Adenosine Triphosphate Availability Research Articles

Pyruvate kinase activators: targeting red cell metabolism in thalassemia.

Thalassemia is an inherited red blood cell disorder whereby the qualitative and/or quantitative imbalance in α- to β-globin ratio results in hemolysis and ineffective erythropoiesis. Oxidative stress, from the precipitated excess globin and free iron, is a major factor that drives hemolysis and ineffective erythropoiesis. Pyruvate kinase activity and adenosine triphosphate availability are reduced due to the overwhelmed cellular antioxidant system from the excessive oxidative stress. Mitapivat, a pyruvate kinase activator in development as a treatment for thalassemia, was shown to increase hemoglobin and reduce hemolysis in a small phase 2 single-arm trial of patients with α- and β-thalassemia. The ongoing phase 3 studies with mitapivat and the phase 2 study with etavopivat will examine the role of pyruvate kinase activators as disease modifying agents in thalassemia.

Frontal adenosine triphosphate markers from 31P MRS are associated with cognitive performance in healthy older adults: preliminary findings.

Aging is associated with declines in mitochondrial efficiency and energy production which directly impacts the availability of adenosine triphosphate (ATP), which contains high energy phosphates critical for a variety of cellular functions. Previous phosphorous magnetic resonance spectroscopy (31P MRS) studies demonstrate cerebral ATP declines with age. The purpose of this study was to explore the functional relationships of frontal and posterior ATP levels with cognition in healthy aging. Here, we measured frontal and posterior ATP levels using 31P MRS at 3 Tesla (3 T) and assessed cognition using the Montreal Cognitive Assessment (MoCA) in 30 healthy older adults. We found that greater frontal, but not posterior, ATP levels were significantly associated with better MoCA performance. This relationship remained significant after controlling for age, sex, years of education, and brain atrophy. In conclusion, our findings indicate that cognition is related to ATP in the frontal cortex. These preliminary findings may have important implications in the search for non-invasive markers of in vivo mitochondrial function and the impact of ATP availability on cognition. Future studies are needed to confirm the functional significance of regional ATP and cognition across the lifespan.

Oxidative phosphorylation in bone cells

The role of energy metabolism in bone cells is an active field of investigation. Bone cells are metabolically very active and require high levels of energy in the form of adenosine triphosphate (ATP) to support their function. ATP is generated in the cytosol via glycolysis coupled with lactic acid fermentation and in the mitochondria via oxidative phosphorylation (OXPHOS). OXPHOS is the final convergent metabolic pathway for all oxidative steps of dietary nutrients catabolism. The formation of ATP is driven by an electrochemical gradient that forms across the mitochondrial inner membrane through to the activity of the electron transport chain (ETC) complexes and requires the presence of oxygen as the final electron acceptor. The current literature supports a model in which glycolysis is the main source of energy in undifferentiated mesenchymal progenitors and terminally differentiated osteoblasts, whereas OXPHOS appears relevant in an intermediate stage of differentiation of those cells. Conversely, osteoclasts progressively increase OXPHOS during differentiation until they become multinucleated and mitochondrial-rich terminal differentiated cells. Despite the abundance of mitochondria, mature osteoclasts are considered ATP-depleted, and the availability of ATP is a critical factor that regulates the low survival capacity of these cells, which rapidly undergo death by apoptosis. In addition to ATP, bioenergetic metabolism generates reactive oxygen species (ROS) and intermediate metabolites that regulate a variety of cellular functions, including epigenetics changes of genomic DNA and histones. This review will briefly discuss the role of OXPHOS and the cross-talks OXPHOS-glycolysis in the differentiation process of bone cells.

Dihydroartemisinin inhibits plasmid transfer in drug-resistant Escherichia coli via limiting energy supply.

