Omentin-1 induces mechanically activated fibroblasts lipogenic differentiation through pkm2/yap/pparγ pathway to promote lung fibrosis resolution.

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal lung disease characterized by extensive extracellular matrix (ECM) deposition by activated myofibroblasts, which are specialized hyper-contractile cells that promote ECM remodeling and matrix stiffening. New insights on therapeutic strategies aimed at reversing fibrosis by targeting myofibroblast fate are showing promise in promoting fibrosis resolution. Previously, we showed that a novel adipocytokine, omentin-1, attenuated bleomycin (BLM)-induced lung fibrosis by reducing the number of myofibroblasts. Apoptosis, deactivation, and reprogramming of myofibroblasts are important processes in the resolution of fibrosis. Here we report that omentin-1 reverses established lung fibrosis by promoting mechanically activated myofibroblasts dedifferentiation into lipofibroblasts. Omentin-1 promotes myofibroblasts lipogenic differentiation by inhibiting dimerization and nuclear translocation of glycolytic enzymes pyruvate kinase isoform M2 (PKM2) and activation of the downstream Yes-associated protein (YAP) by increasing the cofactor fructose-1,6-bisphosphate (F1, 6BP, FBP). Moreover, omentin-1 activates proliferator-activated receptor gamma (PPARγ) signaling, the master regulator of lipogenesis, and promotes the upregulation of the lipogenic differentiation-related protein perilipin 2 (PLIN2) by suppressing the PKM2-YAP pathway. Ultimately, omentin-1 facilitates myofibroblasts transformation into the lipofibroblast phenotype, with reduced collagen synthesis and enhanced degradation properties, which are crucial mechanisms to clear the ECM deposition in fibrotic tissue, leading to fibrosis resolution. Our results indicate that omentin-1 targets mechanical signal accelerates fibrosis resolution and reverses established lung fibrosis by promoting myofibroblasts lipogenic differentiation, which is closely associated with ECM clearance in fibrotic tissue. These findings suggest that targeting mechanical force to promote myofibroblast lipogenic differentiation is a promising therapeutic strategy against persistent lung fibrosis.

MICAL2PV suppresses the formation of tunneling nanotubes and modulates mitochondrial trafficking.

Tunneling nanotubes (TNTs) are actin-rich structures that connect two or more cells and mediate cargo exchange between spatially separated cells. TNTs transport signaling molecules, vesicles, organelles, and even pathogens. However, the molecular mechanisms regulating TNT formation remain unclear and little is known about the endogenous mechanisms suppressing TNT formation in lung cancer cells. Here, we report that MICAL2PV, a splicing isoform of the neuronal guidance gene MICAL2, is a novel TNT regulator that suppresses TNT formation and modulates mitochondrial distribution. MICAL2PV interacts with mitochondrial Rho GTPase Miro2 and regulates subcellular mitochondrial trafficking. Moreover, down-regulation of MICAL2PV enhances survival of cells treated with chemotherapeutical drugs. The monooxygenase (MO) domain of MICAL2PV is required for its activity to inhibit TNT formation by depolymerizing F-actin. Our data demonstrate a previously unrecognized function of MICAL2 in TNT formation and mitochondrial trafficking. Furthermore, our study uncovers a role of the MICAL2PV-Miro2 axis in mitochondrial trafficking, providing a mechanistic explanation for MICAL2PV activity in suppressing TNT formation and in modulating mitochondrial subcellular distribution.

FUS interacts with ATP synthase beta subunit and induces mitochondrial unfolded protein response in cellular and animal models.

FUS (fused in sarcoma) proteinopathy is a group of neurodegenerative diseases characterized by the formation of inclusion bodies containing the FUS protein, including frontotemporal lobar degeneration and amyotrophic lateral sclerosis. Previous studies show that mitochondrial damage is an important aspect of FUS proteinopathy. However, the molecular mechanisms by which FUS induces mitochondrial damage remain to be elucidated. Our biochemical and genetic experiments demonstrate that FUS interacts with the catalytic subunit of mitochondrial ATP synthase (ATP5B), disrupts the formation of ATP synthase complexes, and inhibits mitochondrial ATP synthesis. FUS expression activates the mitochondrial unfolded protein response (UPRmt). Importantly, down-regulating expression of ATP5B or UPRmt genes in FUS transgenic flies ameliorates neurodegenerative phenotypes. Our data show that mitochondrial impairment is a critical early event in FUS proteinopathy, and provide insights into the pathogenic mechanism of FUS-induced neurodegeneration.

