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To investigate the role of oxidative stress in itch-indicative scratching behavior in mice, and furthermore, to define the cellular and molecular mechanisms underlying oxidative stress-mediated itch.
Scratching behavior was induced by intradermal injection of the oxidants hydrogen peroxide (H2O2) or tert-butylhydroperoxide (tBHP) into the nape of the neck in mice. The mice were observed for 30 min.
Intradermal H2O2 (0.03%–1%) or tBHP (1–30 μmol) elicited robust scratching behavior, displaying an inverted U-shaped dose-response curve. Naloxone, an opioid receptor antagonist, but not morphine, largely suppressed the oxidant-induced scratching. Chlorpheniramine, a histamine H1 receptor antagonist, blocked histamine-but not oxidant-induced scratching, indicating the involvement of a histamine-independent mechanism in oxidant-evoked itch. Further, resiniferatoxin treatment abolished oxidant-induced scratching, suggesting an essential role of C-fibers. Notably, blockade of transient receptor potential subtype ankyrin 1 (TRPA1) with the selective TRPA1 antagonist HC-030031, or genetic deletion of Trpa1 but not Trpv1 (subfamily V, member 1) resulted in a profound reduction in H2O2-evoked scratching. Finally, systemic administration of the antioxidant Nacetyl-L-cysteine or trolox (a water-soluble vitamin E analog) attenuated scratching induced by the oxidants.
Oxidative stress by different oxidants induces profound scratching behavior, which is largely histamine- and TRPV1-independent but TRPA1-dependent. Antioxidants and TRPA1 antagonists may be used to treat human itch conditions associated with oxidative stress.
Tong Liu, Phone: +1-617-7328852, Fax: +1-617-7302801, Email: gro.srentrap@5uilt.
Ru-Rong Ji, Phone: +1-617-7328852, Fax: +1-617-7302801, Email: ude.dravrah.hwb.suez@ijrr.