The adverse effects of lipopolysaccharide (LPS) are mediated primarily by tumor necrosis factor alpha (TNF-␣). TNF-␣ production by LPS-stimulated macrophages is regulated at the levels of both transcription and translation. It has previously been shown that several mitogen-activated protein kinases (MAPKs) are activated in response to LPS. We set out to determine which MAPK signaling pathways are activated in our system and which MAPK pathways are required for TNF-␣ gene transcription or TNF-␣ mRNA translation. We confirm activation of the MAPK family members extracellular-signal-regulated kinases 1 and 2 (ERK1 and ERK2), p38, and Jun N-terminal kinase/stress-activated protein kinase (JNK/SAPK), as well as activation of the immediate upstream MAPK activators MAPK/ERK kinases 1 and 4 (MEK1 and MEK4). We demonstrate that LPS also activates MEK2, MEK3, and MEK6. Furthermore, we demonstrate that dexamethasone, which inhibits the production of cytokines, including TNF-␣, significantly inhibits LPS induction of JNK/SAPK activity but not that of p38, ERK1 and ERK2, or MEK3, MEK4, or MEK6. Dexamethasone also blocks the sorbitol but not anisomycin stimulation of JNK/SAPK activity. A kinase-defective mutant of SAPK␤, SAPK␤ K-A, blocked translation of TNF-␣, as determined by using a TNF-␣ translational reporting system. Finally, overexpression of wild-type SAPK␤ was able to overcome the dexamethasone-induced block of TNF-␣ translation. These data confirm that three MAPK family members and their upstream activators are stimulated by LPS and demonstrate that JNK/SAPK is required for LPS-induced translation of TNF-␣ mRNA. A novel mechanism by which dexamethasone inhibits translation of TNF-␣ is also revealed.

The role of ERK-1 and ERK-2 in wild-type (wt) Ha-Ras, phorbol 12-myristate 13-acetate (PMA), and serum-induced AP-1 activity was studied. Microlqjectlon of ERK-specific substrate peptide inhibited the Inducto ofAP-1 activity by all three stimuli, whereas a control peptide had no effect. By using eukaryotic expression constructs encoding wt ERK-1 and kise-deficient mutants of ERKs 1 and 2, it was found that ERK-1 and ERK-2 activities are required for AP-1 activation stmulated by either wt Ha-Ras, PMA, or serum. Overexpression of ERK-1 augmented wt Ha-Ras stimulation of AP-1, while having no effect upon PMA or serum stInulation. Overexpression of either kinase-deficient ERK-1 or kinasedeficient ERK-2 partially inhibited AP-1 activation by wt Ha-Ras but had no effect on PMA or serum-induced activation. Coexpression of both interfering mutants abolished AP-1 induction by wt Ha-Ras, PMA, or serum. We conclude that EkKs are necessary components in the pathway leading to the activation of AP-1 stimulated by these agents.

Objective. To examine the relationship between changes in anti-double-stranded DNA (anti-dsDNA) antibody levels and the risk of renal flare in patients with systemic lupus erythematosus (SLE), using data from 2 randomized, controlled trials.Methods. Analyses were based on 487 patients with SLE and a history of lupus nephritis who had an anti-dsDNA antibody titer >15 IU/ml at baseline, as measured by Farr assay. Results are presented for the combined population of patients, the placebo arms, and the drug treatment arms in which a dsDNA-based bioconjugate (abetimus sodium; LJP 394) was used.Results. Changes in anti-dsDNA antibody levels were inversely correlated with changes in the C3 level (P < 0.0001 in both trials). Cox proportional hazards regression models showed that changes in anti-dsDNA antibody levels correlated with the risk of renal flare. The models predicted that a point estimate of a 50% reduction in anti-dsDNA antibody levels is associated with a 52% reduction (95% confidence interval [95% CI] 26-68%, nominal P ‫؍‬ 0.0007) and a 53% reduction (95% CI 33-69%, nominal P < 0.0001) in the risk of renal flare in the 2 trials, respectively. In the 2 trials, the incidence of renal flare was lower in patients with sustained reductions in anti-dsDNA antibodies (3.0% and 4.1%, respectively) than in patients with stable or increasing antibody levels (21.3% and 20.3%, respectively).Conclusion. Changes in anti-dsDNA antibody levels were directly correlated with the risk of renal flare and inversely correlated with changes in the C3 level. Reducing anti-dsDNA antibody levels may represent a therapeutic objective in SLE patients with lupus nephritis, because it is associated with a reduced risk of renal flare.Anti-double-stranded DNA (anti-dsDNA) antibodies are diagnostic for systemic lupus erythematosus (SLE) (1) and have been implicated in the underlying pathogenesis of SLE renal disease and other disease manifestations (2-7). Immune complexes containing anti-

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Background: Lipopolysaccharide (LPS) is known to activate macrophages, causing the release of toxic cytokines that may provoke inflammation and shock. One of the most important and best studied of these cytokines is tumor necrosis factor (TNF). Details of the signaling pathway leading to TNF biosynthesis remain unclear. The pathway is branched in the sense that TNF gene transcription and TNF mRNA translation are both strongly stimulated by LPS. Recent evidence has indicated that MAP kinase homologs become phosphorylated in LPS-stimulated cells, suggesting their possible involvement in signal transduction. We sought to test this hypothesis. Materials and Methods: Measurements of LPS-induced MEK and ERK2 activity were undertaken in LPS-sensitive and LPS-insensitive cells. Transfection studies, in which dominant inhibitors of ras and raf-I were used to block signaling to the level of MAP kinase, were carried out in order to judge whether the TNF gene transcription and TNF mRNA translation are modulated through this pathway. Results: In RAW 264.7 mouse macrophages, both ERK2 and MEKI activity are induced by LPS treatment. In the same cell line, dominant negative inhibitors of ras and raf-1 block LPS-induced activation of the TNF promoter, as well as derepression of the translational blockade normally imposed by the TNF 3'-untranslated region. A constitutively active form of raf-1 (raf-BXB) was found to augment, but not replace, the LPS signal. In LPS-insensitive cells (RAW 264.7 X NIH 3T3 fusion hybrid cells and primary macrophages derived from C3H/HeJ mice), ERK2 activity was found to be refractory to induction by LPS. Conclusions: The ras/raf-1/MEK/MAPK pathway is chiefly responsible for transduction of the LPS signal to the level of the TNF gene and mRNA. raf and raf-1 lie upstream from (or actually represent) the physical branchpoints of the transcriptional and translation activation signals generated by LPS. The lesions that prevent LPS signaling in macrophages from C3H/HeJ mice, or in RAW 264.7 X NIH 3T3 fusion hybrid cells, occupy a proximal position in the signaling pathway.