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Abstract Background 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. Methods 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. Results 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 DRP1Ser616 phosphorylation through mTOR signaling, which in turn caused surplus mitochondrial fission-mediated necroptosis of macrophages, consequently exacerbating ALI. Conclusion 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.

Alveolar epithelial cell (AEC) senescence is a key driver of a variety of chronic lung diseases. It remains a challenge how to alleviate AEC senescence and mitigate disease progression. Our study identified a critical role of epoxyeicosatrienoic acids (EETs), downstream metabolites of arachidonic acid (ARA) by cytochrome p450 (CYP), in alleviating AEC senescence. In vitro, we found that 14,15-EET content was significantly decreased in senescent AECs. Exogenous EETs supplementation, overexpression of CYP2J2, or inhibition of EETs degrading enzyme soluble epoxide hydrolase (sEH) to increase EETs alleviated AECs' senescence. Mechanistically, 14,15-EET promoted the expression of Trim25 to ubiquitinate and degrade Keap1 and promoted Nrf2 to enter the nucleus to exert an anti-oxidant effect, thereby inhibiting endoplasmic reticulum stress (ERS) and alleviating AEC senescence. Furthermore, in D-galactose (D-gal)-induced premature aging mouse model, inhibiting the degradation of EETs by Trifluoromethoxyphenyl propionylpiperidin urea (TPPU, an inhibitor of sEH) significantly inhibited the protein expression of p16, p21, and γH2AX. Meanwhile, TPPU reduced the degree of age-related pulmonary fibrosis in mice. Our study has confirmed that EETs are novel anti-senescence substances for AECs, providing new targets for the treatment of chronic lung diseases.

Abstract Background Uncontrolled inflammation is an important factor in the occurrence and development of acute lung injury (ALI). Fibroblast growth factor-inducible 14 (Fn14), a plasma membrane-anchored receptor, takes part in the pathological process of a variety of acute and chronic inflammatory diseases. However, the role of Fn14 in ALI has not yet been elucidated. This study aimed to investigate whether the activation of Fn14 exacerbated lipopolysaccharide (LPS)-induced ALI in mice. Methods In vivo, ALI was induced by intratracheal LPS-challenge combined with/without Fn14 receptor blocker aurintricarboxylic acid (ATA) treatment in C57BL/6J mice. Following LPS administration, the survival rate, lung tissue injury, inflammatory cell infiltration, inflammatory factor secretion, oxidative stress, and NLRP3 inflammasome activation were assessed. In vitro, primary murine macrophages were used to evaluate the underlying mechanism by which Fn14 activated the NLRP3 inflammasome. Lentivirus was used to silence Fn14 to observe its effect on the activation of NLRP3 inflammasome in macrophages. Results In this study, we found that Fn14 expression was significantly increased in the lungs of LPS-induced ALI mice. The inhibition of Fn14 with ATA downregulated the protein expression of Fn14 in the lungs and improved the survival rate of mice receiving a lethal dose of LPS. ATA also attenuated lung tissue damage by decreasing the infiltration of macrophages and neutrophils, reducing inflammation, and suppressing oxidative stress. Importantly, we found that ATA strongly inhibited the activation of NLRP3 inflammasome in the lungs of ALI mice. Furthermore, in vitro, TWEAK, a natural ligand of Fn14, amplified the activation of NLRP3 inflammasome in the primary murine macrophage. By contrast, inhibition of Fn14 with shRNA decreased the expression of Fn14, NLRP3, Caspase-1 p10, and Caspase-1 p20, and the production of IL-1β and IL-18. Furthermore, the activation of Fn14 promoted the production of reactive oxygen species and inhibited the activation of Nrf2-HO-1 in activated macrophages. Conclusions Our study first reports that the activation of Fn14 aggravates ALI by amplifying the activation of NLRP3 inflammasome. Therefore, blocking Fn14 may be a potential way to treat ALI.

Alveolar epithelial cell (AEC) senescence is implicated in the pathogenesis of pulmonary fibrosis (PF). However, the exact mechanism underlying AEC senescence during PF remains poorly understood. Here, we reported an unrecognized mechanism for AEC senescence during PF. We found that, in bleomycin (BLM)-induced PF mice, the expressions of isocitrate dehydrogenase 3α (Idh3α) and citrate carrier (CIC) were significantly down-regulated in the lungs, which could result in mitochondria citrate (citratemt) accumulation in our previous study. Notably, the down-regulation of Idh3α and CIC was related to senescence. The mice with AECs-specific Idh3α and CIC deficiency by adenoviral vector exhibited spontaneous PF and senescence in the lungs. In vitro, co-inhibition of Idh3α and CIC with shRNA or inhibitors triggered the senescence of AECs, indicating that accumulated citratemt triggers AEC senescence. Mechanistically, citratemt accumulation impaired the mitochondrial biogenesis of AECs. In addition, the senescence-associated secretory phenotype from senescent AECs induced by citratemt accumulation activated the proliferation and transdifferentiation of NIH3T3 fibroblasts into myofibroblasts. In conclusion, we show that citratemt accumulation would be a novel target for protection against PF that involves senescence.

This study aimed to confirm whether strain ratio should be added after evaluation of lesions with 5-point elasticity scoring for differentiating benign and malignant breast lesions on ultrasonographic elastography(UE).From June 2010 to March 2012, 1080 consecutive female patients with breast lesions were recruited into a multicenter retrospective study, which involved 8 centers across China. Each institutional ethic review board approved the study, and all the patients gave written informed consent. All the patients underwent the UE procedure and the strain ratios were calculated and the final diagnosis was made by histological findings. The sensitivity, specificity, accuracy, PPV and NPV were calculated for each of the two evaluation systems and the areas under the ROC curve were compared.The strain ratios of benign lesions (mean, 2.6±2.0) and malignant lesions (mean,7.9±5.8) were significantly different (p 0.05). The strain ratio method shows better a diagnosis performance of the lesions with elasticity score 3 and 4.Although the two UE methods have similar diagnostic performance, separate calculation of the strain ratios seems compulsory, especially for the large solid breast lesions and the lesions with elasticity score 3 and 4.

The purpose of this study was to analyze the ultrasonic elastography features of phyllodes tumors of the breast comparing with fibroadenomas. A retrospective database was queried for the patients diagnosed as phyllodes tumors and fibroadenomas at Sun Yat-sen Memorial Hospital from January 2008 to August 2012. Three hundred and fifty lesions from 323 consecutive patients were included in the study. All the cases were examined by conventional ultrasonography and ultrasound elastography. Ultrasound elastography was used to calculate strain ratio of the lesions with bilateral breast tissue at the same depth as reference. There were 36 phyllodes tumors (27 benign, 8 borderline, 1 malignant) and 314 fibroadenomas (158 the pericanalicular type, 103 the intracanalicular type, 53 other special types). The strain ratio for phyllodes tumors (3.19 ± 2.33) was significantly higher than for fibroadenomas (1.69 ± 0.88) (p