Effect of serum albumin on vascular smooth muscle metabolism

Effect of long term palmitate treatment on osteogenic differentiation of human mesenchymal stromal cells - Impact of albumin

The long-term effects of palmitate (PA) on osteogenic differentiation capacity of human mesenchymal stromal cells (hMSCs) were investigated by cultivating the cells in osteogenic differentiation medium (O-w/o) and osteogenic medium containing PA (O-BSA-PA) for 21 days. Osteogenic medium containing BSA (O-BSA) was used as a control. By means of rt-qPCR, successful osteogenic differentiation was observed in the O-w/o regarding the levels of osteogenic and cell-communication related genes (OCN, Col1, BMP2, ITGA1, ITGB1, Cx43, sp1) in contrast to expression levels observed in cells incubated within basal medium. However, in the O-BSA, these genes were found to have decreased significantly. In cases of Cx43 and sp1, PA significantly reinforced the reductive effect of BSA alone. O-BSA notably decreased glucose and pyruvate consumption, whereas glutamine consumption significantly increased. In comparison to O-BSA addition of PA significantly reduced glycolysis and glutaminolysis. ToF-SIMS analysis confirmed increased incorporation of supplemented deuterated PA into the cell membranes, while the overall PA-concentration remained unchanged compared to cells incubated in the O-BSA and O-w/o. Therefore, the effects on gene expression and the metabolism did not result from the membrane alterations, but may have risen from inter- and intracellular effects brought on by BSA and PA.

Albumin-like proteins are critical regulators of vascular redox signaling

This laboratory previously identified an albumin-like protein (denoted as p70) as a component of the macromolecular complex assembled within the 5'-regulatory region of redox-sensitive genes in vascular smooth muscle cells (vSMCs). Here we show that p70 is present in the cytosolic and nuclear compartments of vSMCs and dynamically responsive to redox status. Intense cytoplasmic and perinuclear staining, coupled with enhanced nuclear localization, was observed in vSMCs, but not HepG2 cells, treated with benzo(a)pyrene (BaP), H(2)O(2), or N-acetylcysteine, agents known to modulate redox status. 3' RACE indicated that p70 is not generated as a product of endogenous gene expression, but rather taken up from the extracellular compartment. While p70 was undetectable in cells grown for 24 hours under serum-free conditions, cell-associated, acid-resistant albumin was detected 30 min after the addition of exogenous albumin. vSMCs incubated at 4°C with 100  μ g/mL unlabeled BSA and 10  μ g/mL FITC-BSA for 60 minutes and switched to 37°C to examine temperature-sensitive label uptake showed punctate structures throughout the cell consistent with albumin internalization at the higher temperature. Albumin was found to influence redox-signaling, as evidenced by modulation of cyp1a1 gsta1 and Ha-ras gene inducibility. Together, these results implicate albumin and albumin-like proteins as critical regulators of vascular redox signaling.

Effects of L-Ornithine on Metabolic Processes of the Urea Cycle in Human Keratinocytes

The complex metabolic function of L-ornithine has led to a great interest in studying its pharmacotherapeutic potential. L-Ornithine is known to be crucial for the metabolism of keratinocytes, especially in the synthesis of urea, polyamines and precursors of collagen synthesis. In this study, we investigated in vitro the cytotoxicity of L-ornithine, and its influence on urea synthesis and arginase expression in primary human keratinocytes. L-Ornithine (> or =1 mM) induced a decrease in the de novo urea synthesis of keratinocytes and an increase (> or =10 mM) in the expression of the urea-generating enzyme arginase. Up to 20 mM, L-ornithine showed no cytotoxic potential, whereas higher concentrations induced apoptosis in keratinocytes in a concentration- and time-dependent manner.

Identification of albumin precursor protein, Phi AP3, and alpha-smooth muscle actin as novel components of redox sensing machinery in vascular smooth muscle cells

Aerobic organisms are continually subjected to environmental stressors that compromise redox homeostasis and induce cellular injury. In vascular smooth muscle cells (vSMCs), the activation/repression of redox-regulated genes after environmental stress often involves protein binding to cis-acting antioxidant response elements (AREs). The present study was conducted to identify proteins that participate in redox-regulated protein binding to human c-Ha-ras and mouse glutathione S-transferase A1 AREs in vSMCs after oxidant injury. Challenge of vSMCs with 0.3 or 3 microM hydrogen peroxide, 3-methylcholanthrene, benzo[a]pyrene-7,8-diol, 3-hydroxy benzo[a]pyrene, and benzo[a]pyrene-3,6-quinone induced concentration-related increases in ARE protein binding. The profiles of ARE complex assembly were comparable, but exhibited chemical specificity. Pretreatment with 0.5 mM N-acetylcysteine inhibited activation of ARE protein binding in hydrogen peroxide-treated cells. Preparative electrophoretic mobility shift assays coupled to Western analysis identified NF-E2-related proteins 1 and 2 and JunD in complexes assembled on AREs. Polyethylenimine affinity and sequence-specific serial immobilized DNA affinity chromatography followed by N-terminal sequencing identified albumin precursor protein, phi AP3, and alpha-smooth muscle actin as members of the ARE signaling pathway. Sequence analysis of albumin protein revealed homology to the redox-regulated transcription factors Bach1 and 2, as well as cytoskeletal and molecular motor proteins. These results implicate albumin precursor protein, phi AP3, and alpha-smooth muscle actin as participants in redox sensing in vSMCs, and suggest that protein complex assembly involves interactions between leucine zipper and zinc finger transcription factors with cytoskeletal proteins.