Propofol attenuates postoperative hyperalgesia via regulating spinal GluN2B-p38MAPK/EPAC1 pathway in an animal model of postoperative pain

Role of EPAC1 in chronic pain

Chronic pain usually lasts over three months and commonly occurs in chronic diseases (cancer, arthritis, and diabetes), injuries (herniated discs, torn ligaments), and many major pain disorders (neuropathic pain, fibromyalgia, chronic headaches). Unfortunately, there is currently a lack of effective treatments to help people with chronic pain to achieve complete relief. Therefore,it is particularly important to understand the mechanism of chronic pain and find new therapeutic targets. The exchange protein directly activated by cyclic adenosine monophosphate(cAMP) (EPAC) has been recognized for its functions in nerve regeneration, stimulating insulin release, controlling vascular pressure, and controlling other metabolic activities. In recent years, many studies have found that the subtype of EPAC, EPAC1 is involved in the regulation of neuroinflammation and plays a crucial role in the regulation of pain, which is expected to become a new therapeutic target for chronic pain. This article reviews the major contributions of EPAC1 in chronic pain.

The analgesic effect of total intravenous anaesthesia with propofol versus inhalational anaesthesia for acute postoperative pain after hepatectomy: a randomized controlled trial

BACKGROUND

Postoperative pain control can be challenging in patients undergoing hepatectomy. A previous retrospective study on hepatobiliary/ pancreatic surgeries showed better postoperative pain control in patients who received propofol TIVA. The aim of this study was to determine the analgesic effect of propofol TIVA for hepatectomy. This clinical study has been registered at ClinicalTrials.gov (NCT03597997).

METHODS

A prospective randomized controlled trial was performed to compare the analgesic effect of propofol TIVA versus inhalational anaesthesia. Patients aged between 18 and 80 years old with an American Society of Anesthesiologist (ASA) physical status of I-III scheduled for elective hepatectomy were recruited. Ninety patients were randomly allocated to receive either propofol TIVA (TIVA group) or inhalational anaesthesia with sevoflurane (SEVO group). Perioperative anaesthetic/analgesic management was the same for both groups. Numerical rating scale (NRS) pain scores, postoperative morphine consumption, quality of recovery, patient satisfaction and adverse effects were evaluated during the acute postoperative period and at 3 and 6 months after surgery.

RESULTS

No significant differences were found for acute postoperative pain scores (both at rest and during coughing) and postoperative morphine consumption between TIVA and SEVO groups. Patients given TIVA had lower pain scores with coughing at 3 months after surgery (p = 0.014, and FDR < 0.1). TIVA group was associated with better quality of recovery on postoperative day (POD) 3 (p = 0.038, and FDR < 0.1), less nausea (p = 0.011, and FDR < 0.1 on POD 2; p = 0.013, and FDR < 0.1 on POD 3) and constipation (p = 0.013, and FDR < 0.1 on POD 3).

CONCLUSION

Propofol TIVA did not improve acute postoperative pain control compared to inhalational anaesthesia in patients who underwent hepatectomy. Our results do not support the use of propofol TIVA for reducing acute postoperative pain after hepatectomy.

Pretreatment with propofol restores intestinal epithelial cells integrity disrupted by mast cell degranulation in vitro

Propofol has been shown to against intestinal reperfusion injury when treated either before or after ischemia, during which mast cell could be activated. The aim of this study was to evaluate the role of propofol in restoring the intestinal epithelial cells integrity disrupted by mast cell activation or the released tryptase after activation in vitro. We investigated the effect of: (1) tryptase on Caco-2 monolayers in the presence of PAR-2 inhibitor or propofol, (2) mast cell degranulation in a Caco-2/LAD-2 co-culture model in the presence of propofol, and (3) propofol on mast cell degranulation. Epithelial integrity was detected using transepithelial resistance (TER) and permeability to fluorescein isothiocyanate (FITC)-dextran (the apparent permeability coefficient, Papp). The expression of junctional proteins zonula occludens-1 (ZO-1/TJP1) and occludin were determined using western blot analysis and immunofluorescence microscopy. The intracellular levels of reactive oxidative species (ROS) and Ca2+ were measured using flow cytometry. Tryptase directly enhanced intestinal barrier permeability as demonstrated by significant reductions in TER, ZO-1, and occludin protein expression and concomitant increases in Papp. The intestinal barrier integrity was restored by PAR-2 inhibitor but not by propofol. Meanwhile, mast cell degranulation resulted in epithelial integrity disruption in the Caco-2/LAD-2 co-culture model, which was dramatically attenuated by propofol. Mast cell degranulation caused significant increases in intracellular ROS and Ca2+ levels, which were blocked by propofol and NAC. Propofol pretreatment can inhibit mast cell activation via ROS/Ca2+ and restore the intestinal barrier integrity induced by mast cell activation, instead of by tryptase.

