Biology subjects

Palsa, K.

Publications and source records attributed to Palsa, K..

6 recordsLinked to original sources

bioRxiv2026

Iron-deficiency in the tumor microenvironment reprograms tumor-immune interactions in a sex biased manner

BackgroundGlioblastoma (GBM) is a sex-biased disease characterized by higher incidence and poorer survival in males. These sex differences are primarily driven by metabolic and immune signatures, with iron metabolism playing a major role. While iron is essential for tumor cell proliferation, it is also critical for T cell recruitment and function within the tumor microenvironment (TME). Clinical data indicates that iron deficiency impacts GBM survival in a sex-biased manner; however, the underlying mechanisms remain unexplored. MethodsWe employed a FTH1 heterozygous knockdown mouse model to induce tumor iron deficiency in GBM-bearing mice. TME dynamics were interrogated using flow cytometry and spatial transcriptomics (10X Xenium) to analyze immune infiltration, localization, and ligand-receptor signaling between GBM and immune cells. ResultsFTH1 knockdown resulted in iron deficiency in the GBM TME. Iron deficiency altered the TME dynamics in a sex biased manner. FTH1 knockdown in females caused an anti-inflammatory, cytokine deficient TME which failed to recruit CD4 and CD8 T cells. In males, FTH1 knockdown caused a proinflammatory environment by activating the innate immune response. Additionally, FTH1 knockdown increased the density of TAMs in the immediate surrounding of GBM cells in a sex biased manner. ConclusionThese results demonstrate that tumor iron plays a sex-biased role in immune infiltration and anti-tumor immunity.

cancer biology↗

bioRxiv2025

Tumor-associated macrophages protect glioblastoma cells from ferroptosis by inducing the release of ferritin-bound iron via exosomes.

Tumor-associated macrophages (TAMs) are the most abundant non-tumor cell type in glioblastoma (GBM) and act as the pivotal cell type in regulating iron metabolism in the GBM tumor microenvironment. High TAM infiltration into the TME is also associated with increased resistance to ferroptosis, an iron-dependent cell death. However, the exact mechanism by which TAMs make the cancer cells resistant to ferroptosis remains relatively unexplored. Here, we have investigated how TAMs modify iron metabolism in GBM cells to make them more resistant to ferroptotic stress. We utilized GL261 cells, a GBM cell line derived from C57BL6 mice, and syngeneic primary murine bone marrow-derived macrophages (BMDM) to study GBM-TAM interactions in vitro. We found that male macrophages exhibited higher iron uptake, greater iron storage, and a larger labile iron pool compared to female macrophages, indicating intrinsic sex biases in macrophage iron metabolism. Subsequently, we used co-culture experiments to study how macrophages regulate the iron and ferroptotic status of GL261 cells. We discovered that GL261 cells cocultured with BMDMs showed higher resistance to RSL3-induced ferroptotic stress. Mechanistically, BMDMs caused a decrease in total cellular iron in GL261 cells by inducing increased H-ferritin-bound iron release via CD63-positive exosomes; thus, limiting the amount of iron that is available for lipid peroxidation during ferroptosis. This process was moderately sex biased in favor of male macrophages. Finally, we show that this mechanism of BMDM-induced resistance to ferroptosis is independent of Hepcidin regulation and can act as a possible pathway by which GBM cells escape ferroptotic stress during proinflammatory conditions.

cancer biology↗

bioRxiv2025

Extracellular vesicles released from endothelial cells of the blood-brain barrier mediate brain Iron accumulation during LPS-induced brain Inflammation

