Low-density lipoprotein-induced expression of interleukin-6, a marker of human mesangial cell inflammation: effects of oxidation and modulation by lovastatin

LDL Affects the Immunomodulatory Response of Endothelial Cells by Modulation of the Promyelocytic Leukemia Protein (PML) Expression via PKC

In addition to its function as an intravascular lipid transporter, LDL also triggers signal transduction in endothelial cells (ECs), which, among other things, trigger immunomodulatory cascades, e.g., IL-6 upregulation. However, the molecular mechanisms of how these LDL-triggered immunological responses in ECs are realized are not fully understood. Since promyelocytic leukemia protein (PML) plays a role in promoting inflammatory processes, we examined the relationship between LDL, PML, and IL-6 in human ECs (HUVECs and EA.hy926 cells). RT-qPCR, immunoblotting, and immunofluorescence analyses showed that LDL but not HDL induced higher PML expression and higher numbers of PML-nuclear bodies (PML-NBs). Transfection of the ECs with a PML gene-encoding vector or PML-specific siRNAs demonstrated PML-regulated IL-6 and IL-8 expression and secretion after LDL exposure. Moreover, incubation with the PKC inhibitor sc-3088 or the PKC activator PMA showed that LDL-induced PKC activity leads to the upregulation of PML mRNA and PML protein. In summary, our experimental data suggest that high LDL concentrations trigger PKC activity in ECs to upregulate PML expression, which then increases production and secretion of IL-6 and IL-8. This molecular cascade represents a novel cellular signaling pathway with immunomodulatory effects in ECs in response to LDL exposure.

High cortisol levels are associated with oxidative stress and mortality in maintenance hemodialysis patients

Background

Chronic stimulation of the mineralocorticoid receptor has been suggested as one of the potential causes of cardiovascular events and death in patients with end-stage renal disease. This observational cohort study was performed to demonstrate that serum cortisol might be a predictive marker for patient mortality and to evaluate its association with oxidized low-density lipoprotein (oxLDL) in hemodialysis (HD) patients.

Methods

Patients receiving HD three times a week were screened for enrollment at two institutions. Baseline cortisol levels were measured before each HD session, and the patients were divided into two groups according to the median value of serum cortisol before analysis. The baseline characteristics and laboratory values of the high and low cortisol groups were compared. Serum cortisol, adrenocorticotropic hormone, renin, aldosterone, and oxLDL were measured in 52 patients to evaluate the effect of oxidative stress on serum cortisol levels.

Results

A total of 133 HD patients were enrolled in this cohort study. Compared to the patients with low serum cortisol levels, the patients with high serum cortisol levels (baseline cortisol ≥ 10 μg/dL) showed higher rates of cardiovascular disease (59.7% vs. 39.4%, P=0.019) and left ventricular systolic dysfunction (LVSD) (25.9% vs. 8.0%, P=0.016). The patients in the high cortisol group demonstrated higher all-cause mortality than those in the low cortisol group. The serum cortisol level was an independent risk factor for patient mortality (hazard ratio 1.234, 95% confidence interval 1.022-1.49, P=0.029). Among the 52 patients with oxLDL measurements, oxLDL was an independent risk factor for elevated serum cortisol levels (Exp(B) 1.114, P=0.013) and LVSD (Exp(B) 12.308, P=0.045). However, plasma aldosterone levels did not affect serum cortisol levels.

Conclusions

Serum cortisol is a useful predictive marker for all-cause death among patients receiving HD. OxLDL is an independent marker for elevated serum cortisol among HD patients.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12882-022-02722-w.

Towards Better Drug Repositioning: Targeted Immunoinflammatory Therapy for Diabetic Nephropathy

Diabetic nephropathy (DN) is one of the most common and important microvascular complications of diabetes mellitus (DM). The main clinical features of DN are proteinuria and a progressive decline in renal function, which are associated with structural and functional changes in the kidney. The pathogenesis of DN is multifactorial, including genetic, metabolic, and haemodynamic factors, which can trigger a sequence of events. Controlling metabolic risks such as hyperglycaemia, hypertension, and dyslipidaemia is not enough to slow the progression of DN. Recent studies emphasized immunoinflammation as a critical pathogenic factor in the progression of DN. Therefore, targeting inflammation is considered a potential and novel treatment strategy for DN. In this review, we will briefly introduce the inflammatory process of DN and discuss the anti-inflammatory effects of antidiabetic drugs when treating DN.

CD40-Dependent Activation of Phosphatidylinositol 3-Kinase/Akt Pathway Inhibits Apoptosis of Human Cultured Mesangial Cells Induced by Oxidized LDL

Deposition of atherogenic lipoproteins is associated with various glomerular diseases. In particular, oxidized LDL (oxLDL) may affect mesangial cells and favour the development of glomerulosclerosis. The aim of the present study was to investigate on cultured human mesangial cells (HMC) whether oxLDL induces apoptosis by a mechanism dependent on the inhibition of Akt survival pathway, and whether the engagement of mesangial CD40 by its ligand CD154 inhibits the apoptotic effect of oxLDL. Tunel assays demonstrated that incubation of HMC for 24h with oxLDL, but not with unmodified LDL, induced a dose-dependent increase in apoptosis of HMC associated with a decrease in Akt phosphorylation. Enzymatic kinase assay showed that also the Akt activity was reduced in a dose-dependent manner by treatment with oxLDL. Stimulation of mesangial CD40 with sCD154 rescued HMC from oxLDL-dependent apoptosis, while two unrelated pharmacological inhibitors of PI3K LY294002 and wortmannin abrogated this anti-apoptotic effect, suggesting an involvement of the PI3K/Akt pathway. Moreover CD40 stimulation maintained an elevated phosphorylation of Akt and preserved its enzymatic activity in the presence of oxLDL. Indeed, CD154 induced a rapid enhancement in Akt enzymatic activity, that was temporarily correlated with the association of CD40 with TRAF3, TRAF6, c-Cbl and the p85 subunit of PI3K. In conclusion, these results suggest that CD40 stimulation protects HMC from toxic effects of oxLDL by promoting PI3K/Akt-dependent cell survival.

