The Mast Cell Degranulator Compound 48/80 Directly Activates Neurons

Abstract

BackgroundCompound 48/80 is widely used in animal and tissue models as a “selective” mast cell activator. With this study we demonstrate that compound 48/80 also directly activates enteric neurons and visceral afferents.Methodology/Principal FindingsWe used in vivo recordings from extrinsic intestinal afferents together with Ca++ imaging from primary cultures of DRG and nodose neurons. Enteric neuronal activation was examined by Ca++ and voltage sensitive dye imaging in isolated gut preparations and primary cultures of enteric neurons. Intraluminal application of compound 48/80 evoked marked afferent firing which desensitized on subsequent administration. In egg albumen-sensitized animals, intraluminal antigen evoked a similar pattern of afferent activation which also desensitized on subsequent exposure to antigen. In cross-desensitization experiments prior administration of compound 48/80 failed to influence the mast cell mediated response. Application of 1 and 10 µg/ml compound 48/80 evoked spike discharge and Ca++ transients in enteric neurons. The same nerve activating effect was observed in primary cultures of DRG and nodose ganglion cells. Enteric neuron cultures were devoid of mast cells confirmed by negative staining for c-kit or toluidine blue. In addition, in cultured enteric neurons the excitatory action of compound 48/80 was preserved in the presence of histamine H1 and H2 antagonists. The mast cell stabilizer cromolyn attenuated compound 48/80 and nicotine evoked Ca++ transients in mast cell-free enteric neuron cultures.Conclusions/SignificanceThe results showed direct excitatory action of compound 48/80 on enteric neurons and visceral afferents. Therefore, functional changes measured in tissue or animal models may involve a mast cell independent effect of compound 48/80 and cromolyn.

Approaches for Analyzing the Roles of Mast Cells and Their Proteases In Vivo

“…Interestingly, c48/80 can function as a potent adjuvant, and evidence obtained using the so-called MC knockin approach in MC-deficient Kit W/W−v mice suggests that such an adjuvant effect is largely mediated by MCs (McLachlan et al, 2008) (see Section 3.1 for details about the use and potential limitations of the MC knockin model). However, c48/80 can also have direct effects on other cell types, as recently demonstrated for excitation of cultured enteric neurons (Schemann et al, 2012). …”

Protective effects of exogenous and endogenous hydrogen sulfide in mast cell-mediated pruritus and cutaneous acute inflammation in mice

“…Thus, either the intensity of response evoked by histamine released from C48/80 was higher than exogenous histamine when paralleled by the low availability of H2S released from GYY4137 in situ on the peripheral afferent neurons or it is possibly that C48/80 produces scratching behavior that somehow depends on functional changes evoked by direct activation of pruriceptors. While direct excitatory effects of C48/80 on dorsal root ganglion (DRG), enteric neurons and visceral afferents can occur independently of mast cell activation [54], other works show that the mechanism involved in C48/80-induced nociception is mediated by a cascade activation that starts after mast cell activation, including the release of mediators that can activate these nociceptors and promote pain [55].…”

Dual action of neurokinin-1 antagonists on Mas-related GPCRs

“…It was suggested that mast cells may thus play a modulatory role (17). In addition, compound 48/80 directly interacts with sensory nerves, potentially through Mrgprs (19). Since QWF antagonizes the interaction of compound 48/80 with Mrgprs, we examined the capacity of QWF to block compound 48/80-provoked itch.…”