This and the other prior studies in this area have taken what could be considered a cross-sectional approach and examined differences between smokers and non-smokers. In terms of the use of this approach for determining the biological effects of tobacco products with modified toxicant yields, an examination of whether these models possess the ability to discriminate between the sera of individuals before and after either they quit smoking or switch to a reduced exposure tobacco product

is required. Regardless of the method of exposure, an area that has find more received little attention is that of the duration of exposure to cigarette smoke. In the majority of in vitro models, cells are exposed to cigarette smoke extracts or to sera for short periods, typically around 2–48 h. Smoking-related

cardiovascular disease is a disorder which manifests itself over a prolonged period of time and following many years of exposure to cigarette smoke. When the chronic nature of the disease is taken into consideration, the limitations of such an acute exposure period must be addressed. Technical limitations restrict the length of time in which cells can be cultured in vitro and this impacts our ability to expose Venetoclax cells to cigarette smoke for more prolonged periods of time. It is also noteworthy that most experiments involving cigarette smoke exposure apply a single dose of a cigarette smoke extract to the cells. Again, the nature

of the in vivo exposure to cigarette smoke in a smoker, in which the vascular system is exposed to toxicants for brief periods many times a day, may not be adequately reflected in such simple models. When seeking to improve cigarette smoke exposures for in vitro models that better mimic in vivo conditions, insight can perhaps be gained Ergoloid from models of other cardiovascular disease risk factors. One such risk factor for example is obstructive sleep apnoea, a disorder in which upper airway obstruction causes periodic and repetitive decreases in blood oxygen saturation during sleep ( Parish and Somers, 2004). Similar to cigarette smoking, this repeated hypoxic insult may induce oxidative stress in the cardiovascular system, potentially explaining why obstructive sleep apnoea is strongly associated with atherosclerotic cardiovascular disease ( Lavie, 2003, Parish and Somers, 2004 and Priou et al., 2010). In vitro models of obstructive sleep apnoea have utilised the cyclical nature of the hypoxic insult to mimic that seen in vivo. For example, Ryan et al., (2005) demonstrated that periodic exposure of HeLa cells to hypoxia provided a stronger stimulus for the activation of nuclear factor kappa-light-chain-enhancer of activated B cells (NF-κB), an oxidative stress-responsive transcription factor, than sustained hypoxia.