General anesthesia delays the inflammatory response and increases survival for mice with endotoxic shock

Anesthetics, immune cells, and immune responses

General anesthesia accompanied by surgical stress is considered to suppress immunity, presumably by directly affecting the immune system or activating the hypothalamic-pituitary-adrenal axis and the sympathetic nervous system. Along with stress such as surgery, blood transfusion, hypothermia, hyperglycemia, and postoperative pain, anesthetics per se are associated with suppressed immunity during perioperative periods because every anesthetic has direct suppressive effects on cellular and neurohumoral immunity through influencing the functions of immunocompetent cells and inflammatory mediator gene expression and secretion. Particularly in cancer patients, immunosuppression attributable to anesthetics, such as the dysfunction of natural killer cells and lymphocytes, may accelerate the growth and metastases of residual malignant cells, thereby worsening prognoses. Alternatively, the anti-inflammatory effects of anesthetics may be beneficial in distinct situations involving ischemia and reperfusion injury or the systemic inflammatory response syndrome (SIRS). Clinical anesthesiologists should select anesthetics and choose anesthetic methods with careful consideration of the clinical situation and the immune status of critically ill patients, in regard to long-term mortality, morbidity, and the optimal prognosis.

Effects of anesthesia on lipopolysaccharide-induced changes in serum cytokines

BACKGROUND

The pathophysiology of sepsis is incompletely understood, however alterations in systemic inflammation and serum cytokines are thought to play a central role. In the rat, ketamine, but not isoflurane, prevents hepatic injury from lipopolysaccharide (LPS). The effect of these anesthetics on the systemic inflammatory response and other organs remains to be fully elucidated. We hypothesized that ketamine, but not isoflurane, would blunt the cytokine response to LPS administration.

METHODS

Male rats received no anesthesia, intraperitoneal ketamine (70 mg/kg), or inhalational isoflurane. One hour later, LPS (20 mg/kg, intraperitoneal) or saline was given for 5 hours and rats were killed. Gastric fluid volumes were determined as an index of gastric emptying. Serum was collected and cytokines measured via a multiplexed suspension immunoassay.

RESULTS

In nonanesthetized rats, LPS increased gastric luminal fluid accumulation and serum levels of proinflammatory cytokines when compared with saline controls. Anesthesia with either ketamine or isoflurane caused a significant reduction in LPS-induced changes in serum cytokines, although ketamine had a more dramatic reduction in tumor necrosis factor alpha levels than did isoflurane. Both anesthetics reduced the interleukin IL-6/IL-10 ratio in response to LPS when compared with LPS alone. Ketamine, but not isoflurane, prevented LPS-induced gastric luminal fluid accumulation.

CONCLUSIONS

These data indicate that both ketamine and isoflurane diminish the systemic inflammatory response to LPS in the rat as measured by serum cytokines and a reduced IL-6/IL-10 ratio. However, only ketamine improves LPS-induced gastric dysfunction, perhaps secondary to its ability to reduce serum tumor necrosis factor alpha levels more effectively.

Isoflurane preconditioning reduces mouse microglial activation and injury induced by lipopolysaccharide and interferon-gamma

Activation and injury of microglial cells are involved in a broad range of brain diseases including stroke, brain infection and neurodegenerative diseases. However, there is very little information regarding how to reduce microglial reaction and preserve these cells to provide neuroprotection. Here, we showed that the incubation of C8-B4 mouse microglial cells with lipopolysaccharide (LPS) plus interferon-gamma (IFNgamma) for 24 h decreased the viability of these cells. Pretreatment of these cells with 1%, 2% or 3% isoflurane, a commonly used volatile anesthetic, for 1 h at 30 min before the exposure to LPS plus IFNgamma attenuated the reduction of cell viability (preconditioning effect). LPS plus IFNgamma also activated these microglial cells to express inducible nitric oxide synthase (iNOS) and to induce accumulation of nitrite, a stable oxidation product of nitric oxide, in the incubation medium. Isoflurane preconditioning attenuated these LPS plus IFNgamma effects on the iNOS expression and nitrite accumulation. Aminoguanidine, an iNOS inhibitor, attenuated the LPS plus IFNgamma-induced glutamate release and decrease of microglial viability. Isoflurane preconditioning also reduced LPS plus IFNgamma-induced glutamate release. Exogenous glutamate decreased microglial viability. Finally, the isoflurane preconditioning-induced protection was abolished by chelerythrine, a protein kinase C inhibitor. These results suggest that LPS plus IFNgamma activates the iNOS-nitric oxide-glutamate pathway to induce microglial injury and that this activation is attenuated by isoflurane preconditioning. Protein kinase C may be involved in the isoflurane preconditioning effects.