IntroductionBrain inflammation leads to an increase in the amount of iron in brain tissue; however, studies do not address the source of the iron that could lead to the accumulation. Most of the brain iron uptake is mediated through the blood-brain barrier (BBB), but studies have not examined whether inflammation increases or decreases iron flux across the BBB. Our recent in vitro study discovered a novel alternate mechanism that iron transport across the BBB is mediated via the extracellular vesicles (EVs). Herein, we investigated the impact of brain inflammation on iron release and iron transport via EVs from the brain microvasculature (BMV). MethodsFor this study, we developed an in vivo brain inflammation model. We induced brain inflammation in three-month-old C57BL/6 by intracerebroventricular injection of lipopolysaccharide (LPS,12g/mice). For in vitro, we used human blood-brain barrier endothelial cells derived from human-induced pluripotent stem cells (hiPSCs). We separated the BMV from brain parenchyma by using density gradient centrifugation. To inhibit the EVs synthesis, we injected intraperitoneally for 21 days GW4869 (60g/mice), an inhibitor of neutral sphingomyelinase 2, a key regulatory enzyme necessary for EV formation. The brain EVs were isolated by ultracentrifugation. We measured the BMV and parenchyma iron concentration by Inductively coupled plasma mass spectrometry (ICP-MS). Furthermore, we performed immunoblotting to measure the protein expression in BMV and EVs. ResultsThe LPS injection activated microglia and astrocytes as well as increased the brain proinflammatory cytokines compared to the control mice. Furthermore, brain inflammation increased the iron levels in the brain parenchyma but decreased the iron levels in BMV. Brain inflammation was associated with the degradation of ferroportin (FPN1), an iron exporter, in the BMV. CD63, an EVs membrane protein, was increased in the BMV and associated with increased FTH1-iron release via EVs from BMVs to the brain. Moreover, brain inflammation induced iron deficiency in BMV as evidenced by an increase in the transferrin receptor and decreased FTH1, suggestive of increased iron uptake. Pharmacological reduction of EVs by GW4869 reduced iron accumulation in the inflamed brain parenchyma compared to control mice. ConclusionThis is the first study to demonstrate that EV inhibition decreases iron in the brain. Degradation of FPN1 in the BMV during inflammation did not limit iron accumulation but there was an increase in FTH1-iron-enriched EVs indicating these are responsible for brain iron accumulation during inflammation. Thus, in summary, we have discovered a novel mechanism that involves BMV-released EVs enriched with iron that is the mechanism for brain iron accumulation during inflammation.

neuroscience↗

bioRxiv2023

Amyloid-β exposed astrocytes induce iron transport from endothelial cells at the blood-brain barrier by altering the ratio of apo- and holo-transferrin

Excessive brain iron accumulation is observed in early in the onset of Alzheimers disease, notably prior to widespread proteinopathy. These findings suggest that increases in brain iron levels are due to a dysregulation of the iron transport mechanism at the blood-brain barrier. Astrocytes release signals (apo- and holo-transferrin) that communicate brain iron needs to endothelial cells in order to modulate iron transport. Here we use iPSC-derived astrocytes and endothelial cells to investigate how early-disease levels of amyloid-{beta} disrupt iron transport signals secreted by astrocytes to stimulate iron transport from endothelial cells. We demonstrate that conditioned media from astrocytes treated with amyloid-{beta} stimulates iron transport from endothelial cells and induces changes in iron transport pathway protein levels. The mechanism underlying this response begins with increased iron uptake and mitochondrial activity by the astrocytes which in turn increases levels of apo-transferrin in the amyloid-{beta} conditioned astrocyte media leading to increased iron transport from endothelial cells. These novel findings offer a potential explanation for the initiation of excessive iron accumulation in early stages of Alzheimers disease. Whats more, these data provide the first example of how the mechanism of iron transport regulation by apo- and holo-transferrin becomes misappropriated in disease to detrimental ends. The clinical benefit from understanding early dysregulation in brain iron transport in AD cannot be understated. If therapeutics can target this early process, they could possibly prevent the detrimental cascade that occurs with excessive iron accumulation. Significance StatementExcessive brain iron accumulation is hallmark pathology of Alzheimers disease that occurs early in the disease staging and before widespread proteinopathy deposition. This overabundance of brain iron has been implicated to contribute to disease progression, thus understandingthe mechanism of early iron accumulation has significant therapeutic potential to slow to halt disease progression. Here, we show that in response to low levels of amyloid-{beta} exposure, astrocytes increase their mitochondrial activity and iron uptake, resulting in iron deficient conditions. Elevated levels of apo (iron free)-transferrin stimulate iron release from endothelial cells. These data are the first to propose a mechanism for the initiation of iron accumulation and the misappropriation of iron transport signaling leading to dysfunctional brain iron homeostasis and resultant disease pathology.

