TY - JOUR
T1 - Novel CYP2A6 variants identified in African Americans are associated with slow nicotine metabolism in vitro and in vivo
AU - Piliguian, Mark
AU - Zhu, Andy Z X
AU - Zhou, Qian
AU - Benowitz, Neal L.
AU - Ahluwalia, Jasjit S.
AU - Sanderson Cox, Lisa
AU - Tyndale, Rachel F.
PY - 2014/2
Y1 - 2014/2
N2 - OBJECTIVE: Nicotine, the main addictive ingredient in tobacco, is metabolically inactivated to cotinine primarily by the hepatic enzyme CYP2A6. Considerable genetic variation in the CYP2A6 gene results in large variation in the rates of nicotine metabolism, which in turn alters smoking behaviours (e.g. amount of cigarettes smoked, risk for dependence and success in smoking cessation). The aim of this study was to identify and characterize novel variants in CYP2A6. MATERIALS AND METHODS: The CYP2A6 gene from African American phenotypically slow nicotine metabolizers was sequenced and seven novel variants were identified [CYP2A6*39 (V68M), CYP2A6*40 (I149M), CYP2A6*41 (R265Q), CYP2A6*42 (I268T), CYP2A6*43 (T303I), CYP2A6*44 (E390K), CYP2A6*44 (L462P)]. Variants were introduced into a bi-cistronic cDNA expression construct containing CYP2A6 and P450 oxidoreductase and assessed for protein expression, enzymatic activity and stability as evaluated using western blotting and nicotine metabolism. Genotyping assays were developed and allelic frequencies were assessed in 534 African Americans. RESULTS: The variants showed significantly lower protein expression (P<0.001) when compared with the wild-type as well as reduced metabolism of nicotine to cotinine when controlling for cDNA expression using P450 oxidoreductase (P<0.001). The variants also showed reduced stability at 37 C. Allelic frequencies ranged from 0.1 to 0.6% with a collective genotype frequency of 3.2%; the impact in vitro correlated significantly with in-vivo activity (R=0.40-0.48, P<0.05). Together, those with a novel variant had significantly lower nicotine metabolism in vivo than those without genetic variants (P<0.01). CONCLUSION: Here, we identified a number of novel variants with reduced/loss of CYP2A6 activity, increasing our understanding of CYP2A6 genetic variability.
AB - OBJECTIVE: Nicotine, the main addictive ingredient in tobacco, is metabolically inactivated to cotinine primarily by the hepatic enzyme CYP2A6. Considerable genetic variation in the CYP2A6 gene results in large variation in the rates of nicotine metabolism, which in turn alters smoking behaviours (e.g. amount of cigarettes smoked, risk for dependence and success in smoking cessation). The aim of this study was to identify and characterize novel variants in CYP2A6. MATERIALS AND METHODS: The CYP2A6 gene from African American phenotypically slow nicotine metabolizers was sequenced and seven novel variants were identified [CYP2A6*39 (V68M), CYP2A6*40 (I149M), CYP2A6*41 (R265Q), CYP2A6*42 (I268T), CYP2A6*43 (T303I), CYP2A6*44 (E390K), CYP2A6*44 (L462P)]. Variants were introduced into a bi-cistronic cDNA expression construct containing CYP2A6 and P450 oxidoreductase and assessed for protein expression, enzymatic activity and stability as evaluated using western blotting and nicotine metabolism. Genotyping assays were developed and allelic frequencies were assessed in 534 African Americans. RESULTS: The variants showed significantly lower protein expression (P<0.001) when compared with the wild-type as well as reduced metabolism of nicotine to cotinine when controlling for cDNA expression using P450 oxidoreductase (P<0.001). The variants also showed reduced stability at 37 C. Allelic frequencies ranged from 0.1 to 0.6% with a collective genotype frequency of 3.2%; the impact in vitro correlated significantly with in-vivo activity (R=0.40-0.48, P<0.05). Together, those with a novel variant had significantly lower nicotine metabolism in vivo than those without genetic variants (P<0.01). CONCLUSION: Here, we identified a number of novel variants with reduced/loss of CYP2A6 activity, increasing our understanding of CYP2A6 genetic variability.
KW - African Americans
KW - CYP2A6
KW - genetic variation
KW - nicotine metabolism
KW - smoking
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U2 - 10.1097/FPC.0000000000000026
DO - 10.1097/FPC.0000000000000026
M3 - Article
C2 - 24305170
AN - SCOPUS:84894985623
SN - 1744-6872
VL - 24
SP - 118
EP - 128
JO - Pharmacogenetics and genomics
JF - Pharmacogenetics and genomics
IS - 2
ER -