Blockade of PI3K/AKT signaling pathway by Astragaloside IV attenuates ulcerative colitis via improving the intestinal epithelial barrier

Abstract

Abstract Background As a chronic inflammatory disease with recurrent symptoms, ulcerative colitis (UC) is severely threatening human health worldwide with a high prevalence. Intestinal mucosal barriers stand the first line to maintain the balance between food metabolism, nutrient absorption, and pathogen attacks. Although various signaling pathways have been found to be associated with intestinal barrier regulation, whether and how PI3K/AKT pathway is involved in gut mucosal barrier function modulation is still largely unknown. Methods The intestinal tissues from UC patients and colitis mice were collected and mucosal barrier function was measured by colonoscopy and electron microscopy observation, and immunofluorescence staining. PI3K/AKT signaling pathway activator YS-49 and inhibitor LY-29 were administered to colitic mice to uncover the effect of this pathway on gut mucosal barrier modulation. Then, network pharmacology was used to screen the specific PI3K/AKT inhibitor Astragaloside IV (AS-IV). The potential of AS-IV for intestinal barrier function repairment and UC treatment through blockade of PI3K/AKT pathway was further confirmed by histopathological staining, transmission electron microscopy, immunofluorescence, western blotting, and qRT-PCR. Finally, 16S rDNA sequencing was performed to uncover whether AS-IV can also ameliorate UC by regulating gut microbiota homeostasis. Results Mucosal barrier function was significantly damaged in UC patients and murine colitis and activated PI3K/AKT signaling pathway was extensively involved in it, as PI3K/AKT activator YS-49 apparently aggravated, whereas inhibitor LY-29 remarkably attenuated intestinal mucosal permeability of the colitic mice. AS-IV was found to be a specific PI3K/AKT inhibitor which greatly improved DSS-induced murine colitis via maintaining the intestinal crypt, microvilli, and desmosome structures in an orderly arrangement and improving intestinal epithelial permeability with the upregulation of tight junction proteins. Consistently, AS-IV protected Caco2 cells from LPS-induced damage by improving cell viability, inhibiting inflammation, and increasing the expression of tight junction proteins. In addition, microbiomics data found that gut microbiota, which also play critical roles in intestinal barrier disruption, participates in AS-IV–mediated intestinal barrier recovery as well. Conclusions PI3K/AKT is a promising target for UC treatment and AS-IV is a potential candidate to be developed for opening new avenues for rational pharmacological targeting of PI3K/AKT-associated diseases. PubChem CID: Chemical compounds studied in this article: Astragaloside IV (PubChem CID: 13943297); Kaempferol (PubChem CID: 5280863); Formononetin (PubChem CID: 5280378) PDB ID: AKT1(PDB ID: 7NH5)