Purinergic system dysregulation and depression: The neuroinflammatory impact of silica nanoparticles

Major depressive disorder (MDD) is a neuropsychiatric condition linked to neurotransmitter imbalances, neuroinflammation, and purinergic signaling dysregulation. Emerging evidence suggests that environmental pollutants, such as silica nanoparticles (SiNPs), contribute to neuroinflammatory responses and depressive-like behaviors, though the mechanisms remain unclear. This study investigates the effects of repeated SiNP exposure on depressive-like behaviors and purinergic signaling in the hippocampus of adult male rats. Thirty-six Wistar rats were divided into three groups (control, low-dose SiNP, high-dose SiNP) and received intraperitoneal injections for 28 days. Depressive-like behaviors were assessed using the Forced Swimming Test (FST) and Tail Suspension Test (TST), while the enzymatic activities of ectonucleotidases (E-NTPDase, E-NPP, and ecto-5'-nucleotidase) and ATPase function were measured in hippocampal tissue. Gene expression of purinergic receptors (A2A, P2X7, P2Y2) and ectonucleotidases (CD73, NTPDase 1-3) was analyzed via RT-qPCR, with immunohistochemistry and immunofluorescence assessing CD73 and CD90 protein levels. SiNP exposure significantly increased immobility time in both behavioral tests, indicating depressive-like behavior. It also upregulated ectonucleotidase activity, purinergic receptors (A2A, P2X7, P2Y2), and CD73/CD90 expression, while disrupting ATPase function by decreasing both Na⁺/K⁺-ATPase and Ca²⁺-ATPase activities. These findings suggest that SiNPs induce depressive-like behavior through purinergic pathway dysregulation, promoting neuroinflammation and neurotransmission alterations. Further studies are needed to explore purinergic signaling as a potential therapeutic target in depression.