Available online on 15.07.2024 at ijmspr.com

 International Journal of Medical Sciences and Pharma Research 

Open Access to Medical Science and Pharma Research

Copyright  © 2024 The  Author(s): This is an open-access article distributed under the terms of the CC BY-NC 4.0 which permits unrestricted use, distribution, and reproduction in any medium for non-commercial use provided the original author and source are credited

Endoplasmic Reticulum Stress and Vaso-Occlusive Crisis in Sickle Cell Anemia: A Review

Emmanuel Ifeanyi Obeagu *

Department of Medical Laboratory Science, Kampala International University, Uganda

 

 

Introduction

Sickle cell anemia (SCA) is an autosomal recessive genetic disorder caused by a mutation in the β-globin gene, leading to the production of abnormal hemoglobin known as hemoglobin S (HbS). This mutation results in the polymerization of HbS under low oxygen conditions, causing red blood cells (RBCs) to assume a rigid, sickle shape. The distortion of RBCs not only impairs their ability to transport oxygen effectively but also predisposes them to hemolysis and vaso-occlusive crises (VOCs). VOCs are characterized by the occlusion of small blood vessels, leading to acute pain, tissue ischemia, and potential organ damage. The management of SCA has advanced significantly, but VOCs remain a major clinical challenge. Recent research has increasingly focused on the role of endoplasmic reticulum (ER) stress in the pathophysiology of SCA. The ER is an essential organelle involved in the synthesis, folding, and modification of proteins. Disruptions in ER function can lead to the accumulation of misfolded or unfolded proteins, triggering an adaptive response known as the unfolded protein response (UPR). While the UPR aims to restore ER homeostasis, prolonged or unresolved ER stress can result in cellular dysfunction and apoptosis. In the context of SCA, the abnormal folding of HbS may contribute to ER stress in erythroid precursor cells, further complicating the disease's clinical presentation. ER stress has been linked to various pathological mechanisms in SCA, including inflammation, oxidative stress, and apoptosis. The inflammatory response associated with ER stress can exacerbate the complications of SCA by promoting endothelial activation and enhancing the adhesion of sickled RBCs to the vascular endothelium. Additionally, ER stress can induce the production of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α), further contributing to the inflammatory milieu that characterizes VOCs.^1-10

Moreover, ER stress influences erythropoiesis, the process of producing RBCs, by promoting the apoptosis of erythroid progenitor cells. This leads to ineffective erythropoiesis and anemia, which can exacerbate hypoxia and promote the sickling of RBCs. The interplay between anemia, hypoxia, and sickling creates a vicious cycle that increases the risk of VOCs. In addition, the accumulation of reactive oxygen species (ROS) during ER stress contributes to oxidative damage in RBCs, further destabilizing their membranes and promoting hemolysis. The recognition of ER stress as a significant contributor to the pathophysiology of SCA has opened new avenues for therapeutic interventions. Pharmacological agents that alleviate ER stress or modulate the UPR are being explored as potential treatments to improve RBC function and reduce the incidence of VOCs. Furthermore, gene therapy approaches aimed at increasing fetal hemoglobin (HbF) levels have shown promise in mitigating the effects of HbS polymerization, which may subsequently decrease the burden of ER stress in affected individuals.^11-15

