3-(2-4-dichloro-5-methoxyphenyl)-2-sulfanyl-4(3h)-quinazolinone and Acute-Lung-Injury

Necroptosis of macrophages is a necessary element in reinforcing intrapulmonary inflammation during acute lung injury (ALI). However, the molecular mechanism that sparks macrophage necroptosis is still unclear. Triggering receptor expressed on myeloid cells-1 (TREM-1) is a pattern recognition receptor expressed broadly on monocytes/macrophages. The influence of TREM-1 on the destiny of macrophages in ALI requires further investigation.. TREM-1 decoy receptor LR12 was used to evaluate whether the TREM-1 activation induced necroptosis of macrophages in lipopolysaccharide (LPS)-induced ALI in mice. Then we used an agonist anti-TREM-1 Ab (Mab1187) to activate TREM-1 in vitro. Macrophages were treated with GSK872 (a RIPK3 inhibitor), Mdivi-1 (a DRP1 inhibitor), or Rapamycin (an mTOR inhibitor) to investigate whether TREM-1 could induce necroptosis in macrophages, and the mechanism of this process.. We first observed that the blockade of TREM-1 attenuated alveolar macrophage (AlvMs) necroptosis in mice with LPS-induced ALI. In vitro, TREM-1 activation induced necroptosis of macrophages. mTOR has been previously linked to macrophage polarization and migration. We discovered that mTOR had a previously unrecognized function in modulating TREM-1-mediated mitochondrial fission, mitophagy, and necroptosis. Moreover, TREM-1 activation promoted DRP1. In this study, we reported that TREM-1 acted as a necroptotic stimulus of AlvMs, fueling inflammation and aggravating ALI. We also provided compelling evidence suggesting that mTOR-dependent mitochondrial fission is the underpinning of TREM-1-triggered necroptosis and inflammation. Therefore, regulation of necroptosis by targeting TREM-1 may provide a new therapeutic target for ALI in the future.

Topics: Acute Lung Injury; Animals; Inflammation; Lipopolysaccharides; Macrophages; Mice; Mitochondrial Dynamics; Necroptosis; TOR Serine-Threonine Kinases; Triggering Receptor Expressed on Myeloid Cells-1

Sepsis-induced acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is characterized by widespread pulmonary inflammation and immune response, in which proinflammatory polarization of alveolar macrophages (AMs) plays an important role. Mitochondria are the key intracellular signaling platforms regulating immune cell responses. Moreover, accumulating evidence suggests that the mitochondrial dynamics of macrophages are imbalanced in sepsis and severe ALI/ARDS. However, the functional significance of mitochondrial dynamics of AMs in septic ALI/ARDS remains largely unknown, and whether it regulates the polarized phenotype of AMs is also unclear. Here, we demonstrated that the mitochondrial dynamics of AMs are imbalanced, manifested by impaired mitochondrial fusion, increased fission and mitochondrial cristae remodeling, both in septic models and ARDS patients. However, suppressing excessive mitochondrial fission with Mdivi-1 or promoting mitochondrial fusion with PM1 to maintain mitochondrial dynamic equilibrium in AMs could inhibit the polarization of AMs into proinflammatory phenotype and attenuate sepsis-induced ALI. These data suggest that mitochondrial dynamic imbalance mediates altered polarization of AMs and exacerbates sepsis-induced ALI. This study provides new insights into the underlying mechanisms of sepsis-induced ALI, suggesting the possibility of identifying future drug targets from the perspective of mitochondrial dynamics in AMs.

Topics: Acute Lung Injury; Humans; Lipopolysaccharides; Macrophages, Alveolar; Mitochondrial Dynamics; Respiratory Distress Syndrome; Sepsis

Sepsis is among the most devastating events in intensive care units. As a complication of sepsis, acute lung injury (ALI) is common and highly associated with poor outcome. The present study demonstrated that abnormal mitochondrial dynamics play a pivotal role in lipopolysaccharide (LPS)-induced ALI. Inhibiting the mitochondrial fission with the specific inhibitor-1 (Mdivi-1) ameliorated ALI as assessed by hematoxylin and eosin (H&E) staining and wet/dry ratio. Furthermore, Mdivi-1 reduced mitogen-activated protein kinases (MAPKs) activation, oxidative stress and apoptosis in the lungs. Plasma pro-inflammation cytokines were also reduced significantly in Mdivi-1-treated mice. In vitro study revealed that Mdivi-1 protected the macrophages from LPS-induced MAPKs activation, oxidative stress and cell apoptosis. Mdivi-1 also inhibited the release of pro-inflammatory cytokines. Morphological analysis showed that Mdivi-1 rescued the macrophages from LPS-induced mitochondrial fragmentation. Moreover, LPS treatment induced significant phosphorylation of Drp1 at Ser616, dephosphorylation at Ser637 and translocation of Drp1 from the cytoplasm to mitochondria, while Mdivi-1 inhibited those effects. Thus, modification of fission to rebuild mitochondrial homeostasis may offer an innovative opportunity for developing therapeutic strategies against ALI.

Topics: Acute Lung Injury; Animals; Apoptosis; Cytokines; Lipopolysaccharides; Male; MAP Kinase Signaling System; Mice; Mice, Inbred C57BL; Mitochondria; Mitochondrial Dynamics; Models, Animal; Oxidative Stress; Quinazolinones; RAW 264.7 Cells

The regulation of intracellular mitochondria degradation is mediated by mitophagy. While studies have shown that mitophagy can lead to mitochondrial dysfunction and cell damage, the role of Mdivi-1 and mitophagy remains unclear in acute lung injury (ALI) pathogenesis. In this study, we demonstrated that Mdivi-1, which is widely used as an inhibitor of mitophagy, ameliorated acute lung injury assessed by HE staining, pulmonary microvascular permeability assay, measurement of wet/dry weight (W/D) ratio, and oxygenation index (PaO2/FiO2) analysis. Then, the mitophagy related proteins were evaluated by western blot. The results indicated that LPS-induced activation of mitophagy was inhibited by Mdivi-1 treatment. In addition, we found that Mdivi-1 protected A549 cells against LPS-induced mitochondrial dysfunction. We also found that Mdivi-1 reduced pulmonary cell apoptosis in the LPS-challenged rats and protected pulmonary tissues from oxidative stress (represented by the content of superoxide dismutase, malondialdehyde and lipid peroxides in lung). Moreover, Mdivi-1 treatment ameliorated LPS-induced lung inflammatory response and cells recruitment. These findings indicate that Mdivi-1 mitigates LPS-induced apoptosis, oxidative stress, and inflammation in ALI, which may be associated with mitophagy inhibition. Thus, the inhibition of mitophagy may represent a potential therapy for treating ALI.

Topics: A549 Cells; Acute Lung Injury; Animals; Apoptosis; Disease Models, Animal; Humans; Lipopolysaccharides; Male; Mitochondria; Mitophagy; Oxidative Stress; Quinazolinones; Rats; Rats, Sprague-Dawley