Mechanical and Crystallographic Analysis of Cholesterol Crystals Puncturing Biological Membranes

Flexible molecular crystals for optoelectronic applications

The cornerstones of the advancement of flexible optoelectronics are the design, preparation, and utilization of novel materials with favorable mechanical and advanced optoelectronic properties. Molecular crystalline materials have emerged as a class of underexplored yet promising materials due to the reduced grain boundaries and defects anticipated to provide enhanced photoelectric characteristics. An inherent drawback that has precluded wider implementation of molecular crystals thus far, however, has been their brittleness, which renders them incapable of ensuring mechanical compliance required for even simple elastic or plastic deformation of the device. It is perplexing that despite a plethora of reports that have in the meantime become available underpinning the flexibility of molecular crystals, the "discovery" of elastically or plastically deformable crystals remains limited to cases of serendipitous and laborious trial-and-error approaches, a situation that calls for a systematic and thorough assessment of these properties and their correlation with the structure. This review provides a comprehensive and concise overview of the current understanding of the origins of crystal flexibility, the working mechanisms of deformations such as plastic and elastic bending behaviors, and insights into the examples of flexible molecular crystals, specifically concerning photoelectronic changes that occur in deformed crystals. We hope this summary will provide a reference for future experimental and computational efforts with flexible molecular crystals aimed towards improving their mechanical behavior and optoelectronic properties, ultimately intending to advance the flexible optoelectronic technology.

Cholesterol crystals induce mechanical trauma, inflammation, and neo-vascularization in solid cancers as in atherosclerosis

Background and aims

Cancer and atherosclerosis share common risk factors and inflammatory pathways that promote their proliferation via vascular endothelial growth factor (VEGF). Because CCs cause mechanical injury and inflammation in atherosclerosis, we investigated their presence in solid cancers and their activation of IL-1β, VEGF, CD44, and Ubiquityl-Histone H2B (Ub-H2B), that promote cancer growth.

Methods

Tumor specimens from eleven different types of human cancers and atherosclerotic plaques were assessed for CCs, free cholesterol content and IL1-β by microscopy, immunohistochemistry, and biochemical analysis. Breast and colon cancer cell lines were cultured with and without CCs to select for expression of VEGF, CD44, and Ub-H2B. Western blot and immunofluorescence were performed on cells to assess the effect of CCs on signaling pathways.

Results

Cancers displayed higher CC content (+2.29 ± 0.74 vs +1.46 ± 0.84, p < 0.0001), distribution (5.06 ± 3.13 vs 2.86 ± 2.18, p < 0.001) and free cholesterol (3.63 ± 4.02 vs 1.52 ± 0.56 μg/mg, p < 0.01) than cancer free marginal tissues and similarly for atherosclerotic plaques and margins (+2.31 ± 0.51 vs +1.44 ± 0.79, p < 0.02; 14.0 ± 5.74 vs 8.14 ± 5.52, p < 0.03; 0.19 ± 0.14 vs 0.09 ± 0.04 μg/mg, p < 0.02) respectively. Cancers displayed significantly increased expression of IL1-β compared to marginal tissues. CCs treated cancer cells had increased expression of VEGF, CD44, and Ub-H2B compared to control. By microscopy, CCs were found perforating cancer tumors similar to plaque rupture.

Conclusions

These findings suggest that CCs can induce trauma and activate cytokines that enhance cancer growth as in atherosclerosis.

Impact of molecular interactions between hydrophilic phytosterol glycosyl derivatives and bile salts on the micellar solubility of cholesterol

