Upregulation of caveolae-associated structural proteins in the hair follicle bulge of lichen planopilaris and frontal fibrosing alopecia.

Lichen planopilaris (LPP) and frontal fibrosing alopecia (FFA) are primary cicatricial alopecia that cause a major impact on quality of life due to irreversible hair loss and symptoms as itching, burning and pain. They are characterized by permanent loss of hair follicle stem cells (HFSCs) by pathomechanisms still poorly understood, resulting in poor efficacy of currently available treatments. Caveolae are flask-shaped lipid rafts invaginated within the plasma membrane of multiple cell types. Although their role in the HF physiology and pathophysiology is relatively unknown, we have previously demonstrated that the primary structural component of caveolae (caveolin-1 or Cav1) is upregulated in FFA. Thus, we propose to investigate the expression and localization of caveolae-associated structural proteins (Cav1, Cav2, and Cavin-1) and HFSCs (identified by K15) in both LPP and FFA. We analyzed 4 patients with LPP biopsied in affected and non-affected (NA) scalp, 4 patients with FFA biopsied in affected scalp and 4 healthy controls. Affected scalp of LPP and FFA demonstrated increased levels of Cav1 and Cavin-1 compared with HC and LPP-NA. Moreover, Cav1, Cav2 and Cavin1 all exhibit high colocalization with K15 and their expression appears to be negatively correlated, supporting the hypothesis that these proteins are important players in LPP/FFA and may serve as therapeutic targets in future treatments.

Chemical characterization and effects of volatile oil of Alpinia zerumbet on the quality of collagen deposition and caveolin-1 expression in a muscular fibrosis murine model / Caracterização química e efeitos do óleo volátil de Alpinia zerumbet na qualidade da deposição do colágeno e expressão da caveolina-1 em modelo murino de fibrose muscular

Abstract This study evaluated the effect of the volatile oil of Alpinia zerumbet (VOAz) on caveolin-1 gene expression and muscular fibrosis. The rats were immobilized to induce fibrosis of the gastrocnemius muscle, and they were treated with VOAz. Collagen quality was assessed by histology and the expression of the caveolin-1 (CAV-1) gene was evaluated using qPCR. Histomorphological analysis indicated a significant reduction in the perimeter, width, and intensity of collagen in the treated groups, thus showing that the oil was effective in regulating the quality of collagen at the three concentrations. The results of expression levels suggested a decrease in the lesioned group and in two treatment groups (0.0115 µg/g and 0.009 µg/g). However, with the lowest concentration (0.0065 µg/g), no significant difference was observed, with levels similar to those found in healthy tissue. Therefore, the results showed that VOAz has the potential to be a non-invasive and low-cost alternative to aid in the treatment of muscular fibrosis.

Resumo Este estudo avaliou o efeito do óleo volátil de Alpinia zerumbet (OVAz) na expressão do gene da caveolina-1 e na fibrose muscular. Os ratos foram imobilizados para induzir a fibrose do músculo gastrocnêmio, e foram tratados com OVAz. A qualidade do colágeno foi avaliada com histologia e à expressão do gene caveolina-1 (CAV-1) foi avaliada usando qPCR. A análise histomorfológica indicou uma redução significativa no perímetro, largura e intensidade do colágeno nos grupos tratados. Os resultados dos níveis de expressão sugeriram diminuição nos grupos de lesão e em dois grupos de tratamento (0,0115 µg/g e 0,009 µg/g). No entanto, com a menor concentração (0,0065 µg/g), não foi observada diferença significativa, apresentando níveis semelhantes aos encontrados em tecido saudável. O uso do OVAz foi eficaz para reverter as alterações do colágeno causadas pela fibrose, e sua menor concentração apresentou uma possível tendência de aumento na expressão do CAV-1. Portanto, os resultados mostraram que o OVAz tem potencial para ser uma alternativa não invasiva e de baixo custo para auxiliar no tratamento da fibrose muscular.

Prostaglandin E2 Exposure Disrupts E-Cadherin/Caveolin-1-Mediated Tumor Suppression to Favor Caveolin-1-Enhanced Migration, Invasion, and Metastasis in Melanoma Models.

