Several lines of evidence implicate the beta-galactoside-binding lectin galectin-3 in development and pathological processes in renal collecting ducts: galectin-3 is expressed in the ureteric bud/collecting duct lineage during nephrogenesis, modulates collecting duct growth/differentiation in vitro, and is expressed in human autosomal recessive polycystic kidney disease in cyst epithelia, almost all of which arise from collecting ducts. Moreover, exogenous galectin-3 restricts growth of cysts generated by Madin-Darby canine kidney collecting duct-derived cells in three-dimensional culture in collagen. Using the cpk mouse model of recessively inherited polycystic kidney disease, we observed widespread galectin-3 mRNA and protein in cyst epithelia. Exogenous galectin-3 reduced cyst formation in suspension culture, and mice-null mutant for galectin-3 had more extensive renal cysts in vivo. Galectin-3 was also detected for the first time in the centrosome/primary cilium, which has been implicated in diverse polycystic kidney disease. Cilia structure/number appeared normal in galectin-3-null mutants. Finally, paclitaxel, a therapy that retards polycystic kidney disease in cpk mice, increased extracellular galectin-3, in which the lectin could potentially interact with cilia. These data raise the possibility that galectin-3 may act as a natural brake on cystogenesis in cpk mice, perhaps via ciliary roles.

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Background: Purinergic receptors are cell-surface molecules that bind extracellular nucleotides, notably ATP. The P2X family includes seven nonselective ion channels with one member, P2X₇, implicated in cytolytic pore formation and cell death. Materials and Methods: We sought P2X₇ expression in mouse nephrogenesis and cpk/cpk renal cyst growth, conditions in which both proliferation and apoptosis are prominent. Results: P2X₇ immunolocalized to condensed metanephric mesenchyme: both proliferation and apoptosis were detected in this compartment, assessed by proliferating cell nuclear antigen expression and propidium iodide-stained pyknotic nuclei respectively. Later in nephrogenesis, P2X₇ was detected in collecting ducts, a pattern persisting to maturity. A mesenchymal to epithelial shift of P2X₇ expression was also documented in ureter development. In cpk/cpk kidneys, P2X₇-expressing collecting duct cysts dominated histology from two weeks until four weeks after birth, when animals die from uremia. In polycystic kidneys pyknotic nuclei were rarely identified in P2X₇-expressing epithelia, but were detected between cysts, consistent with a non-apoptotic role for P2X₇ in cyst enlargement. Conclusion: P2X₇ is expressed during normal nephrogenesis and in a model of congenital polycystic kidney disease. Further experiments are necessary to define possible functions of P2X₇ in these settings.

-Endoplasmic reticulum (ER) stress was previously reported to contribute to neurogenic hypertension while neuronal angiotensin-converting enzyme type 2 (ACE2) overexpression blunts the disease. To assess which brain regions are important for ACE2 beneficial effects and the contribution of ER stress to neurogenic hypertension, we first used transgenic mice harboring a floxed neuronal hACE2 transgene (SL) and tested the impact of hACE2 knockdown in the subfornical organ (SFO) and paraventricular nucleus (PVN) on deoxycorticosterone acetate (DOCA)-salt hypertension. SL and nontransgenic (NT) mice underwent DOCA-salt or sham treatment while infected with an adenoassociated virus (AAV) encoding Cre recombinase (AAV-Cre) or a control virus (AAV-green fluorescent protein) to the SFO or PVN. DOCA-salt-induced hypertension was reduced in SL mice, with hACE2 overexpression in the brain. This reduction was only partially blunted by knockdown of hACE2 in the SFO or PVN, suggesting that both regions are involved but not essential for ACE2 regulation of blood pressure (BP). DOCA-salt treatment did not increase the protein levels of ER stress and autophagy markers in NT mice, despite a significant increase in BP. In addition, these markers were not affected by hACE2 overexpression in the brain, despite a significant reduction of hypertension in SL mice. To further assess the role of ER stress in neurogenic hypertension, NT mice were infused intracerebroventricularlly with tauroursodeoxycholic acid (TUDCA), an ER stress inhibitor, during DOCA-salt treatment. However, TUDCA infusion failed to blunt the development of hypertension in NT mice. Our data suggest that brain ER stress does not contribute to DOCA-salt hypertension and that ACE2 blunts neurogenic hypertension independently of ER stress. neurogenic hypertension; central nervous system; blood pressure; angiotensin-converting enzyme type 2; deoxycorticosterone acetate THE BRAIN RENIN-ANGIOTENSIN system (RAS) plays a critical role in the regulation of blood pressure (BP) via its actions in various brain regions, such as subfornical organ (SFO), paraventricular nucleus (PVN), rostral ventrolateral medulla (RVLM), and nucleus tractus solitarius (NTS) (17). An overactivated brain RAS leads to the development of neurogenic hypertension at least in part by increasing sympathetic outflow, blunting the baroreflex sensitivity and stimulating vasopressin secretion (17). Angiotensin-converting enzyme type 2 (ACE2), a pivotal RAS component, has been found in many regions in the bran, including SFO and PVN (8). Numerous studies have shown that ACE2 has opposite properties to that of the classic RAS via its conversion of angiotensin (ANG) II into ANG-(1-7) (20). We previously reported that overexpression of ACE2 in the brain blunts the development of hypertension in several animal models (9, 31). However, it is not clear which brain regions might be more important for the preservation of ACE2 compensatory activity.

Riboflavin carrier protein (RCP) is a growth- and development-specific protein. Here, we characterized the expression of this protein in prostate cancer by polyclonal and monoclonal antibodies against chicken RCP. RCP was localized to both androgen-dependent and independent prostate cancer cell lines. Compared to controls, RCP was over-expressed in all 45 prostate adenocarcinomas, irrespective of the Gleason's score or the stage of the disease. The identified RCP had a molecular weight of 38 kDa, similar to RCP purified from chicken. Presence of this protein was also confirmed by siRNA inhibition analysis. Antibodies to chicken RCP inhibited incorporation of tritiated thymidine into DNA and prevented riboflavin uptake in PC3 prostate cancer cells, suggesting a critical function of this protein in prostate cancer cell growth. These data suggest that RCP can be used as a tumor biomarker in prostate cancer.