Neuroimmunomodulatory Properties of Flavonoids and Derivates: A Potential Action as Adjuvants for the Treatment of Glioblastoma

Naringenin Exhibits Antiglioma Activity Related to Aryl Hydrocarbon Receptor Activity and IL-6, CCL2, and TNF-α Expression

BACKGROUND

Glioblastoma (GBM) is a highly aggressive brain tumor characterized by rapid cell proliferation, invasive behavior, and chemoresistance. The aryl hydrocarbon receptor (AhR) is implicated in chemoresistance and immune evasion, making it a promising therapeutic target. Natural compounds such as flavonoids have gained attention for their anti-inflammatory, antioxidant, and anticancer properties. Among them, naringenin, a citrus-derived flavonoid, exerts antiproliferative, pro-apoptotic, and immunomodulatory effects.

OBJECTIVES

This study investigated the antiglioma effects of the flavonoid naringenin on the viability, growth, and migration of glioma cells and its potential role as an AhR modulator.

METHODS

Human (U87) and rat (C6) glioma cell lines were exposed to naringenin (10-300 µM) alone or in combination with the AhR agonist indole-3-carbinol (50 µM) for 24 to 48 h. Cell viability, scratch wound, and cell migration assays were performed. The expression of inflammatory markers was also analyzed by RT-qPCR.

RESULTS

Naringenin exerted dose- and time-dependent inhibition of cell viability and migration. The treatment decreased the gene expression of interleukin-6 (IL-6) and chemokine (CCL2), alongside increased tumor necrosis factor-alpha (TNF-α) expression, an effect reversed by the AhR agonist.

CONCLUSIONS

These findings highlight naringenin's potential as an antiglioma agent and its role in AhR signaling.

Regulation of adipokine and batokine secretion by dietary flavonoids, as a prospective therapeutic approach for obesity and its metabolic complications

Traditionally recognised as the energy reservoir and main site of adaptive thermogenesis, white and brown adipose tissues are complex endocrine organs regulating systemic energy metabolism via the secretion of bioactive molecules, termed "adipokines" and "batokines", respectively. Due to its significant role in regulating whole-body energy metabolism and other physiological processes, adipose tissue has been increasingly explored as a feasible therapeutic target for obesity. Flavonoids are one of the most significant plant polyphenolic compounds holding a great potential as therapeutic agents for combating obesity. However, understanding their mechanisms of action remains largely insufficient to formulate therapeutic theories. This review critically discusses scientific evidence highlighting the role of flavonoids in ameliorating obesity-related metabolic complications, including adipose tissue dysfunction, inflammation, insulin resistance, hepatic steatosis, and cardiovascular comorbidities in part by modulating the release of adipokines and batokines. Further discussion advocates for the use of therapeutics targeting these bioactive molecules as a potential avenue for developing effective treatment for obesity and its adverse metabolic diseases such as type 2 diabetes.

Agathisflavone Inhibits Viability and Modulates the Expression of miR-125b, miR-155, IL-6, and Arginase in Glioblastoma Cells and Microglia/Macrophage Activation

Glioblastomas (GBM) are malignant tumours with poor prognosis. Treatment involves chemotherapy and/or radiotherapy; however, there is currently no standard treatment for recurrence, and prognosis remains unfavourable. Inflammatory mediators and microRNAs (miRNAs) influence the aggressiveness of GBM, being involved in the communication with the cells of the tumour parenchyma, including microglia/macrophages, and maintaining an immunosuppressive microenvironment. Hence, the modulation of miRNAs and inflammatory factors may improve GBM treatments. In this study, we investigated the effects of agathisflavone, a biflavonoid purified from Cenostigma pyramidale (Tul.), on the growth and migration of GBM cells, on the expression of inflammatory cytokines and microRNAs, as well on the response of microglia. Agathisflavone (5-30 μM) induced a dose- and time-dependent reduction in the viability of both human GL-15 and rat C6 cells, as determined by the MTT test, and reduced cell migration, as determined by cell scratch assay. RT-qPCR analysis revealed that agathisflavone (5 μM) down-regulated the expression of miR-125b and miR-155 in the secretome derived from GL-15 cells, which was associated with upregulation of the mRNA expression of IL-6 and arginase-1 immunoregulatory factors. Exposure of human microglia/macrophage to the secretome from GL-15 GMB cells modulated proliferation and morphology, effects that were modulated by agathisflavone treatment. These results demonstrate the effect of flavonoids on the growth of GBM cells, which impacts cells in the microenvironment and can be considered for preclinical studies for adjuvant treatments.

