Caveolin-1-derived peptide limits development of pulmonary fibrosis

The critical roles of caveolin-1 in lung diseases

Caveolin-1 (Cav-1), a structural and functional component in the caveolae, plays a critical role in transcytosis, endocytosis, and signal transduction. Cav-1 has been implicated in the mediation of cellular processes by interacting with a variety of signaling molecules. Cav-1 is widely expressed in the endothelial cells, smooth muscle cells, and fibroblasts in the various organs, including the lungs. The Cav-1-mediated internalization and regulation of signaling molecules participate in the physiological and pathological processes. Particularly, the MAPK, NF-κB, TGFβ/Smad, and eNOS/NO signaling pathways have been involved in the regulatory effects of Cav-1 in lung diseases. The important effects of Cav-1 on the lungs indicate that Cav-1 can be a potential target for the treatment of lung diseases. A Cav-1 scaffolding domain peptide CSP7 targeting Cav-1 has been developed. In this article, we mainly discuss the structure of Cav-1 and its critical roles in lung diseases, such as pneumonia, acute lung injury (ALI), asthma, chronic obstructive pulmonary disease (COPD), pulmonary hypertension, pulmonary fibrosis, and lung cancer.

A water-soluble caveolin-1 peptide inhibits psoriasis-like skin inflammation by suppressing cytokine production and angiogenesis

The plasma membrane protein caveolin-1 (CAV-1) regulates signaling by inhibiting a wide range of kinases and other enzymes. Our previous study demonstrated that the downregulation of CAV-1 in psoriatic epidermal cells contributes to inflammation by enhancing JAK/STAT signaling, cell proliferation, and chemokine production. Administration of the CAV-1 scaffolding domain (CSD) peptide suppressed imiquimod (IMQ)-induced psoriasis-like dermatitis. To identify an optimal therapeutic peptide derived from CAV-1, we have compared the efficacy of CSD and subregions of CSD that have been modified to make them water soluble. We refer to these modified peptides as sCSD, sA, sB, and sC. In IMQ-induced psoriasis-like dermatitis, while all four peptides showed major beneficial effects, sB caused the most significant improvements of skin phenotype and number of infiltrating cells, comparable or superior to the effects of sCSD. Phosphorylation of STAT3 was also inhibited by sB. Furthermore, sB suppressed angiogenesis both in vivo in the dermis of IMQ-induced psoriasis mice and in vitro by blocking the ability of conditioned media derived from CAV-1-silenced keratinocytes to inhibit tube formation by HUVEC. In conclusion, sB had similar or greater beneficial effects than sCSD not only by cytokine suppression but by angiogenesis inhibition adding to its ability to target psoriatic inflammation.

Targeting tumor suppressor p53 for organ fibrosis therapy

Fibrosis is a reparative and progressive process characterized by abnormal extracellular matrix deposition, contributing to organ dysfunction in chronic diseases. The tumor suppressor p53 (p53), known for its regulatory roles in cell proliferation, apoptosis, aging, and metabolism across diverse tissues, appears to play a pivotal role in aggravating biological processes such as epithelial-mesenchymal transition (EMT), cell apoptosis, and cell senescence. These processes are closely intertwined with the pathogenesis of fibrotic disease. In this review, we briefly introduce the background and specific mechanism of p53, investigate the pathogenesis of fibrosis, and further discuss p53's relationship and role in fibrosis affecting the kidney, liver, lung, and heart. In summary, targeting p53 represents a promising and innovative therapeutic approach for the prevention and treatment of organ fibrosis.

Pre-clinical proof-of-concept of anti-fibrotic activity of caveolin-1 scaffolding domain peptide LTI-03 in ex vivo precision cut lung slices from patients with Idiopathic Pulmonary Fibrosis

Rationale: While rodent lung fibrosis models are routinely used to evaluate novel antifibrotics, these models have largely failed to predict clinical efficacy of novel drug candidates for Idiopathic Pulmonary Fibrosis (IPF). Moreover, single target therapeutic strategies for IPF have failed and current multi-target standard of care drugs are not curative. Caveolin-1 (CAV-1) is an integral membrane protein, which, via its caveolin scaffolding domain (CSD), interacts with caveolin binding domains (CBD). CAV-1 regulates homeostasis, and its expression is decreased in IPF lungs. LTI-03 is a seven amino acid peptide derived from the CSD and formulated for dry powder inhalation; it was well tolerated in normal volunteers ( NCT04233814 ) and a safety trial is underway in IPF patients ( NCT05954988 ). Objectives: Anti-fibrotic efficacy of LTI-03 and other CSD peptides has been observed in IPF lung monocultures, and rodent pulmonary, dermal, and heart fibrosis models. This study aimed to characterize progressive fibrotic activity in IPF PCLS explants and to evaluate the antifibrotic effects of LTI-03 and nintedanib in this model. Methods: First, CBD regions were identified in IPF signaling proteins using in silico analysis. Then, IPF PCLS (n=8) were characterized by COL1A1 immunostaining, multiplex immunoassays, and bulk RNA sequencing following treatment every 12hrs with LTI-03 at 0.5, 3.0, or 10 μM; nintedanib at 0.1 μM or 1 μM; or control peptide (CP) at 10 μM. Measurements and Main Results: CBDs were present in proteins implicated in IPF, including VEGFR, FGFR and PDGFR. Increased expression of profibrotic mediators indicated active fibrotic activity in IPF PCLS over five days. LTI-03 dose dependently decreased COL1A1 staining, and like nintedanib, decreased profibrotic proteins and transcripts. Unlike nintedanib, LTI-03 did not induce cellular necrosis signals. Conclusion: IPF PCLS explants demonstrate molecular activity indicative of fibrosis during 5 days in culture and LTI-03 broadly attenuated pro-fibrotic proteins and pathways, further supporting the potential therapeutic effectiveness of LTI-03 for IPF.

Guiding bar motif of thioredoxin reductase 1 modulates enzymatic activity and inhibitor binding by communicating with the co-factor FAD and regulating the flexible C-terminal redox motif

Thioredoxin reductase (TXNRD) is a selenoprotein that plays a crucial role in cellular antioxidant defense. Previously, a distinctive guiding bar motif was identified in TXNRD1, which influences the transfer of electrons. In this study, utilizing single amino acid substitution and Excitation-Emission Matrix (EEM) fluorescence spectrum analysis, we discovered that the guiding bar communicates with the FAD and modulates the electron flow of the enzyme. Differential Scanning Fluorimetry (DSF) analysis demonstrated that the aromatic amino acid in guiding bar is a stabilizer for TXNRD1. Kinetic analysis revealed that the guiding bar is vital for the disulfide reductase activity but hinders the selenocysteine-independent reduction activity of TXNRD1. Meanwhile, the guiding bar shields the selenocysteine residue of TXNRD1 from the attack of electrophilic reagents. We also found that the inhibition of TXNRD1 by caveolin-1 scaffolding domain (CSD) peptides and compound LCS3 did not bind to the guiding bar motif. In summary, the obtained results highlight new aspects of the guiding bar that restrict the flexibility of the C-terminal redox motif and govern the transition from antioxidant to pro-oxidant.

Alpinetin ameliorates bleomycin-induced pulmonary fibrosis by repressing fibroblast differentiation and proliferation

OBJECTIVE

Idiopathic pulmonary fibrosis (IPF) is a progressive and irreversible interstitial lung disease with a poor prognosis. Alpinetin (ALP), derived from Alpinia katsumadai Hayata, has shown potential as a therapeutic measure of various diseases. However, the utilization of ALP in managing pulmonary fibrosis and its underlying mechanisms are still not fully understood.

METHODS

A well-established mouse model of pulmonary fibrosis induced by bleomycin (BLM) was used in this study. The antifibrotic effects of ALP on histopathologic manifestations and expression levels of fibrotic markers were examined. Subsequently, the impact of ALP on fibroblast differentiation, proliferation, apoptosis, and associated signaling pathways was investigated to elucidate the underlying mechanisms.

RESULTS

In the present study, we observed that ALP effectively mitigated BLM-induced pulmonary fibrosis in mice, as evidenced by histopathological manifestations and the expression levels of fibrotic markers. Furthermore, the in vitro experiments demonstrated that ALP treatment attenuated the ability of fibroblasts to differentiate into myofibroblasts. Mechanically, our findings provided evidence that ALP suppressed fibroblast-to-myofibroblast differentiation by repressing TGF-β/ALK5/Smad signaling pathway. ALP was found to possess the capability of inhibiting fibroblast proliferation and promoting apoptosis of fibroblasts induced by TGF-β.

