Reactive Oxygen Species Scavenger Tempol Research Articles

SIRT1-regulated ROS generation activates NMDAR2B phosphorylation to promote central sensitization and allodynia in a male chronic migraine rat model.

Central sensitization is one of the pivotal pathological mechanisms in chronic migraine (CM). Silent information regulator 1 (SIRT1) was shown to be involved in CM, but its specific mechanism is unclear. Reactive oxygen species (ROS) are increasingly regarded as important signaling molecules in several models of pain. However, studies about the role of ROS in the central sensitization of CM model are rare. We thus explored the specific process of SIRT1 involvement in the central sensitization of CM, focusing on the ROS pathway. Inflammatory soup was repeatedly administered to male Sprague-Dawley rats to establish a CM model. The SIRT1 expression level in trigeminal nucleus caudalis (TNC) tissues was assessed by qRT-PCR and Western blotting analysis. The levels of ROS were detected by a Tissue Reactive Oxygen Detection Kit, DHE staining, and the fluorescence signal intensity of 8-OHdG. A ROS scavenger (tempol), a SIRT1 activator (SRT1720), a SIRT1 inhibitor (EX527), and a mitochondrial fission inhibitor (Mdivi-1) were used to investigate the specific molecular mechanisms involved. NMDAR2B, CGRP, ERK, and mitochondrial fission-related protein were evaluated by Western blotting, and the CGRP level in frozen sections of the TNC was detected via immunofluorescence staining. After repeated inflammatory soup infusion and successful establishment of the CM rat model, SIRT1 expression was found to be significantly reduced, accompanied by elevated ROS levels. Treatment with Tempol, SRT1720, or Mdivi-1 alleviated allodynia and reduced the increase in NMDAR2B phosphorylation and CGRP and ERK phosphorylation in the CM rat. In contrast, EX527 had the opposite effect in CM rat. SRT1720 and EX527 decreased and increased ROS levels, respectively, in CM rats, and tempol reversed the aggravating effect of EX527 in CM rats. Furthermore, the regulatory effect of SIRT1 on ROS may include the involvement of the mitochondrial fission protein DRP1. The results indicate the importance of SIRT1 in CM may be due to its role in regulating the production of ROS, which are involved in modulating central sensitization in CM. These findings could lead to new ideas for CM treatment with the use of SIRT1 agonists and antioxidants.

OR06-04 Environmental Pollutants Perfluoroalkyl Acids Potently Stimulated Aldosterone Biosynthesis

Abstract Disclosure: B. Caroccia: None. T.M. Seccia: None. G. Pallafacchina: None. M. Piazza: None. I. Caputo: None. R. Rizzuto: None. G. Rossi: None. A large environmental contamination of drinking water by perfluoroalkyl substances (PFAS) markedly increased by 8-fold the plasma levels of pentadecafluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in a Northern Italy population with that shows a high prevalence of arterial hypertension and cardiovascular disease. As the link between PFAS and arterial hypertension is unknown, we investigated if they could enhance the biosynthesis of aldosterone, the main mineralocorticoid hormone that has pressor effects. We exposed human adrenocortical carcinoma HAC15 cells to 1 µM or 10 µM concentration of PFOA and PFOS, alone or in combination, for 24, 48 or 72 hours and we measured changes in cell viability, aldosterone synthase (CYP11B2) mRNA, cell and mitochondrial reactive oxygen species (ROS), and aldosterone production in the absence or presence of the superoxide scavenger tempol. Experiments were also performed in the presence of 10 or 100 nM Ang II. We found that PFAS increased CYP11B2 mRNA by 3-fold and aldosterone secretion and mitochondrial ROS production by 2-fold over controls (p < 0.01 for all). PFAS also enhanced the effects of the aldosterone secretagogue Ang II on CYP11B2 mRNA and aldosterone secretion: 10 nM or 100 nM Ang II increased CYP11B2 mRNA by 12- and 52-fold, respectively, compared to vehicle (p < 0.001). Moreover, 1 µM PFAS potentiated the effect of 10 nM or 100 nM Ang II on CYP11B2 gene expression by 30- and 80-fold, respectively (p < 0.001). As the ROS scavenger tempol, which decreased ROS, significantly blunted the CYP11B2 gene expression induced by either PFAS alone, or by concomitant exposure to Ang II and PFAS, the effect of PFAS likely occurs via increased ROS generation. These results indicate that at concentrations mimicking those found in human plasma of exposed individuals, PFAS exert a prooxidant effect and act as potent disruptors of human adrenocortical cell function, thus implicating them as causative factors of human arterial hypertension due to aldosteronism. Presentation: Thursday, June 15, 2023

Aldosterone Biosynthesis Is Potently Stimulated by Perfluoroalkyl Acids: A Link between Common Environmental Pollutants and Arterial Hypertension.

