NLRP3 inflammasome of renal tubular epithelial cells induces kidney injury in acute hemolytic transfusion reactions.

BACKGROUND: Blood transfusion, a common basic supporting therapy, can lead to acute hemolytic transfusion reaction (AHTR). AHTR poses a great risk to patients through kidney function damage in a short time. Previous reports found that heme from destroyed red blood cells impaired kidney function, and NLR family pyrin domain containing 3 (NLRP3) inflammasome was augmented in case of kidney injury. However, the detailed mechanism regarding whether NLRP3 inflammasome is involved in kidney function injury in AHTR is not fully understood yet. METHODS: Hemolysis models were established by vein injection with human blood plasma or mouse heme from destroyed red blood cells. The injured renal tubular epithelial cells (RTECs) were evaluated by tubular damage markers staining in hemolysis models and in primary RTECs in vitro. The activation of NLRP3 inflammasome in RTECs by hemes was investigated by Western blot, ELISA, scanning electron microscopy, immunofluorescent staining, flow cytometry, and hemolysis models. NLRP3 gene knockout mice were employed to confirm these observations in vitro and in vivo. The binding between a novel inhibitor (66PR) and NLRP3 was affirmed by molecule docking and co-immunoprecipitation. The rescue of 66PR on kidney function impairment was explored in murine hemolysis models. RESULTS: We found that heme could activate NLRP3 inflammasome in RTECs to induce kidney function injury. NLRP3 gene knockout could prevent the damage of RTECs caused by hemes and recover kidney function in AHTR. Moreover, NLRP3 inflammasome chemical inhibitor, 66PR, could bind to NLRP3 protein and inhibit inflammasome activation in RTECs, which consequently relieved the injury of RTECs caused by hemes, and alleviated kidney function damage in the AHTR model. CONCLUSIONS: Hemes could activate NLRP3 inflammasome in RTECs, and a novel NLRP3 inflammasome inhibitor named 66PR relieved kidney function damage in AHTR. Our findings provided a new possible strategy to treat kidney function failure in AHTR.

The Role of Circulating Cell-Free Hemoglobin in Sepsis-Associated Acute Kidney Injury.

Sepsis is a heterogeneous clinical syndrome that is complicated commonly by acute kidney injury (sepsis-AKI). Currently, no approved pharmacologic therapies exist to either prevent sepsis-AKI or to treat sepsis-AKI once it occurs. A growing body of evidence supports a connection between red blood cell biology and sepsis-AKI. Increased levels of circulating cell-free hemoglobin (CFH) released from red blood cells during hemolysis are common during sepsis and can contribute to sepsis-AKI through several mechanisms including tubular obstruction, nitric oxide depletion, oxidative injury, and proinflammatory signaling. A number of potential pharmacologic therapies targeting CFH in sepsis have been identified including haptoglobin, hemopexin, and acetaminophen, and early phase clinical trials have suggested that acetaminophen may have beneficial effects on lipid peroxidation and kidney function in patients with sepsis. Bedside measurement of CFH levels may facilitate predictive enrichment for future clinical trials of CFH-targeted therapeutics. However, rapid and reliable bedside tests for plasma CFH will be required for such trials to move forward.

Strategies for managing transfusional iron overload: conventional treatments and novel strategies.

PURPOSE OF REVIEW: For individuals who have transfusion-dependent anemia, iron overload is the long-term complication, which results in significant morbidity. Ameliorating this is now the biggest unmet need. This review specifically addresses this issue. RECENT FINDINGS: Over the last decade or so, major advances in the treatment of these individuals, has resulted from novel strategies aimed at reducing transfusion requirement as well as optimizing chelation therapy. This review will summarize these advances and provide insights into some of the therapies in the pipeline. Strategies aimed at reducing transfusion requirement include modulation of erythropoietic regulation by reducing ineffective red cell production through activin trapping, as well as stem cell gene modification approaches, which aim for a cure, and transfusion independence. Refined means of assessing tissue iron and the introduction of oral chelators have facilitated tailoring chelation regimens with closer monitoring and improved compliance. Newer approaches to ameliorate iron toxicity have focused on the hepcidin pathway, all of which would result in increased hepcidin levels and reduction of iron absorption from the intestine, sequestration of iron in normal storage sites and reduced exposure of more susceptible organs, such as the heart and endocrine organs, to the toxic effects of increased iron. SUMMARY: These advances offer the promise of improved management of transfusion-dependent individuals.