Conjugative transfer of antibiotic resistance genes (ARGs) by plasmids is an important route for ARG dissemination. An increasing number of antibiotic and nonantibiotic compounds have been reported to aid the spread of ARGs, highlighting potential challenges for controlling this type of horizontal transfer. Development of conjugation inhibitors that block or delay the transfer of ARG-bearing plasmids is a promising strategy to control the propagation of antibiotic resistance. Although such inhibitors are rare, they typically exhibit relatively high toxicity and low efficacy in vivo and their mechanisms of action are inadequately understood. Here, we studied the effects of dihydroartemisinin (DHA), an artemisinin derivative used to treat malaria, on conjugation. DHA inhibited the conjugation of the IncI2 and IncX4 plasmids carrying the mobile colistin resistance gene ( mcr-1) by more than 160-fold in vitro in Escherichia coli, and more than two-fold (IncI2 plasmid) in vivo in a mouse model. It also suppressed the transfer of the IncX3 plasmid carrying the carbapenem resistance gene bla NDM-5 by more than two-fold in vitro. Detection of intracellular adenosine triphosphate (ATP) and proton motive force (PMF), in combination with transcriptomic and metabolomic analyses, revealed that DHA impaired the function of the electron transport chain (ETC) by inhibiting the tricarboxylic acid (TCA) cycle pathway, thereby disrupting PMF and limiting the availability of intracellular ATP for plasmid conjugative transfer. Furthermore, expression levels of genes related to conjugation and pilus generation were significantly down-regulated during DHA exposure, indicating that the transfer apparatus for conjugation may be inhibited. Our findings provide new insights into the control of antibiotic resistance and the potential use of DHA.

Improving ATP availability by sod1 deletion with a strategy of precursor feeding enhanced S-adenosyl-L-methionine accumulation in Saccharomyces cerevisiae

S-adenosyl-L-methionine (SAM), used in diverse pharmaceutical applications, was biosynthesized from L-methionine (L-met) and adenosine triphosphate (ATP). This study aims to increase the accumulation of SAM in Saccharomyces cerevisiae by promoting ATP availability. Strain ΔSOD1 was obtained from the parent strain WT15–33 (CCTCC M 2021915) by deleting gene sod1, which improved the supply of ATP. The SAM content in strain ΔSOD1 exhibited a 22.3% improvement compared to the parent strain, which reached 93.6 mg g−1. The transformation of NADH (reduced nicotinamide adenine dinucleotide) and the relative expression of ATPase essential genes were investigated, respectively. The results showed that the lack of gene sod1 benefited the generation of ATP, which positively regulated the synthesis of SAM. Besides that, the production of SAM was further enhanced by improving substrate assimilation. With the infusion of 1.44 g L−1L-met and 0.60 g L−1 adenosine at 24 h (h) and 0 h following fermentation, the optimum medium could produce 1.54 g L−1 SAM. Based on the regulations mentioned above, the SAM concentration of strain ΔSOD1 enhanced from 7.3 g L−1 to 10.1 g L−1 in a 5-L fermenter in 118 h. This work introduces a novel idea for the biosynthesis of ATP and SAM, and the strain ΔSOD1 has the potential for industrial production.

Evaluation of aqueous magnesium concentration on performance of Pacific white shrimp (Litopenaeus vannamei) cultured in low salinity water of West Alabama, USA

The ionic profile of inland low salinity water sources can be dramatically different with variable concentrations of magnesium (Mg2+). Inland shrimp farmers in Alabama, USA, supplement Mg2+ at the start of each production cycle to reach concentrations >20 mg/L at 1 to 11 g/L salinities. However, this concentration may not be high enough for larger shrimp in the later phase of the production cycle. Therefore, two field trials were conducted on a commercial shrimp farm in west Alabama to evaluate the effects of Mg2+ concentration in low salinity water on growth, survival, and physiology of Pacific white shrimp, Litopenaeus vannamei. In the first study, additional Mg2+ was supplemented to four production ponds (28 mg/L Mg2+) and compared with four control ponds (12.8 mg/L Mg2+). A stocking density of 27 post-larvae/m2 was used in ponds, and shrimp were offered a commercial feed twice daily. After a 23-week pond trial, whole-body Mg2+ concentrations were higher in shrimp reared in Mg2+ treated ponds, while no significant differences in other study variables were observed between pond groups. After week 15 (shrimp weight > 22 g), weekly body weights of shrimp were significantly lower in the control group compared to the elevated Mg2+ treatment. This could be due to size-dependent deficiency in the availability of adenosine triphosphate (ATP) and Mg2+ to support growth of larger adult shrimp. The second experiment was conducted to evaluate performance of larger shrimp (∼13 g initial weight) reared in two on-levee flow-through tank systems. One tank system received water from a control pond with 12 mg/L Mg2+, while the second system was sourced with water from a production pond with a higher amount of Mg2+ (37 mg/L). In each system, twelve 800 L tanks were stocked with shrimp at three different densities (24, 29, and 35 shrimp/m2) to evaluate possible interactions between stocking density and Mg2+ concentration in water. Following an 8-week tank trial, no significant effect of Mg2+ concentration, stocking density, or their interaction was observed on growth, survival, or physiology of shrimp. Overall, these results confirm that even moderate elevations in Mg2+ in low salinity water are advantageous to adult shrimp (>22 g) in later stages of the production cycle compared to post-larvae, juveniles, or sub-adult shrimp.

