Pathway-Specific Aggregate Biomarker Risk Score Is Associated With Burden of Coronary Artery Disease and Predicts Near-Term Risk of Myocardial Infarction and Death

BACKGROUND

Inflammation, coagulation, and cell stress contribute to atherosclerosis and its adverse events. A biomarker risk score (BRS) based on the circulating levels of biomarkers C-reactive protein, fibrin degradation products, and heat shock protein-70 representing these 3 pathways was a strong predictor of future outcomes. We investigated whether soluble urokinase plasminogen activator receptor (suPAR), a marker of immune activation, is predictive of outcomes independent of the aforementioned markers and whether its addition to a 3-BRS improves risk reclassification.

METHODS AND RESULTS

C-reactive protein, fibrin degradation product, heat shock protein-70, and suPAR were measured in 3278 patients undergoing coronary angiography. The BRS was calculated by counting the number of biomarkers above a cutoff determined using the Youden's index. Survival analyses were performed using models adjusted for traditional risk factors. A high suPAR level ≥3.5 ng/mL was associated with all-cause death and myocardial infarction (hazard ratio, 1.83; 95% confidence interval, 1.43-2.35) after adjustment for risk factors, C-reactive protein, fibrin degradation product, and heat shock protein-70. Addition of suPAR to the 3-BRS significantly improved the C statistic, integrated discrimination improvement, and net reclassification index for the primary outcome. A BRS of 1, 2, 3, or 4 was associated with a 1.81-, 2.59-, 6.17-, and 8.80-fold increase, respectively, in the risk of death and myocardial infarction. The 4-BRS was also associated with severity of coronary artery disease and composite end points.

CONCLUSIONS

SuPAR is independently predictive of adverse outcomes, and its addition to a 3-BRS comprising C-reactive protein, fibrin degradation product, and heat shock protein-70 improved risk reclassification. The clinical utility of using a 4-BRS for risk prediction and management of patients with coronary artery disease warrants further study.

Elevated Levels of Serum Fibrin and Fibrinogen Degradation Products Are Independent Predictors of Larger Coronary Plaques and Greater Plaque Necrotic Core

BACKGROUND

Co-existence of vulnerable plaque and pro-thrombotic state may provoke acute coronary events. It was hypothesized that elevated serum levels of fibrin and fibrinogen degradation products (FDP) are associated with larger total plaque and necrotic core (NC) areas.

METHODS AND RESULTS

Seventy-five patients presenting with stable anginal symptoms (69%) or stabilized acute coronary syndrome (ACS; 31%), and found to have non-obstructive coronary artery disease (CAD) with a fractional flow reserve >0.8, were studied. Invasive virtual histology intravascular ultrasound (VH-IVUS) was performed in 68 LAD arteries, 6 circumflex arteries, and 1 right coronary artery. Serum FDP levels were measured using ELISA technique. Plaque volumetrics and composition were assessed in each VH-IVUS frame and averaged. The median age of patients was 56 (47-63) years; 52% were men and 23% had diabetes. The average length of coronary artery studied was 62 mm. After adjustment for systemic risk factors, medications, CRP levels and ACS, male gender (P<0.001) and serum FDP levels (P=0.02) were independent predictors of a larger NC area. Older age (P<0.001), male gender (P<0.0001) and increased serum FDP level (P=0.03) were associated with a larger plaque area.

CONCLUSIONS

In patients with CAD, a higher serum level of FDP is independently associated with larger plaques and greater plaque NC.

Plasma stromal cell-derived factor 1α/CXCL12 level predicts long-term adverse cardiovascular outcomes in patients with coronary artery disease

OBJECTIVE

Stromal derived factor-1α/CXCL12 is a chemoattractant responsible for homing of progenitor cells to ischemic tissues. We aimed to investigate the association of plasma CXCL12 with long-term cardiovascular outcomes in patients with coronary artery disease (CAD).

METHODS

785 patients aged: 63 ± 12 undergoing coronary angiography were independently enrolled into discovery (N = 186) and replication (N = 599) cohorts. Baseline levels of plasma CXCL12 were measured using Quantikine CXCL12 ELISA assay (R&D systems). Patients were followed for cardiovascular death and/or myocardial infarction (MI) for a mean of 2.6 yrs. Cox proportional hazard was used to determine independent predictors of cardiovascular death/MI.

