Faculty Bibliography

OBJECTIVE. To test the hypothesis that during exacerbations of systemic lupus erythematosus (SLE), endothelial cells are activated to increase their expression of adhesion molecules. METHODS. Endothelial cell expression of E-selectin, vascular cell adhesion molecule 1 (VCAM-1), and intercellular adhesion molecule 1 (ICAM-1) was quantitated immunohistochemically in 20 biopsy specimens from nonlesional, non-sun-exposed skin from 16 SLE patients. Disease activity was evaluated with the SLE Disease Activity Index (SLEDAI) and with measurements of complement components C3a desArg, C3, and C4. RESULTS. The mean expression of all 3 adhesion molecules was significantly elevated in patients with SLE versus healthy controls, as well as in patients with active versus inactive SLE. The mean C3a desArg level was significantly higher in patients with active SLE compared with those with inactive SLE. The SLEDAI scores correlated directly with C3a desArg levels and inversely with C3 and with C4 levels. Evaluation of serial biopsy specimens demonstrated loss of endothelial cell adhesion molecules and reduction of C3a levels with clinical improvement. CONCLUSION. Our findings demonstrate up-regulation of the surface expression of 3 distinct adhesion molecules, E-selectin, VCAM-1, and ICAM-1, in patients with SLE. The abnormal expression of these endothelial cell adhesion molecules is most marked in patients with active disease characterized by significant elevations of the complement split product C3a desArg. We suggest that in certain SLE patients, excessive complement activation in association with primed endothelial cells induces leukocyte-endothelial cell adhesion and leuko-occlusive vasculopathy

Non-steroidal anti-inflammatory drugs (NSAIDs) inhibit neutrophil functions via mechanisms that are independent of their effects on prostaglandin biosynthesis. We examined the effects of sodium salicylate and piroxicam on GTP/GDP exchange by a regulatory G protein (G alpha i). Plasma membrane and cytosol of human neutrophils were prepared by nitrogen cavitation and discontinuous sucrose density centrifugation. Salicylate (3 mM) and piroxicam (50 microM) reduced [35S]GTP gamma S binding to purified plasma membranes [65 +/- 3.7 and 75 +/- 5.3% (P < 0.003) of control, respectively]. Membrane-associated G alpha/beta gamma was solubilized by treatment of plasma membranes with sodium cholate. NSAIDs did not inhibit binding of GTP to solubilized G alpha/beta gamma derived from detergent-treated plasma membranes. Lipid reconstitution was achieved by detergent dialysis followed by the addition of bilayer liposomes (phosphatidylcholine). Salicylate and piroxicam inhibited GTP gamma S binding to G alpha/beta gamma derived from solubilized plasma membranes reconstituted in phosphatidylcholine vesicles (bilayer structures) but had no effect when phosphatidylethanolamine (hexagonal phase II structure) was used for reconstitution. Salicylate and piroxicam had no effect on GTP binding to cytosolic fractions in which soluble G alpha i exists as a free subunit, suggesting that the effect required either assembly of G alpha i/beta gamma heterotrimer or the presence of a lipid bilayer. Although the addition of purified bovine beta gamma subunits to dialyzed cytosol increased both the total GIP binding capacity and the pertussis toxin-dependent ADP-ribosylation of G alpha i, consistent with assembly of a G protein heterotrimer, NSAIDs had no effect on GTP binding. In contrast, NSAIDs inhibited GTP binding to heterotrimeric G alpha cytosol/beta gamma bovine when the complex was inserted into bilayer liposomes. The data indicate that salicylate and piroxicam disrupt neutrophil function via their capacity to interfere with GTP/GDP exchange at an alpha subunit of a regulatory G protein, an effect which requires assembly of the active heterotrimer G alpha i/beta gamma in a phospholipid bilayer

OBJECTIVE. To examine the effects of nitric oxide (NO) and its more stable derivative, S-nitrosoglutathione (SNO-GSH), on the response of activated T lymphocytes. METHODS. The effects of NO and SNO-GSH on DNA synthesis, interleukin-2 (IL-2) production, IL-2 receptor expression, and cGMP accumulation were determined in phytohemagglutinin-activated peripheral blood mononuclear cells (PBMC) and spleen T cells. RESULTS. Nitric oxide (half-life [T1/2] < 15 seconds) did not inhibit T cell proliferation. However, the derivative SNO-GSH (25 microM) (T1/2 > 2 hours) inhibited DNA synthesis by a mean +/- SD of 65 +/- 19.6% (P < 0.001) in PBMC and 75 +/- 15% (P < 0.001) in spleen cells. Macrophage depletion of PBMC did not abrogate the inhibition. SNO-GSH had no effect on IL-2 production or IL-2 receptor expression. NO (25 microM) increased the cGMP content of PBMC (0.65 +/- 0.15 pmoles/10(6) cells; P < 0.04), as did SNO-GSH (25 microM) in both PBMC (3.8 +/- 1; P < 0.001) and spleen T cells (5.2 +/- 1.2; P < 0.001). Methylene blue and hemoglobin, which are NO inhibitors, inhibited SNO-GSH-induced cGMP accumulation (P < 0.001). CONCLUSION. SNO-GSH inhibits T cell DNA synthesis independently of IL-2 production and in association with cGMP accumulation via a NO-dependent mechanism. We suggest that NO and its S-nitrosothiol derivatives may act as endogenous inhibitors of T cell-mediated inflammation