No abstract

Adrenomedullin (AM) is a regulatory peptide whose involvement in tumour progression is becoming more relevant with recent studies. AM is produced and secreted by the tumour cells but also by numerous stromal cells including macrophages, mast cells, endothelial cells, and vascular smooth muscle cells. Most cancer patients present high levels of circulating AM and in some cases these higher levels correlate with a worst prognosis. In some cases it has been shown that the high AM levels return to normal following surgical removal of the tumour, thus indicating the tumour as the source of this excessive production of AM. Expression of this peptide is a good investment for the tumour cell since AM acts as an autocrine/paracrine growth factor, prevents apoptosis-mediated cell death, increases tumour cell motility and metastasis, induces angiogenesis, and blocks immunosurveillance by inhibiting the immune system. In addition, AM expression gets rapidly activated by hypoxia through a HIF-1α mediated mechanism, thus characterizing AM as a major survival factor for tumour cells. Accordingly, a number of studies have shown that inhibition of this peptide or its receptors results in a significant reduction in tumour progression. In conclusion, AM is a great target for drug development and new drugs interfering with this system are being developed.

We previously reported that the human Na ؉ /nucleoside transporter pyrimidine-preferring 1 (hCNT1) is electrogenic and transports gemcitabine and 5-deoxy-5-fluorouridine, a precursor of the active drug 5-fluorouracil. Nevertheless, a complete electrophysiological characterization of the basic properties of hCNT1-mediated translocation has not been performed yet, and the exact role of adenosine in hCNT1 function has not been addressed either. In the present work we have used the two-electrode voltage clamp technique to investigate hCNT1 transport mechanism and study the kinetic properties of adenosine as an inhibitor of hCNT1. We show that hCNT1 exhibits presteady-state currents that disappear upon the addition of adenosine or uridine. Adenosine, a purine nucleoside described as a substrate of the pyrimidine-preferring transporters, is not a substrate of hCNT1 but a high affinity blocker able to inhibit uridine-induced inward currents, the Na ؉ -leak currents, and the presteady-state currents, with a K i of 6.5 M. The kinetic parameters for uridine, gemcitabine, and 5-deoxy-5-fluorouridine were studied as a function of membrane potential; at ؊50 mV, K 0.5 was 37, 18, and 245 M, respectively, and remained voltage-independent. I max for gemcitabine was voltage-independent and accounts for ϳ40% that for uridine at ؊50 mV. Maximal current for 5-DFUR was voltage-dependent and was ϳ150% that for uridine at all membrane potentials. K 0.5 Na ؉ for Na ؉ was voltage-independent at hyperpolarized membrane potentials (1.2 mM at ؊50 mV), whereas I max Na ؉ was voltage-dependent, increasing 2-fold from ؊50 to ؊150 mV. Direct measurements of 3 H-nucleoside or 22 Na fluxes with the charge-associated revealed a ratio of two positive inward charges per nucleoside and one Na ؉ per positive inward charge, suggesting a stoichiometry of two Na ؉ /nucleoside.Nucleoside uptake into cells occurs through specific transport proteins located at the plasma membrane. These transporters belong to two families of integral membrane proteins, the equilibrative nucleoside transporter family or ENT, with broad substrate selectivity, and the concentrative nucleoside transporter family or CNT 1 (1-4). The CNT transporters are Na ϩ -dependent, and they differ in substrate selectivity. Among them, three CNT isoforms have been cloned so far; they are CNT1, which is pyrimidine-preferring, CNT2, which is purinepreferring (2-4), and CNT3, which shows broad selectivity, accepting both pyrimidine and purine nucleosides (5). Besides the important function of nucleosides as precursors of nucleic acid and energy-rich molecules, a variety of nucleoside-derived drugs used in cancer and anti-viral therapies are taken up by the cells through the nucleoside transporters (2, 3, 6, 7).Although the electrogenic property of CNT transporters has been used to study their substrate selectivity at a fixed membrane potential (5-12), the electrophysiological characteristics of the transport mechanism are not known. Therefore, the detailed electrophysiological analysis of hCNT...

Citation: Rey-Funes M, Dorfman VB, Ibarra ME, et al. Hypothermia prevents gliosis and angiogenesis development in an experimental model of ischemic proliferative retinopathy. Invest Ophthalmol Vis Sci. 2013;54:283654: -284654: . DOI:10.1167 PURPOSE. To develop a time course study of vascularization and glial response to perinatal asphyxia in hypoxic-ischemic animals, and to evaluate hypothermia as possible protective treatment. METHODS.We used retinas of 7-, 15-, 21-, and 30-day-old male Sprague-Dawley rats that were exposed to perinatal asphyxia at either 378C (PA) or 158C (HYP). Born to term animals were used as controls (CTL). We evaluated the thickness of the most inner layers of the retina (IR), including internal limiting membrane, the retinal nerve fiber layer, and the ganglion cell layer; and studied glial development, neovascularization, adrenomedullin (AM), and VEGF by immunohistochemistry, immunofluorescence, and Western blot. RESULTS.A significant increment in IR thickness was observed in the PA group from postnatal day (PND) 15 on. This alteration was concordant with an increased number of new vessels and increased GFAP expression. The immunolocalization of GFAP in the internal limiting membrane and perivascular glia of the IR and in the inner processes of Müller cells was coexpressed with AM, which was also significantly increased from PND7 in PA animals. In addition, VEGF expression was immunolocalized in cells of the ganglion cell layer of the IR and this expression significantly increased in the PA group from PND15 on. The retinas of the HYP group did not show differences when compared with CTL at any age.CONCLUSIONS. This work demonstrates that aberrant angiogenesis and exacerbated gliosis seem to be responsible for the increased thickness of the inner retina as a consequence of perinatal asphyxia, and that hypothermia is able to prevent these alterations.

In many tissues, stearoyl-CoA desaturase 1 (SCD1) catalyzes the biosynthesis of monounsaturated fatty acids (MUFAS), (i.e., palmitoleate and oleate) from their saturated fatty acid (SFA) precursors (i.e., palmitate and stearate), influencing cellular membrane physiology and signaling, leading to broad effects on human physiology. In addition to its predominant role in lipid metabolism and body weight control, SCD1 has emerged recently as a potential new target for the treatment for various diseases, such as nonalcoholic steatohepatitis, Alzheimer’s disease, cancer, and skin disorders. Sterculic acid (SA) is a cyclopropene fatty acid originally found in the seeds of the plant Sterculia foetida with numerous biological activities. On the one hand, its ability to inhibit stearoyl-CoA desaturase (SCD) allows its use as a coadjuvant of several pathologies where this enzyme has been associated. On the other hand, additional effects independently of its SCD inhibitory properties, involve anti-inflammatory and protective roles in retinal diseases such as age-related macular degeneration (AMD). This review aims to summarize the mechanisms by which SA exerts its actions and to highlight the emerging areas where this natural compound may be of help for the development of new therapies for human diseases.