CONCLUSION

In general, ALP may exert therapeutic effects on pulmonary fibrosis by modulating the differentiation, proliferation, and apoptosis of fibroblasts. Although its safety has been demonstrated in mice, further studies are required to investigate the efficacy of ALP in treatment of patients with IPF.

The evolution of in vitro models of lung fibrosis: promising prospects for drug discovery

Lung fibrosis is a complex process, with unknown underlying mechanisms, involving various triggers, diseases and stimuli. Different cell types (epithelial cells, endothelial cells, fibroblasts and macrophages) interact dynamically through multiple signalling pathways, including biochemical/molecular and mechanical signals, such as stiffness, affecting cell function and differentiation. Idiopathic pulmonary fibrosis (IPF) is the most common fibrosing interstitial lung disease (fILD), characterised by a notably high mortality. Unfortunately, effective treatments for advanced fILD, and especially IPF and non-IPF progressive fibrosing phenotype ILD, are still lacking. The development of pharmacological therapies faces challenges due to limited knowledge of fibrosis pathogenesis and the absence of pre-clinical models accurately representing the complex features of the disease. To address these challenges, new model systems have been developed to enhance the translatability of preclinical drug testing and bridge the gap to human clinical trials. The use of two- and three-dimensional in vitro cultures derived from healthy or diseased individuals allows for a better understanding of the underlying mechanisms responsible for lung fibrosis. Additionally, microfluidics systems, which replicate the respiratory system's physiology ex vivo, offer promising opportunities for the development of effective therapies, especially for IPF.

YuPingFeng (YPF) upregulates caveolin-1 (CAV1) to alleviate pulmonary fibrosis through the TGF-β1/Smad2 pathway

ETHNOPHARMACOLOGICAL RELEVANCE

Traditional Chinese medicine (TCM) is considered a valuable asset in China's medical tradition. YPF is a classic prescription that has been derived from the "Jiu Yuan Fang" formula and consists of three herbs: Huangqi (Astragalus membranaceus Bunge), Baizhu (Atractylodes rubra Dekker), and Fangfeng (Saposhnikovia divaricata (Turcz.) Schischk). This prescription is widely acclaimed for its exceptional pharmacological properties, including potent antioxidant effects, hormone regulation, and immune modulation effects.

AIM OF THE STUDY

Previous research provides evidence suggesting that YPF may have therapeutic effects on pulmonary fibrosis. Further exploration is essential to confirm its effectiveness and elucidate the fundamental processes.

MATERIALS AND METHODS

First, the active components and target genes of YPF were extracted from the Traditional Chinese Medicine Systems Pharmacology (TCMSP) database. Next, the GSE53845 dataset, which contains information on pulmonary fibrosis, was downloaded from the GEO database. Network informatics methods was then be utilized to identify target genes associated with pulmonary fibrosis. A YPF-based network of protein-protein interactions was constructed to pinpoint possible target genes for pulmonary fibrosis treatment. Additionally, an in vitro model of pulmonary fibrosis induced by bleomycin (BLM) was established to further investigate and validate the possible mechanisms underlying the effectiveness of YPF.

RESULTS

In this study, a total of 24 active ingredients of YPF, along with 178 target genes associated with the treatment, were identified. Additionally, 615 target genes related to pulmonary fibrosis were identified. Functional enrichment analysis revealed that 18 candidate genes (CGs) exhibited significant responses to tumor necrosis factor, NF-kB survival signaling, and positive regulation of apoptosis processes. Among these CGs, CAV1, VCAM1, and TP63 were identified as key target genes. Furthermore, cell experiments confirmed that the expression of CAV1 protein and RNA expression was increased in pulmonary fibrosis, but significantly decreased after treatment with YPF. Additionally, the expression of pSmad2, α-SMA, TGF-β1, and TNF-α was also decreased following YPF treatment.

CONCLUSIONS

Network pharmacology analysis revealed that YPF exhibits significant potential as a therapeutic intervention for pulmonary fibrosis by targeting various compounds and pathways. This study emphasizes that the efficacy of YPF in treating pulmonary fibrosis may be attributed to its ability to up-regulate CAV1 expression and inhibiting pulmonary fibrosis via modulation of the TGF-β1/Smad2 signaling pathway. These findings underscore the promising role of YPF and its ability to potentially alleviate pulmonary fibrosis.

The Peptide DHα-(4-pentenyl)-ANPQIR-NH2 Exhibits Antifibrotic Activity in Multiple Pulmonary Fibrosis Models Induced by Particulate and Soluble Chemical Fibrogenic Agents

Interstitial lung diseases (ILDs) are a group of restrictive lung diseases characterized by interstitial inflammation and pulmonary fibrosis. The incidence of ILDs associated with exposure to multiple hazards such as inhaled particles, fibers, and ingested soluble chemicals is increasing yearly, and there are no ideal drugs currently available. Our previous research showed that the novel and low-toxicity peptide DHα-(4-pentenyl)-ANPQIR-NH2 (DR3penA) had a strong antifibrotic effect on a bleomycin-induced murine model. Based on the druggability of DR3penA, we sought to investigate its effects on respirable particulate silicon dioxide (SiO2)- and soluble chemical paraquat (PQ)-induced pulmonary fibrosis in this study by using western blot, quantitative reverse-transcription polymerase chain reaction (RT-qPCR), immunofluorescence, H&E and Masson staining, immunohistochemistry, and serum biochemical assays. The results showed that DR3penA alleviated the extent of fibrosis by inhibiting the expression of fibronectin and collagen I and suppressed oxidative stress and epithelial-mesenchymal transition (EMT) in vitro and in vivo. Further study revealed that DR3penA may mitigate pulmonary fibrosis by negatively regulating the phosphatidylinositol 3-kinase/protein kinase B (PI3K/AKT) pathway and mitogen-activated protein kinase (MAPK) pathway. Unexpectedly, through the conversion of drug bioavailability under different routes of administration, DR3penA exerted antifibrotic effects equivalent to those of the positive control drug pirfenidone (PFD) at lower doses. In summary, DR3penA may be a promising lead compound for various fibrotic ILDs. SIGNIFICANCE STATEMENT: Our study verified that DHα-(4-pentenyl)-ANPQIR-NH2 (DR3penA) exhibited positive antifibrotic activity in pulmonary fibrosis induced by silicon dioxide (SiO2) particles and soluble chemical paraquat (PQ) and demonstrated a low-dose advantage compared to the small-molecule drug pirfenidone (PFD). The peptide DR3penA can be further developed for the treatment of multiple fibrotic lung diseases.

Caveolin scaffolding domain (CSD) peptide LTI-2355 modulates the phagocytic and synthetic activity of lung derived myeloid cells in Idiopathic Pulmonary Fibrosis (IPF) and Post-acute sequelae of COVID-fibrosis (PASC-F)

Rationale

The role of the innate immune system in Idiopathic Pulmonary Fibrosis (IPF) remains poorly understood. However, a functional myeloid compartment is required to remove dying cells and cellular debris, and to mediate innate immune responses against pathogens. Aberrant macrophage activity has been described in patients with Post-acute sequelae of COVID fibrosis (PASC-F). Therefore, we examined the functional and synthetic properties of myeloid cells isolated from normal donor lung and lung explant tissue from both IPF and PASC-F patients and explored the effect of LTI-2355, a Caveolin Scaffolding Domain (CSD) peptide, on these cells.

Methods & Results

CD45 + myeloid cells isolated from lung explant tissue from IPF and PASC-F patients exhibited an impaired capacity to clear autologous dead cells and cellular debris. Uptake of pathogen-coated bioparticles was impaired in myeloid cells from both fibrotic patient groups independent of type of pathogen highlighting a cell intrinsic functional impairment. LTI-2355 improved the phagocytic activity of both IPF and PASC-F myeloid cells, and this improvement was paired with decreased pro-inflammatory and pro-fibrotic synthetic activity. LTI-2355 was also shown to primarily target CD206-expressing IPF and PASC-F myeloid cells.

Conclusions

Primary myeloid cells from IPF and PASC-F patients exhibit dysfunctional phagocytic and synthetic properties that are reversed by LTI-2355. Thus, these studies highlight an additional mechanism of action of a CSD peptide in the treatment of IPF and progressive fibrotic lung disease.

