Inhibition of TREM-1 and cGAS-STING Pathway Ameliorates Mitochondrial Damage-Associated Molecular Patterns-Mediated Lung Injury in Mice with Ischemia-Reperfusion-Induced AKI

Background: Acute kidney injury (AKI) is the most common cause of distant organ dysfunction in critically ill patients. Acute lung injury (ALI) often accompanies AKI and contributes to even higher morbidity and mortality in these patients. Mitochondrial dysfunction is considered a key mechanism driving the damage after renal ischemia-reperfusion (IR) injury. The damaged mitochondria release mitochondrial damage associated molecular patterns (mtDAMPs) into the cytosol, initiate an innate immune response, and activate the systemic inflammatory response. Methods: To better understand the underlying mechanism, mice were challenged with 30 min of bilateral kidney ischemia followed by 24 h of reperfusion. ALI was confirmed by lung wet/dry ratio and neutrophile infiltration in the Bronchoalveolar Lavage Fluid (BALF) using flow cytometry. The cytokine profiling was used to demonstrate the cytokine changes. Gene expression level were confirmed by WB, qPCR and ELISA. The mitochondria morphologys were observed using transmission electron microscopy (TEM). The cell proliferation, migration and tight junction were measured by Electric Cell-substrate Impedance Sensing (ECIS). Results: The cytokine profiling in mice lung tissue showed that the expression levels of BLC, TIMP-1, TREM-1, JE, IL-16 and ICAM-1 were significantly increased, especially TREM-1 which had a 7-fold increase. WB demonstrated that the cGAS and STING were increased in AKI mice. TEM images from both kidneys and lungs indicated that the mtDAMPs were released from damaged kidney mitochondria. We also induced a similar ALI in mice while injecting them with mtDAMPs. WB, qPCR and ELISA results showed that TREM-1 and cGAS-STING pathway were upregulated in the mtDAMPs injected group. Mouse macrophage and epithelial cell were utilized to verify if inhibiting of the TREM-1 and cGAS-STING pathway reduces mtDAMPs-induced lung injury. ECIS results demonstrated that mtDAMPs treated cells have decreased proliferation, migration and tight junction. On the other hand, inhibiting the TREM-1 and cGAS-STING pathway significantly increased cell proliferation, migration and tight junction. Conclusion: Our findings indicated that targeting TREM-1 and cGAS-STING has the potential to reduce acute lung injury caused by mtDAMPs in IR-AKI. Funding: NIDDK Support