High-density lipoprotein and the acute phase response

Surgical inflammatory stress: the embryo takes hold of the reins again

The surgical inflammatory response can be a type of high-grade acute stress response associated with an increasingly complex trophic functional system for using oxygen. This systemic neuro-immune-endocrine response seems to induce the re-expression of 2 extraembryonic-like functional axes, i.e. coelomic-amniotic and trophoblastic-yolk-sac-related, within injured tissues and organs, thus favoring their re-development. Accordingly, through the up-regulation of two systemic inflammatory phenotypes, i.e. neurogenic and immune-related, a gestational-like response using embryonic functions would be induced in the patient's injured tissues and organs, which would therefore result in their repair. Here we establish a comparison between the pathophysiological mechanisms that are produced during the inflammatory response and the physiological mechanisms that are expressed during early embryonic development. In this way, surgical inflammation could be a high-grade stress response whose pathophysiological mechanisms would be based on the recapitulation of ontogenic and phylogenetic-related functions. Thus, the ultimate objective of surgical inflammation, as a gestational process, is creating new tissues/organs for repairing the injured ones. Since surgical inflammation and early embryonic development share common production mechanisms, the factors that hamper the wound healing reaction in surgical patients could be similar to those that impair the gestational process.

Individual variation in levels of haptoglobin-related protein in children from Gabon

Background

Haptoglobin related protein (Hpr) is a key component of trypanosome lytic factors (TLF), a subset of high-density lipoproteins (HDL) that form the first line of human defence against African trypanosomes. Hpr, like haptoglobin (Hp) can bind to hemoglobin (Hb) and it is the Hpr-Hb complexes which bind to these parasites allowing uptake of TLF. This unique form of innate immunity is primate-specific. To date, there have been no population studies of plasma levels of Hpr, particularly in relation to hemolysis and a high prevalence of ahaptoglobinemia as found in malaria endemic areas.

Methods and Principal Findings

We developed a specific enzyme-linked immunosorbent assay to measure levels of plasma Hpr in Gabonese children sampled during a period of seasonal malaria transmission when acute phase responses (APR), malaria infection and associated hemolysis were prevalent. Median Hpr concentration was 0.28 mg/ml (range 0.03–1.1). This was 5-fold higher than that found in Caucasian children (0.049 mg/ml, range 0.002–0.26) with no evidence of an APR. A general linear model was used to investigate associations between Hpr levels, host polymorphisms, parasitological factors and the acute phase proteins, Hp, C-reactive protein (CRP) and albumin. Levels of Hpr were associated with Hp genotype, decreased with age and were higher in females. Hpr concentration was strongly correlated with that of Hp, but not CRP.

Conclusions/Significance

Individual variation in Hpr levels was related to Hp level, Hp genotype, demographics, malaria status and the APR. The strong correlations between plasma levels of Hp and Hpr suggest that they are regulated by similar mechanisms. These population-based observations indicate that a more dynamic view of the relative roles of Hpr and Hpr-Hb complexes needs to be considered in understanding innate immunity to African trypanosomes and possibly other pathogens including the newly discovered Plasmodium spp of humans and primates.

Exploring the factors that affect blood cholesterol and heart disease risk: is dietary cholesterol as bad for you as history leads us to believe?

This paper summarizes presentations given at the 2011 Experimental Biology meetings about the latest research and a paleoanthropological perspective pertaining to the relationship between dietary cholesterol intake and cardiovascular disease risk. For much of the past 50 years, a great deal of the scientific literature regarding dietary fat and cholesterol intake has indicated a strong positive correlation with heart disease. In recent years, however, there have been a number of epidemiological studies that did not support a relationship between cholesterol intake and cardiovascular disease. Further, a number of recent clinical trials that looked at the effects of long-term egg consumption (as a vehicle for dietary cholesterol) reported no negative impact on various indices of cardiovascular health and disease. Coupled with data indicating that the impact of lowering dietary cholesterol intake on serum LDL levels is small compared with other dietary and lifestyle factors, there is a need to consider how otherwise healthy foods can be incorporated in the diet to meet current dietary cholesterol recommendations. Because eggs are a healthful food, it is particularly important that sensible strategies be recommended for inclusions of eggs in a healthy diet.

