Increased Inflammatory Properties of Neutrophils in Patients with Venous Thromboembolism and the Effect of Simvastatin on Abrogating Inflamed Neutrophils Adhesiveness

Abstract

Neutrophils have a complex migrating process out of the vascular lumen, that consists of chemoattraction and rolling, followed by firm attachment and migration to extravascular tissues. In these sites, neutrophils are capable of promoting phagocytosis, secreting proteases, generating reactive oxygen species (ROS), and probably releasing neutrophil extracellular traps (NETs). Furthermore, neutrophil activation also induces major tissue injury associated with acute and chronic inflammatory disorders, such as the venous thromboembolism (VTE). Recently, animal models and clinical studies in acute VTE have explored the participation of neutrophils in the pathophysiology of VTE. However, VTE has been associated with a chronic inflammatory condition, and it remains unclear whether the activation of neutrophils is persistent after the acute phase of the disease. Furthermore, there are clinical evidences supporting that simvastatin may prevent VTE, since the drug has pleiotropic anti-inflammatory effects. The aim of this study is to evaluate the occurrence of neutrophil activation in patients with VTE compared to health controls and determines the effect of simvastatin in these adhesive properties of the neutrophils. Neutrophils were separated from blood collected over Ficoll-Paque densities. Neutrophils activation was determined by the expression of activated adhesive molecules (LFA-1/CD11a and MAC-1/CD11b) and ROS generation, detected by flow cytometry. Chemotaxis assays (chemoTx, Neuro Probe, Inc) and serum nucleosome, a marker of NETs, were quantified by optical density (OD) (Cell Death Detection ELISAPLUS Kit, Roche). Serum high sensitive CRP (hs-CRP) levels were measured in BN ProSpec System (Siemens) by nephelometry. For CD11a and CD11b integrins expression, cells were evaluated under basal conditions and after TNFα inflammatory stimulus, pretreated, or not, with simvastatin. For the migration assays, neutrophils were treated, or not, with IL-8, a neutrophil chemotactic factor. The results were displayed as mean and standard deviation (±SD). The study group consisted of thirty-seven patients with personal history of VTE, the median time since VTE occurred was 25 months (range 13 - 42 months), the event was spontaneous in 51.35% of the cases and 23 patients presented proximal VTE. Thirty-seven controls, matched with patients according to age, gender and ethnicity, were also included. The mean fluorescence intensity (MFI) of CD11a was higher in VTE patient neutrophils, both in basal conditions (30.84 ± 6.82 vs. 38.72 ± 22.75, P= 0.04) and after TNFα stimulus (34.09 ± 9.64 vs. 45.65 ± 33.06, P= 0.01). Higher MFI of CD11b was observed in patient neutrophils, compared with controls, only after TNFα stimulus (149.10 ± 52.74 vs. 200.0 ± 100.5, P= 0.02), and the stimulus was reverted by pre-treatment with simvastatin (200.8 ± 100.50 vs. 174.60 ± 80.63, P= 0.001). The amount of ROS (MFI) was similar in patients and controls (908.30 ± 423.7 vs. 844.0 ± 312.0, P= 0.83). Neutrophils from VTE patients also presented increased basal chemotaxis (17.55% ± 9.79 vs. 12.64% ± 4.78, P=0.02) and IL-8-stimulated chemotaxis (63.48% ± 29.73 vs. 49.88% ± 19.48%, P=0.06). Serum levels of nucleosomes were similar in patients and controls (1.05 ± 0.81 vs. 0.88 ± 0.62, P= 0.64), however higher levels of circulating nucleosomes were observed in patients with severe post-thrombotic syndrome (PTS), compared to patients with non-severe PTS, without PTS and controls (1.49 ± 0.81 vs. 1.06 ± 0.64 vs. 0.64 ± 0.60 vs. 0.88 ± 0.62, P=0.04). Furthermore, serum levels of hs-CRP were significantly higher in VTE patients when compared with controls (0.59 mg/dl ± 0.58 vs. 0.17 mg/dl ± 0.12, P=0.00). We demonstrated that patients with VTE presented patterns of neutrophil activation long time after the acute thrombotic episode. In particular, the stimuli for neutrophil adhesion and chemotaxis were higher in patients, as detected by the increased activation of adhesive molecules and cell migration. Furthermore, we observed that simvastatin may abrogate the expression of CD11b in inflamed neutrophils. Neutrophil activities associated with ROS generation and the releases of nucleosomes were not increased in these patients. The results may support the hypothesis that increased neutrophils activation is part of the chronic inflammatory condition associated with VTE and may be downregulated by the effects of simvastatin. DisclosuresNo relevant conflicts of interest to declare.