Effectiveness and safety of Tolvaptan in infants with congenital heart disease.

BACKGROUND: Tolvaptan (TLV) is a selective vasopressin receptor 2 antagonist administered for congestive heart failure (CHF) after inadequate response to other diuretics. The effectiveness and safety of TLV have been evaluated well in adult patients. However, reports on its use in pediatric patients, especially infants, are scarce. METHODS: We retrospectively evaluated 41 children younger than 1 year of age who received TLV for CHF for congenital heart disease (CHD) between January 2010 and August 2021. We monitored the occurrence of adverse events, including acute kidney injury and hypernatremia, as well as laboratory data trends. RESULTS: Of the 41 infants included, 51.2% were male. The median age when TLV was initiated was 2 months, interquartile range (IQR) 1-4 months, and all infants had been administered other diuretics previously. The median dose of TLV was 0.1 mg/kg/day (IQR, 0.1-0.1). Urine output increased significantly after 48 h of treatment: baseline, 315 mL/day (IQR, 243-394); 48 h, 381 mL/day (IQR, 262-518) , p = 0.0004; 72 h, 385 mL/day (IQR, 301-569), p = 0.0013; 96 h, 425 mL/day (IQR, 272-524), p = 0.0006; and 144 h, 396 mL/day (IQR, 305-477), p = 0.0036. No adverse events were observed. CONCLUSIONS: Tolvaptan can be used safely and efficiently in infants with CHD. From the perspective of adverse effects, initiating administration at a lower dosage is preferable because this was found to be sufficiently effective.

Impact of acute kidney injury in patients prescribed angiotensin-converting enzyme inhibitors over the first two years of life.

BACKGROUND: The association of long-term acute kidney injury (AKI) risk with angiotensin-converting enzyme (ACE) inhibitor use in neonates/infants is poorly understood. We examined this association to identify potential AKI risk factors. METHODS: We retrospectively evaluated 119 children aged < 2 years (72 boys; median age, 5.0 months) who received ACE inhibitors for congenital heart disease for ≥ 6 months between January 2009 and June 2019. We monitored the occurrence of AKI, defined according to the Kidney Disease Improving Global Outcomes guidelines. Demographic and clinical data were extracted from medical records. Risk factors associated with AKI onset were identified by a Cox proportional hazards regression analysis of variables previously identified as risk factors of AKI and those significant in a univariate analysis. RESULTS: Thirty-three of 119 patients (28%) developed AKI at a median follow-up of 1.3 years (interquartile range, 0.8-3.2 years). AKI incidence was 1257 events per 10,000 patient-years. Concomitant tolvaptan use (hazard ratio [HR], 3.81; 95% confidence interval [CI], 1.82-7.97; P < 0.01) and Down syndrome (HR, 3.22; 95% CI, 1.43-7.29; P < 0.01) were identified as independent risk factors of AKI onset. CONCLUSIONS: AKI was strongly associated with concomitant tolvaptan use and Down syndrome in our study population. Physicians should consider these factors when prescribing ACE inhibitors for neonates/infants. Low-dose ACE inhibitors slow CKD progression because of their antifibrotic properties. ACE inhibitors may be beneficial for patients with Down syndrome who have underlying CKD in a non-acute setting. Therefore, they should be administered to such patients with caution.

Efficient engraftment of genetically modified cells is necessary to ameliorate central nervous system involvement of murine model of mucopolysaccharidosis type II by hematopoietic stem cell targeted gene therapy.

