Oxidized low-density lipoprotein stimulates monocyte adhesion to glomerular endothelial cells

The non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio as a predictive indicator of CKD risk in NAFLD patients: NHANES 2017-2020

Background

Non-alcoholic fatty liver disease (NAFLD) and chronic kidney disease (CKD) are both closely related to dyslipidemia. However, the relationship between dyslipidemia in patients with NAFLD and CKD is not yet clear. The non-high-density lipoprotein cholesterol to high-density lipoprotein cholesterol ratio (NHHR) is an innovative and comprehensive lipid index. The purpose of this study was to investigate the correlation between NHHR and CKD risk in NAFLD patients with or without fibrosis.

Methods

This study used data from the National Health and Nutrition Examination Survey (NHANES) from 2017 to 2020 for analysis, including a total of 4,041 subjects diagnosed with NAFLD. Among the NAFLD subjects, 3,315 individuals without liver fibrosis and 726 individuals with fibrosis. Weighted multivariate linear regression, weighted logistic regression, restricted cubic spline (RCS) curves, and subgroup analysis were used to evaluate the correlation between NHHR and CKD in patients with NAFLD.

Results

Our findings indicate that in NAFLD subjects without liver fibrosis, the highest tertile of NHHR, as compared to the lowest tertile, was inversely related to glomerular filtration rate (eGFR) (β: -2.14, 95% CI: -3.97, -0.32, p < 0.05) and positively related to CKD (OR: 1.67, 95% CI: 1.12, 2.49, p < 0.05). No significant associations were observed between NHHR and eGFR, urinary albumin to creatinine ratio (ACR) in NAFLD subjects with liver fibrosis. The RCS revealed a linear relationship between NHHR and ACR, CKD in NAFLD subjects without liver fibrosis, while a U-shaped relationship was observed between NHHR and ACR, CKD in NAFLD subjects with liver fibrosis.

Conclusion

In patients with non-fibrotic NAFLD, a significantly elevated NHHR is closely associated with an increased risk of CKD and shows a linear relationship with CKD. In patients with fibrotic NAFLD, NHHR shows a U-shaped relationship with CKD. LD, Our findings underscore the practical utility of NHHR as a biomarker for early risk stratification of CKD in patients with NAFLD.

Molecular mechanism of renal lipid accumulation in diabetic kidney disease

Diabetic kidney disease (DKD) is a leading cause of end stage renal disease with unmet clinical demands for treatment. Lipids are essential for cell survival; however, renal cells have limited capability to metabolize overloaded lipids. Dyslipidaemia is common in DKD patients and renal ectopic lipid accumulation is associated with disease progression. Unveiling the molecular mechanism involved in renal lipid regulation is crucial for exploring potential therapeutic targets. In this review, we focused on the mechanism underlying cholesterol, oxysterol and fatty acid metabolism disorder in the context of DKD. Specific regulators of lipid accumulation in different kidney compartment and TREM2 macrophages, a lipid-related macrophages in DKD, were discussed. The role of sodium-glucose transporter 2 inhibitors in improving renal lipid accumulation was summarized.

Signaling pathways of chronic kidney diseases, implications for therapeutics

Chronic kidney disease (CKD) is a chronic renal dysfunction syndrome that is characterized by nephron loss, inflammation, myofibroblasts activation, and extracellular matrix (ECM) deposition. Lipotoxicity and oxidative stress are the driving force for the loss of nephron including tubules, glomerulus, and endothelium. NLRP3 inflammasome signaling, MAPK signaling, PI3K/Akt signaling, and RAAS signaling involves in lipotoxicity. The upregulated Nox expression and the decreased Nrf2 expression result in oxidative stress directly. The injured renal resident cells release proinflammatory cytokines and chemokines to recruit immune cells such as macrophages from bone marrow. NF-κB signaling, NLRP3 inflammasome signaling, JAK-STAT signaling, Toll-like receptor signaling, and cGAS-STING signaling are major signaling pathways that mediate inflammation in inflammatory cells including immune cells and injured renal resident cells. The inflammatory cells produce and secret a great number of profibrotic cytokines such as TGF-β1, Wnt ligands, and angiotensin II. TGF-β signaling, Wnt signaling, RAAS signaling, and Notch signaling evoke the activation of myofibroblasts and promote the generation of ECM. The potential therapies targeted to these signaling pathways are also introduced here. In this review, we update the key signaling pathways of lipotoxicity, oxidative stress, inflammation, and myofibroblasts activation in kidneys with chronic injury, and the targeted drugs based on the latest studies. Unifying these pathways and the targeted therapies will be instrumental to advance further basic and clinical investigation in CKD.

Immunological Aspects of Age-Related Macular Degeneration

Increasing evidence over the past two decades points to a pivotal role for immune mechanisms in age-related macular degeneration (AMD) pathobiology. In this chapter, we will explore immunological aspects of AMD, with a specific focus on how immune mechanisms modulate clinical phenotypes of disease and severity and how components of the immune system may serve as triggers for disease progression in both dry and neovascular AMD. We will briefly review the biology of the immune system, defining the role of immune mechanisms in chronic degenerative disease and differentiating from immune responses to acute injury or infection. We will explore current understanding of the roles of innate immunity (especially macrophages), antigen-specific immunity (T cells, B cells, and autoimmunity), immune amplifications systems, especially complement activity and the NLRP3 inflammasome, in the pathogenesis of both dry and neovascular AMD, reviewing data from pathology, experimental animal models, and clinical studies of AMD patients. We will also assess how interactions between the immune system and infectious pathogens could potentially modulate AMD pathobiology via alterations in in immune effector mechanisms. We will conclude by reviewing the paradigm of "response to injury," which provides a means to integrate various immunologic mechanisms along with nonimmune mechanisms of tissue injury and repair as a model to understand the pathobiology of AMD.

