Emodin protected against synaptic impairment and oxidative stress induced by fluoride in SH-SY5Y cells by modulating ERK1/2/Nrf2/HO-1 pathway

Unraveling the role of abnormal AMPK and CRMP-2 phosphorylation in developmental fluoride neurotoxicity: Implications for synaptic damage and neurological disorders

Excessive fluoride exposure can be neurotoxic, although the exact mechanism remains unknown. This study aimed to investigate the neurotoxicity of continuous sodium fluoride exposure in offspring rats, focusing on the potential effects of fluoride exposure on hippocampal synaptic function and the role of AMPK and CRMP-2 in synaptic damage. We established an SD rat model of fluoride exposure (25, 50, and 100 mg/L NaF) and found that fluoride exposure damaged the learning and memory ability of F1 generation rats and caused ultrastructural changes in the hippocampus. Additionally, after the proteomic and phosphoproteomic analysis of rat hippocampal tissues, the Gene Ontology analysis revealed that sodium fluoride was involved in the enrichment of neuronal differentiation, synaptic signaling, and cytoskeleton-related biological processes. The Kyoto Encyclopedia of Genes and Genomes analysis showed that differential genes were enriched in synapse-related signaling pathways. Thus, we screened three differentially expressed proteins related to synaptic function for validation. The Western blotting analysis showed that AMPK and CRMP-2 were hyperphosphorylated in the hippocampus of fluoride-exposed rats. Our study found that abnormal AMPK and CRMP-2 phosphorylation leads to synaptic damage. This may be an important cause of memory impairment in fluorosis, offering new insights into the mechanism of fluoride-induced neurotoxicity.

The Activity of 1,8-Dihydroanthraquinone Derivatives in Nervous System Cancers

Primary and metastatic tumors of the nervous system represent a diverse group of neoplasms, each characterized by distinct biological features, prognostic outcomes, and therapeutic approaches. Due to their molecular complexity and heterogeneity, nervous system cancers (NSCs) pose significant clinical challenges. For decades, plants and their natural products with established anticancer properties have played a pivotal role in the treatment of various medical conditions, including cancers. Anthraquinone derivatives, a class of tricyclic secondary metabolites, are found in several botanical families, such as Fabaceae, Polygonaceae, Rhamnaceae, and Rubiaceae. In a comprehensive review, recent advancements in the anticancer properties of 1,8-dihydroanthraquinone derivatives-such as emodin, aloe-emodin, hypericin, chrysophanol, rhein, and physcion-were analyzed. These compounds have been studied extensively, both used individually and in combination with other chemotherapeutic agents, using in vitro and in vivo models of nervous system tumors. It was demonstrated that 1,8-dihydroanthraquinone derivatives induce apoptosis and necrosis in cancerous cells, intercalate into DNA, disrupting transcription and replication in rapidly dividing cells, and alter ROS levels, leading to oxidative stress that damages tumor cells. Additionally, they can influence signaling pathways involved in oncogenesis, such as MAPK, PI3K/Akt, or others crucial for the survival and the proliferation of NSC cells. The exploration of 1,8-dihydroanthraquinone derivatives aims to develop novel therapies that could overcome resistance and improve cancer patients' outcomes.

NRF2 Deficiency Promotes Ferroptosis of Astrocytes Mediated by Oxidative Stress in Alzheimer's Disease

Oxidative stress is involved in the pathogenesis of Alzheimer's disease (AD), which is linked to reactive oxygen species (ROS), lipid peroxidation, and neurotoxicity. Emerging evidence suggests a role of nuclear factor (erythroid-derived 2)-like 2 (Nrf2), a major source of antioxidant response elements in AD. The molecular mechanism of oxidative stress and ferroptosis in astrocytes in AD is not yet fully understood. Here, we aimed to investigate the mechanism by which Nrf2 regulates the ferroptosis of astrocytes in AD. We found decreased expression of Nrf2 and upregulated expression of the ROS marker NADPH oxidase 4 (NOX4) in the frontal cortex from patients with AD and in the cortex of 3×Tg mice compared to wildtype mice. We demonstrated that Nrf2 deficiency led to ferroptosis-dependent oxidative stress-induced ROS with downregulated heme oxygenase-1 and glutathione peroxidase 4 and upregulated cystine glutamate expression. Moreover, Nrf2 deficiency increased lipid peroxidation, DNA oxidation, and mitochondrial fragmentation in mouse astrocytes (mAS, M1800-57). In conclusion, these results suggest that Nrf2 deficiency promotes ferroptosis of astrocytes involving oxidative stress in AD.

Micro- and Macronutrients in Endometrial Cancer-From Metallomic Analysis to Improvements in Treatment Strategies

Endometrial cancer is reported to be one of the most prevalent cancers of the female reproductive organs worldwide, with increasing incidence and mortality rates over the past decade. Early diagnosis is critical for effective treatment. Recently, there has been a growing focus on the role of nutrition and micronutrient and macronutrient status in patients with gynecologic cancers, including endometrial cancer. In the following paper, we have conducted an in-depth narrative literature review with the aim of evaluating the results of metallomic studies specifically concerning the micro- and macronutrient status of patients with endometrial cancer. The main objective of the paper was to analyze the results regarding the nutritional status of endometrial cancer patients and describe the role of chosen elements in the onset and progression of endometrial carcinogenesis. Further, we have focused on the evaluation of the usage of the described elements in the potential treatment of the abovementioned cancer, as well as the possible prevention of cancer considering proper supplementation of chosen elements in healthy individuals. Calcium supplementation has been proposed to reduce the risk of endometrial cancer, although some studies offer conflicting evidence. Deficiencies in phosphorus, selenium, and zinc have been inversely associated with endometrial cancer risk, suggesting they may play a protective role, whereas excessive levels of iron, copper, and cadmium have been positively correlated with increased risk. However, the molecular mechanisms by which these elements affect endometrial carcinogenesis are not fully understood, and current findings are often contradictory. Further research is needed to clarify these relationships and to evaluate the potential of nutritional interventions for the prevention and treatment of endometrial cancer.

