Role of growth factors in acute lung injury induced by paraquat in a rat model

Protective effects of Silibinin and cinnamic acid against paraquat-induced lung toxicity in rats: impact on oxidative stress, PI3K/AKT pathway, and miR-193a signaling

Levels of reactive oxygen species (ROS) are the primary determinants of pulmonary fibrosis. It was discovered that antioxidants can ameliorate pulmonary fibrosis caused by prolonged paraquat (PQ) exposure. However, research on the precise mechanisms by which antioxidants influence the signaling pathways implicated in pulmonary fibrosis induced by paraquat is still insufficient. This research utilized a rat model of pulmonary fibrosis induced by PQ to examine the impacts of Silibinin (Sil) and cinnamic acid (CA) on pulmonary fibrosis, with a specific focus on pro-fibrotic signaling pathways and ROS-related autophagy. Lung injury induced by paraquat was demonstrated to be associated with oxidative stress and inflammation of the lungs, downregulated (miR-193a), and upregulated PI3K/AKT/mTOR signaling lung tissues. Expression levels of miR-193a were determined with quantitative real-time PCR, protein level of protein kinase B (Akt), and phosphoinositide 3-Kinase (PI3K) which were determined by western blot analysis. Hydroxyproline levels (HYP) and transforming growth factor-β1 (TGF-β1) were measured by ELISA, malondialdehyde (MDA), total antioxidant capacity (TAC), glutathione peroxidase (GSH), and catalase and were measured in lung tissue homogenates colorimetrically using spectrophotometer. Long-term exposure to paraquat resulted in decreased PI3K/AKT signaling, decreased cell autophagy, increased oxidative stress, and increased pulmonary fibrosis formation. Silibinin and cinnamic acid also decreased oxidative stress by increasing autophagy and miR-193a expression, which in turn decreased pulmonary fibrosis. These effects were associated by low TGF-β1. Silibinin and cinnamic acid inhibited PQ-induced PI3K/AKT by stimulating miR-193-a expression, thus attenuating PQ-induced pulmonary fibrosis.

WTAP mediates FOXP3 mRNA stability to promote SMARCE1 expression and augment glycolysis in colon adenocarcinoma

N6-methyladenosine (m6A) is the most abundant mRNA internal modification and has reportedly been linked to aerobic glycolysis, a hallmark event in tumor development. This work focuses on the role of the m6A methyltransferase WT1-associated protein (WTAP) in metabolic reprogramming and development of colon adenocarcinoma (COAD) and the molecules involved. The WTAP expression in COAD tissues and cells was detected. WTAP was knocked down in two COAD cell lines to figure out its role in the glycolytic activity and malignant phenotype of cancer cells. Cancer cells were further injected into nude mice subcutaneously or via tail vein to evaluate tumor growth and metastasis. The downstream molecules involved were explored using bioinformatics tools, and the molecular interactions were confirmed by immunoprecipitation, luciferase assays, and rescue experiments. WTAP was abundantly expressed in COAD samples. Knockdown of WTAP suppressed glucose consumption, lactate production, and glycolysis, which consequently suppressed cancer cell growth and dissemination in vitro and in vivo. WTAP promoted m6A methylation and stabilized forkhead box P3 (FOXP3) mRNA with the participation of the m6A "reader" YTHDF1. FOXP3 could further bind to SMARCE1 promoter for transcriptional activation. Rescue experiments showed that upregulation of FOXP3 or SMARCE1 restored the glycolytic activity in COAD cells and augmented the growth and mobility of cells both in vitro and in vivo. This study demonstrates that WTAP grants glycolytic activity to COAD and promotes tumor malignant development via the m6A modification of FOXP3 mRNA and the upregulation of SMARCE1.

