Lovastatin Induces Relaxation and Inhibits L-Type Ca2+ Current in the Rat Basilar Artery.

Statins inhibit cholesterol biosynthesis and protect against ischaemic stroke. It has become increasingly apparent that the beneficial effects of statin therapy may extend beyond lowering of serum cholesterol. The present study was done to explore possible pleiotropic statin effects at the level of the cerebral vascular smooth muscle. Lovastatin, lovastatin acid, simvastatin and pravastatin, were added to segments of the rat basilar artery and effects on contraction and Ca2+ handling were examined. Pravastatin had no effect on contraction. Simvastatin, lovastatin, and, to a lesser degree, lovastatin acid, caused relaxation (IC50=0.8, 1.9 and 22 μmol/l) of both intact and denuded arteries precontracted with 5-HT or high-K+. This effect was not reversed by mevalonate, suggesting that it was not related to cholesterol or isoprenoid metabolism. Relaxation was associated with a reduction of the intracellular Ca2+ concentration measured with Fura 2 and with a reduced Mn2+ quench rate, suggesting a direct effect on ion channels in the smooth muscle cell membrane. Current measurements in isolated and voltage clamped basilar artery muscle cells demonstrated that both lovastatin and lovastatin acid inhibit L-type Ca2+ current. We propose that lipophilicity is an important factor behind the effects of statins on vascular tone and that Ca2+ current inhibition is the likely mechanism of action

Regulation of Ca2+ channel and phosphatase activities by polyamines in intestinal and vascular smooth muscle - implications for cellular growth and contractility.

Polyamines added extracellularly to intestinal and vascular smooth muscle cells cause relaxation through inhibition of Ca2+ channel activity. Intracellularly applied polyamines also affect Ca2+ channel properties. Polyamines do not readily pass over the plasma membrane because of their positive charges but in permeabilized smooth muscle preparations they have free access to the cytoplasm. In this system they increase sensitivity of the contractile machinery to Ca2+ through inhibition of myosin phosphatase activity. The magnitude of Ca2+ channel and phosphatase inhibition depends on the number of positive charges on the polyamine molecule. Polyamines have an obligatory, but yet undefined, role in regulation of cell growth and proliferation. Several groups of protein kinases, such as tyrosine and mitogen activated protein (MAP)-kinases transmit the growth signal from the plasma membrane to the cell nucleus where mitosis and protein synthesis are initiated. The data reviewed here show that polyamines may affect such signal transmission via inhibition of phosphatase activity

Expression of microRNAs is essential for arterial myogenic tone and pressure-induced activation of the PI3-kinase/Akt pathway.

The myogenic response is the intrinsic ability of small arteries to constrict in response to increased intraluminal pressure. Although microRNAs have been shown to play a role in vascular smooth muscle function, their importance in the regulation of the myogenic response is not known. In this study, we investigate the role of microRNAs in the regulation of myogenic tone by using smooth muscle-specific and tamoxifen-inducible deletion of the endonuclease Dicer in mice

The complement system is activated in synovial fluid from subjects with knee injury and from patients with osteoarthritis

Concentrations of C4d, C3bBbP and sTCC in synovial fluid. (DOCX 37 kb

Coculture of bovine cartilage with synovium and fibrous joint capsule increases aggrecanase and matrix metalloproteinase activity

Background A hallmark of osteoarthritis is increased proteolytic cleavage of aggrecan. Cross talk between cartilage and the synovium + joint capsule (SJC) can drive cartilage degradation by activating proteases in both tissues. We investigated aggrecan proteolysis patterns in cartilage explants using a physiologically relevant explant model of joint injury combining cartilage mechanical compression and coincubation with SJC. Methods Bovine cartilage explants were untreated; coincubated with SJC; or subjected to mechanical injury and coincubated with SJC, mechanical injury alone, or mechanical injury and incubated with tumor necrosis factor-α (TNF-α). To compare the patterns of aggrecan proteolysis between 6 h and 16 days, release of sulfated glycosaminoglycans and specific proteolytic aggrecan fragments into medium or remaining in cartilage explants was measured by dimethylmethylene blue and Western blot analysis. Results Aggrecanase activity toward aggrecan was observed in all conditions, but it was directed toward the TEGE↓ARGS interglobular domain (IGD) site only when cartilage was coincubated with SJC or TNF-α. Matrix metalloproteinase (MMP) activity at the aggrecan IGD site (IPES↓FFGV) was not detected when cartilage was exposed to TNF-α (up to 6 days), but it was in all other conditions. Compared with when bovine cartilage was left untreated or subjected to mechanical injury alone, additional aggrecan fragment types were released into medium and proteolysis of aggrecan started at an earlier time when SJC was present. Conclusions Indicative of different proteolytic pathways for aggrecan degradation, the SJC increases both aggrecanase and MMP activity toward aggrecan, whereas TNF-α inhibits MMP activity against the IGD of aggrecan.National Institutes of Health (U.S.) (AR060331

Regulation of microRNA expression in vascular smooth muscle by MRTF-A and actin polymerization

Producción CientíficaThe dynamic properties of the actin cytoskeleton in smooth muscle cells play an important role in a number of cardiovascular disease states. The state of actin does not only mediate mechanical stability and contractile function but can also regulate gene expression via myocardin related transcription factors (MRTFs). These transcriptional co-activators regulate genes encoding contractile and cytoskeletal proteins in smooth muscle. Regulation of small non-coding microRNAs (miRNAs) by actin polymerization may mediate some of these effects. MiRNAs are short non-coding RNAs that modulate gene expression by post-transcriptional regulation of target messenger RNA. In this study we aimed to determine a profile of miRNAs that were 1) regulated by actin/MRTF-A, 2) associated with the contractile smooth muscle phenotype and 3) enriched in muscle cells.The Swedish Research Council (grant 2012-2197)The Crafoord Foundation (grant 20150629)Instituto de Salud Carlos III (grant RD12/0042/0006)Ministerio de Economía, Industria y Competitividad (grant BFU2013-45867-R

