Histochemistry of creatine phosphokinase

Over-expression of mitochondrial creatine kinase in the murine heart improves functional recovery and protects against injury following ischaemia-reperfusion

Aims

Mitochondrial creatine kinase (MtCK) couples ATP production via oxidative phosphorylation to phosphocreatine in the cytosol, which acts as a mobile energy store available for regeneration of ATP at times of high demand. We hypothesized that elevating MtCK would be beneficial in ischaemia-reperfusion (I/R) injury.

Methods and results

Mice were created over-expressing the sarcomeric MtCK gene with αMHC promoter at the Rosa26 locus (MtCK-OE) and compared with wild-type (WT) littermates. MtCK activity was 27% higher than WT, with no change in other CK isoenzymes or creatine levels. Electron microscopy confirmed normal mitochondrial cell density and mitochondrial localization of transgenic protein. Respiration in isolated mitochondria was unaltered and metabolomic analysis by 1 H-NMR suggests that cellular metabolism was not grossly affected by transgene expression. There were no significant differences in cardiac structure or function under baseline conditions by cine-MRI or LV haemodynamics. In Langendorff-perfused hearts subjected to 20 min ischaemia and 30 min reperfusion, MtCK-OE exhibited less ischaemic contracture, and improved functional recovery (Rate pressure product 58% above WT; P < 0.001). These hearts had reduced myocardial infarct size, which was confirmed in vivo: 55 ± 4% in WT vs. 29 ± 4% in MtCK-OE; P < 0.0001). Isolated cardiomyocytes from MtCK-OE hearts exhibited delayed opening of the mitochondrial permeability transition pore (mPTP) compared to WT, which was confirmed by reduced mitochondrial swelling in response to calcium. There was no detectable change in the structural integrity of the mitochondrial membrane.

Conclusions

Modest elevation of MtCK activity in the heart does not adversely affect cellular metabolism, mitochondrial or in vivo cardiac function, but modifies mPTP opening to protect against I/R injury and improve functional recovery. Our findings support MtCK as a prime therapeutic target in myocardial ischaemia.

Isolation, characterization and nucleotide sequence of the muscle isoforms of creatine kinase from the Antarctic teleost Chaenocephalus aceratus

Creatine kinase (CK) was isolated from the white muscle of the Antarctic icefish Chaenocephalus aceratus, which is deficient in glycolytic capacity. C. aceratus white myotomal creatine kinase (MMCK) displayed an apparent K(m) at 0.5 degrees C of 0.06 mM for ADP and 17 mM for Phosphocreatine. These K(m) values are similar to those reported for other vertebrate MMCKs at their physiologically relevant body temperatures. C. aceratus MMCK exhibited optimal activity at pH of 7.6-7.7 at 0.5 degrees C, in contrast to rabbit MMCK which had optimum activity at pH 6.2 at 30 degrees C. The apparent V(max) of C. aceratus MMCK at 0.5 degrees C is 94+/-4 S.D. (n=9) micromol ATP/min/mg (i.e. U/mg), which is comparable to rabbit MMCK assayed at 20 degrees C and 8-fold greater than rabbit MMCK measured at 0.5 degrees C. DEAE chromatography of C. aceratus white muscle CK resolved two distinct activity peaks. Cloning and sequencing of C. aceratus CK cDNAs confirmed that two muscle-specific isoforms of CK were expressed that were distinct from the mitochondrial and brain isoforms. Icefish MMCK was sensitive to transient temperature elevation, and the DEAE-fractionated forms were highly unstable. These results indicate that C. aceratus MMCK displays significant activity at physiological temperature and intracellular pH of icefish muscle that could contribute to sustaining energy charge during burst-swimming.

Metabolic compartmentation and substrate channelling in muscle cells. Role of coupled creatine kinases in in vivo regulation of cellular respiration--a synthesis

