Lymphocyte α-kinase is a gout-susceptible gene involved in monosodium urate monohydrate-induced inflammatory responses

The molecular functions and pathophysiologic role of the lymphocyte α-kinase gene (ALPK1) in gout are unknown. We aimed to examine ALPK1 expression in patients with gout and investigate its role in monosodium urate monohydrate (MSU)-induced inflammatory responses. Microarray data mining was performed with six datasets containing three clinical gout and three volunteer samples. Real-time quantitative polymerase chain reaction (qPCR) assay was used to profile ALPK1 mRNA expression in 62 independent samples. RNA interference for ALPK1 suppression in THP1 cells (human monocytic cell line) was used to scrutinize the functional role of ALPK1 in MSU-mediated inflammatory responses, and ALPK1 expression in MSU-treated THP1 cells was determined by qPCR and Western blot analysis. Cytokine mRNA expression in HEK293 cells after incubation with different concentrations of MSU crystals in the presence or absence of ALPK1 was also detected by qPCR, and ERK1/2, p38, and JNK expressions were investigated by Western blot analysis. ALPK1 mRNA was overexpressed in the clinical gout samples. MSU treatment promoted ALPK1 expression at the mRNA and protein levels. Furthermore, ALPK1 knockdown in THP1 cells resulted in a markedly decreased IL-1β, TNF-α, and IL-8 mRNA expression; plasmid ALPK1 transfection and MSU stimulation synergistically increased the mRNA expression of these cytokines in a concentration-dependent manner. The synergistic effect also led to ERK1/2 activation. ALPK1 is a gout-susceptible gene involved in MSU-induced inflammatory responses. It may contribute to the development of gout by enhancing the inflammatory responses via the mitogen-activated protein kinase pathway.