Endoplasmic reticulum stress preconditioning antagonizes low-density lipoprotein-induced inflammation in human mesangial cells through upregulation of XBP1 and suppression of the IRE1α/IKK/NF-κB pathway

Elevated plasma low‑density lipoprotein (LDL) is associated with systemic inflammation, and is an important factor in the pathogenesis of chronic kidney disease. The aim of the present study was to investigate the effects of endoplasmic reticulum (ER) stress preconditioning on LDL‑induced inflammatory responses, in human mesangial cells (HMCs). HMCs were exposed to LDL (200 nm), with or without pretreatment with tunicamycin, an ER stress inducer, and tested for changes to gene expression levels. Small interfering RNA technology was used to knockdown the expression of inositol‑requiring enzyme‑1α (IRE1α) and X‑box‑binding protein‑1 (XBP‑1), in order to determine their effects on LDL‑treated HMCs. LDL treatment resulted in a significant, and time‑dependent, increase in the relative mRNA expression levels of proinflammatory cytokines and CD40, which was coupled with enhanced phosphorylation of IRE1α, IκB kinase (IKK), and nuclear factor (NF)‑κB p65 and p65 nuclear translocation. The LDL‑induced inflammatory responses were significantly reduced in the IRE1α‑depleted HMCs. Furthermore, pretreatment with tunicamycin significantly attenuated the induction of proinflammatory cytokines and CD40, by LDL. Whereas, silencing XBP1 expression significantly restored the production of proinflammatory cytokines, in the LDL‑treated HMCs with ER stress preconditioning. The phosphorylation levels of IRE1α, IKK, and NF‑κB p65 were markedly increased in the XBP1‑depleted HMCs. Conversely, overexpression of XBP1 blocked LDL‑induced inflammation in the HMCs. The results of the present study demonstrate that ER stress preconditioning antagonizes LDL‑induced inflammatory responses in HMCs, which may be mediated through upregulation of XBP1, and subsequent inactivation of the IRE1α/IKK/NF‑κB pathway.

Liver X receptors preserve renal glomerular integrity under normoglycaemia and in diabetes in mice

AIMS/HYPOTHESIS

Liver X receptors (LXRs) α and β are nuclear hormone receptors that are widely expressed in the kidney. They promote cholesterol efflux from cells and inhibit inflammatory responses by regulating gene transcription. Here, we hypothesised (1) that LXR deficiency would promote renal decline in a mouse model of diabetes by accelerating intraglomerular cholesterol accumulation and, conversely, (2) that LXR agonism would attenuate renal decline in diabetes.

METHODS

Diabetes was induced with streptozotocin (STZ) and maintained for 14 weeks in Lxrα/β (+/+) (Lxrα, also known as Nr1h3; Lxrβ, also known as Nr1h2) and Lxrα/β (-/-) mice. In addition, STZ-injected DBA/2J mice were treated with vehicle or the LXR agonist N,N-dimethyl-hydroxycholenamide (DMHCA) (80 mg/kg daily) for 10 weeks. To determine the role of cholesterol in diabetic nephropathy (DN), mice were placed on a Western diet after hyperglycaemia developed.

RESULTS

Even in the absence of diabetes, Lxrα/β (-/-) mice exhibited a tenfold increase in the albumin:creatinine ratio and a 40-fold increase in glomerular lipid accumulation compared with Lxrα/β (+/+) mice. When challenged with diabetes, Lxrα/β (-/-) mice showed accelerated mesangial matrix expansion and glomerular lipid accumulation, with upregulation of inflammatory and oxidative stress markers. In the DN-sensitive STZ DBA/2J mouse model, DMHCA treatment significantly decreased albumin and nephrin excretion (by 50% each), glomerular lipids and plasma triacylglycerol (by 70%) and cholesterol (by 48%); it also decreased kidney inflammatory and oxidative stress markers compared with vehicle-treated mice.

CONCLUSIONS/INTERPRETATION

These data support the idea that LXR plays an important role in the normal and diabetic kidney, while showing that LXR, through its inhibitory effect on inflammation and cholesterol accumulation in glomeruli, could also be a novel therapeutic target for DN.

Dyslipidemia in patients with chronic and end-stage kidney disease

In this review, we discuss the physiology, diagnosis and treatment of dyslipidemia in patients with chronic and end-stage renal disease. The recent important clinical trials in patients with chronic kidney disease and dyslipidemia are reviewed. Because of the lack of evidence in treating lipid abnormalities in this specific patient population, we propose that future studies should focus on the pathophysiological mechanisms and treatment of dyslipidemia in this special patient population.

Lipid nephrotoxicity: new concept for an old disease

The prevalence of obesity in the United States remains high, exceeding 30% in most states. As this trend continues unhindered, we will continue see a persistent rise in obesity-related metabolic effects—hypertension, dyslipidemia, diabetes mellitus, and atherosclerosis. These diseases are also the leading causes of chronic kidney diseases and end-stage renal disease. The lipid nephrotoxicity hypothesis, proposed over three decades ago, suggested that proteinuria, decreased albumin levels, and the resultant hyperlipidemia may cause a glomerulosclerosis similar to atherosclerosis. More recent studies have demonstrated the role of oxidized high-density lipoprotein (HDL) and low-density lipoprotein (LDL) particles in the progression of kidney disease. Elucidation of the role of lipid-lowering therapies and the concomitant improvement in tubulointerstitial and glomerular diseases is a further evidence of the role of lipids in renal injury. Synergistic effects of lipid-lowering drugs and blockers of the renin-angiotensin-aldosterone system (RAAS) in renal protection have also been documented. Dyslipidemia in renal disease is usually characterized by elevated LDL cholesterol, low HDL cholesterol, and high triglycerides. After an initial glomerular injury, likely to be inflammatory, a series of self-perpetuating events occur. Increased glomerular basement permeability leads to loss of lipoprotein lipase activators, which results in hyperlipidemia. Circulating LDL has a charge affinity for glycoaminoglycans in the glomerular basement membrane and further increases its permeability. Substantial amounts of filtered lipoprotein cause proliferation of mesangial cells. Proximal tubules reabsorb some of the filtered lipoprotein, and the remainder is altered during passage through the nephron. If intraluminal pH is close to the isoelectric point of the apoprotein, luminal apoprotein will precipitate, causing tubulointerstitial disease. This review shows the evidence for the role of lipids in development of chronic renal disease, the pathophysiology of lipid nephrotoxicity, and strategies available to clinicians to slow the progression of disease.

Effects of aging and menopause on serum interleukin-6 levels and peripheral blood mononuclear cell cytokine production in healthy nonobese women

Inappropriate interleukin-6 production is thought to play a role in the development of several age-related conditions including atherosclerosis. This study aimed to determine whether aging affects circulating interleukin-6 (IL-6) levels. Healthy, nonobese women (n = 208, 44.5 ± 0.70 years, 22.4 ± 0.17 kg/m(2)) were categorized into four age groups (22-31, 32-41, 42-51, and 52-63 years; cross-sectional study). Cytokine levels in serum and those produced from peripheral blood mononuclear cell (PBMC) were measured. The oldest group had the highest circulating levels of IL-6 and oxidized low-density lipoprotein (ox-LDL) and higher PBMC production of IL-6, tumor necrosis factor-α (TNF-α), and interleukin-1 alpha (IL-1β). Additionally, significant interactions between age and menopause were found for serum IL-6 (P = 0.024), and TNF-α (P = 0.011) and IL-1β (P < 0.001) produced from PBMCs. Serum IL-6 levels positively correlated with age, waist-hip ratio (WHR), systolic blood pressure, circulating levels of TNF-α, IL-1β, and ox-LDL, and urinary 8-epi-prostaglandin F(2)α. Multiple stepwise regression models identified the following factors for contributing to serum IL-6 levels: serum IL-1β, menopause status, WHR, and serum TNF-α in mode I (R(2) = 0.302); serum IL-1β, age, serum TNF-α, and WHR (β = 0.197; P = 0.006) in model II (R(2) = 0.283). Sub-analysis was performed according to menopausal status. Serum IL-6 levels were positively associated with levels of IL-6, TNF-α, and IL-1β in PBMC supernatants (unstimulated) from postmenopausal women, whereas these were negatively associated in premenopausal women. In conclusion, circulating IL-6 levels may be interactively influenced by age and menopause. Additionally, estrogen deprivation after menopause may enhance PBMC cytokine production in postmenopausal women, resulting in increased IL-6 levels which are closely related to oxidative stress.

