Abnormal modulation of cell protective systems in response to ischemic/reperfusion injury is important in the development of mouse sickle cell hepatopathy

Macrophage metabolic rewiring improves heme-suppressed efferocytosis and tissue damage in sickle cell disease

Sickle cell disease (SCD) is hallmarked by an underlying chronic inflammatory condition, which is contributed by heme-activated proinflammatory macrophages. Although previous studies addressed heme ability to stimulate macrophage inflammatory skewing through Toll-like receptor4 (TLR4)/reactive oxygen species signaling, how heme alters cell functional properties remains unexplored. Macrophage-mediated immune cell recruitment and apoptotic cell (AC) clearance are relevant in the context of SCD, in which tissue damage, cell apoptosis, and inflammation occur owing to vaso-occlusive episodes, hypoxia, and ischemic injury. Here we show that heme strongly alters macrophage functional response to AC damage by exacerbating immune cell recruitment and impairing cell efferocytic capacity. In SCD, heme-driven excessive leukocyte influx and defective efferocytosis contribute to exacerbated tissue damage and sustained inflammation. Mechanistically, these events depend on heme-mediated activation of TLR4 signaling and suppression of the transcription factor proliferator-activated receptor γ (PPARγ) and its coactivator peroxisome proliferator-activated receptor γ coactivator 1α (PGC1α). These changes reduce efferocytic receptor expression and promote mitochondrial remodeling, resulting in a coordinated functional and metabolic reprogramming of macrophages. Overall, this results in limited AC engulfment, impaired metabolic shift to mitochondrial fatty acid β-oxidation, and, ultimately, reduced secretion of the antiinflammatory cytokines interleukin-4 (IL-4) and IL-10, with consequent inhibition of continual efferocytosis, resolution of inflammation, and tissue repair. We further demonstrate that impaired phagocytic capacity is recapitulated by macrophage exposure to plasma of patients with SCD and improved by hemopexin-mediated heme scavenging, PPARγ agonists, or IL-4 exposure through functional and metabolic macrophage rewiring. Our data indicate that therapeutic improvement of heme-altered macrophage functional properties via heme scavenging or PGC1α/PPARγ modulation significantly ameliorates tissue damage associated with SCD pathophysiology.

Mn porphyrins as a novel treatment targeting sickle cell NOXs to reverse and prevent acute vaso-occlusion in vivo

In sickle cell disease (SCD), adhesion of sickle red blood cells (SSRBCs) and activated leukocytes in inflamed venules affects blood rheology, causing vaso-occlusive manifestations and vital reduction in microvascular blood flow. Recently, we found that NADPH oxidases (NOXs) create a vicious feedback loop within SSRBCs. This positive feedback loop mediates SSRBC adhesion to the endothelium. We show for the first time the therapeutic effectiveness of the redox-active manganese (Mn) porphyrins MnTnBuOE-2-PyP5+ (MnBuOE; BMX-001) and MnTE-2-PyP5+ (MnE; BMX-010, AEOL10113) to treat established vaso-occlusion in a humanized sickle mouse model of an acute vaso-occlusive crisis using intravital microscopy. These Mn porphyrins can suppress SSRBC NOX activity. Subcutaneous administration of only 1 dose of MnBuOE or MnE at 0.1 to 2 mg/kg after the inflammatory trigger of vaso-occlusion, or simultaneously, reversed and reduced leukocyte and SSRBC adhesion, diminished leukocyte rolling, restored blood flow, and increased survival rate. Furthermore, MnBuOE and MnE administered to sickle mice subcutaneously at 0.1 to 1 mg/kg for 28 days (except on weekends) did not exacerbate anemia, which seemed to be due to downregulation of both SSRBC reactive oxygen species production and exposure of the eryptotic marker phosphatidylserine. In addition, Mn porphyrins ameliorated leukocytosis, venous blood gases, endothelial activation, and organ oxidative damage. Our data suggest that Mn porphyrins, likely by repressing NOX-mediated adhesive function of SSRBCs and activated leukocytes, could represent a novel, safe therapeutic intervention to treat or prevent the establishment of acute pain crises. These NOX-targeted antioxidants merit further assessment in SCD clinical trials.

