ERK contributes to the effects of Smad signaling on oxidized LDL-induced PAI-1 expression in human mesangial cells

Individual variations in cardiovascular-disease-related protein levels are driven by genetics and gut microbiome

Despite a growing body of evidence, the role of the gut microbiome in cardiovascular diseases (CVDs) is still unclear. Here we present a systems-genome-wide and metagenome-wide association study on plasma concentrations of 92 CVD-related proteins in the population cohort Lifelines-DEEP. We identified genetic components for 73 proteins and microbial associations for 41 proteins, of which 31 were associated to both. The genetic and microbial factors identified mostly exert additive effects and collectively explain up to 76.6% of inter-individual variation (17.5% on average). Genetics contributes most to concentrations of immune-related proteins, while the gut microbiome contributes most to proteins involved in metabolism and intestinal health. We found several host-microbe interactions that impact proteins involved in epithelial function, lipid metabolism and central nervous system function. This study reveals important evidence for a joint genetic and microbial effect in cardiovascular disease and provides directions for future applications in personalized medicine.

Protective effect of rosuvastatin treatment by regulating oxidized low-density lipoprotein expression in a rat model of liver fibrosis

The present study aimed to evaluate the protective effect of rosuvastatin treatment on the mechanism of oxidized low-density lipoprotein (Ox-LDL) in rats with liver fibrosis. In total, 72 male Sprague-Dawley rats were divided into 3 groups: 24 in the control group (A), 24 in the obstructive jaundice models group (B) and 24 in the rosuvastatin group (C). Each group was further divided into four subgroups for assessment at different time-points. The obstructive jaundice models were established and rosuvastatin was administered by gavage. Liver fibrosis indicators, Ox-LDL, malonaldehyde (MDA) and superoxide dismutase (SOD), were measured and liver pathological changes were observed at weeks 1, 2, 3 and 4 after model induction. In groups B and C, the rat models were successfully established, and there were significant changes in the expression of Ox-LDL and the three liver fibrosis indicators when compared to group A (P<0.01). However, the expression of Ox-LDL and the three liver fibrosis indicators in group C were decreased compared with group B (P<0.05), while SOD increased (P<0.05) and MDA decreased (P<0.05). The three liver fibrosis indicators were different in comparison to group B (P<0.05). Thus, there appeared to be an association between the expression of Ox-LDL and liver fibrosis. Treatment with rosuvastatin could regulate the expression of Ox-LDL and improve liver fibrosis in rat models with obstructive jaundice.

TGRL Lipolysis Products Induce Stress Protein ATF3 via the TGF-β Receptor Pathway in Human Aortic Endothelial Cells

Studies have suggested a link between the transforming growth factor beta 1 (TGF-β1) signaling cascade and the stress-inducible activating transcription factor 3 (ATF3). We have demonstrated that triglyceride-rich lipoproteins (TGRL) lipolysis products activate MAP kinase stress associated JNK/c-Jun pathways resulting in up-regulation of ATF3, pro-inflammatory genes and induction of apoptosis in human aortic endothelial cells. Here we demonstrate increased release of active TGF-β at 15 min, phosphorylation of Smad2 and translocation of co-Smad4 from cytosol to nucleus after a 1.5 h treatment with lipolysis products. Activation and translocation of Smad2 and 4 was blocked by addition of SB431542 (10 μM), a specific inhibitor of TGF-β-activin receptor ALKs 4, 5, 7. Both ALK receptor inhibition and anti TGF-β1 antibody prevented lipolysis product induced up-regulation of ATF3 mRNA and protein. ALK inhibition prevented lipolysis product-induced nuclear accumulation of ATF3. ALKs 4, 5, 7 inhibition also prevented phosphorylation of c-Jun and TGRL lipolysis product-induced p53 and caspase-3 protein expression. These findings demonstrate that TGRL lipolysis products cause release of active TGF-β and lipolysis product-induced apoptosis is dependent on TGF-β signaling. Furthermore, signaling through the stress associated JNK/c-Jun pathway is dependent on TGF-β signaling suggesting that TGF-β signaling is necessary for nuclear accumulation of the ATF3/cJun transcription complex and induction of pro-inflammatory responses.

