Basic science for the clinician 42: handling the corpses: apoptosis, necrosis, nucleosomes and (quite possibly) the immunopathogenesis of SLE

Elevated plasma level of HMGB1 is associated with disease activity and combined alterations with IFN-α and TNF-α in systemic lupus erythematosus

Recent studies indicate that high-mobility group box protein 1 (HMGB1) contributes to the pathogenesis of diverse autoimmune disorders. It induces the production of interferon-alpha (IFN-alpha) and tumor necrosis factor alpha (TNF-alpha) in vitro. In the present study, plasma HMGB1, TNF-alpha, and IFN-alpha were determined with ELISA in 37 patients with systemic lupus erythematosus (SLE) and 39 age- and sex-matched healthy controls (HC). The possible associations of these cytokines with disease activities, autoantibodies, and certain laboratory parameters were also explored. The plasma levels of HMGB1, TNF-alpha, and IFN-alpha were increased in SLE patients compared with those of HC (P < 0.05). Moreover, the levels of HMGB1 and TNF-alpha in the active SLE patients were elevated compared with those in inactive patients and HC. Additionally, plasma HMGB1 was positively correlated with peripheral neutrophils, and plasma TNF-alpha was positively correlated with anti-Sm, ESR and CRP, while plasma IFN-alpha was inversely correlated with the age and platelet level in SLE patients. Our data indicated that increased plasma HMGB1 was associated with disease activity in SLE, which was similar to TNF-alpha. High level of plasma IFN-alpha may be related to nephritis and thrombocytopenia in SLE.

Diminished prostaglandin E2 contributes to the apoptosis paradox in idiopathic pulmonary fibrosis

RATIONALE

Patients with idiopathic pulmonary fibrosis (IPF), a progressive disease with a dismal prognosis, exhibit an unexplained disparity of increased alveolar epithelial cell (AEC) apoptosis but reduced fibroblast apoptosis.

OBJECTIVES

To examine whether the failure of patients with IPF to up-regulate cyclooxygenase (COX)-2, and thus the antifibrotic mediator prostaglandin (PG)E(2), accounts for this imbalance.

METHODS

Fibroblasts and primary type II AECs were isolated from control and fibrotic human lung tissue. The effects of COX-2 inhibition and exogenous PGE(2) on fibroblast and AEC sensitivity to Fas ligand (FasL)-induced apoptosis were assessed.

MEASUREMENTS AND MAIN RESULTS

IPF lung fibroblasts are resistant to FasL-induced apoptosis compared with control lung fibroblasts. Inhibition of COX-2 in control lung fibroblasts resulted in an apoptosis-resistant phenotype. Administration of PGE(2) almost doubled the rate of FasL-induced apoptosis in fibrotic lung fibroblasts compared with FasL alone. Conversely, in primary fibrotic lung type II AECs, PGE(2) protected against FasL-induced apoptosis. In human control and, to a greater extent, fibrotic lung fibroblasts, PGE(2) inhibits the phosphorylation of Akt, suggesting that regulation of this prosurvival protein kinase is an important mechanism by which PGE(2) modulates cellular apoptotic responses.

CONCLUSIONS

The observation that PGE(2) deficiency results in increased AEC but reduced fibroblast sensitivity to apoptosis provides a novel pathogenic insight into the mechanisms driving persistent fibroproliferation in IPF.