Isolation of novel ligands for MAS-related G protein-coupled receptors X1 and X2, and their effect on mast cell degranulation

Abstract The mast cells are an integral part of the human immune system. They are important modulators of inflammatory and physiological processes. Mast cells exert their functions through degranulation and release of inflammatory mediators, such as histamine, proteases and cytokines. There are two main pathways leading to the mast cell activation, the immunoglobulin-dependent and the immunoglobulin-independent pathway. The latter pathway can be triggered by several non-immunological stimuli, and two novel receptors responsible for the activation have been identified, the MAS-related G protein-coupled receptor X1 (MRGPRX1) and X2. The MRGPRX1 and MRGPRX2 have two established functions: i) they trigger the degranulation of mast cells and ii) they are involved in pain perception and itch on a specific subset of sensory neurons. These receptors are not expressed in all of the populations of mast cells, only in the tryptase and chymase containing mast cells, contributing to the mast cell heterogeneity. Unlike most G protein-coupled receptors, the MRGPRX1 and MRGPRX2 are quite non-selective, binding an ever growing list of different ligands. Their ligands include endogenous neuropeptides, host defense peptides and protein fragments, as well as synthetic compounds such as different antibiotics. Their endogenous ligands could be a triggering signal in some mast cell-related diseases by degranulating mast cells and thereby inducing inflammation. Due to the non-selectivity of MRGPRX1 and MRGPRX2, they probably still have many hitherto unknown ligands. The aim of this study was to isolate novel endogenous ligands for the MRGPRX1 and MRGPRX2 from human tissues with the “reverse pharmacology approach” and to determine their potential to degranulate mast cells. The starting materials for the isolation, human platelets and plasma, contained MRGPRX1 and MRGPRX2 activating compounds. From the human plasma, three fragments of albumin able to activate the MRGPRX2 were isolated and sequenced. These fragments were dose-dependently activating the MRGPRX2 and degranulating mast cells. Two MRGPRX1 activating hemoglobin β-chain fragments were isolated from human platelets. These fragments were dose-dependently activating the MRGPRX1, but had no effect on mast cell degranulation.Tiivistelmä Syöttösolut on tärkeä osa ihmisen immuunijärjestelmää. Ne ovat tärkeitä tulehdus- ja fysiologistenprosessien säätelijöitä. Syöttösolujen vaikutus välittyy degranulaation ja siinä vapautuvien tulehdusvälittäjäaineiden kautta. Vapautuviin aineisiin lukeutuu esim. histamiini ja lukuisia sytokiinejä, sekä proteaaseja. Syöttösolujen aktivaatio voi tapahtua immunoglobuliineista riippuvaa tai immunoglobuliineista riippumatonta reittiä pitkin. Monet ei-immunologiset tekijät voivat laukaista jälkimmäisen reitin ja kaksi uutta tähän vaikuttavaa G-proteiinikytkentäistä reseptoria on löydetty, MAS-related G protein-coupled receptor X1 (MRGPRX1) ja X2. MRGPRX1:llä ja MRGPRX2:lla on kaksi tunnettua tehtävää: i) ne laukaisevat syöttösolujen degranulaation ja ii) ne osallistuvat kivun ja kutinan aistimiseen tietyissä tuntohermoissa. Näitä reseptoreita ei ilmennetä kaikissa syöttösoluissa, vaan ainoastaa tryptaasia ja kymaasia sisältävissä syöttösoluissa, ja täten osaltaan selittävät syöttösolujen monimuotoisuutta. Useimmista G-proteiinikytkentäisistä reseptoreista poiketen MRGPRX1 ja MRGPRX2 ovat laajakirjoisia, sitoen monia erilaisia ligandeja. Ligandeihin kuuluu endogeenisia neuropeptidejä, antimikrobiaalisia peptidejä ja proteiinin fragmentteja, sekä synteettisiä yhdisteitä kuten erilaisia antibiootteja. Reseptoreiden endogeeniset ligandit voivat toimia laukaisijana jossain syöttösoluihin liittyvissä sairauksissa, degranuloidessaan syöttösoluja ja aiheuttaen paikallisen tulehdustilan. Reseptoreiden laajakirjoisuudesta johtuen niillä on oletettavasti monia vielä tuntemattomia ligandeja. Tämän tutkimuksen tarkoitus oli eristää uusia endogeenisiä ligandeja MRGPRX1:lle ja MRGPRX2:lle ihmisen kudoksista ”kääteisfarmakologista lähestymistapaa” hyödyntäen ja selvittää ligandien kyky syöttösolujen degranulaatioon. Lähtömateriaalina käytetyt ihmisen verihiutaleet ja plasma sisälsivät MRGPRX1:ta ja MRGPRX2:ta aktivoivia yhdisteitä. Plasmasta eristettiin ja sekvensoitiin kolme albumiinin fragmenttia, jotka aktivoivat MRGPRX2:ta. Nämä fragmentit aktivoivat MRGPRX2:ta ja degranuloivat syöttösoluja annosriippuvaisesti. Kaksi MRGPRX1:tä aktivoivaa hemoglobiinin β-ketjun fragmenttia eristettiin ihmisen verihiutaleista. Nämä fragmentit tunnistettiin hemorfiineiksi ja ne aktivoivat MRGPRX1:tä annosriippuvaisesti, mutta eivät vaikuttaneet syöttösolujen degranulaatioon

