Zoledronate promotes inflammatory cytokine expression in human CD14-positive monocytes among peripheral mononuclear cells in the presence of γδ T cells.

Bisphosphonates distributed to bone exert toxic effects specifically towards osteoclasts. On the other hand, intravenous administration of a nitrogen-containing bisphosphonate (N-BP) such as zoledronate induces acute-phase reactions (APRs), including influenza-like fever 1 day later, indicating an interaction with immunocompetent cells circulating blood. Although it has been reported that activation of γδ T cells is pivotal to induce an APR following treatment with zoledronate, downstream events, including the production of inflammatory cytokines after activation of γδ T cells, remain obscure. We investigated the effects of zoledronate on inflammatory cytokine expression in human peripheral blood mononuclear cells (PBMCs) in vitro. While zoledronate induced mRNA expressions of tumour necrosis factor-α (TNF-α), interleukin (IL)-1ß, IL-6 and interferon-γ (IFN-γ) in PBMC, depletion of γδ T cells abolished that zoledronate-induced expression of those cytokines, indicating the necessity of γδ T cells for expression induction by zoledronate. However, which types of cells were responsible for the production of those cytokines in blood remained unclear. As it is generally accepted that monocytes and macrophages are primary sources of inflammatory cytokines, CD14+ cells from PBMC were exposed to zoledronate in the presence of PBMC, which resulted in induced expression of mRNAs for IL-1ß, IL-6 and IFN-γ, but not for TNF-α. These results indicate that CD14+ cells are responsible, at least in part, for the production of IL-1ß, IL-6 and IFN-γ in blood exposed to zoledronate. This suggests that CD14+ cells play an essential role in the occurrence of APRs following N-BP administration.

A multicenter prospective cohort study on the effect of smoking cessation on periodontal therapies in Japan.

Few prospective studies have reported the effects of periodontal therapy on patients who attempted to quit smoking. This study aimed to assess how smoking cessation affects periodontal therapy. Twenty-five smokers with periodontitis were investigated by dividing them into two groups, a smoking cessation support group and a continued smoking group. Those in the support group received counseling and nicotine replacement therapy, followed by periodontal treatment conducted by dentists who had completed an e-learning course on smoking cessation. Clinical parameters were measured at baseline, 3, and 6 months. Most clinical parameters improved for those in the smoking cessation support group. There were no significant improvements in bleeding on probing (BOP) or the number of severe periodontal disease sites in the continued smoking group. Probing pocket depth (PPD) and clinical attachment levels (CAL) at sites that received scaling and root planing (SRP) significantly improved in all subjects. BOP did not improve at reevaluation in the smoking relapse subgroup. Patients in the smoking cessation support program led by dental professionals showed more improvement in BOP than those in the continued smoking group.

Comparison of protein profiles of the pellicle, gingival crevicular fluid, and saliva: possible origin of pellicle proteins.

BACKGROUND: The pellicle, the acellular organic material deposited on the surface of tooth enamel, has been thought to be derived from saliva. In this study, protein compositions of the pellicle, gingival crevicular fluid, and saliva collected from healthy adults were compared to elucidate the origin of pellicle proteins. RESULTS: The pellicle, gingival crevicular fluid, and saliva from the parotid gland or mixed gland were collected; subsequently, protein expression in samples from the respective individual was compared by SDS-PAGE and mass spectrometry. Following SDS-PAGE, proteins in the major bands were identified by mass spectrometry. The band pattern of pellicle proteins appeared different from those of gingival crevicular fluid, or saliva samples. Using mass spectrometry, 13 proteins in these samples were identified. The relative abundance of the proteins was quantitatively analyzed using mass spectrometry coupled with stable isotope labeling and by western blot. Cystatin S and α-amylase detected in pellicle were enriched in saliva samples, but not in gingival crevicular fluid, by western blot, and their abundance ratios were high in saliva and low in gingival crevicular fluid when analyzed by stable isotope labeling. Serotransferrin, however, was found only in the pellicle and gingival crevicular fluid by western blot and its abundance ratio was low in saliva. CONCLUSIONS: Our study revealed that the gingival crevicular fluid appears to contribute to pellicle formation in addition to saliva.

