Circulating monocyte populations as biomarker for abdominal aortic aneurysms: a single-center retrospective cohort study.

Background: Abdominal aortic aneurysm (AAA) development is driven by inflammation, in particular myeloid cells, which represent attractive biomarker candidates. Yet to date, the maximum aortic diameter is the only clinically applied predictor of AAA progression and indicator for surgical repair. We postulated that aortic inflammation is reflected in a systemic change of monocyte populations, which we investigated regarding marker potential in AAA diagnosis and prognosis. Methods: We conducted a single-center retrospective cohort study in a diagnostic setting, measuring monocyte subsets by flow cytometry in peripheral blood samples of 47 AAA patients under surveillance, matched with 25 healthy controls and 25 patients with peripheral artery disease (PAD). In a prognostic setting, we acquired longitudinal data of 60 AAA patients including aneurysm growth assessment by computed tomography at 6-month intervals. Results: Blood levels of total monocytes, CD16+ monocytes and particularly intermediate monocytes were significantly increased in AAA patients versus healthy individuals and were also elevated compared to PAD patients. The combination of intermediate monocyte and D-dimer blood levels outperformed the individual diagnostic marker values. Additionally, the elevated concentrations of total monocytes, intermediate monocytes, and monocyte-platelet aggregates (MPA) were suited to predict rapid AAA progression over short-term periods of six months. Of note, MPA were identified as independent predictor of AAA disease progression in multivariable analysis. Conclusion: Circulating monocyte subsets are elevated in AAA patients and support diagnosis and prediction of aneurysm progression. Monocyte subsets and D-dimer reflect different hallmarks (inflammation and hemostasis) of AAA pathology and when combined, may serve as improved biomarker.

Diagnostic Utility of a Combined MPO/D-Dimer Score to Distinguish Abdominal Aortic Aneurysm from Peripheral Artery Disease.

Abdominal aortic aneurysm (AAA) and peripheral artery disease (PAD) share pathophysiological mechanisms including the activation of the fibrinolytic and innate immune system, which explains the analysis of D-dimer and myeloperoxidase (MPO) in both conditions. This study evaluates the diagnostic marker potential of both variables separately and as a combined MPO/D-dimer score for identifying patients with AAA versus healthy individuals or patients with PAD. Plasma levels of MPO and D-dimer were increased in PAD and AAA compared to healthy controls (median for MPO: 13.63 ng/mL [AAA] vs. 11.74 ng/mL [PAD] vs. 9.16 ng/mL [healthy], D-dimer: 1.27 µg/mL [AAA] vs. 0.58 µg/mL [PAD] vs. 0.38 µg/mL [healthy]). The combined MPO/D-dimer score (median 1.26 [AAA] vs. -0.19 [PAD] vs. -0.93 [healthy]) showed an improved performance in distinguishing AAA from PAD when analysed using the receiver operating characteristic curve (area under the curve) for AAA against the pooled data of healthy controls + PAD: 0.728 [MPO], 0.749 [D-dimer], 0.801 [score]. Diagnostic sensitivity and specificity ranged at 82.9% and 70.2% (for score cut-off = 0). These findings were confirmed for a separate collective of AAA patients with 35% simultaneous PAD. Thus, evaluating MPO together with D-dimer in a simple score may be useful for diagnostic detection and the distinction of AAA from athero-occlusive diseases like PAD.

Testicular Rosai-Dorfman disease clonally related to CMML - Case report and literature review.

BACKGROUND: Rosai-Dorfman disease (RDD), a rare form of non-Langerhans cell histiocytosis with heterogenous clinical features, arises from precursor cells that give rise to cells of the histiocytic and monocytic lineages. An association with hematological neoplasms has been reported. Testicular RDD is rarely described, with only 9 reported cases in the literature. Genetic data to assess clonal relationships between RDD and other hematological neoplasms remain scarce. We describe an instance of testicular RDD against a background of chronic myelomonocytic leukemia (CMML), with genetic studies in both neoplasms. CASE PRESENTATION: A 72-year-old patient with a history of CMML sought evaluation of growing bilateral testicular nodules. Solitary testicular lymphoma was suspected; orchidectomy was performed. The diagnosis of testicular RDD was established morphologically and confirmed immunohistochemically. Molecular analysis of testicular lesions and of archived patient bone marrow revealed the KRAS variant c 0.35 G>A / p.G12D in both, suggesting a clonal relationship. CONCLUSION: These observations support classifying RDD as a neoplasm that can be clonally related to myeloid neoplasms.

