Steroids regulate cell proliferation, tissue development, and cell signaling via two pathways: a nuclear receptor mechanism and genome-independent signaling. Sperm activation, egg maturation, and steroid-induced anesthesia are executed via the latter pathway, the key components of which remain unknown. Here, we present characterization of the human sperm progesterone receptor that is conveyed by the orphan enzyme α/β hydrolase domain–containing protein 2 (ABHD2). We show that ABHD2 is highly expressed in spermatozoa, binds progesterone, and acts as a progesterone-dependent lipid hydrolase by depleting the endocannabinoid 2-arachidonoylglycerol (2AG) from plasma membrane. The 2AG inhibits the sperm calcium channel (CatSper), and its removal leads to calcium influx via CatSper and ensures sperm activation. This study reveals that progesterone-activated endocannabinoid depletion by ABHD2 is a general mechanism by which progesterone exerts its genome-independent action and primes sperm for fertilization.

Chronic itch remains a highly prevalent disorder with limited treatment options. Most chronic itch diseases are thought to be driven by both the nervous and immune systems, but the fundamental molecular and cellular interactions that trigger the development of itch and the acute-to-chronic itch transition remain unknown. Here, we show that skin-infiltrating neutrophils are key initiators of itch in atopic dermatitis, the most prevalent chronic itch disorder. Neutrophil depletion significantly attenuated itch-evoked scratching in a mouse model of atopic dermatitis. Neutrophils were also required for several key hallmarks of chronic itch, including skin hyperinnervation, enhanced expression of itch signaling molecules, and upregulation of inflammatory cytokines, activity-induced genes, and markers of neuropathic itch. Finally, we demonstrate that neutrophils are required for induction of CXCL10, a ligand of the CXCR3 receptor that promotes itch via activation of sensory neurons, and we find that that CXCR3 antagonism attenuates chronic itch.

Sphingosine-1-phosphate (S1P) plays important roles as a signaling lipid in a variety of physiological and pathophysiological processes. S1P signals via a family of G protein-coupled receptors (S1P 1–5 ) and intracellular targets. Here, we report on photoswitchable analogs of S1P and its precursor sphingosine, respectively termed PhotoS1P and PhotoSph . PhotoS1P enables optical control of S1P 1–3 , shown through electrophysiology and Ca 2+ mobilization assays. We evaluated PhotoS1P in vivo , where it reversibly controlled S1P 3 -dependent pain hypersensitivity in mice. The hypersensitivity induced by PhotoS1P is comparable to that induced by S1P. PhotoS1P is uniquely suited for the study of S1P biology in cultured cells and in vivo because it exhibits prolonged metabolic stability compared to the rapidly metabolized S1P. Using lipid mass spectrometry analysis, we constructed a metabolic map of PhotoS1P and PhotoSph . The formation of these photoswitchable lipids was found to be light-dependent, providing a novel approach to optically probe sphingolipid biology.

Itch triggers scratching, a behavioural defence mechanism that aids in the removal of harmful irritants and parasites1. Chemical itch is triggered by many endogenous and exogenous cues, such as pro-inflammatory histamine, which is released during an allergic reaction1. Mechanical itch can be triggered by light sensations such as wool fibres or a crawling insect2. In contrast to chemical itch pathways, which have been extensively studied, the mechanisms that underlie the transduction of mechanical itch are largely unknown. Here we show that the mechanically activated ion channel PIEZO1 (ref. 3) is selectively expressed by itch-specific sensory neurons and is required for their mechanically activated currents. Loss of PIEZO1 function in peripheral neurons greatly reduces mechanically evoked scratching behaviours and both acute and chronic itch-evoked sensitization. Finally, mice expressing a gain-of-function Piezo1 allele4 exhibit enhanced mechanical itch behaviours. Our studies reveal the polymodal nature of itch sensory neurons and identify a role for PIEZO1 in the sensation of itch.

