Coffee is one of the most widely consumed beverages worldwide. It is usually identified as a stimulant because of a high content of caffeine. However, caffeine is not the only coffee bioactive component. The coffee beverage is in fact a mixture of a number of bioactive compounds such as polyphenols, especially chlorogenic acids (in green beans) and caffeic acid (in roasted coffee beans), alkaloids (caffeine and trigonelline), and the diterpenes (cafestol and kahweol). Extensive research shows that coffee consumption appears to have beneficial effects on human health. Regular coffee intake may protect from many chronic disorders, including cardiovascular disease, type 2 diabetes, obesity, and some types of cancer. Importantly, coffee consumption seems to be also correlated with a decreased risk of developing some neurodegenerative conditions such as Alzheimer’s disease, Parkinson’s disease, and dementia. Regular coffee intake may also reduce the risk of stroke. The mechanism underlying these effects is, however, still poorly understood. This review summarizes the current knowledge on the neuroprotective potential of the main bioactive coffee components, i.e., caffeine, chlorogenic acid, caffeic acid, trigonelline, kahweol, and cafestol. Data from both in vitro and in vivo preclinical experiments, including their potential therapeutic applications, are reviewed and discussed. Epidemiological studies and clinical reports on this matter are also described. Moreover, potential molecular mechanism(s) by which coffee bioactive components may provide neuroprotection are reviewed.

Neuroprotective Effects of Coffee Bioactive Compounds: A Review.

For years, the consumption of a diet rich in fruits and vegetables has been considered healthy, increasing longevity, and decreasing morbidities. With the assistance of basic research investigating the potential mechanisms, it has become clear that the beneficial effects of plant-based foods are mainly due to the large amount of bioactive phenolic compounds contained. Indeed, substantial dietary intervention studies in humans have supported that the supplementation of polyphenols have various health-promoting effects, especially in the elderly population. In vitro examinations on the anti-aging mechanisms of polyphenols have been widely performed, using different types of natural and synthetic phenolic compounds. The aim of this review is to critically evaluate the experimental evidence demonstrating the beneficial effects of polyphenols on aging-related diseases. We highlight the potential anti-aging mechanisms of polyphenols, including antioxidant signaling, preventing cellular senescence, targeting microRNA, influencing NO bioavailability, and promoting mitochondrial function. While the trends on utilizing polyphenols in preventing aging-related disorders are getting growing attention, we suggest the exploration of the beneficial effects of the combination of multiple polyphenols or polyphenol-rich foods, as this would be more physiologically relevant to daily life.

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Dietary Anti-Aging Polyphenols and Potential Mechanisms.

Chlorogenic acid (CGA), also known as coffee tannic acid and 3-caffeoylquinic acid, is a water-soluble polyphenolic phenylacrylate compound produced by plants through the shikimic acid pathway during aerobic respiration. CGA is widely found in higher dicotyledonous plants, ferns, and many Chinese medicine plants, which enjoy the reputation of “plant gold.” We have summarized the biological activities of CGA, which are mainly shown as anti-oxidant, liver and kidney protection, anti-bacterial, anti-tumor, regulation of glucose metabolism and lipid metabolism, anti-inflammatory, protection of the nervous system, and action on blood vessels. We further determined the main applications of CGA in the food industry, including food additives, food storage, food composition modification, food packaging materials, functional food materials, and prebiotics. With a view to the theoretical improvement of CGA, biological activity mechanism, and subsequent development and utilization provide reference and scientific basis.

https://www.frontiersin.org/articles/10.3389/fnut.2022.943911/pdf

The Biological Activity Mechanism of Chlorogenic Acid and Its Applications in Food Industry: A Review

Alzheimer’s disease (AD) is the most common type of dementia leading to progressive memory loss and cognitive impairment. Considering that pharmacological treatment options for AD are few and not satisfactory, increasing attention is being paid to dietary components that may affect the development of the disease. Such a dietary component may be caffeine contained in coffee, tea or energy drinks. Although epidemiological data suggest that caffeine intake may counteract the development of cognitive impairment, results of those studies are not conclusive. The aim of the present study is to review the existing experimental studies on the efficacy of caffeine against AD and AD-related cognitive impairment, focusing on the proposed protective mechanisms of action. In conclusion, the reports of studies on experimental AD models generally supported the notion that caffeine may exert some beneficial effects in AD. However, further studies are necessary to elucidate the role of caffeine in the effects of its sources on cognition and possibly AD risk.

