scholarly journals Rapid metabolic and bioenergetic adaptations of astrocytes under hyperammonemia – a novel perspective on hepatic encephalopathy

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Marcel Zimmermann ◽  
Andreas S. Reichert
Keyword(s):  
Hepatic Encephalopathy ◽  
Molecular Mechanisms ◽  
Tca Cycle ◽  
Therapeutic Strategies ◽  
Cellular Processes ◽  
Cellular Models ◽  
The Tca Cycle ◽  
Underlying Mechanisms

Abstract Hepatic encephalopathy (HE) is a well-studied, neurological syndrome caused by liver dysfunctions. Ammonia, the major toxin during HE pathogenesis, impairs many cellular processes within astrocytes. Yet, the molecular mechanisms causing HE are not fully understood. Here we will recapitulate possible underlying mechanisms with a clear focus on studies revealing a link between altered energy metabolism and HE in cellular models and in vivo. The role of the mitochondrial glutamate dehydrogenase and its role in metabolic rewiring of the TCA cycle will be discussed. We propose an updated model of ammonia-induced toxicity that may also be exploited for therapeutic strategies in the future.

scholarly journals Metabolomics of aging in primary fibroblasts from small and large breed dogs

GeroScience ◽  
2021 ◽  
Author(s):  
Paul S. Brookes ◽  
Ana Gabriela Jimenez
Keyword(s):  
Aging Process ◽  
Tca Cycle ◽  
Therapeutic Strategies ◽  
Targeted Metabolomics ◽  
The Tca Cycle ◽  
Age Dependent ◽  
Primary Fibroblasts ◽  
Aging Rates ◽  
Underlying Mechanisms ◽  
Coenzyme A Biosynthesis

AbstractAmong several animal groups (eutherian mammals, birds, reptiles), lifespan positively correlates with body mass over several orders of magnitude. Contradicting this pattern are domesticated dogs, with small dog breeds exhibiting significantly longer lifespans than large dog breeds. The underlying mechanisms of differing aging rates across body masses are unclear, but it is generally agreed that metabolism is a significant regulator of the aging process. Herein, we performed a targeted metabolomics analysis on primary fibroblasts isolated from small and large breed young and old dogs. Regardless of size, older dogs exhibited lower glutathione and ATP, consistent with a role for oxidative stress and bioenergetic decline in aging. Furthermore, several size-specific metabolic patterns were observed with aging, including the following: (i) An apparent defect in the lower half of glycolysis in large old dogs at the level of pyruvate kinase. (ii) Increased glutamine anaplerosis into the TCA cycle in large old dogs. (iii) A potential defect in coenzyme A biosynthesis in large old dogs. (iv) Low nucleotide levels in small young dogs that corrected with age. (v) An age-dependent increase in carnitine in small dogs that was absent in large dogs. Overall, these data support the hypothesis that alterations in metabolism may underlie the different lifespans of small vs. large breed dogs, and further work in this area may afford potential therapeutic strategies to improve the lifespan of large dogs.

scholarly journals Tricarboxylic Acid (TCA) Cycle Intermediates: Regulators of Immune Responses

2020 ◽  
Author(s):  
Inseok Choi ◽  
Hyewon Son ◽  
Jea-Hyun Baek
Keyword(s):  
Immune Responses ◽  
Molecular Mechanisms ◽  
Tricarboxylic Acid Cycle ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Cell Stress ◽  
Danger Signals ◽  
Cellular Processes ◽  
The Tca Cycle ◽  
Tca Cycle Intermediates

Tricarboxylic acid cycle (TCA) is a series of chemical reactions in aerobic organisms used to generate energy via the oxidation of acetyl-CoA derived from carbohydrates, fatty acids, and proteins. In the eukaryotic system, the TCA cycle completely occurs in mitochondria, while the intermediates of the TCA cycle are retained in mitochondria due to their polarity and hydrophilicity. Under conditions of cell stress, mitochondria become disrupted and release their contents, which act as danger signals in the cytosol. Of note, the TCA cycle intermediates may also leak from dysfunctioning mitochondria and regulate cellular processes. Increasing evidence shows that the metabolites of the TCA cycle are substantially involved in the regulation of immune responses. In this review, we aimed to provide a comprehensive systematic overview of the molecular mechanisms of each TCA cycle intermediate that may play key roles in regulating cellular immunity in cell stress and discuss their implications for immune activation and suppression.

