LPS-induced Lung Injury In Mice Research Articles

LncRNA SNHG1 knockdown attenuates lipopolysaccharide-induced acute lung injury via regulating miR199a-3p/ROCK2 axis.

Acute lung injury (ALI) is a significant health condition with notable rates of morbidity and mortality globally. Long non-coding ribose nucleic acids (lncRNAs) play vital roles in mitigating various inflammation-related diseases, including ALI. The study aimed to investigate the functional role and molecular mechanisms of lncRNA SNHG1 on ALI in lipopolysaccharide (LPS)-treated A549 cells and in LPS-induced ALI mice. The expression of SNHG1 was initially examined in LPS-treated A549 cells. We further demonstrated the critical function of SNHG1 through various cellular assessments following SNHG1 knockdown, including cell counting kit (CCK)-8 assay, flow cytometry analysis, as well as enzyme-linked immunosorbent assay (ELISA). Reducing SNHG1 levels hindered the negative effects of LPS on cell viability, apoptosis, and inflammation. Moreover, SNHG1 acted as a negative regulator for miR-199a-3p, which targeted downstream ROCK2. Depletion of miR-199a-3p or enhanced expression of ROCK2 abolished the protective effects of SNHG1 knockdown on LPS-induced apoptosis and inflammation. Consistently, silencing SNHG1 alleviated LPS-induced lung injury in mice, demonstrating its potential therapeutic benefits in managing ALI. Overall, this study sheds light on the role of SNHG1 in modulating inflammation and apoptosis in ALI through the miR-199a-3p/ROCK2 pathway, offering new insights for the treatment of this condition.

Eugenol Inhibits Neutrophils Myeloperoxidase In Vitro and Attenuates LPS-Induced Lung Inflammation in Mice.

Eugenol (Eug) is a polyphenol extracted from the essential oil of Syzygium aromaticum (L.) Merr. and Perry (Myrtaceae). The health benefits of eugenol in human diseases were proved in several studies. This work aims to evaluate the effect of eugenol on lung inflammatory disorders. For this, using human neutrophils, the antioxidant activity of eugenol was investigated in vitro. Furthermore, a model of LPS-induced lung injury in mice was used to study the anti-inflammatory effect of eugenol in vivo. Results showed that eugenol inhibits luminol-amplified chemiluminescence of resting neutrophils and after stimulation with N-formyl-methionyl-leucyl-phenylalanine (fMLF) peptide or phorbol myristate acetate (PMA). This effect was dose dependent and was significant from a low concentration of 0.1 µg/mL. Furthermore, eugenol inhibited myeloperoxidase (MPO) activity without affecting its degranulation. Eugenol has no scavenging effect on hydrogen peroxide (H2O2) and superoxide anion (O2-). Pretreatment of mice with eugenol prior to the administration of intra-tracheal LPS significantly reduced neutrophil accumulation in the bronchoalveolar lavage fluid (BALF) and decreased total proteins concentration. Moreover, eugenol clearly inhibited the activity of matrix metalloproteinases MMP-2 (21%) and MMP-9 (28%), stimulated by LPS administration. These results suggest that the anti-inflammatory effect of eugenol against the LPS-induced lung inflammation could be exerted via inhibiting myeloperoxidase and metalloproteinases activity. Thus, eugenol could be a promising molecule for the treatment of lung inflammatory diseases.

Mechanistic insights into targeting caspase-3 activation and alveolar macrophage pyroptosis by Ephedra and bitter almond compounds for treating pediatric pneumonia via network pharmacology and bioinformatics.

