Xuezhao Cao

Postoperative cognitive deficits and neuroinflammation in the hippocampus triggered by surgical trauma are exacerbated in aged rats

Postoperative cognitive dysfunction (POCD) is characterized by the progressive deterioration of intellectual/cognitive function following surgery. It has been suggested that the senile brain, which characteristically expresses higher levels of central proinflammatory cytokines, interleukin (IL)-6, IL-1β, and tumor necrosis factor (TNF)-α, is more susceptible to additional insult following surgery. The authors of this study investigated the expression of central cytokines IL-1β, IL-6 and TNF-α and hippocampal glial cell activation in aged and adult rats following partial hepatectomy. Cognitive function was assessed in a reversal-learning version of the Morris water maze (MWM) before and after surgery. Hippocampal pro-inflammatory cytokines IL-1β, IL-6 and TNF-α and glial cell activation markers glial fibrillary acidic protein (GFAP) and S100β were measured at each time point; CD200 and CD200R were also measured to explore potential mechanisms of glial cell activation. Surgical trauma resulted in impairments in distance and latency only on postoperative day 1 (p<0.001, respectively) in adult rats. Aged rats exhibited impairments on day 1 (p<0.001) that persisted until postoperative day 3 (p=0.002 and p=0.001, respectively). All significant impairments paralleled upregulated cytokine IL-1β and IL-6 expression. Immunohistochemistry assay further showed more hippocampal glial cell activation in aged rats compared to that in adults. Overall, these findings suggest that surgical trauma, rather than anesthesia, resulted in cognitive function impairment potentiated by aging. Hippocampal pro-inflammatory cytokines and glial cell activation might mediate trauma-induced POCD.

Tau hyperphosphorylation is associated with memory impairment after exposure to 1.5% isoflurane without temperature maintenance in rats.

Background and objective There is increasing interest in studying the role of tau hyperphosphorylation associated with memory impairment. We examined the involvement of tau hyperphosphorylation in memory impairment after hypothermia following isoflurane anaesthesia in rats. Methods Adult rats were randomly divided into three groups: the control group received no treatment and others were subjected to 1.5% isoflurane anaesthesia with or without temperature control for 2 h. On the day before anaesthesia and on postanaesthetic days 1, 3 and 7, cognitive functions were assessed in a Y-maze test paradigm. To find the relationship between memory results and tau, we measured the site-specific phosphorylation of tau at Thr-205 and Ser-396 and the activity of protein phosphatase 2A within the hippocampus. Results The spatial learning and memory of animals with hypothermia were impaired at day 1 after anaesthesia, compared with nonanaesthetized rats. Anaesthesia and hypothermia led to tau hyperphosphorylation at the Thr-205 and Ser-396 epitopes in the hippocampus. There was no significant difference in the protein phosphatase 2A activity between the control and the postanaesthetic rat hippocampal samples, whereas nearly 45% protein phosphatase 2A inhibition was detected in the anaesthetized without temperature maintenance rat samples. Conclusion Our results indicate that tau phosphorylation is not a direct result of anaesthesia per se, but it is due to anaesthesia-induced hypothermia and this leads to the inhibition of phosphatase activity as well as tau hyperphosphorylation. Tau hyperphosphorylation is associated with the observed deficits in spatial learning and memory following anaesthesia in hypothermic rats.

Sevoflurane preconditioning ameliorates neuronal deficits by inhibiting microglial MMP-9 expression after spinal cord ischemia/reperfusion in rats

BackgroundMicroglia are the primary immune cells of the spinal cord that are activated in response to ischemia/reperfusion (IR) injury and release various neurotrophic and/or neurotoxic factors to determine neuronal survival. Among them, matrix metalloproteinase-9 (MMP-9), which cleaves various components of the extracellular matrix in the basal lamina and functions as part of the blood spinal cord barrier (BSCB), is considered important for regulating inflammatory responses and microenvironmental homeostasis of the BSCB in the pathology of ischemia. Sevoflurane has been reported to protect against neuronal apoptosis during cerebral IR. However, the effects of sevoflurane preconditioning on spinal cord IR injury remain unclear. In this study, we investigated the role of sevoflurane on potential genetic roles of microglial MMP-9 in tight junction protein breakdown, opening of the BSCB, and subsequent recruitment of microglia to apoptotic spinal cord neurons.ResultsThe results showed significant upregulation of MMP-9 in rats with IR-induced inflammation of the BSCB compared to that of the sham group, manifested as dysfunctional BSCB with increased Evans blue extravasation and reduced expression of occludin protein. Increased MMP-9 expression was also observed to facilitate invasion and migration of activated microglia, imaging as high Iba-1 expression, clustered to neurons in the injured spinal cord, as shown by double immunofluorescence, and increased proinflammatory chemokine production (CXCL10, CCL2). Further, sevoflurane preconditioning markedly improved motor function by ameliorating neuronal apoptosis, as shown by reduced TUNEL-positive cell counts and expression of cleaved caspase-3. These protective effects were probably responsible for downregulation of MMP-9 and maintenance of normal expression of occludin protein indicating BSCB integrity from inflammatory damage, which was confirmed by decreased protein levels of Iba-1 and MMP-9, as well as reduced production of proinflammatory chemokines (CXCL10, CCL2) and proinflammatory cytokines (IL-1β). Intrathecal injection of specific siRNAs targeting MMP-9 had similar protective effects to those of sevoflurane preconditioning.ConclusionsPreconditioning with 2.4% sevoflurane attenuated spinal cord IR injury by inhibiting recruitment of microglia and secretion of MMP-9; thus inhibiting downstream effects on inflammatory damage to BSCB integrity and neuronal apoptosis.

