Adiponectin ameliorates the apoptotic effects of paraquat on alveolar type Ⅱ cells via improvements in mitochondrial function

Oxaloacetate acid ameliorates paraquat-induced acute lung injury by alleviating oxidative stress and mitochondrial dysfunction

Acute lung injury (ALI) is the primary cause of death among patients with acute paraquat (PQ) poisoning, whereby peroxidative damage is an important mechanism underlying PQ-induced lung injury. There is a lack of effective interventional drugs for patients with PQ poisoning. Oxaloacetic acid (OAA) participates in multiple in vivo metabolic processes, whereby it facilitates the clearance of reactive oxygen species (ROS) and improves mitochondrial function. The study aimed to assess the protective effects of OAA on PQ-induced ALI and elucidate the underlying molecular mechanism. Our data demonstrated that OAA treatment significantly alleviated PQ-induced ALI and improved the survival rate of PQ-poisoned mice, and also alleviated PQ-induced cellular oxidative stress and mitochondrial dysfunction. OAA-mediated alleviation of PQ-induced mitochondrial dysfunction depends on the following mechanisms which may explain the above findings: 1) OAA effectively cleared intracellular ROS, inhibited ROS accumulation, and mitochondrial depolarization; 2) OAA inhibited the downregulation of L-OPA1 and MFN2 caused by PQ and promoted a dynamic balance of mitochondrial fusion and fission, and 3) the expression of PGC-1α, TFAM, COX2, and COX4I1, increased significantly following OAA intervention which improved mitochondrial respiratory functions and promoted its biogenesis and energy metabolism in damaged cells. In conclusion, OAA effectively cleared ROS and improved mitochondrial dysfunction, thereby significantly improving ALI caused by PQ poisoning and the animal survival rate. Therefore, OAA may be a potential drug for the treatment of PQ poisoning.

Podocyte Lysosome Dysfunction in Chronic Glomerular Diseases

Podocytes are visceral epithelial cells covering the outer surface of glomerular capillaries in the kidney. Blood is filtered through the slit diaphragm of podocytes to form urine. The functional and structural integrity of podocytes is essential for the normal function of the kidney. As a membrane-bound organelle, lysosomes are responsible for the degradation of molecules via hydrolytic enzymes. In addition to its degradative properties, recent studies have revealed that lysosomes may serve as a platform mediating cellular signaling in different types of cells. In the last decade, increasing evidence has revealed that the normal function of the lysosome is important for the maintenance of podocyte homeostasis. Podocytes have no ability to proliferate under most pathological conditions; therefore, lysosome-dependent autophagic flux is critical for podocyte survival. In addition, new insights into the pathogenic role of lysosome and associated signaling in podocyte injury and chronic kidney disease have recently emerged. Targeting lysosomal functions or signaling pathways are considered potential therapeutic strategies for some chronic glomerular diseases. This review briefly summarizes current evidence demonstrating the regulation of lysosomal function and signaling mechanisms as well as the canonical and noncanonical roles of podocyte lysosome dysfunction in the development of chronic glomerular diseases and associated therapeutic strategies.

8-Formylophiopogonanone B Antagonizes Paraquat-Induced Hepatotoxicity by Suppressing Oxidative Stress

Flavonoids are some of the most important natural products with a variety of physiological activities. 8-Formylophiopogonanone B (8-FOB) is a naturally existing homoisoflavonoid in Ophiopogon japonicus. Paraquat (PQ) has been widely used as a potent herbicide and has high toxicity in humans. The goal of the present study was to investigate whether 8-FOB could protect against PQ-induced hepatotoxicity in vitro and in vivo. We first tested the protective effects of 8-FOB on PQ-induced cytotoxicity in L02 cells by determining cell viability, intracellular oxidative stress levels, mitochondrial function, and apoptosis in vitro. To verify the protective effects of 8-FOB, we pretreated mice with 8-FOB and assessed liver function, hepatic oxidative stress, and histopathological changes after PQ administration. Our results revealed that 8-FOB could antagonize PQ-induced hepatotoxicity in vitro and in vivo. The antagonistic effects could be attributed to suppressing oxidative stress, preserving mitochondrial function, and inhibiting apoptosis. The present study is the first to document that 8-FOB, a homoisoflavonoid compound, is an effective antioxidant for antagonizing PQ-induced hepatotoxicity.