Antitumor Effect of Butia odorata Hydroalcoholic Extract on C6 and U87MG Glioma Cell Lines: Impact on Redox Status and Inflammation Signaling

Among the spectrum of gliomas, glioblastoma stands out as the most aggressive brain tumor affecting the central nervous system. In addressing this urgent medical challenge, exploring therapeutic alternatives becomes imperative to enhance the patient's prognosis. In this regard, Butia odorata (BO) fruit emerges as a promising candidate due to its array of bioactive compounds, including flavonoids, phenolic acids, and carotenoids, known for their antioxidant, anti-inflammatory, and antitumor properties. Thus, this study aimed to investigate the impact of standardized hydroalcoholic extract of BO on rat C6 and human U87MG glioma cell lines. Cells were exposed to varying extract concentrations (125-2000 μg/mL) for intervals of 0, 2, 4, 6, 24, 48, or 72 h. Then, cell viability, proliferation, colony formation, redox equilibrium parameters, cell migration, and the relative mRNA expression of genes related to gliomagenesis were evaluated. Our findings revealed a reduction in viability, proliferation, colony formation, reactive oxygen species, and nitrite levels in both glioma cell lines upon exposure to the extract. Conversely, an increase in sulfhydryl content and the activity of superoxide dismutase and catalase were observed in both glioma cell lines. No significant changes in viability and proliferation were observed in astrocytes. Furthermore, in the C6 cells only, the BO extract reduced the migration and downregulated the relative mRNA expression of matrix metalloproteinase-2, O6-methylguanine-DNA methyltransferase, nuclear factor-kappa B, interleukin-6 genes, and upregulated caspase-3 gene. These results underscore the promising anti-glioma potential of BO extract, attributed to its diverse bioactive composition.

Preparation and Pharmacokinetics of Brain-Targeted Nanoliposome Loaded with Rutin

Rutin is a flavonoid compound with potential for treating Alzheimer's disease, preventing brain damage, mitigating cerebral ischemia-reperfusion injury, and exhibiting anti-glioblastoma activity. However, its efficacy is limited by its low solubility, poor bioavailability, and limited permeability across the blood-brain barrier (BBB). To enhance the bioavailability and brain-targeting ability of Rutin, transferrin-modified Rutin liposome (Tf-Rutin-Lip) was developed using liposomes as a delivery system. Rutin liposomes were prepared using the thin-film dispersion method, and the preparation conditions were optimized using the response surface methodology. Then, transferrin (Tf) was incorporated into the liposomes through covalent modification, yielding Tf-Rutin liposomes. The toxicity of these liposomes on bEnd.3 cells, as well as their impact on the tight junctions of these cells, was rigorously evaluated. Additionally, in vitro and in vivo experiments were conducted to validate the brain-targeting efficacy of the Tf-Rutin liposomes. A susceptible detection method was developed to characterize the pharmacokinetics of Tf-Rutin-Lip further. The optimized conditions for the preparation of Tf-Rutin-Lip were determined as follows: a lipid-to-cholesterol ratio of 4.63:1, a drug-to-lipid ratio of 1:45.84, a preparation temperature of 42.7 °C, a hydration volume of 20 mL, a sonication time of 10 min, a surfactant concentration of 80 mg/mL, a DSPE-MPEG-2000 concentration of 5%, and a DSPE-PEG2000-COOH to DSPE-MPEG-2000 molar ratio of 10%. The liposomes did not affect the cell activity of bEnd.3 cells at 24 h and did not disrupt the tight junction of the blood-brain barrier. Tf-modified liposomes were taken up by bEnd.3 cells, which, in turn, passed through the BBB, thus improving liposomal brain targeting. Furthermore, the results of pharmacokinetic experiments showed that the Cmax, AUC0-∞, AUC0-t, MRT0-∞, and t1/2 of Tf-Rutin-Lip increased 1.99-fold, 2.77-fold, 2.58-fold, 1.26-fold, and 1.19-fold compared to those of free Rutin solution, respectively. These findings suggest that Tf-Rutin-Lip is brain-targeted and may enhance the efficacy of Rutin in the treatment of brain disorders.

