Pulmonary fibrosis arises from the repeated epithelial mild injuries and insufficient repair lead to over activation of fibroblasts and excessive deposition of extracellular matrix, which result in a mechanical stretched niche. However, increasing mechanical stress likely exists before the establishment of fibrosis since early micro injuries increase local vascular permeability and prompt cytoskeletal remodeling which alter cellular mechanical forces. It is noteworthy that COVID-19 patients with severe hypoxemia will receive mechanical ventilation as supportive treatment and subsequent pathology studies indicate lung fibrosis pattern. At advanced stages, mechanical stress originates mainly from the stiff matrix since boundaries between stiff and compliant parts of the tissue could generate mechanical stress. Therefore, mechanical stress has a significant role in the whole development process of pulmonary fibrosis. The alveoli are covered by abundant capillaries and function as the main gas exchange unit. Constantly subject to variety of damages, the alveolar epithelium injuries were recently recognized to play a vital role in the onset and development of idiopathic pulmonary fibrosis. In this review, we summarize the literature regarding the effects of mechanical stress on the fundamental cells constituting the alveoli in the process of pulmonary fibrosis, particularly on epithelial cells, capillary endothelial cells, fibroblasts, mast cells, macrophages and stem cells. Finally, we briefly review this issue from a more comprehensive perspective: the metabolic and epigenetic regulation.

Pulmonary fibrosis (PF) is an interstitial lung disease characterized by the destruction of the pulmonary parenchyma caused by excessive extracellular matrix deposition. Despite the well-known etiological factors such as senescence, aberrant epithelial cell and fibroblast activation, and chronic inflammation, PF has recently been recognized as a metabolic disease and abnormal lipid signature was observed both in serum and bronchoalveolar lavage fluid (BALF) of PF patients and mice PF model. Clinically, observational studies suggest a significant link between high-fat diet (HFD) and PF as manifested by high intake of saturated fatty acids (SFAs) and meat increases the risk of PF and mice lung fibrosis. However, the possible mechanisms between HFD and PF remain unclear. In the current review we emphasize the diversity effects of the epigenetic dysregulation induced by HFD on the fibrotic factors such as epithelial cell injury, abnormal fibroblast activation and chronic inflammation. Finally, we discuss the potential ways for patients to improve their conditions and emphasize the prospect of targeted therapy based on epigenetic regulation for scientific researchers or drug developers.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and fatal interstitial lung disease with unknown etiology. Despite substantial progress in understanding the pathogenesis of pulmonary fibrosis and drug development, there is still no cure for this devastating disease. Fenbendazole (FBZ) is a benzimidazole compound that is widely used as an anthelmintic agent and recent studies have expanded the scope of its pharmacological effects and application prospect. This study demonstrated that FBZ treatment blunted bleomycin-induced lung fibrosis in mice. In vitro studies showed that FBZ inhibited the proliferation and migration of human embryo lung fibroblasts. Further studies showed that FBZ significantly inhibited glucose consumption, moderated glycolytic metabolism in fibroblasts, thus activated adenosine monophosphate-activated protein kinase (AMPK), and reduced the activation of the mammalian target of rapamycin (mTOR) pathway, thereby inhibiting transforming growth factor-β (TGF-β1)-induced fibroblast-to-myofibroblast differentiation and collagen synthesis. In summary, our data suggested that FBZ has potential as a novel treatment for pulmonary fibrosis.

Fat storage-inducing transmembrane proteins (FITMs) were initially identified in 2007 as members of a conserved endoplasmic reticulum (ER) resident transmembrane protein gene family, and were found to be involved in lipid droplet (LD) formation. Recently, several studies have further demonstrated that the ability of FITMs to directly bind to triglyceride and diacylglycerol, and the diphosphatase activity of hydrolyzing fatty acyl-CoA, might enable FITMs to maintain the formation of lipid droplets, engage in lipid metabolism, and protect against cellular stress. Based on the distribution of FITMs in tissues and their important roles in lipid droplet biology and lipid metabolism, it was discovered that FITMs were closely related to muscle development, adipocyte differentiation, and energy metabolism. Accordingly, the abnormal expression of FITMs was not only associated with type 2 diabetes and lipodystrophy, but also with cardiac disease and several types of cancer. This study reviews the structure, distribution, expression regulation, and functionality of FITMs and their potential relationships with various metabolic diseases, hoping to provide inspiration for fruitful research directions and applications of FITM proteins. Moreover, this review will provide an important theoretical basis for the application of FITMs in the diagnosis and treatment of related diseases.

