Genistein inhibits Aβ25–35‐induced SH‐SY5Y cell damage by modulating the expression of apoptosis‐related proteins and Ca2+ influx through ionotropic glutamate receptors

In this study, we investigated the protective effects of genistein against SH‐SY5Y cell damage induced by β‐amyloid 25–35 peptide (Aβ_25–35) and the underlying mechanisms. Aβ‐induced neuronal death, apoptosis, glutamate receptor subunit expression, Ca²⁺ ion concentration, amino acid transmitter concentration, and apoptosis‐related factor expression were evaluated to determine the effects of genistein on Aβ‐induced neuronal death and apoptosis. The results showed that genistein increased the survival of SH‐SY5Y cells and decreased the level of apoptosis induced by Aβ_25–35. In addition, genistein reversed the Aβ_25–35‐induced changes in amino acid transmitters, α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) receptors, and N‐methyl‐d ‐aspartate (NMDA) receptor subunits in SH‐SY5Y cells. Aβ_25–35‐induced changes in Ca²⁺ and B‐cell lymphoma‐2 (Bcl‐2) and Bcl‐2‐associated X (Bax) protein and gene levels in cells were also reversed by genistein. Our data suggest that genistein protects against Aβ_25–35‐induced damage in SH‐SY5Y cells, possibly by regulating the expression of apoptosis‐related proteins and Ca²⁺ influx through ionotropic glutamate receptors.     

Mulberrofuran G Protects Ischemic Injury‐induced Cell Death via Inhibition of NOX4‐mediated ROS Generation and ER Stress

The aim of this study was to investigate the neuroprotective effect of mulberrofuran G (MG) in in vitro and in vivo models of cerebral ischemia. MG was isolated from the root bark of Morus bombycis. MG inhibited nicotinamide adenine dinucleotide phosphate oxidase (NOX) enzyme activity and oxygen–glucose deprivation/reoxygenation (OGD/R)‐induced NOX4 protein expression in SH‐SY5Y cells. MG inhibited the expression of activated caspase‐3 and caspase‐9 and cleaved poly adenine dinucleotide phosphate‐ribose polymerase in OGD/R‐induced SH‐SY5Y cells. In addition, MG protected OGD/R‐induced neuronal cell death and inhibited OGD/R‐induced reactive oxygen species generation in SH‐SY5Y cells. In in vivo model, MG‐treated groups (0.2, 1, and 5 mg/kg) reduced the infarct volume in middle cerebral artery occlusion/reperfusion‐induced ischemic rats. The MG‐treated groups also reduced NOX4 protein expression in middle cerebral artery occlusion/reperfusion‐induced ischemic rats. Furthermore, protein expression of 78‐kDa glucose‐regulated protein/binding immunoglobulin protein, phosphorylated IRE1α, X‐box‐binding protein 1, and cytosine enhancer binding protein homologous protein, mediators of endoplasmic reticulum stress, were inhibited in MG‐treated groups. Taken together, MG showed protective effect in in vitro and in vivo models of cerebral ischemia through inhibition of NOX4‐mediated reactive oxygen species generation and endoplasmic reticulum stress. This finding will give an insight that inhibition of NOX enzyme activity and NOX4 protein expression could be a new potential therapeutic strategy for cerebral ischemia. Copyright © 2016 John Wiley & Sons, Ltd.     

Ampelopsin inhibits high glucose‐induced extracellular matrix accumulation and oxidative stress in mesangial cells through activating the Nrf2/HO‐1 pathway

Oxidative stress plays an important role in diabetic nephropathy (DN), which is a diabetic complication. Ampelopsin (AMP) is a natural flavonoid that has been found to possess antidiabetic and antioxidative activities. However, the effect of AMP on DN remains unclear. In this study, we aimed to evaluate the protective effect of AMP on glomerular mesangial cells (MCs) exposed to high glucose (HG). We found that AMP improved HG‐caused cell viability reduction in MCs. AMP significantly suppressed the intracellular ROS production and expression levels of ROS producing enzymes NADPH oxidase 2 (NOX2) and NOX4. Increased of NOX activity in HG‐stimulated MCs was suppressed by AMP. Pretreatment with AMP inhibited extracellular matrix (ECM) accumulation in HG‐stimulated MCs with decreased expression levels of fibronectin (FN) and collagen type IV (Col IV). Furthermore, AMP elevated the expression levels of nuclear Nrf2 and heme oxygenase‐1 (HO‐1), as well as increased the mRNA levels of Nrf2‐driven genes NAD(P)H dehydrogenase quinone‐1 (NQO‐1) and HO‐1 in HG‐treated MCs. Knockdown of Nrf2 reversed the protective effects of AMP against HG‐induced oxidative stress and EMC accumulation in MCs. In conclusion, these findings indicated that AMP protected MCs from HG‐induced oxidative damage and ECM accumulation, which might be mediated by Nrf2/HO‐1 pathway.     