Endoplasmic Reticulum Stress in Sickle Cell Anemia

Endoplasmic reticulum (ER) stress plays a critical role in the pathophysiology of sickle cell anemia (SCA), a genetic disorder characterized by the production of abnormal hemoglobin, specifically hemoglobin S (HbS). The ER is responsible for the synthesis, folding, and post-translational modification of proteins, including globin chains. In SCA, the presence of HbS leads to the misfolding of globin chains, resulting in the accumulation of abnormal hemoglobin within erythroid precursor cells. This accumulation triggers ER stress, which has significant implications for the cellular and systemic manifestations of the disease. ER stress is primarily induced when the load of misfolded or unfolded proteins exceeds the capacity of the ER's protein folding machinery. In SCA, the polymerization of HbS under low oxygen tension results in the formation of rigid, sickled RBCs that can disrupt normal erythropoiesis. The accumulation of misfolded HbS activates the UPR, a cellular response designed to restore ER homeostasis. The UPR is mediated by three key signaling pathways: inositol-requiring enzyme 1 (IRE1), protein kinase RNA-like ER kinase (PERK), and activating transcription factor 6 (ATF6). Activation of IRE1 leads to the splicing of X-box binding protein 1 (XBP1), which promotes the expression of chaperone proteins that assist in the proper folding of proteins. PERK activation phosphorylates the eukaryotic translation initiation factor 2α (eIF2α), reducing global protein synthesis to alleviate the protein load on the ER. Meanwhile, ATF6 translocates to the Golgi apparatus, where it is processed to activate the transcription of UPR target genes. While these responses initially aim to restore ER function, prolonged or unresolved ER stress can lead to detrimental outcomes, including cell death.^16-25

In the context of SCA, ER stress has profound implications for erythropoiesis, the process of red blood cell production. ER stress-induced apoptosis of erythroid progenitor cells can lead to ineffective erythropoiesis, contributing to anemia. This reduction in functional RBCs exacerbates the hypoxic environment, promoting further sickling of existing RBCs. The cycle of sickling, hemolysis, and ineffective erythropoiesis creates a vicious feedback loop that amplifies the severity of SCA and increases the frequency of vaso-occlusive crises. Additionally, the activation of ER stress pathways has been linked to the production of reactive oxygen species (ROS). The increased oxidative stress resulting from ER dysfunction can lead to further damage to RBC membranes, enhancing hemolysis and increasing the release of free hemoglobin into circulation. Free hemoglobin can scavenge nitric oxide (NO), leading to vasoconstriction and promoting the pathogenesis of VOCs by exacerbating endothelial dysfunction. ER stress is also closely linked to the inflammatory response observed in SCA. The activation of ER stress pathways can lead to the upregulation of pro-inflammatory cytokines, such as interleukin-6 (IL-6) and tumor necrosis factor-alpha (TNF-α). These cytokines can promote endothelial activation, increasing the expression of adhesion molecules that facilitate the binding of sickled RBCs and leukocytes to the vascular endothelium. This adhesion is a critical step in the pathogenesis of VOCs, leading to microvascular obstruction, tissue ischemia, and the characteristic pain crises associated with SCA. Furthermore, ER stress-induced inflammation can perpetuate the cycle of sickling and vaso-occlusion. The inflammatory milieu can exacerbate the sickling process by promoting endothelial dysfunction, increasing blood viscosity, and inducing a pro-coagulant state. The interplay between ER stress, inflammation, and vaso-occlusive phenomena underscores the complexity of SCA and highlights the need for integrated therapeutic strategies.^26-35

Mechanisms Linking ER Stress to Vaso-Occlusive Crises

The link between endoplasmic reticulum (ER) stress and vaso-occlusive crises (VOCs) in sickle cell anemia (SCA) is multifaceted and involves several interrelated mechanisms. These mechanisms encompass inflammation, oxidative stress, erythropoiesis, and cellular apoptosis, each contributing to the exacerbation of the sickling process and the occurrence of VOCs. 

1. Activation of Inflammatory Pathways

ER stress triggers the unfolded protein response (UPR), which activates various signaling pathways that can lead to inflammation. In SCA, the accumulation of misfolded hemoglobin, particularly HbS, can induce the expression of pro-inflammatory cytokines such as interleukin-6 (IL-6), tumor necrosis factor-alpha (TNF-α), and C-reactive protein (CRP). This inflammatory response enhances endothelial activation, resulting in the upregulation of adhesion molecules such as vascular cell adhesion molecule-1 (VCAM-1) and intercellular adhesion molecule-1 (ICAM-1). The increased expression of these adhesion molecules facilitates the binding of sickled RBCs and leukocytes to the vascular endothelium. This adhesion contributes to microvascular obstruction, which is a critical event in the development of VOCs. The inflammatory milieu can also lead to further activation of the coagulation cascade, creating a pro-coagulant state that exacerbates the risk of vaso-occlusion.^36-38