scholarly journals Molecular Mechanisms Contributing to Mesenchymal Stromal Cell Aging

Biomolecules ◽  
2020 ◽  
Vol 10 (2) ◽  
pp. 340 ◽  
Author(s):  
Simona Neri ◽  
Rosa Maria Borzì
Keyword(s):  
Molecular Mechanisms ◽  
Replicative Senescence ◽  
Cell Aging ◽  
In Vitro Expansion ◽  
Aging Mechanisms ◽  
Underlying Mechanisms ◽  
Clinical Conditions

Mesenchymal stem/stromal cells (MSCs) are a reservoir for tissue homeostasis and repair that age during organismal aging. Beside the fundamental in vivo role of MSCs, they have also emerged in the last years as extremely promising therapeutic agents for a wide variety of clinical conditions. MSC use frequently requires in vitro expansion, thus exposing cells to replicative senescence. Aging of MSCs (both in vivo and in vitro) can affect not only their replicative potential, but also their properties, like immunomodulation and secretory profile, thus possibly compromising their therapeutic effect. It is therefore of critical importance to unveil the underlying mechanisms of MSC senescence and to define shared methods to assess MSC aging status. The present review will focus on current scientific knowledge about MSC aging mechanisms, control and effects, including possible anti-aging treatments.

scholarly journals Tricarboxylic Acid (TCA) Cycle Intermediates: Regulators of Immune Responses

Life ◽  
2021 ◽  
Vol 11 (1) ◽  
pp. 69
Author(s):  
Inseok Choi ◽  
Hyewon Son ◽  
Jea-Hyun Baek
Keyword(s):  
Immune Responses ◽  
Molecular Mechanisms ◽  
Tricarboxylic Acid Cycle ◽  
Tca Cycle ◽  
Tricarboxylic Acid ◽  
Cell Stress ◽  
Danger Signals ◽  
Cellular Processes ◽  
The Tca Cycle ◽  
Tca Cycle Intermediates

The tricarboxylic acid cycle (TCA) is a series of chemical reactions used in aerobic organisms to generate energy via the oxidation of acetylcoenzyme A (CoA) derived from carbohydrates, fatty acids and proteins. In the eukaryotic system, the TCA cycle occurs completely in mitochondria, while the intermediates of the TCA cycle are retained inside mitochondria due to their polarity and hydrophilicity. Under cell stress conditions, mitochondria can become disrupted and release their contents, which act as danger signals in the cytosol. Of note, the TCA cycle intermediates may also leak from dysfunctioning mitochondria and regulate cellular processes. Increasing evidence shows that the metabolites of the TCA cycle are substantially involved in the regulation of immune responses. In this review, we aimed to provide a comprehensive systematic overview of the molecular mechanisms of each TCA cycle intermediate that may play key roles in regulating cellular immunity in cell stress and discuss its implication for immune activation and suppression.

scholarly journals Metabolomics of aging in primary fibroblasts from small and large breed dogs

2021 ◽  
Author(s):  
Paul S. Brookes ◽  
Ana G. Jimenez
Keyword(s):  
Aging Process ◽  
Tca Cycle ◽  
Therapeutic Strategies ◽  
Targeted Metabolomics ◽  
The Tca Cycle ◽  
Age Dependent ◽  
Primary Fibroblasts ◽  
Aging Rates ◽  
Underlying Mechanisms ◽  
Metabolomics Analysis

AbstractAmong several animal groups (eutherian mammals, birds, reptiles) lifespan positively correlates with body mass over several orders of magnitude. Contradicting this pattern are domesticated dogs, with small dog breeds exhibiting significantly longer lifespans than large dog breeds. The underlying mechanisms of differing aging rates across body masses are unclear, but it is generally agreed that metabolism is a significant regulator of the aging process. Herein, we performed a targeted metabolomics analysis on primary fibroblasts isolated from small and large breed young and old dogs. Regardless of size, older dogs exhibited lower glutathione and ATP, consistent with a role for oxidative stress and bioenergetic decline in aging. Furthermore, several size-specific metabolic patterns were observed with aging, including: (i) An apparent defect in the lower half of glycolysis in large old dogs at the level of pyruvate kinase. (ii) Increased glutamine anaplerosis into the TCA cycle in large old dogs. (iii) A potential defect in co-enzyme A biosynthesis in large old dogs. (iv) Low nucleotide levels in small young dogs that corrected with age. (v) An age dependent increase in carnitine in small dogs that was absent in large dogs. Overall, these data support the hypothesis that alterations in metabolism may underlie the different lifespans of small versus large breed dogs, and further work in this area may afford potential therapeutic strategies to improve the lifespan of large dogs.

