High density lipoproteins reduce organ injury and organ dysfunction in a rat model of hemorrhagic shock

Association of high-density lipoprotein cholesterol with reduced intracranial haemorrhage and favourable functional outcome after thrombectomy for ischaemic stroke: a propensity-matched analysis

BACKGROUND

Animal studies suggest that high-density lipoprotein cholesterol (HDL-C) attenuates reperfusion injury. We aimed to assess whether higher serum HDL-C levels modulate the risk of intracranial haemorrhage (ICH) after thrombectomy in human stroke survivors.

METHODS

We included consecutive patients from our prospective anterior circulation large vessel occlusion (acLVO) registry who underwent thrombectomy between 01/2017 and 01/2023 at the tertiary stroke centre of the University Hospital Carl Gustav Carus in Dresden, Germany in a propensity score-matched analysis. We assessed the association between serum HDL-C levels and post-interventional ICH as well as 90-day functional outcome quantified by the modified Rankin Scale (mRS). For sensitivity analysis, we used multivariable lasso logistic regression. Analyses were adjusted for demographics, cardiovascular risk profiles, stroke characteristics, and procedural times.

RESULTS

Of 1702 patients screened, 807 (420 women, median age 77 years [66-84, IQR]) were included. Post-interventional ICH reduced the probability of a favourable functional outcome (90-day mRS 0-2) by 14.8% (ß = 0.15; 95% CI [0.06;0.24]; p = 0.001. An HDL-C level above the median (1.15 mmol/L) decreased the probability of ICH by 13.6% (ß = - 0.14; 95CI% [- 0.22; - 0.05]; p = 0.002) and increased the probability of favourable functional outcome by 13.2% (ß = - 0.13; 95CI% [- 0.22; - 0.05]; p = 0.003). In sensitivity analyses, higher HDL-C levels were independently associated with lower odds of ICH (adjusted OR 0.62; 95% CI [0.43;0.88]; p = 0.008) and higher odds of favourable functional outcome (adjusted OR 0.60; 95% CI [0.40; 0.90]; p = 0.015).

CONCLUSIONS

In patients undergoing thrombectomy for acLVO, higher HDL-C levels were associated with a reduced probability of post-interventional ICH and a favourable functional outcome. These observations could not be explained by conventional vascular risk profiles.

High-Density Lipoprotein Anti-Inflammatory Capacity and Acute Kidney Injury After Cardiac and Vascular Surgery: A Prospective Observational Study

OBJECTIVES

Acute kidney injury (AKI) predicts death after cardiac and vascular surgery. Higher preoperative high-density lipoprotein (HDL) concentrations are associated with less postoperative AKI. In animals, HDL's anti-inflammatory capacity to suppress endothelial cell adhesion molecule expression reduces kidney damage due to ischemia and hemorrhagic shock. The objective of this study is to evaluate the statistical relationship between HDL anti-inflammatory capacity and AKI after major cardiac and vascular surgery.

DESIGN

Prospective observational study.

SETTING

Quaternary medical center.

PATIENTS

One hundred adults with chronic kidney disease on long-term statin therapy undergoing major elective cardiac and vascular surgery.

INTERVENTIONS

None.

MEASUREMENTS AND MAIN RESULTS

Apolipoprotein B-depleted serum collected at anesthetic induction was incubated with tumor necrosis factor alpha stimulated human endothelial cells. Reverse transcriptase-polymerase chain reaction was used to measure intercellular adhesion molecule-1 (ICAM-1) messenger RNA. Enzyme-linked immunosorbent assay assays were used to measure apolipoprotein A-I and postoperative soluble ICAM-1 concentrations in patient plasma. HDL concentration did not correlate with HDL ICAM-1 suppression capacity (Spearman R = 0.05; p = 0.64). Twelve patients (12%) were found to have dysfunctional, pro-inflammatory HDL. Patients with pro-inflammatory HDL had a higher rate of postoperative AKI than patients with anti-inflammatory HDL ( p = 0.046). After adjustment for AKI risk factors, a higher preoperative HDL capacity to suppress endothelial ICAM-1 was independently associated with lower odds of AKI (odds ratio, 0.88; 95% CI, 0.80-0.98; p = 0.016). The association between HDL anti-inflammatory capacity and postoperative AKI was independent of HDL concentration ( p = 0.018). Further, a higher long-term statin dose was associated with higher HDL capacity to suppress endothelial ICAM-1 ( p = 0.045).

CONCLUSIONS

Patients with chronic kidney disease undergoing cardiac and vascular surgery who have dysfunctional, pro-inflammatory HDL have a higher risk of postoperative AKI compared with patients with anti-inflammatory HDL. Conversely, a higher HDL anti-inflammatory capacity is associated with a lower risk of postoperative AKI, independent of HDL concentration. Higher long-term statin dose is associated with higher HDL anti-inflammatory capacity.

Association between high-density lipoprotein-related inflammation index and periodontitis: insights from NHANES 2009-2014

BACKGROUND

Periodontitis, a persistent inflammatory condition, significantly impairs individuals' overall quality of life. Lymphocyte-to-high-density lipoprotein cholesterol ratio (LHR), monocyte-to-high-density lipoprotein cholesterol ratio (MHR), neutrophil-to-high-density lipoprotein cholesterol ratio (NHR), and platelet-to-high-density lipoprotein cholesterol ratio (PHR) are new convenient and economical biomarkers. However, whether the above high-density lipoprotein-related inflammatory biomarkers are associated with periodontitis has rarely been investigated. Therefore, the research endeavor focused on uncovering potential relationships.

METHODS

The research encompassed a diverse and extensive sample, comprising 9,470 participants, selected from the National Health and Nutrition Examination Survey spanning the years 2009 to 2014. The association between high-density lipoprotein-related inflammatory biomarkers and periodontitis was explored utilizing a multivariable logistic regression model with weighted analysis. Additionally, the study employed smoothed curve fitting to explore potential nonlinear relationships. Further stratified analyses and interaction tests were performed.

RESULTS

This study indicated no apparent association between MHR and PHR with periodontitis, whereas LHR and NHR demonstrated a statistically significant positive relationship with the prevalence of periodontitis. In the fully adjusted model, participants belonging to the highest tertile of both LHR and NHR showed a notably higher likelihood of having periodontitis compared to those in the lowest tertile (LHR: OR = 1.22, 95% CI: 1.06, 1.39; NHR: OR = 1.27, 95% CI: 1.09, 1.49). Furthermore, smooth curve fitting was employed to investigate the potential nonlinear relationship between LHR, NHR, and periodontitis. The results indicated that there was a significant increase in the occurrence of periodontitis when Log2 (LHR) exceeded 1.01 and Log2(NHR) surpassed 2.16 (Log2(LHR): OR = 1.42; 95% CI: 1.19, 1.69; Log2(NHR): OR = 1.40; 95% CI: 1.15, 1.71). The subgroup analysis revealed that the associations between periodontitis and either LHR or NHR, separately, were more pronounced among individuals under the age of 50 and those without hypertension.

CONCLUSIONS

This cross-sectional study revealed a positive relationship between LHR、NHR and periodontitis, particularly when these indicators exceeded their thresholds. LHR and NHR may serve as potential inflammatory markers for identifying periodontitis, thereby facilitating early warning for both patients and dentists, and enabling early intervention in the oral environment. Besides, extensive prospective cohort investigations are essential to confirm and solidify this observation.

Anti-inflammatory mechanism of Apolipoprotein A-I

Apolipoprotein A-I(ApoA-I) is a member of blood apolipoproteins, it is the main component of High density lipoprotein(HDL). ApoA-I undergoes a series of complex processes from its generation to its composition as spherical HDL. It not only has a cholesterol reversal transport function, but also has a function in modulating the inflammatory response. ApoA-I exerts its anti-inflammatory effects mainly by regulating the functions of immune cells, such as monocytes/macrophages, dendritic cells, neutrophils, and T lymphocytes. It also modulates the function of vascular endothelial cells and adipocytes. Additionally, ApoA-I directly exerts anti-inflammatory effects against pathogenic microorganisms or their products. Intensive research on ApoA-I will hopefully lead to better diagnosis and treatment of inflammatory diseases.

