Insights in caveolae protein structure arrangements and their local lipid environment.

Caveolae are 50-80 nm sized plasma membrane invaginations found in adipocytes, endothelial cells or fibroblasts. They are involved in endocytosis, lipid uptake and the regulation of the cellular lipid metabolism as well as sensing and adapting to changes in plasma membrane tension. Caveolae are characterized by their unique lipid composition and their specific protein coat consisting of caveolin and cavin proteins. Recently, detailed structural information was obtained for the major caveolae protein caveolin1 showing the formation of a disc-like 11-mer protein complex. Furthermore, the importance of the cavin disordered regions in the generation of cavin trimers and caveolae at the plasma membrane were revealed. Thus, finally, structural insights about the assembly of the caveolar coat can be elucidated. Here, we review recent developments in caveolae structural biology with regard to caveolae coat formation and caveolae curvature generation. Secondly, we discuss the importance of specific lipid species necessary for caveolae curvature and formation. In the last years, it was shown that specifically sphingolipids, cholesterol and fatty acids can accumulate in caveolae invaginations and may drive caveolae endocytosis. Throughout, we summarize recent studies in the field and highlight future research directions.

Rab10-CAV1 mediated intraluminal vesicle transport to migrasomes.

Migrasomes, vesicular organelles generated on the retraction fibers of migrating cells, play a crucial role in migracytosis, mediating intercellular communication. The cargoes determine the functional specificity of migrasomes. Migrasomes harbor numerous intraluminal vesicles, a pivotal component of their cargoes. The mechanism underlying the transportation of these intraluminal vesicles to the migrasomes remains enigmatic. In this study, we identified that Rab10 and Caveolin-1 (CAV1) mark the intraluminal vesicles in migrasomes. Transport of Rab10-CAV1 vesicles to migrasomes required the motor protein Myosin Va and adaptor proteins RILPL2. Notably, the phosphorylation of Rab10 by the kinase LRRK2 regulated this process. Moreover, CSF-1 can be transported to migrasomes through this mechanism, subsequently fostering monocyte-macrophage differentiation in skin wound healing, which served as a proof of the physiological importance of this transporting mechanism.

Cinobufagin disrupts the stability of lipid rafts by inhibiting the expression of caveolin-1 to promote non-small cell lung cancer cell apoptosis.

Introduction: The study was designed to explore how cinobufagin (CB) regulates the development of non-small cell lung cancer (NSCLC) cells through lipid rafts. Material and methods: The effects of CB at gradient concentrations (0, 0.5, 1 and 2 µM) on NSCLC cell viability, apoptosis, reactive oxygen species (ROS) level, phosphorylation of Akt, and apoptosis- and lipid raft-related protein expression were assessed by MTT assay, flow cytometry and Western blot. Cholesterol and sphingomyelin were labeled with BODIPY to evaluate the effect of CB (2 µM) on them. Sucrose density gradient centrifugation was used to extract lipid rafts. The effect of CB on the expression and distribution of caveolin-1 was determined by immunofluorescence, quantitative reverse transcription polymerase chain reaction and Western blot. After overexpression of caveolin-1, the above experiments were performed again to observe whether the regulatory effect of CB was reversed. Results: CB inhibited NSCLC cell viability while promoting apoptosis and ROS level. CB redistributed the lipid content on the membrane surface and reduced the content of caveolin-1 in the cell membrane. In addition, CB repressed the activation of AKT. However, caveolin-1 overexpression reversed the effects of CB on apoptosis, AKT activation and lipid raft. Conclusions: CB regulates the activity of Akt in lipid rafts by inhibiting caveolin-1 expression to promote NSCLC cell apoptosis.

Caveolin-2 controls preadipocyte survival in the mitotic clonal expansion for adipogenesis.