Vitamin D Improves Cognitive Function and Modulates Th17/Treg Cell Balance After Hepatectomy in Mice

It is known that surgery-induced tissue damage activates the peripheral immune system resulting in the release of inflammatory mediators and cognitive impairment in aged mice. Vitamin D has been shown to have immunomodulatory function, but the molecular basis for it has not been well understood. In this study, we mainly investigated the efficacy and mechanism of vitamin D against postoperative cognitive dysfunction (POCD). The treatment of C57BL mice with vitamin D significantly preserves postoperative cognitive function, markedly inhibits surgery-induced interleukin (IL)-17, IL-6, transforming growth factor beta (TGF-β), and retinoic acid-related orphan receptor (RORγt) production, and obviously induces IL-10 and forkhead box p3 (Foxp3) expression. These findings indicate that vitamin D amelioration of POCD is, to a large extent, due to inhibit inflammatory CD4_T cell lineage, T helper 17 (Th17) cells, accompanied with expansion in regulatory T cells (Treg cells), a subset of CD4_T cells that are important in inhibiting inflammation. Our results suggest that Th17 and Treg cell imbalance may play a role in the development of POCD. Vitamin D is useful in the control of inflammatory diseases.

Protective effects of lithium treatment for spatial memory deficits induced by tau hyperphosphorylation in splenectomized rats

1. Postoperative cognitive dysfunction has become more prevalent in recent years. We used a splenectomized rat model with postoperative spatial learning and memory deficits to investigate the role of tau hyperphosphorylation and glycogen synthase kinase‐3β (GSK‐3β) within the hippocampus.

Age exacerbates surgery-induced cognitive impairment and neuroinflammation in Sprague-Dawley rats: the role of IL-4

Age is the most prominent risk factor for the development of postoperative cognitive dysfunction. This study investigated the potential role of anti-inflammatory interleukin (IL)-4 in age-related differences of surgery-induced cognitive deficits and neuroinflammatory responses. Both adult and aged Sprague-Dawley male rats were subjected to partial hepatectomy or partial hepatectomy with a cisterna magna infusion of IL-4. On postoperative days 1, 3, and 7, the rats were subjected to a reversed Morris water maze test. Hippocampal IL-1β, IL-6, IL-4, and IL-4 receptor (IL-4R) were measured at each time point. Brain derived neurotrophic factor (BDNF), synaptophysin, Ionized calcium-binding adapter molecule 1 (Iba-1), microglial M2 phenotype marker Arg1, and CD200 were also examined in the hippocampus. Age induced an exacerbated cognitive impairment and an amplified neuroinflammatory response triggered by surgical stress on postoperative days 1 and 3. A corresponding decline in the anti-inflammatory cytokine IL-4 and BDNF were also found in the aged rats at the same time point. Treatment with IL-4 downregulated the expression of proinflammatory cytokines (e.g., IL-1β and IL-6), increased the levels of BDNF and synaptophysin in the brain and improved the behavioral performance. An increased Arg1 expression and a high level of CD200 were also observed after a cisterna magna infusion of IL-4. An age-related decrease in IL-4 expression exacerbated surgery-induced cognitive deficits and exaggerated the neuroinflammatory responses. Treatment with IL-4 potentially attenuated these effects by enhancing BDNF and synaptophysin expression, inhibiting microglia activation and decreasing the associated production of proinflammatory cytokines.

An update on pain management for elderly patients undergoing ambulatory surgery.

Purpose of reviewThe aim of this review is to provide an overview of the drugs and techniques used for multimodal postoperative pain management in the older population undergoing surgery in the ambulatory setting. Recent findingsInterest has grown in the possibility of adding adjuncts to a single shot nerve block in order to prolong the local anesthetic effect. The rapid and short-acting local anesthetics for spinal anesthesia are potentially beneficial for day-case surgery in the older population because of shorter duration of the motor block, faster recovery, and less transient neurologic symptoms. Another recent advance is the introduction of intravenous acetaminophen, which can rapidly achieve rapid peak plasma concentration (<15 min) following infusion and analgesic effect in ∼5 min with a duration of action up to 4 h. SummaryThe nonopioid analgesic therapies will likely assume an increasingly important role in facilitating the recovery process and improving the satisfaction for elderly ambulatory surgery patients. Strategies to avoid the use of opioids and minimize opioid-related side-effects is an important advance as we expand on the use of ambulatory surgery for the aging population.

