Killing of Escherichia coli by Crohn's Disease Monocyte-derived Macrophages and Its Enhancement by Hydroxychloroquine and Vitamin D

Abstract

Article first published online 1 April 2015.

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Abstract

Background:

Crohn's disease (CD) is associated with defective innate immunity, including impaired neutrophil chemotaxis, and mucosal invasion by bacteria, particularly adherent and invasive Escherichia coli that replicate inside macrophage phagolysosomes. We compared CD and healthy control (HC) macrophages for their abilities to kill E. coli and generate neutrophil chemoattractants and also assessed the effects of hydroxychloroquine (HCQ) and vitamin D on killing of phagocytosed E. coli.

Methods:

Peripheral blood monocyte-derived macrophages from CD and HC were compared for bacterial killing and generation of neutrophil chemoattractants in response to CD-derived E. coli. Escherichia coli replication was also assessed in the presence and absence of HCQ, alone and with antibiotics, and vitamin D.

Results:

Monocyte-derived macrophages from patients with CD were similar to HC in allowing replication of phagocytosed CD-derived E. coli: HM605 {CD: N = 10, mean fold replication in 3 hr = 1.08 (95% confidence interval [CI], 0.39–1.78); HC: N = 9, 1.50 (95% CI, 1.02–1.97); P = 0.15} and also in generation of neutrophil chemoattractants in response to E. coli (mean fold chemotaxis relative to control: CD = 2.55 [95% CI, 2.31–2.80]; HC = 2.65 [95% CI, 2.46–2.85], P = 0.42). HCQ and 1,25 OH ₂-vitamin D ₃ both caused dose-dependent inhibition of intramacrophage E. coli replication 3-hour postinfection; HCQ: 73.9% inhibition ( P < 0.001) at 1 μg/mL, accompanied by raised intraphagosomal pH, and 1,25 OH ₂-vitamin D ₃: 80.7% inhibition ( P < 0.05) at 80 nM. HCQ had synergistic effects with doxycycline and ciprofloxacin.

Conclusions:

CD and HC macrophages perform similarly in allowing replication of phagocytosed E. coli and generating neutrophil chemoattractants. Replication of phagocytosed E. coli was substantially decreased by HCQ and vitamin D. These warrant further therapeutic trials in CD in combination with relevant antibiotics.