Human umbilical vein endothelial cells (HUVECs) are a widely used source of primary endothelial cells. First isolated in the 1970s, HUVECs are a popular tool for researchers due to their availability and ease of culture for in vitro studies of the vasculature and angiogenesis. The endothelium is the thin layer of endothelial cells that lines the interior of blood and lymphatic vessels and is important for maintaining vascular homeostasis and regulating inflammatory responses. The regulatory function of the endothelium, also known as the endothelial barrier function, maintains vascular homeostasis and plays a critical role in controlling blood-tissue gas and solute exchange. Endothelial barrier dysfunction is implicated in the pathology of several diseases including atherosclerosis, proteinuria, and Alzheimer’s disease. Therefore, in vitro modeling the endothelial barrier can help researchers better understand disease progression as well as evaluate therapeutic drug candidates. A new 2020 publication by Motawe and Colleagues utilized Lifeline’s HUVEC cells cultured in VascuLife® cell culture medium as an in vitro model of the endothelial barrier to elucidate the role of σ1 receptors in barrier function.

Lifeline® Cell Technology offers high-quality HUVECs for your research as well as a number of other endothelial cell systems. Check out our catalog for more information:

• Aortic endothelial cells
• Coronary endothelial cells
• Lung microvascular endothelial cells
• Dermal microvascular endothelial cells (adult and neonatal)
• Cardiac microvascular endothelial cells
• Iliac artery endothelial cells
• Pulmonary artery endothelial cells
• HUVECs (primary and 10-donor pool)

The Role of σ1 in Maintenance of Endothelial Barrier Function

Motawe and Colleagues investigated the role of σ1 receptors in endothelial barrier function from a mechanistic standpoint under basal conditions and after challenge with barrier disrupters using both genetic and pharmacological strategies. The endothelial-specific contribution of σ1 was evaluated using the σ1 agonist, PRE-084, and with siRNA knockdown of σ1 expression. Endothelial barrier permeability and function were evaluated with electrical cell-substrate impedance sensor (ECIS), Transwell assays, and immunofluorescence labeling of endothelial junction proteins.

Trans-endothelial electrical resistance (TER), as determined by ECIS, measures inter-endothelial adhesion and is a good indicator of barrier function in endothelial cell monolayers. When HUVEC cells were treated with PRE-084, improved barrier function was observed as evidenced by increased TER and decreased endothelial permeability to fluorescently-labeled albumin and dextran in Transwell experiments. siRNA knockdown of HUVEC monolayers showed a higher barrier permeability compared to control cells confirming σ1’s involvement in baseline barrier function.

Previous reports implicate σ1 receptor in mitochondrial function, an organelle important for energy production (stored as adenosine triphosphate (ATP)), which led the authors to investigate how activation of σ1 affects the rate and method ATP production. Interestingly, the data showed no decrease in ATP production with PRE-084 treatment compared to the control group, but rather, the net effect observed was a shift in the overall ATP production pathway from mitochondrial respiration to glycolysis. The authors postulated that PRE-084-induced activation of σ1 and subsequent increase in glycolytic ATP production is a barrier-protective mechanism to compensate for loss of mitochondria function to maintain endogenous ATP levels.

To explore this further, the authors modeled mitochondrial dysfunction using the mitochondrial uncoupler, carbonyl cyanide m-chlorophenyl hydrazone (CCCP). CCCP causes a drop in TER (reduction in barrier function) that was mitigated by PRE-084 treatment, confirming the idea that σ1 activation can at least partially compensate to maintain endothelial barrier function when mitochondrial function is compromised.

Overall, this publication demonstrates that σ1 activation through PRE-084 treatment can counteract barrier dysfunction by increasing glycolysis and subsequent glycolytic ATP production, which are tightly linked to enhanced barrier junctional protein integrity. This suggests that σ1 could potentially serve as a useful therapeutic target to preserve endothelial barrier function in pathologies involving mitochondrial dysfunction caused by disease or injury and warrants further investigation.

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