Biology subjects

Thorp, E. B.

Publications and source records attributed to Thorp, E. B..

13 recordsLinked to original sources

bioRxiv2026

Oligodendrocyte stress response as a driver of vascular dementia

Vascular dementia (VaD) is a prevalent and devastating neurocognitive disorder characterized by profound white matter damage, yet the precise cellular mechanisms linking cerebrovascular stress to demyelination remain poorly understood. Here, we characterize the impact of a chronic cardiometabolic stress regimen combining a high-fat diet and hypertension (HF/HBP) on central nervous system structure and function. Adult HF/HBP mice exhibit progressive oligodendroglial cell loss and myelin thinning, followed by cognitive impairments, anxiety-like behavior, and memory deficits that recapitulate clinical features of VaD. Mechanistically, we identify the integrated stress response (ISR) as a central driver of this pathology; pharmacological inhibition of the ISR restores myelination, while cell-specific genetic deletion of the ISR-activating kinase PERK from oligodendrocytes fully protects mice from HF/HBP-induced pathological and behavioral defects. Furthermore, we provide translational evidence that the ISR is activated in oligodendrocytes in human cases of cerebrovascular disease. Together, these findings reveal a critical, cell-autonomous role for oligodendroglial ISR activation during cerebrovascular stress and position this pathway as a viable therapeutic target to mitigate VaD pathogenesis.

neuroscience↗

bioRxiv2026

Cardiomyocyte-specific loss of Smyd5 leads to a robust activation of inflammatory signaling and heart failure in mice.

Background: Cardiomyocytes respond to stress by undergoing hypertrophic growth driven by dynamic changes in gene expression. Epigenetic mechanisms, including histone methylation, play critical roles in regulating these transcriptional programs, yet the enzymes controlling these modifications during cardiac disease remain largely unknown. The SMYD family of histone methyltransferases regulates gene expression in multiple biological contexts, but the function of SMYD5 in the mammalian heart has never been investigated. Methods: SMYD5 expression was assessed in human heart failure samples and in a mouse model of cardiac hypertrophy. To define its functional role in vivo, we generated inducible cardiomyocyte-specific Smyd5 knockout mice and characterized their cardiac phenotype using molecular, histological, and functional analyses. Chromatin immunoprecipitation-quantitative PCR (ChIP-qPCR) was performed to examine histone H4 lysine 20 trimethylation (H4K20me3) at the Il-6 promoter. Results: SMYD5 expression was altered in diseased human and mouse hearts. Under basal conditions, cardiomyocyte-specific deletion of Smyd5 resulted in baseline structural cardiac remodeling and transcriptional signatures characteristic of pathological stress. Smyd5-deficient hearts exhibited marked inflammatory activation resembling a cytokine storm with immune cell infiltration and heart failure. Notably, Smyd5 knockout mice displayed a 100-fold increase in Il-6 expression, accompanied by a global reduction in H4K20me3. ChIP-qPCR analysis of the Il-6 promoter, together with loss- and gain-of-function analysis of SMYD5, supports a direct epigenetic role of SMYD5 in regulating Il-6 expression through H4K20me3 in cardiomyocytes. Conclusions: SMYD5 is a previously unrecognized epigenetic regulator of cardiac homeostasis that restrains inflammatory signaling in cardiomyocytes under normal conditions. Loss of Smyd5 disrupts H4K20me3, leading to derepression of Il-6 in cardiomyocytes and a robust inflammatory response characterized by immune cell recruitment and fibrosis, accompanied by rapid progression of cardiac remodeling and heart failure. These findings identify SMYD5 as a critical regulator of intrinsic cardiomyocyte inflammatory signaling and reveal a novel chromatin-based mechanism contributing to inflammatory cardiomyopathies.

molecular biology↗

bioRxiv2026

Myeloid-targeted RNA nanotherapeutics rewire cholesterol metabolism to unleash anti-tumor immunity in glioblastoma

