Substance P-immunoreactive sensory nerves in the lower respiratory tract of various mammals including man

Summary The occurrence and origin of substance P (SP)-immunoreactive (IR) nerves in the lower respiratory tract was studied by means of immunohistochemistry in the guinea-pig, rat, cat and man. In addition, biopsies from human material were also analysed by radioimmunoassay. SP-IR nerves were seen in four principal locations: 1) under or within the lining epithelium, 2) around blood vessels, 3) within the bronchial smooth muscle layer, and 4) around local tracheobronchial ganglion cells. Ligation experiments combined with capsaicin pretreatments indicated that all SP-IR nerves in the respiratory tract are sensory. The trachea seems to be mainly supplied by the vagal nerves, while intrapulmonary bronchi and blood vessels receive SP-IR nerves of both vagal and non-vagal (spinal) origin. SP-IR nerves were also found in the human bronchi with principally similar location as in the guinea-pig. The levels of SP-IR in the trachea and peripheral bronchi of man were about 3–4 pmol/g, which is in the same range as the content of corresponding tissues from the guinea-pig.In conclusion, the present experimental findings of SP-IR nerves in the lower respiratory tract in both experimental animals and man support the functional evidence for the importance of SP in the vagal and non-vagal (spinal) control of bronchial smooth muscle tone and vascular permeability.     

Occurrence and effects of multiple tachykinins; substance P, neurokinin A and neuropeptide K in human lower airways

In the present work we have studied the occurrence of different tachykinins (substance P (SP), neurokinin A (NKA) and neuropeptide K (NPK)) in human distal bronchi and pulmonary arteries by means of radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). We have also compared the biological effects of different tachykinins on isolated human bronchi and pulmonary arteries in vitro. The concentration of immunoreactive SP using antiserum SP2 in the pulmonary arteries was higher (1.34 +/- 0.15 pmol/g) than in the bronchi (0.56 +/- 0.05 pmol/g). The contents of other tachykinins than SP measured using antiserum K12 was on the other hand considerably higher in the bronchi (0.33 +/- 0.14 pmol/g) than in pulmonary arteries (0.13 +/- 0.02 pmol/g). Immunoreactive materials corresponding to SP, NKA and NPK were identified in bronchial extracts by RIA combined with HPLC, which also indicated the presence of an eledoisin (ELE)-like component. In vitro studies showed that NKA was the most potent of the tachykinins as a bronchoconstrictor agent, being several hundred-fold more active than SP, acetylcholine and histamine. NPK had an intermediate potency. The bronchoconstrictor effect of NKA was unaffected by atropine, mepyramine and cimetidine. The tachykinins SP and NKA had on the other hand, a rather equal potency in inducing relaxation of serotonin precontracted pulmonary arteries. In conclusion, multiple tachykinins are present in lower airways of man. These peptides exert different biological activities whereby NKA is a very active bronchoconstrictor agent compared to SP while both NKA and SP have rather similar relaxatory activities of vascular smooth muscle.     

Mortality after long-term exposure to radioactive Thorotrast: a forty-year follow-up survey in Sweden

To evaluate temporal patterns of cause-specific mortality after long-term exposure to the alpha-particle-emitting contrast medium Thorotrast, we investigated a cohort consisting of 693 Swedish patients with neurological disorders who received Thorotrast during cerebral angiography, with follow-up ending in 1993. Standardized mortality ratios (SMRs) were calculated as the ratio of observed cases in the cohort to expected cases in the general population. Persons exposed to Thorotrast had significant excesses of all causes of death (SMR = 2.8; 95% CI 2.5-3.0), with similar increases noted for men and women. The largest risks were observed for deaths from hematological causes (SMR = 16.4; n = 8), cerebrovascular diseases (SMR = 10.1; n = 18), gastrointestinal disorders including liver cirrhosis (SMR = 5.2; n = 36), and tumors (SMR = 4.7; n = 187). There was a significant decrease in SMR with time since injection for cerebrovascular and circulatory diseases, indicative of the impact of underlying neurological disorders. In contrast, the SMR increased significantly with time for tumors and gastrointestinal diseases, suggestive of a detrimental effect of cumulative radiation dose. A significant dose-response relationship was found for all causes of death and malignant tumors among all age groups, and since SMR increased with time for the latter category, this is consistent with an effect of cumulative radiation exposure on cancer development. However, the findings should be treated with caution, since selection bias may have influenced some of the results.     

Calcitonin gene-related peptide and the lung: neuronal coexistence with substance P, release by capsaicin and vasodilatory effect

The occurrence and distribution of calcitonin gene-related peptide (CGRP) in the lower airways was studied by means of immunohistochemistry and radioimmunoassay (RIA) in combination with high performance liquid chromatography (HPLC). CGRP-like immunoreactivity (-LI) was observed in nerves from the epiglottis down to peripheral bronchi in rat, cat and guinea pig and also in human bronchi. Double staining revealed colocalization of CGRP-LI and substance P (SP)-LI in cell bodies of nodose and jugular ganglia as well as in axons and nerve terminals of the airways. Systemic capsaicin pretreatment induced a marked loss of the CGRP- and SP-immunoreactive (-IR) nerves in the lower airways. CGRP-IR was also present in epithelial endocrine cells and neuroepithelial bodies. The content of CGRP-LI as measured with RIA in guinea pig bronchi was significantly lower after capsaicin pretreatment. Analysis of human bronchial extracts revealed that CGRP-LI coeluted with synthetic human CGRP on HPLC. In the isolated perfused guinea pig lung capsaicin exposure caused overflow of CGRP-LI suggesting release from peripheral branches of sensory nerves. Both in vivo experiments in the guinea pig measuring insufflation pressure as well as in vitro studies on isolated guinea pig and human bronchi showed that whereas tachykinins contracted bronchial smooth muscle no contractile or relaxing effect was elicited by human or rat CGRP. However, CGRP caused relaxation of serotonin precontracted guinea pig and human pulmonary arteries. In conclusion, the presence and release of CGRP-LI from capsaicin sensitive nerves in the lower airways adds another possible mediator, in addition to tachykinins, of vascular reactions upon sensory nerve irritation.     