Here, we report that Caveolin-2 (Cav-2) is a cell cycle regulator in the mitotic clonal expansion (MCE) for adipogenesis. For the G2/M phase transition and re-entry into the G1 phase, dephosphorylated Cav-2 by protein tyrosine phosphatase 1B (PTP1B) controlled epigenetic activation of Ccnb1, Cdk1, and p21 in a lamin A/C-dependent manner, thereby ensuring the survival of preadipocytes. Cav-2, associated with lamin A/C, recruited the repressed promoters of Ccnb1 and Cdk1 for activation, and disengaged the active promoter of p21 from lamin A/C for inactivation through histone H3 modifications at the nuclear periphery. Cav-2 deficiency abrogated the histone H3 modifications and impeded the transactivation of Ccnb1, Cdk1, and p21, leading to a delay in mitotic entry, retardation of re-entry into G1 phase, and the apoptotic cell death of preadipocytes. Re-expression of Cav-2 restored the G2/M phase transition and G1 phase re-entry, preadipocyte survival, and adipogenesis in Cav-2-deficient preadipocytes. Our study uncovers a novel mechanism by which cell cycle transition and apoptotic cell death are controlled for adipocyte hyperplasia.

Immunoexpression Patterns of Megalin, Cubilin, Caveolin-1, Gipc1 and Dab2IP in the Embryonic and Postnatal Development of the Kidneys in Yotari (Dab1-/-) Mice.

Our study examines the immunoexpression patterns of Megalin, Cubilin, Caveolin-1, Gipc1 and Dab2IP in the embryonic development (E) and postnatal (P) mouse kidney, with a focus on differentiating patterns between wild-type (wt) and yotari, Dab1-/- (yot) mice. Immunofluorescence revealed raised immunoexpression of receptors Megalin and Cubilin at the ampulla/collecting ducts and convoluted tubules across all developmental stages, with the most prominent immunoexpression observed in the convoluted tubules and the parietal epithelium of the Bowman's capsule. Quantitative analysis showed a higher percentage of Megalin and Cubilin in wt compared to yot mice at E13.5. Co-expression of Megalin and Cubilin was observed at the apical membrane of convoluted tubules and the parietal layer of the Bowman's capsule. The staining intensity of Megalin varied across developmental stages, with the strongest reactivity observed at the ampulla and collecting ducts at embryonic day (E) 13.5 in wt mice. In contrast, Caveolin-1 exhibited high immunoexpression in the metanephric mesenchyme, blood vessels, and the border area between the metanephric mesenchyme and renal vesicle, with a decrease in immunoexpression as development progressed. Gipc1 showed diffuse cytoplasmic staining in metanephric mesenchyme, convoluted tubules and collecting ducts, with significant differences in immunoexpression between wild-type and yot mice at both investigated embryonic time points. Dab2IP immunofluorescent staining was most prominent in renal vesicle/glomeruli and ampulla/collecting ducts at E13.5, with mild staining intensity observed in the distal convoluted tubules postnatally. Our findings elucidate distinct immunoexpression of patterns and potential parts of these proteins in the development and function of the kidney, highlighting the importance of further investigation into their regulatory mechanisms.

Lipid Organization by the Caveolin-1 Complex.

Caveolins are lipid-binding proteins that can organize membrane remodeling and oligomerize into the 8S-complex. The CAV1 8S-complex comprises a disk-like structure, about 15nm in diameter, with a central beta barrel. Further oligomerization of 8S-complexes remodels the membrane into caveolae vessels, with a dependence on cholesterol concentration. However, the molecular mechanisms behind membrane remodeling and cholesterol filtering are still not understood. Performing atomistic Molecular Dynamics simulations in combination with advanced sampling techniques, we describe how the CAV1-8S complex bends the membrane and accumulates cholesterol. Here, our simulations show an enhancing effect by the palmitoylations of CAV1, and we predict that the CAV1-8S complex can extract cholesterol molecules from the lipid bilayer and accommodate them in its beta barrel. Through backmapping to the all-atom level we also conclude that the Martini v2 coarse-grained forcefield overestimates membrane bending, as the atomistic simulations exhibit only very localized bending.

Caveolae and caveolin-1 as targets of dietary polyphenols for protection against vascular endothelial dysfunction.

