4 research outputs found
Photoisomerization of retinoic acid and its influence on regulation of human keratinocyte growth and differentiation
71-76Retinoic acid constantly undergoes structural
inter-conversions among the geometrical isomers (all-trans-retinoic acid,
9-cis- retinoic acid, 11-cis-retinoic acid , 13-cis- retinoic
acid and 9-13-di-cis-retinoic acid) by photoisomerization under natural
light. Geometric isomers of retinoic acid thus formed showed different effects on
human epidermal keratinocyte growth and differentiation. The ability of the
isomers to inhibit the synthesis of cornified envelope (terminal event in the keratinocyte
differentiation program) changed rapidly when illuminated by white fluorescent light.
The 11-cis-retinoic acid had a 3-fold stronger activity to inhibit the growth
of keratinocytes than the other geometric isomers. On the other hand, all-trans-
retinoic acid, 9-cis-retinoic acid and 9-13-di-cis-retinoic
acid exhibited a 3-fold greater ability to inhibit synthesis of involucrin,
transglutaminase and the cornified envelopes. The regulation of keratin expression
by the geometric isomers of retinoic acids was extremely complex. Level of
keratin -1 (K1) mRNA was increased by 11-cis- retinoic acid and 13-cis-retinoic
acid, but suppressed by 9, 13-di-cis-retinoic acids while all-trans-retinoic
acid and 9-cis-retinoic acid had no effect. Level of keratin-10 (K10)
mRNA was strongly inhibited by all-trans-retinoic acid, 9-cis-retinoic acid
and 11-cis-retinoic acid as compared to 13-cis-retinoic acid
and 9, 13-di-cis-retinoic acids. The mRNA level of keratin-14 (K14) was
suppressed by all-trans-retinoic acid, 9-cis-retinoic acid
and 11-cis-retinoic acid but not influenced by 13-cis-retinoic
acid and 9, 13-di-cis-retinoic acid. Natural light induced structural
inter-conversions among the geometric isomers of retinoic acids in tissues especially
the skin, might play a crucial role in the regulation of growth and differentiation
of keratinocytes
Constant variation in structure and function of geometrical isomers of acitretin under natural light
22-27Acitretin, a beneficial retinoid, was
shown to undergo constant structural interconversions among its geometrical
isomers (all-trans-acitretin, 9-cis-acitretin, 13-cis-acitretin,
9, 13-di-cis-acitretin, etc.) by photoisomerization under natural light.
The photoisomerization was zero order reaction with an apparent velocity of
4×10-7 M/min under illumination by
white fluorescent lamps (1, 200 1x). An equilibrium
mixture of the geometrical isomers (all-trans-acitretin 20%, 9-cis-acitretin
15%, 13-cis-acitretin 30%, 9, 13-di-cis-acitretin 15%, and unidentified
compounds 20%) was formed at around 30 min. Equilibrium mixtures with similar
composition were obtained by photoisomerization reactions starting from other
geometrical isomers. Geometrical isomers of
acitretin thus formed, showed different effects to induce differentiation of human
acute promyelocytic leukemia cells (HL-60 cells): activity of all-trans-acitretin
(ED50, 3.2×10-6M), 9-cis-acitretin (ED50,
2.3×10-5M), 13-cis-acitretin (ED50, 1.1×10-5M),
9, 13-di-cis-acitretin (ED50, 2.6×10-6M)
9-cis-Acitretin acted synergistically with all-trans-acitretin, 13-cis-acitretin
and 9, 13-di-cis-acitretin on HL-60 cells. On the other side, all-trans-acitretin,
13-cis-acitretin and 9, 13-di-cis-acitretin acted additively. Geometrical
isomers of acitretin showed different effects on differentiation of human epidermal
keratinocytes; expression of keratinocyte differentiation markers, keratin 1 and
kerati 10, were suppressed more strongly by 9-cis-acitretin and 13-cis-acitretin
as compared to all-trans-acitretin or 9, 13-di-cis-acitretin
Structural perturbation and enhancement of the chaperone-like activity of α-crystallin by arginine hydrochloride
Structural perturbation of α-crystallin is shown to enhance its molecular chaperone-like activity in preventing aggregation of target proteins. We demonstrate that arginine, a biologically compatible molecule that is known to bind to the peptide backbone and negatively charged side-chains, increases the chaperone-like activity of calf eye lens α-crystallin as well as recombinant human αA- and αB-crystallins. Arginine-induced increase in the chaperone activity is more pronounced for αB-crystallin than for αA-crystallin. Other guanidinium compounds such as aminoguanidine hydrochloride and guanidine hydrochloride also show a similar effect, but to different extents. A point mutation, R120G, in αB-crystallin that is associated with desmin-related myopathy, results in a significant loss of chaperone-like activity. Arginine restores the activity of mutant protein to a considerable extent. We have investigated the effect of arginine on the structural changes of α-crystallin by circular dichroism, fluorescence, and glycerol gradient sedimentation. Far-UV CD spectra show no significant changes in secondary structure, whereas near-UV CD spectra show subtle changes in the presence of arginine. Glycerol gradient sedimentation shows a significant decrease in the size of α-crystallin oligomer in the presence of arginine. Increased exposure of hydrophobic surfaces of α-crystallin, as monitored by pyrene-solubilization and ANS-fluorescence, is observed in the presence of arginine. These results show that arginine brings about subtle changes in the tertiary structure and significant changes in the quaternary structure of α-crystallin and enhances its chaperone-like activity significantly. This study should prove useful in designing strategies to improve chaperone function for therapeutic applications
In Vitro and In Vivo Demonstration of Human-Ovarian-Cancer Necrosis through a Water-Soluble and Near-Infrared-Absorbing Chlorin
With
the objective of developing efficient sensitizers for therapeutic
applications, we synthesized a water-soluble 5,10,15,20-tetrakis(3,4-dihydroxyphenyl)chlorin
(TDC) and investigated its in vitro and in vivo biological efficacy,
comparing it with the commercially available sensitizers. TDC showed
high water solubility (6-fold) when compared with that of Foscan and
exhibited excellent triplet-excited-state (84%) and singlet-oxygen
(80%) yields. In vitro photobiological investigations in human-ovarian-cancer
cell lines SKOV-3 showed high photocytotoxicity, negligible dark toxicity,
rapid cellular uptake, and specific localization of TDC in neoplastic
cells as assessed by flow-cytometric cell-cycle and propidium iodide
staining analysis. The photodynamic effects of TDC include confirmed
reactive-oxygen-species-induced mitochondrial damage leading to necrosis
in SKOV-3 cell lines. The in vivo photodynamic activity in nude-mouse
models demonstrated abrogation of tumor growth without any detectable
pathology in the skin, liver, spleen, or kidney, thereby demonstrating
TDC application as an efficient and safe photosensitizer