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Tumor necrosis factor-alpha induces apoptosis in immortalized hypothalamic neurons: involvement of
M A Sortino1, F Condorelli, C Vancheri
1Institute of Pharmacology, University of Catania School of Medicine, Italy. msortino@mbox.unict.it
Abstract:
To investigate possible effects that may contribute, together with a direct action on neurohormone secretion, to the impairment of gonadal axis function during inflammation, we evaluated the effect of TNF alpha on the growth and viability of GT1-7 hypothalamic neurons and the intracellular transduction pathways involved in these effects. TNF alpha caused a reduction of cell number and an induction of apoptotic death. These effects were mimicked by cell-permeable analogs of ceramide and by neutral or acidic sphingomyelinase. Exposure to acidic sphingomyelinase induced a persistent (up to 48 h) reduction of cell growth and apoptosis, whereas the effect of neutral sphingomyelinase was time limited. The involvement of acidic sphingomyelinase in TNF alpha action was demonstrated by the partial prevention of ceramide generation, apoptosis, and reduced cell growth by the inhibitor of the acidic sphingomyelinase-generating pathway, D609, whereas the involvement of ceramide was proved by complete prevention of TNF alpha-induced effects by treatment with okadaic acid at concentrations inhibiting ceramide-dependent protein phosphatase. The present data indicate that TNF alpha, through activation of ceramide-generating pathways, is able to affect GT1-7 cell viability, suggesting an additional effect that may contribute to the global action of this cytokine on neuroendocrine activities.
Insights
Tumor necrosis factor-alpha (TNF-α) impairs hypothalamic neuron function by inducing cell death. This effect is mediated by ceramide-generating pathways, impacting neuroendocrine activities.
Area of Science:
- Neuroendocrinology
- Cell Biology
- Inflammation Research
Background:
- Inflammation can disrupt neurohormone secretion and gonadal axis function.
- Tumor necrosis factor-alpha (TNF-α) is a key inflammatory cytokine with potential neuroendocrine effects.
Purpose of the Study:
- To investigate TNF-α's impact on hypothalamic neuron growth and viability.
- To elucidate the intracellular pathways mediating TNF-α's effects on neurons.
Main Methods:
- Exposure of GT1-7 hypothalamic neurons to TNF-α.
- Assessment of cell number, apoptosis, and cell growth.
- Evaluation of sphingomyelinase activity and ceramide generation.
- Use of specific inhibitors (D609, okadaic acid) to probe pathways.
Main Results:
- TNF-α reduced GT1-7 cell number and induced apoptosis.
- Ceramide analogs and sphingomyelinases mimicked TNF-α's cytotoxic effects.
- Acidic sphingomyelinase mediated persistent reduction in cell growth and apoptosis.
- Inhibitors blocked TNF-α-induced ceramide generation, apoptosis, and reduced cell growth.
Conclusions:
- TNF-α negatively affects hypothalamic neuron viability via ceramide-generating pathways.
- This mechanism offers a potential explanation for TNF-α's role in neuroendocrine dysfunction during inflammation.