phenyl-N-tert-butylnitrone Research Articles

Efficient photocatalytic dehydrogenation and synergistic selective oxidation of benzyl alcohol to benzaldehyde for Zn0.5Cd0.5S co-modified with MoS2 nanoflowers and g-C3N4 nanosheets

Zn0.5Cd0.5S solid solution co-modified by MoS2 nanoflowers and g-C3N4 nanosheets (C3N4/MoS2/Zn0.5Cd0.5S) was synthesized with highly efficient photocatalytic dehydrogenation and synergistic selective oxidation of benzyl alcohol (BA) to benzaldehyde (BAD). The photocatalytic dehydrogenation rate and BAD yield are 1.7 mmol·g−1·h−1 and 35.8% for C3N4/MoS2/Zn0.5Cd0.5S, and selective oxidation to BAD is almost 100%. Reaction selectivity was explored by detecting all the substances of the solution after reaction for Zn0.5Cd0.5S and C3N4/Zn0.5Cd0.5S using gas chromatography-mass spectrometry (GCMS), and analysis results indicated that BA was converted to other substances because of the insufficient hole oxidation capacity of the samples. The mechanism for highly efficient photocatalytic dehydrogenation and synergistic selective oxidation of BA to BAD was systematically investigated by electron paramagnetic resonance (EPR) and first-principle density-functional theory calculations. The EPR spectra of the phenyl-N-tert-butyl-nitrone (PBN)-carbon centered radical indicated that ·C induced by photo-generated holes are the key intermediate of the photocatalytic dehydrogenation of BA. The loading of flower-like MoS2 accelerates charge transport and enhances the hole oxidation ability of Zn0.5Cd0.5S, and the introduction of g-C3N4 has a negative valence band potential that can collect photogenerated holes of Zn0.5Cd0.5S, thereby inhibiting photocorrosion. Therefore, the photocatalytic dehydrogenation and synergistic selection of BA to BAD for the C3N4/MoS2/Zn0.5Cd0.5S ternary heterostructure were greatly improved. The research work would provide a feasible, sustainable, economical, and potential technique for the highly efficient dehydrogenation and synergistic selective oxidation of BA based on photocatalysis that excludes the usage of noble metals and sacrificial reagents.

Pretreatment of the ROS Inhibitor Phenyl-N-tert-butylnitrone Alleviates Sleep Deprivation-Induced Hyperalgesia by Suppressing Microglia Activation and NLRP3 Inflammasome Activity in the Spinal Dorsal Cord

Sleep deprivation, a common perioperative period health problem, causes ocular discomfort and affects postsurgical pain. However, the mechanism of sleep deprivation-induced increased pain sensitivity is elusive. This study aims to explore the role of ROS in sleep deprivation (SD)-induced hyperalgesia and the underlying mechanism. A 48-h continuous SD was performed prior to the hind paw incision pain modeling in mice. We measured ROS levels, microglial activation, DNA damage and protein levels of iNOS, NLRP3, p-P65 and P65 in mouse spinal dorsal cord. The involvement of ROS in SD-induced prolongation of postsurgical pain was further confirmed by intrathecal injection of ROS inhibitor, phenyl-N-tert-butylnitrone (PBN). Pretreatment of 48-h SD in mice significantly prolonged postsurgical pain recovery, manifesting as lowered paw withdrawal mechanical threshold and paw withdrawal thermal latency. It caused ROS increase and upregulation of iNOS on both Day 1 and 7 in mouse spinal dorsal cord. In addition, upregulation of NLRP3 and p-P65, microglial activation and DNA damage were observed in mice pretreated with 48-h SD prior to the incision. Notably, intrathecal injection of PBN significantly reversed the harmful effects of SD on postsurgical pain recovery, hyperalgesia, microglial activation and DNA damage via the NF-κB signaling pathway. Collectively, ROS increase is responsible for SD-induced hyperalgesia through activating microglial, triggering DNA damage and enhancing NLRP3 inflammasome activity in the spinal dorsal cord.

