Oxidase Inhibitor Research Articles

Enhancing toxicity of pyrethroids by oxidase and esterase inhibitors in Spodoptera littoralis (Boisd.) larvae

Although pyrethroids are increasingly being used to control a number of agricultural insect pests, especially the cotton leafworm, Spodoptera littoralis (Boisd.), pyrethroid resistance is a major obstacle limiting effective control. With the aim of maintaining the effectiveness of pyrethroids in managing pests, a study was undertaken to evaluated the effectiveness of oxidase and esterase inhibitors for synergizing pyrethroids in S. littoralis larvae. Compared with the insecticide-susceptible strain (L-SS) of S. littoralis, the resistance ratio (RR) in the field population (F-RS) was 271.43–fold to cypermethrin. The use of profenofos as an esterase inhibitor significantly increased larval susceptibility to cypermethrin in the F-RS strain, with a synergy ratio (SR) of up to 192.57–fold. Significant inhibition of esterase by profenofos in the F-RS strain was found in vivo. Also, piperonyl butoxide (PB) as an oxidase inhibitor had slight effect of cypermethrin toxicity, so its addition is not a solution for pyrethroid resistance. Thus, modifying the toxicity of cypermethrin by mixing it with organophosphorus compounds (OPs) increased its toxicity and decreased the population of S. littoralis, which is a successful strategy for managing pyrethroid resistance.

Copper regulation of PtRhRuCu nanozyme targeted boosting peroxidase-like activity for ultrasensitive smartphone-assisted colorimetric sensing of glucose

Point-of-care testing (POCT) is promising for biodetection in home healthcare due to advantages of simplicity, rapidity, low cost, portability, high sensitivity and accuracy, and object-oriented POCT platform can be developed by nanozyme-based biosensing. However, designing high-performance nanozymes with targeted regulated catalytic activity remains challenging. Herein, advanced PtRhRuCu quaternary alloy nanozymes (QANs) were rationally designed and successfully synthesized. Cu atoms induced mechanisms of hydrogen peroxide (H2O2) activation and d-band center regulation, achieving high enhancement of peroxide (POD)-like activity and inhibition of oxidase (OXD)-like activity. Inspired by this, a smartphone-assisted colorimetric platform integrated with test strips was established for glucose detection of soft drinks, with a detection limit of 0.021 mM and a recovery rate of 97.87 to 103.36 %. This work not only provides a novel path for tuning specific enzyme-like activities of metal nanozymes, but also shows the potential feasibility for rational design of POCT sensors in actual samples.

Copper Ions Reduced Toxicity of Sodium Azide and Lipopolysaccharide on Cultured Cerebellar Granule Neurons

Introduction. Copper ions (Cu2+) are structural elements of proteins such as cytochrome с oxidase (Complex IV), an enzyme that catalyzes the final step of electron transfer to oxygen during oxidative phosphorylation in the mitochondria. With Cu2+ homeostasis being of utmost importance, its disturbances in the central nervous system are involved in the mechanisms of many neurodegenerative and other brain disorders.
 This study aimed to assess the effects of non-toxic copper ion levels on death of cerebellar granule neurons associated with lipopolysaccharide (LPS; in vitro inflammation model) or azide sodium (NaN3; cytochrome с oxidase inhibitor).
 Materials and methods. LPS (10 μg/mL) or NaN3 (250 μM) was added on day 7 to 8 to the culture medium with rat cerebellar cells for 24 hours in vitro. Nitrite concentrations were measured in the culture medium by Griess assay; absorbance was recorded with a spectrophotometer at 540 nm, and morphologically intact cells were counted as survived neurons.
 Results. Added to the culture medium, LPS or NaN3 reduced neuron survival to 15 ± 2% or 20 ± 3% vs. control, respectively. Cu2+ (0.5 to 5.0 μM) increased neuron survival in a dose-dependent manner to 78 ± 4% with toxic levels of LPS and to 86 ± 6% with NaN3 with 5 μM Cu2+. The concentration of nitrites in the control culture medium was 2.0 ± 0.2 μM. Added to the cell cultures, LPS increased the concentration of nitrites to 8.5 ± 0.5 μM. Cu2+ 5 μM did not show any significant effects on nitrite accumulation in the culture medium.
 Conclusions. We showed that copper ions can exert protective effects on neurons against LPS-induced or NaN3-induced toxicity. This protection is likely to be associated rather with Cu2+ interaction with Complex IV of the electron transfer chain in the mitochondria than with inhibition of NO production. Effects of Cu2+ on apoptosis pathway proteins also cannot be ruled out.

