Beneficial effects of n-3 polyunsaturated fatty acids administration in a partial lesion model of Parkinson's disease: The role of glia and NRf2 regulation

Nutraceuticals: An integrative approach to starve Parkinson's disease

The therapeutic approach of multifactorial complex diseases is always a challenge; Parkinson's disease (PD) is a heterogeneous neurodegenerative disorder triggered by genetic and environmental factors, contributing to its etiology. Indeed, several pathogenic mechanisms lead to selective dopaminergic neuronal injury, including oxidative stress, mitochondrial dysfunction, alteration of endoplasmic reticulum-to-Golgi protein trafficking, excitotoxicity, and neuroinflammation. Current treatment approaches include mainly dopamine replacement therapy or optimizing dopaminergic transmission; however, these strategies that do not counteract the pathogenic mechanisms underlying PD symptoms and often are less effective over time. Recently, there has been growing interest in the therapeutic use of nutraceuticals, that could represent an integrative approach to the pharmacological standard therapy and specifically affect one or more pathogenic pathways. The intake of nutraceuticals or nutritional modifications are generally safe and can be combined with current common drug therapy in most cases to improve the patient's quality of life and/or mitigate PD symptoms. The current review focuses on several key nutritional compounds and dietary modifications that are effective on several pathogenic pathways involved in PD onset and progression, and further highlights the rationale behind their potential use for the prevention and treatment of PD.

Gender-Specific Beneficial Effects of Docosahexaenoic Acid Dietary Supplementation in G93A-SOD1 Amyotrophic Lateral Sclerosis Mice

Docosahexaenoic acid (DHA) is an essential fatty acid modulating key nervous system functions, including neuroinflammation, and regulation of pre- and postsynaptic membrane formation. DHA concentration decreases in the lumbar spinal cord (LSC) of amyotrophic lateral sclerosis (ALS) patients and murine preclinical models. Using a dietary supplementation, we increased DHA levels (2% mean increase, p < 0.01) in the LSC of the familial ALS murine model B6SJL-Tg(SOD1*G93A)1Gur/J. This DHA-enriched diet significantly increases male mouse survival by 7% (average 10 days over 130 days of life expectancy), and delays motor dysfunction (based on stride length) and transgene-associated weight loss (p < 0.01). DHA supplementation led to an increased anti-inflammatory fatty acid profile (ca 30%, p < 0.01) and a lower concentration of circulating proinflammatory cytokine TNF-α (p < 0.001 in males). Furthermore, although DHA-treated mice did not exhibit generally decreased protein oxidative markers (glutamic and aminoadipic semialdehydes, carboxyethyllysine, carboxymethyllysine, and malondialdehydelysine), dietary intake of DHA reduced immunoreactivity towards DNA oxidative damage markers (8-oxo-dG) in the LSC. In vitro we demonstrate that DHA and α-tocopherol addition to a model of motor neuron demise (neonatal rat organotypic spinal cord model under chronic excitotoxicity) also preserves motor neuron number, in comparison with untreated spinal cords. Also, beneficial effects on cell viability were evidenced for the motor neuron cell line NSC-34 in front of H2O2 insult (p < 0.001). Globally we show a sex-specific benefit of dietary DHA supplementation in the G93A ALS mouse model, compared with mice fed an isocaloric control or a n-3-depleted diet. These changes were associated with an increased DHA concentration in the LSC and were compatible with in vitro results showing DHA neuroprotective properties. These results suggest the need for further study on the interaction of gender-influenced biological parameters and DHA in ALS pathogenesis.

Trans-10-hydroxy-2-decenoic acid protects against LPS-induced neuroinflammation through FOXO1-mediated activation of autophagy

PURPOSE

Neuroinflammation is thought to be associated with the pathogenesis of a series of neurodegenerative diseases. We have previously reported that royal jelly (RJ) has an anti-inflammatory effect on microglial BV-2 cells. However, components contributing to the effect of RJ were largely unexplored. The aim of this study was to assess whether trans-10-hydroxy-2-decenoic acid (10-HDA), the exclusive fatty acid in RJ, can alleviate neuroinflammation and to further explore the underlying mechanisms.

