Protective Effects of Chymostatin on Paraquat-Induced Acute Lung Injury in Mice

Regulation of macrophage polarization and glucose metabolism by the ERK/MAPK-HK1 signaling pathway in paraquat-induced acute lung injury

Acute lung injury is the leading cause of paraquat (PQ) poisoning-related mortality. The mechanism by which macrophages are involved in PQ-induced acute lung injury remains unclear. In recent years, the role of metabolic reprogramming in macrophage functional transformation has received significant attention. The current study aimed to identify the role of altered macrophage glucose metabolism and molecular mechanisms in PQ poisoning-induced acute lung injury. We established a model of acute lung injury in PQ-intoxicated mice via the intraperitoneal injection of PQ. PQ exposure induces macrophage M1 polarization and promotes the release of inflammatory factors, which causes the development of acute lung injury in mice. In vitro analysis revealed that PQ altered glucose metabolism, which could be reversed by siRNA transfection to silence the expression of HK1, a key enzyme in glucose metabolism. RNA sequencing revealed that the ERK/MAPK pathway was the crucial molecular mechanism of PQ pathogenesis. Further, U0126, an ERK inhibitor, could inhibit PQ-induced HK1 activation and macrophage M1 polarization. These findings provide novel insights into the previously unrecognized mechanism of ERK/MAPK-HK1 activation in PQ poisoning.

Astragaloside IV alleviates lung inflammation in Klebsiella pneumonia rats by suppressing TGF-β1/Smad pathway

Astragaloside IV is a biologically active substance derived from the traditional Chinese medicine Astragalus mambranaceus Bunge, and has antioxidant, anti-inflammatory, and anti-apoptotic properties. In this study, we aimed to investigate the effects of astragaloside IV on Klebsiella pneumonia rats and the underlying mechanisms. Klebsiella pneumoniae (K. pneumoniae) rats were treated with different dosages of astragaloside IV (5, 10, and 20 mg/kg) by intragastric administration. The levels of pro-inflammatory cytokines interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α in bronchoalveolar lavage fluid (BALF) were determined. Pathological changes of lung tissue were inspected by HE staining. The expression of transforming growth factor (TGF)-β1 in lung tissue was determined with immunohistochemistry, and the expression levels of TGF-β1, p-Smad2/Smad2, p-Smad3/Smad3, IκBα/p-IκBα, and p65/p-p65 in lung tissue were determined by western blot. The mechanism was further investigated with TGF-β1 inhibitor SB-431542. Astragaloside IV reduced the elevated levels of pro-inflammatory cytokines caused by K. pneumoniae and improved lung tissue damage in a dose-dependent manner. Astragaloside IV also decreased the expression of TGF-β1/Smad signaling pathway-related proteins and decreased the protein levels of inflammation-related p-IκBα and p65 in lung tissues induced by K. pneumoniae. Additionally, it was found that the effects of 20 mg/kg astragaloside IV were similar to SB-431542, which could improve pulmonary fibrosis induced by K. pneumoniae, decrease the levels of TGF-β1/Smad signaling pathway-related proteins in lung, and reduce inflammation at the same time. Astragaloside IV could alleviate the inflammation of rat pneumonia induced by K. pneumoniae through suppressing the TGF-β1/Smad pathway.

Nitric oxide-mediated the therapeutic properties of induced pluripotent stem cell for paraquat-induced acute lung injury