The Cavin-1/Caveolin-1 interaction attenuates BMP/Smad signaling in pulmonary hypertension by interfering with BMPR2/Caveolin-1 binding

Caveolin-1 (CAV1) and Cavin-1 are components of caveolae, both of which interact with and influence the composition and stabilization of caveolae. CAV1 is associated with pulmonary arterial hypertension (PAH). Bone morphogenetic protein (BMP) type 2 receptor (BMPR2) is localized in caveolae associated with CAV1 and is commonly mutated in PAH. Here, we show that BMP/Smad signaling is suppressed in pulmonary microvascular endothelial cells of CAV1 knockout mice. Moreover, hypoxia enhances the CAV1/Cavin-1 interaction but attenuates the CAV1/BMPR2 interaction and BMPR2 membrane localization in pulmonary artery endothelial cells (PAECs). Both Cavin-1 and BMPR2 are associated with the CAV1 scaffolding domain. Cavin-1 decreases BMPR2 membrane localization by inhibiting the interaction of BMPR2 with CAV1 and reduces Smad signal transduction in PAECs. Furthermore, Cavin-1 knockdown is resistant to CAV1-induced pulmonary hypertension in vivo. We demonstrate that the Cavin-1/Caveolin-1 interaction attenuates BMP/Smad signaling and is a promising target for the treatment of PAH.

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.

Caveolin-1-derived peptide attenuates cigarette smoke-induced airway and alveolar epithelial injury

Chronic obstructive pulmonary disease (COPD) is a debilitating lung disease with no effective treatment that can reduce mortality or slow the disease progression. COPD is the third leading cause of global death and is characterized by airflow limitations due to chronic bronchitis and alveolar damage/emphysema. Chronic cigarette smoke (CS) exposure damages airway and alveolar epithelium and remains a major risk factor for the pathogenesis of COPD. We found that the expression of caveolin-1, a tumor suppressor protein; p53; and plasminogen activator inhibitor-1 (PAI-1), one of the downstream targets of p53, was markedly increased in airway epithelial cells (AECs) as well as in type II alveolar epithelial (AT2) cells from the lungs of patients with COPD or wild-type mice with CS-induced lung injury (CS-LI). Moreover, p53- and PAI-1-deficient mice resisted CS-LI. Furthermore, treatment of AECs, AT2 cells, or lung tissue slices from patients with COPD or mice with CS-LI with a seven amino acid caveolin-1 scaffolding domain peptide (CSP7) reduced mucus hypersecretion in AECs and improved AT2 cell viability. Notably, induction of PAI-1 expression via increased caveolin-1 and p53 contributed to mucous cell metaplasia and mucus hypersecretion in AECs, and reduced AT2 viability, due to increased senescence and apoptosis, which was abrogated by CSP7. In addition, treatment of wild-type mice having CS-LI with CSP7 by intraperitoneal injection or nebulization via airways attenuated mucus hypersecretion, alveolar injury, and significantly improved lung function. This study validates the potential therapeutic role of CSP7 for treating CS-LI and COPD. NEW & NOTEWORTHY Chronic cigarette smoke (CS) exposure remains a major risk factor for the pathogenesis of COPD, a debilitating disease with no effective treatment. Increased caveolin-1 mediated induction of p53 and downstream plasminogen activator inhibitor-1 (PAI-1) expression contributes to CS-induced airway mucus hypersecretion and alveolar wall damage. This is reversed by caveolin-1 scaffolding domain peptide (CSP7) in preclinical models, suggesting the therapeutic potential of CSP7 for treating CS-induced lung injury (CS-LI) and COPD.

Caveolin-1 scaffolding domain peptide prevents corpus cavernosum fibrosis and erectile dysfunction in bilateral cavernous nerve injury-induced rats

BACKGROUND

Corpus cavernosum (CC) fibrosis significantly contributes to post-radical prostatectomy erectile dysfunction (pRP-ED). Caveolin-1 scaffolding domain (CSD)-derived peptide has gained significant concern as a potent antagonist of tissue fibrosis. However, applying CSD peptide on bilateral cavernous nerve injury (BCNI)-induced rats remains uninvestigated.

AIM

The aim was to explore the therapeutic outcome and underlying mechanism of CSD peptide for preventing ED in BCNI rats according to the hypothesis that CSD peptide may exert beneficial effects on erectile tissue and function following BCNI through limiting collagen synthesis in CC smooth muscle cells (CCSMCs) and CC fibrosis.

METHODS

After completing a random assignment of male Sprague Dawley rats (10 weeks of age), BCNI rats received either saline or CSD peptide treatment, as opposed to sham-operated rats. The evaluations of erectile function (EF) and succedent collection and histological and molecular biological examinations of penile tissue were accomplished 3 weeks postoperatively. In addition, the fibrotic model of CCSMCs was used to further explore the mechanism of CSD peptide action in vitro.

OUTCOMES

The assessments of EF, SMC/collagen ratio, α-smooth muscle actin, caveolin-1 (CAV1), and profibrotic indicators expressions were conducted.

RESULTS

BCNI rats exhibited significant decreases in EF, SMC/collagen ratio, α-SMA, and CAV1 levels, and increases in collagen content together with transforming growth factor (TGF)-β1/Smad2 activity. However, impaired EF, activated CC fibrosis, and Smad2 signaling were attenuated after 3 weeks of CSD peptide treatment in BCNI rats. In vitro, TGF-β1-induced CCSMCs underwent fibrogenetic transformation characterized by lower expression of CAV1, higher collagen composition, and phosphorylation of Smad2; then, the delivery of CSD peptide could significantly block CCSMC fibrosis by inactivating Smad2 signaling.

CLINICAL IMPLICATIONS

Based on available evidence of CSD peptide in the prevention of ED in BCNI rats, this study can aid in the development and clinical application of CSD peptide targeting pRP-ED.

STRENGTHS AND LIMITATIONS

This study provides data to suggest that CSD peptide protects against BCNI-induced deleterious alterations in EF and CC tissues. However, the available evidence still does not fully clarify the detailed mechanism of action of CSD peptide.

CONCLUSION

Administration of CSD peptide significantly retarded collagen synthesis in CCSMCs, limited CC fibrosis, and prevented ED via confrontation of TGF-β1/Smad signaling in BCNI rats.

Caveolin-1 in endothelial cells: A potential therapeutic target for atherosclerosis

Atherosclerosis (AS) is a chronic vascular disease characterized by lipid accumulation and the activation of the inflammatory response; it remains the leading nation-wide cause of death. Early in the progression of AS, stimulation by pro-inflammatory agonists (TNF-α, LPS, and others), oxidized lipoproteins (ox-LDL), and biomechanical stimuli (low shear stress) lead to endothelial cell activation and dysfunction. Consequently, it is crucial to investigate how endothelial cells respond to different stressors and ways to alter endothelial cell activation in AS development, as they are the earliest cells to respond. Caveolin-1 (Cav1) is a 21-24-kDa membrane protein located in caveolae and highly expressed in endothelial cells, which plays a vital role in regulating lipid transport, inflammatory responses, and various cellular signaling pathways and has atherogenic effects. This review summarizes recent studies on the structure and physiological functions of Cav1 and outlines the potential mechanisms it mediates in AS development. Included are the roles of Cav1 in the regulation of endothelial cell autophagy, response to shear stress, modulation of the eNOS/NO axis, and transduction of inflammatory signaling pathways. This review provides a rationale for proposing Cav1 as a novel target for the prevention of AS, as well as new ideas for therapeutic strategies for early AS.

Prognostic analysis of lung adenocarcinoma based on cancer-associated fibroblasts genes using scRNA-sequencing

Cancer-associated fibroblasts (CAFs) are an important component of the tumor microenvironment (TME). CAFs can promote tumor occurrence and metastasis by promoting cancer cell proliferation, angiogenesis, extracellular matrix (ECM) remodeling, and drug resistance. Nevertheless, how CAFs are related to Lung adenocarcinoma (LUAD) has not yet been revealed, especially since the CAFs-related prediction model has yet to be established. We combined Single-cell RNA-sequencing (scRNA-seq) and Bulk-RNA data to develop a predictive model of 8 CAFs-associated genes. Our model predicted LUAD prognosis and immunotherapy efficacy. TME, mutation landscape and drug sensitivity differences were also systematically analyzed between the LUAD patients of high- and low-risk. Moreover, the model prognostic performance was validated in four independent validation cohorts in the Gene expression omnibus (GEO) and the IMvigor210 immunotherapy cohort.

Therapeutic potential of amitriptyline for paraquat-induced pulmonary fibrosis: Involvement of caveolin-1-mediated anti-epithelial-mesenchymal transition and inhibition of apoptosis

OBJECTIVE

Treatment of pulmonary fibrosis caused by paraquat (PQ) poisoning remains problematic. Amitriptyline (AMT) has multiple pharmacological effects. Here we investigated the anti-fibrotic effect of AMT on PQ-induced pulmonary fibrosis and its possible mechanism.

