Social interactions and olfactory cues are required for contagious itch in mice.

The phenomenon of contagious itch, observed in both humans and rodents, remains a topic of ongoing debate concerning its modulators and underlying pathways. This study delves into the relationship between contagious itch and familiar olfactory cues, a non-visual factor contributing to this intriguing behavior. Our findings showed that contagious itch in observer mice occurs during physical interaction with the cagemate itch-demonstrator but not with a stranger demonstrator or in a non-physical encounter condition. Notably, itch-experienced observer mice displayed an increased contagious itch behavior, highlighting the relevance of itch-associated memory in this phenomenon. Furthermore, anosmic observer mice, whether itch-naïve or itch-experienced, displayed no contagious itch behavior. These results demonstrate that the familiar olfactory cues, specifically cagemate body odors, are required for contagious itch behaviors in mice. In line with these behavioral findings, our study reveals increased activity in brain regions associated with olfaction, emotion, and memory during contagious itch, including the olfactory bulb, the amygdala, the hypothalamus, and the hippocampus, with this activity diminished in anosmic mice. In conclusion, our study unveils the critical role of familiar olfactory cues in driving contagious itch in mice, shedding light on the interplay between social factors, sensory perception, and memory in this phenomenon.

Losartan ointment attenuates imiquimod-induced psoriasis-like inflammation.

BACKGROUND: Psoriasis is a chronic skin condition associated with interleukin-23/interleukin-17 (IL-23/IL-17) pathway. Recent evidence declares that angiotensin II (Ang II) induces a potent IL-17-related inflammation. Meanwhile, Losartan, an angiotensin one receptor (AT1R) antagonist, attenuates the TH17-related responses. Therefore, we investigated the possible beneficial effects of topically applied Losartan1% ointment on imiquimod (IMQ)-induced psoriasis in mice. METHOD: Psoriasis was induced in mice consecutively for five days by topical IMQ on the shaved back. The IMQ-induced psoriasis was treated via topical administration of Losartan1% twice a day. The severity of skin inflammation was evaluated employing Psoriasis Area and Severity Index (PASI) scores. Subsequently, the skin samples were assessed using Baker's scoring system, stereological studies, and biochemical assessment with real-time PCR and immunohistochemistry. RESULTS: IMQ administration induced plaque-type psoriasis and skin inflammation. We characterized psoriatic lesions by hyperkeratosis, Munro abscess, rete ridges, and marked T-cell infiltrates. IMQ significantly increased epidermal volume, mRNA expression of IL-17a, IL-23, Ang II, AT1R, and TNF-α levels compared with the Placebo group. Topical administration of Losartan1% on IMQ-induced psoriasis significantly reduced the PASI scores and alleviated the erythema and scaling. The treatment significantly decreased the psoriatic thickness and dermal T-cell infiltration. Regarding biochemical assessment, Losartan1% considerably reduced the IMQ-induced increase of IL-17a, Ang II, and AT1R expression in the skin. CONCLUSION: Topical Losartan1% significantly alleviates psoriasis by reducing AT1R and IL-17a expression. Our results introduce AT1Rs as a promising therapeutic target in psoriasis and represent a link between angiotensin and TH17-related inflammation. However, the effects of AngII-AT1R systems on IL-17 signaling need to be confirmed by further investigations.