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-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 ß (TGFß)-treated human IPF lung fibroblasts (hIPF-Lfs). Moreover, we found that CSP enhanced the gelatinolytic activity of TGFß-treated hIPF-Lfs. The IRE1α inhibitor; 4µ8C also augmented the gelatinolytic activity of TGFß-treated hIPF-Lfs, supporting the concept that CSP induced inhibition of the IRE1α pathway. Furthermore, CSP significantly elevated expression of MMPs in TGFß-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 TGFß (Ad-TGFß)-induced PF. Our findings provide new insights into the mechanism by which lung fibroblasts contribute to CSP dependent protection against lung fibrosis.

Src-mediated caveolin-1 phosphorylation regulates intestinal epithelial restitution by altering Ca(2+) influx after wounding.

Early mucosal restitution occurs as a consequence of intestinal epithelial cell (IEC) migration to reseal superficial wounds, but its exact mechanism remains largely unknown. Caveolin-1 (Cav1), a major component associated with caveolar lipid rafts in the plasma membrane, is implicated in many aspects of cellular functions. This study determined if c-Src kinase (Src)-induced Cav1 phosphorylation promotes intestinal epithelial restitution after wounding by activating Cav1-mediated Ca(2+) signaling. Src directly interacted with Cav1, formed Cav1-Src complexes, and phosphorylated Cav1 in IECs. Inhibition of Src activity by its chemical inhibitor PP2 or suppression of the functional caveolin scaffolding domain by caveolin-scaffolding domain peptides prevented Cav1-Src interaction, reduced Cav1 phosphorylation, decreased Ca(2+) influx, and inhibited cell migration after wounding. Disruption of caveolar lipid raft microdomains by methyl-ß-cyclodextrin reduced Cav1-mediated Ca(2+) influx and repressed epithelial restitution. Moreover, Src silencing prevented subcellular redistribution of phosphorylated Cav1 in migrating IECs. These results indicate that Src-induced Cav1 phosphorylation stimulates epithelial restitution by increasing Cav1-mediated Ca(2+) signaling after wounding, thus contributing to the maintenance of gut mucosal integrity under various pathological conditions.

A Role of Caveolae in Trabecular Meshwork Mechanosensing and Contractile Tone.

Polymorphisms in the CAV1/2 gene loci impart increased risk for primary open-angle glaucoma (POAG). CAV1 encodes caveolin-1 (Cav1), which is required for biosynthesis of plasma membrane invaginations called caveolae. Cav1 knockout mice exhibit elevated intraocular pressure (IOP) and decreased outflow facility, but the mechanistic role of Cav1 in IOP homeostasis is unknown. We hypothesized that caveolae sequester/inhibit RhoA, to regulate trabecular meshwork (TM) mechanosensing and contractile tone. Using phosphorylated myosin light chain (pMLC) as a surrogate indicator for Rho/ROCK activity and contractile tone, we found that pMLC was elevated in Cav1-deficient TM cells compared to control (131 ± 10%, n = 10, p = 0.016). Elevation of pMLC levels following Cav1 knockdown occurred in cells on a soft surface (137 ± 7%, n = 24, p < 0.0001), but not on a hard surface (122 ± 17%, n = 12, p = 0.22). In Cav1-deficient TM cells where pMLC was elevated, Rho activity was also increased (123 ± 7%, n = 6, p = 0.017), suggesting activation of the Rho/ROCK pathway. Cyclic stretch reduced pMLC/MLC levels in TM cells (69 ± 7% n = 9, p = 0.002) and in Cav1-deficient TM cells, although not significantly (77 ± 11% n = 10, p = 0.059). Treatment with the Cav1 scaffolding domain mimetic, cavtratin (1 µM) caused a reduction in pMLC (70 ± 5% n = 7, p = 0.001), as did treatment with the scaffolding domain mutant cavnoxin (1 µM) (82 ± 7% n = 7, p = 0.04). Data suggest that caveolae differentially regulate RhoA signaling, and that caveolae participate in TM mechanotransduction. Cav1 regulation of these key TM functions provide evidence for underlying mechanisms linking polymorphisms in the Cav1/2 gene loci with increased POAG risk.

