Development of an HPLC method for determination of metabolic compounds in myocardial tissue

Mitochondrial dysfunction and oxidative stress are involved in the mechanism of tramadol-induced renal injury

Tramadol (TMDL) is an opioid analgesic widely administered for the management of moderate to severe pain. On the other hand, TMDL is commonly abused in many countries because of its availability and cheap cost. Renal injury is related to high dose or chronic administration of TMDL. No precise mechanism for TMDL-induced renal damage has been identified so far. The current study aimed to evaluate the potential role of oxidative stress and mitochondrial impairment in the pathogenesis of TMDL-induced renal injury. For this purpose, rats were treated with TMDL (40 and 80 ​mg/kg, i.p, 28 consecutive days). A significant increase in serum Cr and BUN was detected in TMDL groups. On the other hand, TMDL (80 ​mg/kg) caused a substantial increase in urine glucose, ALP, protein, and γ-GT levels. Moreover, urine Cr was significantly decreased in TMDL-treated rats (40 and 80 ​mg/kg). Renal histopathological alterations included inflammation, necrosis, and tubular degeneration in the kidney of TMDL-treated animals. Reactive oxygen species (ROS) formation, increased oxidized glutathione (GSSG), lipid peroxidation, and protein carbonylation was increased, whereas total antioxidant capacity and reduced glutathione levels were considerably decreased in TMDL groups. Significant mitochondrial impairment was also detected in the form of mitochondrial depolarization, adenosine-tri-phosphate (ATP) depletion, mitochondrial permeabilization, lipid peroxidation, and decreased mitochondrial dehydrogenase activity in the kidney of TMDL (80 ​mg/kg)-treated animals. These data suggest mitochondrial impairment and oxidative stress as mechanisms involved in the pathogenesis of TMDL-induced renal injury.

Uridine treatment prevents myocardial injury in rat models of acute ischemia and ischemia/reperfusion by activating the mitochondrial ATP-dependent potassium channel

The effect of uridine on the myocardial ischemic and reperfusion injury was investigated. A possible mechanism of its cardioprotective action was established. Two rat models were used: (1) acute myocardial ischemia induced by occlusion of the left coronary artery for 60 min; and (2) myocardial ischemia/reperfusion with 30-min ischemia and 120-min reperfusion. In both models, treatment with uridine (30 mg/kg) prevented a decrease in cell energy supply and in the activity of the antioxidant system, as well as an increase in the level of lipid hydroperoxides and diene conjugates. This led to a reduction of the necrosis zone in the myocardium and disturbances in the heart rhythm. The blocker of the mitochondrial ATP-dependent potassium (mitoKATP) channel 5-hydroxydecanoate limited the positive effects of uridine. The data indicate that the cardioprotective action of uridine may be related to the activation of the mitoKATP channel. Intravenously injected uridine was more rapidly eliminated from the blood in hypoxia than in normoxia, and the level of the mitoKATP channel activator UDP in the myocardium after uridine administration increased. The results suggest that the use of uridine can be a potentially effective approach to the management of cardiovascular diseases.

Simultaneous determination of cellular adenosine nucleotides, malondialdehyde, and uric acid using HPLC

Adenine nucleotides and malondialdehyde (MDA) are key components involved in energy metabolism and reactive oxygen species (ROS) production. Measuring the levels of these components at the same time would be critical in studying mitochondrial functions. We have established a HPLC method to simultaneously measure adenosine triphosphate, adenosine diphosphate, adenosine monophosphate, MDA, and uric acid (UA). The samples were treated with perchloric acid followed by centrifugation. After neutralization, the supernatant was subjected to HPLC determination. HPLC was performed using a C18 chromatographic column, isocratic elusion, and UV detection. The detection and quantification limits for these components were determined with standard solutions. The precision, repeatability, and 24-h stability were evaluated using cellular samples, and their relative standard deviations were all within 2%. The reproducibility and efficiency were confirmed with sample recovery tests and the observed oxidative effects of H₂ O₂ on Jurkat cells. With this method, we discovered the dependence of energy and oxidative states on the density of Jurkat cells cultured in suspension. We also found a significant correlation between UA in serum and that in saliva. These results indicate that this method has good accuracy and applicability. It can be used in biological, pharmacological, and clinical studies, especially those involving mitochondria, ROS, and purinergic signaling.

Mitochondrial active and relaxed state respiration after heat shock mRNA response in the heart

Induction of Heat Shock Proteins results in cytoprotection. Beneficial effect results from transcription and translational cellular components' involvement that defends metabolism and thus induce ischemic protection of the tissue. Mitochondrial respiration is also involved in stress- induced conditions. It is not a uniform process. Cytochrome c Oxidase (CytOx) representing complex IV of the Electron Transfer Chain (ETC) has a regulatory role for mitochondrial respiratory activity, which is tested in our study after hsp induction. Moreover, protein translation for mitochondrial components was probed by the detection of MT-CO1 for Subunit 1 of CytOx neosynthesis. Wistar rats were subjected to whole-body hyperthermia at 42.0-42.5 °C for 15 min followed by a normothermic recovery period. Heat shock response was monitored time dependent from LV biopsies of all control and heat treated animals with PCR-analysis for hsp 32, 60, 70.1, 70.2, 90 and MT-CO1 expression at 15, 30, 45, 60, 120 and 360 min recovery (n = 5 in each group), respectively. Enzymatic activity of CytOx were evaluated polarographically. High energy phosphates were detected by chromatographic analysis. The mRNA expression of MT-CO1 peaked at 60 min and was accompanied by hsp 32 (r = 0.457; p = 0.037) and hsp 70.2 (r = 0.615; p = 0.003) upregulation. With hsp induction, mitochondrial respiration was increased initially. Enzymatic activity reconciled from active into relaxed status wherein CytOx activity was completely inhibited by ATP. Myocardial ATP content increased from stress induced point i.e. < 1 µmol g^-1 protein w/w to finally 1.5 ± 0.53 µmol g^-1 protein w/w at 120 min recovery interval. Hyperthermic, myocardial hsp- induction goes along with increased CytOx activity representing an increased "active" mitochondrial respiration. In parallel, de -novo holoenzyme assembly of CytOx begins as shown by MT-CO1 upregulation at 60 min recovery time crossing with a final return to the physiological "relaxed" state and ATP -inhibited respiration.

