Therapeutic and Mechanistic Effects of Curcumin in Huntington's Disease

Neuroprotective effect of curcumin against experimental autoimmune encephalomyelitis-induced cognitive and physical impairments in mice: an insight into the role of the AMPK/SIRT1 pathway

Multiple sclerosis (MS) is an incurable chronic neurodegenerative disease where autoimmunity, oxidative stress, and neuroinflammation collaboration predispose myelin sheath destruction. Interestingly, curcumin, a natural polyphenol, showed a neuroprotective effect in numerous neurodegenerative diseases, including MS. Nevertheless, the influence of curcumin against MS-induced cognitive impairment is still vague. Hence, we induced experimental autoimmune encephalomyelitis (EAE) in mice using spinal cord homogenate (SCH) and complete Freund's adjuvant, which eventually mimic MS. This study aimed not only to evaluate curcumin efficacy against EAE-induced cognitive and motor dysfunction, but also to explore a novel mechanism of action, by which curcumin exerts its beneficial effects in MS. Curcumin (200 mg/kg/day) efficacy was evaluated by behavioral tests, histopathological examination, and biochemical tests. Concisely, curcumin amended EAE-induced cognitive and motor impairments, as demonstrated by the behavioral tests and histopathological examination of the hippocampus. Interestingly, curcumin activated the adenosine monophosphate (AMP)-activated protein kinase/silent mating type information regulation 2 homolog 1 (AMPK/SIRT1) axis, which triggered cyclic AMP response element-binding protein/brain-derived neurotrophic factor/myelin basic protein (CREB/BDNF/MBP) pathway, hindering demyelination of the corpus callosum. Furthermore, AMPK/SIRT1 activation augmented nuclear factor erythroid 2-related factor 2 (Nrf2), a powerful antioxidant, amending EAE-induced oxidative stress. Additionally, curcumin abolished EAE-induced neuroinflammation by inhibiting Janus kinase 2 /signal transducers and activators of transcription 3 (JAK2/STAT3) axis, by various pathways, including AMPK/SIRT1 activation. JAK2/STAT3 inhibition halts inflammatory cytokines synthesis. In conclusion, curcumin's neuroprotective effect in EAE is controlled, at least in part, by AMPK/SIRT1 activation, which ultimately minimizes EAE-induced neuronal demyelination, oxidative stress, and neuroinflammation.

Curcumin protects mice with myasthenia gravis by regulating the gut microbiota, short-chain fatty acids, and the Th17/Treg balance

Curcumin is widely used as a traditional drug in Asia. Interestingly, curcumin and its metabolites have been demonstrated to influence the microbiota. However, the effect of curcumin on the gut microbiota in patients with myasthenia gravis (MG) remains unclear. This study aimed to investigate the effects of curcumin on the gut microbiota community, short-chain fatty acids (SCFAs) levels, intestinal permeability, and Th17/Treg balance in a Torpedo acetylcholine receptor (T-AChR)-induced MG mouse model. The results showed that curcumin significantly alleviated the clinical symptoms of MG mice induced by T-AChR. Curcumin modified the gut microbiota composition, increased microbial diversity, and, in particular, reduced endotoxin-producing Proteobacteria and Desulfovibrio levels in T-AChR-induced gut dysbiosis. Moreover, we found that curcumin significantly increased fecal butyrate levels in mice with T-AChR-induced gut dysbiosis. Butyrate levels increased in conjunction with the increase in butyrate-producing species such as Oscillospira, Akkermansia, and Allobaculum in the curcumin-treated group. In addition, curcumin repressed the increased levels of lipopolysaccharide (LPS), zonulin, and FD4 in plasma. It enhanced Occludin expression in the colons of MG mice induced with T-AChR, indicating dramatically alleviated gut permeability. Furthermore, curcumin treatment corrected T-AChR-induced imbalances in Th17/Treg cells. In summary, curcumin may protect mice against myasthenia gravis by modulating both the gut microbiota and SCFAs, improving gut permeability, and regulating the Th17/Treg balance. This study provides novel insights into curcumin's clinical value in MG therapy.

