Lower injection-site reactions and long-term safety, immunogenicity, and efficacy of etanercept biosimilar YLB113: Results from a post-hoc analysis of a double-blind, randomized, phase III comparative study and its open-label extension in patients with rheumatoid arthritis

AIM

YLB113 biosimilar was evaluated in an open-label extension single-arm study to assess long-term safety, efficacy, and immunogenicity in patients with rheumatoid arthritis (RA). We also report post-hoc results on the incidence of injection-site reactions (ISRs) and injection-site erythema (ISE) from a phase III study.

METHOD

Participants from the phase III, double-blind, randomized, 96 week equivalence study who completed the final visit received 50 mg YLB113 subcutaneously every 2 weeks. Key safety end points were assessed through adverse events (AEs), ISRs, ISE, and anti-drug antibody (ADA) incidence. The efficacy end point was change from baseline in Disease Activity Score 28-joint count (DAS28) over time.

RESULTS

Of 201 participants, 184 (91.5%) completed the study. Treatment-emergent AEs were experienced by 93.5% and severe AEs by 10.0% of participants. The discontinuation rate due to AEs was 2.0%. Overall, 20.0% of participants reported an incidence of ISRs throughout the open-label extension study. Two participants developed ADAs, and none developed neutralizing ADAs at any time after study drug administration. The overall DAS28 (mean ± SD) change was 2.22 ± 0.95 at the study transition, 2.10 ± 0.91 at week 72, and 2.06 ± 0.89 at the end of the study. In the post-hoc analysis, YLB113 showed a statistically significant lower incidence of ISRs (10 [3.8%], P < 0.0001) and ISE (5 [1.9%], P < 0.0001) compared with the reference product Enbrel®.

CONCLUSION

YLB113 demonstrated long-term safety and sustained efficacy for up to 96 weeks. Patients on YLB113 experienced significantly lower ISRs and ISE in a post-hoc analysis of the phase III study when compared with reference product.

POS0604 LONG TERM SAFETY AND TOLERABILITY WITH ETANERCEPT BIOSIMILAR (YLB113), RESULTS FROM A 2-YEAR OPEN LABEL EXTENSION STUDY (STUDY NO. YLB113-003)

Background:

Eligible subjects with moderate-to-severely active rheumatoid arthritis (RA) who completed a phase 3 double-blind comparative efficacy and safety study (Study No. YLB113-002; Yamanaka et al, 2019) of 50 mg etanercept biosimilar (YLB113) or etanercept reference product (RP) by subcutaneous administration with concomitant MTX treatment for 52 weeks, were enrolled in this open label extension (OLE) study (Study No. YLB113-003) to assess the long-term safety and tolerability of YLB113 through to 3 years.

Objectives:

This OLE study aimed to evaluate the long-term safety of YLB113 administration in subjects with RA who received RP or YLB113 in a phase 3 active comparator study. The main parameters assessed were safety and tolerability in terms of adverse events (AEs) and injection site reactions (ISRs), incidence of immunogenicity and efficacy as DAS28 improvement (disease activity score in 28 joints).

Methods:

Subjects received 50 mg of YLB113 subcutaneously once every 1 to 2 weeks. Safety was assessed by AEs after study drug administration, ISRs, physical examination findings, and immunogenicity. Efficacy (DAS28 score) was assessed at the time of transition to the OLE study (Week 0), and at weeks 12, 24, 48, 72, 96 and at the end of the study.

Results:

201 (Full analysis set [FAS]) subjects received the study drug and 184 subjects completed the study (91.5% completion rate). The average drug exposure in 94 subjects who continued to receive YLB113 and completed the study (94.0% completion rate) and 90 subjects who switched from RP to YLB113 and completed the study (89.1% completion rate) was 103 weeks providing the long-term drug exposure data of YLB113.

The CTCAE Grade of TEAEs and ADRs observed were Grade 2 or less in severity (with no Grade ≥3). The overall incidence of ISRs was 10.0% (20/201 subjects) 77 events. All the ISRs reported were Grade 1 except for one Grade 2.

An overview of the AEs experienced by the subjects is summarized in the Table 1.

Table 1.

Overview of Adverse events in OLE study

FASn (%)Number of eventsNumber of subjects201-Treatment emergent adverse events (TEAEs)188(93.5)975Adverse drug reactions (ADRs)82(40.8)221Serious adverse events (SAEs)21(10.4)27Serious adverse drug reactions (SADRs)7(3.5)7AEs leading to premature study discontinuation4(2.0)6ADRs leading to premature study discontinuation3(1.5)4SAEs leading to premature study discontinuation3(1.5)4SADRs leading to premature study discontinuation2(1.0)2

n - number of subjects with at least 1 AE in the category

The mean DAS28 (mean ± S.D.) of 2.22 ± 0.95 at the study transition was 2.10 ± 0.91 at Week 72 and 2.06 ± 0.89 at the end of the study. It was confirmed that DAS28 slightly decreased with time after the study transition and continued until the end of the study. The average DAS28 value remained low even with long-term administration of YLB113, suggesting that the effects of the study drug was sustained (Figure 1).

Figure 1.

DAS28 over time with YLB113 N: Number of subjects. * The administration period at the study completion differs for each subject, because the study transition time differs for each subject.

cts who tested positive for anti-drug antibodies (ADA) at least once in the OLE study were 1.0% (2/200 subjects). All ADA were transient and disappeared at study completion. Such transient ADA formation was reported in the phase 3 study as well. In the phase 3 study, ADA formation was more frequent in subjects who received RP at 24 weeks, but all subjects were negative in the OLE study after switching. Therefore, switching did not affect immunogenicity.

Conclusion:

The safety, efficacy and immunogenicity profile of YLB113 was maintained over the long-term through to 3 years. Switching from RP to YLB113 did not impact safety or immunogenicity.

References:

[1]Yamanaka H, Kamatani N, Tanaka Y, et al. A Comparative Study to Assess the Efficacy, Safety, and Immunogenicity of YLB113 and the Etanercept Reference Product for the Treatment of Patients with Rheumatoid Arthritis. Rheumatol Ther. 2020 Mar;7(1):149-163.

Disclosure of Interests:

Yamanaka Hisashi Speakers bureau: YL Biologics Ltd, Consultant of: YL Biologics Ltd, Yoshiya Tanaka Speakers bureau: Received speaking fees and/or honoraria from Daiichi-Sankyo, Eli Lilly, Novartis, YL Biologics, Bristol-Myers, Eisai, Chugai, Abbvie, Astellas, Pfizer, Sanofi, Asahi-kasei, GSK, Mitsubishi-Tanabe, Gilead, Janssen., Grant/research support from: Received research grants from Abbvie, Mitsubishi-Tanabe, Chugai, Asahi-Kasei, Eisai, Takeda, Daiichi-Sankyo., Toshihiko Hibino: None declared, Chirag Shah Shareholder of: Lupin LTD, Employee of: Lupin LTD, Dhananjay Bakhle Shareholder of: As part of Employee Stock Options Plan of Lupin LTD, Employee of: Lupin LTD, Dimitris Stefanidis Employee of: Sr. Director, Global Medical Affairs Lead, Immunology Biosimilars for Viatris GmbH

Trichohyalin-like 1 protein plays a crucial role in proliferation and anti-apoptosis of normal human keratinocytes and squamous cell carcinoma cells

