Role of phosphatidylinositol 3-kinase-protein kinase B signaling pathway in Na+-I- symporter expression for lactating breast cells

Abstract

Objective To elucidate the function of phosphatidylinositol 3-kinase (PI3K)-protein kinase B (AKT) signaling pathway underlying the regulation of Na+-I- symporter (NIS) and the influence of different levels of iodine on PI3K-AKT signaling pathway in lactating breast cells. Methods The primary cultured mammary gland cells were divided into three groups: ①control group [0 μmol/L LY294002+ 0 μg/L insulin-like growth factor Ⅰ (IGF-Ⅰ)]; ②stimulation group(50 μg/L IGF-Ⅰ); ③inhibition group (40 μmol/L LY294002+ 50 μg/L IGF-Ⅰ). In addition, the cells were treated with different iodine contents (0, 5, 50, 1 000, 3 000 μg/L) for low iodine groups 1 and 2, iodine group, high iodine groups 1 and 2, and IGF-I (50 μg/L) was used to stimulate PI3K-AKT signaling pathway. The expressions of AKT and NIS mRNA and protein were determined by real-time quantitative PCR and Western blotting, respectively. Results The expression of AKT mRNA (1.497 ± 0.550) in stimulation group was higher than that in inhibition group (0.777 ± 0.108, P < 0.05), while the expression of NIS mRNA and protein in stimulation group (0.783 ± 0.187, 0.618 ± 0.103) was lower than those in inhibition group (2.430 ± 1.423, 1.417 ± 0.250, all P < 0.05). With the iodine concentration increasing, except high iodine group 1 (1.090 ± 0.356), the expression of AKT mRNA in low iodine groups 1 and 2, iodine group, high iodine group 2 (1.758 ± 0.893, 1.320 ± 0.538, 1.003 ± 0.006, 0.745 ± 0.307) tended to decline; total AKT protein (0.640 ± 0.106, 0.601 ± 0.081, 0.583 ± 0.089, 0.555 ± 0.097, 0.532 ± 0.023) and NIS mRNA (2.259 ± 0.682, 1.823 ± 0.332, 1.409 ± 0.366, 1.321 ± 0.405, 1.150 ± 0.454) tended to decline in low iodine groups 1 and 2, iodine group, high iodine groups 1 and 2; except low iodine group 2 (0.484 ± 0.179), NIS protein expression tended to decline (0.556 ± 0.199, 0.502 ± 0.179, 0.455 ± 0.126, 0.435 ± 0.138); however, except low iodine group 2 (0.076 ± 0.045), the p-AKT protein expressions (0.078 ± 0.049, 0.079 ± 0.040, 0.085 ± 0.055, 0.095 ± 0.051) were on the rise. Conclusion PI3K-AKT signaling pathway may play an inhibition role in the expression of NIS in lactating breast cells. Key words: Iodine; Na+-I- symporter; Insulin-like growth factor Ⅰ