Granzyme B inhibition reduces disease severity in autoimmune blistering diseases.

Pemphigoid diseases refer to a group of severe autoimmune skin blistering diseases characterized by subepidermal blistering and loss of dermal-epidermal adhesion induced by autoantibody and immune cell infiltrate at the dermal-epidermal junction and upper dermis. Here, we explore the role of the immune cell-secreted serine protease, granzyme B, in pemphigoid disease pathogenesis using three independent murine models. In all models, granzyme B knockout or topical pharmacological inhibition significantly reduces total blistering area compared to controls. In vivo and in vitro studies show that granzyme B contributes to blistering by degrading key anchoring proteins in the dermal-epidermal junction that are necessary for dermal-epidermal adhesion. Further, granzyme B mediates IL-8/macrophage inflammatory protein-2 secretion, lesional neutrophil infiltration, and lesional neutrophil elastase activity. Clinically, granzyme B is elevated and abundant in human pemphigoid disease blister fluids and lesional skin. Collectively, granzyme B is a potential therapeutic target in pemphigoid diseases.

Interstitial collagenase is expressed by keratinocytes that are actively involved in reepithelialization in blistering skin disease.

Migrating keratinocytes actively involved in reepithelialization in dermal wounds acquire a collagenolytic phenotype upon contact with the dermal matrix. To determine whether this phenotype is associated with repair in other forms of wounds, we assessed collagenase expression in 50 specimens representing a variety of blistering skin diseases, including subtypes of epidermolysis bullosa, porphyria cutanea tarda, bullous pemphigoid, pemphigus, transient acantholytic dermatosis, and suction blisters. Distinct from that seen in chronic ulcers or in normal healing by second intention, reepithelialization in these blistering conditions was not necessarily associated with a complete loss of basement membrane, as determined by immunostaining for type IV collagen. Collagenase mRNA was detected in the basal keratinocytes of several specimens of epidermolysis bullosa simplex (six of 10) and of pemphigus (three of seven), as well as in one quarter of transient acantholytic dermatosis samples in the presence of an intact basement membrane. In contrast, three of nine porphyria cutanea tarda, one third of epidermolysis bullosa acquisita, and one of 10 bullous pemphigoid samples had collagenase-positive basal keratinocytes with the basement membrane disrupted. The collagenase-positive lesions generally represented older blisters with evidence of epithelial regeneration. Collagenase was also expressed in suction blisters at 2 and 5 d after induction of the blister, but was shut off when the epidermis had healed. Other metalloproteinases were expressed occasionally, if at all. Our results suggest that keratinocyte migration is associated with collagenase expression and that contact of keratinocytes with the dermal matrix is not necessarily needed for collagenase induction.

Cleavage of type VII collagen by interstitial collagenase and type IV collagenase (gelatinase) derived from human skin.

Type VII collagen is the major structural protein of anchoring fibrils, which are believed to be critical for epidermal-dermal adhesion in the basement membrane zone of the skin. To elucidate possible mechanisms for the turnover of this protein, we examined the capacities of two proteases, human skin collagenase, which degrades interstitial collagens, and a protease with gelatinolytic and type IV collagenase activities, to cleave type VII collagen. At temperatures below the denaturation temperature, pepsin cleaves type VII collagen into products of approximately 95 and approximately 75 kDa. Human skin collagenase cleaved type VII collagen into two stable fragments of approximately 83 and approximately 80 kDa, and the type IV collagenase (gelatinase) produced a broad band of approximately 80 kDa as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Cleavage of type VII collagen was linear with time and enzyme concentration for both enzymes. Although the Km values were similar for both enzymes, the catalytic rate of cleavage by type IV collagenase is much faster than by interstitial collagenase, and shows a greater rate of increase with increasing temperature. Sequence analysis of the cleavage products from both enzymes showed typical collagenous sequences, indicating a relaxation in the helical part of the type VII collagen molecule at physiological temperature which makes it susceptible to gelatinolytic degradation. Interstitial collagenase from both normal skin cells and cells from patients with recessive dystrophic epidermolysis bullosa, a severe hereditary blistering disease in which both an anchoring fibril defect and excessive production of collagenase can be observed, produced identical cleavage products from type VII collagen. These data suggest a pathophysiological link between increased enzyme levels and the observed decrease or absence of anchoring fibrils.

