Downregulation of LOX Overexpression Promotes Retinal Ganglion Cells Survival in an Acute Ocular Hypertension Model

PURPOSE

To investigate the effect of reducing Lysyl oxidase (LOX) overexpression on retinal ganglion cells (RGCs) apoptosis in an acute ocular hypertension (AOH) rat model.

METHODS

AOH rat model was performed by anterior chamber perfusion and either received an intravitreal injection with β-aminopropionitrile (BAPN) or normal saline. After 2wk, Quantification of survival RGCs in the retina was performed using Retrograde FluoroGold labeling. The mRNA expression levels of LOX, LOXL1-4, collagen 1a1 (Col1a1), collagen 3a1 (Col3a1), collagen4a1 (Col4a1), elastin (Eln), fibronectin1 (Fbn1), fibronectin4 (Fbn4) were determined by RT-qPCR. LOX expression was determined by Western blot (WB) analysis and immunohistochemistry. The RNA expression of LOX, Eln and Col1a1 in RGCs retrograde-labeled with 1,1'-dioctadecyl-3,3,3',3' tetra-methylindocarbocyanine perchlorate(DiI)that selected through FACS sorting were determined by RT-qPCR analysis. Changes of the retinal function were detected by Electroretinogram (ERG) analysis.

RESULTS

Results showed that significant LOX overexpression and loss of RGCs related to IOP exposure in AOH retinas. PCR analysis indicated significant increased mRNA level of Col1a1, Col3al and Eln in AOH retinas. Significant increase mRNA expression of LOX, Col1a1 and Eln in the RGCs were observed in AOH group compared with CON group. AOH rats injected with BAPN showed a significant decrease in LOX expression, reduced the loss of RGCs and retinal function damage.

CONCLUSIONS

The results demonstrated that changes of LOX and specific ECM components in retina were correlated with AOH. Findings from this study indicated that preventing LOX over-expression may be protective against RGCs loss and retinal function damage in AOH animal model.

A pilot metabolomics study across the continuum of interstitial lung disease fibrosis severity

Interstitial lung diseases (ILDs) include a variety of inflammatory and fibrotic pulmonary conditions. This study employs high-resolution metabolomics (HRM) to explore plasma metabolites and pathways across ILD phenotypes, including non-fibrotic ILD, idiopathic pulmonary fibrosis (IPF), and non-IPF fibrotic ILD. The study used 80 plasma samples for HRM, and involved linear trend and group-wise analyses of metabolites altered in ILD phenotypes. We utilized limma one-way ANOVA and mummichog algorithms to identify differences in metabolites and pathways across ILD groups. Then, we focused on metabolites within critical pathways, indicated by high pathway overlap sizes and low p-values, for further analysis. Targeted HRM identified putrescine, hydroxyproline, prolyl-hydroxyproline, aspartate, and glutamate with significant linear increases in more fibrotic ILD phenotypes, suggesting their role in ILD fibrogenesis. Untargeted HRM highlighted pathway alterations in lysine, vitamin D3, tyrosine, and urea cycle metabolism, all associated with pulmonary fibrosis. In addition, methylparaben level had a significantly increasing linear trend and was higher in the IPF than fibrotic and non-ILD groups. This study highlights the importance of specific amino acids, metabolic pathways, and xenobiotics in the progression of pulmonary fibrosis.

ROS-mediated lysosomal membrane permeabilization and autophagy inhibition regulate bleomycin-induced cellular senescence

Bleomycin exhibits effective chemotherapeutic activity against multiple types of tumors, and also induces various side effects, such as pulmonary fibrosis and neuronal defects, which limit the clinical application of this drug. Macroautophagy/autophagy has been recently reported to be involved in the functions of bleomycin, and yet the mechanisms of their crosstalk remain insufficiently understood. Here, we demonstrated that reactive oxygen species (ROS) produced during bleomycin activation hampered autophagy flux by inducing lysosomal membrane permeabilization (LMP) and obstructing lysosomal degradation. Exhaustion of ROS with N-acetylcysteine relieved LMP and autophagy defects. Notably, we observed that LMP and autophagy blockage preceded the emergence of cellular senescence during bleomycin treatment. In addition, promoting or inhibiting autophagy-lysosome degradation alleviated or exacerbated the phenotypes of senescence, respectively. This suggests the alternation of autophagy activity is more a regulatory mechanism than a consequence of bleomycin-induced cellular senescence. Taken together, we reveal a specific role of bleomycin-induced ROS in mediating defects of autophagic degradation and further regulating cellular senescence in vitro and in vivo. Our findings, conversely, indicate the autophagy-lysosome degradation pathway as a target for modulating the functions of bleomycin. These provide a new perspective for optimizing bleomycin as a clinically applicable chemotherapeutics devoid of severe side-effects.Abbreviations: AT2 cells: type II alveolar epithelial cells; ATG7: autophagy related 7; bEnd.3: mouse brain microvascular endothelial cells; BNIP3L: BCL2/adenovirus E1B interacting protein 3-like; CCL2: C-C motif chemokine ligand 2; CDKN1A: cyclin dependent kinase inhibitor 1A; CDKN2A: cyclin dependent kinase inhibitor 2A; FTH1: ferritin heavy polypeptide 1; γ-H2AX: phosphorylated H2A.X variant histone; GAPDH: glyceraldehyde-3-phosphate dehydrogenase; HUVEC: human umbilical vein endothelial cells; HT22: hippocampal neuronal cell lines; Il: interleukin; LAMP: lysosomal-associated membrane protein; LMP: lysosome membrane permeabilization; MTORC1: mechanistic target of rapamycin kinase complex 1; NAC: N-acetylcysteine; NCOA4: nuclear receptor coactivator 4; PI3K: phosphoinositide 3-kinase; ROS: reactive oxygen species; RPS6KB/S6K: ribosomal protein S6 kinase; SA-GLB1/β-gal: senescence-associated galactosidase, beta 1; SAHF: senescence-associated heterochromatic foci; SASP: senescence-associated secretory phenotype; SEC62: SEC62 homolog, preprotein translocation; SEP: superecliptic pHluorin; SQSTM1/p62: sequestosome 1; TFEB: transcription factor EB.

Assessing Heterogeneity in the N-Telopeptides of Type I Collagen by Mass Spectrometry

Collagen cross-links created by the lysyl oxidase and lysyl hydroxylase families of enzymes are a significant contributing factor to the biomechanical strength and rigidity of tissues, which in turn influence cell signaling and ultimately cell phenotype. In the clinic, the proteolytically liberated N-terminal cross-linked peptide of collagen I (NTX) is used as a biomarker of bone and connective tissue turnover, which is altered in several disease processes. Despite the clinical utility of these collagen breakdown products, the majority of the cross-linked peptide species have not been identified in proteomic datasets. Here we evaluate several parameters for the preparation and identification of these peptides from the collagen I-rich Achilles tendon. Our refined approach involving chemical digestion for protein solubilization coupled with mass spectrometry allows for the identification of the NTX cross-links in a range of modification states. Based on the specificity of the enzymatic cross-linking reaction we utilized follow-up variable modification searches to facilitate identification with a wider range of analytical workflows. We then applied a spectral library approach to identify differences in collagen cross-links in bovine pulmonary hypertension. The presented method offers unique opportunities to understand extracellular matrix remodeling events in development, aging, wound healing, and fibrotic disease that modulate collagen architecture through lysyl-hydroxylase and lysyl-oxidase enzymes.

