Email updates

Keep up to date with the latest news and content from Biology of Mood & Anxiety Disorders and BioMed Central.

Open Access Highly Accessed Research

Increased ratio of anti-apoptotic to pro-apoptotic Bcl2 gene-family members in lithium-responders one month after treatment initiation

Lori Lowthert1, Janine Leffert1, Aiping Lin2, Sheila Umlauf3, Kathleen Maloney1, Anjana Muralidharan1, Boris Lorberg1, Shrikant Mane3, Hongyu Zhao4, Rajita Sinha1, Zubin Bhagwagar15 and Robert Beech1*

Author Affiliations

1 Department of Psychiatry, New Haven, CT, 06511, USA

2 Keck Foundation Biotechnology Biostatistics Resource, New Haven, CT, 06511, USA

3 Center for Genome Analysis, New Haven, CT, 06511, USA

4 Department of Epidemiology and Public Health, Yale University School of Medicine, New Haven, CT, 06511, USA

5 Neuroscience Global Clinical Research, Bristol-Myers Squibb, Wallingford, CT, 06492-1996, USA

For all author emails, please log on.

Biology of Mood & Anxiety Disorders 2012, 2:15  doi:10.1186/2045-5380-2-15

Published: 12 September 2012

Abstract

Background

Lithium is considered by many as the gold standard medication in the management of bipolar disorder (BD). However, the clinical response to lithium is heterogeneous, and the molecular basis for this difference in response is unknown. In the present study, we sought to determine how the peripheral blood gene expression profiles of patients with bipolar disorder (BD) changed over time following intitiation of treatment with lithium, and whether differences in those profiles over time were related to the clinical response.

Methods

Illumina Sentrix Beadchip (Human-6v2) microarrays containing > 48,000 transcript probes were used to measure levels of expression of gene-expression in peripheral blood from 20 depressed subjects with BD prior to and every two weeks during 8 weeks of open-label treatment with lithium.

Changes in gene-expression were compared between treatment responders (defined as a decrease in the Hamilton Depression Rating Scale of 50% or more) and non-responders. Pathway analysis was conducted using GeneGO Metacore software.

Results

127 genes showed a differential response in responders vs. non-responders. Pathway analysis showed that regulation of apoptosis was the most significantly affected pathway among these genes. Closer examination of the time-course of changes among BCL2 related genes showed that in lithium-responders, one month after starting treatment with lithium, several anti-apoptotic genes including Bcl2 and insulin receptor substrate 2 (IRS2) were up-regulated, while pro-apoptotic genes, including BCL2-antagonist/killer 1 (BAK1) and BCL2-associated agonist of cell death (BAD), were down-regulated. In contrast, in lithium non-responders, BCL2 and IRS2 were down-regulated, while BAK1 and BAD up-regulated at the one-month time-point.

Conclusions

These results suggest that differential changes in the balance of pro- and anti- apoptotic gene-expression following treatment with lithium may explain some of the heterogeneity in clinical response in BD patients.

Keywords:
Bipolar disorder; Microarray; Lithium-response; Gene expression; BCL2; Apoptosis; Mitochondria