Redox Control of Skeletal Muscle Regeneration

CRISPR/Cas9-Based Dystrophin Restoration Reveals a Novel Role for Dystrophin in Bioenergetics and Stress Resistance of Muscle Progenitors

Although the lack of dystrophin expression in muscle myofibers is the central cause of Duchenne muscular dystrophy (DMD), accumulating evidence suggests that DMD may also be a stem cell disease. Recent studies have revealed dystrophin expression in satellite cells and demonstrated that dystrophin deficiency is directly related to abnormalities in satellite cell polarity, asymmetric division, and epigenetic regulation, thus contributing to the manifestation of the DMD phenotype. Although metabolic and mitochondrial dysfunctions have also been associated with the DMD pathophysiology profile, interestingly, the role of dystrophin with respect to stem cells dysfunction has not been elucidated. In the past few years, editing of the gene that encodes dystrophin has emerged as a promising therapeutic approach for DMD, although the effects of dystrophin restoration in stem cells have not been addressed. Herein, we describe our use of a clustered regularly interspaced short palindromic repeats/Cas9‐based system to correct the dystrophin mutation in dystrophic (mdx) muscle progenitor cells (MPCs) and show that the expression of dystrophin significantly improved cellular properties of the mdx MPCs in vitro. Our findings reveal that dystrophin‐restored mdx MPCs demonstrated improvements in cell proliferation, differentiation, bioenergetics, and resistance to oxidative and endoplasmic reticulum stress. Furthermore, our in vivo studies demonstrated improved transplantation efficiency of the corrected MPCs in the muscles of mdx mice. Our results indicate that changes in cellular energetics and stress resistance via dystrophin restoration enhance muscle progenitor cell function, further validating that dystrophin plays a role in stem cell function and demonstrating the potential for new therapeutic approaches for DMD. stem cells2019;37:1615–1628

Increased Circulating Levels of Interleukin-6 Affect the Redox Balance in Skeletal Muscle

The extent of oxidative stress and chronic inflammation are closely related events which coexist in a muscle environment under pathologic conditions. It has been generally accepted that the inflammatory cells, as well as myofibers, are sources of reactive species which are, in turn, able to amplify the activation of proinflammatory pathways. However, the precise mechanism underlining the physiopathologic interplay between ROS generation and inflammatory response has to be fully clarified. Thus, the identification of key molecular players in the interconnected pathogenic network between the two processes might help to design more specific therapeutic approaches for degenerative diseases. Here, we investigated whether elevated circulating levels of the proinflammatory cytokine Interleukin-6 (IL-6) are sufficient to perturb the physiologic redox balance in skeletal muscle, independently of tissue damage and inflammatory response. We observed that the overexpression of circulating IL-6 enhances the generation and accumulation of free radicals in the diaphragm muscle of adult NSE/IL-6 mice, by deregulating redox-associated molecular circuits and impinging the nuclear factor erythroid 2-related factor 2- (Nrf2-) mediated antioxidant response. Our findings are coherent with a model in which uncontrolled levels of IL-6 in the bloodstream can influence the local redox homeostasis, inducing the establishment of prooxidative conditions in skeletal muscle tissue.

Muscle Injury Associated Elevated Oxidative Stress and Abnormal Myogenesis in Patients with Idiopathic Scoliosis

