4'-Iodo-α-Pyrrolidinononanophenone Provokes Differentiated SH-SY5Y Cell Apoptosis Through Downregulating Nitric Oxide Production and Bcl-2 Expression.

Abuse of pyrrolidinophenone derivatives (PPs) is known to cause severe damage to the central nervous system due to their high lipophilicity. In this study, we compared sensitivity to toxicity elicited by 4'-iodo-α-pyrrolidinononanophenone (I-α-PNP), one of the most potent cytotoxic derivatives among PPs synthesized previously, between SH-SY5Y cells differentiated by all-trans-retinoic acid (ATRA) and the undifferentiated cells, and found that the differentiated cells are more sensitive to I-α-PNP toxicity than the undifferentiated cells. Treatment with I-α-PNP elicited some apoptotic alterations (Bax expression, loss of mitrochondrial membrane potential, and activation of caspases) in the differentiated cells, whose patterns were similar to those in the undifferentiated cells. I-α-PNP treatment resulted in no significant alteration in Bcl-2 expression in the undifferentiated cells, whereas it considerably downregulated the protein expression in the differentiated cells, suggesting that the high I-α-PNP sensitivity of the differentiated cells is mainly due to downregulation of Bcl-2 expression. I-α-PNP treatment decreased nitric oxide (NO) production and neuronal NOS (nNOS) expression in the differentiated cells, and the patterns of I-α-PNP-evoked alterations in phosphorylation of cAMP response element-binding protein (CREB) and brain-derived neurotrophic factor (BDNF) expression were almost the same as that in nNOS expression. Additionally, the addition of an NO donor restored the I-α-PNP-evoked alterations in expressions of Bcl-2, BDNF, and nNOS in the differentiated cells. These findings suggest that the downregulation of Bcl-2 expression by I-α-PNP in differentiated cells is attributed to the acceleration of two negative feedback loops (nNOS/NO/CREB loop and CREB/BDNF loop) triggered by decreased NO production.

Development of cisplatin resistance in breast cancer MCF7 cells by up-regulating aldo-keto reductase 1C3 expression, glutathione synthesis and proteasomal proteolysis.

Cisplatin (CDDP) is widely prescribed for the treatment of various cancers including bladder cancers, whereas its clinical use for breast cancer chemotherapy is restricted owing to easy acquisition of the chemoresistance. Here, we established a highly CDDP-resistant variant of human breast cancer MCF7 cells and found that procuring the resistance aberrantly elevates the expression of aldo-keto reductase (AKR) 1C3. Additionally, MCF7 cell sensitivity to CDDP was decreased and increased by overexpression and knockdown, respectively, of AKR1C3, clearly inferring that the enzyme plays a crucial role in acquiring the CDDP resistance. The CDDP-resistant cells suppressed the formation of cytotoxic reactive aldehydes by CDDP treatment, and the suppressive effects were almost completely abolished by pretreating with AKR1C3 inhibitor. The resistant cells also exhibited the elevated glutathione amount and 26S proteasomal proteolytic activities, and their CDDP sensitivity was significantly augmented by pretreatment with an inhibitor of glutathione synthesis or proteasomal proteolysis. Moreover, the combined treatment with inhibitors of AKR1C3, glutathione synthesis and/or proteasomal proteolysis potently overcame the CDDP resistance and docetaxel cross-resistance. Taken together, our results suggest that the combination of inhibitors of AKR1C3, glutathione synthesis and/or proteasomal proteolysis is effective as an adjuvant therapy to enhance CDDP sensitivity of breast cancer cells.