Protective effect of carnosic acid against paraquat-induced redox impairment and mitochondrial dysfunction in SH-SY5Y cells: Role for PI3K/Akt/Nrf2 pathway

Paraquat and Parkinson's Disease: The Molecular Crosstalk of Upstream Signal Transduction Pathways Leading to Apoptosis

Parkinson's disease (PD) is a heterogeneous disease involving a complex interaction between genes and the environment that affects various cellular pathways and neural networks. Several studies have suggested that environmental factors such as exposure to herbicides, pesticides, heavy metals, and other organic pollutants are significant risk factors for the development of PD. Among the herbicides, paraquat has been commonly used, although it has been banned in many countries due to its acute toxicity. Although the direct causational relationship between paraquat exposure and PD has not been established, paraquat has been demonstrated to cause the degeneration of dopaminergic neurons in the substantia nigra pars compacta. The underlying mechanisms of the dopaminergic lesion are primarily driven by the generation of reactive oxygen species, decrease in antioxidant enzyme levels, neuroinflammation, mitochondrial dysfunction, and ER stress, leading to a cascade of molecular crosstalks that result in the initiation of apoptosis. This review critically analyses the crucial upstream molecular pathways of the apoptotic cascade involved in paraquat neurotoxicity, including mitogenactivated protein kinase (MAPK), phosphatidylinositol-4,5-bisphosphate 3-kinase (PI3K)/AKT, mammalian target of rapamycin (mTOR), and Wnt/β-catenin signaling pathways.

Exploring the Potential of Rosemary Derived Compounds (Rosmarinic and Carnosic Acids) as Cancer Therapeutics: Current Knowledge and Future Perspectives

Cancer is a global health challenge with high morbidity and mortality rates. However, conventional cancer treatment methods often have severe side effects and limited success rates. In the last decade, extensive research has been conducted to develop safe, and efficient alternative treatments that do not have the limitations of existing anticancer medicines. Plant-derived compounds have shown promise in cancer treatment for their anti-carcinogenic and anti-proliferative properties. Rosmarinic acid (RA) and carnosic acid (CA) are potent polyphenolic compounds found in rosemary (Rosmarinus officinalis) extract. They have been extensively studied for their biological properties, which include anti-diabetic, anti-inflammatory, antioxidant, and anticancer activities. In addition, RA and CA have demonstrated effective anti-proliferative properties against various cancers, making them promising targets for extensive research to develop candidate or leading compounds for cancer treatment. This review discusses and summarizes the anti-tumor effect of RA and CA against various cancers and highlights the involved biochemical and mechanistic pathways.

Swietenine inhibited oxidative stress through AKT/Nrf2/HO-1 signal pathways and the liver-protective effect in T2DM mice: In vivo and in vitro study

Swietenia macrophylla King, belongs to the Meliaceae family, is a valuable medicinal plant and its fruits have been processed commercially to a variety of health foods. The seeds have long been known for their ethnomedicinal significance against these diseases. Swietenine (Swi) was isolated from S. macrophylla and could ameliorate inflammation and oxidative stress. In this study, HepG2 cells induced by H₂ O₂ were used to construct oxidative stress model in vitro. The aim of this study was to investigate the protective effect of Swi on H₂ O₂ induced oxidative injury in HepG2 cells and its molecular mechanism, and to explore the effect of Swi on liver injury in db/db mice and its possible mechanism. The results showed that Swi significantly inhibited HepG2 cells viability and reduced oxidative damage in a dose-dependent manner as evidenced by a range of biochemical analysis and immunoblotting study. Moreover, it induced the protein and mRNA expression of HO-1 together with its upstream mediator Nrf2 and activated the phosphorylation of AKT in HepG2 cells. LY294002, a PI3K/AKT inhibitor, significantly suppressed the Nrf2 nuclear translocation and HO-1 expression in H₂ O₂ induced HepG2 cells treated with Swi. In addition, RNA interference with Nrf2 significantly reduced the expression level of Nrf2 and HO-1 in the nucleus. Swi has a significant protective effect on cell damage in H₂ O₂ induced HepG2 cells by increasing the antioxidant capacity which is achieved through the AKT/Nrf2/HO-1 pathway. Additionally, in vivo, Swi could protect the liver of type 2 diabetic mice by improving lipid deposition in liver tissue and inhibiting oxidative stress. These findings indicated that Swi can be a promising dietary agent to improve type 2 diabetes.

Cannabinoid type 2 receptor activation inhibits MPP+-induced M1 differentiation of microglia through activating PI3K/Akt/Nrf2 signal pathway

BACKGROUND

Growing evidence indicates that cannabinoid type 2 (CB2) receptor activation inhibits neuroinflammation in the pathogenesis of Parkinson's disease (PD). Nonetheless, the precise mechanisms of CB2 receptor-mediated neuroprotection have not been fully elucidated. The differentiation of microglia from the M1 to M2 phenotype plays a vital role in neuroinflammation.

METHODS

In the present study, we investigated the effect of CB2 receptor activation on the M1/M2 phenotypic transformation of microglia treated with 1-methyl-4-phenylpyridinium (MPP+). The M1 phenotype microglia markers, including inducible nitric oxide (iNOS), interleukin 6 (IL-6), and CD86, and the M2 phenotype microglia markers, including arginase-1 (Arg-1), IL-10, and CD206, were detected by western blots and flow cytometry. The levels of phosphoinositide-3-kinase (PI3K)/Akt and nuclear factor erythroid 2-related factor 2 (Nrf2) were determined by Western blots. Subsequent addition of Nrf2 inhibitors initially revealed the specific mechanism by which CB2 receptors affect phenotypic changes in microglia.

RESULTS

Our results showed that pretreatment with JWH133 significantly inhibited the MPP⁺-induced up-regulation of M1 phenotype microglia markers. Meanwhile, JWH133 increased the levels of M2 phenotype microglia markers. JWH133-mediated effects were blocked by co-treatment with AM630. Mechanism studies found that MPP⁺ treatment downregulated PI3K, Akt phosphorylated proteins, and nuclear Nrf2 protein. JWH133 pretreatment promoted PI3K/Akt activation and facilitated nuclear translocation of Nrf2, which was reversed by the PI3K inhibitor. Further studies showed that Nrf2 inhibitors inverted the effect of JWH133 on microglia polarization.

CONCLUSION

The results indicate that CB2 receptor activation promotes MPP⁺-induced microglia transformation from M1 to M2 phenotype through PI3K/Akt/Nrf2 signaling pathway.

The Complex Genetic and Epigenetic Regulation of the Nrf2 Pathways: A Review

Nrf2 is a major transcription factor that significantly regulates-directly or indirectly-more than 2000 genes. While many of these genes are involved in maintaining redox balance, others are involved in maintaining balance among metabolic pathways that are seemingly unrelated to oxidative stress. In the past 25 years, the number of factors involved in the activation, nuclear translocation, and deactivation of Nrf2 has continued to expand. The purpose of this review is to provide an overview of the remarkable complexity of the tortuous sequence of stop-and-go signals that not only regulate expression or repression, but may also modify transcriptional intensity as well as the specificity of promoter recognition, allowing fluidity of its gene expression profile depending on the various structural modifications the transcription factor encounters on its journey to the DNA. At present, more than 45 control points have been identified, many of which represent sites of action of the so-called Nrf2 activators. The complexity of the pathway and the synergistic interplay among combinations of control points help to explain the potential advantages seen with phytochemical compositions that simultaneously target multiple control points, compared to the traditional pharmaceutical paradigm of "one-drug, one-target".

