Increasing neutrophil F‐actin corrects CD11b exposure in Type 2 diabetes

Publisher Website
Google Scholar
Abstract
Background  Leukocyte dysfunction contributes to the pathogenesis of diabetic vascular complications. Neutrophils adhere to the endothelium through the β2integrin CD11b/CD18. In Type 2 diabetes, neutrophil surface CD11b expression is increased and is associated with impaired actin polymerization. This study aimed to determine whether increasing neutrophil actin polymerization could correct the defect in CD11b exposure.Design  Neutrophil actin polymerization was stimulated with the tyrosine phosphatase inhibitor phenylarsine oxide (PAO), and cytoskeletal phosphotyrosine was monitored by immunoblotting Triton X‐100 insoluble fractions of cells. Neutrophil F‐actin was measured with phalloidin‐FITC staining, and surface CD11b expression was determined with anti‐CD11b‐PE before analysis with flow cytometry.Results  Phenylarsine oxide caused an increase in phosphotyrosine in neutrophils from both patients with Type 2 diabetes (DM) and controls (NC) (‐fold increase: NC, 1·43 ± 0·16; DM, 1·46 ± 0·10). The response to PAO in terms of phalloidin‐binding was impaired in neutrophils from patients [phalloidin‐FITC MFI area under the curve, NC 200 ± 5 (× 103), DM 124 ± 9 (× 103), P < 0·0001]. Phenylarsine oxide at concentrations < 10 µmol L−1 also caused loss of CD11b from neutrophil surfaces that was impaired in samples from patients [CD11b sites area under the curve NC 90 ± 6 (× 103), DM 121 ± 9 (× 103), P < 0·002]. However, in neutrophils from patients, incubation with PAO at a concentration of > 10 µmol L−1 caused a significant increase in intracellular F‐actin and CD11b down‐regulation equivalent to that observed in controls.Conclusion  In Type 2 diabetes, impaired neutrophil actin polymerization even in response to increasing cytoskeletal phophotyrosine suggests a downstream defect. Furthermore, increasing actin polymerization, above a minimum threshold level, corrects the defect in integrin exposure. Correction of the actin polymerization defect in Type 2 diabetes could improve the prognosis of diabetic vascular complications.