Caveolae, consisting of caveolin-1 proteins, are ubiquitously present in endothelial cells and contribute to normal cardiovascular functions by acting as a platform for cellular signaling pathways as well as transcytosis and endocytosis. However, caveolin-1 is thought to have a proatherogenic role by inhibiting endothelial nitric oxide synthase activity and Nrf2 activation, or by promoting inflammation through NF-κB activation. Dietary polyphenols were suggested to exert anti-atherosclerotic effects by a mechanism involving the inhibition of endothelial dysfunction, by which they can regulate redox-sensitive signaling pathways in relation to NF-κB and Nrf2 activation. Some monomeric polyphenols and microbiota-derived catabolites from monomeric polyphenols or polymeric tannins might be responsible for the inhibition, because they can be transferred into the circulation from the digestive tract. Several polyphenols were reported to modulate caveolin-1 expression or its localization in caveolae. Therefore, we hypothesized that circulating polyphenols affect caveolae functions by altering its structure leading to the release of caveolin-1 from caveolae, and attenuating redox-sensitive signaling pathway-dependent caveolin-1 overexpression. Further studies using circulating polyphenols at a physiologically relevant level are necessary to clarify the mechanism of action of dietary polyphenols targeting caveolae and caveolin-1.

TrxR1 is involved in the activation of Caspase-11 by regulating the oxidative-reductive status of Trx-1.

Sepsis is a common complication of infections that significantly impacts the survival of critically patients. Currently, effective pharmacological treatment strategies are lacking. Auranofin, known as an inhibitor of Thioredoxin reductase (TrxR), exhibits anti-inflammatory activity, but its role in sepsis is not well understood. Here, we demonstrate the significant inhibitory effect of Auranofin on sepsis in a cecal ligation and puncture (CLP) mouse model. In vitro, Auranofin inhibits pyroptosis triggered by Caspase-11 activation. Further investigations reveal that inhibiting TrxR1 suppresses macrophage pyroptosis induced by E. coli, while TrxR2 does not exhibit this effect. TrxR1, functioning as a reductase, regulates the oxidative-reductive status of Thioredoxin-1 (Trx-1). Mechanistically, the modulation of Trx-1's reductive activity by TrxR1 may be involved in Caspase-11 activation-induced pyroptosis. Additionally, inhibiting TrxR1 maintains Trx-1 in its oxidized state. The oxidized form of Trx-1 interacts with Caveolin-1 (CAV1), regulating outer membrane vesicle (OMV) internalization. In summary, our study suggests that inhibiting TrxR1 suppresses OMV internalization by maintaining the oxidized form of Trx-1, thereby restricting Caspase-11 activation and alleviating sepsis.

Internalisation of immunoglobulin light chains by cardiomyocytes in AL amyloidosis: what can biopsies tell us?

BACKGROUND: Cardiac involvement in systemic light chain amyloidosis (AL) leads to chronic heart failure and is a major prognosis factor. Severe cellular defects are provoked in cardiac cells by tissue-deposited amyloid fibrils of misfolded free immunoglobulin light chains (LCs) and their prefibrillar oligomeric precursors. OBJECTIVE: Understanding the molecular mechanisms behind cardiac cell cytotoxicity is necessary to progress in therapy and to improve patient management. One key question is how extracellularly deposited molecules exert their toxic action inside cardiac cells. Here we searched for direct evidence of amyloid LC uptake by cardiomyocytes in patient biopsies. METHODS: We immunolocalized LCs in cardiac biopsies from four AL cardiac amyloidosis patients and analysed histopathological images by high resolution confocal microscopy and 3D image reconstruction. RESULTS: We show, for the first time directly in patient tissue, the presence of LCs inside cardiomyocytes, and report their proximity to nuclei and to caveolin-3-rich areas. Our observations point to macropinocytosis as a probable mechanism of LC uptake. CONCLUSIONS: Internalisation of LCs occurs in patient cardiomyocytes. This event could have important consequences for the pathogenesis of the cardiac disease by enabling interactions between amyloid molecules and cellular organelles inducing specific signalling pathways, and might bring new insight regarding treatment.

Disintegration of Cav-1/ß-catenin complex attenuates neuronal death after ischemia-reperfusion injury by promoting ß-catenin nuclear translocation.

