Biology subjects

Kourtzelis, I.

Publications and source records attributed to Kourtzelis, I..

6 recordsLinked to original sources

bioRxiv2025

Artemether and Euphorbia Factor L9 suppress kynurenine production through distinct effects on Tryptophan metabolism.

L-Tryptophan (Trp) is an essential amino acid, catabolised through the kynurenine pathway, which is mediated by the enzymes indoleamine-2,3-dioxygenase 1 (IDO1), IDO2, or Trp-2,3-deoxygenase (TDO). Therapeutic targeting of Trp metabolism could be relevant to several pathologies. In cancer, IDO1 acts as an immune checkpoint suppressing effector T cell function. Yet, direct inhibition of IDO1 has had limited success in clinical trials. Therefore, alternative approaches to Trp metabolism therapeutic targeting are needed. We screened a library of 597 natural products (NPs) or NP derivatives for their effect on kynurenine production in triple negative breast cancer cells. This revealed 24 candidate inhibitors of kynurenine production. Amongst them, artemether, a member of the artemisinin family of anti-malarial drugs, suppressed kynurenine production, likely via an endoperoxide bridge-dependent mechanism. The Euphorbia factor L9 (EFL9) inhibited kynurenine production likely via a C7-benzoylation-dependent mechanism. Neither artemether nor EFL9 affected JAK/STAT signaling or IDO1 levels. Targeted metabolomics analyses demonstrated that artemether suppressed kynurenine production through heme sequestration, a mechanism that would affect all members of the IDO/TDO family of metalloenzymes. EFL9 affected purine and amino acid metabolism and the cellular redox balance. Comparisons to the effects of ouabain, a NP regulator of IDO1 levels, and Linrodostat, a clinically used small molecule IDO1 inhibitor, revealed distinct metabolic profiles, with ouabain and EFL9 showing the largest overlap. Importantly, the kynurenine-suppressing activity of artemether and EFL9 is not cancer cell-specific. Overall, our findings set the foundation for the use of derivatives of artemether or EFL9 as novel Trp metabolism-targeting therapeutics.

cancer biology↗

bioRxiv2024

Trained innate immunity attenuates macrophage efferocytosis of cancer cells

Macrophage phagocytosis has been implicated in regulating anti-tumour immunity. Trained innate immunity (TII), induced via modulation of mature myeloid cells or their bone marrow progenitors, mediates sustained increased responsiveness to secondary challenges. Despite the advances in the study of TII-mediated anti-tumour activity, the impact of TII on the orchestration of phagocytosis in the tumour setting requires further elucidation. Here, we investigated whether macrophage phagocytosis of tumour cells can be modulated through induction of TII. To this end, mice were pre-treated with {beta}-glucan, a fungal-derived agonist of TII, and bone marrow was isolated for macrophage differentiation. Macrophages were then co-cultured with tumour cells that were either apoptotic or opsonised with an antibody recognising a tumour antigen, to mimic efferocytosis and antibody-dependent cellular phagocytosis (ADCP), respectively. While TII did not have any impact in the modulation of ADCP, efferocytosis was decreased in trained macrophages. Along the same line, gene expression analysis demonstrated that mRNA levels of molecules promoting efferocytosis were downregulated in trained macrophages. Trained macrophages exerted decreased levels of active caspase-1 and produced decreased levels of interleukin-1{beta} upon efferocytosis of tumour cells. Our findings reveal a hitherto unknown role of TII in the regulation of anti-tumour immunity and may set the stage for designing new cancer immunotherapeutic approaches targeting macrophage efferocytosis.

immunology↗

bioRxiv2024

Malat1 regulates female Th2 cell cytokine expression through controlling early differentiation and response to IL2