RESULTS

The incidence of cardiovascular death/MI was 13% (N = 99). High CXCL12 level based on best discriminatory threshold derived from the ROC analysis predicted risk of cardiovascular death/MI (HR = 4.81, p = 1 × 10(-6)) independent of traditional risk factors in the pooled cohort. Addition of CXCL12 to a baseline model was associated with a significant improvement in c-statistic (AUC: 0.67-0.73, p = 0.03). Addition of CXCL12 was associated with correct risk reclassification of 40% of events and 10.5% of non-events. Similarly for the outcome of cardiovascular death, the addition of the CXCL12 to the baseline model was associated with correct reclassification of 20.7% of events and 9% of non-events. These results were replicated in two independent cohorts.

CONCLUSION

Plasma CXCL12 level is a strong independent predictor of adverse cardiovascular outcomes in patients with CAD and improves risk reclassification.

Soluble urokinase plasminogen activator receptor level is an independent predictor of the presence and severity of coronary artery disease and of future adverse events

Introduction

Soluble urokinase plasminogen activator receptor (suPAR) is an emerging inflammatory and immune biomarker. Whether suPAR level predicts the presence and the severity of coronary artery disease (CAD), and of incident death and myocardial infarction (MI) in subjects with suspected CAD, is unknown.

Methods and Results

We measured plasma suPAR levels in 3367 subjects (67% with CAD) recruited in the Emory Cardiovascular Biobank and followed them for adverse cardiovascular (CV) outcomes of death and MI over a mean 2.1±1.1 years. Presence of angiographic CAD (≥50% stenosis in ≥1 coronary artery) and its severity were quantitated using the Gensini score. Cox's proportional hazard survival and discrimination analyses were performed with models adjusted for established CV risk factors and C‐reactive protein levels. Elevated suPAR levels were independently associated with the presence of CAD (P<0.0001) and its severity (P<0.0001). A plasma suPAR level ≥3.5 ng/mL (cutoff by Youden's index) predicted future risk of MI (hazard ratio [HR]=3.2; P<0.0001), cardiac death (HR=2.62; P<0.0001), and the combined endpoint of death and MI (HR=1.9; P<0.0001), even after adjustment of covariates. The C‐statistic for a model based on traditional risk factors was improved from 0.72 to 0.74 (P=0.008) with the addition of suPAR.

Conclusion

Elevated levels of plasma suPAR are associated with the presence and severity of CAD and are independent predictors of death and MI in patients with suspected or known CAD.

Circulating CD34+ progenitor cells and risk of mortality in a population with coronary artery disease

RATIONALE

Low circulating progenitor cell numbers and activity may reflect impaired intrinsic regenerative/reparative potential, but it remains uncertain whether this translates into a worse prognosis.

OBJECTIVES

To investigate whether low numbers of progenitor cells associate with a greater risk of mortality in a population at high cardiovascular risk.

METHODS AND RESULTS

Patients undergoing coronary angiography were recruited into 2 cohorts (1, n=502 and 2, n=403) over separate time periods. Progenitor cells were enumerated by flow cytometry as CD45(med+) blood mononuclear cells expressing CD34, with additional quantification of subsets coexpressing CD133, vascular endothelial growth factor receptor 2, and chemokine (C-X-C motif) receptor 4. Coefficient of variation for CD34 cells was 2.9% and 4.8%, 21.6% and 6.5% for the respective subsets. Each cohort was followed for a mean of 2.7 and 1.2 years, respectively, for the primary end point of all-cause death. There was an inverse association between CD34(+) and CD34(+)/CD133(+) cell counts and risk of death in cohort 1 (β=-0.92, P=0.043 and β=-1.64, P=0.019, respectively) that was confirmed in cohort 2 (β=-1.25, P=0.020 and β=-1.81, P=0.015, respectively). Covariate-adjusted hazard ratios in the pooled cohort (n=905) were 3.54 (1.67-7.50) and 2.46 (1.18-5.13), respectively. CD34(+)/CD133(+) cell counts improved risk prediction metrics beyond standard risk factors.

CONCLUSIONS

Reduced circulating progenitor cell counts, identified primarily as CD34(+) mononuclear cells or its subset expressing CD133, are associated with risk of death in individuals with coronary artery disease, suggesting that impaired endogenous regenerative capacity is associated with increased mortality. These findings have implications for biological understanding, risk prediction, and cell selection for cell-based therapies.