Agonistic Anti-CD40 Antibody Triggers an Acute Liver Crisis With Systemic Inflammation in Humanized Sickle Cell Disease Mice

Sickle cell disease (SCD) is an inherited hemolytic disorder, defined by a point mutation in the β-globin gene. Stress conditions such as infection, inflammation, dehydration, and hypoxia trigger erythrocyte sickling. Sickled red blood cells (RBCs) hemolyze more rapidly, show impaired deformability, and increased adhesive properties to the endothelium. In a proinflammatory, pro-coagulative environment with preexisting endothelial dysfunction, sickled RBCs promote vascular occlusion. Hepatobiliary involvement related to the sickling process, such as an acute sickle hepatic crisis, is observed in about 10% of acute sickle cell crisis incidents. In mice, ligation of CD40 with an agonistic antibody leads to a macrophage activation in the liver, triggering a sequence of systemic inflammation, endothelial cell activation, thrombosis, and focal ischemia. We found that anti-CD40 antibody injection in sickle cell mice induces a systemic inflammatory and hemodynamic response with accelerated hemolysis, extensive vaso-occlusion, and large ischemic infarctions in the liver mimicking an acute hepatic crisis. Administration of the tumor necrosis factor-α (TNF-α) blocker, etanercept, and the heme scavenger protein, hemopexin attenuated end-organ damage. These data collectively suggest that anti-CD40 administration offers a novel acute liver crisis model in humanized sickle mice, allowing for evaluation of therapeutic proof-of-concept.

Sickle cell disease mice have cerebral oxidative stress and vascular and white matter abnormalities

Strokes are feared complications of sickle cell disease (SCD) and yield significant neurologic and neurocognitive deficits. However, even without detectable strokes, SCD patients have significant neurocognitive deficits in domains of learning and memory, processing speed and executive function. In these cases, mechanisms unrelated to major cerebrovascular abnormalities likely underlie these deficits. While oxidative stress and stress-related signaling pathways play a role in SCD pathophysiology, their role in cerebral injury remains unknown. We have shown that Townes and BERK SCD mice, while not having strokes, recapitulate neurocognitive deficits reported in humans. We hypothesized that cognitive deficits in SCD mice are associated with cerebral oxidative stress. We showed that SCD mice have increased levels of reactive oxygen species, protein carbonylation, and lipid peroxidation in hippocampus and cortex, thus suggesting increased cerebral oxidative stress. Further, cerebral oxidative stress was associated with caspase-3 activity alterations and vascular endothelial abnormalities, white matter changes, and disruption of the blood brain barrier, similar to those reported after ischemic/oxidative injury. Additionally, after repeated hypoxia/reoxygenation exposure, homozygous Townes had enhanced microglia activation. Our findings indicate that oxidative stress and stress-induced tissue damage is increased in susceptible brain regions, which may, in turn, contribute to neurocognitive deficits in SCD mice.

The multifaceted role of ischemia/reperfusion in sickle cell anemia

Sickle cell anemia is a unique disease dominated by hemolytic anemia and vaso-occlusive events. The latter trigger a version of ischemia/reperfusion (I/R) pathobiology that is singular in its origin, cyclicity, complexity, instability, perpetuity, and breadth of clinical consequences. Specific clinical features are probably attributable to local I/R injury (e.g., stroke syndromes) or remote organ injury (e.g., acute chest syndrome) or the systematization of inflammation (e.g., multifocal arteriopathy). Indeed, by fashioning an underlying template of endothelial dysfunction and vulnerability, the robust inflammatory systematization no doubt contributes to all sickle pathology. In this Review, we highlight I/R-targeting therapeutics shown to improve microvascular blood flow in sickle transgenic mice undergoing I/R, and we suggest how such insights might be translated into human therapeutic strategies.

Magnesium for treating sickle cell disease

BACKGROUND

Sickle cell disease is an autosomal recessive inherited haemoglobinopathy which causes painful vaso-occlusive crises due to sickle red blood cell dehydration. Vaso-occlusive crises are common painful events responsible for a variety of clinical complications; overall mortality is increased and life expectancy decreased compared to the general population. Experimental studies suggest that intravenous magnesium has proven to be well-tolerated in individuals hospitalised for the immediate relief of acute (sudden onset) painful crisis and has the potential to decrease the length of hospital stay. Some in vitro studies and open studies of long-term oral magnesium showed promising effect on pain relief but failed to show its efficacy. The studies show that oral magnesium therapy may prevent sickle red blood cell dehydration and prevent recurrent painful episodes. There is a need to access evidence for the impact of oral and intravenous magnesium effect on frequency of pain, length of hospital stay and quality of life. This is an updated version of the review.

OBJECTIVES

To evaluate the effects of short-term intravenous magnesium on the length of hospital stay and quality of life in children and adults with sickle cell disease. To determine the effects of long-term oral magnesium therapy on the frequency of painful crises and the quality of life in children and adults with sickle cell disease.

SEARCH METHODS

We searched the Cochrane Haemoglobinopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books.Date of last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register: 03 February 2019.Date of last search of other resources (clinical trials registries): 04 April 2019.

SELECTION CRITERIA

We searched for published and unpublished randomized controlled studies of oral or intravenous magnesium compared to placebo or no magnesium.

DATA COLLECTION AND ANALYSIS

Authors independently assessed the study quality and extracted the data using standard Cochrane methodologies.