Extended pain relief achieved by analgesic-eluting biodegradable nanofibers in the Nuss procedure: in vitro and in vivo studies

Background

The most common complaint after the Nuss procedure is severe postoperative chest pain. The aim of this study was to evaluate the effectiveness of analgesic-eluting biodegradable nanofibers in pain relief after the Nuss procedure.

Materials and methods

Poly(d,l)-lactide-co-glycolide, lidocaine, and ketorolac were dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol. This solution was electrospun into a nanofibrous membrane. The elution method and high-performance chromatography were used to characterize the in vitro drug release. Stainless steel bars with and without coating of the analgesic-eluting nanofibrous membrane were implanted underneath the sternums of New Zealand white rabbits. The in vivo characteristics were further investigated.

Results

The in vitro study showed that the biodegradable nanofibers released high doses of lidocaine and ketorolac within 10 days. The in vivo study demonstrated high local and systemic concentrations of lidocaine and ketorolac. The serum creatinine level was unaffected. Animals that received implants of the analgesic-eluting nanofiber-coated stainless steel bar exhibited significantly greater food and water ingestion and physical activity than the control group did, indicating effective pain relief.

Conclusion

The proposed analgesic-eluting biodegradable nanofibers contribute to the achievement of extended pain relief after the Nuss procedure, without obvious adverse effects, in an animal model.

Hydrophilic interaction chromatography coupled to tandem mass spectrometry as a method for simultaneous determination of guanidinoacetate and creatine

The biosynthesis of creatine (Cr) is closely related to the bioavailability of guanidinoacetate (GAA). The lack of one or the other may compromise their role in the energy transport and cell signaling. A reliable estimate of their levels in biological samples is imperative since they are important markers of many metabolic disorders. Therefore, a new LC-MS/MS method for simultaneous determination and quantification of GAA and Cr by multiple reaction monitoring (MRM) mode was developed based on the hydrophilic interaction chromatography (HILIC) and response surface methodology (RSM) for the optimization of chromatographic parameters. The optimized parameters ensured good separation of these similar, very polar molecules (chromatographic resolution > 1.5) without prior derivatization step in a short analysis run (6 min). The developed method was validated to ensure accurate (R, 75.1-101.6%), precise (RSD < 20%) and low quantification (LOQ of 0.025 μg mL^-1 for GAA and 0.006 μg mL^-1 for Cr) of the tested analytes and the use of matrix-matched calibration eliminated variable effects of complex matrices such as human plasma and urine. Therefore, this method can be implemented in medical laboratories as a tool for the diagnostics of creatine deficiencies and monitoring of guanidinoacetate and creatine supplementation regimes in biological samples.

Mechanism of valproic acid-induced Fanconi syndrome involves mitochondrial dysfunction and oxidative stress in rat kidney

AIM

Drug-induced kidney proximal tubular injury and renal failure (Fanconi syndrome; FS) is a clinical complication. Valproic acid (VPA) is among the FS-inducing drugs. The current investigation was designed to evaluate the role of mitochondrial dysfunction and oxidative stress in VPA-induced renal injury.

METHODS

Animals received VPA (250 and 500 mg/kg, i.p., 15 consecutive days). Serum biomarkers of kidney injury and markers of oxidative stress were assessed. Moreover, kidney mitochondria were isolated and mitochondrial indices, including succinate dehydrogenase activity (SDA), mitochondrial depolarization, mitochondrial permeability transition pore (MPP), reactive oxygen species (ROS), lipid peroxidation (LPO), mitochondrial glutathione, and ATP were determined.

RESULTS

Valproic acid-treated animals developed biochemical evidence of FS as judged by elevated serum gamma-glutamyl transferase (γ-GT), alkaline phosphatase (ALP), creatinine (Cr), and blood urea nitrogen (BUN) along with hypokalaemia, hypophosphataemia, and a decrease in serum uric acid. VPA caused an increase in kidney ROS and LPO. Renal GSH reservoirs were depleted and tissue antioxidant capacity decreased in VPA-treated animals. Renal tubular interstitial nephritis, tissue necrosis, and atrophy were also evident in VPA-treated rats. Mitochondrial parameters including SDA, MMP, GSH, ATP and MPP were decreased and mitochondrial ROS and LPO were increased with VPA treatment. It was found that carnitine (100 mg/kg, i.p.) mitigated VPA adverse effects towards the kidney.

CONCLUSIONS

These data suggest that mitochondrial dysfunction and oxidative stress contributed to the VPA-induced FS. On the other hand, carnitine could be considered a potentially safe and effective therapeutic option in attenuating VPA-induced renal injury.

Sustained local delivery of high-concentration vancomycin from a hybrid biodegradable, antibiotic-eluting, nanofiber-loaded endovascular prosthesis for treatment of mycotic aortic aneurysms

BACKGROUND

Endovascular repair for mycotic aortic aneurysm (MAA) is a less invasive alternative to open surgery, although the placement of a stent graft in an infected environment remains controversial. In this study, we developed hybrid biodegradable, vancomycin-eluting, nanofiber-loaded endovascular prostheses and evaluated antibiotic release from the endovascular prostheses both in vitro and in vivo.

METHODS

Poly(D,L)-lactide-co-glycolide and vancomycin were dissolved in 1,1,1,3,3,3-hexafluoro-2-propanol. This solution was electrospun into nanofibrous tubes, which were mounted onto commercial vascular stents and endovascular aortic stent grafts. In vitro antibiotic release from the nanofibers was characterized using an elution method and high-performance liquid chromatography. Antibiotic release from the hybrid stent graft was analyzed in a three-dimensional-printed model of a circulating MAA. The in vivo drug release characteristics were examined by implanting the antibiotic-eluting stents in the abdominal aorta of New Zealand white rabbits (n = 15).

RESULTS

The in vitro study demonstrated that the biodegradable nanofibers and the nanofiber-loaded stent graft provided sustained release of high concentrations of vancomycin for up to 30 days. The in vivo study showed that the nanofiber-loaded stent exhibited excellent biocompatibility and released high concentrations of vancomycin into the local aortic wall for 8 weeks.

