Triptolide induces apoptosis and cytoprotective autophagy by ROS accumulation via directly targeting peroxiredoxin 2 in gastric cancer cells.

Triptolide, a natural bioactive compound derived from herbal medicine Tripterygium wilfordii, has multiple biological activities including anti-cancer effect, which is being tested in clinical trials for treating cancers. However, the exact mechanism by which Triptolide exerts its cytotoxic effects, particularly its specific protein targets, remains unclear. Here, we show that Triptolide effectively induces cytotoxicity in gastric cancer cells by increasing reactive oxygen species (ROS) levels. Further investigations reveal that ROS accumulation contributes to the induction of Endoplasmic Reticulum (ER) stress, and subsequently autophagy induction in response to Triptolide. Meanwhile, this autophagy is cytoprotective. Interestingly, through activity-based protein profiling (ABPP) approach, we identify peroxiredoxins-2 (PRDX2), a component of the key enzyme systems that act in the defense against oxidative stress and protect cells against hydroperoxides, as direct binding target of Triptolide. By covalently binding to PRDX2 to inhibit its antioxidant activity, Triptolide increases ROS levels. Moreover, overexpression of PRDX2 inhibits and knockdown of the expression of PRDX2 increases Triptolide-induced apoptosis. Collectively, these results indicate PRDX2 as a direct target of Triptolides for inducing apoptosis. Our results not only provide novel insight into the underlying mechanisms of Triptolide-induced cytotoxic effects, but also indicate PRDX2 as a promising potential therapeutic target for developing anti-gastric cancer agents.

Celastrol Downmodulates Alpha-Synuclein-Specific T Cell Responses by Mediating Antigen Trafficking in Dendritic Cells.

Parkinson's Disease (PD) is a neurodegenerative disease that affects the elderly. It is associated with motor dysfunction due to the accumulation of misfolded or aggregated fibrillar alpha-synuclein (α-syn) in the mid-brain. Current treatments are mainly focused on relieving the symptoms but are accompanied by side effects and are limited in halting disease progression. Increasing evidence points to peripheral immune cells underlying disease development, especially T cells contributing to α-syn-related neuroinflammation in PD. The onset of these cells is likely mediated by dendritic cells (DCs), whose role in α-syn-specific responses remain less studied. Moreover, Traditional Chinese medicine (TCM)-derived compounds that are candidates to treat PD may alleviate DC-T cell-mediated immune responses. Therefore, our study focused on the role of DC in response to fibrillar α-syn and subsequent induction of antigen-specific T cell responses, and the effect of TCM Curcumin-analog C1 and Tripterygium wilfordii Hook F-derived Celastrol. We found that although fibrillar α-syn did not induce significant inflammatory or T cell-mediating cytokines, robust pro-inflammatory T cell responses were found by co-culturing fibrillar α-syn-pulsed DCs with α-syn-specific CD4+ T cells. Celastrol, but not C1, reduced the onset of pro-inflammatory T cell differentiation, through promoting interaction of endosomal, amphisomal, and autophagic vesicles with fibrillar α-syn, which likely lead to its degradation and less antigen peptides available for presentation and T cell recognition. In conclusion, regulating the intracellular trafficking/processing of α-syn by DCs can be a potential approach to control the progression of PD, in which Celastrol is a potential candidate to accomplish this.

A natural product solution to aging and aging-associated diseases.

Aging is a natural biological progress accompanied by the gradual decline in physiological functions, manifested by its close association with an increased incidence of human diseases and higher vulnerability to death. Those diseases include neurological disorders, cardiovascular diseases, diabetes, and cancer, many of which are currently without effective cures. Even though aging is inevitable, there are still interventions that can be developed to prevent/delay the onset and progression of those aging-associated diseases and extend healthspan and/or lifespan. Here, we review decades of research that reveals the molecular pathways underlying aging and forms the biochemical basis for anti-aging drug development. Importantly, due to the vast chemical space of natural products and the rich history of herb medicines in treating human diseases documented in different cultures, natural products have played essential roles in aging research. Using several of the most promising natural products and their derivatives as examples, we discuss how natural products serve as an inspiration resource that helped the identification of key components/pathways underlying aging, their mechanisms of action inside the cell, and the functional scaffolds or targeting mechanisms that can be learned from natural products for drug engineering and optimization. We argue that natural products might eventually provide a solution to aging and aging-associated diseases.

NeuroDefend, a novel Chinese medicine, attenuates amyloid-ß and tau pathology in experimental Alzheimer's disease models.

