Profibrotic epithelial TGF-β1 signaling involves NOX4-mitochondria cross talk and redox-mediated activation of the tyrosine kinase FYN

circGRHPR inhibits aberrant epithelial-mesenchymal transformation progression of lung epithelial cells associated with idiopathic pulmonary fibrosis

Air pollution has greatly increased the risk of idiopathic pulmonary fibrosis (IPF). Circular RNAs (circRNAs) have been found to play a significant role in the advancement of IPF, but there is limited evidence of correlation between circRNAs and lung epithelial cells (LECs) in IPF. This research aimed to explore the influence of circRNAs on the regulation of EMT progression in LECs, with the objective of elucidating its mechanism and establishing its association with IPF. Our results suggested that the downregulation of circGRHPR in peripheral blood of clinical cases was associated with the diagnosis of IPF. Meanwhile, we found that circGRHPR was downregulated in transforming growth factor-beta1 (TGF-β1)-induced A549 and Beas-2b cells. It is a valid model to study the abnormal EMT progression of IPF-associated LECs in vitro. The overexpression of circGRHPR inhibited the abnormal EMT progression of TGF-β1-induced LECs. Furthermore, as the sponge of miR-665, circGRHPR released the expression of E3 ubiquitin-protein ligase NEDD4-like (NEDD4L), thus promoting its downstream transforming growth factor beta receptor 2 (TGFBR2) ubiquitination. It is helpful to reduce the response of LECs to TGF-β1 signaling. In summary, circGRHPR/miR-665/NEDD4L axis inhibited the abnormal EMT progression of TGF-β1-induced LECs by promoting TGFBR2 ubiquitination, which provides new ideas and potential targets for the treatment of IPF.

Fyn-Mediated Paxillin Tyrosine 31 Phosphorylation Regulates Migration and Invasion of Breast Cancer Cells

Metastasis is the leading cause of death in breast cancer patients due to the lack of effective therapies. Elevated levels of paxillin expression have been observed in various cancer types, with tyrosine phosphorylation shown to play a critical role in driving cancer cell migration. However, the specific impact of the distinct tyrosine phosphorylation events of paxillin in the progression of breast cancer remains to be fully elucidated. Here, we found that paxillin overexpression in breast cancer tissue is associated with a patient's poor prognosis. Paxillin knockdown inhibited the migration and invasion of breast cancer cells. Furthermore, the phosphorylation of paxillin tyrosine residue 31 (Tyr31) was significantly increased upon the TGF-β1-induced migration and invasion of breast cancer cells. Inhibiting Fyn activity or silencing Fyn decreases paxillin Tyr31 phosphorylation. The wild-type and constitutively active Fyn directly phosphorylate paxillin Tyr31 in an in vitro system, indicating that Fyn directly phosphorylates paxillin Tyr31. Additionally, the non-phosphorylatable mutant of paxillin at Tyr31 reduces actin stress fiber formation, migration, and invasion of breast cancer cells. Taken together, our results provide direct evidence that Fyn-mediated paxillin Tyr31 phosphorylation is required for breast cancer migration and invasion, suggesting that targeting paxillin Tyr31 phosphorylation could be a potential therapeutic strategy for mitigating breast cancer metastasis.

Environmental toxin chlorpyrifos induces liver injury by activating P53-mediated ferroptosis via GSDMD-mtROS

AIM

We investigate the mechanism whereby chlorpyrifos (CHI), an environmental toxin, causes liver injury by inducing ferroptosis in hepatocytes.

