Effect of methylmercury on histamine release from rat mast cells

Abstract

Methylmercury chloride (MeHgCl) is well known as a significant environmental hazard, particularly as a modulator of the immune system. As it is acknowledged that the critical effector cells in the host response participating in various biological responses are mast cells, we tried to define the possible contribution of mast cells in the development of methylmercury-evoked effects. We investigated the effects of methylmercury on the rat mast cell degranulation induced by non-immunological stimuli (the selective liberator of histamine, compound 48/80, and calcium ionophore A23187) both in vivo and in vitro. Using the cells prepared from methylmercury-intoxicated rats through a 5-day treatment of MeHgCl (10 mg/kg/day), we observed the suppression of calcium ionophore A23187- and 48/80-induced histamine release, which was enhanced with time after treatment. Similar suppression was observed in the ionophore-stimulated release, when cells were prepared from rat with a single treatment of MeHgCl (20 mg/kg). It should be noted that when cells from the control rat were pre-incubated with methylmercury in vitro at a 10(-8) M concentration for 10 min, A23187 and compound 48/80-stimulated histamine release was significantly enhanced. However, when the pre-incubation period was prolonged to 30 min, the release was suppressed. An increase in the methylmercury concentration to 10(-6) M also suppressed the histamine release. These results show that methylmercury treatment can modify mast cell function depending on concentration and time, and might provide an insight into the role of mast cells in the development of methylmercury-stimulated effects.

Microglia trigger astrocyte-mediated neuroprotection via purinergic gliotransmission

“…MeHg has been reported to both facilitate and suppress exocytosis173435. In addition, we recently reported that microglia release ATP by exocytosis via a vesicular nucleotide transporter (VNUT)-mediated pathway(s)11; thus, we next investigated VNUT-mediated ATP release evoked by MeHg.…”

Modulating effects of dietary fats on methylmercury toxicity and distribution in rats

“…These effects include impaired antibody synthesis in rabbit (Koller et al, 1977); thymus and splenic folliculi atrophy in mice (Hirokawa and Hayashi, 1980); reduced mass and cellularity in thymus and lower number of NK cells in spleen and blood in mice (Ilbäck, 1991); alteration in splenocyte and thymocyte subsets in mice (Thompson et al, 1998); lower serum IgG and IgM levels in monkeys (Petruccioli and Turillazzi, 1990); induction of serum autoantibodies against neurotypic and gliotypic proteins in rats (El-Fawal et al, 1996); suppression of calcium ionophore induced histamine release from mast cells in rats (Graevskaya et al, 2003); and impairment of lymphocyte proliferation associated with increasing hair MeHg level in humans (Amorim et al, 2000). However, to our knowledge, this is the first report dealing with the effects of diets on MeHg-induced immunotoxicity.…”

Inhibitory effect of phytoglycoprotein (24kDa) on allergy-related factors in compound 48/80-induced mast cells in vivo and in vitro

“…It has been reported that the degranulation of mast cells can be elicited by non-immunologic stimulators such as neuropeptides, basic compounds, complement components, and certain drugs [4]. It is well known that compound 48/80 (a condensation product of N-methyl-pmethoxyphenethylamine with formaldehyde) has the potential to secrete allergy-related factors from mast cells as stimulators [5].…”