Connection between inflammatory processes and transmittor function-Modulatory effects of interleukin-1

Cells in the nervous system can respond to different kinds of stress, e.g. injury, with production and release of inflammatory molecules, including cytokines. One of the most important proinflammatory cytokines is interleukin-1, affecting most organs of the body. The high constitutive expression of interleukin-1 in the adrenal gland provides a source for local and systemic actions, in addition to activated monocytes. In the brain, the constitutive expression is low, but activated microglia produce and release interleukin-1 during pathological conditions such as neurodegenerative disorders (e.g. stroke, traumatic brain injury, Alzheimer's disease, Parkinson's disease). Interleukin-1 has an important role in mediating 'sickness symptoms' such as fever, in response to infections. Its role in neurodegeneration is not fully elucidated, but there is evidence for involvement in both amyloidosis and tau pathology, major neuropathological hallmarks of Alzheimer's disease. The interleukin-1 family at present consists of 11 members, one of which is the endogenous receptor antagonist. Overexpression of this antagonist in the CNS in a transgenic mouse strain, Tg hsIL-1ra, has allowed studies on morphological and functional effects of blocking interleukin-1 receptor-mediated activity in the brain. Marked alterations of brain morphology such as reduced hippocampal and cortical volume correlate with behavioural deficits. Decreased anxiety and impaired long-term memory are among the consequences. Intact interleukin-1 signalling is important for the brain's ability to adapt to acute and chronic neuroinflammation. Increased amplitude and prolongation of proinflammatory cytokine production underly the behavioural alterations characteristic for ageing. Moreover, deregulated expression of interleukin-1 is associated with ageing-related chronic neurodegenerative disorders.