Caveolin-1 provides palliation for adverse hepatic reactions in hypercholesterolemic rabbits

The effect of dietary total antioxidant capacity (DTAC) and Caveolin-1 gene variant interaction on cardiovascular risk factors among overweight and obese women: A cross-sectional investigation

BACKGROUND

Previous studies have shown that the Caveolin-1 (CAV-1) gene variant may be associated with Cardiovascular disease (CVD) risk. Moreover, dietary total antioxidant capacity (DTAC) has been shown to potentially elicit favorable effects on CVD risk. Therefore, this study sought to investigate the effect of DTAC and CAV-1 interaction on CVD risk factors.

METHODS

This cross-sectional study consisted of 352 women, with overweight and/or obesity, aged 18-48years from Iran. A food frequency questionnaire (FFQ), with 147 items, was used to assess dietary intake. The CAV-1 rs 3807992 and anthropometric data were measured by the PCR-RFLP method and bioelectrical impedance analysis (BIA), respectively. Serum profiles were measured by standard protocols. Participants were also divided into two groups based on DTAC score and rs3807992 genotype.

RESULTS

The mean age of the participants was 37.34 ± 9.11 and 36.01 ± 9.12 years for homozygous (GG) and minor allele carriers (AG + AA) respectively.The mean ± SD of insulin, total cholesterol (TC),high-density lipoprotein (HDL), low-density lipoprotein (LDL) and TG of participants were 1.21 ± 0.23, 185.3 ± 35.77, 46.58 ± 10.86, 95.3 ± 24.12 and 118.1 ± 58.88, respectively. There was a significant difference between genotypes for physical activity (P = 0.05), HDL (P < 0.001), insulin (P = 0.04), CRI-I (TC/HDL-C) (P = 0.01), and CRI-II (LDL-C/HDL-C) (P = 0.04). Our findings also showed, after controlling for confounding factors, significant interactions between DTAC score and the A allele carrier group on TC (Pinteraction = 0.001), LDL (Pinteraction = 0.001), insulin (Pinteraction = 0.08), HOMA-IR (Pinteraction = 0.03), AC ((TC - HDL - C)/HDL - C) (Pinteraction = 0.001), and CHOLINDEX (LDL-C-HDL-C) (Pinteraction = 0.02).

CONCLUSION

The results of the present study indicate that high DTAC intake may modify the odds of risk factors for CVD in AA and AG genotypes of rs 3807992. These results highlight that diet, gene variants, and their interaction, should be considered in CVD risk assessment.

Caveolae and lipid sorting: Shaping the cellular response to stress

Caveolae are an abundant and characteristic surface feature of many vertebrate cells. The uniform shape of caveolae is characterized by a bulb with consistent curvature connected to the plasma membrane (PM) by a neck region with opposing curvature. Caveolae act in mechanoprotection by flattening in response to increased membrane tension, and their disassembly influences the lipid organization of the PM. Here, we review evidence for caveolae as a specialized lipid domain and speculate on mechanisms that link changes in caveolar shape and/or protein composition to alterations in specific lipid species. We propose that high membrane curvature in specific regions of caveolae can enrich specific lipid species, with consequent changes in their localization upon caveolar flattening. In addition, we suggest how changes in the association of lipid-binding caveolar proteins upon flattening of caveolae could allow release of specific lipids into the bulk PM. We speculate that the caveolae-lipid system has evolved to function as a general stress-sensing and stress-protective membrane domain.

Caveolae as Potential Hijackable Gates in Cell Communication

Caveolae are membrane microdomains described in many cell types involved in endocytocis, transcytosis, cell signaling, mechanotransduction, and aging. They are found at the interface with the extracellular environment and are structured by caveolin and cavin proteins. Caveolae and caveolins mediate transduction of chemical messages via signaling pathways, as well as non-chemical messages, such as stretching or shear stress. Various pathogens or signals can hijack these gates, leading to infectious, oncogenic and even caveolin-related diseases named caveolinopathies. By contrast, preclinical and clinical research have fallen behind in their attempts to hijack caveolae and caveolins for therapeutic purposes. Caveolae involvement in human disease is not yet fully explored or understood and, of all their scaffold proteins, only caveolin-1 is being considered in clinical trials as a possible biomarker of disease. This review briefly summarizes current knowledge about caveolae cell signaling and raises the hypothesis whether these microdomains could serve as hijackable “gatekeepers” or “gateways” in cell communication. Furthermore, because cell signaling is one of the most dynamic domains in translating data from basic to clinical research, we pay special attention to translation of caveolae, caveolin, and cavin research into clinical practice.

