Association of D-dimer with Plaque Characteristics and Plasma Biomarkers of Oxidation-Specific Epitopes in Stable Subjects with Coronary Artery Disease

Poricoic acid a ameliorates high glucose-induced podocyte injury by regulating the AMPKα/FUNDC1 pathway

BACKGROUND

Poricoic acid A (PAA), a major triterpenoid component of Poria cocos with anti-tumor, anti-fibrotic, anti-inflammatory, and immune-regulating activities, has been shown to induce podocyte autophagy in diabetic kidney disease (DKD) by downregulating FUN14 domain containing 1 (FUNDC1). This study aimed to identify the role of adenosine monophosphate-activated protein kinase alpha (AMPKα) in PAA-mediated phosphorylation of FUNDC1 in podocyte injury occurring in the pathogenesis of DKD.

METHODS AND RESULTS

A cellular model of renal podocyte injury was established by culturing MPC5 cells under high-glucose (HG) conditions. MPC5 cells were subjected to transfection with small interfering RNA (siRNA) targeting AMPKα or siRNA targeting FUNDC1, an AMPKα activator, or PAA. PAA treatment induced the phosphorylation of AMPKα in HG-cultured podocytes. AMPKα activation was implicated in the inhibitory effect of PAA on FUNDC phosphorylation in HG-cultured podocytes. Treatment targeting the AMPKα activator also significantly augmented proliferation, migration, mitochondrial membrane potential, and autophagy levels, while reducing apoptosis levels, inhibiting oxidative stress, and suppressing the release of proinflammatory factors in HG-cultured MPC5 cells. In contrast, insufficient expression of AMPKα reversed the effects of PAA on the proliferation, migration, and apoptosis of podocytes and further exacerbated the reduction of phosphorylated FUNDC1 expression in podocytes under HG conditions.

CONCLUSIONS

AMPKα is involved in the regulation of FUNDC1 phosphorylation by PAA in HG-induced podocyte injury. Furthermore, the AMPKα/FUNDC1 pathway plays a crucial regulatory role in HG-induced podocyte injury. These findings support AMPKα, FUNDC1, and the AMPKα/FUNDC1 pathway as targets for PAA intervention.

Gray-Scale Median in Patients with Symptomatic and Asymptomatic Carotid Atherosclerosis-Risk Factors and Diagnostic Potential

BACKGROUND

The identification of clinical factors affecting the gray-scale median (GSM) and determination of GSM diagnostic utility for differentiating between symptomatic and asymptomatic internal carotid artery (ICA) stenosis.

METHODS

This study included 45 patients with asymptomatic and 40 patients with symptomatic ICA stenosis undergoing carotid endarterectomy (CEA). Echolucency of carotid plaque was determined using computerized techniques for the GSM analysis. Study groups were compared in terms of clinical risk factors, coexisting comorbidities, and used pharmacotherapy.

RESULTS

Mean GSM values in the symptomatic group were significantly lower than in the asymptomatic group (p < 0.001). Both in the univariate as well as in the multiple regression analysis, GSM was significantly correlated with D-dimers and fasting plasma glucose levels and tended to correlate with β-adrenoceptor antagonist use in the symptomatic group. In asymptomatic patients, GSM was associated with the presence of grade 2 and grade 3 hypertension, and tended to correlate with the use of metformin, sulfonylureas, and statin. Independent factors for GSM in this group remained as grade 3 hypertension and statin's therapy. The receiver operating characteristic (ROC) analysis revealed that GSM differentiated symptomatic from asymptomatic ICA stenosis with sensitivity and specificity of 73% and 80%, respectively.

CONCLUSION

The completely diverse clinical parameters may affect GSM in symptomatic and asymptomatic patients undergoing CEA, whose clinical characteristics were similar in terms of most of the compared parameters. GSM may be a clinically useful parameter for differentiating between symptomatic and asymptomatic ICA stenosis.

