Biology subjects

Kiriazis, H.

Publications and source records attributed to Kiriazis, H..

9 recordsLinked to original sources

bioRxiv2026

Nitric oxide synthase inhibition and biological sex define different cardiac responses to cardiometabolic stress in older mice.

Background: Heart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome associated with ageing, obesity and impaired nitric oxide signalling. Preclinical models often do not capture the sex-specific and cardiometabolic features observed in patients. We hypothesised that biological sex and the degree of nitric oxide synthase (NOS) inhibition would influence development of HFpEF-like versus HFrEF-like phenotypes. Methods and Results: Male and female C57BL/6J mice (>24 weeks) were exposed to a high-fat diet (HFD) combined with low-dose (0.3 g/L; female only) or high-dose (0.5 g/L; male and female) NOS inhibition using N({omega})-nitro-L-arginine methyl ester (L-NAME) for 15 weeks. Female mice receiving low-dose L-NAME+HFD developed a HFpEF-like phenotype characterised by impaired diastolic function, exercise intolerance and preserved systolic function. Increasing NOS inhibition did not worsen diastolic dysfunction but induced inflammatory and stress-associated transcriptional pathways in female hearts. In contrast, male mice given high-dose L-NAME+HFD developed hypertension, elevated ventricular pressures and impaired systolic function, consistent with a HFrEF-like phenotype. Despite different cardiac phenotypes, circulating lipidomic profiling revealed broadly conserved sphingolipid and phospholipid remodelling, with sex-specific regulation of phosphatidylinositol and lysophosphatidylcholine species. Transcriptomic analyses identified shared regulation of extracellular matrix, calcium-handling and metabolic pathways, whereas greater NOS inhibition was associated with transcriptional signatures related to inflammatory signalling, cellular stress responses and mitochondrial homeostasis. Conclusions: Cardiometabolic stress does not produce a uniform HF phenotype. Instead, biological sex and the degree of NOS inhibition direct distinct functional and molecular remodelling trajectories, identifying HFpEF-like dysfunction as one of several potential cardiac responses to cardiometabolic injury.

pathology↗

bioRxiv2026

Ablation of GM3 Gangliosides in cardiomyocytes modestly impacts heart size but does not protect the murine heart against ischemia reperfusion injury

Advances in mass spectrometry have seen the identification of hundreds of new lipid species, some of which have been found to be associated with adverse cardiac remodeling. Key among these are GM3 gangliosides, which have been associated with metabolic disease, and more recently, adverse cardiac remodeling. Whether GM3s have a direct pathophysiological effect in the heart remains unclear. The present study investigated the effects of cardiomyocyte-specific knockout of GM3 synthase (GM3S, enzyme responsible for the synthesis of GM3) in the heart under basal settings and in response to ischemia-reperfusion (I/R) injury. A new cardiomyocyte-specific GM3S knockout (KO) model was generated, with knockout confirmed via lipidomic profiling. Under basal conditions, male GM3SKO mice exhibited reduced heart weight to tibia length (HW/TL) ratios with no evidence of pathological remodeling, while female mice showed no significant morphological differences. Male GM3SKO mice subjected to 1 hour ischemia and 4 weeks reperfusion demonstrated reduced HW/TL ratio compared to control mice subjected to I/R. However, no significant differences were observed in cardiac function, heart failure and fibrotic markers. Lipidomic profiling (49 classes, [~]850 species) revealed significant accumulation of dihexosylceramide, a metabolic precursor of GM3 in the male heart under basal and post-I/R conditions. In male GM3SKO I/R hearts, GM3 reduction was associated with decreases in odd- and branch-chained phospholipids, together with distinct changes in circulating ether lipid species. Collectively, cardiomyocyte-specific GM3 depletion contributed to sphingolipid remodeling but did not confer protection against I/R-mediated injury. These findings suggest that elevated GM3 levels observed in settings of cardiac pathology are not cardiomyocyte driven, highlighting the importance of understanding cell-type specific contributions to adverse cardiac remodeling.

