Long-term Outcomes Are Poor in Intravenous Drug Users Following Infective Endocarditis, Even After Surgery.

BACKGROUND: Previous studies of outcomes in people who inject drugs (PWID) with infective endocarditis (IE) have often been retrospective, have had small sample sizes, and the duration of follow-up has been short and limited to patients who were operated on. METHODS: PWID treated for IE between 1 January 2006 and 31 December 2016 were identified from a prospectively collected database. PWID hospitalized with other infections acted as a novel comparison group. Outcomes were all-cause mortality, cause of death, relapse, recurrence, and reoperation. RESULTS: There were 105 episodes of IE in 92 PWID and 112 episodes of other infections in 107 PWID in whom IE was suspected but rejected. Survival at 30 days for the IE group was 85%, and 30-day survival following surgery was 96%. The most common pathogens were Staphylococcus species (60%) and Streptococcus species (30%). The surgical intervention rate was 47%. Survival for the IE group at 1, 3, 5, and 10 years was 74%, 63%, 58%, and 44%, respectively. This was significantly lower compared with the comparator group of other infections in PWID (P = .0002). Mortality was higher in patients who required surgery compared with those who did not (hazard ratio, 1.8 [95% confidence interval, .95-3.3]). The commonest cause of death was infection (66%), usually a further episode of IE (55%). CONCLUSIONS: Although early survival was good, long-term life expectancy was low. This was attributable to ongoing infection risk, rather than other factors known to affect prognosis in PWID. Surgery conferred no long-term survival advantage. More efforts are needed to reduce reinfection risk following an episode of IE in PWID.While early survival for people who inject drugs (PWID) with infective endocarditis is good, long-term survival is poor due to ongoing infection risk. Surgery conferred no long-term survival advantage, so more efforts are needed to reduce reinfection risks for PWID.

MicroRNA-21 drives the switch to a synthetic phenotype in human saphenous vein smooth muscle cells.

Cardiovascular disease is a leading cause of morbidity and mortality. Smooth muscle cells (SMC) comprising the vascular wall can switch phenotypes from contractile to synthetic, which can promote the development of aberrant remodelling and intimal hyperplasia (IH). MicroRNA-21 (miR-21) is a short, non-coding RNA that has been implicated in cardiovascular diseases including proliferative vascular disease and ischaemic heart disease. However, its involvement in the complex development of atherosclerosis has yet to be ascertained. Smooth muscle cells (SMC) were isolated from human saphenous veins (SV). miR-21 was over-expressed and the impact of this on morphology, proliferation, gene and protein expression related to synthetic SMC phenotypes monitored. Over-expression of miR-21 increased the spread cell area and proliferative capacity of SV-SMC and expression of MMP-1, whilst reducing RECK protein, indicating a switch to the synthetic phenotype. Furthermore, platelet-derived growth factor BB (PDGF-BB; a growth factor implicated in vasculoproliferative conditions) was able to induce miR-21 expression via the PI3K and ERK signalling pathways. This study has revealed a mechanism whereby PDGF-BB induces expression of miR-21 in SV-SMC, subsequently driving conversion to a synthetic SMC phenotype, propagating the development of IH. Thus, these signaling pathways may be attractive therapeutic targets to minimise progression of the disease. © 2018 IUBMB Life, 70(7):649-657, 2018.

Spontaneous Hemothorax Following Cardiac Surgery.

We report a case of spontaneous hemothorax after aortic valve replacement in a 72-year-old female resulting from rupture of a pleural adhesion leading to hemodynamic instability. doi: 10.1111/jocs.12729 (J Card Surg 2016;31:211-213).

Elevated expression levels of miR-143/5 in saphenous vein smooth muscle cells from patients with Type 2 diabetes drive persistent changes in phenotype and function.