MAIN RESULTS

We included five randomized placebo-controlled studies with a total of 386 participants (aged three to 53 years). Of these, two shorter parallel studies (n = 306) compared intravenous magnesium sulphate to placebo (normal saline) for admission to hospital due to a vaso-occlusive crisis, for which we were able to analyse data. The quality of evidence was moderate for studies in this comparison, mainly due to limitations due to risk of bias and imprecision. Two of the three longer-term studies comparing oral magnesium pidolate to placebo had a cross-over design. The third was a parallel factorial study which compared hydroxyurea and oral magnesium to each other and to placebo over a longer period of time; we only present the comparison of oral magnesium to placebo from this study. The quality of evidence was very low with uncertainty of the estimation.The eight-hourly dose levels in the two studies of intravenous magnesium were different; one used 100 mg/kg while the second used 40 mg/kg. Only one of these studies (n = 104) reported the mean daily pain score while hospitalised (a non-significant difference between groups, moderate quality evidence). The second study (n = 202) reported a number of child- and parent-reported quality of life scores. None of the scores showed any difference between treatment groups (low quality evidence). Data from one study (n = 106) showed no difference in length of stay in hospital between groups (low quality evidence). Both studies reported on adverse events, but not defined by severity as we had planned. One study showed significantly more participants receiving intravenous magnesium experienced warmth at infusion site compared to placebo; there were no differences between groups for other adverse events (low quality evidence).Three studies (n = 80) compared oral magnesium pidolate to placebo. None of them reported data which we were able to analyse. One study (n = 24) reported on the number of painful days and stated there was no difference between two groups (low quality evidence). None of the studies reported on quality of life or length of hospital stay. Two studies (n = 68) reported there were no differences in levels of magnesium in either plasma or red blood cells (moderate quality evidence). Two studies (n = 56) reported adverse events. One reported episodes of mild diarrhoea and headache, all of which resolved without stopping treatment. The second study reported adverse events as gastrointestinal disorders, headache or migraine, upper respiratory infections and rash; which were all evenly distributed across treatment groups (moderate quality evidence).

AUTHORS' CONCLUSIONS

Moderate to low quality evidence showed neither intravenous magnesium and oral magnesium therapy has an effect on reducing painful crisis, length of hospital stay and changing quality of life in treating sickle cell disease. Therefore, no definitive conclusions can be made regarding its clinical benefit. Further randomized controlled studies, perhaps multicentre, are necessary to establish whether intravenous and oral magnesium therapies have any effect on improving the health of people with sickle cell disease.

Current challenges in the management of patients with sickle cell disease - A report of the Italian experience

Sickle cell disease (SCD) is an inherited red blood cell disorder caused by a structural abnormality of hemoglobin called sickle hemoglobin (HbS). Clinical manifestations of SCD are mainly characterized by chronic hemolysis and acute vaso-occlusive crisis, which are responsible for severe acute and chronic organ damage. SCD is widespread in sub-Saharan Africa, in the Middle East, Indian subcontinent, and some Mediterranean regions. With voluntary population migrations, people harboring the HbS gene have spread globally. In 2006, the World Health Organization recognized hemoglobinopathies, including SCD, as a global public health problem and urged national health systems worldwide to design and establish programs for the prevention and management of SCD. Herein we describe the historical experience of the network of hemoglobinopathy centers and their approach to SCD in Italy, a country where hemoglobinopathies have a high prevalence and where SCD, associated with different genotypes including ß-thalassemia, is present in the native population.

Peroxiredoxin-2: A Novel Regulator of Iron Homeostasis in Ineffective Erythropoiesis

AIMS

Iron overload (IO) is a life-threatening complication of chronic hemolytic disorders such as β-thalassemia. IO results in severe cellular oxidative damage, leading to organ failure. Peroxiredoxin-2 (Prx2), a typical 2-cysteine-(Cys)-peroxiredoxin, is an important component of the cytoprotective system, but its response to IO is still to be fully defined.

RESULTS

We studied the effects of IO on Prx2-knockout mice (Prx2^-/-). The absence of Prx2 enhanced toxicity due to IO on erythropoiesis. We found that IO failed to induce the typical hepcidin (Hamp) upregulation in Prx2^-/- mice due to its failure to activate the signal transducer and activator of transcription-3 (STAT3) with intact Jak2 signaling. In Prx2^-/- mice, the loss of Hamp response was also observed after administration of a single dose of oral iron. When lipopolysaccharide (LPS) was used to explore IL6-STAT3 activation in Prx2^-/- mice, STAT3 activation and Hamp upregulation were once again defective. Treatment with PEP-fusion-recombinant-Prx2 (PEP Prx2) significantly increased STAT3 activation with upregulation of Hamp expression in both IO- and LPS-exposed Prx2^-/- mice. We also confirmed the beneficial effects of PEP Prx2 on Hamp expression through STAT3 activation in β-thalassemic mice.

INNOVATION

We propose that Prx2 plays a key role in responding to cytotoxicity of IO, directly targeting STAT3-transcriptional factor in a Jak2-independent fashion and regulating Hamp in response to canonical stimuli.

