Sickle cell vaso-occlusive crisis: it's a gut feeling

Differential expression of adhesion molecules in sickle cell anemia and gut microbiome effect

Sickle cell anemia (SCA) causes a long-standing vascular inflammation state, leading to endothelial dysfunction and chronic overexpression of several adhesion molecules, which contributes to acute and constant vaso-occlusive (VOC) episodes. It has been demonstrated that hydroxyurea (HU) can reduce VOC events, organ damage, blood transfusions, and even the adhesion properties to endothelial cells of SCA subjects. Due to VOC episodes, these patients are also more susceptible to recurrent bacterial translocation and dysbiosis. Given this, our study aimed to uncover the interplay between adhesion molecules, gut microbiome, and hydroxyurea in a population of Angolan SCA children. Serum and fecal samples were obtained before and after HU treatment in 35 children. After HU, four of these adhesion molecules were significantly reduced: sE-selectin (p = 0.002), ADAMTS13 (p = 0.023), sICAM-1 (p = 0.003), and sVCAM-1 (p = 0.018). A positive correlation was observed between the number of neutrophils and sICAM-1, platelets, and sP-selectin, and also between leukocytes, sICAM-1, and sVCAM-1. Most taxa showing a significant correlation mainly belonged to the Clostridiales order. Specifically, from the Clostridium genera, the groups g19, g21, and g34 were all negatively correlated with HbF levels; g19, g21, and g24 positively correlated with leukocytes; g19 positively with neutrophils and sVCAM-1; and g34 positively with E- and P-selectin. Serratia, an opportunistic pathogen, was positively correlated with sE-selectin and sICAM-1 levels. Additionally, a negative correlation was observed between sP-selectin and Bifidobacterium. Research studies in this area could improve our understanding and contribute to finding new prognostic biomarkers to guarantee precise SCA patient stratification and predict severe complications.

The Role of Non-genetic Therapies to Reduce the Incidence of Sickle Cell Crisis: A Systematic Review

Sickle cell anemia is a hemoglobinopathy that causes complications such as Vaso-Occlusive Crisis (VOC), stroke, priapism, Acute Chest Syndromes (ACS), and bone infarcts due to blood vessel occlusion, resulting in hypoxia, ischemia, and inflammation. Preventing these incidents improves the quality of life and lowers mortality rates in Sickle Cell Disease (SCD) patients. This systematic review aims to describe the drugs, their mechanisms of action, dosages, changes in hemoglobin parameters, decrease in VOCs, delay the time for the next VOC, decrease in the length of hospital stay, and side effects associated with these drugs. This review adheres to the Preferred Reporting Items for Systematic Review and Meta-Analysis (PRISMA) 2020 guidelines. For this review, we searched the PubMed, Google Scholar, and Cochrane databases and screened them for full free texts published in English and studied in humans in the last five years beginning in 2018. Randomized clinical trials (RCT), observational studies, meta-analyses, systemic reviews, and traditional reviews were all included in the search. According to the type of study, quality assessment tools are used, and eight papers are chosen. Full-text articles from these papers are studied, analyzed, and tabulated. We discussed seven interventions that are used to treat sickle cell disease. Voxelotor, crizanlizumab, L-glutamate, long-term blood transfusions, Zinc (Zn), Niprisan®, and Ciklavit* were found to reduce the number and severity of VOC. We discovered that VOCs containing L -glutamate reduced the length of hospitalization. Magnesium (Mg) did not affect the number and severity of VOCs. This review includes a few articles for the study. Future papers on this subject should include a large sample size and many papers. More clinical trials are required to evaluate the dosages and outcomes of using these drugs in combination to prevent VOCs.

Microbial gut evaluation in an angolan paediatric population with sickle cell disease

