CaMKII Phosphorylation in Primary Somatosensory Cortical Neurons is Involved in the Inhibition of Remifentanil-induced Hyperalgesia by Lidocaine in Male Sprague-Dawley Rats

Pharmacological Interventions for Opioid-Induced Hyperalgesia: A Scoping Review of Preclinical Trials

BACKGROUND

Opioid analgesics are the most effective pharmacological agents for moderate and severe pain. However, opioid use has several limitations such as opioid-induced hyperalgesia (OIH), which refers to the increased pain sensitivity that occurs once analgesia wears off after opioid administration. Several pharmacological interventions have been suggested for OIH, but the current literature does not provide guidelines on which interventions are the most effective and whether they differ depending on the opioid that induces hyperalgesia. This scoping review aimed to identify and describe all the preclinical trials investigating pharmacological interventions for OIH caused by remifentanil, fentanyl, or morphine as the first step towards evaluating whether the most effective OIH interventions are different for different opioids.

METHODS

Electronic database searches were carried out in Embase, PubMed, and Web of Science. Detailed data extraction was conducted on the eligible trials.

RESULTS

72 trials were eligible for the review. Of these, 27 trials investigated remifentanil, 14 trials investigated fentanyl, and 31 trials investigated morphine. A total of 82 interventions were identified. The most studied interventions were ketamine (eight trials) and gabapentin (four trials). The majority of the interventions were studied in only one trial. The most common mechanism suggested for the interventions was inhibition of N-methyl-D-aspartate (NMDA) receptors.

CONCLUSION

This scoping review identified plenty of preclinical trials investigating pharmacological interventions for OIH. Using the current literature, it is not possible to directly compare the effectiveness of the interventions. Hence, to identify the most effective interventions for each opioid, the interventions must be indirectly compared in a meta-analysis.

Potentilla anserine L. polysaccharide protects against cadmium-induced neurotoxicity

Cadmium is a toxic metal that can damage the brain and other organs. This study aimed to explore the protective effects of Potentilla anserine L. polysaccharide (PAP) against CdCl2-induced neurotoxicity in N2a and SH-SY5Y cells and in the cerebral cortex of BALB/c mice. In addition, we aimed to identify the potential mechanisms underlying these protective effects. Relative to CdCl2 treatment alone, pretreatment with PAP prevented the reduction in cell viability evoked by CdCl2, decreased rates of apoptosis, promoted calcium homeostasis, decreased ROS accumulation, increased mitochondrial membrane potential, inhibited cytochrome C and AIF release, and prevented the cleavage of caspase-3 and PARP. In addition, PAP significantly decreased the CdCl2-induced phosphorylation of CaMKII, Akt, and mTOR. In conclusion, PAP represents a potential therapeutic agent for the treatment of Cd-induced neurotoxicity, functioning in part via attenuating the activation of the mitochondrial apoptosis pathway and the Ca2+-CaMKII-dependent Akt/mTOR pathway.

Store-Operated Calcium Channels Contribute to Remifentanil-Induced Postoperative Hyperalgesia via Phosphorylation of CaMKIIα in Rats

Purpose

The mechanisms of remifentanil-induced postoperative hyperalgesia (RIPH) remain unclear. Store-operated calcium channels (SOCCs) are mainly comprised of stromal interaction molecules 1 (STIM1) and pore-forming subunits (Orai1). They were found to take a pivotal part in Ca²⁺-dependent procedures and involved in the development of central sensitization and pain. Ca²⁺/calmodulin-dependent protein kinase IIα (CaMKIIα), regulated by Ca²⁺/calmodulin complex, has been shown to have a crucial role in RIPH. This study aims to determine whether SOCCs contribute to RIPH via activating CaMKIIα.

Materials and Methods

Intra-operative infusion of remifentanil (1.0 µg kg⁻¹ min⁻¹, 60 min) was used to establish a RIPH rat model. The SOCCs blocker (YM-58483) was applied intrathecally to confirm the results. Animal behavioral tests including paw withdrawal thermal latency (PWTL) and paw withdrawal mechanical threshold (PWMT) were performed at −24, 2, 6, 24, 48 h after incision and remifentanil treatments. The protein expression of STIM1, Orai1, CaMKIIα, and p-CaMKIIα was assayed with Western blot, and the number of STIM1 and Orai1 positive cells was shown by immunofluorescence.

Results

Remifentanil administration significantly induced postoperative mechanical and thermal hyperalgesia, as well as increased STIM1 and Orai1 protein expression in the spinal dorsal horn. Furthermore, the intrathecal administration of YM-58483 effectively alleviated remifentanil-induced postoperative mechanical and thermal hyperalgesia according to the behavioral tests. In addition, YM-58483 suppressed the phosphorylation of CaMKIIα but had no effect on the expression of STIM1 and Orai1.

