Anti-apoptotic effect of prolactin in lymphoid cells

There is growing evidence that prolactin protects cells from undergoing programmed cell death. Rat pre-T lymphoma Mb, cells represent a model to study the role of PRL in lymphoid tissue. We investigated the effect of PRL in the prolactindependent Nb2 and independent Nb:-SFJCDl cell line during the apoptotic process. Cells were arrested in the Grphase after 24 h incubation in starvation medium proven by cell-cycle analysis. Dexamethasone (104-10'° M), a potent inductor of programmed cell death, and/or PRL over a concentration range of 10^-7 M to 10"' M were analysed. Apoptosis was measured by FACS analysis after staining with propidium iodide (PI 1 mg/ml). Results: After 18 hours of stimulation apoptosis could be reduced 3 fold by PRL in Nb2 dependent cells. The protective effect of PRL was dose- dependent with a maximal protection between l O^-8 M and l O^-10 M and more effective in the PRL dependent cell line. When PRL was added 10 hours after dexamethasone treatment, apoptosis could not be inhibited. Cell sorting revealed no reversible effect of PRL after starting the apoptotic pathway. At least part of he immunoregulatory effect of prolactin seems to be mediated by its inhibition of apoptosis. To analyse the molecular mechanisms of PRL signal transduction in programmed cell death, the involvement of the bax and bcl-2 protein family in lymphoid cells is currently under investigation.