Objective: Systemic lupus erythematosus (SLE) patients exhibit T cell dysfunction, which can be regulated through mitochondrial transmembrane potential (Δψm) and mammalian target of rapamycin (mTOR) by glutathione (GSH). This randomized, double‐blind, placebo‐controlled study was undertaken to examine the safety, tolerance, and efficacy of the GSH precursor N‐acetylcysteine (NAC).Methods: A total of 36 SLE patients received either daily placebo or 1.2 gm, 2.4 gm, or 4.8 gm of NAC. Disease activity was evaluated monthly by the British Isles Lupus Assessment Group (BILAG) index, the SLE Disease Activity Index (SLEDAI), and the Fatigue Assessment Scale (FAS) before, during, and after a 3‐month treatment period. Mitochondrial transmembrane potential and mTOR were assessed by flow cytometry. Forty‐two healthy subjects matched to patients for age, sex, and ethnicity were studied as controls.Results: NAC up to 2.4 gm/day was tolerated by all patients, while 33% of those receiving 4.8 gm/day had reversible nausea. Placebo or NAC 1.2 gm/day did not influence disease activity. Considered together, 2.4 gm and 4.8 gm NAC reduced the SLEDAI score after 1 month (P = 0.0007), 2 months (P = 0.0009), 3 months (P = 0.0030), and 4 months (P = 0.0046); the BILAG score after 1 month (P = 0.029) and 3 months (P = 0.009); and the FAS score after 2 months (P = 0.0006) and 3 months (P = 0.005). NAC increased Δψm (P = 0.0001) in all T cells, profoundly reduced mTOR activity (P = 0.0009), enhanced apoptosis (P = 0.0004), reversed expansion of CD4−CD8− T cells (mean ± SEM 1.35 ± 0.12‐fold change; P = 0.008), stimulated FoxP3 expression in CD4+CD25+ T cells (P = 0.045), and reduced anti‐DNA production (P = 0.049).Conclusion: This pilot study suggests that NAC safely improves lupus disease activity by blocking mTOR in T lymphocytes.

Objective Peripheral blood lymphocytes (PBLs) from systemic lupus erythematosus (SLE) patients exhibit increased spontaneous and diminished activation‐induced apoptosis. We tested the hypothesis that key biochemical checkpoints, the mitochondrial transmembrane potential (ΔΨm) and production of reactive oxygen intermediates (ROIs), mediate the imbalance of apoptosis in SLE. Methods We assessed the ΔΨm with potentiometric dyes, measured ROI production with oxidation‐sensitive fluorochromes, and monitored cell death by annexin V and propidium iodide staining of lymphocytes, using flow cytometry. Intracellular glutathione levels were measured by high‐performance liquid chromatography, while ATP and ADP levels were assessed by the luciferin‐luciferase assay. Results Both ΔΨm and ROI production were elevated in the 25 SLE patients compared with the 25 healthy subjects and the 10 rheumatoid arthritis patients. Intracellular glutathione contents were diminished, suggesting increased utilization of reducing equivalents in SLE. H₂O₂, a precursor of ROIs, increased ΔΨm and caused apoptosis in normal PBLs. In contrast, H₂O₂‐induced apoptosis and ΔΨm elevation were diminished, particularly in T cells, and the rate of necrotic cell death was increased in patients with SLE. The intracellular ATP content and the ATP:ADP ratio were reduced and correlated with the ΔΨm elevation in lupus. CD3:CD28 costimulation led to transient elevation of the ΔΨm, followed by ATP depletion, and sensitization of normal PBLs to H₂O₂‐induced necrosis. Depletion of ATP by oligomycin, an inhibitor of F₀F₁–ATPase, had similar effects. Conclusion T cell activation and apoptosis are mediated by ΔΨm elevation and increased ROI production. Mitochondrial hyperpolarization and the resultant ATP depletion sensitize T cells for necrosis, which may significantly contribute to inflammation in patients with SLE.

Objective: Systemic lupus erythematosus (SLE) is an autoimmune disease of unknown origin. Current treatment options are often ineffective or poorly tolerated. Recent observations have revealed mitochondrial hyperpolarization and enhanced Ca²⁺ fluxing in T cells from SLE patients. Rapamycin, a lipophilic macrolide antibiotic that regulates mitochondrial transmembrane potential and Ca²⁺ fluxing, has been used safely and effectively to treat renal transplant rejection since 1999. In addition, rapamycin has been shown to ameliorate T cell function and to prolong survival in lupus‐prone MRL/lpr mice. We therefore undertook the present study to investigate whether rapamycin is beneficial in patients with SLE.Methods: Nine patients with clinically active SLE that had been treated unsuccessfully with other immunosuppressive medications began therapy with rapamycin, 2 mg/day orally. Disease activity was assessed with the British Isles Lupus Assessment Group (BILAG) score, SLE Disease Activity Index (SLEDAI), and requirement for prednisone therapy. Mitochondrial transmembrane potential and Ca²⁺ fluxing were assessed by flow cytometry.Results: In patients treated with rapamycin, the BILAG score was reduced by a mean ± SEM of 1.93 ± 0.9 (P = 0.0218), the SLEDAI by 5.3 ± 0.8 (P = 0.00002), and concurrent prednisone use by 26.4 ± 6.7 mg/day (P = 0.0062) compared with pre–rapamycin treatment. While mitochondrial hyperpolarization persisted, pretreatment cytosolic and mitochondrial Ca²⁺ levels and T cell activation–induced rapid Ca²⁺ fluxing were normalized in rapamycin‐treated patients.Conclusion: Rapamycin appears to be a safe and effective therapy for SLE that has been refractory to traditional medications. Mitochondrial dysfunction and Ca²⁺ fluxing could serve as biomarkers to guide decisions regarding future therapeutic interventions in SLE.