METHODS

Immunohistochemistry staining, ELISA, qRT-PCR and Western blot were used to assess the effect of 10-HDA on LPS-induced neuroinflammation both in vivo and in vitro. To determine the extent of inflammatory changes after 10-HDA treatment, RNAseq transcriptomic analysis was conducted.

RESULTS

10-HDA pretreatment significantly reduced the production of pro-inflammatory mediators in LPS-treated C57BL/6J mice and microglial BV-2 cells. 10-HDA inhibited the activation of the TNF-α/NF-κB axis and NLRP3 inflammasome-IL-1β pathway, which may be the anti-neuroinflammatory mechanism of 10-HDA. We also demonstrated that 10-HDA triggered cell autophagy, as evidenced by elevated levels of microtubule-associated protein 1 light chain 3-II (LC3-II) and decreased expression of SQSTM1. More importantly, 10-HDA increased the transcriptional activity of FOXO1 by increasing FOXO1 nuclear localization. Inhibition of FOXO1 and autophagy using chemical inhibitors markedly blunted the effect of 10-HDA on the TNF-α pathway and NLRP3 inflammasome-IL-1β pathway, indicating that 10-HDA alleviates neuroinflammation in BV-2 cells by modulating FOXO1-mediated autophagy.

CONCLUSIONS

10-HDA may be a promising agent for various neuroinflammation-associated diseases.

Neuroprotective effects of protocatechuic aldehyde through PLK2/p-GSK3β/Nrf2 signaling pathway in both in vivo and in vitro models of Parkinson's disease

Mitochondrial dysfunction and oxidative damage are closely related to the pathogenesis of Parkinson's disease (PD). The pharmacological mechanism of protocatechuic aldehyde (PCA) for PD treatment have retained unclear. The purposes of the present study were to clarify the neuroprotective effects of post-treatment of PCA for PD treatment by mitigating mitochondrial dysfunction and oxidative damage, and to further determine whether its effects were mediated by the polo-like kinase 2/phosphorylated glycogen synthase kinase 3 β/nuclear factor erythroid-2-related factor 2 (PLK2/p-GSK3β/Nrf2) pathways. We found that PCA improved 1-methyl-4-phenyl-1, 2, 3, 6-tetrahydropyridine (MPTP)-induced behavioral deficits and dopaminergic cell loss. Moreover, PCA increased the expressions of PLK2, p-GSK3β and Nrf2, following the decrease of α-synuclein (α-Syn) in MPTP-intoxicated mice. Cell viability was increased and the apoptosis rate was reduced by PCA in 1-methyl-4-phenylpyridinium iodide (MPP⁺)-incubated cells. Mitochondrial membrane potential (MMP), mitochondrial complex I activity and reactive oxygen species (ROS) levels in MPP⁺-incubated cells were also ameliorated by treatment with PCA. The neuroprotective effects of PCA were abolished by inhibition or knockdown of PLK2, whereas overexpression of PLK2 strengthened the protection of PCA. Furthermore, GSK3β and Nrf2 were involved in PCA-induced protection. These results indicated that PCA has therapeutic effects on PD by the PLK2/p-GSK3β/Nrf2 pathway.

Visualizing Dynamic Performance of Lipid Droplets in a Parkinson's Disease Model via a Smart Photostable Aggregation-Induced Emission Probe

Parkinson’s disease (PD) is a complex neurodegenerative disease affected by diverse factors, and lipid droplets (LDs) are increasingly recognized as major players in PD because of their relevance to neuron activity. However, long-term dynamic changes of LDs and their relative activity remain unclear. Here, an aggregation-induced emission (AIE) probe named 2-DPAN was prepared and employed to visualize dynamic processes of LDs in a 6-hydroxydopamine model of PD for the first time, and LDs' accumulation-peak/plateau-decrease were confirmed. We further found a close relationship between LDs and variation in mitochondrial activity. Strikingly, the progression of cell death was accelerated by lipase, whereas pre-stimulation of LDs by unsaturated fatty acid-oleic acid decreased the death process by inhibiting excessive reactive oxygen species (ROS) and fatty acid production, thereby protecting mitochondria. The utilization of 2-DPAN demonstrates the importance of LDs in neuronal homeostasis, and effective tuning of LDs may prevent or inhibit PD progression.

