Biochemical and electrophysiological studies on the mechanism of action of PNU-151774E, a novel antiepileptic compound.

PNU-151774E [(S)-(+)-2-(4-(3-fluorobenzyloxy)benzylamino)propanamide methanesulfonate], a new anticonvulsant that displays a wide therapeutic window, has a potency comparable or superior to that of most classic anticonvulsants. PNU-151774E is chemically unrelated to current antiepileptics. In animal seizure models it possesses a broad spectrum of action. In the present study, the action mechanism of PNU-151774E has been investigated using electrophysiological and biochemical assays. Binding studies performed with rat brain membranes show that PNU-151774E has high affinity for binding site 2 of the sodium channel receptor, which is greater than that of phenytoin or lamotrigine (IC50, 8 microM versus 47 and 185 microM, respectively). PNU-151774E reduces sustained repetitive firing in a use-dependent manner without modifying the first action potential in hippocampal cultured neurons. In the same preparation PNU-151774E inhibits tetrodotoxin-sensitive fast sodium currents and high voltage-activated calcium currents under voltage-clamp conditions. These electrophysiological activities of PNU-151774E correlate with its ability to inhibit veratrine and KCl-induced glutamate release in rat hippocampal slices (IC50, 56.4 and 185.5 microM, respectively) and calcium inward currents in mouse cortical neurons. On the other hand, PNU-151774E does not affect whole-cell gamma-aminobutryic acid- and glutamate-induced currents in cultured mouse cortical neurons. These results suggest that PNU-151774E exerts its anticonvulsant activity, at least in part, through inhibition of sodium and calcium channels, stabilizing neuronal membrane excitability and inhibiting transmitter release. The possible relevance of these pharmacological properties to its antiepileptic potential is discussed.

Synthesis and antihypertensive activity of 2,4-dioxoimidazolidin-1-yl and perhydro-2,4-dioxopyrimidin-1-yl ergoline derivatives.

The synthesis and antihypertensive activity of a series of 2,4-dioxoimidazolidin-1-yl and perhydro-2,4-dioxopyrimidin-1-yl ergoline derivatives are reported. The oral antihypertensive activity was studied in spontaneously hypertensive rats (SHRs) by measuring systolic blood pressure by an indirect tail-cuff method at different times after treatment. The prolactin lowering activity (indirectly measured by the nidation test) in rats and the oral acute toxicity in mice were also studied. The results of this study revealed potent antihypertensive ergoline derivatives devoid of side-effects related to the dopaminergic stimulation and the importance of the delta 9,10 double bond for conferring high potency within these compounds.

Long-term thromboxane-synthase inhibition prolongs survival in murine lupus nephritis.

Systemic lupus erythematosus (SLE) is an autoimmune disease, characterized by nephritis, in which mortality is largely influenced by the severity of renal involvement. As there are evidences that thromboxane (TX)A2 plays an important role in the pathogenesis of lupus nephritis, we decided to assess the effects of long-term suppression of TXA2 synthesis on the progression of the disease, by designing a study of TXA2-synthase inhibition having adequate size to detect an effect on mortality as the primary end-point. Thus, we randomized 362 NZBxNZW mice (11-week-old at entry) to one of the following treatments: a TXA2 synthase inhibitor, FCE 22178 (300 mg/kg daily), saline or cyclophosphamide (5 mg/mouse weekly x 4 weeks) used as reference treatment. The TXA2 synthase inhibitor suppressed TXA2 biosynthesis, as reflected by urinary TXB2 and 2,3-dinor-TXB2 excretion (by 78% and 90%, respectively) and significantly reduced mortality (death rate: 34% vs. 61% in controls, at 37 weeks, P < 0.01). A significant reduction in proteinuria (9 +/- 1.6 vs. 17.3 +/- 2.4 mg/24 hr in FCE 22178 vs. saline, P < 0.01) and glomerular lesions was observed up to 30 weeks but not at 37 weeks. In contrast, cyclophosphamide prevented the development of proteinuria and histologic lesions, and reduced mortality to 8% at 37 weeks. Renal plasma flow and glomerular filtration rate were lower (by 29% and 52%, respectively) in 37-week-old as compared to young NZBxNZW mice. These parameters were further depressed by cyclophosphamide (by 48% and 45% vs. age-matched controls, respectively, P < 0.01) but were not altered significantly by FCE 22178.(ABSTRACT TRUNCATED AT 250 WORDS)

Role of enhanced glomerular synthesis of thromboxane A2 in progressive kidney disease.

