Bupivacaine effectively relieves inflammation-induced pain by suppressing activation of the NF-κB signalling pathway and inhibiting the activation of spinal microglia and astrocytes

Effects of Natural Product-Derived Compounds on Inflammatory Pain via Regulation of Microglial Activation

Inflammatory pain is a type of pain caused by tissue damage associated with inflammation and is characterized by hypersensitivity to pain and neuroinflammation in the spinal cord. Neuroinflammation is significantly increased by various neurotransmitters and cytokines that are expressed in activated primary afferent neurons, and it plays a pivotal role in the development of inflammatory pain. The activation of microglia and elevated levels of pro-inflammatory cytokines are the hallmark features of neuroinflammation. During the development of neuroinflammation, various intracellular signaling pathways are activated or inhibited in microglia, leading to the regulation of inflammatory proteins and cytokines. Numerous attempts have been conducted to alleviate inflammatory pain by inhibiting microglial activation. Natural products and their compounds have gained attention as potential candidates for suppressing inflammatory pain due to verified safety through centuries of use. Many studies have also shown that natural product-derived compounds have the potential to suppress microglial activation and alleviate inflammatory pain. Herein, we review the literature on inflammatory mediators and intracellular signaling involved in microglial activation in inflammatory pain, as well as natural product-derived compounds that have been found to suppress microglial activation. This review suggests that natural product-derived compounds have the potential to alleviate inflammatory pain through the suppression of microglial activation.

Intradermal and Intramuscular Bupivacaine Reduces Opioid Use Following Noninstrumented Spine Surgery

OBJECTIVE

To evaluate the efficacy of intraoperative bupivacaine hydrochloride wound infiltration as an adjunct means of pain relief following noninstrumented posterior spine surgery.

METHODS

A retrospective cohort analysis was performed of all patients who underwent posterior spinal decompression surgery at the University of California, San Diego, and at the San Diego VA Medical Center between June 2020 and July 2021, following a change in practice to including bupivacaine infiltration at the end of the surgery. Patients were stratified into groups based on whether they received intrawound bupivacaine during surgery. Demographic and clinical data were extracted from the electronic health record. Postoperative opioid use, visual analog pain scores, heart rate, and blood pressure were compared.

RESULTS

The analysis included 43 patients; 21 received bupivacaine infiltration, and 22 did not. No complications were encountered in the perioperative period. Patients who received bupivacaine consumed significantly less opioids over the 72 hours following surgery, had slightly lower pain scores, and experienced slightly lower heart rates. No significant difference was found between groups with respect to systolic blood pressure, operative time, or length of hospital stay.

CONCLUSIONS

Intraoperative infiltration of the exposed paraspinous musculature and peri-incisional subdermal layer with bupivacaine significantly reduced postoperative opioid consumption for 72 hours after surgery and slightly reduced pain ratings and conferred superior heart rate control. This low-cost intervention produced significant patient benefit with minimal risk and no significant increase in surgical time or hospital stay.

Neuronal toll like receptor 9 contributes to complete Freund’s adjuvant-induced inflammatory pain in mice

Toll like receptor 9 (TLR9) is a critical sensor for danger-associated molecular patterns (DAMPs) and a crucial marker of non-sterile/sterile inflammation among all TLRs. However, the significance of TLR9 in inflammatory pain remains unclear. Here, we subcutaneously injected Complete Freund’s adjuvant (CFA) into the plantar surface of the hind paw, to established a mouse model of inflammatory pain, and we examined expression and distribution of TLR9 in this model. There was a significant increase of TLR9 mRNA and reduction of mechanical paw withdrawal threshold in mice intraplantar injected with CFA. By contrast, mechanical paw withdrawal threshold significantly increased in mice treated with TLR9 antagonist ODN2088. Furthermore, TLR9 is found predominantly distributed in the neurons by immunofluorescence experiment. Accordingly, neuronal TLR9 downregulation in the spinal cord prevented CFA-induced persistent hyperalgesia. Overall, these findings indicate that neuronal TLR9 in the spinal cord is closely related to CFA-induced inflammatory pain. It provides a potential treatment option for CFA-induced inflammatory pain by applying TLR9 antagonist.

