Growth Hormone-Releasing Hormone in Lung Physiology and Pulmonary Disease

Growth hormone-releasing hormone and its analogues in health and disease

Growth hormone-releasing hormone (GHRH) and its ability to stimulate the production and release of growth hormone from the pituitary were discovered more than four decades ago. Since then, this hormone has been studied extensively and research into its functions is still ongoing. GHRH has multifaceted roles beyond the originally identified functions that encompass a variety of direct extrapituitary effects. In this Review, we illustrate the different biological activities of GHRH, covering the effects of GHRH agonists and antagonists in physiological and pathological contexts, along with the underlying mechanisms. GHRH and GHRH analogues have been implicated in cell growth, wound healing, cell death, inflammation, immune functions, mood disorders, feeding behaviour, neuroprotection, diabetes mellitus and obesity, as well as cardiovascular, lung and neurodegenerative diseases and some cancers. The positive effects observed in preclinical models in vitro and in vivo strongly support the potential use of GHRH agonists and antagonists as clinical therapeutics.

Growth hormone-releasing hormone and cancer

The hypothalamic hormone growth hormone-releasing hormone (GHRH), in addition to promoting the synthesis and release of growth hormone (GH), stimulates the proliferation of human normal and malignant cells by binding to GHRH-receptor (GHRH-R) and its main splice variant, SV1. Both GHRH and GHRH-Rs are expressed in various cancers, forming a stimulatory pathway for cancer cell growth; additionally, SV1 possesses ligand independent proliferative effects. Therefore, targeting GHRH-Rs pharmacologically has been proposed for the treatment of cancer. Various classes of synthetic GHRH antagonists have been developed, endowed with strong anticancer activity in vitro and in vivo, in addition to displaying anti-inflammatory, antioxidant and immune-modulatory functions. GHRH antagonists exert indirect effects by blocking the pituitary GH/hepatic insulin-like growth factor I (IGF-I) axis, or directly inhibiting the binding of GHRH on tumor GHRH-Rs. Additionally, GHRH antagonists block the mitogenic functions of SV1 in tumor cells. This review illustrates the main findings on the antitumor effects of GHRH antagonists in experimental human cancers, along with their underlying mechanisms. The development of GHRH antagonists, with reduced toxicity and high stability, could lead to novel therapeutic agents for the treatment of cancer and inflammatory diseases.

Alleviation of LPS-induced Endothelial Injury due to GHRH Antagonist Treatment

Background

GHRH is produced in the hypothalamus and affects various tissues beyond the pituitary, including the lungs. GHRH antagonists exert anti-inflammatory properties in several experimental models of disease, but their role inprotecting the endothelial barrier during inflammation is less understood. This study investigates the effects ofGHRHAnt on LPS-induced endothelial dysfunction.

Methods

BPAEC and HMVEC-L cells were exposed to LPS to induce endothelial injury. GHRHAnt was administered eitherpre- or post-LPS treatment. Western blot analysis was used to evaluate protein expression levels. Paracellularpermeability was assessed utilizing FITC-dextran assay to evaluate endothelial barrier function.

Results

GHRHAnt post-treatment significantly reduced LPS-induced MLC2 phosphorylation and cofilin activation inBPAECs. Furthermore, pretreatment with GHRHAnt enhanced barrier function and ameliorated LPS-inducedhyperpermeability in both human and bovine endothelial cells.

Conclusions

GHRHAnt treatment mitigates LPS-induced endothelial barrier dysfunction. These findings suggest that GHRHAntcould serve as potential therapeutic agents towards endothelial dysfunction-related illness (e.g. sepsis).