BACKGROUND: The roles of Caveolin-1 (Cav-1) and the Wnt/ß-catenin signaling pathways in cerebral ischemia-reperfusion (I/R) injury are well established. The translocation of ß-catenin into the nucleus is critical for regulating neuronal apoptosis, repair, and neurogenesis within the ischemic brain. It has been reported that the scaffold domain of Caveolin-1 (Cav-1) (residues 95-98) interacts with ß-catenin (residues 330-337). However, the specific contribution of the Cav-1/ß-catenin complex to I/R injury remains unknown. METHODS AND RESULTS: To investigate the mechanism underlying the involvement of the Cav-1/ß-catenin complex in the subcellular translocation of ß-catenin and its subsequent effects on cerebral I/R injury, we treated ischemic brains with ASON (Cav-1 antisense oligodeoxynucleotides) or FTVT (a competitive peptide antagonist of the Cav-1 and ß-catenin interaction). Our study demonstrated that the binding of Cav-1 to ß-catenin following I/R injury prevented the nuclear accumulation of ß-catenin. Treatment with ASON or FTVT after I/R injury significantly increased the levels of nuclear ß-catenin. Furthermore, ASON reduced the phosphorylation of ß-catenin at Ser33, Ser37, and Thr41, which contributes to its proteasomal degradation, while FTVT increased phosphorylation at Tyr333, which is associated with its nuclear translocation. CONCLUSIONS: The above results indicate that the formation of the Cav-1/ß-catenin complex anchors ß-catenin in the cytoplasm following I/R injury. Additionally, both ASON and FTVT treatments attenuated neuronal death in ischemic brains. Our study suggests that targeting the interaction between Cav-1 and ß-catenin serve as a novel therapeutic strategy to protect against neuronal damage during cerebral injury.

Interplay between caveolin-1 and mineralocorticoid receptor in cardiometabolic disease.

Over the past decades, research has clearly established the important role of the mineralocorticoid receptor (MR) in both renal and extra-renal tissues. Recently, caveolin-1 (Cav-1) has emerged as a mediator of MR signaling in several tissues, with implications on cardiovascular and metabolic dysfunction. The main structural component of caveolae (plasma membrane invaginations with diverse functions), Cav-1 is a modulator of cardiovascular function, cellular glucose, and lipid homeostasis, via its effects on signal transduction pathways that mediate inflammatory responses and oxidative stress. In this review, we present evidence indicating an overlap between the roles of the MR and Cav-1 in cardiometabolic disease and the relevant signaling pathways involved. Furthermore, we discuss the potential use of Cav-1 as a biomarker and/or target for MR-mediated dysfunction.

Caveolin-1 differentially regulates the transforming growth factor-ß and epidermal growth factor signaling pathways in MDCK cells.

Caveolin-1 is critical for interacting with the TGF-ß receptor (TGFßR) and EGF receptor (EGFR) signaling, often observed in advanced cancers and tissue fibrosis. However, the mechanism underlying caveolin-1-mediated transactivation of TGFßR and EGFR signaling remains unclear. Therefore, we sought to determine whether caveolin-1 is involved in canonical and non-canonical TGFßR and EGFR signaling transactivation in this study. Methyl-ß-cyclodextrin (MßCD) was used to disrupt the cholesterol-containing membranes domains, and the caveolin-1 scaffolding domain (CSD) peptide was used to mimic the CSD of caveolin-1. Additionally, we transfected the Madin-Darby canine kidney cells with wild-type or phosphorylation-defective caveolin-1. We discovered that tyrosine 14 of caveolin-1 was critical for the negative regulation of TGFßR and EGFR canonical signaling. On the contrary, caveolin-1 inhibited TGF-ß1-induced ERK2 activation independent of tyrosine 14 phosphorylation. Although EGF failed to induce Smad3 phosphorylation in caveolin-1 knockdown cells, it activated Smad3 upon MßCD co-treatment, indicating that caveolin-1 indirectly regulated the non-canonical pathway of EGF. In conclusion, caveolin-1 differentially modulates TGFßR and EGFR signaling. Thus, targeting caveolin-1 is a potential strategy for treating diseases involving TGF-ß1 and EGF signaling.

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.

Glial growth factor 2 treatment alleviates ischemia and reperfusion-damaged integrity of the blood-brain barrier through decreasing Mfsd2a/caveolin-1-mediated transcellular and Pdlim5/YAP/TAZ-mediated paracellular permeability.

