N-acetyl Penicillamine Research Articles

Simvastatin acts synergistically with ACE inhibitors or amlodipine to decrease oxygen consumption in rat hearts.

Statin drugs, which are cholesterol-lowering agents, can upregulate endothelial nitric oxide synthase (eNOS) in isolated endothelial cells independent of lipid lowering. We investigated the effect of short-term simvastatin administration on NO-mediated regulation of myocardial oxygen consumption (MV(O2)) in tissue from rat hearts. Male Wistar rats were divided into (a) control group (n = 14), and (b) simvastatin group (n = 10, 20 mg/kg/day by oral gavage). After 2 weeks, left ventricular myocardium was isolated to measure MV(O2) using a Clark-type oxygen electrode, and aortic plasma nitrates and nitrites (NOx) were measured. Baseline plasma NOx levels (19+/-2.6 in control vs. 20+/-2.5 microM/L in simvastatin) and baseline MV(O2) (288+/-23 in control vs. 252+/-11 nmol/g/min; p = 0.09) were not significantly different between the two groups. NO-dependent regulation of MV(O2) in response to bradykinin, ramipril, or amlodipine was augmented in simvastatin rats compared with controls (p < 0.05). Decrease of MV(O2) from baseline in response to highest doses in control versus simvastatin groups was as follows-bradykinin, -28+/-5% vs. -44+/-6%; ramipril, -35+/-5% vs. -50+/-8%; and amlodipine, -32+/-9% vs. -42+/-3%. Response to highest dose of NO donor S-nitroso N-acetyl penicillamine (SNAP) was not significantly different in the two groups (-55+/-5% vs. -52+/-7%). Treatment with Nw-nitro-L-arginine methyl ester, inhibitor of NO synthesis, attenuated the effect of bradykinin, ramipril, and amlodipine on MV(O2) (p < 0.05). In conclusion, short-term administration of simvastatin in rats potentiates the ability of angiotensin-converting enzyme (ACE) inhibitors and amlodipine to cause NO-mediated regulation of MV(O2).

Nitric oxide interacts with oxygen free radicals to evoke the release of adenosine and adenine nucleotides from rat hippocampal slices

The present study examined some possible mechanisms underlying the previously demonstrated release of adenosine by nitric oxide (NO) donors. Perfusion with the NO-donor S-nitroso- N-acetyl penicillamine (SNAP; 300 μM) led to a significant increase in the release of [ 3H]purines from both unstimulated and electrically stimulated hippocampal slices prelabeled with [ 3H]adenine. The NO-donor also evoked the release of endogenous ATP and ADP from unstimulated slices and, when combined with electrical stimulation, the release of ATP, AMP and adenosine. The SNAP-induced [ 3H]purine release was calcium-dependent, but not affected by the glutamate receptor antagonists MK-801 ((+)-5-methyl-10,11-dihydro-5H-dibenzo[a,d]-cyclohepten-5,10-imine;100 nM) and CNQX (6-cyano-7-nitroquinoxaline-2,3-dione; 10 μM). Zaprinast (5 μM), an inhibitor of the cyclic GMP-dependent phosphodiesterase and 8-Br-cyclic GMP (0.01–1 mM) failed to evoke the release of purines, whereas generation of oxygen free radicals by xanthine plus xanthine oxidase did evoke purine release. Coperfusion of SNAP with the free radical scavengers superoxide dismutase (SOD; 60 μg/ml) and catalase (50 μg/ml) reduced or eliminated the ability of the NO-donor to enhance [ 3H]purine release, but the poly (ADP-ribosyl) synthetase (PARS) inhibitor benzamide (500 μM) did not affect it. These data indicate that NO interacts with superoxide, likely forming peroxynitrite, which subsequently acts to release adenosine and adenine nucleotides from hippocampal tissue.

