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This study examines the current status of and issues related to “peer interactions and collaborative learning” in regular schools from the standpoint of special schools. We conducted a case study on two special schools and derived the following four interpretations: first, as children transition from elementary to junior high school, they experience limited peer interactions and collaborative learning; second, individual integration depends on parents’ wishes and the availability of transportation; third, the quality of peer interactions and collaborative learning depends on the awareness and structure of teachers in regular schools; fourth, the implementation and search for implementation methods have been affected by the coronavirus disease 2019 pandemic. Although there are many issues yet to be addressed, the fact that peer interactions and collaborative learning are being encouraged in special schools to promote inclusive education needs to be positively evaluated

This study aimed to analyze the incidence of subclinical rejection (SCR) in kidney transplantation patients and risk factors associated with SCR.We assessed 80 protocol biopsies taken within 2 years postoperatively in 41 adult patients who underwent living donor kidney transplantation between 2017 and 2020. All patients were on immunosuppressant therapy that included tacrolimus, mycophenolate mofetil, and steroids.The prevalence of Banff Borderline classification at 3, 6, and 12 months after transplantation was 4%, 5%, and 8 %, respectively, whereas none of the biopsies met the Banff criteria for acute T cell-mediated rejection throughout the study period. Active antibody-mediated rejection (ABMR) was only present in 8% of patients at 3 months after transplantation and chronic active ABMR at 6, 12, and 24 months after transplantation was detected in 10%, 13%, and 11% of the patients, respectively. Subgroup analysis revealed that 50% of the 6 patients with preformed anti-donor specific antibodies (DSAs) developed clinical or subclinical active ABMR within 3 months after transplantation, followed by chronic active ABMR according to serial histologic assessment. Conversely, only a small proportion of patients (3%) without preformed DSAs exhibited clinically active ABMR.SCR occurs too infrequently in patients with low immunologic risk and strong contemporary immunosuppression therapy to justify the diagnostic effort of serial protocol biopsies. However, protocol biopsies remain an indispensable tool in renal transplant monitoring and may be especially important in immunologically high-risk patients with pre-existing DSAs.

We explored a case study focusing on social development and leaning of elementary school students with developmental disabilities through self-reliance activities in a special needs classes. Before the classes started, we conducted a series of assessment to identify special education needs of the students. Based on the results of the assessment, we set goals of the self-reliance activities for each student, and also considered contents and approaches of the classes. With self-reliance activities including small-group game sessions, the students showed meaningful improvement in their communication and interpersonal behaviors. We examined and analyzed the result of the case study, comparing such factors as student’s behaviors, contents and approaches of the self-reliance activities, and sharing information on special education needs of the students before and after the classes.

The purpose of this study was to examine specific factors of students with medical needs related with psychosomatic disorders in the junior high school and high school sections of special needs schools, was to compare factors including stressor, stress response, cognitive appraisal, coping, and source of social support between students with and without disabilities, and was to clarify interactions among these factors. Results revealed that 74.13% of the students with disabilities experienced school non-attendance, received a diagnosis of psychosomatic disorders, and showed characteristics on developmental disabilities as their basic disabilities. It was also found there was strongly positive correlations between stress response and factors including “depression\anxiety,” “grumpy\angry,” and “physical symptoms” in the students with medical needs, compared to those without disabilities, which seemed to be specifically related to psychosomatic disorders. It was clarified that junior high school and high school students with psychosomatic disabilities could experience physical symptoms when trying to cope with stressful situations, and they also could easily become anxious when trying to ask others for assistance, which could result in conditions where they cannot achieve an appropriate stress-buffering effect.

