Bupivacaine myotoxicity is mediated by mitochondria

Impact of gadolinium-based MRI contrast agent and local anesthetics co-administration on chondrogenic gadolinium uptake and cytotoxicity

The gadolinium-based contrast agent DOTA-Gd is clinically used in combination with local anesthetics for direct magnetic resonance arthrography. It remains unclear whether gadolinium uptake into cartilage is influenced by co-administration of bupivacaine or ropivacaine and whether DOTA-Gd alters their chondrotoxicity. Gadolinium quantification of chondrogenic spheroids revealed enhanced gadolinium uptake after simultaneous exposure to local anesthetics. Analyses of the spatial gadolinium distribution using synchrotron X-ray-fluorescence scanning indicates gadolinium exposed chondrocytes. In vitro exposure to DOTA-Gd does not alter viability and proliferation of human chondrocytes and the chondrotoxic potential of the anesthetics. Reduced viability induced by ropivacaine was found to be reversible, while exposure to bupivacaine leads to irreversible cell death. Our data suggest that ropivacaine is more tolerable than bupivacaine and that DOTA-Gd exposure does not alter the cytotoxicity of both anesthetics. Enhanced gadolinium uptake into cartilage due to co-administration of anesthetics should find attention.

In vitro chondrotoxicity of bupivacaine, levobupivacaine and ropivacaine and their effects on caspase activity in cultured canine articular chondrocytes

Bupivacaine, levobupivacaine and ropivacaine are potent, long acting, amide-type local anesthetics that have several clinical applications including intra-articular administration. The objectives of this study were to evaluate their in vitro effects on cell viability and caspase activity to elucidate whether they activate the extrinsic or intrinsic pathways of apoptosis in canine articular chondrocytes. Chondrocytes in monolayer culture were treated with culture medium as the control, or with 0.062% (0.62 mg/mL) bupivacaine, 0.062% levobupivacaine, and 0.062% ropivacaine for 24 hr. Cell viability was evaluated using the live/dead, 3-(4,5-dimehylthiazolyl-2)-2,5-diphenyltetrazolium bromide (MTT), and Cell Counting Kit-8 (CCK-8) assays. Evaluation of caspase-3, caspase-8, and caspase-9 activity was performed using colorimetric assays. The MTT and CCK-8 assays were used to evaluate the effect of caspase inhibitors on local anesthetic chondrotoxicity. All three local anesthetics decreased chondrocyte viability after 24 hr (P<0.001). Apoptosis was induced through both the extrinsic and intrinsic pathways. Bupivacaine increased caspase-3, caspase-8, and caspase-9 activity (P<0.001). Levobupivacaine increased caspase-3 (P=0.03) while ropivacaine did not significantly upregulate activity for all three caspases. Caspase inhibition did not suppress bupivacaine chondrotoxicity whereas inhibition of caspase-8 and caspase-9 decreased ropivacaine chondrotoxicity and mildly attenuated levobupivacaine chondrotoxicity. In summary, the level of chondrotoxicity, the type of caspase activated, the level of caspase activation, and the response to caspase inhibitors was dependent on the type of local anesthetic. Therefore, ropivacaine may be a safer choice for intra-articular administration compared to levobupivacaine and bupivacaine.

Buprenorphine has a concentration-dependent cytotoxic effect on equine chondrocytes in vitro

OBJECTIVE

To investigate the cytotoxic effects of 2 different concentrations of buprenorphine and compare them with bupivacaine and morphine on healthy equine chondrocytes in vitro.

SAMPLE

Primary cultured equine articular chondrocytes from 3 healthy adult horses.

PROCEDURES

Chondrocytes were exposed for 0 and 2 hours to the following treatments: media (CON; negative control); bupivacaine at 2.2 mg/mL (BUPI; positive control); morphine at 2.85 mg/mL (MOR); buprenorphine at 0.12 mg/mL (HBUPRE); or buprenorphine at 0.05 mg/mL (LBUPRE). Chondrocyte viability was assessed using live/dead staining, water-soluble tetrazolium salt-8 (WST-8) cytotoxic assay, LDH assay, and flow cytometry. All continuous variables were evaluated with a mixed ANOVA with treatment, time, and their interactions as the fixed effects and each horse as the random effect.

RESULTS

Buprenorphine showed a concentration-dependent chondrotoxic effect. The viability of chondrocytes was significantly decreased with exposure to HBUPRE and BUPI compared to CON, MOR, and LBUPRE.

CLINICAL RELEVANCE

Negligible chondrotoxic effects were observed in healthy cultured equine chondrocytes exposed to 0.05 mg/mL of buprenorphine, whereas higher concentrations (0.12 mg/mL) showed a marked cytotoxic effect. Based on these results, low concentrations of buprenorphine appear to be safe for intra-articular administration. Further evaluation of this dose in vivo is needed before recommending its clinical use.

Cytotoxicity of Local Anesthetics on Bone, Joint, and Muscle Tissues: A Narrative Review of the Current Literature

Background

Local anesthetics are commonly used in surgical procedures to control pain in patients. Whilst the cardiotoxicity and neurotoxicity of local anesthetics have received much attention, the cytotoxicity they exert against bone, joint, and muscle tissues has yet to be well recognized.

Objective

This review aimed to raise awareness regarding how local anesthetics may cause tissue damage and provide a deeper understanding of the mechanisms of local anesthetic-induced cytotoxicity. We summarized the latest progress on the cytotoxicity of local anesthetics and the underlying mechanisms and discussed potential strategies to reduce it.

Findings

We found that the toxic effects of local anesthetics on bone, joint, and muscle tissues were time- and concentration-dependent in vitro. Local anesthetics induced apoptosis, necrosis, and autophagy through specific cellular pathways. Altogether, this review indicates that toxicity of local anesthetics may be avoided by rationally selecting the appropriate anesthetic, limiting the total amount, and determining the lowest effective concentration and duration.

A cell model for evaluating mitochondrial damage in cardiomyocytes

Background

Various cellular models were used for assessment of mitochondrial damage in cardiomyocyte, but most of them are based on silent cells without contractility. The mitochondria in cells at working should be more sensitive to toxic or reperfusion damage due to their high level mitochondrial respiration. Therefore, contracting cells can represent inotropic agent-mediated high-energy demand states.

Objective

To establish a cellular model to detect mitochondrial damage in cardiomyocytes at contraction.

Method

Freshly isolated Sprague–Dawley rat cardiomyocytes were incubated with or without bupivacaine, in the presence or absence of isoprenaline, and electrically stimulated to induce rhythmic contractions.

Results

Contraction under electrical field stimulation did not induce mitochondrial swelling or ROS production in DMEM; the silent cells in the presence of bupivacaine showed mild mitochondrial swelling, but contracting cells exhibited significantly higher mitochondrial swelling and increased ROS production (P < 0.05, vs. silent cells). Isoprenaline induced a further enhancement in mitochondrial swelling and ROS production in contracting cells.

Conclusions

Contracting cells are more sensitive to bupivacaine toxicity and could be more accurately represent mitochondrial damage in vivo condition.

