Structural characterization and neuroprotective effect of a polysaccharide from Corydalis yanhusuo

The advancement of polysaccharides in disease modulation: Multifaceted regulation of programmed cell death

Programmed cell death (PCD), also known as regulatory cell death (RCD), is a process that occurs in all organisms and is closely linked to both normal physiological processes and disease states. Various signaling pathways, such as TP53, KRAS, NOTCH, hypoxia, and metabolic reprogramming, have been found to regulate RCD. Polysaccharides, which are essential natural products, have been the subject of extensive research in the fields of food, nutrition, and medicine due to their wide range of pharmacological effects. Studies have shown that polysaccharides have biological activities and the potential to target signal transduction pathways for the treatment of diseases. This paper provides a review of the mechanisms through which polysaccharides exert their therapeutic effects at different levels and explores the relationship between different types of RCD and human diseases. The aim of this review is to provide a theoretical basis for the further clinical use and application of polysaccharide bioactivities.

Corydalis yanhusuo Polysaccharides Ameliorate Chronic Stress-Induced Depression in Mice through Gut Microbiota-Derived Short-Chain Fatty Acid Activation of 5-Hydroxytryptamine Signaling

Depression, a prevalent psychiatric disorder, presents a serious health risk to humans. Increasing evidence suggested that the gut microbiota and the 5-hydroxytryptamine (5-HT) pathway both contribute significantly to depression. This research aimed to investigate how Corydalis yanhusuo polysaccharides (CYP) could potentially alleviate depression induced by chronic unpredictable mild stress in mice, as well as its underlying mechanism. The sucrose preference test, tail suspension test, and forced swimming test were employed to evaluate the behavior of mice. Enzyme-linked immunosorbent assay and PCR techniques were utilized to measure depression-related factors (dopamine [DA], 5-HT, norepinephrine [NE], brain-derived neurotrophic factor [BDNF], tryptophan hydroxylase 2 [TPH-2], 5-hydroxytryptophan [5-HTP], and tryptophan hydroxylase [TPH-1] levels). Hematoxylin and eosin staining and Nissl staining were conducted to observe histopathological changes in the hippocampus, the differences in the diversity of gut flora between groups were analyzed using 16S rRNA sequencing, and gas chromatography-mass spectrometry metabolomics was utilized to evaluate short-chain fatty acid (SCFA) concentrations. The findings indicated that CYP treatment increased the sucrose preference index, decreased the immobility time, and improved neuropathological injury. In depressed mice, CYP improved the dysregulation of the gut microbiota, and increased the SCFA levels. In addition, CYP enhanced the DA, 5-HT, NE, BDNF, and TPH-2 levels in the brain and the expression of 5-HTP and TPH-1 in the colon, while SCFAs were positively correlated with these levels. In summary, our study suggested that CYP may mitigate depression by ameliorating gut microbiota dysregulation, promoting the generation of SCFAs, and activation of 5-HT signaling expression.

Polysaccharides: potential bioactive macromolecules for Alzheimer's disease

Alzheimer's disease (AD) is one of the leading causes of death and disability. AD is a devastating disease that has caused an overwhelming burden. However, no disease-modified treatment was discovered. The approval of sodium oligomannate (GV-971) in mild-moderate AD patients has attracted great attention to investigate the role of saccharides in AD. Therefore, summarizing and explaining the role of saccharides in AD is urgent and promising. Recent studies showed that polysaccharides (PSs) potentially benefit AD in vitro and in vivo. PSs could alleviate the pathological damage and improve cognitive symptoms via (1) antagonizing the toxicity of abnormal amyloid-beta and tau proteins; (2) attenuating oxidative stress and proinflammation; (3) rebuilding neuroplasticity. PSs exhibit one-multiple pathological hits of AD. However, a thorough chemical investigation is needed for further study.

BACE-1 Inhibitors Targeting Alzheimer's Disease

The accumulation of amyloid-β (Aβ) is the main event related to Alzheimer's disease (AD) progression. Over the years, several disease-modulating approaches have been reported, but without clinical success. The amyloid cascade hypothesis evolved and proposed essential targets such as tau protein aggregation and modulation of β-secretase (β-site amyloid precursor protein cleaving enzyme 1 - BACE-1) and γ-secretase proteases. BACE-1 cuts the amyloid precursor protein (APP) to release the C99 fragment, giving rise to several Aβ peptide species during the subsequent γ-secretase cleavage. In this way, BACE-1 has emerged as a clinically validated and attractive target in medicinal chemistry, as it plays a crucial role in the rate of Aβ generation. In this review, we report the main results of candidates in clinical trials such as E2609, MK8931, and AZD-3293, in addition to highlighting the pharmacokinetic and pharmacodynamic-related effects of the inhibitors already reported. The current status of developing new peptidomimetic, non-peptidomimetic, naturally occurring, and other class inhibitors are demonstrated, considering their main limitations and lessons learned. The goal is to provide a broad and complete approach to the subject, exploring new chemical classes and perspectives.

