ISR Autumn Meeting 2019

Young Investigator Award Winner

Mary Canavan

TBA (19A167)

The synovial microenvironment in Rheumatoid Arthritis induces metabolic and functional adaptations in Dendritic cells.

Author(s)

Mary Canavan 1, Trudy McGarry 1, Viviana Marzalioli 1, Douglas J Veale 2, Ursula Fearon 1

Department(s)/Institutions

1 Molecular Rheumatology, Trinity Biomedical Sciences Institute, Trinity College Dublin 2 Centre for Arthritis and Rheumatic Diseases, St Vincents University Hospital, Dublin

Introduction

Immune cells infiltrating the synovium have increased bioenergetic demands which leads to a shift in their metabolic profile. This involves the activation of metabolic pathways which is essential for immune cell function. Proinflammatory DC have previously been identified within the RA
synovium however the contribution of the synovial microenvironment to their function and
metabolic adaptions is unknown.

Aims/Background

To examine if the unique synovial RA microenvironment contributes to DC function,
phenotype and metabolism.

Method

Immature DC were derived from CD14+ monocytes in the presence of GMCSF
(50ng/ml) and IL-4 (70ng/ml). Synovial tissue explants were cultured for 24hr allowing the
spontaneous release of cytokines and soluble mediators into the culture medium. MoDC were
cultured in the presence of explant conditioned medium (ECM) for 24hrs after which
phagocytosis, costimulation and expression of inflammatory mediators was assessed by flow
cytometry and RT-PCR respectively. To investigate the energy pathways used by DC
exposed to synovial ECM, MoDC were treated for 6hr and glucose uptake (2NBDG) was
assessed by flow cytometry, glycolytic genes were assessed by RT-PCR and the
XFeExtracellular Flux Analyzer will be used to measure both measure mitochondrial
respiration and glycolysis.

Results

MoDC stimulated with ECM are significantly less phagocytic (p<0.05), have
increased expression of CD83 (p<0.05), and express higher levels of IL-12p40, IL-12p19, IL-
1β, ICAM-1 and CCR7 (all p<0.05). Moreover the expression of CCR5 is significantly
decreased (p<0.01) collectively indicating that the synovial microenvironment induces DC maturation. In the presence of ECM, glucose uptake is significantly increased (p<0.05) while
the expression of glycolytics genes such as Hexokinase 2, PDK1, PDK2, PFKFB3, and
H6PD were also upregulated. Moreover, using the XFeExtracellular Flux Analyzer, there is a
significant increase in ECAR at 1hr, 3hr and 6hr post ECM exposure (p<0.05) in addition to a
significant increase in the maximal glycolytic capacity (p<0.01).

Conclusions

These data suggests that the synovial microenvironment can induce
inflammatory and glycolytic changes in MoDC. Future work will aim to reduce the
inflammatory potential of synovial DC through metabolic manipulation.