Mason Breitzig

4-hydroxy-2-nonenal: a critical target in oxidative stress?

In this perspective, we summarize and discuss critical advancements in the study of 4-hydroxy-2-nonenal (4-HNE) as it relates to diseases and clinical complications either caused or exacerbated by oxidative stress. Since its identification in 1980, 4-HNE has been extensively studied with an emphasis on its formation, its role in pathology, and its targets. As a reactive aldehyde, and a product of lipid peroxidation, studies corroborate its ability to disrupt signal transduction and protein activity, as well as induce inflammation and trigger cellular apoptosis in conditions of oxidative stress. Notably, we discuss the role of natural enzymes involved in the regulation of 4-HNE, and how they can be applied to its detoxification in various physiological conditions.

SOCS-1 rescues IL-1β-mediated suppression of epithelial sodium channel in mouse lung epithelial cells via ASK-1

Background Acute lung injury (ALI) is characterized by alveolar damage, increased levels of pro-inflammatory cytokines and impaired alveolar fluid clearance. Recently, we showed that the deletion of Apoptosis signal-regulating kinase 1 (ASK1) protects against hyperoxia-induced acute lung injury (HALI) by suppressing IL-1β and TNF-α. Previously, our data revealed that the suppressor of cytokine signaling-1 (SOCS-1) overexpression restores alveolar fluid clearance in HALI by inhibiting ASK-1 and suppressing IL-1β levels. Furthermore, IL-1β is known to inhibit the expression of epithelial sodium channel α-subunit (ENaC) via a p38 MAPK signaling pathway. Objective To determine whether SOCS-1 overexpression in MLE-12 cells would protect against IL-1β-mediated depletion of αENaC by suppressing ASK-1 expression. Methods We co-transfected MLE-12 cells with SOCS-1 overexpressing plasmid with or without IL-1β in the presence or absence of sodium channel inhibitor, amiloride. We measured potential difference, transepithelial current, resistance, and sodium uptake levels across MLE-12 cells. We studied the effect of ASK-1 depletion, as well as ASK-1 and SOCS-1 overexpression on αENaC expression. Results SOCS-1 overexpression sufficiently restored transepithelial current and resistance in MLE-12 cells treated with either IL-1β or amiloride. The αENaC mRNA levels and sodium transport were increased in SOCS-1 overexpressing MLE-12 cells exposed to IL-1β. Depletion of ASK-1 in MLE-12 cells increased αENaC mRNA levels. Interestingly, SOCS-1 overexpression restored αENaC expression in MLE-12 cells in the presence of ASK-1 overexpression. Conclusion Collectively, these findings suggest that SOCS-1 may exert its protective effect by rescuing αENaC expression via suppression of ASK-1.

Hedgehog: the key to maintaining adult lung repair and regeneration

Cells are the building blocks of life, and despite losing a myriad of them each day, we survive. In fact, we thrive, because not all tissues are created equally when it comes to their ability to regenerate. While nerve and heart cells regenerate slowly, if at all, skin and blood cells are constantly regenerating, resulting in a completely new generation every few days. Between these two extremes are cells that have low rates of regeneration, but can experience extensive periods of regeneration after an injury. These tissues are thought to be quiescent. Previously, postnatal tissue quiescence was thought to be the default state of mature tissue when in the absence of a stimulus (Beers and Morrisey 2011, Herriges and Morrisey 2014, Hogan et al. 2014). Furthermore, it remained unclear how the default state was maintained in organs such as the lung and liver where the tissues exhibit low rates of regeneration in adults, but respond to injury with extensive regeneration (Blenkinsopp 1967, Breuer et al. 1990). In a recent issue of Nature, Peng et al. have shed new light on the role of the hedgehog signaling pathway in maintaining adult lung quiescence (Peng et al. 2015). They have shown that the same pathway that is essential for proper embryonic development also regulates quiescence in adult lungs. Peng et al. found that epithelial-specific deletion of sonic hedgehog (shh) during postnatal homeostasis in adult murine lungs results in a rapid expansion of the adjacent lungmesenchyme. In the acute phase of epithelial injury, while the mesenchyme proliferates, hedgehog signaling is initially downregulated, but as quiescence is restored the signaling levels return to the baseline (Peng et al. 2015). If hedgehog is activated instead of being downregulated, tissue regeneration does not occur. On the other hand, if hedgehog signaling is completely eliminated, quiescence is not restored (Peng et al. 2015). In addition to maintaining adult lung quiescence, Peng et al. also found that hedgehog signaling regulates epithelial quiescence and regeneration in response to injury via a mesenchymal feedback mechanism. To reach these results, Peng et al. facilitated a series of procedures stemming from previous research stating that the hedgehog signaling pathway coordinates tissue-tissue interactions in multiple organs during embryonic development via paracrine activation of smoothened (Smo)-mediated downstream signaling events and that Shh expressed by incipient lung endoderm ancestors coordinates cardiopulmonary mesoderm progenitor differentiation into various cardiac and lung mesenchymal cell lineages (McMahon et al. 2003, Lum and Beachy 2004, Peng et al. 2013). To determine whether Hh signaling remains active in the adult lung, Peng et al. utilized Shh in isolated Scgb1a11 club epithelial cells, ciliated epithelium, and Sftpc1 alveolar type II epithelial cells, and analyzed Shh expression by confocal microscopy. Further, Peng et al. examined the expression of Gli1, a target of hedgehog, as well as other markers including Ki67 (cell cycle), by microscopy and lineage tracing with Gli1:R26R. To determine the effects of deleting Shh in the airway, Scgb1a1:Shh adult lungs were examined for cell proliferation in the airway epithelium. * Narasaiah Kolliputi nkollipu@health.usf.edu

