Biology subjects

Nigro, J.

Publications and source records attributed to Nigro, J..

7 recordsLinked to original sources

bioRxiv2026

Impaired proteostasis is an early feature of the diabetic heart in humans and mice

Diabetes and obesity increase cardiac lipid levels leading to cardiomyopathy and heart failure. We hypothesized that intermittent fasting would reduce cardiac lipid levels. Surprisingly, intermittent fasting increased myocardial triglyceride content, but rescued mortality and attenuated cardiomyopathy in mice overexpressing cardiomyocyte acyl-CoA synthetase 1 (MHC-ACSL1). Lipid overload caused cardiomyocyte accumulation of polyubiquitinated protein aggregates containing desmin, a scaffolding intermediate filament protein, which intermittent fasting prevented. Furthermore, intermittent fasting reversed elevated myocardial C16:0 ceramide content, and knockdown of ceramide synthase CerS5 and CerS6 reduced palmitate-induced protein aggregation, highlighting a role for C16:0 ceramides in this pathology. Conversely, impairing aggrephagy with cardiomyocyte-specific p62 ablation induced heart failure in mice fed a high-fat diet, with paradoxically reduced cardiac lipid content. Crucially, non-failing diabetic human hearts also exhibited protein aggregate pathology. Taken together, these results demonstrate that impaired proteostasis characterizes cardiomyopathy from cardiac lipid overload and identify a promising new therapeutic target for this condition.

molecular biology↗

bioRxiv2025

Targeting RUNX1 in Macrophages Facilitates Cardiac Recovery

Despite advances in disease treatment, our understanding of how damaged organs recover and the mechanisms governing this process remain poorly defined. Here, we mapped the transcriptional and regulatory landscape of human cardiac recovery using single cell multiomics. Macrophages emerged as the most reprogrammed cell type. Deep learning identified the transcription factor RUNX1 as a key regulator of this process. Macrophage-specific Runx1 deletion recapitulated the human cardiac recovery phenotype in a chronic heart failure model. Runx1 deletion reprogrammed macrophages to a reparative phenotype, reduced fibrosis, and promoted cardiomyocyte adaptation. RUNX1 chromatin profiling revealed a conserved regulon that diminished during recovery. Mechanistically, the epigenetic reader BRD4 controlled Runx1 expression in macrophages. Chromatin activity mapping, combined with CRISPR perturbations, identified the precise regulatory element governing Runx1 expression. Therapeutically, small molecule Runx1 inhibition was sufficient to promote cardiac recovery. Our findings uncover a druggable RUNX1 epigenetic mechanism that orchestrates recovery of heart function.

immunology↗

bioRxiv2024

Mitophagy Facilitates Cytosolic Proteostasis to Preserve Cardiac Function

BackgroundProtein quality control (PQC) is critical for maintaining sarcomere structure and function in cardiac myocytes, and mutations in PQC pathway proteins, such as CRYAB (arginine to glycine at position 120, R120G) and BAG3 (proline to lysine at position 209, P209L) induce protein aggregate pathology with cardiomyopathy in humans. Novel observations in yeast and mammalian cells demonstrate mitochondrial uptake of cytosolic protein aggregates. We hypothesized that mitochondrial uptake of cytosolic protein aggregates and their removal by mitophagy, a lysosomal degradative pathway essential for myocardial homeostasis, facilitates cytosolic protein quality control in cardiac myocytes. MethodsMice with inducible cardiac myocyte specific ablation of TRAF2 (TRAF2icKO), which impairs mitophagy, were assessed for protein aggregates with biochemical fractionation and super-resolution imaging in comparison to floxed controls. Induced pluripotent stem cell (iPSC)-derived cardiac myocytes with R120G knock-in to the CRYAB locus were assessed for localization of the CRYAB protein. Transgenic mice expressing R120G CRYAB protein (R120G-TG) were subjected to both TRAF2 gain-of-function (with AAV9-cardiac Troponin T promoter-driven TRAF2 transduction) and TRAF2 loss-of-function (with tamoxifen-inducible ablation of one Traf2 allele) in cardiac myocytes to determine the effect of mitophagy modulation on cardiac structure, function, and protein aggregate pathology. ResultsCardiomyocyte-specific ablation of TRAF2 results accumulation of mitochondrial and cytosolic protein aggregates and DESMIN mis-localization to protein aggregates. Isolated mitochondria take up cardiomyopathy-associated aggregate-prone cytosolic chaperone proteins, namely arginine to glycine (R120G) CRYAB mutant and proline to lysine (P209L) BAG3 mutant. R120G-CRYAB mutant protein increasingly localizes to mitochondria in human and mouse cardiomyocytes. R120G-TG mice demonstrate upregulation of TRAF2 in the mitochondrial fraction with increased mitophagy as compared with wild type. Adult-onset inducible haplo-insufficiency of TRAF2 resulted in accelerated mortality, impaired left ventricular systolic function and increased protein aggregates in R120G-TG mice as compared with controls. Conversely, AAV9-mediated TRAF2 transduction in R120G-TG mice reduced mortality and attenuated left ventricular systolic dysfunction, with reduced protein aggregates and restoration of normal localization of DESMIN, a cytosolic scaffolding protein chaperoned by CRYAB, as compared with control AAV9-GFP group. ConclusionsTRAF2-mediated mitophagy in cardiac myocytes facilitates removal of cytosolic protein aggregates and can be stimulated to ameliorate proteotoxic cardiomyopathy.

cell biology↗

bioRxiv2024

Phosphorylation of CRYAB Induces a Condensatopathy to Worsen Post-Myocardial Infarction Left Ventricular Remodeling.

