Effects of triptolide on the synaptophysin expression of hippocampal neurons in the AD cellular model

Triptolide activates the Nrf2 signaling pathway and inhibits the NF-κB signaling pathway to improve Alzheimer disease

Alzheimer disease (AD) is a common neurodegenerative disease with pathological features of accumulated amyloid plaques, neurofibrillary tangles, and the significant inflammatory environment. These features modify the living microenvironment for nerve cells, causing the damage, dysfunction, and death. Progressive neuronal loss directly leads to cognitive decline in AD patients and is closely related to brain inflammation. Therefore, impairing inflammation via signaling pathways may facilitate either the prevention or delay of the degenerative process. Triptolide has been evidenced to possess potent anti-inflammatory effect. In this review, we elaborate on two signaling pathways (the NF-κB and Nrf2 signaling pathways) that are involved in the anti-inflammatory effect of triptolide.

The dual face of microglia (M1/M2) as a potential target in the protective effect of nutraceuticals against neurodegenerative diseases

The pathophysiology of different neurodegenerative illnesses is significantly influenced by the polarization regulation of microglia and macrophages. Traditional classifications of macrophage phenotypes include the pro-inflammatory M1 and the anti-inflammatory M2 phenotypes. Numerous studies demonstrated dynamic non-coding RNA modifications, which are catalyzed by microglia-induced neuroinflammation. Different nutraceuticals focus on the polarization of M1/M2 phenotypes of microglia and macrophages, offering a potent defense against neurodegeneration. Caeminaxin A, curcumin, aromatic-turmerone, myricetin, aurantiamide, 3,6'-disinapoylsucrose, and resveratrol reduced M1 microglial inflammatory markers while increased M2 indicators in Alzheimer's disease. Amyloid beta-induced microglial M1 activation was suppressed by andrographolide, sulforaphane, triptolide, xanthoceraside, piperlongumine, and novel plant extracts which also prevented microglia-mediated necroptosis and apoptosis. Asarone, galangin, baicalein, and a-mangostin reduced oxidative stress and pro-inflammatory cytokines, such as interleukin (IL)-1, IL-6, and tumor necrosis factor-alpha in M1-activated microglia in Parkinson's disease. Additionally, myrcene, icariin, and tenuigenin prevented the nod-like receptor family pyrin domain-containing 3 inflammasome and microglial neurotoxicity, while a-cyperone, citronellol, nobiletin, and taurine prevented NADPH oxidase 2 and nuclear factor kappa B activation. Furthermore, other nutraceuticals like plantamajoside, swertiamarin, urolithin A, kurarinone, Daphne genkwa flower, and Boswellia serrata extracts showed promising neuroprotection in treating Parkinson's disease. In Huntington's disease, elderberry, curcumin, iresine celosia, Schisandra chinensis, gintonin, and pomiferin showed promising results against microglial activation and improved patient symptoms. Meanwhile, linolenic acid, resveratrol, Huperzia serrata, icariin, and baicalein protected against activated macrophages and microglia in experimental autoimmune encephalomyelitis and multiple sclerosis. Additionally, emodin, esters of gallic and rosmarinic acids, Agathisflavone, and sinomenine offered promising multiple sclerosis treatments. This review highlights the therapeutic potential of using nutraceuticals to treat neurodegenerative diseases involving microglial-related pathways.

Triptolide injection reduces Alzheimer's disease-like pathology in mice

Triptolide is an epoxidized diterpene lactone isolated from Tripterygium wilfordii. Studies have shown that triptolide exerts organ-protective effects. However, it remains unknown whether triptolide improves Alzheimer's disease (AD)-like presentations. Thirty healthy 8-week-old male C57BL/6J mice were randomly divided into control (n = 10), model (n = 10), and triptolide (n = 10) groups. Amyloid-β (Aβ)42 was injected bilaterally into the ventricles of mice in the model group. Triptolide was injected intraperitoneally daily after injecting Aβ42 (a total of 30 days) in the triptolide group. Learning and memory were tested using the Morris water maze test. The deposition of Aβ42 in the hippocampus was detected using immunohistochemical staining. In the hippocampus, three synaptic-associated proteins-gephyrin, collybistin, and GABRA₁ -were detected by western blotting. Furthermore, we used ELISA to detect proinflammatory cytokines, including TNF-α and IL-1β, in the blood and hippocampus. Moreover, superoxide dismutase (SOD), malondialdehyde (MDA), and GSH levels were measured using the corresponding kits. We found that triptolide improved spatial learning and memory in AD-like mice. Additionally, triptolide maintained the expression of gephyrin, collybistin, and GABRA₁ and reduced Aβ in these mice. Additionally, triptolide reduced the expression of inflammatory cytokines and decreased oxidative damage in AD-like mice. Our study suggests that triptolide attenuates AD-like changes in the mouse brain.

