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Accumulating data indicate that strigolactones (SLs) are implicated in the response to environmental stress, implying a potential effect of SLs on stomatal response and thus stress acclimatization. In this study, we investigated the molecular mechanism underlying the effect of SLs on stomatal response and their interrelation with abscisic acid (ABA) signaling. The impact of SLs on the stomatal response was investigated by conducting SL-feeding experiments and by analyzing SL-related mutants. The involvement of endogenous ABA and ABA-signaling components in SL-mediated stomatal closure was physiologically evaluated using genetic mutants. Pharmacological and genetic approaches were employed to examine hydrogen peroxide (H2O2) and nitric oxide (NO) production. SL-related mutants exhibited larger stomatal apertures, while exogenous SLs were able to induce stomatal closure and rescue the more widely opening stomata of SL-deficient mutants. The SL-biosynthetic genes were induced by abiotic stress in shoot tissues. Disruption of ABA-biosynthetic genes, as well as genes that function in guard cell ABA signaling, resulted in no impairment in SL-mediated stomatal response. However, disruption of MORE AXILLARY GROWTH2 (MAX2), DWARF14 (D14), and the anion channel gene SLOW ANION CHANNEL-ASSOCIATED 1 (SLAC1) impaired SL-triggered stomatal closure. SLs stimulated a marked increase in H2O2 and NO contents, which is required for stomatal closure. Our results suggest that SLs play a prominent role, together with H2O2/NO production and SLAC1 activation, in inducing stomatal closure in an ABA-independent mechanism.

Hydrogen peroxide (H₂O₂) is produced, via superoxide and superoxide dismutase, by electron transport in chloroplasts and mitochondria, plasma membrane NADPH oxidases, peroxisomal oxidases, type III peroxidases and other apoplastic oxidases. Intracellular transport is facilitated by aquaporins and H₂O₂ is removed by catalase, peroxiredoxin, glutathione peroxidase-like enzymes and ascorbate peroxidase, all of which have cell compartment-specific isoforms. Apoplastic H₂O₂ influences cell expansion, development and defence by its involvement in type III peroxidase-mediated polymer cross-linking, lignification and, possibly, cell expansion via H₂O₂-derived hydroxyl radicals. Excess H₂O₂ triggers chloroplast and peroxisome autophagy and programmed cell death. The role of H₂O₂ in signalling, for example during acclimation to stress and pathogen defence, has received much attention, but the signal transduction mechanisms are poorly defined. H₂O₂ oxidizes specific cysteine residues of target proteins to the sulfenic acid form and, similar to other organisms, this modification could initiate thiol-based redox relays and modify target enzymes, receptor kinases and transcription factors. Quantification of the sources and sinks of H₂O₂ is being improved by the spatial and temporal resolution of genetically encoded H₂O₂ sensors, such as HyPer and roGFP2-Orp1. These H₂O₂ sensors, combined with the detection of specific proteins modified by H₂O₂, will allow a deeper understanding of its signalling roles.

This study aims to conduct a single-blind randomized controlled trial to evaluate the bleaching efficacy and tooth sensitivity (TS) following the use of violet LED associated or not with 35% hydrogen peroxide. Eighty-four participants were randomly allocated into three groups according to bleaching treatments ( n  = 28): 35% hydrogen peroxide (HP) only, Violet LED only (VLED), and an association of 35% HP with violet LED (HP + VLED). Three sessions were performed, with an interval of seven days between each one. Changes in the objective (ΔE ab and ΔE 00 ) and subjective (ΔSGU) color and the Whiteness Index for Dentistry (ΔWI D ) were calculated based on before, and seven and thirty days after treatment using colorimetric measurements. Participants self-reported the risk and intensity of TS on a visual analogue scale (VAS). The color assessments seven and 30 days after bleaching were analyzed by two-way ANOVA and Tukey’s test. The absolute TS risk was analyzed by Fisher’s exact test. The significance level adopted was α = 0.05. HP and HP + VLED treatments showed higher and significant bleaching values (ΔE ab, ΔE 00 , ΔSGU, and ΔWI D ) compared to VLED. The HP + VLED and HP groups presented a higher risk and intensity of TS compared to the VLED group ( p  < 0.05). The bleaching efficacy of VLED alone was lower compared to the HP and HP + VLED protocols both seven and 30 days after the end of treatments.