Pesticides as a risk factor for cognitive impairment: Natural substances are expected to become alternative measures to prevent and improve cognitive impairment

Pesticides are the most effective way to control diseases, insects, weeds, and fungi. The central nervous system (CNS) is damaged by pesticide residues in various ways. By consulting relevant databases, the systemic relationships between the possible mechanisms of pesticides damage to the CNS causing cognitive impairment and related learning and memory pathways networks, as well as the structure-activity relationships between some natural substances (such as polyphenols and vitamins) and the improvement were summarized in this article. The mechanisms of cognitive impairment caused by pesticides are closely related. For example, oxidative stress, mitochondrial dysfunction, and neuroinflammation can constitute three feedback loops that interact and restrict each other. The mechanisms of neurotransmitter abnormalities and intestinal dysfunction also play an important role. The connection between pathways is complex. NMDAR, PI3K/Akt, MAPK, Keap1/Nrf2/ARE, and NF-κB pathways can be connected into a pathway network by targets such as Ras, Akt, and IKK. The reasons for the improvement of natural substances are related to their specific structure, such as polyphenols with different hydroxyl groups. This review's purpose is to lay a foundation for exploring and developing more natural substances that can effectively improve the cognitive impairment caused by pesticides.

Repurposing artemisinins as neuroprotective agents: a focus on the PI3k/Akt signalling pathway

Artemisinin and its derivatives, since their discovery by professor Tu Youyou in the early 1970s, have been the bedrock for the management of malaria globally. Recent works have implied that they could be used to manage other diseases including neurodegenerative disorders. Neurodegenerative disorders mainly occur in the adult population resulting from a progressive deterioration of neuronal structures. These include Parkinson's disease (PD), Alzheimer's disease (AD), Huntington's disease (HD), and Multiple sclerosis (MS), among others. The PI3K/Akt signaling pathway plays a significant role in the central nervous system. It has been investigated extensively for its role in central nervous system physiological processes such as cell survival, autophagy, neuronal proliferation, and synaptic plasticity. Therefore, the modulation of this pathway will be crucial in the management of neurodegenerative disorders. This review seeks to compile most of the research findings on the possible neuroprotective role of artemisinins with special emphasis on their modulatory role on the PI3k/Akt pathway. A literature survey was conducted on PubMed, EBSCO, Web of Science, and EMBASE using the keyword artemisinins, and a total of 10,281 articles were retrieved from 1956 to 2022. Among these, 120 articles were examined using Mesh words like PI3k/Akt, neurodegeneration, and neuroinflammation coupled with boolean operators. Most research revealed that artemisinins could help neurodegenerative disorders by modulating the PI3k/Akt with subsequent inhibition of oxidative stress, neuroinflammation, and apoptosis. This paper illustrates that artemisinins could be repurposed as a neuroprotective agent.

Agathobaculum butyriciproducens Shows Neuroprotective Effects in a 6-OHDA-Induced Mouse Model of Parkinson's Disease

Parkinson's disease (PD) is the second-most prevalent neurodegenerative disease and is characterized by dopaminergic neuronal death in the midbrain. Recently, the association between alterations in PD pathology and the gut microbiota has been explored. Microbiota-targeted interventions have been suggested as a novel therapeutic approach for PD. Agathobaculum butyriciproducens SR79^T (SR79) is an anaerobic bacterium. Previously, we showed that SR79 treatment induced cognitive improvement and reduced Alzheimer's disease pathologies in a mouse model. In this study, we hypothesized that SR79 treatment may have beneficial effects on PD pathology. To investigate the therapeutic effects of SR79 on PD, 6-hydroxydopamine (6-OHDA)-induced mouse models were used. D-Amphetamine sulfate (d-AMPH)-induced behavioral rotations and dopaminergic cell death were analyzed in unilateral 6-OHDA-lesioned mice. Treatment with SR79 significantly decreased ipsilateral rotations induced by d-AMPH. Moreover, SR79 treatment markedly activated the AKT/GSK3β signaling pathway in the striatum. In addition, SR79 treatment affected the Nrf2/ARE signaling pathway and its downstream target genes in the striatum of 6-OHDA-lesioned mice. Our findings suggest a protective role of SR79 in 6-OHDA-induced toxicity by regulating the AKT/Nrf2/ARE signaling pathway and astrocyte activation. Thus, SR79 may be a potential microbe-based intervention and therapeutic strategy for PD.

Preliminary Investigation of the Effects of Rosemary Extract Supplementation on Milk Production and Rumen Fermentation in High-Producing Dairy Cows

Rosemary extract (RE) has been used as an antioxidant in cosmetics and food additives, indicating its potential as a feed additive to improve adaptation in high-producing dairy cows. Here, we investigated the effects of RE supplementation on lactation performance and rumen fermentation in high-producing dairy cows. Thirty multiparous cows were blocked into 15 groups based on milk production and were randomly assigned to one of two treatments: 0 or 28 g/d of RE supplementation to the basic diet per cow. The experiment was conducted over a 74-day period, which included an initial two-week adaptation period. We observed significant increases in milk and milk lactose yields following RE supplementation. Somatic cell count tended to decrease by treatment. Additionally, superoxide dismutase concentration significantly increased and malonaldehyde level decreased after RE supplementation. Sequencing of 16S rRNA revealed that RE supplementation significantly affected the microbial composition and decreased the richness of the microbiota. Specifically, the abundance of the genus Prevotella was significantly decreased by RE supplementation and was correlated with volatile fatty acids in the Mantel test, whereas no significant correlation was found for other genera. Our findings provide fundamental information on the potential for RE as a feed additive for dairy cows to improve antioxidant status and enhance propionate generation.

Multi-Target Effects of ß-Caryophyllene and Carnosic Acid at the Crossroads of Mitochondrial Dysfunction and Neurodegeneration: From Oxidative Stress to Microglia-Mediated Neuroinflammation

Inflammation and oxidative stress are interlinked and interdependent processes involved in many chronic diseases, including neurodegeneration, diabetes, cardiovascular diseases, and cancer. Therefore, targeting inflammatory pathways may represent a potential therapeutic strategy. Emerging evidence indicates that many phytochemicals extracted from edible plants have the potential to ameliorate the disease phenotypes. In this scenario, ß-caryophyllene (BCP), a bicyclic sesquiterpene, and carnosic acid (CA), an ortho-diphenolic diterpene, were demonstrated to exhibit anti-inflammatory, and antioxidant activities, as well as neuroprotective and mitoprotective effects in different in vitro and in vivo models. BCP essentially promotes its effects by acting as a selective agonist and allosteric modulator of cannabinoid type-2 receptor (CB2R). CA is a pro-electrophilic compound that, in response to oxidation, is converted to its electrophilic form. This can interact and activate the Keap1/Nrf2/ARE transcription pathway, triggering the synthesis of endogenous antioxidant “phase 2” enzymes. However, given the nature of its chemical structure, CA also exhibits direct antioxidant effects. BCP and CA can readily cross the BBB and accumulate in brain regions, giving rise to neuroprotective effects by preventing mitochondrial dysfunction and inhibiting activated microglia, substantially through the activation of pro-survival signalling pathways, including regulation of apoptosis and autophagy, and molecular mechanisms related to mitochondrial quality control. Findings from different in vitro/in vivo experimental models of Parkinson’s disease and Alzheimer’s disease reported the beneficial effects of both compounds, suggesting that their use in treatments may be a promising strategy in the management of neurodegenerative diseases aimed at maintaining mitochondrial homeostasis and ameliorating glia-mediated neuroinflammation.

Novel Flavan-3,4-diol vernicidin B from Toxicodendron Vernicifluum (Anacardiaceae) as potent antioxidant via IL-6/Nrf2 cross-talks pathways

BACKGROUND

Oxidative stress is considered to be a pathological factor of various neurodegenerative diseases. Studies have confirmed the antioxidant activity of T. vernicifluum. However, the main active components responsible for antioxidant activity remain unknown.

OBJECTIVE

The aim of this study is to explore the activities of vernicidin B on oxidative stress injury induced by H₂O₂ in SH-SY5Y cells, and the underlying mechanism of vernicidin B in oxidative stress-related neurological diseases is further discussed.

METHODS

Various separation methods were used to isolate and identify the compounds in an EtOAc extract of T. vernicifluum. The structures of the isolates were clarified by HR-TOF-MS and 1D/2D NMR data and compared with findings in previous literature. The MTT assay was used to evaluate the potential antioxidant activity of the isolated flavonoids. The apoptosis rate, mitochondrial reactive oxygen species (ROS) level and mitochondrial potential were measured by flow cytometry and fluorescence microscope. The levels of related proteins were detected by Western blotting.

