Specificity of antibodies to nitric oxide synthase isoforms in human, guinea pig, rat, and mouse tissues

Expression of nitric oxide synthase (NOS) in Anabas testudineus ovary and participation of nitric oxide-cyclic GMP cascade in maintenance of meiotic arrest

Participation of cyclic nucleotide-mediated signaling in nitric oxide/soluble guanylate cyclase (NO/sGC) regulation of oocyte maturation (OM) in perch (Anabas testudineus) follicle-enclosed oocytes has been investigated. Congruent with sharp decline in follicular cyclic GMP (cGMP) level, nitric oxide synthase (NOS)-inhibitor (L-NAME) attenuates protein kinase A (PKA) phosphorylation but promotes p-ERK1/2 and p-p34Cdc2 (Thr-161) in maturing oocytes. Conversely, NO donor (SNP) prevents OM, potentially through elevated cGMP synthesis. Expression and localization of Nos2 and Nos3 immunoreactivity in perch ovary varied considerably at progressively higher stages of folliculogenesis. While sGC inhibitor (ODQ) alone could induce OM, 8-bromo-cGMP attenuates 17,20β-P-induced OM indicating functional significance of NO/sGC/cGMP in perch ovary. Interestingly, high NO/cGMP inhibition of OM shows positive relation with elevated cAMP level. MIS induced OM is more susceptible to the oocyte-specific phosphodiesterase (PDE) 3 than PDE4 inhibition. Collectively, high NO/cGMP attenuation of OM potentially involves PDE3 inhibition, cAMP accumulation and PKA activation.

A Comparison of the Chicken and Turkey Proteomes and Phosphoproteomes in the Development of Poultry-Specific Immuno-Metabolism Kinome Peptide Arrays

The use of species-specific peptide arrays for the study of animal kinomes has a proven track record of success. This technique has been used in a variety of species for the study of host–pathogen interactions and metabolism. Species-specific peptide arrays have been designed previously for use with chicken but a turkey array has never been attempted. In addition, arrays designed around individual cellular functions have been designed and utilized, but cross-function immuno-metabolic arrays have not been considered previously. Antecedent to designing separate chicken and turkey immuno-metabolic kinome peptide arrays, we show that while the chicken and turkey genomes are quite similar, the two species are much more distinct at the proteome and phosphoproteome levels. Despite a genome identity of approximately 90%, we observe that only 83% of chicken and turkey orthologous proteins display sequence matches between the two species. Further, less than 70% of kinase recognition target sequences are exact matches between chicken and turkey. Thus, our analysis shows that, at the proteome and kinome level, these two species must be considered separately in the design of novel peptide arrays. Our ultimate array design covers numerous immune and metabolic processes including innate and adaptive immunity, inflammatory responses, carbohydrate, protein, and fat metabolism, and response to hormones. We have shown the proteomic and phosphoproteomic diversity of chicken and turkey and have designed a valuable research tool for the study of immuno-metabolism within these two species.

Neuronal NOS localises to human airway cilia

BACKGROUND

Airway NO synthase (NOS) isoenzymes are responsible for rapid and localised nitric oxide (NO) production and are expressed in airway epithelium. We sought to determine the localisation of neuronal NOS (nNOS) in airway epithelium due to the paucity of evidence.

METHODS AND RESULTS

Sections of healthy human bronchial tissue in glycol methacrylate resin and human nasal polyps in paraffin wax were immunohistochemically labelled and reproducibly demonstrated nNOS immunoreactivity, particularly at the proximal portion of cilia; this immunoreactivity was blocked by a specific nNOS peptide fragment. Healthy human epithelial cells differentiated at an air-liquid interface (ALI) confirmed the presence of all three NOS isoenzymes by immunofluorescence labelling. Only nNOS immunoreactivity was specific to the ciliary axonemeand co-localised with the cilia marker β-tubulin in the proximal part of the ciliary axoneme.

CONCLUSIONS

We report a novel localisation of nNOS at the proximal portion of cilia in airway epithelium and conclude that its independent and local regulation of NO levels is crucial for normal cilia function.

Modulation of the oscillatory mechanics of lung tissue and the oxidative stress response induced by arginase inhibition in a chronic allergic inflammation model

Background

The importance of the lung parenchyma in the pathophysiology of asthma has previously been demonstrated. Considering that nitric oxide synthases (NOS) and arginases compete for the same substrate, it is worthwhile to elucidate the effects of complex NOS-arginase dysfunction in the pathophysiology of asthma, particularly, related to distal lung tissue. We evaluated the effects of arginase and iNOS inhibition on distal lung mechanics and oxidative stress pathway activation in a model of chronic pulmonary allergic inflammation in guinea pigs.

Methods

Guinea pigs were exposed to repeated ovalbumin inhalations (twice a week for 4 weeks). The animals received 1400 W (an iNOS-specific inhibitor) for 4 days beginning at the last inhalation. Afterwards, the animals were anesthetized and exsanguinated; then, a slice of the distal lung was evaluated by oscillatory mechanics, and an arginase inhibitor (nor-NOHA) or vehicle was infused in a Krebs solution bath. Tissue resistance (Rt) and elastance (Et) were assessed before and after ovalbumin challenge (0.1%), and lung strips were submitted to histopathological studies.

Results

Ovalbumin-exposed animals presented an increase in the maximal Rt and Et responses after antigen challenge (p<0.001), in the number of iNOS positive cells (p<0.001) and in the expression of arginase 2, 8-isoprostane and NF-kB (p<0.001) in distal lung tissue. The 1400 W administration reduced all these responses (p<0.001) in alveolar septa. Ovalbumin-exposed animals that received nor-NOHA had a reduction of Rt, Et after antigen challenge, iNOS positive cells and 8-isoprostane and NF-kB (p<0.001) in lung tissue. The activity of arginase 2 was reduced only in the groups treated with nor-NOHA (p <0.05). There was a reduction of 8-isoprostane expression in OVA-NOR-W compared to OVA-NOR (p<0.001).

Conclusions

In this experimental model, increased arginase content and iNOS-positive cells were associated with the constriction of distal lung parenchyma. This functional alteration may be due to a high expression of 8-isoprostane, which had a procontractile effect. The mechanism involved in this response is likely related to the modulation of NF-kB expression, which contributed to the activation of the arginase and iNOS pathways. The association of both inhibitors potentiated the reduction of 8-isoprostane expression in this animal model.

Dipterinyl calcium pentahydrate inhibits intracellular mycobacterial growth in human monocytes via the C-C chemokine MIP-1β and nitric oxide

Tuberculosis remains one of the top three leading causes of morbidity and mortality worldwide, complicated by the emergence of drug-resistant Mycobacterium tuberculosis strains and high rates of HIV coinfection. It is important to develop new antimycobacterial drugs and immunomodulatory therapeutics and compounds that enhance antituberculous immunity. Dipterinyl calcium pentahydrate (DCP), a calcium-complexed pterin compound, has previously been shown to inhibit human breast cancer cells and hepatitis B virus (HBV). DCP inhibitory effects were attributed to induction of apoptosis and/or increased production of interleukin 12 (IL-12) and granulocyte-macrophage colony-stimulating factor (GM-CSF). In this study, we tested the ability of DCP to mediate inhibition of intracellular mycobacteria within human monocytes. DCP treatment of infected monocytes resulted in a significant reduction in viability of intracellular but not extracellular Mycobacterium bovis BCG. The antimicrobial activity of DCP was comparable to that of pyrazinamide (PZA), one of the first-line antituberculosis drugs currently used. DCP potentiated monocyte antimycobacterial activity by induction of the cysteine-cysteine (C-C) chemokine macrophage inflammatory protein 1β (MIP-1β) and inducible nitric oxide synthase 2. Addition of human anti-MIP-1β neutralizing antibody or a specific inhibitor of the l-arginase-nitric oxide pathway (N(G)-monomethyl l-arginine [l-NMMA] monoacetate) reversed the inhibitory effects of DCP on intracellular mycobacterial growth. These findings indicate that DCP induced mycobacterial killing via MIP-1β- and nitric oxide-dependent effects. Hence, DCP acts as an immunoregulatory compound enhancing the antimycobacterial activity of human monocytes.