CONCLUSIONS

The proposed biodegradable vancomycin-eluting nanofibers significantly contribute to the achievement of local and sustainable delivery of antibiotics to the aneurysm sac and the aortic wall, and these nanofibers may have therapeutic applications for MAAs.

p-Coumaric acid, a novel and effective biomarker for quantifying hypoxic stress by HILIC-ESI-MS

In this study, we report p-coumaric acid as novel and effective response marker for indirectly measuring the levels of hypoxia in normal primary bronchial epithelial cells. We developed a simple and rapid technique based on hydrophilic interaction chromatography-electrospray ionization-mass spectrometry (HILIC-ESI-MS). During 168h of hypoxia without induction of reactive oxygen species (ROS), an almost linear increase of p-coumaric acid levels was observed. We interpret the increasing p-coumaric acid concentrations during hypoxia as a result of cell damage, triggered by reduced co-enzyme Q10 levels, because the oxidative cascade was not able to supply sufficient energy. The HILIC-ESI-MS assay within p-coumaric acid exhibited a linear dynamic range from 60 to 610 ng/μL with correlation coefficient of 0.9998. The precision of the assay was ≤15% RSD and method accuracies between 97 and 108%.

β3-Adrenoceptor Impairs Mitochondrial Biogenesis and Energy Metabolism During Rapid Atrial Pacing-Induced Atrial Fibrillation

BACKGROUND

The β3-adrenoceptor (β3-AR) is implicated in cardiac remodeling. Since metabolic dysfunction due to loss of mitochondria plays an important role in heart diseases, we examined the effects of β3-AR on mitochondrial biogenesis and energy metabolism in atrial fibrillation (AF).

METHODS

Atrial fibrillation was created by rapid atrial pacing in adult rabbits. Rabbits were randomly divided into 4 groups: control, pacing (P7), β3-AR antagonist (L748337), and β3-AR agonist (BRL37344) groups. Atrial effective refractory period (AERP) and AF induction rate were measured. Atrial concentrations of adenine nucleotides and phosphocreatine were quantified through high-performance liquid chromatography. Mitochondrial DNA content was determined. Real-time polymerase chain reaction and Western blot were used to examine the expression levels of signaling intermediates related to mitochondrial biogenesis.

RESULTS

After pacing for 7 days, β3-AR was significantly upregulated, AERP was reduced, and the AF induction rate was increased. The total adenine nucleotides pool was significantly reduced due to the decrease in adenosine triphosphate (ATP). The P7 group showed decreased activity of F0F1-ATPase. Mitochondrial DNA content was decreased and mitochondrial respiratory chain subunits were downregulated after pacing. Furthermore, expression of transcription factors involved in mitochondrial biogenesis, including peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF-1), and mitochondrial transcription factor A (Tfam), was lower in the P7 group in response to β3-AR activation. Further stimulation of β3-AR with BRL37344 exacerbated these effects, together with a significant decrease in the levels of phosphocreatine. In contrast, inhibition of β3-AR with L748337 partially restored mitochondrial biogenesis and energy metabolism of atria in the paced rabbits.

CONCLUSION

The activation of β3-AR contributes to atrial metabolic remodeling via transcriptional downregulation of PGC-1α/NRF-1/Tfam pathway that are involved in mitochondrial biogenesis, which ultimately perturbs mitochondrial function in rapid pacing-induced AF. The β3-AR is therefore a potential novel therapeutic target for the treatment or prevention of AF.

Altered post-mortem metabolism identified in very fast chilled lamb M. longissimus thoracis et lumborum using metabolomic analysis

The aim of this experiment was to use metabolomic techniques to investigate the energy metabolism in lamb M. longissimus thoracis et lumborum subjected to very fast chilling (VFC) post-mortem. The tissue was prepared by 2 different operators and subjected to very fast chilling (less than 0°C within 1.5h of slaughter) or typical chilling regimes (Control; 0°C within 22h of slaughter). Non-targeted metabolomic analysis ((1)H NMR) and targeted analysis ((31)P NMR, HPLC-PDA and HPLC-MS/MS) were used to examine the change in muscle metabolites post-mortem. One VFC treatment, which resulted in a colder core temperature and more tender meat, had higher levels of glycolytic intermediate metabolites pre-rigor as well as more of the end-products of adenosine and nicotine nucleotide metabolism pre-rigor, relative to conventionally chilled treatments. In conclusion, VFC to less than 0°C within 1.5h of slaughter causes considerable changes in metabolism and rigor onset, which are associated with tender meat.

Organ-protective effects on the liver and kidney by minocycline in small piglets undergoing cardiopulonary bypass

Cardiopulmonary bypass (CPB) often is required for the operative correction of congenital heart defects in small infants. Unfortunately, CPB is associated with injury of inner organs such as the brain, kidney, lung, and liver. Renal failure and increase in liver enzymes are typical side effects observed after CPB. Here, we investigate whether organ protection of the kidney and liver can be achieved with the application of minocycline, which is known-besides its anti-infective effects-to act as a poly-ADP-ribose-polymerase inhibitor. Twenty-nine 4-week-old Angler Sattelschwein-piglets (8-15 kg) were divided into four groups: control group (n = 8), CPB group (n = 9), minocycline-control group (n = 6), and the minocycline-CPB group (n = 6). CPB groups were thoracotomized and underwent CPB for 120 min (cross-clamp, 90 min; reperfusion, 30 min) followed by a 90-min recovery time. The control groups also were thoracotomized but not connected to CPB. The minocycline group received 4 mg/kg minocycline before and 2 mg/kg after CPB. In the kidneys, CPB histologically resulted in widening of Bowman's capsule, and-mainly in tubules-formation of poly-ADP-ribose, nitrosylation of tyrosine-residues, nuclear translocation of hypoxia-induced factor HIF-1α, and of apoptosis-inducing factor (AIF). In addition, we found significantly less ATP in the kidney and significantly increased plasma urea and creatinine. Similar but gradually attenuated changes were found in the liver together with significantly elevated de-Ritis coefficient. These changes in the kidney and liver were significantly diminished by minocycline (except AIF in the liver which was similar in all groups). In conclusion, CPB causes damage in the kidney and-to a lower degree-in the liver, which can be attenuated by minocycline.