Sphingosine 1-phosphate (S1P) is a bioactive signaling lipid associated with a variety of chronic pain and itch disorders. S1P signaling has been linked to cutaneous pain, but its role in itch has not yet been studied. Here, we find that S1P triggers itch and pain in male mice in a concentration-dependent manner, with low levels triggering acute itch alone and high levels triggering both pain and itch. Ca imaging and electrophysiological experiments revealed that S1P signals via S1P receptor 3 (S1PR3) and TRPA1 in a subset of pruriceptors and via S1PR3 and TRPV1 in a subset of heat nociceptors. Consistent with these findings, S1P-evoked itch behaviors are selectively lost in mice lacking TRPA1, whereas S1P-evoked acute pain and heat hypersensitivity are selectively lost in mice lacking TRPV1. We conclude that S1P acts via different cellular and molecular mechanisms to trigger itch and pain. Our discovery elucidates the diverse roles that S1P signaling plays in somatosensation and provides insight into how itch and pain are discriminated in the periphery. Itch and pain are major health problems with few effective treatments. Here, we show that the proinflammatory lipid sphingosine 1-phosphate (S1P) and its receptor, S1P receptor 3 (S1PR3), trigger itch and pain behaviors via distinct molecular and cellular mechanisms. Our results provide a detailed understanding of the roles that S1P and S1PR3 play in somatosensation, highlighting their potential as targets for analgesics and antipruritics, and provide new insight into the mechanistic underpinnings of itch versus pain discrimination in the periphery.

These authors contributed equally and order determined by coin toss. Abstract 1Chronic itch remains a highly prevalent disorder with limited treatment options. Most chronic itch 2 diseases are thought to be driven by both the nervous and immune systems, but the 3 fundamental molecular and cellular interactions that trigger the development of itch and the 4 acute-to-chronic itch transition remain unknown. Here, we show that skin-infiltrating neutrophils 5are key initiators of itch in atopic dermatitis, the most prevalent chronic itch disorder. Neutrophil 6 depletion significantly attenuated itch-evoked scratching in a mouse model of atopic dermatitis. 7Neutrophils were also required for several key hallmarks of chronic itch, including skin 8 hyperinnervation, enhanced expression of itch signaling molecules, and upregulation of 9 inflammatory cytokines, activity-induced genes, and markers of neuropathic itch. Finally, we 10 demonstrate that neutrophils are required for induction of CXCL10, a ligand of the CXCR3 11 receptor that promotes itch via activation of sensory neurons, and we find that that CXCR3 12 antagonism attenuates chronic itch. 13 14Introduction 15 Chronic itch is a debilitating disorder that affects millions of people worldwide. 1-3 It is a symptom 16 of a number of skin diseases and systemic disorders, as well as a side effect of a growing list of 17 medications. Like chronic pain, chronic itch can be a disease in and of itself. 4-6 Unlike acute itch, 18 which can facilitate removal of crawling insects, parasites, or irritants, persistent scratching in 19chronic itch disorders has no discernable benefit; scratching damages skin, leading to 20 secondary infection, disfiguring lesions, and exacerbation of disease severity. 2,7,8 The most 21 common chronic itch disorder is atopic dermatitis (AD; commonly known as eczema), which 22 affects fifteen million people in the United States alone. 9 Severe AD can trigger the atopic 23 march, where chronic itch and inflammation progress to food allergy, allergic rhinitis, and 24 asthma. 9,10 25 26Little is known about the underlying mechanisms that drive chronic itch pathogenesis. As such, 27 studies of human chronic itch disorders have sought to identify candidate mechanisms of 28 disease progression. A number of studies have identified biomarkers and disease genes in itchy 29 human AD lesions. [11][12][13][14][15] Indeed, a recent study compared the transcriptomes of healthy skin to 30 itchy and non-itchy skin from psoriasis and AD patients, revealing dramatic changes in 31 expression of genes associated with cytokines, immune cells, epithelial cells, and sensory 32 neurons. 16 However, due to the difficulty in staging lesion development and obtaining staged 33 samples from patients, there is currently no temporal map of when individual molecules and cell 34 types contribute to chronic itch pathogenesis. Furthermore, the use of human patient data does 35 not allow for rigorous mechanistic study of how disease genes contribute to chronic itch. To this 36 end,...

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Somatosensory neurons mediate responses to diverse mechanical stimuli, from innocuous touch to noxious pain. While recent studies have identified distinct populations of A mechanonociceptors (AMs) that are required for mechanical pain, the molecular underpinnings of mechanonociception remain unknown. Here, we show that the bioactive lipid sphingosine 1-phosphate (S1P) and S1P Receptor 3 (S1PR3) are critical regulators of acute mechanonociception. Genetic or pharmacological ablation of S1PR3, or blockade of S1P production, significantly impaired the behavioral response to noxious mechanical stimuli, with no effect on responses to innocuous touch or thermal stimuli. These effects are mediated by fast-conducting A mechanonociceptors, which displayed a significant decrease in mechanosensitivity in S1PR3 mutant mice. We show that S1PR3 signaling tunes mechanonociceptor excitability via modulation of KCNQ2/3 channels. Our findings define a new role for S1PR3 in regulating neuronal excitability and establish the importance of S1P/S1PR3 signaling in the setting of mechanical pain thresholds.