Comparison of in vitro and in vivo Toxicity of Bupivacaine in Musculoskeletal Applications

The recent societal debate on opioid use in treating postoperative pain has sparked the development of long-acting, opioid-free analgesic alternatives, often using the amino-amide local anesthetic bupivacaine as active pharmaceutical ingredient. A potential application is musculoskeletal surgeries, as these interventions rank amongst the most painful overall. Current literature showed that bupivacaine induced dose-dependent myo-, chondro-, and neurotoxicity, as well as delayed osteogenesis and disturbed wound healing in vitro. These observations did not translate to animal and clinical research, where toxic phenomena were seldom reported. An exception was bupivacaine-induced chondrotoxicity, which can mainly occur during continuous joint infusion. To decrease opioid consumption and provide sustained pain relief following musculoskeletal surgery, new strategies incorporating high concentrations of bupivacaine in drug delivery carriers are currently being developed. Local toxicity of these high concentrations is an area of further research. This review appraises relevant in vitro, animal and clinical studies on musculoskeletal local toxicity of bupivacaine.

Downregulation of HSPA12A underlies myotoxicity of local anesthetic agent bupivacaine through inhibiting PGC1α-mediated mitochondrial integrity

Local anesthetics (LAs) are widely used for intraoperative anesthesia and postoperative analgesia. However, LAs (e.g. Bupivacaine) can evoke myotoxicity that closely associated to mitochondrial damage. PGC1a is a mast co-factor for mitochondrial quality control. We have recently demonstrated that PGC1a can be activated by HSPA12A in hepatocytes, suggesting a possibility that HSPA12A protects from LAs myotoxicity through activating PGC1α-mediated mitochondrial integrity. Here, we reported that HSPA12A was downregulated during Bupivacaine-induced myotoxicity in skeletal muscles of mice in vivo and C2c12 myoblast cultures in vitro. Intriguingly, overexpression of HSPA12A attenuated the Bupivacaine-induced C2c12 cell death. We also noticed that the Bupivacaine-induced decrease of glucose consumption and ATP production was improved by HSPA12A overexpression. Moreover, overexpression of HSPA12A in C2c12 cells attenuated the Bupivacaine-induced decrease of mitochondrial contents and increase of mitochondrial fragmentation. The Bupivacaine-induced reduction of PGC1α expression and nuclear localization was markedly attenuated by HSPA12A overexpression. Importantly, pretreatment with a selective PGC1α inhibitor (SR-18292) abolished the protection of HSPA12A from Bupivacaine-induced death and mitochondrial loss in C2c12 cells. Altogether, the findings indicate that downregulation of HSPA12A underlies myotoxicity of Local anesthetic agent Bupivacaine through inhibiting PGC1α-mediated Mitochondrial Integrity. Thus, HSPA12A might represent a viable strategy for preventing myotoxicity of LAs.

Lidocaine Inhibits Myoblast Cell Migration and Myogenic Differentiation Through Activation of the Notch Pathway

Purpose

To assess the cellular and molecular effects of lidocaine on muscles/myoblasts.

Methods

Cultured myogenic precursor (C2C12) cells were treated with varying concentrations of lidocaine.

Results

Cell viability of C2C12 cells was inhibited by lidocaine in a concentration-dependent manner, with concentrations ≥0.08%, producing a dramatic reduction in cell viability. These ≥0.08% concentrations of lidocaine arrested cell cycles of C2C12 cells in the G0/G1 phase. Moreover, lidocaine inhibited cell migration and myogenic processes in C2C12 cells at low concentrations. Results from QRT-PCR assays revealed that following treatment with lidocaine, Notch1, Notch2, Hes1, Csl and Dll4 all showed higher levels of expression, while no changes were observed in Mmal1, Hey1, Dll1 and Jag1.

Conclusion

This work provides the first description of the effects of lidocaine upon the regeneration of muscles and maintenance of satellite cells at the cellular and molecular levels. In specific, we found that the Dll4-Notch-Csl-Hes1 axis was up-regulated suggesting that the Notch signaling pathway was involved in producing these effects of lidocaine. These findings provide a new and important foundation for future investigations into the effects of drug therapies in muscle diseases.

Concerned topics of epidural labor analgesia: labor elongation and maternal pyrexia: a systematic review

Objective:

Labor is a complex process and labor pain presents challenges for analgesia. Epidural analgesia (EA) has a well-known analgesic effect and is commonly used during labor. This review summarized frequently encountered and controversial problems surrounding EA during labor, including the labor process and maternal intrapartum fever, to build knowledge in this area.

Data sources:

We searched for relevant articles published up to 2019 in PubMed using a range of search terms (eg, “labor pain,” “epidural,” “analgesia,” “labor process,” “maternal pyrexia,” “intrapartum fever”).

Study selection:

The search returned 835 articles, including randomized control trials, retrospective cohort studies, observational studies, and reviews. The articles were screened by title, abstract, and then full-text, with a sample independently screened by two authors. Thirty-eight articles were included in our final analysis; 20 articles concerned the labor process and 18 reported on maternal pyrexia during EA.

Results:

Four classic prospective studies including 14,326 participants compared early and delayed initiation of EA by the incidence of cesarean delivery. Early initiation following an analgesia request was preferred. However, it was controversial whether continuous use of EA in the second stage of labor induced adverse maternal and neonatal outcomes due to changes in analgesic and epidural infusion regimens. There was a high incidence of maternal pyrexia in women receiving EA and women with placental inflammation or histologic chorioamnionitis compared with those receiving systemic opioids.

Conclusions:

Early EA (cervical dilation ≥1 cm) does not increase the risk for cesarean section. Continuous epidural application of low doses of analgesics and programmed intermittent epidural bolus do not prolong second-stage labor duration or impact maternal and neonatal outcomes. The association between EA and maternal pyrexia remains controversial, but pyrexia is more common with EA than without. A non-infectious inflammatory process is an accepted mechanism of epidural-related maternal fever.

Bupivacaine-induced myotoxicity during a continuous perineural femoral block: case report

Introduction: Regional anesthesia is widely used for postoperative analgesia in total knee arthroplasty (TKA). Although it is a safe and effective procedure, serious complications may still develop. In the event of an unusual or torpid evolution, the possibility of local anesthetic-induced myotoxicity should be suspected. Case presentation: A 54-year old patient, American Society of Anesthesiologists (ASA) II, underwent TKA due to primary gonarthrosis. The analgesic technique used was a femoral nerve block associated with continuous perineural infusion. 24hours later, the patient’s medical condition deteriorated presenting pain, edema, and functional limitation of the thigh of the operated extremity. The symptoms were suggestive of myotoxicity, confirmed with diagnostic images leading to the removal of the catheter. The patient experienced then a significant improvement and was discharged 5 days after surgery. Conclusion: The diagnosis of myotoxicity from local anesthetics is rare, since its manifestations may be masked by the usual symptoms of the postoperative period. Early identification of the condition is fundamental to reduce its negative impact on the patient’s recovery and satisfaction. Since the scope of the damage depends particularly on the concentration and duration of the exposure to the local anesthetic agent, there is a need to implement protocols that enable an effective block with the lowest concentration and volume of the medication.

Nonbiologic Injections in Sports Medicine

Nonbiologic medications (local anesthetics, corticosteroids, and nonsteroidal anti-inflammatory drugs) are commonly administered to athletes for analgesia after injury. However, the risks of nonbiologic injections often are overlooked simply because of their long-term market availability. A thorough understanding of the mechanism of action, the reported benefits, and the potential risks of nonbiologic medications is crucial prior to their use, especially in the treatment of young athletes. Sports medicine physicians and surgeons must be aware of the systemic and local effects of these medications to ensure an appropriate drug choice that minimizes side effects and avoids recently reported toxicity to myocytes, tenocytes, and chondrocytes.

