Calcineurin inhibitor induces pain hypersensitivity by potentiating pre‐ and postsynaptic NMDA receptor activity in spinal cords

Abstract

Key points• We developed an animal model to study the mechanisms underlying the pain syndrome commonly seen in organ transplant patients receiving calcineurin inhibitors.• Systemic treatment with the calcineurin inhibitor induces long-lasting pain hypersensitivity and increases glutamate receptor activity in the spinal cord.• Blocking glutamate receptor activity at the spinal cord level effectively reduces pain hypersensitivity induced by the calcineurin inhibitor.• This information advances our understanding of the molecular basis of pain caused by calcineurin inhibitors and identifies new strategies for treating such pain syndrome in transplant patients.Abstract Calcineurin inhibitors, such as cyclosporin A and tacrolimus (FK506), have played a pivotal role in the preservation of allograft function. However, these drugs can cause unexplained severe pain in patients, often referred to as calcineurin inhibitor-induced pain syndrome (CIPS). Although calcineurin can regulate NMDA receptor (NMDAR) activity, the causal relationship between spinal synaptic plasticity and CIPS remains unknown. In this study, we showed that systemic administration of FK506 (1.5 mg kg −1 day −1 ) for 7 days in rats led to long-lasting nociceptive and mechanical hypersensitivity. Whole-cell patch-clamp recordings in spinal cord slices revealed that FK506 treatment caused a large increase in the amplitude of NMDAR-mediated excitatory postsynaptic currents (EPSCs) of dorsal horn neurons evoked by dorsal root stimulation. The amplitude of NMDAR currents elicited by puff NMDA application to dorsal horn neurons was also significantly greater in FK506-treated than in vehicle-treated rats. The frequency of spontaneous and miniature EPSCs in most dorsal horn neurons was profoundly increased in FK506-treated rats and was reduced by blocking NMDARs. Furthermore, blocking GluN2A or GluN2B subunits similarly reduced the amplitude of evoked EPSCs and the frequency of miniature EPSCs in dorsal horn neurons of FK506-treated rats. In addition, intrathecal injection of an NMDAR antagonist or systemic administration of memantine effectively reversed nociceptive and mechanical hypersensitivity in FK506-treated rats. Our findings indicate that calcineurin inhibition increases glutamate-mediated nociceptive input by potentiating presynaptic and postsynaptic NMDAR activity in spinal cords. NMDAR antagonists may represent a new therapeutic option for the treatment of CIPS.

Casein Kinase II Inhibition Reverses Pain Hypersensitivity and Potentiated Spinal N-Methyl-d-aspartate Receptor Activity Caused by Calcineurin Inhibitor

“…The primary treatment of CIPS is discontinuation of these agents, which could endanger the transplanted organs and tissues. We demonstrated recently that systemic administration of FK506 can lead to unrestrained nociceptive input by potentiating NMDARs at the spinal cord level (Chen et al, 2014). NMDAR activity and phosphorylation state are dynamically controlled by a balance between the activity of protein kinases and protein phosphatases.…”

“…Eighty-seven adult male SpragueDawley rats (280-320 g; Harlan, Indianapolis, IN) were used for the study. The specific calcineurin inhibitor FK506 was used to induce CIPS in the rats, as we previously described (Chen et al, 2014). FK506 (1.5 mg/kg) was dissolved in dimethylsulfoxide (DMSO) and injected intraperitoneally once a day for 7 days.…”

“…Presynaptic NMDARs regulate synaptic glutamate release in the spinal cord (Zhao et al, 2012). Systemic treatment with FK506 increases synaptic glutamate release through stimulation of presynaptic NMDARs in the spinal cord (Chen et al, 2014). To determine whether CK2 plays a role in FK506 treatment-induced increases in presynaptic NMDAR activity in the spinal cord, we tested the effect of DRB and TBB on glutamatergic mEPSCs (reflecting presynaptic quantal release of glutamate) of lamina II neurons in FK506-treated rats.…”

“…Because the underlying mechanisms of CIPS are not fully known, effective treatments for CIPS are still limited. We recently developed a rat model of CIPS in which systemic administration of FK506 causes a long-lasting pain hypersensitivity (Chen et al, 2014). We have shown that repeated FK506 treatment in rats increases pre-and postsynaptic N-methyl-Daspartate receptor (NMDAR) activity in the spinal dorsal horn and that blocking spinal NMDARs can effectively attenuate the pain hypersensitivity caused by FK506 (Chen et al, 2014).…”

“…NMDAR phosphorylation by the coordinated activities of protein kinases and phosphatases is central to many physiologic functions Mody, 1994, 1999;Tong ABBREVIATIONS: AMPAR, a-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid receptor; AP5, D-2-amino-5-phosphonopentanoate; CIPS, calcineurin inhibitor-induced pain syndrome; CK2, casein kinase II; et al , 1995;MacDonald et al, 1998 (Tong et al, 1995;Chen et al, 2014). On the other hand, inhibition of protein kinase CK2 (formerly known as casein kinase II) can attenuate NMDAR activity in the brain, possibly by reducing NMDAR phosphorylation Mody, 1994, 1999;Tong et al, 1995;Ye et al, 2012).…”