Cinnamaldehyde ameliorates LPS-induced cardiac dysfunction via TLR4-NOX4 pathway: The regulation of autophagy and ROS production

Cinnamaldehyde (CA), amajor bioactive compound extracted fromthe essential oil of Cortex Cinnamomi, exhibits anti-inflammatory activity on endotoxemia. Accumulating evidence indicates reactive oxygen species (ROS) and autophagy play a vital role in the cardiacdysfunction during endotoxemia. The aimof this studywas to unveil the mechanismof CA on ROS production and autophagy during endotoxemia.Male Sprague-Dawley ratswere stim- ulated by LPS (20 mg/kg i.v.) with or without treatment of CA. Cardiac function and histopathological staining were preformed 4 h after LPS stimulation.The levels ofTNF-α, IL-1βand IL-6were detected by ELISA. The expres- sion of p-JNK, p-ERK, p-p38, TLR4, NOX4, NOX2, ATG5 and LC3 proteins were determined by Western blot. The results showed that CA inhibited cardiac dysfunction, inflammatory infiltration and the levels of TNF-α, IL-1β and IL-6 in LPS stimulated rats by blocking the TLR4, NOX4, MAPK and autophagy signalings. In order to obtain further confirmation of the mechanismof CA on endotoxemia in vitro, a limited time-course study was firstly performed by Western blot. TLR4, NOX4 and LC3 were significantly increased after 4 h LPS stimulation. CA re- versed the intracellular ROS production and MAPK signaling activation induced by LPS. Electron microscopy, mRFP-GFP-LC3 transfection and western blot results revealed autophagic flux were attenuated after CA treat- ment. The siRNA and molecular docking results suggest that CA can suppress both TLR4 and NOX4 during endotoxemia. Our data revealed that CA ameliorated LPS-induced cardiac dysfunction by inhibiting ROS produc- tion and autophagy through TLR4-NOX4 pathway.