Neuroprotective potentials of Lead phytochemicals against Alzheimer's disease with focus on oxidative stress-mediated signaling pathways: Pharmacokinetic challenges, target specificity, clinical trials and future perspectives

BACKGROUND

Alzheimer's diseases (AD) and dementia are among the highly prevalent neurological disorders characterized by deposition of beta amyloid (Aβ) plaques, dense deposits of highly phosphorylated tau proteins, insufficiency of acetylcholine (ACh) and imbalance in glutamatergic system. Patients typically experience cognitive, behavioral alterations and are unable to perform their routine activities. Evidence also suggests that inflammatory processes including excessive microglia activation, high expression of inflammatory cytokines and release of free radicals. Thus, targeting inflammatory pathways beside other targets might be the key factors to control- disease symptoms and progression.

PURPOSE

This review is aimed to highlight the mechanisms and pathways involved in the neuroprotective potentials of lead phytochemicals. Further to provide updates regarding challenges associated with their use and their progress into clinical trials as potential lead compounds.

METHODS

Most recent scientific literature on pre-clinical and clinical data published in quality journals especially on the lead phytochemicals including curcumin, catechins, quercetin, resveratrol, genistein and apigenin was collected using SciFinder, PubMed, Google Scholar, Web of Science, JSTOR, EBSCO, Scopus and other related web sources.

RESULTS

Literature review indicated that the drug discovery against AD is insufficient and only few drugs are clinically approved which have limited efficacy. Among the therapeutic options, natural products have got tremendous attraction owing to their molecular diversity, their safety and efficacy. Research suggest that natural products can delay the disease onset, reduce its progression and regenerate the damage via their anti-amyloid, anti-inflammatory and antioxidant potentials. These agents regulate the pathways involved in the release of neurotrophins which are implicated in neuronal survival and function. Highly potential lead phytochemicals including curcumin, catechins, quercetin, resveratrol, genistein and apigenin regulate neuroprotective signaling pathways implicated in neurotrophins-mediated activation of tropomyosin receptor kinase (Trk) and p75 neurotrophins receptor (p75NTR) family receptors.

CONCLUSIONS

Phytochemicals especially phenolic compounds were identified as highly potential molecules which ameliorate oxidative stress induced neurodegeneration, reduce Aβ load and inhibit vital enzymes. Yet their clinical efficacy and bioavailability are the major challenges which need further interventions for more effective therapeutic outcomes.

Recent progress and applications of small molecule inhibitors of Keap1-Nrf2 axis for neurodegenerative diseases

The Kelch-like ECH-associated protein 1 (Keap1)-nuclear factor erythroid 2-related factor 2 (Nrf2) pathway serves as a crucial regulator against oxidative stress (OS) damage in various cells and organs. It has garnered significant attention as a potential therapeutic target for neurodegenerative diseases (NDD). Although progress has been achieved in strategies to regulate the Keap1-Nrf2 pathway, the availability of Nrf2 activators applicable to NDD is currently limited. Currently, the FDA has approved the Nrf2 activators dimethyl fumarate (DMF) and Omaveloxolone (Omav) as novel first-line oral drugs for the treatment of patients with relapsing forms of multiple sclerosis and Friedreich's ataxia. A promising alternative approach involves the direct inhibition of Keap1-Nrf2 protein-protein interactions (PPI), which offers numerous advantages over the use of electrophilic Nrf2 activators, primarily in avoiding off-target effects. This review examines the compelling evidence supporting the beneficial role of Nrf2 in NDD and explores the potential of Keap1 inhibitors and Keap1-Nrf2 PPI inhibitors as therapeutic agents, with the aim to provide further insights into the development of inhibitors targeting this pathway for the treatment of NDD.