Oxidative stress is associated with increased pulmonary artery systolic pressure in humans

Oxidative stress contributes to the development of pulmonary hypertension in experimental models, but this association in humans is unknown. We investigated the relationship between pulmonary artery systolic pressure measured by echocardiography and plasma aminothiol oxidative stress markers, with the hypothesis that oxidative stress will be higher in those with pulmonary hypertension. A group of 347 patients aged 65±12 years from the Emory Cardiovascular Biobank underwent echocardiographic assessment of left ventricular ejection fraction and pulmonary artery systolic pressure. Plasma aminothiols, cysteine, its oxidized form, cystine, glutathione, and its oxidized disulphide were measured and the redox potentials (Eh) of cysteine/cystine and glutathione/oxidized glutathione couples were calculated. Non-normally distributed variables were log transformed (Ln). Univariate predictors of pulmonary artery systolic pressure included age (P<0.001), sex (P=0.002), mitral regurgitation (P<0.001), left ventricular ejection fraction (P<0.001), left atrial size (P<0.001), diabetes mellitus (P=0.03), plasma Ln cystine (β=9.53; P<0.001), Ln glutathione (β=-5.4; P=0.002), and Eh glutathione (β=0.21; P=0.001). A multivariate linear regression model adjusting for all confounding variables demonstrated that Ln cystine (β=6.56; P=0.007), mitral regurgitation (β=4.52; P<0.001), statin use (β=-3.39; P=0.03), left ventricular ejection fraction (β=-0.26; P=0.003), and age (β=0.17; P=0.003) were independent predictors of pulmonary artery systolic pressure. For each 1% increase in plasma cystine, pulmonary artery systolic pressure increased by 16%. This association persisted in the subgroup with preserved left ventricular ejection fraction (≥50%) and no significant mitral regurgitation. Whether treatment of oxidative stress will improve pulmonary hypertension requires further study.

Coronary heart disease alters intercellular communication by modifying microparticle-mediated microRNA transport

Coronary heart disease (CHD) is characterized by abnormal intercellular communication and circulating microRNAs (miRNAs) are likely involved in this process. Here, we show that CHD was associated with changes in the transport of circulating miRNA, particularly decreased miRNA enrichment in microparticles (MPs). Additionally, MPs from CHD patients were less efficient at transferring miRNA to cultured HUVECs, which correlated with their diminished capacity to bind developmental endothelial locus-1 (Del-1). In summary, CHD was associated with distinct changes in circulating miRNA transport and these changes may contribute to the abnormal intercellular communication that underlies CHD initiation and progression.

Biological activity resulting from exposure to aquatic environmental genotoxic pollutants in northern Egypt

We estimated pollution in Lake Edku and the Mediterranean Sea, El-Maadiya Region, with 3 aromatic amines (1-naphthylamine, 2-naphthylamine and benzidine) in the muscle tissue of fish. There were marked seasonal variations in the aromatic amine levels. We also determined oxidative stress (blood glutathione, and catalase activity) and genotoxic effects (chromosomal aberrations and urinary metabolites) in fishermen from each area. The fishermen suffered from oxidative stress and had high levels of the urinary metabolite sulfanilamide [mean (microg/mg creatinine): Lake Edku 20.7, Mediterranean 14.5, controls 5.3]. Frequencies for total chromosomal aberrations were significantly raised in the peripheral blood lymphocytes of fishermen in both areas [frequency (per 100 metaphases): Mediterranean 67, Lake Edku 45, controls 14].

Maternal transmission of Wolbachia in Phlebotomus papatasi (Scopoli)

Attempts have been made to transfer Wolbachia from infected to uninfected, laboratory-reared Phlebotomus papatasi, through mating, and to determine whether the incompatibility phenotype could be expressed through crosses between infected and uninfected flies. In order to test for the intraspecific transmission of Wolbachia in crosses between infected females and uninfected males, or those between uninfected females and infected males, a PCR based on Wolbachia -specific wsp primers was used to test the progeny of each cross and, subsequently, 50 individual flies from the F(3) generation. All the individual flies tested from the F(1) progeny of the crosses between infected males and uninfected females were found to be uninfected. In the crosses involving infected females and uninfected males, however, Wolbachia were found in the progeny of five matings out of the 23 that produced viable eggs. In the F(3), Wolbachia were not detected in any of the individuals resulting from the cross between uninfected females and infected males but they were detected in 52% (26) of the 50 tested individuals resulting from the cross between infected females and uninfected males. No evidence of cytoplasmic incompatibility (CI) was observed in any of the crosses. The absence of CI expression and relatively low frequencies of maternal transmission could hamper the potential use of Wolbachia in a transgenic strategy for the control of leishmaniases.