Endothelial Dysfunction in Neurodegenerative Diseases

The cerebral vascular system stringently regulates cerebral blood flow (CBF). The components of the blood-brain barrier (BBB) protect the brain from pathogenic infections and harmful substances, efflux waste, and exchange substances; however, diseases develop in cases of blood vessel injuries and BBB dysregulation. Vascular pathology is concurrent with the mechanisms underlying aging, Alzheimer's disease (AD), and vascular dementia (VaD), which suggests its involvement in these mechanisms. Therefore, in the present study, we reviewed the role of vascular dysfunction in aging and neurodegenerative diseases, particularly AD and VaD. During the development of the aforementioned diseases, changes occur in the cerebral blood vessel morphology and local cells, which, in turn, alter CBF, fluid dynamics, and vascular integrity. Chronic vascular inflammation and blood vessel dysregulation further exacerbate vascular dysfunction. Multitudinous pathogenic processes affect the cerebrovascular system, whose dysfunction causes cognitive impairment. Knowledge regarding the pathophysiology of vascular dysfunction in neurodegenerative diseases and the underlying molecular mechanisms may lead to the discovery of clinically relevant vascular biomarkers, which may facilitate vascular imaging for disease prevention and treatment.

The therapeutic potential of triptolide and celastrol in neurological diseases

Neurological diseases are complex diseases affecting the brain and spinal cord, with numerous etiologies and pathogenesis not yet fully elucidated. Tripterygium wilfordii Hook. F. (TWHF) is a traditional Chinese medicine with a long history of medicinal use in China and is widely used to treat autoimmune and inflammatory diseases such as systemic lupus erythematosus and rheumatoid arthritis. With the rapid development of modern technology, the two main bioactive components of TWHF, triptolide and celastrol, have been found to have anti-inflammatory, immunosuppressive and anti-tumor effects and can be used in the treatment of a variety of diseases, including neurological diseases. In this paper, we summarize the preclinical studies of triptolide and celastrol in neurological diseases such as neurodegenerative diseases, brain and spinal cord injury, and epilepsy. In addition, we review the mechanisms of action of triptolide and celastrol in neurological diseases, their toxicity, related derivatives, and nanotechnology-based carrier system.

Neuroprotection of Triptolide against Amyloid-Beta1-42-induced toxicity via the Akt/mTOR/p70S6K-mediated Autophagy Pathway

Triptolide is a natural active compound that has significant neuroprotective properties and shows promising effects in the treatment of Alzheimer's disease (AD). Recent studies have shown that autophagy occurs in AD. In this study, we determined whether autophagy regulated by triptolide ameliorates neuronal death caused by amyloid-Beta1-42 (Aβ1-42). We examined the effects of triptolide on cell viability, autophagy, apoptosis, and the protein kinase B/mammalian target of the rapamysin/70 kDa ribosomal protein S6 kinase (Akt/mTOR/p70S6K) signaling pathway in PC12 cells. The results indicated that triptolide treatment exhibited a cytoprotective effect against cell injury induced by Aβ1-42. Triptolide also reduced apoptosis and enhanced cell survival by decreasing autophagosome accumulation and inducing autophagic degradation. Furthermore, our results also showed that activating the Akt/mTOR/p70S6K mechanism was one reason for the protection of triptolide. Triptolide treatment protected against Aβ1-42-induced cytotoxicity by decreasing autophagosome accumulation, and inducing autophagic degradation in PC12 cells. These findings also suggest that the reduction of autophagosome accumulation observed in triptolide-treated cells was Akt/mTOR/p70S6K pathway dependent. Overall, triptolide exhibits a neuron protective effect and this study provides new insight into AD prevention and treatment.

