PB0844 - Activated Protein C ameliorates diabetes induced atherosclerosis by sustaining efferocytosis

Background: Most patients with diabetes mellitus (DM) dye due to cardiovascular disease. Macrophage efferocytosis, the ability of macrophages to phagocyte dead cells, is impaired in diabetes-associated atherosclerosis. Impaired macrophage efferocytosis promotes inflammation and atherosclerosis. Activated protein C (aPC) conveys anti-inflammatory effects and its levels are reduced in patients with diabetes mellitus. Whether aPC modulates efferocytosis remains unknown.

Aims: To gain insight into the effect of aPC on dysfunctional macrophages in diabetes induced atherosclerotic plaque development.

Methods: Bone marrow derived macrophages (BMDMs) isolated from wild type mice or PBMCs from healthy individuals were exposed to high glucose (HG) without or with aPC (20nM) for 24 h. Additionally, PBMCs were isolated from diabetic patients and ex vivo treated with aPC. After 24 h, fluorescently labelled apoptotic Jurkat cells (ACs) were added to BMDMs and macrophages efferocytosis was assessed. ApoE-/- mice (age 8 weeks) was made diabetic by streptozotocin injections. A subgroup of diabetic mice were treated with exogenous aPC (1mg/kg) without or with MerTK inhibition (vivo-morpholino) and analyzed after 20 weeks.

Results: Macrophages efferocytic capability was reduced in cells exposed to glucose ex vivo or isolated from diabetic patients as reflected by decreased expression of proteins involved in phagocytosis (surface MerTK ) and in the efferocytosis pathway (p-Camk2y, Arg1, Rac1). aPC prevented glucose induced impairment of macrophage efferocytosis. Exposure of PBMCs isolated from diabetic patients to aPC ex vivo was sufficient to restore efferocytosis. In Mice, aPC treatment restored macrophage efferocytosis and ameliorated diabetes induced atherosclerosis. Inhibition of MerTK abolished aPC effect on restoring macrophage efferocytosis in diabetes induced atherosclerosis.

Conclusion(s): These data suggest that high glucose induced impairment of macrophage efferocytosis can be reversed by aPC. This suggests that reduced plasma levels of aPC may contribute to atherosclerosis in diabetic patients and that targeting this pathway may allow to restore macrophage efferocytic ability in diabetic patients.