CONCLUSION

Collectively, our data highlight a novel role of Prx2 in iron homeostasis. Prx2 is a key cytoprotector against IO that is induced either by iron supplementation or due to chronic hemolysis as in β-thalassemia. Prx2 is required to support STAT3 transcriptional activity and regulation of Hamp expression. Antioxid. Redox Signal. 28, 1-14.

Magnesium for treating sickle cell disease

BACKGROUND

Sickle cell disease is an autosomal recessive inherited haemoglobinopathy which causes painful vaso-occlusive crises due to sickle red blood cell dehydration. Vaso-occlusive crises are common painful events responsible for a variety of clinical complications; overall mortality is increased and life expectancy decreased compared to the general population. Experimental studies suggest that intravenous magnesium has proven to be well-tolerated in individuals hospitalised for the immediate relief of acute (sudden onset) painful crisis and has the potential to decrease the length of hospital stay. Some in vitro studies and open studies of long-term oral magnesium showed promising effect on pain relief but failed to show its efficacy. The studies show that oral magnesium therapy may prevent sickle red blood cell dehydration and prevent recurrent painful episodes. There is a need to access evidence for the impact of oral and intravenous magnesium effect on frequency of pain, length of hospital stay and quality of life.

OBJECTIVES

To evaluate the effects of short-term intravenous magnesium on the length of hospital stay and quality of life in children and adults with sickle cell disease. To determine the effects of long-term oral magnesium therapy on the frequency of painful crises and the quality of life in children and adults with sickle cell disease.

SEARCH METHODS

We searched the Cochrane Haemoglobinopathies Trials Register, compiled from electronic database searches and handsearching of journals and conference abstract books.Date of last search of the Cochrane Cystic Fibrosis and Genetic Disorders Group's Haemoglobinopathies Trials Register: 01 December 2016.Date of last search of other resources (clinical trials registries): 29 March 2017.

SELECTION CRITERIA

We searched for published and unpublished randomized controlled studies of oral or intravenous magnesium compared to placebo or no magnesium.

DATA COLLECTION AND ANALYSIS

Authors independently assessed the study quality and extracted the data using standard Cochrane methodologies.

MAIN RESULTS

We included five randomized placebo-controlled studies with a total of 386 participants (aged three to 53 years). Two shorter parallel studies (n = 306) compared intravenous magnesium sulphate to placebo (normal saline) for admission to hospital due to a vaso-occlusive crisis, for which we were able to analyse data. The quality of evidence was moderate for studies presenting this comparison mainly due to limitations due to risk of bias and imprecision. Two of the three longer-term studies comparing oral magnesium pidolate to placebo had a cross-over design. The third was a parallel factorial study which compared hydroxyurea and oral magnesium to each other and to placebo over a longer period of time; we only present the comparison of oral magnesium to placebo from this study. The quality of evidence was very low with uncertainty of the estimation.The eight-hourly dose levels in the two studies of intravenous magnesium were different; one used 100 mg/kg while the second used 40 mg/kg. Only one of these studies (n = 104) reported the mean daily pain score while hospitalised (a non-significant difference between groups, moderate quality evidence). The second study (n = 202) reported a number of child- and parent-reported quality of life scores. None of the scores showed any difference between treatment groups (low quality evidence). Data from one study (n = 106) showed no difference in length of stay in hospital between groups (low quality evidence). Both studies reported on adverse events, but not defined by severity as we had planned. One study showed significantly more participants receiving intravenous magnesium experienced warmth at infusion site compared to placebo; there were no differences between groups for other adverse events (low quality evidence).Three studies (n = 80) compared oral magnesium pidolate to placebo. None of them reported data which we were able to analyse. One study (n = 24) reported on the number of painful days and stated there was no difference between two groups (low quality evidence). None of the studies reported on quality of life or length of hospital stay. Two studies (n = 68) reported there were no differences in levels of magnesium in either plasma or red blood cells (moderate quality evidence). Two studies (n = 56) reported adverse events. One reported episodes of mild diarrhoea and headache, all of which resolved without stopping treatment. The second study reported adverse events as gastrointestinal disorders, headache or migraine, upper respiratory infections and rash; which were all evenly distributed across treatment groups (moderate quality evidence).

AUTHORS' CONCLUSIONS

Moderate to low quality evidence showed neither intravenous magnesium and oral magnesium therapy has an effect on reducing painful crisis, length of hospital stay and changing quality of life in treating sickle cell disease. Therefore, no definitive conclusions can be made regarding its clinical benefit. Further randomized controlled studies, perhaps multicentre, are necessary to establish whether intravenous and oral magnesium therapies have any effect on improving the health of people with sickle cell disease.