Plasma orexin-A levels do not undergo circadian rhythm in young healthy male subjects

Abstract Orexin-A (OXA) has been originally isolated from a precursor peptide prepro-orexin from the lateral hypothalamus. The orexin system has been attributed to important functions in sleep, arousal and regulation of energy homeostasis. In addition to its high levels in cerebrospinal fluid, OXA is present in blood. However, reported peptide concentrations in plasma vary significantly depending on the method used. Therefore, a specific and sensitive OXA radioimmunoassay (RIA) with solid phase extraction method was developed to determine whether plasma OXA concentrations is affected by acute feeding and/or wake and sleep in young healthy males. Blood samples were collected for 24 h from nine healthy males (aged 20–24 years; BMI 20.7–26.5) every 2 h starting at 11 a.m. Food was served at 12 p.m, 5:30 p.m, 8 p.m and 8 a.m and the sleep time was between 10 p.m and 7 a.m. Plasma samples were analyzed in addition for cortisol and melatonin levels. Blood pressure was monitored through the experimental period. OXA antibody was raised in rabbits. OXA antiserum had only minor cross-reactivity with prepro-orexin precursor (<0.001%), amino-terminal peptide (<0.001%), carboxy-terminal peptide (0.001%), and orexin-B (0.3%) with high sensitivity (0.15 pg/tube). Plasma OXA levels varied between 0.5 and 16 pg/ml in seven subjects and were undetectable (below 0.5 pg/ml) in two subjects. The OXA concentrations did not correlate to feeding nor wake/sleep, whereas cortisol, melatonin and mean arterial blood pressure presented a clear circadian rhythm in each subject. In conclusion, OXA is present in blood in low amounts and its levels do not follow autonomic nor neuroendocrine circadian rhythms. Thereby, studies examining regulatory mechanisms and influences of OXA from blood samples should interpret results very cautiously

Inhibitory effects of serum from sepsis patients on epithelial cell migration in vitro:a case control study