Effect of bupivacaine and adjuvant drugs on skeletal muscle tissue oximetry and blood flow: an experimental study

Background

Skeletal muscle microvascular blood flow plays a critical role in many myopathologies. The influence of bupivacaine and adjuvants on skeletal muscle microvascular perfusion and tissue oximetry is poorly understood but might be a relevant risk factor for myopathies after local anesthetic administration. The aim of this experimental study was to determine the effects of bupivacaine alone or in combination with epinephrine or clonidine on skeletal muscle perfusion and tissue oximetry.

Methods

Combined tissue spectrophotometry and Laser-Doppler flowmetry and tissue oximetry were used to assess local muscle blood flow in anesthetized pigs after topical administration of test solutions (bupivacaine, bupivacaine with epinephrine or clonidine, saline). Measurements were performed for up to 60 mins.

Results

The application of bupivacaine alone did not alter relative muscle blood flow significantly, whereas the addition of epinephrine or clonidine to bupivacaine resulted in a significant reduction of relative muscle blood flow at T30 and T60. However, bupivacaine resulted in a significant decrease of tissue oximetry values when compared to saline control group at T30 and T60. The application of bupivacaine combined with clonidine or epinephrine resulted in no significant reduction of tissue oximetry when compared to bupivacaine alone.

Conclusion

Bupivacaine alone results in a significant decrease of tissue oximetry in skeletal muscle which is not increased by the addition of epinephrine or clonidine despite further reductions of microcirculatory perfusion. Overall, bupivacaine alone or with adjuvants does produce local muscle ischemia for which pathological consequences need to be addressed in further studies.

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.

Involvement of superoxide generated by NADPH oxidase in the shedding of procoagulant vesicles from human monocytic cells exposed to bupivacaine

It is known that a variety of sized procoagulant vesicles that express tissue factor are released from several types of cells including monocytes by mechanisms related to the induction of apoptosis, while it has not yet been evaluated whether superoxide is involved in the production of such vesicles. Here, we report that a local anesthetic bupivacaine induces apoptosis in human monocytic cells THP-1 within a short observation period, where the shedding of procoagulant vesicles is associated. The property as procoagulant vesicles was evaluated using flow cytometry by the binding of FITC-conjugated fibrinogen to vesicles in the presence of fresh frozen plasma and the suppression of this binding by heparin. Bupivacaine (1 mg/ml) increased the apoptotic cells and procoagulant vesicles. LY294002 (100 µM), that inhibits the recruiting of intracellular component of NADPH oxidase to construct the activated form of this enzyme complex, or superoxide dismutase (1500 unit/ml) suppressed bupivacaine-provoked induction of apoptosis and the increase of procoagulant vesicles. We suggest that this simple experimental system is useful to explore the molecular mechanisms of action of superoxide in the shedding of procoagulant vesicles from human monocytic cells.

ROS-mediated lysosomal membrane permeabilization is involved in bupivacaine-induced death of rabbit intervertebral disc cells

Bupivacaine is frequently administered for diagnosing and controlling spine-related pain in interventional spine procedures. However, the potential cytotoxic effects of bupivacaine on intervertebral disc (IVD) cells and the underlying molecular mechanisms have not yet been fully established. Here, we showed that bupivacaine decreased the viability of rabbit IVD cells in a dose- and time-dependent manner. Moreover, the short-term cytotoxicity of bupivacaine in IVD cells was primarily due to cell necrosis, as assessed by Annexin V-propidium iodide staining and live/dead cell staining. Necrosis was verified by observations of swollen organelles, plasma membrane rupture, and cellular lysis under transmission electronic microscopy. Interestingly, our data indicated that bupivacaine-induced primary necrosis might involve the necroptosis pathway. The key finding of this study was that bupivacaine was able to induce lysosomal membrane permeabilization (LMP) with the release of cathepsins into the cytosol, as evidenced by LysoTracker Red staining, acridine orange staining, and cathepsin D immunofluorescence staining. Consistently, inhibitors of lysosomal cathepsins, CA074-Me and pepstatin A, significantly reduced bupivacaine-induced cell death. Finally, we found that bupivacaine resulted in an increase in intracellular reactive oxygen species (ROS) and that inhibition of ROS by N-acetyl-L-cysteine effectively blocked bupivacaine-induced LMP and cell death. In summary, the results of this in vitro study reveal a novel mechanism underlying bupivacaine-induced cell death involving ROS-mediated LMP. Our findings establish a basis for the further investigation of bupivacaine cytotoxicity in an in vivo system.

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Bupivacaine decreases IVD cell viability in a dose- and time-dependent manner.

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The short-term cytotoxicity of bupivacaine is primarily due to cell necrosis.

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LMP is involved in bupivacaine-induced death of IVD cells.

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ROS is an important mediator in bupivacaine-induced LMP and cell death.

Redox mechanism of levobupivacaine cytostatic effect on human prostate cancer cells

Anti-cancer effects of local anesthetics have been reported but the mode of action remains elusive. Here, we examined the bioenergetic and REDOX impact of levobupivacaine on human prostate cancer cells (DU145) and corresponding non-cancer primary human prostate cells (BHP). Levobupivacaine induced a combined inhibition of glycolysis and oxidative phosphorylation in cancer cells, resulting in a reduced cellular ATP production and consecutive bioenergetic crisis, along with reactive oxygen species generation. The dose-dependent inhibition of respiratory chain complex I activity by levobupivacaine explained the alteration of mitochondrial energy fluxes. Furthermore, the potency of levobupivacaine varied with glucose and oxygen availability as well as the cellular energy demand, in accordance with a bioenergetic anti-cancer mechanism. The levobupivacaine-induced bioenergetic crisis triggered cytostasis in prostate cancer cells as evidenced by a S-phase cell cycle arrest, without apoptosis induction. In DU145 cells, levobupivacaine also triggered the induction of autophagy and blockade of this process potentialized the anti-cancer effect of the local anesthetic. Therefore, our findings provide a better characterization of the REDOX mechanisms underpinning the anti-effect of levobupivacaine against human prostate cancer cells.

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Local anesthetics reduce cancer recurrence in prostate cancer.

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Metabolic reprogramming in a hallmark of cancer.

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Complex I inhibition is a potential anti-cancer bioenergetic therapeutic strategy.

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Levobupivacaine inhibits complex I activity and mitochondrial respiration.

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Autophagy blocker combined with levobupivacaine induces cytostasis in prostate cancer.

Procaine and saline have similar effects on articular cartilage and synovium in rat knee

Background

Intra-articular local anaesthetics are widely used for providing postoperative analgesia and decreasing the need for opioids. Procaine has proven positive effects in carpal tunnel syndrome and chondromalacia patella. However, the effect of procaine on articular cartilage has not yet been studied. The aim of this study was to evaluate the effects of intra-articular procaine injection on the articular cartilage and the synovium.

Methods

Twenty adult Sprague-Dawley rats were enrolled in the study. After providing anaesthesia and aseptic conditions, 0.25 ml of 10% procaine was injected to the right knee joint, and 0.25 ml of normal saline (as control group) was injected to the left knee joint. Knee joint samples were obtained from four rats in each group after appropriate euthanasia on days 1, 2, 7, 14 and 21. The histological sections of the articular and periarticular regions and the synovium were evaluated by two histologists, and inflammatory changes were graded according to a five-point scale in a blinded manner. The apoptosis of chondrocytes was determined by the caspase-3 indirect immunoperoxidase method.

