The M1-like microglia-A1-like astrocyte Axis: A central hub linking BDNF dysregulation in chronic stress to anxiety disorders

The high global prevalence of anxiety disorders, coupled with the limitations of existing treatments, constitutes a severe public health challenge. Chronic stress, as a core environmental trigger, has garnered increasing attention for its mechanism of mediating brain-derived neurotrophic factor (BDNF) imbalance through neuroinflammation. BDNF dysregulation may contribute to anxiety disorders, particularly in subtypes with heightened neuroinflammation. The objective of this review is to comprehensively and methodically explores the potential role of the "M1-like microglia-A1-like astrocyte axis (M1-A1 axis)" in linking chronic stress to BDNF dysregulation in anxiety disorders, and to provide a theoretical basis for intervention strategies targeting this axis. By synthesizing recent relevant clinical and preclinical evidence, this review integrates evidence from molecular to systems levels, focusing on the activation mechanisms of neuroinflammation under chronic stress, the crosstalk between glial cells, and their regulatory network on BDNF. Chronic stress is associated with peripheral and central cascades through hypothalamic-pituitary-adrenal (HPA) axis activation and gut microbiota disruption. Within the central nervous system (CNS), stress induces microglial polarization toward the pro-inflammatory microglial subpopulations (hereinafter referred to as M1-like microglia). The signals released by M1-like microglia, such as Interleukin-1 alpha (IL-1α), Tumor Necrosis Factor-alpha (TNF-α), and Complement Component 1q (C1q) (ITC), drive astrocytes to transform into the neurotoxic astrocyte states (hereinafter referred to as A1-like astrocyte), forming the "M1-A1 axis". This axis contributes to BDNF dysregulation through the following mechanisms: (1) Release of pro-inflammatory cytokines inhibits BDNF transcription and translation; (2) Induction of astrocytic lactate metabolism disruption, which impairs neuronal energy supply and acidifies the microenvironment, further amplifying inflammation and affecting BDNF expression; (3) Compromise of the blood-brain barrier(BBB)enables peripheral immune cells to penetrate into the CNS, and these cells work in synergy with central glial cells to amplify inflammation. The reduction in BDNF and the imbalance in the ratio of its precursor to mature form ultimately lead to impaired synaptic plasticity in brain regions like the hippocampus (HIP) and amygdala, precipitating anxiety-like behaviors. Existing pharmacological interventions are inadequate to reverse this pathological process. The M1-A1 axis may serve as a key node linking chronic stress to BDNF dysregulation and anxiety disorders. Targeting the phenotypic transformation of glial cells, repairing the BBB, or modulating glial cell metabolism (e.g., lactate shuttle) may represent potential strategies requiring further validation. Future research should focus on the spatiotemporal dynamics of this axis and its clinical translation.