The Role of Neutrophils in Lower Limb Peripheral Artery Disease: State of the Art and Future Perspectives

The interaction effect of depressive symptoms and inflammation on the occurrence of cardiovascular diseases

BACKGROUND

Whether there was an interaction effect between depressive symptoms and inflammation on the occurrence of cardiovascular diseases (CVDs) was unclear.

METHODS

In this cross-sectional study, 3346 participants in the National Health and Nutrition Examination Survey (NHANES) were included. Multivariable regression analysis was performed to explore the associations of depressive symptoms or inflammation with CVDs. The attributable proportion of interaction (API), and synergy index (SI) were applied for evaluating the statistical significance of the interaction effect.

RESULTS

Depressive symptoms were associated with 2.31-fold risk of CVDs [odds ratio (OR) = 2.31, 95 % confidence interval (CI): 1.47-3.62). The increased risk of CVDs was observed in people with neutrophil to lymphocyte ratio (NLR) ≥1.88 group (OR = 1.36, 95%CI: 1.01-1.85) and neutrophil/[white blood cell (WBC)-neutrophil] ≥1.35 (OR = 1.52, 95%CI: 1.12-2.07) after adjusting for confounders. The interaction effect of depressive symptoms and high NLR on the risk of CVDs was statistically significant with an OR value of 2.60 (95%CI: 1.43-4.70) compared to low NLR and no depressive symptoms group after adjusting for confounders. The API was 0.66 (95%CI: 0.44-0.89) and SI was 4.23 (95%CI: 2.08-8.59). The interaction effect of depressive symptoms and high neutrophil/(WBC-neutrophil) was associated with the risk of CVDs compared to low neutrophil/(WBC-neutrophil) and no depressive symptoms group (OR = 3.59, 95%CI: 2.00-6.45). The API was 0.78 (95%CI: 0.63-0.93) and SI was 6.75 (95%CI: 3.55-12.82).

CONCLUSION

There was an interaction effect of depressive symptoms and inflammation on the occurrence of CVDs.

Neutrophils for Revascularization Require Activation of CCR6 and CCL20 by TNFα

BACKGROUND

Activation of immune-inflammatory pathways involving TNFα (tumor necrosis factor alpha) signaling is critical for revascularization and peripheral muscle tissue repair after ischemic injury. However, mechanisms of TNFα-driven inflammatory cascades directing recruitment of proangiogenic immune cells to sites of ischemia are unknown.

METHODS

Muscle tissue revascularization after permanent femoral artery ligation was monitored in mutant mice by laser Doppler imaging and light sheet fluorescence microscopy. TNFα-mediated signaling and the role of the CCL20 (C-C motif chemokine ligand 20)-CCR6 (C-C chemokine receptor 6) axis for formation of new vessels was studied in vitro and in vivo using bone marrow transplantation, flow cytometry, as well as biochemical and molecular biological techniques.

RESULTS

TNFα-mediated activation of TNFR (tumor necrosis factor receptor) 1 but not TNFR2 was found to be required for postischemic muscle tissue revascularization. Bone marrow-derived CCR6+ neutrophil granulocytes were identified as a previously undescribed TNFα-induced population of proangiogenic neutrophils, characterized by increased expression of VEGFA (vascular endothelial growth factor A). Mechanistically, postischemic activation of TNFR1 induced expression of the CCL20 in vascular cells and promoted translocation of the CCL20 receptor CCR6 to the cell surface of neutrophils, essentially conditioning VEGFA-expressing proangiogenic neutrophils for CCL20-dependent recruitment to sites of ischemia. Moreover, impaired revascularization of ischemic peripheral muscle tissue in diabetic mice was associated with reduced numbers of proangiogenic neutrophils and diminished CCL20 expression. Administration of recombinant CCL20 enhanced recruitment of proangiogenic neutrophils and improved revascularization of diabetic ischemic skeletal muscles, which was sustained by sequential treatment with fluvastatin.

CONCLUSIONS

We demonstrate that site-specific activation of the CCL20-CCR6 axis via TNFα recruits proangiogenic VEGFA-expressing neutrophils to sites of ischemic injury for initiation of muscle tissue revascularization. The findings provide an attractive option for tissue revascularization, particularly under diabetic conditions.

Biomarkers of Neutrophil Activation in Patients with Symptomatic Chronic Peripheral Artery Disease Predict Worse Cardiovascular Outcome

Neutrophils play a role in cardiovascular (CV) disease. However, relatively scant evidence exists in the setting of peripheral artery disease (PAD). The aims of this study were to measure biomarkers of neutrophil activation in patients with symptomatic chronic PAD compared with healthy controls, to assess their association with PAD severity, and to evaluate their prognostic value in patients with PAD. The following circulating markers of neutrophil degranulation were tested: polymorphonuclear neutrophil (PMN) elastase, neutrophil gelatinase-associated lipocalin (NGAL), and myeloperoxidase (MPO). Neutrophil extracellular traps (NETs) were quantified by measuring circulating MPO–DNA complexes. Patients with PAD underwent a comprehensive series of vascular tests. The occurrence of 6-month major adverse CV (MACE) and limb events (MALE) was assessed. Overall, 110 participants were included, 66 of which had PAD. After adjustment for conventional CV risk factors, PMN-elastase (adjusted odds ratio [OR]: 1.008; 95% confidence interval [CI]: 1.002–1.015; p = 0.006), NGAL (adjusted OR: 1.045; 95%CI: 1.024–1.066; p < 0.001), and MPO (adjusted OR: 1.013; 95%CI: 1.001–1.024; p = 0.028) were significantly associated with PAD presence. PMN-elastase (adjusted hazard ratio [HR]: 1.010; 95%CI: 1.000–1.020; p = 0.040) and MPO (adjusted HR: 1.027; 95%CI: 1.004–1.051; p = 0.019) were predictive of 6-month MACE and/or MALE. MPO displayed fair prognostic performance on receiver operating characteristic (ROC) curve analyses, with an area under the curve (AUC) of 0.74 (95%CI: 0.56–0.91) and a sensitivity and specificity of 0.80 and 0.65, respectively, for a cut-off of 108.37 ng/mL. MPO–DNA showed a weak inverse correlation with transcutaneous oximetry (TcPO2) on proximal foot (adjusted ρ −0.287; p = 0.032). In conclusion, in patients with symptomatic chronic PAD, enhanced neutrophil activity may be associated with an increased risk of acute CV events, rather than correlate with disease severity. Further research is needed to clarify the role of neutrophils in PAD natural history.