Reduced Adenosine Triphosphate Research Articles

Progression of cyclophosphamide-induced acute renal metabolic damage in carnitine-depleted rat model

Little information is available regarding the mechanism of cyclophosphamide (CP)-induced renal damage. Therefore, this study examined whether carnitine deficiency constitutes a risk factor in and should be viewed as a mechanism during development of CP-induced nephrotoxicity and explored whether carnitine supplementation, using propionyl-L-carnitine (PLC), could offer protection against this toxicity. Experimental rats were assigned to one of six groups; the first three groups were injected intraperitoneally with normal saline, PLC (250 mg/kg/day) or D-carnitine (250 mg/kg/day) + Mildronate (200 mg/kg/day), respectively, for 10 successive days. The 4th, 5th and 6th groups received the same doses of normal saline, PLC or D-carnitine + Mildronate, respectively, for 5 successive days before and after a single dose of CP (200 mg/kg). CP significantly increased serum creatinine, blood urea nitrogen (BUN), intramitochondrial acetyl-coenzyme A (CoA) and thiobarbituric acid reactive substances, significantly decreased total carnitine, intramitochondrial CoA-SH, adenosine triphosphate (ATP) and ATP/adenosine diphosphate (ADP) and reduced glutathione in kidney tissues. In carnitine-depleted rats, CP resulted in dramatic increase in serum nephrotoxicity indices and acetyl-CoA and induced progressive reduction in total carnitine, CoA-SH and ATP as well as severe histopathological lesions in kidney tissues. Interestingly, PLC completely reversed the biochemical and histopathological changes induced by CP to normal values. Oxidative stress is not involved in CP-induced renal injury in this model. Carnitine deficiency and energy starvation constitute risk factors in and should be viewed as a mechanism during CP-induced nephrotoxicity. PLC prevents development of CP-induced nephrotoxicity by increasing intracellular carnitine content, intramitochondrial CoA-SH/acetyl-CoA ratio and energy production.

Protective Effects of Ginseng Coffee against Hydrogen Peroxide-induced Oxidative Damage in L6 Muscle Cells

This study investigated the antioxidant effects of ginseng coffee in L6 muscle cells. Ginseng coffee was prepared by coating and digesting coffee beans with ginseng concentrate. The ginseng coffee water extract potently protected against hydrogen peroxide-induced L6 cell death and adenosine triphosphate reduction in a dose-dependent manner; in fact, these cytoprotective effects were significantly greater than those of normal coffee. However, ginseng coffee did not exhibit significant radical scavenging or catalase-like activity. These results suggest that ginseng coffee might act as a cytoprotective agent in muscles, but that the protective effects are not due to a direct radical-reduction property but rather to another intracellular signaling factor.

Carnitine Deficiency Aggravates Cyclophosphamide-Induced Cardiotoxicity in Rats

Background: This study examined, for the first time, the involvement of carnitine deficiency in cardiotoxicity, particularly cyclophosphamide (CP)-induced cardiomyopathy, as well as effects of carnitine supplementation with propionyl-L-carnitine (PLC) on cardiotoxicity. Methods: An animal model of carnitine deficiency was developed in rats treated with D-carnitine (DC)-mildronate (MD). Adult male Wistar albino rats were assigned to one of six treatment groups: the first three groups were injected intraperitoneally with normal saline, PLC (250 mg/kg/day), and DC (250 mg/kg/day) combined with MD (200 mg/kg/day), respectively, for 10 successive days. In groups 4–6, the same doses of normal saline, PLC and DC-MD were injected, respectively, during the 5 successive days before and after a single dose of CP (200 mg/kg). On day 6 after CP treatment, 24-hour urine was collected, then animals were sacrificed, and serum as well as hearts were isolated. Results: CP caused a significant increase in serum creatine phosphokinase isoenzyme (CK-MB), lactate dehydrogenase (LDH), urinary carnitine excretion and clearance and intramitochondrial acetyl-CoA/CoA-SH, and a significant decrease in serum free carnitine, total carnitine and adenosine triphosphate (ATP) contents in cardiac tissue. In the carnitine-depleted rats, CP induced dramatic increases in CK-MB and LDH levels, carnitine clearance and intramitochondrial acetyl-CoA/CoA-SH, as well as progressive reduction in total carnitine and ATP in cardiac tissues. Interestingly, PLC supplementation completely reversed the biochemical and histopathological changes induced by CP to the control values. Conclusion: (1) Carnitine deficiency is a risk factor which is involved in CP-related cardiomyopathy; (2) serum and urinary carnitine levels should be monitored and viewed as indices of CP-induced multiple organ toxicity, and (3) carnitine supplementation, using PLC, prevents the development of CP-induced cardiotoxicity.