Abstract Background: Sepsis delays wound re-epithelialization. In this study we explored the effect of human sepsis sera as well as the effects of cytokines, growth factors and exosomes of sepsis sera treated normal fibroblasts (NF) on keratinocyte migration and proliferation in vitro. Methods: Serum samples were taken on days 1, 4, and 9 from 44 patients diagnosed with severe sepsis, and from 14 matching healthy controls. We evaluated the effects of sepsis serum with or without TNF-α, EGF, EGF receptor inhibitor or exosomes of sepsis sera treated NF on human keratinocyte (HaCaT) proliferation (BrdU assay), viability (MTT assay), and migration (horizontal wound healing model). Cytokine levels of sepsis and healthy sera were measured by multiplex assay. Comparisons between groups were carried out using SPSS statistics and P < 0.05 was considered significant. Results: Severe-sepsis sera collected on days 1, 4, and 9 reduced keratinocyte proliferation by 6% (P = 0.005), 20% (P = 0.001), and 18% (P = 0.002), respectively, compared to control sera. Cell viability in cultures exposed to sepsis sera from days 4 and 9 was reduced by 38% (P = 0.01) and 58% (P < 0.001), respectively. Open-surface wounds exposed to sepsis sera from days 1 and 4 were larger than those exposed to sera from healthy controls (60 vs. 31%, P = 0.034 and 66 vs. 31%, P = 0.023, respectively). Exosomes of sepsis or healthy sera treated NF inhibited keratinocyte migration. We detected higher serum levels of cytokines TNF-α (5.7 vs. 0.7 pg/ml, P < 0.001), IL-6 (24.8 vs. 3.8 pg/ml, P < 0.001), IL-10 (30.0 vs. 11.9 pg/ml, P = 0.040), and VEGF (177.9 vs. 48.1 pg/ml, P = 0.018) in sepsis sera. Levels of EGF were significantly lower in sepsis sera than in that of healthy controls (6.5 vs. 115.6 pg/ml, P < 0.001). Sepsis serum supplemented with EGF 5 ng/ml and TNF-α in all concentrations improved keratinocyte migration. Conclusions: Keratinocyte viability, proliferation and migration were reduced in severe sepsis in vitro. Exosomes from NF added in healthy or sepsis serum media inhibited keratinocyte migration. Decreased levels of EGF in sepsis sera may partially explain the delay of wound healing with severe-sepsis patients. Increased levels of TNF-α in sepsis sera do not explain diminished keratinocyte migration

Preoperative anemia in colorectal cancer:relationships with tumor characteristics, systemic inflammation, and survival

Abstract Anemia is common in colorectal cancer (CRC) but its relationships with tumor characteristics, systemic inflammation, and survival have not been well characterized. In this study, blood hemoglobin levels and erythrocyte mean corpuscular volume (MCV) levels were measured in two independent cohorts of 148 CRC patients and 208 CRC patients, and their correlation with patient and tumor characteristics, systemic inflammatory markers (modified Glasgow Prognostic Score: mGPS; serum levels of thirteen cytokines, C-reactive protein, albumin), and survival were analyzed. We found that anemia, most frequently normocytic, followed by microcytic, was present in 43% of the patients. Microcytic anemia was most commonly associated with proximal colon tumor location. Average MCV and blood hemoglobin levels were lower in tumors with high T-class. Low blood hemoglobin associated with systemic inflammation, including high mGPS and high serum levels of C-reactive protein and IL-8. Particularly, normocytic anemia associated with higher mGPS. Normocytic anemia associated with a tendency towards worse overall survival (multivariate hazard ratio 1.61, 95% confidence interval 1.07–2.42, p = 0.023; borderline statistical significance considering multiple hypothesis testing). In conclusion, anemia in CRC patients is most frequently normocytic. Proximal tumor location is associated with predominantly microcytic anemia and systemic inflammation is associated with normocytic anemia

High-serum MMP-8 levels are associated with decreased survival and systemic inflammation in colorectal cancer

Abstract Background: Matrix metalloproteinase-8 (MMP-8) is a protease mainly expressed by neutrophils that cleaves numerous substrates, including collagens and cytokines. We have previously shown that serum MMP-8 levels increase in colorectal cancer (CRC) and correlate with distant metastasis. However, short follow-up in our prospective cohort did not enable survival analyses at the time of the first publication. Methods: Preoperative serum MMP-8 levels were measured by immunofluorometric assay in 271 CRC patients and related to clinicopathological parameters, markers of systemic inflammation (modified Glasgow Prognostic Score, mGPS; serum levels of C-reactive protein (CRP), albumin and 13 cytokines), the density of six types of tumour-infiltrating immune cells and survival. Results: Increased MMP-8 levels associated with higher mGPS and higher serum levels of CRP and several cytokines, including IL-1ra, IL-7 and IL-8 (p < 0.001 for all). Serum MMP-8 negatively correlated with tumour-infiltrating mast cells (invasive margin: p = 0.005, tumour centre: p = 0.010). The patients with high-serum MMP-8 levels (>100 ng/mL) had poor cancer-specific survival, independent of tumour stage, grade, lymphatic invasion, patient age, BRAF VE1 immunohistochemistry, mismatch repair deficiency, Immunoscore and mGPS (multivariate HR 2.12, 95% CI 1.21–3.71, p = 0.009). Conclusions: High-serum MMP-8 levels are associated with systemic inflammation and adverse outcome in CRC