High Density Lipoprotein and it's Dysfunction

Plasma high-density lipoprotein cholesterol(HDL-C) levels do not predict functionality and composition of high-density lipoprotein(HDL). Traditionally, keeping levels of low-density lipoprotein cholesterol(LDL-C) down and HDL-C up have been the goal of patients to prevent atherosclerosis that can lead to coronary vascular disease(CVD). People think about the HDL present in their cholesterol test, but not about its functional capability. Up to 65% of cardiovascular death cannot be prevented by putative LDL-C lowering agents. It well explains the strong interest in HDL increasing strategies. However, recent studies have questioned the good in using drugs to increase level of HDL. While raising HDL is a theoretically attractive target, the optimal approach remains uncertain. The attention has turned to the quality, rather than the quantity, of HDL-C. An alternative to elevations in HDL involves strategies to enhance HDL functionality. The situation poses an opportunity for clinical chemists to take the lead in the development and validation of such biomarkers. The best known function of HDL is the capacity to promote cellular cholesterol efflux from peripheral cells and deliver cholesterol to the liver for excretion, thereby playing a key role in reverse cholesterol transport (RCT). The functions of HDL that have recently attracted attention include anti-inflammatory and anti-oxidant activities. High antioxidant and anti-inflammatory activities of HDL are associated with protection from CVD.This review addresses the current state of knowledge regarding assays of HDL functions and their relationship to CVD. HDL as a therapeutic target is the new frontier with huge potential for positive public health implications.

Lipid transfer to HDL is higher in marathon runners than in sedentary subjects, but is acutely inhibited during the run

Although exercise increases HDL-cholesterol, exercise-induced changes in HDL metabolism have been little explored. Lipid transfer to HDL is essential for HDL's role in reverse cholesterol transport. We investigated the effects of acute exhaustive exercise on lipid transfer to HDL. We compared plasma lipid, apolipoprotein and cytokine levels and in vitro transfer of four lipids from a radioactively labeled lipid donor nanoemulsion to HDL in sedentary individuals (n = 28) and in marathon runners (n = 14) at baseline, immediately after and 72 h after a marathon. While HDL-cholesterol concentrations and apo A1 levels were higher in marathon runners, LDL-cholesterol, apo B and triacylglycerol levels were similar in both groups. Transfers of non-esterified cholesterol [6.8 (5.7-7.2) vs. 5.2 (4.5-6), p = 0.001], phospholipids [21.7 (20.4-22.2) vs. 8.2 (7.7-8.9), p = 0.0001] and triacylglycerol [3.7 (3.1-4) vs. 1.3 (0.8-1.7), p = 0.0001] were higher in marathon runners, but esterified-cholesterol transfer was similar. Immediately after the marathon, LDL- and HDL-cholesterol concentrations and apo A1 levels were unchanged, but apo B and triacylglycerol levels increased. Lipid transfer of non-esterified cholesterol [6.8 (5.7-7.2) vs. 5.8 (4.9-6.6), p = 0.0001], phospholipids [21.7 (20.4-22.2) vs. 19.1 (18.6-19.3), p = 0.0001], esterified-cholesterol [3.2 (2.2-3.8) vs. 2.3 (2-2.9), p = 0.02] and triacylglycerol [3.7 (3.1-4) vs. 2.6 (2.1-2.8), p = 0.0001] to HDL were all reduced immediately after the marathon but returned to baseline 72 h later. Running a marathon increased IL-6 and TNF-α levels, but after 72 h these values returned to baseline. Lipid transfer, except esterified-cholesterol transfer, was higher in marathon runners than in sedentary individuals, but the marathon itself acutely inhibited lipid transfer. In light of these novel observations, further study is required to clarify how these metabolic changes can influence HDL composition and anti-atherogenic function.

