Regulation of LCN-2/PI3K/Akt on TNF-α induced inflammatory response of porcine intramuscular adipocytes.

Abstract

Lipocalin-2 (LCN-2) has a variety of biological functions and produces various effects on adipocytes, such as promoting cell apoptosis, inhibiting preadipocyte differentiation, and weakening insulin signaling. Tumor necrosis factor-α (TNF-α) is one of the first secreted products discovered in adipocytes, which plays an important role in the regulation of adipose metabolism. This experiment was conducted to investigate the regulatory effect of LCN-2 on TNF-α induced inflammatory response in porcine intramuscular adipocytes. Porcine intramuscular adipocytes were cultured in vitro and treated with LCN-2 overexpression or silencing plasmids. After TNF-α treatment, the expressions of LCN-2, interleukin 6 (IL-6), IL-8, and IL-1β were detected by enzyme-linked immunosorbent assay (ELISA) and quantitative real-time reverse transcription polymerase chain reaction (qRT-PCR). Western blot analysis was used to detect the expression of phosphatidylinositol 3-kinase (PI3K), total protein kinase B (Akt), and phosphorylated Akt (pAkt) proteins. After the action of the PI3K/Akt pathway inhibitor LY294002, the effects of LCN-2 overexpression on IL-6, IL-8, and IL-1β were evaluated. The results showed that TNF-α induced LCN-2 expression in a dose-/time-dependent manner. Overexpression or silencing of LCN-2 had an impact on TNF-α induced IL-6, IL-8, and IL-1β in porcine intramuscular adipocytes. Overexpression of LCN-2 significantly promoted inflammatory factors IL-6, IL-8, and IL-1β secretion while silencing of LCN-2 inhibited the secretion of these inflammatory factors (P < 0.01). Overexpression of LCN-2 significantly increased the expression of pAkt protein in cells, while silencing of LCN-2 decreased pAkt protein expression (P < 0.01). After blocking the PI3K/Akt signaling pathway, compared with the control group, overexpression of LCN-2 affected IL-6, IL-8, and IL-1β secretion, but the impact was not significant (P > 0.05). This study suggests that LCN-2 regulates TNF-ɑ induced IL-6, IL-8, and IL-1β secretion in porcine intramuscular adipocytes by targeting the PI3K/Akt pathway, which provides a theoretical basis for LCN-2 regulating the inflammatory response of porcine intramuscular adipocytes.