Caveolin-1: a critical regulator of lung injury

Advancements in omics technologies: Molecular mechanisms of acute lung injury and acute respiratory distress syndrome (Review)

Acute lung injury (ALI)/acute respiratory distress syndrome (ARDS) is an inflammatory response arising from lung and systemic injury with diverse causes and associated with high rates of morbidity and mortality. To date, no fully effective pharmacological therapies have been established and the relevant underlying mechanisms warrant elucidation, which may be facilitated by multi‑omics technology. The present review summarizes the application of multi‑omics technology in identifying novel diagnostic markers and therapeutic strategies of ALI/ARDS as well as its pathogenesis.

Ganoderic acid a potential protective impact on bleomycin (BLM) -induced lung fibrosis in albino mice: Targeting caveolin 1/TGF-β/ Smad and P38MAPK signaling pathway

BACKGROUND

Bleomycin (BLM), an anticancer medication, can exacerbate pulmonary fibrosis by inducing oxidative stress and inflammation. Anti-inflammatory, anti-fibrotic, and antioxidant properties are exhibited by ganoderic acid A (GAA).

AIM

So, we aim to assess GAA's protective impact on lung fibrosis induced via BLM.

METHOD

Forty mice were randomly classified into four groups. Lung fibrosis was induced by injection of BLM intraperitoneally (15 mg/kg body weight). GAA was given by oral gavage (25 mg/kg body weight). Lung tissue MDA, TAC, and GSH were assessed spectrophotometrically. As well, TGFβ, p38 MAPK, TNF-α, IL-1β, and CAV1 levels were measured by enzyme-linked immunosorbent assay. Gene expression of tumor growth factor beta (TGF-β), Smad2, Smad3, and glutamate-cysteine ligase (GCL) were also evaluated.

RESULTS

GAA had significantly improved biochemical biomarkers as well as histopathology of the lung. The protective impact of GAA may be linked to the upregulation of GCL gene expression and subsequent GSH levels. In addition, the GAA-treated group showed a significant decrement in the levels of TGF-β, Smad2&3, P38 MAPK, TNF-α, IL1β, and MDA compared to BLM induced lung fibrosis group. GAA has a protective impact on lung fibrosis induced by BLM via downregulation of TGF-β and upregulation of CAV1 level and GCL expression which may play a critical role in the improvement of the pathogenesis of lung fibrosis induced via BLM.

Comparative proteomic analysis of retinal hypoxia-ischemia in an acute ocular hypertension model using tandem mass tag-based quantitative proteomics

The main symptom of acute glaucoma is acute ocular hypertension (AOH), which leads to the death of retinal ganglion cells (RGCs) and permanent loss of vision. However, effective treatments for these conditions are lacking. This study aimed to identify major regulators and overall protein changes involved in AOH-induced RGC death. Proteomic patterns of the retinal protein extracts from the AOH and sham groups were analyzed using mass spectrometry (MS), followed by Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analyses. Proteomic analysis revealed 92 proteins in the AOH group compared to the control group; 58 proteins were upregulated and 34 were downregulated. Alterations in fatty acid-binding protein 7 (FABP7) and caveolin-1 (Cav-1), which are related to fatty acid metabolism and ocular inflammatory signaling, were detected using western blotting and biochemical assays. Variations in the expression of galectin-1 (Gal-1), S100 calcium-binding protein A6 (S100a6), and visinin-like protein-1 (VILIP) have been associated with neuronal ischemia. Our investigation demonstrates that neuroinflammation and fatty acid metabolism are involved in retinal impairment following AOH, suggesting a possible treatment approach for acute glaucoma.

Secretome profiling of human epithelial cells exposed to cigarette smoke extract and their effect on human lung microvascular endothelial cells

Cigarette smoke (CS) is one of the leading causes of pulmonary diseases and can induce lung secretome alteration. CS exposure-induced damages to human pulmonary epithelial cells and microvascular endothelial cells have been extensively demonstrated; however, the effects of the secretome of lung epithelial cells exposed to CS extracts (CSE) on lung microvascular endothelial cells are not fully understood. In this study, we aimed to determine the effects of the secretome of lung epithelial cells exposed to CSE on lung microvascular endothelial cells. Human lung epithelial cells, A549, were exposed to CSE, and the secretome was collected. Human lung microvascular endothelial cells, HULEC-5a, were used to evaluate the effect of the secretome of A549 exposed to CSE. Secretome profile, endothelial cell death, inflammation, and permeability markers were determined. CSE altered the secretome expression of A549 cells, and secretome derived from CSE-exposed A549 cells caused respiratory endothelial cell death, inflammation, and moderately enhanced endothelial permeability. This study demonstrates the potential role of cellular interaction between endothelial and epithelial cells during exposure to CSE and provides novel therapeutic targets or beneficial biomarkers using secretome analysis for CSE-related respiratory diseases.

Alveolar-capillary endocytosis and trafficking in acute lung injury and acute respiratory distress syndrome

Acute respiratory distress syndrome (ARDS) is associated with high morbidity and mortality but lacks specific therapeutic options. Diverse endocytic processes play a key role in all phases of acute lung injury (ALI), including the initial insult, development of respiratory failure due to alveolar flooding, as a consequence of altered alveolar-capillary barrier function, as well as in the resolution or deleterious remodeling after injury. In particular, clathrin-, caveolae-, endophilin- and glycosylphosphatidyl inositol-anchored protein-mediated endocytosis, as well as, macropinocytosis and phagocytosis have been implicated in the setting of acute lung damage. This manuscript reviews our current understanding of these endocytic pathways and subsequent intracellular trafficking in various phases of ALI, and also aims to identify potential therapeutic targets for patients with ARDS.

The role of fatty acid metabolism in acute lung injury: a special focus on immunometabolism

Reputable evidence from multiple studies suggests that excessive and uncontrolled inflammation plays an indispensable role in mediating, amplifying, and protracting acute lung injury (ALI). Traditionally, immunity and energy metabolism are regarded as separate functions regulated by distinct mechanisms, but recently, more and more evidence show that immunity and energy metabolism exhibit a strong interaction which has given rise to an emerging field of immunometabolism. Mammalian lungs are organs with active fatty acid metabolism, however, during ALI, inflammation and oxidative stress lead to a series metabolic reprogramming such as impaired fatty acid oxidation, increased expression of proteins involved in fatty acid uptake and transport, enhanced synthesis of fatty acids, and accumulation of lipid droplets. In addition, obesity represents a significant risk factor for ALI/ARDS. Thus, we have further elucidated the mechanisms of obesity exacerbating ALI from the perspective of fatty acid metabolism. To sum up, this paper presents a systematical review of the relationship between extensive fatty acid metabolic pathways and acute lung injury and summarizes recent advances in understanding the involvement of fatty acid metabolism-related pathways in ALI. We hold an optimistic believe that targeting fatty acid metabolism pathway is a promising lung protection strategy, but the specific regulatory mechanisms are way too complex, necessitating further extensive and in-depth investigations in future studies.

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.