METHODS

The toxic dose (LD50 = 50 μM) of CHI for inducing AML12 injury in normal mouse hepatocytes was determined, and the ferroptosis-related indices were measured, including the levels of SOD, MDA and GSH-Px, as well as the cellular content of iron ions. JC-1 and DCFH-DA assays were employed to detect the mtROS levels, the levels of mitochondrial proteins (GSDMD, NT-GSDMD), as well as the cellular levels of ferroptosis-related proteins (P53, GPX4, MDM2, SLC7A11). We knocked out the GSDMD and P53 in AML12 and observed the CHI-induced ferroptosis of ALM12 after applying YGC063, an ROS inhibitor. In animal experiments, we explored the effect of CHI on liver injury by using conditional GSDMD-knockout mice (C57BL/6 N-GSDMD^em1(flox)Cya) and ferroptosis inhibitor Fer-1. Small molecule-protein docking and Pull-down assay were employed to verify the association between CHI and GSDMD.

RESULTS

We found that CHI could induce ferroptosis of AML12. CHI promoted the cleavage of GSDMD, leading to upregulation of mitochondrial NT-GSDMD expression, as well as ROS levels. P53 activation promoted the ferroptosis. Knock out of GSDMD and P53 could inhibit the CHI-induced ferroptosis, and YGC063 could also inhibit ferroptosis. In mice experiments, GSDMD knockout or Fer-1 intervention could significantly inhibit the CHI-induced liver injury. CHI promoted the cleavage of GSDMD by binding to its SER234 site.

CONCLUSION

CHI can bind to GSDMD to promote its cleavage, while NT-GSDMD can open mitochondrial membrane to promote the mtROS release. Cytoplasmic upregulation of ROS levels can facilitate the P53-mediated ferroptosis. GSDMD-mtROS is the primary mechanism whereby CHI induces ferroptosis in hepatocytes.

Differences in Treatment Response in Bronchial Epithelial Cells from Idiopathic Pulmonary Fibrosis (IPF) Patients: A First Step towards Personalized Medicine?

Idiopathic pulmonary fibrosis (IPF) has a detrimental prognosis despite antifibrotic therapies to which individual responses vary. IPF pathology is associated with oxidative stress, inflammation and increased activation of SRC family kinases (SFK). This pilot study evaluates individual responses to pirfenidone, nintedanib and SFK inhibitor saracatinib, markers of redox homeostasis, fibrosis and inflammation, in IPF-derived human bronchial epithelial (HBE) cells. Differentiated HBE cells from patients with and without IPF were analyzed for potential alterations in redox and profibrotic genes and pro-inflammatory cytokine secretion. Additionally, the effects of pirfenidone, nintedanib and saracatinib on these markers were determined. HBE cells were differentiated into a bronchial epithelium containing ciliated epithelial, basal, goblet and club cells. NOX4 expression was increased in IPF-derived HBE cells but differed on an individual level. In patients with higher NOX4 expression, pirfenidone induced antioxidant gene expression. All drugs significantly decreased NOX4 expression. IL-6 (p = 0.09) and IL-8 secretion (p = 0.014) were increased in IPF-derived HBE cells and significantly reduced by saracatinib. Finally, saracatinib significantly decreased TGF-β gene expression. Our results indicate that treatment responsiveness varies between IPF patients in relation to their oxidative and inflammatory status. Interestingly, saracatinib tends to be more effective in IPF than standard antifibrotic drugs.

Small-molecule-mediated OGG1 inhibition attenuates pulmonary inflammation and lung fibrosis in a murine lung fibrosis model

Interstitial lung diseases such as idiopathic pulmonary fibrosis (IPF) are caused by persistent micro-injuries to alveolar epithelial tissues accompanied by aberrant repair processes. IPF is currently treated with pirfenidone and nintedanib, compounds which slow the rate of disease progression but fail to target underlying pathophysiological mechanisms. The DNA repair protein 8-oxoguanine DNA glycosylase-1 (OGG1) has significant roles in the modulation of inflammation and metabolic syndromes. Currently, no pharmaceutical solutions targeting OGG1 have been utilized in the treatment of IPF. In this study we show Ogg1-targeting siRNA mitigates bleomycin-induced pulmonary fibrosis in male mice, highlighting OGG1 as a tractable target in lung fibrosis. The small molecule OGG1 inhibitor, TH5487, decreases myofibroblast transition and associated pro-fibrotic gene expressions in fibroblast cells. In addition, TH5487 decreases levels of pro-inflammatory mediators, inflammatory cell infiltration, and lung remodeling in a murine model of bleomycin-induced pulmonary fibrosis conducted in male C57BL6/J mice. OGG1 and SMAD7 interact to induce fibroblast proliferation and differentiation and display roles in fibrotic murine and IPF patient lung tissue. Taken together, these data suggest that TH5487 is a potentially clinically relevant treatment for IPF but further study in human trials is required.