Tripterygium hypoglaucum (Lévl.) Hutch and Its Main Bioactive Components: Recent Advances in Pharmacological Activity, Pharmacokinetics and Potential Toxicity

Tripterygium hypoglaucum (Lévl.) Hutch (THH) is believed to play an important role in health care and disease treatment according to traditional Chinese medicine. Moreover, it is also the representative of medicine with both significant efficacy and potential toxicity. This characteristic causes THH hard for embracing and fearing. In order to verify its prospect for clinic, a wide variety of studies were carried out in the most recent years. However, there has not been any review about THH yet. Therefore, this review summarized its characteristic of components, pharmacological effect, pharmacokinetics and toxicity to comprehensively shed light on the potential clinical application. More than 120 secondary metabolites including terpenoids, alkaloids, glycosides, sugars, organic acids, oleanolic acid, polysaccharides and other components were found in THH based on phytochemical research. All these components might be the pharmacological bases for immunosuppression, anti-inflammatory and anti-tumour effect. In addition, recent studies found that THH and its bioactive compounds also demonstrated remarkable effect on obesity, insulin resistance, fertility and infection of virus. The main mechanism seemed to be closely related to regulation the balance of immune, inflammation, apoptosis and so on in various disease. Furthermore, the study of pharmacokinetics revealed quick elimination of the main component triptolide. The feature of celastrol was also investigated by several models. Finally, the side effect of THH was thought to be the key for its limitation in clinical application. A series of reports indicated that multiple organs or systems including liver, kidney and genital system were involved in the toxicity. Its potential serious problem in liver was paid specific attention in recent years. In summary, considering the significant effect and potential toxicity of THH as well as its components, the combined medication to inhibit the toxicity, maintain effect might be a promising method for clinical conversion. Modern advanced technology such as structure optimization might be another way to reach the efficacy and safety. Thus, THH is still a crucial plant which remains for further investigation.

Genotype Load Modulates Amyloid Burden and Anxiety-Like Patterns in Male 3xTg-AD Survivors despite Similar Neuro-Immunoendocrine, Synaptic and Cognitive Impairments

The wide heterogeneity and complexity of Alzheimer’s disease (AD) patients’ clinical profiles and increased mortality highlight the relevance of personalized-based interventions and the need for end-of-life/survival predictors. At the translational level, studying genetic and age interactions in a context of different levels of expression of AD-genetic-load can help to understand this heterogeneity better. In the present report, a singular cohort of long-lived (19-month-old survivors) heterozygous and homozygous male 3xTg-AD mice were studied to determine whether their AD-genotype load can modulate the brain and peripheral pathological burden, behavioral phenotypes, and neuro-immunoendocrine status, compared to age-matched non-transgenic controls. The results indicated increased amyloid precursor protein (APP) levels in a genetic-load-dependent manner but convergent synaptophysin and choline acetyltransferase brain levels. Cognitive impairment and HPA-axis hyperactivation were salient traits in both 3xTg-AD survivor groups. In contrast, genetic load elicited different anxiety-like profiles, with hypoactive homozygous, while heterozygous resembled controls in some traits and risk assessment. Complex neuro-immunoendocrine crosstalk was also observed. Bodyweight loss and splenic, renal, and hepatic histopathological injury scores provided evidence of the systemic features of AD, despite similar peripheral organs’ oxidative stress. The present study provides an interesting translational scenario to study further genetic-load and age-dependent vulnerability/compensatory mechanisms in Alzheimer’s disease.

Subchronic neurotoxicity of diazinon in albino mice: Impact of oxidative stress, AChE activity, and gene expression disturbances in the cerebral cortex and hippocampus on mood, spatial learning, and memory function

Diazinon (DZN) with prominent neurotoxic effects perturbs CNS function via multiple mechanisms. This investigation intends to explore mood, spatial learning, and memory dysfunction, acetylcholine esterase (AChE) activity, and neurodegeneration-related gene expression in the cortex and hippocampus regions of mice exposed to DZN for 63 consecutive days (subchronic exposure). Adult male albino mice were orally given sublethal DZN (DZNL = 0.1 mg/kg, DZNM = 1 mg/kg and DZNH = 10 mg/kg). All mice in the DZNH group died within 3 weeks postexposure. DZNL and DZNM caused body and brain weight loss (p < 0.05). Completing 9 weeks of DZN exposure, a marked decline in AChE activity and oxidative stress level was indicated in both brain regions (p < 0.05). Also, synaptophysin, vesicular acetylcholine transferase, and glutamate decarboxylase gene expressions were affected in both brain regions (p < 0.05). Furthermore, the present study revealed that DZN administration increased anxiety and depressive-like behaviors (p < 0.0001). Spatial learning and short- and long-memory were severely affected by DZNL and DZNM treatments (p < 0.0001). Taken together, subchronic exposure to low and medium doses of DZN can cause AChE inhibition, oxidative damage, and neurotransmitter disturbances in brain cells and induce neurodegeneration. These changes would impair mood, spatial learning, and memory function.

