Hydroxychloroquine modulates elevated expression of S100 proteins in systemic lupus erythematosus.

OBJECTIVES: We investigated the effect of hydroxychloroquine (HCQ) on S100A8 and S100A9 serum levels in systemic lupus erythematosus (SLE) patients with low disease activity receiving immunosuppressants. METHODS: SELENA-SLEDAI, Cutaneous Lupus Erythematous Disease Area and Severity Index (CLASI) and serum levels of complement factors, anti-dsDNA antibodies, and white blood cell, lymphocyte, and platelet counts were used to evaluate disease activity, cutaneous disease activity, and immunological activity, respectively. Serum S100A8 and S100A9 were measured at HCQ administration and after 3 or 6 months using ELISA. RESULTS: S100A8 and S100A9 serum levels were elevated at baseline and the magnitude of decrease from baseline at 3 and 6 months after HCQ administration was greater in patients with renal involvement than in those without (baseline: S100A8, p = 0.034; S100A9, p = 0.0084; decrease: S100A8, p = 0.049; S100A9, p = 0.023). S100 modulation was observed in patients with (n = 17; S100A8, p = 0.0011; S100A9, p = 0.0002) and without renal involvement (n = 20; S100A8, p = 0.0056; S100A9, p = 0.0012), and was more apparent in patients with improved CLASI activity scores (improved: S100A8, p = 0.013; S100A9, p = 0.0032; unimproved: S100A8, p = 0.055; S100A9, p = 0.055). No associations were observed for immunological biomarkers. CONCLUSION: HCQ may improve organ involvement in SLE by modulating S100 protein levels, especially in patients with renal or skin involvement.

Stimulation of arachidonic acid release by guanine nucleotide in saponin-permeabilized neutrophils: evidence for involvement of GTP-binding protein in phospholipase A2 activation.

Addition of a guanine nucleotide analog, guanosine 5'-O-(thiotriphosphate) (GTP gamma S)(1-100 microM) induced release of [3H]arachidonic acid from [3H]arachidonate-prelabeled rabbit neutrophils permeabilized with saponin. The chemotactic peptide N-formyl-methionyl-leucyl-phenylalanine (fMLP)-induced arachidonate release was enhanced by GTP gamma S, Ca2+, or their combination. Ca2+ alone (up to 100 microM) did not effectively stimulate lipid turnover. However, the combination of fMLP plus GTP gamma S elicited greater than additional effects in the presence of resting level of free Ca2+. The addition of 100 microM of GTP gamma S reduced the Ca2+ requirement for arachidonic acid liberation induced by fMLP. Pretreatment of neutrophils with pertussis toxin resulted in the abolition of arachidonate release and diacylglycerol formation. Neomycin (1 mM) caused no significant reduction of arachidonate release. In contrast, about 40% of GTP gamma S-induced arachidonate release was inhibited by a diacylglycerol lipase inhibitor, RHC 80267 (30 microM). These observations indicate that liberation of arachidonic acid is mediated by phospholipase A2 and also by phospholipase C/diacylglycerol lipase pathways. Fluoride, which bypasses the receptor and directly activates G proteins, induced arachidonic acid release and diacylglycerol formation. The fluoride-induced arachidonate release also appeared to be mediated by these two pathways. The loss of [3H]arachidonate was seen in phosphatidylinositol, phosphatidylcholine, and phosphatidylethanolamine. These data indicate that a G protein is involved between the binding of fMLP to its receptor and activation of phospholipase A2, and also that the arachidonic acid release is mediated by both phospholipase A2 and phospholipase C/diacylglycerol lipase.