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“N-of-1,” or single subject, clinical trials seek to determine if an intervention strategy is more efficacious for an individual than an alternative based on an objective, empirical, and controlled study. The design of such trials is typically rooted in a simple crossover strategy with multiple intervention response evaluation periods. The effect of serial correlation between measurements, the number of evaluation periods, the use of washout periods, heteroscedasticity (i.e., unequal variances among responses to the interventions) and intervention-associated carry-over phenomena on the power of such studies is crucially important for putting the yield and feasibility of N-of-1 trial designs into context. We evaluated the effect of these phenomena on the power of different designs for N-of-1 trials using analytical theory based on standard likelihood principles assuming an autoregressive lag 1, i.e., AR(1), serial correlation structure among the measurements as well as simulation studies. By evaluating the power to detect effects in many different settings, we show that the influence of serial correlation and heteroscedasticity on power can be substantial, but can also be mitigated to some degree through the use of appropriate multiple evaluation periods. We also show that the detection of certain types of carry-over effects can be heavily influenced by design considerations as well.

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Oxidized low-density lipoprotein (oxLDL) induced a foam-cell-like phenotype of the vascular smooth muscle cells (VSMCs), leading to the inflammatory responses incorporating Toll-like receptor- (Tlr-) mediated cellular alterations. However, the role of Tlr4 in foam cell formation and underlying molecular pathways has not been comprehensively elucidated. To further investigate the mechanism, VSMCs were incubated with different doses of oxLDL, and then, the lipid, reactive oxygen species (ROS) accumulation, Tlr family genes, and the foam cell phenotype were explored. We observed that oxLDL induced foam cell-like phenotype in VSMCs and led to lipid and ROS accumulation in a dose-dependent manner. Furthermore, in the Tlr family, Tlr4 demonstrated the strongest upregulation under oxLDL stimulation. Simultaneously, oxLDL induced activation of Src, higher expression of Nox2, and lower expression of Mnsod, Sirt1, and Sirt3. By interfering the TLR4 expression, the phenotype alteration, lipid accumulation in VSMCs, and Src kinase activation induced by oxLDL were abolished. After interfering Src activation, the oxLDL-induced lipid accumulation and foam cell phenotype in VSMCs were also alleviated. Furthermore, the ROS accumulation, upregulated Nox2 expression, downregulated Sirt1, Sirt3, and Mnsod expression in VSMCs under oxLDL stimulation were also relieved after the knockdown of Tlr4. Additionally, overexpression of Sirt1 and Sirt3 ameliorated the ROS accumulation and foam cell-like marker expression in VSMCs. These results demonstrated that beyond its familiar role in regulating inflammation response, Tlr4 is a critical regulator in oxLDL-induced foam cell formation in VSMCs via regulating Src kinase activation as well as Sirt1 and Sirt3 expression.

Background: Oxidized low-density lipoprotein (oxLDL) induced a foam-cell like phenotype of the vascular smooth muscle cells (VSMCs), leading to the inflammatory responses incorporating Toll-like receptors (Tlrs)-mediated cellular alterations. We previously found that Tlr4 participated in inflammation response in VSMCs under oxLDL stimulation. However, the role of Tlr4 in foam-cell formation and underlying molecular pathways has not been comprehensively elucidated. This study aimed to investigate the role of Tlr4-mediated mechanisms in oxLDL induced foam-cell formation within VSMCs. Methods: After incubated with different dose of oxLDL, the lipid, reactive oxygen species (ROS) accumulation and foam-cell phenotype of the VSMCs were detected. The alteration of Tlr family, ROS and lipid accumulation regulators including the Src kinase, Nox2, Nox4, Mnsod and sirtuins were measured. Then the Tlr4 was knock down and underlying cellular change and altered molecules were detected. Results: We showed that oxLDL induced foam-cell like phenotype in VSMCs and led to lipid and ROS accumulation in a dose-dependent manner. OxLDL induced the strongest upregulation of Tlr4 in the Tlrs family and initiated change of Src activation, Nox2, Mnsod, sirt1 and sirt3 expression. The effect of oxLDL was abolished by Tlr4 knockdown. Furthermore, knocking down of Tlr4 reduced Src activation and led to restored Sirt1/Sirt3 expression. Moreover, inhibiting or knocking down the Src kinase diminished lipid accumulation in VSMCs under oxLDL treatment. And overexpression of Sirt1/3 relieved the oxLDL induced ROS accumulation and foam-cell phenotype in VSMCs.Conclusions: These results demonstrated that Tlr4 is a critical regulator in oxLDL induced foam cell formation of VSMCs via mediating Src kinase as well as Sirt1 and Sirt3. Beyond the role of Tlr4 in inflammation response of VSMCs, we provide an integrated mechanism about TLR4 in VSMCs phenotype transition under oxLDL stimulation.