Meloxicam protects cell damage from 1-methyl-4-phenyl pyridinium toxicity via the phosphatidylinositol 3-kinase/Akt pathway in human dopaminergic neuroblastoma SH-SY5Y cells

Meloxicam Inhibits Apoptosis in Neurons by Deactivating Tumor Necrosis Factor Receptor Superfamily Member 25, Leading to the Decreased Cleavage of DNA Fragmentation Factor Subunit α in Alzheimer's Disease

Neuronal apoptosis is considered to be a critical cause of Alzheimer's disease (AD). Recently, meloxicam has shown neuroprotective effects; however, the inherent mechanisms are highly overlooked. Using APP/PS1 transgenic (Tg) mice as in vivo animal models, we found that meloxicam inhibits apoptosis in neurons by deactivating tumor necrosis factor receptor superfamily member 25 (TNFRSF25), leading to the suppression of the expression of fas-associated protein with death domain (FADD) and the cleavage of DNA fragmentation factor subunit α (DFFA) and cysteine aspartic acid protease-3 (caspase 3) via β-amyloid protein (Aβ)-depressing mechanisms. Moreover, the meloxicam treatment blocked the effects of β-amyloid protein oligomers (Aβo) on stimulating the synthesis of tumor necrosis factor α (TNF-α) and TNF-like ligand 1A (TL1A) in neuroblastoma (N) 2a cells. TNF-α and TL1A induce apoptosis in neurons via TNFR- and TNFRSF25-dependent caspase 3-activating mechanisms, respectively. Knocking down the expression of TNFRSF25 blocked the effects of TL1A on inducing apoptosis in neurons by deactivating the signaling cascades of FADD, caspase 3, and DFFA. Consistently, TNFRSF25 shRNA blocked the effects of Aβo on inducing neuronal apoptosis, which was corroborated by the efficacy of meloxicam in inhibiting Aβo-induced neuronal apoptosis. By ameliorating neuronal apoptosis, meloxicam improved memory loss in APP/PS1 Tg mice.

Reappraisal of metabolic dysfunction in neurodegeneration: Focus on mitochondrial function and calcium signaling

The cellular and molecular mechanisms that drive neurodegeneration remain poorly defined. Recent clinical trial failures, difficult diagnosis, uncertain etiology, and lack of curative therapies prompted us to re-examine other hypotheses of neurodegenerative pathogenesis. Recent reports establish that mitochondrial and calcium dysregulation occur early in many neurodegenerative diseases (NDDs), including Alzheimer's disease, Parkinson's disease, Huntington's disease, and others. However, causal molecular evidence of mitochondrial and metabolic contributions to pathogenesis remains insufficient. Here we summarize the data supporting the hypothesis that mitochondrial and metabolic dysfunction result from diverse etiologies of neuropathology. We provide a current and comprehensive review of the literature and interpret that defective mitochondrial metabolism is upstream and primary to protein aggregation and other dogmatic hypotheses of NDDs. Finally, we identify gaps in knowledge and propose therapeutic modulation of mCa2+ exchange and mitochondrial function to alleviate metabolic impairments and treat NDDs.

Regulation of AKT/AMPK signaling, autophagy and mitigation of apoptosis in Rutin-pretreated SH-SY5Y cells exposed to MPP. Metab Brain Dis 2021;36:315-326. [PMID: 33146846 DOI: 10.1007/s11011-020-00641-z]

Accumulating evidence suggest that apoptosis, autophagy and dysregulation of signaling pathways are common mechanisms involved in Parkinson's disease (PD) pathogenesis, and thus development of therapeutic agents targeting these mechanisms may be useful for the treatment of this disease. Although rutin (a bioflavonoid) is reported to have pharmacological benefits such as antioxidant, anti-inflammatory and antitumor activities, there are very few reports on the activity of this compound in 1-methyl-4-phenylpyridinium (MPP⁺)-induced PD models. Accordingly, we investigated the effects of rutin on apoptosis, autophagy and cell signaling markers (AKT/AMPK) in SH-SY5Y cells exposed to MPP⁺. Results show reduced changes in nuclear morphology and mitigation of caspase 3/7 and 9 activities in rutin pre-treated cells exposed to MPP⁺. Likewise, rutin regulated cell signaling pathways (AKT/AMPK) and significantly decreased protein expression levels of cleaved PARP, cytochrome c, LC3-II and p62. Also, rutin significantly increased protein expression levels of full-length caspase 3 in SH-SY5Y cells treated with MPP⁺. Transmission electron microscope (TEM) images demonstrated a reduction in autophagosomes in rutin-pretreated SH-SY5Y cells exposed to MPP⁺. These results provide experimental support for rutin's neuroprotective activity against MPP⁺-induced toxicity in SH-SY5Y cells, which is as a promising therapeutic agent for clinical trials in humans.

