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Epidermal transient receptor potential vanilloid 1 in idiopathic small nerve fibre disease, diabetic neuropathy and healthy human subjects Aims: The transient receptor potential vanilloid 1 (TRPV1) plays an important role in mediating pain and heat. In painful neuropathies, intraepidermal TRPV1 nerve fibre expression is low or absent, suggesting that pain generated is not directly related to sensory nerve fibres. Recent evidence suggests that keratinocytes may act as thermal receptors via TRPV1. The aim was to investigate epidermal TRPV1 expression in patients with neuropathic conditions associated with pain. Methods and results: In a prospective study of distal small nerve fibre neuropathy (DISN; n = 13) and diabetic neuropathy (DN; n = 12) intraepidermal nerve fibre density was assessed using the pan axonal marker PGP 9.5 and epidermal TPVR1 immunoreactivity compared with controls (n = 9). Intraepidermal nerve fibres failed to show TRPV1 immunoreactivity across all groups. There was moderate and strong TRPV1 reactivity of epidermal keratinocytes in 41.8% and 6% for DISN, 32.9% and 2.9% for DN and 25.4% and 5.1% for controls, respectively. Moderate keratinocyte TRPV1 expression was significantly increased in DISN compared with controls (P = 0.01). Conclusion: Our study suggests that in human painful neuropathies, epidermal TRPV1 expression is mainly in keratinocytes.

Coumarins and its analogues have been widely used as chromophore in design of fluorescent probe, while less coumarin-based fluorescent probe was reported for detection of anion in water. In this article, coumarin-based fluorescent probes with salicylaldehyde functionality as recognition unit have been developed for selective detection of bisulfite anions in water. Four novel fluorescent probes were synthesized from 4-haloresorcinol in three steps. The chemoprobe exhibited selective response to bisulfite over other anions. Moreover, the detection mechanism was studied. Upon bisulfite added, the fluorescent intensity of the probes was enhanced highly due to the nucleophilic addition reaction of formyl group with bisulfite anion.