RESULTS

Four new flavan-3,4-diols (1-4, vernicidins A-D) and 11 known flavonoids (5-15) were purified from the EtOAc extract of T. vernicifluum. Among these compounds, vernicidin B showed the most promising potential for protecting SH-SY5Y cells from H₂O₂-induced oxidative stress. Moreover, pretreatment with vernicidin B decreased ROS production and mitochondrial membrane potential and significantly attenuated H₂O₂-induced apoptosis in a dose-dependent manner. Mechanistically, the antioxidant stress activities of vernicidin B were confirmed to be related to the IL-6/Nrf2 cross-talks pathway and its downstream pathways, including PI3K/Akt/mToR-Gsk3β, JAK2/STAT3 and MAPKs.

CONCLUSIONS

Our findings suggested that vernicidin B can improve the oxidative stress injury induced by H₂O₂ through IL-6/Nrf2 cross-talks pathway, indicating that it may be a potential candidate drug for the treatment of oxidative stress-related neurodegenerative diseases.

Role of Bioactive Compounds in the Regulation of Mitochondrial Dysfunctions in Brain and Age-Related Neurodegenerative Diseases

Mitochondria are multifunctional organelles that participate in a wide range of metabolic processes, including energy production and biomolecule synthesis. The morphology and distribution of intracellular mitochondria change dynamically, reflecting a cell’s metabolic activity. Oxidative stress is defined as a mismatch between the body’s ability to neutralise and eliminate reactive oxygen and nitrogen species (ROS and RNS). A determination of mitochondria failure in increasing oxidative stress, as well as its implications in neurodegenerative illnesses and apoptosis, is a significant developmental process of focus in this review. The neuroprotective effects of bioactive compounds linked to neuronal regulation, as well as related neuronal development abnormalities, will be investigated. In conclusion, the study of secondary components and the use of mitochondrial features in the analysis of various neurodevelopmental diseases has enabled the development of a new class of mitochondrial-targeted pharmaceuticals capable of alleviating neurodegenerative disease states and enabling longevity and healthy ageing for the vast majority of people.

Pharmacological Modulation of Nrf2/HO-1 Signaling Pathway as a Therapeutic Target of Parkinson's Disease

Parkinson’s disease (PD) is a complex neurodegenerative disorder featuring both motor and nonmotor symptoms associated with a progressive loss of dopaminergic neurons in the substantia nigra pars compacta. Oxidative stress (OS) has been implicated in the pathogenesis of PD. Genetic and environmental factors can produce OS, which has been implicated as a core contributor to the initiation and progression of PD through the degeneration of dopaminergic neurons. The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) orchestrates activation of multiple protective genes, including heme oxygenase-1 (HO-1), which protects cells from OS. Nrf2 has also been shown to exert anti-inflammatory effects and modulate both mitochondrial function and biogenesis. Recently, a series of studies have reported that different bioactive compounds were shown to be able to activate Nrf2/antioxidant response element (ARE) and can ameliorate PD-associated neurotoxin, both in animal models and in tissue culture. In this review, we briefly overview the sources of OS and the association between OS and the pathogenesis of PD. Then, we provided a concise overview of Nrf2/ARE pathway and delineated the role played by activation of Nrf2/HO-1 in PD. At last, we expand our discussion to the neuroprotective effects of pharmacological modulation of Nrf2/HO-1 by bioactive compounds and the potential application of Nrf2 activators for the treatment of PD. This review suggests that pharmacological modulation of Nrf2/HO-1 signaling pathway by bioactive compounds is a therapeutic target of PD.

Rosemary and its protective potencies against COVID-19 and other cytokine storm associated infections: A molecular review

BACKGROUND: Nowadays, medicinal plants have attracted great interest in treatment of human diseases. Rosemary is a well-known medicinal plant which has been widely used for different therapeutic purposes. METHODS: This is a narrative review using databases including PubMed, ISI, Scopus, ScienceDirect, Cochrane, and google scholar, the most authoritative articles were searched, screened, and analyzed. RESULTS: Rosemary is a natural antioxidant which removes reactive oxygen species from tissues and increases expression on Nrf2 gene. Rosemary and its metabolites reduce inflammation by inhibiting production of pro-inflammatory cytokines, decreasing expression of NF-κB, inhibiting infiltration of immune cells to inflamed sites, and affecting gut microbiome. Besides, rosmarinic acid in rosemary extract has positive effects on renin-angiotensin-system. Rosemary affects respiratory system by reducing oxidative stress, inflammation, muscle spasm, and also through anti-fibrotic properties. Carnosic acid is able to penetrate blood-brain-barrier and act against free radicals, ischemia and neurodegeneration in brain. Cardioprotective effects include correcting lipid profile, controlling blood pressure by inhibition of ACE, prevention of atherosclerosis, and reduction of cardiac muscle hypertrophy. CONCLUSIONS: Accordingly, rosemary supplementation has potential protective effects against COVID-19 and other cytokine storm associated infections, a conclusion that needs more evaluations in the next clinical trials.

Targeting Mitochondria by Plant Secondary Metabolites: A Promising Strategy in Combating Parkinson's Disease

Parkinson’s disease (PD) is one of the most prevalent and debilitating neurodegenerative conditions, and is currently on the rise. Several dysregulated pathways are behind the pathogenesis of PD; however, the critical targets remain unclear. Accordingly, there is an urgent need to reveal the key dysregulated pathways in PD. Prevailing reports have highlighted the importance of mitochondrial and cross-talked mediators in neurological disorders, genetic changes, and related complications of PD. Multiple pathophysiological mechanisms of PD, as well as the low efficacy and side effects of conventional neuroprotective therapies, drive the need for finding novel alternative agents. Recently, much attention has been paid to using plant secondary metabolites (e.g., flavonoids/phenolic compounds, alkaloids, and terpenoids) in the modulation of PD-associated manifestations by targeting mitochondria. In this line, plant secondary metabolites have shown promising potential for the simultaneous modulation of mitochondrial apoptosis and reactive oxygen species. This review aimed to address mitochondria and multiple dysregulated pathways in PD by plant-derived secondary metabolites.

An Exploration of the Effects of an Early Postpartum Intravenous Infusion with Carnosic Acid on Physiological Responses of Transition Dairy Cows

The objective of the present study was to evaluate the effects of an antioxidant and anti-inflammatory compound found in rosemary plants (Salvia rosmarinus) named carnosic acid during the transition period of dairy cows. From day 1 to 3 after calving, 16 multiparous Holstein cows received a daily intravenous infusion of either 500 mL of saline (NaCl 0.9%; Saline; n = 8) or carnosic acid at a rate of 0.3 mg/kg of BW supplied in 500 mL of saline (CA; n = 8). Blood samples were taken at –7, 2, 5, 7, 14, and 21 d relative to parturition, then analyzed for metabolites related to energy metabolism, muscle mass catabolism, liver function, inflammation, and oxidative stress. CA infusion tended to improve milk performance; however, DMI was unaffected by treatment. At 2 d relative to parturition, CA cows had lower blood concentrations of haptoglobin, paraoxonase, FRAP, and NO₂^– than saline cows. After treatment infusions, haptoglobin remained lower in CA cows than saline at 5 d relative to parturition. Our results demonstrate that carnosic acid promoted positive responses on inflammation and oxidative stress biomarkers and may promote beneficial effects on lactation performance in peripartal dairy cows.

Neuroprotective Natural Products for Alzheimer's Disease

Alzheimer’s disease (AD) is the number one neurovegetative disease, but its treatment options are relatively few and ineffective. In efforts to discover new strategies for AD therapy, natural products have aroused interest in the research community and in the pharmaceutical industry for their neuroprotective activity, targeting different pathological mechanisms associated with AD. A wide variety of natural products from different origins have been evaluated preclinically and clinically for their neuroprotective mechanisms in preventing and attenuating the multifactorial pathologies of AD. This review mainly focuses on the possible neuroprotective mechanisms from natural products that may be beneficial in AD treatment and the natural product mixtures or extracts from different sources that have demonstrated neuroprotective activity in preclinical and/or clinical studies. It is believed that natural product mixtures or extracts containing multiple bioactive compounds that can work additively or synergistically to exhibit multiple neuroprotective mechanisms might be an effective approach in AD drug discovery.