The published experimental data and existing concepts of cellular regulation of respiration are analyzed. Conventional, simplified considerations of regulatory mechanism by cytoplasmic ADP according to Michaelis-Menten kinetics or by derived parameters such as phosphate potential etc. do not explain relationships between oxygen consumption, workload and metabolic state of the cell. On the other hand, there are abundant data in literature showing microheterogeneity of cytoplasmic space in muscle cells, in particular with respect to ATP (and ADP) due to the structural organization of cell interior, existence of multienzyme complexes and structured water phase. Also very recent experimental data show that the intracellular diffusion of ADP is retarded in cardiomyocytes because of very low permeability of the mitochondrial outer membrane for adenine nucleotides in vivo. Most probably, permeability of the outer mitochondrial membrane porin channels is controlled in the cells in vivo by some intracellular factors which may be connected to cytoskeleton and lost during mitochondrial isolation. All these numerous data show convincingly that cellular metabolism cannot be understood if cell interior is considered as homogenous solution, and it is necessary to use the theories of organized metabolic systems and substrate-product channelling in multienzyme systems to understand metabolic regulation of respiration. One of these systems is the creatine kinase system, which channels high energy phosphates from mitochondria to sites of energy utilization. It is proposed that in muscle cells feed-back signal between contraction and mitochondrial respiration may be conducted by metabolic wave (propagation of oscillations of local concentration of ADP and creatine) through cytoplasmic equilibrium creatine and adenylate kinases and is amplified by coupled creatine kinase reaction in mitochondria. Mitochondrial creatine kinase has experimentally been shown to be a powerful amplifier of regulatory action of weak ADP fluxes due to its coupling to adenine nucleotide translocase. This phenomenon is also carefully analyzed.

The polysome as a terminal for the creatine phosphate energy shuttle

The role of the creatine phosphate shuttle in the energetics of muscle protein synthesis in isolated polysomes, from rat hindlimb muscle, was studied. Triton X-100-treated polysomes, following their centrifugation through a 1 M sucrose gradient, contained 38 mU/mg RNA of bound creatine kinase. In the presence of pH 5 enzyme (obtained from rat liver), 0.5 mM ATP, and 1 microM GTP, amino acid (leucine) incorporation by polysomes in the presence of 8 mM creatine phosphate was twice that in the presence of an exogenous ATP regenerating system of 10 mM phospho(enol)pyruvate and 10 U/ml pyruvate kinase. Since added creatine kinase had no effect on incorporation supported by creatine phosphate it is clear that endogenous creatine kinase allows sufficient regeneration of ATP. These data also suggest that nucleoside diphosphokinase must have been associated with the polysome for phosphate was transferred to GTP from [33P]creatine phosphate, and the specific activities of ATP and GTP increased at equal rates, reaching the specific activity of creatine phosphate at 8 min. We conclude that skeletal muscle polysomes have bound creatine kinase activity and they act as terminals for the creatine phosphate energy shuttle. Creatine phosphate regenerates GTP, probably through an intermediate reaction catalyzed by nucleoside diphosphokinase. This provided an added support for the hypothesis of compartmentation of enzymes and substrates and that the transport form of energy between the mitochondria and energy utilizing sites in muscle is creatine phosphate rather than ATP, which extends the general role of the creatine phosphate energy shuttle.

Hemodialysis with calcium-free dialysate prevents myocardial creatine kinase depletion after brief coronary artery occlusion in dogs

To evaluate the effect of hypocalcemia on myocardial creatine kinase (CK) depletion after brief coronary artery occlusion and reperfusion, dogs were rendered hypocalcemic via systemic hemodialysis for eighty minutes in the absence of Ca. Control animals were hemodialysed in the presence of Ca. The left anterior descending coronary artery was then occluded for six minutes and reperfusion for eighty minutes occurred at low flow of dialysate. A 50% decrease in serum Ca of the hypocalcemic animals during the eighty minutes of hemodialysis resulted in a significant (about 35%) decrease of myocardial Ca. Comparison of the myocardial creatine kinase activity following reperfusion showed preservation of the enzyme in the ischemic areas of the hypocalcemic animals, whereas the CK activities of the ischemic areas of the normocalcemic animals were much lower (p less than 0.005). During the reperfusion period serum Ca of the hypocalcemic group increased to 75% of that of the normocalcemic group while myocardial Ca of both ischemic and nonischemic areas reequilibrated to normocalcemic values. Hemodynamic parameters during the various phases of the experiment were not altered significantly. It is concluded that transient decrease of myocardial Ca produced by hypocalcemia prior to occlusion leads to protection against myocardial damage after brief coronary ligation.

