Targeting Cathepsin C in PR3-ANCA Vasculitis.

BACKGROUND: The ANCA autoantigens proteinase 3 (PR3) and myeloperoxidase (MPO) are exclusively expressed by neutrophils and monocytes. ANCA-mediated activation of these cells is the key driver of the vascular injury process in ANCA-associated vasculitis (AAV), and neutrophil serine proteases (NSPs) are disease mediators. Cathepsin C (CatC) from zymogens activates the proteolytic function of NSPs, including PR3. Lack of NSP zymogen activation results in neutrophils with strongly reduced NSP proteins. METHODS: To explore AAV-relevant consequences of blocking NSP zymogen activation by CatC, we used myeloid cells from patients with Papillon-Lefèvre syndrome, a genetic deficiency of CatC, to assess NSPs and NSP-mediated endothelial cell injury. We also examined pharmacologic CatC inhibition in neutrophil-differentiated human hematopoietic stem cells, primary human umbilical vein cells, and primary glomerular microvascular endothelial cells. RESULTS: Patients with Papillon-Lefèvre syndrome showed strongly reduced NSPs in neutrophils and monocytes. Neutrophils from these patients produced a negative PR3-ANCA test, presented less PR3 on the surface of viable and apoptotic cells, and caused significantly less damage in human umbilical vein cells. These findings were recapitulated in human stem cells, in which a highly specific CatC inhibitor, but not prednisolone, reduced NSPs without affecting neutrophil differentiation, reduced membrane PR3, and diminished neutrophil activation upon PR3-ANCA but not MPO-ANCA stimulation. Compared with healthy controls, neutrophils from patients with Papillon-Lefèvre syndrome transferred less proteolytically active NSPs to glomerular microvascular endothelial cells, the cell type targeted in ANCA-induced necrotizing crescentic glomerulonephritis. Finally, both genetic CatC deficiency and pharmacologic inhibition, but not prednisolone, reduced neutrophil-induced glomerular microvascular endothelial cell damage. CONCLUSIONS: These findings may offer encouragement for clinical studies of adjunctive CatC inhibitor in patients with PR3-AAV.

Inherited diseases caused by mutations in cathepsin protease genes.

Lysosomal cathepsins are proteolytic enzymes increasingly recognized as prognostic markers and potential therapeutic targets in a variety of diseases. In those conditions, the cathepsins are mostly overexpressed, thereby driving the respective pathogenic processes. Although less known, there are also diseases with a genetic deficiency of cathepsins. In fact, nowadays 6 of the 15 human proteases called 'cathepsins' have been linked to inherited syndromes. However, only three of these syndromes are typical lysosomal storage diseases, while the others are apparently caused by defective cleavage of specific protein substrates. Here, we will provide an introduction on lysosomal cathepsins, followed by a brief description of the clinical symptoms of the various genetic diseases. For each disease, we focus on the known mutations of which many have been only recently identified by modern genome sequencing approaches. We further discuss the effect of the respective mutation on protease structure and activity, the resulting pathogenesis, and possible therapeutic strategies.

Characterization of neutrophil function in Papillon-Lefèvre syndrome.

Papillon-Lefévre syndrome is a rare, inherited, autosomal-recessive disease, characterized by palmoplantar keratosis and severe prepubertal periodontitis, leading to premature loss of all teeth. Papillon-Lefévre syndrome is caused by a mutation in the cathepsin C gene, resulting in complete loss of activity and subsequent failure to activate immune response proteins. Periodontitis in Papillon-Lefévre syndrome is thought to arise from failure to eliminate periodontal pathogens as a result of cathepsin C deficiency, although mechanistic pathways remain to be elucidated. The aim of this study was to characterize comprehensively neutrophil function in Papillon-Lefévre syndrome. Peripheral blood neutrophils were isolated from 5 patients with Papillon-Lefévre syndrome, alongside matched healthy control subjects. For directional chemotactic accuracy, neutrophils were exposed to the chemoattractants MIP-1α and fMLP and tracked by real-time videomicroscopy. Reactive oxygen species generation was measured by chemiluminescence. Neutrophil extracellular trap formation was assayed fluorometrically, and proinflammatory cytokine release was measured following overnight culture of neutrophils with relevant stimuli. Neutrophil serine protease deficiencies resulted in a reduced ability of neutrophils to chemotax efficiently and an inability to generate neutrophil extracellular traps. Neutrophil extracellular trap-bound proteins were also absent in Papillon-Lefévre syndrome, and Papillon-Lefévre syndrome neutrophils released higher levels of proinflammatory cytokines in unstimulated and stimulated conditions, and plasma cytokines were elevated. Notably, neutrophil chemoattractants MIP-1α and CXCL8 were elevated in Papillon-Lefévre syndrome neutrophils, as was reactive oxygen species formation. We propose that relentless recruitment and accumulation of hyperactive/reactive neutrophils (cytokines, reactive oxygen species) with increased tissue transit times into periodontal tissues, alongside a reduced antimicrobial capacity, create a locally destructive chronic inflammatory cycle in Papillon-Lefévre syndrome.

