Expression of iNOS and NF-κB in melasma: an immunohistochemical study.

OBJECTIVE: To investigate the role of inducible nitric oxide synthases (iNOS) and nuclear factor-kappa B (NF-κB) in the pathogenesis of melasma through their immunohistochemical (IHC) co-localization in skin of melasma and to correlate their expression with the clinical and the histopathological data. STUDY DESIGN: This prospective case-control study was conducted on 34 female patients with melasma and 30 age- and gender-matched healthy subjects as a control group for evaluation of IHC expression of iNOS and NF-κB in melasma. RESULTS: There were significant differences between lesional and perilesional skin regarding iNOS intensity, iNOS histo-score (H-score), NF-κB intensity, and NF-κB H-score (p < 0.001 for all). There were significant associations between the higher values of H-scores for both iNOS and NF-κB and positive family history (p = 0.002 and p = 0.001, respectively) and very severe melasma areas and severity index score (p < 0.001 and p = 0.001, respectively). There was a positive correlation between H-score values of both iNOS and NF-κB (r = +0.604 and p < 0.001). CONCLUSION: The IHC co-localization and direct correlation of both iNOS and NF-κB in melasma could provide evidence about their role as co-players in melanogenesis and might provide new targets for a more efficient treatment for melasma.

Immunolocalization of tenascin-C in vitiligo.

The disappearance of melanocytes because of defective adhesion is one of the accepted theories to explain vitiligo. Tenascin-C is a large, extracellular matrix glycoprotein that is thought to inhibit adhesion of melanocytes to fibronectin. The current study aimed to evaluate the pattern of tenascin-C expression in vitiligenous skin compared with normal pigmented skin by means of immunohistochemistry. The study was carried out on skin biopsies from lesional and perilesional skin of 30 patients with vitiligo and on normal skin of 10 healthy volunteers. Several histopathologic changes were observed in vitiliginous skin such as keratinocyte vacuolization, a thickened basement membrane, and dermal inflammatory changes. Tenascin-C was expressed in keratinocytes of the basal epidermal layer of normal skin biopsies at a mild intensity but it did not stain the dermis, whereas vitiligenous skin showed tenascin-C expression in most cases (93.3% ), in the papillary dermis, epidermis, and in both. Diffuse epidermal expression of tenascin-C correlated with more loss of pigment and continuous staining of tenascin-C in the papillary dermis correlated with progressive forms of vitiligo. Intense tenascin-C expression was associated with a more progressive course of the disease assessed by the vitiligo disease activity score. From this study, tenascin-C is highly expressed in the dermis, epidermis, and both of vitiligo as a secondary event for the disease. Keratinocyte is a source of tenascin-C in vitiligo, and diffuse epidermal expression of tenascin-C may induce more loss of melanocytes and melanin pigment. Dermal expression of tenascin-C in the vitiligenous lesion may be linked to the disease more than epidermal expression, because this pattern is only seen in a vitiligenous lesion and it is completely absent in normal and perilesional skin.

Cathepsin D expression in chronic plaque psoriasis: an immunohistochemical study.

Cathepsins are lysosomal cysteine proteases, which are involved in a variety of physiologic processes such as proenzyme activation, antigen presentation, tissue remodeling, bone matrix resorption, and pathologic processes such as facilitating tumor invasion and modulating the process of programmed cell death. This study aimed to evaluate the pattern of cathepsin D (CD) expression in chronic plaque psoriasis in comparison to normal skin by means of immunohistochemistry. The study included 34 patients presenting with chronic plaque psoriasis and 10 age- and sex-matched normal subjects as control group. Sixty percent of normal skin showed granular positivity for CD confined to basal layer. CD is upregulated in psoaritic lesion with 94.1% positivity making a significant difference between psoriasis and normal skin as regards the percentage and distribution of CD expression, where the latter was predominantly diffuse in psoriatic lesion. The eight cases exposed to PUVA therapy showed reduction of CD positivity to 62.5% with a predominance of mild staining and focal expression compared to pretreatment biopsies. CD may have a role in the pathogenesis of psoriasis in view of its high percentage and diffuse expression in psoriatic epidermis. CD degradative capacity may be responsible for disordered differentiation and scale formation characteristic of psoriasis. Reduction of CD expression may be one of the pathways of PUVA mechanism of action.