Role of Insulin-like Growth Factor-1 Receptor in Tobacco Smoking-Associated Lung Cancer Development

Cancer remains a significant global health concern, with lung cancer consistently leading as one of the most common malignancies. Genetic aberrations involving receptor tyrosine kinases (RTKs) are known to be associated with cancer initiation and development, but RTK involvement in smoking-associated lung cancer cases is not well understood. The Insulin-like Growth Factor 1 Receptor (IGF-1R) is a receptor that plays a critical role in lung cancer development. Its signaling pathway affects the growth and survival of cancer cells, and high expression is linked to poor prognosis and resistance to treatment. Several reports have shown that by activating IGF-1R, tobacco smoke-related carcinogens promote lung cancer and chemotherapy resistance. However, the relationship between IGF-1R and cancer is complex and can vary depending on the type of cancer. Ongoing investigations are focused on developing therapeutic strategies to target IGF-1R and overcome chemotherapy resistance. Overall, this review explores the intricate connections between tobacco smoke-specific carcinogens and the IGF-1R pathway in lung carcinogenesis. This review further highlights the challenges in using IGF-1R inhibitors as targeted therapy for lung cancer due to structural similarities with insulin receptors. Overcoming these obstacles may require a comprehensive approach combining IGF-1R inhibition with other selective agents for successful cancer treatment.

Protective Activities of Growth Hormone-Releasing Hormone Antagonists against Toxin-Induced Endothelial Injury

GHRH regulates the secretion of GH from the anterior pituitary gland, previously associated with cancer progression and inflammation. An emerging body of evidence suggests that GHRHAnt support endothelial barrier function, but the mechanisms mediating these events are not completely understood. In the present study, it is demonstrated that the GHRHAnt JV-1-36 counteracts barrier dysfunction due to LPS or LTA treatment in HUVECs, utilizing the Dextran-FITC assay. Moreover, it is shown in BPAECs that these bacterial toxins increase ROS generation, and that this effect is counteracted by JV-1-36, which reinstates the redox balance. The possible involvement of NEK2 in the beneficial activities of GHRHAnt in IFN-γ- and LPS-triggered hyperpermeability was also assessed, since that kinase is involved in inflammatory responses. NEK2 was increased in the inflamed cells, and JV-1-36 counteracted those endothelial events. Our data support the beneficial effects of GHRHAnt in toxin-induced endothelial injury.

Growth hormone-releasing hormone receptor antagonist MIA-602 attenuates cardiopulmonary injury induced by BSL-2 rVSV-SARS-CoV-2 in hACE2 mice

COVID-19 pneumonia causes acute lung injury and acute respiratory distress syndrome (ALI/ARDS) characterized by early pulmonary endothelial and epithelial injuries with altered pulmonary diffusing capacity and obstructive or restrictive physiology. Growth hormone-releasing hormone receptor (GHRH-R) is expressed in the lung and heart. GHRH-R antagonist, MIA-602, has been reported to modulate immune responses to bleomycin lung injury and inflammation in granulomatous sarcoidosis. We hypothesized that MIA-602 would attenuate rVSV-SARS-CoV-2-induced pulmonary dysfunction and heart injury in a BSL-2 mouse model. Male and female K18-hACE2tg mice were inoculated with SARS-CoV-2/USA-WA1/2020, BSL-2-compliant recombinant VSV-eGFP-SARS-CoV-2-Spike (rVSV-SARS-CoV-2), or PBS, and lung viral load, weight loss, histopathology, and gene expression were compared. K18-hACE2tg mice infected with rVSV-SARS-CoV-2 were treated daily with subcutaneous MIA-602 or vehicle and conscious, unrestrained plethysmography performed on days 0, 3, and 5 (n = 7 to 8). Five days after infection mice were killed, and blood and tissues collected for histopathology and protein/gene expression. Both native SARS-CoV-2 and rVSV-SARS-CoV-2 presented similar patterns of weight loss, infectivity (~60%), and histopathologic changes. Daily treatment with MIA-602 conferred weight recovery, reduced lung perivascular inflammation/pneumonia, and decreased lung/heart ICAM-1 expression compared to vehicle. MIA-602 rescued altered respiratory rate, increased expiratory parameters (Te, PEF, EEP), and normalized airflow parameters (Penh and Rpef) compared to vehicle, consistent with decreased airway inflammation. RNASeq followed by protein analysis revealed heightened levels of inflammation and end-stage necroptosis markers, including ZBP1 and pMLKL induced by rVSV-SARS-CoV-2, that were normalized by MIA-602 treatment, consistent with an anti-inflammatory and pro-survival mechanism of action in this preclinical model of COVID-19 pneumonia.

