Anders Ottosson

Release of Histamine from Dural Mast Cells by Substance P and Calcitonin Gene-Related Peptide

The aim of the present study was to examine if the neuropeptides substance P (SP), calcitonin gene-related peptide (CGRP), neuropeptide Y (NPY) and vasoactive intestinal peptide (VIP) can stimulate histamine release from mast cells in the dura mater and thereby play a role in cranial vasoregulation and local neurogenic inflammation. Dura mater mast cells were compared with peritoneal mast cells in the rat. Histamine was released from dura mater mast cells by compound 48/80, SP and CGRP but from peritoneal mast cells only by compound 8/80 and SP. NPY and VIP released quite small amounts of histamine from dural mast cells. The release on SP and CGRP from rat dura mater mast cells was blocked by the receptor antagonists FK888 and CGRP8-37 respectively, suggesting receptor mediated release mechanisms. None of the stimuli released histamine from human or porcine dural mast cells, possibly because the sampling procedure injures and incapacitates the cells.

Distribution and effects of neuropeptide Y, vasoactive intestinal peptide, substance P, and calcitonin gene-related peptide in human middle meningeal arteries: Comparison with cerebral and temporal arteries

A sparse to moderate supply of nerve fibers containing neuropeptide Y-like immunoreactivity (NPY-LI), vasoactive intestinal polypeptide (VIP-LI), substance P (SP-LI), and calcitonin gene-related peptide (CGRP-LI) was demonstrated in the walls of human middle meningeal arteries. Comparison with similar studies on human cerebral and temporal arteries indicated a similar distribution and density. The immunoreactive material in all three arterial regions was characterized by reversed-phase high pressure liquid chromatography (HPLC) and radioimmunoassay (RIA). The major peak of NPY-LI, VIP-LI, SP-LI, and CGRP-LI in each extract eluted approximately with the same elution volume as that of the corresponding synthetic analogues. The concentration of NPY in the middle meningeal arteries was lower as compared to the temporal arteries. Low concentrations of SP-LI and CGRP-LI were found in the middle meningeal arteries as compared to the cerebral arteries. In isolated ring segments of human middle meningeal and cerebral arteries, NPY caused vasoconstriction but did not potentiate the contractile response of noradrenaline. In the temporal artery, NPY did not induce contraction but potentiated the vasoconstrictor response to noradrenaline. Vasoactive intestinal polypeptide, peptide histidine methionine-27, SP, neurokinin A, and CGRP relaxed all three types of cephalic arteries. The peptide effects were not antagonized by propranolol, atropine, or cimetidine. Comparison of the responses to VIP and SP of vessels from the different regions showed a similar pattern of reactivity. The response to SP was slightly (p less than 0.05) more potent, whereas the responses to CGRP were less potent in the middle meningeal as compared to that in cerebral (p less than 0.005) vessels.

Role of endothelium and nitric oxide in histamine‐induced responses in human cranial arteries and detection of mRNA encoding H1‐ and H2‐receptors by RT‐PCR

Histamine induces relaxation of human cranial arteries. Studies have revealed that the relaxant histamine H1‐receptor predominates in human cerebral and the H2‐receptor in temporal arteries, while H1‐ and H2‐receptors are of equal importance in the middle meningeal artery. The purpose of the present study was to examine the role of the endothelium and nitric oxide in histamine‐induced responses and to show the presence of mRNA encoding H1‐ and H2‐receptors in human cranial arteries. Electrophoresis of polymerase chain reaction (PCR) products from human cerebral, middle meningeal and temporal arteries, demonstrated products corresponding to mRNA encoding both H1‐ and H2‐receptors in arteries with and without endothelium. The amplified PCR products were sequenced and showed 100% homology with the published sequences of these histamine receptors. A sensitive in vitro system was used to study vasomotor responses to histamine. In precontracted cerebral, middle meningeal and temporal arteries with and without endothelium, histamine caused a concentration‐dependent relaxation with Imax values between 87% and 81% and pIC50 values between 8.14 and 7.15. In arteries without endothelium the histamine‐induced relaxation was significantly less potent (Imax values between 87% and 66% and pIC50 values between 7.01 and 6.67) than in cranial arteries with an intact endothelium. The addition of histamine to arteries without endothelium and pretreated with the histamine H2‐antagonist, cimetidine (10−5 M), caused a concentration‐dependent contraction of the cranial arteries with Emax values between 86% and 29% and pEC50 values between 7.53 and 6.77. This contraction was blocked by the histamine H1‐receptor antagonist, mepyramine (10−7 M), and even turned into a relaxation with Imax values between 84% and 14% and pIC50 values between 7.42 and 5.86. The nitric oxide synthase inhibitor NG‐nitro‐L‐arginine methyl ester (L‐NAME, 3×10−5 M) significantly inhibited the relaxant response to histamine in cerebral and temporal arteries (pIC50 values between 7.43 and 7.13). The combined treatment with L‐NAME (3×10−5 M) and cimetidine (10−5 M) caused a further displacement of the concentration‐response curve (pIC50 values between 7.14 and 6.57) and decreased the maximum relaxant responses in all three cranial arteries (Imax values between 62% and 39%). In conclusion, this is the first study which show mRNA encoding histamine H1‐ and H2‐receptors in human cranial arteries. The results indicate that histamine‐induced relaxation of human cranial arteries is partially mediated via an endothelial H1‐receptor coupled to the production of nitric oxide and partially via a H2‐receptor associated with the smooth muscle cells. In addition, there is evidence for a contractile H1‐receptor in the smooth muscle cells in these arteries.