Treatment with rosuvastatin calcium improves liver fibrosis in a rat model of chronic obstructive jaundice

AIM: To investigate the effect of treatment with rosuvastatin calcium on expression of Ox-LDL and liver fibrosis in a rat model of chronic obstructive jaundice.

METHODS: Ninety Sprague-Dawley rats were randomly and equally divided into three groups: control group, and chronic obstructive jaundice group, and rosuvastatin calcium group. Each group was further divided into five subgroups for testing at different time points. Liver function was determined. Expression of Ox-LDL was tested by immunofluorescence, and liver fibrosis was assessed by radioimmunoassay. Pathological changes in liver tissue were observed by optical microscopy at weeks 1, 2, 3, 4, and 5 after model induction. Choledochoduodenostomy was performed at week 4.

RESULTS: Rats with chronic obstructive jaundice showed remarkable jaundice and obvious degeneration and hyperplasia of liver cells. There were also significant changes in expression of Ox-LDL and three liver fibrosis indicators. Jaundice slowly subsided after choledochoduodenostomy. Total bilirubin, expression of Ox-LDL and three liver fibrosis indicators differed significantly at different time points between the chronic obstructive jaundice group and rosuvastatin calcium group (all P < 0.05).

CONCLUSION: There was a significant relation between expression of Ox-LDL and liver fibrosis in rats with chronic obstructive jaundice. Treatment with rosuvastatin calcium could regulate the expression of Ox-LDL and improve liver fibrosis in rats with chronic obstructive jaundice.

Losartan, a therapeutic candidate in congenital muscular dystrophy: studies in the dy(2J) /dy(2J) mouse

OBJECTIVE

Lamininα2-deficient congenital muscular dystrophy type 1A (MDC1A) is a cureless disease associated with severe disability and shortened lifespan. Previous studies have shown reduced fibrosis and restored skeletal muscle remodeling following treatment with losartan, an angiotensin II type I receptor blocker. We therefore evaluated the effect of losartan treatment in the dy(2J) /dy(2J) mouse model of MDC1A.

METHODS

Homozygous dy(2J) /dy(2J) and control mice were treated with losartan or placebo for 12 weeks from 6 weeks of age. Outcome measures included hindlimb and forelimb muscle strength by Grip Strength Meter and quantitative muscle fibrosis parameters. Losartan's effects on transforming growth factor β (TGF-β) and mitogen-activated protein kinase (MAPK) signaling pathways were evaluated with Western blotting, immunofluorescence, and cytokine measurements.

RESULTS

Losartan treatment was associated with significant impressive improvement in muscle strength and amelioration of fibrosis. Administration of losartan inhibited TGF-β signaling pathway, resulting in decreased serum TGF-β1 level and reduced downstream phosphorylated (P) Smad2/3 proteins. Moreover, losartan activated Smad7 protein, a key negative regulator of TGF-β signaling. In addition, losartan treatment inhibited the MAPK cascade as shown by decreased expression of P-p38 MAPK, P-c-jun-N-terminal kinase, and P-extracellular signal-regulated kinases 1 and 2 in the treated mice.

INTERPRETATION

Losartan, a commonly prescribed US Food and Drug Administration-approved medication for hypertension, demonstrated clinical improvement and amelioration of fibrosis in the dy(2J) /dy(2J) mouse model of MDC1A via TGF-β and MAPK signaling pathways. The results of this study support pursuing a clinical trial of losartan treatment in children with MDC1A.

