Neuroprotective Effects of Dexmedetomidine Against Hypoxia-Induced Nervous System Injury are Related to Inhibition of NF-κB/COX-2 Pathways

Morphine Preconditioning Alleviates Ischemia/Reperfusion-induced Caspase-8-dependent Neuronal Apoptosis Through cPKCγ-NF-κB-cFLIP L Pathway

BACKGROUND

Perioperative cerebral ischemia/reperfusion injury is a major contributor to postoperative death and cognitive dysfunction in patients. It was reported that morphine preconditioning (MP) can mimic ischemia/hypoxia preconditioning to protect against ischemia/reperfusion injury. However, the mechanism of MP on the ischemia/reperfusion-induced neuronal apoptosis has not been fully clarified.

METHODS

The middle cerebral artery occlusion/reperfusion (MCAO/R) model of mice and the oxygen-glucose deprivation/reoxygenation (OGD/R) model in primary cortical neurons were used to mimic ischemic stroke. In vivo, the infarct size was measured by using TTC staining; NDSS, Longa score system, and beam balance test were performed to evaluate the neurological deficits of mice; the expression of the protein was detected by using a western blot. In vitro, the viability of neurons was determined by using CCK-8 assay; the expression of protein and mRNA were assessed by using western blot, RT-qPCR, and immunofluorescent staining; the level of apoptosis was detected by using TUNEL staining.

RESULTS

MP can improve the neurological functions of mice following MCAO/R ( P <0.001, n=10 per group). MP can decrease the infarct size ( P <0.001, n=10 per group) and the level of cleaved-caspase-3 of mice following MCAO/R ( P <0.01 or 0.001, n=6 p er group). MP can increase the levels of cPKCγ membrane translocation, p-p65, and cFLIP L , and decrease the levels of cleaved-caspase-8, 3 in neurons after OGD/R or MCAO/R 1 d ( P <0.05, 0.01 or 0.001, n=6 per group). In addition, MP could alleviate OGD/R-induced cell apoptosis ( P <0.001, n=6 per group).

CONCLUSION

MP alleviates ischemia/reperfusion-induced Caspase 8-dependent neuronal apoptosis through the cPKCγ-NF-κB-cFLIP L pathway.

Dexmedetomidine attenuates ferroptosis by Keap1-Nrf2/HO-1 pathway in LPS-induced acute kidney injury

Previous research has demonstrated that Dexmedetomidine (DEX), an α2 adrenergic agonist commonly used for its sedative and analgesic properties, can attenuate lipopolysaccharide (LPS)-induced acute kidney injury (AKI). This study explores the possibility that DEX's protective effects in LPS-induced AKI are mediated through the inhibition of ferroptosis, a form of regulated cell death characterized by iron-dependent lipid peroxidation, and the activation of the antioxidant response through the Keap1/Nrf2/HO-1 signaling pathway. We induced AKI in 42 mice using LPS and divided them into six groups: saline control, LPS, LPS + DEX, LPS + Ferrostatin-1 (LPS + Fer-1; a ferroptosis inhibitor), LPS + DEX with α2-receptor antagonist Altipamizole (LPS + DEX + ATI), and LPS + DEX with Nrf2 inhibitor ML385 (LPS + DEX + ML385). After 24 h, we analyzed blood and kidney tissues. LPS exposure resulted in AKI, with increased serum creatinine, BUN, and cystatin C, and tubular damage, which DEX and Fer-1 ameliorated. However, Altipamizole and ML385 negated these improvements. The LPS group exhibited elevated oxidative stress markers and mitochondrial damage, reduced by DEX and Fer-1, but not when α2-adrenergic or Nrf2 pathways were blocked. Nrf2 and HO-1 expression declined in the LPS group, rebounded with LPS + DEX and LPS + Fer-1, and fell again with inhibitors; inversely, Keap1 expression varied. Our results demonstrate that DEX may protect against LPS-induced AKI, at least partially by regulating ferroptosis and the α2-adrenergic receptor/Keap1/Nrf2/HO-1 pathway, suggesting a potential therapeutic role for DEX in AKI management by modulating cell death and antioxidant defenses.