Determination of Strong Acidic Drugs in Biological Matrices: A Review of Separation Methods

Strong acidic drugs are a class of chemical compounds that normally have high hydrophilicity and large negative charges, such as organophosphatic compounds and organosulphonic compounds. This review focuses on sample preparation and separation methods for this group of compounds in biological matrices in recent years. A wide range of separation techniques, especially chromatographic method, are presented and critically discussed, which include liquid chromatography (e.g., ion-pair and ion-exchange chromatography), capillary electrophoresis (CE), and other types. Due to the extremely low concentration level of target analytes as well as the complexity of biological matrices, sample pretreatment methods, such as dilute and shoot methods, protein precipitation (PP), liquid-liquid extraction (LLE), solid-phase extraction (SPE), degradation, and derivatization strategy, also play important roles for the development of successful analytical methods and thus are also discussed.

Sustained release carrier for adenosine triphosphate as signaling molecule

Adenosine triphosphate (ATP) is a molecule with a fascinating variety of intracellular and extracellular biological functions that go far beyond energy metabolism. Due to its limited passive diffusion through biological membranes, controlled release systems may allow to interact with ATP-mediated extracellular processes. In this study, two release systems were explored to evaluate the capacity for either long-term or short-term release: (i) Poly[(rac-lactide)-co-glycolide] (PLGA) implant rods were capable of ATP release over days to weeks, depending on the PLGA molecular weight and end-group capping, but were also associated with partial hydrolytic degradation of ATP to ADP and AMP, but not adenosine. (ii) Thermosensitive methylcellulose hydrogels with a gelation occurring at body temperature allowed combining adjustable loading levels and the capacity for injection, with injection forces less than 50N even for small 27G needles. Finally, a first in vitro study illustrated purinergic-triggered response of primary murine microglia to ATP released from hydrogels, demonstrating the potential relevance for biomedical applications.

Zirconia--a stationary phase capable of the separation of polar markers of myocardial metabolism in hydrophilic interaction chromatography

Creatine, phosphocreatine, and adenine nucleotides are highly polar markers of myocardial metabolism that are poorly retained on RP silica sorbents. Zirconia represents an alternative material to silica with high promise to be used in hydrophilic interaction chromatography (HILIC). This study describes a first systematic investigation of the ability of ZrO2 to separate creatine, phosphocreatine, adenosine 5'-monophosphate, adenosine 5'-diphosphate, and adenosine 5'-triphosphate and compares the results with those obtained on TiO2 . All analytes showed a HILIC-like retention pattern when mobile phases of different strengths were tested. Stronger retention and better column performance were achieved in organic-rich mobile phases as compared to aqueous conditions, where poor retention and insufficient column performance were observed. The effect of mobile phase pH and ionic strength was evaluated as well. The analysis of myocardial tissue demonstrated that all compounds were separated in a relevant biological material and thus proved ZrO2 as a promising phase for HILIC of biological samples that deserves further investigation.

Simultaneous determination of creatine phosphate, creatine and 12 nucleotides in rat heart by LC-MS/MS

A simple, rapid and sensitive LC-MS/MS method was developed and validated for simultaneous determination of creatine phosphate (CP), creatine (Cr) and 12 nucleotides in rat heart. The analytes, ATP, ADP, AMP, GTP, GDP, GMP, CTP, CDP, CMP, UTP, UDP, UMP, CP, Cr, were extracted from heart tissue with pre-cooled (0°C) methanol/water (1:1, v/v) and separated on a Hypersil Gold AQ C18 column (150mm×4.6mm, 3μm) using an isocratic elution with a mobile phase consisting of 2mmol/L ammonium acetate in water (pH 10.0, adjusted with ammonia). The detection was performed by negative ion electrospray ionization in selective reaction monitoring mode (SRM). In the assay, all the analytes showed good linearity over the investigated concentration range (r>0.99). The accuracy was between 80.7% and 120.6% and the precision expressed in RSD was less than 15.6%. This method was successfully applied to measure the concentrations of the 12 nucleotides, creatine phosphate and creatine in rat heart for the first time.

A novel metabolic balance model for describing the metabolic disruption of and interactions between cardiovascular-related markers during acute myocardial infarction

OBJECTIVE

After acute myocardial infarction (AMI), an integral evaluation of risk using multimarker approach and the understanding of the pathophysiological processes involved have recently received much attention. This study aimed to develop a model to integrally evaluate the metabolic disruption of cardiovascular-related markers and unveil their interactions after AMI.

METHODS

AMI was induced in rats by coronary artery ligation. Several cardiovascular-related markers in plasma and the heart were determined during AMI. A metabolic balance model was developed using matrix equations to assess the metabolic disturbance of, and interactions between, these markers.

RESULTS

Metabolic balance maps intuitively depicted the metabolic disruption of cardiovascular-related markers after AMI. The deviation and magnitude of the disruption were quantitatively and integrally described by φ and k (the dynamic parameter of metabolic balance disruption), respectively. The metabolic balance was disturbed in both the circulatory system and the heart post-AMI. All of the measured markers appeared to be interactional. Among these markers, kidney function and dimethylarginine dimethylaminohydrolase (DDAH) activity in the heart showed a potent effect on the other markers, whereas asymmetric dimethylarginine (ADMA) levels in plasma and adenosine triphosphate (ATP) contents in the heart were susceptible to the effects of the other markers.

CONCLUSION

A metabolic balance model was developed to integrally evaluate the disruption of cardiovascular-related markers after AMI, which proposes a new method for evaluating the disease state post-AMI using a multimarker approach. The unveiled interactions between these cardiovascular-related markers are helpful in understanding the pathophysiological processes.

Increased glucagon-like peptide-1 secretion may be involved in antidiabetic effects of ginsenosides

Panax ginseng is one of the most popular herbal remedies. Ginsenosides, major bioactive constituents in P. ginseng, have shown good antidiabetic action, but the precise mechanism was not fully understood. Glucagon-like peptide-1 (GLP1) is considered to be an important incretin that can regulate glucose homeostasis in the gastrointestinal tract after meals. The aim of this study was to investigate whether ginseng total saponins (GTS) exerts its antidiabetic effects via modulating GLP1 release. Ginsenoside Rb1 (Rb1), the most abundant constituent in GTS, was selected to further explore the underlying mechanisms in cultured NCI-H716 cells. Diabetic rats were developed by a combination of high-fat diet and low-dose streptozotocin injection. The diabetic rats orally received GTS (150 or 300 mg/kg) daily for 4 weeks. It was found that GTS treatment significantly ameliorated hyperglycemia and dyslipidemia, accompanied by a significant increase in glucose-induced GLP1 secretion and upregulation of proglucagon gene expression. Data from NCI-H716 cells showed that both GTS and Rb1 promoted GLP1 secretion. It was observed that Rb1 increased the ratio of intracellular ATP to ADP concentration and intracellular Ca2+ concentration. The metabolic inhibitor azide (3 mM), the KATP channel opener diazoxide (340 μM), and the Ca2+ channel blocker nifedipine (20 μM) significantly reversed Rb1-mediated GLP1 secretion. All these results drew a conclusion that ginsenosides stimulated GLP1 secretion both in vivo and in vitro. The antidiabetic effects of ginsenosides may be a result of enhanced GLP1 secretion.

