J Invest Dermatol. 2021 Apr 1;S0022-202X(21)01129-5. doi: 10.1016/j.jid.2021.03.015.Online ahead of print.

Mechanisms of broad-band ultraviolet B irradiation-induced itch in mice

Liang Cao ¹, Xueping Yue ¹, Yonghui Zhao ¹, Lixia Du ¹, Zili Xie ¹, Yi Yuan ¹, Sha Zhang ², Feng Li ², Jing Feng ³, Hongzhen Hu ¹

• PMID: 33812858
• DOI: 10.1016/j.jid.2021.03.015

Abstract

Although sunburn can produce severe uncontrollable itching, the underlying mechanisms of ultraviolet (UV) irradiation-induced itch are poorly understood because of a lack of experimental animal models of sunburn itch. Here we established a sunburn-related mouse model and found that Broad-band UVB (BB-UVB) irradiation elicited scratching but not wiping behavior in mice. By using a combination of live-cell Ca²⁺ imaging and quantitative RT-PCR on dorsal root ganglion (DRG) neurons, hematoxylin and eosin staining, immunofluorescence staining of skin preparations, behavioral testing, in combination with genetic and pharmacological approaches, we showed that TRPV1-positive DRG neurons but not mast cells are involved in BB-UVB irradiation-induced itch. Moreover, both genetic and pharmacological inhibition of TRPV1 function significantly alleviated BB-UVB irradiation-induced itch response. Collectively, our results suggest that BB-UVB irradiation evokes itch sensation in mice through promoting TRPV1 channel function in DRG neurons and provide potential therapeutic targets for sunburn-related itch.

Keywords: BB-UVB; Itch model; Sunburn-related itch; TRPV1.

Astrocytic STAT3 activation and chronic itch require IP3R1/TRPC-dependent Ca21 signals in mice

Miho Shiratori-Hayashi, PhD,a Chiharu Yamaguchi, MPharm,a Kazushi Eguchi, MPharm,a Yuto Shiraishi, BPharm,a Keita Kohno, BPharm,a Katsuhiko Mikoshiba, MD, PhD,b,c,d Kazuhide Inoue, PhD,e Motohiro Nishida, PhD,f,g and Makoto Tsuda, PhDa 

Background: Chronic itch is a debilitating symptom of inflammatory skin diseases, but the underlying mechanism is poorly understood. We have recently demonstrated that astrocytes in the spinal dorsal horn become reactive in models of atopic and contact dermatitis via activation of the transcription factor signal transducer and activator of transcription 3 (STAT3) and critically contribute to chronic itch. In general, STAT3 is transiently activated; however, STAT3 activation in reactive astrocytes of chronic itch model mice persistently occurs via an unknown mechanism.
Objective: We aimed to determine the mechanisms of persistent activation of astrocytic STAT3 in chronic itch conditions. Methods: To determine the factors that are required for persistent activation of astrocytic STAT3, Western blotting and calcium imaging with cultured astrocytes or spinal cord slices were performed. Thereafter, chronic itch model mice were used for genetic and behavioral experiments to confirm the role of the factors determined to mediate persistent STAT3 activation from in vitro and ex vivo experiments in chronic itch.

Results: IP3 receptor type 1 (IP3R1) knockdown in astrocytes suppressed IL-6–induced persistent STAT3 activation and expression of lipocalin-2 (LCN2), an astrocytic STAT3- dependent inflammatory factor that is required for chronic itch. IP3R1-dependent astrocytic Ca21 responses involved Ca21 influx through the cation channel transient receptor potential canonical (TRPC), which was required for persistent STAT3 activation evoked by IL-6. IL-6 expression was upregulated in dorsal root ganglion neurons in a mouse model of chronic itch. Dorsal root ganglion neuron–specific IL-6 knockdown, spinal astrocyte–specific IP3R1 knockdown, and pharmacologic spinal TRPC inhibition attenuated LCN2 expression and chronic itch.

Conclusion: Our findings suggest that IP3R1/TRPC channel– mediated Ca21 signals elicited by IL-6 in astrocytes are necessary for persistent STAT3 activation, LCN2 expression, and chronic itch, and they may also provide new targets for therapeutic intervention. (J Allergy Clin Immunol 2021;147:1341-53.)

Key words: Contact dermatitis, chronic itch, astrocytes, STAT3, lip- ocalin-2, Ca21 signal, IP3R1, TRPC, IL-6, primary afferent sensory neuron

Epithelia-sensory neuron crosstalk underlies cholestatic itch induced by lysophosphatidylcholine

Yong Chen, Zi-Long Wang, Michele Yeo, Qiao-Juan Zhang, Ana E. López- Romero, Hui-Ping Ding, Xin Zhang, Qian Zeng, Sara L. Morales-Lázaro, Carlene Moore, Ying-Ai Jin, Huang-He Yang, Johannes Morstein, Andrey Bortsov, Marcin Krawczyk, Frank Lammert, Manal Abdelmalek, Anna Mae Diehl, Piotr Milkiewicz, Andreas E. Kremer, Jennifer Y. Zhang, Andrea Nackley, Tony E. Reeves, Mei- Chuan Ko, Ru-Rong Ji, Tamara Rosenbaum, Wolfgang Liedtke

BACKGROUND & AIMS

Limited understanding of pruritus mechanisms in cholestatic liver diseases hinders development of anti-pruritic treatments. Previous studies implicated lysophosphatidic acid (LPA) as a potential mediator of cholestatic pruritus.