Oxidized phospholipids in cardiovascular disease

Prolonged or excessive exposure to oxidized phospholipids (OxPLs) generates chronic inflammation. OxPLs are present in atherosclerotic lesions and can be detected in plasma on apolipoprotein B (apoB)-containing lipoproteins. When initially conceptualized, OxPL-apoB measurement in plasma was expected to reflect the concentration of minimally oxidized LDL, but, surprisingly, it correlated more strongly with plasma lipoprotein(a) (Lp(a)) levels. Indeed, experimental and clinical studies show that Lp(a) particles carry the largest fraction of OxPLs among apoB-containing lipoproteins. Plasma OxPL-apoB levels provide diagnostic information on the presence and extent of atherosclerosis and improve the prognostication of peripheral artery disease and first and recurrent myocardial infarction and stroke. The addition of OxPL-apoB measurements to traditional cardiovascular risk factors improves risk reclassification, particularly in patients in intermediate risk categories, for whom improving decision-making is most impactful. Moreover, plasma OxPL-apoB levels predict cardiovascular events with similar or greater accuracy than plasma Lp(a) levels, probably because this measurement reflects both the genetics of elevated Lp(a) levels and the generalized or localized oxidation that modifies apoB-containing lipoproteins and leads to inflammation. Plasma OxPL-apoB levels are reduced by Lp(a)-lowering therapy with antisense oligonucleotides and by lipoprotein apheresis, niacin therapy and bariatric surgery. In this Review, we discuss the role of role OxPLs in the pathophysiology of atherosclerosis and Lp(a) atherogenicity, and the use of OxPL-apoB measurement for improving prognosis, risk reclassification and therapeutic interventions.

The mediation effect of HDL-C: Non-HDL-C on the association between inflammatory score and recurrent coronary events

Background

Inflammation and lipids are both involved in the pathogenesis of coronary heart disease (CHD). However, the mediation effect of lipoproteins on the association between inflammation and recurrent coronary events in CHD patients remains unclear.

Methods

This was a retrospective study including CHD patients hospitalized in the Department of Cardiovascular Medicine in Sun Yat-sen Memorial Hospital between January 2011 and December 2012 with the endpoint of recurrent coronary events. The study calculated inflammatory score based on six serum inflammatory markers, including complement C3, complement C4, hyper-sensitive CRP, fibrinogen, D-dimer, and white blood cell count. Logistic regression analysis, subgroup analysis and mediation analysis were performed to assess the associations between inflammatory score and recurrent coronary events in different subpopulations and the identification of mediators. Inflammatory cytokine expression, cholesterol efflux capacity, and hepatic cholesterol influx were performed in additional CHD patients and healthy controls.

Results

There were 191 CHD patients included in the analysis with a median inflammatory score of -0.78 (-2.17, 1.35) and 63 cases of recurrent coronary events. Subgroup logistic regression analysis demonstrated that inflammatory score was positively associated with recurrent coronary events only in the diabetic subgroup [OR: 1.241 (1.004, 1.534), P < 0.046]. HDL-cholesterol (HDL-C): non-HDL-C performed 46.74 % of negative mediation effect on this association. CHD patients had lower cholesterol efflux capacity than healthy controls, which was mediated by HDL: non-HDL ratio of 0.4. No difference was found in hepatic cholesterol influx between the two groups.

Conclusion

Inflammatory score was associated with recurrent coronary events mediated by HDL-C: non-HDL-C ratio in diabetic CHD patients, indicating that lipoproteins might aggravate the inflammatory effect on atherosclerosis under hyperglycemia. Our findings suggested that anti-inflammatory and lipid-lowering therapies might be beneficial for this population.