This study investigates the molecular mechanism of Ma Huang-Ku Xing Ren, a traditional Chinese medicine formula, in treating pediatric pneumonia. The focus is on the regulation of caspase-3 activation and reduction of alveolar macrophage necrosis through network pharmacology and bioinformatics analyses of Ephedra and bitter almond components. Active compounds and targets from ephedrine and bitter almond were obtained using TCMSP, TCMID, and GeneCards databases, identifying pediatric pneumonia-related genes. A protein-protein interaction (PPI) network was constructed, and core targets were screened. GO and KEGG pathway enrichment analyses identified relevant genes and pathways. An acute pneumonia mouse model was created using the lipopolysaccharide (LPS) inhalation method, with caspase-3 overexpression induced by a lentivirus. The mice were treated with Ephedra and bitter almond through gastric lavage. Lung tissue damage, inflammatory markers (IL-18 and IL-1β), and cell death-related gene activation were assessed through H&E staining, ELISA, western blot, flow cytometry, and immunofluorescence. The study identified 128 active compounds and 121 gene targets from Ephedra and bitter almond. The PPI network revealed 13 core proteins, and pathway analysis indicated involvement in inflammation, apoptosis, and cell necrosis, particularly the caspase-3 pathway. Invivo results showed that Ephedra and bitter almond treatment significantly mitigated LPS-induced lung injury in mice, reducing lung injury scores and inflammatory marker levels. It also decreased caspase-3 activity and cell death in alveolar macrophages. In conclusion, the active ingredients of Ma Huang-Ku Xing Ren, particularly targeting caspase-3, may effectively treat pediatric pneumonia by reducing apoptosis in alveolar macrophages, as demonstrated by both network pharmacology, bioinformatics analyses, and experimental data.

Functional roles of CD26/DPP4 in lipopolysaccharide-induced lung injury.

Acute respiratory distress syndrome (ARDS) is characterized by dysregulated inflammation and increased permeability of lung microvascular cells. CD26/dipeptidyl peptidase-4 (DPP4) is a type II membrane protein that is expressed in several cell types and mediates multiple pleiotropic effects. We previously reported that DPP4 inhibition by sitagliptin attenuates lipopolysaccharide (LPS)-induced lung injury in mice. The current study characterized the functional role of CD26/DPP4 expression in LPS-induced lung injury in mice, isolated alveolar macrophages, and cultured lung endothelial cells. In LPS-induced lung injury, inflammatory responses [bronchoalveolar lavage fluid (BALF) neutrophil numbers and several proinflammatory cytokine levels] were attenuated in Dpp4 knockout (Dpp4 KO) mice. However, multiple assays of alveolar capillary permeability were similar between the Dpp4 KO and wild-type mice. TNF-α and IL-6 production was suppressed in alveolar macrophages isolated from Dpp4 KO mice. In contrast, in cultured mouse lung microvascular endothelial cells (MLMVECs), reduction in CD26/DPP4 expression by siRNA resulted in greater ICAM-1 and IL-6 expression after LPS stimulation. Moreover, the LPS-induced vascular monolayer permeability in vitro was higher in MLMVECs treated with Dpp4 siRNA, suggesting that CD26/DPP4 plays a protective role in endothelial barrier function. In summary, this study demonstrated that genetic deficiency of Dpp4 attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential functional roles of CD26/DPP4 expression in resident cellular components of the lung. CD26/DPP4 may be a potential therapeutic target for ARDS and warrants further exploration to precisely identify the multiple functional effects of CD26/DPP4 in ARDS pathophysiology.NEW & NOTEWORTHY We aimed to clarify the functional roles of CD26/DPP4 in ARDS pathophysiology using Dpp4-deficient mice and siRNA reduction techniques in cultured lung cells. Our results suggest that CD26/DPP4 expression plays a proinflammatory role in alveolar macrophages while also playing a protective role in the endothelial barrier. Dpp4 genetic deficiency attenuates inflammatory responses but not permeability in LPS-induced lung injury in mice, potentially through differential roles of CD26/DPP4 expression in the resident cellular components of the lung.

