Potential of chlorpyrifos and cypermethrin forming DNA adducts

Area of Science:

• Environmental toxicology
• Molecular toxicology
• Carcinogenesis research

Background:

• DNA adducts, including monoadducts and crosslinks, are critical intermediates in carcinogenesis.
• Insecticides pose potential risks due to their genotoxic effects.
• Understanding the DNA-damaging potential of specific pesticides is crucial for risk assessment.

Purpose of the Study:

• To investigate the genotoxicity of chlorpyrifos and cypermethrin in primary mouse hepatocytes.
• To determine the types of DNA adducts formed by these insecticides.
• To elucidate the role of metabolic activation in cypermethrin-induced DNA damage.

Main Methods:

• Assessment of DNA monoadducts, DNA interstrand crosslinks, and DNA-protein crosslinks using bioluminescence, ethidium bromide fluorescence, and K+-SDS precipitation assays.
• Testing in primary mouse hepatocytes and on calf thymus DNA.
• Inclusion of cytochrome P450 inhibitor (SKF-525A) to study metabolic activation.

Main Results:

• Chlorpyrifos did not induce any detectable DNA adducts.
• Cypermethrin induced DNA monoadducts and DNA interstrand crosslinks in mouse hepatocytes.
• Cypermethrin did not form DNA interstrand crosslinks on calf thymus DNA or in hepatocytes pretreated with a cytochrome P450 inhibitor.
• Evidence suggests that active metabolites of cypermethrin, rather than the parent compound, are responsible for DNA interstrand crosslink formation.

Conclusions:

• Cypermethrin exhibits genotoxic potential by forming DNA adducts, specifically DNA monoadducts and interstrand crosslinks, in mammalian cells.
• The formation of cypermethrin-induced DNA interstrand crosslinks is dependent on metabolic activation, likely mediated by cytochrome P450 enzymes.
• These findings highlight the importance of considering metabolic activation in the toxicological assessment of pesticides like cypermethrin.