Synchronization of Circadian Per2 Rhythms and HSF1-BMAL1:CLOCK Interaction in Mouse Fibroblasts after Short-Term Heat Shock Pulse

Circadian rhythms are the general physiological processes of adaptation to daily environmental changes, such as the temperature cycle. A change in temperature is a resetting cue for mammalian circadian oscillators, which are possibly regulated by the heat shock (HS) pathway. The HS response (HSR) is a universal process that provides protection against stressful conditions, which promote protein-denaturation. Heat shock factor 1 (HSF1) is essential for HSR. In the study presented here, we investigated whether a short-term HS pulse can reset circadian rhythms. Circadian Per2 rhythm and HSF1-mediated gene expression were monitored by a real-time bioluminescence assay for mPer2 promoter-driven luciferase and HS element (HSE; HSF1-binding site)-driven luciferase activity, respectively. By an optimal duration HS pulse (43°C for approximately 30 minutes), circadian Per2 rhythm was observed in the whole mouse fibroblast culture, probably indicating the synchronization of the phases of each cell. This rhythm was preceded by an acute elevation in mPer2 and HSF1-mediated gene expression. Mutations in the two predicted HSE sites adjacent (one of them proximally) to the E-box in the mPer2 promoter dramatically abolished circadian mPer2 rhythm. Circadian Per2 gene/protein expression was not observed in HSF1-deficient cells. These findings demonstrate that HSF1 is essential to the synchronization of circadian rhythms by the HS pulse. Importantly, the interaction between HSF1 and BMAL1:CLOCK heterodimer, a central circadian transcription factor, was observed after the HS pulse. These findings reveal that even a short-term HS pulse can reset circadian rhythms and cause the HSF1-BMAL1:CLOCK interaction, suggesting the pivotal role of crosstalk between the mammalian circadian and HSR systems

A histological and clinical comparison of new and conventional integrated backscatter intravascular ultrasound (IB-IVUS)

Background: While the utilization of integrated backscatter intravascular ultrasound (IB-IVUS) for the quantitative in vivo assessment of coronary plaque continues to grow, the validity of IB-IVUS images obtained from newly developed and conventional systems remains uncertain. Methods and Results: To assess the accuracy and reliability of a newly developed IB-IVUS system (VISIWAVE) as compared to the conventional system (Clearview), we compared quantitative IB-IVUS plaque characteristics in the 2 systems using 125 post-mortem specimens from 26 coronary arteries in 11 cadavers, as well as using 200 clinical plaques in 32 patients undergoing coronary intervention. The overall agreement between the histological and IB-IVUS diagnoses using VISIWAVE (Cohen's κ=0.82, 95%CI: 0.73-0.90) was similar to that using Clearview (Cohen's κ=0.80, 95%CI: 0.71-0.89). The 2 systems also demonstrated comparably high sensitivity and specificity. In the direct comparison, the overall agreement between IB-IVUS diagnoses using VISIWAVE and Clearview was also excellent (Cohen's κ=0.87, 95%CI: 0.78-0.95). In the clinical comparison, measured plaque dimensions were similar (VISIWAVE: 8.27±3.46 mm 2 vs. Clearview; 8.31±3.46 mm 2, P=0.44) and there was strong concordance between both greyscale and IB-IVUS parameters. Conclusions: There was close agreement of analyzed results in both systems when compared with the gold standard of histology. Both systems are able to reliably and accurately characterize coronary plaque and thereby make a valuable contribution to our understanding of atherosclerosis