Neuroprotective Effect of Flavonoid Agathisflavone in the Ex Vivo Cerebellar Slice Neonatal Ischemia

Agathisflavone is a flavonoid that exhibits anti-inflammatory and anti-oxidative properties. Here, we investigated the neuroprotective effects of agathisflavone on central nervous system (CNS) neurons and glia in the cerebellar slice ex vivo model of neonatal ischemia. Cerebellar slices from neonatal mice, in which glial fibrillary acidic protein (GFAP) and SOX10 drive expression of enhanced green fluorescent protein (EGFP), were used to identify astrocytes and oligodendrocytes, respectively. Agathisflavone (10 μM) was administered preventively for 60 min before inducing ischemia by oxygen and glucose deprivation (OGD) for 60 min and compared to controls maintained in normal oxygen and glucose (OGN). The density of SOX-10+ oligodendrocyte lineage cells and NG2 immunopositive oligodendrocyte progenitor cells (OPCs) were not altered in OGD, but it resulted in significant oligodendroglial cell atrophy marked by the retraction of their processes, and this was prevented by agathisflavone. OGD caused marked axonal demyelination, determined by myelin basic protein (MBP) and neurofilament (NF70) immunofluorescence, and this was blocked by agathisflavone preventative treatment. OGD also resulted in astrocyte reactivity, exhibited by increased GFAP-EGFP fluorescence and decreased expression of glutamate synthetase (GS), and this was prevented by agathisflavone pretreatment. In addition, agathisflavone protected Purkinje neurons from ischemic damage, assessed by calbindin (CB) immunofluorescence. The results demonstrate that agathisflavone protects neuronal and myelin integrity in ischemia, which is associated with the modulation of glial responses in the face of ischemic damage.

Insights of immune cell heterogeneity, tumor-initiated subtype transformation, drug resistance, treatment and detecting technologies in glioma microenvironment

BACKGROUND

With the gradual understanding of glioma development and the immune microenvironment, many immune cells have been discovered. Despite the growing comprehension of immune cell functions and the clinical application of immunotherapy, the precise roles and characteristics of immune cell subtypes, how glioma induces subtype transformation of immune cells and its impact on glioma progression have yet to be understood.

AIM OF THE REVIEW

In this review, we comprehensively center on the four major immune cells within the glioma microenvironment, particularly neutrophils, macrophages, lymphocytes, myeloid-derived suppressor cells (MDSCs), and other significant immune cells. We discuss (1) immune cell subtype markers, (2) glioma-induced immune cell subtype transformation, (3) the mechanisms of each subtype influencing chemotherapy resistance, (4) therapies targeting immune cells, and (5) immune cell-associated single-cell sequencing. Eventually, we identified the characteristics of immune cell subtypes in glioma, comprehensively summarized the exact mechanism of glioma-induced immune cell subtype transformation, and concluded the progress of single-cell sequencing in exploring immune cell subtypes in glioma.

KEY SCIENTIFIC CONCEPTS OF REVIEW

In conclusion, we have analyzed the mechanism of chemotherapy resistance detailly, and have discovered prospective immunotherapy targets, excavating the potential of novel immunotherapies approach that synergistically combines radiotherapy, chemotherapy, and surgery, thereby paving the way for improved immunotherapeutic strategies against glioma and enhanced patient outcomes.

