Arsenic is a well-recognized human
carcinogen that causes a number of malignant diseases, including
lung cancer. Previous studies have indicated that
cyclin D1 is frequently over-expressed in many
cancer types. It is also known that
arsenite exposure enhances
cyclin D1 expression, which involves
NF-kappaB activation. However, the mechanism between
cyclin D1 and the
NF-kappaB pathway has not been well studied. This study was designed to characterize the underlying mechanism of induced cell growth and
cyclin D1 expression in response to low concentration
sodium arsenic (NaAsO(2)) exposure through the
NF-kappaB pathway. Cultured human bronchial epithelial cells, BEAS-2B, were exposed to low concentration
sodium arsenite for the indicated durations, and cytotoxicity, gene expression, and
protein activity were assessed. To profile the canonical and non-canonical
NF-kappaB pathways involved in cell growth and
cyclin D1 expression induced by low concentration
arsenite, the
NF-kappaB-specific inhibitor-
phenethyl caffeate (CAPE) and
NF-kappaB2 mRNA target sequences were used, and
cyclin D1 expression in BEAS-2B cells was assessed. Our results demonstrated that exposure to low concentration
arsenite enhanced BEAS-2B cells growth and
cyclin D1 mRNA and
protein expression. Activation and nuclear localization of p52 and Bcl3 in response to low concentration
arsenite indicated that the non-canonical
NF-kappaB pathway was involved in
arsenite-induced
cyclin D1 expression. Moreover, we further demonstrated that p52/Bcl3 complex formation enhanced
cyclin D1 expression through the cyclin D1 gene promoter via its kappaB site. The up-regulation of
cyclin D1 mediated by the p52-Bcl3 complex in response to low concentration
arsenite might be important in assessing the health risk of low concentration
arsenite and understanding the mechanisms of the harmful effects of
arsenite.