Caveolin-1 Protein Expression Research Articles

Caveolin-1 is required for vascular endothelial insulin uptake

As insulin's movement from plasma to muscle interstitium is rate limiting for its metabolic action, defining the regulation of this movement is critical. Here, we address whether caveolin-1 is required for the first step of insulin's transendothelial transport, its uptake by vascular endothelial cells (ECs), and whether IL-6 and TNFα affect insulin uptake or caveolin-1 expression. Uptake of FITC-labeled insulin was measured using confocal microscopy in control bovine aortic ECs (bAECs), in bAECs in which caveolin-1 was either knocked down or overexpressed, in murine ECs from caveolin-1(-/-) mice and in bAECs exposed to inflammatory cytokines. Knockdown of caveolin-1 expression in bAECs using specific caveolin-1 siRNA reduced caveolin-1 mRNA and protein expression by ∼ 70%, and reduced FITC-insulin uptake by 67% (P < 0.05 for each). Over-expression of caveolin-1 increased insulin uptake (P < 0.05). Caveolin-1-null mouse aortic ECs did not take up insulin and re-expression of caveolin-1 by transfecting these cells with FLAG-tagged caveolin-1 DNA rescued FITC-insulin uptake. Knockdown of caveolin-1 significantly reduced both insulin receptor protein level and insulin-stimulated Akt1 phosphorylation. Knockdown of caveolin-1 also inhibited insulin-induced caveolin-1 and IGF-1 receptor translocation to the plasma membrane. Compared with controls, IL-6 or TNFα (20 ng/ml for 24 h) inhibited FITC-insulin uptake as well as the expression of caveolin-1 mRNA and protein (P < 0.05 for each). IL-6 or TNFα also significantly reduced plasma membrane-associated caveolin-1. Thus, we conclude that insulin uptake by ECs requires expression of caveolin-1 supporting a role for caveolae mediating insulin uptake. Proinflammatory cytokines may inhibit insulin uptake, at least in part, by inhibiting caveolin-1 expression.

Leptin upregulates caveolin-1 expression: Implications for development of atherosclerosis

Objective To determine the role of hyperleptinemia on caveolin-1 expression and leptin signaling. Methods Endothelial cells are critical to atherosclerosis development; therefore we investigated hyperleptinemia in cultured vascular endothelial cells. Dose-dependent effect of leptin on caveolin-1 expression was determined by Western blot analysis. Also, the consequence of increased caveolin-1 expression on leptin signaling was investigated by adenovirus mediated caveolin-1 overexpression. The effect of increased caveolin-1 expression on leptin-dependent activation of ERK1/2 and eNOS was determined by Western blot analysis. Results Leptin upregulates caveolin-1 protein expression in a dose dependent manner and increased caveolin-1 expression impairs leptin signaling. Conclusions Leptin increases caveolin-1 protein expression which impairs leptin signaling in vascular endothelial cells. Our study identifies an additional leptin mediated proatherogenic mechanism and a novel caveolin-1 dependent leptin feedback mechanism which may have implications for development of peripheral leptin resistance in the endothelium.

Up-regulation of caveolin-1 and blood–brain barrier breakdown are attenuated by N-acetylcysteine in thiamine deficiency

Wernicke's encephalopathy is a cerebral metabolic disorder caused by thiamine (vitamin B1) deficiency (TD). Neuropathologic consequences of TD include region-selective neuronal cell loss and blood–brain barrier (BBB) breakdown. Caveolin-1 is involved in the regulation of tight junction proteins and BBB permeability, and is modulated by oxidative stress, a feature of vulnerable brain regions in TD. We hypothesized that TD-related oxidative stress alters BBB integrity via induction of the caveolin-1 pathway. TD was induced in C57BL6 mice by treatment with a thiamine-deficient diet and administration of the thiamine antagonist pyrithiamine, in the absence or presence of the antioxidant N-acetylcysteine (NAC). A significant and focal increase in both caveolin-1 gene and protein expression was detected in the thalamus of thiamine-deficient mice, concomitant with IgG extravasation. Reduction of oxidative stress by NAC, as shown by normalization of reduced glutathione levels and attenuation of endothelial heme oxygenase-1 and nitric oxide synthase expression, resulted in prevention of the up-regulation of caveolin-1 in TD. Normalization of caveolin-1 levels by NAC was accompanied by a reduction in BBB breakdown, indicated by decreased IgG extravasation, normalization of occludin levels and prevention of matrix metalloproteinase-9 up-regulation. These findings demonstrate a role for caveolin-1 in TD pathogenesis, and suggest that oxidative stress contributes to BBB alterations in TD via modulation of this pathway.