Natural Flavonoid Apigenin, an Effective Agent Against Nervous System Cancers

Cancer is a serious public health concern worldwide, and nervous system (NS) cancers are among the most life-threatening malignancies. Efforts have been devoted to introduce natural anticancer agents with minimal side effects. Apigenin is an edible flavonoid that is abundantly found in many vegetables and fruits. Various pharmaceutical activities, including anti-inflammatory, antioxidative, antimicrobial, and anticancer effects have been reported for apigenin. This review provides insights into the therapeutic effects of apigenin and flavonoids with similar structure on glioblastoma and neuroblastoma. Current evidence indicates that apigenin has the unique ability to cross the blood-brain barrier, and its antioxidative, anti-inflammatory, neurogenic, and neuroprotective effects have made this flavonoid a great option for the treatment of neurodegenerative disorders. Meanwhile, apigenin has low toxicity on normal neuronal cells, while induces cytotoxicity on NS cancer cells via triggering several signal pathways and molecular targets. Anticancer effects of apigenin have been contributed to various mechanisms such as induction of cell cycle arrest and apoptosis, and inhibition of migration, invasion, and angiogenesis. Although apigenin is a promising pharmaceutical agent, its low bioavailability is an important issue that must be solved before introducing to clinic. Recently, nano-delivery of apigenin by liposomes and poly lactic-co-glycolide nanoparticles has greatly improved functionality of this agent. Hence, investigating pharmaceutical effects of apigenin-loaded nanocarriers on NS cancer cell lines and animal models is recommended for future studies.

Differential Interactions of Flavonoids with the Aryl Hydrocarbon Receptor In Silico and Their Impact on Receptor Activity In Vitro

The molecular mechanisms underlying the observed anticancer effects of flavonoids remain unclear. Increasing evidence shows that the aryl hydrocarbon receptor (AHR) plays a crucial role in neoplastic disease progression, establishing it as a potential drug target. This study evaluated the potential of hydroxy flavonoids, known for their anticancer properties, to interact with AHR, both in silico and in vitro, aiming to understand the mechanisms of action and identify selective AHR modulators. A PAS-B domain homology model was constructed to evaluate in silico interactions of chrysin, naringenin, quercetin apigenin and agathisflavone. The EROD activity assay measured the effects of flavonoids on AHR's activity in human breast cancer cells (MCF7). Simulations showed that chrysin, apigenin, naringenin, and quercetin have the highest AHR binding affinity scores (-13.14 to -15.31), while agathisflavone showed low scores (-0.57 and -5.14). All tested flavonoids had the potential to inhibit AHR activity in a dose-dependent manner in the presence of an agonist (TCDD) in vitro. This study elucidates the distinct modulatory effects of flavonoids on AHR, emphasizing naringenin's newly described antagonistic potential. It underscores the importance of understanding flavonoid's molecular mechanisms, which is crucial for developing novel cancer therapies based on these molecules.

Biosynthesis and Pharmacological Activities of the Bioactive Compounds of White Mulberry (Morus alba): Current Paradigms and Future Challenges

Traditional natural products have been the focus of research to explore their medicinal properties. One such medicinally important plant is the white mulberry, Morus alba, widely distributed in the Asian subcontinent. It is one of the most cultivated species of mulberry tree and has attracted more focus from researchers because of its abundance in phytochemicals as well as multipurpose uses. The leaves, fruits and other parts of the white mulberry plant act as a source of valuable bioactive compounds like flavonoids, phenolic acids, terpenoids and alkaloids. These secondary metabolites have manifold healthy uses as they possess antioxidant, anti-inflammatory, antidiabetic, neutrotrophic, and anticancer properties. Despite the increasing scientific interest in this plant, there are very few reviews that highlight the phytochemistry and biological potential of white mulberry for biomedical research. To this end, this review elaborates the phytochemistry, biosynthetic pathways and pharmacological activities of the glycoside flavonoids of Morus alba. A comprehensive analysis of the available literature indicates that Morus alba could emerge as a promising natural agent to combat diverse conditions including diabetes, cancer, inflammation and infectious diseases. To achieve such important objectives, it is crucial to elucidate the biosynthesis and regulation mechanisms of the bioactive compounds in white mulberry as well as the multifaceted pharmacological effects attributed to this plant resource. The present review paper is intended to present a summary of existing scientific data and a guide for further research in the phytochemistry and pharmacology of white mulberry. Further, a biosynthetic pathway analysis of the glycoside flavonoid in mulberry is also given. Lastly, we discuss the pros and cons of the current research to ensure the prudent and effective therapeutic value of mulberry for promoting human and animal health.

