Soluble CD83 modulates human-monocyte-derived macrophages towards alternative phenotype, function and metabolism

Alterations in macrophage (Mφ) polarization, function and metabolic signature can foster development of chronic diseases, such as autoimmunity, or fibrotic tissue remodeling. Thus, identification of novel therapeutic agents that modulate human Mφ biology is crucial for treatment of such conditions. Herein we demonstrate that the soluble CD83 (sCD83) protein induces pro-resolving features in human monocyte-derived Mφ biology. We show that sCD83 strikingly increases the expression of inhibitory molecules including ILT-2 (immunoglobulin-like transcript 2), ILT-4, ILT-5 and CD163, whilst activation markers, such as MHC-II and MSR-1 were significantly downregulated. This goes along with a decreased capacity to stimulate alloreactive T cells in mixed lymphocyte reaction (MLR) assays. Bulk RNA sequencing and pathway analyses revealed that sCD83 downregulates pathways associated with pro-inflammatory, classically-activated Mφ (CAM) differentiation including HIF-1A, IL-6 as well as cytokine storm, whilst pathways related to alternative Mφ activation and Liver X receptor were significantly induced. By using the LXR pathway antagonist GSK2033, we show that transcription of specific genes (e.g. PPARG, ABCA1, ABCG1, CD36) induced by sCD83 are dependent on LXR activation. In summary, we herein reveal for the first time mechanistic insights into the modulation of human Mφ biology by sCD83, which is a further crucial pre-clinical study for the establishment of sCD83 as a new therapeutical agent to treat inflammatory conditions. RNA sequencing analyses of human monocyte-derived Macrophages, which were treated with sCD83 (25 µg/ml) or the corresponding amount of PBS as control on day 0 as well as day 3 during differentiation process. In detail, PBMCs from three different healthy donors were isolated via density gradient centrifugation and subsequently monocytes were seeded for adherence. Monocytes were differentiated into Mφ in the presence of M-CSF (20 ng/ml), +/- sCD83 (25 µg/ml). sCD83 was added on day 0 as well as day 3 during the differentiation process - or the corresponding amount of PBS as control. Subsequently, Mφ were harvested on day 6 of differentiation and RNA isolation was performed using the RNAeasy Mini Kit (Qiagen). 1 µg RNA was subsequently send for RNA sequencing performed by Novogene.