Enhancement of S-Nitrosylation in Glycosylated Hemoglobin

In this study, we report a novel differential nitric oxide interaction with nonglycosylated and glycosylated hemoglobin. After in vitro incubation of hemoglobin with S-nitroso N-acetyl penicillamine (SNAP), S-nitrosoglutathione, or S-nitrosocysteine, S-nitrosylation was significantly higher in human glycosylated hemoglobin purified from diabetic subjects compared to nondiabetic controls. Inversely, spontaneous decomposition was significantly lower for S-nitrosohemoglobin obtained from glycosylated hemoglobin. Bidimensional isoelectric focusing of hemoglobins incubated in vitro with SNAP also revealed a greater interaction of nitric oxide with glycosylated hemoglobin. In addition, a significantly higher level of S-nitrosohemoglobin was found in erythrocyte lysates from streptozotocin-induced diabetic rats compared to control rats. We suggest that highly glycosylated hemoglobin in diabetic subjects may favor S-nitrosylation, which may in turn impair vascular function, and participate in diabetic microangiopathy.

Antiangiogenesis efficacy of nitric oxide donors.

Angiogenesis is a complex process involving endothelial cell migration, proliferation, invasion, and tube formation. Inhibition of these processes might have implications in various angiogenesis-mediated disorders. Because nitric oxide (NO) is known to play a key role in various vascular diseases, the present study was undertaken to determine the role of NO in angiogenesis-mediated processes using the NO donor, S-nitroso N-acetyl penicillamine (SNAP) and S-nitroso N-acetyl glutathione (SNAG). The antiangiogenic efficacy of these NO donors was examined using in vivo and in vitro model systems. The in vitro studies demonstrated the ability of SNAP to inhibit cytokine fibroblast growth factor (FGF2)-stimulated tube formation and serum-induced cell proliferation. The inhibitory effect on cell proliferation by SNAP concentrations above the millimolar range was associated with significant shifts in the concentration of NO metabolites. Furthermore, using the mouse Matrigel implant model and the chick chorioallantoic membrane (CAM) models, SNAP demonstrated maximal inhibitory efficacy (85-95% inhibition) of cytokine (FGF2)-induced neovascularization in both in vivo models. SNAP and SNAG resulted in 85% inhibition of FGF2-induced neovascularization in the mouse Matrigel model when given at 5 mg/kg/day infusion in minipumps during 14 days and 87% inhibition of angiogenesis induced by FGF2 in the CAM when administered a single dose of 50 microg. Thus, NO donors might be a useful tool for the inhibition of angiogenesis associated with human tumor growth, or neovascular, ocular, and inflammatory diseases.

METAL CHELATORS/ANTIOXIDANTS: APPROACHES TO PROTECT ERYTHROCYTIC OXIDATIVE STRESS INJURY DURING PLASMODIUM BERGHEI INFECTION IN MASTOMYS COUCHA

Desferal, N-acetyl penicillamine (metal chelators) and propylgallate, catechin, and reduced glutathione (antioxidants) suppressed the erythrocytic oxidative damage generated during Plasmodium berghei infection in Mastomys coucha. Superoxide anion and lipid peroxide levels were increased and on the contrary, superoxide dismutase activity was noticeably decreased in the infected erythrocytes. Metal chelators/antioxidant treatment to infected animals resulted in restoration of O2−, LPO and SOD to near normal levels. Furthermore, treatment of the above mentioned agents displayed a controlled mortality/survival time and parasitaemia. In conclusion, metal chelators/antioxidants were found to be effective against oxidative stress injury and parasite growth resulting in prolonged survival time of the host during experimental malaria.

Synergy of amlodipine and angiotensin-converting enzyme inhibitors in regulating myocardial oxygen consumption in normal canine and failing human hearts

