Distribution, chemical coding and origin of nitric oxide synthase-containing nerve fibres in the guinea pig nasal mucosa

Nitrergic perivascular innervation in health and diseases: Focus on vascular tone regulation

For a long time, the vascular tone was considered to be regulated exclusively by tonic innervation of vasoconstrictor adrenergic nerves. However, accumulating experimental evidence has revealed the existence of nerves mediating vasodilatation, including perivascular nitrergic nerves (PNN), in a wide variety of mammalian species. Functioning of nitrergic vasodilator nerves is evidenced in several territories, including cerebral, mesenteric, pulmonary, renal, penile, uterine and cutaneous arteries. Nitric oxide (NO) is the main neurogenic vasodilator in cerebral arteries and acts as a counter-regulatory mechanism for adrenergic vasoconstriction in other vascular territories. In the penis, NO relaxes the vascular and cavernous smooth muscles leading to penile erection. Furthermore, when interacting with other perivascular nerves, NO can act as a neuromodulator. PNN dysfunction is involved in the genesis and maintenance of vascular disorders associated with arterial and portal hypertension, diabetes, ageing, obesity, cirrhosis and hormonal changes. For example defective nitrergic function contributes to enhanced sympathetic neurotransmission, vasoconstriction and blood pressure in some animal models of hypertension. In diabetic animals and humans, dysfunctional nitrergic neurotransmission in the corpus cavernosum is associated with erectile dysfunction. However, in some vascular beds of hypertensive and diabetic animals, an increased PNN function has been described as a compensatory mechanism to the increased vascular resistance. The present review summarizes current understanding on the role of PNN in control of vascular tone, its alterations under different conditions and the associated mechanisms. The knowledge of these changes can serve to better understand the mechanisms involved in these disorders and help in planning new treatments.

Breath biomarkers in diagnosis of pulmonary diseases

Breath analysis provides a convenient and simple alternative to traditional specimen testing in clinical laboratory diagnosis. As such, substantial research has been devoted to the analysis and identification of breath biomarkers. Development of new analytes enhances the desirability of breath analysis especially for patients who monitor daily biochemical parameters. Elucidating the physiologic significance of volatile substances in breath is essential for clinical use. This review describes the use of breath biomarkers in diagnosis of asthma, chronic obstructive pulmonary disease (COPD), cystic fibrosis (CF), lung cancer, as well as other pulmonary diseases. A number of breath biomarkers in lung pathophysiology will be described including nitric oxide (NO), carbon monoxide (CO), hydrogen peroxide (H₂O₂) and other hydrocarbons.

Minimally invasive application of botulinum toxin A in patients with idiopathic rhinitis

Background

Nasal hypersecretion due to idiopathic rhinitis can often not be treated sufficiently by conventional medication. Botulinum toxin A (BTA) has been injected into the nasal mucosa in patients with nasal hypersecretion with a reduction of rhinorrhea lasting for about 4 to 8 weeks. Since the nasal mucosa is well supplied with glands and vessels, the aim of this study was to find out if the distribution of BTA in the nasal mucosa and a reduction of nasal hypersecretion can also be reached by a minimally invasive application by sponges without an injection.

Methods

Patients were randomly divided into two groups. The effect of BTA (group A, C, D) or saline as placebo (group B) was investigated in 20 patients with idiopathic rhinitis by applying it with a sponge soaked with BTA (40 units each nostril) or saline. Subgroups C and D contained these patients of group A and B who did not improve in symptoms one week after the original treatment (either BTA or saline) who then received the alternative medication. Changes of symptoms (rhinorrhea, nasal obstruction) were scored by the patients in a four point scale and counted (consumption of tissues, sneezing) in a diary. The patients were followed up weeks 1, 2, 4, 8 and 12.

Results

There was a clear reduction of the amount of secretion in group A compared to group B, C and D. This did not correlate with the tissue consumption, which was comparably reduced in group A and B, but reduced less in group C and D. Sneezing was clearly reduced in group A but comparably unchanged in group B and C and increased in group D. Nasal congestion remained unchanged.

Conclusion

In some patients with therapy-resistant idiopathic rhinitis BTA applied with a sponge is a long-lasting and minimal invasive therapy to reduce nasal hypersecretion.

Ultrastructural detection of nitric oxide in human nasal mucosa

OBJECTIVE

Nasal vasculature and seromucous glands are exposed to complex mechanisms influenced by external as well as internal stimuli. In addition to classic and peptidergic neurotransmitters, nitric oxide (NO) was increasingly found to be important in the control of various physiologic functions. NO modulates nasal immunology, influences macrophage activity, and has antiviral and bacteriostatic properties. The aim of this study was to show the localization of nitric oxide synthases (NOS) I and III in the normal human nasal mucosa by using immunoelectron microscopical techniques.

STUDY DESIGN

Specimens of noninflammed inferior turbinates from 35 patients who underwent nasal surgery were fixed in phosphate-buffered glutaraldehyde. After dehydration, incubation in unicryl and polymerization, ultrathin sections were cut. Primary antibodies against NOS I and III were applied and the immunocomplexes were visualized by an immunocytochemical staining-technique using gold-labeled antibodies. Immunostained structures were photodocumented using a transmission electron microscope.

RESULTS

NOS-immunoreactive nerve fibers were mainly co-located in parasympathetic nerves in the adventitia of arterial vessels and in periglandular axons. Electron microscopy showed that NOS-positive axons were in close contact with acinus cells. A strong NOS III-immunoreactivity was found in endothelial cells of capillaries near the glands as well as in arterial vessels. Furthermore, immunoreaction products were deposited throughout the cytoplasm of fibroblasts.

