Neurotoxicity Comparison of Two Types of Local Anaesthetics: Amide-Bupivacaine versus Ester-Procaine

Highly Efficient Loading of Procaine on Water-Soluble Carbon Dots toward Long-Acting Anesthesia

Safe and efficient local anesthetic delivery carriers are crucial for long-term anesthesia and analgesics in clinical treatment. But currently, most of the local anesthetic carriers still have some disadvantages such as low drug-loading capacity, drug leakage, and potential side effects. Here, we report red-emissive carbon dots (Cys-CDs) synthesized by choosing cysteine and citric acid as precursors, which contain a large and intact sp2-domain with rich hydrophilic groups around the edge. The special structure of Cys-CDs is conducive to the efficient loading of procaine (PrC) via strong π-π stacking interactions. Based on the strong noncovalent interactions between them, the PrC loaded on Cys-CDs achieved slow release in vitro and had a long-lasting nerve blocking effect in vivo, which is 4-fold more than that of free PrC. More importantly, PrC/Cys-CDs do not cause any toxicity and inflammation during treatment owing to slow release of PrC and good water solubility of Cys-CDs, thus demonstrating the potential clinical application of CDs in long-lasting analgesia.

Effect of Procaine Penicillin G and Flunixin Meglumine on Serum Amyloid A Response in Healthy Adult Horses

This study was designed to determine the effect of PPG and/or flunixin meglumine on SAA response when used at clinical dosing regimens in healthy adult horses. Six healthy adult horses were enrolled in a crossover study design including one control and three treatment groups: no treatment (control); PPG alone (intramuscularly q12h for 72h); flunixin meglumine alone (intravenously q24h for 72h); and PPG (intramuscularly q12h for 72h) and flunixin meglumine (intravenously q24h for 72h). Whole blood was collected at 0, 24, 48, 72, 96 and 120 hours post-initial drug administration to measure SAA using a commercial lateral-flow immunoassay. The washout period was 30 days. Individual SAA values were within the reference range (≤ 20 µg/mL) for almost all horses in the control group. One control horse displayed a SAA value of 28 µg/mL at 72 hours. All horses from the PPG group showed normal SAA values throughout the study. Apart from one horse (SAA of 24 µg/mL at 96 hours) from the flunixin meglumine group, all horses showed normal SAA values. For the PPG and flunixin meglumine group, 5 horses had SAA values within reference range. One horse displayed increased SAA values (32-45 µg/mL) between 48 to 96 hours post-drug administration. There was no difference in area under the SAA time curve amongst control and treatment groups (P > 0.05). The administration of intramuscular PPG and/or intravenous flunixin meglumine does not trigger an inflammatory response that induces a SAA value above reference range in most adult healthy horses.

Tetracaine hydrochloride induces macrophage pyroptosis through caspase‑1/11‑GSDMD signaling pathways

Tetracaine hydrochloride (TTC) is a long-lasting local anesthetic commonly used for topical anesthesia. Inappropriate dosage or allergic reactions to TTC can lead to local anesthetic toxicity. TTC exerts cytotoxic effects on certain cell types by inducing apoptosis and necrosis; however, the effects of TTC on macrophages are currently unclear. In the present study, the RAW 264.7 and BV2 cell lines, and murine peritoneal macrophages, were used to evaluate the cytotoxicity of TTC. The present study demonstrated that TTC caused a decrease in cell viability according to a Cell Counting Kit-8 assay, increased lactate dehydrogenase and IL-1β secretion according to ELISA, and induced morphological changes characteristic of pyroptosis according to western blotting. Moreover, TTC-induced macrophage pyroptosis was mediated by gasdermin (GSDM)D, and the cleavage of GSDMD was modulated by both caspase-1 and caspase-11. These results were experimentally validated using caspase-1 and caspase-11 inhibitors. Furthermore, it was observed that TTC and lipopolysaccharide (LPS) exerted similar effects on macrophages. However, the mechanism of induction of pyroptosis by TTC was different from that of LPS. The present study demonstrated that TTC alone could induce macrophage pyroptosis mediated by canonical and non-canonical inflammatory caspases. Therapies targeting pyroptosis may potentially provide a promising future strategy for the prevention and treatment of local anesthetic toxicity induced by TTC.

