Anticonvulsant activity of a nonpeptide galanin receptor agonist

Galanin is a neuropeptide with a wide variety of biological functions, including that of a strong endogenous anticonvulsant. No nonpeptide ligands, capable of activating galanin receptors, are available today. Based on known pharmacophores of galanin, a combinatorial library was designed, synthesized, and screened at the rat hippocampal galanin receptor. A low molecular weight galanin receptor agonist, 7-((9-fluorenylmethoxycarbonyl)cyclohexylalanyllysyl)amino-4-methylcoumarin (galnon) was found to displace (125)I-galanin with micromolar affinity at Bowes cellular and rat hippocampal membranes. Autoradiographic binding assay on rat spinal cord sections confirmed the ability of galnon to displace (125)I-galanin from its binding sites. Galnon inhibited adenylate cyclase activity, suggesting an agonist action at galanin receptors. When injected i.p. galnon reduced the severity and increased the latency of pentylenetetrazole-induced seizures in mice and reversed the proconvulsant effects of the galanin receptor antagonist M35, injected into a lateral ventricle. Intrahippocampal injection of galnon also shortened the duration of self-sustaining status epilepticus in rats, confirming its agonist properties in vivo. Pretreatment of rats with antisense peptide nucleic acid targeted to galanin receptor type 1 mRNA abolished the effect of galnon, suggesting mediation of its anticonvulsant properties through this receptor subtype. These findings introduce a systemically active nonpeptide galanin agonist anticonvulsant.     

Structure-function relationships in the regulation of energy transfer between mitochondria and ATPases in cardiac cells

The present study discusses the role of structural organization of cardiac cells in determining the mechanisms of regulation of oxidative phosphorylation and interaction between mitochondria and ATPases. In permeabilized adult cardiomyocytes, the apparent K_m (Michaelis-Menten constant) for ADP in the regulation of respiration is far higher than in mitochondria isolated from the myocardium. Respiration of mitochondria in permeabilized cardiomyocytes is effectively activated by endogenous ADP produced by ATPases from exogenous ATP, and the activation of respiration is associated with a decrease in the apparent K_m for ATP in the regulation of ATPase activity compared with this parameter in the absence of oxidative phosphorylation. It has also been shown that a large fraction of the endogenous ADP stimulating respiration remains inaccessible for the exogenous ADP trapping system, consisting of pyruvate kinase and phosphoenolpyruvate, unless the mitochondrial structures are modified by controlled proteolysis. These data point to the endogenous cycling of adenine nucleotides between mitochondria and ATPases. Accordingly, the current hypothesis is that in cardiac cells, mitochondria and ATPases are compartmentalized into functional complexes (ie, intracellular energetic units [ICEUs]), which appear to represent a basic pattern of organization of energy metabolism in these cells. Within the ICEUs, the mitochondria and ATPases interact via different routes: creatine kinase-mediated phosphoryltransfer; adenylate kinase-mediated phosphoryltransfer; and direct ATP and ADP channelling. The function of ICEUs changes not only after selective proteolysis, but also during contraction of cardiomyocytes caused by an increase in cytosolic Ca²⁺ concentration up to micromolar levels. In these conditions, the apparent K_m for exogenous ADP and ATP in the regulation of respiration markedly decreases, and more ADP becomes available for the exogenous pyruvate kinase-phosphoenolpyruvate system, which indicates altered barrier functions of the ICEUs. Thus, structural changes transmitted from the contractile apparatus to mitochondria clearly participate in the regulation of mitochondrial function due to alterations in localized restriction of the diffusion of adenine nucleotides. The importance of strict structural organization in cardiac cells emerged drastically from experiments in which the regulation of mitochondrial respiration was assessed in a novel cardiac cell line, that is, beating and nonbeating HL-1 cells. In these cells, the mitochondrial arrangement is irregular and dynamic, whereas the sarcomeric structures are either absent (in nonbeating HL-1 cells) or only rarely present (in beating HL-1 cells). In parallel, the apparent K_m for exogenous ADP in the regulation of respiration was much lower than that in permeabilized primary cardiomyocytes, and trypsin treatment exerted no impact on the low K_m value for ADP, in contrast to adult cardiomyocytes where it caused a marked decrease in this parameter. The HL-1 cells were also characterized by the absence of direct exchange of adenine nucleotides. The results further support the concept that the ICEUs in adult cardiomyocytes are products of complex structural organization developed to create the most optimal conditions for effective energy transfer and feedback between mitochondria and ATPases.     

