There is increasing evidence that an augmented state of cellular oxidative stress modulates the expression of stress genes implicated in diseases associated with health disparities such as certain cancers and diabetes. Lens epithelium -derived growth factor p75 (LEDGF/ p75), also known as DFS70 autoantigen, is emerging as a survival oncoprotein that promotes resistance to oxidative stress -induced cell death and chemotherapy. We previously showed that LEDGF/p75 is targeted by autoantibodies in prostate cancer patients and is overexpressed in prostate tumors, and that its stress survival activity is abrogated during apoptosis. LEDGF/ p75 has a COOH-terminally truncated splice variant, p52, whose role in stress survival and apoptosis has not been thoroughly investigated. We observed unbalanced expression of these proteins in a panel of tumor cell lines, with LEDGF/p75 generally expressed at higher levels. During apoptosis, caspase-3 cleaved p52 to generate a p38 fragment that lacked the NH 2 -terminal PWWP domain and failed to transactivate the Hsp27 promoter in reporter assays. However, p38 retained chromatin association properties and repressed the transactivation potential of LEDGF/p75. Overexpression of p52 or its variants with truncated PWWP domains in several tumor cell lines induced apoptosis, an activity that was linked to the presence of an intron-derived COOH-terminal sequence. These results implicate the PWWP domain of p52 in transcription function but not in chromatin association and proapoptotic activities. Consistent with their unbalanced expression in tumor cells, LEDGF/p75 and p52 seem to play antagonistic roles in the cellular stress response and could serve as targets for novel antitumor therapies.

SUMMARYThe sympathetic nervous system plays a central role in the pathophysiology not only of hypertension and other cardiovascular diseases but also metabolic disorders including disturbances of glucose and lipid homeostasis. A centrally acting sympathetic agent is therefore attractive not only for lowering blood pressure, but also intervening with multiple disease processes. Older agents such as clonidine and guanabenz have numerous side effects, including sedation and dry mouth that limit their acceptability to patients. Moxonidine and the related agent rilmenidine have greatly reduced side effects, because they have reduced activity at the α 2 -adrenergic receptors that mediate these undesirable actions. Instead, moxonidine and rilmenidine act primarily through a novel cellular site, termed the I 1 -imidazoline receptor. The molecular biology of the I 1 -imidazoline receptor protein has recently been described, and the cell signaling pathways linked to this protein have been characterized. Moxonidine has unique effects on a number of cell types through this unusual cellular site of action. There are multiple therapeutic implications of these cellular actions, especially for metabolic syndrome and its associated derangements in glucose and lipid metabolism. Finally, the clinical trials that seemed to identify an unfavorable outcome in severe heart failure are dissected and critiqued. We conclude that moxonidine and future successors to this agent could be of great value in treating multiple chronic diseases.

Objective. Autoantibodies to DNA topoisomerase I (topo I) are associated with diffuse systemic sclerosis (SSc), appear to be antigen driven, and may be triggered by cryptic epitopes exposed during in vivo topo I fragmentation. These autoantibodies recognize topo I and fragments of this autoantigen generated during apoptosis and necrosis. We undertook this study to determine whether lysosomal cathepsins are involved in topo I fragmentation during necrosis.Methods. Topo I cleavage during necrosis was assessed by immunoblotting of lysates from L929 fibroblasts exposed to tumor necrosis factor ␣ (

High-risk strains of human papillomavirus, including HPV 16, cause human cervical carcinomas, due in part to the activity of their E6 oncogene. E6 interacts with a number of cellular proteins involved in host-initiated apoptotic responses. Paradoxically, literature reports show that E6 can both protect cells from and sensitize cells to tumor necrosis factor (TNF). To examine this apparent contradiction, E6 was transfected into U2OS cells and stable clones were treated with TNF. Intriguingly, clones with a high level of E6 expression displayed an increased sensitivity to TNF by undergoing apoptosis, while those with low expression were resistant. Furthermore, TNF treatment of cells in which the expression of E6 was regulated by the addition of doxycycline demonstrated clearly that while low levels of E6 protect cells from TNF, high levels sensitize cells. Together, these results demonstrate that virus-host interactions can be complex and that both quantitative and qualitative aspects are important in determining outcome.

Metabolic Syndrome X, characterized by insulin resistance, dyslipidemia, obesity, and hypertension, affects over 70 million Americans. Imidazoline drugs, such as moxonidine, are emerging therapeutic agents for conditions associated with Syndrome X. Studies from our laboratory showed a reduction in blood pressure when moxonidine was injected into the rostral ventrolateral medulla (RVLM) of spontaneously hypertensive rats (SHR). Moxonidine also activated the insulin signaling cascade and increased glucose uptake in HEK 293T cells. Recently, we obtained a novel imidazoline compound, S43126. Interestingly, like moxonidine, S43126 reduced blood pressure in SHR rat model, whose effect was offset by I1‐imidazoline antagonist, efaroxan. However, S43126 showed no activity at the adrenoreceptors in rat tail artery. Immunoblotting analyses also showed that S43126 activated components of the insulin signaling pathway, such as protein kinase B (PKB/Akt) and insulin receptor substrates (IRS1/2), which were abolished by efaroxan. Furthermore, treatment of cells overexpressing cloned I1‐imidazoline receptor (IRAS) or siRNA‐silenced IRAS confirmed that the I1‐imidazoline receptor contributed to moxonidine and S43126 stimulation of the insulin signaling cascade. These results implicate S43126 and moxonidine as centrally acting antihypertensive agents that may regulate the insulin receptor signaling. This work is supported by NIH RO3DK067945‐01.

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