High immunoglobulin-M levels to oxidation-specific epitopes are associated with lower risk of acute myocardial infarction

Immunoglobulin M (IgM) autoantibodies to oxidation-specific epitopes (OSEs) can be present at birth and protect against atherosclerosis in experimental models. This study sought to determine whether high titers of IgM titers to OSE (IgM OSE) are associated with a lower risk of acute myocardial infarction (AMI) in humans. IgM to malondialdehyde (MDA)-LDL, phosphocholine-modified BSA, IgM apolipoprotein B100-immune complexes, and a peptide mimotope of MDA were measured within 24 h of first AMI in 4,559 patients and 4,617 age- and sex-matched controls in the Pakistan Risk of Myocardial Infarction Study. Multivariate-adjusted logistic regression was used to estimate odds ratio (OR) and 95% confidence interval for AMI. All four IgM OSEs were lower in AMI versus controls (P < 0.001 for all). Males, smokers and individuals with hypertension and diabetes had lower levels of all four IgM OSE than unaffected individuals (P < 0.001 for all). Compared to the lowest quintile, the highest quintiles of IgM MDA-LDL, phosphocholine-modified BSA, IgM apolipoprotein B100-immune complexes, and MDA mimotope P1 had a lower OR of AMI: OR (95% confidence interval) of 0.67 (0.58-0.77), 0.64 (0.56-0.73), 0.70 (0.61-0.80) and 0.72 (0.62-0.82) (P < 0.001 for all), respectively. Upon the addition of IgM OSE to conventional risk factors, the C-statistic improved by 0.0062 (0.0028-0.0095) and net reclassification by 15.5% (11.4-19.6). These findings demonstrate that IgM OSE provides clinically meaningful information and supports the hypothesis that higher levels of IgM OSE may be protective against AMI.

Association of D-dimer with long-term prognosis in type 2 diabetes mellitus patients with acute coronary syndrome

BACKGROUND AND AIMS

Type 2 diabetes mellitus (DM) accounts for more and more individuals worldwide. D-dimer has been demonstrated to be associated with cardiovascular diseases. The aim is to study the potential impact of D-dimer on the long-term prognosis of acute coronary syndrome (ACS) in the special population with type 2 DM.

METHODS AND RESULTS

A total of 2265 consecutive patients with DM and ACS were eligible in the study. Patients were divided into four groups according to quartiles of D-dimer concentration. Univariate and multivariate Cox regression analysis were conducted to explore the prognostic value of D-dimer for future outcomes. Patients with higher level of D-dimer presented with higher percentage of major adverse cardiovascular events (MACEs) (23.7%), all-cause death (18.3%) and cardiovascular (CV) death (9.4%) in Quartile 4. In multivariate Cox regression analysis, D-dimer was demonstrated to be independently associated with MACEs, all-cause death and CV death. The prognostic value of D-dimer is still significant in subgroups of HbA1C <7% and ≥7%. In Kaplan-Meier analysis, higher D-dimer showed poorer prognosis in MACEs, all-cause death and CV death (all log rank p < 0.001). The area under the curve (AUC) by receiver operating characteristic (ROC) curve analysis is 0.609 for MACEs, 0.708 for all-cause death, 0.747 for CV death (p < 0.001).

CONCLUSION

The present study demonstrated the independent predictive value of D-dimer for outcomes in DM patients with ACS. In addition, for the first time, we explored the prognostic value in different glucose control status.

Prognostic Value of Age-Adjusted D-Dimer Cutoff Thresholds in Patients with Acute Coronary Syndrome Treated by Percutaneous Coronary Intervention

BACKGROUND

Associations between D-dimer and outcomes of patients with acute coronary syndrome (ACS) remain controversial. Using age-adjusted D-dimer cutoff thresholds improve the diagnostic accuracy for thrombotic diseases. This study aimed to investigate the prognostic value of age-adjusted D-dimer in ACS patients treated by percutaneous coronary intervention (PCI).

METHODS

A total of 3972 consecutive patients with ACS treated by PCI were retrospectively recruited. The basal age-adjusted D-dimer threshold was 500 ng/mL and was calculated as age × 10 in patients older than 50 years. Cox regression was used for outcome analysis. C-index, net reclassification index (NRI), and integrated discrimination improvement (IDI) were calculated to assess the additional prognostic value of age-adjusted D-dimer when combined with established clinical risk factors. The primary outcome was all-cause death.

