TGF-β3 Induces Autophagic Activity by Increasing ROS Generation in a NOX4-Dependent Pathway

mTORC1 is required for differentiation of germline stem cells in the Drosophila melanogaster testis

Metabolism participates in the control of stem cell function and subsequent maintenance of tissue homeostasis. How this is achieved in the context of adult stem cell niches in coordination with other local and intrinsic signaling cues is not completely understood. The Target of Rapamycin (TOR) pathway is a master regulator of metabolism and plays essential roles in stem cell maintenance and differentiation. In the Drosophila male germline, mTORC1 is active in germline stem cells (GSCs) and early germ cells. Targeted RNAi-mediated downregulation of mTor in early germ cells causes a block and/or a delay in differentiation, resulting in an accumulation of germ cells with GSC-like features. These early germ cells also contain unusually large and dysfunctional autolysosomes. In addition, downregulation of mTor in adult male GSCs and early germ cells causes non-autonomous activation of mTORC1 in neighboring cyst cells, which correlates with a disruption in the coordination of germline and somatic differentiation. Our study identifies a previously uncharacterized role of the TOR pathway in regulating male germline differentiation.

Redox Biology and Liver Fibrosis

Hepatic fibrosis is a complex process that develops in chronic liver diseases. Even though the initiation and progression of fibrosis rely on the underlying etiology, mutual mechanisms can be recognized and targeted for therapeutic purposes. Irrespective of the primary cause of liver disease, persistent damage to parenchymal cells triggers the overproduction of reactive species, with the consequent disruption of redox balance. Reactive species are important mediators for the homeostasis of both hepatocytes and non-parenchymal liver cells. Indeed, other than acting as cytotoxic agents, reactive species are able to modulate specific signaling pathways that may be relevant to hepatic fibrogenesis. After a brief introduction to redox biology and the mechanisms of fibrogenesis, this review aims to summarize the current evidence of the involvement of redox-dependent pathways in liver fibrosis and focuses on possible therapeutic targets.

Kaempferol inhibits airway inflammation induced by allergic asthma through NOX4-Mediated autophagy

BACKGROUND

Kaempferol has important medicinal value in the treatment of asthma. However, its mechanism of action has not been fully understood and needs to be explored and studied.

METHODS

A binding activity of kaempferol with nicotinamide adenine dinucleotide phosphate oxidase 4 (NOX4) was analyzed by molecular docking. Human bronchial epithelial cells (BEAS-2B) were treated with different concentrations (0, 1, 5, 10, 20, 40 μg/mL) of kaempferol to select its suitable concentration. In the transforming growth factor (TGF)-β1-induced BEAS-2B, cells were treated with 20 μg/mL kaempferol or 20 μM GLX35132 (a NOX4 inhibitor) to analyze its effects on NOX4-mediated autophagy. In the ovalbumin (OVA)-induced mice, 20 mg/kg kaempferol or 3.8 mg/kg GLX351322 administration was performed to analyze the therapeutic effects of kaempferol on NOX4-mediated autophagy. An autophagy activator, rapamycin, was used to confirm the mechanism of kaempferol in treatment of allergic asthma.

RESULTS

A good binding of kaempferol to NOX4 (score = -9.2 kcal/mol) was found. In the TGF-β1-induced BEAS-2B, the NOX4 expression was decreased with kaempferol dose increase. The secretions of IL-25 and IL-33, and the NOX4-mediated autophagy were significantly decreased by kaempferol treatment in the TGF-β1-induced BEAS-2B. In the OVA-challenged mice, kaempferol treatment improved airway inflammation and remodeling through suppressing NOX4-mediated autophagy. The rapamycin treatment clearly hampered the therapeutic effects of kaempferol in the TGF-β1-induced cells and OVA-induced mice.

CONCLUSIONS

This study identifies kaempferol binds NOX4 to perform its functions in the treatment of allergic asthma, providing an effective therapeutic strategy in the further treatment of asthma.

