Effects of combined treatment with cognitive enhancer memantine and antidepressant fluoxetine on CYP2D2 metabolic activity in rats

OBJECTIVES

The drug-drug interactions can result in alterations of the therapeutical responses. The present study was designed to investigate possible pharmacokinetic interactions between the cognitive agent memantine and the antidepressant fluoxetine combined often in treatments of cognitive disorders including Alzheimer disease. The attention was focused on changes of the cytochrome P450 2D2 isoenzyme activity in two animal models.

METHODS AND DESIGN

The tested drugs were administered alone or in a combination to rat males and their effects on the 2D2 isoenzyme activity was determined after in vivo administration. The levels of marker dextromethorphan, its 2D2 specific metabolite dextrorphan were analyzed in plasma of rats and using the model of isolated perfused rat liver in the perfusion medium. The dextromethorphan/dextrorphan (DEM/DEX) metabolic ratios were determined as a sign of inhibitory influences on CYP2D2.

RESULTS

The analyses showed elevation of DEM/DEX metabolic ratio after all treatments: a) memantine, b) fluoxetine and c) memantine+fluoxetine, however the results were not completely identical. The intensity of inhibitory effects on the CYP2D2 activity were: memantine < memantine + fluoxetine < fluoxetine.

CONCLUSION

The results presented suggest that the clinical pharmacotherapeutical approach to combine memantine with fluoxetine is from the point of view of pharmacokinetic drug-drug interaction on the level of CYP2D2 isoenzyme safe and even of benefit as memantine could elicit a suppression of the inhibitory influence of fluoxetine.

Type 2 IP(3) receptors are involved in uranyl acetate induced apoptosis in HEK 293 cells

Calcium released from endoplasmic reticulum through special calcium release channels - inositol 1,4,5-trisphosphate receptors (IP(3)Rs) and ryanodine receptors (RyRs) - serves as a main source of cytosolic calcium signaling in the majority of cell types in physiological state and also in pathological situations. In this work, we studied whether IP(3)Rs can be involved in uranyl acetate induced nephrotoxicity. Using human embryonic kidney cell line (HEK293) as an experimental model we have found that uranyl acetate (5 and 50microM) up-regulates both, mRNA and protein levels of the type 1 and type 2 IP(3) receptors in HEK293 cells. This increase was associated with elevated expression of proapoptotic factors Bax and Caspase 3 and also by higher extent of apoptosis. Vice versa, induction of apoptosis resulted in increased mRNA levels of IP(3)R2 and also elevated levels of apoptotic markers. Therefore we propose that enhanced expression of the type 2 IP(3)Rs can at least partially contribute to increased levels of apoptosis due to uranyl acetate treatment.