physiology↗

bioRxiv2026

Inhibition of Gasdermin D by Disulfiram Attenuates Cardiac Inflammation and Fibrosis following Ischaemia Reperfusion Injury

IntroductionInadequately controlled inflammation is a key driver of adverse cardiac remodelling after acute myocardial infarction (AMI). Central to this process is activation of the NLRP3 inflammasome-gasdermin D (GSDMD) pathway, which promotes pyroptosis and the release of the pro-inflammatory cytokine interleukin-1{beta} (IL-1{beta}), a mediator strongly associated with infarct severity and poor clinical outcomes. This study investigates whether repurposing the FDA-approved therapeutic Disulfiram, recently shown to inhibit GSDMD pore formation, could reduce inflammation and thus improve cardiac injury after AMI. Methods and ResultsCardiac ischemia-reperfusion (I/R) injury was induced in C57BL/6 mice by 60-minute ligation of the left coronary artery followed by reperfusion. Disulfiram (25 or 50 mg/kg) was administered at reperfusion and daily thereafter. Cardiac function was assessed by echocardiography, while fibrosis and inflammation were evaluated by histology, RT-PCR, immunohistochemistry and immunoblotting. Leukocyte populations in blood, spleen, bone marrow and heart were analysed by flow cytometry. In vitro, mouse bone marrow-derived macrophages (BMDMs) and PMA-differentiated THP-1 cells were treated with Disulfiram. Cytokine secretion, inflammatory gene expression and changes in cell viability (propidium iodide (PI) staining and lactate dehydrogenase (LDH) release) were measured. Disulfiram (50 mg/kg) significantly improved cardiac function 7 days post-I/R. This was accompanied by a significant reduction in cardiac fibrosis and inflammation, as reflected by a lower abundance of inflammatory cells in circulation and cardiac tissue. In LPS- and ATP/Nigericin-stimulated BMDMs and THP-1 cells, Disulfiram dose-dependently (0.1-50 {micro}M) reduced IL-1{beta} and IL-6 secretion and attenuated membrane permeability and cell lysis. ConclusionsThis study demonstrates that Disulfiram improves cardiac function post-AMI by ameliorating inflammation and fibrosis, which was associated with reductions in cytokine release from inflammatory cells in vitro. Therefore, targeting GSDMD by "repurposing" the FDA-approved drug, Disulfiram, may represent a novel way to provide cardio-protection post-AMI. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=82 SRC="FIGDIR/small/710794v1_ufig1.gif" ALT="Figure 1"> View larger version (11K): org.highwire.dtl.DTLVardef@7fd82eorg.highwire.dtl.DTLVardef@149de52org.highwire.dtl.DTLVardef@a2fe0eorg.highwire.dtl.DTLVardef@d56b4f_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2026

Inducible Impairment of Polymerase Gamma Activity in Cardiomyocytes Promotes Severe Cardiomyopathy with Cardiac Hepatopathy

Mitochondrial dysfunction is a hallmark feature of heart failure (HF) and cardiomyopathy, with substantial human and preclinical evidence suggesting that congenital mitochondrial defects can directly drive these conditions. Despite these strong links, not all individuals with mitochondrial disease develop cardiomyopathy, and therefore the precise mitochondrial defects that initiate cardiac pathology in this setting remain incompletely understood. Here, we describe a novel mouse model that induces progressive deterioration in mtDNA integrity specifically in cardiomyocytes. This model was generated through a post developmental, cardiomyocyte specific deletion of the exonuclease domain of Polymerase Gamma (PolG), impairing its ability to repair mtDNA. Strikingly, from just 16 weeks post-induction these mice displayed progressive worsening of cardiac output, ejection fraction, global strain and blood pressure culminating in premature death at 28-30 weeks post-mutation. Morphologically, these mice displayed cardinal features of hypertrophic cardiomyopathy with enlarged hearts, ventricles and cardiac fibrosis - but little evidence of congestive HF. We also demonstrate using various transcriptional and proteomic readouts, that signalling pathways characteristic of cardiomyopathy were activated. Interestingly, prior to substantial declines in cardiac function, we detect robust activation of the integrated stress response (ISR) in PolGMut mice, and major rewiring of mitochondrial folate metabolism pathways, suggesting that these pathways underpin the developing pathology. Lastly, we also observed a striking hepatopathy phenotype in mutant mice reminiscent of that observed in patients with HF, a condition not robustly recapitulated previously in other mouse models. Thus, our data establish a direct link between mtDNA instability leading to chronic activation of the ISR and rewiring of folate metabolism in cardiomyocytes, subsequently driving a severe cardiac phenotype associated with hepatopathy.

