The dopaminergic system and Alzheimer's disease

Alzheimer's disease is a common neurodegenerative disorder in older adults.Despite its prevalence,its pathogenesis remains unclea r.In addition to the most widely accepted causes,which in clude excessive amyloid-beta aggregation,tau hyperphosphorylation,and deficiency of the neurotransmitter acetylcholine,numerous studies have shown that the dopaminergic system is also closely associated with the occurrence and development of this condition.Dopamine is a crucial catecholaminergic neurotransmitter in the human body.Dopamine-associated treatments,such as drugs that target dopamine receptor D and dopamine analogs,can improve cognitive function and alleviate psychiatric symptoms as well as ameliorate other clinical manifestations.Howeve r,therapeutics targeting the dopaminergic system are associated with various adverse reactions,such as addiction and exacerbation of cognitive impairment.This review summarizes the role of the dopaminergic system in the pathology of Alzheimer's disease,focusing on currently available dopamine-based therapies for this disorder and the common side effects associated with dopamine-related drugs.The aim of this review is to provide insights into the potential connections between the dopaminergic system and Alzheimer's disease,thus helping to clarify the mechanisms underlying the condition and exploring more effective therapeutic options.

The neuroprotective and regenerative potential of parkin and GDNF/Ret signaling in the midbrain dopaminergic system

Parkinson＇s disease（PD）is the second most common neurodegenerative disease after Alzheimer＇s disease.The etiology of PD is still not completely understood,but the degeneration of dopaminergic（DA）neurons in the substantia nigra pars compacta（SNpc）,loss of DA innervation of the striatum,and protein aggregates in the form of Lewy bodies and neurites are its established hallmarks. In addition to α-synuclein accumu- lation in Lewy bodies and neurites, genetic mutations in the genes encoding parkin, PINK, DJ-1, LRRK2 and other proteins are associated with the inherited form of PD. An association study linked also the receptor tyrosine kinase Ret to PD （Meka et al., 2015）. Currently there are only symptomatic treatments available for PD but no cure. Consequently much effort is being made to find neurotrophic and other factors able to stimulate SNpc DA neuron protection and regeneration.

A review of the neurotransmitter system associated with cognitive function of the cerebellum in Parkinson's disease

The dichotomized brain system is a concept that was generalized from the‘dual syndrome hypothesis’to explain the heterogeneity of cognitive impairment,in which anterior and posterior brain systems are independent but partially overlap.The dopaminergic system acts on the anterior brain and is responsible for executive function,working memory,and planning.In contrast,the cholinergic system acts on the posterior brain and is responsible for semantic fluency and visuospatial function.Evidence from dopaminergic/cholinergic imaging or functional neuroimaging has shed significant insight relating to the involvement of the cerebellum in the cognitive process of patients with Parkinson’s disease.Previous research has reported evidence that the cerebellum receives both dopaminergic and cholinergic projections.However,whether these two neurotransmitter systems are associated with cognitive function has yet to be fully elucidated.Furthermore,the precise role of the cerebellum in patients with Parkinson’s disease and cognitive impairment remains unclear.Therefore,in this review,we summarize the cerebellar dopaminergic and cholinergic projections and their relationships with cognition,as reported by previous studies,and investigated the role of the cerebellum in patients with Parkinson’s disease and cognitive impairment,as determined by functional neuroimaging.Our findings will help us to understand the role of the cerebellum in the mechanisms underlying cognitive impairment in Parkinson’s disease.

One-step cell biomanufacturing platform:porous gelatin microcarrier beads promote human embryonic stem cell-derived midbrain dopaminergic progenitor cell differentiation in vitro and survival after transplantation in vivo

Numerous studies have shown that cell replacement therapy can replenish lost cells and rebuild neural circuitry in animal models of Parkinson’s disease.Transplantation of midbrain dopaminergic progenitor cells is a promising treatment for Parkinson’s disease.However,transplanted cells can be injured by mechanical damage during handling and by changes in the transplantation niche.Here,we developed a one-step biomanufacturing platform that uses small-aperture gelatin microcarriers to produce beads carrying midbrain dopaminergic progenitor cells.These beads allow midbrain dopaminergic progenitor cell differentiation and cryopreservation without digestion,effectively maintaining axonal integrity in vitro.Importantly,midbrain dopaminergic progenitor cell bead grafts showed increased survival and only mild immunoreactivity in vivo compared with suspended midbrain dopaminergic progenitor cell grafts.Overall,our findings show that these midbrain dopaminergic progenitor cell beads enhance the effectiveness of neuronal cell transplantation.

