ObjectiveTo investigate the mechanism by which Tianxiang pills （TXP） alleviates myocardial cell pyroptosis in the rat model of myocardial ischemia/reperfusion （I/R） injury through modulating the reactive oxygen species （ROS）/cysteinyl aspartate-specific proteinase-1 （Caspase-1）/gasdermin D （GSDMD） signaling pathway. MethodsA total of 54 SPF-grade adult male Sprague-Dawley rats were randomized into six groups （n=9）： sham （thoracotomy only without ligation）， I/R （left anterior descending coronary artery ligation for 30 min followed by reperfusion）， NAC （positive control， N-acetylcysteine， 150 mg·kg^-1， by gavage）， low-dose Tianxiang pills （TXP-L， 2.5 g·kg^-1， by gavage）］， medium-dose Tianxiang pills （TXP-M， 5 g·kg^-1， by gavage）， and high-dose Tianxiang pills （TXP-H， 10 g·kg^-1， by gavage）. The fluorescent probe method was employed to measure the ROS level. Biochemical assay kits were employed to determine the Caspase-1 activity， superoxide dismutase （SOD） activity， malondialdehyde （MDA） content， and glutathione peroxidase （GSH-Px） activity. Myocardial infarct size was assessed by 2，3，5-triphenyltetrazolium chloride （TTC） staining. Western blot analysis was performed to evaluate the expression levels of proteins in the ROS/Caspase-1/GSDMD pathway， including GSDMD， cleaved Caspase-1/Caspase-1 ratio， the N-terminal domain of GSDMD （GSDMD-N）， and the p22-phox subunit of the reduced nicotinamide adenine dinucleotide phosphate （NADPH） oxidase complex. Enzyme-linked immunosorbent assay （ELISA） was utilized to determine the concentration of interleukin-1β （IL-1β）. Transmission electron microscopy （TEM） was employed to observe mitochondrial structure and to score the degree of mitochondrial swelling. ResultsCompared with the Sham group， the I/R group exhibited elevated the levels of ROS， Caspase-1 activity， GSDMD expression， IL-1β concentration， MDA content， infarct area， mitochondrial swelling score， cleaved Caspase-1/Caspase-1， GSDMD-N， and p22phox and decreased activities of SOD and GSH-Px （P<0.05）. Compared with the I/R group， NAC and different doses of TXP significantly reduced the ROS level， Caspase-1 activity， GSDMD expression， IL-1β concentration， MDA content， infarct area， and mitochondrial swelling score. Moreover， they downregulated the expression of cleaved Caspase-1/Caspase-1， GSDMD-N， and p22phox and increased the activities of SOD and GSH-Px （P<0.05）. Furthermore， TXP exerted effects on ROS， MDA， SOD， GSH-Px， Caspase-1 activity， GSDMD expression， IL-1β concentration， cleaved Caspase-1/Caspase-1， GSDMD-N， p22phox， infarct area， and mitochondrial swelling score in a dose-dependent manner （P<0.05）. ConclusionTianxiang pills alleviates myocardial I/R injury by mitigating oxidative stress and cell pyroptosis through the inhibition of the ROS/Caspase-1/GSDMD signaling pathway.

Objective:To investigate the changes of gene or protein expression and activity of matrix metalloprotein9 (MMP9) and tissue inhibitor ofmetalloproteinasel (TIMP1) in the carotid artery (CA) of 4 wk hindlimb unweighted rat.Methods:A 4 weeks(wk) hindlimb unweighted (HU) rat model was used to simulate the effect of weightlessness on the cardiovascular system.Transmission electron microscopy was used to detect the content of ECM.Reverse transcriptase polymerase chain reaction(RT-PCR) was conducted to measure the mRNA content MMP and TIMP1.Immunohistochemistry and Western blot technique were used to measure the protein abundance.Gelatin zymography was carried out to detect the activity of MMP9.Results:Compared to the control group (CON),the area of ECM was enhanced (P＜0.05) and the content of collage fiber was increased (P＜0.05) in the CA of HU rats;moreover,HU did not affect the mRNA expression of MMP9,but significantly reduced the protein content (P＜0.05) or enzymatic activity (P＜0.05).Accordingly,the mRNA or protein expression of TIMP1 in the CA was significantly increased by HU (P＜0.05).Conclusion:Simulated weightlessness caused imbalance between MMP and TIMP1 expression,which might contribute to the ECM aggregation and stiffness of CA.