Epigenetic mechanisms underlying the effects of triptolide and tripchlorolide on the expression of neuroligin-1 in the hippocampus of APP/PS1 transgenic mice

Context: Neuroligin-1 (NLGN1) is a cell adhesion protein located on the excitatory postsynaptic membrane. β-Amyloid (Aβ)-induced neuroinflammation decreases NLGN1 expression through epigenetic mechanisms. Triptolide (T10) and tripchlorolide (T4) exert protective effects on synapses in Alzheimer's disease (AD) mice, but the mechanisms remain unclear. Objective: The effects of T10 and T4 on hippocampal NLGN1 expression in AD mice and the epigenetic mechanisms were assessed using chromatin immunoprecipitation and methylated DNA immunoprecipitation. Materials and methods: Sixty APP/PS1 transgenic mice were randomly divided into an AD model group, a T10-treated group and a T4-treated group (n = 20); 20 wild-type littermates served as the control group. APP/PS1 transgenic mice were intraperitoneally injected with T10 (0.1 mg/kg) and T4 (25 μg/kg) once per day for 60 days. NLGN1 expression was examined using western blotting and quantitative PCR. Results: T10 and T4 increased the levels of the NLGN1 protein and mRNA in hippocampus of AD mice. T10 and T4 inhibited the binding of HDAC2 (p< 0.01) and MeCP2 (p< 0.01 and p< 0.05, respectively) to the NLGN1 promoter, and cytosine methylation (1.2305 ± 0.1482/1.2554 ± 0.3570 vs. 1.6578 ± 0.1818, p< 0.01) at the NLGN1 promoter in the hippocampus of AD mice. T10 and T4 increased the level of acetylated histone H3 (0.7733 ± 0.1611/0.8241 ± 0.0964 vs. 0.5587 ± 0.0925, p< 0.01) at the NLGN1 promoter in the hippocampus of AD mice. Conclusions: T10 and T4 may increase hippocampal NLGN1 expression in AD mice through epigenetic mechanisms, providing a new explanation for the mechanism underlying the protective effects of T10 and T4 on synapses.

Triptolide Improves Cognitive Dysfunction in Rats with Vascular Dementia by Activating the SIRT1/PGC-1α Signaling Pathway

Tripterygium Wilfordii Hook F has been exploited as a treatment for several diseases due to its neuroprotective, anti-tumor, and anti-inflammatory effects. Triptolide is one of its key bioactive compounds. Currently, the role of triptolide in cognitive dysfunction remains unclear. Here, the role of triptolide on cognitive dysfunction was investigated using chronic cerebral hypoperfusion-induced vascular dementia (VD) rat model. SD rats were administrated with Triptolide (5 μg/kg) for 6 weeks after undergoing permanent bilateral common carotid artery occlusion. The results show that triptolide treatment conferred neuroprotective effects in VD rats. Intraperitoneal injection of triptolide attenuated oxidative stress, learning and memory deficits, and neuronal apoptosis in the hippocampi. Moreover, triptolide enhanced the expression of SIRT1, PGC-1α, ZO-1, Claudin-5, and decreased the serum levels of NSE and S100B significantly. It also improved CCH-induced learning and memory deficits, and this is attributed to its capacity to promote SIRT1/PGC-1α signaling, confer antioxidant effects, and inhibit neuronal apoptosis. These findings indicate that triptolide may be an effective therapeutic agent for vascular cognitive dysfunction.

Treatment of Neurodegenerative Diseases with Bioactive Components of Tripterygium wilfordii

Tripterygium wilfordii Hook F. (TWHF), a traditional Chinese medicine, has been widely used to treat autoimmune and inflammatory diseases including rheumatoid arthritis, systemic lupus erythematosus and dermatomyositis in China. Recently, studies have demonstrated that the bioactive components of TWHF have effective therapeutic potential for neurodegenerative diseases including Alzheimer's disease, Parkinson's disease and Multiple Sclerosis. In this paper, we summarize the research progress of triptolide and celastrol (the two major TWHF components) as well as their analogues in the treatment of neurodegenerative diseases. In addition, we review and discuss the molecular mechanisms and structure features of those two bioactive TWHF components, highlighting their therapeutic promise in neurodegenerative diseases.