Endothelial nitric oxide synthase is not essential for nitric oxide production by osteoblasts subjected to fluid shear stress in vitro

Endothelial nitric oxide synthase (eNOS) has long been held responsible for NO production by mechanically stimulated osteoblasts, but this has recently been disputed. We investigated whether one of the three known NOS isoforms is essential for NO production by mechanically stimulated osteoblasts in vitro and revisited the bone phenotype of the eNOS-/- mouse. Osteoblasts, obtained as outgrowths from mouse calvaria or long bones of wild-type (WT), eNOS-/-, inducible NOS-/- (iNOS-/-), or neuronal NOS-/- (nNOS-/-) mice, were subjected to mechanical stimulation by means of pulsating fluid flow (PFF); and NO production was determined. Tibiae and femora from 8-week-old mice were subjected to μCT and three-point bending tests. Deletion of single NOS isoforms did not lead to significant upregulation of alternate isoforms in cultured osteoblasts from WT, eNOS-/-, iNOS-/-, or nNOS-/- mice. Expression of eNOS mRNA in osteoblasts was below our detection limit, and no differences in growth between WT and eNOS-/- osteoblasts were found. PFF increased NO production by approximately fourfold in WT and eNOS-/- osteoblasts and significantly stimulated NO production in iNOS-/- and nNOS-/- osteoblasts. Tibiae and femora from WT and eNOS-/- mice showed no difference in bone volume and architecture or in mechanical parameters. Our data suggest that mechanical stimuli can enhance NO production by cultured osteoblasts singly deficient for each known NOS isoform and that lack of eNOS does not significantly affect bone mass and strength at 8 weeks of age. Our data challenge the notion that eNOS is a key effector of mechanically induced bone maintenance.

Involvement of NOS3 in RA-Induced neural differentiation of human NT2/D1 cells

Nitric oxide (NO) plays a key role in neurogenesis as a regulator of cell proliferation and differentiation. NO is synthesized from the amino acid L-arginine by nitric oxide synthases (NOS1, NOS2, and NOS3), which are encoded by separate genes and display different tissue distributions. We used an in vitro model of RA-induced neural differentiation of NT2 cells to examine which of the three NO-synthesizing enzymes is involved in this process. The results revealed a transient induction of NOS3 (known as the constitutively expressed endothelial nitric oxide synthase; eNOS) during the time course of the RA treatment. The peak of gene expression and the nuclear presence of NOS3 protein coincided with cell cycle exit of NT2-derived neuronal precursors. The subsequent analysis of cytosine methylation and histone H3 acetylation of the human NOS3 5' regulatory sequences indicated that epigenetic modifications, especially upstream of the proximal promoter (-734 to -989, relative to exon 2 TSS at +1), were also taking place. NOS1 was expressed only in the differentiated neurons (NT2-N), whereas NOS2 was not expressed at all in this cellular model. Thus, a burst of NO production, possibly required to inhibit neural cell proliferation, was generated by the transient expression of NOS3. This pattern of gene expression, in turn, required epigenetic remodeling of its regulatory region.

Immunolocalization of nitric oxide synthase isoforms in human archival and rat tissues, and cultured cells

Nitric oxide (NO) exerts important physiological and pathological roles in humans. The study of NO requires the immunolocalization of its synthesizing enzymes, neuronal, endothelial and inducible NO synthases (NOS). NOS are labile to formalin-fixation and paraffin-embedding, which are used to prepare human archival tissues. This lability has made NOS immunohistochemical studies difficult, and a detailed protocol is not yet available. We describe here a protocol for the immunolocalization of NOS isoforms in human archival cerebellum and non-nervous tissues, and in rat tissues and cultured cells. Neuronal NOS antigenicity in human archival and rat nervous tissue sections was microwave-retrieved in 50 mM Tris-HCl buffer, pH 9.5, for 20 min at 900 W. Neuronal NOS was expressed in stellate, basket, Purkinje and granule cells in human and rat cerebellum. Archival and frozen human cerebellar sections showed the same neuronal NOS staining pattern. Archival cerebellar sections not subjected to antigen retrieval stained weakly. Antigenicity of inducible NOS in human lung was best retrieved in 10 mM sodium citrate buffer, pH 6.0, for 15 min at 900 W. Inflammatory cells in a human lung tuberculoma were strongly stained by anti-inducible NOS antibody. Anti-endothelial NOS strongly stained kidney glomeruli. Cultured PC12 cells were strongly stained by anti-neuronal NOS without antigen retrieving. The present immunohistochemistry protocol is easy to perform, timeless, and suitable for the localization of NOS isoforms in nervous and non-nervous tissues, in human archival and rat tissues. It has been extensively used in our laboratory, and is also appropriate for other antigens.

Postnatal development of the serotonin signaling system in the mucosa of the guinea pig ileum

BACKGROUND

Serotonin is an important neurohumoral molecule in the gut but its signaling system is not fully developed in the neonatal gastrointestinal (GI) tract. This study aimed to evaluate the postnatal maturation of serotonin signaling in the small intestine.

METHODS

In vitro amperometry for real-time measurement of serotonin at the mucosal surface, immunoblot, immunohistochemistry and high-performance liquid chromatography (HPLC) were used to examine serotonin handling in ileal segments from guinea pigs of different ages.

KEY RESULTS

Extracellular serotonin levels significantly declined over the first three postnatal weeks, after which the levels increased and reached their maximum at 9 weeks postnatally. Serotonin levels were insensitive to the inhibition of the serotonin transporter (SERT) until the animals reached 3 weeks old. Measurement of serotonin and its metabolite 5-hydroxyindole acetic acid (5-HIAA) in the mucosa revealed that the serotonin turnover was significantly lower in neonates. Immunoblot and immunohistochemistry showed that SERT expression was extremely low in the neonatal period. Serotonin staining in cross-section showed that enterochromaffin (EC) cells were preferentially localized in the crypt region in neonates and the number of EC cells was significantly higher in 9-week-old animals.

CONCLUSIONS & INFERENCES

SERT expression is low in the neonatal intestine and serotonin signaling matures postnatally. Extracellular serotonin levels decrease during the first three neonatal weeks as SERT expression increases. Extracellular serotonin levels increase after 3 weeks (weaning) possibly due to an increase in EC cell numbers. Postnatal maturation of serotonin signaling coincides with dietary changes in the developing guinea pig.

Inhibitory neuromuscular transmission to ileal longitudinal muscle predominates in neonatal guinea pigs

BACKGROUND

Inhibitory neurotransmission to the longitudinal muscle is more prominent in the neonatal than in the adult guinea pig ileum.

METHODS

Inhibitory neuromuscular transmission was investigated using in vitro ileal longitudinal muscle myenteric plexus (LMMP) preparations made from neonatal (< or =48 h postnatal) and adult ( approximately 4 weeks postnatal) guinea pigs.

KEY RESULTS

Amperometric measurements of nicotine-induced nitric oxide (NO) release (measured as an oxidation current) from myenteric ganglia revealed larger currents in neonatal (379 +/- 24 pA) vs adult (119 +/- 39 pA, P < 0.05) tissues. Nicotine-induced oxidation currents were blocked by the nitric oxide synthase (NOS) inhibitor, nitro-l-arginine (NLA, 100 micromol L(-1)). Nicotine-induced, NLA-sensitive oxidation currents could be detected in the tertiary plexus of neonatal but not adult tissues. Immunohistochemistry demonstrated stronger NOS immunoreactivity in neonatal compared with adult myenteric ganglia. Western blot studies revealed higher levels of NOS in neonatal compared with adult LMMP. Cell counts revealed that the total number of myenteric neurons in the small intestine was greater in adults than in neonatal guinea pigs, however, the ratio of NOS : Calbindin neurons was significantly higher in neonatal compared with adult tissues.

CONCLUSIONS & INFERENCES

Nitric oxide signaling to the longitudinal muscle is stronger in neonatal compared with adult guinea pig ileum. Nitric oxide synthase-containing neurons are diluted postnatally by cholinergic and other, as yet unidentified neuronal subtypes.

Is apoptosis the cause of noninsertional achilles tendinopathy?

BACKGROUND

The pathogenesis of chronic tendinopathy is unclear but it does not appear to be an inflammatory process. Apoptosis may lead to degenerate tissue through a nitric oxide-mediated pathway. Increased levels of nitric oxide have been demonstrated in Achilles tendinopathy.

HYPOTHESIS

Nitric oxide-mediated apoptosis is an important mechanism in the development of Achilles tendinopathy.

STUDY DESIGN

Controlled laboratory study.

METHODS

Samples were obtained from the Achilles tendons of 14 patients with noninsertional Achilles tendinopathy. Control samples were taken from macroscopically normal tendon correlating with areas of normal tissue on magnetic resonance imaging. Immunohistochemical techniques identified the expression of inducible and endothelial nitric oxide synthase as markers of nitric oxide production. Apoptotic cells were identified using terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling (TUNEL) and the demonstration of caspase-3 activation.

RESULTS

Significant differences were found between the diseased tendon and the controls for all parameters. The mean caspase-3 cell count for diseased tendon was 51.9 versus 28.3 for the controls (P < .001). The mean TUNEL cell count for diseased tendon was 24.1 compared with 14.8 (P < .001). Inducible nitric oxide synthase (iNOS) densitometry revealed a mean of 26.1 for the diseased tissue versus 15.0 for the controls (P < .001) and the values for endothelial nitric oxide synthase (eNOS) were 48.3 and 23.7, respectively (P = .015).

