Sulforaphane attenuates apoptosis of hippocampal neurons induced by high glucose via regulating endoplasmic reticulum

New horizons for promising influences of sulforaphane in the management of metabolic syndrome: a mechanistic review

The disorder known as metabolic syndrome (MetS) represents a substantial threat to society since it is linked to a higher risk of heart disease, diabetes, stroke, and other health issues. Although there is no known cure for metabolic syndrome, lifestyle changes in diet and physical activity can help. Sulforaphane (SFN), a compound in cruciferous vegetables, has been recognized as a promising treatment for addressing metabolic syndrome. The information was compiled after a thorough search of four databases, PubMed, Scopus, Web of Sciences, and Google Scholar. This analysis includes 86 studies that include clinical and nonclinical SFN investigations in diseases connected to metabolic syndrome. Research has shown that sulforaphane is a prospective treatment option for obesity, type 2 diabetes mellitus (T2-DM), and associated metabolic disorders due to its capacity to regulate fatty acid production and glucose management. Many molecular processes have been investigated, including activating nuclear factor erythroid 2-related factor 2(Nrf2), activating nuclear factor erythroid 2(NF-E2), reducing reactive oxygen species, and upregulating insulin receptor substrate 1(IRS-1) and other suggested mechanisms. The current review established many facts in favor of SFN's prospective benefits in metabolic syndrome. More studies in this field involving human studies are necessary to determine whether SFN may effectively treat metabolic syndrome.

Protective role of sulforaphane in lipid metabolism-related diseases

Sulforaphane (SFN) is a phytochemical bioactive substance commonly found in cruciferous plants, such as broccoli and mustard. It has been reported to possess antibacterial, anti-inflammatory, anti-oxidant, anti-cancer and autophagy regulating properties. Recent studies have revealed that SFN regulates fat metabolism both in vivo and in vitro through various mechanisms, including alleviating endoplasmic reticulum stress, inhibiting inflammatory response and improving mitochondrial dysfunction, involving Nrf2/ARE, NF-κB, NLRP3 inflammasome, HDAC8-PGC1α axis and other signaling pathways. By curbing complications associated with abnormal fat metabolic diseases, SFN exhibits therapeutic effects on conditions like obesity, fatty liver disease, atherosclerosis, type 2 diabetes, etc., with minimal side effects. Therefore, it holds promise as a potential alternative treatment for lipid metabolism-related diseases. Although its extraction method has been matured, the thermal instability and preservation difficulties of SFN limit its clinical promotion. More effective and low-cost methods to improve the stability and production of SFN remain to be further studied. This paper reviews the physiological and biological activities of SFN, and summarizes the protective effects and molecular mechanisms of SFN in diseases related to abnormal lipid metabolism. Additionally, it proposes potential challenges, possible solutions and future research directions in the clinical application of SFN.

The role of isothiocyanate-rich plants and supplements in neuropsychiatric disorders: a review and update

Neuroinflammation in response to environmental stressors is an important common pathway in a number of neurological and psychiatric disorders. Responses to immune-mediated stress can lead to epigenetic changes and the development of neuropsychiatric disorders. Isothiocyanates (ITC) have shown promise in combating oxidative stress and inflammation in the nervous system as well as organ systems. While sulforaphane from broccoli is the most widely studied ITC for biomedical applications, ITC and their precursor glucosinolates are found in many species of cruciferous and other vegetables including moringa. In this review, we examine both clinical and pre-clinical studies of ITC on the amelioration of neuropsychiatric disorders (neurodevelopmental, neurodegenerative, and other) from 2018 to the present, including documentation of protocols for several ongoing clinical studies. During this time, there have been 16 clinical studies (9 randomized controlled trials), most of which reported on the effect of sulforaphane on autism spectrum disorder and schizophrenia. We also review over 80 preclinical studies examining ITC treatment of brain-related dysfunctions and disorders. The evidence to date reveals ITC have great potential for treating these conditions with minimal toxicity. The authors call for well-designed clinical trials to further the translation of these potent phytochemicals into therapeutic practice.