Emodin alleviates intestinal ischemia-reperfusion injury through antioxidant stress, anti-inflammatory responses and anti-apoptosis effects via Akt-mediated HO-1 upregulation

BACKGROUND

Intestinal ischemia-reperfusion (I/R) injury is a severe vascular emergency. Previous research indicated the protective effects of Emodin on I/R injury. Our study aims to explore the effect of Emodin on intestinal I/R (II/R) injury and elucidate the underlying mechanisms.

METHODS

C57BL/6 mice and Caco-2 cells were used for in vivo and in vitro studies. We established an animal model of II/R injury by temporarily occluding superior mesenteric artery. We constructed an oxygen-glucose deprivation/reoxygenation (OGD/R) cell model using a hypoxia-reoxygenation incubator. Different doses of Emodin were explored to determine the optimal therapeutic dose. Additionally, inhibitors targeting the protein kinase B (Akt) or Heme oxygenase-1 (HO-1) were administered to investigate their potential protective mechanisms.

RESULTS

Our results demonstrated that in animal experiments, Emodin mitigated barrier disruption, minimized inflammation, reduced oxidative stress, and inhibited apoptosis. When Akt or HO-1 was inhibited, the protective effect of Emodin was eliminated. Inhibiting Akt also reduced the level of HO-1. In cell experiments, Emodin reduced inflammation and apoptosis in the OGD/R cell model. Additionally, when Akt or HO-1 was inhibited, the protective effect of Emodin was weakened.

CONCLUSIONS

Our findings suggest that Emodin may protect the intestine against II/R injury through the Akt/HO-1 signaling pathway.

Exposure to fluoride exacerbates the cognitive deficit of diabetic patients living in areas with endemic fluorosis, as well as of rats with type 2 diabetes induced by streptozotocin via a mechanism that may involve excessive activation of the poly(ADP ribose) polymerase-1/P53 pathway

Epidemiology has shown that fluoride exposure is associated with the occurrence of diabetes. However, whether fluoride affects diabetic encephalopathy is unclear. Elderly diabetic patients in areas with endemic (n = 169) or no fluorosis (108) and controls (85) underwent Montreal Cognitive Assessment. Sprague-Dawley rats receiving streptozotocin and/or different fluoride doses were examined for spatial learning and memory, brain morphology, blood-brain barrier, fasting blood glucose and insulin. Cultured SH-SY5Y cells were treated with 50 mM glucose and/or low- or high-dose fluoride, and P53-knockdown or poly-ADP-ribose polymerase-1 (PARP-1) inhibition. The levels of PARP-1, P53, poly-ADP-ribose (PAR), apoptosis-inducing factor (AIF), and phosphorylated-histone H2A.X (ser139) were measured by Western blotting. Reactive oxygen species (ROS), 8-hydroxydeguanosine (8-OHdG), PARP-1 activity, acetyl-P53, nicotinamide adenine dinucleotide (NAD+), activities of mitochondrial hexokinase1 (HK1) and citrate synthase (CS), mitochondrial membrane potential and apoptosis were assessed biochemically. Cognition of diabetic patients in endemic fluorosis areas was poorer than in other regions. In diabetic rats, fasting blood glucose, insulin resistance and blood-brain barrier permeability were elevated, while spatial learning and memory and Nissl body numbers in neurons declined. In these animals, expression and activity of P53 and PARP-1 and levels of NAD+, PAR, ROS, 8-OHdG, p-histone H2A.X (ser139), AIF and apoptosis content increased; whereas mitochondrial HK1 and CS activities and membrane potential decreased. SH-SY5Y cells exposed to glucose exhibited changes identical to diabetic rats. The changes in diabetic rats and cells treated with glucose were aggravated by fluoride. P53-knockout or PARP-1 inhibition mitigated the effects of glucose with/without low-dose fluoride. Elevation of diabetic encephalopathy was induced by exposure to fluoride and the underlying mechanism may involve overactivation of the PARP-1/P53 pathway.

Fluoride exposure confers NRF2 activation in hepatocyte through both canonical and non-canonical signaling pathways

Due to the high abundance in the Earth's crust and industrial application, fluoride is widely present in our living environment. However, excessive fluoride exposure causes toxicity in different organs. As the most important detoxification and excretion organ, liver is more easily involved in fluoride toxicity than other organs, and oxidative stress is considered as the key mechanism related with fluoride hepatotoxicity. In this study, we mainly investigated the role of nuclear factor erythroid-derived 2-like 2 (NRF2, a core transcription factor in oxidative stress) in fluoride exposure-induced hepatotoxicity as well as the related mechanism. Herein, liver cells (BNL CL.2) were treated with fluoride in different concentrations. The hepatotoxicity and NRF2 signaling pathway were analyzed respectively. Our results indicated that excessive fluoride (over 1 mM) resulted in obvious toxicity in hepatocyte and activated NRF2 and NRF2 target genes. The increased ROS generation after fluoride exposure suppressed KEAP1-induced NRF2 ubiquitylation and degradation. Meanwhile, fluoride exposure also led to blockage of autophagic flux and upregulation of p62, which contributed to activation of NRF2 via competitive binding with KEAP1. Both pharmaceutical activation and genetic activation of NRF2 accelerated fluoride exposure-induced hepatotoxicity. Thus, the upregulation of NRF2 in hepatocyte after fluoride exposure can be regarded as a cellular self-defense, and NRF2-KEAP1 system could be a novel molecular target against fluoride exposure-induced hepatotoxicity.

