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Funder: Lund University, Differentiation of smooth muscle cells (SMCs) depends on serum response factor (SRF) and its co-activator myocardin (MYOCD). The role of MYOCD for the SMC program of gene transcription is well established. In contrast, the role of MYOCD in control of SMC-specific alternative exon usage, including exon splicing, has not been explored. In the current work we identified four splicing factors (MBNL1, RBPMS, RBPMS2, and RBFOX2) that correlate with MYOCD across human SMC tissues. Forced expression of MYOCD family members in human coronary artery SMCs in vitro upregulated expression of these splicing factors. For global profiling of transcript diversity, we performed RNA-sequencing after MYOCD transduction. We analyzed alternative transcripts with three different methods. Exon-based analysis identified 1637 features with differential exon usage. For example, usage of 3´ exons in MYLK that encode telokin increased relative to 5´ exons, as did the 17 kDa telokin to 130 kDa MYLK protein ratio. Dedicated event-based analysis identified 239 MYOCD-driven splicing events. Events involving MBNL1, MCAM, and ACTN1 were among the most prominent, and this was confirmed using variant-specific PCR analyses. In support of a role for RBPMS and RBFOX2 in MYOCD-driven splicing we found enrichment of their binding motifs around differentially spliced exons. Moreover, knockdown of either RBPMS or RBFOX2 antagonized splicing events stimulated by MYOCD, including those involving ACTN1, VCL, and MBNL1. Supporting an in vivo role of MYOCD-SRF-driven splicing, we demonstrate altered Rbpms expression and splicing in inducible and SMC-specific Srf knockout mice. We conclude that MYOCD-SRF, in part via RBPMS and RBFOX2, induce a program of differential exon usage and alternative splicing as part of the broader program of SMC differentiation.

Background & Aims YAP (Yap1) and TAZ (Wwtr1) are transcriptional co-activators and downstream effectors of the Hippo pathway, which play crucial roles in organ size control and cancer pathogenesis. Genetic deletion of YAP/TAZ has shown their critical importance for embryonic development of the heart, vasculature, and gastrointestinal mesenchyme. The aim of this study was to determine the functional role of YAP/TAZ in adult smooth muscle cells in vivo. Methods Because YAP and TAZ are mutually redundant, we used YAP/TAZ double-floxed mice crossed with mice that express tamoxifen-inducible CreERT2 recombinase driven by the smooth muscle–specific myosin heavy chain promoter. Results Double-knockout of YAP/TAZ in adult smooth muscle causes lethality within 2 weeks, mainly owing to colonic pseudo-obstruction, characterized by severe distension and fecal impaction. RNA sequencing in colon and urinary bladder showed that smooth muscle markers and muscarinic receptors were down-regulated in the YAP/TAZ knockout. The same transcripts also correlated with YAP/TAZ in the human colon. Myograph experiments showed reduced contractility to depolarization by potassium chloride and a nearly abolished muscarinic contraction and spontaneous activity in colon rings of YAP/TAZ knockout. Conclusions YAP and TAZ in smooth muscle are guardians of colonic contractility and control expression of contractile proteins and muscarinic receptors. The knockout model has features of human chronic intestinal pseudo-obstruction and may be useful for studying this disease., Graphical abstract

Hypertension remains a major risk factor for cardiovascular diseases, but the underlying mechanisms are not well understood. We hypothesize that appropriate mechanotransduction and contractile function in vascular smooth muscle cells are crucial to maintain vascular wall integrity. The Hippo pathway effectors YAP (yes-associated protein 1) and TAZ (WW domain containing transcription regulator 1) have been identified as mechanosensitive transcriptional coactivators. However, their role in vascular smooth muscle cell mechanotransduction has not been investigated in vivo.We performed physiological and molecular analyses utilizing an inducible smooth muscle-specific YAP/TAZ knockout mouse model.Arteries lacking YAP/TAZ have reduced agonist-mediated contraction, decreased myogenic response, and attenuated stretch-induced transcriptional regulation of smooth muscle markers. Moreover, in established hypertension, YAP/TAZ knockout results in severe vascular lesions in small mesenteric arteries characterized by neointimal hyperplasia, elastin degradation, and adventitial thickening.This study demonstrates a protective role of YAP/TAZ against hypertensive vasculopathy.

Myocardin related transcription factors (MRTFs: MYOCD/myocardin, MRTF-A, and MRTF-B) play a key role in smooth muscle cell differentiation by activating contractile genes. In atherosclerosis, MRTF levels change, and most notable is a fall of MYOCD. Previous work described anti-inflammatory properties of MRTF-A and MYOCD, occurring through RelA binding, suggesting that MYOCD reduction could contribute to vascular inflammation. Recent studies have muddled this picture showing that MRTFs may show both anti- and pro-inflammatory properties, but the basis of these discrepancies remain unclear. Moreover, the impact of MRTFs on inflammatory signaling pathways in tissues relevant to human arterial disease is uncertain. The current work aimed to address these issues. RNA-sequencing after forced expression of myocardin in human coronary artery smooth muscle cells (hCASMCs) showed reduction of pro-inflammatory transcripts, including CCL2, CXCL8, IL6, and IL1B. Side-by-side comparison of MYOCD, MRTF-A, and MRTF-B in hCASMCs, showed that the anti-inflammatory impact was shared among MRTFs. Correlation analyses using human arterial transcriptomic datasets revealed negative correlations between MYOCD, MRTFA, and SRF, on the one hand, and the inflammatory transcripts, on the other. A pro-inflammatory drive from lipopolysaccharide, did not change the size of the suppressive effect of MRTF-A in hCASMCs on either mRNA or protein levels. To examine cell type-dependence, we compared the anti-inflammatory impact in hCASMCs, with that in human bladder SMCs, in endothelial cells, and in monocytes (THP-1 cells). Surprisingly, little anti-inflammatory activity was seen in endothelial cells and monocytes, and in bladder SMCs, MRTF-A was pro-inflammatory. CXCL8, IL6, and IL1B were increased by the MRTF-SRF inhibitor CCG-1423 and by MRTF-A silencing in hCASMCs, but depolymerization of actin, known to inhibit MRTF activity, had no stimulatory effect, an exception being IL1B. Co-immunoprecipitation supported binding of MRTF-A to RelA, supporting sequestration of this important pro-inflammatory mediator as a mechanism. Dexamethasone treatment and silencing of RelA (by 76 ± 1%) however only eliminated a fraction of the MRTF-A effect (≈25%), suggesting mechanisms beyond RelA binding. Indeed, SRF silencing suggested that MRTF-A suppression of IL1B and CXCL8 depends on SRF. This work thus supports an anti-inflammatory impact of MRTF-SRF signaling in hCASMCs and in intact human arteries, but not in several other cell types.