Changes in caveolin-1 expression and vasoreactivity in the aorta and corpus cavernosum of fructose and streptozotocin-induced diabetic rats

Hyperglycemia is a common defining feature in the development of endothelial dysfunction which plays a key role in the pathogenesis of both type 1 and type 2 diabetes. Caveolin-1 is the main structural component of caveolae which might be involved in the pathophysiology of macrovascular complications of diabetes. In this study we aimed to observe the effect of caveolin-1 on functional responses of aorta and corpus cavernosum in the streptozotocin and fructose-induced diabetes groups. Type 1 diabetes was induced by intraperitoneal administration of streptozotocin (60 mg/kg),. Type 2 diabetes by adding fructose in the rat's drinking water (10% (w/v)) for 8 weeks. For insulin treatment; rats were treated with insulin (6 U/kg) for 8 weeks. In Type I and Type II diabetic groups the contractile responses of corpus cavernosum strips to phenylephrine (EC 50:1.82 × 10 − 5 M;1.47 × 10 − 5 M, respectively)and relaxation responses to acetylcholine (EC 50:7.5 × 10 − 5 M;4.48 × 10 − 5 M, respectively)were significantly impaired. Contractile responses of aorticstrips to phenylephrine in diabetic groups were markedly decreased (EC 50:3.7 · 10 − 7 M;2.61 · 10 − 7 M respectively) and dose-dependent relaxation responses to acetylcholine were also attenuated (EC 50:3.23 · 10 − 6 M; 2.0 · 10 − 6 M respectively). Treatment with insulin improved the functional responses in the aorta and corpus cavernosum. Protein expression of caveolin-1 was increased in the aorta and corpus cavernosum of the diabetic groups, but this increase seen in the streptozotocin group was more significant than the fructose group. Our findings indicate that an attenuation of the functional responses in both diabetes groups were probably associated with an enhanced expression of caveolin-1, and therefore a decrease in the eNOS activity with a concomitant decrease in NO synthesis.

Post-translational Regulation of Endothelial Nitric Oxide Synthase (eNOS) by Estrogens in the Rat Vagina

Estrogens control vaginal blood flow during female sexual arousal mostly through nitric oxide (NO). Although vascular effects of estrogens are attributed to an increase in endothelial NO production, the mechanisms of endothelial NO synthase (eNOS) regulation by estrogens in the vagina are largely unknown. Our hypothesis was that estrogens regulate eNOS post-translationally in the vagina, providing a mechanism to affect NO bioavailability without changes in eNOS protein expression. We measured eNOS phosphorylation and eNOS interaction with caveolin-1 and heat shock protein 90 (HSP90) in the distal and proximal vagina of female rats at diestrus, 7 days after ovariectomy and 2 days after replacement of ovariectomized rats with estradiol-17beta (15 microg). Molecular mechanisms of eNOS regulation by estrogen in the rat vagina. We localized phospho-eNOS (Ser-1177) immunohistochemically to the endothelium lining blood vessels and vaginal sinusoids. Estrogen withdrawal decreased phosphorylation of eNOS on its positive regulatory site (Ser-1177) and increased eNOS binding to its negative regulator caveolin-1 (without affecting eNOS/HSP90 interaction), and they were both normalized by estradiol replacement. Protein expressions of phosphorylated Akt (protein kinase B) and extracellular signal-regulated protein kinase 1/2 (ERK1/2) were not affected by estrogen status, suggesting that the effect of estrogens on eNOS (Ser-1177) phosphorylation was not mediated by activated AKT or ERK1/2. eNOS phosphorylation on its negative regulatory site (Ser-114) was increased in the vagina by estrogen withdrawal and normalized by estradiol replacement, implying that the maintenance of low phosphorylation of eNOS on this site by estradiol may limit eNOS interaction with caveolin-1 and preserve the enzyme's activity. Total eNOS, inducible NOS, caveolin-1, and HSP90 protein expressions were not affected by ovariectomy or estradiol replacement in the distal or proximal vagina. These results define novel estrogen signaling mechanisms in the vagina which involve eNOS phosphorylation and eNOS-caveolin-1 interaction.

