Estradiol administration increases anxiety-like behavior following chronic escalating morphine administration in hormone-replaced ovariectomized female rats.

Withdrawal from opioids can induce a state of anxiety and irritability. This negative state can facilitate continued drug taking, as the administration of opioids can alleviate unpleasant symptoms associated with acute and protracted withdrawal. It is, therefore, of interest to investigate factors that can contribute to the severity of anxiety during periods of abstinence. One such factor is the fluctuation of ovarian hormones. Evidence from a non-opioid drug indicates that estradiol increases, while progesterone decreases anxiety during withdrawal. However, no work has yet studied how ovarian hormones might influence the severity of anxiety during withdrawal from opioids. To explore this, we ovariectomized female rats and provided a four-day repeating cycle of ovarian hormone administration (Day 1: estradiol, Day 2: estradiol, Day 3: progesterone, Day 4: peanut oil). Male rats were given sham surgeries and administered peanut oil daily in lieu of hormone replacement. All rats received twice daily injections of morphine (or 0.9 % saline) for 10 days total at a dose that doubled every two days (2.5 mg/kg, 5 mg/kg, 10 mg/kg, 20 mg/kg, 40 mg/kg). Rats underwent spontaneous withdrawal and were tested for anxiety-like behaviors 12 and 108 h after the last morphine treatment. At 12 h, morphine-withdrawn female rats treated with estradiol on the day of testing displayed significantly more anxiety-like behavior in light-dark box testing than female morphine-withdrawn and (marginally) male morphine-withdrawn rats receiving vehicle that day. Somatic withdrawal behaviors (wet dog shakes, head shakes, writhing) were also taken every 12 h through 108 h. We found no meaningful contribution of sex or hormones for these measures. This study is the first of its kind to provide evidence that ovarian hormones influence anxiety-like behavior during morphine withdrawal.

Tamoxifen differentially regulates miR-29b-1 and miR-29a expression depending on endocrine-sensitivity in breast cancer cells.

Endocrine-resistance develops in ∼40% of breast cancer patients after tamoxifen (TAM) therapy. Although microRNAs are dysregulated in breast cancer, their contribution to endocrine-resistance is not yet understood. Previous microarray analysis identified miR-29a and miR-29b-1 as repressed by TAM in MCF-7 endocrine-sensitive breast cancer cells but stimulated by TAM in LY2 endocrine-resistant breast cancer cells. Here we examined the mechanism for the differential regulation of these miRs by TAM in MCF-7 versus TAM-resistant LY2 and LCC9 breast cancer cells and the functional role of these microRNAs in these cells. Knockdown studies revealed that ERα is responsible for TAM regulation of miR-29b-1/a transcription. We also demonstrated that transient overexpression of miR-29b-1/a decreased MCF-7, LCC9, and LY2 proliferation and inhibited LY2 cell migration and colony formation but did not sensitize LCC9 or LY2 cells to TAM. Furthermore, TAM reduced DICER1 mRNA and protein in LY2 cells, a known target of miR-29. Supporting this observation, anti-miR-29b-1 or anti-miR-29a inhibited the suppression of DICER by 4-OHT. These results suggest miR-29b-1/a has tumor suppressor activity in TAM-resistant cells and does not appear to play a role in mediating TAM resistance.