Pregabalin: A New Adjunct in Calcineurin Inhibitor Pain Syndrome Treatment

Characterization of the calcineurin inhibitor pain syndrome in patients undergoing allogeneic hematopoietic cell transplantation

Calcineurin inhibitor pain syndrome (CIPS) is a rare complication of graft-vs-host disease prophylaxis following allogeneic hematopoietic cell transplant (alloHCT). CIPS presents as severe bilateral lower extremity pain, and the incidence, risk factors, and management of CIPS are poorly characterized.This is a single center retrospective study of patients who received tacrolimus (TAC) following alloHCT to describe the characteristics and management of CIPS and compare to a cohort who did not develop CIPS.Fifteen of 585 alloHCT patients (2.6%) developed CIPS at a median of 5 days following TAC initiation and a median level of 10.5 ng/mL. Severe bilateral foot, ankle, or leg pain were the primary symptoms. Patients with CIPS were younger and more frequently received myeloablative conditioning and total body irradiation compared to patients without CIPS. Analgesic regimens included dihydropyridine calcium channel blockers, gabapentinoids, topical diclofenac, and opioids.Clinicians should be aware of this uncommon but severe adverse effect.

Calcineurin Regulates Synaptic Plasticity and Nociceptive Transmission at the Spinal Cord Level

Calcineurin, the predominant Ca2+/calmodulin-dependent serine/threonine protein phosphatase (also known as protein phosphatase 2B), is highly expressed in immune T cells and the nervous system, including the dorsal root ganglion and spinal cord. It controls synaptic transmission and plasticity by maintaining the appropriate phosphorylation status of many ion channels present at presynaptic and postsynaptic sites. As such, normal calcineurin activity in neurons and synapses is mainly involved in negative feedback regulation in response to increased neuronal activity and intracellular Ca2+ levels. Calcineurin inhibitors (e.g., cyclosporine and tacrolimus) are widely used as immunosuppressants in tissue and organ transplantation recipients and for treating autoimmune diseases but can cause severe pain in some patients. Furthermore, diminished calcineurin activity at the spinal cord level may play a major role in the transition from acute to chronic neuropathic pain after nerve injury. Restoring calcineurin activity at the spinal cord level produces long-lasting pain relief in animal models of neuropathic pain. In this article, we provide an overview of recent studies on the critical roles of calcineurin in regulating glutamate NMDA and AMPA receptors, voltage-gated Ca2+ channels, potassium channels, and transient receptor potential channels expressed in the spinal dorsal horn and primary sensory neurons.

Calcineurin Inhibition Causes α2δ-1-Mediated Tonic Activation of Synaptic NMDA Receptors and Pain Hypersensitivity