Serum amyloid A (SAA) induces pentraxin 3 (PTX3) production in rheumatoid synoviocytes

OBJECTIVE

Pentraxin 3 (PTX3) is an acute-phase reactant that is involved in amplification of the inflammatory response and innate immunity. In the present study, we evaluated the relationship between PTX3 and serum amyloid A (SAA), another acute-phase reactant, in rheumatoid synoviocytes.

METHODS

PTX3 mRNA expression was examined by reverse transcription polymerase chain reaction, and PTX3 protein was measured by enzyme-linked immunosorbent assay.

RESULTS

SAA induced PTX3 mRNA and PTX3 protein expression in rheumatoid synoviocytes. SAA-induced PTX3 expression was attenuated when rheumatoid synoviocytes were nucleofected with N-formyl peptide receptor ligand-1 (FPRL-1)-specific siRNA, suggesting the involvement of FPRL-1. Furthermore, SAA-induced PTX3 expression was inhibited by NF-κB or mitogen-activated protein kinase-specific inhibitors. Neither soluble TNF receptor (etanercept) nor recombinant IL-1 receptor antagonist affected PTX3 production by SAA-stimulated synoviocytes, suggesting that SAA directly induces PTX3.

CONCLUSION

Our data suggest that SAA plays a role in the proinflammatory and immune responses in rheumatoid synovium by inducing PTX3. We provide the first evidence that the acute-phase reactant SAA, which is produced systemically by hepatocytes, perpetuates the rheumatoid inflammatory processes by inducing another proinflammatory molecule, PTX3, locally in rheumatoid synovial tissues.

Coupling inflammation with evo-devo

Inflammation integrates diverse mechanisms that are associated not only with pathological conditions, such as cardiovascular diseases, type 2 diabetes, obesity, neurodegenerative diseases and cancer, but also with physiological processes like reproduction i.e. oogenesis and embryogenesis as well as aging. In the current review we firstly propose that the inflammatory response could recapitulate the phylogenia. In this way, highly conserved inflammatory mechanisms that play a main role in the evolutive development of different animal species, both invertebrates as well as vertebrates, are identified. Therefore, we also hypothesize that inflammation could represent a key tool used by nature to modulate organisms according to the environmental conditions in which these develop. Thus, inflammation could be the pathway by which the environmental factors could be related to the evolutionary development. If so, the diverse human chronic inflammatory diseases that nowadays the Western society suffer would represent the way for adapting to the abrupt changes in their lifestyle. Nonetheless, the distribution of the different pathological conditions varies in terms of intensity and magnitude among Western country populations depending on their genetic polymorphism. In this case, it should be considered that this set of diseases, distributed between all the individuals that constitute the Westernized society, would represent a true Social Inflammatory Syndrome whose final result is its remodeling. In this context, the use of inflammation by the Western society could represent the camouflaged expression of efficient mechanisms of evolution and development. In addition, if the different types of the inflammatory response involved in these diverse chronic pathological conditions could trace the biochemical origins of life, perhaps inflammation could represent an archaeological tool of unsuspected usefulness for understanding our own origin.

Portal hypertensive cardiovascular pathology: the rescue of ancestral survival mechanisms?

