Department of Sports Science, College of Nature Science, Chonbuk National University, Republic of Korea.
Arch Oral Biol. 2012 Apr;57(4):392-400. doi: 10.1016/j.archoralbio.2011.09.009. Epub 2011 Oct 11.
PPARγ has an anti-inflammatory effect on LPS-induced pulpal inflammation by decreasing the expression of MMPs, ICAM-1 and VCAM-1. However, the anti-inflammatory mechanism of PPARγ on the cell adhesion molecules and their upper signal pathways has not been clarified in pulp cells. The aim of this study is to investigate the anti-inflammatory mechanism of PPARγ in pulpal inflammation.
Human dental pulp cells (HDPCs) were isolated from freshly extracted third molar and cultured. The over-expression of PPARγ was used by adenoviral PPARγ (Ad/PPARγ). The formation of ROS was analysed using DCFH-DA with FACS, and NO was analysed using colorimetric bioassay. The expression of inflammatory molecules and inflammatory mechanism of PPARγ involved signal pathway were determined by immunoblotting.
LPS-induced HDPC decreased PPARγ expression gradually and strongly activated the ERK1/2 signals amongst the MAPK, and induced NF-κB translocation from the cytosol to the nucleus. On the other hand, the cells to restore PPARγ with Ad/PPARγ were inhibited ERK1/2 despite being stimulated with LPS. In addition, the cells treated with rosiglitazone (PPARγ agonist) also were inhibited ERK1/2 activation, and the expression of ICAM-1, VCAM-1 and NF-κB translocation under LPS stimulation. The GW9667 (PPARγ antagonist)-treated HDPC did not affect the adhesion molecules and signal activation. LPS-induced HDPC produced significant NO and ROS levels, but their production was attenuated in the PPARγ over-expressed cells. Overall, the PPARγ effect under LPS stimulation is due to the removal activity of cellular NO and ROS formation.
These results suggest that anti-inflammatory mechanism of PPARγ is due to the removal activity of NO and ROS, and its removal effect suppressed ERK1/2 signal activation and NF-κB translocation. Therefore, the NO and ROS removal activity of PPARγ suggests major anti-inflammatory mechanism in HDPC, and it might offer us a possible molecule for various types of inflammatory inhibition.
过氧化物酶体增殖物激活受体γ（PPARγ）通过降低基质金属蛋白酶（MMPs）、细胞间黏附分子-1（ICAM-1）和血管细胞黏附分子-1（VCAM-1）的表达，对脂多糖诱导的牙髓炎症发挥抗炎作用。然而，PPARγ 对牙髓细胞中细胞黏附分子及其上游信号通路的抗炎机制尚未阐明。本研究旨在探讨 PPARγ 在牙髓炎症中的抗炎机制。
从新鲜拔出的第三磨牙中分离人牙髓细胞（HDPCs）并进行培养。腺病毒过表达 PPARγ（Ad/PPARγ）用于过表达 PPARγ。用 DCFH-DA 通过流式细胞术分析 ROS 的形成，用比色生物测定法分析 NO 的形成。通过免疫印迹法确定炎症分子的表达和涉及 PPARγ 信号通路的炎症机制。
LPS 诱导的 HDPCs 逐渐强烈地降低了 PPARγ 的表达，并强烈激活了 MAPK 中的 ERK1/2 信号，诱导 NF-κB 从细胞质易位到细胞核。另一方面，用 Ad/PPARγ 恢复 PPARγ 的细胞尽管受到 LPS 的刺激，但仍被抑制 ERK1/2 的激活。此外，用罗格列酮（PPARγ 激动剂）处理的细胞在 LPS 刺激下也抑制了 ERK1/2 的激活以及 ICAM-1、VCAM-1 的表达和 NF-κB 的易位。GW9667（PPARγ 拮抗剂）处理的 HDPC 不影响黏附分子和信号激活。LPS 诱导的 HDPC 产生大量的 NO 和 ROS，但在过表达 PPARγ 的细胞中其产生减少。总的来说，LPS 刺激下的 PPARγ 作用是由于细胞中 NO 和 ROS 形成的清除活性。
这些结果表明，PPARγ 的抗炎机制是由于其对 NO 和 ROS 的清除活性，其清除作用抑制了 ERK1/2 信号的激活和 NF-κB 的易位。因此，PPARγ 的 NO 和 ROS 清除活性表明其在 HDPC 中具有主要的抗炎机制，这可能为各种类型的炎症抑制提供一个潜在的分子靶点。
