MyD88 gene knockout attenuates paraquat-induced acute lung injury

Shiwei Qingwen decoction regulates TLR4/NF-κB signaling pathway and NLRP3 inflammasome to reduce inflammatory response in lipopolysaccharide -induced acute lung injury

ETHNOPHARMACOLOGICAL RELEVANCE

Shiwei Qingwen decoction (SWQ), a Chinese herbal formula based on the classic traditional Chinese medicine prescription Yu Ping Feng San, has shown efficacy in preventing and treating early pneumonia with good clinical outcomes. However, its underlying mechanism is yet unclear.

AIM OF THE STUDY

To clarify the preventive and therapeutic effects of SWQ on lipopolysaccharide (LPS)-induced acute lung injury (ALI) and explore the underlying mechanism by which SWQ influences pneumonia.

MATERIALS AND METHODS

First, the chemical composition of SWQ was preliminarily determined by high performance liquid chromatography (HPLC), and the impact of SWQ (3.27, 6.55, and 13.1 g/kg) was assessed in the LPS-induced ALI rat model. Next, its inflammatory pathway was determined via network pharmacology. Finally, the molecular mechanism of SWQ was validated using a rat ALI model and a THP-1 cell inflammation model.

RESULTS

HPLC identified chlorogenic acid, prime-O-glucosylcimifugin, calycosin, and 5-O-methylaminoside in the chemical profile of SWQ. In the ALI model, SWQ alleviated ALI by reducing lung wet/dry weight ratio (W/D) and preventing histopathological damage to the lungs. At the same time, SWQ decreased penetration of inflammatory mediators by upregulating AQP1 and AQP5 and endothelial nitric oxide synthase (eNOS). Pretreatment with SWQ downregulated white blood cells and neutrophils count in BALF and suppressed LPS-induced expression levels of MPO, NE, and pro-inflammatory factors (TNF-α, IL-1β, IL-6, and iNOS). Network pharmacology showed that SWQ was associated with TLR4/NF-κB inflammation pathway. Moreover, pretreatment with SWQ reduced the expression level of TLR4/NF-κB signaling pathway-associated proteins (TLR4, Myd88, p-IκB, and p-p65) and NLRP3 inflammasome (NLRP3, ASC, caspase-1, and cleaved-IL-1β) in vivo and vitro.

CONCLUSIONS

The present study demonstrates that SWQ can reduce inflammation in ALI by inhibiting TLR4/NF-κB and NLRP3 inflammasome activation.

Role of released mitochondrial DNA in acute lung injury

Acute lung injury(ALI)/acute respiratory distress syndrome(ARDS) is a form of acute-onset hypoxemic respiratory failure characterised by an acute, diffuse, inflammatory lung injury, and increased alveolar-capillary permeability, which is caused by a variety of pulmonary or nonpulmonary insults. Recently, aberrant mitochondria and mitochondrial DNA(mtDNA) level are associated with the development of ALI/ARDS, and plasma mtDNA level shows the potential to be a promising biomarker for clinical diagnosis and evaluation of lung injury severity. In mechanism, the mtDNA and its oxidised form, which are released from impaired mitochondria, play a crucial role in the inflammatory response and histopathological changes in the lung. In this review, we discuss mitochondrial outer membrane permeabilisation (MOMP), mitochondrial permeability transition pore(mPTP), extracellular vesicles (EVs), extracellular traps (ETs), and passive release as the principal mechanisms for the release of mitochondrial DNA into the cytoplasm and extracellular compartments respectively. Further, we explain how the released mtDNA and its oxidised form can induce inflammatory cytokine production and aggravate lung injury through the Toll-like receptor 9(TLR9) signalling, cytosolic cGAS-stimulator of interferon genes (STING) signalling (cGAS-STING) pathway, and inflammasomes activation. Additionally, we propose targeting mtDNA-mediated inflammatory pathways as a novel therapeutic approach for treating ALI/ARDS.