Epidermal differentiation is a complex process that requires the regulated and sequential expression of various genes. Most fused-type S100 proteins are expressed in the granular layer and it is hypothesized that these proteins may be associated with cornification and barrier formation. We previously identified a member of the fused-type S100 proteins, Trichohyalin-like 1 (TCHHL1) protein. TCHHL1 is distributed in the basal layer of the normal epidermis. Furthermore, the expression is markedly increased in cancerous/non-cancerous skin samples with the hyperproliferation of keratinocytes. We herein examined the role of TCHHL1 in normal human keratinocytes (NHKs) and squamous cell carcinoma (SCC). The knockdown of TCHHL1 by transfection with TCHHL1 siRNA significantly inhibited proliferation and induced the early apoptosis of NHKs. In TCHHL1-knockdown NHKs, the level of extracellular signal-regulated kinase 1/2 (ERK1/2) phosphorylation was markedly decreased. In addition, the slight inhibition of v-akt murine thymoma viral oncogene homolog (AKT) phosphorylation and upregulation of forkhead box-containing protein O1(FOXO1), B-cell lymphoma2 (BCL2) and Bcl2-like protein 11 (BCL2L11) was observed. Skin-equivalent models built by TCHHL1-knockdown NHKs showed a markedly hypoplastic epidermis. These findings highlight that TCHHL1 plays an important role in homeostasis of the normal epidermis. TCHHL1 was expressed in the growing cells of cutaneous SCC; therefore, we next examined an association with the cell growth in HSC-1 cells (a human SCC line). In HSC-1 cells, the knockdown of TCHHL1 also suppressed cell proliferation and induced apoptosis. These cells showed an inhibition of phosphorylation of ERK1/2, AKT and signal transducers and activator of transcription 3, and the significant upregulation of FOXO1, BCL2, and BCL2L11. Accordingly, TCHHL1 is associated with survival of cutaneous SCC. In addition, we hypothesize that TCHHL1 may be a novel therapeutic target in cutaneous SCC.

A Comparative Study to Assess the Efficacy, Safety, and Immunogenicity of YLB113 and the Etanercept Reference Product for the Treatment of Patients with Rheumatoid Arthritis

Introduction

YLB113 is a biosimilar of the reference product (RP), etanercept, under development for treatment of patients with moderate-to-severe rheumatoid arthritis (RA) and other approved indications. A phase 3 study was conducted in Europe, Japan, and India to compare the efficacy, safety, and immunogenicity of YLB113 with the RP over a treatment period of 52 weeks.

Methods

Overall, 528 patients with moderate-to-severe RA receiving concomitant methotrexate were randomized to receive a once-weekly, subcutaneous dose of 50 mg YLB113 or the RP. The primary endpoint was ACR20 response rate at week 24, with similarity confirmed if the 95% confidence interval (CI) for YLB113 and the RP was within the range of − 15 to 15%. Safety and immunogenicity endpoints were assessed to week 52.

Results

Based on the European analysis, in the full analysis set, ACR20 response at week 24 was 83.3% and 88.5% for YLB113 and the RP, respectively. Responses were within the predefined clinical equivalence margin. The sensitivity analysis in the per protocol set revealed a similar proportion of subjects exhibiting ACR20 response at week 24 between groups, with a difference of − 5.1% (95% CI − 11.07 to 0.81). The incidence of treatment-emergent adverse events was comparable between groups, and the incidence of antidrug antibody development to week 24 favored YLB113 (0.8 vs. 8.3%).

Conclusions

This study demonstrated biosimilarity of YLB113 to the RP regarding efficacy, safety, and immunogenicity in patients with moderate-to-severe RA. Based on the same mechanism of action, biosimilarity could be extrapolated to other therapeutic indications approved for etanercept.

Trial registration

EudraCT Number: 2015-002,809-12.

Electronic Supplementary Material

The online version of this article (10.1007/s40744-019-00186-3) contains supplementary material, which is available to authorized users.

Determination of contrast medium dose for hepatic CT enhancement with improved body size dependency using a non-linear analysis based on pharmacokinetic principles

AIM

To propose a pharmacokinetic non-linear analysis method to determine contrast medium (CM) dose for computed tomography (CT) hepatic enhancement to improve body size dependency and validate the proposed CM dose determination method through a clinical study.

MATERIALS AND METHODS

Enhancement data of 105 patients who underwent hepatic dynamic CT with a fixed CM dose were analysed. From the analysis results, CM doses as a function of each of four body size indices (body weight [BW], lean body weight [LBW], blood volume [BV], and body surface area [BSA]) for achieving improved body size dependency were determined (proposed method), and the body size dependencies were simulated using the enhancement data from 105 patients. The proposed method was validated with a two-arm clinical study on BW. Body size dependency was evaluated using p-value of correlation coefficient between Body size indices and enhancements (p<0.05: significant dependency) and mean absolute error (MAE).

RESULTS

The simulation showed that significant body size dependencies not considered by the conventional method can be improved by the proposed method. MAEs of BW, LBW, and BV were also significantly reduced (p<0.05). The clinical study with BW demonstrated a similar improvement to that in the simulation result. MAE was also significantly reduced (p<0.001).

CONCLUSION

The proposed method demonstrated more improved BW, LBW, and BV dependence compared to the conventional method. Through the two-arm clinical study, the proposed method using BW only, without height information, is a suitable index for improving body size dependency.

P3718Identification of nine genes as novel susceptibility loci for early-onset ischemic stroke, intracerebral hemorrhage, or subarachnoid hemorrhage

Background

Given that substantial genetic components have been shown in ischemic stroke, intracerebral hemorrhage (ICH), and subarachnoid hemorrhage (SAH), a heritability may be higher in early-onset than late-onset individuals with these conditions. Although genome-wide association studies have identified various genes and loci significantly associated with ischemic stroke, ICH, or intracranial aneurysm mainly in European ancestry populations, genetic variants that contribute to susceptibility to these disorders in Japanese individuals remain to be identified definitively.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to ischemic stroke, ICH, or SAH in Japanese. We have now performed exome-wide association studies (EWASs) in early-onset subjects with these conditions and corresponding controls.

Methods

A total of 6649 individuals aged ≤65 years were examined. For the EWAS of ischemic or hemorrhagic stroke, 6224 individuals (450 subjects with ischemic stroke, 5774 controls) or 6179 individuals (261 subjects with ICH, 176 subjects with SAH, 5742 controls), respectively, were examined. EWASs were performed with the use of Illumina Human Exome-12 v1.2 DNA Analysis BeadChip or Infinium Exome-24 v1.0 BeadChip. To compensate for multiple comparisons of allele frequencies with ischemic stroke, ICH, or SAH, we applied a false discovery rate (FDR) of <0.05 for statistical significance of association.