RESULTS

During a median follow-up of 720 days, a total of 225 deaths occurred. High D-dimer level, as defined by age-adjusted thresholds, was an independent predictor for all-cause death (hazard ratio [HR]: 1.75, 95% confidence interval [CI]: 1.32-2.31, P < 0.001), cardiac death (HR: 1.84, 95% CI: 1.30-2.60, P = 0.001), and MACE (HR: 1.48, 95% CI: 1.19-1.83, P < 0.001). Sensitivity and subgroup analysis showed that high D-dimer levels were constantly associated with worse outcomes across common risk factors and comorbidities. Besides, age-adjusted elevation of D-dimer significantly improved the risk predictions for all-cause death when added to the model of established risk factors (C-index: 0.846 vs 0.838, Δ C-index: 0.008, 95% CI: 0.001-0.015, Pdifference = 0.027; NRI: 0.645, 95% CI: 0.464-0.826, P < 0.001; IDI: 0.008, 95% CI: 0.001-0.017, P = 0.048).

CONCLUSION

In ACS patients treated by PCI, age-adjusted elevation of D-dimer was an independent predictor for adverse outcomes and improved the risk predictions for long-term mortality.

Lipoprotein(a), venous thromboembolism and COVID-19: A pilot study

Background and aims

Thrombosis is a major driver of adverse outcome and mortality in patients with Coronavirus disease 2019 (COVID-19). Hypercoagulability may be related to the cytokine storm associated with COVID-19, which is mainly driven by interleukin (IL)-6. Plasma lipoprotein(a) [Lp(a)] levels increase following IL-6 upregulation and Lp(a) has anti-fibrinolytic properties. This study investigated whether Lp(a) elevation may contribute to the pro-thrombotic state hallmarking COVID-19 patients.

Methods

Lp(a), IL-6 and C-reactive protein (CRP) levels were measured in 219 hospitalized patients with COVID-19 and analyzed with linear mixed effects model. The baseline biomarkers and increases during admission were related to venous thromboembolism (VTE) incidence and clinical outcomes in a Kaplan-Meier and logistic regression analysis.

Results

Lp(a) levels increased significantly by a mean of 16.9 mg/dl in patients with COVID-19 during the first 21 days after admission. Serial Lp(a) measurements were available in 146 patients. In the top tertile of Lp(a) increase, 56.2% of COVID-19 patients experienced a VTE event compared to 18.4% in the lowest tertile (RR 3.06, 95% CI 1.61–5.81; p < 0.001). This association remained significant after adjusting for age, sex, IL-6 and CRP increase and number of measurements. Increases in IL-6 and CRP were not associated with VTE. Increase in Lp(a) was strongly correlated with increase in IL-6 (r = 0.44, 95% CI 0.30–0.56, p < 0.001).

Conclusions

Increases in Lp(a) levels during the acute phase of COVID-19 were strongly associated with VTE incidence. The acute increase in anti-fibrinolytic Lp(a) may tilt the balance to VTE in patients hospitalized for COVID-19.

Prognostic Value of D-dimer in patients with acute coronary syndrome treated by percutaneous coronary intervention: a retrospective cohort study

BACKGROUND

Associations between D-dimer and outcomes of patients with acute coronary syndromes (ACS) remain controversial. This study aimed to investigate the prognostic value of D-dimer in ACS patients treated by percutaneous coronary intervention (PCI).

METHODS

In this observational study, 3972 consecutive patients with ACS treated by PCI were retrospectively recruited. The X-tile program was used to determine the optimal D-dimer thresholds for risk stratifications. Cox regression with multiple adjustments was used for outcome analysis. Restricted cubic spline (RCS) analysis was performed to assess the dose-response association between D-dimer and outcomes. The C-index was calculated to evaluate the additional prognostic value of D-dimer when added to clinical risk factors and commonly used clinical risk scores, with internal validations using bootstrapping methods. The primary outcome was all-cause death.

