Modulatory effects of sesamin on dopamine biosynthesis and l-DOPA-induced cytotoxicity in PC12 cells

The protective role of sesame oil against Parkinson's-like disease induced by manganese in rats

Chronic exposure to manganese (Mn) results in motor dysfunction, biochemical and pathological alterations in the brain. Oxidative stress, inflammation, and dysfunction of dopaminergic and GABAergic systems stimulate activating transcription factor-6 (ATF-6) and protein kinase RNA-like ER kinase (PERK) leading to apoptosis. This study aimed to investigate the protective effect of sesame oil (SO) against Mn-induced neurotoxicity. Rats received 25 mg/kg MnCl2 and were concomitantly treated with 2.5, 5, or 8 ml/kg of SO for 5 weeks. Mn-induced motor dysfunction was indicated by significant decreases in the time taken by rats to fall during the rotarod test and in the number of movements observed during the open field test. Also, Mn resulted in neuronal degeneration as observed by histological staining. The striatal levels of lipid peroxides and reduced glutathione (oxidative stress markers), interleukin-6 and tumor necrosis factor-α (inflammatory markers) were significantly elevated. Mn significantly reduced the levels of dopamine and Bcl-2, while GABA, PERK, ATF-6, Bax, and caspase-3 were increased. Interestingly, all SO doses, especially at 8 ml/kg, significantly improved locomotor activity, biochemical deviations and reduced neuronal degeneration. In conclusion, SO may provide potential therapeutic benefits in enhancing motor performance and promoting neuronal survival in individuals highly exposed to Mn.

Phytochemicals as Substances that Affect Astrogliosis and their Implications for the Management of Neurodegenerative Diseases

Astrocytes are a multifunctional subset of glial cells that are important in maintaining the health and function of the central nervous system (CNS). Reactive astrocytes may release inflammatory mediators, chemokines, and cytokines, as well as neurotrophic factors. There may be neuroprotective (e.g., cytokines, like IL-6 and TGF-b) and neurotoxic effects (e.g., IL-1β and TNF-a) associated with these molecules. In response to CNS pathologies, astrocytes go to a state called astrogliosis which produces diverse and heterogenic functions specific to the pathology. Astrogliosis has been linked to the progression of many neurodegenerative disorders. Phytochemicals are a large group of compounds derived from natural herbs with health benefits. This review will summarize how several phytochemicals affect neurodegenerative diseases (e.g., Alzheimer's disease, Huntington's disease, amyotrophic lateral sclerosis, and Parkinson's disease) in basic medical and clinical studies and how they might affect astrogliosis in the process.

Biodegradable Nanoparticles Loaded with Levodopa and Curcumin for Treatment of Parkinson's Disease

Background: Parkinson’s disease (PD) is the second most common age-related neurodegenerative disorder. Levodopa (L-DOPA) remains the gold-standard drug available for treating PD. Curcumin has many pharmacological activities, including antioxidant, anti-inflammatory, antimicrobial, anti-amyloid, and antitumor properties. Copolymers composed of Poly (ethylene oxide) (PEO) and biodegradable polyesters such as Poly (ε-caprolactone) (PCL) can self-assemble into nanoparticles (NPs). This study describes the development of NH₂–PEO–PCL diblock copolymer positively charged and modified by adding glutathione (GSH) on the outer surface, resulting in a synergistic delivery of L-DOPA curcumin that would be able to pass the blood–brain barrier. Methods: The NH₂–PEO–PCL NPs suspensions were prepared by using a nanoprecipitation and solvent displacement method and coated with GSH. NPs were submitted to characterization assays. In order to ensure the bioavailability, Vero and PC12 cells were treated with various concentrations of the loaded and unloaded NPs to observe cytotoxicity. Results: NPs have successfully loaded L-DOPA and curcumin and were stable after freeze-drying, indicating advancing into in vitro toxicity testing. Vero and PC12 cells that were treated up to 72 h with various concentrations of L-DOPA and curcumin-loaded NP maintained high viability percentage, indicating that the NPs are biocompatible. Conclusions: NPs consisting of NH₂–PEO–PCL were characterized as potential formulations for brain delivery of L-DOPA and curcumin. The results also indicate that the developed biodegradable nanomicelles that were blood compatible presented low cytotoxicity.

