Pyruvate kinase M2 sustains cardiac mitochondrial quality surveillance in septic cardiomyopathy by regulating prohibitin 2 abundance via S91 phosphorylation.

The endogenous mitochondrial quality control (MQC) system serves to protect mitochondria against cellular stressors. Although mitochondrial dysfunction contributes to cardiac damage during many pathological conditions, the regulatory signals influencing MQC disruption during septic cardiomyopathy (SC) remain unclear. This study aimed to investigate the involvement of pyruvate kinase M2 (PKM2) and prohibitin 2 (PHB2) interaction followed by MQC impairment in the pathogenesis of SC. We utilized LPS-induced SC models in PKM2 transgenic (PKM2TG) mice, PHB2S91D-knockin mice, and PKM2-overexpressing HL-1 cardiomyocytes. After LPS-induced SC, cardiac PKM2 expression was significantly downregulated in wild-type mice, whereas PKM2 overexpression in vivo sustained heart function, suppressed myocardial inflammation, and attenuated cardiomyocyte death. PKM2 overexpression relieved sepsis-related mitochondrial damage via MQC normalization, evidenced by balanced mitochondrial fission/fusion, activated mitophagy, restored mitochondrial biogenesis, and inhibited mitochondrial unfolded protein response. Docking simulations, co-IP, and domain deletion mutant protein transfection experiments showed that PKM2 phosphorylates PHB2 at Ser91, preventing LPS-mediated PHB2 degradation. Additionally, the A domain of PKM2 and the PHB domain of PHB2 are required for PKM2-PHB2 binding and PHB2 phosphorylation. After LPS exposure, expression of a phosphorylation-defective PHB2S91A mutant negated the protective effects of PKM2 overexpression. Moreover, knockin mice expressing a phosphorylation-mimetic PHB2S91D mutant showed improved heart function, reduced inflammation, and preserved mitochondrial function following sepsis induction. Abundant PKM2 expression is a prerequisite to sustain PKM2-PHB2 interaction which is a key element for preservation of PHB2 phosphorylation and MQC, presenting novel interventive targets for the treatment of septic cardiomyopathy.

Molecular epidemiological and clinical infection characteristics analysis of Ralstonia.

PURPOSE: This study was to clarify the molecular epidemiology and clinical infection characteristics of Ralstonia pickettii and establish sequence typing system. METHODS: 48 nonrepetitive Ralstonia pickettii strains were collected from January 2008 to December 2013 at the Chinese People's Liberation Army General Hospital (PLAGH) and were identified through a specific PCR experiment, 16 S rDNA experiment and VITEK 2 system to compare the identification accuracy. The sequence types of the strains were analyzed by multilocus sequence typing (MLST) method. The antibiotic sensitivity of these strains was determined with disc diffusion tests and broth microdilution method. The clinical data of Ralstonia pickettii infected patients were collected. RESULTS: All of the 48 strains were identified as Ralstonia pickettii by VITEK 2 system. 30 and 34 strains were identified as Ralstonia pickettii by PCR and 16 S rDNA experiment respectively. ST9 was the most sequence types (STs) in these 18 STs of 42 strains. 42 strains were divided into 2 groups (A and B) and 18 genotypes. Ralstonia pickettii was sensitive to some cephalosporins, ß-lactam/ß-lactamase inhibitor, levofloxacin and trimethoprim/sulfamethoxazole. Cough, sputum, shortness of breath and pulmonary rales were the common clinical symptoms of most Ralstonia pickettii infected patients. CONCLUSION: We established a sequence typing system with a relatively fine resolution and the PCR assay is a faster and more sensitive method for clinical identification of Ralstonia pickettii. ST9 is the most common sequence types of Ralstonia pickettii. The most common clinical characteristics of Ralstonia pickettii infected patients were cough, sputum, shortness of breath and pulmonary rales.

Clinical Features of 85 Fatal Cases of COVID-19 from Wuhan. A Retrospective Observational Study.

