Pharmacological Network Analysis of the Functions and Mechanism of Quercetin From Jisuikang (<scp>JSK</scp>) in Spinal Cord Injury (<scp>SCI</scp>)

Neuroinflammation, especially microglia/macrophage activation, is a hallmark of spinal cord injury (SCI). Jisuikang (JSK) is a clinical experiential Chinese herbal formula for SCI therapy containing Huangqi (Astragali Radix), Danggui (Angelica sinensis Radix), Chishao (Paeoniae Radix Rubra), Dilong (earthworm, Pheretima aspergillum), Chuanxiong (Chuanxiong Rhizoma), Taoren (Persicae Seman) and Honghua (Carthami Flos). Eighteen active ingredients in 6 herbs of JSK were found to be correlated with inflammation, spinal injury and other diseases. These 18 active ingredients target 5464 genes according to the PubChem database. Through comparing differentially expressed genes between SCI and normal samples using GSE datasets, 50 hub genes were identified. These hub-genes were enriched in oxidative stress response and inflammation response. The herb-compound-target, herb-compound-signalling and compound-target-signalling networks were generated and quercetin was identified as the hub compound. A concentration of 25 μM quercetin showed no cytotoxicity but significantly protected microglial cells from LPS-induced inhibition of cell viability. LPS stimulation elevated the levels of iNOS, IL-1β and TNF-α but decreased IL-10 levels, whereas quercetin significantly attenuated LPS-induced alterations in these factors. Moreover, quercetin targeted gene, IL1R1 was reduced by quercetin as predicted. Overexpression of IL1R1 further increased LPS-induced inflammation, which could be partly reversed by quercetin treatment. In vivo, quercetin improved histopathological alterations, inflammation and promoted M2 macrophage polarisation post-injury, whereas IL1R1 overexpression partially attenuated the beneficial effects of quercetin on the rat SCI model. Collectively, quercetin, the main ingredient compound of JSK, protects against LPS-induced cell viability inhibition and cellular inflammation, which could be partially attenuated by IL1R1 overexpression.