43 research outputs found
Survival signaling elicited by 27-hydroxycholesterol through the combined modulation of cellular redox state and ERK/Akt phosphorylation
No full textThe oxysterol 27-hydroxycholesterol (27-OH) is increasingly considered to be involved in a variety of pathophysiological processes, having been shown to modulate cell proliferation and metabolism, and also to exert proinflammatory and proapoptotic effects. This study aimed to elucidate the molecular pathways whereby 27-OH may generate survival signals in cells of the macrophage lineage, and to clarify whether its known prooxidant effect is involved in that process. A net up-regulation of survival signaling, involving the extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase (PI3K)/Akt phosphorylation pathways, was observed in U937 promonocytic cells cultivated over time in the presence of a low micromolar concentration of the oxysterol. Interestingly, the up-regulation of both kinases was shown to be closely dependent on an early 27-OH-induced intracellular increase of reactive oxygen species (ROS). In turn, stimulation of ERK and PI3K/Akt both significantly quenched ROS steady state and markedly phosphorylated Bad, thereby determining a marked delay of the oxysterol׳s proapoptotic action. The 27-OH-induced survival pathways thus appear to be redox modulated and, if they occur within or nearby inflammatory cells during progression of chronic diseases such as cancer and atherosclerosis, they could significantly impact the growth and evolution of such diseases
Ex-527 docked to SIRT6, displayed less flexibility and remained in closer proximity to the hydrophobic pocket compared with Ex-527 of SIRT1.
No full text(A) RMSF of Ex-527 atoms in SIRT6-Ex-527 complex under high salt (HS) conditions (blue) showed lower flexibility, compared with its positive control, Ex-527 of SIRT1-Ex-527 complex (red) during 20 ns of MD simulations. Under low salt, Ex-527 of SIRT1 (green) had shown lower flexibility than Ex-527 of SIRT6 (gray), for most of the residues. (B) Name of all atoms of Ex-527 were given for clear representation of the results in (A). (C) The distance between the center of mass of Ex-527 and the center of mass of the hydrophobic pocket residues of SIRT6 under high salt concentration (blue) persisted around 7 to 10 Å range, while its corresponding positive control (red) had a clear shift from 6 to 12 Å after ~7 ns of MD simulations. Under low salt, distance between Ex-527 to SIRT6 (gray) even got shortened, while that of SIRT1 (green) was lengthened, compared with Ex-527 of SIRT6 under high salt (blue). (D) Distance distribution vs. distance of Ex-527 to the hydrophobic pockets of all complexes in all simulations were given for clear representation of the distance shifts during the MD simulations in (C). a.u. refers to the arbitrary units, indicating the number of times that each distance was encountered during the simulations. Results obtained from this figure was based on the trends shown and statistical analyses given in S6 Fig. Å: Angstrom, C: Carbon, O: Oxygen, N: Nitrogen, Cl: Chloride</p
Hydrophobic pockets of SIRT1 and SIRT6.
No full textComplexes obtained by docking the inhibitor, Ex-527, to the close proximity of hydrophobic pocket of SIRT1 (A) and to the analogous hydrophobic pocket of SIRT6 (B), were used to simulate the permenance of the binding of the inhibitor to the hydrophobic cluster amino acids. Each amino acid was shown for clear positioning of the pockets. SIRT6 hydrophobic pocket amino acids (B) were predicted based on the corresponding amino acids of SIRT1 (A): V113, I183, I59, F62, V68 of SIRT6 were selected based on similarity to I347, I411, I270, F273, I279 of SIRT1. F297, a member of SIRT1 hydrophobic pocket shown in (A), does not have a corresponding hydrophobic residue in SIRT6 structure (B). (C)(D) Alanine and glycine mutations of SIRT1 hydrophobic pocket residues showed destabilizing characteristic (positive ΔΔG values) similar to the mutations of SIRT6, in part, validating the presence of a hydrophobic pocket in SIRT6 structure. FoldX was used to compute ΔΔG values to determine stability change. Protein structures obtained from PDB ID: 4I5I chain A and PDB ID: 3K35 chain A were used as SIRT1 and SIRT6, respectively.</p
Enhancing Antioxidant Cellular Defense by Using Quercetin Loaded TiO2 Nanoparticles in Swiss 3T3 Albino Mouse Fibroblast Cells
No full textThe cofactor of SIRT6, NAD<sup>+</sup> positively regulated nuclear SIRT6 accumulation and total AR expression under hyperosmotic stress.
No full textControl (C) indicates U937 cells treated with 5 mM glucose containing SFM for 16 hrs in (A) and (B). 100 mM N indicates U937 cells further treated with 100 mM NaCl (N) for 16 hrs in (A), (B) and (C). U937 cells were pretreated either with solvent (DMSO) or indicated concentrations of NAD+ or Ex-527 for 1 hr, followed by 16 hrs of 100 mM N treatment in (A), (B) and (C). (A)(C) The cofactor of SIRT6, NAD+, enhanced the nuclear accumulation of SIRT6 and total AR expression in dose-dependent manner under hyperosmotic stress. (B) A specific SIRT1 inhibitor and recently suggested SIRT6 inhibitor, Ex-527 did not altered nuclear SIRT6 expression under hyperosmotic stress, in part, justifying the data obtained in (A). Expressions were evaluated using immunoblotting in cytoplasmic and nuclear extracts in (A) & (B) and in total extracts in (C). Results obtained from this figure was based on the densitometry based statistical analyses, given in S4 Fig.</p