Tumor-associated myeloid cells (TAMCs) dominate the glioblastoma (GBM) microenvironment and suppress anti-tumor immunity. Here, we identify cholesterol efflux via ABCA1 as a targetable metabolic checkpoint controlling TAMC immunosuppression in GBM. Reprogramming TAMC cholesterol metabolism using TAMC-targeting lipid nanoparticle encapsulating ABCA1 siRNA (ABCA1 LNP) converts TAMCs into potent antigen-presenting cells with enhanced pro-inflammatory activity and antigen-presenting capacity, thereby inducing T cell activation, expansion, and tumor infiltration. Mechanistically, ABCA1 blockade induces cholesterol accumulation in TAMC membranes, promoting lipid raft formation and enhancing MHC-I-mediated antigen presentation. In multiple preclinical GBM models, ABCA1 LNP treatment dramatically induces T cell priming, extends animal survival, and overcomes GBM resistance to radiotherapy and immune checkpoint therapy. This efficacy was well-maintained in stem-like and recurrent GBM models, GBM patient specimens, and a renal cell carcinoma model. Altogether, our work identifies cholesterol efflux as a targetable metabolic vulnerability in TAMCs to overcome therapy resistance in myeloid-rich, immunologically "cold" tumors.

immunology↗

bioRxiv2026

The Neonatal Myeloid Hypoxia Response Promotes a Cardiac Regenerative Response through Insulin-Like Growth Factor

BackgroundThe adult mammalian heart lacks the regenerative potential required to replenish depleted cardiomyocytes and restore cardiac function after injury. Ischemic cardiac injury contributes to heart failure, a leading cause of death worldwide. Neonatal mice possess the capacity to regenerate injured myocardium and macrophages contribute to this process. The mechanisms contributing to the regenerative crosstalk between macrophages and cardiomyocytes remain incompletely elucidated and offer potential to inform future therapeutic strategies. MethodsTo test the immune contribution during cardiac regeneration, we studied the response to myocardial ischemia in neonatal mice after silencing myeloid hypoxia inducible factor 1 (Hif1) and reconstituting HIF-dependent mitogens. In parallel, we examined epigenetic and transcriptional signatures of the cardiac macrophage response and focused on intercellular crosstalk with cardiomyocytes. ResultsIn myeloid Hif1 deficient mice, cardiac regenerative function was lost after coronary ligation. This manifested through loss of ventricular systolic function and elevated myocardial scarring. HIF1 was found to be activated in resident-type cardiac macrophages after ischemic insult. Hypoxia stimulated macrophages to secrete insulin-like growth factor 1 (IGF-1), and this required Hif1. Parallel multiomic analysis revealed epigenetic regenerative signatures. ConclusionsThe data reveal an age-restricted requirement for myeloid Hif1 in neonatal cardiac regeneration, likely through IGF-1 signaling.

immunology↗

bioRxiv2026

Machine Learning Identifies Distinct Treg-Mediated Remodeling in HFpEF Hearts Treated with Neonatal Mesenchymal Stem Cells and Their Secretome