Mucopolysaccharidosis type II (MPS II) is a lysosomal storage disease (LSD) caused by a deficiency of the iduronate-2-sulfatase (IDS) that catabolizes glycosaminoglycans (GAGs). Abnormal accumulations of GAGs in somatic cells lead to various manifestations including central nervous system (CNS) disease. Enzyme replacement therapy (ERT) and hematopoietic stem cell transplantation (HSCT) are the currently available therapy for MPS II, but both therapies fail to improve CNS manifestations. We previously showed that hematopoietic stem cell targeted gene therapy (HSC-GT) with lethal irradiation improved CNS involvement in a murine model of MPS II which lacks the gene coding for IDS. However, the strong preconditioning, with lethal irradiation, would cause a high rate of morbidity and mortality. Therefore, we tested milder preconditioning procedures with either low dose irradiation or low dose irradiation plus an anti c-kit monoclonal antibody (ACK2) to assess CNS effects in mice with MPS II after HSC-GT. Mice from all the HSC-GT groups displayed super-physiological levels of IDS enzyme activity and robust reduction of abnormally accumulated GAGs to the wild type mice levels in peripheral organs. However, only the mice treated with lethal irradiation showed significant cognitive function improvement as well as IDS elevation and GAG reduction in the brain. These results suggest that an efficient engraftment of genetically modified cells for HSC-GT requires strong preconditioning to ameliorate CNS involvement in cases with MPS II.

Molecular mechanisms determining severity in patients with Pierson syndrome.

Null variants in LAMB2 cause Pierson syndrome (PS), a severe congenital nephrotic syndrome with ocular and neurological defects. Patients' kidney specimens show complete negativity for laminin ß2 expression on glomerular basement membrane (GBM). In contrast, missense variants outside the laminin N-terminal (LN) domain in LAMB2 lead to milder phenotypes. However, we experienced cases not showing these typical genotype-phenotype correlations. In this paper, we report six PS patients: four with mild phenotypes and two with severe phenotypes. We conducted molecular studies including protein expression and transcript analyses. The results revealed that three of the four cases with milder phenotypes had missense variants located outside the LN domain and one of the two severe PS cases had a homozygous missense variant located in the LN domain; these variant positions could explain their phenotypes. However, one mild case possessed a splicing site variant (c.3797 + 5G>A) that should be associated with a severe phenotype. Upon transcript analysis, this variant generated some differently sized transcripts, including completely normal transcript, which could have conferred the milder phenotype. In one severe case, we detected the single-nucleotide substitution of c.4616G>A located outside the LN domain, which should be associated with a milder phenotype. However, we detected aberrant splicing caused by the creation of a novel splice site by this single-base substitution. These are novel mechanisms leading to an atypical genotype-phenotype correlation. In addition, all four cases with milder phenotypes showed laminin ß2 expression on GBM. We identified novel mechanisms leading to atypical genotype-phenotype correlation in PS.

Independent risk factors and long-term outcomes for acute kidney injury in pediatric patients undergoing hematopoietic stem cell transplantation: a retrospective cohort study.

BACKGROUND: Acute kidney injury (AKI) remains a frequent complication in children undergoing hematopoietic stem cell transplantation (HSCT) and an independent risk factor of the patient's survival and a prognostic factor of progression to chronic kidney disease (CKD). However, the causes of these complications are diverse, usually overlapping, and less well understood. METHODS: This retrospective analysis was performed in 43 patients (28 boys, 15 girls; median age, 5.5 years) undergoing HSCT between April 2006 and March 2019. The main outcome was the development of AKI defined according to the Pediatric Risk, Injury, Failure, Loss, End-stage Renal Disease (pRIFLE) criteria as ≥ 25% decrease in estimated creatinine clearance. The secondary outcome was the development of CKD after a 2-year follow-up. RESULTS: AKI developed in 21 patients (49%) within 100 days after HSCT. After adjusting for possible confounders, posttransplant AKI was associated with matched unrelated donor (MUD) (HR, 6.26; P = 0.042), but not total body irradiation (TBI). Of 37 patients who were able to follow-up for 2 years, 7 patients died, but none had reached CKD during the 2 years after transplantation. CONCLUSIONS: Posttransplant AKI was strongly associated with HSCT from MUD. Although the incidence of AKI was high in our cohort, that of posttransplant CKD was lower than reported previously in adults. TBI dose reduced, GVHD minimized, and infection prevented are required to avoid late renal dysfunction after HSCT in children since their combinations may contribute to the occurrence of AKI.

Glyceraldehyde-3-phosphate dehydrogenase of Mycoplasma pneumoniae induces infection-related glomerulonephritis
.