Novel drug delivery systems and disease models for pulmonary fibrosis

Pulmonary fibrosis (PF) is a serious and progressive lung disease which is possibly life-threatening. It causes lung scarring and affects lung functions including epithelial cell injury, massive recruitment of immune cells and abnormal accumulation of extracellular matrix (ECM). There is currently no cure for PF. Treatment for PF is aimed at slowing the course of the disease and relieving symptoms. Pirfenidone (PFD) and nintedanib (NDNB) are currently the only two FDA-approved oral medicines to slow down the progress of idiopathic pulmonary fibrosis, a specific type of PF. Novel drug delivery systems and therapies have been developed to improve the prognosis of the disease, as well as reduce or minimize the toxicities during drug treatment. The drug delivery routes for these therapies are various including oral, intravenous, nasal, inhalant, intratracheal and transdermal; although this is dependent on specific treatment mechanisms. In addition, researchers have also expanded current animal models that could not fully restore the clinicopathology, and developed a series of in vitro models such as organoids to study the pathogenesis and treatment of PF. This review describes recent advances on pathogenesis exploration, classifies and specifies the progress of drug delivery systems by their delivery routes, as well as an overview on the in vitro and in vivo models for PF research.

Continuous, Automated Breathing Rate and Body Motion Monitoring of Rats With Paraquat-Induced Progressive Lung Injury

Assessments of respiratory response and animal activity are useful endpoints in drug pharmacology and safety research. We investigated whether continuous, direct monitoring of breathing rate and body motion in animals in the home cage using the Vum Digital Smart House can complement standard measurements in enabling more granular detection of the onset and severity of physiologic events related to lung injury in a well-established rodent model of paraquat (PQ) toxicity. In rats administered PQ, breathing rate was significantly elevated while body motion was significantly reduced following dosing and extending throughout the 14-day study duration for breathing rate and at least 5 days for both nighttime and daytime body motion. Time course differences in these endpoints in response to the potential ameliorative test article bardoxolone were also readily detected. More complete than standard in-life measurements, breathing rate and body motion tracked injury progression continuously over the full study time period and aligned with, and informed on interval changes in clinical pathology. In addition, breathing rates correlated with terminal pathology measurements, such as normalized lung weights and histologic alveolar damage and edema. This study is a preliminary evaluation of the technology; our results demonstrate that continuously measured breathing rate and body motion served as physiologically relevant readouts to assess lung injury progression and drug response in a respiratory injury animal model.

Influence of strengthened hemoperfusion combined with continuous venovenous hemofiltration on prognosis of patients with acute paraquat poisoning: SHP + CVVH improve prognosis of acute PQ patients

Background

The success rate of rescue is extremely low in acute paraquat poisoning. This study aimed to assess whether strengthened hemoperfusion (SHP) combined with continuous venovenous hemofiltration (CVVH) improves prognosis in patients with acute paraquat poisoning.

Methods

Patients from January 2005 to December 2018 were enrolled retrospectively. All selected patients were administered conventional therapy. They were divided according to the received treatments in the conventional therapy, hemoperfusion (HP), CVVH, SHP and SHP + CVVH groups. Follow-up was implemented until the 90th day after poisoning. Other outcomes included all-cause mortality on the 15th day after poisoning, and the percentages of respiratory failure and mechanical ventilation use.

Results

The study included 487 patients,and 211 died in all. Mortality rate in the SHP + CVVH group on the 90th day after poisoning was significantly decreased compared with those of other groups (p<0.001). Survival curves of all groups showed significant differences (p<0.001). SHP combined with CVVH was an independent factor reducing mortality risk (p<0.001). Mortality rate in the SHP + CVVH group on the 15th day after poisoning was also significantly decreased (p < 0.05). The proportions of patients in the SHP + CVVH group with acute respiratory failure and mechanical ventilation were significantly lower than those of other groups (p < 0.05).

Conclusions

SHP with CVVH may decrease the mortality rate of patients with acute paraquat poisoning on the 90th day after poisoning and improve the prognosis.

Protective mechanism of 1-methylhydantoin against lung injury induced by paraquat poisoning