Alzheimer's disease (AD) is the most common age-related neurodegenerative disorder. Amyloid-ß (Aß) and hyper-phosphorylated tau accumulation are accountable for the progressive neuronal loss and cognitive impairments usually observed in AD. Currently, medications for AD offer moderate symptomatic relief but fail to cure the disease; hence development of effective and safe drugs is urgently needed for AD treatment. In this study, we investigated a Chinese medicine (CM) formulation named NeuroDefend (ND), for reducing amyloid ß (Aß) and tau pathology in transgenic AD mice models. Regular oral administration of ND improved cognitive function and memory in 3XTg-AD and 5XFAD mice. In addition, ND reduced beta-amyloid precursor protein (APP), APP C-terminal fragments (CTF-ß/α), Aß and 4G8 positive Aß burden in 3XTg-AD and 5XFAD mice. Furthermore, ND efficiently reduced the levels of insoluble phospho-tau protein aggregates and AT8 positive phospho tau neuron load in 3XTg-AD mice. Hence, ND could be a promising candidate for the treatment of AD in humans.

A small molecule transcription factor EB activator ameliorates beta-amyloid precursor protein and Tau pathology in Alzheimer's disease models.

Accumulating studies have suggested that targeting transcription factor EB (TFEB), an essential regulator of autophagy-lysosomal pathway (ALP), is promising for the treatment of neurodegenerative disorders, including Alzheimer's disease (AD). However, potent and specific small molecule TFEB activators are not available at present. Previously, we identified a novel TFEB activator named curcumin analog C1 which directly binds to and activates TFEB. In this study, we systematically investigated the efficacy of curcumin analog C1 in three AD animal models that represent beta-amyloid precursor protein (APP) pathology (5xFAD mice), tauopathy (P301S mice) and the APP/Tau combined pathology (3xTg-AD mice). We found that C1 efficiently activated TFEB, enhanced autophagy and lysosomal activity, and reduced APP, APP C-terminal fragments (CTF-ß/α), ß-amyloid peptides and Tau aggregates in these models accompanied by improved synaptic and cognitive function. Knockdown of TFEB and inhibition of lysosomal activity significantly inhibited the effects of C1 on APP and Tau degradation in vitro. In summary, curcumin analog C1 is a potent TFEB activator with promise for the prevention or treatment of AD.

A modified formulation of Huanglian-Jie-Du-Tang reduces memory impairments and ß-amyloid plaques in a triple transgenic mouse model of Alzheimer's disease.

Alzheimer's disease (AD) is a degenerative disorder typified by progressive deterioration of memory and the appearance of ß-amyloid peptide (Aß)-rich senile plaques. Recently we have identified a novel function of a patented formulation of modified Huanglian-Jie-Tu-Tang (HLJDT-M), a Chinese herbal medicine, in treating AD in in vitro studies (US patent No. 9,375,457). HLJDT-M is a formulation composed of Rhizoma Coptitis, Cortex Phellodendri and Fructus Gardeniae without Radix Scutellariae. Here, we assessed the efficacy of HLJDT-M on a triple transgenic mouse model of AD (3XTg-AD). Oral administration of HLJDT-M ameliorated the cognitive dysfunction of 3XTg-AD mice and lessened the plaque burden. In addition, biochemical assays revealed a significant decrease in levels of detergent-soluble and acid-soluble Aß via decreasing the levels of full length amyloid-ß precursor protein (FL-APP) and C-terminal fragments of APP (CTFs) in brain lysates of HLJDT-M-treated mice. HLJDT-M treatment also significantly reduced the levels of FL-APP and CTFs in N2a/SweAPP cells. In contrast, treatment using the classical formula HLJDT did not reduce the memory impairment of 3XTg-AD mice and, rather, increased the Aß/Fl-APP/CTFs in both animal and cell culture studies. Altogether, our study indicates that HLJDT-M is a promising herbal formulation to prevent and/or cure AD.

Neuroprotective Natural Products for the Treatment of Parkinson's Disease by Targeting the Autophagy-Lysosome Pathway: A Systematic Review.

The autophagy-lysosome pathway (ALP) is a primary means by which damaged organelles and long-lived proteins are removed from cells and their components recycled. Impairment of the ALP has been found to be linked to the pathogenesis of Parkinson's disease (PD), a chronic neurodegenerative disorder characterized by the accumulation of protein aggregates and loss of dopaminergic neurons in the midbrain. In recent years, some active compounds derived from plants have been found to regulate the ALP and to exert neuroprotective effects in experimental models of PD, raising the possibility that autophagy enhancement may be an effective therapeutic strategy in PD treatment. In this review, we summarize recent findings of natural products that enhance ALP and thereby protect against PD. Research articles were retrieved from PubMed using relevant keywords in combination. Papers related to the topic were identified, and then the reliability of the experiments was assessed in terms of methodology. The results suggest that targeting the ALP with natural products is a promising strategy for PD treatment. However, risk of bias exists in some studies due to the defective methodology. Rigorous experimental design following the guidelines of autophagy assays, molecular target identification and in vivo efficacy evaluation is critical for the development of ALP enhancers for PD treatment in future studies. Copyright © 2017 John Wiley & Sons, Ltd.

