pyrimidinones and Pruritus

To address the current trends of therapeutic mechanisms for treatment of allergic conjunctivitis (AC), based on topical antihistamines and mast cell stabilizers (MCS).. The antihistamine drug alcaftadine has H4 receptor inverse agonism, anti-inflammatory and MCS activities. The antihistamines levocabastine and azelastine are more effective than placebo in treatment of AC symptoms in randomized controlled trials (RCTs). The topical dual-action antihistamines/MCS olopatadine, azelastine, ketotifen, and epinastine are commonly used in Europe and in the United States for mild subtypes of AC. For the main symptoms of AC, ocular itch and conjunctival hyperemia, epinastine 0.05% was superior to placebo, but equal or more effective than olopatadine 0.1%, while the later was more effective than ketotifen. High concentration olopatadine 0.77% had longer duration of action, better efficacy on ocular itch, and a similar safety profile to low-concentration olopatadine 0.2%. The new formulas of topical dual-action agents present longer duration of action, leading to a decreased frequency of use.. The topical dual-action agents are the most effective agents treating signs and symptoms of mild forms of AC. There is superiority to the high-concentration olopatadine drug over other agents on ocular itch, with prolonged effect when used once-daily.

Topics: Administration, Ophthalmic; Anti-Allergic Agents; Benzazepines; Conjunctivitis, Allergic; Cromolyn Sodium; Dibenzazepines; Histamine Antagonists; Humans; Hyperemia; Imidazoles; Ketotifen; Nedocromil; Olopatadine Hydrochloride; Phthalazines; Piperidines; Pruritus; Pyridines; Pyrimidinones

Persistent itch is a common symptom of allergic contact dermatitis (ACD) and represents a significant health burden. The chemokine CXCL10 is predominantly produced by epithelial cells during ACD. Although the chemokine CXCL10 and its receptor CXCR3 are implicated in the pathophysiology of ACD, it is largely unexplored for itch and pain accompanying this disorder. Here, we showed that CXCL10 and CXCR3 mRNA, protein, and signaling activity were upregulated in the dorsal root ganglion after contact hypersensitivity (CHS), a murine model of ACD, induced by squaric acid dibutylester. CXCL10 directly activated a subset of cutaneous dorsal root ganglion neurons innervating the area of CHS through neuronal CXCR3. In behavioral tests, a CXCR3 antagonist attenuated spontaneous itch- but not pain-like behaviors directed to the site of CHS. Injection of CXCL10 into the site of CHS elicited site-directed itch- but not pain-like behaviors, but neither type of CXCL10-evoked behaviors was observed in control mice. These results suggest that CXCL10/CXCR3 signaling mediates allergic itch but not inflammatory pain in the context of skin inflammation. Thus, upregulation of CXCL10/CXCR3 signaling in sensory neurons may contribute to itch associated with ACD. Targeting the CXCL10/CXCR3 signaling might be beneficial for the treatment of allergic itch.

Topics: Acetamides; Animals; Anti-Allergic Agents; Cells, Cultured; Chemokine CXCL10; Dermatitis, Allergic Contact; Disease Models, Animal; Ganglia, Spinal; Male; Membrane Potentials; Mice; Mice, Inbred C57BL; Neurons; Pruritus; Pyrimidinones; Receptors, CXCR3; Receptors, G-Protein-Coupled; Signal Transduction; Skin; Up-Regulation

Calcitonin gene-related peptide (CGRP) is a classic molecular marker of peptidergic primary somatosensory neurons. Despite years of research, it is unknown whether these neurons are required to sense pain or other sensory stimuli. Here, we found that genetic ablation of CGRPα-expressing sensory neurons reduced sensitivity to noxious heat, capsaicin, and itch (histamine and chloroquine) and impaired thermoregulation but did not impair mechanosensation or β-alanine itch-stimuli associated with nonpeptidergic sensory neurons. Unexpectedly, ablation enhanced behavioral responses to cold stimuli and cold mimetics without altering peripheral nerve responses to cooling. Mechanistically, ablation reduced tonic and evoked activity in postsynaptic spinal neurons associated with TRPV1/heat, while profoundly increasing tonic and evoked activity in spinal neurons associated with TRPM8/cold. Our data reveal that CGRPα sensory neurons encode heat and itch and tonically cross-inhibit cold-responsive spinal neurons. Disruption of this crosstalk unmasks cold hypersensitivity, with mechanistic implications for neuropathic pain and temperature perception.

Topics: Animals; Calcitonin Gene-Related Peptide; Capsaicin; Cold Temperature; Diphtheria Toxin; Excitatory Postsynaptic Potentials; Female; Ganglia, Spinal; Gene Expression Regulation; Green Fluorescent Proteins; Histamine; Hot Temperature; In Vitro Techniques; Lectins; Male; Mice; Mice, Transgenic; Neurofilament Proteins; Pruritus; Pyrimidinones; Reaction Time; Receptors, Calcitonin Gene-Related Peptide; Sensory Receptor Cells; Sensory Thresholds; Skin; Sural Nerve; Time Factors; TRPM Cation Channels; TRPV Cation Channels; Ubiquitin Thiolesterase

Topics: Administration, Cutaneous; Antipruritics; Female; Humans; Lichen Sclerosus et Atrophicus; Middle Aged; Pruritus; Pyrimidinones; Treatment Outcome; TRPM Cation Channels; Vulvar Lichen Sclerosus