CONCLUSION

Apoptosis may play a role in the development of noninsertional Achilles tendinopathy and appears to be related to the presence of raised eNOS and iNOS levels.

CLINICAL RELEVANCE

A clearer understanding of the tendinopathic process may lead to new treatment strategies aimed at modulating apoptosis.

Immunohistochemical study of nuclear changes associated with male germ cell death and spermiogenesis

In a previous study on the effects of gestational and lactational exposure of para-nonylphenol on male rats, we noted in both induced and uninduced rats, that variations in cleaved caspase-3 immunostaining patterns were associated with distinct nuclear alterations in mainly basally located germ cells (spermatogonia and preleptotene spermatocytes). These were re-analysed and compared with cleaved caspase-3-labeled germ cells in the aging human and the spermatogenically active catfish testis. In the rat testes, cytoplasmic immunostaining was progressively associated with lateral compression of the nucleus, its break up into large pieces which can contain immunostained marginated chromatin masses. The pale remnants of the nucleus continued to shrink in size concomitant with the appearance of blue-purplish stained regions in the cytoplasm similar in color to the condensed chromatin in spermatids, a condition which was TUNEL-negative. These large clumps of chromatin also eventually disappeared, giving rise to cells resembling cytoplasmic ghosts, a condition which was TUNEL-positive. By contrast, the immunolabeled nuclei of human and catfish germ cells condensed into a single mass, after which they lost immunoreactivity. To exclude the possibility that these observations could reflect alterations in Sertoli nuclei, rat testicular sections were probed with a mouse anti-human GATA-4 monoclonal (MHM) antibody. The MHM was, however, the second of two GATA-4 antibodies tested, with a goat anti-mouse polyclonal (GMP) initially used to label the rat Sertoli nuclei. GMP unexpectedly, but distinctly labeled the complete development of the acrosome in the rat testis, a fortuitous finding with utility for staging of the seminiferous epithelium.

Antibody specificity profiling on functional protein microarrays

Antibodies represent the end product of an exquisitely complex biological process including recombination, somatic hypermutation, affinity maturation, and self-tolerance, culminating in binding reagents directed against a vast repertoire of antigens. The resultant high affinity and diversity of specificity of these biomolecules has been exploited through the development of immunoassays and biotherapeutics that inaugurated a new era in experimental molecular biology and pharmaceutical drug development. Despite the utility of antibodies for research applications and in disease treatment, they must be employed in the context of an accurate understanding of their binding profile. High-content microarrays comprised of thousands of native, full length human proteins are an important tool in the assessment of antibody specificity.

Inducible nitric oxide synthase inhibition attenuates lung tissue responsiveness and remodeling in a model of chronic pulmonary inflammation in guinea pigs

We evaluated the influence of iNOS-derived NO on the mechanics, inflammatory, and remodeling process in peripheral lung parenchyma of guinea pigs with chronic pulmonary allergic inflammation. Animals treated or not with 1400 W were submitted to seven exposures of ovalbumin in increasing doses. Seventy-two hours after the 7th inhalation, lung strips were suspended in a Krebs organ bath, and tissue resistance and elastance measured at baseline and after ovalbumin challenge. The strips were submitted to histopathological measurements. The ovalbumin-exposed animals showed increased maximal responses of resistance and elastance (p<0.05), eosinophils counting (p<0.001), iNOS-positive cells (p<0.001), collagen and elastic fiber deposition (p<0.05), actin density (p<0.05) and 8-iso-PGF2alpha expression (p<0.001) in alveolar septa compared to saline-exposed ones. Ovalbumin-exposed animals treated with 1400 W had a significant reduction in lung functional and histopathological findings (p<0.05). We showed that iNOS-specific inhibition attenuates lung parenchyma constriction, inflammation, and remodeling, suggesting NO-participation in the modulation of the oxidative stress pathway.

Nitric oxide: new evidence for novel therapeutic indications

BACKGROUND

Nitric oxide (NO) deficiency is implicated in many pathophysiological processes in mammals. NO is a ubiquitous molecule involved in multiple cellular functions. Uncontrolled or inappropriate production of NO may lead to several disease states including septic shock, rheumatoid and inflammatory arthropathies, and expansion of cerebral damage after stroke. However, to date, there are no therapeutic agents available that can overcome these conditions. Similarly, underproduction of NO by NO synthase or enhanced breakdown of NO also leads to diseases such as hypertension, ischemic conditions, pre-eclampsia, premature delivery, among others. NO donor therapies are indicated in these conditions.

RESULTS

Nitroglycerin and nitrates (NO donors) have been used as therapeutic agents for the past century, particularly to treat vascular disease, and the only significant adverse effects are headaches. NO donors are highly cost-effective and have beneficial effects in multiple body systems. When the body cannot generate NO via NO synthase or due to rapid turnover leading to inadequate amounts of NO available for biological homeostasis, administration of exogenous NO, or prolongation of the actions of endogenous NO, are practical ways to supplement NO.

CONCLUSION

Recipients of such therapy include patients with angina pectoris, coronary artery disease, hypertension, osteoporosis, gastrointestinal motility disorders, pregnancy-related disorders including premature delivery, pre-eclampsia, vulvodynia, and erectile dysfunction in men. Postmenopausal NO deficiency is rectified with hormone replacement therapy, which enhances local production of NO. Declining local NO production secondary to estrogen deficiency in postmenopausal women and perhaps in older men could be one of the reasons for age-related increased incidences of cardiovascular events and sexual dysfunction. Thus, in addition to supplementation of NO compounds in acute situations like alleviating angina and erectile dysfunction, chronic NO therapy is cost-effective in decreasing cardiovascular events, and improving the urogenital system and skeletal health.

Topical glyceryl trinitrate and noninsertional Achilles tendinopathy: a clinical and cellular investigation

BACKGROUND

Topical glyceryl trinitrate (GTN) therapy has been advocated in the treatment of Achilles tendinopathy. The mechanism of action is unknown but may be related to modulation of local nitric oxide levels.

HYPOTHESIS

Topical GTN therapy for noninsertional Achilles tendinopathy will significantly enhance clinical improvement and will be associated with increased collagen synthesis within the tendon.

STUDY DESIGN

Randomized controlled clinical trial; Level of evidence, 1.

METHODS

Forty patients were recruited. Twenty underwent standard nonoperative physical therapy, and 20 underwent physical therapy and topical GTN daily. Clinical outcome was assessed using the Ankle Osteoarthritis Scale (AOS) visual analog score. Patients who failed to improve with conservative measures and who underwent surgical decompression had histological and immunohistochemical examination of samples from the Achilles tendon.

RESULTS

Glyceryl trinitrate did not offer any additional clinical benefit over standard nonoperative treatment for noninsertional Achilles tendinopathy. After 6 months of treatment, there was no significant difference in scores between the groups for pain (3.0 vs 3.1, P = .42) or disability (2.15 vs 2.25, P = .38). Histological examination did not show any difference in neovascularization, collagen synthesis, or stimulated fibroblasts between the 2 groups. There was no evidence of modulation of nitric oxide synthase, a marker of nitric oxide production, in those tendons treated with GTN.

CONCLUSION AND CLINICAL RELEVANCE

This study has failed to support the clinical benefit of GTN patches previously described in the literature. In the available tissue samples, there did not appear to be any histological or immunohistochemical change in Achilles tendinopathy treated with GTN compared with those undergoing standard nonoperative therapy.

A triterpenediol from Boswellia serrata induces apoptosis through both the intrinsic and extrinsic apoptotic pathways in human leukemia HL-60 cells

A triterpenediol (TPD) comprising of isomeric mixture of 3alpha, 24-dihydroxyurs-12-ene and 3alpha, 24-dihydroxyolean-12-ene from Boswellia serrata induces apoptosis in cancer cells. An attempt was made in this study to investigate the mechanism of cell death by TPD in human leukemia HL-60 cells. It inhibited cell proliferation with IC50 approximately 12 microg/ml and produced apoptosis as measured by various biological end points e.g. increased sub-G0 DNA fraction, DNA ladder formation, enhanced AnnexinV-FITC binding of the cells. Further, initial events involved massive reactive oxygen species (ROS) and nitric oxide (NO) formation, which were significantly inhibited by their respective inhibitors. Persistent high levels of NO and ROS caused Bcl-2 cleavage and translocation of Bax to mitochondria, which lead to loss of mitochondrial membrane potential (Deltapsim) and release of cytochrome c, AIF, Smac/DIABLO to the cytosol. These events were associated with decreased expression of survivin and ICAD with attendant activation of caspases leading to PARP cleavage. Furthermore, TPD up regulated the expression of cell death receptors DR4 and TNF-R1 level, leading to caspase-8 activation. These studies thus demonstrate that TPD produces oxidative stress in cancer cells that triggers self-demise by ROS and NO regulated activation of both the intrinsic and extrinsic signaling cascades.