Reactive Oxygen Species Modulator 1 (ROMO1), a New Potential Target for Cancer Diagnosis and Treatment

Today, the incidence of cancer in the world is rising, and it is expected that in the next several decades, the number of people suffering from cancer or (the cancer rate) will double. Cancer is defined as the excessive and uncontrolled growth of cells; of course (in simple terms), cancer is considered to be a set of other diseases that ultimately causes normal cells to be transformed into neoplastic cells. One of the most important causes of the onset and exacerbation of cancer is excessive oxidative stress. One of the most important proteins in the inner membrane of mitochondria is Reactive Oxygen Species (ROS) Modulator 1 (ROMO1) that interferes with the production of ROS, and with increasing the rate of this protein, oxidative stress will increase, which ultimately leads to some diseases, especially cancer. In this overview, we use some global databases to provide information about ROMO1 cellular signaling pathways, their related proteins and molecules, and some of the diseases associated with the mitochondrial protein, especially cancer.

Swim Training Modulates Skeletal Muscle Energy Metabolism, Oxidative Stress, and Mitochondrial Cholesterol Content in Amyotrophic Lateral Sclerosis Mice

Recently, in terms of amyotrophic lateral sclerosis (ALS), much attention has been paid to the cell structures formed by the mitochondria and the endoplasmic reticulum membranes (MAMs) that are involved in the regulation of Ca²⁺ signaling, mitochondrial bioenergetics, apoptosis, and oxidative stress. We assumed that remodeling of these structures via swim training may accompany the prolongation of the ALS lifespan. In the present study, we used transgenic mice with the G93A hmSOD1 gene mutation. We examined muscle energy metabolism, oxidative stress parameters, and markers of MAMs (Caveolin-1 protein level and cholesterol content in crude mitochondrial fraction) in groups of mice divided according to disease progression and training status. The progression of ALS was related to the lowering of Caveolin-1 protein levels and the accumulation of cholesterol in a crude mitochondrial fraction. These changes were associated with aerobic and anaerobic energy metabolism dysfunction and higher oxidative stress. Our data indicated that swim training prolonged the lifespan of ALS mice with accompanying changes in MAM components. Swim training also maintained mitochondrial function and lowered oxidative stress. These data suggest that modification of MAMs might play a crucial role in the exercise-induced deceleration of ALS development.

Caveolin-1 in the regulation of cell metabolism: a cancer perspective

Caveolin-1 (CAV1) is an oncogenic membrane protein associated with endocytosis, extracellular matrix organisation, cholesterol distribution, cell migration and signaling. Recent studies reveal that CAV1 is involved in metabolic alterations – a critical strategy adopted by cancer cells to their survival advantage. Consequently, research findings suggest that CAV1, which is altered in several cancer types, influences tumour development or progression by controlling metabolism. Understanding the molecular interplay between CAV1 and metabolism could help uncover druggable metabolic targets or pathways of clinical relevance in cancer therapy. Here we review from a cancer perspective, the findings that CAV1 modulates cell metabolism with a focus on glycolysis, mitochondrial bioenergetics, glutaminolysis, fatty acid metabolism, and autophagy.

Hepatic caveolin-1 is enhanced in Cyp27a1/ApoE double knockout mice

Sterol 27‐hydroxylase (CYP27A1) is involved in bile acid synthesis and cholesterol homoeostasis. Cyp27a1^(−/−)/Apolipoprotein E^(−/−) double knockout mice (DKO) fed a western diet failed to develop atherosclerosis. Caveolin‐1 (CAV‐1), the main component of caveolae, is associated with lipid homoeostasis and has regulatory roles in vascular diseases. We hypothesized that liver CAV‐1 would contribute to the athero‐protective mechanism in DKO mice. Cyp27a1^(+/+)/ApoE^(−/−) (ApoE KO), Cyp27a1^(+/−)/ApoE^(−/−) (het), and DKO mice were fed a western diet for 2 months. Atherosclerotic plaque and CAV‐1 protein were quantified in aortas. Hepatic Cav‐1 mRNA was assessed using qPCR, CAV‐1 protein by immunohistochemistry and western blotting. Total hepatic and plasma cholesterol was measured using chemiluminescence. Cholesterol efflux was performed in RAW264.7 cells, using mice plasma as acceptor. CAV‐1 protein expression in aortas was increased in endothelial cells of DKO mice and negatively correlated with plaque surface (P < 0.05). In the liver, both CAV‐1 protein and mRNA expression doubled in DKO, compared to ApoE KO and het mice (P < 0.001 for both) and was negatively correlated with total hepatic cholesterol (P < 0.05). Plasma from DKO, ApoE KO and het mice had the same efflux capacity. In the absence of CYP27A1, CAV‐1 overexpression might have an additional athero‐protective role by partly overcoming the defect in CYP27A1‐mediated cholesterol efflux.