METHODS

C57BL/6 mice were randomly divided into control, PQ, PQ + AMT and AMT groups. Histopathology of the lungs, blood gas analysis, and levels of hydroxyproline (HYP), transforming growth factor β1 (TGF-β1) and interleukin 17 (IL-17) were measured. The siRNA transfection inhibited caveolin-1 in A549 cells, which induced epithelial-mesenchymal transition (EMT) by PQ and followed intervention with AMT. E-cadherin, N-cadherin, α-smooth muscle actin (α-SMA) and caveolin-1 were studied by immunohistochemistry and western blot analysis. The apoptosis rate was measured by flow cytometry.

RESULTS

Compared with the PQ group, the PQ + AMT group displayed mild pathological changes in pulmonary fibrosis, lower HYP, IL-17 and TGF- β1 levels in lung, but high TGF- β1 in serum. Levels of N-cadherin and α-SMA in the lungs were significantly decreased, but caveolin-1 was increased, while SaO₂ and PaO₂ levels were higher. Compared with the PQ group, the apoptosis rate, N-cadherin and α-SMA levels in A549 cells were significantly decreased after PQ treatment and high dose AMT intervention (p < 0.01). The expressions of E-cadherin, N-cadherin and α-SMA in the PQ-induced cells transfected with caveolin-1 siRNA or siControl RNA were significantly different (p < 0.01), but the apoptosis rate was unaltered.

CONCLUSION

AMT inhibited PQ-induced EMT in A549 cells and improved lung histopathology and oxygenation in mice by up-regulating caveolin-1.

Caveolin-1-Related Intervention for Fibrotic Lung Diseases

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease (ILD) for which there are no effective treatments. Lung transplantation is the only viable option for patients with end-stage PF but is only available to a minority of patients. Lung lesions in ILDs, including IPF, are characterized by alveolar epithelial cell (AEC) senescence and apoptosis and accumulation of activated myofibroblasts and/or fibrotic lung (fL) fibroblasts (fLfs). These composite populations of fLfs show a high rate of basal proliferation, resist apoptosis and senescence, and have increased migration and invasiveness. They also more readily deposit ECM proteins. These features eventuate in progressive destruction of alveolar architecture and loss of lung function in patients with PF. The identification of new, safer, and more effective therapy is therefore mandatory for patients with IPF or related ILDs. We found that increased caveolin-1 and tumor suppressor protein, p53 expression, and apoptosis in AECs occur prior to and then with the proliferation of fLfs in fibrotic lungs. AECs with elevated p53 typically undergo apoptosis. fLfs alternatively demonstrate strikingly low basal levels of caveolin-1 and p53, while mouse double minute 2 homolog (mdm2) levels and mdm2-mediated degradation of p53 protein are markedly increased. The disparities in the expression of p53 in injured AECs and fLfs appear to be due to increased basal expression of caveolin-1 in apoptotic AECs with a relative paucity of caveolin-1 and increased mdm2 in fLfs. Therefore, targeting caveolin-1 using a caveolin 1 scaffolding domain peptide, CSP7, represents a new and promising approach for patients with IPF, perhaps other forms of progressive ILD or even other forms of organ injury characterized by fibrotic repair. The mechanisms of action differ in the injured AECs and in fLfs, in which differential signaling enables the preservation of AEC viability with concurrent limitation of fLf expansion and collagen secretion. The findings in three models of PF indicate that lung scarring can be nearly abrogated by airway delivery of the peptide. Phase 1 clinical trial testing of this approach in healthy volunteers has been successfully completed; Phase 1b in IPF patients is soon to be initiated and, if successful, will be followed by phase 2 testing in short order. Apart from the treatment of IPF, this intervention may be applicable to other forms of tissue injury characterized by fibrotic repair.

Pulmonary endogenous progenitor stem cell subpopulation: Physiology, pathogenesis, and progress

Lungs are structurally and functionally complex organs consisting of diverse cell types from the proximal to distal axis. They have direct contact with the external environment and are constantly at risk of various injuries. Capable to proliferate and differentiate, pulmonary endogenous progenitor stem cells contribute to the maintenance of lung structure and function both under homeostasis and following injuries. Discovering candidate pulmonary endogenous progenitor stem cell types and underlying regenerative mechanisms provide insights into therapeutic strategy development for lung diseases. In this review, we reveal their compositions, roles in lung disease pathogenesis and injury repair, and the underlying mechanisms. We further underline the advanced progress in research approach and potential therapy for lung regeneration. We also demonstrate the feasibility and prospects of pulmonary endogenous stem cell transplantation for lung disease treatment.

Alpha-1 antitrypsin limits neutrophil extracellular trap disruption of airway epithelial barrier function

Neutrophil extracellular traps contribute to lung injury in cystic fibrosis and asthma, but the mechanisms are poorly understood. We sought to understand the impact of human NETs on barrier function in primary human bronchial epithelial and a human airway epithelial cell line. We demonstrate that NETs disrupt airway epithelial barrier function by decreasing transepithelial electrical resistance and increasing paracellular flux, partially by NET-induced airway cell apoptosis. NETs selectively impact the expression of tight junction genes claudins 4, 8 and 11. Bronchial epithelia exposed to NETs demonstrate visible gaps in E-cadherin staining, a decrease in full-length E-cadherin protein and the appearance of cleaved E-cadherin peptides. Pretreatment of NETs with alpha-1 antitrypsin (A1AT) inhibits NET serine protease activity, limits E-cadherin cleavage, decreases bronchial cell apoptosis and preserves epithelial integrity. In conclusion, NETs disrupt human airway epithelial barrier function through bronchial cell death and degradation of E-cadherin, which are limited by exogenous A1AT.

Critical role of caveolin-1 in intestinal ischemia reperfusion by inhibiting protein kinase C βII

Intestinal ischemia reperfusion (I/R) is a common clinical pathological process. We previously reported that pharmacological inhibition of protein kinase C (PKC) βII with a specific inhibitor attenuated gut I/R injury. However, the endogenous regulatory mechanism of PKCβII inactivation is still unclear. Here, we explored the critical role of caveolin-1 (Cav1) in protecting against intestinal I/R injury by regulating PKCβII inactivation. PKCβII translocated to caveolae and bound with Cav1 after intestinal I/R. Cav1 was highly expressed in the intestine of mice with I/R and IEC-6 cells stimulated with hypoxia/reoxygenation (H/R). Cav1-knockout (KO) mice suffered from worse intestinal injury after I/R than wild-type (WT) mice and showed extremely low survival due to exacerbated systemic inflammatory response syndrome (SIRS) and remote organ (lung and liver) injury. Cav1 deficiency resulted in excessive PKCβII activation and increased oxidative stress and apoptosis after intestinal I/R. Full-length Cav1 scaffolding domain peptide (CSP) suppressed excessive PKCβII activation and protected the gut against oxidative stress and apoptosis due to I/R injury. In summary, Cav1 could regulate PKCβII endogenous inactivation to alleviate intestinal I/R injury. This finding may represent a novel therapeutic strategy for the prevention and treatment of intestinal I/R injury.

Peptide mediated therapy in fibrosis: Mechanisms, advances and prospects

Fibrosis, a disease characterized by an excess accumulation of extracellular matrix components, could lead to organ failure and death, and is to blame for up to 45 % of all fatalities in developed nations. These disorders all share the common trait of an unchecked and increasing accumulation of fibrotic tissue in the affected organs, which leads to their malfunction and eventual failure, even if their underlying causes are highly diverse and, in some cases, remain unclear. Numerous studies have identified activated myofibroblasts as the common cellular elements ultimately responsible for the replacement of normal tissues with nonfunctional fibrotic tissue. The transforming growth factor-β pathway, for instance, plays a significant role in practically all kinds of fibrosis. However, there is no specific drug for the treatment of fibrosis, several medications with anti-hepatic fibrosis properties are still in the research and development stages. Peptide, which refers to a substance consisting of 2-50 amino acids, is characterized by structural diversity, low toxicity, biological activities, easy absorption, specific targeting, few side effects, and has been proven to be effective in anti-fibrosis. Here, we summarized various anti-fibrosis peptides in fibrosis including the liver, lungs, kidneys, and other organs. This review will provide a new insight into peptide mediated anti-fibrosis and is helpful to creation of antifibrotic medications.