Sustained treatment of sickle cell mice with haptoglobin increases HO-1 and H-ferritin expression and decreases iron deposition in the kidney without improvement in kidney function

There is growing evidence that extracellular haemoglobin and haem mediate inflammatory and oxidative damage in sickle cell disease. Haptoglobin (Hp), the scavenger for free haemoglobin, is depleted in most patients with sickle cell disease due to chronic haemolysis. Although single infusions of Hp can ameliorate vaso-occlusion in mouse models of sickle cell disease, prior studies have not examined the therapeutic benefits of more chronic Hp dosing on sickle cell disease manifestations. In the present study, we explored the effect of Hp treatment over a 3-month period in sickle mice at two dosing regimens: the first at a moderate dose of 200 mg/kg thrice weekly and the second at a higher dose of 400 mg/kg thrice weekly. We found that only the higher dosing regimen resulted in increased haem-oxygenase-1 and heavy chain ferritin (H-ferritin) expression and decreased iron deposition in the kidney. Despite the decreased kidney iron deposition following Hp treatment, there was no significant improvement in kidney function. However, there was a nearly significant trend towards decreased liver infarction.

Delayed Healing of Sickle Cell Ulcers Is due to Impaired Angiogenesis and CXCL12 Secretion in Skin Wounds

Leg ulcers are a major complication of sickle cell disease that occur in 2.5-40% of patients. Leg ulcers are responsible for frequent complications because they are often long-lasting and are highly resistant to therapy. Although their occurrence is associated with hyperhemolysis, the mechanisms underlying sickle cell ulcers remain poorly understood. In this study, we show that skin wound healing is severely altered in old SAD sickle cell mice but is normal in young animals, consistent with reports in humans. Alterations of wound healing were associated with impaired blood and lymphatic angiogenesis in the wound beds and poor endothelial progenitor cell mobilization from the bone marrow. CXCL12 secretion by keratinocytes and inflammatory cells was low in the wounds of SAD mice. Local therapy with endothelial progenitor cells or recombinant CXCL12 injections restored wound angiogenesis and rescued the healing defect together with mobilization of circulating endothelial progenitor cells. To our knowledge, this is a previously unreported study of the cellular and molecular mechanisms of sickle cell ulcers in a murine model that provides promising therapeutic perspectives for clinical trials.

Hypoxia-reperfusion affects osteogenic lineage and promotes sickle cell bone disease

Sickle cell disease (SCD) is a worldwide distributed hereditary red cell disorder, characterized by severe organ complication. Sickle bone disease (SBD) affects a large part of the SCD patient population, and its pathogenesis has been only partially investigated. Here, we studied bone homeostasis in a humanized mouse model for SCD. Under normoxia, SCD mice display bone loss and bone impairment, with increased osteoclast and reduced osteoblast activity. Hypoxia/reperfusion (H/R) stress, mimicking acute vaso-occlusive crises (VOCs), increased bone turnover, osteoclast activity (RankL), and osteoclast recruitment (Rank) with upregulation of IL-6 as proresorptive cytokine. This was associated with further suppression of osteogenic lineage (Runx2, Sparc). To interfere with the development of SBD, zoledronic acid (Zol), a potent inhibitor of osteoclast activity/osteoclastogenesis and promoter of osteogenic lineage, was used in H/R-exposed mice. Zol markedly inhibited osteoclast activity and recruitment, promoting osteogenic lineage. The recurrent H/R stress further worsened bone structure, increased bone turnover, depressed osteoblastogenesis (Runx2, Sparc), and increased both osteoclast activity (RankL, Cathepsin k) and osteoclast recruitment (Rank) in SCD mice compared with either normoxic or single-H/R-episode SCD mice. Zol used before recurrent VOCs prevented bone impairment and promoted osteogenic lineage. Our findings support the view that SBD is related to osteoblast impairment, and increased osteoclast activity resulted from local hypoxia, oxidative stress, and the release of proresorptive cytokine such as IL-6. Zol might act on both the osteoclast and osteoblast compartments as multimodal therapy to prevent SBD.

Dietary ω-3 fatty acids protect against vasculopathy in a transgenic mouse model of sickle cell disease

The anemia of sickle cell disease is associated with a severe inflammatory vasculopathy and endothelial dysfunction, which leads to painful and life-threatening clinical complications. Growing evidence supports the anti-inflammatory properties of ω-3 fatty acids in clinical models of endothelial dysfunction. Promising but limited studies show potential therapeutic effects of ω-3 fatty acid supplementation in sickle cell disease. Here, we treated humanized healthy and sickle cell mice for 6 weeks with ω-3 fatty acid diet (fish-oil diet). We found that a ω-3 fatty acid diet: (i) normalizes red cell membrane ω-6/ω-3 ratio; (ii) reduces neutrophil count; (iii) decreases endothelial activation by targeting endothelin-1 and (iv) improves left ventricular outflow tract dimensions. In a hypoxia-reoxygenation model of acute vaso-occlusive crisis, a ω-3 fatty acid diet reduced systemic and local inflammation and protected against sickle cell-related end-organ injury. Using isolated aortas from sickle cell mice exposed to hypoxia-reoxygenation, we demonstrated a direct impact of a ω-3 fatty acid diet on vascular activation, inflammation, and anti-oxidant systems. Our data provide the rationale for ω-3 dietary supplementation as a therapeutic intervention to reduce vascular dysfunction in sickle cell disease.