Visible-Light-Driven Thioesterification of Aryl Halides with Potassium Thiocarboxylates: Transition-Metal Catalyst-Free Incorporation of Sulfur Functionalities into an Aromatic Ring.

Reactions of acceptor-substituted aryl iodides and bromides with potassium thiocarboxylates under white light irradiation allow for the preparation of S-aryl thioesters including synthetically versatile S-aryl thioacetates. This transition-metal and external photocatalyst-free method features extremely mild reaction conditions compared with those used in transition-metal-catalyzed protocols. Reactions proceed via the initial formation of an electron donor-acceptor (EDA) complex in the ground state, which was supported by UV-vis spectra. Electron paramagnetic resonance (EPR) spin-trapping experiments using phenyl-N-tert-butylnitrone (PBN) have revealed the radical nature of the reaction.

Successive Free-Radical C(sp 2 )–C(sp 2 ) Coupling Reactions to Form Graphene

Successive Free-Radical C(sp ² )–C(sp ² ) Coupling Reactions to Form Graphene

Oxidative Stress Contributes to Hyperalgesia in Osteoporotic Mice.

PurposeChronic pain is one of the most common complications of postmenopausal osteoporosis. Since oxidative stress is involved in the pathogenesis of postmenopausal osteoporosis, we explored whether oxidative stress contributes to postmenopausal osteoporotic pain.MethodsOsteoporosis was induced in mice by ovariectomy (OVX). Pain-related behaviours were assessed by measuring sensitivity to mechanical, thermal and cold stimulation. The expression of pain-related transcripts, such acid-sensing ion channel 3 (ASIC3), transient receptor potential vanilloid 1 (TRPV1) and calcitonin gene-related peptide (CGRP), was evaluated. Plasma markers of oxidative stress were also measured. In addition, the effects of the reactive oxygen species scavenger phenyl N-tert-butylnitrone (PBN) on these parameters were assessed.ResultsThe OVX mice presented hyperalgesia, as demonstrated by decreased paw withdrawal thresholds to mechanical stimulation and withdrawal latencies to thermal and cold stimulation, along with upregulated expression of ASIC3, TRPV1 and CGRP in the dorsal root ganglia, spinal cord and thalamus tissue. OVX elevated the plasma levels of malondialdehyde (MDA) and advanced oxidation protein products (AOPPs). However, the administration of PBN alleviated these effects.ConclusionOur results indicated that oxidative stress contributes to hyperalgesia in OVX mice. Enhanced oxidative stress may be associated with osteoporotic pain. Antioxidant treatment could help alleviate chronic pain in postmenopausal osteoporotic patients.

Nicotinamide adenine dinucleotide phosphate oxidase 2-derived reactive oxygen species contribute to long-term potentiation of C-fiber-evoked field potentials in spinal dorsal horn and persistent mirror-image pain following high-frequency stimulus of the sciatic nerve.

High-frequency stimulation (HFS) of the sciatic nerve has been reported to produce long-term potentiation (LTP) and long-lasting pain hypersensitivity in rats. However, the central underlying mechanism remains unclear. Nicotinamide adenine dinucleotide phosphate (NADPH) oxidase (NOX) belongs to a group of electron-transporting transmembrane enzymes that produce reactive oxygen species (ROS). Here, we found that NOX2 was upregulated in the lumbar spinal dorsal horn after HFS of the left sciatic nerve, which induced bilateral pain and spinal LTP in both male and female rats. Blocking NOX2 with blocking peptide or shRNA prevented the development of bilateral mechanical allodynia, the induction of spinal LTP, and the phosphorylation of N-methyl-d-aspartate (NMDA) receptor 2B (GluN2B) and nuclear factor kappa-B (NF-κB) p65 after HFS. Moreover, NOX2 shRNA reduced the frequency and amplitude of both spontaneous excitatory postsynaptic currents and miniature excitatory postsynaptic currents in laminar II neurons. Furthermore, 8-hydroxyguanine (8-OHG), an oxidative stress marker, was increased in the spinal dorsal horn. Spinal application of ROS scavenger, Phenyl-N-tert-butylnitrone (PBN), depressed the already established spinal LTP. Spinal application of H2O2, one ROS, induced LTP and bilateral mechanical allodynia, increased the frequency and amplitude of spontaneous excitatory postsynaptic currents in laminar II neurons, and phosphorylated GluN2B and p65 in the dorsal horn. This study provided electrophysiological and behavioral evidence that NOX2-derived ROS in the spinal cord contributed to persistent mirror-image pain by enhancing the synaptic transmission, which was mediated by increasing presynaptic glutamate release and activation of NMDA receptor and NF-κB in the spinal dorsal horn.

