Sodium Benzoate, a Food Additive and a Metabolite of Cinnamon, Enriches Regulatory T Cells via STAT6-Mediated Upregulation of TGF-ß.

Upregulation and/or maintenance of regulatory T cells (Tregs) during autoimmune insults may have therapeutic efficacy in autoimmune diseases. Earlier we have reported that sodium benzoate (NaB), a metabolite of cinnamon and a Food and Drug Administration-approved drug against urea cycle disorders, upregulates Tregs and protects mice from experimental allergic encephalomyelitis, an animal model of multiple sclerosis. However, mechanisms by which NaB increases Tregs are poorly understood. Because TGF-ß is an important inducer of Tregs, we examined the effect of NaB on the status of TGF-ß. In this study, we demonstrated that NaB induced the expression of TGF-ß mRNA and protein in normal as well as proteolipid protein-primed splenocytes. The presence of a consensus STAT6 binding site in the promoter of the TGF-ß gene, activation of STAT6 in splenocytes by NaB, recruitment of STAT6 to the TGF-ß promoter by NaB, and abrogation of NaB-induced expression of TGF-ß in splenocytes by small interfering RNA knockdown of STAT6 suggest that NaB induces the expression of TGF-ß via activation of STAT6. Furthermore, we demonstrated that blocking of TGF-ß by neutralizing Abs abrogated NaB-mediated protection of Tregs and experimental allergic encephalomyelitis. These studies identify a new function of NaB in upregulating TGF-ß via activation of STAT6, which may be beneficial in MS patients.

PDL-1 upregulation on monocytes and T cells by HIV via type I interferon: restricted expression of type I interferon receptor by CCR5-expressing leukocytes.

The programmed death (PD)-1 interacts with its ligand (PDL-1) delivering a negative signal to T cells. During human immunodeficiency virus (HIV)-1 infection PD-1 and PDL-1 expressions are increased. Here we show that monocytes and CCR5(+) T cells of HIV-uninfected donors upregulated PDL-1 upon in vitro exposure to HIV. HIV-induced PDL-1 required interferon (IFN)-alpha, but not IFN-gamma, production. Inhibition of endocytosis, required for HIV-induced IFN-alpha production, prevented PDL-1 upregulation. IFN-alpha-inducing Toll-like receptor (TLR) agonists increased PDL-1 on monocytes and CCR5(+) T cells. CD80 and CD86 were also increased on monocytes and CCR5(+) T cells after HIV exposure, but only CD80 was IFN-alpha-dependent. IFN-alpha-receptor subunit 2 (IFNAR2), was expressed only by CCR5(+) T cells and monocytes, explaining why these leukocytes responded to HIV-induced IFN-alpha. Finally, T cell proliferation was improved by PDL-1 blockade in HIV-treated PBMC. In the setting of HIV infection, IFN-alpha may negatively affect T cell responses by inducing PDL-1.