dynorphin-(2-17) and Edema

Dynorphin A (Dyn A) is a 17-residue opioid peptide derived from prodynorphin precursors found in mammalian tissues. Removal of Tyr1 from Dyn A produces a peptide that is more potent than Dyn A in attenuating the acute phase of the inflammatory response, as measured by inhibition of heat-induced edema in the anesthetized rat's paw (exposure to 58 degrees C water for 1 min). Dyn A(2-17), however, no longer interacts with opioid receptors. It was postulated that the non-opioid anti-inflammatory actions of Dyn A(2-17) may reside in Dyn A(6-12); that is, Arg-Arg-Ile-Arg-Pro-Lys-Leu. here we report on the activities of Dyn A(6-12) analogs modified by substitutions on the N terminus, by single N-methyl substitution and by single replacement of residues by alanine. The results indicated that the minimal sequence required for an anti-edema ED50 of <1.0 micromol/kg i.v. was anisoyl-Arg6-Arg7-Xaa8-Arg9-Pro10)-Xaa11-+ ++Xaa12-NH2. A prototype, p-anisoyl-[D-Leu12] Dyn A(6-12)-NH2, with an ED50 of 0.20 micromol/kg i.v. compared to an ED50 of 0.08 micromol/kg i.v. for Dyn A(2-17), was selected for further tests of biological activity. This analog, like Dyn A(2-17), lowered blood pressure in anesthetized rats. In a model of neurogenic inflammation, produced by antidromic stimulation of the vagus in the anesthetized rat, p-anisoyl-[D-Leu12] Dyn A(6-12)-NH2, 0.23 micromol/kg i.v., attenuated the negativity of tracheal tissue interstitial pressure (Pif), which normally develops after nerve stimulation. Modulation of interstitial pressure may be the mechanistic basis for the anti-edema properties of these Dyn A(6-12) analogs.

Topics: Animals; Anti-Inflammatory Agents, Non-Steroidal; Dynorphins; Edema; Hindlimb; Hot Temperature; Male; Peptide Fragments; Rats; Rats, Sprague-Dawley

Dynorphin A (DYN) peptides, administered into the central nervous system, have produced inconsistent analgesic actions in tests using thermal stimuli. This study examined antinociceptive effects of intravenous and intraplantar DYN-(2-17) against noxious pressure in rats with Freund's adjuvant-induced unilateral hindpaw inflammation. The effects of DYN-(2-17) were compared to those of the opioid agonists morphine. (D-Ala2,N-Methyl-Phe4,Gly-ol5)-enkephalin (DAMGO) and DYN-(1-17). Intravenous DYN-(2-17) (0.188-10 mg/kg) produced dose-dependent elevations of paw pressure thresholds in inflamed and in non-inflamed paws. These effects were similar in magnitude to those of subcutaneous morphine (2 mg/kg), at doses of 0.375-1.5 mg/kg they were significantly greater on the inflamed (right) than on the non-inflamed (left) paw, and they were not reversible by intravenous naloxone (1-10 mg/kg). Intraplantar Dyn-(2-17)(0.001-0.3 mg) was ineffective, whereas both intraplantar DYN-(1-17)(0.15-0.3 mg) and DAMGO (0.008-0.016 mg) produced dose-dependent and naloxone-reversible elevations of paw pressure thresholds. The intraplantar injection of both Dyn peptides produced a transient increase in the volume of non-inflamed paws. These findings suggest that intravenous DYN-(2-17) produces possibly centrally mediated, non-opioid antinociceptive effects against noxious pressure. At certain doses these effects are more potent in inflamed than in non-inflamed paws. In contrast to the opioid peptides DYN-(1-17) and DAMGO, DYN-(2-17) does not appear to have no peripheral antinociceptive actions.

Topics: Analgesics; Analgesics, Opioid; Animals; Dynorphins; Edema; Enkephalin, Ala(2)-MePhe(4)-Gly(5)-; Enkephalins; Foot; Inflammation; Male; Nociceptors; Peptide Fragments; Rats; Rats, Wistar

In an earlier study, dynorphin A(1-13) [Dyn A(1-13)] was shown to inhibit heat-induced edema in the anesthetized rat's paw but the potency of this action was low, with effective doses in the range of 3-4 mg/kg i.v. In this study, Dyn A and related fragments were tested. Thermal edema was elicited in anesthetized male albino rats by immersion of the hindpaw in 58 degrees C water for 1 min. The median effective dose (ED50 and 95% confidence limits) in mg/kg i.v. for inhibition of edema were: Dyn A, Dyn A(2-17), and Dyn A(1-13), 1.7 (1.2-2.4), 0.15 (0.09-0.24), and 3.2 (1.9-5.5), respectively. The ED50 values of [D-Ala2]Dyn A, [D-Ala2]Dyn A(2-17), and [D-Ala2]Dyn A(2-17)-amide were found to be 0.92 (0.40-2.10), 1.25 (0.60-2.63), and 0.65 (0.36-1.16) mg/kg i.v., respectively. Dyn A(2-17), 0.5 mg/kg i.v., also inhibited pulmonary edema produced by i.v. injection of epinephrine. The anti-edema action of Dyn A(2-17) was not blocked by naloxone, an opioid receptor antagonist, or dependent on the hypotensive action of this peptide. It is postulated that the antiedema activity of Dyn A resides in the core fragment Dyn A(6-12). Two peptides, N-acetyl-Dyn A(6-12)-amide and N-acetyl-[D-Leu12]Dyn A(6-12)-amide, were synthesized and, when tested, were effective in reducing thermal edema with ED50 values of 1.4 (0.6-3.7) and 2.2 (1.2-4.1) mg/kg i.v., respectively.

Topics: Amino Acid Sequence; Animals; Dynorphins; Edema; Hindlimb; Hot Temperature; Male; Molecular Sequence Data; Peptide Fragments; Rats; Rats, Sprague-Dawley