Caveolin-1 (CAV1) is a membrane-bound protein that suppresses tumor development yet also promotes metastasis. E-cadherin is important in CAV1-dependent tumor suppression and prevents CAV1-enhanced lung metastasis. Here, we used murine B16F10 and human A375 melanoma cells with low levels of endogenous CAV1 and E-cadherin to unravel how co-expression of E-cadherin modulates CAV1 function in vitro and in vivo in WT C57BL/6 or Rag-/- immunodeficient mice and how a pro-inflammatory environment generated by treating cells with prostaglandin E2 (PGE2) alters CAV1 function in the presence of E-cadherin. CAV1 expression augmented migration, invasion, and metastasis of melanoma cells, and these effects were abolished via transient co-expression of E-cadherin. Importantly, exposure of cells to PGE2 reverted the effects of E-cadherin expression and increased CAV1 phosphorylation on tyrosine-14 and metastasis. Moreover, PGE2 administration blocked the ability of the CAV1/E-cadherin complex to prevent tumor formation. Therefore, our results support the notion that PGE2 can override the tumor suppressor potential of the E-cadherin/CAV1 complex and that CAV1 released from the complex is phosphorylated on tyrosine-14 and promotes migration/invasion/metastasis. These observations provide direct evidence showing how a pro-inflammatory environment caused here via PGE2 administration can convert a potent tumor suppressor complex into a promoter of malignant cell behavior.

Hypertension depresses but exercise training restores both Mfsd2a expression and blood-brain barrier function within PVN capillaries.

Hypertension augments while exercise training corrects the increased vesicle trafficking (transcytosis) across the blood-brain barrier (BBB) within preautonomic areas and the autonomic imbalance. There is no information on a possible mechanism(s) conditioning these effects. Knowing that Mfsd2a is the major transporter of docosahexaenoic acid (DHA) and that Mfsd2a knockout mice exhibited leaky BBB, we sought to identify its possible involvement in hypertension- and exercise-induced transcytosis across the BBB. Spontaneously hypertensive rats (SHR) and Wistar rats were submitted to treadmill training (T) or kept sedentary (S) for 4 wk. Resting hemodynamic/autonomic parameters were recorded in conscious chronically cannulated rats. BBB permeability within the hypothalamic paraventricular nucleus (PVN) was evaluated in anesthetized rats. Brains were harvested for Mfsd2a and caveolin-1 (an essential protein for vesicle formation) expression. SHR-S versus Wistar-S exhibited elevated arterial pressure (AP) and heart rate (HR), increased vasomotor sympathetic activity, reduced cardiac parasympathetic activity, greater pressure variability, reduced HR variability, and depressed baroreflex control. SHR-S also showed increased BBB permeability, reduced Mfsd2a, and increased caveolin-1 expression. SHR-T versus SHR-S exhibited increased Mfsd2a density, reduced caveolin-1 protein expression, and normalized PVN BBB permeability, which were accompanied by resting bradycardia, partial AP drop, reduced sympathetic and normalized cardiac parasympathetic activity, increased HR variability, and reduced pressure variability. No changes were observed in Wistar-T versus Wistar-S. Training is an efficient tool to rescue Mfsd2a expression, which by transporting DHA into the endothelial cell reduces caveolin-1 availability and vesicles' formation. Exercise-induced Mfsd2a normalization is an important mechanism to correct both BBB function and autonomic control in hypertensive subjects.

Blood-brain barrier lesion - a novel determinant of autonomic imbalance in heart failure and the effects of exercise training.