Synthesis and biological evaluation as well as in silico studies of arylpiperazine-1,2-benzothiazine derivatives as novel anti-inflammatory agents

Novel arylpiperazine-1,2-benzothiazine derivatives have been designed and synthesized as potential anti-inflammatory agents. Their structure and properties have been studied using spectroscopic techniques (¹H NMR, ¹³C NMR, FT-IR), MS, elemental analyses, and single-crystal X-ray diffraction (SCXRD, for compound 7b). This study aimed to evaluate the inhibitory activity of new derivatives against both cyclooxygenase isoforms COX-1 and COX-2 due to the similarity of new compounds to oxicams drugs from the NSAIDs group. All new compounds were divided into two series - A and B - with a different linker between thiazine and piperazines nitrogens. Series A included the three-carbon aliphatic linker and series B - two-carbon with a carbonyl group. According to in vitro and molecular docking studies all new compounds exhibited cyclooxygenase inhibitory activity. The series of A compounds included COX-1 inhibitors only. In contrast, the B series showed inhibition of both COX-1 and COX-2, which suggested the importance of the acetoxy linker for COX-2 inhibition. Moreover, the most selective compound 7b, towards COX-2, was non-toxic for the normal human cell line (in concentration of 10 µM) comparable to reference drug meloxicam. Additionally, investigation of influence on model membranes confirmed the ability of the compound 7b to penetrate lipid bilayers which seemed to be important to the influence with membrane protein-cyclooxygenase.

Neuroprotective effects of low-dose G-CSF plus meloxicam in a rat model of anterior ischemic optic neuropathy

Non-arteritic anterior ischemic optic neuropathy (NAION) causes a sudden loss of vision and lacks effective treatment. Granulocyte colony-stimulating factor (G-CSF) provides neuroprotection against the experimental optic nerve injuries but also induce leukocytosis upon typical administration. We found synergetic neuroprotective effects of meloxicam and low dose G-CSF without leukocytosis in a rat model of anterior ischemic optic neuropathy (rAION). The WBC counts in the low-dose G-CSF-plus meloxicam-treated group were similar to the sham-operated group. Combination treatment of low-dose G-CSF plus meloxicam preserved RGCs survival and visual function, reduced RGC apoptosis and the macrophages infiltration, and promote more M2 phenotype of macrophage/microglial transition than the low-dose GCSF treatment or the meloxicam treatment. Moreover, the combination treatment induced higher serine/threonine kinase 1 (Akt1) expression. The combination treatment of low-dose G-CSF plus meloxicam lessened the leukocytotic side effect and provided neuroprotective effects via Akt1 activation in the rAION model. This approach provides crucial preclinical information for the development of alternative therapy in AION.

Neuroprotective effects of Astilbin on MPTP-induced Parkinson's disease mice: Glial reaction, α-synuclein expression and oxidative stress

Astilbin (AST), a dihydro-flavonol glycoside, is a major bioactive ingredient in Astilbe thunbergii, Engelhardia roxburghiana, Smilax corbularia and Erythroxylum gonocladum, and has been shown to have anti-inflammatory, antioxidative and neuroprotective effects, suggesting potential therapeutic value in the treatment of Parkinson's disease (PD). We explored the neuroprotective effects of AST in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced Parkinson's disease mice. Mice were administered with MPTP (30 mg/kg, i.p) daily for 5 days, to establish a subacute Parkinson's disease model, followed by daily treatment with AST or saline for 7 days. Pole and traction tests showed that AST ameliorated the impaired motor functions in MPTP-induced Parkinson's disease mice. High performance liquid chromatography analysis revealed that AST treatment prevented MPTP-induced decreases in striatal dopamine levels. Immunofluorescence assays showed that AST reduced the loss of dopaminergic neurons and the activation of microglia and astrocytes in the substantia nigra. Western blot analyses revealed that AST suppressed α-synuclein overexpression and activated PI3K/Akt in the striatum following MPTP treatment. AST also prevented the MPTP-induced reduction in total superoxide dismutase and glutathione activity in the striatum. AST exerts neuroprotective effects on MPTP-induced PD mice by suppressing gliosis, α-synuclein overexpression and oxidative stress, suggesting that AST could serve as a therapeutic drug to ameliorate PD.