Diet, Muscle Protein Synthesis and Autophagy Relationships in Cancer: An Attempt to Understand Where Are We Going, and Why

Protein-based structures are indispensable to maintain life, so identification and removal of worn out structures achieved through proteostasis, the sum of micro and macro-autophagy (autophagy) plus ubiquitin-proteasome system, must balance renewal by new synthesis. Many of the elements controlling dynamically equilibria between protein synthesis and protein degradation have been identified and modalities of activation actively studied, still we are quite far from mastering how this balance is ruled. Failure to maintain a positive balance between protein synthesis and protein degradation would result in sarcopenia, defined as the loss of skeletal muscle mass and function, a major clinical problem frequently accompanying chronic illnesses, but peculiarly spotted in cancer and in elderly patients. Also, how cancer is fed, and how nutrition in cancer patients may affect evolution and therapy effectiveness is another field of opinions and uncertainty. On the other hand, exercise and nutrition tailored to provide adequate amounts of amino acids are widely considered a necessary strategy for prevention and treatment of protein synthetic deficits in muscles. This paper will synthetically review how different nutritional strategies and energy production may interconnect efficiently synthesis and scavenging of aged and overused protein molecules by autophagy. Finally, since energy availability rules life and death of cells and organisms, an hypothesis predicting how energy may control the ratios among protein synthesis and autophagy is proposed: in normal conditions, protein syntheses have a key role in autophagy activation by consuming large amounts of energy when forming peptidic bonds, that is adenosine tri-phosphate (ATP) is consumed to mono-phospahate (AMP), thus decreasing ATP to AMP ratios. Conversely, both protein syntheses and autophagy may be scarcely activated when low availability of ATP would result also in lowest concentrations of AMP. In this peculiar setting, reduced rates of both protein syntheses and autophagy would be observed, resulting in worsening of protein balance and functions.

Crowding within synaptic junctions influences the degradation of nucleotides by CD39 and CD73 ectonucleotidases

Synapsed cells can communicate using exocytosed nucleotides like adenosine triphosphate (ATP). Ectonucleotidases localized to synaptic junctions degrade nucleotides into metabolites like adenosine monophosphate (AMP) or adenosine. Oftentimes nucleotide degradation occurs in a sequential manner, of which ATP degradation by CD39 and CD73 is a representative example. Here, CD39 first converts ATP and adenosine diphosphate (ADP) into AMP, after which AMP is dephosphorylated into adenosine by CD73. Hence, the concerted activity of CD39 and CD73 can help shape cellular responses to extracellular ATP. In a previous study, we demonstrated that coupled CD39 and CD73 activity within synapse-like junctions is strongly controlled by the enzymes' co-localization, their surface charge densities, and the electrostatic potential of the surrounding cell membranes. In this study, we demonstrate that crowders within synaptic junctions, which can include globular proteins like cytokines and membrane-bound proteins, impact coupled CD39 and CD73 ectonucleotidase activity and, in turn, the availability of intrasynapse ATP. Specifically, we developed a spatially explicit, reaction-diffusion model for the coupled conversion of ATP → AMP and AMP → adenosine in a model synaptic junction with crowders that is solved via the finite element method. Our modeling results suggest that the association rate for ATP to CD39 is strongly influenced by the density of intrasynaptic protein crowders, as increasing crowder density generally suppressed ATP association kinetics. Much of this suppression can be rationalized based on a loss of configurational entropy. The surface charges of crowders can further influence the association rate, with the surprising result that favorable crowder-nucleotide electrostatic interactions can yield CD39 association rates that are faster than crowder-free configurations. However, attractive crowder-nucleotide interactions decrease the rate and efficiency of adenosine production, which in turn increases the availability of ATP and AMP within the synapse relative to crowder-free configurations. These findings highlight how CD39 and CD73 ectonucleotidase activity, electrostatics, and crowding within synapses influence the availability of nucleotides for intercellular communication.

