The 12/15-lipoxygenase enzymes react with fatty acids producing active lipid metabolites that are involved in a number of significant disease states. The latter include type 1 and type 2 diabetes (and associated complications), cardiovascular disease, hypertension, renal disease, and the neurological conditions Alzheimer’s disease and Parkinson’s disease. A number of elegant studies over the last thirty years have contributed to unraveling the role that lipoxygenases play in chronic inflammation. The development of animal models with targeted gene deletions has led to a better understanding of the role that lipoxygenases play in various conditions. Selective inhibitors of the different lipoxygenase isoforms are an active area of investigation, and will be both an important research tool and a promising therapeutic target for treating a wide spectrum of human diseases.

The transcription factor Pdx1 is expressed in the pancreatic ␤-cell, where it is believed to regulate several ␤-cell-specific genes. Whereas binding by Pdx1 to elements of ␤-cell genes has been demonstrated in vitro, almost none of these genes has been demonstrated to be a direct binding target for Pdx1 within cells (where complex chromatin structure exists). To determine which ␤-cell promoters are bound by Pdx1 in vivo, we performed chromatin immunoprecipitation assays using Pdx1 antiserum and chromatin from ␤-TC3 cells and Pdx1-transfected NIH3T3 cells and subsequently quantitated co-immunoprecipitated promoters using realtime PCR. We compared these in vivo findings to parallel immunoprecipitations in which Pdx1 was allowed to bind to promoter fragments in in vitro reactions. Our results show that in all cells Pdx1 binds strongly to the insulin, islet amyloid polypeptide, glucagon, Pdx1, and Pax4 promoters, whereas it does not bind to either the glucose transporter type 2 or albumin promoters. In addition, no binding by Pdx1 to the glucokinase promoter was observed in ␤-cells. In contrast, in in vitro immunoprecipitations, Pdx1 bound all promoters to an extent approximately proportional to the number of Pdx1 binding sites. Our findings suggest a critical role for chromatin structure in directing the promoter binding selectivity of Pdx1 in ␤-cells and non-␤-cells.

Atrial fibrillation (AF) is the most common form of sustained clinical arrhythmia. We previously mapped an AF locus to chromosome 5p13 in an AF family with sudden death in early childhood. Here we show that the specific AF gene underlying this linkage is NUP155, which encodes a member of the nucleoporins, the components of the nuclear pore complex (NPC). We have identified a homozygous mutation, R391H, in NUP155 that cosegregates with AF, affects nuclear localization of NUP155, and reduces nuclear envelope permeability. Homozygous NUP155(-/-) knockout mice die before E8.5, but heterozygous NUP155(+/-) mice show the AF phenotype. The R391H mutation and reduction of NUP155 are associated with inhibition of both export of Hsp70 mRNA and nuclear import of Hsp70 protein. These human and mouse studies indicate that loss of NUP155 function causes AF by altering mRNA and protein transport and link the NPC to cardiovascular disease.

In both type 1 and type 2 diabetes, pancreatic islet dysfunction results in part from cytokine-mediated inflammation. The ubiquitous eukaryotic translation initiation factor 5A (eIF5A), which is the only protein to contain the amino acid hypusine, contributes to the production of proinflammatory cytokines. We therefore investigated whether eIF5A participates in the inflammatory cascade leading to islet dysfunction during the development of diabetes. As described herein, we found that eIF5A regulates iNOS levels and that eIF5A depletion as well as the inhibition of hypusination protects against glucose intolerance in inflammatory mouse models of diabetes. We observed that following knockdown of eIF5A expression, mice were resistant to β cell loss and the development of hyperglycemia in the low-dose streptozotocin model of diabetes. The depletion of eIF5A led to impaired translation of iNOS-encoding mRNA within the islet. A role for the hypusine residue of eIF5A in islet inflammatory responses was suggested by the observation that inhibition of hypusine synthesis reduced translation of iNOS-encoding mRNA in rodent β cells and human islets and protected mice against the development of glucose intolerance the low-dose streptozotocin model of diabetes. Further analysis revealed that hypusine is required in part for nuclear export of iNOS-encoding mRNA, a process that involved the export protein exportin1. These observations identify the hypusine modification of eIF5A as a potential therapeutic target for preserving islet function under inflammatory conditions.