[Pharmacology, an innovative factor in therapeutic research]. / La pharmacologie, facteur d'innovation en recherche thérapeutique.

As members of the pharmacology training group set up by the committee of pharmacological science of the French Academy of Pharmacy, we examine the situation of pharmacology in drug discovery. Today, it is obvious that by integrating genome sequencing, cellular and molecular biology, and bioinformatics, pharmacology has become a cross-disciplinary science. Pharmacologists must become knowledgeable in a wide range of domains, using the major points in each to direct them towards the discovery and development of new therapeutic agents. It is also clear that pharmacology remains a major factor in the different steps of drug discovery, from the molecular and cellular stages, to clinical and pharmaceutical developments.

[Report of the "Health and Environment" commission of the National Academy of pharmacy. Carbon monoxide and environmental health: are carbon monoxide levels in urban areas a health hazard?]. / Le monoxyde de carbone CO et la santé environnementale: CO est-il nocif aux concentrations urbaines actuelles?

In an urban environment, carbon monoxide is produced by incomplete combustion, particularly in motor vehicles. Air pollution caused by CO produced by motor vehicles is controlled by legislation. Legal regulations have considerably lowered emission levels authorized for new vehicles and total CO emission levels. CO levels in the environment (urban environment in general and zones close to motorways) have thus declined. CO remains a public health concern both as a pollutant and as an indicator of air quality. We recall here the more recent approaches used to assess CO-related hazards developed by the Environmental Protection Agency in the United States and pertinent conclusions backing up previously defined reference levels. We then report recent French data concerning CO emission, environmental levels and evaluation procedures for different situations of human exposure: geographical situations, mode of transportation, police force, air sentinels. The third part of this article is devoted to biological data (interaction between CO and hemo-proteins, CO neurotransmitter?) and epidemiological data (serial surveys). The discussion centers on the limitations of epidemiological data and on the difficulty in evaluating hazards solely on the basis of a carboxyhemoglobin threshold. This latter point is particularly important because carboxyhemoglobin is only one of many indicators of air quality. Finally recommendations are proposed concerning weather-related aspects, evaluation of human exposure, and ways of improving biological and epidemiological data.

[New provisions for prevention and fight against doping]. / Nouvelles dispositions dans la prévention et la lutte contre le dopage.

Doping which is largely a sport-related phenomenon, led the French government of enact a series of laws in 1965, 1984, and 1989. Due to the apparent extension of doping, a new law was enacted on March 23, 1999. This law concerns medical surveillance of athletes and prevention and fight against doping. A council for the prevention and fight against doping was created. This nine-member council includes a representative of the French International Academy of Pharmacy and its president is a state counsellor. The council has three main areas of activity: disciplinary judgements concerning doped athletes, establishment of prevention policies, coordination of scientific research in the field of sport medicine and doping. The law also provides for penal sanctions for resellers. Antidoping activities are also managed on an international level. Contributors include the Council of Europe, the European Community, the International Olympic Committee, and the recently created (1999) World Antidoping Agency.

[Neuronal death: potential role of the nuclear enzyme, poly (ADP-ribose) polymerase]. / Mort neuronale: rôle potentiel d'une enzyme nucléaire, la poly(ADP-ribose) polymérase.

Poly(ADP-ribose) polymerase (PARP, EC 2.4.2.30) is known as a nuclear enzyme that is activated by DNA strand breaks to participate in DNA repair. It is also called poly(ADP-ribose) synthase (PARS) or poly(ADP-ribose) transferase (PADRT). In physiological conditions, PARP plays an important role in maintaining genomic stability. However, for several pathological situations, which include massive DNA injury (brain ischemia for example), excessive activation of PARP can deplete stores of nicotinamide adenine dinucleotide (NAD+), the PARP substrate, which, with the subsequent ATP depletion, leads to cell death. PARP activation appears to play a major role in neuronal death induced by cerebral ischemia, traumatic brain injury, Parkinson disease and other pathologies. PARP inhibitors (3-aminobenzamide and other compounds) and PARP gene deletion induced dramatic neuroprotection in experimental animals (rats, mice). Accordingly, these data suggest that PARP inhibitors could provide a novel therapeutic approach in a wide range of neurodegenerative disorders including cerebral ischemia and traumatic brain injury.

[Inefficacy of N-methyl-D-aspartate receptor complex antagonists on behavioral and histologic consequences of global cerebral ischemia in rats]. / Inefficacité des antagonistes du complexe réceptorial N-méthyl-D-aspartate à l'égard des conséquences comportementales et histologiques d'une ischémie cérébrale globale chez le rat.

