Caveolin-1 confers antiinflammatory effects in murine macrophages via the MKK3/p38 MAPK pathway

Update on Biomarkers of Chronic Inflammatory Processes Underlying Diabetic Neuropathy

There is an increasing prevalence of diabetes mellitus (DM), particularly type 2 DM (T2DM), and its associated complications. T2DM is linked to insulin resistance, chronic inflammation, and oxidative stress, which can lead to both macrovascular and microvascular complications, including peripheral diabetic neuropathy (PDN). Inflammatory processes play a key role in the development and progression of T2DM and its complications, with specific markers like C-reactive protein (CRP), interleukins (ILs), and tumor necrosis factor (TNF)-α being associated with increased risk. Other key inflammatory markers such as nuclear factor kappa B (NF-κB) are activated under hyperglycemic and oxidative stress conditions and contribute to the aggravation of PDN by regulating inflammatory gene expression and enhancing endothelial dysfunction. Other important roles in the inflammatory processes are played by Toll-like receptors (TLRs), caveolin 1 (CAV1), and monocyte chemoattractant protein 1 (MCP1). There is a relationship between vitamin D deficiency and PDN, highlighting the critical role of vitamin D in regulating inflammation and immune responses. The involvement of macrophages in PDN is also suspected, emphasizing their role in chronic inflammation and nerve damage in diabetic patients. Vitamin D supplementation has been found to reduce neuropathy severity, decrease inflammatory markers, and improve glycemic control. These findings suggest that addressing vitamin D deficiency could offer therapeutic benefits for PDN. These molecular pathways are critical in understanding the pathogenesis of DM complications and may offer potential biomarkers or therapeutic targets including anti-inflammatory treatments, vitamin D supplementation, macrophage phenotype modulation, and lifestyle modifications, aimed at reducing inflammation and preventing PDN. Ongoing and more extensive clinical trials with the aim of investigating anti-inflammatory agents, TNF-α inhibitors, and antioxidants are needed to advance deeper into the understanding and treatment of painful diabetic neuropathy.

The critical roles of caveolin-1 in lung diseases

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

Caveolin-1 forms a complex with P2X7 receptor and tunes P2X7-mediated ATP signaling in mouse bone marrow-derived macrophages

The ionotropic purinergic P2X7 receptor responds to extracellular ATP and can trigger proinflammatory immune signaling in macrophages. Caveolin-1 (Cav-1) is known to modulate functions of macrophages and innate immunity. However, it is unknown how Cav-1 modulates P2X7 receptor activity in macrophages. We herein examined P2X7 receptor activity and macrophage functions using bone marrow-derived macrophages (BMDMs) from wild-type (WT) and Cav-1 knockout (KO) mice. ATP (1 mM) application caused biphasic increase in cytosolic [Ca2+] and sustained decrease in cytosolic [K+]. A specific P2X7 receptor blocker, A-740003, inhibited the maintained cytosolic [Ca2+] increase and cytosolic [K+] decrease. Total internal reflection fluorescent imaging and proximity ligation assays revealed a novel molecular complex formation between P2X7 receptors and Cav-1 in WT BMDMs that were stimulated with lipopolysaccharides. This molecular coupling was increased by ATP application. Specifically, the ATP-induced Ca2+ influx and K+ efflux through P2X7 receptors were increased in Cav-1 KO BMDMs, even though the total and surface protein levels of P2X7 receptors in WT and Cav-1 KO BMDMs were unchanged. Cell-impermeable dye (TO-PRO3) uptake analysis revealed that macropore formation of P2X7 receptors was enhanced in Cav-1 KO BMDMs. Cav-1 KO BMDMs increased ATP-induced IL-1β secretion, reactive oxygen species production, Gasdermin D (GSDMD) cleavage, and lactate dehydrogenase release indicating pyroptosis. A-740003 completely prevented ATP-induced pyroptosis. In combination, these datasets show that Cav-1 has a negative effect on P2X7 receptor activity in BMDMs and that Cav-1 in macrophages may contribute to finely tuned immune responses by preventing excessive IL-1β secretion and pyroptosis.NEW & NOTEWORTHY In bone marrow-derived macrophages, Cav-1 suppresses the macropore formation of P2X7 receptors through their direct or indirect interactions, resulting in reduced membrane permeability of cations (Ca2+ and K+) and large cell-impermeable dye (TO-PRO3) induced by ATP. Cav-1 also inhibits ATP-induced IL-1β secretion, ROS production, GSDMD cleavage, and pyroptosis. Cav-1 contributes to the maintenance of proper immune responses by finely tuning IL-1β secretion and cell death in macrophages.

Caveolin-1: A Review of Intracellular Functions, Tissue-Specific Roles, and Epithelial Tight Junction Regulation

Caveolin-1 (Cav1) is a vital protein for many cellular processes and is involved in both the positive and negative regulation of these processes. Cav1 exists in multiple cellular compartments depending on its role. Of particular interest is its contribution to the formation of plasma membrane invaginations called caveolae and its involvement in cytoskeletal interactions, endocytosis, and cholesterol trafficking. Cav1 participates in stem cell differentiation as well as proliferation and cell death pathways, which is implicated in tumor growth and metastasis. Additionally, Cav1 has tissue-specific functions that are adapted to the requirements of the cells within those tissues. Its role has been described in adipose, lung, pancreatic, and vascular tissue and in epithelial barrier maintenance. In both the intestinal and the blood brain barriers, Cav1 has significant interactions with junctional complexes that manage barrier integrity. Tight junctions have a close relationship with Cav1 and this relationship affects both their level of expression and their location within the cell. The ubiquitous nature of Cav1 both within the cell and within specific tissues is what makes the protein important for ongoing research as it can assist in further understanding pathophysiologic processes and can potentially be a target for therapies.

Heterogeneity in the Metastatic Microenvironment: JunB-Expressing Microglia Cells as Potential Drivers of Melanoma Brain Metastasis Progression

Reciprocal signaling between melanoma brain metastatic (MBM) cells and microglia reprograms the phenotype of both interaction partners, including upregulation of the transcription factor JunB in microglia. Here, we aimed to elucidate the impact of microglial JunB upregulation on MBM progression. For molecular profiling, we employed RNA-seq and reverse-phase protein array (RPPA). To test microglial JunB functions, we generated microglia variants stably overexpressing JunB (JunBhi) or with downregulated levels of JunB (JunBlo). Melanoma-derived factors, namely leukemia inhibitory factor (LIF), controlled JunB upregulation through Janus kinase (JAK)/signal transducer and activator of transcription 3 (STAT3) signaling. The expression levels of JunB in melanoma-associated microglia were heterogeneous. Flow cytometry analysis revealed the existence of basal-level JunB-expressing microglia alongside microglia highly expressing JunB. Proteomic profiling revealed a differential protein expression in JunBhi and JunBlo cells, namely the expression of microglia activation markers Iba-1 and CD150, and the immunosuppressive molecules SOCS3 and PD-L1. Functionally, JunBhi microglia displayed decreased migratory capacity and phagocytic activity. JunBlo microglia reduced melanoma proliferation and migration, while JunBhi microglia preserved the ability of melanoma cells to proliferate in three-dimensional co-cultures, that was abrogated by targeting leukemia inhibitory factor receptor (LIFR) in control microglia-melanoma spheroids. Altogether, these data highlight a melanoma-mediated heterogenous effect on microglial JunB expression, dictating the nature of their functional involvement in MBM progression. Targeting microglia highly expressing JunB may potentially be utilized for MBM theranostics.