Effects of chronic L-NAME treatment lung tissue mechanics, eosinophilic and extracellular matrix responses induced by chronic pulmonary inflammation

The importance of lung tissue in asthma pathophysiology has been recently recognized. Although nitric oxide mediates smooth muscle tonus control in airways, its effects on lung tissue responsiveness have not been investigated previously. We hypothesized that chronic nitric oxide synthase (NOS) inhibition by N(omega)-nitro-L-arginine methyl ester (L-NAME) may modulate lung tissue mechanics and eosinophil and extracellular matrix remodeling in guinea pigs with chronic pulmonary inflammation. Animals were submitted to seven saline or ovalbumin exposures with increasing doses (1 approximately 5 mg/ml for 4 wk) and treated or not with L-NAME in drinking water. After the seventh inhalation (72 h), animals were anesthetized and exsanguinated, and oscillatory mechanics of lung tissue strips were performed in baseline condition and after ovalbumin challenge (0.1%). Using morphometry, we assessed the density of eosinophils, neuronal NOS (nNOS)- and inducible NOS (iNOS)-positive distal lung cells, smooth muscle cells, as well as collagen and elastic fibers in lung tissue. Ovalbumin-exposed animals had an increase in baseline and maximal tissue resistance and elastance, eosinophil density, nNOS- and iNOS-positive cells, the amount of collagen and elastic fibers, and isoprostane-8-PGF(2alpha) expression in the alveolar septa compared with controls (P<0.05). L-NAME treatment in ovalbumin-exposed animals attenuated lung tissue mechanical responses (P<0.01), nNOS- and iNOS-positive cells, elastic fiber content (P<0.001), and isoprostane-8-PGF(2alpha) in the alveolar septa (P<0.001). However, this treatment did not affect the total number of eosinophils and collagen deposition. These data suggest that NO contributes to distal lung parenchyma constriction and to elastic fiber deposition in this model. One possibility may be related to the effects of NO activating the oxidative stress pathway.

Atrasentan treatment of pulmonary vascular disease in piglets with increased pulmonary blood flow

We studied the effect of chronic endothelin A receptor blockade by atrasentan on the pulmonary endothelin-1 system and vascular endothelial growth factor (VEGF) expression in piglets with high pulmonary blood flow. Twenty-five 4-week-old piglets with high pulmonary blood flow were randomized to three groups: sham operated (n = 8), placebo (water) (n = 7), or treatment with atrasentan (2 mg/kg per day) (n = 10). After 3 months, mean pulmonary arterial pressure (PAP) was higher in the placebo group than in the sham group [18 +/- 2 mm Hg versus 14 +/- 1 mm Hg; P < 0.05 (ANOVA)]. Atrasentan treatment was associated with lower cardiac output, PAP (14 +/- 1 mm Hg), and medial wall thickness of pulmonary arteries (diameter: 50-150 microM) compared with placebo [13.6 +/- 3.0% versus 18.1 +/- 4.2%; P < 0.05 (ANOVA)]. Quantitative real-time polymerase chain reaction for endothelin-1, endothelin B receptor, and endothelin-converting enzyme-1 mRNA in lung tissue did not differ. However, immunostaining as well as mRNA for VEGF were lower in atrasentan-treated animals (relative gene expression: atrasentan versus placebo: 0.8 +/- 0.3 versus 1.5 +/- 0.3; P = 0.009). Atrasentan treatment effectively reduces medial hypertrophy in piglets with chronic pulmonary hyperperfusion. Chronic endothelin A receptor blockade by atrasentan may interfere with the expression of VEGF.

Identification and localization of a putative ATP-binding cassette transporter in sea lice (Lepeophtheirus salmonis) and host Atlantic salmon (Salmo salar)

Some members of the ABC-transporter superfamily, such as P-glycoprotein and the multidrug resistance associated protein, may confer resistance to the avermectin subclass of macrocyclic lactones. The aim of this study was to examine the presence of ABC transporters in both sea lice (Lepeophtheirus salmonis) and its Atlantic salmon host (Salmo salar) using monoclonal antibodies (C219 and JSB-1, with high selectivity for P-gp) and a new polyclonal antibody (SL0525) generated against a putative sea louse ABC transporter. The antibody raised to SL0525 did not react with rat P-gp, suggesting that an ABC transporter, not necessarily P-gp, was isolated. C219 was the only antibody to localize P-gp in all 3 salmon tissues (intestine, kidney and liver). American lobster (Homarus americanus) was used as a reference crustacean for L. salmonis immunostaining reactions and showed positive staining in the hepatopancreatic and intestinal tissues with all 3 antibodies. The L. salmonis showed positive staining in the intestinal epithelial lining with all antibodies. This report represents the first documented evidence for the expression of ABC transporters in L. salmonis, its Atlantic salmon host, and the American lobster.

Oxidative stress, nitric oxide, and the mechanisms of cell death inLurcherPurkinje cells

Oxidative stress is postulated to play a role in cell death in many neurodegenerative diseases. As a model of neonatal neuronal cell death, we have examined the role of oxidative stress in Purkinje cell death in the heterozygous Lurcher mutant (+/Lc). Lurcher is a gain of function mutation in the delta2 glutamate receptor (GluRdelta2) that turns the receptor into a leaky membrane channel, resulting in chronic depolarization of +/Lc Purkinje cells starting around the first week of postnatal development. Virtually, all +/Lc Purkinje cells die by the end of the first postnatal month. To investigate the role of oxidative stress in +/Lc Purkinje cell death, we have examined nitric oxide synthase (NOS) activity and the expression of two markers for oxidative stress, nitrotyrosine and manganese super oxide dismutase (MnSOD), in wild type and +/Lc Purkinje cells at P10, P15, and P25. The results show that NOS activity and immunolabeling for nitrotyrosine and MnSOD are increased in +/Lc Purkinje cells. To determine whether peroxynitrite formation is a prerequisite for +/Lc Purkinje cell death, +/Lc mutants were crossed with an alpha-nNOS knockout mutant (nNOSalpha(-/-)) to reduce the production of NO. Analysis of the double mutants showed that blocking alpha-nNOS expression does not rescue +/Lc Purkinje cells. However, we present evidence for sustained NOS activity and nitrotyrosine formation in the GluRdelta2(+/Lc):nNOS(-/-) double mutant Purkinje cells, which suggests that the failure to rescue GluRdelta2(+/Lc):nNOS(-/-) Purkinje cells may be explained by the induction of alternative nNOS isoforms.

Pulmonary vascular changes in piglets with increased pulmonary blood flow and pressure

In this model of pulmonary vascular disease, high pulmonary blood flow was created by an anastomosis between the left subclavian artery and the main pulmonary artery [Blalock-Taussig (BT) shunt] in 4-week-old piglets (n = 6). Additional ligation of the left pulmonary artery (LPA) was used to increase pulmonary artery pressure (n = 6). Seven piglets were sham-operated. After 3 months, mean pulmonary artery pressure was higher in animals with BT shunt and LPA ligation (22 +/- 5; mean+/-SD) compared to sham-operated animals (15 +/- 2). In addition, thickening of the medial coat (20.1 +/- 2.8% versus 13.6 +/- 3.1% wall thickness) and increased immunostaining for vascular endothelial growth factor A (VEGF-A) were observed. Relative gene expression for endothelin-converting enzyme-1 (ECE-1) mRNA was 1.8 times higher, and VEGF-A mRNA was 2.5 times higher in pigs with BT shunt and LPA ligation compared with sham-operated animals. VEGF receptor-1 and VEGF receptor-2 mRNA was lower in shunted animals and in animals with additional ligation of LPA. Upregulation of ECE-1 and VEGF-A, as well as changes in VEGFR expression in the pulmonary hypertensive lung, may contribute to pulmonary vascular changes.

Inverse relationship between nitric oxide synthases and endothelin-1 synthesis in bovine corpus luteum: interactions at the level of luteal endothelial cell

Endothelin-1 (ET-1) and nitric oxide (NO) play pivotal roles in corpus luteum (CL) function. The present study examined the interplay between NO and ET-1 synthesis in the bovine CL. We found similar inducible and endothelial NO synthase (iNOS and eNOS, respectively) activities in the young CL (d 1-5) expressing the highest levels of both eNOS and iNOS mRNA. These values later declined at mid-cycle (d 8-15) and remained low at later stages (d 16-18). Luteolysis, initiated by prostaglandin F2alpha analog administration, further reduced NOS mRNA and by 24 h, NOS values dropped to approximately 15% of those at mid-cycle. eNOS protein levels followed a similar pattern to its mRNA. Because endothelial cells (ECs) are the main site for ET-1 and NO production in the CL, we examined the direct effects of the NO donor, NONOate on luteal ECs (LECs). Elevated NO levels markedly decreased ET-1 mRNA, and peptide concentrations in cultured and freshly isolated LECs in a dose-dependent manner. In agreement, NOS inhibitor, NG-nitro-l-arginine methyl ester, stimulated ET-1 mRNA expression in these cells. Interestingly, NO also up-regulated prostaglandin F2alpha receptors in LECs. These data show that there is an inverse relationship between NOS and ET-1 throughout the CL life span, and imply that this pattern may be the result of their interaction within the resident LECs. NOS are expressed in a physiologically relevant manner: elevated NO at an early luteal stage is likely to play an important role in angiogenesis, whereas reduced levels of NO during luteal regression may facilitate the sustained up-regulation of ET-1 levels during luteolysis.