Natural products as a potential modulator of microglial polarization in neurodegenerative diseases

Neurodegenerative diseases (NDs) are characterized by the progressive loss of structure and function of neurons most common in elderly population, mainly including Alzheimer's disease (AD), Parkinson's disease (PD), amyotrophic lateral sclerosis (ALS) and multiple sclerosis (MS). Neuroinflammation caused by microglia as the resident macrophages of the central nervous system (CNS) plays a contributory role in the onset and progression of NDs. Activated microglia, as in macrophages, to be heterogeneous, can polarize into M1 (pro-inflammatory) and M2 (anti-inflammatory) functional phenotypes. The former elaborate pro-inflammatory mediators promoting neuroinflammation and neuronal damage. In contrast, the latter generate anti-inflammatory mediators and neurotrophins that inhibit neuroinflammation and promote neuronal healing. Consistently, the regulation of microglial polarization from M1 to M2 phenotype appears as an outstanding therapeutic and preventive approach for NDs treatment. Although non-steroidal anti-inflammatory drugs (NSAIDs) currently used to alleviate M1 microglia-associated neuroinflammation responsible for the development of NDs, these drugs have different degrees of adverse effects and limited efficacy. As the advantages of novel structure, multi-target, high efficiency and low toxicity, natural products as the modulators of microglial polarization have attracted considerable concerns in the therapeutic areas of NDs. In this review, we mainly summarized the therapeutic potential of natural products and their various molecular mechanisms for NDs treatment through modulating microglial polarization. The aim of the current review is expected to be useful to develop innovative modulators of microglial polarization from natural products for the amelioration and treatment of NDs.

Neuroprotective Effects of the Multitarget Agent AVCRI104P3 in Brain of Middle-Aged Mice

Molecular factors involved in neuroprotection are key in the design of novel multitarget drugs in aging and neurodegeneration. AVCRI104P3 is a huprine derivative that exhibits potent inhibitory effects on human AChE, BuChE, and BACE-1 activities, as well as on AChE-induced and self-induced Aβ aggregation. More recently, cognitive protection and anxiolytic-like effects have also been reported in mice treated with this compound. Now, we have assessed the ability of AVCRI104P3 (0.43 mg/kg, 21 days) to modulate the levels of some proteins involved in the anti-apoptotic/apoptotic processes (pAkt1, Bcl2, pGSK3β, p25/p35), inflammation (GFAP and Iba1) and neurogenesis in C57BL/6 mice. The effects of AVCRI104P3 on AChE-R/AChE-S isoforms have been also determined. We have observed that chronic treatment of C57BL/6 male mice with AVCRI104P3 results in neuroprotective effects, increasing significantly the levels of pAkt1 and pGSK3β in the hippocampus and Bcl2 in both hippocampus and cortex, but slightly decreasing synaptophysin levels. Astrogliosis and neurogenic markers GFAP and DCX remained unchanged after AVCRI104P3 treatment, whereas microgliosis was found to be significantly decreased pointing out the involvement of this compound in inflammatory processes. These results suggest that the neuroprotective mechanisms that are behind the cognitive and anxiolytic effects of AVCRI104P3 could be partly related to the potentiation of some anti-apoptotic and anti-inflammatory proteins and support the potential of AVCRI104P3 for the treatment of brain dysfunction associated with aging and/or dementia.

Identification and functional characterization of diterpene synthases for triptolide biosynthesis from Tripterygium wilfordii

Tripterygium wilfordii, which has long been used as a medicinal plant, exhibits impressive and effective anti-inflammatory, immunosuppressive and anti-tumor activities. The main active ingredients are diterpenoids and triterpenoids, such as triptolide and celastrol, respectively. A major challenge to harnessing these natural products is that they are found in very low amounts in planta. Access has been further limited by the lack of knowledge regarding their underlying biosynthetic pathways, particularly for the abeo-abietane tri-epoxide lactone triptolide. Here suspension cell cultures of T. wilfordii were found to produce triptolide in an inducible fashion, with feeding studies indicating that miltiradiene is the relevant abietane olefin precursor. Subsequently, transcriptome data were used to identify eight putative (di)terpene synthases that were then characterized for their potential involvement in triptolide biosynthesis. This included not only biochemical studies which revealed the expected presence of class II diterpene cyclases that produce the intermediate copalyl diphosphate (CPP), along with the more surprising finding of an atypical class I (di)terpene synthase that acts on CPP to produce the abietane olefin miltiradiene, but also their subcellular localization and, critically, genetic analysis. In particular, RNA interference targeting either both of the CPP synthases, TwTPS7v2 and TwTPS9v2, or the subsequently acting miltiradiene synthase, TwTPS27v2, led to decreased production of triptolide. Importantly, these results then both confirm that miltiradiene is the relevant precursor and the relevance of the identified diterpene synthases, enabling future studies of the biosynthesis of this important bioactive natural product.

