Biology subjects

Keceli, G.

Publications and source records attributed to Keceli, G..

4 recordsLinked to original sources

bioRxiv2024

ATP Citrate Lyase Supports Cardiac Function and NAD+/NADH Balance And Is Depressed in Human Heart Failure

BackgroundATP-citrate lyase (ACLY) converts citrate into acetyl-CoA and oxaloacetate in the cytosol. It plays a prominent role in lipogenesis and fat accumulation coupled to excess glucose, and its inhibition is approved for treating hyperlipidemia. In RNAseq analysis of human failing myocardium, we found ACLY gene expression is reduced; however the impact this might have on cardiac function and/or metabolism has not been previously studied. As new ACLY inhibitors are in development for cancer and other disorders, such understanding has added importance. MethodsCardiomyocytes, ex-vivo beating hearts, and in vivo hearts with ACLY inhibited by selective pharmacologic (BMS303141, ACLYi) or genetic suppression, were studied. Regulation of ACLY gene/protein expression, and effects of ACLYi on function, cytotoxicity, tricarboxylic acid (TCA)-cycle metabolism, and redox and NAD+/NADH balance were assessed. Mice with cardiac ACLY knockdown induced by AAV9-acly-shRNA or cardiomyocyte tamoxifen-inducible Acly knockdown were studied. ResultsAcly gene expression was reduced more in obese patients with heart failure and preserved EF (HFpEF) than HF with reduced EF. In vivo pressure-overload and in vitro hormonal stress increased ACLY protein expression, whereas it declined upon fatty-acid exposure. Acute ACLYi (1-hr) dose-dependently induced cytotoxicity in adult and neonatal cardiomyocytes, and caused substantial reduction of systolic and diastolic function in myocytes and ex-vivo beating hearts. In the latter, ATP/ADP ratio also fell and lactate increased. U13C-glucose tracing revealed an ACLY-dependent TCA-bypass circuit in myocytes, where citrate generated in mitochondria is transported to the cytosol, metabolized by ACLY and then converted to malate to re-enter mitochondria, bypassing several NADH-generating steps. ACLYi lowered NAD+/NADH ratio and restoring this balance ameliorated cardiomyocyte toxicity. Oxidative stress was undetected with ACLYi. Adult hearts following 8-weeks of reduced cardiac and/or cardiomyocyte ACLY downregulation exhibited ventricular dilation and reduced function that was prevented by NAD augmentation. Cardiac dysfunction from ACLY knockdown was worse in hearts subjected to sustained pressure-overload, supporting a role in stress responses. ConclusionsACLY supports normal cardiac function through maintenance of the NAD+/NADH balance and is upregulated by hemodynamic and hormonal stress, but depressed by lipid excess. ACLY levels are most reduced in human HFpEF with obesity potentially worsening cardio-metabolic reserve.

molecular biology↗

bioRxiv2023

Ischemia/Reperfusion Injury and Oxidative Stress Impair Cardiac Desmin Proteostasis

BackgroundThough acute mortality by myocardial infarction (MI) has declined in past decades, MI still represents one of the leading causes of heart failure (HF) development. We recently demonstrated the accumulation of toxic desmin aggregates in patients with HF of ischemic origin. Since desmin aggregates are toxic for the heart we aimed to test whether their formation can be induced by oxidative stress as a proxy for reperfusion injury, as well as addressing the effects of therapeutic strategies aimed at reducing desmin aggregation with cardiac oxidative stress. Methods and ResultsWe demonstrate here that oxidative stress is able to induce desmin aggregation, acutely, in a cell-specific and dose-dependent fashion. We also show that elevation of O-linked {beta}-N-acetylglucosamine (O-GlcNAc) prior to or after oxidative stress reduces the formation of toxic desmin aggregates and its pro-aggregating desmin post-translational modifications (PTM). In addition, we show for the first time a role for the transmembrane protease serine 13 (TMPRSS13) with desmin cleavage in response to oxidative stress while desmins single cysteine plays a protective role from I/R injury, which is independent of gain or loss of desmin function. ConclusionsThe proliferation of desmin PTM-forms (i.e., proteoforms) and its aggregation hallmark acute and chronic cardiac stress and result in both loss of and gain of desmin function. We report here two novel mechanisms that could be targeted for therapy to preserve desmin homeostasis and cardiac function in the acute settings of oxidative stress and reperfusion injury.

