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Mitochondria (mt) represent the vital hub of the molecular physiology of the cell, being decision-makers in cell life/death and information signaling, including major redox regulations and redox signaling. Now we review recent advances in understanding mitochondrial redox homeostasis, including superoxide sources and H2O2 consumers, i.e., antioxidant mechanisms, as well as exemplar situations of physiological redox signaling, including the intramitochondrial one and mt-to-cytosol redox signals, which may be classified as acute and long-term signals. This review exemplifies the acute redox signals in hypoxic cell adaptation and upon insulin secretion in pancreatic β-cells. We also show how metabolic changes under these circumstances are linked to mitochondrial cristae narrowing at higher intensity of ATP synthesis. Also, we will discuss major redox buffers, namely the peroxiredoxin system, which may also promote redox signaling. We will point out that pathological thresholds exist, specific for each cell type, above which the superoxide sources exceed regular antioxidant capacity and the concomitant harmful processes of oxidative stress subsequently initiate etiology of numerous diseases. The redox signaling may be impaired when sunk in such excessive pro-oxidative state.

Active oxygen highly affects the efficiency and stability of perovskite solar cells (PSCs) owing to the capacity to either passivate defects or decompose perovskite lattice. To better understand the in‐depth interaction, we demonstrate for the first time that photooxidation mechanism in all‐inorganic perovskite film dominates the phase deterioration kinetics by forming superoxide species in the presence of light and oxygen, which is significantly different from that in organic‒inorganic hybrid and even tin‐based perovskites. In all‐inorganic perovskites, the superoxide species prefer to oxidize longer and weaker Pb‒I bond to PbO and I2, leaving the much stable CsPbBr3 phase. From this chemical proof‐of‐concept, we employ an organic bioactive factor, Tanshinone IIA, as a superoxide sweeper to enhance the environmental tolerance of inorganic perovskite, serving as a “skincare” agent for anti‐aging organisms. Combined with another key point on healing defective lattice, the best carbon‐based all‐inorganic CsPbI2Br solar cell delivers an efficiency as high as 15.12% and superior stability against oxygen, light, humidity, and heat attacks. This method is also applicable to enhance the efficiency of p‒i‒n inverted (Cs0.05MA0.05FA0.9)Pb(I0.93Br0.07)3 cell to 23.46%. These findings not only help us understand the perovskite decomposition mechanisms in depth but also provide a potential strategy for advanced PSC platforms. We reveal the decomposition mechanism of all‐inorganic mixed‐halide perovskite under light/O2 exposure, which suffers from a photooxidation process by oxidizing Pb‒I bond to PbO and I2, leaving CsPbBr3 phase. A bioinspired “skincare” strategy by adding Tanshinone IIA into perovskite film is proposed to passivate defects and sweep superoxide species, remarkably enhancing the stability and efficiency of PSC.

Strong peroxidase (PRX) and oxidoreductase activities were observed in the barley root tips that were markedly inhibited by NaN3. Rapid and strong nitro-blue tetrazolium chloride (NBT) reduction is associated mainly with the vital functions of root cells but not with superoxide formation. In turn, the inhibition of root surface redox activity by NaN3 strongly reduced the formation of formazan, but its slight accumulation, observed in the root elongation zone, was a result of NADPH oxidase-mediated apoplastic superoxide formation. A longer staining time period with NBT was required for the detection of antimycin A-mediated superoxide formation inside the cells. This antimycin A-induced superoxide was clearly detectable by hydroethidine (HE) after the inhibition of PRXs by NaN3, and it was restricted into the root transition zone. TEMPOL, a superoxide scavenger, strongly inhibited both NBT reduction and HE oxidation in the presence of NaN3. Similarly, the DCDHF-DA and DHR123 oxidation was markedly reduced after the inhibition of apoplastic PRXs by NaN3 and was detectable mainly in the root transition zone. This fluorescence signal was not influenced by the application of pyruvate but was strongly reduced by urea, a peroxynitrite scavenger. The presented results suggest that if the root PRXs and oxidoreductases are inhibited, both NBT and HE detect mainly superoxide, whereas both DCDHF-DA and DHR123 may be efficiently used for the detection of peroxynitrite in intact barley root tips. The inhibition of PRXs and oxidoreductases is crucial for avoiding false-positive reactions in the localization of reactive oxygen species in the intact barley root tip.

