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

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.

Anacardium microcarpum extract and fractions protect against paraquat-induced toxicity in Drosophila melanogaster

Anacardium microcarpum Ducke (Anacardiaceae) is a native species of Brazil used in folk medicine for the treatment of several illnesses although its antioxidant activity has been reported in vitro, there is no evidence of this effect in an in vivo model. Here, we investigated the potential protective effect of hydroalcoholic extract (AMHE), methanol (AMMF) and acetate (AMAF) fraction of A. microcarpum against paraquat toxicity on survivorship, locomotor performance, antioxidant enzymes activity and reactive species using Drosophila melanogaster. Flies were exposed to the extract or fractions (1 and 10 mg/ml) in the presence or absence of paraquat (5 mM) in sucrose solution for 72 h. In addition, total phenolic content of extract and fractions was evaluated as well as ABTS radical scavenging capacity. Our results demonstrated that AMAF presented higher content of phenols and ABTS chelating potential. Treatment of flies with the extract or fractions did not alter the survivorship, locomotor ability, and acetylcholinesterase (AchE) activity per se. Paraquat caused 85 % mortality of flies and 30 % increase in reactive species generation, which were significantly attenuated by AMHE and AMMF. AAMF increased catalase activity (from 66.77 ± 6.64 to 223.94 ± 25.92 mU/mg of protein), while AMAF increased GST activity (from 477.76 ± 92 to 770.19 ± 147.92 mU/mg of protein) and catalase activity (from 66.77 ± 6.64 to 220.54 ± 26.63 mU/mg of protein). AMHE and AMMF were more effective in protecting against paraquat toxicity. Taken together, the data indicate the potential of this plant in acting as a protective and antioxidant agent in vivo.

Toll-like receptor 4 ablation rescues against paraquat-triggered myocardial dysfunction: Role of ER stress and apoptosis

Paraquat is a nitrogen herbicide imposing severe organ toxicity in human leading to acute lung injury and heart failure. The present study was designed to examine the impact of ablation of the innate proinflammatory mediator toll-like receptor 4 (TLR4) in paraquat-induced cardiac contractile dysfunction and the underlying mechanisms involved with a focus on endoplasmic reticulum (ER) stress and apoptosis. Adult male wild-type (WT) and TLR4 knockout (TLR4-/- ) mice were challenged with paraquat (45 mg/kg, i.p.) for 48 h prior to the assessment of myocardial and cardiomyocyte sarcomere function, ER stress, apoptosis and inflammation. Acute paraquat challenge exerted myocardial functional and geometric alterations including enlarged left ventricular end systolic diameter (LVESD), reduced fractional shortening, decreased sarcomere shortening, maximal velocities of sarcomere shortening and relengthening associated with unchanged LV posterior wall thickness, septal thickness, LV end diastolic diameter (LVEDD), heart rate, sarcomere length, time-to-peak shortening and time-to-90% relengthening. Although TLR4 ablation did not affect mechanical properties in the heart, it significantly attenuated or ablated paraquat-induced cardiac contractile anomalies. Moreover, paraquat imposed overt ER stress, apoptosis and inflammation as evidenced by upregulation of Bip, CHOP, Caspase-3, -9, Bax, Bad, and IL-1β, phosphorylation of PERK, eIF2α and IΚB, as well as activation of the stress molecules ERK and p38, with unchanged Caspase-8, Bcl2, TNF-α, p53, HMGB1, MyD88 and phosphorylation of Akt, GSK3β and JNK, the effects of which were attenuated or negated by TLR4 knockout. Taken together, our results suggested that TLR4 ablation alleviated paraquat-induced myocardial contractile dysfunction possibly through attenuation of ER stress, apoptosis and inflammation. © 2016 Wiley Periodicals, Inc. Environ Toxicol 32: 656-668, 2017.

