Elevated cytokine expression in the orbitofrontal cortex of victims of suicide

Abstract

Objective: Based on the reported association between cytokines with depression and suicide, and evidence of increased markers of inflammation in the brain of suicide victims, the present study examined the expression of cytokines in the orbitofrontal cortex of suicide victims.

Method: In a postmortem sample obtained from the Brodman area 11 of suicides (n = 34) and controls (n = 17), real-time RT-PCR was used to compare the expression of mRNA species for tumor necrosis factor-alpha (TNF-alpha), interleukin (IL)-1 beta, 4, 5, 6, and 13.

Results: Increased expression of IL-4 was found in women suicide victims and IL-13 in men suicide victims. Elevated but not significant cytokine expression was also observed for TNF-alpha in women suicide victims.

Conclusion: To our knowledge, these results provide the first evidence of the presence of mRNA transcripts of type 2 T-helper cytokines in the human orbitofrontal cortex and their increased expression in the brain of suicides.

Figures

Fig. 1

Agarose gel electrophoresis images of amplified products after 40 cycles of real-time RT-PCR reaction using the set of primers listed in Table 2. Single bands corresponding to specific cytokines can be observed on top of the primer-dimer bands. RT+: reaction containing cDNA originated from total RNA. RT−: no amplification of product when RNA was amplified without reverse transcriptase step.

Fig. 2

Relative mRNA expression levels of interleukin-1β (IL-1β), IL-6, and tumor necrosis factor-α (TNF-α) in Brodman area 11 of suicide victims with respect to controls that died of other causes. Values are fold increase ±SEM respect to the mean of controls (represented by the number 1).

Fig. 3

Relative mRNA expression levels of interleukin-4 (IL-4), IL-5, and interleukin-13 (IL-13) in Brodman area 11 of suicide victims with respect to controls that died of other causes. Values are fold increase ±SEM respect to the mean of controls (represented by the number 1) (**P < 0.001 respect to control).