Defining the Role of Mitochondrial Fission in Corneal Myofibroblast Differentiation

Purpose

Fibrosis caused by corneal wounding can lead to scar formation, impairing vision. Although preventing fibroblast-to-myofibroblast differentiation has therapeutic potential, effective mechanisms for doing so remain elusive. Recent work shows that mitochondria contribute to differentiation in several tissues. Here, we tested the hypothesis that mitochondrial dynamics, and specifically fission, are key for transforming growth factor (TGF)-β1-induced corneal myofibroblast differentiation.

Methods

Mitochondrial fission was inhibited pharmacologically in cultured primary cat corneal fibroblasts. We measured its impact on molecular markers of myofibroblast differentiation and assessed changes in mitochondrial morphology through fluorescence imaging. The phosphorylation status of established regulatory proteins, both of myofibroblast differentiation and mitochondrial fission, was assessed by Western analysis.

Results

Pharmacological inhibition of mitochondrial fission suppressed TGF-β1-induced increases in alpha-smooth muscle actin, collagen 1, and fibronectin expression, and prevented phosphorylation of c-Jun N-terminal kinase (JNK), but not small mothers against decapentaplegic 3, p38 mitogen-activated protein kinase (p38), extracellular signal-regulated kinase 1 (ERK1), or protein kinase B (AKT). TGF-β1 increased phosphorylation of dynamin-related protein 1 (DRP1), a mitochondrial fission regulator, and caused fragmentation of the mitochondrial network. Although inhibition of JNK, ERK1, or AKT prevented phosphorylation of DRP1, none sufficed to independently suppress TGF-β1-induced fragmentation.

Conclusions

Mitochondrial dynamics play a key role in early corneal fibrogenesis, acting together with profibrotic signaling. This is consistent with mitochondria's role as signaling hubs that coordinate metabolic decision-making. This suggests a feed-forward cascade through which mitochondria, at least in part through fission, reinforce noncanonical TGF-β1 signaling to attain corneal myofibroblast differentiation.

Redox Dysregulation in Aging and COPD: Role of NOX Enzymes and Implications for Antioxidant Strategies

With a rapidly growing elderly human population, the incidence of age-related lung diseases such as chronic obstructive pulmonary disease (COPD) continues to rise. It is widely believed that reactive oxygen species (ROS) play an important role in ageing and in age-related disease, and approaches of antioxidant supplementation have been touted as useful strategies to mitigate age-related disease progression, although success of such strategies has been very limited to date. Involvement of ROS in ageing is largely attributed to mitochondrial dysfunction and impaired adaptive antioxidant responses. NADPH oxidase (NOX) enzymes represent an important enzyme family that generates ROS in a regulated fashion for purposes of oxidative host defense and redox-based signalling, however, the associations of NOX enzymes with lung ageing or age-related lung disease have to date only been minimally addressed. The present review will focus on our current understanding of the impact of ageing on NOX biology and its consequences for age-related lung disease, particularly COPD, and will also discuss the implications of altered NOX biology for current and future antioxidant-based strategies aimed at treating these diseases.