Results

There were no significant differences in inflammation between procaine and saline groups at any of the time intervals. Slight inflammatory infiltration due to injection was seen in both groups on the 1st day. Haemorrhage was observed in both groups at days 1 and 2, and the difference between groups was not found to be significant. No significant difference was detected in the percentage of apoptotic chondrocytes between groups at any of the time intervals.

Conclusions

Injection of procaine seems safe to use intra-articularly based on this in vivo study on rat knee cartilage. However, further studies investigating both the analgesic and histopathological effects of procaine on damaged articular cartilage and synovium models are needed.

Single-dose local anesthetics exhibit a type-, dose-, and time-dependent chondrotoxic effect on chondrocytes and cartilage: a systematic review of the current literature

PURPOSE

Many studies have shown that local anesthetics may impede chondrocyte metabolism. However, the influence of a single-dose local anesthetics is controversial. The aim of this metaanalysis was to review the literature for studies investigating the cytotoxic effects of single-dose local anesthetics on chondrocytes and cartilage.

METHODS

A comprehensive literature search was performed using established search engines (Medline, Embase) to identify studies, investigating the influence of single-dose local anesthetics on cartilage. The systematic analysis included the influence on histology, cell viability, morphology, and matrix production depending upon dose, exposure time, and type of local anesthetics.

RESULTS

Twelve studies with four different local anesthetics were included in this metaanalysis. Bupivacaine and lidocaine were found to be more chondrotoxic than mepivacaine and ropivacaine. The amount of dead cells increased in a substance-, dose-, and time-dependent process. Osteoarthritic cartilage seems to be more vulnerable compared to intact cartilage. The toxic effects occur first in the superficial cartilage layers and include damage to membrane integrity, mitochondrial DNA, and nuclear changes. There is no study that could show a significant chondrotoxic effect with low concentrations of bupivacaine (0.0625%), ropivacaine (0.1 and 0.2%), and mepivacaine (0.5%).

CONCLUSIONS

The cytotoxicity of local anesthetics on chondrocytes is dependent on dose, time, and type of local anesthetics. Single-dose intra-articular administration of local anesthetics impede chondrocyte metabolism and should be performed only with low concentrations for selected diagnostic purposes and painful joints. The use of lidocaine should be avoided.

LEVEL OF EVIDENCE

II.

Exciting perspectives for Translational Myology in the Abstracts of the 2018Spring PaduaMuscleDays: Giovanni Salviati Memorial - Chapter I - Foreword

Myologists working in Padua (Italy) were able to continue a half-century tradition of studies of skeletal muscles, that started with a research on fever, specifically if and how skeletal muscle contribute to it by burning bacterial toxin. Beside main publications in high-impact-factor journals by Padua myologists, I hope to convince readers (and myself) of the relevance of the editing Basic and Applied Myology (BAM), retitled from 2010 European Journal of Translational Myology (EJTM), of the institution of the Interdepartmental Research Center of Myology of the University of Padova (CIR-Myo), and of a long series of International Conferences organized in Euganei Hills and Padova, that is, the PaduaMuscleDays. The 2018Spring PaduaMuscleDays (2018SpPMD), were held in Euganei Hills and Padua (Italy), in March 14-17, and were dedicated to Giovanni Salviati. The main event of the "Giovanni Salviati Memorial", was held in the Aula Guariento, Accademia Galileiana di Scienze, Lettere ed Arti of Padua to honor a beloved friend and excellent scientist 20 years after his premature passing. Using the words of Prof. Nicola Rizzuto, we all share his believe that Giovanni "will be remembered not only for his talent and originality as a biochemist, but also for his unassuming and humanistic personality, a rare quality in highly successful people like Giovanni. The best way to remember such a person is to gather pupils and colleagues, who shared with him the same scientific interests and ask them to discuss recent advances in their own fields, just as Giovanni have liked to do". Since Giovanni's friends sent many abstracts still influenced by their previous collaboration with him, all the Sessions of the 2018SpPMD reflect both to the research aims of Giovanni Salviati and the traditional topics of the PaduaMuscleDays, that is, basics and applications of physical, molecular and cellular strategies to maintain or recover functions of skeletal muscles. The translational researches summarized in the 2018SpPMD Abstracts are at the appropriate high level to attract approval of Ethical Committees, the interest of International Granting Agencies and approval for publication in top quality, international journals. This was true in the past, continues to be true in the present and will be true in the future. All 2018SpPMD Abstracts are indexed at the end of the Chapter IV.

Alginate-liposomal construct for bupivacaine delivery and MSC function regulation

Mesenchymal stromal cell (MSC) therapies have become potential treatment options for multiple ailments and traumatic injuries. In the clinical setting, MSC are likely to be co-administered with local anesthetics (LA) which have been shown to have dose- and potency-dependent detrimental effects on the viability and function of cells. We previously developed and characterized a sustained-release LA delivery formulation comprised of alginate-encapsulated liposomal bupivacaine. The current studies were designed to evaluate the effect of this formulation on the secretion of three key MSC regulatory molecules, interleukin 6 (IL-6), prostaglandin E2 (PGE2), and transforming growth factor-beta 1 (TGF-β1). MSCs were treated with several bupivacaine formulations-bolus, liposome, or alginate-liposome construct (engineered construct)-in the presence or absence of inflammatory stimulus to stimulate an injured tissue environment. Our results indicated that compared to bolus or liposomal bupivacaine, the engineered construct preserved or promoted MSC anti-inflammatory PGE2 secretion; however, the engineered construct did not increase TGF-β1 secretion. Bupivacaine release profile analyses indicated that mode of drug delivery controlled the LA concentration over time and pathway analysis identified several shared and cytokine-specific molecular mediators for IL-6, PGE2, and TGF-β1 which could explain differential MSC secretion responses in the presence of bupivacaine. Collectively, these studies support the potential utility of alginate-encapsulated LA constructs for anti-inflammatory cell therapy co-administration and indicate that mode of local anesthetic delivery can significantly alter MSC secretome function.

In Vitro Chondrotoxicity of Nonsteroidal Anti-inflammatory Drugs and Opioid Medications

BACKGROUND

A variety of medications are administered to the intra-articular space for the relief of joint pain. While amide-type local anesthetics have been extensively studied, there is minimal information regarding the potential chondrotoxicity of nonsteroidal anti-inflammatory drugs (NSAIDs) and opioid medications.

PURPOSE

To investigate the in vitro chondrotoxicity of single-dose equivalent concentrations of ketorolac, morphine, meperidine, and fentanyl on human chondrocytes.

STUDY DESIGN

Controlled laboratory study.

METHODS

Human cartilage was arthroscopically harvested from the intercondylar notch and expanded in vitro. Gene expression of cultured chondrocytes before treatment was performed with quantitative polymerase chain reaction for type I collagen, type II collagen, aggrecan, and SOX9. Chondrocytes were then exposed to 0.01%, 0.02%, and 0.04% morphine sulfate; 0.3% and 0.6% ketorolac tromethamine; 0.5%, 1.0%, and 1.5% meperidine hydrochloride; 0.0005% and 0.001% fentanyl citrate; and saline. A custom bioreactor was used to constantly deliver medications, with the dosage of each medication and the duration of exposure based on standard dose equivalents, medication half-lives, and differences in the surface area between the 6-well plates and the native joint surface. After treatment, a live/dead assay was used to assess chondrocyte viability and if minimal cell death was detected. A subset of samples after treatment was maintained to analyze for possible delayed cell death.

