Effect of lysed and non-lysed sickle red cells on the activation of NLRP3 inflammasome and LTB4 production by mononuclear cells.

OBJECTIVE AND DESIGN: This study tested the hypothesis that sickle red blood cell (SS-RBC) can induce inflammasome NLRP3 components gene expression in peripheral blood mononuclear cells (PBMCs) as well as interleukin-1ß (IL-1ß) and leukotriene B4 (LTB4) production. Additionally, we investigated the effect of hydroxyurea (HU) treatment in these inflammatory markers. METHODS: PBMCs from healthy donors (AA-PBMC) were challenged with intact and lysed RBCs from SCA patients (SS-RBC) and from healthy volunteers (AA-RBC). NLRP3, IL-1ß, IL-18 and Caspase-1 gene expression levels were assessed by quantitative PCR (qPCR). IL-1ß protein levels and LTB4 were measured by ELISA. RESULTS: We observed that lysed SS-RBC induced the expression of inflammasome NLRP3 components, but this increase was more prominent for CASP1 and IL18 expression levels. Moreover, we observed that intact SS-RBC induced higher production of IL-1ß and LTB4 than lysed SS-RBC. Although SCA patients treated with HU have a reduction in NLRP3 gene expression and LTB4 production, this treatment did not modulate the expression of other inflammasome components or IL-1ß production. CONCLUSIONS: Thus, our data suggest that caspase-1, IL-1ß and IL-18 may contribute to the inflammatory status observed in SCA and that HU treatment may not interfere in this inflammatory pathway.

Differential gene expression analysis of sickle cell anemia in steady and crisis state.

Sickle cell anemia is one of the most prevalent genetic diseases worldwide, showing great clinical heterogeneity. This study compared the gene expression patterns between sickle cell anemia pediatric patients in steady state and in crisis state, as compared to age-paired, healthy individuals. RNA sequencing was performed from these groups of patients/controls using Illumina HiSeq 2500 equipment. The resulting differentially expressed genes were loaded into QIAGEN's ingenuity pathway analysis. The results showed that EIF2 pathway and NRF2-mediated oxidative stress-response pathways were more highly activated both in steady state and in crisis patients, as compared to healthy individuals. In addition, we found increased activation of eIF4 and p70S6K signaling pathways in crisis state compared to healthy individuals. The transcription factor GATA-1 was found exclusively in steady state while SPI was found exclusively in crisis state. IL6 and VEGFA were found only in crisis state, while IL-1B was found exclusively in steady state. The regulator effects analysis revealed IgG1 as an upstream regulator in steady state compared to healthy individuals, resulting in invasion of prostate cancer cell lines as the disease/function outcome. For crisis-state patients versus healthy individuals, two networks of regulator effects revealed STAT1, CD40LG, TGM2, IRF7, IRF4, and IRF1 acting as upstream regulators, resulting in disease/function outcomes, including engulfment of cells and aggregation of blood cells and inflammation of joints. Our results indicated genes and pathways that can provide clues on the molecular events involved in the severity of sickle cell disease.

Endothelial Nitric Oxide Synthase (-786T>C) and Endothelin-1 (5665G>T) Gene Polymorphisms as Vascular Dysfunction Risk Factors in Sickle Cell Anemia.

Sickle cell anemia (SCA) patients have vascular complications, and polymorphisms in endothelin-1 (ET-1) and endothelial nitric oxide synthase (eNOS) genes were associated with ET-1 and nitric oxide disturbance. We investigate the association of ET-1 5665G>T and eNOS -786T>C polymorphisms with soluble adhesion molecules (sVCAM-1 and sICAM-1), biochemical markers, and medical history. We studied 101 SCA patients; carriers of eNOS minor allele (C) had the highest levels of sVCAM-1, and carriers of ET-1 minor allele had more occurrence of acute chest syndrome (ACS). The multivariate analysis suggested the influence of the ET-1 gene on ACS outcome and an association of the eNOS gene with upper respiratory tract infection. We suggest that eNOS and ET-1 gene polymorphisms can influence SCA pathophysiology and that eNOS variant in SCA patients might be important to nitric oxide activity and vascular alteration. We found an association of the ET-1 minor allele in ACS, showing the importance of genetic screening in SCA.

