TABLE 2.
Bilirubin affects vascular cell functions: In vitro studies.
| Experimental model | Bilirubin concentration (mg/dl) or μM in cell culture media | Main findings | References |
| Human EC | |||
| HUVECs | 10–20 μM bilirubin | Bilirubin inhibits migration of THP-1 monocytes across activated HUVEC monolayers | Vogel et al., 2017 |
| HUVECs | 20 μM | Bilirubin markedly inhibited the migration of Jurkat cells across TNFα-stimulated HUVEC monolayers by impairing VCAM1 signaling | Zucker et al., 2015 |
| HUVECs | Not evaluated | HMOX1 induction (10 μM CoPPIX) prevents high glucose-induced reduction in NO release and enhanced VEGF-A expression | Maamoun et al., 2017 |
| HUVECs | 50 μM | Bilirubin promoted proliferation of endothelial cells and also affects invasion capability of cells from trophoblast | Ha et al., 2015 |
| HUVECs and VSMCs | Not evaluated | PPAR ligands induce HMOX1 and block the inflammatory response in vascular cells | Krönke et al., 2007 |
| HUVECs, HAECs, HDMECs | 10 μM | HIV protease inhibitors (PIs) induce HMOX1 that, by generating bilirubin, counteract the anti-proliferative and inflammatory actions of PIs | Liu et al., 2016 |
| ECV304 | Not evaluated | Statins increase HMOX1 expression | Grosser et al., 2004 |
| HMEC-1 | Not evaluated | Cell transfection with plasmid vector (pHRE-HO-1) carrying human HMOX1 driven by three hypoxia response elements (HREs) and cultured in 0.5% oxygen, by up-regulating HMOX1, effectively protects against oxidative stress and promotes angiogenesis | Jazwa et al., 2013 |
| HBMECs | 50 or 100 μM UCB in presence of HSA | Short-term exposure to UCB activates endothelial cells and late-term exposure to UCB increases paracellular permeability, overall increasing endothelial damage | Palmela et al., 2012 |
| HAECs | 1–10 μM | Bilirubin increases AKT dependent eNOS phosphorylation and favors leukocyte adhesion migration and tube formation | Ikeda et al., 2015 |
| HCAECs | 1, 5, and 10 μM bilirubin | Niacin increases HMOX1 expression and inhibits TNFα induced endothelial inflammation | Wu et al., 2012 |
| HGEnCs | 10 μM | HMOX1 induction (25 μM CoPPIX) as well as bilirubin supplementation directly reduce ET-1 generation | Bakrania et al., 2018 |
| cEPCs | 10–20 mg/dl | Progenitor endothelial cells induced to proliferate when exposed to 5 mg/dl bilirubin; higher concentrations (up to 20 mg/dl) induce cell death | Jabarpour et al., 2018 |
| EA.hy926 | 0.5–100 μM | Exogenous bilirubin increases endothelial antioxidant activity as well as HMOX1-dependent bilirubin generation | Ziberna et al., 2016 |
| Commercially EC | Not evaluated | EC-transfected with HMOX1 release substances that increase healthy adipocytes | Peterson et al., 2019 |
| Human and non-human EC | |||
| HUVECs and H5V cells | 0.015 μM < Bf < 0.030 μM | UCB, at clinically relevant concentrations, limits over-expression of adhesion molecules and inhibits PMN-endothelial adhesion induced by pro-inflammatory cytokine TNFα, even though UCB itself does not alter expression of these adhesion molecules. Inhibition NF-kappaB transduction pathway | Mazzone et al., 2009a, b |
| HAECs and mAECs | Not evaluated | In HAECs and in primary mAECs from HMOX1+/+ and HMOX1–/–, SDF-1 (100-200 ng/ml) favors angiogenesis through the induction of HMOX1 | Deshane et al., 2007 |
| Non-human EC | |||
| mHEVa and mHEVc | 10–20 μM | Bilirubin inhibits leukocyte transmigration across endothelial cell monolayer | Keshavan et al., 2005 |
| CMVECs | 1 μM | Bilirubin supplementation prevent endothelial apoptosis induced by TNFα by reducing NOX4-derived ROS | Basuroy et al., 2009 |
| bEnd.3 and MS1 | 1–40 μM | Endothelial cells derived from BBB are more sensitive to UCB pro-apoptotic effect than endothelial cells from pancreas | Kapitulnik et al., 2012 |
| mAECs | Not evaluated | Primary endothelial cells from HMOX2–/– mice show an increased oxidative stress, inflammation and excessive angiogenesis | Bellner et al., 2009 |
| BAEC | 1 μM | Bilirubin supplementation restores cell protection against acute high glucose treatment in endothelial cells exposed to HMOX1 inhibitor, preventing HNE production | He et al., 2015 |
| Other cells from cardiovascular system | |||
| Bovine vascular smooth-muscle cells | 0.5–5 μM | Short term treatment with bilirubin as well as HMOX1 induction (25–200 μM hemin) protect against oxidant-mediated damage | Clark et al., 2000 |
| H9c2 | 0.5 μM | Bilirubin treatment as well asHMOX1 induction (5 μM hemin) protects against hypoxia/reoxygenation | Foresti et al., 2001 |
| Primary mice cardiomyocytes | 20 μM | HMOX1 induction (10 μM hemin) as well as bilirubin supplementation limits senescence | Shan et al., 2019 |
BAEC, bovine aortic endothelial cells; b.End3, murine brain microvascular endothelial cell line; Bf, free bilirubin; BBB, blood-brain barrier; cEPCs, circulating endothelial progenitor cells; CMVECs, cerebral microvascular endothelial cells; COPPIX, cobalt protoporphyryn IX; EA.hy926, human endothelial cell line; EC, endothelial cells; ECV304, human endothelial cells derived from umbilical cord; ET-1, vascular endothelin-1; HAECs, human aortic endothelial cells; HBMECs, human brain microvascular endothelial cells; HCAECs, human coronary artery endothelial cells; HDMECs, human dermal microvascular endothelial cells; HGEnCs, immortalized human glomerular endothelial cells; HMEC-1, human microvascular endothelial cells; HREs, hypoxia response elements; HUVECs, human umbilical vein endothelial cells; H5V, murine heart endothelial immortalized cells; H9c2, rat cardiomyocytes; mAECs, mouse aortic endothelial cells; mHEVa/c, murine high endothelial venule-like cells; MS1, microvascular endothelial cell line; PIs, protease inhibitors; PMN, polymorphonuclear neutrophils; ROS, reactive oxygen species; SDF-1, stromal cell-derived factor 1; UCB, unconjugated bilirubin; VSMC, vascular smooth muscle cells.