Relationship between circulating microparticles and hypertension and other cardiac disease biomarkers in the elderly

Prognostic significance of circulating microparticles in IgA nephropathy

PURPOSE

Endothelial injury, involved in the pathogenesis of renal fibrosis, can generate microparticles (MPs). These are 0.1-1 µm membrane-bound vesicles shed from the damaged or activated cell surfaces. We analyzed the presence of circulating MPs and EnMPs in IgAN and correlated with markers of endothelial injury and disease activity.

METHODS

The study included 30 IgAN (mean age 31.5 ± 9 years), 25 healthy controls and Lupus nephritis (n = 10) as disease controls. Circulating MPs were quantitated by Flow cytometry and EnMPs were analyzed using anti-CD31-FITC and anti-CD146-PE antibodies. Their levels were correlated with serum von Willebrand Factor, histological Oxford MEST-C score and renal outcome. A prospective validation group of 20 patients of biopsy-proven IgA nephropathy was also included.

RESULTS

IgAN had significantly higher levels of MPs, EnMPs and vWF compared to controls. On multivariate analysis, plasma levels of total MPs, EnMPs and serum vWF correlated significantly with the presence of hypertension and E1 on histology. E1 and high MPs (> 130 counts/µl) were associated with shorter time to doubling of serum creatinine. MPs cutoff level of 130 counts/µl had a sensitivity of 75%, specificity of 93.3% and diagnostic accuracy of 89.5% for E1 in the validation cohort.

CONCLUSION

Circulating MPs and EnMPs in IgAN correlate with E1 on histology and have a potential as non-invasive biomarkers to predict disease activity and renal outcome.

Procoagulant effect of extracellular vesicles in patients after transcatheter aortic valve replacement or transcatheter aortic valve replacement with percutaneous coronary intervention

Patients with severe aortic stenosis (AS) after replacement of the transcatheter aortic valve (TAVR) are more likely to develop thrombotic complications such as cerebral embolism and artificial valve thrombosis. However, the mechanism is not yet well defined. We aimed to explore the plasma extracellular vesicles (EVs) levels and their role in the induction of procoagulant activity (PCA) in patients receiving TAVR alone or TAVR with percutaneous coronary intervention (PCI). EVs were analyzed with flow cytometer. Markers of platelet and endothelial cell activation were quantified using selective enzyme-linked immunosorbent assay (ELISA) kits. Procoagulant activity (PCA) was assessed by clotting time, purified clotting complex assays, and fibrin production assays. Our results confirmed that EVs with positive phosphatedylserin (PS⁺EV), platelet EVs (PEVs) and positive tissue factor EVs (TF⁺EVs) were higher in patients following TAVR than before TAVR, particularly in TAVR with PCI. Furthermore, endothelial-derived EVs (EEVs) were also higher in patients after TAVR with PCI than pre-TAVR, however, the EEVs levels in TAVR alone patients were gradually reduce than pre-TAVR. In addition, we further proved that total EVs contributed to dramatically shortened coagulation time, increased intrinsic/extrinsic factor Xa and thrombin generation in patients after TAVR, especially in TAVR with PCI. The PCA was markedly attenuated by approximately 80% with lactucin. Our study reveals a previously unrecognized link between plasma EV levels and hypercoagulability in patients after TAVR, especially TAVR with PCI. Blockade of PS⁺EVs may improve the hypercoagulable state and prognosis of patients.

Natural killer cells, gamma delta T cells and classical monocytes are associated with systolic blood pressure in the multi-ethnic study of atherosclerosis (MESA)

Background

Hypertension is a major source of cardiovascular morbidity and mortality. Recent evidence from mouse models, genetic, and cross-sectional human studies suggest increased proportions of selected immune cell subsets may be associated with levels of systolic blood pressure (SBP).

Methods

We assayed immune cells from cryopreserved samples collected at the baseline examination (2000–2002) from 1195 participants from the multi-ethnic study of atherosclerosis (MESA). We used linear mixed models, with adjustment for age, sex, race/ethnicity, smoking, exercise, body mass index, education, diabetes, and cytomegalovirus titers, to estimate the associations between 30 immune cell subsets (4 of which were a priori hypotheses) and repeated measures of SBP (baseline and up to four follow-up measures) over 10 years. The analysis provides estimates of the association with blood pressure level.

Results

The mean age of the MESA participants at baseline was 64 ± 10 years and 53% were male. A one standard deviation (1-SD) increment in the proportion of γδ T cells was associated with 2.40 mmHg [95% confidence interval (CI) 1.34–3.42] higher average systolic blood pressure; and for natural killer cells, a 1-SD increment was associated with 1.88 mmHg (95% CI 0.82–2.94) higher average level of systolic blood pressure. A 1-SD increment in classical monocytes (CD14⁺⁺CD16⁻) was associated with 2.01 mmHG (95% CI 0.79–3.24) lower average systolic blood pressure. There were no associations of CD4⁺ T helper cell subsets with average systolic blood pressure.

Conclusion

These findings suggest that the innate immune system plays a role in levels of SBP whereas there were no associations with adaptive immune cells.

Inflammatory cytokines enhance procoagulant activity of platelets and endothelial cells through phosphatidylserine exposure in patients with essential hypertension

The exact mechanism of the prothrombotic state of essential hypertension (EH) patients remains elusive. Our objective was to assess whether phosphatidylserine (PS) exposure on endothelial cells (ECs), platelets, and microparticles (MPs) can account for the hypercoagulability in EH patients. PS exposure on cells and MPs, mainly from platelets and ECs was analyzed with flow cytometry. Procoagulant activity (PCA) was evaluated by purified coagulation complex assays, clotting time, and fibrin turbidity. We found that EH patients exhibited elevated levels of PS⁺ platelets, serum-cultured ECs, MPs, endothelial-derived MPs and platelet-derived MPs compared to the controls (all P < 0.05). Moreover, platelets and MPs from the patients and their sera-cultured ECs showed markedly enhanced intrinsic/extrinsic FXa, thrombin, and fibrin generation, and greatly shortened coagulation time. This PCA could be blocked approximately 80%, by the addition of lactadherin. Furthermore, we detected elevated levels of IL-8, IL-6, and TNF-α in EH patients could activate platelets/ECs and induce elevated PS exposure on their membranes. Our results suggest that inflammatory cytokines could enhance procoagulant activity of platelets and endothelial cells via their PS exposure in EH patients. As such, a PS blockade may be a viable therapeutic strategy for treating such patients.