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

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

Macrophage migration is differentially regulated by distinct ECM components

Macrophages are indispensable for proper immune surveillance and inflammatory regulation. They also exhibit dramatic phenotypic plasticity and are highly responsive to their local microenvironment, which includes the extracellular matrix (ECM). The present work demonstrates that two fibrous ECM glycoproteins, fibronectin (FN) and laminin (LAM), elicit distinct morphological and migratory responses to macrophages in 2D environments. Laminin 111 inhibits macrophage cell spreading, but drives them to migrate rapidly and less persistently compared to cells on fibronectin. Differential integrin engagement and ROCK/myosin II organization helps explain why macrophages alter their morphology and migration character on these two ECM components. The present study also demonstrates that laminin 111 exerts a suppressive effect toward fibronectin, as macrophages plated on a LAM/FN mixture adopt a morphology and migratory character almost identical to LAM alone. This suggests that distinct responses can be initiated downstream of receptor-ECM engagement, and that one component of the microenvironment may affect the cell's ability to sense another. Overall, macrophages appear intrinsically poised to rapidly switch between distinct migratory modes based on their ECM environments. The role of ECM composition in dictating motile and inflammatory responses in 3D and in vivo contexts warrants further study.

Sialylated IVIg binding to DC-SIGN+ Hofbauer cells induces immune tolerance through the caveolin-1/NF-kB pathway and IL-10 secretion

Although the use of IVIg has increased in various immune-driven diseases and even in pregnancy, the exact action mechanisms of IVIg are not fully understood. Dendritic cell-specific intercellular adhesion molecule-3 grabbing non-integrin (DC-SIGN) is a known receptor for α-2,6-sialylated IgG (sIVIg), which is responsible for the anti-inflammatory effect of IVIg. DC-SIGN is expressed on Hofbauer cells (HBCs) of the fetal villi of the placenta which act as an innate immune modulator at the maternal-fetal interface. Preeclampsia is a major complication in pregnancy and is related to IL-10, a cytokine with an important role in immune tolerance. DC-SIGN interaction with sIVIg in HBCs promoted IL-10 secretion through the activation of the caveolin-1/NF-κB pathway, especially in plasma lipid rafts. Consistent results were obtained for HBCs from patients with preeclampsia. Collectively, the stimulation of DC-SIGN⁺ HBCs with sIVIg enhanced immune tolerance in the feto-maternal environment, suggesting the therapeutic application of sIVIg to prevent preeclampsia.

Caveolin-1 regulates OMV-induced macrophage pro-inflammatory activation and multiple Toll-like receptors

Macrophages (MФ), the primary cell of the innate immune system, serves as the first line of defense. During bacterial infection, Gram-negative (G-) bacteria release nanosized outer membrane vesicles (OMVs), facilitating the crosstalk between the microbe and the host. The underlying mechanisms by which OMVs induced pro-inflammatory (M1) activation are still unknown. Our study shows that OMVs caused M1 activation via modulating various toll-like receptor (TLR) expressions as they contain LPS, LTA, bacterial DNAs, and flagellins. Also, we found that caveolin-1 (cav-1), a 21-kDa scaffolding protein of caveolae and lipid rafts, plays a significant role in OMV-induced pro-inflammatory response in regulating various TLR signaling pathways. Specifically, cav-1 deletion increased the expression of OMV-induced TLRs, pro-inflammatory cytokine secretions (TNF-α and IL-1β), and the reactive oxygen species (ROS) production in MФs. Further, we examined the interaction between Cav-1 and TLR4 by immunoprecipitation, colocalization, and computational models, providing future direction to explore the role of cav-1 in OMV-induced other TLR signaling. Altogether, Cav-1 is a key regulator in OMV-induced multiple TLRs response. This study promotes future research to develop drugs by targeting the specific motif of cav-1 or TLRs against bacterial infection and macrophage-mediated inflammation.

Caveolin-1 in Müller Glia Exists as Heat-Resistant, High Molecular Weight Complexes

Caveolin-1 (Cav1), the core structural and scaffolding protein of caveolae membrane domains, is highly expressed in many retinal cells and is associated with ocular diseases. Cav1 regulates innate immune responses and is implicated in neuroinflammatory and neuroprotective signaling in the retina. We have shown that Cav1 expression in Müller glia accounts for over 70% of all retinal Cav1 expression. However, the proteins interacting with Cav1 in Müller glia are not established. Here, we show that immortalized MIO-M1 Müller glia, like endogenous Müller glia, highly express Cav1. Surprisingly, we found that Cav1 in MIO-M1 cells exists as heat-resistant, high molecular weight complexes that are stable after immunoprecipitation (IP). Mass spectrometric analysis of high molecular weight Cav1 complexes after Cav1 IP revealed an interactome network of intermediate filament, desmosomes, and actin-, and microtubule-based cytoskeleton. These results suggest Cav1 domains in Müller glia act as a scaffolding nexus for the cytoskeleton.

Caveolar and non-Caveolar Caveolin-1 in ocular homeostasis and disease

Caveolae, specialized plasma membrane invaginations present in most cell types, play important roles in multiple cellular processes including cell signaling, lipid uptake and metabolism, endocytosis and mechanotransduction. They are found in almost all cell types but most abundant in endothelial cells, adipocytes and fibroblasts. Caveolin-1 (Cav1), the signature structural protein of caveolae was the first protein associated with caveolae, and in association with Cavin1/PTRF is required for caveolae formation. Genetic ablation of either Cav1 or Cavin1/PTRF downregulates expression of the other resulting in loss of caveolae. Studies using Cav1-deficient mouse models have implicated caveolae with human diseases such as cardiomyopathies, lipodystrophies, diabetes and muscular dystrophies. While caveolins and caveolae are extensively studied in extra-ocular settings, their contributions to ocular function and disease pathogenesis are just beginning to be appreciated. Several putative caveolin/caveolae functions are relevant to the eye and Cav1 is highly expressed in retinal vascular and choroidal endothelium, Müller glia, the retinal pigment epithelium (RPE), and the Schlemm's canal endothelium and trabecular meshwork cells. Variants at the CAV1/2 gene locus are associated with risk of primary open angle glaucoma and the high risk HTRA1 variant for age-related macular degeneration is thought to exert its effect through regulation of Cav1 expression. Caveolins also play important roles in modulating retinal neuroinflammation and blood retinal barrier permeability. In this article, we describe the current state of caveolin/caveolae research in the context of ocular function and pathophysiology. Finally, we discuss new evidence showing that retinal Cav1 exists and functions outside caveolae.

Endothelial caveolin-1 regulates cerebral thrombo-inflammation in acute ischemia/reperfusion injury

BACKGROUND

Thrombo-inflammation is an important checkpoint that orchestrates infarct development in ischemic stroke. However, the underlying mechanism remains largely unknown. Here, we explored the role of endothelial Caveolin-1 (Cav-1) in cerebral thrombo-inflammation.

