Angiotensin II increases adipose angiotensinogen expression

In addition to the well-defined contribution of the liver, adipose tissue has been recognized as an important source of angiotensinogen (AGT). The purpose of this study was to define the angiotensin II (ANG II) receptors involved in regulation of adipose AGT and the relationship of this control to systemic AGT and/or angiotensin peptide concentrations. In LDL receptor-deficient (LDLR(-/-)) male mice, adipose mRNA abundance of AGT was 68% of that in liver, and adipose mRNA abundance of the angiotensin type 1a (AT(1a)) receptor (AT(1a)R) was 38% of that in liver, whereas mRNA abundance of the angiotensin type 2 (AT(2)) receptor (AT(2)R) was 57% greater in adipose tissue than in liver. AGT and angiotensin peptide concentrations were decreased in plasma of AT(1a)R-deficient (AT(1a)R(-/-)) mice and were paralleled by reductions in AGT expression in liver. In contrast, adipose AGT mRNA abundance was unaltered in AT(1a)R(-/-) mice. AT(2)R(-/-) mice exhibited elevated plasma angiotensin peptide concentrations and marked elevations in adipose AGT and AT(1a)R mRNA abundance. Increases in adipose AGT mRNA abundance in AT(2)R(-/-) mice were abolished by losartan. In contrast, liver AGT and AT(1a)R mRNA abundance were unaltered in AT(2)R(-/-) mice. Infusion of ANG II for 28 days into LDLR(-/-) mice markedly increased adipose AGT and AT(1a)R mRNA but did not alter liver AGT and AT(1a)R mRNA. These results demonstrate that differential mRNA abundance of AT(1a)/AT(2) receptors in adipose tissue vs. liver contributes to tissue-specific ANG II-mediated regulation of AGT. Chronic infusion of ANG II robustly stimulated AT(1a)R and AGT mRNA abundance in adipose tissue, suggesting that adipose tissue serves as a primary contributor to the activated systemic renin-angiotensin system.     

Autoantigen-specific TGFbeta-induced Foxp3+ regulatory T cells prevent autoimmunity by inhibiting dendritic cells from activating autoreactive T cells

Several strategies are being designed to test the therapeutic potential of Ag-specific regulatory T cells to prevent or treat autoimmune diseases. In this study, we demonstrate that naive CD4+ Foxp3- T cells specific for a naturally expressed autoantigen (H+/K+ ATPase) can be converted to Foxp3+ T regulatory cells (Tregs) when stimulated in presence of TGFbeta. TGFbeta-induced Tregs (iTregs) have all the characteristics of naturally generated regulatory T cells in vitro, and more importantly, are effective at preventing organ-specific autoimmunity in a murine model of autoimmune gastritis. H+/K+ ATPase specific iTregs were able to inhibit the initial priming and proliferation of autoreactive T cells, and appear to do so by acting on H+/K+ ATPase presenting dendritic cells (DC). DC exposed to iTregs in vivo were reduced in their ability to stimulate proliferation and cytokine production by H+/K+ ATPase specific T cells. iTregs specifically reduced CD80 and CD86 expression on the surface of H+/K+ ATPase presenting DC in vitro. These studies reveal the therapeutic potential of Ag specific iTregs to prevent autoimmunity, and provide a mechanism by which this population of regulatory T cells, and perhaps others, mediate their suppressive effects in vivo.     

Sperm production and mating potential of males after a cold shock on pupae of the parasitoid wasp Dinarmus basalis (Hymenoptera: Pteromalidae)

For ectothermic species, temperature is a key environmental factor influencing several aspects of their physiology and ecology, acting particularly on reproduction. To measure the consequences of a severe thermal stress during development on male reproduction, a cold shock (1h at -18 degrees C) was tested on Dinarmus basalis pupae. D. basalis (Hymenoptera: Pteromalidae) is a parasitoid wasp in which sperm management in both male and female is of prime importance. After a cold shock, developmental success was reduced, with a quarter of cold-shocked males not emerging correctly. The stress effects were estimated at the level of sperm stock in seminal vesicles of males at different ages and on the ability of 2-day-old males to access females in single and multiple mating and in male-male competition. Cold-shocked males had a reduced sperm stock compared to control males and this difference persisted with age. The rate of sperm production was similar in both groups. The consequences of a cold shock on male reproductive ability were perceptible in multiple mating and male-male competition but not in single mating. Cold-shocked males were at a disadvantage, inseminating fewer females and copulating less frequently. Finally, male pupae of D. basalis were able to withstand severe temperature stresses and their reproductive functions were partially preserved.     

Neuroprotection and stroke: time for a compromise

In April 2007, there existed a repertory of 286 trials concerned with acute ischemic stroke on the Stroke Trials Registry ( http://www.strokecenter.org/trials/ ), of which 209 trials were considered as complete (with no evidence of patient benefit unless one considers the much hard fought for and modest results of the tPA studies). Among other questions arising from such failures, one can wonder whether the plethora of pharmacological agents that exhibited neuroprotective properties in pre-clinical studies were selected for clinical trials entirely based upon their experimental efficacy. This mini-review will try to point out some of the weaknesses that could underline the failure of both researchers and clinicians involved in the field of stroke to obtain their ultimate goal – brain protection.     