Results

The relation of allele frequencies of 31,245 single nucleotide polymorphisms (SNPs) that passed quality control to ischemic stroke was examined with Fisher's exact test, and 31 SNPs were significantly (FDR <0.05) associated with ischemic stroke. The relation of allele frequencies of 31,253 or 30,970 SNPs to ICH or SAH, respectively, was examined with Fisher's exact test, and six or two SNPs were significantly (FDR <0.05) associated with ICH or SAH, respectively. Multivariable logistic regression analysis with adjustment for age, sex, and the prevalence of hypertension and diabetes mellitus revealed that 12 SNPs were significantly [P <0.0004 (Bonferroni's correction, 0.05/124)] related to ischemic stroke. Similar analysis with adjustment for age, sex, and the prevalence of hypertension revealed that six or two SNPs were significantly [P <0.0016 (0.05/32)] related to ICH or SAH, respectively. After examination of linkage disequilibrium of identified SNPs and results of previous genome-wide association studies, we have newly identified HHIPL2, CTNNA3, LOC643770, UTP20, and TRIB3 as susceptibility loci for ischemic stroke, DNTTIP2 and FAM205A as susceptibility loci for ICH, and FAM160A1 and OR52E4 as such loci for SAH.

Conclusion

We have thus newly identified nine genes that confer susceptibility to early-onset ischemic stroke, ICH, or SAH. Determination of genotypes for the SNPs in these genes may prove informative for assessment of the genetic risk for ischemic stroke, ICH, or SAH in Japanese.

P4470Identification of four genes as novel susceptibility loci for early-onset type 2 diabetes mellitus, metabolic syndrome, or hyperuricemia in Japanese

Background

Given that early-onset type 2 diabetes mellitus (T2DM), metabolic syndrome, and hyperuricemia have been shown to have strong genetic components, statistical power of a genetic association study may be increased by focusing on early-onset subjects with these conditions. Although genome-wide association studies have identified various genes and loci significantly associated with T2DM, metabolic syndrome, and hyperuricemia, genetic variants that contribute to predisposition to these conditions in Japanese individuals remain to be identified definitively.

Purpose

The purpose of the study was to identify genetic variants that confer susceptibility to early-onset T2DM, metabolic syndrome, or hyperuricemia in Japanese. We have now performed exome-wide association studies (EWASs) for early-onset subjects with T2DM, metabolic syndrome, or hyperuricemia and corresponding controls.

Methods

A total of 8102 individuals aged ≤65 years was enrolled in the study. The EWAS for T2DM was performed with 7407 subjects (1696 cases, 5711 controls), that for metabolic syndrome with 4215 subjects (2296 cases, 1919 controls), and that for hyperuricemia with 7919 subjects (1365 cases, 6554 controls). Single nucleotide polymorphisms (SNPs) were genotyped with Illumina Human Exome-12 DNA Analysis BeadChip or Infinium Exome-24 BeadChip arrays. The relation of allele frequencies for 31,210, 31,521, or 31,142 SNPs that passed quality control to T2DM, metabolic syndrome, or hyperuricemia, respectively, was examined with Fisher's exact test. To compensate for multiple comparisons of genotypes with T2DM, metabolic syndrome, or hyperuricemia, we applied Bonferroni's correction for statistical significance of association.

Results

The EWAS of allele frequencies revealed that four, six, or nine SNPs were significantly associated with T2DM (P<1.60 × 10–6), metabolic syndrome (P<1.59 × 10–6), or hyperuricemia (P<1.61 × 10–6), respectively. Multivariable logistic regression analysis with adjustment for age and sex revealed that three, six, or nine SNPs were significantly related to T2DM (P<0.0031), metabolic syndrome (P<0.0021), or hyperuricemia (P<0.0014). After examination of the association of identified SNPs to T2DM-, metabolic syndrome-, or hyperuricemia-related traits, linkage disequilibrium of the SNPs, and results of previous genome-wide association studies, we have newly identified ZNF860 and OR4F6 as susceptibility loci for T2DM, OR52E4 and OR4F6 for metabolic syndrome, and HERPUD2 for hyperuricemia.

Conclusion

Given that OR4F6 was significantly associated with both T2DM and metabolic syndrome, we thus newly identified four genes (ZNF860, OR4F6, OR52E4, HERPUD2) that confer susceptibility to early-onset T2DM, metabolic syndrome, or hyperuricemia. Determination of genotypes for the SNPs in these genes may prove informative for assessment of the genetic risk for T2DM, metabolic syndrome, or hyperuricemia in Japanese.

Melanoma cell adhesion molecule is the driving force behind the dissemination of melanoma upon S100A8/A9 binding in the original skin lesion

Since metastasis accounts for the majority of cancer-associated deaths, studies on the mechanisms of metastasis are needed to establish innovative strategies for cancer treatment. We previously reported that melanoma cell adhesion molecule (MCAM) functions as a critical receptor for S100A8/A9, and binding of S100A8/A9 to MCAM results in the migration of melanoma cells to lung tissue. However, the critical role of MCAM in the original melanoma skin lesion is still not clear. In this study, we aimed to determine the importance of the S100A8/A9-MCAM axis in melanoma dissemination in a skin lesion as a critical early step for metastasis. Mechanistic studies revealed the downstream signaling of MCAM that signaled the induction of metastasis. S100A8/A9-MCAM binding activates mitogen-activated protein kinase kinase kinase 8 (MAP3K8), also termed TPL2, leading to strong activation of the transcription factor ETV4 and subsequent induction of matrix metalloproteinase-25 (MMP25), and finally to induction of melanoma lung tropic metastasis. Collectively, our results demonstrate a crucial role of the S100A8/A9-MCAM signaling axis in metastatic onset of melanoma cells and indicate that strategies targeting the identified pathway may be useful for the establishment of innovative anti-cancer therapies.

Critical role of the MCAM-ETV4 axis triggered by extracellular S100A8/A9 in breast cancer aggressiveness

Metastatic breast cancer is the leading cause of cancer-associated death in women. The progression of this fatal disease is associated with inflammatory responses that promote cancer cell growth and dissemination, eventually leading to a reduction of overall survival. However, the mechanism(s) of the inflammation-boosted cancer progression remains unclear. In this study, we found for the first time that an extracellular cytokine, S100A8/A9, accelerates breast cancer growth and metastasis upon binding to a cell surface receptor, melanoma cell adhesion molecule (MCAM). Our molecular analyses revealed an important role of ETS translocation variant 4 (ETV4), which is significantly activated in the region downstream of MCAM upon S100A8/A9 stimulation, in breast cancer progression in vitro as well as in vivo. The MCAM-mediated activation of ETV4 induced a mobile phenotype called epithelial-mesenchymal transition (EMT) in cells, since we found that ETV4 transcriptionally upregulates ZEB1, a strong EMT inducer, at a very high level. In contrast, downregulation of either MCAM or ETV4 repressed EMT, resulting in greatly weakened tumor growth and lung metastasis. Overall, our results revealed that ETV4 is a novel transcription factor regulated by the S100A8/A9-MCAM axis, which leads to EMT through ZEB1 and thereby to metastasis in breast cancer cells. Thus, therapeutic strategies based on our findings might improve patient outcomes.