The NAD Kinase Slr0400 Functions as a Growth Repressor in Synechocystis sp. PCC 6803

2021 ◽  
Author(s):  
Yuuma Ishikawa ◽  
Cedric Cassan ◽  
Aikeranmu Kadeer ◽  
Koki Yuasa ◽  
Nozomu Sato ◽  
...  
Keyword(s):  
Constitutive Expression ◽  
Physiological Role ◽  
Tca Cycle ◽  
Growth Conditions ◽  
Deficient Mutant ◽  
Nad Kinase ◽  
Cellular Processes ◽  
The Tca Cycle ◽  
Living Organisms

Abstract NADP+, the phosphorylated form of nicotinamide adenine dinucleotide (NAD), plays an essential role in many cellular processes. NAD kinase (NADK), which is conserved in all living organisms, catalyzes the phosphorylation of NAD+ to NADP+. However, the physiological role of phosphorylation of NAD+ to NADP+ in the cyanobacterium Synechocystis remains unclear. In this study, we report that slr0400, an NADK-encoding gene in Synechocystis, functions as a growth repressor under light-activated heterotrophic growth conditions and light and dark cycle conditions in the presence of glucose. We show, via characterization of NAD(P)(H) content and enzyme activity, that NAD+ accumulation in slr0400-deficient mutant results in the unsuppressed activity of glycolysis and tricarboxylic acid (TCA) cycle enzymes. In determining whether Slr0400 functions as a typical NADK, we found that constitutive expression of slr0400 in an Arabidopsis nadk2-mutant background complements the pale-green phenotype. Moreover, to determine the physiological background behind the growth advantage of mutants lacking slr04000, we investigated the photobleaching phenotype of slr0400-deficient mutant under high-light conditions. Photosynthetic analysis found in the slr0400-deficient mutant resulted from malfunctions in the Photosystem II (PSII) photosynthetic machinery. Overall, our results suggest that NADP(H)/NAD(H) maintenance by slr0400 plays a significant role in modulating glycolysis and the TCA cycle to repress the growth rate and maintain the photosynthetic capacity.

scholarly journals The hexokinase ″HKDC1″ interaction with the mitochondria is essential for hepatocellular carcinoma progression

2021 ◽  
Author(s):  
Md. Wasim Khan ◽  
Alexander Terry ◽  
Medha Priyadarshini ◽  
Grace Guzman ◽  
Jose Cordoba-Chacon ◽  
...  
Keyword(s):  
Hepatocellular Carcinoma ◽  
Mitochondrial Dysfunction ◽  
Tca Cycle ◽  
Metabolic Reprogramming ◽  
Selective Approach ◽  
Glucose Flux ◽  
The Tca Cycle

Hepatocellular carcinoma (HCC) is a leading cause of death from cancer malignancies. Recently, hexokinase domain containing 1 (HKDC1), was shown to have significant overexpression in HCC compared to healthy tissue. Using in vitro and in vivo tools, we examined the role of HKDC1 in HCC progression. Importantly, HKDC1 ablation stops HCC progression by promoting metabolic reprogramming by shifting glucose flux away from the TCA cycle. Next, HKDC1 ablation leads to mitochondrial dysfunction resulting in less cellular energy which cannot be compensated by enhanced glucose uptake. And finally, we show that the interaction of HKDC1 with the mitochondria is essential for its role in HCC progression, and without this mitochondrial interaction mitochondrial dysfunction occurs. In sum, HKDC1 is highly expressed in HCC cells compared to normal hepatocytes, therefore targeting HKDC1, specifically its interaction with the mitochondria, reveals a highly selective approach to target cancer cells in HCC.

scholarly journals ADAMTS5 in Osteoarthritis: Biological Functions, Regulatory Network, and Potential Targeting Therapies

2021 ◽  
Vol 8 ◽  
Author(s):  
Lejian Jiang ◽  
Jiachen Lin ◽  
Sen Zhao ◽  
Jiaqian Wu ◽  
Yongming Jin ◽  
...  
Keyword(s):  
Signaling Pathways ◽  
Molecular Mechanisms ◽  
Biological Process ◽  
Therapeutic Strategies ◽  
Molecular Signaling ◽  
Biological Functions ◽  
Fundamental Understanding

