Biology subjects

Lim, K. L.

Publications and source records attributed to Lim, K. L..

7 recordsLinked to original sources

bioRxiv2026

IFN-γ-Dependent Macrophage Reprogramming Coordinates Inflammatory Resolution and Matrix Remodeling in Heart Regeneration

Heart regeneration requires coordinated immune activation, timely inflammatory resolution, and dynamic extracellular matrix (ECM) remodeling in addition to cardiomyocyte (CM) proliferation. However, the cytokine signals that instruct immune cell functions during cardiac repair remain incompletely understood. Here, we identify interferon-gamma (IFN-{gamma}) as a critical regulator of macrophage plasticity in zebrafish heart regeneration. IFN-{gamma} signaling components are dynamically activated following cardiac injury, with early induction of ifng1 and temporally coordinated receptor expression. Genetic ablation of ifng1 impairs myocardial regeneration, resulting in reduced CM proliferation and persistent fibrotic scarring. Temporal transcriptional profiling reveals sustained inflammatory signatures, impaired efferocytosis, and abolished reparative programs, accompanied by aberrant immune cell dynamics and retention of injury-derived debris in mutant hearts. Transcriptomic analysis of cardiac macrophages further reveals that IFN-{gamma} deficiency disrupts the transition from an inflammatory state to a reparative, ECM-remodeling phenotype, leading to reduced collagen denaturation and diminished CM protrusion at the injury border zone. Inducible- and macrophage-specific blockade of IFN-{gamma} signaling phenocopies defects in global knockout, establishing a cell-autonomous requirement for IFN-{gamma} in coordinating regenerative immune function. Collectively, our findings define an IFN-{gamma}-dependent macrophage reprogramming axis that couples inflammatory resolution to ECM remodeling in heart regeneration, elucidating how cytokine signaling actively instructs tissue repair. GRAPHICAL ABSTRACT O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=118 SRC="FIGDIR/small/712551v1_ufig1.gif" ALT="Figure 1"> View larger version (60K): org.highwire.dtl.DTLVardef@8cb384org.highwire.dtl.DTLVardef@15dd8d6org.highwire.dtl.DTLVardef@46dcc4org.highwire.dtl.DTLVardef@47e2ac_HPS_FORMAT_FIGEXP M_FIG C_FIG

developmental biology↗

bioRxiv2024

Lysosome-acidifying nanoparticles rescue A30P α-synuclein induced neuronal death in cellular and Drosophila models of Parkinson's disease

Parkinsons disease (PD) is an age-related neurodegenerative disease characterized by histopathological hallmarks of Lewy bodies formed by accumulation of -synuclein (Syn) and progressive loss of dopaminergic neurons in the substantia nigra pars compacta of the midbrain, with clinical symptoms of motor deficits. Toxic protein accumulation of Syn in PD is associated with autolysosomal acidification dysfunction that contributes to defective autophagy-lysosomal degradation system. While lysosome-acidifying nanoparticles have been applied as therapeutics to ameliorate dopaminergic neurodegeneration in neurotoxin mediated or Syn aggregates induced mouse model of sporadic PD, lysosome-targeted approach has not yet been applied in synucleinopathy models of familial PD. Here, we report the first application of the new poly(ethylene tetrafluorosuccinate-co-succinate) (PEFSU)-based acidic nanoparticles (AcNPs) in A30P Syn overexpressing SH-SY5Y cells and Drosophila models of PD. In the cellular model, we showed that AcNPs restore lysosomal acidification, promote autophagic clearance of Syn, improve mitochondrial turnover and function, and rescue A30P Syn induced death in SH-SY5Y cells. In the Drosophila model, we demonstrated that AcNPs enhance clearance of Syn and rescue dopaminergic neuronal loss in fly brains and improve their locomotor activity. Our results highlight AcNPs as a new class of lysosome-acidifying therapeutic for treatment of PD and other proteinopathies in general.

neuroscience↗

bioRxiv2023

Fluorescent Peptide-based Probe for the Detection of Alpha-synuclein Aggregates in the Gut

