Liu X, Yanoff M, Li W
Department of Ophthalmology, Hahnemann University, Philadelphia, PA, USA.
Curr Eye Res. 1995 Dec;14(12):1087-93. doi: 10.3109/02713689508995814.
The lethal effect of near ultraviolet (NUV) with low intensity on cultured RPE cells has been investigated. RPE cultures with various cell densities were exposed to NUV (peaking at 365 nm) with or without ambient oxygen in phenol-red-free Dulbecco's PBS containing Ca2+, Mg2+ and glucose (PBS+). The cell viability was determined by dye exclusion and was expressed as cell death ratio (CDR, dead cells/total cells). When RPE cells at 5 x 10(3) cells/cm2, a non-contact low density, were irradiated either at a fixed irradiance (900 microW/cm2) with different exposure times (4 to 8h) or vice versa (8 h with irradiance from 430 to 900 microW/cm2), the change of CDR represented a similar linear function. The replotted data from both the time- and the irradiance-dependent curves indicated that the killing of RPE cells is dependent on the total energy dose of NUV. When a single NUV energy (19.44 J/cm2) was used, CDR was RPE cell density dependent. At confluence, NUV at the highest dosage tested (26 J/cm2) did not show any lethality. An oxygen-free condition abolished the NUV lethality on RPE cells even though the RPE cells were at a non-contact state. The presence of an antioxidant enzyme, catalase, in oxygen-saturated PBS+ protected RPE cells against NUV killing, but superoxide dismutase did not protect the RPE cells against NUV killing. These findings demonstrate that NUV possesses a lethal effect on RPE cells in vitro. Two key factors determine the magnitude and nature of this lethal effect: first, total NUV energy dose determines the nature of NUV's lethal effect; second, RPE growth conditions suggest the importance of cell-cell interaction in protecting these cells from NUV injury. Because an oxygen-free condition abolishes NUV lethality, it suggests that the oxidative stress is directly related to NUV lethal action. The selective inhibition by catalase of NUV killing of RPE cells suggests that the killing is oxidative species specific. NUV radiation might be highly risky to RPE viability in vivo, especially when the integrity of the RPE layer has been lost.
研究了低强度近紫外线（NUV）对培养的视网膜色素上皮（RPE）细胞的致死作用。将不同细胞密度的RPE培养物在含有Ca2+、Mg2+和葡萄糖的无酚红杜氏磷酸盐缓冲液（PBS+）中，在有或无环境氧气的条件下，暴露于NUV（峰值波长为365nm）。通过染料排斥法测定细胞活力，并以细胞死亡比率（CDR，死细胞数/总细胞数）表示。当RPE细胞以5×10(3)个细胞/cm2的非接触低密度，在固定辐照度（900μW/cm2）下照射不同时间（4至8小时），或反之（8小时，辐照度为430至900μW/cm2）时，CDR的变化呈现相似的线性函数。从时间和辐照度依赖性曲线重新绘制的数据表明，RPE细胞的杀伤取决于NUV的总能量剂量。当使用单一的NUV能量（19.44J/cm2）时，CDR取决于RPE细胞密度。在汇合状态下，测试的最高剂量（26J/cm2）的NUV未显示任何致死性。即使RPE细胞处于非接触状态，无氧条件也消除了NUV对RPE细胞的致死性。在氧气饱和的PBS+中存在抗氧化酶过氧化氢酶可保护RPE细胞免受NUV杀伤，但超氧化物歧化酶不能保护RPE细胞免受NUV杀伤。这些发现表明，NUV在体外对RPE细胞具有致死作用。有两个关键因素决定了这种致死作用的程度和性质：第一，NUV总能量剂量决定了NUV致死作用的性质；第二，RPE生长条件表明细胞间相互作用在保护这些细胞免受NUV损伤方面的重要性。由于无氧条件消除了NUV致死性，这表明氧化应激与NUV致死作用直接相关。过氧化氢酶对RPE细胞NUV杀伤的选择性抑制表明，这种杀伤具有氧化物种特异性。NUV辐射可能对体内RPE的生存能力具有高度风险，尤其是当RPE层的完整性丧失时。