MEK inhibitors, novel anti-adhesive molecules, reduce sickle red blood cell adhesion in vitro and in vivo, and vasoocclusion in vivo

In sickle cell disease, sickle erythrocyte (SSRBC) interacts with endothelial cells, leukocytes, and platelets, and activates coagulation and inflammation, promoting vessel obstruction, which leads to serious life-threatening complications, including acute painful crises and irreversible damage to multiple organs. The mitogen-activated protein kinase, ERK1/2, is abnormally activated in SSRBCs. However, the therapeutic potential of SSRBC ERK1/2 inactivation has never been investigated. I tested four different inhibitors of MEK1/2 (MEK), the kinase that activates ERK1/2, in a model of human SSRBC adhesion to TNFα-activated endothelial cells (ECs). SSRBC MEK inhibition abrogated adhesion to non-activated and TNFα-activated ECs to levels below baseline SSRBC adhesion to non-activated ECs in vitro. SSRBC MEK inhibition also prevented SSRBCs from activating naïve neutrophils to adhere to endothelium. To determine the effect of MEK inhibitors on SSRBC adherence in vivo, sham-treated or MEK inhibitor-treated SSRBCs were infused to nude mice previously treated with TNFα. Sham-treated SSRBCs displayed marked adhesion and occlusion of enflamed vessels, both small and large. However, SSRBC treatment with MEK inhibitors ex vivo showed poor SSRBC adhesion to enflamed vessels with no visible vasoocclusion in vivo. In addition, MEK inhibitor treatment of SSRBCs reduced SSRBC organ trapping and increased the number of SSRBCs circulating in bloodstream. Thus, these data suggest that SSRBC ERK1/2 plays potentially a critical role in sickle pathogenesis, and that MEK inhibitors may represent a valuable intervention for acute sickle cell crises.

MP4CO, a pegylated hemoglobin saturated with carbon monoxide, is a modulator of HO-1, inflammation, and vaso-occlusion in transgenic sickle mice

Transgenic sickle mice expressing β(S) hemoglobin have activated vascular endothelium in multiple organs that exhibits enhanced expression of NF-ĸB and adhesion molecules and promotes microvascular stasis in sickle, but not normal, mice in response to hypoxia/reoxygenation (H/R), or heme. Induction of heme oxygenase-1 (HO-1) or administration of its products, carbon monoxide (CO) or biliverdin, inhibits microvascular stasis in sickle mice. Infusion of human hemoglobin conjugated with polyethylene glycol and saturated with CO (MP4CO) markedly induced hepatic HO-1 activity and inhibited NF-ĸB activation and H/R-induced microvascular stasis in sickle mice. These effects were mediated by CO; saline or MP4 saturated with O2 (MP4OX) had little to no effect on H/R-induced stasis, though unmodified oxyhemoglobin exacerbated stasis. The HO-1 inhibitor, tin protoporphyrin, blocked MP4CO protection, consistent with HO-1 involvement in the protection afforded by MP4CO. MP4CO also induced nuclear factor-erythroid 2 p45-related factor 2 (Nrf2), an important transcriptional regulator of HO-1 and other antioxidant genes. In a heterozygous (hemoglobin-AS) sickle mouse model, intravenous hemin induced cardiovascular collapse and mortality within 120 minutes, which was significantly reduced by MP4CO, but not MP4OX. These data demonstrate that MP4CO induces cytoprotective Nrf2 and HO-1 and decreases NF-ĸB activation, microvascular stasis, and mortality in transgenic sickle mouse models.

Hemopexin therapy improves cardiovascular function by preventing heme-induced endothelial toxicity in mouse models of hemolytic diseases

BACKGROUND

Hemolytic diseases are characterized by enhanced intravascular hemolysis resulting in heme-catalyzed reactive oxygen species generation, which leads to endothelial dysfunction and oxidative damage. Hemopexin (Hx) is a plasma heme scavenger able to prevent endothelial damage and tissue congestion in a model of heme overload. Here, we tested whether Hx could be used as a therapeutic tool to counteract heme toxic effects on the cardiovascular system in hemolytic diseases.

