Immune cell neural interactions and their contributions to sickle cell disease

Targeting TRPV1 activity via high-dose capsaicin in patients with sickle cell disease

Evidence suggests neuropathic pain (NP) develops over time in sickle cell disease (SCD), contributing to a complex, difficult-to-treat phenotype, with management based on scant evidence. One characteristic of NP found is hyperalgesia caused by nervous system sensitization, but risk factors for this have not been identified within the SCD population, as exact mechanisms leading to its development are not well defined. The SPICE (Sickle cell Pain: Intervention with Capsaicin Exposure) trial was a pilot safety and feasibility trial of high-dose (8%) topical capsaicin for patients with SCD and recurrent/chronic pain with neuropathic features, aimed at exploring capsaicin's utility as a mechanistic probe and adjunctive pain treatment for this population. Ten participants identifying "target" sites of pain with NP-type qualities consented to treatment. The primary endpoint was safety/tolerability. The novel Localized Peripheral Hypersensitivity Relief score (LPHR) was developed to determine improvement in sensitivity attributable to TRPV1 neutralization. There were no severe treatment-related adverse events. Higher baseline pain sensitivity at a given body site was associated with self-reported history of more frequent localized vaso-occlusive pain episodes at that site. There was a statistically significant improvement in the mean LPHR, evidencing TRPV1's importance to the development of hypersensitivity and a potential therapeutic benefit of capsaicin for SCD.

Acupuncture for Pain Management in Pediatric Patients with Sickle Cell Disease

Pain management in an acute vaso-occlusive episode for pediatric patients with sickle cell disease (SCD) is challenging and often is focused on opioids, IV fluids, regional anesthesia, ketamine infusions, and non-steroidal anti-inflammatory drugs (NSAIDs). Acupuncture has long been studied as an effective method of pain relief, although the use of acupuncture in pediatric patients with SCD during an acute vaso-occlusive pain episode is vastly understudied. This article provides a review of current research regarding the use of acupuncture as a pain treatment strategy for pediatric patients with SCD experiencing acute pain. A literature review of scientific papers published within the last ten years was conducted on the topic. Five primary literature articles on acupuncture for pain management in pediatric patients with SCD were reviewed. Acupuncture is feasible and acceptable, with statistically significant findings for effectiveness as an adjunct treatment for pain in this setting. It is concluded that acupuncture is a promising and understudied therapy for the treatment of pain during an acute pain episode in pediatric patients with SCD. Hopefully, this paper stimulates interest in this specific area of medicine and prompts future research studies to be conducted to reveal conclusive outcomes.

Pain in sickle cell disease: current and potential translational therapies

Pain is a major comorbidity of sickle cell disease (SCD). Patients with SCD may suffer from both acute and chronic pain. Acute pain is caused by recurrent and unpredictable episodes of vaso-occlusive crises (VOC), whereas the exact etiology of chronic pain is still unknown. Opioids are the mainstay for pain treatment, but the opioid epidemic has significantly altered access to prescription opioids and has brought concerns over their long-term use into the forefront, which have negatively impacted the treatment of sickle pain. Opioids remain potent analgesics but growing opioid-phobia has led to the realization of an unmet need to develop nonopioid therapies that can provide relief for severe sickle pain. This realization has contributed to the approval of 3 different drugs by the Food and Drug Administration (FDA) for the treatment of SCD, particularly to reduce VOC and/or have an impact on the pathobiology of SCD. In this review, we outline the challenges and need for validation of side-effects of opioids and provide an update on the development of mechanism-based translational therapies, specifically targeting pain in SCD.

Cell and Gene Therapy for Anemia: Hematopoietic Stem Cells and Gene Editing

Hereditary anemia has various manifestations, such as sickle cell disease (SCD), Fanconi anemia, glucose-6-phosphate dehydrogenase deficiency (G6PDD), and thalassemia. The available management strategies for these disorders are still unsatisfactory and do not eliminate the main causes. As genetic aberrations are the main causes of all forms of hereditary anemia, the optimal approach involves repairing the defective gene, possibly through the transplantation of normal hematopoietic stem cells (HSCs) from a normal matching donor or through gene therapy approaches (either in vivo or ex vivo) to correct the patient’s HSCs. To clearly illustrate the importance of cell and gene therapy in hereditary anemia, this paper provides a review of the genetic aberration, epidemiology, clinical features, current management, and cell and gene therapy endeavors related to SCD, thalassemia, Fanconi anemia, and G6PDD. Moreover, we expound the future research direction of HSC derivation from induced pluripotent stem cells (iPSCs), strategies to edit HSCs, gene therapy risk mitigation, and their clinical perspectives. In conclusion, gene-corrected hematopoietic stem cell transplantation has promising outcomes for SCD, Fanconi anemia, and thalassemia, and it may overcome the limitation of the source of allogenic bone marrow transplantation.

