Anesthetic sevoflurane causes neurotoxicity differently in neonatal naïve and Alzheimer disease transgenic mice

2-Deoxy-D-glucose attenuates isoflurane-induced cytotoxicity in an in vitro cell culture model of H4 human neuroglioma cells

BACKGROUND

β-Amyloid protein (Aβ) accumulation and caspase activation have been shown to contribute to Alzheimer disease neuropathogenesis. Aβ is produced from amyloid precursor protein through proteolytic processing by aspartyl protease β-site amyloid precursor protein-cleaving enzyme (BACE). The inhaled anesthetic isoflurane has been shown to induce caspase activation and increase levels of BACE and Aβ. However, the underlying mechanisms and interventions of the isoflurane-induced neurotoxicity remain largely to be determined. The glucose analog 2-deoxy-d-glucose (2-DG) has neuroprotective effects. Therefore, we sought to determine whether 2-DG can reduce caspase-3 activation and the increase in the levels of BACE and reactive oxygen species (ROS) induced by isoflurane.

METHODS

H4 human neuroglioma cells were treated with saline or 2-DG (5 mM) for 1 hour followed by a control condition or 2% isoflurane for 6 hours. The levels of caspase-3 cleavage (activation), BACE, cytosolic calcium, and ROS were determined. Two-way analysis of variance was used to assess the interactions of 2-DG and isoflurane on caspase-3 activation, and levels of BACE and ROS.

RESULTS

In H4 human neuroglioma cells, 2-DG reduced the caspase-3 activation (477% vs 186%, F = 8.68; P = 0.019) and the increase in BACE levels (345% vs 123%, F = 42.24; P = 0.0002) induced by isoflurane. 2-DG decreased the levels of cytosolic calcium and ROS (100% vs 66%, F = 1.94; P = 0.014).

CONCLUSIONS

These results suggest that 2-DG may decrease oxidative stress and increase cytosolic calcium levels, thus attenuating isoflurane-induced neurotoxicity.

Bioenergetic homeostasis decides neuroprotection or neurotoxicity induced by volatile anesthetics: a uniform mechanism of dual effects

The commonly used volatile anesthetic isoflurane or sevoflurane has been shown to be both neuroprotective and neurotoxic in various cell cultures and animal models. Some possible mechanisms have been raised to elucidate volatile anesthetics-induced neuroprotection or neurotoxicity, respectively. However, none of these can reconcile the linkage between their dual effects. Similar to volatile anesthetics, some drugs and nonpharmacological factors also can produce neuroprotection and neurotoxicity, which is associated with bioenergetic metabolism of neuronal cells. Here we present a uniform mechanism, bioenergetic homeostasis hypothesis, to explain neuroprotection and neurotoxicity induced by volatile anesthetics. The numerous evidences have shown that volatile anesthetics could affect mitochondrial electron transport complexes and glycolysis related pathways in cells, which could alter intracellular calcium homeostasis, ROS production and adenosine triphosphate (ATP) synthesis. Duration and concentration of exposure to volatile anesthetics could play a role on severity of bioenergy inhibition. Mild bioenergetic metabolism inhibition trigger signaling events involving preconditioning on neurons, and further bioenergy impairment could lead to neuronal cellular apoptosis, inhibition of neurogenesis and elevated β-Secretase, which drive pathogenesis of neurodegeneration.

Minocycline may be useful to prevent/treat postoperative cognitive decline in elderly patients

Postoperative cognitive dysfunction (POCD) is reported to occur frequently after all types especially cardiac surgery in elderly patients. It can be short-term or long-term and some cases even develop into Alzheimer's disease (AD). Although multi-risk factors associated with POCD have been identified, the etiology and pathophysiological mechanisms of this surgical complication remain elusive. Therefore, developing strategies for preventing or treating POCD is still challenging. However, increasing evidence suggests that central and systemic inflammation triggered by surgery likely plays a fundamental role in POCD developing and progression. Minocycline, a tetracycline derivative with anti-inflammatory properties, has been shown to be effective in treating neuroinflammatory related conditions or neurodegenerative diseases such as AD, Parkinson's disease, Huntington's disease. Considering that inflammation may be a potential factor of POCD and minocycline is effective in improving cognitive dysfunction induced by inflammation, we hypothesize that minocycline may be useful to treat/prevent the POCD development after surgery in elderly patients.

Brief review: anesthetic neurotoxicity in the elderly, cognitive dysfunction and Alzheimer's disease

PURPOSE

Postoperative cognitive decline in the elderly has emerged as a major health concern. In addition, there is a growing interest in the potential relationship between general anesthetic exposure and the onset and progression of Alzheimer's disease (AD). The available evidence of a possible association between anesthesia, surgery, and long-term cognitive effects, including AD, deserves consideration. In this review, we summarize the evidence for anesthesia-induced neurotoxicity in the elderly, while highlighting the limitations of existing data, and we put the literature into perspective for the clinician.

PRINCIPAL FINDINGS

A growing body of evidence suggests that general anesthetics may be neurotoxic to both young and aging brains. Much of the evidence originates from in vitro and in vivo studies with cells, rodents, and nonhuman primates. Despite the animal data suggesting a relationship between anesthesia and neurotoxicity in the elderly, a definitive link remains elusive in humans.

CONCLUSIONS

The possible relation between anesthetic neurotoxicity, postoperative cognitive dysfunction, and AD remains elusive. It remains unclear whether postoperative cognitive decline in the elderly is related more to perioperative stress and related medical co-morbidities.

CNS animal fMRI in pain and analgesia

Animal imaging of brain systems offers exciting opportunities to better understand the neurobiology of pain and analgesia. Overall functional studies have lagged behind human studies as a result of technical issues including the use of anesthesia. Now that many of these issues have been overcome including the possibility of imaging awake animals, there are new opportunities to study whole brain systems neurobiology of acute and chronic pain as well as analgesic effects on brain systems de novo (using pharmacological MRI) or testing in animal models of pain. Understanding brain networks in these areas may provide new insights into translational science, and use neural networks as a "language of translation" between preclinical to clinical models. In this review we evaluate the role of functional and anatomical imaging in furthering our understanding in pain and analgesia.