Insights into Disease Progression of Translational Preclinical Rat Model of Interstitial Pulmonary Fibrosis through Endpoint Analysis

Idiopathic pulmonary fibrosis (IPF) is a devastating interstitial lung disease characterized by the relentless deposition of extracellular matrix (ECM), causing lung distortions and dysfunction. Animal models of human IPF can provide great insight into the mechanistic pathways underlying disease progression and a means for evaluating novel therapeutic approaches. In this study, we describe the effect of bleomycin concentration on disease progression in the classical rat bleomycin model. In a dose-response study (1.5, 2, 2.5 U/kg i.t), we characterized lung fibrosis at day 14 after bleomycin challenge using endpoints including clinical signs, inflammatory cell infiltration, collagen content, and bronchoalveolar lavage fluid-soluble profibrotic mediators. Furthermore, we investigated fibrotic disease progression after 2 U/kg i.t. bleomycin administration at days 3, 7, and 14 by quantifying the expression of clinically relevant signaling molecules and pathways, epithelial mesenchymal transition (EMT) biomarkers, ECM components, and histopathology of the lung. A single bleomycin challenge resulted in a progressive fibrotic response in rat lung tissue over 14 days based on lung collagen content, histopathological changes, and modified Ashcroft score. The early fibrogenesis phase (days 3 to 7) is associated with an increase in profibrotic mediators including TGFβ1, IL6, TNFα, IL1β, CINC1, WISP1, VEGF, and TIMP1. In the mid and late fibrotic stages, the TGFβ/Smad and PDGF/AKT signaling pathways are involved, and clinically relevant proteins targeting galectin-3, LPA1, transglutaminase-2, and lysyl oxidase 2 are upregulated on days 7 and 14. Between days 7 and 14, the expressions of vimentin and α-SMA proteins increase, which is a sign of EMT activation. We confirmed ECM formation by increased expressions of procollagen-1Aα, procollagen-3Aα, fibronectin, and CTGF in the lung on days 7 and 14. Our data provide insights on a complex network of several soluble mediators, clinically relevant signaling pathways, and target proteins that contribute to drive the progressive fibrotic phenotype from the early to late phase (active) in the rat bleomycin model. The framework of endpoints of our study highlights the translational value for pharmacological interventions and mechanistic studies using this model.

Trigonelline mitigates bleomycin-induced pulmonary inflammation and fibrosis: Insight into NLRP3 inflammasome and SPHK1/S1P/Hippo signaling modulation

AIMS

Pulmonary fibrosis (PF) is a chronic interstitial lung disease with an increasing incidence following the COVID-19 outbreak. Pirfenidone (Pirf), an FDA-approved pulmonary anti-fibrotic drug, is poorly tolerated and exhibits limited efficacy. Trigonelline (Trig) is a natural plant alkaloid with diverse pharmacological actions. We investigated the underlying prophylactic and therapeutic mechanisms of Trig in ameliorating bleomycin (BLM)-induced PF and the possible synergistic antifibrotic activity of Pirf via its combination with Trig.

MATERIALS AND METHODS

A single dose of BLM was administered intratracheally to male Sprague-Dawley rats for PF induction. In the prophylactic study, Trig was given orally 3 days before BLM and then for 28 days. In the therapeutic study, Trig and/or Pirf were given orally from day 8 after BLM until the 28th day. Biochemical assay, histopathology, qRT-PCR, ELISA, and immunohistochemistry were performed on lung tissues.

KEY FINDINGS

Trig prophylactically and therapeutically mitigated the inflammatory process via targeting NF-κB/NLRP3/IL-1β signaling. Trig activated the autophagy process which in turn attenuated alveolar epithelial cells apoptosis and senescence. Remarkably, Trig attenuated lung SPHK1/S1P axis and its downstream Hippo targets, YAP-1, and TAZ, with a parallel decrease in YAP/TAZ profibrotic genes. Interestingly, Trig upregulated lung miR-375 and miR-27a expression. Consequently, epithelial-mesenchymal transition in lung tissues was reversed upon Trig administration. These results were simultaneously associated with profound improvement in lung histological alterations.

SIGNIFICANCE

The current study verifies Trig's prophylactic and antifibrotic effects against BLM-induced PF via targeting multiple signaling. Trig and Pirf combination may be a promising approach to synergize Pirf antifibrotic effect.

Emerging delivery approaches for targeted pulmonary fibrosis treatment

Pulmonary fibrosis (PF) is a progressive, and life-threatening interstitial lung disease which causes scarring in the lung parenchyma and thereby affects architecture and functioning of lung. It is an irreversible damage to lung functioning which is related to epithelial cell injury, immense accumulation of immune cells and inflammatory cytokines, and irregular recruitment of extracellular matrix. The inflammatory cytokines trigger the differentiation of fibroblasts into activated fibroblasts, also known as myofibroblasts, which further increase the production and deposition of collagen at the injury sites in the lung. Despite the significant morbidity and mortality associated with PF, there is no available treatment that efficiently and effectively treats the disease by reversing their underlying pathologies. In recent years, many therapeutic regimens, for instance, rho kinase inhibitors, Smad signaling pathway inhibitors, p38, BCL-xL/ BCL-2 and JNK pathway inhibitors, have been found to be potent and effective in treating PF, in preclinical stages. However, due to non-selectivity and non-specificity, the therapeutic molecules also result in toxicity mediated severe side effects. Hence, this review demonstrates recent advances on PF pathology, mechanism and targets related to PF, development of various drug delivery systems based on small molecules, RNAs, oligonucleotides, peptides, antibodies, exosomes, and stem cells for the treatment of PF and the progress of various therapeutic treatments in clinical trials to advance PF treatment.

Circadian clock molecule REV-ERBα regulates lung fibrotic progression through collagen stabilization

Molecular clock REV-ERBα is central to regulating lung injuries, and decreased REV-ERBα abundance mediates sensitivity to pro-fibrotic insults and exacerbates fibrotic progression. In this study, we determine the role of REV-ERBα in fibrogenesis induced by bleomycin and Influenza A virus (IAV). Bleomycin exposure decreases the abundance of REV-ERBα, and mice dosed with bleomycin at night display exacerbated lung fibrogenesis. Rev-erbα agonist (SR9009) treatment prevents bleomycin induced collagen overexpression in mice. Rev-erbα global heterozygous (Rev-erbα Het) mice infected with IAV showed augmented levels of collagens and lysyl oxidases compared with WT-infected mice. Furthermore, Rev-erbα agonist (GSK4112) prevents collagen and lysyl oxidase overexpression induced by TGFβ in human lung fibroblasts, whereas the Rev-erbα antagonist exacerbates it. Overall, these results indicate that loss of REV-ERBα exacerbates the fibrotic responses by promoting collagen and lysyl oxidase expression, whereas Rev-erbα agonist prevents it. This study provides the potential of Rev-erbα agonists in the treatment of pulmonary fibrosis.

Targeting Lysyl Oxidase as a Potential Therapeutic Approach to Reducing Fibrotic Scars Post-operatively: Its Biological Role in Post-Surgical Scar Development

Abdominal and pelvic surgery, or any surgical injury of the peritoneum, often leads to chronic abdominal adhesions that may lead to bowel obstruction, infertility, and pain. Current therapeutic strategies are usually ineffective, and the pathological mechanisms of the disease are unclear. Excess collagen cross-linking is a key mediator for extra-cellular matrix deposition and fibrogenesis. Lysyl oxidase is a key enzyme that catalyzes the formation of stabilizing cross-links in collagen. Dysregulation of Lysyl oxidase (Lox) expressing upregulates collagen cross-linking, leading ECM deposition. Tissue hypoxia during surgery induces molecular mechanisms and active transcription factors to promote the expression of several genes related to inflammation, oxidative stress, and fibrosis, such as transforming growth factor beta, and Lox. Studies have shown that targeting Lox improves clinical outcomes and fibrotic parameters in liver, lung, and myocardial fibrosis, therefore, Lox may be a potential drug target in the prevention of postsurgical adhesion.

The Restoring Effect of Human Umbilical Cord-Derived Mesenchymal Cell-Conditioned Medium (hMSC-CM) against Carbon Tetrachloride-Induced Pulmonary Fibrosis in Male Wistar Rats

Objective

Pulmonary toxicity induced by CCl₄, a model of idiopathic pulmonary fibrosis (IPF), leads to tissue remodeling and inflammation. Human umbilical cord mesenchymal cell-conditioned medium (hMSC-CM) is a potent anti-inflammatory, antioxidative, and antifibrotic agent.

Methods

Forty male Wistar rats were assigned to the control (C), olive oil control (C.O) (hMSC-CM), control (C.Ms), fibrosis (fb), and fibrosis with hMSC-CM (f.Ms) treatment groups. The groups C, C.O, and C.Ms received PBS (200 µl), olive oil (1 ml/kg), and hMSC-CM (100 μg protein/kg), respectively. The fibrosis group was administered with only CCl4 (1 ml/kg). The last group, f.Ms was treated with CCl₄ (1 ml/kg) and 100 μg protein/kg IV hMSC-CM. While the treatment with olive oil and CCl₄ was performed for 2 days/week from the first week for 12 weeks, the treatment with PBS and hMSC-CM was carried out 2 days/week from week 4^th to week 12^th. The effect of the UC-MSC culture medium treatment on the lung was evaluated by assessing lysyl oxidase (LOX), tumor necrosis factor-alpha (TNF-α), and transforming growth factor-β1 (TGF-β1) genes, and proteins expression by real-time RCR and western blotting, respectively.