Curcumin I Mediates Neuroprotective Effect Through Attenuation of Quinoprotein Formation,p‐p38 MAPK Expression,and Caspase‐3 Activation in 6‐Hydroxydopamine Treated SH‐SY5Y Cells

6‐Hydroxydopamine (6‐OHDA) selectively enters dopaminergic neurons and undergoes auto‐oxidation resulting in the generation of reactive oxygen species and dopamine quinones, subsequently leading to apoptosis. This mechanism mimics the pathogenesis of Parkinson's disease and has been used to induce experimental Parkinsonism in both in vitro and in vivo systems. In this study, we investigated the effects of curcumin I (diferuloylmethane) purified from Curcuma longa on quinoprotein production, phosphorylation of p38 MAPK (p‐p38), and caspase‐3 activation in 6‐OHDA‐treated SH‐SY5Y dopaminergic cells. Pretreatment of SH‐SY5Y with curcumin I at concentrations of 1, 5, 10, and 20 μM, significantly decreased the formation of quinoprotein and reduced the levels of p‐p38 and cleaved caspase‐3 in a dose‐dependent manner. Moreover, the levels of the dopaminergic neuron marker, phospho‐tyrosine hydroxylase (p‐TH), were also dose‐dependently increased upon treatment with curcumin I. Our results clearly demonstrated that curcumin I protects neurons against oxidative damage, as shown by attenuation of p‐p38 expression, caspase‐3‐activation, and toxic quinoprotein formation, together with the restoration of p‐TH levels. This study provides evidence for the therapeutic potential of curcumin I in the chemoprevention of oxidative stress‐related neurodegeneration. Copyright © 2013 John Wiley & Sons, Ltd.     

Neuroprotective effects of Triticum aestivum L. against β‐Amyloid‐induced cell death and memory impairments

β‐Amyloid (Aβ) is a key component of senile plaques, neuropathological hallmarks of Alzheimer's disease (AD) and has been reported to induce cell death via oxidative stress. This study investigated the protective effects of Triticum aestivum L. (TAL) on Aβ‐induced apoptosis in SH‐SY5Y cells and cognitive dysfunctions in Sprague‐Dawley (SD) rats. Cells treated with Aβ exhibited decreased viability and apoptotic features, such as DNA fragmentation, alterations in mitochondria and an increased Bax/Bcl‐2 ratio, which were attenuated by TAL extract (TALE) pretreatment. To elucidate the neuroprotective mechanisms of TALE, the study examined Aβ‐induced oxidative stress and cellular defense. TALE pretreatment suppressed Aβ‐increased intracellular accumulation of reactive oxygen species (ROS) via up‐regulation of glutathione, an essential endogenous antioxidant. To further verify the effect of TALE on memory impairments, Aβ or scopolamine was injected in SD rats and a water maze task conducted as a spatial memory test. Aβ or scopolamine treatment increased the time taken to find the platform during training trials, which was decreased by TALE pretreatment. Furthermore, one of the active components of TALE, total dietary fiber also effectively inhibited Aβ‐induced cytotoxicity and scopolamine‐caused memory deficits. These results suggest that TALE may have preventive and/or therapeutic potential in the management of AD. Copyright © 2009 John Wiley & Sons, Ltd.     

Kaempferol protects HIT‐T15 pancreatic beta cells from 2‐deoxy‐D‐ribose‐induced oxidative damage