Multiple factors to assist human-derived induced pluripotent stem cells to efficiently differentiate into midbrain dopaminergic neurons

Midbrain dopaminergic neurons play an important role in the etiology of neurodevelopmental and neurodegenerative diseases.They also represent a potential source of transplanted cells for therapeutic applications.In vitro differentiation of functional midbrain dopaminergic neurons provides an accessible platform to study midbrain neuronal dysfunction and can be used to examine obstacles to dopaminergic neuronal development.Emerging evidence and impressive advances in human induced pluripotent stem cells,with tuned neural induction and differentiation protocols,makes the production of induced pluripotent stem cell-derived dopaminergic neurons feasible.Using SB431542 and dorsomorphin dual inhibitor in an induced pluripotent stem cell-derived neural induction protocol,we obtained multiple subtypes of neurons,including 20%tyrosine hydroxylase-positive dopaminergic neurons.To obtain more dopaminergic neurons,we next added sonic hedgehog(SHH)and fibroblast growth factor 8(FGF8)on day 8 of induction.This increased the proportion of dopaminergic neurons,up to 75%tyrosine hydroxylase-positive neurons,with 15%tyrosine hydroxylase and forkhead box protein A2(FOXA2)co-expressing neurons.We further optimized the induction protocol by applying the small molecule inhibitor,CHIR99021(CHIR).This helped facilitate the generation of midbrain dopaminergic neurons,and we obtained 31-74%midbrain dopaminergic neurons based on tyrosine hydroxylase and FOXA2 staining.Thus,we have established three induction protocols for dopaminergic neurons.Based on tyrosine hydroxylase and FOXA2 immunostaining analysis,the CHIR,SHH,and FGF8 combined protocol produces a much higher proportion of midbrain dopaminergic neurons,which could be an ideal resource for tackling midbrain-related diseases.

Recent progress in the applications of presynaptic dopaminergic positron emission tomography imaging in parkinsonism

Nowadays,presynaptic dopaminergic positron emission tomography,which assesses deficiencies in dopamine synthesis,storage,and transport,is widely utilized for early diagnosis and differential diagnosis of parkinsonism.This review provides a comprehensive summary of the latest developments in the application of presynaptic dopaminergic positron emission tomography imaging in disorders that manifest parkinsonism.We conducted a thorough literature search using reputable databases such as PubMed and Web of Science.Selection criteria involved identifying peer-reviewed articles published within the last 5 years,with emphasis on their relevance to clinical applications.The findings from these studies highlight that presynaptic dopaminergic positron emission tomography has demonstrated potential not only in diagnosing and differentiating various Parkinsonian conditions but also in assessing disease severity and predicting prognosis.Moreover,when employed in conjunction with other imaging modalities and advanced analytical methods,presynaptic dopaminergic positron emission tomography has been validated as a reliable in vivo biomarker.This validation extends to screening and exploring potential neuropathological mechanisms associated with dopaminergic depletion.In summary,the insights gained from interpreting these studies are crucial for enhancing the effectiveness of preclinical investigations and clinical trials,ultimately advancing toward the goals of neuroregeneration in parkinsonian disorders.

Brain dopaminergic system changes in drug addiction:a review of positron emission tomography findings

Dopamine （DA） is considered crucial for the rewarding effects of drugs of abuse, but its role in addiction remains unclear. Positron emission tomography （PET） is the first technology used for in vivo measurement of components of the dopaminergic system in the human brain. In this article, we review the major findings from PET imaging studies on the involvement of DA in drug addiction, including presynaptic DA synthesis, vesicular monoamine transporter 2, the DA transporter, and postsynaptic DA receptors. These results have corroborated the role of DA in addiction and increased the understanding of its underlying mechanisms.