Rationale: The global death toll from coronavirus disease (COVID-19) virus as of May 12, 2020, exceeds 286,000. The risk factors for death were attributed to advanced age and comorbidities but have not been accurately defined.Objectives: To report the clinical features of 85 fatal cases of COVID-19 in two hospitals in Wuhan.Methods: Medical records were collected of 85 fatal cases of COVID-19 between January 9, 2020, and February 15, 2020. Information recorded included medical history, exposure history, comorbidities, symptoms, signs, laboratory findings, computed tomographic scans, and clinical management.Measurements and Main Results: The median age of the patients was 65.8 years, and 72.9% were male. Common symptoms were fever (78 [91.8%]), shortness of breath (50 [58.8%]), fatigue (50 [58.8%]), and dyspnea (60 [70.6%]). Hypertension, diabetes, and coronary heart disease were the most common comorbidities. Notably, 81.2% of patients had very low eosinophil counts on admission. Complications included respiratory failure (80 [94.1%]), shock (69 [81.2%]), acute respiratory distress syndrome (63 [74.1%]), and arrhythmia (51 [60%]), among others. Most patients received antibiotic (77 [90.6%]), antiviral (78 [91.8%]), and glucocorticoid (65 [76.5%]) treatments. A total of 38 (44.7%) and 33 (38.8%) patients received intravenous immunoglobulin and IFN-α2b, respectively.Conclusions: In this depictive study of 85 fatal cases of COVID-19, most cases were males aged over 50 years with noncommunicable chronic diseases. The majority of the patients died of multiple organ failure. Early onset of shortness of breath may be used as an observational symptom for COVID-19 exacerbations. Eosinophilopenia may indicate a poor prognosis. A combination of antimicrobial drugs did not offer considerable benefit to the outcome of this group of patients.

Melatonin attenuates ER stress and mitochondrial damage in septic cardiomyopathy: A new mechanism involving BAP31 upregulation and MAPK-ERK pathway.

Septic cardiomyopathy is associated with mitochondrial damage and endoplasmic reticulum (ER) dysfunction. However, the upstream mediator of mitochondrial injury and ER stress has not been identified and thus little drug is available to treat septic cardiomyopathy. Here, we explored the role of B-cell receptor-associated protein 31 (BAP31) in septic cardiomyopathy and figure out whether melatonin could attenuate sepsis-mediated myocardial depression via modulating BAP31. Lipopolysaccharide (LPS) was used to establish the septic cardiomyopathy model. Pathway analysis was performed via western blot, quantitative polymerase chain reaction and immunofluorescence. Mitochondrial function and ER stress were detected via enzyme-linked immunosorbent assay, western blot, and immunofluorescence. After exposure to LPS, cardiac function was reduced due to excessive inflammation response and extensive cardiomyocyte death. Mechanistically, melatonin treatment could dose-dependently improve cardiomyocyte viability via preserving mitochondrial function and reducing ER stress. Further, we found that BAP31 transcription was repressed by LPS whereas melatonin could restore BAP31 expression; this effect was dependent on the MAPK-ERK pathway. Inhibition of the ERK pathway and/or knockdown of BAP31 could attenuate the beneficial effects of melatonin on mitochondrial function and ER homeostasis under LPS stress. Altogether, our results indicate that ERK-BAP31 pathway could be used as a critical mediator for mitochondrial function and ER homeostasis in sepsis-related myocardial injury. Melatonin could stabilize BAP31 via the ERK pathway and thus contribute to the preservation of cardiac function in septic cardiomyopathy.

Correction to: DNA­PKcs promotes cardiac ischemia reperfusion injury through mitigating BI­1­governed mitochondrial homeostasis.

Since the publication of the article, the authors found a small problem with Fig. 7e. Unfortunately, Fig. 7e did not contain the correct images. The correct images are shown below and do not change the conclusions.

DNA-PKcs promotes cardiac ischemia reperfusion injury through mitigating BI-1-governed mitochondrial homeostasis.

