Effects of Covalent Conjugates of Fullerene Derivatives with Xanthene Dyes on Activity of Ca2+-ATPase of the Sarcoplasmic Reticulum.

The effects of the newly synthesized covalent conjugates of water-soluble fullerene derivatives (WSFD) with xanthene dyes: polyanionic WSFD-fluorescein (1), polycationic WSFD-fluorescein (2), polyanionic WSFD-eosin (3), and polyanionic WSFD (4), polycationic WSFD (5), fluorescein (6) and eosin (7), on activity of the membrane-bound Ca2+-ATPase of the sarcoplasmic reticulum (SR Ca2+-ATPase) were studied. Compounds 1, 3, 4, 6, and 7 inhibit the hydrolytic function of the enzyme, the inhibition constants for these compounds are Ki=1.3×10-5 M (1), Ki=4.7×10-6 M (3), Ki=2.5×10-6 M (4), Ki=6.1×10-5 M (6), and Ki=5.8×10-6 M (7). The effects of compounds 3, 6, and 7 on the hydrolytic function of the enzyme is competitive; compounds 1 and 4 are noncompetitive. Polycationic WSFD fluorescein (2) and polycationic WSFD (5) do not affect ATP hydrolysis, but inhibit active Ca2+ transport in a concentration of 0.01 mM by 100±10 and 40±4%, respectively. Conjugates 1 and 3 completely inhibit the hydrolytic and transport functions of the enzyme in a concentration of 0.01 mM, and in a concentration of 0.001 mM inhibit active Ca2+ transport by 60±6 and 55±6% uncoupling the hydrolytic and transport functions of SR Ca2+-ATPases. The obtained results demonstrate a significant effect of the studied compounds on the active transmembrane transfer of Ca2+ and make it possible to predict the presence of antimetastatic and antiaggregatory activities of the studied compounds.

The Effect of Nitroxyalkyl Succinimides on Activity of Cyclic Guanosine Monophosphate Phosphodiesterase.

The effect of N-nitroxymethyl succinimide (1), N-(2-nitroxyethyl) succinimide (2) and N-(3-nitroxypropyl) succinimide (3) on enzymatic activity of cyclic guanosine monophosphate (cGMP) phosphodiesterase was studied and crystal structure of compound (2) was determined. It was shown that all studied N-nitroxy succinimides inhibited cGMP phosphodiesterase in a concentration range of 0.1-0.001 mM. Compound (2) noncompetitively and reversibly inhibited hydrolytic function of enzyme with Ki=1.7×10-5 М. Inhibition constant for the reference compound N-(2-nitroethyl) nicotinamide (nicorandil) was 3×10-5 М.

Action of Iron Nitrosyl Complexes, NO Donors, on the Activity of Sarcoplasmic Reticulum Ca2+-ATPase and Cyclic Guanosine Monophosphate Phosphodiesterase.

The effect of iron nitrosyl complexes, NO donors, of a general formula [Fe2(L)2(NO)4] with functional sulfur-containing ligands (L-3-nitro-phenol-2-yl, 4-nitro-phenol-2-yl, or 1-methyl-tetrazol-5-yl) on the activity of sarcoplasmic reticulum Ca2+-ATPase and cyclic guanosine monophosphate phosphodiesterase (cGMP PDE) was studied. The test complexes uncoupled the hydrolytic and transport functions of Ca2+- ATPase, thus disturbing the balance of Ca2+ ions in cells, which may affect the formation of thrombi and adhesion of metastatic cells to the endothelium of capillaries. They also inhibited the activity of cGMP PDE, thereby contributing to the accumulation of the second messenger cGMP. The studied iron nitrosyl complexes can be considered as potential drugs.

Effects of Fullerene Derivatives on Activity of Ca2+-ATPase of the Sarcoplasmic Reticulum and cGMP Phosphodiesterase.

