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Cheryl Chi, Deeba Husain, Celeste Rich, Nicole Siegel, Vickery Trinkaus-Randall; P2X7 Expression in Vitrectomy Samples. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1587.
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P2X7 is an ionotropic receptor activated by ATP released in stress conditions. The full-length form of P2X7 (P2X7A) is associated with the induction of apoptosis in many cell types, but a truncated variant, P2X7j, has also recently been found in transitional states that require cell proliferation. Altered regulation of these forms has been observed in diabetic patients, but specific relationships between the disease and receptor have yet to be elucidated. Our goal is to demonstrate the expression of P2X7A and P2X7j and to correlate this with sulfated glycosaminoglycan (GAG).
Vitreous samples from 46 patients were centrifuged and supernatant collected. Real-time PCR and delta delta Ct analysis were performed to determine expression of P2X7 mRNA. Each form was normalized to 1 using a control sample. Sulfated GAG in the supernatant were measured by Dimethylmethylene Blue. Measurements were averaged and standard statistical tests were performed.
We observed an increased trend in the ratio of P2X7j to P2X7A in diabetic patients over control. The level of P2X7j did not change between diabetic or control patients, but the level of P2X7A decreased in diabetics, indicative of a less apoptotic phenotype. This was supported by lower expression of P2X7A in patients with proliferative diabetic retinopathy. Hypertensive control patients showed a large increase in ratio over non-hypertensive control patients, but no such trend was seen in diabetic patients. Conversely, diabetic patients with retained lens fragments showed larger ratios than those without retained lens fragments, but this trend was not seen in the control population. Diabetic patients overall show decreased sulfated GAG compared to control. Diabetic patients with retained lens fragments show a decrease, but those with hypertension show an increase, when compared to the corresponding control.
Expression of P2X7j or pro-proliferative form, along with a decrease in P2X7A, were reflected in the phenotypic expectations of pathological states. The inflammation associated with hypertensive states is suggested by the increased ratio, and the decreased pro-apoptotic form illustrates cell proliferation in PDR. Changes in P2X7 receptor expression and sulfated GAG reflect the influence of multiple underlying pathologies.
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