RNA inference-mediated caveolin-1 down-regulation decrease estrogen receptor alpha (ERα) signaling in human mammary epithelial cells

Several evidences support that caveolin-1 is associated with mammary cell transformation and oncogenesis. We have previously reported that a cell line, named MCF10A-ST1 (ST1), which only expressed 30% Cav-1 compared with parental cells MCF10A (human mammary epithelial cell line) was isolated by gene trapping. The decreased expression of Cav-1 is sufficient for phenotypic transformation of MCF10A cells, which involved in the loss of anchorage-dependent growth and migration in nude mice with the existence of E2. The previous study in our lab on microarray assay showed that the expression of cyclin D1 (cell cycle protein) was up-regulated in ST1 cell line. Here, we not only confirmed the results by Western Blot but also demonstrated that Cav-1 down-regulation accelerate the progression of mammary cells from G1 phase into S phase by Flow Cytometry (FCM). This proposed that the Cav-1 down-regulation could change the progress of cell cycle in the mammary cells. Otherwise, microarray assay also showed that the transcription factor (c-Jun) was up-regulated. But, the original carcinoma gene (c-Fos) and transcription factor (AP-1) have not obviously changed compared with MCF10A. ST1 cells obtained the morigenicity in nude mice with the existence of E2, and the immunoprecipitation showed the interactions of Cav-1 with ERα in both MCF10A and ST1. ERα expression was increased as further down-regulation of Cav-1. So, we hypothesize that Cav-1 down-regulation could induce the activation of ERα-associated signaling pathway, in order to adjust the development and proliferation. By siRNA technology, the down regulation of Cav-1 could activate MAP kinase and Akt signaling pathway, including the phosphorylation of ERK1/2 and Akt. However, the mechanism of Cav-1 down-regulation in the early transformation and signaling transduction of mammary epithelial cells is unclear. Here, we report that down-regulation of caveolin-1 protein expression leads to deregulate estrogen receptor alpha (ERα) signaling and consequently early transformation in mammary epithelia.

Expression of caveolin-1 and extracellular matrix induced by transforming growth factor beta1 in human fetal lung fibroblasts

