Neopterin as a marker of response to antiviral therapy in hepatitis C virus patients.

Predicting the efficacy of antiviral treatment of hepatitis C virus (HCV) is of importance for both patient well-being and health care expense. The expression of interferon-stimulated genes (IFN-SGs) in the liver was suggested as a marker of response to anti-viral therapy. IFN-SGs encode the guanosine triphosphate cyclohydrolase 1 (GTPCH), a rate-limiting enzyme of pteridines biosynthesis. Neopterin, a stable byproduct of GTPCH-catalyzed reaction, is used as a marker of interferon-induced GTPCH activation. We hypothesized that assessment of neopterin concentrations might predict the response to antiviral therapy. Neopterin concentrations were evaluated in 260 HCV patients treated by pegylated interferon combined with ribavirin. Mean and median pretreatment neopterin concentrations were lower in patients with sustained virological response than in nonresponders. The rate of response was twofold higher among patients with pretreatment neopterin levels <16 nmol/L than in patients with neopterin levels ≥16 nmol/L, even after controlling for HCV genotype status. Our study suggests that the pretreatment level of neopterin might be used in routine clinical practice as rapid and cost-effective marker to predict the response to antiviral therapy in HCV patients.

Effect of methyl derivatives of dopamine on tumor necrosis factor alpha and lipid peroxidation.

We recently demonstrated that melatonin, N-acetylserotonin (NAS), and N-acetyldopamine (NAD) attenuate the synthesis of lipopolysaccharide (LPS)-stimulated tumor necrosis factor-alpha (TNF-alpha) and the generation of oxidant radicals. In this study, we examined whether acetyl and methyl derivatives of dopamine modulate LPS-stimulated TNF-alpha synthesis and LPS- and iron-induced lipid peroxidation. Differentiated THP-1-derived human monocytes were coincubated with Escherichia coli and rising concentrations of NAS, NAD, N-methyldopamine (NMD), or 4-O-methyldopamine (4-O-MD). After 24 h, TNF-alpha was measured in cell supernatants. In addition, lipid peroxidation was induced by adding FeCl(2) solution to mouse brain tissue homogenates in the presence of rising concentrations of NAS, NAD, NMD, or 4-O-MD. Incubating THP-1-derived monocytes with rising concentrations of NAS, NAD, NMD, or 4-O-MD markedly decreased LPS-stimulated TNF-alpha production, which was dose dependent and on the order of 96%-98%. Rising concentrations of NMD markedly inhibited lipid peroxidation by 59%-98%. Our results indicated that the inhibitory effect of NAS, NAD, NMD, or 4-O-MD on LPS-induced TNF-alpha production and FeCl(2)-stimulated lipid peroxidation is robust and dose dependent.

Effect of luzindole and other melatonin receptor antagonists on iron- and lipopolysaccharide-induced lipid peroxidation in vitro.

Melatonin and its precursor, N-acetylserotonin (NAS), have been shown in in vivo and in vitro studies to inhibit iron- and lipopolysaccharide (LPS)-induced lipid peroxidation in rats and mice. Using in vitro studies, we examined whether these effects will be affected by the melatonin receptor antagonists luzindole (a competitive MT(1)/MT(2) antagonist), DH 97 (MT(2)), prazosin (MT(3)), and 4-P-PDOT (MT(2)). Lipid peroxidation in the form of malondialdehyde (MDA) was assayed by measuring thiobarbituric acid-reactive substances. The antagonists did not affect the melatonin and NAS effect on iron- and LPS-induced peroxidation. However, luzindole alone, but not the other antagonists, inhibited the iron- and LPS-induced peroxidation in the rat brain and kidney homogenates. At a dose of 50 microM, luzindole reduced iron-induced MDA levels by 80% in the brain and 84% in the kidney, whereas LPS-induced MDA levels were reduced by 85% in both brain and kidney. A dose of 800 microM prevented lipid peroxidation, bringing the MDA levels to values of samples untreated by iron or LPS.

The in vitro effect of estradiol and testosterone on iron-induced lipid peroxidation in rat brain and kidney tissues.

The effects of estradiol and testosterone on iron-induced lipid peroxidation were compared in rat brain and kidney homogenates in vitro. Lipid peroxidation in the form of malondialdehyde (MDA) was evaluated by the measurement of thiobarbituric acid (TBA) reactive substances. Estradiol inhibited lipid peroxidation in both tissues studied in a dose-dependent manner. The effect was five times stronger in brain than in kidney. Testosterone did not affect lipid peroxidation in either tissue. Estradiol-induced inhibition of brain lipid peroxidation might contribute to the neuroprotective effect of estrogens.

N-acetyldopamine inhibits rat brain lipid peroxidation induced by lipopolysaccharide.

The effects of N-acetyldopamine, a sepiapterin reductase inhibitor, on lipopolysaccharide-induced lipid peroxidation were examined in rat brain homogenates in vitro. Lipid peroxidation in the form of malondialdehyde (MDA) was evaluated by the measurement of thiobarbituric acid (TBA) reactive substances. N-Acetyldopamine inhibited the formation of MDA in a concentration-dependent manner. The effect was similar to that of N-acetylserotonin, but stronger than that of the endogenous antioxidant agent, melatonin. Possible clinical applications of N-acetyldopamine and its derivatives are discussed.