Implications of Necroptosis for Cardiovascular Diseases

Necroptosis is a non-apoptotic programmed cell death pathway, which causes necrosis-like morphologic changes and triggers inflammation in the surrounding tissues. Accumulating evidence has demonstrated that necroptosis is involved in a number of pathological processes that lead to cardiovascular diseases. However, the exact molecular pathways linking them remain unknown. Herein, this review summarizes the necroptosis-related pathways involved in the development of various cardiovascular diseases, including atherosclerosis, cardiac ischemia-reperfusion injury, cardiac hypertrophy, dilated cardiomyopathy and myocardial infarction, and may shed light on the diagnosis and treatment of these diseases.

Elevated oxidized lipids, anti-lipid autoantibodies and oxidized lipid immune complexes in active SLE

BACKGROUND

Here, we explore the serum levels of anti-oxidized lipid autoantibodies as well as immune complexes in patients with SLE and determine their correlation with disease.

METHODS

Serum levels of oxidized-LDL immune complexes, autoantibodies to dsDNA, ox-LDL, MDA-LDL, 9-HODE, 13-HODE and POVPC were detected by ELISA in 64 SLE patients and 9 healthy controls.

RESULTS

Active SLE patients exhibited increased serum levels of autoantibodies compared to healthy controls, including anti-MDA-LDL-IgG (p = .003), anti-ox-LDL-IgG (p = .004), anti-9-HODE-IgG (p = .001), anti-13-HODE-IgG (p = .0003), anti-POVPC-IgG (p = .001) and ox-LDL-IC (p = .003). Serum anti-ox-LDL-IgG was positively correlated with SLEDAI (r = 0.34; p = .01), and negatively with C3 (r = -0.40; p = .01). Anti-9-HODE-IgG and anti-POVPC-IgG were positively correlated with SLEDAI and negatively with C4.

CONCLUSIONS

Active SLE patients exhibit significantly increased serum levels of IgG anti-oxidized-lipid autoantibodies. Coordinated elevation of oxidized lipids, autoantibodies to these lipids, and immune complexes of these lipid-antibody components could potentially serve as pathogenic drivers and serum markers of SLE disease activity.

Renoprotective effect of Caralluma fimbriata against high-fat diet-induced oxidative stress in Wistar rats

The current study was designed to evaluate the renoprotective effect of hydro-alcoholic extract of Caralluma fimbriata (CFE) against high-fat diet-induced oxidative stress in Wistar rats. Male Wistar rats were randomly divided into five groups: control (C), control treated with CFE (C + CFE), high-fat diet fed (HFD), high-fat diet fed treated with CFE (HFD + CFE), and high-fat diet fed treated with metformin (HFD + metformin). CFE was orally administered (200 mg/kg body weight) to Groups C + CFE and HFD + CFE rats for 90 days. Renal functional markers such as, urea, uric acid, and creatinine levels in plasma were quantified during the experimental period. At the end of the experimental period, activities of transaminases and oxidative stress markers, i.e., reduced glutathione (GSH), lipid peroxidation, protein oxidation, and activities of antioxidant enzymes were assayed in renal tissue. Coadministration of CFE along with HF-diet in Group HFD + CFE prevented the rise in the levels of plasma urea, uric acid, and creatinine, and elevated activities of renal transaminases with decreased protein content of Group HFD (p < 0.05). Establishment of oxidative stress in Group HFD, as evident from elevated lipid peroxidation, protein oxidation levels with depleted levels of GSH, and decreased activities of GSH dependent and independent antioxidant enzymes, was prevented in Groups HFD + CFE and HFD + metformin rats. Further, there were no deviations in the studied parameters but there was improved antioxidant status of Group C + CFE from Group C which revealed the nontoxic nature of CFE even under chronic treatment. Thus, CFE treatment effectively alleviated the HF-diet induced renal damage. Hence, this plant could be used as an adjuvant therapy for the prevention and/or management of HF-diet induced renal damage.

Lipid droplet accumulation is associated with an increase in hyperglycemia-induced renal damage: prevention by liver X receptors

Dyslipidemia is a frequent component of the metabolic disorder of diabetic patients contributing to organ damage. Herein, in low-density lipoprotein receptor-deficient hyperlipidemic and streptozotozin-induced diabetic mice, hyperglycemia and hyperlipidemia acted reciprocally, accentuating renal injury and altering renal function. In hyperglycemic-hyperlipidemic kidneys, the accumulation of Tip47-positive lipid droplets in glomeruli, tubular epithelia, and macrophages was accompanied by the concomitant presence of the oxidative stress markers xanthine oxidoreductase and nitrotyrosine, findings that could also be evidenced in renal biopsy samples of diabetic patients. As liver X receptors (LXRα,β) regulate genes linked to lipid and carbohydrate homeostasis and inhibit inflammatory gene expression in macrophages, the effects of systemic and macrophage-specific LXR activation were analyzed on renal damage in hyperlipidemic-hyperglycemic mice. LXR stimulation by GW3965 up-regulated genes involved in cholesterol efflux and down-regulated proinflammatory/profibrotic cytokines, inhibiting the pathomorphology of diabetic nephropathy, renal lipid accumulation, and improving renal function. Xanthine oxidoreductase and nitrotyrosine levels were reduced. In macrophages, GW3965 or LXRα overexpression significantly suppressed glycated or acetylated low-density lipoprotein-induced cytokines and reactive oxygen species. Specifically, in mice, transgenic expression of LXRα in macrophages significantly ameliorated hyperlipidemic-hyperglycemic nephropathy. The results demonstrate the presence of lipid droplet-induced oxidative mechanisms and the pathophysiologic role of macrophages in diabetic kidneys and indicate the potent regulatory role of LXRs in preventing renal damage in diabetes.