Suppressed glucose metabolism in acinar cells might contribute to the development of exocrine pancreatic insufficiency in streptozotocin-induced diabetic mice

High prevalence of exocrine pancreatic insufficiency has been observed in diabetic patients. However, the underlying mechanisms are not well known. Reduced cytosolic Ca 2+ signals in pancreatic acinar cells may contribute to lower digestive enzyme secretion. It is well known that adenosine triphosphate (ATP) regulates cytosolic Ca 2+ signals in acinar cells; however, little is known as to whether diabetes impairs glucose metabolism that produces ATP in acinar cells. Streptozotocin (STZ)-induced diabetic C57BL/6 mouse model was used. Four weeks after being diabetic, pancreatic acinar cells were isolated; and amylase secretion and contents, glucose utilization and oxidation, the activities of several key enzymes for glucose metabolism, and ATP and nicotinamide adenine dinucleotide phosphate (reduced form) (NADPH) contents were determined. Compared with controls, diabetic mice had lower body weight. Cholecystokinin-8– and acetylcholine-stimulated amylase secretion was significantly impaired, and total amylase activity in acinar cells of STZ-diabetic mice was markedly reduced. Glucose utilization and oxidation were suppressed; measured enzyme activities for glucose metabolism and the ATP and NADPH contents were significantly reduced. These data indicate that glucose metabolism and ATP and NADPH productions are very important for maintaining acinar cell normal function. Reduction of ATP (reduces cytosolic Ca 2+ signals) and NADPH (reduces cell capability for antioxidative stress) productions may contribute to the development of exocrine pancreatic insufficiency in STZ-diabetic mice.

Carnitine Deficiency and Oxidative Stress Provoke Cardiotoxicity in an Ifosfamide‐Induced Fanconi Syndrome Rat Model

In addition to hemorrhagic cystitis, Fanconi Syndrome is a serious clinical side effect during ifosfamide (IFO) therapy. Fanconi syndrome is a generalized dysfunction of the proximal tubule which is characterized by excessive urinary excretion of glucose, phosphate, bicarbonate, amino acids and other solutes excreted by this segment of the nephron including L-carnitine. Carnitine is essential cofactor for β-oxidation of long-chain fatty acids in the myocardium. IFO therapy is associated with increased urinary carnitine excretion with subsequent secondary deficiency of the molecule. Cardiac abnormalities in IFO-treated cancer patients were reported as isolated clinical cases. This study examined whether carnitine deficiency and oxidative stress, secondary to Fanconi Syndrome, provoke IFO-induced cardiomyopathy as well as exploring if carnitine supplementation using Propionyl-L-carnitine (PLC) could offer protection against this toxicity. In the current study, an animal model of carnitine deficiency was developed in rats by D-carnitine-mildronate treatment Adult male Wistar albino rats were assigned to one of six treatment groups: the first three groups were injected intraperitoneally with normal saline, D-carnitine (DC, 250 mg/kg/day) combined with mildronate (MD, 200 mg/kg/day) and PLC (250 mg/kg/day), respectively, for 10 successive days. The 4th, 5th and 6th groups were injected with the same doses of normal saline, DC-MD and PLC, respectively for 5 successive days before and 5 days concomitant with IFO (50 mg/kg/day). IFO significantly increased serum creatinine, blood urea nitrogen (BUN), urinary carnitine excretion and clearance, creatine phosphokinase isoenzyme (CK-MB), lactate dehydrogenase (LDH), intramitochondrial acetyl-CoA/CoA-SH and thiobarbituric acid reactive substances (TBARS) in cardiac tissues and significantly decreased adenosine triphosphate (ATP) and total carnitine and reduced glutathione (GSH) content in cardiac tissues. In carnitine-depleted rats, IFO induced dramatic increase in serum creatinine, BUN, CK-MB, LDH, carnitine clearance and intramitochondrial acetyl-CoA/CoA-SH, as well as progressive reduction in total carnitine and ATP in cardiac tissues. Interestingly, PLC supplementation completely reversed the biochemical changes-induced by IFO to the control values. In conclusion, data from the present study suggest that: Carnitine deficiency and oxidative stress, secondary to Fanconi Syndrome, constitute risk factors and should be viewed as mechanisms during development of IFO-induced cardiotoxicity. Carnitine supplementation, using PLC, prevents the development of IFO-induced cardiotoxicity through antioxidant signalling and improving mitochondrial function.

