Arsenic inhibits mast cell degranulation via suppression of early tyrosine phosphorylation events

Abstract

Exposure to arsenic (As) is a global health concern. We previously documented an inhibitory effect of inorganic arsenite on IgE- mediated degranulation of RBL-2H3 mast cells (Hutchinson et al., 2011). Mast cells are tissue-resident cells that are positioned at the host-environment interface, thereby serving vital roles in many physiological processes and disease states, in addition to their well-known roles in allergy and asthma. Upon activation, mast cells secrete several mediators from cytoplasmic granules, in degranulation. The present study is an investigation of arsenite's molecular target(s) in the degranulation pathway. Here, we report that As does not affect degranulation stimulated by either the Ca2+ionophore A23187 or thapsigargin, which both bypass early signaling events. As also does not alter degranulation initiated by another non-IgE-mediated mast cell stimulant, the G-protein activator compound 48/80. However, As inhibits Ca2+ influx into antigen-activated mast cells. These results indicate that arsenic's target in the degranulation pathway is upstream of Ca2+ influx. Phospho-Syk ELISA and phospho-p85 phosphoinositide 3-kinase ELISA data show that arsenic inhibits early phosphorylation events. Taken together, this evidence indicates that the mechanism underlying arsenic's inhibition of mast cell degranulation occurs at the early tyrosine phosphorylation steps in the degranulation pathway.

Cryptotanshinone inhibits IgE‑mediated degranulation through inhibition of spleen tyrosine kinase and tyrosine‑protein kinase phosphorylation in mast cells

“…The activated PLCγ hydrolyses phosphatidylinositol biphosphate (PIP 2 ) to generate second signalling molecules IP 3 and DAG, which activate PKCδ through phosphorylation. Then, activated PKCδ phosphorylates IKKβ so IKKβ moves to the plasma membrane, resulting in the induction of mast cell degranulation (6,11,28,29). In this study, novel function of CRT on phosphorylations of Lyn/Syk kinases in mast cells is elucidated for the first time.…”

“…Mast cells play an important role in type Ⅰ hypersensitivity reactions via the release of histamine, chemokines, and various inflammatory cytokines. Secretion and activation of these strong pro-inflammatory mediators are stimulated by binding of the cross-linked IgE/antigen complex and its high affinity receptor FcεRl on surfaces of mast cells (6). Previous studies have revealed that IgE/antigen-FcεRl binding activates IκB kinase α and β (IKKα and IKKβ), leading to the activation of nuclear factor-κB (NF-κB), which translocates into nucleus to regulate the inflammatory response.…”

Searching for tryptase in the RBL‐2H3 mast cell model: Preparation for comparative mast cell toxicology studies with zebrafish

“…After removal of supernatant, a cell pellet was washed with phosphate‐buffered saline and resuspended in 1× assay buffer. Next, the cell supernatant from the lysate was obtained as described under Syk enzyme‐linked immunosorbent assay (ELISA) assay in (Shim, Kennedy, et al, ) and incubated with tosyl‐Gly‐Pro‐Lys‐pNA substrate. For statistical analysis, first raw absorbance data from each treatment were processed by subtracting average background values (1× assay buffer with substrate) from each sample, and the background‐adjusted triplicates were then averaged.…”

“…Tryptase ELISA kit (Cell Signaling Technologies, Beverly, MA, USA) was used to detect levels of rat ( Rattus norvegicus ) TPSAB1 protein according to the manufacturer's instructions. For this assay, RBL‐2H3 were cultured in six‐well plates, stimulated and lysed as described under Syk ELISA assay in (Shim, Kennedy, et al, ). A volume of 300 μL of cell lysate supernatant was placed into an appropriate ELISA well in duplicates per treatment.…”

“…Previously, we discovered that MC degranulation is disrupted by environmental toxicants, such as arsenic (Hutchinson et al, ; Shim et al, ), and by antimicrobial drug triclosan (TCS) (Palmer et al, ; Weatherly, Kennedy, Shim, & Gosse, ). Along with other cell types, these studies utilized RBL‐2H3 cells and β‐hex detection to quantify MC degranulation.…”