Lin28b and Sox2 regulate anesthesia-induced neural degeneration in neural stem cell derived neurons

A "toxic window" study on the hippocampal development of mice offspring exposed to azithromycin at different doses, courses, and time during pregnancy

BACKGROUND

Azithromycin, one of the new-generation macrolides, is an effective medicine for the treatment of mycoplasma infection during pregnancy. Epidemiological studies have reported adverse pregnancy outcomes with prenatal azithromycin exposure (PAzE). However, the effect of PAzE on fetal hippocampal development is unclear. This study aimed to explore the effects and potential mechanism of PAzE-induced fetal hippocampal development at different doses, courses, and time.

METHOD

Pregnant mice were administered azithromycin by gavage at different doses (50, 100 or 200 mg/kg.d), different courses (gestational day (GD)15-17 for three consecutive days, or GD17 once a day) and different time (GD10-12, GD15-17).

RESULTS

Compared with the control group, morphological development damage of the fetal hippocampus was observed in the PAzE group, with a dysbalance in neuronal proliferation and apoptosis, decreased expression of the neuronal-specific marker Snap25, NeuN, PSD95 and Map2, increased expression of the glial-specific marker Iba1, GFAP, and S-100β, and decreased expression of P2ry12. The PAzE-induced hippocampal developmental deficiency varied based on different doses, courses, and time, and the developmental toxicity was most significant in the late pregnancy, high dose, multi-course group (AZHT). The significant reduction of SOX2 and Wnt, which were related to regulation of neural progenitor cells (NPCs) proliferation in PAzE fetus compared with the control group indicated that the SOX2/Wnt signaling may be involved in PAzE-induced hippocampal developmental toxicity.

CONCLUSION

In this study, PAzE was associated with hippocampal developmental toxicity in a variety of nerve cells. Hippocampal developmental toxicity due to azithromycin was most significant in the late pregnancy, high-dose (equivalent to maximum clinical dose) and multi-course group (AZHT). The findings provide an experimental and theoretical foundation for guiding the sensible use of medications during pregnancy and effectively assessing the risk of fetal hippocampal developmental toxicity.

Longitudinal effects of ketamine on cell proliferation and death in the CNS of zebrafish

Zebrafish is known for its widespread neurogenesis and regenerative capacity, as well as several biological advantages, which turned it into a relevant animal model in several areas of research, namely in toxicological studies. Ketamine is a well-known anesthetic used both in human as well as veterinary medicine, due to its safety, short duration and unique mode of action. However, ketamine administration is associated with neurotoxic effects and neuronal death, which renders its use on pediatric medicine problematic. Thus, the evaluation of ketamine effects administration at early stages of neurogenesis is of pivotal importance. The 1-4 somites stage of zebrafish embryo development corresponds to the beginning of segmentation and formation of neural tube. In this species, as well as in other vertebrates, longitudinal studies are scarce, and the evaluation of ketamine long-term effects in adults is poorly understood. This study aimed to assess the effects of ketamine administration at the 1-4 somites stage, both in subanesthetic and anesthetic concentrations, in brain cellular proliferation, pluripotency and death mechanisms in place during early and adult neurogenesis. For that purpose, embryos at the 1-4 somites stage (10,5hours post fertilization - hpf) were distributed into study groups and exposed for 20minutes to ketamine concentrations at 0.2/0.8mg/mL. Animals were grown until defined check points, namely 50 hpf, 144 hpf and 7 months adults. The assessment of the expression and distribution patterns of proliferating cell nuclear antigen (PCNA), of sex-determining region Y-box 2 (Sox 2), apoptosis-inducing factor (AIF) and microtubule-associated protein 1 light chain 3 (LC3) was performed by Western-blot and immunohistochemistry. The results evidenced the main alterations in 144 hpf larvae, namely in autophagy and in cellular proliferation at the highest concentration of ketamine (0.8mg/mL). Nonetheless, in adults no significant alterations were seen, pointing to a return to a homeostatic stage. This study allowed clarifying some of the aspects pertaining the longitudinal effects of ketamine administration regarding the CNS capacity to proliferate and activate the appropriate cell death and repair mechanisms leading to homeostasis in zebrafish. Moreover, the results indicate that ketamine administration at 1-4 somites stage in the subanesthetic and anesthetic concentrations despite some transitory detrimental effects at 144 hpf, is long-term safe for CNS, which are newly and promising results in this research field.

Research progress on the effects and mechanisms of anesthetics on neural stem cells

Exposure to anesthetic drugs has been proven to seriously affect developing animals in terms of neural stem cells' (NSCs') proliferation, differentiation, and apoptosis. This can severely hamper the development of physiological learning and memory skills. Studies on the effects of anesthetics on NSCs' proliferation and differentiation are thus reviewed here, with the aim to highlight which specific drug mechanisms are the least harmful to NSCs. PubMed has been used as the preferential searching database of relevant literature to identify studies on the effects and mechanisms of NSCs' proliferation and differentiation. It was concluded that propofol and sevoflurane may be the safest options for NSCs during pregnancy and in pediatric clinical procedures, while dexmedetomidine has been found to reduce opioid-related damage in NSCs. It was also found that the growth environment may impact neurodevelopment even more than narcotic drugs. Nonetheless, the current scientific literature available further highlights how more extensive clinical trials are absolutely required for corroborating the conclusion drawn here.