Hydrophilic phytosterol glycosyl derivatives are synthetic phytosterol analogues by coupling with the glycosyl moiety to improve the water solubility and bioaccessibility of free phytosterols. The aim of this study is to clarify the molecular interaction of phytosterol glycosyl derivatives with bile salts and the consequent impact on cholesterol solubilization. Sharp nonlinear decrease in the micellar solubility of cholesterol and accompanying changes in particle size, zeta potential and microtopography of mixed micelles were observed when phytosterol glycosyl derivatives were introduced in cholesterol-loaded bile salt micelles. These results suggested that β-sitosterol glycosyl derivatives molecules indeed participated in the formation of mixed micelles. Further, nuclear magnetic resonance showed that the structural change of mixed micelles was caused by the insertion of β-sitosterol glycosyl derivatives via hydrogen bonds with sodium taurocholate, which resulted in the low cholesterol solubilization. Moreover, the hydrogen-bond interactions were apparently influenced by the glycosyl moiety of β-sitosterol glycosyl derivatives. These molecular mechanisms may contribute to the development of cholesterol-absorption inhibitors.

Interaction between bacteria and cholesterol crystals: Implications for endocarditis and atherosclerosis

Background

The interaction between pathogenic bacteria and cholesterol crystals (CCs) has not been investigated. However, CCs are found extensively in atherosclerotic plaques and sclerotic cardiac valves. Interactions between pathogenic bacteria and CCs could provide insights into destabilization of atherosclerotic plaques and bacterial adhesion to cardiac valves.

Methods

Staphylococcus aureus and Pseudomonas aeruginosa were used to assess in vitro bacterial adhesion to CCs and proliferation in the presence of CCs compared to plastic microspheres and glass shards as controls. Ex vivo studies evaluated bacterial adhesion to atherosclerotic rabbit arteries compared to normal arteries and human atherosclerotic carotid plaques compared to normal carotid arteries. Scanning electron microscopy (SEM) was used to visualize bacterial adhesion to CCs and confocal microscopy was used to detect cholesterol binding to bacteria grown in the presence or absence of CCs.

Results

In vitro, S. aureus and P. aeruginosa displayed significantly greater adhesion, 36% (p<0.0001) and 89% (p<0.0001), respectively, and growth upon exposure to CCs compared to microspheres or glass shards. Rabbit and human atherosclerotic arteries contained significantly greater bacterial burdens compared to controls (4× (p<0.0004); 3× (p<0.019), respectively. SEM demonstrated that bacteria adhered and appeared to degrade CCs. Consistent with this, confocal microscopy indicated increased cholesterol bound to the bacterial cells.

Conclusions

This study is the first to demonstrate an interaction between bacteria and CCs showing that bacteria dissolve and bind to CCs. This interaction helps to elucidate adhesion of bacteria to sclerotic valves and atherosclerotic plaques that may contribute to endocarditis and plaque destabilization.

Cholesterol induced heart valve inflammation and injury: efficacy of cholesterol lowering treatment

BACKGROUND

Heart valves often undergo a degenerative process leading to mechanical dysfunction that requires valve replacement. This process has been compared with atherosclerosis because of shared pathology and risk factors. In this study, we aimed to elucidate the role of inflammation triggered by cholesterol infiltration and cholesterol crystals formation causing mechanical and biochemical injury in heart valves.

METHODS

Human and atherosclerotic rabbit heart valves were evaluated. New Zealand White male rabbits were fed an enriched cholesterol diet alone or with simvastatin and ezetimibe simultaneous or after 6 months of initiating cholesterol diet. Inflammation was measured using C-reactive protein (CRP) and RAM 11 of tissue macrophage content. Cholesterol crystal presence and content in valves was evaluated using scanning electron microscopy.

RESULTS

Cholesterol diet alone induced cholesterol infiltration of valves with associated increased inflammation. Tissue cholesterol, CRP levels and RAM 11 were significantly lower in simvastatin and ezetimibe rabbit groups compared with cholesterol diet alone. However, the treatment was effective only when initiated with a cholesterol diet but not after lipid infiltration in valves. Aortic valve cholesterol content was significantly greater than all other cardiac valves. Extensive amounts of cholesterol crystals were noted in rabbit valves on cholesterol diet and in diseased human valves.

CONCLUSIONS

Prevention of valve infiltration with cholesterol and reduced inflammation by simvastatin and ezetimibe was effective only when given during the initiation of high cholesterol diet but was not effective when given following infiltration of cholesterol into the valve matrix.