Endothelial control of vasomotor tone: the kidney perspective

Endothelial cells are essential regulators of vascular tone. They accomplish this by sensing humoral mediators and transducing their effects to the underlying vascular smooth muscle as well as by synthesizing vasoactive molecules that act in a paracrine fashion. In the kidney, the local release of these endothelial mediators, together with the concourse of specialized endothelial cells in the glomerulus, contribute to regulate renal blood flow, glomerular filtration, and tubular function that are intimately linked to sodium balance because they mutually influence each other. Ultimately, renal circulation and tubular function have a profound influence in systemic blood pressure as a result of the overall regulation of volume homeostasis.

Hypercholesterolemia promotes early renal dysfunction in apolipoprotein E-deficient mice

Background

Aging and dyslipidemia are processes which can lead to deleterious consequences to renal function. Therefore, the aim of this study was to determine the effects of both hypercholesterolemia and aging on renal function in mice.

Methods

Male hypercholesterolemic apolipoprotein E-deficient mice (ApoE, n = 13) and age-matched C57BL/6 control mice (C57, n = 15) were studied at 2 (young) and 8 (adult) month-old. At each time point, animals were placed in metabolic cages for 24 hours to urine volume and urinary creatinine quantification. Blood samples were collected for serum cholesterol, urea and creatinine measurements. Glomerular filtration rate (GFR) was estimated through creatinine clearance determination. Mesangial expansion was evaluated by Periodic Acid Schiff staining, renal fibrosis was determined through Masson's trichrome staining and neuronal nitric oxide synthase (nNOS) expression in the kidney was performed by Western Blotting. To statistical analysis two-way ANOVA followed by Fisher's post hoc test was used.

Results

Total plasma cholesterol was increased about 5-fold in ApoE mice at both time points compared to C57 animals. At 2-month-old, GFR was already markedly reduced in ApoE compared to C57 mice (187 ± 28 vs 358 ± 92 μL/min, p < 0.05). Adult C57 (-77%) and ApoE (-50%) mice also presented a significant reduction of GFR. In addition, serum urea was significantly increased in young ApoE animals compared to C57 mice (11 ± 1.3 vs 7 ± 0.9 mmol/L, p < 0.01). A significant mesangial expansion was observed at 2-month old ApoE mice compared to C57 mice (35 ± 0.6 vs 30 ± 0.9%, respectively, p < 0.05), which was aggravated at 8-month old animals (40 ± 3 and 35 ± 3%, respectively). Tubulointersticial fibrosis was augmented at both young (17 ± 2%, p < 0.05) and adult (20 ± 1%, p < 0.05) ApoE mice compared to respective C57 age controls (8 ± 1 and 12 ± 2%, respectively). The expression of nNOS was markedly reduced in a time-dependent manner in both strains.

Conclusions

These data show that both hypercholesterolemia and aging contribute to the loss of renal function in mice.

Carbamylated LDL

Nonenzymatic modification of protein by cyanate, that is, carbamylation, has received new attention due to its apparent relevance in atherosclerosis. For example, carbamylation of low-density lipoprotein (LDL) is an important mechanism that potentially impacts high-risk atherosclerotic individuals with increased urea (renal insufficiency) or thiocyanate (tobacco smoking). Carbamylated LDL (cLDL) is increased in patients with end-stage kidney disease, especially those with atherosclerosis. In addition, cLDL exhibits distinct cytotoxic effects when tested in vitro on endothelial cells, induces the expression of adhesion molecules, and aggravates the monocyte adhesion to endothelial cells. It also facilitates the proliferation of vascular smooth-muscle cell (VSMC). Studies of potential pharmacological interruption of these processes in vivo may lead to discoveries of novel therapies for atherosclerosis.

Lipotoxicity in macrophages: evidence from diseases associated with the metabolic syndrome

Accumulation of lipid metabolites within non-adipose tissues can induce chronic inflammation by promoting macrophage infiltration and activation. Oxidized and glycated lipoproteins, free fatty acids, free cholesterol, triacylglycerols, diacylglycerols and ceramides have long been known to induce cellular dysfunction through their pro-inflammatory and pro-apoptotic properties. Emerging evidence suggests that macrophage activation by lipid metabolites and further modulation by lipid signaling represents a common pathogenic mechanism underlying lipotoxicity in atherosclerosis, obesity-associated insulin resistance and inflammatory diseases related to metabolic syndrome such as liver steatosis and chronic kidney disease. In this review, we discuss the latest discoveries that support the role of lipids in modulating the macrophage phenotype in different metabolic diseases. We describe the common mechanisms by which lipid derivatives, through modulation of macrophage function, promote plaque instability in the arterial wall, impair insulin responsiveness and contribute to inflammatory liver, muscle and kidney disease. We discuss the molecular mechanism of lipid activation of pro-inflammatory pathways (JNK, NFkappaB) and the key roles played by the PPAR and LXR nuclear receptors-lipid sensors that link lipid metabolism and inflammation.