Brody J, Chen H, Gottlieb DJ, Evans DS, Guo X, Gharib SA, Hale L, Hillman DR, Lutsey PL, Mukherjee S, Ochs-Balcom HM, Palmer LJ, Purcell S, Saxena R, Patel SR, Stone KL, Tranah GJ, Boerwinkle E, Lin X, Liu Y, Psaty BM, Vasan RS, Manichaikul A, Rich SS, Rotter JI, Sofer T, Redline S, Zhu X. Targeted Genome Sequencing Identifies Multiple Rare Variants in Caveolin-1 Associated with Obstructive Sleep Apnea

Rationale: Obstructive sleep apnea (OSA) is a common disorder associated with increased risk for cardiovascular disease, diabetes, and premature mortality. There is strong clinical and epidemiologic evidence supporting the importance of genetic factors influencing OSA but limited data implicating specific genes. Objectives: To search for rare variants contributing to OSA severity. Methods: Leveraging high-depth genomic sequencing data from the NHLBI Trans-Omics for Precision Medicine (TOPMed) program and imputed genotype data from multiple population-based studies, we performed linkage analysis in the CFS (Cleveland Family Study), followed by multistage gene-based association analyses in independent cohorts for apnea-hypopnea index (AHI) in a total of 7,708 individuals of European ancestry. Measurements and Main Results: Linkage analysis in the CFS identified a suggestive linkage peak on chromosome 7q31 (LOD = 2.31). Gene-based analysis identified 21 noncoding rare variants in CAV1 (Caveolin-1) associated with lower AHI after accounting for multiple comparisons (P = 7.4 × 10-8). These noncoding variants together significantly contributed to the linkage evidence (P < 10-3). Follow-up analysis revealed significant associations between these variants and increased CAV1 expression, and increased CAV1 expression in peripheral monocytes was associated with lower AHI (P = 0.024) and higher minimum overnight oxygen saturation (P = 0.007). Conclusions: Rare variants in CAV1, a membrane-scaffolding protein essential in multiple cellular and metabolic functions, are associated with higher CAV1 gene expression and lower OSA severity, suggesting a novel target for modulating OSA severity.

Caveolin-1 rs1997623 variant and adult metabolic syndrome—Assessing the association in three ethnic cohorts of Arabs, South Asians and South East Asians

Background: Animal and cell model studies have implicated CAV1 in the pathophysiology of metabolic disorders. Our previous studies demonstrated a potential association of CAV1 rs1997623 C/A variant with pediatric metabolic syndrome (MetS) in Arab children. In the present study, we evaluate whether the CAV1 variant associates with MetS Arab adults as well. The association signal is further examined for ancestry-specific variation by considering cohorts of other ethnicities.

Method: The CAV1 rs1997623 was genotyped in three cohorts of Arab (n = 479), South Asian (n = 660), and South East Asian (n = 362) ethnic adults from Kuwait. MetS status of the individuals was diagnosed using the IDF criteria (presence of central obesity and at least two abnormalities out of: elevated TG, low HDL, hypertension, or T2D). The quantitative measure of MetS was calculated as siMS = 2 × WC/Height + FBG/5.6 + TG/1.7 + SBP/130–HDL/1.02 for males or HDL/1.28 for females. Allelic associations with quantitative and dichotomous MetS traits were assessed using linear and logistic regression models adjusted for age and sex. In addition, empirical p-values (P_emp) were generated using max(T) permutation procedure based on 10,000 permutations.

Results: The CAV1 variant was significantly associated with MetS status (OR = 1.811 [1.25–2.61]; p-value = 0.0015; P_emp = 0.0013) and with siMS (Effect size = 0.206; p-value = 0.0035; P_emp = 0.0028) in the cohort of Arab individuals. The association was weak and insignificant in the South Asian and South East Asian cohorts (OR = 1.19 and 1.11; p-values = 0.25 and 0.67, respectively).

Conclusion: The reported association of CAV1 rs1997623 C/A with MetS in Arab pediatric population is now demonstrated in an adult Arab cohort as well. The weak association signal seen in the Asian cohorts lead us to propose a certain extent of ethnic-specificity in CAV1 rs1997623 association with MetS.

Protective role of Cav-1 in pneumolysin-induced endothelial barrier dysfunction

Pneumolysin (PLY) is a bacterial pore forming toxin and primary virulence factor of Streptococcus pneumonia, a major cause of pneumonia. PLY binds cholesterol-rich domains of the endothelial cell (EC) plasma membrane resulting in pore assembly and increased intracellular (IC) Ca2+ levels that compromise endothelial barrier integrity. Caveolae are specialized plasmalemma microdomains of ECs enriched in cholesterol. We hypothesized that the abundance of cholesterol-rich domains in EC plasma membranes confers cellular susceptibility to PLY. Contrary to this hypothesis, we found increased PLY-induced IC Ca2+ following membrane cholesterol depletion. Caveolin-1 (Cav-1) is an essential structural protein of caveolae and its regulation by cholesterol levels suggested a possible role in EC barrier function. Indeed, Cav-1 and its scaffolding domain peptide protected the endothelial barrier from PLY-induced disruption. In loss of function experiments, Cav-1 was knocked-out using CRISPR-Cas9 or silenced in human lung microvascular ECs. Loss of Cav-1 significantly enhanced the ability of PLY to disrupt endothelial barrier integrity. Rescue experiments with re-expression of Cav-1 or its scaffolding domain peptide protected the EC barrier against PLY-induced barrier disruption. Dynamin-2 (DNM2) is known to regulate caveolar membrane endocytosis. Inhibition of endocytosis, with dynamin inhibitors or siDNM2 amplified PLY induced EC barrier dysfunction. These results suggest that Cav-1 protects the endothelial barrier against PLY by promoting endocytosis of damaged membrane, thus reducing calcium entry and PLY-dependent signaling.

Caveolin-1 genetic polymorphism interacts with PUFA to modulate metabolic syndrome risk

Several studies have reported a significant association between the metabolic syndrome (MetS) and mortality around the world. Caveolin-1 (CAV-1) has been widely studied in dyslipidaemia, and several studies have indicated that CAV-1 genetic variations may correlate with dietary intake of fatty acids. This study aimed to investigate the interaction of CAV-1 rs3807992 with types of dietary fatty acid in the MetS risk. This cross-sectional study was carried out on 404 overweight and obese females. Dietary intake was obtained from a 147-item FFQ. The CAV-1 genotype was measured using the PCR-restriction fragment length polymorphism method. Anthropometric values and serum levels (TC, LDL, HDL, TAG and FBS) were measured by standard methods. It was observed that the (AA + AG) group had significantly higher BMI, waist circumference and DBP (P = 0·02, P = 0·02, and P = 0·01, respectively) and lower serum LDL, HDL and TC (P < 0·05) than the GG group. It was found that A allele carriers were at higher odds of the MetS (P = 0·01), abdominal obesity (P = 0·06), increased TAG concentration (P = 0·01), elevated blood pressure (BP) (P = 0·01), increased glucose concentration (P = 0·45) and decreased HDL-cholesterol concentration (P = 0·03). Moreover, the interaction of CAV-1 and SFA intake was significant in terms of the MetS (P = 0·03), LDL (P = 0·03) and BP (P = 0·01). Additionally, the (AA + AG) group was significantly related to PUFA intake in terms of the MetS (P = 0·04), TAG (P = 0·02), glucose (P = 0·02) and homoeostasis model assessment insulin resistance (P = 0·01). Higher PUFA consumption might attenuate the CAV-1 rs3807992 associations with the MetS, and individuals with greater genetic predisposition appeared to have a higher risk of the MetS, associated with higher SFA consumption.

Reconstructed signaling and regulatory networks identify potential drugs for SARS-CoV-2 infection

Several molecular datasets have been recently compiled to characterize the activity of SARS-CoV-2 within human cells. Here we extend computational methods to integrate several different types of sequence, functional and interaction data to reconstruct networks and pathways activated by the virus in host cells. We identify key proteins in these networks and further intersect them with genes differentially expressed at conditions that are known to impact viral activity. Several of the top ranked genes do not directly interact with virus proteins. We experimentally tested treatments for a number of the predicted targets. We show that blocking one of the predicted indirect targets significantly reduces viral loads in stem cell-derived alveolar epithelial type II cells (iAT2s).

