Requirement for labile Zn2+ in phagocytosis by murine macrophages

Abstract

IntroductionSystemic Zn2+ deficiency impairs the ability to fight infection. We hypothesized that one mechanism of immune dysfunction in the setting of Zn2+ deficiency is impaired phagocytosis by macrophages.MethodsRAW 264.7 murine macrophages were incubated for three hours with E. coli cell walls labeled with Vybrant and pHrodo fluorescent reporters. Co‐incubation occurred in the presence or absence of two intracellular Zn2+ chelators (high affinity TPEN 10μM, low affinity BAPTA 10μM) and one extracellular zinc chelator (DTPA 10 μM). Confirmatory experiments were performed with mouse peritoneal macrophages.ResultsIntracellular zinc chelators caused reduced phagocytosis vs control (TPEN: 28% ± 8; BAPTA 54% ± 14%, p < 0.02, N = 5). In contrast, chelation of extracellular zinc with DTPA had no effect.ConclusionFree cytoplasmic Zn2+ is required for effective internalization of extracellular bacterial particles by both cultured and primary murine macrophages. Under acute conditions, intracellular stores are sufficient to optimize function.