Background Short-term treatment for people with type 2 diabetes using a low dose of the selective endothelin A receptor antagonist atrasentan reduces albuminuria without causing significant sodium retention. We report the long-term effects of treatment with atrasentan on major renal outcomes.Methods We did this double-blind, randomised, placebo-controlled trial at 689 sites in 41 countries. We enrolled adults aged 18-85 years with type 2 diabetes, estimated glomerular filtration rate (eGFR) 25-75 mL/min per 1.73 m(2) of body surface area, and a urine albumin-to-creatinine ratio (UACR) of 300-5000 mg/g who had received maximum labelled or tolerated renin-angiotensin system inhibition for at least 4 weeks. Participants were given atrasentan 0.75 mg orally daily during an enrichment period before random group assignment. Those with a UACR decrease of at least 30% with no substantial fluid retention during the enrichment period (responders) were included in the double-blind treatment period. Responders were randomly assigned to receive either atrasentan 0.75 mg orally daily or placebo. All patients and investigators were masked to treatment assignment. The primary endpoint was a composite of doubling of serum creatinine (sustained for >= 30 days) or end-stage kidney disease (eGFR = 90 days, chronic dialysis for >= 90 days, kidney transplantation, or death from kidney failure) in the intention-to-treat population of all responders. Safety was assessed in all patients who received at least one dose of their assigned study treatment. The study is registered with ClinicalTrials. gov, number NCT01858532.Findings Between May 17, 2013, and July 13, 2017, 11 087 patients were screened; 5117 entered the enrichment period, and 4711 completed the enrichment period. Of these, 2648 patients were responders and were randomly assigned to the atrasentan group (n=1325) or placebo group (n=1323). Median follow-up was 2.2 years (IQR 1.4-2.9). 79 (6.0%) of 1325 patients in the atrasentan group and 105 (7.9%) of 1323 in the placebo group had a primary composite renal endpoint event (hazard ratio [HR] 0.65 [95% CI 0.49-0.88]; p=0.0047). Fluid retention and anaemia adverse events, which have been previously attributed to endothelin receptor antagonists, were more frequent in the atrasentan group than in the placebo group. Hospital admission for heart failure occurred in 47 (3.5%) of 1325 patients in the atrasentan group and 34 (2.6%) of 1323 patients in the placebo group (HR 1.33 [95% CI 0.85-2.07]; p=0.208). 58 (4.4%) patients in the atrasentan group and 52 (3.9%) in the placebo group died (HR 1.09 [95% CI 0.75-1.59]; p=0.65).Interpretation Atrasentan reduced the risk of renal events in patients with diabetes and chronic kidney disease who were selected to optimise efficacy and safety. These data support a potential role for selective endothelin receptor antagonists in protecting renal function in patients with type 2 diabetes at high risk of developing end-stage kidney disease. Copyright (C) 2019 Elsevier Ltd. All rights reserved.

TAFRO (Thrombocytopenia, Anasarca, Fever and/or elevated C-reactive protein, Renal dysfunction or Reticulin fibrosis, and Organomegaly) syndrome is a unique systemic inflammatory disease, which has recently been proposed from Japan. We report a case showing TAFRO symptoms, the patient’s condition of which allowed histopathological examinations of several biopsy tissues including the kidney. A 37-year-old man was admitted to our hospital for evaluation of fever of unknown origin, pleural effusion and ascites, renal dysfunction, and lymphadenopathy. Serum IL-6 and VEGF were elevated. Histopathologic findings of the lymph node resembled those of mixed type Castleman disease. The bone marrow biopsy specimen revealed normocellular marrow with a mildly increased number of megakaryocytes, but without obvious fibrosis. The renal biopsy material showed glomerular microangiopathy with double contour of the capillary loops and mesangiolysis. In immunohistochemistry, VEGF was retained in podocytes, whereas IL-6 expression was not limited to the specific sites. Glomerular microangiopathy is regarded as a crucial change in TAFRO syndrome, which should be studied further with regard to VEGF and IL-6.

A 77-year-old man presented with a fever, non-productive cough, and edema formation. A laboratory analysis showed an elevated creatinine level (2.5 mg/dL), a high titer of myeloperoxidase (MPO)-anti-neutrophil cytoplasmic antibody (ANCA) (99 U/mL), positive reaction for antinuclear antibody (×320), hematuria, and massive proteinuria (3.33 g/day). A renal biopsy revealed crescentic and necrotizing glomerulonephritis (GN) with membranoproliferative GN features [double contour appearance of the glomerular basement membrane, granular deposition of immunoglobulin (Ig) G, IgM, and C3 along the capillary wall, subendothelial and subepithelial deposits with mesangial interposition]. A potential relationship between MPO-ANCA associated GN and membranoproliferative GN is discussed.

A 61-year-old man was transferred to our hospital with the complaints of dizziness, severe nausea and abdominal discomfort after consuming approximately 50 g of the flowers of Rhododendron japonicum. On admission, hypotension and sinus bradycardia were evident. Symptoms including hypotension and bradycardia completely recovered within 12 hours following normal saline infusion and intravenous atropine. The ingestion of certain types of Rhododendron species can cause intoxication, referred to as "mad honey poisoning", due to the action of grayanotoxins. This is the first local case of acute intoxication caused by Rhododendron japonicum.

Background The management of renal anemia in the pre-dialysis period has been remarkably improved by long-acting erythropoiesis-stimulating agents (ESA). However, many incident dialysis patients cannot achieve target hemoglobin (Hb) levels (> 10 g/dL) and sometimes require blood transfusions. Anemia at the time of dialysis initiation is reportedly correlated with cardiomegaly and early cardiovascular events. Here, we investigated whether this V-shaped depression in Hb level at dialysis initiation adversely affects short-term prognosis. Methods The medical charts of 166 patients who underwent initial dialysis were retrospectively reviewed for Hb level, ESA treatment status, dry weight (DW), cardiothoracic rate (CTR), and brain natriuretic peptide (BNP) level at dialysis initiation and 1 year later. Patients were subdivided into three groups according to the tertile of Hb levels. The risk of mortality within 1 year after initiation was analyzed using multivariable-adjusted Cox proportional hazard model. Result Mean Hb level at initiation was 8.6 ± 1.3 g/dL despite the administration of sufficient ESA. After initiation, Hb levels rapidly increased and the Hb time course showed a V-shape with the bottom at initiation. Hb level, CTR, and log BNP showed a significant negative correlation. The Hb level and CTR 1 year after initiation did not correlate with Hb levels at initiation. Lower Hb levels at initiation as a V-shaped depression do not adversely affect 1-year mortality rate by multivariable-adjusted Cox proportional hazard model. Conclusion Hb level around dialysis initiation showed a V-shaped depression despite ESA use. Our findings suggest that the V-shaped Hb depression at initiation does not affect short-term prognosis.