Effects of nitric oxide synthases in chronic allergic airway inflammation and remodeling

The precise role of each nitric oxide (NO) synthase (NOS) isoform in the pathobiology of asthma is not well established. Our objective was to investigate the contribution of constitutive NO synthase (cNOS) and inducible NOS (iNOS) isoforms to lung mechanics and inflammatory and remodeling responses in an experimental model of chronic allergic pulmonary inflammation. Guinea pigs were submitted to seven ovalbumin exposures with increasing doses (1 approximately 5 mg/ml) for 4 wk. The animals received either chronic L-NAME (N-nitro-L-arginine methyl ester, in drinking water) or 1,400 W (iNOS-specific inhibitor, intraperitoneal) treatments. At 72 h after the seventh inhalation of ovalbumin solution, animals were anesthetized, mechanically ventilated, exhaled NO was collected, and lung mechanical responses were evaluated before and after antigen challenge. Both L-NAME and 1,400 W treatments increased baseline resistance and decreased elastance of the respiratory system in nonsensitized animals. After challenge, L-NAME increased resistance of the respiratory system and collagen deposition on airways, and decreased peribronchial edema and mononuclear cell recruitment. Administration of 1,400 W reduced resistance of the respiratory system response, eosinophilic and mononuclear cell recruitment, and collagen and elastic fibers content in airways. L-NAME treatment reduced both iNOS- and neuronal NOS-positive eosinophils, and 1,400 W diminished only the number of eosinophils expressing iNOS. In this experimental model, inhibition of NOS-derived NO by L-NAME treatment amplifies bronchoconstriction and increases collagen deposition. However, blockage of only iNOS attenuates bronchoconstriction and inflammatory and remodeling processes.

Identification of major cell types in paraffin sections of bovine tissues

Background

Identification of cell types in bovine tissue sections is complicated by the limited availability of anti-bovine antibodies, and by antigen retrieval treatments required for formalin-fixed tissue samples. We have evaluated an antibody and lectin panel for identifying major cell types in paraffin-embedded bovine tissue sections, and report optimized pretreatments for these markers.

Results

We selected 31 useful antibodies and lectins which can be used to identify cell types of epithelia, connective tissue, muscle, and nervous tissue, as well as cell proliferation and apoptosis.

Conclusion

The panel of markers allows the identification of all major cell types in paraffin-embedded cattle tissue sections by immunohistochemistry or lectin histochemistry. Heat-induced epitope retrieval methods are required for most antibodies.

Inhibition by nitric oxide of cytochrome P450 4A activity contributes to endotoxin-induced hypotension in rats

Nitric oxide (NO) production during endotoxemia is associated with decreased total CYP content, CYP 1A1/2, 2B1/2, 2C6, 2C11, 3A1, and 3A2 mRNA, protein expression or activity which is prevented by NO synthase (NOS) inhibitors in rats. This study was conducted to determine if endotoxin-induced hypotension caused by NO production is mediated by inhibition of renal CYP 4A protein expression and activity. In conscious male Sprague-Dawley rats, endotoxin (10 mg/kg, ip) reduced mean arterial pressure (MAP), increased serum and renal nitrite levels, and inducible NOS (iNOS), and decreased renal CYP 4A1/A3 protein and CYP 4A activity. The selective iNOS inhibitor 1,3-PBIT (10 mg/kg, ip; 1h after endotoxin) prevented endotoxin-induced decrease in MAP, renal CYP 4A1/A3 protein level and CYP 4A activity and increase in systemic and renal nitrite production. The selective constitutive NOS (cNOS) inhibitor N(G)-nitro-L-arginine (L-NNA; 20 mg/kg, ip; 1 h after endotoxin) partially attenuated endotoxin-induced decrease in MAP. The selective CYP 4A inhibitor, aminobenzotriazole (50 mg/kg, ip; 1 h after endotoxin) diminished CYP 4A1/A3 protein level and CYP 4A activity. Aminobenzotriazole did not alter the endotoxin-induced decrease in MAP, but it reversed the effect of 1,3-PBIT in preventing endotoxin-induced fall in MAP and CYP 4A activity. These data suggest that the endotoxemia-induced increase in NO production primarily via iNOS suppresses renal CYP 4A expression and activity, and inhibition of iNOS with 1,3-PBIT restores renal CYP 4A protein and activity and MAP presumably due to increased production of arachidonic acid metabolites derived from CYP 4A.

Neurokinins and inflammatory cell iNOS expression in guinea pigs with chronic allergic airway inflammation

In the present study we evaluated the role of neurokinins in the modulation of inducible nitric oxide synthase (iNOS) inflammatory cell expression in guinea pigs with chronic allergic airway inflammation. In addition, we studied the acute effects of nitric oxide inhibition on this response. Animals were anesthetized and pretreated with capsaicin (50 mg/kg sc) or vehicle 10 days before receiving aerosolized ovalbumin or normal saline twice weekly for 4 wk. Animals were then anesthetized, mechanically ventilated, given normal saline or N(G)-nitro-l-arginine methyl ester (l-NAME, 50 mg/kg ic), and challenged with ovalbumin. Prechallenge exhaled NO increased in ovalbumin-exposed guinea pigs (P < 0.05 compared with controls), and capsaicin reduced this response (P < 0.001). Compared with animals inhaled with normal saline, ovalbumin-exposed animals presented increases in respiratory system resistance and elastance and numbers of total mononuclear cells and eosinophils, including those expressing iNOS (P < 0.001). Capsaicin reduced all these responses (P < 0.05) except for iNOS expression in eosinophils. Treatment with l-NAME increased postantigen challenge elastance and restored both resistance and elastance previously attenuated by capsaicin treatment. Isolated l-NAME administration also reduced total eosinophils and mononuclear cells, as well as those cells expressing iNOS (P < 0.05 compared with ovalbumin alone). Because l-NAME treatment restored lung mechanical alterations previously attenuated by capsaicin, NO and neurokinins may interact in controlling airway tone. In this experimental model, NO and neurokinins modulate eosinophil and lymphocyte infiltration in the airways.

Nitric oxide in health and disease of the respiratory system

During the past decade a plethora of studies have unravelled the multiple roles of nitric oxide (NO) in airway physiology and pathophysiology. In the respiratory tract, NO is produced by a wide variety of cell types and is generated via oxidation of l-arginine that is catalyzed by the enzyme NO synthase (NOS). NOS exists in three distinct isoforms: neuronal NOS (nNOS), inducible NOS (iNOS), and endothelial NOS (eNOS). NO derived from the constitutive isoforms of NOS (nNOS and eNOS) and other NO-adduct molecules (nitrosothiols) have been shown to be modulators of bronchomotor tone. On the other hand, NO derived from iNOS seems to be a proinflammatory mediator with immunomodulatory effects. The concentration of this molecule in exhaled air is abnormal in activated states of different inflammatory airway diseases, and its monitoring is potentially a major advance in the management of, e.g., asthma. Finally, the production of NO under oxidative stress conditions secondarily generates strong oxidizing agents (reactive nitrogen species) that may modulate the development of chronic inflammatory airway diseases and/or amplify the inflammatory response. The fundamental mechanisms driving the altered NO bioactivity under pathological conditions still need to be fully clarified, because their regulation provides a novel target in the prevention and treatment of chronic inflammatory diseases of the airways.