The impairment of blood-brain barrier (BBB) integrity is the pathological basis of hemorrhage transformation and vasogenic edema following thrombolysis and endovascular therapy. There is no approved drug in the clinic to reduce BBB damage after acute ischemic stroke (AIS). Glial growth factor 2 (GGF2), a recombinant version of neuregulin-1ß that can stimulates glial cell proliferation and differentiation, has been shown to alleviate free radical release from activated microglial cells. We previously found that activated microglia and proinflammatory factors could disrupt BBB after AIS. In this study we investigated the effects of GGF2 on AIS-induced BBB damage as well as the underlying mechanisms. Mouse middle cerebral artery occlusion model was established: mice received a 90-min ischemia and 22.5 h reperfusion (I/R), and were treated with GGF2 (2.5, 12.5, 50 ng/kg, i.v.) before the reperfusion. We showed that GGF2 treatment dose-dependently decreased I/R-induced BBB damage detected by Evans blue (EB) and immunoglobulin G (IgG) leakage, and tight junction protein occludin degradation. In addition, we found that GGF2 dose-dependently reversed AIS-induced upregulation of vesicular transcytosis increase, caveolin-1 (Cav-1) as well as downregulation of major facilitator superfamily domain containing 2a (Mfsd2a). Moreover, GGF2 decreased I/R-induced upregulation of PDZ and LIM domain protein 5 (Pdlim5), an adaptor protein that played an important role in BBB damage after AIS. In addition, GGF2 significantly alleviated I/R-induced reduction of YAP and TAZ, microglial cell activation and upregulation of inflammatory factors. Together, these results demonstrate that GGF2 treatment alleviates the I/R-compromised integrity of BBB by inhibiting Mfsd2a/Cav-1-mediated transcellular permeability and Pdlim5/YAP/TAZ-mediated paracellular permeability.

Single-cell transcriptional analysis of irradiated skin reveals changes in fibroblast subpopulations and variability in caveolin expression.

BACKGROUND: Radiation-induced fibrosis (RIF) is an important late complication of radiation therapy, and the resulting damaging effects of RIF can significantly impact reconstructive outcomes. There is currently a paucity of effective treatment options available, likely due to the continuing knowledge gap surrounding the cellular mechanisms involved. In this study, detailed analyses of irradiated and non-irradiated human skin samples were performed incorporating histological and single-cell transcriptional analysis to identify novel features guiding development of skin fibrosis following radiation injury. METHODS: Paired irradiated and contralateral non-irradiated skin samples were obtained from six female patients undergoing post-oncologic breast reconstruction. Skin samples underwent histological evaluation, immunohistochemistry, and biomechanical testing. Single-cell RNA sequencing was performed using the 10X single cell platform. Cells were separated into clusters using Seurat in R. The SingleR classifier was applied to ascribe cell type identities to each cluster. Differentially expressed genes characteristic to each cluster were then determined using non-parametric testing. RESULTS: Comparing irradiated and non-irradiated skin, epidermal atrophy, dermal thickening, and evidence of thick, disorganized collagen deposition within the extracellular matrix of irradiated skin were readily appreciated on histology. These histologic features were associated with stiffness that was higher in irradiated skin. Single-cell RNA sequencing revealed six predominant cell types. Focusing on fibroblasts/stromal lineage cells, five distinct transcriptional clusters (Clusters 0-4) were identified. Interestingly, while all clusters were noted to express Cav1, Cluster 2 was the only one to also express Cav2. Immunohistochemistry demonstrated increased expression of Cav2 in irradiated skin, whereas Cav1 was more readily identified in non-irradiated skin, suggesting Cav1 and Cav2 may act antagonistically to modulate fibrotic cellular responses. CONCLUSION: In response to radiation therapy, specific changes to fibroblast subpopulations and enhanced Cav2 expression may contribute to fibrosis. Altogether, this study introduces a novel pathway of caveolin involvement which may contribute to fibrotic development following radiation injury.

Obesity induced caveolin-1 impairs osteogenesis via activating mitophagy and inhibiting Sirt1 signaling.