CXCL16 and oxLDL are induced in the onset of diabetic nephropathy

Diabetic nephropathy (DN) is a major cause of end-stage renal failure worldwide. Oxidative stress has been reported to be a major culprit of the disease and increased oxidized low density lipoprotein (oxLDL) immune complexes were found in patients with DN. In this study we present evidence, that CXCL16 is the main receptor in human podocytes mediating the uptake of oxLDL. In contrast, in primary tubular cells CD36 was mainly involved in the uptake of oxLDL. We further demonstrate that oxLDL down-regulated alpha(3)-integrin expression and increased the production of fibronectin in human podocytes. In addition, oxLDL uptake induced the production of reactive oxygen species (ROS) in human podocytes. Inhibition of oxLDL uptake by CXCL16 blocking antibodies abrogated the fibronectin and ROS production and restored alpha(3) integrin expression in human podocytes. Furthermore we present evidence that hyperglycaemic conditions increased CXCL16 and reduced ADAM10 expression in podocytes. Importantly, in streptozotocin-induced diabetic mice an early induction of CXCL16 was accompanied by higher levels of oxLDL. Finally immunofluorescence analysis in biopsies of patients with DN revealed increased glomerular CXCL16 expression, which was paralleled by high levels of oxLDL. In summary, regulation of CXCL16, ADAM10 and oxLDL expression may be an early event in the onset of DN and therefore all three proteins may represent potential new targets for diagnosis and therapeutic intervention in DN.

Implications of oxidative stress in the pathophysiology of obstructive uropathy

Although the functional and clinical alterations occurring in patients with obstructive uropathy are not well understood, it has been suggested that oxidative stress could contribute in the mechanism responsible for the impairment of sodium and water balance. This study aimed to test the hypothesis that red wine administration causes an amelioration of both the renal damage and impairment of renal Na(+), K(+)-ATPase activity occurring after ureteral obstruction in the rat. Twenty-four male Wistar adult rats weighting 200-250 g were used. Half of them received a 10-week treatment with wine as the sole fluid source, while the other group received water. Both groups were subjected to 24-h unilateral ureteral obstruction (UUO). Kidney tissue was collected following the relief of the ligature to perform the biochemical assessments. Urine and blood samples were taken at baseline and after the relief. Results show that the treatment with red wine significantly enhances the activity of antioxidant enzymes, and thus reduces renal lipid peroxidation secondary to UUO, which correlated negatively with Na(+), K(+)-ATPase activity. Based on this and other previous data, it could be suggested that red wine administration may prevent renal damage secondary to UUO by inducing enhanced antioxidant potential.

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.

Low density lipoproteins transactivate EGF receptor: role in mesangial cell proliferation

Hyperlipidemia and the glomerular accumulation of atherogenic lipoproteins (low density lipoprotein, LDL; and its oxidatively-modified variants, ox-LDL) are commonly associated with the development of glomerular mesangial proliferative diseases. However, cellular signaling mechanisms by which atherogenic lipoproteins stimulate mesangial cell proliferation are poorly defined. In this study, we examined the effect of atherogenic lipoproteins on the activation of mesangial cell epidermal growth factor (EGF) receptor, mitogen activated protein kinase (MAP kinase), Ras, and mesangial cell proliferation. Stimulation of mesangial cells with LDL, and with greater activity, ox-LDL, markedly induced the transactivation of EGF receptor within 5 min of stimulation; the effect persisted up to at least 60 min LDL, and with a greater degree, ox-LDL, increased the activation of Ras, MAP kinase, and mesangial cell proliferation. Inhibition of EGF receptor kinase activity and/or MAP kinase activation blocked both LDL- and ox-LDL-induced mesangial cell proliferation. We suggest that the accumulation of LDL and more potently its oxidized forms within the glomerulus, through the transactivation of EGF receptor, stimulate down-stream Ras-MAP kinase signaling cascade leading to mesangial cell proliferation. Regulation of glomerular accumulation of atherogenic lipoproteins and/or EGF receptor signaling may provide protective environment against mesangial hypercellularity seen in glomerular diseases.

D-4F reduces EO6 immunoreactivity, SREBP-1c mRNA levels, and renal inflammation in LDL receptor-null mice fed a Western diet

LDL receptor-null (LDLR(-/-)) mice on a Western diet (WD) develop endothelial dysfunction and atherosclerosis, which are improved by the apolipoprotein A-I (apoA-I) mimetic peptide D-4F. Focusing on the kidney, LDLR(-/-)mice were fed a WD with D-4F or the inactive control peptide scrambled D-4F (ScD-4F) added to their drinking water. The control mice (ScD-4F) developed glomerular changes, increased immunostaining for MCP-1/CCL2 chemokine, increased macrophage CD68 and F4/80 antigens, and increased oxidized phospholipids recognized by the EO6 monoclonal antibody in both glomerular and tublo-interstitial areas. All of these parameters were significantly reduced by D-4F treatment, approaching levels found in wild-type C57BL/6J or LDLR(-/-) mice fed a chow diet. Sterol-regulatory element binding protein-1c (SREBP-1c) mRNA levels and triglyceride levels were elevated in the kidneys of the control mice (ScD-4F) fed the WD compared with C57BL/6J and LDLR(-/-) mice on chow (P < 0.001 and P < 0.001, respectively) and compared with D-4F-treated mice on the WD (P < 0.01). There was no significant difference in plasma lipids, lipoproteins, glucose, blood pressure, or renal apoB levels between D-4F- and ScD-4F-treated mice. We conclude that D-4F reduced renal oxidized phospholipids, resulting in lower expression of SREBP-1c, which, in turn, resulted in lower triglyceride content and reduced renal inflammation.

Lysophosphatidylcholine stimulates EGF receptor activation and mesangial cell proliferation: regulatory role of Src and PKC

Lysophosphatidylcholine (LPC), a major component of oxidized-low density lipoproteins (ox-LDL), modulates various pathobiological processes involved in vascular and glomerular diseases. Although several studies have shown increased plasma concentrations of ox-LDL as well as LPC in patients with renal disease, the role of LPC in mesangial cell proliferation and associated signaling mechanisms are not clearly understood. In this study, we have shown that LPC induced the phosphorylation of epidermal growth factor receptor (EGFR), as well as the p42/44 MAP kinases. LPC activated Src-kinase and protein kinase C (PKC), and both Src kinase inhibitor PP-2 and PKC inhibitor inhibited the activation of EGFR by LPC. LPC (5-25 microM) stimulated human mesangial cell proliferation by 4-5 fold. Preincubation of mesangial cells with the Src inhibitor (PP-2), or PKC inhibitor (bisindolylmaleimide GF109203-X), or EGF receptor kinase inhibitor (AG1478), or MEK inhibitor (PD98059) significantly inhibited LPC-mediated mesangial cell proliferation. The data suggest that LPC, by activating Src and PKC signaling pathways, stimulates EGF receptor transactivation and down-stream MAP kinase signaling resulting in mesangial hypercellularity, which is a characteristic feature of diverse renal diseases.

