Direct comparison of relaxation and cGMP production in human coronary by-pass grafts in response to stimulation with natriuretic peptides and a nitric oxide donor

Multi-Omics Profiling of Human Endothelial Cells from the Coronary Artery and Internal Thoracic Artery Reveals Molecular but Not Functional Heterogeneity

Major adverse cardiovascular events occurring upon coronary artery bypass graft surgery are typically accompanied by endothelial dysfunction. Total arterial revascularisation, which employs both left and right internal thoracic arteries instead of the saphenous vein to create a bypass, is associated with better mid- and long-term outcomes. We suggested that molecular profiles of human coronary artery endothelial cells (HCAECs) and human internal mammary artery endothelial cells (HITAECs) are coherent in terms of transcriptomic and proteomic signatures, which were then investigated by RNA sequencing and ultra-high performance liquid chromatography-mass spectrometry, respectively. Both HCAECs and HITAECs overexpressed molecules responsible for the synthesis of extracellular matrix (ECM) components, basement membrane assembly, cell-ECM adhesion, organisation of intercellular junctions, and secretion of extracellular vesicles. HCAECs were characterised by higher enrichment with molecular signatures of basement membrane construction, collagen biosynthesis and folding, and formation of intercellular junctions, whilst HITAECs were notable for augmented pro-inflammatory signaling, intensive synthesis of proteins and nitrogen compounds, and enhanced ribosome biogenesis. Despite HCAECs and HITAECs showing a certain degree of molecular heterogeneity, no specific markers at the protein level have been identified. Coherence of differentially expressed molecular categories in HCAECs and HITAECs suggests synergistic interactions between these ECs in a bypass surgery scenario.

Co-Culture of Primary Human Coronary Artery and Internal Thoracic Artery Endothelial Cells Results in Mutually Beneficial Paracrine Interactions

Although saphenous veins (SVs) are commonly used as conduits for coronary artery bypass grafting (CABG), internal thoracic artery (ITA) grafts have significantly higher long-term patency. As SVs and ITA endothelial cells (ECs) have a considerable level of heterogeneity, we suggested that synergistic paracrine interactions between CA and ITA ECs (HCAECs and HITAECs, respectively) may explain the increased resistance of ITA grafts and adjacent CAs to atherosclerosis and restenosis. In this study, we measured the gene and protein expression of the molecules responsible for endothelial homeostasis, pro-inflammatory response, and endothelial-to-mesenchymal transition in HCAECs co-cultured with either HITAECs or SV ECs (HSaVECs) for an ascending duration. Upon the co-culture, HCAECs and HITAECs showed augmented expression of endothelial nitric oxide synthase (eNOS) and reduced expression of endothelial-to-mesenchymal transition transcription factors Snail and Slug when compared to the HCAEC–HSaVEC model. HCAECs co-cultured with HITAECs demonstrated an upregulation of HES1, a master regulator of arterial specification, of which the expression was also exclusively induced in HSaVECs co-cultured with HCAECs, suggestive of their arterialisation. In addition, co-culture of HCAECs and HITAECs promoted the release of pro-angiogenic molecules. To conclude, co-culture of HCAECs and HITAECs results in reciprocal and beneficial paracrine interactions that might contribute to the better performance of ITA grafts upon CABG.

Differential effects of natriuretic peptides on arterial and venous coronary artery bypass conduits

BACKGROUND

Arterial grafts have patency rates superior to venous grafts in patients undergoing coronary bypass grafting surgery. Natriuretic peptides play a major role in vascular homeostasis. We hypothesized that natriuretic peptides might have different effects on arterial and venous conduits.

METHODS

The relaxation responses and tissue levels of cyclic guanosine monophosphate (cGMP) after exposure to atrial natriuretic peptide, brain natriuretic peptide, and C-type natriuretic peptide were assessed in segments of internal mammary artery, radial artery, and saphenous vein obtained from the same patients at the time of bypass surgery (n = 12). Natriuretic peptide receptor (NPR) expression was assessed using immunohistochemistry and Western blotting.

RESULTS

Relaxation of the internal mammary artery and radial artery to all the natriuretic peptides were similar, and greater than that of saphenous vein, correlating with increased tissue levels of cGMP in both arterial conduits. Relaxation responses to all three natriuretic peptides were nearly abolished in the presence of LY83583, an inhibitor of guanylyl cyclase. Exposure of the conduits to N(G)-Nitro-L-arginine methyl ester (nitric oxide synthase inhibitor) resulted in a modest but significant blunting of the relaxation responses. Expression of NPR(A), NPR(B) and NPR(C)was strong in the endothelium and vascular smooth muscle layer of the internal mammary artery and radial artery, and was significantly less in saphenous vein.

CONCLUSIONS

Natriuretic peptides are potent vasodilators of the internal mammary artery and radial artery but not the saphenous vein. The relaxation response is mediated through guanylyl cyclase and nitric oxide synthase. These observations may provide additional insight into the mechanisms that account for superior patency of arterial conduits.

Slower onset of vasodilating action of brain natriuretic peptide (BNP) compared to atrial natriuretic peptide (ANP) in human forearm resistant vessels

PURPOSE

To investigate possible differences in the time course of vasodilating effects of atrial natriuretic peptide (ANP) and brain natriuretic peptide (BNP) in humans.

METHODS

We measured forearm blood flow (FBF) by strain gauge plethymography and cyclic GMP spillover during and after intra-arterial infusions of BNP and ANP at 16.2 pmol/min for 30 min in healthy subjects.

RESULTS

The steady-state responses of FBF and cyclic GMP to the infusion were achieved approximately 20 min after commencement of the infusion of BNP, but within 5 min for ANP, with similar magnitudes of maximum responses. These parameters more slowly returned to the baseline value after withdrawal of the BNP infusion than after the ANP infusion.

CONCLUSION

The onset and disappearance of the guanylate cyclase-stimulating and vasodilating effects of BNP were significantly slower than those of ANP. This differing mode of vasodilator action may be relevant to the therapeutic use of natriuretic peptides.