House Dust Mite Allergen Regulates Constitutive Apoptosis of Normal and Asthmatic Neutrophils via Toll-Like Receptor 4

Abstract

House dust mites (HDMs) induce allergic diseases such as asthma. Neutrophil apoptosis is an important process of innate immunity, and its dysregulation is associated with asthma. In this study, we examined the effects of HDM on constitutive apoptosis of normal and asthmatic neutrophils. Extract of Dermatophagoides pteronissinus (DP) inhibited neutrophil apoptosis, but Dermatophagoides farinae extract had no effect. Anti-apoptotic signaling mediated by DP involves in TLR4, Lyn, PI3K, Akt, ERK, and NF-κB in normal neutrophils. DP delayed cleavage of procaspase 9 and procaspase 3 and the decrease in Mcl-1 expression. Supernatant collected from DP-treated normal neutrophils inhibited the constitutive apoptosis of normal neutrophils, and S100A8 and S100A9 were identified as anti-apoptotic proteins in the supernatant. S100A8 and S100A9 transduced the anti-apoptotic signal via TLR4, Lyn, PI3K, Akt, ERK, and NF-κB. DP also suppressed asthmatic neutrophil apoptosis and induced secretion of S100A8 and S100A9, which delayed the constitutive apoptosis. The anti-apoptotic effects of DP, S100A8 and S100A9 in asthmatic neutrophils are associated with TLR4, Lyn, PI3K, Akt, ERK, and NF-κB. The concentrations of S100A8 and S100A9 were significantly elevated in asthmatic bronchoalveolar lavage fluid (BALF) when compared to normal BALF (p<0.01), but not in serum. S100A8 concentration in BALF was positively correlated with the number of BALF neutrophils and negatively correlated with FEV1(%). These findings improve our understanding of the role of HDM in regulation of neutrophil apoptosis in normal individuals and asthmatics and will enable elucidation of asthma pathogenesis.

S100A8 and S100A9 Secreted by Allergens in Monocytes Inhibit Spontaneous Apoptosis of Normal and Asthmatic Neutrophils via the Lyn/Akt/ERK Pathway

“…S100A8 and S100A9 are effective on suppression of neutrophil apoptosis (Figure 2, 3). The constitutive apoptosis of normal and allergic neutrophils is inhibited by lymphocyte activation due to Der p 1 and Der p 2 [16,19]. The activated lymphocytes secret the cytokines such as IL-6, IL-8, MCP-1, and GM-CSF, which were essential inhibitory molecules of neutrophil apoptosis.…”

“…As shown in Figure 4, S100A8 and S100A9 inhibit neutrophil apoptosis through Lyn, Akt, and ERK. House dust mite regulates neutrophil apoptosis via TLR4, Lyn, PI3K, Akt, ERK, and NF-B [15,16]. Antiapoptotic signaling mediated by MCP-1 is involved in the PI3K/Akt/ERK/NF-B cascade in normal neutrophils [21] Leptin delays neutrophil apoptosis via ERK/NF-B pathway [22].…”

“…Because Der p 1 and Der p 2 are not directly effective on neutrophil apoptosis in normal and asthmatic subjects [16], Der p 1 and Der p 2 indirectly regulate neutrophil apoptosis of normal and asthmatic subjects by increasing S100A8 and S100A9 in monocytes. …”

“…In our previous report, the cDNA of human S100A8 and S100A9 was cloned into pET28 expression vector (Merck Millipore, Darmstadt, Germany) [16]. Recombinant S100A8 and Millipore.…”

Anti-apoptotic Effects of House Dust Mite, S100A8 and S100A9 on Spontaneous Apoptosis of Neutrophils in Coculture with Immune Cells and in the Presence of T Helper Cytokines

“…Data are expressed as the means ± SD and are presented relative to the control, which was set at 100%. **P < 0.01 indicate a significant difference between the untreated control and DP, S100A8, or S100A9-treated groups, and Since DP, S100A8, and S100A9 are associated with regulation of neutrophil apoptosis in our previous study (Kim et al, 2015), we examined whether they alter neutrophil apoptosis in new ex vivo environment similar to disease circumstance. Neutrophil apoptosis is not altered by coculture with eosinophils and lymphocytes, except during incubation with monocytes (Fig.…”