Bicuculline Reverts the Neuroprotective Effects of Meloxicam in an Oxygen and Glucose Deprivation (OGD) Model of Organotypic Hippocampal Slice Cultures

We previously demonstrated that the non-steroidal anti-inflammatory agent meloxicam has neuroprotective effects in an oxygen and glucose deprivation model (OGD) of rat organotypic hippocampal slice cultures. We wondered if GABAergic transmission changed the neuroprotective effects of meloxicam and if meloxicam was able to modulate endoplasmic reticulum stress (ER stress) in this model. Mortality was measured using propidium iodide. Western blot assays were performed to measure levels of cleaved and non-cleaved caspase-3 to quantify apoptosis, while levels of GRP78, GRP94 and phosphorylated eIF2α were used to detect unfolded protein response (UPR). Transcript levels of GRP78, GRP94 and GABAergic receptor α, β, and γ subunits were measured by real-time quantitative polymerase chain reaction (qPCR). In the present study, we show that the presence of meloxicam in a 30 min OGD assay, followed by 24 h of normoxic conditions, presented an antiapoptotic effect. The simultaneous presence of the GABA_A receptor antagonist, bicuculline, in combination with meloxicam blocked the neuroprotective effect provided by the latter. However, in light of its effects on caspase 3 and PARP, bicuculline did not seem to promote the apoptotic pathway. Our results also showed that meloxicam modified the unfolded protein response (UPR), as well as the transcriptional response of different genes, including the GABA_A receptor, alpha1, beta3 and gamma2 subunits. We concluded that meloxicam has a neuroprotective anti-apoptotic action, is able to enhance the UPR independently of the systemic anti-inflammatory response and its neuroprotective effect can be inhibited by blocking GABA_A receptors.

Rapamycin Confers Neuroprotection against Colistin-Induced Oxidative Stress, Mitochondria Dysfunction, and Apoptosis through the Activation of Autophagy and mTOR/Akt/CREB Signaling Pathways

Our previous studies showed that colistin-induced neurotoxicity involves apoptosis and oxidative damage. The present study demonstrates a neuroprotective effect of rapamycin against colistin-induced neurotoxicity in vitro and in vivo. In a mouse model, colistin treatment (18 mg/kg/d; 14 days) produced marked neuronal mitochondria damage in the cerebral cortex and increased activation of caspase-9 and -3. Rapamycin cotreatment (2.5 mg/kg/d) effectively reduced this neurotoxic effect. In an in vitro mouse neuroblastoma-2a (N2a) cell culture model, rapamycin pretreatment (500 nM) reduced colistin (200 μM) induced cell death from ∼50% to 72%. Moreover, rapamycin showed a marked neuroprotective effect in the N2a cells by decreasing intracellular reactive oxygen species (ROS) production and by up-regulating the activities of the anti-ROS enzymes superoxide dismutase and catalase and recovering glutathione (GSH) levels to normal. Moreover, rapamycin pretreatment protected against colistin-induced mitochondrial dysfunction, caspase activation, and subsequent apoptosis by up-regulating autophagy and activating the Akt/CREB, NGF, and Nrf2 pathways, while inhibiting p53 signaling. Taken together, this is the first study to demonstrate that rapamycin protects against colistin-induced neurotoxicity by activating autophagy, inhibiting oxidative stress, mitochondria dysfunction, and apoptosis. Our data highlight that regulating autophagy to rescue neurons from apoptosis may become a new targeted therapy to relieve the adverse neurotoxic effects associated with colistin therapy.