The large environmental contamination of drinking water by perfluoroalkyl substances (PFAS) markedly increased the plasma levels of pentadecafluorooctanoic acid (PFOA) and perfluorooctanesulfonic acid (PFOS) in a Northern Italy population with a high prevalence of arterial hypertension and cardiovascular disease. As the link between PFAS and arterial hypertension is unknown, we investigated if they enhance the biosynthesis of the well-known pressor hormone aldosterone. We found that PFAS increased aldosterone synthase (CYP11B2) gene expression by three-fold and doubled aldosterone secretion and cell and mitochondria reactive oxygen species (ROS) production over controls (p < 0.01 for all) in human adrenocortical carcinoma cells HAC15. They also enhanced the effects of Ang II on CYP11B2 mRNA and aldosterone secretion (p < 0.01 for all). Moreover, when added 1 h before, the ROS scavenger tempol abolished the effect of PFAS on CYP11B2 gene expression. These results indicate that at concentrations mimicking those found in human plasma of exposed individuals, PFAS are potent disruptors of human adrenocortical cell function, and might act as causative factors of human arterial hypertension via increased aldosterone production.

ROS scavenger TEMPOL mitigates TNF alpha induced ER stress in hASM cells

The impact of airway inflammation is mediated by pro-inflammatory cytokines such as tumor necrosis factor alpha (TNFα), which underlies several respiratory diseases, including COVID-19, asthma, chronic bronchitis, and chronic obstructive pulmonary disease (COPD). In human airway smooth muscle (hASM) cells, exposure to TNFα leads to an accumulation of unfolded proteins in the ER, which triggers a homeostatic ER stress response activating a signaling cascade to restore normal function. Previously, we showed that TNFα selectively activates the inositol-requiring enzyme 1α (IRE1α)/X-box binding protein 1 (XBP1) ER stress pathway in hASM cells. Most likely, the protein unfolding in hASM cells caused by TNFα results from an increase in reactive oxygen species (ROS) formation. We hypothesize that ER stress induced by TNFα is mitigated by the ROS scavenger TEMPOL. Primary hASM cells were isolated from bronchiolar tissue samples obtained from 5 patients (both sexes included) who had no history of respiratory diseases. hASM cells were serum deprived for 48 h before treatment with 1) TNFα (20 ng/ml) for 12 h; 2) TEMPOL (500 μM) for 30 min followed by TNFα (20 ng/ml) for 12 h; and 3) untreated control for 12 h. At the end of the treatment period, hASM cells were processed for determination of protein expression through Western blotting. Activation of the ER stress response was assessed by phosphorylation of IRE1α and splicing of XBP1. Confirming our previous results, we found that 12 h TNFα exposure induced an ER stress response in hASM cells, evidence by phosphorylation of IRE1α and XBP1 splicing. Treating hASM cells with TEMPOL before exposure to TNFα mitigated the ER stress response. These results support our hypothesis and indicate that ROS scavenging prevents TNFα induced protein unfolding and triggering of the IRE1α/XBP1 ER stress pathway. R01HL 157984 (GCS) This is the full abstract presented at the American Physiology Summit 2023 meeting and is only available in HTML format. There are no additional versions or additional content available for this abstract. Physiology was not involved in the peer review process.

Characterization of the Dahl salt-sensitive rat as a rodent model of inherited, widespread, persistent pain

Animal models are essential for studying the pathophysiology of chronic pain disorders and as screening tools for new therapies. However, most models available do not reproduce key characteristics of clinical persistent pain. This has limited their ability to accurately predict which new medicines will be clinically effective. Here, we characterize the Dahl salt-sensitive (SS) rat strain as the first rodent model of inherited widespread hyperalgesia. We show that this strain exhibits physiological phenotypes known to contribute to chronic pain, such as neuroinflammation, defective endogenous pain modulation, dysfunctional hypothalamic–pituitary–adrenal axis, increased oxidative stress and immune cell activation. When compared with Sprague Dawley and Brown Norway rats, SS rats have lower nociceptive thresholds due to increased inflammatory mediator concentrations, lower corticosterone levels, and high oxidative stress. Treatment with dexamethasone, the reactive oxygen species scavenger tempol, or the glial inhibitor minocycline attenuated the pain sensitivity in SS rats without affecting the other strains while indomethacin and gabapentin provided less robust pain relief. Moreover, SS rats presented impaired diffuse noxious inhibitory controls and an exacerbated response to the proalgesic mediator PGE2, features of generalized pain conditions. These data establish this strain as a novel model of spontaneous, widespread hyperalgesia that can be used to identify biomarkers for chronic pain diagnosis and treatment.

Tacrolimus Causes Hypertension by Increasing Vascular Contractility via RhoA (Ras Homolog Family Member A)/ROCK (Rho-Associated Protein Kinase) Pathway in Mice.

