Circulating Toll-Like Receptor 4, Nucleotide-Binding Oligomerization Domain-Like Receptor Protein 3, and Cytokines in Patients with Bipolar Depression: A Case-Control Study

Objective: The etiology of bipolar disorder (BD), a complex psychiatric condition, remains uncertain. Previous research has suggested a potential involvement of the host immune system in the development of BD. This study aims to investigate plasma levels of cytokines, circulating toll-like receptor 4 (TLR4), and nucleotide-binding oligomerization domain-like receptor protein 3 (NLRP3) in patients with bipolar depression. Methods: This study recruited patients with a depressive episode of BD and healthy controls (HCs). Inflammatory cytokines were quantified using enzyme linked immunosorbent assay (ELISA) analysis. Results: A total of 26 BD patients with a depressive episode and 14 HCs were enrolled in the study. The findings revealed that individuals with BD with a depressive episode exhibited elevated serum levels of NLRP3 and interleukin-18 compared to HCs. Correlation analyses indicated a favorable association between the frequency of episodes, duration of illness, and TLR4 levels. Conclusion: The results suggest a connection between cytokines associated with the activation of NLRP3 and their potential impact on the pathogenesis of BD.