An 88-year-old woman presented with fever and acute posterior neck pain. A CT scan revealed calcification of the transverse ligament and crown-like calcification around the odontoid process. According to the clinical and radiological findings, she was diagnosed with crowned dens syndrome (CDS). Her symptoms drastically improved following treatment with oral nonsteroidal anti-inflammatory medication. An X-ray of her wrist, elbow, shoulder and knee joints showed asymptomatic calcium deposits, suggesting underlying crystalline deposition disease. CDS may occur as the initial presentation of crystalline deposition disease. The measurement of procalcitonin and an X-ray survey of the major joints may be helpful for the diagnosis of CDS.

Background The parathyroid gland secretes 1-84 and 7-84 parathyroid hormone (PTH) fragments, and its regulation is dependent on stimulation of the extracellular calcium-sensing receptor. While the intact PTH system detects both PTH fragments, the whole PTH system detects the 1-84PTH but not the 7-84PTH. Cinacalcet hydrochloride (CH) binds to calcium-sensing receptor as a calcimimetic. Here we investigated the role of CH treatment in the assessment of parathyroid gland function. Methods Stable adult dialysis patients for whom CH therapy was planned were included. Patients for whom CH therapy was not planned were simultaneously included as the control group. Results The CH group (n = 44) showed significantly higher circulating levels of Ca, intact PTH, and whole PTH, before the CH treatment than the control group (n = 112). The Ca, intact PTH, and whole PTH levels decreased along with the CH therapy, and the Ca levels became comparable in the 8th week of treatment and thereafter. The CH group in the 8th week and thereafter showed significantly lower whole/intact PTH ratios than the control group, while the whole/intact PTH ratio was not significantly different between before and during the CH therapy. A multiple regression analysis revealed that the whole/intact PTH ratio was almost constant, but both the serum Ca level and a CH therapy could potentially modify the fixed number. When the whole PTH levels were estimated by intact PTH levels using the relationship between them in the control group, the levels were clearly overestimated in the CH group. Conclusions Although the direct effect of CH on the whole/intact PTH ratio is masked by its hypocalcemic action, we could successfully demonstrate that the ratio in CH users is lower than that in the non-users with comparable levels of serum Ca. Evaluating parathyroid function with intact PTH according to the clinical practice guidelines in patients being treated with CH may lead to significant overestimation and subsequent overtreatment.

Glomerulonephropathy is a rare complication of Takayasu's arteritis (TA). To date, most glomerulonephropathies associated with TA show the histological feature of mesangial proliferation. Membranous glomerulonephropathy (MG) is a form of glomerulonephropathy in which the mesangial proliferation is not conspicuous and its association with TA is extremely rare. A 54-year-old man was referred to our hospital due to progressive edema in the lower limbs and nephrotic range proteinuria. Five years previously, he underwent percutaneous angioplasty for left subclavian artery stenosis. Kidney biopsy revealed stage II MG. General examination including enhanced CT scan confirmed the presence of TA. He started oral prednisolone therapy at a dose of 40 mg daily. The C-reactive protein level normalized 7 days after the prednisolone therapy. Three months later, proteinuria had remitted. Though the true relationship between MG and TA was not revealed in present case, considering the fact that complete remission of nephrotic syndrome occurred following the improvement of C-reactive protein level in response to steroid therapy, TA might be the secondary cause of MG. To our best knowledge, only two case reports described the association of MG and TA previously. Those two patients, however, also demonstrated the feature of systemic lupus erythematosus in addition to TA. This is the first case report that describes a patient who presented as MG associated with TA, but not complicated by systemic lupus erythematosus.

We report a case of acquired factor V inhibitors (AFVIs) in a patient with end-stage renal disease receiving warfarin therapy for atrial fibrillation. A 72-year-old Japanese man was admitted to our hospital complaining of tarry stools and abdominal pain. The laboratory findings revealed eosinophilia (52.1%), prolonged activated partial thromboplastin time (APTT) (98 s), PT (84 s), a factor V (FV) activity of

Short bowel syndrome (SBS) is characterized by a malabsorptive state. It is conceivable that the coexistence of SBS and end-stage renal disease can lead to severe metabolic acidosis; however, such a condition has rarely been documented. We herein describe the case of a 64-year-old man with SBS who required maintenance hemodialysis. Persistent metabolic acidosis and mineral and bone disorders should be of particular concern in hemodialyzed patients with SBS.

