OGG1 Involvement in High Glucose-Mediated Enhancement of Bupivacaine-Induced Oxidative DNA Damage in SH-SY5Y Cells

Defective autophagy contributes to bupivacaine-induced aggravation of painful diabetic neuropathy in db/db mice

Current evidence suggests that hyperactivated or impaired autophagy can lead to neuronal death. The effect of local anesthetics on painful diabetic neuropathy (PDN) and the role of autophagy in the above pathological process remain unclear, warranting further studies. So, PDN models were established by assessing the paw withdrawal threshold (PWT) and paw withdrawal latency (PWL) in leptin gene-mutation (db/db) mice. Wild type (WT) and PDN mice received intrathecal 0.75% bupivacaine or/with intraperitoneal drug treatment (rapamycin or bafilomycin A1). Subsequently, the PWT and PWL were measured to assess hyperalgesia at 6 h, 24 h, 30 h, and 48 h after intrathecal bupivacaine. Also, sensory nerve conduction velocity (SNCV) and motor nerve conduction velocity (MNCV) were measured before and 48 h after intrathecal bupivacaine treatment. The spinal cord tissue of L4-L6 segments and serum were harvested to evaluate the change of autophagy, oxidative stress, oxidative injury, and apoptosis. We found that bupivacaine induced the activation of autophagy but did not affect the pain threshold, SNCV and MNCV in WT mice at predefined time points. Conversely, bupivacaine lowered autophagosome generation and degradation, slowed SNCV and aggravated spinal dorsal horn neuron oxidative injury and hyperalgesia in PDN mice. The autophagy activator (rapamycin) could decrease spinal dorsal horn neuron oxidative injury, alleviate the alterations in SNCV and hyperalgesia in bupivacaine-treated PDN mice. Meanwhile, the autophagy inhibitor (bafilomycin A1) could exacerbate spinal dorsal horn neuron oxidative injury, the alterations in SNCV and hyperalgesia in bupivacaine-treated PDN mice. Our results showed that bupivacaine could induce defective autophagy, slowed SNCV and aggravate spinal dorsal horn neuron oxidative injury and hyperalgesia in PDN mice. Restoring autophagy may represent a potential therapeutic approach against nerve injury in PDN patients with local anesthesia and analgesia.

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.

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.

KLF9 regulates PRDX6 expression in hyperglycemia-aggravated bupivacaine neurotoxicity

BACKGROUND

Neurotoxicity induced by local anesthetics (LAs) is potentially life threatening, especially for patients with underlying diseases like diabetes. The anesthetic bupivacaine (Bup) has been reported to induce neurotoxicity mediated by reactive oxygen species (ROS), which is aggravated by hyperglycemia. Krüppel-like factor 9 (KLF9), an axon growth-suppressing transcription factor, plays a key role in neuronal maturation and promotes oxidative stress. This study was designed to investigate whether and how KLF9 regulates ROS levels related to LA neurotoxicity under hyperglycemic conditions.

METHODS

Klf9/GFP ShRNA (LV Sh-Klf9) was used to achieve stable Klf9 knockdown in the SH-SY5Y cell line. KLF9-deficient and normal cells were cultured under normal or high-glucose (HG) culture conditions and then exposed to Bup. Cell viability, intracellular and mitochondrial ROS, and mitochondrial membrane potential (ΔΨm) were detected to examine the role of KLF9. Thereafter, KLF9-deficient and normal cells were pretreated with small-interfering RNA targeting peroxiredoxin 6 (siRNA-Prdx6) to determine if PRDX6 was the target protein in HG-aggravated Bup neurotoxicity.

RESULTS

The mRNA and protein levels of KLF9 were increased after Bup and hyperglycemia treatment. In addition, cell survival and mitochondrial function were significantly improved, and ROS production was decreased after Sh-Klf9 treatment compared with Sh-Ctrl. Furthermore, the expression of PRDX6 was suppressed by Bup in hyperglycemic cultures and was upregulated in the Sh-Klf9 group. Moreover, the protection provided by KLF9 deficiency for cell survival, the increase in ROS production in cells and mitochondria, and the disruption of mitochondrial function were abolished by Prdx6 knockdown.

CONCLUSIONS

The results of this study demonstrated that hyperglycemia aggravated Bup neurotoxicity by upregulating KLF9 expression, which repressed the antioxidant PRDX6 and led to mitochondrial dysfunction, ROS burst, and cell death. Understanding this mechanism may, thus, offer valuable insights for the prevention and treatment of neurotoxicity induced by LAs, especially in diabetic patients.

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.

Metformin prevented high glucose-induced endothelial reactive oxygen species via OGG1 in an AMPKα-Lin-28 dependent pathway

AIMS

Metformin improves vascular function in obese type 2 diabetic patients. 8-Oxoguanine glycosylase (OGG1) is a main DNA glycosylase that is involved in vascular complications in various diseases. However, whether metformin suppresses endothelial reactive species oxygen production via the OGG1 pathway is unclear.

MAIN METHODS

Human umbilical vein endothelial cells (HUVECs) were exposed to HG (high glucose) with or without metformin. OGG1 and AMPKα levels were measured after metformin treatment, while HG-induced ROS were measured by a DHE probe.

