Highly purified human peripheral blood monocytes produce IL-6 but not TNFα in response to angiotensin II

Hypothesis: Monocytes produce pro-inflammatory cytokines in response to Angiotensin II (AngII).

Introduction: AngII has been suggested by many to be pro-inflammatory and likely to contribute to the migration of leukocytes in patients with cardiovascular conditions.

Materials and methods: Monocytes were purified from peripheral blood mononuclear cells (PBMCs) by negative selection using antibodies conjugated to magnetic beads. Detection of CD14⁺ and AT₁R expression was achieved by double-labeling flow cytometry. Highly purified monocytes were then stimulated with AngII (6 and 24 h) to assess IL-6 and TNF-α transcript levels by qRT-PCR and protein secretion by ELISA.

Results: Monocytes comprised 9.7 ± 2.0% of the PBMCs. Monocyte isolation by negative selection yielded a purity of up to 99.8%. We demonstrated AT₁R expression on 9.5 ± 0.3% of highly purifed CD14⁺/CD16^- monocytes. Stimulation of highly purified monocytes with AngII resulted in increased transcript levels of IL-6 at 6 h but not at 24 h, and increased secretion of IL-6 in a dose-dependent manner compared with controls (p <0.01). Conversely, there was no increase in TNF-α mRNA transcripts or protein secretion.

Conclusions: We provide evidence that a CD14⁺/CD16^- subset of highly purified human monocytes express AT₁R and respond to AngII exposure in vitro by producing IL-6 but not TNF-α.