Sylvia O. Malomo

Effects of co-administration of artesunate and amodiaquine on some cardiovascular disease indices in rats

The effects of co-administration of artesunate and amodiaquine on some cardiovascular disease indices were investigated in albino rats (Rattus novergicus). The experimental animals were randomly divided into four groups: those administered distilled water (control), those administered artesunate (2 mg/kg body weight), those administered amodiaquine (6.12 mg/kg body weight) and those co-administered artesunate (2 mg/kg body weight) and amodiaquine (6.12 mg/kg body weight). The drugs were orally administered twice daily for three days after which the serum lipid profile, heart MDA content and heart ALP and ACP activities were determined. Artesunate significantly reduced (P<0.05) total cholesterol and HDL-cholesterol concentrations in the serum with no significant effects (P>0.05) on other parameters compared to controls. Amodiaquine, on the other hand, significantly reduced (P<0.05) serum total cholesterol concentration while it significantly increased (P<0.05) serum LDL-cholesterol and heart ACP activity compared to controls. Co-administration of artesunate and amodiaquine significantly reduced (P<0.05) total cholesterol and HDL-cholesterol concentrations in the serum while significantly increasing (P<0.05) serum LDL-cholesterol concentration, atherogenic index (LDL-C/HDL-C) and ACP activity in the heart compared to controls. The results obtained suggest that co-administration of artesunate and amodiaquine to patients with coronary heart disease should be with caution.

Mechanism-Based Inhibition of Myeloperoxidase by Hydrogen Peroxide: Enhancement of Inactivation Rate by Organic Donor Substrates

The effects of two hydrazine derivatives (isoniazid and hydralazine) on the inactivation of myeloperoxidase by H2O2 were investigated. Incubation of 20 nM myeloperoxidase with 0.25 mM H2O2 alone caused a time-dependent irreversible loss of tetramethylbenzidine oxidation activity with a pseudo-first order inactivation rate constant of 0.057 min -1 . The hydrazine derivatives increased the inactivation rate in a concentration-dependent manner. Inactivation of the enzyme by H2O2 with or without the hydrazides showed a saturation kinetics pattern. Steady state kinetics analysis suggests that the hydrazides likely inactivate myeloperoxidase using a similar inactivating species as does H2O2. A bimolecular rate constant, specific inactivation rate enhancement factor (k*enh) is proposed as a formal description of the inactivation rate stimulation by the hydrazides. This parameter potentially avoids confounding the finite inactivation due to H2O2 with that caused by the presence of the hydrazides. The relevance of these findings and the constants derived to the analysis of suicide inactivation of peroxidases by reductant substrates are discussed.

Distinct metal ion requirements for the phosphomonoesterase and phosphodiesterase activities of calf intestinal alkaline phosphatase.

The roles of Mg2+ and Zn2+ ions in promoting phosphoryl transfer catalysed by alkaline phosphatase are yet to be fully characterised. We investigated the divalent metal ion requirements for the monoesterase and diesterase activities of calf intestinal alkaline phosphatase. The synergistic effect of Mg2+ and Zn2+ in promoting the hydrolysis of para-nitrophenyl phosphate (monoesterase reaction) by alkaline phosphatase is not observed in the hydrolysis of the diesterase substrate, bis-para-nitrophenyl phosphate. Indeed, the diesterase reaction is inhibited by concentrations of Mg2+ that were optimal for the monoesterase reaction. This study reveals that the substrate specificities of alkaline phosphatases and related bimetalloenzymes are subject to regulation by changes in the nature and availability of cofactors, and the different cofactor requirements of the monoesterase and diesterase reactions of mammalian alkaline phosphatases could have significance for the biological functions of the enzymes.

Effects of defective in vivo synthesis of mitochondrial proteins on cellular biochemistry and physiology of malnourished rats.