The novel and potent anti-depressive action of triptolide and its influences on hippocampal neuroinflammation in a rat model of depression comorbidity of chronic pain

Chronic pain and depression frequently coexist in clinical setting, and current clinical treatments for this comorbidity have shown limited efficacy. Triptolide (T10), an active component of Tripterygium wilfordii Hook F., has been demonstrated to exert strong analgesic activities in experimental pain models, but whether it possesses anti-depressive actions remains unknown. Using a depression comorbidity of chronic pain rat model induced by spinal nerve ligation (SNL), we investigated the potency of T10 for the treatment of comorbid depression in comparison with a widely used antidepressant, fluoxetine (FLX). Concomitant neuroinflammation changes were also examined in the hippocampus. The results showed that prophylactic and reversal treatments with T10 dose-dependently (30, 100, 300μg/kg) inhibited the depression-like behaviors (DLB) assessed by the forced swim test, sucrose preference test and body weight measurement. The anti-depressive efficacy of T10 at 300μg/kg was significantly stronger than that of FLX at 18mg/kg. T10 at all three doses exhibited more efficient analgesic effects than FLX at 18mg/kg. The combined application of T10 with FLX markedly augmented the effects of T10 or FLX per se, with the facilitating effects of T10 at 30μg/kg being most prominent. In addition, nerve injury caused the activation of microglia and p38 MAPK, the upregulation of IL-1β and TNF-α as well as the downregulation of IL-10 in the hippocampus at postoperative week (POW) 3. These neuroinflammatory responses were reversed by subchronic treatment with T10. Taken together, these results demonstrate that T10 possesses potent anti-depressive function, which is correlated with its immunoregulation in the hippocampus. The combination of a low dose of T10 with FLX may become a more effective medication strategy for the treatment of comorbid depression and chronic pain.

Triptolide attenuated injury via inhibiting oxidative stress in Amyloid-Beta25-35-treated differentiated PC12 cells

BACKGROUND

Recently, an abnormal deposition of Amyloid-Beta (Aβ) was considered the primary cause of the pathogenesis of Alzheimer's disease (AD). And how to inhibit the cytotoxicity is considered an important target for the treatment of AD. Triptolide (TP), a purified diterpenoid from the herb Tripterygium wilfordii Hook.f. (TWHF), has potential neuroprotective effects pertinent to disease of the nervous system. However, whether triptolide and its specific mechanisms have protective functions in differentiated PC12 cells treated with Aβ25-35 remain unclear.

AIMS

The purpose is to investigate the protective functions of triptolide in Aβ25-35-stimulated differentiated PC12 cells.

MAIN METHODS

In the study, we use 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, lactate dehydrogenase (LDH) assay, flow cytometry assay, immunohistochemical staining and Western blot to observe the effects of triptolide on cytotoxicity induced by Aβ25-35 and its mechanism of oxidative stress.

KEY FINDINGS

The result of MTT and LDH assay indicates that triptolide protected PC12 cells against Aβ25-35-induced cytotoxicity. The flow cytometry assay shows that triptolide attenuated Aβ25-35-induced apoptosis in differentiated PC12 cells. Meanwhile, the results give a clear indication that triptolide could downregulate generation of reactive oxygen species (ROS), hydrogen peroxide (H2O2) and malondialdehyde (MDA) induced by Aβ25-35. The apoptotic process triggered by triptolide involved the up-regulation of the activity of superoxide dismutase (SOD).

SIGNIFICANCE

The results suggest that triptolide may serve as an important role in the inhibition of the cell apoptosis induced by Aβ and the decreased oxidative stress is a key mechanism in the protective effect of triptolide in AD.

