Evidence for resveratrol-induced preservation of brain mitochondria functions after hypoxia-reoxygenation.

We have previously shown, as have other authors, that trans-resveratrol (E-resveratrol, 3,4,5-trihydroxy-E-stilbene) reduces reactive oxygen species (ROS) generation of mitochondria freshly isolated from healthy rat brains and that it also counteracts the effect of uncouplers (CCCP) on mitochondrial respiration and oxidative phosphorylation. Two main mechanisms have been shown: firstly, a scavenger effect toward O2- and secondly inhibition of complex III ROS generation. We now report on the effects of resveratrol in a pathological model that mimics the ischemia followed by the reperfusion process which may occur in the human brain. Isolated brain mitochondria were submitted first to hypoxia then to reoxygenation. The aim of this study was to determine the extent of mitochondrial damage induced by this experimental model, to demonstrate which mitochondrial functions were altered and to quantify the extent to which they were prevented by resveratrol. Resveratrol was either added to mitochondria freshly isolated from healthy rat brains or was injected by subcutaneous chronically implanted pumps (0.5, 2 and 10 mg/kg/day for 7 days). The rats were then sacrificed and mitochondria were extracted from brains. To evaluate the respective effects of hypoxia and reoxygenation on mitochondrial functions and the relevant effects of resveratrol, this drug was added (first protocol) either before the complete process (i.e., hypoxia and reoxygenation), or after anoxia before reoxygenation. We found that resveratrol prevented alterations of mitochondrial functions. This substance partly counteracted the decrease in respiratory control and the increase in ROS generation. It fully inhibited the alteration of membrane fluidity and the mitochondrial step of the apoptotic process (evidenced by cytochrome c release and membrane potential collapse). The effects of resveratrol were concentration-dependent (in vitro) or dose-dependent (ex vivo, second protocol). They were not significantly different when the drug was added before or after hypoxia, which suggests that in this model, reoxygenation was the most deleterious process and the stage at which resveratrol was most effective.

[The risk of falling due to benzodiazepine administration, alone or in combination, in elderly subjects]. / Le risque de chutes lié à l'administration de benzodiazépines seules ou associées, chez le sujet âgé.

Benzodiazepines are well tolerated by young adults whereas in elderly people they are less safe and globally induce more central nervous system side-effects and falls. Falls result from a decrease of vigilance and an alteration of postural reflex. This latter includes the reception of sensory information and central integration modulated mainly by dopaminergic D2 receptors and motor stimulation. Benzodiazepines act simultaneously on the three stages, decreasing their efficacy. The risk increases when certain other drugs are coprescribed, especially synergistic drugs such as another psycholeptic drug, an aminoside or a centrally active antihypertensive drug. Thus their co-prescription with a benzodiazepine increases the risk of falls. The pharmacokinetic parameters of benzodiazepines may be modified or remain constant during ageing. The choice of molecules whose parameters do not vary seems advisable. Whatever the selected benzodiazepine, it is obvious that it must be administered at the lowest possible dose, this dose being increased only if necessary, the overall prescription being time limited.

S15176 and S16950 interaction with Cyclosporin A antiproliferative effect on cultured human lymphocytes.

S15176 and S16950 are trimetazidine derivatives that antagonize more strongly than the parent drug mitochondrial toxicity, which leads to cellular hypoxia and nephrotoxicity in kidneys experimentally exposed to cyclosporin A. We have investigated whether every derivative might interact or not with the inhibitory effect of Cyclosporin A on the proliferation of cultured human lymphocytes. S15176 significantly increased the antilymphoproliferative effect of Cyclosporin A, whereas S15176 by itself neither displayed any antilymphoproliferative effect, nor did it induce any apoptotic process in cultured human lymphocytes. The effect of S16950 was not significant.

[The pharmacologic basis of pain treatment]. / Les bases pharmacologiques des traitements des états douloureux.

