Morphological evidence for existence of IL-6 receptor alpha in the glomus cells of rat carotid body

The carotid body (CB) senses changes in arterial blood PO2 and modulates respiratory movement. It is generally accepted that the dopaminergic type I cells in the CB are chemoreceptors. However, it has not been clarified whether the carotid body has the ability to perceive the stimulation of proinflammatory cytokines. Interleukin 6 (IL-6) as a multifunctional cytokine plays a pivotal role in host defense mechanism. In the present study, we observed the expression of IL-6Ralpha mRNA and protein in the carotid body using immunohistochemistry, Western blots, and in situ hybridization. The results confirmed the presence of IL-6Ralpha proteins and mRNAs in the glomus cells of rat carotid body. These results suggest that the function of the carotid body may be influenced by the proinflammatrory cytokines through their receptors.

Adrenomedullin immunoreactivity in the human carotid body

We studied by immunocytochemistry the expression of AM in human carotid bodies, sampled at autopsy from 16 adult subjects (mean age+/-S.D.: 44.3+/-3.4 years) and from six fetuses (mean gestational age+/-S.D.: 167+/-11 days). No AM immunoreactivity was visible in the type II cells of both series. The percentage of immunoreactive type I cells was higher in the adult subjects (32.3+/-7.7%) with respect to the fetuses (11.8+/-2.7%, P < 0.001). Dark cells showed a higher percentage of positive immunoreaction with respect to light cells, both in adult subjects (61.7+/-13.4% versus 19.2+/-5.2%) and in fetuses (25.3+/-4.4% versus 6.2+/-2.0%). AM may play a role in the regulation of chemoreceptor discharge through paracrine releasing action and/or vasodilator effect. The low expression of AM in fetuses may be ascribed to the absence of pulmonary respiration with lack of regulatory role of the carotid body during the prenatal period.

Atrial natriuretic peptide increases cyclic guanosine monophosphate immunoreactivity in the carotid body

The mammalian carotid body is a peripheral arterial chemoreceptor organ involved in the regulation of respiration, and in the modulation of blood pressure through reflex control of peripheral vascular resistance and cardiac output. In addition to its responsiveness to blood gases, the organ is also sensitive to hyperosmotic solutions, and we have recently shown that a systemic hormonal regulator of natriuresis and diuresis, atrial natriuretic peptide, is a potent inhibitor of chemoreceptor activity evoked by hypoxia in the cat carotid body. The present study demonstrates atrial natriuretic peptide immunoreactivity in type I cells of the carotid body, and shows further that a biologically active atrial natriuretic peptide fragment, atriopeptin III, increases cyclic guanosine monophosphate immunoreactivity in type I cells in a dose-dependent manner. Moreover, double-labeling techniques demonstrate co-existence of atrial natriuretic peptide immunoreactivity with the atriopeptin III-enhanced cyclic guanosine monophosphate reaction product. These findings indicate the probable existence of atrial natriuretic peptide receptors coupled to membrane-bound guanylate cyclase on the parenchymal type I cells. Our findings support the view that cyclic guanosine monophosphate functions as a second messenger in this organ, and may serve as a functional activity marker in identifying type I cells which respond to atrial natriuretic peptide.

Chemoreceptor A-fibres in the human carotid body contain tyrosine hydroxylase and neurofilament immunoreactivity

Previous retrograde tracing studies on rat and guinea-pig showed a projection of sensory tyrosine hydroxylase-immunoreactive neurons to the region of the carotid bifurcation via the carotid sinus nerve. In the present study, focussing on the sensory innervation of the human carotid body, antisera to tyrosine hydroxylase and other catecholamine synthesizing enzymes were applied for an immunohistochemical investigation of carotid bodies obtained at autopsy. In addition, an array of antisera directed to non-enzyme antigens known to be present in viscero-afferent neurons were incorporated in the study. The glomic lobules consisting of glomus cells and sustentacular cells contained a variable number of enzyme-immunoreactive glomus cells. Arteries were supplied by nerve fibres displaying the full phenotype of sympathetic noradrenergic axons, i.e. immunoreactivity to tyrosine hydroxylase, aromatic-L-amino-acid-decarboxylase and dopamine-beta-hydroxylase. The glomic lobules, however, were densely innervated by tyrosine hydroxylase-immunoreactive axons lacking immunoreactivity to aromatic-L-amino-acid-decarboxylase and dopamine-beta-hydroxylase. These fibres reacted with neurofilament 160kD-antibody but were devoid of immunoreactivity to all neuropeptides tested (calcitonin gene-related peptide, somatostatin, substance P). Ultrastructurally, tyrosine hydroxylase/neurofilament 160kD-immunoreactive axons gave rise to large axonal swellings filled with mitochondria and vesicles, and established extensive contacts to glomus cells. Nerve bundles surrounded by a perineural sheath contained both myelinated (2.0-2.8 microns in diameter) and unmyelinated (0.14-3.0 microns) tyrosine hydroxylase-immunoreactive axons. Most of the unmyelinated immunoreactive axons were running singularly within a Schwann cell-sheath. Judged from the pattern of immunoreactivities as well as their preterminal and terminal ultrastructure, tyrosine hydroxylase-immunoreactive axons innervating glomus cells are of sensory origin. Although final proof by retrograde tracing cannot be presented in man, this conclusion is supported by experimental evidence in laboratory animals. The myelinated immunoreactive axons correspond to chemoreceptor A-fibres whereas the classification of the large unmyelinated immunoreactive axons has yet to be established. The lack of immunoreactivity to the dopamine-synthesizing enzyme, aromatic-L-amino-acid-decarboxylase, in this fibre type does not support the view of dopamine being the primary transmitter of chemoreceptor afferents.

