Abstract 4363990: Endothelial Dysfunction Induced by 6-Methylnicotine, a Novel Nicotine Analog, in Murine Blood Vessels In Vitro

Abstract

Background: The presence of synthetic nicotine analogs in "tobacco-free" products, such as 6-methylnicotine (6MN) in SPREE BAR (aka Metatine™), presents regulatory and public health challenges. Although SPREE BAR is already in the marketplace, little is known about its potential cardiovascular toxicity. Hypothesis: Because 6MN is structurally similar to nicotine (it has a single added methyl group at 6-position of the pyridine ring), we hypothesized that S -6MN would have similar vascular effects as S -nicotine. Methods: To test our hypothesis, we compared the direct vasoactive effects of S -6MN with S -nicotine in isolated murine blood vessels including aorta and superior mesenteric artery (SMA). Because S -6MN is found in SPREE BAR, we also tested for direct vasoactivity of SPREE BAR Blue Razz Ice E-liquid. Results: S -6MN induced a concentration-and NO-dependent relaxation (EC 50 : 0.9±0.4 µM, n=5) in phenylephrine (PE)-precontracted SMA that was more potent than that of nicotine (EC 50 : 2.7±0.1 µM, n=4; P<0.05, t -test) and sensitive to LNAME. Similarly, either a 5- or 60-min incubation of aorta with S -6MN (300 mM) induced endothelial dysfunction (ED) -- measured as an impaired acetylcholine (ACh)-induced relaxation. For example, the Control ACh relaxation was -86.3±3.4% (n=4) whereas incubation with 300 mM S -6MN diminished ACh relaxation (-69.2±5.6%, n=4; p<0.05 vs Control) and S- nicotine did not alter ACh relaxation (-77.9±2.2%, n=4) indicating that, in both blood vessels, S -6MN was more potent than S -nicotine. Neither S -6MN nor S- nicotine had any effect on the relaxation induced by an NO donor (i.e., sodium nitroprusside). Surprisingly, direct addition of SPREE BAR E-liquid to isolated aorta resulted in significantly and profoundly impaired contractility of either phenylephrine or high potassium – an effect that was slowly reversible with repeated washout. This effect was not observed with either S -6MN or S -nicotine indicating another component is present in SPREE BAR Blue Razz Ice E-liquid that has a profound inhibitory action in blood vessels. Conclusions: These findings reveal that S -6MN, a nicotine analog, has more potent vasoactivity than S -nicotine. As S -6MN induced ED in vitro , it potentially could elevate cardiovascular disease risk in users of products containing 6MN. These data stress the need for immediate FDA regulatory oversight of new and emerging non-nicotine containing products.