Pro-inflammatory polarization of macrophages is associated with reduced endoplasmic reticulum-mitochondria interaction.

Macrophages play a role in host defense, tissue remodeling and inflammation. Different inflammatory stimuli drive macrophage phenotypes and responses. In this study we investigated the relationship between macrophages immune phenotype and mitochondrial bioenergetics, cell redox state and endoplasmic reticulum (ER)-mitochondria interaction. Bacterial lipopolysaccharide (LPS) and interferon-γ (IFNγ) pro-inflammatory stimuli decreased oxidative metabolism (basal, phosphorylating and maximal conditions) and increased baseline glycolysis (117%) and glycolytic capacity (43%) in THP-1 macrophages. In contrast, interleukin-4 (IL4) and interleukin-13 (IL13) anti-inflammatory stimuli increased the oxygen consumption rates in baseline conditions (21%) and associated with ATP production (19%). LPS + IFNγ stimuli reduced superoxide anion levels by accelerating its conversion into hydrogen peroxide (H2O2) while IL4+IL13 decreased H2O2 release rates. The source of these oxidants was extra-mitochondrial and associated with increased NOX2 and SOD1 gene expression. LPS + IFNγ stimuli decreased ER-mitochondria contact sites as measured by IP3R1-VDAC1 interaction (34%) and markedly upregulated genes involved in mitochondrial fusion (9-10 fold, MFN1 and 2) and fission (∼7 fold, DRP1 and FIS1). Conversely, IL4+IL13 stimuli did not altered ER-mitochondria interactions nor MFN1 and 2 expression. Together, these results unveil ER-mitochondria interaction pattern as a novel feature of macrophage immunological, metabolic and redox profiles.