Long non-coding RNA PFI inhibits apoptosis of alveolar epithelial cells to alleviate lung injury via miR-328-3p/Creb1 axis

Acute lung injury (ALI), a common clinical type of critical illness, is an acute hypoxic respiratory insufficiency caused by the damage of alveolar epithelial cells and capillary endothelial cells. In a previous study, we reported a novel lncRNA, lncRNA PFI, which could protect against pulmonary fibrosis in pulmonary fibroblasts. The present study demonstrated that lncRNA PFI was downregulated in alveolar epithelial cell of mice injury lung tissues, and further investigated the role of lncRNA PFI in regulating inflammation-induced alveolar epithelial cell apoptosis. Overexpression of lncRNA PFI could partially abrogated bleomycin induced type II AECs injured. Subsequently, bioinformatic prediction revealed that lncRNA PFI might directly bind to miR-328-3p, and further AGO-2 RNA binding protein immunoprecipitation (RIP) assay confirmed their binding relationship. Furthermore, miR-328-3p promoted apoptosis in MLE-12 cells by limiting the activation of the Creb1, a protein correlated with cell apoptosis, whereas AMO-328-3p ablated the pro-apoptosis effect of silencing lncRNA PFI in MLE-12 cells. While miR-328-3p could also ablate the function of lncRNA PFI in bleomycin treated human lung epithelial cells. Enhanced expression of lncRNA PFI reversed the LPS-induced lung injury in mice. Overall, these data reveal that lncRNA PFI mitigated acute lung injury through miR-328-3p/Creb1 pathway in alveolar epithelial cells.

Oral Hydroxychloroquine Mitigates Lipopolysaccharide-induced Lung Injury by Inhibiting Pyroptosis in Mice.

Hydroxychloroquine (HCQ) is a molecule derived from quinacrine; it displays a wide range of pharmacological properties, including anti-inflammatory, immunomodulatory, and antineoplastic. However, little is known about this molecule's role in lung injury. This study aimed to identify HCQ's regulatory role of HCQ in sepsis-induced lung injury and its molecular mechanism. To test the protective properties of HCQ, we established an in vivo model of lipopolysaccharide (LPS)-induced lung injury in mice. The extent of the injury was determined by evaluating histopathology, inflammatory response, oxidative stress, and apoptosis. Mechanistically, conventional nucleotide-binding oligomerization domain leucine-rich repeat and pyrin domain-containing 3 (NLRP3) knockout mice were employed to investigate whether HCQ exerted pulmonary protection by inhibiting NLRP3-mediated pyroptosis. Our findings revealed that HCQ pretreatment significantly mitigated LPS-induced lung injury in mice in terms of histopathology, inflammatory response, oxidative stress, and apoptosis, while inhibiting LPS-induced NLRP3 inflammasome activation and pyroptosis. Additionally, the indicators of lung injury, including histopathology, inflammatory response, oxidative stress, and apoptosis, were still reduced drastically in LPS-treated NLRP3 (-/-) mice after HCQ pretreatment. Notably, HCQ pretreatment further decreased the levels of pyroptosis indicators, including IL-1β, IL-18 and Cle-GSDMD, in LPS-treated NLRP3 (-/-) mice. Taken together, HCQ protects against lung injury by inhibiting pyroptosis, maybe not only through the NLRP3 pathway but also through non-NLRP3 pathway; therefore, it may be a new therapeutic strategy in the treatment of lung injury.

Involvement of VEGFR1 signaling in LPS-induced lung injury in mice

Involvement of VEGFR1 signaling in LPS-induced lung injury in mice

Quercetin protects against LPS-induced lung injury in mice via SIRT1-mediated suppression of PKM2 nuclear accumulation

The role of NOD-like receptor protein 3 (NLRP3)-mediated macrophages pyroptosis in acute lung injury (ALI) is well-established. Quercetin (Que) is a natural bioflavonoid compound with anti-inflammatory and antioxidative properties that reportedly inhibits the NLRP3 inflammasome in sepsis-induced organ dysfunctions such as ALI. However, the mechanism underlying the inhibitory effect of quercetin on NLRP3 activation remains unclear. In this study, we established an endotoxin-induced ALI mouse model with an in vitro LPS challenge. We demonstrated that the administration of quercetin could significantly reduce pulmonary injury and decrease the production of pro-inflammatory cytokines. Moreover, we found that quercetin could inhibit the activation of the NLRP3 inflammasome by suppressing the nuclear accumulation of PKM2 and increasing SIRT1 levels. Importantly, treatment with SRT1720 (a specific SIRT1 activator) could inhibit the nuclear accumulation of PKM2 and the activation of NLRP3. Besides, preventing PKM2 dimerization with ML265 yielded an anti-inflammatory effect, similar to findings observed for SRT1720. In addition, we found that SIRT1 silencing or inhibition by EX527 could increase NLRP3 activation and nuclear accumulation of PKM2 and override quercetin-mediated anti-inflammatory activity. These findings indicated that quercetin could downregulate NLRP3 inflammasome activation by inhibiting the nuclear accumulation of PKM2 and upregulating SIRT1 expression, expanding the treatment landscape for ARDS.