Identifying cell intrinsic regulators of immune sexual dimorphism is critical for treatment of several immunopathologies. We show that Malat1 is required for appropriate cytokine expression in female but not male Th2 cells. Malat1 deficiency impairs in vitro Th2 differentiation of naive CD4+ T cells from female mice, characterised by transcriptome-wide effects and suppression of cytokine expression, particularly IL10. Upon IL10R blockade a pronounced effect is also seen on IL4 and IL13. Mechanistically, naive CD4+ T cells from Malat1-/- female mice demonstrate altered early activation kinetics and impaired early differentiation gene expression, including up-regulation of an interferon stimulated gene (ISG) module. This is followed by suppression of IL2R and IL2R{gamma} expression and IL2-mediated differentiation. Mimicking the effect of Malat1 loss by maintaining early ISG expression in WT cells with IFN{beta} treatment partially phenocopies the effects of Malat1 deficiency. A subset of the effects of Malat1 loss in female cells is also observed in male cells. However, this does not affect endpoint Th2 differentiation. Male CD4+ T cells demonstrate stronger early activation, higher ISG expression during early differentiation, maintenance of IL2R expression independently of Malat1, and lower sensitivity to exogenous IL2 during late differentiation compared to female cells. In vivo, female, but not male, Malat1-/- mice demonstrate altered Th2 cytokine expression characterised by a reduction in IL10+ Th2 cells in both lung and spleen following priming and challenge with Schistosoma mansoni eggs, a model of lung type 2 inflammation. Overall, these findings reveal Malat1 as a novel determinant of immune sexual dimorphism.

immunology↗

bioRxiv2024

Macrophage-derived developmental endothelial locus 1 (DEL-1) expression promotes an immunoprotective phenotype in experimental visceral leishmaniasis.

The identification of tissue-derived homeostatic molecules regulating immune plasticity is essential for understanding the role of macrophages in immune responses to intra-phagosomal pathogens. Developmental endothelial locus-1 (DEL-1) is a functionally versatile homeostatic factor capable of inhibiting the onset of inflammation and promoting inflammation resolution, but its role in the response to intracellular infections has not been previously addressed. Leishmania, causative agents of the neglected tropical disease leishmaniasis, are intra-phagosomal parasites that establish a replicative niche within macrophages. Here, using a well-established murine model of visceral infection with Leishmania donovani, we establish DEL-1 as a novel regulator of immunity to this infection. Parasite burden was significantly higher in B6.Edil3-/- (Del1-KO) compared to wild type B6 mice, as determined by whole body IVIS imaging, largely as a result of increased liver parasite load. However, lack of DEL-1 enhanced hepatomegaly and enhanced granulomatous inflammation. Conversely, parasite burden and the formation of large granulomas was reduced in mice overexpressing DEL-1 in macrophages but not in endothelial cells. Our findings reveal a hitherto unknown role of DEL-1 in the immune response to L. donovani infection and may represent a novel approach to mitigate immunopathology.

immunology↗

bioRxiv2020

HIF2α is a Direct Regulator of Neutrophil Motility

Orchestrated recruitment of neutrophils to inflamed tissue is essential during initiation of inflammation. Inflamed areas are usually hypoxic, and adaptation to reduced oxygen pressure is typically mediated by hypoxia pathway proteins. However, it is still unclear how these factors influence the migration of neutrophils to and at the site of inflammation either during their transmigration through the blood-endothelial cell barrier, or their motility in the interstitial space. Here, we reveal that activation of the Hypoxia Inducible Factor-2 (HIF2) due to deficiency of HIF-prolyl hydroxylase domain protein-2 (PHD2) boosts neutrophil migration specifically through highly confined microenvironments. In vivo, the increased migratory capacity of PHD2-deficient neutrophils resulted in massive tissue accumulation in models of acute local inflammation. Using systematic RNAseq analyses and mechanistic approaches, we identified RhoA, a cytoskeleton organizer, as the central downstream factor that mediates HIF2-dependent neutrophil motility. Thus, we propose that the here identified novel PHD2-HIF2-RhoA axis is vital to the initial stages of inflammation as it promotes neutrophil movement through highly confined tissue landscapes.

immunology↗

bioRxiv2019

Heme induces innate immunity memory

Trained immunity defines long-lasting adaptive responses of innate immunity, mediated by transcriptional and epigenetic modifications of myeloid cells. Here, we report that labile heme, an alarmin released extracellularily upon tissue damage and hemolysis, induces trained immunity in human and murine primary cells and in mice. Heme-trainning in monocytes is associated with epigenetic and transcriptional profiles that overlap to some extent with those seen in {beta}-glucan-training, the prototype agonist of trained immunity. In sharp contrast to {beta}-glucan training however, heme-training relied on activation of the Syk/JNK-pathway. Heme training in mice was associated with long-lasting expansion of myeloid-biased progenitor cells as well as with altered chromatin accessibility in hematopoietic stem and progenitor cells. Finally, heme-induced training was protective against bacterial sepsis in mice. In conclusion, we reveal that heme, a bona fide alarmin, induces innate immune memory regulating host response to infection.

immunology↗