An update on the lipid nephrotoxicity hypothesis

When the 'lipid nephrotoxicity hypothesis' was proposed in 1982, it brought together several disparate experimental findings in hyperlipidemia and renal disease to suggest that concomitant hyperlipidemia and proteinuria would cause self-perpetuating renal disease once the initial glomerular insult was no longer present. This process would be analogous to atherosclerosis. Since 1982, increasing evidence has supported the hypothesis that lipid abnormalities contribute to both atherosclerosis and glomerulosclerosis. In this Review, we discuss research developments that are relevant to the lipid nephrotoxicity hypothesis. We describe how inflammatory stress accompanying chronic kidney disease modifies lipid homeostasis by increasing cholesterol uptake mediated by lipoprotein receptors, inhibiting cholesterol efflux mediated by the ATP-binding cassette transporter 1 and impairing cholesterol synthesis in peripheral cells. As a result of these events, cholesterol relocates to and accumulates in renal, vascular, hepatic and possibly other tissues. The combination of increased cellular cholesterol influx and reduced efflux causes injury in some tissues and lowers the plasma cholesterol level. In addition, inflammatory stress causes a degree of statin resistance via unknown mechanisms. These phenomena alter traditional understanding of the pathogenesis of lipid-mediated renal and vascular injury and could influence the clinical evaluation of renal and cardiovascular risk and the role of lipid-lowering treatment in affected patients.

HMG CoA reductase inhibitors and renoprotection: the weight of the evidence

Dyslipidemia and the contributions of oxidized low-density lipoproteins (ox-LDL) are independent cardiovascular risk factors. There is growing evidence that dyslipidemia contributes not only to cardiovascular disease but also to the progressive decline of renal function in diabetic and non-diabetic kidney disease. Ox-LDL, by generating inflammation and oxidative stress, contributes to a pro-atherogenic mileu and leads to endothelial dysfunction, subsequent glomerular filtration barrier damage, and progressive renal injury. Chronic kidney disease (CKD), in turn, induces deleterious effects on lipid metabolism. Therefore, by inhibiting cholesterol synthesis and reducing ox-LDL, HMG CoA reductase inhibitors (statins) are attractive therapeutic options to preserve renal function. Current evidence demonstrates a reduction in cardiovascular risk and improved renal outcomes especially in patients with mild to moderate impairment of renal function. Evidence supports a beneficial role of statins thought to extend beyond their lipid-lowering effect, referred to as pleiotropic actions. These actions include modulatory effects on inflammation, oxidative stress and thrombosis, derived from their ability to prevent the formation of isoprenoid intermediates involved in cellular signaling, posttranslational modification of proteins and cellular function. This translates to potential reductions in the rate of decline in GFR in CKD and adverse effects of type 2 diabetes mellitus in the kidney. This review examines the role of statins for reno-protection as well as cardiovascular benefit in patients with CKD.

Comparison of the effect of lipophilic and hydrophilic statins on serum adiponectin levels in patients with mild hypertension and dyslipidemia: Kinki Adiponectin Interventional (KAI) Study

The plasma level of adiponectin, which is known as an anti-atherogenic adipocytokine, correlates inversely with the progression of atherosclerosis. An increase in the serum adiponectin level has been reported after the administration of hydrophilic pravastatin, but not after the administration of lipophilic statins thus far. We investigated whether hydrophilic pravastatin acts distinctly from simvastatin, which has the highest lipophilicity, on the favorable effect on adiponectin in dyslipidemic patients. A total of 27 dyslipidemic patients with mild hypertension were enrolled in this study. The patients were initially treated with simvastatin 10 mg/day for six months or more (mean 7.1 months), and then were switched to pravastatin 20 mg/day. The serum adiponectin, cholesterol fractionated components, and C-reactive protein (CRP) were evaluated after six-month intervals. Switching from simvastatin to pravastatin caused little change in the low-density lipoprotein cholesterol levels (103 mg/dl to 104 mg/dl, p = 0.782) and blood pressure (133/70 mmHg to 132/69 mmHg), while the serum adiponectin level significantly increased (11.9 mug/ml to 13.1 mug/ml, p = 0.009, respectively), and the serum CRP significantly decreased (0.078 mg/dl to 0.062 mg/dl, p = 0.040, respectively). Hydrophilic pravastatin increased the serum adiponectin level and decreased the CRP after switching from lipophilic simvastatin in the absence of any difference in the low-density lipoprotein cholesterol level and blood pressure. It remains possible, however, that this difference was due not only to pharmacologic lipophilicity, but also to some other specific characteristics such as the formula of statins, the subject characteristics, race, body size, high-density lipoprotein cholesterol, etc.

Statin pleiotropy against renal injury

Statins may exhibit significant renoprotective effects beyond their lipid-lowering capacity. Herein, the authors review data from human and animal models of renal disease as well as from studies in cultured renal cells with regard to extralipid renoprotective properties of statins. Statins may exert lipid-independent benefits against renal injury in experimental states of chronic or acute renal function impairment. These include diabetic and hypertensive glomerulosclerosis, autoimmune glomerulonephritis, ischemia/reperfusion-induced renal damage, and unilateral ureteral obstructive nephropathy. Also, statins, by reducing the synthesis of mevalonate products, inhibit the activation of Rho and Ras guanosine triphosphatases that may influence various signaling pathways involving renal inflammatory, fibrogenic, proliferative, and cell-death responses. Therefore, statins exert anti-inflammatory actions in renal tissue, prevent renal scarring, and diminish mesangial or other kidney cell-type proliferation while promoting mesangial cell apoptosis. Renal antioxidant effects with consequent endothelial function regulation of renal vasculature following statin treatment may also account for pleiotropic protection against renal injury.

Effects of different LDL particles on inflammatory molecules in human mesangial cells

AIMS/HYPOTHESIS

Inflammation is a mechanism of glomerular damage in chronic glomerulopathies. LDL may increase the production of inflammatory cytokines in renal tissues. However, the relative role of native, oxidised and glycated LDL in promoting this process has been only partially elucidated.

METHODS

We tested the inflammatory and proapoptotic effects of native, oxidised and glycated LDL in human mesangial cells (HMCs) by measuring levels of IL6, CD40 and macrophage migration inhibitory factor (MIF) genes, MIF protein, release of IL6, soluble CD40, fibronectin and laminin, early and late apoptosis, and extracellular regulated kinases (ERK) 1/2 and c-Jun N-terminal kinase (JNK) activation.

