Genetic regulation of leishmanial and mycobacterial infections: the Lsh/Ity/Bcg gene story continues.

A common basis to genetic regulation of leishmanial and mycobacterial infections is provided by the action of the murine Lsh/Ity/Bcg gene in controlling the priming/activation of macrophages for antimicrobial activity. This relies on the TNF-alpha-dependent sustained expression of the inducible nitric oxide synthase (iNOS) gene responsible for the generation of large amounts of toxic nitric oxide (NO). The Lsh/Ity/Bcg gene has many pleiotropic effects, including differential expression of the early response gene KC following stimulation of macrophages with bacterial lipopolysaccharide (LPS) and mycobacterial lipoarabinomannan (LAM). The major signal transduction pathway involved in KC induction requires the generation of low levels of NO via constitutive nitric oxide synthase (cNOS) activity, leading to activation of guanylate cyclase and the cGMP-dependent kinase pathway. NO therefore appears to provide a common link between the early influence of Lsh in regulating the expression of genes which mediate many pleiotropic effects, and the later production of NO as the final effector mechanism for kill. The recently cloned candidate for Lsh/Ity/Bcg, designated Nramp for Natural resistance associated macrophage protein, encodes a polytopic integral membrane protein that has structural features common to prokaryotic and eukaryotic transporters and includes a conserved binding-protein-dependent transport motif which may be involved in interaction with peripheral ATP-binding subunits. The N-terminal sequence also carries a proline/serine rich putative SH3 binding domain, consistent with a role for tyrosine kinases in regulating Nramp function. (ABSTRACT TRUNCATED AT 250 WORDS)

A brain image database for structure/function analysis.

BACKGROUND AND PURPOSE: Lesion-deficit-based structure-function analysis has traditionally been empirical and nonquantitative. Our purpose was to establish a new brain image database (BRAID) that allows the statistical correlation of brain functional measures with anatomic lesions revealed by clinical brain images. METHODS: Data on 303 participants in the MR Feasibility Study of the Cardiovascular Health Study were tested for lesion/deficit correlations. Functional data were derived from a limited neurologic examination performed at the time of the MR examination. Image data included 3D lesion descriptions derived from the MR examinations by hand segmentation. MR images were normalized in-plane using local, linear Talairach normalization. A database was implemented to support spatial data structures and associated geometric and statistical operations. The database stored the segmented lesions, patient functional scores, and several anatomic atlases. Lesion-deficit association was sought by contingency testing (chi2-test) for every possible combination of each neurologic variable and each labeled atlas structure. Significant associations that confirmed accepted lesion-deficit relationships were sought. RESULTS: Two-hundred thirty-five infarctlike lesions in 117 subjects were viewed collectively after mapping into Talairach cartesian coordinates. Anatomic structures most strongly correlated with neurologic deficits tended to be situated in anatomically appropriate areas. For example, infarctlike lesions associated with visual field defects were correlated with structures in contralateral occipital structures, including the optic radiations and occipital gyri. CONCLUSION: Known lesion-deficit correlations can be established by a database using a standard coordinate system for representing spatial data and incorporating functional and structural data together with appropriate query mechanisms. Improvements and further applications of this methodology may provide a powerful technique for uncovering new structure-function relationships.

An in vitro system for studying cartilage degradation by macrophages.

Cartilage damage in inflammatory arthritis may be mediated by a number of cell types; the macrophage is one of them. To examine their role we developed a new macrophage-cartilage co-culture system on a microscale. This used macrophages derived from the peritoneal cavity of Balb/c mice together with cartilage slices from bovine nasal septa. We examined the effects of macrophages on cartilage proteoglycan loss measured colorimetrically. When chondrocytes were dead, cartilage released proteoglycan; macrophages increase the amount of proteoglycan loss; stimulating macrophages with zymosan further increased proteoglycan loss. With live chondrocytes the situation was different. Macrophages only gave a major increase in cartilage proteoglycan loss when stimulated by zymosan. These results show it is possible to establish a simple model of macrophage-induced cartilage degradation. In this a variety of effects given by macrophages can be demonstrated depending on the presence or absence of live chondrocytes.

Nramp transfection transfers Ity/Lsh/Bcg-related pleiotropic effects on macrophage activation: influence on oxidative burst and nitric oxide pathways.

BACKGROUND: The Ity/Lsh/Bcg gene on mouse chromosome 1 regulates priming/activation of macrophages for antimicrobial and tumouricidal activity. A candidate gene expressed in macrophages has been identified by positional cloning and full-length sequence analysis, and encodes the Natural resistance-associated macrophage protein (Nramp). In this study, we have tested the hypothesis that the Nramp gene corresponds to Ity/Lsh/Bcg. MATERIALS AND METHODS: In vitro transfection was used to introduce the resistant allele into the macrophage cell line RAW 264.7 derived from the recessive susceptible BALB/c mouse strain. Expression of the transgene was monitored on the background of the endogenous susceptible allele by allele-specific oligonucleotide hybridization. RESULTS: Expression of the transgene correlated with three Lshr-associated lipopolysaccharide/interferon-gamma-regulated macrophage activation phenotypes: respiratory burst, nitrite release, and uptake of L-arginine. Endogenous and stimulated L-arginine fluxes were inhibitable with the radical scavengers nordihydroguaiaretic acid and butylated hydroxyanisole. The mitochondrial electron transport inhibitors, rotenone and thenoyltrifluoroacetone, inhibited respiratory burst, and rotenone suppressed L-arginine flux, implying that mitochondrial-derived oxygen radicals are important mediators in Nramp-regulated signal transduction pathways. CONCLUSIONS: These data provide the first direct evidence that Nramp is the product of the Ity/Lsh/Bcg gene, and are consistent with the hypothesis that the many pleiotropic effects of this gene on macrophage activation may all derive from the requirement for mitochondrial generation of oxygen radicals for intracellular signaling.