Isolation of new ligands for orphan receptor MRGPRX1-hemorphins LVV-H7 and VV-H7.

The human MAS-related G protein-coupled receptor X1 (MRGPRX1) is a member of the GPCR family. The receptor is primate specific and expressed in the sensory neurons of dorsal root ganglion and trigeminal ganglion, where it is considered to be involved in the pain perception. The MRGPRX1 has unusual binding mechanism, as it is activated by several different ligands as well as several different fragments of precursor proteins. Thus, we hypothesize that it is activated by several unknown compounds as well since the receptor is still classified as orphan. Here, we describe the isolation of two novel endogenous ligands for the MRGPRX1 from human platelet preparation. The isolated ligands are hemoglobin ß-chain fragments, known members of the hemorphin family.

Mast cell degranulation via MRGPRX2 by isolated human albumin fragments.

BACKGROUND: Mast cells are important modulators of the human immune system via their release of several inflammatory mediators and proteases. The release can be activated by different pathways: the classical immunoglobulin E-dependent pathway and by the non-immunological immunoglobulin E-independent pathway. MAS-related G protein-coupled receptor X2 (MRGPRX2) is expressed in mast cells and it is one of the endogenous receptor responsible for the IgE-independent activation of human mast cell. The MRGPRX2 is classified as orphan receptor and unlike most GPCRs, the MRGPRX2 recognizes a wide range of basic molecules. Thus, there still might be several unknown ligands for the receptor. METHODS: MRGPRX2 activating peptides were isolated from human plasma using consecutive HPLC purification steps. The isolation process was monitored with MRGPRX2 transfected HEK 293 cells. The isolated peptides were sequenced by MS and synthetized. The synthetic peptides were used to determine degranulation of the human LAD 2 mast cell line by measuring ß-hexosaminidase release. RESULTS: Three endogenous MRGPRX2 activating peptides were isolated from human plasma. These peptides are identified as fragments of albumin. The isolated fragments activate MRGPRX2 and degranulate MRGPRX2 expressing LAD 2 cells in dose-dependent manner. CONCLUSIONS: The isolated basic peptides generated from human albumin are able to degranulate mast cells via the MRGPRX2. GENERAL SIGNIFICANCE: These endogenous albumin fragments, cleaved from albumin by mast cell secreted proteases, provide a possible pathway for self-perpetuating mast cell dependent inflammation.

Blister fluid and serum cytokine levels in severe sepsis in humans reflect skin dysfunction.

BACKGROUND: Knowledge of sepsis-related end-organ inflammation in vivo is limited. We investigated the cytokine response in skin and in serum in sepsis and its relation to multiorgan failure (MOF) and survival. METHODS: Cytokines were analysed in serum and in suction blister fluid of intact skin of 44 patients with severe sepsis and 15 healthy controls. Blister fluid and serum samples were collected within 48 h of the first sepsis-induced organ failure. This is a substudy of a larger follow-up study on wound healing in sepsis. RESULTS: Cytokine levels were higher in patients with sepsis vs. controls (interleukin [IL]-10, blisters: 65.9 vs. 4.3 pg/ml, P < 0.001, serum: 25.7 vs. 4.5 pg/ml, P = 0.004; IL-6, blisters: 41.9 vs. 0.03 pg/ml, P < 0.001, serum: 45.5 vs. 2.1 pg/ml, P < 0.001). Patients with MOF had higher levels of IL-10 (116.4 vs. 21.3 pg/ml, P = 0.015), IL-4 (0.7 vs. 0.07 pg/ml, P = 0.013) and basic fibroblast growth factor (bFGF) (25.9 vs. 9.5 pg/ml, P = 0.027) in blister fluid than patients without MOF. In blister fluid, survivors had lower levels of IL-10 (43.3 vs. 181.9 pg/ml, P = 0.024) and bFGF (15.8 vs. 31.9 pg/ml, P = 0.006) than non-survivors. In serum, survivors had higher levels of vascular endothelial growth factor (VEGF) (152.2 vs. 14.7 pg/ml, P = 0.012) and lower levels of IL-6 (38.5 vs. 91.1 pg/ml, P = 0.011) than non-survivors. The blister fluid levels of bFGF, TNF and VEGF did not correlate with the serum levels. CONCLUSIONS: Cytokine responses in skin blister fluid in patients with sepsis differed from those in healthy controls.

MMP-19 deficiency causes aggravation of colitis due to defects in innate immune cell function.