The endothelin type B receptor (ETB or EDNRB) is highly plastic and is upregulated in smooth muscle cells (SMCs) by arterial injury and following organ culture in vitro. We hypothesized that this transcriptional plasticity may arise, in part, because EDNRB is controlled by a balance of transcriptional inputs from myocardin-related transcription factors (MRTFs) and ternary complex factors (TCFs). We found significant positive correlations between the TCFs ELK3 and FLI1 versus EDNRB in human arteries. The MRTF MKL2 also correlated with EDNRB. Overexpression of ELK3, FLI1, and MKL2 in human coronary artery SMCs promoted expression of EDNRB, and the effect of MKL2 was antagonized by myocardin (MYOCD), which also correlated negatively with EDNRB at the tissue level. Silencing of MKL2 reduced basal EDNRB expression, but depolymerization of actin using latrunculin B (LatB) or overexpression of constitutively active cofilin, as well as treatment with the Rho-associated kinase (ROCK) inhibitor Y27632, increased EDNRB in a MEK/ERK-dependent fashion. Transcript-specific primers indicated that the second EDNRB transcript (EDNRB_2) was targeted, but this promoter was largely unresponsive to LatB and was inhibited rather than stimulated by MKL2 and FLI1, suggesting distant control elements or an indirect effect. LatB also reduced expression of endothelin-1, but supplementation experiments argued that this was not the cause of EDNRB induction. EDNRB finally changed in parallel with ELK3 and FLI1 in rat and human carotid artery lesions. These studies implicate the actin cytoskeleton and ELK3, FLI1, and MKL2 in the transcriptional control of EDNRB and increase our understanding of the plasticity of this receptor.

Nexilin, encoded by the NEXN gene, is expressed in striated muscle and localizes to Z-discs, influencing mechanical stability. We examined Nexilin/NEXN in smooth muscle cells (SMCs), and addressed if Nexilin localizes to dense bodies and dense bands and whether it is regulated by actin-controlled coactivators from the MRTF (MYOCD, MKL1, MKL2) and YAP/TAZ (YAP1 and WWTR1) families. NEXN expression in SMCs was comparable to that in striated muscles. Immunofluorescence and immunoelectron microscopy suggested that Nexilin localizes to dense bodies and dense bands. Correlations at the mRNA level suggested that NEXN expression might be controlled by actin polymerization. Depolymerization of actin using Latrunculin B repressed the NEXN mRNA and protein in bladder and coronary artery SMCs. Overexpression and knockdown supported involvement of both YAP/TAZ and MRTFs in the transcriptional control of NEXN. YAP/TAZ and MRTFs appeared equally important in bladder SMCs, whereas MRTFs dominated in vascular SMCs. Expression of NEXN was moreover reduced in situations of SMC phenotypic modulation in vivo. The proximal promoter of NEXN conferred control by MRTF-A/MKL1 and MYOCD. NEXN silencing reduced actin polymerization and cell migration, as well as SMC marker expression. NEXN targeting by actin-controlled coactivators thus amplifies SMC differentiation through the actin cytoskeleton, probably via dense bodies and dense bands.

Cavins belong to a family of proteins that contribute to the formation of caveolae, which are membrane organelles with functional roles in muscle and fat. Here, we investigate the effect of cavin-3 ablation on vascular and urinary bladder structure and function. Arteries and urinary bladders from mice lacking cavin-3 (knockout: KO) and from controls (wild type: WT) were examined. Our studies revealed that the loss of cavin-3 resulted in ∼40% reduction of the caveolae protein cavin-1 in vascular and bladder smooth muscle. Electron microscopy demonstrated that the loss of cavin-3 was accompanied by a reduction of caveolae abundance by 40-45% in smooth muscle, whereas the density of caveolae in endothelial cells was unchanged. Vascular contraction in response to an α1-adrenergic agonist was normal but nitric-oxide-dependent relaxation was enhanced, in parallel with an increased relaxation on direct activation of soluble guanylyl cyclase (sGC). This was associated with an elevated expression of sGC, although blood pressure was similar in WT and KO mice. Contraction of the urinary bladder was not affected by the loss of cavin-3. The proteomic response to outlet obstruction, including STAT3 phosphorylation, the induction of synthetic markers and the repression of contractile markers were identical in WT and KO mice, the only exception being a curtailed induction of the Golgi protein GM130. Loss of cavin-3 thus reduces the number of caveolae in smooth muscle and partly destabilizes cavin-1 but the functional consequences are modest and include an elevated vascular sensitivity to nitric oxide and slightly disturbed Golgi homeostasis in situations of severe cellular stress.

INTRODUCTION AND OBJECTIVE:Nexilin, encoded by the NEXN gene, is expressed in striated muscle where it localizes to Z-discs. Dense bodies and dense bands in smooth muscle cells (SMCs) are functiona...

Myocardin (MYOCD) is a critical regulator of smooth muscle cell (SMC) differentiation, but its transcriptional targets remain to be exhaustively characterized, especially at the protein level. Here we leveraged human RNA and protein expression data to identify novel potential MYOCD targets. Using correlation analyses we found several targets that we could confirm at the protein level, including SORBS1, SLMAP, SYNM, and MCAM. We focused on SYNM, which encodes the intermediate filament protein synemin. SYNM rivalled smooth muscle myosin ( MYH11) for SMC specificity and was controlled at the mRNA and protein levels by all myocardin-related transcription factors (MRTFs: MYOCD, MRTF-A/MKL1, and MRTF-B/MKL2). MRTF activity is regulated by the ratio of filamentous to globular actin, and SYNM was accordingly reduced by interventions that depolymerize actin, such as latrunculin treatment and overexpression of constitutively active cofilin. Many MRTF target genes depend on serum response factor (SRF), but SYNM lacked SRF-binding motifs in its proximal promoter, which was not directly regulated by MYOCD. Furthermore, SYNM resisted SRF silencing, yet the time course of induction closely paralleled that of the SRF-dependent target gene ACTA2. SYNM was repressed by the ternary complex factor (TCF) FLI1 and was increased in mouse embryonic fibroblasts lacking three classical TCFs (ELK1, ELK3, and ELK4). Imaging showed colocalization of SYNM with the intermediate filament proteins desmin and vimentin, and MRTF-A/MKL1 increased SYNM-containing intermediate filaments in SMCs. These studies identify SYNM as a novel SRF-independent target of myocardin that is abundantly expressed in all SMCs.