Silymarin protects against acrylamide-induced neurotoxicity via Nrf2 signalling in PC12 cells

Silymarin (SM) is a well-known antioxidant, anti-inflammatory and anti-cancer compound extracted from the milk thistle. Here, we investigated the protective effect of SM against acrylamide (AA)-induced neurotoxicity, mainly caused by oxidative stress, via activation of the nuclear transcription factor E2-related factor 2 (Nrf2) signalling pathway in PC12 cells. The MTT reduction assay was used to measure cell viability in various drug-treated groups and demonstrated that SM could increase cell viability in AA-treated PC12 cells. We then measured the reactive oxygen species (ROS) levels by the peroxide-sensitive fluorescent probe DCFH-DA and intracellular glutathione (GSH) and malondialdehyde (MDA) levels by absorption spectrophotometry. Our data revealed that SM could reduce ROS and MDA levels and increase GSH levels in AA-induced PC12 cells. To identify a potential mechanism for SM-induced protection, we measured the mRNA and protein expression levels of Nrf2 and its downstream target antioxidants glutathione peroxidase (Gpx), glutamate cysteine ligase catalytic subunit (GCLC) and glutamate cysteine ligase modifier subunit (GCLM) by quantitative real-time PCR and Western blot, respectively. The results suggested that SM could activate Nrf2 signalling and increase the expression of Nrf2, Gpx, GCLC and GCLM in AA-treated PC12 cells. In conclusion, SM can effectively alleviate AA-induced neurotoxicity in PC12 cells.

Carnosic Acid Suppresses the H2O2-Induced Mitochondria-Related Bioenergetics Disturbances and Redox Impairment in SH-SY5Y Cells: Role for Nrf2

The phenolic diterpene carnosic acid (CA, C₂₀H₂₈O₄) exerts antioxidant, anti-inflammatory, anti-apoptotic, and anti-cancer effects in mammalian cells. CA activates the nuclear factor erythroid 2-related factor 2 (Nrf2), among other signaling pathways, and restores cell viability in several in vitro and in vivo experimental models. We have previously reported that CA affords mitochondrial protection against various chemical challenges. However, it was not clear yet whether CA would prevent chemically induced impairment of the tricarboxylic acid cycle (TCA) function in mammalian cells. In the present work, we found that a pretreatment of human neuroblastoma SH-SY5Y cells with CA at 1 μM for 12 h prevented the hydrogen peroxide (H₂O₂)-induced impairment of the TCA enzymes (aconitase, α-ketoglutarate dehydrogenase (α-KGDH), succinate dehydrogenase (SDH)) and abolished the inhibition of the complexes I and V and restored the levels of ATP by a mechanism associated with Nrf2. CA also exhibited antioxidant abilities by enhancing the levels of reduced glutathione (GSH) and decreasing the content oxidative stress markers (cellular 8-oxo-2'-deoxyguanosine (8-oxo-dG), and mitochondrial malondialdehyde (MDA), protein carbonyl, and 3-nitrotyrosine). Silencing of Nrf2 by small interfering RNA (siRNA) abrogated the protective effects elicited by CA in mitochondria of SH-SY5Y cells. Therefore, CA prevented the H₂O₂-triggered mitochondrial impairment by an Nrf2-dependent mechanism. The specific role of Nrf2 in ameliorating the function of TCA enzymes function needs further research.

Pinocembrin Attenuates Mitochondrial Dysfunction in Human Neuroblastoma SH-SY5Y Cells Exposed to Methylglyoxal: Role for the Erk1/2-Nrf2 Signaling Pathway

Pinocembrin (PB; 5,7-dihydroxyflavanone) is found in propolis and exhibits antioxidant activity in several experimental models. The antioxidant capacity of PB is associated with the activation of the nuclear factor erythroid 2-related factor 2/antioxidant response element (Nrf2/ARE) signaling pathway. The Nrf2/ARE axis mediates the expression of antioxidant and detoxifying enzymes, such as glutathione peroxidase (GPx), glutathione reductase (GR), heme oxygenase-1 (HO-1), and the catalytic (GCLC) and regulatory (GCLM) subunits of the rate-limiting enzyme in the synthesis of glutathione (GSH), γ-glutamate-cysteine ligase (γ-GCL). Nonetheless, it is not clear how PB exerts mitochondrial protection in mammalian cells. Human neuroblastoma SH-SY5Y cells were pretreated (4 h) with PB (0-25 µM) and then exposed to methylglyoxal (MG; 500 µM) for further 24 h. Mitochondria were isolated by differential centrifugation. PB (25 µM) provided mitochondrial protection (decreased lipid peroxidation, protein carbonylation, and protein nitration in mitochondrial membranes; decreased mitochondrial free radical production; enhanced the content of GSH in mitochondria; rescued mitochondrial membrane potential-MMP) and blocked MG-triggered cell death by a mechanism dependent on the activation of the extracellular-related kinase (Erk1/2) and consequent upregulation of Nrf2. PB increased the levels of GPx, GR, HO-1, and mitochondrial GSH. The PB-induced effects were suppressed by silencing of Nrf2 with siRNA. Therefore, PB activated the Erk1/2-Nrf2 signaling pathway resulting in mitochondrial protection in SH-SY5Y cells exposed to MG. Our work shows that PB is a strong candidate to figure among mitochondria-focusing agents with pharmacological potential.

