Effect of NADPH oxidase 1 and 4 blockade in activated human retinal endothelial cells

Single-Atom-Based Nanoenzyme in Tissue Repair

Since the discovery of ferromagnetic nanoparticles Fe3O4 that exhibit enzyme-like activity in 2007, the research on nanoenzymes has made significant progress. With the in-depth study of various nanoenzymes and the rapid development of related nanotechnology, nanoenzymes have emerged as a promising alternative to natural enzymes. Within nanozymes, there is a category of metal-based single-atom nanozymes that has been rapidly developed due to low cast, convenient preparation, long storage, less immunogenicity, and especially higher efficiency. More importantly, single-atom nanozymes possess the capacity to scavenge reactive oxygen species through various mechanisms, which is beneficial in the tissue repair process. Herein, this paper systemically highlights the types of metal single-atom nanozymes, their catalytic mechanisms, and their recent applications in tissue repair. The existing challenges are identified and the prospects of future research on nanozymes composed of metallic nanomaterials are proposed. We hope this review will illuminate the potential of single-atom nanozymes in tissue repair, encouraging their sequential clinical translation.

Redox Regulation of Immunometabolism in Microglia Underpinning Diabetic Retinopathy

Diabetic retinopathy (DR) is the leading cause of visual impairment and blindness among the working-age population. Microglia, resident immune cells in the retina, are recognized as crucial drivers in the DR process. Microglia activation is a tightly regulated immunometabolic process. In the early stages of DR, the M1 phenotype commonly shifts from oxidative phosphorylation to aerobic glycolysis for energy production. Emerging evidence suggests that microglia in DR not only engage specific metabolic pathways but also rearrange their oxidation-reduction (redox) system. This redox adaptation supports metabolic reprogramming and offers potential therapeutic strategies using antioxidants. Here, we provide an overview of recent insights into the involvement of reactive oxygen species and the distinct roles played by key cellular antioxidant pathways, including the NADPH oxidase 2 system, which promotes glycolysis via enhanced glucose transporter 4 translocation to the cell membrane through the AKT/mTOR pathway, as well as the involvement of the thioredoxin and nuclear factor E2-related factor 2 antioxidant systems, which maintain microglia in an anti-inflammatory state. Therefore, we highlight the potential for targeting the modulation of microglial redox metabolism to offer new concepts for DR treatment.

Setanaxib mitigates oxidative damage following retinal ischemia-reperfusion via NOX1 and NOX4 inhibition in retinal ganglion cells

Glaucoma, a prevalent cause of permanent visual impairment worldwide, is characterized by the progressive degeneration of retinal ganglion cells (RGCs). NADPH oxidase (NOX) 1 and NOX4 are pivotal nodes in various retinal diseases. Setanaxib, a potent and highly selective inhibitor of NOX1 and NOX4, can impede the progression of various diseases. This study investigated the efficacy of setanaxib in ameliorating retinal ischemia-reperfusion (I/R) injury and elucidated its underlying mechanisms. The model of retinal I/R induced by acute intraocular hypertension and the oxygen-glucose deprivation/reoxygenation (OGD/R) model of primary RGCs were established. By suppressing NOX1 and NOX4 expression in RGCs, setanaxib mitigated I/R-induced retinal neuronal loss, structural disruption, and dysfunction. Setanaxib reduced TUNEL-positive cells, upregulated Bcl-2, and inhibited Bax, Bad, and cleaved-caspase-3 overexpression after I/R injury in vitro and in vivo. Moreover, setanaxib also significantly reduced cellular senescence, as demonstrated by downregulating SA-β-gal-positive and p16-INK4a expression. Furthermore, setanaxib significantly suppressed ROS production, Hif-1α and FOXO1 upregulation, and NRF2 downregulation in damaged RGCs. These findings highlight that the setanaxib effectively inhibited NOX1 and NOX4, thereby regulating ROS production and redox signal activation. This inhibition further prevents the activation of apoptosis and senescence related factors in RGCs, ultimately protecting them against retinal I/R injury. Consequently, setanaxib exhibits promising potential as a therapeutic intervention for glaucoma.

