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Natriuretic peptides exert not only blood-lowering but also kidney-protective effects through guanylyl cyclase-A (GC-A), a natriuretic peptide receptor. Signaling through GC-A has been shown to protect podocytes from aldosterone-induced glomerular injury, and a p38 mitogen-activated protein kinase (MAPK) inhibitor reduced glomerular injury in aldosterone-infused podocyte-specific GC-A knockout mice. To explore the role of p38 MAPK in podocytes, we constructed podocyte-specific p38 MAPK and GC-A double knockout mice (pod-double knockout mice). Unexpectedly, aldosterone-infused and high salt-fed (B-ALDO)-treated pod-double knockout mice resulted in elevated serum creatinine, massive albuminuria, macrophage infiltration, foot process effacement, nephrin and podocin reduction, and additionally, intra-capillary fibrin thrombi, indicating endothelial injury. Microarray analysis showed increased plasminogen activator inhibitor-1 (PAI-1) in glomeruli of B-ALDO-treated pod-double knockout mice. In B-ALDO-treated pod-double knockout mice, PAI-1 increased in podocytes, and treatment with PAI-1 neutralizing antibody ameliorated intra-capillary thrombus formation. In vitro, deletion of p38 MAPK by the CRISPR/Cas9 system and knockdown of GC-A in human cultured podocytes upregulated PAI-1 and transforming growth factor- β1 (TGF-β1). When p38 MAPK knockout podocytes, transfected with a small interfering RNA to suppress GC-A, were co-cultured with glomerular endothelial cells in a transwell system, the expression of TGF-β1 was increased in glomerular endothelial cells. PAI-1 inhibition ameliorated both podocyte and endothelial injury in the transwell system signifying elevated PAI-1 in podocytes is a factor disrupting normal podocyte-endothelial crosstalk. Thus, our results indicate that genetic dual deletion of p38 MAPK and GC-A in podocytes accelerates both podocyte and endothelial injuries, suggesting these two molecules play indispensable roles in podocyte function., (Copyright © 2023 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Purpose: To identify susceptibility genes for macular neovascularization (MNV) development in central serous chorioretinopathy (CSC)., Design: Genome-wide survival analysis using a longitudinal cohort study., Participants: We included 402 and 137 patients with CSC but without MNV at their first visit from the Kyoto CSC Cohort and Kobe CSC dataset, respectively. All patients underwent detailed ophthalmic examinations, including multimodal imaging, such as fundus autofluorescence, spectral-domain OCT, and fluorescein angiography/indocyanine green angiography or OCT angiography., Methods: We conducted a genome-wide survival analysis using the Kyoto CSC Cohort. We applied the Cox proportional hazard model to adjust for age, sex, and the first principal component. Single nucleotide polymorphisms (SNPs) with P values < 1.0 × 10 -5 were carried forward to the replication in the Kobe CSC dataset. Moreover, we evaluated the contribution of previously reported age-related macular degeneration (AMD) susceptibility loci. We used FUMA and ToppFun for the functional enrichment analysis., Main Outcome Measures: The association between SNPs and MNV development in patients with CSC., Results: Rs370974631 near ARMS2 displayed a genome-wide significant association in the meta-analysis of discovery and replication result (hazard ratio [HR] meta , 3.63; P meta  = 5.76 × 10 -9 ). Among previously reported AMD susceptibility loci, we additionally identified CFH rs800292 (HR, 0.39, P = 2.55 × 10 -4 ), COL4A3 rs4276018 (HR, 0.26, P = 1.56 × 10 -3 ), and B3GALTL rs9564692 (HR, 0.56, P = 8.30 × 10 -3 ) as susceptibility loci for MNV development in CSC. The functional enrichment analysis revealed significant enrichment of 8 pathways (GO:0051561, GO:0036444, GO:0008282, GO:1990246, GO:0015272, GO:0030955, GO:0031420, and GO:0005242) related to ion transport., Conclusions: ARMS2, CFH, COL4A3, and B3GALTL were identified as susceptibility genes for MNV development in CSC. These 4 genes are known as susceptibility genes for AMD, whereas COL4A3 and B3GALTL were previously reported to be polypoidal choroidal vasculopathy (PCV)-specific susceptibility genes. Our findings revealed the shared genetic susceptibility between PCV and MNV secondary to CSC., (Copyright © 2022 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Among v-raf murine sarcoma viral oncogene homolog B1 inhibitors, vemurafenib causes a higher incidence of nephrotoxicity. Bai et al. reported that vemurafenib-induced nephrotoxicity is not directly caused by viral oncogene homolog B1 inhibition but is partly caused by ferrochelatase inhibition in renal tubular epithelial cells. Because several other protein kinase inhibitors are also known to cause ferrochelatase inhibition, further studies are needed to elucidate the role of ferrochelatase in renal function and injury., (Copyright © 2021 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