ADAMTS5 is involved in the pathogenesis of OA. As the major aggrecanase-degrading articular cartilage matrix, ADAMTS5, has been regarded as a potential target for OA treatment. We here provide an updated insight on the regulation of ADAMTS5 and newly discovered therapeutic strategies for OA. Pathophysiological and molecular mechanisms underlying articular inflammation and mechanotransduction, as well as chondrocyte hypertrophy were discussed, and the role of ADAMTS5 in each biological process was reviewed, respectively. Senescence, inheritance, inflammation, and mechanical stress are involved in the overactivation of ADAMTS5, contributing to the pathogenesis of OA. Multiple molecular signaling pathways were observed to modulate ADAMTS5 expression, namely, Runx2, Fgf2, Notch, Wnt, NF-κB, YAP/TAZ, and the other inflammatory signaling pathways. Based on the fundamental understanding of ADAMTS5 in OA pathogenesis, monoclonal antibodies and small molecule inhibitors against ADAMTS5 were developed and proved to be beneficial pre-clinically both in vitro and in vivo. Recent novel RNA therapies demonstrated potentials in OA animal models. To sum up, ADAMTS5 inhibition and its signaling pathway–based modulations showed great potential in future therapeutic strategies for OA.

Exploring the Benefits of Cellular Models to Uncover Bioactive Polyphenols for Neurodegeneration

2018 ◽  
Vol 24 (19) ◽  
pp. 2076-2106
Author(s):  
Rita Rosado-Ramos ◽  
Joana Godinho-Pereira ◽  
Ines Figueira ◽  
Carolina Jardim ◽  
Goncalo Garcia ◽  
...  
Keyword(s):  
Biological Activity ◽  
Neurodegenerative Diseases ◽  
Molecular Mechanisms ◽  
Protective Role ◽  
Bioactive Molecules ◽  
Cellular Models ◽  
In Vitro Systems

Our society is currently experiencing increased lifespan; one of the top causes for the high incidence of neurodegenerative disorders. The lack of effective treatments delaying or blocking disease progression has encouraged the active search for novel therapies. Many evidences support the protective role of phytochemicals in the prevention of neurodegenerative diseases, particularly (poly)phenols. In this review, we described the use of cellular-based models of neurodegenerative diseases and the benefits of their use as potent tools in the search for bioactive molecules, particularly (poly)phenols. Studies to assess the biological activity of (poly)phenols involve experimentation with in vitro and in vivo systems. In vitro systems are a useful tool as a first approach to test the underlined molecular mechanisms of candidate molecules. They can provide valuable information about biological activity, which can be then used to design animal and human intervention studies.

scholarly journals The Role of Epac in Cancer Progression

2020 ◽  
Vol 21 (18) ◽  
pp. 6489 ◽  
Author(s):  
Nadine Wehbe ◽  
Hasan Slika ◽  
Joelle Mesmar ◽  
Suzanne A. Nasser ◽  
Gianfranco Pintus ◽  
...  
Keyword(s):  
Cancer Progression ◽  
Molecular Mechanisms ◽  
Effector Protein ◽  
Cancer Cell Proliferation ◽  
Biological Processes ◽  
Oxygen Species ◽  
Malignant Phenotype ◽  
Cellular Processes ◽  
Underlying Mechanisms

Cancer continues to be a prime contributor to global mortality. Despite tremendous research efforts and major advances in cancer therapy, much remains to be learned about the underlying molecular mechanisms of this debilitating disease. A better understanding of the key signaling events driving the malignant phenotype of cancer cells may help identify new pharmaco-targets. Cyclic adenosine 3′,5′-monophosphate (cAMP) modulates a plethora of biological processes, including those that are characteristic of malignant cells. Over the years, most cAMP-mediated actions were attributed to the activity of its effector protein kinase A (PKA). However, studies have revealed an important role for the exchange protein activated by cAMP (Epac) as another effector mediating the actions of cAMP. In cancer, Epac appears to have a dual role in regulating cellular processes that are essential for carcinogenesis. In addition, the development of Epac modulators offered new routes to further explore the role of this cAMP effector and its downstream pathways in cancer. In this review, the potentials of Epac as an attractive target in the fight against cancer are depicted. Additionally, the role of Epac in cancer progression, namely its effect on cancer cell proliferation, migration/metastasis, and apoptosis, with the possible interaction of reactive oxygen species (ROS) in these phenomena, is discussed with emphasis on the underlying mechanisms and pathways.

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