METHODS

The correlation between serum Cav-1 level and clinical outcome was analyzed in acute ischemic stroke patients with successful recanalization. Genetic manipulations by endothelial-specific adeno-associated virus (AAV) and siRNA were applied to investigate the effects of Cav-1 in thrombo-inflammation in a transient middle cerebral artery occlusion (tMCAO) model. Thrombo-inflammation was analyzed by microthrombosis formation, myeloid cell infiltration, and endothelial expression of adhesion molecules as well as inflammatory factors.

FINDINGS

Reduced circulating Cav-1, with the potential to predict microembolic signals, was more frequently detected in recanalized stroke patients without early neurological improvement. At 24 h after tMCAO, serum Cav-1 was consistently reduced in mice. Endothelial Cav-1 was decreased in the peri-infarct region. Cav-1^-/- endothelium, with prominent barrier disruption, displayed extensive microthrombosis, accompanied by increased myeloid cell inflammatory infiltration after tMCAO. Specific enhanced expression of endothelial Cav-1 by AAV-Tie1-Cav-1 remarkably reduced infarct volume, attenuated vascular hyper-permeability and alleviated thrombo-inflammation in both wild-type and Cav-1^-/- tMCAO mice. Transcriptome analysis after tMCAO further designated Rxrg as the most significantly changed molecule resulting from the knockdown of Cav-1. Supplementation of RXR-γ siRNA reversed AAV-Tie1-Cav-1-induced amelioration of thrombo-inflammation without affecting endothelial tight junction.

INTERPRETATION

Endothelial Cav-1/RXR-γ may regulate infarct volume and neurological impairment, possibly through selectively controlling thrombo-inflammation coupling, in cerebral ischemia/reperfusion.

FUNDING

This work was supported by National Natural Science Foundation of China.

Pathophysiology and molecular mechanism of caveolin involved in myocardial protection strategies in ischemic conditioning

Multiple pathophysiological pathways are activated during the process of myocardial injury. Various cardioprotective strategies protect the myocardium from ischemia, infarction, and ischemia/reperfusion (I/R) injury through different targets, yet the clinical translation remains limited. Caveolae and its structure protein, caveolins, have been suggested as a bridge to transmit damage-preventing signals and mediate the protection of ultrastructure in cardiomyocytes under pathological conditions. In this review, we first briefly introduce caveolae and caveolins. Then we review the cardioprotective strategies mediated by caveolins through various pathophysiological pathways. Finally, some possible research directions are proposed to provide future experiments and clinical translation perspectives targeting caveolin based on the investigative evidence.

Regulation of Neuroinflammatory Signaling by PPARγ Agonist in Mouse Model of Diabetes

Many relevant studies, as well as clinical practice, confirm that untreated diabetes predisposes the development of neuroinflammation and cognitive impairment. Having regard for the fact that PPARγ are widely distributed in the brain and PPARγ ligands may regulate the inflammatory process, the anti-inflammatory potential of the PPARγ agonist, pioglitazone, was assessed in a mouse model of neuroinflammation related with diabetes. In this regard, the biochemical and molecular indicators of neuroinflammation were determined in the hippocampus and prefrontal cortex of diabetes mice. The levels of cytokines (IL-1β, IL-6, and TNF) and the expression of genes (Tnfrsf1a and Cav1) were measured. In addition, behavioral tests such as the open field test, the hole-board test, and the novel object recognition test were conducted. A 14-day treatment with pioglitazone significantly decreased IL-6 and TNFα levels in the prefrontal cortex and led to the downregulation of Tnfrsf1a expression and the upregulation of Cav1 expression in both brain regions of diabetic mice. Pioglitazone, by targeting neuroinflammatory signaling, improved memory and exploratory activity in behavioral tests. The present study provided a potential theoretical basis and therapeutic target for the treatment of neuroinflammation associated with diabetes. Pioglitazone may provide a promising therapeutic strategy in diabetes patients with muffled of behavioral activity.

The novel adamantane derivatives as potential mediators of inflammation and neural plasticity in diabetes mice with cognitive impairment

Diabetes is a chronic disease leading to memory difficulties and deterioration of learning abilities. The previous studies showed that modulation of inflammatory pathways in the diabetic brain may reduce dysfunction or cell death in brain areas which are important for control of cognitive function. In the present study, we investigated the neuroprotective actions of newly synthesized adamantane derivatives on diabetes-induced cognitive impairment in mice. Our study relied on the fact that both vildagliptin and saxagliptin belong to DPP4 inhibitors and, contain adamantanyl group. Efficacy of tested compounds at reversing diabetes-induced different types of memory impairment was evaluated with the use of selected behavioural tests. The following neuroinflammatory indicators were also analyzed: neuroinflammatory indicators and the expression of genes involved in the inflammatory response of brain (Cav1, Bdnf). Our study demonstrated that new adamantane derivatives, similarly to DPP4 inhibitors, can restrict diabetes-induced cognitive deficits. We demonstrated that the overexpression of GLP-1-glucagon-like peptide as well as Bdnf, Cav1 genes translate into central blockade of pro-inflammatory synthesis of cytokines and significantly improvement on memory performance in diabetes mice. Newly synthesized adamantane derivatives might have important roles in prevention and treatment of cognitive impairment by inflammatory events in patients with diabetes or related diseases.

Glycyrrhizic Acid Alleviates Lipopolysaccharide (LPS)-Induced Acute Lung Injury by Regulating Angiotensin-Converting Enzyme-2 (ACE2) and Caveolin-1 Signaling Pathway

Acute lung injury (ALI) is mainly caused by severe infection, shock, trauma, and burn, which causes the extensive release of inflammatory factors and other mediators. As a major bioactive constituent of traditional Chinese herb licorice, glycyrrhizic acid (GA) plays an important effect on inflammatory regulation. Nevertheless, the exact mechanism of this effect remains unclear. The present study aims to explore the potential protective effect of GA on LPS-induced ALI. Our results showed that GA significantly attenuated LPS-induced ALI and decreased the production of inflammatory factors, including IL-1β, MCP-1, COX2, HMGB1, and adhesion molecules, such as E-selectin, VCAM-1, and modulated expression of angiotensin-converting enzyme 2 (ACE2). Moreover, treatment of ACE2 inhibitor (MLN-4760) reversed the effects of GA on the secretion of pro-inflammatory factors in ALI. Additionally, GA exerts its protective effect by regulating the ACE2 and caveolin-1/NF-κB signaling pathway. In conclusion, this study showed that GA alleviated LPS-induced ALI by upregulating ACE2 and inhibiting the caveolin-1/NF-κB signaling pathway.

The Potential Immunomodulatory Properties of Levornidazole Contribute to Improvement in Experimental Ulcerative Colitis

The use of an antibiotic with immunomodulatory properties could be fascinating in treating multifactorial inflammatory conditions such as ulcerative colitis (UC). We report our investigations into the immunomodulatory properties of levornidazole, the S-enantiomer of ornidazole, which displayed a tremendous therapeutic potential in UC induced by dextran sodium sulfate (DSS). Levornidazole administration to DSS-colitic mice attenuated the intestinal inflammatory process, with an efficacy better than that shown by 5-amino salicylic acid. This was evidenced by decreased disease activity index, ameliorated macroscopic and microscopic colon damages, and reduced expression of inflammatory cytokines. Additionally, levornidazole displayed anti-inflammatory activity through Caveolin-1-dependent reducing IL-1β and IL-18 secretion by macrophages contributing to its improvement of the intestinal inflammation, as confirmed in vitro and in vivo. In conclusion, these results pointed out that the immunomodulatory effects of levornidazole played a vital role in ameliorating the intestinal inflammatory process, which would be crucial for the translation of its use into clinical settings.