Idiopathic scoliosis (IS) is a disease with unknown etiology characterized by spinal rotation asymmetry. Reports describing the histochemical and pathological analyses of IS patients have shown that necrosis, fibrosis and fatty involution occurred on the apex paraspinal muscles. However, research on the changes in the paraspinal muscles of IS patients compared with those in matched controls is rare; thus, the basic mechanism of how paraspinal muscles are injured in IS patients is still unclear. In this study, we investigated the morphological changes of paraspinal muscles in the control group and IS patients, and the possible mechanisms were examined in vivo and in vitro. Increased myofiber necrosis was found on both sides of the apex paraspinal muscles of IS patients compared with those of the control group, and the number of TUNEL-positive apoptotic cells was also increased. Apoptosis signaling pathways, including pro-apoptosis proteins such as cleaved-caspase 3 and cytochrome c, were markedly upregulated, whereas the anti-apoptotic Bcl-2/Bax was significantly downregulated in IS patients compared with the control group. Moreover, PGC-1α and SOD1 were upregulated in accordance with the increased ROS production in IS patients. The distribution of myofiber types, as well as the mRNA levels of type IIa myofiber marker MYH2 and the important myogenesis regulator MYOG were remarkably changed in IS patients. In addition, C2C12 or human skeletal muscle mesenchymal progenitor cells treated with antimycin A in glucose-free and serum-free culture medium, which can activate oxidative stress and induce apoptosis, showed similar patterns of the changed distribution of myofiber types and downregulation of MYH2 and MYOG. Altogether, our study suggested that the extents of severe muscle injury and accumulated oxidative stress were increased in IS patients compared with the control group, and the abnormal myogenesis was also observed in IS patients. Since elevated oxidative stress can lead to apoptosis and the dysregulation of myogenesis in muscle cells, it may be associated with the pathological changes observed in IS patients and contribute to the development and progression of IS.

Free radical-decellularized tissue promotes enhanced antioxidant and anti-inflammatory macrophage response

Oxidative stress leads to the progression of many diseases including chronic wounds, atherosclerosis, stroke and cancer. The modification of biomolecules with reactive nitrogen or oxygen species has been shown to trigger oxidative stress pathways that are beneficial for healing. Extracellular matrix scaffolds have been used successfully in reconstructive applications due to the beneficial host response they induce. To tailor extracellular matrix scaffolds to enhance antioxidant response, ECM were prepared using reactive nitrogen or oxygen species. These scaffolds were shown to be effectively decellularized and possess oxidative or nitroxidative protein modifications. Macrophage responses in vitro and in an in vivo muscle injury model were shown to have enhanced antioxidant phenotypes without impairment of long-term remodeling. These observations suggest that ECM decellularized with reactive oxygen or nitrogen species could provide better outcomes for the treatment of ischemic diseases.

Tissue-Specific Oxidative Stress Modulation by Exercise: A Comparison between MICT and HIIT in an Obese Rat Model

Background and Aim

Exercise is an effective strategy to reduce obesity-induced oxidative stress. The purpose of this study was to compare the effects of two training modalities (moderate-intensity continuous training (MICT) and high-intensity interval training (HIIT)) on the pro/antioxidant status of different tissues in obese Zucker rats.

Methods

Eight-week-old male Zucker rats (fa/fa, n = 36) were subdivided in three groups: MICT, HIIT, and control (no exercise) groups. Trained animals ran on a treadmill (0° slope), 5 days/week for 10 weeks (MICT: 51 min at 12 m·min^-1; HIIT: 6 sets of 3 min at 10 m·min^-1 followed by 4 min at 18 m·min^-1). Epididymal (visceral) and subcutaneous adipose tissue, gastrocnemius muscle, and plasma samples were collected to measure oxidative stress markers (advanced oxidation protein products (AOPP), oxidized low-density lipoprotein (oxLDL)), antioxidant system markers (ferric-reducing ability of plasma (FRAP), superoxide dismutase (SOD), catalase, and glutathione peroxidase (GPx) activities), and prooxidant enzymes (NADPH oxidase and xanthine oxidase (XO) activities, myeloperoxidase content).

Results

Compared with the control, MICT increased GPx and catalase activities and the FRAP level in epididymal adipose tissue. HIIT increased the AOPP level in subcutaneous adipose tissue. In the muscle, HIIT increased both SOD and GPx activities and reduced the AOPP level, whereas MICT increased only SOD activity. Finally, plasma myeloperoxidase content was similarly decreased by both training modalities, whereas oxLDL was reduced only in the MICT group.

