Abstract: OBJECTIVE To investigate the protective mechanism of overexpression of intermedin (IMD) on myocardial injury in rats with septic shock. METHODS Totally 40 rats were randomly divided into sham operation group (Sham group), cecal ligation and puncture group (CLP group), adeno-associated virus vector (AAV)+CLP group and AAV-IMD+CLP group, with 10 rats in each group. The myocardial vector virus was transfected and verified respectively. After 3 w of successful transfection, the rat model of sepsis was established by cecal ligation and perforation, and the Sham group did not undergo cecal ligation and perforation after laparotomy. After 24 h of surgery, echocardiography was performed to detect the cardiac function of rats, and enzyme-linked immunosorbent assay was adopted to detect the levels of serum cardiac troponin I (cTnI), creatine kinase (CK), lactate dehydrogenase (LDH), tumor necrosis factor α (TNF-α), interleukin 6 (IL-6) and IL-1β. The levels of malondialdehyde (MDA) and superoxide dismutase (SOD) in myocardial tissues were detected, and Western blot was used to detect the protein expression levels of Nod-like and pyrin domain containing receptor 3 (NLRP3), apoptosis-associated speck-like protein containing a caspase recruitment domain (ASC) and Caspase-1 in myocardial tissues. RESULTS After 3 w of myocardial transfection, Western blot results showed that the transfection was successful (P<0.05). Compared with CLP group, the heart rate (HR), left ventricular peak systolic and diastolic velocity (±LVdp/dtmax), left ventricular end diastolic pressure (LVEDP), left ventricular end systolic pressure (LVESP) and mean arterial pressure (mABP) were increased (P<0.05), the levels of serum cTnI, CK and LDH were decreased (P<0.05), and the levels of serum TNF-α, IL-6 and IL-1β were reduced (P<0.05), the MDA level in myocardial tissue was lowered (P<0.05) while the SOD level was risen (P<0.05), and the protein expressions of NLRP3, ASC and Caspase-1 were down-regulated (P<0.05) in AAV-IMD+CLP group. CONCLUSION Overexpression of IMD had a protective effect on myocardial injury in rats with septic shock, which might be associated with the inhibition of NLRP3/ASC/caspase-1 signaling pathway.