Ozone therapy promotes the differentiation of basal keratinocytes via increasing Tp63-mediated transcription of KRT10 to improve psoriasis.

Psoriasis is a chronic immune-mediated inflammatory dermatosis. Recently, ozone therapy has been applicated to psoriasis treatment; however, the mechanism by which ozone therapy improves psoriasis remains unclear. The excessive proliferation and the differentiation of basal keratinocytes have been considered critical issues during pathological psoriasis process, in which keratin 6 (KRT6) and KRT10 might be involved. In the present study, KRT6, IL-17 and IL-22 protein within psoriasis lesions was decreased, while KRT10 and Tp63 protein in psoriasis lesions was increased by ozone treatment in both patient and IMQ mice psoriatic tissues. In the meantime, ozone treatment down-regulated KRT6 mRNA and protein expression while up-regulated KRT10 mRNA and protein expression within IL-22 treated primary KCs; the cell viability of KCs was suppressed by ozone treatment. Moreover, Tp63 bound to KRT10 promoter region to activate its transcription in basal keratinocytes; the promotive effects of ozone on Tp63 and KRT10 were significantly reversed by Tp63 silence. Both TP63 and KRT10 mRNA expression were significantly increased by ozone treatment in psoriasis lesions; there was a positive correlation between Tp63 and KRT10 expression within tissue samples, suggesting that ozone induces the expression of Tp63 to enhance the expression of KRT10 and the differentiation of keratinocytes, therefore improving the psoriasis. In conclusion, the application of ozonated oil could be an efficient and safe treatment for psoriasis; ozone promotes the differentiation of keratinocytes via increasing Tp63-mediated transcription of KRT10, therefore improving psoriasis.

[The metabolic networks of ferroptosis and links to lung diseases].

Ferroptosis is a newly discovered non-apoptotic form of regulated cell death driven by iron-dependent lipid peroxidation. The present studies have shown that many metabolic processes and homeostasis are affected by ferroptosis. It is related to many lung diseases, including acute lung injury, chronic obstructive pulmonary disease and pulmonary fibrosis, etc. Currently, the research on ferroptosis is still in its infancy. Previous studies have confirmed that ferroptosis is regulated by a variety of genes, and the mechanism is complex, mainly involving iron homeostasis and lipid peroxidation metabolism. This review summarizes some regulation networks of metabolic processes associated with ferroptosis and discusses the roles of ferroptosis in the pathophysiological progression of many lung diseases. We expected to provide new ideas and references for the treatment of these diseases.

FUS Interacts with HSP60 to Promote Mitochondrial Damage.

FUS-proteinopathies, a group of heterogeneous disorders including ALS-FUS and FTLD-FUS, are characterized by the formation of inclusion bodies containing the nuclear protein FUS in the affected patients. However, the underlying molecular and cellular defects remain unclear. Here we provide evidence for mitochondrial localization of FUS and its induction of mitochondrial damage. Remarkably, FTLD-FUS brain samples show increased FUS expression and mitochondrial defects. Biochemical and genetic data demonstrate that FUS interacts with a mitochondrial chaperonin, HSP60, and that FUS translocation to mitochondria is, at least in part, mediated by HSP60. Down-regulating HSP60 reduces mitochondrially localized FUS and partially rescues mitochondrial defects and neurodegenerative phenotypes caused by FUS expression in transgenic flies. This is the first report of direct mitochondrial targeting by a nuclear protein associated with neurodegeneration, suggesting that mitochondrial impairment may represent a critical event in different forms of FUS-proteinopathies and a common pathological feature for both ALS-FUS and FTLD-FUS. Our study offers a potential explanation for the highly heterogeneous nature and complex genetic presentation of different forms of FUS-proteinopathies. Our data also suggest that mitochondrial damage may be a target in future development of diagnostic and therapeutic tools for FUS-proteinopathies, a group of devastating neurodegenerative diseases.