Hypoxia induces proliferation via NOX4-Mediated oxidative stress and TGF-β3 signaling in uterine leiomyoma cells

Uterine leiomyomas, the most common tumors of the female reproductive system, are known to have a hypoxic microenvironment. However, the role of such environment in leiomyoma pathobiology remains unknown. The objective was to determine the effects of hypoxia on leiomyoma cells, and the mechanisms. We found that hypoxia induces proliferation and inhibits apoptosis in human leiomyoma cells. This pro-proliferative effect was accompanied by an increase in reactive oxygen species (ROS) generation and the expression of NADPH oxidase 4 (NOX4). The specific NOX4 inhibitor GLX351322 abrogated this hypoxia-induced ROS generation, cellular proliferation, and apoptosis inhibition. To further investigate the mechanism of NOX4-mediated proliferation, we treated leiomyoma cells grown in normoxia with media from leiomyoma cells cultured under hypoxia. This resulted in increased ROS generation and NOX4 expression, suggesting the hypoxia-induced effects are mediated by an autocrine mechanism. We worked to identify the nature of this autocrine factor. We found that the expression of TGF-β3 and its downstream signaling target pSmad3, are increased in hypoxic leiomyoma cells. To examine the hypothesis that TGF-β3 is, at least, a part of this autocrine mechanism, we treated hypoxic leiomyoma cells with the HIF-1α inhibitor KC7F2 which we discovered to ameliorate the hypoxia-induced TGF-β3 expression. Furthermore, pharmacologic inhibition with the TGF-β/Smad inhibitor SB431542 reduced hypoxia-induced NOX4 expression and ROS generation and attenuated cell proliferation. Thus, we have identified a novel mechanism by which hypoxia induces proliferation in leiomyoma cells. This finding adds to our understanding of leiomyoma pathobiology and can help in identifying new therapeutic targets.

DRP1-Mediated Mitochondrial Fission Regulates Lung Epithelial Response to Allergen

Mitochondria regulate a myriad of cellular functions. Dysregulation of mitochondrial control within airway epithelial cells has been implicated in the pro-inflammatory response to allergens in asthma patients. Because of their multifaceted nature, mitochondrial structure must be tightly regulated through fission and fusion. Dynamin Related Protein 1 (DRP1) is a key driver of mitochondrial fission. During allergic asthma, airway epithelial mitochondria appear smaller and structurally altered. The role of DRP1-mediated mitochondrial fission, however, has not been fully elucidated in epithelial response to allergens. We used a Human Bronchial Epithelial Cell line (HBECs), primary Mouse Tracheal Epithelial Cells (MTECs), and conditional DRP1 ablation in lung epithelial cells to investigate the impact of mitochondrial fission on the pro-inflammatory response to house dust mite (HDM) in vitro and in vivo. Our data suggest that, following HDM challenge, mitochondrial fission is rapidly upregulated in airway epithelial cells and precedes production of pro-inflammatory cytokines and chemokines. Further, deletion of Drp1 in lung epithelial cells leads to decreased fission and enhanced pro-inflammatory signaling in response to HDM in vitro, as well as enhanced airway hyper-responsiveness (AHR), inflammation, differential mucin transcription, and epithelial cell death in vivo. Mitochondrial fission, therefore, regulates the lung epithelial pro-inflammatory response to HDM.

The TGF-β/NADPH Oxidases Axis in the Regulation of Liver Cell Biology in Health and Disease

The Transforming Growth Factor-beta (TGF-β) pathway plays essential roles in liver development and homeostasis and become a relevant factor involved in different liver pathologies, particularly fibrosis and cancer. The family of NADPH oxidases (NOXs) has emerged in recent years as targets of the TGF-β pathway mediating many of its effects on hepatocytes, stellate cells and macrophages. This review focuses on how the axis TGF-β/NOXs may regulate the biology of different liver cells and how this influences physiological situations, such as liver regeneration, and pathological circumstances, such as liver fibrosis and cancer. Finally, we discuss whether NOX inhibitors may be considered as potential therapeutic tools in liver diseases.