During the progression of Type 2 diabetes, glucose toxicity is likely to contribute importantly to progressive beta cell failure. Oxidative stress is an important aspect of glucose toxicity in pancreatic beta cells, and reducing sugars, such as 2‐deoxy‐D‐ribose (dRib), produce reactive oxygen species. Furthermore, many of the biological properties of flavonoids are likely to be related to their antioxidant and free‐radical scavenging abilities. Accordingly, in the present study, we investigated whether kaempferol (a flavonol) protects beta cells from dRib‐induced oxidative damage. HIT‐T15 cells were cultured with various concentrations of dRib for 24h. Cell survivals, amounts of reactive oxygen species (ROS) generated, apoptosis, and lipid peroxidation were measured. dRib was found to dose‐dependently reduce cell survival and to markedly increase intracellular ROS levels, apoptosis, and lipid peroxidation. However, kaempferol (10 µM) suppressed dRib (20 mM) induced intracellular ROS, apoptosis, and lipid peroxidation. So, we demonstrate that kaempferol reduces dRib‐mediated beta cell damage interfering with ROS metabolism and protective effects against lipid peroxidation. Our findings indicate that kaempferol protects HIT‐T15 cells from dRib‐induced associated oxidative damage. Copyright © 2009 John Wiley & Sons, Ltd.     

Caffeoylserotonin Protects Human Keratinocyte HaCaT Cells against H2O2‐Induced Oxidative Stress and Apoptosis through Upregulation of HO‐1 Expression via Activation of the PI3K/Akt/Nrf2 Pathway

Caffeoylserotonin (CaS) has strong radical scavenging activity as well as antioxidant activities, protecting cells from lipid peroxidation, intracellular reactive oxygen species generation, DNA damage, and cell death. The molecular mechanism by which CaS protects against oxidative stress is not well understood. Here, we analyzed the cytoprotective activity of CaS in hydrogen peroxide (H₂O₂)‐treated keratinocyte HaCaT cells. H₂O₂ induced apoptosis in the cells through activation of pro‐apoptotic p21, Bax, and caspase‐3. Pretreatment with CaS inhibited apoptotic gene expression and activated the anti‐apoptotic gene, Bcl‐xL. Although CaS did not directly affect heme oxygenase‐1 (HO‐1) expression, pretreatment with CaS augmented HO‐1 expression through an increase in NF‐E2‐related factor (Nrf2) stability and stimulation of Nrf2 translocation to the nucleus upon H₂O₂ exposure. H₂O₂ also induced the phosphorylation and subsequent activation of ERK, p38 MAPK, and Akt. Analysis using specific inhibitors of p38 MAPK and Akt demonstrated that only Akt activation was involved in HO‐1 and Nrf2 expressions. In addition, PI3K and PKC inhibitors suppressed HO‐1/Nrf2 expression and Akt phosphorylation. These results demonstrate that CaS protects against oxidative stress‐induced keratinocyte cell death in part through the activation of Nrf2‐mediated HO‐1 induction via the PI3K/Akt and/or PKC pathways, but not MAPK signaling. Copyright © 2013 John Wiley & Sons, Ltd.     

Genistein protects against amyloid‐beta‐induced toxicity in SH‐SY5Y cells by regulation of Akt and Tau phosphorylation

Alzheimer's disease is a neurodegenerative disorder characterized by extracellular deposition of amyloid‐β (Aβ) peptide and hyperphosphorylation of Tau protein, which ultimately leads to the formation of intracellular neurofibrillary tangles and cell death. Increasing evidence indicates that genistein, a soy isoflavone, has neuroprotective effects against Aβ‐induced toxicity. However, the molecular mechanisms involved in its neuroprotection are not well understood. In this study, we have established a neuronal damage model using retinoic‐acid differentiated SH‐SY5Y cells treated with different concentrations of Aβ_25–35 to investigate the effect of genistein against Aβ‐induced cell death and the possible involvement of protein kinase B (PKB, also termed Akt), glycogen synthase kinase 3β (GSK‐3β), and Tau as an underlying mechanism to this neuroprotection. Differentiated SH‐SY5Y cells were pre‐treated for 24 hr with genistein (1 and 10 nM) and exposed to Aβ_25–35 (25 μM), and we found that genistein partially inhibited Aβ induced cell death, primarily apoptosis. Furthermore, the protective effect of genistein was associated with the inhibition of Aβ‐induced Akt inactivation and Tau hyperphosphorylation. These findings reinforce the neuroprotective effects of genistein against Aβ toxicity and provide evidence that its mechanism may involve regulation of Akt and Tau proteins.     

