Case series supporting heme detoxification via therapeutic plasma exchange in acute multiorgan failure syndrome resistant to red blood cell exchange in sickle cell disease

Position paper on advancing sickle cell disease management in France by bridging the clinical practices and guidelines through expert insights

In France, sickle cell disease (SCD) is the most common rare disease and represents the most prevalent genetic disorder, with 19,800 to 32,400 patients diagnosed in 2016 and 1:714 newborns affected in 2019. SCD is caused by a single mutation in the β-globin gene, resulting in the production of abnormal hemoglobin (called HbS), chronic hemolytic anemia, and impaired red blood cell rheology. SCD patients face several severe acute and chronic complications, including stroke, acute chest syndrome (ACS), painful vaso-occlusive crisis (VOC), organ failure, and a high risk of infections. As patients' care pathway remains unclear in France, a roundtable advisory board meeting was organized in the country to provide insights into the management of SCD in alignment with clinical guidelines. The meeting brought together a panel of esteemed key opinion leaders (KOLs) in SCD management, encompassing both clinical practice and research. During the meeting, the KOLs discussed clinical practices and their alignment with French guidelines, identifying areas of concordance and discrepancy. They also addressed disparities in SCD clinical practices across regions and medical centers. The KOLs discussed the prophylactic and therapeutic options currently available for SCD patients in France, with a focus on transfusion therapies, especially automated red blood cell exchange (aRBCX). The results of this advisory board meeting provide a valuable platform for gathering expert perspectives on SCD management, clinical practices, guideline alignment, and the potential for contributions to guideline updates.

Double-edged functions of hemopexin in hematological related diseases: from basic mechanisms to clinical application

It is now understood that hemolysis and the subsequent release of heme into circulation play a critical role in driving the progression of various diseases. Hemopexin (HPX), a heme-binding protein with the highest affinity for heme in plasma, serves as an effective antagonist against heme toxicity resulting from severe acute or chronic hemolysis. In the present study, changes in HPX concentration were characterized at different stages of hemolytic diseases, underscoring its potential as a biomarker for assessing disease progression and prognosis. In many heme overload-driven conditions, such as sickle cell disease, transfusion-induced hemolysis, and sepsis, endogenous HPX levels are often insufficient to provide protection. Consequently, there is growing interest in developing HPX therapeutics to mitigate toxic heme exposure. Strategies include HPX supplementation when endogenous levels are depleted and enhancing HPX's functionality through modifications, offering a potent defense against heme toxicity. It is worth noting that HPX may also exert deleterious effects under certain circumstances. This review aims to provide a comprehensive overview of HPX's roles in the progression and prognosis of hematological diseases. It highlights HPX-based clinical therapies for different hematological disorders, discusses advancements in HPX production and modification technologies, and offers a theoretical basis for the clinical application of HPX.

Endothelial superoxide dismutase 2 is decreased in sickle cell disease and regulates fibronectin processing

Sickle cell disease (SCD) is a genetic red blood cell disorder characterized by increased reactive oxygen species (ROS) and a concordant reduction in antioxidant capacity in the endothelium. Superoxide dismutase 2 (SOD2) is a mitochondrial-localized enzyme that catalyzes the dismutation of superoxide to hydrogen peroxide. Decreased peripheral blood expression of SOD2 is correlated with increased hemolysis and cardiomyopathy in SCD. Here, we report for the first time that endothelial cells exhibit reduced SOD2 protein expression in the pulmonary endothelium of SCD patients. To investigate the impact of decreased SOD2 expression in the endothelium, SOD2 was knocked down in human pulmonary microvascular endothelial cells (hPMVECs). We found that SOD2 deficiency in hPMVECs results in endothelial cell dysfunction, including reduced cellular adhesion, diminished migration, integrin protein dysregulation, and disruption of permeability. Furthermore, we uncover that SOD2 mediates changes in endothelial cell function via processing of fibronectin through its inability to facilitate dimerization. These results demonstrate that endothelial cells are deficient in SOD2 expression in SCD patients and suggest a novel pathway for SOD2 in regulating fibronectin processing.

