Interactions Between the Ubiquitin-Proteasome System, Nrf2, and the Cannabinoidome as Protective Strategies to Combat Neurodegeneration: Review on Experimental Evidence.

Neurodegenerative disorders are chronic brain diseases that affect humans worldwide. Although many different factors are thought to be involved in the pathogenesis of these disorders, alterations in several key elements such as the ubiquitin-proteasome system (UPS), the nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, and the endocannabinoid system (ECS or endocannabinoidome) have been implicated in their etiology. Impairment of these elements has been linked to the origin and progression of neurodegenerative disorders, while their potentiation is thought to promote neuronal survival and overall neuroprotection, as proved with several experimental models. These key neuroprotective pathways can interact and indirectly activate each other. In this review, we summarize the neuroprotective potential of the UPS, ECS, and Nrf2 signaling, both separately and combined, pinpointing their role as a potential therapeutic approach against several hallmarks of neurodegeneration.

Protective Effect of NO2-OA on Oxidative Stress, Gliosis, and Pro-Angiogenic Response in Müller Glial Cells.

Inflammation and oxidative and nitrosative stress are involved in the pathogenesis of proliferative retinopathies (PR). In PR, a loss of balance between pro-angiogenic and anti-angiogenic factors favors the secretion of vascular endothelial growth factor (VEGF). This vascular change results in alterations in the blood-retinal barrier, with extravasation of plasma proteins such as α2-macroglobulin (α2M) and gliosis in Müller glial cells (MGCs, such as MIO-M1). It is well known that MGCs play important roles in healthy and sick retinas, including in PR. Nitro-fatty acids are electrophilic lipid mediators with anti-inflammatory and cytoprotective properties. Our aim was to investigate whether nitro-oleic acid (NO2-OA) is beneficial against oxidative stress, gliosis, and the pro-angiogenic response in MGCs. Pure synthetic NO2-OA increased HO-1 expression in a time- and concentration-dependent manner, which was abrogated by the Nrf2 inhibitor trigonelline. In response to phorbol 12-myristate 13-acetate (PMA) and lipopolysaccharide (LPS), NO2-OA prevented the ROS increase and reduced the gliosis induced by α2M. Finally, when hypoxic MGCs were incubated with NO2-OA, the increase in VEGF mRNA expression was not affected, but under hypoxia and inflammation (IL-1ß), NO2-OA significantly reduced VEGF mRNA levels. Furthermore, NO2-OA inhibited endothelial cell (BAEC) tubulogenesis. Our results highlight NO2-OA's protective effect on oxidative damage, gliosis; and the exacerbated pro-angiogenic response in MGCs.

Effect of Platelet-Derived Growth Factor C on Mitochondrial Oxidative Stress Induced by High d-Glucose in Human Aortic Endothelial Cells.

Endothelial dysfunction is an early marker for cardiovascular diseases. Hyperglycemia induces endothelial dysfunction, increasing the production of reactive oxygen species. Platelet-derived growth factor C stimulates angiogenesis and revascularization in ischemic tissues of diabetic mice and promotes the migration of progenitors and mature ECs to injury sites; however, the molecular mechanisms of its actions are not described yet. Here, we evaluated the effect of PDGF-C on oxidative stress induced by HG. Human aortic endothelial cells were grown in glucose concentrations ranging from 5 mmol/L to 35 mmol/L for 1 to 24 h. Treatment with 50 ng/mL PDGF-C was done for 1 to 3 h. Cytosolic and mitochondrial ROS were measured by fluorometry, and the expression of antioxidant enzymes was evaluated by Western blot. Nrf2 and Keap1 expression was assessed by real-time PCR. High glucose induced mitochondrial ROS production. PDGF-C diminished the oxidative stress induced by high glucose, increasing SOD2 expression and SOD activity, and modulating the Keap1 expression gene. These results give new evidence about the mitochondrial antioxidant effect that PDGF-C could exert on endothelial cells exposed to high glucose and its considerable role as a therapeutic target in diabetes.

p-Chloro-diphenyl diselenide modulates Nrf2/Keap1 signaling and counteracts renal oxidative stress in mice exposed to repeated dexamethasone administrations.

Dexamethasone is a synthetic glucocorticoid that has been associated with oxidative stress in central and peripheral tissues. p-Chloro-diphenyl diselenide ((p-ClPhSe)2) is an antioxidant organoselenium compound. The present study evaluated whether nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like ECH-associated protein 1 (Keap-1) signaling contributes to the (p-ClPhSe)2 antioxidant effects in the kidney of mice exposed to dexamethasone. Adult Swiss mice received dexamethasone (intraperitoneal) at a dose of 2 mg/kg or its vehicle for 21 days. After that, mice were treated with (p-ClPhSe)2 (intragastric) (1, 5, or 10 mg/kg) for 7 days. Samples of kidneys were collected for biochemical assays. (p-ClPhSe)2 at a dose of 1 mg/kg reversed the renal reactive oxygen species (ROS) and carbonyl protein (CP) levels increased by dexamethasone. (p-ClPhSe)2 at doses of 5 and 10 mg/kg was effective against the increase of thiobarbituric acid reactive substances, ROS, and CP, as well as the decrease of δ-aminolevulinic acid dehydratase activity and nonprotein sulfhydryl levels induced by dexamethasone. At 5 mg/kg, (p-ClPhSe)2 reduced the renal levels of 4-OH-2-HNE and heme oxygenase (HO-1), as well as modulated the Nrf2/Keap-1 signaling in mice exposed to dexamethasone. The present findings revealed that (p-ClPhSe)2 antioxidant effects were associated with the modulation of Nrf2/Keap-1 signaling pathway in the kidney of mice exposed to dexamethasone.

