Pervasive influence of heavy metals on metabolic pathways is potentially relieved by hesperidin to enhance the phytoremediation efficiency of Bassia scoparia

Hesperidin (HSP), a flavonoid, is a potent antioxidant, metal chelator, mediator of signaling pathways, and regulator of metal uptake in plants. The study examined the ameliorative effects of HSP (100 μM) on Bassia scoparia grown under excessive levels of heavy metals (zinc (500 mg kg-1), copper (400 mg kg-1), cadmium (100 mg kg-1), and chromium (100 mg kg-1)). The study clarifies the underlying mechanisms by which HSP lessens metabolic mayhem to enhance metal stress tolerance and phytoremediation efficiency of Bassia scoparia. Plants manifested diminished growth because of a drop in chlorophyll content and nutrient acquisition, along with exacerbated deterioration of cellular membranes reflected in elevated reactive oxygen species (ROS) production, lipid peroxidation, and relative membrane permeability. Besides the colossal production of cytotoxic methylglyoxal, the activity of lipoxygenase was also higher in plants under metal toxicity. Conversely, hesperidin suppressed the production of cytotoxic ROS and methylglyoxal. Hesperidin improved oxidative defense that protected membrane integrity. Hesperidin caused a more significant accumulation of osmolytes, non-protein thiols, and phytochelatins, thereby rendering metal ions non-toxic. Hydrogen sulfide and nitric oxide endogenous levels were intricately maintained higher in plants treated with HSP. Hesperidin increased metal accumulation in Bassia scoparia and thereby had the potential to promote the reclamation of metal-contaminated soils.

Whole-cell cascade for the preparation of enantiopure β-O-4 aryl ether compounds with glutathione recycling

Bacterial β-etherases and glutathione lyases are glutathione-dependent enzymes that catalyze the selective cleavage of β-O-4 aryl ether bonds found in lignin. Their glutathione (GSH) dependence is regarded as major limitation for their application in the production of aromatics from lignin polymer and oligomers, as stoichiometric glutathione amounts are required. Thus, recycling of the GSH cofactor by a NAD(P)H-dependent glutathione reductase was proposed previously. Herein, the use of a whole-cell catalyst was studied for efficient β-O-4 aryl ether bond cleavage with intracellular GSH supply and recycling. After optimization of the whole-cell catalyst as well as reaction conditions, up to 5 mM lignin model substrate 2,6-methoxyphenoxy-α-veratrylglycerone (2,6-MP-VG) were efficiently converted into 2,6-methoxyphenol (2,6-MP) and veratryl glycerone (VG) without addition of external GSH. Unexpectedly, no glucose supply was required for glutathione recycling within the cells up to this substrate concentration. To demonstrate the applicability of this whole-cell approach, a whole-cell cascade combining a stereoselective β-etherase (either LigE from Sphingobium sp. SYK-6 or LigF-NA from Novosphingobium aromaticivorans) and a glutathione lyase (LigG-TD from Thiobacillus denitrificans) was employed in the kinetic resolution of racemic 2,6-MP-VG. This way, enantiopure (S)- and (R)-2,6-MP-VG were obtained on semi-preparative scale without the need for external GSH supply.

A bioactive probe for glutathione-dependent antioxidant capacity in breast cancer patients: implications in measuring biological effects of arsenic compounds

INTRODUCTION

Glutathione, a major cellular non-protein thiol (NPSH), serves a central role in repairing damage induced by cancer drugs, pollutants and radiation and in the detoxification of several cancer chemotherapeutic drugs and toxins. Current methods measure glutathione levels only, which require cellular extraction, rather than the glutathione recycling dependent antioxidant activity in intact cells. Here, we present a novel method using a bioactive probe of the oxidative pentose phosphate cycle, termed the OxPhos™ test, to quantify glutathione recycling dependent antioxidant activity in whole blood and intact human and rodent cells without the need for the isolation and cytoplasm extraction of cells.

METHODS

OxPhos™ test kit (Rockland Immunochemicals, USA), which uses hydroxyethyldisulfide (HEDS) as a probe for the oxidative pentose phosphate cycle, was used in these studies. The results with OxPhos™ test kit in human blood and intact cells were compared with total thiol and high pressure liquid chromatography/electrochemical detection of HEDS metabolism.

RESULTS

The OxPhos™ test measured glutathione-dependent antioxidant activity both in intact human and rodent cells and breast cancer patient's blood with a better correlation coefficient and biological variability than the thiol assay. Additionally, human blood and mammalian cells treated with various arsenicals showed a concentration-dependent decrease in activity.

DISCUSSION

The results demonstrate the application of this test for measuring the antioxidant capacity of blood and the effects of environmental pollutants/toxins. It opens up new avenues for an easy and reliable assessment of glutathione-dependent antioxidant capacity in various diseases such as stroke, blood borne diseases, infection, cardiovascular disease and other oxidative stress related diseases and as a prognostic indicator of chemotherapy response and toxicity. The use of this approach in pharmacology/toxicology including screening drugs that improve the glutathione-dependent antioxidant capacity and not just the glutathione level is clinically relevant since mammalian cells require glutathione dependent pathways for antioxidant activity.