The Interaction of Pemphigus Autoimmunoglobulins with Epidermal Cells: Activation of the Fas Apoptotic Pathway and the Use of Caspase Activity for Pathogenicity Tests of Pemphigus Patients

Abstract

Pemphigus is a fatal autoimmune disease in which autoimmunoglobulins PV-IgG (binding to desmoglein 3) and PF-IgG (binding to desmoglein 1) in pemphigus vulgaris and pemphigus foliaceus, respectively, cause intraepidermal blisters, cell-cell separation (acantholysis), and cell death. The mechanism of acantholytic lesion formation has not yet been elucidated. Recently, we have reported that an apoptotic mechanism might be operative in PV-IgG-induced acantholysis: (1) in patients' lesional and some perilesional skin portions, the FasR pathway is activated as its components were enriched; (2) in cultured keratinocytes, PV-IgG upregulates effectors of the FasR pathway (including the mitochondrial loop), as found by immunodetermination (cytochemistry, Western blot of pathway effectors) and determination of caspases 1, 3, and 8 activity/activation; (3) in organ cultures of skin incubated with PV-IgG, activated caspase 8 was found also in perilesional cells and coaggregated with bound PV-IgG; (4) caspase 8 activation in DISCs precedes caspase 3 activation in keratinocytes in cultures upon incubation with PV-IgG. Because caspase activation was shown to accompany lesion formation in cell and organ cultures incubated with PV-IgG, we used caspase activity to monitor the pathogenicity of PV-IgG in relation to PV-IgG binding to epithelia. A rough correlation was found between sera titers, determined by IIF and by immunoblot binding to desmoglein 3, and activation of caspase 3.

Neural nitric oxide synthase participates in pemphigus vulgaris acantholysis through upregulation of Rous sarcoma, mammalian target of rapamycin and focal adhesion kinase

“…Several groups (36)(37)(38)(39), including ours (15,16), have established that in the acantholytic process, an increase in the Bax/Bcl-2 ratio in addition to an increase in caspase activities may be detected in in vitro or in vivo studies. These findings, along with several reports demonstrating that upregulation of nNOS increases caspase activity (40)(41)(42) and the involvement of the Bcl-2-family members in caspase-dependent apoptosis due to increased NO (43)(44)(45), underline the possible implication of nNOS in promoting PV acantholysis.…”

Antimitochondrial Autoantibodies in Pemphigus Vulgaris

“…Original immunohistochemical studies revealed Fas receptor (FasR) on KCs of lesional epidermis (26). Subsequent studies demonstrated that PVIgG binding to KCs causes secretion of soluble FasL, increased production and cellular amounts of FasR and FasL (soluble and membranal), co-aggregation of FasL and FasR with caspase 8 in a membranal deathinducing signaling complex, and down-regulation of the apoptosis inhibitor FLIP-l (5,10,11,14,27,28). The keratinocyte FasR can be also triggered by FasL expressed by the cytotoxic T cells (29) found in the skin of PV patients (30).…”

Novel Mechanisms of Target Cell Death and Survival and of Therapeutic Action of IVIg in Pemphigus

“…15 More recently, determination of caspase 3 activity in the HaCaT culture treated with PVIgG has been proposed as a test for pathogenic activity of the autoantibodies. 16 It is now well established that intravenous immunoglobulin (IVIg) therapy is an effective treatment modality of PV, 17,18 but the mechanism of therapeutic action of IVIg has not been fully elucidated. The IVIg drug contains purified preparations of immunoglobulins from plasma of healthy human donors, containing predominantly polyclonal IgG, and various immunomodulatory contaminants.…”