Caveolin-1, a novel player in cognitive decline

Cognitive decline (CD), which related to vascular dementia, Alzheimer's disease, Parkinson's disease, Huntington's disease, amyotrophic lateral sclerosis and diabetes mellitus, is a growing health concern that has a great impact on the patients' quality of life. Although extensive efforts, the mechanisms of CD are still far from being clarified, not to mention the effective treatment and prevention strategies. Caveolin-1 (Cav-1), a trans-membrane protein, is a major component of the caveolae structure and scaffolding proteins. Recently, ample evidence depicts a strong correlation between Cav-1 and CD, however, the specific role of Cav-1 in CD has not been clearly examined and how they might be connected have yet to be identified. This review seeks to provide a comprehensive overview about how Cav-1 modulates pathogeneses of CD-associated diseases. In summary, Cav-1 can promote structural and functional plasticity of neurons, improve neurogenesis, relieve mitochondrial dysfunction, inhibit inflammation and suppress oxidative stress, which have shed light on the idea that Cav-1 may be an efficacious therapeutic target to treat CD.

The α2AR/Caveolin-1/p38MAPK/NF-κB axis explains dexmedetomidine protection against lung injury following intestinal ischaemia-reperfusion

Intestinal ischaemia-reperfusion (I/R) injury can result in acute lung injury due to ischaemia and hypoxia. Dexmedetomidine (Dex), a highly selective alpha2-noradrenergic receptor (α2AR) agonist used in anaesthesia, is reported to regulate inflammation in organs. This study aimed to investigate the role and mechanism of Dex in lung injury caused by intestinal I/R. After establishing a rat model of intestinal I/R, we measured the wet-to-dry specific gravity of rat lungs upon treatments with Dex, SB239063 and the α2AR antagonist Atipamezole. Moreover, injury scoring and histopathological studies of lung tissues were performed, followed by ELISA detection on tumour necrosis factor-α (TNF-α), interleukin (IL)-1β and IL-6 expression. Correlation of Caveolin-1 (Cav-1) protein expression with p38, p-p38, p-p65 and p65 in rat lung tissues was analysed, and the degree of cell apoptosis in lung tissues after intestinal I/R injury was detected by TUNEL assay. The lung injury induced by intestinal I/R was a dynamic process. Moreover, Dex had protective effects against lung injury by mediating the expression of Cal-1 and α2A -AR. Specifically, Dex promoted Cav-1 expression via α2A -AR activation and mitigated intestinal I/R-induced lung injury, even in the presence of Atipamezole. The protective effect of Dex on intestinal I/R-induced lung injury was also closely related to α2A -AR/p38 mitogen-activated protein kinases/nuclear factor-kappaB (MAPK/NF-κB) pathway. Dex can alleviate pulmonary inflammation after in intestinal I/R by promoting Cav-1 to inhibit the activation of p38 and NF-κB. In conclusion, Dex can reduce pulmonary inflammatory response even after receiving threats from both intestinal I/R injury and Atipamezole.

Crosstalk Between LXR and Caveolin-1 Signaling Supports Cholesterol Efflux and Anti-Inflammatory Pathways in Macrophages

Macrophages are immune cells that play crucial roles in host defense against pathogens by triggering their exceptional phagocytic and inflammatory functions. Macrophages that reside in healthy tissues also accomplish important tasks to preserve organ homeostasis, including lipid uptake/efflux or apoptotic-cell clearance. Both homeostatic and inflammatory functions of macrophages require the precise stability of lipid-rich microdomains located at the cell membrane for the initiation of downstream signaling cascades. Caveolin-1 (Cav-1) is the main protein responsible for the biogenesis of caveolae and plays an important role in vascular inflammation and atherosclerosis. The Liver X receptors (LXRs) are key transcription factors for cholesterol efflux and inflammatory gene responses in macrophages. Although the role of Cav-1 in cellular cholesterol homeostasis and vascular inflammation has been reported, the connection between LXR transcriptional activity and Cav-1 expression and function in macrophages has not been investigated. Here, using gain and loss of function approaches, we demonstrate that LXR-dependent transcriptional pathways modulate Cav-1 expression and compartmentation within the membrane during macrophage activation. As a result, Cav-1 participates in LXR-dependent cholesterol efflux and the control of inflammatory responses. Together, our data show modulation of the LXR-Cav-1 axis could be exploited to control exacerbated inflammation and cholesterol overload in the macrophage during the pathogenesis of lipid and immune disorders, such as atherosclerosis.

A live attenuated Edwardsiella tarda vaccine induces immunological expression pattern in Japanese flounder (Paralichthys olivaceus) in the early phase of immunization

A previous study showed that an attenuated Edwardsiella tarda strain, TXhfq, as a live vaccine could elicit protective immune effects in fish against E. tarda infection. In the current study, in order to clarify the molecular mechanism of fish immune response at the early stage after TXhfq vaccination, RNA-Seq technology was used to compare the transcriptomes of skin, intestine, and spleen between bath-vaccinated and unvaccinated Japanese flounder (Paralichthys olivaceus). An average of 46.6 million clean reads per library was obtained, ~88.04% of which were successfully mapped to the reference genome, and approximately 24,600 genes were detected in each sample. A total of 565, 878, and 1258 differential expression genes (DEGs) were found in skin, intestine, and spleen, respectively, including 1263 up-regulated genes and 1438 down-regulated genes. The DEGs exhibited different characteristics in each tissue. One hundred and sixteen DEGs belonging to six immune related categories were scrutinized, i.e., inflammatory factors, cytokines, complement and coagulation system, mucins, phagocytosis, and antigen processing and presentation. A protein-protein interaction network was constructed to get the interaction network between immune genes during the early stage of immunization. The top six hub genes highly regulated by TXhfq formed complicated interaction relationship with each other, which were involved in immune processes, notably inflammation and phagocytosis. Our results provide valuable information for the understanding of the immune mechanism underlying the protection of live attenuated vaccines in fish.

Lifestyle intervention in individuals with impaired glucose regulation affects Caveolin-1 expression and DNA methylation

Aims: We investigated whether a lifestyle intervention could influence expression and DNA methylation of diabetes-related genes in patients with impaired glucose regulation (IGR), the results were compared to bariatric surgery, considering it an intensive change. Methods: Twenty participants with IGR had adipose tissue biopsy and blood collected pre- and post-lifestyle (6 months) intervention; 12 obese patients had subcutaneous fat taken before and after bariatric surgery. RNA/DNA was extracted from all samples and underwent qPCR. DNA was bisulphite converted and 12 CpG sites of Caveolin-1 (CAV1) promoter were pyrosequenced. Results: lifestyle intervention resulted in opposite direction changes in fat tissue and blood for CAV1 expression and DNA methylation and these changes were correlated between tissues, while no significative differences were found in CAV1 expression after bariatric surgery. Conclusions: Our findings suggest a role for CAV1 in modulating adipocyte function as a consequence of lifestyle changes, as exercises and diet. These results may provide insights into new therapeutic targets for diabetes prevention.