Dexamethasone Does not Compensate for Local Anesthetic Cytotoxic Effects on Tenocytes: Morphine or Morphine Plus Dexamethasone May Be a Safe Alternative

Purpose

The purposes of this in vitro study were to investigate whether the addition of dexamethasone can compensate for any cytotoxic effects of the amide-type local anesthetics (LA) bupivacaine and ropivacaine and whether morphine and morphine-6-glucuronide (M6G) may be a safe alternative for peritendinous application.

Methods

Biopsies of human biceps tendons (n = 6) were dissected and cultivated. Cells were characterized by the expression for tenocyte markers, collagen I, biglycan, tenascin C, scleraxis, and RUNX via reverse transcriptase-polymerase chain reaction and immunohistochemistry. Tenocytes were incubated with bupivacaine, ropivacaine, morphine, M6G, or a saline control with and without addition of dexamethasone for 15, 60, or 240 min. Cell viability was determined by quantifying the presence of adenosine-triphosphate.

Results

Significant time-dependent cytotoxic effects were observed for LA after all exposure times. After 15, 60, and 240 minutes, cell viability decreased to 81.1%, 49.4% and 0% (P < .001) for bupivacaine and to 81.4%, 69.6%, and 9.3% (P < .001) for ropivacaine compared to saline control. Dexamethasone did not compensate for these cytotoxic effects. Cell viability was not affected after 15, 60-min exposures to morphine and M6G but decreased significantly (P < .001) after 240 minutes compared to saline control. However, in combination with dexamethasone, tenocyte viability was significantly increased at all times for morphine (P < .01) and at 15 and 60 minutes for M6G (P < .01).

Conclusions

The results showed that amide-type LA have a time-dependent cytotoxic effect on human tenocytes in vitro, which could not be compensated for by dexamethasone, whereas morphine and M6G had no cytotoxic effects on tenocytes after 15 and 60 minutes. The addition of dexamethasone to morphine and M6G had a positive effect on viability, which increased significantly compared to the opioids.

Clinical Relevance

It is known that amide-type local anesthetics used for local joint analgesia have chondrotoxic side-effects. The combined application of morphine and dexamethasone may be a safe alternative.

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.

Bupivacaine Induces ROS-Dependent Autophagic Damage in DRG Neurons via TUG1/mTOR in a High-Glucose Environment

Bupivacaine (BP) is a commonly clinically used local anesthetic (LA). Current studies suggest that neurological complications are increased in diabetic patients after LA application, but the molecular mechanism is poorly understood. LA-induced autophagy and neuronal injury have been reported. We hypothesized that a high-glucose environment aggravates BP-induced autophagic damage. Mouse dorsal root ganglion (DRG) neurons were treated with BP in a high-glucose environment, and the results showed that reactive oxygen species (ROS) levels increased, autophagy was activated, autophagy flux was blocked, and cell viability decreased. Pretreatment with the ROS scavenger N-acetyl-cysteine (NAC) attenuated ROS-mediated autophagy regulation. Moreover, the expression of the long noncoding RNA (lncRNA) taurine upregulated gene 1 (TUG1) increased, and NAC and TUG1 siRNA inhibited the expression of TUG1/mammalian target of rapamycin (mTOR) in DRGs treated with BP in a high-glucose environment. Intriguingly, contrary to previous reports on a positive effect on neurons, we found that rapamycin, an autophagy activator, and chloroquine, an autophagy and lysosome inhibitor, both exacerbated autophagic damage. These data suggest that a high-glucose environment exacerbated BP induced ROS-dependent autophagic damage in DRG neurons through the TUG1/mTOR signaling pathway, which provides a theoretical basis and target for the clinical prevention and treatment of BP neurotoxicity in diabeties.

The DNA Repair Enzyme XPD Is Partially Regulated by PI3K/AKT Signaling in the Context of Bupivacaine-Mediated Neuronal DNA Damage