The Phytochemical Agathisflavone Modulates miR146a and miR155 in Activated Microglia Involving STAT3 Signaling

MicroRNAs (miRs) act as important post-transcriptional regulators of gene expression in glial cells and have been shown to be involved in the pathogenesis of neurodegenerative diseases, including Alzheimer's disease (AD). Here, we investigated the effects of agathisflavone, a biflavonoid purified from the leaves of Cenostigma pyramidale (Tul.), on modulating the expression of miRs and inflammatory mediators in activated microglia. C20 human microglia were exposed to oligomers of the β-amyloid peptide (Aβ, 500 nM) for 4 h or to lipopolysaccharide (LPS, 1 µg/mL) for 24 h and then treated or not with agathisflavone (1 µM) for 24 h. We observed that β-amyloid and LPS activated microglia to an inflammatory state, with increased expression of miR-146a, miR-155, IL1-β, IL-6, and NOS2. Treatment with agathisflavone resulted in a significant reduction in miR146a and miR-155 induced by LPS or Aβ, as well as inflammatory cytokines IL1-β, IL-6, and NOS2. In cells stimulated with Aβ, there was an increase in p-STAT3 expression that was reduced by agathisflavone treatment. These data identify a role for miRs in the anti-inflammatory effect of agathisflavone on microglia in models of neuroinflammation and AD.

Naringenin Nanoformulations for Neurodegenerative Diseases

Glioblastoma (GBM) is a grade-IV astrocytoma, which is the most common and aggressive type of brain tumor, spreads rapidly and has a life-threatening catastrophic effect. GBM mostly occurs in adults with an average survival time of 15 to 18 months, and the overall mortality rate is 5%. Significant invasion and drug resistance activity cause the poor diagnosis of GBM. Naringenin (NRG) is a plant secondary metabolite byproduct of the flavanone subgroup. NRG can cross the blood-brain barrier and deliver drugs into the central nervous system when conjugated with appropriate nanocarriers to overcome the challenges associated with gliomas through naringenin-loaded nanoformulations. Here, we discuss several nanocarriers employed that are as delivery systems, such as polymeric nanoparticles, micelles, liposomes, solid lipid nanoparticles (SLNs), nanosuspensions, and nanoemulsions. These naringenin-loaded nanoformulations have been tested in various in vitro and in vivo models as a potential treatment for brain disorders. This review nanoformulations of NRG can a possible therapeutic alternative for the treatment of neurological diseases are discussed.

Interactions between microglia and glioma in tumor microenvironment

Gliomas, the most prevalent primary tumors in the central nervous system, are marked by their immunosuppressive properties and consequent poor patient prognosis. Current evidence emphasizes the pivotal role of the tumor microenvironment in the progression of gliomas, largely attributed to tumor-associated macrophages (brain-resident microglia and bone marrow-derived macrophages) that create a tumor microenvironment conducive to the growth and invasion of tumor cells. Yet, distinguishing between these two cell subgroups remains a challenge. Thus, our review starts by analyzing the heterogeneity between these two cell subsets, then places emphasis on elucidating the complex interactions between microglia and glioma cells. Finally, we conclude with a summary of current attempts at immunotherapy that target microglia. However, given that independent research on microglia is still in its initial stages and has many shortcomings at the present time, we express our related concerns and hope that further research will be carried out to address these issues in the future.

