Biomedical subjects

Paul E Phillips

Publications and source records attributed to Paul E Phillips.

4 recordsLinked to original sources

PubMed2005

Increased prevalence of transfusion-transmitted virus and cross-reactivity with immunodominant epitopes of the HRES-1/p28 endogenous retroviral autoantigen in patients with systemic lupus erythematosus.

OBJECTIVE: Systemic lupus erythematosus (SLE) patients produce autoantibodies to HRES-1/p28, a human endogenous retrovirus-encoded nuclear protein. To identify cross-reactive viral antigens capable of triggering autoreactivity, HRES-1/p28 epitopes were mapped by SLE antibodies. METHODS: Forty-four peptides overlapping HRES-1/p28 and 13 viral peptides were synthesized on cellulose membrane and tested for recognition by antibodies from 16 HRES-1 Western blot seropositive SLE patients. Transfusion-transmitted virus (TTV) was detected by gene amplification in sera of 211 SLE patients, 78 healthy SLE family members, 199 unrelated healthy donors, and 91 rheumatoid arthritis (RA) patients. RESULTS: HRES-1/p28 residues 41-55, 121-135, and 156-170 were recognized by 12/16 (75.0%), 11/16 (68.8%), and 9/16 lupus sera (56.25%) and considered immunodominant. HRES-1/p28 residues 121-135 harbor cross-reactive epitope with retroviral peptides and the 70 K U1snRNP lupus autoantigen. HRES-1/p28 residues 41-55 and 156-170 exhibited the highest prevalence of cross-reactivity with TTV peptide ORF2a (14/16, 87%). Prevalence of TTV DNA was increased in lupus patients (120/211) with respect to healthy (66/199; P < 0.0001) or RA controls (23/91; P < 0.0001). TTV prevalence in healthy lupus relatives (40/78) was decreased with respect to lupus patients (80/121; P = 0.0184) and increased with respect to unrelated healthy donors (66/199; P = 0.0026). HRES-1/p28 Western blot reactivity was observed in 12/23 TTV PCR-negative donors and 43/58 TTV PCR-positive donors (P < 0.0281). CONCLUSIONS: Increased prevalence of TTV and molecular mimicry with HRES-1/p28 may contribute to generation of antinuclear antibodies and pathogenesis of SLE.

Adult↗

PubMed2004

Nitric oxide-dependent mitochondrial biogenesis generates Ca2+ signaling profile of lupus T cells.

Abnormal T cell activation and cell death underlie the pathology of systemic lupus erythematosus. Although mitochondrial hyperpolarization (MHP) represents an early and reversible checkpoint of T cell activation and apoptosis, lupus T cells exhibit persistent MHP. NO has recently been recognized as a key signal of mitochondrial biogenesis and mediator of MHP in human T lymphocytes. In this study, we show that persistent MHP was associated with increased mitochondrial mass (+47.7 +/- 2.8%; p = 0.00017) and increased mitochondrial (+21.8 +/- 4.1%; p = 0.016) and cytoplasmic Ca2+ content in T cells from 19 systemic lupus erythematosus patients with respect to 11 control donors (+38.0 +/- 6.4%; p = 0.0023). Electron microscopy revealed that lupus lymphocytes contained 8.76 +/- 1.0 mitochondria, while control donors contained 3.18 +/- 0.28 mitochondria per cell (p = 0.0009). Increased mitochondrial mass in T cells was associated with 2.08 +/- 0.09-fold enhanced NO production by lupus monocytes (p = 0.0023). Activation of T cells through the TCR initiates a biphasic elevation in cytosolic free Ca2+ concentration, a rapid initial peak observed within minutes, and a plateau phase lasting up to 48 h. In response to CD3/CD28 costimulation, rapid Ca2+ fluxing was enhanced while the plateau phase was diminished in lupus T cells. NO-induced mitochondrial biogenesis in normal T cells enhanced the rapid phase and reduced the plateau of Ca2+ influx upon CD3/CD28 costimulation, thus mimicking the Ca2+ signaling profile of lupus T cells. Mitochondria constitute major Ca2+ stores and NO-dependent mitochondrial biogenesis may account for altered Ca2+ handling by lupus T cells.

Adult↗

PubMed2002

Persistent mitochondrial hyperpolarization, increased reactive oxygen intermediate production, and cytoplasmic alkalinization characterize altered IL-10 signaling in patients with systemic lupus erythematosus.

Abnormal death signaling in lymphocytes of systemic lupus erythematosus (SLE) patients has been associated with elevation of the mitochondrial transmembrane potential (Delta psi(m)) and increased production of reactive oxygen intermediates (ROI). The resultant ATP depletion sensitizes T cells for necrosis that may significantly contribute to inflammation in patients with SLE. In the present study, the role of mitochondrial signal processing in T cell activation was investigated. CD3/CD28 costimulation of PBL elicited transient mitochondrial hyperpolarization and intracellular pH (pH(i)) elevation, followed by increased ROI production. Baseline Delta psi(m), ROI production, and pH(i) were elevated, while T cell activation-induced changes were blunted in 15 patients with SLE in comparison with 10 healthy donors and 10 rheumatoid arthritis patients. Similar to CD3/CD28 costimulation, treatment of control PBL with IL-3, IL-10, TGF-beta(1), and IFN-gamma led to transient Delta psi(m) elevation. IL-10 had diametrically opposing effects on mitochondrial signaling in lupus and control donors. Unlike healthy or rheumatoid arthritis PBL, cells of lupus patients were resistant to IL-10-induced mitochondrial hyperpolarization. By contrast, IL-10 enhanced ROI production and cell death in lupus PBL without affecting ROI levels and survival of control PBL. Ab-mediated IL-10 blockade or stimulation with antagonistic lymphokine IL-12 normalized baseline and CD3/CD28-induced changes in ROI production and pH(i) with no impact on Delta psi(m) of lupus PBL. The results suggest that mitochondrial hyperpolarization, increased ROI production, and cytoplasmic alkalinization play crucial roles in altered IL-10 responsiveness in SLE.

Adolescent↗

PubMed2002

Mitochondrial hyperpolarization and ATP depletion in patients with systemic lupus erythematosus.

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 (deltapsim) and production of reactive oxygen intermediates (ROIs), mediate the imbalance of apoptosis in SLE. METHODS: We assessed the deltapsim 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 deltapsim 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 deltapsim and caused apoptosis in normal PBLs. In contrast, H2O2-induced apoptosis and deltapsim 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 deltapsim elevation in lupus. CD3:CD28 costimulation led to transient elevation of the deltapsim, 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 deltapsim 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.

Adenosine Triphosphate↗