METHODS AND RESULTS

By using a model of heme overload in Hx-null mice, we demonstrated that heme excess in plasma, if not bound to Hx, promoted the production of reactive oxygen species and the induction of adhesion molecules and caused the reduction of nitric oxide availability. Then, we used β-thalassemia and sickle cell disease mice as models of hemolytic diseases to evaluate the efficacy of an Hx-based therapy in the treatment of vascular dysfunction related to heme overload. Our data demonstrated that Hx prevented heme-iron loading in the cardiovascular system, thus limiting the production of reactive oxygen species, the induction of adhesion molecules, and the oxidative inactivation of nitric oxide synthase/nitric oxide, and promoted heme recovery and detoxification by the liver mainly through the induction of heme oxygenase activity. Moreover, we showed that in sickle cell disease mice, endothelial activation and oxidation were associated with increased blood pressure and altered cardiac function, and the administration of exogenous Hx was found to almost completely normalize these parameters.

CONCLUSIONS

Hemopexin treatment is a promising novel therapy to protect against heme-induced cardiovascular dysfunction in hemolytic disorders.

Consequences and management of iron overload in sickle cell disease

The aims of this review are to highlight the mechanisms and consequences of iron distribution that are most relevant to transfused sickle cell disease (SCD) patients and to address the particular challenges in the monitoring and treatment of iron overload. In contrast to many inherited anemias, in SCD, iron overload does not occur without blood transfusion. The rate of iron loading in SCD depends on the blood transfusion regime: with simple hypertransfusion regimes, rates approximate to thalassemia major, but iron loading can be minimal with automated erythrocyte apheresis. The consequences of transfusional iron overload largely reflect the distribution of storage iron. In SCD, a lower proportion of transfused iron distributes extrahepatically and occurs later than in thalassemia major, so complications of iron overload to the heart and endocrine system are less common. We discuss the mechanisms by which these differences may be mediated. Treatment with iron chelation and monitoring of transfusional iron overload in SCD aim principally at controlling liver iron, thereby reducing the risk of cirrhosis and hepatocellular carcinoma. Monitoring of liver iron concentration pretreatment and in response to chelation can be estimated using serum ferritin, but noninvasive measurement of liver iron concentration using validated and widely available MRI techniques reduces the risk of under- or overtreatment. The optimal use of chelation regimes to achieve these goals is described.

Persistent overall survival benefit and no increased risk of second malignancies with bortezomib-melphalan-prednisone versus melphalan-prednisone in patients with previously untreated multiple myeloma

PURPOSE

This final analysis of the phase III VISTA trial (Velcade As Initial Standard Therapy in Multiple Myeloma: Assessment With Melphalan and Prednisone) was conducted to determine whether the overall survival (OS) benefit with bortezomib-melphalan-prednisone (VMP) versus melphalan-prednisone (MP) in patients with myeloma who were ineligible for transplantation was maintained after 5 years of follow-up and to explore the risk of second primary malignancies.

PATIENTS AND METHODS

In all, 682 patients received up to nine 6-week cycles of VMP or MP and were then observed every 12 weeks or less. Data on second primary malignancies were collected by individual patient inquiries at all sites from 655 patients.

RESULTS

After median follow-up of 60.1 months (range, 0 to 74 months), there was a 31% reduced risk of death with VMP versus MP (hazard ratio [HR], 0.695; P < .001; median OS 56.4 v 43.1 months). OS benefit with VMP was seen across prespecified patient subgroups (age ≥ 75 years, stage III myeloma, creatinine clearance < 60 mL/min). Sixty-three percent of VMP patients and 73% of MP patients had received subsequent therapy. Time to next therapy (median, 30.7 v 20.5 months; HR, 0.557; P < .001) was longer with VMP than with MP. Among patients who received subsequent therapies, survival from start of subsequent therapy was similar following VMP (median, 28.1 months) or MP (median, 26.8 months; HR, 0.914). Following VMP/MP, incidence proportions of hematologic malignancies (1%/1%) and solid tumors (5%/3%) and exposure-adjusted incidence rates (0.017/0.013 per patient-year) were similar and were consistent with background rates.

CONCLUSION

VMP resulted in a significant reduction in risk of death versus MP that was maintained after 5 years' follow-up and despite substantial use of novel-agent-based salvage therapies. There is no emerging safety signal for second primary malignancies following VMP.

Pharmacological inhibition of calpain-1 prevents red cell dehydration and reduces Gardos channel activity in a mouse model of sickle cell disease

Sickle cell disease (SCD) is a globally distributed hereditary red blood cell (RBC) disorder. One of the hallmarks of SCD is the presence of circulating dense RBCs, which are important in SCD-related clinical manifestations. In human dense sickle cells, we found reduced calpastatin activity and protein expression compared to either healthy RBCs or unfractionated sickle cells, suggesting an imbalance between activator and inhibitor of calpain-1 in favor of activator in dense sickle cells. Calpain-1 is a nonlysosomal cysteine proteinase that modulates multiple cell functions through the selective cleavage of proteins. To investigate the relevance of this observation in vivo, we evaluated the effects of the orally active inhibitor of calpain-1, BDA-410 (30 mg/kg/d), on RBCs from SAD mice, a mouse model for SCD. In SAD mice, BDA-410 improved RBC morphology, reduced RBC density (D(20); from 1106 ± 0.001 to 1100 ± 0.001 g/ml; P<0.05) and increased RBC-K(+) content (from 364 ± 10 to 429 ± 12.3 mmol/kg Hb; P<0.05), markedly reduced the activity of the Ca(2+)-activated K(+)channel (Gardos channel), and decreased membrane association of peroxiredoxin-2. The inhibitory effect of calphostin C, a specific inhibitor of protein kinase C (PKC), on the Gardos channel was eliminated after BDA-410 treatment, which suggests that calpain-1 inhibition affects the PKC-dependent fraction of the Gardos channel. BDA-410 prevented hypoxia-induced RBC dehydration and K(+) loss in SAD mice. These data suggest a potential role of BDA-410 as a novel therapeutic agent for treatment of SCD.