DNA-dependent protein kinase catalytic subunit (DNA-PKcs) is a novel inducer to promote mitochondrial apoptosis and suppress tumor growth in a variety of cells although its role in cardiovascular diseases remains obscure. This study was designed to examine the role of DNA-PKcs in cardiac ischemia reperfusion (IR) injury and mitochondrial damage. Cardiomyocyte-specific DNA-PKcs knockout (DNA-PKcsCKO) mice were subjected to IR prior to assessment of myocardial function and mitochondrial apoptosis. Our data revealed that IR challenge, hypoxia-reoxygenation (HR) or H2O2-activated DNA-PKcs through post-transcriptional phosphorylation in murine hearts or cardiomyocytes. Mice deficient in DNA-PKcs in cardiomyocytes were protected against cardiomyocyte death, infarct area expansion and cardiac dysfunction. DNA-PKcs ablation countered IR- or HR-induced oxidative stress, mPTP opening, mitochondrial fission, mitophagy failure and Bax-mediated mitochondrial apoptosis, possibly through suppression of Bax inhibitor-1 (BI-1) activity. A direct association between DNA-PKcs and BI-1 was noted where DNA-PKcs had little effect on BI-1 transcription but interacted with BI-1 to promote its degradation. Loss of DNA-PKcs stabilized BI-1, thus offering resistance of mitochondria and cardiomyocytes against IR insult. Moreover, DNA-PKcs ablation-induced beneficial cardioprotection against IR injury was mitigated by concurrent knockout of BI-1. Double deletion of DNA-PKcs and BI-1 failed to exert protection against global IR injury and mitochondrial damage, confirming a permissive role of BI-1 in DNA-PKcs deletion-elicited cardioprotection against IR injury. DNA-PKcs serves as a novel causative factor for mitochondrial damage via suppression of BI-1, en route to the onset and development of cardiac IR injury.

Pirfenidone alleviates lipopolysaccharide-induced lung injury by accentuating BAP31 regulation of ER stress and mitochondrial injury.

Pirfenidone has been widely used in the treatment of idiopathic pulmonary fibrosis (IPF). However, the role of pirfenidone in LPS-induced acute lung injury (ALI) remains unclear. This study aims to investigate the protective effects of pirfenidone in ALI and to explore its underlying mechanism. Pirfenidone clearly reduces LPS-triggered ALI as indicated by significant pathological alterations, reduced oxidative stress and inflammatory responses in vivo. Furthermore, pirfenidone also blocks apoptosis of LPS-induced alveolar epithelial type II (ATII) cells through inhibition of endoplasmic reticulum (ER) stress and mitochondrial injury in vivo and in vitro. A lower expression level of BAP31, an ER transmembrane protein, was found to be associated with ALI followed LPS challenge. The reintroduction of BAP31 blunted LPS induced ER stress and mitochondrial damage and therefore alleviated ATII cell apoptosis, which correlated with pirfenidone treatment. Knockdown of BAP31 expression in pirfenidone treated ATII cells re-activated ER stress, mitochondrial damage and followed cellular apoptosis. In summary, this study confirms the beneficial effect of pirfenidone on ER stress and mitochondrial dysfunction mediated apoptosis via upregulation of BAP31. Our results demonstrated that pirfenidone may be considered as a potential agent for the treatment of ALI in the future.

Pum2-Mff axis fine-tunes mitochondrial quality control in acute ischemic kidney injury.