Effect of endoplasmic reticulum calcium on paraquat‑induced apoptosis of human lung type II alveolar epithelial A549 cells

The present study aimed to explore the role of endoplasmic reticulum calcium (ER Ca2+) in the apoptosis of human lung type II alveolar epithelial A549 cells induced by paraquat (PQ) in vitro. PQ significantly elevated the intracellular Ca2+ concentration. Treatment with the Ca2+‑ATPase inhibitor thapsigargin significantly increased PQ‑induced cytotoxicity, elevated the intracellular level of Ca2+, and increased the apoptosis rate, the protein expression of glucose‑regulated protein 78 (GRP78) and C/EBP homologous protein (CHOP), and the activities of caspase‑7 and caspase‑12 in PQ‑treated cells. By contrast, treatment with heparin, an inositol 1,4,5‑triphosphate receptor inhibitor, remarkably attenuated cytotoxicity and decreased the intracellular level of Ca2+, the apoptosis rate and the expression levels of GRP78, CHOP and Caspases. In conclusion, PQ impaired the regulating function of ER Ca2+ and resulted in an excessive increase of intracellular Ca2+. Therefore, influencing the Ca2+ signaling in the ER influenced the apoptosis of A549 cells via the ER stress pathway.

The Metabolic Cytokine Adiponectin Inhibits Inflammatory Lung Pathology in Invasive Aspergillosis

Systemic immunity and metabolism are coregulated by soluble factors, including the insulin-regulating adipose tissue cytokine adiponectin. How these factors impact detrimental inflammatory responses during fungal infection remains unknown. In this study, we observed that mortality, fungal burden, and tissue histopathology were increased in adiponectin-deficient mice in a neutropenic model of invasive aspergillosis. Lung RNA sequencing, quantitative RT-PCR, and subsequent pathway analysis demonstrated activation of inflammatory cytokine pathways with upstream regulation by IL-1 and TNF in adiponectin-deficient mice with decreased/inhibited anti-inflammatory genes/pathways, suggesting broad cytokine-mediated pathology along with ineffective fungal clearance. Quantitative RT-PCR analysis confirmed increased transcription of IL-1a, IL-6, IL-12b, IL-17A/F, and TNF in adiponectin-deficient mice at early time points postinfection, with a specific increase in intracellular TNF in alveolar macrophages. Although eosinophil recruitment and activation were increased in adiponectin-deficient mice, mortality was delayed, but not decreased, in mice deficient in both adiponectin and eosinophils. Interestingly, neutrophil depletion was required for increased inflammation in adiponectin-deficient mice in response to swollen/fixed conidia, suggesting that immune suppression enhances detrimental inflammation, whereas invasive fungal growth is dispensable. Our results suggest that adiponectin inhibits excessive lung inflammation in invasive aspergillosis. Our study has therefore identified the adiponectin pathway as a potential source for novel therapeutics in immune-compromised patients with detrimental immunity to invasive fungal infection.

Effects of paraquat on IL-6 and TNF-α in macrophages

Effects of paraquat (PQ) on interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α) in macrophages were investigated. Different concentrations of PQ were added to mouse macrophage RAW264.7 for culture. According to different concentrations of PQ, mice were divided into micro concentration (0.01 mmol/l), low concentration (0.1 mmol/l), medium concentration (1 mmol/l), high concentration (10 mmol/l), and control groups without PQ. Trypan blue solution was used for detecting cell viability, a microplate reader for detecting the fluorescence intensity of reactive oxygen species (ROS), ELISA for detecting the expression levels of IL-6 and TNF-α. The medium concentration and the high concentration groups had significantly lower cell viability than the other three groups (P<0.050). The high concentration group had significantly lower cell viability than the medium concentration group (P<0.050). At 1, 4 and 8 h, respectively, the medium and the high concentration groups had significantly higher ROS fluorescence intensity than the other three groups (P<0.050). The high concentration group had significantly higher ROS fluorescence intensity than the medium concentration group (P<0.050). There were significant differences in the expression levels of IL-6 and TNF-α at the 1st, 4th and 8th hour among the five groups (P<0.050). In the micro, the low, the medium and high concentration groups, the expression levels of IL-6 and TNF-α were the lowest at 1 h and the highest at 8 h, which were higher at 4 h than those at 1 h (P<0.050). PQ at a concentration of 1 mmol/l can produce toxicity to macrophages, and greatly increase the ROS fluorescence intensity, the expression levels of IL-6 and TNF-α. PQ poisoning is expected to be treated though IL-6 and TNF-α in the future.