Therapeutic potential and anti-amyloidosis mechanisms of tert-butylhydroquinone for Alzheimer's disease

Alzheimer's disease (AD) is a major cause of dementia in the elderly with no effective treatment. Accumulation of amyloid-β peptide (Aβ) in the brain, one of the pathological features of AD, is considered to be a central disease-causing and disease-promoting event in AD. In this study, we showed that feeding male AβPP/PS1 transgenic mice, a well established mouse model of AD, with a diet containing phenolic antioxidant tert-butylhydroquinone (TBHQ) dramatically reduced brain Aβ load with no significant effect on the amounts of alpha- and beta-C-terminal fragments or full-length AβPP. Further studies showed that TBHQ diet inhibited the expression of plasminogen activator inhibitor-1 (PAI-1), a protease inhibitor which plays a critical role in brain Aβ accumulation in AD, accompanied by increases in the activities of tissue type and urokinase type plasminogen activators (tPA and uPA) as well as plasmin. Moreover, we showed that TBHQ diet increased the expression of low density lipoprotein related protein-1, a multi ligand endocytotic receptor involved in transporting Aβ out of the brain, and plasma Aβ(40) and Aβ(42) levels. We also showed that TBHQ diet increased the concentration of glutathione, an important antioxidant, and suppressed the expression of NADPH oxidase 2 as well as lipid peroxidation. Collectively, our data suggest that TBHQ may have therapeutic potential for AD by increasing brain antioxidant capacity/reducing oxidative stress level and by stimulating Aβ degradation/clearance pathways.

Salvianolic Acid B Inhibits ERK and p38 MAPK Signaling in TGF-β1-Stimulated Human Hepatic Stellate Cell Line (LX-2) via Distinct Pathways

Salvianolic acid B (SA-B) is water-soluble component of Radix Salvia miltiorrhiza. The previous work indicated that SA-B can inhibit MAPK and Smad signaling in activated hepatic stellate cells (HSCs) to perform anti-fibrotic activity Lv et al. 2010. However, some studies have shown that there is cross-talk between MAPK and Smad in certain cell types. Thus, the anti-fibrotic action of SA-B may be through the cross-talk. In order to clarify the mechanism of SA-B further, we knocked down Smad in LX-2 cells (SRV4) via RNAi, and then added TGF-β1, and PD98059 or SB203580 and SA-B. The levels of p-MEK and p-p38 were inhibited by SA-B in SRV4 independent of TGF-β1. The expression of Col I and α-SMA in SRV4 could be reduced by SA-B independent TGF-β1. SB203580 had not significant effect on p-MEK in SRV4 stimulated by TGF-β1. The levels of p-MEK in SRV4 were not increased significantly after TGF-β1 stimulation. PD98059 had no effect on the levels of p-p38 in SRV4 irrespective of TGF-β1. In conclusion, SA-B inhibits the synthesis of Col I in LX-2 cells independent of TGF-β1 stimulation, and the anti-fibrotic effect of SA-B is due to direct inhibition of p38 signaling and inhibition the cross-talk of Smad to ERK signaling.

Oxidized LDL and lysophosphatidylcholine stimulate plasminogen activator inhibitor-1 expression through reactive oxygen species generation and ERK1/2 activation in 3T3-L1 adipocytes

Plasminogen activator inhibitor-1 (PAI-1) is secreted from adipose tissue and is considered to be a risk factor for both atherosclerosis and insulin resistance. Here we report for the first time that PAI-1 expression is enhanced by oxidized low-density lipoprotein (OxLDL) and its lipid component lysophosphatidylcholine (LPC) in mouse 3T3-L1 adipocytes. In fully differentiated 3T3-L1 cells, OxLDL treatment increased the mRNA expression and protein secretion of PAI-1 in a dose- and time-dependent manner, whereas native LDL had no effect. The addition of an anti-CD36 antibody suppressed OxLDL-stimulated PAI-1 expression by 50%, suggesting that adipose-derived CD36 contributes to roughly half of the PAI-1 expression stimulated by OxLDL. In addition, pharmacological experiments showed that the OxLDL-stimulated enhancement in PAI-1 expression was mediated through the generation of reactive oxygen species (ROS) and phosphorylation of extracellular signal-regulated kinase 1/2. Furthermore, LPC, a major lipid component of OxLDL, was responsible for the enhanced expression of PAI-1 as phospholipase A(2)-treated acetyl LDL, which generates LPC, strongly stimulated PAI-1 expression, whereas acetyl LDL itself had no such activity. These data demonstrate that the uptake of OxLDL and, in particular, its lipid component LPC into adipocytes triggers aberrant ROS-mediated PAI-1 expression, which may be involved in the pathogenesis of metabolic syndrome.

