TRPA1-Activated Peptides from Saiga Antelope Horn: Screening, Interaction Mechanism, and Bioactivity

Saiga antelope horn (SAH), a rare traditional Chinese medicine, exhibits activities of anti-feverish convulsions and anti-inflammation, whereas its underlying mechanism and specific pharmacological components are still unclear. In the present study, transient receptor potential ankyrin 1 (TRPA1), a major transient receptor potential cation channel was used as a target protein to identified TRPA1 high-affinity peptides (THPs) from SAH digests. Firstly, the SAH was digested under in vitro gastrointestinal conditions. With the method of affinity ultrafiltration and liquid chromatography-mass spectrometry (AUF-LC/MS), about 200 peptides that have a high-affinity interaction with the TRPA1 protein were screened from SAH digests. Subsequently, bioactivity databases and molecular docking were further exploited to identified three THPs, including RCWPDCR, FGFDGDF, and WFCEGSF. Furthermore, RIN-14B cells, characterized by the high expression of TRPA1 on cell surfaces, were used as the cell model to investigate the biological effect of THPs. Immunofluorescence and ELISA were conducted and showed that THPs can increase the intracellular Ca²⁺ concentration and serotonin (5-HT) secretion in RIN-14B cells by activating TRPA1, which is evidenced by impaired upregulation of intracellular Ca²⁺ levels and 5-HT secretion after pretreatment with the TRPA1 inhibitor (HC-030031). Moreover, an analysis of Western blots displayed that THPs up-regulated the expression levels of the 5-HT synthesis rate-limiting enzyme (TPH1) and 5-hydroxytryptophan decarboxylase (Ddc), while serotonin reuptake transporter (SERT) levels were down-regulated, suggesting that THPs enhance 5-HT secretion by regulating the 5-HT synthesis pathway. In summary, our findings demonstrate that THPs, which were identified from SAH digest via TRPA1-targeted affinity panning, exhibited the activation of the TRPA1 channel and enhanced 5-HT release in RIN-14B cells.