Nanorods assembled 3D microspheres of TiO.sub.2/MnO.sub.2 were prepared via a simple one-pot hydrothermal approach. The resultant composite material exhibited remarkable electrocatalytic activity for hydrogen peroxide (H.sub.2O.sub.2) in comparison to each single component. The electrochemical sensor constructed with TiO.sub.2/MnO.sub.2 exhibited a linear relationship within the range 0.0001-5.6 mmol·L.sup.-1 for H.sub.2O.sub.2. The limit of detection (LOD) and sensitivity for H.sub.2O.sub.2 were 0.03 µmol·L.sup.-1 (S/N = 3) and 316.6 µA (mmol·L.sup.-1).sup.-1 cm.sup.-2. Moreover, this sensor can be employed to detect trace amount of H.sub.2O.sub.2 in serum and urine samples successfully, supporting an insight and strategy for a more sensitive electrochemical sensor. Graphical

Hydrogen peroxide (H 2 O 2 )-based products are effective in tooth whitening; however, their safety is controversial as they may harm patient tissues/cells. These effects are suggested to be concentration-dependent; nonetheless, to date, there are no reports on H 2 O 2 -mediated oxidative damage in the gingival tissue, and neither whether this can be detected in gingival crevicular fluid (GCF) samples. We hypothesize that H 2 O 2 whitening products may cause collateral oxidative tissue damage following in office application. Therefore, H 2 O 2 and nitric oxide (NO) levels were investigated in GCF samples obtained from patients undergoing dental bleaching with H 2 O 2 at different concentrations, in a randomized, double-blind, split-mouth clinical trial. A proteomic analysis of these samples was also performed. H 2 O 2 -based whitening products promoted inflammation which was detected in GCF samples and lasted for longer following 35% H 2 O 2 bleaching. This included time-dependent changes in NO levels and in the abundance of proteins associated with NO synthesis, oxidative stress, neutrophil regulation, nucleic acid damage, cell survival and/or tissue regeneration. Overall, H 2 O 2 -based products used in office promote inflammation irrespective of their concentration. As the inflammation caused by 35% H 2 O 2 is longer , patients may benefit better from using lower concentrations of this bleaching product, as they may result in less tissue damage.

Contact electrification between water and a solid surface is crucial for physicochemical processes at water–solid interfaces. However, the nature of the involved processes remains poorly understood, especially in the initial stage of the interface formation. Here we report that H₂O₂ is spontaneously produced from the hydroxyl groups on the solid surface when contact occurred. The density of hydroxyl groups affects the H₂O₂ yield. The participation of hydroxyl groups in H₂O₂ generation is confirmed by mass spectrometric detection of 18O in the product of the reaction between 4-carboxyphenylboronic acid and 18O–labeled H₂O₂ resulting from 18O₂ plasma treatment of the surface. We propose a model for H₂O₂ generation based on recombination of the hydroxyl radicals produced from the surface hydroxyl groups in the water–solid contact process. Our observations show that the spontaneous generation of H₂O₂ is universal on the surfaces of soil and atmospheric fine particles in a humid environment.

Powdery mildew is an apple disease caused by the obligate trophic fungus Podosphaera leucotricha. Basic helix-loop-helix (bHLH) transcription factors play important roles in plant development and stress responses, and they have been widely studied in model plants such as Arabidopsis thaliana. However, their role in the stress response of perennial fruit trees remains unclear. Here, we investigated the role of MdbHLH093 in the powdery mildew of apples. The expression of MdbHLH093 was significantly induced during the infection of apples with powdery mildew, and the allogenic overexpression of MdbHLH093 in A. thaliana enhanced the resistance to powdery mildew by increasing the accumulation of hydrogen peroxide (H[sub.2]O[sub.2]) and activating the salicylic acid (SA) signaling pathway. The transient overexpression of MdbHLH093 in apple leaves increased the resistance to powdery mildew. Conversely, when MdbHLH093 expression was silenced, the sensitivity of apple leaves to powdery mildew was increased. The physical interaction between MdbHLH093 and MdMYB116 was demonstrated by yeast two-hybrid, bi-molecular fluorescence complementation, and split luciferase experiments. Collectively, these results indicate that MdbHLH093 interacts with MdMYB116 to improve apple resistance to powdery mildew by increasing the accumulation of H[sub.2]O[sub.2] and activating the SA signaling pathway, as well as by providing a new candidate gene for resistance molecular breeding.