Interaction between Dopaminergic and Angiotensinergic Systems on Thirst in Adult Male Rats

Thirst, which provides the motivation to drink, is an important component of the coordinated sequence of physiological responses that maintain the volume and composition of body fluids. Special structures in the central nervous system like periventricular organs detect changes in these parameters continuously. The present study investigated the interaction between dopaminergic and angiotensinergic systems on water intake in adult male rats. Intracerebroventricular (ICV) injections were carried out in all experiments after 24 h deprivation of water intake. After the deprivation interval, the volume of consumed water was measured for 1h. Administration the angiotensinergic (AT1) receptor antagonist Losartan (45 μg/rat), and the dopaminergic antagonist Chlorpromazine (40 μg/rat) significantly decreased water intake when compared to saline-treated controls. In contrast, ICV microinjection of the dopaminergic agonist Bromocriptine (10 μg/rat) significantly increased water intake when compared to saline-treated controls. ICV injection of Bromocriptine 15min after Losartan administration was able to attenuate the inhibitory effect of Losartan on water intake, whereas administration of Chlorpromazine 15 min after Losartan was unable to change the Losartan effect. These results suggest that the dopaminergic system interactions with the angiotensinergic system to regulate water intake through circumventricular organs. Dopaminergic and angiotensinergic neurons can monitor and regulate water intake via the stimulatory and inhibitory effects on each other, respectively.

Cell reprogramming therapy for Parkinson’s disease

Parkinson’s disease is typically characterized by the progressive loss of dopaminergic neurons in the substantia nigra pars compacta.Many studies have been performed based on the supplementation of lost dopaminergic neurons to treat Parkinson’s disease.The initial strategy for cell replacement therapy used human fetal ventral midbrain and human embryonic stem cells to treat Parkinson’s disease,which could substantially alleviate the symptoms of Parkinson’s disease in clinical practice.However,ethical issues and tumor formation were limitations of its clinical application.Induced pluripotent stem cells can be acquired without sacrificing human embryos,which eliminates the huge ethical barriers of human stem cell therapy.Another widely considered neuronal regeneration strategy is to directly reprogram fibroblasts and astrocytes into neurons,without the need for intermediate proliferation states,thus avoiding issues of immune rejection and tumor formation.Both induced pluripotent stem cells and direct reprogramming of lineage cells have shown promising results in the treatment of Parkinson’s disease.However,there are also ethical concerns and the risk of tumor formation that need to be addressed.This review highlights the current application status of cell reprogramming in the treatment of Parkinson’s disease,focusing on the use of induced pluripotent stem cells in cell replacement therapy,including preclinical animal models and progress in clinical research.The review also discusses the advancements in direct reprogramming of lineage cells in the treatment of Parkinson’s disease,as well as the controversy surrounding in vivo reprogramming.These findings suggest that cell reprogramming may hold great promise as a potential strategy for treating Parkinson’s disease.

A novel mechanism of PHB2-mediated mitophagy participating in the development of Parkinson's disease

Endoplasmic reticulum stress and mitochondrial dysfunction play important roles in Parkinson s disease,but the regulato ry mechanism remains elusive.Prohibitin-2(PHB2)is a newly discove red autophagy receptor in the mitochondrial inner membrane,and its role in Parkinson’s disease remains unclear.Protein kinase R(PKR)-like endoplasmic reticulum kinase(PERK)is a factor that regulates cell fate during endoplasmic reticulum stress.Parkin is regulated by PERK and is a target of the unfolded protein response.It is unclear whether PERK regulates PHB2-mediated mitophagy thro ugh Parkin.In this study,we established a 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine(MPTP)-induced mouse model of Parkinson’s disease.We used adeno-associated virus to knockdown PHB2 expression.Our res ults showed that loss of dopaminergic neurons and motor deficits were aggravated in the MPTP-induced mouse model of Parkinson’s disease.Ove rexpression of PHB2 inhibited these abnormalities.We also established a 1-methyl-4-phenylpyridine(MPP+)-induced SH-SY5Y cell model of Parkinson’s disease.We found that ove rexpression of Parkin increased co-localization of PHB2 and microtubule-associated protein 1 light chain 3,and promoted mitophagy.In addition,MPP+regulated Parkin involvement in PHB2-mediated mitophagy through phosphorylation of PERK.These findings suggest that PHB2 participates in the development of Parkinson’s disease by intera cting with endoplasmic reticulum stress and Parkin.