Glutamic acid, an excitatory amino acid, has been proposed to play a major deleterious influence in cerebral ischemia. However, the neuroprotective activity of various glutamate receptor antagonists is often low or absent, according to the animal model used. In the present study, we examined the effect of several antagonists acting on glutamate receptors of the N-methyl-D-aspartate (NMDA) type in rats submitted to a brief (5 minutes) global cerebral ischemia. The different compounds used were poorly active or inactive on behavioural and histologic alterations induced by ischemia. Our results suggest that, in this model, overactivation of NMDA receptor complex does not play a predominant role in the pathogenesis of ischemic brain damage.

A microdialysis study investigating the mechanisms of hydroxyl radical formation in rat striatum exposed to glutamate.

Considerable evidence has linked hydroxyl radicals (.OH) to excitotoxicity. Glutamate infused through a microdialysis probe into rat striatum induced a massive .OH production, which was completely blocked by PBN and attenuated by dizocilpine, 2-amino-5-phosphonopentanoic acid (AP-5), NG-nitro-L-arginine methyl ester (L-NAME) and mepacrine. Thus, we suggest that the neurotoxic effects of glutamate in vivo may derive from an increased formation of .OH resulting from excessive activation of NMDA receptors and downstream enzymes such as NOS and PLA2.

iNOS contribution to the NMDA-induced excitotoxic lesion in the rat striatum.

1. The aim of this study was to assess whether an excitotoxic insult induced by NMDA may induce an iNOS activity which contributes to the lesion in the rat striatum. 2. For this purpose, rats were perfused with 10 mM NMDA through a microdialysis probe implanted in the left striatum. Microdialysate nitrite content, striatal Ca-independent nitric oxide synthase activity and lesion volume were measured 48 h after NMDA exposure in rats treated with dexamethasone (DXM) (3 mg kg(-1) x 4) or aminoguanidine (AG) (100 mg kg(-1) x 4). 3. A significant increase in microdialysate nitrite content and in the Ca-independent NOS activity was observed 48 h after NMDA infusion. Both these increases were reduced by DXM and AG. The NMDA-induced striatal lesion was also reduced by both treatments. 4. Our results demonstrate that NMDA excitotoxic injury induces a delayed, sustained activation of a Ca-independent NOS activity. This activity is blocked by DXM and AG, strongly suggesting the involvement of iNOS. The fact that AG and DXM reduce the NMDA-elicited lesion suggests that iNOS contributes to the brain damage induced by excitotoxic insult.

Protective effect of melatonin in a model of traumatic brain injury in mice.

The pineal hormone melatonin has recently been shown to exert neuroprotective activity in a variety of experimental neuropathologies in which free radicals are involved. This neuroprotective effect has been attributed to the antioxidant properties of melatonin. Considering that free radicals also play a deleterious role in traumatic brain injury (TBI), the purpose of the present study was to determine whether melatonin would have a beneficial effect in this pathology. Head injury was induced in mice and the neurological deficit was evaluated at 24 hr by a grip test. In this model, the free radical scavenger, alpha-phenyl-tert-butyl-nitrone (2 x 100 mg/kg, i.p.) given 5 min and repeated at 4 hr after TBI was neuroprotective. Melatonin (1.25 mg/kg, i.p.) given 5 min and repeated at 1, 2, and 3 hr after head trauma also significantly reduced the neurological deficit. This beneficial effect was not due to melatonin-induced hypothermia since repeated treatment with melatonin did not modify the colonic temperature of mice. This study shows that melatonin exerts a beneficial effect on the neurological deficit induced by traumatic brain injury in mice. The mechanisms of this neuroprotection remains to be established, and more particularly, the contribution of the antioxidant activity of melatonin.

Glutamate induces hydroxyl radical formation in vivo via activation of nitric oxide synthase in Sprague-Dawley rats.

It was recently reported that neuronal nitric oxide synthase (NOS) generates oxygen-derived free radicals in vitro at low concentrations of L-arginine. Using the microdialysis technique, we monitored both hydroxyl radical (.OH) and nitric oxide (.NO) formation in rat striatum perfused with glutamate (500 mM). .OH and .NO were quantitated in microdialysates by measuring the amounts of the non-enzymatic hydroxylation product of salicylate (2,3-dihydroxybenzoic acid) and the metabolites of .NO (nitrite + nitrate), respectively. .OH levels were dramatically increased during glutamate perfusion, while .NO generation was virtually abolished. .OH production was inhibited by the specific NOS blocker, NG-nitro-L-arginine methyl ester. This effect was not reversed but potentiated by L-arginine. Thus, it is likely that NOS generates oxygen-derived free radicals instead of .NO in brain subjected to highly excitotoxic conditions.

Deleterious Ca-independent NOS activity after oxidative stress in rat striatum.