Metabolic determinants of electrical failure in ex-vivo canine model of cardiac arrest: evidence for the protective role of inorganic pyrophosphate

RATIONALE

Deterioration of ventricular fibrillation (VF) into asystole or severe bradycardia (electrical failure) heralds a fatal outcome of cardiac arrest. The role of metabolism in the timing of electrical failure remains unknown.

OBJECTIVE

To determine metabolic factors of early electrical failure in an ex-vivo canine model of cardiac arrest (VF+global ischemia).

METHODS AND RESULTS

Metabolomic screening was performed in left ventricular biopsies collected before and after 0.3, 2, 5, 10 and 20 min of VF and global ischemia. Electrical activity was monitored via plunge needle electrodes and pseudo-ECG. Four out of nine hearts exhibited electrical failure at 10.1±0.9 min (early-asys), while 5/9 hearts maintained VF for at least 19.7 min (late-asys). As compared to late-asys, early-asys hearts had more ADP, less phosphocreatine, and higher levels of lactate at some time points during VF/ischemia (all comparisons p<0.05). Pre-ischemic samples from late-asys hearts contained ∼25 times more inorganic pyrophosphate (PPi) than early-asys hearts. A mechanistic role of PPi in cardioprotection was then tested by monitoring mitochondrial membrane potential (ΔΨ) during 20 min of simulated-demand ischemia using potentiometric probe TMRM in rabbit adult ventricular myocytes incubated with PPi versus control group. Untreated myocytes experienced significant loss of ΔΨ while in the PPi-treated myocytes ΔΨ was relatively maintained throughout 20 min of simulated-demand ischemia as compared to control (p<0.05).

CONCLUSIONS

High tissue level of PPi may prevent ΔΨm loss and electrical failure at the early phase of ischemic stress. The link between the two protective effects may involve decreased rates of mitochondrial ATP hydrolysis and lactate accumulation.

Reno-protective effects of epigallocatechingallate in a small piglet model of extracorporeal circulation

Cardiopulmonary bypass still often is a necessary tool in cardiac surgery in particular in the correction of congenital heart defects in small infants. Nevertheless, among the complications linked to extracorporeal circulation (ECC) with cardiopulmonary bypass (CPB) in both infants and adults one of the most serious problems is renal impairment. Since this might be caused by ischemia/reperfusion injury and accumulation of free radicals, we used (-)-epigallocatechin-3-gallate (EGCG), a derivate from green tea, which is known to possess antioxidant, antiapoptotic and NO-scavenging properties in order to find out whether EGCG may protect the kidney. 23 four-week-old Angler Sattelschwein-piglets (8-15 kg) were divided into three groups: control-group (n=7), ECC-group (n=10), EGCG-group (n=6). The ECC- and EGCG-group were thoracotomized and underwent CPB for 120 min followed by a 90-min recovery-time. The EGCG-group received 10 mg/kg EGCG before and after CPB. Histology revealed that CPB led to widening of Bowman's capsule, and to vacuolization of proximal tubular cells (p<0.05) which could be prevented by EGCG (p<0.05). Using immunohistology, we found significant nuclear translocation of hypoxia-inducible-factor-1-alpha (HIF-1-alpha) and increased nitrotyrosine formation in the ECC-group. Both were significantly (p<0.05) inhibited by EGCG. ECC-induced loss of energy-rich phosphates was prevented by EGCG. In blood samples we found that CPB resulted in increases in creatinine and urea (in serum) and led to loss of total protein (p<0.05), which all was not present in EGCG-treated animals. We conclude that CPB causes damage in the kidney which can be attenuated by EGCG.

Simultaneous determination of adenine nucleotides, creatine phosphate and creatine in rat liver by high performance liquid chromatography-electrospray ionization-tandem mass spectrometry

A high performance liquid chromatography-electrospray ionization-tandem mass spectrometric method (HPLC-ESI-MS/MS) was developed for simultaneous determination of adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP), creatine phosphate (CP), and creatine in rat liver. After extraction with pre-cooled (4 °C) methanol/water (1:1, v/v), the analytes were separated on a porous graphitic carbon (Hypercarb) column (2.1 mm × 150 mm, 5 μm) using a programmed gradient elution with a mobile phase consisting of 2 mmol/L ammonium acetate in water and 2 mmol/L ammonium acetate in acetonitrile (pH=10.0). The analytes were detected in a way of multiple reaction monitoring (MRM) under negative scan mode by a triple quadrupole mass spectrometer with electrospray ionization (ESI). An external calibration method with linear ranges from 10 to 5000 ng/mL for the five target compounds was used for quantification with a correlation coefficients≥0.9973. The limits of detection and limits of quantification for all analytes were in ranges from 0.50 to 1.5 ng/mL and 1.6 to 0.5 ng/mL, respectively. The average recoveries spiked in three levels were from 77.2% to 102% and precisions expressed in RSDs were from 0.2% to 4.8%. The established method was successfully applied to determination of ATP, ADP, AMP, CP and creatine in liver tissue.

Neuronal adenosine release, and not astrocytic ATP release, mediates feedback inhibition of excitatory activity

Adenosine is a potent anticonvulsant acting on excitatory synapses through A1 receptors. Cellular release of ATP, and its subsequent extracellular enzymatic degradation to adenosine, could provide a powerful mechanism for astrocytes to control the activity of neural networks during high-intensity activity. Despite adenosine's importance, the cellular source of adenosine remains unclear. We report here that multiple enzymes degrade extracellular ATP in brain tissue, whereas only Nt5e degrades AMP to adenosine. However, endogenous A1 receptor activation during cortical seizures in vivo or heterosynaptic depression in situ is independent of Nt5e activity, and activation of astrocytic ATP release via Ca(2+) photolysis does not trigger synaptic depression. In contrast, selective activation of postsynaptic CA1 neurons leads to release of adenosine and synaptic depression. This study shows that adenosine-mediated synaptic depression is not a consequence of astrocytic ATP release, but is instead an autonomic feedback mechanism that suppresses excitatory transmission during prolonged activity.