The main symptom of Parkinson's disease (PD) is motor dysfunction and remarkably approximately 30-40% of PD patients exhibit cognitive impairments. Recently, we have developed MF8, a heart-type fatty acid-binding protein (FABP3)-specific ligand, which can inhibit α-synuclein (α-syn) oligomerization induced by arachidonic acid in FABP3 overexpressing neuro2A cells. The present study aimed to determine whether MF8 attenuates dopaminergic neuronal death and motor and cognitive impairments in 1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (MPTP)-induced PD mice model. MF8 can penetrate the blood-brain barrier and its peak brain concentration (21.5 ± 2.1 nM) was achieved 6 h after the oral administration (1.0 mg/kg). We also compared its effects and pharmacological action with those of L-DOPA (3,4-dihydroxy-l-phenylalanine). PD model mice were developed by administering MPTP (25 mg/kg, i.p.) once a day for five consecutive days. Twenty-four hours after the final MPTP injection, mice were administered MF8 (0.3, 1.0 mg/kg, p.o.) or L-DOPA (25 mg/kg, i.p.) once a day for 28 consecutive days and subjected to behavioral and histochemical studies. MF8 (1.0 mg/kg, p.o.), but not L-DOPA, inhibited the dopaminergic neuronal death in the ventral tegmental area and the substantia nigra pars compacta region of the MPTP-treated mice. MF8 also improved both, motor and cognitive functions, while L-DOPA ameliorated only motor dysfunction. Taken together, our results showed that MF8 attenuated the MPTP-induced dopaminergic neuronal death associated with PD pathology. We present MF8 as a novel disease-modifying therapeutic molecule for PD, which acts via a mechanism different from that of L-DOPA., Competing Interests: Declaration of competing interest The authors have no conflicts of interest to declare., (Copyright © 2020 Elsevier Inc. All rights reserved.)

Tubular injury and interstitial fibrosis are the hallmarks of chronic kidney disease. While recent studies have verified that proximal tubular injury triggers interstitial fibrosis, the impact of fibrosis on tubular injury and regeneration remains poorly understood. We generated a novel mouse model expressing diphtheria toxin receptor on renal fibroblasts to allow for the selective disruption of renal fibroblast function. Administration of diphtheria toxin induced upregulation of the tubular injury marker Ngal and caused tubular proliferation in healthy kidneys, whereas administration of diphtheria toxin attenuated tubular regeneration in fibrotic kidneys. Microarray analysis revealed down-regulation of the retinol biosynthesis pathway in diphtheria toxin-treated kidneys. Healthy proximal tubules expressed retinaldehyde dehydrogenase 2 (RALDH2), a rate-limiting enzyme in retinoic acid biosynthesis. After injury, proximal tubules lost RALDH2 expression, whereas renal fibroblasts acquired strong expression of RALDH2 during the transition to myofibroblasts in several models of kidney injury. The retinoic acid receptor (RAR) RARγ was expressed in proximal tubules both with and without injury, and αB-crystallin, the product of an RAR target gene, was strongly expressed in proximal tubules after injury. Furthermore, BMS493, an inverse agonist of RARs, significantly attenuated tubular proliferation in vitro. In human biopsy tissue from patients with IgA nephropathy, detection of RALDH2 in the interstitium correlated with older age and lower kidney function. These results suggest a role of retinoic acid signaling and cross-talk between fibroblasts and tubular epithelial cells during tubular injury and regeneration, and may suggest a beneficial effect of fibrosis in the early response to injury., (Copyright © 2019 International Society of Nephrology. Published by Elsevier Inc. All rights reserved.)

