Abstract
Objectives Although a recent study reported that stimulator of interferon genes (STING) in macrophages has an important regulatory effect on liver ischemia-reperfusion injury (IRI), the underlying mechanism of STING-dependent innate immune activation in liver macrophages (Kupffer cells, KCs) remains unclear. Here, we investigated the effect of STING on liver macrophage pyroptosis and the associated regulatory mechanism of liver IRI. Methods Clodronate liposomes were used to block liver macrophages. AAV-STING-RNAi-F4/80-EGFP, an adenoassociated virus (AAV), was transfected into the portal vein of mice in vivo, and the liver IRI model was established 14 days later. In vitro, liver macrophages were treated with STING-specific siRNA, and a hypoxia-reoxygenation (H/R) model was established. The level of STING was detected via Western blotting (WB), RT-PCR, and immunostaining. Liver tissue and blood samples were collected. Pathological changes in liver tissue were detected by hematoxylin and eosin (H&E) staining. Macrophage pyroptosis was detected by WB, confocal laser scanning microscopy (CLSM), transmission electron microscopy (TEM), and enzyme-linked immunosorbent assay (ELISA). The calcium concentration was measured by immunofluorescence and analyzed with a fluorescence microplate reader. Results The expression of STING increased with liver IRI but decreased significantly after the clodronate liposome blockade of liver macrophages. After knockdown of STING, the activation of caspase 1-GSDMD in macrophages and liver IRI was alleviated. More interestingly, hypoxia/reoxygenation (H/R) increased the calcium concentration in liver macrophages, but the calcium concentration was decreased after STING knockdown. Furthermore, after the inhibition of calcium in H/R-induced liver macrophages by BAPTA-AM, pyroptosis was significantly reduced, but the expression of STING was not significantlydecreased. Conclusions Knockdown of STING reduces calcium-dependent macrophage caspase 1-GSDMD-mediated liver IRI, representing a potential therapeutic approach in the clinic.
Highlights
Liver ischemia-reperfusion injury (IRI) is still a major problem affecting the survival of patients who undergo liver transplantation or partial hepatectomy [1]
We demonstrated that stimulator of interferon genes (STING) increases intracellular calcium in liver macrophages to promote pyroptosis, which leads to an increase in liver inflammation and tissue injury in liver IRI, and calcium promoted by STING in this process may be mainly released from the ER
To investigate whether STING is involved in liver IRI, we first examined the expression of STING in liver tissues in a liver IRI mouse model
Summary
Liver ischemia-reperfusion injury (IRI) is still a major problem affecting the survival of patients who undergo liver transplantation or partial hepatectomy [1]. It has been proposed that warm liver IRI has two distinct phases [2]. The second phase of liver injury is the inflammatory response, which is an important factor that contributes to liver IRI [4]; macrophages play a critical role in this process [5]. The activation of macrophages in response to pathogen-associated molecular patterns (PAMPs) or damage-associated molecular patterns (DAMPs) enhances the recruitment and activation of other innate and adaptive immune cells to amplify intrahepatic inflammation [6].
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