Inhaled deep eutectic solvent based-nanoemulsion of pirfenidone in idiopathic pulmonary fibrosis

Pirfenidone (PRF), the first FDA-approved drug to treat idiopathic pulmonary fibrosis (IPF) and formulated as an oral dosage form, has many side effects. To enhance the therapeutic effect, we discovered a high-load nanoemulsion using a novel deep eutectic solvent (DES) and developed an inhalation drug with improved bioavailability. The DES of PRF and N-acetylcysteine were discovered, and their physicochemical properties were evaluated in this study. The mechanism of DES formation was confirmed by FT-IR and ¹H NMR and suggested to involve hydrogen bonding. The DES nanoemulsion in which the nano-sized droplets were dispersed is optimized by mixing the DES and distilled water in a ratio. The in vivo pharmacokinetic study showed that the pulmonary route of administration is superior to that of the oral route, and the DES nanoemulsion is superior to that of the PRF solution in achieving better bioavailability and lung distribution. The therapeutic effect of PRF for IPF could be confirmed through in vivo pharmacodynamics studies, including lung function assessment, enzyme-linked immunosorbent assay, histology, and micro-computed tomography using the bleomycin-induced IPF rat model. In addition, the pulmonary route administration of PRF is advantageous in reducing the toxicity risk.

The Role of DNA Damage and Repair in Idiopathic Pulmonary Fibrosis

The mortality rate of idiopathic pulmonary fibrosis (IPF) increases yearly due to ineffective treatment. Given that the lung is exposed to the external environment, it is likely that oxidative stress, especially the stimulation of DNA, would be of particular importance in pulmonary fibrosis. DNA damage is known to play an important role in idiopathic pulmonary fibrosis initiation, so DNA repair systems targeting damage are also crucial for the survival of lung cells. Although many contemporary reports have summarized the role of individual DNA damage and repair pathways in their hypotheses, they have not focused on idiopathic pulmonary fibrosis. This review, therefore, aims to provide a concise overview for researchers to understand the pathways of DNA damage and repair and their roles in IPF.

Caveolin-1 and Its Functional Peptide CSP7 Affect Silica-Induced Pulmonary Fibrosis by Regulating Fibroblast Glutaminolysis

Exposure to silica is a cause of pulmonary fibrosis disease termed silicosis, which leads to respiratory failure and ultimately death. However, what drives fibrosis is not fully elucidated and therapeutic options remain limited. Our previous RNA-sequencing analysis showed that the expression of caveolin-1 (CAV1) was downregulated in silica-inhaled mouse lung tissues. Here, we not only verified that CAV1 was decreased in silica-induced fibrotic mouse lung tissues in both messenger RNA and protein levels, but also found that CSP7, a functional peptide of CAV1, could attenuate pulmonary fibrosis in vivo. Further in vitro experiments revealed that CAV1 reduced the expression of Yes-associated protein 1(YAP1) and affected its nuclear translocation in fibroblasts. In addition, Glutaminase 1 (GLS1), a key regulator of glutaminolysis, was identified to be a downstream effector of YAP1. CAV1 could suppress the activity of YAP1 to decrease the transcription of GLS1, thereby inhibiting fibroblast activation. Taken together, our results demonstrated that CAV1 and its functional peptide CSP7 may be potential molecules or drugs for the prevention and intervention of silicosis.

Caveolin-1 scaffolding domain peptide abrogates autophagy dysregulation in pulmonary fibrosis

Idiopathic pulmonary fibrosis (IPF) is the most common and fatal form of interstitial lung disease. IPF is characterized by irreversible scarring of the lungs leading to lung function decline. Although the etiology remains poorly understood, dysregulated autophagy in alveolar-epithelial cells (AECs) together with interplay between apoptotic-AECs and proliferative-myofibroblasts have been strongly implicated in IPF pathogenesis. Recent studies have revealed that a caveolin-1-derived 7-mer peptide, CSP7, mitigates established PF at least in part by improving AEC viability. In the present study, we aimed to determine whether and how CSP7 regulates autophagy in fibrotic-lung AECs. We found that p53 and autophagic proteins were markedly upregulated in AECs from mice with single/multi-doses of bleomycin—or silica-induced PF. This was abolished following treatment of PF-mice with CSP7. Further, CSP7 abrogated silica- or bleomycin-induced p53 and autophagy proteins in AECs. Immunoprecipitation further revealed that CSP7 abolishes the interaction of caveolin-1 with LC3BII and p62 in AECs. AEC-specific p53-knockout mice resisted silica- or bleomycin-induced changes in autophagy proteins, or CSP7 treatment. Our findings provide a novel mechanism by which CSP7 inhibits dysregulated autophagy in injured AECs and mitigates existing PF. These results affirm the potential of CSP7 for treating established PF, including IPF and silicosis.

3D In Vitro Models: Novel Insights into Idiopathic Pulmonary Fibrosis Pathophysiology and Drug Screening

Idiopathic pulmonary fibrosis (IPF) is a progressive and often lethal interstitial lung disease of unknown aetiology. IPF is characterised by myofibroblast activation, tissue stiffening, and alveolar epithelium injury. As current IPF treatments fail to halt disease progression or induce regeneration, there is a pressing need for the development of novel therapeutic targets. In this regard, tri-dimensional (3D) models have rapidly emerged as powerful platforms for disease modelling, drug screening and discovery. In this review, we will touch on how 3D in vitro models such as hydrogels, precision-cut lung slices, and, more recently, lung organoids and lung-on-chip devices have been generated and/or modified to reveal distinct cellular and molecular signalling pathways activated during fibrotic processes. Markedly, we will address how these platforms could provide a better understanding of fibrosis pathophysiology and uncover effective treatment strategies for IPF patients.

Caveolin-1 peptide regulates p53-microRNA-34a feedback in fibrotic lung fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a life-threatening disease resulting from dysregulated repair responses to lung injury. Excessive extracellular matrix deposition by expanding myofibroblasts and fibrotic lung fibroblasts (fLfs) has been implicated in the pathogenesis of PF, including IPF. We explored fLfs' microRNA-34a (miR-34a) expression from IPF tissues. Basal miR-34a levels were decreased with reduced binding of p53 to the promoter DNA and 3'UTR mRNA sequences. Overexpression of miR-34a in fLfs increased p53, PAI-1, and reduced pro-fibrogenic markers. The regulatory effects of miR-34a were altered by modifying the p53 expression. Precursor-miR-34a lung transduction reduced bleomycin-induced PF in wild-type mice. fLfs treated with caveolin-1 scaffolding domain peptide (CSP) or its fragment, CSP7, restored miR-34a, p53, and PAI-1. CSP/CSP7 reduced PDGFR-β and pro-fibrogenic markers, which was abolished in fLfs following blockade of miR-34a expression. These peptides failed to resolve PF in mice lacking miR-34a in fLfs, indicating miR-34a-p53-feedback induction required for anti-fibrotic effects.

Caveolin-1-Derived Peptide Reduces ER Stress and Enhances Gelatinolytic Activity in IPF Fibroblasts

Idiopathic pulmonary fibrosis (IPF) is a fatal disease characterized by an excess deposition of extracellular matrix in the pulmonary interstitium. Caveolin-1 scaffolding domain peptide (CSP) has been found to mitigate pulmonary fibrosis in several animal models. However, its pathophysiological role in IPF is obscure, and it remains critical to understand the mechanism by which CSP protects against pulmonary fibrosis. We first studied the delivery of CSP into cells and found that it is internalized and accumulated in the Endoplasmic Reticulum (ER). Furthermore, CSP reduced ER stress via suppression of inositol requiring enzyme1α (IRE1α) in transforming growth factor β (TGFβ)-treated human IPF lung fibroblasts (hIPF-Lfs). Moreover, we found that CSP enhanced the gelatinolytic activity of TGFβ-treated hIPF-Lfs. The IRE1α inhibitor; 4µ8C also augmented the gelatinolytic activity of TGFβ-treated hIPF-Lfs, supporting the concept that CSP induced inhibition of the IRE1α pathway. Furthermore, CSP significantly elevated expression of MMPs in TGFβ-treated hIPF-Lfs, but conversely decreased the secretion of collagen 1. Similar results were observed in two preclinical murine models of PF, bleomycin (BLM)- and adenovirus expressing constitutively active TGFβ (Ad-TGFβ)-induced PF. Our findings provide new insights into the mechanism by which lung fibroblasts contribute to CSP dependent protection against lung fibrosis.