The role of airway mucus and diseased pulmonary epithelium on the absorption of inhaled antibodies

Inhaled antibody therapy for the treatment of respiratory diseases is a promising strategy to maximize pulmonary exposure and reduce side effects associated with parenteral administration. However, the development of inhaled antibodies is often challenging due to a poor understanding of key mechanisms governing antibody absorption and clearance in healthy and diseased pulmonary epithelium. Here, we utilize well established Human Bronchial Epithelial Cell (HBEC) models grown at air-liquid interface to study the absorption process of antibodies and antibody fragments. With these cellular models, we recapitulate the morphology and function of healthy and diseased pulmonary epithelium, and incorporate the mucosal barrier to enable the investigation of both cellular permeability as well as mucodiffusion. We studied the saturation of antibody transport across the HBEC barriers and estimated the impact of disease-like epithelial barriers on antibody paracellular transport. Additionally, we identified a potential role of neonatal Fc receptor (FcRn)-independent and target-mediated transcytosis in the transport of Fragment antigen-binding (Fab) and F(ab)2 antibody fragments. Lastly, our models were able to pinpoint an impaired antibody diffusion across mucus gels. These mechanistic cellular models are promising in vitro tools to inform Physiologically-based Pharmacokinetic (PBPK) computational models for dose prediction toward de-risking the development of inhaled biologics.

Xiebai Zengye decoction improves respiratory function and attenuates inflammation in juvenile rats with postinfection cough via regulating ERK signaling pathway

This study aimed to determine the effects of Xiebai Zengye decoction (XBZY) on airway inflammation and respiratory function in rats with postinfectious cough (PIC), and its regulatory effects on the extracellular signal-regulated kinase (ERK) signaling pathway. Compared with the normal group, the rats from the PIC group had significantly shortened expiratory time (TE) and enhanced pause (EEP), increased resistance (RT), and enhanced pause (Penh), along with increased levels of serum interleukin-4 (IL-4) and IL-6, and decreased levels of IL-10. The lung and colon tissues of rats from the PIC group showed histopathological changes, including inflammatory cell infiltration, damaged mucosal epithelium, and crypt structure, with significantly increased ERK mRNA and protein expression levels. Treatment with XBZY and montelukast sodium (MAS) improved the respiratory function and serum cytokine levels, reduced tissue inflammation, and decreased ERK mRNA and protein expression levels in the lung and colon tissues. In the lung tissues, XBZY treatment significantly decreased the expression of phosphorylated-ERK (p-ERK) protein, as well as p-MEK1/2, p-ERK1/2, and p-c-Fos proteins, while in the colon tissues, XBZY significantly decreased the expression of p-ERK1/2 and p-c-Fos proteins. However, MAS treatment only showed significant improvement in the lung tissue inflammation score, and the expression level of p-ERK protein in the lung tissue was decreased. In conclusion, the present study suggests that XBZY has a potential therapeutic effect on PIC by improving respiratory function and attenuating inflammation, and this effect may be associated with the inhibition of the ERK signaling pathway. These findings could provide a new direction for the development of treatments for PIC. However, further research is needed to elucidate the underlying molecular mechanisms of XBZY and to confirm its safety and efficacy in clinical trials.