Hydrogen gas alleviates lipopolysaccharide-induced acute lung injury and inflammatory response in mice

BackgroundChronic inflammation and oxidant/antioxidant imbalance are two main pathological features associated with lipopolysaccharide (LPS)-induced acute lung injury (ALI). The following study investigated the protective role of hydrogen (H2), a gaseous molecule without known toxicity, in LPS-induced lung injury in mice and explored its potential molecular mechanisms.MethodsMice were randomly divided into three groups: H2 control group, LPS group, and LPS + H2 group. The mice were euthanized at the indicated time points, and the specimens were collected. The 72 h survival rates, cytokines contents, pathological changes, expression of Toll-like receptor 4 (TLR4), and oxidative stress indicators were analyzed. Moreover, under different culture conditions, RAW 264.7 mouse macrophages were used to investigate the potential molecular mechanisms of H2 in vitro. Cells were divided into the following groups: PBS group, LPS group, and LPS + H2 group. The cell viability, intracellular ROS, cytokines, and expression of TLR4 and nuclear factor kappa-B (NF-κB) were observed.ResultsHydrogen inhalation increased the survival rate to 80%, reduced LPS-induced lung damage, and decreased inflammatory cytokine release in LPS mice. Besides, H2 showed remarked anti-oxidative activity to reduce the MDA and NO contents in the lung. In vitro data further indicated that H2 down-regulates the levels of ROS, NO, TNF-α, IL-6, and IL-1β in LPS-stimulated macrophages and inhibits the expression of TLR4 and the activation of nuclear factor kappa-B (NF-κB).ConclusionHydrogen gas alleviates lipopolysaccharide-induced acute lung injury and inflammatory response most probably through the TLR4-NF-κB pathway.

Abietic acid attenuates LPS-induced acute lung injury by restoring Th17/Treg balance

Purpose: To investigate the mechanism of action and effects of abietic acid (AA) in a mouse acute lung injury (ALI) model.
 Methods: A mouse ALI model was established by lipopolysaccharide (LPS) induction. Lung tissues were examined for histological alterations and scored based on the degree of injury. Myeloperoxidase (MPO), IL-6, IL-1β, and TNF-α levels were measured by enzyme-linked immunosorbent assay (ELISA) while the numbers of Th17 and Treg cells were assessed by immunofluorescence. Protein expression levels of p-STAT3, p-STAT5, RORrt, and FOXP3 were analyzed by immunoblot assay. Expression of peroxisome proliferator-activated receptor γ (PPARγ) was assessed by immunoblot.
 Results: AA ameliorated LPS-induced lung injury in mice. Furthermore, AA ameliorated LPS-induced pneumonia in mice (p < 0.05) and restored Th17/Treg balance and Th17/Treg transcription factor expression that was altered by LPS induction. AA also activated PPARγ expression to restore Th17/Treg balance (p < 0.05).
 Conclusion: The results indicate that AA attenuates LPS-induced ALI in mice by restoring Th17/Treg balance. Thus, AA is a potential drug for the management of ALI; however, AA must first be evaluated in clinical studies.