Preventive Intrathecal Injection of Bupivacaine Alleviated Microglia Activation and Neuropathic Pain in a Rat Model of Chronic Constriction Injury

Spinal microglia are crucial to neuronal hyper-excitability and pain hypersensitivity. The local anesthetic bupivacaine is commonly used for both peripheral and spinal anesthesia. The pain-relief effects resulting from the peripheral and systemic administration of bupivacaine have been previously reported. In this study, the preventive effects of intrathecal bupivacaine administration against neuropathic pain were revealed in a rat model of sciatic nerve chronic constriction injury (CCI). Using a CCI rat model, pain hypersensitivity, characterized by mechanical allodynia and thermal hyperalgesia, correlated well with microglia M1 polarization, activation and pro-inflammatory cytokine expression in both spinal cord dorsal horns and sciatic nerves. Bupivacaine attenuated pain behaviors and inflammatory alternations. We further identified that the Interferon Regulatory Factor 5 (IRF5)/P2X Purinoceptor 4 (P2X4R) and High Mobility Group Box 1 (HMGB1)/Toll-Like Receptor 4 (TLR4)/NF-κB inflammatory axes may each play pivotal roles in the acquisition of microglia M1 polarization and pro-inflammatory cytokine expression under CCI insult. The relief of pain paralleled with the suppression of microglia M1 polarization, elevation of microglia M2 polarization, and inhibition of IRF5/P2X4R and HMGB1/TLR4/NF-κB in both the spinal cord dorsal horns and sciatic nerve. Our findings provide molecular and biochemical evidence for the anti-neuropathic effect of preventive bupivacaine.

Evaluation of the addition of bupivacaine to intrathecal morphine for intraoperative and postoperative pain management in open liver resections

BACKGROUND

Intrathecal morphine is a popular and effective regional technique for pain control after open liver resection, but its delayed analgesic onset makes it less useful for the intraoperative period. The aim of this retrospective study was to compare the analgesic efficacy and other secondary benefits of the addition of hyperbaric bupivacaine to intrathecal morphine ± fentanyl. We hypothesized that bupivacaine could serve as an analgesic "bridge" prior to the onset of intrathecal morphine/fentanyl thereby lowering opioid consumption and enhancing recovery.

METHODS

Cumulative intraoperative and postoperative opioid consumption as well as other intra- and postoperative variables were collected and compared between groups receiving intrathecal morphine alone or intrathecal morphine ± hyperbaric bupivacaine.

RESULTS

Sixty-eight patients were selected for inclusion. Cumulative intraoperative morphine consumption was significantly reduced in the bupivacaine group while other intraoperative parameters such as intravenous fluids, blood loss, and vasopressors did not differ. There was a statistically significant improvement in time to first bowel movement in the experimental group.

DISCUSSION

The intraoperative opioid sparing effects and improved time to bowel function with the addition of hyperbaric bupivacaine to intrathecal morphine may make this technique an easy and low risk method of enhancing recovery after open liver resection.

Systemic lidocaine administration influences NF-kβ gene expression, NF-kβ and TNF- α protein levels on BALB/c mice with musculoskeletal injury

BACKGROUND

The immune system can produce various inflammatory mediators to protect the body from stress and surgical trauma. However, this excessive inflammatory response will interfere with the body's immune system, causing systemic inflammatory response syndrome and multi-organ failure if allowed to continue. Lidocaine as an anti-inflammatory is used to treat surgical pain and pain arising from the disease process and treat ventricular arrhythmias. This study aims to prove the efficacy of systemic lidocaine injection as an anti-inflammatory drug in BALB/c mice with sterile musculoskeletal injuries.

