Examination of the use of human sera as an exposure agent for in vitro studies investigating the effects of cigarette smoking on cellular cardiovascular disease models.

In vitro models of smoking-related diseases and disease processes are valuable for mechanistic understanding and assessment of novel tobacco products. Many laboratories have used particulate phase or aqueous extracts of cigarette smoke as an exposure system for in vitro models. However, this may not be the most relevant method of exposing cells to smoke and its toxicants. Here we have examined the use of human serum as an exposure system. Cultured human umbilical vein endothelial cells were exposed in vitro to sera (50% dilution in culture media) from human volunteers (9 smokers; 10 non-smokers) for 20 h. Statistically-significant differential changes were detected in endothelial migration in an endothelial damage repair model, such that smokers' sera had an inhibitory effect on migration compared with sera from non-smokers (p<0.05). We further observed several statistically-significant differences in cardiovascular disease (CVD)-relevant gene expression between cells exposed to smokers' and non-smokers' sera, as well as differences in levels of cytokines secreted from endothelial cells. Our data demonstrate that human sera from smokers and non-smokers can differentially regulate endothelial function. We suggest that human serum provides a relevant exposure medium for in vitro studies assessing the impact of cigarette smoking on CVD risk potential.

Genetic control of lithium sensitivity and regulation of inositol biosynthetic genes.

Lithium (Li(+)) is a common treatment for bipolar mood disorder, a major psychiatric illness with a lifetime prevalence of more than 1%. Risk of bipolar disorder is heavily influenced by genetic predisposition, but is a complex genetic trait and, to date, genetic studies have provided little insight into its molecular origins. An alternative approach is to investigate the genetics of Li(+) sensitivity. Using the social amoeba Dictyostelium, we previously identified prolyl oligopeptidase (PO) as a modulator of Li(+) sensitivity. In a link to the clinic, PO enzyme activity is altered in bipolar disorder patients. Further studies demonstrated that PO is a negative regulator of inositol(1,4,5)trisphosphate (IP(3)) synthesis, a Li(+) sensitive intracellular signal. However, it was unclear how PO could influence either Li(+) sensitivity or risk of bipolar disorder. Here we show that in both Dictyostelium and cultured human cells PO acts via Multiple Inositol Polyphosphate Phosphatase (Mipp1) to control gene expression. This reveals a novel, gene regulatory network that modulates inositol metabolism and Li(+) sensitivity. Among its targets is the inositol monophosphatase gene IMPA2, which has also been associated with risk of bipolar disorder in some family studies, and our observations offer a cellular signalling pathway in which PO activity and IMPA2 gene expression converge.