Endoplasmic reticulum chaperone GRP78 participates in fluoride-induced autophagy in LS8 cells by regulating the IRE1-TRAF2-JNK pathway

Fluoride induces endoplasmic reticulum (ER) stress in ameloblasts, which is responsible for enamel mineralization disorder. Fluoride induces autophagy in ameloblasts, but the molecular mechanisms through which ameloblasts respond to fluoride-induced cellular stress and autophagy remain unclear. This study investigated ER stress-induced autophagy and the regulatory role of the ER molecular chaperone GRP78 in fluoride-induced autophagy in ameloblast LS8 cells. To explore the relationship between fluoride-induced ER stress and autophagy, we assessed changes in fluoride-induced autophagy in LS8 cells following overexpression and/or silencing of the ER stress molecular chaperone GRP78. We found that autophagy induced by fluoride was further increased after GRP78 overexpression in LS8 cells. Fluoride-induced autophagy was reduced in GRP78-silenced LS8 cells. Furthermore, we found that ER stress can regulate autophagy in fluoride-treated ameloblasts (LS8 cells) and that the GRP78/IRE1/TRAF2/JNK pathway is involved in the underlying regulation. Our study suggests that ER stress plays a role in fluoride-induced damage by inducing ameloblast autophagy.

Emodin attenuates inflammation and demyelination in experimental autoimmune encephalomyelitis

Emodin, a substance extracted from herbs such as rhubarb, has a protective effect on the central nervous system. However, the potential therapeutic effect of emodin in the context of multiple sclerosis remains unknown. In this study, a rat model of experimental autoimmune encephalomyelitis was established by immune induction to simulate multiple sclerosis, and the rats were intraperitoneally injected with emodin (20 mg/kg/d) from the day of immune induction until they were sacrificed. In this model, the nucleotide-binding domain-like receptor family pyrin domain containing 3 (NLRP3) inflammasome and the microglia exacerbated neuroinflammation, playing an important role in the development of multiple sclerosis. In addition, silent information regulator of transcription 1 (SIRT1)/peroxisome proliferator-activated receptor-alpha coactivator (PGC-1α) was found to inhibit activation of the NLRP3 inflammasome, and SIRT1 activation reduced disease severity in experimental autoimmune encephalomyelitis. Furthermore, treatment with emodin decreased body weight loss and neurobehavioral deficits, alleviated inflammatory cell infiltration and demyelination, reduced the expression of inflammatory cytokines, inhibited microglial aggregation and activation, decreased the levels of NLRP3 signaling pathway molecules, and increased the expression of SIRT1 and PGC-1α. These findings suggest that emodin improves the symptoms of experimental autoimmune encephalomyelitis, possibly through regulating the SIRT1/PGC-1α/NLRP3 signaling pathway and inhibiting microglial inflammation. These findings provide experimental evidence for treatment of multiple sclerosis with emodin, enlarging the scope of clinical application for emodin.

Effect of Fluoride on the Expression of 8-Hydroxy-2'-Deoxyguanosine in the Blood, Kidney, Liver, and Brain of Rats

Excessive exposure of fluoride not only leads to damage on bone, but also has an adverse effect on soft tissues. Oxidative DNA damage induced by fluoride is thought to be one of the toxic mechanisms of fluoride effect. However, the dose-response of fluoride on oxidative DNA damage is barely studied in organisms. This study investigated the concentration of fluoride in rat blood, kidney, liver, and brain as well as the dose-time effect of fluoride on the expression of 8-hydroxy-2'-deoxyguanosine (8-OHdG) in the above tissues. Rats were exposed to 0 mg/L, 25 mg/L, 50 mg/L, and 100 mg/L of fluorine ion and treated for one and three months. The results showed that the accumulation of fluoride in soft tissues was very different. At the first month, blood fluoride was increased, liver and brain fluoride showed a U-shaped change, and kidney fluoride was not significant. At the third month, blood fluoride was altered with an inverted U-shaped change, kidney and brain fluoride increased, but liver fluoride decreased. Both the exposure concentration and the time of exposure had a significant effect on the expression of 8-OHdG in the above tissues. However, the effect patterns of fluoride on these tissues were notably different at different times. At the first month of fluoride treatment, blood, kidney, and liver 8-OHdG decreased with the increasing fluoride concentration. At the third month, blood 8-OHdG showed a U-shaped change, but kidney 8-OHdG altered with an inverted U-shaped change. Liver 8-OHdG increased, while brain 8-OHdG decreased at the third month. Correlation analysis showed that only blood 8-OHdG was significantly inversely correlated with blood fluoride and dental fluorosis grade in both the first and third months. Liver 8-OHdG was negatively and significantly correlated with liver fluoride. There was a weak but nonsignificant correlation between kidney and brain 8-OHdG and fluoride in both tissues. Additionally, blood 8-OHdG was positively correlated with kidney and liver 8-OHdG at the first month and positively correlated with brain 8-OHdG at the third month. Taken together, our data suggests that concentration and time of fluoride exposure had a significant effect on 8-OHdG, but the effect patterns of fluoride on 8-OHdG were different in the tissues, which suggests that the impact of fluoride on 8-OHdG may be a tissue-specific, as well as a non-monotonic positive correlation.