Analysis of the DNA-binding sequence specificity of the archaeal transcriptional regulator Ss-LrpB from Sulfolobus solfataricus by systematic mutagenesis and high resolution contact probing

To determine the sequence specificity of dimeric Ss-LrpB, a high resolution contact map was constructed and a saturation mutagenesis conducted on one half of the palindromic consensus box. Premodification binding interference indicates that Ss-LrpB establishes most of its tightest contacts with a single strand of two major groove segments and interacts with the minor groove at the center of the box. The requirement for bending is reflected in the preference for an A+T rich center and confirmed with C.G and C.I substitutions. The saturation mutagenesis indicates that major groove contacts with C.G at position 5 and its symmetrical counterpart are most critical for the specificity and strength of the interaction. Conservation at the remaining positions improved the binding. Hydrogen bonding to the O6 and N7 acceptor atoms of the G5' residue play a major role in complex formation. Unlike many other DNA-binding proteins Ss-LrpB does not establish hydrophobic interactions with the methyls of thymine residues. The binding energies determined from the saturation mutagenesis were used to construct a sequence logo, which pin-points the overwhelming importance of C.G at position 5. The knowledge of the DNA-binding specificity will constitute a precious tool for the search of new physiologically relevant binding sites for Ss-LrpB in the genome.     

Contribution of the FtsQ transmembrane segment to localization to the cell division site

The Escherichia coli cell division protein FtsQ is a central component of the divisome. FtsQ is a bitopic membrane protein with a large C-terminal periplasmic domain. In this work we investigated the role of the transmembrane segment (TMS) that anchors FtsQ in the cytoplasmic membrane. A set of TMS mutants was made and analyzed for the ability to complement an ftsQ mutant. Study of the various steps involved in FtsQ biogenesis revealed that one mutant (L29/32R;V38P) failed to functionally insert into the membrane, whereas another mutant (L29/32R) was correctly assembled and interacted with FtsB and FtsL but failed to localize efficiently to the cell division site. Our results indicate that the FtsQ TMS plays a role in FtsQ localization to the division site.     

The salvador-warts-hippo pathway is required for epithelial proliferation and axis specification in Drosophila

In Drosophila, the body axes are specified during oogenesis through interactions between the germline and the overlying somatic follicle cells [1-5]. A Gurken/TGF-alpha signal from the oocyte to the adjacent follicle cells assigns them a posterior identity [6, 7]. These posterior cells then signal back to the oocyte, thereby inducing the repolarization of the microtubule cytoskeleton, the migration of the oocyte nucleus, and the localization of the axis specifying mRNAs [8-10]. However, little is known about the signaling pathways within or from the follicle cells responsible for these patterning events. We show that the Salvador Warts Hippo (SWH) tumor-suppressor pathway is required in the follicle cells in order to induce their Gurken- and Notch-dependent differentiation and to limit their proliferation. The SWH pathway is also required in the follicle cells to induce axis specification in the oocyte, by inducing the migration of the oocyte nucleus, the reorganization of the cytoskeleton, and the localization of the mRNAs that specify the anterior-posterior and dorsal-ventral axes of the embryo. This work highlights a novel connection between cell proliferation, cell growth, and axis specification in egg chambers.     

Activation of mitochondrial-driven apoptosis in skeletal muscle cells is not mediated by reactive oxygen species production

While the acquisition of apoptosis resistance is part of the differentiation program of skeletal muscle cells, differentiated muscle cells can undergo apoptosis in response to physiological or pathological stimuli. The generation of reactive oxygen species by mitochondria plays a major role in the control of apoptosis in many cell types. Indeed their involvement in controlling apoptosis in differentiated muscle cells, or in generating resistance to apoptosis remains unknown. Moreover, differentiated muscle cells specifically express the uncoupling protein-3, a mitochondrial protein potentially involved in controlling reactive oxygen species production. To study the role of mitochondrial reactive oxygen species in the control of apoptosis in skeletal muscle cells, L6E9 myoblasts and myotubes were exposed to staurosporine, an inducer of apoptosis via mitochondrial pathways. Staurosporine activated apoptotic pathways (i.e. caspase-3 and caspase-9) increasing reactive oxygen species in myoblasts and, to a minor extent, in myotubes. However, the increase in reactive oxygen species was not needed to induce apoptosis nor was it involved in the differential sensitization of myoblasts and myotubes to apoptosis. Moreover, expression of uncoupling protein-3 in myotubes did not affect reactive oxygen species production, although it produced a slight sensitization for staurosporine-induced apoptosis. Results indicate that apoptotic activation in skeletal muscle cells mainly involves reactive oxygen species-independent mechanisms and that mitochondrial uncoupling protein-3 is not protective either for reactive oxygen species production or for apoptotic activation in muscle cells.