Comparison of protein profiles of the pellicle, gingival crevicular fluid, and saliva: possible origin of pellicle proteins

BACKGROUND: The pellicle, the acellular organic material deposited on the surface of tooth enamel, has been thought to be derived from saliva. In this study, protein compositions of the pellicle, gingival crevicular fluid, and saliva collected from healthy adults were compared to elucidate the origin of pellicle proteins. RESULTS: The pellicle, gingival crevicular fluid, and saliva from the parotid gland or mixed gland were collected; subsequently, protein expression in samples from the respective individual was compared by SDS-PAGE and mass spectrometry. Following SDS-PAGE, proteins in the major bands were identified by mass spectrometry. The band pattern of pellicle proteins appeared different from those of gingival crevicular fluid, or saliva samples. Using mass spectrometry, 13 proteins in these samples were identified. The relative abundance of the proteins was quantitatively analyzed using mass spectrometry coupled with stable isotope labeling and by western blot. Cystatin S and α-amylase detected in pellicle were enriched in saliva samples, but not in gingival crevicular fluid, by western blot, and their abundance ratios were high in saliva and low in gingival crevicular fluid when analyzed by stable isotope labeling. Serotransferrin, however, was found only in the pellicle and gingival crevicular fluid by western blot and its abundance ratio was low in saliva. CONCLUSIONS: Our study revealed that the gingival crevicular fluid appears to contribute to pellicle formation in addition to saliva.

Roles of monocarboxylate transporter subtypes in promotion and suppression of osteoclast differentiation and survival on bone.

Monocarboxylate transporters (MCTs) provide transmembrane transport of monocarboxylates such as lactate and pyruvate. The present results showed that α-cyano-4-hydroxycinnamic acid (CHC), an inhibitor of MCTs, promoted osteoclast differentiation from macrophages at lower concentrations (0.1-0.3 mM) and suppressed that at a higher concentration (1.0 mM). On the other hand, CHC reduced the number of mature osteoclasts on the surface of dentin in a concentration-dependent manner. Additionally, macrophages and osteoclasts were found to express the Mct1, Mct2, and Mct4 genes, with Mct1 and Mct4 expression higher in macrophages, and that of Mct2 higher in osteoclasts. Although Mct1 gene knockdown in macrophages enhanced osteoclast formation induced by RANKL, Mct2 gene knockdown suppressed that. Finally, Mct2 gene silencing in mature osteoclasts decreased their number and, thereby, bone resorption. These results suggest that MCT1 is a negative regulator and MCT2 a positive regulator of osteoclast differentiation, while MCT2 is required for bone resorption by osteoclasts.

Visualization of junctional epithelial cell replacement by oral gingival epithelial cells over a life time and after gingivectomy.

Junctional epithelium (JE), which is derived from odontogenic epithelial cells immediately after eruption, is believed to be gradually replaced by oral gingival epithelium (OGE) over a lifetime. However, the detailed process of replacement remains unclear. The aim of the present study was to clarify the process of JE replacement by OGE cells using a green fluorescent protein (GFP)-positive tooth germ transplantation method. GFP-positive JE was partly replaced by OGE cells and completely replaced on day 200 after transplantation, whereas there was no difference in the expression of integrin ß4 (Itgb4) and laminin 5 (Lama5) between JE before and after replacement by OGE cells. Next, GFP-positive JE was partially resected. On day 14 after resection, the regenerated JE consisted of GFP-negative cells and also expressed both Itgb4 and Lama5. In addition, the gene expression profile of JE derived from odontogenic epithelium before gingivectomy was partly different from that of JE derived from OGE after gingivectomy. These results suggest that JE derived from the odontogenic epithelium is gradually replaced by OGE cells over time and JE derived from the odontogenic epithelium might have specific characteristics different to those of JE derived from OGE.

Monocarboxylate transporter-1 promotes osteoblast differentiation via suppression of p53, a negative regulator of osteoblast differentiation.

Monocarboxylate transporter-1 (MCT-1) is a transmembrane transporter for monocarboxylates including lactate and pyruvate. Silencing Mct1 by its small interfering RNA (siRNA) suppressed the expression of marker genes for osteoblast differentiation, namely, Tnap, Runx2, and Sp7, induced by BMP-2 in mouse myoblastic C2C12 cells. Mct1 siRNA also suppressed alkaline phosphatase activity, as well as expressions of Tnap and Bglap mRNAs in mouse primary osteoblasts. On the other hand, Mct1 siRNA did not have effects on the Smad1/5 or ERK/JNK pathways in BMP-2-stimulated C2C12 cells, while it up-regulated the mRNA expression of p53 (Trp53) as well as nuclear accumulation of p53 in C2C12 cells in a BMP-2-independent manner. Suppression of osteoblastic differentiation by Mct1 siRNA in C2C12 cells was abolished by co-transfection of Trp53 siRNA. Together, these results suggest that MCT-1 functions as a positive regulator of osteoblast differentiation via suppression of p53.