Characterization of a rat model of bortezomib-induced painful neuropathy.

Background and PurposeBortezomib (Velcade®) is a breakthrough treatment for multiple myeloma, significantly improving patient survival. However, its use is limited by painful neuropathy often resulting in dose reduction/cessation of first‐line treatment due to lack of treatment. The aim of this study was to characterize a clinically relevant rat model of bortezomib‐induced painful neuropathy, using established evoked measures and novel ethological techniques, to aid drug discovery.Experimental ApproachAdult male Sprague–Dawley rats were injected i.p. with 0.1 and 0.2 mg·kg−1 bortezomib, or its vehicle, on days 0, 3, 7 and 10. Multiple behavioural approaches were utilized: mechanical hypersensitivity, cold allodynia, heat hypersensitivity, motor co‐ordination, burrowing and voluntary wheel running. At maximal bortezomib‐induced mechanical hypersensitivity, 200 mg·kg−1 ethosuximide/vehicle and 100 mg·kg−1 phenyl N‐tert‐butylnitrone (PBN)/vehicle were administered i.p. in separate experiments, and mechanical hypersensitivity assessed 1, 3 and 24 h later.Key ResultsBortezomib induced dose‐related mechanical hypersensitivity for up to 80 days. Bortezomib induced short‐term cold allodynia, but no significant change in heat hypersensitivity, motor co‐ordination, voluntary wheel running and burrowing behaviour compared to vehicle‐treated controls. Systemic PBN and ethosuximide significantly ameliorated bortezomib‐induced mechanical hypersensitivity.Conclusions and ImplicationsThese data characterize a reproducible rat model of clinical‐grade bortezomib‐induced neuropathy demonstrating long‐lasting pain behaviours to evoked stimuli. Inhibition by ethosuximide and PBN suggests involvement of calcium and/or ROS in bortezomib‐induced painful neuropathy. These drugs could be used as preclinical positive controls to assess novel analgesics. As ethosuximide is widely used clinically, translation to the clinic to treat bortezomib‐induced painful neuropathy may be possible.

Variation in Free Radical Yields from U.S. Marketed Cigarettes

Free radicals in tobacco smoke are thought to be an important cause of smoking-induced diseases, yet the variation in free radical exposure to smokers from different brands of commercially available cigarettes is unknown. We measured the levels of highly reactive gas-phase and stable particulate-phase radicals in mainstream cigarette smoke by electron paramagnetic resonance (EPR) spectroscopy with and without the spin-trapping agent phenyl-N-tert-butylnitrone (PBN), respectively, in 27 popular US cigarettes and the 3R4F research cigarette, machine-smoked according to the FTC protocol. We find a 12-fold variation in the levels of gas-phase radicals (1.2 to 14 nmol per cigarette) and a 2-fold variation in the amounts of particulate-phase radicals (44 to 96 pmol per cigarette) across the range of cigarette brands. Gas and particulate-phase radicals were highly correlated across brands (ρ = 0.62, p < 0.001). Both radicals were correlated with TPM (gas-phase: ρ = 0.38, p = 0.04; particulate-phase: ρ = 0.44, p = 0.02) and ventilation (gas- and tar-phase: ρ = -0.58, p = 0.001), with ventilation explaining nearly 30% of the variation in radical levels across brands. Overall, our findings of significant brand variation in free radical delivery under standardized machine-smoked conditions suggest that the use of certain brands of cigarettes may be associated with greater levels of oxidative stress in smokers.

