Acute kidney injury in children with sickle cell disease-compounding a chronic problem

Nox4 is involved in acute kidney injury associated to intravascular hemolysis

Massive intravascular hemolysis occurs not unfrequently in many clinical conditions. Breakdown of erythrocytes promotes the accumulation of heme-derivates in the kidney, increasing oxidative stress and cell death, thus promoting acute kidney injury (AKI). NADPH oxidase 4 (Nox4) is a major source of reactive oxygen species (ROS) in the kidney, however it is unknown the role of Nox4 in hemolysis and whether inhibition of this enzyme may protect from heme-mediated injury. To answer these questions, we elicited intravascular hemolysis in wild type and Nox4 knockout mice. We also evaluated whether nephrotoxic effects of heme may be reduced by using Nox4 siRNA and pharmacologic inhibition with GKT137831, a Nox4 inhibitor, both in vivo and in cultured renal cells. Our results showed that induction of massive hemolysis elicited AKI characterized by loss of renal function, morphological alterations of the tubular epithelium and podocytes, oxidative stress, inflammation, mitochondrial dysfunction, blockade of autophagy and cell death. These pathological effects were significantly prevented in Nox4-deficient mice and in animals treated with GKT137831. In vitro studies showed that Nox4 disruption by specific siRNAs or Nox4 inhibitors declined heme-mediated ROS production and cell death. Our data identify Nox4 as a key enzyme involved in intravascular hemolysis-induced AKI. Thus, Nox4 inhibition may be a potential therapeutic approach to prevent renal damage in patients with severe hemolytic crisis.

Acute Kidney Injury in Children: A Focus for the General Pediatrician

Acute kidney injury (AKI) presents significant challenges in pediatric care, often remaining underrecognized. This paper provides an overview of pediatric AKI, highlighting its epidemiology, pathophysiology, diagnosis, predisposing conditions, and treatment. AKI in children stems from diverse causes, including renal tubular damage, vasoconstriction, and inflammation. Diagnosis relies on traditional markers such as serum creatinine and urine output, alongside emerging biomarkers such as Cystatin C, NGAL, KIM-1, IL-18, TIMP-2 and IGFBP7, urinary calprotectin, URBP4, L-FABP, and clusterin. Various pediatric conditions predispose to AKI, including type 1 diabetes, pneumonia, bronchiolitis, appendicitis, gastroenteritis, COVID-19, multisystem inflammatory syndrome, sickle cell disease, and malignancies. Treatment entails supportive care with fluid management and, in severe cases, renal replacement therapy. Timely recognition and management are essential to mitigating adverse outcomes. Enhanced awareness and integration of novel biomarkers could improve pediatric AKI care, warranting further research for better diagnosis and management.

Heme-induced loss of renovascular endothelial protein C receptor promotes chronic kidney disease in sickle mice

ABSTRACT

Chronic kidney disease (CKD) is a major contributor to morbidity and mortality in sickle cell disease (SCD). Anemia, induced by chronic persistent hemolysis, is associated with the progressive deterioration of renal health, resulting in CKD. Moreover, patients with SCD experience acute kidney injury (AKI), a risk factor for CKD, often during vaso-occlusive crisis associated with acute intravascular hemolysis. However, the mechanisms of hemolysis-driven pathogenesis of the AKI-to-CKD transition in SCD remain elusive. Here, we investigated the role of increased renovascular rarefaction and the resulting substantial loss of the vascular endothelial protein C receptor (EPCR) in the progressive deterioration of renal function in transgenic SCD mice. Multiple hemolytic events raised circulating levels of soluble EPCR (sEPCR), indicating loss of EPCR from the cell surface. Using bone marrow transplantation and super-resolution ultrasound imaging, we demonstrated that SCD mice overexpressing EPCR were protective against heme-induced CKD development. In a cohort of patients with SCD, plasma sEPCR was significantly higher in individuals with CKD than in those without CKD. This study concludes that multiple hemolytic events may trigger CKD in SCD through the gradual loss of renovascular EPCR. Thus, the restoration of EPCR may be a therapeutic target, and plasma sEPCR can be developed as a prognostic marker for sickle CKD.

