Silver Nanoparticle-Directed Mast Cell Degranulation Is Mediated through Calcium and PI3K Signaling Independent of the High Affinity IgE Receptor

Abstract

Engineered nanomaterial (ENM)-mediated toxicity often involves triggering immune responses. Mast cells can regulate both innate and adaptive immune responses and are key effectors in allergic diseases and inflammation. Silver nanoparticles (AgNPs) are one of the most prevalent nanomaterials used in consumer products due to their antimicrobial properties. We have previously shown that AgNPs induce mast cell degranulation that was dependent on nanoparticle physicochemical properties. Furthermore, we identified a role for scavenger receptor B1 (SR-B1) in AgNP-mediated mast cell degranulation. However, it is completely unknown how SR-B1 mediates mast cell degranulation and the intracellular signaling pathways involved. In the current study, we hypothesized that SR-B1 interaction with AgNPs directs mast cell degranulation through activation of signal transduction pathways that culminate in an increase in intracellular calcium signal leading to mast cell degranulation. For these studies, we utilized bone marrow-derived mast cells (BMMC) isolated from C57Bl/6 mice and RBL-2H3 cells (rat basophilic leukemia cell line). Our data support our hypothesis and show that AgNP-directed mast cell degranulation involves activation of PI3K, PLCγ and an increase in intracellular calcium levels. Moreover, we found that influx of extracellular calcium is required for the cells to degranulate in response to AgNP exposure and is mediated at least partially via the CRAC channels. Taken together, our results provide new insights into AgNP-induced mast cell activation that are key for designing novel ENMs that are devoid of immune system activation.

Contribution of engineered nanomaterials physicochemical properties to mast cell degranulation

“…This suggests that ENMs are not altering mast cell activation through an apoptotic or necrotic pathway. A recent study from our laboratory demonstrated that mast cells are not highly phagocytic and therefore are not readily internalizing ENMs, which could account for the difference in cytotoxic responses compared to other immune cell types48. Dendritic cells, neutrophils, and macrophages are all shown to readily phagocytize particles, altering cell viability and function52.…”

Polymeric Nanomicelles: A Potential Hazard for the Cardiovascular System?

“…NPs' exposures induce the releasing of complement components and inflammatory cytokines into the circulation which activate mast cells and mediate systemic inflammation and platelet activation. Noteworthy, either stimulation or inhibition of degranulation is related to physicochemical properties of NPs and types of NP-cell interactions (receptor recognition or endocytic internalization) [12]. However, the mechanism by which NP directly interacts with mast cells and influences degranulation is poorly understood and requires further examination.…”

Antimicrobial agent triclosan suppresses mast cell signaling via phospholipase D inhibition

“…Therefore, we hypothesized that the cellular translocation and activity of Ca 2+ -activated PKC and PLD enzymes, as well as the translocation of PKC substrate MARCKS, would be inhibited by TCS exposure. Biochemically and functionally, RBL-2H3 cells respond to exogenous agents in a fashion similar to that of primary bone marrow-derived MCs, including upon exposure to parasite infection (Thrasher, Scalfone, Holowka, & Appleton, 2013), silver nanoparticles (Alsaleh, Persaud, & Brown, 2016) and endocrine disruptors (Zaitsu et al, 2007). Biochemically and functionally, RBL-2H3 cells respond to exogenous agents in a fashion similar to that of primary bone marrow-derived MCs, including upon exposure to parasite infection (Thrasher, Scalfone, Holowka, & Appleton, 2013), silver nanoparticles (Alsaleh, Persaud, & Brown, 2016) and endocrine disruptors (Zaitsu et al, 2007).…”

“…For these studies, we have utilized RBL-2H3 cells, which contain biochemical signaling machinery closely similar to that of primary human and rodent MCs (Abramson & Pecht, 2007;Fewtrell, Kessler, & Metzger, 1979;Lee, Veatch, Baird, & Holowka, 2012;Metcalfe et al, 1997;Metzger et al, 1986;Seldin et al, 1985). Biochemically and functionally, RBL-2H3 cells respond to exogenous agents in a fashion similar to that of primary bone marrow-derived MCs, including upon exposure to parasite infection (Thrasher, Scalfone, Holowka, & Appleton, 2013), silver nanoparticles (Alsaleh, Persaud, & Brown, 2016) and endocrine disruptors (Zaitsu et al, 2007).…”