Nitric oxide synthase inhibition: therapeutic potential in asthma

Nitric oxide (NO) is synthesized from L-arginine in the human respiratory tract by enzymes of the NO synthase (NOS) family. Levels of NO in exhaled air are increased in asthma, and measurement of exhaled NO has been advocated as a noninvasive tool to monitor the underlying inflammatory process. However, the relation of NO to disease pathophysiology is uncertain, and in particular the fundamental question of whether it should be viewed primarily as beneficial or harmful remains unanswered. Exogenously administered NO has both bronchodilator and bronchoprotective properties. Although it is unlikely that NO is an important regulator of basal airway tone, there is good evidence that endogenous NO release exerts a protective effect against various bronchoconstrictor stimuli. This response is thought to involve one or both of the constitutive NOS isoforms, endothelial NOS (eNOS) and neuronal NOS (nNOS). Therefore, inhibition of these enzymes is unlikely to be therapeutically useful in asthma and indeed may worsen disease control. On the other hand, the high concentrations of NO in asthma, which are believed to reflect upregulation of inducible NOS (iNOS) by proinflammatory cytokines, may produce various deleterious effects. These include increased vascular permeability, damage to the airway epithelium, and promotion of inflammatory cell infiltration. However, the possible effects of iNOS inhibition on allergic inflammation in asthma have not yet been described and studies in animal models have yielded inconsistent findings. Thus, the evidence to suggest that inhibition of iNOS would be a useful therapeutic strategy in asthma is limited at present. More definitive information will require studies combining agents that potently and specifically target individual NOS isoforms with direct measurement of inflammatory markers.

NO-cGMP signaling molecules in the rat epithelial rests of Malassez

The epithelial rests of Malassez (ERM) are derived from the disintegrating epithelial root sheath of Hertwig that guides root formation during tooth development. Low concentrations of nitric oxide (NO) produced by NO-synthase I (NOS I) and NOS III activate intracellular soluble guanylate cyclase (sGC) to produce intracellular cyclic guanosine 3':5'-monophosphate (cGMP), which triggers rapid cellular responses such as cell proliferation, cell differentiation, and apoptosis under physiological conditions. The presence of NOS I-III, sGC (alpha2- and beta1-subunits) and cGMP in the ERM was investigated by immunohistochemistry. Rat molars with periodontium were perfusion and postfixed, decalcified, frozen-sectioned, and sections were immunostained. NOS I, NOS III, sGC (alpha2- and beta1-subunits) and cGMP were localized with different densities in the ERM. The presence of NOS II in the ERM varied. The localization of NOS I, NOS III, sGC and cGMP in the ERM indicates an involvement of NO and/or NO-cGMP signal pathway molecules in homeostasis of a variety of physiological processes in the ERM. These could include regulation of cell proliferation, cell differentiation and apoptosis.

Post-transcriptional regulation of inducible nitric oxide synthase in chronic lymphocytic leukemia B cells in pro- and antiapoptotic culture conditions

Functional inducible NOS (iNOS) may be involved in the prolonged lifespan of chronic lymphocytic leukemia cells (B-CLL), although the exact mechanisms implicated remain elusive as yet. In this work, we have examined iNOS expression in normal B lymphocytes and B-CLL cells in pro- and antiapoptotic conditions. Our results demonstrate: (1) The existence of a new splice variant characterized by a complete deletion of exon 14 (iNOS 13-16(14del)), which was preferentially detected in normal B lymphocytes and may represent an isoform that could play a role in the regulation of enzyme activity. (2) The existence of another alternatively spliced iNOS mRNA transcript involving a partial deletion of the flavodoxin region (iNOS 13-16(neg)) was correlated to a decreased B-CLL cell viability. The 9-beta-D-arabinofuranosyl-2-fluoradenine or fludarabine (F-ara) treatment induced iNOS 13-16(neg) transcript variants, whereas IL-4 enhanced both the transcription of variants, including these exons (iNOS 13-16(pos)), and the expression of a 122 kDa iNOS protein. These results suggest that in B-CLL, a regulation process involving nitric oxide (.- NO) levels could occur by a post-transcriptional mechanism mediated by soluble factors. Our results also provide an insight into a new complementary proapoptotic action of F-ara in B-CLL by the induction of particular iNOS splice variants, leading to the activation of a caspase-3-dependent apoptotic pathway.

Low NO bioavailability in CCl4 cirrhotic rat livers might result from low NO synthesis combined with decreased superoxide dismutase activity allowing superoxide-mediated NO breakdown: A comparison of two portal hypertensive rat models with healthy controls

BACKGROUND: In cirrhotic livers, the balance of vasoactive substances is in favour of vasoconstrictors with relatively insufficient nitric oxide. Endothelial dysfunction has been documented in cirrhotic rat livers leading to a lower activity of endothelial nitric oxide synthase but this might not be sufficient to explain the low nitric oxide presence. We compared the amount of all nitric oxide synthase isoforms and other factors that influence nitric oxide bioavailability in livers of two portal hypertensive rat models: prehepatic portal hypertension and carbon tetrachloride induced cirrhosis, in comparison with healthy controls. RESULTS: Endothelial nitric oxide synthase was the solely detected isoform by Western blotting in all livers. In cirrhotic livers, the amount of endothelial nitric oxide synthase protein was lower than in healthy controls, although an overlap existed. Levels of caveolin-1 messenger RNA were within the normal range but endothelin-1 messenger RNA levels were significantly higher in cirrhotic livers (p < 0.05). A markedly lower superoxide dismutase activity was observed in cirrhotic livers as compared to healthy controls (p < 0.05). CONCLUSIONS: In contrast to prehepatic portal hypertension, cirrhotic livers had decreased endothelial nitric oxide synthase protein and enhanced endothelin-1 messenger RNA amount. We hypothesise that a vasodilator/vasoconstrictor imbalance may be further aggravated by the reduced activity of superoxide dismutase. Decreased activity allows enhanced superoxide action, which may lead to breakdown of nitric oxide in liver sinusoids.

Evidence for the existence of two distinct functions for the inducible NO synthase in the rat kidney: effect of aminoguanidine in rats with 5/6 ablation

The functional role of the NO synthase (NOS) isoforms in the normal or diseased kidney is uncertain. This study examined the renal expression of the endothelial (eNOS), neuronal (nNOS), and inducible (iNOS) isoforms by both immunohistochemistry and Western blot analyses in sham-operated rats (S) and in rats subjected to 5/6 nephrectomy (Nx). Primary antibodies from two different sources were used to detect iNOS. Additional S and Nx rats were chronically treated with aminoguanidine (AG), a selective iNOS inhibitor. All three isoforms were clearly expressed in S kidney. Their renal abundance, evaluated by Western blot analysis, fell in Nx rats. With the use of anti-iNOS antibodies from two distinct sources, the immunohistochemical analysis showed the presence of what appeared to be two distinct iNOS fractions: a "tubular" fraction, present in S and with decreased intensity in Nx; and an "interstitial" fraction, observed only in inflamed areas of Nx rats. AG treatment greatly attenuated renal injury in Nx rats by a direct antiinflammatory effect, likely related to iNOS inhibition, rather than to amelioration of renal hemodynamics or to reduced protein glycation. These observations suggest that: (1) the functional role of the renal iNOS isoform may vary dramatically under different physiologic conditions; (2) caution should be taken in the interpretation of immunohistochemical iNOS data, because antibodies from different sources may detect different iNOS fractions; and (3) AG treatment may become useful in the treatment of human progressive nephropathies, even those not associated with diabetes or aging.

Differential expression and localization of nitric oxide synthases in cirrhotic livers of bile duct-ligated rats

Increased vascular nitric oxide (NO) production has been implicated in the pathogenesis of the hyperdynamic circulation in liver cirrhosis. This study investigated the expression of three isoforms of NO synthase (NOS) in rat cirrhotic livers. Cirrhosis was induced by chronic bile duct ligation (BDL). NOS enzyme activity was assessed by L-citrulline generation. Competitive RT-PCR was performed to detect the mRNA levels of NOS. In situ hybridization was done to localize NOS mRNA. Protein expression of NOS was evaluated by Western blotting and immunohistochemistry. The L-citrulline assay showed that constitutive NOS (cNOS) enzymatic activity was decreased, while inducible NOS (iNOS) activity was increased in BDL livers. Both endothelial NOS (eNOS) and neuronal NOS (nNOS) mRNA were detected in BDL and sham rats, but with enhanced expression in BDL rats. eNOS protein was redistributed with less expression in sinusoidal endothelial cells, but the total levels in liver were not changed. nNOS was induced in hepatocytes of BDL rats, in contrast to only a weak signal observed around some blood vessels in sham livers. Intense mRNA and protein expression of iNOS was induced in livers of BDL rats and was localized in hepatocytes, with no or a negligible amount in control livers. In conclusion, iNOS was induced in cirrhotic liver with its activity increased. In contrast, cNOS activity was impaired, regardless of unchanged eNOS protein levels and enhanced nNOS expression. These results suggest that all three types of NOS have a role in cirrhosis, but their expression and regulation are different.