Bupivacaine, a local anesthetic widely used for regional anesthesia and pain management, has been reported to induce neuronal injury, especially DNA damage. Neurons employ different pathways to repair DNA damage. However, the mechanism underlying bupivacaine-mediated DNA damage repair is unclear. A rat neuronal injury model was established by intrathecal injection of (3%) bupivacaine. An in vitro neuronal injury model was generated by exposing SH-SY5Y cells to bupivacaine (1.5 mmol/L). Then, a cDNA plate array was used to identify the DNA repair genes after bupivacaine exposure. The results showed that xeroderma pigmentosum complementary group D (XPD) of the nuclear excision repair (NER) pathway was closely associated with the repair of DNA damage induced by bupivacaine. Subsequently, Western blot assay and immunohistochemistry indicated that the expression of the repair enzyme XPD was upregulated after DNA damage. Downregulation of XPD expression by a lentivirus aggravated the DNA damage induced by bupivacaine. In addition, phosphatidyl-3-kinase (PI3K)/AKT signaling in neurons was inhibited after exposure to bupivacaine. After PI3K/AKT signaling was inhibited, bupivacaine-mediated DNA damage was further aggravated, and the expression of XPD was further upregulated. However, knockdown of XPD aggravated bupivacaine-mediated neuronal injury but did not affect PI3K/AKT signaling. In conclusion, the repair enzyme XPD, which was partially regulated by PI3K/AKT signaling, responded to bupivacaine-mediated neuronal DNA damage. These results can be used as a reference for the treatment of bupivacaine-induced neurotoxicity.

MiRNA-494-3p Regulates Bupivacaine-Induced Neurotoxicity by the CDK6-PI3K/AKT Signaling

Bupivacaine (BUP) is a long-acting amide local anesthetic that may induce strong neurotoxicity and neurological complications. In this study, we elucidate the influence of microRNA-494-3p (miR-494-3p) in BUP-induced neurotoxicity in primary mouse hippocampal neuronal cells. In this study, primary hippocampal neurons were isolated from neonatal C57BL/6 mice. The isolated neurons were treated with various doses of BUP. MTT assay was conducted to analyze neuronal viability. Gene expression measurement was done by RT-qPCR. The impact of miR-494-3p in BUP-mediated neural injury was examined using TUNEL, flow cytometry, western blotting, and ROS activity detection. The regulatory relationship between miR-494-3p and cyclin-dependent kinases 4 and 6 (CDK6) was identified using a luciferase reporter assay. BUP treatment led to neurotoxicity and miR-494-3p upregulation in primary cultured hippocampal neurons. Functionally, miR-494-3p depletion alleviated neuronal apoptosis and oxidative damage induced by BUP. We verified that miR-494-3p targeted and negatively modulated CDK6. MiR-494-3p depletion also activated PI3K/AKT signaling by elevating CDK6 expression in BUP-treated neurons. Furthermore, CDK6 knockdown or PI3K/AKT inactivation attenuated the neuroprotective role of miR-494-3p depletion. Silencing miR-494-3p exerts neuroprotective function in hippocampal neuronal cells against BUP-induced injury by the CDK6-PI3K/AKT pathway.

Effects of prolonged peri-neural bupivacaine infusion in rat sciatic nerves (axon and myelin)

BACKGROUND/OBJECTIVE

Peripheral-nerve blocks (PNBs) using continuous-infusion of local anesthetics are used to provide perioperative analgesia. Yet little research exists to characterize the histopathological effects of continuous long-duration PNBs. Herein we test the hypothesis that continuous peri-neural bupivacaine infusion (3-day vs. 7-day infusion) contributes to histologic injury in a duration-dependent manner using an in vivo model of rat sciatic nerves.

METHODS

We placed indwelling catheters in 22 rats for infusion with low-dose (0.5mg/kg/hr) bupivacaine or normal saline proximal to the right sciatic nerves for 3 or 7 consecutive days. Hind-limb analgesia was measured using Von-Frey nociceptive testing. At infusion end, rats were sacrificed, bilateral nerves were sectioned and stained with hematoxylin and eosin and CD68 for evaluation of inflammatory response, and eriochrome to assess damage to myelin.

RESULTS

Animals receiving continuous infusion of bupivacaine maintained analgesia as demonstrated by significant decrease (50% on average) in nociceptive response in bupivacaine-infused limbs across time points. Both 7-day saline and bupivacaine-infused sciatic nerves showed significantly-increased inflammation by H&E staining compared to untreated native nerve controls (P = 0.0001, P < 0.0001). Extent of inflammation did not vary significantly based on infusate (7-day saline vs. 7-day bupivacaine P > 0.99) or duration (3-day bupivacaine vs 7-day bupivacaine P > 0.99). No significant change in sciatic nerve myelin was found in bupivacaine-infused animals compared to saline-infused controls, regardless of duration.

CONCLUSIONS

Long-duration (7-day) bupivacaine infusion provided durable post-operative analgesia, yet contributed to equivalent neural inflammation as short duration (3-day) infusion of bupivacaine or saline with no evidence of demyelination.