Lack of cathelicidin processing in Papillon-Lefèvre syndrome patients reveals essential role of LL-37 in periodontal homeostasis.

BACKGROUND: Loss-of-function point mutations in the cathepsin C gene are the underlying genetic event in patients with Papillon-Lefèvre syndrome (PLS). PLS neutrophils lack serine protease activity essential for cathelicidin LL-37 generation from hCAP18 precursor. AIM: We hypothesized that a local deficiency of LL-37 in the infected periodontium is mainly responsible for one of the clinical hallmark of PLS: severe periodontitis already in early childhood. METHODS: To confirm this effect, we compared the level of neutrophil-derived enzymes and antimicrobial peptides in gingival crevicular fluid (GCF) and saliva from PLS, aggressive and chronic periodontitis patients. RESULTS: Although neutrophil numbers in GCF were present at the same level in all periodontitis groups, LL-37 was totally absent in GCF from PLS patients despite the large amounts of its precursor, hCAP18. The absence of LL-37 in PLS patients coincided with the deficiency of both cathepsin C and protease 3 activities. The presence of other neutrophilic anti-microbial peptides in GCF from PLS patients, such as alpha-defensins, were comparable to that found in chronic periodontitis. In PLS microbial analysis revealed a high prevalence of Aggregatibacter actinomycetemcomitans infection. Most strains were susceptible to killing by LL-37. CONCLUSIONS: Collectively, these findings imply that the lack of protease 3 activation by dysfunctional cathepsin C in PLS patients leads to the deficit of antimicrobial and immunomodulatory functions of LL-37 in the gingiva, allowing for infection with A. actinomycetemcomitans and the development of severe periodontal disease.

Confirmation of oxidative stress and fatty acid disturbances in two further Papillon-Lefèvre syndrome families with identification of a new mutation.

BACKGROUND: We have previously reported oxidative and fatty acids disturbances in one Papillon-Lefèvre syndrome (PLS) family. This Mendelian condition characterized by palmar plantar keratosis and severe aggressive periodontitis, is caused by mutations in the cathepsin C (CTSC) gene. In this study, we have analysed two further unrelated PLS families to confirm this association. METHODS: Mutations were identified by direct sequencing of CTSC. Biochemical analyses were performed in probands and their relatives in order to determine plasma levels of vitamin E, CoQ10 , lipid hydroperoxides (HP) and fatty acid patterns. RESULTS: Pathogenic CTSC mutations were identified in both families including a new mutation (c504C>G). Both probands showed low levels of vitamin E and CoQ10 , and high levels of lipid HP, and also very low levels of docohexaenoic acid. CONCLUSIONS: The previously reported oxidative and fatty acids disturbances were confirmed as a feature of this condition in two further families. There are low levels of antioxidant markers and high levels of oxidative markers, in addition of low levels of some anti-inflammatory fatty acids in persons suffering PLS and some of their relatives.

Cytokines, matrix metalloproteinases and tissue inhibitor of metalloproteinases-1 in gingival crevicular fluid from patients with Papillon-Lefèvre syndrome.

The aim of the present study was to compare concentrations of cytokines, matrix metalloproteinases (MMPs) and a metalloproteinase inhibitor (TIMP-1) in gingival crevicular fluids (GCF) from sites with gingival inflammation in 28 young patients with Papillon-Lefèvre syndrome (PLS), and in age- and gender-matched controls. Each group consisted of 17 females and 11 males with a mean age of 11.0 years (range 4-22 years). In both groups, anterior upper sites with a clinical diagnosis of gingival inflammation and with pockets < or = 3 mm were selected for sampling of GCF, which was carried out with filter disks inserted into the gingival crevice until saturated. The concentrations of cytokines (IL-1alpha, IL-1beta, TNF-alpha, and IL-8), matrix metalloproteinases (MMP-1, MMP-3, MMP-8, and MMP-9), and their tissue inhibitor (TIMP-1) were analysed using commercial ELISA kits. Significantly higher levels of IL-1beta (P < 0.001) and MMP-8 (P < 0.05) were disclosed among the PLS patients compared with their controls, while the opposite was found for IL-8 (P < 0.05) and MMP-1 (P < 0.001). The individual variations were considerable in both groups. When comparing the expression of cytokines, MMPs, and TIMP-1 in PLS patients with clinically active and non-active periodontitis, the non-active PLS patients showed significantly higher values of IL-1beta than the patients with active periodontal disease (ANOVA, P < 0.01). In conclusion, this study was unable to demonstrate a clear-cut pathognomonic expression of cytokines or MMPs in patients with PLS, but further studies on cytokine and MMP output are warranted.