Coexisting peptides in capsaicin-sensitive sensory neurons: release and actions in the respiratory tract of the guinea-pig

Release of substance P (SP) and neurokinin A (NKA), was demonstrated in the isolated perfused guinea-pig lung. Significant release was obtained by perfusion with capsaicin, high potassium, histamine, bradykinin dimethylphenylpiperazinium, and by electrical vagal nerve stimulation. Capsaicin-induced peptide release was not blocked by 1 microM clonidine. SP and NKA contracted respiratory smooth muscle, NKA being 42 times more potent. Both tachykinins were equipotent in relaxing pulmonary artery. It is concluded that multiple tachykinin can be released from capsaicin-sensitive sensory nerves in the respiratory tract, exerting multiple effects on the target tissues.     

Innervation of lower airways and neuropeptide effects on bronchial and vascular tone in the pig

Summary The occurrence and distribution of peptide-containing nerve fibres [substance P (SP), calcitonin gene-related peptide (CGRP), vasoactive intestinal polypeptide (VIP), peptide histidine isoleucine (PHI), neuropeptide Y (NPY)] and noradrenergic nerve fibres [tyrosine hydroxylase (TH)- and dopamine beta hydroxylase (DBH)-positive] in the airways of the pig were studied by means of immunohistochemistry. SP- and CGRP-immunoreactive (-IR) nerve fibres were present close to and within the lining respiratory epithelium, around blood vessels, within the tracheobronchial smooth muscle layer and around local tracheobronchial ganglion cells. The content of CGRP- and neurokinin A (NKA)-like immunoreactivity (-LI) measured by radioimmunoassay (RIA) was twice as high in the trachea compared to that in the peripheral bronchi. SP was a more potent constrictor agent than NKA on pig bronchi in vitro. CGRP had a relaxant effect on precontracted pig bronchi. On blood vessels CGRP exerted a relaxant effect that was more pronounced on pulmonary arteries than on bronchial arteries. VIP/PHI-IR fibres were seen in association with exocrine glands and in the tracheobronchial smooth muscle layer. VIP-positive nerve fibres were abundant around blood vessels in the trachea but sparse or absent around blood vessels in the peripheral bronchi. This histological finding was supported by RIA; it was shown that the content of peptides displaying VIP-like immunoreactivity (-LI) was 18 times higher in the trachea compared to peripheral bronchi. VIP was equally potent as CGRP in relaxing precontracted pig bronchi in vitro. Both bronchial and pulmonary arteries were relaxed by VIP. NPY was colocalized with VIP in tracheal periglandular nerve fibres and in nerve fibres within the tracheobronchial smooth muscle layer. NPY was also present in noradrenergic (DBH-positive) vascular nerve fibres. The content of NPY was much higher (15-fold) in the trachea compared to small bronchi. NPY caused a contraction of both pulmonary and bronchial arteries. The bronchial smooth muscle contraction to field stimulation in vitro was purely cholinergic. A non-cholinergic relaxatory effect following field stimulation was observed after bronchial precontraction. Capsaicin had no effect on pig bronchi in vitro.     

Co-existence of peptide HI (PHI) and VIP in nerves regulating blood flow and bronchial smooth muscle tone in various mammals including man

By immunohistochemistry it was found that PHI- and VIP-like immunoreactivity (-IR) occurred in the same autonomic neurons in the upper respiratory tract, tongue and salivary glands with associated ganglia in rat, guinea-pig, cat, pig and man. VIP- and PHI-like immunoreactivity was also found in similar locations in the human heart. The N-terminally directed, but not the C-terminally directed, PHI antiserum or the VIP antiserum stained endocrine cells in the pig duodenum. This suggests the existence of an additional PHI-like peptide. Ligation of nerves acutely caused marked overlapping axonal accumulations of PHI- and VIP-IR central to the lesion. Two weeks after transection of the nerves, both types of immunoreactivities were still observed in accumulations both in the axons as well as in the corresponding cell bodies. The levels of PHI- and VIP-IR in normal tissues from the cat were around 10-50 pmol/g with a molar ratio of about 1 to 2. Systemic administrations of PHI and VIP induced hypotension, probably due to peripheral vasodilation in both guinea-pig and cat. Furthermore, both PHI and VIP caused an inhibition of the vagally induced increase in respiratory insufflation pressure in guinea-pig. PHI and VIP relaxed the guinea-pig trachea in vitro, suggesting a direct action on tracheobronchial smooth muscle. VIP was about 5-10 times more potent than PHI with regard to hypotensive effects and 2-3-fold, considering respiratory smooth muscle-relaxant effects in the guinea-pig. PHI was about 50-fold less potent to induce hypotension in the cat than in the guinea-pig. Although species differences seem to exist as regards biological potency, PHI should also be considered when examining the role of VIP as an autonomic neurotransmitter.