Biology subjects

Irimia, D.

Publications and source records attributed to Irimia, D..

9 recordsLinked to original sources

bioRxiv2025

Plasmodium falciparum subverts neutrophil function via host miR-451a loaded extracellular vesicles driving bacterial superinfection susceptibility

Malaria caused by Plasmodium falciparum (Pf) compromise innate immunity, yet the underlying mechanisms remain elusive. The immune dysregulation caused by the parasite may lead to bacterial superinfections and increase mortality. We reveal that Pf exploits extracellular vesicles (EVs) secreted by infected red blood cells (iRBC-EVs) to deliver host-derived miR451a to human neutrophils, impairing their antimicrobial defences. Neutrophil phagocytosis of iRBC-EVs suppresses reactive oxygen species (ROS) production and compromised microbicidal activity against Salmonella typhimurium. Microfluidic assays show that miR451a transfer significantly disrupts neutrophil chemotaxis and swarming upon microbial challenge. Transcriptomic profiling indicates that EVs and miR451a reprogram neutrophil gene expression, notably upregulating ferroptosis-related genes, suggesting a role in further impairing immune responses. We have uncovered a novel mechanism of iRBC-EVs-induced neutrophil immune suppression and provide insights into increased susceptibility to bacterial superinfections in malaria. These findings have implications for therapeutic strategies aimed at mitigating bacterial superinfections and sepsis in malaria-endemic regions.

immunology↗

bioRxiv2023

Self-extinguishing relay waves enable homeostaticcontrol of human neutrophil swarming

Neutrophils exhibit self-amplified swarming to sites of injury and infection. How swarming is controlled to ensure the proper level of neutrophil recruitment is unknown. Using an ex vivo model of infection, we find that human neutrophils use active relay to generate multiple pulsatile waves of swarming signals. Unlike classic active relay systems such as action potentials, neutrophil swarming relay waves are self-extinguishing, limiting the spatial range of cell recruitment. We identify an NADPH-oxidase-based negative feedback loop that is needed for this self-extinguishing behavior. Through this circuit, neutrophils adjust the number and size of swarming waves for homeostatic levels of cell recruitment over a wide range of initial cell densities. We link a broken homeostat to neutrophil over-recruitment in the context of human chronic granulomatous disease.

cell biology↗

bioRxiv2022

Predestined neutrophil heterogeneity in homeostasis varies in transcriptional and phenotypic response to Candida

Once perceived to be homogenous effector cells, neutrophils have since been shown to exhibit population heterogeneity. Here, we established an experimental model of clonal neutrophil heterogeneity using conditionally immortalized clonal granulocyte monocyte progenitors (GMPs) and their mature neutrophil progeny. Transcriptional and epigenetic profiling showed conserved genome-wide signatures of transcription and chromatin accessibility that were specific to individual GMP clones and their paired neutrophil progeny, suggesting that clone specificity is established as early as the GMP stage. Clone-specific genes in vital regulatory pathways were pre-programmed and exhibited delayed expression in the mature neutrophil stage. The clone-specific gene expression in the mature neutrophils paired to enhancer activation in their parental GMPs. To determine whether transcriptional heterogeneity predicted the response to fungal pathogens, neutrophil clones were functionally profiled. Clones demonstrated heterogeneous responses to fungal pathogens in vitro and revealed neutrophil subsets with evidence for tailored functional responses to Candida spp. as well as specific transcriptional and epigenetic patterns that may explain these differences. Together, this work establishes that heterogenous GMP and neutrophil compartments exist under homeostatic conditions and that these represent predefined clusters that are uniquely adapted to control invasive fungal pathogens. Short SummaryClonal neutrophil progenitors demonstrate heterogeneity in transcription and chromatin accessibility which may inform response to later fungal challenges.

immunology↗

bioRxiv2022

Mechanical competition promotes selective listening to receptor inputs to resolve directional dilemmas in neutrophil migration

As neutrophils navigate complex environments to reach sites of infection, they may encounter obstacles that force them to split their front into multiple leading edges, raising the question of how the cell selects which front to maintain and which front(s) to abandon. Here we challenge chemotaxing HL60 neutrophil-like cells with symmetric bifurcating microfluidic channels, enabling us to probe the cell-intrinsic properties of their decision-making process. Using supervised statistical learning, we demonstrate that cells commit to one leading edge late in the decision- making process, rather than amplifying early pre-existing asymmetries. Furthermore, we use optogenetic tools to show that receptor inputs only bias the decision similarly late, once mechanical stretching begins to weaken each front. Finally, optogenetic attempts to reverse cell decisions reveal that, once an edge begins retracting, it commits to this fate, with the kinase ROCK limiting its sensitivity to inputs until the retraction is complete. Collectively our results suggest a "selective listening" model in which both actively protruding cell fronts and actively retracting cell rears have strong commitment to their current migratory program.

cell biology↗

bioRxiv2021

Neutrophil Profiles of Pediatric COVID-19 and Multisystem Inflammatory Syndrome in Children