To investigate the expressions of caveolin-1, collagen-I and alpha-SMA in human fetal lung fibroblasts induced by transforming growth factor beta(1) (TGF-beta(1)). Human fetal lung fibroblasts (HFLF) were cultured in vitro, and exposed to TGF-beta(1) with different final concentrations (2, 5, 10 microg/L). Cells without TGF-beta(1) exposure served as the control. Caveolin-1 mRNA and protein, collagen-I and alpha-SMA proteins in cell (at least 5 x 10(8)) lysates, were detected at different points after the treatment of TGF-beta(1), by RT-PCR, Western blot and Immunohistochemistry. Each experiment was repeated 3 times. One-way analysis of variance (ANOVA) was used to compare data among groups, and linear regression was established for correlation analysis. TGF-beta(1) reduced caveolin-1 mRNA and protein expressions in a dose- and time-dependent manner, measured by integral optical density. Compared with the control group (1.22 +/- 0.12 and 1.45 +/- 0.06), caveolin-1 mRNA and protein expressions (0.59 +/- 0.06 and 0.53 +/- 0.04) were significantly reduced, with statistical significance (F = 29.279 and F = 95.786, P < 0.01), in cells exposed to TGF-beta(1) (5 microg/L) for 12 h. The collagen-I and alpha-SMA protein expressions (1.35 +/- 0.09 and 0.75 +/- 0.06) measured by integral optical density increased after stimulation, peaked at 24 h in 5 microg/L TGF-beta(1) group. At that time point, the collagen-I and alpha-SMA protein expressions were 4.2 and 4.8 times of the control group (0.28 +/- 0.04 and 0.18 +/- 0.04), F = 81.221 and F = 65.477, P < 0.01. Caveolin-1 expression had a negative correlation with collagen-I (r = -0.923, P < 0.05) and alpha-SMA protein expression (r = -0.793, P < 0.05). The reduced caveolin-1, which was negatively correlated with expressions of collagen-I and alpha-SMA proteins in HFLF cells exposed to TGF-beta(1), may be related to the development and progress of pulmonary fibrosis.

Diphtheria toxin mutant CRM197-mediated transcytosis across blood-brain barrier in vitro.

Blood-brain barrier (BBB) is specialized to limit brain drug delivery. Cross-reacting material 197 (CRM197), a non-toxic mutant of diphtheria toxin, could act as a diphtheria toxin receptor-specific carrier protein and deliver drugs across the BBB. CRM197 has previously been shown to inhibit phospatidyl-3-inositol-kinase (PI3K)/Akt signaling. Other studies have demonstrated a link between PI3K/Akt signaling and forkhead transcription factors in endothelial cells. We therefore investigated the effects and mechanisms underlying the potential of CRM197, not only as a carrier protein for targeted drug delivery to the brain, but also for inducing signaling to affect endocytosis in endothelial cells. The hCMEC/D3 cell line had been used to establish a BBB in vitro model; the transport efficiency of CRM197 was analyzed both by association and transcytosis experiments. CRM197 was shown to prefer apical-to-basal transcytosis, which involved the caveolae-mediated pathway. The uptake of CRM197 conjugates by endothelial cells reached equilibrium after 60 min of treatment. The caveolin-1 mRNA and protein expression levels were significantly increased by CRM197. The up-regulation of caveolin-1 may be mediated by CRM197 via a PI3K/Akt dependent pathway and reduction of the phospho-FOXO1A (forkhead box O) transcription factor. Our results indicate that carrier protein CRM197-mediated delivery across the BBB is involved in the induction of FOXO1A transcriptional activity and upregulation of caveolin-1 expression.

Role of caveolin and heat shock protein 70 interaction in the antioxidative effects of an angiotensin II type 1 receptor blocker in spontaneously hypertensive rats proximal tubules

Role of caveolin and heat shock protein 70 interaction in the antioxidative effects of an angiotensin II type 1 receptor blocker in spontaneously hypertensive rats proximal tubules

Abstract C84: Inhibition of cholesterol esterification by fenretinide in osteosarcoma in vitro

Abstract Osteosarcoma remains the most common primary malignant bone cancer affecting children and adolescents. Although the combination of systemic chemotherapy and surgery enables long-term survival in most cases, the poor prognosis of patients with metastatic or recurrent disease and the lack of establishment of second-line chemotherapy suggest that novel therapeutic strategies for this tumor are needed. Here we show that fenretinide, a synthetic derivative of all-trans-retinoic acid, is active against osteosarcoma in vitro, at concentrations identical or lower to those detectable in breast cancer patients plasma during chemopreventive clinical trials. Cell lines were HOS and MG63, known to be resistant to methotrexate and cyclophosphamide, drugs in use in osteosarcoma treatment. We demonstrate for the first time that fenretinide is active in this tumor and that the molecular basis of fenretinide activity is the inhibition of cholesterol esterification, with down-regulation of ACAT and MDR1 mRNA, followed by downregulation of caveolin-1 protein expression. This result is in line with our recent results obtained in VSMC and in leukemia cells. The confirmation and extention of these data to different human tumors will provide evidence of a novel mechanism of either cancer or human vascular proliferation disease control by the inhibition of cholesterol esterification. Grants from MIUR, Carisbo Foundation, Pallotti's Legacy for Cancer Research and University of Bologna. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):C84.

