Major Depressive Disorder (MDD) is a debilitating and multifactorial neuropsychiatric condition that significantly contributes to the global burden of disease. Its clinical spectrum encompasses persis Show more
Major Depressive Disorder (MDD) is a debilitating and multifactorial neuropsychiatric condition that significantly contributes to the global burden of disease. Its clinical spectrum encompasses persistent low mood, anhedonia, cognitive decline, neurovegetative disturbances, and suicidality. This review synthesizes current evidence on the neurovascular, neurochemical, genetic, and psychosocial mechanisms underlying MDD. A narrative review approach was employed, incorporating data from peer-reviewed publications retrieved through systematic searches in biomedical databases. Emphasis was placed on recent findings that elucidate the interplay between neurobiological dysfunction and systemic influences in MDD pathogenesis. MDD pathophysiology is intricately linked to dysregulation of monoaminergic neurotransmission, aberrant hypothalamic-pituitary-adrenal (HPA) axis activity, and chronic neuroinflammation. Glial cell impairment, particularly involving astrocytes and microglia, disrupts synaptic homeostasis and neurovascular integrity. Genetic analyses estimate a heritability range of 30-50%, with genome-wide association studies identifying susceptibility loci in synaptic and immune pathways. Epigenetic modifications and perturbations of the gut- brain axis modulate vulnerability and progression. Oxidative stress and attenuated neurotrophic signalling, especially involving brain-derived neurotrophic factor (BDNF), further exacerbate neural circuit dysfunction. Sociodemographic determinants, including sex, psychosocial stressors, and socioeconomic adversity, also shape disease onset and trajectory. Although therapeutic modalities exist, limitations in early detection, treatment response, and long-term remission underscore the need for individualized strategies. Emerging approaches integrating epigenetic biomarkers and systems biology hold potential for precision psychiatry. A systems-level, biopsychosocial understanding of MDD is essential to advance targeted, personalized interventions, ultimately improving clinical outcomes in this complex disorder. Show less
Neuroinflammation appears in a variety of neurological disorders, including multiple sclerosis (MS), Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis. The adenosin Show more
Neuroinflammation appears in a variety of neurological disorders, including multiple sclerosis (MS), Parkinson's disease (PD), Alzheimer's disease (AD), and amyotrophic lateral sclerosis. The adenosine A₂A receptor (A₂AR), a Gs protein-coupled receptor that affects cAMP signaling and downstream kinases like PKA, CREB, and NF-κB, is one of the primary regulators of this process. Context-dependent effects of A₂AR activation include lowering acute inflammation and promoting neuronal survival when stimulated moderately, but increasing glial activation and cytokine production when overexpressed over an extended period of time. In microglia and astrocytes, A₂AR signaling regulates inflammatory pathways mediated by NF-κB and MAPK, affecting oxidative stress, blood-brain barrier (BBB) stability, and excitotoxicity. Acute or transient (short-term) A₂AR activation, on the other hand, increases the production of anti-inflammatory cytokines like IL-10 and enhances neurotrophic support through BDNF. A₂AR antagonists, including istradefylline and SCH58261, may reduce microglial triggering and have neuroprotective benefits, according to clinical and experimental data. The context-dependent activity of the receptor is shown by the fact that total receptor blockage interferes with adaptive immune control. Therefore, the therapeutic challenge is to carefully modify A₂AR signaling in particular cell populations, specifically targeting astrocytic or microglial receptors while maintaining the peripheral immunoregulatory activities. The dual regulatory role of A₂AR in neuroinflammation is summarized in this review along with its molecular mechanisms, disease-specific actions, and therapeutic significance. Developing next-generation neuroprotective strategies that reduce A₂AR signaling's pro-inflammatory and neurotoxic effects while preserving its beneficial homeostatic effects will require an understanding of the temporal and cell-specific dynamics of this signaling. Show less