Neurogenic Traditional Chinese Medicine as a Promising Strategy for the Treatment of Alzheimer's Disease.

Hippocampal neurogenesis plays a critical role in the formation of new neurons during learning and memory development. Attenuation of neurogenesis in the brain is one of the primary causes of dementia in Alzheimer's disease (AD), and, conversely, modulating the process of hippocampal neurogenesis benefit patients with AD. Traditional Chinese medicine (TCM), particularly herbal medicine, has been in use for thousands of years in Asia and many regions of the world for the treatment of cancer, cardiovascular diseases and neurodegenerative diseases. In this review, we summarize the role of neurotrophic factors, signal transducing factors, epigenetic modulators and neurotransmitters in neurogenesis, and we also discuss the functions of several Chinese herbs and their active molecules in activating multiple pathways involved in neurogenesis. TCM herbs target pathways such as Notch, Wnt, Sonic Hedgehog and receptor tyrosine kinase pathway, leading to activation of a signaling cascade that ultimately enhances the transcription of several important genes necessary for neurogenesis. Given these pathway activating effects, the use of TCM herbs could be an effective therapeutic strategy for the treatment of AD.

N-Propargyl Caffeate Amide (PACA) Potentiates Nerve Growth Factor (NGF)-Induced Neurite Outgrowth and Attenuates 6-Hydroxydopamine (6-OHDA)-Induced Toxicity by Activating the Nrf2/HO-1 Pathway.

Insufficient production of neurotrophic factors is implicated in the pathogenesis of various neurodegenerative disorders. The aim of the present study was to evaluate the potential of N-propargyl caffeate amide (PACA) to enhance nerve growth factor (NGF)-induced neurite outgrowth and the underlying mechanisms. We discovered that PACA not only potentiated NGF-induced neurite outgrowth but also attenuated 6-hydroxydopamine (6-OHDA) neurotoxicity in dopaminergic PC12 cells and primary rat midbrain neurons. To identify the PACA-binding proteins, we introduced a biotin tag to the covalent PACA-protein adducts via "click chemistry" alkyne-azido cycloaddition. As a result, kelch-like ECH-associated protein 1 (Keap1) was isolated as the predominant protein from PACA treated PC12 cells. We demonstrated that the formation of PACA-Keap1 conjugates induced the nuclear translocation of transcription factor Nrf2 and the expression of antioxidant heme oxygenase-1 (HO-1). Importantly, specific HO-1 inhibitor SnPP diminished the neuroprotective and neuritogenic activities of PACA. Moreover, PACA attenuated 6-OHDA-induced production of neurotoxic reactive oxygen species and reactive nitrogen species. PACA also preserved mitochondrial membrane integrity and enhanced the cellular resistance against 6-OHDA neurotoxicity. These results suggest that PACA may exhibit neuroprotective and neuritogenic activities via activating the Nrf2/HO-1 antioxidant pathway.

Bioactivity-guided fractionation identifies amygdalin as a potent neurotrophic agent from herbal medicine Semen Persicae extract.

Herbal medicine Semen Persicae is widely used to treat blood stasis in Chinese medicine and other oriental folk medicines. Although little is known about the effects of Semen Persicae and its active compounds on neuron differentiation, our pilot study showed that Semen Persicae extract promoted neurite outgrowth in rat dopaminergic PC12 cells. In the present study, we developed a bioactivity-guided fractionation procedure for the characterization of the neurotrophic activity of Semen Persicae extract. The resultant fractions were assayed for neurite outgrowth in PC12 cells based on microscopic assessment. Through liquid-liquid extraction and reverse phase HPLC separation, a botanical glycoside amygdalin was isolated as the active compound responsible for the neurotrophic activity of Semen Persicae extract. Moreover, we found that amygdalin rapidly induced the activation of extracellular-signal-regulated kinase 1/2 (ERK1/2). A specific ERK1/2 inhibitor PD98059 attenuated the stimulatory effect of amygdalin on neurite outgrowth. Taken together, amygdalin was identified as a potent neurotrophic agent from Semen Persicae extract through a bioactivity-guided fractional procedure. The neurotrophic activity of amygdalin may be mediated by the activation of ERK1/2 pathway.