Heme changes HIF-α, eNOS and nitrite production in HUVECs after simvastatin, HU, and ascorbic acid therapies.

The sickle cell disease (SCD) is a hemolytic genetic anemia characterized by free heme and hemoglobin release into intravascular spaces, with endothelial activation. Heme is a proinflammatory molecule able to directly activate vascular endothelium, thus, endothelial dysfunction and vascular disease are major chronic events described in SCD. The aim of this study was to evaluate the production of endothelial nitric oxide synthase (eNOS), nitrite and hypoxia inducible factor alpha (HIF-α) in HUVECs (human umbilical vein endothelial cells) activated by heme in response to simvastatin, hydroxyurea (HU), and ascorbic acid therapies. eNOS and HIF-α production were evaluated by ELISA and nitrite was measured by the Griess technique. The production of HIF-α increased when the cells were stimulated by heme (p<0.01), while treatment with HU and simvastatin reduced the production (p<0.01), and treatment with ascorbic acid increased HIF-1a production by the cells (p<0.01). Heme increased eNOS production, (p<0.01) but showed a heterogeneous pattern, and the lowest concentrations of all the treatments reduced the enzyme production (p<0.01). The nitrite production by HUVECs was enhanced by stimulation with heme (p<0.001) and was reduced by treatment with HU (p<0.001), ascorbic acid (p<0.001) and simvastatin (p<0.01). In summary, our results suggest that the hemolytic vascular microenvironment in SCD requires different therapeutic approaches to promote clinical improvement, and that a combination of therapies may be a viable strategy for treating patients.

Sickle red cells as danger signals on proinflammatory gene expression, leukotriene B4 and interleukin-1 beta production in peripheral blood mononuclear cell.

This study tested the hypothesis that sickle red blood cell (SS-RBC) induce Toll-like receptors (TLR) and Nod-like receptor family, pyrin domain containing 3 (NLRP3)- inflammasome expression in peripheral blood mononuclear cells (PBMC). TLR and NLRP3 inflammasome could contribute to the maintenance of the inflammatory status in sickle cell anemia (SCA) patients, since SS-RBC act as danger signals activating these pathways. In this study, first, we evaluated TLR (2, 4, 5 and 9), NLRP3, Caspase-1, interleukin (IL)-1ß and IL-18 expression in PBMC freshly isolated from SCA patients (SS-PBMC) in comparison with PBMC from healthy individuals (AA-PBMC). In the second moment, we investigated whether SS-RBC could interfere with the expression of these molecules in PBMC from healthy donor, in the absence or presence of hydroxyurea (HU) in vitro. TLRs and NLRP3 inflammasome expression were investigated by qPCR. IL-1ß, Leukotriene-B4 (LTB4) and nitrite production were measured in PBMC (from healthy donor) culture supernatants. TLR2, TLR4, TLR5, NLRP3 and IL-1ß were highly expressed in SS-PBMC when compared to AA-PBMC. Additionally, SS-RBC induced TLR9, NLRP3, Caspase-1, IL-1ß and IL-18 expression and induced IL-1ß, LTB4 and nitrite production in PBMC cultures. HU did not prevent TLR and NLRP3 inflammasome expression, but increased TLR2 and IL-18 expression and reduced nitrite production. In conclusion, our data suggest that TLR and inflammasome complexes may be key inducers of inflammation in SCA patients, probably through SS-RBC; also, HU does not prevent NLRP3 inflammasome- and TLR-dependent inflammation, indicating the need to develop new therapeutic strategies to SCA patients that act with different mechanisms of those observed for HU.