Dynamics of LDL oxidation in ischemic stroke patients

Apolipoprotein B100/Low-Density Lipoprotein Regulates Proteolysis and Functions of von Willebrand Factor under Arterial Shear

BACKGROUND

 Proteolytic cleavage of von Willebrand factor (VWF) by a plasma a disintegrin and metalloproteinase with a thrombospondin type 1 motifs, member 13 (ADAMTS13) is regulated by shear stress and binding of coagulation factor VIII, platelets or platelet glycoprotein 1b, and ristocetin to VWF.

OBJECTIVE

 Current study aims to identify novel VWF binding partners that may modulate VWF functions under physiological conditions.

METHODS

 A deoxyribonucleic acid aptamer-based affinity purification of VWF, followed by tandem mass spectrometry, functional, and binding assays was employed.

RESULTS

 Apolipoprotein B100/low-density lipoprotein (apoB100/LDL) was identified as a novel VWF-binding partner. Purified apoB100/LDL was able to accelerate the proteolytic cleavage of VWF by ADAMTS13 under shear in a concentration-dependent manner. This rate-enhancing activity was dramatically reduced when apoB100/LDL was oxidized. More interestingly, the oxidized apoB100/LDL appeared to compete with native apoB100/LDL for its enhancing activity on VWF proteolysis under shear. As a control, a purified apoA1/high-density lipoprotein (apoA1/HDL) or apoB48 exhibited a minimal or no activity enhancing VWF proteolysis by ADAMTS13 under the same conditions. Both VWF and ADAMTS13 were able to bind native or oxidized apoB100/LDL with high affinities. No binding interaction was detected between VWF (or ADAMTS13) and apoA1/HDL (or apoB48). Moreover, apoB100/LDL but not its oxidized products inhibited the adhesion of platelets to ultra large VWF released from endothelial cells under flow. Finally, significantly reduced ratios of high to low molecular weight of VWF multimers with increased levels of plasma VWF antigen were detected in LDLR-/- mice fed with high cholesterol diet.

CONCLUSION

 These results indicate that apoB100/LDL may be a novel physiological regulator for ADAMTS13-VWF functions.

The relationship between oxidized low-density lipoprotein and related ratio and acute cerebral infarction

This study aimed to study the value of oxidized low-density lipoprotein (OX-LDL) and related ratio in the diagnosis of acute cerebral infarction and the classification of acute cerebral infarction.Of the 129 patients enrolled in this study, 94 patients with acute cerebral infarction were assigned to the case group, and 35 healthy subjects were enrolled as control group (n = 35). And then the case group were divided into large-artery atherosclerosis (LAA) group (n = 61) and small-artery occlusion (SAO) group (n = 33) according to the TOAST classification standard. Plasma OX-LDL levels were determined by enzyme-linked immunosorbent assay. OX-LDL/total cholesterol (OX-LDL/TC), OX-LDL/high-density lipoprotein (OX-LDL/HDL), OX-LDL/LDL were calculated.There were significant differences in OX-LDL, OX-LDL/TC, OX-LDL/HDL, and OX-LDL/LDL in patients with acute cerebral infarction and those in control group (P < .001). The area under the receiver-operating characteristic curve of OX-LDL and related ratio was >0.7 (P < .001). There was a slight positive correlation between OX-LDL/TC and National Institutes of Health Stroke Scale score at admission (r = 0.265, P = .039) in the LAA group.OX-LDL, OX-LDL/TC, OX-LDL/HDL, and OX-LDL/LDL were closely related to acute cerebral infarction, especially with large atherosclerotic cerebral infarction. OX-LDL/TC can reflect the severity of acute cerebral infarction for LAA, but it cannot predict the short-term prognosis of acute cerebral infarction.