Mitochondrial fission factor (Mff) has been demonstrated to play a role in the activation of mitochondrial cleavage and mitochondrial death, denoting its role in the regulation of mitochondrial quality control. Recent evidence suggested that the mRNA translation of Mff is under the negative regulation by the RNA-binding protein Pumilio2 (Pum2). This study was designed to examine the role of Pum2 and Mff in the governance of mitochondrial quality control in a murine model of acute ischemic kidney injury. Our results indicated that genetic deletion of Mff overtly attenuated ischemic acute kidney injury (AKI)-induced renal failure through inhibition of pro-inflammatory response, tubular oxidative stress, and ultimately cell death in the kidney. Furthermore, Mff inhibition effectively preserved mitochondrial homeostasis through amelioration of mitochondrial mitosis, restoration of Sirt1/3 expression, and boost of mitochondrial respiration. Western blot analysis revealed that levels of Pum2 were significantly downregulated by ischemic AKI, inversely coinciding with levels of Mff. Overexpression of Pum2 reduced ischemic AKI-mediated Mff upregulation and offered protection on renal tubules through modulation of mitochondrial quality control. Taken together, our data have unveiled the molecular mechanism of the Pum2-Mff axis in mitochondrial quality control in a mouse model of ischemic AKI. These data indicated the therapeutic potential of Pum2 activation and Mff inhibition in the management of ischemic AKI.

NR4A1 aggravates the cardiac microvascular ischemia reperfusion injury through suppressing FUNDC1-mediated mitophagy and promoting Mff-required mitochondrial fission by CK2α.

Mitochondrial fission and mitophagy are considered key processes involved in the pathogenesis of cardiac microvascular ischemia reperfusion (IR) injury although the upstream regulatory mechanism for fission and mitophagy still remains unclear. Herein, we reported that NR4A1 was significantly upregulated following cardiac microvascular IR injury, and its level was positively correlated with microvascular collapse, endothelial cellular apoptosis and mitochondrial damage. However, NR4A1-knockout mice exhibited resistance against the acute microvascular injury and mitochondrial dysfunction compared with the wild-type mice. Functional studies illustrated that IR injury increased NR4A1 expression, which activated serine/threonine kinase casein kinase2 α (CK2α). CK2α promoted phosphorylation of mitochondrial fission factor (Mff) and FUN14 domain-containing 1 (FUNDC1). Phosphorylated activation of Mff enhanced the cytoplasmic translocation of Drp1 to the mitochondria, leading to fatal mitochondrial fission. Excessive fission disrupted mitochondrial function and structure, ultimately triggering mitochondrial apoptosis. In addition, phosphorylated inactivation of FUNDC1 failed to launch the protective mitophagy process, resulting in the accumulation of damaged mitochondria and endothelial apoptosis. By facilitating Mff-mediated mitochondrial fission and FUNDC1-required mitophagy, NR4A1 disturbed mitochondrial homeostasis, enhanced endothelial apoptosis and provoked microvascular dysfunction. In summary, our data illustrated that NR4A1 serves as a novel culprit factor in cardiac microvascular IR injury that operates through synchronous elevation of fission and suppression of mitophagy. Novel therapeutic strategies targeting the balance among NR4A1, fission and mitophagy might provide survival advantage to microvasculature following IR stress.

Protective role of melatonin in cardiac ischemia-reperfusion injury: From pathogenesis to targeted therapy.

Acute myocardial infarction (MI) is a major cause of mortality and disability worldwide. In patients with MI, the treatment option for reducing acute myocardial ischemic injury and limiting MI size is timely and effective myocardial reperfusion using either thombolytic therapy or primary percutaneous coronary intervention (PCI). However, the procedure of reperfusion itself induces cardiomyocyte death, known as myocardial reperfusion injury, for which there is still no effective therapy. Recent evidence has depicted a promising role of melatonin, which possesses powerful antioxidative and anti-inflammatory properties, in the prevention of ischemia-reperfusion (IR) injury and the protection against cardiomyocyte death. A number of reports explored the mechanism of action behind melatonin-induced beneficial effects against myocardial IR injury. In this review, we summarize the research progress related to IR injury and discuss the unique actions of melatonin as a protective agent. Furthermore, the possible mechanisms responsible for the myocardial benefits of melatonin against reperfusion injury are listed with the prospect of the use of melatonin in clinical application.

Inhibitory effect of melatonin on necroptosis via repressing the Ripk3-PGAM5-CypD-mPTP pathway attenuates cardiac microvascular ischemia-reperfusion injury.