Reactive oxygen species increase neuronal excitability via activation of nonspecific cation channel in rat medullary dorsal horn neurons.

The caudal subnucleus of the spinal trigeminal nucleus (medullary dorsal horn; MDH) receives direct inputs from small diameter primary afferent fibers that predominantly transmit nociceptive information in the orofacial region. Recent studies indicate that reactive oxygen species (ROS) is involved in persistent pain, primarily through spinal mechanisms. In this study, we aimed to investigate the role of xanthine/xanthine oxidase (X/XO) system, a known generator of superoxide anion (O2·−), on membrane excitability in the rat MDH neurons. For this, we used patch clamp recording and confocal imaging. An application of X/XO (300 µM/30 mU) induced membrane depolarization and inward currents. When slices were pretreated with ROS scavengers, such as phenyl N-tert-butylnitrone (PBN), superoxide dismutase (SOD), and catalase, X/XO-induced responses decreased. Fluorescence intensity in the DCF-DA and DHE-loaded MDH cells increased on the application of X/XO. An anion channel blocker, 4,4-diisothiocyanatostilbene-2,2-disulfonic acid (DIDS), significantly decreased X/XO-induced depolarization. X/XO elicited an inward current associated with a linear current-voltage relationship that reversed near −40 mV. X/XO-induced depolarization reduced in the presence of La3+, a nonselective cation channel (NSCC) blocker, and by lowering the external sodium concentration, indicating that membrane depolarization and inward current are induced by influx of Na+ ions. In conclusion, X/XO-induced ROS modulate the membrane excitability of MDH neurons, which was related to the activation of NSCC.

Catalytic 1,2-dihydronaphthalene and E-aryl-diene synthesis via CoIII-Carbene radical and o-quinodimethane intermediates.

Catalytic synthesis of substituted 1,2-dihydronaphthalenes via metalloradical activation of o-styryl N-tosyl hydrazones ((E)-2-(prop-1-en-1-yl)benzene-N-tosyl hydrazones) is presented, taking advantage of the intrinsic reactivity of a cobalt(iii)-carbene radical intermediate. The method has been successfully applied to a broad range of substrates with various R1 substituents at the aromatic ring, producing the desired ring products in good to excellent isolated yields for substrates with an R2 = COOEt substituent at the vinylic position (∼70-90%). Changing the R2 moiety from an ester to other substituents has a surprisingly large influence on the (isolated) yields. This behaviour is unexpected for a radical rebound ring-closure mechanism, and points to a mechanism proceeding via ortho-quinodimethane (o-QDM) intermediates. Furthermore, substrates with an alkyl substituent on the allylic position reacted to form E-aryl-dienes in excellent yields, rather than the expected 1,2-dihydronaphthalenes. This result, combined with the outcome of supporting DFT calculations, strongly points to the release of reactive o-QDM intermediates from the metal centre in all cases, which either undergo a 6π-cyclisation step to form the 1,2-dihydronaphthalenes, or a [1,7]-hydride shift to produce the E-aryl-dienes. Trapping experiments using TEMPO confirm the involvement of cobalt(iii)-carbene radical intermediates. EPR spectroscopic spin-trapping experiments using phenyl N-tert-butylnitrone (PBN) confirm the radical nature of the catalytic reaction.

