Exclusion of NFAT5 from Mitotic Chromatin Resets Its Nucleo-Cytoplasmic Distribution in Interphase

The transcription factor NFAT5 is a major inducer of osmoprotective genes and is required to maintain the proliferative capacity of cells exposed to hypertonic stress. In response to hypertonicity, NFAT5 translocates to the nucleus, binds to regulatory regions of osmoprotective genes and activates their transcription. Besides stimulus-specific regulatory mechanisms, the activity of transcription factors in cycling cells is also regulated by the passage through mitosis, when most transcriptional processes are downregulated. It was not known whether mitosis could be a point of control for NFAT5.Using confocal microscopy we observed that NFAT5 was excluded from chromatin during mitosis in both isotonic and hypertonic conditions. Analysis of NFAT5 deletions showed that exclusion was mediated by the carboxy-terminal domain (CTD). NFAT5 mutants lacking this domain showed constitutive binding to mitotic chromatin independent of tonicity, which caused them to localize in the nucleus and remain bound to chromatin in the subsequent interphase without hypertonic stimulation. We analyzed the contribution of the CTD, DNA binding, and nuclear import and export signals to the subcellular localization of this factor. Our results indicated that cytoplasmic localization of NFAT5 in isotonic conditions required both the exclusion from mitotic DNA and active nuclear export in interphase. Finally, we identified several regions within the CTD of NFAT5, some of them overlapping with transactivation domains, which were separately capable of causing its exclusion from mitotic chromatin.Our results reveal a multipart mechanism regulating the subcellular localization of NFAT5. The transactivating module of NFAT5 switches its function from an stimulus-specific activator of transcription in interphase to an stimulus-independent repressor of binding to DNA in mitosis. This mechanism, together with export signals acting in interphase, resets the cytoplasmic localization of NFAT5 and prevents its nuclear accumulation and association with DNA in the absence of hypertonic stress

Effects of PPARs Agonists on Cardiac Metabolism in Littermate and Cardiomyocyte-Specific PPAR-γ –Knockout (CM-PGKO) Mice

Understanding the molecular regulatory mechanisms controlling for myocardial lipid metabolism is of critical importance for the development of new therapeutic strategies for heart diseases. The role of PPARγ and thiazolidinediones in regulation of myocardial lipid metabolism is controversial. The aim of our study was to assess the role of PPARγ on myocardial lipid metabolism and function and differentiate local/from systemic actions of PPARs agonists using cardiomyocyte-specific PPARγ –knockout (CM-PGKO) mice. To this aim, the effect of PPARγ, PPARγ/PPARα and PPARα agonists on cardiac function, intra-myocyte lipid accumulation and myocardial expression profile of genes and proteins, affecting lipid oxidation, uptake, synthesis, and storage (CD36, CPT1MIIA, AOX, FAS, SREBP1-c and ADPR) was evaluated in cardiomyocyte-specific PPARγ –knockout (CM-PGKO) and littermate control mice undergoing standard and high fat diet (HFD). At baseline, protein levels and mRNA expression of genes involved in lipid uptake, oxidation, synthesis, and accumulation of CM-PGKO mice were not significantly different from those of their littermate controls. At baseline, no difference in myocardial lipid content was found between CM-PGKO and littermate controls. In standard condition, pioglitazone and rosiglitazone do not affect myocardial metabolism while, fenofibrate treatment significantly increased CD36 and CPT1MIIA gene expression. In both CM-PGKO and control mice submitted to HFD, six weeks of treatment with rosiglitazone, fenofibrate and pioglitazone lowered myocardial lipid accumulation shifting myocardial substrate utilization towards greater contribution of glucose. In conclusion, at baseline, PPARγ does not play a crucial role in regulating cardiac metabolism in mice, probably due to its low myocardial expression. PPARs agonists, indirectly protect myocardium from lipotoxic damage likely reducing fatty acids delivery to the heart through the actions on adipose tissue. Nevertheless a direct non- PPARγ mediated mechanism of PPARγ agonist could not be ruled out

Human aldose reductase expression accelerates diabetic atherosclerosis in transgenic mice

Direct evidence that hyperglycemia, rather than concomitant increases in known risk factors, induces atherosclerosis is lacking. Most diabetic mice do not exhibit a higher degree of atherosclerosis unless the development of diabetes is associated with more severe hyperlipidemia. We hypothesized that normal mice were deficient in a gene that accelerated atherosclerosis with diabetes. The gene encoding aldose reductase (AR), an enzyme that mediates the generation of toxic products from glucose, is expressed at low levels in murine compared with human tissues. Mice in which diabetes was induced through streptozotocin (STZ) treatment, but not nondiabetic mice, expressing human AR (hAR) crossed with LDL receptor–deficient (Ldlr–/–) C57BL/6 male mice had increased aortic atherosclerosis. Diabetic hAR-expressing heterozygous LDL receptor–knockout mice (Ldlr+/–) fed a cholesterol/cholic acid–containing diet also had increased aortic lesion size. Lesion area at the aortic root was increased by STZ treatment alone but was further increased by hAR expression. Macrophages from hAR-transgenic mice expressed more scavenger receptors and had greater accumulation of modified lipoproteins than macrophages from nontransgenic mice. Expression of genes that regulate regeneration of glutathione was reduced in the hAR-expressing aortas. Thus, hAR increases atherosclerosis in diabetic mice. Inhibitors of AR or other enzymes that mediate glucose toxicity could be useful in the treatment of diabetic atherosclerosis

Novel euglycemic and hypolipidemic agents: Pyridine containing unsaturated thiazolidinediones

403-406Pyridyl containing 2,4-thiazolidinediones having cyclic amine as linker have been synthesized. Both unsaturated thiazolidinedione <span style="font-size:15.5pt; mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman";mso-fareast-font-family:="" "times="" roman";mso-ansi-language:en-us;mso-fareast-language:en-us;="" mso-bidi-language:ar-sa"="">6<span style="font-size:15.5pt;mso-bidi-font-size: 8.5pt;font-family:" times="" new="" roman";mso-fareast-font-family:"times="" roman";="" mso-ansi-language:en-us;mso-fareast-language:en-us;mso-bidi-language:ar-sa"=""> and saturated thiazolidinedione 5 and their various salts have been evaluated in db/db mice for euglycemic and hypolipidemic effects. The maleate salt of TZD 6a is found to be a very potent euglycemic and hypolipidemic compound.</span