Exploring the therapeutic effects of sulforaphane: an in-depth review on endoplasmic reticulum stress modulation across different disease contexts

The endoplasmic reticulum (ER) is an intracellular organelle that contributes to the folding of proteins and calcium homeostasis. Numerous elements can disrupt its function, leading to the accumulation of proteins that are unfolded or misfolded in the lumen of the ER, a condition that is known as ER stress. This phenomenon can trigger cell death through the activation of apoptosis and inflammation. Glucoraphanin (GRA) is the predominant glucosinolate found in cruciferous vegetables. Various mechanical and biochemical processes activate the enzyme myrosinase, leading to the hydrolysis of glucoraphanin into the bioactive compound sulforaphane. Sulforaphane is an organosulfur compound that belongs to the isothiocyanate group. It possesses a wide range of activities and has shown remarkable potential as an anti-inflammatory, antioxidant, antitumor, and anti-angiogenic substance. Additionally, sulforaphane is resistant to oxidation, has been demonstrated to have low toxicity, and is considered well-tolerable in individuals. These properties make it a valuable natural dietary supplement for research purposes. Sulforaphane has been demonstrated as a potential candidate drug molecule for managing a range of diseases, primarily because of its potent antioxidant, anti-inflammatory, and anti-apoptotic properties, which can be mediated by modulation of ER stress pathways. This review seeks to cover a wealth of data supporting the broad range of protective functions of sulforaphane, improving various diseases, such as cardiovascular, central nervous system, liver, eye, and reproductive diseases, as well as diabetes, cancer, gastroenteritis, and osteoarthritis, through the amelioration of ER stress in both in vivo and in vitro studies.

Progress in Research on the Role of the Thioredoxin System in Chemical Nerve Injury

(1) Background: Various factors, such as oxidative stress, mitochondrial dysfunction, tumors, inflammation, trauma, immune disorders, and neuronal toxicity, can cause nerve damage. Chemical nerve injury, which results from exposure to toxic chemicals, has garnered increasing research attention. The thioredoxin (Trx) system, comprising Trx, Trx reductase, nicotinamide adenine dinucleotide phosphate, and Trx-interacting protein (TXNIP; endogenous Trx inhibitor), helps maintain redox homeostasis in the central nervous system. The dysregulation of this system can cause dementia, cognitive impairment, nerve conduction disorders, movement disorders, and other neurological disorders. Thus, maintaining Trx system homeostasis is crucial for preventing or treating nerve damage. (2) Objective: In this review study, we explored factors influencing the homeostasis of the Trx system and the involvement of its homeostatic imbalance in chemical nerve injury. In addition, we investigated the therapeutic potential of the Trx system-targeting active substances against chemical nerve injury. (3) Conclusions: Chemicals such as morphine, metals, and methylglyoxal interfere with the activity of TXNIP, Trx, and Trx reductase, disrupting Trx system homeostasis by affecting the phosphatidylinositol-3-kinase/protein kinase B, extracellular signal-regulated kinase, and apoptotic signaling-regulated kinase 1/p38 mitogen-activated protein kinase pathways, thereby leading to neurological disorders. Active substances such as resveratrol and lysergic acid sulfide mitigate the symptoms of chemical nerve injury by regulating the Ras/Raf1/extracellular signal-regulated kinase pathway and the miR-146a-5p/TXNIP axis. This study may guide the development of Trx-targeting modulators for treating neurological disorders and chemical nerve injuries.

A mechanistic overview of sulforaphane and its derivatives application in diabetes and its complications

Sulforaphane (SFN) is a type of phytochemical found in many cruciferous vegetables that has been shown to positively benefit the control of Type 2 Diabetes Mellitus (T2DM). The search was done from 2000 until December 2022 using PubMed, Scopus, Web of Sciences, and Google Scholar databases. We included all in vitro, in vivo, and clinical trials. Sulforaphane has been demonstrated to activate the PI3K/AKT and AMP-activated protein kinase pathways and the glucose transporter type 4 to increase insulin production and reduce insulin resistance. Interestingly, SFN possesses protective effects against diabetes complications, such as diabetic-induced hepatic damage, vascular inflammation and endothelial dysfunction, nephropathy, and neuropathy via nuclear factor erythroid 2-related factor 2 activation that leads to the translation of several anti-oxidant enzymes and regulation glycolysis, pentose phosphate pathway, fatty acid metabolism, glutamine metabolism, and glutathione metabolism. Furthermore, multiple clinical trial studies emphasized the ameliorating effects of SFN on T2DM patients. This review provides sufficient evidence for further research and development of sulforaphane as a hypoglycemic drug.