Prior stressor exposure delays the recovery of surgery-induced cognitive impairment and prolongs neuroinflammation in aged rats

UNLABELLED Increasing evidence indicates that stress potentiates pro-inflammatory response to a subsequent peripheral immune challenge. The present study investigated if prior exposure to inescapable tailshock (IS) delayed the recovery of surgery-induced spatial learning and memory impairment and prolonged hippocampus interleukin (IL)-1β and IL-6 expression. METHODS A total of 192 aged rats were trained with Morris water-maze (MWM) for 6 consecutive days. A single session of inescapable tailshock was performed on day 6 after training. Then, the rats subjected to partial hepatectomy. Hippocampal-dependent spatial learning and memory were assessed on postoperative days 1, 3 and 7. The cytokines IL-1β and IL-6 and ionized calcium binding adaptor protein (Iba)-1 were measured at each time point. Cluster of differentiation 200 (CD200) was also measured to explore potential mechanisms of glial cell activation. RESULTS Exposure of IS alone failed to affect the latency to platform and increase hippocampal cytokine levels at each time point. However, IS alone significantly increased the expression levels of Iba-1. A prolonged latency and additional significant increase in hippocampal levels of IL-1β and IL-6 were observed when partial hepatectomy was performed in aged rats exposed to IS 24h later. The combination of IS and surgical trauma dramatically upregulated the levels of Iba-1 and significantly decreased the expression of CD200. CONCLUSION IS alone failed to induce cognitive deficits and increase pro-inflammatory cytokines expression. However, IS delayed the recovery of surgery-induced spatial learning and memory impairment and prolonged pro-inflammatory response to the subsequent surgery challenge.

Chronic unpredictable stress exacerbates surgery-induced sickness behavior and neuroinflammatory responses via glucocorticoids secretion in adult rats

Accumulated evidence indicates that stress sensitizes neuroinflammatory responses to a subsequent peripheral immune challenge. The present study investigated whether chronic unpredictable stress (CUS) aggravated surgery-induced sickness behavior and neuroinflammatory processes via glucocorticoids secretion in the adult brain. Methods Sprague-Dawley adult male rats (12–14 weeks old) were exposed to 14-day CUS and then subjected to partial hepatectomy 24 h after the last stress session. The rats were pretreated with an antagonist of the glucocorticoids (GCs) receptor RU486 (30 mg/kg, i.p.) 1 h prior to stress exposure. The behavioral changes were evaluated with open field test and elevated plus-maze test. The hippocampal cytokines interleukin (IL)-1β and IL-6 were measured on postoperative days 1, 3 and 7. Ionized calcium binding adaptor protein (Iba)-1, microglial M2 phenotype marker Arg1, brain derived neurotrophic factor (BDNF) and CD200 were also examined at each time point. Results CUS exacerbated surgery-induced sickness behavior. Exposure to CUS alone failed to alter the levels of pro-inflammatory cytokines in the brain. However, CUS exaggerated surgery-induced pro-inflammatory cytokines expression (e.g. IL-1β and IL-6) and upregulated the levels of Iba-1 on postoperative days 1 and 3. An additional significant decreased BDNF, CD200 and a lower level of Arg1 were also observed in the stressed rats following surgical procedure. Pretreatment with RU486 blunted the potentiating effects of CUS on surgery-induced sickness behavior and neuroinflammatory responses. Conclusion Chronic unpredictable stress enhanced surgery-induced sickness behavior and neuroinflammatory responses. Stress-induced GCs played a pivotal role in enhancing surgery-induced neuroinflammatory processes by modulation of microglia functions.

Effect of High-Intensity Laser Treatments on Chronic Pain Related to Osteoarthritis in Former Professional Athletes: A Case Series

Background: We evaluated the use of a new higher intensity 42 Watt cold laser for treating chronic pain related to osteoarthritis (OA) in former NFL football players. Methods: 39 consenting former NFL football players with OA underwent 1-3 treatment sessions lasting 10-20 min with a 42 Watt FDA-approved high-intensity cold laser (Phoenix thera-lase, Dallas, TX) at a wavelength of 1275 nm. We recorded their pain verbal rating scale (VRS) score at rest and with activity before and after each treatment using an 11-point VRS with 0=no pain to 10=worst pain imaginable. In addition, we assessed the duration of the painrelieving effect produced by each laser treatment, as well as its effects on other OA-related symptoms. Results: The chronic pain scores were significantly reduced both at rest and with activity after each treatment. Baseline VRS pain scores were 3.5 ± 2.9 at rest and 6.0 ± 2.6 with activity. After the initial treatment, the pain scores were reduced to 1.2 ± 1.8 (p<0.01) at rest and to 2.0 ± 2.0 (p<0.01) with activity. The overall beneficial effect was 7.2 ± 1.8 on a scale from 0=no relief to 10=complete relief, and the duration of the beneficial effect lasted 1-3 weeks in 64% of the players treated. Finally, 90% of the players would recommend the laser treatment to their colleagues. Conclusion: High-intensity cold laser treatments reduced chronic OA-related pain in former NFL football players by ~67% at rest and with activity and the beneficial effect typically persisted for 1 week or longer after 1-3 treatments in the majority of these chronic pain patients.