MicroRNA-182 Promotes Lipoprotein Lipase Expression and Atherogenesisby Targeting Histone Deacetylase 9 in Apolipoprotein E-Knockout Mice.

BACKGROUND: Lipoprotein lipase (LPL) expressed in macrophages plays an important role in promoting the development of atherosclerosis or atherogenesis. MicroRNA-182 (miR-182) is involved in the regulation of lipid metabolism and inflammation. However, it remains unclear how miR-182 regulates LPL and atherogenesis.Methods and Results:Using bioinformatics analyses and a dual-luciferase reporter assay, we identified histone deacetylase 9 (HDAC9) as a target gene of miR-182. Moreover, miR-182 upregulated LPL expression by directly targetingHDAC9in THP-1 macrophages. Hematoxylin-eosin (H&E), Oil Red O and Masson's trichrome staining showed that apolipoprotein E (ApoE)-knockout (KO) mice treated with miR-182 exhibited more severe atherosclerotic plaques. Treatment with miR-182 increased CD68 and LPL expression in atherosclerotic lesions in ApoE-KO mice, as indicated by double immunofluorescence staining in the aortic sinus. Increased miR-182-induced increases in LPL expression in ApoE-KO mice was confirmed by real-time quantitative polymerase chain reaction and western blotting analyses. Treatment with miR-182 also increased plasma concentrations of proinflammatory cytokines and lipids in ApoE-KO mice. CONCLUSIONS: The results of the present study suggest that miR-182 upregulates LPL expression, promotes lipid accumulation in atherosclerotic lesions, and increases proinflammatory cytokine secretion, likely through targetingHDAC9, leading to an acceleration of atherogenesis in ApoE-KO mice.

Apelin-13 inhibits lipoprotein lipase expression via the APJ/PKCα/miR-361-5p signaling pathway in THP-1 macrophage-derived foam cells.

Atherosclerotic lesions are characterized by the accumulation of abundant lipids and chronic inflammation. Previous researches have indicated that macrophage-derived lipoprotein lipase (LPL) promotes atherosclerosis progression by accelerating lipid accumulation and pro-inflammatory cytokine secretion. Although apelin-13 has been regarded as an atheroprotective factor, it remains unclear whether it can regulate the expression of LPL. The aim of this study was to explore the effects of apelin-13 on the expression of LPL and the underlying mechanism in THP-1 macrophage-derived foam cells. Apelin-13 significantly decreased cellular levels of total cholesterol, free cholesterol, and cholesterol ester at the concentrations of 10 and 100 nM. ELISA analysis confirmed that treatment with apelin-13 reduced pro-inflammatory cytokine secretion, such as interleukin-6 (IL-6), interleukin-1ß (IL-1ß) and tumor necrosis factor-alpha (TNF-α). It was also found that apelin-13 inhibited the expression of LPL as revealed by western blot and real-time PCR analyses. Bioinformatics analyses and dual-luciferase reporter assay indicated that miR-361-5p directly downregulated the expression of LPL by targeting the 3'UTR of LPL. In addition, apelin-13 + miR-361-5p mimic significantly downregulated the expression of LPL in cells. Finally, we demonstrated that apelin-13 downregulated the expression of LPL through activating the activity of PKCα. Taken together, our results showed that apelin-13 downregulated the expression of LPL via activating the APJ/PKCα/miR-361-5p signaling pathway in THP-1 macrophage-derived foam cells, leading to inhibition of lipid accumulation and pro-inflammatory cytokine secretion. Therefore, our studies provide important new insight into the inhibition of lipid accumulation and pro-inflammatory cytokine secretion by apelin-13, and highlight apelin-13 as a promising therapeutic target in atherosclerosis.

MicroRNA-134 actives lipoprotein lipase-mediated lipid accumulation and inflammatory response by targeting angiopoietin-like 4 in THP-1 macrophages.