Crosstalk between neurological, cardiovascular, and lifestyle disorders: insulin and lipoproteins in the lead role

Insulin resistance and impaired lipoprotein metabolism contribute to a plethora of metabolic and cardiovascular disorders. These alterations have been extensively linked with poor lifestyle choices, such as consumption of a high-fat diet, smoking, stress, and a redundant lifestyle. Moreover, these are also known to increase the co-morbidity of diseases like Type 2 diabetes mellitus and atherosclerosis. Under normal physiological conditions, insulin and lipoproteins exert a neuroprotective role in the central nervous system. However, the tripping of balance between the periphery and center may alter the normal functioning of the brain and lead to neurological disorders such as Alzheimer's disease, Parkinson's disease, stroke, depression, and multiple sclerosis. These neurological disorders are further characterized by certain behavioral and molecular changes that show consistent overlap with alteration in insulin and lipoprotein signaling pathways. Therefore, targeting these two mechanisms not only reveals a way to manage the co-morbidities associated with the circle of the metabolic, central nervous system, and cardiovascular disorders but also exclusively work as a disease-modifying therapy for neurological disorders. In this review, we summarize the role of insulin resistance and lipoproteins in the progression of various neurological conditions and discuss the therapeutic options currently in the clinical pipeline targeting these two mechanisms; in addition, challenges faced in designing these therapeutic approaches have also been touched upon briefly.

Replenishing HDL with synthetic HDL has multiple protective effects against sepsis in mice

Sepsis is a major health issue with mortality exceeding 30% and few treatment options. We found that high-density lipoprotein cholesterol (HDL-C) abundance was reduced by 45% in septic patients compared to that in nonseptic patients. Furthermore, HDL-C abundance in nonsurviving septic patients was substantially lower than in those patients who survived. We therefore hypothesized that replenishing HDL might be a therapeutic approach for treating sepsis and found that supplementing HDL with synthetic HDL (sHDL) provided protection against sepsis in mice. In mice subjected to cecal ligation and puncture (CLP), infusing the sHDL ETC-642 increased plasma HDL-C amounts and improved the 7-day survival rate. Septic mice treated with sHDL showed improved kidney function and reduced inflammation, as indicated by marked decreases in the plasma concentrations of blood urea nitrogen (BUN) and the cytokines interleukin-6 (IL-6) and IL-10, respectively. We found that sHDL inhibited the ability of the endotoxins LPS and LPA to activate inflammatory pathways in RAW264.7 cells and HEK-Blue cells expressing the receptors TLR4 or TLR2 and NF-κB reporters. In addition, sHDL inhibited the activation of HUVECs by LPS, LTA, and TNF-α. Together, these data indicate that sHDL treatment protects mice from sepsis in multiple ways and that it might be an effective therapy for patients with sepsis.

Targeting HDL in tumor microenvironment: New hope for cancer therapy

Epidemiological studies have shown that plasma HDL-C levels are closely related to the risk of prostate cancer, breast cancer, and other malignancies. As one of the key carriers of cholesterol regulation, high-density lipoprotein (HDL) plays an important role in tumorigenesis and cancer development through anti-inflammation, antioxidation, immune-modulation, and mediating cholesterol transportation in cancer cells and noncancer cells. In addition, the occurrence and progression of cancer are closely related to the alteration of the tumor microenvironment (TME). Cancer cells synthesize and secrete a variety of cytokines and other factors to promote the reprogramming of surrounding cells and shape the microenvironment suitable for cancer survival. By analyzing the effect of HDL on the infiltrating immune cells in the TME, as well as the relationship between HDL and tumor-associated angiogenesis, it is suggested that a moderate increase in the level of HDL in vivo with consequent improvement of the function of HDL in the TME and induction of intracellular cholesterol efflux may be a promising strategy for cancer therapy.

Changes in High-Density Lipoproteins Related to Outcomes in Patients with Acute Stroke

Modifications in high-density lipoprotein (HDL) particle sizes and HDL-binding proteins have been reported in stroke patients. We evaluated whether the lipoprotein profile, HDL composition and functionality were altered in stroke patients according to their clinical outcome using the modified Rankin Score at 3 months. Plasma samples were obtained from stroke patients treated with intravenous thrombolysis. Levels of cardiovascular and inflammatory markers in plasma were measured using the Human CVD Panel 1 (Milliplex^® MAP). Lipoprotein subfractions from plasma were quantified by non-denaturing acrylamide gel electrophoresis, using the Lipoprint^®-System (Quantimetrix^®), and HDLs were isolated by ultracentrifugation. Relative amounts of paraoxonase-1 (PON1) and alpha-1 anti-trypsin (AAT) in the isolated HDLs were determined by Western blot. HDL anti-inflammatory function was evaluated in human blood-brain barrier endothelial cells stimulated with 100 ng/mL TNFα, and HDL antioxidant function was evaluated via their capacity to limit copper-induced low-density lipoprotein oxidation. Stroke patients with unfavorable outcomes had a lower proportion of small-sized HDLs and increased plasma levels of E-selectin (SELE) and the intercellular adhesion molecule 1 (ICAM1). HDLs from patients with unfavorable outcomes had lower levels of PON1 and displayed a blunted capacity to reduce the expression of SELE, interleukin 8 (IL8) and the monocyte chemoattractant protein-1 (MCP1) mRNA induced by TNFα in endothelial cells. These HDLs also had a reduced antioxidant capacity relative to HDLs from healthy donors. In conclusion, an increased ratio of large/small HDLs with impaired anti-inflammatory and antioxidant capacities was associated with unfavorable outcomes in stroke patients. Alteration of HDL functionality was mainly associated with a low amount of PON1 and high amount of AAT.

Effects of grape products on blood lipids: a systematic review and dose–response meta-analysis of randomized controlled trials

Grape products through several plausible mechanisms-of-action are reported to improve lipid profile. The present systematic review revealed that grape product supplementation might have a positive effect on achieving a lipid profile target.

High-Density Lipoprotein Regulation of Mitochondrial Function

Lipoproteins play a key role in regulating plasma and tissue levels of cholesterol. Apolipoprotein B (apoB)-containing lipoproteins, including chylomicrons, very-low density lipoprotein (VLDL) and low-density lipoprotein (LDL), serve as carriers of triglycerides and cholesterol and deliver these metabolites to peripheral tissues. In contrast, high-density lipoprotein (HDL) mediates Reverse Cholesterol Transport (RCT), a process by which excess cholesterol is removed from the periphery and taken up by hepatocytes where it is metabolized and excreted. Anti-atherogenic properties of HDL have been largely ascribed to apoA-I, the major protein component of the lipoprotein particle. The inflammatory response associated with atherosclerosis and ischemia-reperfusion (I-R) injury has been linked to the development of mitochondrial dysfunction. Under these conditions, an increase in reactive oxygen species (ROS) formation induces damage to mitochondrial structural elements, leading to a reduction in ATP synthesis and initiation of the apoptotic program. Recent studies suggest that HDL-associated apoA-I and lysosphingolipids attenuate mitochondrial injury by multiple mechanisms, including the suppression of ROS formation and induction of autophagy. Other apolipoproteins, however, present in lower abundance in HDL particles may exert opposing effects on mitochondrial function. This chapter examines the role of HDL-associated apolipoproteins and lipids in the regulation of mitochondrial function and bioenergetics.

Elevation of serum sphingosine-1-phosphate attenuates impaired cardiac function in experimental sepsis

Serum levels of the lipid mediator sphingosine-1-phosphate (S1P) are reduced in septic patients and are inversely associated with disease severity. We show that serum S1P is reduced in human sepsis and in murine models of sepsis. We then investigated whether pharmacological or genetic approaches that alter serum S1P may attenuate cardiac dysfunction and whether S1P signaling might serve as a novel theragnostic tool in sepsis. Mice were challenged with lipopolysaccharide and peptidoglycan (LPS/PepG). LPS/PepG resulted in an impaired systolic contractility and reduced serum S1P. Administration of the immunomodulator FTY720 increased serum S1P, improved impaired systolic contractility and activated the phosphoinositide 3-kinase (PI3K)-pathway in the heart. Cardioprotective effects of FTY720 were abolished following administration of a S1P receptor 2 (S1P₂) antagonist or a PI3K inhibitor. Sphingosine kinase-2 deficient mice had higher endogenous S1P levels and the LPS/PepG-induced impaired systolic contractility was attenuated in comparison with wild-type mice. Cardioprotective effects of FTY720 were confirmed in polymicrobial sepsis. We show here for the first time that the impaired left ventricular systolic contractility in experimental sepsis is attenuated by FTY720. Mechanistically, our results indicate that activation of S1P₂ by increased serum S1P and the subsequent activation of the PI3K-Akt survival pathway significantly contributes to the observed cardioprotective effect of FTY720.