Transmembrane signaling pathway mediates oxidized low-density lipoprotein-induced expression of plasminogen activator inhibitor-1 in vascular endothelial cells

Atherosclerotic cardiovascular disease is the number one cause of death for adults in Western society. Plasminogen activator inhibitor-1 (PAI-1), the major physiological inhibitor of plasminogen activators, has been implicated in both thrombogenesis and atherogenesis. Previous studies demonstrated that copper-oxidized low-density lipoprotein (C-oLDL) stimulated production of PAI-1 in vascular endothelial cells (EC). The present study examined the involvement of lectin-like oxidized LDL receptor-1 (LOX-1) and Ras/Raf-1/ERK1/2 pathway in the upregulation of PAI-1 in cultured EC induced by oxidized LDLs. The results demonstrated that C-oLDL or FeSO(4)-oxidized LDL (F-oLDL) increased the expression of PAI-1 or LOX-1 in human umbilical vein EC (HUVEC) or coronary artery EC (HCAEC). Treatment with C-oLDL significantly increased the levels of H-Ras mRNA, protein, and the translocation of H-Ras to membrane fraction in EC. LOX-1 blocking antibody, Ras farnesylation inhibitor (FTI-277), or small interference RNA against H-Ras significantly reduced C-oLDL or LDL-induced expression of H-Ras and PAI-1 in EC. Incubation with C-oLDL or F-oLDL increased the phosphorylation of Raf-1 and ERK1/2 in EC compared with LDL or vehicle. Treatment with Raf-1 inhibitor blocked Raf-1 phosphorylation and the elevation of PAI-1 mRNA level in EC induced by C-oLDL or LDL. Treatment with PD-98059, an ERK1/2 inhibitor, blocked C-oLDL or LDL-induced ERK1/2 phosphorylation or PAI-1 expression in EC. The results suggest that LOX-1, H-Ras, and Raf-1/ERK1/2 are implicated in PAI-1 expression induced by oxidized LDLs or LDL in cultured EC.

Lovastatin inhibits oxidized low-density lipoprotein-induced plasminogen activator inhibitor and transforming growth factor-beta1 expression via a decrease in Ras/extracellular signal-regulated kinase activity in mesangial cells

Oxidized low-density lipoprotein (Ox-LDL) might be involved in the progression of renal disease. Ox-LDL stimulation of plasminogen activator inhibitor-1 (PAI-1) expression via transforming growth factor-beta (TGF-beta)/Smad signaling in mesangial cells required activation of extracellular signal-regulated kinase (ERK). Mevalonate depletion by 3-hydroxy-3-methylglutaryl-CoA (HMG-CoA) reductase inhibitors, or statins, decreases the levels of farnesyl pyrophosphate (FPP) for isoprenylation of Ras. We postulate that statins may ameliorate the Ox-LDL-induced mesangial matrix accumulation by inhibiting Ras/ERK activation with subsequent downregulation of TGF-beta target genes. Quiescent mesangial cells were incubated for 18 h with and without the presence of lovastatin before 50 microg/mL of Ox-LDL treatment for 1 h. Lovastatin inhibited markedly the stimulatory effects of Ox-LDL on ERK1/2 activation, nuclear Smad3 expression, TGF-beta1 and PAI-1 mRNA and protein expression, and PAI-1 luciferase activity. These inhibitory effects of lovastatin were reversed almost completely by mevalonate or FPP. Similar to lovastatin, FTI-277, which is an inhibitor of Ras farnesylation, decreased the Ox-LDL-induced activation of ERK/Smad3 and induction of TGF-beta1/PAI-1. These results indicate that lovastatin prevents the Ox-LDL-induced Ras/ERK activation that results in inhibition of Smad3 activation in mesangial cells with subsequent downregulation of TGF-beta target genes. Thus, statins seem to have antifibrotic effects through their anti-TGF-beta response that are relevant in the treatment of chronic renal disease with dyslipidemia.