MicroRNAs: Important Regulatory Molecules in Acute Lung Injury/Acute Respiratory Distress Syndrome

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is an overactivated inflammatory response caused by direct or indirect injuries that destroy lung parenchymal cells and dramatically reduce lung function. Although some research progress has been made in recent years, the pathogenesis of ALI/ARDS remains unclear due to its heterogeneity and etiology. MicroRNAs (miRNAs), a type of small noncoding RNA, play a vital role in various diseases. In ALI/ARDS, miRNAs can regulate inflammatory and immune responses by targeting specific molecules. Regulation of miRNA expression can reduce damage and promote the recovery of ALI/ARDS. Consequently, miRNAs are considered as potential diagnostic indicators and therapeutic targets of ALI/ARDS. Given that inflammation plays an important role in the pathogenesis of ALI/ARDS, we review the miRNAs involved in the inflammatory process of ALI/ARDS to provide new ideas for the pathogenesis, clinical diagnosis, and treatment of ALI/ARDS.

The Ameliorative Effects of Arctiin and Arctigenin on the Oxidative Injury of Lung Induced by Silica via TLR-4/NLRP3/TGF-β Signaling Pathway

Silicosis remains one of the most serious diseases worldwide, with no effective drug for its treatment. Our research results have indicated that arctiin and arctigenin could increase the mitochondrial membrane potential, which in turn reduces the production of reactive oxygen species (ROS), blocks the polarization of macrophages, and inhibits the differentiation of myofibroblasts to reduce oxidative stress, inflammation, and fibrosis. Further, our study revealed that arctiin and arctigenin suppressed the activation of NLRP3 inflammasome through the TLR-4/Myd88/NF-κB pathway and the silica-induced secretion of TNF-α, IL-1β, TGF-β, and α-SMA. Besides, the silica-induced increase in the levels of serum ceruloplasmin and HYP was also inhibited. Results of metabolomics indicated that arctiin and arctigenin could regulate the abnormal metabolic pathways associated with the development of silicosis, which involve pantothenate and CoA biosynthesis, cysteine and methionine metabolism, linoleic acid metabolism, and arginine and proline metabolism successively. Furthermore, the analysis of metabolomics, together with network topological analysis in different phases of silicosis, revealed that urine myristic acid, serum 4-hydroxyproline, and L-arginine could be regarded as diagnosis biomarkers in the early phase and formation of pulmonary fibrosis in the latter phases of silicosis. Arctiin and arctigenin could downregulate the increased levels of myristic acid in the early phase and serum 4-hydroxyproline in the latter phase of silicosis. Interestingly, the integration of TLR-4/NLRP3/TGF-β signaling and metabolomics verified the importance of macrophage polarization in the silicosis fibrosis process. To the best of our knowledge, this is the first study reporting that arctiin and arctigenin both can ameliorate silicosis effectively, and the former is a little stronger than its aglycone arctigenin because of its high oral bioavailability, low toxicity, and multimolecular active metabolites as determined by AdmetSAR and molecular docking analysis.

Overexpression of TOLLIP Protects against Acute Kidney Injury after Paraquat Intoxication through Inhibiting NLRP3 Inflammasome Activation Modulated by Toll-Like Receptor 2/4 Signaling