Nox4 as a novel therapeutic target for diabetic vascular complications

Diabetic vascular complications can affect both microvascular and macrovascular. Diabetic microvascular complications, such as diabetic nephropathy, diabetic retinopathy, diabetic neuropathy, and diabetic cardiomyopathy, are believed to be caused by oxidative stress. The Nox family of NADPH oxidases is a significant source of reactive oxygen species and plays a crucial role in regulating redox signaling, particularly in response to high glucose and diabetes mellitus. This review aims to provide an overview of the current knowledge about the role of Nox4 and its regulatory mechanisms in diabetic microangiopathies. Especially, the latest novel advances in the upregulation of Nox4 that aggravate various cell types within diabetic kidney disease will be highlighted. Interestingly, this review also presents the mechanisms by which Nox4 regulates diabetic microangiopathy from novel perspectives such as epigenetics. Besides, we emphasize Nox4 as a therapeutic target for treating microvascular complications of diabetes and summarize drugs, inhibitors, and dietary components targeting Nox4 as important therapeutic measures in preventing and treating diabetic microangiopathy. Additionally, this review also sums up the evidence related to Nox4 and diabetic macroangiopathy.

Sustained Upregulation of Endothelial Nox4 Mediates Retinal Vascular Pathology in Type 1 Diabetes

NADPH oxidase 4 (Nox4) is a major source of reactive oxygen species (ROS) in retinal endothelial cells (ECs) and is upregulated under hyperglycemic and hypoxic conditions. However, the role of endothelial Nox4 upregulation in long-term retinal blood vessel damage in diabetic retinopathy (DR) remains undefined. Here, we attempted to address this question using humanized EC-specific Nox4 transgenic (hNox4EC-Tg) and EC-specific Nox4 knockout (Nox4EC-KO) mouse models. Our results show that hNox4EC-Tg mice at age of 10-12 months exhibited increased tortuosity of retinal blood vessels, focal vascular leakage, and acellular capillary formation. In vitro study revealed enhanced apoptosis in brain microvascular ECs derived from hNox4EC-Tg mice, concomitant with increased mitochondrial ROS, elevated lipid peroxidation, decreased mitochondrial membrane potential, and reduced mitochondrial respiratory function. In contrast, EC-specific deletion of Nox4 decreased mitochondrial ROS generation, alleviated mitochondrial damage, reduced EC apoptosis, and protected the retina from acellular capillary formation and vascular hyperpermeability in a streptozotocin-induced diabetes mouse model. These findings suggest that sustained upregulation of Nox4 in the endothelium contributes to retinal vascular pathology in diabetes, at least in part, through impairing mitochondrial function. Normalization of Nox4 expression in ECs may provide a new approach for prevention of vascular injury in DR.

The Effects of Nicotinamide Adenine Dinucleotide Phosphate (NADPH) Oxidase and Erythropoietin, and Their Interactions in Angiogenesis: Implications in Retinopathy of Prematurity

Retinopathy of prematurity (ROP) is a leading cause of vision impairment and blindness in premature infants. Oxidative stress is implicated in its pathophysiology. NADPH oxidase (NOX), a major enzyme responsible for reactive oxygen species (ROS) generation in endothelial cells, has been studied for its involvement in physiologic and pathologic angiogenesis. Erythropoietin (EPO) has gained interest recently due to its tissue protective and angiogenic effects, and it has been shown to act as an antioxidant. In this review, we summarize studies performed over the last five years regarding the role of various NOXs in physiologic and pathologic angiogenesis. We also discuss the effect of EPO in tissue and vasoprotection, and the intersection of EPO and NOX-mediated oxidative stress in angiogenesis and the pathophysiology of ROP.

Mitoquinone intravitreal injection ameliorates retinal ischemia-reperfusion injury in rats involving SIRT1/Notch1/NADPH axis

