Bentazon triggers the promotion of oxidative damage in the Portuguese ricefield cyanobacterium Anabaena cylindrica: Response of the antioxidant system

Abstract

Rice fields are frequently exposed to environmental contamination by herbicides and cyanobacteria, as primary producers of these aquatic ecosystems, are adversely affected. Anabaena cylindrica is a cyanobacterium with a significantly widespread occurrence in Portuguese rice fields. This strain was studied throughout 72 h in laboratory conditions for its stress responses to sublethal concentrations (0.75-2 mM) of bentazon, a selective postemergence herbicide recommended for integrated weed management in rice, with special reference to oxidative stress, role of proline and intracellular antioxidant enzymes in herbicide-induced free radicals detoxification. Activities of antioxidant enzymes such as superoxide dismutase (SOD), catalase (CAT), ascorbate peroxidase (APX), and glutathione S-transferase (GST) increased in a time- and herbicide dose-response manner and were higher than those in the control samples after 72 h. A time- and concentration-dependent increase of malondialdehyde (MDA) levels and the enhanced cell membrane leakage following bentazon exposure are indicative of lipid peroxidation, free radicals formation, and oxidative damage, while increased amounts of SOD, CAT, APX, GST, and proline indicated their involvement in free radical scavenging mechanisms. The appreciable decline in the reduced glutathione (GSH) pool after 72 h at higher bentazon concentrations could be explained by the reduction of the NADPH-dependent glutathione reductase (GR) activity. The obtained results suggested that the alterations of antioxidant systems in A. cylindrica might be useful biomarkers of bentazon exposure. As the toxic mechanism of bentazon is a complex phenomenon, this study also adds relevant findings to explain the oxidative stress pathways of bentazon promoting oxidative stress in cyanobacteria.

The Effects of Long-Term Chaetomellic Acid A Administration on Renal Function and Oxidative Stress in a Rat Model of Renal Mass Reduction

“…The supernatant, kept at 0°C, was used for the GSH and GSSG assays on the same day. This determination was done by spectrofluorimetry, as previously described [25, 26]. Briefly, GSH was measured by fluorescence using a Varian Eclipse spectrofluorimeter with emission and excitation wavelengths of 426 and 339 nm, respectively, after incubation of 50  μ L of supernatant with 1.95 mL of 100 mM K-phosphate buffer (pH 8.0) plus 5 mM EDTA and 200  μ L of the fluorescence reagent, o-phthalaldehyde (OPT) (1 mg mL −1 ), for 15 min in the dark and at room temperature (25°C).…”

Time-Dependent Effects of Bentazon Application on the Key Antioxidant Enzymes of Soybean and Common Ragweed

“…Bentazon competes with quinone B (Q B ) for its binding site in the reaction centre of Photosystem II (PSII), thus decreasing the rate of the electron flow as Q A is unable to reoxidize. Light-induced PSII blockage by bentazon promotes the generation of triplet-chlorophyll ( 3 Chl) and the formation of singlet oxygen ( 1 O 2 ) upon reaction with molecular oxygen [11][12][13]. Bentazon-promoted oxidative stress damages the proteins and membranes of photosynthetic cells and induces cell death in weeds [12,[14][15][16].…”

Alterations in phospholipidomic profile in the brain of mouse model of depression induced by chronic unpredictable stress

“…The supernatant, kept at 0ºC, was used for the GSH and GSSG assays on the same day. This determination was done by spectrofluorimetry, as previously described by Galhano et al (Galhano et al, 2010). .…”