Synergistic Effect of Lovastatin and Selegiline on the Differentiation of Bone Marrow Stromal Cells Into Neuron-Like Cells

Background: The effect of selegiline as an oxidase inhibitor on cell differentiation into neuron-like cells has been demonstrated by altering gene expression. Based on the results of studies on the role of statins in neurotrophin regulation, in this study, we examined the effect of lovastatin (HMG-CoA reductase inhibitor) on the differentiation of bone marrow mesenchymal cells (BMSCs) into neuron-like cells. Selegiline is an irreversible inhibitor of monoamine oxidase (MAO) type B. Since dopamine in the human brain is metabolized primarily by MAO-B, selegiline increases dopamine levels in the central nervous system. In addition to inhibiting MAO-B, selegiline also inhibits the uptake of dopamine and norepinephrine into presynaptic nerves and increases dopamine turnover. Methods: Bone marrow mesenchymal cells were collected from 28-day-old rats and cultured under standard conditions on the medium. The experimental groups in this study were as follows: BMSCs (control); BMSCs induced with 20 µM selegiline for 24 hours (experiment 1); BMSCs induced with 6 µM lovastatin for 24 hours (experiment 2); BMSCs were induced with 20 µM selegiline for 24 hours and 6 µM lovastatin for the next 24 hours (experiment 3). Real-time RT-PCR was performed to determine the mRNA levels of the nestin and NF-68 genes. Results: Real-time RT-PCR results showed that nestin and NF-68 mRNA levels were significantly increased in the co-treatment group (experiment 3) compared to the other experimental groups (P < 0.05). Conclusions: Based on the increased expression of nestin and NF-68 genes, the presence of lovastatin has a synergistic effect on neuronal differentiation and optimization of stem cell therapeutic approaches.

Xanthine oxidase/NADPH oxidase inhibition by hydralazine attenuates acute kidney injury and prevents the transition of acute kidney injury to chronic kidney disease

AimsThe enhancement of inflammation and reactive oxygen species leads to the damage of renal tubular cells in acute kidney injury (AKI), and the upregulation of inflammation increases the risk of AKI being converted into chronic kidney disease (CKD). Hydralazine has shown renoprotective effects in multiple kidney diseases and was shown to be a potent xanthine oxidase (XO) inhibitor. This study aimed to investigate the mechanisms of hydralazine in ischemia–reperfusion (I/R)-stimulated renal proximal tubular epithelial cells in vitro and in AKI animals in vivo. Main methodsThe effects of hydralazine in AKI-to-CKD transition were also evaluated. Human renal proximal tubular epithelial cells were stimulated by I/R conditions in vitro. To generate a mouse model of AKI, a right nephrectomy was performed, followed by left renal pedicle I/R using a small atraumatic clamp. Key findingsIn the in vitro part, hydralazine could protect renal proximal tubular epithelial cells against insults from the I/R injury through XO/NADPH oxidase inhibition. In the in vivo part, hydralazine preserved renal function in AKI mice and improved the AKI-to-CKD transition by decreasing renal glomerulosclerosis and fibrosis independently of blood pressure lowering. Furthermore, hydralazine exerted antioxidant, anti-inflammatory, and anti-fibrotic effects both in vitro and in vivo. SignificanceHydralazine, as a XO/NADPH oxidase inhibitor, could protect renal proximal tubular epithelial cells from the insults of I/R and prevent kidney damage in AKI and AKI-to-CKD. The above experimental studies strengthen the possibility of repurposing hydralazine as a potential renoprotective agent through its antioxidative mechanisms.

In vitro-in vivo assessments of apocynin-hybrid nanoparticle-based gel as an effective nanophytomedicine for treatment of rheumatoid arthritis.