Heart failure (HF) is characterized by reduced ventricular function, compensatory activation of neurohormonal mechanisms and marked autonomic imbalance. Exercise training (T) is effective to reduce neurohormonal activation but the mechanism underlying the autonomic dysfunction remains elusive. Knowing that blood-brain barrier (BBB) lesion contributes to autonomic imbalance, we sought now to investigate its involvement in HF- and exercise-induced changes of autonomic control. Wistar rats submitted to coronary artery ligation or SHAM surgery were assigned to T or sedentary (S) protocol for 8 weeks. After hemodynamic/autonomic recordings and evaluation of BBB permeability, brains were harvesting for ultrastructural analysis of BBB constituents, measurement of vesicles trafficking and tight junction's (TJ) tightness across the BBB (transmission electron microscopy) and caveolin-1 and claudin-5 immunofluorescence within autonomic brain areas. HF-S rats versus SHAM-S exhibited reduced blood pressure, augmented vasomotor sympathetic activity, increased pressure and reduced heart rate variability, and, depressed reflex sensitivity. HF-S also presented increased caveolin-1 expression, augmented vesicle trafficking and a weak TJ (reduced TJ extension/capillary border), which determined increased BBB permeability. In contrast, exercise restored BBB permeability, reduced caveolin-1 content, normalized vesicles counting/capillary, augmented claudin-5 expression, increased TJ tightness and selectivity simultaneously with the normalization of both blood pressure and autonomic balance. Data indicate that BBB dysfunction within autonomic nuclei (increased transcytosis and weak TJ allowing entrance of plasma constituents into the brain parenchyma) underlies the autonomic imbalance in HF. Data also disclose that exercise training corrects both transcytosis and paracellular transport and improves autonomic control even in the persistence of cardiac dysfunction.

Loss of Caveolin-1 Expression in Tumor Cells is Associated with Increased Aggressiveness and Cell Invasion in Oral Squamous Cell Carcinoma.

BACKGROUND: Changes in Caveolin-1 (CAV-1) expression are related to tumorigenesis. The aim of this study was to evaluate the role of CAV-1 in tumor progression in oral squamous cell carcinoma (SCC) tissue samples and the effect of CAV-1 silencing on two oral tongue SCC (OTSCC) cell lines (SCC-25, from a primary tumor, and HSC-3 from lymph node metastases). METHODS: Mycroarray hybridization, mRNA expression, and immunohistochemistry were performed on OSCC tissue samples and corresponding non-tumoral margin tissues. The effects of CAV-1 silencing (siCAV-1) on cell viability, membrane fluidity, on the expression of epithelial to mesenchymal transition (EMT) markers and on cell migration and invasion capacity of OTSCC cell lines were evaluated. RESULTS: Microarray showed a greater CAV-1 expression (1.77-fold) in OSCC tumors than in non-tumoral tissues and 2.0-fold more in less aggressive OSCCs. However, significant differences in CAV-1 gene expression were not seen between tumors and non-tumoral margins nor CAV-1 with any clinicopathological parameters. CAV-1 protein was localized both in carcinoma and in spindle cells of the tumor microenvironment (TME), and CAV-1 positive TME cells were associated with smaller/more aggressive tumors, independent of the carcinoma cells' expression. Silencing of CAV-1 increased cell viability only in SCC-25 cells. It also stimulated the invasion of HSC-3 cells and increased ECAD and BCAT mRNA in these cells; however, the protein levels of the EMT markers were not affected. CONCLUSION: Decreased expression of CAV-1 by tumor cells in OSCC and an increase in the TME were associated with increased cell invasiveness and tumor aggressiveness.

Cholesterol depletion affects caveolin-1 expression, migration and invasion of oral tongue squamous cell carcinoma cell lines.

INTRODUCTION: Cholesterol is a key lipid molecule within cell membranes. This is especially true in cavelolas, invaginated membrane nanodomains, which present the protein caveolin-1 (CAV-1). It is important to note that this structure is involved in many cell signalling pathways. Additionally, high cholesterol is seen in different tumor types but little is known in regards to oral tongue squamous cell carcinoma (OTSCC). The aim of this study was to evaluate the influence of cholesterol depletion on primary (SCC-25) and metastatic (HSC-3) OTSCC cell lines. MATERIALS AND METHODS: Cell membrane fluidity, cell viability, gene and protein expression of CAV-1 and of epithelial-mesenchymal transition (EMT) markers, cell migration in Myogel and invasion-myoma assay were evaluated after cholesterol depletion with methyl-ß-cyclodextrin (MßCD - 7.5, 10 or 15 mM) RESULTS: Decreased cell viability and increased membrane fluidity of SCC-25 cells was seen with cholesterol depletion but cell viability was less affected and there was no effect on membrane fluidity in HSC-3. Cholesterol depletion also decreased CAV-1 at 6 h but increased it after 24 h.; both epithelial and mesenchymal EMT genes were upregulated after 6 h, followed by downregulation at 24 h in SCC-25. In HSC-3, CAV-1 was downregulated, and E-cadherin gene (ECAD) was upregulated at 6 h. Only the protein ß-catenin in SCC-25 was affected, and cell migration of both cell lines was decreased, affecting SCC-25 more intensely. The invasive capacity within human myoma organotypic model was increased in SCC-25 and decreased in HSC-3. CONCLUSION: Cholesterol depletion affects CAV-1 and ECAD inversely. This affect also depends on cell type since the invasive capacity was augmented in primary cells while decreased in metastatic cells.