The treatment of chronic pain uses drugs from different pharmacological classes. Analgesics are the common basis of these treatments. Peripheral analgesics (or minor analgesics such as paracetamol) and non-steroidal anti-inflammatory drugs are used for moderate pain (grade I of WHO). Major analgesics, opioids, are used for more severe pain (grades II and III). When pain can be related to a precise cause or location, more specific drugs may be used. This is done in migraine, facial pain, muscular spasms, dental pain, local inflammation. Chronic pain of grades II and III is treated with opioids. According to the severity, agents of different powers are used: partial agonists, full agonists of receptors OP3 (mu) and OP2 (kappa). According to other pathological signs linked to pain, coanalgesic drugs may be used in association: psychotropic drugs, either psycholeptic drugs which act synergistically with analgesics and bring their own effects, anxiolytic and/or neuroleptic, or anti-depressants which inhibit the depression state that may be associated with pain. Corticosteroids are also very useful for the numerous effects they induce: inhibition of the inflammation process, CNS stimulation, analgesics in medullary, or plexus compressions and in elevations of intracranial hypertension. Moreover their metabolic effects may be useful in cachectic states. The pharmacological treatment of chronic pain of grades II and III poses the problem of chronic administration of increasing doses of opioids and of their coprescription, of acquired tolerance, of dependence and of toxicity induced by drug accumulation.

[Allergen potential of drugs and ex vivo demonstration of an immune response]. / Potentiel allergénique des médicaments et mise en évidence ex vivo d'une réponse immunitaire.

Drugs are able to activate the immune system, which may generate hypersensitivity states in individuals. In a first part, this article deals with the critical processes that are involved in drug sensitizations: what are the specific features of drugs as immunogens; how drugs are recognized as non-self by immunocompetent cells; what is the spontaneous outcome of drug allergic states, does a genetic predisposition regulate the immune response. The second part is mostly devoted to the biological investigation of drug sensitizations: what are we looking for and why, are all the available methods equally suitable for routine diagnosis, what are the major methological problems that we have to face at and how to escape them.

[Interactions and incompatibilities in prescription drugs. Incidents in dental surgery]. / Interactions et incompatibilités de prescription médicamenteuse. Incidences en chirurgie dentaire.

Drug interactions can be classified according to their pharmacodynamic and pharmacokinetic mechanisms. Pharmacodynamic interactions are observed when two drugs share a common effect or have the same effect on different receptors of a common function. They can be predicted if the elementary effects of each drug are known. Such are pharmacodynamic interactions are particularly interesting as they are selective for the common effect(s). Pharmacokinetic interactions are more difficult to predict. They occur when one drug modifies the pharmacokinetic parameters of a second drug. Modification may involve variations in oral absorption, tissue distribution, rate of metabolism and/or rate of renal excretion. This interaction cannot be selective as drug concentrations are modified, affecting all the concentration-dependent effects. Mastering drug interactions involve the knowledge of the underlying mechanisms. Answers to following questions are needed: does the association produce conjugated effects? can one drug modify pharmacokinetic parameters of another? Potentially toxic effects may be suspected when at least one drug involved is known for its toxicity. Risk is increased when it also exhibits a narrow range between active and toxic concentrations. Many databases in printed form or as interactive software provide information on drug interactions. Clinicians can also consult a Pharmacovigilance Center for a safe prescription procedure. Finally, the main danger lies in the simultaneous prescriptions by different practitioners unaware of their colleagues prescription. In this case, the pharmacist plays an important role of evaluation of the drugs prescribed.

[Pharmacologic and biologic basis of drug allergies]. / Bases pharmacologiques et biologiques des allergies médicamenteuses.

