RESUMO
Objective:To observe the influence of NOD-like receptor thermal protein domain associated protein 6 (NLRP6) on hepatic ischemia-reperfusion injury (IRI), and elucidate the related mechanism.Methods:Thirty C57BL/6 mice with body weight of (18.80±1.99) g, were divided randomly into 5 groups, with 6 mice in each group: the mice that experienced only exploratory laparotomy were Sham group; that only underwent an operation to establish a hepatic IRI model were IRI group; that were treated with tail intravenous injection of clodronate (Clo) liposomes before the establishment of hepatic IRI model were Clo group; that received tail intravenous injection of clodronate liposomes and transfusion of bone marrow derived macrophages (BMDM) before the operation were Clo+ BMDM group; that received preoperative tail intravenous injection of clodronate liposomes and transfusion of BMDM with NLRP6 knockdown were Clo+ NLRP6-knockdown group. Real time quantitative polymerase chain reaction analysis (RT-PCR) and Western blot were performed to analyze the expressions of pyroptosis related proteins and factors. Simulate a hypoxia/reoxygenation (H/R) model in vitro, and set up experimental groups: lipopolysaccharide (LPS) + adenosine triphosphate (ATP), LPS+ ATP+ NLRP6-knockdown, H/R, and H/R+ NLRP6-knockdown. The changes of expressions of pyroptosis related proteins and factors were detected by RT-PCR and Western blot. Expression of NF-κB in vivo and in vitro was measured.Results:Compared with those in Sham group, protein expressions of NLRP6, NLRP3, Caspase-1, gasdermin D (GSDMD), IL-1β and IL-18 were remarkably increased in IRI group, but the levels of these proteins were dramatically decreased in Clo group with the exhaustion of macrophages in comparison with in IRI group, which were significantly different statistically (all P<0.05). The levels of these proteins were enhanced again in Clo+ BMDM group with the reconstruction of macrophages in contrast to those in Clo group, while the enhancements were more obvious in Clo+ NLRP6-knockdown group comparing to those in Clo+ BMDM group, with significant differences (all P<0.05). In vitro, pyroptosis rate for LPS+ ATP group was (16.39±1.06)%, which was lower than (27.34±2.79)% for LPS+ ATP+ NLRP6-knockdown group, with a statistical significance ( P<0.05). Meanwhile, pyroptosis rate for H/R group was (20.59±5.66)%, also much more reduced than (37.76±2.00)% for H/R+ NLRP6-knockdown group ( P<0.05). Expressions of NLRP3, Caspase-1, GSDMD, IL-1β, IL-18 and NF-κB p65 in LPS+ ATP+ NLRP6-knockdown group were more elevated than in LPS+ ATP group, and these indices were also more enhanced in H/R+ NLRP6-knockdown group than which in H/R group. Compared to the Sham group, expression of NF-κB p65 significantly increased in IRI group, which was reversed in Clo group, but enhanced again in Clo+ BMDM group and reached a peak in Clo+ NLRP6-knockdown group. Conclusions:Macrophage plays a critical role in immune response to hepatic IRI, wherein NLRP6 functions specifically. NLRP6 acts to suppress inflammation during hepatic IRI through regulating macrophage pyroptosis via inhibiting NF-κB.