Actin-Cytoskeleton Drives Caveolae Signaling to Mitochondria during Postconditioning.

Caveolae-associated signaling toward mitochondria contributes to the cardioprotective mechanisms against ischemia-reperfusion (I/R) injury induced by ischemic postconditioning. In this work, we evaluated the role that the actin-cytoskeleton network exerts on caveolae-mitochondria communication during postconditioning. Isolated rat hearts subjected to I/R and to postconditioning were treated with latrunculin A, a cytoskeleton disruptor. Cardiac function was compared between these hearts and those exposed only to I/R and to the cardioprotective maneuver. Caveolae and mitochondria structures were determined by electron microscopy and maintenance of the actin-cytoskeleton was evaluated by phalloidin staining. Caveolin-3 and other putative caveolae-conforming proteins were detected by immunoblot analysis. Co-expression of caveolin-3 and actin was evaluated both in lipid raft fractions and in heart tissue from the different groups. Mitochondrial function was assessed by respirometry and correlated with cholesterol levels. Treatment with latrunculin A abolishes the cardioprotective postconditioning effect, inducing morphological and structural changes in cardiac tissue, reducing F-actin staining and diminishing caveolae formation. Latrunculin A administration to post-conditioned hearts decreases the interaction between caveolae-forming proteins, the co-localization of caveolin with actin and inhibits oxygen consumption rates in both subsarcolemmal and interfibrillar mitochondria. We conclude that actin-cytoskeleton drives caveolae signaling to mitochondria during postconditioning, supporting their functional integrity and contributing to cardiac adaption against reperfusion injury.

Caveolae Microdomains Mediate STAT5 Signaling Induced by Insulin in MCF-7 Breast Cancer Cells.

Caveolae are small plasma membrane invaginations constituted for membrane proteins namely caveolins and cytosolic proteins termed cavins, which can occupy up to 50% of the surface of mammalian cells. The caveolae have been involved with a variety of cellular processes including regulation of cellular signaling. Insulin is a hormone that mediates a variety of physiological processes through activation of insulin receptor (IR), which is a tyrosine kinase receptor expressed in all mammalian tissues. Insulin induces activation of signal transducers and activators of transcription (STAT) family members including STAT5. In this study, we demonstrate, for the first time, that insulin induces phosphorylation of STAT5 at tyrosine-694 (STAT5-Tyr(P)694), STAT5 nuclear accumulation and an increase in STAT5-DNA complex formation in MCF-7 breast cancer cells. Insulin also induces nuclear accumulation of STAT5-Tyr(P)694, caveolin-1, and IR in MCF-7 cells. STAT5 nuclear accumulation and the increase of STAT5-DNA complex formation require the integrity of caveolae and microtubule network. Moreover, insulin induces an increase and nuclear accumulation of STAT5-Tyr(P)694 in MDA-MB-231 breast cancer cells. In conclusion, results demonstrate that caveolae and microtubule network play an important role in STAT5-Tyr(P)694, STAT5 nuclear accumulation and STAT5-DNA complex formation induced by insulin in breast cancer cells.

Role of Caveolin-1 in Sepsis - A Mini-Review.