Conclusion

Both HIIT and MICT improved the pro/antioxidant status. However, HIIT was more efficient than MICT in the skeletal muscle, whereas MICT was more efficient in epididymal adipose tissue. This suggests that oxidative stress responses to HIIT and MICT are tissue-specific. This could result in ROS generation via different pathways in these tissues. From a practical point of view, the two training modalities should be combined to obtain a global response in people with obesity.

Activation of cannabinoid type 2 receptor protects skeletal muscle from ischemia-reperfusion injury partly via Nrf2 signaling

AIMS

Cannabinoid type 2 (CB₂) receptor activation has been shown to attenuate IRI in various organs. NF-E2-related factor (Nrf2) is an anti-oxidative factor that plays multiple roles in regulating cellular redox homeostasis and modulating cell proliferation and differentiation. The protective effects of CB₂ receptor activation on skeletal muscle IRI and the underlying mechanism that involves Nrf2 signaling remain unknown.

MAIN METHODS

We evaluated the in vivo effect of CB₂ receptor activation by the CB₂ receptor agonist AM1241 on IR-induced skeletal muscle damage and early myogenesis. We also assessed the effects of CB₂ receptor activation on C2C12 myoblasts differentiation and H₂O₂-induced C2C12 myoblasts damage in vitro, with a focus on the mechanism of Nrf2 signaling.

KEY FINDINGS

Our results showed that CB₂ receptor activation reduced IR-induced histopathological lesions, edema, and oxidative stress 1 day post-injury and accelerated early myogenesis 4 days post-injury in mice. Nrf2 knockout mice that were treated with AM1241 exhibited deteriorative skeletal muscle oxidative damage and myogenesis. In vitro, pretreatment with AM1241 significantly increased the expression of Nrf2 and its nuclear translocation, attenuated the decrease in H₂O₂-induced C2C12 cell viability, and decreased reactive oxygen species generation and apoptosis. CB₂ receptor activation also significantly enhanced C2C12 myoblasts differentiation, which was impaired by silencing Nrf2.

SIGNIFICANCE

Overall, CB₂ receptor activation protected skeletal muscle against IRI by ameliorating oxidative damage and promoting early skeletal muscle myogenesis, which was partly via Nrf2 signaling.

The Role of Metabolic Remodeling in Macrophage Polarization and Its Effect on Skeletal Muscle Regeneration

Significance: Macrophages are crucial for tissue homeostasis. Based on their activation, they might display classical/M1 or alternative/M2 phenotypes. M1 macrophages produce pro-inflammatory cytokines, reactive oxygen species (ROS), and nitric oxide (NO). M2 macrophages upregulate arginase-1 and reduce NO and ROS levels; they also release anti-inflammatory cytokines, growth factors, and polyamines, thus promoting angiogenesis and tissue healing. Moreover, M1 and M2 display key metabolic differences; M1 polarization is characterized by an enhancement in glycolysis and in the pentose phosphate pathway (PPP) along with a decreased oxidative phosphorylation (OxPhos), whereas M2 are characterized by an efficient OxPhos and reduced PPP. Recent Advances: The glutamine-related metabolism has been discovered as crucial for M2 polarization. Vice versa, flux discontinuities in the Krebs cycle are considered additional M1 features; they lead to increased levels of immunoresponsive gene 1 and itaconic acid, to isocitrate dehydrogenase 1-downregulation and to succinate, citrate, and isocitrate over-expression. Critical Issues: A macrophage classification problem, particularly in vivo, originating from a gap in the knowledge of the several intermediate polarization statuses between the M1 and M2 extremes, characterizes this field. Moreover, the detailed features of metabolic reprogramming crucial for macrophage polarization are largely unknown; in particular, the role of β-oxidation is highly controversial. Future Directions: Manipulating the metabolism to redirect macrophage polarization might be useful in various pathologies, including an efficient skeletal muscle regeneration. Unraveling the complexity pertaining to metabolic signatures that are specific for the different macrophage subsets is crucial for identifying new compounds that are able to trigger macrophage polarization and that might be used for therapeutical purposes.

