Topical application of Nexrutine inhibits ultraviolet B-induced cutaneous inflammatory responses in SKH-1 hairless mouse.

BACKGROUND: Ultraviolet B (UVB) radiation is the major contributor to skin inflammation which leads to the development of skin cancer. Hence, in this study, we studied the effect of Nexrutine (NX) on UVB-induced cutaneous inflammation and its mediators. METHODS: Ultraviolet absorption spectra of NX were measured by spectrophotometer. To conduct the photoprotective studies, SKH-1 hairless mice were topically treated with NX, 30 minutes before to the UVB (180 mJ/cm2 ) exposure. Twenty hours of post-UVB irradiation, mouse skin was used for edema measurements, H & E staining, myeloperoxidase (MPO) activity, and estimation of plasma cytokines. In addition, expression levels of inflammatory cytokines, cyclooxygenase-2 (COX-2), and inducible nitric oxide synthase (iNOS) were also determined by Western blot analysis. RESULTS: Nexrutine displayed absorbance over the UVB spectrum. NX significantly decreased the UVB-induced epidermal edema, skin thickness, leukocyte infiltration, number of the sunburn, and TUNEL-positive cells. NX treatment also decreased the number of mast cells, MPO activity, expression of pro-inflammatory cytokines, and inflammation mediator protein in mouse skin. CONCLUSION: These results provide evidences that NX inhibits the UVB-induced cutaneous inflammatory responses in SKH-1 mouse skin.

Mitigation of radiation-induced dermatitis by activation of aldehyde dehydrogenase 2 using topical alda-1 in mice.

Radiation-induced dermatitis is a debilitating clinical problem in cancer patients undergoing cancer radiation therapy. It is also a possible outcome of exposure to high levels of radiation due to accident or hostile activity. We report that activation of aldehyde dehydrogenase 2 (ALDH2) enzymatic activity using the allosteric agonist, Alda-1, significantly reduced 4-hydroxynonenal adducts accumulation, delayed the onset of radiation dermatitis and substantially reduced symptoms in a clinically-relevant model of radiation-induced dermatitis. Importantly, Alda-1 did not radioprotect tumors in mice. Rather, it increased the sensitivity of the tumors to radiation therapy. This is the first report of reactive aldehydes playing a role in the intrinsic radiosensitivity of normal and tumor tissues. Our findings suggest that ALDH2 represents a novel target for the treatment of radiation dermatitis without reducing the benefit of radiotherapy.

Telomerase activity in radiation-induced chronic human skin ulcers.

An increasing activity of telomerase is considered to be a reliable molecular biological marker for malignancy. There is much research work on telomerase detection in malignant tumors, but no such investigation was carried out in chronic skin ulcers induced by radiation. We investigated the levels of telomerase activity in radiation-induced chronic human skin ulcers and the possible relationship between the enzyme and cancer transformation. We used the nonisotopic telomere repeat amplification protocol (TRAP) in 20 cases of chronic human skin ulcers induced by radiation, 5 cases of normal skin, 2 of burned skin, and 5 of carcinoma. Our results showed that the positive rate for telomerase activity was 30% in chronic radiation skin ulcers, 0% in normal and burned skin, and 100% in carcinoma. The telomerase activity in radiation ulcers was weaker than that detected in carcinoma. We suggest that the telomerase activity assay could be used as a marker for predicting the prognosis and the effect of treatment in chronic human skin ulcers induced by radiation.

Atypical cells in radiation dermatitis express factor XIIIa.

Dendritic cells that express factor XIIIa are present in the normal dermis and are increased in a variety of pathologic conditions. Atypical dermal cells are often seen in biopsy specimens of skin that has been previously irradiated. We sought to determine whether the atypical dermal cells in chronic radiation dermatitis express factor XIIIa. We employed standard immunohistochemical techniques with antibodies to factor XIIIa and CD34 to study 16 biopsy samples showing changes of radiation dermatitis. All cases showed diffuse positive cytoplasmic staining of atypical dermal cells with antibody to factor XIIIa. Of 16 cases, 10 showed focal staining of dermal cells with antibody to CD34, but this antibody did not react with most of the atypical dermal cells. We conclude that the majority of atypical dermal cells in radiation dermatitis are derived from dermal dendritic cells which express factor XIIIa.

Expression of 72-kDa gelatinase (MMP-2), collagenase (MMP-1), and tissue metalloproteinase inhibitor (TIMP) in primary pig skin fibroblast cultures derived from radiation-induced skin fibrosis.

In addition to producing matrix degradation for normal tissue remodeling and repair, matrix metalloproteinases (MMPs) are also involved in various pathologic processes. MMPs and the tissue inhibitor of MMPs (TIMP) were investigated in primary cultures of pig fibroblasts from radiation-induced dermal fibrosis and compared to normal dermal fibroblasts. The free gelatinolytic, collagenolytic, and caseinolytic activities secreted into the culture medium were evaluated against specific 3H denatured collagen type I, native helical collagen, and casein alpha, respectively. The 72- and 68-kilodalton (kDa) forms of type IV collagenase were investigated by protease zymography and quantified by semi-automated image analysis. Transcription of the interstitial collagenase (MMP-1) and TIMP genes was studied by Northern hybridization analysis. Results revealed that in fibrotic fibroblasts, the amount of MMP-1 mRNA was greatly reduced to undetectable levels whereas the amount of TIMP mRNA was increased fourfold compared to controls. Functional assays using specific 3H substrates demonstrated an overall decrease in free MMP activities. Concomitantly, catheptic collagenolytic activity decreased in fibrotic fibroblast extracts compared to controls. These results indicate that in addition to accumulating large amounts of collagen, proteoglycans, and fibronectin, pig fibroblasts from radiation-induced dermal fibrosis also promote connective tissue matrix formation by repressing MMP-1 and stimulating TIMP expression at the transcriptional level, and by reducing overall free MMP and catheptic collagenolytic activities at the post-transcriptional level. In contrast, enzymography assays and automated image analysis demonstrated no significant change in the 72-kDa type IV collagenase activity of fibrotic pig skin fibroblasts. This opposite regulation of 72-kDa collagenase type IV to that of MMP-1 seems to indicate that it has a specific role in remodeling the extracellular matrix during wound healing, fibrogenesis, and angiogenesis.