Remigiusz Kazimierczyk

Activity of the kynurenine pathway and its interplay with immunity in patients with pulmonary arterial hypertension

Objective We evaluated blood concentrations of kynurenine pathway metabolites, natural and induced regulatory T cells (nTreg, iTreg), and Th17 cells in order to examine the activity of the kynurenine pathway and its relation to immune status in patients with pulmonary arterial hypertension (PAH). Methods Plasma concentrations of tryptophan, kynurenine, kynurenic acid, anthranilic acid, and 3-hydroxykynurenine were quantified in 26 patients with PAH (vs 30 healthy controls) at baseline and after 6 months, and assessed them in relation to clinical parameters, frequencies of lymphocyte subsets, and outcome. Results The PAH group presented higher concentrations of tryptophan (52.9 (IQR 46.3–57.5) vs 40.3 (35.2–46.3) µmol/L, p=0.00003), kynurenine 2.8 (2.4−3.4) vs 1.9 (1.5–2.3) µmol/L, p=0.000007), kynurenine/tryptophan ratio (0.051 (0.044–0.064) vs 0.043 (0.039–0.055), p=0.03), iTreg frequencies (10.5 (8.8–13.9)% vs 6.8 (5.2–9.5)%, p=0.002) and iTreg/Th17 (1.73 (1.2–2.8) vs 0.93 (0.61–1.27), p=0.003) together with lower ratios of kynurenic acid/kynurenine, 3-hydroxykynurenine/kynurenine, and anthranilic acid/kynurenine. Kynurenine concentrations and kynurenine/tryptophan ratio correlated positively with iTreg/Th17, and inversely with Th17 subsets, whereas kynurenic acid/kynurenine and anthranilic acid/kynurenine ratios correlated positively with Th17. Adverse outcomes occurred in 9 of 26 patients and they showed higher baseline concentrations of kynurenine (3.6 (2.8–4.3) vs 2.7 (2.1–3.2) µmol/L, p=0.033). Median kynurenine values ≥3.4 µmol/L (67% sensitivity, 94% specificity) identified patients with a worse clinical course. Conclusions PAH is characterised by upregulated tryptophan metabolism and enhanced biosynthesis of kynurenine. Elevated kynurenine concentration is associated with an adverse clinical course. Dysregulated immunity, delineated by Treg-Th17 imbalance, is directly related to diverse activation of the kynurenine pathway, indicating the potential interplay between kynurenines and the immune system in PAH.

The causes of thrombocytopenia after transcatheter aortic valve implantation

INTRODUCTION Even though thrombocytopenia following transcatheter aortic valve implantation (TAVI) has been described, further investigation of this phenomenon is needed. AIMS To determine which factors may explain the fall in platelet count that occurs after implantation of a TAVI device, including markers of platelet and blood coagulation activation. MATERIAL AND METHODS 32 patients without previous indications for dual antiplatelet therapy (mean age 78.5±7.9 years, 62% females) with severe aortic valve stenosis (mean gradient 54.6±16.9mmHg) who qualified for TAVI procedure (Edwards Sapien XT) were prospectively analyzed. Platelet counts were analyzed before the surgery, on the day of the procedure and for the three following postoperative days (POD 1 to 3). To assess platelet activation P-selectin (PS, serum) and platelet factor 4 (PF-4, CTAD plasma) were measured, whereas for the evaluation of coagulation activation prothrombin fragments 1+2 (F1+2, plasma) were assessed before the procedure, on POD-1 and POD-3 (ELISA). RESULTS During the postoperative period a significant platelet count drop, the most evident on POD-2, was observed followed by a platelet count raise. The platelet count drop correlated directly with the amount of iodinated contrast agent (r=0.42, p=0.016) and inversely with baseline mean platelet volume (r=-0.37, p=0.046). Neither clinical nor perioperative parameters, except contrast medium, influenced platelet count decrease. No significant differences regarding the concentration of the evaluated markers in patients with and without thrombocytopenia were found. PF-4 and F1+2 significantly changed during the study (p<0.05). Greater acute PF-4 decrease correlated with greater acute platelet count drop (r=0.48, p=0.043), and during the study slower PF-4 increase correlated with higher platelet count increase on POD-3 (r=-0.505, p=0.032). Lower baseline PS correlated with lower baseline platelet count and higher platelet count increase on POD-3 (r=0.45, p=0.04 and =-0.55, p=0.02, respectively). No significant correlations between F1+2 concentrations and platelet count changes have been found. CONCLUSIONS Platelet reduction shortly after TAVI procedure is related to the amount of contrast agent applied during the procedure. Platelet activation and blood coagulation along with impaired baseline platelet renewal might be the mechanisms of thrombocytopenia following TAVI procedure.

