Biomarkers of Subclinical Atherosclerosis and Natural Products as Complementary Alternative Medicine

Chaperone duality: the role of extracellular and intracellular HSP70 as a biomarker of endothelial dysfunction in the development of atherosclerosis

The 70-kDa heat shock proteins (HSP70) may provide relevant information about the endothelial dysfunction in cardiovascular diseases. Located in the intracellular milieu (iHSP70), they are essential chaperones that inhibit nuclear factor kappa B activation, stimulate nitric oxide production and superoxide dismutase activity, and inhibit apoptosis. However, under stressful conditions, HSP70 can be released into the extracellular medium (eHSP70) and act as an inflammatory mediator. Although studies have reported the vasoprotective role of iHSP70, the evidence regarding eHSP70 is contradictory. eHSP70 can activate NFκB and activator protein-1, thus stimulating the release of inflammatory cytokines and production of reactive oxygen species. Due to the antagonistic nature of HSP70 according to its location, the eHSP70/iHSP70 ratio (Heck index) has been proposed as a better marker of inflammatory status; however, more studies are required to confirm this hypothesis. Therefore, this review summarises studies that, together, describe the role of HSP70 in endothelial dysfunction.

Leaf extracts of Campomanesia xanthocarpa positively regulates atherosclerotic-related protein expression

Atherosclerosis is caused by a monocyte-mediated inflammatory process that, in turn, is stimulated by cytokines and adhesion molecules. Monocytes are then differentiated into macrophages, leading to the formation of arterial atherosclerotic plaques. Recently, guavirova leaf extracts from Campomanesia xanthocarpa (EG) have shown potential effects on the treatment of plaque formation by reducing cholesterol, LDL levels and serum oxidative stress. We evaluated the effect of EG on the viability of human monocytic and endothelial cell lines at three time points (24, 48 and 72 hours) and whether it can modulate the migration and in vitro expression of CD14, PECAM-1, ICAM-1, HLA-DR and CD105. Cell viability was affected only at higher concentrations and times. We observed decreased ICAM-1 expression in cells treated with 50 μg/ml EG and CD14 expression with IFN-γ and without IFN-γ. CD14 also decreased endothelial cell expression in the presence of IFN-γ and GE. We also found decreased expression of PECAM-1 when treated with EG and IFN-γ. In addition, EG-treated endothelial cells showed higher migration than the control group. Reduced expression of these markers and increased migration may lead to decreased cytokines, which may be contributing to decreased chronic inflammatory response during atherosclerosis and protecting endothelial integrity.

Bergaptol from blossoms of Citrus aurantium L. var. amara Engl inhibits LPS-induced inflammatory responses and ox-LDL-induced lipid deposition

Aberrant activation of inflammation and excess accumulation of lipids play pivotal roles in atherosclerosis (AS) progression. Constituents from Citrus aurantium Linn variant amara Engl (CAVA) were effectively investigated for their various bioactivities, especially anti-inflammation. Bergaptol (BER) is particularly abundant in Citrus products. Accumulating studies have confirmed its predominant anti-cancer and antioxidant functions, whereas few studies focused on its antiatherogenic functions. In the current study, BER was isolated from CAVA for the first time. Macrophages were stimulated with lipopolysaccharides (LPSs) or oxidized low-density lipoproteins (ox-LDL) to mimic inflammatory responses and AS development. BER treatment significantly inhibited LPS-induced production of nitric oxide (NO), interleukin-6 (IL-6), and tumor necrosis factor-α (TNF-α), and gene expression of inducible nitric oxide synthase (iNOS), IL-6, TNF-α, interleukin-1 beta (IL-1β) and cyclooxygenase-2 (COX-2). BER also potently blocked LPS-induced mitogen-activated protein kinase (MAPK) phosphorylation and nuclear factor-kappa B (NF-κB) activation, as evidenced by the inhibitory effects on c-Jun N-terminal kinase (JNK), P38, P65, IκBα and IκKα/β phosphorylation, and NF-κB nuclear translocation. Furthermore, BER treatment markedly mitigated ox-LDL-induced foam cell formation by inhibiting scavenger receptor class A type I (SRA1) and cluster of differentiation 36 (CD36)-dependent cholesterol uptake. In conclusion, BER might be a novel therapeutic agent for AS prevention through inhibiting inflammatory responses and cholesterol uptake.