Wolbachia infection and the expression of cytoplasmic incompatibility in sandflies (Diptera: Psychodidae) from Egypt

A PCR-based method was used to screen four laboratory colonies of sandflies for Wolbachia infection. The colonies - one of Phlebotomus langeroni, one of P. bergeroti and two of P. papatasi - were all derived from sandflies collected in Egypt. Only one of the colonies, derived from P. papatasi collected in Sinai, was found infected. The sequence of the PCR product for this colony was identical to that previously reported for the Wolbachia in P. papatasi from Israel. The induction with tetracycline of cytoplasmic incompatibility (CI) in flies from the P. papatasi (Sinai) colony was then investigated, through reciprocal crosses between treated and untreated P. papatasi siblings. Partial CI expression was attained in the crosses involving antibiotic-treated (i.e. uninfected) females, whether the males used were infected with Wolbachia or had also been cleared of Wolbachia by antibiotic treatment. Most (75%) of the eggs oviposited by uninfected females that had been crossed with infected males, and most (58%) of those laid by uninfected females that had been crossed with uninfected males, failed to hatch. These results provide the first published evidence showing that Wolbachia infection in sandflies is advantageous to the insects. The failure to detect Wolbachia in one of the colonies derived from Egyptian P. papatasi or in the colonies derived from Egyptian P. bergeroti and P. langeroni may indicate that the inter- and intra-specific spread of Wolbachia is discontinuous, even within one country.

Ovarian development and blood-feeding activity in Phlebotomus bergeroti Parrot (Diptera: Psychodidae) from Egypt

The ovarian development and blood-feeding of Phlebotomus bergeroti were investigated using a laboratory colony derived from Egyptian flies. Most (89%) of the females in this colony were autogenous. The level of ovarian development observed at the time of blood-feeding varied between Christophers' stages IIB and V, indicating that vitellogenesis did not inhibit blood-feeding and that the females that ingested blood before their initial egg-laying were facultative, not obligatory, blood-feeders. The females ingested blood 2-8 days after they had emerged, the probability of a female taking an offered bloodmeal being highest between days 4 and 7 post-emergence. Blood-feeding significantly increased fecundity, significantly reduced the number of eggs that were not laid although apparently mature, and decreased the mean duration of the gonotrophic cycle by almost 1 day. Bloodmeals increased fecundity by stimulating the previtellogenic primary follicles of the autogenous females to precipitate yolk, possibly by initiating concurrent vitellogenesis in the primary and secondary follicles of the same ovarioles. Autogeny in P. bergeroti probably has little influence on the transmission of Leishmania parasites by this species.

Evaluation of avermectins as sandfly control agents

The potential of avermectins as environmentally safe agents for the control of the sandfly vectors of Leishmania spp. was investigated in the laboratory. Female Phlebotomus papatasi and P. langeroni were fed either bloodmeals containing laboratory-grade ivermectin or sugarmeals containing a commercial-product based on abamectin. Low concentrations of either avermectin killed the sandflies, with median lethal concentrations (LC(50)) of just 13 ng ivermectin or 0.5 ng abamectin/ml for P. papatasi and 44 ng ivermectin or 35 ng abamectin/ml for P. langeroni. The feeding of female sandflies of both species with generally sublethal doses (LC(30)) of ivermectin in blood led to markedly reduced survival and fecundity (i.e. number of eggs laid/ovipositing female). However, addition of ivermectin to the bloodmeal (or of abamectin to the sugarmeal) of the females had no statistically significant effect on the proportion of their eggs that hatched. The results indicate that very small amounts of avermectin in their blood- or sugar-meals could control P. papatasi and P. langeroni, by killing many flies and, in the case of ivermectin, by reducing the fecundity of the survivors.