To provide tacrolimus is first-line treatment after liver and kidney transplantation. However, hypertension and nephrotoxicity are common tacrolimus side effects that limit its use. Although tacrolimus-related hypertension is well known, the underlying mechanisms are not. Here, we test whether tacrolimus-induced hypertension involves the RhoA (Ras homolog family member A)/ROCK (Rho-associated protein kinase) pathway in male C57Bl/6 mice. Intra-arterial blood pressure was measured under anesthesia. The reactivity of renal afferent arterioles and mesenteric arteries were assessed in vitro using microperfusion and wire myography, respectively. Tacrolimus induced a transient rise in systolic arterial pressure that was blocked by the RhoA/ROCK inhibitor Fasudil (12.0±0.9 versus 3.2±0.7; P<0.001). Moreover, tacrolimus reduced the glomerular filtration rate, which was also prevented by Fasudil (187±20 versus 281±8.5; P<0.001). Interestingly, tacrolimus enhanced the sensitivity of afferent arterioles and mesenteric arteries to Ang II (angiotensin II), likely due to increased intracellular Ca2+ mobilization and sensitization. Fasudil prevented increased Ang II-sensitivity and blocked Ca2+ mobilization and sensitization. Preincubation of mouse aortic vascular smooth muscle cells with tacrolimus activated the RhoA/ROCK/MYPT-1 (myosin phosphatase targeting subunit 1) pathway. Further, tacrolimus increased cytoplasmic reactive oxygen species generation in afferent arterioles (107±5.9 versus 163±6.4; P<0.001) and in cultured mouse aortic vascular smooth muscle cells (100±7.5 versus 160±23.2; P<0.01). Finally, the reactive oxygen species scavenger Tempol inhibited tacrolimus-induced Ang II hypersensitivity in afferent arterioles and mesenteric arteries. The RhoA/ROCK pathway may play an important role in tacrolimus-induced hypertension by enhancing Ang II-specific vasoconstriction, and reactive oxygen species may participate in this process by activating the RhoA/ROCK pathway.

Cellular Senescence and the Associated Secretome Contribute to Age‐Related Vascular Dysfunction

Age‐related vascular dysfunction (e.g., large elastic artery [aorta] stiffening and endothelial dysfunction) is mediated by excess reactive oxygen species (ROS) leading to lower nitric oxide (NO) bioavailability. The upstream mechanisms mediating excess ROS are mostly unknown. Cellular senescence is a principal mechanism of aging and the senescence associated secretory phenotype (SASP) may exacerbate ROS.PurposeTo: 1) determine if senescent cell clearance (senolysis) lowers aortic stiffness (pulse wave velocity [PWV]) and increases endothelial function (endothelium‐dependent dilation [EDD]), and if these effects are mediated by reduced ROS and increased NO bioavailability; and 2) isolate the influence of the circulating SASP on age‐related vascular dysfunction.Methods and ResultsYoung (6 mo) and old (27 mo) adult male and female p16‐3MR mice were treated with vehicle ([V]; saline) or a p16‐3MR senolytic, ganciclovir (GCV; 25 mg/kg/day) injected intraperitoneally for 5 days. This resulted in 4 groups/sex (Young‐V [YV], n = 23; Young‐GCV [Y‐GCV]; n = 16, Old‐V [OV]; n = 22, Old‐GCV [O‐GCV]; n = 21). No sex differences were observed, so results were combined.Aortic Stiffness. Aortic PWV (aPWV) was assessed pre and post V and GCV treatment. Old mice had higher aPWV at baseline vs young (aPWV [cm/sec]: O‐GCV, 450 ± 16; OV, 441 ± 13; YV, 352 ± 7; Y‐GCV, 351 ± 12; P&lt;.05). Following GCV treatment, old mice had reduced aPWV (pre: 441 ± 13 vs post: 375 ± 5 cm/sec, P&lt; .05), which was not different from YV (P= .63) or Y‐GCV (P= .72). These data suggest that cellular senescence mediates aortic stiffening with advancing age.Endothelial function. OV animals had impaired ex vivocarotid artery EDD to acetylcholine (an established assay of endothelial function) relative to young and GCV treatment resulted in greater peak EDD (Peak EDD [%]: O‐GCV, 95 ± 1; OV, 83 ± 4; YV, 93 ± 4; Y‐GCV, 95 ± 1; P&lt;.05). Addition of the NO‐synthase inhibitor, L‐NAME, abolished group differences suggesting the age‐related increase in cellular senescence reduced EDD by lowering NO bioavailability. Administration of the ROS scavenger TEMPOL eliminated group differences in EDD, implying that cellular senescence causes endothelial dysfunction with aging by amplifying ROS.SASP. To determine the effect of the circulating SASP on aortic stiffness, we incubated aortic rings from young adult (6 mo) male and female C57BL/6 mice, with plasma from sex‐matched OV and O‐GCV mice, or under fetal bovine serum (control). Following a 48h incubation, we assessed intrinsic mechanical wall stiffness (elastic modulus [EM]), an established ex vivomeasure of aortic stiffness. OV plasma resulted in 1.5 ± .01‐fold greater EM vs control (P&lt; .05), which did not occur in O‐GCV plasma (P= 0.84 vs control), suggesting the SASP may increase age‐related aortic stiffening.Conclusion. The circulating SASP factors may be a mechanism by which cellular senescence induces age‐related vascular dysfunction, and as such, these processes represent novel therapeutic targets.

