Effect of IRAK1 on Apoptosis and Necroptosis of Hepatoma Cell Line SK-Hep1

Zhijia Pan,Changshi Qian,Xiaolei Zhang,Xiaochen Liu,Xinglin Jin

doi:10.4236/cm.2019.101003

Abstract

Interleukin I receptor associated kinase 1 (IRAK1) is a downstream signal molecule of activated MyD88 recruitment, which can activate Fas associated death domain protein (FADD) to induce apoptosis. IRAK1 can also activate tumor necrosis factor-related factor 6 (TRAF6) and induce the expression of a series of downstream specific genes. IRAK1 is an essential factor in the induction of mitochondrial division and necroptosis. In the current study, RNAi technique was used to silence IRAK1, and the apoptosis and necroptosis rate of SK-Hep1 cells were detected by flow cytometry. The apoptosis and the necroptosis pathway of hepatoma SK-Hep1 cells were blocked separately, and the expressions of FADD, RIP1 and TRAF6 genes were silenced separately. The results showed when the expression of IRAK1 was down-regulated, the apoptosis and necroptosis rate of SK-Hep1 cells were significantly increased. With silenced FADD, RIP1 and TRAF6, respectively, the expression of IRAK1 protein had no significant change. However, the expression of IRAK1 mRNA decreased significantly (p < 0.01) after the silencing of RIP1 and TRAF6 genes, while the IRAK1 mRNA did not change significantly after the silencing of FADD genes; when z-VAD-FMK was interfered, the expression of IRAK1 mRNA decreased significantly after the silencing of TRAF6 genes, while the IRAK1 mRNA did not change significantly after the silencing of FADD and RIP1genes. The study shows that RAK1 gene inhibits apoptosis and necroptosis in SK-Hep1 cells. TRAF6 gene affected the role of IRAK1 in apoptosis and necroptosis, RIP1 gene affected the role of IRAK1 in apoptosis, while FADD gene did not affect the role of IRAK1 in apoptosis and necroptosis.

Highlights

Most primary hepatocellular carcinoma (HCC) is associated with inflammation and cirrhosis [1] [2] [3] [4] [5]
tumor necrosis factor-related factor 6 (TRAF6) gene affected the role of I receptor associated kinase 1 (IRAK1) in apoptosis and necroptosis, Receptor-interacting protein-1 (RIP1) gene affected the role of IRAK1 in apoptosis, while Fas associated death domain protein (FADD) gene did not affect the role of IRAK1 in apoptosis and necroptosis
The results showed that the apoptosis rate was 1.53% in blank transfection group, 14.93% in IRAK1siRNA transfection group, the necroptosis rate was 3.08% in blank transfection group and 18.23% in IRAK1siRNA transfection group

Summary

Introduction

Most primary hepatocellular carcinoma (HCC) is associated with inflammation and cirrhosis [1] [2] [3] [4] [5]. Chronic injury and inflammation are closely related to tumorigenesis [6]. TLR4 activates downstream signal transduction elements through two downstream pathways MyD88-dependent and MyD88-independent to induce apoptosis and necroptosis [7]. IRAK1 is a downstream signal molecule of activated MyD88 recruitment, which can activate FADD to induce apoptosis. Receptor-interacting protein-1 (RIP1) is a downstream signaling molecule in the MyD88-independent pathway, which is a necessary condition for initiating necroptosis, and a key factor for inhibiting necroptosis [9]. RIP1 limits caspase-dependent tumor necrosis factor (TNF)-induced apoptosis and is involved in receptor-interacting protein-3 (RIP3)-dependent TNF-induced necroptosis [10]. Decreasing the expression of IRAK1 can inhibit the activity of ERK signaling pathway, reduce the activity of NF-kB, and inhibit the proliferation of mesenchymal stem cells [11]

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