Development of a pathogenesis-based therapy for peeling skin syndrome type 1.

BACKGROUND: Peeling skin syndrome type 1 (PSS1) is a rare and severe autosomal recessive form of congenital ichthyosis. Patients are affected by pronounced erythroderma accompanied by pruritus and superficial generalized peeling of the skin. The disease is caused by nonsense mutations or complete deletion of the CDSN gene encoding for corneodesmosin (CDSN). PSS1 severely impairs quality of life and therapeutic approaches are totally unsatisfactory. OBJECTIVES: The objective of this study was to develop the first steps towards a specific protein replacement therapy for CDSN deficiency. Using this approach, we aimed to restore the lack of CDSN and improve cell-cell cohesion in the transition area of the stratum granulosum (SG) to the stratum corneum. METHODS: Human CDSN was recombinantly expressed in Escherichia coli. A liposome-based carrier system, prepared with a cationic lipopeptide to mediate the transport to the outer membrane of keratinocytes, was developed. This formulation was chosen for CDSN delivery into the skin. The liposomal carrier system was characterized with respect to size, stability and toxicity. Furthermore, the interaction with primary keratinocytes and human epidermal equivalents was investigated. RESULTS: The liposomes showed an accumulation at the membranes of keratinocytes. CDSN-deficient epidermal equivalents that were treated with liposomal encapsulated CDSN demonstrated presence of CDSN in the SG. Finally, the penetration assay and histological examinations revealed an improved epidermal integrity for CDSN-deficient epidermal equivalents, if they were treated with liposomal encapsulated CDSN. CONCLUSIONS: This study presents the first preclinical in vitro experiments for a future specific protein replacement therapy for patients affected by PSS1.

Refining the dermatological spectrum in primary immunodeficiency: mucosa-associated lymphoid tissue lymphoma translocation protein 1 deficiency mimicking Netherton/Omenn syndromes.

The proteinase mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1), which forms part of the caspase recruitment domain-containing protein 11-B-cell lymphoma 10-MALT1 signalosome complex, plays a direct role in nuclear factor kappa B activation. Here, we describe the case of a female infant with severe immune dysregulation leading to recurrent systemic infections, failure to thrive and severe crises of ichthyosiform erythroderma with high levels of serum IgE. Hence, initial symptoms indicated Netherton syndrome or Omenn syndrome. Surprisingly, sequence analyses of SPINK5 and RAG1/RAG2, respectively, excluded these diseases. During the hospital stay the patient's health deteriorated, despite intensive care therapy, and she died. In order to delineate the diagnosis, whole-exome sequencing was performed. Two compound heterozygous mutations in MALT1 were found and verified by Sanger sequencing (exon 2 c.245T>C, exon 2 c.310dup), which led to a MALT1 deficiency at the protein level. Based on these results, an immunological analysis was performed, as was immunofluorescence staining of key skin proteins, to confirm a diagnosis of MALT1 deficiency. This case report provides a closer description of the clinical and histological skin phenotype of MALT1 deficiency, and we conclude that MALT1 deficiency must be considered a possible differential diagnosis of Netherton and Omenn syndromes. What's already known about this topic? Mucosa-associated lymphoid tissue lymphoma translocation protein 1 (MALT1) deficiency is a combined immunodeficiency. MALT1 is part of the caspase recruitment domain-containing protein 11-B-cell lymphoma 10-MALT1 signalosome complex, which is essential for nuclear factor kappa B activation. Current publications describe a phenotype of recurrent systemic infections; only in a few cases has an inflammatory involvement of the integument been described. What does this study add? A closer description of the cutaneous phenotype of MALT1 deficiency in a patient with two novel MALT1 mutations. Immune mapping of follicular epidermis shows lympho-epithelial Kazal-type-related inhibitor is reduced in MALT1 deficiency and absent on interfollicular staining. Clinically, MALT1 deficiency mimics Netherton syndrome and Omenn syndrome, and should be considered a differential diagnosis.