Sex-disaggregated analysis of acute kidney injury in hospitalized children with sickle cell anemia in Uganda

A growing body of research is categorizing sex differences in both sickle cell anemia (SCA) and acute kidney injury (AKI); however, most of this work is being conducted in high-resource settings. Here, we evaluated risk factors and clinical parameters associated with AKI and AKI severity, stratified by sex, in a cohort of children hospitalized with SCA and vaso-occlusive pain crisis (VOC). The purpose of this study was to explore sex disparities in a high-risk, vulnerable population. This study was a secondary analysis of data collected from a cohort of Ugandan children between 2 and 18 yr of age prospectively enrolled. A total of 185 children were enrolled in the primary study; 41.6% were female and 58.4% were male, with a median age of 8.9 yr. Incident or worsening AKI (P = 0.026) occurred more frequently in female compared with male children, despite no differences in AKI on admission. Female children also had altered markers of renal function including higher creatinine levels at admission (P = 0.03), higher peak creatinine (P = 0.006), and higher urine neutrophil gelatinase-associated lipocalin (NGAL) at admission (P = 0.003) compared with male children. Female children had elevated total (P = 0.045) and conjugated bilirubin at admission (P = 0.02) compared with male children and higher rates of hematuria at admission (P = 0.004). Here, we report sex differences in AKI in children with SCA and VOC, including increased incidence and worsening of AKI in female pediatric patients, in association with an increase in biological indicators of poor renal function including creatinine, estimated glomerular filtration rate, and NGAL.NEW & NOTEWORTHY In this study, we report an increased risk of developing acute kidney injury (AKI) during hospitalization, worsening AKI, and death among females with sickle cell anemia (SCA) hospitalized with an acute pain crisis compared with males. The sex differences in AKI were not explained by socioeconomic differences, severity of pain, or disease severity among females compared with males. Together, these data suggest that female children with SCA may be at increased risk of AKI.

Two-Dimensional Ultrasound Assessment of Long-Term Intra-Abdominal Organ Changes in Children with Sickle Cell Anemia during Steady State: A Comparative Study

BACKGROUND

Sickle cell anemia (SCA) is a hereditary blood disorder with global prevalence, including in Nigeria. Despite advancements in SCA care management, understanding the long-term impact on organs during steady state has remained inconclusive.

AIM

This study aimed to investigate the long-term changes in intra-abdominal organs of SCA children compared with non-SCA children during steady state using two-dimensional ultrasound assessment.

MATERIALS AND METHODS

A total of 116 children (58 SCA and 58 controls) were enrolled between June 2021 and July 2022. Clinico-demographic data were collected through an interviewer-administered questionnaire. Two-dimensional ultrasound was used to measure the liver, spleen, kidneys, and inferior vena cava in all subjects. Age-matched controls had AA or AS genotypes.

RESULTS

Of the 58 patients with SCA, 65.5% were males with an overall mean age of 8.1 ± 3.4 years, while among the non-SCA cohort (n = 58), 48.3% were males with an overall mean age of 8.7 ± 3.9 years. There was no statistically significant difference in the age and gender distribution between the SCA and non-SCA cohorts (P = 0.390 and P = 0.091, respectively). SCA subjects had a larger mean hepatic size than non-SCA subjects (12.09 cm ± 2.23 vs. 11.67 cm ± 1.96; P = 0.276) but smaller mean splenic size (8.01 cm ± 1.89 vs. 8.19 cm ± 1.61; P = 0.577) and inferior vena cava diameter (1.16 cm ± 0.29 vs. 1.25 cm ± 0.33; P = 0.100). Left kidney length and breadth were significantly greater in SCA patients (8.91 ± 1.16 vs. 8.27 ± 1.30; P = 0.006 and 4.15 ± 0.92 vs. 3.79 ± 0.48; P = 0.008, respectively).

CONCLUSION

This study highlights the utility of two-dimensional ultrasound assessment in monitoring intra-abdominal organ changes in SCA children, suggesting its cost-effective benefits in monitoring health outcomes in SCA patients.