Obesity has become a major global health problem and the effect on bone formation has received increasing attention. However, the interaction between obesity and bone metabolism is complex and still not fully understood. Here, we show that caveolin-1 (Cav1), a membrane scaffold protein involved in regulating a variety of cellular processes, plays a key regulatory role as a bridge connecting obesity and bone metabolism. High-fat diet (HFD)-induced obese C57BL/6J mouse displayed a significant increase in Cav1 expression and lower osteogenic activity; In vitro treatment of osteoblastic MC3T3-E1 cells with 1 mM free fatty acids (FFA) significantly promoted Cav1 expression and PINK1/Parkin regulated mitophagy, but inhibited the expression of osteogenic marker genes. Conversely, reduced expression of the Cav1 gene prevented these effects. Both endogenous oxidative stress and Sirt1 pathway were also significantly reduced after Cav1 knockdown in FFA-treated cells. Finally, Cav1-Sirt1 docking and co-immunoprecipitation results showed that Cav1 interacted with Sirt1 and FFA enhanced the interaction. Taken together, these results suggest that obesity impairs bone development and formation through up-regulation of the Cav1 gene, which lead to inhibition of Sirt1/FOXO1 and Sirt1/PGC-1α signaling pathways through interacting with Sirt1 molecule, and an increase of mitophagy level.

Exploration of the Molecular Mechanism by Which Caveolin-1 Regulates Changes in Blood-Brain Barrier Permeability Leading to Eosinophilic Meningoencephalitis.

Angiostrongylus cantonensis, a zoonotic parasite, can invade the human central nervous system (CNS) and cause acute eosinophilic meningitis or eosinophilic meningoencephalitis. Mice infected with A. cantonensis show elevated levels of pro-inflammatory cytokines, plasminogen activators, and matrix metalloproteinase-9, resulting in disruption of the blood-brain barrier (BBB) and immune cell infiltration into the CNS. Caveolin-1 (Cav-1) regulates the permeability of the BBB, which affects immune cells and cerebrospinal fluid. This intricate interaction ultimately fuels the progression of brain damage and edema. This study aims to investigate the regulatory role of Cav-1 in the pathogenesis of meningoencephalitis induced by A. cantonensis infection. We investigated pathological alterations by triphenyl-tetrazolium chloride, brain water content, BBB permeability, Western blot analysis, and gelatin zymography in BALB/c mice after A. cantonensis. The study evaluates the critical role of Cav-1 regulation through the TLR4/MyD88 signaling pathway, modulates tight junction proteins, influences BBB permeability, and contributes to brain damage in A. cantonensis-induced meningoencephalitis.

Salvianolic acid B enhances tissue repair and regeneration by regulating immune cell migration and Caveolin-1-mediated blastema formation in zebrafish.

INTRODUCTION: Non-healing wounds resulting from trauma, surgery, and chronic diseases annually affect millions of individuals globally, with limited therapeutic strategies available due to the incomplete understanding of the molecular processes governing tissue repair and regeneration. Salvianolic acid B (Sal B) has shown promising bioactivities in promoting angiogenesis and inhibiting inflammation. However, its regulatory mechanisms in tissue regeneration remain unclear. PURPOSE: This study aims to investigate the effects of Sal B on wound healing and regeneration processes, along with its underlying molecular mechanisms, by employing zebrafish as a model organism. METHODS: In this study, we employed a multifaceted approach to evaluate the impact of Sal B on zebrafish tail fin regeneration. We utilized whole-fish immunofluorescence, TUNEL staining, mitochondrial membrane potential (MMP), and Acridine Orange (AO) probes to analyze the tissue repair and regenerative under Sal B treatment. Additionally, we utilized transgenic zebrafish strains to investigate the migration of inflammatory cells during different phases of fin regeneration. To validate the importance of Caveolin-1 (Cav1) in tissue regeneration, we delved into its functional role using molecular docking and Morpholino-based gene knockdown techniques. Additionally, we quantified Cav1 expression levels through the application of in situ hybridization. RESULTS: Our findings demonstrated that Sal B expedites zebrafish tail fin regeneration through a multifaceted mechanism involving the promotion of cell proliferation, suppression of apoptosis, and enhancement of MMP. Furthermore, Sal B was found to exert regulatory control over the dynamic aggregation and subsequent regression of immune cells during tissue regenerative processes. Importantly, we observed that the knockdown of Cav1 significantly compromised tissue regeneration, leading to an excessive infiltration of immune cells and increased levels of apoptosis. Moreover, the knockdown of Cav1 also affects blastema formation, a critical process influenced by Cav1 in tissue regeneration. CONCLUSION: The results of this study showed that Sal B facilitated tissue repair and regeneration through regulating of immune cell migration and Cav1-mediated fibroblast activation, promoting blastema formation and development. This study highlighted the potential pharmacological effects of Sal B in promoting tissue regeneration. These findings contributed to the advancement of regenerative medicine research and the development of novel therapeutic approaches for trauma.