Neuroplastin-β mediates S100A8/A9-induced lung cancer disseminative progression

Compiling evidence indicates an unusual role of extracellular S100A8/A9 in cancer metastasis. S100A8/A9 secreted from either cancer cells or normal cells including epithelial and inflammatory cells stimulates cancer cells through S100A8/A9 sensor receptors in an autocrine or paracrine manner, leading to cancer cell metastatic progression. We previously reported a novel S100A8/A9 receptor, neuroplastin-β (NPTNβ), which plays a critical role in atopic dermatitis when it is highly activated in keratinocytes by an excess amount of extracellular S100A8/A9 in the inflammatory skin lesion. Interestingly, our expression profiling of NPTNβ showed significantly high expression levels in lung cancer cell lines in a consistent manner. We hence aimed to determine the significance of NPTNβ as an S100A8/A9 receptor in lung cancer. Our results showed that NPTNβ has strong ability to induce cancer-related cellular events, including anchorage-independent growth, motility and invasiveness, in lung cancer cells in response to extracellular S100A8/A9, eventually leading to the expression of a cancer disseminative phenotype in lung tissue in vivo. Mechanistic investigation revealed that binding of S100A8/A9 to NPTNβ mediates activation of NFIA and NFIB and following SPDEF transcription factors through orchestrated upstream signals from TRAF2 and RAS, which is linked to anchorage-independent growth, motility and invasiveness. Overall, our results indicate the importance of the S100A8/A9-NPTNβ axis in lung cancer disseminative progression and reveal a pivotal role of its newly identified downstream signaling, TRAF2/RAS-NFIA/NFIB-SPDEF, in linking to the aggressive development of lung cancers.

Newly developed anti-S100A8/A9 monoclonal antibody efficiently prevents lung tropic cancer metastasis

The metastatic dissemination of cancer cells to remote areas of the body is the most problematic aspect in cancer patients. Among cancers, melanomas are notoriously difficult to treat due to their significantly high metastatic potential even during early stages. Hence, the establishment of advanced therapeutic approaches to regulate metastasis is required to overcome the melanoma disease. An accumulating mass of evidence has indicated a critical role of extracellular S100A8/A9 in melanoma distant metastasis. Lung S100A8/A9 is induced by melanoma cells from distant organs and it attracts these cells to its enriched lung environment since melanoma cells possess several receptors that sense the S100A8/A9 ligand. We hence aimed to develop a neutralizing antibody against S100A8/A9 that would efficiently block melanoma lung metastasis. Our protocol provided us with one prominent antibody, Ab45 that efficiently suppressed not only S100A8/A9-mediated melanoma mobility but also lung tropic melanoma metastasis in a mouse model. This prompted us to make chimeric Ab45, a chimera antibody consisting of mouse Ab45-Fab and human IgG2-Fc. Chimeric Ab45 also showed significant inhibition of the lung metastasis of melanoma. From these results, we have high hopes that the newly produced antibody will become a potential biological tool to block melanoma metastasis in future clinical settings.

exSSSRs (extracellular S100 soil sensor receptors)-Fc fusion proteins work as prominent decoys to S100A8/A9-induced lung tropic cancer metastasis

Within the "seed and soil" theory of organ tropic cancer metastasis is a growing compilation of evidence that S100A8/A9 functions as a soil signal that attracts cancer cells to certain organs, which prove beneficial to their growth. S100A8/A9-sensing receptors including Toll-like receptor 4 (TLR4), advanced glycation end products (RAGE), and also important receptors we recently succeeded in identifying (EMMPRIN, NPTNβ, MCAM, and ALCAM) have the potential to become promising therapeutic targets. In our study, we prepared extracellular regions of these novel molecules and fused them to human IgG2-Fc to extend half-life expectancy, and we evaluated the anti-metastatic effects of the purified decoy proteins on metastatic cancer cells. The purified proteins markedly suppressed S100A8/A9-mediated lung tropic cancer metastasis. We hence expect that our novel biologics may become a prominent medicine to prevent cancer metastasis in clinical settings through cutting the linkage between "seed and soil".

Marked Changes in Lamellar Granule and Trans-Golgi Network Structure Occur during Epidermal Keratinocyte Differentiation

Epidermal lamellar granules transport various lipids, proteins, and protein inhibitors from the trans-Golgi network to the extracellular space, and play an important role in skin barrier formation. We elucidated the 3-dimensional structure of lamellar granules and the trans-Golgi network in normal human skin by focused ion beam scanning electron microscopy. Reconstructed focused ion beam scanning electron microscopy 3-dimensional images revealed that the overall lamellar granule structure changed from vesicular to reticular within the second layer of the stratum granulosum. Furthermore, the trans-Golgi network was well developed within this layer and spread through the cytoplasm with branched, tubular structures that connected to lamellar granules. Our study reveals the unique overall 3-dimensional structure of lamellar granules and the trans-Golgi network within the cells of the epidermis, and provides the basis for an understanding of the skin barrier formation.

Plasminogen Activator and Plasminogen Activator Inhibitor Associated with Granulomatous Inflammation: A Study with Murine Leprosy

Plasminogen activator that is associated with the development of hypersensitivity granulomas (gPA) was partially purified from a saline soluble fraction of murine lepromas elicited in “resistant” mice, C57BL/6N. The gPA was shown to consist of two subspecies (23,000 and 48,000 in molecular weight) with essentially identical enzymologic properties. The gPA was found to be a relatively heat stable weakly alkaline serine proteinase with trypsin-like characteristics in the specificity for synthetic substrates and proteinase inhibitors. It showed a high affinity for H- D-Ile-Pro-Arg-pNA (Km = 1.4 × 10-4 M) H-D-Val-Leu-Lys- pNA (Km = 5.2 × 10-4 M), and L-pyroGlu-Gly-Arg-pNA (Km = 9.3 × 10-4 M). The gPA did not demonstrate antigenic cross reaction with urokinase-type or tissue-type plasminogen activator.

Two distinct enzymatic regulators of the gPA were also demonstrated in the saline soluble fraction of the hypersensitivity granulomas. The gPA and its regulation are assumed to be correlated with macrophage activation in the hypersensitivity granulomas

Inhibitory effects of mycosporine-2-glycine isolated from a halotolerant cyanobacterium on protein glycation and collagenase activity

Mycosporine-2-glycine (M2G), isolated from the halotolerant cyanobacterium Aphanothece halophytica, was purified and characterized in order to determine its utility as a cosmetic and pharmaceutical ingredient. M2G efficiently inhibited protein crosslinking. The inhibitory activity of M2G was significantly greater than that of the well-known Maillard reaction inhibitor aminoguanidine. In addition, M2G and other known mycosporine-like amino acids inhibited bacterial collagenase activity. To the best of our knowledge, this is the first report describing that M2G specifically inhibits the formation of advanced glycation end-products (AGEs), which play a critical role in ageing process and age-related diseases. These observations indicate that M2G may have potential therapeutic applications by suppressing the formation of AGEs and inhibiting excess collagenase activity.

SIGNIFICANCE AND IMPACT OF THE STUDY

Mycosporine-like amino acids (MAAs) are known as multifunctional natural compounds. The MAA mycosporine-2-glycine (M2G), isolated from the halotolerant cyanobacterium Aphanothece halophytica, has potential therapeutic applications for the prevention of skin ageing. Purified M2G was endotoxin-free. M2G had greater inhibitory activity of protein cross-linking compared with well-known inhibitor, aminoguanidine and hindered bacterial collagenase activity. The mechanisms for these inhibitory activities of M2G are discussed in this study.