Recovery of blood flow regulation in microvascular resistance networks during regeneration of mouse gluteus maximus muscle

KEY POINTS

Skeletal muscle regenerates after injury, however the recovery of its microvascular supply is poorly understood. We injured the gluteus maximus muscle in mice aiming to investigate the recovery of blood flow regulation in microvascular resistance networks. We hypothesized that blood flow regulation recovers in concert with myofibre regeneration. Microvascular perfusion ceased within 1 day post injury and was restored at 5 days coincident with the appearance of new myofibres; however, the resistance network was dilated and unresponsive to vasoactive agents. Spontaneous vasomotor tone, endothelium-dependent dilatation and adrenergic vasoconstriction increased at 10 days in concert with myofibre regeneration. Vasomotor control recovered at 21 days, when regenerated myofibres matured and active force production stabilized. Functional vasodilatation in response to muscle contraction recovered at 35 days. Physiological integrity of microvascular smooth muscle and endothelium recovers in parallel with myofibre regeneration. Additional time is required to restore the efficacy of signalling between myofibres and microvascular networks controlling their oxygen supply.

ABSTRACT

Myofibre regeneration after skeletal muscle injury is well-studied, although little is known about how microvascular perfusion is restored. The present study aimed to evaluate the recovery of blood flow regulation during skeletal muscle regeneration. In anaesthetized male C57BL/6J mice (aged 4 months), the gluteus maximus muscle (GM) was injured by local injection of barium chloride solution (1.2%, 75 μL). Functional integrity of the resistance network was evaluated at 5, 10, 21 and 35 days post-injury vs. Control by measuring internal diameter of feed arteries, first-, second- and third-order arterioles supplying the GM using intravital microscopy. The resting diameters of all branch orders were significantly greater (P < 0.05) than Control at 5 and 10 days and recovered to Control by 21 days, as did spontaneous vasomotor tone. Vasodilatation to ACh and vasoconstriction to phenylephrine (10^-9 to 10^-5  m) were absent at 5 days, increased at 10 days and recovered to Control by 21 days; reactivity improved in a distal-to-proximal gradient. Across branch orders, functional vasodilatation to single tetanic contraction (100 Hz, 500 ms) and to rhythmic twitch contractions (4 Hz, 30 s) was impaired at 5 days, improved through 21 days and was not different from Control at 35 days. Peak force development (g) was 60% of Control at 10 days and recovered by 21 days. Diminished vasomotor tone during the initial stages of regeneration promotes tissue perfusion as myofibre recovery begins. Recovery of tone and vasomotor responses to agonists occur in concert with myofibre regeneration. Delayed recovery of functional vasodilatation indicates that additional time is required to restore signalling between contracting myofibres and their vascular supply.

Changes in Redox Signaling in the Skeletal Muscle with Aging

Reduction in muscle strength with aging is due to both loss of muscle mass (quantity) and intrinsic force production (quality). Along with decreased functional capacity of the muscle, age-related muscle loss is associated with corresponding comorbidities and healthcare costs. Mitochondrial dysfunction and increased oxidative stress are the central driving forces for age-related skeletal muscle abnormalities. The increased oxidative stress in the aged muscle can lead to altered excitation-contraction coupling and calcium homeostasis. Furthermore, apoptosis-mediated fiber loss, atrophy of the remaining fibers, dysfunction of the satellite cells (muscle stem cells), and concomitant impaired muscle regeneration are also the consequences of increased oxidative stress, leading to a decrease in muscle mass, strength, and function of the aged muscle. Here we summarize the possible effects of oxidative stress in the aged muscle and the benefits of physical activity and antioxidant therapy.

