Basic aspects of vasorelaxant and bronchodilating peptides in clinical use: urodilatin (INN: Ularitide), VIP, and PACAP

Transglutaminase-mediated polyamination of vasoactive intestinal peptide (VIP) Gln16 residue modulates VIP/PACAP receptor activity

Previous data showing an increase of receptor binding activity of [R16]VIP, a vasoactive intestinal peptide (VIP) structural analogue containing arginine at the position 16 of its amino acid sequence, have pointed out the importance of a positive charge at this site. Here, the functional characterization of three VIP polyaminated adducts (VIPDap, VIPSpd, and VIPSpm), obtained by a transglutaminase-catalysed reaction between the VIP Gln16 residue and 1,3-diaminopropane (Dap), spermidine (Spd), or spermine (Spm), is reported. Appropriate binding assays and adenylate cyclase enzymatic determinations have shown that these VIP adducts act as structural VIP agonists, both in vitro and in vivo. In particular, their IC50 and EC50 values of human and rat VIP/pituitary adenylate cyclase activating peptide (PACAP)1 and VIP/PACAP2 receptors indicate that VIPDap is a VIP agonist, with an affinity and a potency higher than that of VIP, while VIPSpd and VIPSpm are also agonists but with affinities lower than that of VIP. These findings suggest that the difference in adduct agonist activity reflects the differences in the positive charge and carbon chain length of the polyamine covalently linked with the VIP Gln16 residue. In addition, the data obtained strongly suggest that the length of polyamine carbon chain could be critical for the interaction of the agonist with its receptor, even though possible hydrophobic interaction cannot be ruled out. In vivo experiments on murine J774 macrophage cell cultures have shown the ability of these compounds to stimulate the inducible nitric oxide synthase activity at the transcriptional level.

Neuropeptides and neurotrophins in neonatal blood of children with autism or mental retardation

There has been little exploration of major biologic regulators of cerebral development in autism. In archived neonatal blood of children with autistic spectrum disorders (n = 69), mental retardation without autism (n = 60), or cerebral palsy (CP, n = 63) and of control children (n = 54), we used recycling immunoaffinity chromatography to measure the neuropeptides substance P (SP), vasoactive intestinal peptide (VIP), pituitary adenylate cyclase-activating polypeptide (PACAP), calcitonin gene-related peptide (CGRP), and the neurotrophins nerve growth factor (NGF), brain-derived neurotrophic factor (BDNF), neurotrophin 3 (NT3), and neurotrophin 4/5 (NT4/5). Neonatal concentrations of VIP, CGRP, BDNF, and NT4/5 were higher (ANOVA, all p values < 0.0001 by Scheffe test for pairwise differences) in children in the autistic spectrum and in those with mental retardation without autism than in control children. In 99% of children with autism and 97% with mental retardation, levels of at least one of these substances exceeded those of all control children. Concentrations were similar in subgroups of the autistic spectrum (core syndrome with or without mental retardation, other autistic spectrum disorders with or without mental retardation) and in the presence or absence of a history of regression. Among children with mental retardation, concentrations did not differ by severity or known cause (n = 11, including 4 with Down syndrome). Concentrations of measured substances were similar in children with CP as compared with control subjects. SP, PACAP, NGF, and NT3 were not different by diagnostic group. No measured analyte distinguished children with autism from children with mental retardation alone. In autism and in a heterogeneous group of disorders of cognitive function, overexpression of certain neuropeptides and neurotrophins was observed in peripheral blood drawn in the first days of life.

Hemodynamic effects of continuous urodilatin infusion: a dose-finding study

OBJECTIVE

To evaluate the effects of urodilatin (INN, ularitide) on systemic and renal hemodynamic parameters.

METHODS

Twenty healthy male subjects were included in this double-blind, randomized placebo-controlled trial and assigned to receive either continuous intravenous infusion of different doses of 7.5, 15, or 22.5 ng/kg body weight/min urodilatin or placebo over 300 minutes. Cardiac performance, systolic time intervals, and airway function were measured noninvasively. The effects on renal hemodynamic values were assessed with para-aminohippurate and inulin clearance techniques.

RESULTS

Urodilatin was well tolerated by all subjects at doses of 7.5 and 15 ng/kg/min. Infusion was stopped prematurely for the group that received 22.5 ng/kg/min urodilatin group because of systemic hypotensive responses with nausea and dizziness. Infusion of 15 ng/kg/min urodilatin significantly increased urine flow by a maximum of 165%, filtration fraction by 46%, renal resistance by 49%, and systemic vascular resistance by 45%. It decreased renal plasma flow by a maximum of 31% from baseline value. No change in cardiac inotropic function was detectable, but cardiac output decreased in all dose groups. Effects on glomerular filtration rate, forced expiratory volume, blood pressure, and pulse were not different from those with placebo.

CONCLUSION

Continuous infusion of 7.5 ng/kg/min and 15 ng/kg/min urodilatin exerts a significant increase in systemic and renal vascular resistance. Results of our experiments suggested that the therapeutic window for continuous urodilatin infusion is small and that doses higher than approximately 20 ng/kg/min urodilatin carry high risk for adverse drug reactions.