Paraquat (PQ) can cause multiorgan failure including acute kidney injury (AKI). Our prior study showed that Toll-interacting protein (TOLLIP) protected against PQ-induced acute lung injury. However, the role of TOLLIP in PQ-induced AKI remains undefined. This study was aimed at understanding the role and mechanism of TOLLIP in AKI. Six-eight-week-old male Wistar rats were intraperitoneally injected with 25 mg/kg PQ to induce AKI for 24 h in vivo. HK-2 cells were treated with 300 μM PQ for 24 h to induce cellular injury in vitro or 300 μM PQ and 5 μM nuclear factor-κB (NF-κB) inhibitor BAY11-7082 for 24 h. Rats were infected with adenovirus carrying TOLLIP shRNA via tail vein injection and HK-2 cells with adenovirus carrying TOLLIP shRNA or TOLLIP 48 h before PQ exposure. Results showed that TOLLIP and Toll-like receptor 2/4 (TLR2/4) expressions were boosted in the kidney after PQ intoxication. The toxic effect of PQ on the kidney and HK-2 cells was exacerbated by TOLLIP knockdown, as evidenced by aggravated glomerulus and tubule injury, inflammatory infiltration, and cell apoptosis in the kidney and increased loss of cell viability and apoptotic cells in HK-2 cells. TOLLIP knockdown also enhanced PQ-induced NLR family pyrin domain-containing 3 (NLRP3) inflammasome activation in vivo and in vitro and TLR2/4-NF-κB signaling in vitro, reflected by increased contents of proinflammatory cytokines and expressions of NLRP3 inflammasome-related proteins in the kidney and HK-2 cells and expressions of TLR2, TLR4, and nuclear NF-κB p65 in HK-2 cells. However, TOLLIP overexpression inhibited PQ-induced loss of cell viability, cell apoptosis, NLRP3 inflammasome activation, and TLR2/4-NF-κB signaling in vitro. Additionally, BAY11-7082 abolished TOLLIP knockdown-induced NLRP3 inflammasome activation in vitro, indicating that TOLLIP protected against NLRP3 inflammasome activation in PQ-induced AKI through inhibiting TLR2/4-NF-κB signaling. This study highlights the importance of TOLLIP in AKI after PQ intoxication.

Lipoxin A4 protects against paraquat‑induced acute lung injury by inhibiting the TLR4/MyD88‑mediated activation of the NF‑κB and PI3K/AKT pathways

Paraquat (PQ) causes serious oxidative stress and inflammatory responses, particularly to the lungs. Since lipoxin A4 (LXA4) functions as an anti‑inflammatory mediator, the present study aimed to explore its effects on PQ‑induced acute lung injury (ALI) and to elucidate the possible underlying mechanisms. PQ was administered to male SD rats and RAW264.7 cells to establish a model of poisoning, and LXA4 was used as an intervention drug. LXA4 treatment attenuated PQ‑induced lung injury, and this was accompanied by decreased tumor necrosis factor (TNF)‑α and interleukin (IL)‑1β secretion levels, and reduced oxidative stress damage. Additionally, LXA4 treatment inhibited the activation of the inflammation‑related signaling molecules, Toll‑like receptor 4 (TLR4), myeloid differentiation primary response 88 (MyD88), nuclear factor (NF)‑κB p65, p‑phosphoinositide 3‑kinase (PI3K) and p‑AKT. Furthermore, the in vitro experiments further confirmed that the beneficial effects of LXA4 on PQ‑induced damage were TLR4‑dependent. Hence, the present study demonstrated that LXA4 attenuated PQ‑induced toxicity in lung tissue and RAW264.7 macrophages, and that this protective effect may be closely related to the mitigation of inflammatory responses, oxidative stress damage and the TLR4/MyD88‑mediated activation of the PI3K/AKT/NF‑κB pathway.

Trauma-induced lung injury is associated with infiltration of activated TLR expressing myeloid cells

INTRODUCTION

Traumatic injury with hemorrhage (TH) induces an inflammatory response in the lung resulting in lung injury involving activation of immune cells including myeloid cells (i.e., monocytes, granulocytes and macrophages), in part through TLRs. TLRs, via the recognition of damage associated molecular patterns (DAMPs), are a key link between tissue injury and inflammation. Nonetheless, the role of TLRs in myeloid cell activation and TH-induced lung injury remains ill defined.

METHODS

C57BL/6 male mice were subjected to TH or sham treatment (n = 4-6 /group). Lung tissues were collected two hrs. after injury. Single cells were isolated from the lungs by enzymatic digestion and myeloid cell TLR expression and activation (i.e., cytokine production) were assessed using flow cytometry techniques.

RESULTS

The injury was associated with a profound change in the lung myeloid cell population. TH markedly increased lung CD11b⁺ monocyte numbers and Gr1⁺ granulocyte numbers as compared to sham mice. The number of cells expressing TLR2, TLR4, and TLR9 were increased 4-7 fold in the TH mice. Activation for elevated cytokine (TNFα, IL-10) production was observed in the lung monocyte population of the TH mice.

