|LETTER TO EDITOR
|Year : 2008 | Volume
| Issue : 2 | Page : 169-170
Engin Senel, Deniz Seckin
Department of Dermatology, Baskent University Faculty of Medicine, Ankara, Turkey
Department of Dermatology, Baskent University, Faculty of Medicine, 5. Sokak No: 48 Bahcelievler, Ankara - 06490
Source of Support: None, Conflict of Interest: None
|How to cite this article:|
Senel E, Seckin D. Author's reply. Indian J Dermatol Venereol Leprol 2008;74:169-70
We appreciate the comments of Dr. Eapen on our letter.  In his reply, it is emphasized that enhanced activation of Toll-like receptors 7 and 8 due to imiquimod treatment may trigger the ubiquitin-mediated proteolysis and apoptosis, and this mechanism may have a role in the pathogenesis of imiquimod-related vitiligo-like depigmentation.
Besides IFN-α and TNF-α, imiquimod treatment leads to the increased production of various other cytokines and chemokines. Along with IFN-α, increased production of IL-6 and IL-8 by imiquimod stimulates the cytotoxic T-cell-mediated immune response, which is known to play a major role in the pathogenesis of vitiligo.  Furthermore, some of the cytokines triggered by imiquimod, namely IL-6, IL-1 and TNF-α, cause a dose-dependent decrease in the activity of the enzyme tyrosinase, suggesting a role for paracrine and possibly autocrine regulation of melanocytes by immune modulators. IL-6 can also increase melanocyte ICAM-1 expression, which may increase the leukocyte-melanocyte attachment and result in melanocyte damage in vitiligo. This IL-6-induced ICAM-1 expression may also be the triggering factor in imiquimod-induced vitiligo-like depigmentation.  It is also possible that imiquimod-induced production of TNF-α and IFN-α plays a role in auto-destruction of melanocytes by enhancing the release of nitric oxide.  In summary, considering the mechanisms of actions of imiquimod, vitiligo-like depigmentation is not a surprising adverse effect of this drug.
| References|| |
|1.||Senel E, Seckin D. Imiquimod-induced vitiligo-like depigmentation. Indian J Dermatol Venereol Leprol 2007;73:423. [PUBMED] [FULLTEXT]|
|2.||Mashiah J, Brenner S. Possible mechanisms in the induction of vitiligo-like hypopigmentation by topical imiquimod. Clin Exp Dermatol 2008;33:74-6. [PUBMED] [FULLTEXT]|
|3.||Swope VB, Abdel-Malek Z, Kassem LM. Interleukins 1 alpha and 6 and tumor necrosis factor-alpha are paracrine inhibitors of human melanocyte proliferation and melanogenesis. J Invest Dermatol 1991;96:180-5. |
|4.||Rocha IM, Oliveira LJ, De Castro LC. Recognition of melanoma cell antigens with antibodies present in sera from patients with vitiligo. Int J Dermatol 2000;39:840-3. |