Plasma NAP-2 levels are associated with critical limb ischemia in peripheral arterial disease patients

Neutrophil-activating Peptide 2 as a Novel Modulator of Fibrin Clot Properties in Patients with Atrial Fibrillation

Neutrophil-activating peptide 2 (NAP-2, CXCL7), a platelet-derived neutrophil chemoattractant, is involved in inflammation. We investigated associations between NAP-2 levels, neutrophil extracellular traps (NETs) formation, and fibrin clot properties in atrial fibrillation (AF). We recruited 237 consecutive patients with AF (mean age, 68 ± 11 years; median CHA2DS2VASc score of 3 [2-4]) and 30 apparently healthy controls. Plasma NAP-2 concentrations were measured, along with plasma fibrin clot permeability (Ks) and clot lysis time (CLT), thrombin generation, citrullinated histone H3 (citH3), as a marker of NETs formation, and 3-nitrotyrosine reflecting oxidative stress. NAP-2 levels were 89% higher in AF patients than in controls (626 [448-796] vs. 331 [226-430] ng/ml; p < 0.0001). NAP-2 levels were not associated with demographics, CHA2DS2-VASc score, or the AF manifestation. Patients with NAP-2 in the top quartile (> 796 ng/ml) were characterized by higher neutrophil count (+ 31.7%), fibrinogen (+ 20.8%), citH3 (+ 86%), and 3-nitrotyrosine (+ 111%) levels, along with 20.2% reduced Ks and 8.4% prolonged CLT as compared to the remaining subjects (all p < 0.05). NAP-2 levels were positively associated with fibrinogen in AF patients (r = 0.41, p = 0.0006) and controls (r = 0.65, p < 0.01), along with citH3 (r = 0.36, p < 0.0001) and 3-nitrotyrosine (r = 0.51, p < 0.0001) in the former group. After adjustment for fibrinogen, higher citH3 (per 1 ng/ml β = -0.046, 95% CI -0.029; -0.064) and NAP-2 (per 100 ng/ml β = -0.21, 95% CI -0.14; -0.28) levels were independently associated with reduced Ks. Elevated NAP-2, associated with increased oxidative stress, has been identified as a novel modulator of prothrombotic plasma fibrin clot properties in patients with AF.

Autophagy-related genes analysis reveals potential biomarkers for prediction of the impaired walking capacity of peripheral arterial disease

BACKGROUND

The role of autophagy and autophagy-related genes in peripheral arterial disease (PAD) remains unknown and may be of diagnostic and prognostic value. The aim of this study is to investigate the relationship between autophagy and PAD, and identify potential diagnostic or prognostic biomarkers for medical practice.

METHODS

Differentially expressed autophagy-related genes in PAD were explored from GSE57691 and validated in our WalkByLab registry participants by quantitative real-time polymerase chain reaction (qRT-PCR). The level of autophagy in peripheral blood mononuclear cells (PBMCs) of WalkByLab participants was assessed by analyzing autophagic marker proteins (beclin-1, P62, LC3B). Single sample gene set enrichment analysis (ssGSEA) was used to evaluate the immune microenvironment within the artery wall of PAD patients and healthy persons. Chemokine antibody array and enzyme-linked immunosorbent assay were used to assess the chemokines in participants' plasma. Treadmill testing with Gardner protocol was used to evaluate participants' walking capacity. Pain-free walking distance, maximum walking distance, and walking time were recorded. Finally, a nomogram model based on logistic regression was built to predict impaired walking performance.

RESULTS

A total of 20 relevant autophagy-related genes were identified, and these genes were confirmed to be expressed at low levels in our PAD participants. Western blotting demonstrated that the expression of autophagic marker proteins beclin-1 and LC3BII were significantly reduced in PAD patients' PBMCs. ssGSEA revealed that most of the autophagy-related genes were strongly correlated with immune function, with the largest number of associated genes showing interaction between cytokine-and-cytokine receptors (CCR). In this context, the chemokines growth-related oncogene (GRO) and neutrophil activating protein2 (NAP2) are highly expressed in the plasma of WalkByLab PAD patients and were significantly negatively correlated with the walking distance assessed by Gardner treadmill testing. Finally, the plasma NAP2 level (AUC: 0.743) and derived nomogram model (AUC: 0.860) has a strong predictive potential to identify a poor walking capacity.

CONCLUSIONS

Overall, these data highlight both the important role of autophagy and autophagy-related genes in PAD and link them to vascular inflammation (expression of chemokines). In particular, chemokine NAP2 emerged as a novel biomarker that can be used to predict the impaired walking capacity in PAD patients.