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C. A. Opere, J. M. Jamil, A. Wright, T. Durand, J.-M. Galano, A. Guy, Y. Njie-Mbye, S. E. Ohia; Regulation of [3H]D-Aspartate Release by Neuroprostanes in Bovine Retina, in vitro. Invest. Ophthalmol. Vis. Sci. 2010;51(13):3315.
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Although isoprostanes (IsoPs) have been reported to regulate excitatory amino acid neurotransmitter release from mammalian neural retina , in vitro (LeDay et al. Curr Eye Res 28:367-372, 2004; Opere et al. Neurochem Res 30(1):129-137, 2005), the pharmacological/physiological role of IsoP-like compounds such as neuroprostanes (NP)s on the eye is unclear.
In the present study, we investigated the effect of oxidant stress induced by peroxides on production of NPs. Furthermore, we studied the effect of NPs on K+-induced [3H]D-aspartate release in isolated bovine retinae.
Freshly isolated bovine retinae were either exposed (a) to hydrogen peroxide (H2O2) and cumene hydroperoxide (cuOOH) for up to 6h, in vitro for measurement of NPs using the stable isotope dilution methods employing GS/negative ion chemical ionization MS or (b) incubated in oxygenated Krebs solution containing 200nM of [3H] D-aspartate for 60 mins and then prepared for studies of neurotransmitter release using the superfusion method. Release of [3H]D-aspartate was evoked by iso-osmotic concentration of K+ (50mM)-stimuli applied at 80-88 mins (S1) and 116-124 mins (S2) after the onset of superfusion.
H2O2 (1 mM) increased production of A4-nP levels by 15% and 56% after 1 and 6h periods of treatment, respectively. Similarly, cuOOH (1 mM) enhanced (p<0.001) A4-nP levels by 408% and 420% after 1h and 6h periods of exposure to the oxidant, respectively. In the concentration range, 1 nM to 3 µM, the decosapentaenoic acid-derived NPs, BA-12low and BA-12high inhibited [3H]D-aspartate release in a concentration dependent manner, with BA-12low achieving a maximum inhibitory effect of 16% at 0.1 µM while BA-12high achieved a maximal inhibitory effect of 37.2% (p<0.01) at 1 µM. Similarly, in the concentration range, 1nM to 1µM, the docosahexaenoic acid metabolite, CO3-475 exhibited a concentration-dependent attenuation of [3H]D-aspartate release, with a maximal inhibitory effect of 26.6% (p<0.01) being observed at the 0.1 µM concentration.
We conclude that oxidative stress can enhance endogenous NP levels in bovine retina. Furthermore, NPs exhibit an inhibitory effect on excitatory neurotransmitter release in isolated bovine retinae. Taken together, our findings support a pharmacological role for NPs on amino acid neurotransmission in the retina.
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