Glioblastomas (GBMs) are tumors that have a high ability to migrate, invade and proliferate in the healthy tissue, what greatly impairs their treatment. These characteristics are associated with the complex microenvironment, formed by the perivascular niche, which is also composed of several stromal cells including astrocytes, microglia, fibroblasts, pericytes and endothelial cells, supporting tumor progression. Further microglia and macrophages associated with GBMs infiltrate the tumor. These innate immune cells are meant to participate in tumor surveillance and eradication, but they become compromised by GBM cells and exploited in the process. In this review we discuss the context of the GBM microenvironment together with the actions of flavonoids, which have attracted scientific attention due to their pharmacological properties as possible anti-tumor agents. Flavonoids act on a variety of signaling pathways, counteracting the invasion process. Luteolin and rutin inhibit NFκB activation, reducing IL-6 production. Fisetin promotes tumor apoptosis, while inhibiting ADAM expression, reducing invasion. Naringenin reduces tumor invasion by down-regulating metalloproteinases expression. Apigenin and rutin induce apoptosis in C6 cells increasing TNFα, while decreasing IL-10 production, denoting a shift from the immunosuppressive Th2 to the Th1 profile. Overall, flavonoids should be further exploited for glioma therapy.

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.

Background: Glioblastomas (GBMs) are the most aggressive and common neoplasms that affect glial cells, presenting rapid growth, invasion, and resistance to treatments. Studies have demonstrated the potentially inhibitory effect of flavonoids on glioblastoma cells’ stemness and viability. However, further research is needed to explore sensitivity and the mechanism of action in chemoresistant cells. Methods: In this study, we characterized the impact of apigenin treatment on the viability and differentiation of human GBM cells in vitro and its effects on tumorigenesis and regulation of the inflammatory response in vivo. Results: The flavonoid apigenin reduced the viability of U-251 cells, patient-derived cells TG-1 and OB-1 stem cells in a dose-dependent manner, associated with the induction of acidic vesicle organelles formation and apoptosis. Treatment with apigenin also inhibited migration and induced neural differentiation in the remaining viable cells, characterized by a decrease in the expression of the precursor marker nestin and an increase in the expression of astrocyte and neuron markers, GFAP and β-III tubulin, respectively. The xenotransplantation of apigenin-pretreated U251 cells into rat brains did not lead to tumor formation, unlike untreated cells. The surrounding area of transplanted untreated U251 cells exhibited reactive microglia and astrocytes, along with increased VEGF expression, which was absent in implant sites of apigenin-pretreated GBM cells. Moreover, in this implant area, we observed a significant decrease in the expression of mRNA for inflammatory factors IL-1β, TNF, and NOS2, and the downregulation of IL-10 and IL-4. Conclusions: These results demonstrate that apigenin inhibits the growth of tumoral cells, affecting the viability of tumor stem cells and impairing tumorigenicity, while altering the regulatory profile of immunomodulatory proteins. Therefore, this flavonoid can be considered for further studies to determine its use as an adjuvant to the treatment of human GBMs.

Nuclear receptors such as glucocorticoid receptors (GRs) are transcription factors with prominent regulatory effects on neuroinflammation. Agathisflavone is a biflavonoid that demonstrates neurogenic, neuroprotective, anti-inflammatory, antioxidant, and pro-myelinogenic effects in vitro. This study investigated whether the control of glial reactivity by agathisflavone is mediated by GRs. Primary cultures of astrocytes and microglia were induced to neuroinflammation by lipopolysaccharides (LPSs) and exposed to agathisflavone or not in the presence or absence of mifepristone, a GR antagonist. The microglia morphology and reactivity were evaluated by immunofluorescence against calcium-binding ionized adapter (Iba-1) and CD68. The astrocyte morphology and reactivity were evaluated by immunofluorescence against glial fibrillary acidic protein (GFAP). The inflammatory profile was evaluated by RT-qPCR. Molecular docking was performed to characterize agathisflavone and GR interactions. Microglial branching was increased in response to agathisflavone, an effect that was inhibited by mifepristone. CD68 and GFAP expression was decreased by agathisflavone but not in the presence of mifepristone. Agathisflavone decreased the expression of the pro-inflammatory cytokine IL-1β and increased the expression of the regulatory cytokine IL-10. The increase in IL-10 mRNA was inhibited by the GR antagonist. The in silico analysis showed that agathisflavone binds to a pocket at the glucocorticoid receptor. These interactions were stronger than mifepristone, dexamethasone, and the agathisflavone monomer apigenin. These results indicate that the GR is involved in the regulatory effects of agathisflavone on microglia and astrocyte inflammation, contributing to the elucidation of the molecular mechanisms of agathisflavone’s effects in the nervous system.

