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Leong, K.

Publications and source records attributed to Leong, K..

4 recordsLinked to original sources

A Selective Multivalent NET-Associated Chromatin Neutralizer Resolves Infection-Associated Inflammation in Severe Sepsis

Targeting the overwhelming inflammation driven by neutrophil extracellular traps (NETs) during infection provides an opportunity to manage severe sepsis. This potential needs to be realized by exploring selective NET-neutralization materials, which remains a challenge. Herein, we report a multivalent macromolecular strategy that targets NET-associated DNA-histone chromatin complexes while preserving antibacterial activity of aminoglycoside. We identify 8-arm PEG-conjugated netilmicin (8-arm Netil) as a lead NETs-neutralizer from a library of multivalent aminoglycoside-displayed materials. When compared with 2- and 4-arm counterparts, 8-arm Netil exhibits potent antibacterial activity and high-affinity binding to DNA-histone chromatin complexes through stable multivalent noncovalent interactions, thereby suppressing NET-induced TLR4/TLR9 activation and macrophage inflammatory responses. In severe septic mice, intravenously administered 8-arm Netil preferentially accumulates in inflamed tissues, leading to improved survival protection, owing to the reduction of bacterial dissemination, NET accumulation, systemic cytokine production, and multiple-organ injury. These findings establish NET-associated DNA-histone chromatin complexes as actionable extracellular targets and demonstrate multivalent chromatin targeting as a rational material design strategy for selective NET neutralization and inflammation control in severe sepsis.

bioengineering↗

Mitofusin agonists enhances long-term engraftment and potency of cultured hematopoietic stem cells

Umbilical cord blood (CBU) is a valuable source of hematopoietic stem cells (HSCs) due to lower incidence of graft-versus-host disease. However, limited HSC counts restrict use in adults, necessitating improved methods for ex vivo expansion and improved HSC function. Mitofusin 2 (MFN2), a mitochondrial membrane fusion protein, is necessary for preserving HSC function and mitofusin agonists have been characterized. We report ex vivo culture of CBU HSCs with mitofusin agonists (MAs) enhances long-term repopulating activity by over five-fold in both primary and secondary transplantation assays without changes of total nucleated cells or phenotypic HSCs. Mechanistically, MA-treated HSCs show suppressed protein synthesis, increased autophagic flux, and elevated lysosomal mass. Transcriptomic analysis implicates downregulation of MTOR signaling, and immunoprecipitation studies suggest MFN2 interacts with MTOR. These data support a model in which fusion-competent MFN2 sequesters MTOR, promoting a catabolic state that preserves HSC potency. Our findings suggest a novel MFN2-MTOR regulatory axis that enhances the function of human HSCs cultured ex vivo for potential therapeutic application.

cell biology↗

Spatiotemporal Mapping of brain cilia length and orientation reveals region-specific Oscillation

In this study, we conducted high-throughput spatiotemporal analysis of primary cilia length and orientation across 22 mouse brain regions. We developed automated image analysis algorithms, which enabled us to examine over 10 million individual cilia, generating the largest spatiotemporal atlas of cilia. We found that cilia length and orientation display substantial variations across different brain regions and exhibit fluctuations over a 24-hour period, with region-specific peaks during light-dark phases. Our analysis revealed unique orientation patterns of cilia at 45{degrees} intervals, suggesting that cilia orientation within the brain is not random but follows specific patterns. Using BioCycle, we identified circadian rhythms of cilia length in five brain regions: nucleus accumbens core, somatosensory cortex, and three hypothalamic nuclei. Our findings present novel insights into the complex relationship between cilia dynamics, circadian rhythms, and brain function, highlighting cilia crucial role in the brains response to environmental changes and regulation of time-dependent physiological processes. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=138 SRC="FIGDIR/small/546950v3_ufig1.gif" ALT="Figure 1"> View larger version (37K): org.highwire.dtl.DTLVardef@153135corg.highwire.dtl.DTLVardef@11c1d7eorg.highwire.dtl.DTLVardef@d47014org.highwire.dtl.DTLVardef@10a65ca_HPS_FORMAT_FIGEXP M_FIG C_FIG

neuroscience↗

A histone methylation-MAPK signaling axis drives durable epithelial-mesenchymal transition in hypoxic pancreas cancer

Here, we show that hypoxia drives especially long-lasting epithelial-mesenchymal transition (EMT) in pancreatic ductal adenocarcinoma (PDAC) primarily through a positive-feedback histone methylation-MAPK signaling axis. We find that transformed cells preferentially undergo EMT in hypoxic tumor regions in multiple model systems and that hypoxia drives a cell-autonomous EMT in PDAC cells which, unlike EMT in response to growth factors, can last for weeks. We further demonstrate that hypoxia reduces histone demethylase KDM2A activity, suppresses PP2 family phosphatase expression, and activates MAPKs to post-translationally stabilize histone methyltransferase NSD2, leading to an H3K36me2-dependent EMT in which hypoxia-inducible factors play only a supporting role. This mechanism can be antagonized in vivo by combinations of MAPK inhibitors that may be effective in multi-drug therapies designed to target EMT.

cancer biology↗