RESULTS

During a median follow-up of 720 days, 225 deaths occurred. Based on the thresholds generated by X-tile, ACS-PCI patients with median (420-1150 ng/mL, hazard ratio [HR]: 1.58, 95 % confidence interval [CI]: 1.14-2.20, P = 0.007) and high (≥ 1150 ng/mL, HR: 1.98, 95 % CI: 1.36-2.89, P < 0.001) levels of D-dimer showed substantially higher risk of death compared to those with low D-dimer (< 420 ng/mL). RCS analysis depicted a constant relation between D-dimer and various outcomes. The addition of D-dimer levels significantly improved risk predictions for all-cause death when combined with the fully adjusted models (C-index: 0.853 vs. 0.845, P difference = 0.021), the GRACE score (C-index: 0.826 vs. 0.814, P difference = 0.027), and the TIMI score (C-index: 0.804 vs. 0.776, P difference < 0.001). The predicted mortality at the median follow-up (two years) was 1.7 %, 5.2 %, and 10.9 % for patients with low, median, and high D-dimer, respectively, which was well matched with the observed mortality (low D-dimer group: 1.2 %, median D-dimer group: 5.2 %, and high D-dimer group: 12.6 %).

CONCLUSIONS

For ACS patients treated by PCI, D-dimer level was an independent predictor for adverse outcomes, and provided additional prognostic value when combined with clinical risk factors and risk scores. Risk stratifications based on D-dimer was plausible to differentiate ACS-PCI patients with higher risk of death.

Chemokine Receptor-6 Promotes B-1 Cell Trafficking to Perivascular Adipose Tissue, Local IgM Production and Atheroprotection

Chemokine receptor-6 (CCR6) mediates immune cell recruitment to inflammatory sites and has cell type-specific effects on diet-induced atherosclerosis in mice. Previously we showed that loss of CCR6 in B cells resulted in loss of B cell-mediated atheroprotection, although the B cell subtype mediating this effect was unknown. Perivascular adipose tissue (PVAT) harbors high numbers of B cells including atheroprotective IgM secreting B-1 cells. Production of IgM antibodies is a major mechanism whereby B-1 cells limit atherosclerosis development. Yet whether CCR6 regulates B-1 cell number and production of IgM in the PVAT is unknown. In this present study, flow cytometry experiments demonstrated that both B-1 and B-2 cells express CCR6, albeit at a higher frequency in B-2 cells in both humans and mice. Nevertheless, B-2 cell numbers in peritoneal cavity (PerC), spleen, bone marrow and PVAT were no different in ApoE ^-/- CCR6 ^-/- compared to ApoE ^-/- CCR6 ^+/+ mice. In contrast, the numbers of atheroprotective IgM secreting B-1 cells were significantly lower in the PVAT of ApoE ^-/- CCR6 ^-/- compared to ApoE ^-/- CCR6 ^+/+ mice. Surprisingly, adoptive transfer (AT) of CD43^- splenic B cells into B cell-deficient μMT ^-/- ApoE ^-/- mice repopulated the PerC with B-1 and B-2 cells and reduced atherosclerosis when transferred into ApoE ^-/- CCR6 ^+/+ sIgM ^-/- mice only when those cells expressed both CCR6 and sIgM. CCR6 expression on circulating human B cells in subjects with a high level of atherosclerosis in their coronary arteries was lower only in the putative human B-1 cells. These results provide evidence that B-1 cell CCR6 expression enhances B-1 cell number and IgM secretion in PVAT to provide atheroprotection in mice and suggest potential human relevance to our murine findings.

Predictive values of D-dimer for the long-term prognosis of acute ST-segment elevation infarction: A retrospective study in southwestern China