Collagenase expression in skin fibroblasts from families with recessive dystrophic epidermolysis bullosa.

The collagenase production of cultured skin fibroblasts from Scandinavian families with dominant (D-EBD) and recessive (R-EBD) epidermolysis bullosa dystrophica has been investigated. Heterogeneity as a result of body location origin has been ruled out as fibroblasts obtained from predilection sites produce the same amount of immunoreactive collagenase as those obtained from non-predilection sites of the same subjects. Large variations in in vitro collagenase production were found between individuals and families. Within the R-EBD group, four out of eighteen patients showed an in vitro elevated level of immunoreactive collagenase compared to their healthy relatives, other EB types, and the control group. This shows that an in vitro elevated collagenase production is not a marker for the entire disease group and that the disease denoted as R-EBD probably is etiologically and pathogenetically heterogeneous.

A perspective on the role of collagenase in recessive dystrophic epidermolysis bullosa.

The pathophysiology of tissue fragility in recessive dystrophic epidermolysis bullosa may be due in part to excessive destruction of interstitial collagens by a structurally altered, but catalytically active, form of human skin collagenase. Therapeutic attempts directed toward reducing the expression of this enzyme have resulted in clinical improvement in some patients with the disease.

Response of epidermolysis bullosa fibroblasts to factors derived from macrophages and polymorphonuclear leukocytes in terms of collagenase production.

In order to investigate the role of inflammatory cells in altering the collagenase production by epidermolysis bullosa (EB) fibroblasts, macrophage and polymorphonuclear leukocyte (PMN) factors obtained from mouse peritoneal fluids were added to the fibroblast culture system, and collagenase activity was assayed after a 48-h incubation. Data obtained here revealed that the response of collagenase production by fibroblasts was quite different, depending on the type of EB. Namely, EB dystrophica recessiva (EBDR) (n = 2) fibroblasts produced significant amounts of collagenase in the range of 5.07 (U/ml) to 6.04 in response to macrophage-conditioned medium, macrophage lysate, and PMN lysate, compared with 0.13 in the absence of these. On the other hand, EB dystrophica dominans (EBDD) (n = 1) fibroblasts showed little or no overt increase in enzyme production in the presence of macrophage lysate and PMN lysate, which resulted in a moderate increase to 3.82 in response to macrophage-conditioned medium. Furthermore, EB simplex (EBS) (n = 1) fibroblasts produced collagenase up to 3.84 in response to these three factors. These factors can be inactivated by treating with trypsin, pronase, and phenylglyoxal. Our data clearly indicated that, in the comparisons of EBDD and EBS fibroblasts, EBDR fibroblasts showed quite high response to factors derived from macrophages and PMNs in terms of collagenase production. This fact may raise a clue that accounts for the high levels of tissue collagenase activity, which plays a potentially major role in blister formation in EBDR.

The association of congenital skin disorders with acetylcholinesterase in amniotic fluid.

We describe a fetus with epidermolysis bullosa dystrophica and a fetus with aplasia cutis congenita who were normal by careful ultrasound examination but whose midtrimester amniotic fluids exhibited elevated concentrations of alpha-fetoprotein and presence of acetylcholinesterase. These cases show that serious fetal skin pathology can be a source of amniotic fluid acetylcholinesterase and elevated alpha-fetoprotein concentration and should be considered as part of the differential diagnosis of these amniotic fluid findings.

Elevated serum chymotrypsin levels in a patient with junctional epidermolysis bullosa. Normalization after UVB therapy with good clinical response.

A 36-year-old Hispanic woman, covered with blisters since birth, was found to have markedly elevated chymotrypsin levels in her serum. This proteolytic enzyme is thought to digest laminin, thus causing separation of the basement membrane at the level of the lamina lucida, corroborating findings on electron microscopy. On the basis that the sun-exposed areas of the skin were relatively less involved, she received a course of UVB therapy, with total clinical clearance of her lesions after 3 weeks. A repeat estimation of serum chymotrypsin at this time revealed normal levels of this enzyme. It is thought that the elevated chymotrypsin levels were either released from the Langerhans cells themselves or from lymphocytes or keratinocytes as a result of Langerhans cell activity, and that the suppression of Langerhans cell activity by UVB inhibited the release of this proteolytic enzyme, resulting in the suppression of blister formation in our patient.