IGF-1 protects SH-SY5Y cells against MPP+-induced apoptosis via PI3K/PDK-1/Akt pathway

Insulin-like growth factor (IGF)-1 is a well-known anti-apoptotic pro-survival factor and phosphatidylinositol-3-kinase (PI3K)/Akt pathway is linked to cell survival induced by IGF-1. It is also reported that Akt signaling is modulated by 3-phosphoinositide-dependent kinase-1 (PDK1). In the current study, we investigated whether the anti-apoptotic effect of IGF-1 in SH-SY5Y cells exposed to 1-methyl-4-phenylpyridinium (MPP⁺) is associated with the activity of PI3K/PDK1/Akt pathway. Treatment of cells with IGF-1 inhibited MPP⁺-induced apoptotic cell death. IGF-1-induced activation of Akt and the protective effect of IGF-1 on MPP⁺-induced apoptosis were abolished by chemical inhibition of PDK1 (GSK2334470) or PI3K (LY294002). The phosphorylated levels of Akt and PDK1 were significantly suppressed after MPP⁺ exposure, while IGF-1 treatment completely restored MPP+-induced reductions in phosphorylation. IGF-1 protected cells from MPP⁺ insult by suppressing intracellular reactive oxygen species (ROS) production and malondialdehyde levels and increasing superoxide dismutase activity. Mitochondrial ROS levels were also increased during MPP⁺ exposure, which were attenuated by IGF-1 treatment. In addition, IGF-1-treated cells showed increased activities of succinate dehydrogenase and citrate synthase, stabilization of mitochondrial transmembrane potential, increased ratio of Bcl-2 to Bax, prevention of cytochrome c release and inhibition of caspase-3 activation with PARP cleavage. Furthermore, the protective effects of IGF-1 on oxidative stress and mitochondrial dysfunction were attenuated when cells were preincubated with GSK2334470 or LY294002. Our data suggest that IGF-1 protects SH-SY5Y cells against MPP⁺-associated oxidative stress by preserving mitochondrial integrity and inhibiting mitochondrial apoptotic cascades via the activation of PI3K/PDK1/Akt pathway.

Design, synthesis and evaluation of indole derivatives as multifunctional agents against Alzheimer's disease

A series of indole derivatives was designed and synthesised to improve on activity and circumvent pharmacokinetic limitations experienced with the structurally related compound, ladostigil. The compounds consisted of a propargylamine moiety (a known MAO inhibitor and neuroprotector) at the N1 position and a ChE inhibiting diethyl-carbamate/urea moiety at the 5 or 6 position of the indole ring. In order to prevent or slow down the in vivo hydrolysis and deactivation associated with the carbamate function of ladostigil, a urea moeity was incorporated into selected compounds to obtain more metabolically stable structures. The majority of the synthesised compounds showed improved MAO-A inhibitory activity compared to ladostigil. The compounds possessing the propargylamine moiety showed good MAO-B inhibitory activity with 6 and 8 portraying IC₅₀ values between 14-20 fold better than ladostigil. The ChE assay results indicated that the compounds have non-selective inhibitory activities on eeAChE and eqBuChE regardless of the type or position of substitution (IC₅₀: 2-5 μM). MAO-A and MAO-B docking results showed that the propargylamine moiety was positioned in close proximity to the FAD cofactor suggesting that the good inhibitory activity may be attributed to the propargylamine moiety and irreversible inhibition as confirmed in the reversibility studies. Docking results also indicated that the compounds have interactions with important amino acids in the AChE and BuChE catalytic sites. Compound 6 was the most potent multifunctional agent showing better inhibitory activity than ladostigil in vitro on all enzymes tested (hMAO-A IC₅₀ = 4.31 μM, hMAO-B IC₅₀ = 2.62 μM, eeAChE IC₅₀ = 3.70 μM, eqBuChE IC₅₀ = 2.82 μM). Chemical stability tests confirmed the diethyl-urea containing compound 6 to be more stable than its diethyl-carbamate containing counterpart compound 8. Compound 6 also exerted significant neuroprotection (52.62% at 1 μM) against MPP⁺ insult to SH-SY5Y neural cells and has good in silico predicted ADMET properties. The favourable neuronal enzyme inhibitory activity, likely improved pharmacokinetic properties in vivo and the potent neuroprotective ability of compound 6 make it a promising compound for further development.

