Subcellular site of superoxide dismutase expression differentially controls AP-1 activity and injury in mouse liver following ischemia/reperfusion.

Acute damage following ischemia and reperfusion (I/R) in the liver is in part caused by the generation of reactive oxygen species, such as superoxides, during the reperfusion event. Gene therapy directed at attenuating mitochondrial superoxide production following warm I/R injury in the liver has demonstrated great promise in reducing acute hepatocellular damage. In the present study, we have compared the therapeutic effects of ectopic expression of mitochondrial (MnSOD) and cytoplasmic (Cu/ZnSOD) superoxide dismutase using recombinant adenoviral vectors for reducing I/R damage in the liver. Consistent with previous observations, recombinant adenoviral delivery of MnSOD to the liver significantly attenuated both acute liver damage and AP-1 activation following I/R injury to the livers of mice. However, ectopic expression of Cu/ZnSOD diminished neither I/R-induced elevations in serum alanine transaminase (ALT) nor AP-1 activation. Interestingly, baseline activation of AP-1 before I/R-induced injury was seen in livers infected with recombinant Ad.Cu/ZnSOD, but not Ad.MnSOD or Ad.LacZ, vectors. The level of Cu/ZnSOD-induced AP-1 activation was significantly reduced by ablation of Kupffer cells or by coexpression of catalase, suggesting that increased H(2)O(2) production facilitated by Cu/ZnSOD in hepatocytes and/or Kupffer cells may be responsible for AP-1 activation. In vitro reconstitution studies using hepatocyte and macrophage cell lines demonstrated that Cu/ZnSOD overexpression induces AP-1 in both cell types, and that secretion of a Cu/ZnSOD-induced macrophage factor is capable of elevating AP-1 in hepatocytes. In summary, our findings demonstrate that subcellular sites of superoxide production in the liver can differentially affect the outcome of I/R injury in the liver and selectively influence AP-1 activation.

Developmental expression of catenins and associated proteins during submucosal gland morphogenesis in the airway.

Although lymphoid enhancer binding factor-1 (Lef-1) plays an obligatory role in airway submucosal gland (SMG) development, its expression alone is not an adequate signal for initiating gland morphogenesis. Because Lef-1 forms a bipartite transcription factor with beta-catenin to mediate wnt pathway signaling, we investigated the expression of beta-catenin and associated proteins during SMG development with both in situ hybridization and immunocytochemistry. Unexpectedly, high levels of E-cadherin mRNA were expressed by cells in developing gland buds from the earliest stages through subsequent differentiation into mature glands. In contrast, a decreased level of E-cadherin immunoreactivity in stage I gland bud cells suggested that post-translational modulation of E-cadherin protein levels may play a critical role in early stages of gland morphogenesis. Adenomatous polyposis coli (APC) mRNA was expressed relatively weakly in the developing ferret trachea, but higher levels of protein staining were observed throughout the cytoplasm of gland buds and surface epithelial cells. B-Catenin mRNA was abundantly expressed throughout the tracheal epithelium and at the highest levels in primordial gland buds. B-Catenin protein localized to the basolateral membranes of all airway epithelial cell types. However, no detectable increases in nuclear or cytoplasmic staining were associated with gland buds, as would be expected if beta-catenin served as a transcriptional cofactor for Lef-1 in gland morphogenesis. Additional studies demonstrated the gamma-catenin distribution to be remarkably similar to that of beta-catenin, whereas alpha-catenin staining was more diffuse in the cytoplasm of airway epithelial and gland bud cells. These descriptive results do not rule out a role for wnt signaling in SMG development , but provide no evidence that beta-catenin, or gamma-catenin, is a cofactor in Lef-1 regulation of SMG development.