Background: Although cardiac sarcoidosis is associated with poor prognosis, diagnosis of the disease is challenging and the sensitivity and specificity of diagnostic modalities are limited. This study was performed to evaluate the potential of serum microRNAs (miRNAs) as diagnostic biomarkers for cardiac sarcoidosis., Methods: We performed genome-wide expression profiling for 2565 miRNAs (Human-miRNA ver.21) using peripheral blood samples from 5 patients with cardiac sarcoidosis (61±9 years) and 3 healthy controls (54±7 years). From this screening study, we selected 12 miRNAs that were significantly related to cardiac sarcoidosis. Next, we performed real-time polymerase chain reaction (PCR) on blood samples from 15 new patients with cardiac sarcoidosis and 4 healthy controls to quantify the expression of these 12 miRNAs., Results: In the screening study, 12 miRNAs were differentially expressed (p<0.01) in all 5 patients with cardiac sarcoidosis, showing greater fold-change values (>4 or <0.25) compared with the expression in the 3 healthy controls. Analysis of the real-time PCR for blood samples from the other 15 patients and 4 controls using Mann-Whitney U tests revealed that the expression of miR-126 and miR-223 was significantly higher in the patients than in the healthy individuals. However, there were no differences in the expressions of miRNA-126 and miR-223 between patients with only cardiac lesions and those with extra-cardiac lesions., Conclusions: Our results demonstrate the potential of serum miR-126 and miR-223 as new-generation biomarkers for the differential diagnosis of cardiac sarcoidosis in patients with heart failure., (Copyright © 2018 Japanese College of Cardiology. Published by Elsevier Ltd. All rights reserved.)

Previous studies have reported genome-wide mutation profile analyses in ovarian clear cell carcinomas (OCCCs). This study aims to identify specific novel molecular alterations by combined analyses of somatic mutation and copy number variation. We performed whole exome sequencing of 39 OCCC samples with 16 matching blood tissue samples. Four hundred twenty-six genes had recurrent somatic mutations. Among the 39 samples, ARID1A (62%) and PIK3CA (51%) were frequently mutated, as were genes such as KRAS (10%), PPP2R1A (10%), and PTEN (5%), that have been reported in previous OCCC studies. We also detected mutations in MLL3 (15%), ARID1B (10%), and PIK3R1 (8%), which are associations not previously reported. Gene interaction analysis and functional assessment revealed that mutated genes were clustered into groups pertaining to chromatin remodeling, cell proliferation, DNA repair and cell cycle checkpointing, and cytoskeletal organization. Copy number variation analysis identified frequent amplification in chr8q (64%), chr20q (54%), and chr17q (46%) loci as well as deletion in chr19p (41%), chr13q (28%), chr9q (21%), and chr18q (21%) loci. Integration of the analyses uncovered that frequently mutated or amplified/deleted genes were involved in the KRAS/phosphatidylinositol 3-kinase (82%) and MYC/retinoblastoma (75%) pathways as well as the critical chromatin remodeling complex switch/sucrose nonfermentable (85%). The individual and integrated analyses contribute details about the OCCC genomic landscape, which could lead to enhanced diagnostics and therapeutic options., (Copyright © 2017 American Society for Investigative Pathology. Published by Elsevier Inc. All rights reserved.)

Kidney transplant recipients (KTRs) taking immunosuppressive drugs have a 20-fold greater risk of nontyphoidal Salmonella (NTS) infection than the healthy adult population. Among KTRs, the urinary tract is the most common site of infection. However, few cases of urinary tract infection caused by NTS have been documented in KTRs, and only one in Japan. Furthermore, it frequently induces acute allograft rejection with high mortality. Salmonella enterica subsp. enterica serovar Schwarzengrund (S. Schwarzengrund) is now among the more common Salmonella serovars isolated in Japan and is likely to be invasive. We present a case of a 45-year old female with vesicoureteral reflux to her transplanted kidney who developed kidney allograft pyelonephritis caused by S. Schwarzengrund. She was admitted to our hospital with fever, urodynia, lower abdominal pain, gross hematuria, and cloudy urine. Urine cultures were positive for S. Schwarzengrund. Exposure to cats, especially stray cats, were identified as the most likely source. We administered antibiotics for 4 weeks (ceftriaxone then amoxicillin, each for 2 weeks) and educated her about pet safety. She experienced no recurrence of infection or clinical kidney allograft rejection for 3 months post-treatment. NTS should be considered as a possible pathogen of urinary tract infection among KTRs, especially in cases with animal exposure or structural urologic abnormalities. When the pathogen is NTS, appropriate antibiotics and treatment periods are essential for preventing recurrence and allograft rejection after the completion of treatment., (Copyright © 2017 Japanese Society of Chemotherapy and The Japanese Association for Infectious Diseases. Published by Elsevier Ltd. All rights reserved.)