The Potential Contribution of Caveolin 1 to HIV Latent Infection

Combinatorial antiretroviral therapy (cART) suppresses HIV replication to undetectable levels and has been effective in prolonging the lives of HIV infected individuals. However, cART is not capable of eradicating HIV from infected individuals mainly due to HIV’s persistence in small reservoirs of latently infected resting cells. Latent infection occurs when the HIV-1 provirus becomes transcriptionally inactive and several mechanisms that contribute to the silencing of HIV transcription have been described. Despite these advances, latent infection remains a major hurdle to cure HIV infected individuals. Therefore, there is a need for more understanding of novel mechanisms that are associated with latent infection to purge HIV from infected individuals thoroughly. Caveolin 1(Cav-1) is a multifaceted functional protein expressed in many cell types. The expression of Cav-1 in lymphocytes has been controversial. Recent evidence, however, convincingly established the expression of Cav-1 in lymphocytes. In lieu of this finding, the current review examines the potential role of Cav-1 in HIV latent infection and provides a perspective that helps uncover new insights to understand HIV latent infection.

Caveolin-1 in oncogenic metabolic symbiosis

Metabolic phenotypes of cancer cells are heterogeneous and flexible as a tumor mass is a hurriedly evolving system capable of constant adaptation to oxygen and nutrient availability. The exact type of cancer metabolism arises from the combined effects of factors intrinsic to the cancer cells and factors proposed by the tumor microenvironment. As a result, a condition termed oncogenic metabolic symbiosis in which components of the tumor microenvironment (TME) promote tumor growth often occurs. Understanding how oncogenic metabolic symbiosis emerges and evolves is crucial for perceiving tumorigenesis. The process by which tumor cells reprogram their TME involves many mechanisms, including changes in intercellular communication, alterations in metabolic phenotypes of TME cells, and rearrangement of the extracellular matrix. It is possible that one molecule with a pleiotropic effect such as Caveolin-1 may affect many of these pathways. Here, we discuss the significance of Caveolin-1 in establishing metabolic symbiosis in TME.

Caveolin as a Novel Potential Therapeutic Target in Cardiac and Vascular Diseases: A Mini Review

Caveolin, a structural protein of caveolae, play roles in the regulation of endothelial function, cellular lipid homeostasis, and cardiac function by affecting the activity and biogenesis of nitric oxide, and by modulating signal transduction pathways that mediate inflammatory responses and oxidative stress. In this review, we present the role of caveolin in cardiac and vascular diseases and the relevant signaling pathways involved. Furthermore, we discuss a novel therapeutic perspective comprising crosstalk between caveolin and autophagy.

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.

Caveolin-1 in Stroke Neuropathology and Neuroprotection: A Novel Molecular Therapeutic Target for Ischemic-Related Injury

Cardiovascular disease and associated cerebral stroke are a global epidemic attributed to genetic and epigenetic factors, such as diet, life style and an increasingly sedentary existence due to technological advances in both the developing and developed world. There are approximately 5.9 million stroke-related deaths worldwide annually. Current epidemiological data indicate that nearly 16.9 million people worldwide suffer a new or recurrent stroke yearly. In 2014 alone, 2.4% of adults in the United States (US) were estimated to experience stroke, which is the leading cause of adult disability and the fifth leading cause of death in the US There are 2 main types of stroke: Hemorrhagic (HS) and ischemic stroke (IS), with IS occurring more frequently. HS is caused by intra-cerebral hemorrhage mainly due to high blood pressure, while IS is caused by either embolic or thrombotic stroke. Both result in motor impairments, numbness or abnormal sensations, cognitive deficits, and mood disorders (e.g. depression). This review focuses on the 1) pathophysiology of stroke (neuronal cell loss, defective blood brain barrier, microglia activation, and inflammation), 2) the role of the membrane protein caveolin- 1 (Cav-1) in normal brain physiology and stroke-induced changes, and, 3) we briefly discussed the potential therapeutic role of Cav-1 in recovery following stroke.

Caveolin-1 Controls Vesicular TLR2 Expression, p38 Signaling and T Cell Suppression in BCG Infected Murine Monocytic Myeloid-Derived Suppressor Cells

Monocytic myeloid-derived suppressor cells (M-MDSCs) and granulocytic MDSCs (G-MDSCs) have been found to be massively induced in TB patients as well in murine Mtb infection models. However, the interaction of mycobacteria with MDSCs and its role in TB infection is not well studied. Here, we investigated the role of Cav-1 for MDSCs infected with Mycobacterium bovis Bacille-Calmette-Guerín (BCG). MDSCs that were generated from murine bone marrow (MDSCs) of wild-type (WT) or Cav1^−/− mice upregulated Cav-1, TLR4 and TLR2 expression after BCG infection on the cell surface. However, Cav-1 deficiency resulted in a selective defect of intracellular TLR2 levels predominantly in the M-MDSC subset. Further analysis indicated no difference in the phagocytosis of BCG by M-MDSCs from WT and Cav1^−/− mice or caveosome formation, but a reduced capacity to up-regulate surface markers, to secrete various cytokines, to induce iNOS and NO production required for suppression of T cell proliferation, whereas Arg-1 was not affected. Among the signaling pathways affected by Cav-1 deficiency, we found lower phosphorylation of the p38 mitogen-activated protein kinase (MAPK). Together, our findings implicate that (i) Cav-1 is dispensable for the internalization of BCG, (ii) vesicular TLR2 signaling in M-MDSCs is a major signaling pathway induced by BCG, (iii) vesicular TLR2 signals are controlled by Cav-1, (iv) vesicular TLR2/Cav-1 signaling is required for T cell suppressor functions.

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.

Moxifloxacin suppresses airway inflammation and modulates expression of caveolin-1 and flotillin-1 in airway smooth muscle cells of asthmatic rats

Background

Moxifloxacin (MXF) possesses anti-inflammatory properties on asthmatic airway smooth muscle cells (ASMCs) beyond their antimicrobial effects, but the mechanisms are still unknown. This study was to investigate effects of MXF on expression of caveolin-1 (Cav-1) and flotillin-1 (FLOT1) in ASMCs in asthmatic rats.

Methods

ASMCs were collected from the airway and cultured in vitro. Cells from normal rats were treated with normal saline (Group N); cells from asthmatic rats were incubated with normal saline (Group A) or MXF (20 mg/L) (Group M); Cav-1 expression was up-regulated by transferring Cav-1 expressing lentivirus (Group L) and FLOT1 expression down-regulated by using siRNA in cells from asthmatic rats (Group S). The expressions of Cav-1, FLOT1 and p65 NF-κB were measured by Western blotting and quantificational real-time polymerase chain reaction (qRT-PCR), and interleukin-8 (IL-8) and eotaxin contents were measured by enzyme-linked immunosorbent assay (ELISA).

