Biology subjects

Franklin, B. S.

Publications and source records attributed to Franklin, B. S..

6 recordsLinked to original sources

bioRxiv2025

NLRP3 is a thermosensor that is negatively regulated by high temperature

Inflammation is an essential response to infection and injury, but unregulated inflammation is damaging and must be limited by negative feedback signalling. Inflammasome signalling drives local inflammation and systemic responses like fever. However, our understanding of how inflammasome signalling is negatively regulated is limited. NLRP3 is activated by a vast number of stimuli and senses perturbations of cytoplasmic homeostasis. As temperature is a fundamental environmental stressor, we hypothesised that NLRP3 inflammasome signalling would be sensitive to increased temperatures and so we investigated the effects of high temperatures on NLRP3 in macrophages. Short-term incubation at high fever range temperatures significantly inhibits NLRP3 activation, while secretion of the inflammasome-independent cytokines TNF and IL-6 are much less affected. High temperature blocks NLRP3 inflammasome formation in a transcription-independent manner, and NLRP3 is highly sensitive to temperature-mediated inhibition relative to the NLRC4, AIM2, and NLRP1 inflammasomes. Using cellular assays and molecular simulations we show that the effect of high temperature on NLRP3 is protein intrinsic. NLRP3 activation is associated with a decrease in the thermal stability of the protein and multiscale molecular dynamics simulations identified a peptide in the C-terminal of the FISNA domain (COFI) that is highly flexible and undergoes a significant conformational shift at high temperature. Cellular assays demonstrate that the COFI regulates NLRP3 stability and is required for activation. Furthermore, mice exposed to high temperature display attenuated inflammatory cytokine production upon in vivo LPS challenge. Our studies thus reveal that high temperatures associated with fever limit NLRP3 activity and identify a novel role for NLRP3 as a protein thermosensor.

immunology↗

bioRxiv2022

Platelets supply p38 MAPK signaling that licenses pro-inflammatory cytokine responses of human monocytes

CD14+ monocytes, the predominant population in human blood, are primarily engaged in host defense and pro-inflammatory cytokine responses. Aberrant monocyte activity causes life-threatening cytokine storms, while dysfunctional monocytes lead to immunoparalysis. Understanding the mechanisms controlling monocyte functions is therefore paramount. Here, we reveal platelets vital role in human monocytes pro-inflammatory responses. Low platelet counts in immune thrombocytopenia (ITP) patients, or platelet depletion in healthy monocytes result in monocyte immunoparalysis, characterized by reduced pro-inflammatory gene expression and weakened cytokine responses to immune challenge. Remarkably, adding fresh platelets reverses monocyte immunoparalysis. In mice, thrombocytopenia results in down-regulation of myeloid innate immune genes, and compromised host defense transcriptional programs in monocytes despite normal responses to LPS. Platelets control monocyte cytokines independently of traditional cross-talk pathways, acting as reservoirs of transcription factors like NF{kappa}B and MAPK p38. We pinpointed megakaryocyte-derived NF{kappa}B2 transfer to human monocytes by mass spectrometry-based proteomics. Functionally, platelets proportionally restored impaired cytokine secretion in human monocytes lacking p38a and NF{kappa}B. We unveil the intercellular transfer of inflammatory regulators, positioning platelets as central checkpoints in monocyte-mediated inflammation. Key PointsO_LIPlatelets are essential to TLR and NLR cytokine responses of human monocytes, C_LIO_LIImmune thrombocytopenia leads to monocyte immunoparalysis; C_LIO_LIPlatelet supplementation reverses monocyte immunoparalysis; C_LIO_LIPlatelets transfer NF{kappa}B that reactivates cytokine production in genetically deficient monocytes. C_LI

immunology↗

bioRxiv2022

IL-33 regulates age-dependency of long-term immune dysfunction induced by sepsis

Sepsis survival in adults is commonly followed by immunosuppression and increased susceptibility to secondary infections. However, the long-term immune consequences of pediatric sepsis are unknown. Here, we compared the frequency of Tregs, the activation of the IL-33/ILC2s axis in M2 macrophages, and the DNA methylation of epithelial lung cells from post-septic infant and adult mice. In contrast to adults, infant mice were resistant to secondary infection and did not show impairment in tumour controls upon melanoma challenge. Mechanistically, increased IL-33 levels, Tregs expansion, and activation of ILC2s and M2-macrophages were observed in post-septic adults but not infant mice. Impaired IL-33 production in post-septic infant mice was associated with increased DNA-methylation on lung epithelial cells. Notably, IL-33 treatment boosted the expansion of Tregs and induced immunosuppression in infant mice. Clinically, adults but not pediatric post-septic patients exhibited higher counts of Tregs and sera IL-33 levels. Hence, we describe a crucial and age-dependent role for IL-33 in post-sepsis immunosuppression.