RESULTS

All tested concentrations of ketorolac and meperidine caused significantly increased cell death versus the saline control, demonstrating a dose-response relationship. The morphine and fentanyl groups did not show increased chondrotoxicity compared with the saline group, even after 2 weeks of additional culture.

CONCLUSION

In vitro exposure of chondrocytes to single-dose equivalent concentrations of either ketorolac or meperidine demonstrated significant chondrotoxicity, while exposure to morphine or fentanyl did not lead to increased cell death.

Local anaesthetics or their combination with morphine and/or magnesium sulphate are toxic for equine chondrocytes and synoviocytes in vitro

Background

Chondrotoxic effects of local anaesthetics are well reported in humans and some animal species but knowledge on their toxic effects on synoviocytes or equine chondrocytes or the effects on cellular production of inflammatory cytokines is limited. The purpose of this study was to evaluate the in vitro effects of local anaesthetics, morphine, magnesium sulphate (MgSO₄) or their combinations on cell viability and pro-inflammatory cytokine gene expression of equine synoviocytes and chondrocytes.

Equine synoviocytes and cartilage explants harvested from normal joints in a co-culture system were exposed to mepivacaine (4.4 mg/ml), bupivacaine (2.2 mg/ml), morphine (2.85 mg/ml) and MgSO₄ (37 mg/ml) alone or each local anaesthetic plus morphine or MgSO₄ or both together. Chondrocyte and synoviocyte cell viability was assessed by CellTiter-Glo Luminescent Cell Viability Assay. Synoviocyte gene expression of IL-1β, IL-6 or TNF-α was measured and compared using the ∆∆CT method.

Results

Morphine alone, MgSO₄ alone or their combination did not alter cell viability or the expression of IL-1β, IL-6 or TNF-α. However, local anaesthetics alone or in combination with morphine and/or MgSO₄ reduced cell viability and increased the gene expression of IL-1β, IL-6 or TNF-α. Single short exposure to local anaesthetics is toxic to both chondrocytes and synoviocytes and their combination with morphine and/or MgSO₄ enhanced the cytotoxic effects.

Conclusions

This in vitro study gives further evidence of the absence of cytotoxic effects of morphine alone, MgSO₄ alone or their combination on normal articular tissues. However, local anaesthetics alone or in combination with morphine and/or MgSO₄ have cytotoxic effects on equine articular tissues.

Electronic supplementary material

The online version of this article (10.1186/s12917-017-1244-8) contains supplementary material, which is available to authorized users.

[Direct mechanism of action in toxic myopathies]

Toxic myopathies are a large group of disorders generated by surrounding agents and characterized by structural and/or functional disturbances of muscles. The most recurrent are those induced by commonly used medications. Illicit drugs, environmental toxins from animals, vegetables, or produced by micro-organisms as well as chemical products commonly used are significant causes of such disorders. The muscle toxicity results from multiple mechanisms at different biological levels. Many agents can induce myotoxicity through a direct mechanism in which statins, glucocorticoids and ethyl alcohol are the most representative. Diverse mechanisms were highlighted as interaction with macromolecules and induction of metabolic and cellular dysfunctions. Muscle damage can be related to amphiphilic properties of some drugs (chloroquine, hydroxychloroquine, etc.) leading to specific lysosomal disruptions and autophagic dysfunctions. Some agents affect the whole muscle fiber by inducing oxidative stress (ethyl alcohol and some statins) or triggering cell death pathways (apoptosis or necrosis) resulting in extensive alterations. More studies on these mechanisms are needed. They would allow a better knowledge of the intracellular mediators involved in these pathologies in order to develop targeted therapies of high efficiency.

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

Local anaesthetics (LAs) may lead to neurological complications, but the underlying mechanism is still unclear. Many neurotoxicity research studies have examined different LAs, but none have comprehensively explored the distinct mechanisms of neurotoxicity caused by amide- (bupivacaine) and ester- (procaine) type LAs. Here, based on a CCK8 assay, LDH assay, Rhod-2-AM and JC-1 staining, 2′,7′-dichlorohy-drofluorescein diacetate and dihydroethidium probes, an alkaline comet assay, and apoptosis assay, we show that both bupivacaine and procaine significantly induce mitochondrial calcium overload and a decline in the mitochondrial membrane potential as well as overproduction of ROS, DNA damage and apoptosis (P < 0.05). There were no significant differences in mitochondrial injury and apoptosis between the bupivacaine and procaine subgroups (P > 0.05). However, to our surprise, the superoxide anionic level after treatment with bupivacaine, which leads to more severe DNA damage, was higher than the level after treatment with procaine, while procaine produced more peroxidation than bupivacaine. Some of these results were also affirmed in dorsal root ganglia neurons of C57 mice. The differences in the superoxidation and peroxidation induced by these agents suggest that different types of LAs may cause neurotoxicity via different pathways. We can target more accurate treatment based on their different mechanisms of neurotoxicity.

N-acetyl cysteine protects cells from chondrocyte death induced by local anesthetics

Local anesthetics (LA) are among the drugs most frequently used for musculoskeletal problems, in procedures ranging from diagnosis to postoperative pain control. Chondrocyte toxicity induced by LA is an emerging area of concern. The purpose of this study was to determine whether N-acetyl cysteine (NAC), an antioxidant, will exert cytoprotective effects against chondrocyte death induced by LA. Primary cultured human chondrocytes were used for this study. This study used control, NAC, LA, and NAC-LA groups. Cytotoxicity was induced in the LA subgroups and their paired NAC-LA subgroups through exposure to ropivacaine (0.075%), bupivacaine (0.05%), or lidocaine (0.2%) for 24 h. The NAC-LA subgroups were exposed to 10 mM NAC for 1 h, before LA exposure. These study groups were evaluated for rates of cell viability, apoptosis, necrosis, intracellular ROS production, and caspase-3/7 activity. Cell viability in all LA subgroups was significantly lower than in the control group (p < 0.001). Cell viability in the NAC-LA subgroups was significantly higher than in their paired LA subgroups (p < 0.001). In the LA subgroups, rates of apoptosis and necrosis, intracellular ROS production, and caspase-3/7 activity were significantly higher than in the control group (p ≤ 0.029). In the NAC-LA subgroups, rates of apoptosis and necrosis, intracellular ROS production, and caspase-3/7 activity were significantly lower than in their paired LA subgroups (p ≤ 0.023). These results indicate that N-acetyl cysteine, an antioxidant, has cytoprotective effects against LA-induced toxicity to chondrocytes in vitro. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 35:297-303, 2017.

L-carnitine reduces susceptibility to bupivacaine-induced cardiotoxicity: an experimental study in rats

BACKGROUND

The primary aim of this study was to evaluate the effect of acute administration of L-carnitine 100 mg·kg^-1 iv on susceptibility to bupivacaine-induced cardiotoxicity in rats.