Procaine-The Controversial Geroprotector Candidate: New Insights Regarding Its Molecular and Cellular Effects

Since its discovery in 1905 and its employment in everyday medical practice as a local anesthetic, to its highly controversial endorsement as an "anti-aging" molecule in the sixties and seventies, procaine is part of the history of medicine and gerontoprophylaxis. Procaine can be considered a "veteran" drug due to its long-time use in clinical practice, but is also a molecule which continues to incite interest, revealing new biological and pharmacological effects within novel experimental approaches. Therefore, this review is aimed at exploring and systematizing recent data on the biochemical, cellular, and molecular mechanisms involved in the antioxidant and potential geroprotective effects of procaine, focusing on the following aspects: (1) the research state-of-the-art, through an objective examination of scientific literature within the last 30 years, describing the positive, as well as the negative reports; (2) the experimental data supporting the beneficial effects of procaine in preventing or alleviating age-related pathology; and (3) the multifactorial pathways procaine impacts oxidative stress, inflammation, atherogenesis, cerebral age-related pathology, DNA damage, and methylation. According to reviewed data, procaine displayed antioxidant and cytoprotective actions in experimental models of myocardial ischemia/reperfusion injury, lipoprotein oxidation, endothelial-dependent vasorelaxation, inflammation, sepsis, intoxication, ionizing irradiation, cancer, and neurodegeneration. This analysis painted a complex pharmacological profile of procaine: a molecule that has not yet fully expressed its therapeutic potential in the treatment and prevention of aging-associated diseases. The numerous recent reports found demonstrate the rising interest in researching the multiple actions of procaine regulating key processes involved in cellular senescence. Its beneficial effects on cell/tissue functions and metabolism could designate procaine as a valuable candidate for the well-established Geroprotectors database.

Exaggerated activities of TRPM7 underlie bupivacaine-induced neurotoxicity in the SH-SY5Y cells preconditioned with high glucose

Hyperglycemia is considered a risk factor for the enhancement of local anesthetic-induced neurotoxicity. Transient receptor potential melastatin 7 (TRPM7), a kinase-coupled cation channel, has been implicated in a variety of neuropathological processes, including intracellular calcium disturbance and high glucose-induced neuropathy. In this study, we investigated whether TRPM7-related pathophysiology is involved in bupivacaine-induced neurotoxicity in SH-SY5Y cells and how hyperglycemia acts as a risk factor. For initial neurotoxicity evaluation, it was confirmed that cell damage and apoptosis induced by acute exposure to bupivacaine were dependent on its concentration and glucose preconditioning. High glucose preconditioning facilitated the bupivacaine-induced fast and temporary rise in intracellular free calcium concentration ([Ca²⁺ ]_i ), which was attributed to both calcium influx through TRPM7 and calcium store release. Additionally, bupivacaine was shown to increase TRPM7-like currents, particularly in cells preconditioned with high glucose. Bupivacaine-induced neurotoxicity in hyperglycemia was correlated with extracellular signal-regulated kinase (ERK), but not protein kinase B (AKT) activation. Inhibition of TRPM7 and ERK activity alleviates bupivacaine neurotoxicity. These results suggest that therapeutically targeting TRPM7-related pathophysiological changes could be a potential strategy for treating local anesthetic-induced neurotoxicity exacerbated by hyperglycemia.

The roles of PARP-1 and XPD and their potential interplay in repairing bupivacaine-induced neuron oxidative DNA damage

Bupivacaine has been widely used in clinical Anesthesia, but its neurotoxicity has been frequently reported, implicating cellular oxidative DNA damage as the major underlying mechanism. However, the mechanism underlying bupivacaine-induced oxidative DNA damage is unknown. We, thus, exposed SH-SY5Y cells to 1.5mM bupivacaine to induce neurotoxicity. Then, iTRAQ proteomic analysis was used to explore the repair of neuronal oxidative DNA damage. By analyzing the STRING version 11.0 database, the bioinformatics relationship between key repair enzymes was tracked. Subsequently, immunofluorescence co-localization and immunoprecipitation were used to investigate the interaction between key repair enzymes. The iTRAQ showed that Poly [ADP-ribose] polymerase 1 (PARP-1) from the base excision repair pathway participated closely in the repair of oxidative DNA damage induced by bupivacaine, and inhibition of PARP-1 expression significantly aggravated bupivacaine-induced DNA damage and apoptosis. Interestingly, this study showed that there were interactions and co-expression between PARP-1 and XPD (xeroderma pigmentosum D), another key protein of the nucleic acid excision repair pathway. After inhibiting XPD, PARP-1 expression was significantly reduced. However, simultaneous inhibition of both XPD and PARP-1 did not further increase DNA damage. It is concluded that PARP-1 may repair bupivacaine-induced oxidative DNA damage through XPD-mediated interactions.

