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Cell-free hemoglobin augments acute kidney injury during experimental sepsis.

ABSTRACT: Acute kidney injury is a common complication of severe sepsis and contributes to high mortality. The molecular mechanisms of acute kidney injury during sepsis are not fully understood. Because hemoproteins, including myoglobin and hemoglobin, are known to mediate kidney injury during rhabdomyolysis, we hypothesized that cell-free hemoglobin (CFH) would exacerbate acute kidney injury during sepsis. Sepsis was induced in mice by intraperitoneal injection of cecal slurry (CS). To mimic elevated levels of CFH observed during human sepsis, mice also received a retroorbital injection of CFH or dextrose control. Four groups of mice were analyzed: sham treated (sham), CFH alone, CS alone, and CS + CFH. The addition of CFH to CS reduced 48-h survival compared with CS alone (67% vs. 97%, P = 0.001) and increased the severity of illness. After 24 and 48 h, CS + CFH mice had a reduced glomerular filtration rate from baseline, whereas sham, CFH, and CS mice maintained baseline glomerular filtration rate. Biomarkers of acute kidney injury, neutrophil gelatinase-associated lipocalin (NGAL) and kidney injury molecule-1 (KIM-1), were markedly elevated in CS+CFH compared with CS (8-fold for NGAL and 2.4-fold for KIM-1, P < 0.002 for each) after 48 h. Histological examination showed a trend toward increased tubular injury in CS + CFH-exposed kidneys compared with CS-exposed kidneys. However, there were similar levels of renal oxidative injury and apoptosis in the CS + CFH group compared with the CS group. Kidney levels of multiple proinflammatory cytokines were similar between CS and CS + CFH groups. Human renal tubule cells (HK-2) exposed to CFH demonstrated increased cytotoxicity. Together, these results show that CFH exacerbates acute kidney injury in a mouse model of experimental sepsis, potentially through increased renal tubular injury.

SUBMITTER: Shaver CM

PROVIDER: S-EPMC6843044 | biostudies-literature | 2019 Oct

REPOSITORIES: biostudies-literature

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Cell-free hemoglobin augments acute kidney injury during experimental sepsis.

Shaver Ciara M CM Paul Melinda G MG Putz Nathan D ND Landstreet Stuart R SR Kuck Jamie L JL Scarfe Lauren L Skrypnyk Nataliya N Yang Haichun H Harrison Fiona E FE de Caestecker Mark P MP Bastarache Julie A JA Ware Lorraine B LB

American journal of physiology. Renal physiology 20190731 4

Acute kidney injury is a common complication of severe sepsis and contributes to high mortality. The molecular mechanisms of acute kidney injury during sepsis are not fully understood. Because hemoproteins, including myoglobin and hemoglobin, are known to mediate kidney injury during rhabdomyolysis, we hypothesized that cell-free hemoglobin (CFH) would exacerbate acute kidney injury during sepsis. Sepsis was induced in mice by intraperitoneal injection of cecal slurry (CS). To mimic elevated lev ...[more]

PMID: 31364379

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Project description:Cell-free hemoglobin (CFH) levels are elevated in septic shock and are higher in nonsurvivors. Whether CFH is only a marker of sepsis severity or is involved in pathogenesis is unknown. This study aimed to investigate whether CFH worsens sepsis-associated injuries and to determine potential mechanisms of harm. Fifty-one, 10-12 kg purpose-bred beagles were randomized to receive Staphylococcus aureus intrapulmonary challenges or saline followed by CFH infusions (oxyhemoglobin >80%) or placebo. Animals received antibiotics and intensive care support for 96 h. CFH significantly increased mean pulmonary arterial pressures and right ventricular afterload in both septic and nonseptic animals, effects that were significantly greater in nonsurvivors. These findings are consistent with CFH-associated nitric oxide (NO) scavenging and were associated with significantly depressed cardiac function, and worsened shock, lactate levels, metabolic acidosis, and multiorgan failure. In septic animals only, CFH administration significantly increased mean alveolar-arterial oxygenation gradients, also to a significantly greater degree in nonsurvivors. CFH-associated iron levels were significantly suppressed in infected animals, suggesting that bacterial iron uptake worsened pneumonia. Notably, cytokine levels were similar in survivors and nonsurvivors and were not predictive of outcome. In the absence and presence of infection, CFH infusions resulted in pulmonary hypertension, cardiogenic shock, and multiorgan failure, likely through NO scavenging. In the presence of infection alone, CFH infusions worsened oxygen exchange and lung injury, presumably by supplying iron that promoted bacterial growth. CFH elevation, a known consequence of clinical septic shock, adversely impacts sepsis outcomes through more than one mechanism, and is a biologically plausible, nonantibiotic, noncytokine target for therapeutic intervention.NEW & NOTEWORTHY Cell-free hemoglobin (CFH) elevations are a known consequence of clinical sepsis. Using a two-by-two factorial design and extensive physiological and biochemical evidence, we found a direct mechanism of injury related to nitric oxide scavenging leading to pulmonary hypertension increasing right heart afterload, depressed cardiac function, worsening circulatory failure, and death, as well as an indirect mechanism related to iron toxicity. These discoveries alter conventional thinking about septic shock pathogenesis and provide novel therapeutic approaches.

