Tepoxalin, a dual inhibitor of cyclooxygenase (CO) and 5-lipoxygenase (5LO) with cytokine modifying activity, is also a potent inhibitor of the transcription factor, nuclear factor kappa B (NF kappa B). NF kappa B is a pleiotropic activator that is involved in the regulation of many genes whose products participate in immune or inflammatory responses. Tepoxalin inhibited in a dose related manner NF kappa B activation by PMA + ionomycin or H2O2 in Jurkat and HeLa cells. TNF-alpha-induced NF kappa B was also inhibited by tepoxalin in HeLa cells, while relatively less marked inhibition was observed in Jurkat cells. Activation of NF kappa B in several monocytic cell lines was also suppressed by tepoxalin. However AP-1 stimulation under the same conditions was not affected by tepoxalin. Other CO, LO inhibitors such as naproxen or zileuton did not inhibit NF kappa B activities. This inhibitory activity of tepoxalin was further illustrated by its suppression of NF kappa B regulated genes such as IL-6 in PMA stimulated human PBL and c-myc in IL-2 dependent T cell lines. Tepoxalin also blocked PMA + ionomycin-induced I kappa B degradation in a time-dependent fashion. The possible mechanism of tepoxalin in NF kappa B activation and its potential clinical application are discussed.

The effect of alloxan diabetes on the activity of monoamine oxidase was studied in three regions of the rat brain at various time intervals after the onset of diabetes. It was observed that monoamine oxidase activity was decreased at early time intervals after diabetes, followed by a recovery in all three regions of the brain. A reversal of the effect was observed with insulin administration to the diabetic rats.

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Hormone-dependent phosphorylation of progesterone receptors (PRs) plays a functional role in their transcriptional activity. However, hormone-independent phosphorylation has also been shown to modulate the chicken PR-mediated trans-activation in the presence of phosphorylating agents. The present study was designed to investigate the effects of protein kinase A- and protein kinase C-mediated signal transduction pathways on the regulation of the activity of the two forms of human PR (hPRA and hPRB). Similar to chicken PR, hPR was activated by 8-bromo-cAMP (8-Br-cAMP) in the absence of ligand, whereas 8-Br-cAMP synergized with the progestin agonist R5020 to amplify hPRA- and hPRB-mediated reporter activity. Interestingly, the effect of 8-Br-cAMP was much more pronounced on hPRA-induced trans-activation than on hPRB. This differential regulation by 8-Br-cAMP could also be mimicked by okadaic acid. Both mouse mammary tumor virus-thymidine kinase-chloramphenicol acetyl transferase and progesterone response element-thymidine kinase-chloramphenicol acetyl transferase showed a similar response to 8-Br-cAMP in the presence of R5020. Protein kinase C, on the other hand, did not discriminate between hPRA- and hPRB-mediated trans-activation. Unlike 8-Br-cAMP, phorbol 12-myristate 13-acetate did not cause marked ligand-independent trans-activation through either of the two receptor forms. RU486, an antagonist of progestin, preferentially blocked R5020-induced trans-activation compared to R5020 + 8-Br-cAMP synergism. As expected, H-89, a specific inhibitor of protein kinase A was more effective in inhibiting ligand-independent activity. Western analysis of transfected receptors suggested that 8-Br-cAMP and 8-Br-cAMP + R5020 but not R5020 alone down-regulated the level of hPRB in COS-1 cells. Only marginal modulation of hPRA levels was observed with R5020 treatment in the presence and absence of 8-Br-cAMP. These data suggest that R5020 and 8-Br-cAMP mediate PR-dependent transactivation through distinct pathways, and that phosphorylation can differentially regulate the activity of hPRA and hPRB forms, an observation which may be important for selective target gene activation in vivo by progestins.

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