Angiopoietin-like 4 (Angptl4), a secreted protein, is an important regulator to irreversibly inhibit lipoprotein lipase (LPL) activity. Macrophage LPL contributes to foam cell formation via a so-called"molecular bridge" between lipoproteins and receptors on cell surface. It has been reported that macrophage ANGPTL4 suppresses LPL activity, foam cell formation and inflammatory gene expression to reduce atherosclerosis development. Recently, some studies demonstrated that microRNA-134 is upregulated in atherosclerotic macrophages. Here we demonstrate that miR-134 directly binds to 3'UTR of ANGPTL4 mRNA to suppression the expression of ANGPTL4. To investigate the potential roles of macrophage miR-134, THP-1 macrophages were transfected with miR-134 mimics or inhibitors. Our results showed that LPL activity and protein were dramatically increased. We also found that miR-134 activated LPL-mediated lipid accumulation. Collectively, our findings indicate that miR-134 may regulate lipid accumulation and proinfiammatory cytokine secretion in macrophages by targeting the ANGPTL4 gene. Our results have also suggested a promising and potential therapeutic target for atherosclerosis.

MiR-486 regulates cholesterol efflux by targeting HAT1.

RATIONALE: Excessive cholesterol accumulation in macrophages is a major factor of foam cell formation and development of atherosclerosis. Previous studies suggested that miR-486 plays an important role in cardiovascular diseases, but the underlying mechanism is still unknown. OBJECTIVE: The purpose of this study is to determine whether miR-486 regulates ATP-binding cassette transporter A1 (ABCA1) mediated cholesterol efflux, and also explore the underlying mechanism. METHODS AND RESULTS: Based on bioinformatics analysis and luciferase reporter assay, we transfected miR-486 mimic and miR-486 inhibitor into THP-1 macrophage-derived foam cells, and found that miR-486 directly bound to histone acetyltransferase-1 (HAT1) 3'UTR, and downregulated its mRNA and protein expression. In addition, our studies through transfection with wildtype HAT1 or shHAT1 (short hairpin HAT1) revealed that HAT1 could promote the expression of ABCA1 at both mRNA and protein levels. At the same time, the acetylation levels of the lysines 5 and 12 of histone H4 were upregulated after overexpression with HAT1. Meanwhile, the results of liquid scintillation counter and high performance liquid chromatography (HPLC) showed that miR-486 promoted cholesterol accumulation in THP-1 macrophages. CONCLUSION: These data indicated that miR-486 aggravate the cholesterol accumulation in THP-1 cells by targeting HAT1.

Cystathionine γ-lyase(CSE)/hydrogen sulfide system is regulated by miR-216a and influences cholesterol efflux in macrophages via the PI3K/AKT/ABCA1 pathway.

This study was designed to evaluate whether CSE/H2S system, which is regulated by miR-216a, regulated ABCA1-mediated cholesterol efflux and cholesterol contents in THP-1 macrophages-derived foam cells. Our qPCR and western blotting results showed that CSE/H2S significantly up-regulated the expression of ATP-binding cassette transporter A1 (ABCA1) mRNA and protein via PI3K/AKT pathway in foam cells derived from human THP-1 macrophages. The miR-216a directly targeted 3' untranslated region of CSE. It significantly reduced CSE and ABCA1 expression, and also decreased the phosphorylation of PI3K and AKT. Additionally, cholesterol efflux decreased, and cholesterol levels increased in THP-1 macrophage-derived foam cells in response to treatment with miR-216a. Our study demonstrates that CSE/H2S system is regulated by miR-216a, and regulates ABCA1-mediated cholesterol efflux and cholesterol levels through the PI3K/AKT pathway.

USP33 mediates Slit-Robo signaling in inhibiting colorectal cancer cell migration.

