prostaglandin-d2 and Insulinoma

The pro-inflammatory cytokine IL-1β leads to losses in functional β-cell mass in part by inducing the expression of genes that produce soluble mediators of inflammation, such as cyclooxygenase-2 (COX2). In the current study, we sought to understand what factors control the COX2 gene in response to IL-1β and how prostaglandins downstream of COX2 impact pro-inflammatory gene transcription in pancreatic β-cells. We analyzed COX2 gene expression in response to different maneuvers impacting NF-κB proteins. Also, we report alterations in the expression of COX2, EP-3 and EP-4 receptor genes by PGD(2) and PGE(2). Moreover, we examined whether PGD(2) and PGE(2) regulated NF-κB and interferon-gamma activated sequence (GAS) reporter gene activity. IL-1β-mediated induction of the COX2 gene requires the p65 and p50 subunits of NF-κB. In addition, PGD(2) and PGE(2) coordinately alter COX2 and EP receptor gene expression patterns and potentiate the cytokine-mediated transcriptional activity of promoters containing NF-κB or GAS response elements.

Topics: Animals; Cell Line, Tumor; Cyclooxygenase 2; Dinoprostone; Gene Expression Regulation, Enzymologic; Genes, Reporter; Inflammation Mediators; Insulin-Secreting Cells; Insulinoma; Interleukin-1beta; NF-kappa B p50 Subunit; Pancreatic Neoplasms; Promoter Regions, Genetic; Prostaglandin D2; Prostaglandins; Rats; Receptors, Prostaglandin E, EP3 Subtype; Receptors, Prostaglandin E, EP4 Subtype; Transcription Factor RelA

Peroxisome proliferator-activated receptor-gamma (PPARgamma) ligands have been shown to possess anti-inflammatory properties that include the inhibition of transcription factor activation and the expression of inflammatory genes. Using pancreatic beta-cells, we have shown that PPARgamma ligands such as 15-deoxy-Delta(12,14)-prostaglandin J(2) (PGJ(2)) attenuate interferon-gamma-induced signal transducer and activator of transcription 1 activation and interleukin (IL)-1beta-induced nuclear factor-kappaB activation by a pathway that correlates with endoplasmic reticulum stress and the induction of the unfolded protein response (UPR). The UPR is a conserved cellular response activated by a number of cell stressors and is believed to alleviate the stress and promote cell survival. However, prolonged activation of the UPR results in cellular death by apoptosis. In this report, we have examined the effects of PGJ(2) on UPR activation and the consequences of this activation on cell survival. Consistent with induction of a cell death pathway, treatment of rat islets and RINm5F cells for 24 h with PGJ(2) results in caspase-3 activation and caspase-dependent beta-cell death. The actions of these ligands do not appear to be selective for beta-cells, because PGJ(2) stimulates macrophage apoptosis in a similar fashion. Associated with cell death is the enhanced phosphorylation of eukaryotic initiation factor 2alpha (eIF2alpha), and in cells expressing a mutant of eIF2alpha that cannot be phosphorylated, the stimulatory actions of PGJ(2) on caspase-3 activation are augmented. These findings suggest that, whereas PGJ(2)-induced UPR activation is associated with an inhibition of cytokine signaling, prolonged UPR activation results in cell death, and that eIF2alpha phosphorylation may function in a protective manner to attenuate cell death.

Topics: Animals; Apoptosis; Caspase 3; Cells, Cultured; Enzyme Activation; Eukaryotic Initiation Factor-2; Insulin-Secreting Cells; Insulinoma; Ligands; Macrophages; Male; Mice; Mutation; Pancreatic Neoplasms; Phosphorylation; PPAR gamma; Prostaglandin D2; Protein Folding; Rats; Rats, Sprague-Dawley; Time Factors