CONCLUSION

Nitric oxide in nerve fibers, seromucous glands, and endothelial cells of capillaries and arterial vessels suggest that NO takes part in the regulation of physiologic processes of the human nasal mucosa. NOS was co-localized in parasympathetic nerves and plays a role in the neurotransmission and neuromodulation of the vascular tone and glandular secretion. Arteries showed a distinctly developed nitrergic innervation and endothelial accumulation. The NO production in axons of the adventitia and in the endothelium of arteries demonstrated that these vessels are influenced by a dual NO system. NO could mainly act on these structures with vasodilatatory effects. Finally, NO would be able to influence the functions of perivascular fibroblasts.

Neuronal nitric oxide synthase-immunoreactivity. A neuromodulating system independent of peripheral nasal gland denervation in guinea pig nasal mucosal tissue after treatment with botulinum toxin type A

The influence of botulinum toxin type A (BTA) on cellular mechanisms has not been studied in much detail. Since nitric oxide (NO) is of increasing interest as a neuromodulator in the innervation of the nose, its localization was examined in the nasal mucosa of guinea pigs treated with BTA or saline. Neuronal nitric oxide synthase-immunoreactivity (nNOS-IR) was found around vessels and nasal glands. Immunoreactivity was seen in the respiratory epithelium, in the periost and the osteocytes of the turbinate bone. A distinct interindividual difference in the strength of nNOS-IR was obvious among the animals, but there was no difference in the strength of immunoreactivity between the animals treated with BTA or saline. NO might therefore contribute to the regulation of vascular tone, glandular function, respiratory epithelial cell function and bone metabolism. BTA does not seem to influence the processes regulated and modulated by NO. This may represent a benefit for the application of BTA.

Neurology of allergic inflammation and rhinitis

Afferent nerves, derived from the trigeminal ganglion, and postganglionic autonomic nerves, derived from sympathetic and parasympathetic ganglia expressing many different neurotransmitters, innervate the nose. Reflexes that serve to optimize the air-conditioning function of the nose by altering sinus blood flow, or serve to protect the nasal mucosal surface by mucus secretion, vasodilatation, and sneezing, can be initiated by a variety of stimuli, including allergen, cold air, and chemical irritation. Activation of nasal afferent nerves can also have profound effects on respiration, heart rate, blood pressure, and airway caliber (the diving response). Dysregulation of the nerves in the nose plays an integral role in the pathogenesis of allergic rhinitis. Axon reflexes can precipitate inflammatory responses in the nose, resulting in plasma extravasation and inflammatory cell recruitment, while allergic inflammation can produce neuronal hyper-responsiveness. Targeting the neuronal dysregulation in the nose may be beneficial in treating upper airway disease.

Expression of immunoreactivity to neurokinin-1 receptor by subsets of cranial parasympathetic neurons: correlation with neuropeptides, nitric oxide synthase, and pathways

We examined the patterns of coexistence of immunoreactivity to the neurokinin-1 (NK(1)) tachykinin receptor, nitric oxide synthase, and neuropeptides in the sphenopalatine and otic ganglia of guinea pigs using a combination of multiple-labeling immunohistochemistry and pathway tracing in vitro. Most neurons had immunoreactivity to vasoactive intestinal peptide (85-96%) and neuropeptide Y (60%). Subpopulations of vasoactive intestinal peptide-immunoreactive neurons also had immunoreactivity to nitric oxide synthase (37-48%) or enkephalin (25-35%), but these formed mutually exclusive populations. Almost all neurons expressing NK(1) receptor immunoreactivity contained immunoreactivity to enkephalin, vasoactive intestinal peptide, and neuropeptide Y, but not nitric oxide synthase. Using a combination of retrograde axonal tracing and axonal crushing, we found that most neurons with immunoreactivity to nitric oxide synthase projected along the nasopalatine and ethmoidal nerves to the nasal mucosa. In contrast, most neurons with immunoreactivity to enkephalin followed the zygomatic nerve to the facial skin and lacrimal gland. Based on their peptide content, we conclude that the neurons with immunoreactivity to enkephalin and NK(1) receptor projected selectively to the skin. In both the sphenopalatine and the otic ganglia, about half of the neurons with NK(1) receptor immunoreactivity were surrounded by varicose nerve fibers with substance P immunoreactivity. Many of these fibers are likely to have originated in the trigeminal ganglion. Taken together, these observations establish a strong anatomical basis for a range of interactions between trigeminal and cranial parasympathetic pathways that may underlie pathophysiological conditions such as trigeminal neuralgia.

Botulinum toxin type A induces apoptosis in nasal glands of guinea pigs

Nasal hypersecretion is predominantly caused by overaction of nasal glands, which are mainly under cholinergic control. In this work, we investigated the influence of botulinum toxin A (BTA) on the nasal mucosal tissue of the maxillary sinus turbinates of guinea pigs (n = 10) that were painlessly sacrificed 10 days (short-term group) or 3 months (long-term group) after local treatment with 20 units of BTA (Botox) or 0.2 mL of 0.9% sodium chloride (control). Histologic investigation of the nasal mucosal tissue of the BTA-treated animals (short-term group) showed degeneration of glands and ducts and apoptotic nuclei on TUNEL staining of these structures. The control animals revealed normal glandular tissue and no apoptosis. The animals of the long-term group showed almost normal glandular tissue and only a few apoptotic nuclei. In conclusion, BTA induces temporary apoptosis in the nasal glandular compartment of guinea pigs.