Signal transducer and activator of transcription (Stat)5 was originally identified as a mammary gland factor (MGF) that binds to promoter sequences of milk protein genes and activates their transcription. We have generated isoform-specific antibodies against Stat5a or Stat5b and show that both isoforms are present in similar amounts at the protein level in mammary tissues of virgin, pregnant, lactating, and involuting mice. In contrast, Stat5 phosphorylation is very low in immature virgins, rises sharply during late pregnancy, and declines rapidly during involution. Upon phosphorylation, Stat5a and Stat5b form homo- and heterodimers. The induction of Stat5 phosphorylation during late pregnancy correlates with the transcriptional activation of milk protein genes. Using electrophoretic mobility shift assay and supershift analysis, we demonstrated that the DNA-binding activity detected during lactation is composed of both Stat5a and Stat5b, but not of other STATs. The hypothesis that Stat5 is directly involved in mammary cell differentiation was tested in estrous cycle and in transgenic mice with impaired mammary development. Transient differentiation of mammary alveolar cells and milk protein gene expression during estrus in virgin female mice coincide with transient Stat5 phosphorylation. Impaired mammary development and very low levels of milk protein gene expression in mice carrying the truncated form of the cell fate protein Int3 correlated with reduced phosphorylation and heterodimer formation.

Our goal was to test the effects of insulin-like growth factor I (IGF-I) treatment on clinical deficits, lesion number and lesion size in acute demyelinating experimental autoimmune encephalomyelitis (EAE) induced in Lewis rats with an emulsion containing guinea pig spinal cord. In this EAE model, there is severe immune-mediated demyelination, which resembles that seen in actively demyelinating MS lesions. On day 12-13 after EAE induction, a total of 23 pairs of rats with the same mild degree of tail and hind limb weakness were given either intravenous IGF-I or placebo twice daily for 8 days. The daily IGF-I dose used in the first trial was 200 micrograms (about 0.6 mg kg-1) and in the second and third trials was 1 mg (about 3.0 mg kg-1). IGF-I treatment reduced permeability of the blood-spinal cord barrier to Evans blue-albumin. Maximum clinical deficit scores of IGF-I-treated rats were significantly lower and treated rats recovered faster than controls. IGF-I treatment produced significant reductions in weight loss and hind limb weakness. Treatment also improved treadmill walking, stride length and climbing performance. Morphometric analysis showed that spinal cord inflammatory lesions were significantly smaller and fewer in IGF-I-treated rats. The higher IGF-I dose produced a greater reduction in clinical and pathological deficits. We conclude that IGF-I treatment promotes clinical recovery by reducing EAE-induced blood-spinal cord barrier changes and the associated immune-mediated inflammatory lesions. Our results suggest that IGF-I may be useful in treating patients with multiple sclerosis and other demyelinating diseases.

Head and neck irradiation (IR) during cancer treatment causes by-stander effects on the salivary glands leading to irreversible loss of saliva secretion. The mechanism underlying loss of fluid secretion is not understood and no adequate therapy is currently available. Delivery of an adenoviral vector encoding human aquaporin-1 (hAQP1) into the salivary glands of human subjects and animal models with radiation-induced salivary hypofunction leads to significant recovery of saliva secretion and symptomatic relief in subjects. To elucidate the mechanism underlying loss of salivary secretion and the basis for AdhAQP1-dependent recovery of salivary gland function we assessed submandibular gland function in control mice and mice 2 and 8 months after treatment with a single 15-Gy dose of IR (delivered to the salivary gland region). Salivary secretion and neurotransmitter-stimulated changes in acinar cell volume, an in vitro read-out for fluid secretion, were monitored. Consistent with the sustained 60% loss of fluid secretion following IR, a carbachol (CCh)-induced decrease in acinar cell volume from the glands of mice post IR was transient and attenuated as compared with that in cells from non-IR age-matched mice. The hAQP1 expression in non-IR mice induced no significant effect on salivary fluid secretion or CCh-stimulated cell volume changes, except in acinar cells from 8-month group where the initial rate of cell shrinkage was increased. Importantly, the expression of hAQP1 in the glands of mice post IR induced recovery of salivary fluid secretion and a volume decrease in acinar cells to levels similar to those in cells from non-IR mice. The initial rates of CCh-stimulated cell volume reduction in acinar cells from hAQP1-expressing glands post IR were similar to those from control cells. Altogether, the data suggest that expression of hAQP1 increases the water permeability of acinar cells, which underlies the recovery of fluid secretion in the salivary glands functionally compromised post IR.