Sesamin and sesamol attenuate H2O2-induced oxidative stress on human neuronal cells via the SIRT1-SIRT3-FOXO3a signaling pathway

Background: An imbalance of free radicals and antioxidant defense systems in physiological processes can result in protein/DNA damage, inflammation, and cellular apoptosis leading to neurodegenerative disorders such as Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD). Sesamin and sesamol, compounds derived from sesame seeds and oil, have been reported to exert various pharmacological effects, especially antioxidant activity. However, their molecular mechanisms against the oxidative stress induced by exogenous hydrogen peroxide (H₂O₂) remain to be elucidated. Aim: In this study, neuroprotective effects of sesamin and sesamol on H₂O₂-induced human neuroblastoma (SH-SY5Y) cell death and possible signaling pathways in the cells were explored. Methods: MTT assay and flow cytometry were conducted to determine cell viability and apoptotic profiles of neuronal cells treated with sesamin and sesamol. Carboxy-DCFDA assay was used to measure reactive oxygen species (ROS). Moreover, Western blot analysis was performed to investigate protein profiles associated with neuroprotection. Results: Pretreatment of the cells with 1 µM of sesamin and sesamol remarkably reduced the SH-SY5Y cell death induced by 400 µM H₂O₂ as well as the intracellular ROS production. Moreover, the molecular mechanisms underlying neuroprotection of the compounds were associated with activating SIRT1-SIRT3-FOXO3a expression, inhibiting BAX (proapoptotic protein), and upregulating BCL-2 (anti-apoptotic protein). Conclusion: The findings suggest that sesamin and sesamol are compounds that potentially protect neuronal cells against oxidative stress similar to that of the resveratrol, the reference compound. These antioxidants are thus of interest for further investigation in in vivo models of neuroprotection.

Sesamin Promotes Neurite Outgrowth under Insufficient Nerve Growth Factor Condition in PC12 Cells through ERK1/2 Pathway and SIRT1 Modulation

The promotion of neurogenesis can be a promising strategy to improve and restore neuronal function in neurodegenerative diseases. Nerve growth factor (NGF) plays a key role in neurite outgrowth and synaptic formation during brain repair stage. Nowadays, there are several studies on the developing methods to enhance the endogenous NGF activity for treatment and restore the neuronal function. In this study, the potentiating effect of sesamin, a major lignan in sesame seeds (Sesamum indicum) and oil, on NGF-induced neurogenesis and its involved mechanisms were firstly reported. Sesamin effectively enhanced the PC12 neuron-like cell differentiation and neurite length under insufficient conditions of NGF. The neuronal markers including synaptophysin and growth-associated protein-43 along with the synaptic connections were significantly increased in combination treatment between sesamin and NGF. Moreover, sesamin also increased the level of phospho-ERK1/2 and SIRT1 protein, an important regulatory protein of the neurogenesis process. The neurogenesis was blocked by the specific SIRT1 inhibitor, JGB1741, suggesting that the neuritogenic effect of sesamin was associated with SIRT1 protein modulation. Taken together, the potentiating effect of sesamin on NGF-induced neurogenesis in this finding could be used for alternative treatment in neurodegenerative diseases, including Alzheimer's disease.

Sesamin prevents apoptosis and inflammation after experimental myocardial infarction by JNK and NF-κB pathways

Myocardial infarction is a devastating event, especially when reperfusion is not performed. The inflammatory response has been associated with the pathogenesis of left ventricular remodeling after myocardial infarction. This study focused on the anti-apoptotic and anti-inflammatory effects of sesamin on ligation of the left anterior descending artery in an experimental mouse model and the potential mechanism underlying the activation of JNK and NF-κB pathways. Mice with MI induced by surgical left anterior descending coronary artery ligation were treated with sesamin by gavage for 1 week. Results showed that after treatment with sesamin, MI-induced cardiac damage was alleviated significantly, indicated by the histopathological examination. The myocardial apoptosis in the border zone was dramatically reduced by sesamin, resulting from the altered expression of apoptosis factors. Moreover, treatment with sesamin also mitigated the inflammatory response, decreased expression of cytokines and the inactivation of NF-κB (nuclear factor κB) signaling. Sesamin decreased the levels of p-JNK protein, which in turn inactivated pro-apoptotic signaling events by restoring the balance between mitochondrial pro-apoptotic Bcl-2 and Bax proteins. Thus, our study suggests that sesamin could alleviate MI-induced cardiac dysfunction through decrease of myocardial apoptosis and inflammatory response.