The molecular features of necroptosis in cardiac ischemia-reperfusion (IR) injury have been extensively explored. However, there have been no studies investigating the physiological regulatory mechanisms of melatonin acting on necroptosis in cardiac IR injury. This study was designed to determine the role of necroptosis in microvascular IR injury, and investigate the contribution of melatonin in repressing necroptosis and preventing IR-mediated endothelial system collapse. Our results demonstrated that Ripk3 was primarily activated by IR injury and consequently aggravated endothelial necroptosis, microvessel barrier dysfunction, capillary hyperpermeability, the inflammation response, microcirculatory vasospasms, and microvascular perfusion defects. However, administration of melatonin prevented Ripk3 activation and provided a pro-survival advantage for the endothelial system in the context of cardiac IR injury, similar to the results obtained via genetic ablation of Ripk3. Functional investigations clearly illustrated that activated Ripk3 upregulated PGAM5 expression, and the latter increased CypD phosphorylation, which obligated endothelial cells to undergo necroptosis via augmenting mPTP (mitochondrial permeability transition pore) opening. Interestingly, melatonin supplementation suppressed mPTP opening and interrupted endothelial necroptosis via blocking the Ripk3-PGAM5-CypD signal pathways. Taken together, our studies identified the Ripk3-PGAM5-CypD-mPTP axis as a new pathway responsible for reperfusion-mediated microvascular damage via initiating endothelial necroptosis. In contrast, melatonin treatment inhibited the Ripk3-PGAM5-CypD-mPTP cascade and thus reduced cellular necroptosis, conferring a protective advantage to the endothelial system in IR stress. These findings establish a new paradigm in microvascular IR injury and update the concept for cell death management handled by melatonin under the burden of reperfusion attack.

Melatonin suppresses platelet activation and function against cardiac ischemia/reperfusion injury via PPARγ/FUNDC1/mitophagy pathways.

Platelet activation is a major (patho-) physiological mechanism that underlies ischemia/reperfusion (I/R) injury. In this study, we explored the molecular signals for platelet hyperactivity and investigated the beneficial effects of melatonin on platelet reactivity in response to I/R injury. After reperfusion, peroxisome proliferator-activated receptor γ (PPARγ) was progressively downregulated in patients with acute myocardial infarction undergoing coronary artery bypass grafting (CABG) surgery and in mice with I/R injury model. Loss of PPARγ was closely associated with FUN14 domain containing 1 (FUNDC1) dephosphorylation and mitophagy activation, leading to increased mitochondrial electron transport chain complex (ETC.) activity, enhanced mitochondrial respiratory function, and elevated ATP production. The improved mitochondrial function strongly contributed to platelet aggregation, spreading, expression of P-selectin, and final formation of micro-thromboses, eventually resulting in myocardial dysfunction and microvascular structural destruction. However, melatonin powerfully suppressed platelet activation via restoration of the PPARγ content in platelets, which subsequently blocked FUNDC1-required mitophagy, mitochondrial energy production, platelet hyperactivity, and cardiac I/R injury. In contrast, genetic ablation of PPARγ in platelet abolished the beneficial effects of melatonin on mitophagy, mitochondrial ATP supply, and platelet activation. Our results lay the foundation for the molecular mechanism of platelet activation in response to I/R injury and highlight that the manipulation of the PPARγ/FUNDC1/mitophagy pathway by melatonin could be a novel strategy for cardioprotection in the setting of cardiac I/R injury.

Melatonin protects cardiac microvasculature against ischemia/reperfusion injury via suppression of mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis.