BackgroundHeart failure with preserved ejection fraction (HFpEF) remains a major therapeutic challenge due to its complex pathophysiology and pronounced heterogeneity. Regenerative approaches using neonatal mesenchymal stromal cells (nMSCs) and their secretome (SEC) have shown promise in other heart failure contexts. ObjectivesHowever, the effect of these therapies in HFpEF, and the underlying molecular mechanisms and causal pathways remain poorly understood. MethodsHFpEF was established in two distinct murine models, followed by treatment with either nMSCs or SEC. Functional and histological endpoints were assessed. We developed a novel machine learning framework, VIPcell, which integrates data augmentation, Partial Least Squares (PLS) regression, and causal structure inference to identify genes causally linked to cardiac function using single-nucleus RNA sequencing (snRNA-seq) data. VIPcell was applied to heart tissues from treated HFpEF animals to uncover key regulators of cardiac remodeling. ResultsBoth nMSC and SEC therapies significantly improved diastolic function in two independent rodent HFpEF models. These improvements were associated with reduced inflammation, attenuated myocardial fibrosis, and improved exercise capacity. Intercellular communication analysis revealed widespread, system-level signaling in nMSC-treated hearts, compared to more localized endothelial-cardiomyocyte crosstalk in SEC-treated hearts. Causal inference via VIPcell suggested overlapping upstream regulators in both treatment groups, particularly genes involved in regulatory T cell (Treg) biology and immunomodulatory signaling pathways, including FOXO signaling, NLRP3 inflammasome inhibition, and Tie2 activation. In vivo validation confirmed selective expansion of Tregs following nMSC and SEC therapy. In vitro, nMSCs induced significantly greater Treg expansion compared to multiple adult stem cell types. Critically, chemical depletion of Tregs abrogated the therapeutic effects of both treatments, establishing Tregs as central mediators of diastolic function recovery in the HFpEF preclinical model. ConclusionsnMSC and SEC therapies improve diastolic function in HFpEF through distinct remodeling mechanisms converging on Treg-mediated immune modulation. VIPcell supported identification of causal regulators, highlighting Treg-related signaling as a key driver of myocardial recovery in HFpEF. These findings offer mechanistic insight into cellular therapies for HFpEF and support the development of targeted, Treg-focused interventions.

physiology↗

bioRxiv2025

APOL1 G1 and G2 risk alleles modulate severity of diet-induced obesity in a transgenic mouse model

APOL1 G1 and G2 risk alleles are associated with an increased risk of chronic kidney disease. However, a causal relationship between these alleles and cardiometabolic traits has not been experimentally validated. To address this gap, we placed transgenic APOL1 G0, G1, and G2 FVB/NJ mice on a high-fat diet and analyzed them for weight gain as well as obesity-related cardiometabolic phenotypes. To test whether APOL1 risk alleles modulate the inflammatory basis of obesity, we also exposed bone marrow derived macrophages from these mice to pro-inflammatory, pro-hypertensive, and dyslipidemic conditions. APOL1 high-risk allele female mice gained fat mass more readily than their low-risk female counterparts, while APOL1 high-risk male mice gained fat mass less readily than low-risk males. A parallel sex difference was seen in expression of higher levels of Abca1, Hmox1, and Srebf1 in lipid-loaded female bone-marrow derived macrophages expressing G1 and G2 APOL1, along with minor differences in cardiac function. However, this finding occurred independently of hypertension and insulin resistance, and with only minor albuminuria. Thus, our results highlight the importance of sex as a biological variable in future APOL1 experiments.

genomics↗

bioRxiv2025

LncRNA H19 Upregulation Links Hypoplastic Left Heart Syndrome to Impaired PINK1/Parkin-Mediated Mitophagy and Ischemic Vulnerability

