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18 November 2009
Depression occurs more frequently in people
with temporal lobe epilepsy (TLE) than in
the general UK population (GPUK). In fact
between 20-40% of people with TLE also show
depressive symptoms, which when compared
to 7-12% of the GPUK is a significant difference.
The reason for this increase is not fully
understood, however evidence suggests that
a cytokine known as interleukin-1beta (IL1b)
might be an important factor.
Cytokines are signalling molecules that
play a vital role in inflammation and immunity.
They act on specific receptors and cause
a cascade of effects within nearby cells.
Studies have shown that in TLE, levels of
IL1b in the hippocampus (an important memory
centre located in the temporal lobe) are
increased. Other evidence suggests that
a chronic increase in the blood concentration
of certain cytokines, IL1b included, can
cause depression. So is the increased level
of hippocampal IL1b the cause of depression
in TLE?
Researchers at the University of California,
US have recently tested this theory. They
induced status epilepticus in a group of
animal models using a substance known as
pilocarpine, and selected those that subsequently
developed signs of depression according
to set behavioural and biochemical criteria.
The 'depressed' models were then treated
for two weeks with an interleukin-1 receptor
antagonist (IL1RA), via infusion into the
hippocampus from both sides.
A receptor antagonist stops a particular
molecule from binding to its receptor, for
example by occupying the receptor itself,
or causing the shape of the binding site
to change (so the molecule will no longer
fit). In the current study, IL1RA was used
to block the effects of IL1b. If the theory
is correct, we would expect the depression
in the models to improve.
Sure enough, the animals treated with IL1RA
showed improvement in all the depressive
'characteristics' examined; whilst both
their 'normal functioning' and seizure frequency
were unaffected.
These results are exciting, because IL1b
receptor blockers could potentially be successful
in the treatment of depression in TLE, in
the future.
Read
more here
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