The cystine transporter solute carrier family 7 member 11 (SLC7A11; also called xCT) protects cancer cells from oxidative stress and is overexpressed in many cancers. Here we report a surprising finding that, whereas moderate overexpression of SLC7A11 is beneficial for cancer cells treated with H 2 O 2 , a common oxidative stress inducer, its high overexpression dramatically increases H 2 O 2 -induced cell death. Mechanistically, high cystine uptake in cancer cells with high overexpression of SLC7A11 in combination with H 2 O 2 treatment results in toxic buildup of intracellular cystine and other disulfide molecules, NADPH depletion, redox system collapse, and rapid cell death (likely disulfidptosis). We further show that high overexpression of SLC7A11 promotes tumor growth but suppresses tumor metastasis, likely because metastasizing cancer cells with high expression of SLC7A11 are particularly susceptible to oxidative stress. Our findings reveal that SLC7A11 expression level dictates cancer cells’ sensitivity to oxidative stress and suggests a context-dependent role for SLC7A11 in tumor biology. The cystine transporter SLC7A11 protects cancer cells from oxidative stress by supporting glutathione synthesis. Here, the authors show that the expression level of SLC7A11 leads to different outcomes depending on context, so high expression promotes primary tumour growth but promotes disulfide stress under oxidative stress conditions and impairs metastasis.

Hydrogen peroxide (H2O2) is a compound involved in some mammalian reactions and processes. It modulates and signals the redox metabolism of cells by acting as a messenger together with hydrogen sulfide (H2S) and the nitric oxide radical (•NO), activating specific oxidations that determine the metabolic response. The reaction triggered determines cell survival or apoptosis, depending on which downstream metabolic pathways are activated. There are several ways to produce H2O2 in cells, and cellular systems tightly control its concentration. At the cellular level, the accumulation of hydrogen peroxide can trigger inflammation and even apoptosis, and when its concentration in the blood reaches toxic levels, it can lead to bioenergetic failure. This review summarizes existing research from a chemical perspective on the role of H2O2 in various enzymatic pathways and how this biochemistry leads to physiological or pathological responses.

Objective This study compares the effects of Nanosil ® mouthwash, a multi-component formulation containing hydrogen peroxide, silver ions, eugenol, and menthol and chlorhexidine on healing, pain, and complications following impacted mandibular third molar surgery. Impacted mandibular third molars extraction, often accompanied by complications like pain, dry socket, swelling, trismus, and infection. Mouthwashes are used to reduce infection risk and promote healing by eliminating oral microorganisms. Methodology : This double-blind, randomized clinical trial involved 62 patients (aged 18–50 years) with Pell and Gregory A and B impacted third molars. Participants were allocated to two groups: 15 cc of Nanosil ® mouthwash and 250 ml of 0.2% chlorhexidine mouthwash (Najo ® ) before and after surgery. Pain was assessed with the Visual Analog Scale (VAS), swelling was measured on days 1, 3, and 7, and wound healing was evaluated. Data were analyzed using t-tests and Mann-Whitney tests. Results Healing on day 3 was significantly better in the Nanosil group ( p  = 0.001). No infections or discharge were observed. A dry socket occurred in one patient in the Nanosil group, but it was not statistically significant. Swelling was significantly lower in the Nanosil group on day 3 ( p  < 0.001). Pain levels were similar in both groups. Conclusion Nanosil promoted better healing and reduced swelling compared to chlorhexidine on the third day post-surgery. No significant differences were found regarding pain, infection, discharge, or dry socket. Trial registration: The study was registered in the Iranian Clinical Trials Center with the code IRCT20171216037893N6 on 16/12/2021. https://irct.behdasht.gov.ir/trial/60568 .