Brassinin,a phytoalexin in cruciferous vegetables,suppresses obesity‐induced inflammatory responses through the Nrf2‐HO‐1 signaling pathway in an adipocyte‐macrophage co‐culture system

The aim of this study was to investigate the effect of brassinin (BR), a phytoalexin found in plants belonging to the Brassicaceae family, on the obesity‐induced inflammatory response and its molecular mechanism in co‐culture of 3T3‐L1 adipocytes and RAW264.7 macrophages. BR effectively suppressed lipid accumulation by down‐regulating the expression of adipogenic factors, which in turn, were regulated by early adipogenic factors such as CCAAT‐enhancer‐binding protein‐β and Kruppel‐like factor 2. Production of inflammatory cytokines and reactive oxygen species, induced by adipocyte‐conditioned medium, was significantly decreased in BR‐treated cells. This effect of BR was more prominent in contact co‐culture of adipocytes and macrophages with a 90% and 34% reduction in IL‐6 and MCP‐1 levels, respectively. BR also restored adiponectin expression, which was significantly reduced by culturing adipocytes in macrophage‐conditioned medium. In the transwell system, BR increased the protein levels of nuclear factor (erythroid‐derived 2)‐like 2 (Nrf2) and its target molecule, hemoxygenase‐1 (HO‐1), by 55%–93% and 45%–48%, respectively, and also increased Nrf2 translocation into the nucleus. However, knockdown of Nrf2 or HO‐1 in RAW264.7 cells restored this BR‐mediated inhibition of IL‐6 and MCP‐1 production. These results indicated that BR inhibited obesity‐induced inflammation via the Nrf2‐HO‐1 pathway.     

Ferulic acid reinstates mitochondrial dynamics through PGC1α expression modulation in 6‐hydroxydopamine lesioned rats

Disruption of the tightly regulated mitochondrial dynamics and energy homeostasis leads to oxidative stress and apoptotic cell death, as observed in neurodegenerative disorders such as Parkinson's disease (PD). Polyphenolic plant derivatives have been shown to alleviate such pathological features and have been used in models of neurodegenerative disorders in previous reports. In the current study, we utilized a 6‐hydroxydopamine (6‐OHDA) lesioned rat model of PD to explore the protective efficacy of polyphenolic phytochemical ferulic acid (FA) against mitochondrial dysfunction and explored its effect on gene and protein expression of mitochondrial dynamics regulators dynamin‐related protein 1 (Drp1)/mitofusin 2 (Mfn2) in lesioned animals. We also evaluated its effect on expression of mitochondrial biogenesis regulator PGC1α and apoptotic regulators BAX, cyt c, p53, and cleaved PARP. We found that oral FA supplementation alleviated 6‐OHDA induced oxidative stress, DNA fragmentation, morphological changes, and blocked apoptotic cascade. FA also reduced mitochondrial Drp1 expression and increased gene and protein expression of PGC1α, thereby regulating expression of its downstream target Mfn2 and restoring mitochondrial dynamics in lesioned animals. Our data suggest that targeting mitochondrial dynamics through modulation of PGC1α can prove to be a potent preventive strategy against PD pathology.     

Neuroprotective effect of salidroside against central nervous system inflammation‐induced cognitive deficits: A pivotal role of sirtuin 1‐dependent Nrf‐2/HO‐1/NF‐κB pathway

Central nervous system (CNS) inflammation occurs in cognitive dysfunctions, but the underlying mechanisms remain unclear. Here, we investigated the role of sirtuin 1 (SIRT1) and salidroside in CNS inflammation‐induced cognitive deficits model. In vivo, CNS inflammation was initiated by a single intracerebroventricular injection of lipopolysaccharide (LPS). The levels of inflammatory cytokines and the capability of free radial scavenging were determined after the LPS challenge. In vivo, salidroside and nicotinamide, a SIRT1 inhibitor, were used in PC12 cell. Of note, with the treatment of salidroside, LPS‐induced learning and memory impairments were effectively improved. Salidroside also remarkably inhibited the inflammatory cytokines, up‐regulated the concentration of superoxide dismutase and inhibited the vitalities of malondialdehyde in serum, hippocampus, and cell supernatant. Besides, the expression of Sirt1, Nrf‐2, HO‐1, Bax, Bcl‐2, caspase‐9, and caspase‐3 and the phosphorylation of AMPK, NF‐κBp65, and IκBα were increased accompanying with the LPS‐induced cognitive impairments, which were significantly suppressed by salidroside treatment. In PC12 cell model, nicotinamide significantly abrogated the beneficial effects of salidroside, as indicated by the antioxidant, anti‐inflammatory, and antiapoptosis signaling. Together, our results showed that salidroside may be a novel therapy drug in neurodegenerative diseases, and the protective effect was involved in SIRT1‐dependent Nrf‐2/HO‐1/NF‐κB pathway.     