A vaccine to prevent initial loss of cognition and eventual Alzheimer's disease in elderly persons.

Prevention is better than cure and prevention of Alzheimer's disease (AD) may be possible. In elderly persons who are cognitively normal, synaptic hypometabolism as shown by reduced cerebral uptake of fluorodeoxyglucose (18F‐FDG), provides a premonitory signal of potential, future loss of cognition if those individuals also have present evidence of amyloid deposition seen in the Pittsburgh compound B positron emission tomography (PIB‐PET) scan for amyloid. Those are the persons who should be targeted if one aims to prevent AD. The synaptic hypometabolism implies that the brain's availability of adenosine triphosphate (ATP) is inadequate for performance of all required synaptic functions. This review first describes the basis for asserting that reduced cerebral uptake of 18F‐FDG accurately reflects synaptic hypometabolism; second, explains the basis for asserting that hypometabolism implies inadequate ATP; third, shows that amyloid beta (Aβ) itself, Aβ modified by pyroglutamate to become a molecule termed pE(3)Aβ, and cyclophilin‐D, in concert are the main contributors to inadequate synaptic ATP and that, therefore, reducing all of their levels would neutralize their combined effect and correct the hypometabolism. pE(3)Aβ is more neurotoxic than unmodified Aβ; and cyclophilin D inhibits ATP synthase and reduces ATP formation. Finally, this review describes an mRNA self‐replicating vaccine that will raise brain levels of ATP by reducing Aβ, pyroglutamate‐modified Aβ, and cyclophilin‐D, and thereby—in cognitively normal elderly persons who have synaptic hypometabolism—prevent initiation of the process that terminates in AD.

Triose phosphate utilization limitation: an unnecessary complexity in terrestrial biosphere model representation of photosynthesis

Triose phosphates are the principal product of photosynthesis. They are used within the chloroplast for starch synthesis, or translocated to the cytosol where they are used to fuel sucrose synthesis. Use of triose phosphate releases inorganic phosphate, and is under strict metabolic control that matches the supply of triose phosphate from the Calvin-Benson cycle to the demand for carbon by sinks (Heldt & Heldt, 2011; McClain & Sharkey, 2019). However, a low rate of triose phosphate utilization (TPU) can deplete the phosphate pool, restrict ATP synthesis and reduce the availability of ATP to power the Calvin-Benson cycle, thereby limiting photosynthesis (Sharkey, 1985).

Depressed Cardiac Mechanical Energetic Efficiency: A Contributor to Cardiovascular Risk in Common Metabolic Diseases-From Mechanisms to Clinical Applications.