The production of endogenous nitric oxide, which regulates myocardial oxygen consumption, is decreased in heart failure. As with angiotensin-converting enzyme (ACE) inhibitors, amlodipine, a calcium antagonist, increases kinin-mediated nitric oxide production in coronary microvessels. We investigated the possibility of synergy between ACE inhibitors and amlodipine in regulating myocardial oxygen consumption. Left ventricular myocardium was isolated from 6 healthy dog hearts and 5 human hearts with end-stage heart failure at the time of orthotopic heart transplantation. Myocardial oxygen consumption was measured before and after administration of bradykinin, S-nitroso N-acetyl penicillamine (SNAP, a nitric oxide donor), ramiprilat (an ACE inhibitor), amlodipine, and the combination of a subthreshold dose of ramiprilat (10 −8 mol/L) + amlodipine. These experiments were repeated with l-nitro-arginine methyl ester (L-NAME, an inhibitor of nitric oxide synthesis), dichloroisocoumarin (an inhibitor of kinin synthesis), and HOE 140 (a B 2 kinin–receptor antagonist). Baseline myocardial oxygen consumption in canine hearts was 182 ± 21 nmol/g/min. Bradykinin and SNAP caused dose-dependent reductions in myocardial oxygen consumption (p <0.05). Ramiprilat and amlodipine caused a 10 ± 3.2% and 11 ± 0.8% reduction in myocardial oxygen consumption, respectively, when used alone (p <0.05). In the presence of a subthreshold dose of ramiprilat, amlodipine caused a larger (15 ± 1.7%) reduction in myocardial oxygen consumption compared with either drug used alone (p <0.05). In human hearts, baseline myocardial oxygen consumption was 248 ± 57 nmol/g/min. Amlodipine caused a larger reduction in myocardial oxygen consumption when used with ramiprilat (22 ± 3.2%) as compared with amlodipine alone (15 ± 2.6%). The effect of both drugs was attenuated by L-NAME, dichloroisocoumarin, and HOE 140 (p <0.05). In conclusion, ACE inhibitors and amlodipine act synergistically to regulate myocardial oxygen consumption by modulating kinin-mediated nitric oxide release, and this combination of drugs may be useful in the treatment of heart failure.

Poly(ADP-ribose) synthetase activation mediates increased permeability induced by peroxynitrite in Caco-2BBe cells

Background & Aims: Peroxynitrite induces cytotoxicity by generating DNA single-strand breaks and activating poly(ADP-ribose) synthetase (PARS), a nuclear enzyme that consumes oxidized nicotinamide adenine dinucleotide (NAD +) and depletes cellular adenosine triphosphate (ATP). The aim of this study was to examine this mechanism of injury in an intestinal epithelial cell model after exposure to exogenous peroxynitrite (ONOO −) and nitric oxide (NO). Methods: Caco-2BBe cell monolayers exposed to donors of peroxynitrite (3-morpholino-sydnonimine [SIN-1], 3 mmol/L) or NO ( S-nitroso- N-acetyl penicillamine [SNAP]; 3 mmol/L) were analyzed for DNA strand breaks, [NAD +], [ATP], and transepithelial flux of fluorescein sulfonic acid. Results: SIN-1 but not SNAP induced DNA single-strand breakage. Both SIN-1 and SNAP reduced [ATP], but only SIN-1 reduced [NAD +]. Inhibition of PARS activity by the PARS inhibitors 5-iodo-6-amino 1,2- benzopyrone or 3-aminobenzamide prevented the SIN-1–induced reduction in [NAD +] and [ATP] but had no effect on the SNAP-induced reduction in [ATP]. PARS inhibition reduced SIN-1–but not SNAP-induced hyperpermeability. Conclusions: Peroxynitrite but not NO increases transepithelial permeability by inducing DNA strand breaks that activate the PARS pathway and cause the depletion of intracellular energy stores. Inhibition of PARS activity may represent a novel strategy in ameliorating peroxynitrite-mediated epithelial injury during intestinal inflammation. GASTROENTEROLOGY 1998;114:510-518

Testing of chelating agents and vitamins against lead toxicity using mammalian cell cultures.

Mammalian cell cultures were used to determine the capacity of antidotes to modify (a) lead uptake, (b) lead toxicity and (c) lead release from cells. The following chelating agents were tested: Na, Ca-ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), nitriloacetic acid, ethylene glycol-bis(aminoethyl)tetraacetic acid (EGTA), D,L-mercaptosuccinic acid (MSA), meso-2,3-dimercaptopropanesuccinic acid (MSA), D,L-2,3-dimercaptopropane-1-sulfonic acid (DMPS), penicillamine (PA), N-acetylpenicillamine (NAPA), and diethylcarbodithioate (DDTC). The following vitamins were tested: thiamine (B1), riboflavine (B2), pyridoxine (B6), cobalamin (B12) and ascorbic acid (C). Inhibition of lead uptake was produced by EDTA, EGTA, DMSA, DMPS, MSA, PA, NAPA and vitamins B1, B6 and C, vitamins B2 and B12 being ineffective. The same compounds reduced lead cytotoxicity. Interestingly DDTC and DTPA increased lead uptake, but did not exacerbate lead toxicity. Significant release of lead from preloaded cells was caused by DTPA, NAPA, DMPS and PA, while the other chelators were ineffective.

