neurokinin-a and Dermatitis--Contact

This study addresses the hypothesis that the early symptoms of chemically induced skin irritation are neurally mediated. Several approaches were used to affect nerve transmission in adult Balb/c female mice. These included general anesthesia (i.e., sodium pentobarbital), systemic capsaicin treatment, and pretreatment with specific pharmacological antagonists of the neuropeptides substance P (SP) and neurokinin A (NKA). After these treatments, a strongly irritating dose of dinitrofluorobenzene (DNFB) was applied to the ear and its swelling was measured over several postexposure times as an index of tissue irritation. Ear swelling in Nembutal (30 mg/kg)-anesthetized mice was depressed 62 and 76% at 4 and 24 hr postexposure compared to DNFB-treated unanesthetized animals measured at the same time points. Multiple injections of capsaicin (cumulative dose 30 mg/kg) depressed DNFB-ear swelling relative to non-capsaicin, DNFB-treated controls by 15, 40 (ip), and 44 and 43% (sc) at 4 and 24 hr postexposure, respectively. In mice exposed to acute or multiple injections of the SP antagonist CP-96,345 before DNFB application, ear swelling was depressed (relative to DNFB-treated animals) by 64 and 36% (acute, sc, 10 mg/kg) and 91 and 88% (multiple, ip, cumulative 35 mg/kg) at 0.5 and 1 hr postexposure, respectively. Mice exposed to the NKA antagonist, SR 48968, alone and in combination with the SP antagonist CP-96,345 were also examined after DNFB application. Ear swelling was diminished in mice pretreated with the NKA antagonist (1.0 mg/kg) by 17, 24, 34, and 40% at 0.5, 1, 4, and 24 hr postexposure. When used in combination with the SP antagonist, DNFB-induced ear swelling was reduced by 95% compared to unantagonized, DNFB-exposed mice at the 0.5- and 1-hr time points and remained significantly depressed by 33 and 46% at 4 and 24 hr postexposure. Taken in concert, these data suggest that neuropeptides, especially the tachykinins SP and NKA, modulate the early stages of chemically induced skin irritation.

Topics: Administration, Cutaneous; Animals; Benzamides; Biphenyl Compounds; Capsaicin; Dermatitis, Contact; Dinitrofluorobenzene; Disease Models, Animal; Dose-Response Relationship, Drug; Ear, External; Female; Irritants; Mice; Mice, Inbred BALB C; Neurokinin A; Neuropeptides; Piperidines; Skin; Substance P; Synaptic Transmission

1. Measurement of plasma protein extravasation induced by the natural tachykinins following intradermal administration in rat skin indicated equipotency between substance P (SP), neurokinin A (NKA) and neurokinin B (NKB). The selective NK1 receptor agonist, [Sar9]SP sulphone was 10-100 times more potent than SP. The synthetic hexapeptide, septide, [pGlu6, Pro9]SP-(6-11), which has been proposed to act on a distinct NK1 receptor subtype/binding site was equipotent with [Sar9]SP sulphone. 2. The selective NK2 receptor agonist [beta Ala8]NKA(4-10) (0.1-1 nmol) and the selective NK3 receptor agonist, senktide (0.1-1 nmol) were both ineffective in producing oedema. The selective NK2 receptor antagonist, SR 48, 968 (0.3 mumol kg-1) had no significant inhibitory effects upon oedema induced by approximately equiactive doses of SP (0.2 nmol), septide (0.002 nmol), [Sar9]SP sulphone (0.002 nmol), or NKB (0.3 nmol). These results together suggest that neither NK2 nor NK3 receptors are involved in oedema formation in rat skin. 3. The non-peptide tachykinin NK1 receptor antagonist, RP 67,580 (1-3 mumol kg-1), inhibited plasma protein extravasation induced by septide (0.002 nmol) to a greater extent than that to SP (0.2 nmol). RP 67,580 (1 mumol kg-1) produced a significant inhibition of approximately 66% of the response to septide (0.002 nmol) only. Increasing the dose of RP 67,580 3 fold resulted in inhibition of the response to SP (0.2 nmol) and [Sar9]SP sulphone (0.002 nmol) by approximately 66% and 64% respectively with the response to septide being inhibited by approximately 70%. 4. Co-administration of the nitric oxide (NO) synthase inhibitor, NG-nitro-L-arginine methyl ester (L-NAME)(0.1 micromol) with the relevant tachykinin, resulted in a significant attenuation of the oedemaresponse to septide (0.1 nmol) producing only an approximate 56% inhibition of the response. The response to 0.2 nmol SP was unaffected whereas the response to a higher dose of 1 nmol was lowered byL-NAME but this did not reach significance.5. Degranulation of mast cells, achieved by pretreatment with compound 48/80 (5 mg kg-1) for 3 consecutive days, significantly inhibited the oedema responses to only high dose SP (1 nmol) and[Sar9SP sulphone (0.002 nmol). SP (0.2 nmol), septide (0.002 nmol), NKA (0.2 nmol) and NKB(0.3 nmol) were unaffected by this treatment.6. RP 67,580 (0.3-3 microM kg-1) inhibited oedema induced by both 0.002 nmol and 0.1 nmol of septide.When using equiactive doses o

Topics: Analgesics; Animals; Anti-Inflammatory Agents, Non-Steroidal; Blood Proteins; Capillary Permeability; Dermatitis, Contact; Dose-Response Relationship, Drug; Edema; Indoles; Isoindoles; Male; Neurokinin A; Neurokinin B; Neurokinin-1 Receptor Antagonists; Nitric Oxide Synthase; p-Methoxy-N-methylphenethylamine; Peptide Fragments; Pyrrolidonecarboxylic Acid; Rats; Rats, Wistar; Receptors, Neurokinin-1; Receptors, Neurokinin-2; Substance P

Neuropeptides in primary afferent neurons have been found to be engaged in the immediate type of hypersensitivity. However, their role in the delayed form of hypersensitivity is not yet established. The hypothesis that substance P (SP), neurokinin A (NKA), and calcitonin gene-related peptide (CGRP) are involved in delayed hypersensitivity was tested in oxazolone-induced, murine ear allergic contact dermatitis. Concentrations of immunoreactive SP, NKA, and CGRP were measured in extracts of the eczema ears (n = 26), whereas extracts of the opposite ears were used as controls. The SP, NKA, and CGRP contents in the treated ears were on the average 28% (p = 0.001), 32% (p = 0.004), and 15% (p = 0.016), respectively, lower than in the control ears. Lower peptide concentrations in the eczema ears indicate increased release of the peptides because the peptides are rapidly metabolized locally when released and only replenished by axonal transport from the cell bodies. Our results indicate that peptides released from primary afferent neurons play a role in the delayed type of hypersensitivity reactions.

Topics: Animals; Calcitonin Gene-Related Peptide; Dermatitis, Contact; Ear; Male; Mice; Mice, Inbred C57BL; Neurokinin A; Oxazoles; Oxazolone; Substance P; Tachykinins