physiology↗

bioRxiv2024

Single-cell transcriptional and epigenetic mapping reveals cellular and molecular mechanisms driving non-ischemic cardiac fibrosis

Cardiac fibrosis is a major cause of cardiac dysfunction. Recently, single-cell genomic approaches have revealed in unprecedented resolution the orchestrated cellular responses driving cardiac fibrosis. Yet, the fibrosis-causing phenotypes that emerge in the heart following non-ischemic cardiac stress, and the transcriptional circuits that govern cell identity and drive fibrosis, are not well understood. Applying a paired multiomic approach, we reveal key transcriptional circuits, in mouse and human hearts, which are associated with fibrosis development following non-ischemic cardiac insults, independent of disease model, species or biological sex. Strikingly, we find the key regulatory events driving fibrosis are reversible at the single-cell transcriptional and epigenomic level, further pointing to key factors regulating fibrosis development and resolution. The transcriptional regulators identified in this study represent promising targets to ameliorate the development of fibrosis in the context of chronic stressors such as aging and hypertension.

cell biology↗

bioRxiv2024

Sex-specific regulation of the cardiac transcriptome by the protein phosphatase 2A regulatory subunit B55α

1.Protein phosphatase 2A (PP2A) regulatory subunit B55 has been implicated in the transcriptional regulation of cardiac growth and fibrosis by suppressing HDAC5/MEF2 signalling in cardiomyocytes. We created and characterised two mouse models with global or cardiomyocyte-specific disruption of the gene encoding B55 (Ppp2r2a) to conduct the first detailed exploration of B55 in the heart. Global homozygous B55 knockout mice died in utero, while heterozygous mice had thinner left ventricular walls at 12 months, an effect more pronounced in males. At 10-12 weeks of age, cardiomyocyte-specific B55 knockout mice displayed normal cardiac morphology with increased left ventricular collagen deposition, identifying B55 as a negative regulator of cardiac fibrosis. Gene expression analyses revealed extensive remodelling of the cardiac transcriptome in male but not female mice, identifying a sexually dimorphic role for B55 in cardiac transcriptional regulation. These findings provide a basis for future work investigating B55 in cardiac stress settings.

physiology↗

bioRxiv2022

Maternal diet and gut microbiota influence predisposition to cardiovascular disease in the offspring

Cardiovascular disease is one of the most significant causes of death globally, especially in regions where unhealthy diets are prevalent and dietary fibre intake is low.1,2 Fibre, particularly prebiotic types that feed gut microbes, is essential for maintaining healthy gut microbial ecosystems.3 One assumption has been that cardiovascular health relates directly to lifestyle choices in adult life. Here, we show in mice that some of these benefits operate from the prenatal stage and relate to the diet and gut microbiome of the mother. Intake of fibre during pregnancy shaped the mothers gut microbiome, which had a lasting founding effect on the offsprings microbial composition and function. Maternal fibre intake during pregnancy significantly changed the cardiac cellular and molecular landscape in the offspring, protecting them against the development of cardiac hypertrophy, remodelling, and inflammation. These suggest a role for foetal exposure to maternal-derived gut microbial metabolites, which are known to cross the placenta and drive epigenetic changes. Maternal fibre intake led to foetal epigenetic reprogramming of the atrial natriuretic peptide gene (Nppa), protective against heart failure. These results underscore the importance of dietary intake and the gut microbiome of the mother during pregnancy for cardiovascular disease in the offspring.