Infection-related glomerulonephritis (IRGN) was previously thought to be due mostly to Streptococcus species, but is now known to be caused by a variety of other pathogens. Nephritis-associated plasmin receptor (NAPlr) was originally isolated from group A streptococci as the protein responsible for acute poststreptococcal glomerulonephritis, and was shown to be identical to streptococcal glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Here, we describe a 7-year-old boy diagnosed with Mycoplasma pneumoniae IRGN presenting with acute nephritic syndrome. Laboratory data revealed a significant increase in serum anti-M. pneumoniae antibody titer. Renal biopsy revealed diffuse global endocapillary proliferation and cellular crescents in 5/43 glomeruli examined. Although antistreptolysin O antibody titer and serum complement C3 level were within the respective normal ranges, glomeruli showed positive staining for NAPlr and upregulation of plasmin activity. In addition, positive staining for NAPlr in the glomeruli was abolished by preabsorption of anti-NAPlr antibody with recombinant M. pneumoniae GAPDH. Western blotting analysis revealed anti-NAPlr antibody reactivity with a band at around the predicted size of GAPDH in the protein isolate of M. pneumoniae (37 kDa). Furthermore, immobilized M. pneumoniae GAPDH bound to anti-NAPlr antibody as well as plasmin in vitro. These data suggest that M. pneumoniae GAPDH has a function similar to streptococcal GAPDH (NAPlr) and may induce plasmin-related glomerular damage in M. pneumoniae IRGN. NAPlr could be a marker of glomerulonephritis related to infection not only by streptococci but also by &M. pneumoniae.

A review of clinical characteristics and genetic backgrounds in Alport syndrome.

Alport syndrome (AS) is a progressive hereditary renal disease that is characterized by sensorineural hearing loss and ocular abnormalities. It is divided into three modes of inheritance, namely, X-linked Alport syndrome (XLAS), autosomal recessive AS (ARAS), and autosomal dominant AS (ADAS). XLAS is caused by pathogenic variants in COL4A5, while ADAS and ARAS are caused by those in COL4A3/COL4A4. Diagnosis is conventionally made pathologically, but recent advances in comprehensive genetic analysis have enabled genetic testing to be performed for the diagnosis of AS as first-line diagnosis. Because of these advances, substantial information about the genetics of AS has been obtained and the genetic background of this disease has been revealed, including genotype-phenotype correlations and mechanisms of onset in some male XLAS cases that lead to milder phenotypes of late-onset end-stage renal disease (ESRD). There is currently no radical therapy for AS and treatment is only performed to delay progression to ESRD using nephron-protective drugs. Angiotensin-converting enzyme inhibitors can remarkably delay the development of ESRD. Recently, some new drugs for this disease have entered clinical trials or been developed in laboratories. In this article, we review the diagnostic strategy, genotype-phenotype correlation, mechanisms of onset of milder phenotypes, and treatment of AS, among others.

Independent Risk Factors and 2-Year Outcomes of Acute Kidney Injury after Surgery for Congenital Heart Disease.

BACKGROUND: Data are limited regarding risk factors for acute kidney injury (AKI) following cardiac surgery in children with congenital heart disease (CHD). This observational study was performed to examine temporal trends in AKI incidence according to the Pediatric Risk, Injury, Failure, Loss, End-Stage Renal Disease (pRIFLE) criteria, identify independent risk factors for AKI after cardiac surgery, and examine associations between AKI and long-term mortality. METHODS: We retrospectively evaluated 418 patients (259 males, 159 females; median age, 5 months) who underwent cardiac surgery for CHD between April 2007 and August 2013. Patients were followed up for 2 years. AKI was defined according to the pRIFLE criteria as ≥25% decrease in estimated creatinine clearance. RESULTS: AKI developed postoperatively in 104 cases (24.9%). Approximately 80% belonged to the "Risk" category according to the pRIFLE criteria, and only 21 cases (5%) required renal replacement therapy (peritoneal dialysis in all cases). Multivariate analysis revealed 3 independent risk factors for onset of AKI: young age (<1 year), surgery in Risk Adjustment in Congenital Heart Surgery (RACHS-1) category ≥4, and long cardiopulmonary bypass (CPB) time (≥90 min). Twenty-three patients (22%) with AKI died during the 2-year follow-up. In multivariate cox hazard regression analysis, the most significant contributor to risk of mortality was AKI. CONCLUSIONS: Postoperative AKI was strongly associated with young age, high RACHS-1 category, and prolonged CPB time. In addition, mortality rate was higher in patients who survived after recovery from AKI than in those without AKI, even among the lower pRIFLE categories.