Purpose: Age-related macular degeneration (AMD) is the leading cause of severe visual impairment. Despite treatment, a central scotoma often remains. The size of the scotoma depends on the lesion size of the choroidal neovascular membrane and significantly affects the patient's quality of life, and the lesion size of neovascularization also affects response to treatments. The aim of this study was to identify genes associated with the neovascular lesion size in neovascular AMD., Design: A genome-wide association study (GWAS)., Participants: We included 1146 Japanese patients with neovascular AMD., Methods: We performed a 2-stage GWAS for the lesion size of AMD as a quantitative trait among 1146 (first stage: 727, second stage: 419) Japanese patients with neovascular AMD. Lesion size was determined by the greatest linear dimension measured with fluorescein angiography examination before treatment. We examined the association between the genotypic distribution of each single nucleotide polymorphism (SNP) and the trait using an additive model adjusted for age and sex. To evaluate the associations between AMD development and SNPs associated with lesion size, we also performed a case-control study by using the genotype data from these 1146 Japanese patients as case subjects and the fixed dataset from the Nagahama Study as control subjects., Main Outcome Measures: Genes associated with the lesion size in neovascular AMD., Results: In the discovery stage, rs10895322 in MMP20 showed a genome-wide significant P value of 6.95×10(-8), and rs2284665 in ARMS2/HTRA1 showed a P value of 1.55×10(-7). The associations of these 2 SNPs were successfully replicated in the replication stage, and a meta-analysis of both stages showed genome-wide significant P values (2.80×10(-9) and 4.41×10(-9), respectively). In a case-control study using 3248 Japanese subjects as controls, we could not find contribution of MMP20 rs10895322 for AMD development. Although MMP20 has been thought to be expressed only in dental tissues, we confirmed MMP20 expression in the human retina and retinal pigment epithelium/choroid with polymerase chain reaction., Conclusions: The growth of choroidal neovascularization in AMD would be affected by 2 genes: MMP20, a newly confirmed gene expressed in the retina, and ARMS2/HTRA1, a well-known susceptibility gene for AMD., (Copyright © 2015 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Purpose: To investigate the association between the vascular endothelial growth factor (VEGF) gene polymorphism and the response to anti-VEGF treatment for choroidal neovascularization (CNV) in highly myopic eyes., Design: Retrospective cohort study., Participants: A total of 357 unrelated highly myopic Japanese patients with axial lengths ≥26.0 mm in both eyes were eligible, and 83 patients who received anti-VEGF therapy for CNV and could be followed for more than 1 year were included., Methods: We genotyped a functional single nucleotide polymorphism in the VEGF gene, rs2010963. The associations between the distribution of the rs2010963 genotype and the number of eyes with maintained or improved visual acuity (VA) were analyzed. Furthermore, multivariable logistic regression analysis was performed to adjust for 7 possible prognostic factors, including age, sex, CNV size, CNV location, administration of loading dose, pretreatment VA, and number of additional treatments., Main Outcome Measures: The primary end point was maintenance of VA, and secondary end points were progression of chorioretinal atrophy (CRA) and recurrence of CNV., Results: Mean age and mean axial length were not significantly different among 3 genotypes of rs2010963. The percentage of eyes with maintained or improved VA was significantly higher with the G allele of rs2010963 (P =0.016), and stepwise analysis revealed that both rs2010963 and CNV size were associated with VA maintenance (P =0.040 and 0.033, respectively). The secondary analysis revealed that administration of a loading dose was significantly associated with both CRA progression (P =0.031) and recurrence of CNV (P =0.020), whereas rs2010963 was not., Conclusions: These results suggest that the VEGF polymorphism influences the VA prognosis in highly myopic eyes with CNV within 1 year after anti-VEGF treatment. This association was still observed after removing its confounding effect through CNV size. The rs2010963 polymorphism was not associated with CNV recurrence or CRA progression, which indicates that these changes are not tied to intrinsic factors and may be controllable by improving treatment methods., (Copyright © 2014 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