Establishment of mouse gingival junctional epithelial cell line using a bioengineered tooth system.

Junctional epithelium (JE), one of the constituents of periodontal tissue, has several unique features to prevent bacterial infection. However, the molecular mechanisms of these cells remain to be completely elucidated because there has been no JE cell line to date. We have succeeded in isolating JE cells expressing green fluorescent protein (GFP) by using a bioengineered tooth technique in mice. The gene expressions of GFP-positive JE cells, isolated from around the erupted bioengineered teeth using flow cytometry, were analyzed by RNA sequencing. GFP-positive cells derived from the bioengineered tooth germs showed similar gene expression patterns to primary JE cells. The isolated GFP-positive JE cells were immortalized by transducing the simian virus 40 large T antigen using lentiviral vectors. The established GFP-positive JE cells maintained proliferative activity for more than 20 passages, and did not show cellular senescence as demonstrated by ß-galactosidase assay. These cells also expressed similar gene expression patterns to primary JE cells. The established cell lines may prove useful for future investigation of JE characteristics in vitro.

Prevalence and risk factors for peri-implant diseases in Japanese adult dental patients.

We investigated the prevalences and risk factors for peri-implant diseases in Japanese adult dental patients attending a follow-up visit at dental hospitals or clinics as part of their maintenance program. This cross-sectional multicenter study enrolled patients with dental implants who attended regular check-ups as part of a periodontal maintenance program during the period from October 2012 through September 2013. Patients with implants with at least 3 years of loading time were included in the study. The condition of peri-implant tissue was examined and classified into the following categories: healthy, peri-implant mucositis, and peri-implantitis. Patients were also evaluated for implant risk factors. A total of 267 patients (110 men, 157 women; mean age: 62.5 ± 10.7 years) were analyzed. The prevalence of patient-based peri-implant mucositis was 33.3% (n = 89), and the prevalence of peri-implantitis was 9.7% (n = 26). Poor oral hygiene and a history of periodontitis were strong risk factors for peri-implant disease. The present prevalences were lower than those previously reported. The quality of periodontal therapy before and after implant installation and patient compliance and motivation, as indicated by plaque control level, appear to be important in maintaining peri-implant tissue health.

Thymus-expressed chemokine enhances Porphyromonas gingivalis LPS-induced osteoclast formation via NFATc1 activation.

OBJECTIVE: P. gingivalis is a gram-negative anaerobic bacterium and a major periodontal pathogen. LPS produced by P. gingivalis promotes osteoclast formation. TECK is a CC chemokine whose expression is increased in gingival epithelial cells exposed to P. gingivalis LPS. In this study, we investigated the effect of TECK in osteoclastogenesis induced by P. gingivalis LPS. DESIGNS: Real time reverse transcriptase polymerase chain reaction (RTPCR) analysis and western blotting were performed to confirm TECK in MG63, human osteoblast cell line and primary murine osteoblasts and CCR9 in RAW 264.7 cells and murine bone marrow macrophages (BMMs) as osteoclast precursors. P. gingivalis LPS-treated BMMs and Raw 264.7 cells were cultured with or without TECK or TECK antibody to examine the effect of TECK on osteoclast formation. Cocultures with murine osteoblasts and bone marrow cells were also treated with or without TECK or TECK antibody. Luciferase assay and western blotting were used to determine whether TECK-CCR9 induced osteoclastogenesis was mediated through NFATc1 or NF-kB signaling. RESULTS: TECK was shown to be expressed by osteoblasts, and its receptor, CCR9, by osteoclast precursors. TECK increased P. gingivalis LPS-induced osteoclast numbers in an in vitro osteoclast formation assay using osteoclast precursors. The enhanced osteoclast formation by TECK was mediated by NFATc1, but not by NF-kB signaling. CONCLUSION: TECK may be a novel regulator of osteoclast formation induced by P. gingivalis LPS in periodontitis.