Further evidence for the benefit of therapeutic plasma exchange for acute multi-organ failure syndrome refractory to red cell exchange in sickle cell disease

Acute multiorgan failure syndrome (MOFS) remains a significant cause of mortality in sickle cell disease (SCD) patients despite red cell exchange (RCE). In small case series and reports, therapeutic plasma exchange (TPE) has shown benefit in MOFS. As further support for consideration of this modality, we present two patients with SCD and MOFS refractory to RCE who were subsequently treated with TPE. Fresh frozen plasma was used as the replacement fluid. Despite estimated hospital mortality of 40% at the time of intensive care unit admission, both patients showed marked clinical improvement with TPE treatment. Our cases add to the evidence supporting the potential inclusion of MOFS secondary to acute SCD as an indication for TPE in the next edition of the American Society of Apheresis Guidelines on the Use of Therapeutic Apheresis in Clinical Practice.

Vasculo-toxic and pro-inflammatory action of unbound haemoglobin, haem and iron in transfusion-dependent patients with haemolytic anaemias

Increasing evidence suggests that free haem and iron exert vasculo‐toxic and pro‐inflammatory effects by activating endothelial and immune cells. In the present retrospective study, we compared serum samples from transfusion‐dependent patients with β‐thalassaemia major and intermedia, hereditary spherocytosis and sickle cell disease (SCD). Haemolysis, transfusions and ineffective erythropoiesis contribute to haem and iron overload in haemolytic patients. In all cohorts we observed increased systemic haem and iron levels associated with scavenger depletion and toxic ‘free’ species formation. Endothelial dysfunction, oxidative stress and inflammation markers were significantly increased compared to healthy donors. In multivariable logistic regression analysis, oxidative stress markers remained significantly associated with both haem‐ and iron‐related parameters, while soluble vascular cell adhesion molecule 1 (sVCAM‐1), soluble endothelial selectin (sE‐selectin) and tumour necrosis factor α (TNFα) showed the strongest association with haem‐related parameters and soluble intercellular adhesion molecule 1 (sICAM‐1), sVCAM‐1, interleukin 6 (IL‐6) and vascular endothelial growth factor (VEGF) with iron‐related parameters. While hereditary spherocytosis was associated with the highest IL‐6 and TNFα levels, β‐thalassaemia major showed limited inflammation compared to SCD. The sVCAM1 increase was significantly lower in patients with SCD receiving exchange compared to simple transfusions. The present results support the involvement of free haem/iron species in the pathogenesis of vascular dysfunction and sterile inflammation in haemolytic diseases, irrespective of the underlying haemolytic mechanism, and highlight the potential therapeutic benefit of iron/haem scavenging therapies in these conditions.

Multiple sclerosis in a young woman with sickle cell disease

BACKGROUND

Comorbidities can impose diagnostic and treatment challenges in patients with multiple sclerosis (MS). Sickle cell disease (SCD) and MS are both inflammatory diseases featuring immune system dysregulation, and the reciprocal interaction of these diseases deserves investigation.

METHODS/RESULTS

We present the case of a 28-year-old woman with SCD who developed a sickle cell crisis and acute chest syndrome during corticosteroid treatment for a first MS attack. We then provide a review of the literature on co-management of SCD and MS. In patients with SCD experiencing an acute MS exacerbation, pre-treatment with red blood cell exchange transfusion before corticosteroids may reduce adverse vaso-occlusive events. Plasma exchange may also be considered. Finally, we discuss innovative pre-clinical research that suggests that natalizumab or dimethyl fumarate may ameliorate SCD symptoms while preventing MS relapses; human trials, however, are needed.

CONCLUSION

The co-occurrence of inflammatory disorders, in this case MS and SCD, requires providers to appropriately manage each condition with consideration of the other. Future studies may generate shared avenues for treatment.

The cause and pathogenesis of hemolytic transfusion reactions in sickle-cell disease

PURPOSE OF REVIEW

The current review aims to summarize the epidemiology, cause, pathophysiology, and management of hemolytic transfusion reactions in sickle-cell disease (SCD).

RECENT FINDINGS

Patients undergoing occasional, isolated transfusions have been shown to have a higher risk of developing this condition. Despite the identification of well known risk factors, including alloimmunization, the pathophysiology of this syndrome remains unclear, as very severe forms with hyperhemolysis may develop in the absence of detectable antibodies, or with antibodies that are not considered to be clinically significant. Complement plays a crucial role in this reaction, particularly in cases of intravascular hemolysis. Complement triggers the reaction, but it also amplifies the inflammatory response and aggravates tissue damage. Free heme and hemoglobin are released and interact with complement, causing tissue damage.