Dipeptidyl peptidase-4 inhibitors (DPP-4i) have become widely used in hemodialysis patients with type 2 diabetes mellitus (T2DM). This study aimed at testing the hypothesis that administration of alogliptin, a DPP-4i, soon after hemodialysis initiation improves beta cell function in hemodialysis patients with T2DM. Patients with end-stage renal disease and T2DM (n = 10) not previously treated with DPP-4i (mean age, 54.2 years) were enrolled. The study end point was the acute insulin response to glucose assessed by a frequently sampled intravenous glucose tolerance test (IVGTT) that was conducted during the hemodialysis session just before lunch using an external circulation circuit. All patients received 6.25 mg alogliptin for 2 weeks. Blood glucose (Glu), serum insulin (IRI), and C-peptide (CPR) were measured before (0 min) in addition to 5 and 15 min after the glucose load. Glucagon-like peptide-1 (GLP-1) was measured before the glucose load. Glu(0) significantly decreased after the 2-week DPP-4i treatment (174 ± 20 vs. 150 ± 27 mg/dL, P = 0.023). IRI(5) significantly increased after the DPP-4i treatment (14.6 ± 31.7 vs. 23.4 ± 16.6 μU/mL, P = 0.038), but IRI(0) and IRI(15) did not change significantly. GLP-1 also significantly increased after the DPP-4i treatment (6.6 ± 4.4 vs. 2.6 ± 0.8 pmol/L, P = 0.012). Inhibition of DPP-4 with alogliptin improved endogenous insulin secretion in response to intravenous glucose in hemodialysis patients with T2DM.

A 61-year-old man was transferred to our hospital with the complaints of dizziness, severe nausea and abdominal discomfort after consuming approximately 50 g of the flowers of Rhododendron japonicum. On admission, hypotension and sinus bradycardia were evident. Symptoms including hypotension and bradycardia completely recovered within 12 hours following normal saline infusion and intravenous atropine. The ingestion of certain types of Rhododendron species can cause intoxication, referred to as "mad honey poisoning", due to the action of grayanotoxins. This is the first local case of acute intoxication caused by Rhododendron japonicum.

Eosinophilic granulomatous with polyangiitis (EGPA) is systemic vasculitis characterized by concomitant symptoms of asthma, allergic rhinitis, and marked increase in peripheral eosinophilia. It was previously known as Churg-Strauss syndrome. EGPA incidence in Japan is very low, with only approximately 1,800 cases reported. Renal involvement occurs in approximately 20-25% of EGPA patients, and the most typical expression is pauciimmune crescentic glomerulonephritis. We herein report a case of 69-year-old Japanese woman with fever and high titer of myeloperoxidase-antineutrophil cytoplasmic antibodies (MPO-ANCA) and eosinophilia. Her renal biopsy showed massive interstitial nephritis with granulomatous vasculitis like lesion without apparent active crescent formation in glomeruli. Immediately after steroid treatment (prednisolone [PSL] 30 mg/day), she had symptomatic relief and was discharged with a reduction in MPO-ANCA.

OBJECTIVE Megalin, an endocytic receptor in proximal tubule cells, is involved in the mechanisms of albuminuria in diabetic nephropathy (DN). To develop efficient novel biomarkers associated with the pathogenesis of DN, we investigated urinary megalin excretion in type 2 diabetes. RESEARCH DESIGN AND METHODS Sandwich enzyme-linked immunosorbent assay systems were established with monoclonal antibodies against the NH2 (amino [A]-megalin assay) and COOH (C-megalin assay) termini of megalin to analyze urinary forms of megalin in 68 patients with type 2 diabetes. RESULTS The A-megalin assay mainly detected a megalin ectodomain form in the soluble urinary fraction, whereas the C-megalin assay identified a full-length form in both soluble and insoluble fractions. Urinary C-megalin levels were significantly high in patients with normoalbuminuria, were elevated in line with increased albuminuria, and showed a better association with estimated glomerular filtration rate (eGFR) ( CONCLUSIONS Urinary full-length megalin excretion as measured by the C-megalin assay is well associated with reduced eGFR and linked to the severity of DN, phosphate dysregulation, and anemia, whereas urinary excretion of megalin ectodomain as measured by the A-megalin assay may be associated with distinctive mechanisms of earlier DN in type 2 diabetes.