Type 2 diabetes (T2DM) promotes premature atherosclerosis and inferior prognosis after arterial reconstruction. Vascular smooth muscle cells (SMC) respond to patho/physiological stimuli, switching between quiescent contractile and activated synthetic phenotypes under the control of microRNAs (miRs) that regulate multiple genes critical to SMC plasticity. The importance of miRs to SMC function specifically in T2DM is unknown. This study was performed to evaluate phenotype and function in SMC cultured from non-diabetic and T2DM patients, to explore any aberrancies and investigate underlying mechanisms. Saphenous vein SMC cultured from T2DM patients (T2DM-SMC) exhibited increased spread cell area, disorganised cytoskeleton and impaired proliferation relative to cells from non-diabetic patients (ND-SMC), accompanied by a persistent, selective up-regulation of miR-143 and miR-145. Transfection of premiR-143/145 into ND-SMC induced morphological and functional characteristics similar to native T2DM-SMC; modulating miR-143/145 targets Kruppel-like factor 4, alpha smooth muscle actin and myosin VI. Conversely, transfection of antimiR-143/145 into T2DM-SMC conferred characteristics of the ND phenotype. Exposure of ND-SMC to transforming growth factor beta (TGFß) induced a diabetes-like phenotype; elevated miR-143/145, increased cell area and reduced proliferation. Furthermore, these effects were dependent on miR-143/145. In conclusion, aberrant expression of miR-143/145 induces a distinct saphenous vein SMC phenotype that may contribute to vascular complications in patients with T2DM, and is potentially amenable to therapeutic manipulation.

p38 MAPK alpha mediates cytokine-induced IL-6 and MMP-3 expression in human cardiac fibroblasts.

Pre-clinical studies suggest that the p38 MAPK signaling pathway plays a detrimental role in cardiac remodeling, but its role in cardiac fibroblast (CF) function is not well defined. We aimed to identify the p38 MAPK subtypes expressed by human CF, study their activation in response to proinflammatory cytokines, and determine which subtypes were important for expression of specific cytokines and matrix metalloproteinases (MMPs). Quantitative real-time RT-PCR analysis of mRNA levels in human CF cultured from multiple patients revealed a consistent pattern of expression with p38α being most abundant, followed by p38γ, then p38δ and only low expression of p38ß (3% of p38α mRNA levels). Immunoblotting confirmed marked protein expression of p38α, γ and δ, with little or no expression of p38ß. Phospho-ELISA and combined immunoprecipitation/immunoblotting techniques demonstrated that the proinflammatory cytokines IL-1α and TNFα selectively activated p38α and p38γ, but not p38δ. Selective p38α siRNA gene silencing reduced IL-1α-induced IL-6 and MMP-3 mRNA expression and protein secretion, without affecting IL-1α-induced IL-1ß and MMP-9 mRNA expression. In conclusion, human CF express the α, γ and δ subtypes of p38 MAPK, and the α subtype is important for IL-1α-induced IL-6 and MMP-3 expression in this cell type.

MMP-3 (5A/6A) polymorphism does not influence human smooth muscle cell invasion.

BACKGROUND: Stromelysin (MMP-3) is an important regulator of vascular smooth muscle cell (SMC) invasion, a key contributor to saphenous vein (SV) bypass graft failure. The 5A allele of the common -1612 MMP-3 5A/6A promoter polymorphism reportedly confers increased promoter activity, MMP-3 tissue expression, and susceptibility to a number of vascular pathologies. The aim of this study was to determine whether the MMP-3 5A/6A polymorphism directly influences endogenous MMP-3 expression levels and, consequently, cell invasion, in SV-derived SMC cultured from patients with different genotypes. MATERIAL AND METHODS: Genotyping of 226 patients revealed -1612 MMP-3 5A/6A genotype frequencies of 20.8% 5A/5A, 52.7% 5A/6A, and 26.5% 6A/6A. Using a standardized, controlled protocol, we investigated cytokine- and growth factor-induced MMP-3 expression (real-time polymerase chain reaction [RT-PCR], ELISA) and SV-SMC invasion (Boyden chamber with Matrigel barrier) using cultured SV-SMC from patients with different MMP-3 genotypes. RESULTS: Despite observing a strong correlation between MMP-3 mRNA levels and MMP-3 protein secretion, no significant differences were apparent in MMP-3 expression levels or cell invasion between cells with different MMP-3 5A/6A genotypes. CONCLUSIONS: Our data suggest that the MMP-3 5A/6A promoter polymorphism in isolation does not influence levels of MMP-3 secretion or cellular invasion in human SV-SMC.

Role of MicroRNA-145 in DNA Damage Signalling and Senescence in Vascular Smooth Muscle Cells of Type 2 Diabetic Patients.