Paraquat (PQ), one of the most widely used herbicides worldwide, causes severe toxic effects in humans and animals. 1-methylhydantoin (MH) is an active ingredient of Ranae Oviductus, which has broad pharmacological activities, e.g., eliminating reactive oxygen species and inhibiting inflammation. This study investigated the effects of MH on lung injury induced by PQ. A PQ poisoning model was established by intragastric infusion of PQ (25 mg/kg), and the control group was simultaneously gavaged with the same dose of saline. The MH group was intraperitoneally injected with 100 mg/kg once per day after intragastric infusion of PQ (25 mg/kg) for five consecutive days. All animals were sacrificed on the sixth day, and the lung tissues were dissected for metabolomics analysis. The lactate dehydrogenase (LDH) activity, superoxide dismutase (SOD) activity, TNF-α and malondialdehyde (MDA) content were determined according to the instructions of the detection kit. Compared with that in the control group, the content of LDH, TNF-α and MDA in the lung tissue of the PQ group was significantly higher, and the activity of SOD in the lung tissue was significantly lower (all p<0.05). Compared with that in the control group, the content of LDH, TNF-α and MDA in the MH group was significantly higher, and the activity of SOD was significantly lower (all p<0.05). However, the differences in SOD activity, LDH activity between the PQ and MH groups were not statistically significant (all p > 0.05). There were significant differences in MDA and TNF-α content between the PQ group and MH group (all p<0.05). MH decreased the production of malondialdehyde and TNF-α to protect against the lung injury caused by PQ poisoning, but it had no significant effect on the activity of LDH and SOD. There were significant differences in metabolomics between the MH group and the PQ poisoning group, primarily in bile acid biosynthesis and metabolism of cholesterol, nicotinate, nicotinamide, alanine, aspartate, glutamate, glycine, threonine, serine, phenylalanine and histidine. Therefore, this study highlights that MH has non-invasive mechanisms and may be a promising tool to treat lung injury induced by PQ poisoning.

NLRP inflammasome as a key role player in the pathogenesis of environmental toxicants

Exposure to environmental toxicants (ET) results in specific organ damage and auto-immune diseases, mostly mediated by inflammatory responses. The NLRP3 inflammasome has been found to be the major initiator of the associated pathologic inflammation. It has been found that ETs can trigger all the signals required for an NLRP3-mediated response. The exaggerated activation of the NLRP3 inflammasome and its end product IL-1β, is responsible for the pathogenesis caused by many ETs including pesticides, organic pollutants, heavy metals, and crystalline compounds. Therefore, an extensive study of these chemicals and their mechanisms of inflammasome (INF) activation may provide the scientific evidence for possible targeting of this pathway by proposing possible protective agents that have been previously shown to affect INF compartments and its activation. Melatonin and polyunsaturated fatty acids (PUFA) are among the safest and the most studied of these agents, which affect a wide variety of cellular and physiological processes. These molecules have been shown to suppress the NLRP3 inflammasome mostly through the regulation of cellular redox status and the nuclear factor-κB (NF-κB) pathway, rendering them potential promising compounds to overcome ET-mediated organ damage. In the present review, we have made an effort to extensively review the ETs that exert their pathogenesis via the stimulation of inflammation, their precise mechanisms of action and the possible protective agents that could be potentially used to protect against such toxicants.

Insulin-Like Growth Factor-1 Signaling in Lung Development and Inflammatory Lung Diseases

Insulin-like growth factor-1 (IGF-1) was firstly identified as a hormone that mediates the biological effects of growth hormone. Accumulating data have indicated the role of IGF-1 signaling pathway in lung development and diseases such as congenital disorders, cancers, inflammation, and fibrosis. IGF-1 signaling modulates the development and differentiation of many types of lung cells, including airway basal cells, club cells, alveolar epithelial cells, and fibroblasts. IGF-1 signaling deficiency results in alveolar hyperplasia in humans and disrupted lung architecture in animal models. The components of IGF-1 signaling pathways are potentiated as biomarkers as they are dysregulated locally or systemically in lung diseases, whereas data may be inconsistent or even paradoxical among different studies. The usage of IGF-1-based therapeutic agents urges for more researches in developmental disorders and inflammatory lung diseases, as the majority of current data are collected from limited number of animal experiments and are generally less exuberant than those in lung cancer. Elucidation of these questions by further bench-to-bedside researches may provide us with rational clinical diagnostic approaches and agents concerning IGF-1 signaling in lung diseases.

