Impact of Resolvin E1 on Murine Neutrophil Phagocytosis in Type 2 Diabetes

Abstract

Diabetic complications involve inflammation-mediated microvascular and macrovascular damage, disruption of lipid metabolism, glycosylation of proteins, and abnormalities of neutrophil-mediated events. Resolution of inflamed tissues to health and homeostasis is an active process mediated by endogenous lipid agonists, including lipoxins and resolvins. This proresolution system appears to be compromised in type 2 diabetes (T2D). The goal of this study was to investigate unresolved inflammation in T2D. Wild-type (WT) and genetically engineered mice, including T2D mice (db/db), transgenic mice overexpressing the human resolvin E1 (RvE1) receptor (ERV1), and a newly bred strain of db/ERV1 mice, were used to determine the impact of RvE1 on the phagocytosis of Porphyromonas gingivalis in T2D. Neutrophils were isolated and incubated with fluorescein isothiocyanatelabeled P. gingivalis, and phagocytosis was measured in a fluorochrome-based assay by flow cytometry. Mitogen-activated protein kinase (MAPK) (p42 and p44) and Akt (Thr308 and Ser473) phosphorylation was analyzed by Western blotting. The mouse dorsal air pouch model was used to evaluate the in vivo impact of RvE1. Results revealed that RvE1 increased the neutrophil phagocytosis of P. gingivalis in WT animals but had no impact in db/db animals. In ERV1-transgenic and ERV1-transgenic diabetic mice, phagocytosis was significantly increased. RvE1 decreased Akt and MAPK phosphorylation in the transgenic animals. In vivo dorsal air pouch studies revealed that RvE1 decreases neutrophil influx into the pouch and increases neutrophil phagocytosis of P. gingivalis in the transgenic animals; cutaneous fat deposition was reduced, as was macrophage infiltration. The results suggest that RvE1 rescues impaired neutrophil phagocytosis in obese T2D mice overexpressing ERV1.

Pro-resolving mediators in the regulation of periodontal disease

“…The important principles demonstrated by these studies are that resolvins and lipoxins act to modulate the inflammatory response essentially aborting and reversing the chronic phase, promoting more rapid resolution, and that elimination of inflammation in a healing lesion promotes tissue regeneration. In small animals, these findings are not limited to the rabbit, but have been reproduced in mice and rats as well (54, 95). …”

“…ERV1 transgenic diabetic mice exhibited significantly reduced fat accumulation. Concomitantly, the macrophage accumulation in the fat was significantly reduced suggesting reduced production of inflammatory mediators by fat tissue in the transgenic animals that is likely contributing to the non-inflammatory phenotype and protection from disease (95). …”

“…To assess the role of resolution of inflammation in T2D-associated periodontitis, the ERV1 transgenic mouse overexpressing the receptor for RvE1 was employed in gain-of-function studies (95). Periodontitis was induced in wild type (Panel A), ERV1 transgenic (panel B), T2D ( db/db leptin receptor deficient, Panel C) and T2D ( db/db ) mice overexpressing ERV1 (Panel D) by P. gingivalis gavage).…”

Role of n-3 PUFAs in inflammationviaresolvin biosynthesis

“…RvE1 regulates phosphorylation of Akt and ribosomal protein rS6 via RvE1-specific interaction with ChemR23 on both human ChemR23-transfected CHO cells and human macrophages enhancing phagocytosis (Ohira et al, 2010). A decrease in p42 and p44 MAP kinase phosphorylation, induced by a bacteria, is also observed when neutrophils in culture are pretreated 15 min before challenge bacteria with 100 ng/ml RvE1 (Herrera et al, 2015).…”

Specialised lipid mediators and their targets

“…Extending these studies using a rabbit model of periodontitis, Hasturk et al [98] reveal that RvE1 administration reduces PMN infiltration and alveolar bone loss. RvE1 has potent effects on PMNs, displaying decreased migration, inhibition of rolling, enhanced CCR5 expression and attenuation of NF-B signalling [99]. Intriguingly a recent study by Herová et al [100] demonstrates ChemR23 expression is restricted to naïve and classical macrophages (M1) but not alternatively activated (M2).…”