Neuropathic pain in sickle cell disease: measurement and management

The identification of chronic pain and neuropathic pain as common contributors to the overall pain experience of patients with sickle cell disease (SCD) has altered the way we should evaluate difficult-to-treat pain. The recognition of these 2 entities is not generally routine among various medical specialties and provider levels that treat SCD. Due to the relative recency with which neuropathic pain was first described in SCD, validated assessment tools and evidence-based treatments remain lacking. Although clinical assessment and judgment must continue to inform all decision making in this understudied area of SCD pain management, a number of validated neuropathic pain assessment tools exist that can make possible a standardized evaluation process. Similarly, investigation of available neuropathic pain treatments for the uniquely complex pain phenotypes of SCD has only just begun and is better established in pain conditions other than SCD. The aim of this review is to briefly summarize the proposed basic pathophysiology, assessment, and treatment of neuropathic pain in patients with SCD. Furthermore, the aim of this review is to encourage an expanded framework for the assessment and treatment of SCD pain that appreciates the hidden complexities of this common complication of SCD.

Considerations for Cannabis Use to Treat Pain in Sickle Cell Disease

Pain in Sickle Cell Disease (SCD) is a major comorbidity and unique with acute pain due to recurrent and episodic vaso-occlusive crises as well as chronic pain, which can span an individual's entire life. Opioids are the mainstay treatment for pain in SCD. Due to recent health crises raised by adverse effects including deaths from opioid use, pain management in SCD is adversely affected. Cannabis and its products are most widely used for pain in multiple conditions and also by patients with SCD on their own. With the availability of "Medical Cannabis" and approval to use cannabis as medicine across majority of States in the United States as well as over-the-counter preparations, cannabis products are being used increasingly for SCD. The reliability of many of these products remains questionable, which poses a major health risk to the vulnerable individuals seeking pain relief. Therefore, this review provides up to date insights into available categories of cannabis-based treatment strategies, their mechanism of action and pre-clinical and clinical outcomes in SCD. It provides evidence for the benefits and risks of cannabis use in SCD and cautions about the unreliable and unvalidated products that may be adulterated with life-threatening non-cannabis compounds.

Integrative approaches to treating pain in sickle cell disease: Pre-clinical and clinical evidence

Sickle cell disease (SCD) is a genetic disorder characterized by hemolysis, end-organ damage, inflammation, and pain. Recurrent and unpredictable episodes of acute pain due to vaso-occlusive crises are a unique feature of SCD. Many patients also develop lifelong chronic pain. Opioids are the primary method of pain treatment in SCD; however, continued use is associated with several adverse effects. Integrative approaches to treating pain in SCD are increasingly being explored to prevent the side effects associated with opioids. In this review, we highlight the mechanisms of pain in SCD and describe mechanism-based integrative approaches for treating pain.

Identification of Gain and Loss of Function Missense Variants in MRGPRX2's Transmembrane and Intracellular Domains for Mast Cell Activation by Substance P

The neuropeptide substance P (SP) contributes to neurogenic inflammation through the activation of human mast cells via Mas-related G protein-coupled receptor-X2 (MRGPRX2). Using pertussis toxins and YM-254890, we demonstrated that SP induces Ca²⁺ mobilization and degranulation via both the Gαi and Gαq family of G proteins in rat basophilic leukemia (RBL-2H3) cells stably expressing MRGPRX2. To determine the roles of MRGPRX2's transmembrane (TM) and intracellular domains on SP-induced responses, we utilized information obtained from both structural modeling and naturally occurring MRGPRX2 missense variants. We found that highly conserved residues in TM6 (I225) and TM7 (Y279) of MRGPRX2 are essential for SP-induced Ca²⁺ mobilization and degranulation in transiently transfected RBL-2H3 cells. Cells expressing missense variants in the receptor's conserved residues (V123F and V282M) as well as intracellular loops (R138C and R141C) failed to respond to SP. By contrast, replacement of all five Ser/Thr residues with Ala and missense variants (S325L and L329Q) in MRGPRX2's carboxyl-terminus resulted in enhanced mast cell activation by SP when compared to the wild-type receptor. These findings suggest that MRGPRX2 utilizes conserved residues in its TM domains and intracellular loops for coupling to G proteins and likely undergoes desensitization via phosphorylation at Ser/Thr residues in its carboxyl-terminus. Furthermore, identification of gain and loss of function MRGPRX2 variants has important clinical implications for SP-mediated neurogenic inflammation and other chronic inflammatory diseases.