Results

Lysyl oxidase (LOX), tumor necrosis factor-alpha (TNF-α), transforming growth factor-b1 (TGF-β1), malondialdehyde (MDA), and oxidative stress levels were markedly higher in the fibrosis group than in the control groups (p ≤ 0.001). Additionally, glutathione (GSH) in the fibrosis group was markedly lower than those in the control groups (p ≤ 0.001). Fibrosis in the UC-MSC treatment group had milder histopathological injuries than in the fibrosis group.

Conclusion

hMSC-MSC as a strong anti-inflammatory, antioxidative, and antifibrotic decreases the level of oxidative stress, proinflammatory cytokines, and MDA causing a restoring effect against CCl₄-induced pulmonary fibrosis.

Metabolic Reprogramming of Liver Fibrosis

Liver fibrosis is an excessive and imbalanced deposition of fibrous extracellular matrix (ECM) that is associated with the hepatic wound-healing response. It is also the common mechanism that contributes to the impairment of the liver function that is observed in many chronic liver diseases (CLD). Despite the efforts, no effective therapy against fibrosis exists yet. Worryingly, due to the growing obesity pandemic, fibrosis incidence is on the rise. Here, we aim to summarize the main components and mechanisms involved in the progression of liver fibrosis, with special focus on the metabolic regulation of key effectors of fibrogenesis, hepatic stellate cells (HSCs), and their role in the disease progression. Hepatic cells that undergo metabolic reprogramming require a tightly controlled, fine-tuned cellular response, allowing them to meet their energetic demands without affecting cellular integrity. Here, we aim to discuss the role of ribonucleic acid (RNA)-binding proteins (RBPs), whose dynamic nature being context- and stimuli-dependent make them very suitable for the fibrotic situation. Thus, we will not only summarize the up-to-date literature on the metabolic regulation of HSCs in liver fibrosis, but also on the RBP-dependent post-transcriptional regulation of this metabolic switch that results in such important consequences for the progression of fibrosis and CLD.

The challenge of determining lysyl oxidase activity: Old methods and novel approaches

The lysyl oxidase (LOX) family of enzymes catalyze the oxidative deamination of lysine and hydroxylysine residues in collagen and elastin in the initiation step of the formation of covalent cross-linkages, an essential process for extracellular matrix (ECM) maturation. Elevated LOX expression levels leading to increased LOX activity is associated with diverse pathologies including fibrosis, cancer, and cardiovascular diseases. Different protocols have been so far established to detect and quantify LOX activity from tissue samples and cultured cells, all of them showing advantages and drawbacks. This review article presents a critical overview of the main features of currently available methods as well as introduces some recent technologies called to revolutionize our approach to LOX catalysis.

Azithromycin Attenuates Bleomycin-Induced Pulmonary Fibrosis Partly by Inhibiting the Expression of LOX and LOXL-2

Pulmonary fibrosis (PF) is a chronic and progressive process of tissue repair. Azithromycin (AZM) may be beneficial for the treatment of PF because AZM has anti-inflammatory and immune regulatory roles and inhibits remodeling, but the mechanism is not entirely clear. In this study, we established a mouse PF model induced by bleomycin (BLM) and primary mouse lung fibroblasts stimulated by transforming growth factor (TGF)-β1 to explore the possible mechanisms of AZM in PF. Results showed that AZM reduces mortality and lung inflammation and attenuates BLM-induced PF in mice. AZM effectively reduced the expression of α-smooth muscle actin (SMA) and type I collagen. Meanwhile, expression of lysyl oxidase (LOX) and lysyl oxidase-like protein (LOXL)-2 in the lung tissue of mice after AZM treatment was significantly lower than in the BLM group. In addition, this study found that AZM significantly inhibits the TGF-β1/Smad and JNK/c-Jun signaling pathways in vivo, and expression of a-SMA, type I collagen, LOX and LOXL-2 in the lung tissue of mice treated with AZM was significantly lower than that in the BLM group. In vitro, AZM also effectively inhibited type I collagen, LOX, LOXL-2 and JNK-c-Jun signaling pathways in TGF-β1-stimulated primary mouse fibroblasts, and this effect was similar to that of a JNK-specific inhibitor (SP600125). In conclusion, AZM effectively attenuated BLM-induced PF in mice, which may play a role by partially inhibiting the JNK/c-Jun and TGF-β1/Smad signaling pathways and reducing production of LOX and LOXL2.

Nutritional immunity: the impact of metals on lung immune cells and the airway microbiome during chronic respiratory disease

Nutritional immunity is the sequestration of bioavailable trace metals such as iron, zinc and copper by the host to limit pathogenicity by invading microorganisms. As one of the most conserved activities of the innate immune system, limiting the availability of free trace metals by cells of the immune system serves not only to conceal these vital nutrients from invading bacteria but also operates to tightly regulate host immune cell responses and function. In the setting of chronic lung disease, the regulation of trace metals by the host is often disrupted, leading to the altered availability of these nutrients to commensal and invading opportunistic pathogenic microbes. Similarly, alterations in the uptake, secretion, turnover and redox activity of these vitally important metals has significant repercussions for immune cell function including the response to and resolution of infection. This review will discuss the intricate role of nutritional immunity in host immune cells of the lung and how changes in this fundamental process as a result of chronic lung disease may alter the airway microbiome, disease progression and the response to infection.

Inhibitory effects of alkaline extract from the pericarp of Citrus reticulata Blanco on collagen behavior in bleomycin-induced pulmonary fibrosis

ETHNOPHARMACOLOGICAL RELEVANCE

Peel of Citrus reticulata, a Chinese herbal drug with functions of regulating Qi and expelling phlegm, has been used for the treatment of lung related diseases in Chinese medicine for a long time. Its detailed effects on collagen in anti-idiopathic pulmonary fibrosis (IPF) is still unclear.

AIM OF THE STUDY

To explore the effects of citrus alkaline extract (CAE) on collagen synthesis, crosslinking and deposition in pulmonary fibrosis and understand the possible signal pathways involved in the activity.

MATERIALS AND METHODS

CAE was prepared from C. reticulata. Bleomycin-induced pulmonary fibrosis mouse model was applied. Pulmonary fibrosis of lung was estimated with histopathology analysis, and collagen deposition was evaluated with immunohistochemistry. Collagen crosslinking related biomarkers and enzymes were analyzed with chemical methods, immunohistochemical and western blot analyses.

RESULTS

CAE oral administration lowered hydroxyproline content, inhibited the collagen deposition including expressions of collagen I and III, and relieved bleomycin-induced pulmonary fibrosis in mice model. The productions of a collagen crosslink pyridinoline and crosslinking related enzymes including lysyl oxidase (LOX), lysyl oxidase-like protein 1 (LOXL1) in lung were suppressed by CAE treatment. Furthermore, the protein expressions of TGF-β1 and Smad3 levels in lungs were also downregulated by CAE.

CONCLUSIONS

This study demonstrated that CAE inhibited collagen synthesis, crosslinking and deposition, and ameliorated bleomycin-induced pulmonary fibrosis. Preliminary mechanism study revealed that CAE exerted its bioactivity at least via downregulation of TGF-β1/Smad3 pathway. Our findings provided a great potential in fighting IPF based on CAE.

GLP-1 Receptor Signaling Differentially Modifies the Outcomes of Sterile vs Viral Pulmonary Inflammation in Male Mice

A number of disease states, including type 2 diabetes (T2D), are associated with an increased risk of pulmonary infection. Glucagon-like peptide-1 (GLP-1) receptor agonists are used to treat T2D and exert anti-inflammatory actions through a single, well-defined GLP-1 receptor (GLP-1R). Although highly expressed in the lung, little is known about the role of the GLP-1R in the context of pulmonary inflammation. Here we examined the consequences of gain or loss of GLP-1R activity in infectious and noninfectious lung inflammation. We studied wild-type mice treated with a GLP-1R agonist, and Glp1r-/- mice, in the setting of bleomycin-induced noninfectious lung injury and influenza virus infection. Loss of the GLP-1R attenuated the severity of bleomycin-induced lung injury, whereas activation of GLP-1R signaling increased pulmonary inflammation via the sympathetic nervous system. In contrast, GLP-1R agonism reduced the pathogen load in mice with experimental influenza virus infection in association with increased expression of intracellular interferon-inducible GTPases. Notably, the GLP-1 receptor agonist liraglutide improved the survival rate after influenza virus infection. Our results reveal context-dependent roles for the GLP-1 system in the response to lung injury. Notably, the therapeutic response of GLP-1R agonism in the setting of experimental influenza virus infection may have relevance for ongoing studies of GLP-1R agonism in people with T2D susceptible to viral lung injury.