METHODS

In the first of two experiments, L-carnitine 100 mg·kg^-1 iv (n = 10) or saline iv (n = 10) was administered to anesthetized and mechanically ventilated Sprague-Dawley rats following which an infusion of bupivacaine 2.0 mg·kg^-1·min^-1 iv was given until asystole occurred. The primary outcome was the probability of survival. Secondary outcomes included times to asystole, first dysrhythmia, and to 50% reductions in heart rate (HR) and mean arterial pressure (MAP). To determine whether the same dose of L-carnitine is effective in treating established bupivacaine cardiotoxicity, we also conducted a second experiment in which bupivacaine 20 mg·kg^-1 iv was infused over 20 sec. Animals (n = 10 per group) received one of four iv treatments: 30% lipid emulsion 4.0 mL·kg^-1, L-carnitine 100 mg·kg^-1, 30% lipid emulsion plus L-carnitine, or saline. The primary outcome was the return of spontaneous circulation (ROSC) during resuscitation.

RESULTS

In the first study, L-carnitine 100 mg·kg^-1 increased the probability of survival during bupivacaine infusion (hazard ratio, 12.0; 95% confidence interval, 3.5 to 41.5; P < 0.001). In L-carnitine-treated animals, the times to asystole, first dysrhythmia, and to 50% reductions in HR and MAP increased by 33% (P < 0.001), 65% (P < 0.001), 71% (P < 0.001), and 63% (P < 0.001), respectively. In the second study, no animal in the control or L-carnitine alone groups achieved ROSC when compared with the lipid emulsion groups (P < 0.01).

CONCLUSION

These findings suggest that acute administration of L-carnitine 100 mg·kg^-1 decreases susceptibility to bupivacaine cardiotoxicity, but is ineffective during resuscitation from bupivacaine-induced cardiac arrest.

Forty years later: Mitochondria as therapeutic targets in muscle diseases

The hypothesis that mitochondrial dysfunction can be a general mechanism for cell death in muscle diseases is 40 years old. The key elements of the proposed pathogenetic sequence (cytosolic Ca2+ overload followed by excess mitochondrial Ca2+ uptake, functional and then structural damage of mitochondria, energy shortage, worsened elevation of cytosolic Ca2+ levels, hypercontracture of muscle fibers, cell necrosis) have been confirmed in amazing detail by subsequent work in a variety of models. The explicit implication of the hypothesis was that it "may provide the basis for a more rational treatment for some conditions even before their primary causes are known" (Wrogemann and Pena, 1976, Lancet, 1, 672-674). This prediction is being fulfilled, and the potential of mitochondria as pharmacological targets in muscle diseases may soon become a reality, particularly through inhibition of the mitochondrial permeability transition pore and its regulator cyclophilin D.

Increased sodium channel use-dependent inhibition by a new potent analogue of tocainide greatly enhances in vivo antimyotonic activity

Although the sodium channel blocker, mexiletine, is the first choice drug in myotonia, some myotonic patients remain unsatisfied due to contraindications, lack of tolerability, or incomplete response. More therapeutic options are thus needed for myotonic patients, which require clinical trials based on solid preclinical data. In previous structure-activity relationship studies, we identified two newly-synthesized derivatives of tocainide, To040 and To042, with greatly enhanced potency and use-dependent behavior in inhibiting sodium currents in frog skeletal muscle fibers. The current study was performed to verify their potential as antimyotonic agents. Patch-clamp experiments show that both compounds, especially To042, are greatly more potent and use-dependent blockers of human skeletal muscle hNav1.4 channels compared to tocainide and mexiletine. Reduced effects on F1586C hNav1.4 mutant suggest that the compounds bind to the local anesthetic receptor, but that the increased hindrance and lipophilia of the N-substituent may further strengthen drug-receptor interaction and use-dependence. Compared to mexiletine, To042 was 120 times more potent to block hNav1.4 channels in a myotonia-like cellular condition and 100 times more potent to improve muscle stiffness in vivo in a previously-validated rat model of myotonia. To explore toxicological profile, To042 was tested on hERG potassium currents, motor coordination using rotarod, and C2C12 cell line for cytotoxicity. All these experiments suggest a satisfactory therapeutic index for To042. This study shows that, owing to a huge use-dependent block of sodium channels, To042 is a promising candidate drug for myotonia and possibly other membrane excitability disorders, warranting further preclinical and human studies.

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To040 and To042 are potent use-dependent hNav1.4 sodium channel blockers.

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The compounds strengthen the molecular interaction at the local anesthetic receptor.

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To042 is 120-fold more potent than mexiletine in vitro in myotonia-like conditions.

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To042 is 100-fold more potent than mexiletine in vivo in a rat model of myotonia.

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To042 is a promising antimyotonic drug deserving further investigation.

Inflammation and Epidural-Related Maternal Fever: Proposed Mechanisms

Intrapartum fever is associated with excessive maternal interventions as well as higher neonatal morbidity. Epidural-related maternal fever (ERMF) contributes to the development of intrapartum fever. The mechanism(s) for ERMF has remained elusive. Here, we consider how inflammatory mechanisms may be modulated by local anesthetic agents and their relevance to ERMF. We also critically reappraise the clinical data with regard to emerging concepts that explain how anesthetic drug-induced metabolic dysfunction, with or without activation of the inflammasome, might trigger the release of nonpathogenic, inflammatory molecules (danger-associated molecular patterns) likely to underlie ERMF.

Hyaluronan suppresses lidocaine-induced apoptosis of human chondrocytes in vitro by inhibiting the p53-dependent mitochondrial apoptotic pathway

AIM

Intra-articular injection of local anesthetics (LAs) is a common procedure for therapeutic purposes. However, LAs have been found toxic to articular cartilage, and hyaluronan may attenuate this toxicity. In this study we investigated whether hyaluronan attenuated lidocaine-induced chondrotoxicity, and if so, to elucidate the underlying mechanisms.

METHODS

Human chondrocyte cell line SW1353 and newly isolated murine chondrocytes were incubated in culture medium containing hyaluronan and/or lidocaine for 72 h. Cell viability was evaluated using MTT assay. Cell apoptosis was detected with DAPI staining, caspase 3/7 activity assay and flow cytometry. Cell cycle distributions, ROS levels and mitochondrial membrane potential (ΔΨm) were determined using flow cytometry. The expression of p53 and p53-regulated gene products was measured with Western blotting.

RESULTS

Lidocaine (0.005%-0.03%) dose-dependently decreased the viability of SW1353 cells. This local anesthetic (0.015%, 0.025%) induced apoptosis, G2/M phase arrest and loss of ΔΨm, and markedly increased ROS production in SW1353 cells. Hyaluronan (50-800 μg/mL) alone did not affect the cell viability, but co-treatment with hyaluronan (200 μg/mL) significantly attenuated lidocaine-induced apoptosis and other abnormalities in SW1353 cells. Furthermore, co-treatment with lidocaine and hyaluronan significantly decreased the levels of p53 and its transcription targets Bax and p21 in SW1353 cells, although treatment with lidocaine alone did not significantly change these proteins. Similar results were obtained in ex vivo cultured murine chondrocytes.

CONCLUSION

Hyaluronan suppresses lidocaine-induced apoptosis of human chondrocytes in vitro through inhibiting the p53-dependent mitochondrial apoptotic pathway.