Key component of inflammasome, NLRC4, was identified in the lesional epidermis of psoriatic patients

Inflammasomes are multimolecular complexes that control the inflammatory response. The function of inflammasomes in the pathogenesis of psoriasis is still unclear. To clarify the relationship between inflammasomes and the pathophysiology of psoriasis, and in particular, to identify molecules interacting with caspase-1, a crucial component of inflammasomes, scale extracts obtained from patients with psoriasis were immunoprecipitated with anti-caspase-1 antibody and analyzed by liquid chromatography coupled with electrospray tandem mass spectrometry (LC-MS/MS). The expression of the inflammasome component was assessed by immunohistochemical analysis and an in vitro assay. We identified several candidates for caspase-1-interacting proteins from the psoriatic scale extracts by immunoprecipitation and LC-MS/MS. Nucleotide-binding oligomerization domain-containing protein-like receptor family CARD domain-containing protein 4 (NLRC4) was the only inflammasome component among the candidates; thus, the protein is considered to be a key factor of inflammasomes in psoriasis. No inflammasome component was found in the extracts of atopic dermatitis or normal skin by LC-MS/MS. Immunohistochemical analysis demonstrated upregulation of NLRC4 in the lesional epidermis of some psoriatic patients whereas weak expression of NLRC4 was detected in the normal and non-lesional epidermis. The mRNA expression of the NLRC4 gene increased in keratinocytes at confluency, 48 h after air exposure and after the addition of 1.5 mmol/L calcium chloride. Our findings suggest that NLRC4 may be involved in the exacerbation or modification of psoriatic lesions.

Endothelin-1 Elicits TRP-Mediated Pain in an Acid-Induced Oral Ulcer Model

Oral ulcer is the most common oral disease and leads to pain during meals and speaking, reducing the quality of life of patients. Recent evidence using animal models suggests that oral ulcers induce cyclooxygenase-dependent spontaneous pain and cyclooxygenase-independent mechanical allodynia. Endothelin-1 is upregulated in oral mucosal inflammation, although it has not been shown to induce pain in oral ulcers. In the present study, we investigated the involvement of endothelin-1 signaling with oral ulcer-induced pain using our proprietary assay system in conscious rats. Endothelin-1 was significantly upregulated in oral ulcers experimentally induced by topical acetic acid treatment, while endothelin-1 production was suppressed by antibacterial pretreatment. Spontaneous nociceptive behavior in oral ulcer model rats was inhibited by swab applications of BQ-788 (ET_B receptor antagonist), ONO-8711 (prostanoid receptor EP₁ antagonist), and HC-030031 (TRPA1 antagonist). Prostaglandin E₂ production in the ulcers was suppressed by BQ-788. Mechanical allodynia in the model was inhibited not only by BQ-788 and HC-030031 but also by BQ-123 (ET_A receptor antagonist), SB-366791 (TRPV1 antagonist), and RN-1734 (TRPV4 antagonist). In naive rats, submucosal injection of endothelin-1 caused mechanical allodynia that was sensitive to HC-030031 and SB-366791 but not to RN-1734. These results suggest that endothelin-1 production following oral bacterial invasion via ulcerative regions elicits TRPA1-mediated spontaneous pain. This pain likely occurs through an indirect route that involves ET_B receptor-accelerated prostanoid production. Endothelin-1 elicits directly TRPA1- and TRPV1-mediated mechanical allodynia via both ET_A and ET_B receptors on nociceptive fibers. The TRPV4-mediated allodynia component seems to be independent of endothelin signaling. These findings highlight the potential of endothelin signaling blockers as effective analgesic approaches for oral ulcer patients.

β-1,3-Galactosyl-O-Glycosyl-Glycoprotein β-1,6-N-Acetylglucosaminyltransferase 3 Increases MCAM Stability, Which Enhances S100A8/A9-Mediated Cancer Motility

We previously identified novel S100A8/A9 receptors, extracellular matrix metalloproteinase inducer (EMMPRIN), melanoma cell adhesion molecule (MCAM), activated leukocyte cell adhesion molecule (ALCAM), and neuroplastin (NPTN) β, that are critically involved in S100A8/A9-mediated cancer metastasis and inflammation when expressed at high levels. However, little is known about the presence of any cancer-specific mechanism(s) that modifies these receptors, further inducing upregulation at protein levels without any transcriptional regulation. Expression levels of glycosyltransferase-encoding genes were examined by a PCR-based profiling array followed by confirmation with quantitative real-time PCR. Cell migration and invasion were assessed using a Boyden chamber. Western blotting was used to examine the protein level, and the RNA level was examined by Northern blotting. Immunohistochemistry was used to examine the expression pattern of β-1,3-galactosyl-O-glycosyl-glycoprotein β-1,6-N-acetylglucosaminyltransferase 3 (GCNT3) and MCAM in melanoma tissue. We found that GCNT3 is overexpressed in highly metastatic melanomas. Silencing and functional inhibition of GCNT3 greatly suppressed migration and invasion of melanoma cells, resulting in the loss of S100A8/A9 responsiveness. Among the novel S100A8/A9 receptors, GCNT3 favorably glycosylates the MCAM receptor, extending its half-life and leading to further elevation of S100A8/A9-mediated cellular motility in melanoma cells. GCNT3 expression is positively correlated to MCAM expression in patients with high-grade melanomas. Collectively, our results showed that GCNT3 is an upstream regulator of MCAM protein and indicate the possibility of a potential molecular target in melanoma therapeutics through abrogation of the S100A8/A9-MCAM axis.

MCAM, as a novel receptor for S100A8/A9, mediates progression of malignant melanoma through prominent activation of NF-κB and ROS formation upon ligand binding

The dynamic interaction between tumor cells and their microenvironment induces a proinflammatory milieu that drives cancer development and progression. The S100A8/A9 complex has been implicated in chronic inflammation, tumor development, and progression. The cancer microenvironment contributes to the up-regulation of this protein complex in many invasive tumors, which is associated with the formation of pre-metastatic niches and poor prognosis. Changing adhesive preference of cancer cells is at the core of the metastatic process that governs the reciprocal interactions of cancer cells with the extracellular matrices and neighboring stromal cells. Cell adhesion molecules (CAMs) have been confirmed to have high-level expression in various highly invasive tumors. The expression and function of CAMs are profoundly influenced by the extracellular milieu. S100A8/A9 mediates its effects by binding to cell surface receptors, such as heparan sulfate, TLR4 and RAGE on immune and tumor cells. RAGE has recently been identified as an adhesion molecule and has considerably high identity and similarity to ALCAM and MCAM, which are frequently over-expressed on metastatic malignant melanoma cells. In this study, we demonstrated that ALCAM and MCAM also function as S100A8/A9 receptors as does RAGE and induce malignant melanoma progression by NF-κB activation and ROS formation. Notably, MCAM not only activated NF-κB more prominently than ALCAM and RAGE did but also mediated intracellular signaling for the formation of lung metastasis. MCAM is known to be involved in malignant melanoma development and progression through several mechanisms. Therefore, MCAM is a potential effective target in malignant melanoma treatment.