Upregulation of Akt/NF-κB-regulated inflammation and Akt/Bad-related apoptosis signaling pathway involved in hepatic carcinoma process: suppression by carnosic acid nanoparticle

Primary liver cancer is globally the sixth most frequent cancer, and the second leading cause of cancer death and its incidence is increasing in many countries, becoming a serious threat to human health. Many researches focused on the treatment and prevention of liver cancer. However, due to the underlying molecular mechanism of liver cancer still not fully understood, the studies and development of treatments were forced to be delayed. Akt has been suggested to play an essential role in the progression of inflammation response and apoptosis. Hence, in this study, Akt-knockout mice and cells of liver cancer were used as a model to investigate the molecular mechanism of Akt-associated inflammatory and apoptotic signaling pathway linked with NF-κB and Bcl-2-associated death promoter (Bad) for the progression of liver cancer. Carnosic acid (CA), as a phenolic diterpene with anticancer, antibacterial, antidiabetic, as well as neuroprotective properties, is produced by many species from Lamiaceae family. Administration of CA nanoparticles was sufficient to lead to considerable inhibition of liver cancer progression. The results indicated that, compared to the normal liver cells, the expression of Akt was significantly higher in liver cancer cell lines. Also, we found that Akt-knockout cancer cell lines modulated inflammation response and apoptosis via inhibiting NF-κB activation and inducing apoptotic reaction. Our results indicated that the downstream signals, including cytokines regulated by NF-κB and caspase-3-activated apoptosis affected by Bad, were re-modulated for knockout of Akt. And CA nanoparticles, acting as Akt-knockout, could inhibit inflammation and accelerate apoptosis in liver cancer by altering NF-κB activation and activating caspase-3 through Bad pathway. These findings demonstrated that the nanoparticulate drug CA performed its effective role owing to its ability to reduce inflammatory action and enhance apoptosis for the overexpression of NF-κB and Bad via Akt signaling pathway, playing a direct role in liver cancer progression. Thus, nanoparticle CA might be an important and potential choice for the clinical treatment in the future.

Tanshinone I Attenuates the Effects of a Challenge with H2O2 on the Functions of Tricarboxylic Acid Cycle and Respiratory Chain in SH-SY5Y Cells

Tanshinone I (T-I; C₁₈H₁₂O₃) is a cytoprotective molecule. T-I has been viewed as an antioxidant and anti-inflammatory agent exerting neuroprotective actions in several experimental models. Nonetheless, the mechanisms underlying the beneficial effects of T-I in mammalian cells are not completely understood yet. Mitochondrial dysfunction has been associated with several neurodegenerative diseases which remain uncured. Therefore, there is increasing interest in compounds that may be used in the prevention or treatment of those pathologies. Since T-I presents an antioxidant capacity, we investigated here whether and how this compound would prevent mitochondrial impairment in SH-SY5Y cells exposed to hydrogen peroxide (H₂O₂), which has been involved in the triggering of deleterious effects in several experimental models mimicking neurodegenerative processes. We found that a pretreatment with T-I at 2.5 μM for 2 h suppressed the pro-oxidant effects of H₂O₂ on mitochondrial membranes. Furthermore, T-I prevented the H₂O₂-elicited inhibition of the tricarboxylic acid (TCA) cycle enzymes (aconitase, α-ketoglutarate dehydrogenase, and succinate dehydrogenase) and of the mitochondrial complexes I and V. T-I also abrogated the mitochondrial depolarization and the mitochondrial failure to produce ATP in cells exposed to H₂O₂. T-I upregulated the levels of reduced glutathione (GSH) in the mitochondria of SH-SY5Y cells. T-I induced mitochondrial protection, at least in part, by activating the nuclear factor erythroid 2-related factor 2 (Nrf2), because silencing of Nrf2 by using small interference RNA (SiRNA) blocked these effects. Therefore, T-I afforded mitochondrial protection (involving both redox and bioenergetics-related aspects) against H₂O₂ through the activation of Nrf2.

