Dysfunction in mononuclear phagocyte (MP, macrophages and microglia) immunity is thought to play a significant role in the pathogenesis of HIV-1 associated dementia (HAD). In particular, elevated extracellular concentrations of the excitatory neurotransmitter glutamate, produced by MP as a consequence of viral infection and immune activation, can induce neuronal injury. To determine the mechanism by which MP-mediated neuronal injury occurs, the concentration and rates of production of extracellular glutamate were measured in human monocyte-derived macrophage (MDM) supernatants by reverse phase high-performance liquid chromatography (RP-HPLC). Measurements were taken of supernatants from MDM infected with multiple HIV-1 strains including ADA and DJV (macrophage tropic, M-tropic), and 89.6 (dual tropic). High levels of glutamate were produced by MDM infected with M-tropic viruses. AZT, an inhibitor of HIV-1 replication, inhibited glutamate generation, demonstrating a linkage between HIV-1 infection and enhanced glutamate production. In our culture system, glutamate production was dependent upon the presence of glutamine and was inhibited by 6-diazo-5-oxo-L-norleucine, a glutaminase inhibitor. Supernatants collected from HIV-1-infected MP generated more glutamate following glutamine addition than supernatants isolated from uninfected MP. These findings implicate the involvement of a glutamate-generating enzyme, such as phosphate-activated mitochondrial glutaminase (PMG) in MP-mediated glutamate production.

crown-6)] + (KC) cations are used for cocrystallization with manganese halides, producing isostructural single crystals of organic− inorganic hybrid complexes, [K(dibenzo-18-crown-6)] 2 MnX 4 (abbreviated (KC) 2 MnX 4 ) (X = Cl, Br), which feature one-dimensional morphology and green phosphorescence with considerable photoluminescence quantum yields accompanied by excellent optical waveguide behavior with a low loss coefficient. More interestingly, (KC) 2 MnX 4 crystallizes in the monoclinic space group Cc belonging to the achiral point group m (C s ), where the non-centrosymmetric arrangement of racemic units, with right-and left-handed rotating optical axes, endows these achiral single crystals with circularly polarized luminescence, observed for the first time.

Mononuclear phagocyte (macrophages and microglia) dysfunction plays a significant role in the pathogenesis of human immunodeficiency virus (HIV) associated dementia (HAD) through the production and release of soluble neurotoxic factors including glutamate. The mechanism of glutamate regulation by HIV-1 infection remains unclear. In this report, we investigated whether the enzyme glutaminase is responsible for glutamate generation by HIV-1 infected monocytederived macrophages. We tested the functionality of novel small molecule inhibitors designed to specifically block the activity of glutaminase. Glutaminase inhibitors were first characterized in a kinetic assay with crude glutaminase from rat brain revealing an uncompetitive mechanism of inhibition. The inhibitors were then tested in vitro for their ability to prevent glutamate generation by HIV-infected macrophages, their effect upon macrophage viability, and HIV infection. To validate these findings, glutaminase specific siRNA was tested for its ability to prevent glutamate increase during infection. Our results show that both glutaminase specific small molecule inhibitors and glutaminase specific siRNA were effective at preventing increases in glutamate by HIV-1 infected macrophage. These findings support glutaminase as a potential component of the HAD pathogenic process and identify a possible therapeutic avenue for the treatment of neuroinflammatory states such as HAD. HIV-1 associated dementia (HAD) is a significant consequence of HIV infection resulting in a chronic, progressive dementia. The dementia is a consequence of neuronal damage that results from prolonged inflammation in the CNS. Mononuclear phagocytes (MP) are critical to HAD pathogenesis and have been hypothesized to induce neuronal injury through the production and release of various soluble neurotoxic factors including glutamate (Giulian et al. 1993;Pulliam et al. 1994;Zink et al. 1999;Belmadani et al. 2001;Jiang et al. 2001). Glutamate mediates numerous physiological functions through activation of multiple receptors (Cutler and Dudzinski 1974;Fonnum 1984;Orrego and Villanueva 1993); however, high concentrations of extracellular glutamate induce neuronal damage (Olney 1971;McCall et al. 1979;Choi 1988;Newcomb et al. 1997). HIV-1 infected macrophages are an important cellular source of extracellular glutamate (Jiang et al. 2001), and HIV-1-infected patients have significantly higher concentrations of glutamate in plasma as compared with uninfected controls (Droge et al. 1987; Ollenschlager Received December 11, 2006; accepted February 2, 2007. Address correspondence and reprint requests to Jialin Zheng, Laboratory of Neurotoxicology, Center for Neurovirology and Neurodegenerative Disorders and Departments of Pharmacology/Experimental Neuroscience and Pathology/Microbiology, 985880 Nebraska Medical Center, Omaha, NE 68198-5880, USA. E-mail: jzheng@unmc.edu 1 These authors contributed equally to this work.

Mononuclear phagocyte (MP, macrophages and microglia) dysfunction plays a significant role in the pathogenesis of HIV‐1‐associated dementia (HAD) through the production and release of soluble neurotoxic factors including glutamate. Glutamate production is greatly increased following HIV‐1 infection of cultured MP, a process dependent upon the glutamate‐generating enzyme glutaminase. Glutaminase inhibition was previously found to significantly decrease macrophage‐mediated neurotoxicity. Potential mechanisms of glutaminase‐mediated excitotoxicity including enzyme up‐regulation, increased enzyme activity and glutaminase localization were investigated in this report. RNA and protein analysis of HIV‐infected human primary macrophage revealed up‐regulation of the glutaminase isoform GAC, yet identified no changes in the kidney‐type glutaminase isoform over the course of infection. Glutaminase is a mitochondrial protein, but was found to be released into the cytosol and extracellular space following infection. This released enzyme is capable of rapidly converting the abundant extracellular amino acid glutamine into excitotoxic levels of glutamate in an energetically favorable process. These findings support glutaminase as a potential component of the HAD pathogenic process and identify a possible therapeutic avenue for the treatment of neuroinflammatory states such as HAD.

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Background: Decreased tryptophan (TRP) and increased kynurenine (KYN) and kynurenic acid (KYNA) in blood have been reported in patients and experimental animals with renal diseases. We investigated if these compounds could be used as new biomarkers for the assessment of renal function. Methods: Eighty hospitalized hypertensive patients (20 with chronic kidney disease (CKD), and other 60 were considered as control) were enrolled for the investigation. Plasma TRP, KYN, and KYNA were determined by high-performance liquid chromatography. Change rate (CR) was employed to evaluate the sensitivity of the parameters of renal function. Results: CR of plasma KYNA/TRP ratio (þ103%) was much higher than the CRs of blood urea nitrogen (þ44%), serum creatinine (þ56%) and estimated glomerular filtration rate (-35%). Plasma KYNA/TRP ratio was in close relationship with blood urea nitrogen (r ¼ 0.622), serum creatinine (r ¼ 0.797), urine microalbumin/24-h (r ¼ 0.518) and estimated glomerular filtration rate (r ¼ -0.662), respectively, with all p-values <0.001. Conclusions: Plasma KYNA/TRP ratio was sensitive and reliable to indicate renal function and could be used as a new biomarker to assess the risk or presence of kidney disease.

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