Fisetin Supplementation Improves Age‐Related Vascular Endothelial Function by Suppressing Cellular Senescence and Mitochondrial Oxidative Stress

Age‐related vascular endothelial dysfunction is mediated by excess reactive oxygen species (ROS)—mitochondria (mito) being a key source—which can reduce nitric oxide (NO) bioavailability. Cellular senescence, a fundamental mechanism of aging, may exacerbate mito ROS and be a potential therapeutic target to combat age‐related vascular dysfunction.PurposeTo determine if treatment with the natural flavonoid fisetin improves endothelial function with aging by suppressing cellular senescence, scavenging excess whole‐cell and mito ROS, and increasing NO bioavailability.Methods &amp; ResultsOld (27 mo) male C57BL/6 mice were treated with vehicle (V; 10% EtOH, 30% PEG400 and 60% Phosal 50 PG; n = 9) or fisetin (Fis; 50 mg/kg/day in V; n = 10) by oral gavage following a 1 wk on – 2 wk off – 1 wk on dosing paradigm.Endothelial functionEndothelial function was assessed by ex vivo carotid artery endothelium‐dependent dilation (EDD) and endothelium‐independent dilation (EID) to increasing doses of acetylcholine and sodium nitroprusside, respectively. EDD was greater in Fis vs V treated mice (Peak EDD [%]: 97 ± 1 vs 84 ± 3, P &lt; .05) and no differences were observed among groups in EID (P = .54).Cellular senescenceFis‐treated mice had lower vascular abundance of p16, an established marker of cellular senescence (Fis, .12 ± .01 vs V, .19 ± .02 chemiluminescence units [CU], P &lt; .05). Next, we administered Fis or V to old (27 mo) p16‐3MR mice (a model that allows for clearance of senescent cells with ganciclovir [GCV]; n = 6/group). Fis‐treated p16‐3MR mice had greater EDD (Peak EDD [%]: Fis, 93 ± 2 vs V, 74 ± 5, P &lt; .05). Ex vivo carotid artery incubations with GCV eliminated group differences in EDD, suggesting that Fis reduced senescent cells to improve EDD.Whole‐cell ROSElectron paramagnetic resonance (EPR) spectroscopy was used to assess whole‐cell vascular (aortic) ROS. Fis‐treated mice had lower whole‐cell ROS (Fis, 4703 ± 455 vs V, 8173 ± 1243 amplitude units [AU], P &lt; .05). Incubation with the ROS scavenger TEMPOL eliminated group differences in EDD, implying that Fis ameliorated ROS‐related suppression of EDD.Mito ROSEPR was used to assess vascular mito ROS. Fis‐treated mice had lower mito ROS (Fis, 2527 ±440 vs V, 6603 ± 1956 AU, P &lt; .05). Further, Fis‐treated mice had lower abundance of vascular p‐p66SHC, a recognized marker of mito oxidative stress (Fis, .029 ± .003 vs V, .049 ± .008 CU, P &lt; .05) and greater abundance of Mn superoxide dismutase, a mito antioxidant enzyme (Fis, .41 ± .1 vs V, .20 ± .02 CU, P &lt; .05). Incubation with the mito‐specific antioxidant, MitoQ, eliminated group differences in EDD, implying that Fis ameliorated mito ROS‐related suppression of EDD.NOAddition of the NO‐synthase inhibitor, L‐NAME, abolished group differences in EDD suggesting Fis improved age‐related EDD impairments by increasing NO bioavailability.ConclusionFisetin supplementation may be a novel strategy to target excess cellular senescence and thereby reduce mito ROS to improve NO‐mediated endothelial function with aging.

Myeloperoxidase Controls Bone Turnover by Suppressing Osteoclast Differentiation Through Modulating Reactive Oxygen Species Level.

ABSTRACTMyeloperoxidase (MPO) is a heme peroxidase that plays an important role in innate immunity for host defense against invading microorganisms by catalyzing hydrogen peroxide (H2O2)‐mediated reactions. Although many reports indicate MPO exerts beneficial or detrimental effects on a variety of inflammatory diseases, little is known with regard to its functional role in bone homeostasis in vivo. Here, our work demonstrates that MPO was transcriptionally downregulated in response to osteoclastogenic stimuli and that exogenous alteration of MPO expression negatively regulated osteoclast (OC) differentiation in vitro. Genetic ablation of Mpo resulted in osteoporotic phenotypes and potentiated bone‐resorptive capacity in mice. Mechanistically, accumulation of intracellular H2O2 and reactive oxygen species (ROS) were observed in MPO deficiency, and MPO overexpression suppressed ROS production in mouse OC precursors. Moreover, a ROS scavenger Tempol inhibited the effect of MPO deficiency on OC formation and function as well as on receptor activator of nuclear factor‐κB ligand (RANKL)‐initiated transduction signal activation including NF‐κB, mitogen‐activated protein kinases (MAPKs), and Akt, indicating the increased ROS caused by MPO deficiency contributes to osteoclastogenesis. Taken together, our data demonstrate that MPO has a protective role in bone turnover by limiting osteoclastogenesis and bone resorption physiologically through modulating intracellular H2O2 level. © 2020 The Authors. Journal of Bone and Mineral Research published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research (ASBMR).

Hypoxia/reoxygenation decreases endothelial glycocalyx via reactive oxygen species and calcium signaling in a cellular model for shock.

