In familial Mediterranean fever, soluble TREM-1 plasma level is higher in case of amyloidosis

sTREM-1 promotes the phagocytic function of microglia to induce hippocampus damage via the PI3K-AKT signaling pathway

Soluble triggering receptor expressed on myeloid cells-1 (sTREM-1) is a soluble form of TREM-1 released during inflammation. Elevated sTREM-1 levels have been found in neuropsychiatric systemic lupus erythematosus (NPSLE) patients; yet, the exact mechanisms remain unclear. This study investigated the role of sTREM-1 in brain damage and its underlying mechanism. The sTREM-1 recombinant protein (2.5 μg/3 μL) was injected into the lateral ventricle of C57BL/6 female mice. After intracerebroventricular (ICV) injection, the damage in hippocampal neurons increased, and the loss of neuronal synapses and activation of microglia increased compared to the control mice (treated with saline). In vitro. after sTREM-1 stimulation, the apoptosis of BV2 cells decreased, the polarization of BV2 cells shifted to the M1 phenotype, the phagocytic function of BV2 cells significantly improved, while the PI3K-AKT signal pathway was activated in vivo and in vitro. PI3K-AKT pathway inhibitor LY294002 reversed the excessive activation and phagocytosis of microglia caused by sTREM-1 in vivo and in vitro, which in turn improved the hippocampus damage. These results indicated that sTREM-1 activated the microglial by the PI3K-AKT signal pathway, and promoted its excessive phagocytosis of the neuronal synapse, thus inducing hippocampal damage. sTREM-1 might be a potential target for inducing brain lesions.

[Role of TREM-1 in cardiovascular diseases]

The innate immune system plays a crucial role in cardiovascular disease initiation, progression and complications. TREM-1, a receptor mainly expressed by myeloid cells, orchestrates inflammatory responses and amplifies cytokine and chemokine production as well as oxidative burst. Recent experimental studies have demonstrated that TREM-1 blockade is protective, limiting atherosclerosis and abdominal aortic aneurysm development, as well as adverse tissue remodeling after cardiac or cerebral ischemic injuries. Plasma soluble TREM-1 level is a promising biomarker in patients with cardiovascular diseases for risk stratification, paving the way for personalized immune-modulatory approaches.

Shear wave elastography evaluation of liver, pancreas, spleen and kidneys in patients with familial mediterranean fever and amyloidosis

OBJECTIVES

Amyloid deposits in a visceral organ can contribute to tissue stiffness that could be measured with shear wave elastography (SWE). We aimed to investigate changes in organ stiffness in conjunction with laboratory parameters in patients with Familial Mediterranean Fever (FMF) and amyloidosis.

METHODS

This prospective study included 27 FMF patients, 11 patients with amyloidosis, and 38 healthy controls. Median shear wave elasticity values of the liver, spleen, both kidneys, and pancreas on SWE were compared among study and control groups. The mean values of CRP (C-reactive protein) and ESR (erythrocyte sedimentation rate) were compared by the t-test and the median of SAA (serum amyloid A protein) was compared with the Mann-Whitney U test between FMF groups with and without amyloidosis. Spearman's correlation analysis was performed to reveal the association between stiffness values and laboratory parameters.

RESULTS

The median liver, spleen, kidney, and pancreas elasticity values were significantly higher in the FMF group with amyloidosis compared to control subjects. The median kidney stiffness values in the FMF group with or without amyloidosis were significantly higher compared to control subjects. Median liver stiffness values in FMF patients with amyloidosis were significantly higher than FMF patients without amyloidosis. There were statistically significant positive correlations between the CRP (p = 0.001, r = 0.56), ESR (p = 0.001, r = 0.61), and SAA (p = 0.002, r = 0.53) levels with spleen stiffness, and CRP (p = 0.006, r = 0.48) and ESR (p = 0.001,r = 0.61) levels with pancreas stiffness, and ESR (p = 0.004, r = 0.51) levels with the left kidney stiffness.

CONCLUSION

SWE could be a potential tool for noninvasive follow-up of FMF patients and also amyloid deposition.

ADVANCES IN KNOWLEDGE

Both acute inflammation and amyloidosis in the FMF patients could increase organ stiffness.

