Bilateral Paraventricular Nucleus Upregulation of Extracellular Superoxide Dismutase Decreases Blood Pressure by Regulation of the NLRP3 and Neurotransmitters in Salt-Induced Hypertensive Rats

Aims: Long-term salt diet induces the oxidative stress in the paraventricular nucleus (PVN) and increases the blood pressure. Extracellular superoxide dismutase (Ec-SOD) is a unique antioxidant enzyme that exists in extracellular space and plays an essential role in scavenging excessive reactive oxygen species (ROS). However, the underlying mechanism of Ec-SOD in the PVN remains unclear.Methods: Sprague–Dawley rats (150–200 g) were fed either a high salt diet (8% NaCl, HS) or normal salt diet (0.9% NaCl, NS) for 6 weeks. Each group of rats was administered with bilateral PVN microinjection of AAV-Ec-SOD (Ec-SOD overexpression) or AAV-Ctrl for the next 6 weeks.Results: High salt intake not only increased mean arterial blood pressure (MAP) and the plasma noradrenaline (NE) but also elevated the NAD(P)H oxidase activity, the NAD(P)H oxidase components (NOX2 and NOX4) expression, and ROS production in the PVN. Meanwhile, the NOD-like receptor protein 3 (NLRP3)–dependent inflammatory proteins (ASC, pro-cas-1, IL-β, CXCR, CCL2) expression and the tyrosine hydroxylase (TH) expression in the PVN with high salt diet were higher, but the GSH level, Ec-SOD activity, GAD67 expression, and GABA level were lower than the NS group. Bilateral PVN microinjection of AAV-Ec-SOD decreased MAP and the plasma NE, reduced NAD(P)H oxidase activity, the NOX2 and NOX4 expression, and ROS production, attenuated NLRP3-dependent inflammatory expression and TH, but increased GSH level, Ec-SOD activity, GAD67 expression, and GABA level in the PVN compared with the high salt group.Conclusion: Excessive salt intake not only activates oxidative stress but also induces the NLRP3-depensent inflammation and breaks the balance between inhibitory and excitability neurotransmitters in the PVN. Ec-SOD, as an essential anti-oxidative enzyme, eliminates the ROS in the PVN and decreases the blood pressure, probably through inhibiting the NLRP3-dependent inflammation and improving the excitatory neurotransmitter release in the PVN in the salt-induced hypertension.

Neonatal Extracellular Superoxide Dismutase Knockout Mice Increase Total Superoxide Dismutase Activity and VEGF Expression after Chronic Hyperoxia

Bronchopulmonary dysplasia (BPD) is a common lung disease affecting premature infants that develops after exposure to supplemental oxygen and reactive oxygen intermediates. Extracellular superoxide dismutase (SOD3) is an enzyme that processes superoxide radicals and has been shown to facilitate vascular endothelial growth factor (VEGF) and nitric oxide (NO) signaling in vascular endothelium. We utilized a mouse model of neonatal hyperoxic lung injury and SOD3 knockout (KO) mice to evaluate its function during chronic hyperoxia exposure. Wild-type age-matched neonatal C57Bl/6 (WT) and SOD3−/− (KO) mice were placed in normoxia (21% FiO2, RA) or chronic hyperoxia (75% FiO2, O2) within 24 h of birth for 14 days continuously and then euthanized. Lungs were harvested for histologic evaluation, as well as comparison of antioxidant enzyme expression, SOD activity, VEGF expression, and portions of the NO signaling pathway. Surprisingly, KO-O2 mice survived without additional alveolar simplification, microvascular remodeling, or nuclear oxidation when compared to WT-O2 mice. KO-O2 mice had increased total SOD activity and increased VEGF expression when compared to WT-O2 mice. No genotype differences were noted in intracellular antioxidant enzyme expression or the NO signaling pathway. These results demonstrate that SOD3 KO mice can survive prolonged hyperoxia without exacerbation of alveolar or vascular phenotype.