Ischemia/reperfusion injury (IRI) has been shown to cause endothelial glycocalyx (EG) damage.Whether the hypoxic/ischemic insult or the oxidative and inflammatory stress of reperfusion plays a greater part in glycocalyx damage is not known. Furthermore, the mechanisms by which IRI causes EG damage have not been fully elucidated. The aims of this study were to determine if hypoxia alone or hypoxia/reoxygenation (H/R) caused greater damage to the glycocalyx, and if this damage was mediated by reactive oxygen species (ROS) and Ca signaling. Human umbilical vein endothelial cells were cultured to confluence and exposed to either normoxia (30 minutes), hypoxia (2% O2 for 30 minutes), or H/R (30 minutes hypoxia followed by 30 minutes normoxia). Some cells were pretreated with ROS scavengers TEMPOL, MitoTEMPOL, Febuxostat, or Apocynin, or with the Ca chelator BAPTA or Ca channel blockers 2-aminoethoxydiphenyl borate, A967079, Pyr3, or ML204. Intracellular ROS was quantified for all groups. Endothelial glycocalyx was measured using fluorescently tagged wheat germ agglutinin and imaged with fluorescence microscopy. Glycocalyx thickness was decreased in both hypoxia and H/R groups, with the decrease being greater in the H/R group. TEMPOL, MitoTEMPOL, BAPTA, and 2-aminoethoxydiphenyl borate prevented loss of glycocalyx in H/R. The ROS levels were likewise elevated compared with normoxia in both groups, but were increased in the H/R group compared with hypoxia alone. BAPTA did not prevent ROS production in either group. In our cellular model for shock, we demonstrate that although hypoxia alone is sufficient to produce glycocalyx loss, H/R causes a greater decrease in glycocalyx thickness. Under both conditions damage is dependent on ROS and Ca signaling. Notably, we found that ROS are generated upstream of Ca, but that ROS-mediated damage to the glycocalyx is dependent on Ca.

NADPH oxidase 2-mediated NLRP1 inflammasome activation involves in neuronal senescence in hippocampal neurons in vitro

Oxidative stress and inflammation are closely related to neuron ageing. NADPH oxidase 2 (NOX2) is a major source of reactive oxygen species (ROS) generation in brain. The nucleotide-binding oligomerisation domain (NOD)-like receptor protein 1 (NLRP1) inflammasome is responsible for the formation of proinflammatory molecules in neurons. We hypothesize that NOX2-derived ROS accumulation mediates activation of NLRP1 inflammasome, which is involved in age-related neuronal damage. In the present study, we investigated the changes of NOX2-NLRP1 signaling pathway in primary hippocampal neurons cultured for different time (6, 9 and 12 days, d). Meanwhile, we further examined the effect of ROS inhibitor and NLRP1-siRNA on neuronal senescence. The results showed that, compared with 6 d group, the neuronal apoptosis and β-Galactosidase (β-Gal) expression were significantly increased, and the microtubule-associated protein 2 (MAP2) expression significantly decreased in primary hippocampal neurons cultured for 12 d. In addition, the results also showed that the production of ROS, the expressions of NOX2 and NLRP1 inflammasome were significantly increased with the prolongation of culture time in hippocampal neurons. Moreover, the NOX inhibitor (apocynin) and ROS scavenger (tempol) significantly decreased ROS production and alleviated neuronal damage. Meanwhile, the tempol and apocynin treatment significantly decreased the expression of NLRP1 inflammasome in hippocampal neurons. Furthermore, the NLRP1-siRNA and caspase-1 inhibitor treatment also alleviated neuronal damage. These results suggest that NOX2-derived ROS generation may induce brain inflammation via NLRP-1 inflammasome activation and lead to age-related neuronal damage. The NADPH oxidase and NLRP1 inflammasome may be important therapeutic targets for age-related neuronal damage.

Abstract 032: Reconstitution of Autophagy Ameliorates Endothelium-Dependent Relaxation, Vascular Smooth Muscle Calcium Sensitization, &amp; Arterial Stiffening in Spontaneously Hypertensive Rats

Insufficient autophagy has been proposed as a mechanism of cellular aging, as this leads to the accumulation of dysfunctional macromolecules and organelles. Premature vascular aging occurs in hypertension. In fact, many factors that contribute to the deterioration of vascular function as we age are accelerated in clinical and experimental hypertension. Previously, we have reported decreased autophagic activity in arteries from spontaneously hypertensive rats (SHR); however, the effects of restoring autophagic activity on blood pressure and vascular function are currently unknown. We hypothesized that reconstitution of arterial autophagy in SHR would decrease blood pressure and improve endothelium-dependent relaxation. We treated 13-18 week old Wistar and SHR with autophagy activator trehalose (2% in drinking water) for 28 days. Blood pressure was measured by telemetry and vascular function was performed on isolated mesenteric resistance arteries using wire and pressure myographs. Treatment with trehalose had no effect on mean arterial pressure in SHR (p&gt;0.05). Trehalose treatment in SHR improved the relaxation to acetylcholine (ACh) [%Relaxation (ACh 1 μM), vehicle: 59.6±8.4 vs. trehalose: 82.4±4.2; p&lt;0.05], and this was not different from arteries incubated with cyclooxygenase inhibitor indomethacin and reactive oxygen species scavenger tempol [%Relaxation (ACh 1 μM), trehalose: 82.4±4.2 vs. vehicle+indomethacin: 92.7±3.9 and vehicle+tempol: 89.3±5.4; both p&gt;0.05]. Trehalose treatment in SHR also prevented the relaxation to Rho kinase inhibition [%Relaxation (Y-27632 0.3 μM), vehicle: 30.4±4.3 vs. trehalose: 8.4±3.5; p&lt;0.05]. Finally, trehalose treatment in SHR decreased arterial stiffness as indicated by the slope of the stress-strain curve [β (stress-strain), vehicle: 8.3±0.6 vs. trehalose: 5.5±0.2; p&lt;0.05]. Overall these data indicate that reconstitution of arterial autophagy in SHR improves endothelial and vascular smooth muscle function, which could synergize to prevent arterial stiffening. As a result, restoration of arterial autophagic activity could be a novel therapeutic for premature vascular aging in hypertension, a recently adopted clinical guideline for cardiovascular disease prevention.

