Cell cycle activation contributes to isoflurane-induced neurotoxicity in the developing brain and the protective effect of CR8

Research progress on molecular mechanisms of general anesthetic-induced neurotoxicity and cognitive impairment in the developing brain

General anesthetics-induced neurotoxicity and cognitive impairment in developing brains have become one of the current research hotspots in the medical science community. The underlying mechanisms are complex and involve various related molecular signaling pathways, cell mediators, autophagy, and other pathological processes. However, few drugs can be directly used to treat neurotoxicity and cognitive impairment caused by general anesthetics in clinical practice. This article reviews the molecular mechanism of general anesthesia-induced neurotoxicity and cognitive impairment in the neonatal brain after surgery in the hope of providing critical references for the treatments of clinical diseases.

Longitudinal impact on rat cardiac tissue transcriptomic profiles due to acute intratracheal inhalation exposures to isoflurane

Isoflurane (ISO) is a widely used inhalation anesthetic in experiments with rodents and humans during surgery. Though ISO has not been reported to impart long-lasting side effects, it is unknown if ISO can influence gene regulation in certain tissues, including the heart. Such changes could have important implications for use of this anesthetic in patients susceptible to heart failure/other cardiac abnormalities. To test if ISO could alter gene regulation/expression in heart tissues, and if such changes were reversible, prolonged, or late onset with time, SHR (spontaneously hypertensive) rats were exposed by intratracheal inhalation to a 97.5% air/2.5% ISO mixture on two consecutive days (2 hr/d). Control rats breathed filtered air only. On Days 1, 30, 240, and 360 post-exposure, rat hearts were collected and total RNA was extracted from the left ventricle for global gene expression analysis. The data revealed differentially-expressed genes (DEG) in response to ISO (compared to naïve control) at all post-exposure timepoints. The data showed acute ISO exposures led to DEG associated with wounding, local immune function, inflammation, and circadian rhythm regulation at Days 1 and 30; these effects dissipated by Day 240. There were other significantly-increased DEG induced by ISO at Day 360; these included changes in expression of genes associated with cell signaling, differentiation, and migration, extracellular matrix organization, cell-substrate adhesion, heart development, and blood pressure regulation. Examination of consistent DEG at Days 240 and 360 indicated late onset DEG reflecting potential long-lasting effects from ISO; these included DEG associated with oxidative phosphorylation, ribosome, angiogenesis, mitochondrial translation elongation, and focal adhesion. Together, the data show acute repeated ISO exposures could impart variable effects on gene expression/regulation in the heart. While some alterations self-resolved, others appeared to be long-lasting or late onset. Whether such changes occur in all rat models or in humans remains to be investigated.

Cell cycle activation contributes to isoflurane-induced neurotoxicity in the developing brain and the protective effect of CR8

AIMS

It is well established that exposure of common anesthetic isoflurane in early life can induce neuronal apoptosis and long-lasting cognitive deficit, but the underlying mechanisms were not well understood. The cell cycle protein Cyclin B1 plays an important role in the survival of postmitotic neurons. In the present study, we investigated whether cyclin B1-mediated cell cycle activation pathway is a contributing factor in developmental isoflurane neurotoxicity.

METHODS

Postnatal day 7 mice were exposed to 1.2% isoflurane for 6 hours. CR8 (a selective inhibitor of cyclin-dependent kinases) was applied before isoflurane treatment. Brain samples were collected 6 hours after discontinuation of isoflurane, for determination of neurodegenerative biomarkers and cell cycle biomarkers.

RESULTS

We found that isoflurane exposure leads to upregulated expression of cell cycle-related biomarkers Cyclin B1, Phospho-CDK1(Thr-161), Phospho-n-myc and downregulated Phospho-CDK1 (Tyr-15). In addition, isoflurane induced increase in Bcl-xL phosphorylation, cytochrome c release, and caspase-3 activation that resulted in neuronal cell death. Systemic administration of CR8 attenuated isoflurane-induced cell cycle activation and neurodegeneration.

CONCLUSION

These findings suggest the role of cell cycle activation to be a pathophysiological mechanism for isoflurane-induced apoptotic cell death and that treatment with cell cycle inhibitors may provide a possible therapeutic target for prevention of developmental anesthetic neurotoxicity.