The significance of diminished sTWEAK and P-selectin content in platelets of patients with pulmonary arterial hypertension

HighlightsPatients with PAH present comparable serum sTWEAK concentrations as controls.Platelet content of TWEAK and P‐selectin is diminished in patients with PAH.Lower platelet TWEAK is associated with clinical indices of more advanced disease.Patients with lowest platelet TWEAK more frequently develop detoriation of PAH.sTWEAK secreted by platelets may affect PAH progression and prognosis. &NA; Pulmonary arterial hypertension (PAH) is a progressive disease characterized by proliferative changes in pulmonary arteries. There is growing evidence suggesting that soluble tumor necrosis factor‐like weak inducer of apoptosis (sTWEAK) and P‐selectin could be involved in PAH development and progression. Here we investigate whether circulating platelets may be a source of sTWEAK and contribute to diminished availability of sTWEAK and P‐selectin in PAH patients. We have prospectively enrolled two independent study groups of stable patients with confirmed PAH and age matched controls: derivation (10 PAH; 15 controls) and validation (20 PAH; 12 controls). P‐selectin and sTWEAK concentrations were measured in platelet‐poor plasma and platelet lysate. To avoid procedural bias, in each group we employed different protocols for platelet isolation. Consistently, both in derivation and validation groups PAH patients presented significantly lower sTWEAK content in platelets than control group with no significant differences in plasma levels. Similarly, patients presented comparable to controls plasma P‐selectin concentrations and lower concentration in platelet lysate. Kaplan‐Meier analysis revealed that patients with low platelet sTWEAK/total protein concentration ratio had more frequently detoriation of PAH in the follow‐up (16.51 ± 3.32 months), log‐rank test, p = .03. Patients diagnosed with pulmonary arterial hypertension present diminished sTWEAK and P‐selectin storage capacity in platelets. Thrombocytes appear to be a major source of sTWEAK that could be released upon local injury and its decreased availability could have an impact on pathophysiology and prognosis in PAH.

Increased Platelet Content of SDF-1alpha is Associated with Worse Prognosis in Patients with Pulmonary Arterial Hypertension

Abstract Inflammatory processes and platelet activity play an important role in the pathophysiology of pulmonary arterial hypertension (PAH). Enhanced IL-6 signaling and higher concentration of stromal-derived factor alpha (SDF-1) have been previously shown to be linked with prognosis in PAH. We hypothesized that platelets of PAH patients have higher content of IL-6 and SDF-1 and thus are involved in disease progression. We enrolled into study 22 PAH patients and 18 healthy controls. Patients with PAH presented significantly higher plasma concentrations and platelet contents of IL-6, sIL-6R, and SDF-1 than healthy subjects (platelet content normalized to protein concentration: IL-6 (0.85*10–10 [0.29 – 1.37] vs. 0.45*10–10 [0.19–0.65], sIL-6R 1.54*10–7 [1.32–2.21] vs. 1.14*10–7 [1.01–1.28] and SDF-1 (2.72*10–7 [1.85–3.23] vs. 1.70*10–7 [1.43–2.60], all p < 0.05). Patients with disease progression (death, WHO class worsening, or therapy escalation, n = 10) had a significantly higher platelet SDF-1/total platelet protein ratio (3.68*10–7 [2.45–4.62] vs. 1.69*10–7 [1.04–2.28], p = 0.001), with no significant differences between plasma levels. Kaplan–Meier analysis revealed that patients with higher platelet SDF-1/total platelet protein ratio had more frequently deterioration of PAH in the follow-up (15.24 ± 4.26 months, log-rank test, p = 0.01). Concentrations of IL-6, sIL-6 receptor and SDF-1 in plasma and platelets are elevated in PAH patients. Higher content of SDF-1 in platelets is associated with poorer prognosis. Our study, despite of limitation due to small number of enrolled patients, suggests that activated platelets may be an important source of cytokines at the site of endothelial injury, but their exact role in the pathogenesis of PAH requires further investigation.