The effect of adiponectin on LPS-induced inflammation via autophagy in RAW 264.7 macrophages

Mitochondrial dysfunction is involved in the process of sepsis and leads to the accumulation of reactive oxygen species (ROS), which breaks cellular homeostasis and activates the downstream inflammatory cascade. The autophagic removal of ROS is a well-established cellular adaptive mechanism. Adiponectin is an adipocytokine that plays an important role in metabolic and inflammatory regulation. In this study, we investigated the anti-inflammatory effect of adiponectin in a sepsis model and its potential association with autophagy. We induced RAW 264.7 macrophages with lipopolysaccharide (LPS) to set up the sepsis model and treated them with adiponectin, an inhibitor of the nucleotide-binding domain and leucine-rich repeat containing family pyrin domain–containing 3 (NLRP3), ROS, Complex I, and an autophagy inhibitor. Flow cytometry and western blot analysis were performed to detect the expression levels of ROS, NLRP3, interleukin-1 beta (IL-1β), microtubule-associated protein 1A/1B-light chain 3II/I (LC3II/I), and adenosine monophosphate–activated protein kinase (AMPK). Expression levels of NLRP3, IL-1β, and ROS were significantly increased following LPS induction, and adiponectin reversed this up-regulation. Meanwhile, adiponectin also enhanced the expression of LC3II/I, an autophagosome marker, but an autophagy inhibitor and AMPK inhibitor depleted (reversed) the anti-inflammatory and antioxidant effect of adiponectin. Taken together, in the LPS-induced sepsis model, adiponectin alleviated the inflammatory reaction by reducing ROS production, possibly by enhancing autophagy via the AMPK pathway. The activation of autophagy may therefore be a key mechanism by which adiponectin ameliorates the inflammatory reactions of sepsis.

Inhibition of connective tissue growth factor attenuates paraquat-induced lung fibrosis in a human MRC-5 cell line

Chronic exposure to Paraquat (PQ) may result in progressive pulmonary fibrosis and subsequent chronic obstructive pulmonary malfunction. Connective tissue growth factor (CTGF) has been proposed as a key determinant in the development of lung fibrosis. We investigated thus whether knock down of CTGF can prevent human lung fibroblasts (MRC-5) activation and proliferation with the subsequent inhibition of PQ-induced fibrosis. MRC-5 was transfected with CTGF-siRNAs and exposed to different concentrations of PQ. The siRNA-silencing efficacy was evaluated using western blotting analyses, qRT-PCR and flow cytometry. Next, the viability and migration of MRC-5 was determined. MMP-2, MMP-9, and TIMP-1 accumulation were quantified to evaluate the lung fibrosis exposure to PQ. Over expression of CTGF mRNA was observed in human MRC-5 cell as early as 6 h following PQ stimulation. CTGF gene expression in MRC-5 cells was substantially reduced by RNAi, which significantly suppressed the expression of the lung fibrosis markers such as tissue inhibitor of metalloproteinase-2 (TIMP-2), Matrix metalloproteinase-2 (MMP-2) and Matrix metalloproteinase-9 (MMP-9) that were stimulated by PQ. Inhibition of CTGF expression suppressed impeded the proliferation and migration ability of MRC-5 cells and resulted in cell-extracellular matrix (ECM) protein accumulation in cells. Our results suggest that CTGF promoted the development of PQ-induced lung fibrosis in collaboration with transforming growth factor β1 (TGFβ1). Furthermore, the observed arresting effects of CTGF knock down during this process suggested that CTGF is the potential target site for preventing PQ-induced pulmonary fibrosis. © 2015 Wiley Periodicals, Inc. Environ Toxicol 31: 1620-1626, 2016.

NLRP3 inflammasome activation is essential for paraquat-induced acute lung injury

The innate immune response is important in paraquat-induced acute lung injury, but the exact pathways involved are not elucidated. The objectives of this study were to determine the specific role of the NLRP3 inflammasome in the process. Acute lung injury was induced by administering paraquat (PQ) intraperitoneally. NLRP3 inflammasome including NLRP3, ASC, and caspase-1 mRNA and protein expression in lung tissue and IL-1β and IL-18 levels in BALF were detected at 4, 8, 24, and 72 h after PQ administration in rats. Moreover, rats were pretreated with 10, 30, and 50 mg/kg NLRP3 inflammasome blocker glybenclamide, respectively, 1 h before PQ exposure. At 72 h after PQ administration, lung histopathology changes, NLRP3, ASC, and caspase-1 protein expression, as well as secretion of cytokines including IL-1β and IL-18 in BALF were investigated. The NLRP3 inflammasome including NLRP3, ASC, caspase-1 expression, and cytokines IL-1β and IL-18 levels in PQ poisoning rats were significantly higher than that in the control group. NLRP3 inflammasome blocker glybenclamide pretreatment attenuated lung edema, inhibited the NLRP3, ASC, and caspase-1 activation, and reduced IL-1β and IL-18 levels in BALF. In the in vitro experiments, IL-1β and IL-18 secreted from RAW264.7 mouse macrophages treated with paraquat were attenuated by glybenclamide. In conclusion, paraquat can induce IL-1β/IL-18 secretion via NLRP3-ASC-caspase-1 pathway, and the NLRP3 inflammasome is essential for paraquat-induced acute lung injury.