Toxicity Evaluation and Controlled-Release of Curcumin-Loaded Amphiphilic Poly-N-vinylpyrrolidone Nanoparticles: In Vitro and In Vivo Models

Curcumin attracts huge attention because of its biological properties: it is antiproliferative, antioxidant, anti-inflammatory, immunomodulatory and so on. However, its usage has been limited by poor water solubility and low bioavailability. Herein, to solve these problems, we developed curcumin-loaded nanoparticles based on end-capped amphiphilic poly(N-vinylpyrrolidone). Nanoparticles were obtained using the solvent evaporation method and were characterized by dynamic and electrophoretic light scattering, transmission electron (TEM) and atomic force (AFM) microscopy. The average particle size was 200 nm, and the ζ-potential was -4 mV. Curcumin-release studies showed that nanoparticles are stable in aqueous solutions. An in vitro release study showed prolonged action in gastric, intestinal and colonic fluids, consistently, and in PBS. In vitro studies on epidermoid carcinoma and human embryonic kidney cells showed that the cells absorbed more curcumin in nanoparticles compared to free curcumin. Nanoparticles are safe for healthy cells and show high cytotoxicity for glioblastoma cells in cytotoxicity studies in vitro. The median lethal dose was determined in an acute toxicity assay on zebrafish and was 23 μM. Overall, the curcumin-loaded nanoparticles seem promising for cancer treatment.

A review of traditional Chinese medicine Curcumae Rhizoma for treatment of glioma

Glioma is the most common primary central nervous tumor and its malignant and high recurrence rate are seriously threatening patient's life. The prognosis of glioma patients is still poor with a variety of modern treatments. Traditional Chinese medicine (TCM) is widely used in the adjuvant treatment or alternative medicine of glioma. Curcumae Rhizoma is one of the most commonly used in traditional Chinese medicine prescriptions for its anti-tumor characteristics. There are also many studies that reveals the anti-tumor effect of its active ingredients and some of which have been made into drugs and have been used in clinical practice. This review summarizes the new research progress on Curcumae Rhizoma for the treatment of glioma in recent years.

Antiradical and Antioxidant Activity of Compounds Containing 1,3-Dicarbonyl Moiety: An Overview

Free radicals and oxidants may cause various damages both to the lifeworld and different products. A typical solution for the prophylaxis of oxidation-caused conditions is the usage of various antioxidants. Among them, various classes are found-polyphenols, conjugated polyalkenes, and some sulfur and nitrogen derivatives. Regarding the active site in the molecules, a widely discussed group of compounds are 1,3-dicarbonyl compounds. Among them are natural (e.g., curcumin and pulvinic acids) and synthetic (e.g., 4-hydroxy coumarins, substituted Meldrum's acids) compounds. Herein, information about various compounds containing the 1,3-dicarbonyl moiety is covered, and their antiradical and antioxidant activity, depending on the structure, is discussed.

Mitochondria in Huntington's disease: implications in pathogenesis and mitochondrial-targeted therapeutic strategies

Huntington's disease is a genetic disease caused by expanded CAG repeats on exon 1 of the huntingtin gene located on chromosome 4. Compelling evidence implicates impaired mitochondrial energetics, altered mitochondrial biogenesis and quality control, disturbed mitochondrial trafficking, oxidative stress and mitochondrial calcium dyshomeostasis in the pathogenesis of the disorder. Unfortunately, conventional mitochondrial-targeted molecules, such as cysteamine, creatine, coenzyme Q10, or triheptanoin, yielded negative or inconclusive results. However, future therapeutic strategies, aiming to restore mitochondrial biogenesis, improving the fission/fusion balance, and improving mitochondrial trafficking, could prove useful tools in improving the phenotype of Huntington's disease and, used in combination with genome-editing methods, could lead to a cure for the disease.

Potential roles and molecular mechanisms of bioactive ingredients in Curcumae Rhizoma against breast cancer

BACKGROUND

Breast cancer is the most prevalent cancer worldwide, with high morbidity and mortality. Despite great advances in the therapeutic strategies, the survival rate in the past decades of patients with breast cancer remains unsatisfactory. Growing evidence has demonstrated that Curcumae Rhizoma, called Ezhu in Chinese, showed various pharmacological properties, including anti-bacterial, anti-oxidant, anti-inflammatory and anti-tumor activities. It has been widely used in Chinese medicine to treat many types of human cancer.

PURPOSE

To comprehensively summarize and analyze the effects of active substances in Curcumae Rhizoma on breast cancer malignant phenotypes and the underlying mechanisms, as well as discuss its medicinal value and future perspectives.