RESULTS

IL6 and CD40 mRNA were dose-dependently upregulated by all three species; this was closely paralleled by their increased release. MIF mRNA was potently stimulated by modified LDL, as confirmed by immunostaining. Fibronectin and laminin release was stimulated by both oxidised and glycated, but not native, LDL. All LDL species induced some increase in late, but not early, apoptosis, and similarly activated JNK2/3 phosphorylation; in contrast, ERK1/2 phosphorylation was more strongly upregulated by oxidised than either native or glycated LDL.

CONCLUSIONS

In HMCs, the production and release of IL6 and CD40 is stimulated by both native and modified LDL, while MIF is more strongly stimulated by oxidised LDL. Regarding the pattern of mesangial expansion, fibronectin and laminin are upregulated by oxidised and glycated LDL. Apoptosis, if modest, is induced by all species. Intracellular signalling of native and modified LDL involves JNK2/3 and, perhaps more specifically, ERK1/2. Tight control of the lipid profile may be useful in preserving kidney function in patients with metabolic alterations.

Atorvastatin induces associated reductions in platelet P-selectin, oxidized low-density lipoprotein, and interleukin-6 in patients with coronary artery diseases

The development and progression of atherosclerosis comprises various processes, such as endothelial dysfunction, chronic inflammation, thrombus formation, and lipid profile modification. Statins are 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitors that have pleiotropic effects in addition to cholesterol-lowering properties. However, the mechanisms of these effects are not completely understood. Here, we investigated whether atorvastatin affects the levels of malondialdehyde-modified low-density lipoprotein (MDALDL), an oxidized LDL, the proinflammatory cytokine interleukin-6 (IL-6), or platelet P-selectin, a marker of platelet activation, relative to that of LDL cholesterol (LDL-C). Forty-eight patients with coronary artery disease and hyperlipidemia were separated into two groups that were administered with (atorvastatin group) or without (control group) atorvastatin. The baseline MDA-LDL level in all participants significantly correlated with LDL-C (r = 0.71, P < 0.01) and apolipoprotein B levels (r = 0.66, P < 0.01). Atorvastatin (10 mg/day) significantly reduced the LDL-C level within 4 weeks and persisted for a further 8 weeks of administration. Atorvastatin also reduced the MDA-LDL level within 4 weeks and further reduced it over the next 8 weeks. Platelet P-selectin expression did not change until 4 weeks of administration and then significantly decreased at 12 weeks, whereas the IL-6 level was gradually, but not significantly, reduced at 12 weeks. In contrast, none of these parameters significantly changed in the control group within these time frames. The reduction (%) in IL-6 between 4 and 12 weeks after atorvastatin administration significantly correlated with that of MDALDL and of platelet P-selectin (r = 0.65, P < 0.05 and r = 0.70, P < 0.05, respectively). These results suggested that the positive effects of atorvastatin on the LDL-C oxidation, platelet activation and inflammation that are involved in atherosclerotic processes are exerted in concert after lowering LDL-C.

Chronic kidney disease as a cardiovascular risk state and considerations for the use of statins

Chronic kidney disease (CKD) creates one of the highest risk atherosclerotic states that can occur in human beings. The use of 3-hydroxy-3-methylglutaryl coenzyme reductase inhibitors (statins) has gained widespread acceptance in the general population for the purposes of lowering low-density lipoprotein cholesterol (LDL-C) and reducing the future risks of myocardial infarction, stroke, and cardiac death. In patients with CKD, the balance of benefits and risks of statins appears to be different than that in the general population. Reductions in LDL-C with statins may be associated with a reduced progression of CKD. Importantly, recent studies suggest statins are associated with a reduction in rates of acute kidney injury, mediated by ischemic insults and oxidative stress, after cardiac surgery and exposure to iodinated contrast. A reduction in cardiovascular events with LDL-C reduction in CKD and dialysis patients is yet to be proven. In addition, studies suggest that there are higher adverse drug effects with statins in CKD. This work will address the benefits and risks of this important treatment option for the growing population of patients with CKD, who have not undergone renal transplantation, and are at very high risk of cardiovascular events.

The roles of oxidized low-density lipoprotein and interleukin-6 levels in acute atherothrombotic and lacunar ischemic stroke

The role of circulating, oxidized low-density lipoprotein and interleukin-6 levels in acute ischemic stroke considering the primary-vessel disease was investigated. The study consisted of 28 patients with acute ischemic stroke and 23 control subjects. Patients were subdivided into large-vessel (n = 12) and small-vessel (n =16) disease stroke groups according to the Trial of Org 10172 in Acute Stroke Treatment (TOAST) criteria. The means of oxidized low-density lipoprotein and interleukin-6 levels of patients with acute ischemic stroke were higher than controls (P < .01, P < .05). Mean oxidized low-density lipoprotein level was higher in the large-vessel disease group than in the small-vessel disease group (P < .01). The mean of inteleukin-6 levels was higher in the small-vessel disease group (P < .01). The results of the present study showed that oxidative stress promotes large-vessel disease rather than small-vessel disease stroke, and inflammation may play important an role in the development of small-vessel disease stroke.

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.

Effects of Atorvastatin on C-reactive Protein Secretions by Adipocytes in Hypercholesterolemic Rabbits

C-reactive protein (CRP) is a powerful predictor for coronary heart diseases. Recent study has revealed that adipocytes can produce CRP. Peroxisome proliferator-activated receptor (PPAR) gamma, an important nuclear transcriptional factor, can be predominately detected in adipocytes and exert several biological properties, including antiinflammatory effects. The authors investigated the effects of 2-week atorvastatin treatment on CRP secretions by adipocytes in hypercholesterolemic rabbits. CRP concentrations in serum and adipocytes culture supernatants were measured by latex particle-enhanced immunoturbidometric method. RT-PCR was used to evaluate PPARgamma mRNA expression. Two weeks of atorvastatin treatment resulted in significant reductions of circulating CRP concentrations, which were associated with CRP secretions in adipocytes (r = 0.688, P = 0.007). Meanwhile, CRP secretions in adipocytes were intimately related to low-density lipoprotein (LDL) cholesterol levels (r = 0.869, P < 0.001) and PPARgamma mRNA expressions in adipocytes (r = -0.857, P < 0.001). These data demonstrate that hypercholesterolemia may induce CRP secretions in adipocytes; short-term atorvastatin treatment reduces CRP secretions in adipocytes, possibly through lowering blood cholesterol levels and upregulating PPARgamma expressions in adipocytes. These findings enrich the pharmacological effects of statins and also enlighten the relationship between adipocytes and hypercholesterolemia.

HMG-CoA reductase inhibitors and the kidney

During the last two decades, numerous studies have demonstrated that 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) diminish the risk of cardiovascular morbidity and mortality. Although these studies have focused primarily on the ability of statins to lower circulating levels of low-density lipoprotein cholesterol, more recent research has shown that statins may protect the vasculature via pleiotropic effects not directly related to lipid lowering. These include adjustments in cell-signaling pathways that play a role in atherogenesis and that affect the expression of inflammatory elements, curtail oxidative stress, and enhance endothelial function. More recently, researchers have begun to explore whether these agents exert similar beneficial effects in renal parenchymal and renovascular disease. This review examines the available evidence that dyslipidemia may augment the inflammatory reaction of cytokines in patients with renal disease and that statins may improve renal dysfunction by altering the response of the kidney to dyslipidemia, even in persons with end-stage renal disease on dialysis or with renal transplantation. In this context, some data suggest that statin-mediated alterations in inflammatory responses and endothelial function may reduce proteinuria and the rate of progression of kidney disease.