Comparative effects of dexmedetomidine and propofol on brain and lung damage in experimental acute ischemic stroke

Acute ischemic stroke is associated with pulmonary complications, and often dexmedetomidine and propofol are used to decrease cerebral metabolic rate. However, it is unknown the immunomodulatory actions of dexmedetomidine and propofol on brain and lungs during acute ischemic stroke. The effects of dexmedetomidine and propofol were compared on perilesional brain tissue and lung damage after acute ischemic stroke in rats. Further, the mean amount of both sedatives was directly evaluated on alveolar macrophages and lung endothelial cells primarily extracted 24-h after acute ischemic stroke. In twenty-five Wistar rats, ischemic stroke was induced and after 24-h treated with sodium thiopental (STROKE), dexmedetomidine and propofol. Dexmedetomidine, compared to STROKE, reduced diffuse alveolar damage score [median(interquartile range); 12(7.8–15.3) vs. 19.5(18–24), p = 0.007)], bronchoconstriction index [2.28(2.08–2.36) vs. 2.64(2.53–2.77), p = 0.006], and TNF-α expression (p = 0.0003), while propofol increased VCAM-1 expression compared to STROKE (p = 0.0004). In perilesional brain tissue, dexmedetomidine, compared to STROKE, decreased TNF-α (p = 0.010), while propofol increased VCAM-1 compared to STROKE (p = 0.024). In alveolar macrophages and endothelial cells, dexmedetomidine decreased IL-6 and IL-1β compared to STROKE (p = 0.002, and p = 0.040, respectively), and reduced IL-1β compared to propofol (p = 0.014). Dexmedetomidine, but not propofol, induced brain and lung protection in experimental acute ischemic stroke.

The potential role of dexmedetomidine on neuroprotection and its possible mechanisms: Evidence from in vitro and in vivo studies

Neurological disorders following brain injuries and neurodegeneration are on the rise worldwide and cause disability and suffering in patients. It is crucial to explore novel neuroprotectants. Dexmedetomidine, a selective α2-adrenoceptor agonist, is commonly used for anxiolysis, sedation and analgesia in clinical anaesthesia and critical care. Recent studies have shown that dexmedetomidine exerts protective effects on multiple organs. This review summarized and discussed the current neuroprotective effects of dexmedetomidine, as well as the underlying mechanisms. In preclinical studies, dexmedetomidine reduced neuronal injury and improved functional outcomes in several models, including hypoxia-induced neuronal injury, ischaemic-reperfusion injury, intracerebral haemorrhage, post-traumatic brain injury, anaesthetic-induced neuronal injury, substance-induced neuronal injury, neuroinflammation, epilepsy and neurodegeneration. Several mechanisms are associated with the neuroprotective function of dexmedetomidine, including neurotransmitter regulation, inflammatory response, oxidative stress, apoptotic pathway, autophagy, mitochondrial function and other cell signalling pathways. In summary, dexmedetomidine has the potential to be a novel neuroprotective agent for a wide range of neurological disorders.

Dexmedetomidine reduces the apoptosis of rat hippocampal neurons via mediating ERK1/2 signal pathway by targeting miR-155

Rat hippocampal neurons were isolated and divided into Normal, oxygen glucose deprivation/reoxygenation (OGD/R), OGD/R + DEX, OGD/R + NC mimic, OGD/R + miR-155 mimic and OGD/R + DEX + miR-155 mimic groups. In OGD/R group, LDH, ROS and MDA levels and apoptosis rate was increased, with up-regulations of miR-155, Cyt c and Bax/Bcl-2 ratio, but decreases of SOD, GSH-Px and MMP levels, as well as down-regulations of p-ERK1/2/ERK1/2. As compared to the OGD/R group, parameters above in the OGD/R + DEX group were ameliorated evidently, while OGD/R + miR-155 mimic group manifested the opposite changes. Besides, miR-155 mimic could abolish the protective effect of DEX on the hippocampal neurons under OGD/R. DEX, via down-regulating the expression of miR-155, could activate the ERK1/2 pathway, thereby mitigating the apoptosis and oxidative stress injury and increasing the MMP, thereby protecting hippocampal cells from OGD/R injury.