Sepsis is a generalized disease characterized by an extreme response to a severe infection. Moreover, challenges remain in the diagnosis, treatment and management of septic patients. In this mini-review we demonstrate developments on cellular pathogenesis and the role of Caveolin-1 (Cav-1) in sepsis. Studies have shown that Cav-1 has a significant role in sepsis through the regulation of membrane traffic and intracellular signaling pathways. In addition, activation of apoptosis/autophagy is considered relevant for the progression and development of sepsis. However, how Cav-1 is involved in sepsis remains unclear, and the precise mechanisms need to be further investigated. Finally, the role of Cav-1 in altering cell permeability during inflammation, in sepsis caused by microorganisms, apoptosis/autophagy activation and new therapies under study are discussed in this mini-review.

Caveolin-1 influences mitochondrial plasticity and function in hepatic stellate cell activation.

Caveolin-1 (Cav-1) is an integral membrane protein present in all organelles, responsible for regulating and integrating multiple signals as a platform. Mitochondria are extremely adaptable to external cues in chronic liver diseases, and expression of Cav-1 may affect mitochondrial flexibility in hepatic stellate cells (HSCs) activation. We previously demonstrated that exogenous expression of Cav-1 was sufficient to increase some classical markers of activation in HSCs. Here, we aimed to evaluate the influence of exogenous expression and knockdown of Cav-1 on regulating the mitochondrial plasticity, metabolism, endoplasmic reticulum (ER)-mitochondria distance, and lysosomal activity in HSCs. To characterize the mitochondrial, lysosomal morphology, and ER-mitochondria distance, we perform transmission electron microscope analysis. We accessed mitochondria and lysosomal networks and functions through a confocal microscope and flow cytometry. The expression of mitochondrial machinery fusion/fission genes was examined by real-time polymerase chain reaction. Total and mitochondrial cholesterol content was measured using Amplex Red. To define energy metabolism, we used the Oroboros system in the cells. We report that GRX cells with exogenous expression or knockdown of Cav-1 changed mitochondrial morphometric parameters, OXPHOS metabolism, ER-mitochondria distance, lysosomal activity, and may change the activation state of HSC. This study highlights that Cav-1 may modulate mitochondrial function and structural reorganization in HSC activation, being a potential candidate marker for chronic liver diseases and a molecular target for therapeutic intervention.

Melanosomal targeting via caveolin-1 dependent endocytosis mediates ZN(II) phthalocyanine phototoxic action in melanoma cells.

Melanosomes have been considered crucial targets in melanoma treatments. In this study we explored the role of melanosomes in photodynamic therapy (PDT), employing the synthetic Zn(II) phthalocyanine Pc13, a potent photosensitizer that promotes melanoma cell death after irradiation. Phototoxic action is mediated by reactive oxygen species increase. The internalization mechanism of Pc13 and its consequent subcellular localization were evaluated in melanotic B16-F0 cells. Pharmacological inhibitors of dynamin or caveolae, but not of clathrin, decreased Pc13 cellular uptake and phototoxicity. Similar results were obtained when cells over-expressed dominant negative mutants of dynamin-2 and caveolin-1, indicating that Pc13 is internalized by caveolae-mediated endocytosis. Confocal microscopy analysis revealed that Pc13 targets melanosomes and damage of these structures after irradiation was demonstrated by transmission electron microscopy. Treatment of pigmented B16-F0 and WM35 melanoma cells with the melanin synthesis inhibitor phenylthiourea for 48 h led to cell depigmentation and enhanced cell death after irradiation, whereas a 3-h period of inhibition did not modify melanin content but produced a marked reduction of Pc13 phototoxicity, together with a decrease of oxidative melanin synthesis intermediates. In contrast, the effect of Pc13 in amelanotic A375 cells was not altered by phenylthiourea treatment. These results provide evidence that melanosomes have a dual role in the efficacy of PDT. While melanin antagonizes the phototoxic action of Pc13, the release of cytotoxic synthetic intermediates to cytosol after irradiation and melanosome damage is conducive to the phototoxic response. Based on these findings, we demonstrate that melanosome-targeted PDT could be an effective approach for melanoma treatment.

Chemical characterization and effects of volatile oil of Alpinia zerumbet on the quality of collagen deposition and caveolin-1 expression in a muscular fibrosis murine model.

