Myeloid cell-derived coagulation tissue factor is associated with renal tubular damage in mice fed an adenine diet.

Patients with chronic kidney disease (CKD) commonly exhibit hypercoagulability. Increased levels of uremic toxins cause thrombogenicity by increasing tissue factor (TF) expression and activating the extrinsic coagulation cascade. TF is induced in monocytes and macrophages under pathological conditions, such as inflammatory diseases. However, the role of monocyte myeloid cell TF in CKD progression remains unclear. We aimed to clarify this issue, and the present study found that patients with CKD had elevated levels of D-dimer, a marker of fibrin degradation, which was associated with decreased estimated glomerular filtration rate and increased serum levels of uremic toxins, such as indoxyl sulfate. In vitro studies showed that several uremic toxins increased cellular TF levels in monocytic THP-1 cells. Mice with TF specifically deleted in myeloid cells were fed an adenine diet to cause uremic kidney injury. Myeloid TF deletion reduced tubular injury and pro-inflammatory gene expression in the kidneys of adenine-induced CKD but did not improve renal function as measured by plasma creatinine or blood urea nitrogen. Collectively, our findings suggest a novel concept of pathogenesis of coagulation-mediated kidney injury, in which elevated TF levels in monocytes under uremic conditions is partly involved in the development of CKD.

Nicotinamide Attenuates the Progression of Renal Failure in a Mouse Model of Adenine-Induced Chronic Kidney Disease.

Nicotinamide adenine dinucleotide (NAD+) supplies energy for deoxidation and anti-inflammatory reactions fostering the production of adenosine triphosphate (ATP). The kidney is an essential regulator of body fluids through the excretion of numerous metabolites. Chronic kidney disease (CKD) leads to the accumulation of uremic toxins, which induces chronic inflammation. In this study, the role of NAD+ in kidney disease was investigated through the supplementation of nicotinamide (Nam), a precursor of NAD+, to an adenine-induced CKD mouse model. Nam supplementation reduced kidney inflammation and fibrosis and, therefore, prevented the progression of kidney disease. Notably, Nam supplementation also attenuated the accumulation of glycolysis and Krebs cycle metabolites that occurs in renal failure. These effects were due to increased NAD+ supply, which accelerated NAD+-consuming metabolic pathways. Our study suggests that Nam administration may be a novel therapeutic approach for CKD prevention.

Protease-activated receptor 2 contributes to placental development and fetal growth in mice.

BACKGROUND: Protease-activated receptor 2 (PAR2) is activated by serine proteases such as coagulation tissue factor/VIIa complex, factor Xa or trypsin and is pro-angiogenic in several disease models. Impaired angiogenesis in placenta causes placental dysfunction and fetal growth restriction. PAR2 is expressed in the placenta trophoblast. However, the role of PAR2 in pregnancy remains unknown. OBJECTIVE: The present study aimed to examine the role of PAR2 in placental development and fetal growth using a murine model. METHODS: PAR2-/- or PAR2+/+ mice in the ICR background were used. Female PAR2-/- mice were mated with male PAR2-/- mice, and female PAR2+/+ mice were mated with male PAR2+/+ mice to obtain PAR2-/- and PAR2+/+ fetuses, respectively. The day a virginal plug was observed in the morning was determined as 0.5-day post-coitum (dpc). Pregnant mice were sacrificed on 13.5 or 18.5 dpc to collect samples. RESULTS: A deficiency of PAR2 significantly reduced the fetal and placental weight and impaired placental labyrinth development in mice on 18.5 dpc. Collagen IV expression in placenta labyrinth was smaller in PAR2 knockout mice compared to that of wild-type mice. A deficiency of PAR2 also reduced the expression levels of genes related to angiogenesis and coagulation in placenta. CONCLUSION: Our data suggest that PAR2 is required for fetal growth and angiogenesis in the placenta and is thus important for a normal pregnancy.

