Do lipoxygenases modulate normal or aberrant lympho-hematopoiesis?

Assessing 12(S)-lipoxygenase inhibitory activity using colorectal cancer cells overexpressing the enzyme

12(S)-Lipoxygenase (LOX) is regarded as a pro-tumorigenic enzyme and as a potential target for therapy and prevention of cancer so that the search for specific 12(S)-LOX inhibitors is part of drug development strategies. To facilitate the identification of specific 12(S)-LOX inhibitors we have created an assay cell line by introducing a12(S)-LOX expression vector into SW480 colorectal cancer cells. When arachidonic acid was supplied in the medium both transiently and stably overexpressing cells produced 12(S)-hydroxytetraenic acid (HETE) originating from the transfected gene at 4-5-fold the amount obtained from control transfectants. 12(S)-HETE production was 1913.7+/-17.2pg/ml and reached a steady state level 24h after addition of arachidonic acid. To demonstrate the models suitability of 12(S)-LOX overexpressing SW480 cells they were used to measure the inhibitory activity of the plant phenols baicalein, kaempferol, quercetin, nordihydroguaretic acid and resveratrol which are known for their chemopreventive as well as LOX-inhibitory activity in different tumour models. All 5 compounds inhibited 12(S)-HETE production at concentrations below those necessary for growth inhibition.

[Corticoid-sensitive nephrotic syndrome in children with myelodysplastic syndromes]

Several reports have documented various forms of glomerular diseases in adults with myelodysplastic syndromes (MDS), but similar reports in children are lacking. We describe two children with MDS-associated with steroid-responsive nephrotic syndrome (NS). Patient 1, who had MDS with myelofibrosis, presented also hepatosplenomegaly, pancytopenia, chronic hepatitis, moderate proteinuria, hypocomplementamia and elevated ANA titer. During initial prednisone treatment proteinuria markedly diminished and partial but transient haematological improvement occurred. Relapse subsequently occurred that was manifested by overt NS and pancytopenia. High doses of prednisolone led to remission of the renal disease but haematological remission did not occur. Persisting pancytopenia and repeated infections terminated in sepsis, two years after the onset of MDS. Patient 2, who had refractory anaemia with clonal monosomy 19, manifested bowel disease, hepatosplenomegaly, anaemia and non-organic specific autoantibodies. Prednisone led to both clinical and haematological remission. Haematologic disease relapsed 12 months later, when nephrotic-range proteinuria, haematuria and mild azotaemia were also found. Corticosteroid treatment led to long-lasting renal and haematologic remission, maintained by a small dosage of prednisone. In both patients, renal biopsy findings were consistent with those seen in idiopathic NS. A Medline search disclosed 16 cases of glomerulopathy in the course of MDS in adult patients. Clinical features included NS, usually accompanied by renal insufficiency with either acute, chronic, or rapidly progressive glomerulonephritis. On biopsy, membranous nephropathy, crescentic or mesangial proliferative glomerulonephritis and AL amyloidosis, were found. We conclude: (1) that glomerular disease may be present and should be searched for in patients with MDS; (2) that MDS can be added to the list of rare conditions associated with corticosteroid-responsive NS in children.

Monohydroxylated fatty acid content in peripheral blood mononuclear cells and immune status of people at long times after the Chernobyl accident

The monohydroxylated fatty acid content of peripheral blood mononuclear cells from 23 cleanup workers and 16 unexposed individuals was studied in relation to their immune status after the Chernobyl accident. Men with absorbed doses below 0.32 Gy showed higher levels of free and esterified 12-hydroxyeicosatetraenoic acid (12-HETE) than unexposed men, whereas 15-HETE and the 17-hydroxy derivative of C22 fatty acid (17-OH 22), either free or esterified in phospholipids, were increased in a dose-dependent manner. The percentage of CD4-positive cells was also increased significantly in heavily irradiated men, whereas the percentage of CD8-positive cells tended to decrease with dose. Furthermore, the absolute count of CD4-positive cells was correlated positively with the amount of esterified 15-HETE in the phospholipid fraction of the mononuclear cells and with the total 15-HETE. These results show for the first time that the accumulation of autoxidized/lipoxygenase products of polyunsaturated fatty acids in the mononuclear cells of irradiated individuals was associated with immune imbalance. This may be the basis for certain late effects of radiation such as autoimmune disorders, somatic and neoplastic diseases, and early aging.

5-Lipoxygenase is required for proliferation of immature cerebellar granule neurons in vitro

Primary cultures of rat cerebellar granule neurons express 5-lipoxygenase, an enzyme from the inflammatory pathway of arachidonic acid. Outside the central nervous system (CNS) 5-lipoxygenase participates in cell proliferation. We hypothesized that 5-lipoxygenase is needed for proliferation of immature cerebellar granule neurons. Using cultures prepared from 7-day-old rat pups, we confirmed in vitro neurogenesis by immunocytolabeling with 2-bromo-5-deoxyuridine and beta-tubulin isotype III and quantified the rate of cell proliferation by assaying [3H]thymidine incorporation. We found that immature cerebellar granule neurons express large amounts of 5-lipoxygenase, and that treatment with a 5-lipoxygenase antisense, to reduce expression of this gene, decreased significantly (by 60%) the content of 5-lipoxygenase protein and effectively reduced cell proliferation. [3H]thymidine incorporation was significantly reduced by each of the three 5-lipoxygenase inhibitors we tested: AA-861 [2-(12-hydroxydodeca-5, 10-diynyl)-3,5,6-trimethyl-1,4-benzoquinone], MK-886 (C(27)H(33)ClNO(2)S.Na), and L-655,238 [alpha-penyl-3-(2-quinolinylmethoxy)-benzenemethanol]. Their anti-proliferative effect was reversible. We propose that neuronal expression of 5-lipoxygenase is crucial for neurogenesis in vitro, and possibly also in vivo.