Maternal sciatic nerve administered bupivacaine induces hippocampal cell apoptosis in offspring

BACKGROUND

Bupivacaine, an amid-type local anesthetic, is widely used for clinical patients especially in pregnant women. In addition to neurotoxicity effect of bupivacaine, it can cross the placenta, accumulates in this tissue and retained in fetal tissues. Nevertheless, whether bupivacaine can cause neurotoxicity in fetus remains unclear. Hence, this study was design to investigate the effects of maternal bupivacaine use on fetus hippocampal cell apoptosis and the possible related mechanism.

METHODS

On day 15 of pregnancy, sciatic nerve of pregnant wistar rat (180-200 g) were exposed by lateral incision of the right thigh and 0.2 ml of bupivacaine was injected. After their delivery, we randomly selected one male offspring of every mother. On day 30 after of their birth, the rat's hippocampi were isolated for molecular studies. Western blotting was used to examine the expression of cleaved caspase-3, caspase-8 and p-Akt in fetal hippocampus.

RESULTS

Our results showed that maternal bupivacaine use caused a significant increment of cleaved caspase-3 and caspase-8 expression in fetal hippocampus compared with the sham group. In addition, maternally administered bupivacaine could significantly decrease hippocampal P.Akt/T.Akt ratio which was concurrent with an increment of cleaved caspase-3 and caspase-8 expression.

CONCLUSION

Our data suggest that maternal bupivacaine use increases fetal hippocampal cell apoptosis markers such as caspase 8 and cleaved caspase 3, at least in part, via inhibiting the Akt activation.

Effects of Dexamethasone on Bupivacaine-Induced Peripheral Nerve Injection Injury in the Rat Sciatic Model

INTRODUCTION

The aim of this study was to investigate the effect of perineural dexamethasone against intraneural bupivacaine.

MATERIAL AND METHODS

Rats were divided into 9 groups with 6 animals in each group; Group 1 (Intraneural saline 600 µL-2ndday), Group 2 (Intraneural saline 600 µL-7th day), Group 3 (Intraneural saline 600 µL + perineural dexamethasone 0.5 mg/kg-2nd day), Group 4 (Intraneural saline 600 µL + perineural dexamethasone 0.5 mg/kg-7th day), Group 5 (Intraneural bupivacaine 10 mg/kg-2nd day), Group 6 (Intranueral bupivacaine 10 mg/kg-7th day), Group 7 (Intraneural bupivacaine 10 mg/kg + perineurald exam ethasone 0.5 mg/kg-2nd day), Group 8 (Intraneural bupivacaine 10 mg/kg + perineural dexamethasone 0.5 mg/kg-7th day), Group 9 (Control group). At the end of the application period, histopathological and immunohistochemical examinations were analyzed.

RESULTS AND CONCLUSION

It was observed that caspase 3 levels significantly increased in the 5th and 6th groups compared to the 1st and 2nd groups (p < 0.01). However, in the 7th and 8th groups, these levels were similar with 1st and 2nd groups. While a significant decrease in S 100 levels was detected in group 6 (p < 0.05), a significant increase occurred in Group 8 and reached the same levels as Group 2. According to histopathological evaluation, edema, vacuolization and myelin degeneration were significantly increased in groups 5 and 6 (p < 0.05). However, in the 8th group, the mentioned data showed a significant decrease and reached the same levels as group 2. As a result, perineural dexamethasone was found to have protective effects against intraneural bupivacaine induced sciatic nerve damage.

