Utilization and outcome disparities in allogeneic hematopoietic stem cell transplant in the United States.

Allogeneic hematopoietic stem cell transplant (allo-HSCT) is increasingly being used in the United States (US) and across the world as a curative therapeutic option for patients with certain high-risk hematologic malignancies and non-malignant diseases. However, racial and ethnic disparities in utilization of the procedure and in outcome following transplant remain major problems. Racial and ethnic minority patients are consistently under-represented in the proportion of patients who undergo allo-HSCT in the US. The transplant outcomes in these patients are also inferior. The interrelated driving forces responsible for the differences in the utilization and transplant outcome of the medical intervention are socioeconomic status, complexity of the procedure, geographical barriers, and the results of differences in the genetics and comorbidities across different races. Bridging the disparity gaps is important not only to provide equity and inclusion in the utilization of this potentially life-saving procedure but also in ensuring that minority groups are well represented for research studies about allo-HSCT. This is required to determine interventions that may be more efficacious in particular racial and ethnic groups. Various strategies at the Federal, State, and Program levels have been designed to bridge the disparity gaps with varying successes. In this review paper, we will examine the disparities and discuss the strategies currently available to address the utilization and outcome gaps between patients of different races in the US.

Effects of GBT1118, a voxelotor analog, on intestinal pathophysiology in sickle cell disease.

Voxelotor is an allosteric haemoglobin (Hb) modulator that binds covalently and reversibly to Hb alpha chain to facilitate improved Hb-O2 affinity and arterial oxygen. It, therefore, reduces the susceptibility of erythrocytes carrying Haemoglobin S to sickle. In this study, we have used GBT1118, an analog of voxelotor, to treat male Townes sickle cell disease (SCD) mice to investigate whether the Hb modulator could attenuate the intestinal pathophysiologic changes associated with SCD. Compared with mice fed with control chow, GBT1118-treated mice showed improvement in the intestinal pathophysiology. These mice exhibited improved small intestinal barrier functions, reduced intestinal microbial density, reduced enterocyte injury, lower serum lipopolysaccharides and smaller spleens. These improvements were observed after only 3 weeks of GBT1118 treatment. Benefits were also observed after experimentally-induced vaso-occlusive crisis (VOC). Recovery from the VOC-induced changes was faster in mice that were treated with GBT1118. The improved small intestinal barrier function was associated with higher expression of genes encoding enterocyte E-cadherin, JAM-A, ZO-1, MUC-2 and occludin while the lower intestinal microbial density associated with higher expression of genes encoding the antimicrobial peptides defensin-α 1 and defensin-α 4. Our findings provide the evidence to support the beneficial effects of GBT1118 in SCD-related intestinal pathophysiology.

Intestinal barrier functions in hematologic and oncologic diseases.

The intestinal barrier is a complex structure that not only regulates the influx of luminal contents into the systemic circulation but is also involved in immune, microbial, and metabolic homeostasis. Evidence implicating disruption in intestinal barrier functions in the development of many systemic diseases, ranging from non-alcoholic steatohepatitis to autism, or systemic complications of intestinal disorders has increased rapidly in recent years, raising the possibility of the intestinal barrier as a potential target for therapeutic intervention to alter the course and mitigate the complications associated with these diseases. In addition to the disease process being associated with a breach in the intestinal barrier functions, patients with hematologic and oncologic diseases are particularly at high risks for the development of increased intestinal permeability, due to the frequent use of broad-spectrum antibiotics and chemoradiation. They also face a distinct challenge of being intermittently severely neutropenic due to treatment of the underlying conditions. In this review, we will discuss how hematologic and oncologic diseases are associated with disruption in the intestinal barrier and highlight the complications associated with an increase in the intestinal permeability. We will explore methods to modulate the complication. To provide a background for our discussion, we will first examine the structure and appraise the methods of evaluation of the intestinal barrier.

Intestinal pathophysiological abnormalities in steady state and after vaso-occlusive crisis in murine sickle cell disease.