Lipid emulsion reverses bupivacaine-induced apoptosis of h9c2 cardiomyocytes: PI3K/Akt/GSK-3β signaling pathway

Some findings have suggested that the rescue of bupivacaine (BPV)-induced cardiotoxicity by lipid emulsion (LE) is associated with inhibition of mitochondrial permeability transition pore (mPTP). However, the mechanism of this rescue action is not clearly known. In this study, the roles of phosphoinositide 3-kinase (PI3K)/Akt and glycogen synthase kinase-3β (GSK-3β) in the molecular mechanism of LE-induced protection and its relationship with mPTP were explored. h9c2 cardiomyocytes were randomly divided into several groups: control, BPV, LE, BPV+LE. To study the effect of LE on mPTP, atractyloside (Atr, 20 μM, mPTP opener) and cyclosporine A (CsA, 10 μM, mPTP blocker) were used. To unravel whether LE protects heart through the PI3K/Akt/GSK-3β signaling pathway, cells were treated with LY294002 (LY, 30 μM, PI3K blocker) or TWS119 (TWS 10 μM, GSK-3β blocker). Later mitochondrial respiratory chain complexes, apoptosis, opening of mPTP and phosphorylation levels of Akt/GSK-3β were measured. LE significantly improved the mitochondrial functions in h9c2 cardiomyocytes. LE reversed the BPV-induced apoptosis and the opening of mPTP. The effect of LE was not only enhanced by CsA and TWS, but also abolished by Atr and LY. LE also increased the phosphorylation levels of Akt and GSK-3β. These results suggested that LE can reverse the apoptosis in cardiomyocytes by BPV and a mechanism of its action is inhibition of mPTP opening through the PI3K/Akt/GSK-3β signaling pathway.

Ropivacaine- and bupivacaine-induced death of rabbit annulus fibrosus cells in vitro: involvement of the mitochondrial apoptotic pathway

OBJECTIVE

The purposes of this study were to assess whether local anesthetics (LAs), such as ropivacaine and bupivacaine, could induce apoptosis of rabbit annulus fibrosus (AF) cells in vitro and further to explore the possible underlying mechanism.

METHODS

Rabbit AF cells at second passage were treated with saline solution and various concentrations of LAs. Apoptosis of AF cells were examined by cell counting kit-8 (CCK-8), Annexin V assays, Hoechst 33342 staining, and Caspase-3, -9 activity assays. The expression of apoptosis-related markers was detected by real-time PCR (RT-PCR) and Western Blot. The JC-1 staining was used to evaluate the change of mitochondrial membrane potential (MMP). Moreover, the levels of reactive oxygen species (ROS) were determined with fluorescent probe DCFH-DA.

RESULTS

The results of flow cytometry indicated that LAs could induce apoptosis of rabbit AF cells in a dose-dependent manner. Apoptosis was confirmed by cell morphology, condensed nuclei and activation of Caspase-3 and -9. In addition, the molecular data showed that LAs could significantly up-regulate the expression of Bax, accompanied by a significant down-regulation of Bcl-2 expression. Furthermore, we also observed that LAs resulted in alteration of MMP and accumulation of intracellular ROS in AF cells. Blockade of ROS production by N-acetyl-l-cysteine (NAC) inhibited LAs-induced apoptosis.

CONCLUSIONS

These findings suggest that LAs in clinically relevant concentrations could induce apoptosis of rabbit AF cells in vitro, and the mitochondrial pathway was, at least in part, involved in the LAs-mediated apoptosis. Further investigations focusing on the potential cytotoxicity of LAs on IVD cells are needed.

In vitro myotoxic effects of bupivacaine on rhabdomyosarcoma cells, immortalized and primary muscle cells

BACKGROUND

Rhabdomyosarcoma is a rare malignant skeletal muscle tumor. It mainly occurs in children and young adults and has an unsatisfactory prognosis. Prior studies showed a direct myotoxic effect of bupivacaine on differentiated muscle cells in vitro and in vivo. Exact mechanisms of this myotoxicity are still not fully understood, but a myotoxic effect on malignant muscle tumor cells has not been examined so far. Thus, the aim of this study was to examine if bupivacaine has cytotoxic effects on rhabdomyosarcoma cells, immortalized muscle cells and differentiated muscle cells.

METHODS

Cell lines of rhabdomyosarcoma cells, immortalized muscle cells and differentiated muscle cells were established. After microscopic identification, cells were exposed to various concentrations of bupivacaine (500, 1,000, 1,750, 2,500 and 5,000 ppm) for 1 and 2 h, respectively. 24 and 28 h after incubation the cultures were stained with propidium iodid and analyzed by flow cytometry. The fraction of dead cells was calculated for each experiment and the concentration with 50% cell survival (IC50) was computed. Cell groups as well as incubation and recovery time were compared (ANOVA/Bonferroni p < 0.01).

RESULTS

The total number of cultured cells was similar for the different local anesthetics and examined concentrations. Increasing concentrations of bupivacaine led to a decrease in survival of muscle cells. IC50 was highest for immortalized cells, followed by rhabdomyosarcoma cells and differentiated cells. Exposure time, but not recovery time, had an influence on survival.

CONCLUSION

Bupivacaine has clear but different cytotoxic effects on various muscle cell types in vitro. Differentiated primary cells seem to be more vulnerable than tumor cells possibly because of more differentiated intracellular structures.

The causes of drug-induced muscle toxicity

PURPOSE OF REVIEW

Clinically identified myopathies are frequently a consequence of medication toxicities. However, recognizing drug-induced myopathies is sometimes difficult. Developing a greater understanding of the underlying mechanisms of drug-induced muscle toxicity will promote enhanced awareness and recognition, and improved management of these syndromes.

RECENT FINDINGS

The adverse impact of certain drugs on muscle metabolism, muscle cell atrophy, and myocyte apoptosis is increasingly clear. Glucocorticoids impair glucose handling and directly promote protein catabolism. Statins impair mitochondrial function and alter intracellular signaling proteins, which can lead to myocyte apoptosis. Alternatively, statins can induce an autoimmune necrotizing myositis. Several medications impair autophagy, thus limiting access to the needed glycogen stores.

SUMMARY

This review provides an overview of the main underlying mechanisms of drug-induced myopathies. These myopathies will most often be related to a drug's ability to alter metabolism and protein balance, induce necrosis, or impair autophagy.

Bupivacaine induces apoptosis through caspase-dependent and -independent pathways in canine mammary tumor cells

Local anesthetics have been reported to induce apoptosis in various cell lines. In this study, we showed that bupivacaine also induced apoptosis in DTK-SME cells, a vimentin(+)/AE1(+)/CK7(+)/HSP27(+), tumorigenic, immortalized, canine mammary tumor cell line. Bupivacaine induced apoptosis in DTK-SME cells in a time- and concentration-dependent manner. Apoptosis-associated morphological changes, including cell shrinkage and rounding, chromatin condensation, and formation of apoptotic bodies, were observed in the bupivacaine-treated DTK-SME cells. Apoptosis was further confirmed with annexin V staining, TUNEL staining, and DNA laddering assays. At the molecular level, the activation of caspases-3, -8, and -9 corresponded well to the degree of DNA fragmentation triggered by bupivacaine. We also demonstrated that the pan-caspase inhibitor, z-VAD-fmk, only partially inhibited the apoptosis induced by bupivacaine. Moreover, treated cells increased expression of endonuclease G, a death effector that acts independently of caspases. Our data suggested that bupivacaine-induced apoptosis occurs through both caspase-dependent and caspase-independent apoptotic pathways.