Multiple subregions within the caveolin-1 scaffolding domain inhibit fibrosis, microvascular leakage, and monocyte migration

The caveolin-1 scaffolding domain (CSD, amino acids 82-101 of caveolin-1) has been shown to suppress bleomycin-induced lung and skin fibrosis and angiotensin II (AngII)-induced myocardial fibrosis. To identify active subregions within CSD, we split its sequence into three slightly overlapping 8-amino acid subregions (82-89, 88-95, and 94-101). Interestingly, all three peptides showed activity. In bleomycin-treated mice, all three subregions suppressed the pathological effects on lung and skin tissue morphology. In addition, while bone marrow monocytes isolated from bleomycin-treated mice showed greatly enhanced migration in vitro toward CXCL12, treatment in vivo with CSD and its subregions almost completely suppressed this enhanced migration. In AngII-induced heart failure, both 82-89 and 88-95 significantly suppressed fibrosis (both Col I and HSP47 levels), microvascular leakage, and heart weight/ body weight ratio (HW/BW) while improving ventricular function. In contrast, while 94-101 suppressed the increase in Col I, it did not improve the other parameters. The idea that all three subregions can be active depending on the assay was further supported by experiments studying the in vitro migration of human monocytes in which all three subregions were extremely active. These studies are very novel in that it has been suggested that there is only one active region within CSD that is centered on amino acids 90-92. In contrast, we demonstrate here the presence of other active regions within CSD.

Update on Novel Targeted Therapy for Pleural Organization and Fibrosis

Pleural injury and subsequent loculation is characterized by acute injury, sustained inflammation and, when severe, pathologic tissue reorganization. While fibrin deposition is a normal part of the injury response, disordered fibrin turnover can promote pleural loculation and, when unresolved, fibrosis of the affected area. Within this review, we present a brief discussion of the current IPFT therapies, including scuPA, for the treatment of pathologic fibrin deposition and empyema. We also discuss endogenously expressed PAI-1 and how it may affect the efficacy of IPFT therapies. We further delineate the role of pleural mesothelial cells in the progression of pleural injury and subsequent pleural remodeling resulting from matrix deposition. We also describe how pleural mesothelial cells promote pleural fibrosis as myofibroblasts via mesomesenchymal transition. Finally, we discuss novel therapeutic targets which focus on blocking and/or reversing the myofibroblast differentiation of pleural mesothelial cells for the treatment of pleural fibrosis.

Low-intensity pulsed ultrasound ameliorates angiotensin II-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway

OBJECTIVES

Cardiac hypertrophy and fibrosis are major pathological manifestations observed in left ventricular remodeling induced by angiotensin II (AngII). Low-intensity pulsed ultrasound (LIPUS) has been reported to ameliorate cardiac dysfunction and myocardial fibrosis in myocardial infarction (MI) through mechano-transduction and its downstream pathways. In this study, we aimed to investigate whether LIPUS could exert a protective effect by ameliorating AngII-induced cardiac hypertrophy and fibrosis and if so, to further elucidate the underlying molecular mechanisms.

METHODS

We used AngII to mimic animal and cell culture models of cardiac hypertrophy and fibrosis. LIPUS irradiation was applied in vivo for 20 min every 2 d from one week before mini-pump implantation to four weeks after mini-pump implantation, and in vitro for 20 min on each of two occasions 6 h apart. Cardiac hypertrophy and fibrosis levels were then evaluated by echocardiographic, histopathological, and molecular biological methods.

RESULTS

Our results showed that LIPUS could ameliorate left ventricular remodeling in vivo and cardiac fibrosis in vitro by reducing AngII-induced release of inflammatory cytokines, but the protective effects on cardiac hypertrophy were limited in vitro. Given that LIPUS increased the expression of caveolin-1 in response to mechanical stimulation, we inhibited caveolin-1 activity with pyrazolopyrimidine 2 (pp2) in vivo and in vitro. LIPUS-induced downregulation of inflammation was reversed and the anti-fibrotic effects of LIPUS were absent.

CONCLUSIONS

These results indicated that LIPUS could ameliorate AngII-induced cardiac fibrosis by alleviating inflammation via a caveolin-1-dependent pathway, providing new insights for the development of novel therapeutic apparatus in clinical practice.

Protein and peptide delivery to lungs by using advanced targeted drug delivery

The challenges and difficulties associated with conventional drug delivery systems have led to the emergence of novel, advanced targeted drug delivery systems. Therapeutic drug delivery of proteins and peptides to the lungs is complicated owing to the large size and polar characteristics of the latter. Nevertheless, the pulmonary route has attracted great interest today among formulation scientists, as it has evolved into one of the important targeted drug delivery platforms for the delivery of peptides, and related compounds effectively to the lungs, primarily for the management and treatment of chronic lung diseases. In this review, we have discussed and summarized the current scenario and recent developments in targeted delivery of proteins and peptide-based drugs to the lungs. Moreover, we have also highlighted the advantages of pulmonary drug delivery over conventional drug delivery approaches for peptide-based drugs, in terms of efficacy, retention time and other important pharmacokinetic parameters. The review also highlights the future perspectives and the impact of targeted drug delivery on peptide-based drugs in the coming decade.

ER-anchored CRTH2 antagonizes collagen biosynthesis and organ fibrosis via binding LARP6

Excessive deposition of extracellular matrix, mainly collagen protein, is the hallmark of organ fibrosis. The molecular mechanisms regulating fibrotic protein biosynthesis are unclear. Here, we find that chemoattractant receptor homologous molecule expressed on TH2 cells (CRTH2), a plasma membrane receptor for prostaglandin D2, is trafficked to the endoplasmic reticulum (ER) membrane in fibroblasts in a caveolin-1-dependent manner. ER-anchored CRTH2 binds the collagen mRNA recognition motif of La ribonucleoprotein domain family member 6 (LARP6) and promotes the degradation of collagen mRNA in these cells. In line, CRTH2 deficiency increases collagen biosynthesis in fibroblasts and exacerbates injury-induced organ fibrosis in mice, which can be rescued by LARP6 depletion. Administration of CRTH2 N-terminal peptide reduces collagen production by binding to LARP6. Similar to CRTH2, bumetanide binds the LARP6 mRNA recognition motif, suppresses collagen biosynthesis, and alleviates bleomycin-triggered pulmonary fibrosis in vivo. These findings reveal a novel anti-fibrotic function of CRTH2 in the ER membrane via the interaction with LARP6, which may represent a therapeutic target for fibrotic diseases.

Understanding idiopathic pulmonary fibrosis - Clinical features, molecular mechanism and therapies

Idiopathic pulmonary fibrosis (IPF) is a chronic lung fibrosing disease with high prevalence that has a prognosis worse than many cancers. There has been a recent influx of new observations aimed at explaining the mechanisms responsible for the initiation and progression of pulmonary fibrosis. However, despite this, the pathogenesis of the disease is largely unclear. Recent progress has been made in the characterization of specific pathologic and clinical features that have enhanced the understanding of pathologically activated molecular pathways during the onset and progression of IPF. This review highlights several of the advances that have been made and focus on the pathobiology of IPF. The work also details the different factors that are responsible for the disposition of the disease - these may be internal factors such as cellular mechanisms and genetic alterations, or they may be external factors from the environment. The changes that primarily occur in epithelial cells and fibroblasts that lead to the activation of profibrotic pathways are discussed in depth. Finally, a complete repertoire of the treatment therapies that have been used in the past as well as future medications and therapies is provided.

Cellular Senescence: Pathogenic Mechanisms in Lung Fibrosis

Pulmonary fibrosis is a chronic and fatal lung disease that significantly impacts the aging population globally. To date, anti-fibrotic, immunosuppressive, and other adjunct therapy demonstrate limited efficacies. Advancing our understanding of the pathogenic mechanisms of lung fibrosis will provide a future path for the cure. Cellular senescence has gained substantial interest in recent decades due to the increased incidence of fibroproliferative lung diseases in the older age group. Furthermore, the pathologic state of cellular senescence that includes maladaptive tissue repair, decreased regeneration, and chronic inflammation resembles key features of progressive lung fibrosis. This review describes regulatory pathways of cellular senescence and discusses the current knowledge on the senescence of critical cellular players of lung fibrosis, including epithelial cells (alveolar type 2 cells, basal cells, etc.), fibroblasts, and immune cells, their phenotypic changes, and the cellular and molecular mechanisms by which these cells contribute to the pathogenesis of pulmonary fibrosis. A few challenges in the field include establishing appropriate in vivo experimental models and identifying senescence-targeted signaling molecules and specific therapies to target senescent cells, known collectively as "senolytic" or "senotherapeutic" agents.

A systematic dissection of the epigenomic heterogeneity of lung adenocarcinoma reveals two different subclasses with distinct prognosis and core regulatory networks

BACKGROUND

Lung adenocarcinoma (LUAD) is a highly malignant and heterogeneous tumor that involves various oncogenic genetic alterations. Epigenetic processes play important roles in lung cancer development. However, the variation in enhancer and super-enhancer landscapes of LUAD patients remains largely unknown. To provide an in-depth understanding of the epigenomic heterogeneity of LUAD, we investigate the H3K27ac histone modification profiles of tumors and adjacent normal lung tissues from 42 LUAD patients and explore the role of epigenetic alterations in LUAD progression.