immunology↗

bioRxiv2020

A distinct fingerprint of inflammatory mediators and miRNAs in Plasmodium vivax severe thrombocytopenia

BackgroundSevere thrombocytopenia can be a determinant factor in the morbidity of Plasmodium vivax (Pv), the most widespread human malaria. Although immune mechanisms may drive Pv-induced severe thrombocytopenia (PvST), the current data on the cytokine landscape in PvST is scarce, and often conflicting. The analysis of the bidirectional circuit of inflammatory mediators and miRNAs would lead to a better understanding of the mechanisms underlying PvST. MethodsWe combined Luminex proteomics, NanoString miRNA quantification, and machine learning, to evaluate an extensive array of plasma mediators in uncomplicated Pv patients, whose blood platelet counts varied from reference values to PvST. ResultsUnsupervised clustering analysis identified PvST-linked signatures comprised of both inflammatory (CXCL10, CCL4, and IL-18) and regulatory (IL-10, IL-1Ra, HGF) mediators. As part of PvST signatures, IL-6 and IL-8 were critical to discriminate Pv subgroups, while CCL2 and IFN-{gamma} from healthy controls. Supervised machine learning spotlighted IL-10 in Pv-mediated thrombocytopenia, and provided evidence for a potential signaling route involving IL-8 and HGF. Finally, we identified a set of miRNAs capable of modulating these signaling pathways. ConclusionsThe results place IL-10 and IL-8/HGF in the center of PvST and propose investigating these signaling pathways across the spectrum of malaria infections.

microbiology↗

bioRxiv2019

Platelets fuel the inflammasome activation of innate immune cells

The inflammasomes control the bioactivity of pro-inflammatory cytokines of the interleukin (IL)-1 family. The inflammasome assembled by NLRP3 has been predominantly studied in homogenous cell populations in vitro, neglecting the influence of cellular interactions that occur in vivo. Here, we show that platelets, the second most abundant cells in the blood, boost the inflammasome capacity of human macrophages and neutrophils, and are critical for IL-1 production by monocytes. Platelets license NLRP3 transcription, thereby enhancing ASC nucleation, caspase-1 activity, and IL-1{beta} maturation. Platelet depletion attenuated LPS-induced IL-1{beta} in vivo, and platelet counts correlate with plasma concentrations of IL-1{beta} in malaria patients. Furthermore, a platelet gene signature was enriched among the highest expressed transcripts in IL-1{beta}-driven autoinflammatory diseases. The platelet-mediated enhancement of inflammasome activation was independent of cell-to-cell contacts, platelet-derived lipid mediators, purines, nucleic acids and a host of platelet cytokines, and involved the triggering of calcium sensing receptors on macrophages by a calcium-dependent protein commonly released by platelets and megakaryocytes. Finally, we report that platelets provide an additional layer of regulation of inflammasomes in vivo.

immunology↗

bioRxiv2018

Charcot-Leyden Crystals activate the NLRP3 inflammasome and cause IL-1β inflammation

Charcot-Leyden crystals (CLCs) are Galectin-10 protein crystals that can form after eosinophils degranule. CLCs can appear and persist in tissues from patients with eosinophilic disorders, such as asthma, allergic reactions, fungal, and helminthic infections. Despite abundant reports of their occurrence in human disease, the inflammatory potential of CLCs has remained unknown. Here we show that CLCs induce IL-1{beta} release upon their uptake by primary human macrophages in vitro, and that they induce inflammation in vivo in mouse models of acute peritonitis and bronchitis. CLC-induced IL-1{beta} was dependent on NLRP3 and caspase-1, and their instillation in inflammasome reporter mice promoted the assembly of ASC complexes and IL-1{beta} secretion in the lungs. Our findings reveal that CLCs are recognized by the NLRP3 inflammasome, which may sustain inflammation that follows eosinophilic inflammatory processes.

immunology↗