Inflammatory monocyte gene expression: trait or state marker in bipolar disorder?

Area of Science:

• Immunology
• Psychiatry
• Genetics

Background:

• Bipolar disorder (BD) is a mood disorder characterized by alternating episodes of mania and depression.
• The role of inflammation in BD pathophysiology is increasingly recognized, but whether it represents a trait or state marker remains unclear.

Purpose of the Study:

• To investigate if inflammatory gene expression in monocytes differs between healthy controls (HC), euthymic BD patients, and BD patients experiencing a mood episode.
• To determine if inflammatory gene expression serves as a state-dependent marker in bipolar disorder.

Main Methods:

• Quantitative polymerase chain reaction (qPCR) was used to assess the expression of 35 inflammatory genes in monocytes.
• Gene expression scores were calculated for individuals, including comparisons between different mood states within the same patients.
• Participants included 69 HC, 82 euthymic BD patients, and 8 BD patients with a mood episode (7 depressed, 1 manic).

Main Results:

• No significant differences in inflammatory gene expression were found between HC and euthymic BD patients.
• BD patients experiencing a mood episode exhibited significantly higher total inflammatory gene expression scores compared to HC and euthymic BD patients.
• This elevation was particularly noted in sub-cluster 1 gene expression and was significant even when compared to the patients' own euthymic state scores.

Conclusions:

• Inflammatory monocyte gene expression in bipolar disorder is elevated during mood episodes, suggesting it is a state marker.
• These findings contribute to understanding the dynamic interplay between immune function and mood states in BD.
• The results underscore the potential for targeting inflammatory pathways during acute mood episodes in BD treatment.