Conformationally restricted PACAP27 analogues incorporating type II/II' IBTM beta-turn mimetics. Synthesis, NMR structure determination, and binding affinity.

To probe the importance of a proposed beta-turn within residues S9-R12 of PACAP for recognition by VIP/PACAP receptors, compounds 1 and 2, two conformationally restricted analogues of PACAP27 incorporating respectively (S)- or (R)-IBTM as type II or II' beta-turn dipeptide mimetic at the Y10-S11 position, were synthesized. According to 1H NMR conformational analyses in aqueous solution and 30% TFE, both PACAP27 and the [S-IBTM(10,11)]PACAP27 analogue 1 adopt similar ordered structures. PACAP27 shows an N-terminal disordered region (residues H1-F6) and an alpha-helical conformation within segment T7-L27. For residues S9-R12, our data seem more compatible with a segment of the alpha-helix than with the beta-turn previously proposed for this fragment. In compound 1 the alpha-helix, also spanning T7-L27 residues, appears slightly distorted at the N-terminus relative to the native peptide. Although this distortion could lead to the marked decrease in binding affinity of this compound at the VIP/PACAP receptors, the lack of the Y10 side chain in analogues 1 and 2 could also significantly affect the binding of these compounds.

BDNF mediates the neuroprotective effect of PACAP-38 on rat cortical neurons.

In primary cultures from rat cerebral cortex, pituitary adenylate cyclase-activating polypeptide (PACAP-38) exerted a protective effect on cell death induced by the excitotoxin NMDA in neuron-enriched cultures and also on apoptotic cell death induced by serum deprivation in mixed neuronal-glial cultures. The neuroprotective effect was already observed at subnanomolar concentrations of PACAP and was slightly more pronounced against excitotoxic cell death. BDNF protein expression was reduced by NMDA and much more markedly by serum deprivation (approximately 28 and 93% reduction respectively). In both cellular injury conditions, the diminished BDNF expression was significantly prevented by PACAP. When purified neuronal cultures were preincubated with an antiserum anti-BDNF, at a concentration without any intrinsic effect on cell viability, the neuprotective effect of PACAP was no longer observed. The results suggest that the neuroprotective effect of PACAP-38 is mediated, at least in part, by preventing the suppressed expression of a neurotrophin essential for cortical neuron survival.

Inotropic and chronotropic effects of 4-(4'-n-butylaniline)-7,8- dimethoxy-5H-pyrimido[5,4-b]indole in guinea-pig atria.

Cardiotonic effect of 4-(4'-n-butylaniline)-7,8-dimethoxy- 5H-pyrimido[5,4-b]indole (B11) was investigated in isolated cardiac tissue preparations. The action of this agent on force of contraction, beating frequency and cyclic nucleotide phosphodiesterase (PDE) activity was studied. Amrinone was used for comparison. B11 produced concentration-dependent (5 x 10(6)-1 x 10(-4)M) positive inotropic and positive chronotropic responses in guinea-pig atrial tissues. The potency of B11 was greater than that of amrinone. The cardiotonic effects of B11 were not modified by beta-adrenoceptor blockade. Carbachol inhibited the positive inotropic effect of B11. The activity of B11 was increased in desensitized left atrial tissues. B11 inhibited the activities of PDE isoenzymes (type I, II, IV and V) from dog heart ventricle and PDE type IV from guinea-pig heart ventricle nonselectively. It is concluded that B11 possesses potent positive inotropic activity in guinea-pig atria, and the effect is probably mediated by a non-selective inhibition of PDE activity.

Inhibition of inflammation and gastric damage in rats by copper (II) complexes.

Anti-inflammatory activity and the effect on gastric damage of some copper(II) complexes has been investigated. In a preliminary screening the compounds were studied on the carrageenin paw edema model and two complexes showed inhibitory action on acute as well as subacute models of inflammation. This activity does not seem to be related to an inhibitory effect on prostaglandin biosynthesis or with leukocyte migration into inflamed tissue. These complexes showed an inhibitory effect on volume exudate in experimental pleurisy and on the production of superoxide anions. These inhibitory effects could explain, at least in part, their anti-inflammatory activity. Also, these complexes protected gastric mucosa against the damage induced by HCl and by oral administration of indometacin.

VIP suppression in the intestine and cerebral cortex following administration of VIP antiserum to newborn rats.

The administration of vasoactive intestinal peptide (VIP) antiserum to newborn rats significantly reduced the VIP content, both in the cerebral cortex and in intestinal epithelial cells. The decrease was observed at postnatal days 14 and 21 and also in 90 day-old animals. The neonatal treatment produced a significant increase in the density of high- and low-affinity binding sites for VIP in the cerebral cortex at post-natal days 14 and 21 whereas in the intestinal epithelial cells only the low-affinity binding sites were up-regulated at the same time points. VIP suppression induced by neonatal administration of the corresponding antiserum may represent a useful approach to further characterize the physiological role of this neuropeptide.

On the mechanism of the anti-inflammatory activity of some copper (II) complexes.

The mechanism of the antiinflammatory activity of three copper(II) complexes: tetrachlorocuprate(II) of bis(2.4.6-trimethylpyridinio), tetrachlorocuprate(II) of bis(2.4-dimethylpyridinio) and tetrachlorocuprate(II) of bis-pyridinio, has been investigated. The antiinflammatory activity does not seem to be related to an inhibitory effect on prostaglandin biosynthesis or with leukocyte migration into inflamed tissue. These complexes showed an inhibitory effect on volume exudate in experimental pleurisy. They showed also a potent inhibitory effect on the production of superoxide anions. These inhibitory effects could explain, at least in part, their antiinflammatory activity.

Anti-inflammatory activity of some copper(II) complexes.

Anti-inflammatory activity of some copper(II) neutral complexes and complexated salts on different animal models of inflammation has been investigated. In a preliminary screening 5 complexes were selected for a more extensive study based on their capacity inhibiting the rat hind paw edema induced by carrageenin. These selected complexes showed inhibitory action on acute and subacute inflammation with an activity degree higher than that of indometacin. They were also effective inhibitors of primary and secondary lesions in the adjuvant-induced arthritis, with an activity similar to phenylbutazone. These complexes had no topical anti-inflammatory effect.