Retinal ischemia-reperfusion injury (RIRI) is an important pathological process of many ocular diseases. Mitoquinone (MitoQ), a mitochondrial targeted antioxidant, is a potential compound for therapeutic development of RIRI. This study observed the effect of MitoQ on RIRI, and further explored its possible molecular mechanism. Temporary increase in intraocular pressure was used to establish rat model of RIRI to observe the effect of MitoQ treatment on retinal function, pathological injury, oxidative stress, inflammation and apoptosis. Immunohistochemistry and Western blot were used to detect expressions of cleaved caspase 3, B cell leukemia/lymphoma 2 associated X (Bax), nicotinamide adenine dinucleotide phosphate oxidase (NOX1), NOX4, cleaved-Notch 1, hairy and enhancer of split 1 (Hes1), and sirtuin 1 (SIRT 1) in retina were detected by immunohistochemistry and Western blot. MitoQ treatment significantly improved retinal function and pathological injury, inhibited the over-production of reactive oxygen species, increased the expression of superoxide dismutase 1 (SOD 1), suppressed the releases of inflammatory cytokines, and inhibited retinal cells apoptosis. MitoQ also down-regulated the expressions of cleaved caspase 3, Bax, NOX 1, NOX 4, cleaved-Notch 1, and Hes 1, increased the expression of SIRT 1 protein and its activity. These effects were significantly reversed by SIRT1 inhibitor EX527. Our data suggests that MitoQ, as a potentially effective drug for improving RIRI, may act through the SIRT1/Notch1/NADPH signal axis.

Role of Oxidative Stress in Retinal Disease and the Early Intervention Strategies: A Review

The retina, owing to its cellular anatomy and physical location, is susceptible to generating reactive oxygen species (ROS), which are associated with several major retinal diseases. When ROS exceeds the body's natural antioxidants, the retina is in a state of oxidative stress, which is recognized as the pathogenesis of retinal diseases. The early stage of the pathogenic process is an adaptive change in which oxidative stress and endogenous defense mechanisms occur. If no treatment is applied, the retinal diseases will progress to the pathological stage with neuronal and vascular dysfunction or damage and even blindness. This review summarizes the role of oxidative stress in several common retinal diseases, including retinitis pigmentosa, age-related macular degeneration, diabetic retinopathy, glaucoma, and retinopathy of prematurity. In addition, we discuss the early intervention strategies for these diseases. An outline is provided to identify potential intervention targets for further research. Early intervention for retinal diseases is necessary and urgent and may offer hope to improve patients' quality of life through functional vision.

Long-term inhibition of UCHL1 decreases hypertension and retinopathy in spontaneously hypertensive rats

OBJECTIVE

To investigate the role of the deubiquitinase ubiquitin C-terminal hydrolase L1 (UCHL1) in hypertension and retinopathy in the spontaneously hypertensive rat (SHR).

METHODS

Wistar-Kyoto (WKY) rats and SHRs were administered the UCHL1 inhibitor LDN57444 (20 μg/kg/day) for 4 months. Pathological changes were detected with hematoxylin and eosin, immunofluorescence, and dihydroethidium staining. The mRNA and protein expression of UCHL1 were examined by real-time PCR and immunoblotting analysis.

RESULTS

At 6 months of age, SHRs showed significantly increased mRNA and protein levels of UCHL1 in the retina compared with WKY rats. Moreover, SHRs exhibited significantly increased central retinal thickness, inflammation, and reactive oxygen species production compared with WKY rats, and these effects were markedly attenuated by systemic administration of the UCHL1 inhibitor LDN57444. The beneficial effects of LDN57444 were possibly associated with reduced blood pressure and the inactivation of several signaling pathways.

CONCLUSION

UCHL1 is involved in hypertension and retinopathy in SHRs, suggesting that UCHL1 may be used as a potential therapeutic target for treating hypertensive retinopathy.

Diabetic Retinopathy and NADPH Oxidase-2: A Sweet Slippery Road

Diabetic retinopathy remains the leading cause of vision loss in working-age adults. The multi-factorial nature of the disease, along with the complex structure of the retina, have hindered in elucidating the exact molecular mechanism(s) of this blinding disease. Oxidative stress appears to play a significant role in its development and experimental models have shown that an increase in cytosolic Reacttive Oxygen Speies (ROS) due to the activation of NADPH oxidase 2 (Nox2), is an early event, which damages the mitochondria, accelerating loss of capillary cells. One of the integral proteins in the assembly of Nox2 holoenzyme, Rac1, is also activated in diabetes, and due to epigenetic modifications its gene transcripts are upregulated. Moreover, addition of hyperlipidemia in a hyperglycemic milieu (type 2 diabetes) further exacerbates Rac1-Nox2-ROS activation, and with time, this accelerates and worsens the mitochondrial damage, ultimately leading to the accelerated capillary cell loss and the development of diabetic retinopathy. Nox2, a multicomponent enzyme, is a good candidate to target for therapeutic interventions, and the inhibitors of Nox2 and Rac1 (and its regulators) are in experimental or clinical trials for other diseases; their possible use to prevent/halt retinopathy will be a welcoming sign for diabetic patients.