α-Lipoic acid alleviates ferroptosis in the MPP+ -induced PC12 cells via activating the PI3K/Akt/Nrf2 pathway

Parkinson's disease (PD) is a typical neurodegenerative disease. α-Lipoic acid (α-LA) can reduce the incidence of neuropathy. The present study explored the role and mechanism of α-LA in 1-methyl-4-phenylpyridinium (MPP⁺ )-induced cell model of PD. The PD model was induced via treating PC12 cells with MPP⁺  at different concentrations. MPP⁺  and α-LA effects on PC12 cells were assessed from cell viability and ferroptosis. Cell viability was detected using the cell counting kit-8 assay. Malondialdehyde (MDA), 4-hydroxynonenal (4-HNE), iron, reactive xygen species (ROS), and glutathione (GSH) concentrations, and ferroptosis-related protein SLC7A11 and GPx4 expressions were used for ferroptosis evaluation. p-PI3K, p-Akt, and nuclear factor erythroid 2-related factor 2 (Nrf2) protein levels were detected. The PI3K/Akt/Nrf2 pathway inhibitors were applied to verify the role of the PI3K/Akt/Nrf2 pathway in α-LA protection against MPP⁺ -induced decreased cell viability and ferroptosis. MPP⁺ -reduced cell viability and induced ferroptosis as presented by increased MDA, 4-HNE, iron, and ROS concentrations, and reduced levels of GSH and ferroptosis marker proteins (SLC7A11 and GPx4). α-LA attenuated MPP⁺ -induced cell viability decline and ferroptosis. The PI3K/Akt/Nrf2 pathway was activated after α-LA treatment. Inhibiting the PI3K/Akt/Nrf2 pathway weakened the protection of α-LA against MPP⁺  treatment. We highlighted that α-LA alleviated MPP⁺ -induced cell viability decrease and ferroptosis in PC12 cells via activating the PI3K/Akt/Nrf2 pathway.

p62-Nrf2-p62 Mitophagy Regulatory Loop as a Target for Preventive Therapy of Neurodegenerative Diseases

Turnover of the mitochondrial pool due to coordinated processes of mitochondrial biogenesis and mitophagy is an important process in maintaining mitochondrial stability. An important role in this process is played by the Nrf2/ARE signaling pathway, which is involved in the regulation of the expression of genes responsible for oxidative stress protection, regulation of mitochondrial biogenesis, and mitophagy. The p62 protein is a multifunctional cytoplasmic protein that functions as a selective mitophagy receptor for the degradation of ubiquitinated substrates. There is evidence that p62 can positively regulate Nrf2 by binding to its negative regulator, Keap1. However, there is also strong evidence that Nrf2 up-regulates p62 expression. Thereby, a regulatory loop is formed between two important signaling pathways, which may be an important target for drugs aimed at treating neurodegeneration. Constitutive activation of p62 in parallel with Nrf2 would most likely result in the activation of mTORC1-mediated signaling pathways that are associated with the development of malignant neoplasms. The purpose of this review is to describe the p62-Nrf2-p62 regulatory loop and to evaluate its role in the regulation of mitophagy under various physiological conditions.

Carnosic acid improves porcine early embryonic development by inhibiting the accumulation of reactive oxygen species

Carnosic acid (CA), a natural catechol rosin diterpene, is used as an additive in animal feeds and human foods. However, the effects of CA on mammalian reproductive processes, especially early embryonic development, are unclear. In this study, we added CA to parthenogenetically activated porcine embryos in an in vitro culture medium to explore the influence of CA on apoptosis, proliferation, blastocyst formation, reactive oxygen species (ROS) levels, glutathione (GSH) levels, mitochondrial membrane potential, and embryonic development-related gene expression. The results showed that supplementation with 10 μM CA during in vitro culture significantly improved the cleavage rates, blastocyst formation rates, hatching rates, and total numbers of cells of parthenogenetically activated porcine embryos compared with no supplementation. More importantly, supplementation with CA also improved GSH levels and mitochondrial membrane potential, reduced natural ROS levels in blastomeres, upregulated Nanog, Sox2, Gata4, Cox2, Itga5, and Rictor expression, and downregulated Birc5 and Caspase3 expression. These results suggest that CA can improve early porcine embryonic development by regulating oxidative stress. This study elucidates the effects of CA on early embryonic development and their potential mechanisms, and provides new applications for improving the quality of in vitro-developed embryos.

Analysis of microRNA expression profiling during paraquat-induced injury of murine lung alveolar epithelial cells

Paraquat (PQ) as a non-selective heterocyclic herbicide, has been applied worldwide for over a few decades. But PQ is very harmful to humans and rodents. The lung is the main target organ of PQ poisoning. It is an important event that lung epithelial cells are injured during PQ-induced acute lung injury and pulmonary fibrosis. As a regulator of mRNA expression, microRNA (miRNA) may play an important role in the progress. Our study was to investigate the mechanisms of PQ-induced injury of pulmonary epithelial cells through analyzing the profiling of miRNAs and their target genes. As a result, 11 differentially expressed miRNAs were screened, including 1 upregulated miRNA and 10 downregulated miRNAs in PQ-treated murine lung alveolar epithelial cells (MLE-12 cells). The bioinformatic analyses suggested that the target genes of these miRNAs were involved in mitochondrial apoptosis pathway and DNA methylation, and participated in the regulation of PI3K-Akt, mTOR, RAS, TNF, MAPK and other signal pathways which related to oxidative stress and apoptosis. This indicated that miRNAs were an important regulator of oxidative stress and apoptosis during PQ-induced injury of murine lung alveolar epithelial cells. The findings would deepen our understanding of the mechanisms of PQ-induced pulmonary injury and might provide new treatment targets for this disease.

Oxidative stress and mitochondrial dysfunction in organophosphate pesticide-induced neurotoxicity and its amelioration: a review

Organophosphorus pesticides (OPs) are widely used for controlling pests worldwide. The inhibitory effects of these pesticides on acetylcholinesterase lead to neurotoxic damages. The oxidative stress is responsible for several neurological diseases, including Parkinson's disease, seizure, depression, and Alzheimer's disease. Strong evidence suggests that dysfunction of mitochondria and oxidative stress are involved in neurological diseases. OPs can disturb the function of mitochondria by inducing oxidative stress. In the present study, we tried to highlight the role of dysfunction of mitochondria and the induction of oxidative stress in the neurotoxicity induced by OPs. Additionally, the amelioration of OP-induced oxidative damage and mitochondrial dysfunctional through the chemical and natural antioxidants have been discussed.

Rosemary Diterpenes and Flavanone Aglycones Provide Improved Genoprotection against UV-Induced DNA Damage in a Human Skin Cell Model

Overexposure to solar ultraviolet (UV) radiation is the major cause of a variety of cutaneous disorders, including sunburn, photoaging, and skin cancers. UVB radiation (290–320 nm) causes multiple forms of DNA damage, p53 induction, protein and lipid oxidation, and the generation of harmful reactive oxygen species (ROS). In recent years, botanicals containing polyphenols with antioxidant and anti-inflammatory properties as skin photoprotective agents have emerged. This study evaluated the protective effects of two formulations against UVB-induced damage in a skin cell model. One of the formulations (F2) contained a combination of citrus and olive extracts and the other one (F1) also contained a rosemary extract. The antioxidant capacity of both formulations was estimated by different in vitro methods, and the cell viability, intracellular ROS generation, mitochondrial depolarization, and DNA damage were studied in UVB-irradiated human keratinocytes. Both formulations exerted photoprotective effects on skin cells and decreased mitochondrial depolarization and DNA damage. F1 which contained iridoids, rosemary diterpenes, glycosides and aglycones of citrus flavanones, and monohydroxylated flavones exhibited higher cellular photoprotective effects and mitochondrial membrane potential restoration, as well as an enhanced capacity to decrease DNA double strand breaks and the DNA damage response. In contrast, F2, which contained mostly iridoids, citrus flavanone aglycones, and mono- and dihydroxylated flavones, exhibited a higher capacity to decrease intracellular ROS generation and radical scavenging capacity related to metal ion chelation. Both formulations showed a similar capability to decrease the number of apoptotic cells upon UVB radiation. Based on our results and those of others, we postulate that the stronger capacity of F1 to protect against UVB-induced DNA damage in human keratinocytes is related to the presence of rosemary diterpenes and citrus flavanone aglycones. Nevertheless, the presence of the dihydroxylated flavones in F2 may contribute to inhibiting the generation of metal-related free radicals. To confirm the efficacy of these formulations as potential candidates for oral/topical photoprotection, human trials are required to circumvent the limitations of the cellular model.