High-density lipoprotein, mitochondrial dysfunction and cell survival mechanisms

Ischemic injury is associated with acute myocardial infarction, percutaneous coronary intervention, coronary artery bypass grafting and open heart surgery. The timely re-establishment of blood flow is critical in order to minimize cardiac complications. Reperfusion after a prolonged ischemic period, however, can induce severe cardiomyocyte dysfunction with mitochondria serving as a major target of ischemia/reperfusion (I/R) injury. An increase in the formation of reactive oxygen species (ROS) induces damage to mitochondrial respiratory complexes leading to uncoupling of oxidative phosphorylation. Mitochondrial membrane perturbations also contribute to calcium overload, opening of the mitochondrial permeability transition pore (mPTP) and the release of apoptotic mediators into the cytoplasm. Clinical and experimental studies show that ischemic preconditioning (ICPRE) and postconditioning (ICPOST) attenuate mitochondrial injury and improve cardiac function in the context of I/R injury. This is achieved by the activation of two principal cell survival cascades: 1) the Reperfusion Injury Salvage Kinase (RISK) pathway; and 2) the Survivor Activating Factor Enhancement (SAFE) pathway. Recent data suggest that high density lipoprotein (HDL) mimics the effects of conditioning protocols and attenuates myocardial I/R injury via activation of the RISK and SAFE signaling cascades. In this review, we discuss the roles of apolipoproteinA-I (apoA-I), the major protein constituent of HDL, and sphingosine 1-phosphate (S1P), a lysosphingolipid associated with small, dense HDL particles as mediators of cardiomyocyte survival. Both apoA-I and S1P exert an infarct-sparing effect by preventing ROS-dependent injury and inhibiting the opening of the mPTP.

Protective Effects of HDL Against Ischemia/Reperfusion Injury

Several lines of evidence suggest that, besides being a strong independent predictor of the occurrence of primary coronary events, a low plasma high density lipoprotein (HDL) cholesterol level is also associated with short- and long-term unfavorable prognosis in patients, who have recovered from a myocardial infarction, suggesting a direct detrimental effect of low HDL on post-ischemic myocardial function. Experiments performed in ex vivo and in vivo models of myocardial ischemia/reperfusion (I/R) injury have clearly shown that HDL are able to preserve cardiac function when given before ischemia or at reperfusion; the protective effects of HDL against I/R injury have been also confirmed in other tissues and organs, as brain and hind limb. HDL were shown to act on coronary endothelial cells, by limiting the increase of endothelium permeability and promoting vasodilation and neoangiogenesis, on white blood cells, by reducing their infiltration into the ischemic tissue and the release of pro-inflammatory and matrix-degrading molecules, and on cardiomyocytes, by preventing the activation of the apoptotic cascade. Synthetic HDL retains the cardioprotective activity of plasma-derived HDL and may become a useful adjunctive therapy to improve clinical outcomes in patients with acute coronary syndromes or undergoing coronary procedures.

High-density lipoproteins in stroke

Besides their well-documented function of reverse transport of cholesterol, high-density lipoproteins (HDLs) display pleiotropic effects due to their antioxidant, antithrombotic, anti-inflammatory and antiapoptotic properties that may play a major protective role in acute stroke, in particular by limiting the deleterious effects of ischaemia on the blood-brain barrier (BBB) and on the parenchymal cerebral compartment. HDLs may also modulate leukocyte and platelet activation, which may also represent an important target that would justify the use of HDL-based therapy in acute stroke. In this review, we will present an update of all the recent findings in HDL biology that could support a potential clinical use of HDL therapy in ischaemic stroke.

High-density lipoproteins potentiate α1-antitrypsin therapy in elastase-induced pulmonary emphysema

Several studies report that high-density lipoproteins (HDLs) can carry α1-antitrypsin (AAT; an elastase inhibitor). We aimed to determine whether injection of exogenous HDL, enriched or not in AAT, may have protective effects against pulmonary emphysema. After tracheal instillation of saline or elastase, mice were randomly treated intravenously with saline, human plasma HDL (75 mg apolipoprotein A1/kg), HDL-AAT (75 mg apolipoprotein A1-3.75 mg AAT/kg), or AAT alone (3.75 mg/kg) at 2, 24, 48, and 72 hours. We have shown that HDL-AAT reached the lung and prevented the development of pulmonary emphysema by 59.3% at 3 weeks (alveoli mean chord length, 22.9 ± 2.8 μm versus 30.7 ± 4.5 μm; P < 0.001), whereas injection of HDL or AAT alone only showed a moderate, nonsignificant protective effect (28.2 ± 4.2 μm versus 30.7 ± 5 μm [P = 0.23] and 27.3 ± 5.66 μm versus 30.71 ± 4.96 μm [P = 0.18], respectively). Indeed, protection by HDL-AAT was significantly higher than that observed with HDL or AAT (P = 0.006 and P = 0.048, respectively). This protective effect was associated (at 6, 24, and 72 h) with: (1) a reduction in neutrophil and macrophage number in the bronchoalveolar lavage fluid; (2) decreased concentrations of IL-6, monocyte chemoattractant protein-1, and TNF-α in both bronchoalveolar lavage fluid and plasma; (3) a reduction in matrix metalloproteinase-2 and matrix metalloproteinase-9 activities; and (4) a reduction in the degradation of fibronectin, a marker of tissue damage. In addition, HDL-AAT reduced acute cigarette smoke-induced inflammatory response. Intravenous HDL-AAT treatment afforded a better protection against elastase-induced pulmonary emphysema than AAT alone, and may represent a significant development for the management of emphysema associated with AAT deficiency.

HDL and endothelial protection

High-density lipoproteins (HDLs) represent a family of particles characterized by the presence of apolipoprotein A-I (apoA-I) and by their ability to transport cholesterol from peripheral tissues back to the liver. In addition to this function, HDLs display pleiotropic effects including antioxidant, anti-apoptotic, anti-inflammatory, anti-thrombotic or anti-proteolytic properties that account for their protective action on endothelial cells. Vasodilatation via production of nitric oxide is also a hallmark of HDL action on endothelial cells. Endothelial cells express receptors for apoA-I and HDLs that mediate intracellular signalling and potentially participate in the internalization of these particles. In this review, we will detail the different effects of HDLs on the endothelium in normal and pathological conditions with a particular focus on the potential use of HDL therapy to restore endothelial function and integrity.

High-density lipoproteins limit neutrophil-induced damage to the blood-brain barrier in vitro

Breakdown of the blood-brain barrier (BBB) is a key step associated with ischemic stroke and its increased permeability causes extravasation of plasma proteins and circulating leukocytes. Polymorphonuclear neutrophil (PMN) proteases may participate in BBB breakdown. We investigated the role of PMNs in ischemic conditions by testing their effects on a model of BBB in vitro, under oxygen-glucose deprivation (OGD) to mimic ischemia, supplemented or not with high-density lipoproteins (HDLs) to assess their potential protective effects. Human cerebral endothelial cells cultured on transwells were incubated for 4 hours under OGD conditions with or without PMNs and supplemented or not with HDLs or alpha-1 antitrypsin (AAT, an elastase inhibitor). The integrity of the BBB was then assessed and the effect of HDLs on PMN-induced proteolysis of extracellular matrix proteins was evaluated. The release of myeloperoxidase and matrix metalloproteinase 9 (MMP-9) by PMNs was quantified. Polymorphonuclear neutrophils significantly increased BBB permeability under OGD conditions via proteolysis of extracellular matrix proteins. This was associated with PMN degranulation. Addition of HDLs or AAT limited the proteolysis and associated increased permeability by inhibiting PMN activation. Our results suggest a deleterious, elastase-mediated role of activated PMNs under OGD conditions leading to BBB disruption that could be inhibited by HDLs.

High-density lipoprotein-based therapy reduces the hemorrhagic complications associated with tissue plasminogen activator treatment in experimental stroke

BACKGROUND AND PURPOSE

We have previously reported that intravenous injection of high-density lipoproteins (HDLs) was neuroprotective in an embolic stroke model. We hypothesized that HDL vasculoprotective actions on the blood-brain barrier (BBB) may decrease hemorrhagic transformation-associated with tissue plasminogen activator (tPA) administration in acute stroke.

