Butachlor induced dissipation of mitochondrial membrane potential, oxidative DNA damage and necrosis in human peripheral blood mononuclear cells

Toxicology. 2012 Dec 8;302(1):77-87. doi: 10.1016/j.tox.2012.07.014. Epub 2012 Aug 3.


Butachlor is a systemic herbicide widely applied on rice, tea, wheat, beans and other crops; however, it concurrently exerts toxic effects on beneficial organisms like earthworms, aquatic invertebrates and other non-target animals including humans. Owing to the associated risk to humans, this chloroacetanilide class of herbicide was investigated with the aim to assess its potential for the (i) interaction with DNA, (ii) mitochondria membrane damage and DNA strand breaks and (iii) cell cycle arrest and necrosis in butachlor treated human peripheral blood mononuclear (PBMN) cells. Fluorescence quenching data revealed the binding constant (Ka=1.2×10(4)M(-1)) and binding capacity (n=1.02) of butachlor with ctDNA. The oxidative potential of butachlor was ascertained based on its capacity of inducing reactive oxygen species (ROS) and substantial amounts of promutagenic 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodG) adducts in DNA. Also, the discernible butachlor dose-dependent reduction in fluorescence intensity of a cationic dye rhodamine (Rh-123) and increased fluorescence intensity of 2',7'-dichlorodihydro fluorescein diacetate (DCFH-DA) in treated cells signifies decreased mitochondrial membrane potential (ΔΨm) due to intracellular ROS generation. The comet data revealed significantly greater Olive tail moment (OTM) values in butachlor treated PBMN cells vs untreated and DMSO controls. Treatment of cultured PBMN cells for 24h resulted in significantly increased number of binucleated micronucleated (BNMN) cells with a dose dependent reduction in the nuclear division index (NDI). The flow cytometry analysis of annexin V(-)/7-AAD(+) stained cells demonstrated substantial reduction in live population due to complete loss of cell membrane integrity. Overall the data suggested the formation of butachlor-DNA complex, as an initiating event in butachlor-induced DNA damage. The results elucidated the oxidative role of butachlor in intracellular ROS production, and consequent mitochondrial dysfunction, oxidative DNA damage, and chromosomal breakage, which eventually triggers necrosis in human PBMN cells.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Acetanilides / administration & dosage
  • Acetanilides / toxicity*
  • Animals
  • Cattle
  • Chromosome Breakage / drug effects
  • Comet Assay
  • DNA / drug effects
  • DNA / metabolism
  • DNA Breaks / drug effects
  • DNA Damage / drug effects*
  • Dose-Response Relationship, Drug
  • Flow Cytometry
  • Herbicides / administration & dosage
  • Herbicides / toxicity*
  • Humans
  • Leukocytes, Mononuclear / drug effects*
  • Leukocytes, Mononuclear / metabolism
  • Membrane Potential, Mitochondrial / drug effects*
  • Necrosis / chemically induced
  • Oxidation-Reduction
  • Reactive Oxygen Species / metabolism
  • Spectrometry, Fluorescence


  • Acetanilides
  • Herbicides
  • Reactive Oxygen Species
  • DNA
  • calf thymus DNA
  • butachlor