Regulation of smooth muscle dystrophin and synaptopodin 2 expression by actin polymerization and vascular injury

Producción CientíficaObjective: Actin dynamics in vascular smooth muscle is known to regulate contractile differentiation and may play a role in the pathogenesis of vascular disease. However, the list of genes regulated by actin polymerization in smooth muscle remains incomprehensive. Thus, the objective of this study was to identify actin-regulated genes in smooth muscle and to demonstrate the role of these genes in the regulation of vascular smooth muscle phenotype. Approach and Results: Mouse aortic smooth muscle cells were treated with an actin-stabilizing agent, jasplakinolide, and analyzed by microarrays. Several transcripts were upregulated including both known and previously unknown actin-regulated genes. Dystrophin and synaptopodin 2 were selected for further analysis in models of phenotypic modulation and vascular disease. These genes were highly expressed in differentiated versus synthetic smooth muscle and their expression was promoted by the transcription factors myocardin and myocardin-related transcription factor A. Furthermore, the expression of both synaptopodin 2 and dystrophin was significantly reduced in balloon-injured human arteries. Finally, using a dystrophin mutant mdx mouse and synaptopodin 2 knockdown, we demonstrate that these genes are involved in the regulation of smooth muscle differentiation and function. Conclusions: This study demonstrates novel genes that are promoted by actin polymerization, that regulate smooth muscle function, and that are deregulated in models of vascular disease. Thus, targeting actin polymerization or the genes controlled in this manner can lead to novel therapeutic options against vascular pathologies that involve phenotypic modulation of smooth muscle cells.Instituto de Salud Carlos III - Fondo Europeo de Desarrollo Regional (grant RD12/0042/0006)Ministerio de Economía, Industria y Competitividad (grants BFU2010-15898 and BFU2013-45867-R

Glucosylceramide synthase deficiency in the heart compromises β1-adrenergic receptor trafficking

Aims: Cardiac injury and remodelling are associated with the rearrangement of cardiac lipids. Glycosphingolipids are membrane lipids that are important for cellular structure and function, and cardiac dysfunction is a characteristic of rare monogenic diseases with defects in glycosphingolipid synthesis and turnover. However, it is not known how cardiac glycosphingolipids regulate cellular processes in the heart. The aim of this study is to determine the role of cardiac glycosphingolipids in heart function.Methods and results: Using human myocardial biopsies, we showed that the glycosphingolipids glucosylceramide and lactosylceramide are present at very low levels in non-ischaemic human heart with normal function and are elevated during remodelling. Similar results were observed in mouse models of cardiac remodelling. We also generated mice with cardiomyocyte-specific deficiency in Ugcg, the gene encoding glucosylceramide synthase (hUgcg-/- mice). In 9- to 10-week-old hUgcg-/- mice, contractile capacity in response to dobutamine stress was reduced. Older hUgcg-/- mice developed severe heart failure and left ventricular dilatation even under baseline conditions and died prematurely. Using RNA-seq and cell culture models, we showed defective endolysosomal retrograde trafficking and autophagy in Ugcg-deficient cardiomyocytes. We also showed that responsiveness to β-adrenergic stimulation was reduced in cardiomyocytes from hUgcg-/- mice and that Ugcg knockdown suppressed the internalization and trafficking of β1-adrenergic receptors.Conclusions: Our findings suggest that cardiac glycosphingolipids are required to maintain β-adrenergic signalling and contractile capacity in cardiomyocytes and to preserve normal heart function.</p

Knee injuries and their consequences – the impact of impact

Anterior cruciate ligament (ACL) injuries are common, severe knee injuries that result in a high risk of developing knee osteoarthritis (OA) in the affected individuals. As proof of high impact forces applied to cartilage and bone at the time of injury, traumatic bone marrow lesions and osteochondral fractures, located predominantly in the lateral tibiofemoral compartment, are commonly associated with an ACL injury. The subsequent risk of OA may be closely associated with the knee injury mechanism and the panorama of injuries in the knee sustained at the onset of injury. The purpose of this work was to acquire a better understanding of how the initial impact, related to the trauma mechanism of acute knee injuries, may influence acute and chronic knee pathology. In this work it was found that subjects with post-traumatic OA secondary to an ACL injury have more joint space narrowing and more osteophytes in the lateral compartment than in the medial compartment, compared with subjects with non-traumatic OA. Furthermore, it was found that an acute knee injury is associated with instant and sustained synovial fluid biochemical alterations within the first month of knee injury, suggestive of increased cartilage turnover and severe joint inflammation. Those subjects who sustained an osteochondral fracture with disrupted cortical bone in association with the soft tissue knee injury had increased joint inflammation. In an in vitro bovine cartilage study, mechanical injury to cartilage increased the matrix metalloproteinase-induced cleavage of cartilage aggrecan. Moreover, findings from this model suggest that the aggrecan degradation may differ between cytokine-stimulated cartilage explants compared with cartilage explants mechanically injured and (or) co-incubated with joint capsule. Conclusively, the findings in this work underline the fact that the initial impact associated with an ACL appears to be important in terms of the risk of developing post-traumatic OA. In addition, this work emphasizes how the acute biological response to injury could be involved in cartilage degradation. A greater understanding of these processes could lead to the improved management of knee-injured patients and possibly delay, or even prevent, OA development