# Anti-Inflammatory Effects of Alpha-Lipoic Acid Modulate Cystathionine-γ-Lyase Expression in RAW 264.7 Macrophages

## TL;DR

Alpha-lipoic acid reduces inflammation in macrophages by lowering the expression of an enzyme that produces hydrogen sulfide.

## Contribution

This study is the first to show that alpha-lipoic acid's anti-inflammatory effects are linked to reduced cystathionine-γ-lyase expression in LPS-stimulated macrophages.

## Key findings

- Alpha-lipoic acid significantly reduced inflammatory markers like TNF-α, IL-6, and MCP-1 in LPS-stimulated macrophages.
- Alpha-lipoic acid decreased CSE expression in a time-dependent manner in both pre- and post-treated macrophages.
- The anti-inflammatory effects of alpha-lipoic acid were associated with reduced oxidative stress and improved catalase activity.

## Abstract

Alpha-lipoic acid (ALA) is a naturally occurring organosulfur compound with antioxidant and anti-inflammatory activities. The time-dependent effects of ALA and mechanism of interaction with cystathionine-γ-lyase (CSE—an enzyme responsible for hydrogen sulfide—H2S synthesis) in RAW 264.7 macrophages remain unknown. In this study, we report results supporting the hypothesis that anti-inflammatory effects of ALA are associated with the reduction in CSE expression. To investigate the temporal effect of ALA in lipopolysaccharide (LPS—a potent stimulator of inflammation) treated RAW 264.7 macrophages, ALA was administered 1 h before LPS stimulation and 1, 3, and 6 h post LPS stimulation. Effects of ALA on different inflammatory and oxidative stress biomarkers including tumor necrosis factor-alpha (TNF-α), interleukin-6 (IL-6), monocyte chemoattractant protein-1 (MCP-1), catalase activity (CAT), and malondialdehyde (MDA) levels were investigated. LPS stimulation significantly increased TNF- α, IL-6, MCP-1, MDA levels, and CSE expression and decreased CAT activity compared with the control group (p < 0.05 to 0.0001). ALA treatment at 1000 µM significantly attenuated LPS-stimulated inflammatory response in the macrophages across different time points (p < 0.05 to 0.0001). Furthermore, we found that ALA treatment reduced the expression of CSE in both pre- and post-treated LPS-stimulated macrophages in a time-dependent manner. In conclusion, this study demonstrated for the first time that the protective effects of ALA are dependent on the reduction in CSE expression in LPS-stimulated RAW 264.7 macrophages.