The relative efficacy of aminoguanidine and pentoxifylline in modulating endotoxin-induced cardiac stress

This study investigates the effect of aminoguanidine (AG), a selective inducible nitric oxide synthase (iNOS) inhibitor, and pentoxifylline (PTX), a tumour necrosis factor-alpha (TNF-α) inhibitor, on lipopolysaccharide (LPS)-induced cardiac stress. Rats were divided into four groups: group I served as a control, group II (LPS) received a single intraperitoneal injection of LPS (10 mg·kg(-1) ), group III (LPS+AG) and group IV (LPS+PTX) were injected with either AG (100 mg·kg(-1) ) or PTX (150 mg·kg(-1) ) intraperitoneally 10 days prior to LPS administration. Normalization of cardiac levels of nitrite/nitrate (NO(X) ), malondialdehyde (MDA), glutathione (GSH), heme oxygenase-1 (HO-1), glutathione peroxidase (GPx) and Na(+) , K(+) -ATPase activities was evident in the AG group. Both AG and PTX decreased the elevated serum TNF-α levels, the activities of lactate dehydrogenase (LDH), creatine kinase (CK) and cardiac myeloperoxidase (MPO). The levels of adenosine triphosphate (ATP), adenosine diphosphate (ADP) and phosphocreatine (PCr) were enhanced following AG and PTX pretreatments. Calcium (Ca(2+) ) levels were altered, and the histopathological observations supported the described results. Conclusively, the study highlights the cardioprotective potential of AG and PTX with superior results from AG. These findings reveal the relative contribution of nitric oxide and TNF-α to oxidative stress and energy failure during endotoxemia.

Adenosine triphosphate-dependent calcium signaling during ventilator-induced lung injury is amplified by hypercapnia

Adenosine triphosphate (ATP) is released by alveolar epithelial cells during ventilator-induced lung injury (VILI) and regulates fluid transport across epithelia. High CO(2) levels are observed in patients with "permissive hypercapnia," which inhibits alveolar fluid reabsorption (AFR) in alveolar epithelial cells. The authors set out to determine whether VILI affects AFR and whether the purinergic pathway is modulated in cells exposed to hypercapnia. Control group was compared against VILI (tidal volume [Vt] = 35 mL/kg, zero positive end-expiratory pressure [PEEP]) and protective ventilation (Vt = 6 mL/kg, PEEP = 10 cm H(2)O) groups. Lung mechanics, histology, and AFR were evaluated. Alveolar epithelial cells (AECs) were loaded with Fura 2-AM to measure intracellular calcium in the presence ATP (10 μM) at 5% or 10% CO(2) as compared with baseline. High tidal volume ventilation impairs lung mechanics and AFR. Hypercapnia (HC) increases intracellular calcium levels in response to ATP stimulation. HC + ATP is the most detrimental combination decreasing AFR. Purinergic signaling in AECs is modulated by high CO(2) levels via increased cytosolic calcium. The authors reason that this modulation may play a role in the impairment of alveolar epithelial functions induced by hypercapnia.

Effects of caffeic acid phenethyl ester on endotoxin-induced cardiac stress in rats: a possible mechanism of protection

Endotoxins (lipopolysaccharides; LPS) are known to cause multiple organ failure, including myocardial dysfunction. The present study aimed to investigate the mechanism of caffeic acid phenethyl ester (CAPE) protection against LPS-induced cardiac stress. Rats were allocated into three groups; group 1 served as a normal control group, group 2 (LPS) received a single intraperitoneal injection of LPS (10 mg/kg), group 3 (LPS + CAPE) was injected intraperitoneally with CAPE (10 mg/kg/day; solubilized in saline containing 20% tween 20) throughout a period of 10 days prior to LPS injection. Rats were maintained 4 h before sacrifice. Caffeic acid phenethyl ester pretreatment normalized LPS-enhanced activities of serum creatine kinase (CK) and lactate dehydrogenase (LDH) as well as glutathione peroxidase (GPx), and myeloperoxidase (MPO) in cardiac tissue. A significant reduction of the elevated levels of serum tumor necrosis factor-alpha (TNF-α) as well as serum and cardiac nitrite/nitrate (NOx) ) was achieved after CAPE pretreatment. CAPE also restored malondialdelyde (MDA), reduced glutathione (GSH), and cytosolic calcium (Ca2+ ) levels in the heart. A marked induction of cardiac heme oxygenase-1 (HO-1) protein level was detected in CAPE-pretreated group. Whereas, LPS-induced reduction of adenosine triphosphate (ATP) and phosphocreatine (PCr) levels was insignificantly changed. Conclusively, the early treatment with CAPE maintained antioxidant defences, reduced oxidative injury, cytokine damage, and inflammation but did not markedly improve energy status in cardiac tissue. The beneficial effect of CAPE might be mediated, at least in part, by the superinduction of HO-1.

Metabolic regulation of coronary vascular tone: role of hydrogen peroxide, purinergic components, and angiotensin

Metabolic regulation plays an important role in modifying coronary vascular tone. We hypothesized that hydrogen peroxide, purinergic components, and angiotensin, produced by cardiac myocytes control coronary vascular tone in proportion to metabolism. We measured changes in the diameter of isolated, pressurized coronary arterioles in response to supernatant from isolated cardiac myocytes in rats (stimulated for 20-, 60-, and 120-min at 400 bpm). Changes in the diameter of arterioles were determined under control conditions following treatment of arterioles with an adenosine receptor antagonist, 8-PSPT, a P2Y1 receptor antagonist, MRS-2179, or an angiotensin II receptor antagonist, olmesartan. A supernatant (500 microl to a 2 ml bath) from myocytes stimulated for 20-, 60- and 120-min caused graded vasodilation (14.1+/-0.4, 20.2+/-1.6, 53.8+/-6.2%, P<0.01 vs. non-stimulated, respectively). In 20-min stimulation, catalase with myocyte supernatants eliminated vasodilation. Following 60-min stimulation, catalase converted myocyte supernatant-induced vasodilation to a vasoconstriction (-15.1+/-1.0%), and this vasoconstriction was eliminated by olmesartan. Upon 120-min stimulation, catalase partially reduced the vasodilation by myocyte supernatants (37.2+/-3.8%). The remaining vasodilation was converted to a vasoconstriction with 8-PSPT and MRS-2179, and this vasoconstriction was completely eliminated with olmesartan. Cardiac myocytes modulate vascular tone through the net effects of hydrogen peroxide, purinergic components (adenosine and ADP), and angiotensin in proportion to ischemia.