Growth hormone-releasing hormone antagonist MIA-602 inhibits inflammation induced by SARS-CoV-2 spike protein and bacterial lipopolysaccharide synergism in macrophages and human peripheral blood mononuclear cells

COVID-19 is characterized by an excessive inflammatory response and macrophage hyperactivation, leading, in severe cases, to alveolar epithelial injury and acute respiratory distress syndrome. Recent studies have reported that SARS-CoV-2 spike (S) protein interacts with bacterial lipopolysaccharide (LPS) to boost inflammatory responses in vitro, in macrophages and peripheral blood mononuclear cells (PBMCs), and in vivo. The hypothalamic hormone growth hormone-releasing hormone (GHRH), in addition to promoting pituitary GH release, exerts many peripheral functions, acting as a growth factor in both malignant and non-malignant cells. GHRH antagonists, in turn, display potent antitumor effects and antinflammatory activities in different cell types, including lung and endothelial cells. However, to date, the antinflammatory role of GHRH antagonists in COVID-19 remains unexplored. Here, we examined the ability of GHRH antagonist MIA-602 to reduce inflammation in human THP-1-derived macrophages and PBMCs stimulated with S protein and LPS combination. Western blot and immunofluorescence analysis revealed the presence of GHRH receptor and its splice variant SV1 in both THP-1 cells and PBMCs. Exposure of THP-1 cells to S protein and LPS combination increased the mRNA levels and protein secretion of TNF-α and IL-1β, as well as IL-8 and MCP-1 gene expression, an effect hampered by MIA-602. Similarly, MIA-602 hindered TNF-α and IL-1β secretion in PBMCs and reduced MCP-1 mRNA levels. Mechanistically, MIA-602 blunted the S protein and LPS-induced activation of inflammatory pathways in THP-1 cells, such as NF-κB, STAT3, MAPK ERK1/2 and JNK. MIA-602 also attenuated oxidative stress in PBMCs, by decreasing ROS production, iNOS and COX-2 protein levels, and MMP9 activity. Finally, MIA-602 prevented the effect of S protein and LPS synergism on NF-кB nuclear translocation and activity. Overall, these findings demonstrate a novel antinflammatory role for GHRH antagonists of MIA class and suggest their potential development for the treatment of inflammatory diseases, such as COVID-19 and related comorbidities.

Discovery of potential biomarkers for lung cancer classification based on human proteome microarrays using Stochastic Gradient Boosting approach

PURPOSE

Early identification of lung cancer (LC) will considerably facilitate the intervention and prevention of LC. The human proteome micro-arrays approach can be used as a "liquid biopsy" to diagnose LC to complement conventional diagnosis, which needs advanced bioinformatics methods such as feature selection (FS) and refined machine learning models.

METHODS

A two-stage FS methodology by infusing Pearson's Correlation (PC) with a univariate filter (SBF) or recursive feature elimination (RFE) was used to reduce the redundancy of the original dataset. The Stochastic Gradient Boosting (SGB), Random Forest (RF), and Support Vector Machine (SVM) techniques were applied to build ensemble classifiers based on four subsets. The synthetic minority oversampling technique (SMOTE) was used in the preprocessing of imbalanced data.

RESULTS

FS approach with SBF and RFE extracted 25 and 55 features, respectively, with 14 overlapped ones. All three ensemble models demonstrate superior accuracy (ranging from 0.867 to 0.967) and sensitivity (0.917 to 1.00) in the test datasets with SGB of SBF subset outperforming others. The SMOTE technique has improved the model performance in the training process. Three of the top selected candidate biomarkers (LGR4, CDC34, and GHRHR) were highly suggested to play a role in lung tumorigenesis.

CONCLUSION

A novel hybrid FS method with classical ensemble machine learning algorithms was first used in the classification of protein microarray data. The parsimony model constructed by the SGB algorithm with the appropriate FS and SMOTE approach performs well in the classification task with higher sensitivity and specificity. Standardization and innovation of bioinformatics approach for protein microarray analysis need further exploration and validation.

