The conformational changes of a calcium transport ATPase were investigated with molecular dynamics (MD) simulations as well as fluorescence resonance energy transfer (FRET) measurements to determine ...the significance of a discrete structural element for regulation of the conformational dynamics of the transport cycle. Previous MD simulations indicated that a loop in the cytosolic domain of the SERCA calcium transporter facilitates an open-to-closed structural transition. To investigate the significance of this structural element, we performed additional MD simulations and new biophysical measurements of SERCA structure and function. Rationally designed in silico mutations of three acidic residues of the loop decreased SERCA domain–domain contacts and increased domain–domain separation distances. Principal component analysis of MD simulations suggested decreased sampling of compact conformations upon N-loop mutagenesis. Deficits in headpiece structural dynamics were also detected by measuring intramolecular FRET of a Cer–YFP–SERCA construct (2-color SERCA). Compared with WT, the mutated 2-color SERCA shows a partial FRET response to calcium, whereas retaining full responsiveness to the inhibitor thapsigargin. Functional measurements showed that the mutated transporter still hydrolyzes ATP and transports calcium, but that maximal enzyme activity is reduced while maintaining similar calcium affinity. In live cells, calcium elevations resulted in concomitant FRET changes as the population of WT 2-color SERCA molecules redistributed among intermediates of the transport cycle. Our results provide novel insights on how the population of SERCA pumps responds to dynamic changes in intracellular calcium.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
Increased arterial stiffness is associated with atherosclerosis in humans, but there have been limited animal studies investigating the relationship between these factors. We bred elastin wildtype ...(Eln+/+) and heterozygous (Eln+/-) mice to apolipoprotein E wildtype (Apoe+/+) and knockout (Apoe-/-) mice and fed them normal diet (ND) or Western diet (WD) for 12 weeks. Eln+/- mice have increased arterial stiffness. Apoe-/- mice develop atherosclerosis on ND that is accelerated by WD. It has been reported that Apoe-/- mice have increased arterial stiffness and that the increased stiffness may play a role in atherosclerotic plaque progression. We found that Eln+/+Apoe-/- arterial stiffness is similar to Eln+/+Apoe+/+ mice at physiologic pressures, suggesting that changes in stiffness do not play a role in atherosclerotic plaque progression in Apoe-/- mice. We found that Eln+/-Apoe-/- mice have increased structural arterial stiffness compared to Eln+/+Apoe-/- mice, but they only have increased amounts of ascending aortic plaque on ND, not WD. The results suggest a change in atherosclerosis progression but not end stage disease in Eln+/-Apoe-/- mice due to increased arterial stiffness. Possible contributing factors include increased blood pressure and changes in circulating levels of interleukin-6 (IL6) and transforming growth factor beta 1 (TGF-β1) that are also associated with Eln+/- genotype.
Abstract Background and aims High blood pressure and reduced aortic compliance are associated with increased atherosclerotic plaque accumulation in humans. Animal studies support these associations, ...but additional factors, such as fragmented elastic fibers, are present in most previous animal studies. Elastin heterozygous ( Eln+/− ) mice have high blood pressure and reduced aortic compliance, with no evidence of elastic fiber fragmentation and represent an appropriate model to directly investigate the effects of these factors on atherosclerosis. Methods and results Eln +/− and Eln +/+ mice were crossed with low density lipoprotein receptor knockout ( Ldlr−/− ) and wild-type ( Ldlr +/+) mice and fed normal or Western diet (WD) for 16 weeks. We hypothesized that on WD, Eln +/ −Ldlr−/− mice with high blood pressure and reduced aortic compliance would have increased atherosclerotic plaque accumulation compared to Eln +/+ Ldlr−/− mice. We measured serum cholesterol and cytokine levels, blood pressure, aortic compliance, and plaque accumulation. Contrary to our hypothesis, we found that on WD, Eln +/ −Ldlr−/− mice do not have increased plaque accumulation compared to Eln +/+ Ldlr−/− mice. At the aortic root, there are no significant differences in plaque area between Eln +/ −Ldlr−/− and Eln +/+ Ldlr−/− mice on WD (p = 0.89), while in the ascending aorta, Eln +/ −Ldlr−/− mice on WD have 29% less normalized plaque area than Eln +/+ Ldlr−/− mice on WD (p = 0.009). Conclusion Using an atherogenic mouse model, we conclude that increased blood pressure and reduced aortic compliance are not direct causes of increased aortic plaque accumulation. We propose that additional insults, such as fragmentation of elastic fibers, are necessary to alter plaque accumulation.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Numerous diseases have been linked to genetic mutations that lead to reduced amounts or disorganization of arterial elastic fibres. Previous work has shown that mice with reduced amounts of elastin ...(Eln+/−) are able to live a normal lifespan through cardiovascular adaptations, including changes in haemodynamic stresses, arterial geometry and arterial wall mechanics. It is not known if the timeline and presence of these adaptations are consistent in other mouse models of elastic fibre disease, such as those caused by the absence of fibulin-5 expression (Fbln5−/−). Adult Fbln5−/− mice have disorganized elastic fibres, decreased arterial compliance and high blood pressure. We examined mechanical behaviour of the aorta in Fbln5−/− mice through early maturation when the elastic fibres are being assembled. We found that the physiologic circumferential stretch, stress and modulus of Fbln5−/− aorta are maintained near wild-type levels. Constitutive modelling suggests that elastin contributions to the total stress are decreased, whereas collagen contributions are increased. Understanding how collagen fibre structure and mechanics compensate for defective elastic fibres to meet the mechanical requirements of the maturing aorta may help to better understand arterial remodelling in human elastinopathies.
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Background:
The differences in cardiovascular risk between males and females has been well established and the real difference (utilizing the natural log function) has been used to ...describe sex differences in incidents like motor vehicle accident rates. However, the “real difference” has not been applied to cardiovascular outcomes previously. The purpose of this study was to apply the “real difference” to cardiovascular death rates while evaluating the relationship between the “real difference” and established economic markers.
Methods:
OECD Statistics, a freely available online database, was accessed for data retrieval. Male and female cardiovascular death statistics (per 100,000) in all 38 OECD countries were acquired from the freely available online database, OECD Statistics. The real difference was calculated using Ln(Male CVD Rate) - Ln(Female CVD). A multivariate analysis was run to establish the relationships between different economic markers and the calculated “real difference”.
Results:
Mexico was found to have the smallest real difference at 0.211 while France had the largest real difference at 0.542. Figure 1 demonstrates the variation between real and raw difference for each country. Multi-variate analysis revealed a significant effect on real difference (
F
(32)=4.185, p<0.01) with 40% (R
2
=0.395) of the variation explained by the following factors- Estimated Female Earned Income (US$ PPP), Life Expectancy Gap, % of Women of Total Employment, Wage Gap, and Government Representation of Women.
Discussion:
The results of the multi-variate analysis demonstrate that sex disparities in cardiovascular death is related to the combined effects of multiple economic factors. The real difference is a valuable metric for assessing sex disparities and further studies should be conducted to further elucidate and account for the difference in CV mortality in different countries.
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