Nicotine-free e-cigarettes have had devastating effects on the lungs
In an effort to kick the habit of smoking, modern people are turning to substitutes - supposedly safer and non-addictive e-cigarettes or vapes, including nicotine-free liquids. Despite their growing popularity (and the parallel banning of such nicotine-containing products), there is still not much research in this area. Although there are known clinical cases of lung damage and vascular disease in e-cigarette smokers, both with and without nicotine.
To understand more about how devices that create flavored vapor for inhalation affect the pulmonary endothelium, scientists from Anglia Ruskin University in Cambridge, UK, took on the task. Their paper appeared in the journal Microvascular Research.
"Using a common brand of electronic cigarettes (eVape) as an example using an in vitro model of the human lung microcirculatory bed, we investigated the effects of nicotine-free eVape liquid on lung endothelial barrier integrity, oxidative stress and inflammation profile," the biomedical scientists said.
The analysis used three types of disposable watermelon-flavored e-cigarettes: with or without 10 and 20 milligrams of nicotine benzoate. These liquids and distilled water were used to prepare a solution with concentrations ranging from 0 to 20%, which was used for different periods of time to expose endothelial cells cultured in a growth medium.
The scientists then measured levels of cytokines, intracellular calcium, reactive oxygen species (ROS), nitric oxide (NO) production, mitochondrial membrane potential (Δψm), VE-cadherin (vascular endothelial cell adhesion protein) and ICAM-1 cell adhesion molecule expression. The permeability of the endothelial monolayer was also assessed.
As a result, the authors concluded that exposure to eVape liquid and its vapors caused severe cell death (apoptosis), impaired the barrier function of the pulmonary microcirculatory bed, and resulted in increased release of cytokines IL-6, IL-8, TNF-α, IL-1β, and IL-18 and higher expression of ICAM-1.
Samples with any nicotine level were found to be harmful. And the nicotine-free liquids had the same chemical composition as the nicotine-containing liquids, except for the actual nicotine content.
"All three nicotine concentrations in the eVape caused endothelial cell death, but the liquid with 10 milligrams (eV10) provoked the most significant decrease in cell viability. <...> Endothelial cell death was accelerated when all three nicotine concentrations were studied. Apoptosis induced by eV0 (no nicotine) occurred at 5% solution concentration, whereas eV5 (five milligrams) and eV10 induced apoptosis from 1%. All samples increased calcium release in pulmonary microvascular endothelial cells starting at 2.5% solution concentration," the researchers elaborated.
They also found that the nicotine-free liquid aggravated the accumulation of AFCs in endothelial cells, namely, excessive amounts of reactive oxygen species damage cells and lead to the development of cardiovascular diseases, cancer, arthritis and others. In addition, the regulation of a number of genes related to adhesion compounds was disturbed: the level of ARF6 protein was most strongly increased. Further analysis showed that ARF6 is a key regulator of pulmonary endothelial dysfunctions.