The aim of this study was to assess whether oxidative stress induces deleterious NOS activity in the central nervous system (CNS). For this purpose, the mitochondrial toxin malonate, which promotes free radical production, was infused into the left striatum of rats. Forty-eight hours after injection, an increase in Ca-independent NOS activity was observed in the injected striatum. This increase was blocked by alpha-phenyl-tert-butyl-nitrone, a free radical scavenger, and by aminoguanidine, an inhibitor of NOS 2. Both these drugs reduced the malonate-induced striatal necrotic volume. These results suggest that in the CNS oxidative stress can induce a Ca-independent NOS, probably of type 2, which contributes to the lesion.

alpha-Phenyl-N-tert-butylnitrone attenuates excitotoxicity in rat striatum by preventing hydroxyl radical accumulation.

Various in vitro experiments have indicated that oxygen-derived free radicals may contribute to excitotoxic neuronal death. In the present study we induced excitotoxicity in rat striatum by perfusing glutamate at a high concentration through a microdialysis probe. We observed an increased formation of hydroxyl radicals (.OH) during the perfusion of the excitotoxin and an extensive striatal lesion 24 h after the insult. The spin trap, alpha-phenyl-N-tert-butylnitrone (PBN), attenuated both hydroxyl radical levels and the volume of the lesion. This result suggests that the neuroprotection may be due to a free radical scavenging mechanism. It also implies that PBN may be used in pathological situations involving excitotoxicity such as stroke, brain trauma, and chronic neurologic diseases.

Dose- and time-dependence of L-NAME neuroprotection in transient focal cerebral ischaemia in rats.

1. In this study the effect of the dose and administration time of NG-nitro-L-arginine methyl ester (L-NAME), an NO-synthase inhibitor, in a model of transient focal cerebral ischaemia in rats was investigated. 2. Two injections of L-NAME were given, of 1, 3 and 10 mg kg-1, 5 min and 3 h after the onset of ischaemia. None of the doses gave any striatal neuroprotection, but 1 and 3 mg kg-1 L-NAME reduced the infarcted volume in the cortex (by 26%, P < 0.01 for 1 mg kg-1 and 21%, P < 0.05 for 3 mg kg-1), whereas 10 mg kg-1 had no neuroprotective effect. 3. Single injections of L-NAME 1 mg kg-1, given 5 min or 3 h after ischaemia onset, had similar neutoprotective effects on the cortical infarction as did the repeated injections. 4. L-NAME 1 mg kg-1 given 3, 6 or 9 h after ischaemia induction reduced the cortical infarct volume by 19% (P < 0.01) when given 3 h after ischaemia, by 21% (P < 0.01) when given at 6 h, and by 16% (P < 0.05) when given at 9 h, but had no neuroprotective activity when given 12 h after ischaemia. 5. Thus a low dose of L-NAME is neuroprotective in a model of transient focal ischaemia, with a wide therapeutic window, much larger than that found or MK-801.

Calcium-independent NO-synthase activity and nitrites/nitrates production in transient focal cerebral ischaemia in mice.

1. The temporal changes in constitutive NO-synthase (cNOS) and in calcium-independent NO-synthase activities were studied in mice subjected to 2 h of transient focal cerebral ischaemia. The changes in brain nitrites/nitrates (NOx) content were also studied. 2. NOS activities were measured by the conversion of L-[14C]-arginine to L-[14C]-citrulline. Brain NOx contents were investigated by the Griess colourimetric method. 3. cNOS activity in the infarcted cortical area was significantly reduced after 6 h of reperfusion and this activity remained attenuated for up to 10 days after ischaemia. A calcium-independent NOS activity began to increase 48 h after reperfusion, reached a maximum at 7 days and returned to baseline at 10 days. 4. There was a significant increase of brain NOx content beginning after 3 days of reperfusion. This increase was maximal at 7 days and returned to baseline at 10 days. 5. Thus, ischaemia followed by recirculation leads to a rapid, prolonged drop in cNOS activity in the infarcted cortex. There is also a substantial appearance of calcium-independent NOS activity in the later phase of transient ischaemia, leading to an important increase of NOx production.

Short therapeutic window for MK-801 in transient focal cerebral ischemia in normotensive rats.

The present study investigates the role of N-methyl-D-aspartate (NMDA) receptors in a model of transient focal cerebral ischemia in normotensive rats. The left middle cerebral artery and both common carotid arteries were occluded for 60 min. Preliminary studies indicated that this gave reproducible infarctions of the cortex and striatum. These infarctions were the result of severe ischemia followed by complete reperfusion after clamp removal, as showed by striatal tissue Po2 monitoring. Microdialysis indicated that glutamate concentration increased immediately after occlusion and returned to the baseline value 40 min after clamp removal. MK-801 (1 mg kg-1 i.v.), an antagonist of the NMDA glutamatergic receptor, reduced the cortical infarct volume by 29% (p < 0.001) and the striatal infarct volume by 14% (p < 0.05) when given just prior to ischemia, but had no neuroprotective activity when given 30 min after the onset of ischemia. This short therapeutic window for MK-801 suggests that NMDA receptors play only a transient role in reversible focal ischemia in rats.

