Placenta growth factor (PlGF) is a member of the vascular endothelial growth factor family of cytokines that control vascular and lymphatic endothelium development. It has been implicated in promoting angiogenesis in pathological conditions via signaling to vascular endothelial growth factor receptor-1. PlGF expression is induced by hypoxia and proinflammatory stimuli. Metal responsive transcription factor 1 (MTF-1) was shown to take part in the hypoxic induction of PlGF in Ras-transformed mouse embryonic fibroblasts. Here we report that PlGF expression is also controlled by NF-kappaB. We identified several putative binding sites for NF-kappaB in the PlGF promoter/enhancer region by sequence analyses, and show binding and transcriptional activity of NF-kappaB p65 at these sites. Expression of NF-kappaB p65 from a plasmid vector in HEK293 cells caused a substantial increase of PlGF transcript levels. Furthermore, we found that hypoxic conditions induce nuclear translocation and interaction of MTF-1 and NF-kappaB p65 proteins, suggesting a role for this complex in hypoxia-induced transcription of PlGF.
Article NF-κB contributes to transcription of placenta growth factor and interacts with metal responsive transcription factor-1 in hypoxic human cells was published on January 1, 2006 in the journal Biological Chemistry (volume 387, issue 1).
Hair cells are the most vulnerable elements in the inner ear and their degeneration is the most common cause of hearing loss. In the last few years progress has been made in uncovering the molecular mechanisms involved in hair cell damage and death. However, little is known about factors important for hair cell survival. Recently, it has been demonstrated that the transcription factor NF-kappaB is required for survival of immature auditory hair cells in vitro. Here we used DNA microarray technology to explore NF-kappaB downstream events in organ of Corti explants of postnatal day-5 Sprague-Dawley rats which were exposed to a cell-permeable NF-kappaB-inhibitory peptide. Gene expression was analyzed using DNA microarray technology. Genes were selected on the basis of comparative analysis, which reliably distinguished the NF-kappaB inhibitor-treated samples from control samples. Interestingly, among the up-regulated genes was the gene coding for the regulatory subunit of phosphatidylinositol 3-kinase. Moreover, inhibition of the phosphatidylinositol 3-kinase signaling pathway in organ of Corti explants exposed to the NF-kappaB inhibitor reduced caspase-3 activation. These data link NF-kappaB-dependent hair cell death to phosphatidylinositol 3-kinase signaling.
Abstract Objective/Hypothesis: Mammalian auditory hair cells that are unable to regenerate and various agents, including gentamicin, can irreversibly damage the hair cells. Erythropoietin, known as the primary regulator of erythropoiesis, exerts also neuroprotective effects by binding to its receptor. We tested whether erythropoietin can protect the hair cells from gentamicin‐induced damage. Study Design: This study localized the erythropoietin receptor in the cochlea and analyzed the effect of erythropoietin on gentamicin‐damaged hair cells in vitro. Methods: Expression of erythropoietin receptor in the rat cochlea was analyzed by reverse transcriptase–polymerase chain reaction (RT‐PCR) and immunohistochemistry. Protection of auditory hair cells from gentamicin was tested in vitro by exposing cultured rat organs of Corti with increasing concentrations of erythropoietin (0.1 U/mL, 1 U/mL, and 10 U/mL). Results: We detected erythropoietin and erythropoietin receptor mRNA expression in the organ of Corti, spiral ganglion, and stria vascularis by RT‐PCR. Immunohistochemistry revealed that the erythropoietin receptor localizes to the outer and inner hair cells and supporting cells of the organ of Corti, as well as to the spiral ganglion cells and the stria vascularis. Significantly less hair cell loss occurred in the organs of Corti that were pretreated with 0.1 U/mL erythropoietin as compared with samples treated with gentamicin only. Conclusion: Decreased hair cell loss in erythropoietin‐treated organs of Corti that had been exposed to gentamicin provides evidence for a protective effect of erythropoietin in aminoglycoside‐induced hair cell death.