Tolvaptan in a pediatric patient with diuretic-resistant heart and kidney failure.

Despite conventional diuretic therapy, volume overload persists in many patients with decompensated heart failure. Adverse effects of diuretics are common, including worsening kidney function and electrolyte disturbance. Furthermore, decreased kidney function also affects the response to diuretics and is associated with an increased risk of mortality. A 10-year-old boy with congestive heart failure (CHF) complicated by advanced chronic kidney disease (CKD) presented with oliguria and generalized edema. He was being treated with furosemide and spironolactone, and these doses were increased to 3 mg/kg/day after admission. Although edema decreased temporarily, the symptoms worsened and furosemide resistance developed 2 months later. Tolvaptan (0.1 mg/kg/day) was started, resulting in a gradual increase in the plasma sodium level and adequate decongestion of the volume overload state. Cardiac function also improved. The use of tolvaptan should be considered in pediatric cases of conventional diuretic-resistant CHF, even when complicated by advanced CKD.

Familial juvenile hyperuricemia in early childhood in a boy with a novel gene mutation.

Familial juvenile hyperuricemic nephropathy (FJHN) is a rare autosomal dominant disease caused by mutations in the uromodulin (UMOD) gene. It is characterized by the development of gout, tubulointerstitial nephropathy, and end-stage renal disease. Here we report a case of FJHN that was diagnosed in early childhood in a boy with a novel gene mutation. At the age of 4 years, the patient was admitted with a diagnosis of purpura nephritis. He was discharged following symptom alleviation. However, hyperuricemia (7-9 mg/dL) and mild renal dysfunction [creatinine-estimated glomerular filtration rate (eGFR): 80-90 mL/min/1.73 m2] persisted after discharge. FJHN was suspected on the basis of a maternal family history of hyperuricemia, renal dysfunction, and dialysis. Direct sequence analysis performed at the age of 5 years revealed a novel missense mutation (c766T > G), p.Cys256Gly, in exon 3. Urate-lowering therapy was started, which provided good uric acid control (6.0 mg/dL). At the age of 8 years, persistent renal dysfunction was observed (eGFR: 80-90 mL/min/1.73 m2). Interestingly, cases of FJHN with c744C > G (p.Cys248Trp) mutations also exhibit a high incidence of juvenile onset, and identical disulfide bridges are considered responsible for the accumulation of mutant UMOD in the endoplasmic reticulum. Pediatricians should consider UMOD mutation analysis for families with autosomal dominant tubulointerstitial kidney disease (ADTKD) and a bland urinary sediment, even if hyperuricemia is mild. Also, sex and genotype are very important prognostic factors for ADTKD caused by UMOD mutations.

Elevated concentrations of sphingosylphosphorylcholine in cerebrospinal fluid after subarachnoid hemorrhage: a possible role as a spasmogen.

This study investigates the role of sphingosylphosphorylcholine (SPC) in the mechanisms underlying cerebral vasospasm after subarachnoid hemorrhage (SAH). The levels of SPC were measured in cerebrospinal fluid (CSF) of patients with SAH and also in an experimental canine model. CSF samples were collected from 11 patients with SAH, and from dogs that had received an injection of SPC into the cisterna magna to examine SPC kinetics in the CSF. SPC was assayed using solid-phase extraction and triple quadrupole mass spectrometry. The SPC concentrations in SAH patients on days 3, 8, and 14 after the onset of SAH were significantly higher than those in normal CSF. In the canine model, rapid dilution of SPC in CSF was observed. In combination with data from previous studies, these results suggest that SPC is involved in the development of cerebral vasospasm. Rapid dilution of SPC in CSF suggests that SPC is released into CSF at higher concentrations than those measured in the present study.