Molecular Mechanisms That Link Oxidative Stress, Inflammation, and Fibrosis in the Liver.

Activated hepatic stellate cells (HSCs) and myofibroblasts are the main producers of extracellular matrix (ECM) proteins that form the fibrotic tissue that leads to hepatic fibrosis. Reactive oxygen species (ROS) can directly activate HSCs or induce inflammation or programmed cell death, especially pyroptosis, in hepatocytes, which in turn activates HSCs and fibroblasts to produce ECM proteins. Therefore, antioxidants and the nuclear factor E2-related factor-2 signaling pathway play critical roles in modulating the profibrogenic response. The master proinflammatory factors nuclear factor-κB (NF-κB) and the nucleotide-binding oligomerization domain (NOD)-like receptor protein 3 (NLRP3) inflammasome may coordinate to produce and activate profibrogenic molecules such as interleukins 1ß and 18, which effectively activate HSCs, to produce large amounts of fibrotic proteins. Furthermore, the NLRP3 inflammasome activates pro-caspase 1, which is upregulated by NF-κB, to produce caspase 1, which induces pyroptosis via gasdermin and the activation of HSCs. ROS play central roles in the activation of the NF-κB and NLRP3 signaling pathways via IκB (an inhibitor of NF-κB) and thioredoxin-interacting protein, respectively, thereby linking the molecular mechanisms of oxidative stress, inflammation and fibrosis. Elucidating these molecular pathways may pave the way for the development of therapeutic tools to interfere with specific targets.

Diphenyl diselenide is as effective as Ebselen in a juvenile rat model of cisplatin-induced nephrotoxicity.

BACKGROUND: Cisplatin (CIS) is widely used in the chemotreatment of pediatric tumors. However, the CIS use is limited because of its high incidence of toxicity, mainly nephrotoxicity. Although there are many studies about CIS-related nephrotoxicity in animal models, only a few studies focus on juvenile animals. Because redox disturbances have been associated with kidney damage induced by CIS, this study aimed to compare the effectiveness of Ebselen and diphenyl diselenide (PhSe)2 against nephrotoxicity induced by CIS in juvenile rats. METHODS: Juvenile Wistar rats were randomly divided into six groups: rats from groups I to III received an intraperitoneal (i.p.) injection with saline solution. The other groups received CIS (i.p., 6 mg/kg) on the first day. One hour before CIS injection and on the next four days, animals of groups III and V were intragastrically treated with Ebselen (11 mg/kg) whereas those from groups IV and VI received (PhSe)2 (12 mg/kg). After 24 h of the last treatment, blood and kidney were collected, and the parameters of renal function and oxidative stress were determined. RESULTS: Kidney damage induced by CIS was confirmed by the increase of creatinine, urea and uric acid levels in the blood of juvenile rats. The renal oxidative disturbance was characterized by an increase in the levels of thiobarbituric acid reactive substances (TBARS), protein carbonyl, and nitrogen oxides (Nox), as well as the decrease in non-protein thiol content (NPSH), glutathione-S-transferase (GST), catalase (CAT) and superoxide dismutase (SOD) activities. CIS inhibited the activities of δ-aminolevulinic acid dehydratase (δ-ALA-D) and Na+, K+-ATPase and down-regulated the Nrf2/Keap-1/HO-1 pathway in the kidney of juvenile rats. CONCLUSION: Both Ebselen and (PhSe)2 modulated back to the normal levels all parameters altered by the CIS administration in the kidney of juvenile rats. Thus, this study shows that (PhSe)2 was as effective as Ebselen in protecting the kidney against oxidative damage caused by CIS in rats.

Diphenyl diselenide regulates Nrf2/Keap-1 signaling pathway and counteracts hepatic oxidative stress induced by bisphenol A in male mice.

Bisphenol A (BPA) is a chemical toxicant that has deleterious effects on human. BPA causes oxidative stress in tissues, including the liver. Diphenyl diselenide (PhSe)2 improves the antioxidant response via activation of the nuclear factor (erythroid-derived 2)-like 2 (Nrf2)/Kelch-like ECH-associated protein (keap 1) pathway in macrophage cells. In the present study, we investigated whether (PhSe)2 counteracts hepatic oxidative stress induced by BPA in male and female Swiss mice. Three-week-old mice received by the intragastric (i.g.) route BPA (5 mg/kg) from 21st to 60th postnatal day (PND). At PND 61, the mice were treated with (PhSe)2 (1 mg/kg, i.g.) for seven days. Parameters of hepatic damage and oxidative stress were determined in male and female mice. The results show that BPA increased the activity of aspartate aminotransferase in female mice, and in male mice the activity of alanine aminotranseferase was increased. Male and female mice had an increase in fat mass accumulation. Male mice showed an increase in hepatic oxidative damage of proteins and a decrease in non-enzymatic (ascorbic acid and non-protein thiol) and enzymatic (superoxide dismutase) defenses, which are consistent with oxidative stress status. Male mice were more susceptible than female mice to hepatic oxidative stress induced by BPA. BPA decreased Nrf2/Keap1 protein content in male mice. (PhSe)2 reduced hepatic oxidative stress induced by BPA in male mice. Our results demonstrate that male mice were more susceptible to hepatic oxidative stress induced by BPA than female mice. (PhSe)2 regulated Nrf2/Keap-1 signaling pathway and countered hepatic oxidative stress induced by BPA in male mice.