Intermittent fasting attenuates lipopolysaccharide-induced acute lung injury in mice by modulating macrophage polarization

Acute lung injury (ALI) is a spectrum of acute and life-threatening pulmonary inflammatory conditions. Treatment of ALI remains a clinical challenge. Recently, intermittent fasting (IF) has been shown to improve health and alleviate many diseases. In this study, we tested whether IF attenuated ALI and investigated the mechanism underlying this process. In vivo, the effects of IF on ALI were evaluated in a lipopolysaccharide (LPS)-induced murine ALI model. We found that two times of 24-h fasting in a week before ALI efficiently ameliorated LPS-induced lung injury in mice, characterized by alleviated lung lesions, wet-to-dry weight ratio, myeloperoxidase activity, malondialdehyde content, and lower levels of tumor necrosis factor-α, interleukin-6, and interleukin-1β. In vitro, functional assays were conducted to assess IF on the inflammatory response and macrophage polarization of bone marrow-derived macrophages (BMDMs) treated with LPS or IL-4. And PPARγ antagonist GW9662 and AMPK siRNA were used to test the role of PPARγ and AMPK in the IF-mediated improvement of ALI. The results showed that IF (serum deprivation) suppressed macrophage M1 activation and promoted M2 activation in LPS-treated BMDMs. While, IF also augmented macrophage M2 polarization in IL-4-treated BMDMs. Further mechanistic studies showed that the promotive effect of IF on M2 polarization was related to the activation of the PPARγ and AMPK pathways. In conclusion, this study suggests that IF enhances M2 polarization by activating the AMPK and PPARγ pathways, thus facilitating anti-inflammatory response and ameliorating ALI.

Fraxinol attenuates LPS-induced acute lung injury by equilibrating ACE-Ang II-AT1R and ACE2-Ang (1-7)-Mas and inhibiting NLRP3

Context Acute lung injury (ALI) is a serious heterogenous pulmonary disorder. Fraxinol was selected for this study since it is a simple coumarin compound, not previously investigated in ALI. Objectives This study investigates the ALI therapeutic effect and mechanisms of fraxinol. Materials and methods Male BALB/c mice were treated with fraxinol (20, 40, and 80 mg/kg) following intranasal injection of lipopolysaccharide (LPS; 10 μg in 50 μL). The mice in control group were intratracheally injected with 50 μL phosphate buffered saline (PBS). Raw264.7 cells were treated with fraxinol by 100 ng/mL LPS for 6 h, then treated by different concentrations of fraxinol (5, 10, and 25 μM) for 48 h. Cells in control group were treated with PBS. Results Fraxinol with doses of 20, 40, and 80 mg/kg significantly attenuated LPS-induced lung injury in mice (lung injury score, 10.4, 31.2, 50.3%). Fraxinol attenuated the apoptosis and nucleotide-binding oligomerization domain-like receptor family pyrin domain-containing-3 (NLRP3) activation induced by LPS (apoptosis, 18.3, 30.2, 55.6%; NLRP3, 30.0, 47.7, 63.6%). The anti-apoptosis and anti-inflammation effects of fraxinol were also confirmed in Raw264.7 cells (apoptosis, 38.8, 55.3, 68.9%; NLRP3, 20.6, 55.7, 73.9%). Discussion and conclusion The anti-ALI effects of fraxinol maybe by equilibrating ACE-Ang II-AT1R and ACE2-Ang (1-7)-Mas axis and inhibiting NLRP3 inflammasome. Our research provides a candidate drug in the treatment of ALI.

NF-κB and AMPK-Nrf2 pathways support the protective effect of polysaccharides from Polygonatum cyrtonema Hua in lipopolysaccharide-induced acute lung injury