Randomized Placebo-Controlled and Controlled Non-Inferiority Phase III Trials Comparing Trafermin, a Recombinant Human Fibroblast Growth Factor 2, and Enamel Matrix Derivative in Periodontal Regeneration in Intrabony Defects.

We investigated the efficacy, safety, and clinical significance of trafermin, a recombinant human fibroblast growth factor (rhFGF)-2, for periodontal regeneration in intrabony defects in Phase III trials. Study A, a multicenter, randomized, double-blind, placebo-controlled study, was conducted at 24 centers. Patients with periodontitis with 4-mm and 3-mm or deeper probing pocket depth and intrabony defects, respectively, were included. A total of 328 patients were randomly assigned (2:1) to receive 0.3% rhFGF-2 or placebo, and 323 patients received the assigned investigational drug during flap surgery. One of the co-primary endpoints, the percentage of bone fill at 36 weeks after drug administration, was significantly greater in the rhFGF-2 group at 37.131% (95% confidence interval [CI], 32.7502 to 41.5123; n = 208) than it was in the placebo group at 21.579% (95% CI, 16.3571 to 26.8011; n = 100; p < 0.001). The other endpoint, the clinical attachment level regained at 36 weeks, was not significantly different between groups. Study B, a multicenter, randomized, blinded (patients and evaluators of radiographs), and active-controlled study was conducted at 15 centers to clarify the clinical significance of rhFGF-2. Patients with 6-mm and 4-mm or deeper probing pocket depth and intrabony defects, respectively, were included. A total of 274 patients were randomly assigned (5:5:2) to receive rhFGF-2, enamel matrix derivative (EMD), or flap surgery alone. A total of 267 patients received the assigned treatment during flap surgery. The primary endpoint, the linear alveolar bone growth at 36 weeks, was 1.927 mm (95% CI, 1.6615 to 2.1920; n = 108) in the rhFGF-2 group and 1.359 mm (95% CI, 1.0683 to 1.6495; n = 109) in the EMD group, showing non-inferiority (a prespecified margin of 0.3 mm) and superiority of rhFGF-2 to EMD. Safety problems were not identified in either study. Therefore, trafermin is an effective and safe treatment for periodontal regeneration in intrabony defect, and its efficacy was superior in rhFGF-2 compared to EMD treatments.

Expression of nephronectin is inhibited by oncostatin M via both JAK/STAT and MAPK pathways.

Nephronectin (Npnt), also called POEM, is an extracellular matrix protein considered to play critical roles as an adhesion molecule in the development and functions of various tissues, such as the kidneys, liver, and bones. In the present study, we examined the molecular mechanism of Npnt gene expression and found that oncostatin M (OSM) strongly inhibited Npnt mRNA expression in MC3T3-E1 cells from a mouse osteoblastic cell line. OSM also induced a decrease in Npnt expression in both time- and dose-dependent manners via both the JAK/STAT and MAPK pathways. In addition, OSM-induced inhibition of osteoblast differentiation was recovered by over-expression of Npnt. These results suggest that OSM inhibits Npnt expression via the JAK/STAT and MAPK pathways, while down-regulation of Npnt by OSM influences inhibition of osteoblast differentiation.

Lipoproteins of Actinomyces viscosus induce inflammatory responses through TLR2 in human gingival epithelial cells and macrophages.

Actinomyces viscosus has been suggested to be associated with periodontal disease. However, the pathogenicity of this bacterium is not known. In this study, we examined inflammation-inducing activity by A. viscosus. Whole cells and a lipophilic fraction of A. viscosus ATCC19246 induced production of interleukin-8 and tumor necrosis factor alpha from both human oral epithelial cells and human monocytoid cells. This cytokine production was blocked by lipoprotein lipase treatment of the lipophilic fraction. In addition, anti-Toll-like receptor 2 antibody blocked the cytokine production. These results suggest that lipoprotein of A. viscosus triggers inflammatory responses in periodontitis by activation of Toll-like receptor 2.

Gene delivery system involving Bubble liposomes and ultrasound for the efficient in vivo delivery of genes into mouse tongue tissue.