SUMMARY

Hemolytic transfusion reactions are the most feared complications of blood transfusion in patients with SCD. This reaction is underdiagnosed because it mimics a vaso-occlusive crisis. Alloimmunization against red blood cell antigens is known to be a major trigger of this reaction, but abnormal complement activation and the underlying condition in patients with chronic hemolysis, may amplify the reaction. There is an urgent need to develop evidence-based approaches for preventing and treating this reaction.

What Is Next in This "Age" of Heme-Driven Pathology and Protection by Hemopexin? An Update and Links with Iron

This review provides a synopsis of the published literature over the past two years on the heme-binding protein hemopexin (HPX), with some background information on the biochemistry of the HPX system. One focus is on the mechanisms of heme-driven pathology in the context of heme and iron homeostasis in human health and disease. The heme-binding protein hemopexin is a multi-functional protectant against hemoglobin (Hb)-derived heme toxicity as well as mitigating heme-mediated effects on immune cells, endothelial cells, and stem cells that collectively contribute to driving inflammation, perturbing vascular hemostasis and blood–brain barrier function. Heme toxicity, which may lead to iron toxicity, is recognized increasingly in a wide range of conditions involving hemolysis and immune system activation and, in this review, we highlight some newly identified actions of heme and hemopexin especially in situations where normal processes fail to maintain heme and iron homeostasis. Finally, we present preliminary data showing that the cytokine IL-6 cross talks with activation of the c-Jun N-terminal kinase pathway in response to heme-hemopexin in models of hepatocytes. This indicates another level of complexity in the cell responses to elevated heme via the HPX system when the immune system is activated and/or in the presence of inflammation.

Reversal of Severe Multiorgan Failure Associated With Sickle Cell Crisis Using Plasma Exchange: A Case Series

OBJECTIVE

Red blood cell exchange (RBCE) is the standard of care for patients with sickle cell disease (SCD) who present with severe vaso-occlusive crisis (VOC). However, subsets of these critically ill patients have progressive multiorgan failure (MOF) despite RBCE therapy. The purpose of this case series is to describe the use of plasma exchange (PLEX) for the treatment of SCD-related MOF that is refractory to RBCE.

METHODS

A retrospective case review of patients with severe MOF from sickle cell crisis unresponsive to RBCE who underwent PLEX in a 14-bed adult medical intensive care unit (ICU) at a tertiary care university hospital over a 4-year time period. Key laboratory data including complete blood count, indices of hemolysis, and markers of organ failure were recorded before and after both RBCE and PLEX.

RESULTS

Our primary objective is to evaluate the effectiveness of PLEX, in addition to RBCE, on organ dysfunction, laboratory indices, and mortality. Of the 7 patients, 6 survived. Of the patients who survived, all remained hemodynamically stable during PLEX sessions and showed both clinical and laboratory evidences of improvement in hemolysis and organ function. Average time from completion of first PLEX treatment to initial laboratory signs of organ failure reversal for patients who survived was 15.6 hours, the average length of stay in the ICU was 5.6 days, and the average total length of stay in the hospital was 14 days.

CONCLUSIONS

Plasma exchange, in addition to RBCE, may be a novel synergistic treatment option to decrease risk of mortality in patients with refractory VOC and MOF.

Complement activation during intravascular hemolysis: Implication for sickle cell disease and hemolytic transfusion reactions

Intravascular hemolysis is a hallmark of a large spectrum of diseases, including the sickle cell disease (SCD), and is characterized by liberation of red blood cell (RBC) degradation products in the circulation. Released Hb, heme, RBC fragments and microvesicles (MVs) exert pro-inflammatory, pro-oxidative and cytotoxic effects and contribute to vascular and tissue damage. The innate immune complement system not only contributes to the RBC lysis, but it is also itself activated by heme, RBC MVs and the hypoxia-altered endothelium, amplifying thus the cell and tissue damage. This review focuses on the implication of the complement system in hemolysis and hemolysis-mediated injuries in SCD and in cases of delayed hemolytic transfusion reactions (DHTR). We summarize the evidences for presence of biomarkers of complement activation in patients with SCD and the mechanisms of complement activation in DHTR. We discuss the role of antibodies-dependent activation of the classical complement pathway as well as the heme-dependent activation of the alternative pathway. Finally, we describe the available evidences for the efficacy of therapeutic blockade of complement in cases of DHTR. In conclusion, complement blockade is holding promises but future prospective studies are required to introduce Eculizumab or another upcoming complement therapeutic for DHTR and even in SCD.