RESULTS

A high intertumoral epigenetic heterogeneity is observed across the LUAD H3K27ac profiles. We quantitatively model the intertumoral variability of H3K27ac levels at proximal gene promoters and distal enhancers and propose a new epigenetic classification of LUAD patients. Our classification defines two LUAD subgroups which are highly related to histological subtypes. Group II patients have significantly worse prognosis than group I, which is further confirmed in the public TCGA-LUAD cohort. Differential RNA-seq analysis between group I and group II groups reveals that those genes upregulated in group II group tend to promote cell proliferation and induce cell de-differentiation. We construct the gene co-expression networks and identify group-specific core regulators. Most of these core regulators are linked with group-specific regulatory elements, such as super-enhancers. We further show that CLU is regulated by 3 group I-specific core regulators and works as a novel tumor suppressor in LUAD.

CONCLUSIONS

Our study systematically characterizes the epigenetic alterations during LUAD progression and provides a new classification model that is helpful for predicting patient prognosis.

Tauroursodeoxycholic acid alleviates pulmonary endoplasmic reticulum stress and epithelial-mesenchymal transition in bleomycin-induced lung fibrosis

Background

Several studies demonstrate that endoplasmic reticulum (ER) stress-mediated epithelial-mesenchymal transition (EMT) is involved in the process of bleomycin (BLM)-induced pulmonary fibrosis. Tauroursodeoxycholic acid (TUDCA), a bile acid with chaperone properties, is an inhibitor of ER stress. This study aimed to investigate the preventive effects of TUDCA on BLM-induced EMT and lung fibrosis.

Methods

The model of lung fibrosis was established by intratracheal injection with a single dose of BLM (3.0 mg/kg). In TUDCA + BLM group, mice were intraperitoneally injected with TUDCA (250 mg/kg) daily.

Results

BLM-induced alveolar septal destruction and inflammatory cell infiltration were alleviated by TUDCA. BLM-induced interstitial collagen deposition, as determined by Sirius Red staining, was attenuated by TUDCA. BLM-induced elevation of pulmonary α-smooth muscle actin (α-SMA) and reduction of pulmonary E-cadherin were attenuated by TUDCA. BLM-induced pulmonary Smad2/3 phosphorylation was suppressed by TUDCA. BLM-induced elevation of Ki67 and PCNA was inhibited by TUDCA in mice lungs. In addition, BLM-induced elevation of HO-1 (heme oxygenase-1) and 3-NT (3-nitrotyrosine) was alleviated by TUDCA. Finally, BLM-induced upregulation of pulmonary GRP78 and CHOP was attenuated by TUDCA.

Conclusions

These results provide evidence that TUDCA pretreatment inhibits Smad2/3-medited EMT and subsequent lung fibrosis partially through suppressing BLM-induced ER stress and oxidative stress.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12890-021-01514-6.

Characterization of a Novel Caveolin Modulator That Reduces Vascular Permeability and Ocular Inflammation

Purpose

Caveolin (Cav) regulates various aspect of endothelial cell signaling and cell-permeable peptides (CPPs) fused to domains of Cav can reduce retinal damage and inflammation in vivo. Thus, the goal of the present study was to identify a novel CPP that improves delivery of a truncated Cav modulator in vitro and in vivo.

Methods

Phage display technology was used to identify a small peptide (RRPPR) that was internalized into endothelial cells. Fusions of Cav with the peptide were compared to existing molecules in three distinct assays, vascular endothelial growth factor-A (VEGF) induced nitric oxide (NO) release, VEGF induced vascular leakage, and in a model of immune mediated uveitis.

Results

RRPPR was internalized efficiently and was potent in blocking NO release. Fusing RRPPR with a minimal Cav inhibitory domain (CVX51401) dose-dependently blocked NO release, VEGF induced permeability, and retinal damage in a model of uveitis.

Conclusions

CVX51401 is a novel Cav modulator that reduces VEGF and immune mediated inflammation.

Translational Relevance

CVX51401 is an optimized Cav modulator that reduces vascular permeability and ocular inflammation that is poised for clinical development.

Pathogenesis of fibrosis in interstitial lung disease

PURPOSE OF REVIEW

Pulmonary fibrosis is a chronic and progressive lung disease involving unclear pathological mechanisms. The present review presents and discusses the major and recent advances in our knowledge of the pathogenesis of lung fibrosis.

RECENT FINDINGS

The past months have deepened our understanding on the cellular actors of fibrosis with a better characterization of the abnormal lung epithelial cells observed during lung fibrosis. Better insight has been gained into fibroblast biology and the role of immune cells during fibrosis. Mechanistically, senescence appears as a key driver of the fibrotic process. Extracellular vesicles have been discovered as participating in the impaired cellular cross-talk during fibrosis and deeper understanding has been made on developmental signaling in lung fibrosis.

SUMMARY

This review emphasizes the contribution of different cell types and mechanisms during pulmonary fibrosis, highlights new insights for identification of potential therapeutic strategies, and underlines where future research is needed to answer remaining open questions.

Dopamine receptor agonists ameliorate bleomycin-induced pulmonary fibrosis by repressing fibroblast differentiation and proliferation

Idiopathic pulmonary fibrosis (IPF) is the most common fatal interstitial lung disease, with limited therapeutic options. The abnormal and uncontrolled differentiation and proliferation of fibroblasts have been confirmed to play a crucial role in driving the pathogenesis of IPF. Therefore, effective and well-tolerated antifibrotic agents that interfere with fibroblasts would be an ideal treatment, but no such treatments are available. Remarkably, we found that dopamine (DA) receptor D1 (D1R) and DA receptor D2 (D2R) were both upregulated in myofibroblasts in lungs of IPF patients and a bleomycin (BLM)-induced mouse model. Then, we explored the safety and efficacy of DA, fenoldopam (FNP, a selective D1R agonist) and sumanirole (SMR, a selective D2R agonist) in reversing BLM-induced pulmonary fibrosis. Further data showed that DA receptor agonists exerted potent antifibrotic effects in BLM-induced pulmonary fibrosis by attenuating the differentiation and proliferation of fibroblasts. Detailed pathway analysis revealed that DA receptor agonists decreased the phosphorylation of Smad2 induced by TGF-β1 in primary human lung fibroblasts (PHLFs) and IMR-90 cells. Overall, DA receptor agonists protected mice from BLM-induced pulmonary fibrosis and may be therapeutically beneficial for IPF patients in a clinical setting.

The Caveolin-1 Scaffolding Domain Peptide Reverses Aging-Associated Deleterious Changes in Multiple Organs

Aging is a progressive, multifactorial, degenerative process in which deleterious changes occur in the biochemistry and function of organs. We showed that angiotensin II (AngII)-induced pathologies in the heart and kidney of young (3-month-old) mice are suppressed by the caveolin-1 scaffolding domain (CSD) peptide. Because AngII mediates many aging-associated changes, we explored whether CSD could reverse pre-existing pathologies and improve organ function in aged mice. Using 18-month-old mice (similar to 60-year-old humans), we found that >5-fold increases in leakage of serum proteins and >2-fold increases in fibrosis are associated with aging in the heart, kidney, and brain. Because tyrosine phosphorylation of cell junction proteins leads to the loss of microvascular barrier function, we analyzed the activation of the receptor tyrosine kinase PDGFR and the nonreceptor tyrosine kinases c-Src and Pyk2. We observed 5-fold activation of PDGFR and 2- to 3-fold activation of c-Src and Pyk2 in aged mice. Treatment with CSD for 4 weeks reversed these pathologic changes (microvascular leakage, fibrosis, kinase activation) in all organs almost down to the levels in healthy, young mice. In studies of heart function, CSD reduced the aging-associated increase in cardiomyocyte cross-sectional area and enhanced ventricular compliance in that echocardiographic studies demonstrated improved ejection fraction and fractional shortening and reduced isovolumic relation time. These results suggest that versions of CSD may be developed as treatments for aging-associated diseases in human patients based on the concept that CSD inhibits tyrosine kinases, leading to the inhibition of microvascular leakage and associated fibrosis, thereby improving organ function. SIGNIFICANCE STATEMENT: The caveolin-1 scaffolding domain (CSD) peptide reverses aging-associated fibrosis, microvascular leakage, and organ dysfunction in the heart, kidneys, and brain via a mechanism that involves the suppression of the activity of multiple tyrosine kinases, suggesting that CSD can be developed as a treatment for a wide range of diseases found primarily in the aged.