Spinal mitochondrial-derived ROS contributes to remifentanil-induced postoperative hyperalgesia via modulating NMDA receptor in rats

BackgroundActivation of N-methyl-d-aspartate (NMDA) receptor by reactive oxygen species (ROS) in the spinal cord plays an important role in the development of hyperalgesia in several neuropathic pain models. The study examined the involvement of ROS-NMDA signaling pathway in remifentanil-induced postoperative hyperalgesia. MethodsNociceptive responses were measured by paw withdrawal mechanical threshold (PWT) and paw withdrawal thermal latency (PWL) before and up to day 5 after remifentanil infusion. Spinal delivery of MitoSOX red was performed to detect mitochondrial ROS. Changes in expression of NMDA receptor subunits (NR1 and NR2B) in the spinal cord were analyzed by immunofluorescence and Western blotting. Intraperitoneal injection of phenyl-N-tert-butylnitrone (PBN), a non-selective ROS scavenger, was administrated to investigate the role of ROS in remifentanil-induced postoperative hyperalgesia. ResultsIntraoperative infusion of remifentanil induced postoperative mechanical allodynia and thermal hyperalgesia. ROS production, phosphorylated NR1 and NR2B subunits of NMDA receptor were found to be significantly increased in the spinal dorsal horn after intraoperative remifentanil infusion. However, remifentanil-induced postoperative hyperalgesia was suppressed by pretreatment of PBN. In addition, reduction of ROS by PBN prevented enhanced phosphorylation of NR1 and NR2B subunits. ConclusionThese findings indicated that ROS-dependent activation of NMDA receptor in the spinal cord might be a potential mechanism underlying remifentanil-induced postoperative hyperalgesia.

Co(III)-Carbene Radical Approach to Substituted 1H-Indenes.

A new strategy for the catalytic synthesis of substituted 1H-indenes via metalloradical activation of o-cinnamyl N-tosyl hydrazones is presented, taking advantage of the intrinsic reactivity of a Co(III) carbene radical intermediate. The reaction uses readily available starting materials and is operationally simple, thus representing a practical method for the construction of functionalized 1H-indene derivatives. The cheap and easy to prepare low spin cobalt(II) complex [Co(II)(MeTAA)] (MeTAA = tetramethyltetraaza[14]annulene) proved to be the most active catalyst among those investigated, which demonstrates catalytic carbene radical reactivity for a nonporphyrin cobalt(II) complex, and for the first time catalytic activity of [Co(II)(MeTAA)] in general. The methodology has been successfully applied to a broad range of substrates, producing 1H-indenes in good to excellent yields. The metallo-radical catalyzed indene synthesis in this paper represents a unique example of a net (formal) intramolecular carbene insertion reaction into a vinylic C(sp(2))-H bond, made possible by a controlled radical ring-closure process of the carbene radical intermediate involved. The mechanism was investigated computationally, and the results were confirmed by a series of supporting experimental reactions. Density functional theory calculations reveal a stepwise process involving activation of the diazo compound leading to formation of a Co(III)-carbene radical, followed by radical ring-closure to produce an indanyl/benzyl radical intermediate. Subsequent indene product elimination involving a 1,2-hydrogen transfer step regenerates the catalyst. Trapping experiments using 2,2,6,6-tetra-methylpiperidine-1-oxyl (TEMPO) radical or dibenzoylperoxide (DBPO) confirm the involvement of cobalt(III) carbene radical intermediates. Electron paramagnetic resonance spectroscopic spin-trapping experiments using phenyl N-tert-butylnitrone (PBN) reveal the radical nature of the reaction.

PBN (Phenyl-N-Tert-Butylnitrone)-Derivatives Are Effective in Slowing the Visual Cycle and Rhodopsin Regeneration and in Protecting the Retina from Light-Induced Damage.