We showed in the present study that, not unlike in adult patients with sickle cell disease (SCD), Townes mice exhibit increases in serum intestinal fatty acid binding proteins and lipopolysaccharides (LPS), together with a breach in the intestinal barrier. These abnormalities increased rapidly after the induction of vaso-occlusive crisis (VOC). We also confirmed higher intestinal microbial density in SCD. These findings support the concept that SCD and/or its complications, and not hospitalisation or medications, are responsible for the intestinal pathophysiological changes. The present results provide the basis for use of Townes mice to further elucidate the mechanistic relationship between intestinal pathophysiology and VOC.

L-glutamine for sickle cell disease: more than reducing redox.

Oxidative stress is a major contributor to the pathophysiology of sickle cell disease (SCD) including hemolysis and vaso-occlusive crisis (VOC). L-glutamine is a conditionally essential amino acid with important roles, including the synthesis of antioxidants, such as reduced glutathione and the cofactors NAD(H) and NADP(H), as well as nitric oxide. Given the increased levels of oxidative stress and lower (NADH):(NAD + + NADH) ratio in sickle erythrocytes that adversely affects the blood rheology compared to normal red blood cells, L-glutamine was investigated for its therapeutic potential to reduce VOC. While L-glutamine was approved by the United States (US) Food and Drug Administration to treat SCD, its impact on the redox environment in sickle erythrocytes is not fully understood. The mechanism through which L-glutamine reduces VOC in SCD is also not clear. In this paper, we will summarize the results of the Phase 3 study that led to the approval of L-glutamine for treating SCD and discuss its assumed mechanisms of action. We will examine the role of L-glutamine in health and propose how the extra-erythrocytic functions of L-glutamine might contribute to its beneficial effects in SCD. Further research into the role of L-glutamine on extra-erythrocyte functions might help the development of an improved formulation with more efficacy.

Genes modulating intestinal permeability and microbial community are dysregulated in sickle cell disease.

Based on previous studies showing abnormalities in the intestinal pathophysiology characterized by disruption in the gut barrier functions, and alteration in the intestinal microbial load and composition, we set out in the study to examine the expression of genes that might be involved in mediating these changes in Townes sickle cell disease (SCD) mice at 6 months old compared to non-SCD control mice. Using qPCR on total RNA isolated from the intestine, we found downregulation of the TJ genes JAM-A, Occludin, and ZO-1 in both the small intestine and colon. E-Cadherin and MUC2 were also downregulated. In contrast, gene encoding claudin-2 that mediates increase permeability to water and ions was upregulated in the small intestine. Claudin-2 upregulation is usually also associated with ongoing inflammation. Intestinal epithelium also includes Paneth cells that produce antimicrobial peptides (AMPs) that regulate intestinal microbial community. We also found that the expression of the genes encoding the AMPs defensin-α4 was reduced in the small intestine and colon and defensin-α1 in the colon in the SCD mice. Our findings are novel and provide direction for further studies into the characteristics and mechanisms of the intestinal pathophysiologic changes observed in SCD.

Vaso-occlusive crisis in sickle cell disease: a vicious cycle of secondary events.

Painful vaso-occlusive crisis (VOC) remains the most common reason for presenting to the Emergency Department and hospitalization in patients with sickle cell disease (SCD). Although two new agents have been approved by the Food and Drug Administration for treating SCD, they both target to reduce the frequency of VOC. Results from studies investigating various approaches to treat and shorten VOC have so far been generally disappointing. In this paper, we will summarize the complex pathophysiology and downstream events of VOC and discuss the likely reasons for the disappointing results using monotherapy. We will put forward the rationale for exploring some of the currently available agents to either protect erythrocytes un-involved in the hemoglobin polymerization process from sickling induced by the secondary events, or a multipronged combination approach that targets the complex downstream pathways of VOC.

Gain-of-function mutagenesis through activation tagging identifies XPB2 and SEN1 helicase genes as potential targets for drought stress tolerance in rice.