Pinocembrin Provides Mitochondrial Protection by the Activation of the Erk1/2-Nrf2 Signaling Pathway in SH-SY5Y Neuroblastoma Cells Exposed to Paraquat

Pinocembrin (PB; 5,7-dihydroxyflavanone; C₁₅H₁₂O₄) is a flavonoid found in propolis and exerts antioxidant, anti-inflammatory, and antimicrobial effects. Furthermore, PB has been studied as a neuroprotective agent. However, it remains to be understood whether and how PB would induce mitochondrial protection in mammalian cells. Therefore, we investigated here the mechanism involved in the protective effects elicited by PB in paraquat (PQ; 100 μM)-treated SH-SY5Y neuroblastoma cells. PB (25 μM) pretreatment (for 4 h) downregulated the levels of Bcl-2-associated X protein (Bax), blocked the release of cytochrome c to the cytosol, and inhibited the PQ-induced activation of caspase-9 and caspase-3. Besides, PB prevented mitochondrial dysfunction by suppressing the PQ-elicited inhibition of complexes I and V. Moreover, PB abrogated the loss of mitochondrial membrane potential (MMP) and the decline in ATP levels in the cells exposed to PQ. PB exerted antioxidant effects on mitochondria by decreasing the levels of redox impairment markers in mitochondrial membranes. Importantly, PB enhanced the levels of mitochondrial reduced glutathione (GSH). Upregulation of enzymes involved in the synthesis of GSH was seen in the cells exposed to PB. PB afforded mitochondrial protection by activating the extracellular signal-regulated kinase/nuclear factor erythroid 2-related factor 2 (Erk1/2-Nrf2) axis, since inhibition of Erk1/2 or silencing of Nrf2 abrogated these effects. Therefore, PB exerted mitochondrial and cellular protection by an Erk1/2-Nrf2-dependent mechanism.

Relevance of carnosic acid to the treatment of several health disorders: Molecular targets and mechanisms

Carnosic acid is a phenolic diterperne compound found in abundance in sage and rosemary, which are both widely used in traditional medicine. Research over the past decade indicates that carnosic acid has multiple bioactive properties including antioxidant, anti-inflammatory and anticancer activities among others. This review summarizes the current in vitro and in vivo data about the efficacy of carnosic acid in the prevention or treatment of various experimental health disorders. The analysis of the literature allows an insight into the participation of numerous signaling pathways modulated by carnosic acid, into its synergistic potential and, thus, into the divergence in cellular mechanisms of action of this molecule.

Carnosic acid attenuates unilateral ureteral obstruction-induced kidney fibrosis via inhibition of Akt-mediated Nox4 expression

Fibrosis represents a common pathway to end-stage renal disease. Transforming growth factor-β (TGF-β) plays a critical role in the progression of kidney fibrosis. In the present study, we explored the effect of carnosic acid (CA) against TGF-β-induced fibroblast activation in vitro and unilateral ureteral obstruction (UUO)-induced kidney fibrosis in vivo. CA attenuated TGF-β-induced up-regulation of profibrogenic proteins, α-smooth muscle actin (α-SMA), collagen I (COLI), fibronectin (FN), and plasminogen activator inhibitor-1 (PAI-1) in kidney fibroblast cells (NRK-49F). CA inhibited TGF-β-induced hydrogen peroxide generation via inhibition of NADPH oxidase 4 (Nox4) expressions. In mice, CA-administration markedly mitigated the UUO-induced interstitial extension, collagen deposition, superoxide anion formation, hydrogen peroxide production, and lipid peroxidation. In addition, CA significantly attenuated the expression of α-SMA, COLI, FN, PAI-1, and Nox4 in UUO-induced kidneys. These results indicated that CA attenuated oxidative stress via inhibition of Nox4 expression in TGF-β-stimulated fibroblasts and UUO operated-kidneys, suggesting that CA may be useful for the treatment of fibrosis-related diseases.

