vasoactive-intestinal-peptide and Pulmonary-Edema

Excitatory amino acid toxicity, resulting from overactivation of N-methyl-D-aspartate (NMDA) glutamate receptors, is a major mechanism of neuronal cell death in acute and chronic neurological diseases. We have investigated whether excitotoxicity may occur in peripheral organs, causing tissue injury, and report that NMDA receptor activation in perfused, ventilated rat lungs triggered acute injury, marked by increased pressures needed to ventilate and perfuse the lung, and by high-permeability edema. The injury was prevented by competitive NMDA receptor antagonists or by channel-blocker MK-801, and was reduced in the presence of Mg2+. As with NMDA toxicity to central neurons, the lung injury was nitric oxide (NO) dependent: it required L-arginine, was associated with increased production of NO, and was attenuated by either of two NO synthase inhibitors. The neuropeptide vasoactive intestinal peptide and inhibitors of poly(ADP-ribose) polymerase also prevented this injury, but without inhibiting NO synthesis, both acting by inhibiting a toxic action of NO that is critical to tissue injury. The findings indicate that: (i) NMDA receptors exist in the lung (and probably elsewhere outside the central nervous system), (ii) excessive activation of these receptors may provoke acute edematous lung injury as seen in the "adult respiratory distress syndrome," and (iii) this injury can be modulated by blockade of one of three critical steps: NMDA receptor binding, inhibition of NO synthesis, or activation of poly(ADP-ribose) polymerase.

Topics: Animals; Arginine; Benzamides; Cyclic GMP; Enzyme Inhibitors; In Vitro Techniques; Lung; Lung Injury; Magnesium; Male; Models, Biological; N-Methylaspartate; NG-Nitroarginine Methyl Ester; Nitric Oxide; Nitric Oxide Synthase; Nitroarginine; Perfusion; Poly(ADP-ribose) Polymerase Inhibitors; Pulmonary Edema; Rats; Rats, Sprague-Dawley; Receptors, N-Methyl-D-Aspartate; Vasoactive Intestinal Peptide

Hyperpermeability is the crux of pathogenesis of sudden lung edema in many pulmonary disorders, especially in acute lung injury and acute respiratory distress syndrome (ARDS). Using our modified method for assessment of pulmonary vascular permeability, we observed the effects of xanthine with xanthine oxidase (X-XO) perfused in rat pulmonary artery and the protection of vasoactive intestinal polypeptide (VIP) against the injury of pulmonary vascular permeability. After addition of xanthine oxidase in the perfusate reservoir containing xanthine, 125I-albumin leak index (125I-ALI) was remarkably increased while peak airway pressure (Paw) showed no significant increase, and perfusion pressure of pulmonary artery (Ppa) and lung wet/dry weight ratio (W/D) were only slightly increased. Xanthine plus xanthine oxidase also increased thromboxane B2 (TX B2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in the perfusate. Treatment with VIP obviously reduced or totally prevented all signs of injury. Simultaneously, VIP also diminished or abolished the associated generation of arachidonate products. The results indicated that VIP has potent protective activity against injury of pulmonary vascular permeability and may be a physiological modulator of inflammatory damage to vascular endothelium associated with toxic oxygen metabolites.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Antioxidants; Capillary Permeability; Lung; Male; Pulmonary Edema; Rats; Rats, Sprague-Dawley; Thromboxane B2; Vasoactive Intestinal Peptide; Xanthine Oxidase; Xanthines

Hyperpermeability is a crux of pathogenesis of sudden lung edema in many pulmonary disorders, especially in acute lung injury and adult respiratory distress syndrome (ARDS). Using our modified method for assessment of pulmonary vascular permeability, we observed the effects of xanthine with xanthine oxidase (X-XO) perfused in rat pulmonary artery and the protection of vasoactive intestinal polypeptide (VIP) against the injury of pulmonary vascular permeability. After addition of xanthine oxidase in the perfusate reservoir containing xanthine, 125I-albumin leak index (125IALI) was remarkably increased while peak airway pressure (Paw) was not significantly increased, and perfusion pressure of pulmonary artery (Ppa) and lung wet/dry weight ratio (W/D) were only slightly increased. Xanthine plus xanthine oxidase also increased thromboxane B2 (TX B2) and 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha) in the perfusate. Treatment with VIP obviously reduced or totally prevented all signs of injury. Simultaneously, VIP also diminished or abolished the associated generation of arachidonate products. The results indicated that VIP has potent protective activity against injury of pulmonary vascular permeability and may be a physiological modulator of inflammatory damage to vascular endothelium associated with toxic oxygen metabolites.

Topics: 6-Ketoprostaglandin F1 alpha; Animals; Capillary Permeability; Free Radical Scavengers; Male; Pulmonary Artery; Pulmonary Edema; Rats; Rats, Sprague-Dawley; Thromboxane B2; Vasoactive Intestinal Peptide; Xanthine; Xanthine Oxidase; Xanthines

Acute, diffuse lung injury, the principal lesion in ARDS, is often refractory to treatment. Recently, pretreatment with several pulmonary vasodilators that increase cAMP levels: isoproterenol, terbutaline, theophylline, and prostacyclin, was found to reduce the severity of lung injury in animal models. We have investigated the possible modulation of HCl-induced pulmonary edema in rats by VIP, a lung neuropeptide with potent vasodilator and cAMP-producing properties. The lungs of rats were perfused in situ at 10 ml/min with Krebs-4% albumin solution, and ventilated at constant tidal volume (6.5 ml/kg). Peak airway pressure (PAW), mean pulmonary arterial pressure (PPA) were measured throughout the experiment, and wet to dry lung weight ratio (W/D), afterwards. All animals were observed for one hour. In 6 rats receiving HCl only, 0.2 N-HCl was instilled intratracheally at 2 ml/kg. Four rats received 2 ml/kg of physiological saline intratracheally as control. In 6 other animals, VIP was infused into the pulmonary artery at 1 micrograms/kg/min, beginning 10 minutes before HCl and for the rest of the experiment. Another 6 rats were pretreated with atrial natriuretic peptide (ANP, atriopeptin II) just like the VIP group. Lungs of saline control animals showed little or no chage in PAW or PPA. With HCl alone, PAW increased immediately and continued to rise for the rest of the hour, reaching 500% of basal value at 30 minutes. PPA increased by 68% and W/D by 74% compared to saline-instilled lungs. In the VIP + HCl group, all abnormalities were significantly reduced relative to the HCl group. The rise in PAW was attenuated by 79% (p less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)

Topics: Acute Disease; Animals; Burns, Chemical; Hydrochloric Acid; In Vitro Techniques; Lung Injury; Male; Pulmonary Edema; Rats; Rats, Inbred Strains; Vasoactive Intestinal Peptide