α-melanocyte-stimulating hormone modulates lipopolysaccharide plus interferon-γ-induced tumor necrosis factor-α expression but not tumor necrosis factor-α receptor expression in cultured hypothalamic neurons.

In a previous work we showed that the melanocortin alpha-melanocyte-stimulating hormone (α-MSH) exerts anti-inflammatory action through melanocortin 4 receptor (MC4R) in vivo in rat hypothalamus. In this work, we examined the effect of α-MSH on the expression of tumor necrosis factor-α (TNF-α) and interleukin-1β (IL-1β) and their receptors in primary cultured rat hypothalamic neurons. We also investigated α-MSH's possible mechanism/s of action. α-MSH (5 μM) decreased TNF-α expression induced by 24h administration of a combination of bacterial lipopolysaccharide (LPS, 1 μg/ml) plus interferon-γ (IFN-γ, 50 ng/ml). Expression of TNF-α and IL-1β receptors TNFR1, TNFR2 and IL-1RI, was up-regulated by LPS+IFN-γ whereas α-MSH did not modify basal or LPS+IFN-γ-induced-TNFRs or IL-1RI expression. Both α-MSH and LPS+IFN-γ treatments increased CREB activation. α-MSH did not modify NF-κB activation induced by LPS+IFN-γ in hypothalamic neurons. In conclusion, our data show that α-MSH reduces TNF-α expression in hypothalamic neurons by a mechanism which could be mediated by CREB. The regulation of inflammatory processes in the hypothalamus by α-MSH might help to prevent neurodegeneration resulting from inflammation.