Apocynin (APO), a well-known bioactive plant-based phenolic phytochemical with renowned anti-inflammatory andantioxidant pharmacological activities, has recently emerged as a specific nicotinamide adenine dinucleotide phosphate-oxidase (NADPH) oxidase inhibitor. As far as we know, no information has been issued yet regarding its topical application as a nanostructured-based delivery system. Herein, APO-loaded Compritol® 888 ATO (lipid)/chitosan (polymer) hybrid nanoparticles (APO-loaded CPT/CS hybrid NPs) were successfully developed, characterized, and optimized, adopting a fully randomized design (32) with two independent active parameters (IAPs), namely, CPT amount (XA) and Pluronic® F-68 (PF-68) concentration (XB), at three levels. Further in vitro-ex vivo investigation of the optimized formulation was performed before its incorporation into a gel base matrix to prolong its residence time with consequent therapeutic efficacy enhancement. Subsequently, scrupulous ex vivo-in vivo evaluations of APO-hybrid NPs-based gel (containing the optimized formulation) to scout out its momentous activity as a topical nanostructured system for beneficial remedy of rheumatoid arthritis (RA) were performed. Imperatively, the results support an anticipated effectual therapeutic activity of the APO-hybrid NPs-based gel formulation against Complete Freund's Adjuvant-induced rheumatoid arthritis (CFA-induced RA) in rats. In conclusion, APO-hybrid NPs-based gel could be considered a promising topical nanostructured system to break new ground for phytopharmaceutical medical involvement in inflammatory-dependent ailments.

Up-regulated Expression of a TOR2A Gene Product-Salusin-β in the Paraventricular Nucleus Enhances Sympathetic Activity and Cardiac Sympathetic Afferent Reflex in Rats with Chronic Heart Failure Induced by Coronary Artery Ligation.

Enhanced cardiac sympathetic afferent reflex (CSAR) promotes sympathetic hyperactivation in chronic heart failure (CHF). Salusin-β is a torsin family 2 member A gene product and a cardiovascular active peptide closely associated with cardiovascular diseases. We aimed to determine the roles of salusin-β in the paraventricular nucleus (PVN) in modulating enhanced CSAR and sympathetic hyperactivation in rats with CHF induced by coronary artery ligation and elucidate the underlying molecular mechanisms. CSAR was evaluated based on the responses of mean arterial pressure (MAP) and renal sympathetic nerve activity (RSNA) to the epicardial administration of capsaicin in rats under anaesthesia. Salusin-β protein expression was up-regulated in the PVN of the CHF compared with sham-operated rats. Salusin-β microinjection into the PVN dose-dependently increased MAP and RSNA and enhanced CSAR, while anti-salusin-β IgG exerted opposite effects. The effect of salusin-β was inhibited by reactive oxygen species (ROS) scavenger or NAD(P)H oxidase inhibitor but promoted by superoxide dismutase inhibitor. The effect of anti-salusin-β IgG was interdicted by nitric oxide (NO) synthase inhibitor. Furthermore, chronic salusin-β gene knockdown in PVN attenuated CSAR, reduced sympathetic output, improved myocardial remodelling and cardiac function, decreased NAD(P)H oxidase activity and ROS levels, and increased NO levels in the CHF rats. Increased salusin-β activity in the PVN contributes to sympathetic hyperactivation and CSAR in CHF by inhibiting NO release and stimulating NAD(P)H oxidase-ROS production. Reducing endogenous central salusin-β expression might be a novel strategy for preventing and treating CHF in the future.

APX‑115A, a pan‑NADPH oxidase inhibitor, reduces the degree and incidence rate of dry eye in the STZ‑induced diabetic rat model.

Dye eye disease (DED) is a common ocular disorder in patients with diabetes. It has been reported that APX-115A, a pan-nicotinamide adenine dinucleotide phosphate (NAPDH) oxidase inhibitor, has an apoptosis-inducing effect on Epstein-Barr virus-infected retinal epithelial cells, but its effects in DED are poorly understood. Therefore, a rat model of diabetes was used in the present study to investigate whether APX-115A has an impact on DED in diabetic rats. A diabetic model was established in male Sprague Dawley rats via the intraperitoneal injection of streptozotocin. The eyeballs of the rats were treated with a solution containing APX-115A or a saline control. Tear secretion was measured with the phenol red thread tear test, and the morphology of the eyeball and lacrimal gland tissues was determined using hematoxylin and eosin staining. In addition, localization of NAPDH oxidase 2 (NOX2) in the eyeball and lacrimal gland tissues was detected by immunohistochemistry. The APX-115A treatment had no effect on body weight, blood glucose level or the size of the lacrimal glands. However, morphological changes, namely intracellular vacuoles and acinar atrophy, were observed in the lacrimal glands of the diabetic rats, and APX-115A treatment attenuated these changes. Immunohistochemistry revealed that NOX2 expression was decreased in the lacrimal glands of the diabetic rats, and APX-115A treatment did not attenuate the reduction in NOX2. The corneas of the diabetic rats treated with APX-115A exhibited no change in thickness but had lower NOX2 expression levels compared with those of the control diabetic rats. APX-115A also increased tear secretion and ameliorated the histological changes associated with diabetes. Furthermore, the NOX2 expression levels in the corneas of the diabetic rats treated with APX-115A were restored to the levels observed in normal rats. These findings suggest that APX-115A has potential as a therapeutic agent for DED.