Role of CAGA boxes in the plasminogen activator inhibitor-1 promoter in mediating oxidized low-density lipoprotein-induced transcriptional activation in mesangial cells

Oxidized low-density lipoprotein (Ox-LDL) activates transforming growth factor-beta (TGF-beta)/Smad signaling to stimulate plasminogen activator inhibitor-1 (PAI-1) expression in mesangial cells. Smad-binding sequences, termed CAGA boxes, are present in the promoter of human PAI-1 gene, and they mediate TGF-beta transcriptional induction. However, the functional role of each CAGA box in the Ox-LDL-induced PAI-1 promoter activation is unknown. In this study, mutation of 1 of the 3 CAGA boxes located at -730, -580, and -280 of the PAI-1 promoter decreased the Ox-LDL-induced luciferase activity by 40 to 58%, whereas mutations in 2 sites reduced it over 75% or completely abolished it. Overexpression of Smad3 in N-terminal tagged Smad3-transfected cells increased the Ox-LDL-induced transcriptional activation of the PAI-1 promoter, whereas mutation of Smad3 abolished it. Electrophoretic mobility shift assay showed that the labeled -280, -580, and -730 CAGA box probes detected DNA/protein complexes induced by Ox-LDL, whereas mutant probes did not. When nuclear extracts were preincubated with a 100-fold of an unlabeled -280, -580, and -730 CAGA oligonucleotide, the formation of complexes was prevented but not with mutant CAGA box competitors. The addition of anti-Smad3 to the reaction with the labeled -280 or -580 CAGA box probe resulted in a supershift, but not with the -730 CAGA box probe. These results suggest that the 3 CAGA elements in the PAI-1 promoter mediate the Ox-LDL-induced PAI-1 transcription to a different degree, of which the -280 and -580 CAGA regions directly bind to Smad3.

TGF-beta type II receptor deficiency prevents renal injury via decrease in ERK activity in crescentic glomerulonephritis

The role of transforming growth factor-beta (TGF-beta) receptor complex in the pathogenesis of crescentic glomerulonephritis (GN) is not clear. To test the hypothesis that TGF-beta signaling plays a crucial role in the development and progression of crescentic GN by inducing the activation of extracellular signal-regulated kinase (ERK) and expression of its target genes, anti-glomerular basement membrane (GBM) GN was induced in TGF-beta type II receptor (TGF-betaIIR) gene heterozygous (TGF-betaIIR(+/-)) C57BL/6J mice and wild-type animals. GN was initiated in preimmunized mice by administration of rabbit anti-mouse GBM serum. TGF-betaIIR deficiency was significantly associated with decreased renal damage at days 14, 21, and 28 after induction of GN: renal function impairment, proteinuria, proportion of crescents, glomerular accumulation of periodic acid-Schiff-positive material, relative cortical interstitial volume, as well as renal cortical phosphorylation of ERK and plasminogen activator inhibitor type I (PAI-1) and alpha2(I) collagen mRNA levels were significantly decreased in TGF-betaIIR(+/-) mice compared with wild-type animals. These results provide the first direct evidence that TGF-betaIIR deficiency protects against renal injury in crescentic GN, possibly by inhibiting the sustained activation of ERK and PAI-1 and alpha2(I) collagen gene expression. Thus, TGF-beta signaling appears to play an important role in the development and progression of crescentic GN by inducing the ERK activity, and PAI-1 and alpha2(I) mRNA expression.