ELISA detection of MPO-DNA complexes in human plasma is error-prone and yields limited information on neutrophil extracellular traps formed in vivo.

Over the past years, neutrophil extracellular traps (NETs) were shown to contribute to states of acute and chronic inflammatory disease. They are composed of expelled chromatin and decorated by neutrophil-derived proteins. Therefore, the analysis of DNA complexes with myeloperoxidase (MPO) by ELISA has become an attractive tool to measure NET formation in in vitro and in vivo samples. When we used a published MPO-DNA ELISA protocol and included an isotype control for the anti-MPO coating antibody, we observed high assay specificity for in vitro prepared NET samples, whereas the specificity for in vivo plasma samples was low. In addition, the assay failed to detect in vitro generated MPO-DNA complexes when spiked into plasma. Therefore, we set out to improve the specificity of the MPO-DNA ELISA for plasma samples. We found that the use of Fab fragments or immunoglobulins from different species or reversal of the antibody pair led to either a high background or a low dynamic range of detection that did not improve the specificity for plasma samples. Also, the use of higher plasma dilutions or pre-clearing of plasma immunoglobulins were ineffective. Finally, we found that a commercial reagent designed to block human anti-mouse antibodies and multivalent substances increased the detection window between the MPO antibody and isotype control for highly diluted plasma. We applied this modified ELISA protocol to analyze MPO-DNA complexes in human blood samples of acute and chronic inflammatory conditions. While markers of neutrophil activation and NET formation such as MPO, elastase and citrullinated histone H3 correlated significantly, we observed no correlation with the levels of MPO-DNA complexes. Therefore, we conclude that ELISA measurements of MPO-DNA complexes in human plasma are highly questionable regarding specificity of NET detection. In general, plasma analyses by ELISA should more frequently include isotype controls for antibodies to demonstrate target specificity.

Abdominal aortic aneurysm and virus infection: A potential causative role for cytomegalovirus infection?

An abdominal aortic aneurysm (AAA) is a multifactorial disease with a variety of genetic and environmental risk factors, but the exact mechanism of AAA formation and progression is still not well understood. The present study investigated the frequency of cytomegalovirus (CMV), Epstein-Barr virus (EBV), and papillomavirus types 6 and 11 (HPV6 and HPV11), their impact on clinical manifestations of cardiovascular diseases, and their possible association with inflammation in patients with AAA and healthy volunteers. Genotyping of CMV UL75, EBV LMP-1, and HPV6, and HPV11 E6 was performed by polymerase chain reaction (PCR), while the viral DNA loads were measured by quantitative real-time PCR. Cytokine levels were determined by enzyme-linked immunosorbent assays. The CMV UL75 was detected more frequently in the blood of patients with AAA than in the blood of healthy volunteers (32.7% vs. 6.3%, p < .0001). Neither EBV LMP-1 nor HPV6 E6 was found in blood and aortic wall biopsies, while the HPV11 E6 was detected in 36.4% of AAA walls. The CMV infection in patients with AAA was associated with an increased risk of hypertension and coronary artery disease (OR, 9.057; 95% CI, 1.141-71.862; p = .037; and OR, 2.575; 95% CI, 1.002-6.615; p = .049, respectively). Additionally, CMV-infected patients with AAA had higher tumor necrosis factor-α levels compared with noninfected subjects (p = .017). Our findings suggest that CMV infection can stimulate local inflammation in the aorta but is not a direct cause of most abdominal aortic aneurysms.

Histone citrullination as a novel biomarker and target to inhibit progression of abdominal aortic aneurysms.