KEY FINDINGS

Metformin reduced HG-induced endothelial ROS by upregulating OGG1. Additionally, OGG1 protein expression was dependent on its mRNA stability, which was reversed by genetic inhibition of AMPKα and Lin-28. Furthermore, the effect of OGG1 on HG-induced ROS was partially dependent on the AHR/Nrf2 pathway in HUVECs.

SIGNIFICANCE

These results suggested that metformin modulated HG-induced endothelial ROS via the AMPKα/Lin-28/OGG1 pathway.

The effect of astaxanthin supplementation on the post-thaw quality of dog semen

Astaxanthin is a member of the carotenoid family well known for its anti-cancer, anti-diabetic, anti-inflammatory and antioxidant nature. This study was designed to investigate the effects of astaxanthin supplementation of the extender (buffer 2) on post-thaw dog semen quality. Semen from four healthy dogs was collected by digital manipulation twice a week. The ejaculates were pooled, washed, divided into four equal aliquots, diluted with the extender supplemented with different concentrations of astaxanthin (0, 0.5, 1 and 2 µM) and cryopreserved. The results showed that 1 µM astaxanthin was the optimum concentration that led to significantly higher (p < .05) post-thaw motility, kinematic parameters and viability than the other groups. In comparison with the control group, sperm samples supplemented with 1 µM astaxanthin showed significantly higher (p < .05) sperm counts with intact membranes (55.7 ± 0.6% vs. 51.3 ± 0.9%), intact acrosome (58.4 ± 0.7% vs. 53.5 ± 0.6%), active mitochondria (54.9 ± 0.5% vs. 42.6 ± 0.6%) and normal chromatin (67.6 ± 0.9% vs. 61.7 ± 0.6%). Furthermore, astaxanthin-supplemented samples showed significantly lower expression levels (p < .05) of pro-apoptotic (BAX), oxidative induced DNA damage repair (OGG1), oxidative stress-related (ROMO1) genes and higher expression levels of anti-apoptotic (BCL2), and sperm acrosome-associated (SPACA3) genes compared to the control. Thus, supplementation of 1 µM astaxanthin in semen extender results in improved freeze-thaw sperm quality of the dog.

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.

Chronic administration of [Pyr1] apelin-13 attenuates neuropathic pain after compression spinal cord injury in rats

Apelin is an endogenous ligand for apelin receptor (APJ) with analgesic effect on visceral, analgesic and proanalgesic influences on acute pains in animal models. The purpose of this study was to determine the possible analgesic effects of [Pyr¹] apelin-13 on chronic pain after spinal cord injury (SCI) in rats. Animals were randomly divided into three major groups as intact, sham and SCI. The SCI group randomly allocated to four subgroups as no treatment, vehicle-treatment (normal saline: 10μl, intrathecally) and two subgroups with intrathecal injection (i.t) of 1μg and 5μg of [Pyr¹] apelin-13. After laminectomy at T6-T8 level, spinal cord compression injury was induced using an aneurysm clip. Vehicle or [Pyr¹] apelin-13 injected from day1 post SCI and continued for a week on a daily basis. Pain behaviors and locomotor activity were monitored up to 8weeks. At the end of the experiments, intracardial paraformaldehyde perfusion was made under deep anesthesia in some animals for histological and immunohistochemistry evaluations. Western blot technique was also done to detect caspase-3 in fresh spinal cord tissues. SCI decreased nociceptive thresholds and locomotor scores. Administration of [Pyr¹] apelin-13 (1μg and 5μg) improved locomotor activity and reduced pain symptoms, cavity size and caspase-3 levels. Results showed long-term beneficial effects of [Pyr¹] apelin-13 on neuropathic pain and locomotion. Therefore, we may suggest [Pyr¹] apelin-13 as a new option for further neuropathic pain research and a suitable candidate for ensuing clinical trials in spinal cord injury arena.

Spermine reduces reactive oxygen species levels and decreases cryocapacitation in canine sperm cryopreservation

The objective of this study was to determine the ability of spermine to act as an antioxidant in scavenging reactive oxygen species (ROS), maintaining sperm function and decreasing cryocapacitation after cryopreservation. Although motility did not increase with spermine treatment, values for membrane integrity were significantly increased (P < 0.05). Higher percentages of linearity and straightness with a lower amplitude of lateral head displacement (ALH) indicated that spermine inhibits hyperactivation. Concentrations of intracellular and extracellular ROS were decreased in the treatment group (P < 0.05). Higher expression of an anti-apoptotic gene (Bcl-2) and lower expression of a pro-apoptotic gene (Bax), together with decreased expression of the mitochondrial ROS modulator ROMO1, DNA repair due to oxidative damage (OGG1), spermine synthase (SMS), NADPH oxidase associated with motility (NOX5) and spermine amino oxidase (SMOX), all showed that 5.0 mM spermine treatment was beneficial to spermatozoa. Furthermore, the proportion of live spermatozoa with intact acrosomes after thawing in the treatment group was higher than in the control. After incubation in canine capacitating medium, numbers of live capacitated spermatozoa with reacted acrosomes were higher than in the control. Our results indicate that 5.0 mM spermine is an optimal concentration for maintaining sperm function, reducing ROS production, preventing apoptosis and adverse effects of cryocapacitation during canine sperm cryopreservation.