Drugs are able to activate the immune system, which may generate hypersensitivity states in individuals. This article first deals with the critical processes that are involved in drug sensitizations: what are the specific features of drugs as immunogens; how are drugs recognized as non-self by activated immune cells; what is the spontaneous outcome of an immune response to drugs in individuals; does a genetic predisposition regulate the immune response to drug antigens; how much are biotransformation processes involved in the immunogenicity of drugs? The second part is mostly devoted to the biological investigation of drug sensitizations: what are we looking for and why; are all the available methods equally suitable for routine diagnosis; what are the major methological problems that we have to deal with in investigating patients who have presented with symptoms which are clinically suspected to be of immuno-allergic origin?

[Exploration of 112 children suspected of amoxicillin allergy. Indications and efficacy of oral provocation test]. / Exploration de 112 enfants suspects d'allergie à l'amoxicilline. Indications et intérêt du test de provocation oral.

BACKGROUND: One to 10% of treatments using betalactams, particularly synthetic penicillin, are complicated by allergic reactions, usually cutaneous, and not easily imputable to immunologic sensitization in children. PATIENTS AND METHODS: The aim of this study was to identify, using cutaneous and biological tests, those from a group of 112 children suspected of amoxicillin allergy (evidenced by rash) who were actually sensitized, and to confirm the absence of allergy in others by an oral provocation test (OPT) associated to a long-term survey. The cutaneous tests were made by prick test and intra-dermo reaction (IDR) with Allergopen and with amoxicillin or amoxicillin + clavulanic acid. The biological tests included examination for penicillin and amoxicillin antibodies by using various techniques including enzyme-linked immunosorbent assay (ELISA) immunoglobulin G (IgG) and IgE, FARR, radioallergo sorbent test (RAST) and a histaminoliberation. When these tests were negative, an OPT with the suspected antibiotic was subsequently performed. RESULTS: Thirty-nine children (36.4%) confidently presented at least one positive cutaneous test (38 Allergopen, ten amoxicillin); 25 biological tests were positive (16 ELISA IgE, one ELISA IgG and eight histaminolibarations), seven times with negative cutaneous test. Forty-five children were judged to be sensitized to amoxicillin, with only one who subsequently took amoxicillin again. Among the 67 others, 52 received an OPT, six of them with moderate cutaneous reactions. Fifty-one (45.5%) children were allergic and 46 (41%) were allowed to take amoxicillin again; 17 did, one of them with a benign cutaneous reaction. CONCLUSION: Efficacy and safety of this type of investigation seems clear; it will have to be confirmed by other studies.

Systemic antifungal agents. Drug interactions of clinical significance.

There are 3 main classes of systemic antifungals: the polyene macrolides (e.g. amphotericin B), the azoles (e.g. the imidazoles ketoconazole and miconazole and the triazoles itraconazole and fluconazole) and the allylamines (e.g. terbinafine). Other systemic antifungals include griseofulvin and flucytosine. Most drug-drug interactions involving systemic antifungals have negative consequences. The interactions of amphotericin B, flucytosine, griseofulvin, terbinafine and azole antifungals can be divided into the following categories: (i) additive dangerous interactions; (ii) modifications of antifungal kinetics by other drugs; and (iii) modifications of the kinetics of other drugs by antifungals. Amphotericin B and flucytosine mainly interact with other agents pharmacodynamically. Clinically important drug interactions with amphotericin B cause nephrotoxicity, hypokalaemia and blood dyscrasias. The most important drug interaction of flucytosine occurs with myelotoxic agents. Hypokalaemia can precipitate the long QT syndrome, as well as potentially lethal ventricular arrhythmias like torsade de pointes. Synergism is likely to occur when either QT interval-modifying drugs (e.g. terfenadine and astemizole) and drugs that induce hypokalaemia (e.g. amphotericin B) are coadministered. Induction and inhibition of cytochrome P450 enzymes at hepatic and extrahepatic sites are the mechanisms that underlie the most serious pharmacokinetic drug interactions of the azole antifungals. These agents have been shown to notably decrease the catabolism of numerous drugs: histamine H1 receptor antagonists, warfarin, cyclosporin, tacrolimus, digoxin, felodipine, lovastatin, midazolam, triazolam, methylprednisolone, glibenclamide (glyburide), phenytoin, rifabutin, ritonavir, saquinavir, nevirapine and nortriptyline. Non-antifungal drugs like carbamazepine, phenobarbital (phenobarbitone), phenytoin and rifampicin (rifampin) can induce the metabolism of azole antifungals. The bioavailability of ketoconazole and itraconazole is also reduced by drugs that increase gastric pH, such as H2 receptor antagonists, proton pump inhibitors, sucralfate and didanosine. Griseofulvin is an enzymatic inducer of coumarin-like drugs and estrogens, whereas terbinafine seems to have a low potential for drug interactions. Despite important advances in our understanding of the mechanisms underlying pharmacokinetic drug interactions during the 1990s, at this time they still remain difficult to predict in terms of magnitude in individual patients. This is because of the large interindividual and intraindividual variations in the catalytic activity of those metabolising enzymes that can either be induced or inhibited by various drugs. Notwithstanding these variations, increasing clinical experience is allowing pharmacokinetic interactions to be used to advantage in order to improve the tolerability of some drugs, as recently exemplified by the use of a fixed combination of ketoconazole and cyclosporin.