Ethnopharmacological relevanceThe raw and honey-processed P. cyrtonema recorded in ancient classics of Chinese medicine as having the effect of moisturizing the lungs and relieving coughs, and it has also been proved to have therapeutic effects on lung diseases in modern research. Polysaccharides are the main components with biological activities in raw and honey-processed P. cyrtonema, but there is no research for their lung-protective effect. Aim of studyThis study aimed to investigate the protective effect and the possible mechanism of polysaccharides from raw and honey-processed P. cyrtonema in LPS-induced acute lung injury in mice. Materials and methodsPolysaccharides, PCP and HPCP, were respectively separated and extracted from raw and honey-processed P. cyrtonema, and the molecular weight, monosaccharide composition and other basic chemical characteristics were analyzed by HPGCP, HPLC, FI-IR, and NMR. The model of ALI mice was established by intratracheal instillation of LPS. Moreover, the protective effects of PCP and HPCP for ALI mice were evaluated by detecting the wet-to-dry ratio and histopathology in the lungs, the content of inflammatory factors TNF-α, IL-6, IL-1β in BLAF, and the content of MPO and SOD in lung tissue. In addition, the lung-protective mechanism of PCP and HPCP was explored by detecting the levels of some proteins and mRNA related to inflammation and oxidative stress pathways. ResultsPCP and HPCP with molecular weights of 8.842 × 103 and 5.521 × 103Da were mainly composed of three monosaccharides. Moreover, it is found that fructose and galactose were mainly β-D, and glucose was α-D. Both PCP and HPCP could significantly improve lung injury, reduce the level of inflammatory factors in BALF and the level of MPO in lung tissue, and increase the level of SOD. In addition, PCR and WB indicated that PCP and HPCP at least inhibited pulmonary inflammation through the NF-κB pathway, and reduced the occurrence of pulmonary oxidative stress through the AMPK-Nrf2 pathway. ConclusionsPolysaccharides from raw and honey-processed P. cyrtonema had a protective effect in LPS-induced lung injury in mice. This effect may be related to the antioxidant and anti-inflammatory activities of PCP and HPCP in the lungs through the NF-κB pathway and AMPK-Nrf2 pathway. And HPCP seems to perform more than PCP.

Protective effect of VEGFR1 signaling on LPS-induced lung injury in mice

Protective effect of VEGFR1 signaling on LPS-induced lung injury in mice

Extracellular citrate serves as a DAMP to activate macrophages and promote LPS-induced lung injury in mice

Citrate has a prominent role as a substrate in cellular energy metabolism. Recently, citrate has been shown to drive inflammation. However, the role of citrate in lipopolysaccharide (LPS)-induced acute lung injury (ALI) remains unclear. Here, we aimed to clarify whether extracellular citrate aggravated the LPS-induced ALI and the potential mechanism. Our findings demonstrated that extracellular citrate aggravated the pathological lung injury induced by LPS in mice, characterized by up-regulation of pro-inflammatory factors and over-activation of NACHT, LRR, and PYD domains-containing protein 3 (NLRP3) inflammasome in the lungs. In vitro, we found that citrate treatment significantly augmented the expression of NLRP3 and pro-IL-1β and enhanced the translocation of NF-κB/p65 into the nucleus. Furthermore, extracellular citrate plus adenosine-triphosphate (ATP) significantly increased the production of reactive oxygen species (ROS) in primary murine macrophages. Inhibiting the production of ROS with a ROS scavenger N-acetyl-L-cysteine (NAC) attenuated the activation of NLRP3 inflammasome. Altogether, we conclude that extracellular citrate may serve as a damage-associated molecular pattern (DAMP) and aggravates LPS-induced ALI by activating the NLRP3 inflammasome.

Novel clerodane-type diterpenoid Cintelactone A suppresses lipopolysaccharide -induced inflammation by promoting ubiquitination, proteasomal degradation of TRAF6

Cellular inflammation is the underlying cause of several diseases and development of a safe and effective anti-inflammatory drug is need-of-the hour for treatment of diseases like lung inflammation. Callicarpa integerrima Champ. is a well-known herbal medicine with hemostatic and anti-inflammatory functions. However, the exact ingredient exhibiting anti-inflammatory activity in C. integerrima Champ. is largely unknown. Here, we first isolated, purified and characterized a novel clerodane-type diterpenoid Cintelactone A (CA) from C. integerrima Champ. We demonstrated that CA could significantly inhibit lipopolysaccharide (LPS)-induced pro-inflammatory cytokines and mediators production both in mouse peritoneal macrophages and THP1 cells. Consistently, CA also relieved inflammation and reduced LPS-induced lung injury in mice. We systematically elucidated the mechanism of action as well. CA interacted with Arg78 of tumor necrosis factor receptor-associated factor 6 (TRAF6) by hydrogen bonding. It further promoted the K48-linked ubiquitination and proteasomal degradation of TRAF6, and suppressed the activation of NF-κB and MAPKs signaling pathways. Collectively, our study reveals that new clerodane-type diterpenoid CA suppresses LPS-induced inflammation by promoting TRAF6 degradation, suggesting that CA as the potential therapeutic candidate for the treatment of inflammation associated diseases.