This study evaluated the effect of the volatile oil of Alpinia zerumbet (VOAz) on caveolin-1 gene expression and muscular fibrosis. The rats were immobilized to induce fibrosis of the gastrocnemius muscle, and they were treated with VOAz. Collagen quality was assessed by histology and the expression of the caveolin-1 (CAV-1) gene was evaluated using qPCR. Histomorphological analysis indicated a significant reduction in the perimeter, width, and intensity of collagen in the treated groups, thus showing that the oil was effective in regulating the quality of collagen at the three concentrations. The results of expression levels suggested a decrease in the lesioned group and in two treatment groups (0.0115 µg/g and 0.009 µg/g). However, with the lowest concentration (0.0065 µg/g), no significant difference was observed, with levels similar to those found in healthy tissue. Therefore, the results showed that VOAz has the potential to be a non-invasive and low-cost alternative to aid in the treatment of muscular fibrosis.

Transcytosis within PVN capillaries: a mechanism determining both hypertension-induced blood-brain barrier dysfunction and exercise-induced correction.

Although hypertension disrupts the blood-brain barrier (BBB) integrity within the paraventricular nucleus of hypothalamus (PVN) and increases the leakage into the brain parenchyma, exercise training (T) was shown to correct it. Since there is scarce and contradictory information on the mechanism(s) determining hypertension-induced BBB deficit and nothing is known about T-induced improvement, we sought to evaluate the paracellular and transcellular transport across the BBB within the PVN in both conditions. Spontaneously hypertensive rats (SHR) and WKY submitted to 4-wk aerobic T or sedentary (S) protocol were chronically catheterized for hemodynamic recordings at rest and intra-arterial administration of dyes (Rhodamine-dextran 70 kDa + FITC-dextran 10 kDa). Brains were harvesting for FITC leakage examination, qPCR evaluation of different BBB constituents and protein expression of caveolin-1 and claudin-5, the main markers of transcytosis and paracellular transport, respectively. Hypertension was characterized by increased arterial pressure and heart rate, augmented sympathetic modulation of heart and vessels, and reduced cardiac parasympathetic control, marked FITC extravasation into the PVN which was accompanied by increased caveolin-1 gene and protein expression, without changes in claudin-5 and others tight junctions' components. SHR-T vs. SHR-S showed a partial pressure reduction, resting bradycardia, improvement of autonomic control of the circulation simultaneously with correction of both FITC leakage and caveolin-1 expression; there was a significant increase in claudin-5 expression. Caveolin-1 content was strongly correlated with improved autonomic control after exercise. Data indicated that within the PVN the transcytosis is the main mechanism governing both hypertension-induced BBB leakage, as well as the exercise-induced correction.

Clustering of adenosine A2B receptors with ectonucleotidases in caveolin-rich lipid rafts underlies immunomodulation by Leishmania amazonensis.

Extracellular adenosine plays important roles in modulating the immune responses. We have previously demonstrated that infection of dendritic cells (DC) by Leishmania amazonensis leads to increased expression of CD39 and CD73 and to the selective activation of the low affinity A2B receptors (A2B R), which contributes to DC inhibition, without involvement of the high affinity A2A R. To understand this apparent paradox, we now characterized the alterations of both adenosine receptors in infected cells. With this aim, bone marrow-derived DC from C57BL/6J mice were infected with metacyclic promastigotes of L. amazonensis. Fluorescence microscopy revealed that L. amazonensis infection stimulates the recruitment of A2B R, but not of A2A R, to the surface of infected DC, without altering the amount of mRNA or the total A2B R density, an effect dependent on lipophosphoglycan (LPG). Log-phase promastigotes or axenic amastigotes of L. amazonensis do not stimulate A2B R recruitment. A2B R clusters are localized in caveolin-rich lipid rafts and the disruption of these membrane domains impairs A2B R recruitment and activation. More importantly, our results show that A2B R co-localize with CD39 and CD73 forming a "purinergic cluster" that allows for the production of extracellular adenosine in close proximity with these receptors. We conclude that A2B R activation by locally produced adenosine constitutes an elegant and powerful evasion mechanism used by L. amazonensis to down-modulate the DC activation.

COVID-19: Immunohistochemical Analysis of TGF-ß Signaling Pathways in Pulmonary Fibrosis.