Sesamin encouraging effects on chondrogenic differentiation of human amniotic fluid-derived mesenchymal stem cells

Worldwide, the most recognized musculoskeletal degenerative disease is osteoarthritis (OA). Sesamin, a major abundant lignan compound present in Sesamun Indicum Linn, has been described for its various pharmacological effects and health benefits. However, the promoting effects of sesamin on chondrogenic differentiation have not yet been observed. Herein, the aim of this study was to investigate the effects of sesamin on cell cytotoxicity and the potent supporting effects on chondrogenic differentiation of human amniotic fluid-derived mesenchymal stem cells (hAF-MSCs). The results indicated that sesamin was not toxic to hAF-MSCs after sesamin treatment. When treating the cells with a combination of sesamin and inducing factors, sesamin was able to up-regulate the expression level of specific genes which play an essential role during the cartilage development process, including SOX9, AGC, COL2A1, COL11A1, and COMP and also simultaneously promote the cartilage extracellular protein synthesis, aggrecan and type II collagen. Additionally, histological analysis revealed a high amount of accumulated sGAG staining inside the porous scaffold in the sesamin co-treating group. In conclusion, the results of this study have indicated that sesamin can be considered a chondrogenic inducing factor and a beneficial dietary supplement for cartilage repair.

Effects of asarinin on dopamine biosynthesis and 6-hydroxydopamine-induced cytotoxicity in PC12 cells

This study investigated the effects of asarinin on dopamine biosynthesis and 6-hydroxydopamine (6-OHDA)-induced cytotoxicity in rat adrenal pheochromocytoma (PC12) cells. Treatment with asarinin (25-50 μM) increased intracellular dopamine levels and enhanced L-DOPA-induced increases in dopamine levels. Asarinin (25 μM) induced cyclic AMP-dependent protein kinase A (PKA) signaling, leading to increased cyclic AMP-response element binding protein (CREB) and tyrosine hydroxylase (TH) phosphorylation, which in turn stimulated dopamine production. Asarinin (25 μM) also activated transient phosphorylation of extracellular signal-regulated kinase (ERK1/2) and Bad phosphorylation at Ser 112, both of which have been shown to promote cell survival. In contrast, asarinin (25 μM) inhibited sustained ERK1/2, Bax, c-Jun N-terminal kinase (JNK1/2) and p38 mitogen-activated protein kinase (p38MAPK) phosphorylation and caspase-3 activity, which were induced by 6-OHDA (100 μM). These results suggest that asarinin induces dopamine biosynthesis via activation of the PKA-CREB-TH system and protects against 6-OHDA-induced cytotoxicity by inhibiting the sustained activation of the ERK-p38MAPK-JNK1/2-caspase-3 system in PC12 cells.

Gintonin, a novel ginseng-derived lysophosphatidic acid receptor ligand, stimulates neurotransmitter release

Gintonin is a novel ginseng-derived G protein-coupled lysophosphatidic acid (LPA) receptor ligand. Gintonin elicits an intracellular calcium concentration [Ca(2+)]i transient via activation of LPA receptors and regulates calcium-dependent ion channels and receptors. [Ca(2+)]i elevation by neurotransmitters or depolarization is usually coupled to neurotransmitter release in neuronal cells. Little is known about whether gintonin-mediated [Ca(2+)]i transients are also coupled to neurotransmitter release. The PC12 cell line is derived from a pheochromocytoma of the rat adrenal medulla and is widely used as a model for catecholamine release. In the present study, we examined the effects of gintonin on dopamine release in PC12 cells. Application of gintonin to PC12 cells induced [Ca(2+)]i transients in concentration-dependent and reversible manners. However, ginsenoside Rg3, another active ingredient of ginseng, induced a lagged and irreversible [Ca(2+)]i increase. The induction of gintonin-mediated [Ca(2+)]i transients was attenuated or blocked by the LPA1/3 receptor antagonist Ki16425, a phospholipase C inhibitor, an inositol 1,4,5-triphosphate receptor antagonist, and an intracellular Ca(2+) chelator. Repeated treatment with gintonin induced homologous desensitization of [Ca(2+)]i transients. Gintonin treatment in PC12 cells increased the release of dopamine in a concentration-dependent manner. Intraperitoneal administration of gintonin to mice also increased serum dopamine concentrations. The present study shows that gintonin-mediated [Ca(2+)]i transients are coupled to dopamine release via LPA receptor activation. Finally, gintonin-mediated [Ca(2+)]i transients and dopamine release via LPA receptor activation might explain one mechanism of gintonin-mediated inter-neuronal modulation in the nervous system.