Caspase-14 protocols

Unlike other caspase family members, caspase-14 shows restricted expression, being found mostly in epidermis and its appendages. It has been suggested that caspase-14 is not involved in apoptosis or inflammation, but participates in keratinocyte terminal differentiation. Its activation occurs at the corneocyte formation. In previous work, we have purified active caspase-14 from human corneocyte extracts. In addition, we have clarified activation mechanism of caspase-14, where kallikrein-related peptidase 7 (KLK7) generates an intermediate form from procaspase-14 and this form finally converts procaspase-14 to active, mature caspase-14. Here we describe techniques for measurement of caspase-14 activity using synthetic substrate, purification of caspase-14 from corneocyte extract, preparation of constitutively active caspase-14 and specific antibody, quantification of total and active caspase-14 in corneocyte extracts using ELISA, as well as methods for caspase-14 activation and its visualization by immunohistochemistry.

DNAX-activating protein 10 (DAP10) membrane adaptor associates with receptor for advanced glycation end products (RAGE) and modulates the RAGE-triggered signaling pathway in human keratinocytes

The receptor for advanced glycation end products (RAGE) is involved in the pathogenesis of many inflammatory, degenerative, and hyperproliferative diseases, including cancer. Previously, we revealed mechanisms of downstream signaling from ligand-activated RAGE, which recruits TIRAP/MyD88. Here, we showed that DNAX-activating protein 10 (DAP10), a transmembrane adaptor protein, also binds to RAGE. By artificial oligomerization of RAGE alone or RAGE-DAP10, we found that RAGE-DAP10 heterodimer formation resulted in a marked enhancement of Akt activation, whereas homomultimeric interaction of RAGE led to activation of caspase 8. Normal human epidermal keratinocytes exposed to S100A8/A9, a ligand for RAGE, at a nanomolar concentration mimicked the pro-survival response of RAGE-DAP10 interaction, although at a micromolar concentration, the cells mimicked the pro-apoptotic response of RAGE-RAGE. In transformed epithelial cell lines, A431 and HaCaT, in which endogenous DAP10 was overexpressed, and S100A8/A9, even at a micromolar concentration, led to cell growth and survival due to RAGE-DAP10 interaction. Functional blocking of DAP10 in the cell lines abrogated the Akt phosphorylation from S100A8/A9-activated RAGE, eventually leading to an increase in apoptosis. Finally, S100A8/A9, RAGE, and DAP10 were overexpressed in the psoriatic epidermis. Our findings indicate that the functional interaction between RAGE and DAP10 coordinately regulates S100A8/A9-mediated survival and/or apoptotic response of keratinocytes.

Mesotrypsin and caspase-14 participate in prosaposin processing: potential relevance to epidermal permeability barrier formation

A proteomics-based search for molecules interacting with caspase-14 identified prosaposin and epidermal mesotrypsin as candidates. Prosaposin is a precursor of four sphingolipid activator proteins (saposins A-D) that are essential for lysosomal hydrolysis of sphingolipids. Thus, we hypothesized that caspase-14 and mesotrypsin participate in processing of prosaposin. Because we identified a saposin A sequence as an interactor with these proteases, we prepared a specific antibody to saposin A and focused on saposin A-related physiological reactions. We found that mesotrypsin generated saposins A-D from prosaposin, and mature caspase-14 contributed to this process by activating mesotrypsinogen to mesotrypsin. Knockdown of these proteases markedly down-regulated saposin A synthesis in skin equivalent models. Saposin A was localized in granular cells, whereas prosaposin was present in the upper layer of human epidermis. The proximity ligation assay confirmed interaction between prosaposin, caspase-14, and mesotrypsin in the granular layer. Oil Red staining showed that the lipid envelope was significantly reduced in the cornified layer of skin from saposin A-deficient mice. Ultrastructural studies revealed severely disorganized cornified layer structure in both prosaposin- and saposin A-deficient mice. Overall, our results indicate that epidermal mesotrypsin and caspase-14 work cooperatively in prosaposin processing. We propose that they thereby contribute to permeability barrier formation in vivo.

Keratinocyte-specific mesotrypsin contributes to the desquamation process via kallikrein activation and LEKTI degradation

Kallikrein-related peptidases (KLKs) have critical roles in corneocyte desquamation and are regulated by lymphoepithelial Kazal-type inhibitor (LEKTI). However, it is unclear how these proteases are activated and how activated KLKs are released from LEKTI in the upper cornified layer. Recently, we reported cloning of a PRSS3 gene product, keratinocyte-specific mesotrypsin, from a cDNA library. We hypothesized that mesotrypsin is involved in the desquamation process, and the aim of the present study was to test this idea by examining the effects of mesotrypsin on representative desquamation-related enzymes pro-KLK5 and pro-KLK7. Incubation of mesotrypsin and these zymogens resulted in generation of the active forms. KLK activities were effectively inhibited by recombinant LEKTI domains D2, D2-5, D2-6, D2-7, D5, D6, D6-9, D7, D7-9, and D10-15, whereas mesotrypsin activity was not susceptible to these domains, and in fact degraded them. Immunoelectron microscopy demonstrated that mesotrypsin was localized in the cytoplasm of granular cells and intercellular spaces of the cornified layer. Proximity ligation assay showed close association between mesotrypsin and KLKs in the granular to cornified layers. Age-dependency analysis revealed that mesotrypsin was markedly downregulated in corneocyte extract from donors in their sixties, compared with younger donors. Collectively, our findings suggest that mesotrypsin contributes to the desquamation process by activating KLKs and degrading the intrinsic KLKs' inhibitor LEKTI.

Kallikrein-related peptidase 5 functions in proteolytic processing of profilaggrin in cultured human keratinocytes

Filaggrin protein is synthesized in the stratum granulosum of the skin and contributes to the formation of the human skin barrier. Profilaggrin is cleaved by proteolytic enzymes and converted to functional filaggrin, but its processing mechanism remains not fully elucidated. Kallikrein-related peptidase 5 (KLK5) is a major serine protease found in the skin, which is secreted from lamellar granules following its expression in the stratum granulosum and activated in the extracellular space of the stratum corneum. Here, we searched for profilaggrin-processing protease(s) by partial purification of epidermal extracts and found KLK5 as a possible candidate. We used high performance liquid chromatography coupled with electrospray tandem mass spectrometry to show that KLK5 cleaves profilaggrin. Furthermore, based on a proximity ligation assay, immunohistochemistry, and immunoelectron microscopy analysis, we reveal that KLK5 and profilaggrin co-localize in the stratum granulosum in human epidermis. KLK5 knockdown in normal cultured human epidermal keratinocytes resulted in higher levels of profilaggrin, indicating that KLK5 potentially functions in profilaggrin cleavage.

Protease activity enhances production of thymic stromal lymphopoietin and basophil accumulation in flaky tail mice

Epidermal barrier abnormality due to filaggrin deficiency is an important predisposing factor in the development of atopic dermatitis (AD). In addition, the expression of thymic stromal lymphopoietin (TSLP) in keratinocytes (KCs), induced by barrier disruption, can promote type 2 helper T-cell polarization. Protease activity, including protease-activated receptor-2 (PAR-2), is also known to be involved in epidermal barrier function in AD. However, to our knowledge, the relationship between protease activity and filaggrin deficiency from the perspective of AD has not been elucidated. Flaky tail (Flg(ft)) mice, known to have a mutation in the filaggrin gene, were used to assess the role of protease in KCs in the steady state and the mite-induced AD-like skin inflammation model. In the steady state, the expression and activity levels of endogenous proteases, kallikreins 5, 7, and 14, in the skin and TSLP were higher in Flg(ft) than in control mice. In addition, activation of PAR-2 by its agonist induced the production of TSLP in KCs of Flg(ft) mice, which was abrogated by a newly developed PAR-2 antagonist. Application of the PAR-2 antagonist improved symptoms and basophil accumulation in Flg(ft) mice treated with mite extracts. These results suggest that possibly through the PAR-2 activation in KCs, filaggrin deficiency induces TSLP production and basophil accumulation, which play important roles in the establishment of AD.