Oral squamous cell carcinoma is the most common type of head and neck cancer. Recently, efficient, easy, and minimally invasive gene delivery methods are expected to be developed as cancer gene therapies. However, the optimal method for delivering therapeutic genes into oral tissue for cancer treatment has not been elucidated. Therefore, we hypothesized that the tongue is a good target tissue for gene delivery with Bubble liposomes and ultrasound. To assess this, we attempted to deliver a mixture of plasmid DNA encoding a luciferase or enhanced green fluorescent protein, and Bubble liposomes into murine tongue with or without ultrasound exposure. The ultrasound conditions were 1 MHz, 2 W/cm(2), 60s, and duty cycle: 50%. The time-course of gene expression in the tongue was investigated with a luciferase assay and fluorescent microscopy. Luciferase expression was significantly increased in tongue transfected using Bubble liposomes and ultrasound compared with that of the tongue untreated with ultrasound, and this high level of luciferase activity was maintained for 2 weeks. From these results, Bubble liposomes can be used in combination with ultrasound to efficiently deliver plasmid DNA into the tongue in vivo. This technique is a highly promising approach for gene delivery into oral tissue.

Surface lipoprotein PpiA of Streptococcus mutans suppresses scavenger receptor MARCO-dependent phagocytosis by macrophages.

Streptococcus mutans is associated with the initiation and progression of human dental caries and is occasionally isolated from the blood of patients with bacteremia and infective endocarditis. For the pathogen to survive in the infected host, surface lipoproteins of S. mutans are likely to play important roles in interactions with the innate immune system. To clarify the role that a putative lipoprotein, peptidyl-prolyl cis/trans-isomerase (PpiA), of S. mutans plays in the macrophage response, we investigated the response of THP-1-derived macrophages to S. mutans challenge. The deletion of the gene encoding Lgt eliminated PpiA on the cell surface of S. mutans, which implies that PpiA is a lipoprotein that is lipid anchored in the cell membrane by Lgt. Human and murine peritoneal macrophages both showed higher phagocytic activities for the ppiA and lgt mutants than the wild type, which indicates that the presence of PpiA reduces S. mutans phagocytosis. In addition, infection with S. mutans markedly induced mRNAs of macrophage receptor with collagenous structure (MARCO) and scavenger receptor A (SR-A) in human macrophages. In particular, transcriptional and translational levels of MARCO in human macrophages infected with the ppiA mutant were higher than those in macrophages infected with the wild type. Phagocytosis of S. mutans by human macrophages markedly decreased after treatment with anti-MARCO IgG. These results demonstrate that the S. mutans lipoprotein PpiA contributes to suppression of MARCO-mediated phagocytosis of this bacterium by macrophages.

Expression of POEM, a positive regulator of osteoblast differentiation, is suppressed by TNF-α.

POEM, also known as nephronectin, is an extracellular matrix protein considered to be a positive regulator of osteoblast differentiation. In the present study, we found that tumor necrosis factor-α (TNF-α), a key regulator of bone matrix properties and composition that also inhibits terminal osteoblast differentiation, strongly inhibited POEM expression in the mouse osteoblastic cell line MC3T3-E1. TNF-α-induced down-regulation of POEM gene expression occurred in both time- and dose-dependent manners through the nuclear factor kappa B (NF-κB) pathway. In addition, expressions of marker genes in differentiated osteoblasts were down-regulated by TNF-α in a manner consistent with our findings for POEM, while over-expression of POEM recovered TNF-α-induced inhibition of osteoblast differentiation. These results suggest that TNF-α inhibits POEM expression through the NF-κB signaling pathway and down-regulation of POEM influences the inhibition of osteoblast differentiation by TNF-α.

Docosahexaenoic acid induces adipose differentiation-related protein through activation of retinoid x receptor in human choriocarcinoma BeWo cells.

Adipose differentiation-related protein (ADRP) is associated with intracellular lipid droplets that accumulate neutral lipids. Here we report that ADRP expression in a human choriocarcinoma cell line, BeWo, is regulated through activation of retinoid X receptor (RXR) and peroxisome proliferator-activated receptor-gamma (PPARgamma). Incubation with docosahexaenoic acid (DHA) or oleic acid (OA) induced accumulation of triacylglycerol (TG) and ADRP in BeWo cells. DHA-induced ADRP expression was suppressed by RXR-antagonists, PA452 and HX531. However, oleic acid-induced ADRP expression was not blocked by the RXR-antagonists but by a PPARgamma-antagonist. Treatment of the cells with RXR-agonists, HX630 and PA024, increased Adrp transcripts, however, they alone did not change the levels of ADRP protein and TG in BeWo cells. Induction of ADRP protein was observed in the presence of a proteasome inhibitor, suggesting that ADRP is degraded under lipid-poor conditions. These results suggest that expression of ADRP is in part regulated by RXR and PPARgamma transcription factors, and DHA induces ADRP by acting as an endogenous agonist of RXR.