A Novel Mechanism for the Treatment of Angina, Arrhythmias, and Diastolic Dysfunction: Inhibition of Late INa Using Ranolazine

Inhibition of the persistent or late Na current (INa) using ranolazine (Ranexa) represents a novel mechanism of action that was approved in the United States in 2006 and only recently in the European Union for use in patients with stable angina pectoris. In general, myocardial ischemia is associated with reduced adenosine triphosphate fluxes and decreased energy supply, resulting in severe disturbances of intracellular ion homeostasis in cardiac myocytes. In the recent years, increased late INa was suggested to contribute to this phenomenon by elevating intracellular Na concentration with subsequent rise in diastolic Ca levels by means of the sarcolemmal Na-Ca exchange system. Ranolazine, a specific inhibitor of late INa, reduces Na influx and hence ameliorates disturbed Na and Ca homeostasis. This is associated with a symptomatic improvement of angina in patients unlike other antianginal drugs without affecting heart rate or systemic blood pressure as shown in placebo-controlled studies. Therefore, ranolazine is a useful new option for patients with chronic stable angina not only as an add-on therapy. New clinical and experimental studies even point to potential antiarrhythmic effects, beneficial effects in diastolic heart failure, and under hyperglycemic conditions. In the present article, the relevant pathophysiological concepts for the role of late INa inhibition are reviewed and the most recent data from basic studies and clinical trials are summarized.

Accumulation and acute toxicity of silver in Potamogeton crispus L.

In the present study, Potamogeton crispus L. plants exposed to various concentrations of silver (Ag) (5, 10, 15, and 20 microM) for 5d were investigated to determine the accumulating potential of Ag and its influence on nutrient elements, chlorophyll pigments and fluorescence, various antioxidant enzymes and compounds, adenosine triphosphate (ATP), protein content and ultrastructure. The accumulation of Ag was found to increase in a concentration dependent manner with a maximum of 29.3 microg g(-1) at 20 microM. The nutrient elements (except Ca), photosynthetic pigments, chlorophyll a fluorescence parameters (Fo, Fv, Fv/Fm, Fv/Fo), malondialdehyde (MDA), ATP, peroxidase (POD) activity, ascorbate (AsA), reduced glutathione (GSH) and protein contents decreased significantly as concentration of Ag augmented. In contrast, an induction in SOD activity was recorded, while an initial rise in Ca content and CAT activity was followed by subsequent decline. Morphological symptoms of senescence phenomena such as chlorosis and damage of chloroplasts and mitochondria were observed even at the lowest concentration of Ag, which suggested that Ag hastened the senescence of the tested plants. The loss of nutrients and chlorophyll content and damage of chloroplasts were associated with disturbances in photosynthetic capacity as indicated by the quenching of chlorophyll a fluorescence. Decreased chlorophyll and protein contents suggest oxidative stress induced by Ag. In addition, both the reduction of ATP and the damage to the ultrastructure of organelles were indicative of general disarray in the cellular functions exerted by Ag.