Anti-hyperlipidemic effects of Campomanesia xanthocarpa aqueous extract and its modulation on oxidative stress and genomic instability in Wistar rats

The use of natural products from herbs may be a therapeutic option in dyslipidemia treatment. Campomanesia xanthocarpa (Mart.) O. Berg (Myrtaceae) leaves have been used to decrease cholesterol levels. However, studies to determine activities of this plant on triglycerides metabolism have received little attention. The aim of this study was to examine anti-hyperlipidemic effects of a C. xanthocarpa aqueous leaf extract (CxAE) and assess protective actions against oxidative stress and DNA damage. The tyloxapol-induced hyperlipidemia model was used in Wistar rats. Rats were treated orally with CxAE either 250 or 500 mg/kg/day for 7 days prior to tyloxapol administration. Biochemical parameters, oxidative stress levels, and genomic instability were assessed in several tissues. CxAE decreased cholesterol and triglyceride levels in serum and hepatic and renal DNA damage in tyloxapol-treated rats. There was no marked effect on the micronucleus frequency in bone marrow. The extract increased catalase activity and decreased glutathione S-transferase activity in kidney tissue. CxAE showed anti-hyperlipidemic effects, improved oxidative parameters, and protected DNA against damage induced by tyloxapol-induced hyperlipidemia, suggesting C. xanthocarpa leaves may be useful in preventing dyslipidemias.Abbreviations: ALP: Alkaline phosphatase; ALT: Aspartate aminotransferase; ANOVA: Analysis of variance; AST: Aspartate aminotransferase; Ator: Atorvastatin; CAT: Catalase; Chol: Cholesterol; CxAE: Campomanesia xanthocarpa aqueous extract; GST: Glutathione S-transferase; HDL: High density cholesterol; i.p.: Intraperitoneal; NCE: Normochromatic erythrocyte; PBS: Phosphate buffer solution; PCE: Polychromatic erythrocyte; ROS: Reactive oxygen species; SD: Standard deviation; SOD: Superoxide dismutase; T: Tyloxapol; TBARS: Thiobarbituric acid reacting substances; TG: Triglyceride.

Toxicological aspects of Campomanesia xanthocarpa Berg. associated with its phytochemical profile

Campomanesia xanthocarpa leaves are used as tea to treat diarrhea, inflammation, and hypercholesterolemia. Some pharmacological studies noted its beneficial uses of C. xanthocarpa; however, few investigations examined the toxicological profile of this plant. The aim of this study was to determine the chemical composition, genotoxic, and mutagenic potential of an aqueous extract of C. xanthocarpa leaves (CxAE), and potential protective effects against oxidative damage. Phytochemical constituents were determined using HPLC, and antioxidant effect in vitro was measured using 2,2-diphenyl-1-picrylhydrazyl (DPPH) free radical assay. Genotoxic effects and chromosomic mutations were assessed using comet assay and micronucleus (MN) test in Wistar rats treated with CxAE at 250, 500 or 1000 mg/kg for 7 consecutive days. Lipid peroxidation and antioxidant enzyme activities were measured in several tissues. CxAE induced mutations in TA98, TA97a, and TA102 strains. However, in the presence of metabolic activation, data were negative for all strains tested. Lack of mutagenicity was also observed in the MN test. This extract did not induce DNA damage, except when the highest concentration was used. DNA oxidative damage induced by hydrogen peroxide (H₂O₂) decreased in blood after treatment with CxAE. Lipid peroxidation levels were reduced while superoxide dismutase (SOD) activity increased in kidneys. The inhibitory concentration of CxAE required to lower DPPH levels to 50% was 38.47 ± 2.06 μg/ml. In conclusion, frameshift and oxidative mutations were observed only in the absence of metabolic activation which may be attributed to the presence of flavonoids such as quercetin. It is of interest that CxAE also showed protective effects against DNA oxidative damage associated with presence of ellagic acid, a phenolic acid with antioxidant activities. CxAE did not induce in vivo mutagenicity, suggesting that this extract poses a low toxic hazard over the short term.