Localized Delivery of Caveolin-1 Peptide Assisted by Ultrasound-Mediated Microbubble Destruction Potentiates the Inhibition of Nitric Oxide-Dependent Vasodilation Response.

In the endothelium, nitric oxide synthase (eNOS) is the enzyme that generates nitric oxide, a key molecule involved in a variety of biological functions and cancer-related events. Therefore, selective inhibition of eNOS represents an attractive therapeutic approach for NO-related diseases and anticancer therapy. Ultrasound-mediated microbubble destruction (UMMD) conjugated with cell-permeable peptides has been investigated as a drug delivery system for effective delivery of anticancer molecules. We investigated the feasibility of loading antennapedia-caveolin-1 peptide (AP-Cav), a specific eNOS inhibitor, onto microbubbles to be delivered by UMMD in rat aortic endothelium. AP-Cav-loaded microbubbles (AP-Cav-MBs) and US parameters were characterized. Aortas were treated with UMMD for 30 s with 1.3 × 108 MBs/mL AP-Cav (8 µM)-MBs at 100-Hz pulse repetition frequency, 0.5-MPa acoustic pressure, 0.5 mechanical index and 10% duty cycle. NO-dependent vascular responses were assessed using an isolated organ system, 21 h post-treatment. Maximal relaxation response was inhibited 61.8% ± 1.6% in aortas treated with UMMD-AP-Cav-MBs, while in aortas treated with previously disrupted AP-Cav-MBs and then US, the inhibition was 31.6% ± 1.6%. The vascular contractile response was not affected. The impact of UMMD was evaluated in aortas treated with free AP-Cav; 30 µM of free AP-Cav was necessary to reach an inhibition response similar to that obtained with UMMD-AP-Cav-MBs. In conclusion, UMMD enhances the delivery and potentiates the effect of AP-Cav in the endothelial layer of rat aorta segments.

Caveolin-1 scaffolding domain peptides enhance anti-inflammatory effect of heme oxygenase-1 through interrupting its interact with caveolin-1.

Caveolin-1(Cav-1) scaffolding domain (CSD) peptides compete with the plasma membrane Cav-1, inhibit the interaction of the proteins and Cav-1, and re-store the functions of Cav-1 binding proteins. Heme oxygenase-1 (HO-1) binds to Cav-1 and its enzymatic activity was inhibited. In this study, we investigated the effect of CSD peptides on interaction between HO-1 and Cav-1, and on the HO-1 activity in vitro and in vivo. Our data showed that CSD peptides decreased the compartmentalization of HO-1 and Cav-1, and increased the HO-1 activity both in LPS-treated alveolar macrophages and in mice. Meanwhile, CSD peptides obviously ameliorated the pathology changes in mice and lowered the following injury indexes: the wet/dry ratio of lung tissues, total cell numbers in bronchoalveolar lavage fluid and lactate dehydrogenase activity in the serum. Mechanistically, it was firstly found that CSD peptides promoted alveolar macrophages polarization to M2 phenotype and inhibited the IκB degeneration. Furthermore, CSD peptides down-regulated the expression of IL-1ß, IL-6, TNF-α, MCP-1, and iNOS in alveolar macrophages and in lung tissue. However, the protective role of CSD peptides on LPS-induced acute lung injury in mice could be abolished by zinc protoporphyrin IX (ZnPP, a HO-1 activity inhibitor). In summary, CSD peptides have beneficial anti-inflammatory effects by restoring the HO-1 activity suppressed by Cav-1 on plasma membrane.