The portal system derives from the vitelline system, which is an extra-embryonic venous system. It could be suggested that this extraembryonic origin determines some of the characteristics attributed to portal hypertension, both compensated, i.e. prehepatic, and decompensated, i.e. fibrotic or cirrhotic. The experimental models most frequently used for studying both types of portal hypertension are portal vein ligation and common bile duct ligation in rats, respectively. We propose that in partial portal vein ligated rats, a low-grade inflammatory response, formed by the successive expression of three overlapping phenotypes - ischemia-reperfusion, vitellogenic-like and remodeling or gastrulation-like - is produced. The names of these inflammatory phenotypes developed in compensated portal hypertension are based on some metabolic similarities that can be established with the abovementioned phases of embryonic development. In bile-duct ligated rats, decompensation related to hepatic insufficiency would induce a high-grade inflammatory response. In this experimental model, the splanchnic interstitium, the mesenteric lymph and the peritoneal mesothelium seem to create an inflammatory axis that produces ascites. The functional comparison between the ascitic and the amniotic fluids would imply that, in the decompensated portal hypertensive syndrome, the abdominal mesothelium acquires properties of the amniotic membranes or amnion. In conclusion, the hypothetical comparison between the inflammatory portal hypertensive evolutive types and the evolutive phases of embryonic development could allow for translational research.

Effects of alpha-lipoic acid supplementation on inflammation, oxidative stress, and serum lipid profile levels in patients with end-stage renal disease on hemodialysis

OBJECTIVE

We examined the effects of alpha-lipoic acid (ALA) supplementation on inflammation, oxidative stress, and serum lipid profile levels in hemodialysis (HD) patients.

DESIGN

This was a double-blinded, randomized, placebo-controlled clinical trial.

SETTING

The present study involved HD centers in Tabriz, Iran.

PATIENTS

Participants included 63 patients with end-stage renal disease (43 men and 20 women; age range: 22-79 years) undergoing maintenance HD.

INTERVENTION

HD patients were randomly assigned into the supplemented group (n = 31), receiving a daily dose of ALA (600 mg), or a control group (n = 32), receiving placebo for 8 weeks.

MAIN OUTCOME MEASURES

High sensitivity C-reactive protein (hsCRP), malondialdehyde, total antioxidant status, total cholesterol, triglyceride, high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were measured at baseline and after 8 weeks of supplementation.

RESULTS

At the end of intervention, 11 patients were excluded from the study. HsCRP levels decreased by 18.7% in the supplemented group after 8 weeks of supplementation, and the reduction was significant in comparison with the placebo group (P < .05); this finding was also significant after adjusting for baseline values of hsCRP. The mean malondialdehyde and total antioxidant status levels did not change significantly in the 2 groups during the study. The mean high-density lipoprotein cholesterol concentrations increased significantly in the supplemented group at the end of the study (P < .05); however, this improvement was not statistically significant as compared with the placebo group. No significant alterations were observed in the other lipid profile parameters within each group during the study.

CONCLUSION

ALA supplementation significantly reduced hsCRP levels, which is a risk factor for cardiovascular disease in HD patients.

Metabolic nuclear receptor signaling and the inflammatory acute phase response

The acute phase response (APR) classically refers to the rapid reprogramming of gene expression and metabolism in response to inflammatory cytokine signaling. As components of the innate immune system, hepatocyte-derived acute phase proteins (APPs) play a central role in restoring tissue homeostasis. Recently, an intriguing 'metaflammatory' facet of the APR became evident with chronically elevated APP levels being connected to metabolic syndrome disorders. The causality of these connections is unclear but could relate to adverse metabolic and inflammatory disturbances, particularly those affecting lipoprotein properties, cholesterol metabolism and atherogenesis. Here we review these aspects with an emphasis on the emerging importance of lipid-sensing nuclear receptors (LXRs, LRH-1, PPARs), in conjunction with anti-inflammatory transrepression pathways, as physiological and pharmacological relevant modulators of the APR.

High density lipoprotein: it's not just about lipid transport anymore

Plasma levels of high density lipoprotein cholesterol (HDL-C) have long been associated with protection against cardiovascular disease (CVD) in large populations. However, HDL-C has been significantly less useful for predicting CVD risk in individual patients. This has ignited a new debate on the merits of measuring HDL quantity versus quality in terms of protective potential. In addition, numerous recent studies have begun to uncover HDL functions that vary surprisingly from traditional lipid transport roles. In this paper, we review recent findings that point to important functions for HDL that go well beyond lipid transport. These discoveries suggest that HDL might be a platform that mediates protection from a host of disease states ranging from CVD to diabetes to infectious disease.

