Current Biotechnological Approaches to the Prevention of Restenosis

No systemic pharmacological treatment has been convincingly shown to reduce the incidence of restenosis after angioplasty in patients. The lack of success of many pharmaceutical agents in reducing restenosis rates post-angioplasty and following stent implantation, as documented in dozens of clinical trials, has encouraged the development of new biotechnological approaches to the treatment of restenosis. Gene therapy and other agents, including antibodies, fusion toxins and ribozymes, have the potential to prevent some of the sequelae after arterial injury, particularly cell proliferation. Mechanical methods of preventing restenosis, for example sophisticated local drug delivery strategies and biodegradable stents using new materials, in combination with novel therapeutic agents or radiation, may also be of use.     

Dual action of angiotensin II on coronary resistance in the isolated perfused rabbit heart

Summary We studied the functional role of angiotensin II (AII) receptor subtypes and vasodilatory endothelial autacoid release in response to AII in isolated perfused rabbit hearts. AII infusion induced biphasic changes in coronary perfusion pressure (CPP): an initial increase was followed by a decrease until a plateau was reached. At higher concentrations of AII (10 nmol/l) this plateau phase was lower than the initial CPP level. AII infusion elicited inverse changes in peak left ventricular pressure (LVP): coronary constriction was associated with a transient decline, and during the plateau phase LVP was clearly increased. AII also moderately augmented prostacyclin (PGI₂) release from the coronary vascular bed. The AII-induced changes in CPP, LVP, and PGI₂ release were effectively inhibited by the AT₁ receptor subtype antagonist ICI D8731 (30 nmol/l), but not by the AT₂ receptor antagonist CGP 42112 (30 nmol/l). The adenosine A₁ receptor antagonist 8-phenyltheophylline (0.1 mol/l) attenuated the decline in CPP following the constriction phase without affecting the changes in LVP during AII infusion. The cyclooxygenase inhibitor diclofenac (1 mmol/l) had no effect on the AII-induced changes in CPP, whereas the nitric oxide-synthase inhibitor N^G-nitro-L-arginine (30 mol/l) markedly potentiated the vasoconstriction but was without effect on the plateau phase of the response. In contrast to AII, the thromboxane analogue U46619 elicited sustained increases in CPP which were associated with slight decreases in LVP.In conclusion, AII induced a biphasic pressor response in the rabbit coronary vascular bed consisting of a transient vasoconstriction followed by a dilatation especially at higher concentrations of AII, an effect which was independent of the endothelial autacoids nitric oxide and PGI₂. The AII-induced dilatation probably reflected rapid desensitization of the coronary arterial smooth muscle to the constrictor effect, and the concomitant accumulation of vasodilatory metabolites such as adenosine, generated during the positive inotropic action of AII. All the effects of AII in the rabbit heart appeared to be mediated via the AT, receptor subtype localized on coronary endothelial and smooth muscle cells, as well as on cardiomyocytes.On leave from the Department of Biomedical Sciences, University of Tampere, P.O. Box 607, FIN-33101 Tampere, FinlandCorrespondence to: I. Pörsti     

Histamine H3 receptor-mediated inhibition of noradrenaline release in pig retina discs

Summary Discs of pig retina were preincubated with ³H-noradrenaline, ³H-dopamine or ³H-serotonin and then superfused. Electrical field stimulation increased the outflow of tritium from discs preincubated with ³H-noradrenaline or ³H-dopamine, but no from discs preincubated with ³H-serotonin. The tritium content at the end of superfusion was similar in discs preincubated with ³H-noradrenaline or ³H-dopamine but about tenfold lower in discs preincubated with ³H-serotonin. The tritium content in discs preincubated with ³H-noradrenaline was markedly reduced when desipramine was present during preincubation but was not affected by selective inhibitors of dopamine and serotonin uptake. The tritium content in discs preincubated with 3Hdopamine and ³H-serotonin, in contrast, was reduced or tended to be reduced by a selective dopamine and serotonin uptake inhibitor, respectively.The electrically evoked overflow of tritium from discs preincubated with ³H-noradrenaline was abolished by tetrodotoxin or omission of Ca²⁺. In discs superfused with desipramine, the electrically evoked overflow was enhanced by phentolamine but not affected by histamine. When both desipramine and phentolamine were present in the superfusion medium, histamine inhibited the evoked overflow (pIC₁₅ 6.85). This effect was mimicked by the histamine H₃ receptor agonist R-(–)--methylhistamine as well as by its S-(+)-enantiomer (pIC₁₅ 7.85 and 5.30, respectively) but not by the H₁ receptor agonist 2-(2-thiazolyl)ethylamine and the H₂ receptor agonist dimaprit (each 10 mol/l). The inhibitory effect of histamine was abolished by the H₃ receptor antagonist thioperamide 0.32 mol/l and attenuated by impromidine 3.2 mol/l but not affected by the H₁ receptor antagonist dimetindene 3.2 mol/l and the H₂ receptor antagonist ranitidine 10 mol/l.The results suggest that, in the pig retina, noradrenaline is taken up into, and released from, noradrenergic neurones (most likely vascular postganglionic sympathetic nerve fibres, less probably tissue-specific noradrenergic neurones of the retina) and that noradrenaline release is subject to modulation via H₃ receptors and probably also a-adrenoceptors.Send offprint requests to E. Schlicker at the above address     