Caveolin-1 Expression Ameliorates Nephrotic Damage in a Rabbit Model of Cholesterol-Induced Hypercholesterolemia

Caveolin-1 (CAV-1) participates in regulating vesicular transport, signal transduction, tumor progression, and cholesterol homeostasis. In the present study, we tested the hypothesis that CAV-1 improves dyslipidemia, inhibits cyclophilin A (CypA)- mediated ROS production, prevents mitochondrial compensatory action and attenuates oxidative stress responses in cholesterol-induced hypercholesterolemia. To determine the role of CAV-1 in mediating oxidative and antioxidative as well as cholesterol homeostasis, hypercholesterolemic rabbits were intravenously administered antenapedia-CAV-1 (AP-CAV-1) peptide for 2 wk. AP-CAV-1 enhanced CAV-1 expression by ˃15%, inhibited CypA expression by ˃50% (P < 0.05) and significantly improved dyslipidemia, thus reducing neutral lipid peroxidation. Moreover, CAV-1 attenuated hypercholesterolemia-induced changes in mitochondrial morphology and biogenesis and preserved mitochondrial respiratory function. In addition, CAV-1 protected against hypercholesterol-induced oxidative stress responses by reducing the degree of oxidative damage and enhancing the expression of antioxidant enzymes. CAV-1 treatment significantly suppressed apoptotic cell death, as evidenced by the reduction in the number of terminal deoxynucleotidyl transferase dUTP nick end-labeling-positive cells. We concluded that CAV-1 plays a critical role in inhibiting CypA-mediated ROS production, improving dyslipidemia, maintaining mitochondrial function, and suppressing oxidative stress responses that are vital for cell survival in hypercholesterol-affected renal organs.

Leukemia Inhibitory Factor Protects Neurons from Ischemic Damage via Upregulation of Superoxide Dismutase 3

Leukemia inhibitory factor (LIF) has been shown to protect oligodendrocytes from ischemia by upregulating endogenous antioxidants. The goal of this study was to determine whether LIF protects neurons during stroke by upregulating superoxide dismutase 3 (SOD3). Animals were administered phosphate-buffered saline (PBS) or 125 μg/kg LIF at 6, 24, and 48 h after middle cerebral artery occlusion or sham surgery. Neurons were isolated from rat pups on embryonic day 18 and used between 7 and 15 days in culture. Cells were treated with LIF and/or 10 μM Akt inhibitor IV with PBS and 0.1 % DMSO acting as vehicle controls. Neurons transfected with scrambled or SOD3 small interfering RNA (siRNA) were subjected to 24-h ischemia after PBS or LIF treatment. LIF significantly increased superoxide dismutase activity and SOD3 expression in ipsilateral brain tissue compared to PBS. Following 24-h ischemia, LIF reduced cell death and increased SOD3 messenger RNA (mRNA) in vitro compared to PBS. Adding Akt inhibitor IV with LIF counteracted the decrease in cell death. Partially silencing the expression of SOD3 using siRNA prior to LIF treatment counteracted the protective effect of LIF-alone PBS treatment. These results indicate that LIF protects neurons in vivo and in vitro via upregulation of SOD3.