Neuroprotective effects of Danshensu on rotenone-induced Parkinson's disease models in vitro and in vivo

Background

Danshensu is an active constituent in the extracts of Danshen which is a traditional Chinese medical herb. Rotenone inhibits complex I of the mitochondrial electron transport chain in dopaminergic neurons leading to glutathione (GSH) level reduction and oxidative stress. The aim of this study is to investigate neuroprotective effects of Danshensu on rotenone-induced Parkinson’s disease (PD) in vitro and in vivo.

Methods

In vitro, SH-SY5Y human neuroblastoma cell line was pretreated with Danshensu and challenged with rotenone. Then the reactive oxygen species (ROS) production was assayed. In vivo, male C57BL/6 mice were intragastrically administered with Danshensu (15, 30, or 60 mg/kg), followed by oral administration with rotenone at a dose of 30 mg/kg. Pole and rotarod tests were carried out at 28 d to observe the effects of Danshensu on PD.

Results

Danshensu repressed ROS generation and therefore attenuated the rotenone-induced injury in SH-SY5Y cells. Danshensu improved motor dysfunction induced by rotenone, accompanied with reducing MDA content and increasing GSH level in striatum. Danshensu increased the number of TH positive neurons, the expression of TH and the dopamine contents. The expressions of p-PI3K, p-AKT, Nrf2, hemeoxygenase (HO-1), glutathione cysteine ligase regulatory subunit (GCLC), glutathione cysteine ligase modulatory subunit (GCLM) were significantly increased and the expression of Keap1 was decreased in Danshensu groups.

Conclusions

The neuroprotective effects of Danshensu on rotenone-induced PD are attributed to the anti-oxidative properties by activating PI3K/AKT/Nrf2 pathway and increasing Nrf2-induced expression of HO-1, GCLC, and GCLM, at least in part.

Antioxidant Therapies for Neuroprotection-A Review

Although moderate concentrations of reactive oxygen species (ROS) and reactive nitrogen species (RNS) are crucial for various physiological processes within the human body, their overproduction leads to oxidative stress, defined as the imbalance between the production and accumulation of ROS and the ability of the body to neutralize and eliminate them. In the brain, oxidative stress exhibits significant effects, due to its increased metabolical activity and limited cellular regeneration. Thus, oxidative stress is a major factor in the progressive loss of neurons structures and functions, leading to the development of severe neurodegenerative disorders. In this context, recent years have witnessed tremendous advancements in the field of antioxidant therapies, with a special emphasis for neuroprotection. The aim of this paper is to provide an overview of the oxidative stress and antioxidant defense mechanisms and to present the most recent studies on antioxidant therapies for neuroprotection.

Shaping the Nrf2-ARE-related pathways in Alzheimer's and Parkinson's diseases

A failure in redox homeostasis is a common hallmark of Alzheimer's Disease (AD) and Parkinson's Disease (PD), two age-dependent neurodegenerative disorders (NDD), causing increased oxidative stress, oxidized/damaged biomolecules, altered neuronal function and consequent cell death. Activation of nuclear factor erythroid 2-related factor 2 (Nrf2), a redox-regulated transcription factor, results in upregulation of cytoprotective and antioxidant enzymes/proteins, protecting against oxidative stress. Nrf2 regulation is achieved by various proteins and pathways, at both cytoplasmatic and nuclear level; however, the elaborate network of mechanisms involved in Nrf2 regulation may restrain Nrf2 pathway normal activity. Indeed, altered Nrf2 activity is involved in aging and NDD, such as AD and PD. Therefore, understanding the diversity of Nrf2 control mechanisms and regulatory proteins is of high interest, since more effective NDD therapeutics can be identified. In this review, we first introduce Keap1-Nrf2-ARE structure, function and regulation, with a special focus on the several pathways involved in Nrf2 positive and negative modulation, namely p62, PKC, PI3K/Akt/GSK-3β, NF-kB and p38 MAPK. We then briefly describe the evidences for oxidative stress and Nrf2 pathway deregulation in different stages of NDDs. Finally, we discuss the potential of Nrf2-related pathways as potential therapeutic targets to possibly prevent or slowdown NDD progression.

Metal Chelation Therapy and Parkinson's Disease: A Critical Review on the Thermodynamics of Complex Formation between Relevant Metal Ions and Promising or Established Drugs

The present review reports a list of approximately 800 compounds which have been used, tested or proposed for Parkinson’s disease (PD) therapy in the year range 2014–2019 (April): name(s), chemical structure and references are given. Among these compounds, approximately 250 have possible or established metal-chelating properties towards Cu(II), Cu(I), Fe(III), Fe(II), Mn(II), and Zn(II), which are considered to be involved in metal dyshomeostasis during PD. Speciation information regarding the complexes formed by these ions and the 250 compounds has been collected or, if not experimentally available, has been estimated from similar molecules. Stoichiometries and stability constants of the complexes have been reported; values of the cologarithm of the concentration of free metal ion at equilibrium (pM), and of the dissociation constant K_d (both computed at pH = 7.4 and at total metal and ligand concentrations of 10⁻⁶ and 10⁻⁵ mol/L, respectively), charge and stoichiometry of the most abundant metal–ligand complexes existing at physiological conditions, have been obtained. A rigorous definition of the reported amounts is given, the possible usefulness of this data is described, and the need to characterize the metal–ligand speciation of PD drugs is underlined.

Promotion of mitochondrial protection by naringenin in methylglyoxal-treated SH-SY5Y cells: Involvement of the Nrf2/GSH axis

Disruption of the mitochondrial function has been associated with redox impairment and triggering of cell death in nucleated human cells, as observed in several diseases. The administration of chemicals that would prevent mitochondrial dysfunction is an attractive strategy in cases of neurodegeneration, cardiovascular diseases, and metabolic disorders. Methylglyoxal (MG) is a dicarbonyl compound that exhibits an important role as a mitochondrial toxicant in neurodegenerative diseases (such as Alzheimer's disease and Parkinson's disease) and diabetes mellitus. On the other hand, naringenin (NGN; C₁₅H₁₂O₅) is a natural antioxidant that also presents anti-inflammatory effects in mammalian cells. In this context, we have evaluated whether and how NGN would be able to prevent the mitochondria-related bioenergetics and redox dysfunctions induced by MG in the human neuroblastoma SH-SY5Y cells. The cells were pretreated (for 2 h) with NGN (at 10-80 μM) and then challenged with MG at 500 μM for 24 h. NGN significantly attenuated the effects of MG on the mitochondrial function and redox environment in this experimental model. Moreover, NGN prevented the MG-triggered mitochondria-related cell death in SH-SY5Y cells. Nonetheless, the inhibition of the synthesis of glutathione (GSH, a major non-enzymatic antioxidant) suppressed the promotion of mitochondrial protection by NGN in MG-treated cells. We also found that the synthesis of GSH was induced by NGN through a mechanism associated with the transcription factor nuclear factor (erythroid-derived 2)-like 2 (Nrf2). Therefore, NGN caused mitochondrial protection by an Nrf2/GSH-dependent manner in SH-SY5Y cells exposed to MG.