Fluoride Induced Neurobehavioral Impairments in Experimental Animals: a Brief Review

Fluoride is one of the major toxicants in the environment and is often found in drinking water at higher concentrations. Living organisms including humans exposed to high fluoride levels are found to develop mild-to-severe detrimental pathological conditions called fluorosis. Fluoride can cross the hematoencephalic barrier and settle in various brain regions. This accumulation affects the structure and function of both the central and peripheral nervous systems. The neural ultrastructure damages are reflected in metabolic and cognitive activities. Hindrances in synaptic plasticity and signal transmission, early neuronal apoptosis, functional alterations of the intercellular signaling pathway components, improper protein synthesis, dyshomeostasis of the transcriptional and neurotrophic factors, oxidative stress, and inflammatory responses are accounted for the fluoride neurotoxicity. Fluoride causes a decline in brain functions that directly influence the overall quality of life in both humans and animals. Animal studies are widely used to explore the etiology of fluoride-induced neurotoxicity. A good number of these studies support a positive correlation between fluoride intake and toxicity phenotypes closely associated with neurotoxicity. However, the experimental dosages highly surpass the normal environmental concentrations and are difficult to compare with human exposures. The treatment procedures are highly dependent on the dosage, duration of exposure, sex, and age of specimens among other factors which make it difficult to arrive at general conclusions. Our review aims to explore fluoride-induced neuronal damage along with associated histopathological, behavioral, and cognitive effects in experimental models. Furthermore, the correlation of various molecular mechanisms upon fluoride intoxication and associated neurobehavioral deficits has been discussed. Since there is no well-established mechanism to prevent fluorosis, phytochemical-based alleviation of its characteristic indications has been proposed as a possible remedial measure.

The Role of Caspases in Alzheimer's Disease: Pathophysiology Implications and Pharmacologic Modulation

Alzheimer's disease (AD) is the most common neurodegenerative disorder worldwide. Although the main cause of the onset and development of AD is not known yet, neuronal death due to pathologic changes such as amyloid-β (Aβ) deposition, tau aggregation, neuroinflammation, oxidative stress, and calcium dyshomeostasis are considered to be the main cause. At the present, there is no cure for this insidious disorder. However, accurate identification of molecular changes in AD can help provide new therapeutic goals. Caspases are a group of proteases which are known because of their role in cellular apoptosis. In addition, different caspases are involved in other cellular responses to the environment, such as induction of inflammation. Emerging evidence suggest that these proteases play a central role in AD pathophysiology due to their role in the processing of amyloid-β protein precursor, tau cleavage, and neuroinflammation. Therefore, it seems that targeting caspases may be a suitable therapeutic option to slow the progression of AD. This review focuses on the role of caspases in AD pathophysiology and introduce results from studies targeted caspases in different models of AD.

Emodin protects against apoptosis and inflammation by regulating reactive oxygen species-mediated NF-κB signaling in interleukin-1β-stimulated human nucleus pulposus cells

Intervertebral disc degeneration (IDD) is a complex degradative disorder associated with inflammation. Emodin, an anthraquinone derivative, possesses strong anti-inflammatory activity. This study focused on the in vitro therapeutic action of emodin in a cellular model of IDD. Human nucleus pulposus cells (NPCs) were stimulated with interleukin-1β (IL-1β) to induce inflammation. Cell Counting Kit-8 and terminal deoxynucleotidyl transferase dUTP nick end labeling staining assays were performed to evaluate the viability and apoptosis of NPCs, respectively. Caspase-3 activity was measured to indirectly assess cell apoptosis. Western blot analysis was performed to detect protein expression levels. Reverse transcription-polymerase chain reaction was performed for the detection of relative mRNA levels of tumor necrosis factor-α (TNF-α) and IL-6. Enzyme-linked immunosorbent assay was performed to analyze TNF-α and IL-6 secretion. Our results showed that emodin treatment mitigated IL-1β-induced reduction of cell viability in NPCs. Moreover, the increase in reactive oxygen species (ROS) production, apoptotic rate, and caspase-3 activity in IL-1β-stimulated NPCs was reduced by emodin treatment. Treatment with emodin also abolished IL-1β-induced inflammation in NPCs, as indicated by reduced secretion of IL-6 and TNF-α. Besides, the increase in expression levels of phosphorylated p65 and nuclear p65 in IL-1β-stimulated NPCs was suppressed by emodin treatment. Furthermore, inhibition of nuclear factor kappa B (NF-κB) activation with pyrrolidine dithiocarbamate aggravated the protective effects of emodin. These results suggested that emodin protected NPCs against IL-1β-induced apoptosis and inflammation via inhibiting ROS-mediated activation of NF-κB.

Extract of Ginkgo biloba leaves attenuates neurotoxic damages in rats and SH-SY5Y cells exposed to a high level of fluoride

BACKGROUND

Potential protection against the neurotoxic damages of high levels of fluoride on rats and SH-SY5Y cells by extract of Ginkgo biloba leaves, as well as underlying mechanisms, were examined.