Heme Oxygenase-1 Is Involved in the Repair of Oxidative Damage Induced by Oxidized Fish Oil in Litopenaeus vannamei by Sulforaphane

Heme oxygenase-1 (HO-1), which could be highly induced under the stimulation of oxidative stress, functions in reducing the damage caused by oxidative stress, and sulforaphane (SFN) is an antioxidant. This study aims to investigate whether HO-1 is involved in the repair of oxidative damage induced by oxidized fish oil (OFO) in Litopenaeus vannamei by sulforaphane (SFN). The oxidative stress model of L. vannamei was established by feeding OFO feed (OFO accounts for 6%), and they were divided into the following four groups: control group (injected with dsRNA-EGFP and fed with common feed), dsRNA-HO-1 group (dsRNA-HO-1, common feed), dsRNA-HO-1 + SFN group (dsRNA-HO-1, supplement 50 mg kg-1 SFN feed), and SFN group (dsRNA-EGFP, supplement 50 mg kg-1 SFN feed). The results showed that the expression level of HO-1 in the dsRNA-HO-1 + SFN group was significantly increased compared with the dsRNA-HO-1 group (p < 0.05). The activities of SOD in muscle and GPX in hepatopancreas and serum of the dsRNA-HO-1 group were significantly lower than those of the control group, and MDA content in the dsRNA-HO-1 group was the highest among the four groups. However, SFN treatment increased the activities of GPX and SOD in hepatopancreas, muscle, and serum and significantly reduced the content of MDA (p < 0.05). SFN activated HO-1, upregulated the expression of antioxidant-related genes (CAT, SOD, GST, GPX, Trx, HIF-1α, Nrf2, prx 2, Hsp 70), and autophagy genes (ATG 3, ATG 5), and stabilized the expression of apoptosis genes (caspase 2, caspase 3) in the hepatopancreas (p < 0.05). In addition, knocking down HO-1 aggravated the vacuolation of hepatopancreas and increased the apoptosis of hepatopancreas, while the supplement of SFN could repair the vacuolation of hepatopancreas and reduce the apoptosis signal. In summary, HO-1 is involved in the repair of the oxidative damage induced by OFO in L. vannamei by SFN.

Restoring glomerular filtration rate by sulforaphane modulates ERK1/2/JNK/p38MAPK, IRF3/iNOS, Nrf2/HO-1 signaling pathways against folic acid-induced acute renal injury in rats

BACKGROUND

Folic acid (FA)-induced acute renal injury (AKI) is a commonly and highly reproducible model used to study AKI. The current study aims to evaluate the possible protective effects of sulforaphane (SFN) against FA-induced renal damage and explore the underlying molecular mechanism.

METHODS

The animals were divided into four groups (6 rats/group) as follows: normal group (received vehicle, p.o.), FA group (received 250 mg/kg, i.p.), SFN low dose group (received 15 mg/kg, p.o. plus FA 250 mg/kg, i.p.), SFN high dose group (30 mg/kg, p.o. plus FA 250 mg/kg, i.p.). At the end of the experiment, serum samples and kidney tissues were obtained to perform biochemical, molecular, and histopathological investigations.

RESULTS

The present study showed that FA-caused AKI was confirmed by a significant elevation of kidney function biomarkers serum levels accompanied by an observation of histopathologic changes. Interestingly, SFN-administration significantly improved kidney function, reduced oxidative stress markers; MDA, NADPH oxidase, MPO, iNOS with up-regulation of GSH, GCLM, GPX4, SOD, NQO1, HO-1 and Nrf2 levels. SFN also downregulated proinflammatory markers. The results also demonstrated the anti-apoptotic effect of SFN through its ability to increase the antiapoptotic Bcl-2 protein and to decrease caspase-3. Moreover, SFN significantly decreased the relative expression of JNK, ERK-1/2, IRF3, and p38MAPK as compared to the FA-nephrotoxic group.

