Interactions between drugs of abuse and HIV protease inhibitors
Abstract
Drug abuse is an escalating problem prevalent in both large metropolitan and rural
places and is a major cause of mortality and morbidity all over the world. Drugs of abuse
such as morphine and nicotine are consumed by people for prolonged periods of times to
improve their physical and mental condition as well as to get relief from pain and other
medical conditions. This prolonged intake often overlaps with the clinical regimen of
several chronic neuropsychological, cardiovascular, pulmonary, infectious and neoplastic
diseases. One in four patients living with human immunodeficiency virus (HIV) infection
reported use of drugs of abuse. Achieving target intracellular concentrations during long
term therapy of several diseases can be challenging due to number of factors such as poor
adherence, drug resistance and drug-drug interactions. One important mechanism of
multidrug resistance involves the up-regulation of multidrug resistance transporter, pglycoprotein
(p-gp), member of ATP binding cassette (ABC) superfamily that effluxes
most of the therapeutic drugs and reduce their intracellular accumulation. Drug-drug
interactions can result from inhibition and induction of the cytochrome P450 enzymes and/or efflux transporters. Drugs of abuse have the ability to potentiate or attenuate the
effects of co-administered therapeutic drugs that can lead to toxic effects or a reduction in
the therapeutic activity of the co-administered drugs. This thesis investigates the chronic
effect of morphine and nicotine on the expression and functional activity of efflux
transporters (MDR1, MRP2, and BCRP) and metabolizing enzymes (CYP3A4).
Induction of Pregnane-X-Receptor (PXR) was found to regulate the induction of MDR1
and CYP3A4 gene expression. Interactions between drugs of abuse and therapeutic
drugs provide crucial insights into the failure of clinical regimen in patients suffering
from HIV, cancer and other infections. Results from this thesis elucidate the mechanism
behind the interactions between morphine and nicotine and HIV protease inhibitors.
Studies were performed primarily through the use of in vitro models; e.g. LS180 and
Caco-2 (for intestine) and HepG2 (for liver).
In the second set of my studies, expression and functional activity of efflux
transporters in Calu-3, human airway epithelial cell line was investigated. Expression and
functionality of efflux and influx transporters in the airways is poorly identified and
characterized. Results from this project allow understanding of the drug absorption in
airways. As part of the study, molecular and functional activity of breast cancer
resistance protein was identified for the first time. Folic acid receptor-alpha and proton
coupled folic acid transporter expression was identified at molecular and protein level
across human bronchial epithelial cell line, Calu-3. Since nicotine is smoked through
lungs, effect of nicotine on the expression and functional activity of efflux transporters and metabolizing enzymes was determined. Nicotine was found to induce MDR1, BCRP
expression and CYP3A4/A5 metabolism in Calu-3 cells. Male Sprague Dawley rats were
treated with nicotine to investigate the effect of nicotine on CYP3A4 mediated rat lung
metabolism. Cortisol was used as a model substrate to evaluate CYP3A4 mediated
metabolism. Cortisol metabolism enhanced in nicotine treated rats than control rats
signifying the enhanced CYP3A4/A5 metabolism. Furthermore, cortisol metabolism
enhanced in microsomes obtained from smokers when compared to microsomes obtained
from non-smokers
Table of Contents
Introduction -- Literature review -- To investigate the chronic effect of nicotine and morphine on expression and functional activity of efflux transporters and metabolizing enzymes and to study their contribution to the intracellular accumulation of HIV protease inhibitors -- Influx transporters in lungs: expression of folic acid carriers in human bronchial epithelial cell line, CALU-3 -- To study the role of efflux
transporters in human bronchial epithelial cell line, CALU-3 -- To characterize the molecular and functional activity of breast cancer resistance protein in human bronchial epithelial cells, CALU-3 -- To investigate the effect of chronic nicotine exposure on the levels of efflux transporters and metabolizing enzymes in CALU-3 CELLS and rat lungs -- Summary and recommendations
Degree
Ph. D.