Increased cardiovascular morbidity and mortality in individuals with type 2 diabetes (T2DM) is a significant clinical problem. Despite advancements in achieving good glycaemic control, this patient population remains susceptible to macrovascular complications. We previously discovered that vascular smooth muscle cells (SMC) cultured from T2DM patients exhibit persistent phenotypic aberrancies distinct from those of individuals without a diagnosis of T2DM. Notably, persistently elevated expression levels of microRNA-145 co-exist with characteristics consistent with aging, DNA damage and senescence. We hypothesised that increased expression of microRNA-145 plays a functional role in DNA damage signalling and subsequent cellular senescence specifically in SMC cultured from the vasculature of T2DM patients. In this study, markers of DNA damage and senescence were unambiguously and permanently elevated in native T2DM versus non-diabetic (ND)-SMC. Exposure of ND cells to the DNA-damaging agent etoposide inflicted a senescent phenotype, increased expression of apical kinases of the DNA damage pathway and elevated expression levels of microRNA-145. Overexpression of microRNA-145 in ND-SMC revealed evidence of functional links between them; notably increased secretion of senescence-associated cytokines and chronic activation of stress-activated intracellular signalling pathways, particularly the mitogen-activated protein kinase, p38α. Exposure to conditioned media from microRNA-145 overexpressing cells resulted in chronic p38α signalling in naïve cells, evidencing a paracrine induction and reinforcement of cell senescence. We conclude that targeting of microRNA-145 may provide a route to novel interventions to eliminate DNA-damaged and senescent cells in the vasculature and to this end further detailed studies are warranted.

Chronic hypoxia inhibits MMP-2 activation and cellular invasion in human cardiac myofibroblasts.

Cardiac myofibroblasts are pivotal to adaptive remodelling after myocardial infarction (MI). These normally quiescent cells invade and proliferate as a wound healing response, facilitated by activation of matrix metalloproteinases, particularly MMP-2. Following MI these reparative events occur under chronically hypoxic conditions yet the mechanisms by which hypoxia might modulate MMP-2 activation and cardiac myofibroblast invasion have not been investigated. Human cardiac myofibroblasts cultured in collagen-supplemented medium were exposed to normoxia (20% O(2)) or hypoxia (1% O(2)) for up to 48 h. Secreted levels of total and active MMP-2 were quantified using gelatin zymography, TIMP-2 and membrane-associated MT1-MMP were quantified with ELISA, whole cell MT1-MMP by immunoblotting and immunocytochemistry and MT1-MMP mRNA with real-time RT-PCR. Cellular invasion was assessed in modified Boyden chambers and migration by scratch wound assay. In the human cardiac myofibroblast, MT1-MMP was central to MMP-2 activation and activated MMP-2 necessary for invasion, confirmed by gene silencing. MMP-2 activation was substantially attenuated by hypoxia (P<0.001), paralleled by inhibition of myofibroblast invasion (P<0.05). In contrast, migration was independent of either MT1-MMP or MMP-2. Reduced membrane expression of MT1-MMP (P<0.05) was responsible for the hypoxic reduction of MMP-2 activation, with no change in either total MMP-2 or TIMP-2. In conclusion, hypoxia reduces MMP-2 activation and subsequent invasion of human cardiac myofibroblasts by reducing membrane expression of MT1-MMP and may delay healing after MI. Regulation of these MMPs remains an attractive target for therapeutic intervention.

Inherent differences in morphology, proliferation, and migration in saphenous vein smooth muscle cells cultured from nondiabetic and Type 2 diabetic patients.