Lysyl oxidase inhibition enhances browning of white adipose tissue and adaptive thermogenesis

Accumulating evidence from both animal and human studies suggests that activation of beige fat increases cellular energy expenditure, ultimately reducing adiposity. Here, we report the central role of adipocyte-derived lysyl oxidase (Lox) in the formation of thermogenic beige fat. Mice exposed to cold or a β3 agonist showed drastically lower Lox expression in thermogenically activated beige fat. Importantly, inhibition of Lox activity with BAPN stimulated biogenesis of beige fat in inguinal white adipose tissue (iWAT) under housing conditions and potentiated cold-induced adaptive thermogenesis and beiging in both iWAT and epididymal white adipose tissue (eWAT). Notably, white adipocytes with Lox repression undergo transdifferentiation into beige adipocytes which can be suppressed by tumor necrosis factor-α (TNFα) via ERK activation. This work provides new insight into the molecular control to expand beige fat by Lox inhibition and suggest the potential for utilizing inhibitor of Lox to treat the emerging epidemics of obesity and diabetes.

Lysyl oxidase directly contributes to extracellular matrix production and fibrosis in systemic sclerosis

Pulmonary fibrosis is one of the important causes of morbidity and mortality in fibroproliferative disorders such as systemic sclerosis (SSc) and idiopathic pulmonary fibrosis (IPF). Lysyl oxidase (LOX) is a copper-dependent amine oxidase whose primary function is the covalent crosslinking of collagens in the extracellular matrix (ECM). We investigated the role of LOX in the pathophysiology of SSc. LOX mRNA and protein levels were increased in lung fibroblasts of SSc patients compared with healthy controls and IPF patients. In vivo, bleomycin induced LOX mRNA expression in lung tissues, and LOX activity increased in the circulation of mice with pulmonary fibrosis, suggesting that circulating LOX parallels levels in lung tissues. Circulating levels of LOX were reduced upon amelioration of fibrosis with an antifibrotic peptide. LOX induced ECM production at the transcriptional level in lung fibroblasts, human lungs, and human skin maintained in organ culture. In vivo, LOX synergistically exacerbated fibrosis in bleomycin-treated mice. Further, LOX increased the production of interleukin (IL)-6, and the increase was mediated by LOX-induced c-Fos expression, the nuclear localization of c-Fos, and its engagement with the IL-6 promoter region. Our findings demonstrate that LOX expression and activity correlate with fibrosis in vitro, ex vivo, and in vivo. LOX induced ECM production via upregulation of IL-6 and nuclear localization of c-Fos. Thus, LOX has a direct pathogenic role in SSc-associated fibrosis that is independent of its crosslinking function. Our findings also suggest that measuring circulating LOX levels and activity can be used for monitoring response to antifibrotic therapy.

Lysyl oxidases: Emerging biomarkers and therapeutic targets for various diseases

Therapeutic targeting of extracellular proteins has attracted huge attention in treating human diseases. The lysyl oxidases (LOXs) are a family of secreted copper-dependent enzymes which initiate the covalent crosslinking of collagen and elastin fibers in the extracellular microenvironment, thereby facilitating extracellular matrix (ECM) remodeling and ECM homeostasis. Apart from ECM-dependent roles, LOXs are also involved in other biological processes such as epithelial-to-mesenchymal transition (EMT) and transcriptional regulation, especially following hypoxic stress. Dysregulation of LOXs is found to underlie the onset and progression of multiple pathologies, such as carcinogenesis and cancer metastasis, fibrotic diseases, neurodegeneration and cardiovascular diseases. In this review, we make a comprehensive summarization of clinical and experimental evidences that support roles of for LOXs in disease pathology and points out LOXs as promising therapeutic targets for improving prognosis. Additionally, we also propose that LOXs reshape cell-ECM interaction or cell-cell interaction due to ECM-dependent and ECM-independent roles for LOXs. Therapeutic intervention of LOXs may have advantages in the maintenance of communication between ECM and cell or intercellular signaling, finally recovering organ function.

Use of the Reversible Myogenic to Lipogenic Transdifferentiation Switch for the Design of Pre-clinical Drug Screening in Idiopathic Pulmonary Fibrosis

Idiopathic Pulmonary Fibrosis (IPF) is an end-stage lung disease characterized by excessive extracellular matrix (ECM) deposition from activated myofibroblasts (MYFs) and tissue scarring. Eventually leading to stiffening of the lung, capable of assuming only limited gas exchange function. So far two drugs, pirfenidone [acting via TGF-β (transforming growth factor beta) inhibition] and nintedanib (a pan-tyrosine kinase receptor inhibitor) have been approved for IPF patients. They both act on the activated MYF by reducing the expression of fibrotic markers. Unfortunately, these drugs are only slowing down fibrosis formation and as such do not represent a cure for this lethal, devastating disease. We previously reported that activated MYF originate, at least in part, from lung fibroblast resident cells called lipofibroblasts (LIF). During resolution, these activated MYF can transdifferentiate into LIF. We propose that this reversible myogenic/lipogenic transdifferentiation switch paradigm can be used to screen for drugs capable of triggering the lipogenic differentiation of activated MYFs. Ideally, these drugs should also induce the reduction of pro-fibrotic markers alpha smooth muscle actin2 (ACTA2) and collagen 1A1 (COL1A1) in activated MYF and as such would represent important alternatives to the approved drugs. The goal of this review is to summarize the current knowledge and limitations of the current strategies aiming to carry out methodical pre-clinical drug screening in pertinent in vitro, ex vivo, and in vivo models of IPF. These models include (1) in vitro culture of primary fibroblasts from IPF patients, (2) ex vivo culture of precision cut lung slices from end-stage IPF lungs obtained from transplant patients, and (3) bleomycin-induced fibrosis mouse models in the context of lineage tracing of activated MYF during resolution. For all these assays, we propose the innovative use of lipogenic read outs for the LIFs.

Microenvironment stiffness requires decellularized cardiac extracellular matrix to promote heart regeneration in the neonatal mouse heart

The transient period of regeneration potential in the postnatal heart suggests molecular changes with maturation influence the cardiac response to damage. We have previously demonstrated that injury and exercise can stimulate cardiomyocyte proliferation in the adult heart suggesting a sensitivity to exogenous signals. Here, we consider whether exogenous fetal ECM and mechanically unloading interstitial matrix can drive regeneration after myocardial infarction (MI) surgery in low-regenerative hearts of day5 mice. Compared to controls, exogenous fetal ECM increases cardiac function and lowers fibrosis at 3 weeks post-injury and this effect can be augmented by softening heart tissue. In vitro experiments support a mechano-sensitivity to exogenous ECM signaling. We tested potential mechanisms and observed that fetal ECM increases nuclear YAP localization which could be enhanced by pharmacological stabilization of the cytoskeleton. Blocking YAP expression lowered fetal ECM effects though not completely. Lastly we observed mechanically unloading heart interstitial matrix increased agrin expression, an extracellular node in the YAP signaling pathway. Collectively, these data support a combined effect of exogenous factors and mechanical activity in altering agrin expression, cytoskeletal remodeling, and YAP signaling in driving cardiomyocyte cell cycle activity and regeneration in postnatal non-regenerative mice. STATEMENT OF SIGNIFICANCE: With the purpose of developing regenerative strategies, we investigate the influence of the local niche on the cardiac injury response. We conclude tissue stiffness, as anticipated in aging or disease, impairs regenerative therapeutics. Most novel, mechanical unloading facilitates enhanced cardiac regeneration only after cells are pushed into a permissive state by fetal biomolecules. Specifically, mechanical unloading appears to increase extracellular agrin expression that amplifies fetal-stimulation of nuclear YAP signaling which correlates with observed increases of cell cycle activity in cardiomyocytes. The results further suggest the cytoskeleton is critical to this interaction between mechanical unloading and independently actived YAP signaling. Using animal models, tissue explants, and cells, this work indicates that local mechanical stimuli can augment proliferating-permissive cardiomyocytes in the natural cardiac niche.