Differential effects of zidovudine and zidovudine triphosphate on mitochondrial permeability transition and oxidative phosphorylation.

1. The effects of zidovudine (ZDV) and zidovudine triphosphate (ZDV-3P) on Ca2+-induced mitochondrial permeability transition (MPT), respiratory control ratio (RCR) and ATP synthesis have been investigated on isolated rat liver mitochondria. 2. ZDV slightly but significantly decreased RCR and ATP synthesis but was ineffective in inhibiting MPT. In contrast, ZDV-3P did not alter RCR and ATP synthesis but strongly inhibited MPT (IC50 = 3.0 +/- 0.9 microM). 3. The effect of ZDV-3P on mitochondrial swelling required a preincubation time. When incubated 10 min with mitochondria, ZDV-3P (8 microM) totally inhibited the rate of swelling. 4. ADP, ATP and atractyloside, which are agents known to interact with the mitochondrial adenine nucleotide carrier (ANC), antagonized the effect of ZDV-3P on mitochondrial swelling. Indeed, the IC50 value of ZDV-3P increased from 3.0 to 17.4, 93.6 and 66.5 microM, in the presence of 20 microM, ADP, ATP or atractyloside, respectively. 5. ZDV-3P did not displace [3H]-ATP from its mitochondrial binding site(s) whereas ADP and atractyloside did, suggesting that ZDV-3P and [3H]-ATP do not share the same binding sites. 6. ZDV-3P did not affect either mitochondrial respiration or ATP synthesis but inhibited Ca2+-dependent mitochondrial swelling. It was concluded that mitochondrial toxic effects observed during the chronic administration of ZDV cannot be related to its active metabolite (ZDV-3P).

[Value of protecting mitochondrial functions during treatment with cyclosporin A]. / L'intérêt de la protection des fonctions mitochondriales au cours d'un traitement par la cyclosporine A.

The use of cyclosporin A is often limited by its nephrotoxicity. This dose-dependent toxicity can occur in all kinds of transplantation and is reversed with drug withdrawal. Cyclosporin A induces a vasoconstriction leading to an increase of renal vascular resistance and a reduction of glomerular filtration. Histochemical studies show mitochondrial alterations and an excess of cytosolic and mitochondrial calcium leading to a decrease of ATP synthesis. Two strategies can be evoked for limiting cyclosporin-A-induced nephrotoxicity. First, the use of drugs counteracting the vasoconstriction has been proposed. Second, drugs acting by restoration of ATP synthesis could also be of interest. For example, calcium channel blockers may be used for limiting the Ca2+ fluxes into cells. Another way to protect ATP synthesis is to inhibit the cyclosporin-A-induced increase of mitochondrial Ca2+ concentrations; Trimetazidine has shown its efficiency in vitro for protecting mitochondria against these modifications of Ca2+ homeostasis and is under clinical evaluation.