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2-DPAN monitors the dynamic changes of Lipid droplets (LDs) in Parkinson disease

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LDs' dynamic change process including three phases, accumulation-plateau-decrease

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LDs' change trend was highly correlated with mitochondrial disruption

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Efficient tuning of LDs could slow the PD progress

Omega-3 Docosahexaenoic Acid Is a Mediator of Fate-Decision of Adult Neural Stem Cells

The mammalian brain is enriched with lipids that serve as energy catalyzers or secondary messengers of essential signaling pathways. Docosahexaenoic acid (DHA) is an omega-3 fatty acid synthesized de novo at low levels in humans, an endogenous supply from its precursors, and is mainly incorporated from nutrition, an exogeneous supply. Decreased levels of DHA have been reported in the brains of patients with neurodegenerative diseases. Preventing this decrease or supplementing the brain with DHA has been considered as a therapy for the DHA brain deficiency that could be linked with neuronal death or neurodegeneration. The mammalian brain has, however, a mechanism of compensation for loss of neurons in the brain: neurogenesis, the birth of neurons from neural stem cells. In adulthood, neurogenesis is still present, although at a slower rate and with low efficiency, where most of the newly born neurons die. Neural stem/progenitor cells (NSPCs) have been shown to require lipids for proper metabolism for proliferation maintenance and neurogenesis induction. Recent studies have focused on the effects of these essential lipids on the neurobiology of NSPCs. This review aimed to introduce the possible use of DHA to impact NSPC fate-decision as a therapy for neurodegenerative diseases.

Activation of microglia synergistically enhances neurodegeneration caused by MPP+ in human SH-SY5Y cells

While MPP⁺ may not directly activate microglia, the initial neuronal damage inflicted by the toxin may trigger microglia, possibly leading to synergistic pro-apoptotic interaction between neuro-inflammation and toxin-induced neurotoxicity, which may further aggravate neurodegeneration. However, what molecular targets are synergistically up or downregulated during this interaction is not well understood. Here, we addressed this by co-culturing fully differentiated human SH-SY5Y cells treated with parkinsonian toxin 1-Methyl-4-phenylpyridinium (MPP⁺), with endotoxin-activated microglial cell line EOC 20 to determine how this interaction affects pro-apoptotic (p38, JNK, and bax:bcl2 ratios) and pro-survival (NF-κB, MEK1) signaling at both mRNA and protein levels. Concurrent MPP⁺ and endotoxin-treatment aggravated a decrease in SH-SY5Y cell viability and caused strong synergistic increases in the bax:bcl2 ratio, but also NF-κB and JNK signaling. These effects were attenuated by microglia inhibitor minocycline. Altogether, these data provide further molecular insights into the important role or even conditional requirement of microglia activation in the progressive neurodegenerative nature of PD.

The Role of Lipids in Parkinson's Disease

Parkinson’s disease (PD) is a neurodegenerative disease characterized by a progressive loss of dopaminergic neurons from the nigrostriatal pathway, formation of Lewy bodies, and microgliosis. During the past decades multiple cellular pathways have been associated with PD pathology (i.e., oxidative stress, endosomal-lysosomal dysfunction, endoplasmic reticulum stress, and immune response), yet disease-modifying treatments are not available. We have recently used genetic data from familial and sporadic cases in an unbiased approach to build a molecular landscape for PD, revealing lipids as central players in this disease. Here we extensively review the current knowledge concerning the involvement of various subclasses of fatty acyls, glycerolipids, glycerophospholipids, sphingolipids, sterols, and lipoproteins in PD pathogenesis. Our review corroborates a central role for most lipid classes, but the available information is fragmented, not always reproducible, and sometimes differs by sex, age or PD etiology of the patients. This hinders drawing firm conclusions about causal or associative effects of dietary lipids or defects in specific steps of lipid metabolism in PD. Future technological advances in lipidomics and additional systematic studies on lipid species from PD patient material may improve this situation and lead to a better appreciation of the significance of lipids for this devastating disease.