ABSTRACT
Keratinocytes are pivotal cells in the pathogenesis of atopic dermatitis (AD) as much as Th2 cells. In this sense, regulation of pro-inflammatory features of keratinocytes might be useful for AD patients. P2X7R-mediated activation of NLRP3 inflammasome (N3I) in keratinocytes and myeloid cells plays crucial roles in AD. Nonetheless, inhibition of P2X7R has not been feasible because of polymorphisms and ubiquitous expression of P2X7R. Here, we report that GPCR19 colocalizes with P2X7R, and a GPCR19 agonist (taurodeoxycholate [TDCA]) inhibits the activation of P2X7R. Noncistronically, TDCA inhibits NF-kB activation via the adenylate cyclase-PKA pathway and BzATP-mediated Ca++ mobilization. Cistronically, TDCA suppresses the expression of P2X7R and N3I components in keratinocytes. NLRP3 oligomerization and the production of mature IL-1ß and IL-18 was suppressed by TDCA treatment in keratinocytes. Topical TDCA treatment ameliorates proinflammatory features of AD in mice induced by DNCB, MC903, or oxazolone. Taken together, a GPCR19 agonist such as TDCA might inhibit P2X7R-mediated N3I activation of keratinocytes, which is crucial for the pathogenesis of AD.
Subject(s)
Dermatitis, Atopic , Mice , Animals , Dermatitis, Atopic/drug therapy , NLR Family, Pyrin Domain-Containing 3 Protein/metabolism , Mice, Inbred BALB C , Keratinocytes/metabolism , Inflammasomes/metabolism , Cytokines/metabolismABSTRACT
Amyloid ß (Aß) and/or ATP activate the NLRP3 inflammasome (N3I) via P2X7R in microglia, which is crucial in neuroinflammation in Alzheimer's disease (AD). Due to polymorphisms, subtypes, and ubiquitous expression of P2X7R, inhibition of P2X7R has not been effective for AD. We first report that taurodeoxycholate (TDCA), a GPCR19 ligand, inhibited the priming phase of N3I activation, suppressed P2X7R expression and P2X7R-mediated Ca++ mobilization and N3I oligomerization, which is essential for production of IL-1ß/IL-18 by microglia. Furthermore, TDCA enhanced phagocytosis of Aß and decreased the number of Aß plaques in the brains of 5x Familial Alzheimer's disease (5xFAD) mice. TDCA also reduced microgliosis, prevented neuronal loss, and improved memory function in 5xFAD mice. The pleiotropic roles of GPCR19 in P2X7R-mediated N3I activation suggest that targeting GPCR19 might resolve neuroinflammation in AD patients.
Subject(s)
Alzheimer Disease , Amyloid beta-Peptides , Alzheimer Disease/metabolism , Amyloid beta-Peptides/metabolism , Animals , Disease Models, Animal , Humans , Inflammasomes/metabolism , Mice , Microglia/metabolism , NLR Family, Pyrin Domain-Containing 3 Protein/metabolismABSTRACT
NO (Nitric oxide) has been known as a biological signaling molecule that can function as a beneficial agent in physiologically essential functions such as differentiation or neurotransmission. In this study, we elucidated how nicotine inhibits neuronal differentiation induced by the basic fibroblast growth factor (bFGF) in hippocampal cell line, H19-7 cells, because nicotine is one of the key neuroregulatory components. Treatment of H19-7 cells with bFGF increased NO production through upregulated iNOS/ nNOS expression, and also increased expressions of neuronal markers such as brain-derived neurotrophic factor (BDNF), neurotrophin-3 (NT3) and Neuro-D. Pretreatment of the cells with nicotine decreased iNOS promoter activity as well as iNOS/nNOS expression induced by bFGF, resulting in decreased NO production. Nicotine also suppressed expressions of BDNF, NT3 and Neuro-D, resulting in decreased bFGF-induced neurite outgrowth. These results indicate that nicotine inhibits bFGF-induced neuronal differentiation in H19-7 cells through inhibition of NO formation by suppressing iNOS/nNOS expressions.
