The effect of substance P on nitric oxide release in a rheumatoid arthritis model.

OBJECTIVE: The inflammatory mediator substance P (SP) acts principally through the neurokinin (NK1) receptor. We assessed the influence of SP on production of NO and its possible role in the pathogenesis of rheumatoid arthritis (RA). METHODS: The effect of SP (0.1-100 nM) on concentrations of the NO metabolite, nitrite, produced by synovial fibroblasts from RA patients was studied. For comparison, the effects of TNF-alpha (0.57 pM-5.7 nM) and IL-1beta (0.57 pM-5.7 nM) were also studied. In parallel studies, footpad inflammation was induced in NK1 receptor knock-out (KO) and wild-type (WT) mice, and swelling and NO metabolite levels were measured. RESULTS: In cultured synoviocytes, SP, TNF-alpha and IL-1beta induced significantly increased nitrite concentrations. Consistent with a role for NO in SP-mediated inflammatory reactions, the plasma NO metabolite level in WT mice was significantly increased at 3 days following an injection of 10 mg/ml Mycobacterium tuberculosis, but there was no significant change in NK1 KO mice. These results were paralleled by the changes in footpad swelling in WT mice compared to NK1 KO mice. CONCLUSION: SP, like TNF-alpha and IL-1beta, induces NO in both rheumatoid synoviocytes and experimental models of inflammation. Treatments directed against SP may have important and hitherto unrecognised anti-inflammatory effects.

Nitric oxide mediates 17beta-estradiol-stimulated human and rodent osteoblast proliferation and differentiation.

Oestradiol can stimulate osteoblast activity. Osteoblast function is thought to be regulated by nitric oxide (NO). We hypothesised that the effect of 17beta-oestradiol (17beta-E(2)) on osteoblast activity is mediated by NO. This hypothesis was tested using osteoblasts isolated from human trabecular bone, calvariae of rats, endothelial NO synthase (eNOS) gene-deficient mice, and their wild-type counterparts. Our results show that 17beta-E(2) dose-dependently stimulated proliferation and differentiation of primary human, rat and wild-typeosteoblasts. The presence of N(G)-monomethyl-l-arginine (10(-3) M), an inhibitor of NOS activity, blocked the 17beta-E(2)-(10(-7) M)-induced increases in thymidine incorporation (P < 0.01), alkaline phosphatase activity (P < 0.01) and bone nodule formation (P < 0.01) of wild-type, human and rat osteoblasts, respectively. Moreover, 17beta-E(2) did not induce a response in eNOS gene-deficient osteoblasts. 17beta-E(2) also increased total eNOS enzyme expression in rat osteoblasts. These findings indicate 17beta-E(2) modulates osteoblast function by NO-dependent mechanisms mediated via the eNOS isoform.

Iron chelation in haematomas at fracture sites.

Previous work suggested that during the catabolism of haemoglobin a physico-chemical form of iron was released which was more readily chelatable by desferrioxamine than normal storage forms, as ferritin-haemosiderin. Desferrioxamine chelation was therefore investigated in five patients with major fractures in which haemoglobin catabolism is greatly enhanced by the red cell destruction which proceeds in the associated haematoma. Considerable increases in the amounts of iron mobilized by desferrioxamine were observed from the second day after injury. In severe interstitial haemorrhage, these values tended to increase until 10 to 20 days, and sometimes were as high as chelation values seen in haemochromatosis. These results are considered to support the hypothesis that a highly chelatable form of iron is found at some stage during haemoglobin catabolism.

Differential ferrioxamine test in idiopathic haemochromatosis and transfusional haemosiderosis.

The differential ferrioxamine test measures the amount of body iron as ferrioxamine (Fv) chelated by a standard dose of desferrioxamine.Five patients with untreated, uncomplicated idiopathic haemochromatosis and one with transfusion haemosiderosis gave Fv in the range 1,948 to 2,462 mug./kg. (normal 110 to 500). One case of transfusion haemochromatosis with haemolytic anaemia and renal failure gave an Fv value of 8,019 mug./kg. Four patients with idiopathic haemochromatosis after therapeutic venesection gave Fv values of 212 to 885 mug./kg. One relative with a value for Fv of 776 mug./kg. was shown to have early cirrhosis by liver biopsy. Serial Fv measurement after venesection in this patient provided a preliminary assessment of the relationship between Fv values and available iron stores up to about 2,000 mg. iron. This relationship applies only when red cell survival is normal. Approximate figures for the range of available storage iron in 31 healthy men are deduced, namely, 200 mg. to 1,000 mg. (3 to 14 mg./kg.). The test should prove useful in the diagnosis of iron overload, in the screening of relatives for early haemochromatosis, and in the management of iron storage diseases.