Results

Compared with normal control, Cav-1 expression significantly decreased in asthmatic groups (P<0.01); MXF up-regulated Cav-1 expression in asthmatic groups (P<0.01). However, compared with normal control, the expression of FLOT1 and p65 NF-κB dramatically increased in asthmatic groups (P<0.01); MXF down-regulated the expression of FLOT1 and p65 NF-κB in asthmatic groups (P<0.01); meanwhile, the expressions of FLOT1 and p65 NF-κB decreased after up-regulation of Cav-1 expression in asthmatic groups (P=0.01). Compared with asthmatic groups, the IL-8 and eotaxin contents significantly decreased in MXF Groups, Cav-1 up-regulation asthmatic groups and FLOT1 down-regulation asthmatic groups (P<0.01).

Conclusions

MXF can modulate the airway inflammation, upregulate Cav-1 expression, downregulate the expression of FLOT1 and p65 NF-κB in asthmatic rat ASMCs, which may be related to the anti-inflammatory effects of MXF in asthmatic ASMCs.

Penehyclidine hydrochloride alleviates lipopolysaccharide‑induced acute lung injury in rats: Potential role of caveolin‑1 expression upregulation

The aim of the present study was to examine the protective effect of caveolin-1 (Cav-1) in the penehyclidine hydrochloride (PHC)-based inhibition of lipopolysaccharide (LPS)-induced acute lung injury (ALI) in vivo and in vitro, in addition to the potential underlying mechanisms. In vivo, an ALI rat model was established via intratracheal administration of LPS (5 mg/kg), and PHC (2 mg/kg) was administered 30 min following LPS treatment. In vitro, the Cav-1 gene was knocked down by small interfering (si)RNA in J774A.1 cells. Cells were incubated with LPS (1 µg/ml) for 2 h, and subsequently incubated with PHC (2 µg/ml) for an additional 2 h. Lung injury was assessed by lung histology and the ratio of polymorphonuclear leukocytes (PMNs) to total cells was assessed in bronchoalveolar lavage fluid (BALF), myeloperoxidase (MPO) activity, BALF protein content and lung wet/dry (W/D) ratio. The levels of pro-inflammatory factors, including tumor necrosis factor-α (TNF-α), interleukin (IL)-6 and IL-1β, in the sera of rats and cell culture supernatant were determined by ELISA. The protein expression levels of Cav-1, toll-like receptor 4 (TLR4), phosphorylated (p)-p38 mitogen activated protein kinases (p38 MAPKs) and nuclear factor kappa-light-chain-enhancer of activated B cells transcription factor p65 subunit (NF-κB p65) in lung tissues and J774A.1 cells were analyzed by western blot analysis. The results indicated that PHC effectively alleviated lung injury by decreasing neutrophil infiltration and protein concentration in BALF, and the lung W/D ratio and MPO activity and pro-inflammatory cytokine production induced by LPS. Furthermore, PHC significantly decreased the degrees of histopathological changes and pulmonary dysfunction. In vitro, treatment with PHC inhibited pro-inflammatory cytokine levels and MPO activity in LPS-stimulated J774A.1 cells. However, the results in the J774A.1 cells with Cav-1 gene knockdown were contrary. In addition, PHC decreased TLR4, p-p38 MAPKs and nuclear NF-κB p65 expression levels and upregulated the expression level of Cav-1, in vivo and in vitro. These data demonstrated that PHC exhibited a protective effect against LPS-induced ALI in rats and LPS-stimulated J774A.1 cells, which may be due to the inhibition of p38 MAPKs phosphorylation and TLR4/NF-κB signaling pathway by Cav-1 upregulation.

Abrogated Caveolin-1 expression via histone modification enzyme Setdb2 regulates brain edema in a mouse model of influenza-associated encephalopathy

Influenza-associated encephalopathy (IAE) is a serious complication that can follow influenza virus infection. Once a cytokine storm is induced during influenza virus infection, tight junction protein disruption occurs, which consequently leads to blood-brain barrier (BBB) breakdown. However, the details of IAE pathogenesis are not well understood. Here, we established a murine IAE model by administration of lipopolysaccharide following influenza virus infection. Brains from IAE model mice had significantly higher expression of type I interferons and inflammatory cytokines. In addition, the expression of Caveolin-1, one of the key proteins that correlate with protection of the BBB, was significantly lower in brains from the IAE group compared with the control group. We also found that, among 84 different histone modification enzymes, only SET domain bifurcated 2 (Setdb2), one of the histone methyltransferases that methylates the lysine 9 of histone H3, showed significantly higher expression in the IAE group compared with the control group. Furthermore, chromatin immunoprecipitation revealed that methylation of histone H3 lysine 9 was correlated with repression of the Caveolin-1 promoter region. These studies identify Caveolin-1 as a key regulator of BBB permeability in IAE and reveal that it acts through histone modification induced by Setdb2.

Downregulated Caveolin-1 expression in circulating monocytes may contribute to the pathogenesis of psoriasis

Caveolin-1 (CAV-1) is the principal component of caveolae that regulates a variety of signaling molecules and receptors. Our previous study revealed CAV-1 reduction in the epidermis of patients with psoriasis, which leads to enhanced Janus kinase/signal transducer and activator of transcription activation and cytokine production, suggesting that aberrant CAV-1 expression may contribute to psoriatic inflammation. This study aimed to investigate whether abnormal modulation of CAV-1 on immune cells is involved in the pathogenesis of psoriasis. We observed that CAV-1 level in psoriasis patients was apparently reduced in peripheral blood mononuclear cells (PBMCs) and it was prominent in CD14⁺ monocytes. CAV-1 silencing in monocytes represented elevated levels of interleukin (IL)-1β and IL-6, and those had enhanced chemotaxis activity. In a murine model of psoriasis-like inflammation induced by imiquimod, we observed a significant CAV-1 reduction in PBMCs. Systemic administration of CAV-1 scaffolding domain peptide significantly improved the skin phenotype with less macrophage infiltration. Taken together, aberrant CAV-1 expression in monocytes may be involved in the pathogenesis of psoriasis.

Low-intensity pulsed ultrasound attenuates cardiac inflammation of CVB3-induced viral myocarditis via regulation of caveolin-1 and MAPK pathways

The aggressive immunological activity elicited by acute viral myocarditis contributes to a large amount of cardiomyocytes loss and poor prognosis of patients in clinic. Low-intensity pulsed ultrasound (LIPUS), which is an effective treatment modality for osteoarthropathy, has been recently illustrated regulating the overactive inflammatory response in various diseases. Here, we aimed to investigate whether LIPUS could attenuate coxsackievirus B3 (CVB3) infection-induced injury by coordinating the inflammatory response. Male BALB/c mice were inoculated intraperitoneally with CVB3 to establish the model of acute viral myocarditis. LIPUS treatment was given on Day 1, Day 1, 3 and Day 1, 3, 5 post-inoculation, respectively. All mice were followed up for 14 days. Day 1, 3, 5 LIPUS treatment significantly improved the survival rate, attenuated the ventricular dysfunction and ameliorated the cardiac histopathological injury of CVB3-infected mice. Western blotting analysis showed Day 1, 3, 5 LIPUS treatment decreased pro-inflammatory cytokines, increased the activation of caveolin-1 and suppressed p38 mitogen-activated protein kinase (MAPK) and extracellular signal-regulated kinase (ERK) signallings in heart tissue. RAW264.7 cells were treated with lipopolysaccharides (LPS) to simulate the augmented inflammatory response in vivo. LIPUS treatment on RAW264.7 inhibited the expression of pro-inflammatory cytokines, activated caveolin-1 and suppressed p38 MAPK and ERK signallings. Transfecting RAW264.7 with caveolin-1 siRNA blunted the suppression of pro-inflammatory cytokines and MAPK signallings by LIPUS treatment. Taken together, we demonstrated for the first time that LIPUS treatment attenuated the aggressive inflammatory response during acute viral myocarditis. The underlying mechanism may be activating caveolin-1 and suppressing MAPK signallings.

