Hyaluronan Synthesis Is Required for IL-2-Mediated T Cell Proliferation

Abstract

Hyaluronan (HA) is a glycosaminoglycan composed of N-acetylglucosamine and glucuronic acid subunits. Previous studies have suggested that CD44 expressed by T cells bind exogenous HA for their proliferation. However, HA endogenously synthesized by T cells may participate in their autocrine proliferation. In this study, we examined the role of endogenous HA in T cell proliferation using the highly specific HA synthase inhibitor, 4-methylumbelliferone (4-MU). We found that 4-MU inhibited the mitogen-induced synthesis of HA by T cells. Moreover, 4-MU inhibited T cell proliferation in a dose-dependent manner when cells were cultured with different stimuli, including Con A, PMA/ionomycin, and allogeneic spleen cells. Furthermore, 4-MU inhibited mitogen-stimulated IL-2 secretion, suggesting that HA may play a role in the production of this cytokine. Addition of IL-2 to T cells treated with 4-MU and Con A reversed the block in cell proliferation, showing that impaired IL-2 production is a likely mechanism for the inhibited division of T cells. Surprisingly, an anti-CD44 Ab antagonistic for HA binding did not reduce IL-2 secretion or T cell proliferation. Importantly, 4-MU did not alter the surface expression of CD44 or the ability of CD44 to bind to HA. Thus, HA-mediated IL-2 production and T cell proliferation are CD44 independent. Our results strongly suggest that HA synthesized by T cells themselves is critical for their IL-2-mediated proliferation and have revealed a previously unrecognized role for endogenous HA in T cell biology.

The effects of 4-methylumbelliferone on hyaluronan synthesis, MMP2 activity, proliferation, and motility of human aortic smooth muscle cells

“…Such results highlighted the possibility that the reduction of HA synthesis can also be ascribed to some cytotoxic effects that 4-MU has on AoSMCs besides the effects on the UDP-GlcUA concentration and HA metabolic enzymes expression. A similar 4-MU reduction in proliferation has also been observed in other cell types (Rilla et al 2004;Mahaffey and Mummert 2007).…”

Inhibition of Hyaluronan Synthesis Reduces Versican and Fibronectin Levels in Trabecular Meshwork Cells

“…[51] Other studies have reported changes in CD44 and decorin levels in response to HAS gene silencing or 4MU treatment. [52], [53], [54], [55] For instance, total CD44 mRNA expression was reduced in HAS2 siRNA-treated human breast cancer cells, while a different study reported that certain CD44 alternative transcripts were down-regulated in HAS1 siRNA-treated bladder cancer cells. [52], [54] Conversely, there was no effect of 4MU treatment on CD44 protein levels in T-cells.…”

Inhibition of Hyaluronan Synthesis Protects against Central Nervous System (CNS) Autoimmunity and Increases CXCL12 Expression in the Inflamed CNS

“…Vivo-We used 4MU, a well established and specific inhibitor of hyaluronan production (3,7,(13)(14)(15)(16)(17)20), to modulate hyaluronan synthesis. First, we confirmed the inhibitory influence of 4MU on hyaluronan synthesis by in vitro experiments.…”

“…Several studies suggest that hyaluronan may have proinflammatory roles in the context of CNS autoimmunity: 1) it accumulates in demyelinated CNS lesions in MS and EAE (5,6); 2) HA production by dendritic cells and T-cells promotes antigen presentation and enhances T-cell activation and proliferation (2,3,7,8); 3) HA-CD44 interactions at the CNS vascular endothelium facilitate lymphocyte binding to vessels and CNS infiltration (9 -11); and 4) hyaluronan fragments signal through both Toll-like receptors (TLR) 2 and 4 and thereby stimulate inflammatory gene expression in immune cells (12).…”