BackgroundParkinsons disease (PD) is diagnosed clinically by motor symptoms, with no molecular diagnostic test currently available. By the time motor symptoms manifest, significant irreversible neurodegeneration has already occurred, limiting the effectiveness of neuroprotective therapies and drug interventions. Recent identification of pathological alpha-synuclein (-syn) aggregates in the gastrointestinal (GI) tract of prodromal PD patients offer a potential avenue for early disease diagnosis. This study aims to explore specific fluorescence labelling of -syn aggregates in the GI tract using a peptide-based probe for early diagnosis of PD. MethodsWe used primary hippocampal neuronal cells and wild-type mouse tissues with the addition of pre-formed -syn fibrils to identify the most suitable peptide fluorescent probe (P1) for staining -syn aggregates in cells and tissues. We validated the probe labelling in GI tract tissues from three mouse models, including PFF-injected mice and two transgenic PD mouse strains. We quantified labelling accuracy by confocal imaging and protein analysis. ResultsWe found that P1 labelled -syn aggregates with high accuracy (87% in comparison to Serine129-phosphorylated -syn antibody) and high specificity for labelling their aggregated forms over monomeric forms. In GI tract tissues, P1 labelled -syn aggregates across tissue layers (mucosa, sub-mucosa, muscularis externa) and achieved comparable performance to antibody staining. Higher degree of probe labelling was found in older mice due to increased accumulation of -syn aggregates with ageing. Notably, -syn aggregates were readily detectable in the colonic mucosae using P1, indicating the potential use of this probe for early PD diagnosis during colonic examinations like colonoscopy. ConclusionWe have developed a peptide-based fluorescent probe and demonstrated its rapid and specific labelling of -syn aggregates. We highlight the probes ability to label these aggregates rapidly over -syn monomers and survey the abundance of -syn aggregates throughout the entire length of the GI tract. These support the further development of P1 as a specific fluorescent imaging biomarker for colonic -syn aggregates for the early detection of PD.

neuroscience↗

bioRxiv2023

Age-linked lung pathology is reduced by immunotherapeutic targeting of isoDGR protein damage

Advancing age is the primary risk factor for pulmonary diseases. Our investigation revealed an 8-fold increase in aging induced isoDGR-damaged proteins in lung tissue from human pulmonary fibrosis patients compared to healthy tissues, accompanied by elevated frequencies of CD68+/CD11b+ macrophages, indicating lung tissue is susceptible to time-dependent accumulation of isoDGR-proteins. To elucidate the mechanisms through which isoDGR-proteins may exacerbate aging lung disorders for potential therapeutic targeting, we assessed the functional role of this isoDGR-motif in naturally-aged mice and mice lacking the corresponding isoDGR repair enzyme (Pcmt1-/-). IsoDGR-protein accumulation in mouse lung tissue and blood vessels correlated with chronic low-grade inflammation, pulmonary edema, and hypoxemia. IsoDGR accretion induced mitochondrial and ribosomal dysfunctions, cellular senescence, and apoptosis, contributing to progressive lung damage over time. Treatment with anti-isoDGR antibodies suppressed TLR pathway activity, mitigated cytokine-driven inflammation, restored mtDNA expression, and significantly reduced lung pathology in-vivo. Similarly, exposure of lung endothelial cells to isoDGR-modified fibronectin impaired oxygen consumption, increased reactive oxygen species levels, and disrupted acidification, but these effects were efficiently reversed by target-specific antibody therapy. Collectively, our findings underscore the significant contribution of isoDGR-damaged proteins to age-linked lung pathology. IsoDGR-specific therapy emerges as a promising treatment approach for pulmonary disorders in older patients.

pathology↗

bioRxiv2023

Antibody targeting of aging damaged isoDGR-protein doubles lifespan in a mouse model of chronic inflammation