Neutrophil extracellular traps (NETs) have been implicated in the pathogenesis of abdominal aortic aneurysms (AAAs). This study has addressed the notion that NET components might serve as AAA biomarkers or novel targets of AAA therapy. Thus, parameters of neutrophil activation and NET formation were measured in plasma. Their diagnostic marker value was explored in 41 AAA patients and 38 healthy controls. The NET parameter citrullinated histone H3 (citH3) was then validated in 63 AAA patients and 63 controls matched for cardiovascular disease. The prognostic marker potential was investigated in 54 observation periods of AAA growth over 6 months. NETs were further assessed in conditioned medium and sections of aortic tissue. CitH3 was found to be increased in blood (median 362 vs 304 ng/mL, P = 0.004) and aortic tissue (50 vs 1.5 ng/mg, P < 0.001) of AAA patients compared to healthy controls and accumulated in the intraluminal thrombus (629 ng/mg). The diagnostic potential of citH3 ranged at 0.705 area under the ROC curve (AUROC) and was validated with the independent sample set. Furthermore, plasma citH3 predicted AAA growth over the next 6 months (AUROC: 0.707, P = 0.015) and dropped significantly after surgical aneurysm repair. In an angiotensin II - based mouse model of experimental AAA, an inhibitor of histone citrullination was applied to block NET formation and AAA progression. Of note, further growth of an established aneurysm was prevented in mice treated with the NET inhibitor (P = 0.040). In conclusion, histone citrullination represents a promising AAA biomarker and potential therapeutic target to control disease progression.

Complement Factor C5a Is Increased in Blood of Patients with Abdominal Aortic Aneurysm and Has Prognostic Potential for Aneurysm Growth.

In this observational case-control study, circulating levels of complement factors C3a and C5a and leukotriene B4 (LTB4) were analysed in abdominal aortic aneurysm (AAA) patients regarding their association with diagnosis and prognosis. Serum C5a was significantly raised in AAA patients compared to healthy controls-median 84.5 ng/ml (IQR = 37.5 ng/ml) vs. 67.7 ng/ml (IQR = 26.2 ng/ml), p = 0.007-but was not elevated in patients with athero-occlusive disease. Serum C5a levels correlated significantly with the increase in maximum AAA diameter over the following 6 months (r = 0.319, p = 0.021). The median growth in the lowest quartile of C5a (< 70 ng/ml) was 50% less compared to the highest C5a quartile (> 101 ng/ml): 1.0 mm/6 months (IQR = 0.8 mm) vs. 2.0 mm/6 months (IQR = 1.5 mm), p = 0.014. A log-linear mixed model predicted AAA expansion based on current diameter and C5a level. To our knowledge, this is the first study linking complement activation, in particular C5a serum level, with AAA progression.

Polymorphisms in the IL-6 and TNF-α gene are associated with an increased risk of abdominal aortic aneurysm.

BACKGROUND: An abdominal aortic aneurysm (AAA) is a complex disease of the aging population that is associated with inflammation and the cellular immune response. To investigate the influence of interleukin (IL)-6 and tumor necrosis factor (TNF)-α single nucleotide polymorphisms (SNPs) on the risk of AAA formation and progression, the frequency of AAA and its associated risk factors were determined. METHOD: Four SNPs in the IL-6 (-174G/C, rs1800795; -572G/C, rs1800796) and TNF-α (-238G/A, rs361525; -308G/A, rs1800629) genes were studied by the polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) in patients with AAA and healthy volunteers. The mRNA expression and plasma IL-6 and TNF-α levels were also determined. RESULTS: A mutation detected in at least one allele of the IL-6 -174G/C SNP was associated with a 2-fold increased risk of AAA occurrence (OR: 2.08; 95% CI: 1.15-3.76; p = 0.014, in the dominant model). An increased risk of AAA incidence among heterozygous carriers of the TNF-α - 308G/A genotype was observed (OR: 2.06; 95% CI: 1.17-3.62; p = 0.011, in the overdominant model). The wild-type genotypes of the IL-6 -174G/C and the TNF-α -308G/A SNPs coexisted more frequently in healthy subjects than in AAA patients and was associated with decreased risk of AAA (p < 0.001). Moreover, elevated levels of IL-6 and TNF-α were associated with an increased risk of hypertension (p < 0.001 and p = 0.022, respectively). CONCLUSIONS: The IL-6 -174G/C and the TNF-α -238G/A gene polymorphisms are associated with an increased risk of abdominal aortic aneurysm development.

TLR2 2029C/T and TLR3 1377C/T and -7C/A Polymorphisms Are Associated with the Occurrence of Abdominal Aortic Aneurysm.