Seasonal regulation of metabolism:the effect of wintertime fasting and autumnal fattening on key central regulators of metabolism and the metabolic profile of the raccoon dog (Nyctereutes Procyonoides)

Abstract Investigations into the mechanisms regulating obesity are frantic and novel translational approaches are needed. The raccoon dog (Nyctereutes procyonoides) is a canid species representing a promising model to study metabolic regulation in a species undergoing cycles of seasonal obesity and fasting. To understand the molecular mechanisms of metabolic regulation in seasonal adaptation, we analyzed key central nervous system and peripheral signals regulating food intake and metabolism from raccoon dogs after autumnal fattening and winter fasting. Expressions of neuropeptide Y (NPY), orexin-2 receptor (OX2R), pro-opiomelanocortin (POMC) and leptin receptor (ObRb) were analyzed as examples of orexigenic and anorexigenic signals using qRT-PCR from raccoon dog hypothalamus samples. Plasma metabolic profiles were measured with ¹H NMR-spectroscopy and LC-MS. Circulating hormones and cytokines were determined with canine specific antibody assays. Surprisingly, NPY and POMC were not affected by the winter fasting nor autumn fattening and the metabolic profiles showed a remarkable equilibrium, indicating conserved homeostasis. However, OX2R and ObRb expression changes suggested seasonal regulation. Circulating cytokine levels were not increased, demonstrating that the autumn fattening did not induce subacute inflammation. Thus, the raccoon dog developed seasonal regulatory mechanisms to accommodate the autumnal fattening and prolonged fasting making the species unique in coping with the extreme environmental challenges

Alterations in serum amino-acid profile in the progression of colorectal cancer:associations with systemic inflammation, tumour stage and patient survival

Abstract Background: Cancer cachexia is a complex wasting syndrome affecting patients with advanced cancer, with systemic inflammation as a key component in pathogenesis. Protein degradation and release of amino acids (AAs) in skeletal muscle are stimulated in cachexia. Here, we define factors contributing to serum AA levels in colorectal cancer (CRC). Methods: Serum levels of nine AAs were characterised in 336 CRC patients and their relationships with 20 markers of systemic inflammatory reaction, clinicopathological features of cancers and patient survival were analysed. Results: Low serum glutamine and histidine levels and high phenylalanine levels associated with indicators of systemic inflammation, including high modified Glasgow Prognostic Score, high blood neutrophil/lymphocyte ratio and high serum levels of CRP, IL-6 and IL-8. Low levels of serum glutamine, histidine, alanine and high glycine levels also associated with advanced cancer stage and with poor cancer-specific survival in univariate analysis. Conclusions: In CRC, serum AA levels are associated with systemic inflammation and disease stage. These findings may reflect muscle catabolism induced by systemic inflammation in CRC

Platelet count, aspirin use, and characteristics of host inflammatory responses in colorectal cancer

Abstract Background: Platelets not only contribute to hemostasis but also to the regulation of inflammatory reactions and cancer pathogenesis. We hypothesized that blood platelet count would be associated with systemic inflammation, the densities of tumor infiltrating immune cells, and survival in colorectal cancer (CRC), and these relationships could be altered by aspirin use. Methods: We measured blood platelet count in a cohort of 356 CRC patients and analyzed its relationships with tumor and patient characteristics including aspirin use, markers of systemic inflammation (modified Glasgow Prognostic Score, mGPS; serum levels of CRP, albumin, and 13 cytokines), blood hemoglobin levels, five types of tumor infiltrating immune cells (CD3, CD8, FoxP3, Neutrophil elastase, mast cell tryptase), and survival. Results: Platelet count inversely correlated with blood hemoglobin levels (p < 0.001) and positively correlated with serum levels of CRP and multiple cytokines including IL-1RA, IL-4, IL-6, IL-7, IL-8, IL-12, IFNγ, and PDGF-BB (p < 0.001 for all), while aspirin use was not associated with the levels of systemic inflammatory markers. High platelet count was also associated with high mGPS (p < 0.001) but did not show statistically significant multivariable adjusted associations with the densities of tumor infiltrating immune cells. Higher platelet counts were observed in higher tumor stage (p < 0.001), but platelet count or aspirin use were not associated with patient survival. Conclusions: High platelet count is associated with systemic inflammation in CRC. This study could not demonstrate statistically significant associations between platelet count, aspirin use, and the densities of tumor infiltrating immune cells