METHODS

We used tPA alone or in combination with HDLs in vivo in 2 models of focal middle cerebral artery occlusion (MCAO) (embolic and 4-hour monofilament MCAO) and in vitro in a model of BBB. Sprague-Dawley rats were submitted to MCAO, n=12 per group. The rats were then randomly injected with tPA (10 mg/kg) or saline with or without human plasma purified-HDL (10 mg/kg). The therapeutic effects of HDL and BBB integrity were assessed blindly 24 hours later. The integrity of the BBB was also tested using an in vitro model of human cerebral endothelial cells under oxygen-glucose deprivation.

RESULTS

tPA-treated groups had significantly higher mortality and rate of hemorrhagic transformation at 24 hours in both MCAO models. Cotreatment with HDL significantly reduced stroke-induced mortality versus tPA alone (by 42% in filament MCAO, P=0.009; by 73% in embolic MCAO, P=0.05) and tPA-induced intracerebral parenchymal hematoma (by 92% in filament MCAO, by 100% in embolic MCAO; P<0.0001). This was consistent with an improved BBB integrity. In vitro, HDLs decreased oxygen-glucose deprivation-induced BBB permeability (P<0.05) and vascular endothelial cadherin disorganization.

CONCLUSIONS

HDL injection decreased tPA-induced hemorrhagic transformation in rat models of MCAO. Both in vivo and in vitro results support the vasculoprotective action of HDLs on BBB under ischemic conditions.

Elevation of plasma high-density lipoproteins inhibits development of experimental abdominal aortic aneurysms

OBJECTIVE

Patients with abdominal aortic aneurysms have lower concentrations of high-density lipoproteins (HDLs), leading us to investigate whether increasing plasma HDLs could influence aneurysm formation.

METHODS AND RESULTS

Using the angiotensin II-induced hypercholesterolemic and the CaCl(2)-induced normocholesterolemic mouse model of AAA, we investigated the hypothesis that elevation of HDLs inhibits AAA. HDLs elevated before or at the time of AAA induction reduced AAA formation in both models but had no effect on early ruptures. Analysis of protein lysates from specific aortic segments demonstrated site-specific effects of HDLs on early signal transduction and cellular attrition. We found that HDLs reduced extracellular signal related kinases 1/2 activation in the suprarenal segment, while having no effect on p38 mitogen-associated protein kinase activation in any aortic segment and inhibiting c-Jun N-terminal kinase activation in all aortic segments. In addition, HDL elevation inhibited angiotensin II-induced apoptosis while inducing autophagy in the suprarenal segment of the aorta. Using Illumina gene array profiling we investigated the ability of HDL to modulate basal suprarenal aortic gene expression.

CONCLUSIONS

Increasing plasma HDLs inhibit experimental AAA formation, independent of hypercholesterolemia via reduced extracellular signal related kinases 1/2 activation and alteration of the balance of cellular attrition. HDLs modulate genes involved in matrix remodelling, cell migration, and proliferation.

HDL functionality

PURPOSE OF REVIEW

HDL cholesterol concentration is inversely correlated with cardiovascular disease and has a wide range of functions involved in many systems. The purpose of this review is to summarize HDL functionality, its relevance to atherosclerosis and factors affecting HDL functions.

RECENT FINDINGS

The contribution of HDL to reverse cholesterol transport may not be as great as first envisaged. However, it still plays an important role in cholesterol efflux from peripheral tissues. The capacity of HDL to promote cellular cholesterol efflux in an ex-vivo model has been reported to correlate more closely with carotid intima-media thickness than HDL cholesterol concentration. Recently, a variety of other functions of HDL have been described including antimicrobial, antioxidant, antiglycation, anti-inflammatory, nitric oxide--inducing, antithrombotic and antiatherogenic activity and immune modulation as well as a potential role in glucose homeostasis, diabetes pathophysiology and complications.

SUMMARY

HDL has a wide range of functions some of which are independent of its cholesterol content. Its cargo of apolipoproteins, various proteins and phospholipids contributes most to its various functions. These functions are affected by a number of genetic, physiological and pathological factors.

Deletion of scavenger receptor A gene in mice resulted in protection from septic shock and modulation of TLR4 signaling in isolated peritoneal macrophages

Scavenger receptor A (Sra), also known as macrophage scavenger receptor 1 (Msr1), is a surface glycoprotein preferentially present in macrophages that plays a primary role in innate immunity. Previous studies have shown that Sra is a modifier gene for the response to bacterial LPS in mice at the level of IL-10 production, in particular. In the present study, we found that Sra(-/-) mice are more resistant to septic shock induced by cecal ligation and puncture than wild-type C57BL/6 J (B6) mice. In addition, Sra(-/-) mice displayed initial elevated high density lipoprotein (HDL) circulating levels. Naïve peritoneal macrophages (PMs) were isolated from Sra(-/-) mice to understand the possible protective mechanism. Incubation of these cells with LPS was found to modulate TLR4 signaling, leading to a reduction in IL-10 and IL-6 mRNA levels, but not TNF-α expression, at low concentrations of LPS in comparison with PMs isolated from B6 mice. No differences were found in LPS binding between PMs derived from Sra(-/-) or B6 mice. The lack of Sra binding to LPS was confirmed after transfection of Chinese hamster ovary (CHO) cells with the Sra gene. The contribution of Sra to the outcome of sepsis may be a combination of changes in TLR4 signaling pathway and elevated levels of HDL in circulation, but also LPS toxicity.

Acute alcohol intoxication reduces mortality, inflammatory responses and hepatic injury after haemorrhage and resuscitation in vivo

BACKGROUND AND PURPOSE

Haemorrhagic shock and resuscitation (H/R) induces hepatic injury, strong inflammatory changes and death. Alcohol intoxication is assumed to worsen pathophysiological derangements after H/R. Here, we studied the effects of acute alcohol intoxication on survival, liver injury and inflammation after H/R, in rats.

EXPERIMENTAL APPROACH

Rats were given a single oral dose of ethanol (5 g·kg(-1) , 30%) or saline (control), 12 h before they were haemorrhaged for 60 min and resuscitated (H/R). Sham groups received the same procedures without H/R. Measurements were made 2, 24 and 72 h after resuscitation. Survival was assessed 72 h after H/R.

KEY RESULTS

Ethanol increased survival after H/R three-fold and also induced fatty changes in the liver. H/R-induced liver injury was amplified by ethanol at 2 h but inhibited 24 h after H/R. Elevated serum IL-6 levels as well as hepatic IL-6 and TNF-α gene expression 2 h after H/R were reduced by ethanol. Ethanol enhanced serum IL-1β at 2 h, but did not affect increased hepatic IL-1β expression at 72 h after H/R. Local inflammatory markers, hepatic infiltration with polymorphonuclear leukocytes and intercellular adhesion molecule 1 expression decreased after ethanol compared with saline, following H/R. Ethanol reduced H/R-induced IκBα activation 2 h after H/R, and NF-κB-dependent gene expression of MMP9.

CONCLUSIONS AND IMPLICATIONS

Ethanol reduced H/R-induced mortality at 72 h, accompanied by a suppression of proinflammatory changes after H/R in ethanol-treated animals. Binge-like ethanol exposure modulated the inflammatory response after H/R, an effect that was associated with NF-κB activity.

Cholesterol and lipoprotein dynamics in a hibernating mammal

Hibernating mammals cease feeding during the winter and rely primarily on stored lipids to fuel alternating periods of torpor and arousal. How hibernators manage large fluxes of lipids and sterols over the annual hibernation cycle is poorly understood. The aim of this study was to investigate lipid and cholesterol transport and storage in ground squirrels studied in spring, summer, and several hibernation states. Cholesterol levels in total plasma, HDL and LDL particles were elevated in hibernators compared with spring or summer squirrels. Hibernation increased plasma apolipoprotein A-I expression and HDL particle size. Expression of cholesterol 7 alpha-hydroxylase was 13-fold lower in hibernators than in active season squirrels. Plasma triglycerides were reduced by fasting in spring but not summer squirrels. In hibernators plasma β-hydroxybutyrate was elevated during torpor whereas triglycerides were low relative to normothermic states. We conclude that the switch to a lipid-based metabolism during winter, coupled with reduced capacity to excrete cholesterol creates a closed system in which efficient use of lipoproteins is essential for survival.