TLRs are a family of signaling sensors that play a crucial role in the host immune response and are involved in the modulation of inflammatory processes. To study their contribution to abdominal aortic aneurysm (AAA) formation and development, we determined the frequency of TLR2, TLR3, TLR4, and TLR9 single-nucleotide polymorphisms (SNPs) and investigated the association between polymorphisms and the risk of AAA incidence. A total of 104 patients with AAAs and 112 healthy, unrelated volunteers were screened for the presence of TLR2 (2029C/T and 2258G/A), TLR3 (1377C/T, 1234C/T, and -7C/A), TLR4 (896A/G, 1196C/T, and 3266G/A), and TLR9 (-1237T/C, -1486T/C, 1174G/A, and 2848C/T) SNPs by using PCR-RFLP analysis. The heterozygous genotype of the TLR2 2029C/T SNP was more common in patients with AAA than in healthy subjects (p < 0.0001) and was associated with at least an 8-fold increased risk of AAA incidence (p < 0.001). The wild-type genotype of the TLR3 -7C/A SNP was associated with a 3-fold increased risk of hypertension (p = 0.026). The heterozygous TLR3 genotype 1377C/T and -7C/A SNPs were less common in patients with AAA than in healthy subjects (p < 0.0001 and p = 0.0004, respectively) and were associated with a decreased risk of AAA occurrence (p < 0.001 and p = 0.0012, respectively). No relation to AAA risk was found for TLR4 SNPs. Heterozygous genotypes of the TLR2 2029C/T and TLR3 1377C/T and -7C/A SNPs may serve as genetic biomarkers of AAA incidence.

A Novel Diagnostic and Prognostic Score for Abdominal Aortic Aneurysms Based on D-Dimer and a Comprehensive Analysis of Myeloid Cell Parameters.

The pathogenesis of abdominal aortic aneurysm (AAA) involves a central component of chronic inflammation which is predominantly mediated by myeloid cells. We hypothesized that the local inflammatory activity may be reflected in systemic alterations of neutrophil and monocyte populations as well as in soluble factors of myeloid cell activation and recruitment. To establish their marker potential, neutrophil and monocyte sub-sets were measured by flow cytometry in peripheral blood samples of 41 AAA patients and 38 healthy controls matched for age, sex, body mass index and smoking habit. Comparably, circulating factors reflecting neutrophil and monocyte activation and recruitment were assayed in plasma. Significantly elevated levels of CD16+ monocytes, activated neutrophils and newly released neutrophils were recorded for AAA patients compared with controls. In line, the monocyte chemoattractant C-C chemokine ligand 2 and myeloperoxidase were significantly increased in patients' plasma. The diagnostic value was highest for myeloperoxidase, a mediator which is released by activated neutrophils as well as CD16+ monocytes. Multivariable regression models using myeloid activation markers and routine laboratory parameters identified myeloperoxidase and D-dimer as strong independent correlates of AAA. These two biomarkers were combined to yield a diagnostic score which was subsequently challenged for confounders and confirmed in a validation cohort matched for cardiovascular disease. Importantly, the score was also found suited to predict rapid disease progression. In conclusion, D-dimer and myeloperoxidase represent two sensitive biomarkers of AAA which reflect distinct hallmarks (thrombus formation and inflammation) of the pathomechanism and, when combined, may serve as diagnostic and prognostic AAA score warranting further evaluation.

Neutrophil-Mediated Proteolysis of Thrombospondin-1 Promotes Platelet Adhesion and String Formation.

