Genetic heterogeneity among slow acetylator N-acetyltransferase 2 phenotypes in cryopreserved human hepatocytes

Area of Science:

• Pharmacogenomics
• Metabolism and Carcinogenesis

Background:

• Genetic polymorphisms in human N-acetyltransferase 2 (NAT2) significantly influence the metabolism of drugs and carcinogens.
• These variations affect drug efficacy, toxicity, and cancer risk from carcinogen exposure.
• Previous research indicated potential differences in how various NAT2 slow acetylator genotypes function.

Purpose of the Study:

• To investigate the NAT2 phenotype in vitro and in situ using human hepatocytes.
• To explore phenotypic heterogeneity among different NAT2 slow and intermediate acetylator genotypes.
• To correlate NAT2 genotype with N-acetylation activity for specific substrates.

Main Methods:

• Human hepatocytes from individuals with various NAT2 slow and intermediate acetylator genotypes were used.
• N-acetylation activity was measured in vitro and in situ.
• Substrates included the NAT2-specific drug sulfamethazine, the arylamine carcinogen 4-aminobiphenyl (a substrate for NAT1 and NAT2), and the NAT1-specific substrate p-aminobenzoic acid.

Main Results:

• A clear gene dose response (NAT2*5B/*5B > NAT2*5B/*6A > NAT2*6A/*6A) was observed for sulfamethazine N-acetylation in both in vitro and in situ human hepatocyte models.
• The N-acetylation of 4-aminobiphenyl showed a similar trend, though not statistically significant (p > 0.05).
• No significant differences in N-acetylation were found between NAT2 intermediate acetylator genotypes (NAT2*4/*5B vs. NAT2*4/*6B) for any substrate.

Conclusions:

• The findings provide further evidence for phenotypic heterogeneity among NAT2 slow acetylator genotypes.
• This heterogeneity suggests differential risks for drug failure, toxicity, and cancer associated with carcinogen exposure.
• Understanding NAT2 genotype-phenotype relationships is crucial for personalized medicine and risk assessment.