Role of MicroRNAs in Anesthesia-Induced Neurotoxicity in Animal Models and Neuronal Cultures: a Systematic Review

Exposure to anesthetic agents in early childhood or late intrauterine life might be associated with neurotoxicity and long-term neurocognitive decline in adulthood. This could be attributed to induction of neuroapoptosis and inhibition of neurogenesis by several mechanisms, with a pivotal role of microRNAs in this milieu. MicroRNAs are critical regulators of gene expression that are differentially expressed in response to internal and external environmental stimuli, including general anesthetics. Through this systematic review, we aimed at summarizing the current knowledge apropos of the roles and implications of deregulated microRNAs pertaining to anesthesia-induced neurotoxicity in animal models and derived neuronal cultures. OVID/Medline and PubMed databases were lastly searched on April 1st, 2019, using the Medical Subject Heading (MeSH) or Title/Abstract words ("microRNA" and "anesthesia"), to identify all published research studies on microRNAs and anesthesia. During the review process, data abstraction and methodological assessment was done by independent groups of reviewers. In total, 29 studies were recognized to be eligible and were thus involved in this systematic review. Anesthetic agents studied included sevoflurane, isoflurane, propofol, bupivacaine, and ketamine. More than 40 microRNAs were identified to have regulatory roles in anesthesia-induced neurotoxicity. This field of study still comprises several gaps that should be filled by conducting basic, clinical, and translational research in the future to decipher the exact role of microRNAs and their functions in the context of anesthesia-induced neurotoxicity.

Does Rebound Pain after Peripheral Nerve Block for Orthopedic Surgery Impact Postoperative Analgesia and Opioid Consumption? A Narrative Review

Regional anesthesia has been considered a great tool for maximizing post-operative pain control while minimizing opioid consumption. Post-operative rebound pain, characterized by hyperalgesia after the peripheral nerve block, can however diminish or negate the overall benefit of this modality due to a counter-productive increase in opioid consumption once the block wears off. We reviewed published literature describing pathophysiology and occurrence of rebound pain after peripheral nerve blocks in patients undergoing orthopedic procedures. A search of relevant keywords was performed using PubMed, EMBASE, and Web of Science. Twenty-eight articles (n = 28) were included in our review. Perioperative considerations for peripheral nerve blocks and other alternatives used for postoperative pain management in patients undergoing orthopedic surgeries were discussed. Multimodal strategies including preemptive analgesia before the block wears off, intra-articular or intravenous anti-inflammatory medications, and use of adjuvants in nerve block solutions may reduce the burden of rebound pain. Additionally, patient education regarding the possibility of rebound pain is paramount to ensure appropriate use of prescribed pre-emptive analgesics and establish appropriate expectations of minimized opioid requirements. Understanding the impact of rebound pain and strategies to prevent it is integral to effective utilization of regional anesthesia to reduce negative consequences associated with long-term opioid consumption.

Anesthetics: from modes of action to unconsciousness and neurotoxicity

Modern anesthetic compounds and advanced monitoring tools have revolutionized the field of medicine, allowing for complex surgical procedures to occur safely and effectively. Faster induction times and quicker recovery periods of current anesthetic agents have also helped reduce health care costs significantly. Moreover, extensive research has allowed for a better understanding of anesthetic modes of action, thus facilitating the development of more effective and safer compounds. Notwithstanding the realization that anesthetics are a prerequisite to all surgical procedures, evidence is emerging to support the notion that exposure of the developing brain to certain anesthetics may impact future brain development and function. Whereas the data in support of this postulate from human studies is equivocal, the vast majority of animal research strongly suggests that anesthetics are indeed cytotoxic at multiple brain structure and function levels. In this review, we first highlight various modes of anesthetic action and then debate the evidence of harm from both basic science and clinical studies perspectives. We present evidence from animal and human studies vis-à-vis the possible detrimental effects of anesthetic agents on both the young developing and the elderly aging brain while discussing potential ways to mitigate these effects. We hope that this review will, on the one hand, invoke debate vis-à-vis the evidence of anesthetic harm in young children and the elderly, and on the other hand, incentivize the search for better and less toxic anesthetic compounds.

Procaine penicillin alters swimming behaviour and physiological parameters of Daphnia magna

Procaine penicillin (PP) is a β-lactam antibiotic widely used in human and veterinary medicine. Although PP is detected in surface water, little is known on its effects on aquatic invertebrates. Our aim was to determine the influence of PP on swimming behaviour (track density, swimming speed, turning angle, hopping frequency) and physiological activity (oxygen consumption, heart rate, thoracic limb movement) of a freshwater invertebrate Daphnia magna exposed to PP at concentrations of 11.79 mg/L, 117.9 mg/L and 1179 mg/L for 2 h and 24 h. The results showed no mortality; however, reduction of swimming activity manifested by the decreased track density, swimming speed and turning angle noted in Daphnia exposed to all the concentrations of PP. Increase of oxygen consumption was observed after 2-h exposure; however, decrease of this parameter was found after 24 h. PP also reduced heart rate and thoracic limb movement in a concentration-dependent manner. The results suggest that the antibiotic should not induce mortality; however, it may affect swimming behaviour and physiological parameters of Daphnia magna particularly inhabiting aquaculture facilities with intensive antibiotic treatment. On the basis of the present results, we also suggest higher sensitivity of behavioural and physiological parameters of cladocerans than the commonly used endpoints: mortality or immobilisation and their possible application as a part of early warning systems in monitoring of surface water toxicity.