Autophagy Modulators From Chinese Herbal Medicines: Mechanisms and Therapeutic Potentials for Asthma

Asthma has become a global health issue, suffering more than 300 million people in the world, which is a heterogeneous disease, usually characterized by chronic airway inflammation and airway hyperreactivity. Combination of inhaled corticosteroids (ICS) and long acting β-agonists (LABA) can relieve asthma symptoms and reduce the frequency of exacerbations, especially for patients with refractory asthma, but there are limited treatment options for people who do not gain control on combination ICS/LABA. The increase in ICS dose generally provides little additional benefit, and there is an increased risk of side effects. Therefore, therapeutic interventions integrating the use of different agents that focus on different targets are needed to overcome this set of diseases. Some findings suggest autophagy is closely correlated with the severity of asthma through eosinophilic inflammation, and its modulation may provide novel therapeutic approaches for severe allergic asthma. The chinese herbal medicine (CHM) have been demonstrated clinically as potent therapeutic interventions for asthma. Moreover some reports have found that the bioactive components isolated from CHM could modulate autophagy, and exhibit potent Anti-inflammatory activity. These findings have implied the potential for CHMs in asthma or allergic inflammation therapy via the modulation of autophagy. In this review, we discuss the basic pathomechanisms underpinning asthma, and the potential role of CHMs in treating asthma with modulating autophagy.

Differential gene expression response of synovial fibroblasts from temporomandibular joints and knee joints to dynamic tensile stress

Purpose

Apart from other risk factors, mechanical stress on joints can promote the development of osteoarthritis (OA), which can also affect the temporomandibular joint (TMJ), resulting in cartilage degeneration and synovitis. Synovial fibroblasts (SF) play an important role in upkeeping joint homeostasis and OA pathogenesis, but mechanical stress as a risk factor might act differently depending on the type of joint. We thus investigated the relative impact of mechanical stress on the gene expression pattern of SF from TMJs and knee joints to provide new insights into OA pathogenesis.

Methods

Primary SF isolated from TMJs and knee joints of mice were exposed to mechanical strain of varying magnitudes. Thereafter, the expression of marker genes of the extracellular matrix (ECM), inflammation and bone remodelling were analysed by quantitative real-time polymerase chain reaction (RT-qPCR).

Results

SF from the knee joints showed increased expression of genes associated with ECM remodelling, inflammation and bone remodelling after mechanical loading, whereas TMJ-derived SF showed reduced expression of genes associated with inflammation and bone remodelling. SF from the TMJ differed from knee-derived SF with regard to expression of ECM, inflammatory and osteoclastogenesis-promoting marker genes during mechanical strain.

Conclusions

Osteoarthritis-related ECM remodelling markers experience almost no changes in strain-induced gene expression, whereas inflammation and bone remodelling processes seem to differ depending on synovial fibroblast origin. Our data indicate that risk factors for the development and progression of osteoarthritis such as mechanical overuse have a different pathological impact in the TMJ compared to the knee joint.

Supplementary Information

The online version of this article (10.1007/s00056-021-00309-y) contains supplementary material, which is available to authorized users.

Ascorbic Acid Suppresses House Dust Mite-Induced Expression of Interleukin-8 in Human Respiratory Epithelial Cells

House dust mite (HDM) is one of the significant causes for airway inflammation such as asthma. It induces oxidative stress and an inflammatory response in the lungs through the release of chemokines such as interleukin-8 (IL-8). Reactive oxygen species (ROS) activate inflammatory signaling mediators such as mitogen-activated protein kinases (MAPKs) and redox-sensitive transcription factors including NF-κB and AP-1. Ascorbic acid shows an antioxidant and anti-inflammatory activities in various cells. It ameliorated the symptoms of HDM-induced rhinitis. The present study was aimed to investigate whether HDM could induce IL-8 expression through activation of MAPKs, NF-κB, and AP-1 and whether ascorbic acid could inhibit HDM-stimulated IL-8 expression by reducing ROS and suppressing activation of MAPKs, NF-κB, and AP-1 in respiratory epithelial H292 cells. H292 cells were treated with HDM (5 μg/mL) in the absence or presence of ascorbic acid (100 or 200 μM). HDM treatment increased ROS levels, and activated MAPKs, NF-κB, and AP-1 and thus, induced IL-8 expression in H292 cells. Ascorbic acid reduced ROS levels and inhibited activation of MAPKs, NF-κB and AP-1 and L-8 expression in H292 cells. In conclusion, consumption of ascorbic acid-rich foods may be beneficial for prevention of HDM-mediated respiratory inflammation by suppressing oxidative stress-mediated MAPK signaling pathways and activation of NF-kB and AP-1.