Individuals with Type 2 diabetes mellitus (T2DM) are at increased risk of saphenous vein (SV) graft stenosis following coronary artery bypass. Graft stenosis is caused by intimal hyperplasia, a pathology characterized by smooth muscle cell (SMC) proliferation and migration. We hypothesized that SV-SMC from T2DM patients were intrinsically more proliferative and migratory than those from nondiabetic individuals. SV-SMC were cultured from nondiabetic and T2DM patients. Cell morphology (light microscopy, immunocytochemistry), S100A4 expression (real-time RT-PCR, immunoblotting), proliferation (cell counting), migration (Boyden chamber assay), and cell signaling (immunoblotting with phosphorylation state-specific antibodies) were studied. SV-SMC from T2DM patients were morphologically distinct from nondiabetic patients and exhibited a predominantly rhomboid phenotype, accompanied by disrupted F-actin cytoskeleton, disorganized alpha-smooth muscle actin network, and increased focal adhesion formation. However, no differences were observed in expression of the calcium-binding protein S100A4, a marker of rhomboid SMC phenotype, between the two cell populations. T2DM cells were less proliferative in response to fetal calf serum than nondiabetic cells, but both populations had similar proliferative responses to insulin plus PDGF. Under high glucose concentration conditions in the presence of insulin, migration of diabetic SV-SMC was greater than nondiabetic cells. Glucose concentration did not affect SV-SMC proliferation. No differences in insulin or PDGF-induced phosphorylation of ERK-1/2 or components of the Akt pathway (Akt-Ser473, Akt-Thr308, and GSK-3beta) were apparent between the two populations. In conclusion, SV-SMC from T2DM patients differ from nondiabetic SV-SMC in that they exhibit a rhomboid phenotype and are more migratory, but less proliferative, in response to serum.

Interleukin-1alpha stimulates proinflammatory cytokine expression in human cardiac myofibroblasts.

Cardiac myofibroblasts (CMF) play a key role in infarct repair and scar formation following myocardial infarction (MI) and are also an important source of proinflammatory cytokines. We postulated that interleukin-1alpha (IL-1alpha), a potential early trigger of acute inflammation post-MI, could stimulate human CMF to express additional proinflammatory cytokines. Furthermore, we hypothesized that these effects may be modulated by the anti-inflammatory cytokine interleukin-10 (IL-10). Human CMF were cultured from atrial biopsies from multiple patients. Interleukin-1beta (IL-1beta), tumor necrosis factor-alpha (TNF-alpha), interleukin-6 (IL-6), and cardiotrophin-1 (CT-1) mRNA expression and secretion were measured using quantitative real-time RT-PCR and enzyme-linked immunosorbent assay. IL-1alpha (0.001-10 ng/ml, 0-6 h) stimulated IL-1beta, TNF-alpha, and IL-6 mRNA expression with distinct temporal and concentration profiles, resulting in increased cytokine secretion. The response to IL-1alpha was much greater than with TNF-alpha. Neither IL-1alpha nor TNF-alpha treatment modulated CT-1 mRNA expression. Immunoblotting with phosphospecific antibodies revealed that IL-1alpha stimulated the extracellular signal-regulated kinase (ERK)-1/2, p38 mitogen-activated protein kinase (MAPK), c-Jun NH(2)-terminal kinase (JNK), phosphatidylinositol 3-kinase (PI 3-kinase)/protein kinase B (Akt), and nuclear factor (NF)-kappaB signaling pathways. Pharmacological inhibitor studies indicated roles for PI 3-kinase/Akt and NF-kappaB pathways in mediating IL-1beta expression, and for NF-kappaB and p38 MAPK pathways in mediating TNF-alpha expression. IL-1alpha-induced IL-6 mRNA expression was reduced by p38 MAPK inhibition, but increased by ERK and JNK pathway inhibitors. IL-10 produced a consistent but modest reduction in IL-1alpha-induced IL-6 mRNA levels (not IL-1beta or TNF-alpha), but this was not reflected by reduced IL-6 protein secretion. In conclusion, IL-1alpha stimulates human CMF to express IL-1beta, TNF-alpha, and IL-6 via specific signaling pathways, responses that are unaffected by IL-10 exposure.

Peroxisome proliferator-activated receptor gamma-independent effects of thiazolidinediones on human cardiac myofibroblast function.