Protective role of sulphated polysaccharides in abating the hyperlipidemic nephropathy provoked by cyclosporine A

Cyclosporine A (CsA)-induced nephrotoxicity hampers the immense therapeutic potential of such a powerful immunosuppressant. The present study was conducted with an aim to explicate the contribution of sulphated polysaccharides (SPS) in abating the lipid abnormalities induced by CsA in the rat kidney. Hyperlipidemia associated with nephrotic syndrome may play a role in the worsening of renal function. Male albino Wistar rats sorted into four groups were used for the study. CsA was given at a dose of 25 mg/kg body weight, orally for 21 days. Significant alterations in the lipid profile as well an increase in the activity of cholesterol ester synthase, coupled with a decrease in cholesterol ester hydrolase and lipoprotein lipase enzyme activities were noted in the plasma and kidneys of CsA-administered rats. A marked increase in the lipoprotein fractions, low-density lipoprotein (LDL) and very low density lipoprotein (VLDL), along with a decrease in the HDL level were found in CsA-administered rats. The degree of nephrotoxicity allied with lipid discrepancies was evident from augmented urinary excretion of urea, uric acid and creatinine. Further, an enhanced susceptibility of the apo B-containing lipoproteins (LDL + VLDL) to oxidation in vitro, induced by copper ions was also found in the plasma of CsA given groups. While SPS co-treated groups (5 mg/kg body weight, subcutaneously) revealed a normalized lipid profile and lipid metabolizing enzymes, the supplementation of SPS also brought back the elevated urinary constituents close to that of the controls and substantially minimized the oxidative changes. With these observations, it may be concluded herein that SPS may be an ideal choice as a renoprotective and hypolipidemic agent against CsA-induced hyperlipidemic nephropathy.

Group IVA phospholipase A2-mediated production of fibronectin by oxidized LDL in mesangial cells

The deposition of atherogenic lipoproteins such as oxidized low-density lipoprotein (oxLDL) within the mesangium is involved in the overproduction of extracellular matrix proteins, a key event in the progression of glomerular diseases including glomerulosclerosis. To clarify the mechanisms underlying the oxLDL-induced production of extracellular matrix proteins, we examined the possible involvement of group IVA phospholipase A(2) (PLA(2)) using human mesangial cells and group IVA PLA(2)-deficient mouse mesangial cells. oxLDL accelerated the production of fibronectin and collagen (type IV), components of extracellular matrix proteins, with the preceding release of arachidonic acid. Methyl arachidonyl fluorophosphonate (MAFP), known as an inhibitor of group IVA PLA(2), markedly suppressed the oxLDL-induced production of fibronectin as well as the release of arachidonic acid, whereas it did not inhibit the production of collagen. The inhibitory effect of MAFP on the production of fibronectin was reversed by adding arachidonic acid and 12-hydroxyeicosatetraenoic acid. Furthermore, we found that in group IVA PLA(2)-deficient mouse mesangial cells, the production of fibronectin in response to oxLDL was weak as compared with that in wild-type cells. However, the production by oxLDL of collagen was not suppressed in the group IVA PLA(2)-deficient cells. These findings suggest that group IVA PLA(2) is involved in the production of fibronectin in oxLDL-stimulated mesangial cells.

Cyclic arginine-glycine-aspartic acid peptide inhibits macrophage infiltration of the kidney and carotid artery lesions in apo-E-deficient mice

Interactions of leukocytes with the vascular endothelium culminating in their diapedesis represent not only a crucial event in immune surveillance and defense but are also critically involved in the pathogenesis of many inflammatory diseases, including atherosclerosis. Our previous in vitro studies using atomic force microscopy measurement of monocyte-endothelial cell interaction have demonstrated that a cyclic arginine-glycine-aspartic acid peptide (cRGD) inhibited their adhesion through very late antigen (alpha4beta1-integrin; VLA4)-vascular cell adhesion molecule-1 by 60% with the IC50 = 100 nM. To elucidate the potential efficacy of this peptide in vivo in preventing atherogenesis, experiments were performed in apolipoprotein E (ApoE)-deficient (-/-) mice fed a Western diet and receiving chronic treatment with cRGD peptide for 2-4 wk. In addition, some animals were subjected to a temporary carotid artery ligation while receiving the above treatment. Formation of fatty streaks and infiltration of the vascular wall with macrophages were not affected by cRGD treatment. Infiltration of the carotid artery postligation was significantly reduced in the cRGD-treated animals, as was the lipid accumulation. Furthermore, cRGD-treated ApoE-/- mice exhibited significantly lesser macrophage infiltration and lipid accumulation in the kidneys, the site of the highest expression of VLA4. These data demonstrated that cRGD peptide is a potent inhibitor of monocyte/macrophage infiltration of the injured macrovasculature and of the renal microvasculature, where it results in the attenuation of lipid accumulation. Formation of fatty streaks in the aortic root was not inhibitable by this treatment.