Objective Smooth muscle cells contribute significantly to lipid-laden foam cells in atherosclerotic plaques. However, the underlying mechanisms transforming smooth muscle cells into foam cells are poorly understood. The purpose of this study was to gain insight into the molecular mechanisms regulating smooth muscle foam cell formation. Approach and results Using human coronary artery smooth muscle cells we found that the transcriptional co-activator MRTFA promotes lipid accumulation via several mechanisms, including direct transcriptional control of LDL receptor, enhanced fluid-phase pinocytosis and reduced lipid efflux. Inhibition of MRTF activity with CCG1423 and CCG203971 significantly reduced lipid accumulation. Furthermore, we demonstrate enhanced MRTFA expression in vascular remodeling of human vessels. Conclusions This study demonstrates a novel role for MRTFA as an important regulator of lipid homeostasis in vascular smooth muscle cells. Thus, MRTFA could potentially be a new therapeutic target for inhibition of vascular lipid accumulation.

Background: Serotonin (5-HT) is considered to play a role in pulmonary arterial hypertension by regulating vascular remodeling and smooth muscle contractility. Here, arteries from mice with inducible and smooth muscle-specific deletion of Dicer were used to address mechanisms by which microRNAs control 5-HT-induced contraction. Methods: Mice were used 5 weeks after Dicer deletion, and pulmonary artery contractility was analyzed by wire myography. Results: No change was seen in right ventricular systolic pressure following dicer deletion, but systemic blood pressure was reduced. Enhanced 5-HT-induced contraction in Dicer KO pulmonary arteries was associated with increased 5-HT2A receptor mRNA expression whereas 5-HT1B and 5-HT2B receptor mRNAs were unchanged. Contraction by the 5-HT2A agonist TCB-2 was increased in Dicer KO as was the response to the 5-HT2B agonist BW723C86. Effects of Src and protein kinase C inhibition were similar in control and KO arteries, but the effect of inhibition of Rho kinase was reduced. We identified miR-30c as a potential candidate for 5-HT2A receptor regulation as it repressed 5-HT2A mRNA and protein. Conclusion: Our findings show that 5-HT receptor signaling in the arterial wall is subject to regulation by microRNAs and that this entails altered 5-HT2A receptor expression and signaling.

Members of the myocardin family bind to the transcription factor serum response factor (SRF) and act as coactivators controlling genes of relevance for myogenic differentiation and motile function. Binding of SRF to DNA is mediated by genetic elements called CArG boxes, found often but not exclusively in muscle and growth controlling genes. Studies aimed at defining the full spectrum of these CArG elements in the genome (i.e. the CArGome) have in recent years, unveiled unexpected roles of the myocardin family proteins in lipid and glucose homeostasis. This coactivator family includes the protein myocardin (MYOCD), the myocardin-related transcription factors A and B (MRTF-A/MKL1 and MRTF-B/MKL2) and MASTR (MAMSTR). Here we discuss growing evidence that SRF-driven transcription is controlled by extracellular glucose through activation of the Rho-kinase pathway and actin polymerization. We also describe data showing that adipogenesis is influenced by MLK activity through actions upstream of peroxisome proliferator-activated receptor γ with consequences for whole body fat mass and insulin sensitivity. The recently demonstrated involvement of myocardin coactivators in the biogenesis of caveolae, Ω-shaped membrane invaginations of importance for lipid and glucose metabolism, is finally discussed. These novel roles of myocardin proteins may open the way for new unexplored strategies to combat metabolic diseases such as diabetes, which, at the current incidence, is expected to reach 333 million people worldwide by 2025. This review highlights newly discovered roles of myocardin-related transcription factors in lipid and glucose metabolism as well as novel insights into their well-established role as mediators of stretch-dependent effects in smooth muscle. As co-factors for serum response factor (SRF), MKLs regulates transcription of genes involved in the contractile function of smooth muscle cells. In addition to mechanical stimuli, this regulation has now been found to be promoted by extracellular glucose levels in smooth muscle. Recent reports also suggest that MKLs can regulate a subset of genes involved in the formation of lipid-rich invaginations in the cell membrane called caveolae. Finally, a potential role of MKLs in non-muscle cells has been discovered as they negatively influence adipocyte differentiation.

Thrombospondin-4 (TSP-4) is a multidomain calcium-binding protein that has both intracellular and extracellular functions. As an extracellular matrix protein, it is involved in remodeling processes. Previous work showed that, in the cardiovascular system, TSP-4 expression is induced in the heart in response to experimental pressure overload and infarction injury. Intracellularly, it mediates the endoplasmic reticulum stress response in the heart. In this study, we explored the role of TSP-4 in hypertension. For this purpose, wild-type and TSP-4 knockout ( Thbs4 −/−) mice were treated with angiotensin II (ANG II). Hearts from ANG II-treated Thbs4 −/− mice showed an exaggerated hypertrophic response. Interestingly, aortas from Thbs4 −/− mice treated with ANG II showed a high incidence of aneurysms. In resistance arteries, ANG II-treated wild-type mice showed impaired endothelial-dependent relaxation. This was not observed in ANG II-treated Thbs4 −/− mice or in untreated controls. No differences were found in the passive pressure-diameter curves or stress-strain relationships, although ANG II-treated Thbs4 −/− mice showed a tendency to be less stiff, associated with thicker diameters of the collagen fibers as revealed by electron microscopy. We conclude that TSP-4 plays a role in hypertension, affecting cardiac hypertrophy, aortic aneurysm formation, as well as endothelial-dependent relaxation in resistance arteries.

ApoA-I, the main protein component of HDL, is suggested to be involved in metabolic homeostasis. We examined the effects of Milano, a naturally occurring ApoA-I variant, about which little mechanistic information is available. Remarkably, high-fat-fed mice treated with Milano displayed a rapid weight loss greater than ApoA-I WT treated mice, and a significantly reduced adipose tissue mass, without an inflammatory response. Further, lipolysis in adipose cells isolated from mice treated with either WT or Milano was increased. In primary rat adipose cells, Milano stimulated cholesterol efflux and increased glycerol release, independently of β-adrenergic stimulation and phosphorylation of hormone sensitive lipase (Ser563) and perilipin (Ser522). Stimulation with Milano had a significantly greater effect on glycerol release compared with WT but similar effect on cholesterol efflux. Pharmacological inhibition or siRNA silencing of ABCA1 did not diminish Milano-stimulated lipolysis, although binding to the cell surface was decreased, as analyzed by fluorescence microscopy. Interestingly, methyl-β-cyclodextrin, a well-described cholesterol acceptor, dose-dependently stimulated lipolysis. Together, these results suggest that decreased fat mass and increased lipolysis following Milano treatment in vivo is partly explained by a novel mechanism at the adipose cell level comprising stimulation of lipolysis independently of the canonical cAMP/protein kinase A signaling pathway.. J. Lipid Res. 2015. 56: 2248–2259.