Conclusion

Our study demonstrated that SOCCs are involved in RIPH. The over-expressed STIM1 and Orai1 in the spinal cord contribute to RIPH via mediating the phosphorylation of CaMKIIα. Blockade of SOCCs may provide an effective therapeutic approach for RIPH.

Intravenous Magnesium - Lidocaine - Ketorolac Cocktail for Postoperative Opioid Resistant Pain: A Case Series of Novel Rescue Therapy

BACKGROUND

Severe postoperative pain is principally managed by opioids. While effective, opioids do not provide adequate relief in many patients and cause many side effects, including antinociceptive tolerance and opioid-induced hyperalgesia. To evaluate if a combination of intravenous Magnesium, Lidocaine, Ketorolac (MLK cocktail) is a useful rescue therapy through synergistic pharmacological mechanisms for acute pain relief. We present the intravenous combination of magnesium, lidocaine, and ketorolac (MLK cocktail) as a possible rescue for opioid insensitive severe post-operative pain.

MATERIALS AND METHODS

The principal settings were the post-operative care unit (PACU) and the surgical ward. We retrospectively analyzed the electronic medical record and anesthesia documents of 14 patients experiencing severe postoperative pain, >7/10 visual-analogue pain score (VAS), despite receiving at least 8 mg of intravenous morphine milligram equivalents (MME) after arrival in the LAC+USC Medical Center PACU between September 2012 and January 2013. The data reviewed included patients' demographics, disease etiology, surgical procedure, opioids received perioperatively, and visual-analogue pain scores before and after each analgesic received, and after the MLK cocktail. The a priori primary outcome and a posteriori secondary outcome of this study are mean visual-analogue pain score and morphine milligram equivalent dose administered per hour, respectively. The main tool evaluated has been VAS score.

RESULTS

In patients who failed to respond to opioid analgesics, administration of the MLK cocktail improved the VAS pain scores immediately from 9.4 ± 1.0 to 3.6 ± 3.5. The MLK cocktail also decreased the MME doses/hour in the immediate 12 hours postoperative period from 12.4 ± 5.6 to 1.1 ± 0.9.

CONCLUSION

In patients experiencing opioid-resistant severe postoperative pain, the magnesium, lidocaine, and ketorolac combination may be an effective nonopioid rescue therapy. Additionally, magnesium, lidocaine, and ketorolac may be utilized in cases complicated by either antinociceptive tolerance or opioid-induced hyperalgesia and can restore opioid responsiveness.

In vivo reduction of hippocampal Caveolin-1 by RNA interference alters morphine addiction and neuroplasticity changes in male mice

Prescription opioids are powerful pain-controlling medications that have both benefits and potentially serious risks. Morphine is one of the preferred analgesics that are widely used to treat chronic pain. However, chronic morphine exposure has been found to cause both functional and structural changes in several brain regions, including the medial prefrontal cortex (mPFC), ventral tegmental area (VTA), and hippocampus (HPC), which lead to addictive behavior. Caveolin-1 (Cav-1), a scaffolding protein of membrane lipid rafts (MLRs), has been shown to organize GPCRs and multiple synaptic signaling proteins within the MLRs to regulate synaptic signaling and neuroplasticity. Previously, we showed that in vitro morphine treatment significantly elevates Cav-1 expression and causes neuroplasticity changes. In this study, we confirmed that chronic morphine exposure can significantly increase Cav-1 expression (P < 0.05) and microtubule-associated protein (MAP-2)-positive neuronal dendritic growth in the hippocampus. Moreover, the rewarding effect and dendritic growth in the HPC induced by chronic morphine exposure were significantly inhibited by hippocampal Cav-1 knockdown. Together, these data suggest that Cav-1 in the hippocampus plays an essential role in the neuroplasticity changes that underlie morphine addiction behaviors.

Dezocine attenuates the remifentanil-induced postoperative hyperalgesia by inhibition of phosphorylation of CaMKⅡα