NOX Inhibitors: From Bench to Naxibs to Bedside

Reactive oxygen species (ROS) are ubiquitous metabolic products and important cellular signaling molecules that contribute to several biological functions. Pathophysiology arises when ROS are generated either in excess or in cell types or subcellular locations that normally do not produce ROS or when non-physiological types of ROS (e.g., superoxide instead of hydrogen peroxide) are formed. In the latter scenario, antioxidants were considered as the apparent remedy but, clinically, have consistently failed and even sometimes induced harm. The obvious reason for that is the non-selective ROS scavenging effects of antioxidants which interfere with both qualities of ROS, physiological and pathological. Therefore, it is essential to overcome this "antidote or neutralizer" strategy. We here review the most promising alternative approach by identifying the disease-relevant enzymatic sources of ROS, target these selectively, but leave physiological ROS signaling through other sources intact. Among all ROS sources, NADPH oxidases (NOX1-5 and DUOX1-2) stand out as their sole function is to produce ROS, whereas most other enzymatic sources only produce ROS as a by-product or upon biochemical uncoupling or damage. This qualifies NOXs as the main potential drug-target candidates in diseases associated with dysfunction in ROS signaling. As a reflection of this, the development of several NOX inhibitors has taken place. Recently, the WHO approved a new stem, "naxib," which refers to NADPH oxidase inhibitors, and thereby recognized NOX inhibitors as a new therapeutic class. This has been announced while clinical trials with the first-in-class compound, setanaxib (initially known as GKT137831) had been initiated. We also review the differences between the seven NOX family members in terms of structure and function in health and disease and then focus on the most advanced NOX inhibitors with an exclusive focus on clinically relevant validations and applications. Therapeutically relevant NADPH oxidase isoforms type 1, 2, 4, and 5 (NOX1, NOX2, NOX4, NOX5). Of note, NOX5 is not present in mice and rats and thus pre-clinically less studied. NOX2, formerly termed gp91^phox, has been correlated with many, too many, diseases and is rather relevant as genetic deficiency in chronic granulomatous disease (CGD), treated by gene therapy. Overproduction of ROS through NOX1, NOX4, and NOX5 leads to the indicated diseases states including atherosclerosis (red), a condition where NOX4 is surprisingly protective.

Oxidative Stress and Vascular Dysfunction in the Retina: Therapeutic Strategies

Many retinal diseases, such as diabetic retinopathy, glaucoma, and age-related macular (AMD) degeneration, are associated with elevated reactive oxygen species (ROS) levels. ROS are important intracellular signaling molecules that regulate numerous physiological actions, including vascular reactivity and neuron function. However, excessive ROS formation has been linked to vascular endothelial dysfunction, neuron degeneration, and inflammation in the retina. ROS can directly modify cellular molecules and impair their function. Moreover, ROS can stimulate the production of inflammatory cytokines, such as tumor necrosis factor-alpha (TNF-α) and interleukin-6 (IL-6) causing inflammation and cell death. However, there are various compounds with direct or indirect antioxidant activity that have been used to reduce ROS accumulation in animal models and humans. In this review, we report on the physiological and pathophysiological role of ROS in the retina with a special focus on the vascular system. Moreover, we present therapeutic approaches for individual retinal diseases targeting retinal signaling pathways involving ROS.

Lutein and zeaxanthin attenuates VEGF-induced neovascularisation in human retinal microvascular endothelial cells through a Nox4-dependent pathway

Age-related macular degeneration (AMD) and proliferative diabetic retinopathy (DR) are two of the most common and severe causes of vision loss in the population. Both conditions are associated with excessive levels of vascular endothelial growth factor (VEGF) in the eye which results in an increase in the formation of new blood vessels through a process called neovascularisation. As such, anti-VEGF therapies are currently utilised as a treatment for patients with AMD however they are associated with painful administration of injections and potential degeneration of healthy endothelium. There is therefore growing interest in alternate treatment options to reduce neovascularisation in the eye. The use of carotenoids, lutein (L) and zeaxanthin (Z), has been shown to improve vision loss parameters in patients with AMD, however the underlying mechanisms are not well-understood. We studied the impact of these compounds on neovascularisation processes using an in vitro cell model of the retinal microvascular endothelium. Our findings show that L and Z reduced VEGF-induced tube formation whilst, in combination (5:1 ratio), the compounds significantly blocked VEGF-induced neovascularisation. The carotenoids, individually and in combination, reduced VEGF-induced oxidative stress concomitant with increased activity of the NADPH oxidase, Nox4. We further demonstrated that the Nox4 inhibitor, GLX7013114, attenuated the protective effect of L and Z. Taken together, these findings indicate the protective effect of the carotenoids, L and Z, in reducing VEGF-mediated neovascularisation via a Nox4-dependent pathway. These studies implicate the potential for these compounds to be used as a therapeutic approach for patients suffering from AMD and proliferative DR.