Background: Pathophysiological mechanisms of associations between airflow limitation (AL) and arterial stiffness remain unclear. One factor that might affect both AL and arterial stiffness is habitual smoking. The aim of this study is to investigate a possible interaction of smoking on the association between AL and arterial stiffness., Methods: Study subjects consisted of 8790 apparently healthy community residents. Airflow limitation was defined as a ratio of forced expiratory volume in 1 s (FEV1) to forced vital capacity of less than 70%. Brachial-to-ankle pulse wave velocity (baPWV) was used as an index of arterial stiffness. Smoking habit was investigated using a structured questionnaire., Results: Subjects with AL had significantly higher baPWV (AL 1381 ± 334, control 1261 ± 227 cm/s, p < 0.001). In a separate analysis by smoking habit, advanced arterial stiffness in AL was observed only in smokers (non-smokers: AL 1300 ± 220, control 1260 ± 218; smokers: AL 1436 ± 384, control 1264 ± 243 cm/s). Other clinical features of subjects with AL were older age; increased plasma hsCRP levels; and a high prevalence of male sex, hypertension, and smoking experience. Multiple linear regression analysis adjusted for these covariates identified the smoking × AL interaction as an independent determinant of baPWV (β = 0.066, p < 0.001). Conversely, baPWV was an independent determinant of AL in current and past smokers, but not in never smokers., Conclusions: AL arising from cigarette smoking, but not AL in non-smokers, was associated with arterial stiffness in a general population independently of established risk factors. Measurement of subclinical arterial change in smokers may be useful in identifying persons at risk for AL., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Background: Central blood pressure (cSBP) is suggested to be a better predictor of cardiovascular risk than brachial BP. Although brachial BP levels among smokers have been reported to be the same or somewhat lower than those in nonsmokers, it is suggested that smoking might have a substantial impact on cSBP., Methods: We conducted a cross-sectional study to clarify the association of smoking habit with arterial tone and cSBP in a general population of 8557 participants using urinary cotinine levels as an objective marker of smoking intensity. Absolute pressure of the late systolic peak (SBP2) was obtained by calibrating the radial waveform with brachial systolic BP (bSBP) and considered to be the cSBP., Results: Confounding factor-adjusted mean pulse pressure amplification (PPa = bSBP-cSBP) was significantly smaller in habitual smokers (current, 9.3 ± 0.15; past, 10.2 ± 0.13; never, 10.6 ± 0.10 mmHg; p<0.001). Further, among smokers, PPa was linearly decreased with increasing urinary cotinine quartile (Q1, 10.9 ± 0.38; Q2, 10.9 ± 0.39; Q3, 10.4 ± 0.39; Q4, 9.7 ± 0.41 mmHg; p = 0.020). Multiple linear regression analysis identified both smoking habit (p = 0.003) and urinary cotinine levels (p = 0.008) as independent determinants of PPa. Urinary cotinine was also detected in a small fraction of never smokers (1.8%). These passive smokers showed a smaller PPa (passive smoker, 9.4 ± 0.4; never smoker, 10.4 ± 0.12 mmHg, p = 0.020) but not bSBP (122.7 ± 0.6, 123.1 ± 0.2 mmHg, p = 0.474)., Conclusions: Not only habitual smoking but also passive smoking had harmful effects on AIx and central BP. Our results strongly emphasize the importance of avoiding passive smoking to the prevention of cardiovascular risks of which the subject is likely unaware., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Purpose: To investigate whether photodynamic therapy (PDT) outcomes of polypoidal choroidal vasculopathy (PCV) are related to baseline clinical characteristics, smoking history, or genetic factors by analyzing the retreatment-free period after the first PDT., Design: Retrospective cohort study., Participants: The study consisted of 167 patients with PCV who underwent PDT as their first treatment., Methods: We targeted 638 single nucleotide polymorphisms (SNPs) in 42 possible susceptible genes for age-related macular degeneration to evaluate their relation to the effectiveness of PDT for PCV. For this evaluation, we used 2 methods: (1) survival analysis, with the retreatment-free period as the target; and (2) logistic regression test between the need for additional therapy within 3 months after the first PDT and the genotypes, with age, gender, smoking status, and greatest linear dimension (GLD) at baseline as covariates. The contributions of smoking status and GLD at baseline for the retreatment-free period also were evaluated. Contributions of these factors to visual prognosis were evaluated for 1 year after PDT., Main Outcome Measures: Retreatment-free period after the first PDT for PCV. Secondary outcome measures included correlation of the susceptible factor to the retreatment requirement within the 3-month follow-up and the mean visual acuity change., Results: In survival analyses, SERPINF1 rs12603825 showed a significant association with the retreatment-free period after the first PDT; those patients homozygous for the minor allele A of rs12603825 received additional treatment after PDT within significantly shorter times than those with other genotypes (P = 0.0038). There was no significant difference in the retreatment-free period between baseline GLD and smoking status. Retreatment within 3 months was required significantly more in patients with the AA genotype, even after taking into consideration the effect of clinical characteristics (age, gender), baseline PCV lesion size, and smoking status (P = 0.0027). Furthermore, patients with the AA genotype showed significantly worse visual prognosis after PDT (P = 0.013)., Conclusions: Pigment epithelium-derived factor (SERPINF1 or PEDF) polymorphisms may influence the initial response to and visual prognosis after PDT for PCV. Our findings may lead to understanding the pathogenesis of PCV and modification of the effects of PDT., (Copyright © 2011 American Academy of Ophthalmology. Published by Elsevier Inc. All rights reserved.)

