Mesenchymal stromal cells inhibit aerobic glycolysis in activated T-cells by negatively regulating hexokinase II activity through PD-1/PD-L1 interaction

Abstract Mesenchymal stromal cells (MSCs) have been shown to inhibit aerobic glycolysis in activated T-cells, leading to increased autophagy. Although tryptophan depletion induced by indoleamine 2,3-dioxygenase (IDO) generated by MSCs has been suggested as a potential mechanism, we found that this inhibition was completely abolished when T-cells were physically separated from MSCs using the transwell system. Instead, in the current study, we demonstrate that PD-1 and PD-L1, the expression of which is induced on activated T-cells and MSCs in response to interferon-γ, respectively, are involved in this inhibition. Blockade of PD-1/PD-L1 interaction by blocking antibodies significantly restored glucose uptake, glycolytic activity, and cluster formation of activated T-cells, whereas a specific inhibitor of IDO, 1-methyl-DL-tryptophan, had no effect. Neither surface nor cytoplasmic glucose transporter-1 expression on T-cells was changed by MSCs. Also, glycolytic gene expression in activated T-cells was not inhibited despite the presence of MSCs. However, we found that hexokinase II (HK2) protein expression was markedly decreased in activated T-cells that had been co-cultured with MSCs. PD-1 blocking antibody restored HK2 protein expression. Taken together, the PD-1/PD-L1 axis is involved in the MSC-mediated suppression of T-cell glycolysis by negatively regulating HK2 activity at the protein but not mRNA level.