Sphingosylphosphorylcholine is a novel messenger for Rho-kinase-mediated Ca2+ sensitization in the bovine cerebral artery: unimportant role for protein kinase C.

Although recent investigations have suggested that a Rho-kinase-mediated Ca2+ sensitization of vascular smooth muscle contraction plays a critical role in the pathogenesis of cerebral and coronary vasospasm, the upstream of this signal transduction has not been elucidated. In addition, the involvement of protein kinase C (PKC) may also be related to cerebral vasospasm. We recently reported that sphingosylphosphorylcholine (SPC), a sphingolipid, induces Rho-kinase-mediated Ca2+ sensitization in pig coronary arteries. The purpose of this present study was to examine the possible mediation of SPC in Ca2+ sensitization of the bovine middle cerebral artery (MCA) and the relation to signal transduction pathways mediated by Rho-kinase and PKC. In intact MCA, SPC induced a concentration-dependent (EC50=3.0 micromol/L) contraction, without [Ca2+]i elevation. In membrane-permeabilized MCA, SPC induced Ca2+ sensitization even in the absence of added GTP, which is required for activation of G-proteins coupled to membrane receptors. The SPC-induced Ca2+ sensitization was blocked by a Rho-kinase inhibitor (Y-27632) and a dominant-negative Rho-kinase, but not by a pseudosubstrate peptide for conventional PKC, which abolished the Ca2+-independent contraction induced by phorbol ester. In contrast, phorbol ester-induced Ca2+ sensitization was resistant to a Rho-kinase inhibitor and a dominant-negative Rho-kinase. In primary cultured vascular smooth muscle cells, SPC induced the translocation of cytosolic Rho-kinase to the cell membrane. We propose that SPC is a novel messenger for Rho-kinase-mediated Ca2+ sensitization of cerebral arterial smooth muscle and, therefore, may play a pivotal role in the pathogenesis of abnormal contraction of the cerebral artery such as vasospasm. The SPC/Rho-kinase pathway functions independently of the PKC pathway.

Involvement of Src family protein tyrosine kinases in Ca(2+) sensitization of coronary artery contraction mediated by a sphingosylphosphorylcholine-Rho-kinase pathway.

We recently reported that sphingosylphosphorylcholine (SPC) is a novel messenger for Rho-kinase-mediated Ca(2+) sensitization of vascular smooth muscle (VSM) contraction. Subcellular localization and kinase activity of Src family protein kinases (SrcPTKs), except for c-Src, is controlled by a reversible S-palmitoylation, an event inhibited by eicosapentaenoic acid (EPA). We examined the possible involvement of SrcPTKs in SPC-induced Ca(2+) sensitization and effects of EPA. We used porcine coronary VSM and rat aortic VSM cells (VSMCs) in primary culture. An SrcPTKs inhibitor, PP1, and EPA inhibited SPC-induced contraction, concentration-dependently, without affecting [Ca(2+)](i) levels and the Ca(2+)-dependent contraction induced by high K(+) depolarization. A digitized immunocytochemical analysis in VSMCs revealed that SPC induced translocation of Fyn, but not of c-Src, from the cytosol to the cell membrane, an event abolished by EPA. Translocation of Rho-kinase from the cytosol to the cell membrane by SPC was also inhibited by EPA and PP1. The SPC-induced activation of SrcPTKs was blocked by EPA and PP1, but not by Y27632, an Rho-kinase inhibitor. Rho-kinase-dependent phosphorylation of myosin phosphatase induced by SPC was inhibited by EPA, PP1, and Y27632. Translocation and activation of SrcPTKs, including Fyn, play an important role in Ca(2+) sensitization of VSM contractions mediated by a SPC-Rho-kinase pathway.