2. Induction of Apoptosis in Erythroid Cells

ER stress can lead to programmed cell death (apoptosis) in erythroid progenitor cells, particularly in the bone marrow. In SCA, the misfolding of hemoglobin during erythropoiesis can overwhelm the ER's protein folding capacity, triggering apoptosis via UPR pathways. The activation of key mediators, such as CCAAT/enhancer-binding protein homologous protein (CHOP), promotes apoptotic signaling. The apoptosis of erythroid precursor cells results in ineffective erythropoiesis, leading to decreased production of functional RBCs and exacerbating anemia. Anemia contributes to a hypoxic environment, further increasing the likelihood of sickling and subsequent vaso-occlusion. This cycle of anemia, hypoxia, and sickling creates a feedback loop that increases the frequency and severity of VOCs.^39-40

3. Increased Oxidative Stress

ER stress is associated with increased production of reactive oxygen species (ROS), which can have deleterious effects on cellular function. The accumulation of misfolded proteins and the activation of the UPR can lead to mitochondrial dysfunction, contributing to the generation of ROS. In the context of SCA, oxidative stress has significant implications for RBC integrity and function. Increased ROS levels can lead to oxidative damage to the RBC membrane, resulting in hemolysis and the release of free hemoglobin into circulation. Free hemoglobin scavenges nitric oxide (NO), leading to vasoconstriction and impaired endothelial function. The combination of oxidative stress and endothelial dysfunction exacerbates the risk of microvascular obstruction, thereby promoting VOCs.^41-43

4. Altered Blood Rheology

ER stress and the associated inflammatory response can alter blood rheology, contributing to the occurrence of VOCs. In SCA, the sickling of RBCs leads to changes in blood viscosity and flow properties. The inflammatory cytokines released during ER stress can further increase blood viscosity by promoting the activation of coagulation factors and the aggregation of RBCs. Additionally, the interaction between sickled RBCs and activated endothelium can lead to the formation of microthrombi, exacerbating the occlusion of small blood vessels. This alteration in blood rheology can create a detrimental cycle, as increased viscosity and impaired blood flow contribute to tissue hypoxia and further sickling of RBCs.^44-45

 

5. Impairment of Nitric Oxide Signaling

Nitric oxide (NO) is a crucial vasodilator that plays a key role in maintaining vascular homeostasis. In SCA, ER stress-induced inflammation and oxidative stress can impair NO signaling. The scavenging of NO by free hemoglobin, as well as the endothelial dysfunction induced by inflammatory mediators, leads to reduced bioavailability of NO. The decreased availability of NO exacerbates vasoconstriction and contributes to the dysregulation of vascular tone, increasing the risk of vaso-occlusion. Furthermore, impaired NO signaling can lead to a state of chronic inflammation, perpetuating the cycle of ER stress and its associated pathologies in SCA.^46-47

Implications for Therapeutic Strategies

The intricate relationship between endoplasmic reticulum (ER) stress and vaso-occlusive crises (VOCs) in sickle cell anemia (SCA) presents several opportunities for the development of targeted therapeutic strategies. Understanding the mechanisms by which ER stress influences the pathophysiology of SCA can inform the design of interventions aimed at alleviating the detrimental effects of ER stress, improving red blood cell (RBC) function, and reducing the frequency and severity of VOCs. Pharmacological agents that modulate the UPR offer a promising approach to alleviate ER stress in SCA. Compounds that enhance the protein folding capacity of the ER, such as chemical chaperones (e.g., tauroursodeoxycholic acid), may help mitigate the accumulation of misfolded HbS and restore ER homeostasis. By promoting the proper folding of globin chains, these agents can reduce the burden of ER stress, thereby improving erythropoiesis and decreasing the risk of VOCs. Additionally, agents that selectively activate the protective branches of the UPR can provide a cytoprotective effect. For instance, targeting the IRE1 pathway to enhance X-box binding protein 1 (XBP1) splicing could increase the expression of chaperone proteins, helping to restore ER function. Such strategies may be beneficial in reducing the apoptotic signaling associated with prolonged ER stress and improving the overall survival of erythroid progenitor cells. Given the role of ER stress in promoting inflammation and endothelial activation in SCA, anti-inflammatory therapies may offer a viable strategy to mitigate the impact of VOCs. Corticosteroids and non-steroidal anti-inflammatory drugs (NSAIDs) can reduce the production of pro-inflammatory cytokines and attenuate the inflammatory response associated with ER stress. By decreasing endothelial activation and improving vascular health, these agents may help reduce the frequency of VOCs. Novel anti-inflammatory agents, such as biologics targeting specific cytokines (e.g., IL-6 or TNF-α), could further enhance therapeutic efficacy by directly addressing the inflammatory milieu that exacerbates vaso-occlusion. Such targeted therapies may also help prevent the long-term complications associated with chronic inflammation in SCA.^48-56