Calcium-calmodulin-dependent protein kinase mediates the intracellular signalling pathways of cardiac apoptosis in mice with impaired glucose tolerance.

Spontaneous sarcoplasmic reticulum (SR) Ca2+ release events increased in fructose-rich diet mouse (FRD) myocytes vs. control diet (CD) mice, in the absence of significant changes in SR Ca2+ load. In HEK293 cells, hyperglycaemia significantly enhanced [3 H]ryanodine binding and Ca2+ /calmodulin-dependent protein kinase II (CaMKII) phosphorylation of RyR2-S2814 residue vs. normoglycaemia. These increases were prevented by CaMKII inhibition. FRD significantly augmented cardiac apoptosis in WT vs. CD-WT mice, which was prevented by co-treatment with the reactive oxygen species scavenger Tempol. Oxidative stress was also increased in FRD-SR-autocamide inhibitory peptide (AIP) mice, expressing the SR-targeted CaMKII inhibitor AIP, without any significant enhancement of apoptosis vs. CD-SR-AIP mice. FRD produced mitochondrial swelling and membrane depolarization in FRD-WT mice but not in FRD-S2814A mice, in which the CaMKII site on ryanodine receptor 2 was ablated. FRD decreased mitochondrial area, mean Feret diameter and the mean distance between SR and the outer mitochondrial membrane vs. CD hearts. This remodelling was prevented in AC3I mice, with cardiac-targeted CaMKII inhibition. The impact of cardiac apoptosis in pre-diabetic stages of diabetic cardiomyopathy is unknown. We show that myocytes from fructose-rich diet (FRD) animals exhibit arrhythmias produced by exacerbated Ca2+ /calmodulin-protein kinase (CaMKII) activity, ryanodine receptor 2 (RyR2) phosphorylation and sarcoplasmic reticulum (SR) Ca2+ leak. We tested the hypothesis that this mechanism also underlies cardiac apoptosis in pre-diabetes. We generated a pre-diabetic model in FRD mice. FRD mice showed an increase in oxidative stress, hypertrophy and systolic dysfunction. FRD myocytes exhibited enhanced SR Ca2+ spontaneous events in the absence of SR Ca2+ load alterations vs. control-diet (CD) myocytes. In HEK293 cells, hyperglycaemia significantly enhanced [3 H]ryanodine binding and CaMKII phosphorylation of RyR2-S2814 residue vs. normoglycaemia. CaMKII inhibition prevented hyperglycaemia-induced alterations. FRD also evoked cardiac apoptosis in WT mice vs. CD-WT mice. Co-treatment with the reactive oxygen species scavenger Tempol prevented FRD-induced apoptosis in WT mice. In contrast, FRD enhanced oxidative stress but not apoptosis in FRD-SR-AIP mice, in which a CaMKII inhibitor is targeted to the SR. FRD produced mitochondrial membrane depolarization in WT mice but not in S2814A mice, in which the CaMKII phosphorylation site on RyR2 was ablated. Furthermore, FRD decreased mitochondrial area, mean Feret diameter and mean SR-mitochondrial distance vs. CD-WT hearts. This remodelling was prevented in AC3I mice, with cardiac-targeted CaMKII inhibition. CaMKII phosphorylation of RyR2, SR Ca2+ leak and mitochondrial membrane depolarization are critically involved in the apoptotic pathway of the pre-diabetic heart. The FRD-induced decrease in SR-mitochondrial distance is likely to additionally favour Ca2+ transit between the two organelles.

Distinct contributions of reactive oxygen species in amygdala to bee venom-induced spontaneous pain-related behaviors

Reactive oxygen species (ROS), such as superoxide and hydrogen peroxide, play essential roles in physiological plasticity and are also involved in the pathogenesis of persistent pain. Roles of peripheral and spinal ROS in pain have been well established, but much less is known about ROS in the amygdala, a brain region that plays an important role in pain modulation. The present study explored the contribution of ROS in the amygdala to bee venom (BV)-induced pain behaviors. Our data show that the amygdala is activated following subcutaneous BV injection into the left hindpaw, which is reflected in the increased number of c-Fos positive cells in the central and basolateral amygdala nuclei in the right hemisphere. Stereotaxic administration of a ROS scavenger (tempol, 10mM), NADPH oxidase inhibitor (baicalein, 5mM) or lipoxygenase inhibitor (apocynin, 10mM) into the right amygdala attenuated the BV-induced spontaneous licking and lifting behaviors, but had no effect on BV-induced paw flinch reflexes. Our study provides further evidence for the involvement of the amygdala in nociceptive processing and pain behaviors, and that ROS in amygdala may be a potential target for treatment strategies to inhibit pain.

