Additive effects of inhibiting both mTOR and glutamine metabolism on the arthritis in SKG mice

Yo Ueda,Sho Sendo,Takaichi Okano,Keisuke Nishimura,Hirotaka Yamada,Akio Morinobu,Jun Saegusa

doi:10.1038/s41598-019-42932-1

Abstract

Glutamine metabolism and the mechanistic target of rapamycin (mTOR) pathway are activated cooperatively in the differentiation and activation of inflammatory immune cells. But the combined inhibition of both pathways was rarely investigated. This study investigated how inhibiting both glutamine metabolism with 6-diazo-5-oxo-L-norleucine (DON) and mTOR with rapamycin affects immune cells and the arthritis in a mouse model. We revealed that rapamycin and DON additively suppressed CD4+ T cell proliferation, and both of them inhibited Th17 cell differentiation. While DON inhibited the differentiation of dendritic cells and macrophages and facilitated that of Ly6G+ granulocytic (G)-MDSCs more strongly than did rapamycin, G-MDSCs treated with rapamycin but not DON suppressed CD4+ T cell proliferation in vitro. The combination of rapamycin and DON significantly suppressed the arthritis in SKG mice more strongly than did each monotherapy in vivo. The numbers of CD4+ T and Th17 cells in the spleen were lowest in mice treated with the combination therapy. Thus, combined treatment with rapamycin and DON additively ameliorated the arthritis in SKG mice, possibly by suppressing CD4+ T cell proliferation and Th17 differentiation. These results suggest the combination of rapamycin and DON may be a potential novel therapy for arthritis.

Highlights

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by infiltrations of various leukocyte subpopulations into the synovial space and the developing pannus in multiple joints, leading to inflammation, cartilage destruction, and bone erosion[1]
Our study demonstrated for the first time that the combination of rapamycin and DON had additive effects on immune cells in vitro and in vivo
Our study is the first to demonstrate that inhibiting both mechanistic target of rapamycin (mTOR) and glutamine metabolism had an additive effect on CD4+ T cells

Summary

Introduction

Rheumatoid arthritis (RA) is a chronic inflammatory disease characterized by infiltrations of various leukocyte subpopulations into the synovial space and the developing pannus in multiple joints, leading to inflammation, cartilage destruction, and bone erosion[1]. The metabolism of immune cells changes according to their state of activation or differentiation; this is called metabolic reprogramming. Since rapamycin was originally identified as a potent suppressor of T cell proliferation[3], the mechanistic target of rapamycin (mTOR) pathway becomes known as one of the main signaling pathways upregulated during the differentiation and activation of inflammatory immune cells. Myeloid-derived suppressor cells (MDSCs) are a heterogeneous population of immature immunosuppressive cells This population expands in response to pathologies such as tumor or inflammation, while the normal differentiation into other myeloid cells is disturbed[13]. MDSCs have several mechanisms for suppressing immune functions They suppress T cell responses by producing arginase 1 (Arg-1), inducible nitric oxide synthase (iNOS), reactive oxygen species (ROS), and TGFβ, and by upregulating PD-L114,15

Methods

Results

Conclusion