Carnosic Acid Pretreatment Attenuates Mitochondrial Dysfunction in SH-SY5Y Cells in an Experimental Model of Glutamate-Induced Excitotoxicity

Mitochondria are the major site of adenosine triphosphate (ATP) production in mammalian cells. Moreover, mitochondria produce most of the reactive oxygen species (ROS) in nucleated cells. Redox and bioenergetic abnormalities have been seen in mitochondria during the onset and progression of neurodegenerative diseases. In that context, excitotoxicity induced by glutamate (GLU) plays an important role in mediating neurotoxicity. Several drugs have been used in the treatment of diseases involving excitotoxicity. Nonetheless, some patients (20-30%) present drug resistance. Thus, it is necessary to find chemicals able to attenuate mitochondrial dysfunction in the case of excitotoxicity. In this work, we treated the human neuroblastoma SH-SY5Y cell line with the diterpene carnosic acid (CA) at 1 μM for 12 h prior to the exposure to GLU for further 24 h. We found that CA prevented the GLU-induced mitochondrion-related redox impairment and bioenergetic decline in SH-SY5Y cells. CA also downregulated the pro-apoptotic stimulus elicited by GLU in this experimental model. CA exerted mitochondrial protection by a mechanism associated with the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2), since silencing of this protein with small interfering RNA (siRNA) suppressed the CA-induced protective effects. Future directions include investigating whether CA would be able to modulate mitochondrial function and/or dynamics in in vivo experimental models of excitotoxicity.

Procyanidin protects against 6-hydroxydopamine-induced dopaminergic neuron damage via the regulation of the PI3K/Akt signalling pathway

Over the past 200 years, Parkinson's disease (PD) has remained an insurmountable challenge. Despite the existence of numerous therapeutic drugs, there are still not enough treatments in the face of the complex pathogenesis of PD. Therefore, the search for more effective therapeutic drugs for PD has extremely important practical significance. Procyanidin (PC), widely found in plants such as grapes, is a bioflavonoid antioxidant with a special molecular structure that can effectively remove free radicals in the human body. To explore its possible mechanism in PD, we used 6-hydroxydopamine (6-OHDA, 8 μg) to mimic dopaminergic (DA) neuronal damage and validated this model in vivo and in vitro. in vivo, we detected an effect of PC (60 mg/kg) on the behavioural changes exhibited in 6-OHDA model rats, the number of DA neurons and the phosphorylation of protein kinase B (Akt). in vitro, we detected changes in cell viability, mitochondrial membrane potential (MMP) and total superoxide dismutase (SOD) and explored the role of PC (50 μM) by inhibiting the phosphoinositide 3-kinase (PI3K)/Akt signalling pathway with LY294002 (20 μM). The present study demonstrates that PC plays a protective role against 6-OHDA-induced neurotoxicity, which may be mediated through the activation of the PI3K/Akt signalling pathway. This study indicates a potential use for PC in the treatment and prevention of PD.

Effects of paraquat on IL-6 and TNF-α in macrophages

Effects of paraquat (PQ) on interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in macrophages were investigated. Different concentrations of PQ were added to mouse macrophage RAW264.7 for culture. According to different concentrations of PQ, mice were divided into micro concentration (0.01 mmol/l), low concentration (0.1 mmol/l), medium concentration (1 mmol/l), high concentration (10 mmol/l), and control groups without PQ. Trypan blue solution was used for detecting cell viability, a microplate reader for detecting the fluorescence intensity of reactive oxygen species (ROS), ELISA for detecting the expression levels of IL-6 and TNF-α. The medium concentration and the high concentration groups had significantly lower cell viability than the other three groups (P<0.050). The high concentration group had significantly lower cell viability than the medium concentration group (P<0.050). At 1, 4 and 8 h, respectively, the medium and the high concentration groups had significantly higher ROS fluorescence intensity than the other three groups (P<0.050). The high concentration group had significantly higher ROS fluorescence intensity than the medium concentration group (P<0.050). There were significant differences in the expression levels of IL-6 and TNF-α at the 1st, 4th and 8th hour among the five groups (P<0.050). In the micro, the low, the medium and high concentration groups, the expression levels of IL-6 and TNF-α were the lowest at 1 h and the highest at 8 h, which were higher at 4 h than those at 1 h (P<0.050). PQ at a concentration of 1 mmol/l can produce toxicity to macrophages, and greatly increase the ROS fluorescence intensity, the expression levels of IL-6 and TNF-α. PQ poisoning is expected to be treated though IL-6 and TNF-α in the future.

Baicalein protects human vitiligo melanocytes from oxidative stress through activation of NF-E2-related factor2 (Nrf2) signaling pathway

Vitiligo is a complex disorder characterized by patchy loss of skin pigmentation due to abnormal melanocyte function. Overwhelming evidences have suggested that oxidative stress plays a major role in the loss of melanocytes thereby mediating the onset and progression of vitiligo. The nuclear factor erythroid 2-like factor 2 (Nrf2) is a master regulator of cellular redox homeostasis and the activation of Nrf2 signaling pathway is impaired in the vitiligo melanocytes. Baicalein, as flavonoid extracted from the Scutellaria baicalensis, has been proved to possess the ability to activate Nrf2 signaling pathway in other cell types and mouse model. Our previous data found that baicalein exerts a cytoprotective role in H₂O₂-induced apoptosis in human melanocytes cell line (PIG1). Based on these founding, we hypothesized that baicalein activates Nrf2 signaling pathway, alleviates H₂O₂-induced mitochondrial dysfunction and cellular damage, thereby protecting human vitiligo melanocytes from oxidative stress. In the present study, we found that baicalein effectively inhibited H₂O₂-induced cytotoxicity and apoptosis in human vitiligo melanocytes (PIG3V). Further results demonstrated that baicalein promoted Nrf2 nucleus translocation as well as up-regulated the expression of Nrf2 and its target gene, heme oxygenase-1 (HO-1). Moreover, the protective effects of baicalein against H₂O₂-induced cellular damage and apoptosis as well as mitochondrial dysfunction were abolished by Nrf2 knockdown. Additionally, we observed that Nrf2 knockdown suppressed proliferation and increased the sensitivity of PIG3V cells to H₂O₂ treatment. Finally, we explored the mechanism of baicalein associated with Nrf2 activation and found that the phosphorylation of Nrf2 as well as ERK1/2and PI3K/AKT signaling were not involved in the baicalein-induced activation of Nrf2. Taken together, these data clearly suggest that baicalein enhances cellular antioxidant defense capacity of human vitiligo melanocytes through the activation of the Nrf2 signaling pathway, providing beneficial evidence for the application of baicalein in the vitiligo treatment.

Bacopa monnieri alleviates paraquat induced toxicity in Drosophila by inhibiting jnk mediated apoptosis through improved mitochondrial function and redox stabilization

Paraquat (PQ) is an organic chemical compound and a member of redox active family of heterocycles. In spite of its high toxicities, it is used as one of the potent herbicide throughout the world. Though its toxic manifestations are observed in different organs, its principal toxic effect is manifested in the brain leading to the development of Parkinsonian symptoms. PQ exposure adversely affects dopaminergic (DA-ergic) neuron-rich region in the substantia nigra pars compacta (SNPC) of brain in the animal models of Parkinson's disease (PD), thereby mimicking PD like symptoms. Currently, lack of a potential drug to counter the toxic effect of PQ makes the management difficult. Bacopa monnieri extract (BME) has been shown to have promising effect against neurodegenerative disorders. Therefore, the present study evaluated the role of BME against PQ induced toxicity in Drosophila model of PD, the results of which are reproducible in higher animal models including human subjects. Here, we showed that BME treatment attenuates acute PQ induced toxicity in Drosophila by decreasing mortality and improving climbing ability. BME functions by optimizing redox equilibrium, mitochondrial function and depreciating apoptosis level. The underlying mechanisms were attributed to optimization of active JNK and cleaved Caspase-3 activity along with transcriptional stabilization of the genes regulating oxidative stress and apoptosis (jnk, caspase-3, damb and nrf-2). These results showed therapeutic efficacy of BME against PQ toxicity in the brain. Our results pave the way for further detailed analysis of BME to combat the development of Parkinson's like symptoms following exposure to PQ toxicity in the brain of higher animal models.