Upregulation of caveolin-1 expression is associated with structural modifications of endothelial cells in diabetic lung

Diabetes and the associated hyperglycemia affect pulmonary physiology and biochemistry inducing endothelial impairment, as the first step in lung vascular dysfunction. Caveolin-1, a characteristic protein of endothelial caveolae, acts as a scaffolding protein involved in signal transduction, cholesterol homeostasis, and vesicular trafficking. To document the effect of hyperglycemia on lung endothelial cells, we designed experiments on streptozotocin-induced diabetes and on double transgenic diabetic mice and investigated (1) the early morphological changes occurring in endothelial cells, (2) the ACE activity and cholesterol content of caveolae-rich membrane microdomains, and (3) the protein and gene expression of caveolin-1. We provide evidence that in diabetic lung, the endothelial cell displays an increased number of caveolae and enlarged surface area and a well-developed synthetic machinery, changes that correlate with an overall augmented ACE activity and cholesterol content and overexpression (gene and protein) of caveolin-1. Targeting the endothelial cell surface molecules modulated by hyperglycemia, such as caveolin-1 and ACE could be an additional therapeutic strategy in diabetes.

The relationship between expression of Caveolin-1 and epithelial-mesenchymal transition in hepatocellular carcinoma

Objective To study the relationship between the expression of Caveolin-1 and epithelial-mesenchymal transition (EMT) in hepatoeellular carcinoma (HCC).Methods The protein and mRNA expression of Caveolin-1 and markers of EMT in human HCC cell lines and tissue specimens of HCC was detected by using immunohistochemistry, Western blot, and real time PCR.Results In HepG2 and SMMC7721, Caveolin-1 mRNA (0.03 ± 0.01 and 26.63 ± 0.49) and protein (0.00 ± 0.00 and 1.56 ± 0.17) expression was negatively correlated with E-cadherin,but positively with N-cadherin and Vimentin.In tissue specimens of HCC,the Caveolin-1 expression in tumor tissues was significantly lower than that in adjacent tumor tissues,and correlate negatively with ZO-1 and E-eadberin, but positively with N-cadherin.Conclusion Overexpression of Caveolin-1 is correlated with metastasis and EMT in HCC. Key words: Carcinoma, hepatocellular; Caveolin-1 ; Metastasis

Quercetin blocks caveolae-dependent pro-inflammatory responses induced by co-planar PCBs

Polychlorinated biphenyls (PCBs) are widespread environmental contaminants, and co-planar PCBs can induce oxidative stress and activation of pro-inflammatory signaling cascades which are associated with atherosclerosis. The majority of the toxicological effects elicited by the co-planar PCB exposure are associated to the activation of the aryl hydrocarbon receptor (AHR) and subsequent induction of responsive genes. Previous studies from our group have shown that quercetin, a nutritionally relevant flavonoid can significantly reduce PCB77 induction of oxidative stress and expression of the AHR responsive gene cytochrome P450 1A1 (CYP1A1). We also have evidence that membrane domains called caveolae may regulate PCB-induced inflammatory parameters. Thus, we hypothesized that quercetin can modulate PCB-induced endothelial inflammation associated with caveolae. To test this hypothesis, endothelial cells were exposed to co-planar PCBs in combination with quercetin, and the expression of pro-inflammatory genes was analyzed by real-time PCR. Quercetin co-treatment significantly blocked both PCB77 and PCB126 induction of CYP1A1, vascular cell adhesion molecule 1 (VCAM-1), E-selectin and P-selectin. Exposure to PCB77 also induced caveolin-1 protein expression, which was reduced by co-treatment with quercetin. Our results suggest that inflammatory pathways induced by co-planar PCBs can be down-regulated by the dietary flavonoid quercetin through mechanisms associated with functional caveolae.

