Yuji Oe

Metabolic alterations by indoxyl sulfate in skeletal muscle induce uremic sarcopenia in chronic kidney disease

Sarcopenia is associated with increased morbidity and mortality in chronic kidney disease (CKD). Pathogenic mechanism of skeletal muscle loss in CKD, which is defined as uremic sarcopenia, remains unclear. We found that causative pathological mechanism of uremic sarcopenia is metabolic alterations by uremic toxin indoxyl sulfate. Imaging mass spectrometry revealed indoxyl sulfate accumulated in muscle tissue of a mouse model of CKD. Comprehensive metabolomics revealed that indoxyl sulfate induces metabolic alterations such as upregulation of glycolysis, including pentose phosphate pathway acceleration as antioxidative stress response, via nuclear factor (erythroid-2-related factor)-2. The altered metabolic flow to excess antioxidative response resulted in downregulation of TCA cycle and its effected mitochondrial dysfunction and ATP shortage in muscle cells. In clinical research, a significant inverse association between plasma indoxyl sulfate and skeletal muscle mass in CKD patients was observed. Our results indicate that indoxyl sulfate is a pathogenic factor for sarcopenia in CKD.

Reduced Uterine Perfusion Pressure (RUPP) Model of Preeclampsia in Mice

Preeclampsia (PE) is a pregnancy-induced hypertension with proteinuria that typically develops after 20 weeks of gestation. A reduction in uterine blood flow causes placental ischemia and placental release of anti-angiogenic factors such as sFlt-1 followed by PE. Although the reduced uterine perfusion pressure (RUPP) model is widely used in rats, investigating the role of genes on PE using genetically engineered animals has been problematic because it has been difficult to make a useful RUPP model in mice. To establish a RUPP model of PE in mice, we bilaterally ligated ovarian vessels distal to ovarian branches, uterine vessels, or both in ICR-strain mice at 14.5 days post coitum (dpc). Consequently, these mice had elevated BP, increased urinary albumin excretion, severe endotheliosis, and mesangial expansion. They also had an increased incidence of miscarriage and premature delivery. Embryonic weight at 18.5 dpc was significantly lower than that in sham mice. The closer to the ligation site the embryos were, the higher the resorption rate and the lower the embryonic weight. The phenotype was more severe in the order of ligation at the ovarian vessels < uterine vessels < both. Unlike the RUPP models described in the literature, this model did not constrict the abdominal aorta, which allowed BP to be measured with a tail cuff. This novel RUPP model in mice should be useful for investigating the pathogenesis of PE in genetically engineered mice and for evaluating new therapies for PE.

Coagulation Factor Xa and Protease-Activated Receptor 2 as Novel Therapeutic Targets for Diabetic Nephropathy

Objective—The role of hypercoagulability in the pathogenesis of diabetic nephropathy (DN) remains elusive. We recently reported the increased infiltration of macrophages expressing tissue factor in diabetic kidney glomeruli; tissue factor activates coagulation factor X (FX) to FXa, which in turn stimulates protease-activated receptor 2 (PAR2) and causes inflammation. Approach and Results—Here, we demonstrated that diabetes mellitus increased renal FX mRNA, urinary FXa activity, and FX expression in glomerular macrophages. Administration of an oral FXa inhibitor, edoxaban, ameliorated DN with concomitant reductions in the expression of PARs (Par1 and Par2) and of proinflammatory and profibrotic genes. Diabetes mellitus induced PAR2, and lack of Par2 ameliorated DN. FXa or PAR2 agonist increased inflammatory cytokines in endothelial cells and podocytes in vitro. Conclusions—We conclude that enhanced FXa and PAR2 exacerbate DN and that both are promising targets for preventing DN. Alleviating inflammation is probably more important than inhibiting coagulation per se when treating kidney diseases using anticoagulants.

