Biology subjects

Murdoch, C.

Publications and source records attributed to Murdoch, C..

3 recordsLinked to original sources

bioRxiv2024

Knock out of the intracellular calcium conducting ion channel Mitsugumin 23 (MG23) protects against pressure overload induced left ventricular hypertrophy and cardiac dysfunction.

BackgroundIn cardiac dysfunction, intracellular Ca2+-dynamics are disrupted leading to leakage of Ca2+ from the sarcoplasmic reticulum (SR). This results in diminished cardiac contractility and impaired cardiac function. In cardiac tissue, the underlying molecular mechanisms responsible for RyR2-independent Ca2+ leak are poorly understood. Mitsugumin 23 (MG23) is an intracellular Ca2+-conducting ion channel located on ER/SR and nuclear membranes. We propose that MG23 contributes to regulation of intracellular Ca2+-homeostasis, and that altered MG23 function may drive progression of cardiac dysfunction. The aim of this research was to investigate the role of MG23 in SR Ca2+ leak, and whether knock out of Mg23 protects the heart against pressure-overload induced left ventricular hypertrophy. MethodsCardiac pressure-overload was induced in wild type (WT) and Mg23-knock out (KO) mice through subcutaneous Angiotensin II (AngII, 1.1 mg/kg/day) infusion via osmotic pump. After 10-days infusion, in vivo pressure-volume dynamics were measured by insertion of a pressure-volume catheter into the left ventricle. MG23 protein expression was assessed through Western blot analysis. Ventricular fibrosis and cardiomyocyte size were measured using histological and immunofluorescence approaches. Cardiomyocytes were isolated from WT and Mg23-KO hearts and intracellular Ca2+ dynamics assessed through live cell imaging using the Ca2+ indicator Fluo-4. ResultsAngII-induced cardiac pressure-overload increased expression of MG23 in WT mouse hearts. Knock out of Mg23 protected hearts against AngII-induced cardiac hypertrophy. Compared to WT animals, AngII treated Mg23-KO mice displayed a significant reduction in left ventricular fibrosis and displayed normal cardiac functioning. In Mg23-KO hearts, no alteration in expression of key Ca2+ handling proteins was identified, but cardiomyocytes displayed altered Ca2+ spark profiles consistent with a role for MG23 in SR Ca2+ leak. ConclusionMG23 plays a key role in driving Ca2+ dysregulation observed in the early pathological stages of pressure-overload induced heart failure.

physiology↗

bioRxiv2024

A Novel Role of Hyaluronan and its Membrane Receptors, CD44 and RHAMM in Obesity-Related Glomerulopathy

Obesity-related glomerulopathy (ORG) contributes to diabetic nephropathy and kidney cancer, leading to chronic/end-stage kidney disease. To date, treatments for ORG are limited because of incomplete understanding of the disease pathogenesis. Here, we identified a novel role for hyaluronan (HA) and its membrane receptors, CD44 and RHAMM in obesity-associated renal inflammation, fibrosis, tubular injury, and kidney dysfunction. Pharmacological and genetic ablation of HA, CD44 or RHAMM reversed these renal disorders induced by high fat diet feeding in mice in vivo. Increased HA content, and CD44 and RHAMM expression damaged the kidney via activation of TGF-{beta}1/Smad2/3, P38/JNK MAPK and ROCK/ERK pathways. We further established a link between renal insulin resistance and ECM remodelling using human kidney cells in vitro, shedding mechanistic insight into the role of HA, CD44 and RHAMM in the pathogenesis of ORG. Furthermore, in human kidney biopsies gene expression of CD44 and RHAMM was increased in chronic kidney disease and diabetic nephropathy, and their levels were correlated with markers of kidney (dys)function (GFR, serum creatinine, proteinuria). Our findings provide evidence for HA-CD44/RHAMM as a potential therapeutic target in ORG and consequent prevention of chronic kidney disease.

physiology↗

bioRxiv2023

Extracellular Matrix Abnormalities Contribute to Cardiac Insulin Resistance and Associated Dysfunction in Diet-induced Obese Mice

Increased deposition of extracellular matrix (ECM) components such as collagens and hyaluronan contributes to the pathogenesis of obesity-associated insulin resistance in muscle, liver, and adipose tissue. Despite the significance of the heart in cardiovascular and metabolic diseases, maladaptive ECM remodelling in obesity-associated cardiac insulin resistance and cardiac dysfunction has not been studied. Using genetic and pharmacological approaches in mice fed a high fat (HF) diet, we demonstrated a tight association between increased ECM deposition with cardiac insulin resistance. Increased collagen deposition by genetic deletion of matrix metalloproteinase 9 (MMP9) exacerbated cardiac insulin resistance and decreased hyaluronan deposition by treatment with PEGylated human recombinant hyaluronidase PH20 (PEGPH20) improved cardiac insulin resistance in obese mice. These relationships corresponded to functional changes in the heart. PEGPH20 treatment in obese mice ameliorated HF diet-induced abnormal myocardial remodelling. In addition to hyaluronan, increased collagen deposition is a characteristic of the obese mouse heart. We further demonstrated that pirfenidone, a clinically available anti-fibrotic medication which inhibits collagen expression, improved cardiac insulin resistance and cardiac function in obese mice. Our results provide important new insights into the role of ECM remodelling in the pathogenesis of cardiac insulin resistance and associated dysfunction in obesity of distinct mouse models. These findings support the novel therapeutic potential of targeting early cardiac ECM abnormalities in the prevention and treatment of obesity-related cardiovascular complications.

physiology↗