ROS scavenger decreases basal perfusion pressure, vasoconstriction and NO synthase activity in pulmonary circulation during pulmonary microembolism.

Two mechanisms contribute in the development of pulmonary hypertension in pulmonary embolism (PE) - obstruction of pulmonary blood vessels and vasoconstriction. We hypothesize that hypoxia, increased shear stress and/or activation of gathered leukocytes in the PE may cause a release of reactive oxygen species (ROS). Therefore our aim was to determine the influence of the ROS scavenger Tempol on pulmonary hypertension and to describe NO synthase activity and production of NO oxidative products (NOx) after PE. In general anesthesia sephadex microspheres suspended in PSS were applied in right jugular vein as the pulmonary microembolism. Than we measured in isolated salt solution-perfused lungs the changes in perfusion pressure, activity of NO synthase and NOx plasma concentration in 7 groups of rats: C: control group (n=5), CN: C + sodium nitroprusside (SN) (n=5), EN: PE + SN (n=5), ETN: Tempol + PE + SN (n=5), CL: C + L-NAME (n=5), EL: PE + L-NAME (n=5), ETL: Tempol + PE + L-NAME (n=5). Tempol was applied intraperitoneally before PE. Animals that received Tempol (groups TN, TL) had significantly lower basal perfusion pressure than those which did not receive Tempol (EN, EL). Overall we measured a higher decrease of perfusion pressure than in the control group (C) after application of SN. Administration of L-NAME after PE (EL) increased the pressure more than in the control group (NL). NOx concentration was higher after PE. We found that preventive administration of Tempol decreases the increase in perfusion pressure after PE. PE increased NO release and concentration of NOx.

Cardiac melanocytes influence atrial reactive oxygen species involved with electrical and structural remodeling in mice.

Cardiac melanocyte-like cells (CMLCs) contribute to atrial arrhythmias when missing the melanin synthesis enzyme dopachrome tautomerase (Dct). While scavenging reactive oxygen species (ROS) in Dct-null mice partially suppressed atrial arrhythmias, it remains unclear if CMLCs influence atrial ROS and structure or if the electrical response of CMLCs to ROS differs from that of atrial myocytes. This study is designed to determine if CMLCs contribute to overall atrial oxidative stress or structural remodeling, and if ROS affects the electrophysiology of CMLCs differently than atrial myocytes. Immunohistochemical analysis showed higher expression of the oxidative marker 8-hydroxy-2′-deoxyguanosine in Dct-null atria versus Dct-heterozygous (Dct-het) atria. Exposing isolated CMLCs from Dct-het and Dct-null mice to hydrogen peroxide increased superoxide anion more in Dct-null CMLCs. Trichrome staining showed increased fibrosis in Dct-null atria, and treating Dct-null mice with the ROS scavenger Tempol reduced atrial fibrosis. Action potential recordings from atrial myocytes and isolated Dct-het and Dct-null CMLCs in response to hydrogen peroxide showed that the EC50 for action potential duration (APD) prolongation of Dct-null CMLCs was 8.2 ± 1.7 μmol/L versus 16.8 ± 2.0 μmol/L for Dct-het CMLCs, 19.9 ± 2.1 μmol/L for Dct-null atrial myocytes, and 20.5 ± 1.9 μmol/L for Dct-het atrial myocytes. However, APD90 was longer in CMLCs versus atrial myocytes in response to hydrogen peroxide. Hydrogen peroxide also induced more afterdepolarizations in CMLCs compared to atrial myocytes. These studies suggest that Dct within CMLCs contributes to atrial ROS balance and remodeling. ROS prolongs APD to a greater extent and induces afterdepolarizations more frequently in CMLCs than in atrial myocytes.

Reactive oxygen species mediate visceral pain-related amygdala plasticity and behaviors.

Accumulating evidence suggests an important contribution of reactive oxygen species (ROS) to pain and neuropsychiatric disorders, but their role in pain-related plasticity in the brain is largely unknown. Neuroplasticity in the central nucleus of the amygdala (CeA) correlates positively with pain behaviors in different models. Little is known, however, about mechanisms of visceral pain-related amygdala changes. The electrophysiological and behavioral studies reported here addressed the role of ROS in the CeA in a visceral pain model induced by intracolonic zymosan. Vocalizations to colorectal distension and anxiety-like behavior increased after intracolonic zymosan and were inhibited by intra-CeA application of a ROS scavenger (tempol, a superoxide dismutase mimetic). Tempol also induced a place preference in zymosan-treated rats but not in controls. Single-unit recordings of CeA neurons in anesthetized rats showed increases of background activity and responses to visceral stimuli after intracolonic zymosan. Intra-CeA application of tempol inhibited the increased activity but had no effect under normal conditions. Whole-cell patch-clamp recordings of CeA neurons in brain slices from zymosan-treated rats showed that tempol decreased neuronal excitability and excitatory synaptic transmission of presumed nociceptive inputs from the brainstem (parabrachial area) through a combination of presynaptic and postsynaptic actions. Tempol had no effect in brain slices from sham controls. The results suggest that ROS contribute to visceral pain-related hyperactivity of amygdala neurons and amygdala-dependent behaviors through a mechanism that involves increased excitatory transmission and excitability of CeA neurons.