Receptor-mediated endocytosis is a pivotal function of renal proximal tubule epithelial cells (PTECs) to reabsorb and metabolize substantial amounts of proteins and other substances in glomerular filtrates. The function accounts for the conservation of nutrients, including carrier-bound vitamins and trace elements, filtered by glomeruli. Impairment of the process results in a loss of such substances and development of proteinuria, an important clinical sign of kidney disease and a risk marker for cardiovascular disease. Megalin is a multiligand endocytic receptor expressed at clathrin-coated pits of PTEC, playing a central role in the process. Megalin cooperates with various membrane molecules and interacts with many intracellular adaptor proteins for endocytic trafficking. Megalin is also involved in signaling pathways in the cells. Megalin-mediated endocytic overload leads to damage of PTEC. Further studies are needed to elucidate the mechanism of megalin-mediated endocytosis and develop strategies for preventing the damage of PTEC.

Impairment of proximal tubular endocytosis of glomerular-filtered proteins including albumin results in the development of proteinuria/albuminuria in patients with chronic kidney disease. However, the mechanisms regulating the proximal tubular function are largely unknown. This study aimed to investigate the role of angiotensin II type 1A receptor (AT1AR)- and insulin-mediated signaling pathways in regulating the expression of megalin, a multiligand endocytic receptor in proximal tubule cells (PTCs). Opossum kidney PTC-derived OK cells that stably express rat AT1AR but are deficient in endogenous angiotensin II receptors (AT1AR-OK cells) were used for this study. Treatment of the cells with angiotensin II suppressed mRNA and protein expression of megalin at 3- and 24-h incubation time points, respectively. Cellular uptake and degradation of albumin and receptor-associated protein, megalin’s endocytic ligands were suppressed 24 h after angiotensin II treatment. The AT1AR-mediated decrease in megalin expression was partially prevented by ERK inhibitors. Insulin competed with the AT1AR-mediated ERK activation and decrease in megalin expression. Inhibitors of phosphatidylinositol 3-kinase (PI3K), a major component of insulin signaling, also suppressed megalin expression, and activation of the insulin receptor substrate (IRS)/PI3K system was prevented by angiotensin II. Collectively the AT1AR-mediated ERK signaling is involved in suppressing megalin expression in the OK cell line, and insulin competes with this pathway. Conversely, the insulin-IRS/PI3K signaling, with which angiotensin II competes, tends to stimulate megalin expression. In conclusion, there is AT1AR- and insulin-mediated competitive signaling cross talk to regulate megalin expression in cultured PTCs.Angiotensin II type 1A receptor- and insulin-mediated competitive signaling cross-talk regulates the expression of megalin, a multi-ligand endocytic receptor, in cultured proximal tubule cells.

Background/Aims: Mutations of the endosomal chloride/proton exchanger gene, CLCN5, cause Dent’s disease, an X-linked recessive proximal tubular disorder. The renal endocytic system was found to be affected in clcn5 knockout mice. However, the impaired endocytic machinery of Dent’s disease patients has not been thoroughly investigated. Methods: The CLCN5 gene was sequenced in a Japanese patient with Dent’s disease and his family. The loss-of-function phenotype of the missense CLCN5 mutation was investigated by gene expression in Xenopus oocytes and CHO cells. Immunohistochemical analysis was performed on kidney biopsy specimens for endocytic machinery proteins, megalin, cubilin, and disabled-2 (Dab2) in proximal tubules. Results: Genomic analysis revealed a novel G-to-A transition at the first nucleotide of the 333rd codon of CLCN5, causing a substitution of glycine with arginine. Inefficient expression of the mutant gene in Xenopus oocytes resulted in abolished chloride currents. Impaired N-glycosylation of the mutant protein was evident in the DNA-transfected CHO cells. Proximal tubular expression of megalin, cubilin, and Dab2 was markedly reduced and irregular staining in some portions was observed in the patient compared with controls. Conclusions: A novel G333R CLCN5 mutation caused defective expression of megalin, cubilin, and Dab2 in a patient with Dent’s disease.

Megalin is expressed at the apical membranes of proximal tubule cells, acting as an endocytic receptor for a variety of ligands filtered by glomeruli. Megalin, also known as a Ca(2+)-binding receptor, is thought to be involved in systemic and intrarenal calcium and phosphate homeostasis. The complex of 25(OH)D(3) and vitamin D-binding protein is endocytosed via megalin into proximal tubule cells, leading to the activation of 25(OH)D(3) to 1, 25(OH)D(3) in the cells. Megalin knockout mice revealed impaired osteogenesis due to vitamin D deficiency. Megalin is also involved in the metabolism of parathyroid hormone and the regulation of the sodium phosphate cotransporter NaPi-IIa. Decreased expression of megalin may be associated with the pathogenesis of hyperphosphaturia observed in patients with Dent's disease. Further studies will elucidate more detailed roles of megalin in pathological states and the mechanisms for interacting with other molecules for the endocytic functions.

