Purinergic signaling induces cyclooxygenase-1-dependent prostanoid synthesis in microglia: roles in the outcome of excitotoxic brain injury

Cyclooxygenases (COX) are prostanoid synthesizing enzymes constitutively expressed in the brain that contribute to excitotoxic neuronal cell death. While the neurotoxic role of COX-2 is well established and has been linked to prostaglandin E(2) synthesis, the role of COX-1 is not clearly understood. In a model of N-Methyl-D-aspartic acid (NMDA) induced excitotoxicity in the mouse cerebral cortex we found a distinctive temporal profile of COX-1 and COX-2 activation where COX-1, located in microglia, is responsible for the early phase of prostaglandin E(2) synthesis (10 minutes after NMDA), while both COX-1 and COX-2 contribute to the second phase (3-24 hours after NMDA). Microglial COX-1 is strongly activated by ATP but not excitatory neurotransmitters or the Toll-like receptor 4 ligand bacterial lipopolysaccharide. ATP induced microglial COX-1 dependent prostaglandin E(2) synthesis is dependent on P2X7 receptors, extracellular Ca(2+) and cytoplasmic phospholipase A2. NMDA receptor activation induces ATP release from cultured neurons leading to microglial P2X7 receptor activation and COX-1 dependent prostaglandin E(2) synthesis in mixed microglial-neuronal cultures. Pharmacological inhibition of COX-1 has no effect on the cortical lesion produced by NMDA, but counteracts the neuroprotection exerted by inhibition of COX-2 or observed in mice lacking the prostaglandin E(2) receptor type 1. Similarly, the neuroprotection exerted by the prostaglandin E(2) receptor type 2 agonist butaprost is not observed after COX-1 inhibition. P2X7 receptors contribute to NMDA induced prostaglandin E(2) production in vivo and blockage of P2X7 receptors reverses the neuroprotection offered by COX-2 inhibition. These findings suggest that purinergic signaling in microglia triggered by neuronal ATP modulates excitotoxic cortical lesion by regulating COX-1 dependent prostanoid production and unveil a previously unrecognized protective role of microglial COX-1 in excitotoxic brain injury.

Profiling human gene expression with cDNA microarrays

As a result of genomics initiatives worldwide, it has become increasingly easy to obtain cDNA clones representing the 3 ends of many human genes. This unit describes methods that allow these clones to be used as hybridization detectors in a highly parallel assay of gene expression. Protocols are provided for preparing cDNA microarrays, extracting RNA from cells of interest and preparing fluorescently labeled cDNA representations of the message pools, and hybridizing the labeled cDNAs to the microarrays.

Profiling human gene expression with cDNA microarrays

As a result of genomics initiatives worldwide, it has become increasingly easy to obtain cDNA clones representing the 3' ends of many human genes. This unit describes methods that allow these clones to be used as hybridization detectors in a highly parallel assay of gene expression. Protocols are provided for preparing cDNA microarrays, extracting RNA from cells of interest and preparing fluorescently labeled cDNA representations of the message pools, and hybridizing the labeled cDNAs to the microarrays.

Molecular classification of cutaneous malignant melanoma by gene expression profiling

The most common human cancers are malignant neoplasms of the skin. Incidence of cutaneous melanoma is rising especially steeply, with minimal progress in non-surgical treatment of advanced disease. Despite significant effort to identify independent predictors of melanoma outcome, no accepted histopathological, molecular or immunohistochemical marker defines subsets of this neoplasm. Accordingly, though melanoma is thought to present with different 'taxonomic' forms, these are considered part of a continuous spectrum rather than discrete entities. Here we report the discovery of a subset of melanomas identified by mathematical analysis of gene expression in a series of samples. Remarkably, many genes underlying the classification of this subset are differentially regulated in invasive melanomas that form primitive tubular networks in vitro, a feature of some highly aggressive metastatic melanomas. Global transcript analysis can identify unrecognized subtypes of cutaneous melanoma and predict experimentally verifiable phenotypic characteristics that may be of importance to disease progression.

Tc-99m-labeled nonspecific polyclonal human immunoglobulin G is taken up by malignant tumors

A new agent originally introduced for localizing inflammatory lesions is Tc-99m human immunoglobulin G (HIG). Recently, focal uptake of this agent was seen in malignant lesions in a limited number of patients during inflammation imaging studies. In this prospective clinical study, the authors aimed to evaluate the uptake of Tc-99m HIG in malignant lesions. Nineteen patients with histopathologically proven malignant tumors were studied (seven had distant metastases, the primary tumor was surgically removed in two). There was no evidence of inflammation or infection in any patient. The authors imaged patients at 1, 4, and 24 hours after injection. The dose was 15-20 mCi (555-740 MBq). Focal uptake was detected in the primary tumor in six patients and in the metastases in five patients, raising some question about the specificity of Tc-99m HIG imaging for the detection of inflammation and infection.

Tumour localisation with a radioactively labelled reshaped human monoclonal antibody

A genetically reshaped human IgG1 monoclonal antibody (Hu2PLAP) with anti-tumour specificity, was radiolabelled with Indium-111 by chelation with a new macrocyclic compound (DOTA) which allows the production of stable radioimmunoconjugates for in vivo application. This was used to image seven patients with malignant disease, of whom two had been previously exposed to mouse monoclonal antibodies and had developed human anti-mouse antibodies (HAMA). Successful tumour localisation was seen in the four patients with active disease and antigen positive tumours. No patient showed any antibody responses against Hu2PLAP, but three out of six patients tested showed an immune response against the macrocycle DOTA. Reshaped human monoclonal antibodies with anti-tumour specificity may facilitate repeated administrations of radioactive antibodies, thus allowing new possibilities, both in the diagnosis and treatment of cancer.

Distribution of intestinal mast cell proteinase in blood and tissues of normal and Trichinella-infected mice

A sensitive and specific enzyme-linked immunosorbent assay (ELISA) was developed for mouse intestinal mast cell proteinase (IMCP). Specificity was demonstrated by the absence of immunoreactivity with extracts of isolated serosal mast cells (SMC), or with high concentrations (50 micrograms/ml) of the antigenically similar rat mast cell proteinases I or II. The small and large intestines in normal mice were the major sources of IMCP, there being little or no IMCP in non-mucosal tissues. Concentrations of IMCP in normal (non-parasitized) mice were low, but were increased 100-1000-fold intestines of mice infected 10 days earlier with Trichinella spiralis. The kinetic response of secreted IMCP into the blood of mice following infection with T. spiralis was also studied. Systemic release of IMCP coincided with the immune expulsion of adult worms from the intestine, and peak concentrations (9.45 micrograms/ml IMCP) occurred 9 days after infection. The tissue distribution of IMCP, its secretion into blood, and its enteric accumulation during parasite infection, are consistent with a mucosal mast cell (MMC) source for IMCP. The results are discussed in the context of similar findings for rat mast cell proteinase II.