CONCLUSION

The present study revealed that SFN possess an antioxidant, anti-inflammatory and antiapoptotic activity by modulating caspase-3, Bcl-2, ERK1/2, JNK, GCLM, NQO1, GPX4, Nrf2, HO-1 and P38 signaling pathways in a dose dependent manner which provides a potential therapeutic strategy for preventing FA-induced AKI.

Spermidine inhibits high glucose-induced endoplasmic reticulum stress in HT22 cells by upregulation of growth differentiation factor 11

Hyperglycemia-induced neuronal endoplasmic reticulum (ER) stress is particularly important for the pathogenesis of diabetic encephalopathy. Spermidine (Spd) has neuroprotection in several nervous system diseases. Our current study to explore the potential protective role of Spd in hyperglycemia-induced neuronal ER stress and the underlying mechanisms. HT22 cells were treated with high glucose (HG) to establish an in-vitro model of hyperglycemia toxicity. The HT22 cells' activity was tested by cell counting kit-8 assay. RNA interference technology was used to silence the expression of growth differentiation factor 11 (GDF11) in HT22 cells. The GDF11 expression levels of mRNA were assessed using reverse transcription-PCR (RT-PCR). Western blotting analysis was applied to evaluate the expressions of GRP78 and cleaved caspase-12. Spd markedly abolished HG-exerted decline in cell viability as well as upregulations of GRP78 and cleaved caspase-12 in HT22 cells, indicating the protection of Spd against HG-induced neurotoxicity and ER stress. Furthermore, we showed that Spd upregulated the expression of GDF11 in HG-exposed HT22 cells. While, silenced GDF11 expression by RNA interference reversed the protective effects of Spd on HG-elicited neurotoxicity and ER stress in HT22 cells. These results indicated that Spd prevents HG-induced neurotoxicity and ER stress through upregulation of GDF11. Our findings identify Spd as a potential treatment for diabetic encephalopathy as well as ER stress-related neurologic diseases.

Sulforaphane Upregulates Cultured Mouse Astrocytic Aquaporin-4 Expression through p38 MAPK Pathway

Protein misfolding and/or aggregation are common pathological features associated with a number of neurodegenerative diseases, including Alzheimer's disease (AD) and Parkinson disease (PD). Abnormal protein aggregation may be caused by misfolding of the protein and/or dysfunction of the protein clearance system. Recent studies have demonstrated that the specific water channel protein, aquaporin-4 (AQP4), plays a role in the pathogenesis of neurodegenerative diseases involving protein clearance system. In this study, we aimed to investigate the role of sulforaphane (SFN) in the upregulation of AQP4 expression, along with its underlying mechanism using cultured mouse astrocytes as a model system. At low concentrations, SFN was found to increase cell proliferation and result in the activation of astrocytes. However, high SFN concentrations were found to suppress cell proliferation of astrocytes. In addition, our study found that a 1 μM concentration of SFN resulted in the upregulation of AQP4 expression and p38 MAPK phosphorylation in cultured mouse astrocytes. Moreover, we demonstrated that the upregulation of AQP4 expression was significantly attenuated when cells were pretreated with SB203580, a p38 MAPK inhibitor. In conclusion, our findings from this study revealed that SFN exerts hormesis effect on cultured mouse astrocytes and can upregulate astrocytic AQP4 expression by targeting the p38 MAPK pathway.

