The evaluation of constant coronary artery flow versus constant coronary perfusion pressure during normothermic ex situ heart perfusion

Qingkailing injection induces pseudo-allergic reactions via the MRGPRX2 pathway

OBJECTIVE

Qingkailing Injection (QKLI) is a traditional Chinese medicine injection mainly used for sedation, heat clearing, and other treatments. However, recent clinical studies have shown a risk of pseudo-allergic reactions. The purpose of this study is to elucidate the underlying mechanism of QKLI-induced mast cell degranulation in Laboratory of Allergic Diseases 2 (LAD2) and to validate QKLI-induced activation of guinea pig IgE-independent allergic responses.

METHODS

Levels of β-hexosaminidase (β-Hex), histamine (His), and complement pathway-related indicators in guinea pigs and LAD2 cells were assayed using the Enzyme-linked Immunosorbent Assay (ELISA). The release rates of β-Hex and His from LAD2 cells were measured using the o-phthalaldehyde (OPA) fluorimetric method. The antagonist for complement component 3a (C3a) receptors, SB290157 and siRNAs were used to inhibit the C3a pathway and the Mas-related G-protein-coupled receptor X2 (MRGPRX2) pathway. The MRGPRX2 pathway and its downstream proteins were detected by Western Blot (WB).

RESULTS

The results show that QKLI significantly increased levels of β-Hex, His, C3a, complement component 5a (C5a), and terminal complement complex C5b-9 (SC5b-9) in guinea pigs, while levels of interleukin 4 (IL-4), interleukin 13 (IL-13), and interleukin 6 (IL-6) were unaffected. The C3a receptor inhibitor SB290157 significantly reduced levels of β-Hex and His. In LAD2 cells, QKLI increased the release rates of β-Hex and His in a time-dependent manner and decreased the phosphorylation of Extracellular Signal-regulated Kinase 1/2 (ERK1/2) proteins downstream of the MRGPRX2 pathway. The effective components of QKL, baicalin (BA) and geniposide (GE), individually enhance the allergic responses of LAD2 cells to some extent. However, the use of QKL is significantly superior to the individual use of its components.

CONCLUSIONS

We found that QKLI induced pseudoanaphylaxis via an IgE-independent response in guinea pigs and through the MRGPRX2 pathway in human LAD2 cells. Among these, the main ingredients causing pseudoallergic reactions in QKLI were BA and GE. Our research contributes to a better understanding of the mechanisms underlying drug hypersensitivity reactions (DHRs).

A Smart Computational Tool for Personalized Coronary Blood Flow Settings During Normothermic Ex Situ Heart Perfusion

Myocardial edema significantly develops during current subnormothermic ex situ heart perfusion (ESHP) procedures, resulting in myocardial function decline during prolonged perfusion. A relatively high coronary blood flow (CBF) during ESHP is thought to be responsible for this high degree of myocardial edema formation. In this study, we present a novel tool to calculate CBF based on individual donor (sex and body weight) and perfusate (hemoglobin concentration, oxygen saturation, partial pressure of oxygen [PO2]) characteristics. The tool continuously evaluates the balance between myocardial oxygen consumption (MVO2) and delivery to facilitate adequate and preventing excess perfusion. Taking this personalized approach, the CBF can potentially be lowered while still providing sufficient oxygen to the donor heart. Furthermore, the tool automatically calculates MVO2, ΔPO2, and coronary vascular resistance during ESHP, which aids in the qualitative assessment of the heart before transplantation.

Myocardial oxygen handling and metabolic function of ex-situ perfused human hearts from circulatory death donors

Background

This study investigated oxygen handling of human hearts donated after circulatory death (DCD) on normothermic ex-situ heart perfusion (ESHP) and evaluated oxygen handling markers as adjuncts to cardiac viability assessment.

Methods

This single-center retrospective study included human DCD heart transplantation procedures using ESHP. Lactate concentrations, blood gas, myocardial oxygen consumption (MVO2), delivery (MDO2), and extraction (MEO2), coronary blood flow (CBF), coronary vascular resistance (CVR), and adenosine infusion were reported over time. Correlation between parameters was assessed, and statistical testing compared patients who did and did not require extracorporeal membrane oxygenation (ECMO) support after transplantation.

Results

Lactate concentrations decreased during ESHP in all transplanted hearts (n = 25) and increased in 1 rejected heart. Arterial partial pressure of oxygen (PO2) was 75.2 ± 2.9 kPa, with an arteriovenous ΔPO2 of 44.8 ± 10.4 kPa. Oxygen saturation was 100% in most arterial and venous samples. Average MVO2 was 2.7 ± 0.6 ml/min/100 g myocardium, MDO2 98.5 ± 20.4 ml/min, and MEO2 8.6 ± 1.8%. Average CVR was 0.025 ± 0.006 mm Hg min/ml/100 g and increased over time. ΔPO2 correlated strongly with MVO2 (R = 0.797, p < 0.001) and lactate trend (R = 0.799, p < 0.001) in transplanted hearts, without differences compared to the rejected heart with increasing lactate. Adenosine infusion on ESHP was significantly higher in patients requiring ECMO post-transplantation vs non-ECMO cases (11.7 (4.5-21.0) vs 2.2 (1.5-6.7) ml/h, p = 0.039).

Conclusions

Hearts on normothermic ESHP receive excessive MDO2, due to high PO2 and CBF, while the MVO2 is relatively low. Thus, CBF and PO2 can potentially be lowered. Furthermore, ΔPO2 could serve as additional marker of metabolic function under these hyperoxic circumstances. The adenosine infusion rate might predict post-transplantation ECMO requirement.

The Effects of Oxygen-Derived Free-Radical Scavengers During Normothermic Ex-Situ Heart Perfusion

Oxidative stress occurs during ex-situ heart perfusion (ESHP) and may negatively affect functional preservation of the heart. We sought to assess the status of key antioxidant enzymes during ESHP, and the effects of augmenting these antioxidants on the attenuation of oxidative stress and improvement of myocardial and endothelial preservation in ESHP. Porcine hearts were perfused for 6 hours with oxygen-derived free-radical scavengers polyethylene glycol (PEG)-catalase or PEG-superoxide dismutase (SOD) or with naive perfusate (control). The oxidative stress-related modifications were determined in the myocardium and coronary vasculature, and contractile function, injury, and endothelial integrity were compared between the groups. The activity of key antioxidant enzymes decreased and adding catalase and SOD restored the enzyme activity. Cardiac function and endothelial integrity were preserved better with restored catalase activity. Catalase and SOD both decreased myocardial injury and catalase reduced ROS production and oxidative modification of proteins in the myocardium and coronary vasculature. The activity of antioxidant enzymes decrease in ESHP. Catalase may improve the preservation of cardiac function and endothelial integrity during ESHP. While catalase and SOD may both exert cardioprotective effects, unbalanced SOD and catalase activity may paradoxically increase the production of reactive species during ESHP.