Cyclosporin A Inhibits the Activation of Membrane-Bound Guanylate Cyclase GC-A of Atrial Natriuretic Factor via NAD(P)H Oxidase.

Cyclosporin A (CsA) is a common immunosuppressant wildly used in patients with organ transplant and autoimmune diseases; however, it can cause several adverse effects, such as nephrotoxicity and hypertension. The detailed mechanisms have not been completely understood. Atrial natriuretic factor (ANF) and its receptor (mGC-A) have been shown to play a crucial role in the regulation of blood pressure. Here, we investigated the effects of CsA on the activation of mGC-A in ANF-treated LLC-PK1 cells. In our study, ANF-induced mGC-A activities and superoxide generation in LLC-PK1 cells were measured by guanosine 3',5'-cyclic monophosphate (cGMP) radioimmunoassay and lucigenin-dependent chemiluminescence, respectively. We found that CsA can reduce about 60% of mGC-A activities in ANF-treated LLC-PK1 cells. CsA is known to induce superoxide. Addition of superoxide generators menadione and diamide mimicked the effects of CsA, whereas DPI (a reduced nicotinamide adenine dinucleotide phosphate (NAD(P)H) oxidase inhibitor) and Tiron (a superoxide quencher) blocked the suppressive effects of CsA on ANF-induced mGC-A activities. We previously showed that the catalytic domain of GC-A (GC-c) expresses guanylate cyclase activities. Addition of menadione, diamide, or peroxynitrite or transfection of Nox-4 NAD(P)H oxidase abolished GC-c activities. In conclusion, CsA inhibits ANF-stimulated mGC-A activities through superoxide and/or peroxynitrite generated by an NAD(P)H oxidase by interacting with the catalytic domain of mGC-A.

Effects of modified atmosphere packaging on the postharvest quality of mulberry leaf vegetable

Fresh mulberry leaf vegetable is nutritive and becoming popular. However, available preservation technologies are deficient. In present work, the effects of two kinds of modified atmosphere packaging on postharvest quality of fresh mulberry leaf vegetable stored at 4 °C were evaluated. The respiration rate of samples in the modified polyethylene packages (MP20) was 12.88–22.65% lower than that in normal polyethylene packaging (CK). The content of total soluble solids, soluble protein, and total polyphenol in MP20 was less changed than that in CK, and the vitamin C retention was higher as well. Moreover, the lignin content in MP20 was lower than that in CK during storage (19.79% vs 13.38% at day 8), and that was significantly positively related to the polyphenol oxidase and peroxidase activities inhibition. Taken together, a packaging with moderate gas permeability (MP20) is suitable for nutrition maintenance and lignification inhibition of fresh mulberry leaf vegetable during cold storage.

Abstract 3183: Targeting a myofibroblastic prostate cancer-associated fibroblast subtype through pharmacological inhibition of NADPH oxidase 4