Role of the L-arginine-nitric oxide pathway in the basal hydroxyl radical production in the striatum of awake rats as measured by brain microdialysis.

In the present study, using the microdialysis technique, we provided evidence of the existence of hydroxyl radicals (.OH) in the striatum of awake rats under physiological conditions. This .OH generation was virtually abolished by the N-methyl-D-aspartate (NMDA) receptor antagonist dizocilpine. On the contrary, it was significantly enhanced by the .NO synthase inhibitor NG-nitro-L-arginine methyl ester (L-NAME). The effect of L-NAME was completely reversed by L-arginine. These results suggest that the basal .OH production is largely the consequence of an NMDA receptor-mediated glutamatergic tone. Moreover, it is likely that endogenous .NO exerts an antioxidant activity in brain by preventing the rise in .OH levels.

Loss of NADPH-diaphorase containing neurones after reversible focal ischaemia in rats delayed by L-NAME.

In the present study, NADPH-diaphorase histochemistry was used to assess the temporal evolution of the number of nitric oxide (NO)-synthase containing neurones after reversible focal cerebral ischaemia in rats. The number of NADPH-diaphorase containing neurones was reduced by 50% and 90% respectively 6 and 24 h after ischaemia. L-NAME, a NO-synthase inhibitor, prevented the loss of NADPH-diaphorase containing neurones observed 6 h after ischemia but not 24 h after ischaemia, suggesting that in the early phase, nitric oxide is involved in this phenomenon.

Detection of hydroxyl radicals in rat striatum during transient focal cerebral ischemia: possible implication in tissue damage.

As increasing arguments suggest that the reperfusion phase following an ischemic insult may aggravate tissue injury by yielding hydroxyl radicals ('OH), we examined whether these oxyradicals are generated in rat striatum during transient focal cerebral ischemia. .OH were detected in dialysate samples by intrastriatal microdialysis coupled with the technique of salicylate hydroxylation. Ischemia was achieved by tandem occlusion of the left middle cerebral artery and common carotid arteries (45 min) followed by reperfusion. An .OH formation occurred both during ischemia and early reperfusion. Additionally, the volume of the striatal infarct induced by ischemia correlated positively with the amount of .OH produced during ischemia and reperfusion. Taken together, these results provide evidence of the formation of cytotoxic .OH in rat striatum which might participate in the ischemic injury of this structure.

Striatal dopamine participates in glutamate-induced hydroxyl radical generation.

Using a microdialysis technique we showed that the exposure of the rat striatum to glutamate yields hydroxyl radicals and results in striatal damage. We postulated that dopamine release is enhanced by glutamate perfusion and that the enzymatic metabolism of dopamine may account for this hydroxyl radical formation. The inhibition of monoamine oxidases by i.p. co-administration of clorgy-line and deprenyl reduced hydroxyl radical production induced by glutamate perfusion, but significantly increased the striatal damage. Our results suggest that the enzymatic metabolism of dopamine participates in glutamate-induced hydroxyl radical generation but that other by-products of dopamine may be responsible for the aggravation of the striatal injury.

Brain catecholamines, serotonin and their metabolites in mice selected for low (MGL) and high (MGH) blood magnesium levels.

Brain noradrenaline, dopamine, DOPAC (3-4 dihydroxyphenylacetic acid), HVA (homovanillic acid), serotonin and 5-HIAA (5-hydroxyindolacetic acid) were determined by high performance liquid chromatography with amperimetric detection in adult male mice from three different strains : mice with genetically low (MGL) or high (MGH) blood magnesium levels, obtained by selective breeding and outbred Swiss albino mice. Noradrenaline levels were significantly higher (P < or = 0.001) in MGL than in MGH and Swiss mice : DOPAC levels were lower (P < or = 0.001) in MGL than in MGH and Swiss. Little or no differences were found for these variables between MGH and Swiss mice. MGL and MGH animals had similar brain dopamine, HVA and serotonin contents. These results suggest that the mere selection for genetic traits inducing low blood magnesium levels increases the synthesis of noradrenaline or decreases its catabolism. The above data together with the higher urinary noradrenalin excretion previously observed in the MGL line might account for the higher sensitivity and/or reactivity of MGL animals to stress. Swiss mice had significantly lower (P < or = 0.001) brain dopamine and serotonin contents than both MGL and MGH lines; indeed Swiss mice and MGL/MGH mice were issued from very different populations and had vastly different stocks of genes. Brain 5-HIAA content was also found higher (P < or = 0.01) in MGH than in MGL and Swiss mice; this latter result needs to be confirmed by further research.