Faculty Bibliography

Nitric oxide synthesized by inducible nitric oxide synthase (iNOS) has been implicated as a mediator of inflammation in rheumatic and autoimmune diseases. We report that exposure of lipopolysaccharide-stimulated murine macrophages to therapeutic concentrations of aspirin (IC50 = 3 mM) and hydrocortisone (IC50 = 5 microM) inhibited the expression of iNOS and production of nitrite. In contrast, sodium salicylate (1-3 mM), indomethacin (5-20 microM), and acetaminophen (60-120 microM) had no significant effect on the production of nitrite at pharmacological concentrations. At suprapharmacological concentrations, sodium salicylate (IC50 = 20 mM) significantly inhibited nitrite production. Immunoblot analysis of iNOS expression in the presence of aspirin showed inhibition of iNOS expression (IC50 = 3 mM). Sodium salicylate variably inhibited iNOS expression (0-35%), whereas indomethacin had no effect. Furthermore, there was no significant effect of these nonsteroidal anti-inflammatory drugs on iNOS mRNA expression at pharmacological concentrations. The effect of aspirin was not due to inhibition of cyclooxygenase 2 because both aspirin and indomethacin inhibited prostaglandin E2 synthesis by > 75%. Aspirin and N-acetylimidazole (an effective acetylating agent), but not sodium salicylate or indomethacin, also directly interfered with the catalytic activity of iNOS in cell-free extracts. These studies indicate that the inhibition of iNOS expression and function represents another mechanism of action for aspirin, if not for all aspirin-like drugs. The effects are exerted at the level of translational/posttranslational modification and directly on the catalytic activity of iNOS

In these studies we provide conclusive evidence that (beta/gamma) actin present in human neutrophils is a substrate for nitric oxide (NO)-dependent ADP ribosylation and that this modification is associated with the inhibition of actin polymerization. A 43-kDa substrate for NO-dependent ADP ribosylation was identified as actin by four methods: (1) comigration with the botulinum C2 toxin substrate by two-dimensional gel electrophoresis (pI 5.2), (2) identity between the peptide map generated by V8 protease digestion of the NO and botulinum C2 substrates, (3) immunoprecipitation with antiactin antibodies, and (4) the ability of NO to ADP ribosylate purified neutrophil G-actin in the presence of plasma membrane cofactors. Because the ADP ribosylation of actin by the botulinum C2 toxin is known to inhibit F-actin polymerization, we examined the effect of NO on actin assembly. Flow cytometry revealed that NO inhibited formyl-methionine-leucine-phenylalanine (fMLP)-dependent (30 s at 37 degrees C) F-actin formation (108 +/- 8 vs. 89 +/- 6 relative fluorescence units, P < .02). These results were confirmed by quantification of F-actin formation by gel scanning (10% sodium dodecyl sulfate gel, Coomassie, and densitometry): pretreatment of polymorphonuclear leukocytes with NO resulted in a reduction of fMLP-induced, cytoskeletal-associated F-actin, which was accompanied by an increase of Triton-soluble G-actin. NO also inhibited F-actin formation, as observed by means of rhodamine phalloidin staining of neutrophils adherent to a fibronectin-coated surface. This effect was accompanied by a dose-dependent inhibition of neutrophil adherence in NO-treated cells. The data indicate that NO inhibits cytoskeletal assembly and adherence in human neutrophils in association with the ADP ribosylation of actin

The destructive capacity of the neutrophil has long been appreciated, and the presence of extraordinary numbers of neutrophils in the synovial fluid of patients with RA supports a role for these cells in the pathogenesis of joint destruction. In this article, we reviewed the current state of knowledge of neutrophil function in the inflammatory response, and emphasized the subjects of neutrophil/endothelial adhesion and the role of chemoattractants and cytokines in neutrophil mobilization. We also discussed the mechanisms of action of neutrophil destruction of cartilage and the interplay of signals between the neutrophil and the chondrocyte. The capacity of many of the drugs used to treat RA to interfere with one or several of these processes underscores the importance of the neutrophil in RA and suggests that future therapeutic strategies could target neutrophil activation within the synovial space

Activation of the membrane-associated NADPH oxidase of neutrophils requires several cytosolic factors including p47phox, p67phox and p21rac2. We compared NADPH oxidase activity with the membrane translocation of p47phox, p67phox, and p21rac2. In a cell-free system, GTP gamma S stimulated translocation of p47phox and p67phox to the plasma membrane only in the presence of arachidonate, and this translocation correlated with NADPH oxidase activity of the reisolated plasma membranes (R = 0.94 and 0.97, respectively). In contrast, GTP gamma S-stimulated p21rac2 translocation with or without arachidonate, and the extent of translocation did not correlate with oxidase activity (R = 0.17). Neutrophil cytoplasts were used to relate membrane translocation of p47phox, p67phox and p21rac2 to membrane oxidase activity in response to the inflammatory agonists. Whereas N-formyl-methionyl-leucyl-phenylalanine stimulated equimolar, transient membrane translocation of p47phox and p67phox which kinetically paralleled NADPH oxidase activity, relatively little p21rac2 translocated (moles of p47phox/p21rac2 = 16.6). Moreover, although phorbol 12-myristate 13-acetate stimulated both the stable translocation of p47phox and p67phox and sustained NADPH oxidase activity, it did not stimulate p21rac2 translocation. From these data we conclude that membrane translocation of p21rac2 does not regulate NADPH oxidase activity stoichiometrically

The medical records of patients receiving cyclophosphamide for lupus nephritis between 1987 and 1993 at the New York University/Hospital for Joint Diseases Lupus Study Group Institutions were retrospectively reviewed. We identified 45 patients (38 female, seven male) who received a mean of 9 +/- 1 (range 2-23) pulses of intravenous cyclophosphamide for diffuse proliferative glomerulonephritis (n = 28), focal proliferative glomerulonephritis (n = 7), membranous nephropathy (n = 5), mesangial nephropathy with sclerosis (n = 1) or nephritis without biopsy (n = 4). Forty-two of the 45 patients received cyclophosphamide after failing steroid therapy. During a follow-up period of 52 +/- 3 months, nine patients progressed to end-stage renal disease (ESRD) with three additional patients experiencing a doubling of the creatinine and two patients persistent nephrotic range proteinuria. There were no deaths directly attributable to cyclophosphamide and no patients developed hemorrhagic cystitis or malignancy. Ten of 37 women had ceased menstruating prior to cyclophosphamide therapy. Treatment-associated amenorrhea occurred in only three patients all over 27 years of age. Intermittent intravenous cyclophosphamide therapy of lupus nephritis is well tolerated and usually effective in maintaining renal function in patients unresponsive to steroids although, in our experience, 20% of patients developed ESRD and a total of 14 of 45 (30%) patients had unsatisfactory outcomes