METHODS

This study used a prospective experimental laboratory study on experimental animals of BALB/c mice using a simple randomized design. Sixteen adult white BALB/c mice (male, healthy, 10-12 weeks old, 35-40 g body weight, and no disability) were selected and randomly divided into two groups: the group given lidocaine (2 mg/kg body weight) and a group that was given sterile distilled water. NF-kβ and TNF-α protein levels were detected by ELISA, while mRNA expression of NF-kβ was analyzed and determined by quantitative real-time PCR.

RESULTS

Musculoskeletal injury significantly increased the expression of both mRNA and protein levels of NF-kβ and TNF-α protein level. In addition, the NF-kβ (protein and mRNA) and TNF-α (protein) levels in rats experiencing inflammation due to musculoskeletal injury were significantly decreased in the lidocaine group (p < 0.001).

CONCLUSIONS

The administration of systemic lidocaine injection was able to inhibit the expression of mRNA NF-kβ, the protein levels of NF-kβ, and protein levels of TNF-α in mice with musculoskeletal injuries.

Impact of Bupivacaine on malignant proliferation, apoptosis and autophagy of human colorectal cancer SW480 cells through regulating NF-κB signaling path

To probe into the impact of Bupivacaine on colorectal cancer (CRC) proliferation, apoptosis, and autophagy through regulating the NF-κB signaling pathway. Our work treated CRC cells with Bupivacaine, detected cell vitality through MTT assay, apoptosis through flow cytometry, cell migration through wound healing assay, NF-κB activity through immunofluorescence, inflammatory factor level, including TNF-α, IL-1β as well as IL-6 through ESLIA, apoptosis factor mRNA expression, including Bcl-2, Bax and caspase-3q through qRT-PCR, and protein expression linking with NF-κB signaling pathway as well as autophagy-related proteins via western blot. In in vivo experiments, we explored the impact of Bupivacaine on tumor volume, tumor and NF-κB expression. The results showed that 1 mM Bupivacaine was available to signally inhibit CRC cell vitality, promoted apoptosis rate and apoptosis gene expression, like Bax, and caspase-3, inhibited Bcl-2 expression, inhibited cancer cell migration, promoted autophagy-related protein LC3B II/LC3B I ratio and beclin-1 expression, and inhibited p62 expression. Additionally, it could elevate inflammatory factor level and induce IKK and IκB phosphorylation as well as NF-κB proteins. In in vivo experiments, Bupivacaine inhibited tumor volume and tumor, as well as NF-κB expression. In short, bupivacaine is available to inhibit CRC proliferation through regulating NF-κB signaling pathway, promote apoptosis and autophagy, and can be used as a potential drug to treat CRC in the future.

Ultrasound-guided transversus abdominis plane block vs trigger point injections for chronic abdominal wall pain: a randomized clinical trial

ABSTRACT

The primary aim of this randomized clinical trial is to investigate the effects of ultrasound-guided transversus abdominis plane (TAP) vs ultrasound-guided trigger point injections (TPIs) on numerical rating scale pain scores at month 3 follow-up in patients with a chronic abdominal wall pain. The primary outcome measure was the difference in mean numeric rating scale pain scores between the TAP and TPI groups at month 3 in an intent-to-treat (ITT) analysis. A total of 60 patients were randomized 1:1 to receive an ultrasound-guided TAP block (n = 30) or an ultrasound-guided TPI (n = 30). No significant group differences in baseline demographic or clinical characteristics were observed. The mean baseline pain score for the TAP and TPI groups was 5.5 and 4.7, respectively. In the ITT analysis at month 3, the between-group difference in pain scores was 1.7 (95% confidence interval, 0.3-3.0) favoring the TPI group. In a secondary per-protocol analysis, the between-group difference in pain scores was 1.8 (95% confidence interval, 0.4-3.2) favoring the TPI group. For the ITT and per-protocol analyses, the group differences in pain scores were consistent with a medium effect size. The main finding of this randomized clinical trial is that adults with chronic abdominal wall pain who received a TPI reported significantly lower pain scores at month 3 follow-up compared with patients who received a TAP block.