KEY MESSAGE: XPB2 and SEN1 helicases were identified through activation tagging as potential candidate genes in rice for inducing high water-use efficiency (WUE) and maintaining sustainable yield under drought stress. As a follow-up on the high-water-use-efficiency screening and physiological analyses of the activation-tagged gain-of-function mutant lines that were developed in an indica rice variety, BPT-5204 (Moin et al. in Plant Cell Environ 39:2440-2459, 2016a, https://doi.org/10.1111/pce.12796 ), we have identified two gain-of-function mutant lines (XM3 and SM4), which evidenced the activation of two helicases, ATP-dependent DNA helicase (XPB2) and RNA helicase (SEN1), respectively. We performed the transcript profiling of XPB2 and SEN1 upon exposure to various stress conditions and found their significant upregulation, particularly in ABA and PEG treatments. Extensive morpho-physiological and biochemical analyses based on 24 metrics were performed under dehydration stress (PEG) and phytohormone (ABA) treatments for the wild-type and the two mutant lines. Principal component analysis (PCA) performed on the dataset captured 72.73% of the cumulative variance using the parameters influencing the first two principal components. The tagged mutants exhibited reduced leaf wilting, improved revival efficiency, constant amylose:amylopectin ratio, high chlorophyll and proline contents, profuse tillering, high quantum efficiency and yield-related traits with respect to their controls. These observations were further validated under greenhouse conditions by the periodic withdrawal of water at the pot level. Germination of the seeds of these mutant lines indicated their insensitivity to high ABA concentration. The associated upregulation of stress-specific genes further suggests that their drought tolerance might be because of the coordinated expression of several stress-responsive genes in these two mutants. Altogether, our results provided a firm basis for SEN1 and XPB2 as potential candidates for manipulation of drought tolerance and improving rice performance and yield under limited water conditions.

Obesity and diabetes mellitus in patients with sickle cell disease.

Obesity and diabetes mellitus are prevalent among the African-American/Black population. They result in multiple chronic conditions that impact the quality and lifespan of the patients. Their occurrence in patients with sickle cell disease (SCD) will increase the risks for multimorbidity in these patients. We have carried out a chart survey of a cohort of 449 patients with SCD to determine the prevalence rates of obesity and diabetes mellitus in these patients. SCD patients were less likely to develop obesity and diabetes mellitus, compared to their peers of the same race/ethnicity. The lower prevalence rates were observed in those over the age of 6 years, irrespective of the gender of the patients. Their life-time probabilities for obesity and diabetes mellitus were also low. Within this group of SCD patients, obesity was associated with significantly higher prevalence of diabetes mellitus. The underlying reasons for our observed results of low prevalence rate of obesity in SCD remain speculative but may be related to reduced calorie intake, increased calorie use due to hypermetabolism, reduced intestinal absorption, or intestinal dysbiosis.

A small-molecule inhibitor of the DNA recombinase Rad51 from Plasmodium falciparum synergizes with the antimalarial drugs artemisinin and chloroquine.

Malaria parasites repair DNA double-strand breaks (DSBs) primarily through homologous recombination (HR). Here, because the unrepaired DSBs lead to the death of the unicellular parasite Plasmodium falciparum, we investigated its recombinase, PfRad51, as a potential drug target. Undertaking an in silico screening approach, we identified a compound, B02, that docks to the predicted tertiary structure of PfRad51 with high affinity. B02 inhibited a drug-sensitive P. falciparum strain (3D7) and multidrug-resistant parasite (Dd2) in culture, with IC50 values of 8 and 3 µm, respectively. We found that B02 is more potent against these P. falciparum strains than against mammalian cell lines. Our findings also revealed that the antimalarial activity of B02 synergizes with those of two first-line malaria drugs, artemisinin (ART) and chloroquine (CQ), lowering the IC50 values of ART and CQ by 15- and 8-fold, respectively. Our results also provide mechanistic insights into the anti-parasitic activity of B02, indicating that it blocks the ATPase and strand-exchange activities of PfRad51 and abrogates the formation of PfRad51 foci on damaged DNA at chromosomal sites, probably by blocking homomeric interactions of PfRad51 proteins. The B02-mediated PfRad51 disruption led to the accumulation of unrepaired parasitic DNA and rendered parasites more sensitive to DNA-damaging agents, including ART. Our findings provide a rationale for targeting the Plasmodium DSB repair pathway in combination with ART. We propose that identification of a specific inhibitor of HR in Plasmodium may enable investigations of HR's role in Plasmodium biology, including generation of antigenic diversity.

Intestinal pathophysiological and microbial changes in sickle cell disease: Potential targets for therapeutic intervention.