Increased vascular smooth muscle cell (VSMC) proliferation is a factor in atherosclerosis and injury-induced arterial (re) stenosis. Inhibition of polyamine synthesis by α-difluoro-methylornithine (DFMO), an irreversible inhibitor of ornithine decarboxylase, attenuates VSMC proliferation with high sensitivity and specificity. However, cells can escape polyamine synthesis blockade by importing polyamines from the environment. To address this issue, polyamine transport inhibitors (PTIs) have been developed. We investigated the effects of the novel trimer44NMe (PTI-1) alone and in combination with DFMO on VSMC polyamine uptake, proliferation and phenotype regulation. PTI-1 efficiently inhibited polyamine uptake in primary mouse aortic and human coronary VSMCs in the absence as well as in the presence of DFMO. Interestingly, culture with DFMO for 2 days substantially (>95%) reduced putrescine (Put) and spermidine (Spd) contents without any effect on proliferation. Culture with PTI-1 alone had no effect on either polyamine levels or proliferation rate, but the combination of both treatments reduced Put and Spd levels below the detection limit and inhibited proliferation. Treatment with DFMO for a longer time period (4 days) reduced Put and Spd below their detection limits and reduced proliferation, showing that only a small pool of polyamines is needed to sustain VSMC proliferation. Inhibited proliferation by polyamine depletion was associated with maintained expression of contractile smooth marker genes. In cultured intact mouse aorta, PTI-1 potentiated the DFMO-induced inhibition of cell proliferation. The combination of endogenous polyamine synthesis inhibition with uptake blockade is thus a viable approach for targeting unwanted vascular cell proliferation in vivo, including vascular restenosis.

Hypertension is a dominating risk factor for cardiovascular disease. To characterize the genomic response to hypertension, we administered vehicle or angiotensin II to mice and performed gene expression analyses. AngII treatment resulted in a robust increase in blood pressure and altered expression of 235 genes in the aorta, including Gucy1a3 and Gucy1b3 which encode subunits of soluble guanylyl cyclase (sGC). Western blotting and immunohistochemistry confirmed repression of sGC associated with curtailed relaxation via sGC activation. Analysis of transcription factor binding motifs in promoters of differentially expressed genes identified enrichment of motifs for RBPJ, a component of the Notch signaling pathway, and the Notch coactivators FRYL and MAML2 were reduced. Gain and loss of function experiments demonstrated that JAG/NOTCH signaling controls sGC expression together with MAML2 and FRYL. Reduced expression of sGC, correlating with differential expression of MAML2, in stroke prone and spontaneously hypertensive rats was also seen, and RNA-Seq data demonstrated correlations between JAG1, NOTCH3, MAML2 and FRYL and the sGC subunits GUCY1A3 and GUCY1B3 in human coronary artery. Notch signaling thus provides a constitutive drive on expression of the major nitric oxide receptor (GUCY1A3/GUCY1B3) in arteries from mice, rats, and humans, and this control mechanism is disturbed in hypertension.

Objective— Pressure-induced myogenic tone is involved in autoregulation of local blood flow and confers protection against excessive pressure levels in small arteries and capillaries. Myogenic tone is dependent on smooth muscle microRNAs (miRNAs), but the identity of these miRNAs is unclear. Furthermore, the consequences of altered myogenic tone for hypertension-induced damage to small arteries are not well understood. Approach and Results— The importance of smooth muscle–enriched microRNAs, miR-143/145, for myogenic tone was evaluated in miR-143/145 knockout mice. Furthermore, hypertension-induced vascular injury was evaluated in mesenteric arteries in vivo after angiotensin II infusion. Myogenic tone was abolished in miR-143/145 knockout mesenteric arteries, whereas contraction in response to calyculin A and potassium chloride was reduced by ≈30%. Furthermore, myogenic responsiveness was potentiated by angiotensin II in wild-type but not in knockout mice. Angiotensin II administration in vivo elevated systemic blood pressure in both genotypes. Hypertensive knockout mice developed severe vascular lesions characterized by vascular inflammation, adventitial fibrosis, and neointimal hyperplasia in small mesenteric arteries. This was associated with depolymerization of actin filaments and fragmentation of the elastic laminae at the sites of vascular lesions. Conclusions— This study demonstrates that miR-143/145 expression is essential for myogenic responsiveness. During hypertension, loss of myogenic tone results in potentially damaging levels of mechanical stress and detrimental effects on small arteries. The results presented herein provide novel insights into the pathogenesis of vascular disease and emphasize the importance of controlling mechanical factors to maintain structural integrity of the vascular wall.

Atherosclerosis is a disease in which atheromatous plaques develop inside arteries, leading to reduced or obstructed blood flow that in turn may cause stroke and heart attack. Rose hip is the fruit of plants of the genus Rosa, belonging to the Rosaceae family, and it is rich in antioxidants with high amounts of ascorbic acid and phenolic compounds. Several studies have shown that fruits, seeds and roots of these plants exert antidiabetic, antiobesity and cholesterol-lowering effects in rodents as well as humans. The aim of this study was to elucidate the mechanisms by which rose hip lowers plasma cholesterol and to evaluate its effects on atherosclerotic plaque formation. ApoE-null mice were fed either an HFD (CTR) or HFD with rose hip supplementation (RH) for 24 weeks. At the end of the study, we found that blood pressure and atherosclerotic plaques, together with oxidized LDL, total cholesterol and fibrinogen levels were markedly reduced in the RH group. Fecal cholesterol content, liver expression of Ldlr and selected reverse cholesterol transport (RCT) genes such as Abca1, Abcg1 and Scarb1 were significantly increased upon RH feeding. In the aorta, the scavenger receptor Cd36 and the proinflammatory Il1β genes were markedly down-regulated compared to the CTR mice. Finally, we found that RH increased nitric oxide-mediated dilation of the caudal artery. Taken together, these results suggest that rose hip is a suitable dietary supplement for preventing atherosclerotic plaques formation by modulating systemic blood pressure and the expression of RCT and inflammatory genes.

Caveolae are membrane invaginations present at high densities in muscle and fat. Recent work has demonstrated that myocardin family coactivators (MYOCD, MKL1), which are important for contractile differentiation and cell motility, increase caveolin (CAV1, CAV2, CAV3) and cavin (CAVIN1, CAVIN2, CAVIN3) transcription, but several aspects of this control mechanism remain to be investigated. Here, using promoter reporter assays we found that both MKL1/MRTF-A and MKL2/MRTF-B control caveolins and cavins via their proximal promoter sequences. Silencing of MKL1 and MKL2 in smooth muscle cells moreover reduced CAV1 and CAVIN1 mRNA levels by well over 50%, as did treatment with second generation inhibitors of MKL activity. GATA6, which modulates expression of smooth muscle-specific genes, reduced CAV1 and CAV2, whereas the cavins were unaffected or increased. Viral overexpression of MKL1 and myocardin induced caveolin and cavin expression in bladder smooth muscle cells from rats and humans and MYOCD correlated tightly with CAV1 and CAVIN1 in human bladder specimens. A recently described activator of MKL-driven transcription (ISX) failed to induce CAV1/CAVIN1 which may be due to an unusual transactivation mechanism. In all, these findings further support the view that myocardin family coactivators are important transcriptional drivers of caveolins and cavins in smooth muscle.

