Mediators: nitric oxide and other toxic oxygen species

The return of the Scarlet Pimpernel: cobalamin in inflammation II - cobalamins can both selectively promote all three nitric oxide synthases (NOS), particularly iNOS and eNOS, and, as needed, selectively inhibit iNOS and nNOS

The up-regulation of transcobalamins [hitherto posited as indicating a central need for cobalamin (Cbl) in inflammation], whose expression, like inducible nitric oxide synthase (iNOS), is Sp1- and interferondependent, together with increased intracellular formation of glutathionylcobalamin (GSCbl), adenosylcobalamin (AdoCbl), methylcobalamin (MeCbl), may be essential for the timely promotion and later selective inhibition of iNOS and concordant regulation of endothelial and neuronal NOS (eNOS/nNOS.) Cbl may ensure controlled high output of nitric oxide (NO) and its safe deployment, because: (1) Cbl is ultimately responsible for the synthesis or availability of the NOS substrates and cofactors heme, arginine, BH(4) flavin adenine dinucleotide/flavin mononucleotide (FAD/FMN) and NADPH, via the far-reaching effects of the two Cbl coenzymes, methionine synthase (MS) and methylmalonyl CoA mutase (MCoAM) in, or on, the folate, glutathione, tricarboxylic acid (TCA) and urea cycles, oxidative phosphorylation, glycolysis and the pentose phosphate pathway. Deficiency of any of theNOS substrates and cofactors results in 'uncoupled' NOS reactions, decreasedNO production and increased or excessive O(2) (-), H(2)O(2), ONOO(-) and other reactive oxygen species (ROS), reactive nitric oxide species (RNIS) leading to pathology. (2) Cbl is also the overlooked ultimate determinant of positive glutathione status, which favours the formation of more benign NO species, s-nitrosothiols, the predominant form in which NO is safely deployed. Cbl status may consequently act as a 'back-up disc' that ensures the active status of antioxidant systems, as well as reversing and modulating the effects of nitrosylation in cell signal transduction.New evidence shows that GSCbl can significantly promote iNOS/ eNOS NO synthesis in the early stages of inflammation, thus lowering high levels of tumour necrosis factor-a that normally result in pathology, while existing evidence shows that in extreme nitrosative and oxidative stress, GSCbl can regenerate the activity of enzymes important for eventual resolution, such as glucose 6 phosphate dehydrogenase, which ensures NADPH supply, lactate dehydrogenase, and more; with human clinical case studies of OHCbl for cyanide poisoning, suggesting Cbl may regenerate aconitase and cytochrome c oxidase in the TCA cycle and oxidative phosphorylation. Thus, Cbl may simultaneously promote a strong inflammatory response and the means to resolve it.

Inflammation and its role in neuroprotection, axonal regeneration and functional recovery after spinal cord injury

Trauma to the central nervous system (CNS) triggers intraparenchymal inflammation and activation of systemic immunity with the capacity to exacerbate neuropathology and stimulate mechanisms of tissue repair. Despite our incomplete understanding of the mechanisms that control these divergent functions, immune-based therapies are becoming a therapeutic focus. This review will address the complexities and controversies of post-traumatic neuroinflammation, particularly in spinal cord. In addition, current therapies designed to target neuroinflammatory cascades will be discussed.