Acute respiratory distress syndrome (ARDS) followed by repair with lung remodeling is observed in COVID-19. These findings can lead to pulmonary terminal fibrosis, a form of irreversible sequelae. There is evidence that TGF-ß is intimately involved in the fibrogenic process. When activated, TGF-ß promotes the differentiation of fibroblasts into myofibroblasts and regulates the remodeling of the extracellular matrix (ECM). In this sense, the present study evaluated the histopathological features and immunohistochemical biomarkers (ACE-2, AKT-1, Caveolin-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-ß1 tissue expression) involved in the TGF-ß1 signaling pathways and pulmonary fibrosis. The study consisted of 24 paraffin lung samples from patients who died of COVID-19 (COVID-19 group), compared to 10 lung samples from patients who died of H1N1pdm09 (H1N1 group) and 11 lung samples from patients who died of different causes, with no lung injury (CONTROL group). In addition to the presence of alveolar septal fibrosis, diffuse alveolar damage (DAD) was found to be significantly increased in the COVID-19 group, associated with a higher density of Collagen I (mature) and III (immature). There was also a significant increase observed in the immunoexpression of tissue biomarkers ACE-2, AKT-1, CD44v6, IL-4, MMP-9, α-SMA, Sphingosine-1, and TGF-ß1 in the COVID-19 group. A significantly lower expression of Caveolin-1 was also found in this group. The results suggest the participation of TGF-ß pathways in the development process of pulmonary fibrosis. Thus, it would be plausible to consider therapy with TGF-ß inhibitors in those patients recovered from COVID-19 to mitigate a possible development of pulmonary fibrosis and its consequences for post-COVID-19 life quality.

Caveolin-1 suppresses tumor formation through the inhibition of the unfolded protein response.

Caveolin-1 (CAV1), is a broadly expressed, membrane-associated scaffolding protein that acts both, as a tumor suppressor and a promoter of metastasis, depending on the type of cancer and stage. CAV1 is downregulated in human tumors, tumor cell lines and oncogene-transformed cells. The tumor suppressor activity of CAV1 is generally associated with its presence at the plasma membrane, where it participates, together with cavins, in the formation of caveolae and also has been suggested to interact with and inhibit a wide variety of proteins through interactions mediated by the scaffolding domain. However, a pool of CAV1 is also located at the endoplasmic reticulum (ER), modulating the secretory pathway in a manner dependent on serine-80 (S80) phosphorylation. In melanoma cells, CAV1 expression suppresses tumor formation, but the protein is largely absent from the plasma membrane and does not form caveolae. Perturbations to the function of the ER are emerging as a central driver of cancer, highlighting the activation of the unfolded protein response (UPR), a central pathway involved in stress mitigation. Here we provide evidence indicating that the expression of CAV1 represses the activation of the UPR in vitro and in solid tumors, reflected in the attenuation of PERK and IRE1α signaling. These effects correlated with increased susceptibility of cells to ER stress and hypoxia. Interestingly, the tumor suppressor activity of CAV1 was abrogated by site-directed mutagenesis of S80, correlating with a reduced ability to repress the UPR. We conclude that the tumor suppression by CAV1 involves the attenuation of the UPR, and identified S80 as essential in this context. This suggests that intracellular CAV1 regulates cancer through alternative signaling outputs.

Loss of Caveolin-1 Is Associated with a Decrease in Beta Cell Death in Mice on a High Fat Diet.