BACKGROUNDThe myocardium in hypoplastic left heart syndrome (HLHS) exhibits immature metabolic programming, impaired mitochondrial quality control, and heightened susceptibility to ischemic and hypoxic injury during palliative surgery. The long non-coding RNA H19 suppresses translation of PTEN-induced putative kinase 1 (PINK1) mRNA and modulates mitochondrial quality control and ischemia/reperfusion injury (IRI) in adult hearts. Whether--and how--H19 regulates mitophagy and IRI in HLHS or in immature animals remains unknown. METHODSWe investigated H19 regulation and its role in mitophagy and ischemia/reperfusion or hypoxia/reoxygenation injury in myocardial tissue from HLHS patients, HLHS-specific induced pluripotent stem cell-derived cardiomyocytes (HLHS-iPSC-CMs), and immature rat hearts. Mechanistic interactions among H19, PINK1/Parkin signaling, and mitophagosome formation were assessed using loss-of-function approaches. RESULTSHLHS myocardium exhibited markedly elevated H19 expression, accompanied by reduced PINK1 and Parkin protein abundance and diminished mitophagosome formation. Similar findings were observed in HLHS-iPSC-CMs exposed to hypoxia/reoxygenation and in immature rat hearts subjected to myocardial IRI. H19 knockdown in HLHS-iPSC-CMs attenuated hypoxia/reoxygenation-induced lactate dehydrogenase release and restored PINK1 and Parkin protein levels. In immature rats, myocardial H19 silencing reduced infarct size, enhanced mitochondrial PINK1 and Parkin expression, and improved post-reperfusion cardiac function for up to 28 days. Conversely, knockdown of PINK1 or Parkin reduced mitophagosome formation and exacerbated functional deterioration during IRI. CONCLUSIONSH19 upregulation impairs PINK1/Parkin-dependent mitophagy and increases susceptibility to ischemic and hypoxic injury in HLHS and the immature heart. These findings identify H19 as a key regulator of mitochondrial quality control and a potential therapeutic target for mitigating IRI in early-life cardiac disease. O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=134 SRC="FIGDIR/small/694773v1_ufig1.gif" ALT="Figure 1"> View larger version (50K): org.highwire.dtl.DTLVardef@193defdorg.highwire.dtl.DTLVardef@114ce7forg.highwire.dtl.DTLVardef@1010d05org.highwire.dtl.DTLVardef@1fdeac1_HPS_FORMAT_FIGEXP M_FIG O_FLOATNOGraphical AbstractC_FLOATNO C_FIG Novelty and SignificanceO_ST_ABSWhat Is Known?C_ST_ABSO_LIThe myocardium in hypoplastic left heart syndrome (HLHS) exhibits immature metabolic programming, abnormal coronary perfusion, and impaired mitochondrial quality control, rendering it highly susceptible to ischemic and hypoxic injury. C_LIO_LIBoth structural limitations and intrinsic mitochondrial dysfunction contribute to the reduced ischemic tolerance of the HLHS heart, particularly during surgical and hemodynamic stress. C_LIO_LIThe long noncoding RNA H19 regulates mitochondrial quality control and modulates myocardial ischemia/reperfusion injury (IRI) in adult hearts. C_LIO_LIH19 inhibits the binding of the translation initiation factor eIF4A2 to PTEN-induced putative kinase 1 (PINK1) mRNA, thereby suppressing PINK1 protein synthesis and influencing PINK1-dependent mitophagy in adult mice. C_LI What New Information Does This Article Contribute?O_LIThis study identifies robust upregulation of H19 in HLHS myocardium, HLHS-specific induced pluripotent stem cell-derived cardiomyocytes (HLHS-iPSC-CMs) exposed to hypoxia/reoxygenation, and in immature rats subjected to myocardial IRI. C_LIO_LIElevated H19 is associated with suppressed PINK1/Parkin-dependent mitophagy, exacerbated IRI, and adverse post-injury remodeling. C_LIO_LIKnockdown of H19 restores mitochondrial PINK1 and Parkin protein levels, enhances mitophagy, reduces infarct size, and improves long-term recovery of cardiac function--demonstrating a previously unrecognized pathogenic role for H19 in the immature heart under stress. C_LIO_LIKnockdown of PINK1 or Parkin decreases mitophagosomes and exacerbates myocardial IRI in immature rats. C_LI

genomics↗

bioRxiv2025

Endothelial Prolyl Hydroxylase 3 Mitigates Maladaptive Inflammation to Promote Post-Ischemic Kidney Repair