There is a large therapeutic gap in the treatment of sickle cell disease (SCD). Recent studies demonstrated the presence of pathophysiological and microbial changes in the intestine of patients with SCD. The intestinal microbes have also been found to regulate neutrophil ageing and possible basal activation of circulating neutrophils. Both aged and activated neutrophils are pivotal for the pathogenesis of vaso-occlusive crisis in SCD. In this paper, we will provide an overview of the intestinal pathophysiological and microbial changes in SCD. Based on these changes, we will propose therapeutic approaches that could be investigated for treating SCD.

Intestinal injury and gut permeability in sickle cell disease.

BACKGROUND: Due to recurrent hypoxia-reperfusion injury induced by vaso-occlusive crises (VOC), patients with sickle cell disease (SCD) may have intestinal injury and increased permeability. These may explain the qualitative and quantitative neutrophil abnormalities observed in these patients. METHODS: Serum intestinal fatty-acid binding protein (iFABP), lipopolysaccharides (LPS), and CD62L were measured by ELISA. Multicolor flow cytometry was used to measure circulating aged neutrophils. RESULTS: Compared to controls, SCD individuals had higher iFABP (median: 1.38 ng/ml vs 0.81 ng/ml; p = 0.04) and LPS (median: 2.15 µg/ml vs 0.69 µg/ml; p = 0.03), indicating intestinal injury and increased intestinal bacterial translocation into the systemic circulation. They also had higher soluble CD62L (median: 1.38 µg/ml vs 1.11 µg/ml; p = 0.04). Among SCD individuals, soluble CD62L correlated positively with circulating aged neutrophils (R = 0.7, p = 0.03) and LPS (R = 0.66, p = 0.027). Surprisingly, serum iFABP in SCD correlated negatively with both LPS (R = - 0.7, p = 0.02) and soluble CD62L (R = - 0.56, p = 0.08). CONCLUSIONS: Since LPS translocation across the intestinal barrier may be due to increases in the intestinal bacterial density, gut permeability, or both, the negative correlations between iFABP and LPS, and CD62L raise the possibility that any damage-associated molecular patterns induced by intestinal injury may modulate the degree of bacterial translocation. Our results provide the first evidence of the presence of intestinal injury and increased gut permeability in SCD.

Phenomenological models as effective tools to discover cellular design principles.

Microbes have proved useful to us in many different ways. To utilize microbes, we have mostly focused on maximizing growth, to improve yield of chemicals derived from the microbes. However, to truly tap into their potential, we should also aim to understand microbial physiology. We present a historical perspective of the developments in the field of Microbial Biotechnology, focusing on how the growth-modelling approaches have changed. Starting from simple empirical growth models, we have evolved towards mechanistic and phenomenological models which use molecular and physiological details to drastically improve prediction power of these models. Lastly, we explore the as of yet unsolved questions in microbial physiology, and discuss how the ability to monitor microbial growth at single cell resolution using the lab-on-a-chip technologies is uncovering previously unobservable causal principles underlying microbial growth.

Endari treatment ameliorates sickle cell-related disruption in intestinal barrier functions and is associated with prolonged survival in sickle cell mice.

BACKGROUND: Endari (L-glutamine) is a conditional amino acid that reduces the frequency of vaso-occlusive crisis (VOC) in sickle cell disease (SCD). AIM: To investigate whether Endari could ameliorate intestinal barrier function and improve survival outcomes in SCD. METHODS: We treated female Townes SCD mice with Endari and evaluated their intestinal barrier functions by measuring the recovery of orally administered fluorescein isothiocyanate (FITC)-conjugated dextran 4 kDa in serum, and serum intestinal fatty acid binding proteins (iFABP) and lipopolysaccharide (LPS) concentrations by ELISA. We also explored the impact the Endari has on the survival of the SCD mice that underwent repeated experimentally-induced VOC. RESULTS: Compared to SCD mice treated with water only, Endari-treated mice showed improved intestinal barrier functions, with decrease in the barrier permeability and reduction in the translocation of lipopolysaccharides from the intestinal lumen into the circulation. These changes occurred after only 4 weeks of Endari treatment. Improved intestinal barrier function was also associated with prolonged survival in Endari-treated SCD mice after repeated experimentally-induced VOC. CONCLUSION: Our findings provide the evidence supporting the beneficial effects of Enadri in improving intestinal barrier function and associated survival outcomes in SCD.