Urinary Biomarkers for the Assessment of Acute Kidney Injury of Pediatric Sickle Cell Anemia Patients Admitted for Severe Vaso-occlusive Crises

Sickle cell nephropathy is a progressive morbidity, beginning in childhood, which is incompletely understood partially due to insensitive measures. We performed a prospective pilot study of pediatric and young adult patients with sickle cell anemia (SCA) to assess urinary biomarkers during acute pain crises. Four biomarkers were analyzed with elevations potentially suggesting acute kidney injury: (1) neutrophil gelatinase-associated lipocalin (NGAL), (2) kidney injury molecule-1, (3) albumin, and (4) nephrin. Fourteen unique patients were admitted for severe pain crises and were found to be representative of a larger SCA population. Urine samples were collected at the time of admission, during admission, and at follow-up after discharge. Exploratory analyses compared cohort values to the best available population values; individuals were also compared against themselves at various time points. Albumin was found to be moderately elevated for an individual during admission compared with follow-up ( P = 0.006, Hedge g : 0.67). Albumin was not found to be elevated compared with population values. Neutrophil gelatinase-associated lipocalin, kidney injury molecule-1, and nephrin were not found to be significantly elevated compared with population values or comparing admission to follow-up. Though albumin was found to be minimally elevated, further research should focus on alternative markers in efforts to further understand kidney disease in patients with SCA.

Role of GSTM1 in Hypertension, CKD, and Related Diseases across the Life Span

Over 20 years after the introduction of angiotensin-converting enzyme inhibitors and angiotensin receptor blockers, CKD remains a major public health burden with limited therapeutic options to halt or slow kidney disease progression at all ages. The consensus is that oxidative stress contributes to CKD development and progression. Yet, to date, there is no clear evidence that broad use of antioxidant therapy provides a beneficial effect in CKD. Understanding the specific pathophysiologic mechanisms in those who are genetically most susceptible to oxidative stress is a crucial step to inform therapy in an individualized medicine approach, considering differing exposures and risks across the life span. Glutathione-S-transferase μ 1 (GSTM1) is a phase 2 enzyme involved in inactivation of reactive oxygen species and metabolism of xenobiotics. In particular, those with the highly prevalent GSTM1 null genotype (GSTM1[0/0]) may be more susceptible to kidney disease progression, due to impaired capacity to handle the increased oxidative stress burden in disease states, and might specifically benefit from therapy that targets the redox imbalance mediated by loss of the GSTM1 enzyme. In this review, we will discuss the studies implicating the role of GSTM1 deficiency in kidney and related diseases from experimental rodent models to humans, from the prenatal period through senescence, and the potential underlying mechanism.

Intravenous Fluid Administration and the Risk of Adverse Outcomes in Sickle Cell Disease Patients Hospitalized for Vaso-Occlusive Crisis

Vaso-occlusive crisis (VOC) is the leading cause of hospitalization in sickle cell disease (SCD). Intravenous fluid (IVF) administration is the usual practice during VOC episodes to slow the sickling process. In the absence of an evidence-based, clear-cut consensus on the optimal choice, route, and rate of fluid administration, there has been a wide variability in the practice of IVF administration in the treatment of VOC. However, there are growing concerns about the safety of this practice. This systematic review summarized the current evidence on the risk of negative outcomes in SCD patients treated for VOC with IVFs. A database search of Medline/PubMed, EMBASE, Scopus, Web of Science, CINAHL, Wiley Cochrane Library, Clinicaltrials.gov, and conference proceedings of the European Hematology Association (EHA) and American Society of Hematology (ASH) were performed. The results were presented using narrative analysis of quantitative data. Of the 2,821 identified records, a total of three eligible retrospective cohort studies with a total demographic population of 549 SCD patients were included in this review. Normal saline, a frequently used IVF for VOC may be associated with adverse outcomes such as poor pain control and volume overload. Volume overload, new oxygen requirement, acute chest syndrome, and acute kidney injury are potential adverse outcomes of inappropriate IVF use in VOC. There is limited evidence supporting the current practice of IVF use in VOC. Randomized controlled trials are required to fully clarify the place and safety of IVF in the management of VOC.

Sickle cell nephropathy: insights into the pediatric population

The life expectancy of individuals with sickle cell disease has increased over the years, majorly due to an overall improvement in diagnosis and medical care. Nevertheless, this improved longevity has resulted in an increased prevalence of chronic complications such as sickle cell nephropathy (SCN), which poses a challenge to the medical care of the patient, shortening the lifespan of patients by 20-30 years. Clinical presentation of SCN is age-dependent, with kidney dysfunction slowly beginning to develop from childhood, progressing to chronic kidney disease and kidney failure during the third and fourth decades of life. This review explores the epidemiology, pathology, pathophysiology, clinical presentation, and management of SCN by focusing on the pediatric population. It also discusses the factors that can modify SCN susceptibility.