Introduction: Glioblastoma (GBM) is the most aggressive primary tumor of the central nervous system and is highly resistant to temozolomide (TMZ). Rutin is a potent antioxidant with immunomodulatory and anti-glioma effects in vitro, although its mechanisms of action remain incompletely understood. This study investigated the effects of rutin on morphology, viability, redox balance, and pro-tumoral signaling in GBM 2D cultures and 3D spheroids, as well as its association with TMZ sensitivity. Methods: GL15 and U343 human GBM cell lines and primary astrocytes were treated with rutin (5–30 μM) and/or TMZ (125–4000 μM). Cell metabolic activity and viability were assessed by MTT, PI/DiOC18(3) or PI/Hoechst. Cell migration was assessed from spheroid-derived cells, and extracellular matrix (ECM) components (fibronectin and laminin) were evaluated by immunofluorescence. Intracellular reactive oxygen species (ROS) were measured by DCFH-DA fluorescence. IL-6, STAT3, NOS2, and IDO1 gene expression were determined by RT-qPCR, and protein expression of MMP2, fibronectin, STAT3, PI3K, and AKT by Western blotting. Nitric oxide (NO) and L-kynurenine levels were quantified in the supernatant by colorimetric assays. Results: Rutin reduced cell viability and enhanced TMZ cytotoxicity in both 2D and 3D cultures, while exerting selective effects by increasing metabolic activity and attenuating TMZ-induced effects in non-tumoral primary astrocytes. In 3D spheroids, rutin affected structural organization and reduced spheroid-derived cell migration, accompanied by changes in ECM components, including MMP2, fibronectin, and laminin. Rutin decreased intracellular ROS levels and suppressed the TMZ-induced increase in ROS and NOS signaling. These effects were accompanied by modulation of IL-6/STAT3 signaling, along with reduced STAT3, PI3K, and AKT protein levels. Rutin also modulated immunometabolic parameters, including extracellular L-kynurenine and nitric oxide levels, and enhanced TMZ responsiveness following pre-sensitization. Conclusions: Rutin enhances TMZ responsiveness by modulating interconnected pro-tumoral mechanisms, including redox balance, pro-survival signaling, ECM remodeling and migratory behavior, and immunometabolic pathways linked to chemoresistance, supporting its potential as an adjuvant therapeutic strategy.

Introduction: Rutin is a heterocyclic flavonol glycoside found in plants like apples, citrus fruits and buckwheat, with demonstrated anti-inflammatory properties. However, the molecular mechanisms underlying rutin’s direct effects on microglia, the main immune effector cells in the central nervous system, are not fully understood. The SHH/GLI-1 pathway is a neuronal repair pathway that modulates microglial activity and cell proliferation. Objective: For better compression of the rutin anti-inflammatory effects, this work evaluated the action of rutin on SHH/GLI-1 regulation. Methodology: For this, primary cultures of microglia from postnatal P0–2 days Wistar rats were stimulated with LPS (1 µg/mL) and/or treated with rutin (0.5–1 µM). Microglia morphology was characterized by immunofluorescence for Iba1. Gene expression of cytokines, inflammasome, glial-derived neurotrophic factors (GDNFs), and Sonic Hedgehog and family zinc finger-1 (SHH/GLI) were evaluated by real-time qPCR. Result: The results demonstrated that rutin inhibited the LPS-induced inflammatory response in microglia regulating negatively TNF-alpha, IL-6, and NLR family pyrin domain-containing 3 (NLRP3) mRNA expression. In addition, rutin increased GDNF and SHH-GLI-1 mRNA expression. Furthermore, conditioned medium from rutin-treated microglia showed a protective effect on PC-12 cells against LPS-induced cytotoxicity, reducing cell death as measured by the propidium iodide test and preserving cell morphology. Conclusions: This is the first evidence of the effect of rutin in SHH-GLI-1 signaling, contributing to the understanding of its pharmacological mechanisms and potentially revealing new molecular targets for treatment of neuroinflammatory diseases.