We developed a novel diagnostic system for continuous peritoneal dialysis, which evaluates the peritoneal permeability and hydraulic conductance (peritoneal function) by applying the kinetic model and a clinical test with minimum nursing time. Kinetic parameters for the peritoneal function were determined by the simultaneous numerical optimization techniques (SNOT). Furthermore dialysis outcome and ultrafiltration volume were estimated and predicted by using the kinetic model with a set of optimal kinetic parameters, which were in agreement with measured data (r(2)>0.82). The clinical implementation of the SNOT is very useful to explore the better prescriptions for each patient's clinical condition.

Antibodies against citrullinated proteins are highly specific for rheumatoid arthritis. We previously reported that functional variants of the gene encoding peptidylarginine deiminase type 4 were closely associated with RA. The purpose of this study was to investigate the citrullinated autoantigens recognized by serum samples from patients with RA. The human chondrocyte cDNA expression library was citrullinated by PADI4 and was immunoscreened with anti-modified citrulline antibodies and sera from patients with rheumatoid arthritis. One immunoreactive cDNA clone containing a 2480-base pair insert was isolated and sequence analysis revealed that the cDNA included a part of the eukaryotic translation initiation factor 4G1. Immunoreactivity against a recombinant citrullinated eIF4G1 fragment was observed with high specificity in 50.0% of RA patients. The levels of antibodies against citrullinated eIF4G1 were correlated with those of anti-CCP antibodies. Citrullinated eIF4G1 was identified as a candidate citrullinated autoantigen in RA patients. Citrullination of eIF4G1 may thus be involved in the pathogenesis of RA.

The authors developed a computer-aided diagnosis system that includes a simple clinical test for the chronic renal disease patient who needs an integrated approach that combines both peritoneal dialysis and hemodialysis (PD-HD therapy). In this case study, the system simulated and estimated the dialysis outcome, the ultrafiltration volume and nutritional analysis by employing a pharmacokinetic model, and assessed the peritoneal permeable enhancement that can be a grave complication with peritoneal dialysis. This system requires only a minimum amount of nursing time and may be able to predict the optimal treatment schedule for PD-HD therapy and provide therapeutic monitoring in long-term peritoneal dialysis.