Emulsifiers’ Composition Modulates Venous Irritation of the Nanoemulsions as a Lipophilic and Venous Irritant Drug Delivery System

In this study, a nanoemulsion (NE) system was investigated for intravenous delivery of lipophilic and venous irritant drugs. NEs were prepared to deliver diallyl trisulfide (DT) for systemic therapy of bacterial and fungal infection, egg phospholipid was chosen as the main emulsifier, and two co-emulsifiers were also incorporated, including Poloxamer 188 (P188) and Solutol HS 15 (S15). Soybean oil was used as the dispersed phases, forming stable DT NEs with small particle sizes. The venous irritation of DT NEs was evaluated by in vitro human umbilical cord endothelial cells (CRL 1730) compatibility model with the intracellular adenosine triphosphate (ATP) and guanosine triphosphate (GTP) concentrations as the indices. The intracellular ATP and GTP reduction changed with the incorporation of a variety of co-emulsifiers, which varied in a free DT concentration-dependent manner. It was deduced that the free DT concentrations of NEs containing co-emulsifiers were determined by the partition coefficient of DT between oil and surfactant buffer solution. In conclusion, NE was an appropriate delivery system for lipophilic and venous irritant drug, and optimization of the composition of emulsifiers was an effective method to alleviate the venous irritation of DT NEs.

Malonyl-CoA decarboxylase inhibition is selectively cytotoxic to human breast cancer cells

Fatty acid synthase (FAS) inhibition initiates selective apoptosis of cancer cells both in vivo and in vitro, which may involve malonyl-CoA metabolism. These findings have led to the exploration of malonyl-CoA decarboxylase (MCD) as a potential novel target for cancer treatment. MCD regulates the levels of cellular malonyl-CoA through the decarboxylation of malonyl-CoA to acetyl-CoA. Malonyl-CoA is both a substrate for FAS and an inhibitor of fatty acid oxidation acting as a metabolic switch between anabolic fatty acid synthesis and catabolic fatty acid oxidation. We now report that the treatment of human breast cancer (MCF7) cells with MCD small interference RNA (siRNA) reduces MCD expression and activity, reduces adenosine triphosphate levels, and is cytotoxic to MCF7 cells, but not to human fibroblasts. In addition, we synthesized a small-molecule inhibitor of MCD, 5-{(Morpholine-4-carbonyl)-[4-(2,2,2-trifluoro-1-hydroxy-1-trifluoromethyl-ethyl)-phenyl]-amino}-pentanoic acid methyl ester (MPA). Similar to MCD siRNA, MPA inhibits MCD activity in MCF7 cells, increases cellular malonyl-CoA levels and is cytotoxic to a number of human breast cancer cell lines in vitro. Taken together, these data indicate that MCD-induced cytotoxicity is likely mediated through malonyl-CoA metabolism. These findings support the hypothesis that MCD is a potential therapeutic target for cancer therapy.

Targeted Expression of Uncoupling Protein 2 to Mouse Liver Increases the Susceptibility to Lipopolysaccharide/Galactosamine-Induced Acute Liver Injury†

Normal hepatocytes do not express endogenous uncoupling protein 2 (UCP2) in adult liver, although Kupffer cells do, and it is strikingly induced in hepatocytes in steatotic liver and obese conditions. However, the direct link of UCP2 with the pathogenic development of liver diseases and liver injury remains elusive. Here we report that targeted expression of UCP2 to mouse liver increases susceptibility to acute liver injury induced by lipopolysaccharide (LPS) and galactosamine (GalN). UCP2 appears to enhance proton leak, leading to mild uncoupling in a guanosine diphosphate-repressible manner. Indeed, mitochondria from the genetically manipulated mouse liver have increased state 4 respiration, lower respiratory control ratio, and reduced adenosine triphosphate (ATP) levels, which altered mitochondrial physiology. To address the underlying mechanism of how UCP2 and the reduced energy coupling efficiency enhance cell death in mouse liver, we show that the reduced ATP levels lead to activation of 5'AMP-activated protein kinase (AMPK) and its downstream effector, c-Jun N-terminal kinase; thus, the increased sensitivity toward LPS/GalN-induces apoptosis. Importantly, we show that inhibition of UCP2 activity by its pharmacological inhibitor genipin prevents LPS/GalN-induced ATP reduction, AMPK activation, and apoptosis. Also, inhibition of ATP production by oligomycin promotes LPS/GalN-induced cell death both in vivo and in vitro. Our results clearly show that targeted expression of UCP2 in liver may result in compromised mitochondrial physiology that contributes to enhanced cell death and suggests a potential role of UCP2 in the development of liver diseases.