Antioxidant therapies aimed at reducing oxidative stress can also play a significant role in alleviating the consequences of ER stress in SCA. Compounds such as N-acetylcysteine (NAC) and glutathione precursors can enhance the antioxidant capacity of cells, reducing the levels of reactive oxygen species (ROS) generated during ER stress. By mitigating oxidative damage to RBC membranes and endothelial cells, these antioxidants may help preserve RBC integrity and function, thereby reducing hemolysis and promoting better oxygen delivery. Furthermore, antioxidants can enhance the bioavailability of nitric oxide (NO) by preventing its scavenging by free hemoglobin. Improved NO signaling can promote vasodilation and help restore normal vascular tone, decreasing the risk of vaso-occlusion and improving overall blood flow. Gene therapy represents a transformative strategy for addressing the underlying genetic defect responsible for SCA. Techniques such as gene editing (e.g., CRISPR/Cas9) and gene transfer can be employed to correct the mutation in the β-globin gene or to promote the expression of fetal hemoglobin (HbF), which inhibits HbS polymerization. Increasing HbF levels can significantly reduce the polymerization of HbS, thereby alleviating the ER stress associated with the production of misfolded hemoglobin. By reducing the burden of HbS in the circulation, gene therapy may also decrease the frequency of hemolysis and its associated oxidative stress, thereby improving the overall clinical course of SCA. Early clinical trials using gene therapy approaches have shown promising results, highlighting the potential for these strategies to revolutionize the management of SCA. Given the multifactorial nature of SCA and the interplay between ER stress, inflammation, and oxidative stress, combination therapies may offer a comprehensive approach to managing the disease. Utilizing agents that target multiple pathways simultaneously can provide synergistic benefits, enhancing treatment efficacy and improving patient outcomes. For example, combining anti-inflammatory agents with antioxidants may effectively address both the inflammatory response and oxidative stress associated with ER dysfunction. Additionally, integrating pharmacological interventions with gene therapy may further enhance the therapeutic impact, providing both immediate relief from VOCs and long-term correction of the underlying genetic defect. Such multi-faceted approaches will require careful consideration of drug interactions and patient-specific factors to optimize treatment regimens.^57-61

Conclusion

Endoplasmic reticulum (ER) stress plays a critical role in the pathophysiology of sickle cell anemia (SCA), significantly contributing to the occurrence and severity of vaso-occlusive crises (VOCs). The mechanisms linking ER stress to VOCs involve a complex interplay of inflammatory responses, oxidative stress, apoptosis, and altered blood rheology, all of which exacerbate the clinical manifestations of SCA.  Emerging research highlights the potential for innovative interventions that can modulate ER stress and its associated pathways. Therapeutic approaches, including the use of pharmacological agents that enhance the unfolded protein response, anti-inflammatory therapies, antioxidants, and gene therapy techniques, offer promising avenues for improving patient outcomes. Additionally, combination therapies that integrate multiple strategies may provide synergistic benefits, effectively addressing the multifactorial nature of SCA.