Acute kidney injury (AKI) is a major health concern and well-established risk factor for the development of chronic kidney disease (CKD). Tissue hypoxia is a prominent feature of the injured kidney that shapes the biological behavior of parenchymal and immune cells. Endothelial cells have important immunomodulatory roles, but the impact of dysregulated oxygen sensing on their responses remains poorly understood. By leveraging a combination of conditional mouse strains, single-cell analyses of mouse and human samples, and in vitro experiments, we demonstrate that the oxygen sensor PHD3 in the endothelium suppresses maladaptive inflammatory responses, thereby promoting kidney repair. Specifically, post-ischemic inactivation of endothelial PHD3, but not PHD1, leads to maladaptive kidney repair, characterized by increased fibrosis and inflammation. scRNA-seq analysis of the postischemic endothelial PHD3-haplodeficient kidney shows an endothelial IFN-{gamma} gene signature, resembling the responses seen in patients with severe AKI. By performing loss- and gain-of-function experiments in vitro, we demonstrate that PHD3 regulates IFN-{gamma} responsive pro-inflammatory signatures in a HIF-dependent manner. Consistent with this, simultaneous deletion of ARNT in endothelial PHD3-deficient mice restored kidney repair. Thus, our findings provide novel mechanistic insights into endothelial oxygen sensing and the AKI-to-CKD transition, highlighting potential therapeutic avenues for mitigating disease progression. TRANSLATIONAL STATEMENTUsing a genetic approach, we identified endothelial PHD3 as a critical regulator of kidney repair. Post-ischemic loss of endothelial PHD3--but not PHD1--led to maladaptive outcomes marked by increased injury, fibrosis, and inflammation. Mechanistically, we show that PHD3 restrains IFN-{gamma}-driven pro-inflammatory signaling through a HIF-dependent pathway. These findings reveal a central role for endothelial oxygen sensing in dictating kidney recovery and underscore the importance of cellular context in responses to hypoxia. Given the expanding clinical use of non-selective PHD inhibitors, our work highlights the need for more targeted, cell-specific approaches to modulate hypoxia pathways in kidney disease.

molecular biology↗

bioRxiv2025

Tissue-resident skeletal muscle macrophages promote recovery from viral pneumonia-induced sarcopenia in normal aging.

Sarcopenia, which diminishes lifespan and healthspan in the elderly, is commonly exacerbated by viral pneumonia, including influenza and COVID-19. In a study of influenza A pneumonia in mice, young mice fully recovered from sarcopenia, while older mice did not. We identified a population of tissue-resident skeletal muscle macrophages that form a spatial niche with satellite cells and myofibers in young mice but are lost with age. Mice with a gain-of-function mutation in the Mertk receptor maintained this macrophage-myofiber interaction during aging and fully recovered from influenza-induced sarcopenia. In contrast, deletion of Mertk in macrophages or loss of Cx3cr1 disrupted this niche, preventing muscle regeneration. Heterochronic parabiosis did not restore the niche in old mice. These findings suggest that age-related loss of Mertk in muscle tissue-resident macrophages disrupts the cellular signaling necessary for muscle regeneration after viral pneumonia, offering a potential target to mitigate sarcopenia in aging.

immunology↗

bioRxiv2024

HIF-1alpha is Required to Differentiate the Neonatal Macrophage Secretome from Adults

The immune response to stress diverges with age, with neonatal macrophages implicated in tissue regeneration versus tissue scarring and maladaptive inflammation in adults. Integral to the macrophage stress response is the recognition of hypoxia and pathogen-associated molecular patterns (PAMPs), which are often coupled. The age-specific, cell-intrinsic nature of this stress response remains vague. To uncover age-defined divergences in macrophage crosstalk potential after exposure to hypoxia and PAMPs, we interrogated the secreted proteomes of neonatal versus adult macrophages via non-biased mass spectrometry. Through this approach, we newly identified age-specific signatures in the secretomes of neonatal versus adult macrophages in response to hypoxia and the prototypical PAMP, lipopolysaccharide (LPS). Neonatal macrophages polarized to an anti-inflammatory, regenerative phenotype protective against apoptosis and oxidative stress, dependent on hypoxia inducible transcription factor-1 (HIF-1). In contrast, adult macrophages adopted a pro-inflammatory, glycolytic phenotypic signature consistent with pathogen killing. Taken together, these data uncover fundamental age and HIF-1 dependent macrophage programs that may be targeted to calibrate the innate immune response during stress and inflammation.

immunology↗

bioRxiv2023

Post-ischemic inactivation of HIF prolyl hydroxylases in endothelium promotes maladaptive kidney repair by inducing glycolysis

