Body fluid status in patients with pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension

Introduction

Body fluid status can be determined by plasma volume status and extracellular water to total body water (ECW/TBW) ratio and is a well-known parameter associated with survival in patients with chronic heart failure (1–3). However, its prognostic impact in patients with pulmonary arterial hypertension (PAH) and chronic thromboembolic pulmonary hypertension (CTEPH) is not fully understood.

Methods

409 patients with PAH and CTEPH who entered the Giessen PH registry were included in this study (4). Plasma volume status was estimated using Duarte formula (ePVS = (1 − hematocrit) / hemoglobin × 100). ECW was calculated via Peters formula ((−2.47 × 0.842 + 8.76 × body surface area) for men and (−1.96 × 0.572 + 8.05 × body surface area) for women) and TBW via Watson formula ((2.447 − [0.09516 × age] + [0.1073 × height] + [0.3362 × body weight]) for men and (−2.097 + [0.1069 × height] + [0.2466 × body weight]) for women). Statistical analyzes were performed with R (The R Foundation).

Results

Median age of the included patients was 65 [53, 74] years. Median ePVS and ECW/TBW ratio were 4.5 [3.9, 5.5] and 0.39 [0.37, 0.40]. Correlation analyses revealed that ePVS correlates with pulmonary artery wedge pressure (PAWP), pulmonary vascular resistance (PVR), cardiac index, and mixed venous oxygen saturation (SvO2), whereas ECW/TBW ratio did not correlate with pulmonary hemodynamics. Accordingly, univariate Cox regression revealed that ePVS but not ECW/TBW ratio was associated with mortality (HR: 1.18 [1.02, 1.37]). ePVS remained as an independent prognostic parameter in multivariate Cox regression analysis. Patients with high ePVS showed significantly decreased survival rates (log-rank p<0.001).

Conclusion

ePVS but not ECW/TBW ratio is associated with prognostic parameters such as PVR, cardiac index and SvO2. Thus, ePVS may be an independent prognostic parameter in patients with PAH and CTEPH.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): Deutsche Forschungsgemeinschaft (DFG, German Research Foundation)

C0-C1f region of cardiac myosin binding protein-C induces pro-inflammatory responses in fibroblasts

Background

Cardiac myosin binding protein-C is a protein expressed in the myosin thick filament backbone that was recently described as a novel cardiac biomarker. Its N-terminal region, C0-C1f, is released within the first minutes of ischemia and plays a crucial role in the initiation of inflammation in bone marrow-derived macrophages. Long-term C0-C1f exposure induces cardiac fibrosis in transgenic mice; however, the mechanism by which C0-C1f causes fibrosis is unclear. The aim of the study was to investigate the effects of C0-C1f on fibroblasts, which are the main contributor to cardiac fibrosis, in vitro. We determined whether C0-C1f directly activates fibroblasts and causes a transdifferentiation to myofibroblasts or induces inflammatory responses. Moreover, we clarify whether other cell types could be involved in inducing fibrosis, i.e. by the release of pro-inflammatory cytokines upon C0-C1f interaction.

Methods

A novel human fibroblast cell line (huFib) was treated with C0-C1f, C0-Linker, TGF-β, or LPS for different time periods. Inflammatory and fibrotic responses were evaluated at the RNA and protein level using different techniques including microarray, qRT-PCR, and immunofluorescence imaging. For signalling pathway analysis, TLR4 and NFκB were inhibited using chemical compounds TAK-242 or Bay11–0785 respectively.

Results

C0-C1f treatment induced an increase in mRNA corresponding to pro-inflammatory genes in huFib cells (i.a. CXL1 upon 24 hours treatment: 29 fold, p<0.001 and CCL2 4-fold, p<0.001). The mRNA expression levels of pro-fibrotic genes such as ACTA2 or COL1A1, which were upregulated by TGF-β, were not reduced by C0-C1f (ACTA2 induced by TGF-β: 3,8 fold, p<0.001, co-stimulation with C0-C1f: 1,8 fold, p=0.11 compared to control; COL1A1 induced by TGF-β: 2,94 fold, p<0.001, co-stimulation with C0-C1f: 2.09 fold (p<0.01) compared to control. Interestingly, co-stimulation of fibroblasts with C0-C1f and TGF-β led also to markedly lower inflammatory response compared to C0-C1f treatment alone (CXCL1 induction upon co-stimulation: 2,0 fold, p<0.001, CCL2: 1,9 fold, p=0.001, which is a reduction by 27 fold, p<0.001 or 2 fold, p=0.002, respectively). Inhibition of TLR4 or NFκB signaling diminished C0-C1f-mediated inflammatory responses.

Conclusion

C0-C1f induces inflammation in fibroblasts via TLR4/NFκB signalling pathway. Downregulation of C0-C1f mediated inflammatory responses upon co-stimulation with TGF-β suggests crosstalk between the two signaling pathways. Contrary, C0-C1f reduced TGF-β mediated pro-fibrotic responses reflected by conversion of fibroblasts into myofibroblasts was not observed. Taken together, these data are consistent with the idea that C0-C1f might play a key role in the early initiation of inflammation upon myocardial infarction, also in fibroblasts, and that TGF-β acts as a counterpart at later stages of cardiac remodeling.

Funding Acknowledgement

Type of funding sources: Foundation. Main funding source(s): William G. Kerckhoff Stiftung für wissenschaftliche Forschung und Fortbildung