Cardiac mechanical energetic efficiency is the ratio of external work (EW) to the total energy consumption. EW performed by the left ventricle (LV) during a single beat is represented by LV stroke work and may be calculated from the pressure–volume loop area (PVLA), while energy consumption corresponds to myocardial oxygen consumption (MVO2) expressed on a per-beat basis. Classical early human studies estimated total mechanical LV efficiency at 20–30%, whereas the remaining energy is dissipated as heat. Total mechanical efficiency is a joint effect of the efficiency of energy transfer at three sequential stages. The first step, from MVO2 to adenosine triphosphate (ATP), reflects the yield of oxidative phosphorylation (i.e., phosphate-to-oxygen ratio). The second step, from ATP split to pressure–volume area, represents the proportion of the energy liberated during ATP hydrolysis which is converted to total mechanical energy. Total mechanical energy generated per beat—represented by pressure–volume area—consists of EW (corresponding to PVLA) and potential energy, which is needed to develop tension during isovolumic contraction. The efficiency of the third step of energy transfer, i.e., from pressure–volume area to EW, decreases with depressed LV contractility, increased afterload, more concentric LV geometry with diastolic dysfunction and lower LV preload reserve. As practical assessment of LV efficiency poses methodological problems, De Simone et al. proposed a simple surrogate measure of myocardial efficiency, i.e., mechano-energetic efficiency index (MEEi) calculated from LV stroke volume, heart rate and LV mass. In two independent cohorts, including a large group of hypertensive subjects and a population-based cohort (both free of prevalent cardiovascular disease and with preserved ejection fraction), low MEEi independently predicted composite adverse cardiovascular events and incident heart failure. It was hypothesized that the prognostic ability of low MEEi can result from its association with both metabolic and hemodynamic alterations, i.e., metabolic syndrome components, the degree of insulin resistance, concentric LV geometry, LV diastolic and discrete systolic dysfunction. On the one part, an increased reliance of cardiomyocytes on the oxidation of free fatty acids, typical for insulin-resistant states, is associated with both a lower yield of ATP per oxygen molecule and lesser availability of ATP for contraction, which might decrease energetic efficiency of the first and second step of energy transfer from MVO2 to EW. On the other part, concentric LV remodeling and LV dysfunction despite preserved ejection fraction can impair the efficiency of the third energy transfer step. In conclusion, the association of low MEEi with adverse cardiovascular outcome might be related to a multi-step impairment of energy transfer from MVO2 to EW in various clinical settings, including metabolic syndrome, diabetes, hypertension and heart failure. Irrespective of theoretical considerations, MEEi appears an attractive simple tool which couldt improve risk stratification in hypertensive and diabetic patients for primary prevention purposes. Further clinical studies are warranted to estimate the predictive ability of MEEi and its post-treatment changes, especially in patients on novel antidiabetic drugs and subjects with common metabolic diseases and concomitant chronic coronary syndromes, in whom the potential relevance of MEE can be potentiated by myocardial ischemia.

PERIPHERAL BLOOD LYMPHOCYTES ADENOSINE TRIPHOSPHATE AVAILABILITY AMONG THE RESIDENTS OF THE NORTHERN EUROPEAN RUSSIA

Metabolic pathways participating in adenosine triphosphate (ATP) synthesis play an important role in lymphocytes normal development and functioning. Energetic metabolism has an influence on differentiation, proliferation and fate of lymphocytes. The aim of the study is to define ATP availability of peripheral blood lymphocytes and the level of mitochondrial metabolism regulator sirtuin 3 (SIRT3) in healthy northerners. Methods. 106 volunteers, habitants of Arkhangelsk (76 women and 30 men, 21-63 years old) were surveyed. Amounts of immunocompetent cells with receptors (CD3, CD4, CD8, CD10, CD16, CD71, CD23, CD25, HLA DR, CD95) were determined by indirect immunoperoxidase method, ATP concentration in lymphocytes by bioluminescent method, and additionally SIRT3 (23 volunteers) by enzyme immunoassay. Two groups were selected using "k-means" cluster analysis which differed statistically significantly in all studied parameters. Results. It was found that 78 % of the surveyed participants were in the group where ATP concentration was 0,95 (0,487) mcmol/106 cells, in other group with 22 % participants it was 3,71 (1,319) mcmol/106 cells, р < 0,0001. Difference in relative amounts of particular cell phenotypes was revealed in the mentioned groups: in the group with lower ATP levels the higher was percentage of CD95+, CD23+ and HLA DR cells. In the group with higher ATP levels the higher was percentage of CD3+, CD4+, CD8+, CD71+ cells and shift of CD10/CD95 and CD4/CD23 ratios was also detected in favor of CD10+ и CD4+ cells with high levels of metabolic activity. Difference of ATP levels was omni-directional with SIRT3, regulator of mitochondrial metabolism, level with concentrations 0,15 (0,039) and 0,39 (0,198) pg/106 cells, р = 0,0097. Conclusion. Intersectionality of ATP availability and reactivity of T cells was identified. It appears to be promising to determine the level of ATP for evaluation of lymphocytes functioning.