Investigations were carried out to find the biochemical and bioenergetic implications of a defective in vivo synthesis of mitochondrial proteins during dietary-protein depletion. 3.4% dietary protein was fed to 21-day-old weanling rats for 30 days (experimental), while 21.0% dietary protein was fed to controls. A close simulation of marasmic-kwashiorkor syndrome was obtained in the experimental group. Rat liver mitochondria were isolated, and the functional and structural integrity was determined using biochemical standard parameters. Results show that the respiratory control ratio (RCR) is reduced by 50% in the experimental group, using any of the pyruvate/malate, beta-hydroxybutyrate or succinate as substrate. The effects of storage at 0 degree C were more pronounced in mitochondria from protein-depleted rats as these mitochondria are more leaky to protons (H+); hence they are defective in carrying out chemiosmotic oxidative phosphorylation. There is a drastic reduction in the basal ATPase and cytochrome oxidase activities with low ATP production and a decline in energy expenditure. This led to serious bioenergetic consequences culminating in heavy dependence on glycolysis and other biochemical aberrations.

Comparative effects of three naturally occurring furanocoumarins on mitochondrial bioenergetics

Oxygraphic measurements of the rates of mitochondrial respiration in the presence of varying amounts of chalepin, imperatorin and marmesin, three naturally occurring furanocoumarins, revealed that the oxidation of NAD(+)-linked substrates was inhibited by chalepin and imperatorin and less significantly by marmesin. The order of potency being rotenone much greater than chalepin imperatorin greater than marmesin. There was no effect whatsoever on succinate oxidation by the furanocoumarins tested (up to 60 microM). State 3 respiration was also inhibited by these furanocoumarins; by at least 80% by 10 microM chalepin and by 48 and 29% with 60 microM imperatorin and 60 microM marmesin, respectively. Consequently, ADP control of respiration was diminished by those concentrations of furanocoumarins that inhibited respiration. At 60 microM, respiratory control ratio was reduced by about 88, 49 and 28% with chalepin, imperatorin and marmesin, respectively. A measurement of the rate of proton and Ca2(+)-movements across the mitochondrial coupling membrane demonstrated that succinate-supported transport was not affected by these furanocoumarins. On the other hand, pyruvate/malate-supported proton ejection was significantly inhibited by chalepin, imperatorin and marmesin. The order of the degree of inhibition of proton flux is rotenone much greater than chalepin greater than imperatorin greater than marmesin. The pattern of the inhibition of pyruvate/malate-supported Ca2(+)-transport was identical to that seen during proton transport. A comparison of the effects of chalepin to that of rotenone suggests that chalepin might be about 10 times less potent than rotenone.

Protonophoric properties of fluorinated arylalkylsulfonamides: observations with perfluidone

The acidity and lipophilicity of the fluorinated arylalkylsulphonamides are determined by the nature of the substituents on their aromatic rings. Herbicidal and anti-inflammatory effects of these compounds appear to increase with their lipophilicity. According to Mitchells chemiosmotic theory, lipophilic weak-acid uncoupling agents act by transporting protons across the inner mitochondrial membrane and thus destroying the proton-electrochemical potential gradient required for ATP synthesis and ion transport. 1:1:1-Trifluoro-N-[2-methyl-4-(phenylsulphonyl) phenyl]methanesulphonamide (Perfluidone), a pre- and post-emergence herbicide (at 20 microM concentration), in isolated rat-liver mitochondria caused (1) a 2-fold stimulation of metabolic state-4 respiration, (2) a reduction of respiratory control ratio (RCR) by at least 50%, (3) an enhancement of latent ATPase activity by 40%, (4) a significant passive swelling of mitochondria in 0.15 N NH4Cl(delta A520 = -0.46 +/- 0.003), (5) proton intrusion during state-4 respiration (356 ng H+/min/mg protein; ng H+/min/mg protein with 5 microM perfluidone), and (6) at least 100% stimulation of oligomycin-inhibited respiration. These profiles are qualitatively comparable with those of the classical lipophilic weak-acid uncoupler, carbonylcyanide-trifluoro-methoxyphenylene hydrazone (FCCP), which acts by promoting the electrogenic transport of H+ ions across mitochondrial membrane.