Nicotinamide benefits both mothers and pups in two contrasting mouse models of preeclampsia

Significance Preeclampsia (PE), high blood pressure and protein in the urine in the last third of pregnancy, complicates about 1 in 20 human pregnancies, and it is one of the leading causes of pregnancy-related maternal deaths. The only definitive treatment, induced delivery, invariably results in premature babies. Blood pressure-lowering drugs help, but results in preventing preterm delivery and correcting the fetal growth restriction (FGR) that also occurs in PE have been disappointing. Here we show that feeding high doses of nicotinamide, a vitamin, improves the maternal condition, prolongs pregnancies, and prevents FGR in mice having PE-like conditions due to two contrasting causes. Because nicotinamide benefits both mothers and pups, it merits evaluation for preventing or treating PE in humans. Preeclampsia (PE) complicates ∼5% of human pregnancies and is one of the leading causes of pregnancy-related maternal deaths. The only definitive treatment, induced delivery, invariably results in prematurity, and in severe early-onset cases may lead to fetal death. Many currently available antihypertensive drugs are teratogenic and therefore precluded from use. Nonteratogenic antihypertensives help control maternal blood pressure in PE, but results in preventing preterm delivery and correcting fetal growth restriction (FGR) that also occurs in PE have been disappointing. Here we show that dietary nicotinamide, a nonteratogenic amide of vitamin B3, improves the maternal condition, prolongs pregnancies, and prevents FGR in two contrasting mouse models of PE. The first is caused by endotheliosis due to excess levels in the mothers of a soluble form of the receptor for vascular endothelial growth factor (VEGF), which binds to and inactivates VEGF. The second is caused by genetic absence of Ankiryn-repeat-and-SOCS-box–containing-protein 4, a factor that contributes to the differentiation of trophoblast stem cells into the giant trophoblast cells necessary for embryo implantation in mice; its absence leads to impaired placental development. In both models, fetal production of ATP is impaired and FGR is observed. We show here that nicotinamide decreases blood pressure and endotheliosis in the mothers, probably by inhibiting ADP ribosyl cyclase (ADPRC), and prevents FGR, probably by normalizing fetal ATP synthesis via the nucleotide salvage pathway. Because nicotinamide benefits both dams and pups, it merits evaluation for preventing or treating PE in humans.

Heavy chain deposition disease: an overview

Heavy chain deposition disease (HCDD) is one of three entities of monoclonal immunoglobulin deposition disease, characterized histopathologically by the presence of nodular glomerulosclerosis and glomerular and tubular deposition of monoclonal heavy chains without associated light chains. Although HCDD is an extremely rare disease, >30 cases have been reported to date in the literature. Of these cases, only three cases have been reported in Japan. The majority of the patients presents with nephrotic syndrome, hematuria, and hypertension, and develop progressive renal failure with or without the complication of multiple myeloma. Some cases have been treated successfully using chemotherapy. Because of its rarity, a thorough understanding of HCDD is essential for both accurate diagnosis and adequate subsequent treatment.

Protease–activated receptor 2 exacerbates adenine–induced renal tubulointerstitial injury in mice

Hypercoagulability is associated with chronic kidney disease (CKD). Tissue factor/factor VIIa complex and factor Xa in the coagulation cascade are known to activate protease-activated receptor 2 (PAR2), and to cause inflammation and tissue injury. Although PAR2 is highly expressed in the kidney, it is unclear whether PAR2 plays a pathogenic role in CKD. To test this, we fed the mice lacking Par2 (F2rl1-/-) and wild type (F2rl1+/+) mice with adenine diet to induce tubulointerstitial injury, a hallmark of CKD. Adenine-treated mice showed severe renal dysfunction, tubular atrophy, and fibrosis. Fibrin deposition and the expression of tissue factor and PARs markedly increased in their kidneys. Lack of Par2 attenuated renal histological damage and reduced the expression levels of genes related to inflammation, fibrosis, and oxidative stress. Our data indicate that PAR2 is critically important in the pathogenesis of adenine-induced tubular injury. PAR2 antagonists under development could be useful to treat and prevent CKD.

Impact of the Oral Adsorbent AST-120 on Organ-Specific Accumulation of Uremic Toxins: LC-MS/MS and MS Imaging Techniques

Elevated circulating uremic toxins are associated with a variety of symptoms and organ dysfunction observed in patients with chronic kidney disease (CKD). Indoxyl sulfate (IS) and p-cresyl sulfate (PCS) are representative uremic toxins that exert various harmful effects. We recently showed that IS induces metabolic alteration in skeletal muscle and causes sarcopenia in mice. However, whether organ-specific accumulation of IS and PCS is associated with tissue dysfunction is still unclear. We investigated the accumulation of IS and PCS using liquid chromatography/tandem mass spectrometry in various tissues from mice with adenine-induced CKD. IS and PCS accumulated in all 15 organs analyzed, including kidney, skeletal muscle, and brain. We also visualized the tissue accumulation of IS and PCS with immunohistochemistry and mass spectrometry imaging techniques. The oral adsorbent AST-120 prevented some tissue accumulation of IS and PCS. In skeletal muscle, reduced accumulation following AST-120 treatment resulted in the amelioration of renal failure-associated muscle atrophy. We conclude that uremic toxins can accumulate in various organs and that AST-120 may be useful in treating or preventing organ dysfunction in CKD, possibly by reducing tissue accumulation of uremic toxins.