Single-neuron neurodegeneration as a degenerative model for Parkinson’s disease

The positive effect of levodopa in the treatment of Parkinson’s disease,although it is limited in time and has severe side effects,has encouraged the scientific community to look for new drugs that can stop the neurodegenerative process or even regenerate the neuromelanin-containing dopaminergic nigrostriatal neurons.Successful preclinical studies with coenzyme Q10,mitoquinone,isradipine,nilotinib,TCH346,neurturin,zonisamide,deferiprone,prasinezumab,and cinpanemab prompted clinical trials.However,these failed and after more than 50 years levodopa continues to be the key drug in the treatment of the disease,despite its severe side effects after 4–6 years of chronic treatment.The lack of translated successful results obtained in preclinical investigations based on the use of neurotoxins that do not exist in the human body as new drugs for Parkinson’s disease treatment is a big problem.In our opinion,the cause of these failures lies in the experimental animal models involving neurotoxins that do not exist in the human body,such as 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine and 6-hydroxydopamine,that induce a very fast,massive and expansive neurodegenerative process,which contrasts with the extremely slow one of neuromelanin-containing dopaminergic neurons.The exceedingly slow progress of the neurodegenerative process of the nigrostriatal neurons in idiopathic Parkinson’s patients is due to(i)a degenerative model in which the neurotoxic effect of an endogenous neurotoxin affects a single neuron,(ii)a neurotoxic event that is not expansive and(iii)the fact that the neurotoxin that triggers the neurodegenerative process is produced inside the neuromelanin-containing dopaminergic neurons.The endogenous neurotoxin that fits this degenerative model involving one single neuron at a time is aminochrome,since it(i)is generated within neuromelanin-containing dopaminergic neurons,(ii)does not cause an expansive neurotoxic effect and(iii)triggers all the mechanisms involved in the neurodegenerative process of the nigrostriatal neurons in idiopathic Parkinson’s disease.In conclusion,based on the hypothesis that the neurodegenerative process of idiopathic Parkinson’s disease corresponds to a single-neuron neurodegeneration model,we must search for molecules that increase the expression of the neuroprotective enzymes DT-diaphorase and glutathione transferase M2-2.It has been observed that the activation of the Kelch-like ECH-associated protein 1/nuclear factor(erythroid-derived 2)-like 2 pathway is associated with the transcriptional activation of the DT-diaphorase and glutathione transferase genes.

Thrombin-induced microglial activation contributes to the degeneration of nigral dopaminergic neurons in vivo

Objective To evaluate the role of thrombin-activated microglia in the neurodegeneration of nigral dopaminergic neurons in the rat substantia nigra （SN） in vivo. Methods After stereotaxic thrombin injection into unilateral SN of rats, immunostaining, reverse transcription polymerase chain reaction （RT-PCR） and biochemical methods were used to observe tyrosine hydroxylase （TH） irnmunoreactive positive cells, microglia activation, nitric oxide （NO） amount and inducible nitricoxide synthase （iNOS） expression. Results （1） Selective damage to dopaminergic neurons was produced after thrombin injection, which was evidenced by loss of TH imrnunostaining in time-dependent manner; （2） Strong microglial activation was observed in the SN; （3） RT-PCR demonstrated the early and transient expression of neurotoxic factors iNOS mRNA in the SN. Immunofluorescence results found that thrombin induced expression of iNOS in microglia. The NO production in the thrombininjected rats was significantly higher than that of controls （P 〈 0.05）. Conclusion Thrombin intranigral injection can injure the dopaminergic neurons in the SN. Thrombin-induced microglia activation precedes dopaminergic neuron degeneration, which suggest that activation of microglia and release of NO may play important roles in dopaminergic neuronal death in the SN.

TREM-1 mediates interaction between substantia nigra microglia and peripheral neutrophils

Microglia-mediated neuroinflammation is considered a pathological feature of Parkinson's disease.Triggering receptor expressed on myeloid cell-1(TREM-1)can amplify the inherent immune response,and crucially,regulate inflammation.In this study,we found marked elevation of serum soluble TREM-1 in patients with Parkinson's disease that positively correlated with Parkinson's disease severity and dyskinesia.In a mouse model of 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine-induced Parkinson's disease,we found that microglial TREM-1 expression also increased in the substantia nigra.Further,TREM-1 knockout alleviated dyskinesia in a mouse model of Parkinson's disease and reduced dopaminergic neuronal injury.Meanwhile,TREM-1 knockout attenuated the neuroinflammatory response,dopaminergic neuronal injury,and neutrophil migration.Next,we established an in vitro 1-methyl-4-phenyl-pyridine-induced BV2 microglia model of Parkinson's disease and treated the cells with the TREM-1 inhibitory peptide LP17.We found that LP17 treatment reduced apoptosis of dopaminergic neurons and neutrophil migration.Moreover,inhibition of neutrophil TREM-1 activation diminished dopaminergic neuronal apoptosis induced by lipopolysaccharide.TREM-1 can activate the downstream CARD9/NF-κB proinflammatory pathway via interaction with SYK.These findings suggest that TREM-1 may play a key role in mediating the damage to dopaminergic neurons in Parkinson's disease by regulating the interaction between microglia and peripheral neutrophils.

