Citrate pathway and NF-κB: role in immunometabolism and critical targets for modulation of macrophage function induced by Aglianico del Vulture red wine

Pro-inflammatory stimuli, such as lipopolysaccharides (LPS), induce a metabolic reprogramming in macrophages. Of note is the broken Krebs cycle which allows for the export of citrate from the mitochondria and its accumulation in the cytosol. The mitochondrial citrate carrier (CIC) transports citrate that, once in the cytosol, is broken by ATP citrate lyase (ACLY) into acetyl-CoA and oxaloacetate, precursors for the biosynthesis of chemical mediators of inflammation, namely reactive oxygen species (ROS), nitric oxide (NO•) and prostaglandin E2 (PGE2). Citrate also acts as signaling molecule in the inflammatory cascade. The citrate pathway is one of the main players in immunometabolism, an emerging frontier at the interface between immunity and metabolism. We observed that ACLY, even if is downstream of CIC, is upregulated earlier than CIC and its protein and mRNA levels as well as activity fluctuate over time in the first moments of LPS stimulation. We demonstrated that the short-term activation of ACLY is necessary to sustain histone acetylation and transcription of IL-1β, IL6 and PTGS2 proinflammatory genes. We identified the citrate pathway as a target of Aglianico del Vulture red wine in carrying out its anti-inflammatory and immunomodulatory activities. In LPS-activated human macrophages, phenolic compounds of Aglianico del Vulture red wine powder (RWP) reduce the secretion of pro-inflammatory cytokines IL-1β, IL-6 and TNF-α and increase the release of IL-10 anti-inflammatory cytokine. Noteworthy, RWP acts on NF-κB signaling pathway by lowering NF-κB protein levels, promoter activity, and p65 nuclear translocation. Because of NF-κB inhibition, reduced promoter activities of SLC25A1 – encoding CIC - and ACLY metabolic genes have been detected. RWP downregulates CIC and ACLY, decreases ACLY activity, the cytosolic citrate concentration, and in turn ROS, NO•, PGE2 and H3 histone acetylation levels. In addition, RWP restores Annexin A1 levels, involved in the resolution of inflammation. All the evidence suggest that the powder of Aglianico del Vulture potentially restores the homeostasis of LPS-triggerd macrophages by suppressing inflammatory pathways and activating pro-resolutive processes.