Wang Hong P, Schafer Freya Q, Goswami Prabhat C, Oberley Larry W, Buettner Garry R
Free Radical and Radiation Biology and The Holden Comprehensive Cancer Center, The University of Iowa, Iowa City, IA 52242-1101, USA.
Free Radic Res. 2003 Jun;37(6):621-30. doi: 10.1080/1071576031000088283.
Phospholipid hydroperoxide glutathione peroxidase (PhGPx) is an antioxidant enzyme that reduces cellular phospholipid hydroperoxides (PLOOHs) to alcohols. Cellular peroxide tone has been implicated in cell growth and differentiation. By reducing the PLOOH level in the cell membrane, PhGPx regulates the peroxide tone and thereby might be involved in cell growth. We hypothesized that overexpression of PhGPx in human breast cancer cells would decrease their growth rate. We stably transfected MCF-7 cells (Wt) with L-PhGPx and measured cell doubling time, plating efficiency, and cell cycle phase transit times. P-4 cells (8-fold increase in PhGPx activity) showed a 2-fold increase in doubling time; doubling time increased directly with PhGPx activity (r = 0.95). The higher the PhGPx activity, the lower the plating efficiency (r = -0.86). The profile of other antioxidant enzymes was unchanged. Overexpression of PhGPx lowered the steady-state level of PLOOH (by > 60%). Results from bromodeoxyuridine pulse-chase experiments and flow cytometry indicate that PhGPx induced a delay in MCF-7 proliferation that was primarily due to a slower progression from G1 to S. These results support the hypothesis that PhGPx plays a regulatory role in the progression of MCF-7 cells from G1 to S possibly by regulating the steady-state levels of PLOOH. These data suggest that PhGPx can lower the peroxide tone, which might change the cellular redox environment resulting in a delay in G1 transit. Thus, PhGPx could be an important factor in cell growth.
磷脂氢过氧化物谷胱甘肽过氧化物酶（PhGPx）是一种抗氧化酶，可将细胞内的磷脂氢过氧化物（PLOOHs）还原为醇类。细胞内的过氧化物状态与细胞生长和分化有关。通过降低细胞膜中的PLOOH水平，PhGPx调节过氧化物状态，从而可能参与细胞生长。我们假设在人乳腺癌细胞中过表达PhGPx会降低其生长速率。我们用L-PhGPx稳定转染MCF-7细胞（野生型），并测量细胞倍增时间、接种效率和细胞周期阶段过渡时间。P-4细胞（PhGPx活性增加8倍）的倍增时间增加了2倍；倍增时间与PhGPx活性直接相关（r = 0.95）。PhGPx活性越高，接种效率越低（r = -0.86）。其他抗氧化酶的情况未发生变化。PhGPx的过表达降低了PLOOH的稳态水平（降低>60%）。溴脱氧尿苷脉冲追踪实验和流式细胞术的结果表明，PhGPx诱导MCF-7细胞增殖延迟，这主要是由于从G1期到S期的进程较慢。这些结果支持了以下假设：PhGPx可能通过调节PLOOH的稳态水平，在MCF-7细胞从G1期到S期的进程中发挥调节作用。这些数据表明，PhGPx可以降低过氧化物状态，这可能会改变细胞氧化还原环境，导致G1期过渡延迟。因此，PhGPx可能是细胞生长中的一个重要因素。
