Voss S H, Park Y, Kwon S O, Whalen R, Boyer T D
Emory University School of Medicine, Division of Digestive Diseases, Atlanta, GA 30322, USA.
Biochem J. 1996 Jul 15;317 ( Pt 2)(Pt 2):627-32. doi: 10.1042/bj3170627.
The effect of recombinant interleukin 6 (rIL-6) on the transcript levels of rat glutathione S-transferase (GST) genes rGSTA2, rGSTP1, rGSTM1 and rGSTM2 was examined in primary cultures of rat hepatocytes. rIL-6 had little effect on the increase in expression of rGSTP1 that occurs in cultured hepatocytes. Dexamethasone (DEX), in contrast, prevented the expression of rGSTP1 by hepatocytes, and rIL-6 in combination with DEX had no additional effect. Neither rIL-6 nor DEX alone had a significant effect on the transcript levels of rGSTA2, rGSTM1 and rGSTM2 in cultured hepatocytes. However, when both were present (15 ng/ml rIL-6 and 10(-7) M DEX) the transcript levels of rGSTA2, rGSTM1 and rGSTM2 decreased significantly (P < 0.05) after 48 h in culture. If the rIL-6 was removed from the cultures after 24 h, the levels of transcripts recovered and were the same at 48 h as cells cultured without rIL-6 for the entire period. Dose-response relationships of rIL-6 with 10(-7) M DEX were determined for transcripts of each GST isoenzyme and the IC50 values were between 1.5 and 7.5 ng/ml. Declines in transcript levels of rGSTA2 were observed with rIL-6 plus 10(-8) or 10(-7) M DEX but not with rIL-6 plus 10(-9), 10(-6), or 10(-5) M DEX. To determine if the cytokine and glucocorticoid effects were mediated by sequences in the 5'-flanking sequence of rGSTA2, a plasmid construct containing a 1.6 kb fragment of the 5'-flanking sequence of the rGSTA2 gene and the chloramphenicol acetyltransferase (CAT) reporter gene was used to transfect rat hepatocytes in primary culture. The addition of rIL-6 and DEX to the culture medium caused a significant (P < 0.05) decrease in CAT activity after 48 h in culture. If rIL-6 was removed after 24 h in culture, CAT activity after an additional 24 h in culture was greater than the CAT activity in cells cultured for 48 h without rIL-6. Therefore cytokines and glucocorticoids may be important physiological regulators of GST expression.
在大鼠肝细胞原代培养物中，研究了重组白细胞介素6（rIL-6）对大鼠谷胱甘肽S-转移酶（GST）基因rGSTA2、rGSTP1、rGSTM1和rGSTM2转录水平的影响。rIL-6对培养的肝细胞中rGSTP1表达的增加影响很小。相比之下，地塞米松（DEX）可抑制肝细胞中rGSTP1的表达，rIL-6与DEX联合使用无额外作用。单独的rIL-6和DEX对培养的肝细胞中rGSTA2、rGSTM1和rGSTM2的转录水平均无显著影响。然而，当两者同时存在（15 ng/ml rIL-6和10⁻⁷ M DEX）时，培养48小时后，rGSTA2、rGSTM1和rGSTM2的转录水平显著降低（P < 0.05）。如果在24小时后从培养物中去除rIL-6，转录水平会恢复，且在48小时时与整个培养期间未添加rIL-6的细胞相同。确定了rIL-6与10⁻⁷ M DEX对每种GST同工酶转录本的剂量反应关系，IC50值在1.5至7.5 ng/ml之间。观察到rIL-6加10⁻⁸或10⁻⁷ M DEX时rGSTA2的转录水平下降，但rIL-6加10⁻⁹、10⁻⁶或10⁻⁵ M DEX时未出现这种情况。为了确定细胞因子和糖皮质激素的作用是否由rGSTA2 5'侧翼序列中的序列介导，使用了一个包含rGSTA2基因5'侧翼序列1.6 kb片段和氯霉素乙酰转移酶（CAT）报告基因的质粒构建体转染原代培养的大鼠肝细胞。向培养基中添加rIL-6和DEX后，培养48小时后CAT活性显著降低（P < 0.05）。如果在培养24小时后去除rIL-6，再培养24小时后的CAT活性高于未添加rIL-6培养48小时的细胞中的CAT活性。因此，细胞因子和糖皮质激素可能是GST表达的重要生理调节因子。