Sickle cell disease (SCD) is one of the most common genetic conditions worldwide. It can contribute up to 90% of under-5 mortality in sub-Saharan Africa. Clinical manifestations are very heterogeneous, and the intestinal microbiome appears to be crucial in the modulation of inflammation, cell adhesion and induction of aged neutrophils, the main interveners of recurrent vaso-occlusive crisis. Enterocyte injury, increased permeability, altered microbial composition and bacterial overgrowth have all been documented as microbial and pathophysiologic changes in the gut microbiome of SCD patients in recent studies. Our aim was to sequence the bacterial 16S rRNA gene in order to characterize the gut microbiome of Angolan children with SCA and healthy siblings as a control. A total of 72 stool samples were obtained from children between 3 and 14 years old. Our data showed that the two groups exhibit some notable differences in microbiota relative abundance at different classification levels. Children with SCA have a higher number of the phylum Actinobacteria. As for the genus level, Clostridium cluster XI bacteria was more prevalent in the SCA children, whereas the siblings had a higher abundance of Blautia, Aestuariispira, Campylobacter, Helicobacter, Polaribacter and Anaerorhabdus. In this study, we have presented the first microbiota analysis in an Angolan paediatric population with SCD and provided a detailed view of the microbial differences between patients and healthy controls. There is still much to learn before fully relying on the therapeutic approaches for gut modulation, which is why more research in this field is crucial to making this a reality.

How Hydroxyurea Alters the Gut Microbiome: A Longitudinal Study Involving Angolan Children with Sickle Cell Anemia

Sickle cell anemia (SCA) is an inherited hematological disorder and a serious global health problem, especially in Sub-Saharan Africa. Although hydroxyurea (HU) is the leading treatment for patients with SCA, its effects on the gut microbiome have not yet been explored. In this context, the aim of this study was to investigate this association by characterizing the gut microbiome of an Angolan SCA pediatric population before and after 6 months of HU treatment. A total of 66 stool samples were obtained and sequenced for the 16S rRNA gene (V3-V4 regions). Significant associations were observed in alpha and beta-diversity, with higher values of species richness for the children naïve for HU. We also noticed that children after HU had higher proportions of several beneficial bacteria, mostly short-chain fatty acids (SCFAs) producing species, such as Blautia luti, Roseburia inulinivorans, Eubacterium halli, Faecalibacterium, Ruminococcus, Lactobacillus rogosae, among others. In addition, before HU there was a higher abundance of Clostridium_g24, which includes C. bolteae and C. clostridioforme, both considered pathogenic. This study provides the first evidence of the HU effect on the gut microbiome and unravels several microorganisms that could be considered candidate biomarkers for disease severity and HU efficacy.

Co-existing sickle cell anaemia and inflammatory bowel disease: case report and review of the literature

Sickle cell anaemia (SCA) is a chronic haemolytic anaemia associated with vaso-occlusive painful crises which may affect several systems including the gastro-intestinal system, resulting in abdominal pain. The concurrence of inflammatory bowel disease and haemoglobinopathy is rare. No previously reported concurrent cases of both SCA and ulcerative colitis (UC) in sub-Saharan Africa were found in the literature. A 16-year-old girl with concurrent SCA and UC is presented. She was admitted to University College Hospital, Ibadan with a 1-year history of recurrent peri-umbilical pain and bloody stools. These symptoms were mainly attributed to SCA at the referring hospital, and she was managed for chronic tropical diarrhoea without a remarkable clinical response. This case illustrates the concurrent presentation of SCA and ulcerative colitis which led to the missed and delayed diagnosis of ulcerative colitis.

Antibiotics to modify sickle cell disease vaso-occlusive crisis?

Despite the availability of hydroxyurea, the clinical use of the medication among patients with sickle cell disease (SCD) remains low in the United States. Given the high healthcare utilization cost, SCD requires new therapeutic approaches. Recent studies demonstrated bacterial overgrowth and dysbiosis-related intestinal pathophysiological changes in SCD. Intestinal microbes regulate neutrophil ageing. Aged and activated neutrophils contribute to the pathogenesis of vaso-occlusive crisis (VOC) in SCD. In this paper, we will review the pre-clinical and clinical data on how antibiotics might reduce the intestinal microbial density and influence the course of VOC. Based on these observations, we will discuss rationales for and potential challenges to antibiotic-based therapeutic approaches that may modify the clinical course of VOC in 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.

Invasive non-typhoidal Salmonella in sickle cell disease in Africa: is increased gut permeability the missing link?

Non-typhoidal Salmonella usually induces self-limiting gastroenteritis. However, in many parts of Africa, especially in individuals who are malnourished, infected with malaria, or have sickle cell disease, the organism causes serious and potentially fatal systemic infections. Since the portal of entry of non-typhoidal Salmonella into the systemic circulation is by way of the intestine, we argue that an increased gut permeability plays a vital role in the initiation of invasive non-typhoidal Salmonella in these patients. Here, we will appraise the evidence supporting a breach in the intestinal barrier and propose the mechanisms for the increased risks for invasive non-typhoidal Salmonella infections in these individuals.