Multisystem Inflammatory Syndrome in Children (MIS-C) is a delayed-onset, COVID-19-related hyperinflammatory systemic illness characterized by SARS-CoV-2 antigenemia, cytokine storm and immune dysregulation; however, the role of the neutrophil has yet to be defined. In adults with severe COVID-19, neutrophil activation has been shown to be central to overactive inflammatory responses and complications. Thus, we sought to define neutrophil activation in children with MIS-C and acute COVID-19. We collected samples from 141 children: 31 cases of MIS-C, 43 cases of acute pediatric COVID-19, and 67 pediatric controls. We found that MIS-C neutrophils display a granulocytic myeloid-derived suppressor cell (G-MDSC) signature with highly altered metabolism, which is markedly different than the neutrophil interferon-stimulated gene (ISG) response observed in pediatric patients during acute SARS-CoV-2 infection. Moreover, we identified signatures of neutrophil activation and degranulation with high levels of spontaneous neutrophil extracellular trap (NET) formation in neutrophils isolated from fresh whole blood of MIS-C patients. Mechanistically, we determined that SARS-CoV-2 immune complexes are sufficient to trigger NETosis. Overall, our findings suggest that the hyperinflammatory presentation of MIS-C could be mechanistically linked to persistent SARS-CoV-2 antigenemia through uncontrolled neutrophil activation and NET release in the vasculature. One Sentence SummaryCirculating SARS-CoV-2 antigen:antibody immune complexes in Multisystem Inflammatory Syndrome in Children (MIS-C) drive hyperinflammatory and coagulopathic neutrophil extracellular trap (NET) formation and neutrophil activation pathways, providing insight into disease pathology and establishing a divergence from neutrophil signaling seen in acute pediatric COVID-19.

immunology↗

bioRxiv2021

Directional reorientation of migrating neutrophils is limited by suppression of receptor input signaling at the cell rear through myosin II activity

To migrate efficiently to target locations, cells must integrate receptor inputs while maintaining polarity: a distinct front that leads and a rear that follows. Here we investigate what is necessary to overwrite pre-existing front/rear polarity in neutrophil-like HL60 cells migrating inside straight microfluidic channels. Using subcellular optogenetic receptor activation, we show that receptor inputs can reorient weakly polarized cells, but the rear of strongly polarized cells is refractory to new inputs. Transient stimulation reveals a multi-step repolarization process, confirming that cell rear sensitivity to receptor input is the primary determinant of large-scale directional reversal. We demonstrate that the RhoA/ROCK/myosin II pathway limits the ability of receptor inputs to signal to Cdc42 and reorient migrating neutrophils. We discover that by tuning the phosphorylation of myosin regulatory light chain we can modulate the activity and localization of myosin II and thus the amenability of the cell rear to listen to receptor inputs and respond to directional reprogramming.

cell biology↗

bioRxiv2019

Dynamics of diffusive cell signaling relays

Cells can communicate with each other by emitting diffusible signaling molecules into the surrounding environment. However, simple diffusion is slow. Even small molecules take hours to diffuse millimeters away from their source, making it difficult for thousands of cells to coordinate their activity over millimeters, as happens routinely during development and immune response. Moreover, simple diffusion creates shallow, Gaussian-tailed concentration profiles. Attempting to move up or down such shallow gradients - to chemotax - is a difficult task for cells, as they see only small spatial and temporal concentration changes. Here, we demonstrate that cells utilizing diffusive relays, in which the presence of one type of diffusible signaling molecule triggers participation in the emission of the same type of molecule, can propagate fast-traveling diffusive waves that give rise to steep chemical gradients. Our methods are general and capture the effects of dimensionality, cell density, signaling molecule degradation, pulsed emission, and cellular chemotaxis on the diffusive wave dynamics. We show that system dimensionality - the size and shape of the extracellular medium and the distribution of the cells within it - can have a particularly dramatic effect on wave initiation and asymptotic propagation, and that these dynamics are insensitive to the details of cellular activation. As an example, we show that neutrophil swarming experiments exhibit dynamical signatures consistent with the proposed signaling motif. Interpreted in the context of these experiments, our results provide insight into the utility of signaling relays in immune response.

biophysics↗

bioRxiv2019

Megakaryocytes Display Innate Immune Cell Functions and Respond during Sepsis

Megakaryocytes (MKs) are precursors to platelets, the second most abundant cells in the peripheral circulation. However, while platelets are known participate in immune responses and play significant roles during infections, the role of MKs within the immune system has not been explored. Here we utilize in vitro techniques to show that both cord blood-derived MKs (CB MKs) and MKs from a human megakaryoblastic leukemia cell line (Meg-01) chemotax towards pathogenic stimuli, phagocytose bacteria, and release chromatin webs in response to bacteria. Moreover, in patients with sepsis, we found that MK counts were significantly higher in the peripheral blood, and CD61+ staining was increased in the kidneys and lungs, correlated with the development of organ dysfunction. Overall, our study suggests that MK cells display basic innate immune cell functions and respond during infections and sepsis.

immunology↗

bioRxiv2019

Chemotaxis and swarming in differentiated HL60 neutrophil-like cells

Human leukemia cell line (HL-60) is an alternative to primary neutrophils in research studies. However, because HL-60 cells proliferate in an incompletely differentiated state, they must undergo differentiation before they acquire the functional properties of neutrophils. Here we provide evidence of swarming and chemotaxis in HL-60 neutrophil-like cells using precision microfluidic assays. We found that dimethyl sulfoxide (DMSO) differentiated HL-60 cells have larger size, increased length, and lower ability to squeeze through narrow channels compared to primary neutrophils. They migrate through tapered microfluidic channels slower than primary neutrophils, but faster than HL60s differentiated by other protocols, e.g. using all-trans retinoic acid. We found that differentiated HL-60 can swarm toward zymosan particle clusters, though they display disorganized migratory patterns and produce swarms of smaller size compared to primary neutrophils.

cell biology↗