Pongapin and Karanjin,furanoflavanoids of Pongamia pinnata,induce G2/M arrest and apoptosis in cervical cancer cells by differential reactive oxygen species modulation,DNA damage,and nuclear factor kappa‐light‐chain‐enhancer of activated B cell signaling

In this study, the antitumor activity of two furanoflavanoid derivatives, Pongapin and Karanjin, was evaluated in comparison with Plumbagin, a plant‐derived polyphenol with proven antitumor activity. The compounds differentially inhibit the growth of different cancer cell lines (most effective on HeLa cells), with very low inhibitory effect on the growth of normal mouse embryonic fibroblast cell line. Pongapin like Plumbagin could significantly increase the intracellular reactive oxygen species (ROS) in the HeLa cells by stabilization of nuclear factor of kappa light polypeptide gene enhancer in B‐cells inhibitor (I‐κB) expression and reduction of nuclear factor kappa‐light‐chain‐enhancer of activated B cells (NF‐κB) expression. In contrast, Karanjin could decrease ROS level by inhibition of I‐κB degradation resulting restriction of NF‐κB nuclear translocation. Pongapin and Plumbagin significantly increased DNA damage‐induced p53 expression and p21 nuclear expression. However, Karanjin treatment showed low DNA damage with increased p53 expression. The compounds induced G2/M arrest and increase in SubG1 population, indicating induction of apoptosis. Apoptosis was further validated by acridine orange/ethidium bromide dual staining and terminal deoxynucleotidyl transferase dUTP nick‐end labeling assay in HeLa cells after treatment with the compounds. The compounds induced caspase‐dependent apoptosis through induction of Bax/Bcl‐2 ratio either through increased expression of Bax by Pongapin and Plumbagin or low expression of Bcl‐2 by Karanjin. Thus, Pongapin and Karanjin may be potential natural anticancer agents in the future, like Plumbagin.     

Anthocyanidin attenuates myocardial ischemia induced injury via inhibition of ROS‐JNK‐Bcl‐2 pathway: New mechanism of anthocyanidin action

Despite treatment options available to date, myocardial ischemia (MI) remains the leading cause of death worldwide. Studies are focused on finding effective therapeutic strategies against MI injury. Growing interest has been developed in natural compounds possessing medicinal properties with scarcer side effects. Here, we have evaluated the cardioprotective potential of anthocyanidin against MI injury and explored its underlying protective mechanism. Left anterior descending coronary artery was ligated to induce MI in mice. Neonatal mice cardiomyocytes were treated with H₂O₂ to induce oxidative stress (a major contributor to MI injury) in vitro. Anthocyanidin pretreatment significantly reduced the infarct size, preserved the cell viability, and protected against ischemia‐induced cardiac injury in treatment groups compared with the H₂O₂‐treated group in vitro. Measurement of reactive oxygen species (ROS) validated the strong antioxidant potential of anthocyanidin, as significant reduction in oxidative stress was observed in anthocyanidin‐pretreated groups. Mechanistically, pretreatment with anthocyanidin significantly subdued the activation of JNK (to p‐JNK) and elevated Bcl‐2 levels. Both in vivo and in vitro findings suggest that anthocyanidin can induce a state of myocardial resistance against ischemic insult. We have provided the experimental evidence for inhibition of ROS/p‐JNK/Bcl‐2 pathway being the underlying mechanism of action of anthocyanidin. Our results support the use of anthocyanidin as therapeutic strategy against MI injury.     

Eupatolide Inhibits PDGF‐induced Proliferation and Migration of Aortic Smooth Muscle Cells Through ROS‐dependent Heme Oxygenase‐1 Induction