METHODS

The rats were divided randomly into 4 groups, i.e., control, treatment with the extract (100 mg/kg body weight, gavage once daily), treatment with fluoride (50 ppm F^- in drinking water) and combined treatment with both; SH-SY5Y cells exposed to fluoride and fluoride in combination with the extract or 4-Amino-1,8-naphthalimide (4-ANI), an inhibitor of poly (ADP-ribose) polymerase-1 (PARP-1). Spatial learning and memory in the rats were assessed employing Morris water maze test; the contents of fluoride in brains and urine by fluoride ion-selective electrode; cytotoxicity of fluoride was by CCK-8 kit; the activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px), and the content of malondialdehyde (MDA) by appropriate kits; the level of 8-hydroxydeoxyguanosine (8-OHdG) was by ELISA; the content of ROS and frequency of apoptosis by flow cytometry; the expressions of phospho-histone H2A.X_(Ser139), PARP-1, poly (ADP-ribose) (PAR) and Sirtuin-1 (SIRT1) by Western blotting or immunofluorescence.

RESULTS

The rats with prolong treatment of fluoride exhibited dental fluorosis, the increased contents of fluoride in brains and urine and the declined ability of learning and memory. In the hippocampus of the rats and SH-SY5Y cells exposed to fluoride, the levels of ROS, MDA, apoptosis, 8-OHdG and the protein expressions of histone H2A.X_(Ser139), PARP-1 and PAR were all elevated; the activities of SOD and GSH-Px and the protein expression of SIRT1 reduced. Interestingly, the treatment of Ginkgo biloba extract attenuated these neurotoxic effects on rats and SH-SY5Y cells exposed to fluoride and the treatment of 4-ANI produced a neuroprotective effect against fluoride exposure.

CONCLUSION

Ginkgo biloba extract attenuated neurotoxic damages induced by fluoride exposure to rats and SH-SY5Y cells and the underlying mechanism might involve the inhibition of PARP-1 and the promotion of SIRT1.

Excessive Lysosomal Stress Response and Consequently Impaired Autophagy Contribute to Fluoride-Induced Developmental Neurotoxicity

Fluoride can cause developmental neurotoxicity; however, the precise mechanism has yet to be determined. We aimed to explore the possible role and mechanism of fluoride-induced developmental neurotoxicity, specifically the significance of the lysosomal stress response. As an in vivo model, Sprague Dawley rats were exposed to sodium fluoride (NaF) from embryo to 2 months of age. We found that NaF caused autophagic flux blockage and apoptosis in the rat hippocampus. These results were validated in human neuroblastoma (SH-SY5Y) cells in vitro. In addition, in SH-SY5Y cells, NaF hindered autophagosome-lysosome fusion, decreased lysosomal degradation, and elevated lysosomal pH, which is the most prominent hallmark of a lysosomal stress response. Interestingly, rapamycin promoted autophagosome-lysosome fusion, effectively restoring autophagic flux and reducing apoptosis. Notably, bafilomycin A1, a lysosomal lumen alkalizer, unsurprisingly exacerbated the NaF-induced increase in lysosomal pH and decreased lysosomal degradability, as well as enhanced apoptosis of SH-SY5Y cells. In conclusion, our results suggest that NaF exposure initiates excessive lysosomal stress response, resulting in elevated lysosomal pH, decreased lysosomal degradation, and blocked autophagic flux, which leads to neuronal apoptosis. Thus, the lysosomal stress response may be a promising target for the prevention and treatment of fluoride-induced developmental neurotoxicity.

Role of oxidative stress-mediated cell death and signaling pathways in experimental fluorosis

Free radicals and other oxidants have enticed the interest of researchers in the fields of biology and medicine, owing to their role in several pathophysiological conditions, including fluorosis (Fluoride toxicity). Radical species affect cellular biomolecules such as nucleic acids, proteins, and lipids, resulting in oxidative stress. Reactive oxygen species-mediated oxidative stress is a common denominator in fluoride toxicity. Fluorosis is a global health concern caused by excessive fluoride consumption over time. Fluoride alters the cellular redox homeostasis, and its toxicity leads to the activation of cell death mechanisms like apoptosis, autophagy, and necroptosis. Even though a surfeit of signaling pathways is involved in fluorosis, their toxicity mechanisms are not fully understood. Thus, this review aims to understand the role of reactive species in fluoride toxicity with an outlook on the effects of fluoride in vitro and in vivo models. Also, we emphasized the signal transduction pathways and the mechanism of cell death implicated in fluoride-induced oxidative stress.

Effects of fluoride exposure on mitochondrial function: Energy metabolism, dynamics, biogenesis and mitophagy

Fluoride is ubiquitous in the environment. Furthermore, drinking water represents the main source of exposure to fluoride for humans. Interestingly, low fluoride concentrations have beneficial effects on bone and teeth development; however, chronic fluoride exposure has harmful effects on human health. Besides, preclinical studies associate fluoride toxicity with oxidative stress, inflammation, and apoptosis. On the other hand, it is well-known that mitochondria play a key role in reactive oxygen species production. By contrast, fluoride's effect on processes such as mitochondrial dynamics, biogenesis and mitophagy are little known. These processes modulate the size, content, and distribution of mitochondria and their depuration help to counter the reactive oxygen species production and cytochrome c release, thereby allowing cell survival. However, a maladaptive response could enhance fluoride-induced toxicity. The present review gives a brief account of fluoride-induced mitochondrial alterations on soft and hard tissues, including liver, reproductive organs, heart, brain, lung, kidney, bone, and tooth.