Kidney in early atherosclerosis

Atherosclerosis represents one of the major causes of premature death in the United States today, and it is frequently associated with, exacerbates, and is aggravated by chronic kidney disease (CKD). Atherosclerosis integrates the response to a number of insults, and consequently, the accelerated atherosclerosis found in CKD patients is associated with activation of a variety of humoral and tissue mechanisms. Hypertension, diabetes, dyslipidemia, obesity, metabolic syndrome, and additional nontraditional risk factors can damage the kidney directly and by promoting intrarenal atherogenesis, even in the absence of obstructive lesions in the renal artery. Evidence indicates that increased oxidative stress and inflammation may mediate a large part of the effects of risk factors on the kidney. In turn, progressive deterioration of renal function in CKD may lead to dyslipidemia or accumulation of uremic toxins, which can induce production of free radicals and activate proinflammatory and fibrogenic factors, leading to vascular endothelial cell dysfunction and injury, and favoring development of atherosclerosis. Therefore, the kidney can be a villain or a victim during atherogenesis. The purpose of this review is to provide new insights into the mechanisms by which atherogenic factors may instigate early renal injury.

9HODE stimulates cell proliferation and extracellular matrix synthesis in human mesangial cells via PPARgamma

Plasma oxidized low-density lipoprotein (OX-LDL) levels are elevated in patients with renal diseases, including diabetic nephropathy. We examined effects of OX-LDL on cell proliferation and extracellular matrix (ECM) production by using normal human mesangial cells. Furthermore, we examined possible involvement of peroxisome proliferator-activated receptor gamma (PPARgamma). Mesangial cell proliferation with OX-LDL, 9-hydroxy-10,12-octadecadienoic acid (9HODE), and 13-hydroxy-9,11-octadecadienoic acid (13HODE), the major components of OX-LDL, were determined by 5-bromo-2'-deoxyuridine (BrdU) or 3-(4,5-dimethylthiazol-2-yl)-2, 5-diphenyl tetrazolium bromide (MTT) incorporation. The effect of OX-LDL on mesangial cell proliferation with PD98059 pretreatment was determined by BrdU incorporation. Type IV collagen, fibronectin, and PPARgamma expression with OX-LDL or 9HODE or 13HODE was determined by Western blotting. Type IV collagen expression with antisense oligonucleotide against PPARgamma pretreatment was also determined by Western blotting. The effect of PD98059 pretreatment on PPARgamma expression was determined by Western blotting. In mesangial cells exposed to isolated OX-LDL from human plasma, BrdU incorporation was increased, and this increase was deleted by PD98059. Type IV collagen expression was significantly increased by OX-LDL. 9HODE and 13HODE increased BrdU and MTT incorporation into mesangial cells and also increased expressions of Type IV collagen and fibronection, the major components of ECM. PPARgamma expression in mesangial cells was stimulated by 9HODE. The reduction of PPARgamma synthesis by pretreatment of antisense oligonucleotide against PPARgamma remarkably attenuated Type IV collagen synthesis induced by 9HODE. PPARgamma expression induced by 9HODE was also reduced by PD98059 pretreatment. These findings demonstrate that 9HODE, the major component of OX-LDL, stimulates cell proliferation and ECM production of human mesangial cells. In addition, the stimulatory effects are, at least in part, mediated by PPARgamma, which may exist in downstream of ERK1/2 pathway.

Urine of Patients with Nephrotic Syndrome Contains the Plasma Type of PAF-Acetylhydrolase Associated with Lipoproteins

BACKGROUND

Platelet-activating factor (PAF) is a proinflammatory phospholipid mediator involved in the pathogenesis of glomerulonephritis (GN). In plasma, PAF is hydrolyzed and inactivated by PAF-acetylhydrolase (PAF-AH), an enzyme associated with lipoproteins, mainly with the low-density lipoprotein. PAF-AH activity has been found in urine of patients with primary GN, however the source and type of urinary PAF-AH remain unknown. We characterized the type of PAF-AH excreted in the urine of patients with primary GN and studied the possible relationship of this enzyme with the lipiduria and proteinuria observed in these patients.

METHODS

Eighteen patients with primary GN (8 with nephrotic syndrome (NS) and 10 with non-nephrotic range proteinuria (NNRP)) and 20 normolipidemic age- and sex-matched controls participated in the study. PAF-AH activity in plasma, in urine and in individual lipoprotein particles was determined by the trichloroacetic acid precipitation procedure, whereas the PAF-AH protein was detected by Western blotting analysis. Plasma and urine lipoproteins were fractionated by gradient ultracentrifugation and characterized by Western blotting analysis.

RESULTS

Plasma PAF-AH activity was higher in NS patients compared with NNRP patients and controls, whereas the enzyme activity associated with high-density lipoprotein was significantly lower in both patient groups compared with controls. PAF-AH was detected only in the urine of NS patients. It was the plasma type of PAF-AH and was associated with lipoprotein particles. Enzyme activity was also positively correlated with urine cholesterol levels.

CONCLUSION

Urine of NS patients contains the plasma type of PAF-AH, which is related to the extent of lipiduria and is associated with urine lipoproteins.

Involvement of reactive oxygen species and SP-1 in fibronectin production by oxidized LDL

We examined the mechanisms responsible for the production of fibronectin induced by oxidized low-density lipoprotein (oxLDL) in rat mesangial cells. oxLDL accelerated the production of fibronectin with the preceding generation of reactive oxygen species (ROS). Pretreatment with N-acetylcysteine suppressed the oxLDL-induced fibronectin production as well as ROS generation. oxLDL also elicited the activation of SP-1, nuclear factor-kappaB, and cAMP response element-binding protein, but not activator protein-1. Among these activated transcription factors, N-acetylcysteine inhibited the activation of SP-1 only. 7-Ketocholesterol, an oxidized lipid in oxLDL particles, induced the production of fibronectin and the activation of SP-1, those which were suppressed by N-acetylcysteine. Furthermore, mithramycin A, an inhibitor of SP-1, also suppressed the oxLDL- and 7-ketocholesterol-stimulated production of fibronectin. These results suggest that oxLDL stimulates fibronectin production, at least in part, through the ROS-dependent activation of SP-1 in rat mesangial cells, and further that the ROS-dependent cellular responses may be elicited by 7-ketocholesterol.