1. Thiazolidinediones (TZDs) are peroxisome proliferator-activated receptor (PPAR) gamma agonists that are used to lower insulin resistance in Type 2 diabetic patients. Although TZDs exhibit beneficial effects on the vasculature, their effects on the heart are less clear and are the subject of current clinical debate. Thiazolidinediones have been reported to reduce adverse myocardial remodelling, a pathology in which cardiac myofibroblasts (CMF) are pivotal. 2. The aim of the present study was to investigate whether TZDs modulate specific human CMF functions of importance to the myocardial remodelling process and to determine whether any of these effects were mediated via PPARgamma activation. 3. Immunoblotting of cultured human CMF homogenates revealed strong expression of PPARgamma (approximately 50 kDa). Three different TZDs (ciglitazone, rosiglitazone and troglitazone) and the endogenous PPARgamma ligand 15-deoxy-delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) inhibited CMF proliferation (cell number and expression of proliferating cell nuclear antigen) in a concentration-dependent manner (range 0.1-10 micromol/L) with similar potencies. This antiproliferative effect of TZDs was not reversed by the PPARgamma antagonists GW9662 or T0070907 (10-25 micromol/L). None of the TZDs or 15d-PGJ(2) affected cell migration or invasion (Boyden chamber assays without or with Matrigel barrier), matrix metalloproteinase-2 or -9 secretion (gelatin zymography) or the actin cytoskeleton (rhodamine/phalloidin fluorescent confocal microscopy). 4. In conclusion, TZDs reduce human CMF proliferation via a PPARgamma-independent mechanism. Although TZDs do not inhibit CMF invasion, their antiproliferative activity may contribute to the ability of this class of drugs to modulate adverse myocardial remodelling.

Mechanism of TNFalpha-induced IL-1alpha, IL-1beta and IL-6 expression in human cardiac fibroblasts: effects of statins and thiazolidinediones.

OBJECTIVE: In addition to direct effects on myocardial cell function, tumor necrosis factor alpha (TNFalpha) contributes to adverse cardiac remodeling by increasing production of other pro-inflammatory cytokines [e.g. interleukin (IL)-1 and IL-6]. Both statins and thiazolidinediones (TZDs) have beneficial effects on cardiac remodeling, possibly due to their anti-inflammatory properties. The present study examined the mechanisms by which TNFalpha stimulates expression of pro-inflammatory cytokines in cultured human cardiac fibroblasts and determined the effects of statin or TZD treatment. METHODS: Human cardiac fibroblasts were cultured from biopsies of right atrial appendages. Cytokine mRNA expression and secretion was measured using quantitative real-time RT-PCR and ELISA. Activation of signaling pathways was determined by immunoblotting with phospho-specific antibodies. RESULTS: TNFalpha (0.1-10 ng/ml) stimulated IL-6, IL-1alpha and IL-1beta mRNA expression in cardiac fibroblasts in a concentration-dependent manner. Pharmacological inhibitors and receptor-neutralizing antibodies established that both TNFalpha-induced IL-6 and IL-1beta expression was mediated via the TNFRI receptor and p38 mitogen-activated protein kinase (MAPK), phosphoinositide 3-kinase (PI3K)/Akt and nuclear factor (NF)-kappaB pathways. In contrast, TNFalpha-induced IL-1alpha expression required both TNFRI and TNFRII subtypes and p38 MAPK and PI3K/Akt pathways, but was negatively regulated by the NF-kappaB pathway. Neither statins (simvastatin, fluvastatin) nor TZDs (ciglitazone, rosiglitazone, troglitazone) had inhibitory effects on TNFalpha-induced IL-6 secretion or IL-1alpha/beta mRNA expression; indeed, cytokine expression was increased in response to TZDs. CONCLUSIONS: Our data provide important insights into the regulation of pro-inflammatory cytokine expression in human cardiac fibroblasts and suggest that the myocardial anti-inflammatory effects of statins and TZDs are not due to inhibition of TNFalpha-induced IL-1 or IL-6 expression by cardiac fibroblasts.

Mapping the methylation status of the miR-145 promoter in saphenous vein smooth muscle cells from individuals with type 2 diabetes.