Calcineurin inhibitors, such as tacrolimus (FK506) and cyclosporine, are widely used as standard immunosuppressants in organ transplantation recipients. However, these drugs can cause severe pain in patients, commonly referred to as calcineurin inhibitor-induced pain syndrome (CIPS). Although calcineurin inhibition increases NMDAR activity in the spinal cord, the underlying mechanism remains enigmatic. Using an animal model of CIPS, we found that systemic administration of FK506 in male and female mice significantly increased the amount of α2δ-1-GluN1 complexes in the spinal cord and the level of α2δ-1-bound GluN1 proteins in spinal synaptosomes. Treatment with FK506 significantly increased the frequency of mEPSCs and the amplitudes of monosynaptic EPSCs evoked from the dorsal root and puff NMDAR currents in spinal dorsal horn neurons. Inhibiting α2δ-1 with gabapentin or disrupting the α2δ-1-NMDAR interaction with α2δ-1Tat peptide completely reversed the effects of FK506. In α2δ-1 gene KO mice, treatment with FK506 failed to increase the frequency of NMDAR-mediated mEPSCs and the amplitudes of evoked EPSCs and puff NMDAR currents in spinal dorsal horn neurons. Furthermore, systemic administration of gabapentin or intrathecal injection of α2δ-1Tat peptide reversed thermal and mechanical hypersensitivity in FK506-treated mice. In addition, genetically deleting GluN1 in dorsal root ganglion neurons or α2δ-1 genetic KO similarly attenuated FK506-induced thermal and mechanical hypersensitivity. Together, our findings indicate that α2δ-1-bound NMDARs mediate calcineurin inhibitor-induced tonic activation of presynaptic and postsynaptic NMDARs at the spinal cord level and that presynaptic NMDARs play a prominent role in the development of CIPS.SIGNIFICANCE STATEMENT Calcineurin inhibitors are immunosuppressants used to prevent rejection of transplanted organs and tissues. However, these drugs can cause severe, unexplained pain. We showed that calcineurin inhibition enhances physical interaction between α2δ-1 and NMDARs and their synaptic trafficking in the spinal cord. α2δ-1 is essential for calcineurin inhibitor-induced aberrant activation of presynaptic and postsynaptic NMDARs in the spinal cord. Furthermore, inhibiting α2δ-1 or disrupting α2δ-1-NMDAR interaction reduces calcineurin inhibitor-induced pain hypersensitivity. Eliminating NMDARs in primary sensory neurons or α2δ-1 KO also attenuates calcineurin inhibitor-induced pain hypersensitivity. This new information extends our mechanistic understanding of the role of endogenous calcineurin in regulating synaptic plasticity and nociceptive transmission and suggests new strategies for treating this painful condition.

Tacrolimus-Induced Pain Syndrome After Bone Marrow Transplantation: A Case Report and Literature Review

BACKGROUND

Calcineurin-inhibitor-induced pain syndrome (CIPS), a rare complication seen in patients with bone marrow transplants, is associated with the use of cyclosporine A (CsA) or tacrolimus (FK506). This case demonstrates the successful pain control of FK506-related CIPS in a 23-year-old male patient with previously reported characteristic clinical features of CIPS in addition to neuropathic symptoms and uncharacteristic imaging findings. On day 15 after the transplantation, the patient complained of severe pain in the lower limbs. Afterwards, the patient started to complain of pain on his hands and back too. During this period, FK506 levels ranged from 9.5 to 16.1 ng/mL. All laboratory exams were normal, except for an increased level of alkaline phosphatase (141 U/L). The pain was not ameliorated by various analgesic drugs. Although MRI done for our patient showed no typical radiological signs such as bone marrow edema, CIPS was suggested based on characteristic clinical features of CIPS. Of note, our patient's pain had neuropathic pain-like characteristics, unlike the pain in previously reported patients with CIPS.

CONCLUSION

The patient was treated successfully by switching FK506 to CsA and administrating gabapentin and nifedipine. Heightened awareness of this complication after bone marrow transplants may be needed for hematologists, otherwise CIPS can result in catastrophic consequences.

An Unusual Manifestation of Calcineurin Inhibitor-Induced Pain Syndrome in Kidney Transplantation: A Case Report and Literature Review

Patient: Female, 23

Final Diagnosis: Calcineurin inhibitor-induced pain syndrome

Symptoms: Back pain

Medication: —

Clinical Procedure: Supportive treatment

Specialty: Transplantology

Immunosuppressant Medication-Induced Lower Extremity Pain After Combined Liver and Kidney Transplant: A Case Report

Calcineurin inhibitors are imperative in the success of a transplanted organ. However, these immunosuppressants can lead to a rare complication known as calcineurin inhibitor-induced pain syndrome, which may not be recognized early and managed appropriately. We present a case of a 35-year-old woman who underwent a combined liver/kidney transplant and developed lower extremity pain while being maintained on tacrolimus. This case illustrates a patient with previously reported characteristic clinical features of calcineurin inhibitor-induced pain syndrome in addition to uncharacteristic neuropathic symptoms and imaging findings. The patient was treated successfully with gabapentin, calcitonin nasal spray, and acupuncture. Early recognition of this syndrome can help improve a patient's quality of life.

LEVEL OF EVIDENCE

V.