A2E and related toxic molecules are part of lipofuscin found in the retinal pigment epithelial (RPE) cells in eyes affected by Stargardt’s disease, age-related macular degeneration (AMD), and other retinal degenerations. A novel therapeutic approach for treating such degenerations involves slowing down the visual cycle, which could reduce the amount of A2E in the RPE. This can be accomplished by inhibiting RPE65, which produces 11-cis-retinol from all-trans-retinyl esters. We recently showed that phenyl-N-tert-butylnitrone (PBN) inhibits RPE65 enzyme activity in RPE cells. In this study we show that like PBN, certain PBN-derivatives (PBNDs) such as 4-F-PBN, 4-CF3-PBN, 3,4-di-F-PBN, and 4-CH3-PBN can inhibit RPE65 and synthesis of 11-cis-retinol in in vitro assays using bovine RPE microsomes. We further demonstrate that systemic (intraperitoneal, IP) administration of these PBNDs protect the rat retina from light damage. Electroretinography (ERG) and histological analysis showed that rats treated with PBNDs retained ~90% of their photoreceptor cells compared to a complete loss of function and 90% loss of photoreceptors in the central retina in rats treated with vehicle/control injections. Topically applied PBN and PBNDs also significantly slowed the rate of the visual cycle in mouse and baboon eyes. One hour dark adaptation resulted in 75–80% recovery of bleachable rhodopsin in control/vehicle treated mice. Eye drops of 5% 4-CH3-PBN were most effective, inhibiting the regeneration of bleachable rhodopsin significantly (60% compared to vehicle control). In addition, a 10% concentration of PBN and 5% concentration of 4-CH3-PBN in baboon eyes inhibited the visual cycle by 60% and by 30%, respectively. We have identified a group of PBN related nitrones that can reach the target tissue (RPE) by systemic and topical application and slow the rate of rhodopsin regeneration and therefore the visual cycle in mouse and baboon eyes. PBNDs can also protect the rat retina from light damage. There is potential in developing these compounds as preventative therapeutics for the treatment of human retinal degenerations in which the accumulation of lipofuscin may be pathogenic.

Noise-Induced Neural Degeneration and Therapeutic Effect of Antioxidant Drugs.

The primary site of lesion induced by noise exposure is the hair cells in the organ of Corti and the primary neural degeneration occurs in synaptic terminals of cochlear nerve fibers and spiral ganglion cells. The cellular basis of noise-induced hearing loss is oxidative stress, which refers to a severe disruption in the balance between the production of free radicals and antioxidant defense system in the cochlea by excessive production of free radicals induced by noise exposure. Oxidative stress has been identified by a variety of biomarkers to label free radical activity which include four-hydroxy-2-nonenal, nitrotyrosine, and malondialdehyde, and inducible nitric oxide synthase, cytochrome-C, and cascade-3, 8, 9. Furthermore, oxidative stress is contributing to the necrotic and apoptotic cell deaths in the cochlea. To counteract the known mechanisms of pathogenesis and oxidative stress induced by noise exposure, a variety of antioxidant drugs including oxygen-based antioxidants such as N-acetyl-L-cystein and acetyl-L-carnitine and nitrone-based antioxidants such as phenyl-N-tert-butylnitrone (PBN), disufenton sodium, 4-hydroxy PBN, and 2, 4-disulfonyl PBN have been used in our laboratory. These antioxidant drugs were effective in preventing or treating noise-induced hearing loss. In combination with other antioxidants, antioxidant drugs showed a strong synergistic effect. Furthermore, successful use of antioxidant drugs depends on the optimal timing of treatment and the duration of treatment, which are highly related to the time window of free radical formation induced by noise exposure.

