Upregulation of caveolin-1 and its colocalization with cytokine receptors contributes to beta cell apoptosis

Caveolin-1 deficiency alleviates palmitate-induced intracellular lipid accumulation and inflammation in pancreatic β cells

Lipotoxicity-induced pancreatic β cell damage is a strong predictor of type 2 diabetes mellitus (T2DM). Our previous work showed that Caveolin-1 (Cav-1) depletion decreased β-cell apoptosis and improved β-cell viability. Further microarray analysis indicated significant changes in the expression of genes related to fatty acid metabolism and inflammation. The objective of this study was to explore the role of Cav-1 in intracellular lipid accumulation and inflammation in β cells under lipotoxic conditions. Here, we established a β-cell-specific Cav-1 knockout (β-Cav-1 KO) mouse model and a CAV-1 depleted β cell line (NIT-1). We found that Cav-1 silencing significantly reduced palmitate (PA)-induced intracellular triglyceride (TG) accumulation and decreased proinflammatory factor expression in both the mouse and cell models. Further mechanistic investigation revealed that amelioration of lipid metabolism was achieved through the downregulation of lipogenic markers (SREBP-1c, FAS and ACC) and upregulation of a fatty acid oxidation marker (CPT-1). Meanwhile, decrease of inflammatory cytokines (IL-6, TNF-α, and IL-1β) secretion was found with the involvement of the IKKβ/NF-κB signaling pathways. Our findings suggest that Cav-1 is of considerable importance in regulating lipotoxicity-induced β-cell intracellular lipid accumulation and inflammation.

Pancreatic Beta-cell Dysfunction in Type 2 Diabetes

Pancreatic β-cells produce and secrete insulin to maintain blood glucose levels within a narrow range. Defects in the function and mass of β-cells play a significant role in the development and progression of diabetes. Increased β-cell deficiency and β-cell apoptosis are observed in the pancreatic islets of patients with type 2 diabetes. At an early stage, β-cells adapt to insulin resistance, and their insulin secretion increases, but they eventually become exhausted, and the β-cell mass decreases. Various causal factors, such as high glucose, free fatty acids, inflammatory cytokines, and islet amyloid polypeptides, contribute to the impairment of β-cell function. Therefore, the maintenance of β-cell function is a logical approach for the treatment and prevention of diabetes. In this review, we provide an overview of the role of these risk factors in pancreatic β-cell loss and the associated mechanisms. A better understanding of the molecular mechanisms underlying pancreatic β-cell loss will provide an opportunity to identify novel therapeutic targets for type 2 diabetes.

Panax notoginseng alleviates oxidative stress through miRNA regulations based on systems biology approach

BACKGROUND

Herbal medicine Sanqi (SQ), the dried root or stem of Panax notoginseng (PNS), has been reported to have anti-diabetic and anti-obesity effects and is usually administered as a decoction for Chinese medicine. Alternative to utilizing PNS pure compound for treatment, we are motivated to propose an unconventional scheme to investigate the functions of PNS mixture. However, studies providing a detailed overview of the transcriptomics-based signaling network in response to PNS are seldom available.

METHODS

To explore the reasoning of PNS in treating metabolic disorders such as insulin resistance, we implemented a systems biology-based approach with RNA sequencing (RNA-seq) and miRNA sequencing data to elucidate key pathways, genes and miRNAs involved.

RESULTS

Functional enrichment analysis revealed PNS up-regulating oxidative stress-related pathways and down-regulating insulin and fatty acid metabolism. Superoxide dismutase 1 (SOD1), peroxiredoxin 1 (PRDX1), heme oxygenase-1 (Hmox1) and glutamate cysteine ligase (GCLc) mRNA and protein levels, as well as related miRNA levels, were measured in PNS treated rat pancreatic β cells (INS-1). PNS treatment up-regulated Hmox1, SOD1 and GCLc expression while down-regulating miR-24-3p and miR-139-5p to suppress oxidative stress. Furthermore, we verified the novel interactions between miR-139-5p and miR-24-3p with GCLc and SOD1.