Heparin use in a rat hemorrhagic shock model induces biologic activity in mesenteric lymph separate from shock

Experimental data have shown that mesenteric lymph from rats subjected to trauma-hemorrhagic shock (THS) but not trauma-sham shock induces neutrophil activation, cytotoxicity, decreased red blood cell (RBC) deformability, and bone marrow colony growth suppression. These data have led to the hypothesis that gut factors produced from THS enter the systemic circulation via the mesenteric lymphatics and contribute to the progression of multiple organ failure after THS. Ongoing studies designed to identify bioactive lymph agents implicated factors associated with the heparin use in the THS procedure. We investigated if heparin itself was responsible for reported toxicity to human umbilical vein endothelial cells (HUVECs). Human umbilical vein endothelial cell toxicity was not induced by lymph when alternate anticoagulants (citrate and EDTA) were used in THS. Human umbilical vein endothelial cell toxicity was induced by lymph after heparin but not saline or citrate injection into trauma-sham shock and naive animals and was dose dependent. Activities of both heparin-releasable lipases (lipoprotein and hepatic) were detected in the plasma and lymph from THS and naive animals receiving heparin but not citrate or saline. Lymph-induced HUVEC toxicity correlated with lymph lipase activities. Finally, incubation of HUVECs with purified lipoprotein lipase added to naive lymph-induced toxicity in vitro. These data show that heparin, not THS, is responsible for the reported lymph-mediated HUVEC toxicity through its release of lipases into the lymph. These findings can provide alternative explanations for several of the THS effects reported in the literature using heparin models, thus necessitating a review of previous work in this field.

Claude H. Organ, Jr. memorial lecture: splanchnic hypoperfusion provokes acute lung injury via a 5-lipoxygenase-dependent mechanism

Postinjury multiple organ failure (MOF) is the net result of a dysfunctional immune response to injury characterized by a hyperactive innate system and a suppressed adaptive system. Acute lung injury (ALI) is the first clinical manifestation of organ failure, followed by renal and hepatic dysfunction. Circulatory shock is integral in the early pathogenesis of MOF, and the gut has been invoked as the motor of MOF. Mesenteric lymph is recognized as the mechanistic link between splanchnic ischemia/reperfusion and distant organ dysfunction, but the specific mediators remain to be defined. Current evidence suggests the lipid fraction of postshock mesenteric lymph is central in the etiology of ALI. Specifically, our recent work suggests that intestinal phospholipase A2 generated arachidonic acid and its subsequent 5-lipoxygenase products are essential in the pathogenesis of ALI. Proteins conveyed via postshock mesenteric lymph also may have an important role. Elucidating these mediators and the timing of their participation in pulmonary inflammation is critical in translating our current knowledge to new therapeutic strategies at the bedside.

Intravenous sphingosylphosphorylcholine protects ischemic and postischemic myocardial tissue in a mouse model of myocardial ischemia/reperfusion injury

HDL, through sphingosine-1-phosphate (S1P), exerts direct cardioprotective effects on ischemic myocardium. It remains unclear whether other HDL-associated sphingophospholipids have similar effects. We therefore examined if HDL-associated sphingosylphosphorylcholine (SPC) reduces infarct size in a mouse model of transient myocardial ischemia/reperfusion. Intravenously administered SPC dose-dependently reduced infarct size after 30 minutes of myocardial ischemia and 24 hours reperfusion compared to controls. Infarct size was also reduced by postischemic, therapeutical administration of SPC. Immunohistochemistry revealed reduced polymorphonuclear neutrophil recruitment to the infarcted area after SPC treatment, and apoptosis was attenuated as measured by TUNEL. In vitro, SPC inhibited leukocyte adhesion to TNFα-activated endothelial cells and protected rat neonatal cardiomyocytes from apoptosis. S1P₃ was identified as the lysophospholipid receptor mediating the cardioprotection by SPC, since its effect was completely absent in S1P₃-deficient mice. We conclude that HDL-associated SPC directly protects against myocardial reperfusion injury in vivo via the S1P₃ receptor.

Polyphenols of Camellia sinenesis decrease mortality, hepatic injury and generation of cytokines and reactive oxygen and nitrogen species after hemorrhage/resuscitation in rats

Background

Reactive oxygen species (ROS) and reactive nitrogen species (RNS) are produced during hemorrhagic shock and resuscitation (H/R), which may contribute to multiple organ failure. The Aim of this study was to test the hypothesis that green tea (Camellia sinenesis) extract containing 85% polyphenols decreases injury after H/R in rats by scavenging ROS and RNS.

Methods

Female Sprague Dawley rats were given 100 mg polyphenol extract/kg body weight or vehicle 2 h prior to hemorrhagic shock. H/R was induced by two protocols: 1) withdrawal of blood to a mean arterial pressure of 40 mm Hg followed by further withdrawals to decrease blood pressure progressively to 28 mm Hg over 1 h (severe), and 2) withdrawal of blood to a sustained hypotension of 40 mm Hg for 1 h (moderate). Rats were then resuscitated over 1 h with 60% of the shed blood volume plus twice the shed blood volume of lactated Ringer's solution. Serum samples were collected at 10 min and 2 h after resuscitation. At 2 or 18 h, livers were harvested for cytokine and 3-nitrotyrosine quantification, immunohistochemical detection of 4-hydroxynonenol (4-HNE) and inducible nitric oxide synthase (iNOS) protein expression.

Results

After severe H/R, 18-h survival increased from 20% after vehicle to 70% after polyphenols (p < 0.05). After moderate H/R, survival was greater (80%) and not different between vehicle and polyphenols. In moderate H/R, serum alanine aminotransferase (ALT) increased at 10 min and 2 h postresuscitation to 345 and 545 IU/L, respectively. Polyphenol treatment blunted this increase to 153 and 252 IU/L at 10 min and 2 h (p < 0.01). Polyphenols also blunted increases in liver homogenates of TNFα (7.0 pg/mg with vehicle vs. 4.9 pg/mg with polyphenols, p < 0.05), IL-1β (0.80 vs. 0.37 pg/mg, p < 0.05), IL-6 (6.9 vs. 5.1 pg/mg, p < 0.05) and nitrotyrosine (1.9 pg/mg vs. 0.6 pg/mg, p < 0.05) measured 18 h after H/R. Hepatic 4-HNE immunostaining indicative of lipid peroxidation also decreased from 4.8% after vehicle to 1.5% after polyphenols (p < 0.05). By contrast, polyphenols did not block increased iNOS expression at 2 h after H/R.

Conclusion

Polyphenols decrease ROS/RNS formation and are beneficial after hemorrhagic shock and resuscitation.

Protective effect of high-density lipoprotein-based therapy in a model of embolic stroke

BACKGROUND AND PURPOSE

High-density lipoprotein (HDL) levels are inversely associated with stroke incidence, suggesting a protective effect. Using a rat model, we tested the hypothesis that HDL exerts direct vasculo-/neuroprotective effects when administered during the acute phase of embolic stroke.

METHODS

After embolic occlusion, Sprague-Dawley rats were randomly treated intravenously with purified HDL versus saline immediately (2, 10 mg/kg) or 3 or 5 hours (10 mg/kg) after stroke. The effects of HDL were assessed blindly 24 hours later by evaluating neurological deficit score and measuring the infarct volume and blood-brain barrier breakdown. Protease activities and neutrophil infiltration were also evaluated.

RESULTS

HDL injection immediately after stroke (10 mg/kg) reduced by 68% the mortality at 24 hours (P=0.015). HDL administration immediately or at 3 or 5 hours after stroke also reduced cerebral infarct volume by 74%, 68%, and 70.7%, respectively (P=0.0003, P=0.011, and P=0.019; n=17 per group). The neurological deficit at 24 hours in the HDL-treated group was decreased versus the saline-treated group (P=0.015). Ischemia-induced blood-brain barrier breakdown was significantly reduced in HDL-treated rats versus controls (P=0.0045). Neuroprotective effects of HDL were associated with decreased neutrophil recruitment in the infarct area (P=0.0027) accompanied by reduced matrix metalloproteinase gelatinase activity. Immunostaining showed that HDL was associated with endothelial and glial cells, and also that intercellular adhesion molecule-1 expression was decreased in vessels within the infarct area.

CONCLUSIONS

Administration of HDL is neuroprotective when performed up to 5 hours after experimental stroke. This effect may be attributed to the ability of HDL to protect the blood-brain barrier and limit neutrophil recruitment.

