Topoisomerase poisons activate the transcription factor NF-kappaB in ACH-2 and CEM cells

The nuclear factor kappaB (NF-kappaB) is involved in T cell activation and enhances HIV-1 gene expression. It is activated in response to numerous stimuli, including oxidative stress. Oxidative stress damages membrane lipids, proteins and nucleic acids. We have shown previously that oxidative DNA damage generated by photosensitization could trigger activation of NF-kappaB. We now show that a series of topoisomerase poisons (actinomycin D, camptothecin, daunomycin and etoposide) also activate NF-kappaB (NFKB1/RelA dimer) in ACH-2 and CEM cells. This activation is inhibited by pyrrolidine dithiocarbamate. In ACH-2 cells latently infected by HIV-1, camptothecin, daunomycin and etoposide are able to enhance virus production. Since topoisomerase poisons cause the formation of single- and double-strand breaks in DNA, these lesions might be capable of triggering NF-kappaB activation. Indeed, DNA damaging agents generating adducts (trans-platin and 4-nitroquinoline 1-oxide) and/or crosslinks in DNA (cisplatin and mitomycin C) do not or only weakly activate NF-kappaB in T cell lines.     

Immunoglobulin heavy chain junctional diversity in young and aged humans

The important role of hyperglycemia in the genesis of diabetic renal disease has been strengthened by tissue culture studies, experimental animal models, and clinical trials. A mechanistic understanding of the cellular and biochemical processes that link hyperglycemia with the development of diabetic nephropathy is indispensable for directing the most optimal therapeutic interventions. Likely mediators of the effects of high ambient glucose include activation of the polyol pathway, increased protein kinase C activity, nonenzymatic glycation of circulating or matrix proteins, and/or aberrant synthesis or actions of cytokines and vasomodulatory agents. The latter include angiotensin II, thromboxane, platelet-derived growth factor, endothelins, insulin-like growth factor-1, and transforming growth factor-beta. The studies we review here argue strongly in support of the hypothesis that elevated production and/or activity of transforming growth factor-beta in the kidney is a final common mediator of diabetic renal hypertrophy and mesangial matrix expansion.     

Role of nuclear factor-kappaB activation in cytokine- and sphingomyelinase-stimulated inducible nitric oxide synthase gene expression in vascular smooth muscle cells

Inflammatory cytokines, such as interleukin-1beta (IL-1beta) and tumor necrosis factor-alpha (TNF alpha), are known to activate sphingomyelinase (SMase) and nuclear factor-kappaB (NF-kappaB) in certain cell types, which also stimulate inducible nitric oxide synthase (iNOS) gene in vascular smooth muscle cells (VSMCs). However, it remains unknown whether the SMase pathway is involved in iNOS gene expression in VSMCs. Therefore, the present study was designed to examine whether SMase induces iNOS gene expression via the NF-kappaB activation pathway similar to that of IL-1beta and TNF alpha in cultured rat VSMCs. Neutral SMase, although less potently than IL-1beta and TNF alpha, stimulated nitrite/nitrate (NOx) production, and iNOS messenger RNA and protein expression, as assessed by Northern and Western blot analyses, respectively. Neutral SMase, IL-1beta, and TNF alpha activated NF-kappaB, as revealed by electrophoretic mobility shift assay, and its nuclear translocation, as demonstrated by immunocytochemical study. Neutral SMase potentiated NOx production, iNOS expression, and NF-kappaB activation stimulated by TNF alpha, but not by IL-1beta. Aldehyde peptide proteasome inhibitors completely blocked NOx production, iNOS expression, NF-kappaB activation, and its nuclear translocation induced by cytokines and neutral SMase. IL-1beta and TNF alpha, but not neutral SMase, caused a transient decrease in IkappaB-alpha protein levels, whereas IkappaB-beta protein expression was not affected by either agent. Proteasome inhibitors prevented cytokine-mediated IkappaB-alpha degradation. Several cell-permeable ceramide analogs (C2, C6, and C8), hydrolysis products of sphingomyelin, activated NF-kappaB less potently than neutral SMase, but had no effect on NOx production. These results demonstrate an essential role of NF-kappaB activation in mediation of neutral SMase-induced iNOS expression, but distinct from the proteasome-mediated IkappaB-alpha degradation by cytokines, suggesting the possible involvement of an additional signaling pathway(s).     

Congenital scoliosis caused by a unilateral failure of vertebral segmentation with contralateral hemivertebrae

The complex process of wound healing as well as the signaling systems orchestrating this intricate process remain incompletely defined. Using human keratinocytes in primary culture, we sought to characterize their NF-kappaB responses to wounding alone or in combination with other treatments. We initially characterized these cultured human keratinocytes responses to known NF-kappaB activators (PMA, TNF-alpha and IL-1) using two different assays, immunohistochemistry and electrophoretic mobility shift (EMSA). After eliciting the expected NF-kappaB responses, we applied these same assays to assess responses to either wounding or HeNe irradiation alone. The results obtained indicated that only a modest/sporadic activation of NF-kappaB was elicited by these which was only detectable using immunohistochemistry. When the combination of wounding and HeNe irradiation on NF-kappaB status was assessed, a marked, localized activation of NF-kappaB in keratinocytes along the wound edge was found. Treatment induced NF-kappaB activation (e.g., wounding, HeNe irradiation and combined wounding and HeNe irradiation) was abrogated by pyrrolidine dithiocarbamate (PDTC) which inhibits NF-kappaB activation through an as yet incompletely understood (antioxidant?) mechanism. These data therefore suggest that NF-kappaB and oxidation mediated changes in its activation state likely play important roles in normal cutaneous wound healing.