CONCLUSION

This work has demonstrated the mechanism of how PNS regulates cellular molecules in metabolic disorders. Therefore, combining omics data with a systems biology strategy could be a practical means to explore the potential function and molecular mechanisms of Chinese herbal medicine in the treatment of metabolic disorders.

Adipose Tissue Caveolin-1 Upregulation in Obesity Involves TNF-α/NF-κB Mediated Signaling

Obesity is characterized by chronic low-grade inflammation. Obese people have higher levels of caveolin-1 (CAV1), a structural and functional protein present in adipose tissues (ATs). We aimed to define the inflammatory mediators that influence CAV1 gene regulation and the associated mechanisms in obesity. Using subcutaneous AT from 27 (7 lean and 20 obese) normoglycemic individuals, in vitro human adipocyte models, and in vivo mice models, we found elevated CAV1 expression in obese AT and a positive correlation between the gene expression of CAV1, tumor necrosis factor-alpha (TNF-α), and the nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB). CAV1 gene expression was associated with proinflammatory cytokines and chemokines and their cognate receptors (r ≥ 0.447, p ≤ 0.030), but not with anti-inflammatory markers. CAV1 expression was correlated with CD163, indicating a prospective role for CAV1 in the adipose inflammatory microenvironment. Unlike wild-type animals, mice lacking TNF-α exhibited reduced levels of CAV1 mRNA/proteins, which were elevated by administering exogenous TNF-α. Mechanistically, TNF-α induces CAV1 gene transcription by mediating NF-κB binding to its two regulatory elements located in the CAV1 proximal regulatory region. The interplay between CAV1 and the TNF-α signaling pathway is intriguing and has potential as a target for therapeutic interventions in obesity and metabolic syndromes.

An overview of the intracellular localization of high-Z nanoradiosensitizers

Radiation therapy (RT) is a method commonly used for cancer treatment worldwide. Commonly, RT utilizes two routes for combating cancers: 1) high-energy radiation to generate toxic reactive oxygen species (ROS) (through the dissociation of water molecules) for damaging the deoxyribonucleic acid (DNA) inside the nucleus 2) direct degradation of the DNA. However, cancer cells have mechanisms to survive under intense RT, which can considerably decrease its therapeutic efficacy. Excessive radiation energy damages healthy tissues, and hence, low doses are applied for cancer treatment. Additionally, different radiosensitizers were used to sensitize cancer cells towards RT through individual mechanisms. Following this route, nanoparticle-based radiosensitizers (herein called nanoradiosensitizers) have recently gained attention owing to their ability to produce massive electrons which leads to the production of a huge amount of ROS. The success of the nanoradiosensitizer effect is closely correlated to its interaction with cells and its localization within the cells. In other words, tumor treatment is affected from the chain of events which is started from cell-nanoparticle interaction followed by the nanoparticles direction and homing inside the cell. Therefore, passive or active targeting of the nanoradiosensitizers in the subcellular level and the cell-nano interaction would determine the efficacy of the radiation therapy. The importance of the nanoradiosensitizer's targeting is increased while the organelles beyond nucleus are recently recognized as the mediators of the cancer cell death or resistance under RT. In this review, the principals of cell-nanomaterial interactions and which dominate nanoradiosensitizer efficiency in cancer therapy, are thoroughly discussed.

Nicotine Exposure during Rodent Pregnancy Alters the Composition of Maternal Gut Microbiota and Abundance of Maternal and Amniotic Short Chain Fatty Acids

Tobacco smoking is the leading cause of preventable death. Numerous reports link smoking in pregnancy with serious adverse outcomes, such as miscarriage, stillbirth, prematurity, low birth weight, perinatal morbidity, and infant mortality. Corollaries of consuming nicotine in pregnancy, separate from smoking, are less explored, and the mechanisms of nicotine action on maternal–fetal communication are poorly understood. This study examined alterations in the maternal gut microbiome in response to nicotine exposure during pregnancy. We report that changes in the maternal gut microbiota milieu are an important intermediary that may mediate the prenatal nicotine exposure effects, affect gene expression, and alter fetal exposure to circulating short-chain fatty acids (SCFAs) and leptin during in utero development.