Versatility of 7-Substituted Coumarin Molecules as Antimycobacterial Agents, Neuronal Enzyme Inhibitors and Neuroprotective Agents

A medium-throughput screen using Mycobacterium tuberculosis H37Rv was employed to screen an in-house library of structurally diverse compounds for antimycobacterial activity. In this initial screen, eleven 7-substituted coumarin derivatives with confirmed monoamine oxidase-B and cholinesterase inhibitory activities, demonstrated growth inhibition of more than 50% at 50 µM. This prompted further exploration of all the 7-substituted coumarins in our library. Four compounds showed promising MIC₉₉ values of 8.31–29.70 µM and 44.15–57.17 µM on M. tuberculosis H37Rv in independent assays using GAST-Fe and 7H9+OADC media, respectively. These compounds were found to bind to albumin, which may explain the variations in MIC between the two assays. Preliminary data showed that they were able to maintain their activity in fluoroquinolone resistant mycobacteria. Structure-activity relationships indicated that structural modification on position 4 and/or 7 of the coumarin scaffold could direct the selectivity towards either the inhibition of neuronal enzymes or the antimycobacterial effect. Moderate cytotoxicities were observed for these compounds and slight selectivity towards mycobacteria was indicated. Further neuroprotective assays showed significant neuroprotection for selected compounds irrespective of their neuronal enzyme inhibitory properties. These coumarin molecules are thus interesting lead compounds that may provide insight into the design of new antimicrobacterial and neuroprotective agents.

Salidroside attenuates colistin-induced neurotoxicity in RSC96 Schwann cells through PI3K/Akt pathway

Neurotoxicity is a key dose-limiting factor for colistin therapy. This study aimed to investigate the protective effect of Salidroside on colistin-induced neurotoxicity in RSC96 Schwann cells and the underlying mechanisms. After Salidroside (12.5, 25, 50 μg/mL) treatment for 2 h, the cells were cultured with 250 μg/mL colistin for 24 h. In order to investigate the role of phosphatidylinositol 3-kinase/protein kinase B (PI3K/Akt) pathway, the cells were pre-treated with LY294002 (12.5 μmol/L, a specific inhibitor of PI3K phosphorylation) for 1 h before Salidroside (50 μg/mL) treatment, then were co-cultured with colistin (250 μg/mL) for 24 h. The results showed that colistin treatment could induce apoptotic cell death which was associated with oxidative stress injury. Salidroside could reduce colistin-induced neurotoxicity, decrease the effect of colistin on the reduced expression levels of p-Akt and Bcl-2, and increased the expresion of Bax, release of Cyt c, and activation of caspase-3. However, the protective effect of Salidroside against colistin-induced apoptosis was partly abolished by LY294002. These findings suggest that Salidroside could attenuate colistin-induced neurotoxicity in RSC96 Schwann cells via the PI3K/Akt pathway.

Neuroprotective Effects of Salidroside in the MPTP Mouse Model of Parkinson's Disease: Involvement of the PI3K/Akt/GSK3β Pathway

The degenerative loss through apoptosis of dopaminergic neurons in the substantia nigra pars compacta plays a primary role in the progression of Parkinson's disease (PD). Our in vitro experiments suggested that salidroside (Sal) could protect against 1-methyl-4-phenylpyridine-induced cell apoptosis in part by regulating the PI3K/Akt/GSK3β pathway. The current study aims to increase our understanding of the protective mechanisms of Sal in the 1-methyl-4-phenyl-1,2,3,6-tetrahydropypridine- (MPTP-) induced PD mouse model. We found that pretreatment with Sal could protect against MPTP-induced increase of the time of turning downwards and climbing down to the floor. Sal also prevented MPTP-induced decrease of locomotion frequency and the increase of the immobile time. Sal provided a protection of in MPTP-induced loss of tyrosine hydroxylase-positive neurons in SNpc and the level of DA, DOPAC, and HVA in the striatum. Furthermore, Sal could increase the phosphorylation level of Akt and GSK3β, upregulate the ratio of Bcl-2/Bax, and inhibit the activation of caspase-3, caspase-6, and caspase-9. These results show that Sal prevents the loss of dopaminergic neurons and the PI3K/Akt/GSK3β pathway signaling pathway may have mediated the protection of Sal against MPTP, suggesting that Sal may be a potential candidate in neuroprotective treatment for PD.