CONCLUSIONS

Trauma-induced lung injury is associated with infiltration of the lungs with TLR expressing myeloid cells that are activated for elevated cytokine responses. This elevation in TLR expression may contribute to DAMP-mediated pulmonary complications of an inflammatory nature and warrants further investigation.

The herbicide paraquat-induced molecular mechanisms in the development of acute lung injury and lung fibrosis

The herbicide paraquat (PQ; 1,1'-dimethyl-4,4'-bipyridylium dichloride) is a highly toxic organic heterocyclic herbicide that has been widely used in agricultural settings. Since its commercial introduction in the early 1960s, numerous cases of fatal PQ poisonings attributed to accidental and/or intentional ingestion of PQ concentrated formulations have been reported. The clinical manifestations of the respiratory system during the acute phase of PQ poisoning mainly include acute lung injury (ALI)/acute respiratory distress syndrome (ARDS), followed by pulmonary fibrosis in a later phase. The focus of this review is to summarize the most recent publications related to PQ-induced lung toxicity as well as the underlying molecular mechanisms for PQ-mediated pathologic processes. Growing sets of data from in vitro and in vivo models have demonstrated the involvement of the PQ in regulating lung oxidative stress, inflammatory response, epigenetics, apoptosis, autophagy, and the progression of lung fibrosis. The article also summarizes novel therapeutic avenues based on a literature review, which can be explored as potential means to combat PQ-induced lung toxicity. Finally, we also presented clinical studies on the association of PQ exposure with the incidence of lung injury and pulmonary fibrosis.

Protective effect of toll-interacting protein overexpression against paraquat-induced lung injury in mice and A549 cells through inhibiting oxidative stress, inflammation, and NF-κB signaling pathway

Toll-interacting protein (Tollip) is a pivotal negative regulator of inflammatory response. In the present study, the effects of Tollip overexpression on paraquat (PQ)-induced lung injury were explored through in vivo and in vitro investigations. Upon stimulation with PQ in mice, the expression of Tollip was down-regulated. Histopathological analysis revealed that the overexpression of Tollip significantly decreased inflammatory cell infiltration. Similarly, the levels of myeloperoxidase (MPO) and interleukin-1β (IL-1β) were lowered by Tollip overexpression in PQ-administrated mice. Besides, the overexpression of Tollip reduced reactive oxygen species (ROS) generation and malondialdehyde (MDA) level but enhanced superoxide dismutase (SOD) activity in PQ-treated A549 cells. Meanwhile, Tollip overexpression lowered the level of IL-1β and decreased the protein expressions of p-p65 in the cytoplasm and nuclear p65. Importantly, inhibition of NF-κB signaling pathway probably by decreasing NF-κB p65-DNA binding activity was induced by Tollip overexpression. Taken together, Tollip overexpression attenuated PQ-initiated lung injury possibly via reduction of oxidative stress and inflammation and suppression of NF-κB signaling pathway activation, which provided some novel ideas for the treatment of lung damage mediated by PQ.

Continuous hemoperfusion relieves pulmonary fibrosis in patients with acute mild and moderate paraquat poisoning

Acute paraquat poisoning (APP) is a serious public health problem with a high mortality rate and there is no specific antidote for APP in clinical. Early haemoperfusion (HP) treatment is effective in APP rescue. In this study, we compared the influence of routine HP and continuous HP on the survival rate and the treatment of pulmonary fibrosis in mild and moderate APP patients. Eighty-two cases of mild and moderate APP patients who were admitted to our hospital from January of 2017 to December of 2018 were selected. All patients were randomly divided into a routine haemoperfusion (HP) group (n = 40) and a continuous haemoperfusion (CHP) group (n = 42). Compared with the HP group, the 28-day survival rate of mild and moderate APP patients was elevated in the CHP group. Blood N-terminal procollagen Ш propeptide (PIIINP) levels in APP patients were positively related with paraquat (PQ) concentration (r = 0.309, P = 0.000). There were statistically significant differences in the levels of PIIINP, Collage TypeIV (CIV), transforming growth factor-beta 1 (TGF-β1), malondialdehyde (MDA), superoxide dismutase (SOD) activity and sequential organ failure assessment (SOFA) score between the two groups both on the third and seventh days after treatment, and the treatment effect of the CHP group on pulmonary fibrosis in APP patients was better than that of the HP group. In conclusion, CHP treatment had a significant therapeutic effect on mild and moderate APP patients, which could effectively improve the survival rate and relieve pulmonary fibrosis.

