γ射线对磷脂酰胆碱大单层囊泡中心磷脂过氧化的辐射产率

Ahmed-Adrar Nazha Sid, Collin Fabrice, Couturier Martine, Vitrac Heidi, Bonnefont-Rousselot Dominique, Jore Daniel, Gardès-Albert Monique

Laboratoire de Chimie-Physique, CNRS UMR 8601, UFR Biomédicale, Université Paris Descartes, 75006 Paris, France.

Radiat Res. 2009 May;171(5):622-30. doi: 10.1667/RR1473.1.

Large unilamellar vesicles of 1-hexanoyl-2-(9Z-12Z-octadecadienoyl)-sn-glycero-3-phosphocholine (PLPC) have been used as model membrane to investigate the effect of increasing amount of cardiolipin (1',3'-bis-[1,2-Di-(9Z-12Z-octadecadienoyl)-sn-glycero-3-phospho]-sn-glycerol, CL) on the peroxidizability of the lipid phase. Hydroxyl radicals generated by gamma radiolysis of water initiated the lipid peroxidation. Both peroxidation products (conjugated dienes and hydroperoxides of PLPC, mono- and dihydroperoxides of CL) and disappearance of CL and PLPC were assessed as a function of the radiation dose (25 to 400 Gy, I = 10 Gy min(-1)). Our results show that the addition of 5% to 15% CL to large unilamellar vesicles (concentration ratio) produces almost complete inhibition of PLPC peroxidation. Thus, for 15% CL (known to be the proportion of CL in the inner mitochondrial membrane), the radiolytic yield of formation of PLPC hydroperoxides is reduced to zero, whereas it is equal to (3.1 +/- 0.2) x 10(-7) mol J(-1) for CL hydroperoxides, showing the importance of the targeted CL. For this concentration ratio (CL/ PLPC 15%), we have established the balance equation between the consumption of CL [G(-CL) = (2.8 +/- 0.1) x 10(-7) mol J(-1)] and the formation of CL hydroperoxides [G(CLOOH(T)) = (3.1 +/- 0.2) x 10(-7) mol J(-1)]. In addition, the radiolytic yields of disappearance of PLPC and CL have been determined [(1.5 +/- 0.1) x 10(-7) mol J(-1) and (2.8 +/- 0.1) x 10(-7) mol J(-1), respectively], their sum [(4.3 +/- 0.2) x 10(-7) mol J(-1)] being higher than G(HO.) (2.8 x 10(-7) mol J(-1)). However, there is no balance between the radiolytic yield of formation of PLPC hydroperoxides [G (PCOOH(T)) approximately 0] and the yield of disappearance of PLPC [(1.5 +/- 0.1) x 10(-7) mol J(-1)], likely because lipid fragments (not measured in this work) could be generated from HO(.) reaction on the polar head of PLPC. These results have been interpreted by assuming that the hydroxyl radicals attack in competition both lipid targets, i.e. PLPC and CL, with a higher sensitivity to CL oxidation. It can be concluded that a little amount of CL (10-15% CL/ PLPC concentration ratio) may exert a strong protective effect against the HO(.)-induced peroxidation of PLPC.

1-己酰基-2-(9Z,12Z-十八碳二烯酰基)-sn-甘油-3-磷酸胆碱（PLPC）的大单层囊泡已被用作模型膜，以研究增加心磷脂（1',3'-双-[1,2-二-(9Z,12Z-十八碳二烯酰基)-sn-甘油-3-磷酸]-sn-甘油，CL）的量对脂质相过氧化能力的影响。水经γ辐射分解产生的羟基自由基引发脂质过氧化。作为辐射剂量（25至400 Gy，I = 10 Gy min⁻¹）的函数，评估了过氧化产物（PLPC的共轭二烯和氢过氧化物、CL的单氢过氧化物和二氢过氧化物）以及CL和PLPC的消失情况。我们的结果表明，向大单层囊泡中添加5%至15%的CL（浓度比）几乎完全抑制了PLPC的过氧化。因此，对于15%的CL（已知是线粒体内膜中CL的比例），PLPC氢过氧化物形成的辐射产率降至零，而CL氢过氧化物的辐射产率等于(3.1 ± 0.2)×10⁻⁷ mol J⁻¹，表明靶向CL的重要性。对于该浓度比（CL/PLPC为15%），我们建立了CL消耗[G(-CL) = (2.8 ± 0.1)×10⁻⁷ mol J⁻¹]与CL氢过氧化物形成[G(CLOOH(T)) = (3.1 ± 0.2)×10⁻⁷ mol J⁻¹]之间的平衡方程。此外，还测定了PLPC和CL消失的辐射产率[分别为(1.5 ± 0.1)×10⁻⁷ mol J⁻¹和(2.8 ± 0.1)×10⁻⁷ mol J⁻¹]，它们的总和[(4.3 ± 0.2)×10⁻⁷ mol J⁻¹]高于G(HO·)（2.8×10⁻⁷ mol J⁻¹）。然而，PLPC氢过氧化物形成的辐射产率[G(PCOOH(T))≈0]与PLPC消失的产率[(1.5 ± 0.1)×10⁻⁷ mol J⁻¹]之间不存在平衡，可能是因为HO·与PLPC极性头部反应可能产生脂质碎片（本研究未测定）。这些结果通过假设羟基自由基竞争性攻击两个脂质靶点即PLPC和CL来解释，其中对CL氧化更敏感。可以得出结论，少量的CL（10 - 15%的CL/PLPC浓度比）可能对HO·诱导的PLPC过氧化发挥强大的保护作用。