Ghost protein damage by peroxynitrite and its protection by melatonin.

We have studied the effect of peroxynitrite (ONOO-) on the membrane cytoskeleton of red blood cells and its protection by melatonin. Analysis of the protein fraction of the preparation by SDS-PAGE revealed a dose-dependent (0-600 microM ONOO-) disappearance at pH 7. 4 of the main proteins: spectrin, band 3, and actin, with the concomitant formation of high-molecular weight aggregates resistant to reduction by ss-mercaptoethanol (2%) at room temperature for 20 min. These aggregates were not solubilized by 8 M urea. Incubation of the membrane cytoskeleton with ONOO- was characterized by a marked depletion of free sulfhydryl groups (50% at 250 microM ONOO-). However, a lack of effect of ss-mercaptoethanol suggests that, under our conditions, aggregate formation is not mediated only by sulfhydryl oxidation. The lack of a protective effect of the metal chelator diethylenetriaminepentaacetic acid confirmed that (ONOO-)-induced oxidative damage does not occur only by a transition metal-dependent mechanism. However, we demonstrated a strong protection against cytoskeletal alterations by desferrioxamine, which has been described as a direct scavenger of the protonated form of peroxynitrite. Desferrioxamine (0.5 mM) also inhibited the loss of tryptophan fluorescence observed when the ghosts were treated with ONOO-. Glutathione, cysteine, and Trolox (1 mM), but not mannitol (100 mM), were able to protect the proteins against the effect of ONOO- in a dose-dependent manner. Melatonin (0-1 mM) was especially efficient in reducing the loss of spectrin proteins when treated with ONOO- (90% at 500 microM melatonin). Our findings show that the cytoskeleton, and in particular spectrin, is a sensitive target for ONOO-. Specific antioxidants can protect against such alterations, which could seriously impair cell dynamics and generate morphological changes.

Ghost protein damage by peroxynitrite and its protection by melatonin

We have studied the effect of peroxynitrite (ONOO-) on the membrane cytoskeleton of red blood cells and its protection by melatonin. Analysis of the protein fraction of the preparation by SDS-PAGE revealed a dose-dependent (0-600 µM ONOO-) disappearance at pH 7.4 of the main proteins: spectrin, band 3, and actin, with the concomitant formation of high-molecular weight aggregates resistant to reduction by ß-mercaptoethanol (2 percent) at room temperature for 20 min. These aggregates were not solubilized by 8 M urea. Incubation of the membrane cytoskeleton with ONOO- was characterized by a marked depletion of free sulfhydryl groups (50 percent at 250 µM ONOO-). However, a lack of effect of ß-mercaptoethanol suggests that, under our conditions, aggregate formation is not mediated only by sulfhydryl oxidation. The lack of a protective effect of the metal chelator diethylenetriaminepentaacetic acid confirmed that ONOO--induced oxidative damage does not occur only by a transition metal-dependent mechanism. However, we demonstrated a strong protection against cytoskeletal alterations by desferrioxamine, which has been described as a direct scavenger of the protonated form of peroxynitrite. Desferrioxamine (0.5 mM) also inhibited the loss of tryptophan fluorescence observed when the ghosts were treated with ONOO-. Glutathione, cysteine, and Trolox® (1 mM), but not mannitol (100 mM), were able to protect the proteins against the effect of ONOO- in a dose-dependent manner. Melatonin (0-1 mM) was especially efficient in reducing the loss of spectrin proteins when treated with ONOO- (90 percent) at 500 µM melatonin). Our findings show that the cytoskeleton, and in particular spectrin, is a sensitive target for ONOO-. Specific antioxidants can protect against such alterations, which could seriously impair cell dynamics and generate morphological changes

Nitric oxide is released in regenerating liver after partial hepatectomy.

The induction of hepatic nitric oxide synthase (NOS) and the biosynthesis of nitric oxide (NO) were studied in liver after partial hepatectomy (PH). NOS activity in the liver remnant was observed 4 to 6 hours after PH, and no differences were evidenced between the proximal and distal surgical areas. The form of NOS expressed in liver was independent of calcium and calmodulin, and the messenger RNA levels were first detected 2 hours after hepatectomy using a probe corresponding to the cytokine-induced macrophage NOS. The seric concentration of nitrites remained unchanged after hepatectomy, whereas the content in nitrates and in S-nitrosylated proteins progressively increased in parallel with the NOS activity. The spectra of hemoglobin in the 400-to 460-nm region failed to exhibit the characteristic shift caused by the formation of the nitrosyl-hemoglobin complex, suggesting that NO was rapidly metabolized in liver. Treatment of the animals with substrate analogue NOS inhibitors blocked the pattern of DNA ploidy elicited after hepatectomy, suggesting a role for NO in the regenerative process. Peritoneal resident macrophages were used as an alternative reporter cell system for the assessment of NOS expression. Incubation ex vivo of peritoneal macrophages from animals that underwent hepatectomy induced the expression of NOS in a cytokine-modulated fashion, suggesting that macrophages were primed as a result of the hepatectomy. When peritoneal macrophages from control rats were incubated with the sera of animals that underwent hepatectomy, a time-dependent induction of NOS was observed, with a maximal induction corresponding to sera collected 2 hours after PH. These results indicate that NO might be involved in the control of early responses after PH.

Serum alkaline deoxyribonuclease activity, a sensitive marker for the therapeutic monitoring of cancer patients: methodological aspects.

Alkaline deoxyribonuclease (DNase) is present in human circulating serum but its physiological role and signification of its variations are still largely unknown. The present report demonstrates that between 37 degrees C and 50 degrees C, as measured in the presence of 0.25 mmol/l Ca2+ and 5 mmol/l Mg2+, serum alkaline DNase activity increases, in most sera, reaching a level far higher than expected from thermal activation. This observation is thought to be due to the thermal inactivation of a serum inhibitor of the enzyme, which limits its usefulness as a therapeutic marker. By measuring serum alkaline DNase activity at 50 degrees C, the authors have developed a clinical test which has been successfully applied to the therapeutic monitoring of patients with various types of cancers.

[Possible value of variations in the serum alkaline DNAse activity in the prognosis of cancers of the upper respiratory-digestive tract treated by chemotherapy]. / Valeur prédictive des variations de l'activité sérique de la DNAse alcaline dans le pronostic des cancers des voies aérodigestives supérieures traités par chimiothérapie.

Variations in serum alkaline DNase activity before and repeatedly after standardized chemotherapy were examined in patients with head and neck carcinomas. The enzyme activity was measured by way of a modified spectrophotometric method. No variations of such activity observed in patients without therapeutic response or with minor response could be considered as a marker of primary or acquired resistance to chemotherapy. Distinct variations in serum alkaline DNase activity (a steep decrease after therapy followed a few weeks later by a regain of values higher than the initial value) correspond to complete or partial positive responses. Such observations of the variations in enzyme activity in relation to individual initial values measured before therapy could be considered as a reliable prognostic test for the therapy of many head and neck carcinomas.