Antinociceptive effects of fisetin against diabetic neuropathic pain in mice: Engagement of antioxidant mechanisms and spinal GABAA receptors

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Fisetin, a naturally occurring flavonoid, has been reported to exert antidepressant-like effect in previous studies. As antidepressant drugs are employed clinically to treat neuropathic pain, this work aimed to investigate whether fisetin posses beneficial effect on diabetic neuropathic pain and explore the mechanism(s). We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (200mg/kg), and von Frey test or Hargreaves test was used to assess mechanical allodynia or thermal hyperalgesia, respectively. Chronic treatment of diabetic mice with fisetin not only ameliorated the established symptoms of thermal hyperalgesia and mechanical allodynia, but also arrested the development of neuropathic pain when given at low doses. Although chronic fisetin administration did not impact on the symptom of hyperglycemia in diabetic mice, it reduced exacerbated oxidative stress in tissues of spinal cord, dorsal root ganglion (DRG) and sciatic verve. Furthermore, the analgesic actions of fisetin were abolished by repetitive co-treatment with the reactive oxygen species (ROS) donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the ROS scavenger phenyl-N-tert-butylnitrone (PBN). Finally, acute blockade of spinal GABAA receptors by bicuculline totally counteracted such fisetin analgesia. These findings indicate that chronic fisetin treatment can delay or correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the present fisetin analgesia may be associated with its antioxidant activity, and spinal GABAA receptors are likely rendered as downstream targets.

Secoisolariciresinol diglycoside, a flaxseed lignan, exerts analgesic effects in a mouse model of type 1 diabetes: Engagement of antioxidant mechanism

Peripheral painful neuropathy is one of the most common complications in diabetes and necessitates improved treatment. Secoisolariciresinol diglycoside (SDG), a predominant lignan in flaxseed, has been shown in our previous studies to exert antidepressant-like effect. As antidepressant drugs are clinically used to treat chronic neuropathic pain, this work aimed to investigate the potential analgesic efficacy of SDG against diabetic neuropathic pain in a mouse model of type 1 diabetes. We subjected mice to diabetes by a single intraperitoneal (i.p.) injection of streptozotocin (STZ, 200mg/kg), and Hargreaves test or von Frey test was used to assess thermal hyperalgesia or mechanical allodynia, respectively. Chronic instead of acute SDG treatment (3, 10 or 30mg/kg, p.o., twice per day for three weeks) ameliorated thermal hyperalgesia and mechanical allodynia in diabetic mice, and these analgesic actions persisted about three days when SDG treatment was terminated. Although chronic treatment of SDG to diabetic mice did not impact on the symptom of hyperglycemia, it greatly attenuated excessive oxidative stress in sciatic nerve and spinal cord tissues, and partially counteracted the condition of weight decrease. Furthermore, the analgesic actions of SDG were abolished by co-treatment with the reactive oxygen species donor tert-butyl hydroperoxide (t-BOOH), but potentiated by the reactive oxygen species scavenger phenyl-N-tert-butylnitrone (PBN). These findings indicate that chronic SDG treatment can correct neuropathic hyperalgesia and allodynia in mice with type 1 diabetes. Mechanistically, the analgesic actions of SDG in diabetic mice may be associated with its antioxidant activity.

Highly reactive free radicals in electronic cigarette aerosols.

Electronic cigarette (EC) usage has increased exponentially, but limited data are available on its potential harmful effects. We tested for the presence of reactive, short-lived free radicals in EC aerosols by electron paramagnetic resonance spectroscopy (EPR) using the spin-trap phenyl-N-tert-butylnitrone (PBN). Radicals were detected in aerosols from all ECs and eliquids tested (2.5 × 10(13) to 10.3 × 10(13) radicals per puff at 3.3 V) and from eliquid solvents propylene glycol and glycerol and from "dry puffing". These results demonstrate, for the first time, the production of highly oxidizing free radicals from ECs which may present a potential toxicological risk to EC users.