Acute Kidney Injury Caused by Evans Syndrome with Systemic Lupus Erythematosus and Systemic Sclerosis

A 65-year-old woman with systemic sclerosis and systemic lupus erythematosus developed acute kidney injury (AKI), Coombs-positive autoimmune hemolytic anemia and autoimmune thrombocytopenia; therefore, she was diagnosed with Evans syndrome (ES). Intravascular hemolysis was suggested as the cause of AKI based on the presence of acute tubular injury and trace hemosiderin deposits on the renal biopsy. The renal function, hemolytic anemia and thrombocytopenia were restored by an increased dose of glucocorticoids, hemodialysis, and plasma exchange. Although ES with severe hemolytic anemia is very rare, it is important to detect possible renal dysfunction when encountering patients with severe hemolysis.

Investigations of Kidney Dysfunction-Related Gene Variants in Sickle Cell Disease Patients in Cameroon (Sub-Saharan Africa)

BACKGROUND

Renal dysfunctions are associated with increased morbidity and mortality in sickle cell disease (SCD). Early detection and subsequent management of SCD patients at risk for renal failure and dysfunctions are essential, however, predictors that can identify patients at risk of developing renal dysfunction are not fully understood.

METHODS

In this study, we have investigated the association of 31 known kidney dysfunctions-related variants detected in African Americans from multi-ethnic genome wide studies (GWAS) meta-analysis, to kidney-dysfunctions in a group of 413 Cameroonian patients with SCD. Systems level bioinformatics analyses were performed, employing protein-protein interaction networks to further interrogate the putative associations.

RESULTS

Up to 61% of these patients had micro-albuminuria, 2.4% proteinuria, 71% glomerular hyperfiltration, and 5.9% had renal failure. Six variants are significantly associated with the two quantifiable phenotypes of kidney dysfunction (eGFR and crude-albuminuria): A1CF-rs10994860 (P = 0.02020), SYPL2-rs12136063 (P = 0.04208), and APOL1 (G1)-rs73885319 (P = 0.04610) are associated with eGFR; and WNT7A-rs6795744 (P = 0.03730), TMEM60-rs6465825 (P = 0.02340), and APOL1 (G2)-rs71785313 (P = 0.03803) observed to be protective against micro-albuminuria. We identified a protein-protein interaction sub-network containing three of these gene variants: APOL1, SYPL2, and WNT7A, connected to the Nuclear factor NF-kappa-B p105 subunit (NFKB1), revealed to be essential and might indirectly influence extreme phenotypes. Interestingly, clinical variables, including body mass index (BMI), systolic blood pressure, vaso-occlusive crisis (VOC), and haemoglobin (Hb), explain better the kidney phenotypic variations in this SCD population.

CONCLUSION

This study highlights a strong contribution of haematological indices (Hb level), anthropometric variables (BMI, blood pressure), and clinical events (i.e., vaso-occlusive crisis) to kidney dysfunctions in SCD, rather than known genetic factors. Only 6/31 characterised gene-variants are associated with kidney dysfunction phenotypes in SCD samples from Cameroon. The data reveal and emphasise the urgent need to extend GWAS studies in populations of African ancestries living in Africa, and particularly for kidney dysfunctions in SCD.

Ketamine and lidocaine infusions decrease opioid consumption during vaso-occlusive crisis in adolescents with sickle cell disease

PURPOSE OF REVIEW

Recurrent exposure to opioids can lead to development of opioid tolerance and opioid-induced hyperalgesia through activation of N-methyl-D-aspartate receptors. N-methyl-D-aspartate receptor antagonists ketamine and lidocaine can modulate development of opioid tolerance and OIH. This study evaluated the utility of ketamine and/or lidocaine in decreasing opioid consumption during acute pain episodes in adolescents with sickle cell disease. There has been an increased effort to promote opioid-sparing pain relieving methods given the ongoing opioid epidemic.

