| In vitro: |
| Mol Cell Biochem. 2007 Mar;297(1-2):121-9. | | A novel agent, methylophiopogonanone B, promotes Rho activation and tubulin depolymerization.[Pubmed: 17029007] | Cytoskeletal reorganization, including reconstruction of actin fibers and microtubules, is essential for various biological processes, such as cell migration, proliferation and dendrite formation.
METHODS AND RESULTS:
We show here that Methylophiopogonanone B (MOPB) induces cell morphological change via melanocyte dendrite retraction and stress fiber formation. Since members of the Rho family of small GTP-binding proteins act as master regulators of dendrite formation and actin cytoskeletal reorganization, and activated Rho promotes dendrite retraction and stress fiber formation, we studied the effects of MOPB on the small GTPases using normal human epidermal melanocytes and HeLa cells. In in vitro binding assay, MOPB significantly increased GTP-Rho, but not GTP-Rac or GTP-CDC42. Furthermore, a Rho inhibitor, a Rho kinase inhibitor and a small GTPase inhibitor each blocked MOPB-induced stress fiber formation. The effect of MOPB on actin reorganization was blocked in a Rho dominant negative mutant. These results suggest MOPB acts via the Rho signaling pathway, and it may directly or indirectly activate Rho. Quantitative Western blot analysis indicated that MOPB also induced microtubule destabilization and tubulin depolymerization.
CONCLUSIONS:
Thus, MOPB appears to induce Rho activation, resulting in actin cytoskeletal reorganization, including dendrite retraction and stress fiber formation. | | Int.J. Cosmetic Sci., 2006, 28(2):148-148. | | Control of melanosome transfer by promoting shrinkage or expansion of melanocyte dendrites.[Reference: WebLink] | Melanosomes synthesized within melanocytes are transferred to keratinocytes through melanocyte dendrites, resulting in a constant supply of melanin to the epidermis which determines skin pigmentation. Theoretically, if we can find an effective way to control this supply of melanin to the epidermis, skin colour could be darkened or lightened.
METHODS AND RESULTS:
The objective of this study was to find safe and effective methods to inhibit or promote melanosome transfer by the shrinkage or expansion of melanocyte dendrites. Methylophiopogonanone B and centaureidin inhibited melanosome transfer to keratinocytes as well as melanocyte dendrite outgrowth. Methylswertianin and comfrey extract promoted not only melanosome transfer to keratinocytes but also expansion of melanocyte dendrites. Methylophiopogonanone B and centaureidin suppressed pigmentation in a three-dimensional skin culture model through the inhibition of melanocyte dendrite outgrowth. Methylswertianin and comfrey extract activated pigmentation in a three-dimensional skin culture model by expansion of melanocyte dendrites.
CONCLUSIONS:
Our experimental findings suggest the possibility of manipulating human skin colour by controlling melanosome transfer to cause shrinkage or expansion of dendrites. A combination of effective agents, in addition to the ones identified in this work, could result in the creation of very unique cosmetic products that would precisely control the darkening or lightening of skin tone. |
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