Contributions of spinal d-amino acid oxidase to chronic morphine-induced hyperalgesia

Spinal d-amino acid oxidase (DAAO) is an FAD-dependent peroxisomal flavoenzyme which mediates the conversion of neutral and polar d-amino acids (including d-serine) to the corresponding α-keto acids, and simultaneously produces hydrogen peroxide and ammonia. This study has aimed to explore the potential contributions of spinal DAAO and its mediated hydrogen peroxide/d-serine metabolism to the development of morphine-induced hyperalgesia. Bi-daily subcutaneous injections of morphine to mice over 7 days induced thermal hyperalgesia as measured by both the hot-plate and tail-immersion tests, and spinal astroglial activation with increased spinal gene expression of DAAO, glial fibrillary acidic protein (GFAP) and pro-inflammatory cytokines (interleukin-1β (IL-1β), interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α)). Subcutaneous injections of the potent DAAO inhibitor CBIO (5-chloro-benzo[d]isoxazol-3-ol) prevented and reversed the chronic morphine-induced hyperalgesia. CBIO also inhibited both astrocyte activation and the expression of pro-inflammatory cytokines. Intrathecal injection of the hydrogen peroxide scavenger PBN (phenyl-N-tert-butylnitrone) and of catalase completely reversed established morphine hyperalgesia, whereas subcutaneous injections of exogenous d-serine failed to alter chronic morphine-induced hyperalgesia. These results provided evidence that spinal DAAO and its subsequent production of hydrogen peroxide rather than the d-serine metabolism contributed to the development of morphine-induced hyperalgesia.

Is nitrate a good biomarker of the nitric oxide status? / Este ionul nitrat un bun biomarker al producţiei endogene de monoxid de azot?

AbstractA method of measuring in vivo nitric oxide (NO) levels is required to detect pathological conditions in which endogenous production is decreased or to identify agents able to release this biomolecule. Unfortunately, nitric oxide has a very short biological half-life and is very difficult to measure. Assay of the oxidative products’ of NO levels, nitrite (NORabbits were used as experimental animals, a validated HPLC-UV/VIS method was used for speciation of nitrite and nitrate. The following substances were administered: blank; “negative blank”: phenyl-N-tert-butylnitrone (PBN); “positive blank” (nitroglycerin); nitrite.PBN administration significantly increased nitrate and decreased nitrite levels, nitrite administration excessively increased nitrate levels, while nitroglycerin (1 mg/kg) significantly increased both nitrate and nitrite levels.Results show that NOx test cannot be considered accurate in acute nitric oxide status testing. Nitrite alone should be used as an in vivo released nitric oxide marker.

Protection of blue light induced retinal degeneration by the free radical scavenger Phenyl‐N‐tert‐butylnitrone and a serotonin receptor 5‐HT1a agonist in rats

AbstractPurpose Blue light exposition of rat retina induces retinal damages that mimic age‐related macular degeneration (AMD), showing severe photoreceptor cell death, apoptosis of RPE cells, and progressive outer nuclear layer destruction due to reactive oxygen species, and therefore providing an useful model to test potential AMD treatments. Here we proposed to compare the protective effects of two compounds, the antioxidant free radical scavenger, Phenyl‐N‐tert‐butylnitrone (PBN) and the serotonin receptor 5‐HT1a agonist 8‐Hydroxy‐2‐(di‐n‐propylamino)tetralin, 8‐OH‐DPAT, on photo‐oxidative stress in rat retina.Methods After a period of dark adaptation, Sprague‐Dawley rats were exposed to blue light during 6 hours. Animals were divided in three groups: 50 mg/kg PBN injected intraperitoneally on the day of induction, 500µg/kg 8‐OH‐DPAT or NaCl 0.9% subcutaneously injected once a day, starting 2 days before light exposure. Retinal function and anatomical integrity were evaluated by scotopic electroretinography (ERG) and optical coherence tomography, respectively, 1 and 2 weeks after induction. Outer nuclear layer thickness was measured on histological sections harvested 2 weeks after the induction.Results Significant protection of retina from degeneration was achieved with both compounds, which effectively rescued a wave and b wave amplitudes of ERG responses and preserved photoreceptor layer thickness.Conclusion The serotonin receptor 5‐HT1a could be a valuable target for AMD and other retinal degenerative diseases. Commercial interest