N-ACETYL PENICILLAMINE A PROTECTOR OFPLASMODIUM BERGHEIINDUCED STRESS ORGAN INJURY IN MICE

N-acetyl penicillamine (NAP), a derivative of penicillamine and copper chelator has been employed as a potential protector of host stress organ injury duringPlasmodium bergheiinfection in mice. Intramuscular injection of NAP (60 mg kg−1body wt for 10 days) toP. bergheimice was able to restrict the hepato- and splenomegaly. The mortality rate of infected mice was decreased by 50% by NAP. The decreased protein and lipid peroxidation and increased copper contents duringP. berghewere almost normalized after NAP treatment. The increased levels of erythrocytic superoxide anion and lipid peroxides due to infection were almost normalized after NAP treatment.

Release of adenosine from rat hippocampal slices by nitric oxide donors.

In the present study we have used perfused hippocampal slices to examine the hypothesis that nitric oxide (NO) can evoke the release of adenosine from nervous tissue. ATP stores were labeled by incubation with [3H]adenine. Electrical field stimulation at 5 Hz for 5 min evoked the release of 3H-purines, and this was enhanced by the NO donor S-nitroso-N-acetylpenicillamine (SNAP). Stimulation at 10 Hz for 15 min evoked a larger release of 3H-purines, which was enhanced in a concentration-dependent manner by both SNAP and sodium nitroprusside (SNP), with SNP being 100-fold less potent than SNAP. N-Acetylpenicillamine (N-AP) was without effect. SNAP had a markedly reduced, although significant, effect when given in the absence of field stimulation. Using HPLC it was found that SNAP enhanced the release of both endogenous and labeled adenosine in a concentration-dependent manner. At the highest concentration used (1 mM), SNAP increased electrically evoked release of endogenous adenosine 100-fold and unstimulated adenosine release eightfold. The ability of SNAP to enhance adenosine release was eliminated in the added presence of hemoglobin (10 microM), further supporting the proposal that the effects of SNAP were due to the liberation of NO. These data provide direct evidence that NO evokes a concentration-dependent release of adenosine from both stimulated and unstimulated nerves of the hippocampus. It is suggested that such NO-stimulated adenosine release may contribute to some of the reported effects of NO donors in the nervous system.

Inhibition of vesicular stomatitis virus infection by nitric oxide

Inhibitory effects of nitric oxide (NO) on vesicular stomatitis virus (VSV) infection were investigated by using a VSV-susceptible mouse neuroblastoma cell line, NB41A3. Productive VSV infection of NB41A3 cells was significantly inhibited by an organic NO donor, S-nitro-N-acetylpenicillamine (SNAP), while the control compound N-acetylpenicillamine (NAP) had no effect. Survival rate of VSV-infected cells was greatly increased by the treatment with SNAP, while the NAP treatment did not have any effect. Adding SNAP 30 min prior to infection resulted in complete inhibition of viral production when a low multiplicity of infection (MOI) was used. Substantial inhibition of viral production was also obtained with treating cells 6 h earlier before infection with a higher MOI. Activating the neuronal NO synthase by treating cells with N-methyl-D-aspartate (NMDA) led to significant inhibition of viral production by cells infected at the three doses of virus tested (MOIs of 0.1, 1, and 5). The inhibitory effect of NMDA on viral infection was totally blocked by the NO synthase inhibitor N-methyl-L-arginine. However, adding hemoglobin, a strong NO-binding protein and thus an inactivator of NO activity, did not reverse the NMDA-induced inhibition of viral production, suggesting that NO might exert its antiviral effects inside the NO-producing cells. Collectively, these data support the anti-VSV effects of NO, which might be one of the important factors of natural immunity in controlling the initial stages of VSV infection in the central nervous system.

