Antiproliferative effects of delta opioids on highly purified CD4+ and CD8+ murine T cells

Numerous studies have shown that opioids modulate the proliferative response of mixed splenocytes to T cell mitogens. To identify the T cell subpopulations affected by opioids, splenocytes from C57BL/6 and CD1 mice were separated using a fluorescent activated cell sorter (FACS) to obtain 98 to 99% pure populations of either CD4+ or CD8+ T cells. Cells were stimulated to proliferate in serum-free medium by cross-linking the T cell receptor using plate-coated anti-CD3-epsilon, then 3H-thymidine uptake and cell number were measured at 48 and 72 hr. [D-Ala2]-deltorphin 1 (deltorphin) dose-dependently inhibited the proliferation of C57BL/6 CD4+ T cells by approximately 50%. This effect was maximal when cells were preincubated with deltorphin 60 min before activation, whereas deltorphin was ineffective when added at the time of activation. Similarly, [D-Ala2]-Met-Enkephalinamide (DAME) 10(-11) to 10(-7) M inhibited CD4+ T cell proliferation. Naltrindole 10(-12) M abolished the antiproliferative effect of 10(-7) M deltorphin on CD4+ T cells. Proliferation of CD8+ T cells from C57BL/6 mice also was dose-dependently inhibited by deltorphin. At all concentrations to deltorphin, the antiproliferative effects were greater after 48 compared to 72 hr in culture. The effect of deltorphin and DAME on secretion of the T cell growth factor, IL-2, was determined by ELISA analysis of supernatants obtained from CD4+ T cells after 48-hr culture. Deltorphin showed a biphasic effect: 10(-11) M enhanced IL-2 secretion, whereas higher concentrations (10(-9)-10(-7) M) were inhibitory.(ABSTRACT TRUNCATED AT 250 WORDS)