Editorial [Hot-Topic: Anti-inflammatory and Anti-Allergy Functions of Capsaicin in Association with its Actions on Primary Sensory Neurons (Guest Editor: Akio Hiura & Gabor Jancso)]

Capsaicin and its analogs induce anti-inflammatory and anti-allergic functions as well as causing inflammation and allergy, principally acting on the small primary sensory neurons. This special issue is focused on capsaicin-sensitive (chemo-sensitive) somatic and visceral C-fibers responsible for inflammation and allergy, resulting in the trigger of hyperalgesia, headache, airway sensitivity (cough and hypersensitivity), and itching sensation. Especially, non Ca++-selective, a molecular integrator of nociception, TRPV1 and TRPA1 receptors are highlighted to explain the relationships between inflammatory diseases and efferent functions of chemo-sensitive C fiber terminals. Furthermore, causal interactions (autocrine and paracrine functions) in milieu of C fiber terminals and mast cells are considered for inflammation and allergy in the itch. The direct or indirect mediators participating in inflammation and allergy, such as neuropeptids (especially, calcitonin gene-related peptide), decomposed neuropeptids by protease (their protease-activated receptors as well), prostaglandins, histamine, growth factors, nuclear factor-kappa B (NF-κB) and some cytokines are brought up for discussion of the complicated vital phenomenon. Vanilloid agonists, exerting anti-nociceptive, anti-allergic and anti-inflammatory agents, are surveyed from experimental studies of the topical, perineural and subarachnoidal applications for their available therapeutic use.