Potential of Caffeine in Alzheimer's Disease-A Review of Experimental Studies.

Neurodegenerative diseases, including Alzheimer's disease (AD), Parkinson's disease (PD), and Huntington's disease (HD), are characterized by the progressive degeneration of neurons. Although the etiology and pathogenesis of neurodegenerative diseases have been studied intensively, the mechanism is still in its infancy. In general, most neurodegenerative diseases share common molecular mechanisms, and multiple risks interact and promote the pathologic process of neurogenerative diseases. At present, most of the approved drugs only alleviate the clinical symptoms but fail to cure neurodegenerative diseases. Numerous studies indicate that dietary plant polyphenols are safe and exhibit potent neuroprotective effects in various neurodegenerative diseases. However, low bioavailability is the biggest obstacle for polyphenol that largely limits its adoption from evidence into clinical practice. In this review, we summarized the widely recognized mechanisms associated with neurodegenerative diseases, such as misfolded proteins, mitochondrial dysfunction, oxidative damage, and neuroinflammatory responses. In addition, we summarized the research advances about the neuroprotective effect of the most widely reported dietary plant polyphenols. Moreover, we discussed the current clinical study and application of polyphenols and the factors that result in low bioavailability, such as poor stability and low permeability across the blood-brain barrier (BBB). In the future, the improvement of absorption and stability, modification of structure and formulation, and the combination therapy will provide more opportunities from the laboratory into the clinic for polyphenols. Lastly, we hope that the present review will encourage further researches on natural dietary polyphenols in the treatment of neurodegenerative diseases.

https://downloads.hindawi.com/journals/omcl/2022/5288698.pdf

Dietary Plant Polyphenols as the Potential Drugs in Neurodegenerative Diseases: Current Evidence, Advances, and Opportunities

Purpose Chlorogenic acid (CGA), a phenolic acid isolated from fruits and vegetables, has been established to have neuroprotective properties in relation to Alzheimer's disease (AD). However, the precise mechanism by which CGA prevents cognitive deficits in AD has not been well studied. This study aimed to explore the potential molecular mechanism of CGA action using an Aβ25-35-induced SH-SY5Y neuron injury and cogxnitive deficits model in APP/PS1 mice. Methods Three-month-old male APP/PS1 double transgenic mice and a human neuroblastoma cell line (SH-SY5Y) were used to assess the effects of CGA on AD in vivo and in vitro, respectively. Cognitive function in mice was measured using a Morris water maze (MWM) test. Hematoxylin and eosin, monodansylcadaverine fluorescence, LysoTracker Red (LTR), and immunofluorescence staining were used to evaluate the morphological changes in vivo and in vitro. The protein expressions of autophagy markers (LC3B-II/LC3B-I, p62/SQSTM, beclin1 and Atg5) and lysosomal-function-related markers (cathepsin D, mTOR, p-mTOR P70S6K, p-p70s6k and TFEB) were analyzed with Western blot analyses. Results CGA treatment significantly improved spatial memory, relieved neuron damage, and inhibited autophagy in APP/PS1 mice (P<0.05). Moreover, CGA notably suppressed autophagosome production and enhanced autophagy flux in SH-SY5Y cells induced by Aβ25-35 (P<0.05). Further analysis showed that CGA markedly promoted lysosomal activity, and this was accompanied by upregulated cathepsin D protein expression, which was induced by the mTOR/TFEB signaling pathway in APP/PS1 mice and Aβ25-35-exposed SH-SY5Y cells (P<0.05). Conclusion CGA treatment restored autophagic flux in the brain and alleviated cognitive impairments in APP/PS1 mice via enhanced activation of the mTOR/TFEB signaling pathway.