Abstract Recent developments in single cell sequencing have revealed significant heterogeneity in the stromal tumor microenvironment. It is now widely accepted that there are different cancer-associated fibroblast (CAF) subtypes with different functions and effects on tumor progression. Since CAFs are generally considered an emerging therapeutic target, it is crucial to identify those subtypes that are tumor-promoting and to characterize their driver pathways. In this study we describe a population of CAFs in prostate cancer (PCa) that express elevated levels of NADPH oxidase 4 (Nox4) and localize adjacent to tumor foci. We previously showed that Nox4 is essential for TGFβ-mediated differentiation to a myofibroblastic CAF phenotype and that its increased expression is associated with biochemical relapse and reduced survival. Thus, this study aims to investigate whether pharmacological Nox4 inhibition can be used as an adjuvant therapeutic approach in PCa and which molecular pathways are regulated by Nox4 in the tumor microenvironment. Experiments using GKT831, a small molecule Nox1/Nox4 inhibitor with promising effects in clinical trials for fibrotic diseases, so far support its use as a therapeutic target. Most importantly, Nox4 inhibition reduced CAF marker expression in primary prostate CAFs and attenuated the expression of PSA, the key clinical biomarker of PCa progression, in ex vivo cultured human PCa tissue. The translational application of Nox4 inhibition is currently under investigation in vivo using CAF-PCa cell xenografts. To elucidate the molecular mechanisms regulated by Nox4 we performed integrative bioinformatics and functional assays, which revealed that Nox4 regulates CAF adhesion and migration. In addition, we found that Nox4 regulated genes were associated with a YAP signature and the transcription factor TEAD1, a major cofactor of YAP. Ongoing experiments suggest that during adhesion Nox4 signals via oxidation of SHP2, a redox-sensitive phosphatase that has previously been implicated in regulating YAP transcriptional activity. Previous studies have shown that adhesion and mechanotransduction pathways are commonly altered in myofibroblastic CAFs and that they support the formation of a tumor-promoting microenvironment. Our data suggest that Nox4 acts as a central regulator of these key oncogenic pathways and thus represents a promising therapeutic target. Citation Format: Elena Brunner, Lucy Neumann, Elisabeth Damisch, Martin Puhr, Georg Schäfer, Cédric Szyndralewiez, Helmut Klocker, Natalie Sampson. Targeting a myofibroblastic prostate cancer-associated fibroblast subtype through pharmacological inhibition of NADPH oxidase 4 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 3183.

Oxime derivative TFOBO promotes cell death by modulating reactive oxygen species and regulating NADPH oxidase activity in myeloid leukemia

Several derivatives derived from the oxime structure have been reported as potential anticancer agents in various cancers. Here, we first tested a novel oxime-containing derivative of 2-((2,4,5-trifluorobenzyl)oxy)benzaldehyde oxime (TFOBO) to evaluate its anticancer effect in myeloid leukemic cells. Compared to (2-((2,4,5-trifluorobenzyl)oxy)phenyl)methanol (TFOPM), the oxime derivative TFOBO suppresses leukemic cell growth by significantly increasing reactive oxygen species (ROS) levels and cell death. Leukemic cells treated with TFOBO displayed apoptotic cell death, as indicated by nuclear condensation, DNA fragmentation, and annexin V staining. TFOBO increases Bax/Bcl2 levels, caspase9, and caspase3/7 activity and decreases mitochondrial membrane potential. ROS production was reduced by N-acetyl-l-cysteine, a ROS scavenger, diphenyleneiodonium chloride, a nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor, after exogenous TFOBO treatment. ROS inhibitors protect leukemic cells from TFOBO-induced cell death. Thus, our study findings suggest that TFOBO promotes apoptosis by modulating ROS and regulating NADPH oxidase activity. Collectively, the oxime-containing derivative TFOBO is a novel therapeutic drug for myeloid leukemia.

Acute Kynurenine Exposure of Rat Thoracic Aorta Induces Vascular Dysfunction <i>via</i> Superoxide Anion Production

The accumulation of uremic toxins is known to be one of the causes of cardiovascular disorder related to renal disease. Among the many uremic toxins, we focused on kynurenine (kyn), whose levels have been shown to be positively correlated with vascular endothelial dysfunction markers, and directly evaluated the influence of kyn on the rat thoracic aorta. Exposure of the endothelium-intact aorta to kyn markedly attenuated the acetylcholine (ACh)-induced relaxation and significantly increased superoxide anion (O2·-) production. These effects were ameliorated by pretreatment with ascorbic acid, an antioxidant, and CH223191, an aryl hydrocarbon receptor (AhR) inhibitor, but not by apocynin, a reduced nicotinamide adenine dinucleotide phosphate (NADPH) oxidase inhibitor. In the endothelium-denuded aorta, kyn significantly attenuated the nitric oxide (NO) donor sodium nitroprusside (SNP)-induced vasorelaxation and increased the O2·- production. Ascorbic acid treatment significantly ameliorated these effects, whereas CH223191 and apocynin treatments did not. Kyn had no influence on the vasorelaxant response to BAY 41-2272, a soluble guanylate cyclase stimulator. This suggested that kyn attenuates the NO-mediated vasorelaxation response by promoting O2·- production in thoracic aorta to inactivate NO. O2·- production is likely stimulated in both vascular endothelium and smooth muscle, the former of which may be mediated by AhR activation.