Lipid composition of outer stratum corneum in hereditary palmoplantar keratodermas.

BACKGROUND: The analysis of lipid composition of the outer stratum corneum is a promising approach to study the pathophysiology of inherited disorders of keratinization. OBJECTIVE: The purpose of the study was the search for biochemical alterations of stratum corneum lipids in hereditary palmoplantar keratoderma (PPK). METHODS: Using high-performance thin-layer chromatography, we performed an analysis of all major stratum corneum lipid classes in scales of 29 patients with 8 different types of hereditary PPK. RESULTS: In comparison to the controls, slight differences in the lipid pattern were found in all keratodermas. Reduced amounts of total ceramides and increased levels of free fatty acids were noted in nearly all types. CONCLUSIONS: The study indicates that the abnormal composition of stratum corneum lipids in PPK is probably not caused by genetic defects of the epidermal lipid metabolism, but it appears to represent an epiphenomenon of a disturbed cornification.

Structure of human dipeptidyl peptidase I (cathepsin C): exclusion domain added to an endopeptidase framework creates the machine for activation of granular serine proteases.

Dipeptidyl peptidase I (DPPI) or cathepsin C is the physiological activator of groups of serine proteases from immune and inflammatory cells vital for defense of an organism. The structure presented shows how an additional domain transforms the framework of a papain-like endopeptidase into a robust oligomeric protease-processing enzyme. The tetrahedral arrangement of the active sites exposed to solvent allows approach of proteins in their native state; the massive body of the exclusion domain fastened within the tetrahedral framework excludes approach of a polypeptide chain apart from its termini; and the carboxylic group of Asp1 positions the N-terminal amino group of the substrate. Based on a structural comparison and interactions within the active site cleft, it is suggested that the exclusion domain originates from a metallo-protease inhibitor. The location of missense mutations, characterized in people suffering from Haim-Munk and Papillon-Lefevre syndromes, suggests how they disrupt the fold and function of the enzyme.

Elevated hydroperoxide levels and antioxidant patterns in Papillon-Lefèvre syndrome.

BACKGROUND: Since it has been found that reactive oxygen species seem to be involved in the pathogenesis of both periodontitis and hyperkeratotic syndromes, we studied a group of patients belonging to 3 generations of a family with different degrees of severity of Papillon-Lefèvre syndrome (PLS) to ascertain whether altered concentrations of the most important hydrophobic and hydrophilic plasma antioxidants as well as products of oxidative damage are present in PLS. METHODS: Coenzyme Q (CoQ), vitamin E, glutathione (GSH), and uric acid were evaluated by high-performance liquid chromatography (HPLC) (supplied with electrochemical detector) techniques and hydroperoxides by a spectrophotometric method. RESULTS: GSH and uric acid were in the range of reference values; CoQ was very low in both the child of the third generation and his mother, and these 2 subjects had the highest hydroperoxide levels. The child also had extremely low values of vitamin E. In general, all family members showed abnormally high hydroperoxide levels, with the exception of those members who are phenotypically healthy. CONCLUSIONS: Since the subjects with the lowest hydroperoxide contents are phenotypically healthy, whereas the affected individuals presented lower antioxidant levels and very high hydroperoxide concentrations, it has been suggested that a specific antioxidant therapy could be a promising approach in treating some PLS subjects. Moreover, unexpected manifestations of heterozygosity in the child of the third generation were also detected.

Papillon-Lefèvre syndrome.

A patient, with Papillon-Lefèvre syndrome, presented with a premature loss of both deciduous and permanent teeth and hyperkeratosis palmaris et plantaris. Other abnormalities such as psoriasiform hyperkeratosis, calcification of the falx, and frequent infections can be seen. Although no etiologic factor is known for this aberration, an autosomal recessive inheritance is established. Treatment usually consists of dental hygiene only since dermatologic therapy is usually unrewarding. A new finding resulted when fibroblasts from involved gingiva were compared with either uninvolved gingiva or controlled gingiva. The protein and collagen synthesis of the involved tissue was about twice that of the latter two groups.