Project description:OBJECTIVES:To determine the relationship between the production of cell-free plasma hemoglobin and acute kidney injury in infants and children undergoing cardiopulmonary bypass for cardiac surgery. DESIGN:Prospective observational study. SETTING:Twelve-bed cardiac ICU in a university-affiliated children's hospital. PATIENTS:Children were prospectively enrolled during their preoperative outpatient appointment with the following criteria: greater than 1 month to less than 18 years old, procedures requiring cardiopulmonary bypass, no preexisting renal dysfunction. INTERVENTIONS:None. MEASUREMENTS AND MAIN RESULTS:Plasma and urine were collected at baseline (in a subset), the beginning and end of cardiopulmonary bypass, and 2 hours and 24 hours after cardiopulmonary bypass in 60 subjects. Levels of plasma hemoglobin increased during cardiopulmonary bypass and were associated (p < 0.01) with cardiopulmonary bypass duration (R = 0.22), depletion of haptoglobin at end and 24 hours after cardiopulmonary bypass (R = 0.12 and 0.15, respectively), lactate dehydrogenase levels at end cardiopulmonary bypass (R = 0.27), and change in creatinine (R = 0.12). Forty-three percent of patients developed acute kidney injury. There was an association between plasma hemoglobin level and change in creatinine that varied by age (overall [R = 0.12; p < 0.01]; in age > 2 yr [R = 0.22; p < 0.01]; and in < 2 yr [R = 0.03; p = 0.42]). Change in plasma hemoglobin and male gender were found to be risk factors for acute kidney injury (odds ratio, 1.02 and 3.78, respectively; p < 0.05). CONCLUSIONS:Generation of plasma hemoglobin during cardiopulmonary bypass and male gender are associated with subsequent renal dysfunction in low-risk pediatric patients, especially in those older than 2 years. Further studies are needed to determine whether specific subgroups of pediatric patients undergoing cardiopulmonary bypass would benefit from potential treatments for hemolysis and plasma hemoglobin-associated renal dysfunction.

Project description:To identify mechanisms associated with sepsis-acute kidney injury based on the expression levels of renal injury biomarkers, neutrophil gelatinase-associated lipocalin, and kidney injury molecule-1 in renal biopsies which may allow the identification of sepsis-acute kidney injury patient subtypes.DesignProspective, clinical laboratory study using "warm" human postmortem sepsis-acute kidney injury kidney biopsies.SettingResearch laboratory at university teaching hospital.SubjectsAdult patients who died of sepsis in the ICU and control patients undergoing tumor nephrectomy.Measurements and main resultsReverse transcription quantitative polymerase chain reaction and immunohistochemical staining were used to quantify messenger RNA and protein expression levels of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in the kidney of sepsis-acute kidney injury patients and control subjects. Morphometric analysis was used to quantify renal and glomerular neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 protein levels. Neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 messenger RNA and protein levels were increased in kidneys of sepsis-acute kidney injury patients compared with control kidney tissue. Neutrophil gelatinase-associated lipocalin was localized in the distal tubules, collecting ducts, the adventitia of the renal arterioles, and in the glomerular tufts of renal biopsies from sepsis-acute kidney injury patients. In contrast, kidney injury molecule-1 was localized at the brush border of the proximal tubules. There was no correlation between neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 levels. Furthermore, renal neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 levels were not associated with the extent of renal injury, the severity of critical illness, or serum creatinine levels at either ICU admission or day of expiration. By laser microdissecting glomeruli, followed by reverse transcription quantitative polymerase chain reaction, we identified heterogenous glomerular neutrophil gelatinase-associated lipocalin production in the kidney of sepsis-acute kidney injury patients.ConclusionWe found differences in the expression of neutrophil gelatinase-associated lipocalin and kidney injury molecule-1 in patients with the same syndrome "sepsis-acute kidney injury" meaning there is no single pathway leading to sepsis-acute kidney injury. This underscores the beliefs that there are many/different pathophysiological pathways that can cause sepsis-acute kidney injury. Hence, patients with criteria that meet the definitions of both acute kidney injury and sepsis can be divided into subtypes based on pathophysiological features.

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Cell-free hemoglobin augments acute kidney injury during experimental sepsis.

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Cell-free hemoglobin augments acute kidney injury during experimental sepsis.

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