The cardiac microvascular system, which is primarily composed of monolayer endothelial cells, is the site of blood supply and nutrient exchange to cardiomyocytes. However, microvascular ischemia/reperfusion injury (IRI) following percutaneous coronary intervention is a woefully neglected topic, and few strategies are available to reverse such pathologies. Here, we studied the effects of melatonin on microcirculation IRI and elucidated the underlying mechanism. Melatonin markedly reduced infarcted area, improved cardiac function, restored blood flow, and lower microcirculation perfusion defects. Histological analysis showed that cardiac microcirculation endothelial cells (CMEC) in melatonin-treated mice had an unbroken endothelial barrier, increased endothelial nitric oxide synthase expression, unobstructed lumen, reduced inflammatory cell infiltration, and less endothelial damage. In contrast, AMP-activated protein kinase α (AMPKα) deficiency abolished the beneficial effects of melatonin on microvasculature. In vitro, IRI activated dynamin-related protein 1 (Drp1)-dependent mitochondrial fission, which subsequently induced voltage-dependent anion channel 1 (VDAC1) oligomerization, hexokinase 2 (HK2) liberation, mitochondrial permeability transition pore (mPTP) opening, PINK1/Parkin upregulation, and ultimately mitophagy-mediated CMEC death. However, melatonin strengthened CMEC survival via activation of AMPKα, followed by p-Drp1S616 downregulation and p-Drp1S37 upregulation, which blunted Drp1-dependent mitochondrial fission. Suppression of mitochondrial fission by melatonin recovered VDAC1-HK2 interaction that prevented mPTP opening and PINK1/Parkin activation, eventually blocking mitophagy-mediated cellular death. In summary, this study confirmed that melatonin protects cardiac microvasculature against IRI. The underlying mechanism may be attributed to the inhibitory effects of melatonin on mitochondrial fission-VDAC1-HK2-mPTP-mitophagy axis via activation of AMPKα.

DNA-PKcs Phosphorylates Cofilin2 to Induce Endothelial Dysfunction and Microcirculatory Disorder in Endotoxemic Cardiomyopathy.

The presence of endotoxemia is strongly linked to the development of endothelial dysfunction and disruption of myocardial microvascular reactivity. These factors play a crucial role in the progression of endotoxemic cardiomyopathy. Sepsis-related multiorgan damage involves the participation of the catalytic subunit of DNA-dependent protein kinase (DNA-PKcs). However, whether DNA-PKcs contributes to endothelial dysfunction and myocardial microvascular dysfunction during endotoxemia remains unclear. Hence, we conducted experiments in mice subjected to lipopolysaccharide (LPS)-induced endotoxemic cardiomyopathy, as well as assays in primary mouse cardiac microvascular endothelial cells. Results showed that endothelial-cell-specific DNA-PKcs ablation markedly attenuated DNA damage, sustained microvessel perfusion, improved endothelial barrier function, inhibited capillary inflammation, restored endothelium-dependent vasodilation, and improved heart function under endotoxemic conditions. Furthermore, we show that upon LPS stress, DNA-PKcs recognizes a TQ motif in cofilin2 and consequently induces its phosphorylation at Thr25. Phosphorylated cofilin2 shows increased affinity for F-actin and promotes F-actin depolymerization, resulting into disruption of the endothelial barrier integrity, microvascular inflammation, and defective eNOS-dependent vasodilation. Accordingly, cofilin2-knockin mice expressing a phospho-defective (T25A) cofilin2 mutant protein showed improved endothelial integrity and myocardial microvascular function upon induction of endotoxemic cardiomyopathy. These findings highlight a novel mechanism whereby DNA-PKcs mediates cofilin2Thr25 phosphorylation and subsequent F-actin depolymerization to contribute to endotoxemia-related cardiac microvascular dysfunction.

Molecular Mechanisms of Mitochondrial Quality Control in Ischemic Cardiomyopathy.