D-dimer is a primary degradation product of cross-linked fibrin, and can be an effective diagnostic factor of venous thromboembolism. However, its prognostic role in patients with acute ST-segment elevation myocardial infarction (STEMI) remains controversial. This study aimed to investigate whether D-dimer has a predictive value for long-term prognosis in patients with STEMI.We retrospectively enrolled 872 STEMI patients treated with primary percutaneous coronary intervention. Patients were divided into quartiles according to their admission D-dimer increased multiple, with the highest quartile (G4) (n = 219) defined as increased multiple ≧1.33, and the lowest quartile (G1) (n = 215) as increased multiple ≦0.33.Compared with G1, higher in-hospital heart failure (40.2% vs 10.2%, P < .0001), malignant arrhythmia (14.2% vs 2.3%, P < .0001), and all-cause mortality (5.9% vs 0%, P < .0001) rates were observed in G4. After a follow-up period of 29 months, 84 patients had died. In the Cox multivariate analysis, a high admission D-dimer increased multiple (≧1.33) was found to be an independent predictor of all-cause mortality (hazards ratio: 2.53, 95% confidence interval: 1.02-6.26, P = .045).Thus, there was an association between a high D-dimer level and the increase in in-hospital major adverse cardiovascular events, such as heart failure, malignant arrhythmias, and death. High D-dimer level was also an independent predictor of long-term all-cause mortality.

D-dimer as a thrombus biomarker for predicting 2-year mortality after percutaneous coronary intervention

Background:

D-dimer has predictive value for mortality in some diseases. This study aimed to evaluate the correlation between D-dimer and mortality in patients undergoing percutaneous coronary intervention (PCI).

Methods:

We examined 10,724 consecutive patients who underwent PCI between January 2013 and December 2013. The primary endpoint was all-cause mortality, and the secondary endpoint was cardiac mortality. Patients were divided according to the median D-dimer level of 0.28 μg/ml. Multivariable model were including age, sex, and risk factors after stepwise selection.

Results:

After a 2-year follow up, 8565 patients with D-dimer data were analyzed. There were 116 (1.35%) all-cause deaths and 64 (0.75%) cardiac deaths. D-dimer levels were significantly higher in the all-cause mortality group [0.42 (0.29, 0.68) μg/ml] and cardiac mortality group [0.48 (0.30, 0.81) μg/ml] than in the survival group [0.28 (0.20, 0.41) μg/ml] (both p < 0.001). Multivariate-adjusted Cox hazard analysis showed that high D-dimer levels (⩾0.28 μg/ml) were significantly associated with all-cause mortality in the total population [hazard ratio (HR): 2.35, 95% confidence interval (CI): 1.44–3.84, p = 0.001], acute coronary syndrome (ACS) subgroup (HR: 1.91, 95% CI: 1.08–3.38, p = 0.027), and stable coronary artery disease (SCAD) subgroup (HR: 3.82, 95% CI: 1.45–10.10, p = 0.007). High D-dimer levels were significantly associated with cardiac mortality in the total population (HR: 3.44, 95% CI: 1.61–7.36, p = 0.001) and the ACS subgroup (HR: 3.33, 95% CI: 1.38–8.03, p = 0.007), but not in the SCAD subgroup (HR: 3.68, 95% CI: 0.80–16.91, p = 0.094).

Conclusions:

D-dimer levels are independently associated with 2-year all-cause mortality and cardiac mortality in patients undergoing PCI.

Hospital mortality in acute coronary syndrome: adjustment of GRACE score by D-dimer enables a more accurate prediction in a prospective cohort study

Backgroud

To assess the value of D-dimer and its combination with The Global Registry of Acute Coronary Events (GRACE) score in predicting in-hospital mortality in patients with acute coronary syndrome (ACS) undergoing percutaneous coronary intervention (PCI).

Methods

In 5923 ACS patients undergoing PCI, the role of D-dimer and the added value of D-dimer to GRACE score for predicting in-hospital mortality were tested.

Results

After multivariable adjustment, D-dimer could significantly predict in-hospital mortality. Also, it could significantly improve the prognostic performance of GRACE score (C-statistic: z = 2.269, p = 0.023; IDI: 0.016, p = 0.032; NRI: 0.291, p = 0.035).

Conclusion

In patients with ACS undergoing PCI, D-dimer was an independent predictor of in-hospital death. It could also improve the prognostic performance of GRACE score.

