Description
Changes in the regulation of connective tissue ATP-mediated mechano-transduction and remodeling may be
an important link to the pathogenesis of chronic pain. It has been demonstrated that mast cell-derived
histamine plays an important role in painful fibrotic diseases. Here we analyzed the involvement of ATP in the
response of human subcutaneous fibroblasts to histamine. Acute histamine application caused a rise in
intracellular Ca2+ ([Ca2+]i) and ATP release from human subcutaneous fibroblasts via H1 receptor activation.
Histamine-induced [Ca2+]i rise was partially attenuated by apyrase, an enzyme that inactivates extracellular
ATP, and by blocking P2 purinoceptors with pyridoxal phosphate-6-azo(benzene-2,4-disulfonic acid)
tetrasodium salt and reactive blue 2. [Ca2+]i accumulation caused by histamine was also reduced upon blocking
pannexin-1 hemichannels with 10Panx, probenecid, or carbenoxolone but not when connexin hemichannels
were inhibited with mefloquine or 2-octanol. Brefeldin A, an inhibitor of vesicular exocytosis, also did not block
histamine-induced [Ca2+]i mobilization. Prolonged exposure of human subcutaneous fibroblast cultures to
histamine favored cell growth and type I collagen synthesis via the activation of H1 receptor. This effect was
mimicked by ATP and its metabolite, ADP, whereas the selective P2Y1 receptor antagonist, MRS2179, partially
attenuated histamine-induced cell growth and type I collagen production. Expression of pannexin-1 and ADPsensitive
P2Y1 receptor on human subcutaneous fibroblasts was confirmed by immunofluorescence confocal
microscopy and Western blot analysis. In conclusion, histamine induces ATP release from human
subcutaneous fibroblasts, via pannexin-1 hemichannels, leading to [Ca2+]i mobilization and cell growth through
the cooperation of H1 and P2 (probably P2Y1) receptors.
; Paramos-de-Carvalho, Diogo 