The inhibition of heme oxigenase-1 (HO-1) abolishes the mitochondrial protection induced by sesamol in LPS-treated RAW 264.7 cells

Redox impairment and mitochondrial dysfunction have been seen in inflammation. Thus, there is interest in studies aiming to find molecules that would exert mitochondrial protection in mammalian tissues undergoing inflammation. Sesamol (SES) is an antioxidant and anti-inflammatory molecule as demonstrated in both in vitro and in vivo experimental models. Nonetheless, it was not previously demonstrated whether and how SES would cause mitochondrial protection during inflammation. Thus, we investigated here whether a pretreatment (for 1 h) with SES (1-100 μM) would prevent mitochondrial impairment in lipopolysaccharide (LPS)-treated RAW 264.7 cells. It was also evaluated whether the heme oxigenase-1 (HO-1) would be involved in the effects on mitochondria induced by SES. We found that SES reduced the levels of lipid peroxidation and protein nitration in the membranes of mitochondria obtained from LPS-treated RAW 264.7 cells. SES also attenuated the production of superoxide anion radical (O₂^-•) and nitric oxide (NO^•) in this experimental model. SES suppressed the LPS-elicited mitochondrial dysfunction, as assessed through the analyses of the activities of the mitochondrial complexes I and V. SES also abrogated the LPS-induced decrease in the levels of adenosine triphosphate (ATP) and in the mitochondrial membrane potential (MMP). SES induced mitochondria-related anti-apoptotic effects in LPS-treated cells. Besides, SES pretreatment abrogated the LPS-triggered inflammation by decreasing the levels of pro-inflammatory proteins. The SES-induced mitochondria-associated protection was blocked by the specific inhibitor of HO-1, ZnPP IX (20 μM). Therefore, SES induced mitochondrial protection in LPS-treated cells by a mechanism involving HO-1.

Comparing the role of Ginkgolide B and Ginkgolide K on cultured astrocytes exposed to oxygen‑glucose deprivation

Ginkgolide B (GB) and ginkgolide K (GK) are two main active monomers of ginkgolides that present a unique group of diterpenes found naturally in the leaves of the Ginkgo biloba tree. Astrocytes are the most abundant cell type within the central nervous system (CNS) and serve essential roles in maintaining healthy brain function. The present study compared the biological effects of GB and GK on astrocytes exposed to oxygen-glucose deprivation (OGD). The results demonstrated that GB and GK exhibit many different actions. The level of the platelet-activating factor (PAF) was elevated on astrocytes exposed to OGD, and inhibited by GB and GK treatment. Although GB and GK inhibited the expression of p-NF-κB/p65, GK exerted stronger anti-inflammatory and antioxidant effects on astrocytes exposed to OGD than GB by inhibiting interleukin (IL)-6 and tumor necrosis factor-α, and inducing IL-10 and the nuclear factor-erythroid 2-related factor 2/HO-1 signaling pathway. When compared with GB treatment, GK treatment maintained high levels of phosphoinositide 3-kinase/phosphorylated-protein kinase B expression, and induced a marked upregulation of Wnt family member 1 and brain derived neurotrophic factor, indicating that GK, as a natural plant compound, may have more attractive prospects for clinical application in the treatment of neurological disorders than GB.

Carnosic acid improves diabetic nephropathy by activating Nrf2/ARE and inhibition of NF-κB pathway

BACKGROUND

Diabetic nephropathy (DN), one of the most serious complications of diabetes, is the leading cause of morbidity and mortality of end-stage renal disease. Our previous research found that carnosic acid (CA) or rosemary extract can effectively improve glucose and lipid metabolism disorder by inhibiting SREBPs.

PURPOSE

In this study, we aimed to explore the therapeutic effects of CA on the DN.

METHODS

The mice glomerular mesangial cells (mGMCs) were used to evaluate the anti-oxidative and anti-inflammation effects of CA under high glucose (HG) condition. Furthermore, db/db mice and streptozotocin (STZ)-induced diabetic mice were used to investigate the effects of CA against DN in vivo.

RESULTS

The results showed that CA activated Nrf2, inhibited NF-κB pathway and regulated related downstream genes in mGMC under HG condition. A 14-week treatment of mice with CA reduced water uptake and urine volume, attenuated diabetes-induced albuminuria, increased urine creatinine, and subsequently improved the glomerular sclerosis and mesangial expansion in db/db mice. Similarly, a 20-week oral administration of CA improved kidney damage in STZ-induced diabetic mice. In addition, CA inhibited the expression of profibrotic factors, such as TGF-β1, fibronectin and E-cadherin. Compared to irbesartan, CA exerted better glucose lowering effect, and in kidney, CA was more potent to reduce fibronectin and E-cadherin expression. In all the animal experiment, CA did not lead to abnormal damages to other tissues.

CONCLUSION

These findings suggest that CA is a safe compound which exerts the protective effects on diabetes-induced kidney complications.

Inhibition of the Nrf2/HO-1 Axis Suppresses the Mitochondria-Related Protection Promoted by Gastrodin in Human Neuroblastoma Cells Exposed to Paraquat

Mitochondria are double-membrane organelles involved in the transduction of energy from different metabolic substrates into adenosine triphosphate (ATP) in mammalian cells. The oxidative phosphorylation system is comprised by the activity of the respiratory chain and the complex V (ATP synthase/ATPase). This system is dependent on oxygen gas (O₂) in order to maintain a flux of electrons in the respiratory chain, since O₂ is the final acceptor of these electrons. Electron leakage from this complex system leads to the continuous generation of reactive species in the cells. The mammalian cells exhibit certain mechanisms to attenuate the consequences originated from the constant exposure to these reactive species. In this context, the transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) and one of the enzymes whose expression is modulated by Nrf2, heme oxygenase-1 (HO-1), take a central role in inducing cytoprotection in humans. Mitochondrial abnormalities are observed during intoxication and in certain diseases, including neurodegeneration. Mitochondrial protection promoted by natural compounds has attracted the attention of researchers due to the promising effects these agents induce experimentally. In this regard, we examined here whether and how gastrodin (GAS), a phenolic glucoside, would prevent the paraquat (PQ)-induced mitochondrial impairment in the SH-SY5Y cells. The cells were exposed to GAS (25 μM) for 4 h prior to the challenge with PQ at 100 μM for additional 24 h. The silencing of Nrf2 by siRNA or the inhibition of HO-1 by ZnPP IX suppressed the GAS-elicited cytoprotection. Therefore, GAS promoted mitochondrial protection by an Nrf2/HO-1-dependent manner.

Evaluation of the Mitochondria-Related Redox and Bioenergetics Effects of Gastrodin in SH-SY5Y Cells Exposed to Hydrogen Peroxide

Mitochondrion is the main site of ATP production in animal cells and also orchestrates signaling pathways associated with cell survival and death. Mitochondrial dysfunction has been linked to bioenergetics and redox impairment in human diseases, such as neurodegeneration and cardiovascular disease. Protective agents able to attenuate mitochondrial impairment are of pharmacological interest. Gastrodin (GAS; 4-hydroxybenzyl alcohol 4-O-beta-D-glucoside) is a phenolic glucoside obtained from the Chinese herbal medicine Gastrodia elata Blume and exhibits antioxidant, anti-inflammatory, and antiapoptotic effects in several cell types. GAS is able to cross the blood-brain barrier, reducing the impact of different stressors on the cognition of experimental animals. In the present work, we investigated whether GAS would protect mitochondria of human SH-SY5Y neuroblastoma cells against an exposure to a pro-oxidant agent. The cells were treated with GAS at 25 μM for 30 min before the administration of hydrogen peroxide (H₂O₂) at 300 μM for an additional 3 or 24 h, depending on the assay. We evaluated both mitochondrial redox state and function parameters and analyzed the mechanism by which GAS protected mitochondria in this experimental model. Silencing of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor suppressed the GAS-induced mitochondrial protection seen here. Moreover, Nrf2 knockdown abrogated the effects of GAS on cell viability, indicating a potential role for Nrf2 in both mitochondrial and cellular protection promoted by GAS. Further research would be necessary to investigate whether GAS would be able to induce similar effects in in vivo experimental models.