Type I nitric oxide synthase in the human lung is predominantly expressed in capillary endothelial cells

Nitric oxide (NO) has important functions in the regulation of pulmonary smooth muscle tone. In the human lung, published data on the expression and distribution of neuronal nitric oxide synthase (NOS-I) are contradictory. The aim of this study, therefore, was to determine the predominant cells expressing NOS-I in the human lung. Immunofluorescence double staining techniques were applied to normal human lung tissue using established monospecific antibodies directed against NOS-I. Suprisingly, capillary endothelial cells in the alveolar septa were identified as the major sites of NOS-I expression. Neither alveolar nor bronchiolar epithelium, nor the alveolar macrophages, expressed NOS-I. These results indicate that the predominant sites of NOS-I expression in the human lung are confined to non-neuronal, i.e. capillary endothelial cells and suggest a role for NO in the regulation of pulmonary endothelial cell permeability.

Inducible nitric oxide synthase and glomerular hemodynamics in rats with liver cirrhosis

This study was designed to test the hypothesis that glomerular de novo expression of inducible nitric oxide synthase (iNOS) contributes to renal hemodynamic abnormalities in liver cirrhosis developed 3 wk after common bile duct ligature (CBDL). De novo expression of iNOS mRNA was detected by RT-PCR in RNA extracts from isolated CBDL rat glomeruli whereas no iNOS mRNA was found in control rat glomerular RNA. Immunohistochemical staining for iNOS was negative in control animals whereas, in CBDL rats, positive iNOS staining was detected in an apparently mesangial pattern in all glomeruli. Western blots of protein extracts from isolated glomeruli of CBDL rats, but not control animals, showed a prominent iNOS band of 130 kDa. Mean arterial pressure (MAP), renal plasma flow (RPF; p-aminohippurate clearance), and glomerular filtration rate (GFR; inulin clearance) were unaltered in CBDL rats, but the application of 4 mg/kg L-N(6)-(1-iminoethyl)lysine, a specific inhibitor of iNOS, reduced GFR and RPF significantly in CBDL rats, whereas control animals were not affected. Similar results were obtained with lipopolysaccharide (LPS)-pretreated animals, which were studied as a positive control for iNOS expression and as a model for recent iNOS induction. We conclude that de novo expression of iNOS occurs in glomeruli of rats with liver cirrhosis and that nitric oxide, generated by iNOS, contributes to the maintenance of glomerular filtration in the early state of this disease.

Allergen-induced impairment of bronchoprotective nitric oxide synthesis in asthma

BACKGROUND

Endogenous nitric oxide protects against airway hyperresponsiveness (AHR) to bradykinin in mild asthma, whereas AHR to bradykinin is enhanced by inhaled allergens.

OBJECTIVE

Hypothesizing that allergen exposure impairs bronchoprotective nitric oxide within the airways, we studied the effect of the inhaled nitric oxide synthase (NOS) inhibitor N(G)-monomethyl-L-arginine (L-NMMA) on AHR to bradykinin before and after allergen challenge in 10 subjects with atopic asthma.

METHODS

The study consisted of 3 periods (1 diluent and 2 allergen challenges). AHR to bradykinin (PD(20)BK) was examined before and 48 hours after allergen challenge, both after double-blinded pretreatment with L-NMMA or placebo. The accompanying expression of the various NOS isoforms (ecNOS, nNOS, and iNOS) was examined by means of immunohistochemistry in bronchial biopsies obtained after diluent and allergen challenge.

RESULTS

After placebo, AHR to BK worsened after allergen challenge in comparison with before allergen challenge (PD(20)BK, 70.8 nmol [range, 6.3-331] and 257 nmol [35.5-2041], respectively; P =.0004). After L-NMMA, preallergen and postallergen PD(20)BK values (50.1 nmol [1.8-200] vs 52.5 nmol [6.9-204]; P =.88) were similarly reduced (P <.01) and not different from the postplacebo/postallergen value (P >.05). After allergen challenge, the intensity of staining in bronchial epithelium decreased for ecNOS (P =.03) and increased for iNOS (P =.009). These changes in immunostaining were correlated with the accompanying worsening in AHR to BK (R(s) = -0.66 and 0.71; P <.04).

CONCLUSIONS

These data indicate that allergen exposure in asthma induces increased airway hyperresponsiveness to bradykinin through impaired release of bronchoprotective nitric oxide associated with downregulation of ecNOS. This suggests that new therapeutic strategies towards restoring the balance among the NOS isoforms during asthma exacerbations are warranted.

Regulation of murine airway responsiveness by endothelial nitric oxide synthase

Nitric oxide (NO) is a potent vasodilator, but it can also modulate contractile responses of the airway smooth muscle. Whether or not endothelial (e) NO synthase (NOS) contributes to the regulation of bronchial tone is unknown at present. Experiments were designed to investigate the isoforms of NOS that are expressed in murine airways and to determine whether or not the endogenous release of NO modulates bronchial tone in wild-type mice and in mice with targeted deletion of eNOS [eNOS(-/-)]. The presence of neuronal NOS (nNOS), inducible NOS (iNOS), and eNOS in murine trachea and lung parenchyma was assessed by RT-PCR, immunoblotting, and immunohistochemistry. Airway resistance was measured in conscious unrestrained mice by means of a whole body plethysmography chamber. The three isoforms of NOS were constitutively present in lungs of wild-type mice, whereas only iNOS and nNOS were present in eNOS(-/-) mice. Labeling of nNOS was localized in submucosal airway nerves but was not consistently detected, and iNOS immunoreactivity was observed in tracheal and bronchiolar epithelial cells, whereas eNOS was expressed in endothelial cells. In wild-type mice, treatment with N-nitro-L-arginine methyl ester, but not with aminoguanidine, potentiated the increase in airway resistance produced by inhalation of methacholine. eNOS(-/-) mice were hyperresponsive to inhaled methacholine and markedly less sensitive to N-nitro-L-arginine methyl ester. These results demonstrate that the three NOS isoforms are expressed constitutively in murine lung and that NO derived from eNOS plays a physiological role in controlling bronchial airway reactivity.

NADPH diaphorase is developmentally regulated in rat olfactory epithelium

In vertebrate olfactory receptor neurons, NO synthase (NOS) has been detected in embryonic and early postnatal stages. However, expression of the enzyme in the mature epithelium is still controversial. We analyzed the developmental expression pattern of the histochemical NOS-marker NADPH diaphorase (NADPHd) in the olfactory epithelium of young rats. NADPHd was expressed in a small subset of olfactory receptor neurons as early as P0. Between P0 and P24 the number of labeled neurons increased 10-fold, stabilizing thereafter. Whereas NADPHd was generally found in the somata, a transitory dendritic expression was observed between P2 and P5. This dynamic postnatal regulation of the cellular distribution of NADPHd appears to reflect developmental processes within the olfactory epithelium.

The foreign body reaction to a biodegradable biomaterial differs between rats and mice

Before a biomaterial can be applied in the clinic, biocompatibility must be tested in in vivo models, by monitoring the foreign body reaction. In this study, we compared the foreign body reaction (FBR) to the biodegradable biomaterial hexamethylenediisocyanate crosslinked dermal sheep collagen (HDSC) between several strains of rats and mice. HDSC disks were implanted subcutaneously on the backs of AO, BN, F344, LEW, and PVG rats and on the backs of 129 SVEV, BALB/c, and C57BL/6 mice. Materials were explanted after 7, 14, 21, and 28 days and processed for (immuno) light and transmission electron microscopic evaluation. In all rat strains, giant cell formation and phagocytosis of HDSC bundles were comparable. In addition, in the PVG rat, many plasma cells infiltrated the HDSC disks. Only a few T cells were present in AO and PVG rats, whereas, in F344 and LEW rats, the presence of T cells was more pronounced. BN rats showed an intermediate T-cell infiltration. In mice, the FBR to HDSC was comparable between the different strains. Compared with rats, giant cell formation was limited, whereas stroma formation was more abundant. Phagocytosis of HDSC bundles rarely occurred in mice, whereas calcification was observed more often. It is concluded that the FBR to HDSC clearly differs between rats and mice. This has consequences for assessment studies on biocompatibility and also on fundamental biomaterial research.

Collar-induced elevation of mRNA and functional activity of 5-HT(1B) receptor in the rabbit carotid artery

Hypersensitivity to serotonin (5-HT) develops in rabbit collared carotid arteries. Previous data demonstrated the involvement of 5-HT(1)-like receptors which are not active in normal carotid arteries. This study investigated the interaction in the rabbit carotid artery between 5-HT and a moderate tone as this can uncover functional 5-HT(1)-like receptors. Furthermore, the expression of messenger RNA (mRNA) and protein of 5-HT(1B), 5-HT(1D) and 5-HT(2A) receptors was addressed. Silicone collars were placed around the carotid arteries of male New Zealand White rabbits for 1 week. Rings from inside (=collar) and outside (=sham) the collar were either mounted in isolated organ baths for isometric force measurements or frozen in liquid nitrogen to isolate total RNA or proteins which were subsequently analysed by respectively reverse transcriptase-polymerase chain reaction and Western blot analysis. In sham and collared rings concentration-response curves (CRC's) to 5-HT were monophasic. Only in collared segments the presence of a 5-HT(2A) antagonist (spiperone or ketanserin, 0.1 microM) revealed a biphasic CRC which was even more pronounced when a moderate tone was induced by KCl pointing to functional 5-HT(1)-like receptors. The rabbit carotid artery constitutively expressed 5-HT(1B) and 5-HT(2A) mRNA, not 5-HT(1D) mRNA. Manipulation of the carotid artery increased the 5-HT(1B) mRNA level. Collar placement raised it even further. The 5-HT(2A) mRNA level remained unchanged. All the anti-5-HT receptor antibodies tested resulted in variable, non specific patterns with multiple bands. In conclusion, collar placement elevates mRNA expression and activity of the 5-HT(1B) receptor in the rabbit carotid artery.