The cellular stress response and temperature: Function, regulation, and evolution.

The cellular stress response (CSR) is critical for enabling organisms to cope with thermal damage to proteins, nucleic acids, and membranes. It is a graded response whose properties vary with the degree of cellular damage. Molecular damage has positive, as well as negative, function-perturbing effects. Positive effects include crucial regulatory interactions that orchestrate involvement of the different components of the CSR. Thermally unfolded proteins signal for rapid initiation of transcription of genes encoding heat shock proteins (HSPs), central elements of the heat shock response (HSR). Thermal disruption of messenger RNA (mRNA) secondary structures in untranslated regions leads to the culling of the mRNA pool: thermally labile mRNAs for housekeeping proteins are degraded by exonucleases; heat-resistant mRNAs for stress proteins like HSPs then can monopolize the translational apparatus. Thus, proteins and RNA function as "cellular thermometers," and evolved differences in their thermal stabilities enable rapid initiation of the CSR whenever cell temperature rises significantly above the normal thermal range of a species. Covalent DNA damage, which may result from increased production of reactive oxygen species, is temperature-dependent; its extent may determine cellular survival. High levels of stress that exceed capacities for molecular repair can lead to proteolysis, inhibition of cell division, and programmed cell death (apoptosis). Onset of these processes may occur later in the stress period, after initiation of the HSR, to allow HSPs opportunity to restore protein homeostasis. Delay of these energy costly processes may also result from shortfalls in availability of adenosine triphosphate and reducing power during times of peak stress.

Participation of phosphoryl transfer network on branchial energetic imbalance of matrinxã (Brycon amazonicus) exposed to air: Notable involvement of creatine kinase

Concerns about common aquaculture procedures have been currently raised, including air exposure, since usually they cause a variable degree of stress and contribute to fish mortality. Energetic alterations during exposure to air have been extensively reported, but their effects linked to phosphoryl transfer network, an essential network of enzymes to precise coupling of the adenosine triphosphate (ATP)-production and ATP-consuming process for maintenance of bioenergetic homeostasis remain unknown. Thus, the aim of this study was to evaluate whether the phosphoryl transfer network could be a pathway involved in the bioenergetic imbalance of matrinxã (Brycon amazonicus) exposed to air. Branchial cytosolic and mitochondrial creatine kinase (CK) activities were significantly lower at 30 and 60 min post-stress in fish subjected to air exposure than in the control group. Branchial ATP content and sodium‑potassium pump (Na+, K+-ATPase) activity were significantly lower at 30 and 60 min post-stress in fish subjected to air exposure than in the control group, while reactive oxygen species (ROS) and lipid peroxidation levels were significantly higher in the same moments in fish subjected to air exposure than in the control group. No significant difference was observed between groups or over the time regarding adenylate kinase and pyruvate kinase activities. Based on these data, impairment of CK activity elicited by air exposure disrupted branchial energetic balance via reduction on ATP availability in the gills and provoked impairment of Na+, K +ATPase activity, which appears to be mediated by ROS overproduction and lipid peroxidation.

Saprolegnia parasitica impairs branchial phosphoryl transfer network in naturally infected grass carp (Ctenopharyngodon idella): prejudice on bioenergetic homeostasis

