The Role Of Proteases In The Basement Membrane Injury In Autoimmune Disease

Bullous pemphigoid (BP) is an autoimmune subepidermal blistering disease that is characterized by the development of tense, fluid-filled blisters on the body, separation of the epidermis from the dermis, an intense inflammatory infiltrate, and the destruction of components of the hemidesmosome and extracellular matrix. BP is associated with autoantibodies against the hemidesmosomal proteins BP180and BP230. Via passive transfer model, we know some mechanisms that possibly involved in the formation of BP bilster. In the IgG passive transfer model of BP, blister formation is triggered by anti-BP180IgG and depends on complement activation, mast cell degranulation, and neutrophil recruitment. Additionally, several proteinases are found in BP blister fluid, including plasmin, collagenase, elastase, and matrix metalloproteinase. These proteolytic enzymes may play a crucial role subepidermal blister formation in BP via their ability to degrade extracellular matrix proteins.These suggest that these proteolytic enzymes are new possible targets for treatment in human BP.Here, we demonstrated that NE and mMCP-4play a role in mediating tissue damage in experimental bullous pemphigoid via gene knockout and inflammatory cells reconstitution, and NE and mMCP-4are new possible targets for human BP treatment.Our data demonstrated that NE degrades recombinant mouse BP180within the immunodominant extracellular domain at amino acid positions506and561, generating peptide p561and peptide p506. Peptide p561is chemotactic for neutrophils both in vitro and in vivo. Local injection of NE into B6mice recruits neutrophils to the skin, and neutrophil infiltration is completely blocked by co-injection with the NE inhibitor al-proteinase inhibitor. More importantly, NE directly cleaves BP180in mouse and human skin, as well as the native human BP180trimer molecule. These results demonstrate that (i) NE directly damages the extracellular matrix and (â…±) NE degradation of mouse BP180generates neutrophil chemotactic peptides that amplify disease severity at the early stage of the disease.Besides, mouse mast cell protease-4(mMCP-4) has been linked to autoimmune and inflammatory diseases, although the exact mechanisms underlying its role in these pathological conditions remain unclear. Here, we have found that mMCP-4is critical in a mouse model of the autoimmune skin blistering disease bullous pemphigoid (BP). Mice lacking mMCP-4were resistant to experimental BP. Complement activation, mast cell (MC) degranulation, and the early phase of neutrophil (PMN) recruitment occurred comparably in mMCP-4-/-and WT mice. However, without mMCP-4, activation of matrix metalloproteinase (MMP)-9was impaired in cultured mMCP-4-/-MCs and in the skin of pathogenic IgG-injected mMCP-4-/-mice. MMP-9activation was not fully restored by local reconstitution with WT or mMCP-4-/-PMNs. Local reconstitution with mMCP-4+/+MCs, but not with mMCP-4-/-MCs, restored blistering, MMP-9activation, and PMN recruitment in mMCP-4-/-mice. mMCP-4also degraded the hemidesmosomal transmembrane protein BP180both in the skin and in vitro. These results demonstrate that mMCP-4plays two different roles in the pathogenesis of experimental BP, by both activating MMP-9and by cleaving BP180, leading to injury of the hemidesmosomes and extracellular matrix of the basement membrane zone.