Normotensive rats of the Milan strain (MNS) spontaneously develop focal glomerulosclerosis. In order to explore the contribution of glomerular thromboxane (TX) A2 synthesis to the development of the disease, we have characterized the time course of renal functional and biochemical changes, and their modification by long-term treatment with a TX-synthase inhibitor. Oral administration (150 mg.kg-1 from 1 to 14 months of age) of FCE 22178 suppressed enhanced glomerular TXB2 production at all experimental times (mean inhibition 80%) and proteinuria (varying between 27.1 and 73.0%) while preserving renal blood flow and glomerular filtration rate. These effects of TX-synthase inhibition were seen in the absence of any statistically significant changes in systemic blood pressure. Moreover, FCE 22178 had no antihypertensive effects in hypertensive rats of the Milan strain (MHS) nor in spontaneously hypertensive rats (SHR). Treatment also prevented the age-related hypoalbuminemia and hyperlipidemia observed in control MNS and significantly (P less than 0.01) reduced glomerular histologic damage, as demonstrated by light microscopy studies and measurement of sclerotic area. We conclude that: 1) MNS rats provide an animal model of long-lasting proteinuria characterized by an age-related increase in glomerular TXB2 production paralleled by progressive loss of renal structural integrity and function and by a secondary dyslipidemia; 2) pharmacological inhibition of glomerular TX-synthase attenuates the structural as well as the functional expression of kidney disease, without a primary effect on systemic blood pressure. These data are suggestive of an important modulating role of TXA2 in the progression of MNS renal disease.

Antihypertensive ergoline derivatives.

Novel ergolines were synthesized and screened in spontaneous hypertensive rats (SHR) with the aim of finding a new class of ergot related antihypertensives. Their prolactin inhibitory effect (measured as nidation inhibition in rats), acute toxicity (LD50) and interference with CNS function (Irwin test) were also evaluated as a measure of selectivity and safety. Modification of the C8 side-chain enhanced antihypertensive activity selectively, while the introduction of substituents in other positions of the ergoline skeleton generally yielded unfavourable results, either by decreasing selectivity or by increasing toxicity.

Cardiovascular effects of a new antihypertensive agent in several species.

The effects on blood pressure and heart rate of a new ergoline derivative, 2(R,S)-Cyano-3-(6-methylergolin-8 beta-yl)-propionamide (355/1057), were evaluated in different models of experimental hypertension as well as in normotensive rats, dogs and cats. Its interference with sympathetic neurotransmission was also studied in anaesthetized cats and dogs and in pithed rats. Dose-related hypotensive effects were found after single oral, intraduodenal and intravenous administration. In all the studied experimental models 355/1057 showed a prompt onset of action and a prolonged effect on blood pressure at low doses without substantially modifying heart rate. Some comparative results obtained with other commercially available antihypertensive agents are also reported. One month daily oral administration in SH-rats produced an antihypertensive effect persisting trough the entire experiment with no signs of tachyphylaxis. In anaesthetized dogs 355/1057 inhibited sthe pressor response elicited by bilateral carotid occlusion and in anaesthetized cats it reduced the response of the nictitating membrane elicited by electrical stimulation of both the pre- and post-ganglionic fibers but not by norepinephrine bolus injection.

beta Thalassemia associated with increased HB F production. Evidence for the existence of a heterocellular hereditary persistence of fetal hemoglobin (HPFH) determinant linked to beta thalassemia in a southern Italian population.

A family has been observed in which a beta thalassemia determinant is inherited over three generations together with high Hb F level (8-12%) and increased number of fetal-hemoglobin-containing-cells (F-cells). The values of red cell indices and globin chain synthesis ratios, yet typical of beta thalassemia, were significantly shifted to the normal values when compared with those of typical beta thalassemia heterozygotes belonging to the same family group. The occurrence in these individuals of a heterocellular hereditary persistence of fetal hemoglobin (HPFH) determinant and its linkage relationship with the beta thalassemia is discussed. In the third generation two adult individuals were beta thalassemia homozygotes having inherited a beta thalassemia determinant from one parent and a beta thalassemia together with the HPFH determinant from the other. They showed an extremely mild clinical condition, and 11-12 g/dl of mainly Hb F without having ever required blood transfusions. Virtually all the red cells were F-cells in both subjects. The importance of the coexistence of HPFH determinants capable of increasing the size of the F-cell population in patients affected by homozygous thalassemia is discussed, considering the sensible benefit which derives from enhanced Hb F production in this syndrome.