Phenotypic modulation of smooth muscle cells is a hallmark of disease. The associated expansion of endoplasmic reticulum (ER) volume remains unexplained. Thrombospondin-4 was recently found to promote ATF6α activation leading to ER expansion. Using bladder outlet obstruction as a paradigm for phenotypic modulation, we tested if thrombospondin-4 is induced in association with ATF6α activation and ER expansion. Thrombospondin-4 was induced and ATF6α was activated after outlet obstruction in rodents. Increased abundance of spliced of Xbp1, another ER-stress sensor, and induction of Atf4 and Creb3l2 was also seen. Downstream of ATF6α, Calr, Manf, Sdf2l1 and Pdi increased as did ER size, whereas contractile markers were reduced. Overexpression of ATF6α, but not of thrombospondin-4, increased Calr, Manf, Sdf2l1 and Pdi and caused ER expansion, but the contractile markers were inert. Knockout of thrombospondin-4 neither affected bladder growth nor expression of ATF6α target genes, and repression of contractile markers was the same, even if ATF6α activation was curtailed. Increases of Xbp1s, Atf4 and Creb3l2 were similar. Our findings demonstrate reciprocal regulation of the unfolded protein response, including ATF6α activation and ER expansion, and reduced contractile differentiation in bladder outlet obstruction occurring independently of thrombospondin-4, which however is a sensitive indicator of obstruction.

A senescent phenotype in endothelial cells is associated with increased apoptosis, reduced endothelial nitric oxide synthase (eNOS) and inflammation, which are implicated in arterial dysfunction and disease in humans. We tested the hypothesis that changes in microRNAs are associated with a senescent phenotype in human aortic endothelial cells (HAEC). Compared with early-passage HAEC, late-passage HAEC had a reduced proliferation rate and increased staining for senescence-associated beta-galactosidase and the tumor suppressor p16(INK4a). Late-passage senescent HAEC had reduced expression of proliferation-stimulating/apoptosis-suppressing miR-21, miR-214 and miR-92 and increased expression of tumor suppressors and apoptotic markers. eNOS-suppressing miR-221 and miR-222 were increased and eNOS protein and eNOS activation (phosphorylation at serine1177) were lower in senescent HAEC. Caveolin-1 inhibiting miR-133a was reduced and caveolin-1, a negative regulator of eNOS activity, was elevated in senescent HAEC. Inflammation-repressing miR-126 was reduced and inflammation-stimulating miR-125b was increased, whereas inflammatory proteins were greater in senescent HAEC Development of a senescent arterial endothelial cell phenotype featuring reduced cell proliferation, enhanced apoptosis and inflammation and reduced eNOS is associated with changes in miRNAs linked to the regulation of these processes. Our results support the hypothesis that miRNAs could play a critical role in arterial endothelial cell senescence. (C) 2011 Elsevier Inc. All rights reserved. (Less)

Thickening of the intimal layer of arteries characterized by expression of smooth muscle α-actin (SMαA), collagen deposition, and inflammation is an important pathophysiological change with aging assumed to be mediated by smooth muscle cells migrating from the medial layer. We tested the novel hypothesis that these characteristics could also reflect an endothelial-mesenchymal (smooth muscle-like) transition (EnMT). Late (‘old’) compared with early (‘young’) passage (45.0 ± 1.2 vs. 27.1 ± 0.5 population doublings) human aortic endothelial cells demonstrated greater smooth muscle (spindle) morphological changes, expression of SMαA and collagen I, nuclear factor-ĸB activation, and transforming growth factor-β (TGF-β) (all p < 0.05). Based on increases in SMαA, stimulation with the proinflammatory cytokine tumor necrosis factor-α, but not with TGF-β, induced EnMT in early passage cells similar to that observed in late passage cells. Here, we present the first evidence for EnMT induced in a model of endothelial cell aging and provide support for proinflammatory signaling in mediating this phenotypic change.

Background and purpose: Caveolin-1-deficiency is associated with substantial urogenital alterations. Here, a mechanical, histological and biochemical characterization of female detrusors from wild-type (WT) and caveolin-1-deficient (KO) mice was made to increase the understanding of detrusor changes caused by lack of caveolae. Experimental approach: Length-tension relationships were generated, and we recorded responses to electrical field stimulation (EFS), the muscarinic receptor agonist carbachol, and the purinoceptor agonist ATP. Tyrosine nitration and the contents of caveolin-1, cavin-1, muscarinic M(3) receptors, phospholipase C(β1) (PLC(β1) ), muscle-specific kinase (MuSK), and L-type Ca(2+) -channels were determined by immunoblotting. Innervation was assessed by immunohistochemistry. Key results: Bladder to body weight ratio was not changed, nor was there any change in the optimum circumference for force development. Depolarization- and ATP-induced stress was reduced, as was carbachol-induced stress between 0.1 and 3 µM, but the supramaximal relative (% K(+) ) response to carbachol was increased, as was M(3) expression. The scopolamine-sensitive component of the EFS-response was impaired, and yet bladder nerves contained little caveolin-1. The density of cholinergic nerves was unchanged, whereas CART- and CGRP-positive nerves were reduced. Immunoblotting revealed loss of MuSK. Conclusions and implications: Ablation of caveolae in the female detrusor leads to generalised impairment of contractility, ruling out prostate hypertrophy as a contributing factor. Cholinergic neuroeffector transmission is impaired without conspicuous changes in the density of cholinergic nerves or morphology of their terminals, but correlating with reduced expression of MuSK. (Less)

Soluble guanylyl cyclase (sGC) is an effector enzyme of nitric oxide (NO). Recent work has unravelled how levels of this enzyme are controlled, and highlighted a role in vascular disease. We provide a timely summary of available knowledge on transcriptional regulation of sGC, including influences from the NOTCH signalling pathway and genetic variants. It is speculated that hypertension-induced repression of sGC starts a vicious circle that can be initiated by periods of stress, diet or genetic factors, and a key tenet is that reduction in sGC further raises blood pressure. The idea that dysregulation of sGC contributes to syndromes caused by defective NOTCH signalling is advanced, and we discuss drug repositioning for vascular disease prevention. The advantage of targeting sGC expression rather than activity is also considered. It is argued that transcriptional inputs on sGC arise from interactions with other cells, the extracellular matrix and microRNAs (miRNAs), and concluded that the promise of sGC as a target for prevention of cardiovascular disease has increased in recent time.