DOCK7 is a critical regulator of the RAGE-Cdc42 signaling axis that induces formation of dendritic pseudopodia in human cancer cells

Cellular migration is a fundamental process linked to cancer metastasis. Growing evidence indicates that the receptor for advanced glycation end products (RAGE) plays a pivotal role in this process. With regard to downstream signal transducers of RAGE, diaphanous-1 and activated small guanine nucleotide triphosphatases, Rac1 and Cdc42, have been identified. To obtain precise insight into the direct downstream signaling mechanism of RAGE, we screened for proteins interacting with the cytoplasmic domain of RAGE employing an immunoprecipitation-liquid chromatography coupled with an electrospray tandem mass spectrometry system. In the present study, we found that the cytoplasmic domain of RAGE interacted with an atypical DOCK180-related guanine nucleotide exchange factor, dedicator of cytokinesis protein 7 (DOCK7). DOCK7 bound to the RAGE cytoplasmic domain and transduced a signal to Cdc42, resulting in the formation of abundant highly branched filopodia-like protrusions, dendritic pseudopodia. Blocking of the function of DOCK7 greatly abrogated the formation of dendritic pseudopodia and suppressed cellular migration. These results indicate that DOCK7 functions as an essential and downstream regulator of RAGE-mediated cellular migration through the formation of dendritic pseudopodia.

Separation of ion components produced by plasma-assisted catalytic ionization

Positive and negative hydrogen ions are produced by plasma-assisted catalytic ionization using a porous nickel plate, where the irradiation current density and energy of positive ions produced by discharge to the porous plate are controlled. The ion energy distributions are analyzed from the properties of current densities of positive and negative ions extracted from the porous surface. Positive ions passing through fine pores of the porous plate and positive and negative ions produced on the porous surface are observed. It is clarified that the produced fluxes of positive and negative ions and the flux balance between them are controlled by the irradiation current density and energy, respectively.

Kallikrein-related peptidase-7 regulates caspase-14 maturation during keratinocyte terminal differentiation by generating an intermediate form

The maturation and activation mechanisms of caspases are generally well understood, except for those of caspase-14, which is activated at the onset of keratinocyte terminal differentiation. We investigated the possible involvement of epidermal proteases expressed in the late stage of differentiation, and found that the chymotrypsin-like serine protease kallikrein-related peptidase-7 (KLK7) cleaved procaspase-14 at Tyr(178), generating an intermediate form that consists of a large (20 kDa) and a small subunit (8 kDa). We prepared an antibody directed to this cleavage site (h14Y178 Ab), and confirmed that it recognized a 20-kDa band formed when procaspase-14 was incubated with chymotrypsin or KLK7. We then constructed a constitutively active form of the intermediate, revC14-Y178. The substrate specificity of revC14-Y178 was completely different from that of caspase-14, showing broad specificity for various caspase substrates except WEHD-7-amino-4-trifluoromethylcoumarin (AFC), the preferred substrate of active, mature caspase-14. K(m) values for VEID-AFC, DEVD-AFC, LEVD-AFC, and LEHD-AFC were 0.172, 0.261, 0.504, and 0.847 μM, respectively. We confirmed that the mature form of caspase-14 was generated when procaspase-14 was incubated with KLK7 or revC14-Y178. Expression of constitutively active KLK7 in cultured keratinocytes resulted in generation of both the intermediate form and the mature form of caspase-14. Immunohistochemical analysis demonstrated that the intermediate form was localized at the granular layer. Our results indicate that regulation of procaspase-14 maturation during terminal differentiation is a unique two-step process involving KLK7 and an activation intermediate of caspase-14.

TIRAP, an adaptor protein for TLR2/4, transduces a signal from RAGE phosphorylated upon ligand binding

The receptor for advanced glycation end products (RAGE) is thought to be involved in the pathogenesis of a broad range of inflammatory, degenerative and hyperproliferative diseases. It binds to diverse ligands and activates multiple intracellular signaling pathways. Despite these pivotal functions, molecular events just downstream of ligand-activated RAGE have been surprisingly unknown. Here we show that the cytoplasmic domain of RAGE is phosphorylated at Ser391 by PKCζ upon binding of ligands. TIRAP and MyD88, which are known to be adaptor proteins for Toll-like receptor-2 and -4 (TLR2/4), bound to the phosphorylated RAGE and transduced a signal to downstream molecules. Blocking of the function of TIRAP and MyD88 largely abrogated intracellular signaling from ligand-activated RAGE. Our findings indicate that functional interaction between RAGE and TLRs coordinately regulates inflammation, immune response and other cellular functions.

Bleomycin hydrolase is regulated biphasically in a differentiation- and cytokine-dependent manner: relevance to atopic dermatitis

Loss-of-function mutation in the profilaggrin gene is a major risk factor for atopic dermatitis (AD). Previously, we showed that a neutral cysteine protease, bleomycin hydrolase (BH), has a role in generating natural moisturizing factors, and calpain I is an upstream protease in the filaggrin degradation pathway. Here, we investigated the transcriptional regulatory mechanisms of BH and the relevance of BH to AD. First, we cloned the 5'-flanking region of BH. Deletion analyses identified a critical region for BH promoter activity within -216 bp upstream. Electrophoretic mobility shift assay revealed that MZF-1, Sp-1, and interferon regulatory factor-1/2 could bind to this region in vitro. Moreover, site-directed mutagenesis of the MZF-1 and Sp-1 motifs markedly reduced BH promoter activity. These data indicate that BH expression is up-regulated via MZF-1 and Sp-1. Interestingly, a Th1 cytokine, IFN-γ, significantly reduced the expression of BH. Analyses with site-directed mutagenesis and small interference RNA supported the suppressing effect of IFN-γ on BH expression. On the other hand, a Th2 cytokine, IL-4, did not show any direct effect on BH expression. However, it down-regulated MZF-1 and Sp-1 in cultured keratinocytes, indicating that IL-4 could work as a suppressor in BH regulation. Lastly, we examined expression of BH in skins of patients with AD. BH activity and expression were markedly decreased in AD lesional skin, suggesting a defect of the filaggrin degradation pathway in AD. Our results suggest that BH transcription would be modulated during both differentiation and inflammation.