Markers of Accelerated Skeletal Muscle Regenerative Response in Murphy Roths Large Mice: Characteristics of Muscle Progenitor Cells and Circulating Factors

The "super-healing" Murphy Roths Large (MRL/MpJ) mouse possesses a superior regenerative capacity for repair of many tissues, which makes it an excellent animal model for studying molecular and cellular mechanisms during tissue regeneration. As the role of muscle progenitor cells (MPCs) in muscle-healing capacity of MRL/MpJ mice has not been previously studied, we investigated the muscle regenerative capacity of MRL/MpJ mice following muscle injury, and the results were compared to results from C57BL/6J (B6) age-matched control mice. Our results show that muscle healing upon cardiotoxin injury was accelerated in MRL/MpJ mice and characterized by reduced necrotic muscle area, reduced macrophage infiltration, and more regenerated myofibers (embryonic myosin heavy chain+/centronucleated fibers) at 3, 5, and 12 days postinjury, when compared to B6 age-matched control mice. These observations were associated with enhanced function of MPCs, including improved cell proliferation, differentiation, and resistance to stress, as well as increased muscle regenerative potential when compared to B6 MPCs. Mass spectrometry of serum proteins revealed higher levels of circulating antioxidants in MRL/MpJ mice when compared to B6 mice. Indeed, we found relatively higher gene expression of superoxide dismutase 1 (Sod1) and catalase (Cat) in MRL/MpJ MPCs. Depletion of Sod1 or Cat by small interfering RNA impaired myogenic potential of MRL/MpJ MPCs, indicating a role for these antioxidants in muscle repair. Taken together, these findings provide evidence that improved function of MPCs and higher levels of circulating antioxidants play important roles in accelerating muscle-healing capacity of MRL/MpJ mice. Stem Cells 2019;37:357-367.

Catechins enhance skeletal muscle performance

Muscle-related disorders, such as sarcopenia and cachexia, caused by aging and chronic diseases can lead to the loss of muscle mass and strength to different degrees, severely affecting human health. Globally, tea is one of the three most popular beverages, and its major active ingredient catechins have been reported to delay muscular atrophy and enhance movement. However, currently, there is no systematic review to elaborate its roles and the associated mechanisms. This article reviews the (1) functions and mechanisms of catechins in the differentiation of myogenic stem cells, biogenesis of mitochondria, synthesis and degradation of proteins, regulation of glucose level, and metabolism of lipids in muscle cells; and (2) effect of catechins on the blood vessels, bones, and nerves that are closely related to the skeletal muscles. Catechins could prevent, mitigate, delay, and even treat muscle-related disorders caused by aging and diseases.

The roles of base excision repair enzyme OGG1 in gene expression

Modifications of DNA strands and nucleobases-both induced and accidental-are associated with unfavorable consequences including loss or gain in genetic information and mutations. Therefore, DNA repair proteins have essential roles in keeping genome fidelity. Recently, mounting evidence supports that 8-oxoguanine (8-oxoG), one of the most abundant genomic base modifications generated by reactive oxygen and nitrogen species, along with its cognate repair protein 8-oxoguanine DNA glycosylase1 (OGG1), has distinct roles in gene expression through transcription modulation or signal transduction. Binding to 8-oxoG located in gene regulatory regions, OGG1 acts as a transcription modulator, which can control transcription factor homing, induce allosteric transition of G-quadruplex structure, or recruit chromatin remodelers. In addition, post-repair complex formed between OGG1 and its repair product-free 8-oxoG increases the levels of active small GTPases and induces downstream signaling cascades to trigger gene expressions. The present review discusses how cells exploit damaged guanine base(s) and the authentic repair protein to orchestrate a profile of various transcriptomes in redox-regulated biological processes.

Cellular mechanisms and signals that coordinate plasma membrane repair

Plasma membrane forms the barrier between the cytoplasm and the environment. Cells constantly and selectively transport molecules across their plasma membrane without disrupting it. Any disruption in the plasma membrane compromises its selective permeability and is lethal, if not rapidly repaired. There is a growing understanding of the organelles, proteins, lipids, and small molecules that help cells signal and efficiently coordinate plasma membrane repair. This review aims to summarize how these subcellular responses are coordinated and how cellular signals generated due to plasma membrane injury interact with each other to spatially and temporally coordinate repair. With the involvement of calcium and redox signaling in single cell and tissue repair, we will discuss how these and other related signals extend from single cell repair to tissue level repair. These signals link repair processes that are activated immediately after plasma membrane injury with longer term processes regulating repair and regeneration of the damaged tissue. We propose that investigating cell and tissue repair as part of a continuum of wound repair mechanisms would be of value in treating degenerative diseases.