Nitric oxide pros and cons: The role of L-arginine, a nitric oxide precursor, and idebenone, a coenzyme-Q analogue in ameliorating cerebral hypoxia in rat

Evidence exists that nitric oxide (NO) may mediate both protective and pathological responses during brain hypoxia (HP). Reactive oxygen species have also been implicated in the pathophysiological response of the brain tissues to HP. Therefore, this study investigated whether a NO precursor, l-arginine (l-arg), a free radical scavenger, idebenone (ID), and their combination would reduce neurological injury resulting from hemic hypoxia (HP) in rats. Adult male Wistar albino rats were injected with sodium nitrite (60 mg/kg, s.c.) to establish hemic hypoxia. ID (100 mg kg(-1), i.p.) and/or l-arg (100 mg kg(-1), i.p.) were administrated 24 and 1h prior to sodium nitrite intoxication, respectively. Hypoxia significantly decreased hemoglobin concentration, while significantly increased serum lactate dehydrogenase (LDH), creatine phosphokinase (CPK), total nitrate/nitrite, sialic, and uric acids concentrations. Moreover, brain lipid peroxides were significantly enhanced, while reduced glutathione, l-ascorbic acids, adenosine triphosphate (ATP) contents, and the activities of catalase and superoxide dismutase, were significantly reduced in the brain tissue. Pretreatment with either ID or l-arg altered the majority of the above-mentioned biochemical changes in hypoxic rats. Additionally, the combination of these two agents significantly reduced injury marker enzyme activities as well as serum sialic, and uric acids level (P>0.05 vs. control). Moreover, this combination exerted a synergistic antioxidant effect by blocking the induction of lipid peroxidation, preserving brain energy (ATP) content, and greatly reducing the hypoxic alterations in brain enzymatic and non-enzymatic antioxidants. Histopathological examination of the brain tissue supported these biochemical findings. This study showed that ID and l-arg were capable of reducing neurological injury following HP in rat, and support the idea of the usefulness of l-arg and ID as prophylaxis from hypoxic brain injury.

Adenosine A1 receptors mediate local anti-nociceptive effects of acupuncture

Acupuncture is an invasive procedure commonly used to relieve pain. Acupuncture is practiced worldwide, despite difficulties in reconciling its principles with evidence-based medicine. We found that adenosine, a neuromodulator with anti-nociceptive properties, was released during acupuncture in mice and that its anti-nociceptive actions required adenosine A1 receptor expression. Direct injection of an adenosine A1 receptor agonist replicated the analgesic effect of acupuncture. Inhibition of enzymes involved in adenosine degradation potentiated the acupuncture-elicited increase in adenosine, as well as its anti-nociceptive effect. These observations indicate that adenosine mediates the effects of acupuncture and that interfering with adenosine metabolism may prolong the clinical benefit of acupuncture.

Perturbations in mitochondrial dynamics induced by human mutant PINK1 can be rescued by the mitochondrial division inhibitor mdivi-1

Mutations in the mitochondrial encoded protein PTEN-induced putative kinase 1 (PINK1) cause autosomal recessive Parkinson disease (PD). In mammalian cells, mutant PINK1 has been reported to promote fission or inhibit fusion in mitochondria; however, the mechanism by which this process occurs remains elusive. Using an ecdysone-inducible expression system in mammalian dopaminergic neuronal cells, we report here that human mutant PINK1 (L347P and W437X) mediates an overall fission effect by increasing the ratio of mitochondrial fission over fusion proteins, leading to excessive dysfunctional fragmented mitochondria. Knocking down endogenous Pink1 produces similar effects. In contrast, overexpressing human wild type PINK1 produces a pro-fusion effect by increasing the ratio of mitochondrial fusion/fission proteins without resulting in functionally compromised mitochondria. Parkin knockdown blocks the imbalance in fission/fusion proteins. Furthermore, overexpressing parkin and ubiquitin increases degradation of the mitochondrial fission hFis1 protein, suggesting PINK1 and parkin maintain proper mitochondrial function and integrity via the fission/fusion machinery. Through genetic manipulations and treatment with the small molecule mitochondrial division inhibitor (mdivi-1), which inhibits DLP1/Drp1, both structural and functional mitochondrial defects induced by mutant PINK1 were attenuated, highlighting a potential novel therapeutic avenue for Parkinson disease.

Mitochondrial role in ischemia-reperfusion of rat hearts exposed to high-K+ cardioplegia and clonazepam: energetic and contractile consequences

The role of the mitochondrial Na/Ca-exchanger (mNCX) in hearts exposed to ischemia-reperfusion (I/R) and pretreated with cardioplegia (CPG) was studied from a mechano-calorimetric approach. No-flow ischemia (ISCH) and reperfusion (REP) were developed in isolated rat hearts pretreated with 10 micromol/L clonazepam (CLZP), an inhibitor of the mNCX, and (or) a high K+ - low Ca2+ solution (CPG). Left ventricular end diastolic pressure (LVEDP), pressure development during beats (P), and the steady heat release (Ht) were continuously measured and muscle contents of ATP and PCr were analyzed at the end of REP. During REP, Ht increased more than P, reducing muscle economy (P/Ht) and the ATP content. CPG induced an increase in P recovery during REP (to 90% +/- 10% of preISCH) with respect to nonpretreated hearts (control, C, to 64% +/- 10%, p < 0.05). In contrast, CLZP reduced P recovery of CPG-hearts (50% +/- 6.4%, p < 0.05) and increased LVEDP in C hearts. To evaluate effects on sarcoplasmic reticulum (SR) function, ischemic hearts were reperfused with 10 mmol/L caffeine -36 mmol/L Na (C - caff - low Na). It increased LVEDP, which afterwards slowly relaxed, whereas Ht increased (by about 6.5 mW/g). CLZP sped up the relaxation with higher DeltaHt, C - caff - low Na produced higher contracture and lower Ht in perfused than in ischemic hearts. Values of DeltaHt were compared with reported fluxes of Ca2+-transporters, suggesting that mitochondria may be in part responsible for the DeltaHt during C - caff - low Na REP. Results suggest that ISCH-REP reduced the SR store for the recovery of contractility, but induced Ca2+ movement from the mitochondria to the SR stores. Also, mitochondria and SR are able to remove cytosolic Ca2+ during overloads (as under caffeine), through the mNCX and the uniporter. CPG increases Ca2+ cycling from mitochondria to the SR, which contributes to the higher recovery of P. In contrast, CLZP produces a deleterious effect on ISCH-REP associated with higher heat release and reduced resynthesis of high energy phosphates, which suggests the induction of mitochondrial Ca cycling and uncoupling.

