The role of P2X7 ATP receptors in the nervous system: potential implications in inflammatory and depression-like diseases
© Csölle and Spelágh; licensee BioMed Central Ltd. 2009
Published: 12 November 2009
The P2X7 receptor is a ligand-gated ion channel expressed in neuronal, glial and immune cells and is implicated in a wide range of pathological conditions, including ischemia, and inflammation. The P2X7 receptor can modulate the maturation and release of the proinflammatory cytokine, interleukin-1β (IL-1β). IL-1β is suggested to be involved in the pathophysiology of depression and sickness behaviour, elicited by peripherally administered bacterial lipopolysaccharide (LPS).
The levels of IL-1β production were quantified in the hippocampi of rodents, using an ELISA kit. In order to identify genes involved in LPS-induced changes in P2X7 receptor knock-out (KO) and wild-type (WT) mouse amygdala we performed whole mouse genome microarray analysis of mRNA extracted after six hours of intaperitoneal LPS injection.
We showed that in vivo LPS challenge elevated IL-1β levels in the rodent hippocampus. Antagonists of P2X receptors inhibited LPS-induced IL-1β levels with a pharmacological profile similar to that of P2X7 receptors and their inhibitory effect was attenuated in the absence of P2X7 receptors. In WT mice, LPS overexpressed mRNA encoding P2X4 and P2X7 receptors in the hippocampus and also caused a remarkable increase in the levels of IL-1β in the blood serum. The hippocampal increase of IL-1β was substantially alleviated when contamination by circulating blood cells was excluded by transcardial perfusion, indicating the peripheral origin of hippocampal IL-1β elevation. Six h after i.p. injection of LPS, the expression of 74 transcripts (41 upregulated and 33 downregulated) was significantly altered two-fold or more in mouse amygdala. These genes can be classified according to their biological function as follows: inflammatory response: Il4ra, Ccl21b; depression-associated genes: Slc17a7, Nfatc1, Creb3l3. Our microarray studies have identified 8,165 transcripts that were significantly affected by the deficiency of P2X7 receptors indicating that the deletion of P2X7 receptors causes genome-wide alterations of gene expression including depression-related genes in mouse amygdale (GABAA, GABAC receptors, AMPA and NMDA2B ionotropic and mGlu5, mGlu7 metabotropic glutamate receptors were downregulated in KO mice).
These results point to the key role of the endogenous activation of P2X7 receptors in the level of IL-1β and in the regulation of individual protein which could be of potential interest for the study of the neurobiological basis underlying psychiatric diseases like depression.
This article is published under license to BioMed Central Ltd.