Aim: Compared to neutral globular proteins, neutral polysaccharides, such as dextran, pullulan and Ficoll, appear hyperpermeable across the glomerular filtration barrier. This has been attributed to an increased flexibility and/or asymmetry of polysaccharides. The present study investigates whether polysaccharides are hyperpermeable also across the continuous capillaries in the rat peritoneum. Methods: In anesthetized Wistar rats, FITC-Ficoll or FITC-pullulan together with (125)I-human serum albumin (RISA) or neutralized (125)I-bovine serum albumin (nBSA) were given intravenously, after which peritoneal dialysis using conventional peritoneal dialysis fluid (Gambrosol 1.5%) was performed for 120 min. Concentrations of FITC-polysaccharides and radioactive albumin species in plasma and dialysis fluid were analyzed with high performance size exclusion chromatography and a gamma counter, respectively. Transperitoneal clearance values were calculated for polysaccharides in the molecular radius range 36-150 A, and for RISA and nBSA. Results: Ficoll and pullulan showed more or less identical permeabilities, compared to RISA and nBSA, across the peritoneal membrane. Although RISA-clearance, 5.50+/-0.28 (muL/min; +/-SEM), tended to be lower than the clearances of Ficoll(36A) (6.55+/-0.25), pullulan(36A) (6.08+/-0.22) and nBSA (6.56+/-0.23), the difference was not statistically significant. This is in contrast to the hyperpermeability exhibited by polysaccharides across the glomerular filtration barrier and also contrasts with the charge selectivity of the latter. Conclusion: The phenomenon of molecular flexibility is more important for a macromolecule's permeability through the glomerular filter than across the continuous peritoneal capillary endothelium. Furthermore, it seems that charge plays a subordinate role in the steady-state transport across the combined peritoneal capillary-interstitial barrier. (Less)

The hypothalamus is the main appetite-regulating center in the brain receiving peripheral signals regarding the metabolic status of the body. Pancreatic procolipase has recently been identified in rat hypothalamus. Procolipase is known mainly for its actions in the intestine where it is cleaved to colipase, an enzyme required for the maintenance of pancreatic lipase activity, and enterostatin, a peptide involved in appetite regulation through the gut-brain axis. Colipase is able to increase the activity of pancreatic lipase-related protein-2 (PLRP2), a lipase also expressed in extra-pancreatic tissues. This study was performed to elucidate if PLRP2, in addition to colipase, is expressed in the hypothalamus and if the mRNAs of colipase and PLRP2 respond to metabolic challenges such as fasting, high-fat feeding or feeding sugar solutions. RNA from rat hypothalamus was extracted and subjected to RT-PCR. For quantitative mRNA analysis of hypothalamic tissue from the different metabolic situations real-time RT-PCR was used. We found PLRP2 and colipase mRNA to be expressed in the hypothalamus. An overnight fast resulted in down-regulated colipase (3-fold) and PLRP2 (7-fold) mRNA compared to freely fed rats. Conversely, high-fat feeding resulted in up-regulated colipase and PLRP2 mRNA (1.3-fold and 1.8-fold, respectively) compared to standard chow-fed rats. A similar up-regulation in mRNA expression was observed after offering sugar solutions. In conclusion, PLRP2 mRNA is expressed in the rat hypothalamus and both procolipase and PLRP-2 mRNA are down-regulated during fasting and up-regulated during conditions of metabolic excess, suggesting an involvement in signaling energy availability.

Aim: Polysaccharides and many other non-protein polymers generally have a more open, flexible and asymmetrical structure compared with globular proteins. For a given molecular weight (MW), the Stokes–Einstein radius (ae) of the following polymers increases in the order: Ficoll < dextran ≤ pullulan < polyethylene oxide (PEO). We have tested the hypothesis that such an increase in 'molecular extension' will increase the molecule's glomerular permeability. Thus, we investigated the glomerular sieving coefficients (θ) of the mentioned polymers and of the negatively charged and extended protein bikunin. Methods: In anaesthetized Wistar rats, glomerular sieving curves were generated for each FITC-labelled polymer from their respective concentration in urine and plasma, determined by size exclusion chromatography. The θ for bikunin was measured using a tissue uptake technique. Results: For a molecule of ae = 55 A (cf. IgG), θ increased in the order: Ficoll (0.00035 ± 0.000013) < dextran (0.022 ± 0.0029) < pullulan (0.033 ± 0.0024) < PEO (0.12 ± 0.0055). For ae = 36 A (cf. albumin) the order was: Ficoll (0.076 ± 0.0061) < dextran (0.45 ± 0.037) = pullulan (0.45 ± 0.021) < PEO (0.65 ± 0.0076). θ for bikunin (0.089 ± 0.0045) was 150 times higher than that of albumin, having an equivalent ae and net negative charge. Conclusion: From these results it is concluded that for flexible and asymmetric macromolecules, their degree of glomerular hyperpermeability is proportional to their degree of 'molecular extension'. Thus, compared with globular proteins, the polysaccharides investigated, including Ficoll, were found to be hyperpermeable across the glomerular filter in vivo. (Less)

Members of the myocardin family bind to the transcription factor serum response factor (SRF) and act as coactivators controlling genes of relevance for myogenic differentiation and motile function. Binding of SRF to DNA is mediated by genetic elements called CArG boxes, found often but not exclusively in muscle and growth controlling genes. Studies aimed at defining the full spectrum of these CArG elements in the genome (i.e. the CArGome) have in recent years, unveiled unexpected roles of the myocardin family proteins in lipid and glucose homeostasis. This coactivator family includes the protein myocardin (MYOCD), the myocardin-related transcription factors A and B (MRTF-A/MKL1 and MRTF-B/MKL2) and MASTR (MAMSTR). Here we discuss growing evidence that SRF-driven transcription is controlled by extracellular glucose through activation of the Rho-kinase pathway and actin polymerization. We also describe data showing that adipogenesis is influenced by MLK activity through actions upstream of peroxisome proliferator-activated receptor γ with consequences for whole body fat mass and insulin sensitivity. The recently demonstrated involvement of myocardin coactivators in the biogenesis of caveolae, Ω-shaped membrane invaginations of importance for lipid and glucose metabolism, is finally discussed. These novel roles of myocardin proteins may open the way for new unexplored strategies to combat metabolic diseases such as diabetes, which, at the current incidence, is expected to reach 333 million people worldwide by 2025. This review highlights newly discovered roles of myocardin-related transcription factors in lipid and glucose metabolism as well as novel insights into their well-established role as mediators of stretch-dependent effects in smooth muscle. As co-factors for serum response factor (SRF), MKLs regulates transcription of genes involved in the contractile function of smooth muscle cells. In addition to mechanical stimuli, this regulation has now been found to be promoted by extracellular glucose levels in smooth muscle. Recent reports also suggest that MKLs can regulate a subset of genes involved in the formation of lipid-rich invaginations in the cell membrane called caveolae. Finally, a potential role of MKLs in non-muscle cells has been discovered as they negatively influence adipocyte differentiation.