OxLDL upregulates caveolin‐1 expression in macrophages: Role for caveolin‐1 in the adhesion of oxLDL‐treated macrophages to endothelium

Caveolin-1, a principle component of caveolae, is present in several cell types known to play an important role in the development of atherosclerosis. In this study, its distribution and expression were studied in the arterial walls of hypercholesterolemic rabbits and apo-E-deficient mice and in oxidized low-density lipoprotein (oxLDL)-treated RAW264.7 macrophages. Immunohistochemical studies showed that staining for caveolin-1 expression was stronger in atherosclerotic lesions in hypercholesterolemic rabbits and apo-E-deficient mice compared to normal rabbits and mice and was closely associated with macrophages. OxLDL treatment increased caveolin-1 protein expression in RAW264.7 macrophages in a time- and dose-dependent manner. The increase in caveolin-1 expression was dependent on phosphorylation of the mitogen-activated protein kinases (MAPKs) extracellular signal-regulated kinase1/2 (ERK1/2), p38, and Jun N-terminal kinase (JNK) and the transcriptional activation and translocation of nuclear factor-?B (NF-kappaB). OxLDL also induced caveolin-1 mRNA expression and this effect was not seen in the presence of inhibitors for transcription or de novo protein synthesis. OxLDL increased the adhesion of RAW264.7 macrophages to endothelial cells via an increase in caveolin-1 expression, and the adhesion was reduced by the use of anti-caveolin-1 antibody or caveolin-1-specific shRNA. These results show that oxLDL increases caveolin-1 expression in macrophages through the MAPKs/NF-kappaB pathway. The caveolin-1 levels are closely associated with the adherence of monocytes/macrophages to endothelial cells and their accumulation within the arterial intima after hypercholesterolemia insult, resulting in the progression of atherosclerosis.

Caveolin-1 −/− Null Mammary Stromal Fibroblasts Share Characteristics with Human Breast Cancer-Associated Fibroblasts

Recently, we reported that human breast cancer-associated fibroblasts show functional inactivation of the retinoblastoma (RB) tumor suppressor and down-regulation of caveolin-1 (Cav-1) protein expression. However, it remains unknown whether loss of Cav-1 is sufficient to confer functional RB inactivation in mammary fibroblasts. To establish a direct cause-and-effect relationship, mammary stromal fibroblasts (MSFs) were prepared from Cav-1(-/-) null mice and subjected to phenotypic analysis. Here, we provide evidence that Cav-1(-/-) MSFs share many characteristics with human cancer-associated fibroblasts. The Cav-1(-/-) MSF transcriptome significantly overlaps with human cancer-associated fibroblasts; both show a nearly identical profile of RB/E2F-regulated genes that are up-regulated, which is consistent with RB inactivation. This Cav-1(-/-) MSF gene signature is predictive of poor clinical outcome in breast cancer patients treated with tamoxifen. Consistent with these findings, Cav-1(-/-) MSFs show RB hyperphosphorylation and the up-regulation of estrogen receptor co-activator genes. We also evaluated the paracrine effects of "conditioned media" prepared from Cav-1(-/-) MSFs on wild-type mammary epithelia. Our results indicate that Cav-1(-/-) MSF "conditioned media" is sufficient to induce an epithelial-mesenchymal transition, indicative of an invasive phenotype. Proteomic analysis of this "conditioned media" reveals increased levels of proliferative/angiogenic growth factors. Consistent with these findings, Cav-1(-/-) MSFs are able to undergo endothelial-like transdifferentiation. Thus, these results have important implications for understanding the role of cancer-associated fibroblasts and RB inactivation in promoting tumor angiogenesis.