References

1. Alenzi FQ, AlShaya DS. Biochemical and molecular analysis of the beta-globin gene on Saudi sickle cell anemia. Saudi Journal of Biological Sciences. 2019;26(7):1377-1384. https://doi.org/10.1016/j.sjbs.2019.03.003 PMid:31762599 PMCid:PMC6864391

2. Williams TN, Thein SL. Sickle cell anemia and its phenotypes. Annual review of genomics and human genetics. 2018;19(1):113-147. https://doi.org/10.1146/annurev-genom-083117-021320 PMid:29641911 PMCid:PMC7613509

3. Obeagu EI, Ochei KC, Nwachukwu BN, Nchuma BO. Sickle cell anaemia: a review. Scholars Journal of Applied Medical Sciences. 2015;3(6B):224422-52.

4. Obeagu EI. Erythropoeitin in Sickle Cell Anaemia: A Review. International Journal of Research Studies in Medical and Health Sciences. 2020;5(2):22-28. https://doi.org/10.22259/ijrsmhs.0502004

5. Obeagu EI. Sickle Cell Anaemia: Haemolysis and Anemia. Int. J. Curr. Res. Chem. Pharm. Sci. 2018;5(10):20-21.

6. Obeagu EI, Muhimbura E, Kagenderezo BP, Uwakwe OS, Nakyeyune S, Obeagu GU. An Update on Interferon Gamma and C Reactive Proteins in Sickle Cell Anaemia Crisis. J Biomed Sci. 2022;11(10):84.

7. Obeagu EI, Ogunnaya FU, Obeagu GU, Ndidi AC. Sickle cell anaemia: a gestational enigma. European Journal of Biomedical and Pharmaceutical Sciences. 2023;10((9): 72-75

8. Obeagu EI. An update on micro RNA in sickle cell disease. Int J Adv Res Biol Sci. 2018; 5:157-158.

9. Obeagu EI, Babar Q. Covid-19 and Sickle Cell Anemia: Susceptibility and Severity. J. Clinical and Laboratory Research. 2021;3(5):2768-2487.

10. Obeagu EI. Depression in Sickle Cell Anemia: An Overlooked Battle. Int. J. Curr. Res. Chem. Pharm. Sci. 2023;10(10):41-.

11. Gkaliagkousi E, Ritter J, Ferro A. Platelet-derived nitric oxide signaling and regulation. Circulation research. 2007 Sep 28;101(7):654-662. https://doi.org/10.1161/CIRCRESAHA.107.158410 PMid:17901370

12. Tran N, Garcia T, Aniqa M, Ali S, Ally A, Nauli SM. Endothelial nitric oxide synthase (eNOS) and the cardiovascular system: in physiology and in disease states. American journal of biomedical science & research. 2022;15(2):153. https://doi.org/10.34297/AJBSR.2022.15.002087

13. Obeagu EI, Obeagu GU. Evaluation of Hematological Parameters of Sickle Cell Anemia Patients with Osteomyelitis in A Tertiary Hospital in Enugu, Nigeria. Journal of Clinical and Laboratory Research.2023;6(1):2768-0487.

14. Obeagu EI, Dahir FS, Francisca U, Vandu C, Obeagu GU. Hyperthyroidism in sickle cell anaemia. Int. J. Adv. Res. Biol. Sci. 2023;10(3):81-89.

15. Njar VE, Ogunnaya FU, Obeagu EI. Knowledge And Prevalence of The Sickle Cell Trait Among Undergraduate Students Of The University Of Calabar. Prevalence.;5(100):0-5.

16. Swem CA, Ukaejiofo EO, Obeagu EI, Eluke B. Expression of micro RNA 144 in sickle cell disease. Int. J. Curr. Res. Med. Sci. 2018;4(3):26-32.

17. Obeagu EI. Sickle cell anaemia: Historical perspective, Pathophysiology and Clinical manifestations. Int. J. Curr. Res. Chem. Pharm. Sci. 2018;5(11):13-15.

18. Obeagu EI, Obeagu GU. Sickle Cell Anaemia in Pregnancy: A Review. International Research in Medical and Health Sciences. 2023 Jun 10;6(2):10-13.