Improved cardiovascular risk profile and renal function in renal transplant patients after randomized conversion from cyclosporine to tacrolimus

Cyclosporine is considered to contribute to the high cardiovascular morbidity and mortality in patients after renal transplantation. Tacrolimus may be more favorable in this respect, but controlled data are scarce. In this prospective randomized study in 124 stable renal transplant patients, the effects of conversion from cyclosporine to tacrolimus on cardiovascular risk factors and renal function were investigated. Follow-up was 6 mo. Statistical analysis was performed by ANOVA for repeated measurements. The serum creatinine level decreased from 137 +/- 30 micromol/L to 131 +/- 29 micromol/L (P < 0.01). Three months after conversion from cyclosporine to tacrolimus, mean BP significantly decreased from 104 +/- 13 to 99 +/- 12 mmHg (P < 0.001). Serum LDL cholesterol decreased from 3.48 +/- 0.80 to 3.11 +/- 0.74 mmol/L (P < 0.001,) and serum apolipoprotein B decreased from 1018 +/- 189 to 935 +/- 174 mg/L (P < 0.001). Serum triglycerides decreased from 2.11 +/- 1.12 to 1.72 +/- 0.94 mmol/L (P < 0.001). In addition, both rate and extent of LDL oxidation were reduced. The fibrinogen level decreased from 3638 +/- 857 to 3417 +/- 751 mg/L (P < 0.05). Plasma homocysteine concentration did not change. Three months after conversion, plasma fasting glucose level temporarily increased from 5.4 +/- 1.3 mmol/L to 5.8 +/- 1.9 mmol/L (P < 0.05). Conversion to tacrolimus resulted in a significant reduction of the Framingham risk score. In conclusion, conversion from cyclosporine to tacrolimus in stable renal transplant patients has a beneficial effect on renal function, BP, serum concentration and atherogenic properties of serum lipids, and fibrinogen.

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.

Different mechanisms of adhesion molecule expression in human dermal microvascular endothelial cells by xanthoma tissue-mediated and copper-mediated oxidized low density lipoproteins

BACKGROUND

Oxidation of low density lipoprotein (LDL) has been implicated in infiltration of foam cells derived from circulating monocytes. Monocyte adhesion to endothelial cells and migration into dermis are essential steps for infiltration of foam cells.

OBJECTIVE

We investigated the role of adhesion molecules contributing to the process of monocyte adhesion to human dermal microvascular endothelial cells (HDMEC). Special attention was paid to the signal transduction for adhesion molecule expression induced by two distinct types of oxidized LDL.

METHODS

HDMEC were incubated with xanthoma tissue-modified LDL (x-LDL), a model of extravasated LDL oxidized in xanthoma lesions, or Cu(2+)-treated LDL (Cu-LDL), a model of oxidized LDL. Adhesion of U937 cells, a human monocytic leukemia cell line, to HDMEC and expression of endothelial cell adhesion molecules on HDMEC were examined. Signal transduction pathways for the adhesion molecule expression were evaluated by employing specific inhibitors.

RESULTS

x-LDL induced adhesion of U937 cells to HDMEC through vascular cell adhesion molecule-1 (VCAM-1) and E-selectin by activating tyrosine kinase pathway. Cu-LDL up-regulated the adhesion through not only VCAM-1 and E-selectin but also intercellular cell adhesion molecule-1 (ICAM-1) by activating G(i) protein pathway.

CONCLUSION

Extravasated and oxidized LDL in xanthoma lesions contributes to foam cell recruitment by activating tyrosine kinase pathway and inducing adhesion of monocytes to HDMEC through VCAM-1 and E-selectin. Cu-LDL, on the other hand, activates G(i) protein pathway and induces the adhesion through ICAM-1, VCAM-1 and E-selectin.

The aryl hydrocarbon receptor and its xenobiotic ligands: a fundamental trigger for cardiovascular diseases

This review reconsiders a major cause of cardiovascular diseases, tobacco smoking, as the activation of the Aryl hydrocarbon Receptor (AhR), also known as the dioxin receptor, by aryl hydrocarbons from the tar fraction of tobacco in various organs of the cardiovascular domain. This concept sheds new light on well-known albeit controversial epidemiological concepts such as the Mediterranean diet and the French paradox. We also review the discovery that resveratrol, a natural AhR antagonist, may be of interest in the prevention and treatment of cardiovascular diseases.

Renal function tests on diabetes-induced and non-induced APA hamsters

Although it has been said that Syrian hamsters of the APA strain (APA hamsters) spontaneously develop glomerulosclerosis with age, more prominent and severe glomerulosclerosis with proteinuria as well as arteriosclerosis is induced in diabetic APA hamsters. In this study, in order to supply new information on APA hamsters, tests on renal function and histology were done on non-diabetic and streptozotocin (SZ)-induced diabetic APA hamsters (APA-N and APA-D, respectively), and the data were compared with those of normal Syrian (golden) hamsters (GOL). At 4, 8, 12, 20, and 32 weeks of age, the markers indicating renal function, serum urea nitrogen and creatinine levels and the urinary total protein level were measured and thereafter histological studies were done. Although there were no remarkable differences between APA-N and GOL in serum urea nitrogen and creatinine levels, APA-N excreted more urinary total protein from the early weeks of age. In APA-D, an apparent worsening in these markers indicating renal function was detected and diabetic nephropathy in this model was confirmed also in terms of renal function. In the histological studies, the major lesion observed in APA-D was diffuse glomerulosclerosis. This may mean that renal dysfunction in APA-D was mainly caused by the glomerular change and that it is similar to other experimental diabetic animals and human diabetic patients. These data show that the diabetic APA hamster is a desirable model of human diabetic nephropathy.