Originally discovered in neuronal guidance, the Slit-Robo pathway is emerging as an important player in human cancers. However, its involvement and mechanism in colorectal cancer (CRC) remains to be elucidated. Here, we report that Slit2 expression is reduced in CRC tissues compared with adjacent noncancerous tissues. Extensive promoter hypermethylation of the Slit2 gene has been observed in CRC cells, which provides a mechanistic explanation for the Slit2 downregulation in CRC. Functional studies showed that Slit2 inhibits CRC cell migration in a Robo-dependent manner. Robo-interacting ubiquitin-specific protease 33 (USP33) is required for the inhibitory function of Slit2 on CRC cell migration by deubiquitinating and stabilizing Robo1. USP33 expression is downregulated in CRC samples, and reduced USP33 mRNA levels are correlated with increased tumor grade, lymph node metastasis and poor patient survival. Taken together, our data reveal USP33 as a previously unknown tumor-suppressing gene for CRC by mediating the inhibitory function of Slit-Robo signaling on CRC cell migration. Our work suggests the potential value of USP33 as an independent prognostic marker of CRC.

Apelin-13 impedes foam cell formation by activating Class III PI3K/Beclin-1-mediated autophagic pathway.

Apelin-13, an adipokine, promotes cholesterol efflux in macrophages with antiatherosclerotic effect. Autophagy, an evolutionarily ancient response to cellular stress, has been involved in atherosclerosis. Therefore, the purpose of this study was to investigate whether apelin-13 regulates macrophage foam cell cholesterol metabolism through autophagy, and also explore the underlying mechanisms. Here, we revealed that apelin-13 decreased lipid accumulation in THP-1 derived macrophages through markedly enhancing cholesterol efflux. Our study further demonstrated that apelin-13 induced autophagy via activation of Class III phosphoinositide 3-kinase (PI3K) and Beclin-1. Inhibition of Class III PI3K and Beclin-1 suppressed the stimulatory effects of apelin-13 on autophagy activity. The present study concluded that apelin-13 reduces lipid accumulation of foam cells by activating autophagy via Class III PI3K/Beclin-1 pathway. Therefore, our results provide brand new insight about apelin-13 inhibiting foam cell formation and highlight autophagy as a promising therapeutic target in atherosclerosis.

DNA methylation modification in Idiopathic pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a chronic, progressive, and irreversible interstitial lung disease with a prognosis worse than lung cancer. It is a fatal lung disease with largely unknown etiology and pathogenesis, and no effective therapeutic drugs render its treatment largely unsuccessful. With continuous in-depth research efforts, the epigenetic mechanisms in IPF pathogenesis have been further discovered and concerned. As a widely studied mechanism of epigenetic modification, DNA methylation is primarily facilitated by DNA methyltransferases (DNMTs), resulting in the addition of a methyl group to the fifth carbon position of the cytosine base, leading to the formation of 5-methylcytosine (5-mC). Dysregulation of DNA methylation is intricately associated with the advancement of respiratory disorders. Recently, the role of DNA methylation in IPF pathogenesis has also received considerable attention. DNA methylation patterns include methylation modification and demethylation modification and regulate a range of essential biological functions through gene expression regulation. The Ten-Eleven-Translocation (TET) family of DNA dioxygenases is crucial in facilitating active DNA demethylation through the enzymatic conversion of the modified genomic base 5-mC to 5-hydroxymethylcytosine (5-hmC). TET2, a member of TET proteins, is involved in lung inflammation, and its protein expression is downregulated in the lungs and alveolar epithelial type II cells of IPF patients. This review summarizes the current knowledge of pathologic features and DNA methylation mechanisms of pulmonary fibrosis, focusing on the critical roles of abnormal DNA methylation patterns, DNMTs, and TET proteins in impacting IPF pathogenesis. Researching DNA methylation will enchance comprehension of the fundamental mechanisms involved in IPF pathology and provide novel diagnostic biomarkers and therapeutic targets for pulmonary fibrosis based on the studies involving epigenetic mechanisms.

NMDAR activation attenuates the protective effect of BM-MSCs on bleomycin-induced ALI via the COX-2/PGE2 pathway.

