Differential sensitivities of plant and animal mitochondria to the herbicide paraquat

Abstract

Paraquat herbicide is toxic to animals, including humans, via putative toxicity mechanisms associated to microsomal and mitochondrial redox systems. It is also believed to act in plants by generating highly reactive oxygen free radicals from electrons of photosystem I on exposure to light. Paraquat also acts on non-chlorophyllous plant tissues, where mitochondria are candidate targets, as in animal tissues. Therefore, we compared the interaction of paraquat with the mitochondrial bioenergetics of potato tuber, using rat liver mitochondria as a reference. Paraquat depressed succinate-dependent mitochondrial Delta(psi), with simultaneous stimulation of state 4 O2 consumption. It also induced a slow time-dependent effect for respiration of succinate, exogenous NADH, and N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD)/ascorbate, which was more pronounced in rat than in potato mitochondria. However, with potato tuber mitochondria, the Delta(psi) promoted by complex-I-dependent respiration is insensitive to this effect, indicating a protection against paraquat radical afforded by complex I redox activity, which was just the reverse of to the findings for rat liver mitochondria. The experimental set up with the tetraphenyl phosphonium (TPP+)-electrode also indicated production of the paraquat radical in mitochondria, also suggesting its accessibility to the outside space. The different activities of protective antioxidant agents can contribute to explain the different sensitivities of both kinds of mitochondria. Values of SOD activity and alpha-tocopherol detected in potato mitochondria were significantly higher than in rat mitochondria, which, in turn, revealed higher values of lipid peroxidation induced by paraquat.

Comparative effects of the herbicides dicamba, 2,4-D and paraquat on non-green potato tuber calli

“…For controls, herbicides alone were tested for spectroscopic interferences of fluorescein measurement at 458 nm, and no effects were detected (data not shown). fractions (Vicente et al, 2001) previously showed no sensitivity of swelling dependent on permeabilization to H + (even with 30 mM paraquat), in contrast with H + permeabilization induced by 2,4-D and dicamba (Peixoto et al, 2004). These results indicate the capability of 2,4-D and dicamba to disrupt the membrane integrity, probably as a consequence of perturbation of membrane structure upon partition of the herbicides.…”

“…Furthermore, it has also been shown that plant mitochondria are better protected at the antioxidant level, but still susceptible to paraquat toxicity (Vicente et al, 2001;Peixoto et al, 2004). All the herbicides tested deplete ATP and ADP with a correspondent increase of AMP (data not shown).…”

“…Our earlier studies comparing the effect of paraquat in plant and animal mitochondria have shown that this herbicide strongly decreases the bioenergetic capacity in animal mitochondria, as a result of oxidative stress promoted by paraquat (Vicente et al, 2001). Furthermore, it has also been shown that plant mitochondria are better protected at the antioxidant level, but still susceptible to paraquat toxicity (Vicente et al, 2001;Peixoto et al, 2004).…”

FRIENDLY Regulates Mitochondrial Distribution, Fusion, and Quality Control in Arabidopsis

“…A mutant allele of FRIENDLY (noxy38) was identified in a screen for insensitivity to the oxylipin pathogen defense mediator 9-hydroxy-10,12, 15-octadecatrienoic acid in Arabidopsis (Vicente et al, 2001;Vellosillo et al, 2013). The noxy38 mutant showed an up-regulation of alternative oxidase expression and a decreased capacity to fight bacterial infection (Vellosillo et al, 2013).…”

Herbicides: the Face and the Reverse of the Coin. An in Vitro Approach to the Toxicity of Herbicides in Non-Target Organisms

“…Comparative studies of the effect of paraquat on mitochondrial bioenergetics of rat liver and potato mitochondria confirmed the protonophoric action of herbicide on both mitochondrial membranes. However, the sensitivity of potato tuber mitochondria to paraquat was lower than that of rat liver mitochondria (Vicente et al, 2001). Differences between rat liver and potato tuber mitochondria were also observed on the effects of paraquat on both ΔΨ and oxygen consumption of complex-I-dependent respiration.…”