Combination of Danshen and ligustrazine has dual anti-inflammatory effect on macrophages and endothelial cells

Ethnopharmacological relevance: Salvia Miltiorrhiza Radix et Rhizoma (Danshen) and Chuanxiong Rhizoma (Chuanxiong) are both traditional Chinese medicines with vascular protective effects, and their combination is widely used in China to treat occlusive or ischemic diseases of the cerebrovascular or cardiovascular system. Although it is widely accepted that these diseases have high relevance to inflammation, little is known about the anti-inflammatory effect of Danshen, Chuanxiong, and their combination.

Aim of study: We aimed to investigate the complex mode of action of Danshen, Chuanxiong, and their combination and the molecular mechanisms underlying their anti-inflammatory activity. Specifically, toll-like receptor (TLR1/2, 3, and 4)-triggered macrophages and endothelial cells, the two major cell players in atherosclerosis as well as in related cardiovascular and cerebrovascular injuries, were emphasized.

Methods: TLR1/2-, TLR3-, and TLR4-induced bone marrow macrophages (BMMs) and human umbilical vein endothelial cells (HUVECs) were treated with Danshen extract (S. miltiorrhiza extract, SME), ligustrazine (2, 3, 5, 6-tetramethylpyrazine, TMP), and their combination (S. miltiorrhiza and TMP injection, SLI), respectively. The proinflammatory cytokines interleukin 6 (IL-6), IL-12, and tumor necrosis factor alpha (TNF-α) were detected as the preliminary indicators of inflammation. In addition, RNA sequencing (RNA-seq)-based transcriptional profiling analyses were conducted for TLR2-activated BMMs to determine the molecular mode of action of SLI as well as the contribution of SME to SLI activity.

Results: SLI mitigated inflammation in both BMMs and HUVECs. Refer to the combination, SME had pronounced anti-inflammatory effect on BMMs but had only a slight effect on HUVECs. In contrast, TMP had considerable anti-inflammatory effect on HUVECs but not on BMMs. Bioinformatic analysis identified a broad spectrum of regulatory genes, in addition to IL-6 gene, and C-X-C motif chemokine ligand 10 (CXCL10) appeared to be another key molecule involved in the mechanism underlying SLI and SME effects. At the molecular level, SME was a major contributor of the anti-inflammatory activity of SLI.

Conclusions: In TLR-activated inflammation, SLI exhibits a "multiple ingredient-multiple target" effect, with SME primarily affecting macrophages and TMP affecting HUVECs. Our study provides evidence for the clinical application of SLI in treating complex diseases involving inflammation-induced injury of both macrophages and epithelial cells. Further bioinformatics studies are required to reveal the entire molecular network involved in TMP, SME, and SLI activity.

Keywords: Danshen; IL-6; RNA-seq; inflammation; ligustrazine.