Cyclooxygenase inhibition improves endothelium-dependent vasodilatation in patients with chronic renal failure.

BACKGROUND: Some studies have demonstrated beneficial effects of L-arginine as a substrate for nitric oxide synthesis, and diclofenac as an inhibitor of cyclooxygenase (COX)-derived vasoconstrictive agents on vascular responses in humans during several pathological conditions. The aim of the present study was to investigate the acute effects of L-arginine and diclofenac on endothelium-dependent vasodilatation (EDV) and endothelium-independent vasodilatation (EIDV) in patients with chronic renal failure (CRF). METHODS: Effects of L-arginine and diclofenac on EDV and EIDV were measured in 15 patients with CRF and in 15 healthy controls by means of forearm blood flow measurements with venous occlusion plethysmography during local intra-arterial infusions of methacholine (2 and 4 micro g/min evaluating EDV) and sodium nitroprusside (5 and 10 micro g/min evaluating EIDV). RESULTS: L-Arginine infusion increased methacholine-induced vasodilatation both in patients with CRF and healthy controls. Diclofenac infusion increased methacholine-induced vasodilatation only in patients with CRF. There was no significant change in nitroprusside-induced vasodilatation after L-arginine and diclofenac infusions both in patients with CRF and healthy controls. CONCLUSIONS: These results suggest that COX inhibition reduces the levels of a prostanoid-derived vasoconstrictive agent contributing to the impaired EDV in patients with CRF, while in this age group L-arginine improves EDV regardless of renal function.     

Association of in utero exposure to maternal smoking with reduced semen quality and testis size in adulthood: a cross-sectional study of 1,770 young men from the general population in five European countries

Between 1996 and 1999, the authors invited all young men from five European countries who were undergoing compulsory medical examination for possible military service to participate in a study on male reproductive health. The participation rate was 19% in two cities in Denmark (n = 889), 17% in Oslo, Norway (n = 221), 13% in Turku, Finland (n = 313), 14% in Kaunas, Lithuania (n = 157), and 19% in Tartu, Estonia (n = 190). Each man provided a semen sample, was examined by a physician, and, in collaboration with his mother, completed a questionnaire about general and reproductive health, current smoking habits, and exposure to smoking in utero. After adjustment for confounding factors, men exposed to smoking in utero had a reduction in sperm concentration of 20.1% (95% confidence interval (CI): 6.8, 33.5) and a reduction in total sperm count of 24.5% (95% CI: 9.5, 39.5) in comparison with unexposed men. Percentages of motile and morphologically normal sperm cells were 1.85 (95% CI: 0.46, 3.23) and 0.64 (95% CI: -0.02, 1.30) percentage points lower, respectively, among men exposed in utero, and exposed men had a 1.15-ml (95% CI: 0.66, 1.64) smaller testis size. The associations were present when data from the study centers were analyzed separately (though not in Lithuania, where only 1% of mothers smoked during pregnancy), although the strength of the association varied. Maternal smoking may have long-term implications for the reproductive health of the offspring. This is another good reason to advise pregnant women to avoid smoking.     

<Emphasis Type="Italic">N-acetyltransferase 8</Emphasis>, a positional candidate for blood pressure and renal regulation: resequencing,association and <Emphasis Type="Italic">in silico</Emphasis> study

Background  

Kidneys have an important function in blood pressure (BP) regulation and elevated BP may lead to kidney failure. Chr2p12-p13 region linked to BP traits in multiple studies harbours a potential candidate for BP and renal function, N-acetyltransferase 8 (NAT8) expressed in embryonic and adult kidney and associated with nephrotoxicity response.