Type 2 diabetes mellitus prevalence is growing globally, and the leading cause of mortality in these patients is cardiovascular disease. Epigenetic mechanisms such as microRNAs (miRs) and DNA methylation may contribute to complications of type 2 diabetes mellitus. We discovered an aberrant type 2 diabetes mellitus-smooth muscle cell phenotype driven by persistent up-regulation of miR-145. This study aimed to determine whether elevated expression was due to changes in methylation at the miR-145 promoter. Smooth muscle cells were cultured from saphenous veins of 22 non-diabetic and 22 type 2 diabetes mellitus donors. DNA was extracted, bisulphite treated and pyrosequencing used to interrogate methylation at 11 CpG sites within the miR-145 promoter. Inter-patient variation was high irrespective of type 2 diabetes mellitus. Differential methylation trends were apparent between non-diabetic and type 2 diabetes mellitus-smooth muscle cells at most sites but were not statistically significant. Methylation at CpGs -112 and -106 was consistently lower than all other sites explored in non-diabetic and type 2 diabetes mellitus-smooth muscle cells. Finally, miR-145 expression per se was not correlated with methylation levels observed at any site. The persistent up-regulation of miR-145 observed in type 2 diabetes mellitus-smooth muscle cells is not related to methylation at the miR-145 promoter. Crucially, miR-145 methylation is highly variable between patients, serving as a cautionary note for future studies of this region in primary human cell types.

Simvastatin inhibits MMP-9 secretion from human saphenous vein smooth muscle cells by inhibiting the RhoA/ROCK pathway and reducing MMP-9 mRNA levels.

Increased matrix metalloproteinase-9 (MMP-9) expression is associated with intimal hyperplasia in saphenous vein (SV) bypass grafts. Recent evidence suggests that HMG-CoA reductase inhibitors (statins) can prevent the progression of vein graft failure. Here we investigated whether statins inhibited MMP-9 secretion from cultured human SV smooth muscle cells (SMC) and examined the underlying mechanisms. SV-SMC from different patients were exposed to phorbol ester (TPA) or PDGF-BB plus interleukin-1alpha (IL-1). MMP-9 secretion and mRNA expression were analyzed using gelatin zymography and RT-PCR, respectively. Specific signal transduction pathways were investigated by immunoblotting and pharmacological inhibition. Simvastatin reduced TPA- and PDGF/IL-1-induced MMP-9 secretion and mRNA levels, effects reversed by geranylgeranyl pyrophosphate and mimicked by inhibiting Rho geranylgeranylation or Rho-kinase (ROCK). MMP-9 secretion induced by PDGF/IL-1 was mediated via the ERK, p38 MAPK, and NFkappaB pathways, whereas that induced by TPA was mediated specifically via the ERK pathway. Simvastatin failed to inhibit activation of these signaling pathways. Moreover, simvastatin did not affect MMP-9 mRNA stability. Together these data suggest that simvastatin reduces MMP-9 secretion from human SV-SMC by inhibiting the RhoA/ROCK pathway and decreasing MMP-9 mRNA levels independently of effects on signaling pathways required for MMP-9 gene expression.

Tumor necrosis factor alpha induces human atrial myofibroblast proliferation, invasion and MMP-9 secretion: inhibition by simvastatin.

OBJECTIVE: Tumor necrosis factor alpha (TNFalpha) is implicated in myocardial remodeling, a process in which activated cardiac fibroblasts (myofibroblasts) secrete matrix-degrading metalloproteinases (MMPs) and undergo increased proliferation and invasion. Statins are cholesterol-lowering drugs that also have direct cellular effects, which may underlie their ability to reduce myocardial remodeling. This study investigated the effect of TNFalpha on human cardiac myofibroblast proliferation, invasion and MMP-9 secretion, and determined whether these properties were modulated by simvastatin. METHODS: Human cardiac myofibroblasts were cultured from right atrial appendage. TNF receptor expression was quantified by immunoblotting. Cell proliferation, invasion, MMP-9 secretion and MMP-9 mRNA expression were determined by cell counting, Matrigel-coated modified Boyden chamber assays, gelatin zymography and RT-PCR, respectively. RESULTS: Human atrial myofibroblasts expressed the TNF-RI and TNF-RII receptor subtypes. TNFalpha (1 ng/ml) induced a 23.1+/-3.9% increase in cell number after 4 days (P<0.001). Additionally, TNFalpha (1-10 ng/ml) significantly (P<0.01) increased myofibroblast invasion, with a concomitant increase in MMP-9 secretion, that was due to increased MMP-9 mRNA levels. Using TNF-R-specific neutralizing antibodies, we determined that these cellular effects of TNFalpha were predominantly TNF-RI-mediated. Simvastatin (0.1-10 mumol/l) concentration dependently inhibited TNFalpha-induced myofibroblast proliferation, invasion and MMP-9 secretion. CONCLUSIONS: TNFalpha, acting predominantly via the TNF-R1 receptor, increased human atrial myofibroblast proliferation, invasion and MMP-9 secretion, all of which were inhibited by simvastatin. Inhibition of cytokine-induced cardiac myofibroblast activation by statins provides a rationale for their use in patients with cardiac pathologies characterized by adverse myocardial remodeling.