Kidney function, blood pressure and proteinuria were associated with pregnancy outcomes of pregnant women with chronic kidney disease: a single-center, retrospective study in the Asian population.

BACKGROUND: Studies among pregnant Asian women with chronic kidney disease (CKD) have not been widely performed; therefore, clinical criteria for these patients have not been well established. METHODS: We conducted a retrospective study among pregnant women with CKD who received prenatal care at our institution for 8 consecutive years. Primary outcome was the development of severe adverse events (SAEs). We analyzed correlations between primary outcome and CKD parameters [age, body mass index (BMI), estimated glomerular filtration rate (eGFR), urinary protein-creatinine ratio (UP), systolic blood pressure (SBP), diastolic blood pressure (DBP), and not normal blood pressure (non-NBP)] at the time of referral. Secondary outcomes were low birth weight (LBW), preterm delivery (PreD), and small for gestational age (SGA). We divided into two categories, CKD stage G1, and G2 or higher according to eGFR, and proteinuria negative and proteinuria positive according to UP, respectively. RESULTS: We observed 89 pregnancies. SAE was observed in 28 pregnancies. In live birth cases, there were 28 PreD, 28 LBW and 13 SGA. Major SAEs included preeclampsia, superimposed preeclampsia, unscheduled cesarean section, neonatal intensive care unit admission, and fetal death. Stepwise logistic regression analysis selected eGFR (OR = 0.847, p = 0.026), SBP (OR = 1.897, p = 0.006) and proteinuria positive (OR = 2.96, p = 0.046) as the significant predictors of SAEs. There were no significant differences among the baseline characteristics stratified by SGA. CONCLUSIONS: This is the first study to report pregnancy outcomes among Japanese non-disease-oriented patients with CKD. In Asians, especially in the Japanese population, kidney function, blood pressure and proteinuria might affect pregnancy outcomes.

Dual blockade of protease-activated receptor 1 and 2 additively ameliorates diabetic kidney disease.

Protease-activated receptors (PARs) are coagulation protease targets, and they increase expression of inflammatory cytokines and chemokines in various diseases. Of all PARs, previous reports have shown that PAR1 or PAR2 inhibition is protective against diabetic glomerular injury. However, how PAR1 and PAR2 cooperatively contribute to diabetic kidney disease (DKD) pathogenesis and whether dual blockade of PARs is more effective in DKD remain elusive. To address this issue, male type I diabetic Akita mice heterozygous for endothelial nitric oxide synthase were used as a model of DKD. Mice (4 mo old) were divided into four treatment groups and administered vehicle, PAR1 antagonist (E5555, 60 mg·kg-1·day-1), PAR2 antagonist (FSLLRY, 3 mg·kg-1·day-1), or E5555 + FSLLRY for 4 wk. The results showed that the urinary albumin creatinine ratio was significantly reduced when both PAR1 and PAR2 were blocked with E5555 + FSLLRY compared with the vehicle-treated group. Dual blockade of PAR1 and PAR2 by E5555 + FSLLRY additively ameliorated histological injury, including mesangial expansion, glomerular macrophage infiltration, and collagen type IV deposition. Marked reduction of inflammation- and fibrosis-related gene expression in the kidney was also observed. In vitro, PAR1 and PAR2 agonists additively increased mRNA expression of macrophage chemoattractant protein 1 or plasminogen activator inhibitor-1 in human endothelial cells. Changes induced by the PAR1 agonist were blocked by a NF-κB inhibitor, whereas those of the PAR2 agonist were blocked by MAPK and/or NF-κB inhibitors. These findings suggest that PAR1 and PAR2 additively contribute to DKD pathogenesis and that dual blockade of both could be a novel therapeutic option for treatment of patients with DKD.

Biallelic variants/mutations of IL1RAP in patients with steroid-sensitive nephrotic syndrome.