METHODS

Pruritogenicity of LPC, LPA’s precursor, was examined in naïve mice, cholestatic mice, and nonhuman primates. LPC’s pruritogenicity involving keratinocyte-TRPV4 was studied using genetic and pharmacological approaches, cultured keratinocytes, ion channel physiology and structural-computational modeling. Activation of pruriceptor-sensory neurons by microRNA-146a (miR-146a), secreted from keratinocytes, was identified by in-vitro and ex-vivo Ca²⁺-imaging assays. Sera from primary biliary cholangitis (PBC) patients were used for measuring the levels of LPC and miR-146a.

RESULTS

LPC was robustly pruritic in mice. TRPV4 in skin keratinocytes was essential for LPC-induced itch and itch in mice with cholestasis. 3D-structural modeling, site-directed mutagenesis and channel function analysis suggested a TRPV4 C-terminal motif for LPC binding and channel activation. In keratinocytes, TRPV4-activation by LPC induced extracellular release of miR-146a, which activated TRPV1⁺-sensory neurons to cause itch. Both LPC and miR-146a levels were elevated in sera of PBC patients with itch and correlated with itch intensity. Moreover, LPC and miR-146a were also increased in sera of cholestatic mice and elicited itch in nonhuman primates.

CONCLUSIONS

We identified LPC as a novel cholestatic pruritogen that induces itch through epithelia-sensory neuron crosstalk, whereby it directly activates skin keratinocyte-TRPV4, which rapidly release miR-146a to activate skin-innervating TRPV1⁺-pruriceptor sensory neurons. Our findings support the new concept of the skin, as a sensory organ, playing a critical role in cholestatic itch, beyond liver, peripheral sensory neurons and central neural pathways supporting pruriception.

The CysLT2R receptor mediates leukotriene C4-driven acute and chronic itch

ABSTRACT

Acute and chronic itch are burdensome manifestations of skinpathologies including allergic skin diseases and atopic dermatitis,but the underlying molecular mechanisms are not well understood.Cysteinyl leukotrienes (CysLTs), comprising LTC4,LTD4, and LTE4,areproduced by immune cells during type 2 inflammation. Here, weuncover a role for LTC4and its signaling through the CysLT receptor2 (CysLT2R) in itch.Cysltr2transcript is highly expressed in dorsalroot ganglia (DRG) neurons linked to itch in mice. We also detectedCYSLTR2in a broad population of human DRG neurons. Injection ofleukotriene C4(LTC4) or its nonhydrolyzable form NMLTC4,butnei-ther LTD4nor LTE4, induced dose-dependent itch but not pain be-haviors in mice. LTC4-mediated itch differed in bout duration andkinetics from pruritogens histamine, compound 48/80, and chloro-quine. NMLTC4-induced itch was abrogated in mice deficient forCysltr2or when deficiency was restricted to radioresistant cells. Itchwas unaffected in mice deficient forCysltr1,Trpv1, or mast cells(WShmice). CysLT2R played a role in itch in the MC903 mouse modelof chronic itch and dermatitis, but not in models of dry skin or com-pound 48/80- orAlternaria-induced itch. In MC903-treated mice,CysLT levels increased in skin over time, andCysltr2−/−mice showeddecreased itch in the chronic phase of inflammation. Collectively,our study reveals that LTC4acts through CysLT2R as its physiologicalreceptor to induce itch, and CysLT2R contributes to itch in a model ofdermatitis. Therefore, targeting CysLT signaling may be a promisingapproach to treat inflammatory itch.

Keywords: itch, neuroimmune, atopic dermatitis, skin, inflammation

Transl Psychiatry. 2019 Aug 5;9(1):189. doi: 10.1038/s41398-019-0525-3.

Fecal microbiota transplantation alleviated Alzheimer’s disease-like pathogenesis in APP/PS1 transgenic mice

Jing Sun ¹, Jingxuan Xu ², Yi Ling ¹, Fangyan Wang ³, Tianyu Gong ⁴, Changwei Yang ⁴, Shiqing Ye ⁴, Keyue Ye ⁴, Dianhui Wei ⁴, Ziqing Song ⁴, Danna Chen ⁴, Jiaming Liu ^5 6

• PMID: 31383855
• PMCID: PMC6683152
• DOI: 10.1038/s41398-019-0525-3

Abstract

Alzheimer’s disease (AD) is the most common dementia in the elderly. Treatment for AD is still a difficult task in clinic. AD is associated with abnormal gut microbiota. However, little is known about the role of fecal microbiota transplantation (FMT) in AD. Here, we evaluated the efficacy of FMT for the treatment of AD. We used an APPswe/PS1dE9 transgenic (Tg) mouse model. Cognitive deficits, brain deposits of amyloid-β (Aβ) and phosphorylation of tau, synaptic plasticity as well as neuroinflammation were assessed. Gut microbiota and its metabolites short-chain fatty acids (SCFAs) were analyzed by 16S rRNA sequencing and ¹H nuclear magnetic resonance (NMR). Our results showed that FMT treatment could improve cognitive deficits and reduce the brain deposition of amyloid-β (Aβ) in APPswe/PS1dE9 transgenic (Tg) mice. These improvements were accompanied by decreased phosphorylation of tau protein and the levels of Aβ40 and Aβ42. We observed an increases in synaptic plasticity in the Tg mice, showing that postsynaptic density protein 95 (PSD-95) and synapsin I expression were increased after FMT. We also observed the decrease of COX-2 and CD11b levels in Tg mice after FMT. We also found that FMT treatment reversed the changes of gut microbiota and SCFAs. Thus, FMT may be a potential therapeutic strategy for AD.