Enzyme polymorphism and genetic variability of laboratory populations of Phlebotomus papatasi, P. bergeroti, P. langeroni, and P. perniciosus

Enzyme allomorph frequency and electrophoretic mobility were evaluated to clearly separate between morphologically similar sandfly species and to yield quantitative measures of their genetic similarity. Twelve enzyme systems were studied in laboratory colonies of Phlebotomus perniciosus, P. langeroni, P. papatasi, and P. bergeroti. Phlebotomus perniciosus and P. langeroni confirmed vectors of visceral leishmaniasis, were found to have fixed diagnostic allomorph differences at 3 enzyme loci (ICD-2, FUM, XDH). Phlebotomus papatasi, a known vector of cutaneous leishmaniasis and phleboviruses and P. bergeroti, a newly colonized suspected vector, were clearly differentiated from each other by a fixed allomorph at the MPI locus. Polymorphism at loci in these sandfly colonies ranged from 6.7% (P. perniciosus) to 43.7% (P. papatasi), with lowest levels seen in the older colonies. Expected heterozygosity was highest in P. papatasi, despite 33 generations of inbreeding, and comparable to that of P. bergeroti in its 7th generation. Against a scale of 0 for completely different, and 1.0 for identical genotypes, the enzyme data yielded indices of genetic identity (I) between P. perniciosus and P. langeroni and between P. papatasi and P. bergeroti of 0.783 and 0.737, respectively. These relatively high levels of genetic identity, paralleling similarities between species in morphology, inbreeding compatibility, and vectorial attributes, provide evidence of comparable and recent evolutionary divergence.

Optimised dietary regimens for the laboratory maintenance of Phlebotomus langeroni nitzulescu (Diptera: Psychodidae)

The optimal feeding conditions for laboratory colonies of Phlebotomus langeroni, the vector of infantile visceral leishmaniasis in Egypt, were investigated. Sugarmeals were offered only before bloodmeals (the SB regimen), only after blood (BS), or both before and after blood (SBS). In each regimen, three different solutions of sucrose (10%, 30% and 50%, w/v) were tested as the source of sugarmeals. In general, the concentration of sucrose used had no significant effect on female longevity, although the longest lived females were those fed on 30% sucrose. Females on the BS regimen were the longest lived whereas those on the SB were the shortest lived. Sucrose concentration did not significantly affect total fecundity, the number of eggs oviposited by females, or the proportion of each egg batch that remained unlaid, but female flies fed 30% sucrose laid more eggs than those fed 10% or 50%, and SBS females laid more eggs than SB or BS. Sucrose concentration and dietary regimen both significantly affected the proportion of laid eggs that hatched, 30% sucrose giving significantly higher proportions than 10% or 50% (in all tested regimens), and the SBS regimen producing higher proportions than the SB or BS. Provision of 30% sucrose before and after bloodmeals is therefore recommended for the laboratory maintenance of P. langeroni.

Enzyme polymorphism and genetic variability of one colonized and several field populations of Phlebotomus papatasi (Diptera: Psychodidae)

The Alexandria laboratory colony and five field populations of Phlebotomus papatasi (Scopoli) from Egypt were analyzed for genetic variation at 17 enzyme loci. The laboratory colony was characterized by a low level of genetic variation as measured by the average number of alleles per locus (A = 1.70 +/- 0.16) and the average expected heterozygosity (He = 0.06 +/- 0.02). Polymorphism was observed at 23.5% of the examined loci, and genotype frequencies at two loci (PGM, AK-2) were found to deviate slightly from the Hardy-Weinberg equilibrium. In contrast, the average number of alleles per locus for field populations ranged from A = 2.35 +/- 0.20 to 2.76 +/- 0.10, and He ranged from 0.15 +/- 0.03 to 0.21 +/- 0.05. All loci of field populations exhibited polymorphism, ranging from 47.0% to 76.5%, and four to seven loci in each population were found to deviate from the Hardy-Weinberg equilibrium. Deviations in both colonized and field populations were caused by heterozygote deficiency. Despite geographic isolation and some individual deviations from the Hardy-Weinberg equilibrium, no evidence of significant genetic difference was obtained for any of the populations sampled. Calculated indices of genetic distance and genetic identity for the five field populations showed minor variation but were collectively representative of a single, genetically uniform population.