Single cell atlas for 11 non-model mammals, reptiles and birds

The availability of viral entry factors is a prerequisite for the cross-species transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2). Large-scale single-cell screening of animal cells could reveal the expression patterns of viral entry genes in different hosts. However, such exploration for SARS-CoV-2 remains limited. Here, we perform single-nucleus RNA sequencing for 11 non-model species, including pets (cat, dog, hamster, and lizard), livestock (goat and rabbit), poultry (duck and pigeon), and wildlife (pangolin, tiger, and deer), and investigated the co-expression of ACE2 and TMPRSS2. Furthermore, cross-species analysis of the lung cell atlas of the studied mammals, reptiles, and birds reveals core developmental programs, critical connectomes, and conserved regulatory circuits among these evolutionarily distant species. Overall, our work provides a compendium of gene expression profiles for non-model animals, which could be employed to identify potential SARS-CoV-2 target cells and putative zoonotic reservoirs.

The interactions between dietary fats intake and Caveolin 1 rs 3807992 polymorphism with fat distribution in overweight and obese women: a cross-sectional study

BACKGROUND

It has been reported that dietary fats and genetic factors in individuals are associated with the pattern of fat distribution. This study aimed to evaluate the interaction between dietary fats intake and Caveolin1 (CAV-1) rs 3807s992 polymorphism with fat distribution in overweight and obese women.

METHODS

A total of 221 participants were included in the current cross-sectional study. Body composition, biochemical parameters were evaluated by body composition analyzer and Pars Azmoon kits and genotypes determination was performed by PCR-RFLP, dietary fats were measured using a validated semi-quantitative food frequency questionnaire (FAQ).

RESULTS

The frequency of GG, AA and AG genotypes were 53.1, 24.6, and 22.3%, respectively, and the mean intake of total dietary fat intake was 97.47 ± 36.87 g. There was positive significant interaction between total fat intake and AA genotype on visceral fat level (p = 0.001), trunk fat (p = 0.01) and waist circumference (p = 0.05), positive significant interaction between total fat intake and AG genotype on the waist to hip ratio (WHR) (p = 0.02) and visceral fat level (p = 0.05), positive borderline significant interaction between saturated fatty acid and AA genotype on the trunk fat (p = 0.06), and between trans-fatty acids and AG genotype on WHR (p = 0.04), visceral fat level (p = 0.01), and between monounsaturated fatty acid and AG genotype on WHR (p = 0.04), and a borderline interaction between polyunsaturated fatty acid and AA genotypes on visceral fat level (p = 0.06), negative significant interaction between AG genotypes and linolenic acid on WHR (p = 0.04), borderline significant interaction between ALA and AG genotype on WHR (p = 0.06).

CONCLUSIONS

Our findings showed that CAV-1 rs 3807992 polymorphism and dietary fats were associated with fat distributions in individuals.

Pioglitazone restores phosphorylation of downregulated caveolin-1 in right ventricle of monocrotaline-induced pulmonary hypertension

BACKGROUND

Caveolin-1 (cav-1) plays a role in pulmonary arterial hypertension (PAH). Monocrotaline (MCT)-induced PAH is characterized by a loss of cav-1 in pulmonary arteries; however, less is known regarding its role in the hypertrophied right ventricle (RV). We aimed to characterize the role of cav-1 and Hsp90 in the RV of MCT-induced PAH and their impact on endothelial nitric oxide synthase (eNOS). Additionally, we focused on restoration of cav-1 expression with pioglitazone administration.

METHODS

Male 12-week-old Wistar rats were injected subcutaneously with monocrotaline (60 mg/kg). Selected proteins (cav-1, eNOS, pSer1177eNOS, Hsp90) and mRNAs (cav-1α, cav-1β, eNOS) were determined in the RV and left ventricle (LV) 4 weeks later. In a separate MCT-induced PAH study, pioglitazone (10 mg/kg/d, orally) administration started on day 14 after MCT.

RESULTS

MCT induced RV hypertrophy and lung enlargement. Cav-1 and pTyr14cav-1 were decreased in RV. Caveolin-1α (cav-1α) and caveolin-1β (cav-1β) mRNAs were decreased in both ventricles. Hsp90 protein was increased in RV. eNOS and pSer1177eNOS proteins were unchanged in the ventricles. eNOS mRNA was reduced in RV. Pioglitazone treatment increased oxygen saturation and pTyr14cav-1 vs. MCT group.

CONCLUSIONS

Restoration of pTyr14cav-1 did not lead to amelioration of the disease, nor did it prevent RV hypertrophy and fibrosis, which was indicated by an increase in Acta2, Nppb, Col3a1, and Tgfβ1 mRNA.

Transcriptomic Analysis of Polyhexamethyleneguanidine-Induced Lung Injury in Mice after a Long-Term Recovery

Polyhexamethyleneguanidine phosphate (PHMG-P) is one of the causative agents of humidifier disinfectant-induced lung injury. Direct exposure of the lungs to PHMG-P causes interstitial pneumonia with fibrosis. Epidemiological studies showed that patients with humidifier disinfectant-associated lung injuries have suffered from restrictive lung function five years after the onset of the lung injuries. We investigated whether lung damage was sustained after repeated exposure to PHMG-P followed by a long-term recovery and evaluated the adverse effects of PHMG-P on mice lungs. Mice were intranasally instilled with 0.3 mg/kg PHMG-P six times at two weeks intervals, followed by a recovery period of 292 days. Histopathological examination of the lungs showed the infiltration of inflammatory cells, the accumulation of extracellular matrix in the lung parenchyma, proteinaceous substances in the alveoli and bronchiolar–alveolar hyperplasia. From RNA-seq, the gene expression levels associated with the inflammatory response, leukocyte chemotaxis and fibrosis were significantly upregulated, whereas genes associated with epithelial/endothelial cells development, angiogenesis and smooth muscle contraction were markedly decreased. These results imply that persistent inflammation and fibrotic changes caused by repeated exposure to PHMG-P led to the downregulation of muscle and vascular development and lung dysfunction. Most importantly, this pathological structural remodeling induced by PHMG-P was not reversed even after long-term recovery.

Caveolin-1 Deficiency Protects Mice Against Carbon Tetrachloride-Induced Acute Liver Injury Through Regulating Polarization of Hepatic Macrophages

Polarization of hepatic macrophages plays a crucial role in the injury and repair processes of acute and chronic liver diseases. However, the underlying molecular mechanisms remain elusive. Caveolin-1 (Cav1) is the structural protein of caveolae, the invaginations of the plasma membrane. It has distinct functions in regulating hepatitis, cirrhosis, and hepatocarcinogenesis. Given the increasing number of cases of liver cancer, nonalcoholic steatohepatitis, and non-alcoholic fatty liver disease worldwide, investigations on the role of Cav1 in liver diseases are warranted. In this study, we aimed to investigate the role of Cav1 in the pathogenesis of acute liver injury. Wild-type (WT) and Cav1 knockout (KO) mice (Cav1^tm1Mls) were injected with carbon tetrachloride (CCl₄). Cav1 KO mice showed significantly reduced degeneration, necrosis, and apoptosis of hepatocytes and decreased level of alanine transaminase (ALT) compared to WT mice. Moreover, Cav1 was required for the recruitment of hepatic macrophages. The analysis of the mRNA levels of CD86, tumor necrosis factor (TNF), and interleukin (IL)-6, as well as the protein expression of inducible nitric oxide synthase (iNOS), indicated that Cav1 deficiency inhibited the polarization of hepatic macrophages towards the M1 phenotype in the injured liver. Consistent with in vivo results, the expressions of CD86, TNF, IL-6, and iNOS were significantly downregulated in Cav1 KO macrophages. Also, fluorescence-activated cell sorting (FACS) analysis showed that the proportion of M1 macrophages was significantly decreased in the liver tissues obtained from Cav1 KO mice following CCl₄ treatment. In summary, our results showed that Cav1 deficiency protected mice against CCl₄-induced acute liver injury by regulating polarization of hepatic macrophages. We provided direct genetic evidence that Cav1 expressed in hepatic macrophages contributed to the pathogenesis of acute liver injury by regulating the polarization of hepatic macrophages towards the M1 phenotype. These findings suggest that Cav1 expressed in macrophages may represent a potential therapeutic target for acute liver injury.