The abnormal proliferation and migration of vascular smooth muscle cell (VSMC) contributes importantly to the pathogenesis of atherosclerosis and restenosis. Here, we investigated the effects of eupatolide (EuTL), a sesquiterpene lactone isolated from the medicinal plant Inula britannica, on platelet‐derived growth factor (PDGF)‐induced proliferation and migration of primary rat aortic smooth muscle cells (RASMCs), as well as its underlying mechanisms. EuTL remarkably inhibited PDGF‐induced proliferation and migration of RASMCs. Treatment of RASMCs with EuTL induced both protein and mRNA expression of heme oxygenase‐1 (HO‐1). SB203580 (a p38 inhibitor), SP600125 (a JNK inhibitor), U0126 (a MEK inhibitor) and LY294002 (a PI3K inhibitor) did not suppress EuTL‐induced HO‐1 expression; however, N‐acetylcysteine (NAC, an antioxidant) blocked EuTL‐induced HO‐1 expression. Moreover, treatment of RASMCs with EuTL increased reactive oxygen species (ROS) accumulation and nuclear translocation of nuclear factor‐E2‐related factor 2 (Nrf2); however, this translocation was also inhibited by NAC. NAC or inhibition of HO‐1 significantly attenuated the inhibitory effects of EuTL on PDGF‐induced proliferation and migration of RASMCs. Taken together, these findings suggest that EuTL could suppress PDGF‐induced proliferation and migration of VSMCs through HO‐1 induction via ROS‐Nrf2 pathway and may be a potential HO‐1 inducer for preventing or treating vascular diseases. Copyright © 2013 John Wiley & Sons, Ltd.     

Phloroglucinol Protects INS‐1 Pancreatic β‐cells Against Glucotoxicity‐Induced Apoptosis

Decreasing numbers, and impaired function, of pancreatic β‐cells are key factors in the development of type 2 diabetes. This study was designed to investigate whether phloroglucinol protected pancreatic β‐cells against glucotoxicity‐induced apoptosis using a rat insulinoma cell line (INS‐1). High glucose treatment (30 mM) induced INS‐1 cell death; however, the level of glucose‐induced apoptosis was significantly reduced in cells treated with 100‐μM phloroglucinol. Treatment with 10–100‐μM phloroglucinol increased cell viability and decreased intracellular levels of reactive oxygen species, nitric oxide, and lipid peroxidation dose‐dependently in INS‐1 cells pretreated with high glucose. Furthermore, phloroglucinol treatment markedly reduced the protein expression of Bax, cytochrome c, and caspase 9, while increasing anti‐apoptotic Bcl‐2 protein expression. Cell death type was examined using annexin V/propidium iodide staining, revealing that phloroglucinol markedly reduced high glucose‐induced apoptosis. These results demonstrated that phloroglucinol could be useful as a potential therapeutic agent for the protection of pancreatic β‐cells against glucose‐induced apoptosis. Copyright © 2015 John Wiley & Sons, Ltd.     

The novel protective effects of loganin against 1‐methyl‐4‐phenylpyridinium‐induced neurotoxicity: Enhancement of neurotrophic signaling,activation of IGF‐1R/GLP‐1R,and inhibition of RhoA/ROCK pathway

Loganin, a major iridoid glycoside obtained from fruits of Cornus officinalis, possesses anti‐inflammatory, antitumor, antidiabetic, and osteoporosis prevention effects. Loganin has been linked to neuroprotection in several models of neurodegeneration, including Parkinson's disease (PD). However, mechanisms underlying the neuroprotective effects of loganin are still mostly unknown. Here, we demonstrated the protective effects of loganin against PD mimetic toxin 1‐methyl‐4‐phenylpyridinium (MPP⁺) and the important roles of insulin‐like growth factor 1 receptor (IGF‐1R) and glucagon‐like peptide 1 receptor (GLP‐1R) in the neuroprotective mechanisms of loganin. In primary mesencephalic neuronal cultures treated with or without MPP⁺, loganin up‐regulated expressions of neurotrophic signals including IGF‐1R, GLP‐1R, p‐Akt, BDNF, and tyrosine hydroxylase. Loganin protected against MPP⁺‐induced apoptosis by up‐regulating antiapoptotic protein and down‐regulating proapoptotic protein. Moreover, loganin attenuated MPP⁺‐induced neurite damage via up‐regulation of GAP43 and down‐regulation of membrane‐RhoA/ROCK2/p‐LIMK/p‐cofilin. Loganin also attenuated MPP⁺‐induced reactive oxygen species (ROS) production. However, both AG1024, an IGF‐1R antagonist, and exendin 9‐39, a GLP‐1R antagonist, attenuated the protective effects of loganin on MPP⁺‐induced cytotoxicity, apoptosis, neurite length decrease, and ROS production. Our results suggest that loganin attenuates MPP⁺‐induced apoptotic death, neurite damage, and oxidative stress through enhancement of neurotrophic signaling, activation of IGF‐1R/GLP‐1R, and inhibition of RhoA/ROCK pathway, providing the evidence that loganin possesses novel neuroprotective effects.