CHCHD2 Thr61Ile mutation impairs F1F0-ATPase assembly in in vitro and in vivo models of Parkinson's disease

Mitochondrial dysfunction is a significant pathological alte ration that occurs in Parkinson's disease(PD),and the Thr61lle(T61I)mutation in coiled-coil helix coiled-coil helix domain containing 2(CHCHD2),a crucial mitochondrial protein,has been reported to cause Parkinson's disease.FIFO-ATPase participates in the synthesis of cellular adenosine triphosphate(ATP)and plays a central role in mitochondrial energy metabolism.However,the specific roles of wild-type(WT)CHCHD2 and T611-mutant CHCHD2 in regulating F1FO-ATPase activity in Parkinson's disease,as well as whether CHCHD2 or CHCHD2 T61I affects mitochondrial function through regulating F1FO-ATPase activity,remain unclea r.Therefore,in this study,we expressed WT CHCHD2 and T61l-mutant CHCHD2 in an MPP^(+)-induced SH-SY5Y cell model of PD.We found that CHCHD2 protected mitochondria from developing MPP^(+)-induced dysfunction.Under normal conditions,ove rexpression of WT CHCHD2 promoted F1FO-ATPase assembly,while T61I-mutant CHCHD2 appeared to have lost the ability to regulate F1FO-ATPase assembly.In addition,mass spectrometry and immunoprecipitation showed that there was an interaction between CHCHD2 and F1FO-ATPase.Three weeks after transfection with AAV-CHCHD2 T61I,we intraperitoneally injected 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine into mice to establish an animal model of chronic Parkinson's disease and found that exogenous expression of the mutant protein worsened the behavioral deficits and dopaminergic neurodegeneration seen in this model.These findings suggest that WT CHCHD2 can alleviate mitochondrial dysfunction in PD by maintaining F1F0-ATPase structure and function.

NOX4 exacerbates Parkinson's disease pathology by promoting neuronal ferroptosis and neuroinflammation

Parkinson's disease is primarily caused by the loss of dopaminergic neurons in the substantia nigra compacta.Ferroptosis,a novel form of regulated cell death characterized by iron accumulation and lipid peroxidation,plays a vital role in the death of dopaminergic neurons.However,the molecular mechanisms underlying ferroptosis in dopaminergic neurons have not yet been completely elucidated.NADPH oxidase 4 is related to oxidative stress,however,whether it regulates dopaminergic neuronal ferroptosis remains unknown.The aim of this study was to determine whether NADPH oxidase 4 is involved in dopaminergic neuronal ferroptosis,and if so,by what mechanism.We found that the transcriptional regulator activating transcription factor 3 increased NADPH oxidase 4 expression in dopaminergic neurons and astrocytes in an 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine-induced Parkinson's disease model.NADPH oxidase 4 inhibition improved the behavioral impairments observed in the Parkinson's disease model animals and reduced the death of dopaminergic neurons.Moreover,NADPH oxidase 4 inhibition reduced lipid peroxidation and iron accumulation in the substantia nigra of the Parkinson's disease model animals.Mechanistically,we found that NADPH oxidase 4 interacted with activated protein kinase Cαto prevent ferroptosis of dopaminergic neurons.Furthermore,by lowering the astrocytic lipocalin-2 expression,NADPH oxidase 4 inhibition reduced 1-methyl-4-phenyl-1,2,3,6 tetrahydropyridine-induced neuroinflammation.These findings demonstrate that NADPH oxidase 4 promotes ferroptosis of dopaminergic neurons and neuroinflammation,which contribute to dopaminergic neuron death,suggesting that NADPH oxidase 4 is a possible therapeutic target for Parkinson's disease.