Rheumatoid arthritis (RA) is one of the most common autoimmune diseases, but its autoimmune mechanisms are not clearly understood. Recently, anti-citrullinated peptide antibodies have been specifically observed in sera of RA patients. Furthermore, we identified RA-susceptible variant in a gene encoding citrullinating enzyme, peptidylarginine deiminase type 4 (PADI4). Therefore, we hypothesized that proteins which are modified in RA synovium by PADI4 act as autoantigens. Subsequently, we obtained human collagen type I (huCI) as one of the autoantigens using a RA synoviocyte cDNA library by immunoscreening. We also investigated that the levels of anti-citrullinated huCI were significantly higher in RA patient sera than in normal control sera with high specificity (99%) and positively correlated with the levels of anti-cyclic citrullinated peptide (anti-CCP) antibodies. We concluded that huCI is a novel substrate protein of PADIs and that citrullinated huCI is a candidate autoantigen of RA.

Inflammatory diseases encompass a variety of medical conditions. In this chapter, autoimmune diseases and allergic disorders will be our focus. The autoimmune diseases include organ-specific autoimmunities, such as type I diabetes mellitus and autoimmune thyroiditis (AITD), and organ non-specific disorders such as systemic lupus erythematosus (SLE). All of them seem to share aspects of aberrant immunologic tolerance toward self-antigens. Asthma and atopic diathesis are among the allergies. Crohn disease and SLE are relatively rare with a prevalence of 10-50 per 100,000, and rheumatoid arthritis (RA), psoriasis, AITD and asthma are commoner with a prevalence of 500 per 100,000 or much higher. The difference among ethnic groups is not prominent for rheumatoid arthritis, psoriasis, AITD or asthma, but Crohn disease and SLE affect some ethnic populations more than others. Although all of these disorders have some environmental component, asthma and atopy seem most affected by environmental factors, as is suggested by the significant increase in their incidence over the last several decades with changes in various environmental factors, especially in developed countries. Over the last 10 years, multiple linkage studies revealed many disease-linked loci throughout the genome with various consistencies. As implicated by some pathophysiological studies of inflammatory immune system related disorders, certain loci are involved in multiple disorders. In the following sections, reports on the identification of disease-associated genes or markers will be summarized for individual diseases (cytotoxic T lymphocyte-associated 4 (CTLA4), CARD15, DLG5, SLC22A4/A5, programmed cell death 1 (PDCD1), RUNX1, SLC9A3R1/NAT9, PADI4, ADAM33, DPP10, PHF11 and GPRA), followed by a discussion of the genes that have been implicated in multiple disorders.

Anticitrullinated peptide antibodies seem to be one of the most clinically reliable serologic markers for rheumatoid arthritis (RA). A genetic approach revealed that one of the citrullinating enzymes has a RA-susceptible variant. Peptidyl citrullination alters the chemical character of peptides and, subsequently, their antigenicity as well. This change in antigenicity of self-peptides seems to invoke citrulline-related autoimmunity. Although the precise physiologic role of citrullination is still unknown, accumulating data indicate that citrullination has a definite role in biologic phenomena, along with other posttranslational protein modifications, such as methylation and phosphorylation. In RA synovial tissue, two of five PADI isotypes are known to be expressed, and their expression is regulated at multiple steps: transcription, translation, intracellular localization, and activation/inactivation of PADI proteins. Further investigations on citrulline and PADIs from various aspects will provide a more profound understanding of RA-related autoimmunity.

In the sera of rheumatoid arthritis (RA) patients, autoantibodies directed to citrullinated proteins are found with high specificity for RA. Peptidylarginine deiminases (PADIs) are enzymes responsible for protein citrullination. Among many isoforms of PADIs, only PADI4 has been identified as an RA-susceptibility gene. To understand the mechanisms of the initiation and progression of RA, we compared the properties of two PADIs, human PADI2 and human PADI4, which are present in the synovial tissues of RA patients. We confirmed their precise distribution in the RA synovium and compared the stability, Ca2+ dependency, optimal pH range, and substrate specificity. Small but significant differences were found in the above-mentioned properties between hPADI2 and hPADI4. Using LC/MS/MS analysis, we identified the sequences in human fibrinogen indicating that hPADI2 and hPADI4 citrullinate in different manners. Our results indicate that hPADI2 and hPADI4 have different roles under physiological and pathological conditions. Further studies are needed for the better understanding of the role of hPADIs in the initiation and progression of RA.