Suicide attempters have lower levels of neuroprotective substances in the cerebrospinal fluid
[NEWS, 21 November 2012] In a novel study, researchers at Karolinska Institutet report that patients with suicidal behavior had lower levels in the cerebrospinal fluid of the signaling molecule interleukin-8 and growth factor VEGF, which both effect the growth and protection of neurons. The most depressed of the patients had also the lowest levels of VEGF. According to the researchers, this discovery may lead to a better understanding of underlying neurobiology of suicidal behavior and improved treatment of suicide attempters.
Interleukin-8 (IL-8) is important in neuroprotection and innate immunity, while VEGF (vascular endothelial growth factor) is a vital angiogenic factor and plays a role in regulating the growth of neurons in the hippocampus, a brain area of importance in depression. VEGF is also important in neurogenesis and synaptogenesis, and there are several animal studies suggesting that VEGF mediates the biological effect of electroconvulsive seizures and common antidepressants (SSRI). Earlier studies have also shown that suicidal patients had higher levels of the inflammatory marker interleukin-6 (IL-6) in the cerebrospinal fluid, which has been interpreted as a support of the theory that inflammation of the brain can be a contributing cause in severe depression.
In their study in Translational Psychiatry, the research team shows that low cerebrospinal fluid VEGF and IL-8 is associated with an increased risk of suicide attempt. 43 suicide attempters and 20 healthy volunteers participated in the study. Depression severity was measured with the rating scale MADRS.
The results showed that suicide attempters had lower levels of VEGF and IL-8 in the cerebrospinal fluid, compared to healthy volunteers. The suicide attempters with highest depression scores had the lowest VEGF levels. However, when measuring the levels of IL-6 in the cerebrospinal fluid, researchers found no difference between patients and controls.
"It is important to study growth factors and inflammatory markers in patients with different psychiatric diagnoses to assess if these changes cross diagnostic boundaries", says Dr Jussi Jokinen, researcher at the Department of Clinical Neuroscience. "One possible interpretation of the role of low VEGF levels in suicidal behavior may be related to treatment resistance of depression. Time spent as depressed heightens risk for suicidal behavior."
Low vascular endothelial growth factor and interleukin-8 in cerebrospinal fluid of suicide attempters
Translational Psychiatry, online 21 November 2012, doi:10.1038/tp.2012.123