neuroscience↗

bioRxiv2023

Apo- and holo- transferrin differentially interact with ferroportin and hephaestin to regulate iron release at the blood-brain barrier

AO_SCPLOWBSTRACTC_SCPLOWO_ST_ABSBackgroundC_ST_ABSApo- (iron free) and holo- (iron bound) transferrin (Tf) participate in precise regulation of brain iron uptake at endothelial cells of the blood-brain barrier. Apo-Tf indicates an iron deficient environment and stimulates iron release, while holo-Tf indicates an iron sufficient environment and suppresses additional iron release. Free iron is exported through ferroportin, with hephaestin as an aid to the process. Until now, the molecular mechanism of apo- and holo-Tfs influence on iron release was largely unknown. MethodsHere we use a variety of cell culture techniques, including co-immunoprecipitation and proximity ligation assay, in iPSC-derived endothelial cells and HEK 293 cells to investigate the mechanism of apo- and holo-Tfs influence over iron release. We placed our findings in physiological context by further deciphering how hepcidin played a role in this mechanism as well. ResultsWe demonstrate that holo-Tf induces the internalization of ferroportin through the established ferroportin degradation pathway. Furthermore, holo-Tf directly binds to ferroportin, whereas apo-Tf directly binds to hephaestin. Only pathological levels of hepcidin disrupt the interaction between holo-Tf and ferroportin, and no amount of hepcidin disrupts the interaction between apo-Tf and hephaestin. The disruption of the holo-Tf and ferroportin interaction by hepcidin is due to hepcidins ability to rapidly internalize ferroportin compared to holo-Tf. ConclusionsThese novel findings provide a molecular mechanism for apo- and holo-Tf regulation of iron release from endothelial cells. They further demonstrate how hepcidin impacts these protein-protein interactions, and offer a model for how holo-Tf and hepcidin corporate to suppress iron release. We have established a more thorough understanding of the mechanisms behind iron release regulation with great clinical impact for a variety of neurological conditions in which iron release is dysregulated.

cell biology↗

bioRxiv2022

Iron Inhibits Glioblastoma Cell Migration and Polarization

Glioblastoma is one of the deadliest malignancies facing modern oncology today. The ability of glioblastoma cells to diffusely spread into neighboring healthy brain makes complete surgical resection nearly impossible and contributes to the recurrent disease faced by most patients. Although research into the impact of iron on glioblastoma has addressed proliferation, there has been little investigation into how cellular iron impacts the ability of glioblastoma cells to migrate - a key question especially in the context of the diffuse spread observed in these tumors. Herein, we show that increasing cellular iron content results in decreased migratory capacity of human glioblastoma cells. The decrease in migratory capacity was accompanied by a decrease in cellular polarization in the direction of movement. Expression of CDC42, a Rho GTPase that is essential for both cellular migration and establishment of polarity in the direction of cell movement, was reduced upon iron treatment. Bioinformatic analysis of CDC42 mRNA revealed a potential iron-responsive element that may contribute to the regulation of CDC42 by iron. We then analyzed a single-cell RNA-seq dataset of human glioblastoma samples and found that cells at the tumor periphery had a gene signature that is consistent with having lower levels of cellular iron. Altogether, our results suggest that cellular iron content is impacting glioblastoma cell migratory capacity and that cells with higher iron levels exhibit reduced motility.

cancer biology↗