Impact of EcSOD Perturbations in Cancer Progression

Reactive oxygen species (ROS) are a normal byproduct of cellular metabolism and are required components in cell signaling and immune responses. However, an imbalance of ROS can lead to oxidative stress in various pathological states. Increases in oxidative stress are one of the hallmarks in cancer cells, which display an altered metabolism when compared to corresponding normal cells. Extracellular superoxide dismutase (EcSOD) is an antioxidant enzyme that catalyzes the dismutation of superoxide anion (O2−) in the extracellular environment. By doing so, this enzyme provides the cell with a defense against oxidative damage by contributing to redox balance. Interestingly, EcSOD expression has been found to be decreased in a variety of cancers, and this loss of expression may contribute to the development and progression of malignancies. In addition, recent compounds can increase EcSOD activity and expression, which has the potential for altering this redox signaling and cellular proliferation. This review will explore the role that EcSOD expression plays in cancer in order to better understand its potential as a tool for the detection, predicted outcomes and potential treatment of malignancies.

Extracellular Superoxide Dismutase (EC-SOD) Regulates Gene Methylation and Cardiac Fibrosis During Chronic Hypoxic Stress

Chronic hypoxic stress induces epigenetic modifications mainly DNA methylation in cardiac fibroblasts, inactivating tumor suppressor genes (RASSF1A) and activating kinases (ERK1/2) leading to fibroblast proliferation and cardiac fibrosis. The Ras/ERK signaling pathway is an intracellular signal transduction critically involved in fibroblast proliferation. RASSF1A functions through its effect on downstream ERK1/2. The antioxidant enzyme, extracellular superoxide dismutase (EC-SOD), decreases oxidative stress from chronic hypoxia, but its effects on these epigenetic changes have not been fully explored. To test our hypothesis, we used an in-vitro model: wild-type C57B6 male mice (WT) and transgenic males with an extra copy of human hEC-SOD (TG). The studied animals were housed in hypoxia (10% O2) for 21 days. The right ventricular tissue was studied for cardiac fibrosis markers using RT-PCR and Western blot analyses. Primary C57BL6 mouse cardiac fibroblast tissue culture was used to study the in-vitro model, the downstream effects of RASSF-1 expression and methylation, and its relation to ERK1/2. Our findings showed a significant increase in cardiac fibrosis markers: Collagen 1, alpha smooth muscle actin (ASMA), and SNAIL, in the WT hypoxic animals as compared to the TG hypoxic group (p < 0.05). The expression of DNA methylation enzymes (DNMT 1&3b) was significantly increased in the WT hypoxic mice as compared to the hypoxic TG mice (p < 0.001). RASSF1A expression was significantly lower and ERK1/2 was significantly higher in hypoxia WT compared to the hypoxic TG group (p < 0.05). Use of SiRNA to block RASSF1A gene expression in murine cardiac fibroblast tissue culture led to increased fibroblast proliferation (p < 0.05). Methylation of the RASSF1A promoter region was significantly reduced in the TG hypoxic group compared to the WT hypoxic group (0.59 vs. 0.75, respectively). Based on our findings, we can speculate that EC-SOD significantly attenuates RASSF1A gene methylation and can alleviate cardiac fibrosis induced by hypoxia.

The impact of SOD3 on prostatic diseases: elevated SOD3 is a novel biomarker for the diagnosis of chronic nonbacterial prostatiti

Prostate is the most common gland for the three major diseases in men, such as chronic nonbacterial prostatitis (CNP), benign prostatic hyperplasia (BPH) and prostate cancer (PCa). However, there is lack of ideal biomarker for diagnosis with prostatic diseases. This prospective study quantified extracellular superoxide dismutase (SOD3) levels in serum or expressed prostatic secretion (EPS) with CNP, and in the prostatic tissues with BPH or PCa, to evaluate SOD3 as possible surrogate markers for diagnosis and treatment efficacy. The diagnostic ability of SOD3 with CNP was estimated by ROC analysis. The potential function of SOD3 in prostatic disoders was further investigated via bioinformatic analysis. As a result, SOD3 was significantly increased in CNP and BPH, but dereased in PCa compared to controls. SOD3 was significantly elevated in patients with CNP III (6.491643 ± 1.592292, P༜0.001), CNP IV (8.617879 ± 1.535176, P༜0.001) compared to normal controls (4.705892 ± 1.484917), discriminating CNP versus normal controls (accuracy = 0.831, 95%CI: 0.726–0.937, P༜0.001), CNP III versus CNP IV (accuracy = 0.868, 95%CI: 0.716–0.940, P༜0.001). Furthermore, SOD3 in serum were associated with clinical characteristics of patients with CNP including plevic pain, blood pressure and lecithin/leukocyte in EPS. Functionally, SOD3 mainly interacted with CP, DSG2, RBP4, and CFP via spercific amino acid residue, and participated in the signal pathway of superoxide radicals degradation and apoptotic execution phase. Our findings suggested that SOD3 and its interactors might play an important role in prostatic diseases, and SOD3 could be an ideal diagnostic marker and therapeutic target for CNP.

