Tumor necrosis factor-α and interleukin-6 regulate secretion of brain-derived neurotrophic factor in human monocytes

Activated macrophages have been shown to produce brain-derived neurotrophic factor (BDNF) in diseases such as multiple sclerosis (MS) or allergic bronchial asthma (BA). However, there is little data on BDNF regulation in these cells. We demonstrate that unstimulated human peripheral blood monocytes, but not lymphocytes, constitutively secrete BDNF. IL-6 and TNF-α specifically enhanced BDNF secretion in monocytes, whereas typical Th1- and Th2-cytokines did not show any effect. None of the cytokines induced BDNF secretion in T- or B-cells. Thus, our data provide evidence that IL-6 and TNF-α represent a specific link between monocyte infiltration and neuronal changes in inflammatory diseases.