock by direct LPS-induced eNOS activation in large systemic vessels, and its inhibition in concomitant small splanchnic vasculature by iNOS synthesized NO.     

Expression and function of recombinant endothelial nitric oxide synthase in human endothelial cells

Endothelial dysfunction is frequently involved in the pathogenesis of vascular disease. While nitric oxide (NO) inhibits smooth muscle cell proliferation, its effect on endothelial cell proliferation is unclear. The aim of this study was to determine if adenoviral-mediated gene transfer of endothelial NO synthase (eNOS) to human umbilical vein endothelial cells (HUVECs) would result in increased generation of NO and affect endothelial cell proliferation. HUVECs were transduced with adenoviral vectors encoding eNOS (AdeNOS) or beta-galactosidase (Ad beta gal) or exposed to diluent (control). AdeNOS-transduced cells showed increased eNOS expression as detected by Western blot analysis, and increased concentrations of cGMP (control 0.7 +/- 0.1; Ad beta gal 0.9 +/- 0.2; AdeNOS 3.1 +/- 0.5 pmol/mg protein; p < 0.001) and nitrite (control 11.8 +/- 1.2; Ad beta gal 13.3 +/- 1.7; AdeNOS 21.1 +/- 2.2 nmol/mg protein/hour; p < 0.01). DNA synthesis as assessed by [(3)H]thymidine incorporation and cell counts were significantly reduced (by approximately 30%) in AdeNOS-transduced HUVECs. Expression of mitogen-activated protein kinase was also decreased in AdeNOS-transduced cells. This study shows that adenoviral-mediated gene transfer of eNOS to HUVECs inhibits endothelial cell proliferation.     

Expression of inducible nitric oxide synthase in human coronary atherosclerotic plaque.

OBJECTIVE: Macrophages in atherosclerotic plaque may express the inducible isoform of NO synthase (iNOS), which produces large amounts of NO. On one hand, the production of NO can be protective by its vasodilatory, antiaggregant and antiproliferative effects. On the other hand, the formation of peroxynitrite from NO may favour vasospasm and thrombogenesis. In this study, we investigated whether iNOS is present in human coronary atherosclerotic plaque, and we correlated these data with the clinical instability of the patients. METHODS: Fragments were retrieved by coronary atherectomy from 24 patients with unstable angina and 12 patients with stable angina. The presence of macrophages, and the production of TNF alpha, iNOS and nitrotyrosine were detected by immunocytochemistry. RESULTS: Macrophage clusters were found in 67% of stable patients and 87% of patients with unstable angina (NS). TNF alpha was expressed in about 50% of cases in both groups. iNOS was not expressed in fragments from stable patients but was found in macrophages from 58% of unstable patients (P < 0.001). The expression of iNOS was associated with the presence of nitrotyrosine residues, a marker of peroxynitrite formation. Expression of iNOS was correlated both with complaints of angina at rest (P < 0.05) and with the presence of thrombus at morphological examination (P < 0.001). CONCLUSION: The expression of iNOS may be induced in human coronary atherosclerotic plaque and is associated with different factors of instability.     

Role of neuronal nitric oxide synthase and inducible nitric oxide synthase in intestinal injury in neonatal rats

AIM: To investigate the dynamic change and role of neuronal nitric oxide synthase (nNOS) and inducible nitric oxide synthase (iNOS) in neonatal rat with intestinal injury and to define whether necrotizing enterocolitis (NEC) is associated with the levels of nitric oxide synthase (NOS) in the mucosa of the affected intestine tissue. METHODS: Wistar rats less than 24 h in age received an intraperitoneal injection with 5 mg/kg lipopolysaccharide (IPS). Ileum tissues were collected at 1, 3, 6, 12 and 24 h following LPS challenge for histological evaluation of NEC and for measurements of nNOS and iNOS. The correlation between the degree of intestinal injury and levels of NOS was determined. RESULTS: The LPS-injected pups showed a significant increase in injury scores versus the control. The expression of nNOS protein and mRNA was diminished after LPS injection. There was a negative significant correlation between the nNOS protein and the grade of median intestinal injury within 24 h. The expression of iNOS protein and mRNA was significantly increased in the peak of intestinal injury. CONCLUSION: nNOS and iNOS play different roles in LPS-induced intestinal injury. Caution should be exerted concerning potential therapeutic uses of NOS inhibitors in NEC.     

Inducible but not endothelial nitric oxide synthase polymorphism is associated with susceptibility to rheumatoid arthritis in northwest Spain

OBJECTIVE: To assess the influence of inducible and endothelial nitric oxide synthase (iNOS and eNOS) polymorphisms in susceptibility to rheumatoid arthritis (RA). METHODS: Two hundred RA patients fulfilling the 1987 American College of Rheumatology classification criteria followed at the out-patient rheumatology clinic of the Hospital Xeral-Calde (Lugo, Spain) and 251 ethnically matched controls were studied. Patients and controls were genotyped by PCR-based techniques for a multiallelic (CCTTT)(n) repeat in the promoter region of the iNOS gene and for a T/C polymorphism at position -786 in the promoter region and a polymorphism in exon 7 (298Glu/Asp or 5557G/T) of the eNOS gene. RESULTS: No significant difference in allele or genotype frequencies for either polymorphism in the eNOS gene was observed between RA patients and controls. The overall iNOS CCTTT(n) allelic or genotypic distribution did not show statistical significant differences between RA patients and controls. Interestingly, when we stratified the iNOS alleles into short (8-11) and long (12-16) repeats, significant differences were observed between RA patients and controls (P = 0.021; odds ratio = 1.37, 95% confidence interval 1.04-1.81). Of note, individuals carrying two alleles with a repeat number less than 12 (fewer than 196 base pairs) exhibited a double risk of developing RA (P = 0.005, odds ratio 2.26, 95% confidence interval 1.25-4.08). CONCLUSIONS: Significant differences in the iNOS promoter polymorphism genotype frequency between northwest Spanish RA patients and controls suggest a potential role for this polymorphism in susceptibility to RA.