Thrombospondin-1 (TSP-1) is primarily expressed by platelets and endothelial cells (ECs) and rapidly released upon their activation. It functions in haemostasis as a bridging molecule in platelet aggregation, by promoting platelet adhesion to collagen and by protecting von Willebrand factor strings from degradation. In blood of patients undergoing surgery and in co-cultures of neutrophils with platelets or ECs, we observed proteolysis of the 185 kDa full-length TSP-1 to a 160-kDa isoform. We hypothesized that TSP-1 processing may alter its haemostatic properties. Selective enzyme inhibitors in co-cultures revealed that neutrophil proteases elastase and cathepsin G mediate TSP-1 processing. The cut site of cathepsin G was mapped to TSP-1 amino acids R237/T238 by Edman sequencing. Formation of neutrophil extracellular traps protected TSP-1 from complete degradation and promoted controlled processing to the 160-kDa isoform. Haemostatic properties were tested by platelet aggregation, adhesion, coagulation and string formation under flow. Platelets from TSP-1 deficient mice did not differ from wild-type in platelet aggregation but showed severe impairment of platelet adhesion to collagen and string formation under flow. Reconstitution experiments revealed that the 160-kDa TSP-1 isoform was markedly more potent than the 185-kDa full-length molecule in restoring function. Thus, TSP-1 processing by neutrophil proteases yields a 160-kDa isoform which shows enhanced potency to promote platelet adhesion and string formation. This finding reveals a novel mechanism of neutrophil-mediated thrombus formation and provides first evidence for the impact of TSP-1 proteolysis on its haemostatic properties.

Simvastatin Treatment Upregulates HO-1 in Patients with Abdominal Aortic Aneurysm but Independently of Nrf2.

Heme oxygenase-1 (HO-1), encoded by HMOX1 gene and regulated by Nrf2 transcription factor, is a cytoprotective enzyme. Its deficiency may exacerbate abdominal aortic aneurysm (AAA) development, which is also often associated with hyperlipidemia. Beneficial effects of statins, the broadly used antilipidemic drugs, were attributed to modulation of Nrf2/HO-1 axis. However, the effect of statins on Nrf2/HO-1 pathway in patients with AAA has not been studied yet. We analyzed AAA tissue from patients treated with simvastatin (N = 28) or without statins (N = 14). Simvastatin treatment increased HO-1 protein level in AAA, both in endothelial cells (ECs) and in smooth muscle cells (SMCs), but increased Nrf2 localization was restricted only to vasa vasorum. Nrf2 target genes HMOX1, NQO1, and GCLM expression remained unchanged in AAA. In vitro studies showed that simvastatin raises HO-1 protein level slightly in ECs and to much higher extent in SMCs, which is not related to Nrf2/ARE activation, although HMOX1 expression is upregulated by simvastatin in both cell types. In conclusion, simvastatin-induced modulation of HO-1 level in ECs and SMCs in vitro is not related to Nrf2/ARE activity. Likewise, divergent HO-1 and Nrf2 localization together with stable expression of Nrf2 target genes, including HMOX1, in AAA tissue denotes Nrf2 independency.

Inhibition of the transcriptional repressor complex Bcl-6/BCoR induces endothelial sprouting but does not promote tumor growth.

The oncogenic potential of the transcriptional repressor Bcl-6 (B-cell lymphoma 6) was originally discovered in non-Hodgkin patients and the soluble Bcl-6 inhibitor 79-6 was developed to treat diffuse large B-cell lymphomas with aberrant Bcl-6 expression. Since we found Bcl-6 and its co-repressor BCoR (Bcl-6 interacting co-repressor) to be regulated in human microvascular endothelium by colorectal cancer cells, we investigated their function in sprouting angiogenesis which is central to tumor growth. Based on Bcl-6/BCoR gene silencing we found that the transcriptional repressor complex in fact constitutes an endogenous inhibitor of vascular sprouting by supporting the stalk cell phenotype: control of Notch target genes (HES1, HEY1, DLL4) and cell cycle regulators (cyclin A and B1). Thus, when endothelial cells were transiently transfected with Bcl-6 and/or BCoR siRNA, vascular sprouting was prominently induced. Comparably, when the soluble Bcl-6 inhibitor 79-6 was applied in the mouse retina model of physiological angiogenesis, endothelial sprouting and branching were significantly enhanced. To address the question whether clinical treatment with 79-6 might therefore have detrimental therapeutic effects by promoting tumor angiogenesis, mouse xenograft models of colorectal cancer and diffuse large B-cell lymphoma were tested. Despite a tendency to increased tumor vessel density, 79-6 therapy did not enhance tumor expansion. In contrast, growth of colorectal carcinomas was significantly reduced which is likely due to a combined 79-6 effect on cancer cells and tumor stroma. These findings may provide valuable information regarding the future clinical development of Bcl-6 inhibitors.