Characterization of histamine receptors in isolated human cerebral arteries.

1 The subtypes of histamine‐receptors which mediate dilatation of small human cerebral arteries have been characterized in vitro using ‘selective’ agonists and antagonists. 2 Dilator responses were studied after preconstriction with prostaglandin F2α, since contraction was not seen with histamine concentrations up to 10−4 m. Histamine caused a concentration‐related relaxation of cerebral vessels with an IC50 value of 5.2 ± 1.6 × 10−8 m. 3 Mepyramine caused a parallel shift to the right of the histamine concentration‐response curve whereas cimetidine was without observable effect. This suggests the presence of histamine H1‐receptors only. However, combined treatment with mepyramine and cimetidine caused a more marked displacement of the concentration‐response curve to the right. Schild analysis indicated that in situations of near complete blockade of either of the histamine receptor subtypes, simple competitive antagonism both at H1‐ and H2‐receptors can be revealed with a pA2 value of 8.64 for mepyramine and a pA2 value of 6.52 for cimetidine. 4 The ‘selective’ H1‐receptor agonists pyridylethylamine, 2‐methylhistamine (2‐Me‐histamine) and thiazolylethylamine, and the H2‐receptor agonists dimaprit, impromidine and 4‐methylhistamine (4‐Me‐histamine) all mimicked the histamine response, but were less potent than histamine. The order of potency was thiazolylethylamine > dimaprit > impromidine > 2‐Me‐histamine > pyridylethylamine > 4‐Me‐histamine. 5 These results indicate that the histamine‐induced dilatation in small human cerebral arteries is mediated by both H1‐ and H2‐receptors and that the former subtype of histamine receptor predominates.

Contractile endothelin-B (ETB) receptors in human small bronchi

Endothelins (ETs) are a family of novel regulatory peptides and various lines of evidence suggest an important role for ETs in regulating pulmonary function. Two receptors for endothelin, ETA and ETB, have been found in the human lung, and according to recent studies a non-ETA receptor seems to mediate the contraction of large sized human bronchi. Several studies have emphasized the importance of small bronchi in the pathogenesis of airway disease. In the present paper, improved methodology was used which enables in vitro studies of small human bronchi down to a diameter of 0.5-1.0 mm. Using the new methodology we have tried to further characterize this receptor. Small bronchi from the distal parts of the bronchial tree were obtained from pulmonary tissue removed from 15 patients with lung cancer. They were dissected and cut into ring segments, in which isometric tension was recorded. ET-1, ET-2 and ET-3 elicited strong concentration-dependent contractions of the human small bronchus. Basically, the three peptides were equipotent with about the same maximal response. Upon reapplication, they all showed the same tachyphylaxis pattern, reaching half the initial contraction. Comparative analysis of IRL 1620, a selective ETB receptor agonist, revealed that the effect of the ETB agonist was, in all respects, similar to the responses induced by the ETs. PD 145065, a combined ETA/ETB receptor antagonist competitively inhibited the contractions induced by IRL 1620, whereas FR139317, a selective ETA receptor antagonist, was without effect. In conclusion, the present study shows that accurate measurements can be made in vitro on small human bronchi and all present data are in favour of an ETB receptor mediating endothelin-induced contraction of human bronchi smaller than 1.0 mm.

Histamine Receptors in the Isolated Human Middle Meningeal Artery. A Comparison with Cerebral and Temporal Arteries

The subtypes of histamine receptors mediating dilatation of human meningeal arteries have been tested in vitro, using “selective” antagonists, and compared with cerebral and temporal arteries previously examined. Dilatory responses were tested after preconstriction with prostaglandin F2a. Both mepyramine and cimetidine caused a parallel shift to the right of the histamine concentration-response curve, suggesting the presence of both H1- and H2- receptors. Combined treatment with mepyramine and cimetidine caused further displacement of the concentration-response curve to the right. Schild analysis indicated pA2 values of 6.3 for cimetidine and 9.8 for mepyramine in situations of near complete blockade of either of the receptors. Both H1- and H2- receptors seem of importance for the histamine-induced dilatation in meningeal arteries and neither appear to dominate. The data considered in conjunction with our previous findings support the finding that experimental histamine-induced headache due to vasodilatation is intracranial of origin.