Molecular Mechanisms of Lipid Metabolism Disorders in Infectious Exacerbations of Chronic Obstructive Pulmonary Disease

Exacerbations largely determine the character of the progression and prognosis of chronic obstructive pulmonary disease (COPD). Exacerbations are connected with changes in the microbiological landscape in the bronchi due to a violation of their immune homeostasis. Many metabolic and immune processes involved in COPD progression are associated with bacterial colonization of the bronchi. The objective of this review is the analysis of the molecular mechanisms of lipid metabolism and immune response disorders in the lungs in COPD exacerbations. The complex role of lipid metabolism disorders in the pathogenesis of some infections is only beginning to be understood, however, there are already fewer and fewer doubts even now about its significance both in the pathogenesis of infectious exacerbations of COPD and in general in the progression of the disease. It is shown that the lipid rafts of the plasma membranes of cells are involved in many processes related to the detection of pathogens, signal transduction, the penetration of pathogens into the cell. Smoking disrupts the normally proceeded processes of lipid metabolism in the lungs, which is a part of the COPD pathogenesis.

Heterogeneous Nuclear Ribonucleoprotein A1 Loads Batched Tumor-Promoting MicroRNAs Into Small Extracellular Vesicles With the Assist of Caveolin-1 in A549 Cells

MicroRNAs in small extracellular vesicle (sEV-miRNAs) have been widely investigated as crucial regulated molecules secreted by tumor cells to communicate with surroundings. It is of great significance to explore the loading mechanism of sEV-miRNAs by tumor cells. Here, we comprehensively illustrated a reasoned loading pathway of batched tumor-promoting sEV-miRNAs in non-small cell lung cancer (NSCLC) cell line A549 with the application of a multi-omics method. The protein heterogeneous nuclear ribonucleoprotein A1 (hnRNPA1) was strictly selected as a powerful sEV-miRNA loading protein from miRNA-binding proteome and further verified through small RNA sequencing after hnRNPA1 silence. In terms of the mechanism, SUMOylated hnRNPA1 in sEVs was verified to control sEV-miRNA loading. Subsequently, as a scaffolding component of caveolae, caveolin-1 (CAV1) was detailedly demonstrated to assist the loading of SUMOylated hnRNPA1 and its binding miRNAs into sEVs. Inhibition of CAV1 significantly prevented SUMOylated hnRNPA1 from encapsulating into sEVs, resulting in less enrichment of sEV-miRNAs it loaded. Finally, we confirmed that hnRNPA1-loaded sEV-miRNAs could facilitate tumor proliferation and migration based on database analysis and cytological experiments. Our findings reveal a loading mechanism of batched tumor-promoting sEV-miRNAs, which may contribute to the selection of therapeutic targets for lung cancer.

Reconstruction of Ultra-thin Alveolar-capillary Basement Membrane Mimics

Alveolar-capillary basement membrane (BM) is ultra-thin (<2 µm) extracellular matrix that maintains integral epithelial-endothelial cell layers. In vitro reconstructions of alveolar-capillary barrier supported on synthetic scaffolds closely resembling the fibrous and ultra-thin natural BM are essential in mimicking the lung pathophysiology. Although BM topology and dimensions are well known to significantly influence cellular behavior, conventionally used BM mimics fail to recreate this natural niche. To overcome this, electrospun ultra-thin 2 µm poly(caprolactone) (PCL) nanofibrous mesh is used to establish an alveolar-capillary barrier model of lung endothelial/epithelial cells. Transepithelial electrical resistance (TEER) and permeability studies reveal integral tight junctions and improved mass transport through the highly porous PCL meshes compared to conventional dense membranes with etched pores. The chemotaxis of neutrophils is shown across the barrier in presence of inflammatory response that is naturally impeded in confined regions. Conventional requirement of 3 µm or larger pore size can lead to barrier disruption due to epithelial/endothelial cell invasion. Despite high porosity, the interconnected BM mimic prevents barrier disruption and allows neutrophil transmigration, thereby demonstrating the physiological relevance of the thin nanofibrous meshes. It is envisioned that these bipolar cultured barriers would contribute to an organ-level in vitro model for pathological disease, environmental pollutants, and nanotoxicology.

Exosomal microRNAs in the development of essential hypertension and its potential as biomarkers

MicroRNAs (miRNAs) are small regulatory molecules that are involved in posttranscriptional modifications. These noncoding RNAs are usually ferried by extracellular carriers such as exosomes or other protein and lipid carriers inside a range of body fluids including plasma and urine. Due to their ability to withstand harsh external conditions, exosomal miRNAs possess enormous potential as noninvasive disease biomarkers for, notably hypertension, whereby exosomal miRNAs have been implicated in its pathophysiological processes. More importantly, alterations in the microenvironment as a result of disease progression can induce active and selective loading of miRNAs into exosomes. In this paper, we first review the mechanisms of miRNA loading into exosomes, followed by the roles of exosomal miRNAs in the development of hypertension, and the potentials of exosomal miRNAs as biomarkers in comparison with other free circulating miRNAs. Finally, challenges and future research surrounding exosomal miRNAs will also be discussed. This review will aid in the understanding of noninvasive biomarkers for the early diagnosis of hypertension and for probing therapeutic efficacy.

The Evolving Role of Caveolin-1: A Critical Regulator of Extracellular Vesicles

Emerging evidence suggests that extracellular vesicles (EVs) play an essential role in mediating intercellular communication and inter-organ crosstalk both at normal physiological conditions and in the pathogenesis of human diseases. EV cargos are made up of a broad spectrum of molecules including lipids, proteins, and nucleic acids such as DNA, RNA, and microRNAs. The complex EV cargo composition is cell type-specific. A dynamic change in EV cargos occurs along with extracellular stimuli and a change in the pathophysiological status of the host. Currently, the underlying mechanisms by which EVs are formed and EV cargos are selected in the absence and presence of noxious stimuli and pathogens remain incompletely explored. The term EVs refers to a heterogeneous group of vesicles generated via different mechanisms. Some EVs are formed via direct membrane budding, while the others are produced through multivesicular bodies (MVBs) or during apoptosis. Despite the complexity of EV formation and EV cargo selection, recent studies suggest that caveolin-1, a well-known structural protein of caveolae, regulates the formation and cargo selection of some EVs, such as microvesicles (MVs). In this article, we will review the current understanding of this emerging and novel role of cav-1.

ABCA1 Regulates IOP by Modulating Cav1/eNOS/NO Signaling Pathway

Purpose

This study aimed to investigate the role and pathophysiological mechanism of ATP binding cassette transporter A1 (ABCA1) in regulating the IOP and aqueous humor outflow.

Methods

ABCA1 expression was measured in trabecular meshwork samples obtained from patients with POAG and human donor eyes by Western blot. To further evaluate the functional significance of ABCA1, porcine angular aqueous plexus (AAP) cells, which are equivalent to human Schlemm's canal endothelial cells, were either treated with ABCA1 agonist GW3965 or transduced with lentivirus expressing ABCA1-shRNA. Transendothelial electrical resistance, protein expression, and nitric oxide (NO) concentration were measured. GW3965 was administered by intracameral injection. IOP and aqueous humor outflow facility were also measured.

Results

ABCA1 expression was significantly higher in the trabecular meshwork tissue of patients with POAG compared with controls. ABCA1 upregulation in angular aqueous plexus cells decreased the transendothelial electrical resistance in the angular aqueous plexus monolayers accompanied by a 0.56-fold decrease in caveolin-1 expression and a 2.85-fold and 1.17-fold increase in endothelial NO synthase expression and NO concentration, respectively (n = 3, P < 0.05). Conversely, ABCA1 downregulation increased transendothelial electrical resistance and caveolin-1 expression and decreased endothelial NO synthase expression and NO production (n = 3, P < 0.05). GW3965 decreased IOP and significantly increased conventional outflow facility (P < 0.05).

