Neurotrophomodulatory effect of TNF-α through NF-κB in rat cortical astrocytes.

Abstract

Tumor necrosis factor alpha (TNF-α) is a well-known pro-inflammatory cytokine originally recognized for its ability to induce apoptosis and cell death. However, recent research has revealed that TNF-α also plays a crucial role as a mediator of cell survival, influencing a wide range of cellular functions. The signaling of TNF-α is mediated through two distinct receptors, TNFR1 and TNFR2, which trigger various intracellular pathways, including NF-κB, JNK, and caspase signaling cascades. Both TNFR1 and TNFR2 are expressed in astrocytes, which are specialized glial cells essential for maintaining the structural and functional integrity of the central nervous system (CNS). Astrocytes support neuronal function by regulating brain homeostasis, maintaining synaptic function, and supplying metabolic substrates. In addition, astrocytes are known to secrete a variety of growth factors and neurotrophins, such as nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT-3), and NT-4/5. These neurotrophins play a critical role in supporting neuronal survival, synaptic plasticity, and myelination within the brain. The present study focuses on the role of TNF-α in modulating neurotrophin expression and secretion in rat cortical astrocytes. We demonstrate that TNF-α induces the upregulation of neurotrophins, particularly NGF and BDNF, in cultured astrocytes. This effect is accompanied by an increase in the expression of their respective receptors (TrkA & TrkB), further suggesting a functional modulation of neurotrophic signaling pathways. Notably, we show that the modulation of neurotrophin expression by TNF-α is mediated via the NF-κB signaling pathway. Additionally, we observed that TNF-α also regulates the secretion levels of NGF and BDNF into the culture media of astrocytes in a dose-dependent manner, indicating that TNF-α can modulate both the production and release of these growth factors. Taken together, our findings highlight a previously underexplored neuroprotective role of TNF-α in astrocytes. Specifically, we propose that TNF-α, through the upregulation of neurotrophins, may contribute to maintaining neuronal health and supporting neuroprotection under disease conditions.