Safety and efficacy of various combinations of injectable anesthetics in BALB/c mice

Four combinations of drugs--ketamine-xylazine, ketamine-xylazine-acepromazine (KXA), ketamine-xylazine-buprenorphine, and ketamine-xylazine-carprofen--were compared for their ability to produce anesthesia in BALB/c mice. Induction time, anesthetic duration, blood pressure, pulse rate, and time to recovery were recorded. The anesthesia induced by each anesthetic combination was assessed by using reflex responses to standardized stimuli. The KXA combination produced stable physiologic parameters and was associated with the longest duration of anesthesia (40 +/- 8 min); immobility was produced in all other groups (38 +/- 5 min), but a surgical plane of anesthesia could not be confirmed. All anesthetic protocols produced significant hypotension. No deaths occurred. We recommend KXA as a safe and reliable anesthetic for mice requiring a surgical plane of anesthesia.

The reduction of tumor necrosis factor-alpha release and tissue damage by pentobarbital in the experimental endotoxemia model

Sepsis is the leading cause of death for intensive care patients. Lipopolysaccharide (LPS) administration to animals under anesthesia is a strategy for the study of uncontrolled release of proinflammatory cytokines. Anesthetics have been indicated that they can specially affect immune responses, such as the inflammatory response. Pentobarbital is an anesthetic used mainly in animal studies. Thus, the effect of pentobarbital on tumor necrosis factor-alpha (TNF-alpha) release was determined. The results revealed that pentobarbital suppressed the expression of TNF-alpha mRNA and its proteins, which may result from the decrease in the activities of nuclear factor-kappaB and activator protein 1 and the reduction of the expression of p38 mitogen-activated protein kinase by pentobarbital. After the inhibitory activity of the pentobarbital for TNF-alpha release was proven in vivo, the cytotoxic effects of LPS were examined in vivo with or without pentobarbital treatments. In vivo results indicated that plasma levels of alanine aminotransferase, aspartate aminotransferase, lactic dehydrogenase, creatine kinase, serum urea nitrogen, and amylase decreased dramatically in the anesthetic group with pentobarbital administration. Finally, the effect of pentobarbital on TNF-alpha-related cell death was monitored in vitro, and the results indicated the pentobarbital could directly enhance the viabilities of cells under the treatment of TNF-alpha and protected cells from apoptosis induced by deferoxamine mesylate-induced hypoxia. These results suggest that pentobarbital significantly influences the LPS-induced inflammatory response and protects cells from death directly and indirectly induced by TNF-alpha. The information provides a perspective to re-evaluate the results of the experiments in which animals were anesthetized with pentobarbital. The anti-inflammatory effects of the drugs may have been caused by the synergistic effect of pentobarbital.

Isoflurane inhalation after induction of endotoxemia in rats attenuates the systemic cytokine response

BACKGROUND/AIMS

Volatile anesthetics are frequently utilized in clinical routine. Isoflurane has been shown to attenuate the response to inflammatory stimuli such as lipopolysaccharide (LPS) when administered before induction of endotoxemia. We aimed therefore to evaluate the effect of isoflurane after administration of LPS on the cytokine release as a therapeutic option.

MATERIALS AND METHODS

21 male Sprague-Dawley rats were randomly assigned to the following groups: animals that received LPS (5 mg/kg, i.v.) without further intervention (LPS group), animals that received continuous inhalation of 1 minimum alveolar concentration (MAC) isoflurane 15 min after administration of LPS (Iso group) and no specific intervention (sham group). Four hours following LPS injection, plasma levels of tumor necrosis factor-alpha (TNF-alpha), interleukin-1 beta (IL-1 beta), IL-6 and IL-10 were determined. Furthermore, nitrite release from cultured alveolar macrophages was analyzed.