Precise coupling of spatially separated intracellular adenosine triphosphate (ATP) producing and ATP-consuming exerts a key role in bioenergetic balance, and the phosphoryl transfer network, catalyzed by creatine kinase (CK), adenylate kinase (AK), and pyruvate kinase (PK), is fundamental in energetic homeostasis of tissues with high-energy requirements, as the branchial tissue. This whole system is very sensitive, and our hypothesis is that it can be altered in cases of infectious diseases in fish, such as that caused by the oomycete Saprolegnia parasitica. The effects of S. parasitica infection on gills remain poorly understood and limited only to histopathological studies. Thus, the aim of this study was to evaluate whether natural infection by S. parasitica impairs the enzymes of the phosphoryl transfer network in gills of grass carp (Ctenopharyngodon idella), as well as the pathways involved in this inhibition. In this study, we used sick carp and compared to healthy carp, fish of similar age and receiving the same feed, but allocated in different tanks. Branchial CK (cytosolic and mitochondrial) activity and ATP levels decreased in infected fish compared to uninfected on day 7 post-infection (PI), while no significant difference was observed between groups regarding branchial AK and PK activities. Branchial sodium-potassium ion pump (Na+, K+-ATPase) activity decreased in infected carp compared to uninfected on day 7 PI, while reactive oxygen species (ROS) and thiobarbituric acid reactive substance (TBARS) levels were higher. Gill histopathology revealed massive necrosis, loss of branchial epithelium, and detachment of the epithelium interlayer with structural loss of secondary lamellae. Based on these data, the impairment of CK activity elicited by S. parasitica caused an impairment in branchial energetic homeostasis, reducing the ATP availability in the gills and provoking an impairment on Na+, K+-ATPase activity. Moreover, the inhibition on CK activity appears to be mediated by ROS overproduction and lipid peroxidation, which contribute to disease pathogenesis linked to branchial tissue.

Impairment of branchial energy transfer pathways in disease pathogenesis of Providencia rettgeri infection in juvenile Nile tilapia (Oreochromis niloticus): Remarkable involvement of creatine kinase activity

It is becoming evident that bacterial infectious diseases negatively affect gill energy metabolism, mainly because it causes alterations of enzymes that belong to the phosphotransfer network, such as creatine kinase (CK), adenylate kinase (AK) and pyruvate kinase (PK). Thus, the aim of this study was to evaluate whether the phosphotransfer network could be one pathway involved in the bioenergetic imbalance during Providencia rettgeri infection, as well as to investigate the bacteria's influence on adenosine triphosphate (ATP)-dependent enzymes. In this study, branchial cytosolic and mitochondrial CK activity decreased in infected animals on day 14 post-infection (PI) when compared to its respective control group. Moreover, branchial sodium-potassium pump (Na+/K+-ATPase) and proton-pump (H+-ATPase) activities decreased in infected animals on day 14 PI compared to the control. Finally, branchial thiobarbituric acid reactive substance levels increased in infected animals on day 14 PI, while non-protein thiol (NPSH) levels decreased. No significant difference was observed between groups regarding AK and PK activities. In summary, the impairment of CK activity elicited by P. rettgeri caused an impairment in branchial energetic homeostasis, reducing ATP availability in the gills. Moreover, inhibition of CK activity provokes an impairment of ATP-dependent enzymes, such as Na+/K+-ATPase and H+-ATPase, which can be mediated by lipid oxidative damage and reduction of NPSH content.

Thiamethoxam induced hepatic energy changes in silver catfish via impairment of the phosphoryl transfer network pathway: Toxicological effects on energetics homeostasis

Precise coupling of spatially separated intracellular adenosine triphosphate (ATP)-producing and ATP-consuming processes exerts a pivotal role in bioenergetic homeostasis of living organisms, and the phosphotransfer network pathway, catalyzed by adenylate kinase (AK) and pyruvate kinase (PK), is fundamental in cellular and tissue energetic homeostasis. Measurement of the phosphotransfer network can provide new information for understanding the alterations in hepatic energetic metabolism during exposition to insecticides, such as thiamethoxam. Therefore, the aim of this study was to evaluate whether exposition to thiamethoxam negatively affects the hepatic enzymes of the phosphotransfer network in silver catfish (Rhamdia quelen). Hepatic AK and PK activities were inhibited at 3.75 μg L−1 after 24 h of exposure and at 1.125 and 3.75 μg L−1 after 96 h of exposure compared with the control group. The hepatic ATP levels were decreased following 3.75 μg L−1 thiamethoxam treatment after 24 h of exposure and at 1.125 and 3.75 μg L−1 after 96 h of exposure compared with the control group. The enzymatic activity of the phosphotransfer network and ATP levels did not recover after 48 h of recovery in clean water. Thus, the inhibition of hepatic AK and PK activities by thiamethoxam caused impairment of energy homeostasis in liver tissue, decreasing hepatic ATP availability. Moreover, the absence of a mutual compensatory mechanism between these enzymes directly contributes to ATP depletion and to a severe energetic dysregulation, which may contribute to toxic effects caused by thiamethoxam.