Matrix metalloproteinases (MMPs) are potential biomarkers for disease activity in inflammatory bowel disease (IBD). However, clinical trials targeting MMPs have not succeeded, likely due to poor understanding of the biological functions of individual MMPs. Here, we explore the role of MMP-19 in IBD pathology. Using a DSS-induced model of colitis, we show evidence for increased susceptibility of Mmp-19-deficient (Mmp-19(-/-)) mice to colitis. Absence of MMP-19 leads to significant disease progression, with reduced survival rates, severe tissue destruction, and elevated levels of pro-inflammatory modulators in the colon and plasma, and failure to resolve inflammation. There was a striking delay in neutrophil infiltration into the colon of Mmp-19(-/-) mice during the acute colitis, leading to persistent inflammation and poor recovery; this was rescued by reconstitution of irradiated Mmp-19(-/-) mice with wild-type bone marrow. Additionally, Mmp-19-deficient macrophages exhibited decreased migration in vivo and in vitro and the mucosal barrier appeared compromised. Finally, chemokine fractalkine (CX3CL1) was identified as a novel substrate of MMP-19, suggesting a link between insufficient processing of CX3CL1 and cell recruitment in the Mmp-19(-/-) mice. MMP-19 proves to be a critical factor in balanced host response to colonic pathogens, and for orchestrating appropriate innate immune response in colitis.

Stage-dependent alterations of the serum cytokine pattern in colorectal carcinoma.

BACKGROUND: Inflammation contributes to the pathogenesis of colorectal cancer (CRC), and cytokine levels are altered during colorectal carcinogenesis. METHODS: The serum levels of 13 cytokines and their relation to clinical and pathological parameters, and systemic inflammatory response (mGPS, CRP and neutrophil-lymphocyte ratio), were analysed from a prospective series of 148 CRC patients and 86 healthy age- and sex-matched controls. RESULTS: CRC patients had higher serum platelet-derived growth factor, interleukin (IL)-6, IL-7, and IL-8 levels and lower monocyte chemotactic protein-1 (MCP-1) levels than the controls. A logistic regression model for discriminating the patients from the controls - including the five most predictive cytokines (high IL-8, high IL-6, low MCP-1, low IL-1ra, and low IP-10) - yielded an area under curve value of 0.890 in receiver operating characteristics analysis. Serum cytokines showed distinct correlation with other markers of systemic inflammatory response, and advanced CRCs were associated with higher levels of IL-8, IL-1ra, and IL-6. A metastasised disease was accompanied by an orientation towards Th2 cytokine milieu. CONCLUSION: CRC is associated with extensive alterations in serum cytokine environment, highlighting the importance of studying relative cytokine level alterations. Serum cytokine profile shows promise in separating CRC patients from healthy controls but its clinical value is yet to be confirmed.

Effect of diet-induced weight loss on plasma apelin and cytokine levels in individuals with the metabolic syndrome.

BACKGROUND AND AIMS: Adipose tissue is an active endocrine organ that secretes signaling molecules involved in the regulation of insulin sensitivity, food intake and inflammation. Apelin is a peptide secreted by adipose tissue that has been shown to modulate cardiovascular tone in animals. The aim of this study was to measure abdominal fat, blood pressure and circulating apelin, adiponectin, leptin, ghrelin, TNF-alpha and IL-6 levels in patients with the metabolic syndrome after a diet-induced weight loss. METHODS AND RESULTS: 35 obese individuals with the metabolic syndrome underwent an 8-week very-low-calorie diet (VLCD) and a 6-month weight maintenance period (WM) with 120mg orlistat or placebo administered 3 times daily. VLCD and WM (-15.1+/-1.0kg) decreased mean arterial pressure (MAP), insulin, leptin, triglycerides and visceral and subcutaneous adipose tissue. Moreover, adiponectin increased in response to the weight loss. However, the overall changes in plasma apelin, TNF-alpha and IL-6 were non-significant. A correlation between plasma apelin and TNF-alpha was observed at baseline (0.41, p<0.05), and the minor changes in plasma apelin levels were associated with changes in BMI during VLCD and MAP and TNF-alpha during VLCD and WM periods. CONCLUSION: Despite reductions in BMI, body adiposity, MAP and enhancement of glucose metabolism and adiponectin in response to weight loss, no significant changes in plasma apelin, TNF-alpha and IL-6 were observed. However, apelin significantly correlated with TNF-alpha and MAP. These results suggest that apelin may not be that strongly correlated with the fat mass as an adipokine like the more abundant adipokines adiponectin or leptin and it might be involved in the regulation of inflammation and cardiovascular tone.