IFN-gamma down-regulates Secretoglobin 3A1 gene expression.

STAT1 mediates Interferon (IFN)-dependent positive and negative regulation of inflammatory gene expression in lung. In this study, we examined the effect of IFN-gamma on the expression of SCGB3A1 which is thought to play crucial roles in inflammation and epithelial cell differentiation in lung. We found that expression of SCGB3A1 was down-regulated by IFN-gamma in a time- and dose-dependent manner in the murine transformed Clara Cells (mtCC) line. IFN-gamma induced the phosphorylation of STAT1, which binds to a STAT-binding element (SBE) in the SCGB3A1 gene promoter, leading to decreased transcriptional activation of this gene.

Inflammatory cytokines correlated with clinical outcome of temporomandibular joint irrigation in patients with chronic closed lock.

OBJECTIVE: This study investigated the correlation of clinical outcomes of temporomandibular joint (TMJ) irrigation with the occurrence and concentrations of tumor necrosis factor (TNF)-alpha, interleukin (IL)-1beta, IL-6, IL-8, IL-12, and IL-10 in the washed-out synovial fluid (SF) in patients with chronic closed lock (CCL) of the TMJ. STUDY DESIGN: Thirty-six patients underwent a visually guided TMJ irrigation (VGIR). SF samples were collected immediately before VGIR. The patients were divided into either successful (s-group; n = 25) or unsuccessful groups (u-group; n = 11). The detection rates and concentrations of each cytokine per milligram of total protein in the SF were measured, and then compared between the s- and u-groups. RESULTS: All of the investigated cytokines were detectable with various rates, concentrations, and combination patterns. The detection rate and concentrations of IL-6 were significantly higher in the u-group, and those of IL-10 were significantly higher in the s-group. CONCLUSIONS: The investigated cytokines were suggested to be involved in the pathophysiology of TMJ CCL. The results also suggest that IL-6 in the SF is an indicator of an unsuccessful outcome, and that IL-10 is a significant predictor of a successful outcome of TMJ irrigation for CCL.

A novel mutation of the cathepsin C gene in a thai family with Papillon-Lefevre syndrome.

BACKGROUND: Papillon-Lefevre syndrome (PLS) is a rare autosomal recessive disorder characterized by palmar- plantar hyperkeratosis and rapid periodontal destruction of both primary and permanent dentitions. It has been shown that the disease is caused by cathepsin C gene (CTSC) mutation leading to the deficiency of cathepsin C enzymatic activity. This study demonstrates the clinical manifestations and CTSC mutational and enzymatic activity analyses in a 5-year-old Thai male PLS patient and his parents. METHODS: Peripheral blood samples were obtained for genomic DNA isolation. All exons of the CTSC gene were amplified by polymerase chain reaction (PCR) using specific primers. Mutations were identified by DNA sequencing. Verification of the mutation was performed by digestion of PCR products by restriction endonucleases. The cathepsin C enzymatic activity was determined using the synthetic substrate glycyl- L-arginine-7-amino-4-methylcoumarin. RESULTS: The patient demonstrated classical characteristics of PLS, including hyperkeratotic skin lesions. By the age of 5, all of his primary teeth were extracted due to severe periodontal infection. The parents had no physical abnormalities. The periodontal examination revealed localized mild periodontal destruction. Sequence analysis showed a nucleotide change at position 90 from C >A (c.90C >A) which resulted in a change from cysteine residue to a premature stop codon at the amino acid position 30 in the exon 1. The HpyCH4V digestion revealed that the patient was homozygous, whereas both the father and mother were heterozygous carriers of this mutation. The cathepsin C activity was reduced in the patient's mother, and the activity in the patient was almost completely lost. CONCLUSIONS: This is the first study to demonstrate a CTSC gene mutation in a Thai family with PLS. The identified mutation is novel and potentially leads to the drastic reduction of the cathepsin C enzymatic activity. This suggests that the mutation is pathogenetic, causing the PLS. Mutational analysis in more members of the family is warranted to identify whether the mutation is inherited from a common ancestor.