Lysyl Oxidase (LOX) Family Members: Rationale and Their Potential as Therapeutic Targets for Liver Fibrosis

The cross-linking of structural extracellular matrix (ECM) components, especially fibrillar collagens and elastin, is strongly implicated in fibrosis progression and resistance to fibrosis reversal. Lysyl oxidase family members (LOX and LOXL1 [lysyl oxidase-like 1], LOXL2 [lysyl oxidase-like 2], LOXL3 [lysyl oxidase-like 3], and LOXL4 [lysyl oxidase like 4]) are extracellular copper-dependent enzymes that play a key role in ECM cross-linking, but have also other intracellular functions relevant to fibrosis and carcinogenesis. Although the expression of most LOX family members is elevated in experimental liver fibrosis of diverse etiologies, their individual contribution to fibrosis is incompletely understood. Inhibition of the LOX family as a whole and of LOX, LOXL1, and LOXL2 specifically has been shown to suppress fibrosis progression and accelerate its reversal in rodent models of cardiac, renal, pulmonary, and liver fibrosis. Recent disappointing clinical trials with a monoclonal antibody against LOXL2 (simtuzumab) in patients with pulmonary and liver fibrosis dampened enthusiasm for LOX family member inhibition. However, this unexpected negative outcome may be related to the inefficient antibody, rather than to LOXL2, not qualifying as a relevant antifibrotic target. Moreover, LOX family members other than LOXL2 may prove to be attractive therapeutic targets. In this review, we summarize the structural hallmarks, expression patterns, covalent cross-linking activities, and modes of regulation of LOX family members and discuss the clinical potential of their inhibition to treat fibrosis in general and liver fibrosis in particular.

Lysyl Oxidase (LOX): Functional Contributions to Signaling Pathways

Cu-dependent lysyl oxidase (LOX) plays a catalytic activity-related, primary role in the assembly of the extracellular matrix (ECM), a dynamic structural and regulatory framework which is essential for cell fate, differentiation and communication during development, tissue maintenance and repair. LOX, additionally, plays both activity-dependent and independent extracellular, intracellular and nuclear roles that fulfill significant functions in normal tissues, and contribute to vascular, cardiac, pulmonary, dermal, placenta, diaphragm, kidney and pelvic floor disorders. LOX activities have also been recognized in glioblastoma, diabetic neovascularization, osteogenic differentiation, bone matrix formation, ligament remodeling, polycystic ovary syndrome, fetal membrane rupture and tumor progression and metastasis. In an inflammatory context, LOX plays a role in diminishing pluripotent mesenchymal cell pools which are relevant to the pathology of diabetes, osteoporosis and rheumatoid arthritis. Most of these conditions involve mechanisms with complex cell and tissue type-specific interactions of LOX with signaling pathways, not only as a regulatory target, but also as an active player, including LOX-mediated alterations of cell surface receptor functions and mutual regulatory activities within signaling loops. In this review, we aim to provide insight into the diverse ways in which LOX participates in signaling events, and explore the mechanistic details and functional significance of the regulatory and cross-regulatory interactions of LOX with the EGFR, PDGF, VEGF, TGF-β, mechano-transduction, inflammatory and steroid signaling pathways.

Mechano-therapeutics: Targeting Mechanical Signaling in Fibrosis and Tumor Stroma

Pathological remodeling of the extracellular matrix (ECM) by activated myofibroblasts is a hallmark of fibrotic diseases and desmoplastic tumors. Activation of myofibroblasts occurs in response to fibrogenic tissue injury as well as in tumor-associated fibrotic reactions. The molecular determinants of myofibroblast activation in fibrosis and tumor stroma have traditionally been viewed to include biochemical agents, such as dysregulated growth factor and cytokine signaling, which profoundly alter the biology of fibroblasts, ultimately leading to overexuberant matrix deposition and fibrosis. More recently, compelling evidence has shown that altered mechanical properties of the ECM such as matrix stiffness are major drivers of tissue fibrogenesis by promoting mechano-activation of fibroblasts. In this Review, we discuss new insights into the role of the biophysical microenvironment in the amplified activation of fibrogenic myofibroblasts during the development and progression of fibrotic diseases and desmoplastic tumors. We also summarize novel therapeutic targets for anti-fibrotic therapy based on the mechanobiology of tissue fibrosis and tumor stroma, a class of drugs known as "mechano-therapeutics".

Triptolide alleviates radiation-induced pulmonary fibrosis via inhibiting IKKβ stimulated LOX production

Lysyl oxidase (LOX) is involved in fibrosis by catalyzing collagen cross-linking. Previous work observed that Triptolide (TPL) alleviated radiation-induced pulmonary fibrosis (RIPF), but it is unknown whether the anti-RIPF effect of TPL is related to LOX. In a mouse model of RIPF, we found that LOX persistently increased in RIPF which was significantly lowered by TPL. Excessive LOX aggravated fibrotic lesions in RIPF, while LOX inhibition mitigated RIPF. Irradiation enhanced the transcription and synthesis of LOX by lung fibroblasts through IKKβ/NFκB activation, and siRNA knockdown IKKβ largely abolished LOX production. By interfering radiation induced IKKβ activation, TPL prevented NFκB nuclear translocation and DNA binding, and potently decreased LOX synthesis. Our results demonstrate that the anti-RIPF effect of TPL is associated with reduction of LOX production which mediated by inhibition of IKKβ/NFκB pathway.

Downregulation of lysyl oxidase in venous malformations: Association with vascular destabilization and sclerotherapy

Venous malformations (VM) are localized defects in vascular morphogenesis manifested by dilated venous channels with reduced perivascular cell coverage. As a vital enzyme for extracellular matrix (ECM) deposition, lysyl oxidase (LOX) plays important roles in vascular development and diseases. However, the expression and significance of LOX are unknown in VM. Herein, 22 VM specimens and eight samples of normal skin tissues were evaluated immunohistochemically for the expression of LOX, α-smooth muscle cell actin (α-SMA) and transforming growth factor-β (TGF-β). In vitro studies on human umbilical vein endothelial cells (HUVEC) were employed for determining potential mechanisms. Our results showed that LOX expression was significantly reduced in VM compared with normal skin tissues, in parallel with attenuated perivascular α-SMA⁺ cell coverage and TGF-β downregulation in VM. Further correlation analysis indicated that LOX expression was positively correlated with perivascular α-SMA⁺ cell coverage and TGF-β expression in VM. Moreover, marked elevation of LOX, TGF-β and α-SMA was observed in bleomycin-treated VM samples. Furthermore, our in vitro data demonstrated that both recombinant TGF-β and bleomycin induced obvious increase of LOX expression and activity and a concomitant increase in ECM components in HUVEC, which could be reversed by LOX inhibition. To our best knowledge, this study revealed for the first time the downregulation of LOX in VM and its correlation with vascular destabilization and TGF-β-induced endothelial ECM deposition. Moreover, our results highlighted that LOX may be implicated in the sclerotherapy of VM and holds promise as a therapeutic target.

Therapeutic effects of shibashin misena® against fine-dust-induced pulmonary disorders in mice

INTRODUCTION

In recent decades, fine-dust particulate matter (FM) has become a potential health hazard, causing various pathological respiratory disorders around the world. Inflammation induced by FM is regarded as a major cause of respiratory disorder in humans. The purpose of this study was to evaluate the therapeutic efficacy of Shibashin Misena®, a functional food composed of various bioactive ingredients, on FM-induced respiratory disorders in mice.

MATERIALS AND METHODS

Briefly, 40 mice were divided equally into four groups: normal controls (NC); FM-induced control group (FC); FM group treated with Shibashin Misena® 0.1 mL/head/day (FM0.1); FM group treated with Shibashin Misena® 0.2 mL/head/day (FM0.2).

RESULTS

FM significantly induced TNF-α, IL-17A, IL-1β, and TGF-β in bronchoalveolar lavage fluid (BALF) collected from the FM mice. Compared with FC, Shibashin Misena® decreased TNF-α, IL-17A, and IL-1β levels in BALF, and histopathologic evaluations revealed that Shibashin Misena® treatment significantly reduced inflammatory-cell infiltration and fibrosis related collagen deposition in lung tissue.

