Inhibitory Effects of 1‐(5‐Benzyl‐4‐(4‐chlorophenyl)‐2‐methylfuran‐3‐yl)ethan‐1‐one on Allergic Inflammatory Responses in Rat Basophilic Leukemia Cells

Abstract

Mast cells play a key role in allergic inflammatory process. Mast cell activation is controlled by immunoglobulin E (IgE). Aggregated FcεRI, IgE receptor on the surface of mast cells, triggers biological events such as degranulation and secretion of inflammatory mediators. 1 In addition, aggregation of FcεRI triggers the activation of intracellular signaling pathways, leading to increased intracellular calcium influx; cytoskeleton rearrangement; activation of Lyn, Syk, protein kinase C (PKC), and mitogen-activated protein kinases (MAPKs) 2 ; the and subsequent release of several inflammatory mediators, including histamine, proteases, de novo synthesized cytokines, and eicosanoids. 3 Rat basophilic leukemia-2H3 cells (RBL-2H3) secrete various inflammatory mediators and have been used extensively for the study of allergic responses. 3-9 Phorbol 12-myristate 13-acetate (PMA), an activator of PKC, and A23187, a calcium ionophore, increase intracellular calcium influx in RBL-2H3 cells, 3-10 thereby activating allergic inflammatory responses. Thus, in the present study, we used PMA and A23187 to examine the antiallergic effects of furan derivatives ( Figure 1) in RBL-2H3 cells.The inhibitory effects of furan derivatives on degranulation were evaluated by the activity of β-hexosaminidase. 3,6,8,10 Treatment of RBL-2H3 cells with 10 furan derivatives, followed by stimulation with PMA and A23187, revealed that compound F4 inhibited the release of β-hexosaminidase ( Figure 2). Moreover, this effect was dose dependent, at 100 μM concentration, blocking β-hexosaminidase release by 50% compared with the untreated control ( Figure 3). However, human T lymphoid cell line (Molt-4) and mouse leukemic monocyte/macrophage cell line (Raw264.7) were not affected in their immunological activities by this chemical (data not shown). MTT (3-(4,5-Dimethyl-2-thiazolyl)-2,5-diphenyl-2H-tetrazolium bromide) assays 3 revealed that up to 100 μM concentration did not cause significant cytotoxicity in RBL-2H3 cells (Figure 4). Thus, these results indicated that compound F4 inhibited degranulation of RBL-2H3 cells but did not have cytotoxic effects in this cell line.It is also known that furan is listed as a possible carcinogen in humans, as well as in rat and mouse. 11 At a concentration of 50 μM, compound F4 did not show cytotoxicity or proliferation effect in human hepatocellular carcinoma cell line (HepG2) and human normal liver cell line (Chang). However, at 100 μM, cell proliferation of HepG2 cells was increased by 15 AE 8.2% and cell viability of Chang cells was decreased by 8 AE 3.8% compared with control. These findings need to be confirmed using further studies in future.Next, we investigated the inhibitory degranulation mechanism on MAPK signaling by immunoblotting. [3][4][5][6][7][8][9] MAPKs are key factors regulating the expression of inflammatory cytokine genes in immune cells 2,12,13 and phosphorylate a series of downstream factors in response to activation by several extracellular factors. 14,15 Thus, the development of MAPK inhi...