Progress in mass spectroscopy of posttranslational oxidative modifications has enabled researchers to experimentally verify the concept of redox signaling. We focus here on redox signaling originating from mitochondria under physiological situations, discussing mechanisms of transient redox burst in mitochondria, as well as the possible ways to transfer such redox signals to specific extramitochondrial targets. A role of peroxiredoxins is described which enables redox relay to other targets. Examples of mitochondrial redox signaling are discussed: initiation of hypoxia-inducible factor (HIF) responses; retrograde redox signaling to PGC1α during exercise in skeletal muscle; redox signaling in innate immune cells; redox stimulation of insulin secretion, and other physiological situations.

Investigation of the chemical constituents from the fruits of Citrus medica L. var. sarcodactylis Swingle has led to the characterization of a new sesquiterpene 1 along with thirty-two known compounds. The structure of 1 was established on the basis of 2D NMR spectroscopic and mass spectrometric analyses, and the known compounds were identified by comparison of their physical and spectroscopic data with those reported in the literature. In addition, most of the isolated compounds were evaluated for the activity assayed by the in vitro inhibition of superoxide anion generation and elastase release by human neutrophils. The results showed that only 6,7-dimethoxycoumarin (5) exhibited significant inhibition of superoxide anion generation, with IC50 value of 3.8 ± 1.4 μM.

This study was conducted to investigate the potential for increased oxidative stress of high- vs. average-producing dairy cows. Two experiments were performed using 11 and 13 Holstein cows (53±2 d postpartum). Lipohydroperoxides (LHP) were determined in serum lipids (experiment 1) and low-density lipoprotein (experiment 2) via oxidation of ferrous to ferric ions through LHP using thiocyanate as chromogen. In experiment 1, differing milk yield and milk energy output corresponded to different concentrations of LHP. In experiment 2, analysis of regression resulted in a significant relationship between milk yield and LHP. Phospholipids isolated from lipids with 6.5μM of LHP evoked in monocytic cells a transient increase in superoxide formation, indicating inflammatory potential. The results show that high milk productivity can associate with oxidative stress indicated by oxidative modifications of circulating lipids and their changed bioactivity.

In order to explore the relationship between sclerotial formation and antioxidant enzymes under abiotic stresses, the effects of abiotic stresses including temperature, pH value, osmotic pressure, limited nitrogen, and hydrogen peroxide (H2O2) on the activities of antioxidant enzymes, ascorbate peroxidase (APX), superoxide dismutase (SOD), peroxidase (POD), and catalase (CAT) in Pleurotus tuber-regium were studied. Meanwhile, the sclerotial formation under these abiotic stress conditions was also investigated. It was found that low temperature, weak alkaline, appropriate osmotic stress, and H2O2 can promote sclerotial formation, and sclerotial formation always tended to occur when the activities of antioxidant enzymes were at a high value. During the prolonged low temperature stress, SOD acted mainly in the early stage of stress, while POD and CAT had higher activity in the middle and late stage. Moreover, the reverse transcription quantitative polymerase chain reaction (RT-qPCR) results showed that SOD.193 and POD.535 were significantly down-regulated in sclerotia, and CAT.1115 and POD.401 were up-regulated instead. These antioxidant enzyme genes played an important role in the sclerotial formation under low temperature stress. It is strongly suggested that antioxidant enzymes and abiotic stresses are closely related to sclerotial formation in P. tuber-regium.Key points• Low temperature and H2O2 can promote sclerotial formation.• Sclerotia are more likely to form under high antioxidant enzyme activity.• POD.401, POD.535, SOD.193, and CAT.1115 are important for sclerotial formation.