The mortality rate associated with acute lung injury (ALI) and its severe form, acute respiratory distress syndrome, is high. Induced pluripotent stem cell (iPSC) therapy is a potential treatment method for ALI, but its therapeutic efficacy is limited in injured lungs. Nitric oxide (NO) has various physiological actions. The current study investigated the effect of iPSCs pretreated with NO donors in paraquat (PQ)-induced ALI mouse model. Male C57BL/6 mice were intraperitoneally injected with PQ, followed by infusion of phosphate-buffered saline, iPSCs, L-arginine pretreated iPSCs, or Nitro-L-arginine methylester (L-NAME) pretreated iPSCs through the tail veins. Histopathological changes, pulmonary microvascular permeability, and inflammatory cytokine levels were analyzed after 3 or 28 d. The effects on iPSC proliferation, migration, and adhesion were evaluated in vitro. More L-arginine-pretreated iPSCs were selectively trafficked into the injured pulmonary tissue of mice with LPS-induced ALI, drastically diminishing the histopathologic changes and inflammatory cytokine levels (IL-1β and IL-6). There was also markedly improved pulmonary microvascular permeability and pulmonary function. The NO inhibitor abolished the protective effects of iPSCs. In addition, the ability of L-arginine to promote the proliferation and migration of iPSCs was decreased by L-NAME pretreatment, suggesting that NO might mediate the therapeutic benefits of iPSC. The improvement of the iPSC physiological changes by the endogenous gaseous molecule NO reduces lung injury severity. L-Arginine represents a pharmacologically important strategy for enhancing the therapeutic potential of iPSCs.

Dimethyl fumarate attenuates paraquat-induced pulmonary oxidative stress, inflammation and fibrosis in mice

Paraquat (PQ) is the most important cationic bipyridyl herbicide in the agricultural industry, which is very toxic to humans and animals and causes disruption in many organs, mainly in the lungs. Dimethyl fumarate (DMF) is an immune-modulating drug used in the treatment of multiple sclerosis and psoriasis shows antioxidant, anti-inflammatory, and antifibrotic effects. In this study, the ameliorative effects of DMF (10, 30 and 100 mg/kg, orally) on PQ (30 mg/kg) model of lung damage were evaluated in male mice. DMF was given daily for 7 days and PQ was administrated in the fourth day in a single dose. On the eighth day, the animals were sacrificed, and their lung tissue were removed. The results indicated that DMF can ameliorate PQ-induced the significant increase in lung index, hydroxyproline, as well as TBARS, TGF-β, NF-κB and decrease in the amount of total thiol, catalase, glutathione peroxidase, superoxide dismutase, Nrf-2, and INF-γ. The histopathological results confirmed indicated findings. The results showed that the protective effect of DMF on PQ-induced toxicity is mediated through antioxidant, anti-inflammatory and antifibrotic activities.

Orthotopic foetal lung tissue direct injection into lung showed a preventive effect against paraquat-induced acute lung injury in mice

OBJECTIVES

Lung transplantation is the only effective therapy for patients with end-stage lung disease but an organ shortage crisis necessitates the development of alternative therapies. Recent studies have highlighted the potential of foetal tissue transplantation to facilitate the regeneration of vital organs such as liver that have been damaged by lethal diseases. Herein, with the aim of restoring pulmonary function, we hypothesized that allogenic foetal lung tissue implantation would attenuate severe respiratory failure.

METHODS

Lung tissue from the foetuses of pregnant green fluorescent protein-C57BL/6 mice at 13.5 days of gestation was injected into the left lungs of recipient mice. Severe lung injury was induced by paraquat, and we analysed the survival rate and pathohistological findings after 1 month.

RESULTS

The survival rate of the therapy group was 39%, which was significantly higher than the vehicle group at 5.9% (P = 0.034). Immunochemical staining showed that positive cytoplasmic stained cells with anti-interleukin-10 antibody were identified in the gland-like structure of embryonic day 13.5 foetal lung. At 4 weeks after orthotopic implantation, haematoxylin and eosin staining showed reduced lung inflammatory cells, reduced lung oedema and increased active cell proliferation of foetal lung cells. Lung injury score showed that the airway septal thickening revealed statistically significant differences between vehicle and foetal lung therapy (P < 0.001).

CONCLUSIONS

Immature foetal lungs improved the survival rate of mice with paraquat-induced severe lung injury, establishing the need for systematic follow-up studies. The anti-inflammatory cytokine in the tissue from embryonic day 13.5 foetal lung might suppress severe lung injury.

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.