Megalin is an endocytic receptor on the apical membranes of proximal tubule cells (PTC) in the kidney, and is involved in the reabsorption and metabolism of various proteins that have been filtered by glomeruli. Patients with diabetes, especially type 2 diabetes, or metabolic syndrome are likely to have elevated serum levels of advanced glycation end products, liver-type fatty acid binding protein, angiotensin II, insulin and leptin, and renal metabolism of these proteins is potentially overloaded. Some of these proteins are themselves nephrotoxic, while others are carriers of nephrotoxic molecules. Megalin is involved in the proximal tubular uptake of these proteins. We hypothesize that megalin-mediated metabolic overload in PTC leads to compensatory cellular hypertrophy and sustained Na+ reabsorption, causing systemic hypertension and glomerular hyperfiltration via tubuloglomerular feedback, and named this as 'protein metabolic overload hypothesis'. Impaired metabolism of bioactive proteins such as angiotensin II and insulin in PTC may enhance hypertrophy of PTC and/or Na+ reabsorption. Sleep apnoea syndrome, a frequent complication of diabetes and metabolic syndrome, may cause renal hypoxia and result in relative overload of protein metabolism in the kidneys. The development of strategies to identify patients with diabetes or metabolic syndrome who are at high risk for renal metabolic overload would allow intensive treatment of these patients in an effort to prevent the development of nephropathy. Further studies on the intracellular molecular signalling associated with megalin-mediated metabolic pathways may lead to the development of novel strategies for the treatment of nephropathies related to diabetes and metabolic syndrome.

Liver-type fatty acid binding protein (L-FABP) binds with high affinity to hydrophobic molecules including free fatty acid, bile acid and bilirubin, which are potentially nephrotoxic, and is involved in their metabolism mainly in hepatocytes. L-FABP is released into the circulation, and patients with liver damage have an elevated plasma L-FABP level. L-FABP is also present in renal tubules; however, the precise localization of L-FABP and its potential role in the renal tubules are not known. In this study, we examined the cellular and subcellular localization of L-FABP in the rat kidney and tried to determine from where the L-FABP in kidney tissues had originated. Immunohistochemical studies of kidney sections localized L-FABP in the lysosomes of proximal tubule cells (PTC). In rats with carbon tetrachloride (CCl4)-induced acute liver injury, we detected high levels of L-FABP in the circulation and in the kidney compared with those in the control rat by immunoblotting, while reverse transcription-polymerase chain reaction showed that the level of L-FABP mRNA expression in the kidney of CCl4-treated rats was low and did not differ from that in the control rat. When 35S-L-FABP was intravenously administered to rats, the kidneys took up 35S-L-FABP more preferentially than the liver and heart, and histoautoradiography of kidney sections revealed that 35S-L-FABP was internalized via the apical domains of PTC. Quartz-crystal microbalance analysis revealed that L-FABP bound to megalin, a multiligand endocytotic receptor on PTC, in a Ca2+-dependent manner. Degradation assays using megalin-expressing rat yolk sac tumor-derived L2 cells demonstrated that megalin mediated the cellular uptake and catabolism of 125I-L-FABP. In conclusion, circulatory L-FABP was found to be filtered by glomeruli and internalized by PTC probably via megalin-mediated endocytosis. These results suggest a novel renal uptake pathway for L-FABP, a carrier of hydrophobic molecules, some of which may exert nephrotoxic effects.

Podocalyxin (PC) is the major sialoglycoprotein expressed on the apical membrane of the podocyte. Previously it was shown that PC is connected to actin through the PC/NHERF2/ezrin complex, and this connection is disrupted in the nephrotic syndrome. For assessing whether expression of PC affects the organization of the actin cytoskeleton, MDCK cell lines stably expressing either full-length PC or a PC mutant lacking the NHERF binding site was established. It was found that full-length PC but not the PC mutant is connected to actin, induces redistribution of actin toward the apical membrane, and leads to increased RhoA activity. By immunofluorescence redistribution of RhoA and RhoGDI was observed in the presence of both full-length PC and the PC mutant. With the use of pulldown assays, PC and ezrin were found to interact directly and the ezrin binding site was mapped to the juxtamembrane region of PC’s cytoplasmic tail. It is concluded that PC binds to ezrin both directly and indirectly. PC activates RhoA through NHERF and ezrin, leading to redistribution of actin filaments. These results suggest that in podocytes, PC may also regulate foot process architecture through RhoA.