Polyphenol-containing azuki bean ( Vigna angularis) extract attenuates blood pressure elevation and modulates nitric oxide synthase and caveolin-1 expressions in rats with hypertension

Background and aims Azuki beans ( Vigna angularis) contain polyphenols such as proanthocyanidins that exhibit potential radical scavenging activities. We herein investigated the effects of polyphenol-containing azuki bean extract (ABE) on elevated blood pressure, nitric oxide (NO) production, and expressions of endothelial NO synthase (eNOS), inducible NOS (iNOS), and caveolin-1 proteins in the aorta and kidney of chronically hypertensive rats. Methods and results Spontaneously hypertensive rats (SHRs/Izm) with approximately 200 mm Hg systolic blood pressure (SBP) were randomly divided into 2 groups fed either 0% or 0.9% ABE-containing diet. Age-matched normotensive Wistar–Kyoto rats were used as the control. The content of 24-h urinary nitrate/nitrite (NOx) excretion was measured to evaluate NO production. After 8 weeks of treatment, the eNOS, iNOS, and caveolin-1 protein expressions in the aorta and kidney were analyzed by western blotting. The SBP of the ABE-treated SHR was significantly lower than that of the untreated SHR. The level of 24-h urinary NOx excretion was significantly higher in the ABE-treated SHR than in the untreated SHR. The eNOS and iNOS expressions in the aorta and kidney were remarkably upregulated in the untreated SHR but suppressed in the ABE-treated SHR. The vascular and renal caveolin-1 expressions were upregulated in the ABE-treated SHR. Conclusions ABE reduced the elevated blood pressure and increased NO production in long-term treatment. It may be associated with the modulation of eNOS and iNOS protein expressions in the aorta and kidney during the development of hypertension.

Long-term effects of prenatal hypoxia on endothelium-dependent relaxation responses in pulmonary arteries of adult sheep

Chronic hypoxia during the course of pregnancy is a common insult to the fetus. However, its long-term effect on the pulmonary vasculature in adulthood has not been described. In this study, the vasorelaxation responses of conduit pulmonary arteries in adult female sheep that were chronically hypoxic as fetuses and raised postnatally at sea level were investigated. Vessel tension studies revealed that endothelium-dependent relaxation responses were attenuated in pulmonary arteries from adult sheep that experienced prenatal hypoxia. Endothelial nitric oxide synthase (eNOS) protein expression was unchanged, but eNOS activity was significantly decreased in pulmonary arteries from prenatally hypoxic sheep. Protein expression of eNOS partners, caveolin-1, calmodulin, and heat shock protein 90 (Hsp90) did not change following prenatal hypoxia. However, the association between eNOS and caveolin-1, its inhibitory binding partner, was significantly increased, whereas association between eNOS and its stimulatory partners calmodulin and Hsp90 was greatly decreased. Furthermore, phosphorylation of Ser(1177) in eNOS decreased, whereas phosphorylation of Thr(495) increased, in the prenatally hypoxic pulmonary arteries, events that are related to eNOS activity. These data demonstrate that prenatal hypoxia results in persistent abnormalities in endothelium-dependent relaxation responses of pulmonary arteries in adult sheep due to decreased eNOS activity resulting from altered posttranslational regulation.

Heat shock protein 90-eNOS interactions mature with postnatal age in the pulmonary circulation of the piglet