Transoral laser surgery for early glottic carcinoma

This prospective study evaluates the oncological results of transoral laser surgery (TLS) for glottic carcinoma categorized Tis, T1 and T2 in a large, unselected group of 285 consecutive patients from a university-based referral center that uses transoral laser surgery as the standard approach to these tumors. Patients were treated between 1 January 1987 and 31 December 1996. Thirty-three patients had Tis disease, 174 T1 tumors and 113 T2. Main outcome measures were local control with initial therapy, ultimate local control, regional control, organ preservation, overall survival and cause-specific survival. The 5-year uncorrected actuarial survival for all 285 patients was 71.1%, and cause-specific actuarial survival was 98.7%. Local control with initial treatment was 85.9%, ultimate local control with salvage for local treatment failures 98.5%, and regional control 98.4%. In all, 94.3% had their larynges preserved after 5 years. Although favorable oncological results for early laryngeal carcinoma treated with laser surgery are supported this study, no definitive recommendations can be given for the best single treatment. Partial laryngectomies lead to the highest local control rates reported so far, radiotherapy is believed to preserve voice best and laser surgery is associated with time- and cost-effectiveness, low morbidity, fair local control rates and excellent re-treatment options in case of local failure. All specialists dealing with the treatment of early glottic carcinoma should be able to offer these different treatment modalities to their patients and to deal specifically with each patient’s individual needs and preferences. Received: 29 October 1998 / Accepted: 2 July 1999     

Involvement of nitric oxide synthase in the physiology and pathophysiology of facial nerve function and dysfunction

To date few reports have discussed the presence and function of nitric oxide (NO) in structures of the facial nerve. We performed nicotinamide adenine dinucleotide phosphate (NADPH-d)-diaphorase-histochemistry and immunohistochemistry on the intratemporal portion of the facial nerve, including the geniculate ganglion, of guinea pigs using specific antibodies to the three known isoforms of NO synthase and soluble guanylyl-cyclase (sGC). Normal facial nerves were compared to those treated intratympanically with bacterial lipopolysaccharides (LPS) and tumor necrosis factor-α (TNF-α). Both constitutive NOS isoforms and sGC could be detected in the bipolar ganglion cells of normal animals, while the inducible isoform (iNOS or NOS II) was not found. Endothelial NOS (NOS III) and sGC were present in blood vessels and were predominantly found in the perineurial sheath and less in the endoneurium. sGC could be detected in all fibers in a cross section of the facial nerve. LPS and TNF treatment led to the detection of iNOS in the perikaryia of the geniculate ganglion and the perineural sheath. These findings imply that NO may be involved in neurotransmission at least in the visceroafferent system. NO regulates vascular tone of nutrient blood vessels in the perineural sheath and endoneurium. The presence of sGC indicates that NO acts via its second messenger cGMP. NOS II expression may be a contributing factor to facial nerve palsy via two different mechanisms: NOS II-generated NO may lead to an overstimulation of the visceroefferent nerve fibers and motor fibers of the facial nerve. Dysregulation in facial nerve blood vessels could lead to edema and elevated pressure on the nerve within its osseous canal. Received: 13 April 1999 / Accepted: 12 August 1999     

Prostanoid receptors of the EP3 subtype mediate the inhibitory effect of prostaglandin E2 on noradrenaline release in the mouse brain cortex

Mouse or rat brain cortex slices were preincubated with ³H-noradrenaline and superfused with physiological salt solution containing desipramine. We studied the effects of prostaglandin E₂ (PGE₂), prostaglandin D₂ (PGD₂) and related drugs on the electrically evoked (50 mA, 2 ms, 0.3 Hz) tritium overflow.PGE₂ inhibited the electrically evoked tritium overflow from mouse brain cortex slices; the maximum effect of PGE₂ (79010) was attenuated by the ₂-adrenoceptor agonist talipexole (to 52010) and enhanced by the ₂-adrenoceptor antagonist rauwolscine (to 92%). Rauwolscine was added to the superfusion medium in all subsequent experiments. The effect of PGE₂ was readily reversible upon withdrawal from the medium and remained constant upon prolonged exposure of the tissue to the prostanoid. Studies with EP receptor agonists, mimicking the inhibitory effect of PGE₂, showed the following potencies (pIC₅₀): sulprostone (8.22); misoprostol (8.00); PGE₂ (7.74); PGEZ (7.61); iloprost (5.86). The concentration-response curve of PGE₂ was marginally shifted to the right by the EP₁ receptor antagonist AH 6809 (6-isopropoxy-9-oxoxanthene-2-carboxylic acid; apparent pA₂ 3.97) and by the TP receptor antagonist vapiprost (4.50). AH 6809, by itself, did not affect the evoked overflow whereas vapiprost increased it. PGD2 inhibited the evoked overflow at high concentrations (pIC₅₀ 4.90); this effect was not altered by the DP receptor antagonist BW A868C (3-benzyl-5-(6-carboxyhexyl)-1-(2-cyclohexyl-2hydroxyethylamino)hydantoin), which, by itself, did not affect the evoked overflow. Indometacin slightly increased the evoked overflow and tended to increase the inhibitory effect of PGE₂. PGE₂ inhibited the electrically evoked tritium overflow also in rat brain cortex slices. The maximum effect (obtained in the presence of rauwolscine) was 61%; the pIC₃₀ value was 7.67.The present study suggests that PGE₂ inhibits noradrenaline release from mouse brain cortex via EP₃ receptors and that its maximum effect is more marked in the mouse than in the rat. The inhibitory effect of PGD₂ (in the mouse brain) does not involve DP receptors and may also be related to EP₃ receptors. The EP₃ receptors interact with a2-adrenoceptors and may be activated by endogenous prostanoids.     