LEKTI domains D6, D7 and D8+9 serve as substrates for transglutaminase 1: implications for targeted therapy of Netherton syndrome.

BACKGROUND: Transglutaminase (TG)1 plays a key role in the formation of the cornified envelope and thus in the maintenance of the epidermal barrier. Patients with Netherton syndrome (LEKTI deficiency) have increased activity of both TG1 and serin proteases. OBJECTIVES: To determine whether there is a functional biochemical link between TG1 and LEKTI and whether LEKTI domains could possibly serve as substrates for TG1. METHODS: We analysed the protein sequence of LEKTI for possible TG1 recognition sites using bioinformatics. Synthetic peptides and recombinant LEKTI domains D6, D7 and D8+9 were examined in vitro and in situ for possible substrate specificity. The recombinant LEKTI domains were studied for inhibitory activity in a kallikrein (KLK)5 activity test. RESULTS: We identified possible TG1 consensus sequences in LEKTI domains D6, D7 and D8+9, pointing to a novel biological link between these two proteins. Indeed, synthesized short peptides from these consensus sequences were incorporated into the TG1 activity zone of the epidermis. In vitro the entire recombinant domains of LEKTI showed substrate specificity for TG1, which was again confirmed in situ. The inhibitory activity of the recombinant LEKTI domains was confirmed by a KLK5 inhibition test. The strongest inhibition was observed for domains D8+9. CONCLUSIONS: There are specific domains of LEKTI that are recognized and processed by TG1. LEKTI domains D6, D7 and D8+9 contribute to the formation and protection of the cornified envelope. These results impact the development of protein replacement therapy approaches for Netherton syndrome. What's already known about this topic? LEKTI and transglutaminase (TG)1 are key proteins involved in the terminal differentiation of the epidermis. Lack of LEKTI causes Netherton syndrome; TG1 deficiency causes lamellar ichthyosis. The serine protease inhibitor LEKTI is processed into different functional units. Among different target proteases, kallikrein (KLK)5 appears to be a key player in disease pathology. It has been demonstrated that LEKTI domain 6 inhibits KLK5 and KLK7; LEKTI domains 8-11 also inhibit KLK14. What does this study add? The single LEKTI domains 6, 7 and the functional unit of domains 8 and 9 contain recognition motifs for TG1. We show that these domains and unit are crosslinked into the epidermis by TG1. Functional analyses of the recombinant LEKTI domains revealed that LEKTI D8+9 has the strongest inhibitory effect on KLK5. What is the translational message? The novel functional link between LEKTI and TG1 should be taken into account when considering the development of a targeted topical protein therapy for Netherton syndrome. The unit of domains D8+9 may be sufficient for this purpose.

Lu 25-109, a combined m1 agonist and m2 antagonist, modulates regulated processing of the amyloid precursor protein of Alzheimer's disease.

To examine the effects of the combined muscarinic ml-agonist/m2-antagonist Lu 25-109 on regulated processing of the amyloid protein precursor (APP), we used both transfected cells expressing human muscarinic m1 or m2 acetylcholine receptors, and fresh rat hippocampal slices. Lu 25-109 readily stimulated APPs secretion from HEK 293 cells overexpressing m1, but not m2, receptors, as well as from the hippocampal brain slices. Time-course analyses revealed a rapid (5-35 minutes), and a delayed (55-75 minutes) secretory response to Lu 25-109 with distinct concentration profiles suggesting two distinct cell biological mechanisms. Both responses appeared to reflect post-translational mechanisms because levels of APP message were unchanged after 60 minutes of stimulation with Lu 25-109. In comparison to carbachol, Lu 25-109 had a significantly lower intrinsic activity at muscarinic m1 receptors, compatible with a pharmacological profile as a partial agonist at recombinantly expressed m1 receptors. In as much as stimulation of APPs secretion is associated with reduced formation of A beta peptides, Lu 25-109 may be useful to reduce A beta generation, and thus, slow amyloid plaque formation. Moreover, Lu 25-109 may be useful in promoting the known neurotrophic and neuroprotective biological functions of secreted APPs.