The role of club cell phenoconversion and migration in idiopathic pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is an age-related multifactorial disease featuring non-uniform lung fibrosis. The decisive cellular events at early stages of IPF are poorly understood. While the involvement of club cells in IPF pathogenesis is unclear, their migration has been associated with lung fibrosis. In this study, we labeled club cells immunohistochemically in IPF lungs using a club cell marker Claudin-10 (Cldn10), a unique protein based on the recent report which demonstrated that the appearance of Cldn10 in developing and repairing lungs precedes other club cell markers including club cell secretory protein (CCSP). Cldn10-positive cells in IPF lungs displayed marked pleomorphism and were found in varied arrangements, suggesting their phenoconversion. These results were corroborated by immunogold labeling for Cldn10. Further, immunohistochemical double-labeling for Cldn10 and α-smooth muscle actin (α-SMA) demonstrated that aberrant α-SMA signals are frequently encountered near disorganized Cldn10-positive cells in hyperplastic bronchiolar epithelium and thickened interstitium of IPF lungs. Collectively, these data indicate that club cells actively participate in the initiation and progression of IPF through phenoconversion involving the acquisition of proliferative and migratory abilities. Thus, our new findings open the possibility for club cell-targeted therapy to become a strategic option for the treatment of IPF.

Epigenetics of Mucus Hypersecretion in Chronic Respiratory Diseases

Abstract Asthma, chronic obstructive pulmonary disease, and cystic fibrosis are three chronic pulmonary diseases that affect an estimated 420 million individuals across the globe. A key factor contributing to each of these conditions is mucus hypersecretion. Although management of these diseases is vastly studied, researchers have only begun to scratch the surface of the mechanisms contributing to mucus hypersecretion. Epigenetic regulation of mucus hypersecretion, other than microRNA post‐translational modification, is even more scarcely researched. Detailed study of epigenetic mechanisms, such as DNA methylation and histone modification, could not only help to better the understanding of these respiratory conditions but also reveal new treatments for them. Because mucus hypersecretion is such a complex event, there are innumerable genes involved in the process, which are beyond the scope of a single review. Therefore, the purpose of this review is to narrow the focus and summarize specific epigenetic research that has been conducted on a few aspects of mucus hypersecretion in asthma, chronic obstructive pulmonary disease, cystic fibrosis, and some cancers. Specifically, this review emphasizes the contribution of DNA methylation and histone modification of particular genes involved in mucus hypersecretion to identify possible targets for the development of future therapies for these conditions. Elucidating the role of epigenetics in these respiratory diseases may provide a breath of fresh air to millions of affected individuals around the world.

Global gene profiling of aging lungs in Atp8b1 mutant mice.

Objective Recent studies implicate cardiolipin oxidation in several age-related diseases. Atp8b1 encoding Type 4 P-type ATPases is a cardiolipin transporter. Mutation in Atp8b1 gene or inflammation of the lungs impairs the capacity of Atp8b1 to clear cardiolipin from lung fluid. However, the link between Atp8b1 mutation and age-related gene alteration is unknown. Therefore, we investigated how Atp8b1 mutation alters age-related genes. Methods We performed Affymetrix gene profiling of lungs isolated from young (7-9 wks, n=6) and aged (14 months, 14 M, n=6) C57BL/6 and Atp8b1 mutant mice. In addition, Ingenuity Pathway Analysis (IPA) was performed. Differentially expressed genes were validated by quantitative real-time PCR (qRT-PCR). Results Global transcriptome analysis revealed 532 differentially expressed genes in Atp8b1 lungs, 157 differentially expressed genes in C57BL/6 lungs, and 37 overlapping genes. IPA of age-related genes in Atp8b1 lungs showed enrichment of Xenobiotic metabolism and Nrf2-mediated signaling pathways. The increase in Adamts2 and Mmp13 transcripts in aged Atp8b1 lungs was validated by qRT-PCR. Similarly, the decrease in Col1a1 and increase in Cxcr6 transcripts was confirmed in both Atp8b1 mutant and C57BL/6 lungs. Conclusion Based on transcriptome profiling, our study indicates that Atp8b1 mutant mice may be susceptible to age-related lung diseases.