Plasma fibrinogen levels and cardiovascular risk factors in Japanese schoolchildren

BACKGROUND

Plasma fibrinogen level has been recognized as an independent risk factor for atherosclerosis and its thrombotic complications in adults. The present study aimed to clarify the association between plasma fibrinogen levels and cardiovascular risk factors in Japanese children.

METHODS

A total of 294 schoolchildren (145 boys and 149 girls) aged 10-13 years in a town in Nagano Prefecture, Japan, were surveyed in 2000 for body mass index (BMI), plasma fibrinogen, serum C-reactive protein (CRP), serum total cholesterol, serum high-density lipoprotein (HDL) cholesterol, hemoglobin (Hb) A1c, and ratio of serum total cholesterol to serum HDL cholesterol (TCHR).

RESULTS

The mean value and standard deviation of plasma fibrinogen level among the schoolchildren was 226.0+/-39.7 mg/dL for boys and 245.3+/-40.9 mg/dL for girls; significantly higher for girls. Among plasma fibrinogen tertiles, serum CRP tended to increase with plasma fibrinogen in both boys and girls. An increasing trend was also found in serum total cholesterol in boys, and in TCHR, HbA1c and BMI in girls. Multiple linear regression analysis revealed significant associations of plasma fibrinogen with serum CRP and HbA1c in both sexes, with TCHR in boys, and with BMI in girls.

CONCLUSIONS

Plasma fibrinogen levels were associated with cardiovascular risk factors such as serum CRP, TCHR, HbA1c, and BMI in Japanese schoolchildren.

Adenovirus-mediated gene transfer and lipoprotein-mediated protein delivery of plasma PAF-AH ameliorates proteinuria in rat model of glomerulosclerosis

Oxidative stress has been proposed to play a crucial role in glomerulosclerosis, although its in vivo demonstration has proved taxing given the difficulty of inducing gene expression in specific renal cells. In this study, we examined whether the liver-directed expression of plasma platelet-activating factor acetylhydrolase (PAF-AH) would affect the glomerular pathophysiology in Imai rats, an animal model for glomerulosclerosis. Adenovirus-mediated liver-directed gene delivery of human PAF-AH resulted in a significant increase in plasma PAF-AH activity, which was detected almost exclusively on HDL. Histological examination of rats overexpressing PAF-AH showed not only the deposition of PAF-AH in mesangial cells, but also a reduction in hydroxynonenal and matrix protein content in the glomeruli. In situ hybridization analysis was negative for human PAF-AH mRNA in the kidney, while injection of HDL abundant in PAF-AH resulted in the deposition of PAF-AH in mesangial cells. Urine protein levels did not increase in rats overexpressing PAF-AH, while those of control rats increased significantly with age. This study provides direct evidence of the in vivo role of an enzyme that degrades lipid peroxides during the progression of glomerulosclerosis. Adenovirus-mediated extrarenal gene expression and lipoprotein-mediated glomeruli-targeted protein delivery promise to be a novel therapeutic approach to glomerulosclerosis.

Pleiotropic effects of 3-hydroxy-3-methylglutaryl coenzyme a reductase inhibitors on renal function

Pleiotropic, or non-lipid-dependent, effects mediated by 3-hydroxy-3-methylglutaryl coenzyme A reductase inhibitors (statins) have important clinical implications for the cardiovascular (CV) system. Atherosclerosis is an inflammatory process accompanied by increases in levels of plasma inflammatory markers and accumulation of immune cells within atherosclerotic plaques. Statins not only decrease serum lipid levels, but also inhibit signaling molecules at several points in inflammatory pathways. The anti-inflammatory effects and improved endothelial function associated with statin therapy are thought to be partly responsible for the reduction in CV morbidity and mortality. In analogy, patients with chronic kidney disease administered statins for CV risk reduction show evidence of improved renal function. However, whether statins confer similar protective benefits on the kidney has not been established. Several lines of evidence suggest that similar etiologic and pathological processes may be involved in CV and chronic kidney diseases. If inflammation and functional changes in the renovascular endothelium contribute to the progression of kidney disease, statins are likely to be effective in the treatment of renal disease. In this review, we critically consider emerging data indicating that statins may modulate renal function by altering the inflammatory response of the kidney and renal vasculature to dyslipidemia. Whether the amelioration of renal function by statins is separable from the lipid-lowering effects of these drugs still remains to be delineated. Other questions that remain to be addressed and issues that should be investigated also are presented.

IGF-1 induces rat glomerular mesangial cells to accumulate triglyceride

Rat glomerular mesangial cells (MC) become lipid-laden foam cells when they are exposed to IGF-1. IGF-1 increased accumulation of triglyceride (TG) 2.5-fold in MC after 7 days. TG accumulation resulted from enhanced macropinocytosis and decreased efflux secondary to a 40-50% reduction in peroxisome proliferator-activated receptor (PPAR)-delta (PPARdelta). There was no evidence of primary or secondary changes in cholesterol or TG synthesis, increased uptake by LDL or scavenger receptors, or reduced efflux via ATP-binding cassette A-1. Although the lipid moiety taken up can be influenced by the concentration of cholesterol or TG in the medium, in standard medium MC preferentially accumulate TG. TG-rich MC foam cells fail to contract in response to angiotensin II (Berfield AK, Andress DL, and Abrass CK. Kidney Int 62: 1229-1237, 2002); however, their migratory response to IGF binding protein-5 is unaffected. This differs from cholesterol loading, which impairs both phagocytosis and migration. These findings have important implications for understanding the mechanisms that contribute to lipid accumulation in MC and the functional consequences of different forms of foam cells. These observations are relevant to understanding vascular disease and progressive renal diseases that are accelerated by abnormalities in lipid metabolism.

Paraoxonase-1 (PON-1) genotype and activity and in vivo oxidized plasma low-density lipoprotein in Type II diabetes

The HDL (high-density lipoprotein)-associated enzyme PON (paraoxonase)-1 protects LDL (low-density lipoprotein) from oxidative modification in vitro, although it is unknown if this anti-atherogenic action occurs in vivo. In a cross-sectional study of 58 Type II diabetic subjects and 50 controls, we examined the fasting plasma LDL basal conjugated diene concentration [a direct measurement of circulating oxLDL (oxidatively modified LDL)], lipoprotein particle size by NMR spectroscopy, PON-1 polymorphisms (coding region polymorphisms Q192R and L55M, and gene promoter polymorphisms −108C/T and −162G/A), PON activity (with paraoxon or phenyl acetate as the substrates) and dietary antioxidant intake. Plasma oxLDL concentrations were higher in Type II diabetic patients (males, P=0.048; females, P=0.009) and unrelated to NMR lipoprotein size, PON-1 polymorphisms or PON activity (with paraoxon as the substrate) in any group. In men with Type II diabetes, however, there was a direct relationship between oxLDL concentrations and PON activity (with phenyl acetate as the substrate; r=0.611, P=0.0001) and an atherogenic NMR lipid profile in those who were PON-1 55LL homozygotes. Circulating oxLDL concentrations in vivo were unrelated to PON-1 genotypes or activity, except in male Type II diabetics where there was a direct association between PON activity (with phenyl acetate as the substrate) and oxLDL levels. These in vivo data contrast with in vitro data, and may be due to confounding by dietary fat intake. Male Type II diabetic subjects with PON-1 55LL homozygosity have an atherogenic NMR lipid profile independent of LDL oxidation. These data do not support an in vivo action of PON on LDL oxidation.

