Inhibition of hexokinase and protein kinase activities of tumor cells by a chloromethyl ketone derivative of lactic acid

Examining the effect of ions and proteins on the heat dissipation of iron oxide nanocrystals

In this paper, the effect and contribution of physiological components like ions and proteins under an applied alternating magnetic field (AMF) towards heat dissipation of superparamagnetic iron oxide nanoparticles (SPIONs) are discussed. Our results have shown that under an applied AMF, magnetic hyperthermia efficiency could be significantly enhanced if SPIONs were suspended in 1× phosphate buffered saline (PBS) compared to a suspension in de-ionized (DI) water. However, no heat enhancement was found when SPIONs were suspended in blood which is an amalgamation of physiological ions and proteins. Closer investigations have revealed that the presence of physiological ions can contribute positively to heating efficiency, and the heating efficiency increases with concentration of ions, ionic mass and solubility. However, the heating efficiency of ions can be suppressed to an insignificant level (comparable with measurement error), in the presence of physiological proteins in 1×PBS. Our electrochemical studies also showed that ionic mobility can be reduced significantly if proteins were present in the solution, thus retarding the heating efficiency.

Effects of 4-alkylmorpholine N-oxides on ATP-producing processes in Ehrlich ascites and L1210 leukaemia cells

The main purpose of the present investigation was to study the effect of the homologous series of 4-alkylmorpholine N-oxides on ATP-producing processes in Ehrlich ascites and L1210 murine leukaemia cells. The effects on aerobic glucose consumption, lactic acid formation, content of total (T-SH) and non-protein thiol groups (NP-SH), endogenous and exogenous respiration and the level of ATP in tumour cells incubated in vitro were investigated. 4-Dodecylmorpholine N-oxide (DMNO), one of the most active compounds, decreased the level of ATP immediately after addition to the suspension of Ehrlich cells in an ice bath. After 2 h incubation at 37 degrees C the drop in the ATP level was much lower. A possible explanation for the decrease in the ATP level might be interaction of the amine oxide with the cell membrane.

Biochemical basis of cytotoxic activity of some new N'-oxides of N',N'-dimethylaminoalkylamides of dodecanoic acid

The objective of the present investigation was to screen a series of new N'-oxides of N',N'-dimethylaminoalkylamides of dodecanoic acid for activity in vitro and to investigate the biochemical mode of action. On the basis of primary screening, one of the most active compounds, namely the N'-oxide of 10-(N',N'-dimethylaminodecyl)amide of dodecanoic acid (n = 10) was chosen for detailed biochemical study. This compound inhibited the incorporation of 14C-precursors (adenine, valine, thymidine, uridine) into appropriate macromolecules of P388 murine leukemia and Ehrlich ascites carcinoma cells. The amine oxide also interfered with energy-yielding processes (aerobic glycolysis, endogenous respiration). Cytotoxicity is a consequence of the cytolytic activity of the compounds mentioned above. Membranous effects were demonstrated by the measuring of the release of cytoplasmic materials absorbing at 260 and 280 nm, marker enzyme activities (LDH, MDH), release of protein from the cells into the culture medium, as well as by morphological examination. It is evident that the site of action of the amine oxides investigated was the biological membrane which, after interaction with the amine oxides, showed changes in molecular organization and osmotic and permeability characteristics.

Decay of mammalian hexokinase: characterization of the specific proteolytic activity

Hexokinase-degrading activity (HKDA) is associated with hexokinase throughout purification. It is not ubiquitin-dependent. With glucose present, HKDA requires MgATP. It is triggered by removal (or ATP-dependent consumption) of glucose, and masked when glucose is restored. PCMB, TLCK and TPCK suppress hexokinase and activate HKDA. Glucose removal and active-site blockage appear to induce HKDA.

Effect of rhein on the glucose metabolism of Ehrlich ascites tumor cells

The effect of rhein, 4,5-dihydroxyanthraquinone-2-carboxylic acid, on oxygen consumption and the rate of aerobic and anaerobic lactate production by Ehrlich ascites tumor cells has been investigated. The rate of oxygen uptake decreases with the increase of rhein concentration. Rhein also inhibits aerobic and anaerobic glycolysis. The rate of aerobic lactate production decreases with the drug concentration and the maximal effect was observed at 0.100 mM. Anaerobic lactate production is also inhibited and the maximum effect is reached at 0.220 mM. The possibility that the lactate production decrease was secondary to an effect on mitochondrial ATPase was excluded on the basis of the data with DNP and oligomycin. Rhein reduces the intracellular level of lactate, pyruvate and glucose-6-phosphate. Glucose utilization and 2-deoxy-D-glucose uptake are decreased to the same extent as the inhibition of aerobic lactate production, whereas glucose phosphorylation is unaffected. It is, therefore, concluded that the inhibition of glycolysis of Ehrlich ascites tumor cells by rhein is caused by an impairment of glucose uptake.

Synthesis and targeting of hexokinase to mitochondria in hepatoma cells

The synthesis and turnover of hexokinase has been measured in Zajdela hepatoma ascites cells labeled for short periods with [35S]methionine. Digitonin fractionation of the labeled cells into a soluble and a membrane fraction showed that only a small part of the newly labeled hexokinase is transferred to mitochondrial binding sites. The soluble enzyme disappears, however, with a half-life of less than 2 h. Glucose had no effect on the stability of the soluble enzyme in intact cells. Our experiments suggest that Zajdela cell hexokinase is synthesized in excess of binding sites and that the excess enzyme is not stable.

Effect of hyperthermia on electron transport in Ehrlich ascites tumor mitochondria

The effect of hyperthermia (1 hr, 41 degrees C) on the functional properties of Ehrlich ascites tumor mitochondria was investigated. Mitochondria isolated from Ehrlich ascites tumor after exposure of whole cells to 41 degrees C for 1 hr still phosphorylate and maintain a normal acceptor control ratio (ACR). The temperature decreases state 4 and ADP-and FCCP-stimulated respiration on various substrates entering at three energy-conserving sites of the respiratory chain. The inhibition of oxygen consumption by NAD- and FAD-linked substrates was 40% for state 4 and 70% for ADP- or FCCP-stimulated respiration. State 4 and FCCP-stimulated respiration of mitochondria on TMPD + ascorbate was affected 38% and 45%, respectively. ATPase activity was unaffected by hyperthermia, indicating that under these experimental conditions, the inhibition of ADP-stimulated respiration does not depend on an effect on either Fo F1-ATPase or adenine translocase, the activity of which is required for ATP entry prior to ATPase activity. Because of the inability to detect a specific site of action of temperature, it is conceivable that hyperthermia might inhibit substrate oxidation by altering some components of the inner mitochondrial membrane, which regulates the kinetic properties of the membrane-associated enzymes.