Leptin is secreted by adipocytes and is a circulating factor that regulates food intake and energy expenditure. Its serum level is elevated in patients with renal failure and has been suggested to be associated with malnutritional factors in these patients. Leptin has been suggested to be primarily metabolized by the kidneys, although the precise molecular mechanisms are not known. The purpose of this study was to determine the nephron segments and potential receptors involved in renal leptin metabolism. To determine the segment involved in leptin uptake, we performed histoautoradiography of kidney sections obtained from rats that had been injected iv with 125 I-leptin. The ability of megalin, a multiligand endocytic receptor in the proximal tubules, to bind and endocytose leptin was examined by ligand blotting analysis, quartz-crystal microbalance, and degradation assays using megalin-expressing rat yolk sac L2 cells. Immunohistochemistry was performed to localize leptin receptors (LEP-R) in the rat kidney using two antibodies that recognize different epitopes on the LEP-R proteins. Circulating 125 I-leptin was filtered by glomeruli and internalized by proximal convoluted tubules. Megalin bound leptin in the presence of Ca 2 and mediated its cellular internalization and degradation. On immunohistochemistry, LEP-R were localized in the proximal straight tubules, loops of Henle, distal tubules, and collecting ducts. In conclusion, circulating leptin was filtered by glomeruli and taken up by proximal convoluted tubules, where megalin likely mediates its binding and uptake. The localization of LEP-R suggests that they are not primarily involved in leptin metabolism in the proximal tubules. (Endocrinology 145: 3935–3940, 2004)

Megalin is an endocytic receptor that binds multiple ligands and is essential for many physiological processes such as brain development and uptake of proteins by the kidney tubule, yolk sac, and thyroid. The cytoplasmic tail of megalin contains two FXNPXY motifs. Autosomal recessive hypercholesterolemia (ARH) is an adaptor protein that binds to the FXNPXY motif of the low-density lipoprotein receptor as well as clathrin and AP-2. We found that ARH also binds to the first FXNPXY motif of megalin in two-hybrid, pull-down and coimmunoprecipitation assays. ARH colocalizes with megalin in clathrin coated pits and in recycling endosomes in the Golgi region. When cells are treated with nocodazole, the recycling endosomes containing megalin and ARH disperse. On internalization of megalin, ARH and megalin are first seen in clathrin coated pits followed by sequential localization in early endosomes and tubular recycling endosomes in the pericentriolar region followed by their reappearance at the cell surface. Expression of ARH in Madin-Darby canine kidney cells expressing megalin mini-receptors enhances megalin-mediated uptake of125I-lactoferrin, a megalin ligand. These results show that ARH facilitates endocytosis of megalin, escorts megalin along its endocytic route and raise the possibility that transport through the endosomal system is selective and requires interaction with specific adaptor proteins.

During development, glomerular visceral epithelial cells, or podocytes, undergo extensive morphologic changes necessary for the creation of the glomerular filter. These changes include formation of interdigitating foot processes, replacement of tight junctions with slit diaphragms, and the concomitant opening of filtration slits. It was postulated previously and confirmed recently that podocalyxin, a sialomucin, plays a major role in keeping the urinary space open by virtue of the physicochemical properties of its highly negatively charged ectodomain. By a cell aggregation assay, the expression level of podocalyxin correlated closely with the anti-adhesion effect. Treatment of the cells with sialidase reversed the inhibitory effect of podocalyxin, indicating that sialic acid residue is required for inhibition of cell adhesion. In addition to its ectodomain, the highly conserved cytoplasmic tail of podocalyxin may contribute to the unique organization of podocytes. By immunocytochemistry, it was shown that two cytosolic adaptor proteins, Na(+)/H(+)-exchanger regulatory factor 2 (NHERF2) and ezrin, colocalize with podocalyxin along the apical plasma membrane of podocytes, where they form a co-immunoprecipitable complex. Moreover, the podocalyxin/NHERF2 /ezrin complex interacts with the actin cytoskeleton, and this interaction is disrupted in pathologic conditions associated with changes in the foot processes, indicating its importance in maintaining the unique organization of this epithelium. Further studies will be needed to identify the signaling molecules responsible for the regulation of this complex in podocyte damage.

Advanced glycation end products (AGE) are filtered by glomeruli and reabsorbed and metabolized by proximal tubule cells (PTC). In renal failure, decreased renal AGE metabolism likely accounts for the accumulation in serum that is related to uremic complications. In diabetes, AGE generation is increased, and the handling mechanisms in PTC are likely associated with the pathogenesis of tubulointerstitial injury. It is therefore important to clarify the mechanisms of the AGE metabolism to develop a strategy for removing AGE in uremia and to elucidate the pathogenesis of diabetic nephropathy. To this end, this study focused on the molecular analysis of megalin, a multi-ligand endocytic receptor, in PTC. AGE uptake analysis was performed using the rat yolk sac-derived L2 cell line system established for the analysis of megalin's endocytic functions. The cells mediated specific internalization and degradation of AGE, which were significantly blocked by anti-megalin IgG, indicating that megalin is involved in the cellular processes. However, cell surface AGE-binding assays and ligand blot analysis revealed no evidence that megalin is a direct AGE receptor. Affinity chromatography and ligand blot analysis originally revealed that 200-kD and 400-kD proteins in the cells bind to AGE and the 200-kD protein to megalin in a Ca(2+)-dependent manner. The binding of megalin with the 200-kD protein was suppressed by receptor-associated protein (RAP), a ligand for megalin. In conclusion, megalin functions for endocytosis of AGE via an indirect mechanism. L2 cells express novel AGE-binding proteins, one of which may interact with megalin.