Potential interest of anti-ischemic agents for limiting cyclosporin A nephrotoxicity.

Chronic administration of cyclosporin A induces nephrotoxicity in humans. This is related to a cyclosporin A-induced constriction of afferent glomerular arterioles and mesangial cells, which leads to a decrease in filtration pressure and creatinine clearance. Afterwards, cellular lesions are observed involving mainly tubular atrophy and interstitial fibrosis, both of which are nonspecific. The initial mechanism of its toxicity is not clearly explained. The current pharmacological approach is symptomatic in order to counteract or minimize the consequences of a prime cause, which still remains to be defined. However, cyclosporin A has a deletereous effect on mitochondrial functions and mainly on ATP synthesis, which occurs when Ca2+ accumulates in matrix mitochondria. The effects of trimetazidine, an antischemic drug used in the treatment of angina pectoris, have been assessed. This drug is effective in experimental models of hypoxia induced by cyclosporin A: it restores ATP synthesis previously decreased by Ca2+ and cyclosporin A, and releases a part of Ca2+ excess accumulated by mitochondria at concentrations reached in humans at usual dosage regimens. At higher concentrations, it reverses the mitochondrial permeability transition previously generated (opened) by Ca2+ and a pro-oxidant such as terbutylperoxide (t-BH). It was also observed that trimetazidine does not modify the immunosuppressive effects of cyclosporin A in various models. These data suggest that nephrotoxicity of cyclosporin A is not irrevocably linked to its immunosuppressive effect but that it may be possible to counteract at least partly its nephrotoxic effects without altering its effectiveness in preventing graft rejection.

Trimetazidine does not modify blood levels and immunosuppressant effects of cyclosporine A in renal allograft recipients.

AIMS: In renal allograft recipients, trimetazidine (Vastarel) was proposed to be associated with the classic immunosuppressant treatments because it displays anti-ischaemic effects which may protect against cyclosporine A nephrotoxicity. The objective of this work was to assess the possibility of coadministering cyclosporin A, Sandimmun, and trimetazidine. METHODS: Twelve renal transplant patients were selected on the basis of the stability of their cyclosporine A blood concentrations for the previous 3 months. They received trimetazidine, 40 mg twice daily orally for 5 days. Other coadministered drugs were kept unchanged during the study. Before and after trimetazidine administration, cyclosporine A blood concentrations, plasma interleukin-2 and soluble interleukin-2 receptor levels were measured. RESULTS: The data showed that neither cyclosporin A blood pharmacokinetic parameters, Cmax, tmax, AUC, nor the concentrations of interleukin-2 and soluble interleukin-2 receptors were significantly modified. CONCLUSIONS: Therefore, it was suggested that trimetazidine may be coadministered with cyclosporine A without cyclosporine A dosage adjustment.

[Can one adjust the distribution of a drug in an organism to its target sites? The example of antihistaminics (anti-H1) and cetirizine]. / Peut-on adapter la distribution d'un médicament dans l'organisme aux localisations de ses cibles? L'exemple des antihistaminiques (anti H1) et de la cétirizine.

When comparing the fate of a drug in the body with the location of its receptors, it appears that a large amount of the administered dosage will never reach these receptors. Thus this large amount is useless in terms of drug efficacy whereas it may generate side of toxic effects in other tissues. An attempt to optimize drug distribution is to limit or even to suppress its useless localisations. This is possible with H1 antagonists as these drugs develop benefic effects in organs which are distinct from those where toxic effects may occur. Cetirizine is an example of choice of this strategy. It is poorly distributed into tissues, especially in heart and liver which favors preferential binding at its target H1 selected receptors.