Impaired Autophagosome Clearance Contributes to Local Anesthetic Bupivacaine-induced Myotoxicity in Mouse Myoblasts

Background:

The current study examined the role(s) of autophagy in myotoxicity induced by bupivacaine in mouse myoblast C2c12 cells.

Methods:

C2c12 cells were treated with bupivacaine. Myotoxicity was evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay (n = 3 to 30), live/dead assay (n = 3 to 4), and morphological alterations (n = 3). Autophagosome formation was reflected by microtubule-associated protein light chain 3 conversion (n = 4 to 12) and light chain 3 punctation (n = 4 to 5). Autophagosome clearance was evaluated by p62 protein level (n = 4) and autolysosomes generation (n = 3).

Results:

Bupivacaine induced significant cell damage. Notably, there was a significant increase in autophagosome generation as evidenced by light chain 3 puncta formation (72.7 ± 6.9 vs. 2.1 ± 1.2) and light chain 3 conversion (2.16 ± 0.15 vs. 0.33 ± 0.04) in bupivacaine-treated cells. Bupivacaine inactivated the protein kinase B/mammalian target of rapamycin/p70 ribosomal protein S6 kinase signaling. However, cellular levels of p62 protein were significantly increased upon bupivacaine treatment (1.29 ± 0.15 vs. 1.00 ± 0.15), suggesting that the drug impaired autophagosome clearance. Further examination revealed that bupivacaine interrupted autophagosome–lysosome fusion (10.87% ± 1.48% vs. 32.94% ± 4.22%). Administration of rapamycin increased autophagosome clearance and, most importantly, improved the survival in bupivacaine-treated cells. However, knockdown of autophagy-related protein 5 (atg5) exacerbated bupivacaine-induced impairment of autophagosome clearance and myotoxicity.

Conclusions:

The data suggest that autophagosome formation was induced as a stress response mechanism after bupivacaine challenge; however, autophagosome clearance was impaired due to inadequate autophagosome–lysosome fusion. Therefore, impairment of autophagosome clearance appears to be a novel mechanism underlying bupivacaine-induced myotoxicity.

Photo-induction and automated quantification of reversible mitochondrial permeability transition pore opening in primary mouse myotubes

Opening of the mitochondrial permeability transition pore (mPTP) is involved in various cellular processes including apoptosis induction. Two distinct states of mPTP opening have been identified allowing the transfer of molecules with a molecular weight <1500 Da or <300 Da. The latter state is considered to be reversible and suggested to play a role in normal cell physiology. Here we present a strategy combining live-cell imaging and computer-assisted image processing allowing spatial visualization and quantitative analysis of reversible mPTP openings ("ΔΨ flickering") in primary mouse myotubes. The latter were stained with the photosensitive cation TMRM, which partitions between the cytosol and mitochondrial matrix as a function of mitochondrial membrane potential (ΔΨ). Controlled illumination of TMRM-stained primary mouse myotubes induced ΔΨ flickering in particular parts of the cell ("flickering domains"). A novel quantitative automated analysis was developed and validated to detect and quantify the frequency, size, and location of individual ΔΨ flickering events in myotubes.

Increased levels of urinary phenylacetylglycine associated with mitochondrial toxicity in a model of drug-induced phospholipidosis

BACKGROUND

Phospholipidosis (PLD) is a lysosomal storage disorder induced by a class of cationic amphiphilic drugs. However, drug-induced PLD is reversible. Evidence of PLD from animal studies with some compounds has led to discontinuation of development. Regulatory authorities are likely to request additional studies when PLD is linked to toxicity.

OBJECTIVE

We conducted a trial to investigate urinary phenylacetylglycine (uPAG) as a biomarker for PLD.

MATERIALS AND METHODS

Five groups of 12 male Wistar rats were dosed once with vehicle, 300 mg/kg or 1500 mg/kg of compound A (known to induce PLD), or 300 mg/kg or 1000 mg/kg of compound B (similar structure, but does not induce PLD) to achieve similar plasma exposures. Following dosing, urine and blood samples underwent nuclear magnetic resonance (NMR), proteomic, and biochemical analyses. Necropsies were performed at 48 and 168 h, organ histopathology evaluated, and gene expression in liver analyzed by microarray. Electron microscopic examination of peripheral lymphocytes was performed.

RESULTS

For compound A, uPAG increased with dose, correlating with lamellar inclusion bodies formation in peripheral lymphocytes. NMR analysis showed decreased tricarboxylic acid cycle intermediates, inferring mitochondrial toxicity. Mitochondrial dysfunction was suggested by uPAG increase, resulting from a switch to anaerobic metabolism or disruption of the urea cycle.

DISCUSSION AND CONCLUSION

uPAG shows utility as a noninvasive biomarker for mitochondrial toxicity associated with drug-induced PLD, providing a mechanistic hypothesis for toxicity associated with PLD likely resulting from combined direct and indirect mitochondrial toxicity via impairment of the proton motor force and alteration of fatty acid catabolism.

Comparison of toxicity effects of ropivacaine, bupivacaine, and lidocaine on rabbit intervertebral disc cells in vitro

BACKGROUND CONTEXT

It has been shown that bupivacaine, the most commonly used local anesthetic to relieve or control pain in interventional spine procedures, is cytotoxic to intervertebral disc (IVD) cells in vitro. However, some other common local anesthetics, such as ropivacaine and lidocaine, are also frequently used in the treatment of spine-related pain, and the potential effects of these agents remain unclear.

PURPOSE

The purpose of this study was to evaluate the effect of various local anesthetics on rabbit IVD cells in vitro and further compare the cytotoxicity of ropivacaine, bupivacaine, lidocaine, and saline solution control.

STUDY DESIGN

Controlled laboratory study.

SUBJECTS

Rabbit annulus fibrosus (AF) and nucleus pulposus (NP) cells were isolated from Japanese white rabbits.

METHODS

Both AF and NP cells at the second generation maintained in monolayer were exposed to various concentrations of local anesthetics (eg, bupivacaine) or different durations of exposure and evaluated for cell viability by use of cell counting kit-8 (CCK-8). In addition, to compare the cytotoxicity of ropivacaine, bupivacaine, lidocaine, and saline solution control in commercial concentration, the viability was analyzed by flow cytometry after 60-minute exposure, and the morphologic changes were observed by the phase-contrast microscopy. Apoptosis and necrosis of IVD cells were confirmed by using fluorescence microscopy with double staining of Hoechst 33342 and propidium iodide.

RESULTS

Rabbit IVD cell death demonstrated a time and dose dependence in response to bupivacaine and lidocaine. However, ropivacaine only exerted a significant time-dependent effect on IVD cells. There was no significant difference in IVD viability after treatment with different doses of ropivacaine. In addition, the results showed that lidocaine was the most toxic of the three local anesthetics and that ropivacaine presented less cytotoxicity than lidocaine and bupivacaine. Fluorescence microscopy also confirmed that the short-term toxic effect of local anesthetics on both AF and NP cells was mainly caused by necrosis rather than apoptosis.

CONCLUSIONS

Results show that bupivacaine and lidocaine decrease cell viability in rabbit IVD cells in a dose- and time-dependent manner. All local anesthetics should be avoided if at all possible. Ropivacaine may be a choice if necessary, but it is also toxic. The increase in cell death is more related with cell necrosis rather than cell apoptosis. If these results can be corroborated in tissue explant models or animal studies, caution regarding diagnosing, treating, and controlling spine-related pain with local anesthetics is prompted.