The relationship between oxidized low-density lipoprotein and the NIHSS score among patients with acute ischemic stroke: The SOS-Stroke Study

BACKGROUND AND AIMS

Oxidized low-density lipoprotein (oxLDL) has a defined role in the genesis and development of atherosclerosis, however, whether it is related to severity of neurological deficits is rarely reported. The aim of our study was to investigate the potential association between oxLDL and the National Institutes of Health Stroke Scale (NIHSS) score among patients with acute ischemic stroke.

METHODS

Between January 2014 and October 2014, we recruited 4111 patients with acute ischemic stroke (AIS), who were admitted within 7 days-43 hospitals in China, and participated in the SOS-Stroke Study. We collected detailed clinical data and then tested the relationship between oxLDL and the NIHSS score using a multivariate linear regression analysis.

RESULTS

After adjusting for age, gender, ethnicity, marriage and other confounding variables, the elevated NIHSS score was significantly associated with increased oxLDL levels, and each 1-μg/dL elevation in oxLDL concentration resulted in an increase of 0.027 in the NIHSS score.

CONCLUSIONS

A positive correlation was found between plasma levels of oxLDL and the NIHSS score in patients with acute ischemic stroke. Higher plasma levels of oxLDL potentially suggest a worse prognosis in AIS patients.

Intracellular GSH of Streptococcus thermophilus shows anti-oxidative activity against low-density lipoprotein oxidation in vitro and in a hyperlipidaemic hamster model

Streptococcus thermophilus YIT 2001 (ST-1), a lactic acid bacterial strain, was shown to have inhibitory effects on the oxidation of low-density lipoprotein (LDL) and the development of aortic fatty lesions in an animal model, and lower the serum levels of malondialdehyde-modified LDL, an oxidative modification product of LDL, in a clinical trial. This study aimed to identify the intracellular active component of ST-1 associated with anti-oxidative activity against LDL oxidation. High-performance liquid chromatography-electrospray ionisation mass spectrometry analysis after fractionation of the cellular extract by reversed-phase chromatography demonstrated that the active fraction contained reduced glutathione (GSH). GSH showed anti-oxidative activity in a dose-dependent manner, while this activity disappeared following thiol derivatisation. ST-1 had the strongest anti-oxidative activity against LDL oxidation and the highest level of intracellular GSH among five strains of S. thermophilus. In addition, the anti-oxidative activity of ST-1 after thiol derivatisation decreased by about half, which was similar to that of three other strains containing poor or no intracellular GSH or thiol components. Moreover, anti-oxidative activity against LDL oxidation was observed in hyperlipidaemic hamsters fed with high GSH ST-1 cells but not in those given low GSH cells. These findings suggest that intracellular GSH in ST-1 may provide beneficial effects via anti-oxidative activity against LDL oxidation and excess oxidative stress in the blood.

Lipoprotein-associated oxidative stress: a new twist to the postprandial hypothesis

Oxidative stress is recognized as one of the primary processes underlying the initiation and progression of atherosclerotic vascular disease. Under physiological conditions, the balance between reactive oxygen species (ROS) generation and ROS scavenging is tightly controlled. As part of normal cellular metabolism, regulated oxidative stress is responsible for a variety of cellular responses. Excess generation of ROS that could not be compensated by antioxidant system has been suggested to be responsible for a number of pathological conditions. Due to their short biological half-lives, direct measurement of ROS is not available and surrogate measures are commonly used. Plasma lipoproteins, by virtue of their close interactions with endothelial cells in the vasculature and the susceptibility of their surface lipids to oxidative modification, are perfect biological sensors of oxidative stress in the arterial wall. In particular, with each consumed meal, triglyceride-rich lipoproteins, secreted by the intestine into the circulation, are responsible for the delivery of 20–40 grams of fat to the peripheral tissues. This flux of dietary lipids is accompanied by concomitant increases in glucose, insulin and other meal-associated metabolites. The contribution of postprandial lipemia to the pathogenesis of atherosclerosis has been previously suggested by several lines of investigation. We have extended this hypothesis by demonstrating the acute generation of oxidative epitopes on plasma lipoproteins as well as transient changes in the oxidative susceptibility of plasma lipoproteins.