Background: Idiopathic pulmonary fibrosis (IPF) is a fatal lung disease characterized by aberrant fibroblast activation and extracellular matrix deposition. Emerging evidence implicates mitochondrial dysfunction in IPF pathogenesis. Although CAMKK2 has been implicated in mitochondrial function associated with diabetic nephropathy, its role and underlying mechanisms in IPF remain unclear. This study aims to investigate the role of CAMKK2 in IPF. Methods: This study employed AAV-CAMKK2 mice, primary human/mouse lung fibroblasts, MRC-5 cells, and IPF patient samples. The CAMKK2 inhibitor (STO-609), shCAMKK2 and Flag-CAMKK2 overexpression plasmid were used to investigate the role of CAMKK2 in lung fibroblasts. Fibroblast activity was assessed by transwell migration, collagen contraction, and wound-healing assays. Mitochondrial function (ROS, mitochondrial membrane potential (MMP), ATP and oxygen consumption rate (OCR)) was measured by ROS assay, JC-1 assay, ATP assay and Seahorse assay. Mitochondrial dynamics (MFN1/MFN2, DRP1), PGC-1α, and p- ^T172 AMPK were analyzed alongside fibrotic markers (FN1, COL1A1 and α-SMA) by Western blotting and RT-qPCR. The AMPK inhibitor (Compound C) and PGC-1α inhibitor (SR-18292) were used to investigate the role of AMPK and PGC-1α in this study. Results: This study revealed that CAMKK2 expression was significantly downregulated in pulmonary fibrosis, concomitant with impaired mitochondrial function-related proteins (PGC-1α, MFN1and MFN2). In vitro experiments demonstrated that CAMKK2 inhibition or shCAMKK2 knockdown exacerbated fibroblast activation and extracellular matrix (ECM) production in both MRC-5 cells and primary mouse lung fibroblasts. Conversely, CAMKK2 overexpression attenuated TGF-β1-induced fibroblast activation and ECM deposition in MRC-5 cells and primary human lung fibroblasts. Further investigation established that CAMKK2 overexpression normalized mitochondrial morphology, enhanced MMP, ATP content and respiratory capacity to ameliorate mitochondrial dysfunction in TGF-β1–induced MRC-5 cells. Moreover, CAMKK2 upregulated mitochondrial fusion protein expression (MFN1 and MFN2) and suppressed fission (DRP1) in MRC-5 cells. Mechanistically, CAMKK2 regulated mitochondrial dynamics and OXPHOS function via the AMPK/PGC-1α pathway in TGF-β1–induced MRC-5 cells, as evidenced by rescued protein expression (MFN1 and MFN2), and reversal of these effects following AMPK or PGC-1α inhibition. In vivo studies showed that AAV-mediated CAMKK2 delivery significantly attenuated bleomycin-induced pulmonary fibrosis in mice. Conclusions: In summary, these findings collectively demonstrate that CAMKK2 regulated mitochondrial dynamics and OXPHOS function via AMPK/PGC-1α signaling pathway to alleviate pulmonary fibrosis in lung fibroblasts. Therefore, targeting CAMKK2 presents a novel and promising therapeutic strategy for the treatment of pulmonary fibrosis.

Background: The mechanisms of mitochondria damage of AEC2 in ventilation-induced lung injury (VILI) remained unclear. Objective: To determine whether KLF2 (Krüppel-like factor 2) inhibits VILI via alleviating mitochondria damage of AEC2 through facilitating mitophagy. Methods: Transmission electron microscope (TEM), seahorse XF, RNA-seq, Sftpc-CreERT2-Klf2f/f mice, primary AEC2, Adeno-associated virus (AAV) and molecular biology methods were used. Results: The mitochondria function were compromised in AEC2 of the Mice ventilation model and RNAseq together with GEO data analysis showed KLF2 was downregulated. Loss of function of KLF2 in mice AEC2 exacerbated VILI. Overexpression of KLF2 in mice AEC2 using the AAV system significantly alleviated VILI. The key markers of mitochondrial quality control (biogenesis, fission/fusion and mitophagy) were analyzed and found that PINK1 was decreased upon ventilation but was restored by KLF2 overexpression. As a transcriptional factor, KLF2 could bind to the promoter region of PINK1 and facilitate its transcription. Furthermore, we demonstrated that GC-1 a thyroid hormone receptorβ selective agonist could inhibit VILI by upregulating KLF2. Conclusions: We unveiled KLF2 as a novel and vital mediator that restores the mitochondrial function of AEC2 by facilitating mitophagy. Pharmaceutically activating KLF2 expression with GC-1 could alleviate VILI. erj;64/suppl_68/PA4435/F1 F1 F1