Conclusions

Regulation of aqueous humor outflow via the caveolin-1/endothelial NO synthase/NO pathway is a newly defined function of ABCA1 that is different from its traditional role in mediating cholesterol efflux. ABCA1 is a compelling, novel therapeutic candidate for the treatment of glaucoma and ocular hypertension.

Epithelial membrane protein 2 governs transepithelial migration of neutrophils into the airspace

Whether respiratory epithelial cells regulate the final transit of extravasated neutrophils into the inflamed airspace or are a passive barrier is poorly understood. Alveolar epithelial type 1 (AT1) cells, best known for solute transport and gas exchange, have few established immune roles. Epithelial membrane protein 2 (EMP2), a tetraspan protein that promotes recruitment of integrins to lipid rafts, is highly expressed in AT1 cells but has no known function in lung biology. Here, we show that Emp2-/- mice exhibit reduced neutrophil influx into the airspace after a wide range of inhaled exposures. During bacterial pneumonia, Emp2-/- mice had attenuated neutrophilic lung injury and improved survival. Bone marrow chimeras, intravital neutrophil labeling, and in vitro assays suggested that defective transepithelial migration of neutrophils into the alveolar lumen occurs in Emp2-/- lungs. Emp2-/- AT1 cells had dysregulated surface display of multiple adhesion molecules, associated with reduced raft abundance. Epithelial raft abundance was dependent upon putative cholesterol-binding motifs in EMP2, whereas EMP2 supported adhesion molecule display and neutrophil transmigration through suppression of caveolins. Taken together, we propose that EMP2-dependent membrane organization ensures proper display on AT1 cells of a suite of proteins required to instruct paracellular neutrophil traffic into the alveolus.

Milrinone Attenuates Heart and Lung Remote Injury after Abdominal Aortic Cross-Clamping

BACKGROUND

Phosphodiesterase enzymes play a pivotal role in the pathogenesis of ischemia/reperfusion (IR). We examined the role of milrinone (MIL), a phosphodiesterase 3 inhibitor, on remote injury of the heart and lung after abdominal aortic cross-clamping.

DESIGN

Experimental study.

METHODS

Twenty-one Wistar rats were divided into 3 groups: (1) control (C, n = 7), underwent laparotomy and exploration of abdominal aorta only; (2) IR (n = 7), normal saline was applied intraperitoneally (i.p) before IR induced by clamping of the abdominal aorta for 1 hr and then allowing reperfusion for 1 hr; and (3) MIL + IR (n = 7), MIL was given (0.5 mg/kg, i.p) before IR. After sacrification, the lungs and hearts were taken out for analyses and the tissue malondialdehyde (MDA) and glutathione (GSH) were studied. All tissues were examined under light microscopy and transmission electron microscopy (TEM). Expressions of caveolin (Cav)-1 in the lung and Cav-1 and Cav-3 in the heart were examined immunohistochemically.

RESULTS

The MIL + IR group had significantly a lower magnitude of oxidative stress than the IR group both in the lung and heart (lung: P = 0.03 for MDA and 0.001 for GSH and heart: P = 0.002 for MDA and 0.000 for GSH). In light microscopy, the MIL + IR group had statistically a lower total injury score than the IR group for both the lung and heart tissue (P = 0.03 and P = 0.04, respectively). In TEM, regression of mitochondrial degeneration and lamellar bodies in type II pneumocytes in the lungs and obvious improvements in disruption at the intercalated discs and mitochondrial degeneration in the hearts in the MIL + IR group were detected compared with the IR group. The expression of both Cav-1 and Cav-3 in the MIL + IR group was improved compared with the IR group (P = 0.03 for both).

CONCLUSIONS

MIL attenuates remote injury of heart and lung in lower body IR by inhibiting oxidative stress. Moreover, Cav-1 and Cav-3 might have a potential role in MIL-induced cardioprotection.

Factors preventing materno-fetal transmission of SARS-CoV-2

Although many pregnant women have been infected by coronavirus, the presence of intrauterine vertical transmission has not been conclusively reported yet. What prevents this highly contagious virus from reaching the fetus? Is it only the presence of a strong placental barrier, or is it the natural absence of the some receptor that the viruses use for transmission? We, therefore, need to comprehensively understand the mechanism of action of the mammalian epithelial barriers located in two different organs with functional similarity. The barriers selected as potential targets by SARS-CoV-2 are the alveolo-capillary barrier (ACB), and the syncytio-capillary barrier (SCB). Caveolae are omega-shaped structures located on the cell membrane. They consist of caveolin-1 protein (Cav-1) and are involved in the internalisation of some viruses. By activating leukocytes and nuclear factor-κB, Cav-1 initiates inflammatory reactions. The presence of more than one Cav-1 binding sites on coronavirus is an important finding supporting the possible relationship between SARS-CoV-2-mediated lung injury. While the ACB cells express Cav-1 there is no caveolin expression in syncytiotrophoblasts. In this short review, we will try to explain our hypothesis that the lack of caveolin expression in the SCB is one of the most important physiological mechanisms that prevents vertical transmission of SARS-CoV-2. Since the physiological Cav-1 deficiency appears to prevent acute cell damage treatment algorithms could potentially be developed to block this pathway in the non-pregnant population affected by SARS-CoV-2.

•

Syncytiotrophoblasts do not express caveolin.

•

SARS-CoV-2 does not bind to syncytiotrophoblasts.

•

Placental barrier does not allow passage of SARS-CoV-2.

Role of Caveolin-1 in Diabetes and Its Complications

It is estimated that in 2017 there were 451 million people with diabetes worldwide. These figures are expected to increase to 693 million by 2045; thus, innovative preventative programs and treatments are a necessity to fight this escalating pandemic disorder. Caveolin-1 (CAV1), an integral membrane protein, is the principal component of caveolae in membranes and is involved in multiple cellular functions such as endocytosis, cholesterol homeostasis, signal transduction, and mechanoprotection. Previous studies demonstrated that CAV1 is critical for insulin receptor-mediated signaling, insulin secretion, and potentially the development of insulin resistance. Here, we summarize the recent progress on the role of CAV1 in diabetes and diabetic complications.

Molecular regulation and clinical significance of caveolin-1 methylation in chronic lung diseases

Chronic lung diseases represent a largely global burden whose pathogenesis remains largely unknown. Research increasingly suggests that epigenetic modifications, especially DNA methylation, play a mechanistic role in chronic lung diseases. DNA methylation can affect gene expression and induce various diseases. Of the caveolae in plasma membrane of cell, caveolin-1 (Cav-1) is a crucial structural constituent involved in many important life activities. With the increasingly advanced progress of genome-wide methylation sequencing technologies, the important impact of Cav-1 DNA methylation has been discovered. The present review overviews the biological characters, functions, and structure of Cav-1; epigenetic modifications of Cav-1 in health and disease; expression and regulation of Cav-1 DNA methylation in the respiratory system and its significance; as well as clinical potential as disease-specific biomarker and targets for early diagnosis and therapy.

Hyperoxia causes miR199a-5p-mediated injury in the developing lung

BACKGROUND

Hyperoxia-induced acute lung injury (HALI) is characterized by increased permeability and infiltration of inflammatory cells, impairment of alveolar development, and compromised lung function. Recent evidence has determined that microRNAs (miRs) are implicated in hyperoxia-induced lung injury, including bronchopulmonary dysplasia (BPD). However, the expression profile and functional role of miR199a-5p in developing lungs have not been reported.