Inhibition of mitochondrial respiration by chalepin, a naturally occurring furocoumarin

Polarographic measurements of the rates of oxygen consumption by isolated rat liver mitochondria respiring on pyruvate/malate in metabolic state 4 revealed that additions of micromolar amounts of chalepin, a naturally occurring furocoumarin resulted in significant decreases in respiratory rates. At 16 microM chalepin, respiration was inhibited by at least 40%. A maximum inhibition of 60% was obtained at 80 microM chalepin. Whereas 16 microM chalepin gave 76% reduction of respiratory control ratio, at most 80% reduction was obtained at greater than or equal to 80 microM chalepin. There was no significant effect on either metabolic state 4 respiration or respiratory control ratio when succinate was used as electron donor. A comparison with the effects of rotenone indicates that chalepin is probably only one-tenth as potent as this classical inhibitor of respiration. These results show that chalepin-like rotenone is an inhibitor of energy coupling site 1.

Anti-inflammatory and bronchodilatory constituents of leaf extracts of Anacardium occidentale L. in animal models

OBJECTIVE Anacardium occidentale L. leaf is useful in the treatment of inflammation and asthma, but the bioactive constituents responsible for these activities have not been characterized. Therefore, this study was aimed at identifying the bioactive constituent(s) of A. occidentale ethanolic leaf extract (AOEL) and its solvent-soluble portions, and evaluating their effects on histamine-induced paw edema and bronchoconstriction. METHODS The bronchodilatory effect was determined by measuring the percentage protection provided by plant extracts in the histamine-induced bronchoconstriction model in guinea pigs. The anti-inflammatory effect of the extracts on histamine-induced paw edema in rats was determined by measuring the increase in paw diameter, after which the percent edema inhibition was calculated. The extracts were analyzed using gas chromatography-mass spectrometry to identify the bioactive constituents. Column chromatography and Fourier transform infrared spectroscopy were used respectively to isolate and characterize the constituents. The bronchodilatory and anti-inflammatory activities of the isolated bioactive constituent were evaluated. RESULTS Histamine induced bronchoconstriction in the guinea pigs and edema in the rat paw. AOEL, hexane-soluble portion of AOEL, ethyl acetate-soluble portion of AOEL, and chloroform-soluble portion of AOEL significantly increased bronchodilatory and anti-inflammatory activities (P < 0.05). Oleamide (9-octadecenamide) was identified as the most abundant compound in the extracts and was isolated. Oleamide significantly increased bronchodilatory and anti-inflammatory activities by 32.97% and 98.41%, respectively (P < 0.05). CONCLUSION These results indicate that oleamide is one of the bioactive constituents responsible for the bronchodilatory and anti-inflammatory activity of A. occidentale leaf, and can therefore be employed in the management of bronchoconstriction and inflammation.

Mitochondrial bioenergetics during exposure of rats to perfluidone, a fluorinated arylalkylsulphonamide

Apart from the symptoms of poisoning which the fluorinated arylalkylsulphonamides share with the classical protonphore and uncoupler of oxidative phosphorylation, carbonylcyanide p-trifluoromethoxyphenylhydrazone (FCCP), the direct correlation between the lipophilic weak acid properties of these chemicals and their biological activity suggests that permeation of the inner mitochondrial membrane could be the initial step in the molecular mechanism of their biological activity. Mitochondria isolated from the livers of rats intraperitoneally exposed to varying doses (0-80 mg/kg body wt.) of perfluidone (1,1,1-trifluoro-N-(2 methyl-4-(phenylsulphonyl)phenyl methanesulphonamide), a fluorinated arylalkylsulphonamide pesticide, exhibit the following dose-dependent features: (i) increased state-4 respiration: stimulation being maximal (greater than or equal to 400%) at 80 mg perfluidone per kg body wt.), (ii) release of respiratory control by ADP: least respiratory control ratios (RCRs) (less than or equal to 1.2) were obtained at 80 mg perfluidone per kg body wt., (iii) reduced ADP/O ratios, (iv) increased mitochondrial passive swelling, (vi) reduced rates of mitochondrial proton ejection during succinate oxidation, (vi) reduced rates of respiration-dependent Ca2+ accumulation and (vii) an enhanced oligomycin-sensitive ATPase action. These features which are qualitatively identical to those of the classical protonophore FCCP, suggest that permeation of the inner mitochondrial membrane by perfluidone is accompanied by a movement of protons into the matrix such that the proton motive force required for ATP synthesis and ion transport becomes small or not formed at all.