Growth hormone-releasing hormone antagonists protect against hydrochloric acid-induced endothelial injury in vitro

Growth hormone-releasing hormone (GHRH) regulates the synthesis of growth hormone from the anterior pituitary gland, and it is involved in inflammatory responses. On the other hand, GHRH antagonists (GHRHAnt) exhibit the opposite effects, resulting in endothelial barrier enhancement. Exposure to hydrochloric acid (HCL) is associated with acute and chronic lung injury. In this study, we investigate the effects of GHRHAnt in HCL-induced endothelial barrier dysfunction, utilizing commercially available bovine pulmonary artery endothelial cells (BPAEC). Cell viability was measured by utilizing 3-(4,5-dimethylthiazol2-yl)- 2,5-diphenyltetrazolium bromide (MTT) assay. Moreover, fluorescein isothiocyanate (FITC)-dextran was used to assess barrier function. Our observations suggest that GHRHAnt exert protective effects against HCL-induced endothelial breakdown, since those peptides counteract HCL-triggered paracellular hyperpermeability. Based on those findings, we propose that GHRHAnt represent a new therapeutic approach towards HCL-induced endothelial injury.

Silica-collagen nanoformulations with extended human growth hormone release

Growth hormone deficiency has been treated by the daily administration of recombinant human growth hormone (hGH) for decades. Patient compliance to this treatment is generally incomplete due to challenges including dose frequency and lack of perceived benefits. This stimulates the research on new formulations to reduce the number of periodic administrations. In this study silica nanoparticles and silica-collagen nanocomposites were evaluated for hGH loading and release. Bare nanoparticles showed higher hGH adsorption capacity than thiol- and isobutyl-bearing particles of similar diameters. Monitoring of bound protein conformation changes indicated hGH structure retention when adsorbed on bare silica nanoparticles and suggested no alterations on protein activity. Protein-loaded particles incorporated into collagen matrices (silica-collagen nanocomposites) showed a progressive protein release profile different from the observed for hGH-loaded silica nanoparticles and hGH-loaded collagen matrices. While both the collagen and the silica nanoparticle systems reached a 100 % release after 4 and 7 days respectively, silica-collagen nanocomposites showed a bi-phasic prolonged hGH release reaching approximately an 80 % after 15 days. These findings suggest that biocompatible silica-collagen nanocomposites could be used as vehicles for the prolonged delivery of hGH which could lead to a potential reduction in the number of periodic administrations.

Alveolar epithelial cell growth hormone releasing hormone receptor in alveolar epithelial inflammation

Purpose: Growth hormone-releasing hormone (GHRH) is a 44-amino acid peptide that regulates growth hormone (GH) secretion. We hypothesized that GHRH receptor (GHRH-R) in alveolar type 2 (AT2) cells could modulate pro-inflammatory and possibly subsequent pro-fibrotic effects of lipopolysaccharide (LPS) or cytokines, such that AT2 cells could participate in lung inflammation and fibrosis. Methods: We used human alveolar type 2 (iAT2) epithelial cells derived from induced pluripotent stem cells (iPSC) to investigate how GHRH-R modulates gene and protein expression. We tested iAT2 cells' gene expression in response to LPS or cytokines, seeking whether these mechanisms caused endogenous production of pro-inflammatory molecules or mesenchymal markers. Quantitative real-time PCR (RT-PCR) and Western blotting were used to investigate differential expression of epithelial and mesenchymal markers. Result: Incubation of iAT2 cells with LPS increased expression of IL1-β and TNF-α in addition to mesenchymal genes, including ACTA2, FN1 and COL1A1. Alveolar epithelial cell gene expression due to LPS was significantly inhibited by GHRH-R peptide antagonist MIA-602. Incubation of iAT2 cells with cytokines like those in fibrotic lungs similarly increased expression of genes for IL1-β, TNF-α, TGFβ-1, Wnt5a, smooth muscle actin, fibronectin and collagen. Expression of mesenchymal proteins, such as N-cadherin and vimentin, were also elevated after prolonged exposure to cytokines, confirming epithelial production of pro-inflammatory molecules as an important mechanism that might lead to subsequent fibrosis. Conclusion: iAT2 cells clearly expressed the GHRH-R. Exposure to LPS or cytokines increased iAT2 cell production of pro-inflammatory factors. GHRH-R antagonist MIA-602 inhibited pro-inflammatory gene expression, implicating iAT2 cell GHRH-R signaling in lung inflammation and potentially in fibrosis.