Sulforaphane Induces Glioprotection After LPS Challenge

Sulforaphane is a natural compound that presents anti-inflammatory and antioxidant properties, including in the central nervous system (CNS). Astroglial cells are involved in several functions to maintain brain homeostasis, actively participating in the inflammatory response and antioxidant defense systems. We, herein, investigated the potential mechanisms involved in the glioprotective effects of sulforaphane in the C6 astrocyte cell line, when challenged with the inflammogen, lipopolysaccharide (LPS). Sulforaphane prevented the LPS-induced increase in the expression and/or release of pro-inflammatory mediators, possibly due to nuclear factor κB and hypoxia-inducible factor-1α activation. Sulforaphane also modulated the expressions of the Toll-like and adenosine receptors, which often mediate inflammatory processes induced by LPS. Additionally, sulforaphane increased the mRNA levels of nuclear factor erythroid-derived 2-like 2 (Nrf2) and heme oxygenase-1 (HO1), both of which mediate several cytoprotective responses. Sulforaphane also prevented the increase in NADPH oxidase activity and the elevations of superoxide and 3-nitrotyrosine that were stimulated by LPS. In addition, sulforaphane and LPS modulated superoxide dismutase activity and glutathione metabolism. Interestingly, the anti-inflammatory and antioxidant effects of sulforaphane were blocked by HO1 pharmacological inhibition, suggesting its dependence on HO1 activity. Finally, in support of a glioprotective role, sulforaphane prevented the LPS-induced decrease in glutamate uptake, glutamine synthetase activity, and glial-derived neurotrophic factor (GDNF) levels, as well as the augmentations in S100B release and Na+, K+ ATPase activity. To our knowledge, this is the first study that has comprehensively explored the glioprotective effects of sulforaphane on astroglial cells, reinforcing the beneficial effects of sulforaphane on astroglial functionality.

Matrine alleviates spatial learning and memory impairment in diabetic mice by inhibiting endoplasmic reticulum stress and through modulation of PK2/PKRs pathway

Clinical and epidemiological studies indicate that diabetic cognitive impairment often occurs in diabetes mellitus patients. Matrine (Mat), an active component of Sophora flavescens Ait root extracts, has widely pharmacological activities including anti-tumor, anti-diabetes, cardioprotective and neuroprotective effects. The present study was designed to elucidate the possibly neuroprotective effects of Mat against diabetic spatial learning and memory impairment caused by high-fat diet and streptozotocin injection in mice. The results showed that Mat treatment significantly ameliorated fasting blood glucose level, impaired glucose tolerance, and lipid metabolism disorder in diabetic mice. In addition, diabetic mice exhibited spatial learning and memory impairment in the Morris water maze test, which could be attenuated by Mat treatment. Moreover, administration of Mat remarkably alleviated histological damage in diabetic hippocampus. Also, further investigations showed that Mat treatment abated endoplasmic reticulum stress induced hippocampal ultra-structure injury as evidenced by increasing the numbers of rough endoplasmic reticulum and mitochondria, as well as down-regulating endoplasmic reticulum stress related protein levels (GRP78, CHOP, ATF6 and Caspase-12). Furthermore, administration of Mat enhanced hippocampal protein expressions of PK2, PKR1 and PKR2, which decreased significantly in diabetic mice. Collectively, these findings suggested that Mat could ameliorate diabetes-induced spatial learning and memory impairment, possibly by alleviating ER stress, and partly through modulation of PK2/PKRs pathway.

Role of Thioredoxin-1 and its inducers in human health and diseases

Thioredoxin-1 (Trx-1) is a small redox-active protein normally found in mammalian cells that responds to the changing redox environment by contributing electrons or regulating related proteins. There is growing evidence that Trx-1 has multiple functions, including cytoprotective, anti-apoptotic, antioxidant and anti-inflammatory effects. To date, researchers have found that Trx-1 deficiency leads to severe damage in various disease models, such as atherosclerosis, cerebral ischemia, diabetes and tumors. Conversely, activation of Trx-1 has a protective effect against these diseases. Accordingly, a variety of Trx-1 inducers have been widely used in the clinic with significant therapeutic value. In this paper, we summarize the pathogenesis of Trx-1 involvement in the above-mentioned diseases and describe the protective effects of Trx-1 inducers on them.

Phytochemical based Modulation of Endoplasmic Reticulum Stress in Alzheimer's Disease

Alzheimer's disease (AD) is a severe progressive neurodegenerative condition that shows misfolding and aggregation of proteins contributing to a decline in cognitive function involving multiple behavioral, neuropsychological, and cognitive domains. Multiple epi (genetic) changes and environmental agents have been shown to play an active role in ER stress induction. Neurodegeneration due to endoplasmic reticulum (ER) stress is considered one of the major underlying causes of AD. ER stress may affect essential cellular functions related to biosynthesis, assembly, folding, and post-translational modification of proteins leading to neuronal inflammation to promote AD pathology. Treatment with phytochemicals has been shown to delay the onset and disease progression and improve the well-being of patients by targeting multiple signaling pathways in AD. Phytochemical's protective effect against neuronal damage in AD pathology may be associated with the reversal of ER stress and unfolding protein response by enhancing the antioxidant and anti-inflammatory properties of the neuronal cells. Hence, pharmacological interventions using phytochemicals can be a potential strategy to reverse ER stress and improve AD management. Towards this, the present review discusses the role of phytochemicals in preventing ER stress in the pathology of AD.