Inhibition of c-Jun N-terminal kinase after hemorrhage but before resuscitation mitigates hepatic damage and inflammatory response in male rats

Inhibition of c-Jun N-terminal kinase (JNK) by a cell-penetrating, protease-resistant JNK peptide (D-JNKI-1) before hemorrhage and resuscitation (H/R) ameliorated the H/R-induced hepatic injury and blunted the proinflammatory changes. Here we tested the hypothesis if JNK inhibition at a later time point-after hemorrhagic shock but before the onset of resuscitation-in a rat model of H/R also confers protection. Twenty-four male Sprague-Dawley rats (250 - 350 g) were randomly divided into 4 groups: 2 groups of shock animals were hemorrhaged to a MAP of 32 to 37 mmHg for 60 min and randomly received either D-JNKI-1 (11 mg/kg i.p.) or sterile saline as vehicle immediately before the onset of resuscitation. Two groups of sham-operated animals underwent surgical procedures without H/R and were either D-JNKI-1 or vehicle treated. Rats were killed 2 h later. Serum activity of alanine aminotransferase and serum lactate dehydrogenase after H/R increased 3.5-fold in vehicle-treated rats as compared with D-JNKI-1-treated rats. Histopathological analysis revealed that hepatic necrosis and apoptosis (hematoxylin-eosin, TUNEL, and M30, respectively) were significantly inhibited in D-JNKI-1-treated rats after H/R. Hepatic oxidative (4-hydroxynonenal) and nitrosative (3-nitrotyrosine) stress as well as markers of inflammation (hepatic and serum IL-6 levels and hepatic infiltration with polymorphonuclear leukocytes) were also reduced in D-JNKI-1-treated rats. LPS-stimulated TNF-alpha release from whole blood from hemorrhaged and resuscitated animals was higher in vehicle-treated rats as compared with D-JNKI-1-treated rats. c-Jun N-terminal kinase inhibition after hemorrhage before resuscitation resulted in a reduced activation of c-Jun. Taken together, these results indicate that D-JNKI-1 application after hemorrhagic shock before resuscitation blunts hepatic damage and proinflammatory changes during resuscitation. Hence, JNK inhibition is even protective when initiated after blood loss before resuscitation. These experimental results indicate that the JNK pathway may be a possible treatment option for the harmful consequences of H/R.

Statins for the prevention of dementia

BACKGROUND

This is an update of a Cochrane review first published in 2001. At that stage there was insufficient evidence to recommend statins for the prevention of Alzheimer's disease (AD). The scope of this review has been expanded to include all forms of dementia.

OBJECTIVES

To assess the effects of statins in the prevention of dementia.

SEARCH STRATEGY

The Specialized Register of the Cochrane Dementia and Cognitive Improvement Group, The Cochrane Library, MEDLINE, EMBASE, PsycINFO, CINAHL and LILACS were searched on 10 October 2007 using the terms statin*, lovastatin*, pravastatin*, simvastatin*, fluvastatin*, atorvastatin* and rosuvastatin*. The CDCIG Register contains records from many healthcare databases, SIGLE, LILACS as well as many trials databases and is updated regularly.

SELECTION CRITERIA

Double-blind randomized placebo-controlled trials of statins in people at risk of AD and dementia.

DATA COLLECTION AND ANALYSIS

Two independent reviewers extracted and assessed data independently and agreement was reached after discussion. Adverse effects were noted.

MAIN RESULTS

Two trials were identified with 26,340 participants; HPS 2002 and PROSPER 2002. Age range was 40-82 years across the two studies, PROSPER 2002 included 5804 patients aged 70-82 years and HPS included 20,536 patients with 5806 at least 70 years old at study entry. Mean total cholesterol 5.9 mmol/l, LDL cholesterol 3.4 mmol/l at study entry with mean reduction in LDL cholesterol of 1.0 mmol/l in simvastatin treated patients compared to placebo in HPS 2002. Mean total cholesterol 5.7 mmol/l, LDL cholesterol 3.8 mmol/l at study entry with mean reduction in LDL cholesterol of 1.02 mmol/l in pravastatin treated patients compared to placebo in PROSPER 2002. Mean follow-up 3.2 years in PROSPER, 5 years in HPS 2002. Cognition was measured at different times and with different scales so could not be combined in a meta-analysis. There was no difference in incidence of dementia in HPS 2002 (31 cases in simvastatin group, 31 cases in placebo group) nor in performance on the modified Telephone Interview for Cognitive Status at final follow-up (23.7% simvastatin group cognitively impaired vs 24.2% in placebo group). There was no difference in cognition between groups either in relation to age at study entry or previous history of cerebrovascular disease. Cognitive function declined at the same rate in both treatment groups in PROSPER 2002, there was no significant difference between pravastatin treated and placebo groups in performance on letter digit codes, picture word learning test, Stroop and Mini Mental State Examination. There was no evidence that statins were detrimental to cognition.

AUTHORS' CONCLUSIONS

There is good evidence from RCTs that statins given in late life to individuals at risk of vascular disease have no effect in preventing AD or dementia. Biologically it seems feasible that statins could prevent dementia due to their role in cholesterol reduction and initial evidence from observational studies was very promising. Indication bias may have been a factor in these studies however and the evidence from subsequent RCTs has been negative.

The paraoxonases: role in human diseases and methodological difficulties in measurement

Research into the paraoxonase (PON) gene family has flourished over the past few years. In the 1970s and 1980s, only PON1 was known, and the investigations were conducted, essentially, by toxicologists focusing on protection against organophosphate poisoning. Since then, two new members of the family, PON2 and PON3, have been identified, both being shown to play antioxidant and anti-inflammatory roles. Evidence exists indicating that the PON family is central to a wide variety of human illnesses such as cardiovascular disease, diabetes mellitus, metabolic syndrome, obesity, non-alcoholic steatohepatitis, and several mental disorders. However, research is hampered considerably by the methods currently available to measure the activity of these enzymes. In this review, we summarize the state of knowledge on PON biochemistry and function, the influence of genetic variations, and the involvement of PON in several diseases. The problems associated with PON measurement, such as sample acquisition, lack of reference methods, and variety of substrates, will be presented. Also, we cover some of the present lines of research and propose some others for future progress in this field.

APOE genotype affects outcome in a murine model of sepsis: implications for a new treatment strategy

In this study, we assessed whether apolipoprotein E (APOE) polymorphism affects inflammatory responses and mortality in the caecal ligation and puncture model of peritonitis. In addition, we determined the effects of APOE mimetic peptide administration in this sepsis model. Differences in survival between targeted replacement mice expressing the human APOE3 allele (APOE3TR) and the APOE4 allele (APOE4TR) mice were assessed. In a separate series of experiments, COG1410, an apoE-mimetic peptide, was administered intravenously at 12-hour intervals for 72 hours and compared to vehicle-treated control animals. End-points included mortality and serum levels of interleukin-1beta, interleukin-6, interleukin-12 and tumour necrosis factor-alpha. Mice expressing the human APOE4 allele (n = 16) demonstrated an increase in mortality following caecal ligation and puncture compared with APOE3TR mice (n = 22; P = 0.039). Administration of the apolipoprotein E mimetic COG1410 was well tolerated and APOE3TR mice treated with peptide (n = 20) demonstrated a significant reduction in mortality compared with vehicle treated animals (n = 20; P = 0.007). A similar effect was also observed in APOE4TR animals, in which treatment with COG1410 was associated with reduced mortality compared with vehicle treatment (n =16 animals/group; P = 0.027). COG1410 was also associated with a reduction in TNFalpha, interleukin-1beta, interleukin-6 and interleukin-12 levels in both APOE3TR and APOE4TR (n = 5 animals/group) assessed at 24 hours. Thus, administration of an apolipoprotein E-mimetic peptide is well tolerated, suppresses inflammatory responses, and improves mortality in a caecal ligation and puncture model of sepsis.

Sphingosine-1-phosphate as a mediator of high-density lipoprotein effects in cardiovascular protection

Sphingosine-1-phosphate (S1P) has gained special attention in the high-density lipoprotein (HDL) field because HDL is the most prominent plasma carrier of S1P and because the S1P content of HDL may be responsible for many of the pleiotropic functions of HDL. This revelation has come from the evidence that HDL employ S1P receptors and signalling pathways to implement several HDL-ascribed biological effects as diverse as endothelial nitric oxide production, vasodilation, survival, and cardioprotection. This review focuses on HDL effects that are completely or partially mediated by the S1P content of the HDL particle and differentiates them from genuine HDL effects that are S1P-independent. In addition, the functional properties of 'free', HDL-unbound S1P are sometimes different from or even contrary to those of HDL-associated S1P. The nature of the physical interactions between HDL and local and systemic S1P production will be discussed as well as their consequences for organ function. Finally, we will elucidate the potential benefits and limitations of S1P analogues as a new class of functional HDL mimetics for cardiovascular therapy.

