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

Apnea of prematurity induces short and long-term development-related transcriptional changes in the murine cerebellum

Apnea of prematurity (AOP) affects more than 50% of preterm infants and leads to perinatal intermittent hypoxia (IH) which is a major cause of morbimortality worldwide. At birth, the human cerebellar cortex is still immature, making it vulnerable to perinatal events. Additionally, studies have shown a correlation between cerebellar functions and the deficits observed in children who have experienced AOP. Yet, the cerebellar alterations underpinning this link remain poorly understood. To gain insight into the involvement of the cerebellum in perinatal hypoxia-related consequences, we developed a mouse model of AOP. Our previous research has revealed that IH induces oxidative stress in the developing cerebellum, as evidenced by the over-expression of genes involved in reactive oxygen species production and the under-expression of genes encoding antioxidant enzymes. These changes suggest a failure of the defense system against oxidative stress and could be responsible for neuronal death in the cerebellum. Building upon these findings, we conducted a transcriptomic study of the genes involved in the processes that occur during cerebellar development. Using real-time PCR, we analyzed the expression of these genes at different developmental stages and in various cell types. This enabled us to pinpoint a timeframe of vulnerability at P8, which represents the age with the highest number of downregulated genes in the cerebellum. Furthermore, we discovered that our IH protocol affects several molecular pathways, including proliferation, migration, and differentiation. This indicates that IH can impact the development of different cell types, potentially contributing to the histological and behavioral deficits observed in this model. Overall, our data strongly suggest that the cerebellum is highly sensitive to IH, and provide valuable insights into the cellular and molecular mechanisms underlying AOP. In the long term, these findings may contribute to the identification of novel therapeutic targets for improving the clinical management of this prevalent pathology.

Oxidative DNA Damage-induced PARP-1-mediated Autophagic Flux Disruption Contributes to Bupivacaine-induced Neurotoxicity During Pregnancy

OBJECTIVE

Severe neurologic complications after spinal anesthesia are rare but highly distressing, especially in pregnant women. Bupivacaine is widely used in spinal anesthesia, but its neurotoxic effects have gained attention.

METHODS

Furthermore, the etiology of bupivacaine-mediated neurotoxicity in obstetric patients remains unclear. Female C57BL/6 mice were intrathecally injected with 0.75% bupivacaine on the 18th day of pregnancy. We used immunohistochemistry to examine DNA damage after bupivacaine treatment in pregnant mice and measured γ-H2AX (Ser139) and 8-OHdG in the spinal cord. A PARP-1 inhibitor (PJ34) and autophagy inhibitor (3-MA) were administered with bupivacaine in pregnant mice. Parp-1flox/flox mice were crossed with Nes-Cre transgenic mice to obtain neuronal conditional knockdown mice. Then, LC3B and P62 staining were performed to evaluate autophagic flux in the spinal cords of pregnant wild-type (WT) and Parp-1-/- mice. We performed transmission electron microscopy (TEM) to evaluate autophagosomes.

RESULTS

The present study showed that oxidative stress-mediated DNA damage and neuronal injury were increased after bupivacaine treatment in the spinal cords of pregnant mice. Moreover, PARP-1 was significantly activated, and autophagic flux was disrupted. Further studies revealed that PARP-1 knockdown and autophagy inhibitors could alleviate bupivacaine-mediated neurotoxicity in pregnant mice.

CONCLUSION

Bupivacaine may cause neuronal DNA damage and PARP-1 activation in pregnant mice. PARP-1 further obstructed autophagic flux and ultimately led to 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.