A review of the role of cav-1 in neuropathology and neural recovery after ischemic stroke

Ischemic stroke starts a series of pathophysiological processes that cause brain injury. Caveolin-1 (cav-1) is an integrated protein and locates at the caveolar membrane. It has been demonstrated that cav-1 can protect blood–brain barrier (BBB) integrity by inhibiting matrix metalloproteases (MMPs) which degrade tight junction proteins. This article reviews recent developments in understanding the mechanisms underlying BBB dysfunction, neuroinflammation, and oxidative stress after ischemic stroke, and focuses on how cav-1 modulates a series of activities after ischemic stroke. In general, cav-1 reduces BBB permeability mainly by downregulating MMP9, reduces neuroinflammation through influencing cytokines and inflammatory cells, promotes nerve regeneration and angiogenesis via cav-1/VEGF pathway, reduces apoptosis, and reduces the damage mediated by oxidative stress. In addition, we also summarize some experimental results that are contrary to the above and explore possible reasons for these differences.

Circulating miRNAs as Predictive Biomarkers of Type 2 Diabetes Mellitus Development in Coronary Heart Disease Patients from the CORDIOPREV Study

Circulating microRNAs (miRNAs) have been proposed as type 2 diabetes biomarkers, and they may be a more sensitive way to predict development of the disease than the currently used tools. Our aim was to identify whether circulating miRNAs, added to clinical and biochemical markers, yielded better potential for predicting type 2 diabetes. The study included 462 non-diabetic patients at baseline in the CORDIOPREV study. After a median follow-up of 60 months, 107 of them developed type 2 diabetes. Plasma levels of 24 miRNAs were measured at baseline by qRT-PCR, and other strong biomarkers to predict diabetes were determined. The ROC analysis identified 9 miRNAs, which, added to HbA1c, have a greater predictive value in early diagnosis of type 2 diabetes (AUC = 0.8342) than HbA1c alone (AUC = 0.6950). The miRNA and HbA1c-based model did not improve when the FINDRISC was included (AUC = 0.8293). Cox regression analyses showed that patients with low miR-103, miR-28-3p, miR-29a, and miR-9 and high miR-30a-5p and miR-150 circulating levels have a higher risk of disease (HR = 11.27; 95% CI = 2.61-48.65). Our results suggest that circulating miRNAs could potentially be used as a new tool for predicting the development of type 2 diabetes in clinical practice.

The autophagic degradation of Cav-1 contributes to PA-induced apoptosis and inflammation of astrocytes

The accumulation of palmitic acid (PA), implicated in obesity, can induce apoptotic cell death and inflammation of astrocytes. Caveolin-1 (Cav-1), an essential protein for astrocytes survival, can be degraded by autophagy, which is a double-edge sword that can either promote cell survival or cell death. The aim of this study was to delineate whether the autophagic degradation of Cav-1 is involved in PA-induced apoptosis and inflammation in hippocampal astrocytes. In this study we found that: (1) PA caused apoptotic death and inflammation by autophagic induction; (2) Cav-1 was degraded by PA-induced autophagy and PA induced autophagy in a Cav-1-independent manner; (3) the degradation of Cav-1 was responsible for PA-induced autophagy-dependent apoptotic cell death and inflammation; (4) chronic high-fat diet (HFD) induced Cav-1 degradation, apoptosis, autophagy, and inflammation in the hippocampal astrocytes of rats. Our results suggest that the autophagic degradation of Cav-1 contributes to PA-induced apoptosis and inflammation of astrocytes. Therefore, Cav-1 may be a potential therapeutic target for central nervous system injuries caused by PA accumulation.

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.

Caveolin-1 and Caveolin-2 Can Be Antagonistic Partners in Inflammation and Beyond

Caveolins, encoded by the CAV gene family, are the main protein components of caveolae. In most tissues, caveolin-1 (Cav-1) and caveolin-2 (Cav-2) are co-expressed, and Cav-2 targeting to caveolae depends on the formation of heterooligomers with Cav-1. Notwithstanding, Cav-2 has unpredictable activities, opposing Cav-1 in the regulation of some cellular processes. While the major roles of Cav-1 as a modulator of cell signaling in inflammatory processes and in immune responses have been extensively discussed elsewhere, the aim of this review is to focus on data revealing the distinct activity of Cav-1 and Cav-2, which suggest that these proteins act antagonistically to fine-tune a variety of cellular processes relevant to inflammation.

Is There a Potential Therapeutic Role for Caveolin-1 in Fibrosis?

Fibrosis is a process of dysfunctional wound repair, described by a failure of tissue regeneration and excessive deposition of extracellular matrix, resulting in tissue scarring and subsequent organ deterioration. There are a broad range of stimuli that may trigger, and exacerbate the process of fibrosis, which can contribute to the growing rates of morbidity and mortality. Whilst the process of fibrosis is widely described and understood, there are no current standard treatments that can reduce or reverse the process effectively, likely due to the continuing knowledge gaps surrounding the cellular mechanisms involved. Several cellular targets have been implicated in the regulation of the fibrotic process including membrane domains, ion channels and more recently mechanosensors, specifically caveolae, particularly since these latter contain various signaling components, such as members of the TGFβ and MAPK/ERK signaling pathways, all of which are key players in the process of fibrosis. This review explores the anti-fibrotic influences of the caveola, and in particular the key underpinning protein, caveolin-1, and its potential as a novel therapeutic target.

The ubiquitin ligase ZNRF1 promotes caveolin-1 ubiquitination and degradation to modulate inflammation

Caveolin-1 (CAV1), the major constituent of caveolae, plays a pivotal role in various cellular biological functions, including cancer and inflammation. The ubiquitin/proteasomal pathway is known to contribute to the regulation of CAV1 expression, but the ubiquitin ligase responsible for CAV1 protein stability remains unidentified. Here we reveal that E3 ubiquitin ligase ZNRF1 modulates CAV1 protein stability to regulate Toll-like receptor (TLR) 4-triggered immune responses. We demonstrate that ZNRF1 physically interacts with CAV1 in response to lipopolysaccharide and mediates ubiquitination and degradation of CAV1. The ZNRF1-CAV1 axis regulates Akt-GSK3β activity upon TLR4 activation, resulting in enhanced production of pro-inflammatory cytokines and inhibition of anti-inflammatory cytokine IL-10. Mice with deletion of ZNRF1 in their hematopoietic cells display increased resistance to endotoxic and polymicrobial septic shock due to attenuated inflammation. Our study defines ZNRF1 as a regulator of TLR4-induced inflammatory responses and reveals another mechanism for the regulation of TLR4 signalling through CAV1.