Elevated free fatty acids (FFAs) impair beta cell function and reduce beta cell mass as a consequence of the lipotoxicity that occurs in type 2 diabetes (T2D). We previously reported that the membrane protein caveolin-1 (CAV1) sensitizes to palmitate-induced apoptosis in the beta pancreatic cell line MIN6. Thus, our hypothesis was that CAV1 knock-out (CAV1 KO) mice subjected to a high fat diet (HFD) should suffer less damage to beta cells than wild type (WT) mice. Here, we evaluated the in vivo response of beta cells in the pancreatic islets of 8-week-old C57Bl/6J CAV1 KO mice subjected to a control diet (CD, 14% kcal fat) or a HFD (60% kcal fat) for 12 weeks. We observed that CAV1 KO mice were resistant to weight gain when on HFD, although they had high serum cholesterol and FFA levels, impaired glucose tolerance and were insulin resistant. Some of these alterations were also observed in mice on CD. Interestingly, KO mice fed with HFD showed an adaptive response of the pancreatic beta cells and exhibited a significant decrease in beta cell apoptosis in their islets compared to WT mice. These in vivo results suggest that although the CAV1 KO mice are metabolically unhealthy, they adapt better to a HFD than WT mice. To shed light on the possible signaling pathway(s) involved, MIN6 murine beta cells expressing (MIN6 CAV) or not expressing (MIN6 Mock) CAV1 were incubated with the saturated fatty acid palmitate in the presence of mitogen-activated protein kinase inhibitors. Western blot analysis revealed that CAV1 enhanced palmitate-induced JNK, p38 and ERK phosphorylation in MIN6 CAV1 cells. Moreover, all the MAPK inhibitors partially restored MIN6 viability, but the effect was most notable with the ERK inhibitor. In conclusion, our results suggest that CAV1 KO mice adapted better to a HFD despite their altered metabolic state and that this may at least in part be due to reduced beta cell damage. Moreover, they indicate that the ability of CAV1 to increase sensitivity to FFAs may be mediated by MAPK and particularly ERK activation.

Caveolin-1 function at the plasma membrane and in intracellular compartments in cancer.

Caveolin-1 (CAV1) is commonly considered to function as a cell surface protein, for instance in the genesis of caveolae. Nonetheless, it is also present in many intracellular organelles and compartments. The contributions of these intracellular pools to CAV1 function are generally less well understood, and this is also the case in the context of cancer. This review will summarize literature available on the role of CAV1 in cancer, highlighting particularly our understanding of the canonical (CAV1 in the plasma membrane) and non-canonical pathways (CAV1 in organelles and exosomes) linked to the dual role of the protein as a tumor suppressor and promoter of metastasis. With this in mind, we will focus on recently emerging concepts linking CAV1 function to the regulation of intracellular organelle communication within the same cell where CAV1 is expressed. However, we now know that CAV1 can be released from cells in exosomes and generate systemic effects. Thus, we will also elaborate on how CAV1 participates in intracellular communication between organelles as well as signaling between cells (non-canonical pathways) in cancer.

Src-family kinase inhibitors block early steps of caveolin-1-enhanced lung metastasis by melanoma cells.

In advanced stages of cancer disease, caveolin-1 (CAV1) expression increases and correlates with increased migratory and invasive capacity of the respective tumor cells. Previous findings from our laboratory revealed that specific ECM-integrin interactions and tyrosine-14 phosphorylation of CAV1 are required for CAV1-enhanced melanoma cell migration, invasion and metastasis in vivo. In this context, CAV1 phosphorylation on tyrosine-14 mediated by non-receptor Src-family tyrosine kinases seems to be important; however, the effect of Src-family kinase inhibitors on CAV1-enhanced metastasis in vivo has not been studied. Here, we evaluated the effect of CAV1 and c-Abl overexpression, as well as the use of the Src-family kinase inhibitors, PP2 and dasatinib (more specific for Src/Abl) in lung metastasis of B16F10 melanoma cells. Overexpression of CAV1 and c-Abl enhanced CAV1 phosphorylation and the metastatic potential of the B16F10 murine melanoma cells. Alternatively, treatment with PP2 or dasatinib for 2 h reduced CAV1 tyrosine-14 phosphorylation and levels recovered fully within 12 h of removing the inhibitors. Nonetheless, pre-treatment of cells with these inhibitors for 2 h sufficed to prevent migration, invasion and trans-endothelial migration in vitro. Importantly, the transient decrease in CAV1 phosphorylation by these kinase inhibitors prevented early steps of CAV1-enhanced lung metastasis by B16F10 melanoma cells injected into the tail vein of mice. In conclusion, this study underscores the relevance of CAV1 tyrosine-14 phosphorylation by Src-family kinases during the first steps of the metastatic sequence promoted by CAV1. These findings open up potential options for treatment of metastatic tumors in patients in which Src-family kinase activation and CAV1 overexpression favor dissemination of cancer cells to secondary sites.