Nephrotic syndrome (NS) is a renal disease characterized by severe proteinuria and hypoproteinemia. Although several single-gene mutations have been associated with steroid-resistant NS, causative genes for steroid-sensitive NS (SSNS) have not been clarified. While seeking to identify causative genes associated with SSNS by whole-exome sequencing, we found compound heterozygous variants/mutations (c.524T>C; p.I175T and c.662G>A; p.R221H) of the interleukin-1 receptor accessory protein (IL1RAP) gene in two siblings with SSNS. The siblings' parents are healthy, and each parent carries a different heterozygous IL1RAP variant/mutation. Since IL1RAP is a critical subunit of the functional interleukin-1 receptor (IL-1R), we investigated the effect of these variants on IL-1R subunit function. When stimulated with IL-1ß, peripheral blood mononuclear cells from the siblings with SSNS produced markedly lower levels of cytokines compared with cells from healthy family members. Moreover, IL-1R with a variant IL1RAP subunit, reconstituted on a hematopoietic cell line, had impaired binding ability and low reactivity to IL-1ß. Thus, the amino acid substitutions in IL1RAP found in these NS patients are dysfunctional variants/mutations. Furthermore, in the kidney of Il1rap-/- mice, the number of myeloid-derived suppressor cells, which require IL-1ß for their differentiation, was markedly reduced although these mice did not show significantly increased proteinuria in acute nephrotic injury with lipopolysaccharide treatment. Together, these results identify two IL1RAP variants/mutations in humans for the first time and suggest that IL1RAP might be a causative gene for familial NS.

Glomerular Injury Is Exacerbated in Lupus-Prone MRL/lpr Mice Treated with a Protease-Activated Receptor 2 Antagonist.

Systemic lupus erythematosus (SLE) is characterized by the production of autoantibodies, which causes multi-organ injury such as lupus nephritis. SLE is associated with hypercoagulability. Activated coagulation factors such as tissue factor and VIIa complex and factor Xa activate protease-activated receptor 2 (PAR2). PAR2 promotes cytokine production through mitogen-activated protein kinase or nuclear factor kappa B signaling, and previous reports demonstrated that inhibition of PAR2 alleviated kidney injuries such as diabetic kidney disease and renal fibrosis in animal models. However, the involvement of PAR2 in the pathogenesis of SLE remains unclear. We therefore administered a selective PAR2 peptide antagonist, FSLLRY-NH2, to SLE-prone 4-month-old MRL-Faslpr mice for 4 weeks. Treatment with FSLLRY-NH2 caused the significant increases in the glomerular mesangial proliferation, glomerular deposition of both immunoglobulin G and complement factor C3d, and glomerular infiltration of Mac2-positive macrophages and CD3-positive T cells, compared with MRL-Faslpr mice treated with saline. In addition, the treatment with the PAR2 antagonist increased renal expression levels of tumor necrosis factor-α (Tnfa) and monocyte chemoattractant protein 1 (Mcp1) mRNA. Collectively, these results suggest that inhibition of PAR2 may increase the severity of inflammation in lupus nephritis; namely, opposite to previous observations, PAR2 has anti-inflammatory properties. We propose that activation of PAR2 could serve as a potential therapeutic option for patients with SLE.

A Catastrophic Case of Idiopathic Cholesterol Crystal Embolism with Multiple Lethal Complications: A Labyrinth Underneath the Diagnosis of Skin Ulcers in Chronic Kidney Disease Patients.

A 66-year-old man was admitted to our hospital because of multiple refractory skin ulcers. Based on his severe systemic arterial calcification and severe calcium-phosphate imbalance due to severe kidney dysfunction, we initially considered calciphylaxis. However, a skin biopsy provided a diagnosis of cholesterol crystal embolization. Although we initiated hemodialysis, steroid treatment, and low-density lipoprotein-cholesterol apheresis, he died of multiple intestinal perforation. An autopsy showed cholesterol crystals occluding multiple organ arterioles. This case suggests that skin ulcers in patients with chronic kidney disease may be an important diagnostic hallmark and may be associated with several serious diseases.