Endothelin-1 Induced Phosphorylation of Caveolin-1 and Smad2C in Human Vascular Smooth Muscle Cells: Role of NADPH Oxidases, c-Abl, and Caveolae Integrity in TGF-β Receptor Transactivation

Caveolin-1(Cav-1) is one of the most important components of caveolae in the cell membrane, which plays an important role in cell signaling transduction, such as EGFR and TGF-β receptor transactivation. The purpose of this study was to evaluate the effect of c-Abl and NAD(P)H oxidases (NOX) on phosphorylation of Cav-1 and consequently their effect on phosphorylation of Smad2C induced by Endothelin-1 in human vascular smooth muscle cells (VSMCs). In this study, all experiments were performed using human VSMCs. The phosphorylation level of the Caveolin-1 and Smad2C proteins were assessed by western blotting using Phospho-Caveolin-1 (Tyr14) antibody and phospho-Smad2 (Ser465/467) antibody. The data were reported as mean ± SEM. The VSMCs treated with endothelin-1(ET-1) (100 nanomolar (nmol)) demonstrated a time-dependent increase in the pCav-1 level (p<0.05). The inhibitors of NOX (diphenyleneiodonium) (p<0.05), cholesterol depleting agent (beta-cyclodextrin) (p<0.05) and c-Abl inhibitor (PP1) (p<0.01) were able to reduce the level of the phospho-Cav-1 and phospho-Smad2C induced by Et-1 (p<0.05). Our results proposed that caveolae structure, NOX, c-Abl played an important role in the phosphorylation of Cav-1 induced by ET-1 in the human VSMCs. Furthermore, our findings showed that phosphoCav-1 involved in TGFR transactivation. Thus, Et-1 via a transactivation-dependent mechanism can cause phosphorylation of Smad2C.

Plasma exosomal caveolin-1 predicts Poor Prognosis in Ovarian Cancer

Objective: In this study, we aimed to evaluate the levels of plasma exosomal caveolin-1(CAV1) and determine its prognostic value in ovarian cancer patients.

Patients and Methods: Exosome-rich fractions were isolated from the plasma of 155 patients with ovarian cancer. TEM, NTA and western blot analysis were used to confirm the exosome integrity and purification.

Results: Compared with healthy controls, plasma exosomal CAV1 levels in ovarian cancer patient were significantly down-regulated (P < 0.001). The low plasma levels of exosomal CAV1 in ovarian cancer patient plasma were related to FIGO stages, grades and lymph node metastasis (all P < 0.01). Among all ovarian cancer patients, DFS was worse in patients who had low plasma exosomal CAV1 levels compared with that in patients with high plasma exosomal CAV1 levels (P < 0.001). The OS of patients with low plasma exosomal CAV1 levels was shorter than that in patients with high plasma exosomal CAV1 levels (P < 0.001). The AUROC of plasma exosomal CAV1 was 0.76 (95% CI: 0.68-0.82) for DFS prediction in ovarian cancer patients, with a sensitivity 52.9 (95% CI: 42.8-62.9) and a specificity 88.7 (95% CI: 77.0-95.7). For OS prediction in ovarian cancer patients, the AUROC of plasma exosomal CAV1 was 0.78 (95% CI: 0.70-0.84), with a sensitivity 65.1 (95% CI: 49.1-79.0) and a specificity 81.2 (95% CI: 72.8-88.0).

Conclusions: Low exosomal CAV1 levels were closely related to the FIGO stages I/II, low grade, lymph node metastasis and prognosis of ovarian cancer patients. Plasma exosomal CAV1 may be a potential biomarker for the prognosis in ovarian cancer patients.

A Cell Membrane-Level Approach to Cicatricial Alopecia Management: Is Caveolin-1 a Viable Therapeutic Target in Frontal Fibrosing Alopecia?