biochemistry↗

bioRxiv2022

A Remarkable Adaptive Paradigm Of Heart Performance And Protection Emerges In Response To The Constitutive Challenge Of Marked Cardiac-Specific Overexpression Of Adenylyl Cyclase Type 8

Adult mice with cardiac-specific overexpression of adenylyl cyclase (AC) type VIII (TGAC8) adapt to an incessantly increased cAMP-induced cardiac workload ([~]30% increases in heart rate, ejection fraction and cardiac output) for up to a year without signs of heart failure or excessive mortality. Here we show that despite markedly increased cardiac work, classical cardiac hypertrophy markers were absent in TGAC8, total left ventricular (LV) mass was not increased: a reduced LV cavity volume in TGAC8 was encased by thicker LV walls harboring an increased number of small cardiac myocytes and a network of small interstitial non-cardiac myocytes, manifesting increased proliferation markers and compared to WT. Protein synthesis, proteosome activity, autophagy, and Nrf-2, Hsp90, ACC2 protein levels were increased in TGAC8, but LV ATP and phosphocreatine levels in vivo did not differ by genotype. 2,323 transcripts and 2,184 proteins identified in unbiased omics analyses, spanning a wide array of biological processes and molecular functions in numerous cellular compartments differed in TGAC8 vs WT; and over 250 canonical signaling pathways characteristic of adaptive survival circuitry of cancers, including PI3K and growth factor signaling, cytokine and T cell receptor signaling, immune responses, ROS scavenging, proliferation, protection from apoptosis, and nutrient sensing, were activated in TGAC8; and compared to WT there was a shift from fatty acid oxidation to increased aerobic glycolysis in the context of increased utilization of the pentose phosphate shunt and nucleotide synthesis. Thus, the adaptive paradigm, that becomes activated in the LV of TGAC8 in response to severe chronic, intense AC/PKA/Ca2+ signaling embodies many hallmarks of cancer.

physiology↗

bioRxiv2020

UPREGULATION OF SUPEROXIDE DISMUTASE 2 BY ASTROCYTES IN THE SIV/MACAQUE MODEL OF HIV-ASSOCIATED NEUROLOGIC DISEASE

HIV-associated neurocognitive disorders (HAND) remain prevalent despite implementation of antiretroviral therapy (ART). Development of HAND is linked to mitochondrial dysfunction and oxidative stress in the brain; therefore, upregulation of antioxidant defenses is critical to curtail neuronal damage. Superoxide dismutase 2 (SOD2) is a mitochondrial antioxidant enzyme essential for maintaining cellular viability. We hypothesized that SOD2 was upregulated during retroviral infection. Using a simian immunodeficiency virus (SIV)-infected macaque model of HIV, quantitative PCR showed elevated SOD2 mRNA in cortical gray (GM, 7.6-fold for SIV vs. uninfected) and white matter (WM, 77-fold for SIV vs. uninfected) during SIV infection. Further, SOD2 immunostaining was enhanced in GM and WM from SIV-infected animals. Double immunofluorescence labeling illustrated that SOD2 primarily co-localized with astrocyte marker glial fibrillary acidic protein (GFAP) in SIV-infected animals. Interestingly, in ART-treated SIV-infected animals, brain SOD2 RNA levels were similar to uninfected animals. Additionally, using principal component analysis in a transcriptomic approach, SOD2 and GFAP expression separated SIV-infected from uninfected brain tissue. Projection of these data into a HIV dataset revealed similar expression changes, thereby validating the clinical relevance. Together, our findings suggest that novel SOD2-enhancing therapies may delay the onset or reduce severity of HAND seen in ART-treated HIV-infected patients.

neuroscience↗