CONCLUSION

This study demonstrated that Shibashin Misena® decreased FM-induced inflammation and fibrosis in lung tissue. Thus, Shibashin Misena® could be an effective supplement to prevent or improve FM-induced pulmonary disorders.

Time-course transcriptomic alterations reflect the pathophysiology of polyhexamethylene guanidine phosphate-induced lung injury in rats

Objective: Humidifier-disinfectant-induced lung injury is a new syndrome associated with a high mortality rate and characterized by severe hypersensitivity pneumonitis, acute interstitial pneumonia, or acute respiratory distress syndrome. Polyhexamethylene guanidine phosphate (PHMG-P), a guanidine-based antimicrobial agent, is a major component associated with severe lung injury. In-depth studies are needed to determine how PHMG-P affects pathogenesis at the molecular level. Therefore, in this study, we analyzed short-term (4 weeks) and long-term (10 weeks) PHMG-P-exposure-specific gene-expression patterns in rats to improve our understanding of time-dependent changes in fibrosis.Materials and methods: Gene-expression profiles were analyzed in rat lung tissues using DNA microarrays and bioinformatics tools.Results: Clustering analysis of gene-expression data showed different gene-alteration patterns in the short- and long-term exposure groups and higher sensitivity to gene-expression changes in the long-term exposure group than in the short-term exposure group. Supervised analysis revealed 34 short-term and 335 long-term exposure-specific genes, and functional analysis revealed that short-term exposure-specific genes were involved in PHMG-P-induced initial inflammatory responses, whereas long-term exposure-specific genes were involved in PHMG-P-related induction of chronic lung fibrosis.Conclusion: The results of transcriptomic analysis were consistent with lung histopathology results. These findings indicated that exposure-time-specific changes in gene expression closely reflected time-dependent pathological changes in PHMG-P-induced lung injury.

Inhibition of lysyl oxidase ameliorates renal injury by inhibiting CD44-mediated pericyte detachment and loss of peritubular capillaries

Renal fibrosis is a common pathological manifestation of almost all forms of kidney disease irrespective of the etiological cause. Microvascular rarefaction represents itself as an important phenomenon associated with renal fibrosis and shows strong correlation with decline in renal functions. Lysyl oxidase (LOX) catalyzes crosslinking of extracellular matrix (ECM) proteins including collagens, plays an important role in stabilization of degradation resistant matrix. Since, there seems to be a causal link between deposition of excessive ECM and microvascular rarefaction, we investigated the effects of reduction in renal fibrosis on microvascular rarefaction in acute as well as end stage kidney. We used a well-established unilateral ureteral obstruction (UUO)-induced renal fibrosis model to produce renal fibrosis in animals. We treated animals with a LOX inhibitor, β-aminopropionitrile (BAPN, 100 mg/kg, i.p.) and investigated effects on renal fibrosis and microvascular rarefaction. We observed that LOX inhibition was associated with reduction in collagen deposition in UUO-induced renal fibrosis animal model. Further, ECM normalization by LOX inhibition decreased the loss of peritubular capillaries (PTCs) in fibrotic kidney in acute study while the LOX inhibition failed to inhibit PTCs loss in end stage kidney. The results of present study suggested that inhibition of LOX reduces collagen deposition and renal fibrosis. Further, the reduction in fibrosis fails to protect from PTCs loss in chronic study suggesting the absence of strong link between reduction in fibrosis and improvement in PTCs in an end stage kidney.

Molecular regulation of TLR signaling in health and disease: mechano-regulation of macrophages and TLR signaling

Immune cells encounter tissues with vastly different biochemical and physical characteristics. Much of the research emphasis has focused on the role of cytokines and chemokines in regulating immune cell function, but the role of the physical microenvironment has received considerably less attention. The tissue mechanics, or stiffness, of healthy tissues varies dramatically from soft adipose tissue and brain to stiff cartilage and bone. Tissue mechanics also change due to fibrosis and with diseases such as atherosclerosis or cancer. The process by which cells sense and respond to their physical microenvironment is called mechanotransduction. Here we review mechanotransduction in immunologically important diseases and how physical characteristics of tissues regulate immune cell function, with a specific emphasis on mechanoregulation of macrophages and TLR signaling.

Lysyl Oxidases: Functions and Disorders

Lysyl oxidases (LOX) are copper-dependent enzymes that oxidize lysyl and hydroxylysyl residues in collagen and elastin, as a first step in the stabilization of these extracellular matrix proteins through the formation of covalent cross-linkages, an essential process for connective tissue maturation. Five different LOX enzymes have been identified in mammals, LOX and LOX-like (LOXL) 1 to 4, being genetically different protein products with a high degree of homology in the catalytic carboxy terminal end and a more variable amino terminal proregion. Intensive investigation in the last years has delineated the main biological functions of these enzymes and their involvement in several pathologies including fibrosis, cancer, and ocular disorders. This review article summarizes the major findings on the role of LOX isoforms, with particular focus on their contribution to the development and progression of human disorders.

Targeting metabolic dysregulation for fibrosis therapy

Fibrosis is the abnormal deposition of extracellular matrix, which can lead to organ dysfunction, morbidity, and death. The disease burden caused by fibrosis is substantial, and there are currently no therapies that can prevent or reverse fibrosis. Metabolic alterations are increasingly recognized as an important pathogenic process that underlies fibrosis across many organ types. As a result, metabolically targeted therapies could become important strategies for fibrosis reduction. Indeed, some of the pathways targeted by antifibrotic drugs in development - such as the activation of transforming growth factor-β and the deposition of extracellular matrix - have metabolic implications. This Review summarizes the evidence to date and describes novel opportunities for the discovery and development of drugs for metabolic reprogramming, their associated challenges, and their utility in reducing fibrosis. Fibrotic therapies are potentially relevant to numerous common diseases such as cirrhosis, non-alcoholic steatohepatitis, chronic renal disease, heart failure, diabetes, idiopathic pulmonary fibrosis, and scleroderma.

Matrix Mechanics as Regulatory Factors and Therapeutic Targets in Hepatic Fibrosis

The hallmark of liver fibrosis is excessive extracellular matrix (ECM) synthesis and deposition that improve liver matrix remodeling and stiffening. Increased matrix stiffness is not only a pathological consequence of liver fibrosis in traditional view, but also recognized as a key driver in pathological progression of hepatic fibrosis. Cells can perceive changes in the mechanical characteristics of hepatic matrix and respond by means of mechanical signal transduction pathways to regulate cell behavior. In this review, the authors first classify causes of liver matrix stiffening during fibrotic progression, such as higher degree of collagen cross-linking. The latest advances of the research on the matrix mechanics in regulating activation of HSCs or fibroblasts under two-dimensional (2D) and three-dimensional (3D) microenvironment is also classified and summarized. The mechanical signaling pathways involved in the process of hepatic matrix stiffening, such as YAP-TAZ signaling pathway, are further summarized. Finally, some potential therapeutic concepts and strategies based on matrix mechanics will be detailed. Collectively, these findings reinforce the importance of matrix mechanics in hepatic fibrosis, and underscore the value of clarifying its modulation in hopes of advancing the development of novel therapeutic targets and strategies for hepatic fibrosis.

B lymphocytes directly contribute to tissue fibrosis in patients with IgG4-related disease

BACKGROUND

IgG₄-related disease (IgG₄-RD) is a fibroinflammatory condition marked by rapid clinical improvement after selective depletion of B lymphocytes with rituximab. This feature suggests that B cells might participate in fibrogenesis and wound healing.

OBJECTIVE

In the present work we aimed to demonstrate that B lymphocytes contribute directly to tissue fibrosis in patients with IgG₄-RD.

METHODS

Total circulating CD19⁺ B lymphocytes, naive B cells, memory B cells, or plasmablasts from patients with IgG₄-RD were cultivated with human fibroblasts. Profibrotic soluble factors and collagen production in cocultures were assessed by using ELISAs and Luminex assays. RNA sequencing and quantitative RT-PCR were used to assess fibroblast activation in the presence of B cells, as well as induction of profibrotic pathways in B-cell subsets. Relevant profibrotic and inflammatory molecules were confirmed in vitro by using functional experiments and on IgG₄-RD tissue sections by using multicolor immunofluorescence studies.