Irreversible destruction of the hair follicle (HF) in primary cicatricial alopecia and its most common variant, frontal fibrosing alopecia (FFA), results from apoptosis and pathological epithelial-mesenchymal transition (EMT) of epithelial HF stem cells (eHFSCs), in conjunction with the collapse of bulge immune privilege (IP) and interferon-gamma-mediated chronic inflammation. The scaffolding protein caveolin-1 (Cav1) is a key component of specialized cell membrane microdomains (caveolae) that regulates multiple signaling events, and even though Cav1 is most prominently expressed in the bulge area of human scalp HFs, it has not been investigated in any cicatricial alopecia context. Interestingly, in mice, Cav1 is involved in the regulation of (1) key HF IP guardians (TGF-β and α-MSH signaling), (2) IP collapse inducers/markers (IFNγ, substance P and MICA), and (3) EMT. Therefore, we hypothesize that Cav1 may be an unrecognized, important player in the pathobiology of cicatricial alopecias, and particularly, in FFA, which is currently considered as the most common type of primary lymphocytic scarring alopecia in the world. We envision that localized therapeutic inhibition of Cav1 in management of FFA (by cholesterol depleting agents, i.e., cyclodextrins/statins), could inhibit and potentially reverse bulge IP collapse and pathological EMT. Moreover, manipulation of HF Cav1 expression/localization would not only be relevant for management of cicatricial alopecia, but FFA could also serve as a model disease for elucidating the role of Cav1 in other stem cell- and/or IP collapse-related pathologies.

Cytokine-Mediated Inflammation in the Oral Cavity and Its Effect on Lipid Nanocarriers

Topical drug administration to the oral mucosa proves to be a promising treatment alternative for inflammatory diseases. However, disease-related changes in the cell barrier must be considered when developing such delivery systems. This study aimed at investigating the changes in the lining mucosa caused by inflammation and evaluating the consequences on drug delivery systems such as nanostructured lipid carriers (NLC). For this, TR146 cells were treated with inflammatory cytokines and bacterial components. Cell viability and integrity, reactive oxygen species (ROS), and interleukin (IL)-8 release were used as endpoints to assess inflammation. Translocation of phosphatidylserine, cytoskeletal arrangement, opening of desmosomes, and cell proliferation were examined. Transport studies with NLC were performed considering active and passive pathways. The results showed that IL-1ß and tumor necrosis factor α induced inflammation by increasing IL-8 and ROS production (22-fold and 2-fold). Morphologically, loss of cell–cell connections and formation of stress fibers and hyperplasia were observed. The charge of the cell membrane shifted from neutral to negative, which increased the absorption of NLC due to the repulsive interactions between the hydrophobic negative particles and the cell membrane on the one hand, and interactions with lipophilic membrane proteins such as caveolin on the other.

Increased ERK phosphorylation and caveolin-1 expression on K562 human chronic myelogenous leukemia cells by jacalin, a dietary plant lectin

The potential antitumor effects of jacalin, the plant lectin that specifically recognizes the tumor-associated Thomsen-Friedenreich antigen has been extensively studied. We had earlier reported jacalin to be mitogenic to K562, the Bcr-Abl expressing erythroleukemia cell line. The dearth of studies highlighting the proliferative effects of jacalin and other lectins motivated us to unveil the mechanism underlying the mitogenic effects of jacalin. Caveolin-1 (cav-1) is an integral membrane protein, known to play a crucial role in cell signaling, lipid transport, and membrane trafficking. The role of cav-1 in tumorigenesis is considered to be controversial as it can suppress as well as promote tumor growth, depending on the cellular context. In the present study, we propose that cav-1 plays the central role in the mitogenic effects of jacalin on the K562 cells. In accordance, the mRNA, as well as protein expression of cav-1 was found to be upregulated in the jacalin-treated K562 cells as compared to the untreated control. Further, jacalin stimulation also increased the phosphorylation of ERK and Akt. The rationale that leads to the initial conjecture about cav-1 was that the sequence of jacalin possesses a cav-1-binding site.