Purification and characterization of active caspase-14 from human epidermis and development of the cleavage site-directed antibody

Restricted expression of caspase-14 in differentiating keratinocytes suggests the involvement of caspase-14 in terminal differentiation. We purified active caspase-14 from human cornified cells with sequential chromatographic procedures. Specific activity increased 764-fold with a yield of 9.1%. Purified caspase-14 revealed the highest activity on WEHD-methylcoumaryl-amide (MCA), although YVAD-MCA, another caspase-1 substrate, was poorly hydrolyzed. The purified protein was a heterodimer with 17 and 11 kDa subunits. N-terminal and C-terminal analyses demonstrated that the large subunit consisted of Ser(6)-Asp(146) and N-terminal of small subunit was identified as Lys(153). We successfully developed an antiserum (anti-h14D146) directed against the Asp(146) cleavage site, which reacted only with active caspase-14 but not with procaspase-14. Furthermore we confirmed that anti-h14D146 did not show any reactivity to the active forms of other caspases. Immunohistochemical analysis demonstrated that anti-h14D146 staining was mostly restricted to the cornified layer and co-localized with some of the TUNEL positive-granular cells in the normal human epidermis. UV radiation study demonstrated that caspase-3 was activated and co-localized with TUNEL-positive cells in the middle layer of human epidermis. In contrast, we could not detect caspase-14 activation in response to UV. Our study revealed tightly regulated action of caspase-14, in which only the terminal differentiation of keratinocytes controls its activation process.

Glycolic acid induces keratinocyte proliferation in a skin equivalent model via TRPV1 activation

BACKGROUND

Glycolic acid (GA) is the most commonly used alpha-hydroxy acid (AHA) for dermatologic applications, and is considered as a versatile superficial peeling agent for facial rejuvenation. Its therapeutic effect includes acceleration of epidermal turnover without apparent inflammation, and its action is pH-dependent. However, little is known about the molecular mechanism of GA-induced peeling.

OBJECTIVE

To investigate the effects of topical application of GA on cell proliferation using a skin equivalent model and to examine the molecular mechanisms of GA-induced peeling.

METHODS

GA solution was applied on the surface of a skin equivalent model, and cell proliferation was measured by means of BrdU-incorporation and immunohistochemical methods. Release of chemical mediators such as ATP into the medium was examined. The effects of antagonists of ion channels were also analyzed.

RESULTS

At 24h after GA application, BrdU-incorporation into basal keratinocytes was significantly increased. Induction of keratinocyte proliferation was pH-dependent, and was inhibited by antagonists of TRPV1, an acid-sensitive ion channel. Furthermore, transient ATP release was detected in the culture medium after GA stimulation, and this was also suppressed by TRPV1 antagonists.

CONCLUSION

These results suggest that one of the mechanisms of GA-induced epidermal proliferation is a growth response of basal keratinocytes to the local elevation of H(+)-ion concentration by infiltrated GA. This response is mediated by TRPV1 activation and ATP release. Activation of P2 receptors by the released ATP may also be involved.

Up-regulation of serpin SCCA1 is associated with epidermal barrier disruption

BACKGROUND

Parakeratosis, the persistent presence of nuclei in the stratum corneum (SC) is associated with serious disruption of skin barrier function. Squamous cell carcinoma antigen 1 (SCCA1) is strongly up-regulated in inflamed and parakeratotic skin.

OBJECTIVE

To find a biochemical marker for the SC barrier disruption, especially the disruption associated with parakeratosis.

METHODS

An ELISA assay system was established to quantify SCCA1 in the extract of tape-stripped cornified cells. Transepidermal water loss (TEWL) and other skin parameters were measured and compared with the amount of SCCA1. Localization of SCCA1 was investigated immunohistochemically in various skin diseases with parakeratosis. Nuclei and SCCA1 on the skin surface were detected by staining of corniocytes collected on an adhesive-coated slide glass.

RESULTS

SCCA1 showed strong up-regulation in lesional skin with psoriasis (466-fold), hayfever skin caused by Japanese ceder pollen (232-fold) and sun-exposed skin of healthy individuals (90-fold) compared to their normal sun-protected skin. The increased levels of SCCA1 were well correlated with increased values of TEWL and the number of parakeratotic cells in the SC. Furthermore, subjects with high levels of SCCA1 in the epidermis were more susceptible to barrier disruption by external stimuli, and this was accompanied with a further increase of SCCA1. We confirmed that localization of SCCA1 was limited to parakeratotic areas by using the skin surface staining technique. Immunohistochemical study also demonstrated that SCCA1 was always present at high levels in parakeratotic epidermis.

CONCLUSION

All of our findings indicate that SCCA1 plays an important role in the induction of epidermal barrier disruption. SCCA1 may be a critical determinant of barrier function in the epidermis.

Keratinocytes synthesize enteropeptidase and multiple forms of trypsinogen during terminal differentiation

Members of the trypsin-like and chymotrypsin-like kallikrein family are important in the desquamation process. In this study, we isolated cDNA clones encoding trypsinogen 4 (brain trypsinogen) and a previously unreported isoform of trypsinogen from a human keratinocyte cDNA library. The nucleotide sequence of the new isoform only differs from those of trypsinogen 3 (mesotrypsinogen) and trypsinogen 4 in an exon encoding the N-terminal region, indicating that this isoform is an alternative splicing variant of the mesotrypsinogen gene PRSS3. Both isoforms contained the sequence DDDDK-I, a putative cleavage site for activation by enteropeptidase. Thus, after activation, mesotrypsin would be produced. Immunohistochemical and in situ hybridization studies revealed that trypsinogens were expressed and localized in the upper epidermis, especially in the granular layer. In cultured keratinocytes, enteropeptidase mRNA was expressed at the confluent stage, and its expression was strongly upregulated after air exposure. Interestingly, it was synthesized and localized only at the granular layer, suggesting that the generation of active mesotrypsin is restricted to this layer. The enteropeptidase-cleavage product was also found at the same layer. When a skin equivalent model was cultured in the medium without air exposure, the cornified layer was not formed, and many cells expressed trypsinogens and enteropeptidase. Those cells were found to be TUNEL positive. Because mesotrypsin is resistant to naturally occurring trypsin inhibitors, confined expression of the isoforms of mesotrypsinogens and enteropeptidase may indicate that mesotrypsin is involved in keratinocyte terminal differentiation.

Neutral cysteine protease bleomycin hydrolase is essential for the breakdown of deiminated filaggrin into amino acids

Filaggrin is a component of the cornified cell envelope and the precursor of free amino acids acting as a natural moisturizing factor in the stratum corneum. Deimination is critical for the degradation of filaggrin into free amino acids. In this study, we tried to identify the enzyme(s) responsible for the cleavage of deiminated filaggrin in vitro. First, we investigated citrulline aminopeptidase activity in the extract of newborn rat epidermis by double layer fluorescent zymography and detected strong activity at neutral pH. Monitoring the citrulline-releasing activity, we purified an enzyme of 280 kDa, comprised of six identical subunits of 48 kDa. The NH(2) terminus of representative tryptic peptides perfectly matched the sequence of rat bleomycin hydrolase (BH). The enzyme released various amino acids except Pro from beta-naphthylamide derivatives and hydrolyzed citrulline-beta-naphthylamide most effectively. Thus, to break down deiminated filaggrin, another protease would be required. Among proteases tested, calpain I degraded the deiminated filaggrin effectively into many peptides of different mass on the matrix-assisted laser desorption/ionization-time of flight mass spectrum. We confirmed that various amino acids including citrulline were released by BH from those peptides. On the other hand, caspase 14 degraded deiminated filaggrin into a few peptides of limited mass. Immunohistochemical analysis of normal human skin revealed co-localization of BH and filaggrin in the granular layer. Collectively, our results suggest that BH is essential for the synthesis of natural moisturizing factors and that calpain I would play a role as an upstream protease in the degradation of filaggrin.