Serum Amyloid A in Inflammatory Rheumatic Diseases: A Compendious Review of a Renowned Biomarker

Serum amyloid A (SAA) is an acute phase protein with a significant importance for patients with inflammatory rheumatic diseases (IRD). The central role of SAA in pathogenesis of IRD has been confirmed by recent discoveries, including its involvement in the activation of the inflammasome cascade and recruitment of interleukin 17 producing T helper cells. Clinical utility of SAA in IRD was originally evaluated nearly half a century ago. From the first findings, it was clear that SAA could be used for evaluating disease severity and monitoring disease activity in patients with rheumatoid arthritis and secondary amyloidosis. However, cost-effective and more easily applicable markers, such as C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR), overwhelmed its use in clinical practice. In the light of emerging evidences, SAA has been discerned as a more sensitive biomarker in a wide spectrum of IRD, especially in case of subclinical inflammation. Furthermore, a growing number of studies are confirming the advantages of SAA over many other biomarkers in predicting and monitoring response to biological immunotherapy in IRD patients. Arising scientific discoveries regarding the role of SAA, as well as delineating SAA and its isoforms as the most sensitive biomarkers in various IRD by recently developing proteomic techniques are encouraging the revival of its clinical use. Finally, the most recent findings have shown that SAA is a biomarker of severe Coronavirus disease 2019 (COVID-19). The aim of this review is to discuss the SAA-involving immune system network with emphasis on mechanisms relevant for IRD, as well as usefulness of SAA as a biomarker in various IRD. Therefore, over a hundred original papers were collected through an extensive PubMed and Scopus databases search. These recently arising insights will hopefully lead to a better management of IRD patients and might even inspire the development of new therapeutic strategies with SAA as a target.

Serum sTREM-1 in adult-onset Still's disease: a novel biomarker of disease activity and a potential predictor of the chronic course

Objectives

Triggering receptor expressed on myeloid cells-1 (TREM-1) is an amplifier of inflammatory signals. Recently, a soluble form of TREM-1 (sTREM-1) was described. This study aimed to investigate the role of serum sTREM-1 in patients with adult-onset Still’s disease (AOSD).

Methods

Serum sTREM-1 levels were detected in 108 AOSD patients, 88 RA patients and 112 healthy controls (HC). The correlations of sTREM-1 with disease activity, clinical characteristics and laboratory parameters in AOSD patients were analysed by the Spearman correlation test. Risk factors for the chronic course of AOSD were evaluated by multivariate logistic regression analysis.

Results

AOSD patients had significantly higher serum sTREM-1 levels than RA patients and HC, and serum sTREM-1 levels were correlated with the systemic score, ferritin, leucocyte count, CRP, IL-1β and IL-6. The elevation in the initial sTREM-1 level by itself could discriminate patients developing the chronic course from patients developing the nonchronic course. Moreover, an elevated sTREM-1 level (> 526.4475 pg/ml) was an independent risk factor for the chronic course in active AOSD patients. Furthermore, interfering with TREM-1 engagement led to reductions in the secretion of pro-inflammatory cytokines, such as IL-1β, IL-6 and TNF-α, in neutrophils and monocytes from active AOSD patients.

Conclusion

Serum sTREM-1 levels are correlated with disease activity, and an elevation in the initial serum sTREM-1 level is a potential predictor of the chronic course in AOSD patients, which currently provides the best predictive model for identifying patients prone to developing the chronic course of AOSD.

Soluble TREM-1 Levels in Familial Mediterranean Fever Related AA-Amyloidosis

Objectives: Triggering Receptor Expressed on Myeloid cells-1 (TREM-1) is a monocyte and neutrophil receptor functioning in innate immunity. TREM-1 activity has been studied in various autoimmune diseases such as RA and SLE but there is no data in autoinflammatory pathologies. We studied soluble TREM-1 (sTREM-1) activity in Familial Mediterranean Fever (FMF) cases to evaluate the clinical role of TREM-1 in amyloidosis. Methods: The study includes 62 patients with FMF (42 with amyloidosis) who are regular attendees of a tertiary center for autoinflammatory diseases. For control purposes, 5 patients with AA amyloidosis secondary to other inflammatory diseases, and 20 healthy individuals were also included. Soluble TREM-1 levels were measured using enzyme-linked immunosorbent assay (ELISA). All FMF patients were in an attack-free period during the collection of the blood samples.Results: Soluble TREM-1 levels were found to be significantly higher in the FMF amyloidosis group compared to FMF without amyloidosis group and healthy controls (p = .001 and 0.002). Nevertheless, this difference between sTREM-1 levels was not found among FMF amyloidosis and other AA amyloidosis groups (p = .447) as well as between only FMF patients and healthy controls (p = .532). Soluble TREM-1 levels were found in correlation with creatinine and CRP in the FMF patient group regardless of their amyloidosis diagnosis (r = 0.314, p = .013; r = 0.846, p < .001).Conclusion: TREM-1 seems to be related to renal function rather than disease activity in FMF. Its role as an early diagnostic marker of amyloidosis in FMF complicated with AA amyloidosis should be tested in larger patient groups.