Search Results (3)

Background: The sequential processes that lead to pathological cardiovascular remodeling are unclear. From the multiple components that constitute the cardiovascular system, it is believed that vascular smooth muscle cells (SMCs) play a central role. SMCs have the ability to differentiate into a proliferative and migratory phenotype which supports vessel homeostasis. These synthetic SMCs display increased oxidative stress, secrete extracellular vesicles, and promote vascular calcification. SMC driven calcification is regulated by vitamin K-dependent matrix Gla protein (MGP). Since vitamin K promotes energy to bacteria, and vitamin K can scavenge free radicals and reduce oxidative stress, we reasoned that vitamin K can have non-canonical functions to decrease vascular calcification. Aim: We investigated the potential of vitamin K to reduce oxidative stress and support ATP synthesis in SMCs. Methods: Primary SMCs were cultured in M199 medium containing 20% FBS and 1% P/S. Warfarin (vitamin K antagonist; 10 microM) and MK-7 (10 microM) were added and ATP (luminescence), oxidative stress (DCFDA) and extracellular vesicles (EV: CD63-CD81-PE bead-assay) were measured. Results: We show that SMCs take up MK-7 very efficiently. Interference with vitamin K metabolism using warfarin resulted in increased intracellular oxidative stress (4 fold; p < 0.005) and EV release (2.5 fold; p < 0.01). The addition of MK-7 counteracts intracellular oxidative stress, both under normal conditions (2 fold; p < 0.05), as well as under warfarin-induced oxidative stress conditions (4 fold; p < 0.001). Additionally, chronic hypoxia induced by the HIF1a stabilizing cobalt chloride induced increased oxidative stress (2.5 fold; p < 0.01), and MK-7 could counteract oxidative stress, indicative for improved mitochondrial activity. Finally, MK-7 increased ATP production as compared to vehicle (15%; p < 0.05), even in the presence of warfarin. Conclusion: Our experiments show that in primary human SMCs, MK-7 lowers oxidative stress and EV release and increases ATP production. This pathway points to a non-canonical role of MK-7 in the prevention of vascular calcification, unrelated to its canonical role as a cofactor for the posttranslational modification of MGP. Full article

Dry pomegranate peel was extracted with acetone and the extract was added to a Phillips type polyethylene. The concentration of the extract was changed from 0 to 1000 ppm in six steps and stabilization efficiency was checked by the multiple extrusion of the polymer followed by the characterization of chemical structure, processing, and residual stability. The results confirmed the excellent processing stabilization efficiency of the extract, but also the poor long-term stability of PE containing it in accordance with previously published results. The extract is amorphous and its solubility is relatively large in the polymer; thus, these factors cannot be the reason for the poor stabilization efficiency in an oxygen-rich environment. Chemical factors like the self-interaction of the polyphenol molecules, the stability of the radicals forming after hydrogen abstraction, and the lack of hydrogens with the necessary reactivity must be considered during the evaluation of the efficiency of the extract. These factors as well as the insufficient number of active hydrogens hinder the reaction of the additive molecules with oxygen-centered radicals, thus leading to inferior long-term stability. The extract can be used for the processing stabilization of polymers, but for applications requiring long-term stability, it must be combined with other natural antioxidants like flavonoids or Vitamin E. Full article

Given the long-term problem of polyethylene wear, medical interest in the new improved cross-linked polyethylene (XLPE), with or without the adding of vitamin E, has risen. The main aim of this study is to gain further insights into the mutual effects of radiation cross-linking and addition of vitamin E on the wear performance of ultra-high-molecular-weight polyethylene (UHMWPE). We tested four different batches of polyethylene (namely, a standard one, a vitamin E-stabilized, and two cross-linked) in a hip joint simulator for five million cycles where bovine calf serum was used as lubricant. The acetabular cups were then analyzed using a confocal profilometer to characterize the surface topography. Moreover; the cups were analyzed by using Fourier Transformed Infrared Spectroscopy and Differential Scanning Calorimetry in order to assess the chemical characteristics of the pristine materials. Comparing the different cups’ configuration, mass loss was found to be higher for standard polyethylene than for the other combinations. Mass loss negatively correlated to the cross-link density of the polyethylenes. None of the tested formulations showed evidence of oxidative degradation. We found no correlation between roughness parameters and wear. Furthermore, we found significantly differences in the wear behavior of all the acetabular cups. XLPEs exhibited lower weight loss, which has potential for reduced wear and decreased osteolysis. However, surface topography revealed smoother surfaces of the standard and vitamin E stabilized polyethylene than on the cross-linked samples. This observation suggests incipient crack generations on the rough and scratched surfaces of the cross-linked polyethylene liners. Full article