High Mobility Group Box 1 Levels as an Inflammatory Mediator in Bipolar Mania

High mobility group box 1 protein (HMGB1) is a member of the molecular family known as damage-associated molecular patterns, which is implicated to have a role in neuroinflammation processes. In recent years, a growing number of studies have focused on the role of inflammation in Bipolar Disorder (BD). This study aimed to investigate the serum levels of HMGB1 and other inflammatory markers in patients with bipolar manic episodes compared to those in healthy controls (HC).

A single-center, observational, case-control study was conducted. Thirty-five patients with BD in manic episodes and 35 HC were assessed. Young Mania Rating Scale (YMRS) was used to assess the symptom severity of the patient group. While inflammatory markers (such as HMGB1, C-reactive protein (CRP) and white blood cell count) were assessed at the first three and the last day of hospitalization in the patient group, they were evaluated once in HC. Levels of inflammatory markers were compared between (patient-HC) and within groups (before-after treatment).

No difference was observed in serum HMGB1 levels of bipolar patients with manic episodes compared to the HC (p>0.05). C-reactive protein levels of manic patients were higher than HC (p<0.001), and the difference persisted even after treatment (p=0.007). In addition, there was a significant positive correlation between CRP levels and antipsychotic drug dosage (r=0.382, p=0.024).

There were no differences in HMGB1 levels between bipolar patients with acute manic episode and HC. However, higher CRP levels in bipolar patients support the low-grade inflammation hypothesis in the etiology of BD.