A test for muscle lesions and their regeneration following intramuscular drug application

A standard infiltration of the rat tibialis anterior muscle with 0.1 ml of local anesthetics was used as a model to help choose criteria for testing the intramuscular toxicity of drugs. Anesthetics used were 0.2% carbisocaine, 1% and 2% Lidocaine, 0.5% Marcaine, 1% and 2% Mesocaine, 1% and 2% Procaine. Increases in the serum levels of creatine kinase were monitored for 24 hours, and the weight, as well as macro- and microscopic changes in the muscle for a period of 1 month. Exposure of the muscle to local anesthetics resulted in 2 types of lesions. One was characterized by selective muscle fiber damage in the injected area. The other type of lesion was a generalized one that involved a number of cell types. To assess the intramuscular toxicity of drugs we defined the type of lesion, its size, and the rate of subsequent muscle regeneration. We recommend the following criteria for the assay of myotoxicity of new drugs being developed as pharmaceutical agents: 1) serum creatine kinase level 1 hour after intramuscular injection of the drug; 2) microscopic findings at 3, 7, and 21 days; 3) the cross-sectional area of the lesion at 3 days; and 4) the weight of the muscle at 7 and 21 days.

Homogeneous chicken heart mitochondrial creatine kinase purified by dye-ligand and transition-state analog-affinity chromatography

A method for the preparation of homogeneous mitochondrial creatine kinase from chicken heart is presented. The two-column procedure, which can be completed in 2 days, uses Procion red dye and transition-state analog-affinity chromatography. The transition-state analog-affinity chromatographic system utilizes an ADP-hexane-agarose column in conjunction with the transition-state analog complex originally developed by E. J. Milner-White and D. C. Watts (1971, Biochem, J. 122, 727-740) composed of KNO3, MgCl2, creatine, and ADP. The enzyme is a dimer composed of 2 Mr 43,000 subunits. The sequence of the first N-terminal 20 amino acids shows that the enzyme is different from the cytosolic isozymes but similar to human mitochondrial creatine kinase. The enzyme has an extinction coefficient of epsilon 280 nm = 2.22 +/- 0.10 ml X mg-1 X cm-1 and a maximum velocity of 200 IU/ml at pH 7.0. The kinetic constants for the chicken heart mitochondrial isozyme are comparable to values for the canine and human heart isozyme.

Local tissue damage after intramuscular injections in rabbits and pigs: quantitation by determination of creatine kinase activity at injection sites

The creatine kinase (CK) method, which is based on difference in CK activity at injection sites and in control tissue, was used for quantitation of local tissue damage after intramuscular injection of varying volumes and preparations in rabbits and pigs. Injections were given in the central part of the longissimus dorsi muscle. Three days after the injections the animals were killed and the arbitrary amounts of tissue without CK were calculated from the CK activity in muscle tissue at the injection sites and in control tissue. Determination of tissue damage by the CK method was in good agreement with macroscopic and microscopic changes, whether a well demarcated necrotic area or little or no necrosis was found at the injection site. Tissue damage was proportional to injection volumes between 0.25 and 1 ml in rabbits and 0.5 and 3 ml in pigs. In rabbits tissue damage per injected ml was found to be more than twice the damage seen in pigs. It is concluded that the CK method is a reliable method for quantitation of local tissue damage after intramuscular injections and that injection of even small volumes of 0.25-0.5 ml in the longissimus dorsi muscle of rabbits is a sensitive test of the local toxicity of drugs.

Effect of hypocalcemia on isoproterenol induced cardiotoxicity in dogs

The effect of serum calcium on the myocardial damages produced by isoproterenol was studied in the dog. Hemodialysis for 80 min in the absence of calcium was used to alter serum calcium concentration in seven experimental animals. The same number of animals were dialysed in the presence of calcium and were used as controls. After hemodialysis all animals were infused with isoproterenol 2.0 micrograms/kg/min for 4 hours. The myocardial damage was assessed by comparing serial measurements of the serum cardiac enzyme activities CK and CK-MB and the electrocardiographic findings of the two groups, before, during and after isoproterenol infusion. Serum calcium decreased significantly after dialysis only in the experimental group (1.15 vs 2.19 mmol X L-1). Total CK activities of the experimental group during and after isoproterenol infusion were 2 to 3 times lower than in the controls (190-360 vs 410-1370 IU X L-1). Changes of the CK-MB isoenzyme activities were more profound, these were detectable and measured only in 4 of the experimental animals and in much lower activities than in the controls (25-61 vs 45-445 IU X L-1). A positive correlation was found (r = 0.673, p less than 0.05) between the highest value of CK-MB of both groups and the serum calcium concentration after hemodialysis. In accordance to the differences of the biochemical estimates the effect of serum calcium on the cardiotoxic effect of isoproterenol has been further emphasized by the electrocardiographic findings. Thus arrhythmias, negative T-waves and significant ST segment depression were observed only in one experimental animal. In contrast these electrocardiographic disturbances were common and marked findings in all but one of the control animals. In both groups these electrocardiographic findings were reversed one to three hours after the termination of the isoproterenol infusion. Myocardial calcium at the end of the experiment was lower in the experimentals compared to the controls (0.23 vs 0.30 mmol X kg-1 wet weight). On the contrary magnesium concentration increased respectively. It is concluded that low serum calcium has a protective effect against the cardiotoxic action of isoproterenol. This protective action may be relevant to the decreased calcium and increased magnesium of the heart of the animals hemodialysed in the absence of calcium.