Aging is the result of the accumulation of molecular damages that impair normal biochemical activities. We previously reported that aging-damaged amino acid sequence NGR (Asn-Gly-Arg) results in a gain-of-function conformational switching to isoDGR (isoAsp-Gly-Arg) motif. This integrin-binding motif activates leukocytes to induce chronic inflammation, which are characteristic features of age-linked cardiovascular disorders. We now report that anti-isoDGR immunotherapy doubles lifespan in mouse model of chronic inflammation. We observed extensive accumulation of isoDGR and inflammatory cytokine expression in multiple tissues from Pcmt1-KO and old WT animals, which could also be induced via injection of isoDGR-modified plasma proteins or synthetic peptides into young WT animals. However, weekly injection of anti-isoDGR mAb (1mg/kg) was sufficient to significantly reduce isoDGR-modified proteins and pro-inflammatory cytokine expression, improve behaviour and coordination, and double the average lifespan of Pcmt1-KO mice. Mechanistically, isoDGR-mAb mediated the immune clearance of damaged isoDGR-proteins by antibody-dependent cellular phagocytosis. These results indicate that immunotherapy targeting aging-damaged proteins may represent effective interventions for a range of age-linked degenerative disorders. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=105 SRC="FIGDIR/small/532237v1_ufig1.gif" ALT="Figure 1"> View larger version (12K): org.highwire.dtl.DTLVardef@81610borg.highwire.dtl.DTLVardef@a22aaorg.highwire.dtl.DTLVardef@169fe50org.highwire.dtl.DTLVardef@1b73d11_HPS_FORMAT_FIGEXP M_FIG Anti-isoDGR immunotherapy induces immune clearance of aging damaged isoDGR-proteins to reduce chronic inflammation, improve behaviour and coordination, and double lifespan in PCMT-/- mice. C_FIG

biochemistry↗

bioRxiv2020

mTOR S-nitrosylation inhibits autophagy and lysosomal proteolysis

Mammalian Target of Rapamycin (mTOR) is a master regulator of autophagy and lysosomes, and its downstream kinase-dependent pathways have been extensively characterized. Here, we report an unexpected kinase-independent regulation of autophagy and lysosomes by S-nitrosylation at Cys423 position of mTOR that resulted in suppression of VPS34 and PIKfyve-dependent phosphoinositide synthesis. Physiologically, S-nitrosylation of mTOR reduced basal lysosomal proteolysis via nitric oxide synthase (NOS)-mediated synthesis of NO from lysosomal arginine precursor, a marker of cellular nutrition status. Significantly, we found increased lysosomal NOS-mTOR complexes in APP-PS1 Alzheimers disease (AD) murine model, and increased mTOR S-nitrosylation in AD patient-derived fibroblasts. Lastly, we demonstrated that pharmacological inhibition of NOS or overexpression of mTORCys423Ala mutant reversed lysosomal and autophagic dysfunction in AD patient-derived fibroblasts, suggesting novel therapeutic strategies for autophagosome-lysosomal activation.

cell biology↗

bioRxiv2019

The mood stabilizer lithium slows down synaptic vesicle cycling at glutamatergic synapses

Lithium is a mood stabilizer broadly used to prevent and treat symptoms of mania and depression in people with bipolar disorder (BD). Little is known, however, about its mode of action. Here, we analyzed the impact of lithium on synaptic vesicle (SV) cycling at presynaptic terminals releasing glutamate, a neurotransmitter previously implicated in BD and other neuropsychiatric conditions. We used the pHluorin-based synaptic tracer vGpH and a fully automated image processing pipeline to quantify the effect of lithium on both SV exocytosis and endocytosis in hippocampal neurons. We found that lithium selectively reduces SV exocytic rates during electrical stimulation, and markedly slows down SV recycling post-stimulation. Analysis of single bouton responses revealed the existence of functionally distinct excitatory synapses with varying sensitivity to lithium [-] some terminals show responses similar to untreated cells, while others are markedly impaired in their ability to recycle SVs. While the cause of this heterogeneity is unclear, these data indicate that lithium interacts with the SV machinery and influences glutamate release in a large fraction of excitatory synapses. Together, our findings show that lithium down modulates SV cycling, an effect consistent with clinical reports indicating hyperactivation of glutamate neurotransmission in BD.

neuroscience↗