Ischemic acute kidney injury (AKI) is common in hospitalized patients and increases the risk for chronic kidney disease (CKD). Impaired endothelial cell (EC) functions are thought to contribute in AKI to CKD transition, but the underlying mechanisms remain unclear. Here, we identify a critical role for endothelial oxygen sensing prolyl hydroxylase domain (PHD) enzymes 1-3 in regulating post-ischemic kidney repair. In renal endothelium, we observed compartment-specific differences in the expression of the three PHD isoforms in both mice and humans. We found that post-ischemic concurrent inactivation of endothelial PHD1, PHD2, and PHD3 but not PHD2 alone promoted maladaptive kidney repair characterized by exacerbated tissue injury, fibrosis, and inflammation. Single-cell RNA-seq analysis of the post-ischemic endothelial PHD1, PHD2 and PHD3 deficient (PHDTiEC) kidney revealed an endothelial glycolytic transcriptional signature, also observed in human kidneys with severe AKI. This metabolic program was coupled to upregulation of the SLC16A3 gene encoding the lactate exporter monocarboxylate transporter 4 (MCT4). Strikingly, treatment with the MCT4 inhibitor syrosingopine restored adaptive kidney repair in PHDTiEC mice. Mechanistically, MCT4 inhibition suppressed pro-inflammatory EC activation reducing monocyte-endothelial cell interaction. Our findings suggest avenues for halting AKI to CKD transition based on selectively targeting the endothelial hypoxia-driven glycolysis/MCT4 axis.

molecular biology↗

bioRxiv2023

Augmentation of Histone Deacetylase 6 Activity Impairs Mitochondrial Respiratory Complex I in Ischemic/Reperfused Diabetic Hearts

BACKGROUNDDiabetes augments activity of histone deacetylase 6 (HDAC6) and generation of tumor necrosis factor (TNF) and impairs the physiological function of mitochondrial complex I (mCI) which oxidizes reduced nicotinamide adenine dinucleotide (NADH) to nicotinamide adenine dinucleotide to sustain the tricarboxylic acid cycle and {beta}-oxidation. Here we examined how HDAC6 regulates TNF production, mCI activity, mitochondrial morphology and NADH levels, and cardiac function in ischemic/reperfused diabetic hearts. METHODSHDAC6 knockout, streptozotocin-induced type 1 diabetic, and obese type 2 diabetic db/db mice underwent myocardial ischemia/reperfusion injury in vivo or ex vivo in a Langendorff-perfused system. H9c2 cardiomyocytes with and without HDAC6 knockdown were subjected to hypoxia/reoxygenation injury in the presence of high glucose. We compared the activities of HDAC6 and mCI, TNF and mitochondrial NADH levels, mitochondrial morphology, myocardial infarct size, and cardiac function between groups. RESULTSMyocardial ischemia/reperfusion injury and diabetes synergistically augmented myocardial HDCA6 activity, myocardial TNF levels, and mitochondrial fission and inhibited mCI activity. Interestingly, neutralization of TNF with an anti-TNF monoclonal antibody augmented myocardial mCI activity. Importantly, genetic disruption or inhibition of HDAC6 with tubastatin A decreased TNF levels, mitochondrial fission, and myocardial mitochondrial NADH levels in ischemic/reperfused diabetic mice, concomitant with augmented mCI activity, decreased infarct size, and ameliorated cardiac dysfunction. In H9c2 cardiomyocytes cultured in high glucose, hypoxia/reoxygenation augmented HDAC6 activity and TNF levels and decreased mCI activity. These negative effects were blocked by HDAC6 knockdown. CONCLUSIONSAugmenting HDAC6 activity inhibits mCI activity by increasing TNF levels in ischemic/reperfused diabetic hearts. The HDAC6 inhibitor, tubastatin A, has high therapeutic potential for acute myocardial infarction in diabetes. Novelty and SignificanceO_ST_ABSWhat Is Known?C_ST_ABSO_LIIschemic heart disease (IHS) is a leading cause of death globally, and its presence in diabetic patients is a grievous combination, leading to high mortality and heart failure. C_LIO_LIDiabetes impairs assembly of mitochondrial complex I (mCI), complex III dimer, and complex IV monomer into the respiratory chain supercomplexes, resulting in electron leak and the formation of reactive oxygen species (ROS). C_LIO_LIBy oxidizing reduced nicotinamide adenine dinucleotide (NADH) and reducing ubiquinone, mCI physiologically regenerates NAD+ to sustain the tricarboxylic acid cycle and {beta}-oxidation. C_LI What New Information Does This Article Contribute?O_LIMyocardial ischemia/reperfusion injury (MIRI) and diabetes as comorbidities augment myocardial HDCA6 activity and generation of tumor necrosis factor (TNF), which inhibit myocardial mCI activity. C_LIO_LIGenetic disruption of histone deacetylase 6 (HDAC6) decreases mitochondrial NADH levels and augments mCI activity in type 1 diabetic mice undergoing MIRI via decreasing TNF production, leading to decreases in MIRI. C_LIO_LIPretreatment of type 2 diabetic db/db mice with a HDAC6 inhibitor, tubastatin A (TSA), decreases mitochondrial NADH levels and augments mCI activity by decreasing TNF levels, leading to improvements in cardiac function. C_LI Patients with diabetes are more susceptible to MIRI than non-diabetics with greater mortality and resultant heart failure. There is an unmet medical need in diabetic patients for the treatment of IHS. Our biochemical studies find that MIRI and diabetes synergistically augment myocardial HDAC6 activity and generation of TNF, along with cardiac mitochondrial fission and low bioactivity of mCI. Intriguingly, genetic disruption of HDAC6 decreases the MIRI-induced increases in TNF levels, concomitant with augmented mCI activity, decreased myocardial infarct size, and ameliorated cardiac dysfunction in T1D mice. Importantly, treatment of obese T2D db/db mice with TSA reduces the generation of TNF and mitochondrial fission and enhances mCI activity during reperfusion after ischemia. Our isolated heart studies revealed that genetic disruption or pharmacological inhibition of HDAC6 reduces mitochondrial NADH release during ischemia and ameliorates dysfunction of diabetic hearts undergoing MIRI. Furthermore, HDAC6 knockdown in cardiomyocytes blocks high glucose- and exogenous TNF-induced suppression of mCI activity in vitro, implying that HDAC6 knockdown can preserve mCI activity in high glucose and hypoxia/reoxygenation. These results demonstrate that HDAC6 is an important mediator in MIRI and cardiac function in diabetes. Selective inhibition of HDAC6 has high therapeutic potential for acute IHS in diabetes.