Persistently elevated plasma heart-type fatty acid binding protein concentration is related with poor outcome in acute decompensated heart failure patients

BACKGROUND The aim of the study was to determine clinical and prognostic role of repeated heart-type fatty acid binding protein (hFABP) measurements in acute decompensated HF (ADHF) patients. METHODS In seventy-seven ADHF patients (III and IV NYHA class, mean age 70 ± 12.7 years, mean left ventricle ejection fraction [LVEF] 29.73 ± 13.3%) plasma hFABPs concentrations (SunRed Biological Technology) were measured twice - on admission and at discharge (mean time of hospitalization 10.7 ± 4.9 days). Combined end point (CEP), assessed after mean 9.2 ± 7.3 months, was defined as death or the need of HF re-hospitalization. RESULTS Median hFABP concentration on admission was significantly lower than at discharge. hFABP concentrations on admission significantly correlated with echocardiographic parameters of LV remodeling. Among fifty-six patients (72.7%) who reached CEP, significantly higher admission and discharge hFABP concentrations were found. Patients with plasma discharge hFABP concentrations higher than 7.8 ng/mL were at higher risk of CEP (log-rank test, p = 0.01). Logistic stepwise regression analysis revealed discharge hFABP, LVEF and left ventricle mass index independent and significant predictors of CEP (p < 0.05). CONCLUSIONS In ADHF patients plasma hFABP admission concentrations are related with LV remodeling. Persistently elevated hFABP concentrations have prognostic value, as may reflect continuous myocardial damage despite effective treatment and clinical improvement.

The role of platelets in the development and progression of pulmonary arterial hypertension

Pulmonary arterial hypertension is a multifactorial disease characterized by vasoconstriction, vascular remodeling, inflammation and thrombosis. Although an increasing number of research confirmed that pulmonary artery endothelial cells, pulmonary artery smooth muscle cells as well as platelets have a role in the pulmonary arterial hypertension pathogenesis, it is still unclear what integrates these factors. In this paper, we review the evidence that platelets through releasing a large variety of chemokines could actively impact the pulmonary arterial hypertension pathogenesis and development. A recent publication revealed that not only an excess of platelet derived cytokines, but also a deficiency may be associated with pulmonary arterial hypertension development and progression. Hence, a simple platelet blockade may not be a correct action to treat pulmonary arterial hypertension. Our review aims to analyse the interactions between the platelets and different types of cells involved in pulmonary arterial hypertension pathogenesis. This knowledge could help to find novel therapeutic options and improve prognosis in this devastating disease.

Perioperative thrombocytopenia predicts poor outcome in patients undergoing transcatheter aortic valve implantation

PURPOSE To determine the time point at which thrombocytopenia after TAVI procedure is an indicator of the worst prognosis, with special consideration of perioperative platelet and coagulation activation as its potential causes. METHODS Thirty two patients (mean age 78.5±7.9years, 62% females) qualified for TAVI procedure were prospectively evaluated. Platelet counts were assessed at baseline and for the next three postoperative (POD) days. Platelet activation was evaluated by P-selectin (PS, serum, ELISA) and platelet factor 4 (PF-4, CTAD plasma), and blood coagulation activation by prothrombin fragments 1+2 (F1+2, plasma, ELISA). Composite end point (CEP) including death and the need of cardiovascular rehospitalization was assessed after a mean of 14.1±6.7months. RESULTS During the follow up period half of the patients reached CEP. Thrombocytopenia was more profound and frequent in patients with CEP as compared to those without (p<0.05). No differences regarding either the biomarkers of platelet (PS, PF-4) or coagulation (F1+F2) activation between the groups with and without CEP were found. Patients with moderate-to-severe thrombocytopenia at baseline had worse prognosis (log-rank test, p=0.0003). Based on the receiver operating characteristic curve analysis, the differences between platelet count on each postoperative day and the baseline count did not have any predictive value in CEP occurrence. CONCLUSIONS Patients with thrombocytopenia following TAVI procedure have poor prognosis, however, the changes on the particular days are not more important than initial platelet count. Further studies are needed to evaluate platelet and blood coagulation activation as potential causes of thrombocytopenia and impaired prognosis related to it.