Triptolide treatment reduces Alzheimer's disease (AD)-like pathology through inhibition of BACE1 in a transgenic mouse model of AD

The complex pathogenesis of Alzheimer’s disease (AD) involves multiple contributing factors, including amyloid β (Aβ) peptide accumulation, inflammation and oxidative stress. Effective therapeutic strategies for AD are still urgently needed. Triptolide is the major active compound extracted from Tripterygium wilfordii Hook.f., a traditional Chinese medicinal herb that is commonly used to treat inflammatory diseases. The 5-month-old 5XFAD mice, which carry five familial AD mutations in the β-amyloid precursor protein (APP) and presenilin-1 (PS1) genes, were treated with triptolide for 8 weeks. We observed enhanced spatial learning performances, and attenuated Aβ production and deposition in the brain. Triptolide also inhibited the processing of amyloidogenic APP, as well as the expression of βAPP-cleaving enzyme-1 (BACE1) both in vivo and in vitro. In addition, triptolide exerted anti-inflammatory and anti-oxidative effects on the transgenic mouse brain. Triptolide therefore confers protection against the effects of AD in our mouse model and is emerging as a promising therapeutic candidate drug for AD.

The potential of follicle-stimulating hormone peptide-modified triptolide-loaded nanoparticles to induce a mouse model of premature ovarian insufficiency

The use of triptolide (TP) is limited by its poor water solubility and severe toxicity. In this study, we developed an active drug delivery system (TP-loaded nanoparticles) that could help improve the water solubility of TP and decrease its toxicity. Then, we investigated whether TP-loaded nanoparticles could be used to establish a novel premature ovarian insufficiency mouse model. The mice treated with TP-loaded nanoparticles for 35 days displayed normal growth, decreased serum antimullerian hormone, prominent ovarian fibrosis and vacuolar changes, fewer follicles and corpus lutea, increased collapsed oocytes and follicle apoptosis, and sterility. In conclusion, this model appears to show the reproductive characteristics associated with premature ovarian insufficiency in women and will allow us to study the mechanism of the effects of traditional Chinese medicine on gonadal toxicity.

Triptolide preserves cognitive function and reduces neuropathology in a mouse model of Alzheimer's disease

Triptolide, a major bioactive ingredient of a widely used herbal medicine, has been shown to possess multiple pharmacological functions, including potential neuroprotective effects pertinent to Alzheimer's disease (AD) in vitro. However, the therapeutic potential of triptolide for AD in vivo has not been thoroughly evaluated. In the present study, we investigated the impact of peripherally administered triptolide on AD-related behavior and neuropathology in APP_swe/PS1_ΔE9 (APP/PS1) mice, an established model of AD. Our results showed that two-month treatment with triptolide rescued cognitive function in APP/PS1 mice. Immunohistochemical analyses indicated that triptolide treatment led to a significant decrease in amyloid-β (Aβ) deposition and neuroinflammation in treated mice. In contrast to previous findings in vitro, biochemical analyses showed that triptolide treatment did not significantly affect the production pathway of Aβ in vivo. Intriguingly, further analyses revealed that triptolide treatment upregulated the level of insulin-degrading enzyme, a major Aβ-degrading enzyme in the brain, indicating that triptolide treatment reduced Aβ pathology by enhancing the proteolytic degradation of Aβ. Our findings demonstrate that triptolide treatment ameliorates key behavioral and neuropathological changes found in AD, suggesting that triptolide may serve as a potential therapeutic agent for AD.

Triptolide: progress on research in pharmacodynamics and toxicology

ETHNOPHARMACOLOGICAL RELEVANCE

Tripterygium wilfordii Hook. f. (Tripterygium wilfordii), also known as Huangteng and gelsemium elegan, is a traditional Chinese medicine that has been marketed in China as Tripterygium wilfordii glycoside tablets. Triptolide (TP), an active component in Tripterygium wilfordii extracts, has been used to treat various diseases, including lupus, cancer, rheumatoid arthritis and nephritic syndrome. This review summarizes recent developments in the research on the pharmacodynamics, pharmacokinetics, pharmacy and toxicology of TP, with a focus on its novel mechanism of reducing toxicity. This review provides insight for future studies on traditional Chinese medicine, a field that is both historically and currently important.

MATERIALS AND METHODS

We included studies published primarily within the last five years that were available in online academic databases (e.g., PubMed, Google Scholar, CNKI, SciFinder and Web of Science).

