Inhibition of LPS-induced inflammatory response in RAW264.7 cells by natural Chlorogenic acid isomers involved with AKR1B1 inhibition

Inflammation is the physiological response of the immune system to injury or infection, typically manifested by local tissue congestion, swelling, heat, and pain. Prolonged or excessive inflammation can lead to tissue damage and the development of many diseases. The anti-inflammatory effects of natural ingredients have been extensively researched and confirmed. This study investigated the effects of Chlorogenic acid (CGA) isomers -- 3-Caffeolyquninic acid (3-CQA), 4-Caffeolyquninic acid (4-CQA), and 5-Caffeolyquninic acid (5-CQA) -- on the inflammatory response and oxidative stress reaction induced by LPS in RAW264.7 cells. Overall, 3-CQA exhibited the most significant reduction in levels of TNF-α, IL-6, NO, and ROS. 4-CQA showed superior inhibition of TNF-α compared to 5-CQA (p < 0.05), while no significant difference in other parameters. We further used DARTS and CETSA to demonstrate that CGA isomers have stable affinity with AKR1B1. As a positive control, the AKR1B1 antagonist epalrestat exhibited similar effects to the CGA isomers. 3-CQA having the smallest half-inhibitory concentration (IC50) for AKR1B1, while 4-CQA and 5-CQA have similar values. AutoDock simulations of the docking conformations revealed minimal differences in the average binding energies of the CGA isomers. The main differences were that VAL47 formed a hydrogen bond with 3-CQA, whereas GLN49 formed hydrogen bonds with 4-CQA and 5-CQA. Additionally, the number of hydrophobic bonds involving PHE122 and LEU300 varies. Our conclusion is that differences in non-covalent interactions result in the varying inhibitory abilities of CGA isomers on AKR1B1, which further affect the anti-inflammatory and antioxidant effects of CGA isomers.