Attenuation of experimentally induced atopic dermatitis in mice by sulforaphane: effect on inflammation and apoptosis

Atopic dermatitis (AD) is characterized by progressive skin inflammation. In addition, sulforaphane is an isothiocyanate organosulfur compound from cruciferous vegetables. Sulforaphane was reported to ameliorate inflammatory responses. Therefore, this study was conducted to evaluate the protective effects of sulforaphane in AD through affecting the balance between pro-inflammatory and anti-inflammatory cytokines and to evaluate its effect on AD-induced activation of the apoptotic pathway. The method of repeated rubbing of 2,4-dinitrochlorobenzene (DNCB) on shaved dorsal skin and ears of mice was used for induction of AD. After the development of AD, part of the mice was injected with 1 mg/kg sulforaphane, subcutaneously three times weekly. Samples of skin were isolated for assessment of gene and protein expression of 8-hydroxy2'-deoxyguanosine, IgE, NFκB, TNF-α, IL-1β, IL-4, IL-10, Nrf2, and caspase-3. In addition, skin sections from different groups were stained with anti-caspase-3 antibodies. Mice in the AD group were characterized by increased gene and protein expression of 8-hydroxy2'-deoxyguanosine, IgE, NFκB, TNF-α, IL-1β, and caspase-3 associated with reduced expression of Nrf2, IL-4, and IL-10. Treatment of AD mice with sulforaphane significantly reduced the number of scratches, dermatitis score, and ear thickness. In addition, sulforaphane significantly attenuated the gene and protein expressions produced by AD. Therefore, sulforaphane alleviated AD induced in mice through inhibition of oxidative stress, oxidative DNA damage, inflammation, and apoptosis. HIGHLIGHTSAtopic dermatitis is a chronic relapsing inflammatory disease.Sulforaphane is an isothiocyanate organosulfur compound obtained from cruciferous vegetables.Sulforaphane alleviated AD induced in mice.Sulforaphane inhibits oxidative stress, oxidative DNA damage, inflammation, and apoptosis.

Astaxanthin-s-allyl cysteine diester against high glucose-induced neuronal toxicity in vitro and diabetes-associated cognitive decline in vivo: Effect on p53, oxidative stress and mitochondrial function

Neuroprotective effect of astaxanthin-s-allyl cysteine diester (AST-SAC) against high glucose (HG)-induced oxidative stress in in vitro and cognitive decline under diabetes conditions in in vivo has been explored. Pretreatment of AST-SAC (5, 10 and 15 μM) dose-dependently preserved the neuronal cells (SH-SY5Y) viability against HG toxicity through i) decreasing oxidative stress (decreasing reactive oxygen species generation and increasing endogenous antioxidants level); ii) protecting mitochondrial function [oxidative phosphorylation (OXPHOS) complexes activity and mitochondrial membrane potential (MMP)]; and iii) decreasing p53 level thereby subsequently decreasing the level of apoptotic marker proteins. Male Spraque-Dawley rats were orally administered AST-SAC (1 mg/kg/day) for 45 days in streptozotocin-induced diabetes mellitus (DM) rats. AST-SAC administration prevented the loss of spatial memory in DM rats as determined using the novel object location test. AST-SAC administration alleviated the DM-induced injury in brain such as increased cholinesterases activity, elevated oxidative stress and mitochondrial dysfunction. Altogether, the results from the present study demonstrated that AST-SAC averted the neuronal apoptosis and preserved the cognitive function against HG toxicity under DM conditions.

