HOTAIR alleviates ox-LDL-induced inflammatory response in Raw264.7 cells via inhibiting NF-κB pathway

To investigate the possible role of hox transcript antisense intergenic RNA (HOTAIR) in the pathogenesis of atherosclerosis and its underlying mechanism.

The expression of HOTAIR in peripheral blood lymphocytes of atherosclerosis (AS) and healthy controls was detected by quantitative Real-time-polymerase chain reaction (qRT-PCR). In vitro AS model was established by ox-LDL induction in Raw264.7 cells. Viability of Raw264.7 cells after ox-LDL induction was detected by cell counting kit-8 (CCK-8) assay. Levels of TC (total cholesterol), TG (triglyceride), LDL-C (low density lipoprotein cholesterol) and HDL-C (high density lipoprotein cholesterol) in Raw264.7 cells were detected by enzyme-linked immunosorbent assay (ELISA). Overexpression plasmid of HOTAIR was constructed. Levels of TG, TC, LDL-C, and HDL were detected again after HOTAIR overexpression by ELISA. CD68+ cells and CD168+ cells in Raw264.7 cells were detected by flow cytometry. Protein expressions of pro-inflammatory and anti-inflammatory genes were detected by Western blot. Lipid metabolism in Raw264.7 cells was evaluated by oil red O staining and Western blot, respectively. Finally, rescue experiments were conducted to explore the specific mechanism of HOTAIR in regulating AS development.

HOTAIR was lowly expressed in peripheral blood lymphocytes of AS patients and Raw264.7 cells induced by ox-LDL. Overexpression of HOTAIR upregulated adipose genes (PPARα and CPT-1) and downregulated lipogenesis genes (SREBP-1c and ACS). Besides, overexpression of HOTAIR decreased expressions of pro-inflammatory cytokines (TNF-α and IL-1β), but increased expressions of anti-inflammatory cytokines (IL-4 and IL-10). In the in vitro AS model, FXR1 was remarkably downregulated in Raw264.7 cells. HOTAIR reduced inflammatory response via promoting FXR1 expression in Raw264.7 cells. Rescue experiments showed that the effect of HOTAIR on nuclear factor-kappa B (NF-κB) pathway was reversed by FXR1 knockdown.

We found that TAIR was lowly expressed in AS patients. Overexpression of HOTAIR can reduce the lipid accumulation and inhibit inflammatory response by suppressing FXR1 via NF-κB pathway.