Ischemic cardiomyopathy (ICM) is a special type of coronary heart disease or an advanced stage of the disease, which is related to the pathological mechanism of primary dilated cardiomyopathy. Ischemic cardiomyopathy mainly occurs in the long-term myocardial ischemia, resulting in diffuse myocardial fibrosis. This in turn affects the cardiac ejection function, resulting in a significant impact on myocardial systolic and diastolic function, resulting in a decrease in the cardiac ejection fraction. The pathogenesis of ICM is closely related to coronary heart disease. Mainly due to coronary atherosclerosis caused by coronary stenosis or vascular occlusion, causing vascular inflammatory lesions and thrombosis. As the disease progresses, it leads to long-term myocardial ischemia and eventually ICM. The pathological mechanism is mainly related to the mechanisms of inflammation, myocardial hypertrophy, fibrosis and vascular remodeling. Mitochondria are organelles with a double-membrane structure, so the composition of the mitochondrial outer compartment is basically similar to that of the cytoplasm. When ischemia-reperfusion induces a large influx of calcium into the cell, the concentration of calcium ions in the mitochondrial outer compartment also increases. The subsequent opening of the membrane permeability transition pore in the inner mitochondrial membrane and the resulting calcium overload induces the homeostasis of cardiomyocytes and activates the mitochondrial pathway of apoptosis. Mitochondrial Quality Control (MQC), as an important mechanism for regulating mitochondrial function in cardiomyocytes, affects the morphological structure/function and lifespan of mitochondria. In this review, we discuss the role of MQC (including mitophagy, mitochondrial dynamics, and mitochondrial biosynthesis) in the pathogenesis of ICM and provide important evidence for targeting MQC for ICM.

A novel lncRNA DFRV plays a dual function in influenza A virus infection.

Long noncoding RNAs (lncRNAs) have been associated with a variety of biological activities, including immune responses. However, the function of lncRNAs in antiviral innate immune responses are not fully understood. Here, we identified a novel lncRNA, termed dual function regulating influenza virus (DFRV), elevating in a dose- and time-dependent manner during influenza A virus (IAV) infection, which was dependent on the NFκB signaling pathway. Meanwhile, DFRV was spliced into two transcripts post IAV infection, in which DFRV long suppress the viral replication while DFRV short plays the opposite role. Moreover, DFRV regulates IL-1ß and TNF-α via activating several pro-inflammatory signaling cascades, including NFκB, STAT3, PI3K, AKT, ERK1/2 and p38. Besides, DFRV short can inhibit DFRV long expression in a dose-dependent manner. Collectively, our studies reveal that DFRV may act as a potential dual-regulator to preserve innate immune homeostasis in IAV infection.

NR4A1 Promotes LPS-Induced Acute Lung Injury through Inhibition of Opa1-Mediated Mitochondrial Fusion and Activation of PGAM5-Related Necroptosis.

Mitochondrial dysfunction and necroptosis have been perceived as the primary molecular mechanisms underscoring acute lung injury. Meanwhile, nuclear receptor subfamily 4 group A member 1 (NR4A1) is considered a regulator of inflammation-related endothelial injury in lung tissue although the downstream molecular events remain elusive. In this study, we employed NR4A1-/- mice to decipher the role of NR4A1 in the onset and progression of acute lung injury with a focus on mitochondrial damage and necroptosis. Our results demonstrated that NR4A1 was significantly upregulated in lipopolysaccharide- (LPS-) treated lung tissues. Knockout of NR4A1 overtly improved lung tissue morphology, inhibited inflammation, and reduced oxidative stress in LPS-treated lung tissue. A cell signaling study suggested that NR4A1 deletion repressed levels of PGAM5 and attenuated LPS-mediated necroptosis in primary murine alveolar epithelial type II (ATII) cells, the effects of which were mitigated by PGAM5 overexpression. Moreover, LPS-mediated mitochondrial injury including mitochondrial membrane potential collapse and mitochondrial oxidative stress was drastically improved by NR4A1 deletion. Furthermore, NR4A1 deletion preserved mitochondrial homeostasis through activation of Opa1-related mitochondrial fusion. Silencing of Opa1 triggered mitochondrial dysfunction in NR4A1-deleted ATII cells. Taken together, our data identified NR4A1 as a novel regulator of LPS-related acute lung injury through regulation of mitochondrial fusion and necroptosis, indicating therapeutic promises of targeting NR4A1 in the treatment of acute lung injury in clinical practice.