Peroxisome proliferator-activated receptor-alpha contributes to the resolution of inflammation after renal ischemia/reperfusion injury

This study was designed to elucidate the role of peroxisome proliferator-activated receptor (PPAR)-alpha in the development of inflammation after ischemia/reperfusion injury of the kidney. We have evaluated the effects of ischemia/reperfusion on renal dysfunction, injury, and inflammation in wild-type mice or mice in which the gene for PPAR-alpha has been deleted [PPAR-alpha(-/-)] and then treated with the PPAR-alpha agonist fenofibrate. Mice were subjected to bilateral renal ischemia (30 min) and reperfusion (24 h) and received fenofibrate (3 mg/kg i.p.) before reperfusion. Plasma creatinine, urea, and aspartate aminotransferase were all used as indicators of renal dysfunction and injury. Kidneys were used for histological and immunohistochemical analysis and markers of inflammation. Fenofibrate significantly attenuated the degree of renal dysfunction, injury, and inflammation caused by ischemia/reperfusion injury. The degree of renal dysfunction, injury, and inflammation caused by ischemia/reperfusion was also significantly augmented in PPAR-alpha(-/-) mice compared with their wild-type littermates. It is interesting that fenofibrate did not protect PPAR-alpha(-/-) mice against ischemia/reperfusion injury. Therefore, we propose that ligands of PPAR-alpha may be useful in the treatment of renal ischemia/reperfusion injury and that endogenous PPAR-alpha limits the degree of renal dysfunction, injury, and inflammation associated with ischemia/reperfusion injury.

Targeted inactivation of endothelial lipase attenuates lung allergic inflammation through raising plasma HDL level and inhibiting eosinophil infiltration

Endothelial lipase (EL) is a novel phospholipase that determines plasma high-density lipoprotein cholesterol (HDL-C) levels. We have investigated the role of HDL-C in lung allergic inflammation by using EL knockout (EL-KO) mice that are high in HDL-C. EL-KO and wild-type control mice were sensitized and challenged with ovalbumin to evoke eosinophilic inflammation in the lung. EL was expressed in epithelial cells, alveolar type II cells, and endothelial cells in the lung, and its expression was upregulated during inflammation. Concomitant with attenuated hyperresponsiveness of the airway smooth muscles, the number of eosinophils in bronchoalveolar lavage and the expression of VCAM-1 were lower in EL-KO mice than in control mice. HDL reduced cytokine-induced VCAM-1 expression in cultured endothelial cells. When plasma HDL levels were decreased to similar levels in both mouse groups by adenovirus-mediated overexpression of EL, however, eosinophil infiltration was still lower in EL-KO mice. In vitro adhesion assays revealed that EL expression on the cell surface promoted the interaction of eosinophils through the ligand-binding function of EL. In summary, targeted inactivation of EL attenuated allergic inflammation in the lung, and the protective effects in EL-KO mice were associated with high plasma HDL levels, downregulation of VCAM-1, and loss of the direct ligand-binding function of EL. Thus EL is a novel modulator of the progression of allergic asthma.

HDL-replacement therapy: mechanism of action, types of agents and potential clinical indications

HDL-replacement therapy is a promising new treatment strategy involving the acute administration of HDL to rapidly stabilize patients at imminent risk for developing a myocardial infarction, such as those with acute coronary syndrome. This review will first focus on the anti-atherogenic mechanisms for HDL, such as the stimulation of the reverse cholesterol transport pathway, and then discuss the other potential beneficial biological effects of HDL on atherosclerosis. The various types of HDL-replacement therapies that are being investigated and developed will be reviewed and ongoing clinical trials and other possible clinical indications for HDL-replacement therapy besides the prevention of myocardial infarction will also be described. Finally, HDL-replacement therapy will be put into perspective by summarizing the current gaps in our knowledge of HDL metabolism and identifying challenges for future research in this area.

A peptide inhibitor of C-jun N-terminal kinase modulates hepatic damage and the inflammatory response after hemorrhagic shock and resuscitation

Hemorrhage and resuscitation (H/R) leads to phosphorylation of mitogen-activated stress kinases, an event that is associated with organ damage. Recently, a specific, cell-penetrating, protease-resistant inhibitory peptide of the mitogen-activated protein kinase c-JUN N-terminal kinase (JNK) was developed (D-JNKI-1). Here, using this peptide, we tested if inhibition of JNK protects against organ damage after H/R. Male Sprague-Dawley rats were treated with D-JNKI-1 (11 mg/kg, i.p.) or vehicle. Thirty minutes later, rats were hemorrhaged for 1 h to a MAP of 30 to 35 mmHg and then resuscitated with 60% of the shed blood and twice the shed blood volume as Ringer lactate. Tissues were harvested 2 h later. ANOVA with Tukey post hoc analysis or Kruskal-Wallis ANOVA on ranks, P < 0.05, was considered significant. c-JUN N-terminal kinase inhibition decreased serum alanine aminotransferase activity as a marker of liver injury by 70%, serum creatine kinase activity by 67%, and serum lactate dehydrogenase activity by 60% as compared with vehicle treatment. The histological tissue damage observed was blunted after D-JNKI-1 pretreatment both for necrotic and apoptotic cell death. Hepatic leukocyte infiltration and serum IL-6 levels were largely diminished after D-JNKI-1 pretreatment. The extent of oxidative stress as evaluated by immunohistochemical detection of 4-hydroxynonenal was largely abrogated after JNK inhibition. After JNK inhibition, activation of cJUN after H/R was also reduced. Hemorrhage and resuscitation induces a systemic inflammatory response and leads to end-organ damage. These changes are mediated, at least in part, by JNK. Therefore, JNK inhibition deserves further evaluation as a potential treatment option in patients after resuscitated blood loss.

High density lipoprotein-associated sphingosine 1-phosphate promotes endothelial barrier function

High density lipoproteins (HDL) are major plasma carriers of sphingosine 1-phosphate (S1P). Here we show that HDL increases endothelial barrier integrity as measured by electric cell substrate impedance sensing. S1P was implicated as the mediator in this process through findings showing that pertussis toxin, an inhibitor of Gi-coupled S1P receptors, as well as antagonists of the S1P receptor, S1P1, inhibited barrier enhancement by HDL. Additional findings show that HDL stimulates endothelial cell activation of Erk1/2 and Akt, signaling pathway intermediates that have been implicated in S1P-dependent endothelial barrier activity. HDL was also found to promote endothelial cell motility, a process that may also relate to endothelial barrier function in the context of a vascular injury response. The effects of HDL on endothelial cell Erk1/2 and Akt activation and motility were suppressed by pertussis toxin and S1P1 antagonists. However, both HDL-induced barrier enhancement and HDL-induced motility showed a greater dependence on Akt activation as compared with Erk1/2 activation. Together, the findings indicate that HDL has endothelial barrier promoting activities, which are attributable to its S1P component and signaling through the S1P1/Akt pathway.

Low dose apolipoprotein A-I rescues carotid arteries from inflammation in vivo

This study investigates the ability of a single, low dose of apolipoprotein (apo) A-I, the main lipoprotein of high density lipoproteins (HDL), to inhibit acute vascular inflammation in normocholesterolemic New Zealand White rabbits. Acute vascular inflammation was induced in the animals by placing a non-occlusive, silastic collar around the left common carotid artery. The animals (n=5/group) received a single, low dose infusion of saline or lipid-free apoA-I at the time of, or 3 or 9h after collar insertion. The animals were sacrificed 24h post-collar insertion. Inflammatory markers in the artery wall were quantitated immunohistochemically. The saline-treated animals exhibited substantial pan-arterial inflammation, which was inhibited by a single apoA-I infusion (2 or 8 mg/kg) at the time of collar insertion. A single 8 mg/kg infusion of lipid-free apoA-I administered 3h post-collar insertion reduced neutrophil recruitment into the vessel wall, and MPO expression, as well as endothelial expression of vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1) by >85% (p<0.01 for all). A single 8 mg/kg infusion of lipid-free apoA-I administered 9h after collar insertion decreased VCAM-1 expression, neutrophil infiltration and MPO expression by 88% (p<0.001), 47% (p<0.01), and 90% (p<0.01), respectively. This indicates that a single low dose infusion of apoA-I administered after the onset of acute inflammation in carotid arteries decreases neutrophil infiltration and inhibits neutrophil and endothelial cell activation. These findings have potential implications for treating acute vascular inflammation in conditions such as acute coronary and stroke syndromes.