Metabolomics Approach Based on Multivariate Techniques for Blood Transfusion Reactions.

Blood transfusions temporarily improve the physical state of the patient but exert widespread effects on immune and non-immune systems. Perioperative allogeneic blood transfusions (ABT) are associated with various risks, including coagulopathy, incompatibility, transmission of infectious agents, and allergic reactions. Nevertheless, little is known about the global metabolic alterations that reflect the possible reactions of blood transfusions. In this study, we investigated metabolite changes generated by ABT in a rat model using metabolomics technology. To further profile the "metabolome" after blood transfusions, we used both liquid chromatography-quadrupole time-of-flight high-definition mass spectrometry and gas chromatography-mass spectrometry. ABT promoted a stimulatory microenvironment associated with a relative increase in glucose transporter 1/4 (GLUT1/GLUT4) expression. Supporting this result, glucose metabolism-related enzyme IRS1 and interleukin-6 (IL-6) were abnormally expressed, and levels of lysophosphatidylcholine (LysoPC) and its related enzyme phospholipase A2 (PLA2) were significantly altered in allogeneic groups compared to those in autologous groups. Finally, amino acid metabolism was also altered following ABT. Taken together, our results show a difference between autologous and allogeneic blood transfusions and demonstrate correlations with cancer-associated metabolic changes. Our data provide endogenous information for a better understanding of blood transfusion reactions.

Diagnosis and treatment of cardiac iron overload in transfusion-dependent thalassemia patients.

INTRODUCTION: Thalassemia is among the most common genetic diseases. Patients with severe forms of the disease are transfusion-dependent, leading to iron overload. A condition which can eventually develop in the iron-loaded heart is iron overload cardiomyopathy, a debilitating disease that accounts for the majority of deaths in thalassemia patients. Areas covered: This review article provides a comprehensive summary of the diagnosis and treatment of cardiac iron overload in transfusion-dependent thalassemia patients, with discussion covering current weak points and potential improvements of the relevant diagnostic and therapeutic strategies. Expert commentary: Current limitations of various diagnostic techniques for iron overload cardiomyopathy include suboptimal accuracy, untimely detection, or inadequate accessibility, and novel modalities are required to overcome these shortcomings. Treatment should address key pathophysiologic mechanisms of iron overload cardiomyopathy, which include cardiac iron mishandling and iron-induced oxidative injury. Apart from the promotion of iron removal by chelators, prevention of cardiac iron deposition and attenuation of oxidative damage should also be rigorously investigated on a cell-to-bedside basis.

Iron overload in myelodysplastic syndromes (MDS).

Iron overload (IOL) starts to develop in MDS patients before they become transfusion-dependent because ineffective erythropoiesis suppresses hepcidin production in the liver and thus leads to unrestrained intestinal iron uptake. However, the most important cause of iron overload in MDS is chronic transfusion therapy. While transfusion dependency by itself is a negative prognostic factor reflecting poor bone marrow function, the ensuing transfusional iron overload has an additional dose-dependent negative impact on the survival of patients with lower risk MDS. Cardiac dysfunction appears to be important in this context, as a consequence of chronic anemia, age-related cardiac comorbidity, and iron overload. Another potential problem is iron-related endothelial dysfunction. There is some evidence that with increasing age, high circulating iron levels worsen the atherosclerotic phenotype. Transfusional IOL also appears to aggravate bone marrow failure in MDS, through unfavorable effects on mesenchymal stromal cells as well a hematopoietic cells, particularly erythroid precursors. Patient series and clinical trials have shown that the iron chelators deferoxamine and deferasirox can improve hematopoiesis in a minority of transfusion-dependent patients. Analyses of registry data suggest that iron chelation provides a survival benefit for patients with MDS, but data from a prospective randomized clinical trial are still lacking.