A multinational study of the relationships between nighttime urinary melatonin production, age, gender, body size, and latitude

Overnight urines were collected each month for 12–16 months from 321 normal subjects at 19 medical centers in 14 countries distributed on 5 continents at latitudes from 31 01 South to 77 00 North. Mean melatonin concentration was found to negatively correlate with age, weight, and height. When the sexes were considered separately melatonin only correlated with age for female and with age and weight for males. A weak correlation with latitude, but not longitude, was also found. Received: 26 February 1998 / Accepted: 9 September 1999     

Divalent Cations Modulate the Inhibitory Substrate Properties of Murine Glia-derived J1-160 and J1-180 Extracellular Matrix Glycoproteins for Neuronal Adhesion

J1-160 and J1-180 are developmentally late appearing J1 extracellular matrix glycoproteins derived from oligodendrocytes. They prevent adhesion of neurons (but not of astrocytes or fibroblasts) when offered as a substrate in mixture with laminin (Pesheva et al., J. Cell Biol., 109, 1765 - 1778, 1989). In the present study we have examined the influence of divalent cations on the inhibitory substrate properties of J1-160/180 glycoproteins towards adhesion of neurons. By metal chelate affinity chromatography, we show that J1-180, but not J1-160, binds Ca2+, while both J1 components are capable of binding Zn2+ and other divalent metal ions. Divalent cation binding was observed by gel filtration, aggregation assays with coated latex beads and electron microscopic examination to elicit aggregation of the molecules. Divalent cation binding also affects their non-permissive substrate properties towards neurons from early postnatal mouse cerebellum. Without divalent cations, J1-160 and J1-180 are inhibitory for substrate adhesion of neurons independently of the adhesive substrate present (laminin or poly-l-lysine). This effect is neutralized when J1-180 is preincubated with Ca2+ or Zn2+ prior to coating as substrate. In contrast, preincubation with Ca2+ ions does not affect the inhibitory substrate properties of J1-160 under these conditions. These observations show that J1-160/180 molecules may undergo self-aggregation in a divalent cation-dependent mechanism, which correlates with the neutralization of their inhibitory effect on neuronal adhesion. The aggregation state of the molecules may thus influence the process of myelination by a homophilic binding mechanism and determine the effectiveness of neurite extension during central nervous system development and under traumatic conditions in the adult.     

Interaction of phenylbutazone with racemic phenprocoumon and its enantiomers in rats

The interaction of phenylbutazone with the enantiomers and racemic [ ³ H]phenprocoumon was studied in male inbred Wistar-Lewis rats following a single i.v. dose of the three forms of phenprocoumon and chronic oral treatment with phenylbutazone (average plasma concentration of about 60 g/ml). Phenylbutazone augmented the anticoagulant effect of R(+), S(–), and R, S (±) phenprocoumon to a similar extent. The free fraction of drug in the plasma of the enantiomers and racemic phenprocoumon increased in the presence of phenylbutazone. However, the rate of elimination of total drug from plasma and liver and the distribution between liver and plasma of all three forms of phenprocoumon remained nearly unaffected by phenylbutazone. Thus there is no evidence for a stereoselective drug interaction between phenprocoumon and phenyl-butazone. For racemic [ ³ H]phenprocoumon it was possible to follow the kinetics of free drug in plasma and liver along with the time course of anticoagulant activity. In these studies, free drug concentrations in plasma and liver increased during treatment with phenylbutazone, but the elimination rate constant of free racemic phenprocoumon in plasma and liver remained essentially unchanged. Phenylbutazone markedly decreased the volume of distribution referenced to free drug and the clearance of free phenprocoumon (i.e., intrinsic metabolic clearance). Whereas the total (bound and unbound) drug concentration-effect relationship in plasma and liver was shifted to the left in rats treated with phenylbutazone, such shift was not seen in the free drug concentration-response relationship. In conclusion, the increase in the free concentration of phenprocoumon in plasma and liver and the concomitant decrease in the clearance of free drug are the mechanisms responsible for the marked and sustained enhancement of the anticoagulant effect which follows treatment with phenbutazone.This work was supported by the Deutsche Forschungsgemeinschaft.