We studied the effects of new water-soluble polysubstituted fullerene C60 (PFD) derivatives on activity of Ca2+-Mg2+ ATPase of the sarcoplasmic reticulum and cGMP phosphodiesterase. All examined fullerene derivatives inhibited activity of both enzymes. For instance, PFD-I, PFD-II, PFD-III, PFD-V, PFD-IX, PFD-X, and PFD-XI in a concentration of 5×10-5 M completely inhibited hydrolytic and transport functions of Ca2+-ATPase. These compounds in a concentration of 5×10-6 suppressed active transport of calcium ions by 51±5, 77±8, 52±5, 52±5, 100±10, 80±8, and 100±10%, respectively, and inhibited ATP hydrolysis by 31±3, 78±8, 18±2, 29±3, 78±8, 63±7, and 73±9%, respectively, uncoupling the hydrolytic and transport functions of the enzyme. PFD-I noncompetitive and reversibly reduced activity of Ca2+-ATPase (Ki=2.3×10-6 M). All the studied fullerene derivatives (except for PFD-VII) inhibited cGMP phosphodiesterase by more than 80% in concentration of 10-4 M and higher and by more than 50% in concentration of 10-5 M. PFD-I is a non-competitive reversible inhibitor of cGMP phosphodiesterase (Ki=7×10-6 M). These results allow us to expect antimetastatic, antiaggregatory, antihypertensive and vasodilative activity of the studied compounds.

Effects of Nitrosyl Iron Complexes with Thiocarbamide and Its Aliphatic Derivatives on Activities of Ca2+-ATPase of Sarcoplasmic Reticulum and cGMP Phosphodiesterase.

We studied the effects of water-soluble cationic dinitrosyl iron complexes with thiocarbamide and its aliphatic derivatives, new synthetic analogs of natural NO donors, active centers of nitrosyl [1Fe-2S]proteins, on activities of Ca2+-ATPase of sarcoplasmic reticulum and cGMP phosphodiesterase. Nitrosyl iron complexes [Fe(C3N2H8S)Cl(NO)2]0[Fe(NO)2(C3N2H8S)2]+Cl- (I), [Fe(SC(N(CH3)2)2(NO)2]Cl (II), [Fe(SC(NH2)2)2(NO)2Cl×H2O (III), and [Fe(SC(NH2)2)2(NO)2]2SO4×H2O (IV) in a concentration of 10-4 M completely inhibited the transporting and hydrolytic functions of Ca2+-ATPase. In a concentration of 10-5 M, they inhibited active Ca2+ transport by 57±6, 75±8, 80±8, and 85±9% and ATP hydrolysis by 0, 40±4, 48±5, and 38±4%, respectively. Complex II reversibly and noncompetitively inhibited the hydrolytic function of Ca2+-ATPase (Ki=1.7×10-6 M). All the studied iron-sulphur complexes in a concentration of 10-4 M inhibited cGMP phosphodiesterase function. These data suggest that the studied complexes can exhibit antimetastatic, antiaggregation, vasodilatatory, and antihypertensive activities.

[Modulation of reactivity of cyclic adenosine monophosphate phosphodiesterase under the effect of pyridinecarboxylic acid derivatives and Pt(IV) metal complexes on their basis].

The effect of substituted nicotinamides and isonicotinamides and Pt(IV) metal complexes based on the substituted nicotinamides and isonicotinamides on the activity of cAMP phosphodiesterase was studied. Isonicotinamide derivatives are efficient enzyme activators, whereas substituted nicotine amides are inhibitors of enzymatic cAMP phosphodiesterase activity; their inhibitory potency is comparable to that of theophylline used as a reference drug.

[Inhibition of active transport of calcium ions by PT(IV) and PD(II) metal complexes. Correlation between the process and antimetastatic action of drugs].

Newly synthesized compounds, namely, platinum and palladium metal complexes based on substituted pyridinecarboxylic acids inhibit both active transport of Ca ions and hydrolysis of ATP, catalyzed by sarcoplasmic reticulum Ca(2+)-ATPase. The degree of active transport of Ca ions to vesicles correlated to the inhibition of metastases of experimental melanoma B16 by compounds studied. We suggest that the mechanism responsible for inhibition of metastases by newly synthesized compounds consists in change of normal ratio of extra- and intracellular content of Ca2+ ions that influences platelet aggregation, required for adhesion of metastasizing tumor cells to vascular walls.