Skin/muscle incision and retraction regulates the persistent postoperative pain in rats by the Epac1/PKC-βII pathway

Persistent postoperative pain causes influence the life quality of many patients. The Epac/PKC pathway has been indicated to regulate mechanical hyperalgesia. The present study used skin/muscle incision and retraction (SMIR) to induce postoperative pain in rats and evaluated the Epac/PKC pathway in postoperative pain. Mechanical allodynia was assessed by paw withdrawal threshold before and after incision. The levels of Epac, PKC, proinflammatory cytokines, and blood-nerve barrier-related proteins were assessed using Western blotting. We found that SMIR induced the activation of the Epac/PKC pathway, mechanical allodynia, and upregulation of Glut1, VEGF, and PGP9.5 proteins in dorsal root ganglia. Under the influence of agonists of Epac/PKC, normal rats showed mechanical allodynia and increased Glut1, VEGF, and PGP9.5 proteins. After inhibition of Epac1 in rats with SMIR, mechanical allodynia was alleviated, and proinflammatory cytokines and Glut1, VEGF, and PGP9.5 proteins were decreased. Moreover, dorsal root ganglia neurons showed abnormal proliferation under the activation of the Epac/PKC pathway. Using Captopril to protect vascular endothelial cells after SMIR had a positive effect on postoperative pain. In conclusion, SMIR regulates the persistent postoperative pain in rats by the Epac/PKC pathway.

Unraveling the role of Epac1-SOCS3 signaling in the development of neonatal-CRD-induced visceral hypersensitivity in rats

Aims

Visceral hypersensitivity in irritable bowel syndrome (IBS) is widespread, but effective therapies for it remain elusive. As a canonical anti‐inflammatory protein, suppressor of cytokine signaling 3 (SOCS3) reportedly relays exchange protein 1 directly activated by cAMP (Epac1) signaling and inhibits the intracellular response to inflammatory cytokines. Despite the inhibitory effect of SOCS3 on the pro‐inflammatory response and neuroinflammation in PVN, the systematic investigation of Epac1‐SOCS3 signaling involved in visceral hypersensitivity remains unknown. This study aimed to explore Epac1‐SOCS3 signaling in the activity of hypothalamic paraventricular nucleus (PVN) corticotropin‐releasing factor (CRF) neurons and visceral hypersensitivity in adult rats experiencing neonatal colorectal distension (CRD).

Methods

Rats were subjected to neonatal CRD to simulate visceral hypersensitivity to investigate the effect of Epac1‐SOCS3 signaling on PVN CRF neurons. The expression and activity of Epac1 and SOCS3 in nociceptive hypersensitivity were determined by western blot, RT‐PCR, immunofluorescence, radioimmunoassay, electrophysiology, and pharmacology.

Results

In neonatal‐CRD‐induced visceral hypersensitivity model, Epac1 and SOCS3 expressions were downregulated and IL‐6 levels elevated in PVN. However, infusion of Epac agonist 8‐pCPT in PVN reduced CRF neuronal firing rates, and overexpression of SOCS3 in PVN by AAV‐SOCS3 inhibited the activation of PVN neurons, reduced visceral hypersensitivity, and precluded pain precipitation. Intervention with IL‐6 neutralizing antibody also alleviated the visceral hypersensitivity. In naïve rats, Epac antagonist ESI‐09 in PVN increased CRF neuronal firing. Consistently, genetic knockdown of Epac1 or SOCS3 in PVN potentiated the firing rate of CRF neurons, functionality of HPA axis, and sensitivity of visceral nociception. Moreover, pharmacological intervention with exogenous IL‐6 into PVN simulated the visceral hypersensitivity.