Trimetazidine reverses calcium accumulation and impairment of phosphorylation induced by cyclosporine A in isolated rat liver mitochondria.

When applied to rat liver mitochondria in contact with Ca++, cyclosporine A (CsA) induced both an accumulation of this ion and a decrease in oxidative phosphorylation. Trimetazidine (TMZ) reversed both phenomena in a dose-dependent manner. These two effects were demonstrated in separate experiments. A decrease in oxidative phosphorylation was observed with succinate as substrate. V3 and P/O (ratio corresponds to the number of ADP molecules added in the medium per oxygen atom consumed during phosphorylation and represents the yield of ATP synthesis) were simultaneously decreased by CsA (1 microM) and restored by TMZ. Ca++ accumulation in mitochondria was observed when it was added to the mitochondrial suspension; its uptake was followed by a new equilibrium. CsA prolonged its duration, whereas TMZ reduced it in a dose-dependent manner. The same phenomenon was observed when ADP was used instead of CsA. Ca++ efflux from mitochondria could be induced by TMZ without the addition of CsA. It was immediate and always partial and followed by a reuptake process only observed at concentrations of TMZ of >1 microM. Compared with ruthenium red, which blocks Ca++ uniporter, TMZ seemed to act on Ca++ efflux mechanisms. Interestingly, low TMZ doses promote a Ca++ efflux process without activating reentry mechanism, which may explain the correction of deleterious effect of CsA on V3 and P/O. As nephrotoxicity observed in humans after CsA chronic administration is considered to be related, at least in part, to an alteration of Ca++ intracellular homeostasis, TMZ seems to be a candidate for alleviation of CsA nephrotoxic effects in humans.

Lack of pharmacodynamic interaction between trimetazidine and cyclosporin A in human lymphoproliferative and mouse delayed hypersensitivity response models.

The hypothesis of an interaction between trimetazidine and the immunosuppressive effect of cyclosporin A was investigated in two models: a) ex vivo, the lymphoproliferative response of normal human lymphocytes to phytohemagglutinin and a murine monoclonal antibody against the CD3 T-lymphocyte membrane complex; b) in vivo, the delayed hypersensitivity response model in mouse. The uptake of methyl-3H-thymidine was measured in both models. For the lymphoproliferative response, statistical analysis showed that there was a significant inhibitory effect of cyclosporin A on cell proliferation (P < 0.001) and confidence intervals obtained by ANOVA showed the equivalence of the results when trimetazidine was combined with cyclosporin A (all CI95% < or = 10). In the delayed hypersensitivity model, cyclosporin A was also found to be very effective in inhibiting the immune response (P < 0.001), while trimetazidine did not interfere with cyclosporin A's effect. It was concluded that trimetazidine exerted neither an immunostimulatory nor an immunosuppressive effect in the two models, suggesting of the absence of interaction between trimetazidine and cyclosporin A's effectiveness when both drugs are given in combination.

[Cyclosporin A and ketoconazole, drug interaction or therapeutical combination?]. / Ciclosporine A et kétoconazole, interaction médicamenteuse ou association thérapeutique?

Cyclosporin A is potentiated by ketoconazole, mainly by inhibiting its P-450 dependent biotransformations. The other interest of ketoconazole is related to its antifungal effect, which is often used in immunodepressed patients. Thus for both pharmacodynamic and pharmacokinetic reasons, the combination of the two drugs is of interest. Another advantage is that whereas ketoconazole is a cheap drug, cyclosporin A is an expensive one, thus their combination may save a part of the cyclosporin A cost. Various questions remain to be solved: is it useful to combine in the same tablet selected amounts of the two drugs and if so in which ratio? Such a strategy supposes that intra and inter-individual variability of cyclosporin A metabolism in humans can be tightly monitored. Is it without risk to definitely inhibit some P-450 isoenzymes? Could not the expected simplification of drug dosages generate the need for more cyclosporin A blood level assays, thus leading to an additional cost?