19. Obeagu EI, Mohamod AH. An update on Iron deficiency anaemia among children with congenital heart disease. Int. J. Curr. Res. Chem. Pharm. Sci. 2023;10(4):45-48.

20. Edward U, Osuorji VC, Nnodim J, Obeagu EI. Evaluationof Trace Elements in Sickle Cell Anaemia Patients Attending Imo State Specialist Hospital, Owerri. Madonna University journal of Medicine and Health Sciences ISSN: 2814-3035. 2022 Mar 4;2(1):218-234. https://doi.org/10.59298/NIJRMS/2023/10.2.1400

21. Umar MI, Aliyu F, Abdullahi MI, Aliyu MN, Isyaku I, Aisha BB, Sadiq RU, Shariff MI, Obeagu EI. Assessment Of Factors Precipitating Sickle Cell Crises Among Under 5-Years Children Attending Sickle Cell Clinic Of Murtala Muhammad Specialist Hospital, Kano. blood.;11:16.

22. Obeagu EI. Vaso-occlusion and adhesion molecules in sickle cells disease. Int J Curr Res Med Sci. 2018;4(11):33-35.

23. Ifeanyi OE, Stella EI, Favour AA. Antioxidants In The Management of Sickle Cell Anaemia. Int J Hematol Blood Disord (Internet) 2018 (cited 2021 Mar 4); 3. Available from: https://symbiosisonlinepublishing. com/hematology/hema tology25. php. 2018 Sep.

24. Buhari HA, Ahmad AS, Obeagu EI. Current Advances in the Diagnosis and Treatment of Sickle Cell Anaemia. APPLIED SCIENCES (NIJBAS). 2023;4(1). https://doi.org/10.59298/NIJBAS/2023/1.1.11111

25. Obeagu EI, Obeagu GU. Hemolysis Challenges for Pregnant Women with Sickle Cell Anemia: A Review. Elite Journal of Haematology. 2024;2(3):67-80.

26. Obeagu EI, Obeagu GU, Hauwa BA. Optimizing Maternal Health: Addressing Hemolysis in Pregnant Women with Sickle Cell Anemia. Journal home page: http://www. journalijiar. com.;12(01).

27. Vilas-Boas W, Cerqueira BA, Zanette AM, Reis MG, Barral-Netto M, Goncalves MS. Arginase levels and their association with Th17-related cytokines, soluble adhesion molecules (sICAM-1 and sVCAM-1) and hemolysis markers among steady-state sickle cell anemia patients. Annals of hematology. 2010; 89:877-882. https://doi.org/10.1007/s00277-010-0954-9 PMid:20405289 PMCid:PMC2908460

28. Nnodim J, Uche U, Ifeoma U, Chidozie N, Ifeanyi O, Oluchi AA. Hepcidin and erythropoietin level in sickle cell disease. British Journal of Medicine and Medical Research. 2015;8(3):261-265. https://doi.org/10.9734/BJMMR/2015/17480

29. Obeagu EI. BURDEN OF CHRONIC OSTEOMYLITIS: REVIEW OF ASSOCIATIED FACTORS. Madonna University journal of Medicine and Health Sciences. 2023;3(1):1-6.

30. Aloh GS, Obeagu EI, Okoroiwu IL, Odo CE, Chibunna OM, Kanu SN, Elemchukwu Q, Okpara KE, Ugwu GU. Antioxidant-Mediated Heinz Bodies Levels of Sickle Erythrocytes under Drug-Induced Oxidative Stress. European Journal of Biomedical and Pharmaceutical sciences. 2015;2(1):502-507.

31. Obeagu EI, Obeagu GU. Sickle Cell Anaemia in Pregnancy: A Review. International Research in Medical and Health Sciences. 2023;6 (2):10-13.

32. Obeagu EI, Ogbuabor BN, Ikechukwu OA, Chude CN. Haematological parameters among sickle cell anemia patients' state and haemoglobin genotype AA individuals at Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria. International Journal of Current Microbiology and Applied Sciences. 2014;3(3):1000-1005.