Chemical stabilization of a vasoactive S-nitrosothiol with cyclodextrins without loss of pharmacologic activity.

S-Nitrosothiols have been proposed as the endogenous chemical representing the vasoactive endothelium-derived relaxing factor, as well as the active cellular intermediates responsible for the therapeutic action of organic nitrates. The relatively stable analogue S-nitroso N-acetyl penicillamine (SNAP) is a potent vasodilator producing less pharmacologic tolerance than nitroglycerin upon prolonged administration. The therapeutic potential of this new class of vasodilators, however, may be limited by their chemical instability in solution (t1/2 of SNAP is 26 hr in 5% dextrose). We examined the usefulness of several cyclodextrins (CD) to stabilize this polar compound in solution. At cyclodextrin concentrations of 12 mM, hydroxypropyl-beta CD was most effective at stabilizing SNAP (t1/2 = 77 hr) when compared to alpha CD (41 hr), beta CD (69 hr), gamma CD (36 hr), and beta CD-tetradecasulfate (38 hr). Stability constants for the complexation of SNAP with the various cyclodextrins were determined by the classical solubility technique and were found to range from 26 to 435 M-1. Increased complexation brought about better SNAP stability. Complexation of SNAP with cyclodextrins, however, did not decrease the relaxation potency of SNAP as determined in an in vitro blood vessel preparation. Cyclodextrin complexation may be a useful approach to stabilize labile and polar compounds, such as S-nitrosothiols, without loss of pharmacologic activity.

The metabolism and disposition of D-penicillamine in the DA-strain rat.

Radiolabelled [35S]-D-penicillamine was administered orally to DA-strain rats. After 72 hours approximately 65% of the dose was excreted with no significant differences between male and female animals. The major urinary product was inorganic sulphate with small amounts of D-penicillamine. Penicillamine disulphide, penicillamine-cysteine, S-methyl penicillamine and N-acetyl penicillamine were also found as metabolites. The female rat excreted significantly less sulphate (P less than 0.1) and more penicillamine disulphide (P less than 0.01) than the male. The residual radioactivity was found in the carcass, with slight concentration in the gut, skin, kidney, bladder and liver.

N-acetylpenicillamine potentiation of biliary excretion of methyl mercury: influence of glutathione depletors.

The effect of 1-chloro-2,4-dinitrobenzene (DNB), sulfobromophtalein (BSP) and cyclohexene oxide (cho) on N-acetylpenicillamine (NAPA) potentiated biliary excretion of methyl mercury in rats pretreated with cho for liver glutathione (GSH) depletion, has been tested. DNB, BSP and cho depressed NAPA potentiation of methyl mercury excretion in bile, while simultaneously biliary sulfhydryl concentration increased, due mainly to a relatively large proportion of unchanged NAPA, being excreted in bile. The fact that relatively large amounts of unchanged NAPA are excreted in bile, without affecting mercury excretion, indicates that NAPA per se cannot carry methyl mercury from liver to bile. In addition to unchanged NAPA, bile collected after administration of NAPA and DNB or BSP contained relatively large amounts of GSH conjugates of DNB or BSP, respectively, together with smaller amounts of GSH and another methyl mercury carrying component. The data are interpreted as suggesting that NAPA potentiation of methyl mercury excretion in bile can be due to an increased availability of GSH. However, it cannot be excluded that methyl mercury carrying components other than GSH and NAPA appearing in bile upon NAPA administration could play a role in NAPA potentiation of methyl mercury excretion in bile.

Influence of several chelating agents on the excretion and organ concentration of copper in the rat

The copper-mobilizing effect of 16 substances has been studied in rats. Among these, sodium 2,3-dimercaptopropane-1-sulfonate (DMPS), d-penicillamine (PA), N-acetylpenicillamine (NAPA), and triethylenetetramine (TRIEN) showed the best efficacy. Combined treatment with DMPS PA , DMPS TRIEN , or TRIEN PA was not superior to any one of the compounds in a corresponding dosage.