METHOD

We used "Curcumae Rhizoma" or the name of crude extracts and bioactive components in Curcumae Rhizoma in combination with "breast cancer" as key words. Studies focusing on their anti-breast cancer activities and mechanisms of action were extracted from Pubmed, Web of Science and CNKI databases up to October 2022. The Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) 2020 guideline was followed.

RESULTS

Crude extracts and 7 main bioactive phytochemicals (curcumol, β-elemene, furanodiene, furanodienone, germacrone, curdione and curcumin) isolated from Curcumae Rhizoma have shown many anti-breast cancer pharmacological properties, including inhibiting cell proliferation, migration, invasion and stemness, reversing chemoresistance, and inducing cell apoptosis, cycle arrest and ferroptosis. The mechanisms of action were involved in regulating MAPK, PI3K/AKT and NF-κB signaling pathways. In vivo and clinical studies demonstrated that these compounds exhibited high anti-tumor efficacy and safety against breast cancer.

CONCLUSION

These findings provide strong evidence that Curcumae Rhizoma acts as a rich source of phytochemicals and has robust anti-breast cancer properties.

Multiple mechanisms of curcumin targeting spinal cord injury

Spinal cord injury (SCI) is an irreversible disease process with a high disability and mortality rate. After primary spinal cord injury, the secondary injury may occur in sequence, which is composed of ischemia and hypoxia, excitotoxicity, calcium overload, oxidative stress and inflammation, resulting in massive death of parenchymal cells in the injured area, followed by the formation of syringomyelia. Effectively curbing the process of secondary injury can promote nerve repair and improve functional prognosis. As the main active ingredient in turmeric, curcumin can play an important role in reducing inflammation and oxidation, protecting the neurons, and ultimately reducing spinal cord injury. This article reviews the effects of curcumin on the repair of nerve injury, with emphasis on the various mechanisms by which curcumin promotes the treatment of spinal cord injury.

Non-Enzymatic Antioxidants against Alzheimer's Disease: Prevention, Diagnosis and Therapy

Alzheimer's disease (AD) is a neurodegenerative disorder characterized by progressive memory loss and cognitive decline. Although substantial research has been conducted to elucidate the complex pathophysiology of AD, the therapeutic approach still has limited efficacy in clinical practice. Oxidative stress (OS) has been established as an early driver of several age-related diseases, including neurodegeneration. In AD, increased levels of reactive oxygen species mediate neuronal lipid, protein, and nucleic acid peroxidation, mitochondrial dysfunction, synaptic damage, and inflammation. Thus, the identification of novel antioxidant molecules capable of detecting, preventing, and counteracting AD onset and progression is of the utmost importance. However, although several studies have been published, comprehensive and up-to-date overviews of the principal anti-AD agents harboring antioxidant properties remain scarce. In this narrative review, we summarize the role of vitamins, minerals, flavonoids, non-flavonoids, mitochondria-targeting molecules, organosulfur compounds, and carotenoids as non-enzymatic antioxidants with AD diagnostic, preventative, and therapeutic potential, thereby offering insights into the relationship between OS and neurodegeneration.

Nrf2 Pathway in Huntington's Disease (HD): What Is Its Role?

Huntington's disease (HD) is an autosomal dominant neurodegenerative disease that occurs worldwide. Despite some progress in understanding the onset of HD, drugs that block or delay symptoms are still not available. In recent years, many treatments have been proposed; among them, nuclear transcriptional factor-2 (Nrf2) enhancer compounds have been proposed as potential therapeutic agents to treat HD. Nrf2 triggers an endogenous antioxidant pathway activated in different neurodegenerative disorders. Probably, the stimulation of Nrf2 during either the early phase or before HD symptoms' onset, could slow or prevent striatum degeneration. In this review, we present the scientific literature supporting the role of Nrf2 in HD and the potential prophylactic and therapeutic role of this compound.