METHODS

The present study was undertaken to explore the role of miR199a-5p in developing mice lungs and human neonates. We exposed neonatal mice for 7 days, mouse lung epithelial cells (MLE12), mouse lung endothelial cells (MLECs), and macrophages (RAW246.7), to hyperoxia at different time points.

RESULTS

Our results demonstrated enhanced miR199a-5p expression in hyperoxia-exposed mice lungs and cells, as well as in tracheal aspirates of infants developing BPD, with significant reduction in the expression of its target, caveolin-1. Next, we observed that miR199a-5p-mimic worsens HALI as evidenced by increased inflammatory cells, cytokines, and lung vascular markers. Conversely, miR199a-5p-inhibitor treatment attenuated HALI.

CONCLUSION

Thus, our findings suggest that miR199a-5p is a potential target for attenuating HALI pathophysiology in the developing lung. Moreover, miR199a-5p-inhibitor could be part of a novel therapeutic strategy for improving BPD in preterm neonates.

Caveolin-1 as a critical component in the pathogenesis of lung fibrosis of different etiology: Evidences and mechanisms

Caveolin is a structural protein of flask-shaped invaginations of the plasma membrane termed as caveolae and is widely expressed on the endothelial cells, smooth muscle cells and fibroblasts in the different parts of the body including the lung tissues. The expression of caveolin-1 in the lung tissues is important to prevent the fibrogenic actions of TGF-β1 in lung fibrosis of different etiology including idiopathic pulmonary fibrosis, systemic sclerosis-associated interstitial lung disease and allergen-induced airway remodeling. Caveolin-1-mediated internalization and degradation of TGF-β1 receptors may possibly account for the decreased actions of TGF-β1. Studies have shown that the deficiency of caveolin-1 is very important in inducing lung fibrosis and its upregulation is reported to prevent lung fibrosis. The biological actions of caveolin-1 involve signaling pathways including JNK signaling, IL-4, STAT-3, miR199a-5p, CXCR4⁺ and CXCL12. The present review discusses the key role of caveolin and associated signaling pathways in the pathogenesis of lung fibrosis of different etiology.

Host's Endogenous Caveolin-1 Expression is Downregulated in the Lung During Sepsis to Promote Cytoprotection

The present study focuses on the profile of "endogeneous" caveolin-1 protein in septic lung (CLP model).Caveolin-1, CD25, pP38, pAkt, and 14-3-3b protein expression profiles were studied using flow cytometry and immunohistochemistry 6, 12, 24, 36, and 48 h after sepsis induction. Cell viability was determined by 7-AAD staining and fibrosis by Masson trichrome stain. The effect of protein C zymogen concentrate (PC) on caveolin-1 expression was also investigated given that PC, once dissociated from caveolin-1, elicits a PAR-1-mediated protective signaling by forming a complex with endothelial protein C receptor (EPCR).CLP treatment increased lung inflammation and cell apoptosis. Fibrosis was apparent in vessels and alveoli. Caveolin-1+ cells presented reduced protein expression, especially 12 h post-CLP (P = 0.002). Immunohistochemistry revealed caveolin-1 positive expression mainly in regions with strong inflammatory reaction. Early induction of pP38+ cell population (P = 0.014) and gradual increase of CD25+ cells were also observed. Alternations in 14-3-3b expression related to apoptosis were apparent and accompanied by increased AKT phosphorylation activity late during sepsis progression.After PC administration, cell apoptosis was reduced (P = 0.004) and both the percentile and expression intensity of caveolin-1 positive cells were compromised (P = 0.009 and P = 0.027, respectively). 14-3-3b, CD25, and pP38 protein expression were decreased (P = 0.014, P = 0.004, and P = 0.007, respectively), whereas pAkt expression was induced (P = 0.032).The observed decline of endogenous caveolin-1 protein expression during sepsis implies its involvement in host's cytoprotective reaction either directly, by controlling caveolae population to decrease bacterial burden, or indirectly via regulating 14-3-3b-dependent apoptosis and EPCR-PAR-1-dependent protective signaling.

Caveolin-1 selectively regulates microRNA sorting into microvesicles after noxious stimuli

Emerging evidence suggests that extracellular vesicle (EV)-containing miRNAs mediate intercellular communications in response to noxious stimuli. It remains unclear how a cell selectively sorts the cellular miRNAs into EVs. We report that caveolin-1 (cav-1) is essential for sorting of selected miRNAs into microvesicles (MVs), a main type of EVs generated by outward budding of the plasma membrane. We found that cav-1 tyrosine 14 (Y14)-phosphorylation leads to interactions between cav-1 and hnRNPA2B1, an RNA-binding protein. The cav-1/hnRNPA2B1 complex subsequently traffics together into MVs. Oxidative stress induces O-GlcNAcylation of hnRNPA2B1, resulting in a robustly altered hnRNPA2B1-bound miRNA repertoire. Notably, cav-1 pY14 also promotes hnRNPA2B1 O-GlcNAcylation. Functionally, macrophages serve as the principal recipient of epithelial MVs in the lung. MV-containing cav-1/hnRNPA2B1 complex-bound miR-17/93 activate tissue macrophages. Collectively, cav-1 is the first identified membranous protein that directly guides RNA-binding protein into EVs. Our work delineates a novel mechanism by which oxidative stress compels epithelial cells to package and secrete specific miRNAs and elicits an innate immune response.

Mechanism of the JAK2/STAT3-CAV-1-NR2B signaling pathway in painful diabetic neuropathy

PURPOSE

The aim of the present study was to further elucidate the role of JAK2/STAT3-CAV-1-NR2B on painful diabetic neuropathy.

METHODS

In vivo, the mechanical withdrawal threshold and thermal withdrawal latency were measured to evaluate neuropathic pain behaviors (n= 8), while western blot (n= 5) and an immunofluorescence double staining experiment (n= 6) were performed to understand the molecular mechanism. In vitro, the individual culture of BV2 mouse microglia cell lines, the co-culture of BV2 mouse microglia cell lines and PC12 rat neuron cell lines, and western blot analysis were performed to understand the molecular mechanism between microglia and neurons.

RESULTS

The expression of p-JAK2, p-STAT3, t-CAV-1, and p-NR2B was upregulated in the dorsal horn of DNP rats throughout the experiment. Through the immunofluorescence double staining experiment, it was found that p-STAT3 was mainly expressed in activated microglia, and this condition can be stably maintained for approximately 2 weeks after the establishment of the DNP model. The intrathecal injection of JAK2 inhibitor AG490 can relieve the abnormal expression of p-JAK2, p-STAT3, t-CAV-1, and p-NR2B, and relieve pain. The remission of AG490 began on the third day, and it could be stably sustained for 14 days. In vitro high-glucose induced the activation of p-STAT3 in microglia, thereby upregulating the expression of p-CAV-1 and p-NR2B in neurons in the co-culture system. JAK2 inhibitor AG490 can alleviate the abnormal expression of these proteins in the JAK2/STAT3-CAV-1-NR2B signaling pathway in vitro.

CONCLUSIONS

Microglial JAK2/STAT3 signaling probably contributes to neuropathic pain by activating the CAV-1-NR2B pathway.

Caveolae, caveolin-1 and lung diseases of aging

INTRODUCTION

Flask-shaped plasma membrane (PM) invaginations called caveolae and their constitutive caveolin and cavin proteins regulate cellular function via plasma membrane and intracellular signal transduction pathways. Caveolae are present in a variety of cells in the lung including airway smooth muscle (ASM) where they interact with other proteins, receptors, and ion channels and thereby have the potential to affect both normal and disease processes such as inflammation, contractility, and fibrosis. Given their involvement in cell signaling, caveolae may play important roles in mediating and modulating aging processes, and contribute to lung diseases of aging. Areas covered: This review provides a broad overview of the current state of knowledge regarding caveolae and their constituent proteins in lung diseases in the elderly and identifies potential mechanisms that can be targeted for future therapies. Expert Commentary: Caveolin-1 may play a protective role in lung disease. What is less clear is whether altered caveolin-1 with aging is a natural process, or a biomarker of disease progression in the elderly.