High-density lipoprotein administration attenuates liver proinflammatory response, restores liver endothelial nitric oxide synthase activity, and lowers portal pressure in cirrhotic rats

In patients with cirrhosis, endotoxic shock is a major complication of portal hypertension, which is related partly to intrahepatic endothelial nitric oxide synthase (eNOS) down-regulation. High-density lipoproteins (HDLs), whose plasma levels are reduced in cirrhosis, have an anti-inflammatory effect by neutralizing circulating lipopolysaccharide (LPS), and they increase eNOS activity in endothelial cells. Therefore, the aim of this study was to assess the effects of reconstituted high-density lipoprotein (rHDL) administration on the LPS-induced proinflammatory response, intrahepatic eNOS regulation, and portal hypertension in cirrhotic rats. Cirrhotic and control rats were pretreated with rHDL or saline and challenged with LPS or saline. The neutralization of LPS in HDL was assessed by the measurement of HDL-bound fluorescent LPS levels. Plasma tumor necrosis factor alpha (TNFalpha) and lipopolysaccharide binding protein (LBP) levels were measured. The expression of hepatic TNFalpha, LBP, inducible nitric oxide synthase (iNOS), and caveolin-1 (a major eNOS inhibitor) and the activity of protein kinase B (Akt; a major eNOS activator) and eNOS were determined. The portal pressure was measured. The plasma HDL levels were significantly lower in cirrhotic rats than in control rats. In cirrhotic rats, the plasma levels of HDL-bound fluorescent LPS were 50% lower than those in controls, and they were restored after rHDL administration. The plasma TNFalpha levels were significantly higher in LPS-challenged cirrhotic rats than in controls and significantly decreased after rHDL administration. rHDL administration decreased hepatic TNFalpha, LBP, iNOS, and caveolin-1 expression, restored hepatic eNOS and Akt activity, and significantly lowered the portal pressure and intrahepatic vascular resistance.

CONCLUSION

In cirrhotic rats, rHDL administration decreases the hepatic proinflammatory signals induced by LPS, restores the hepatic eNOS activity, and lowers the portal pressure. This suggests that the decrease in circulating HDL in cirrhosis plays a role in the excessive proinflammatory response and intrahepatic eNOS down-regulation.

Oxidation–reduction potential and paraoxonase–arylesterase activity in trauma patients

The amount of oxidative stress in severely traumatized patients is usually based on various individual parameters such as total antioxidants and lipid peroxidation. Serial measurements of plasma oxidation-reduction potential (ORP) in severely traumatized patients as a simple mean of assessing overall oxidative stress is described. Serial whole blood samples were obtained from multi-trauma patients (N=39) and healthy individuals (N=10). Plasma ORP in multi-trauma patients increased during the first few days of hospitalization and approached normal ORP levels upon discharge. On the ORP maxima day (5.8 days+/-0.5 SEM), a statistically significant decrease (p<0.05) was observed for negative acute phase reactants such as plasma paraoxonase-arylesterase (PON-AE) activity and total plasma protein in comparison with admission plasma levels. Monitoring ORP could be a useful tool for assessing the degree of oxidative stress, inflammation, severity of injury, and potential efficacy of treatment.

High-density lipoproteins: a therapeutic target for atherosclerotic cardiovascular disease

Despite great progress being made during the last two decades in cardiovascular disease prevention, especially by lowering low-density lipoprotein-cholesterol with statins, cardiovascular events continue to occur. Plasma high-density lipoprotein (HDL) exerts multiple protective effects on the arterial wall, through promotion of reverse cholesterol transport, prevention of endothelial dysfunction and inhibition of lipid oxidation. Therapeutic interventions raising plasma HDL levels or directly mimicking its beneficial effects represent the next frontier in the prevention and treatment of cardiovascular disease.

Selective melanocortin MC4 receptor agonists reverse haemorrhagic shock and prevent multiple organ damage

BACKGROUND AND PURPOSE

In circulatory shock, melanocortins have life-saving effects likely to be mediated by MC4 receptors. To gain direct insight into the role of melanocortin MC4 receptors in haemorrhagic shock, we investigated the effects of two novel selective MC4 receptor agonists.

EXPERIMENTAL APPROACH

Severe haemorrhagic shock was produced in rats under general anaesthesia. Rats were then treated with either the non-selective agonist [Nle4, D-Phe7]-melanocyte-stimulating hormone (NDP--MSH) or with the selective MC4 agonists RO27-3225 and PG-931. Cardiovascular and respiratory functions were continuously monitored for 2 h; survival rate was recorded up to 24 h. Free radicals in blood were measured using electron spin resonance spectrometry; tissue damage was evaluated histologically 25 min or 24 h after treatment.

KEY RESULTS

All shocked rats treated with saline died within 30-35 min. Treatment with NDP--MSH, RO27-3225 and PG-931 produced a dose-dependent (13-108 nmol kg-1 i.v.) restoration of cardiovascular and respiratory functions, and improved survival. The three melanocortin agonists also markedly reduced circulating free radicals relative to saline-treated shocked rats. All these effects were prevented by i.p. pretreatment with the selective MC4 receptor antagonist HS024. Moreover, treatment with RO27-3225 prevented morphological and immunocytochemical changes in heart, lung, liver, and kidney, at both early (25 min) and late (24 h) intervals.

CONCLUSIONS AND IMPLICATIONS

Stimulation of MC4 receptors reversed haemorrhagic shock, reduced multiple organ damage and improved survival. Our findings suggest that selective MC4 receptor agonists could have a protective role against multiple organ failure following circulatory shock.

High-density lipoproteins: an emerging target in the prevention of cardiovascular disease

High-density lipoproteins (HDLs) have been well established to protect against the development of atherosclerotic cardiovascular disease. It has become apparent that in addition to the promotion of reverse cholesterol transport, HDLs possess a number of additional functional properties that may contribute to their beneficial influence on the arterial wall. A number of exciting therapeutic strategies have been developed that target HDL and its ability to protect against the development of atherosclerotic plaque. This paper will review how the promotion of the functional properties of HDL inhibits the formation of atherosclerotic plaque and stabilises lesions in patients with established disease.

Lipoproteins in inflammation and sepsis. I. Basic science

BACKGROUND

High-density lipoproteins (HDL) have been shown to bind and neutralize lipopolysaccharide (LPS) and are regarded as possible therapeutic agents for sepsis and conditions associated with local or systemic inflammation. However, in recent years, a multitude of possible immunomodulatory properties other than LPS neutralization have become evident.

DISCUSSION

This review highlights the advances in the understanding of how HDL is protective in both in vitro and in vivo inflammatory settings, including the ability of HDL to modulate adhesion molecule expression, upregulate endothelial nitric oxide synthase and counteract oxidative stress. Also, the active components of HDL and the recent discovery of novel lipid modulators of inflammation are discussed.

Normal mesenteric lymph blunts the pulmonary inflammatory response to endotoxin

BACKGROUND

Mesenteric lymph may provide the mechanistic link between gut ischemia and acute lung injury after hemorrhagic shock (HS). Studies have focused on the toxic mediators that develop in the post-shock mesenteric lymph (PSML). However, a complementary possibility is that there is loss of protective mediators found in pre-shock normal mesenteric lymph (NML) after HS. We hypothesize that NML protects against inflammatory insults to the pulmonary endothelium and that this effect is lost in PSML.

MATERIALS AND METHODS

Primary human pulmonary endothelial cells (HMVECs) were incubated with NML or PSML collected from rats subjected to HS and resuscitation and then stimulated with 20 ng/mL LPS. ICAM-1 surface expression was measured by flow cytometry. In subsequent experiments, lipoproteins were extracted from NML before incubation and LPS-induced ICAM-1 expression determined.

RESULTS

Mean fluorescent intensity (MFI) of LPS-induced ICAM-1 in NML and PSML treated HMVECs were 10.1 +/- 2.3 versus 27.7 +/- 0.83, respectively (P < 0.05). This represented at 71% decrease in ICAM-1 expression by NML compared to ICAM-1 expression in LPS-induced controls (MFI: 34.6 +/- 6.9). Lipoprotein extraction from NML abolished this protective effect (MFI: 31.2 +/- 5.3 versus Control + LPS: 33.5 +/- 3.6, P > 0.05). Baseline ICAM-1 levels were not significantly different among control, NML, and PSML groups.

CONCLUSION

Lipoproteins in NML contain anti-inflammatory properties that decrease ICAM-1 expression induced by LPS in pulmonary endothelium. Decreased protective lipoproteins after HS and resuscitation may contribute to the toxicity associated with PSML from the ischemic gut.