Tetramethylpyrazine attenuated bupivacaine-induced neurotoxicity in SH-SY5Y cells through regulating apoptosis, autophagy and oxidative damage

Background: Bupivacaine (BUP) acts as a local anesthetic, which is extensively used for clinical patients but could generate neurotoxicity in neurons. Tetramethylpyrazine (TET) exhibits strong neuron protective effects against neurotoxicity. Hence, we investigate the effect of TET on BUP-induced neurotoxicity in SH-SY5Y cells.

Methods: CCK-8 assay was used to detect cell proliferation in SH-SY5Y cells. In addition, Western blotting was used to examine Bax, Bcl-2, active caspase 3, LC3II, Beclin 1 and p-62 protein levels in cells. Moreover, ELISA assay was used to detect the levels of total glutathione (GS), superoxide dismutase (SOD) and malondialdehyde (MDA) in cells.

Results: In this study, we found that TET attenuated the neurotoxicity of BUP on SH-SY5Y cells. Meanwhile, TET alleviated BUP-induced apoptosis in SH-SY5Y cell via decreasing the expressions of active caspase-3 and Bax and increasing the expression of Bcl-2. In addition, monodansylcadaverine staining assay and Western blotting results confirmed that TET induced autophagy in SH-SY5Y cells via increasing the LC3II/I and Beclin 1 levels. Furthermore, TET attenuated BUP-induced oxidative damage in SH-SY5Y cells via upregulation of the levels of total GS and SOD and downregulation of the level of MDA. Interesting, the protective effects of TET against BUP-induced neurotoxicity in SH-SY5Y cells were reversed by autophagy inhibitor 3-methyladenine (3MA).

Conclusion: These data indicated that TET may play a neuroprotective role via inhibiting apoptosis and inducing autophagy in SH-SY5Y cells. Therefore, TET may be a potential agent for the treatment of human neurotoxicity induced by BUP.

High Glucose Enhances Bupivacaine-Induced Neurotoxicity via MCU-Mediated Oxidative Stress in SH-SY5Y Cells

Bupivacaine, a typical local anesthetic, induces neurotoxicity via reactive oxygen species regulation of apoptosis. High glucose could enhance bupivacaine-induced neurotoxicity through regulating oxidative stress, but the mechanism of it is not clear. Mitochondrial calcium uniporter (MCU), a key channel for regulating the mitochondrial Ca2+ (mCa2+) influx, is closely related to oxidative stress via disruption of mCa2+ homeostasis. Whether MCU is involved in high glucose-sensitized bupivacaine-induced neurotoxicity remains unknown. In this study, human neuroblastoma (SH-SY5Y) cells were cultured with high glucose and/or bupivacaine, and the data showed that high glucose enhanced bupivacaine-induced MCU expression elevation, mCa2+ accumulation, and oxidative damage. Next, Ru360, an inhibitor of MCU, was employed to pretreated SH-SY5Y cells, and the results showed that it could decrease high glucose and bupivacaine-induced mCa2+ accumulation, oxidative stress, and apoptosis. Further, with the knockdown of MCU with a specific small interfering RNA (siRNA) in SH-SY5Y cells, we found that it also could inhibit high glucose and bupivacaine-induced mCa2+ accumulation, oxidative stress, and apoptosis. We propose that downregulation expression or activity inhibition of the MCU channel might be useful for restoring the mitochondrial function and combating high glucose and bupivacaine-induced neurotoxicity. In conclusion, our study demonstrated the crucial role of MCU in high glucose-mediated enhancement of bupivacaine-induced neurotoxicity, suggesting the possible use of this channel as a target for curing bupivacaine-induced neurotoxicity in diabetic patients.