N-methyl-d-aspartate (NMDA) receptor (NMDAR) activation mediates glutamate (Glu) toxicity and involves bleomycin (BLM)-induced acute lung injury (ALI). We have reported that bone marrow-derived mesenchymal stem cells (BM-MSCs) are NMDAR-regulated target cells, and NMDAR activation inhibits the protective effect of BM-MSCs on BLM-induced pulmonary fibrosis, but its effect on ALI remains unknown. Here, we found that Glu release was significantly elevated in plasma of mice at d 7 after intratracheally injected with BLM. BM-MSCs were pretreated with NMDA (the selective agonist of NMDAR) and transplanted into the recipient mice after the BLM challenge. BM-MSCs administration significantly alleviated the pathological changes, inflammatory response, myeloperoxidase activity, and malondialdehyde content in the damaged lungs, but NMDA-pretreated BM-MSCs did not ameliorate BLM-induced lung injury in vivo. Moreover, NMDA down-regulated prostaglandin E2 (PGE2) secretion and cyclooxygenase (COX)-2 expression instead of COX-1 expression in BM-MSCs in vitro. We also found that NMDAR1 expression was increased and COX-2 expression was decreased, but COX-1 expression was not changed in primary BM-MSCs of BLM-induced ALI mice. Further, the cultured supernatants of lipopolysaccharide (LPS)-pretreated RAW264.7 macrophages were collected to detect inflammatory factors after co-culture with NMDA-pretreated BM-MSCs. The co-culture experiments showed that NMDA precondition inhibited the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation, and PGE2 could partially alleviate this inhibition. Our findings suggest that NMDAR activation attenuated the protective effect of BM-MSCs on BLM-induced ALI in vivo. NMDAR activation inhibited COX-2 expression and PGE2 secretion in BM-MSCs and weakened the anti-inflammatory effect of BM-MSCs on LPS-induced macrophage inflammation in vitro. In conclusion, NMDAR activation attenuates the protective effect of BM-MSCs on BLM-induced ALI via the COX-2/PGE2 pathway. Keywords: Acute Lung Injury, BM-MSCs, NMDA receptor, COX-1/2, PGE2.

A novel senolytic drug for pulmonary fibrosis: BTSA1 targets apoptosis of senescent myofibroblasts by activating BAX.

Idiopathic pulmonary fibrosis is a progressive and age-related disease that results from impaired lung repair following injury. Targeting senescent myofibroblasts with senolytic drugs attenuates pulmonary fibrosis, revealing a detrimental role of these cells in pulmonary fibrosis. The mechanisms underlying the occurrence and persistence of senescent myofibroblasts in fibrotic lung tissue require further clarification. In this study, we demonstrated that senescent myofibroblasts are resistant to apoptosis by upregulating the proapoptotic protein BAX and antiapoptotic protein BCL-2 and BCL-XL, leading to BAX inactivation. We further showed that high levels of inactive BAX-mediated minority mitochondrial outer membrane permeabilization (minority MOMP) promoted DNA damage and myofibroblasts senescence after insult by a sublethal stimulus. Intervention of minority MOMP via the inhibition of caspase activity by quinolyl-valyl-O-methylaspartyl-[2,6-difluorophenoxy]-methyl ketone (QVD-OPH) or BAX knockdown significantly reduced DNA damage and ultimately delayed the progression of senescence. Moreover, the BAX activator BTSA1 selectively promoted the apoptosis of senescent myofibroblasts, as BTSA1-activated BAX converted minority MOMP to complete MOMP while not injuring other cells with low levels of BAX. Furthermore, therapeutic activation of BAX with BTSA1 effectively reduced the number of senescent myofibroblasts in the lung tissue and alleviated both reversible and irreversible pulmonary fibrosis. These findings advance the understanding of apoptosis resistance and cellular senescence mechanisms in senescent myofibroblasts in pulmonary fibrosis and demonstrate a novel senolytic drug for pulmonary fibrosis treatment.

Abnormal mitochondrial iron metabolism damages alveolar type II epithelial cells involved in bleomycin-induced pulmonary fibrosis.