Scutellarin-induced A549 cell apoptosis depends on activation of the transforming growth factor-β1/smad2/ROS/caspase-3 pathway

Scutellarin plays an anti-tumor role in A549 lung cancer cells, but the underlying mechanism is unclear. In this study, scutellarin was used to treat A549 cells for 12, 24, and 48 h, followed by the addition of Tempo, a selective scavenger of mitochondrial reactive oxygen species (ROS) and SB431542, a transforming growth factor (TGF)-β1 receptor inhibitor. A dihydroethidium fluorescence probe was used to measure the intracellular ROS level, Cell Counting Kit-8 (CCK-8) was used to detect cell viability, and flow cytometry was performed to examine apoptosis. Western blots were used to detect the total protein level of TGF-β1, p-smad2, and cleaved caspase-3 in A549 cells. The results showed that scutellarin significantly inhibited cell viability and increased apoptosis. Scutellarin also promoted intracellular ROS production, TGF-β1/smad2 signaling pathway activation, and cleaved caspase-3 expression, which was partly reversed by Tempo. Moreover, scutellarin-induced intracellular ROS production and cleaved caspase-3 expression were inhibited by blocking the TGF-β1/smad2 pathway with SB431542. In conclusion, scutellarin promoted apoptosis and intracellular ROS accumulation, which could be abrogated by Tempo and SB431542 treatment in A549 cells. Our study indicated that scutellarin induced A549 cell apoptosis via the TGF-β1/smad2/ROS/caspase-3 pathway.

Paraquat but not diquat induces TGF-β expression and thus activates calcium-NFAT axis for epithelial-mesenchymal transition

Paraquat (PQ) and diquat (DQ), two highly efficient herbicides sharing similar chemical backbone, both induce reactive oxygen species and are highly toxic to humans and livestock, however, PQ but not DQ poisoning result in pulmonary fibrosis, the leading cause of high mortality rate in patients suffering PQ toxicity. Understanding the unique mechanism of PQ different from DQ therefore would provide potential strategies to reduce PQ-induced pulmonary fibrosis. Here, we identified that PQ but not DQ continuously upregulates TGF-β expression in alveolar type II (AT II) cells. Importantly, such high expression of TGF-β increases cytosolic calcium levels and further promotes the activation of calcineurin-NFAT axis. TGF-β mainly activates NFATc1 and NFATc2, but not NFATc3 or NFATc4. Administration of the inhibitors targeting cytosolic calcium or calcineurin largely reverses PQ-induced epithelial-mesenchymal transition (EMT), whereas DQ has little effects on activation of NFAT and EMT. Ultimately, PQ poisoned patients exhibit significantly reduced blood calcium levels compared to DQ poisoning, possibly via the large usage of calcium by AT II cells. All in all, we found a vicious cycle that the upregulated TGF-β in PQ-induced EMT further aggravates EMT via promotion of the calcium-calcineurin axis, which could be potential drug targets for treating PQ-induced pulmonary fibrosis.

Structural insights into redox-active cysteine residues of the Src family kinases

The Src Family Kinases (SFKs) are pivotal regulators of cellular signal transduction and highly sought-after targets in drug discovery. Their actions within cells are controlled by alterations in protein phosphorylation that switch the SFKs from autoinhibited to active states. The SFKs are also well recognized to contain redox-active cysteine residues where oxidation of certain residues directly contribute to kinase function. To more completely understand the factors that influence cysteine oxidation within the SFKs, a review is presented of the local structural environments surrounding SFK cysteine residues compared to their quantified oxidation in vivo from the Oximouse database. Generally, cysteine local structure and degree of redox sensitivity vary with respect to sequence conservation. Cysteine residues found in conserved positions are more mildly redox-active as they are found in hydrophobic environments and not fully exposed to solvent. Non-conserved redox-active cysteines are generally the most reactive with direct solvent access and/or in hydrophilic environments. Results from this analysis motivate future efforts to conduct comprehensive proteome-wide analysis of redox-sensitivity, conservation, and local structural environments of proteins containing reactive cysteine residues.