Decoding the Papain Inhibitor from Streptomyces mobaraensis as Being Hydroxylated Chymostatin Derivatives: Purification, Structure Analysis, and Putative Biosynthetic Pathway

Streptomyces mobaraensis produces the papain inhibitor SPI consisting of a 12 kDa protein and small active compounds (SPI_ac). Purification of the papain inhibitory compounds resulted in four diverse chymostatin derivatives that were characterized by NMR and MS analysis. Chymostatins are hydrophobic tetrapeptide aldehydes from streptomycetes, e.g., S. lavendulae and S. hygroscopicus, that reverse chymosin-mediated angiotensin activation and inhibit other serine and cysteine proteases. Chymotrypsin and papain were both inhibited by the SPI_ac compounds in the low nanomolar range. SPI_ac differs from the characterized chymostatins by the exchange of phenylalanine for tyrosine. The crystal structure of one of these chymostatin variants confirmed its molecular structure and revealed a S-configured hemithioacetal bond with the catalytic Cys25 thiolate as well as close interactions with hydrophobic S1 and S2 subsite amino acids. A model for chymostatin biosynthesis is provided based on the discovery of clustered genes encoding several putative nonribosomal peptide synthetases; among them, there is the unusual CstF enzyme that accommodates two canonical amino acid activation domains as well as three peptide carrier protein domains.

Glycyrrhetinic acid alleviates acute lung injury by PI3K/AKT suppressing macrophagic Nlrp3 inflammasome activation

Glycyrrhetinic acid (GA), a triterpene saponins, has been widely proven to have multiple medicinal properties. Our study aimed to figure out the protective effect of GA on acute lung injury (ALI) and the underlying mechanism. The LPS-induced ALI model mice were intratracheally administrated with 10 mg/kg LPS. Pretreatment with GA (10, 20, 40 mg/kg, i.g.) ameliorated acute lung injury pathological damage, macrophage infiltration and lung edema. In the lung tissue, immunofluorescence (IF) and Immunohistochemistry (IHC) were performed to detect macrophage Nod-like receptor 3 (Nlrp3) inflammasome activation and interleukin-1β (IL-1β) protein expression. In macrophages, the co-localization of Nlrp3 with caspase-1 and Nlrp3 with ASC were assessed by IF. The translational and transcriptional level of Nlrp3, cle-caspase-1 and apoptosis-associated speck-like protein containing CARD (ASC), were examined by Western blot and Real time PCR (RT-PCR). The protein expression of Cle-caspase-1 was remarkably suppressed via sh-Nlrp3 transfection compared with LPS groups. GA notably attenuated ALI by inhibiting Nlrp3 formation and activation. Furthermore, GA downregulated the production of reactive oxygen species (ROS) and the phosphorylation level of PI3K and AKT in macrophages. These findings indicate that GA ameliorated ALI in mice by suppressing the activation of Nlrp3 inflammasome which may be mediated by ROS-PI3K/AKT pathway. GA may serve as a promising agent for the attenuation of ALI-related inflammation and pathology.

Diosmin ameliorative effects on oxidative stress and fibrosis in paraquat-induced lung injury in mice

Paraquat (PQ) induces pulmonary fibrosis, a progressive lung disorder resulting in severe respiratory failure and death. Increased oxidative stress, inflammatory reactions, and multiple fibrotic lesions are major features of PQ-induced lung injury. Diosmin (Dio) is a safe drug that is available for clinical use for vascular disorders. Dio exhibits antioxidant, anti-inflammatory, and antifibrotic activities. Accordingly, the aim of this study was to evaluate the protective effect of diosmin on PQ-induced lung injury in mice and the underlying mechanisms involved. Lung injury was induced by PQ (30 mg/kg, intraperitoneally) in NMRI albino mice and Dio (50 and 100 mg/kg, gavage) was administrated 3 days before PQ and continued for 10 or 24 days. After euthanizing the mice, the biochemical and histopathological markers of lung tissue were determined. PQ significantly increased oxidative stress, inflammatory, and fibrotic markers. PQ increased the level of malonedaldehyde (MDA) and hydroxyproline (HYP) and decreased the level of glutathione (GSH) and catalase activity in the lung. Dio (50 and 100 mg/kg) significantly increased GSH levels and catalase activity and decreased HYP content and MDA levels. In addition, Dio reduced histopathological injuries in hematoxylin and eosin-stained and Masson's trichrome-stained sections. These findings suggest that Dio has protective effects against PQ-induced lung injury, which may be due to its antioxidant, anti-inflammatory, and antifibrotic effects.