Remifentanil, ultra-short-acting μ-opioid receptor agonist, has the greatest advantage in analgesia but could increase postoperative pain scores and induces postoperative hyperalgesia. Dezocine is a mixed opioid receptor partial agonist/antagonist and has been used for postoperative hyperalgesia management in clinical patients,but the potential molecular mechanism is still unclear. Ca²⁺/calmodulin-dependent protein kinase Ⅱ(CaMKⅡ) has been reported involved in remifentanil-induced hyperalgesia (RIH) in previous studies, but the relationship between CaMKⅡ and dezocine in RIH is still unclear. To investigate the mechanism of dezocine in RIH, we used a remifentanil induced postoperative hyperalgesia (RIPH) in incisional pain model of mouse. We subcutaneously infused remifentanil (40 μg/kg) to induce postoperative hyperalgesia. Dezocine (1.5 mg/kg, 3.0 mg/kg, and 6.0 mg/kg) was infused subcutaneously with remifentanil using the apparatus pump for 30 min. Paw withdrawal thermal latency (PWTL) and paw withdrawal mechanical threshold (PWMT) were used to assess thermal hyperalgesia and mechanical allodynia. Western blotting analysis and immunohistochemistry analysis were used to assess the expression of phosphorylated CaMKⅡα (p-CaMKⅡα) in somatosensory cortex, hippocampus and spinal cord. Subcutaneous infusion of remifentanil enhanced postoperative pain induced by surgical incision and increased PWTL and PWMT. Dezocine dose-dependently decreased the PWTL and PWMT in RIPH model. Correlating with behavioral effects, dezocine inhibited remifentanil-induced up-regulation of p-CaMKⅡα expression in somatosensory cortex, hippocampus and spinal cord. Dezocine could attenuate RIPH by suppressing p-CaMKⅡα.

Ketamine reduces remifentanil-induced postoperative hyperalgesia mediated by CaMKII-NMDAR in the primary somatosensory cerebral cortex region in mice

Remifentanil is commonly used clinically for perioperative pain relief, but it may induce postoperative hyperalgesia. Low doses of ketamine have remained a common choice in clinical practice, but the mechanisms of ketamine have not yet been fully elucidated. In this study, we examined the possible effects of ketamine on calcium/calmodulin-dependent protein kinase II α (CaMKIIα) and N-methyl-d-aspartate receptor (NMDAR) subunit NR2B in a mouse model of remifentanil-induced postoperative hyperalgesia (RIPH) in the primary somatosensory cerebral cortex (SI) region. The paw withdrawal mechanical threshold (PWMT) and paw withdrawal thermal latency (PWTL) were used to assess mechanical allodynia and thermal hyperalgesia, respectively, before and after intraoperative remifentanil administration. Before surgery, mice received intrathecal injections of the following drugs: ketamine, NMDA, BayK8644 (CaMKII activator), and KN93 (CaMKII inhibitor). Immunofluorescence was performed to determine the anatomical location and expression of activated CaMKIIα, phosphorylated CaMKIIα (p-CaMKIIα). Additionally, western blotting was performed to assess p-CaMKIIα and NMDAR expression levels in the SI region. Remifentanil decreased the PWMT and PWTL at 0.5 h, 2 h, and 5 h and increased p-CaMKIIα expression in the SI region. Ketamine increased the PWMT and PWTL and reversed the p-CaMKIIα upregulation. Both BayK8644 and NMDA reversed the effect of ketamine, decreased the PWMT and PWTL, and upregulated p-CaMKIIα expression. In contrast, KN93 enhanced the effect of ketamine by reducing hyperalgesia and downregulating p-CaMKIIα expression. These results suggested that ketamine reversed RIPH by inhibiting the phosphorylation of CaMKIIα and the NMDA receptor in the SI region in mice.

The increased release of amino acid neurotransmitters of the primary somatosensory cortical area in rats contributes to remifentanil-induced hyperalgesia and its inhibition by lidocaine

Background

Studies have confirmed that activation of the neurons of primary somatosensory cortex (S1) is involved in the process of remifentanil (Remi)-induced hyperalgesia (RIH), which can be suppressed by lidocaine (Lido). A total intravenous anesthesia model of rats mimicking clinical Remi-based anesthesia was set up to explore the release of amino acid neurotransmitters of S1 cortex in RIH and its inhibition by Lido in this study.

Materials and methods

Sprague Dawley rats were randomly divided into the following four groups: propofol (Pro), Remi, Remi combined Lido, and Lido groups. Mechanical hyperalgesia was evaluated by von Frey test; the amino acid neurotransmitters in the microdialysates of S1 area were detected by high-performance liquid chromatography (HPLC)-fluorescence, and conventional protein kinase C (cPKC)γ levels in the whole-cell lysates and membrane lipid rafts (MLRs) were determined by Western blotting.

Results

The von Frey test showed that co-administration of Lido significantly inhibited a Remi-induced decrease in the threshold of the paw withdrawal response in Remi group at 2 h postinfusion. Meanwhile, the Remi-induced increases in both the excitatory and inhibitory amino acid releases in S1 were suppressed by co-administrating Lido within 5 h postinfusion. Western blotting showed that the increased cPKCγ level in the membrane lipid rafts (MLR) induced by Remi was also inhibited by Lido.

Conclusion

The increased release of amino acid neurotransmitters and the translocation of cPKCγ in MLR suggest the activation of S1 neurons, which may be one of the mechanisms underlying RIH. Lido reduces the release of amino acid neurotransmitters in S1 neurons and the translocation of cPKCγ in MLRs after stopping Remi, which may be one of its antihyperalgesic mechanisms.