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Chlorogenic Acid Alleviates Aβ 25-35 -Induced Autophagy and Cognitive Impairment via the mTOR/TFEB Signaling Pathway

Autophagy serves an important role in amyloid-β (Aβ) metabolism and τ processing and clearance in Alzheimer's disease. The progression of Aβ plaque accumulation and hyperphosphorylation of τ proteins are enhanced by oxidative stress. A hydrogen peroxide (H2O2) injury cell model was established using SH-SY5Y cells. Cells were randomly divided into normal, H2O2 and chlorogenic acid (5-caffeoylquinic acid; CGA) groups. The influence of CGA on cell viability was evaluated using a Cell Counting Kit-8 assay and cell death was assessed using Hoechst 33342 nuclear staining. Autophagy induction and fusion of autophagic vacuoles assays were performed using monodansylcadaverine staining. Additionally, SH-SY5Y cells expressing Ad-mCherry-green fluorescent protein-LC3B were established to detect autophagic flow. LysoTracker Red staining was used to evaluate lysosome function and LysoSensor™ Green staining assays were used to assess lysosomal acidification. The results demonstrated that CGA decreased the apoptosis rate, increased cell viability and improved cell morphology in H2O2-treated SH-SY5Y cells. Furthermore, CGA alleviated the accumulation of autophagic vacuoles, reduced the LC3BII/I ratio and decreased P62 levels, resulting in increased autophagic flux. Additionally, CGA upregulated lysosome acidity and increased the expression levels of cathepsin D. Importantly, these effects of CGA on H2O2-treated SH-SY5Y cells were mediated via the mTOR-transcription factor EB signaling pathway. These results indicated that CGA protected cells against H2O2-induced oxidative damage via the upregulation of autophagosomes, which promoted autophagocytic degradation and increased autophagic flux.

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Chlorogenic acid enhances autophagy by upregulating lysosomal function to protect against SH‑SY5Y cell injury induced by H 2 O 2

Ligustilide is a phenolic compound isolated from Asian plants of Umbelliferae family. This study was aimed at exploring the neuroprotective effects of Ligustilide from the perspective of endoplasmic reticulum stress (ERS) and autophagy. The Alzheimer's disease (AD) cell models were constructed by SH-SY5Y cell line, which was exposed to 20 μM Aβ25-35 . CCK-8 was used to evaluate the cell viability of Ligustilide on AD cell model. Hoechst staining and LysoTracker Red were used to test the cell apoptosis and Lysosome function, respectively. ERS in living cells were detected by Thioflavin T. The expression of autophagy-related proteins (LC3B-II/I, P62/SQSTM1, Beclin1, and Atg5), ERS marker proteins (PERK, GRP78, and CHOH), and apoptosis proteins (Bax, Bcl-2, and Caspase-12) were analyzed by Western blot analyses. Aβ25-35 could induce ERS and autophagy in a time-dependent manner in SH-SY5Y cells. We demonstrated that Ligustilide significantly decreased the rate of apoptosis, and improved the viability of cells. Simultaneously, Ligustilide effectively modulated ERS via inhibiting the over-activation of GRP78/PERK/CHOP signaling pathway. In addition, Ligustilide alleviated the accumulation of autophagy vacuoles, reduced the ratio of LC3B-II/I and the level of P62/SQSTM1. Ligustilide significantly up-regulated lysosomal acidity and the expression of Cathepsin D (CTSD). Ligustilide could rescue lysosomal function to promote autophagy flux and inhibit the over-activation of ERS. This finding may contribute to the development of new therapeutic strategies for AD.

Li-Juan Gao

Papers

Chlorogenic Acid Alleviates Aβ 25-35 -Induced Autophagy and Cognitive Impairment via the mTOR/TFEB Signaling Pathway

Chlorogenic acid enhances autophagy by upregulating lysosomal function to protect against SH‑SY5Y cell injury induced by H 2 O 2

Ligustilide alleviates neurotoxicity in SH-SY5Y cells induced by Aβ 25-35 via regulating endoplasmic reticulum stress and autophagy