Inhibition of 4E-BP1 Sensitizes U87 Glioblastoma Xenograft Tumors to Irradiation by Decreasing Hypoxia Tolerance

Eukaryotic initiation factor 4E (eIF4E) is an essential rate-limiting factor for cap-dependent translation in eukaryotic cells. Elevated eIF4E activity is common in many human tumors and is associated with disease progression. The growth-promoting effects of eIF4E are in turn negatively regulated by 4E-BP1. However, although 4E-BP1 harbors anti-growth activity, its expression is paradoxically elevated in some tumors. The aim of this study was to investigate the functional role of 4E-BP1 in the context of solid tumors. In vitro and in vivo growth properties, hypoxia tolerance, and response to radiation were assessed for HeLa and U87 cells, after stable expression of shRNA specific for 4E-BP1. We found that loss of 4E-BP1 expression did not significantly alter in vitro growth but did accelerate the growth of U87 tumor xenografts, consistent with the growth-promoting function of deregulated eIF4E. However, cells lacking 4E-BP1 were significantly more sensitive to hypoxia-induced cell death in vitro. Furthermore, 4E-BP1 knockdown cells produced tumors more sensitive to radiation because of a reduction in the viable fraction of radioresistant hypoxic cells. Decreased hypoxia tolerance in the 4E-BP1 knockdown tumors was evident by increased cleaved caspase-3 levels and was associated with a reduction in adenosine triphosphate (ATP). Our results suggest that although tumors often demonstrate increases in cap-dependent translation, regulation of this activity is required to facilitate energy conservation, hypoxia tolerance, and tumor radioresistance. Furthermore, we suggest that targeting translational control may be an effective way to target hypoxic cells and radioresistance in metabolically hyperactive tumors.

Integrative Proteomic and Cytological Analysis of the Effects of Extracellular Ca2+ Influx on Pinus bungeana Pollen Tube Development

Ca (2+) is an essential ion in the control of pollen germination and tube growth. However, the control of pollen tube development by Ca (2+) signaling and its interactions with cytoskeletal components, energy-providing pathways, and cell-expansion machinery remain elusive. Here, we used nifedipine (Nif) to study Ca (2+) functions in differential protein expression and other cellular processes in Pinus bungeana pollen tube growth. Proteomics analysis indicated that 50 proteins showed differential expression with varying doses of Nif. Thirty-four of these were homologous to previously reported proteins and were classified into different functional categories closely related to tip-growth machinery. Blocking the L-type Ca (2+) channel with Nif in the pollen tube membrane induced several early alterations within a short time, including a reduction of extracellular Ca (2+) influx and a subsequently dramatic decrease in cytosolic free Ca (2+) concentration ([Ca (2+)] c), concomitant with ultrastructural abnormalities and changes in the abundance of proteins involved in energy production and signaling. Secondary alterations included actin filament depolymerization, disrupted patterns of endocytosis/exocytosis, and cell wall remodeling, along with changes in the proteins involved in these processes. These results suggested that extracellular Ca (2+) influx was necessary for the maintenance of the typical tip-focused [Ca (2+)] c gradient in the P. bungeana pollen tube, and that reduced adenosine triphosphate production (ATP), depolymerization of the cytoskeleton, and abnormal endocytosis/exocytosis, together with enhanced rigidity of cell walls, were responsible for the growth arrest observed in pollen tubes treated with Nif.

