Co-Regulation ofCYP3A4andCYP3A5and Contribution to Hepatic and Intestinal Midazolam Metabolism

Abstract

We recently demonstrated that a variant allele of CYP3A5 (CYP3A5*3) confers low CYP3A5 expression as a result of improper mRNA splicing. In this study, we further evaluated the regulation of CYP3A5 in liver and jejunal mucosa from white donors. For all tissues, high levels of CYP3A5 protein were strongly concordant with the presence of a wild-type allele of the CYP3A5 gene (CYP3A5*1). CYP3A5 represented greater than 50% of total CYP3A content in nearly all of the livers and jejuna that carried the CYP3A5*1 wild-type allele. Overall, CYP3A5 protein content accounted for 31% of the variability in hepatic midazolam hydroxylation activity. Improperly spliced mRNA (SV1-CYP3A5) was found only in tissues containing a CYP3A5*3 allele. Properly spliced CYP3A5 mRNA (wt-CYP3A5) was detected in all tissues, but the median wt-CYP3A5 mRNA was 4-fold higher in CYP3A5*1/*3 livers compared with CYP3A5*3/*3 livers. Differences in wt-CYP3A5 and CYP3A4 mRNA content explained 53 and 51% of the interliver variability in CYP3A5 and CYP3A4 content, respectively. Hepatic CYP3A4 and CYP3A5 contents were not correlated when all livers were compared. However, for CYP3A5*1/*3 livers, levels of the two proteins were strongly correlated (r ϭ 0.93) as were wt-CYP3A5 and CYP3A4 mRNA (r ϭ 0.76). These findings suggest that CYP3A4 and CYP3A5 genes share a common regulatory pathway for constitutive expression, possibly involving conserved elements in the 5Ј-flanking region.CYP3A contributes to the metabolism of numerous therapeutic agents and endogenous molecules. Substrates of CYP3A include benzodiazepines, hydroxymethyl glutarylCoA reductase inhibitors, dihydropyridine calcium channel blockers, human immunodeficiency virus protease inhibitors, antiepileptics, chemotherapeutics, and immunosuppressants (Guengerich, 1999). Interindividual differences in the oral bioavailability and systemic clearance of CYP3A substrates can be attributed in large part to variable expression of CYP3A in the liver (Thummel et al., 1994) and mucosal epithelium of the small intestine (DeWaziers et al., 1990;Paine et al., 1996Paine et al., , 1997. CYP3A4 is the dominant CYP3A isoform in the liver and small intestine of most white adults, whereas CYP3A7 is primarily a fetal enzyme (Kitada and Kamataki, 1994). More recently, human CYP3A43 has been identified and cloned , although its contribution to hepatic or extrahepatic CYP3A-dependent drug clearance is thought to be negligible (Westlind et al., 2001). CYP3A5 is also found in the liver and intestinal mucosa (Wrighton et al., 1990;Paine et al., 1997) and other extrahepatic tissues, including the kidney (Haehner et al., 1996), lung (Kivistö et al., 1996), and prostate gland (Yamakoshi et al., 1999). Its expression is polymorphic, with readily detectable levels in 25 to 30% and very low or undetectable levels in 70 to 75% of livers and small intestines examined (Wrighton et al., 1990;Paine et al., 1997;Tateishi et al., 1999).The genetic basis for polymorphic CYP3A5 expression was first examined by Jounä idi et al....

Influence of CYP3A5 and drug transporter polymorphisms on imatinib trough concentration and clinical response among patients with chronic phase chronic myeloid leukemia

“…2, 8,9 Although few common CYP3A4 polymorphisms have been identified with in vivo effect on enzyme activity, CYP3A5 expression is strongly correlated with a single-nucleotide polymorphism (SNP) within intron 3 (6986A4G; CYP3A5*3). 10 This allele is prevalent among Japanese individuals, 11 suggesting that germline CYP3A5 SNPs may influence IM trough concentration and drug efficacy in this population.…”

Cytochrome P450 3A5 is highly expressed in normal prostate cells but absent in prostate cancer

“…CYP3A4 is the predominant form in liver and small intestine (Lin et al 2002). CYP3A5 is also present in liver and gastrointestinal tract but at lower levels and in a bimodal manner due to CYP3A5*3, CYP3A5*6, and CYP3A5*7 defective alleles, the last two present only in Africans (Hustert et al 2001, Kuehl et al 2001, Lin et al 2002, Lee et al 2003. CYP3A7 is primarily expressed in fetal stages, but CYP3A7*1C allele triggers its expression in adult stages (Kuehl et al 2001, Sim et al 2005.…”

Single nucleotide polymorphisms and haplotype frequencies ofCYP3A5 in a Japanese population

“…One family member, CYP3A5 (MIM# 605325), is highly polymorphic in the human liver with its mRNA and protein detectable in only 20-40% adults (Aoyama et al, 1989;Wrighton et al, 1990;Tateishi et al, 1999). It is clinically important to predict CYP3A5 levels in the liver or other tissues since its contribution to total CYP3A activity is considerably high if it is expressed (Lin et al, 2002). Previously, we reported that no single nucleotide polymorphism (SNP) was found in the proximal promoter region from the analysis of genomic DNA from 86 established cell lines from Japanese individuals, and thus nucleotide changes in this region were not responsible for the polymorphic expression of CYP3A5 (Nakamura et al, 2001).…”