Rationale: Pulmonary fibrosis is a chronic progressive lung disease with limited therapeutic options. We previously revealed that there is iron deposition in alveolar epithelial type II cell (AECII) in pulmonary fibrosis, which can be prevented by the iron chelator deferoxamine. However, iron in the cytoplasm and the mitochondria has two relatively independent roles and regulatory systems. In this study, we aimed to investigate the role of mitochondrial iron deposition in AECII injury and pulmonary fibrosis, and to find potential therapeutic strategies. Methods: BLM-treated mice, MLE-12 cells, and primary AECII were employed to establish the mouse pulmonary fibrosis model and epithelial cells injury model, respectively. Mitochondrial transplantation, siRNA and plasmid transfection, western blotting (WB), quantitative real-time polymerase chain reaction (RT-qPCR), polymerase chain reaction (PCR), immunofluorescence, immunoprecipitation (IP), MitoSOX staining, JC-1 staining, oxygen consumption rate (OCR) measurement, and Cell Counting Kit-8 (CCK8) assay were utilized to elucidate the role of mitochondrial iron deposition in cell and lung fibrosis and determine its mechanism. Results: This study showed that prominent mitochondrial iron deposition occurs within AECII in bleomycin (BLM)-induced pulmonary fibrosis mouse model and in BLM-treated MLE-12 epithelial cells. Further, the study revealed that healthy mitochondria rescue BLM-damaged AECII mitochondrial iron deposition and cell damage loss. Mitoferrin-2 (MFRN2) is the main transporter that regulates mitochondrial iron metabolism by transferring cytosolic iron into mitochondria, which is upregulated in BLM-treated MLE-12 epithelial cells. Direct overexpression of MFRN2 causes mitochondrial iron deposition and cell damage. In this study, decreased ubiquitination of the ubiquitin ligase F-box/LRR-repeat protein 5 (FBXL5) degraded iron-reactive element-binding protein 2 (IREB2) and promoted MFRN2 expression as well as mitochondrial iron deposition in damaged AECII. Activation of the prostaglandin E2 receptor EP4 subtype (EP4) receptor signaling pathway counteracted mitochondrial iron deposition by downregulating IREB2-MFRN2 signaling through upregulation of FBXL5. This intervention not only reduced mitochondrial iron content but also preserved mitochondrial function and protected against AECII damage after BLM treatment. Conclusion: Our findings highlight the unexplored roles, mechanisms, and regulatory approaches of abnormal mitochondrial iron metabolism of AECII in pulmonary fibrosis. Therefore, this study deepens the understanding of the mechanisms underlying pulmonary fibrosis and offers a promising strategy for developing effective therapeutic interventions using the EP4 receptor activator.

Sulfasalazine ameliorates lipopolysaccharide-induced acute lung injury by inhibiting oxidative stress and nuclear factor-kappaB pathways.

Acute lung injury/acute respiratory distress syndrome (ALI/ARDS) has a high mortality rate and incidence of complications. The pathophysiology of ALI/ARDS is still not fully understood. The lipopolysaccharide (LPS)-induced mouse model of ALI has been widely used to study human ALI/ARDS. Sulfasalazine (SASP) has antibacterial and anti-inflammatory effects and is used for treating inflammatory bowel and rheumatic diseases. However, the effect of SASP on LPS-induced ALI in mice has not yet been reported. Therefore, we aimed to investigate the effect of SASP on LPS-induced ALI in mice. Mice were intraperitoneally injected with SASP 2 h before or 4 h after LPS modeling. Pulmonary pathological damage was measured based on inflammatory factor expression (malondialdehyde and superoxide dismutase levels) in the lung tissue homogenate and alveolar lavage fluid. The production of inflammatory cytokines and occurrence of oxidative stress in the lungs induced by LPS were significantly mitigated after the prophylactic and long-term therapeutic administration of SASP, which ameliorated ALI caused by LPS. SASP reduced both the production of inflammatory cytokines and occurrence of oxidative stress in RAW264.7 cells, which respond to LPS. Moreover, its mechanism contributed to the suppression of NF-κB and nuclear translocation. In summary, SASP treatment ameliorates LPS-induced ALI by mediating anti-inflammatory and antioxidant effects, which may be attributed to the inhibition of NF-κB activation and promotion of antioxidant defenses. Thus, SASP may be a promising pharmacologic agent for ALI therapy.