Regulation of alveolar epithelial function by hypoxia

Patients with acute respiratory distress syndrome and high-altitude pulmonary oedema build up excess lung fluid, which leads to alveolar hypoxia. In patients with acute respiratory distress syndrome and hypoxia, there is a decrease in oedema fluid clearance, due in part to the downregulation of plasma membrane sodium-potassium adenosine triphosphatase (Na,K-ATPase). In alveolar epithelial cells, acute hypoxia promotes Na,K-ATPase endocytosis from the plasma membrane to intracellular compartments, resulting in inhibition of Na,K-ATPase activity. Exposure to prolonged hypoxia leads to degradation of plasma membrane Na,K-ATPase. The downregulation of plasma membrane Na,K-ATPase reduces adenosine triphosphate demand, as part of a survival mechanism of cellular adaptation to hypoxia. Hypoxia has also been shown to disassemble and degrade the keratin intermediate filament network, a fundamental component of the cell cytoskeleton, affecting epithelial barrier function. Accordingly, better understanding of the mechanisms regulating cellular adaptation to hypoxia may lead to the development of novel therapeutic strategies for acute respiratory distress syndrome and high-altitude pulmonary oedema patients.

Reduced rate of adenosine triphosphate synthesis by in vivo 31P nuclear magnetic resonance spectroscopy and downregulation of PGC-1β in distal skeletal muscle following burn

Using a mouse model of burn trauma, we tested the hypothesis that severe burn trauma corresponding to 30% of total body surface area (TBSA) causes reduction in adenosine triphosphate (ATP) synthesis in distal skeletal muscle. We employed in vivo 31P nuclear magnetic resonance (NMR) in intact mice to assess the rate of ATP synthesis, and characterized the concomitant gene expression patterns in skeletal muscle in burned (30% TBSA) versus control mice. Our NMR results showed a significantly reduced rate of ATP synthesis and were complemented by genomic results showing downregulation of the ATP synthase mitochondrial F1 F0 complex and PGC-1beta gene expression. Our findings suggest that inflammation and muscle atrophy in burns are due to a reduced ATP synthesis rate that may be regulated upstream by PGC-1beta. These findings implicate mitochondrial dysfunction in distal skeletal muscle following burn injury. That PGC-1beta is a highly inducible factor in most tissues and responds to common calcium and cyclic adenosine monophosphate (cAMP) signaling pathways strongly suggests that it may be possible to develop drugs that can induce PGC-1beta.

Slow degradation of ATP in simulated martian environments suggests long residence times for the biosignature molecule on spacecraft surfaces on Mars