Exercise and exerkine upregulation:Brain-derived neurotrophic factor as a potential non-pharmacological therapeutic strategy for Parkinson’s disease

Physical activity and exercise have several beneficial roles in enhancing both physiological and psychological well-being of an individual.In addition to aiding the regulation of aerobic and anaerobic metabolism,exercise can stimulate the synthesis of exerkine hormones in the circulatory system.Among several exerkines that have been investigated for their therapeutic potential,Brain-derived neurotrophic factor(BDNF)is considered the most promising candidate,especially in the management of neurodegenerative diseases.Owing to the ability of physical activity to enhance BDNF synthesis,several experimental studies conducted so far have validated this hypothesis and produced satisfactory results at the pre-clinical level.This review highlights some of the recent animal model studies that have evaluated the efficiency of exercise in enhancing BDNF synthesis and promoting neuroprotective effects.Further,this review focuses on understanding the therapeutic benefits of exercise-induced exerkine synthesis as a non-pharmacological strategy in Parkinson’s disease(PD).Regarding physical activity and exerkine induction,the neuromuscular electrical stimulation(NMES)strategy could be considered as an alternate treatment modality for patients affected with PD.

Future directions:combination of acupuncture with mesenchymal stem cells for Parkinson’s disease

Parkinson’s disease(PD)is a progressive chronic disease currently with no radical cure drugs and means due to the complex pathological mechanisms and limited regenerative capacity of neurons.Acupuncture aids in neuronal regeneration via various signaling routes like ROCK,Wnt,and Notch,safeguarding dopaminergic neurons against inflammation,oxidative stress,and cell death,which in turn enhances the progression of PD progression.Numerous research findings indicate that integrating acupuncture with mesenchymal stem cells(MSCs)transplantation is more effective than using either acupuncture or MSCs infusion alone.The combined treatment improves the survival rate of MSCs,promotes the generation of functional neural networks by stimulating the secretion of neurotrophic factors,and ultimately improves the disease microenvironment.In this review,we state the neuroprotective effects of acupuncture or MSCs treament alone in PD,then summarize the application of acupuncture combined with MSCs therapy in other diseases.Consequently,we anticipate that integrating acupuncture with MSCs transplantation may emerge as a novel and efficient approach for managing PD.This possibility needs to be verified through further basic and clinical research.

Effects of a Cocktail Supplement of Ginkgo Biloba and Acai Extract on Cognitive Symptoms of Parkinson’s Disease

Parkinson’s Disease (PD) is a neurodegenerative disorder characterized by motor and non-motor symptoms, including cognitive impairment. Current treatments often involve synthetic drugs with significant side effects and potential for dependency. This study investigates the effects of a natural supplement combination of Ginkgo Biloba and Acai Extract on cognitive symptoms in a 77-year-old male with PD. The participant underwent a three-month supplementation regimen, with cognitive function assessed using the Montreal Cognitive Assessment (MoCA) test before and after the intervention. The results indicated an improvement in cognitive scores, suggesting that the combination of Ginkgo Biloba and Acai Extract may offer a promising alternative or adjunct to conventional PD treatments. This study highlights the potential of natural supplements in managing PD symptoms and calls for further research with larger sample sizes to confirm these findings. Human data was performed in accordance with the Declaration of Helsinki by the Roxbury District IRB Board (IRB Number: IRB00011767).

Ginsenoside Rb1 protects dopaminergic neurons from inflammatory injury induced by intranigral lipopolysaccharide injection