Catalpol Exerts Antidepressant-Like Effects by Enhancing Anti-oxidation and Neurotrophy and Inhibiting Neuroinflammation via Activation of HO-1

Catalpol is an iridoid glycoside with rich content, rich nutrition, and numerous biological activities in Rehmanniae Radix contained in classic antidepressant prescriptions in Chinese clinical medicine. Catalpol has been confirmed previously its exact antidepressant-like effect involved heme oxygenase (HO)-1, but its antidepressant molecular targets and mechanism are still unclear. Here, catalpol's antidepressant-like molecular target was diagnosed and confirmed by ZnPP intervention [the antagonist of HO-1, (10 μg/rat), intracerebroventricular] for the first time, and its molecule mechanism network was determined through HO-1 related pathway and molecules in the hippocampus. Results showed that ZnPP significantly abolished catalpol's (10 mg/kg) reversal on depressive-like behaviors of chronic unpredictable mild stress rats, abolished catalpol's up-regulation on the phosphorylation level of extracellular regulated protein kinases (ERK)1/2 and brain-derived neurotrophic factor (BDNF)'s receptor tropomyosin-related kinase B (TrkB), the nuclear expression level of nuclear factor E 2-related factor 2 (Nrf2), the levels of anti-oxidant factors (such as HO-1, SOD, GPX, GST, GSH) and BDNF, and abolished catalpol's down-regulation on the levels of peroxide and neuroinflammation factors [cyclooxygenase-2 (COX-2), induced nitrogen monoxide synthase (iNOS), nitric oxide (NO)]. Thus, HO-1 could serve as an important potential molecular target for catalpol's antidepressant-like process, and the antidepressant-like mechanism of catalpol could at least involve the activation of HO-1 triggering the up-regulation of the ERK1/2/Nrf2/HO-1 pathway-related factors to enhance the anti-oxidant defense, triggering the down-regulation of the COX-2/iNOS/NO pathway-related factors to inhibit neuroinflammation, and triggering the up-regulation of the BDNF/TrkB pathway to enhance neurotrophy.

Samhwangsasim-tang attenuates neuronal apoptosis and cognitive decline through BDNF-mediated activation of tyrosin kinase B and p75-neurotrophin receptors

BACKGROUND

Samhwangsasim-tang (SST) is a traditional medicine used to treat hypertension and arteriosclerosis. Additionally, due to the effects of its constituent herbs, SST is considered effective for memory-related disorders.

PURPOSE

We investigated the effects of SST on neuronal survival and memory in glutamate-induced hippocampal cells and in a mouse model of scopolamine-induced memory impairment.

METHODS

SST components were identified using 3D-ultra performance liquid chromatography (3D-UPLC). In vitro, we induced glutamate-induced excitotoxicity in HT22 cells after SST pretreatment. We used a cell counting kit-8 and cell cytotoxicity assay, flow cytometry, and western blotting to test the protective effects of SST on neuronal death. In vivo, C57BL/6J mice were administered with 150 and 300 mg/kg SST once daily for 7 days and then intraperitoneally injected with 1 mg/kg scopolamine for 7 days to induce cognitive impairment. We then measured cognitive behavior using a novel object recognition test (NORT) and passive avoidance test (PAT) and analyzed the histological and protein changes.

RESULTS

Our results showed that treatment with 50 and 100 μg/ml SST provided significant protection against glutamate-induced cell death. Flow cytometry and western blotting results suggested that 100 μg/ml SST treatment reduced oxidative stress and mitochondrial dysfunction. SST treatment also increased brain-derived neurotrophic factor (BDNF), its receptor, TrkB receptor, and cAMP-response element binding protein (CREB) activation while reducing the P75NTR and JNK signaling activation. Our in vivo results showed that SST administration improved cognitive impairment, similar to donepezil treatment (as a positive control), in NORT and PAT. SST and donepezil decreased neuronal cell death and apoptosis, and acetylcholine levels were increased in the scopolamine-treated hippocampus. Additionally, SST promoted CREB phosphorylation and BDNF maturation while reducing JNK and P75NTR activation; in contrast, donepezil did not alter levels of these proteins in the scopolamine-treated mouse hippocampus.

CONCLUSION

Our results suggest that SST has neuroprotective effects to attenuate neuronal cell death and oxidative stress through CREB/JNK signaling via BDNF activation. SST may regulate endogenous survival factors in the hippocampus, which may be a safe and potential clinical treatment for cognitive impairment in AD.

New 18β-Glycyrrhetinic Acid-Emodin Esters Synthetized by a One-Step Innovative Route, Its Structural Characterization, and in Vivo Toxicity Assessed on Zebrafish Models

