Secondhand smoke exposure-induced nucleocytoplasmic shuttling of HMGB1 in a rat premature skin aging model.

Secondhand cigarette smoke exposure (SSE) has been linked to carcinogenic, oxidative, and inflammatory reactions. Herein, we investigated whether premature skin aging could be induced by SSE in a rat model, and assessed the cytoplasmic translocation of high mobility group box 1 (HMGB1) protein and collagen loss in skin tissues. Animals were divided into two groups: SSE and controls. Whole body SSE was carried out for 12 weeks. Dorsal skin tissue specimens were harvested for HMGB1 and Mallory's azan staining. Correlations between serum HMGB1 and collagen levels were determined. Rat skin exposed to secondhand smoke lost collagen bundles in the papillary dermis and collagen decreased significantly (p<0.05) compared with control rats. In epidermal keratinocytes, cytoplasmic HMGB1 staining was more diffuse and there were more HMGB1-positive cells after four weeks in SSE compared to control rats. A negative correlation between HMGB1 serum and collagen levels (r=-0.631, p=0.28) was also observed. Therefore, cytoplasmic HMGB1 expression in skin tissues might be associated with skin collagen loss upon the initiation of SSE. Additionally, long-term SSE might affect the appearance of the skin, or could accelerate the skin aging process.