Accumulating studies suggest that neuroinflammation characterized by microglial overactivation plays a pivotal role in the pathogenesis of Parkinson’s disease.As such,inhibition of microglial overactivation might be a promising treatment strategy to delay the onset or slow the progression of Parkinson’s disease.Ginsenoside Rbl,the most active ingredient of ginseng,reportedly exerts neuroprotective effects by suppressing inflammation in vitro.The present study aimed to evaluate the neuroprotective and anti-inflammatory effects of ginsenoside Rbl in a lipopolysaccharide-induced rat Parkinson’s disease model.Rats were divided into four groups.In the control group,sham-operated rats were intraperitoneally administered normal saline for 14 consecutive days.In the ginsenoside Rbl group,ginsenoside Rb1(20 mg/kg)was intraperitoneally injected for 14 consecutive days after sham surgery.In the lipopolysaccharide group,a single dose of lipopolysaccharide was unilaterally microinjected into the rat substantial nigra to establish the Parkinson’s disease model.Lipopolysaccharide-injected rats were treated with normal saline for 14 consecutive days.In the ginsenoside Rbl +lipopolysaccharide group,lipopolysaccharide was unilaterally microinjected into the rat substantial nigra.Subsequently,ginsenoside Rbl was intraperitoneally injected for 14 consecutive days.To investigate the therapeutic effects of ginsenoside Rbl,behavioral tests were performed on day 15 after lipopolysaccharide injection.We found that ginsenoside Rbl treatment remarkably reduced apomorphine-induced rotations in lipopolysaccharide-treated rats compared with the lipopolysaccharide group.To investigate the neurotoxicity of lipopolysaccharide and potential protective effect of ginsenoside Rbl,contents of dopamine and its metabolites in the striatum were measured by high-performance liquid chromatography.Compared with the lipopolysaccharide group,ginsenoside Rbl obviously attenuated the lipopolysaccharide-induced depletion of dopamine and its metabolites in the striatum.To further explore the neuroprotective effect of ginsenoside Rbl against lipopolysaccharide-induced neurotoxicity,immunohistochemistry and western blot assay of tyrosine hydroxylase were performed to evaluate dopaminergic neuron degeneration in the substantial nigra par compacta.The results showed that lipopolysaccharide injection caused a large loss of tyrosine hydroxylase-immunoreactive neurons in the substantia nigra and a significant decrease in overall tyrosine hydroxylase expression.However,ginsenoside Rb1 noticeably reversed these changes.To investigate whether the neuroprotective effect of ginsenoside Rbl was associated with inhibition of lipopolysaccharide-induced microglial activation,we examined expression of the microglia marker Iba-1.Our results confirmed that lipopolysaccharide injection induced a significant increase in Iba-1 expression in the substantia nigra;however,ginsenoside Rbl effectively suppressed lipopolysaccharide-induced microglial overactivation.To elucidate the inhibitory mechanism of ginsenoside Rb1,we examined expression levels of inflammatory mediators(tumor necrosis factor-a,interleukin-1β,inducible nitric oxide synthase,and cyclooxygenase 2)and phosphorylation of nuclear factor kappa B signaling-related proteins(IκB,IKK)in the substantia nigra with enzyme-linked immunosorbent and western blot assays.Our results revealed that compared with the control group,phosphorylation and expression of inflammatory mediators IκB and IKK in the substantia nigra of lipopolysaccharide group rats were significantly increased;whereas,ginsenoside Rbl obviously reduced lipopolysaccharide-induced changes on the lesioned side of the substantial nigra par compacta.These findings confirm that ginsenoside Rbl can inhibit inflammation induced by lipopolysaccharide injection into the substantia nigra and protect dopaminergic neurons,which may be related to its inhibition of the nuclear factor kappa B signaling pathway.This study was approved by the Experimental Animal Ethics Committee of Shandong University of China in April 2016(approval No.KYLL-2016-0148).

Differentiation of Mesenchymal Stem Cells Into Dopaminergic Neuron-like Cells in vitro

To explore the way to induce mesenchymal stem cells (MSCs) to differentiate into dopaminergic neurons in vitro. Methods MSCs were obtained from rat bone marrow, cultured and passaged. MSCs used in this experiment had multipotency, which was indirectly proved by being induced to differentiate into chondrocytes and adipocytes. MSCs were cultured in medium containing 0.5 mmol/L IBMX for 2 days. Then the medium was replaced with induction medium, which contained GDNF, IL-1β, mesencephalic glial-cell-conditioned medium and flash-frozen mesencephalic membrane fragments. The surface markers of the differentiated neurons, such as NSE, nestin, MAP-2a, b and TH were detected by immunocytochemistry and Western blot after MSCs were cultured in induction medium for 7 days and 15 days. Results MSCs differentiated into neural progenitors and expressed nestin after MSCs were incubated with medium containing IBMX for 2 d. After the medium was replaced with induction medium containing many inducing agents, MSCs differentiated into neuron-like cells and dopaminergic neuron-like cells and expressed NSE, MAP-2a, b and TH. The percentage of NSE-positive cells, MAP-2a, b-positive cells and TH-positive cells was 30.032±2.489%, 41.580±5.101% and 34.958±5.534%, respectively after MSCs were induced in medium containing GDNF, IL-1β, mesencephalic glial-cell-conditioned medium and flash-frozen mesencephalic membrane fragments for 15 days. Conclusion MSCs can differentiate into dopaminergic neuron-like cells and are a new cell source for the treatment of neurodegeneration diseases and have a great potential for wide application