Effect of caveolin-1 scaffolding domain peptides on heme oxygenase-1 activity increasing and M1/M2 phenotype polarization in rat alveolar macrophages induced by lipopolysaccharide / 中华危重病急救医学

Objective To investigate the effect of caveolin-1 scaffolding domain (CSD) peptides on heme oxygenase-1 (HO-1) activity increasing and M1/M2 phenotype polarization in rat alveolar macrophages (AMs) induced by lipopolysaccharide (LPS).Methods Bioinformatics was used to analyze the binding of full-length wild-type CSD polypeptide and 101 amino acid deleted truncated mutant CSD polypeptide (Δ101CSD) to HO-1. Primary AMs were isolated from rats, when cell fusion reached 80％, they were synchronized with serum-free medium and divided into five groups: no treatment was given to the blank control group; LPS group was treated with 100μg/L LPS for 16 hours;LPS+ hemin group was treated with 100μg/L LPS and 20μmol/L hemin for 16 hours; wild-type CSD polypeptide+ LPS+hemin group was pretreated with 10μmol/L wild-type CSD polypeptide 6 hours before LPS treatment; Δ101CSD+ LPS+hemin group was pretreated with 10μmol/L Δ101CSD polypeptide 6 hours before LPS treatment. After treatment for 16 hours, the co-localization between caveolin-1 (Cav-1) and HO-1 was displayed by confocal microscope; the mRNA expressions of inflammatory cytokines interleukin-1β (IL-1β) and monocyte chemoattractant protein-1 (MCP-1) and M1/M2 polarization cytokines tumor necrosis factor-α (TNF-α), inducible nitric oxide synthase (iNOS), leukocyte differentiation antigen 206 (CD206) and IL-10 were determined by real-time fluorescent quantitative reverse transcription-polymerase chain reaction (RT-qPCR); the HO-1 activity and nitric oxide (NO) production were determined by spectrophotometry.Results Bioinformatics analysis showed: both wild-type CSD and Δ101CSD peptides could bind to HO-1, and there was no significant difference in the binding ability between the two peptides, but the deletion of 101 Arg resulted in the disappearance of part of the binding region between Δ101CSD and HO-1. The results of laser confocal microscopy showed: the expressions of Cav-1 and HO-1 were lowed in the blank control group, and Cav-1 was bound to HO-1 in LPS group and LPS+ hemin group. Both wild-type CSD and Δ101CSD peptides pretreatment could significantly reduce the binding of HO-1 to Cav-1 induced by LPS. HO-1 activity analysis showed: after LPS stimulation, the activity of HO-1 was significantly higher than that of the blank control group; the activity of HO-1 induced by LPS was increased by hemin; after pretreatment with two kinds of CSD peptides, the activity of HO-1 was further increased, and the effect of wild-type CSD peptide was more significant, which showed a statistically significant difference as compared with that of LPS+ hemin group (pmol·mg-1·h-1: 3683±266 vs. 2408±132,P < 0.05). RT-qPCR results showed: LPS could induce elevation of cytokines and M1 markers and decrease of M2 markers, while hemin could inhibit LPS-induced inflammatory response and M1/M2 phenotypic polarization. Compared with LPS+ hemin group, after pretreatment with wild-type CSD peptide, the levels of inflammatory factors in AMs were decreased, and the mRNA expression levels of TNF-α and iNOS, M1 markers, were decreased [TNF-α mRNA (2-??Ct): 6.82±0.05 vs. 8.70±0.24, iNOS mRNA (2-??Ct): 331.50±32.05 vs. 506.70±0.10, bothP < 0.05], and IL-10 mRNA expression level was increased (2-??Ct: 269.09±6.54 vs. 119.05±3.30,P < 0.05). The deletion of 101 site partially weakened the inhibitory effect of CSD peptides on inflammatory factors and only reduced the expression of iNOS mRNA (2-??Ct: 429.11±8.92 vs. 506.70±0.10,P < 0.05), indicating that its ability to transform AMs from M1 phenotype to M2 phenotype was poor. The two peptides had no effect on the expression of CD206.Conclusion Wild-type CSD had beneficial effects of anti-inflammation by reducing Cav-1 binding to HO-1 induced by LPS, restoring the HO-1 activity and driving M2 phenotype in alveolar macrophages.