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Regulation of diurnal and circadian rhythms and cell proliferation are coupled in all mammals, including humans. However, the molecular mechanisms by which diurnal and circadian rhythms regulate cell proliferation are relatively poorly understood. In this study, we report that tumor growth in nude rats bearing human steroid receptor-negative MCF-7 breast tumors can be significantly accelerated by exposing the rats to light at night (LAN). Under normal conditions of an alternating light/dark cycle, proliferating cell nuclear antigen (PCNA) levels in tumors were maximal in the early light phase but remained at very low levels throughout the daily 24-hour cycle period monitored. Surprisingly, PCNA was expressed in tumors continually at a high level throughout the entire 24-hour period in LAN-exposed nude rats. Daily fluctuations of Akt and mitogen activated protein kinase activation in tumors were also disrupted by LAN. These fluctuations did not track with PCNA changes, but we found that activation of the Akt stimulatory kinase phosphoinositide-dependent protein kinase 1 (PDK1) directly correlated with PCNA levels. Expression of insulin-like growth factor 1 receptor (IGF-1R), an upstream signaling molecule for PDK1, also correlated with fluctuations of PDK1/PCNA in the LAN group. In addition, circulating IGF-1 concentrations were elevated in LAN-exposed tumor-bearing nude rats. Finally, RNAimediated knockdown of PDK1 led to a reduction in PCNA expression and cell proliferation in vitro and tumor growth in vivo, indicating that PDK1 regulates breast cancer growth in a manner correlated with PCNA expression. Taken together, our findings demonstrate that LAN exposure can accelerate tumor growth in vivo, in part through continuous activation of IGF-1R/PDK1 signaling. Cancer Res; 71(7); 2622-31. Ó2011 AACR.

The causal relationship between neurogenesis and the recovery of poststroke cognitive function has not been properly explored. The current study aimed to determine whether depleting neuroprogenitor cells (NPCs) affects poststroke functional outcome in nestin-␦-HSV-TK-EGFP transgenic mice, in which the expression of a truncated viral thymidine kinase gene and EGFP was restricted to nestinexpressing NPCs. Ganciclovir (GCV; 200 mg/kg/d) or saline was continuously administered via osmotic pumps in mice for 4 weeks before the induction of experimental stroke. Both baseline and stroke-induced type 1 and type 2 NPCs were conditionally ablated. GCV eliminated NPCs in a duration-dependent fashion, but it did not attenuate the genesis of astroglia or oligodendrocytes in the peri-infarct cortex, nor did it affect infarct size or cerebral blood reperfusion after stroke. Transgenic stroke mice given GCV displayed impaired spatial learning and memory in the Barnes maze test compared with saline control or wild-type stroke mice given GCV, suggesting a contributing role of stroke-induced neurogenesis in the recovery of cognitive function. However, there was no significant difference in poststroke motor function between transgenic mice treated with GCV and those treated with vehicle, despite a significant ablation of NPCs in the subventricular zone of the former. Furthermore, nestin-␦-HSV-TK-EGFP mice treated with GCV had fewer retrogradely labeled neurons in the entorhinal cortex (EC) when injected with the polysynaptic viral marker PRV614 in the dentate gyrus (DG), suggesting that there might be reduced synaptic connectivity between the DG and EC following ablation of NPCs, which may contribute to impaired poststroke memory function.

