Nicotine does not modify LPS induced vascular dysfunction in vitro

Neil Cartwright, Timothy W Evans and Jane A Mitchell. Department of Critical Care, National Heart and Lung Institute, Imperial College, London SW3 6LY.

The vagus nerve has been implicated in modulating the systemic inflammatory response to endotoxin through an anti-inflammatory pathway mediated by the nicotinic acetylcholinergic receptor (Wang et al., 2003) : Vagal nerve stimulation can prevent endotoxic shock (Borovikova et al., 2000) . Here we investigate the effect of nicotine on in vitro vascular dysfunction due to lipopolysaccharide (LPS).

Male wild-type C57BK/6 mice (29-30g) were killed by overdose of CO2, and the descending thoracic aortae removed. Two rings of aortae, were cultured in DMEM alone (control) and two in DMEM containing nicotine (10 μM) for 30 minutes. After 30 minutes LPS (10 μg/ml) was added to one control vessels and one vessel treated with nicotine. Following culture for 24h with or without LPS, aortic rings were mounted on a DMT wire myograph in physiological saline solution containing L-arginine (10-3 M) at 37°C bubbled with 5%CO2, 95%O2 (PSS). Phenylephrine (PE) was added cumulatively (10-8–3x10-6 M) and isometric force was measured. Tension was calculated from vessel length. Results were analysed by 2-way ANOVA, p<0.05 was considered significant.

Figure 1. Culture of murine aortae with LPS caused hyporesponsiveness to phenylephrine. However pre-incubation with nicotine did not modify responses seen in control vessels nor those incubated with LPS.

LPS induced significant hyporesponsiveness to phenylephrine in vessels treated with nicotine (n=5, p<0.001) and those cultured in DMEM without nicotine (n=5, p<0.001). There was no significant difference in the contractility of vessels cultured without LPS (with and without nicotine; n=5, p=0.3859). Similarly, there was no significant difference in contractility between LPS treated vessels treated with and without nicotine (n=5, p=0.6720) (figure 1).

We conclude that in vitro culture of vessels with nicotine does not effect contractility of vessels to phenylephrine. Furthermore, the degree of hyporesponsiveness caused by culture with LPS is not influenced by the presence of nicotine. The mechanism by which nicotine modifies shock caused by endotoxaemia is not by direct effects on the vasculature or responses of vessels to pathogens.

Borovikova, L .V ., et al. (2000). Nature, 405, 458-62.
Wang, H ., et al. (2004). Nature Med., 10, 1216-1221.

This work was funded by the British Heart Foundation