A novel model of fibroblast-mediated cartilage destruction

In rheumatoid arthritis (RA), fibroblasts have been shown to be crucial for disease progression as well as joint destruction. In the model of human/murine SCID arthritis, synovial explants as well as fibroblasts from human rheumatoid synovial membrane induce destructive arthritis in immunodeficient mice. Hereby, the underlying cartilage destruction is accomplished by murine fibroblasts. Therefore, murine destructive fibroblasts represent a promising tool to investigate destruction of articular cartilage and bone. In this context, a novel destructive murine fibroblast line (LS48) was examined for morphological, ultrastructural, immunological and functional cellular parameters. These cells were injected into knees of SCID mice. Subsequently, the animals were monitored for joint swelling and serological parameters of arthritis by radiological methods. Finally, cartilage destruction was assessed morphologically. Cultured LS48 cells exhibit characteristic features that resemble those of activated synovial fibroblasts in human RA. Expression levels of inducible nitric oxide synthase, interleukin-6, tumour necrosis factor-alpha and matrix metalloproteinases were comparable to those detected in invasive human fibroblasts. The instillation of 5 x 10(5) LS48 cells into the knee joints of SCID mice initiated a rapid progressive process, that caused cartilage destruction within 10 days, and morphological examinations revealed that articular cartilage was infiltrated by the fibroblasts injected previously. In summary, the intra-articular application of LS48 cells represents a rapid and highly reproducible model to investigate the initiation and progression of cartilage destruction in connection with RA therapy and represents an easy-to-handle animal model.

Phenotype, intestinal morphology, and survival of homozygous and heterozygous endothelin B receptor--deficient (spotting lethal) rats

BACKGROUND/PURPOSE

Spotting lethal (sl) rats, a model for Hirschsprung's disease, recently have been found to carry a deletion in the endothelin B (ET(B)) gene, causing functional lack of ET(B) receptors. The ET(B) receptor mediates, together with and in counterbalance to the ET(A) receptor, endothelin actions on vessels, cell proliferation, and migration. The authors investigated the effect of homozygosity (sI/sI) or heterozygosity (+/sl) on phenotype, intestinal morphology, and survival.

METHODS

Weight, circumference, and serum albumin were measured. Histological tests of major organs and immunoperoxidase reaction for Peripherin, glial fibrillary acid protein (GFAP), and S-100 in small and large intestine were performed. Peripherin-immunostained sections of colon and jejunum were analyzed morphometrically. Screening for sepsis included search for enterocolitis, bacterial infection, endotoxin, and iNOS mRNA.

RESULTS

Sl/sl rats died within 4 weeks of life, showing an early and a later death group. Serum albumin levels were decreased in sl/sl rats, whereas signs of sepsis were rare. Immunostaining uncovered alterations in nerve and glial cells in the whole gut of sl/sl rats, and to a subtle degree also in +/sl rats, which appear clinically normal. Morphometric quantification yielded statistically significant alterations in sl/sl rats only. No obvious abnormalities were found in other organs.

CONCLUSIONS

Sl/sl rats die from malnutrition rather than sepsis, too early for ischemic complications to occur. Rats of the later death group are a suitable model for studying the ET8 receptor in vivo. Subtle abnormalities in the enteric nervous system of heterozygous rats underline the critical role of the "gene dose" for functional compensation.

Granulocyte-colony stimulating factor inhibits inducible nitric oxide synthase gene expression in pulmonary epithelial cells in vitro

Excessive release of nitric oxide (NO) is most likely a crucial pathophysiological pathway leading to pulmonary dysfunction. Thus, repression of supranormal NO production might be one beneficial mechanism of granulocyte-colony stimulating factor (G-CSF) in inflammatory processes. The aim of this study was to investigate the influence of G-CSF on inducible nitric oxide synthase gene expression in the alveolar epithelial cell line L2. We show that G-CSF suppresses interferon-gamma/tumor necrosis factor-alpha (TNF-alpha) induced inducible nitric oxide synthase gene expression detected as inducible nitric oxide synthase cDNA (cDNA concentration was 633 +/- 38 amol/microg total RNA following 24 h incubation with 100 U/ml interferon-gamma/500 U/ml TNF-alpha, and 440 +/- 14 amol/microg total RNA following 24 h incubation with 250 U/ml G-CSF +/- 100 U/ml interferon-gamma/500 U/ml TNF-alpha, respectively). In addition, application of G-CSF resulted in a decreased synthesis of inducible nitric oxide synthase protein and diminished NO release mediated by the cytokines. The suppression of inducible nitric oxide synthase gene expression in L2 cells by G-CSF may represent a beneficial counterregulatory effect on excessive NO synthesis induced by proinflammatory cytokines in the lung.