The Extracellular Superoxide Dismutase Sod5 From Fusarium oxysporum Is Localized in Response to External Stimuli and Contributes to Fungal Pathogenicity

Reactive oxygen species (ROS) produced by hosts serve as a general defense mechanism against various pathogens. At the interaction site between the host and pathogen, host cells rapidly accumulate high concentrations of ROS, called the oxidative burst, that damage and kill the invading microbes. However, successful pathogens usually survive in a high ROS environment and have evolved strategies to overcome these detrimental effects. Here we characterized the biological function of the extracellular superoxide dismutase (SOD) FoSod5 from Fusarium oxysporum f. sp. vasinfectum. FoSOD5 is strongly up-regulated during infection of cotton, and a ΔFoSOD5 mutant was significantly reduced in virulence on cotton. Purified 6 × His-FoSod5 could significantly inhibit the reduction of NBT and WST-1, indicating that FoSod5 was a functional SOD protein. Based on CRISPR/Cas9 technology, several different FoSod5 variants were generated and used to assess the secretion, expression, and subcellular localization of FoSod5 in F. oxysporum. The subcellular localization of FoSod5 is altered under different environmental conditions. During normal growth conditions, FoSod5 was primarily localized to the phialides; however, in a nutrient-limited environment, FoSod5 was localized to a wide array of fungal structures including the septum and cell wall. FoSod5 is an alkaline-induced glycosylphosphatidylinositol (GPI) protein and the GPI anchor was required for proper protein subcellular localization. The multiple mechanisms fungi utilize to tolerate the oxidative burst is indicative of the importance of this plant defense response; however, the presence of a conserved extracellular SOD in many phytopathogenic fungi suggests tolerance to ROS is initiated prior to the ROS entering the fungal cell.

Extracellular Vesicles from SOD3-Transduced Stem Cells Exhibit Improved Immunomodulatory Abilities in the Murine Dermatitis Model

The immunoregulatory abilities of mesenchymal stem cells (MSCs) have been investigated in various autoimmune and allergic diseases. However, the therapeutic benefits observed in preclinical settings have not been reproducible in clinical trials. This discrepancy is due to insufficient efficacy of MSCs in harsh microenvironments, as well as batch-dependent variability in potency. Therefore, to achieve more beneficial and uniform outcomes, novel strategies are required to potentiate the therapeutic effect of MSCs. One of simple strategies to augment cellular function is genetic manipulation. Several studies showed that transduction of antioxidant enzyme into cells can increase anti-inflammatory effects. Therefore, we evaluated the immunoregulatory abilities of MSCs introduced with extracellular superoxide dismutase 3 (SOD3) in the present study. SOD3-overexpressed MSCs (SOD3-MSCs) reduced the symptoms of murine model of atopic dermatitis (AD)-like inflammation, as well as the differentiation and activation of various immune cells involved in AD progression. Interestingly, extracellular vesicles (EVs) isolated from SOD3-MSCs delivered SOD3 protein. EVs carrying SOD3 also exerted improved therapeutic efficacy, as observed in their parent cells. These results suggest that MSCs transduced with SOD3, an antioxidant enzyme, as well as EVs isolated from modified cells, might be developed as a promising cell-based therapeutics for inflammatory disorders.