Intermittent Hypoxia Affects the Spontaneous Differentiation In Vitro of Human Neutrophils into Long-Lived Giant Phagocytes

Abstract EN

Previously we identified, for the first time, a new small-size subset of neutrophil-derived giant phagocytes (Gϕ) which spontaneously develop in vitro without additional growth factors or cytokines.

Gϕ are CD66b+/CD63+/MPO+/LC3B+ and are characterized by extended lifespan, large phagolysosomes, active phagocytosis, and reactive oxygen species (ROS) production, and autophagy largely controls their formation.

Hypoxia, and particularly hypoxia/reoxygenation, is a prominent feature of many pathological processes.

Herein we investigated Gϕ formation by applying various hypoxic conditions.

Chronic intermittent hypoxia (IH) (29 cycles/day for 5 days) completely abolished Gϕ formation, while acute IH had dose-dependent effects.

Exposure to 24 h (56 IH cycles) decreased their size, yield, phagocytic ability, autophagy, mitophagy, and gp91-phox/p22-phox expression, whereas under 24 h sustained hypoxia (SH) the size and expression of LC3B and gp91-phox/p22-phox resembled Gϕ formed in normoxia.

Diphenyl iodide (DPI), a NADPH oxidase inhibitor, as well as the PI3K/Akt and autophagy inhibitor LY294002 abolished Gϕ formation at all oxygen conditions.

However, the potent antioxidant, N-acetylcysteine (NAC) abrogated the effects of IH by inducing large CD66b+/LC3B+ Gϕ and increased both NADPH oxidase expression and phagocytosis.

These findings suggest that NADPH oxidase, autophagy, and the PI3K/Akt pathway are involved in Gϕ development.