New Therapeutic Options for the Treatment of Sickle Cell Disease

Sickle cell disease (SCD; ORPHA232; OMIM # 603903) is a chronic and invalidating disorder distributed worldwide, with high morbidity and mortality. Given the disease complexity and the multiplicity of pathophysiological targets, development of new therapeutic options is critical, despite the positive effects of hydroxyurea (HU), for many years the only approved drug for SCD. New therapeutic strategies might be divided into (1) pathophysiology-related novel therapies and (2) innovations in curative therapeutic options such as hematopoietic stem cell transplantation and gene therapy. The pathophysiology related novel therapies are: a) Agents which reduce sickling or prevent sickle red cell dehydration; b) Agents targeting SCD vasculopathy and sickle cell-endothelial adhesive events; c) Anti-oxidant agents. This review highlights new therapeutic strategies in SCD and discusses future developments, research implications, and possible innovative clinical trials.

How I safely transfuse patients with sickle-cell disease and manage delayed hemolytic transfusion reactions

Transfusions can be a life-saving treatment of patients with sickle-cell disease (SCD). However, availability of matched units can be limiting because of distinctive blood group polymorphisms in patients of African descent. Development of antibodies against the transfused red blood cells (RBCs), resulting in delayed hemolytic transfusion reactions (DHTRs), can be life-threatening and pose unique challenges for this population with regard to treatment strategies and transfusion management protocols. In cases where the transfused cells and the patient's own RBCs are destroyed, diagnosis of DHTR can be difficult because symptoms may mimic vaso-occlusive crisis, and frequently, antibodies are undetectable. Guidelines are needed for early diagnosis of DHTR because treatment may need to include temporarily withholding any new transfusions to avoid further hemolysis. Also needed are case-control studies to optimally tailor treatments based on the severity of DHTR and develop preventive transfusion strategies for patients at DHTR risk. Here, we will review gaps in knowledge and describe through case studies our recommended approach to prevent alloimmunization and to diagnose and treat symptomatic DHTRs for which complementary mechanistic studies to understand their pathogenesis are sorely needed.

Haptoglobin and hemopexin inhibit vaso-occlusion and inflammation in murine sickle cell disease: Role of heme oxygenase-1 induction

During hemolysis, hemoglobin and heme released from red blood cells promote oxidative stress, inflammation and thrombosis. Plasma haptoglobin and hemopexin scavenge free hemoglobin and heme, respectively, but can be depleted in hemolytic states. Haptoglobin and hemopexin supplementation protect tissues, including the vasculature, liver and kidneys. It is widely assumed that these protective effects are due primarily to hemoglobin and heme clearance from the vasculature. However, this simple assumption does not account for the consequent cytoprotective adaptation seen in cells and organs. To further address the mechanism, we used a hyperhemolytic murine model (Townes-SS) of sickle cell disease to examine cellular responses to haptoglobin and hemopexin supplementation. A single infusion of haptoglobin or hemopexin (± equimolar hemoglobin) in SS-mice increased heme oxygenase-1 (HO-1) in the liver, kidney and skin several fold within 1 hour and decreased nuclear NF-ĸB phospho-p65, and vaso-occlusion for 48 hours after infusion. Plasma hemoglobin and heme levels were not significantly changed 1 hour after infusion of haptoglobin or hemopexin. Haptoglobin and hemopexin also inhibited hypoxia/reoxygenation and lipopolysaccharide-induced vaso-occlusion in SS-mice. Inhibition of HO-1 activity with tin protoporphyrin blocked the protections afforded by haptoglobin and hemopexin in SS-mice. The HO-1 reaction product carbon monoxide, fully restored the protection, in part by inhibiting Weibel-Palade body mobilization of P-selectin and von Willebrand factor to endothelial cell surfaces. Thus, the mechanism by which haptoglobin and hemopexin supplementation in hyperhemolytic SS-mice induces cytoprotective cellular responses is linked to increased HO-1 activity.