Acute kidney injury (AKI) is a major clinical concern in sickle cell disease (SCD). Clinical evidence suggests that red cell alarmins may cause AKI in SCD however the sterile inflammatory process involved has hitherto not been defined. We discovered that hemopexin deficiency in SCD is associated with a compensatory increase in alpha-1-microglobulin (A1M) resulting in up to 10-fold higher A1M/hemopexin ratio in SCD compared to health controls. The A1M/hemopexin ratio is associated with markers of hemolysis and AKI in both humans and mice with SCD. Studies in mice showed that excess heme is directed to the kidneys in SCD in a process involving A1M causing AKI while excess heme in controls is transported to the liver as expected. Using genetic and bone marrow chimeric tools, we confirmed that hemopexin deficiency promotes AKI in sickle mice under hemolytic stress. However, AKI was blocked when hemopexin deficiency in sickle mice was corrected with infusions of purified hemopexin prior to the induction of hemolytic stress. This study identifies acquired hemopexin deficiency as a risk factor of AKI in SCD and hemopexin replacement as a potential therapy.
Introduction: Our urology residency program transitioned to a night float system, where dedicated residents cover nights and are off duty during the day. Junior residents previously covered 5 hospitals every 5 to 7 nights and worked the following day (home call). This prospective observational study compared the 2 systems before and after the transition.Methods: A validated survey was administered to residents and faculty to evaluate patient care, communication, quality of life, resident education, and duty hour violations. A separate survey was administered to nurses evaluating the on-call resident. Sleep was measured using actigraphy.Results: Survey response rates were 80% to 100%. Junior residents rated night float as equivalent to home call for surgical case volume and superior in all other respects (p <0.05). Senior residents rated night float as superior for continuity of care, compassion, safety, efficiency for the day team, communication with nurses, quality of life, and time for reading and research (p <0.05). Faculty rated night float as superior for efficiency for the day team, handoffs, quality of life, and time for research (p <0.05). Nurses rated night float higher for availability, knowledge of plan for patient, respectfulness, communication, and ability to identify the resident on call (p <0.05). Mean duration of sleep was 2.5 and 7.1 hours for home call and night float, respectively (p <0.001). Junior residents reported fewer violations of the 80-hour and 8-hour-off rules with night float (p <0.001).Conclusions: Physicians and nurses perceived night float to improve multiple domains. Residents slept more and had fewer duty hour violations on night float.
Acute kidney injury (AKI) is a major clinical concern during episodes of acute chest syndrome and vaso-occlusive crisis in sickle cell disease (SCD). AKI increases the risk of chronic kidney disease (CKD) and end stage renal disease (ESRD). We previously showed that alpha-1-microglobulin (A1M), a low affinity heme-binding protein that carries heme for renal clearance is elevated in patients and mice with homozygous SCD (SS). Hemopexin (Hx), which primarily scavenges circulating heme to the liver, is exhausted in SCD. In this study, we explored the idea that acquired Hx deficiency in SCD is a risk factor for AKI development in SCD. We studied mice with a global knockout of Hx with no detectable plasma Hx at baseline. Plasma A1M was significantly elevated in the Hx-/-mice compared to control (Hx+/+) mice (n=5; p<0.01). We then transplanted whole bone marrow cells from SS mice into Hx+/+and Hx-/-mice to create bone marrow chimeric SSHx+/+and SSHx-/-mice with SCD phenotype. The chimeras had elevated plasma A1M compared to recipient littermates (Hx+/+and Hx-/-) and low baseline glomerular filtration rate (GFR). Modest elevation of circulating heme with infusion of hemin (20 μmoles/kg bw) worsened GFR and caused severe AKI. Next, to determine whether hemin induced AKI is attenuated by elevation of circulating Hx, we infused SS mice with purified Hx, and control SS mice with either purified A1M or vehicle immediately prior to the hemin challenge. We observed improved GFR in the Hx-treated SS mice, while vehicle and A1M-treated mice suffered 23% and 39% loss of GFR respectively compared to their baseline. In agreement with the GFR data, the levels of several AKI diagnostic markers, plasma creatinine (plasma Cr), urinary albumin-creatinine ratio (uACR) and kidney injury molecule (uKIM-1) were elevated significantly in vehicle and A1M treated mice following hemin challenge. In Hx-treated mice, these biomarkers remained unaltered. Importantly, Hx infusions re-directed excess heme in SS mice to the liver, while A1M infusion significantly increased total heme content in the kidneys. Two-way ANOVA analysis of GFR (p<0.01) and plasma Cr (p<0.001) revealed significant exacerbation of kidney injury in A1M treated SS mice compared to vehicle treated mice. Histopathology of renal tissue showed considerable tissue damage in vehicle and A1M infused SS mice, while Hx treated SS mice kidneys appeared relatively normal. This study provides genetic evidence that hemopexin deficiency promotes AKI development in SCD, and we provide proof-of-principle for hemopexin replacement therapy to treat AKI in SCD. Disclosures Ofori-Acquah: Shire Human Genetic Therapies Inc: Other: Financial Relationship.
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