The TSPO-NOX1 axis controls phagocyte-triggered pathological angiogenesis in the eye

Aberrant immune responses including reactive phagocytes are implicated in the etiology of age-related macular degeneration (AMD), a major cause of blindness in the elderly. The translocator protein (18 kDa) (TSPO) is described as a biomarker for reactive gliosis, but its biological functions in retinal diseases remain elusive. Here, we report that tamoxifen-induced conditional deletion of TSPO in resident microglia using Cx3cr1CreERT2:TSPOfl/fl mice or targeting the protein with the synthetic ligand XBD173 prevents reactivity of phagocytes in the laser-induced mouse model of neovascular AMD. Concomitantly, the subsequent neoangiogenesis and vascular leakage are prevented by TSPO knockout or XBD173 treatment. Using different NADPH oxidase-deficient mice, we show that TSPO is a key regulator of NOX1-dependent neurotoxic ROS production in the retina. These data define a distinct role for TSPO in retinal phagocyte reactivity and highlight the protein as a drug target for immunomodulatory and antioxidant therapies for AMD.

Spermine oxidase: A promising therapeutic target for neurodegeneration in diabetic retinopathy

Diabetic Retinopathy (DR), is a significant public health issue and the leading cause of blindness in working-aged adults worldwide. The vision loss associated with DR affects patients' quality of life and has negative social and psychological effects. In the past, diabetic retinopathy was considered as a vascular disease; however, it is now recognized to be a neuro-vascular disease of the retina. Current therapies for DR, such as laser photocoagulation and anti-VEGF therapy, treat advanced stages of the disease, particularly the vasculopathy and have adverse side effects. Unavailability of effective treatments to prevent the incidence or progression of DR is a major clinical problem. There is a great need for therapeutic interventions capable of preventing retinal damage in DR patients. A growing body of evidence shows that neurodegeneration is an early event in DR pathogenesis. Therefore, studies of the underlying mechanisms that lead to neurodegeneration are essential for identifying new therapeutic targets in the early stages of DR. Deregulation of the polyamine metabolism is implicated in various neurodegenerative diseases, cancer, renal failure, and diabetes. Spermine Oxidase (SMOX) is a highly inducible enzyme, and its dysregulation can alter polyamine homeostasis. The oxidative products of polyamine metabolism are capable of inducing cell damage and death. The current review provides insight into the SMOX-regulated molecular mechanisms of cellular damage and dysfunction, and its potential as a therapeutic target for diabetic retinopathy. Structural and functional changes in the diabetic retina and the mechanisms leading to neuronal damage (excitotoxicity, loss of neurotrophic factors, oxidative stress, mitochondrial dysfunction etc.) are also summarized in this review. Furthermore, existing therapies and new approaches to neuroprotection are discussed.

Putative Nox2 inhibitors worsen homocysteine-induced impaired acetylcholine-mediated relaxation

BACKGROUND AND AIM

Increased homocysteine (Hcy) is associated with coronary artery disease (CAD). Hcy increases reactive oxygen species (ROS) via NADPH oxidases (Nox), reducing acetylcholine-mediated vasorelaxation. We aimed to determine if putative Nox2 inhibitors prevent Hcy-impaired acetylcholine-mediated vasorelaxation.