RESULTS

B cells from patients with IgG₄-RD (1) produced the profibrotic molecule platelet-derived growth factor B and stimulated collagen production by fibroblasts; (2) expressed enzymes implicated in extracellular matrix remodeling, such as lysyl oxidase homolog 2; (3) produced the chemotactic factors CCL4, CCL5, and CCL11; and (4) induced production of these same chemokines by activated fibroblasts. Plasmablasts expressed sets of genes implicated in fibroblast activation and proliferation and therefore represent cells with intrinsic profibrotic properties.

CONCLUSION

We have demonstrated that B cells contribute directly to tissue fibrosis in patients with IgG₄-RD. These unanticipated profibrotic properties of B lymphocytes, particularly plasmablasts, might be relevant for fibrogenesis in patients with other fibroinflammatory disorders and for wound-healing processes in physiologic conditions.

Lysyl oxidase-like 2 depletion is protective in age-associated vascular stiffening

Vascular stiffening and its sequelae are major causes of morbidity and mortality in the elderly. The increasingly accepted concept of "smooth muscle cell (SMC) stiffness syndrome" along with matrix deposition has emerged in vascular biology to account for the mechanical phenotype of arterial aging, but the molecular targets remain elusive. In this study, using an unbiased proteomic analysis, we identified lysyl oxidase-like 2 (LOXL2) as a critical SMC mediator for age-associated vascular stiffening. We tested the hypothesis that loss of LOXL2 function is protective in aging-associated vascular stiffening. We determined that exogenous and endogenous nitric oxide markedly decreased LOXL2 abundance and activity in the extracellular matrix of isolated SMCs and LOXL2 endothelial cells suppress LOXL2 abundance in the aorta. In a longitudinal study, LOXL2+/- mice were protected from age-associated increase in pulse-wave velocity, an index of vascular stiffening, as occurred in littermate wild-type mice. Using isolated aortic segments, we found that LOXL2 mediates vascular stiffening in aging by promoting SMC stiffness, augmented SMC contractility, and vascular matrix deposition. Together, these studies establish LOXL2 as a nodal point for a new therapeutic approach to treat age-associated vascular stiffening. NEW & NOTEWORTHY Increased central vascular stiffness augments risk of major adverse cardiovascular events. Despite significant advances in understanding the genetic and molecular underpinnings of vascular stiffening, targeted therapy has remained elusive. Here, we show that lysyl oxidase-like 2 (LOXL2) drives vascular stiffening during aging by promoting matrix remodeling and vascular smooth muscle cell stiffening. Reduced LOXL2 expression protects mice from age-associated vascular stiffening and delays the onset of isolated systolic hypertension, a major consequence of stiffening.

Pulmonary environmental cues drive group 2 innate lymphoid cell dynamics in mice and humans

Group 2 innate lymphoid cells (ILC2s) are enriched in mucosal tissues (e.g., lung) and respond to epithelial cell-derived cytokines initiating type 2 inflammation. During inflammation, ILC2 numbers are increased in the lung. However, the mechanisms controlling ILC2 trafficking and motility within inflamed lungs remain unclear and are crucial for understanding ILC2 function in pulmonary immunity. Using several approaches, including lung intravital microscopy, we demonstrate that pulmonary ILC2s are highly dynamic, exhibit amoeboid-like movement, and aggregate in the lung peribronchial and perivascular spaces. They express distinct chemokine receptors, including CCR8, and actively home to CCL8 deposits located around the airway epithelium. Within lung tissue, ILC2s were particularly motile in extracellular matrix-enriched regions. We show that collagen-I drives ILC2 to markedly change their morphology by remodeling their actin cytoskeleton to promote environmental exploration critical for regulating eosinophilic inflammation. Our study provides previously unappreciated insights into ILC2 migratory patterns during inflammation and highlights the importance of environmental guidance cues in the lung in controlling ILC2 dynamics.

Inhibition of Diabetes-Induced Lysyl Oxidase Overexpression Prevents Retinal Vascular Lesions Associated With Diabetic Retinopathy

Purpose

The purpose of this study was to investigate the effect of reducing diabetes-induced lysyl oxidase (LOX) overexpression on vascular cell apoptosis and blood-retinal barrier (BRB) characteristics in diabetic rats.

Methods

Nondiabetic rats, diabetic rats, and diabetic rats intravitreally (IV) injected with LOX siRNA or scrambled (scram) siRNA were used in the study. One month after the onset of diabetes, intravitreal injections were initiated at monthly intervals for up to three times. At the end of study, retinal capillary networks were isolated, stained with periodic acid-Schiff (PAS) and hematoxylin, and assessed for acellular capillaries (AC) and pericyte loss (PL). To assess vascular leakage, extravasation of FITC-dextran was evaluated in retinal capillaries after tail vein injection of FITC-dextran. Western blot analysis was performed to determine retinal LOX level and confirm LOX downregulation via LOX siRNA intravitreal injection.

Results

LOX expression was significantly upregulated in retinas of diabetic rats compared with that of nondiabetic rats. Diabetic rats injected with LOX siRNA showed a significant decrease in retinal LOX expression compared with those of diabetic rats or scram siRNA-injected rats. In diabetic retinas, AC and PL were significantly increased compared with those of nondiabetic retinas. Importantly, diabetic rats treated with LOX siRNA exhibited a significant decrease in AC and PL counts compared with those of untreated diabetic rats. Furthermore, diabetic rats treated with LOX siRNA showed significant decrease in retinal vascular permeability compared with that of untreated diabetic rats.

Conclusions

Findings suggest LOX siRNA intravitreal injection may be effective against diabetes-induced LOX overexpression in preventing apoptosis and vascular leakage associated with diabetic retinopathy.

Fibre-based spectral ratio endomicroscopy for contrast enhancement of bacterial imaging and pulmonary autofluorescence

Fibre-based optical endomicroscopy (OEM) permits high resolution fluorescence microscopy in endoscopically accessible tissues. Fibred OEM has the potential to visualise pathologies targeted with fluorescent imaging probes and provide an in vivo in situ molecular pathology platform to augment disease understanding, diagnosis and stratification. Here we present an inexpensive widefield ratiometric fibred OEM system capable of enhancing the contrast between similar spectra of pathologically relevant fluorescent signals without the burden of complex spectral unmixing. As an exemplar, we demonstrate the potential of the platform to detect fluorescently labelled Gram-negative bacteria in the challenging environment of highly autofluorescent lung tissue in whole ex vivo human lungs.

LOX/LOXL in pulmonary fibrosis: potential therapeutic targets

Lysyl oxidase (LOX) and lysyl oxidase-like proteins (LOXL), a family of extracellular matrix (ECM) crosslinking enzymes that have been recognised as playing an important role in fibrogenesis for more than 40 years, are logical targets for antifibrotic treatments. Pulmonary fibrosis, especially idiopathic pulmonary fibrosis (IPF), is a progressive and lethal disease characterised by excessive deposition of ECM in the lung parenchyma. In this review, we discuss the current clinical approaches for IPF and review members of LOX family-LOX, LOXL1, LOXL2, LOXL3 and LOXL4 in IPF patients and in animal models of bleomycin-induced pulmonary fibrosis. Although these findings are controversial and require further validation, LOX/LOXL1/LOXL2 as potential therapeutic targets for IPF deserve continued attention. So far to our knowledge, LOXL3 or LOXL4 has not clearly shown specific therapeutic potential.

Telomere shortening activates TGF-β/Smads signaling in lungs and enhances both lipopolysaccharide and bleomycin-induced pulmonary fibrosis

Telomere shortening is associated with idiopathic pulmonary fibrosis (IPF), a high-morbidity and high-mortality lung disease of unknown etiology. However, the underlying mechanisms remain largely unclear. In this study, wild-type (WT) mice with normal telomeres and generation 3 (G3) or G2 telomerase RNA component (TERC) knockout Terc^-/- mice with short telomeres were treated with and without lipopolysaccharide (LPS) or bleomycin by intratracheal injection. We show that under LPS induction, G3 Terc^-/- mice develop aggravated pulmonary fibrosis as indicated by significantly increased α-SMA, collagen I and hydroxyproline content. Interestingly, TGF-β/Smads signaling is markedly activated in the lungs of G3 Terc^-/- mice, as indicated by markedly elevated levels of phosphorylated Smad3 and TGF-β1, compared with those of WT mice. This TGF-β/Smads signaling activation is significantly increased in the lungs of LPS-treated G3 Terc^-/- mice compared with those of LPS-treated WT or untreated G3 Terc^-/- mice. A similar pattern of TGF-β/Smads signaling activation and the enhancing role of telomere shortening in pulmonary fibrosis are also confirmed in bleomycin-induced model. Moreover, LPS challenge produced more present cellular senescence, apoptosis and infiltration of innate immune cells, including macrophages and neutrophils in the lungs of G3 Terc^-/- mice, compared with WT mice. To our knowledge, this is the first time to report telomere shortening activated TGF-β/Smads signaling in lungs. Our data suggest that telomere shortening cooperated with environment-induced lung injury accelerates the development of pulmonary fibrosis, and telomere shortening confers an inherent enhancing factor to the genesis of IPF through activation of TGF-β/Smads signaling.