33. Ifeanyi OE, Nwakaego OB, Angela IO, Nwakaego CC. Haematological parameters among sickle cell anaemia... Emmanuel Ifeanyi1, et al. pdf• Obeagu. Int. J. Curr. Microbiol. App. Sci. 2014;3(3):1000-1005.

34. Obeagu EI, Opoku D, Obeagu GU. Burden of nutritional anaemia in Africa: A Review. Int. J. Adv. Res. Biol. Sci. 2023;10(2):160-163.

35. Ifeanyi E. Erythropoietin (Epo) Level in Sickle Cell Anaemia (HbSS) With Falciparum Malaria Infection in University Health Services, Michael Okpara University of Agriculture, Umudike, Abia State, Nigeria. PARIPEX - INDIAN JOURNAL OF RESEARCH, 2015; 4(6): 258-259

36. Tsikas D. Does the inhibitory action of asymmetric dimethylarginine (ADMA) on the endothelial nitric oxide synthase activity explain its importance in the cardiovascular system? The ADMA paradox. Journal of Controversies in Biomedical Research. 2017;3(1):16-22. https://doi.org/10.15586/jcbmr.2017.22

37. Martins R, Knapp S. Heme and hemolysis in innate immunity: adding insult to injury. Current opinion in immunology. 2018; 50:14-20. https://doi.org/10.1016/j.coi.2017.10.005 PMid:29107115

38. Wu G, Meininger CJ, McNeal CJ, Bazer FW, Rhoads JM. Role of L-arginine in nitric oxide synthesis and health in humans. Amino acids in nutrition and health: Amino acids in gene expression, metabolic regulation, and exercising performance. 2021:167-87. https://doi.org/10.1007/978-3-030-74180-8_10 PMid:34251644

39. Ifeanyi OE, Nwakaego OB, Angela IO, Nwakaego CC. Haematological parameters among sickle cell anaemia patients in steady state and haemoglobin genotype AA individuals at Michael Okpara, University of Agriculture, Umudike, Abia State, Nigeria. Int. J. Curr. Microbiol. App. Sci. 2014;3(3):1000-1005.

40. Ifeanyi OE, Stanley MC, Nwakaego OB. Comparative analysis of some haematological parameters in sickle cell patients in steady and crisis state at michael okpara University of agriculture, Umudike, Abia state, Nigeria. Int. J. Curr. Microbiol. App. Sci. 2014;3(3):1046-1050.

41. Ifeanyi EO, Uzoma GO. Malaria and The Sickle Cell Trait: Conferring Selective Protective Advantage to Malaria. J Clin Med Res. 2020; 2:1-4. https://doi.org/10.37191/Mapsci-2582-4333-2(2)-026

42. Obeagu EI, Obeagu GU. Oxidative Damage and Vascular Complications in Sickle Cell Anemia: A Review. Elite Journal of Haematology, 2024; 2 (3).:58-66.

43. Roberts BW, Mitchell J, Kilgannon JH, Chansky ME, Trzeciak S. Nitric oxide donor agents for the treatment of ischemia/reperfusion injury in human subjects: a systematic review. Shock. 2013;39(3):229-339. https://doi.org/10.1097/SHK.0b013e31827f565b PMid:23358103

44. Obeagu EI, Obeagu GU. Addressing Myths and Stigmas: Breaking Barriers in Adolescent Sickle Cell Disease Education. Elite Journal of Health Science. 2024;2(2):7-15. https://doi.org/10.2147/JBM.S462758 PMid:39081620 PMCid:PMC11288316

45. Obeagu EI, Obeagu GU. Implications of climatic change on sickle cell anemia: A review. Medicine. 2024 Feb 9;103(6):e37127. https://doi.org/10.1097/MD.0000000000037127 PMid:38335412 PMCid:PMC10860944

46. Obeagu EI. Chromium VI: A Silent Aggressor in Sickle Cell Anemia Pathophysiology. Elite Journal of Haematology, 2024; 2 (3).:81-95.