Cytochrome c Oxidase Inhibition by ATP Decreases Mitochondrial ROS Production.

This study addresses the eventual consequence of cytochrome c oxidase (CytOx) inhibition by ATP at high ATP/ADP ratio in isolated rat heart mitochondria. Earlier, it has been demonstrated that the mechanism of allosteric ATP inhibition of CytOx is one of the key regulations of mitochondrial functions. It is relevant that aiming to maintain a high ATP/ADP ratio for the measurement of CytOx activity effectuating the enzymatic inhibition as well as mitochondrial respiration, optimal concentration of mitochondria is critically important. Likewise, only at this concentration, were the differences in ΔΨm and ROS concentrations measured under various conditions significant. Moreover, when CytOx activity was inhibited in the presence of ATP, mitochondrial respiration and ΔΨm both remained static, while the ROS production was markedly decreased. Consubstantial results were found when the electron transport chain was inhibited by antimycin A, letting only CytOx remain functional to support the energy production. This seems to corroborate that the decrease in mitochondrial ROS production is solely the effect of ATP binding to CytOx which results in static respiration as well as membrane potential.

ISOLATION OF FLAVONOID XANTHINE OXIDASE INHIBITORS FROM KNOTWEED HERB. CHEMICAL NA-TURE AND MECHANISM OF ACTION

The aim is to isolate flavonoid xanthine oxidase (XO) inhibitors from the herb of Knotweed, to characterize their nature and to determine the mechanism of action inhibitors.
 Objectives: 1. To isolate the amount of flavonoids from the herb of Knotweed and to assess their effect on the activity of XO. 2. Purify the total extract and obtain active fractions containing XO inhibitors, identify their nature. 3. Determine the mechanism of inhibition of XO, isolated by flavonoids.
 Methodology: Grass P. hydropiper extracted with 90% ethanol (70 °C for 1 h). A native extract obtained with a flavonoid content of 1.51%. The extract fractionated with heptane and ion exchange chromatography. The anti-xanthine oxidase activity of the fractions assessed by the spectrophotometric method. KO activity expressed in IU / g. The mechanism of action of KO inhibitors in the fractions was determined by constructing kinetic curves of the enzymatic reaction and calculating Km. Flavonoids were identified by TLC, PC, spectrophotometry.
 The obtained results and conclusions: 1. The sum of flavonoids from the herb of Knotweed inhibit the activity of KO at a concentration of 2.5 mg / ml. 2. Chalcones inhibiting XO were isolated from the native extract of the herb of Knotweed. 3. Flavonoids in the active fraction reversibly inhibit milk XO by a competitive mechanism
 Practical significance and directions for further research: The information obtained is the basis for the development of a new drug used to treat gout. It is necessary to develop a method for isolating a homogeneous flavonoid and conduct its pharmacokinetic studies.

The Effect of p-Coumaric Acid on Browning Inhibition in Potato Polyphenol Oxidase-Catalyzed Reaction Mixtures.

There has been considerable interest in using natural polyphenol oxidase (PPO) inhibitors to control browning in fruit and vegetable products. p-Coumaric acid (pCA), a common secondary metabolite of plants, has been studied as an inhibitor of PPOs/tyrosinases from several foods (e.g., mushroom, apple, and potato). However, studies on the use of pCA for the inhibition of PPO-initiated browning in actual food systems are limited. Therefore, a study was carried out to ascertain the efficacy of using pCA to limit PPO-initiated browning in fresh potato juice. The extent of browning inhibition by pCA was shown to be reaction system-dependent. Browning in potato juice was unexpectedly enhanced by the addition of pCA. This was interpreted as pCA acting as an alternative substrate with significantly higher browning efficiency; extent of browning under this condition was higher than that observed in the native potato juice. The addition of pCA to any of the model reaction mixtures (i.e., those containing semi-purified enzymes and substrates) significantly inhibited browning. The discrepancy in pCA effects on browning inhibition in different reaction systems is postulated to be mainly due to non-enzyme and non-substrate components in potato juice that participate in the post-PPO reaction sequences, which ultimately lead to brown color formation.

Anti-Herbivore Resistance Changes in Tomato with Elevation.