Resistance training and L-arginine supplementation are determinant in genomic stability, cardiac contractility and muscle mass development in rats

L-arginine supplementation has been related to increased maximum strength and improvement of hemodynamic parameters in several diseases. The aim of our study was to evaluate the effect of L-arginine supplementation and resistance training on muscle mass, hemodynamic function and DNA damage in healthy rats subjected to a low-arginine concentration diet. Twenty three Wistar rats (290-320g) were divided into 4 groups: Sedentary (SED-Arg, n = 6), Sedentary+Arg (SED+Arg, n = 6), Resistance Training (RT-Arg, n = 5), Resistance Training+Arg (RT+Arg, n = 6). Trained animals performed resistance training protocol in a squat apparatus adapted for rats (4 sets of 10–12 repetitions, 90s of interval, 4x/week, 65–75% of One Maximum Repetition, for 8 weeks). Comet assay was performed to measure DNA damage in leukocytes. The resistance training induced higher muscle mass in trained groups. The L-arginine supplementation increased both gastrocnemius and left ventricle to body mass ratio and increased left ventricle contractility without changing hemodynamic variables. The SED+Arg group showed higher concentration of extracellular heat shock protein 72 (eHSP72) and total testosterone, as well as lower uric acid concentration in blood versus SED-Arg group. The administration of isolated L-arginine supplementation and its association with resistance training promoted less damage in leukocytes DNA. In conclusion, the L-arginine supplementation showed synergistic effect with resistance training regarding leukocyte genomic stability in a low-L-arginine diet scenario.

The role of Pitx2 and Pitx3 in muscle stem cells gives new insights into P38α MAP kinase and redox regulation of muscle regeneration

Skeletal muscle regeneration depends on satellite cells. After injury these muscle stem cells exit quiescence, proliferate and differentiate to regenerate damaged fibres. We show that this progression is accompanied by metabolic changes leading to increased production of reactive oxygen species (ROS). Using Pitx2/3 single and double mutant mice that provide genetic models of deregulated redox states, we demonstrate that moderate overproduction of ROS results in premature differentiation of satellite cells while high levels lead to their senescence and regenerative failure. Using the ROS scavenger, N-Acetyl-Cysteine (NAC), in primary cultures we show that a physiological increase in ROS is required for satellite cells to exit the cell cycle and initiate differentiation through the redox activation of p38α MAP kinase. Subjecting cultured satellite cells to transient inhibition of P38α MAP kinase in conjunction with NAC treatment leads to their rapid expansion, with striking improvement of their regenerative potential in grafting experiments.

Macrophage-derived superoxide production and antioxidant response following skeletal muscle injury

Macrophages are key players of immunity that display different functions according to their activation states. In a regenerative context, pro-inflammatory macrophages (Ly6C^pos) are involved in the mounting of the inflammatory response whereas anti-inflammatory macrophages (Ly6C^neg) dampen the inflammation and promote tissue repair. Reactive oxygen species (ROS) production is a hallmark of tissue injury and of subsequent inflammation as described in a bacterial challenge context. However, whether macrophages produce ROS following a sterile tissue injury is uncertain. In this study, we used complementary in vitro, ex vivo and in vivo experiments in mouse to show that macrophages do not release ROS following a sterile injury in skeletal muscle. Furthermore, expression profiles of genes involved in the response to oxidative stress in Ly6C^pos and Ly6C^neg macrophage subsets did not indicate any antioxidant response in this context. Finally, in vivo, pharmacological antioxidant supplementation with N-Acetyl-cysteine (NAC) following skeletal muscle injury did not alter macrophage phenotype during skeletal muscle regeneration. Overall, these results indicate that following a sterile injury, macrophage-derived ROS release is not involved in the regulation of the inflammatory response in the regenerating skeletal muscle.