Naringenin Attenuates H2O2-Induced Mitochondrial Dysfunction by an Nrf2-Dependent Mechanism in SH-SY5Y Cells

Mitochondria are the major site of ATP production in mammalian cells. Furthermore, these organelles are a source and a target of reactive oxygen species (ROS), such as radical anion superoxide (O₂^-·) and hydrogen peroxide (H₂O₂). The transcription factor nuclear factor erythroid 2-related factor 2 (Nrf2) is the master regulator of the mammalian redox biology and controls the expression of antioxidant and phase II detoxifying enzymes in several cell types. Naringenin (NGN, 5,7-dihydroxy-2-(4-hydroxyphenyl)-2,3-dihydrochromen-4-one), a flavanone, exhibits cytoprotective effects by acting as an antioxidant and anti-inflammatory agent. NGN is a potent activator of Nrf2. Nonetheless, it was not examine yet whether NGN would induce mitochondrial protection in cells under redox stress. Therefore, we investigate here whether Nrf2 would be involved in the mitochondrial protection elicited by NGN in SH-SY5Y cells exposed to H₂O₂. We observed that a pretreatment with NGN at 80 µM for 2 h reduced the levels of lipid peroxidation, protein carbonylation, and protein nitration in the membranes of mitochondria obtained from H₂O₂-treated SH-SY5Y cells. Additionally, NGN prevented the H₂O₂-induced impairment in the function of the enzymes aconitase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase. The activites of the complexes I and V, as well as the production of ATP, were restored by NGN. NGN also suppressed the H₂O₂-induced mitochondria-related apoptosis. Interestingly, NGN promoted an increase in the levels of both total and mitochondrial glutathione (GSH). Silencing of Nrf2 abolished the protective effects induced by NGN. Overall, NGN induced mitochondrial protection by an Nrf2-dependent mechanism in H₂O₂-treated SH-SY5Y cells.

Sulforaphane Promotes Mitochondrial Protection in SH-SY5Y Cells Exposed to Hydrogen Peroxide by an Nrf2-Dependent Mechanism

Sulforaphane (SFN; C₆H₁₁NOS₂) is an isothiocyanate found in cruciferous vegetables, such as broccoli, kale, and radish. SFN exhibits antioxidant, anti-apoptotic, anti-tumor, and anti-inflammatory activities in different cell types. However, it was not previously demonstrated whether and how this natural compound would exert mitochondrial protection experimentally. Therefore, we investigated here the effects of a pretreatment (for 30 min) with SFN at 5 μM on mitochondria obtained from human neuroblastoma SH-SY5Y cells exposed to hydrogen peroxide (H₂O₂) at 300 μM for 24 h. We found that SFN prevented loss of viability in H₂O₂-treated SH-SY5Y cells. Furthermore, SFN decreased lipid peroxidation, protein carbonylation, and protein nitration in mitochondrial membranes of H₂O₂-exposed cells. Importantly, SFN enhanced the levels of both cellular and mitochondrial glutathione (GSH). SFN also suppressed the H₂O₂-mediated inhibition of mitochondrial components involved in the maintenance of the bioenergetics state, such as aconitase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase, as well as complexes I and V. Consequently, SFN prevented the decline induced by H₂O₂ on the levels of ATP in SH-SY5Y cells. Silencing of the nuclear factor erythroid 2-related factor 2 (Nrf2) transcription factor by using small interfering RNA (siRNA) abolished the mitochondrial and cellular protection elicited by SFN. Therefore, SFN abrogated the H₂O₂-induced mitochondrial impairment by an Nrf2-dependent manner.

Daphnetin-mediated Nrf2 antioxidant signaling pathways ameliorate tert-butyl hydroperoxide (t-BHP)-induced mitochondrial dysfunction and cell death

Daphnetin (Daph), a natural coumarin derivative isolated from plants of the Genus Daphne, possesses abundant biological activities, such as anti-inflammatory, antioxidant and anticancer properties. In the present study, we focused on investigating the protective effect of Daph against tert-butyl hydroperoxide (t-BHP)-induced oxidative damage, mitochondrial dysfunction and the involvement of underlying molecular mechanisms. Our findings indicated that Daph effectively inhibited t-BHP-stimulated cytotoxicity, cell apoptosis, and mitochondrial dysfunction, which are associated with suppressed reactive oxygen species (ROS) generation, decreased malondialdehyde (MDA) formation, increased superoxide dismutase (SOD) levels and glutathione (GSH)/GSSG (oxidized GSH) ratio. Further investigation indicated that Daph significantly suppressed cytochrome c release and NLRP3 inflammasome activation and modulated apoptosis-related protein Bcl-2, Bax, and caspase-3 expression. Moreover, Daph dramatically induced the expression of the glutamate-cysteine ligase modifier (GCLM) subunit and the glutamate-cysteine ligase catalytic (GCLC) subunit, heme oxygenase-1 (HO-1), and NAD (P) H: quinone oxidoreductase (NQO1), which is largely dependent on upregulating the nuclear factor-erythroid 2-related factor 2 (Nrf2) nuclear translocation, reducing the Keap1 protein expression, and strengthening the antioxidant response element (ARE) promoter activity. Additionally, Daph remarkably activated a c-Jun NH2-terminal kinase (JNK) and extracellular signal-regulated kinase (ERK) phosphorylation, but ERK and JNK inhibitor pretreatment exhibited an evident decrease of the level of Daph-enhanced Nrf2 nuclear translocation. Furthermore, Daph exposure suppressed t-BHP-induced cytotoxicity and ROS overproduction, which are mostly blocked in Nrf2 knockout RAW 264.7 cells and peritoneal macrophages. Accordingly, Daph exhibited protective roles against t-BHP-triggered oxidative damage and mitochondrial dysfunction by the upregulation of Nrf2 antioxidant signaling pathways, which may be involved in the activation of JNK and ERK.

Natural antioxidants in the treatment and prevention of diabetic nephropathy; a potential approach that warrants clinical trials

Diabetic nephropathy is the major cause of end-stage renal disease and effective and new therapeutic approaches are needed in diabetic nephropathy and chronic kidney diseases. Oxidative stress and inflammatory process are important factors contributing to kidney damage by increasing production of oxidants. KEAP1/Nrf2/ARE pathway regulates the transcription of many antioxidant genes and modulation of the pathway up regulates antioxidants. NFB controls the expression of genes involved in the inflammatory response. Natural substances have antioxidant and anti-inflammatory activities and have an impact on NFB and KEAP1/Nrf2/ARE pathways. The preclinical studies explored the effectiveness of whole herbs, plants or seeds and their active ingredients in established diabetic nephropathy. They ameliorate oxidative stress induced kidney damage, enhance antioxidant system, and decrease inflammatory process and fibrosis; most likely by activating KEAP1/Nrf2/ARE pathway and by deactivating NFB pathway. Whole natural products contain balanced antioxidants that might work synergistically to induce beneficial therapeutic outcome. In this context, more clinical studies involving whole plants or herbal products or mixtures of different herbs and plants and their active ingredients might change our strategies for the management of diabetic nephropathy. The natural products might be useful as preventive interventions and studies are required in this field.

Protective effects of lichen metabolites evernic and usnic acids against redox impairment-mediated cytotoxicity in central nervous system-like cells

Lichens species produce unique secondary metabolites that attract increasing pharmacological interest, including their redox modulatory activities. Current work evaluated for the first time the in vitro cytoprotective properties, based on the antioxidant activities, of the Parmeliaceae lichens Evernia prunastri and Usnea ghattensis and the mechanism of action of their major phenolic constituents: the evernic and usnic acids, respectively. In two models of central nervous system-like cells (U373-MG and SH-SY5Y cell lines), exogenous H₂O₂ induced oxidative stress-mediated cytotoxicity. We first assessed their radical scavenging capacities (ORAC and DPPH tests) and the phenolic content of the extracts. At the optimal concentrations, pretreatments with evernic acid displayed significant protection against H₂O₂-induced cytotoxic damage in both models. It reversed the alterations in oxidative stress markers (including ROS generation, glutathione system and lipid peroxidation levels) and cellular apoptosis (caspase-3 activity). Such effects were in part mediated by a notable enhancement of the expression of intracellular phase-II antioxidant enzymes; a plausible involvement of the Nrf2 cytoprotective pathway is suggested. Usnic acid exerted similar effects, to some extent more moderate. Results suggest that lichen polyketides evernic and usnic acids merit further research as promising antioxidant candidates in the therapy of oxidative stress-related diseases, including the neurodegenerative disorders.