Profiles of inflammatory markers and lipoprotein subclasses in patients undergoing continuous ambulatory peritoneal dialysis

BACKGROUND

Patients undergoing continuous ambulatory peritoneal dialysis (CAPD) often have inflammation and dyslipidemia that accelerate to atherosclerosis. This study aimed to evaluate chronic inflammation and dyslipidemia in CAPD patients.

METHODS

We measured inflammatory markers and lipoprotein subclasses in 20 CAPD patients (12 men and 8 women, aged 59.5 ± 9.9 y) and 20 gender-matched controls. Lipoproteins were separated by high-performance liquid chromatography (HPLC) using an anion-exchange column.

RESULTS

High-sensitivity C-reactive protein and serum amyloid A protein (SAA) were higher among CAPD patients vs. controls (1.6 ± 2.2 vs. 0.8 ± 1.2 mg/l, p<0.05; 11.9 ± 12.8 vs. 4.5 ± 2.4 mg/l). HPLC analysis revealed that chylomicron, VLDL, and IDL cholesterol levels were higher among CAPD vs. controls. In contrast, HDL cholesterol was lower among CAPD patients vs. controls. In the subgroup analysis, SAA levels were significantly lower among patients receiving CAPD for >3 y than among controls. However, IDL cholesterol was consistently higher among CAPD patients vs. controls.

CONCLUSIONS

CAPD patients have chronic inflammation and dyslipidemia. IDL cholesterol is the only lipoprotein subclass that is consistently elevated regardless of CAPD duration. More attention should be paid to dyslipidemia in the management of the CAPD patients.

Relative roles of various efflux pathways in net cholesterol efflux from macrophage foam cells in atherosclerotic lesions

PURPOSE OF REVIEW

Cholesterol efflux mechanisms are essential for macrophage cholesterol homeostasis. HDL, an important cholesterol efflux acceptor, comprises a class of heterogeneous particles that induce cholesterol efflux via distinct pathways. This review focuses on the understanding of the different cholesterol efflux pathways and physiological acceptors involved, and their regulation in atherosclerotic lesions.

RECENT FINDINGS

The synergistic interactions of ATP-binding cassette transporters A1 and G1 as well as ATP-binding cassette transporter A1 and scavenger receptor class B type I are essential for cellular cholesterol efflux and the prevention of macrophage foam cell formation. However, the importance of aqueous diffusion should also not be underestimated. Significant progress has been made in understanding the mechanisms underlying ATP-binding cassette A1-mediated cholesterol efflux and regulation of its expression and trafficking. Conditions locally in the atherosclerotic lesion, for example, lipids, cytokines, oxidative stress, and hypoxia, as well as systemic factors, including inflammation and diabetes, critically influence the expression of cholesterol transporters on macrophage foam cells. Furthermore, HDL modification and remodeling in atherosclerosis, inflammation, and diabetes impairs its function as an acceptor for cellular cholesterol.

SUMMARY

Recent advances in the understanding of the regulation of cholesterol transporters and their acceptors in atherosclerotic lesions indicate that HDL-based therapies should aim to enhance the activity of cholesterol transporters and improve both the quantity and quality of HDL.