Are 3-Hydroxy-3-Methylglutaryl-CoA Reductase Inhibitors Renoprotective?: Table 1

Statins reduce serum cholesterol and cardiovascular morbidity and mortality. The mechanisms for these beneficial effects are reviewed. Altered inflammatory responses and improved endothelial function mediated by statins are thought to be partly responsible for the reduction of morbidity and mortality as a result of cardiovascular events. In analogy, whether statins confer similar benefits on the kidney has not been established. This review critically considers the available data whereby dyslipidemia mediates renal dysfunction by modulating the inflammatory response to diverse cytokines. Also reviewed is the emerging database indicating that statins may modulate renal function by altering the response of the kidney to dyslipidemia.

The role of lipids in the development of diabetic microvascular complications: implications for therapy

Dyslipidemia is a major factor responsible for coronary heart disease and its reduction decreases coronary risk in patients with diabetes mellitus. However, the association of dyslipidemia with microvascular complications and the effect of intervention with lipid-lowering therapy in diabetes have been less investigated. We present the systematic review of association and intervention studies pertaining to dyslipidemia and microvascular disease in diabetes and also review possible mechanisms. Dyslipidemia may cause or exacerbate diabetic retinopathy and nephropathy by alterations in the coagulation-fibrinolytic system, changes in membrane permeability, damage to endothelial cells and increased atherosclerosis. Hyperlipidemia is associated with faster decline in glomerular filtration rate and progression of albuminuria and nephropathy. Recent evidence also suggests a role of lipoprotein(a) in progression of retinopathy and nephropathy in patients with diabetes mellitus. Lipid-lowering therapy, using single agents or a combination of drugs may significantly benefit diabetic retinopathy and diabetic nephropathy. In particular, hydroxymethyl glutaryl coenzyme A reductase inhibitors may be effective in preventing or retarding the progression of microvascular complications because of their powerful lipid-lowering effects and other additional mechanisms. However, most of the data are based on short-term studies, and need to be ascertained in long-term studies. Until more specific guidelines are available, aggressive management of diabetic dyslipidemia, according to currently accepted guidelines, should be continued for the prevention of macrovascular disease which would also benefit microvascular complications.

Differential effects of simvastatin on mesangial cells

BACKGROUND

Statins are increasingly recognized as mediators of direct cellular effects independent of their lipid lowering capacity. Therefore, the time and concentration dependence of various statin-mediated cellular alterations was compared in renal mesangial cells.

METHODS

The effects of statins on cell proliferation, gene expression, cytoskeletal alterations, apoptosis, and cytotoxicity were analyzed in cultured mesangial cells using standard techniques.

RESULTS

Simvastatin and lovastatin decreased proliferation and cell number of rat mesangial cells concentration-dependently. Concurrently, the expression of the fibrogenic protein connective tissue growth factor (CTGF) was impaired and actin stress fibers, which are typical of mesangial cells in culture, became disassembled by simvastatin. A decrease of the posttranslational modification of RhoA by geranylgeranyl moieties was detected, supporting a role for RhoA as mediator of statin effects. Induction of apoptosis, determined by activation of caspase-3 and DNA fragmentation, and necrosis only occurred at later time points, when the morphology of the cells was strongly altered and the cells detached from the surface due to changes in the actin cytoskeleton. Basically, the same results were obtained with a human mesangial cell line. Furthermore, statin effects were mimicked by inhibition of the geranylgeranyltransferase.

CONCLUSION

Most of the cellular effects of the lipophilic statins occurred within the same time and concentration range, suggesting a common molecular mechanism. Only apoptosis and necrosis were observed at later time points or with higher concentrations of simvastatin and thus seem to be secondary to the changes in gene expression and alterations of the actin cytoskeleton.

Simvastatin Induces Death of Multiple Myeloma Cell Lines

Background

Accumulating reports indicate that statins widely prescribed for hypercholesteromia have antineoplastic activity. We hypothesized that because statins inhibit farnesylation of Ras that is often mutated in multiple myeloma (MM), as well as the production of interleukin (IL)-6, a key cytokine in MM, they may have antiproliferative and/or proapoptotic effects in this malignancy.

Methods

U266, RPMI 8226, and ARH77 were treated with simvastatin (0–30 μM) for 5 days. The following aspects were evaluated: viability (IC50), cell cycle, cell death, cytoplasmic calcium ion levels, supernatant IL-6 levels, and tyrosine kinase activity.

Results

Exposure of all cell lines to simvastatin resulted in reduced viability with IC50s of 4.5 μM for ARH77, 8 μM for RPMI 8226, and 13 μM for U266. The decreased viability is attributed to cell-cycle arrest (U266, G1; RPMI 8226, G2M) and cell death. ARH77 underwent apoptosis, whereas U266 and RPMI 8226 displayed a more necrotic form of death. Cytoplasmic calcium levels decreased significantly in all treated cell lines. IL-6 secretion from U266 cells was abrogated on treatment with simvastatin, whereas total tyrosine phosphorylation was unaffected. Conclusions: Simvastatin displays significant antimyeloma activity in vitro. Further research is warranted for elucidation of the modulated molecular pathways and clinical relevance.

The effect of statins versus untreated dyslipidaemia on renal function in patients with coronary heart disease. A subgroup analysis of the Greek atorvastatin and coronary heart disease evaluation (GREACE) study

BACKGROUND

Little is known about statins in the prevention of dyslipidaemia induced renal function decline. The secondary coronary heart disease (CHD) prevention GREACE study suggested that dose titration with atorvastatin (10-80 mg/day, mean dose 24 mg/day) achieves the national cholesterol educational programme treatment goals and significantly reduces morbidity and mortality, compared with usual care.

AIMS

To report the effect of statin on renal function compared with untreated dyslipidaemia in both treatment groups.

METHODS/RESULTS

All patients had plasma creatinine values within the reference range < 115 micro mol/litre (13 mg/litre). The on study creatinine clearance (CrCl), as estimated (for up to 48 months) by the Cockroft-Gault formula, was compared within and between treatment groups using analysis of variance to assess differences over time. Patients from both groups not treated with statins (704) showed a 5.2% decrease in CrCl (p < 0.0001). Usual care patients on various statins (97) had a 4.9% increase in CrCl (p = 0.003). Structured care patients on atorvastatin (783) had a 12% increase in CrCl (p < 0.0001). This effect was more prominent in the lower two quartiles of baseline CrCl and with higher atorvastatin doses. After adjustment for 25 predictors of all CHD related events, multivariate analysis revealed a hazards ratio of 0.84 (confidence interval 0.73 to 0.95; p = 0.003) with every 5% increase in CrCl.

