Melatonin attenuates acute and chronic itch in mice: the antioxidant and anti-inflammatory effects of melatonin receptors

Itch is a common symptom of skin diseases and significantly reduces patients' quality of life. Melatonin has anti-inflammatory and antioxidant effects. Our study examined the potential anti-itch effects of melatonin (N-acetyl-5-methoxytryptamine) in mice.

Collectively, our results indicate that melatonin attenuates acute and chronic itch, possibly via melatonin receptors, and its antioxidant, and anti-inflammatory effects in mice.

We detected the effects of melatonin and its receptors on acute and chronic itch by conducting itching behavioral experiments in male C57 mice. Reactive oxygen species (ROS) levels and calcium ion (Ca2+) mobilization during acute itching production were explored using flow cytometry and calcium imaging techniques. Melatonin expression in the serum of the chronic itch model mice was determined by enzyme-linked immunoassays. Hematoxylin and eosin staining show the effects of melatonin on skin thickness in a chronic itch model. Cytokine and chemokine levels were determined by quantitative polymerase chain reaction.

We discovered that compound 48/80 (C48/80)- and chloroquine (CQ)-induced scratching were significantly decreased by intraperitoneal (i.p), intradermal, and intrathecal administration of melatonin in a dose-dependent manner in mice, and the co-administration of melatonin receptor antagonists abolished the anti-itch effects of i.d melatonin. The incubation of melatonin significantly decreased the intracellular ROS levels induced by C48/80 and CQ in cultured ND7/23 cells from a mouse x rat hybridoma nerve as neuron. Melatonin inhibited intracellular Ca2+ increases induced by CQ (but not C48/80) in cultured dorsal root ganglia (DRG) neurons. Melatonin (50 mg/kg i.p) attenuated imiquimod (IMQ)- or acetone and diethyl ether followed by acetone-ether-water (AEW)-induced chronic itch and epidermal hyperplasia in mice. Finally, melatonin treatment reduced the IMQ-induced expression of ST2 and interleukin-33 (IL-33) or the AEW-induced expression of interleukin 31 (IL-31) and interleukin 31 receptor A (IL-31 RA) in the mice. Conclusions: Collectively, our results indicate that melatonin attenuates acute and chronic itch, possibly via melatonin receptors, and its antioxidant, and anti-inflammatory effects in mice.