RECENT FINDINGS

There have been six studies published over the past decade that highlight the ability of ketamine to reduce opioid consumption in the management of sickle cell disease-related pain, primarily in adult patients. There has been one study (2015) that demonstrated a similar benefit with lidocaine, however this was also in adult patients.

SUMMARY

We retrospectively evaluated treatment with ketamine and/or lidocaine infusions in adolescents hospitalized for vaso-occlusive crisis (VOC). Patients served as self-controls using a comparison with a previous control admission for VOC. The use of ketamine and/or lidocaine as adjuncts to opioids resulted in lower daily opioid consumption in three of four patients. Our study suggests that ketamine and/or lidocaine infusions may be useful adjuncts in reducing opioid exposure during VOC pain.

Stable renal function in children and adolescents with sickle cell disease after nonmyeloablative hematopoietic stem cell transplantation

BACKGROUND

Sickle cell disease (SCD) is associated with renal complications starting as early as infancy. Allogeneic hematopoietic stem cell transplant (HSCT) treatments using newer nonmyeloablative (NMA) conditioning regimens show promising results in treating SCD in the pediatric population, but renal outcome parameters after transplantation have not been described.

AIM

To describe baseline renal parameters as well as short- and long-term renal outcomes in pediatric patients with SCD who underwent NMA-HSCT.

METHODS

A retrospective chart review of pediatric patients who received NMA-HSCT in Alberta, Canada. Short-term renal outcomes evaluated were: (1) acute kidney injury (AKI), (2) fluid overload (FO), and (3) hypertension. Long-term outcomes evaluated were: (1) estimated glomerular filtration rate (eGFR) development and at last follow-up with hyperfiltration defined as eGFR ≥ 150 mL/min/1.73 m² , (2) proteinuria, and (3) hypertension.

RESULTS

The mean follow-up time was 128.6 weeks (standard deviations, 69.3). No posttransplant AKI events or FO were observed. eGFR remained > 90 mL/min/1.73 m² at last follow-up in all patients, whereas hyperfiltration was present in eight (44.4%) and four (22.2%) patients pre- and post-HSCT, respectively, which are significantly different (P < 0.0001). Consequently, median GFR was significantly higher pre-HSCT compared with 24 months HSCT (P < 0.009). Long-term hypertension post-HSCT was present in six patients (33.3%).

CONCLUSION

This study describes stable kidney function in children with SCD after NMA-HSCT without evidence of AKI or FO episodes. Rates of hyperfiltration decreased post-HSCT, which signifies that NMA-HSCT could potentially preserve long-term renal function in this population at risk of progressive chronic kidney disease. Further prospective studies are needed to confirm these novel findings.

Acute kidney injury in paediatric patients with sickle cell disease is associated with increased morbidity and resource utilization

Renal disease is a common complication experienced by patients with sickle cell disease (SCD), though the epidemiology of acute kidney injury (AKI) in paediatric patients and its impact on long-term renal outcomes is unclear. We utilized the Pediatric Health Information System (PHIS) to identify inpatient encounters of paediatric patients with SCD admitted for vaso-occlusive pain crisis (VOC). Overall, 1·4% of patients experienced at least one episode of AKI and 2·5% of admissions were complicated by AKI. Patients with at least one episode of AKI were more likely to be adolescents or young adults at the time of their initial admission, had increased rates of admission to the ICU, longer lengths of stay, increased costs of hospitalization, increased risk of readmission and increased rates of SCD-related comorbidities. Generalized estimating equation modelling demonstrated that increasing age, history of hypertension, history of haematuria and history of chronic kidney disease were associated with increased odds of developing AKI, though hydroxycarbamide use (OR 0·64, 95% CI 0·44-0·94) was protective. Episodes of AKI during hospitalization in children with SCD are associated with increased morbidity and utilization of hospital resources. Increasing the use of hydroxycarbamide may decrease the likelihood of this complication.