CONCLUSIONS

In untreated dyslipidaemic patients with CHD and normal renal function at baseline, CrCl declines over a period of three years. Statin treatment prevents this decline and significantly improves renal function, potentially offsetting an additional factor associated with CHD risk.

Oxidized low-density lipoprotein is present in astrocytes surrounding cerebral infarcts and stimulates astrocyte interleukin-6 secretion

Ischemic injury to brain is associated with both disruption of the blood-brain barrier and increased oxidative stress. Given the neurotoxicity associated with exposure to oxidized low-density lipoprotein (oxLDL) in vitro, we tested the hypothesis that oxLDL may be present in parenchymal cells of cerebrum after infarction and that oxLDL may influence the pathophysiology of cerebral infarction. Our results showed that the subacute phase of cerebral infarction in patients was characterized by the appearance of oxLDL epitopes in astrocytes, but not neurons or microglia, in the perinecrotic zone. We further demonstrated that minimally oxLDL was most effectively internalized by primary cultures of rat astrocytes, and that exposure to minimal oxLDL stimulated astrocyte interleukin-6 secretion but did not alter nitric oxide production. These results demonstrate for the first time that oxLDL is present in brain parenchyma of patients with ischemic infarction and suggest a potential mechanism by which oxLDL may activate innate immunity and thereby indirectly influence neuronal survival.

Cellular lipid metabolism and the role of lipids in progressive renal disease

Dyslipidemia contributes to the rate of progression of atherosclerosis and chronic kidney disease. Also, chronic kidney disease leads to the development of secondary abnormalities in lipid metabolism that contribute to increased cardiovascular morbidity and mortality. This review presents the mechanisms that underlie this risk. The mechanisms of normal cellular lipid metabolism and the abnormalities that develop in association with inflammation are reviewed. There is a special emphasis on foam cells in the kidney and on lipid-mediated changes in intrinsic kidney cells that lead to glomerulosclerosis and interstitial fibrosis. Correlates to studies performed in whole animals and humans are included.

Atorvastatin reduces interleukin-6 plasma concentration and adipocyte secretion of hypercholesterolemic rabbits

BACKGROUND

Interleukin-6 (IL-6) is secreted by adipocytes and may be involved in atherosclerosis. Few studies have assessed the influence of statins on IL-6 secretion in adipocytes.

METHODS

Rabbits on high-cholesterol diets were randomly given either atorvastatin 1.5 mg/kg day(-1) (n=5) or starch (n=5) for 2 weeks. Subcutaneous adipose was collected for adipocytes culture. IL-6 concentrations in plasma and adipocytes culture supernatant were measured by ELISA. RT-PCR was used to evaluate peroxisome proliferator-activated receptor (PPAR) gamma mRNA expression. The in vitro effect of atorvastatin on IL-6 production in adipocytes was observed.

RESULTS

Two weeks atorvastatin treatment resulted in significant reduction of circulating IL-6 concentrations, which was associated with IL-6 secretion in adipocytes (r=0.849, P<0.01). Meanwhile mRNA expression of PPARgamma in adipocytes was intimately related to the IL-6 secretion in adipocytes (r=-0.900, P<0.01). Atorvastatin induced the decreased IL-6 secretion in dose-dependent manner.

CONCLUSIONS

Atorvastatin can inhibit IL-6 secretion in adipocytes possibly through upregulating PPARgamma, which may help to explain the anti-inflammatory effects of statins use.

C-reactive protein concentration and concentrations of blood vitamins, carotenoids, and selenium among United States adults

OBJECTIVE

To examine the relationships between circulating concentrations of C-reactive protein and concentrations of retinol, retinyl esters, vitamin C, vitamin E, carotenoids, and selenium.

DESIGN

Cross-sectional study using National Health and Nutrition Examination Survey III (1988-1994) data.

SETTING

United States population.

SUBJECTS

Up to 14 519 US noninstitutionalized civilian men and women aged > or=20 y.

RESULTS

C-reactive protein concentration (dichotomized at the sex-specific 85th percentile) was inversely and significantly associated with concentrations of retinol, retinyl esters, vitamin C, alpha-carotene, beta-carotene, cryptoxanthin, lutein/zeaxanthin, lycopene, and selenium after adjustment for age, sex, race or ethnicity, education, cotinine concentration, body mass index, leisure-time physical activity, and aspirin use.

CONCLUSIONS

These results suggest that the inflammatory process, through the production of reactive oxygen species, may deplete stores of antioxidants. Whether increased consumption of foods rich in antioxidants or supplementation with antioxidants can provide health benefits to people characterized by elevated C-reactive protein concentrations may be worthy of further study.

Lipid abnormalities and renal disease: is dyslipidemia a predictor of progression of renal disease?

Dyslipidemia is a cardiovascular disease (CVD) risk factor that is associated with enhanced atherosclerosis and plaque instability. Renal insufficiency is associated with abnormalities in lipoprotein metabolism in both the early and the advanced stages of chronic renal failure. These include alterations in apolipoprotein A (apo A)- and B- containing lipoproteins, high-density lipoproteins, and triglycerides. In animal models, these alterations in lipid metabolism and action lead to macrophage activation and infiltration in the kidney with resultant tubulointerstitial and endothelial cell injury. Limited data in humans suggest that, in addition to contributing to CVD, dyslipidemia may be a risk factor for the progression of renal disease. The effects of dyslipidemia on the kidney are mainly observed in those with other risk factors for renal disease progression such as hypertension, diabetes, and proteinuria. Renal disease is a strong risk factor for CVD and African Americans have high rates of renal disease. Therefore, examining the effects of dyslipidemia on the development or progression or renal disease will be an important question for the Jackson Heart Study and is the topic of this review.

Reduction of serum C-reactive protein by statin therapy may reflect decreased isoprenylation of Rac-1, a mediator of the IL-6 signal transduction pathway

Recent studies demonstrate that statin therapy decreases plasma levels of C-reactive protein (CRP), a potent risk factor for thrombotic vascular events. CRP is an acute phase reactant, and most circulating CRP is synthesized by hepatocytes in response to IL-6. Since statins do not appear to have a consistent impact on serum levels of IL-6, their impact on plasma CRP very likely reflects down-regulation of hepatocyte responsiveness to this cytokine. The ability of IL-6 to promote transcription of CRP is mediated, in large part, by activation of the transcription factor STAT3; this activation requires both a tyrosine phosphorylation (mediated by the IL-6 receptor complex) and a serine phosphorylation (Ser-727), the origin of which has been more obscure. There is new evidence that, when hepatocytes are exposed to IL-6, the consequent serine phosphorylation of STATS is mediated by a signal transduction pathway in which the G-protein Rac-1 plays an obligate role. Inasmuch as the proper function of Rac-1 is contingent on isoprenylation that anchors it to the plasma membrane, it is reasonable to hypothesize that statin therapy interferes with IL-6 signaling in hepatocytes by suppressing the isoprenylation of Rac-1; a decrease in the transcription of CRP would be a likely consequence of this effect. Whether or not a reduction in elevated CRP is directly beneficial to vascular health, statins can exert direct effects on vascular endothelial function that should help prevent vascular inflammation and thrombosis, and thus should be of particular benefit to subjects - such as those with high CRP levels - who are at high risk for vascular events.