Paeonol ameliorates CFA-induced inflammatory pain by inhibiting HMGB1/TLR4/NF-κB p65 pathway

The enhanced release of inflammatory cytokines mediated by high mobility group box1 (HMGB1) leads to pain sensation, and has been implicated in the etiology of inflammatory pain. Paeonol (PAE), a major active phenolic component in Cortex Moutan, provides neuroprotective efficacy via exerting anti-inflammatory effect. However, the role and mechanism of PAE in inflammatory pain remain to be fully clarified. In this study, we showed that PAE treatment significantly ameliorated mechanical and thermal hyperalgesia of mice induced by complete Freund's adjuvant (CFA). The analgesic effect of PAE administration was associated with suppressing the enhanced expression of HMGB1 as well as the downstream signaling molecules including toll-like receptor 4 (TLR4), the nuclear NF-κB p65, TNF-α and IL-1β after CFA insult in the anterior cingulate cortex (ACC), a key brain region responsible for pain processing. Furthermore, inhibition of HMGB1 activity by glycyrrhizin (GLY), an HMGB1 inhibitor, alleviated CFA-induced pain and also facilitated PAE-mediated analgesic effect in mice along with the decreased expression of TLR4, NF-κB p65, TNF-α and IL-1β upon CFA injury. Collectively, we showed PAE exerted analgesic effect through inhibiting the HMGB1/TLR4/NF-κB p65 pathway and subsequent generation of cytokines TNF-α and IL-1β in the ACC.

Low concentration of Bupivacaine ameliorates painful diabetic neuropathy by mediating miR-23a/PDE4B axis in microglia

Bupivacaine (Bup) has a certain research basis in pain-related diseases, but it has not been studied in painful diabetic neuropathy. In this study, we investigated the role of Bupivacaine in painful diabetic neuropathy. Mouse model with painful diabetic neuropathy was established, and then treated with different concentrations of Bupivacaine. The blood glucose level in the tail vein and the changes in body weight was measured. The mechanical allodynia, thermal hyperalgesia and thermal allodynia was assessed by pain behavioral tests. Microglia were treated with high glucose (HG) and different concentrations of Bupivacaine. The levels of inflammatory cytokines were detected by using Enzyme-linked immunosorbent assays. Dual luciferase reporter assay explored the relationship between miR-23a and phosphodiesterase 4 B (PDE4B). The results displayed that Bupivacaine ameliorated the mechanical allodynia, thermal hyperalgesia, and thermal allodynia in mice with painful diabetic neuropathy, and is more effective at low concentration. Moreover, low concentration of Bupivacaine inhibited inflammation and promoted miR-23a expression in mice with painful diabetic neuropathy and in microglia induced by HIGH GLUCOSE. Overexpression of miR-23a reduced the levels of inflammatory cytokines by down-regulating PDE4B expression. Knockdown of miR-23a reversed the inhibition effect of Bupivacaine on microglial inflammation. These results revealed that low concentration of Bupivacaine inhibited microglial inflammation through down-regulating PDE4B via miR-23a, thereby attenuated painful diabetic neuropathy.

Local Retropharyngeal Space Anesthetic for Dysphagia Reduction after Anterior Cervical Discectomy and Fusion Surgery: A Single-Center, Prospective, Randomized, Double-Blinded, Placebo-Controlled Clinical Trial

OBJECTIVE

The main objective of this study was to analyze the ability of local anesthetic instillation into the retropharyngeal space to reduce dysphagia symptoms and occurrence rates in patients undergoing anterior cervical discectomy and fusion (ACDF) procedures.

METHODS

A single-center, prospective, randomized, double-blinded, and placebo-controlled clinical study was performed. We enrolled patients undergoing one- or two-level ACDF procedures for cervical degenerative disc disease with disc herniation, radiculopathy and/or myelopathy symptoms. The patients were randomly assigned (1:1 ratio) to receive either 0.5% bupivacaine hydrochloride or 0.9% NaCl solution.

