Glutamate, the major excitatory neurotransmitter in the central nervous system, gates three types of ionotropic receptors: NMDA, 1 AMPA, and kainate (3). Five kainate receptor subunits in two homology groups have been identified: KA1, KA2, and GluR5, GluR6, and GluR7 (4, 5). Expression of individual GluR5-7 subunits in heterologous systems results in homomeric receptors that respond to glutamate or kainic acid with a rapidly desensitizing current (5, 6). KA1 and KA2, on the other hand, are functional only when coexpressed with GluR5, -6, or -7 (5, 6).PSD-95, also known as synapse-associated protein 90, is a scaffold protein that contains three PDZ domains, a SH3 domain, and a guanylate kinase domain (7). The PDZ domains have been shown to bind to the C terminus of NMDA receptor NR2 and kainate receptor GluR6 subunits, and these interactions are important for the clustering of NMDA or kainate receptors in the postsynaptic membrane (7-9). In addition, PSD-95 also binds to cytoskeletal linker proteins and cytoplasmic signaling proteins such as neuronal nitric oxide synthase and the Src family protein tyrosine kinase Fyn (10, 11). PSD-95 appears to link NMDA or kainate receptors to a variety of cellular signaling cascades. In transgenic mice lacking PSD-95, although the localization of NMDA receptors at post-synaptic density remains unaltered, the frequency dependence of NMDAdependent long-term potentiation and long-term depression is shifted, and spatial learning is severely impaired (12). Suppression of PSD-95 expression inhibits NMDA receptor-mediated activation of nitric-oxide synthase and neuronal excitotoxicity (13), which suggests that PSD-95 is critical in coupling glutamate receptors to cellular signaling networks and plays an important role in their biological function within the central nervous system. JNK is a major stress-activated kinase in mammalian systems that is implicated in mediating neuronal death induced by various detrimental stimuli and by glutamate-mediated excitotoxicity (14 -16). In the absence of JNK3, a neuronal form of JNK, kainic acid-induced seizure activity and neuronal degeneration are significantly attenuated (1). This phenotype is strikingly similar to that observed in GluR6-deficient mice (2), which suggests that JNK activation may be involved in GluR6-mediated excitotoxicity.Both MLK2 and MLK3 are members of the mixed lineage kinase family typified by a N-terminal SH3 domain, a middle kinase domain, and a C-terminal proline-rich region that may bind to SH3 domain-containing proteins. MLK2/3 can directly bind and activate MKK4 and MKK7, which in turn phosphorylate and activate JNKs (17-18). Studies from our group and others show that expression of MLK2 induces JNK activation and apoptotic cell death (18 -19).The current study was undertaken to investigate the molec-* This work is supported by United States Army Medical Research and Materiel Command under cooperative agreement DAMD17-00-2-0012 (to Y. F. L.). The costs of publication of this article were defrayed in part by the pay...

Objective. The IKK complex regulates NF-B activation, an important pathway implicated in the rheumatoid arthritis (RA) disease process. This study was undertaken to assess the efficacy of N-(6-chloro-7-methoxy-9H-␤-carbolin-8-yl)-2-methylnicotinamide (ML120B), a potent and selective small molecule inhibitor of IKK␤.Methods. Polyarthritis was induced in rats by injection of Freund's complete adjuvant into the hind footpad. ML120B was administered orally twice daily, either prophylactically or therapeutically. Paw volumes and body weights were measured every 2-3 days throughout the study. We assessed bone erosions by several methods: histologic evaluation, quantitative micro-computed tomography (micro-CT) imaging analysis, and measurement of type I collagen fragments in the serum. Quantitative polymerase chain reaction was used to evaluate expression of messenger RNA for genes related to inflammation and to bone and cartilage integrity.Results. Oral administration of ML120B inhibited paw swelling in a dose-dependent manner (median effective dosage 12 mg/kg twice daily) and offered significant protection against arthritis-induced weight loss as well as cartilage and bone erosion. We were able to directly demonstrate that NF-B activity in arthritic joints was reduced after ML120B administration. Also, we observed that down-regulation of the NF-B pathway via IKK␤ inhibition dampened the chronic inflammatory process associated with rat adjuvant-induced arthritis.Conclusion. The results of the present study suggest that IKK␤ inhibition is an effective therapeutic approach to treat both the inflammation and the bone/ cartilage destruction observed in RA. Methods for the determination of serum markers for bone and cartilage destruction, as well as micro-CT analysis, may aid in predicting and evaluating the therapeutic efficacy of IKK␤ inhibition therapy in humans.

The role of major histocompatibility complex (MHC) class I- and class II-restricted functions in Helicobacter pyloriinfection and immunity upon oral immunization was examined in vivo. Experimental challenge with H. pylori SS1 resulted in significantly greater (P ≤ 0.025) colonization of MHC class I and class II mutant mice than C57BL/6 wild-type mice. Oral immunization with H. pylori whole-cell lysates and cholera toxin adjuvant significantly reduced the magnitude of H. pylori infection in C57BL/6 wild-type (P = 0.0083) and MHC class I knockout mice (P = 0.0048), but it had no effect on the H. pylori infection level in MHC class II-deficient mice. Analysis of the anti-H. pyloriantibody levels in serum showed a dominant serum immunoglobulin G1 (IgG1) response in immunized C57BL/6 wild-type and MHC class I mutant mice but no detectable serum IgG response in MHC class II knockout mice. Populations of T-cell-receptor (TCR) αβ+CD4+ CD54+ cells localized to gastric tissue of immunized C57BL/6 wild-type and MHC class I knockout mice, but TCRαβ+ CD8+ cells predominated in the gastric tissue of immunized MHC class II-deficient mice. These observations show that CD4+ T cells engaged after mucosal immunization may be important for the generation of a protective anti-H. pylori immune response and that CD4+CD8− and CD4− CD8+ T cells regulate the extent of H. pylori infection in vivo.

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