Euphorbia cuneata Represses LPS-induced Acute Lung Injury in Mice via its Antioxidative and Anti-inflammatory Activities.

Euphorbia cuneata (EC; Euphorbiaceae), which widely grows in Saudi Arabia and Yemen, is used traditionally to treat pain and inflammation. This study aimed to evaluate the protective anti-inflammatory effect of a standardized extract of EC against lipopolysaccharide (LPS)-induced acute lung injury (ALI) in mice and the possible underlying mechanism(s) of this pharmacologic activity. ALI was induced in male Balb/c mice using intraperitoneal injection of LPS. A standardized total methanol extract of EC or dexamethasone was administered 5 days prior to LPS challenge. Bronchoalveolar fluid (BALF) and lung samples were collected for analysis. The results demonstrated the protective anti-inflammatory effect of EC against LPS-induced ALI in mice. Standardized EC contained 2R-naringenin-7-O-β-glucoside (1), kaempferol-7-O-β-glucoside (2), cuneatannin (3), quercetin (4), and 2R-naringenin (5) in concentrations of 6.16, 4.80, 51.05, 13.20, and 50.00 mg/g of extract, respectively. EC showed a protective effect against LPS-induced pulmonary damage. EC reduced lung wet/dry weight (W/D) ratio and total protein content in BALF, indicating attenuation of the pulmonary edema. Total and differential cell counts were decreased in EC-treated animals. Histopathological examination confirmed the protective effect of EC, as indicated by an amelioration of LPS-induced lesions in lung tissue. EC also showed a potent anti-oxidative property as it decreased lipid peroxidation and increased the antioxidants in lung tissue. Finally, the anti-inflammatory activity of EC was obvious through its ability to suppress the activation of nuclear factor-κB (NF-κB), and hence its reduction of the levels of downstream inflammatory mediators. In conclusion, these results demonstrate the protective effects of EC against LPS-induced lung injury in mice, which may be due to its antioxidative and anti-inflammatory activities.

Suppression of NLRP3 Inflammasome by Erythropoietin via the EPOR/JAK2/STAT3 Pathway Contributes to Attenuation of Acute Lung Injury in Mice.

Acute lung injury (ALI) and acute respiratory distress syndrome (ARDS) are common and devastating clinical disorders with high mortality and no specific therapy. An excessive inflammatory response results in the progression of ALI/ARDS, and the NLRP3 inflammasome is a key participant in inflammation. Erythropoietin (EPO), which is clinically used for anemia, reportedly exerts pleiotropic effects in ALI. However, whether EPO could protect against lipopolysaccharide (LPS)-induced ALI by regulating the NLRP3 inflammasome and its underlying mechanisms remain poorly elucidated. This study aimed to explore whether the therapeutic effects of EPO rely on the suppression of the NLRP3 inflammasome and the specific mechanisms in an LPS-induced ALI mouse model. ALI was induced in C57BL/6 mice by intraperitoneal (i.p.) injection of LPS (15 mg/kg). EPO was administered intraperitoneally at 5 U/g after LPS challenge. The mice were sacrificed 8 h later. Our findings indicated that application of EPO markedly diminished LPS-induced lung injury by restoring histopathological changes, lessened lung wet/dry (W/D) ratio, protein concentrations in bronchoalveolar lavage fluid (BALF) and myeloperoxidase (MPO) levels. Meanwhile, EPO evidently decreased interleukin-1β (IL-1β) and interleukin-18 (IL-18) secretion, the expression of NLRP3 inflammasome components including pro-IL-1β, NLRP3, and cleaved caspase-1 as well as phosphorylation of nuclear factor-κB (NF-κB) p65, which may be associated with activation of EPO receptor (EPOR), phosphorylation of Janus-tyrosine kinase 2 (JAK2) and signal transducer and activator of transcription 3 (STAT3). However, all the beneficial effects of EPO on ALI and modulation NLRP3 inflammasome were remarkably abrogated by the inhibition of EPOR/JAK2/STAT3 pathway and knockout (KO) of NLRP3 gene. Taken together, this study indicates that EPO can effectively attenuate LPS-induced lung injury in mice by suppressing the NLRP3 inflammasome, which is dependent upon activation of EPOR/JAK2/STAT3 signaling and inhibition of the NF-κB pathway.