Sesamin attenuates neurotoxicity in mouse model of ischemic brain stroke

Stroke is a severe neurological disorder characterized by the abrupt loss of blood circulation into the brain resulting into wide ranging brain and behavior abnormalities. The present study was designed to evaluate molecular mechanism by which sesamin (SES) induces neuroprotection in mouse model of ischemic stroke. The results of this study demonstrate that SES treatment (30 mg/kg bwt) significantly reduced infarction volume, lipid per-oxidation, cleaved-caspase-3 activation, and increased GSH activity following MCAO in adult male mouse. SES treatment also diminished iNOS and COX-2 protein expression, and significantly restored SOD activity and protein expression level in the ischemic cortex of the MCAO animals. Furthermore, SES treatment also significantly reduced inflammatory and oxidative stress markers including Iba1, Nox-2, Cox-2, peroxynitrite compared to placebo MCAO animals. Superoxide radical production, as studied by DHE staining method, was also significantly reduced in the ischemic cortex of SES treated compared to placebo MCAO animals. Likewise, downstream effects of superoxide free radicals i.e. MAPK/ERK and P38 activation was also significantly attenuated in SES treated compared to placebo MCAO animals. In conclusion, these results suggest that SES induces significant neuroprotection, by ameliorating many signaling pathways activated/deactivated following cerebral ischemia in adult mouse.

Real-time electrochemical recording of dopamine release under optogenetic stimulation

Dopaminergic PC12 cells can synthesize and release dopamine, providing a good cellular model for investigating dopamine regulation. Optogenetic stimulation of channelrhodopsin-2 provides high spatial and temporal precision for selective stimulation as a powerful neuromodulation tool for neuroscience studies. The aim of this study is to measure dopamine release from dopaminergic PC12 cells under optogenetic stimulation using electrochemical recording of self-assembled monolayers modified microelectrode with amperometric measurement in real time. The activation of PC12 cells under various optogenetic stimulation schemes are characterized by measuring single-cell Ca²⁺ imaging. After 10 seconds of optogenetic stimulation, the evoked intracellular Ca²⁺ level and dopamine current of channelrhodopsin-2-transfected PC12 cells were 1.6- and 3.5-fold higher than those of the control cells. The optogenetic stimulation effects on Ca²⁺ influx and dopamine release were 81% and 63% inhibition by using a Ca²⁺ channel antagonist Nifedipine. The results indicate that optogenetic stimulation can evoke voltage-gated Ca²⁺ channel-dependent dopamine exocytosis from PC12 cells in a cell specific, temporally precise and dose-dependent manner. This proposed dopamine recording system can be developed to be a good cell model for dopamine regulation and drug screening in vitro, or dopaminergic cell implantation therapy in vivo using optogenetic stimulation in a precise and convenient way.

Aromatic L-amino acid decarboxylase (AADC) is crucial for brain development and motor functions

Aromatic L-amino acid decarboxylase (AADC) deficiency is a rare pediatric neuro-metabolic disease in children. Due to the lack of an animal model, its pathogenetic mechanism is poorly understood. To study the role of AADC in brain development, a zebrafish model of AADC deficiency was generated. We identified an aadc gene homolog, dopa decarboxylase (ddc), in the zebrafish genome. Whole-mount in situ hybridization analysis showed that the ddc gene is expressed in the epiphysis, locus caeruleus, diencephalic catecholaminergic clusters, and raphe nuclei of 36-h post-fertilization (hpf) zebrafish embryos. Inhibition of Ddc by AADC inhibitor NSD-1015 or anti-sense morpholino oligonucleotides (MO) reduced brain volume and body length. We observed increased brain cell apoptosis and loss of dipencephalic catecholaminergic cluster neurons in ddc morphants (ddc MO-injected embryos). Seizure-like activity was also detected in ddc morphants in a dose-dependent manner. ddc morphants had less sensitive touch response and impaired swimming activity that could be rescued by injection of ddc plasmids. In addition, eye movement was also significantly impaired in ddc morphants. Collectively, loss of Ddc appears to result in similar phenotypes as that of ADCC deficiency, thus zebrafish could be a good model for investigating pathogenetic mechanisms of AADC deficiency in children.