pharmacology and toxicology↗

bioRxiv2021

Bone Marrow-Derived AXL Tyrosine Kinase Promotes Mitogenic Crosstalk and Cardiac Allograft Vasculopathy

Cardiac Allograft Vasculopathy (CAV) is a leading contributor to late transplant rejection. Although implicated, the mechanisms by which bone marrow-derived cells promote CAV remain unclear. Emerging evidence implicates the cell surface receptor tyrosine kinase AXL to be elevated in rejecting human allografts. AXL protein is found on multiple cell types, including bone marrow-derived myeloid cells. The causal role of AXL from this compartment and during transplant is largely unknown. This is important because AXL is a key regulator of myeloid inflammation. Utilizing experimental chimeras deficient in the bone marrow-derived Axl gene, we report that Axl antagonizes cardiac allograft survival and promotes CAV. Flow cytometric and histologic analyses of Axl-deficient transplant recipients revealed reductions in both allograft immune cell accumulation and vascular intimal thickness. Co-culture experiments designed to identify cell-intrinsic functions of Axl uncovered complementary cell-proliferative pathways by which Axl promotes CAV-associated inflammation. Specifically, Axl-deficient myeloid cells were less efficient at increasing the replication of both antigen-specific T cells and vascular smooth muscle cells (VSMCs), the latter a key hallmark of CAV. For the latter, we discovered that Axl-was required to amass the VSMC mitogen Platelet-Derived Growth Factor. Taken together, our studies reveal a new role for myeloid Axl in the progression of CAV and mitogenic crosstalk. Inhibition of AXL-protein, in combination with current standards of care, is a candidate strategy to prolong cardiac allograft survival.

immunology↗