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The huge diversity of secondary bioactive metabolites, such as antibiotic and anticancer compounds produced by Micromonospora sp., makes it an attractive target for study. Here, we explored the anti-proliferative activities of Micromonospora sp. M2 extract (MBE) in relation to its pro-oxidative activities in A549 and MCF7 cell lines. Anti-proliferative effects were assessed by treating cells with MBE. We found that treatment with MBE decreased cell proliferation and increased intracellular reactive oxygen species, and that these observations were facilitated by the suppression of the PI3K-AKT pathway, alterations to the Bcl/Bad ratio, and increased caspase activity. These observations also demonstrated that MBE induced apoptotic cell death in cell lines. In addition, the phosphorylation of P38 and c-Jun N-terminal kinase (JNK) were upregulated following MBE treatment in both cell lines. Collectively, these results indicate that MBE acts as an anticancer agent via oxidative stress and JNK/mitogen-activated protein kinase pathway activation, enhancing apoptotic cell death in cell lines., (© The Author(s) 2024. Published by Oxford University Press on behalf of Japan Society for Bioscience, Biotechnology, and Agrochemistry.)

Ascorbate peroxidase (APX) is an important reactive oxygen species (ROS)-scavenging enzyme, which catalyzes the removal of hydrogen peroxide (H2O2) to prevent oxidative damage. The peroxidase activity of APX is regulated by posttranslational modifications (PTMs), such as S-nitrosylation, tyrosine nitration, and S-sulfhydration. In addition, it has been recently reported that APX functions as a molecular chaperone, protecting rice against heat stress. In this study, we attempted to identify the various functions of APX in Arabidopsis and the effects of PTMs on these functions. Cytosol type APX1 from Arabidopsis thaliana (AtAPX1) exists in multimeric forms ranging from dimeric to high-molecular-weight (HMW) complexes. Similar to the rice APX2, AtAPX1 plays a dual role behaving both as a regular peroxidase and a chaperone molecule. The dual activity of AtAPX1 was strongly related to its structural status. The main dimeric form of the AtAPX1 protein showed the highest peroxidase activity, whereas the HMW form exhibited the highest chaperone activity. Moreover, in vivo studies indicated that the structure of AtAPX1 was regulated by heat and salt stresses, with both involved in the association and dissociation of complexes, respectively. Additionally, we investigated the effects of S-nitrosylation, S-sulfhydration, and tyrosine nitration on the protein structure and functions using gel analysis and enzymatic activity assays. S-nitrosylation and S-sulfhydration positively regulated the peroxidase activity, whereas tyrosine nitration had a negative impact. However, no effects were observed on the chaperone function and the oligomeric status of AtAPX1. Our results will facilitate the understanding of the role and regulation of APX under abiotic stress and posttranslational modifications. [ABSTRACT FROM AUTHOR]

Deinococcus radiodurans R1 is extremely resistant to ionizing radiation and oxidative stress. In this study, we characterized DR0846, a candidate peroxiredoxin in D. radiodurans. DR0846 is a peroxiredoxin Q containing two conserved cysteine residues. DR0846 exists mainly in monomeric form with an intramolecular disulfide bond between the two cysteine residues. We found that DR0846 functions as a molecular chaperone as well as a peroxidase. A mutational analysis indicates that the two cysteine residues are essential for enzymatic activity. A double‐deletion mutant lacking DR0846 and catalase DR1998 exhibits decreased oxidative and heat shock stress tolerance with respect to the single mutants or the wild‐type cells. These results suggest that DR0846 contributes to resistance against oxidative and heat stresses in D. radiodurans. [ABSTRACT FROM AUTHOR]

Peroxynitrite (ONOO−), a highly reactive oxygen species generated by the reaction of nitric oxide and superoxide radical anion, is involved in numerous physiological and pathological processes in the human body. To identify important pathogenic mechanisms, it is crucial to develop a reliable tool for detecting peroxynitrite in living systems. In the present study, a new difluoroboron β-diketonate-based fluorescent probe for detecting exogenous and endogenous peroxynitrite in living systems was designed. The red emitting fluorophore can be synthesized in a simple three-step procedure. This probe reacts quickly and selectively with peroxynitrite and its detection limit is determined to be as low as 19.8 nM. It allows for clear imaging of peroxynitrite in RAW 264.7 cells and was successfully applied to visualize changes of intracellular peroxynitrite induced by reactive oxygen species inhibitors. This designed probe is an effective tool for investigating the physiological and pathological role of peroxynitrite in living cells. Image 1 • We synthesized an activatable fluorescence probe to detect intracellular ONOO−. • QPP (1) rapidly and selectively reacts with peroxynitrite over other reactive species. • The activated fluorophore displayed a red emission wavelength in live cells. • A small amount of probe clearly visualized exogenous and endogenous ONOO− in cells. • QPP (1) can be used to study the physiological and pathological roles of ONOO−. [ABSTRACT FROM AUTHOR]

Abstract: Application of chemical probes, for detection of reactive oxygen species (ROS), was tested during γ-irradiation. The ethanol/α-(4-pyridyl-1-oxide)-N-tert-butylnitrone (4-POBN) and 3,3′-diaminobenzidine (DAB) were structurally stable enough to detect OH and H2O2, increasingly generated by γ-irradiation up to 1000Gy. Interestingly, the production rate of H2O2, but not OH, during γ-irradiation, was significantly different between in vitro systems of lettuce and spinach. These results suggest that 4-POBN and DAB could be utilized as a semi-quantitative probe to quantify OH and H2O2, produced by γ-irradiation up to 1000Gy. [Copyright &y& Elsevier]

Abstract: Salinization plays a primary role in soil degradation and reduced agricultural productivity. We observed that salt stress reversed photosynthesis and reactive oxygen scavenging responses in leaves or roots of two rice cultivars, a salt-tolerant cultivar Pokkali and a salt-sensitive cultivar IR-29. Salt treatment (100 mM NaCl) on IR-29 decreased the maximum photochemical efficiency (Fv/Fm) and the photochemical quenching coefficient (qP), thereby inhibiting photosynthetic activity. By contrast, the salt treatment on Pokkali had the converse effect on Fv/Fm and qP, while increasing the nonphotochemical quenching coefficient (NPQ), thereby favoring photosynthetic activity. Notably, chloroplast or root cells in Pokkali maintained their ultrastructures largely intact under the salt stress, but, IR-29 showed severe disintegration of existing grana stacks, increase of plastoglobuli, and swelling of thylakoidal membranes in addition to collapsed vascular region in adventitious roots. Pokkali is known to have higher hydrogen peroxide (H2O2)-scavenging enzyme activities in non-treated seedlings, including ascorbate peroxidase, catalase, and peroxidase activities. However, these enzymatic activities were induced to a greater extent in IR-29 by the salt stress. While the level of endogenous H2O2 was lower in Pokkali than in IR-29, it was reversed upon the salt treatment. Nevertheless, the decreased amount of H2O2 in IR-29 upon the salt stress didn't result in a high scavenging activity of total cell extracts for H2O2, as well as O2 − and OH species. The present study suggests that the tolerance to the moderate salinity in Pokkali derives largely from the constitutively maintained antioxidant enzymatic activities as well as the induced antioxidant enzyme system. [Copyright &y& Elsevier]