Local adaptations of host plants to climatic conditions along an elevation gradient can affect insect-plant interactions. Using local accessions sampled from different elevations within South America, plant defense responses and herbivore growth were evaluated on two host plants: a) cherry tomato, Solanum lycopersicum var. cerasiforme, and b) wild tomato, Solanum pimpinellifolium. The elevational origin of the accessions ranged from 100 to 3000m above sea level. We hypothesized a higher level of defensive compounds in plants originating from lower elevations and, consequently, stronger resistance to insect herbivory. Interestingly, plant resistance to insect herbivory, as demonstrated by a reduction in Helicoverpa zea growth, was stronger for middle and high-elevation accessions. Total phenolic content increased with elevation in both herbivore-damaged and undamaged leaves, augmenting plant resistance. However, an elevational gradient was not evident for plant defensive proteins (polyphenol oxidase and trypsin protease inhibitors) or the density of leaf trichomes. Tradeoffs between constitutive and induced defenses were evident in both tomato genotypes. Future studies should test the role of plasticity in plant defense systems in restricting or facilitating range expansion of insect herbivores with climate change.

Xanthine Oxidase Inhibitory Mechanism of Fisetin and Hesperitin

Fisetin and hesperitin are two common flavonoids in plant medicines. In this paper, the mechanism of xanthine oxidase (XO) inhibition was systematically studied by combining experimental and theoretical methods. The HPLC results suggested that the XO inhibitory activity of fisetin (IC50, 0.140 mM) was superior to that of hesperitin (IC50, 0.635 mM). The spectrofluorimetry results showed flavonoids could induce the static fluorescence quenching of XO, indicating that they played the inhibitory activity by forming the complexes with XO. We showed the paramount force of fisetin and XO was hydrophobic; in the complex of hesperidin and XO, hydrogen bonding and van der Waals force were crucial forces. We used Autodock software for molecular docking. The results suggested that both fisetin and hesperitin entered the active pocket of XO, and the complexes were maintained by hydrogen bonding and hydrophobic interaction, which coincided with the experimental results.

Dual Monoamine Oxidase and Cholinesterase Inhibitors with Different Heterocyclic Scaffolds.

For the last two decades, there has been research interest on the design of molecules possessing dual inhibitory potential on cholinesterase and monoamine oxidase enzymes, particularly for the treatment of two major neurodegenerative diseases, Alzheimer's Disease (AD) and Parkinson's disease (PD). Many compounds have been synthesized for this purpose, and some of them have been shown to display activities comparable or superior to the activities of current drugs used for the treatment of AD and PD. Within the concept of this review study, we have aimed to present the current drugs used for the treatment of AD and PD, their mechanism of action, the discussion behind the theory of designing dual inhibitor agents, and the presentation of the most active compounds with diverse heterocyclic scaffolds displayed in research studies published in the recent period.

Elastic Laminar Reorganization Occurs with Outward Diameter Expansion during Collateral Artery Growth and Requires Lysyl Oxidase for Stabilization.

When a large artery becomes occluded, hemodynamic changes stimulate remodeling of arterial networks to form collateral arteries in a process termed arteriogenesis. However, the structural changes necessary for collateral remodeling have not been defined. We hypothesize that deconstruction of the extracellular matrix is essential to remodel smaller arteries into effective collaterals. Using multiphoton microscopy, we analyzed collagen and elastin structure in maturing collateral arteries isolated from ischemic rat hindlimbs. Collateral arteries harvested at different timepoints showed progressive diameter expansion associated with striking rearrangement of internal elastic lamina (IEL) into a loose fibrous mesh, a pattern persisting at 8 weeks. Despite a 2.5-fold increase in luminal diameter, total elastin content remained unchanged in collaterals compared with control arteries. Among the collateral midzones, baseline elastic fiber content was low. Outward remodeling of these vessels with a 10–20 fold diameter increase was associated with fractures of the elastic fibers and evidence of increased wall tension, as demonstrated by the straightening of the adventitial collagen. Inhibition of lysyl oxidase (LOX) function with β-aminopropionitrile resulted in severe fragmentation or complete loss of continuity of the IEL in developing collaterals. Collateral artery development is associated with permanent redistribution of existing elastic fibers to accommodate diameter growth. We found no evidence of new elastic fiber formation. Stabilization of the arterial wall during outward remodeling is necessary and dependent on LOX activity.