Deletion 101 residue at caveolin-1 scaffolding domain peptides impairs the ability of increasing heme oxygenase-1 activity

OBJECTIVE

Resident alveolar macrophages (AMs) are activated and release proinflammatory mediators and chemokines during acute lung injury. We have previous reported that caveolin-1 (Cav-1) scaffolding domain (CSD) peptide inhibited the proinflammatory cytokines expression by up-regulating heme oxygenase-1 (HO-1) activity. In this study, we aimed to investigate the effect of residue R101 in CSD peptide on the activity of HO-1 in AMs.

METHODS

The binding mode between HO-1 and CSD peptides (WT CSD and Δ101 CSD truncation peptides) was analyzed and the free energy was calculated. The inflammatory genes and M1/M2macrophage polarization-associated genes expression were measured by real-time PCR. The activities of HO-1 were determined by the spectrophotometical method. Western blot analyzed the content of Cav-1, HO-1, IκB and MAPK signals (phosphorylated ERK, JNK and p38 MAPK).

RESULTS

Δ101CSD peptide could bind to HO-1 protein and to disrupt the interaction of HO-1 and Cav-1. However, Δ101CSD peptide had lower activity of HO-1 in LPS-treated AMs compared with WT CSD. The expression of IL-1β and MCP-1 and NO content were decreased by WT CSD peptide in LPS treated AMs. However, only MCP-1 expression and NO content were downregulated byΔ101CSD peptide. Meanwhile, compared with those in LPS + hemin + WT CSD group, the mRNA expression of TNF-α, Cd86, IL-12b and NOS2 significantly increased while expression of IL10, Arg1 and CD163 significantly decreased in LPS + hemin + Δ101CSD group. The effect of WT CSD peptide on the inhibition of MAPK signaling pathway were stronger than Δ101 CSD peptide evidenced by the level of phosphorylated ERK, JNK and p38 MAPK.

CONCLUSION

Deletion of residue R101 impairs the ability of CSD peptide to increase HO-1 activity and to dampen inflammatory response in LPS-challenged rat AMs.

Loss of Caveolin-1 in Metastasis-Associated Macrophages Drives Lung Metastatic Growth through Increased Angiogenesis

Although it is well established that tumor-associated macrophages take part in each step of cancer progression, less is known about the distinct role of the so-called metastasis-associated macrophages (MAMs) at the metastatic site. Previous studies reported that Caveolin-1 (Cav1) has both tumor-promoting and tumor-suppressive functions. However, the role of Cav1 in bone-marrow-derived cells is unknown. Here, we describe Cav1 as an anti-metastatic regulator in mouse models of lung and breast cancer pulmonary metastasis. Among all the recruited inflammatory cell populations, we show that MAMs uniquely express abundant levels of Cav1. Using clodronate depletion of macrophages, we demonstrate that macrophage Cav1 signaling is critical for metastasis and not for primary tumor growth. In particular, Cav1 inhibition does not affect MAM recruitment to the metastatic site but, in turn, favors angiogenesis. We describe a mechanism by which Cav1 in MAMs specifically restrains vascular endothelial growth factor A/vascular endothelial growth factor receptor 1 (VEGF-A/VEGFR1) signaling and its downstream effectors, matrix metallopeptidase 9 (MMP9) and colony-stimulating factor 1 (CSF1).

•

Macrophage Cav1 signaling is critical for restraining lung metastatic growth

•

Cav1 deletion in macrophages favors angiogenesis at the lung metastatic site

•

Cav1 suppresses VEGF-A/VEGFR1 activity and its downstream effectors, MMP9 and CSF1

Cav-1 promotes atherosclerosis by activating JNK-associated signaling

The objective of the study is to calculate the role and underlying the molecular mechanisms of caveolin-1 (Cav-1) in atherosclerosis (AS). Cav-1 was mainly expressed in the endothelial cells of atherosclerotic lesions in both human patients and apolipoprotein E deficient (ApoE^-/-) mice. Cav-1 deficiency (Cav-1^-/-) attenuated high-fat diet (HFD)-induced atherosclerotic lesions in ApoE^-/- mice, supported by the reduced aortic plaques. Cav-1^-/- reduced the macrophage content and decreased the release of inflammation-related cytokines or chemokine in serum or abdominal aortas, accompanied with the inactivation of inhibitor κB kinase κ (IKKβ)/p65/IκBα signaling pathway. Also, the activity of mitogen-activated protein kinases 7/c-Jun-N-terminal kinase (MKK7/JNK) signaling was decreased by Cav-1^-/-. In addition, oxidative stress induced by HFD in ApoE^-/- mice was alleviated by Cav-1^-/-. In response to HFD, Cav-1^-/- markedly reduced triglyceride (TG), total cholesterol (TC), low-density lipoprotein-cholesterol (LDLC) and very low-density lipoprotein-cholesterol (VLDLC) in serum of HFD-fed ApoE^-/- mice, whereas enhanced high-density lipoprotein-cholesterol (HDLC) contents. Consistent with these findings, haematoxylin and eosin (H&E) and Oil Red O staining showed fewer lipid droplets in the liver of Cav-1-deficient mice. Further, real time-quantitative PCR (RT-qPCR) analysis indicated that Cav-1^-/- alleviated dyslipidemia both in liver and abdominal aortas of ApoE^-/- mice fed with HFD. Cav-1 inhibition-induced attenuation of inflammatory response, oxidative stress and dyslipidemia were confirmed in vitro using mouse vascular smooth muscle cells (VSMCs) treated with ox-LDL. Surprisingly, the processes regulated by Cav-1-knockdown could be abolished through promoting JNK activation in ox-LDL-treated VSMCs. In conclusion, Cav-1 expression could promote HFD-induced AS in a JNK-dependent manner.

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-1β, 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.

Lung Protective Effects of Low-Volume Resuscitation and Pharmacologic Treatment of Swine Subjected to Polytrauma and Hemorrhagic Shock

Hemorrhage is a common cause of death in the battlefield. Valproic acid (VPA) has been associated with improved outcomes in multiple models of trauma, when combined with isotonic fluid resuscitation. However, isotonic fluid administered in this setting is logistically impractical and may be associated with complications. In this study, we sought to evaluate the feasibility and immunologic impact of combining VPA treatment with low-volume hypertonic saline (HTS). In vivo: female Yorkshire swine were subjected to hemorrhage (40% total blood volume) and polytrauma (rib fracture and delayed liver injury). Animals were kept in shock for 30 minutes and resuscitated with (1) normal saline (NS, 3× hemorrhaged volume), (2) HTS (7.5% saline, 4 mL/kg), or (3) HTS + VPA (4 mg/kg; 150 mg/kg; n = 3/cohort). After 18 hours of observation, animals were euthanized and the lungs evaluated for acute injury and expression of myeloperoxidase (MPO) and caveolin-1 (Cav-1). In vitro: human umbilical vein endothelial cells (HUVECs) were exposed to anoxic conditions (5% CO₂, 95% N₂) for 16 hours in (1) normosmotic, (2) hyperosmotic (400 mOsm), or (3) hyperosmotic + VPA (4 mM) media. Immunohistochemistry and Western blots were performed to determine Cav-1 expression. Lungs from VPA-treated animals demonstrated decreased acute injury, MPO expression, and endothelial expression of Cav-1 when compared to lungs from animals resuscitated with NS or HTS alone. Similarly, HUVECs cultured in hyperosmotic media containing VPA demonstrated decreased expression of Cav-1. This study demonstrates that combined treatment with VPA and HTS is a viable strategy in hemorrhagic shock and polytrauma. Attenuation of lung injury following VPA treatment may be related to modulation of the inflammatory response.

