TNF-alpha-induced neuronal necroptosis contributes to anxiety-like behaviors in mice under restraint stress
Stress exposure leads to imbalance in brain immunity and increased risks of psychiatric diseases. Excessive production of inflammatory cues under stress alters the survival, phenotypes and functions of neurons and neuroglia in particular brain regions, which are often manifested as emotional and cognitive disorders. Tumor necrosis factor-alpha (TNF-alpha) stands out among the pivotal inflammatory mediators due to its extensive targets and mechanisms. Here, we focused on its potential effects on anxiety-like mouse models. Flow cytometry and immunostaining revealed microglial activation and microglia-derived TNF-alpha overproduction in the olfactory ventricle (E/OV) and basolateral amygdala (BLA) of a stress-induced anxiety-like model. Immunostaining, immunoblotting and electron microscopy confirmed necroptosis of immature neurons in E/OV and mature neurons in BLA of mice under chronic restraint stress is synchronized with astrocytic A1 polarization, while this A1 polarization was further proved to promote neuronal necroptosis via in vitro coculture. The application of necroptosis inhibitor and TNF-alpha neutralizing antibody uniformly verified the described neuronal death as TNF-alpha-induced, RIPK1-dependent necroptosis accompanied by the downregulation of receptor for activated C kinase 1 (RACK1), which was later found to be responsible for inhibiting neuronal necroptosis by interacting with phosphorylated RIPK1. We concluded that microglial activation and subsequent astrocyte A1 polarization in the E/OV and BLA of mice under chronic restraint stress lead to excessive TNF-alpha secretion, which triggers neuronal necroptosis within the cerebral microenvironment and thus contributes to anxiety-like behaviors. Thus, the expressional regulation of TNF-alpha and RACK1 could serve as promising therapeutic targets for the treatment of stress-related emotional disorders.