RESULTS

Forty-three (74%) and 41 (77%) of patients reported dysphagia symptoms at the time of discharge in the investigational and control groups, respectively. There were no statistically significant differences in duration of dysphagia symptoms, Swallowing-Quality of Life (SWAL-QOL) survey or pain scores between the investigational and control patient groups at any of the follow-up time points. Controlling for independent variables, only younger age significantly predicted dysphagia symptoms at discharge, 2-week, and 3-month follow-ups (P ≤ 0.03; R ≥ -0.038; OR 0.96, 95% CI 0.93-0.99. Female sex was associated with lower SWAL-QOL scores at discharge (P = 0.046; R = 0.87; OR 2.38, 95% CI 1.02-5.56). A total of 8 (13.8%) and 6 (11.3%) patients in the investigational and control groups, respectively, were referred to a specialist or underwent speech therapy for their dysphagia symptoms. There were no adverse reactions to the study drug observed.

CONCLUSIONS

Local retropharyngeal space anesthetic instillation did not reduce dysphagia symptoms or occurrence rates in patients undergoing anterior discectomy and fusion surgeries.

A controlled release bupivacaine-alginate construct: Effect on chondrocyte hypertrophy conversion

Objective:

Osteoarthritis is a degenerative disease of the joint, affecting over 30 million people in the US¹. A key characteristic of OA is chondrocyte hypertrophy, characterized by chondrocyte changes to a more rounded and osteoblastic phenotype, characterized by increased IL-6 and IL-8 secretion². While there are no cures for OA, treatments focus on mitigating pain and inflammation, the two main symptoms of OA. However, the analgesics, NSAIDS and corticosteroids commonly used, do not target regeneration and have negative side effects. Local anesthetics (LA) can be used as a pain management alternative but are usually short lasting and therefore, not suited for chronic conditions such as OA. Our engineered sustained release local anesthetic construct successfully delivers bupivacaine for an extended period of time^3–5. This study is designed to evaluate the effect of the LA system on chondrocytes in an inflammatory OA-like environment.

Design:

Chondrocytes were cultured with bolus, liposomal, or construct LA and either untreated or treated with TNF-α and IL-1α for 24 hrs, 48 hrs, or 96 hrs. Chondrocyte viability, interleukin-8 (IL-8), interleukin-6 (IL-6), collagenase activity and proteoglycan deposition were assessed.

Results:

In the presence of the engineered construct, the chondrocytes retained viability and regenerative function. Moreover, the construct allowed for higher initial doses to be used, which promoted more regeneration and decreased inflammation without compromising cellular viability.

Conclusions:

The construct promotes a less hypertrophic chondrocyte environment while promoting a more anti-inflammatory environment. These two factors are consistent with a less OA progressive environment when using the engineered construct, compared to bolus LA.

Effect of intraperitoneal bupivacaine on postoperative pain in laparoscopic bariatric surgeries

BACKGROUND

Postoperative pain has many adverse effects and, if not properly controlled, it may lead to a wide range of complications. Opioids, as frequently used drugs for pain control, have some serious respiratory and gastrointestinal complications, especially in obese patients.

OBJECTIVES

In this study, we planned to evaluate the effect of intraperitoneal bupivacaine lavage on postoperative pain in laparoscopic bariatric surgeries.

SETTING

The study was conducted in Firoozgar Hospital (affiliated to Iran University of Medical Sciences), Tehran, Iran.

METHODS

In this clinical trial, 106 patients scheduled for laparoscopic bariatric surgery, randomly assigned to receive either intraperitoneal lavage with 50 mL of .2% bupivacaine or the same volume of normal saline during the operation. One-gram intravenous paracetamol was infused for all patients at the end of surgery, and all patients received intravenous paracetamol infusion for 1 day after surgery. Pain level, assessed by visual analog scale, was recorded at 1, 4, 8, and 24 hours after surgery. Total additive analgesics administered during the first day after surgery was also recorded.

