Modulation of murine EL-4 thymic lymphoma cell proliferation and cytokine production by vitamin E succinate

RRR-alpha-tocopheryl succinate (VES) was studied for effects on murine EL-4 cell proliferation and production of interleukin-2 (IL-2) and transforming growth factor-beta (TGF-beta). VES was biphasic in its actions: 0.1 microgram/ml enhanced EL-4 cell proliferation, whereas 10-20 microgram/ml inhibited cellular proliferation. Cell-conditioned media (CM) from EL-4 cells treated with 0.2 ng/ml phorbol myristate acetate (PMA) + 0.1 microgram/ml VES contained increased amounts of IL-2, as determined by the murine cytotoxic T cell IL-2-dependent CTLL-2 bioassay. VES at 0.1 microgram/ml or 0.1 microgram/ml VES + 0.2 ng/ml PMA induced the expression of IL-2 mRNA by EL-4 cells three to nine hours after treatment. CM from EL-4 cells treated with VES at 10-20 microgram/ml exhibited potent antiproliferative activity when tested in the TGF-beta-responsive mink lung cell (Mv1Lu) bioassay and showed reduced inhibitory effects when tested on TGF-beta receptor-negative mink lung (DRA-27) cells. CM from control-treated EL-4 cells exhibited no antiproliferative activity. The VES-induced antiproliferative activity was characterized as TGF-beta by neutralization analyses and immunoprecipitation of metabolically labeled proteins with TGF-beta-specific reagents. VES treatment of EL-4 cells had no effect on TGF-beta 1 mRNA expression while downregulating TGF-beta 3 mRNA expression. In summary, these studies showed that 0.1 microgram/ml VES enhanced cellular proliferation, in part, via increased IL-2 production, whereas 10-20 micrograms/ml VES inhibited cellular proliferation, in part, via the secretion of biologically active TGF-beta.

Effects of RRR-alpha-tocopheryl succinate on IL-1 and PGE2 production by macrophages

Vitamin E is thought to enhance immunity by increasing interleukin-1 (IL-1) production and by downregulating prostaglandin E2 (PGE2) synthesis. In an effort to understand the mechanism(s) whereby the form of vitamin E known as RRR-alpha-tocopheryl succinate [also called vitamin E succinate (VES)] ameliorates retrovirus-induced immune dysfunctions, peritoneal exudate cells (PECs) derived from normal chickens and avian and murine macrophage cell lines were used as in vitro model systems to test the effects of VES treatments on PGE2 and IL-1 production. Supernatants from PECs that were exposed to avian erythroblastosis virus (AEV) for 45 minutes exhibited a 256% increase in PGE2 levels compared with supernatants from replica cultures of PECs not exposed to AEV. Pretreatment of PECs with VES before exposure to AEV maintained PGE2 levels at normal control levels. VES treatment enhanced IL-1 production by avian (HD11) and murine (P388D1) macrophage cells, respectively. Supernatants from VES-treated HD11- and P388D1-stimulated cells contained IL-1 activity 196% and 385%, respectively, greater than that observed with supernatants from untreated control cells. On the basis of these studies, downregulation of retrovirus-induced PGE2 production and/or upregulation of IL-1 production by VES are potential mechanisms for VES amelioration of retrovirus-induced immune suppression.