The Role of Caveolin 1 in HIV Infection and Pathogenesis

Caveolin 1 (Cav-1) is a major component of the caveolae structure and is expressed in a variety of cell types including macrophages, which are susceptible to human immunodeficiency virus (HIV) infection. Caveolae structures are present in abundance in mechanically stressed cells such as endothelial cells and adipocytes. HIV infection induces dysfunction of these cells and promotes pathogenesis. Cav-1 and the caveolae structure are believed to be involved in multiple cellular processes that include signal transduction, lipid regulation, endocytosis, transcytosis, and mechanoprotection. Such a broad biological role of Cav-1/caveolae is bound to have functional cross relationships with several molecular pathways including HIV replication and viral-induced pathogenesis. The current review covers the relationship of Cav-1 and HIV in respect to viral replication, persistence, and the potential role in pathogenesis.

Dihydroartemisinin inhibits the viability of cervical cancer cells by upregulating caveolin 1 and mitochondrial carrier homolog 2: Involvement of p53 activation and NAD(P)H:quinone oxidoreductase 1 downregulation

Dihydroartemisinin (DHA) has been shown to inhibit the viability of various cancer cells. Previous studies have revealed that the mechanisms involved in the inhibitory effects of DHA are based on theactivation of p53 and the mitochondrial-related cell death pathway. However, the exact association between upstream signaling and the activation of cell death pathway remains unclear. In this study, we found that DHA treatment induced the upregulation of caveolin 1 (Cav1) and mitochondrial carrier homolog 2 (MTCH2) in HeLa cells, and this was associated with the DHA-induced inhibition of cell viability and DHA-induced apoptosis. Additionally, the overexpression of Cav1 and MTCH2 in HeLa cells enhanced the inhibitory effects of DHA on cell viability. Moreover, we also found that the upregulation of Cav1 contributed to the DHA-mediated p53 activation and the downregulation of the redox enzyme, NAD(P)H:quinone oxidoreductase 1 (NQO1), which have been reported to contribute to the activation of the cell death pathway. Of note, we also found that DHA induced the nuclear translocation and accumulation of both Cav1 and p53, indicating a novel potential mechanism, namely the regulation of p53 activation by Cav1. On the whole, our study identified Cav1 and MTCH2 as the molecular targets of DHA and revealed a new link between the upstream Cav1/MTCH2 upregulation and the downstream activation of the cell death pathway involved in the DHA-mediated inhibition of cell viability.

Sclareol inhibits cell proliferation and sensitizes cells to the antiproliferative effect of bortezomib via upregulating the tumor suppressor caveolin-1 in cervical cancer cells

The anticancer effect of sclareol has long been reported, however, the exact mechanisms underlying the antitumorigenic effect of sclareol in cervical carcinoma remain to be fully elucidated. The present study analyzed cell proliferation and cell apoptosis by MTT and FITC-Annexin V assays. The protein levels of caveolin-1 (Cav-1) and copper-zinc superoxide dismutase (SOD)1 were determined by western blotting, and the interaction of Cav1 and HSC70 was investigated by co-immunoprecipitation experiments. The present study found that sclareol inhibited cell proliferation and induced apoptosis in HeLa cells. Two cancer-associated proteins, Cav1 and SOD1 were identified as potential targets of sclareol in HeLa cells. The expression of Cav1 increased when the cells were treated with sclareol, and the protein level of SOD1 was negatively correlated with Cav1. The overexpression of Cav1 enhanced the sensitivity of the HeLa cells to sclareol treatment and downregulated the protein level of SOD1, which exhibited potential associations between Cav1 and SOD1. In addition, sclareol significantly sensitized several cancer cells to the anticancer effect of bortezomib by targeting Cav1 and SOD1. Taken together, the results of the present study demonstrated that sclareol inhibited tumor cell growth through the upregulation of Cav1, and provides a potential therapeutic target for human cancer.

c-Jun N-terminal kinase activity is required for efficient respiratory syncytial virus production

Respiratory syncytial virus (RSV) is a major cause of respiratory infections in infants and the elderly, leading to more deaths than influenza each year worldwide. With no RSV antiviral or efficacious vaccine currently available, improved understanding of the host-RSV interaction is urgently required. Here we examine the contribution to RSV infection of the host stress-regulated c-Jun N-terminal kinase (JNK), for the first time. Peak JNK1/2 phosphoactivation is observed at ∼24 h post-infection, correlating with the time of virus assembly. The release of infectious RSV virions from infected cells was significantly reduced by either JNK1/2 siRNA knockdown or treatment with the JNK-specific inhibitor, JNK-IN-VIII. High resolution microscopy confirmed RSV accumulation in the host cell cytoplasm. The results implicate JNK1/2 as a key host factor for RSV virus production, raising the possibility of agents targeting JNK activity as potential anti-RSV therapeutics.

TLR4 and Caveolin-1 in Monocytes Are Associated With Inflammatory Conditions in Diabetic Neuropathy

The purpose of this study was to investigate the expression of TLR4 and caveolin‐1 in monocytes among healthy volunteers as well as those with type‐2 diabetes mellitus (T2DM) and diabetic peripheral neuropathy (DPN). Nineteen healthy control subjects, 18 patients with T2DM, and 20 patients with DPN were enrolled. Toll‐like receptor (TLR)4, caveolin‐1, MyD88, phosphorylated IκB, and plasma TNF‐α and interleukin (IL)‐6 were measured using real‐time polymerase chain reaction, Western blotting, and enzyme‐linked immunosorbent assay. Compared with the other two groups, the DPN group had higher expression of TLR4, MyD88, phosphorylated IκB, TNF‐α, and IL‐6, but significantly lower levels of caveolin‐1 and total IκB in monocytes. Plasma concentrations of TNF‐α and IL‐6 were positively correlated with TLR4 and negatively correlated with caveolin‐1 in patients with DPN. Plasma concentration of TLR4 was negatively correlated with caveolin‐1 in patients with DPN. Reduced expression of caveolin‐1 in monocytes could aggravate the TLR4‐mediated inflammatory cascade.

Overexpression of caveolin-1 attenuates brain edema by inhibiting tight junction degradation

Cerebral edema from the disruption of the blood-brain barrier (BBB) after cerebral ischemia is a major cause of morbidity and mortality as well as a common event in patients with stroke. Caveolins (Cavs) are thought to regulate BBB functions. Here, we report for the first time that Cav-1 overexpression (OE) decreased brain edema from BBB disruption following ischemic insult. Edema volumes and Cav-1 expression levels were measured following photothrombosis and middle cerebral artery occlusion (MCAO). Endothelial cells that were transduced with a Cav-1 lentiviral expression vector were transplanted into rats. BBB permeability was quantified with Evans blue extravasation. Edema volume was determined from measures of the extravasation area, brain water content, and average fluorescence intensity after Cy5.5 injections. Tight junction (TJ) protein expression was measured with immunoblotting. Cav-1 expression levels and vasogenic brain edema correlated strongly after ischemic insult. Cav-1 expression and BBB disruption peaked 3 d after the MCAO. In addition, intravenous administration of endothelial cells expressing Cav-1 effectively increased the Cav-1 levels 3 d after the MCAO ischemic insult. Importantly, Cav-1 OE ameliorated the vasogenic edema by inhibiting the degradation of TJ protein expression in the acute phase of ischemic stroke. These results suggested that Cav-1 OE protected the integrity of the BBB mainly by preventing the degradation of TJ proteins in rats. These findings need to be confirmed in a clinical setting in human subjects.