microbiology↗

bioRxiv2021

Detailed metabolic phenotyping of four tissue specific Cas9 transgenic mouse lines

CRISPR/Cas9 technology has revolutionized gene editing and fast tracked our capacity to manipulate genes of interest for the benefit of both research and therapeutic applications. Whilst many advances have, and continue to be made in this area, perhaps the most utilized technology to date has been the generation of knockout cells, tissues and animals by taking advantage of Cas9 function to promote indels in precise locations in the genome. Whilst the advantages of this technology are many fold, some questions still remain regarding the effects that long term expression of foreign proteins such as Cas9, have on mammalian cell function. Several studies have proposed that chronic overexpression of Cas9, with or without its accompanying guide RNAs, may have deleterious effects on cell function and health. This is of particular concern when applying this technology in vivo, where chronic expression of Cas9 in tissues of interest may promote disease-like phenotypes and thus confound the investigation of the effects of the gene of interest. Although these concerns remain valid, no study to our knowledge has yet to demonstrate this directly. Thus, in this study we used the lox-stop-lox (LSL) spCas9 ROSA26 transgenic (Tg) mouse line to generate four tissue-specific Cas9-Tg models with expression in the heart, liver, skeletal muscle and adipose tissue. We performed comprehensive phenotyping of these mice up to 20-weeks of age and subsequently performed molecular analysis of their organs. We demonstrated that Cas9 expression in these tissues had no detrimental effect on whole body health of the animals, nor did it induce any tissue-specific effects on energy metabolism, liver health, inflammation, fibrosis, heart function or muscle mass. Thus, our data suggests that these models are suitable for studying the tissue specific effects of gene deletion using the LSL-Cas9-Tg model, and that phenotypes observed utilizing these models can be confidently interpreted as being gene specific, and not confounded by the chronic overexpression of Cas9.

molecular biology↗

bioRxiv2021

Loss of the Long Non-coding RNA OIP5-AS1 Exacerbates Heart Failure in a Sex-Specific Manner

BackgroundLong ncRNAs (lncRNAs) are known to influence numerous biological processes including cellular differentiation and tissue development. They are also implicated in the maintenance, health and physiological function of many tissues including the heart. Indeed, manipulating the expression of specific lncRNAs has been shown to improve pathological cardiac phenotypes such as heart failure. One lncRNA studied in various settings is OIP5-AS1 (also known as 1700020I14Rik and Cyrano), however its role in cardiac pathologies remains mostly uncharacterised. MethodsWe used data generated from FACS sorted murine cardiomyocytes, human iPSC derived cardiomyocytes, as well as heart tissue from various animal models to investigate OIP5-AS1 expression in health and disease. Using CRISPR we engineered a global OIP5-AS1 knock out (KO) mouse model and performed cardiac pressure overload experiments to study heart failure in these animals. RNA-sequencing of left ventricles provided mechanistic insight between WT and KO mice. ResultsWe demonstrate that OIP5-AS1 expression is regulated during cardiac development and cardiac specific pathologies in both rodent and human models. Moreover, we demonstrate that global female OIP5-AS1 KO mice develop exacerbated heart failure, but male mice do not. Transcriptomics and gene set enrichment analysis suggests that OIP5-AS1 may regulate pathways that impact mitochondrial function. ConclusionsOIP5-AS1 is regulated in cardiac tissue and its deletion leads to worsening heart function under pressure overload in female mice. This may be due to impairments in mitochondrial function, highlighting OIP5-AS1 as a gene of interest in sex-specific differences in heart failure.

physiology↗