Intersection of interferon and hypoxia signal transduction pathways in nitric oxide-induced tumor apoptosis.

Activated macrophages play a central role in antitumor immunity. However, the stimuli that activate macrophages to kill tumor cells are not completely understood. Because the center of solid tumors can be hypoxic, we hypothesized that hypoxia may be an important signal in activating macrophages to kill tumor cells. Hypoxia stimulates IFN-primed macrophages to express the inducible nitric oxide synthase (NOS2) and to synthesize nitric oxide (NO). We show that this synergy between IFN and hypoxia is mediated by the direct interaction of the hypoxia inducible factor-1 (HIF-1) and IFN regulatory factor-1 (IRF-1), which are both required for the hypoxic transcription of NOS2. This interaction between HIF-1 and IRF-1 may explain the mechanism by which macrophages infiltrating into tumors are activated to express NOS2 and to produce NO, a mediator of tumor apoptosis.

The orphan receptor hepatic nuclear factor 4 functions as a transcriptional activator for tissue-specific and hypoxia-specific erythropoietin gene expression and is antagonized by EAR3/COUP-TF1.

The erythropoietin (Epo) gene is regulated by hypoxia-inducible cis-acting elements in the promoter and in a 3' enhancer, both of which contain consensus hexanucleotide hormone receptor response elements which are important for function. A group of 11 orphan nuclear receptors, transcribed and translated in vitro, were screened by the electrophoretic mobility shift assay. Of these, hepatic nuclear factor 4 (HNF-4), TR2-11, ROR alpha 1, and EAR3/COUP-TF1 bound specifically to the response elements in the Epo promoter and enhancer and, except for ROR alpha 1, formed DNA-protein complexes that had mobilities similar to those observed in nuclear extracts of the Epo-producing cell line Hep3B. Moreover, both anti-HNF-4 and anti-COUP antibodies were able to supershift complexes in Hep3B nuclear extracts. Like Epo, HNF-4 is expressed in kidney, liver, and Hep3B cells but not in HeLa cells. Transfection of a plasmid expressing HNF-4 into HeLa cells enabled an eightfold increase in the hypoxic induction of a luciferase reporter construct which contains the minimal Epo enhancer and Epo promoter, provided that the nuclear hormone receptor consensus DNA elements in both the promoter and the enhancer were intact. The augmentation by HNF-4 in HeLa cells could be abrogated by cotransfection with HNF-4 delta C, which retains the DNA binding domain of HNF-4 but lacks the C-terminal activation domain. Moreover, the hypoxia-induced expression of the endogenous Epo gene was significantly inhibited in Hep3B cells stably transfected with HNF-4 delta C. On the other hand, cotransfection of EAR3/COUP-TF1 and the Epo reporter either with HNF-4 into HeLa cells or alone into Hep3B cells suppressed the hypoxia induction of the Epo reporter. These electrophoretic mobility shift assay and functional experiments indicate that HNF-4 plays a critical positive role in the tissue-specific and hypoxia-inducible expression of the Epo gene, whereas the COUP family has a negative modulatory role.

[Characteristics of the action of excess thyroid hormones in guinea pigs]. / Osobennosti deistviia izbytka tireoidnykh gormonov u morskikh svinok.

A study was made of the action of various doses of thyroidin in its prolonged administration to guinea pigs on the functional and morphological changes of the thyroid gland and the adenohypophysis. A high sensitivity of guinea pigs to the excess of thyroid hormone in comparison with such in dogs was shown. Already with the less thyroidin doses guinea pigs displayed an increased oxygen consumption under conditions of the basic metabolism, a marked increase of the content of protein-bound iodine in the blood serum and of the corticosteroid urinary excretion. There were revealed no significant differences in the thyroidin action depending on the method of its administration, i.e. in case of a gradual increase of the doses or in the administration of high doses from the very beginning. The presence of significant individual differences in guinea pigs in the resistance to the excess of the thyroid hormones was demonstrated.

[Development of experimental obesity from the overfeeding of rats at sexually immature and mature ages. The effect of the food composition on the development of alimentary obesity in rats]. / Razvitie éksperimental'nogo ozhireniia pri izbytochnom pitanii u krys nepolovozrelogo i polovozrelogo vozrasta. Vliianie sostava pishchi na razvitie alimentarnogo ozhireniia u krys.

Overfeeding Wistar rats starting one and a half months before sexual maturation led to a more marked adiposity than in the animals in which overfeeding was started after the occurrence of sexual maturity. The first category of the animals displayed an increase in the adipose tissue cell count, whereas rats overfed after reaching maturity showed an enlargement of these cells without increase in their number. Adiposity was more pronounced in rats given excessive food consisting mainly of carbohydrates in comparison with the animals of the same age chiefly given an excess of fats. The same rats showed an increase in the relative area of the islar tissue of the pancreas and of the beta-cell mass.