Idiopathic pulmonary fibrosis: Epithelial-mesenchymal interactions and emerging therapeutic targets

Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic disease of the lung that is marked by progressive decline in pulmonary function and ultimately respiratory failure. Genetic and environmental risk factors have been identified that indicate injury to, and dysfunction of the lung epithelium is central to initiating the pathogenic process. Following injury to the lung epithelium, growth factors, matrikines and extracellular matrix driven signaling together activate a variety of repair pathways that lead to inflammatory cell recruitment, fibroblast proliferation and expansion of the extracellular matrix, culminating in tissue fibrosis. This tissue fibrosis then leads to changes in the biochemical and biomechanical properties of the extracellular matrix, which potentiate profibrotic mechanisms through a "feed-forward cycle." This review provides an overview of the interactions of the pathogenic mechanisms of IPF with a focus on epithelial-mesenchymal crosstalk and the extracellular matrix as a therapeutic target for idiopathic pulmonary fibrosis.

Laminin α1 is a genetic modifier of TGF-β1-stimulated pulmonary fibrosis

The pathogenetic mechanisms underlying the pathologic fibrosis in diseases such as idiopathic pulmonary fibrosis (IPF) are poorly understood. To identify genetic factors affecting susceptibility to IPF, we analyzed a murine genetic model of IPF in which a profibrotic cytokine (TGF-β1) was expressed in the lungs of 10 different inbred mouse strains. Surprisingly, the extent of TGF-β1-induced lung fibrosis was highly strain dependent. Haplotype-based computational genetic analysis and gene expression profiling of lung tissue obtained from fibrosis-susceptible and -resistant strains identified laminin α1 (Lama1) as a genetic modifier for susceptibility to IPF. Subsequent studies demonstrated that Lama1 plays an important role in multiple processes that affect the pulmonary response to lung injury and susceptibility to fibrosis, which include: macrophage activation, fibroblast proliferation, myofibroblast transformation, and the production of extracellular matrix. Also, Lama1 mRNA expression was significantly increased in lung tissue obtained from IPF patients. These studies identify Lama1 as the genetic modifier of TGF-β1 effector responses that significantly affects the development of pulmonary fibrosis.

The apparent competitive action of ECM proteases and cross-linking enzymes during fibrosis: Applications to drug discovery

Progressive loss of organ function in most organs is associated with fibrosis, a tissue state associated with abnormal matrix buildup. If highly progressive, the fibrotic process eventually leads to organ failure and death. Fibrosis is a basic connective tissue lesion defined by the increase in the amount of fibrillar extracellular matrix (ECM) components in a tissue or organ. In addition, intrinsic changes in important structural cells can induce the fibrotic response by regulating the differentiation, recruitment, proliferation and activation of extracellular matrix-producing myofibroblasts. ECM enzymes belonging to the family of matrix metalloproteinases (MMPs) and lysyl oxidases (LOXs) play a crucial role in ECM remodeling and regeneration. MMPs have a catalytic role in degradation of ECM, whereas LOX/LOXLs mediate ECM, especially collagen, cross-linking and stiffening. Importantly, enzymes from both families are elevated during the fibrotic response to tissue injury and its resolution. Yet, the apparent molecular competition or antagonistic activities of these enzyme families during the various stages of fibrosis is often overlooked. In this review, we discuss the diverse roles of MMPs and LOX/LOXL2 in chronic organ fibrosis. Finally, we review contemporary therapeutic strategies for fibrosis treatment, based on neutralization of MMP and LOX activity, as well as the development of novel drug delivery approaches.

Matrix Stiffness: the Conductor of Organ Fibrosis

PURPOSE OF REVIEW

Organ fibrosis is a lethal component of scleroderma. The hallmark of scleroderma fibrosis is extensive extracellular matrix (ECM) deposition by activated myofibroblasts, specialized hyper-contractile cells that promote ECM remodeling and matrix stiffening. The purpose of this review is to discuss novel mechanistic insight into myofibroblast activation in scleroderma.

RECENT FINDINGS

Matrix stiffness, traditionally viewed as an end point of organ fibrosis, is now recognized as a critical regulator of tissue fibrogenesis that hijacks the normal physiologic wound-healing program to promote organ fibrosis. Here, we discuss how matrix stiffness orchestrates fibrosis by controlling three fundamental pro-fibrotic mechanisms: (a) mechanoactivation of myofibroblasts, (b) integrin-mediated latent transforming growth factor beta 1 (TGF-β1) activation, and (c) activation of non-canonical TGF-β1 signaling pathways. We also summarize novel therapeutic targets for anti-fibrotic therapy based on the mechanobiology of scleroderma. Future research on mechanobiology of scleroderma may lead to important clinical applications such as improved diagnosis and treatment of patients with scleroderma and other fibrotic-related diseases.

IGFBP-5 Promotes Fibrosis via Increasing Its Own Expression and That of Other Pro-fibrotic Mediators

Pulmonary fibrosis is a hallmark of diseases such as systemic sclerosis (SSc, scleroderma) and idiopathic pulmonary fibrosis (IPF). To date, the therapeutic options for patients with pulmonary fibrosis are limited, and organ transplantation remains the most effective option. Insulin-like growth factor-binding protein 5 (IGFBP-5) is a conserved member of the IGFBP family of proteins that is overexpressed in SSc and IPF. In this study, we demonstrate that both exogenous and adenovirally expressed IGFBP-5 promote fibrosis by increasing the production of extracellular matrix (ECM) genes and the expression of pro-fibrotic genes in primary human lung fibroblasts. IGFBP-5 increased expression of the pro-fibrotic growth factor CTGF and levels of the matrix crosslinking enzyme lysyl oxidase (LOX). Silencing of IGFBP-5 had different effects in lung fibroblasts from normal donors and patients with SSc or IPF. Moreover, we show that IGFBP-5 increases expression of ECM genes, CTGF, and LOX in human lung tissues maintained in organ culture. Together, our data extend our previous findings and demonstrate that IGFBP-5 exerts its pro-fibrotic activity by directly inducing expression of ECM and pro-fibrotic genes. Further, IGFBP-5 promotes its own expression, generating a positive feedback loop. This suggests that IGFBP-5 likely acts in concert with other growth factors to drive fibrosis and tissue remodeling.

Hypoxia-inducible factor-1α regulates epithelial-to-mesenchymal transition in paraquat-induced pulmonary fibrosis by activating lysyl oxidase

Pulmonary fibrosis (PF) is one of the most prevalent causes of death following paraquat (PQ) poisoning. As demonstrated in previous studies by the present authors, epithelial-to-mesenchymal transition (EMT) is associated with PQ-induced PF. In addition, hypoxia-inducible factor-1α (HIF-1α) and lysyl oxidase (LOX) promote EMT following PQ poisoning. However, the association between HIF-1α- and LOX-mediated regulation of EMT remains unclear. The present study investigated the association between HIF-1α and LOX with regard to PQ-induced EMT. A549 and RLE-6TN cells were treated with PQ, and HIF-1α and LOX expression was silenced with short interfering RNAs. Changes in the expression of HIF-1α, LOX, β-catenin and EMT-related makers were detected using real-time quantitative polymerase chain reaction, immunofluorescence, and western blotting. HIF-1α and LOX were associated with PQ-induced EMT, and their expression levels were significantly increased (P<0.05). LOX expression was significantly decreased following PQ poisoning when HIF-1α expression was inhibited (P<0.05). However, the level of HIF-1α did not change significantly when LOX was silenced. The expression level of β-catenin and the degree of EMT were significantly decreased following HIF-1α and LOX silencing in both cell lines (P<0.05). The association between HIF-1α and LOX in regulating EMT during PQ-induced PF may be unidirectional. HIF-1α may regulate PQ-induced EMT through the LOX/β-catenin pathway.