Mast cell degranulation mediates compound 48/80-induced hyperalgesia in mice

Abstract

Mast cells mediate allergies, hypersensitivities, host defense, and venom neutralization. An area of recent interest is the contribution of mast cells to inflammatory pain. Here we found that specific, local activation of mast cells produced plantar hyperalgesia in mice. Basic secretagogue compound 48/80 induced plantar mast cell degranulation accompanied by thermal hyperalgesia, tissue edema, and neutrophil influx in the hindpaws of ND4 Swiss mice. Blocking mast cell degranulation, neutrophil extravasation, and histamine signaling abrogated these responses. Compound 48/80 also produced edema, pain, and neutrophil influx in WT C57BL/6 but not in genetically mast cell-deficient C57BL/6-Kit(W-sh)(/)(W-sh) mice. These responses were restored following plantar reconstitution with bone marrow-derived cultured mast cells.

Figure 1. Compound 48/80-induced plantar mast cell degranulation causes thermal hyperalgesia in mice

Compound 48/80 (0.3μg/paw)-treated plantar tissue shows increased thermal hyperalgesia (A), edema (B), histological evidence of mast cell degranulation (C-E; 4μm; Tb, 400x), and extent of degranulation (F) compared to saline controls and SCG-pretreated tissue (80mg/kg i.p.). Tissue histamine levels are lower in c48/80-treated paws than saline or SCG pre-treated paws (G). * significant compared to Sal/Sal; # significant compared to Sal/c48/80. n=3-10 mice per treatment group; data represent ≥3 separate experiments.

Figure 2. Neutrophil infiltration caused by c48/80-induced mast cell degranulation mediates the hyperalgesic response

Compound 48/80 (1.5μg/paw i.pl.) treated paws contain more neutrophils (A-C) and show higher MPO activity (D) than saline-treated or SCG (80mg/kg i.p.) pre-treated paws. Fucoidan (20mg/kg i.v.) pre-treatment reduces c48/80-mediated plantar MPO levels (D) and significantly blocks thermal hyperalgesia (E) and edema (F). * significant compared to Sal/Sal; # significant compared to Sal/c48/80. n=3-10 mice per treatment group; data represent ≥3 separate experiments.

Figure 3. Histamine receptor antagonism abrogates c48/80-induced thermal hyperalgesia

ND4 mice pre-treated with diphenhydramine (20mg/kg) and thioperamide (10mg/kg) intraperitoneally 1hour prior to c48/80 (1.5μg/paw i.pl.) have reduced thermal hyperalgesia (A) and partially reduced hindpaw edema (B). Both pre-treatments reduced MPO activity at 2.5 hours post-treatment (C). * significant compared to Sal/Sal; # significant compared to Sal/c48/80. n=3-10 mice per treatment group; data represent ≥3 separate experiments.

Figure 4. Hyperalgesia and paw edema induced by c48/80-mediated mast cell degranulation in WT C57BL/6 mice are abrogated in Wsh/Wsh mice and restored with plantar mast cell reconstitution

Thermal (A) and mechanical (B) hyperalgesia induced by intraplantar c48/80 (1.5μg/paw) was absent in Wsh/Wsh mice and restored in Wsh/Wsh:WT mice engrafted with plantar mast cells. Cutaneous mast cells are present in Tb-stained sections of WT and Wsh/Wsh:WT but not in Wsh/Wsh hindpaws (C-E). WT and reconstituted Wsh/Wsh:WT mice have comparable levels of mast cell degranulation following c48/80 administration (F). Hindpaw edema is reduced in Wsh/Wsh mice and partially restored in Wsh/Wsh:WT mice (G). * significant compared to WT c48/80; # significant compared to Wsh/Wsh c48/80; + significant compared to WT saline. n=3-10 mice per treatment group; data represent ≥3 separate experiments.