Liver X receptor-dependent inhibition of microglial nitric oxide synthase 2.

BACKGROUND: The nuclear receptor liver X receptor (LXR) exerts transcriptional control over lipid metabolism and inflammatory response in cells of the myeloid lineage, suggesting that LXR may be a potential target in a number of chronic neuroinflammatory and neurodegenerative diseases where persistent microglial activation has been implicated in the pathogenesis. METHODS: The effect of LXR activation on microglia and central nervous system (CNS) inflammation was studied using a synthetic LXR agonist in cultured microglia, a microglial cell line and experimental allergic encephalomyelitis (EAE), an animal model of CNS inflammation. RESULTS: LXR activation inhibited nitric oxide synthase 2, inducible (Nos2) expression and nitric oxide production in lipopolysaccharide (LPS)-stimulated microglia. Inhibition of microglial activation in response to interferon-γ was less reliable. In LPS-stimulated cells, LXR activation did not inhibit nuclear translocation of NF-kappaB1 p50. Instead, LXR-dependent Nos2 repression was associated with inhibition of histone 4 acetylation and inhibition of NF-kappaB1 p50 binding at the Nos2 promoter. Histone acetylation and NF-kappaB1 p50 binding were mechanistically linked, and histone deacetylase (HDAC) activity appeared to be important for LXR-dependent transcriptional repression of Nos2. Analysis of CNS gene expression in animals undergoing EAE showed that the expressions of Lxr and LXR-dependent genes were downregulated during CNS inflammation. Nevertheless, administration of LXR agonist GW3965 during the effector phase of EAE delayed the onset of clinical disease and reversed the diminished expression of LXR-dependent reverse cholesterol transport genes. However, the CNS expressions of Nos2 and other inflammatory genes were not significantly inhibited by LXR activation in EAE, and clinical disease severity was comparable to vehicle controls at later time points in LXR agonist treated animals. CONCLUSIONS: LXR can be targeted to modulate microglial activation. LXR-dependent repression of inflammatory genes may be stimulus-dependent and impaired by HDAC inhibition. Endogenous LXR activity does not appear to modulate CNS inflammation, but LXR activity can be partially restored in the CNS by administration of exogenous LXR agonist with an impact on clinical disease severity at early, but not late, time points in EAE.

Attenuated dopamine receptor signaling in nucleus accumbens core in a rat model of chemically-induced neuropathy.

Neuropathy is major source of chronic pain that can be caused by mechanically or chemically induced nerve injury. Intraplantar formalin injection produces local necrosis over a two-week period and has been used to model neuropathy in rats. To determine whether neuropathy alters dopamine (DA) receptor responsiveness in mesolimbic brain regions, we examined dopamine D1-like and D2-like receptor (D1/2R) signaling and expression in male rats 14 days after bilateral intraplantar formalin injections into both rear paws. D2R-mediated G-protein activation and expression of the D2R long, but not short, isoform were reduced in nucleus accumbens (NAc) core, but not in NAc shell, caudate-putamen or ventral tegmental area of formalin- compared to saline-treated rats. In addition, D1R-stimulated adenylyl cyclase activity was also reduced in NAc core, but not in NAc shell or prefrontal cortex, of formalin-treated rats, whereas D1R expression was unaffected. Other proteins involved in dopamine neurotransmission, including dopamine uptake transporter and tyrosine hydroxylase, were unaffected by formalin treatment. In behavioral tests, the potency of a D2R agonist to suppress intracranial self-stimulation (ICSS) was decreased in formalin-treated rats, whereas D1R agonist effects were not altered. The combination of reduced D2R expression and signaling in NAc core with reduced suppression of ICSS responding by a D2R agonist suggest a reduction in D2 autoreceptor function. Altogether, these results indicate that intraplantar formalin produces attenuation of highly specific DA receptor signaling processes in NAc core of male rats and suggest the development of a neuropathy-induced allostatic state in both pre- and post-synaptic DA receptor function.

The cancer recognition (CARE) antibody test.

The cancer recognition (CARE) antibody (Ab) test is a serologic assay for a specific IgM that is elevated in cancer patients. All tests are measured using an indirect enzyme-linked immunosorbent assay (ELISA) of human serum. The target polypeptide in the CARE Ab test is the IgM binding epitope (LT-11) of the CARE antigen (Ag) consisting of a 16 mer structure that has been produced synthetically. The mean relative concentration (MRC) is determined relative to standard, normalized human plasma. Non-parametric analysis showed median MRC values of healthy volunteers (HVs) with no history of cancer (n =47), family history of cancer (n = 126) and a previous cancer history (n = 24) to be 26, 34 and 46, respectively. It was determined that there was no significance found among the medians of the three HV groups (P = 0.53). The specificity of the HV types was between 87 and 98%. Benign/non-cancer surgical patients (n = 27) had a median value of 20 with a specificity of 96%. The cancer patients (n = 61) had a median value of 246 with a sensitivity of 89%. There was a significant difference between the HV and cancer patients (P < 0.0001) as well as between the benign/surgical non-cancerous group and cancer patients (P < 0.0001). The IgM antibody is heat stable at room temperature for two days versus being frozen at -80 degrees C (r2 = 0.97). Either serum or plasma samples may be used in the CARE Ab test (r2 = 0.92). The CARE Ab was almost exclusively IgM with no serum conversion to IgG in sequential measurements of patients with cancer over a six-month period. Preliminary data from patients undergoing post-operative cancer treatment showed that decreasing Ab levels revealed patients negative for residual cancer or undergoing remission, while relapsing patients show an increase in Ab levels. A return to a positive Ab level shortly after treatment is a poor prognostic sign while in advanced cancers the Ab levels may be depressed significantly.