Simvastatin reduces human atrial myofibroblast proliferation independently of cholesterol lowering via inhibition of RhoA.

OBJECTIVE: Adverse atrial and ventricular myocardial remodeling is characterized by fibrosis, myocyte death or hypertrophy and fibroblast proliferation. HMG-CoA reductase inhibitors (statins) are widely prescribed cholesterol-lowering drugs that also appear to have beneficial effects on myocardial remodeling. Although statins are known to reduce myocyte hypertrophy, their effect on cardiac fibroblast proliferation is unknown. The purpose of this study was to investigate the effects of simvastatin on human atrial myofibroblast proliferation. METHODS: Cardiac myofibroblasts were cultured from biopsies of human right atrial appendage. Proliferation was quantified by cell counting and cell cycle progression determined by immunoblotting for Cyclin A. The expression, activation and intracellular localization of RhoA were investigated using immunoblotting and immunocytochemistry. RESULTS: Simvastatin (0.1-1.0 micromol/l) inhibited serum-induced myofibroblast proliferation in a concentration-dependent manner at a point upstream of Cyclin A expression. These effects were reversed by mevalonate or geranylgeranyl pyrophosphate (GGPP), but not squalene or farnesyl pyrophosphate (FPP), indicating a mechanism involving inhibition of Rho-family GTPases and independent of cholesterol synthesis. The effects of simvastatin were mimicked by inhibiting Rho geranylgeranylation or Rho-kinase activation. Furthermore, we demonstrated that simvastatin inhibited RhoA function by preventing its association with the plasma membrane and hence, its interaction with downstream effectors required for cell proliferation. CONCLUSIONS: Simvastatin reduced proliferation of cultured human atrial myofibroblasts independently of cholesterol synthesis via a mechanism involving inhibition of RhoA geranylgeranylation. Statins may therefore have an important role in preventing adverse myocardial remodeling associated with cardiac myofibroblast proliferation.

Aberrant phenotype in human endothelial cells of diabetic origin: implications for saphenous vein graft failure?

Type 2 diabetes (T2DM) confers increased risk of endothelial dysfunction, coronary heart disease, and vulnerability to vein graft failure after bypass grafting, despite glycaemic control. This study explored the concept that endothelial cells (EC) cultured from T2DM and nondiabetic (ND) patients are phenotypically and functionally distinct. Cultured human saphenous vein- (SV-) EC were compared between T2DM and ND patients in parallel. Proliferation, migration, and in vitro angiogenesis assays were performed; western blotting was used to quantify phosphorylation of Akt, ERK, and eNOS. The ability of diabetic stimuli (hyperglycaemia, TNF-α, and palmitate) to modulate angiogenic potential of ND-EC was also explored. T2DM-EC displayed reduced migration (~30%) and angiogenesis (~40%) compared with ND-EC and a modest, nonsignificant trend to reduced proliferation. Significant inhibition of Akt and eNOS, but not ERK phosphorylation, was observed in T2DM cells. Hyperglycaemia did not modify ND-EC function, but TNF-α and palmitate significantly reduced angiogenic capacity (by 27% and 43%, resp.), effects mimicked by Akt inhibition. Aberrancies of EC function may help to explain the increased risk of SV graft failure in T2DM patients. This study highlights the importance of other potentially contributing factors in addition to hyperglycaemia that may inflict injury and long-term dysfunction to the homeostatic capacity of the endothelium.

Endothelin-1 is an essential co-factor for beta2-adrenergic receptor-induced proliferation of human cardiac fibroblasts.