Acute phase proteins and oxidised low-density lipoprotein in association with ischemic stroke subtype, severity and outcome

OBJECTIVES

The goal of our study was to investigate the associations of oxidized LDL (apoB100 aldehyde-modified form) and acute phase proteins (fibrinogen, CRP) with acute ischemic stroke severity and outcome.

MATERIALS AND METHODS

The study included 61 ischemic stroke patients and 64 controls. Strokes were subtyped according to TOAST criteria, the severity and outcome of stroke (at 1 year) were measured.

RESULTS

The mean triglyceride, fibrinogen, CRP and glucose values were significantly higher among cases. The median oxLDL value for patients with large artery atherosclerosis (LAA) type of stroke was significantly higher than for other subtypes. The oxLDL values did not correlate with age, stroke severity and outcome.

CONCLUSIONS

Inflammatory markers (fibrinogen and CRP) predicted the stroke severity and outcome whereas elevation of oxLDL levels did not. Our data refer to possibility that there may exist some links between the LAA subtype of stroke and elevated oxLDL (apoB100 aldehyde-modified form).

Oxidative stress during the chronic phase after stroke

Stroke is a complex disease originating and developing on the background of genetic predisposition and interaction between different risk factors that chronically damage blood vessels. The search for an effective treatment of stroke patients is the main priority of basic and clinical sciences. The chronic phase of stroke provides possibilities for therapy directed toward stimulation of recovery processes as well as prophylaxis, which reduces the probability of subsequent cerebrovascular events. Oxidative stress is a potential contributor to the pathophysiological consequences of stroke. The aim of the present review is to summarize the current knowledge of the role of oxidative stress during the chronic phase after stroke and its contribution to the initiation of subsequent stroke. The relationship among inflammation, hemostatic abnormalities, and platelet activation in chronic stroke patients is discussed in the context of ongoing free radical processes and oxidative damage. Free radical-mediated effects of increased plasma level of homocysteine and its possible contribution to the processes leading to recurrent stroke are discussed as well. The status of the antioxidant defense system and the degree of oxidative damage in the circulation of stroke survivors are examined. The results are interpreted in view of the effects of the vascular risk factors for stroke that include additional activation of inflammatory and free radical mechanisms. Also, the possibilities for combined therapy including antioxidants in the acute and convalescent stages of stroke are considered. Future investigations are expected to elucidate the role of free radical processes in the chronic phase after stroke and to evaluate the prophylactic and therapeutic potential of anti-radical agents.

Plasma antioxidant activity and vascular dementia

Little is known about the role of antioxidant activity in the pathogenesis of stroke-associated neuronal damage and impairment following a stroke. Increased free radical formation together with reduced antioxidant defense may increase neuronal injury. A low concentration of antioxidants such as alpha-tocopherol may influence the development of post-stroke dementia. The aim of this study was to evaluate the level of alpha-tocopherol and susceptibility of LDL to oxidation in a group of patients with dementia in comparison to controls. In a group of 68 patients with dementia, according to DSM-IV criteria, 42 with vascular dementia (VaD), 26 with Alzheimer type of dementia (AD) and 46 age-matched persons, with no signs of cognitive disorders (control group), we measured lipids, alpha-tocopherol and the kinetics of LDL oxidation. The levels of triglycerides (TG) and low-density lipoprotein (LDL) were significantly lower in patients with VaD in comparison to AD patients, but the atherogenic index was similar in both groups. alpha-Tocopherol was significantly lower in patients with VaD in comparison to patients with AD and controls: 9.9, 12.6 and 12.6 ng/ml, respectively, p<0.0001. Susceptibility of LDL to oxidation, measured by duration of lag phase did not reveal statistically significant differences between the groups. In patients with VaD, low levels of plasma alpha-tocopherol were observed, which indicate a reduced antioxidant defense in these subjects.