Caveolae are membrane organelles that play roles in glucose and lipid metabolism and in vascular function. Formation of caveolae requires caveolins and cavins. The make-up of caveolae and their density is considered to reflect cell-specific transcriptional control mechanisms for caveolins and cavins, but knowledge regarding regulation of caveolae genes is incomplete. Myocardin (MYOCD) and its relative MRTF-A (MKL1) are transcriptional coactivators that control genes which promote smooth muscle differentiation. MRTF-A communicates changes in actin polymerization to nuclear gene transcription. Here we tested if myocardin family proteins control biogenesis of caveolae via activation of caveolin and cavin transcription. Using human coronary artery smooth muscle cells we found that jasplakinolide and latrunculin B (LatB), substances that promote and inhibit actin polymerization, increased and decreased protein levels of caveolins and cavins, respectively. The effect of LatB was associated with reduced mRNA levels for these genes and this was replicated by the MRTF inhibitor CCG-1423 which was non-additive with LatB. Overexpression of myocardin and MRTF-A caused 5-10-fold induction of caveolins whereas cavin-1 and cavin-2 were induced 2-3-fold. PACSIN2 also increased, establishing positive regulation of caveolae genes from three families. Full regulation of CAV1 was retained in its proximal promoter. Knock down of the serum response factor (SRF), which mediates many of the effects of myocardin, decreased cavin-1 but increased caveolin-1 and -2 mRNAs. Viral transduction of myocardin increased the density of caveolae 5-fold in vitro. A decrease of CAV1 was observed concomitant with a decrease of the smooth muscle marker calponin in aortic aneurysms from mice (C57Bl/6) infused with angiotensin II. Human expression data disclosed correlations of MYOCD with CAV1 in a majority of human tissues and in the heart, correlation with MKL2 (MRTF-B) was observed. The myocardin family of transcriptional coactivators therefore drives formation of caveolae and this effect is largely independent of SRF.

This study was performed to evaluate the alterations of glomerular filtration barrier characteristics following acute renal ischemia-reperfusion (I/R). Ischemia was induced in anesthetized rats by unilateral renal artery occlusion for either 20 or 60 min, followed by reperfusion during 20 or 60 min, respectively, with the contralateral kidney serving as control. Sieving coefficients (θ) were obtained by analyzing Ficoll [mol.radius ( ae) 13–85 Å] in urine and plasma after 20 and 60 min I/R. Furthermore, θ for human serum albumin (HSA) was estimated using a tissue uptake technique after 20 and 60 min of I/R, while clearance of HSA compared with that for neutralized HSA (nHSA) was assessed after 20 min of I/R only. Glomerular filtration rate (GFR) was measured by [51Cr]EDTA and inulin. I/R reduced GFR and increased θ for Ficoll molecules of ae>55 Å and θ for albumin. θ for Ficoll vs. ae, analysed using a two-pore model, demonstrated that, despite increases in θ, the large-pore fractional ultrafiltration coefficient (αL) was unchanged after 20 min of I/R, owing to the decline in GFR, but increased after 60 min of I/R. However, the apparent αLfor albumin increased already after 20 min of I/R ( P < 0.005) and the nHSA/HSA clearance ratio was slightly reduced, possibly reflecting a diminished negative charge barrier. In conclusion, after 20 min of I/R, indications of a reduced charge selectivity were noted, while after 60 min of I/R, there was mainly a reduction in size selectivity, compatible with an increased formation of large pores.

It is established that the glomerular filter sieves macromolecules based on their size, shape, and charge. Anionic proteins are thus retarded compared with their neutral or cationic counterparts. However, recent studies have indicated that charge effects are small, or even "anomalous," for polysaccharides. We therefore investigated the impact of charge on the glomerular permeability to polysaccharides by comparing sieving coefficients (theta; primary urine-to-plasma concentration ratio) for negatively charged, carboxymethylated (CM) FITC-Ficoll and FITC-dextran with their neutral counterparts. For these probes, theta were determined in anesthetized Wistar rats [269 +/- 2.7 g (+/-SE; n = 36)], whose ureters were cannulated for urine sampling. The glomerular filtration rate was assessed using FITC-inulin. Polysaccharides were constantly infused, and after equilibration, urine was collected and a midpoint plasma sample was taken. Size and concentration determinations of the FITC-labeled polysaccharides were achieved by size-exclusion HPLC (HPSEC). For CM-Ficoll, theta was significantly increased (32 times at 55 A) compared with that of uncharged Ficoll. A small increase in theta for CM-dextran compared with neutral dextran was also observed (1.8 times at 55 A). In conclusion, negatively charged Ficoll relative to neutral Ficoll was found to be markedly hyperpermeable across the glomerular filter. Furthermore, negatively charged Ficoll was observed to be larger on HPSEC compared with its neutral counterpart of the same molecular weight. It is proposed that the introduction of negative charges in the "dendrimeric," cross-linked Ficoll molecule may alter its configuration, so as to make it more extended, and conceivably, more flexible, thereby increasing its glomerular permeability.

Caveolae are Ω-shaped vesicular structures postulated to play a role in transvascular protein transport. Studies on mice lacking endothelial caveolae, caveolin-1 knockout (Cav-1-KO) mice, indicate increased macromolecular transport rates. This was postulated to be due to the appearance of an alternative pathway. The present study tested whether an alternative pathway had appeared in Cav-1-KO mice. Male Cav-1-KO ( n = 12) and male control mice ( n = 13) were intubated and anesthetized using 2% isoflurane.125I-labeled albumin,131I-labeled immunoglobulin M (IgM), and polydisperse FITC-Ficoll were administered intravenously. During tracer administration, a 90-min peritoneal dialysis dwell was performed. Clearance of tracers to dialysate and permeability-surface area product for glucose were assessed. Transvascular protein transport was higher in Cav-1-KO compared with control mice. Albumin clearance from plasma to peritoneum was 0.088 ± 0.008 μl/min in control and 0.179 ± 0.012 μl/min in Cav-1-KO ( P = 0.001) mice. IgM clearance was 0.049 ± 0.003 and 0.083 ± 0.010 μl/min in control and Cav-1-KO mice, respectively ( P = 0.016). Ficoll clearance was increased in Cav-1-KO mice. In conclusion, the lack of caveolae in Cav-1-KO mice resulted in a marked increase in macromolecular transport. A two-pore analysis of the Ficoll clearance data revealed that the higher transport rate in Cav-1-KO mice was not compatible with the appearance of an alternative pathway for macromolecular transport. In contrast, the higher transperitoneal protein and Ficoll clearance is consistent with passive porous transport through an unperturbed two-pore system, presumably at an elevated capillary hydraulic pressure. Alternatively, the data may be explained by reductions in the selectivity of the endothelial glycocalyx, leading to an increased capillary hydraulic conductivity and large solute filtration.