We previously demonstrated that chronic stimulation of the beta2-adrenergic receptor (beta2-AR) increases proliferation of cultured human cardiac fibroblasts (CF) via an autocrine mechanism. Here, we investigated the role of endothelin-1 (ET-1) in this process. ETA-receptor antagonism or protein kinase C inhibition abolished the beta2-AR-induced increase in cell proliferation. RT-PCR and ELISA analysis demonstrated that although CF synthesized and secreted ET-1, this occurred independently of beta2-AR stimulation. Furthermore, despite activation of the MAP kinase pathway, ET-1 treatment did not stimulate CF proliferation. Therefore, the role of ET-1 in this process is that of an essential co-factor acting independently of beta2-AR stimulation.

15 deoxy delta12,14 PGJ2 induces procoagulant activity in cultured human endothelial cells.

15 deoxy delta12,14 PGJ2 (15d-PGJ2), a high affinity ligand of peroxisome proliferator-activated receptor gamma (PPARgamma) has been proposed to act as a negative feedback regulator of the inflammatory response. We investigated the effect of 15d-PGJ2 on the anticoagulant property of endothelial cells. 15d-PGJ2 stimulated a moderate but sustained increase in tissue factor (TF) activity in HUVECs and EA.hy926 cells while causing a partial loss of thrombomodulin (TM) activity. When cells were co-treated with 15d-PGJ2 and TNF-alpha, the subsequent elevation of TF activity was synergistically increased over that of cells treated with TNF-alpha alone and the decline of TF activity after 24 h was less marked than TNF-alpha alone. The induction of TF by 15d-PGJ2 alone and in combination with TNF-alpha was reduced in the presence of PD 98059, suggesting the participation of the MEK/ERK pathway. The thiazolidinedione PPARgamma agonist ciglitazone had no effect on TF levels but reduced the expression of endothelial protein C receptor. The ability of 15d-PGJ2 to enhance a procoagulant phenotype arising from TNF-alpha suggests a pro-inflammatory role for the prostaglandin.

Type 2 diabetes impairs venous, but not arterial smooth muscle cell function: possible role of differential RhoA activity.

BACKGROUND/PURPOSE: Coronary heart disease is the leading cause of morbidity in patients with type 2 diabetes mellitus (T2DM), frequently resulting in a requirement for coronary revascularization using the internal mammary artery (IMA) or saphenous vein (SV). Patency rates of SV grafts are inferior to IMA and further impaired by T2DM whilst IMA patencies appear similar in both populations. Smooth muscle cells (SMC) play a pivotal role in graft integration; we therefore examined the phenotype and proliferative function of IMA- and SV-SMC isolated from non-diabetic (ND) patients or those diagnosed with T2DM. METHODS/MATERIALS: SMC were cultured from fragments of SV or IMA. Morphology was analyzed under light microscopy (spread cell area measurements) and confocal microscopy (F-actin staining). Proliferation was analyzed by cell counting. Levels of RhoA mRNA, protein and activity were measured by real-time RT-PCR, western blotting and G-LISA respectively. RESULTS: IMA-SMC from T2DM and ND patients were indistinguishable in both morphology and function. By comparison, SV-SMC from T2DM patients exhibited significantly larger spread cell areas (1.5-fold increase, P<0.05), truncated F-actin fibers and reduced proliferation (33% reduction, P<0.05). Furthermore, lower expression and activity of RhoA were observed in SV-SMC of T2DM patients (37% reduction in expression, P<0.05 and 43% reduction in activity, P<0.01). CONCLUSIONS: IMA-SMC appear impervious to phenotypic modulation by T2DM. In contrast, SV-SMC from T2DM patients exhibit phenotypic and functional changes accompanied by reduced RhoA activity. These aberrancies may be epigenetic in nature, compromising SMC plasticity and SV graft adaptation in T2DM patients. SUMMARY: The internal mammary artery (IMA) is the conduit of choice for bypass grafting and is generally successful in all patients, including those with type 2 diabetes (T2DM). By contrast, saphenous vein (SV) is inferior to IMA and furthermore patients with T2DM suffer strikingly poorer outcomes than their non-diabetic (ND) counterparts. We discovered that SV-SMC from T2DM patients exhibit altered persistent morphology and function compared to ND SV-SMC, with differential expression and activity of the small GTPase RhoA, yet ND and T2DM IMA-SMC were indistinguishable. These data offer an explanation for the superior patency of IMA grafting independent of the presence of diabetes.