Qingkailing injection induces pseudo-allergic reactions via the MRGPRX2 pathway.

OBJECTIVE: Qingkailing Injection (QKLI) is a traditional Chinese medicine injection mainly used for sedation, heat clearing, and other treatments. However, recent clinical studies have shown a risk of pseudo-allergic reactions. The purpose of this study is to elucidate the underlying mechanism of QKLI-induced mast cell degranulation in Laboratory of Allergic Diseases 2 (LAD2) and to validate QKLI-induced activation of guinea pig IgE-independent allergic responses. METHODS: Levels of β-hexosaminidase (β-Hex), histamine (His), and complement pathway-related indicators in guinea pigs and LAD2 cells were assayed using the Enzyme-linked Immunosorbent Assay (ELISA). The release rates of β-Hex and His from LAD2 cells were measured using the o-phthalaldehyde (OPA) fluorimetric method. The antagonist for complement component 3a (C3a) receptors, SB290157 and siRNAs were used to inhibit the C3a pathway and the Mas-related G-protein-coupled receptor X2 (MRGPRX2) pathway. The MRGPRX2 pathway and its downstream proteins were detected by Western Blot (WB). RESULTS: The results show that QKLI significantly increased levels of β-Hex, His, C3a, complement component 5a (C5a), and terminal complement complex C5b-9 (SC5b-9) in guinea pigs, while levels of interleukin 4 (IL-4), interleukin 13 (IL-13), and interleukin 6 (IL-6) were unaffected. The C3a receptor inhibitor SB290157 significantly reduced levels of β-Hex and His. In LAD2 cells, QKLI increased the release rates of β-Hex and His in a time-dependent manner and decreased the phosphorylation of Extracellular Signal-regulated Kinase 1/2 (ERK1/2) proteins downstream of the MRGPRX2 pathway. The effective components of QKL, baicalin (BA) and geniposide (GE), individually enhance the allergic responses of LAD2 cells to some extent. However, the use of QKL is significantly superior to the individual use of its components. CONCLUSIONS: We found that QKLI induced pseudoanaphylaxis via an IgE-independent response in guinea pigs and through the MRGPRX2 pathway in human LAD2 cells. Among these, the main ingredients causing pseudoallergic reactions in QKLI were BA and GE. Our research contributes to a better understanding of the mechanisms underlying drug hypersensitivity reactions (DHRs).