Glucocorticoid receptors and oligodendrocyte precursor NG2-cells as potential molecular targets in the pathophysiology of depression and stress-related disorders

Background

Major depressive disorder (MDD) is a highly prevalent and disabling psychiatric condition characterized by persistent low mood, anhedonia, and cognitive impairments. Its etiology is complex and multifactorial, involving genetic vulnerability, neurobiological alterations, and environmental stressors. Among these, chronic stress has been consistently identified as a major risk factor for the development of depression. Prolonged activation of the hypothalamic-pituitary-adrenal (HPA) axis results in sustained glucocorticoid release, which can negatively impact brain structure, synaptic plasticity, and neuronal survival. In this context, glucocorticoid receptors (GR) play a critical role in mediating stress responses and feedback regulation of the HPA axis. Additionally, oligodendrocyte precursor cells expressing NG2 proteoglycan have emerged as important contributors to brain plasticity and stress adaptation. The endocannabinoid system, particularly cannabinoid type 1 receptors (CB1), has also been implicated in emotional regulation and stress resilience. However, the potential interaction and coordinated involvement of GR, NG2, and CB1 in the neurobiology of depression remain insufficiently understood.

Objectives

The aim of this study was to investigate the expression patterns of GR, NG2, and CB1 in the cerebral cortex using two complementary approaches: (1) postmortem prefrontal cortex samples from MDD subjects and matched controls, and (2) cortical tissue from mice exposed to chronic corticosterone administration as an established preclinical model of stress-induced depression.

Methods

Human postmortem prefrontal cortex samples were obtained from subjects diagnosed with MDD (n=20) and matched controls (n=20). For the preclinical model, adult male C57BL/6J mice received corticosterone (6-10 mg/kg/day) in drinking water for four weeks (n=10), while controls received vehicle (n=10). Following treatment, cortical tissues were collected and processed. Protein expression levels of NG2, GR, and CB1 were quantified using Western blot analysis in both human and mouse cortical homogenates. Statistical analyses were conducted using unpaired two-tailed Student’s t-tests to assess group differences.

Results

In human postmortem samples, NG2 expression was significantly increased in MDD subjects compared to controls (p<0.01), suggesting alterations in oligodendrocyte precursor cell dynamics. In contrast, GR and CB1 protein levels did not show significant differences between groups. In the rodent model, chronic corticosterone exposure resulted in a significant reduction in cortical GR expression (p<0.001), consistent with receptor downregulation following prolonged glucocorticoid stimulation. NG2 levels showed a non-significant upward trend, while CB1 expression remained unchanged.

Conclusions

The significant GR downregulation observed in corticosterone-treated mice supports the hypothesis that chronic glucocorticoid exposure induces receptor desensitization, potentially contributing to HPA axis dysregulation and impaired stress feedback. In contrast, elevated NG2 expression in human MDD samples suggests that oligodendrocyte precursor cell alterations may represent a disease-related or compensatory response in the human prefrontal cortex. The lack of CB1 changes in both models indicates that cortical endocannabinoid signaling at the receptor level may not be a primary feature of stress-induced or clinical depression in these contexts. Together, these translational findings highlight GR and NG2 as potential molecular targets warranting further investigation in the pathophysiology of MDD and stress-related disorders.

References

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