Bupivacaine increases the rate of motoneuron death following peripheral nerve injury

Long-term sensorimotor changes after a sciatic nerve block with bupivacaine and liposomal bupivacaine in a high-fat diet/low-dose streptozotocin rodent model of diabetes

Introduction

It is unclear whether patients with diabetes are more susceptible to nerve toxicity of local anesthetics or whether nerve blocks can accelerate the progression of diabetic peripheral neuropathy. Bupivacaine is one of the most widely used local anesthetics for regional anesthesia despite many pre-clinical studies demonstrating neurotoxicity. Herein, we report the long-term functional consequences of sciatic nerve block with bupivacaine and liposomal bupivacaine (Exparel®) in an animal model of diabetes.

Methods

Male Sprague Dawley rats were subject to standard chow/vehicle or high-fat diet/low-dose streptozotocin to induce a diabetic phenotype. Animals were then subdivided into groups that received repeated sciatic nerve blocks of saline, bupivacaine, or liposomal bupivacaine. Mechanical allodynia and thermal hyperalgesia were assessed prior to and 12 weeks following nerve blocks utilizing the von Frey and Hargreaves tests, respectively. Exploratory and locomotor activity were assessed with open field testing, and nerve conduction velocity testing was conducted prior to the termination of the study at 28 weeks.

Results

Animals in the diabetic group developed sustained hyperglycemia >200 mg/dl and signs of peripheral neuropathy six weeks after treatment with streptozotocin, which persisted until the end of the study. Twelve weeks after a repeated sciatic nerve block with saline, bupivacaine, or liposomal bupivacaine, results indicate significant interaction effects of the disease group (control vs. diabetic) and local anesthetic treatment. Overall, diabetic status resulted in worse sensorimotor function compared to control animals. Treatment with perineural bupivacaine resulted in worse sensorimotor functions in both control and diabetic animals. Furthermore, bupivacaine treatment in diabetic animals with pre-existing neuropathy exacerbated sensorimotor function in some measures. In contrast, liposomal bupivacaine did not appear to cause any negative effects on functional outcomes for control or diabetic animals.

Conclusion

Our data indicate that bupivacaine, and not liposomal bupivacaine, causes long-term changes in tactile allodynia, thermal hyperalgesia, locomotor behaviors, and nerve conduction velocity in control as well as a high-fat diet/low-dose streptozotocin rodent model of diabetes. These results highlight the necessity to investigate safe peripheral nerve block strategies to preserve long-term functional independence in patients with or at risk for diabetic peripheral neuropathy.

P53 and taurine upregulated gene 1 promotes the repair of the DeoxyriboNucleic Acid damage induced by bupivacaine in murine primary sensory neurons

The research aimed to explore the biological role of p53 protein and long non-coding RNA (lncRNA) taurine upregulated gene 1 (TUG1) in bupivacaine (bup)-induced neurotoxicity. Our work treated dorsal root ganglion (DRG) cells with bup, detected cell viability through CCK-8, apoptosis through TUNEL assays, DeoxyriboNucleic Acid (DNA) damage through γ-H2AX protein and comet assay, including p53 mRNA, protein and TUG1 expression through q-PCR and western blot, furthermore, cell viability and DNA damage were determined after the silencing of p53 and TUG1, biological information and TUG1 FISH combined with p53 protein immunofluorescence (IF) was performed to determine the cellular localization of these molecule. In vivo experiments, we explored the impact of intrathecal injection of bup on p53 mRNA and protein, TUG1, γ-H2AX protein expression. The results showed that bup was available to signally decreased cell viability, promoted apoptosis rate and DNA damage, additionally, bup increased p53 mRNA and protein and TUG1 expression. P53 siRNA and TUG1 siRNA significantly increased DNA damage. Furthermore, bioinformatics analysis and colocalization experiments revealed that the p53 protein is a transcription factor of TUG1, in vivo experiment, intrathecal injection of bup increased the p53 mRNA, p53 protein, TUG1 and γ-H2AX protein in the murine DRG. In this study, it was found p53 and TUG1 promote the repair of the DNA damage induced by bup in murine dorsal root ganglion cells, suggesting a new strategy for the amelioration of bup-induced neurotoxicity.

Distinct neurotoxic effects of select local anesthetics on facial nerve injury and recovery

BACKGROUND

Local anesthetic toxicity has been well-documented to cause neuronal injury, death, and dysfunction, particularly in a susceptible nerve.

OBJECTIVE

To determine whether select local anesthetics affect neuron survival and/or functional recovery of an injured nerve.