Binding of endothelial nitric oxide synthase (eNOS) to the chaperone protein, Hsp90, promotes coupled eNOS synthetic activity. Using resistance level pulmonary arteries (PRA) from 2-day-, 5- to 7-day-, and 12-day-old piglets, we tested the hypothesis that Hsp90-eNOS interactions are developmentally regulated in the early neonatal period. PRA were isolated for coimmunoprecipitation and immunoblot analyses or cannulated for continuous diameter measurements using the pressurized myography technique. NOS inhibition caused less constriction in PRA from 2-day- compared with 5- to 7-day- and 12-day-old piglets. No age-related differences were found in dilation responses to an NO donor or in protein expression of Hsp90, phospho-eNOS (Ser(1177)), Akt, phospho-Akt, or caveolin-1. Compared with the older animals, PRA from 2-day-old piglets had higher total eNOS expression but displayed less binding of eNOS to Hsp90 and Akt. Hsp90 antagonism with radicicol induced greatest constriction in PRA from 12-day-old piglets. ACh stimulation caused dilation in PRA from 5- to 7-day- and 12-day-old but not 2-day-old animals, despite rapid and equivalent ACh-mediated eNOS phosphorylation (Ser(1177)) in all three age groups. Hsp90 inhibition abolished ACh-mediated dilation in PRA from the older piglets. ACh failed to stimulate Hsp90-eNOS binding in 2-day-old but induced a significant increase in Hsp90-eNOS coimmunoprecipitation in PRA from the older age groups, which was blocked by Hsp90 antagonism. We conclude that physical interactions between Hsp90 and eNOS mature over the first weeks of life, likely contributing to the postnatal fall in pulmonary vascular resistance and changes in agonist-induced pulmonary vascular responses characteristic of the early neonatal period.

Caveolin-1 as a Prognostic Marker for Local Control After Preoperative Chemoradiation Therapy in Rectal Cancer

Caveolin-1 is a protein marker for caveolae organelles and has an essential impact on cellular signal transduction pathways (e.g., receptor tyrosine kinases, adhesion molecules, and G-protein-coupled receptors). In the present study, we investigated the expression of caveolin-1 in patients with rectal adenocarcinoma and correlated its expression pattern with the risk for disease recurrences after preoperative chemoradiation therapy (CRT) and surgical resection. Caveolin-1 mRNA and protein expression were evaluated by Affymetrix microarray analysis (n = 20) and immunohistochemistry (n = 44) on pretreatment biopsy samples of patients with locally advanced adenocarcinoma of the rectum, and were correlated with clinical and histopathologic characteristics as well as with 5-year rates of local failure and overall survival. A significantly decreased median caveolin-1 intracellular mRNA level was observed in tumor biopsy samples as compared with noncancerous mucosa. Individual mRNA levels and immunohistologic staining, however, revealed an overexpression in 7 of 20 patients (35%) and 17 of 44 patients (38.6%), respectively. Based on immunohistochemical evaluation, local control rates at 5 years for patients with tumors showing low caveolin-1 expression were significantly better than for patients with high caveolin-1-expressing carcinoma cells (p = 0.05; 92%, 95% confidence interval [95% CI] = 82-102% vs. 72%, 95% CI = 49-84%). A low caveolin-1 protein expression was also significantly related to an increased overall survival rate (p = 0.05; 45%, 95% CI 16-60% vs. 82%, 95% CI = 67-97%). Caveolin-1 may provide a novel prognostic marker for local control and survival after preoperative CRT and surgical resection in rectal cancer.

Clinical significance and association of caveolin-1 and Dnmt1 gene with carcinogenesis, development of gastric carcinomas

AIM: To investigate the expression of caveolin-1and Dnmt1 genes in normal gastric mucosa and gastric carcinoma, and to detect methylation status of CpG is land of caveol in-1 gene promoter region located in exon 1 and its clinical significance in gastric carcinoma. METHODS: Methylation status of caveolin-1 gene in 60 gastric carcinoma cases and 14 normal gastric tissues was detected using Methylation-specific PCR (MSP). SP immunohistochemcal method and in site hybridization (ISH) were used to detect the expression of caveolin-1 protein and Dnmt1 protein and mRNA. RESULTS: The methylation rate of the 5' CpG island of caveolin-1 gene was 0% in 14 normal gastric tissues, and 73.3% in 60 gastric carcinoma cases. There was significant difference between two groups (P＜0.005). Methylation status of caveolin-1 gene was related to the patient's age. The positive rates of caveolin-1 protein, Dnmt1 protein and mRNA were 30%, 63.3% and 53.3% in 60 gastric carcinoma cases. CONCLUSION: The methylation and inactivation of caveolin-1 gene leads to carcinogenesis and development of gastric carcinomas by the function of Dnmt1 gene.