Adenylate kinase 1 overexpression increases locomotor activity in medaka fish

Maintenance of the energy balance is indispensable for cell survival and function. Adenylate kinase (Ak) is a ubiquitous enzyme highly conserved among many organisms. Ak plays an essential role in energy regulation by maintaining adenine nucleotide homeostasis in cells. However, its role at the whole organism level, especially in animal behavior, remains unclear. Here, we established a model using medaka fish (Oryzias latipes) to examine the function of Ak in environmental adaptation. Medaka overexpressing the major Ak isoform Ak1 exhibited increased locomotor activity compared to that of the wild type. Interestingly, this increase was temperature dependent. Our findings suggest that cellular energy balance can modulate locomotor activity.

Elovl2-Ablation Leads to Mitochondrial Membrane Fatty Acid Remodeling and Reduced Efficiency in Mouse Liver Mitochondria

The fatty acid elongase ELOngation of Very-Long-chain fatty acids protein 2 (ELOVL2) controls the elongation of polyunsaturated fatty acids (PUFA) producing precursors for omega-3, do-cosahexaenoic acid (DHA), and omega-6, docosapentaenoic acid (DPAn6) in-vivo. Expectedly, Elovl2-ablation drastically reduced the DHA and DPAn6 in liver mitochondrial membranes. Unexpectedly, however, total PUFAs levels decreased further than could be explained by Elovl2 ablation. The lipid peroxidation process was not involved in PUFAs reduction since malondial-dehyde-lysine (MDAL) and other oxidative stress biomarkers were not enhanced. The content of mitochondrial respiratory chain proteins remained unchanged. Still, membrane remodeling was associated with high voltage-dependent anion channel (VDAC) and adenine nucleotide trans-locase 2 (ANT2), a possible reflection of the increased demand on phospholipid transport to the mitochondria. Mitochondrial function was impaired despite preserved content of the respiratory chain proteins and the absence of oxidative damage. Oligomycin-insensitive oxygen consumption increased, and coefficients of respiratory control were reduced by 50%. The mitochondria became very sensitive to fatty acid-induced uncoupling and permeabilization, where ANT2 is involved. Mitochondrial volume and number of peroxisomes increased as revealed by transmission elec-tron microscopy. In conclusion, the results imply that endogenous DHA production is vital for the normal function of mouse liver mitochondria and could be relevant not only for mice but also for human metabolism.

Pannexin Channel Regulation of Cell Migration: Focus on Immune Cells

The role of Pannexin (PANX) channels during collective and single cell migration is increasingly recognized. Amongst many functions that are relevant to cell migration, here we focus on the role of PANX-mediated adenine nucleotide release and associated autocrine and paracrine signaling. We also summarize the contribution of PANXs with the cytoskeleton, which is also key regulator of cell migration. PANXs, as mechanosensitive ATP releasing channels, provide a unique link between cell migration and purinergic communication. The functional association with several purinergic receptors, together with a plethora of signals that modulate their opening, allows PANX channels to integrate physical and chemical cues during inflammation. Ubiquitously expressed in almost all immune cells, PANX1 opening has been reported in different immunological contexts. Immune activation is the epitome coordination between cell communication and migration, as leukocytes (i.e., T cells, dendritic cells) exchange information while migrating towards the injury site. In the current review, we summarized the contribution of PANX channels during immune cell migration and recruitment; although we also compile the available evidence for non-immune cells (including fibroblasts, keratinocytes, astrocytes, and cancer cells). Finally, we discuss the current evidence of PANX1 and PANX3 channels as a both positive and/or negative regulator in different inflammatory conditions, proposing a general mechanism of these channels contribution during cell migration.

Life-long sports engagement enhances adult erythrocyte adenylate energetics

Regular physical activity reduces age-related metabolic and functional decline. The energy stored in adenine nucleotides (ATP, ADP, and AMP) is essential to enable multiple vital functions of erythrocytes and body tissues. Our study aimed to predict the rate of age-related changes in erythrocyte adenylate energetics in athletes and untrained controls. The erythrocyte concentration of adenylates was measured in 68 elite endurance runners (EN, 20–81 years), 58 elite sprinters (SP, 21–90 years), and 62 untrained individuals (CO, 20–68 years). Resting concentrations of ATP, total adenine nucleotide pool, and ADP/AMP ratio were lowest in the CO group and highest in the SP group. The concentration of erythrocyte ADP and AMP was lowest in the EN group and highest in the CO group. In all studied groups, we found a significant increase in the concentration of most erythrocyte adenylate metabolites with age. For ADP and AMP, the trend was also significant but decreasing. Our study strongly suggests that lifelong sports and physical activity participation supports erythrocyte energetics preservation. Although the direction and the predicted rates of change are similar regardless of the training status, the concentrations of particular metabolites are more advantageous in highly trained athletes than in less active controls. Of the two analyzed types of physical training, sprint-oriented training seems to be more efficient in enhancing erythrocyte metabolism throughout adulthood and old age than endurance training.

Genistein regulates adipogenesis by blocking the function of adenine nucleotide translocase-2 in the mitochondria

Genistein exerts anti-adipogenic effects, but its target molecules remain unclear. Here, we delineated the molecular mechanism underlying the anti-adipogenic effect of genistein. A pulldown assay using genistein-immobilized beads identified adenine nucleotide translocase-2 as a genistein-binding protein in adipocytes. Adenine nucleotide translocase-2 exchanges ADP/ATP through the mitochondrial inner membrane. Similar to the knockdown of adenine nucleotide translocase-2, genistein treatment decreased ADP uptake into the mitochondria and ATP synthesis. Genistein treatment and adenine nucleotide translocase-2 knockdown suppressed adipogenesis and increased phosphorylation of AMP-activated protein kinase. Adenine nucleotide translocase-2 knockdown reduced the transcriptional activity of CCAAT/enhancer-binding protein β, whereas AMP-activated protein kinase inhibition restored the suppression of adipogenesis by adenine nucleotide translocase-2 knockdown. These results indicate that genistein interacts directly with adenine nucleotide translocase-2 to suppress its function. The downregulation of adenine nucleotide translocase-2 reduces the transcriptional activity of CCAAT/enhancer-binding protein β via activation of AMP-activated protein kinase, which consequently represses adipogenesis.