MnTMPyP inhibits paraquat-induced pulmonary epithelial-like cell injury by inhibiting oxidative stress

OBJECTIVE

To investigate the protective effect and underlying mechanism of the superoxide dismutase mimic, manganese (III) tetrakis (1-methyl-4-pyridyl) porphyrin pentachloride (MnTMPyP), on paraquat (PQ)-induced lung alveolar epithelial-like cell injury.

METHODS

Lung alveolar epithelial-like cells (A549) were pretreated with 10 μM MnTMPyP for 1.5 hr and then cultured with or without PQ (750 uM) for 24 hr. Cell survival was determined using the MTT assay. Apoptosis, mitochondrial transmembrane potential, reactive oxygen species (ROS) production, and Ca²⁺ levels were measured using flow cytometry. Glutathione reductase activity (GR activity) and caspase-3 activation were determined using spectrophotometry. Expression of the apoptosis proteins, Bcl-2 and Bax, and the endoplasmic reticulum (ER) stress proteins, glucose regulatory protein 78 (Grp78) and C/EBP homologous protein (CHOP), was measured using Western blot analysis.

RESULTS

Cell viability, mitochondrial membrane potential, GR activity, and Bcl-2 expression were decreased, but apoptosis, ROS production, caspase-3 activity, cytoplasmic Ca²⁺ levels, and Bax, Grp78 and CHOP expression were all increased in the PQ group compared to the control group. There were no statistically significant changes in the MnTMPyP group. Cell viability, GR activity, mitochondrial membrane potential, and Bcl-2 protein expression were all increased, while apoptosis, ROS production, cytoplasmic Ca²⁺ levels, caspase-3 activity, and Bax, Grp78 and CHOP expression were all significantly reduced in the MnTMPyP group compared to PQ group.

CONCLUSION

MnTMPyP effectively reduced PQ-induced lung epithelial-like cell injury, and the underlying mechanism is related to antagonism of PQ-induced oxidative stress.

Inhibition of pannexin-1 channel activity by adiponectin in podocytes: Role of acid ceramidase activation

The pannexin-1 (Panx1) channel has been reported to mediate the release of ATP that is involved in local tissue inflammation, obesity, and many chronic degenerative diseases. It remains unknown whether Panx1 is present in podocytes and whether this channel in podocytes mediates ATP release leading to glomerular inflammation or fibrosis. To answer these questions, we first characterized the expression of Panx channels in podocytes. Among the three known pannexins, Panx1 was the most enriched in podocytes, either cultured or native in mouse glomeruli. Using a Port-a-Patch planar patch-clamp system, we recorded a large voltage-gated outward current through podocyte membrane under the Cs⁺in/Na⁺out gradient. Substitution of gluconate or aspartate for chloride in the bath solution blocked voltage-gated outward currents and shifted the reversal potential of Panx1 currents to the right, indicating the anion permeability of this channel. Pharmacologically, the recorded voltage-gated outward currents were substantially attenuated by specific Panx1 channel inhibitors. Given the anti-inflammatory and intracellular ATP restorative effects of adiponectin, we tested whether this adipokine inhibits Panx1 channel activity to block ATP release. Adiponectin blocked Panx1 channel activity in podocytes. Mechanistically, inhibition of acid ceramidase (AC) remarkably enhanced Panx1 channel activity under control conditions and prevented the inhibition of Panx1 channel by adiponectin. Correspondingly, intracellular addition of AC products, sphingosine or sphingosine-1-phosphate (S1P), blocked Panx1 channel activity, while elevation of intracellular ceramide had no effect on Panx1 channel activity. These results suggest that adiponectin inhibits Panx1 channel activity in podocytes through activation of AC and associated elevation of intracellular S1P.