Here, we demonstrate that arginine vasopressin (AVP) induces multiple intracellular signal transduction pathways in rat intestinal epithelial IEC-18 cells via a V 1A receptor. Addition of AVP to these cells induces a rapid and transient increase in cytosolic Ca 2ϩ concentration and promotes protein kinase D (PKD) activation through a protein kinase C (PKC)-dependent pathway, as revealed by in vitro kinase assays and immunoblotting with an antibody that recognizes autophosphorylated PKD at Ser 916 . AVP also stimulates the tyrosine phosphorylation of the nonreceptor tyrosine kinase proline-rich tyrosine kinase 2 (Pyk2) and promotes Src family kinase phosphorylation at Tyr 418 , indicative of Src activation. AVP induces extracellular signal-related kinase (ERK)-1 (p44 mapk ) and ERK-2 (p42 mapk ) activation, a response prevented by treatment with mitogen-activated protein kinase kinase (MEK) inhibitors (PD-98059 and U-0126), specific PKC inhibitors (GF-I and Ro-31-8220), depletion of Ca 2ϩ (EGTA and thapsigargin), selective epidermal growth factor receptor (EGFR) tyrosine kinase inhibitors (tyrphostin AG-1478, compound 56), or the selective Src family kinase inhibitor PP-2. Furthermore, AVP acts as a potent growth factor for IEC-18 cells, inducing DNA synthesis and cell proliferation through ERK-, Ca 2ϩ -, PKC-, EGFR tyrosine kinase-, and Src-dependent pathways. arginine vasopressin; protein kinase D; protein kinase C; Src; proline-rich tyrosine kinase 2; intestinal epithelial proliferation THE SEQUENTIAL PROLIFERATION, lineage-specific differentiation, migration, and cell death of epithelial cells of the intestinal mucosa is a tightly regulated process that is modulated by a broad spectrum of regulatory peptides (8,36,70). The nontransformed IEC-6 and IEC-18 cells, derived from rat small intestinal crypt (56), have provided an in vitro model to examine intestinal epithelial cell migration, differentiation, and proliferation (16,27,58,70). Previous studies demonstrated that the proliferation and migration of these intestinal epithelial cells is regulated by a variety of polypeptide growth factors, including epidermal growth factor (EGF), insulin-like growth factor I, and hepatocyte growth factor, which act via single-pass transmembrane tyrosine kinase receptors (3,17,51). Neuropeptides and vasoactive peptides that signal through G protein-coupled receptors (GPCRs), characterized by seven-transmembrane helices, also act as potent cellular growth factors for a variety of cell types (63,64,66,67). However, the role of GPCRs and their ligands in intestinal epithelial cell signaling and proliferation remains poorly understood.The neurohypophysial nonapeptide arginine vasopressin (AVP), also known as antidiuretic hormone, is traditionally recognized for its role as a vasoconstrictor hormone acting on vascular smooth muscle cells and its antidiuretic effect via the renal collecting system. In addition to its function in the regulation of body fluid osmolality, vascular tone, and blood pressure, AVP acts as a growth-promo...

Apart from its role in axon guidance, netrin-1 is also known to be pro-angiogenic. The aim of this study is to determine whether adeno-associated viral (AAV) mediated overexpression of netrin-1 improves post-stroke neurovascular structure and recovery of function. AAV-Netrin-1 or AAV-LacZ of 1×1010 genome copies each was injected medial and posterior to ischemic lesion at one hour following reperfusion using the distal middle cerebral artery occlusion (MCAO) method. Quantitative RT-PCR revealed that the expression of netrin-1 transgene began as early as one day and increased dramatically about 3 weeks following vector injection. Western blot analysis and confocal microscopy suggested that both the endogenous and transduced netrin-1 were expressed in the neurons of the peri-infarct cortex after MCAO. AAV-mediated netrin-1 overexpression significantly increased vascular density in the peri-infarct cortex and promoted the migration of immature neurons into the peri-infarct white matter, but it did not significantly reduce infarct size. Netrin-1 overexpression also enhanced post-stroke locomotor activity, improved exploratory behavior, and reduced ischemia-induced motor asymmetry in forelimb usage. However, it had little effect on post-stroke spatial learning and memory. Our results suggest that AAV mediated netrin-1 overexpression improves peri-infarct vascular density and post stroke motor function.

Research on milk fat globule membrane (MFGM) is gaining traction. The interest is two-fold; on the one hand, it is a unique trilayer structure with specific secretory function. On the other hand, it is the basis for ingredients with the presence of phospho- and sphingolipids and glycoproteins, which are being used as food ingredients with valuable functionality, in particular, for use as a supplement in infant nutrition. This last application is at the center of this Review, which aims to contribute to understanding MFGM’s function in the proper development of immunity, cognition, and intestinal trophism, in addition to other potential effects such as prevention of diseases including cardiovascular disease, impaired bone turnover and inflammation, skin conditions, and infections as well as age-associated cognitive decline and muscle loss. The phospholipid composition of MFGM from bovine milk is quite like human milk and, although there are some differences due to dairy processing, these do not result in a chemical change. The MFGM ingredients, as used to improve the formulation in different clinical studies, have indeed increased the presence of phospholipids, sphingolipids, glycolipids, and glycoproteins with the resulting benefits of different outcomes (especially immune and cognitive outcomes) with no reported adverse effects. Nevertheless, the precise mechanism(s) of action of MFGM remain to be elucidated and further basic investigation is warranted.

It is possible that tacrolimus may benefit selected patients with steroid-dependent UC, including those who are intolerant of 6-mercaptopurine or azathioprine. Conversely, patients with steroid-resistant UC are unlikely to sustain a prolonged clinical response to tacrolimus and seem to require colectomy eventually. Careful considerations of risk versus benefit, as well as close monitoring for adverse effects, are essential in all patients.

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