Qi-Dong-Huo-Xue-Yin Inhibits Inflammation in Acute Lung Injury in Mice via Toll-Like Receptor 4/Caveolin-1 Signaling

Acute lung injury (ALI) is a critical illness with no current effective treatment. Caveolin-1 indirectly activates inflammation-associated signaling pathways by inhibiting endothelial nitric oxide synthase (eNOS). This induces an imbalance between pro- and anti-inflammatory cytokine levels, which are involved in the pathogenesis of ALI. The compound Chinese prescription Qi-Dong-Huo-Xue-Yin (QDHXY) is efficacious for ALI treatment via an anti-inflammatory effect; however, the exact underlying mechanism is unknown. Therefore, we explored the protective effect of QDHXY against lipopolysaccharide- (LPS-) induced ALI in mice. Histopathological changes in mouse lung tissues were studied. Furthermore, alterations in the serum levels of pro- and anti-inflammatory cytokines were investigated. The levels of tumor necrosis factor- (TNF-)α, interleukin- (IL-) 6, IL-1β, and interferon-γ-induced protein 10 in bronchoalveolar lavage fluid were measured. Additionally, the expression levels of myeloid differentiation factor 88 (MyD88), caveolin-1, and eNOS were assessed. QDHXY significantly reduced lung infiltration with inflammatory cells and the production of serum pro- and anti-inflammatory cytokines and inhibited the expression of TNF-α, IL-1β, caveolin-1, and MyD88 but not eNOS. These indicate that QDHXY significantly improved the balance between pro- and anti-inflammatory cytokine levels, possibly by inhibiting the caveolin-1 signaling pathway. Therefore, QDHXY may be a potential treatment for ALI.

Caveolins as Regulators of Stress Adaptation

Caveolins have been recognized over the past few decades as key regulators of cell physiology. They are ubiquitously expressed and regulate a number of processes that ultimately impact efficiency of cellular processes. Though not critical to life, they are central to stress adaptation in a number of organs. The following review will focus specifically on the role of caveolin in stress adaptation in the heart, brain, and eye, three organs that are susceptible to acute and chronic stress and that show as well declining function with age. In addition, we consider some novel molecular mechanisms that may account for this stress adaptation and also offer potential to drive the future of caveolin research.

New insights into the mechanisms of pulmonary edema in acute lung injury

Appearance of alveolar protein-rich edema is an early event in the development of acute respiratory distress syndrome (ARDS). Alveolar edema in ARDS results from a significant increase in the permeability of the alveolar epithelial barrier, and represents one of the main factors that contribute to the hypoxemia in these patients. Damage of the alveolar epithelium is considered a major mechanism responsible for the increased pulmonary permeability, which results in edema fluid containing high concentrations of extravasated macromolecules in the alveoli. The breakdown of the alveolar-epithelial barrier is a consequence of multiple factors that include dysregulated inflammation, intense leukocyte infiltration, activation of pro-coagulant processes, cell death and mechanical stretch. The disruption of tight junction (TJ) complexes at the lateral contact of epithelial cells, the loss of contact between epithelial cells and extracellular matrix (ECM), and relevant changes in the communication between epithelial and immune cells, are deleterious alterations that mediate the disruption of the alveolar epithelial barrier and thereby the formation of lung edema in ARDS.

Identification and characterization of molluscan caveolin-1 ortholog from Haliotis discus discus: Possible involvement in embryogenesis and host defense mechanism against pathogenic stress

Caveolins are principal membrane proteins of caveolae that play a central role in signal transduction, substrate transport, and membrane trafficking in various cell types. Numerous studies have reported the crucial role of caveolin-1 (CAV1) in response to invading microbes; yet, very little is known about molluscan CAV1. In this study, we identified and characterized CAV1 ortholog from the disk abalone, Haliotis discus discus (HdCAV1). The cDNA sequence of HdCAV1 is 826 bp long and encodes a 127-amino acid polypeptide. Characteristic caveolin superfamily domain (Glu³ - Lys¹²⁶) and two possible transmembrane domains (Cys⁴⁸ - Tyr⁶⁷ and Ile¹⁰³ - Phe¹²⁰) were identified in the HdCAV1 protein. Homology analysis revealed that HdCAV1 shared higher identity (>47%) with molluscans, but lower identity with other species. Phylogenetic tree constructed by the neighbor-joining (NJ) method revealed a distinct evolutionary pathway for molluscans. Transcriptional analysis by SYBR Green qPCR showed the highest expression of HdCAV1 mRNA in late veliger stage, as compared to that in other embryonic developmental stages of disk abalone. In adult animals, gill tissue showed highest HdCAV1 transcript levels under normal physiological condition. Stimulations with two bacteria (Vibrio parahaemolyticus and Listeria monocytogenes), viral hemorrhagic septicemia virus, and two pathogen-associated molecular patterns (LPS and poly I:C) significantly modulated the expression of HdCAV1 transcripts. Collectively, these data suggest that CAV1 plays an important role in embryogenesis and host immune defense in disk abalone.

Dynamic expression of transformating growth factor-β1 and caveolin-1 in the lung of Bleomycin-induced interstitial lung disease

BACKGROUND

Interstitial lung disease (ILD) is a disease with high mortality worldwide. Unfortunately, its prognosis is still very poor. Therefore, developing the target molecular is very important for ILD diagnosis and treatment. Caveolin-1 (Cav-1) can regulate the formation of fibrosis by linking to the signaling pathway of transforming growth factor-β1 (TGF-β1), which is generally considered to be the most effective approach to solve the problem of ILD.

METHODS

The rat model of ILD was induced by disposable transtracheal injection of bleomycin hydrochloride. Rats were sacrificed in batches on days 7, 14, 21 and 28 after modeling, and the lung tissues was obtained for histopathological examination (HE) and Masson staining. Expressions of TGF-β1 and Cav-1 in the lungs were measured by western blot and real-time polymerase chain reaction (RT-PCR).

RESULTS

Pulmonary inflammation was observed in lung tissue from day 7 after modeling; fibrosis was observed from day 14 after modeling; the collagen deposition reached the peak on day 21. Significant TGF-β1 up-regulation and Cav-1 down-regulation appeared in the inflammatory phase (7d); TGF-β1 expression level reached the peak and Cav-1 expression level reached the minimum on day 21-28 with the most obvious fibrosis.

CONCLUSIONS

The rat model of bleomycin induced pulmonary fibrosis can be used to dynamically observe the progress of ILD. In the lung tissues from inflammation to fibrosis, TGF-β1 expression was significantly up-regulated and Cav-1 expression was significantly down-regulated. The regulation of two protein expressions is closely related to the occurrence and development of ILD in rats. The regulation of TGF-β1 and Cav-1 expressions and the balance between the two can be used as a possible target of ILD therapeutic intervention.

Staphylococcus aureus pore-forming toxins: The interface of pathogen and host complexity

Staphylococcus aureus is a prominent human pathogen capable of infecting a variety of host species and tissue sites. This versatility stems from the pathogen's ability to secrete diverse host-damaging virulence factors. Among these factors, the S. aureus pore-forming toxins (PFTs) α-toxin and the bicomponent leukocidins, have garnered much attention for their ability to lyse cells at low concentrations and modulate disease severity. Although many of these toxins were discovered nearly a century ago, their host cell specificities have only been elucidated over the past five to six years, starting with the discovery of the eukaryotic receptor for α-toxin and rapidly followed by identification of the leukocidin receptors. The identification of these receptors has revealed the species- and cell type-specificity of toxin binding, and provided insight into non-lytic effects of PFT intoxication that contribute to disease pathogenesis.