To integrate the active advantages of 18β-glycyrrhetinic acid (18β-GA) and emodin, improve bioavailability, increase efficiency, and reduce toxicity, a one-step innovative synthetic route was set up for the first time: 4-dimethylaminopyridine (DMAP) was used as catalyst, 1-ethyl-(3-dimethylaminopropyl)carboimide hydrochloride (EDCI) as condensation agent, dry dichloromethane (DCM) as solvent at 25 °C for 12 h, the three target products were obtained and purified by high performance liquid chromatography (HPLC), the chemical structures of them were characterized by nuclear magnetic resonance (NMR) technique and high resolution electron ionization mass spectrometry (HREI-MS), namely, 18β-glycyrrhetinic acid-3-emodin ester (1, yield 78.83 %, known), di-18β-glycyrrhetinic acid-1-emodin ester (2, yield 6.49 %, new), and di-18β-glycyrrhetinic acid-8-emodin ester (3, yield 1.81 %, new). To estimate their effects of the products on toxicity in zebrafish embryos and juvenile fishes, the two precursors and three target products were assayed involving in hatching rate, survival rate, morphology, heart rate, and apoptosis of cardiomyocytes. The results showed that the target products enhanced the hatching and survival rate of zebrafish embryos, decreased the malformation rate and the apoptosis of cardiomyocytes. It should be suggested that the one-step synthesis route with high yield makes the industrial application of the target products possible due to significantly reduced toxicity. The two new by-products provide potential candidates for the applications of pharmaceutical industry in the future.

Emodin Protects SH-SY5Y Cells Against Zinc-Induced Synaptic Impairment and Oxidative Stress Through the ERK1/2 Pathway

Zinc is an essential trace element important for the physiological function of the central nervous system. The abnormal accumulation of zinc inside neurons may induce mitochondrial dysfunction and oxidative stress, which contribute to many brain diseases. We hypothesized that natural anthraquinone derivative emodin can protect against neurotoxicity induced by pathological concentrations of zinc via the extracellular signal-regulated kinase 1/2 (ERK1/2) signaling pathway and alleviate oxidative stress and mitochondrial dysfunction. Human neuroblastoma (SH-SY5Y 26 cells) was treated with zinc sulfate and different concentrations of emodin, and changes in the levels of ETK1/2 expression, oxidative stress (DCFH-DA staining), mitochondrial function (JC-1 staining), lipid peroxidation (4-hydroxynonenal staining), and DNA oxidation (8-hydroxy-2-deoxyguanosine staining) were examined. Emodin ameliorated zinc-induced altered expression of levels of phosphorylated ERK1/2 (not total ETK1/2) and synaptic proteins (presynaptic SNAP 25, synaptophysin and postsynaptic PSD95) in SH-SY5Y cells. Moreover, emodin inhibited the generation of reactive oxygen species and oxidative stress and facilitated the collapse of mitochondrial membrane potential (ΔΨm) in SH-SY5Y cells. In conclusion, our results indicated that emodin exerts neuroprotective effects against zinc by normalizing synaptic impairment by decreasing the phosphorylation of ERK1/2, reducing reactive oxygen species and protecting mitochondrial function.

Emodin Attenuates the ECM Degradation and Oxidative Stress of Chondrocytes through the Nrf2/NQO1/HO-1 Pathway to Ameliorate Rat Osteoarthritis

Osteoarthritis (OA) substantially reduces the quality of life of the elderly. OA therapy remains a challenge since no treatment options for its causes are so far available. Over recent years, researchers have speculated that emodin may represent a potential treatment strategy for OA. However, it remains unclear whether the mechanism of action of emodin is associated with the inhibition of OA-induced oxidative stress. In the present study, the potential antioxidant mechanism of action of emodin and its protective properties against the development of OA were investigated both in vitro and in vivo. In vitro, emodin inhibited the production of reactive oxygen species (ROS) in chondrocytes induced by hydrogen peroxide (H2O2) and reduced the expression of matrix metalloproteinase (MMP)3 and MMP13 in a concentration-dependent manner. It was found that emodin upregulated the Nrf2/NQO1/HO-1 pathway, thereby attenuating the effects of oxidative stress caused by OA. In a rat model of posttraumatic OA induced by anterior cruciate ligament transection (ACLT), emodin reduced the extent of joint swelling. Emodin attenuated oxidative damage in the cartilage by upregulating superoxide dismutase (SOD), catalase (CAT), and glutathione (GSH) activity, reducing malondialdehyde (MDA) concentration and inhibiting the expression of the extracellular matrix (ECM) degradation biomarkers cartilage oligomeric matrix protein (COMP), and C-terminal telopeptide of type I collagen (CTX-I) and type II collagen (CTX-II), thereby reducing cartilage damage. In summary, the present study indicates that emodin reduces ECM degradation and oxidative stress in chondrocytes via the Nrf2/NQO1/HO-1 pathway, thereby ameliorating OA in rats.

Emodin ameliorates antioxidant capacity and exerts neuroprotective effect via PKM2-mediated Nrf2 transactivation

Pyruvate kinase M2 (PKM2) is overexpressed in neuronal cells. However, there are few studies on the involvement of PKM2 modulators in neurodegenerative diseases. Emodin, a dominating anthraquinone derivative extracting from the rhizome of rhubarb, has received expanding consideration due to its pharmacological properties. Our data reveal that emodin could resist hydrogen peroxide- or 6-hydroxydopamine-mediated mitochondrial fission and apoptosis in PC12 cells (a neuron-like rat pheochromocytoma cell line). Notably, emodin at nontoxic concentrations significantly inhibits PKM2 activity and promotes dissociation of tetrameric PKM2 into dimers in cells. The PKM2 dimerization enhances the interaction of PKM2 and NFE2-related factor 2 (Nrf2), which further triggers the activation of the Nrf2/ARE pathway to upregulate a panel of cytoprotective genes. Modulating the PKM2/Nrf2/ARE axis by emodin unveils a novel mechanism for understanding the pharmacological functions of emodin. Our findings indicate that emodin is a potential candidate for the treatment of oxidative stress-related neurodegenerative disorders.