In tissue culture, efficient nutrient availability and effective control of callus contamination are crucial for successful plantlet regeneration. This study was aimed to enhance callogenesis, callus regeneration, control callus contamination, and substitute iron (Fe) source with FeO-NPs in Murashige and Skoog (MS) media. Nanogreen iron oxide (FeO-NPs) were synthesized and well characterized with sizes ranging from 2 to 7.5 nm. FeO-NPs as a supplement in MS media at 15 ppm, significantly controlled callus contamination by (80%). Results indicated that FeCl 3 -based FeO-NPs induced fast callus induction (72%) and regeneration (43%), in contrast FeSO 4 -based FeO-NPs resulted in increased callus weight (516%), diameter (300%), number of shoots (200%), and roots (114%). Modified media with FeO-NPs as the Fe source induced fast callogenesis and regeneration compared to normal MS media. FeO-NPs, when applied foliar spray, increased Plant fresh biomass by 133% and spike weight by 350%. Plant height increased by 54% and 33%, the number of spikes by 50% and 265%, and Chlorophyll content by 51% and 34% in IRRI-6 and Kissan Basmati, respectively. Additionally, APX (Ascorbate peroxidase), SOD (Superoxide dismutase), POD (peroxidase), and CAT (catalase) increased in IRRI-6 by 27%, 29%, 283%, 62%, while in Kissan Basmati, APX increased by 70%, SOD decreased by 28%, and POD and CAT increased by 89% and 98%, respectively. Finally, FeO-NPs effectively substituted Fe source in MS media, shorten the plant life cycle, and increase chlorophyll content as well as APX, SOD, POD, and CAT activities. This protocol is applicable for tissue culture in other cereal crops as well.

Skeletal fluorosis is a chronic metabolic bone disease caused by long-term excessive fluoride intake. Abnormal differentiation of osteoblasts plays an important role in disease progression. Research on the mechanism of fluoride-mediated bone differentiation is necessary for the prevention and treatment of skeletal fluorosis. In the present study, a rat model of fluorosis was established by exposing it to drinking water containing 50 mg/L F−. We found that fluoride promoted Runt-related transcription factor 2 (RUNX2) as well as superoxide dismutase 2 (SOD2) and sirtuin 3 (SIRT3) expression in osteoblasts of rat bone tissue. In vitro, we also found that 4 mg/L sodium fluoride promoted osteogenesis-related indicators as well as SOD2 and SIRT3 expression in MG-63 and Saos-2 cells. In addition, we unexpectedly discovered that fluoride suppressed the levels of reactive oxygen species (ROS) and mitochondrial reactive oxygen species (mtROS) in osteoblasts. When SOD2 or SIRT3 was inhibited in MG-63 cells, fluoride-decreased ROS and mtROS were alleviated, which in turn inhibited fluoride-promoted osteogenic differentiation. In conclusion, our results suggest that SIRT3/SOD2 mediates fluoride-promoted osteoblastic differentiation by down-regulating reactive oxygen species.

Superoxide dismutases (SODs) have been shown to exhibit high levels of conservation and exist in almost all aerobic organisms and even many strict anaerobes. There are four SODs in Bacillus cereus 0–9, and this coexistence of multiple homologous enzymes is of great significance in the evolution of bacteria. We hypothesized that the four sod genes in B. cereus 0–9 constituted non-redundant protection against oxidative damage in vivo and played unique roles in the pathogenicity of B. cereus 0–9 during different phases or growth environments. To test this hypothesis, we constructed four single-knockout mutants (∆sodA1, ∆sodA2, ∆sodS, and ∆sodC) and a mutant lacking all four sod genes (∆sod-4) of B. cereus 0–9 and assessed their various phenotypes. Our results indicated that sodA1 plays a major role in tolerance to intracellular oxidative stress and spore formation. The ∆sodA1 and ∆sod-4 mutants were very sensitive to oxidants. The spore formation of the ∆sodA1 mutant was dramatically delayed, and the ∆sod-4 mutant did not form any spores under our experimental conditions. The sodA2 gene may play an important role in negative regulation of swarming motility, pathogenicity, and phospholipase and haemolytic activity of B. cereus but also a role in positive regulation of biofilm formation under our experimental conditions. The other two genes, sodS and sodC, were key to the pathogenicity of B. cereus. The lethal rates of Helicoverpa armigera infected by the ∆sodS and ∆sodC mutants were only 26.67%, while wild-type B. cereus 0–9 caused lethality in up to 86.67% of the insects at 24 h after injection. Moreover, the ∆sod-4 mutant caused a reduced death rate of H. armigera of 46.70%, which was slightly higher than that caused by the ∆sodS and ∆sodC strains. Thus, these four sod genes were non-redundant for oxidative stress and may play different additional roles in B. cereus 0–9. These results can help us to further understand the biocontrol characteristics of B. cereus 0–9 and lay a theoretical foundation for further research.