What primary cellular mechanism causes tissue damage during paraquat poisoning?

Redox cycling creating reactive oxygen species

The toxicity of paraquat is driven by its ability to engage in redox cycling within cells. Once inside, the paraquat molecule accepts an electron to form a radical. This radical interacts with molecular oxygen, resulting in the formation of damaging reactive oxygen species such as superoxide radicals. This cycle repeats continuously, depleting the cell of its natural antioxidant defenses and overwhelming its ability to repair itself. This process leads to severe oxidative stress, causing lipid peroxidation of cellular membranes and resulting in catastrophic cell death, particularly in the tissues that selectively take up the chemical.