Analysis of adenosine by RP-HPLC method and its application to the study of adenosine kinase kinetics

An RP-HPLC method for the analysis of adenosine (ADO) has been developed and validated. In the present study, we report an RP-HPLC-based method with modifications of mobile phase and shorter retention time that substantially improved the efficiency of ADO analysis. The HPLC separation of the ADO was achieved on a C18 column, using a mobile phase consisting of water, containing 7% v/v ACN, at a flow rate of 0.8 mL/min. The column effluent was monitored by UV detection at 260 nm. A linear response was achieved over the concentration range of 0.25-100.00 micromol/L. The analytical method inter- and intra-run accuracy and precision were better than +/- 15%. The LOQ was 0.25 micromol/L, with ADO detection in the range of 6.25 pmol per sample. The method has been applied to the study of adenosine kinase (AK) kinetics.

Pressure overload-induced cardiomyopathy in heterozygous carrier mice of carnitine transporter gene mutation

Primary systemic carnitine deficiency is an autosomal recessive disorder caused by a decreased renal reabsorption of carnitine because of mutations of the carnitine transporter OCTN2 gene, and hypertrophic cardiomyopathy is a common clinical feature of homozygotes. Although heterozygotes for OCTN2 mutations are generally healthy with normal cardiac performance, heterozygotes may be at risk for cardiomyopathy in the presence of additional risk factors, such as hypertension. To test this hypothesis, we investigated the effects of surgically induced pressure overload on the hearts of heterozygous mutants of a murine model of OCTN2 mutation, juvenile visceral steatosis mouse (jvs/+). Eleven-week-old jvs/+ mice and age-matched wild-type mice were used. At baseline, there were no differences in physical characteristics between wild-type and jvs/+ mice. However, plasma and myocardial total carnitine levels in jvs/+ mice were lower than in wild-type mice. Both wild-type and jvs/+ mice were subjected to ascending aortic constriction with or without 1% l-carnitine supplementation for 4 weeks. At 4 weeks after ascending aortic constriction, jvs/+ mice showed an exaggeration of cardiac hypertrophy and pulmonary congestion, further increased gene expression of atrial natriuretic peptide in the left ventricles, further deterioration of left ventricular fractional shortening, reduced myocardial phosphocreatine:adenosine triphosphate ratio, and increased mortality compared with wild-type mice; l-carnitine supplementation prevented these changes in jvs/+ mice subjected to ascending aortic constriction. In conclusion, cardiomyopathy and heart failure with energy depletion may be induced by pressure overload in heterozygotes for OCTN2 mutations and could be prevented by l-carnitine supplementation.

Effects of Salviae Mitiorrhizae and Cortex Moutan extract on the rat heart after myocardial infarction: a proteomic study

In this study, we characterized the therapeutical effects of Salviae Mitiorrhizae (Danshen) and Cortex Moutan (Danpi) extract (SDD) on Sprague-Dawley rats subjected to coronary artery ligation, and applied proteomic approach to investigate its potential mechanism of action. The chemical composition of SDD was investigated by HPLC/MS(n) analysis. Measurement for serum levels of creatine kinase (CK), creatine kinase-MB (CK-MB), nitrite and histological study for infarct area of heart were performed. Moreover, protein abundance profiles of myocardium were compared by two-dimensional gel electrophoresis and altered proteins were identified by MALDI-TOF-MS. The results showed SDD significantly decreased CK, CK-MB concentration in serum and infarct area of heart, while increased the release of nitrite in rats with coronary occlusion. Increased concentration of ATP and total adenine nucleotide indicated the energy metabolism has been improved in ischemic heart induced by SDD. Proteomic data revealed that 23 proteins associated with energy metabolism, oxidative stress and cytoskeleton were modulated in SDD treated rats.

Participation of Na/Ca-exchanger and sarcoplasmic reticulum in the high [K]-protection against ischaemia-reperfusion dysfunction in rat hearts

AIM

Na/Ca-exchanger (NCX) and sarcoplasmic reticulum (SR) roles during the protection by a cardioplegic solution (25 mm K and 0.5 mm Ca, CPG) against ischaemia-reperfusion was studied.

METHODS

Contractile performance (CP) and high energy phosphates contents (HEP) were evaluated in isolated ventricles from rats. They were pre-treated with Krebs (C) or CPG and submitted to no-flow ischaemia and reperfusion (I-R). KB-R7943 5 microm (inhibitor of NCX in reverse mode), 8 mm caffeine and ionic changes were used pre-ischaemically to evaluate each pathway role.

RESULTS

During R, CP recovered to 77 +/- 8% of basal in CPG-hearts vs. 55 +/- 8% (P < 0.05) in C-ones. CPG avoided the increases in end diastolic pressure (LVEDP) and in PCr/ATP ratio during I-R. Low [Na]o (78 mm) under both, CPG-2 mm Ca and C, increased further the LVEDP during I-R. LVEDP was also transiently increased by caffeine-CPG, but not modified by KB-R7943. The recovery of CP during reperfusion of CPG-hearts was decreased either, by caffeine (to approximately 75%), low [Na]o-2 mm Ca-CPG (to approximately 40%) and KB-R7943 (to approximately 16%).

CONCLUSIONS

CPG protected hearts from ischaemic contracture by attenuating the fall in ATP and removing diastolic Ca by means of NCX in forward mode. Moreover, CPG induces higher CP recovery during reperfusion by participation of SR and NCX in reverse mode. This work remarks the use of CPG based on the functional role of these Ca handling-mechanisms in a pathophysiological condition as ischaemia-reperfusion.