Permeability barrier disruption alters the localization and expression of TNF?/protein in the epidermis

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Abstract
Previous studies have shown that (1) epidermal TNFα mRNA levels are increased following acute disruption of the cutaneous permeability barrier; (2) this increase is maximal at 1 h and decreases to control levels by 8 h; and (3) in essential fatty acid-deficient (EFAD) mice, a chronic model of barrier perturbation, TNFα mRNA levels are also elevated several-fold over controls. In the present study we determined, using immunocytochemical procedures, epidermal TNFα protein levels following either acute of chronic barrier disruption and the localization of any increase. Frozen, paraffin and Antibed sections of skin were incubated with polyclonal anti-mouse TNFα antisera and detection was accomplished by either immunoperoxidase or fluorescence procedures. We found that (1) TNFα-immunoreactive protein was present in normal mouse epidermis, and was primarily localized to the upper nucleated layers where it displayed a diffuse cytosolic pattern; (2) acute disruption of the barrier with acetone or tape-stripping resulted in TNFα staining that was more intense throughout all of the nucleated epidermal cell layers in comparison with normal epidermis; (3) the increase in TNFα staining occurred as early as 2 h after barrier disruption; and (4) increased TNFα staining was also observed in the stratum corneum of EFAD mice. These results indicate that epidermal TNFα protein levels increase after both acute and chronic barrier disruption, and are consistent with the hypothesis that TNFα may signal and/or coordinate portions of the cutaneous response to barrier disruption.