Docosahexaenoic acid reversed atherosclerotic changes in human endothelial cells induced by palmitic acid in vitro

Abnormal activity of atherosclerotic endothelial cells paving luminal surface of blood vessels has been described in many diseases. It has been reported that natural polyunsaturated fatty acids such as docosahexaenoic acid exert therapeutic effects in atherosclerotic condition. Human umbilical vein endothelial cells were treated with 1mM palmitic acid for 48 hours and exposed to 40μM docosahexaenoic acid for the next 24 hours. Real-time polymerase chain reaction analysis was used to measure the expression of PTX3, iNOS, and eNOS. The level of nitric oxide was detected by Griess reagent. The transcription level of genes participating in coagulation and blood pressure was studied by polymerase chain reaction array. Docosahexaenoic acid improved the survival rate by reducing apoptosis rate (P < .05). Compared with that of the group given palmitic acid, attenuation of proinflammatory status was indicated by reduced interleukin-6 (P < .05) and prostaglandin E₂ levels. All genes PTX3, iNOS, and eNOS were down-regulated after being exposed to docosahexaenoic acid. Nitric oxide contents were not changed in cells exposed to docosahexaenoic acid. Polymerase chain reaction array confirmed the reduction of LPA, PDGFβ, ITGA2, SERPINE1, and FGA after exposure to docosahexaenoic acid for 24 hours (P < .05). Docosahexaenoic acid had potential to blunt atherosclerotic changes in the modulation of genes controlling blood coagulation, pressure, and platelet function.

SIGNIFICANCE OF THE STUDY

The current experiment showed that docosahexaenoic acid could reverse atherosclerotic changes in human endothelial cells induced by palmitic acid. The increased levels of interleukin-6 and prostaglandin E₂ in atherosclerotic cells were returned to near-to-normal status. Gene expression analysis showed a reduced activity of genes participating in atherosclerotic endothelial cells treated by docosahexaenoic acid. The expression of genes related to cell clotting activity was also similar to that of normal cells.

Chronic administration of antioxidant resin from Virola oleifera attenuates atherogenesis in LDLr -/- mice

ETHNOPHARMACOLOGICAL RELEVANCE

Virola oleifera (Schott) A. C. Smith, Myristicaceae has been largely used in traditional folk medicine in Brazil as an anti-inflammatory agent and our previous data indicated the antioxidant properties in other oxidative stress-related models. However, its effects on atherosclerosis (AT) are not yet investigated.

AIMS OF THE STUDY

To evaluate the influence of resin from Virola oleifera (RV) on progression of AT in LDLr^-/- mice.

MATERIALS AND METHODS

LDLr^-/- mice were divided into 4 groups: 1) The ND group received a normal diet without treatment. 2) The HD group received a high-fat diet without treatment. 3) The HD-V50 received a high-fat diet and was orally treated with RV at 50mg/Kg. 4) The HD-V300 received a high-fat diet and was orally treated with RV at 300mg/Kg. After 4 weeks, blood was collected to quantify biochemical parameters and ROS total and the aorta was removed to measure the lipid deposition by en face analysis. The liver was also collected to determine total lipids and lipid and protein oxidation. In order to investigate in more detail the contributions of RV in the vascular structure, we carried out the in vitro tests using four cellular types: macrophages, fibroblasts, vascular smooth muscle and endothelial cells.

RESULTS

We showed that the chronic treatment of RV at both doses reduced vascular lipid accumulation (~50%, p<0.05), probably through systemic and hepatic antioxidant effects, independent of dyslipidemia. Moreover, the in vitro assay results demonstrated that RV develops antioxidant properties on the vascular smooth muscle and endothelial cells, reinforcing the protective role of RV in progression of AT. LPS-stimulated macrophages treated with RV resulted in a significant reduction of NO production in a concentration-dependent manner.

CONCLUSIONS

Chronic treatment with RV diminishes lipid deposition in atherosclerotic mice, which may be justified, at least in part, by antioxidant systemic and local mechanisms, reinforcing the protective role this resin in the setting of vascular lipid deposition, independent of hypercholesterolemia.