Calcitonin gene-related peptide immunoreactivity in the nucleus of the tractus solitarius and the carotid receptors of the cat originates from peripheral afferents

The presence and distribution of the calcitonin gene-related peptide was studied, using immunohistochemical techniques, in carotid receptors, in the nodose and glossopharyngeal ganglia and in the nucleus tractus solitarii of the cat. Seventy-seven per cent of the 42% of the nodose ganglion cells were labeled. Fine, sparsely branched immunoreactive terminal axonal arborizations were found in the carotid body; they disappeared after petrosal ganglionectomy. The intense immunoreactivity present in fibers in the commissural, medial, interstitial, gelatinosus, dorsal, intermediate and rostral gustatory subnuclei of the nucleus tractus solitarius was drastically reduced after removal of the ipsilateral nodose and petrosal ganglia. The central distribution of the immunoreactive axons, the morphology of the terminals in the carotid receptors and their dependence on an intact peripheral innervation are consistent with the idea that in the cat the calcitonin gene-related peptide is present in a high proportion of the primary visceral afferents, most of them unmyelinated.

Distribution of serotonin-immunoreactive cells around arteries arising from the common carotid artery in the chicken

By using an immunoperoxidase method with antiserotonin antiserum, the distribution of serotonin-immunoreactive cells in the carotid body region was investigated in chickens. The thyroid gland, cranial and caudal parathyroid glands, carotid body, and ultimobranchial gland of chickens were located along the common carotid artery as a continuous series and were supplied with branches arising from the artery. Almost all chief cells of the chick carotid bodies were immunoreactive for serotonin. Furthermore, numerous serotonin-immunoreactive cells were widely distributed in the adventitial connective tissue around those arteries that issued from the common carotid artery to supply each endocrine organ, i.e., the carotid body artery, the esophagotracheobronchial artery, the ascending esophageal artery, and the inferior thyroid artery. These arteries usually arose by one trunk from the lateral aspect of the middle portion of the common carotid artery. The serotonin cells were most numerous around the carotid body artery and were dispersed along the whole length of the artery. In addition, they were detected around the common trunk of each artery and the roots of the ascending esophageal artery, the inferior thyroid artery, and the esophagotracheobronchial artery. The serotonin cells were also distributed in the tunica media of the common carotid artery. In that place, they were concentrated around the origin of the common trunk of each artery and were scattered below the origin along the longitudinal axis and on the opposite side of the origin. The serotonin-immunoreactive cells distributed around and in the arteries may be involved in the control of blood flow and may have chemoreceptive properties.

Chronic carotid glomitis

Both carotid bodies were obtained at necropsy from each of 75 subjects, 38 male and 37 female, ranging in age from 14 to 90 years. In each case the histological features were classified as one of four age-related patterns. The presence and distribution of lymphocytes were noted. They presented either as a diffuse scattering throughout the stroma or as large focal aggregates. In subjects over the age of 50 years the diffuse infiltrates occurred in 56% of cases and were virtually all T-cells. In the same age group the aggregates of lymphocytes were found in 21% of cases. These findings indicate that there is a disease of human carotid bodies characterized by focal aggregates of lymphocytes that begins in middle age and becomes increasingly common with advancing years, affecting 29% of subjects aged 70 years or over. It is not related to any co-existing disease but seems to be a response to the degenerative changes in the glomic tissues that occur with age. By analogy with comparable changes in the thyroid and salivary glands, the disease may have a basis in auto-immunity.