Alteration of hepatic structure and oxidative stress induced by intravenous nanoceria

Beyond the traditional use of ceria as an abrasive, the scope of nanoceria applications now extends into fuel cell manufacturing, diesel fuel additives, and for therapeutic intervention as a putative antioxidant. However, the biological effects of nanoceria exposure have yet to be fully defined, which gave us the impetus to examine its systemic biodistribution and biological responses. An extensively characterized nanoceria (5 nm) dispersion was vascularly infused into rats, which were terminated 1 h, 20 h or 30 days later. Light and electron microscopic tissue characterization was conducted and hepatic oxidative stress parameters determined. We observed acute ceria nanoparticle sequestration by Kupffer cells with subsequent bioretention in parenchymal cells as well. The internalized ceria nanoparticles appeared as spherical agglomerates of varying dimension without specific organelle penetration. In hepatocytes, the agglomerated nanoceria frequently localized to the plasma membrane facing bile canaliculi. Hepatic stellate cells also sequestered nanoceria. Within the sinusoids, sustained nanoceria bioretention was associated with granuloma formations comprised of Kupffer cells and intermingling CD3⁺ T cells. A statistically significant elevation of serum aspartate aminotransferase (AST) level was seen at 1 and 20 h, but subsided by 30 days after ceria administration. Further, elevated apoptosis was observed on day 30. These findings, together with increased hepatic protein carbonyl levels on day 30, indicate ceria-induced hepatic injury and oxidative stress, respectively. Such observations suggest a single vascular infusion of nanoceria can lead to persistent hepatic retention of particles with possible implications for occupational and therapeutic exposures.

The clinical safety of lenalidomide in multiple myeloma and myelodysplastic syndromes

INTRODUCTION

Lenalidomide is an IMiDs® oral immunomodulatory compound developed for the treatment of patients with multiple myeloma (MM) and myelodysplastic syndromes (MDS). Long-term continuous treatment with lenalidomide beyond first response may be important to optimize responses and delay relapse.

AREAS COVERED

This review summarizes the lenalidomide mechanism of action, pharmacodynamics, key clinical studies with a focus on safety and post-marketing surveillance data. The necessity for early adverse-event management, including dose modifications for neutropenia and thrombocytopenia, and venous thromboembolism prophylaxis, where applicable, in order to maintain patients on treatment and achieve optimal efficacy, is discussed. Secondary primary malignancies in MM and progression to acute myeloid leukemia in MDS patients in the context of lenalidomide treatment are also discussed. Finally, as lenalidomide is renally excreted, the requirement for dose adjustment according to creatinine clearance is discussed.

EXPERT OPINION

Lenalidomide is highly effective and generally well tolerated. Most adverse events occur early during the course of treatment and are manageable. Lenalidomide is not associated with peripheral neuropathy and has a lack of cumulative toxicity, making it an effective treatment option for long-term use in the management of MM and low/intermediate-1-risk MDS, specifically with chromosome 5q deletion with or without other cytogenetic abnormalities.

Treatment strategies in relapsed and refractory multiple myeloma: a focus on drug sequencing and 'retreatment' approaches in the era of novel agents

Treatment of multiple myeloma has evolved over the last decade, most notably with the introduction of highly effective novel agents. It is now possible to aim for deep disease responses in a greater number of patients in an attempt to prolong remission duration and survival. Initially introduced in the relapsed setting, the novel agents, namely thalidomide, bortezomib and lenalidomide, are now being increasingly incorporated into upfront treatment strategies, raising questions about the feasibility of 'retreatment' with such agents. Also, in a disease that is characterized by multiple relapses, the 'sequencing' of the different effective options is an important question. In the frontline setting, the first remission is likely to be the period during which patients will enjoy the best quality of life. Thus, the goal should be to achieve a first remission that is the longest possible by using the most effective treatment upfront. At relapse, the challenge is to select the optimal treatment for each patient while balancing efficacy and toxicity. The decision will depend on both disease- and patient-related factors. This review aimed to assess the available research data addressing 'retreatment' approaches, drug 'sequencing' and the long-term impact of upfront therapy with novel drugs.