Apolipoprotein A1 -75 G/A and +83 C/T polymorphisms: susceptibility and prognostic implications in breast cancer

Apolipoprotein A1 (ApoA1) is the major apoprotein constituent of high-density lipoprotein that can play important roles in tumor invasion and metastasis. In the current report, we evaluated the role of the functional ApoA1 polymorphisms (-75 G/A and +83 C/T) as genetic markers for breast cancer susceptibility and prognosis. We used the polymerase chain reaction and restriction enzyme digestion (RFLP-PCR) to characterize the variations of the ApoA1 gene in 295 unrelated Tunisian patients with breast carcinoma and 197 healthy control subjects. No association was found between the +83 C/T genetic variation in ApoA1 gene and the risk of breast cancer occurrence. The presence of the (+83) T allele appeared however to be associated with an increased risk of lymph node metastasis occurrence (OR = 2.94; P = 0.01). Furthermore, a positive association was found between ApoA1 -75 A allele carriers and breast cancer risk (OR = 1.57; P = 0.02). Regarding prognostic indicators, a significant association was found between ApoA1 (-75) A allele carriers and the premenopausal status of breast cancer patients (OR = 1.73; P = 0.03). Additionally, the presence of the -75 A allele was correlated with the oestrogen receptor status among premenopausal women (OR = 2.45; P = 0.02). This is the first report on the studies of ApoA1 single nucleotide polymorphisms (SNPs) in breast carcinomas. Our data suggest that these genetic variations of ApoA1 may represent a marker for the increased risk of breast cancer.

Extracellular ubiquitin: immune modulator and endogenous opponent of damage-associated molecular pattern molecules

Ubiquitin is a post-translational protein modifier and plays essential roles in all aspects of biology. Although the discovery of ubiquitin introduced this highly conserved protein as a molecule with extracellular actions, the identification of ubiquitin as the ATP-dependent proteolysis factor 1 has focused subsequent research on its important intracellular functions. Little attention has since been paid to its role outside of the cell. During recent years, multiple observations suggest that extracellular ubiquitin can modulate immune responses and that exogenous ubiquitin has therapeutic potential to attenuate exuberant inflammation and organ injury. These observations have not been integrated into a comprehensive assessment of its possible role as an endogenous immune modulator. This review recapitulates the current knowledge about extracellular ubiquitin and discusses an emerging facet of its role in biology during infectious and noninfectious inflammation. The synopsis of these data along with the recent identification of ubiquitin as a CXCR4 agonist suggest that extracellular ubiquitin may have pleiotropic roles in the immune system and functions as an endogenous opponent of DAMPs. Functions of extracellular ubiquitin could constitute an evolutionary conserved control mechanism aimed to balance the immune response and prevent exuberant inflammation. Further characterization of its mechanism of action and cellular signaling pathways is expected to provide novel insights into the regulation of the innate immune response and opportunities for therapeutic interventions.

Nuclear Magnetic Resonance Lipoprotein Subclasses and the APOE Genotype Influence Carotid Atherosclerosis in Patients with Systemic Lupus Erythematosus

Objective.

Patients with systemic lupus erythematosus (SLE) have accelerated atherosclerosis. Since the conventional lipid profile (total plasma cholesterol, triglycerides, low and high density lipoprotein cholesterol) is not consistently altered in SLE, we hypothesized that investigation of lipoprotein subclasses would improve prediction of risk of atherosclerosis in these patients.

Methods.

As a quantitative index of atherosclerosis, we measured the carotid intima-media thickness (IMT) in 68 patients with SLE and related the atherosclerosis to a detailed lipoprotein profile generated using nuclear magnetic resonance (NMR). We measured the cholesterol transported by the pool of remnant lipoproteins (RLPc) and evaluated the modulatory effect of the APOE genotype on the lipoprotein subclass profile and atherosclerosis associated with SLE.

Results.

Circulating lipoprotein remnant particles [RLPc and intermediate density lipoprotein (IDL)] were positively correlated with IMT, and among them, the indicator that explained 20.2% of the variability in carotid atherosclerosis measured in these patients was IDL, as assessed by NMR. Carriers of the APOE2 allele were at increased risk due to a significant accumulation of IDL particles.

Conclusion.

Lipoprotein subclasses are more associated with subclinical atherosclerosis in patients with SLE than the lipid variables that are routinely measured. The IDL fraction, which is significantly modulated by the APOE genotype, is the most strongly, significantly, and positively correlated with IMT.