OS 21-08 NOVEL REDUCED UTERINE PERFUSION PRESSURE (RUPP) MODEL OF PREECLAMPSIA IN MICE.

Objective: Preeclampsia (PE) is a pregnancy-induced hypertension with proteinuria that typically develops after 20 weeks of gestation. A reduction in uterine blood flow causes placental ischemia and placental release of anti-angiogenic factors such as soluble fms-like tyrosine kinase (sFlt-1) followed by PE. Although the reduced uterine perfusion pressure (RUPP) model is widely used in rats, investigating the genetics of PE has been problematic because it has been difficult to make a useful RUPP model in mice. The aim of the present study is to establish a novel PE model using an improved RUPP method in mice. Design and Method: As shown in the Figure 1B, we bilaterally ligated ovarian vessels distal to ovarian branches, uterine vessels, or both in ICR-strain mice at 14.5 days post coitum (dpc). BP, renal phenotype and pregnancy outcome were analyzed. Results: Unlike the RUPP models described in the literature, this model did not constrict the abdominal aorta, which allowed BP to be measured with a tail cuff. RUPP in mice had elevated BP, increased urinary albumin excretion, severe endotheliosis, and mesangial expansion. They also had an increased incidence of miscarriage and premature delivery. Embryonic weight at 18.5 dpc was significantly lower than that in sham mice. The closer to the ligation site the embryos were, the higher the resorption rate and the lower the embryonic weight. The phenotype was more severe in the order of ligation at the ovarian vessels < uterine vessels < both. Conclusions: We developed a novel RUPP mouse model that recapitulates the phenotype of PE. This model is expected to be useful for investigating pathogenesis of PE in genetically engineered mice and for evaluating new therapies for PE.

Proliferative glomerulonephritis with monoclonal IgM-κ deposits in chronic lymphocytic leukemia/small lymphocytic leukemia: case report and review of the literature

A 48-year-old man with chronic lymphocytic leukemia presented with nephrotic syndrome, hematuria, and mild deterioration of renal function. Further analysis using serum immunofixation electrophoresis detected monoclonal immunoglobulin (Ig) M-κ and IgG-κ M-protein. Testing for cryoglobulin in serum was negative. Light microscopy of a renal biopsy specimen showed membranoproliferative glomerulonephritis features with marked mononuclear cell infiltration in the interstitium. On immunofluorescence study, the deposition of IgM heavy chain was predominantly observed with the same distribution of κ light chain, whereas no λ light chain was found. Electron microscopy revealed fine granular deposits in the mesangial, subendothelial, and subepithelial areas, mimicking those observed in the immune complex-mediated glomerulonephritis. These pathological findings were consistent with recently described cases of proliferative glomerulonephritis with monoclonal IgG deposits. Thus, monoclonal IgM deposition can also cause proliferative glomerulonephritis.

Nicotinamide ameliorates a preeclampsia-like condition in mice with reduced uterine perfusion pressure

Preeclampsia (PE) is pregnancy-induced hypertension with proteinuria that typically develops after 20 wk of gestation. Antihypertensives currently used for PE reduce blood pressure of PE mothers but do not prevent preterm delivery and do not alleviate fetal growth restriction (FGR) associated with PE. We have recently shown that the activation of the endothelin (ET) system exacerbates PE. However, ET receptor antagonists are teratogenic and not suitable for pregnant women. The vitamin B3 nicotinamide (Nam) inhibits vasoconstriction by ET and is generally considered safe and harmless to babies. Nam also alleviates oxidative stress, which exacerbates PE and FGR. The aim of the present study was to evaluate therapeutic effects of Nam on the PE-like phenotype using a reduced uterine perfusion pressure (RUPP) model in mice that we have recently developed. We bilaterally ligated uterine vessels of pregnant mice and administered Nam or water daily by gavage. Nam improved maternal hypertension, proteinuria, and glomerular endotheliosis in RUPP mice. Moreover, Nam prolonged pregnancies and improved survival and growth of the embryos in RUPP PE mice. In conclusion, Nam alleviates the PE-like phenotype and FGR in the murine RUPP model. Nam could help treat maternal hypertension and FGR in human PE.