Neuroprotective effects of naturally sourced bioactive polysaccharides: an update

Polysaccharides are macromolecular complexes that have various biological activities. In vivo and in vitro studies have shown that polysaccharides play neuroprotective roles through multiple mechanisms; consequently, they have potential in the prevention and treatment of neurodegenerative diseases. This paper summarizes related research published during 2015-2020 and reviews advances in the understanding of the neuroprotective effects of bioactive polysaccharides. This review focuses on 15 bioactive polysaccharides from plants and fungi that have neuroprotective properties against oxidative stress, apoptosis, neuroinflammation, and excitatory amino acid toxicity mainly through the regulation of nuclear factor kappa-B, phosphatidylinositol-3-kinase/protein kinase B, mitogen-activated protein kinase, nuclear factor-E2-related factor 2/ hemeoxygenase-1, c-jun N-terminal kinase, protein kinase B-mammalian target of rapamycin, and reactive oxygen species-nucleotide-binding oligomerization domain, leucine-rich repeat and pyrin domain-containing 3 signaling pathways. Natural bioactive polysaccharides have potential in the prevention and treatment of neurodegenerative diseases because of their advantageous characteristics, including multi-targeting, low toxicity, and synergistic effects. However, most of the recent related research has focused on cell and animal models. Future randomized clinical trials involving large sample sizes are needed to validate the therapeutic benefits of these neuroprotective polysaccharides in patients having neurodegenerative diseases.

Natural Polysaccharides as Preventive and Therapeutic Horizon for Neurodegenerative Diseases

Neurodegenerative diseases are a serious and widespread global public health burden amongst aging populations. The total estimated worldwide global cost of dementia was US$818 billion in 2015 and has been projected to rise to 2 trillion US$ by 2030. While advances have been made to understand different neurodegenerative disease mechanisms, effective therapeutic strategies do not generally exist. Several drugs have been proposed in the last two decades for the treatment of different types of neurodegenerative diseases, with little therapeutic benefit, and often with severe adverse and side effects. Thus, the search for novel drugs with higher efficacy and fewer drawbacks is an ongoing challenge in the treatment of neurodegenerative disease. Several natural compounds including polysaccharides have demonstrated neuroprotective and even therapeutic effects. Natural polysaccharides are widely distributed in plants, animals, algae, bacterial and fungal species, and have received considerable attention for their wide-ranging bioactivity, including their antioxidant, anti-neuroinflammatory, anticholinesterase and anti-amyloidogenic effects. In this review, we summarize different mechanisms involved in neurodegenerative diseases and the neuroprotective effects of natural polysaccharides, highlighting their potential role in the prevention and therapy of neurodegenerative disease.

A novel pectin from Polygala tenuifolia blocks Aβ42 aggregation and production by enhancing insulin-degradation enzyme and neprilysin

More and more evidences show that pectin polysaccharide may have impact on Aβ_42, one important molecule implicated in Alzhemer's disease pathology. We speculate special structural motif of pectin might have better bioactivity on Aβ₄₂. To address this hypothesis, we reported structure and impact of a novel pectin RP02-1 with the molecular weight of 116.0 kDa from roots of Polygala tenuifolia on Aβ₄₂ aggregation and production and the underlying mechanism. Its structure is characterized as a backbone of alternate 1, 2, 4-linked α-Rhap and 1, 4-linked α-GalpA, with branches of terminal (T) -, 1, 3-,1, 4-, 1, 6- and 1, 3, 6-linked β-Galp, T-, 1, 5- and 1, 3, 5-linked α-Araf substituted at C-4 of 1, 2, 4-linked α-Rhap. Bioactivity study shows that this pectin may significantly block the aggregation of Aβ₄₂. We further show that RP02-1 suppresses Aβ₄₂ production with no apparent cytotoxicity in both CHO/APPBACE1 and HEK293-APPsw cells. Mechanism study demonstrates that RP02-1 may enhance the expression of insulin-degradation enzyme (IDE) and neprilysin (NEP), which are the main enzymes involved in Aβ degradation. These results suggest that RP02-1 may be a candidate leading compound for anti-Alzheimer's disease new drug development by attenuating Aβ₄₂ production and inhibiting Aβ₄₂ aggregation.