IGF-1-induced lipid accumulation impairs mesangial cell migration and contractile function

BACKGROUND

Chronic treatment of mesangial cells with insulin-like growth factor-1 (IGF-1) results in intracellular lipid accumulation. These mesangial cells resemble foam cells.

METHODS

To determine whether this phenotype affects cell function, lipid-laden mesangial cells were tested for their ability to migrate in response to IGF-binding protein-5 (IGFBP-5) and to contract in response to angiotensin II (Ang II). IGFBP-5 binding and subsequent activation of the signal transduction cascade for migration were examined. To confirm that lipid accumulation was responsible for impaired contractility, lipid was removed from lipid-laden mesangial cells and the cells were re-tested for contractile response to Ang II.

RESULTS

In comparison to control mesangial cells, lipid-laden cells failed to migrate in response to IGFBP-5. Although cellular binding of IGFBP-5 was not altered by lipid accumulation, IGFBP-5 failed to activate cdc42, a Rho GTPase required for IGFBP-5-mediated mesangial cell migration. These data indicate that lipid accumulation within the mesangial cell interferes with the signal transduction response to IGFBP-5. In addition, mesangial cells treated with IGF-1 had reduced contraction to Ang II. When lipid accumulation was exaggerated by adding cholesteryl esters to the culture medium, mesangial cells failed to contract in response to Ang II. Following removal of excess lipid from these mesangial cells, the contractile response to Ang II was restored.

CONCLUSIONS

IGF-1 induces lipid accumulation in mesangial cells, which impairs their ability to respond to specific migratory and contractile stimuli. These observations are relevant to understanding functional abnormalities in diseases where mesangial foam cells occur, such as focal and segmental glomerulosclerosis and diabetic nephropathy.

Circulating oxidized LDL is associated with subclinical atherosclerosis development and inflammatory cytokines (AIR Study)

OBJECTIVE

Circulating oxidized LDL (Ox-LDL) is associated with clinical manifestations of atherosclerosis. However, no previous study has examined the relationship between subclinical atherosclerosis and Ox-LDL. The aims of the present study were to investigate the relationship between clinically silent ultrasound-assessed atherosclerotic changes in the carotid and femoral arteries and Ox-LDL and to explore the relationship between Ox-LDL, C-reactive protein, and the inflammatory cytokines interleukin-6 and tumor necrosis factor-alpha.

METHODS AND RESULTS

The study group (n=391) consisted of clinically healthy, 58-year-old men recruited from the general population. Ox-LDL was measured by using a specific monoclonal antibody, mAb-4E6. The results showed that Ox-LDL was related to intima-media thickness and plaque occurrence in the carotid and femoral arteries. In addition, Ox-LDL was associated with tumor necrosis factor-alpha and C-reactive protein. Circulating Ox-LDL was also associated with LDL cholesterol but not with blood pressure or smoking. When adjusting for other risk factors, both LDL cholesterol and Ox-LDL seemed to be independent predictors of plaque occurrence in the carotid and femoral arteries (odds ratios for quintile 5 versus quintile 1 were 2.17, P=0.049 and 2.25, P=0.050, for LDL cholesterol and Ox-LDL, respectively).

CONCLUSIONS

Ox-LDL was associated with both subclinical atherosclerosis and inflammatory variables, supporting the concept that oxidatively modified LDL may play a major role in atherosclerosis development, although no causality can be shown in this cross-sectional study.

Role of oxidized low-density lipoprotein in renal disease

Accelerated atherosclerosis is often observed in patients with chronic renal failure. In the present review we summarize and discuss the recent literature on the pathogenic role of low-density lipoproteins modified by oxidative processes in atherosclerosis and the possible role in renal diseases. Pathogenetically, the oxidation of low-density lipoproteins is considered to be a key event in the development of atherosclerosis, in part by causing enhanced uptake of lipids by macrophages. In addition, oxidation of low-density lipoproteins exerts cytotoxic, proinflammatory and immunogenic properties, all of which could potentially contribute to the development and progression of atherosclerosis.

The role of risk factors in the development of atherosclerosis

Our understanding of risk factors for atherogenesis has changed significantly over the last decade. In addition to better grasp of the mechanism of action of the "classic" (causal) risk factors, a number of potentially important new factors has emerged. In this review we briefly summarize the evidence of the relation between atherosclerosis and the currently recognized causal risk factors, namely, age, smoking, LDL cholesterol, HDL cholesterol, hypertension, and diabetes. More emphasis has been put on description of the emerging entities such as atherogenic profile of plasma lipoproteins with discussion of LDL and HDL subclasses, Lp(a), homocysteine, and, last but not least, on the role of infection and inflammation in atherogenesis. Whenever possible, we tried to summarize the relevant lines of evidence such as epidemiological, pathological, genetic, and clinical trial data linking the specific factor with atherosclerosis.

Rho-dependent inhibition of the induction of connective tissue growth factor (CTGF) by HMG CoA reductase inhibitors (statins)

It was supposed that inhibitors of 3-hydroxy-3-methylglutaryl-coenzyme A (HMG CoA) reductase (statins) might inhibit the expression of the fibrosis-related factor CTGF (connective tissue growth factor) by interfering with the isoprenylation of Rho proteins. The human renal fibroblast cell line TK173 was used as an in vitro model system to study the statin-mediated modulation of the structure of the actin cytoskeleton and of the expression of CTGF mRNA. Incubation of the cells with simvastatin or lovastatin time-dependently and reversibly changed cell morphology and the actin cytoskeleton with maximal effects observed after about 18 h. Within the same time period, statins reduced the basal expression of CTGF and interfered with CTGF induction by lysophosphatidic acid (LPA) or transforming growth factor beta. Simvastatin and lovastatin proved to be much more potent than pravastatin (IC(50) 1 - 3 microM compared to 500 microM). The inhibition of CTGF expression was prevented when the cells were incubated with mevalonate or geranylgeranylpyrophosphate (GGPP) but not by farnesylpyrophosphate (FPP). Specific inhibition of geranylgeranyltransferase-I by GTI-286 inhibited LPA-mediated CTGF expression whereas an inhibitor of farnesyltransferases FTI-276 was ineffective. Simvastatin reduced the binding of the small GTPase RhoA to cellular membranes. The effect was prevented by mevalonate and GGPP, but not FPP. These data are in agreement with the hypothesis that interference of statins with the expression of CTGF mRNA is primarily due to interference with the isoprenylation of RhoA, in line with previous studies, which have shown that RhoA is an essential mediator of CTGF induction. The direct interference of statins with the synthesis of CTGF, a protein functionally related to the development of fibrosis, may thus be a novel mechanism underlying the beneficial effects of statins observed in renal diseases.