Mating attenuates aging-associated increase of lipid peroxidation activity in C57BL/6J mice.

In the frame of the free-radical hypothesis of aging and literature data on increased life span of mated animals, we evaluated brain, kidney, and liver lipid peroxidation in C57Bl/6J mice of various ages and compared lipid peroxidation activity in mated and non-mated mice of both genders. An aging-associated increase (from 3 to 12 months of age) of lipid peroxidation, as measured by malonaldehyde and 4-hydroxyalkenals (MDA + HAE) levels, was observed in the liver and kidney, but not in the brain. Tissue MDA + HAE levels were lower in 12-month old mated mice (housed with animals of opposite gender from three to five months of age) than in 12-month old non-mated animals. There were no gender differences in the observed effect. It is suggested that mating might attenuate the increase of lipid peroxidation associated with aging.

Differential effects of lipopolysaccharide on lipid peroxidation in F344N, SHR rats and BALB/c mice, and protection of melatonin and NAS against its toxicity.

The effect of bacterial lipopolysaccharide (LPS) injection on the lipid peroxidation process in Fischer (F344N) rats, spontaneously hypertensive (SHR) rats, and BALB/c mice was studied. Lipid peroxidation, as measured by malondialdehyde + 4-hydroxyalkenals (MDA + HAE) levels, was decreased in brain, kidney, and liver homogenates of F344N rats injected with lower LPS doses of 0.5, 1.0, and 2.0 mg/kg, but was increased with the highest dose of 10 mg/kg body weight. The dose of 10 mg/kg LPS decreased the MDA + HAE levels in SHR brain homogenates and increased levels in the liver homogenates. MDA + HAE levels in the brain and liver but not kidney homogenates in BALB/c mice also increased after administration of LPS at the highest dose (10 mg/kg body weight). The effect of melatonin, N-acetylserotonin (NAS), and GR-135,531 (a melatonin ligand with high affinity for MT3 receptor) on the survival of BALB/c mice injected with lethal dose of LPS was also tested. A single dose of 5 mg/kg of melatonin or NAS simultaneously injected with LPS (25 mg/kg body weight) markedly protected mice from the lethal effect of LPS with survival rates of 90% and 95% for melatonin and NAS, respectively, and 59% for mice injected with just LPS after 24 hours; a survival rate of 50% for both melatonin and NAS, and 32% was obtained for mice injected with just LPS after five days. GR-135,531 did not show protection against a lethal dose of LPS. Our results indicated that the effect of LPS on lipid peroxidation is dose-, time-, and species-dependent, and that melatonin and NAS are equally effective in protecting mice from lethality caused by LPS.

Melatonin and jet lag syndrome: experimental model and clinical implications.

What is the effect of melatonin on jet lag syndrome? Jet lag desynchronizes the internal sleep-wakefulness cycle with the environmental light/dark cycle. Advance (but not delay) of light onset is known to abolish pineal N-acetyltransferase activity and urine excretion of 6-sulphatoxymelatonin. Measurements of pineal serotonin, the substrate of melatonin biosynthesis; N-acetylserotonin (NAS), the immediate melatonin precursor; and melatonin (high-performance liquid chromatography-fluorimetric method) in the animal (rat) model of jet lag revealed that prolonged delay of dark-phase onset disrupted the rhytms in comparable ways as the advance of light-phase onset. Advance of dark phase onset resulted in less severe disturbances of rhythms as compared with the advance of light phase onset. Melatonin, but not NAS, injections at the beginning of a new dark period accelerated recovery of NAS and melatonin, but not serotonin, rhythms. Spontaneously hypertensive rats were more sensitive to advance of light onset and less responsive to melatonin injections than normotensive rats. NAS and methylene blue, an inhibitor of monoamine oxidase A, attenuated light-induced disruption of NAS but not melatonin rhythms. We draw the following conclusions from our data: the beginning of the dark period may be preferable to the beginning of light period as the arrival time on eastward flights; the efficacy of melatonin in alleviating jet lag may be enhanced by administering it before, during and after rapid transition through time zones; and hypertension may exaggerate jet lag syndrome.

Ontogenetic effects of MAO-A inhibition on rat pineal n-acetylserotonin and melatonin during the first month of neonatal life.

Inhibitors of monoamine oxidase A (MAO-A) but not MAO-B stimulate the activity of pineal serotonin N-acetyltransferase (AANAT) in the adult rat pineal leading to increased formation of N-acetyl serotonin (NAS) and melatonin (MEL). The pineal gland of the neonatal rat has AANAT activity, but the second enzyme in melatonin biosynthesis, HIOMT (hydroxyindole-O-methyltransferase) converting NAS to MEL, is absent during the first week of neonatal life. In this study we examined the effects of acute clorgyline treatment in vitro and in vivo, on pineal indoles over the first month of neonatal life. The results show that clorgyline stimulates NAS production by pineal both in vitro and in vivo from day five on with a marked increase between day 14 and day 21. In contrast, MEL is not increased until day 21, with a sharp rise thereafter. Copyright 2000 John Wiley & Sons, Ltd.