Prelaunch planetary protection protocols on spacecraft are designed to reduce the numbers and diversity of viable bioloads on surfaces in order to mitigate the forward contamination of planetary surfaces. In addition, there is a growing appreciation that prelaunch spacecraft cleaning protocols will be required to reduce the levels of biogenic signature molecules on spacecraft to levels that will not compromise life-detection experiments on landers. The biogenic molecule, adenosine triphosphate (ATP) was tested for long-term stability under simulated Mars surface conditions of high UV flux, low temperature, low pressure, Mars atmosphere, and clear-sky dust loading conditions. Data on UV-induced ATP degradation rates were then extrapolated to a diversity of global conditions using a radiative transfer model for UV on Mars. The UV-induced degradation of ATP tested at 4.1 W m −2 UVC (200–280 nm), −10 °C, 7.1 mb, 95% CO 2 gas composition, and an atmospheric opacity of τ = 0.1 yielded a half-life for ATP of 1342 kJ m −2; or extrapolated to approximately 22 sols on equatorial Mars with an atmospheric opacity of τ = 0.5 . Temperature was found to moderately affect ATP degradation rates under martian conditions; tests at −80 or 20 °C yielded ATP half-lives of 2594 or 1183 kJ m −2, respectively. The ATP degradation rates reported here are over 10 orders of magnitude slower than the UV-induced biocidal rates reported in the literature on the inactivation of strongly UV-resistant bacterial spores from Bacillus pumilus SAFR-032 [Schuerger, A.C., Richards, J.T., Newcombe, D.A., Venkateswaran, K.J., 2006. Icarus 181, 52–62]. Extrapolating results to global Mars conditions, residence times for a 99% reduction of ATP on spacecraft surfaces ranged from 158 sols on Sun-exposed surfaces to approximately 32,000 sols for the undersides of landers similar to Viking. However, spacecraft materials greatly affected the survival times of ATP under martian conditions. Stainless steel was found to enhance the UV degradation of ATP by over 2 orders of magnitude compared to ATP-doped iridited aluminum, graphite, and astroquartz coupons. Extrapolating these results to global conditions, ATP on stainless steel might be expected to persist between 2 and 320 sols for upper and lower surfaces of landers. Liquid chromatography-mass spectrometry data supported the conclusion that UV irradiation acted to remove the γ-phosphate group from ATP, and no evidence was observed for the UV-degradation of d-ribose or adenine moieties. Long residence times for ATP on spacecraft materials under martian conditions suggest that prelaunch cleaning protocols may need to be strengthened to mitigate against possible ATP contamination of life-detection experiments on Mars landers.

Mitochondrial dysfunction and age

Mitochondrial dysfunction is commonly thought to result from oxidative damage that leads to defects in the electron transport chain (ETC). In this review, we highlight new research indicating that there are early changes in mitochondrial function that precede ETC defects and are reversible thereby providing the possibility of slowing the tempo of mitochondrial aging and cell death. Increased mitochondrial uncoupling - reduced adenosine triphosphate (ATP) produced per O2 uptake - and cell ATP depletion are evident in human muscle nearly a decade before accumulation of irreversible DNA damage that causes ETC defects. New evidence points to reduction in activators of biogenesis (e.g. PGC-1alpha) and to degradation of mitochondria allowing accumulation of molecular and membrane damage in aged mitochondria. The early dysfunction appears to be reversible based on improved mitochondrial function in vivo and elevated gene expression levels after exercise training. New molecular and in vivo findings regarding the onset and reversibility of mitochondrial dysfunction with age indicate the potential: 1) for diagnostic tools to identify patients at risk for severe irreversible defects later in life; and 2) of an intervention to delay the tempo of aging and improve the quality of life of the elderly.

Elevated Hydrostatic Pressure Triggers Mitochondrial Fission and Decreases Cellular ATP in Differentiated RGC-5 Cells

Mitochondrial fission is a cellular response to stress that has an important role in neuronal cell death in neurodegenerative diseases. The purpose of this study was to determine whether elevated hydrostatic pressure induces mitochondrial fission and dysfunction in cultured retinal ganglion cells. RGC-5 cells were differentiated with succinyl concanavalin A (50 microg/mL) and transferred to a pressurized incubator in which 30 mm Hg of pressure was applied for 1, 2, or 3 days. As a control, differentiated cells from an identical passage were incubated simultaneously in a conventional incubator at each of the time points. Live RGC-5 cells were then labeled with a red fluorescent mitochondrial dye and mitochondrial morphology was assessed by fluorescence microscopy and electron microscopy. After elevated hydrostatic pressure, the cellular adenosine triphosphate (ATP) levels were also measured by a luciferase-based assay. Mitochondrial fission, characterized by the conversion of tubular fused mitochondria into isolated small organelles, was triggered in >74.3% +/- 1.9% of mitochondria at 3 days after elevated hydrostatic pressure. Only 4.7% +/- 1.4% of nonpressurized control cells displayed mitochondrial fission after 3 days. Electron microscopy showed that elevated hydrostatic pressure for 3 days induced abnormal cristae depletion and decreased the length of the mitochondria. On elevation of hydrostatic pressure, the fission-linked protein, Drp-1 was translocated from the cytosol to the mitochondria. Elevated hydrostatic pressure also resulted in a significant, time-dependent reduction of cellular ATP. Elevated hydrostatic pressure triggered mitochondrial fission, abnormal cristae depletion, Drp-1 translocation, and cellular ATP reduction in differentiated RGC-5 cells. Increased understanding of the molecular mechanisms that regulate the cellular response to elevated pressure including mitochondrial fission may provide new therapeutic targets for protecting RGCs from elevated hydrostatic pressure.