The Potential Role and Regulatory Mechanisms of MUC5AC in Chronic Obstructive Pulmonary Disease

Chronic obstructive pulmonary disease (COPD) is associated with high morbidity and mortality globally. Studies show that airway mucus hypersecretion strongly compromises lung function, leading to frequent hospitalization and mortality, highlighting an urgent need for effective COPD treatments. MUC5AC is known to contribute to severe muco-obstructive lung diseases, worsening COPD pathogenesis. Various pathways are implicated in the aberrant MUC5AC production and secretion MUC5AC. These include signaling pathways associated with mucus-secreting cell differentiation [nuclear factor-κB (NF-κB)and IL-13-STAT6- SAM pointed domain containing E26 transformation-specific transcription factor (SPDEF), as well as epithelial sodium channel (ENaC) and cystic fibrosis transmembrane conductance regulator (CFTR)], and signaling pathways related to mucus transport and excretion-ciliary beat frequency (CBF). Various inhibitors of mucus hypersecretion are in clinical use but have had limited benefits against COPD. Thus, novel therapies targeting airway mucus hypersecretion should be developed for effective management of muco-obstructive lung disease. Here, we systematically review the mechanisms and pathogenesis of airway mucus hypersecretion, with emphasis on multi-target and multi-link intervention strategies for the elucidation of novel inhibitors of airway mucus hypersecretion.

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

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

Pharmacological management of vascular endothelial dysfunction in diabetes: TCM and western medicine compared based on biomarkers and biochemical parameters

Diabetes, a worldwide health concern while burdening significant populace of countries with time due to a hefty increase in both incidence and prevalence rates. Hyperglycemia has been buttressed both in clinical and experimental studies to modulate widespread molecular actions that effect macro and microvascular dysfunctions. Endothelial dysfunction, activation, inflammation, and endothelial barrier leakage are key factors contributing to vascular complications in diabetes, plus the development of diabetes-induced cardiovascular diseases. The recent increase in molecular, transcriptional, and clinical studies has brought a new scope to the understanding of molecular mechanisms and the therapeutic targets for endothelial dysfunction in diabetes. In this review, an attempt made to discuss up to date critical and emerging molecular signaling pathways involved in the pathophysiology of endothelial dysfunction and viable pharmacological management targets. Importantly, we exploit some Traditional Chinese Medicines (TCM)/TCM isolated bioactive compounds modulating effects on endothelial dysfunction in diabetes. Finally, clinical studies data on biomarkers and biochemical parameters involved in the assessment of the efficacy of treatment in vascular endothelial dysfunction in diabetes was compared between clinically used western hypoglycemic drugs and TCM formulas.

Colocalization of MID1IP1 and c-Myc is Critically Involved in Liver Cancer Growth via Regulation of Ribosomal Protein L5 and L11 and CNOT2

Though midline1 interacting protein 1 (MID1IP1) was known as one of the glucose-responsive genes regulated by carbohydrate response element binding protein (ChREBP), the underlying mechanisms for its oncogenic role were never explored. Thus, in the present study, the underlying molecular mechanism of MID1P1 was elucidated mainly in HepG2 and Huh7 hepatocellular carcinoma cells (HCCs). MID1IP1 was highly expressed in HepG2, Huh7, SK-Hep1, PLC/PRF5, and immortalized hepatocyte LX-2 cells more than in normal hepatocyte AML-12 cells. MID1IP1 depletion reduced the viability and the number of colonies and also increased sub G1 population and the number of TUNEL-positive cells in HepG2 and Huh7 cells. Consistently, MID1IP1 depletion attenuated pro-poly (ADP-ribose) polymerase (pro-PARP), c-Myc and activated p21, while MID1IP1 overexpression activated c-Myc and reduced p21. Furthermore, MID1IP1 depletion synergistically attenuated c-Myc stability in HepG2 and Huh7 cells. Of note, MID1IP1 depletion upregulated the expression of ribosomal protein L5 or L11, while loss of L5 or L11 rescued c-Myc in MID1IP1 depleted HepG2 and Huh7 cells. Interestingly, tissue array showed that the overexpression of MID1IP1 was colocalized with c-Myc in human HCC tissues, which was verified in HepG2 and Huh7 cells by Immunofluorescence. Notably, depletion of CCR4-NOT2 (CNOT2) with adipogenic activity enhanced the antitumor effect of MID1IP1 depletion to reduce c-Myc, procaspase 3 and pro-PARP in HepG2, Huh7 and HCT116 cells. Overall, these findings provide novel insight that MID1IP1 promotes the growth of liver cancer via colocalization with c-Myc mediated by ribosomal proteins L5 and L11 and CNOT2 as a potent oncogenic molecule.

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.