Adiponectin protects against lung ischemia-reperfusion injury in rats with type 2 diabetes mellitus

Adiponectin (APN) has been associated with the pathogenesis of acute brain, liver and heart injury. However, the role of APN in lung ischemia-reperfusion injury (LIRI) in diabetes mellitus remains unclear. To investigate this, the present study evaluated the effects of APN on lung dysfunction and pathological alterations in rats with type 2 diabetes mellitus via lung ischemia/reperfusion (I/R). The lung‑protective effects of APN globular domain (gAPN) in rats with type 2 diabetes mellitus were also investigated by measuring the oxygenation index, inflammatory cytokines, lung edema, histopathology, oxidative stress, apoptosis and the protein expression levels of phosphorylated 5'adenosine monophosphate‑activated protein kinase (p‑AMPK), endothelial nitric oxide synthase (eNOS) and inducible nitric oxide synthase (iNOS). The results of the present study demonstrated that the diabetes mellitus rats + I/R (DIR) group exhibited greater concentrations of tumor necrosis factor‑α and interleukin‑6, and increases in the wet‑weight to dry‑weight ratio, lung injury score, oxidative stress and cellular apoptosis. These effects were accompanied by lower pulmonary oxygenation compared with the normal rat + I/R (NIR) group (P<0.05). Additionally, all of these alterations were attenuated in the NIR + gAPN and DIR + gAPN groups compared with in the NIR and DIR groups, respectively. In the DIR group, the expression levels of p‑AMPK/AMPK and eNOS were significantly downregulated, and the levels of iNOS were upregulated, compared with those of the NIR group. Treatment with APN activated AMPK, increased eNOS expression and attenuated iNOS expression. The results of the present study demonstrated that APN exerted protective effects against LIRI via its anti‑inflammatory, antioxidative stress and anti‑apoptotic activities. These protective effects of APN were eliminated in rats with type 2 diabetes mellitus, in which LIRI was exacerbated. The present study indicated that APN may be a potential therapeutic agent for LIRI in type 2 diabetes mellitus.

Crosstalk between Mitochondrial Fission and Oxidative Stress in Paraquat-Induced Apoptosis in Mouse Alveolar Type II Cells

Paraquat (PQ), as a highly effective and nonselective herbicide, induces cell apoptosis through generation of superoxide anions which forms reactive oxygen species (ROS). Mitochondria, as regulators for cellular redox signaling, have been proved to play an important role in PQ-induced cell apoptosis. This study aimed to evaluate whether and how mitochondrial fission interacts with oxidative stress in PQ-induced apoptosis in mouse alveolar type II (AT-II) cells. Firstly, we demonstrated that PQ promoted apoptosis and release of cytochrome-c (Cyt-c). Furthermore, we showed that PQ broke down mitochondrial network, enhanced the expression of fission-related proteins, increased Drp1 mitochondrial translocation while decreased the expression of fusion-related proteins in AT-II cells. Besides, inhibiting mitochondrial fission using mdivi-1, a selective inhibitor of Drp1, markedly attenuated PQ-induced apoptosis, release of Cyt-c and the generation of ROS. These results indicate that mitochondrial fission involves in PQ-induced apoptosis. Further study demonstrated that antioxidant ascorbic acid inhibited Drp1 mitochondrial translocation, mitochondrial fission and attenuated PQ-induced apoptosis. Overall, our findings suggest that mitochondrial fission interplays with ROS in PQ-induced apoptosis in mouse AT-II cells and mitochondrial fission could serve as a potential therapeutic target in PQ poisoning.

Mitochondrial dysfunction in alveolar and white matter developmental failure in premature infants

At birth, some organs in premature infants are not developed enough to meet challenges of the extra-uterine life. Although growth and maturation continues after premature birth, postnatal organ development may become sluggish or even arrested, leading to organ dysfunction. There is no clear mechanistic concept of this postnatal organ developmental failure in premature neonates. This review introduces a concept-forming hypothesis: Mitochondrial bioenergetic dysfunction is a fundamental mechanism of organs maturation failure in premature infants. Data collected in support of this hypothesis are relevant to two major diseases of prematurity: white matter injury and broncho-pulmonary dysplasia. In these diseases, totally different clinical manifestations are defined by the same biological process, developmental failure of the main functional units-alveoli in the lungs and axonal myelination in the brain. Although molecular pathways regulating alveolar and white matter maturation differ, proper bioenergetic support of growth and maturation remains critical biological requirement for any actively developing organ. Literature analysis suggests that successful postnatal pulmonary and white matter development highly depends on mitochondrial function which can be inhibited by sublethal postnatal stress. In premature infants, sublethal stress results mostly in organ maturation failure without excessive cellular demise.