Pyrrolizidine alkaloids crosslink DNA with actin

Area of Science:

• Toxicology
• Molecular Biology
• Biochemistry

Background:

• Pyrrolizidine alkaloids (PAs) are toxic plant compounds found in herbal products.
• PA toxicity is linked to their ability to form DNA-protein complexes (DPCs).
• Previous research suggested actin might be involved in PA-induced DPCs.

Purpose of the Study:

• To investigate the role of actin in pyrrolizidine alkaloid-induced DNA-protein complexes (DPCs).
• To explore the mechanism of pyrrole crosslinking with DNA and proteins.
• To identify potential nucleophilic competitors in PA-induced crosslinking.

Main Methods:

• Nuclei from MDBK and MCF-7 cells were treated with pyrrolic PAs (dehydrosenecionine and dehydromonocrotaline).
• DNA-protein complexes (DPCs) were purified and analyzed using Western immunoblotting.
• Pyrroles were crosslinked with lambda phage DNA in the presence of varying amounts of glutathione, cysteine, or methionine.

Main Results:

• Actin was identified in DPCs induced by dehydrosenecionine and dehydromonocrotaline, as well as by cisplatinum and mitomycin C.
• Glutathione and cysteine, but not methionine, competed with lambda phage DNA for crosslinking with pyrroles.
• This suggests a role for reduced thiols in nucleophilic reactions with pyrroles.

Conclusions:

• Actin crosslinking in PA-induced DPCs is a novel finding, potentially a significant mechanism for PA toxicity.
• The involvement of actin, a crucial protein, highlights a new pathway for understanding PA bioactivity.
• Reduced thiols may participate in the nucleophilic reactions underlying PA-induced cellular damage.