Combination of Polygoni Multiflori Radix Praeparata and Acori Tatarinowii Rhizoma Alleviates Learning and Memory Impairment in Scopolamine-Treated Mice by Regulating Synaptic-Related Proteins

Polygoni Multiflori Radix Praeparata (ZhiHeShouWu, PMRP) and Acori Tatarinowii Rhizoma (ShiChangPu, ATR) and their traditional combination (PA) are frequently used in traditional Chinese medicine to prevent and treat Alzheimer disease (AD) based on the theory that PMRP tonifies the kidney and ATR dissipates phlegm. However, the components of PA and their mechanisms of action are not known. The present study analyzed the active components of PA, and investigated the protective effect of PA against cognitive impairment induced by scopolamine in mice along with the underlying mechanism.The aqueous extract of PA was analyzed by high-performance liquid chromatography–mass spectrometry (HPLC-MS) and gas chromatography (GC)-MS in order to identify the major components. To evaluate the protective effect of PA against cognitive dysfunction, mice were orally administered PA, PMRP, or ATR for 30 days before treatment with scopolamine. Learning and memory were assessed in mice with the Morris water maze test; neurotransmitter levels in the hippocampus were analyzed by HPLC-MS; and the expression of synapse-related proteins in the hippocampus was detected by western blotting and immunohistochemistry. Eight active compounds in PA and rat plasma were identified by HPLC-MS and GC-MS. Plasma concentrations of 2,3,5,4′-tetrahydroxystilbene-2-O-β-d-glucoside, emodin, α-asarone, and asarylaldehyde were increased following PA administration; meanwhile, gallic acid, emodin-8-O-β-d-glucopyranoside, β-asarone, and cis-methyl isoeugenol concentrations were similar in rats treated with PA, PMRP, and ATR. In scopolamine-treated mice, PA increased the concentrations of neurotransmitters in the hippocampus, activated the brain-derived neurotrophic factor (BDNF)/extracellular signal-regulated kinase (ERK)/cAMP response element binding protein (CREB) signaling pathway, and increased the expression of p90 ribosomal S6 kinase (p90RSK) and postsynaptic density (PSD)95 proteins. Thus, PA alleviates cognitive deficits by enhancing synaptic-related proteins, suggesting that it has therapeutic potential for the treatment of aging-related diseases such as AD.

Effects of Fluoride on Oxidative Stress Markers of Lipid, Gene, and Protein in Rats

Endemic fluorosis is a systemic chronic disease caused by excessive intake of fluoride. It is widely accepted that oxidative stress is closely related to fluorosis; however, molecular mechanism of oxidative stress in fluorosis remains unclear. This study investigated the effects of fluoride (F) on oxidative stress markers of lipid, gene, and protein in rats for revealing molecular mechanism of oxidative stress in fluorosis. The results showed concentration and exposure time of fluoride both had a significant effect on MDA and 8-OHdG. Fluoride concentration significantly impacted AGEs level, but exposure time did not. AOPP was not statistically different among the groups. AGEs decreased with the increase of fluoride in the rats with 3 months of fluoride treatment. The correlation analysis showed the degree of dental fluorosis was significantly negatively correlated with 8-OHdG at 1 month and 3 months, and negatively correlated with AGEs at 3 months. In the rats with 100 mg/L of fluoride treatment, MDA was significant positively correlated with 8-OHdG, and negatively correlated with AGEs. 8-OHdG was significantly negatively correlated with AGEs in the control group and 100 mg/L fluoride group. Taken together, fluoride had different effects on oxidative stress markers of lipid, gene, and protein. Excessive fluoride could increase MDA content, and decrease 8-OHdG and AGEs. These findings suggest that oxidative stress involved in molecular pathogenesis of fluorosis is complicated, and needs to furtherly study in the future.

Effects of triclosan on the RedoximiRs/Sirtuin/Nrf2/ARE signaling pathway in mosquitofish (Gambusia affinis)

Triclosan (TCS) has been widely used in daily life for its broad-spectrum antibacterial property and subsequently detected frequently in aquatic waterborne. Environmental relevant concentrations of TCS in water (ng-μg/L) may pose potential unexpected impact on non-target aquatic organisms. In the present work, we investigated the transcriptional responses of Nrf2 as well as its downstream genes, sirtuins and redox-sensitive microRNAs (RedoximiRs) in livers of the small freshwater fish mosquitofish (Gambusia affinis) which were exposed to environmental relevant concentrations of TCS (0.05 μg/L, 0.5 μg/L and 5 μg/L for 24 h and 168 h). Results showed there were similar up-regulations in Nrf2 and its target genes (e. g. NQO1, CAT and SOD) at transcriptional, enzymatic and protein levels, reflecting oxidative stress of TCS to mosquitofish. Meanwhile, up-regulations of Sirt1, Sirt2 and down-regulations of miR-34b, miR-200b-5p and miR-21 could modulate antioxidant system via the Nrf2/ARE signaling pathway by the post-transcriptional regulations. Some oxidative stress-related biomarkers displayed in concentration-dependent manners (e. g. NQO1 mRNA, CAT mRNA) and/or time-dependent manners (e. g. GSH contents). This study indicated that the RedoximiRs/Sirtuin/Nrf2/ARE signaling pathway played a crucial role in mosquitofish exposed to TCS, and there might be potentially profound effects for TCS on the aquatic ecological safety.