Pompella A, Paolicchi A, Dominici S, Comporti M, Tongiani R
Istituto di Patologia Generale, Università di Siena, Italy.
Histochem Cell Biol. 1996 Sep;106(3):275-82. doi: 10.1007/BF02473237.
A number of studies indicate that cell proliferation can be modulated by changes in the redox balance of (soluble and protein) cellular thiols. Free radical processes, including lipid peroxidation (LPO), can affect such a balance, and a role for LPO in multistage carcinogenesis has been envisaged. The present study was aimed to assess the relationships between the protein thiol redox status and the LPO process in chemically induced preneoplastic tissue. The Solt-Farber's initiation-promotion model of chemical carcinogenesis in the rat liver was used. In fresh cryostat sections, preneoplastic lesions were identified by the reexpression of gamma-glutamyltranspeptidase (GGT) activity. In serial sections, different classes of protein thiols were stained; in additional sections, LPO was elicited by various prooxidant mixtures and determined thereafter by the hydroxynaphthoic hydrazide-Fast Blue B procedure. The incubation of sections in the presence of chelated iron plus substrates for GGT activity leads to the development of LPO in selected section areas closely corresponding to GGT-positive lesions, indicating the ability of GGT activity to initiate LPO. Protein-reactive thiols, as well as total protein sulfur, were decreased by 20-25% in cells belonging to GGT-positive preneoplastic nodules, suggesting the occurrence of oxidative conditions in vivo. The incubation of additional adjacent sections with the prooxidant mixture H2O2 plus iron(II), in order to induce the complete oxidation of lipid present in the section, showed a decreased basal concentration of oxidizable lipid substrate in GGT-rich areas. The decreased levels of both protein thiols and lipid-oxidizable substrate in GGT-positive nodules suggest that the observed GGT-dependent pathway of LPO initiation can be chronically operative in vivo during early stages of chemical carcinogenesis, in cells expressing GGT as part of their transformed phenotype.
多项研究表明，细胞增殖可通过（可溶性和蛋白质）细胞硫醇的氧化还原平衡变化进行调节。包括脂质过氧化（LPO）在内的自由基过程可影响这种平衡，并且已设想LPO在多阶段致癌过程中发挥作用。本研究旨在评估化学诱导的癌前组织中蛋白质硫醇氧化还原状态与LPO过程之间的关系。采用了大鼠肝脏化学致癌的索尔特 - 法伯起始 - 促进模型。在新鲜的低温切片中，通过γ-谷氨酰转肽酶（GGT）活性的重新表达来识别癌前病变。在连续切片中，对不同类别的蛋白质硫醇进行染色；在另外的切片中，用各种促氧化剂混合物引发LPO，然后通过羟基萘甲酸酰肼 - 固蓝B法进行测定。在存在螯合铁和GGT活性底物的情况下孵育切片会导致在与GGT阳性病变紧密对应的选定切片区域中发生LPO，这表明GGT活性能够引发LPO。在属于GGT阳性癌前结节的细胞中，蛋白质反应性硫醇以及总蛋白质硫含量降低了20 - 25%，这表明体内存在氧化条件。用促氧化剂混合物过氧化氢加亚铁离子孵育另外相邻的切片，以诱导切片中存在的脂质完全氧化，结果显示富含GGT的区域中可氧化脂质底物的基础浓度降低。GGT阳性结节中蛋白质硫醇和脂质可氧化底物水平的降低表明，在化学致癌早期阶段，在体内表达GGT作为其转化表型一部分的细胞中，观察到的依赖GGT的LPO起始途径可能长期起作用。