METHODS AND RESULTS

New Zealand White rabbit and wild-type (C57BL/6) and Nox2^-/- (NOX) mice aortic rings were mounted in organ baths. Rabbit rings were incubated with either apocynin (10 μM), gp91ds-tat (GP, 1 μM) or PhoxI2 (1 μM) and mice rings GP (1 μM) only. Some rabbit rings were incubated with 3 mM Hcy, before pre-contraction, followed by dose-response relaxation to acetylcholine (ACh; 0.01μM-10μM). In rabbit rings treated with Hcy and GP, O₂‾ donor pyrogallol (1 μM) or Akt activator SC79 (1 μM) was added 5 min before ACh. Mice rings were used to compare Nox2 deletion to normal acetylcholine-mediated relaxation. In rabbits, Hcy reduced acetylcholine-mediated relaxation vs. control (p < 0.0001). Treatment + Hcy reduced relaxation compared with treatment alone (p < 0.0001). Pyrogallol and SC79 reversed the response of GP + Hcy (p = 0.0001). In mice, Nox2 deletion reduced acetylcholine-mediated vasorelaxation. Rabbit tissue analysis revealed that Hcy reduced eNOS phosphorylation at Thr⁴⁹⁵ and increased eNOS phosphorylation at Ser¹¹⁷⁷; no further alteration at Thr⁴⁹⁵ was observed with GP. In contrast, GP prevented increased phosphorylation at Ser¹¹⁷⁷.

CONCLUSIONS

Apocynin, GP and PhoxI2 worsens acetylcholine-mediated vascular relaxation in rabbit aorta, which is supported by results from mouse Nox2 deletion data. These inhibitors worsen Hcy-induced vascular dysfunction, suggesting that current putative Nox2 inhibitors might not be useful in treating HHcy.

Diabetic retinopathy: Focus on NADPH oxidase and its potential as therapeutic target

Diabetic retinopathy is a common complication of diabetes that affects the retina due to a sustained high blood sugar level. Recent studies have demonstrated that high glucose-driven oxidative stress plays an important role in the microvascular complications of retina in diabetes. Oxidative stress occurs due to the excess of reactive oxygen species, which causes oxidative damage to retina, leading to the leak of tiny blood vessels, or acts as signaling molecules to trigger neovascularization, resulting in new fragile vessels. NADPH oxidase (NOX) is a key enzymatic source of reactive oxygen species in the retina, and it is involved in the early as well as the advanced stage of diabetic retinopathy. To date, at least 7 NOX isoforms, including NOX1 to NOX5, dual oxidase1 and dual oxidase 2, have been identified. It has been shown that NOX isoforms exert different roles in the pathogenesis of diabetic retinopathy. Intervention of NOX by its inhibitors or modulators shows beneficial effect on improving the retinal functions in the models of diabetic retinopathy in vivo or in vitro. Thereby, NOX might be a potential target for the therapy of diabetic retinopathy. The present review focuses on the role of NOX, particularly the NOX isoforms, in promoting the development of diabetic retinopathy. In addition, NOX isoforms as potential targets for therapy of diabetic retinopathy are also discussed.

G Protein-Coupled Estrogen Receptor Protects From Angiotensin II-Induced Increases in Pulse Pressure and Oxidative Stress

Our previous work showed that the G protein-coupled estrogen receptor (GPER) is protective in the vasculature and kidneys during angiotensin (Ang) II-dependent hypertension by inhibiting oxidative stress. The goal of the current study was to assess the impact of GPER deletion on sex differences in Ang II-induced hypertension and oxidative stress. Male and female wildtype and GPER knockout mice were implanted with radiotelemetry probes for measurement of baseline blood pressure before infusion of Ang II (700 ng/kg/min) for 2 weeks. Mean arterial pressure was increased to the same extent in all groups, but female wildtype mice were protected from Ang II-induced increases in pulse pressure, aortic wall thickness, and Nox4 mRNA. In vitro studies using vascular smooth muscle cells found that pre-treatment with the GPER agonist G-1 inhibited Ang II-induced ROS and NADP/NADPH. Ang II increased while G-1 decreased Nox4 mRNA and protein. The effects of Ang II were blocked by losartan and Nox4 siRNA, while the effects of G-1 were inhibited by adenylyl cyclase inhibition and mimicked by phosphodiesterase inhibition. We conclude that during conditions of elevated Ang II, GPER via the cAMP pathway suppresses Nox4 transcription to limit ROS production and prevent arterial stiffening. Taken together with our previous work, this study provides insight into how acute estrogen signaling via GPER provides cardiovascular protection during Ang II hypertension and potentially other diseases characterized by increased oxidative stress.