47. Obeagu EI. Maximizing longevity: erythropoietin's impact on sickle cell anemia survival rates. Annals of Medicine and Surgery. 2024:10-97. https://doi.org/10.1097/MS9.0000000000001763 PMid:38463100 PMCid:PMC10923353

48. Samidurai A, Xi L, Das A, Kukreja RC. Beyond erectile dysfunction: cGMP-specific phosphodiesterase 5 inhibitors for other clinical disorders. Annual review of pharmacology and toxicology. 2023;63(1):585-615. https://doi.org/10.1146/annurev-pharmtox-040122-034745 PMid:36206989

49. Obeagu EI, Ubosi NI, Obeagu GU, Egba SI, Bluth MH. Understanding apoptosis in sickle cell anemia patients: Mechanisms and implications. Medicine. 2024;103(2):e36898. https://doi.org/10.1097/MD.0000000000036898 PMid:38215146 PMCid:PMC10783340

50. Obeagu EI, Ayogu EE, Anyanwu CN, Obeagu GU. Drug-Drug Interactions in the Management of Coexisting Sickle Cell Anemia and Diabetes. Elite Journal of Health Science. 2024;2(2):1-9.

51. Obeagu EI, Obeagu GU. Dual Management: Diabetes and Sickle Cell Anemia in Patient Care. Elite Journal of Medicine. 2024;2(1):47-56.

52. Obeagu EI, Obeagu GU, Hauwa BA. Optimizing Maternal Health: Addressing Hemolysis in Pregnant Women with Sickle Cell Anemia. Journal home page: http://www. journalijiar. com.;12(01).

53. Obeagu EI, Obeagu GU. Synergistic Care Approaches: Integrating Diabetes and Sickle Cell Anemia Management. Elite Journal of Scientific Research and Review. 2024;2(1):51-64.

54. Grzywa TM, Sosnowska A, Matryba P, Rydzynska Z, Jasinski M, Nowis D, Golab J. Myeloid cell-derived arginase in cancer immune response. Frontiers in immunology. 2020; 11:938. https://doi.org/10.3389/fimmu.2020.00938 PMid:32499785 PMCid:PMC7242730

55. Obeagu EI, Obeagu GU. Improving Outcomes: Integrated Strategies for Diabetes and Sickle Cell Anemia. Int. J. Curr. Res. Chem. Pharm. Sci. 2024;11(2):20-9.

56. Obeagu EI, Obeagu GU. The Role of Parents: Strengthening Adolescent Education for Sickle Cell Disease Prevention. Elite Journal of Public Health. 2024;2(1):15-21. https://doi.org/10.2147/JBM.S462758 PMid:39081620 PMCid:PMC11288316

57. Obeagu EI, Obeagu GU. Hemolysis Challenges for Pregnant Women with Sickle Cell Anemia: A Review. Elite Journal of Haematology, 2024; 2 (3).:67-80.

58. Obeagu EI, Obeagu GU. Overcoming Hurdles: Anemia Management in Malaria-Affected Childhood. Elite Journal of Laboratory Medicine. 2024;2(1):59-69.

59. Bontempo P, Capasso L, De Masi L, Nebbioso A, Rigano D. Therapeutic Potential of Natural Compounds Acting through Epigenetic Mechanisms in Cardiovascular Diseases: Current Findings and Future Directions. Nutrients. 2024;16(15):2399. https://doi.org/10.3390/nu16152399

60. Cao M, Zhao Y, He H, Yue R, Pan L, Hu H, Ren Y, Qin Q, Yi X, Yin T, Ma L. New applications of HBOC-201: a 25-year review of the literature. Frontiers in Medicine. 2021; 8:794561. https://doi.org/10.3389/fmed.2021.794561 PMid:34957164 PMCid:PMC8692657

61. Brun M, Bourdoulous S, Couraud PO, Elion J, Krishnamoorthy R, Lapoumeroulie C. Hydroxyurea downregulates endothelin-1 gene expression and upregulates ICAM-1 gene expression in cultured human endothelial cells. The Pharmacogenomics Journal. 2003;3(4):215-226. https://doi.org/10.1038/sj.tpj.6500176 PMid:12931135