Role of Nrf2 in aging, Alzheimer's and other neurodegenerative diseases

Nuclear Factor-Erythroid Factor 2 (Nrf2) is an important transcription factor that regulates the expression of large number of genes in healthy and disease states. Nrf2 is made up of 605 amino acids and contains 7 conserved regions known as Nrf2-ECH homology domains. Nrf2 regulates the expression of several key components of oxidative stress, mitochondrial biogenesis, mitophagy, autophagy and mitochondrial function in all organs of the human body, in the peripheral and central nervous systems. Mounting evidence also suggests that altered expression of Nrf2 is largely involved in aging, neurodegenerative diseases, including Alzheimer's disease, Parkinson's disease, Huntington's diseases, Amyotrophic lateral sclerosis, Stroke, Multiple sclerosis and others. The purpose of this article is to detail the essential role of Nrf2 in oxidative stress, antioxidative defense, detoxification, inflammatory responses, transcription factors, proteasomal and autophagic/mitophagic degradation, and metabolism in aging and neurodegenerative diseases. This article also highlights the Nrf2 structural and functional activities in healthy and disease states, and also discusses the current status of Nrf2 research and therapeutic strategies to treat aging and neurodegenerative diseases.

Curcumin Interacts with α-Synuclein Condensates To Inhibit Amyloid Aggregation under Phase Separation

The amyloid aggregation of α-synuclein (α-Syn) is highly associated with Parkinson's disease (PD). Discovering α-Syn amyloid inhibitors is one of the strategies for PD therapies. Recent studies suggested that α-Syn undergoes phase separation to accelerate amyloid aggregation. Molecules modulating α-Syn phase separation or transition have the potential to regulate amyloid aggregation. Here, we discovered that curcumin, a small natural molecule, interacts with α-Syn during phase separation. Our study showed that curcumin neither affects the formation of α-Syn condensates nor influences the initial morphology of α-Syn condensates. However, curcumin decreases the fluidity of α-Syn inside the condensates and efficiently inhibits α-Syn from turning into an amyloid. It also inhibits the amyloid aggregations of PD disease-related α-Syn E46K and H50Q mutants under phase separation. Furthermore, curcumin can destabilize preformed α-Syn amyloid aggregates in the condensates. Together, our findings demonstrate that curcumin regulates α-Syn amyloid formation during protein phase separation and reveal that α-Syn amyloid aggregation under phase separation can be modulated by small molecules.

Curcumin as a Holistic Treatment for Tau Pathology

Global forecasts for prevalence of Alzheimer’s Disease (AD) estimate that 152.8 million people will have dementia in 2050, a sharp rise from 57.4 million in 2019 (GBD 2019). This rise can be attributable to increases in population growth and aging, but in the absence of disease-modifying therapies it poses a huge societal challenge that must be addressed urgently. One way to combat this challenge is to explore the utility of holistic treatments that may protect against AD, including traditional herbs, spices and other nutraceuticals that are pharmacologically safe, inexpensive and readily available. In this light, the spice turmeric, and its active ingredient curcumin, has been investigated as a potential holistic treatment for AD over the past 2 decades; however, promising results with animal studies have not translated to success in clinical trials. One issue is that most animal models examining the effects of curcumin and curcumin derivatives in AD have been done with a focus at ameliorating amyloid pathology. Due to the limited success of Amyloid-β-based drugs in recent clinical trials, tau-focused therapeutics provide a promising alternative. In this article, we aim to provide a clearer picture of what is currently known about the effectiveness of curcumin and curcumin derivatives to ameliorate tau pathology. Tau focused studies may help inform more successful clinical studies by placing greater emphasis on the development and optimised delivery of curcumin derivatives that more effectively target tau pathology.

A review on Huntington protein Insight into protein aggregation and therapeutic interventions

Huntington disease (HD) is a distressing, innate neurodegenerative disease that descends from CAG repeat expansion in the huntingtin gene causing behavioral changes, motor dysfunction, and dementia in children and adults. Mutation in huntingtin (HTT) protein has been suggested to cause neuron loss in the cortex and striatum through various mechanisms including abnormal regulation of transcription, proteasomal dysfunction, post-translational modification, and other events, regulating toxicity. Pathogenesis of HD involves cleavage of the huntingtin protein followed by the neuronal accumulation of its aggregated form. Several research groups made possible efforts to reduce huntingtin gene expression, protein accumulation, and protein aggregation using inhibitors and molecular chaperones as developing drugs against HD. Herein, we review the mechanism proposed towards the formation of HTT protein aggregation and the impact of therapeutic strategies for the treatment of HD.