METHODS

This report describes 6 separate experiments that test immediate or delayed application of local anesthetics in 3 nerve injury models. Adult C57/black6 male mice underwent a facial nerve sham, transection, or crush injury. Local anesthetic or saline was applied to the facial nerve at the time of injury (immediate) or 1 day after injury (delayed). Average percent facial motoneuron (FMN) survival was evaluated four-weeks after injury. Facial nerve regeneration was estimated by observing functional recovery of eye blink reflex and vibrissae movement after facial nerve crush injury.

RESULTS

FMN survival after: transection + immediate treatment with ropivacaine (54.8%), bupivacaine (63.2%), or tetracaine (66.9%) was lower than saline (85.5%) and liposomal bupivacaine (85.0%); crush + immediate treatment with bupivacaine (92.8%) was lower than saline (100.7%) and liposomal bupivacaine (99.3%); sham + delayed treatment with bupivacaine (89.9%) was lower than saline (96.6%) and lidocaine (99.5%); transection + delayed treatment with bupivacaine (67.3%) was lower than saline (78.4%) and liposomal bupivacaine (77.6%); crush + delayed treatment with bupivacaine (85.3%) was lower than saline (97.9%) and lidocaine (96.0%). The average post-operative time for mice to fully recover after: crush + immediate treatment with bupivacaine (12.83 days) was longer than saline (11.08 days) and lidocaine (10.92 days); crush + delayed treatment with bupivacaine (16.79 days) was longer than saline (12.73 days) and lidocaine (11.14 days).

CONCLUSIONS

Our data demonstrate that some local anesthetics, but not all, exacerbate motoneuron death and delay functional recovery after a peripheral nerve injury. These and future results may lead to clinical strategies that decrease the risk of neural deficit following peripheral nerve blocks with local anesthetics.

Dexmedetomidine suppresses bupivacaine-induced parthanatos in human SH-SY5Y cells via the miR-7-5p/PARP1 axis-mediated ROS

This study aims to explore the regulatory mechanisms of dexmedetomidine in parthanatos. MTT assay was applied to reveal cell viability; JC-1 staining assay was utilized to reveal mitochondrial membrane potential. Reactive oxygen species (ROS) probe, DCFH-DA, was used to detect intracellular ROS production. Luciferase activity assay was applied to measure the binding between miR-7-5p and PARP1. We first identified that bupivacaine inhibited the viability and induced the parthanatos of human neuroblastoma SH-SY5Y cells. In addition, dexmedetomidine, a potent α2-adrenoceptor agonist, reversed the regulatory effect of bupivacaine on parthanatos of SH-SY5Y. More importantly, dexmedetomidine counteracted bupivacaine-induced changes of mitochondrial membrane potential and ROS production in SH-SY5Y cells. Hyper-activation of PARP1 plays a vital role in parthanatos. Further exploration of our study identified that bupivacaine triggered overexpression of PARP1 in SH-SY5Y cells. Bioinformatics analysis revealed that miR-7-5p targeted the 3' untranslated region (3' UTR) of PARP1 to inhibit PARP1 expression. In addition, dexmedetomidine recovered the suppressive effects of bupivacaine on miR-7-5p expression. Dexmedetomidine suppressed bupivacaine-induced parthanatos in SH-SY5Y cells via the miR-7-5p/PARP1 axis, which may shed a new insight into parthanatos-dependent neuronal injury.

Paeoniflorin attenuated bupivacaine-induced neurotoxicity in SH-SY5Y cells via suppression of the p38 MAPK pathway

Bupivacain, a common local anesthetic, can cause neurotoxicity and permanent neurological disorders. Paeoniflorin has been widely reported as a potential neuroprotective agent in neural injury models. However, the roles and molecular basis of paeoniflorin in bupivacaine-induced neurotoxicity are still undefined. In the current study, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay was performed to detect cell viability. Apoptotic rate was measured through double-staining of Annexin V-FITC and propidium iodide on a flow cytometer. Western blot assay was carried out to examine the protein levels of p38 mitogen-activated protein kinase (p38 MAPK), phosphorylated-p38 MAPK (p-p38 MAPK), Bcl-2, and Bax. caspase-3 activity was determined using a caspase-3 activity assay kit. We found that paeoniflorin dose-dependently attenuated bupivacaine-induced viability inhibition and apoptosis in SH-SY5Y cells. Moreover, paeoniflorin inhibited bupivacaine-induced activation of p38 MAPK pathway in SH-SY5Y cells. Paeoniflorin alone showed no significant effect on cell viability, apoptosis and p38 MAPK signaling in SH-SY5Y cells. Inhibition of p38 MAPK signaling by SB203580 or small interfering RNA targeting p38 (si-p38) abated bupivacaine-induced viability inhibition and apoptosis in SH-SY5Y cells. In conclusion, paeoniflorin alleviated bupivacaine-induced neurotoxicity in SH-SY5Y cells via suppression of the p38 MAPK pathway, highlighting the potential values of paeoniflorin in relieving bupivacaine-induced neurotoxicity.