The role of β-endorphin (β-EP) in ethanol-altered NK cell cytolytic activity is studied using male Fischer-344 rats as an animal model. Ethanol was administered for 1, 2, 3, or 4 wk in a liquid diet containing 8.7% ethanol (v/v), which means that 37% of the total calories were derived from ethanol. Rats treated with ethanol for 1 wk showed an increase in hypothalamic and plasma levels of immunoreactive (IR)-β-EP, but displayed no significant effect on NK cell activity determined by 51Cr release assay, as compared with those in pair-fed and ad libitum-fed animals. However, animals treated with ethanol for 2, 3, or 4 wk showed decreased hypothalamic and plasma levels of IR-β-EP and decreased splenic NK cell activity. No significant decrease in the number of splenocytes and NK cells or in the percentage of NK cells was seen until after 3 and 4 wk of ethanol treatment. Exposure in vitro of splenic lymphocytes obtained from control animals to various concentrations of β-EP increased NK cell activity. The opiate antagonist naltrexone blocked the β-EP-stimulated effect. The in vitro NK cell response to β-EP was reduced in the splenocytes obtained from animals treated with ethanol for 2 wk, but not in those obtained from animals treated with ethanol for 1 wk as compared with those in control animals. Additionally, β-EP administration into the paraventricular nucleus of the hypothalamus stimulated NK cell cytolytic activity, whereas the opiate blocker administration reduced NK cell activity. The NK cell responses to paraventricular nucleus β-EP were reduced in the animals treated with ethanol for 2 wk. These data provide evidence for the first time that ethanol inhibits NK cell cytolytic activity, possibly by reducing β-EP-regulated splenic NK cell function.

Neurobehavioral stress has been shown to promote tumor growth and progression as well as dampen the immune system. In this study, we investigated whether inhibiting stress hormone production could inhibit the development of mammary carcinoma and metastasis in a rat model of breast carcinogenesis. To enhance β-endorphin (BEP), the endogenous opioid polypeptide that boosts immune activity and decreases stress, we generated - BEP neurons by in vitro differentiation from fetal neuronal stem cells and transplanted them into the hypothalami of rats subjected to breast carcinogenesis. BEP transplanted rats displayed a reduction in mammary tumor incidence, growth, malignancy rate, and metastasis compared to cortical cells transplanted rats. BEP neuron transplants also reduced inflammation and epithelial to mesenchymal transition (EMT) in the tumor tissues. In addition, BEP neuron transplants increased peripheral natural killer (NK) cell and macrophage activities, elevated plasma levels of anti-inflammatory cytokines and reduced plasma levels of inflammatory cytokines. Anti-metastatic effects along with stimulation of NK cells and macrophages could be reversed by treatment with the opiate antagonist naloxone, the β-receptor agonist metaproterenol, or the nicotine acetylcholine receptor antagonist methyllycaconitine. Together, our findings establish a protective role for BEP against the growth and metastasis of mammary tumor cells by altering autonomic nervous system activities that enhance innate immune function.

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These results suggest that chronic alcohol administration reduces immune function partly by decreasing the opioid-regulated mitogen-stimulated proliferation of lymphocyte subsets.

These results suggest that chronic alcohol administration reduces immune function partly by decreasing the opioid-regulated mitogen-stimulated proliferation of lymphocyte subsets.

These data suggest that chronic ethanol consumption may suppress NK cell cytolytic activity in male Fischer rats by decreasing the production, activity, or both of granzyme B, perforin, and IFN-gamma.

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