Immunocytochemical demonstration of IGF-II-like immunoreactivity in human paraganglioma of the craniocervical region

Insulin-like-growth factor (IGF)-II-like immunoreactivity was examined in two carotid bodies and six extra-adrenal paragangliomas with use of monoclonal antibody against rat IGF-II, which crossreacts with human IGF-II. Chief cells but not sustentacular cells of the carotid body were positive at about 10% in one case and less than 1% in another case. Among four carotid body tumours, a possible vagal body tumour and one glomus jugulare tumour, all but the glomus jugulare tumour exhibited positive tumour cells irrespective of histological variations. The frequency of positive cells ranged from 20 to 60%. IGF-II like immunoreactivity, therefore, might be widely distributed in human extra-adrenal paraganglionic tissues and tumours, although its biological role in these cells remains to be elucidated.

Retrograde neuronal labelling and double-staining immunohistochemistry of tachykinin- and calcitonin gene-related peptide-immunoreactive pathways in the carotid sinus nerve of the guinea pig

The origin of tachykinin- and calcitonin gene-related peptide-like immunoreactive (CGRP-LI) nerve fibres in the guinea pig carotid body and carotid sinus was determined by retrograde labelling of the carotid sinus nerve with Fluoro-gold and immunohistochemical double staining with fluorescein- and rhodamine-conjugated second antisera. Fluoro-gold-labelled perikarya with characteristic features of primary sensory neurones were numerous in the glossopharyngeal (petrosal) ganglion and occurred rarely in the closely attached superior vagal (jugular) ganglion. An efferent pathway from the brainstem could not be detected. Co-existence of tachykinin- and CGRP-LI was observed in 25-47% of labelled sensory neurones; less than 1% of Fluoro-gold-containing perikarya were exclusively stained by CGRP antiserum. Co-existence of tachykinin- and CGRP-LI was also demonstrated in nerve fibres of the carotid body and carotid sinus. Somatostatin-, cholecystokinin- and dynorphin-LI did not co-exist with tachykinin-LI in these fibres. Thus, tachykinin/CGRP-LI fibres in the carotid presso- and chemoreceptive areas exhibit a peptide pattern being generally characteristic for sensory fibres supplying great vessels in the guinea pig. In view of the present findings doubt is raised as to a primary involvement of these fibres in presso- or chemoreception, although a modulatory influence on these specific functions appears to be likely.

Bombesin/gastrin-releasing peptide (GRP)- and Met5-enkephalin-Arg6-Gly7-Leu8-like immunoreactivities in small intensely fluorescent (SIF) cells and nerve fibers of rat sympathetic ganglia

Superior cervical and hypogastric ganglia were removed from rats that had been perfused with a mixture of 4% paraformaldehyde and 0.25% glutaraldehyde. Specific antisera against Met5-enkephalin-Arg6-Gly7-Leu8 (MEAGL) and bombesin/gastrin-releasing peptide (BN/GRP) were used in the immunofluorescence procedure. In hypogastric ganglia, a subpopulation of small intensely fluorescent (SIF) cells, as identified by their aqueous aldehyde (Faglu)-induced fluorescence, showed MEAGL- and BN/GRP-like immunolabeling. SIF cells in the superior cervical ganglia were unlabeled. In both ganglia, varicose nerve fiber networks and nerve terminals surrounding principal ganglion cells showed MEAGL- and BN/GRP-like immunoreactivities. Unlabeled SIF cells often were in close contact with nerve fibers that had MEAGL-like immunolabeling. Immunoreactivities against MEAGL- and BN/GRP-like neuropeptides in nerve fibers and terminals suggest a neurotransmitter or neuromodulator role for these peptides. In addition, labeling in SIF cells implies their possible endocrine function.

Localization of enkephalin-like immunoreactivity in the cat carotid and aortic body chemoreceptors

The purpose of this study was to determine if enkephalin-like immunoreactivity was present in the glomus cells of the carotid and aortic body peripheral arterial chemoreceptors. Cat carotid and aortic bodies were reacted with antisera to met- and leu-enkephalin using the indirect peroxidase-antiperoxidase immunocytochemical method of Sternberger (1979). Both the carotid and aortic bodies demonstrated clusters of immunoreactive cells for both met- and leu-enkephalin. Additionally, met-enkephalin-like immunoreactivity was observed in many of the dense-core vesicles of the glomus cells of the carotid body. The glomus cells of these chemoreceptors are known to contain catecholamines which may modulate chemoreceptor activity. The presence of opioid peptide-like substances co-existing with the glomus cell catecholamines, perhaps in the same vesicles, may have important implications for a trophic influence of these peptides on glomus cell chemoreceptor modulation.