Behavior of epidermolysis bullosa fibroblasts in a hydrated collagen lattice.

To determine if an altered ability to contract a hydrated collagen lattice is characteristic of fibroblasts from patients with recessive dystrophic epidermolysis bullosa (RDEB), we examined contraction by fibroblasts from normal subjects and patients with RDEB, dominant dystrophic epidermolysis bullosa (DDEB), and dominant epidermolysis bullosa simplex (DEBS). An extremely broad range of contractility (normal, poor, and hypercontraction) was observed in all types of epidermolysis bullosa (EB). When contraction in control fibroblasts was defined as the mean +/- 2 SD, (all control values were within this range) and the data were analyzed by the chi-square test, only 32% of EB cells fell within this range, with 47% poorly contractile and 21% hypercontractile. These data, derived from 34 patients, indicate that no single genetic defect resulting in altered contractility in the 3 distinct types of EB is likely. Neither cell viability, collagenase expression, nor PGE2 synthesis as correlated with gel contraction in any group. Indomethacin had no effect on contraction in RDEB. It is possible that the genetic defects in EB cause blister formation in vivo and may lead in some way to an abnormal interaction of fibroblasts with the extracellular matrix resulting in an altered collagen lattice contraction in vitro.

Antenatal diagnosis of recessive dystrophic epidermolysis bullosa: collagenase expression in cultured fibroblasts as a biochemical marker.

We performed fetoscopy and skin biopsy on a 19-week fetus at risk for recessive dystrophic epidermolysis bullosa (RDEB). Ultrastructural analysis of the tissue revealed dermolytic blister formation in the skin characteristic of the disease. To develop a biochemical test for use in antenatal diagnosis of RDEB, we established skin fibroblast cultures from the 20-week aborted fetus. The collagenase production by fetal RDEB fibroblast cultures was greater than seen in normal fetal fibroblast cultures. The concentration in culture medium from fetal RDEB cultures was 5.42 +/- 0.74 micrograms/ml (mean +/- SE) compared with 2.24 +/- 1.11 micrograms/ml in normal adult control cultures and 2.05 +/- 0.61 micrograms/ml in cultures from patients with other genetic forms of epidermolysis bullosa (p less than 0.025). In contrast, the concentration of collagenase in the fetal RDEB culture medium was not different from that seen in cell cultures from known patients with RDEB (5.34 +/- 1.12 micrograms/ml). Collagenase activity of the fetal RDEB medium was also increased approximately 3.5-fold. These data indicate that enhanced expression of collagenase by fetal RDEB skin fibroblasts can serve as a biochemical adjunct, and possibly an alternative, to morphologic examination of tissue for antenatal diagnosis.

Gelatinase expression in generalized epidermolysis bullosa simplex fibroblasts.

The use of gelatinase expression in dermal fibroblast cultures as a marker for generalized epidermolysis bullosa simplex (D-EBS-Köbner) has been tested. None of the 6 Köbner patients tested (from 3 families) produced reduced amounts of gelatinase compared with their healthy relatives and other control groups. This shows that a reduced production of gelatinase from dermal fibroblasts is not uniformly a marker for D-EBS-K.

Characterization of elastase-like enzymes in various blistering diseases.

Blister fluid samples were collected from suction induced control blisters and from spontaneous blisters from various blistering diseases for the measurement of elastase-like enzyme activities using synthetic succinyl-L-(alanyl)3-paranitroanilide (SAPNA) and alanyl paranitroanilide (ala-PNA) as the substrates. The blister fluids derived from bullous pemphigoid, pyoderma or epidermolysis bullosa dystroficans lesions contained higher levels of elastase-like enzyme activities than burn blisters or fresh suction blisters. The gel filtration studies using Sepharose CL-4B chromatography revealed two major peaks of SAPNA hydrolysing enzyme activity in burn blister and in bullous pemphigoid blister. The first peak eluted in void volume, and the second peak had an apparent molecular weight of 2.5 X 10(5) daltons. The results indicate that various proteinases are present in blisters fluids and that they may participate in the blister formation by degrading structural components of the basement membrane zone and the dermis.