Biological effects and mechanisms of fisetin in cancer: a promising anti-cancer agent

Fisetin, a natural flavonoid, possesses numerous biological activities that have been extensively studied in various diseases. When it comes to cancer, fisetin exhibits a range of biological effects, such as suppressing cell growth, triggering programmed cell death, reducing the formation of new blood vessels, protecting against oxidative stress, and inhibiting cell migration. Moreover, fisetin has the ability to enhance the effectiveness of chemotherapy. The anticancer properties of fisetin can be attributed to a diverse array of molecules and signaling pathways, including vascular endothelial growth factor (VEGF), mitogen-activated protein kinase (MAPK), nuclear factor-kappa B (NF-κB), PI3K/Akt/mTOR, and Nrf2/HO-1. Consequently, fisetin holds promise as a therapeutic agent for anticancer treatment. In this review, we place emphasis on the biological functions and various molecular targets of fisetin in anticancer therapy.

A Review of Classification, Biosynthesis, Biological Activities and Potential Applications of Flavonoids

Flavonoids represent the main class of plant secondary metabolites and occur in the tissues and organs of various plant species. In plants, flavonoids are involved in many biological processes and in response to various environmental stresses. The consumption of flavonoids has been known to reduce the risk of many chronic diseases due to their antioxidant and free radical scavenging properties. In the present review, we summarize the classification, distribution, biosynthesis pathways, and regulatory mechanisms of flavonoids. Moreover, we investigated their biological activities and discuss their applications in food processing and cosmetics, as well as their pharmaceutical and medical uses. Current trends in flavonoid research are also briefly described, including the mining of new functional genes and metabolites through omics research and the engineering of flavonoids using nanotechnology. This review provides a reference for basic and applied research on flavonoid compounds.

Quercetin Suppresses Human Glioblastoma Migration and Invasion via GSK3β/β-catenin/ZEB1 Signaling Pathway

High invasiveness is a biological and clinical characteristic of glioblastoma and predicts poor prognosis of patients. Quercetin, a natural flavonoid compound, exhibits anticancer activity. However, we have a limited understanding of the possible underlying mechanism of quercetin in glioblastoma. In this study, we investigated the anticancer effect of quercetin in human glioblastoma cells. Our results showed that quercetin markedly suppressed the viability of glioblastoma cells in vitro and in vivo, and significantly inhibited glioblastoma cell migration and invasion. Moreover, quercetin reversed EMT-like mesenchymal phenotype and reduced the expression levels of EMT-related markers. Furthermore, we found that quercetin suppressed GSK-3β/β-catenin/ZEB1 signaling in glioblastoma. Taken together, our results demonstrate that quercetin inhibited migration and invasion of human glioma cells by suppressing GSK3β/β-catenin/ZEB1 signaling. Our study provides evidence that quercetin is a promising therapeutic natural compound to treat glioblastoma.

A Novel CRISPR/Cas9 Screening Potential Index for Prognostic and Immunological Prediction in Low-Grade Glioma

Glioma is a malignancy with the highest mortality in central nervous system disorders. Here, we implemented the computational tools based on CRISPR/Cas9 to predict the clinical outcomes and biological characteristics of low-grade glioma (LGG). The transcriptional expression profiles and clinical phenotypes of LGG patients were retrieved from The Cancer Genome Atlas and Chinese Glioma Genome Atlas. The CERES algorithm was used to screen for LGG-lethal genes. Cox regression and random survival forest were adopted for survival-related gene selection. Nonnegative matrix factorization distinguished patients into different clusters. Single-sample gene set enrichment analysis was employed to create a novel CRISPR/Cas9 screening potential index (CCSPI), and patients were stratified into low- and high-CCSPI groups. Survival analysis, area under the curve values (AUCs), nomogram, and tumor microenvironment exploration were included for the model validation. A total of 20 essential genes in LGG were used to classify patients into two clusters and construct the CCSPI system. High-CCSPI patients were associated with a worse prognosis of both training and validation set (p < 0.0001) and higher immune fractions than low-CCSPI individuals. The CCSPI system had a promising performance with 1-, 3-, and 5-year AUCs of 0.816, 0.779, 0.724, respectively, and the C-index of the nomogram model reached 0.743 (95% CI = 0.725–0.760). Immune-infiltrating cells and immune checkpoints such as PD-1/PD-L1 and POLD3 were positively associated with CCSPI. In conclusion, the CCSPI had prognostic value in LGG, and the model will deepen our cognition of the interaction between the CNS and immune system in different LGG subtypes.