Effect of Conjugated Linoleic Acid on Nuclear Factor- Activation and Tumor Necrosis Factor- Production in RAW 264.7 Cells Exposed to High Concentration of Glucose

Diabetes-related complications in human and veterinary medicine have been shown to be associated with hyperglycemia-induced inflammation. It has been recently suggested that the onset of insulin resistance may be caused by over-production of inflammatory cytokines such as tumor necrosis factor (TNF)-${\alpha}$ from immune cells. Conjugated linoleic acid (CLA) regulates inflammatory response through modulation of TNF-${\alpha}$ expression. The objective of this study was to examine the effect of CLA on nuclear factor kappaB (NF-${\kappa}B$) p65 binding activity, inhibitory kappaB ($I{\kappa}B$)-${\alpha}$ expression, and TNF-${\alpha}$ production from high glucose-treated RAW 264.7 cells. CLA was added to RAW cells that had been previously cultured with low or high concentration of glucose. The levels of TNF-${\alpha}$ protein in the culture supernatant of RAW cells exposed to high concentrations of glucose were higher than those of cells exposed to low concentrations of glucose. The treatment with the high concentration of glucose in RAW cells increased levels of NF-${\kappa}B$ p65 binding activity and the decreased $I{\kappa}B-{\alpha}$ expression when compared with those of low glucose. The treatments in combination with CLA and glucose (low and high) glucose in RAW cells increased TNF-${\alpha}$ production when compared with that glucose alone. These treatments with CLA increased TNF-${\alpha}$ production in high glucose-treated RAW cells than those with low glucose. These treatments of CLA also showed higher NF-${\kappa}B$ p65 binding activity and lower $I{\kappa}B-{\alpha}$ expression in high glucose than those in low glucose condition. This suggests that CLA can increase NF-${\kappa}B$ p65 binding activity and TNF-${\alpha}$ production from high glucose-treated RAW 264.7 cells and is likely to promote hyperglycemia-induced inflammation.

고농도의 당에 노출된 RAW 264.7 세포에서 conjugated linoleic acid의 TNF- 생산과 NF-의 활성 효과

고혈당으로 야기된 염증은 당뇨병에서 합병증을 일으키는 주된 요인이다. 최근 연구에 따르면 면역세포에서 TNF-${\alpha}$ 같은 염증성 cytokine의 과도한 생성은 인슐린 저항성을 야기시킨다고 한다. Conjugated linoleic acid (CLA)는 TNF-${\alpha}$ 생산에 관여하여 면역반응을 조절하는 것으로 알려져 있다. 본 연구는 고농도의 당으로 처리한 RAW 264.7 세포에서 TNF-${\alpha}$ 생산, NF-${\kappa}B$의 활성과 $I{\kappa}B-{\alpha}$ 분해에 대한 CLA 효과를 검토하였다. 고농도의 당에 노출된 RAW세포는 저농도의 당에 노출된 RAW 세포보다 NF-${\kappa}B$의 활성과 $I{\kappa}B-{\alpha}$ 분해가 증가되었으며 RAW 세포의 배양 상층액 중에 TNF-${\alpha}$ 생산을 증가시켰다. CLA와 고농도 또는 저농도의 당을 같이 처리한 군은 당만 단일 처리한 군보다 TNF-${\alpha}$ 생산, NF-${\kappa}B$의 활성 및 $I{\kappa}B-{\alpha}$ 분해가 증가되었다. 그리고 고농도의 당과 CLA를 처리한 군에서 저농도의 당과 CLA 처리군에 비해 NF-${\kappa}B$의 활성과 $I{\kappa}B-{\alpha}$ 분해가 증가되었으며 이와 더불어 TNF-${\alpha}$의 양이 증가되었다. 이상의 결과로부터, CLA는 고농도의 당에 노출된 RAW 세포에서 NF-${\kappa}B$의 활성을 높이고 TNF-${\alpha}$ 생산을 증가시키며 이는 고혈당으로 유발되는 염증반응을 촉진하는 인자로 작용할 수 있음을 시사하였다.