Natural Compounds as Promising Adjuvant Agents in The Treatment of Gliomas

In humans, glioblastoma is the most prevalent primary malignant brain tumor. Usually, glioblastoma has specific characteristics, such as aggressive cell proliferation and rapid invasion of surrounding brain tissue, leading to a poor patient prognosis. The current therapy-which provides a multidisciplinary approach with surgery followed by radiotherapy and chemotherapy with temozolomide-is not very efficient since it faces clinical challenges such as tumor heterogeneity, invasiveness, and chemoresistance. In this respect, natural substances in the diet, integral components in the lifestyle medicine approach, can be seen as potential chemotherapeutics. There are several epidemiological studies that have shown the chemopreventive role of natural dietary compounds in cancer progression and development. These heterogeneous compounds can produce anti-glioblastoma effects through upregulation of apoptosis and autophagy; allowing the promotion of cell cycle arrest; interfering with tumor metabolism; and permitting proliferation, neuroinflammation, chemoresistance, angiogenesis, and metastasis inhibition. Although these beneficial effects are promising, the efficacy of natural compounds in glioblastoma is limited due to their bioavailability and blood-brain barrier permeability. Thereby, further clinical trials are necessary to confirm the in vitro and in vivo anticancer properties of natural compounds. In this article, we overview the role of several natural substances in the treatment of glioblastoma by considering the challenges to be overcome and future prospects.

Curcumin-cisplatin chemotherapy: A novel strategy in promoting chemotherapy efficacy and reducing side effects

The efficacy of chemotherapy in cancer therapy is limited due to resistance, treatment selectivity, and severe adverse effects. Immunotherapy, chemotherapy, targeted therapy, radiation, and surgery are the most common therapeutic strategies for treatment, with chemotherapy being the most successful. Nonetheless, these treatments exhibit poor effectiveness due to toxicity and resistance. Therefore, combination therapies of natural products may be used as an effective and novel strategy to overcome such barriers. Cisplatin is a platinum-based chemotherapy agent, and when administered alone, it can lead to severe adverse effects and resistance mechanism resulting in therapeutic failure. Curcumin is a polyphenolic compound extracted from turmeric (Curcuma longa) exhibiting anticancer potential with minimal adverse effects. The combination therapy of curcumin and cisplatin is a novel strategy to mitigate/attenuate cisplatin-related adverse effects and improve the barrier of resistance reducing unwanted effects. However, there are uncertainties on the efficacy of curcumin, and more in depth and high-quality studies are needed. This review aims to explain the adverse effects related to individual cisplatin delivery, the positive outcome of individual curcumin delivery, and the combination therapy of curcumin and cisplatin from nano platform as a novel strategy for cancer therapy.

Epigenetic regulation by polyphenols in diabetes and related complications

Diabetes mellitus (DM) is a chronic metabolic disorder and one of the most challenging health problems worldwide. Left untreated, it may progress causing serious complications. Genetics, epigenetics, and environmental factors are known to play an overlapping role in the pathogenesis of DM. Growing evidence suggests the hypothesis that the environment induces changes in the early phases of growth and development, influencing health and disease in the adulthood through the alteration in genetic expression of an individual, at least in part. DNA methylation, histone modifications and miRNAs are three mechanisms responsible for epigenetic alterations. The daily diet contains a number of secondary metabolites, with polyphenols being highest in abundance, which contribute to overall health and may prevent or delay the onset of many chronic diseases. Polyphenols have the ability to alter metabolic and signaling pathways at various levels, such as gene expression, epigenetic regulation, protein expression and enzyme activity. The potential efficacy of polyphenolic compounds on glucose homeostasis has been evidenced from in vitro, in vivo and clinical studies. The present review is designed to focus on epigenetic regulation exerted by polyphenolic compounds in DM and their complications, as well as to summarize clinical trials involving polyphenols in DM.