Changes in the cerebral phosphotransfer network impair energetic homeostasis in an aflatoxin B1-contaminated diet.

The phosphotransfer network system, through the enzymes creatine kinase (CK), adenylate kinase (AK), and pyruvate kinase (PK), contributes to efficient intracellular energetic communication between cellular adenosine triphosphate (ATP) consumption and production in tissues with high energetic demand, such as cerebral tissue. Thus, the aim of this study was to evaluate whether aflatoxin B1 (AFB1) intoxication in diet negatively affects the cerebral phosphotransfer network related to impairment of cerebral ATP levels in silver catfish (Rhamdia quelen). Brain cytosolic CK activity decreased in animals fed with a diet contaminated with AFB1 on days 14 and 21 post-feeding, while mitochondrial CK activity increased, when compared to the control group (basal diet). Also, cerebral AK and PK activity decreased in animals fed with a diet contaminated with AFB1 on days 14 and 21 post-feeding, similarly to the results observed for cerebral ATP levels. Based on this evidence, inhibition of cerebral cytosolic CK activity is compensated by stimulation of mitochondrial CK activity in an attempt to prevent impairment of communication between sites of ATP generation and ATP utilization. The inhibition of cerebral AK and PK activity leads to impairment of cerebral energy homeostasis, decreasing the brain's ATP availability. Moreover, the absence of a reciprocal compensatory mechanism between these enzymes contributes to cerebral energetic imbalance, which may contribute to disease pathophysiology.

Improving mitochondrial function significantly reduces metabolic, visual, motor and cognitive decline in aged Drosophila melanogaster

Mitochondria play a major role in aging. Over time, mutations accumulate in mitochondrial DNA leading to reduced adenosine triphosphate (ATP) production and increased production of damaging reactive oxygen species. If cells fail to cope, they die. Reduced ATP will result in declining cellular membrane potentials leading to reduced central nervous system function. However, aged mitochondrial function is improved by long wavelength light (670 nm) absorbed by cytochrome c oxidase in mitochondrial respiration. In Drosophila, lifelong 670-nm exposure extends lifespan and improves aged mobility. Here, we ask if improved mitochondrial metabolism can reduce functional senescence in metabolism, sensory, locomotor, and cognitive abilities in old flies exposed to 670 nm daily for 1 week. Exposure significantly increased cytochrome c oxidase activity, whole body energy storage, ATP and mitochondrial DNA content, and reduced reactive oxygen species. Retinal function and memory were also significantly improved to levels found in 2-week-old flies. Mobility improved by 60%. The mode of action is likely related to improved energy homeostasis increasing ATP availability for ionic ATPases critical for maintenance of neuronal membrane potentials. 670-nm light exposure may be a simple route for resolving problems of aging.

Different dose rate-dependent responses of human melanoma cells and fibroblasts to low dose fast neutrons

Purpose: To analyze the dose rate influence in hyper-radiosensitivity (HRS) of human melanoma cells to very low doses of fast neutrons and to compare to the behaviour of normal human skin fibroblasts.Materials and methods: We explored different neutron dose rates as well as possible implication of DNA double-strand breaks (DSB), apoptosis, and energy-provider adenosine-triphosphate (ATP) levels during HRS.Results: HRS in melanoma cells appears only at a very low dose rate (VLDR), while a high dose rate (HDR) induces an initial cell-radioresistance (ICRR). HRS does not seem to be due either to DSB or to apoptosis. Both phenomena (HRS and ICRR) appear to be related to ATP availability for triggering cell repair. Fibroblast survival after neutron irradiation is also dose rate-dependent but without HRS.Conclusions: Melanoma cells or fibroblasts exert their own survival behaviour at very low doses of neutrons, suggesting that in some cases there is a differential between cancer and normal cells radiation responses. Only the survival of fibroblasts at HDR fits the linear no-threshold model. This new insight into human cell responses to very low doses of neutrons, concerns natural radiations, surroundings of accelerators, proton-therapy devices, flights at high altitude. Furthermore, ATP inhibitors could increase HRS during high-linear energy transfer (high-LET) irradiation.