Downregulation of MicroRNA-33-5p Protected Bupivacaine-Induced Apoptosis in Murine Dorsal Root Ganglion Neurons Through GDNF

In this work, we evaluated the functional role of microRNA-33-5p (miR-33-5p) in regulating bupivacaine (Bv)-induced neural apoptosis in dorsal root ganglion (DRG) cells. DRG was extracted from adult mice and treated with BV in vitro. A TUNEL assay was applied to assess neural apoptosis among DRG cells. A qRT-PCR assay was applied to assess miR-33-5p expression among BV-treated DRG cells. MiR-33-5p was genetically knocked down in DRG cells. Its effect on BV-induced neural apoptosis was further evaluated by TUNEL assay. Correlation between miR-33-5p and its putative downstream target gene, glial cell-derived neurotrophic factor (GDNF), was assessed by dual-luciferase activity and qRT-PCR assays, respectively. GDNF was then inhibited in miR-33-5p-downregulated DRG cells to further assess its functional regulation in BV-induced neural apoptosis. BV induced significant neural apoptosis, in a dose-dependent manner, in DRG cells in vitro. MiR-33-5p was upregulated by BV treatment, also in a dose-dependent manner in DRG cells. On the other hand, downregulation of miR-33-5p protected BV-induced DRG neural apoptosis. GDNF was shown to be inversely correlated with miR-33-5p in BV-treated DRG cells. Moreover, inhibiting GDNF was able to reverse the protection of miR-33-5p-downregulation on BV-induced DRG neural apoptosis. MiR-33-5p, through its inverse regulation on DGNF gene, modulates anesthesia-induced neural apoptosis in DRG cells.

Comprehensive exploration of the anticancer activities of procaine and its binding with calf thymus DNA: a multi spectroscopic and molecular modelling study

Procaine is an anesthetic drug commonly administrated topically or intravenously for use in local anesthesia. Promisingly, some anticancer activities of procaine have also been reported. Therefore, the mechanism of interaction between anesthetic drug procaine with ct-DNA was determined collectively by means of various spectroscopic and molecular docking methods. Minor groove 1 : 1 binding of procaine to the ct-DNA was evidenced from absorption spectroscopy, fluorescence quenching, DNA melting, competitive binding measurements with EB and DAPI dyes, viscosity and CD spectroscopy together with molecular docking simulations and DFT calculations. Molecular docking on five different B-DNA structures (taken from the Protein Data Bank) shows that procaine binds in the AT rich region of all five B-DNA structures. Thermodynamic parameters, evaluated using van't Hoff's isotherm, shown that the interaction was feasible and the binding forces involved were hydrophobic as well as hydrogen bonding which were, further, confirmed by molecular docking. The frontier molecular orbitals (HOMO and LUMO) of procaine and DNA bases have been calculated by DFT method and the chemical potential (μ), chemical hardness (η) and fraction number of electrons (ΔN) from procaine to DNA bases were evaluated, which have shown that procaine acts as an electron donor to the DNA bases. Simultaneously, anticancer activities of procaine alone and in combination with doxorubicin were observed on the MCF-7 breast cancer cell line. The results showed that the combined treatment with both procaine and doxorubicin enhanced the cytotoxic and apoptotic inducing potential of doxorubicin.

An evaluation of the analgesic effect of AnestaGel™ on mechanical allodynia in a rat model of postoperative incisional pain

Purpose

Sustained release hydrogel with bupivacaine (AnestaGel^™) is a novel formulation of extended release bupivacaine in a biohydrogel Matrix^™. We sought to compare the analgesic effects via mechanical allodynia, the pharmacokinetic characteristics via serum blood levels, and the local tissue effects via pathology, following injection of either sustained release hydrogel with bupivacaine, liposome bupivacaine, or hydrogel only (negative control group).

Materials and methods

Ninety rats (30 in each group) were randomized to receive a sciatic nerve block injection of either sustained release hydrogel with bupivacaine, liposome bupivacaine (Exparel^®), or a biohydrogel matrix. The total force generated was obtained at varying time points. Pathologic analysis was undertaken on days 5 and 42 of the study. Six additional rats (two in each group) were randomized to receive a sciatic nerve block injection of either sustained release hydrogel with bupivacaine, liposome bupivacaine, or bupivacaine and pharmacokinetic data were obtained for up to 120 hours.

Results

The sustained release hydrogel with bupivacaine group had significantly better response to mechanical allodynia compared to the other two groups. The pathology showed no significant adverse events at 42 days in any group. Finally, bupivacaine was present longer in the serum of sustained release hydrogel with bupivacaine group than the other two groups.

Conclusion

The sustained release hydrogel with bupivacaine achieved longer lasting analgesia with no significant findings on pathology at 42 days when compared to both positive and negative controls.