Protective effects of thalidomide on pulmonary injuries in a rat model of paraquat intoxication

Background

This study was designed to evaluate the protective effects of thalidomide on paraquat (PQ)-induced lung injuries in a rat model and to explore the underlying mechanisms.

Methods

Rats were exposed to 50 mg/kg PQ by oral gavage, and treated with thalidomide through oral administration at 60 mg/kg once a day, 6 days/week for 2 weeks. Serum levels of IL-6, TNF-alpha, TGFbeta1 and COL1A1 were detected at different time points after paraquat exposure. At the end of the study, lung tissues were collected for pathological inspection as well as analyses of water content and expression levels of IL-6, TNF-alpha, TGFbeta1 and COL1A1 mRNA.

Results

The results showed that thalidomide treatment could significantly alleviate PQ-induced pathological changes in lung tissue and severity of lung edema. Thalidomide treatment after PQ exposure resulted in significantly reduced serum levels of IL-6, TNF-alpha, TGF-beta1 and COL1A1, as compared to PQ group. PCR analysis demonstrated that expression levels of IL-6, TNF-alpha, TGF-beta1 and COL1A1 in lung tissue were significantly increased after PQ exposure but reduced by thalidomide, which were confirmed by immunohistochemistry staining.

Conclusions

Our results indicated that inflammatory factors played important roles in PQ-induced lung injuries and thalidomide could protect rats from PQ-induced lung injuries by inhibiting the upregulation of inflammatory factors.

Molecular mechanisms of paraquat-induced acute lung injury: a current review

Paraquat is an organic heterocyclic herbicide that is widely used in agriculture, especially in Asian countries. The prevalence of paraquat poisonings has increased dramatically in the past two decades in China. Nearly all paraquat poisonings resulted from intentional or accidental oral administration leading to acute lung injury and, ultimately, acute respiratory distress syndrome. The mortality rate has been reported to be greater than 90%. However, the exact toxic mechanism remains unclear. Herein, we reviewed and summarized the most recent publications related to the molecular mechanisms of paraquat-induced acute lung injury.

Protective effects of caffeic acid phenethyl ester on dose-dependent intoxication of rats with paraquat

PURPOSE

Paraquat (PQ; 1,1'dimethyl-bipyridilium 4,4'-dichloride), which is used extensively throughout the world, is highly toxic to humans. We aimed to investigate the protective effects of different doses of caffeic acid phenethyl ester (CAPE) on PQ-intoxicated rats.

MATERIALS AND METHODS

A total of 80 rats were divided into the following eight groups, comprising 10 rats in each group: group 1: control; group 2: administered with CAPE (10 µmol/kg); group 3: administered with 15 mg/kg PQ (PQ15 group); group 4: administered with 30 mg/kg PQ (PQ30 group); group 5: administered with 45 mg/kg PQ (PQ45 group); group 6: administered with 15 mg/kg PQ + CAPE; group 7: administered with 30 mg/kg PQ + CAPE and group 8: administered with 45 mg/kg PQ + CAPE. Both PQ and CAPE were injected intraperitoneally. Pancreatic tissue was examined with both haematoxylin and eosin and immunochemical staining.

RESULTS

The ratio of the immunohistochemical staining area to the total pancreatic area of the β cells revealed that statistically significant differences were observed only between the PQ and PQ + CAPE groups (p < 0.05).

DISCUSSION

The evaluation of the data suggests that CAPE can be used to prevent acute effects of PQ intoxication.