Protective effects of febuxostat against paraquat-induced lung toxicity in rats: Impact on RAGE/PI3K/Akt pathway and downstream inflammatory cascades

AIMS

The herbicide paraquat causes fatal lung toxicity by induction of xanthine oxidase, production of free radicals and inflammation. Febuxostat, a xanthine oxidase inhibitor and anti-gout has recently shown anti-inflammatory activity. Accordingly, this study was carried out to investigate whether febuxostat may attenuate paraquat-induced lung toxicity and to explore the possible underlying mechanisms.

MAIN METHODS

Rats were administered either vehicle, a single dose of paraquat (30 mg/kg, i.p.), febuxostat (15 mg/kg, oral), or both for 14 successive days. Serum LDH and sRAGE were estimated. Lung tissue xanthine oxidase activity, SOD, TAC, MDA, and RAGE, HMGB1 gene expression, PI3K/Akt and β-catenin protein expression, MMP-9, IL-8, VEGF and COX-2 gene expression were estimated.

KEY FINDINGS

Results showed that paraquat induced lung injury characterized by enhanced oxidative stress and inflammation, upregulated RAGE, HMGB1 gene expression, PI3K/Akt and β-catenin protein expression. Administration of febuxostat inhibited the deleterious effects of paraquat on lung through inhibition of xanthine oxidase activity and related oxidative stress, downregulation of RAGE/PI3K/Akt pathway, and suppression of β-catenin protein expression and its downstream inflammatory mediators.

SIGNIFICANCE

The present study showed that febuxostat may abrogate paraquat-induced lung toxicity and demonstrated a novel mechanism for its ameliorative effects.

Mesenchymal stem cell therapy for paraquat poisoning: A systematic review and meta-analysis of preclinical studies

Background

Paraquat (PQ) poisoning can cause multiple organ failure, in which the lung is the primary target organ. There is currently no treatment for PQ poisoning. Mesenchymal stem cells (MSCs), which differentiate into multiple cell types, have generated much enthusiasm regarding their use for the treatment of several diseases. The aim of this study was to systematically review and analyze published preclinical studies describing MSC administration for the treatment of PQ poisoning in animal models to provide a basis for cell therapy.

Methods

The electronic databases PubMed and CBMdisc were searched in this systematic review and meta-analysis. The MSC treatment characteristics of animal models of PQ poisoning were summarized. After quality assessment was performed, the effects of MSC transplantation were evaluated based on the survival rate, lung wet/dry weight, fibrosis scores, oxidative stress response, and inflammatory response. Publication bias was assessed.

Results

Eleven controlled preclinical studies involving MSC transplantation in animal models of PQ poisoning were included in this review. MSC therapy improved the survival rate and reduced the lung wet/dry weight and histopathological fibrosis changes in most studies. MSCs decreased serum or plasma malondialdehyde levels in the acute phase after 7 and 14 d and increased serum or plasma superoxide dismutase and glutathione levels at the same time points. IL-1β, TNF-α and TGF-β1 levels in blood or lung tissues were decreased to different degrees by MSCs. Lung hydroxyproline was decreased by MSCs after 14 d. No obvious evidence of publication bias was found.

Conclusion

MSCs showed anti-fibrosis therapeutic effects in animal models of lung injury caused by PQ poisoning, which may be related to reduced oxidative stress and inflammatory cytokine levels. Our review indicates a potential therapeutic role for MSC therapy to treat PQ poisoning and serves to augment the rationale for clinical studies.