Exercise-Induced Changes in Caveolin-1, Depletion of Mitochondrial Cholesterol, and the Inhibition of Mitochondrial Swelling in Rat Skeletal Muscle but Not in the Liver

The reduction in cholesterol in mitochondria, observed after exercise, is related to the inhibition of mitochondrial swelling. Caveolin-1 (Cav-1) plays an essential role in the regulation of cellular cholesterol metabolism and is required by various signalling pathways. Therefore, the aim of this study was to investigate the effect of prolonged swimming on the mitochondrial Cav-1 concentration; additionally, we identified the results of these changes as they relate to the induction of changes in the mitochondrial swelling and cholesterol in rat skeletal muscle and liver. Male Wistar rats were divided into a sedentary control group and an exercise group. The exercised rats swam for 3 hours and were burdened with an additional 3% of their body weight. After the cessation of exercise, their quadriceps femoris muscles and livers were immediately removed for experimentation. The exercise protocol caused an increase in the Cav-1 concentration in crude muscle mitochondria; this was related to a reduction in the cholesterol level and an inhibition of mitochondrial swelling. There were no changes in rat livers, with the exception of increased markers of oxidative stress in mitochondria. These data indicate the possible role of Cav-1 in the adaptive change in the rat muscle mitochondria following exercise.

Identification of siRNA delivery enhancers by a chemical library screen

Most delivery systems for small interfering RNA therapeutics depend on endocytosis and release from endo-lysosomal compartments. One approach to improve delivery is to identify small molecules enhancing these steps. It is unclear to what extent such enhancers can be universally applied to different delivery systems and cell types. Here, we performed a compound library screen on two well-established siRNA delivery systems, lipid nanoparticles and cholesterol conjugated-siRNAs. We identified fifty-one enhancers improving gene silencing 2–5 fold. Strikingly, most enhancers displayed specificity for one delivery system only. By a combination of quantitative fluorescence and electron microscopy we found that the enhancers substantially differed in their mechanism of action, increasing either endocytic uptake or release of siRNAs from endosomes. Furthermore, they acted either on the delivery system itself or the cell, by modulating the endocytic system via distinct mechanisms. Interestingly, several compounds displayed activity on different cell types. As proof of principle, we showed that one compound enhanced siRNA delivery in primary endothelial cells in vitro and in the endocardium in the mouse heart. This study suggests that a pharmacological approach can improve the delivery of siRNAs in a system-specific fashion, by exploiting distinct mechanisms and acting upon multiple cell types.

β3-Adrenoceptor Impairs Mitochondrial Biogenesis and Energy Metabolism During Rapid Atrial Pacing-Induced Atrial Fibrillation

BACKGROUND

The β3-adrenoceptor (β3-AR) is implicated in cardiac remodeling. Since metabolic dysfunction due to loss of mitochondria plays an important role in heart diseases, we examined the effects of β3-AR on mitochondrial biogenesis and energy metabolism in atrial fibrillation (AF).

METHODS

Atrial fibrillation was created by rapid atrial pacing in adult rabbits. Rabbits were randomly divided into 4 groups: control, pacing (P7), β3-AR antagonist (L748337), and β3-AR agonist (BRL37344) groups. Atrial effective refractory period (AERP) and AF induction rate were measured. Atrial concentrations of adenine nucleotides and phosphocreatine were quantified through high-performance liquid chromatography. Mitochondrial DNA content was determined. Real-time polymerase chain reaction and Western blot were used to examine the expression levels of signaling intermediates related to mitochondrial biogenesis.

RESULTS

After pacing for 7 days, β3-AR was significantly upregulated, AERP was reduced, and the AF induction rate was increased. The total adenine nucleotides pool was significantly reduced due to the decrease in adenosine triphosphate (ATP). The P7 group showed decreased activity of F0F1-ATPase. Mitochondrial DNA content was decreased and mitochondrial respiratory chain subunits were downregulated after pacing. Furthermore, expression of transcription factors involved in mitochondrial biogenesis, including peroxisome proliferator-activated receptor γ coactivator 1α (PGC-1α), nuclear respiratory factor 1 (NRF-1), and mitochondrial transcription factor A (Tfam), was lower in the P7 group in response to β3-AR activation. Further stimulation of β3-AR with BRL37344 exacerbated these effects, together with a significant decrease in the levels of phosphocreatine. In contrast, inhibition of β3-AR with L748337 partially restored mitochondrial biogenesis and energy metabolism of atria in the paced rabbits.

CONCLUSION

The activation of β3-AR contributes to atrial metabolic remodeling via transcriptional downregulation of PGC-1α/NRF-1/Tfam pathway that are involved in mitochondrial biogenesis, which ultimately perturbs mitochondrial function in rapid pacing-induced AF. The β3-AR is therefore a potential novel therapeutic target for the treatment or prevention of AF.