Nrf2 Plays a Protective Role Against Intravascular Hemolysis-Mediated Acute Kidney Injury

Massive intravascular hemolysis is associated with acute kidney injury (AKI). Nuclear factor erythroid-2-related factor 2 (Nrf2) plays a central role in the defense against oxidative stress by activating the expression of antioxidant proteins. We investigated the role of Nrf2 in intravascular hemolysis and whether Nrf2 activation protected against hemoglobin (Hb)/heme-mediated renal damage in vivo and in vitro. We observed renal Nrf2 activation in human hemolysis and in an experimental model of intravascular hemolysis promoted by phenylhydrazine intraperitoneal injection. In wild-type mice, Hb/heme released from intravascular hemolysis promoted AKI, resulting in decreased renal function, enhanced expression of tubular injury markers (KIM-1 and NGAL), oxidative and endoplasmic reticulum stress (ER), and cell death. These features were more severe in Nrf2-deficient mice, which showed decreased expression of Nrf2-related antioxidant enzymes, including heme oxygenase 1 (HO-1) and ferritin. Nrf2 activation with sulforaphane protected against Hb toxicity in mice and cultured tubular epithelial cells, ameliorating renal function and kidney injury and reducing cell stress and death. Nrf2 genotype or sulforaphane treatment did not influence the severity of hemolysis. In conclusion, our study identifies Nrf2 as a key molecule involved in protection against renal damage associated with hemolysis and opens novel therapeutic approaches to prevent renal damage in patients with severe hemolytic crisis. These findings provide new insights into novel aspects of Hb-mediated renal toxicity and may have important therapeutic implications for intravascular hemolysis-related diseases.

Acute hydroxyurea treatment reduces tubular damage following bilateral ischemia-reperfusion injury in a mouse model of sickle cell disease

Ischemic injury is a primary contributor to the initiation of renal tubular epithelial cell damage in sickle cell disease (SCD). In this study, we investigated the effects of bilateral ischemia-reperfusion injury, which is a common type of acute kidney injury (AKI), in male and female genetic mouse model of SCD. Bilateral occlusion of both renal hila for 21 min led to a significantly higher detection of established serum markers of AKI (creatinine, KIM-1 and NGAL) compared to sham-operated male SCD mice. Severe damage to the outer medullary tubules was determined in the ischemia-reperfision injury (IRI)-treated SCD male mice. In female SCD mice with a longer ischemic time (23 min), the serum markers of AKI were not as highly elevated compared to their male counterparts, and the extent of outer medullary tubular injury was less severe. To assess the potential benefit in the use of hydroxyurea (50 mg/kg IP) following bilateral renal IRI, we observed that the serum markers of AKI and the outer medullary tubular damage were markedly improved compared to male SCD mice that were not treated with hydroxyurea. In this study, we confirmed that male SCD mice were more susceptible to increased tubular damage and a loss in renal function compared to female SCD mice, and that hydroxyurea may partially prevent the extent of tubular injury following severe ischemia-reperfusion injury in SCD.

Care of the Critically Ill Pediatric Sickle Cell Patient

Sickle cell disease is the most common inherited disease in the United States. Through the effects of hemolysis and vaso-occlusion, it has the potential to incite critical illness involving multiple organ systems. Children with sickle cell disease are at risk of multiple types of shock resulting in a need for ICU care. Our youngest patients with sickle cell disease are at highest risk of infection due to lack of splenic function, and this can present with septic shock. Hypovolemic shock can occur secondary to severe acute anemia as seen with splenic sequestration or a delayed transfusion reaction. As one ages, the risk of cardiac dysfunction – diastolic and systolic dysfunction as well as pulmonary hypertension – can result in cardiogenic shock. In addition to shock, patients with sickle cell disease are at risk for respiratory failure from acute chest syndrome as well as acute neurologic deterioration from stroke. For these reasons, critical care physicians must be familiar with the unique management of sickle cell complications in order to provide the best possible care for this vulnerable population.

Evans Syndrome Complicated by Intratubular Hemoglobin Cast Nephropathy

Evans syndrome (ES) is a rare autoimmune disorder whose exact pathophysiology is unknown. It is characterized by the simultaneous or subsequent development of autoimmune hemolytic anemia (AIHA) and immune thrombocytopenia (ITP). Intravascular hemolysis, with hemoglobinemia, is known to produce acute kidney injury; however, the development of intratubular hemoglobin casts (hemoglobin cast nephropathy) in the setting of acute hemolysis is uncommon. Likewise, the association of ES and acute renal failure is equally uncommon. We present a case of a 7-year-old girl with ES who developed acute kidney injury in the setting of intravascular hemolysis and had widespread intratubular hemoglobin casts.