Objective To evaluate the effect of dexmedetomidine (Dex) on serum inflammatory factors and Nod‑like receptor pyrin domain 3 (NLRP3) inflammasome in endotoxemic mice. Methods According to the random number table method, 96 ICR male mice were divided into four groups (n=24): a control group (group C), a lipopolysaccharide (LPS) group (group L), a LPS+Dex group (group LD), and a LPS+Dex+atipamezole group (group LDT). Mice in groups L, LD, and LDT were intraperitoneally injected with LPS at 10 mg/kg to construct an endotoxemia model. Meanwhile, those in group LDT were intraperitoneally injected with atipamezole at 750 μg/kg immediately after intraperitoneal injection of LPS, once every 24 h, twice in total. Then, 30 min after modeling, mice in groups LDT and LD were intraperitoneally injected with Dex at a loading dose of 1.0 µg/kg. Then, the Alzet Osmotic Pumps were subcutaneously implanted in the left back of the mice. Dex was continuously pumped into groups LDT and LD via the capsule osmotic pump at a rate of 1.0 μg·kg−1·h−1, while an equal volume of normal saline was pumped into groups L and C. Then, 48 h after modeling, blood samples and myocardial tissues were collected. The activities of creatine kinase‑MB (CK‑MB) and lactate dehydrogenase (LDH) in plasma were measured by an automatic biochemical analyzer. The levels of serum cardiac troponin I (cTnI), tumor necrosis factor‑α (TNF‑α), interleukin‑6 (IL‑6) and interleukin‑1β (IL‑1β) were measured by enzyme‑linked immune sorbent assay (ELISA). The levels of total anti‑oxidation competence (T‑AOC) in the myocardium were detected by kits. The myocardial tissues were frozen and then sliced into thin sections. The levels of reactive oxygen species (ROS) were detected by dihydroethidium (DHE) staining. The protein levels of NLRP3, the active subunit p20 of caspase‑1 (caspase‑1 p20), apoptosis‑associated microprotein (ASC), and Sestrin2 were detected by Western blot. The apoptotic rate of cardiomyocytes was observed by terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) staining. The pathological changes of the myocardium were observed by hematoxylin and eosin (H‑E) staining. Results Compared with group C, groups L, LD and LDT showed increases in the activity of serum CK‑MB and LDH and the levels of serum cTnI, TNF‑α, IL‑6 and IL‑1β (P<0.05), decreases in the levels of T‑AOC (P<0.05) and increases in the levels of ROS in the myocardium (P<0.05), increases in the apoptotic rate of cardiomyocytes (P<0.05), up‑regulated protein levels of NLRP3, caspase‑1 p20 and Sestrin2 in the myocardium (P<0.05), and pathological damage in the myocardium; the protein levels of ASC were up‑regulated in groups L and LDT (P<0.05), without statistical difference in the protein levels of ASC in group LD (P>0.05). Compared with group L, group LD showed decreases in the activity of serum CK‑MB and LDH and the levels of serum cTnI, TNF‑α, IL‑6, and IL‑1β (P<0.05), increases in the levels of T‑AOC and decreases in the levels of ROS in the myocardium, decreases in the apoptotic rate of cardiomyocytes (P<0.05), down‑regulated protein levels of NLRP3, caspase‑1 p20 and ASC in the myocardium (P<0.05), without statistical difference in the protein levels of Sestrin2 (P>0.05), and the pathological damage in the myocardium was alleviated in group LD. Compared with group LD, group LDT showed increases in the activity of serum CK‑MB and LDH and the levels of serum cTnI, TNF‑α, IL‑6, and IL‑1β (P<0.05), decreases in the levels of T‑AOC and increases in the levels of ROS in the myocardium, increases in the apoptotic rate of cardiomyocytes (P<0.05), up-regulated protein levels of NLRP3, caspase‑1 p20 and ASC in the myocardium (P<0.05), and down‑regulated protein levels of Sestrin2 (P<0.05), and the pathological injury in the myocardium was aggravated in group LDT. Conclusions Dex can relieve endotoxin⁃induced myocardial injury in mice, which may be related to activation of Sestrin2. Sestrin2 exhibits protective effect on the myocardium of endotoxemic mice through inhibiting ROS production, and then suppressing the activation of NLRP3 inflammasome and its mediated inflammatory response.