Role of Mitochondrial Membrane Potential and Lactate Dehydrogenase A in Apoptosis

: Apoptosis is a programmed cell death that occurs due to the production of several catabolic enzymes. During this process, several morphological and biochemical changes occur in mitochondria, the main organelle in the cell that participates in apoptosis and control apoptotic pathways. During apoptosis, cytochrome c is released from mitochondria, and different proteins activate caspase cascades that carry out the cell towards the death process. Apoptosis mainly occurs due to p53 protein that allows the abnormal cells to proliferate. Bcl-2 and Bcl-xl are two anti-apoptotic members of the protein family that prevents apoptosis. The membrane potential of mitochondria decreases by opening of the permeability transition pore (PTP). These PTP are formed by the binding of Bax with adenine nucleotide translocator (ANT) and cause depolarization in the membrane. The depolarization releases apoptogenic factors (cytochrome c) that result in the loss of oxidative phosphorylation. Knockdown in lactate dehydrogenase (LDH) is the cause of the decrease in mitochondrial membrane potential elevating the levels of reactive oxygen species (ROS) and Bax. Consequently, causing an increase in the release of cytochrome c that ultimately leads to apoptosis. In this review, we have summarized the combined effect of mitochondrial membrane potential and LDH enzyme that triggers apoptosis in cells and their role in the mechanism of apoptosis.

Adenine Nucleotide Metabolites in Uremic Erythrocytes as Metabolic Markers of Chronic Kidney Disease in Children

Chronic kidney disease (CKD) is associated with multifaceted pathophysiological lesions including metabolic pathways in red blood cells (RBC). The aim of the study was to determine the concentration of adenine nucleotide metabolites, i.e., nicotinamide adenine dinucleotide (NAD)-oxidized form, nicotinamide adenine dinucleotide hydrate (NADH)-reduced form, nicotinic acid mononucleotide (NAMN), β-nicotinamide mononucleotide (NMN), nicotinic acid adenine dinucleotide (NAAD), nicotinic acid (NA) and nicotinamide (NAM) in RBC and to determine a relationship between NAD metabolites and CKD progression. Forty-eight CKD children and 33 age-matched controls were examined. Patients were divided into groups depending on the CKD stages (Group II-stage II, Group III- stage III, Group IV- stage IV and Group RRT children on dialysis). To determine the above-mentioned metabolites concentrations in RBC liquid chromatography-mass spectrometry was used. Results: the only difference between the groups was shown concerning NAD in RBC, although the values did not differ significantly from controls. The lowest NAD values were found in Group II (188.6 ± 124.49 nmol/mL, the highest in group IV (324.94 ± 63.06 nmol/mL. Between Groups II and IV, as well as III and IV, the differences were statistically significant (p < 0.032, p < 0.046 respectively). Conclusions. CKD children do not have evident abnormalities of RBC metabolism with respect to adenine nucleotide metabolites. The significant differences in erythrocyte NAD concentrations between CKD stages may suggest the activation of adaptive defense mechanisms aimed at erythrocyte metabolic stabilization. It seems that the implementation of RRT has a positive impact on RBC NAD metabolism, but further research performed on a larger population is needed to confirm it.

Mitochondria Isolated from Hearts Subjected to Ischemia/Reperfusion Benefit from Adenine Nucleotide Translocase 1 Overexpression

Reperfusion is the only feasible therapy following myocardial infarction, but reperfusion has been shown to damage mitochondrial function and disrupt energy production in the heart. Adenine nucleotide translocase 1 (ANT1) facilitates the transfer of ADP/ATP across the inner mitochondrial membrane; therefore, we tested whether ANT1 exerts protective effects on mitochondrial function during ischemia/reperfusion (I/R). The hearts of wild-type (WT) and transgenic ANT1-overexpressing (ANT1-TG) rats were exposed to I/R injury using the standard Langendorff technique, after which mitochondrial function, hemodynamic parameters, infarct size, and components of the contractile apparatus were determined. ANT1-TG hearts expressed higher ANT protein levels, with reduced levels of oxidative 4-hydroxynonenal ANT modifications following I/R. ANT1-TG mitochondria isolated from I/R hearts displayed stable calcium retention capacity (CRC) and improved membrane potential stability compared with WT mitochondria. Mitochondria isolated from ANT1-TG hearts experienced less restricted oxygen consumption than WT mitochondria after I/R. Left ventricular diastolic pressure (Pdia) decreased in ANT1-TG hearts compared with WT hearts following I/R. Preserved diastolic function was accompanied by a decrease in the phospho-lamban (PLB)/sarcoplasmic reticulum calcium ATPase (SERCA2a) ratio in ANT1-TG hearts compared with that in WT hearts. In addition, the phosphorylated (P)-PLB/PLB ratio increased in ANT1-TG hearts after I/R but not in WT hearts, which indicated more effective calcium uptake into the sarcoplasmic reticulum in ANT1-TG hearts. In conclusion, ANT1-TG rat hearts coped more efficiently with I/R than WT rat hearts, which was reflected by preserved mitochondrial energy balance, diastolic function, and calcium dynamics after reperfusion.