The GCC repeat length in the 5'UTR of MRP1 gene is polymorphic: a functional characterization of its relevance for cystic fibrosis

Multidrug resistance-associated protein 1 (MRP1/ABCC1) polymorphism: from discovery to clinical application

Multidrug resistance-associated protein 1(MRP1/ABCC1) is the first identified member of ABCC subfamily which belongs to ATP-binding cassette (ABC) transporter superfamily. It is ubiquitously expressed in almost all human tissues and transports a wide spectrum of substrates including drugs, heavy metal anions, toxicants, and conjugates of glutathione, glucuronide and sulfate. With the advance of sequence technology, many MRP1/ABCC1 polymorphisms have been identified. Accumulating evidences show that some polymorphisms are significantly associated with drug resistance and disease susceptibility. In vitro reconstitution studies have also unveiled the mechanism for some polymorphisms. In this review, we present recent advances in understanding the role and mechanism of MRP1/ABCC1 polymorphisms in drug resistance, toxicity, disease susceptibility and severity, prognosis prediction, and Methods to select and predict functional polymorphisms.

Genetic Variations and Haplotype Structures of the ABC Transporter Gene ABCC1 in a Japanese Population

Multidrug resistance-related protein 1 (MRP1), an ATP-binding cassette transporter encoded by the ABCC1 gene, is expressed in many tissues, and functions as an efflux transporter for glutathione-, glucuronate- and sulfate-conjugates as well as unconjugated substrates. In this study, the 31 exons and their flanking introns of ABCC1 were comprehensively screened for genetic variations in 153 Japanese subjects to elucidate the linkage disequilibrium (LD) profiles and haplotype structures of ABCC1 that is necessary for pharmacogenetic studies of the substrate drugs. Eighty-six genetic variations including 31 novel ones were found: 1 in the 5'-flanking region, 1 in the 5'-untranslated region (UTR), 20 in the coding exons (9 synonymous and 11 nonsynonymous variations), 4 in the 3'-UTR, and 60 in the introns. Of these, eight novel nonsynonymous variations, 726G>T (Trp242Cys), 1199T>C (Ile400Thr), 1967G>C (Ser656Thr), 2530G>A (Gly844Ser), 3490G>A (Val1164Ile), 3550G>A (Glu1184Lys), 3901C>T (Arg1301Cys), and 4502A>G (Asp1501Gly), were detected with an allele frequency of 0.003. Based on the LD profiles, the analyzed regions of the gene were divided into five LD blocks (Blocks -1 and 1 to 4). The multiallelic repeat polymorphism in the 5'-UTR was defined as Block -1. For Blocks 1, 2, 3 and 4, 32, 23, 23 and 13 haplotypes were inferred, and 9, 7, 7 and 6 haplotypes commonly found on > or = 10 chromosomes accounted for > or = 91% of the inferred haplotypes in each block. Haplotype-tagging single nucleotide polymorphisms for each block were identified to capture the common haplotypes. This study would provide fundamental and useful information for the pharmacogenetic studies of MRP1-dependently effluxed drugs in Japanese.

Anti-inflammatory effects of azithromycin in cystic fibrosis airway epithelial cells

We aimed at identifying molecular mechanisms for anti-inflammatory effects of azithromycin (AZM) suggested by clinical evidences. IL-8 expression and DNA binding activity of two key pro-inflammatory transcription factors (TF), NF-kappaB and AP-1, were investigated in cystic fibrosis (CF) and isogenic non-CF airway epithelial cell lines. AZM reduced about 40% of IL-8 mRNA and protein expression (n=9, p=0.02, and n=4, p=0.00011) in CF cells reaching the levels of non-CF cells. In the presence of AZM we found about 50% and 70% reduction of NF-kappaB and AP-1 DNA binding, respectively (n=3, p=0.01, and n=3, p=0.0017), leading to levels of non-CF cells. The relevance of NF-kappaB and AP-1 in regulating IL-8 promoter transcriptional activity was demonstrated by gene reporter assays (n=4, p=8.54x10(-7), and n=4, p=6.45x10(-6)). Our data support the anti-inflammatory effects of AZM in CF cells, indicating inhibition of transcription of pro-inflammatory genes as possible mechanism, thus providing a rationale for the possible use of specific TF inhibitors for therapy.