Multiple Polymorphisms Affect Expression and Function of the Neuropeptide S Receptor (NPSR1)

Peer reviewe

Surgical trauma, inflammation and tissue injury

Surgical tissue trauma is a strong stimulus for local inflammation, including leukocyte recruitment. While such a response may be of importance for the defense against microorganisms, it is also clear that inflammation may contribute to further tissue injury. After skin flap surgery, both decreased blood perfusion and inflarnmation may contribute to necrosis fon-nation in flap tissue. In this thesis, based on an experimental skin flap model in the rat, the potential negative effects of the inflammatory response on tissue viability were examined, with special reference to the role of neutrophils in the development of post-surgical skin necrosis. We found that the survival rate and degree of inflammation in rat skin flaps varied significantly with the time lag between transportation of the animals from the supplier and flap surgery, apparently in relation to the level of environmental stress. Thus, as compared to acclimatized rat, flap survival was increased and neutrophil recruitment decreased in recently transported animals. Moreover, plasma corticosterone levels were elevated during the first days of acclimatization, and treatment of rats accustomed to their new environment with the glucocorticoid dexamethasone increased flap survival and decreased neutrophil accumulation to levels near those observed in animals operated on arrival. Treatment with leukotriene-synthesis inhibitors significantly increased skin flap survival, while a cysteinyl-leukotriene receptor antagonist did not. These findings suggest that leukotrienes are involved in the development of necrosis in surgical skin flaps in the rat, possibly via leukotriene B4-induced neutrophil recruitment. Survival of rat skin flaps was significantly increased by i.v. treatment with a monoclonal antibody blocking rat leukocyte CD18 function. This antibody also significantly inhibited accumulation of neutrophils in the flap tissue, strongly suggesting that neutrophil recruitment plays an important role in the development tissue necrosis in this experimental flap model. Systemic perioperative treatment with heparin significantly increased the viability of skin flaps in the rat. This effect of heparin appeared to correlate with its ability to prolong clotting time, but not with the degree of total flap blood flow or surgery-induced neutrophil accumulation in the flap. Similar effects on flap viability were observed with the low molecular weight heparin dalteparin, which had minor effects on clotting time and significantly reduced flap neutrophil recruitment without affecting leukocyte rolling. While treatment with heparins may be useful as prophylaxis or for salvage of threatened surgical flaps, their mechanism(s) of action need further investigation. Very low doses of calcitonin-gene related peptide i.p. significantly improved the survival of rat skin flaps. This beneficial effect by CGRP appeared to be related to a reduction in the surgically induced neutrophil recruitment into the flap, and not to hemodynamic changes. Taken together, while being an important host-defence mechanism, surgically induced inflammation, and in particular neutrophil recruitment, appears to be detrimental to skin flap survival. Thus, in efforts to improve skin flap viability, it may be of value to consider anti-inflammatory treatment in addition to agents that increase tissue blood flow

Polymorphism in the Retinoic Acid Metabolizing Enzyme CYP26B1 and the Development of Crohn’s Disease

<div><p>Several studies suggest that Vitamin A may be involved in the pathogenesis of inflammatory bowel disease (IBD), but the mechanism is still unknown. Cytochrome P450 26 B1 (CYP26B1) is involved in the degradation of retinoic acid and the polymorphism rs2241057 has an elevated catabolic function of retinoic acid, why we hypothesized that the rs2241057 polymorphism may affect the risk of Crohn’s disease (CD) and Ulcerative Colitis (UC). DNA from 1378 IBD patients, divided into 871 patients with CD and 507 with UC, and 1205 healthy controls collected at Örebro University Hospital and Karolinska University Hospital were analyzed for the <i>CYP26B1</i> rs2241057 polymorphism with TaqMan® SNP Genotyping Assay followed by allelic discrimination analysis. A higher frequency of patients homozygous for the major (T) allele was associated with CD but not UC compared to the frequency found in healthy controls. A significant association between the major allele and non-stricturing, non-penetrating phenotype was evident for CD. However, the observed associations reached borderline significance only, after correcting for multiple testing. We suggest that homozygous carriers of the major (T) allele, relative to homozygous carriers of the minor (C) allele, of the <i>CYP26B1</i> polymorphism rs2241057 may have an increased risk for the development of CD, which possibly may be due to elevated levels of retinoic acid. Our data may support the role of Vitamin A in the pathophysiology of CD, but the exact mechanisms remain to be elucidated.</p></div

Genotype frequencies of the polymorphism <i>rs2241057</i> in the <i>CYP26B1</i> gene for patients with Crohn’s disease and healthy controls, displayed for sub phenotypes and clinical features.

<p>Chi-square test used for <i>P</i>-values unless otherwise stated. Odds ratio and confidence interval estimated using 2×2 contingency tables. C =  minor allele, T =  major allele. OR =  odds ratio, CI =  95% confidence interval. ^*Patients with combination of two locations are excluded in this overview, ^† Fisher’s two tailed exact test used.</p

Clinical characteristics of patients with inflammatory bowel disease.

<p>CD =  Crohn’s disease, UC =  Ulcerative colitis.</p

Genotype frequencies of the polymorphism rs2241057 in the <i>CYP26B1</i> gene in patients with inflammatory bowel disease <i>vs</i>. healthy controls.

<p>Chi-square test used for <i>P</i>-values. Odds ratio and confidence interval estimated using 2×2 contingency tables. CD =  Crohn’s disease, UC =  Ulcerative colitis, C =  minor allele, T =  major allele. OR =  odds ratio, CI =  95% confidence interval. ^* Uncorrected P-value/FDR corrected P-value.</p