Remission of fibrosis: rage to the rescue

Idiopathic pulmonary fibrosis (IPF) is characterized by a progressive and permanent decline of lung function that eventually leads to expiry. A study published in 2017 performed by Kumar et al. revealed that the disease may not be as irreversible as was once believed. The research discovered a novel role for the receptor for advanced glycation end-products (RAGE) in which it acts as a master regulator for DNA double-strand break repair. In doing so, Kumar et al. may have made a breakthrough that could redefine the translational approaches of IPF.

The novel truncated isoform of human manganese superoxide dismutase has a differential role in promoting metastasis of lung cancer cells: Diverse roles of MnSOD isoforms on metastasis

Growing evidences have demonstrated alternative splicing makes great contribution to tumor metastasis since multiple protein isoforms from a single gene that often display different functions in the cell. Human manganese superoxide dismutase (hMnSOD) was revealed dysregulation in progress of tumor metastasis, while the effect of hMnSOD isoforms on metastasis remained unclear. In this study, we showed a novel truncated hMnSOD isoform hMnSOD183, which lacked 39 amino acids compared with hMnSOD222. We expressed two hMnSOD protein isoforms in Escherichia coli, respectively, and found that the MnSOD activity of truncated hMnSOD isoform was especially weaker. In 95‐D cells, mRNA levels of hMnSOD variants and MnSOD activity were significantly increased than that in A549 cells. Furthermore, the hMnSODc exhibited lower mRNA level than hMnSODa/b in A549 and 95‐D cells. Additionally, the effects of two isoforms were assessed about cell invasion, overexpression of hMnSOD222 but not hMnSOD183 promoted 95‐D cells metastasis, and hMnSOD knockdown significantly reduced cells invasive behavior. Overexpression of hMnSOD isoforms also caused changes of metastasis associated proteins, such as up‐regulation of MMPs, VEGF and Vimentin and down‐regulation of E‐cadherin. Moreover, overexpression of hMnSOD183 had weaker effect on metastasis related signaling proteins, such as Akt, JNK and IKKβ, compared to hMnSOD222. In conclusion, our study identified that hMnSOD isoforms induced lung cancer cells invasion through Akt‐JNK‐IKKβ signaling pathways and the hMnSOD183 isoform played a weaker role than hMnSOD222. Characterization of hMnSOD isoforms is useful for future investigation on metastasis of lung cancer cells.

miR‐330‐3p promotes lung cancer cells invasion, migration, and metastasis by directly targeting hSOD2b

Lung cancer is a serious threat to human health. Studies have revealed that human manganese superoxide dismutase (hSOD2) and miRNAs play an essential role in the metastasis process of lung cancer. However, the miRNAs that associated with hSOD2 and involved in metastasis, remain elusive. After databases analysis and dual luciferase reporter validation, we demonstrated that miR‐330‐3p expression inversely correlated with hSOD2b expression level, and that miR‐330‐3p directly targeted the 3′untranslated region (3′UTR) of hSOD2b. Furthermore, overexpression of miR‐330‐3p promoted whereas knockdown of miR‐330‐3p inhibited invasion/migration and the epithelial–mesenchymal transition (EMT) process of lung cancer cells in vitro. Knockdown of miR‐330‐3p inhibited metastasis of lung cancer cells in vivo. Moreover, miR‐330‐3p‐mediated enhancement of invasion/migration in 95‐D cells could be rescued by over‐expression of hSOD2. In conclusion, we demonstrated that miR‐330‐3p promoted metastasis of lung cancer cells by suppressing hSOD2b expression and unveiled a new clinical application of miR‐330‐3p in the therapy of lung cancer.

Thyroid Hormone: A resurgent treatment for an emergent concern

The story of thyroid hormone in human physiology is one of mixed emotions. Studying past literature on its use leads one to believe that it serves only a few functions in a handful of diseases. In reality, the pathophysiological role of thyroid hormone is an uncharted expanse. Over the past few decades, research on thyroid hormone has been understandably monopolized by studies of hypo- and hyperthyroidism and cancers. However, in our focused pursuit, we have neglected to observe its role in systems that are not so easily relatable. Recent evidence in lung disease suggests that the thyroid hormone is capable of preserving mitochondria in an indirect manner. This is an exciting revelation given the profound implications of mitochondrial dysfunction in several lung diseases. When paired with known links between thyroid hormone and fibrotic pathways, thyroid hormone-based therapies become more enticing for research. In this article, we inspect the sudden awareness surrounding thyroid hormone and discuss why it is of paramount importance that further studies scrutinize the potential of thyroid hormone, and/or thyromimetics, as therapies for lung diseases.