Antagonist of Growth Hormone-Releasing Hormone Potentiates the Antitumor Effect of Pemetrexed and Cisplatin in Pleural Mesothelioma

Pleural mesothelioma (PM) is an aggressive cancer with poor prognosis and no effective therapies, mainly caused by exposure to asbestos. Antagonists of growth hormone-releasing hormone (GHRH) display strong antitumor effects in many experimental cancers, including lung cancer and mesothelioma. Here, we aimed to determine whether GHRH antagonist MIA-690 potentiates the antitumor effect of cisplatin and pemetrexed in PM. In vitro, MIA-690, in combination with cisplatin and pemetrexed, synergistically reduced cell viability, restrained cell proliferation and enhanced apoptosis, compared with drugs alone. In vivo, the same combination resulted in a strong growth inhibition of MSTO-211H xenografts, decreased tumor cell proliferation and increased apoptosis. Mechanistically, MIA-690, particularly with chemotherapeutic drugs, inhibited proliferative and oncogenic pathways, such as MAPK ERK1/2 and cMyc, and downregulated cyclin D1 and B1 mRNAs. Inflammatory pathways such as NF-kB and STAT3 were also reduced, as well as oxidative, angiogenic and tumorigenic markers (iNOS, COX-2, MMP2, MMP9 and HMGB1) and growth factors (VEGF and IGF-1). Overall, these findings strongly suggest that GHRH antagonists of MIA class, such as MIA-690, could increase the efficacy of standard therapy in PM.

Interplay Between the Immune and Endocrine Systems in the Lung: Implications for TB Susceptibility

The role of the endocrine system on the immune response, especially in the lung, remains poorly understood. Hormones play a crucial role in the development, homeostasis, metabolism, and response to the environment of cells and tissues. Major infectious and metabolic diseases, such as tuberculosis and diabetes, continue to converge, necessitating the development of a clearer understanding of the immune and endocrine interactions that occur in the lung. Research in bacterial respiratory infections is at a critical point, where the limitations in identifying and developing antibiotics is becoming more profound. Hormone receptors on alveolar and immune cells may provide a plethora of targets for host-directed therapy. This review discusses the interactions between the immune and endocrine systems in the lung. We describe hormone receptors currently identified in the lungs, focusing on the effect hormones have on the pulmonary immune response. Altered endocrine responses in the lung affect the balance between pro- and anti-inflammatory immune responses and play a role in the response to infection in the lung. While some hormones, such as leptin, resistin and lipocalin-2 promote pro-inflammatory responses and immune cell infiltration, others including adiponectin and ghrelin reduce inflammation and promote anti-inflammatory cell responses. Furthermore, type 2 diabetes as a major endocrine disease presents with altered immune responses leading to susceptibility to lung infections, such as tuberculosis. A better understanding of these interactions will expand our knowledge of the mechanisms at play in susceptibility to infectious diseases and may reveal opportunities for the development of host-directed therapies.

Molecular mechanisms of coronary microvascular endothelial dysfunction in diabetes mellitus: focus on mitochondrial quality surveillance

Coronary microvascular endothelial dysfunction is both a culprit and a victim of diabetes, and can accelerate diabetes-related microvascular and macrovascular complications by promoting vasoconstrictive, pro-inflammatory and pro-thrombotic responses. Perturbed mitochondrial function induces oxidative stress, disrupts metabolism and activates apoptosis in endothelial cells, thus exacerbating the progression of coronary microvascular complications in diabetes. The mitochondrial quality surveillance (MQS) system responds to stress by altering mitochondrial metabolism, dynamics (fission and fusion), mitophagy and biogenesis. Dysfunctional mitochondria are prone to fission, which generates two distinct types of mitochondria: one with a normal and the other with a depolarized mitochondrial membrane potential. Mitochondrial fusion and mitophagy can restore the membrane potential and homeostasis of defective mitochondrial fragments. Mitophagy-induced decreases in the mitochondrial population can be reversed by mitochondrial biogenesis. MQS abnormalities induce pathological mitochondrial fission, delayed mitophagy, impaired metabolism and defective biogenesis, thus promoting the accumulation of unhealthy mitochondria and the activation of mitochondria-dependent apoptosis. In this review, we examine the effects of MQS on mitochondrial fitness and explore the association of MQS disorders with coronary microvascular endothelial dysfunction in diabetes. We also discuss the potential to treat diabetes-related coronary microvascular endothelial dysfunction using novel MQS-altering drugs.