Demonstration of Perivascular Peptides and Changes in Concentration with Age in Man

By immunocytochemistry, human cerebral arteries have been found to be invested by perivascular fibres which contain neuropeptide Y, substance P and vasoactive intestinal polypeptide (VIP). The concentrations of the peptides are comparable for substance P and VIP, whereas that of neuropeptide Y is much higher. A marked reduction in radioimmunoassayable peptide levels was observed with advancing age of the patients.

Analysis of pre-hospital rescue times on mortality in trauma patients in a Scandinavian urban setting

Objective To analyze if pre-hospital rescue times were associated with mortality in a trauma cohort arriving by ambulance to hospital in a Scandinavian urban setting. Methods Between 2011 and 2013, individuals and pre-hospital rescue times were identified in Emergency Medical Dispatcher Centre, hospital, and forensic records in red alarm trauma. Major trauma was defined as a New Injury Severity Score (NISS)>15. Results Overall, 89% of 378 trauma patients received hospital care within 60 min; 51% had a response time of ≤8 min, and 95% had response time within ≤20 min. The on-scene time (p < 0.05) and total pre-hospital time (p < 0.05) were longer for patients ≥65 years, in comparison with patients <65 years. The patients with penetrating trauma had shorter on-scene time (p < 0.01), total pre-hospital time (p < 0.01), and shorter transport distance from trauma scene to hospital (p = 0.004), compared to those with blunt trauma. Patients with NISS > 15 were found to have the same pre-hospital rescue times as those with NISS ≤ 15. There was a trend that the occurrence of gunshots was associated with increased mortality (p = 0.074). When entering age, NISS, penetrating versus blunt injury, response time, and on-scene time in a multivariate regression analysis, age (p < 0.001), NISS (p < 0.001), and penetrating injury (p = 0.009) remained as independent factors associated with mortality and a trend for shorter on-scene time (p = 0.093). Conclusions Pre-hospital rescue times had less impact on mortality than injury severity, age, and penetrating trauma. Even though penetrating traumas were associated with shorter on-scene time and shorter transport distance to hospital, mortality was increased in this Scandinavian urban setting.

Postmortem heart weight modelled using piecewise linear regression in 27,645 medicolegal autopsy cases

The interpretation of postmortem heart weight is often difficult, and references for normal heart weight are important. However, to assess the cause of death at a medicolegal autopsy it is also important to have references based on an unselected population of medicolegal autopsy cases with non-natural causes of death (not due directly to disease). We aimed at studying and deriving references for adult heart weight by considering sex, age and body size in cases with an external cause of death. We identified all medicolegal autopsies in Sweden from 1999 to 2013 (n=79,778) and included 27,645 cases. We applied multivariate piecewise linear regression models in three strata of body mass-underweight, normal-/overweight and obesity. We observed that approximately 50% of the variation in heart weight was explained by age, sex and body size. These variables were slightly less important in explaining the variation in heart weight in the underweight and obese compared to in those normal or overweight. Based on the linear regression models we present equations to calculate the predicted heart weight with reference intervals using age, sex, body weight and height. We provide an online heart weight calculator (http://lundforensicmedicine.com) based on these equations. In the forensic interpretation of postmortem heart weights, we suggest that heart weight references derived in cases with an external cause of death is an important complement to references solely based on healthy and normal hearts. Furthermore, the heart weight references presented are derived from a large population, with sufficient numbers for separate models in underweight, normal-/overweight and obese populations.

The association between obesity and lethal blood alcohol concentrations: A nationwide register-based study of medicolegal autopsy cases in Sweden.

Obesity is a global problem and in aspects of lethal ethanol intoxications virtually unexplored. The cause of death in ethanol intoxication is generally considered to be suppression of the respiratory function. Previous research indicates that respiratory function is more vulnerable in obese subjects than in those of normal weight. We hypothesized that lethal blood alcohol concentration (BAC) is lower in obese subjects compared to those of normal weight. We used the Swedish medicolegal autopsy register and identified all medicolegal autopsy cases in Sweden during the period from 1999 to 2013 (N=79,060), and identified 1545 cases with ethanol intoxication identified as the primary cause of death. We studied the association between body mass index and lethal BAC using logistic regression models that we adjusted using several potential confounders such as age, sex, drugs, and extent of decomposition. We observed an association between obesity and lower lethal BACs. The estimated adjusted odds ratio of the association between obesity and a lethal BAC >3‰, using subjects of normal weight as reference, was 0.54, 95% confidence interval: 0.39-0.74. The result indicates that in obese subjects the lethal BAC is lower than in those of normal weight.