Potential Glioprotective Strategies Against Diabetes-Induced Brain Toxicity

Astrocytes are crucial for the maintenance of brain homeostasis by actively participating in the metabolism of glucose, which is the main energy substrate for the central nervous system (CNS), in addition to other supportive functions. More specifically, astrocytes support neurons through the metabolic coupling of synaptic activity and glucose utilization. As such, diabetes mellitus (DM) and consequent glucose metabolism disorders induce astrocyte damage, affecting CNS functionality. Glioprotective molecules can promote protection by improving glial functions and avoiding toxicity in different pathological conditions, including DM. Therefore, this review discusses specific pathomechanisms associated with DM/glucose metabolism disorder-induced gliotoxicity, namely astrocyte metabolism, redox homeostasis/mitochondrial activity, inflammation, and glial signaling pathways. Studies investigating natural products as potential glioprotective strategies against these deleterious effects of DM/glucose metabolism disorders are also reviewed herein. These products include carotenoids, catechins, isoflavones, lipoic acid, polysaccharides, resveratrol, and sulforaphane.

Thioredoxin-1 Is a Target to Attenuate Alzheimer-Like Pathology in Diabetic Encephalopathy by Alleviating Endoplasmic Reticulum Stress and Oxidative Stress

Varying degrees of central nervous system neuropathy induced by diabetes mellitus (DM) contribute to a cognitive disorder known as diabetic encephalopathy (DE), which is also one of the independent risk factors for Alzheimer's disease (AD). Endoplasmic reticulum stress (ERS) plays a critical role in the occurrence and development of DE and AD. However, its molecular mechanism remains largely unknown. This study aims to investigate whether thioredoxin-1 (Trx-1) could alleviate DE and AD through ERS, oxidative stress (OS) and apoptosis signaling pathways. Mice were randomly divided into a wild-type group (WT-NC), a streptozotocin (STZ)-treated DM group (WT-DM), a Trx-1-TG group (TG-NC) and a Trx-1-TG DM group (TG-DM). Diabetic animals showed an increase in the time spent in the target quadrant and the number of platform crossings as well as AD-like behavior in the water maze experiment. The immunocontent of the AD-related protein Tau and the levels of cell apoptosis, β-amyloid (Aβ) plaque formation and neuronal degeneration in the hippocampus of the diabetic group were increased. Some key factors associated with ERS, such as protein disulfide isomerase (PDI), glucose-regulated protein 78 (GRP78), inositol-requiring enzyme 1α (IRE1α), tumor necrosis factor receptor-associated factor 2 (TRAF2), apoptosis signal-regulating kinase-1 (ASK1), c-Jun N-terminal kinase (JNK), protein kinase RNA (PKR)-like ER kinase (PERK), and C/EBP homologous protein (CHOP), were upregulated, and other factors related to anti-oxidant stress, such as nuclear factor erythroid 2-related factor (Nrf2), were downregulated in the DM group. Moreover, DM caused an increase in the immunocontents of caspase-3 and caspase-12. However, these changes were reversed in the Trx-1-tg DM group. Therefore, we conclude that Trx-1 might be a key factor in alleviating DE and AD by regulating ERS and oxidative stress response, thus preventing apoptosis.

Trichostatin A increases BDNF protein expression by improving XBP-1s/ATF6/GRP78 axis in Schwann cells of diabetic peripheral neuropathy

Diabetic peripheral neuropathy (DPN) is the common complication of diabetes mellitus. Histone deacetylase (HDAC) inhibitor trichostatin A (TSA) is reported to ameliorate the peripheral nerves degeneration of DPN. However, the exact mechanism is still not well elucidated. Here, we first revealed that TSA promoted nerve conduction and brain derived neurotrophic factor (BDNF) expression in the sciatic nerves of diabetic mice. In line, TSA also reversed high glucose-reduced mature BDNF expression in vitro cultured rat Schwann cells (RSC96). Then unexpectedly, the downstream targets of TSA HDAC1 and HDAC5 were not involved in TSA-improved BDNF expression. Furthermore, unfolded protein response (UPR) chaperone GRP78 was revealed to be downregulated with high glucose stimulation in RSC96 cells, which was avoided with TSA treatment. Also, GRP78 upregulation mediated TSA-improved mature BDNF expression in high glucose-cultured RSC96 cells by binding with BDNF. As well, TSA treatment enhanced the binding of GRP78 with BDNF in RSC96 cells. Again, UPR-associated transcription factors XBP-1s and ATF6 were involved in TSA-increased GRP78 expression in high glucose-stimulated RSC96 cells. Finally, conditioned medium from high glucose-cultured RSC96 cells delayed neuron SH-SY5Y differentiation and that from TSA-treated high glucose-cultured RSC96 cells promoted SH-SY5Y cell differentiation. Taken together, our findings suggested that TSA increased BDNF expression to ameliorate DPN by improving XBP-1s/ATF6/GRP78 axis in Schwann cells.