TLR3 is involved in paraquat-induced acute renal injury

AIMS

To investigate the role of Toll-like receptor 3 (TLR3) in mouse paraquat-induced acute renal injury.

MATERIALS AND METHODS

Acute renal injury was established in C57BL/6J mice by intraperitoneal injection of paraquat (28 mg/kg). The mice were also injected intraperitoneally with TLR3 agonist poly I:C (20 mg/kg) or TLR3/dsRNA complex inhibitor (1 mg) 1 h before paraquat exposure. At 72 hour post paraquat exposure, the mice were sacrificed and the blood and renal tissues were collected to examine TLR3 expression in renal tissues, pathological injury in renal tissues, renal function, inflammation, and cell apoptosis.

KEY FINDINGS

After paraquat exposure, TLR3 expression in mouse renal tissues was significantly increased, and pathological changes to the renal tissues and remarkable renal impairment were present. Compared to the paraquat group, the poly I:C group showed no significant difference in renal pathology, renal function, inflammation, or cell apoptosis. However, TLR3 inhibitor treatment significantly alleviated injury to the renal tissues, improved renal function, inhibited NF-κB activation, suppressed the infiltration of neutrophils, and lessened the expression of IL-1β, TNF-α, and keratinocyte chemoattractant (KC) in renal tissues. TLR3 inhibitor treatment also suppressed the activation of caspase-8 and caspase-3 and reduced apoptosis in the renal tissues.

SIGNIFICANCE

Paraquat exposure significantly upregulates TLR3 expression in renal tissues, and activation of the TLR3 signaling pathway is an important contributor to paraquat nephrotoxicity. TLR3 activation exacerbates inflammation and cell apoptosis in renal tissues by activating NF-κB and caspase-8, thus promoting paraquat-induced acute renal injury.

Toll-like receptor 9 mediates paraquat-induced acute lung injury: an in vitro and in vivo study

AIMS

This study aimed to investigate the role of Toll-like receptor 9 in paraquat-induced acute lung injury (ALI).

MAIN METHODS

For in vivo study,C57BL mice were randomly assigned into the vehicle control group, paraquat group, paraquat + TLR9 antagonist (ODN2088) group, and TLR9 antagonist (ODN2088) group (n=36 per group). After paraquat 30mg/kg ip for 2, 24 and 48h, serum samples and lung tissues were collected to evaluate ALI and TLR9 signaling by lung injury score, protein levels of TLR9, MyD88, p-IRAK4, p-p65, and serum TNF-α and IL-1β levels. As for in vitro research A549 cells were randomly divided into the control group, paraquat group, paraquat + TLR9 siRNA group, and TLR9 siRNA group. After paraquat treatment for 24h, the cells and supernatant were collected to measureTLR9, TNF-α, IL-1 mRNA expression, and detect activation of NF-κB, caspase-3.

KEY FINDINGS

In vivo, the lung injury score, the TLR9, MyD88, p-IRAK4 and p-p65 protein levels, and cytokines TNF-α and IL-1β levels in paraquat group were significantly higher than that in the control group;TLR9 blocker ODN2088 pretreatment attenuated lung injury, inhibited MyD88 and NF-κB activation, and reduced TNF-α and IL-1β in serum. In vitro result shows that the gene silencing of TLR9 reduced the mRNA expression of TLR9, TNF-α and IL-1, inhibited NF-κB and caspase-3 activation, attenuated cell apoptosis.

SIGNIFICANCE

TLR9 mediates paraquat-induced ALI, antagonizing TLR9 or silencing TLR9gene may attenuate paraquat-induced ALI.