Protein aggregates are emerging therapeutic targets in rare monogenic causes of cardiomyopathy and amyloid heart disease, but their role in more prevalent heart failure syndromes remains mechanistically unexamined. We observed mis-localization of desmin and sarcomeric proteins to aggregates in human myocardium with ischemic cardiomyopathy and in mouse hearts with post-myocardial infarction ventricular remodeling, mimicking findings of autosomal-dominant cardiomyopathy induced by R120G mutation in the cognate chaperone protein, CRYAB. In both syndromes, we demonstrate increased partitioning of CRYAB phosphorylated on serine-59 to NP40-insoluble aggregate-rich biochemical fraction. While CRYAB undergoes phase separation to form condensates, the phospho-mimetic mutation of serine-59 to aspartate (S59D) in CRYAB mimics R120G-CRYAB mutants with reduced condensate fluidity, formation of protein aggregates and increased cell death. Conversely, changing serine to alanine (phosphorylation-deficient mutation) at position 59 (S59A) restored condensate fluidity, and reduced both R120G-CRYAB aggregates and cell death. In mice, S59D CRYAB knock-in was sufficient to induce desmin mis-localization and myocardial protein aggregates, while S59A CRYAB knock-in rescued left ventricular systolic dysfunction post-myocardial infarction and preserved desmin localization with reduced myocardial protein aggregates. 25-Hydroxycholesterol attenuated CRYAB serine-59 phosphorylation and rescued post-myocardial infarction adverse remodeling. Thus, targeting CRYAB phosphorylation-induced condensatopathy is an attractive strategy to counter ischemic cardiomyopathy.

cell biology↗

bioRxiv2022

Dapagliflozin improves endothelial integrity and hemodynamics in endotoxin treated mice through an apolipoprotein M dependent pathway

RationaleSodium-glucose co-transporter inhibitors (SGLT2i) are under active clinical investigation in patients with acute inflammatory conditions, based on their clinical cardio-and nephroprotective effects, and a pre-clinical study that demonstrated SGLT2i improve renal outcomes and survival in a lipopolysaccharide (LPS) model. However, a unified mechanism that explains how SGLT2i could prevent hemodynamic consequences of inflammatory conditions has not been described. Apolipoprotein M (ApoM) is inversely associated with mortality in inflammatory conditions and improves cardiac function in endotoxin-treated mice via sphingosine-1-phosphate (S1P) signaling. ObjectiveTest the hypothesis that pre-treatment with SGLT2i dapagliflozin (Dapa) improves hemodynamics in endotoxin-treated mice via the ApoM/S1P pathway. Methods and ResultsMice with diet-induced obesity were gavaged with vehicle or Dapa for 4 days prior to LPS (10 mg/kg, IP). We found that mice receiving Dapa restored circulating ApoM levels, likely by increasing expression of the multi-ligand protein receptor megalin in the proximal tubules. Dapa attenuated LPS-induced reductions in cardiac dysfunction including reductions in ejection fraction, cardiac index, and coronary sinus area as well as vascular permeability as ascertained by intravital microscopy. Using both ApoM transgenic and knockout mice and S1P receptor inhibitors, we show that the ApoM/S1P pathway is important for the beneficial effects of Dapa in the LPS model. ConclusionsIn the setting of acute inflammation, our data suggest that SGLT2i maintains levels of megalin, leading to preservation of ApoM, which in turn promotes endothelial barrier integrity and improves hemodynamics. Our studies suggest a novel mechanism by which SGLT2i can preserve intravascular volume in the acute inflammatory setting.

physiology↗

bioRxiv2021

Transcriptomes and metabolism define mouse and human MAIT cell heterogeneity

Mucosal-associated invariant T (MAIT) cells are a subpopulation of T lymphocytes that respond to microbial metabolites. We performed single-cell RNA sequencing and metabolic analyses of MAIT cell subsets in thymus and peripheral tissues from mice and humans to define the heterogeneity and developmental pathway of these innate-like lymphocytes. We show that the predominant mouse subset, which produces IL-17 (MAIT17), and the subset that produces IFN{gamma} (MAIT1), have greatly different transcriptomes and metabolic states in the thymus and periphery. A splenic MAIT subset has a transcriptome similar to circulating lymphocytes, and in mice these also are found in recent thymic emigrants, suggesting partially mature cells emigrate from the thymus. Human MAIT cells are predominantly MAIT1 cells, but have a different metabolism from their mouse counterparts with increased fatty acid uptake and storage. Although mouse and human subsets are similar in thymus, in the periphery they diverge, likely reflecting environmental influences.

immunology↗

bioRxiv2021

Quantification of breeding sites parameters in shaping bacterial communities in Aedes aegypti (Diptera: Culicidae).

Studies have demonstrated the importance of breeding site, few had disentangled the role of microbiome, physico-chemical and biological factors of water as well as landuse on larval microbial communities and their recruitment in mosquito. A quantitative exploration of the interplay of multiple factors on mosquito microbiome was performed using a dataset obtained through a field survey undertaken in French Guiana. Two complementary hypotheses were tested (i) the most dissimilar larval microbiome structures in breeding sites displayed the most contrasting water properties and land-use, (ii) a higher specificity level of environmental parameters have an incidence on larval microbiome. Variance partitioning approach validated the two hypothesis by providing evidence that water bacterial community is a most significant driver shaping the structure of the bacteriome in mosquito than other environmental parameters from the breeding sites. However, land-use does not play such important role to explain variance. Our results consolidate and complement the knowledge shaping mosquito microbiota but also highlighted the large unknown in understanding the ecology of the recruitment into host.

ecology↗