The P2X(7) loss-of-function Glu496Ala polymorphism affects ex vivo cytokine release and protects against the cytotoxic effects of high ATP-levels

BACKGROUND: The P2X(7) receptor plays an important role in cytokine release during the inflammatory response in vivo. Polymorphisms within the P2X(7) receptor gene that lead to loss of receptor function may contribute to impaired cytokine release by immune cells. Therefore, we investigated whether a known loss-of-function polymorphism (Glu496Ala) in the P2X(7) receptor gene leads to alterations in cytokine release in response to ATP.

RESULTS: An ex vivo whole blood model was used to induce an inflammatory reaction with the pro-inflammatory stimuli LPS and PHA (phytohemagglutinin). Blood from n=9 subjects with the Glu496Ala P2X7 SNP (P2X7MUT) and n=7 'wild-type' subjects (no P2X7 SNP; P2X7WT) was used.Addition of ATP (0.9-3 mM) to LPS/PHA-stimulated whole blood induced an increase in IL-1β release in P2X7MUT subjects, whereas decreased release was observed in P2X7WT subjects. Decreased levels of IL-6 and TNF-α in response to ATP were shown in both P2X7MUT and P2X7WT subjects, which was less pronounced in P2X7MUT subjects. ATP at 3 mM also significantly decreased levels of lactate dehydrogenase (LDH) in P2X7MUT subjects compared to P2X7WT subjects.

CONCLUSIONS: The presence of the non-synonymous Glu496Ala loss-of-function polymorphism within the P2X(7) receptor gene is likely to be of importance in the release of cytokines during inflammation. Furthermore, this study suggests that carriers of the Glu496Ala loss-of-function polymorphism are protected against the cytotoxic effects of high ATP-levels.