Neuroprotection Effect of Astragaloside IV from 2-DG-Induced Endoplasmic Reticulum Stress

Objective

Astragaloside IV shows neuroprotective activity, but its mechanism remains unclear. To investigate whether astragaloside IV protects from endoplasmic reticulum stress (ERS), we focus on the regulation of glycogen synthase kinase-3β (GSK-3β) and mitochondrial permeability transition pore (mPTP) by astragaloside IV in neuronal cell PC12.

Methods and Results

PC12 cells treated with different concentrations of ERS inductor 2-deoxyglucose (2-DG) (25-500 μM) showed a significant increase of glucose-regulated protein 78 (GRP 78) and GRP 94 expressions and a decrease of tetramethylrhodamine ethyl ester (TMRE) fluorescence intensity and mitochondrial membrane potential (∆Ψm), with the peak effect seen at 50 μM, indicating that 2-DG induces ERS and the mPTP opening. Similarly, 50 μM of astragaloside IV increased the GSK-3β phosphorylation at Ser9 most significantly. Next, we examined the neuroprotection of astragaloside IV by dividing the PC12 cells into control group, 2-DG treatment group, astragaloside IV plus 2-DG treatment group, and astragaloside IV only group. PC12 cells treated with 50 μM 2-DG for different time courses (0-36 hr) showed a significant increase of Cleaved-Caspase-3 with the peak at 6 hr. 2-DG significantly induced cell apoptosis and increased the green fluorescence intensity of Annexin V-FITC, and these effects were reversed by astragaloside IV. Such a result indicates that astragaloside IV protected neural cell survival from ERS. 2-DG treatment significantly increased the expressions of inositol-requiring ER-to-nucleus signal kinase 1 (IRE1), phosphor-protein kinase R-like ER kinase (p-PERK), but not affect the transcription factor 6 (ATF6) expression. 2-DG treatment significantly decreased the phosphorylation of GSK-3β and significantly reduced the TMRE fluorescence intensity and ∆Ψm, following mPTP open. Astragaloside IV significantly inhibited the above effects caused by 2-DG, except the upregulation of ATF6 protein. Taken together, astragaloside IV significantly inhibited the ERS caused by 2-DG.

Conclusion

Our data suggested that astragaloside IV protects PC12 cells from ERS by inactivation of GSK-3β and preventing the mPTP opening. The GRP 78, GRP 94, IRE1, and PERK signaling pathways but not ATF6 are responsible for GSK-3β inactivation and neuroprotection by astragaloside IV.

The interaction of ASIC1a and ERS mediates nerve cell apoptosis induced by insulin deficiency

Diabetes-related brain complications are the most serious complications of terminal diabetes. The increasing evidence have showed that the predisposing factor is not only hyperglycemia, but also insulin deficiency. In this study, we demonstrated that insulin deficiency was involved in the apoptosis of nerve cells, and it was related to the interaction between acid-sensitive ion channel 1a (ASIC1a) and endoplasmic reticulum stress (ERS). By silencing C/EBP homologous protein (CHOP) and ASIC1a, the pro-apoptotic effect of insulin deficiency on NS20y cells was relieved. Further research found that the binding of CHOP and C/EBPα was increased in the nucleus of cells cultured without insulin, and C/EBPα was competitively inhibited as a negative regulator of ASIC1a, which further increased the ERS and lead to neuronal apoptosis. In summary, ERS and ASIC1a play an important role in neurological damage caused by insulin deficiency. Our finding may lead to new ideas and treatment of diabetes-related brain complications.