A 62-year-old-Japanese man had a history of probable granulomatosis with polyangiitis (GPA) from 7 years previously, showing kidney and vasculitis symptoms with PR3-ANCA (864 EU) without renal biopsy. Remission with normalization of renal function and urinary findings was induced by corticosteroid therapy. Prednisolone (PSL) was tapered to 5 mg/day and maintained for 6.5 years with a low positive titer of PR3-ANCA. After 7 years of remission, he was referred to our hospital because of arthralgia, fever, general fatigue and appetite loss with apparent urinary abnormality, increased serum Cr (1.8 mg/dL) and C reactive protein (CRP : 30.1 mg/dL). On admission, he showed a high titer of PR3-ANCA (300 U/mL). Renal biopsy demonstrated the existence of the pauci-immune type of severe crescentic necrotizing glomerulonephritis, tubulo-interstitial damage and perivascular granuloma. He was diagnosed as relapse of GPA (kidney-localized type) without upper respiratory tract (E) and lung (L) symptoms. Accordingly, he received steroid pulse therapy leading to improvement of these symptoms and renal function. Oral PSL at the dosage of 40 mg/day was administered after steroid pulse therapy, and then tapered to 20 mg/day. Cyclophosphamide was added within 8 weeks. He was discharged 8 weeks after treatment with a decreased level of Cr (1.5 mg/dL) and PR3-ANCA (244 U/mL). After discharge, PSL was tapered to 10 mg/day during the course of stability resulting in a further improved level of Cr (1.2 mg/dL), PR3-ANCA 40 U/mL in the outpatient clinic. In Japan, PR3-ANCA-positive GPA has a lower incidence than MPO-ANCA-positive microscopic vasculitis. In GPA, the kidney-localized (K) type without upper respiratory tract (E, L) symptoms is rare. Histologically, not only necrotizing crescentic glomerulonephritis but also perivascular granuloma in the kidney are very rare and interesting.

The origin of crescent forming cells in human glomerulonephritis (GN) remains unknown. Some animal studies demonstrated that parietal epithelial cells of Bowman’s capsule (PECs) were the main component of proliferating cells and PEC-specific tight junction protein claudin-1 was expressed in crescentic lesions. We investigated the expression of claudin-1 in human GN. Immunohistochemistry for claudin-1 was performed on 17 kidney biopsy samples with crescent formation. Colocalization of claudin-1 with intracellular tight junction protein ZO-1 was also evaluated by immunofluorescence double staining. Claudin-1 is expressed mainly at the cell to cell contact site of proliferating cells in cellular crescentic lesions in patients with these forms of human GN. Small numbers of crescent forming cells showed extrajunctional localization of claudin-1. Colocalization of claudin-1 with ZO-1 was found at cell to cell contact sites of adjacent proliferating cells. In control samples, staining of claudin-1 was positive in PECs, but not in podocytes. Our findings suggest that claudin-1 contributes to crescent formation as a component of the tight junction protein complex that includes ZO-1. Co-localization of claudin-1 with ZO-1 implies the formation of functional tight junction complexes in crescentic lesions to prevent the interstitial damage caused by penetration of filtered molecules from Bowman’s space.

Gαi3 is found both on the plasma membrane and on Golgi membranes. Calnuc, an EF hand protein, binds both Gαi3 and Ca 2+ and is found both in the Golgi lumen and in the cytoplasm. To investigate whether Gαi3 binds calnuc in living cells and where this interaction takes place we performed fluorescence resonance energy transfer (FRET) analysis between Gαi3 and calnuc in COS-7 cells expressing Gαi3-yellow fluorescent protein (YFP) and calnuc-cyan fluorescent protein (CFP). The tagged proteins have the same localization as the endogenous, nontagged proteins. When Gαi3-YFP and calnuc-CFP are coexpressed, a FRET signal is detected in the Golgi region, but no FRET signal is detected on the plasma membrane. FRET is also seen within the Golgi region when Gαi3 is coexpressed with cytosolic calnuc(ΔN2–25)-CFP lacking its signal sequence. No FRET signal is detected when Gαi3(ΔC12)-YFP lacking the calnuc-binding region is coexpressed with calnuc-CFP or when Gαi3-YFP and calnuc(ΔEF-1,2)-CFP, which is unable to bind Gαi3, are coexpressed. Gαi3(G2AC3A)-YFP lacking its lipid anchors is localized in the cytoplasm, and no FRET signal is detected when it is coexpressed with wild-type calnuc-CFP. These results indicate that cytosolic calnuc binds to Gαi3 on Golgi membranes in living cells and that Gαi3 must be anchored to the cytosolic surface of Golgi membranes via lipid anchors for the interaction to occur. Calnuc has the properties of a Ca 2+ sensor protein capable of binding to and potentially regulating interactions of Gαi3 on Golgi membranes.