Tanshinone I Induces Mitochondrial Protection through an Nrf2-Dependent Mechanism in Paraquat-TreatedHuman Neuroblastoma SH-SY5Y Cells

Tanshinone I (T-I; 1,6-Dimethylnaphtho[1,2-g][1]benzofuran-10,11-dione; C₁₈H₁₂O₃), which may be found in Salvia miltiorrhiza Bunge (Danshen), is a potent anti-inflammatory, antioxidant, and anti-cancer agent. At least in part, T-I exerts antioxidant activity by activating signaling pathways associated with the maintenance of the redox state in mammalian cells. In this context, the upregulation of nuclear factor (erythroid-derived 2)-like 2 (Nrf2) has received attention regarding the role of this transcription factor in modulating the expression of antioxidant enzymes and the metabolism of glutathione (GSH). Even though there is a growing body of evidence suggesting that T-I mediates protection against several pro-oxidant challenges in both in vitro and in vivo experimental models, it remains to be examined whether and how T-I would modulate mitochondrial function during redox disturbances. Therefore, we aimed to reveal whether T-I would exhibit protective effects on mitochondria of SH-SY5Y cells treated with paraquat (PQ), a well-known mitochondrial toxic agent. We found that T-I pretreatment significantly protected mitochondria against PQ-induced redox impairment through an Nrf2-dependent mechanism involving upregulation of antioxidant enzymes, such as Mn-superoxide dismutase (Mn-SOD), glutathione peroxidase (GPx), and both catalytic and modifier subunits of γ-glutamate-cysteine ligase (γ-GCL). T-I prevented complex I and mitochondrial membrane potential (MMP) impairments elicited by PQ. Thus, T-I may be viewed as a new mitochondrial protective agent whose complete mechanism of action needs to be investigated, but it seems to involve mitochondriotropic aspects related to the chemistry of this molecule.

Fluoxetine and the mitochondria: A review of the toxicological aspects

Fluoxetine (a selective serotonin reuptake inhibitor (SSRI)) is used as an antidepressant by modulating the levels of serotonin in the synaptic cleft. Nevertheless, fluoxetine also induces undesirable effects, such as anxiety, sexual dysfunction, sleep disturbances, and gastrointestinal impairments. Fluoxetine has been viewed as an agent that may interfere with cell fate by triggering apoptosis. On the other hand, fluoxetine intake has been associated with increased cancer risk. Nonetheless, data remain contradictory and no conclusions were taken. Several studies demonstrated that fluoxetine interacts with mitochondria triggering apoptosis and/or altering mitochondrial function by modulating the activity of respiratory chain components and enzymes of the Krebs cycle. Furthermore, fluoxetine affects mitochondria-related redox parameters in different experimental models. In this review, data demonstrating the effects of fluoxetine upon mammalian mitochondria are described and discussed, as well as several unsolved questions in this field of research are addressed. A separate section deals with future needs regarding the research involving the impact of fluoxetine treatment upon mitochondria and mitochondria-related signaling.

Carnosic Acid Affords Mitochondrial Protection in Chlorpyrifos-Treated Sh-Sy5y Cells

Carnosic acid (CA; C20H28O4) is a phenolic diterpene found in rosemary (Rosmarinus officinalis L.) and exhibits protective properties, e.g., antioxidant, anti-inflammatory, antitumor, and antimicrobial activities. In this context, CA has been viewed as a neuroprotective agent due to its ability in rescuing neuronal cells from pro-oxidant and pro-apoptotic challenges. In the present work, we found that CA pretreatment at 1 µM for 12 h suppressed the mitochondria-related pro-oxidant and mitochondria-dependent pro-apoptotic effects of chlorpyrifos (CPF) in human neuroblastoma SH-SY5Y cells. CA prevented mitochondrial membrane potential disruption and decreased the levels of oxidative stress markers in mitochondrial membranes obtained from cells exposed to CPF. CA also inhibited cytochrome c release and activation of the caspases-9 and -3, as well as decreased DNA fragmentation, in CPF-treated cells. CA upregulated the content of glutathione (GSH) in mitochondria by a mechanism involving the activation of the phosphoinositide-3-kinase (PI3K)/Akt/nuclear factor erythroid 2-related factor 2 (Nrf2) signaling pathway, since inhibition of PI3K/Akt or silencing of Nrf2 using siRNA strategy abolished the protection exerted by CA in SH-SY5Y cells. Therefore, CA protected mitochondria of SH-SY5Y cells through the activation of the PI3K/Akt/Nrf2 axis, causing upregulation of the mitochondrial GSH content and consequent antioxidant and anti-apoptotic effects.