Conclusions

Inactivation of Epac1‐SOCS3 pathway contributed to the neuroinflammation accompanied by the sensitization of CRF neurons in PVN, precipitating visceral hypersensitivity and pain in rats experiencing neonatal CRD.

Propofol total intravenous anaesthesia versus inhalational anaesthesia for acute postoperative pain in patients with morphine patient-controlled analgesia: a large-scale retrospective study with covariate adjustment

Background

To compare the postoperative analgesic effect of propofol total intravenous anaesthesia (TIVA) versus inhalational anaesthesia (GAS) in patients using morphine patient-controlled analgesia (PCA).

Methods

A retrospective cohort study was performed in a single tertiary university hospital. Adult patients who used PCA morphine after general anaesthesia across 15 types of surgeries were included. Patients who received propofol TIVA were compared to those who had inhalational anaesthesia. Primary outcomes assessed were postoperative numerical rating scale (NRS) pain scores and postoperative opioid consumption.

Results

Data from 4202 patients were analysed. The overall adjusted NRS pain scores were significantly lower in patients who received propofol TIVA at rest (GEE: β estimate of the mean on a 0 to 10 scale = -0.56, 95% CI = (-0.74 to -0.38), p < 0.001; GAS as reference group) and with movement (β estimate = -0.89, 95% CI = (-1.1 to -0.69), p < 0.001) from postoperative days (POD) 1–3. Propofol TIVA was associated with lower overall adjusted postoperative morphine consumption (β estimate = -3.45, 95% CI = (-4.46 to -2.44), p < 0.001). Patients with propofol TIVA had lower adjusted NRS pain scores with movement for hepatobiliary/pancreatic (p < 0.001), upper gastrointestinal (p < 0.001) and urological surgeries (p = 0.005); and less adjusted postoperative morphine consumption for hepatobiliary/pancreatic (p < 0.001), upper gastrointestinal (p = 0.006) and urological surgeries (p = 0.002). There were no differences for other types of surgeries.

Conclusion

Propofol TIVA was associated with statistically significant, but small reduction in pain scores and opioid consumption in patients using PCA morphine. Subgroup analysis suggests clinically meaningful analgesia possibly for hepatobiliary/pancreatic and upper gastrointestinal surgeries.

Trial registration

This study is registered at ClinicalTrials.gov (NCT03875872).

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-022-01683-9.

Pharmacologic Modulation of Noxious Stimulus-evoked Brain Activation in Cynomolgus Macaques Observed with Functional Neuroimaging

Maintaining effective analgesia during invasive procedures performed under general anesthesia is important for minimizing postoperative complications and ensuring satisfactory patient wellbeing and recovery. While patients under deep sedation may demonstrate an apparent lack of response to noxious stimulation, areas of the brain related to pain perception may still be activated. Thus, these patients may still experience pain during invasive procedures. The current study used anesthetized or sedated cynomolgus macaques and functional magnetic resonance imaging (fMRI) to assess the activation of the parts of the brain involved in pain perception during the application of peripheral noxious stimuli. Noxious pressure applied to the foot resulted in the bilateral activation of secondary somatosensory cortex (SII) and insular cortex (Ins), which are both involved in pain perception, in macaques under either propofol or pentobarbital sedation. No activation of SII/Ins was observed in macaques treated with either isoflurane or a combination of medetomidine, midazolam, and butorphanol. No movement or other reflexes were observed in response to noxious pressure during stimulation under anesthesia or sedation. The current findings show that despite the lack of visible behavioral symptoms of pain during anesthesia or sedation, brain activation suggests the presence of pain depending on the anesthetic agent used. These data suggest that fMRI could be used to noninvasively assess pain and to confirm the analgesic efficacy of currently used anesthetics. By assessing analgesic efficacy, researchers may refine their experiments, and design protocols that improve analgesia under anesthesia.