Immune response and Raman scattering assessment in rats skin after contact with Fusarium oxysporum metabolites

Abstract The secondary metabolites produced by Fusarium can cause disease and death when consumed and produce biological responses even in the absence of the microorganism. The IL-6, TNF-α and TGF-β1 cytokines immune reactivity was associated with histopathological and physico-chemical changes in skin of immune competent rats after administration of Fusarium oxysporum crude extract. Rats were intradermally injected with 50 μl of 0.5 mg/ml crude extract and were euthanized at 3, 6, 12 and 24 h after injection. The inflammatory response was quantified by enzyme myeloperoxidase activity and by immunohistochemical method to detect the IL-6, TNF-α and TGF-β1. Physico-chemical analysis was performed using FT-Raman Spectroscopy. The inflammatory response was most intense at 6 and 12 h after crude extract administration and the most significant histopathological changes were observed in the dermis. Myeloperoxidase activity was intense from 3 to 24 h after injection. The immunostaining of pro-inflammatory cytokines IL-6 and TNF-α peaked at 6 h. Immunostaining for TGF-β1 was highest at 12 and 24 h. FT-Raman spectral analysis showed both, the most intense Fusarium interaction with the skin at 6 h, as revealed by the changes in the stretching of –CH bands (3100–2800 cm−1) in the dermis, and skin recovery trending after 12 h after crude extract injection. The results showed that secondary metabolites stimulated histopathologic changes and inflammatory responses even in the absence of the fungus, increasing myeloperoxidase activity and pro-inflammatory cytokine expression besides promoting physico-chemical changes.