The purpose of the present study was to assess the role of diffusion and convection during filtration of Ficoll across the glomerular filter by comparing glomerular sieving coefficients (theta) to neutral fluorescein isothiocyanate (FITC)-Ficoll 70/400 obtained at low (hydropenic) vs raised (normal) glomerular filtration rates (GFRs). The theta for FITC-Ficoll was determined in anesthetized Wistar rats (304 +/- 18 g) following laparotomy and cannulation of the ureters, used for urine sampling. After surgery, GFR was 1.2 +/- 0.16 ml/min (+/- s.e.), assessed using the plasma to urine clearance of FITC-inulin and (51)Cr-ethylenediaminetetraacetic acid. FITC-Ficoll 70/400 was infused intravenously (i.v.) following an initial bolus dose. To raise GFR, to an average of approximately 2 ml/min, 5 ml of serum together with glucagon (3 microg/min) was given i.v. FITC-inulin and FITC-Ficoll were determined in plasma and urine using size-exclusion high-performance liquid chromatography. The theta for Ficoll as a function of Stokes-Einstein radius was significantly reduced in the range of 13-43 A when GFR was raised. The maximal theta lowering effect, in relative terms, of raising GFR was obtained for a Ficoll a(e) of approximately 32 A. For Ficoll(36 A) (cf. albumin), theta was reduced from 0.111+/- 0.009 to 0.081+/- 0.012 (P0.05; n = 7) for the GFR increment imposed. The reduction in theta for Ficoll after raising GFR indicates the presence of a high diffusive component of glomerular Ficoll filtration in rats in vivo and contradicts the notion of a significant concentration polarization effect in the glomerular filter upon Ficoll molecules50 A in radius.

Much evidence highlights the importance of polyamines for VSMC (vascular smooth muscle cell) proliferation and migration. Cav-1 (caveolin-1) was recently reported to regulate polyamine uptake in intestinal epithelial cells. The aim of the present study was to assess the importance of Cav-1 for VSMC polyamine uptake and its impact on cell proliferation and migration. Cav-1 KO (knockout) mouse aortic cells showed increased polyamine uptake and elevated proliferation and migration compared with WT (wild-type) cells. Both Cav-1 KO and WT cells expressed the smooth muscle differentiation markers SM22 and calponin. Cell-cycle phase distribution analysis revealed a higher proportion of Cav-1 KO than WT cells in the S phase. Cav-1 KO cells were hyper-proliferative in the presence but not in the absence of extracellular polyamines, and, moreover, supplementation with exogenous polyamines promoted proliferation in Cav-1 KO but not in WT cells. Expression of the solute carrier transporters Slc7a1 and Slc43a1 was higher in Cav-1 KO than in WT cells. ODC (ornithine decarboxylase) protein and mRNA expression as well as ODC activity were similar in Cav-1 KO and WT cells showing unaltered synthesis of polyamines in Cav-1 KO cells. Cav-1 was reduced in migrating cells in vitro and in carotid lesions in vivo. Our data show that Cav-1 negatively regulates VSMC polyamine uptake and that the proliferative advantage of Cav-1 KO cells is critically dependent on polyamine uptake. We provide proof-of-principle for targeting Cav-1-regulated polyamine uptake as a strategy to fight unwanted VSMC proliferation as observed in restenosis., We demonstrate that caveolin-1 negatively regulates vascular smooth muscle cell polyamine uptake and show that caveolin-1-regulated polyamine uptake is critical for proliferative advantage of caveolin-1 deficient cells, providing proof-of-principle for targeting this mechanism as a strategy to fight unwanted proliferation.

The permeability-surface area product of procolipase and its apparent distribution volume in rat tissues were assessed using a tissue uptake technique. Procolipase was investigated together with51Cr-EDTA, used as an inert extracellular marker, and131I-albumin, used as a plasma volume marker. The tissue uptake of procolipase seemed to occur by passive transport in most of the organs studied, such as in muscle, liver, lung, adipose tissue, adrenal glands, colon, and skin. However, throughout the gastrointestinal tract, except in the colon, there was a high uptake of procolipase, greatly exceeding that of51Cr-EDTA. This was especially evident in the stomach, in which the procolipase uptake was nonsaturable within the experimental period. Also, in the central nervous system (CNS), there was evidence of specific, possibly carrier-mediated, transport. These results suggest that procolipase may have specific, conceivably receptor-mediated, transport pathways across the microvascular endothelium in the stomach, pancreas, duodenum, ileum, and the CNS.

Enterostatin, the N-terminal activation peptide of pancreatic procolipase, has been identified in three different forms in rat: VPDPR (Val-Pro-Asp-Pro-Arg), APGPR (Ala-Pro-Gly-Pro-Arg) and VPGPR (Val-Pro-Gly-Pro-Arg). We investigated the possibility for a species to have several isoforms of enterostatin. Pancreas was purified from four different species (rat, mouse, cat and pig) and the enterostatin sequences were identified. At the same time, the activities of pancreatic lipase and colipase were measured. In rat and mouse pancreas APGPR was the only form of enterostatin identified. The colipase activity was 188 ± 25 U/mg protein in rat and 189 ± 16 U/mg in mouse and the lipase activity 354 ± 33 U/mg and 292 ± 19 U/mg respectively. Rat and mouse had a colipase/lipase ratio close to 0.5. In pancreas from cat and pig we only detected the form VPDPR (Val-Pro-Asp-Pro-Arg). We found the colipase activity in cat to be 493 ± 92 U/mg, while the lipase activity was three times lower, 167 ± 18 U/mg. Pig pancreas concentrations of colipase was 110 ± 8 U/mg and of lipase 38 ± 5 U/mg. In both cat and pig the colipase/lipase ratio was close to 3. This suggests that colipase might have an additional role than to restore the activity of lipase. Our hypothesis is that an overproduction of colipase and hence also enterostatin is involved in the regulation of fat metabolism.

Caveolae are invaginations in the plasma membrane that depend on caveolins and cavins for maturation. Here, we investigated the pulmonary phenotype in mice lacking cavin-1. Bright field and electron-microscopy showed that the cavin-1-deficient mice lacked caveolae in the lung, had an increased lung tissue density, and exhibited hypertrophic remodeling of pulmonary arteries. The right ventricle of the heart moreover had an increased mass and the right ventricular pressure was elevated. A microarray analysis revealed upregulation of Arg1 and downregulation of Ddah1, molecules whose altered expression has previously been associated with pulmonary arterial hypertension. Taken together, this work demonstrates vascular remodeling and increased pulmonary blood pressure in cavin-1 deficient mice and associates this phenotype with altered expression of Arg1 and Ddah1.