Periadventitial inducible nitric oxide synthase expression and intimal thickening

Positioning a silicone collar around the rabbit carotid artery induces a smooth muscle cell-rich intimal thickening. We investigated the localization of inducible nitric oxide synthase (iNOS) during thickening of the intima, the effect of iNOS inhibition on intimal thickness, and the effect of oxidized LDL (ox-LDL) on iNOS expression in the vessel wall. Collars were positioned for 18 hours or for 3, 7, or 14 days. Arterial cross sections were immunostained for iNOS, including naïve, sham-operated, and carotid arteries in which ox-LDL had been infused locally for 14 days. Furthermore, collars were connected to osmotic minipumps for local delivery (5 microL. h(-1), 14 days, n=12) of saline or the iNOS inhibitor L-N(6)-(1-iminoethyl)-lysine-HCl (L-NIL, 10 mmol/L). In the adventitia and the periadventitial granulation tissue of collared arteries, iNOS-positive macrophages and T lymphocytes were present from 18 hours onward. The media and intima were negative for iNOS. Reverse transcription-polymerase chain reaction revealed iNOS mRNA in collared but not in sham-operated arteries. Local inhibition of iNOS doubled the intimal thickness and decreased nitrotyrosine staining. Ox-LDL-treated arteries, which had a thicker intima, showed a pronounced influx of macrophages and T lymphocytes in all layers of the vessel wall, accompanied by iNOS expression in a subpopulation of these cells. Our study indicates that iNOS was not induced in intimal thickenings predominantly consisting of smooth muscle cells. However, iNOS was expressed in (peri)adventitial tissue and counteracted the progression of intimal thickening. Ox-LDL treatment was accompanied by an abundant influx of iNOS-positive macrophages and T lymphocytes in the vessel, but this could not prevent the progression of intimal thickening.

Expression of neuronal nitric oxide synthase in several cell types of the rat gastric epithelium

The aim of this study was to identify which cell types of the rat gastric epithelium express neuronal nitric oxide synthase (nNOS) because the results of the previous studies have been very divergent regarding this point. By the combination of immunohistochemical (IHC) and in situ hybridization (ISH) techniques, we detected expression of nNOS in chief and mucosecretory cells of the gastric epithelium. Moreover, some gastric endocrine cells were immunoreactive for nNOS, although they could not be distinguished in sections treated with ISH techniques. The strongest signal for all antibodies in IHC techniques was obtained when microwave (MW) heating was performed before the IHC procedure. Our results indicate that in the gastric epithelium a variety of cell types are able to produce NO. The NO produced by the different cell types (chief, mucous, and endocrine) may form a complex network of paracrine communication with an important role in gastric physiology.

Ultrastructural localization of nitrotyrosine within the caudate-putamen nucleus and the globus pallidus of normal rat brain

Nitration of protein tyrosine residues by nitric oxide (NO)-derived reactive species results in the production of stable nitrotyrosine (NT) moieties that are immunochemically detectable in many regions of normal brain and enriched in those areas containing constitutive nitric oxide synthase (cNOS). These include the caudate-putamen nucleus (CPN) and the globus pallidus, which receives major inhibitory input from the CPN. To determine the functional sites for NT production in these critical motor nuclei, we examined the electron microscopic immunocytochemical localization of NT and cNOS in rat brain. In the CPN, NT was localized to the somata and dendrites of cNOS-containing interneurons and spiny neurons, some of which received input from cNOS-labeled terminals. The NT immunoreactivity was most prevalent on outer mitochondrial membranes and nearby segments of the plasma membranes in dendrites and within asymmetric synapses on dendritic spines. In the CPN and globus pallidus, there was also a prominent labeling of NT in astrocytic processes, small axons, and tubulovesicles and/or synaptic vesicles in axon terminals. These terminals formed mainly asymmetric synapses in the CPN and inhibitory-type synapses in the globus pallidus where they often apposed cNOS-containing terminals that also formed asymmetric, excitatory-type synapses. Our results suggest that NT is generated by mechanisms requiring the dual actions of excitatory transmitters and NO derived either from interneurons in the CPN or from excitatory afferents in the globus pallidus. The findings also implicate NT in the physiological actions of NO within the striatal circuitry and, particularly, in striatopallidal neurons severely affected in Huntington's disease.

No colocalization of immunoreactivities for VIP and neuronal NOS, and a differential relation to cGMP-immunoreactivity in bovine penile smooth muscle

The distribution of immunoreactivity (IR) for the neuropeptide vasoactive intestinal polypeptide (VIP) and neuronal nitric oxide synthase (nNOS) in the bovine retractor penis muscle (RP) and penile artery (PA) was studied by using two different methods. The distribution of these immunoreactivities was also compared with that of the immunoreactivity for cyclic guanosine monophosphate (cGMP). In both tissues the nerve fibers and terminals immunoreactive for VIP had a distribution that was completely different from that of the nerve fibers and terminals immunoreactive for nNOS. This contrasts with the previous observations in penile smooth muscle of other species. In the RP, as well as in the PA, many of the VIP-IR fibers were also immunoreactive for neurofilaments (NF), whereas the nNOS-IR fibers were consistently devoid of NF-IR. Stimulation with sodium nitroprusside, a nitric oxide donor, considerably increased cGMP-IR in the smooth muscle cells in both RP and PA, and in several nerve fibers in PA. Many of these cGMP-IR nerve fibers exhibited nNOS-IR, whereas none of them was immunoreactive for VIP. Our results suggest that the degree of coexistence of VIP-IR and nNOS-IR in the nerve fibers and terminals innervating penile smooth muscle show wide species differences. They also suggest that the mechanisms by which VIP could be involved in neurogenic penile erection may vary between species.

Foreign-body reaction to dermal sheep collagen in interferon-gamma-receptor knock-out mice

This study was performed to gain more insight into the role of interferon-gamma (IFN-gamma), a potent macrophage activator, in the foreign-body reaction to hexamethylenediisocyanate-crosslinked dermal sheep collagen (HDSC). Because the results of earlier studies aimed at modulating the foreign-body reaction in AO rats by local or systemic treatment with anti-IFN-gamma were not completely unambiguous, we extended our investigations to IFN-gamma-receptor knock-out (KO) mice. Several parameters (i.e., macrophages, giant cells, T-cells, B-cells, granulocytes, expression of MHC class II, stroma formation, and degradation and calcification of the biomaterial) were compared between wild-type (WT) and KO mice. Remarkably, the foreign-body reaction was very similar in WT and KO mice. In both, giant cells were formed, but in contrast to previous results in AO rats, phagocytosis of HDSC bundles occurred hardly at all up to 9 weeks, and MHC class II expression was minimal. Stroma formation and vascularization were high and calcification occurred. T-cells comprised less than 1%; a few plasma cells were present in the KO mice at later time points. Granulocytes, mainly eosinophils, were present at all explantation time points. Because of the similar results in WT and KO mice, we question whether IFN-gamma plays a role at all in the foreign-body reaction in mice.

Syntrophin isoforms at the neuromuscular junction: developmental time course and differential localization

The syntrophins are a family of cytoplasmic adapter proteins that associate with dystrophin family proteins and have putative signaling and structural roles at the neuromuscular junction. We have localized the syntrophin family members within the rodent junction from birth to adulthood. Alpha-syntrophin is the only isoform on the postsynaptic membrane at birth. In the adult, it occurs on the crests of the junctional folds, with utrophin, and in the troughs, with dystrophin. Surprisingly, neuronal nitric oxide synthase (nNOS) does not accompany alpha-syntrophin onto the crests. Beta2-syntrophin, a junction-specific form, is not present at birth and occurs mainly in the troughs in the adult. Beta1-syntrophin is a sarcolemmal form at birth, not concentrated at the junction, and disappears entirely from most fibers by 6 weeks. In positive fibers, junctional beta1-syntrophin occurs exclusively in the troughs. These results suggest that the syntrophin isoforms have distinct functions at the junction and show that the known protein-protein associations of the syntrophins and nNOS in skeletal muscle are not sufficient to explain their localizations.