calpain and Lupus-Erythematosus--Systemic

The alpha-fodrin N-terminal portion (AFN) autoantigen mediates in vivo immunoregulation of autoimmune responses in primary Sjögren's syndrome (SS). We further examined this process and found that cleavage products of AFN were frequently detected in the salivary gland duct cells of SS patients. In in vitro studies using human salivary gland HSY cells, anti-Fas-induced apoptosis resulted in specific cleavage of alpha-fodrin into the 120-kd fragment, in association of alpha-fodrin with mu-calpain, and activation of caspase 3. Significant proliferative responses against AlphaFN autoantigen were observed in the peripheral blood mononuclear cells (PBMCs) from SS patients with higher pathological score (grade 4) and with short duration from onset (within 5 years). In vivo roles of AFN peptides were investigated using PBMCs from patients with SS, systemic lupus erythematosus, and rheumatoid arthritis. Significant proliferative T-cell responses of PBMCs to AFN peptide were detected in SS but not in systemic lupus erythematosus or rheumatoid arthritis. AFN peptide induced Th1-immune responses and accelerated down-regulation of Fas-mediated T-cell apoptosis in SS. Our data further elucidate the in vivo role of AFN autoantigen on the development of SS and suggest that the AFN autoantigen is a novel participant in peripheral tolerance.

Topics: Amino Acid Sequence; Antibodies, Monoclonal; Apoptosis; Arthritis, Rheumatoid; Autoantigens; Blotting, Western; Calpain; Carrier Proteins; Case-Control Studies; Caspase 3; Caspases; CD4-Positive T-Lymphocytes; CD8-Positive T-Lymphocytes; Cells, Cultured; Coculture Techniques; Enzyme Activation; fas Receptor; Female; Furans; Glutathione Transferase; Humans; Immunohistochemistry; Japan; Leukocytes, Mononuclear; Lupus Erythematosus, Systemic; Microfilament Proteins; Molecular Sequence Data; Molecular Weight; Parotid Gland; Recombinant Fusion Proteins; Sjogren's Syndrome; Thymidine

In vitro activation of PBLs from HIV+ individuals resulted in programmed cell death (PCD) within 2 days in 58 of 95 HIV+ blood donors, in contrast to only two of 30 control HIV- donors. CD4+ and CD8+ T cells from HIV+ donors died under these conditions, and these cells showed apoptotic nuclear morphology and DNA fragmentation. To test the hypothesis that this cell death shares a common biochemical pathway with that induced by TCR cross-linking in normal dividing T cells, inhibitors of the calcium-activated cysteine protease calpain were tested for their ability to block the activation-induced PCD of HIV+ donors. The E-64 (epoxysuccinyl) class of cysteine protease inhibitors gave 40% to 60% inhibition of HIV+ PCD responses, while the aldehyde inhibitors, leupeptin and calpain inhibitor II, gave 60% to 67% inhibition. The involvement of this calpain-dependent death pathway in HIV-induced functional T helper cell deficiency was tested by examining the effect of calpain inhibitors on the defective Ag- and mitogen-dependent proliferative responses of HIV+ donors. Twenty to fifty percent of such defective responses were significantly restored toward normal levels by calpain inhibitors, whereas control responses by normal donors were largely unaffected. These data suggest that a calpain-dependent PCD pathway contributes to HIV-associated immunodeficiency and suggest the use of calpain inhibitors as a possible route to therapy of HIV infection.

Topics: Apoptosis; Blood Donors; Calpain; Cells, Cultured; Cysteine Proteinase Inhibitors; HIV Seropositivity; Humans; Lupus Erythematosus, Systemic; Lymphocyte Activation; T-Lymphocytes