Protection against MPP(+)-induced neurotoxicity in SH-SY5Y cells by tormentic acid via the activation of PI3-K/Akt/GSK3β pathway

The cause of Parkinson's disease (PD) could be ascribed to the progressive and selective loss of dopaminergic neurons in the substantia nigra pars compacta, and thus molecules with neuroprotective ability may have therapeutic value against PD. In the current study, the neuroprotective effects and underlying mechanisms of tormentic acid (TA), a naturally occurring triterpene extracted from medicinal plants such as Rosa rugosa and Potentilla chinensis, were evaluated in a widely used cellular PD model in which neurotoxicity was induced by MPP(+) in cultured SH-SY5Y cells. We found that TA at 1-30 μM substantially protected against MPP(+)-induced neurotoxicity, as evidenced by the increase in cell viability, decrease in lactate dehydrogenase release and the reduction in apoptotic nuclei. Moreover, TA effectively inhibited the elevated intracellular accumulation of reactive oxygen species as well as Bax/Bcl-2 ratio caused by MPP(+). Most importantly, TA markedly reversed the inhibition of protein expression of phosphorylated Akt (Ser 473) and phosphorylated GSK3β (Ser 9) caused by MPP(+). LY294002, the specific inhibitor of PI3-K, significantly abrogated the up-regulated phosphorylated Akt and phosphorylated GSK3β offered by TA, suggesting that the neuroprotection of TA was mainly dependent on the activation of PI3-K/Akt/GSK3β signaling pathway. The results taken together indicate that TA may be a potential candidate for further preclinical study aimed at the prevention and treatment of PD.

Meloxicam inhibits fipronil-induced apoptosis via modulation of the oxidative stress and inflammatory response in SH-SY5Y cells

Oxidative stress and inflammatory responses have been identified as key elements of neuronal cell apoptosis. In this study, we investigated the mechanisms by which inflammatory responses contribute to apoptosis in human neuroblastoma SH-SY5Y cells treated with fipronil (FPN). Based on the cytotoxic mechanism of FPN, we examined the neuroprotective effects of meloxicam against FPN-induced neuronal cell death. Treatment of SH-SY5Y cells with FPN induced apoptosis via activation of caspase-9 and -3, leading to nuclear condensation. In addition, FPN induced oxidative stress and increased expression of cyclooxygenase-2 (COX-2) and tumor necrosis factor-α (TNF-α) via inflammatory stimulation. Pretreatment of cells with meloxicam enhanced the viability of FPN-exposed cells through attenuation of oxidative stress and inflammatory response. FPN activated mitogen activated protein kinase (MAPK) and inhibitors of MAPK abolished FPN-induced COX-2 expression. Meloxicam also attenuated FPN-induced cell death by reducing MAPK-mediated pro-inflammatory factors. Furthermore, we observed both nuclear accumulation of p53 and enhanced levels of cytosolic p53 in a concentration-dependent manner after FPN treatment. Pretreatment of cells with meloxicam blocked the translocation of p53 from the cytosol to the nucleus. Together, these data suggest that meloxicam may exert anti-apoptotic effects against FPN-induced cytotoxicity by both attenuating oxidative stress and inhibiting the inflammatory cascade via inactivation of MAPK and p53 signaling.

RESP18 is involved in the cytotoxicity of dopaminergic neurotoxins in MN9D cells

RESP18 (Regulated endocrine-specific protein, 18 kDa) was first identified as a dopaminergic drugs-regulated intermediate pituitary transcript. RESP18 protein is a unique endoplasmic reticulum (ER) resident protein. Its functions in the brain especially in the nervous system disorders remain unknown. ER stress (ERS) has been proved to be one of the important pathogenesis of neurodegenerative diseases, including Parkinson's disease (PD). Here, we explored the association of RESP18 and ERS in cell models of PD. Dopaminergic neurotoxin 1-methyl-4-phenyl-pyridinium ion (MPP⁺), 6-hydroxydopamine (6-OHDA), and rotenone evoked dramatic MN9D cell death. The transcriptional expressions of RESP18 and two ERS markers--binding immunoglobulin protein/glucose-regulated protein 78 (BiP/GRP78) and CCAAT/enhancer-binding protein homologous protein (CHOP) manifested differential changes in MN9D cells treated with MPP⁺, 6-OHDA, and rotenone. The RESP18 protein levels increased in MPP⁺ and 6-OHDA-treated cells, but did not change in the cells treated with rotenone, while the protein levels of ER molecular chaperone heat shock protein 90 kDa beta member 1/glucose-regulated protein 94 (HSP90B1/GRP94) and BiP in the cells were up-regulated by MPP⁺ and 6-OHDA, respectively. Salubrinal, an ERS inhibitor, significantly reduced MPP⁺ and 6-OHDA-induced cell death. Moreover, ERS inducer--thapsigargin and tunicamycin, decreased the expression of RESP18, which is different from the changes of BiP, GRP94, and CHOP. Silencing RESP18 expression with Lenti-shRNA alleviated MPP⁺-induced cell death, while over-expression of RESP18 resulted in aggravated cell death induced by MPP⁺ and 6-OHDA. Taken together, our results suggest that RESP18 is involved in the cytotoxicity of dopaminergic neurotoxins.