The Muscle Stem Cell Niche in Health and Disease

The regulation of stem cells that maintain and regenerate postnatal tissues depends on extrinsic signals originating from their microenvironment, commonly referred to as the stem cell niche. Complex higher-order regulatory interrelationships with the tissue and factors in the systemic circulation are integrated and propagated to the stem cells through the niche. The stem cell niche in skeletal muscle tissue is both a paradigm for a structurally and functionally relatively static niche that maintains stem cell quiescence during tissue homeostasis, and a highly dynamic regenerative niche that is subject to extensive structural remodeling and a flux of different support cell populations. Conditions ranging from aging to chronically degenerative skeletal muscle diseases affect the composition of the niche and thereby impair the regenerative potential of muscle stem cells. A holistic and integrative understanding of the extrinsic mechanisms regulating muscle stem cells in health and disease in a broad systemic context will be imperative for the identification of regulatory hubs in the niche interactome that can be targeted to maintain, restore, or enhance the regenerative capacity of muscle tissue. Here, we review the microenvironmental regulation of muscle stem cells, summarize how niche dysfunction can contribute to disease, and discuss emerging therapeutic implications.

The physiopathologic role of oxidative stress in skeletal muscle

Muscle senescence is a complex mechanism that is usually associated with a decrease in mass, strength and velocity of contraction. This state, known as sarcopenia, is a multifactorial process and it may be the consequence of several events, including accumulation of oxidative stress. The role of oxidative stress in the physiopathology of skeletal muscle is quite complex. Transiently increased levels of oxidative stress might reflect a potentially health promoting process, while an uncontrolled accumulation might have pathological implication. The physiopathological role of oxidative stress on skeletal muscle, its involvement in aging-induced sarcopenia, and potential countermeasures will be discussed.

Cyclooxygenase-2 Inhibition Limits Angiotensin II-Induced DNA Oxidation and Protein Nitration in Humans

Compared to other cyclooxygenase-2 inhibitors, celecoxib is associated with a lower cardiovascular risk, though the mechanism remains unclear. Angiotensin II is an important mediator of oxidative stress in the pathophysiology of vascular disease. Cyclooxygenase-2 may modify the effects of angiotensin II though this has never been studied in humans. The purpose of the study was to test the effects of selective cyclooxygenase-2 inhibition on plasma measures of oxidative stress, the vasoconstrictor endothelin-1, and nitric oxide metabolites, both at baseline and in respose to Angiotensin II challenge in healthy humans. Measures of 8-hydroxydeoxyguanosine, advanced oxidation protein products, nitrotyrosine, endothelin-1, and nitric oxide metabolites were assessed from plasma samples drawn at baseline and in response to graded angiotensin II infusion (3 ng/kg/min × 30 min, 6 ng/kg/min × 30 min) before and after 14 days of cyclooxygenase-2 inhibition in 14 healthy subjects (eight male, six female) in high salt balance, a state of maximal renin angiotensin system suppression. Angiotensin II infusion significantly increased plasma oxidative stress compared to baseline (8-hydroxydeoxyguanosine; +17%; advanced oxidation protein products; +16%), nitrotyrosine (+76%). Furthermore, levels of endothelin-1 levels were significantly increased (+115%) and nitric oxide metabolites were significantly decreased (−20%). Cycloxygenase-2 inhibition significantly limited the increase in 8-hydroxydeoxyguanosine, nitrotyrosine and the decrease in nitric oxide metabolites induced by angiotensin II infusion, though no changes in advanced oxidation protein products and endothelin-1 concentrations were observed. Cyclooxygenase-2 inhibition with celecoxib partially limited the angiotensin II-mediated increases in markers of oxidative stress in humans, offering a potential physiological pathway for the improved cardiovascular risk profile of this drug.