Phellodendrine inhibits oxidative stress and promotes autophagy by regulating the AMPK/mTOR pathway in burn sepsis-induced intestinal injury

Intestinal injury is an important complication of burn sepsis with limited therapeutic choices. Phellodendrine is a promising compound for gastrointestinal inflammatory diseases and is extracted from the traditional Chinese medicine phellodendron bark. The study aimed to explore the role of phellodendrine against oxidative stress and autophagy in burn sepsis-induced intestinal injury. A mouse model of burn sepsis model was established by intraperitoneally injecting 10 mg/kg lipopolysaccharide (LPS) to mice burned by boiled water. Phellodendrine (30 mg/kg) was injected into mice in the drug group after scalding and before LPS injection. Hematoxylin and eosin staining was performed to observe histopathological changes in murine small intestines. TdT-mediated dUTP Nick-End Labeling (TUNEL) assay was performed to evaluate intestinal cell apoptosis. Immunofluorescence staining was performed to measure the expression and distribution of autophagy markers, light chain 3II (LC3II) and p62 in intestinal tissues. Oxidative stress indicators were detected using corresponding commercial kits. Protein levels of apoptotic markers, autophagy markers, and factors involved in adenosine monophosphate-activated protein kinase (AMPK)/mechanistic target of rapamycin (mTOR) pathway in intestines were quantified by western blotting. Phellodendrine attenuated bun sepsis-induced intestinal pathological changes. Meanwhile, aggravated cell apoptosis, reduction of antioxidant enzymes, and downregulation of autophagy markers in intestinal tissues of burn sepsis group were all improved by phellodendrine. In addition, phellodendrine activated the phosphorylation (p) of AMPK and inhibited p-mTOR signaling in intestines of burn septic mice. In conclusion, phellodendrine suppresses oxidative stress and activates autophagy in burn sepsis-induced intestinal injury by activating AMPK and inhibiting mTOR signaling.