Salidroside protects PC12 cells from MPP⁺-induced apoptosis via activation of the PI3K/Akt pathway

Oxidative stress plays an important role in the pathogenesis of Parkinson's disease (PD). Salidroside (SAL), a phenylpropanoid glycoside isolated from Rhodiola rosea L., can exert potent antioxidant properties. In this study, we investigated the protective effects, and the possible mechanism of action, of SAL against 1-methyl-4-phenylpyridinium (MPP(+))-induced cell damage in rat adrenal pheochromocytoma PC12 cells. Pretreatment of PC12 cells with SAL significantly reduced the ability of MPP(+) to induce apoptosis in a dose and time-dependent manner. SAL significantly and dose-dependently inhibited MPP(+)-induced chromatin condensation and MPP(+)-induced release of lactate dehydrogenase by PC12 cells. SAL enhanced Akt phosphorylation in PC12 cells, and the protective effects of SAL against MPP(+)-induced apoptosis were abolished by LY294002, a specific inhibitor of phosphatidylinositol 3-kinase (PI3K) phosphorylation. These findings suggest that SAL prevents MPP(+)-induced apoptosis in PC12 cells, at least in part through activation of the PI3K/Akt pathway.

Involvement of activation of PI3K/Akt pathway in the protective effects of puerarin against MPP+-induced human neuroblastoma SH-SY5Y cell death

In an attempt to clarify the protective effect of puerarin on toxin-insulted dopaminergic neuronal death, this present study was carried out by using a typical Parkinson's disease (PD) model - 1-methyl-4-phenylpyridinium iodide (MPP(+))-induced dopaminergic SH-SY5Y cellular model. Data are presented, which showed that puerarin up-regulated Akt phosphorylation in both of MPP(+)-treated and non-MPP(+)-treated cells. The presence of PI3K inhibitor LY294002 completely blocked puerarin-induced activation of Akt phosphorylation. Moreover, puerarin decreased MPP(+)-induced cell death, which was blocked by phosphoinositide 3-kinase (PI3K) inhibitor LY294002. We further demonstrated that puerarin protected against MPP(+)-induced p53 nuclear accumulation, Puma (p53-upregulated mediator of apoptosis) and Bax expression and caspase-3-dependent programmed cell death (PCD). This protection was blocked by applying a PI3K/Akt inhibitor. Additionally, it was Pifithrin-α, but not Pifithrin-μ, which blocked MPP(+)-induced Puma and Bax expression, caspase-3 activation and cell death. Collectively, these data suggest that the activation of PI3K/Akt pathway is involved in the protective effect of puerarin against MPP(+)-induced neuroblastoma SH-SY5Y cell death through inhibiting nuclear p53 accumulation and subsequently caspase-3-dependent PCD. Puerarin might be a potential therapeutic agent for PD.

Akt as a victim, villain and potential hero in Parkinson's disease pathophysiology and treatment

There are two major purposes of this essay. The first is to summarize existing evidence that irrespective of the initiating causes, neuron death and degeneration in Parkinson's disease (PD) are due to the common feature of failure of signaling by Akt, a kinase involved in neuron survival and maintenance of synaptic contacts. The second is to consider possible means by which such a failure of Akt signaling might be benignly prevented or reversed in neurons affected by PD, so as to treat PD symptoms, block disease progression, and potentially, promote recovery.