DPP4 inhibition by sitagliptin attenuates LPS-induced lung injury in mice.

Acute respiratory distress syndrome (ARDS) is a severe clinical condition marked by acute respiratory failure and dysregulated inflammation. Pulmonary vascular endothelial cells (PVECs) function as an important pro-inflammatory source in ARDS, suggesting that modulation of inflammatory events at the endothelial level may have a therapeutic benefit. Dipeptidyl peptidase-4 (DPP4) inhibitors, widely used for the treatment of diabetes mellitus, have been reported to have possible anti-inflammatory effects. However, the potential anti-inflammatory effects of DPP4 inhibition on PVEC function and ARDS pathophysiology are unknown. Therefore, we evaluated the effects of sitagliptin, a DPP4 inhibitor in wide clinical use, on LPS-induced lung injury in mice and in human lung ECs in vitro. In vivo, sitagliptin reduced serum DPP4 activity, bronchoalveolar lavage protein concentration, cell number, and proinflammatory cytokine levels after LPS and alleviated histological findings of lung injury. LPS decreased the expression levels of CD26/DPP4 on pulmonary epithelial cells and PVECs isolated from mouse lungs, and the effect was partially reversed by sitagliptin. In vitro, human lung microvascular ECs (HLMVECs) expressed higher levels of CD26/DPP4 than human pulmonary arterial ECs. LPS induced the release of TNFα, IL-6, and IL-8 by HLMVECs that were inhibited by sitagliptin. LPS promoted the proliferation of HLMVECs, and sitagliptin suppressed this response. However, sitagliptin failed to reverse LPS-induced permeability in cultured ECs or lung epithelial cells in vitro. In summary, sitagliptin attenuates LPS-induced lung injury in mice and exerts anti-inflammatory effects on HLMVECs. These novel observations indicate DPP4 inhibitors may have potential as therapeutic drugs for ARDS.

Ginsenoside Rh2 Ameliorates Lipopolysaccharide-Induced Acute Lung Injury by Regulating the TLR4/PI3K/Akt/mTOR, Raf-1/MEK/ERK, and Keap1/Nrf2/HO-1 Signaling Pathways in Mice.

The anti-inflammatory effect of ginsenoside Rh2 (GRh2) has labeled it as one of the most important ginsenosides. The purpose of this study was to identify the anti-inflammatory and antioxidant effects of GRh2 using a lipopolysaccharide (LPS) challenge lung-injury animal model. GRh2 reduced LPS-induced proinflammatory mediator nitric oxide (NO), tumor necrosis factor-alpha, interleukin (IL)-1β, and anti-inflammatory cytokines (IL-4, IL-6, and IL-10) production in lung tissues. GRh2 treatment decreased the histological alterations in the lung tissues and bronchoalveolar lavage fluid (BALF) protein content; total cell number also reduced in LPS-induced lung injury in mice. Moreover, GRh2 blocked iNOS, COX-2, the phosphorylation of IκB-α, ERK, JNK, p38, Raf-1, and MEK protein expression, which corresponds with the growth of HO-1, Nrf-2, catalase, SOD, and GPx expression in LPS-induced lung injury. An in vivo experimental study suggested that GRh2 has anti-inflammatory effects, and has potential therapeutic efficacy in major anterior segment lung diseases.