Increased ischemic injury in old mouse liver: An ATP-dependent mechanism

Although livers exhibit only minimal morphologic changes with age, how older livers tolerate pathologic conditions such as normothermic ischemia is unknown. Young 6-week-old mice and old 60-week-old mice underwent 60 minutes of hepatic ischemia and various periods of reperfusion. Markers of hepatocyte injury, hepatic energy content, and mitochondrial function were determined. Ischemic preconditioning and glucose injection were evaluated as protective strategies against reperfusion injury in old mice. Reperfusion injury was far worse in old mice compared with mice in the young control group. Ischemic preconditioning was highly protective against reperfusion injury in young but not in old mice. Older livers had dramatically reduced adenosine triphosphate (ATP) levels and glycogen contents. The low intrahepatic energy level in old mice was associated with a reduced mitochondrial ATP production. Preoperative injection of glucose restored the intrahepatic ATP content and protected against reperfusion injury. Furthermore, glucose injection restored the protective effect of ischemic preconditioning, resulting in additive protection when both strategies were combined. Aging of the liver is associated with mitochondrial dysfunction and decreased intrahepatic energy content, resulting in poorer tolerance against ischemic injury. Improving intrahepatic ATP levels in old livers by glucose injection protects the old liver against ischemic injury and restores the protective effects of ischemic preconditioning.

Long-term changes in microbial and biochemical parameters in the Central Indian Basin

Natural kilometer-scale spatial variability and seasonal variability in deep-sea sediments at ∼5000 m depth was studied at two reference sites in the Central Indian Basin. Biochemical parameters such as the labile organic matter (LOM) (consisting of carbohydrates, protein and lipids) and total organic matter (TOM) and biological parameters such as total counts of bacteria and adenosine triphosphate (ATP) were estimated after an interval of 54 months. These were compared with nine locations (12–17 km away) where an artificial sediment disturbance was created by a hydraulic benthic disturber. Besides the above-mentioned parameters, extracellular enzymes, alkaline phosphatase, aminopeptidase and lipase were also monitored at these nine locations. Post-disturbance (PoD1) observations were carried out immediately after the benthic disturbance experiment and compared with the pre-disturbance (PreD) pattern. The restoration process in the test site was studied after a period of 44 months (PoD2). There was a drastic reduction in total counts of bacteria, ATP, carbohydrates and lipids accompanied by a two- to four-fold increase in protein content at the undisturbed reference sites after 54 months. A similar reduction in these parameters was observed in the PoD1 compared to the PreD stage at the test site. An initial increase in TOM content and in the activities of three extracellular enzymes in the PoD1 stage was followed by a reduction in TOM, ATP and organic P content and activities of the extracellular enzymes in the PoD2 phase (i.e. after 44 months). Reduction in ATP levels suggests a negative impact of resedimentation on living biomass in the sediments. Although LOM, protein concentrations and the protein/carbohydrate ratio increased in the PoD2 phase relative to the PoD1 phase, the bacterial numbers were below the concentrations in the PreD stage, indicating slow restoration of benthic conditions. Long-term analyses of the indicator parameters thus showed mixed effects of sediment disturbance. A similar pattern at the undisturbed reference location suggests that natural (seasonal) variability outweighed artificial variability caused by the benthic disturbance in the Central Indian Basin and the former is responsible for bringing about changes in deep-sea benthic ecosystem on long-time scales.

The 58th Annual Meeting of the American Academy of Neurology San Diego, California April 1-8, 2006

The 58th Annual Meeting of the American Academy of Neurology San Diego, California April 1-8, 2006