Biomimetic lipid Nanocomplexes incorporating STAT3-inhibiting peptides effectively infiltrate the lung barrier and ameliorate pulmonary fibrosis

Activation of signal transducer and activator of transcription 3 (STAT3) under conditions of inflammation plays a crucial role in the pathogenesis of life-threatening pulmonary fibrosis (PF), initiating pro-fibrotic signaling following its phosphorylation. While there have been attempts to interfere with STAT3 activation and associated signaling as a strategy for ameliorating PF, potent inhibitors with minimal systemic toxicity have yet to be developed. Here, we assessed the in vitro and in vivo therapeutic effectiveness of a cell-permeable peptide inhibitor of STAT3 phosphorylation, designated APTstat3-9R, for ameliorating the indications of pulmonary fibrosis. Our results demonstrate that APTstat3-9R formulated with biomimetic disc-shaped lipid nanoparticles (DLNPs) markedly enhanced the penetration of pulmonary surfactant barrier and alleviated clinical symptoms of PF while causing negligible systemic cytotoxicity. Taken together, our findings suggest that biomimetic lipid nanoparticle-assisted pulmonary delivery of APTstat3-9R may be a feasible therapeutic option for PF in the clinic, and could be applied to treat other fibrotic diseases.

Endothelial caveolin and its scaffolding domain in cancer

Since the initial reports implicating caveolin-1 (CAV1) in neoplasia, the scientific community has made tremendous strides towards understanding how CAV1-dependent signaling and caveolae assembly modulate solid tumor growth. Once a solid neoplastic tumor reaches a certain size, it will increasingly rely on its stroma to meet the metabolic demands of the rapidly proliferating cancer cells, a limitation typically but not exclusively addressed via the formation of new blood vessels. Landmark studies using xenograft tumor models have highlighted the importance of stromal CAV1 during neoplastic blood vessel growth from preexisting vasculature, a process called angiogenesis, and helped identify endothelium-specific signaling events regulated by CAV1, such as vascular endothelial growth factor (VEGF) receptors as well as the endothelial nitric oxide (NO) synthase (eNOS) systems. This chapter provides a glimpse into the signaling events modulated by CAV1 and its scaffolding domain (CSD) during endothelial-specific aspects of neoplastic growth, such as vascular permeability, angiogenesis, and mechanotransduction.

Evaluation of Pirfenidone and Nintedanib in a Human Lung Model of Fibrogenesis

Introduction: Idiopathic pulmonary fibrosis (IPF) is a progressive, fatal lung disease with a poor prognosis and increasing incidence. Pirfenidone and nintedanib are the only approved treatments for IPF but have limited efficacy and their mechanisms of action are poorly understood. Here we have examined the effects of pirfenidone and nintedanib in a human model of lung fibrogenesis, and compared these with the putative anti-fibrotic compounds Lipoxin A4 (LXA4), and senicapoc, a K_Ca3.1 ion channel blocker. Methods: Early fibrosis was induced in cultured human lung parenchyma using TGFβ1 for 7 days, ± pirfenidone, nintedanib, or LXA4. Pro-fibrotic responses were examined by RT-PCR, immunohistochemistry and soluble collagen secretion. Results: Thirty six out of eighty four IPF and fibrosis-associated genes tested were significantly upregulated by TGFβ1 in human lung parenchyma with a ≥0.5 log2FC (n = 32). Nintedanib (n = 13) reduced the mRNA expression of 14 fibrosis-associated genes including MMPs (MMP1,-4,-13,-14), integrin α2, CXCR4 and PDGFB, but upregulated α-smooth muscle actin (αSMA). Pirfenidone only reduced mRNA expression for MMP3 and -13. Senicapoc (n = 11) previously attenuated the expression of 28 fibrosis-associated genes, including αSMA, several growth factors, collagen type III, and αV/β6 integrins. Pirfenidone and nintedanib significantly inhibited TGFβ1-induced fibroblast proliferation within the tissue, but unlike senicapoc, neither pirfenidone nor nintedanib prevented increases in tissue αSMA expression. LXA4 was ineffective. Conclusions: Pirfenidone and nintedanib demonstrate modest anti-fibrotic effects and provide a benchmark for anti-fibrotic activity of new drugs in human lung tissue. Based on these data, we predict that the K_Ca3.1 blocker senicapoc will show greater benefit than either of these licensed drugs in IPF.

A Landscape of lncRNA Expression Profile and the Predictive Value of a Candidate lncRNA for Silica-Induced Pulmonary Fibrosis

Silicosis is the most common type of pneumoconiosis with the fastest progress and the most serious harm. At present, there is still a lack of effective treatment for silicosis, and the molecular mechanism of silicosis is very complex, which is not completely clear. This study aimed to identify crucial long noncoding RNA (lncRNA)-mRNA networks for silica-induced pulmonary fibrosis using microarray data from Gene Expression Omnibus database, including human lung epithelial cells Beas-2B and continuously exposed to 5 μg/mL amorphous silica nanoparticles for 40 passages. Differently expressed genes were calculated by "DESeq2" R package. Then we selected the differently expressed mRNAs (DEmRNAs) and differently expressed long noncoding RNAs (DElncRNAs) data construct lncRNA-mRNA coexpression network using weighted gene coexpression network analysis (WCGNA). A total of 1140 DEmRNA and 1406 DElncRNAs were identified, including 20 upregulated DEmRNAs, 1120 downregulated DEmRNAs as well as 213 upregulated DElncRNAs and 1193 downregulated DElncRNAs. Furthermore, we demonstrate that lncRNA AK131029 was specifically overexpressed in silicosis. Loss-of-function assay indicated that silencing AK131029 of inhibited cell proliferation in human lung fibroblast cells. In conclusion, this study preliminarily indicates that lncRNA AK131029 may play a role in pulmonary fibrosis.

MG53/CAV1 regulates transforming growth factor-β1 signaling-induced atrial fibrosis in atrial fibrillation

Atrial fibrosis plays a significant role in the development of atrial fibrillation (AF). Previously, we showed that mitsugumin 53 (MG53) regulates TGF-β1 signaling pathway-induced atrial fibrosis. Recent studies have shown that caveolin-1 (CAV1) is an important anti-fibrosis signaling mediator that inhibits the TGF-β1 signaling pathway. Here, we further study the mechanism underlying the related action of MG53 and CAV1. We demonstrate that CAV1 expression was decreased while MG53 expression was increased in atrial tissue from AF patients. In cultured atrial fibroblasts, MG53 depletion by siRNA caused CAV1 upregulation and TGF-β1/SMAD2 signaling pathway downregulation, while MG53 overexpression via adenovirus had the opposite effect. CAV1 inactivated the TGF-β1/SMAD2 signaling pathway. In addition, using an Ang II-induced fibrosis model, we show that MG53 regulates TGF-β1 signaling via CAV1. Therefore, CAV1 is critical for the MG53 regulation of TGF-β1 signaling pathway-induced atrial fibrosis in AF. These findings reveal the related underlying mechanism of action of MG53 and CAV1 and provide a potential therapeutic target for fibrosis and AF.

Caveolin-1 scaffolding domain peptide regulates glucose metabolism in lung fibrosis

Increased metabolism distinguishes myofibroblasts or fibrotic lung fibroblasts (fLfs) from the normal lung fibroblasts (nLfs). The mechanism of metabolic activation in fLfs has not been fully elucidated. Furthermore, the antifibrogenic effects of caveolin-1 scaffolding domain peptide CSP/CSP7 involving metabolic reprogramming in fLfs are unclear. We therefore analyzed lactate and succinate levels, as well as the expression of glycolytic enzymes and hypoxia inducible factor-1α (HIF-1α). Lactate and succinate levels, as well as the basal expression of glycolytic enzymes and HIF-1α, were increased in fLfs. These changes were reversed following restoration of p53 or its transcriptional target microRNA-34a (miR-34a) expression in fLfs. Conversely, inhibition of basal p53 or miR-34a increased glucose metabolism, glycolytic enzymes, and HIF-1α in nLfs. Treatment of fLfs or mice having bleomycin- or Ad-TGF-β1-induced lung fibrosis with CSP/CSP7 reduced the expression of glycolytic enzymes and HIF-1α. Furthermore, inhibition of p53 or miR-34a abrogated CSP/CSP7-mediated restoration of glycolytic flux in fLfs in vitro and in mice with pulmonary fibrosis and lacking p53 or miR-34a expression in fibroblasts in vivo. Our data indicate that dysregulation of glucose metabolism in fLfs is causally linked to loss of basal expression of p53 and miR-34a. Treatment with CSP/CSP7 constrains aberrant glucose metabolism through restoration of p53 and miR-34a.