Prevention of obesity-linked renal disease: age-dependent effects of dietary food restriction

BACKGROUND

Hyperphagic obese Zucker rats develop glomerular injury and die of renal disease, an outcome prevented by food restriction at an early age. We examined the effects of food restriction imposed at different ages on systemic, renal hemodynamic, and hormonal changes to gain insight into the mechanisms of obesity-linked glomerular injury.

METHODS

At 6 weeks of age obese Zucker rats were either fed ad libitum or were restricted in food intake at various ages (6, 12, 26, or 50 weeks) to that consumed by lean Zucker rats (14 g/day). Every four weeks 24-hour urine collections, blood pressure, and venous blood samples were obtained until the end of study (60 weeks).

RESULTS

Food restriction at 6 or 12 weeks of age prevented glomerular injury and hypertrophy and delayed the development of hypertension, hypercholesterolemia, and hyperinsulinemia. Food restriction at 26 weeks of age reduced proteinuria, while restriction at 50 weeks prevented further increases in proteinuria without altering pre-existing hypercholesterolemia, hypertension, or hyperinsulinemia. Hypertriglyceridemia and glomerular hyperfiltration in the obese animals were reversed at any age by food restriction. Plasma leptin levels were elevated in all obese groups.

CONCLUSIONS

(1) Early food restriction provided the greatest metabolic and renal benefits; (2) glomerular injury correlated with hyperphagia-induced hyperfiltration and hypertriglyceridemia and both were prevented by food restriction; (3) hypercholesterolemia was due to an increase in LDL and/or VLDL cholesterol; and (4) leptin does not directly contribute to glomerular injury in the obese Zucker rat.

Effects of antioxidants on kidney disease

Kidney mesangial cells (MCs) and vascular smooth muscle cells (VSMCs) are closely related in terms of origin, microscopic anatomy, histochemistry, and contractility. This relationship suggests a similarity between kidney glomerular sclerosis and atherosclerosis. Vitamin E appears beneficial in the prevention and treatment of coronary disease and also inhibits the proliferation of VSMCs in vitro. We used vitamin E and probucol to treat glomerular sclerosis and MC-proliferative glomerulonephritis (GN) in two animal models of glomerular disease. Using rats, a remnant kidney model accelerated with hyperlipidemia was employed to reflect progressive glomerular sclerosis leading to chronic renal failure, and an anti-thymocyte serum treatment was used to model acute MC-proliferative GN. Supplemental dietary antioxidants suppress MC proliferation and glomerular sclerosis in models of glomerular disease in rats. These results suggest that treatment with antioxidants may be a promising intervention to prevent progression of kidney disease.

Oxidative modification of low-density lipoproteins and the outcome of renal allografts at 1 1/2 years

BACKGROUND

Previous studies reported a significant association between hyperlipidemia of the recipient and chronic allograft nephropathy (CAN). However, the nature and the pathogenic mechanism of circulating lipid abnormalities in CAN remain unclear.

METHODS

In a prospective study of 50 consecutive adult recipients of a cadaveric renal allograft, we investigated the impact of lipid abnormalities on the outcome of the graft at 1 1/2 years. Besides morphometric analysis of implantation and protocol biopsies, clinical and biochemical variables were studied at three-month intervals. Plasma concentrations of oxidized low-density lipoprotein (OxLDL) were determined by means of enzyme-linked immunosorbent assay. Immunohistochemical staining for OxLDL and macrophages was performed on paired renal biopsies. Study end points were the fractional interstitial volume and the 24-hour creatinine clearance at 11/2 years.

RESULTS

High-density lipoprotein (HDL) cholesterol of the recipient < or =47 mg/dL was a risk factor for the functional (RR = 1.56; 95% CI, 0.978 to 2.497) and the morphological (RR = 2.75; 95% CI, 1.075 to 7.037) outcome of the graft, mainly in patients without acute rejection (RR = 2.03; 95% CI, 1.13 to 3.65, and RR = 4.67; 95% CI, 1.172 to 18.582, respectively). Interstitial accumulation of OxLDL was inversely associated with HDL cholesterol (R = -0.476, P = 0.019), and was associated with a higher density of tubulointerstitial macrophages (R = 0.656, P = 0.001) and a higher fractional interstitial volume at 11/2 years (P = 0.049).

CONCLUSION

Decreased HDL cholesterol levels of the recipient adversely affect the outcome of renal allografts through the accumulation of OxLDL in the renal interstitium of the graft. Interstitial accumulation of OxLDL was associated with the presence of macrophages and the development of interstitial fibrosis.

Lipid oxidation products in cell signaling

The recent research on the impact that oxidative changes of biolipids could have in pathophysiology serves to explain how free radical-driven reactions not only are considered as mere toxicologic events, but also modulators of cell activity and function. Oxidatively modified low-density lipoproteins are known to affect various cellular processes by modulating various molecular pathways and signaling nuclear transcription. Among the lipid oxidation products detectable in ox-LDLs, and also in the atherosclerotic plaques, 4-hydroxynonenal has been widely investigated. This aldehyde was shown to upregulate AP-1 transcription factor, signaling through the MAP kinase pathway, with eventual nuclear localization and induction of a series of genes. Further, oxidation products of cholesterol and cholesterol esters, in ox-LDL are of similar interest, especially in relation to the pathogenesis of fibrosclerotic lesions of the arterial wall.