2,4,5-T effects on cardiac and serum lactic dehydrogenase (LDH) and creatine kinase (CK) isozymes. II. Neonatal enzyme activities and isozyme profiles

Neonates from CD-1 mice, which were treated during gestation with 100 mg/kg of 2,4,5-T, were studied from day 1 to 30 postpartum (pp) for effects on cardiac development by determining total cardiac activities and isozyme profiles of LDH and CK. On day 1pp, the total activities and isozyme profiles of LDH of the neonatal hearts were normal. During the developmental period of day 7 through 15, changes were noted in the developmental pattern of LDH isozymes some of which continued to day 30. The CK isozyme profile on day 1pp showed a significant change and changes continued throughout the lactational period. During this period, the normal developmental isozyme patterns of LDH and CK were altered by prenatal exposure to 2,4,5-T suggesting metabolic derangement or pathological changes in the neonatal heart.

The role of creatine phosphokinase in supplying energy for the calcium pump system of heart sarcoplasmic reticulum

An investigation of isolated and purified heart sarcoplasmic reticulum performed in the current study indicates the presence of significant creatine phosphokinase (CPK) activity in this preparation. The localization of CPK on the membrane of sarcoplasmic reticulum has been revealed also by an electron microscopic histochemical method. Under the conditions of the Ca(2+)-ATPase reaction in the presence of creatine phosphate, the release of creatine into the reaction medium is observed, the rate of the latter process being dependent on the MgATP concentration in accordance with the kinetic parameters of the Ca2+-ATPase reaction. CPK localized on the reticular membrane is able to maintain the high rate of calcium consumption by the sarcoplasmic reticulum vesicles. The results obtained demonstrate the close functional coupling between CPK and Ca2+-ATPase in the membrane of sarcoplasmic reticulum and indicate the important functional role of CPK in supplying energy for the Ca(2+)-ATPase reaction and ion transport across the membrane of heart sarcoplasmic reticulum.

[Immunohistochemical localization of creatinkinase isoenzymes in human tissue (author's transl)]

The use of an immunohistochemical method permits the localization of creatine kinase isoenzymes MM and BB in tissue sections. Frozen sections are first incubated with the specific antiserum and secondly with the soluble antigen under investigation. The antibody fixed creatine kinase can then be visualized by the tetrazolium-salt linked histochemical reaction. In this way CK-BB was found in the smooth muscle and the mucosa of the human colon. In sections of skeletal muscle CK-MM was predominantly localized in the intermyofibrillar space. Membrane bound activity could be demonstrated in the sarcoplasmic reticulum and the surface membrane after elution of the cytoplasmic enzyme. In the human tonsilla CK-BB was localized in lymphatic and epithelial tissues, CK-MM in the muscle fibers. The isoenzyme patterns in single sections of tonsilla were in parallel determined by the immunotitration assay. The results indicate the usefulness of the combined application of histochemistry and immunotitration in serial tissue sections.

An electron microscopic histochemical investigation of the localization of creatine phosphokinase in heart cells

The results of an electron microscopic histochemical investigation performed in the current study indicate that in heart cells creatine phosphokinase is localized: (1) inside mitochondria mainly on the cristae membranes, (2) on the membrane of the sarcoplasmic reticulum, (3) on myofibrils (and in cytoplasm), (4) on the plasma membrane of the cells, (5) on the membrane of the cell nuclei.