Antagonist of growth hormone-releasing hormone MIA-690 attenuates the progression and inhibits growth of colorectal cancer in mice

Colorectal cancer (CRC) is an aggressive tumor in which new treatment options deliver negative results on cure rates and long-term survival. The anticancer effects of growth hormone-releasing hormone (GHRH) antagonists have been reported in various experimental tumors, but their activity in CRC is unknown. In the present study, we demonstrated that chronic treatment with GHRH antagonist of MIAMI class, MIA-690, promoted survival and gradually blunted tumor progression in experimentally induced colitis-associated cancer in mice, paralleled by reduced inflammation in colon tissue. In particular, MIA-690 improved disease activity index score, and reduced loss of weight and mortality, by improving the survival rates, compared with vehicle-treated group. MIA-690 was also found to reduce various inflammatory and oxidative markers, such as serotonin, prostaglandin (PG)E2 and 8-iso-PGF2α levels, as well as COX-2, iNOS, TNF-α, IL-6 and NF-kB gene expression. Moreover, MIA-690 inhibited the protein expression of c-Myc, P-AKT and Bcl-2 and upregulated p53 protein expression. In conclusion, we showed that MIA-690 suppresses CRC progression and growth by reducing inflammatory and oxidative markers and modulating apoptotic and oncogenic pathways. Further investigations are required for translating these findings into the clinics.

Regulation of the IGF1 signaling pathway is involved in idiopathic pulmonary fibrosis induced by alveolar epithelial cell senescence and core fucosylation

Idiopathic pulmonary fibrosis (IPF) mainly occurs in elderly people over the age of sixty. IPF pathogenesis is associated with alveolar epithelial cells (AECs) senescence. Activation of PI3K/AKT signaling induced by insulin-like growth factor 1 (IGF1) participates in AEC senescence and IPF by releasing CTGF, TGF-β1, and MMP9. Our previous study demonstrated that core fucosylation (CF) modification, catalyzed by a specific core fucosyltransferase (FUT8) can regulate the activation of multiple signaling pathways, and inhibiting CF can alleviate pulmonary fibrosis in mice induced by bleomycin. However, whether CF is involved in IGF1-mediated AEC senescence in IPF remains unclear. In this study, we found that the IGF1/PI3K/AKT signaling pathway was activated in IPF lung tissue. Meanwhile, CF was present in senescent AECs. We also showed that IGF1 could induce AECs senescence with enhanced CF in vivo and in vitro. Inhibiting CF alleviated AECs senescence and pulmonary fibrosis induced by IGF1. In addition, activation of IGF1/PI3K/AKT signaling depends on CF. In conclusion, this study confirmed that CF is an important target regulating the IGF1 signaling pathway in AEC senescence and IPF, which might be a candidate target to treat IPF in the future.

Unfolded Protein Response: A Regulator of the Endothelial Barrier

Recent evidence suggest that the endothelial barrier function is enhanced by the mild activation of the unfolded protein response (UPR), which aims to suppress abnormal increases of endoplasmic reticulum stress. Heat shock protein 90 inhibitors and growth hormone releasing hormone antagonists exert the capacity to activate this multifaceted cellular mechanism (UPR). Thus, investigations on the signalling network involved in those events, may deliver exciting opportunities in diseases related to endothelial barrier dysfunction. The diverse spectrum of those pathologies include sepsis and Acute Respiratory Distress Syndrome (ARDS).