Low caveolin-1 levels and symptomatic intracranial haemorrhage risk in large-vessel occlusive stroke patients after endovascular thrombectomy.

BACKGROUND AND PURPOSE: Caveolin-1 (Cav-1) is reported to mediate blood-brain barrier integrity after ischaemic stroke. Our purpose was to assess the role of circulating Cav-1 levels in predicting symptomatic intracranial haemorrhage (sICH) amongst ischaemic stroke patients after endovascular thrombectomy (EVT). METHODS: Patients with large-vessel occlusive stroke after EVT from two stroke centres were prospectively included. Serum Cav-1 level was tested after admission. sICH was diagnosed according to the Heidelberg Bleeding Classification. RESULTS: Of 325 patients (mean age 68.6 years; 207 men) included, 47 (14.5%) were diagnosed with sICH. Compared with patients without sICH, those with sICH had a lower concentration of Cav-1. After adjusting for potential confounders, multivariate regression analysis demonstrated that the increased Cav-1 level was associated with a lower sICH risk (odds ratio 0.055; 95% confidence interval 0.005-0.669; p = 0.038). Similar results were obtained when Cav-1 levels were analysed as a categorical variable. Using a logistic regression model with restricted cubic splines, a linear and negative association of Cav-1 concentration was found with sICH risk (p = 0.001 for linearity). Furthermore, the performance of the conventional risk factors model in predicting sICH was substantially improved after addition of the Cav-1 levels (integrated discrimination index 2.7%, p = 0.002; net reclassification improvement 39.7%, p = 0.007). CONCLUSIONS: Our data demonstrate that decreased Cav-1 levels are related to sICH after EVT. Incorporation of Cav-1 into clinical decision-making may help to identify patients at a high risk of sICH and warrants further consideration.

Exerkine FNDC5/irisin-enriched exosomes promote proliferation and inhibit ferroptosis of osteoblasts through interaction with Caveolin-1.

Postmenopausal osteoporosis is a prevalent metabolic bone disorder characterized by a decrease in bone mineral density and deterioration of bone microstructure. Despite the high prevalence of this disease, no effective treatment for osteoporosis has been developed. Exercise has long been considered a potent anabolic factor that promotes bone mass via upregulation of myokines secreted by skeletal muscle, exerting long-term osteoprotective effects and few side effects. Irisin was recently identified as a novel myokine that is significantly upregulated by exercise and could increase bone mass. However, the mechanisms underlying exercise-induced muscle-bone crosstalk remain unclear. Here, we identified that polyunsaturated fatty acids (arachidonic acid and docosahexaenoic acid) are increased in skeletal muscles following a 10-week treadmill exercise programme, which then promotes the expression and release of FNDC5/irisin. In osteoblasts, irisin binds directly to Cav1, which recruits and interacts with AMP-activated protein kinase α (AMPKα) to activate the AMPK pathway. Nrf2 is the downstream target of the AMPK pathway and increases the transcription of HMOX1 and Fpn. HMOX1 is involved in regulating the cell cycle and promotes the proliferation of osteoblasts. Moreover, upregulation of Fpn in osteoblasts enhanced iron removal, thereby suppressing ferroptosis in osteoblasts. Additionally, we confirmed that myotube-derived exosomes are involved in the transportation of irisin and enter osteoblasts through caveolae-mediated endocytosis. In conclusion, our findings highlight the crucial role of irisin, present in myotube-derived exosomes, as a crucial regulator of exercise-induced protective effects on bone, which provides novel insights into the mechanisms underlying exercise-dependent treatment of osteoporosis.