Diversification and CXCR4-Dependent Establishment of the Bone Marrow B-1a Cell Pool Governs Atheroprotective IgM Production Linked to Human Coronary Atherosclerosis

RATIONALE

B-1 cell-derived natural IgM antibodies against oxidation-specific epitopes on low-density lipoprotein are anti-inflammatory and atheroprotective. Bone marrow (BM) B-1a cells contribute abundantly to IgM production, yet the unique repertoire of IgM antibodies generated by BM B-1a and the factors maintaining the BM B-1a population remain unexplored. CXCR4 (C-X-C motif chemokine receptor 4) has been implicated in human cardiovascular disease and B-cell homeostasis, yet the role of B-1 cell CXCR4 in regulating atheroprotective IgM levels and human cardiovascular disease is unknown.

OBJECTIVE

To characterize the BM B-1a IgM repertoire and to determine whether CXCR4 regulates B-1 production of atheroprotective IgM in mice and humans.

METHODS AND RESULTS

Single-cell sequencing demonstrated that BM B-1a cells from aged ApoE^-/- mice with established atherosclerosis express a unique repertoire of IgM antibodies containing increased nontemplate-encoded nucleotide additions and a greater frequency of unique heavy chain complementarity determining region 3 sequences compared with peritoneal cavity B-1a cells. Some complementarity determining region 3 sequences were common to both compartments suggesting B-1a migration between compartments. Indeed, mature peritoneal cavity B-1a cells migrated to BM in a CXCR4-dependent manner. Furthermore, BM IgM production and plasma IgM levels were reduced in ApoE^-/- mice with B-cell-specific knockout of CXCR4, and overexpression of CXCR4 on B-1a cells increased BM localization and plasma IgM against oxidation specific epitopes, including IgM specific for malondialdehyde-modified LDL (low-density lipoprotein). Finally, in a 50-subject human cohort, we find that CXCR4 expression on circulating human B-1 cells positively associates with plasma levels of IgM antibodies specific for malondialdehyde-modified LDL and inversely associates with human coronary artery plaque burden and necrosis.

CONCLUSIONS

These data provide the first report of a unique BM B-1a cell IgM repertoire and identifies CXCR4 expression as a critical factor selectively governing BM B-1a localization and production of IgM against oxidation specific epitopes. That CXCR4 expression on human B-1 cells was greater in humans with low coronary artery plaque burden suggests a potential targeted approach for immune modulation to limit atherosclerosis.

Lipoproteins as targets and markers of lipoxidation

Lipoproteins are essential systemic lipid transport particles, composed of apolipoproteins embedded in a phospholipid and cholesterol monolayer surrounding a cargo of diverse lipid species. Many of the lipids present are susceptible to oxidative damage by lipid peroxidation, giving rise to the formation of reactive lipid peroxidation products (rLPPs). In view of the close proximity of the protein and lipid moieties within lipoproteins, the probability of adduct formation between rLPPs and amino acid residues of the proteins, a process called lipoxidation, is high. There has been interest for many years in the biological effects of such modifications, but the field has been limited to some extent by the availability of methods to determine the sites and exact nature of such modification. More recently, the availability of a wide range of antibodies to lipoxidation products, as well as advances in analytical techniques such as liquid chromatography tandem mass spectrometry (LC-MSMS), have increased our knowledge substantially. While most work has focused on LDL, oxidation of which has long been associated with pro-inflammatory responses and atherosclerosis, some studies on HDL, VLDL and Lipoprotein(a) have also been reported. As the broader topic of LDL oxidation has been reviewed previously, this review focuses on lipoxidative modifications of lipoproteins, from the historical background through to recent advances in the field. We consider the main methods of analysis for detecting rLPP adducts on apolipoproteins, including their advantages and disadvantages, as well as the biological effects of lipoxidized lipoproteins and their potential roles in diseases.

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Lipoproteins can be modified by reactive Lipid Peroxidation Products (rLPPs).

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Lipoprotein lipoxidation is known to occur in several inflammatory diseases.

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Biochemical, immunochemical and mass spectrometry methods can detect rLPP adducts.

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Due to higher information output, MS can facilitate localization of modifications.

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Antibodies against some rLPPs have been used to identify lipoxidation in vivo.