RESULTS

The pain score during the first 24 hours after surgery decreased significantly in both groups, but comparing the groups showed that pain level at 1, 4, 8, and 24 hours after surgery in the bupivacaine group was significantly lower than the normal saline group (P < .05). Also, opioid consumption during 24 hours was significantly lower in the bupivacaine group (P < .001).

CONCLUSIONS

Intraperitoneal lavage with bupivacaine is an effective approach to control postoperative pain in obese patients undergoing laparoscopic bariatric surgery.

Anti-inflammatory effects induced by ultralow concentrations of bupivacaine in combination with ultralow concentrations of sildenafil (Viagra) and vitamin D3 on inflammatory reactive brain astrocytes

Network coupled cells, such as astrocytes, regulate their cellular homeostasis via Ca²⁺ signals spread between the cells through gap junctions. Intracellular Ca²⁺ release is controlled by different signaling pathways that can be stimulated by ATP, glutamate and serotonin (5-HT). Based on our findings, all these pathways are influenced by inflammatory agents and must be restored to fully recover the Ca²⁺ signaling network. An ultralow concentration of the local anesthetic agent bupivacaine reduced 5-HT-evoked intracellular Ca²⁺ release, and an ultralow concentration of the phosphodiesterase-5 inhibitor sildenafil in combination with vitamin D3 reduced ATP-evoked intracellular Ca²⁺ release. Combinations of these three substances downregulated 5-HT-, glutamate- and ATP-evoked intracellular Ca²⁺ release to a more normal Ca²⁺ signaling state. Furthermore, inflammatory Toll-like receptor 4 expression decreased with a combination of these three substances. Substance P receptor neurokinin (NK)-1 expression was reduced by ultralow concentrations of bupivacaine. Here, bupivacaine and sildenafil (at extremely low concentrations) combined with vitamin D3 have potential anti-inflammatory properties. According to the present study, drug combinations at the right concentrations, especially extremely low concentrations of bupivacaine and sildenafil, affect different cellular biochemical mechanisms and represent a potential solution for downregulating inflammatory parameters, thereby restoring cells or networks to normal physiological homeostasis.

Loss of Microglia and Impaired Brain-Neurotrophic Factor Signaling Pathway in a Comorbid Model of Chronic Pain and Depression

Major depressive disorder (MDD) and chronic pain are two complex disorders that often coexist. The underlying basis for this comorbidity is unknown. In the current investigation, microglia and the brain-derived neurotrophic factor (BDNF)-cAMP response element-binding protein (CREB) pathway were investigated. A comorbidity model, with characteristics of both MDD and chronic pain, was developed by the administration of dextran sodium sulfate (DSS) and the induction of chronic unpredictable psychological stress (CUS). Mechanical threshold sensory testing and the visceromotor response (VMR) were employed to measure mechanical allodynia and visceral hypersensitivity, respectively. RT-qPCR and western blotting were used to assess mRNA and protein levels of ionized calcium-binding adaptor molecule 1 (Iba-1), nuclear factor-kappa B (NF-κB), nuclear factor of kappa light polypeptide gene enhancer in B-cells inhibitor, alpha (IκBa), BDNF, and CREB. In comorbid animals, mechanical allodynia and visceral hypersensitivities were significant with increased mRNA and protein levels for NF-κB-p65 and IκBa. Furthermore, the comorbid animals had deceased mRNA and protein levels for Iba-1, BDNF, and CREB as well as a reduced number and density of microglia in the medial prefrontal cortex (mPFC). These results together suggest that DSS and CUS can induce the comorbidities of chronic pain and depression-like behavior. The pathology of this comorbidity involves loss of microglia within the mPFC with subsequent activation of NF-κB-p65 and down-regulation of BDNF/p-CREB signaling.