RESULTS

Inhalation of isoflurane after induction of endotoxemia attenuated the release of TNF-alpha (-52%, p < 0.05) and IL-1 beta (-39%, p < 0.05) as compared to the LPS group, while IL-6 and IL-10 levels were not significantly altered. Nitrite release was significantly increased in the Iso group as compared to the LPS group (+115%, p < 0.05).

CONCLUSION

Inhalation of 1 MAC isoflurane after induction of endotoxemia in rats attenuates the systemic release of proinflammatory cytokines and concurrently enhances the production of nitrite in cultured alveolar macrophages.

Isoflurane protects against renal ischemia and reperfusion injury and modulates leukocyte infiltration in mice

Inflammation after renal ischemia-reperfusion (IR) injury is a major contributor to renal cell death. We previously demonstrated that several volatile anesthetics protect against renal IR injury and necrosis in rats in vivo. We subsequently showed that volatile anesthetics produced direct anti-inflammatory and anti-necrotic effects in cultured proximal tubule cells in vitro. In this study, we wanted to determine whether the volatile anesthetic isoflurane protects against renal IR injury by producing anti-inflammatory effects in mice. C57BL/6 mice subjected to renal IR under isoflurane anesthesia demonstrated improved renal function and reduced necrosis compared with mice subjected to renal IR under pentobarbital anesthesia. Mice subjected to renal IR under isoflurane anesthesia also showed a reduction in inflammation evidenced by a reduced renal influx of neutrophils and macrophages, reduced ICAM-1 expression, less upregulation of proinflammatory mRNAs (TNF-alpha, ICAM-1, KC, and IL-1beta) as well as reduced nuclear translocation of NF-kappaB 24 h after renal IR injury. Analysis of specific lymphocyte subset trafficking to the kidney using flow cytometry demonstrated that isoflurane anesthesia reduced intrarenal influx of CD3+, CD4+, CD8+, and NK1.1+ lymphocytes at 3 h after renal ischemia compared with pentobarbital anesthesia. However, only the differential reduction of NK1.1+ lymphocytes persisted 24 h after renal ischemia. Therefore, we conclude that isoflurane anesthesia significantly attenuated renal IR injury in mice by reducing inflammation and modulating leukocyte influx. In particular, neutrophil, macrophage, and NK1.1+ lymphocyte cell modulation may play a significant role in renal protection by isoflurane anesthesia.

Isoflurane improves survival and protects against renal and hepatic injury in murine septic peritonitis

We have demonstrated that volatile anesthetics reduce inflammation after renal ischemia/reperfusion injury in vivo. As hyperactive uncontrolled inflammation can lead to mortality and morbidity during early sepsis, we questioned whether the volatile anesthetic isoflurane could reduce mortality and protect against sepsis induced renal and hepatic dysfunction. Mice were anesthetized with isoflurane or with pentobarbital and subjected to cecal ligation and puncture (CLP) to induce septic peritonitis. Mice were anesthetized for an additional 3 h after CLP with either isoflurane or pentobarbital. Renal and hepatic function was assessed 24 h later and survival after CLP was assessed for 7 days. To determine if isoflurane protects by reducing inflammation, we quantified renal tubular expression of pro-inflammatory (intercellular adhesion molecule 1, tumor necrosis factor alpha [TNF-alpha], and interleukin [IL] 1beta) messenger RNA with reverse transcriptase-polymerase chain reaction. We also measured the plasma levels of the pro-inflammatory cytokines TNF-alpha, keratinocyte-derived chemokine (KC), and IL-6 and an anti-inflammatory cytokine IL-10. Renal cortical apoptosis was also assessed 24 h after CLP. Twenty-four hours after the septic insult, isoflurane-treated mice had significantly improved renal and hepatic function compared with mice anesthetized with pentobarbital. Renal cortices of isoflurane-treated mice had significantly reduced expression of intercellular adhesion molecule 1, TNF-alpha, and IL-1beta messenger RNA and showed less apoptosis. Isoflurane-treated mice had lower plasma levels of TNF-alpha, KC, and IL-6. Isoflurane-anesthetized mice also had significantly prolonged and increased survival compared with pentobarbital-anesthetized mice. Therefore, isoflurane anesthesia conferred significant protection against renal and hepatic dysfunction and death after septic peritonitis and attenuated renal inflammation and apoptosis compared with pentobarbital anesthesia.