RESULTS

TP has a long history of use in China because it displays multiple pharmacological activities, including anti-rheumatism, anti-inflammatory, anti-tumor and neuroprotective properties. It has been widely used for the treatment of various diseases, such as rheumatoid arthritis, nephritic syndrome, lupus, Behcet׳s disease and central nervous system diseases. Recently, numerous breakthroughs have been made in our understanding of the pharmacological efficacy of TP. Although TP has been marketed as a traditional Chinese medicine, its multi-organ toxicity prevents it from being widely used in clinical practice.

CONCLUSIONS

Triptolide, a biologically active natural product extracted from the root of Tripterygium wilfordii, has shown promising pharmacological effects, particularly as an anti-tumor agent. Currently, in anti-cancer research, more effort should be devoted to investigating effective anti-tumor targets and confirming the anti-tumor spectrum and clinical indications of novel anti-tumor pro-drugs. To apply TP appropriately, with high efficacy and low toxicity, the safety and non-toxic dose range for specific target organs and diseases should be determined, the altered pathways and mechanisms of exposure need to be clarified, and an early warning system for toxicity needs to be established. With further in-depth study of the efficacy and toxicity of TP, we believe that TP will become a promising multi-use drug with improved clinical efficacy and safety in the future.

In silico design of BACE1 inhibitor for Alzheimer's disease by traditional Chinese medicine

The β-site APP cleaving enzyme 1 (BACE1) is an important target for causing Alzheimer's disease (AD), due to the brain deposition peptide amyloid beta (Aβ) require cleavages of amyloid precursor protein (APP) by BACE1 and γ-secretase, but treatments of AD still have side effect in recent therapy. This study utilizes the world largest traditional Chinese medicine (TCM) database and database screening to provide potential BACE1 inhibited compound. Molecular dynamics (MD) simulation was carried out to observe the dynamics structure after ligand binding. We found that Triptofordin B1 has less toxicity than pyrimidine analogue, which has more potent binding affinity with BACE1. For trajectory analysis, all conformations are tending to be stable during 5000 ps simulation time. In dynamic protein validation, the residues of binding region are still stable after MD simulation. For snapshot comparison, we found that Triptofordin B1 could reduce the binding cavity; the results reveal that Triptofordin B1 could bind to BACE1 and better than control, which could be used as potential lead drug to design novel BACE1 inhibitor for AD therapy.

Effects of triptolide on degeneration of dendritic spines induced by Aβ1-40 injection in rat hippocampus

Although the exact cause of Alzheimer's disease (AD) remains elusive, mounting evidence continues to support the involvement of neuroinflammation in the development of AD. Triptolide isolated from the herb Tripterygium wilfordii Hook F has anti-inflammatory and immunosuppressive activities. In this study, we observed the effects of triptolide on dendritic spines of hippocampal neurons in model rats with AD. Thirty male SD rats were randomly divided into control group, AD model group and triptolide-treated group. The AD model group was made with bilateral microinjection of aggregated beta-amyloid protein (Aβ)1-40 into hippocampus in rats and the control group rats were injected with normal saline in the same way. The triptolide-treated group rats were administered triptolide intraperitoneally for 30 days after microinjection of aggregated Aβ1-40 into hippocampus. Dendritic morphology of hippocampal neurons in each group was analyzed using Golgi staining and ImageJ software. Our data showed that the total number of intersection points of dendrites and spine density in hippocampal neurons in the AD model group were decreased as compared with the control group. However, the total number of intersection points of dendrites and spine density in hippocampal neurons in the triptolide-treated group were increased as compared with the AD model group. Our results indicate that triptolide can alleviate the degeneration of dendritic spines in hippocampal neurons in model rats with AD.

Triptolide with potential medicinal value for diseases of the central nervous system

Tripterygium wilfordii Hook.f. (TWHF) has a long history as a Traditional Chinese Medicine (TCM) herb that aids in treating inflammatory and autoimmune diseases. The major bioactive component of TWHF is triptolide, which has been recognized to possess a broad spectrum of biological profiles including antiinflammatory, immunosuppressive, antifertility, and antitumor activities, as well as neurotrophic and neuroprotective effects. Limitation of triptolide, such as poor water solubility and severe systemic toxicity, has postponed clinical development and trials; however, the wide range of medicinal value of triptolide has been drawing intensive worldwide attention. In particular, triptolide has been shown to have significant effects on central nervous system (CNS) diseases, such as Parkinson's disease, Alzheimer's disease, spinal cord and brain injury, and multiple sclerosis. This review focuses on the potential therapeutic role of triptolide on CNS diseases, and discusses the structural features, potential modifications, and the other pharmacological activities of triptolide.