COX-2 is involved in vascular oxidative stress and endothelial dysfunction of renal interlobar arteries from obese Zucker rats

Obesity is related to vascular dysfunction through inflammation and oxidative stress and it has been identified as a risk factor for chronic renal disease. In the present study, we assessed the specific relationships among reactive oxygen species (ROS), cyclooxygenase 2 (COX-2), and endothelial dysfunction in renal interlobar arteries from a genetic model of obesity/insulin resistance, the obese Zucker rats (OZR). Relaxations to acetylcholine (ACh) were significantly reduced in renal arteries from OZR compared to their counterpart, the lean Zucker rat (LZR), suggesting endothelial dysfunction. Blockade of COX with indomethacin and with the selective blocker of COX-2 restored the relaxations to ACh in obese rats. Selective blockade of the TXA2/PGH2 (TP) receptor enhanced ACh relaxations only in OZR, while inhibition of the prostacyclin (PGI2) receptor (IP) enhanced basal tone and inhibited ACh vasodilator responses only in LZR. Basal production of superoxide was increased in arteries of OZR and involved NADPH and xanthine oxidase activation and NOS uncoupling. Under conditions of NOS blockade, ACh induced vasoconstriction and increased ROS generation that were augmented in arteries from OZR and blunted by COX-2 inhibition and by the ROS scavenger tempol. Hydrogen peroxide (H2O2) evoked both endothelium- and vascular smooth muscle (VSM)-dependent contractions, as well as ROS generation that was reduced by COX-2 inhibition. In addition, COX-2 expression was enhanced in both VSM and endothelium of renal arteries from OZR. These results suggest that increased COX-2-dependent vasoconstriction contributes to renal endothelial dysfunction through enhanced (ROS) generation in obesity. COX-2 activity is in turn upregulated by ROS.

MTOR inhibition with temsirolimus causes acute increases in glomerular permeability, but inhibits the dynamic permeability actions of puromycin aminonucleoside.

Inhibitors of the mammalian target of rapamycin (mTORi) can produce de novo proteinuria in kidney transplant patients. On the other hand, mTORi has been shown to suppress disease progression in several animal models of kidney disease. In the present study, we investigated whether glomerular permeability can be acutely altered by the mTORi temsirolimus and whether mTORi can affect acute puromycin aminonucleoside (PAN) or angiotensin II (ANG II)-induced glomerular hyperpermeability. In anesthetized Wistar rats, the left ureter was cannulated for urine collection, while simultaneously blood access was achieved. Temsirolimus was administered as a single intravenous dose 30 min before the start of the experiments in animals infused with PAN or ANG II or in nonexposed animals. Polydispersed FITC-Ficoll-70/400 (molecular radius 10-80 Å) and (51)Cr-EDTA infusion was given during the whole experiment. Measurements of Ficoll in plasma and urine were performed sequentially before the temsirolimus injection (baseline) and at 5, 15, 30, 60, and 120 min after the start of the experiments. Urine and plasma samples were analyzed by high-performance size-exclusion chromatography (HPSEC) to assess glomerular sieving coefficients (θ) for Ficoll10-80Å. Temsirolimus per se increased baseline glomerular permeability to Ficoll50-80Å 45 min after its administration, a reactive oxygen species (ROS)-dependent phenomenon. PAN caused a rapid and reversible increase in glomerular permeability, peaking at 5 min, and again at 60-120 min, which could be blocked by the ROS scavenger tempol. mTORi abrogated the second permeability peak induced by PAN. However, it had no effect on the immediate ANG II- or PAN-induced increases in glomerular permeability.

Angiotensin‐II promotes ACE2 shedding by increasing ADAM17 expression and oxidative stress in Neuro2A cells (874.10)

Decrease of Angiotensin‐converting enzyme 2 (ACE2) expression and activity in the brain has been shown to be associated with neurogenic hypertension. We recently reported that up‐regulation of the matrix metalloprotease A Disintegrin And Metalloprotease 17 (ADAM17) expression in hypertension mediates ACE2 shedding in neurons. To study the contribution of Ang II Type 1 Receptor (AT1R) and oxidative stress on ACE2 shedding, Neuro2A (neuronal cell line) were first transfected with human ACE2 (hACE2) then pretreated with AT1R blocker Losartan (10 µM) or the reactive oxygen species scavenger Tempol (10 µM), 30 min prior to treatment with AngII (100 and 300 nM). Western blotting revealed that ACE2 expression was decreased (12 and 40%, respectively), while ADAM17 expression was increased (30 and 36%, respectively) in Neuro2A cells after Ang II treatment. Pretreatment with losartan or tempol attenuated the effect of Ang II on ADAM17 expression (18 and 19%, respectively). To further study the involvement of oxidative stress in Ang II‐induced ADAM17 expression, another set of Neuro2A cells were studied without transfection with hACE2. In these cells treated with Ang II (100 nM), ADAM17 expression was similarly decreased by tempol. These data suggest that ADAM17 expression is increased by an AT1R‐dependent, as well as oxidative stress‐dependent mechanism, leading to enhanced ACE2 shedding in neurons.Grant Funding Source: Supported by AHA 12EIA8030004, CNPq