We previously demonstrated that nicotinamide adenine dinucleotide phosphate oxidase 4 (Nox4) mediates increased monocyte priming and chemotaxis under conditions of diabetic metabolic stress, and emerging data indicate that group VIA phospholipase A₂ (iPLA₂β) also participates in regulating monocyte chemotaxis. Here, we examined relationships between iPLA₂β expression and Nox4 action in mouse peritoneal macrophages subjected to diabetic metabolic stress.

Increased iPLA₂β expression and activity were observed in macrophages from low-density lipoprotein receptor knockout mice that were fed a high-fat diet, and this was associated with time-dependent increases in atherosclerotic lesion size and macrophage content. Incubating macrophages with 30 mmol/L D-glucose, 100 μg/mL low-density lipoprotein, or both (D-glucose+low-density lipoprotein) induced a robust increase in iPLA₂β expression and activity and in cell migration in response to monocyte chemoattractant protein-1. The increases in iPLA₂β activity and cell migration were prevented by a bromoenol lactone iPLA₂β suicide inhibitor or an iPLA₂β antisense oligonucleotide. Incubating macrophages under conditions that mimic diabetic metabolic stress ex vivo resulted in increased Nox4 expression and activity and hydrogen peroxide generation compared with controls. Bromoenol lactone prevented those effects without affecting Nox2 expression. Nox4 inhibition eliminated diabetic metabolic stress–induced acceleration of macrophage migration. Lysophosphatidic acid restored Nox4 expression, hydrogen peroxide generation, and migration to bromoenol lactone–treated cells, and a lysophosphatidic acid receptor antagonist abrogated iPLA₂β-mediated increases in Nox4 expression.

Taken together, these observations identify iPLA₂β and lysophosphatidic acid derived from its action as critical in regulating macrophage Nox4 activity and migration in the diabetic state in vivo and under similar conditions ex vivo.