Current Drug Metabolism - Volume 12, Issue 2, 2011

The expression and activity of drug-metabolizing enzymes (DME) is influenced by variety of physiological factors (e.g. age, sex, pregnancy, menstrual cycle) and patho-physiological states of human organism (e.g. inflammation, infection, cancer, diabetes). Environmental factors (chemicals, radiation, microorganisms etc.) and gene polymorphisms have a great impact on activity of DME. Regulation of DME at mole Read More

Retinoic acid receptors (RARs), retinoid X receptors (RXRs) and thyroid hormone receptors (TRs) are nuclear receptors that are crucial transcriptional regulators of many cellular processes such as differentiation, development, apoptosis, carbohydrate and lipid metabolism, homeostasis etc. In addition, RXRs are common heterodimerization partners for several receptors including vitamin D receptor, pregna Read More

The aryl hydrocarbon receptor (AhR) is a ligand-activated transcription factor, which plays a major role in toxic effects of environmental pollutants. It is a pivotal regulator of several xenobiotic-metabolizing enzymes (XMEs), and is now considered to play an important role also in control of cell cycle, apoptosis and cell differentiation. The accumulating evidence suggests that there exists a multiple crosstalk between AhR activati Read More

Phase II biotransformation enzymes conjugate xenobiotics using small, organic donor molecules, such as glutathione, UDPglucuronic acid, S-adenosyl-L-methionine, acetyl coenzyme A and amino acids (primarily glycine). These reactions generally resulted in detoxification by the loss of pharmacological activity and by quickening the elimination of xenobiotics from the body, however bioactivation is also known to be occu Read More

The central and peripheral nervous systems are important factors influencing the functioning of liver cytochrome P450 (CYP). It has been shown that changes in the brain monoaminergic systems affect liver cytochrome P450 (CYP) expression (CYP1A, CYP2B, CYP2C11 and CYP3A). The brain dopaminergic system has been established as an important center regulating the liver CYP. This regulation proceeds via the tuberoinfun Read More

Eleven members of the human organic anion transporter (OATP) family (grouped into six families) facilitate the Na+- independent transmembrane transport of various endo- and xenobiotics (bile acids, bilirubin, steroid hormone conjugates, thyroid hormones, prostaglandins, clinically used drugs, and toxins). OATPs are 12-transmembrane glycoproteins (643-722 amino acids) and contain many conserved structural features, Read More

Cytochrome P450 (P450) monooxygenases are capable of catalyzing metabolism of various endogenous and exogenous compounds, such as bile acids, fatty acids, retinoids, steroids, drugs and other xenobiotics. The enzymes, belonging to CYP1, CYP2 and CYP3 families are primarily involved in the metabolism of drugs and xenobiotics. P450-mediated defense mechanism protects organisms from the potentially toxic effects of Read More

Cytochromes P450 of the liver are involved in maintenance of lipid homeostasis (cholesterol, vitamin D, oxysterol and bile acid metabolism) and in detoxification processes of endogenous compounds (i. e. bile acids) and xenochemicals (drugs). This review describes the roles of various CYPs in production of cholesterol related endogenous metabolites. These metabolites (oxysterols, bile acids, vitamin D3) act as activators of a b Read More

Unlike most cytochrome P450 (CYP) enzymes, murine hepatic CYP2A5 is induced during pathological conditions that result in liver injury including hepatotoxicity mediated by xenobiotics, hepatitis caused by various microbial agents and liver neoplasia. Since CYP2A5 metabolizes various important xenobiotics including nicotine and pro-carcinogens such as nitrosamines and aflatoxin B1, altered gene expression could affec Read More

Aryl hydrocarbon receptor (AhR) is an important transcriptional regulator of drug metabolizing enzymes that dominantly controls the expression of cytochrome P450 CYP1 family genes and some phase II enzymes. AhR also has many endogenous functions including cell cycle control, immune response, and cell differentiation. In addition, AhR is well-known to be involved in chemicallyinduced carcinogenesis. AhR is activated by Read More