Genome-wide association study identifies seven novel loci associating with circulating cytokines and cell adhesion molecules in Finns

Abstract Background: Inflammatory processes contribute to the pathophysiology of multiple chronic conditions. Genetic factors play a crucial role in modulating the inflammatory load, but the exact mechanisms are incompletely understood. Objective: To assess genetic determinants of 16 circulating cytokines and cell adhesion molecules (inflammatory phenotypes) in Finns. Methods: Genome-wide associations of the inflammatory phenotypes were studied in Northern Finland Birth Cohort 1966 (N=5284). A subsequent meta-analysis was completed for 10 phenotypes available in a previous genome-wide association study, adding up to 13 577 individuals in the study. Complementary association tests were performed to study the effect of the ABO blood types on soluble adhesion molecule levels. Results: We identified seven novel and six previously reported genetic associations (p&#60;3.1×10−9). Three loci were associated with soluble vascular cell adhesion molecule-1 (sVCAM-1) level, one of which was the ABO locus that has been previously associated with soluble E-selectin (sE-selectin) and intercellular adhesion molecule-1 (sICAM-1) levels. Our findings suggest that the blood type B associates primarily with sVCAM-1 level, while the A1 subtype shows a robust effect on sE-selectin and sICAM-1 levels. The genotypes in the ABO locus associating with higher soluble adhesion molecule levels tend to associate with lower circulating cholesterol levels and lower cardiovascular disease risk. Conclusion: The present results extend the knowledge about genetic factors contributing to the inflammatory load. Our findings suggest that two distinct mechanisms contribute to the soluble adhesion molecule levels in the ABO locus and that elevated soluble adhesion molecule levels per se may not increase risk for cardiovascular disease

Could vitamin D reduce obesity-associated inflammation?:observational and Mendelian randomization study

Abstract Background: Obesity is associated with inflammation but the role of vitamin D in this process is not clear. Objectives: We aimed to assess the associations between serum 25-hydroxyvitamin D [25(OH)D], BMI, and 16 inflammatory biomarkers, and to assess the role of vitamin D as a potential mediator in the association between higher BMI and inflammation. Methods: Northern Finland Birth Cohort 1966 (NFBC1966) 31-y data on 3586 individuals were analyzed to examine the observational associations between BMI, 25(OH)D, and 16 inflammatory biomarkers. Multivariable regression analyses and 2-sample regression-based Mendelian randomization (MR) mediation analysis were performed to assess any role of vitamin D in mediating a causal effect of BMI on inflammatory biomarkers [soluble intercellular adhesion molecule 1 (sICAM-1), high sensitivity C-reactive protein (hs-CRP), and α1-acid glycoprotein (AGP)] for which observational associations were detected. For MR, genome-wide association study summary results ranging from 5163 to 806,834 individuals were used for biomarkers, 25(OH)D, and BMI. Findings were triangulated with a literature review of vitamin D supplementation trials. Results: In NFBC1966, mean BMI (kg/m²) was 24.8 (95% CI: 24.7, 25.0) and mean 25(OH)D was 50.3 nmol/L (95% CI: 49.8, 50.7 nmol/L). Inflammatory biomarkers correlated as 4 independent clusters: interleukins, adhesion molecules, acute-phase proteins, and chemokines. BMI was positively associated with 9 inflammatory biomarkers and inversely with 25(OH)D (false discovery rate &lt; 0.05). 25(OH)D was inversely associated with sICAM-1, hs-CRP, and AGP, which were positively associated with BMI. The MR analyses showed causal association of BMI on these 3 inflammatory biomarkers. There was no observational or MR evidence that circulating 25(OH)D concentrations mediated the association between BMI and these 3 inflammatory markers. Review of randomized controlled trials (RCTs) supported our findings showing no impact of vitamin D supplementation on inflammatory biomarkers. Conclusions: The findings from our observational study and causal MR analyses, together with data from RCTs, do not support a beneficial role of vitamin D supplementation on obesity-related inflammation