Identification of inflammation‑associated circulating long non‑coding RNAs and genes in intracranial aneurysm rupture‑induced subarachnoid hemorrhage

Ruptured intracranial aneurysm (IA)-induced subarachnoid hemorrhage (SAH) triggers a series of immune responses and inflammation in the brain and body. The present study was conducted to identify additional circulating biomarkers that may serve as potential therapeutic targets for SAH-induced inflammation. Differentially expressed (DE) long non-coding RNAs (lncRNAs; DElncRNAs) and genes (DEGs) in the peripheral blood mononuclear cells between patients with IA rupture-induced SAH and healthy controls were identified in the GSE36791 dataset. DEGs were used for weighted gene co-expression network analysis (WGCNA), and SAH-associated WGCNA modules were identified. Subsequently, an lncRNA-mRNA regulatory network was constructed using the DEGs in SAH-associated WGCNA modules. A total of 25 DElncRNAs and 1,979 DEGs were screened from patients with IA-induced SAH in the GSE36791 dataset compared with the controls. A total of 11 WGCNA modules, including four upregulated modules significantly associated with IA rupture-induced SAH were obtained. The DEGs in the SAH-associated modules were associated with Gene Ontology biological processes such as ‘regulation of programmed cell death’, ‘apoptosis’ and ‘immune response’. The subsequent lncRNA-mRNA regulatory network included seven upregulated lncRNAs [HCG27, ZNFX1 antisense RNA 1, long intergenic non-protein coding RNA (LINC)00265, murine retrovirus integration site 1 homolog-antisense RNA 1, cytochrome P450 1B1-AS1, LINC01347 and LINC02193] and 375 DEGs. Functional enrichment analysis and screening in the Comparative Toxicogenomics Database demonstrated that SAH-associated DEGs, including neutrophil cytosolic factor (NCF)2 and NCF4, were enriched in ‘chemokine signaling pathway’ (hsa04062), ‘leukocyte transendothelial migration’ (hsa04670) and ‘Fc gamma R-mediated phagocytosis’ (hsa04666). The upregulated lncRNAs and genes, including NCF2 and NCF4, in patients with IA rupture-induced SAH indicated their respective potentials as anti-inflammatory therapeutic targets.

Dexmedetomidine: What's New for Pediatrics? A Narrative Review

Over the past few years, despite the lack of approved pediatric labelling, dexmedetomidine’s (DEX) use has become more prevalent in pediatric clinical practice as well as in research trials. Its respiratory-sparing effects and bioavailability by various routes are only some of the valued features of DEX. In recent years the potential organ-protective effects of DEX, with the possibility for preserving neurocognitive function, has put it in the forefront of clinical and bench research. This comprehensive review focused on the pediatric literature but presents relevant, supporting adult and animal studies in order to detail the recent growing body of literature around the pharmacology, end-organ effects, organ-protective effects, alternative routes of administration, synergetic effects, and clinical applications, with considerations for the future.

The JAK2/STAT3 pathway is involved in dexmedetomidine-induced myocardial protection in rats undergoing cardiopulmonary bypass

Background

Many studies have reported that dexmedetomidine protects organs from ischemia/reperfusion-induced injury. However, the mechanism of this protective effect remains inconclusive.

Methods

Rats were randomly divided into 6 groups (n=8). Rats in the sham group were not subjected to cardiopulmonary bypass (CPB) while rats in the other groups underwent CPB for 2 h. Groups L and H received a low and a high dose of dexmedetomidine, respectively. Rats in group AG490 received 10 mg/kg of the Janus kinase 2 (JAK2) inhibitor, AG490, 30 min before anesthesia. Plasma levels of the inflammatory cytokines, interleukin (IL)-6 and IL-10, were measured by enzyme-linked immunosorbent (ELISA), and the apoptosis rate of myocardial cells, the expression of JAK2 and signal transducer and activator of transcription (STAT)3 mRNA, and the protein expression of JAK2, STAT3, pJAK2, pSTAT3, and caspase-3 were analyzed in myocardial tissues by real-time quantitative polymerase chain reaction (qRT-PCR), western blotting, and immunohistochemistry.

Results

We observed that, in both group L and group H, the level of IL-6 decreased (P<0.05), and the apoptosis rate of myocardial cells were reduced (P<0.05) compared to those in the CPB group. Moreover, qRT-PCR results revealed that dexmedetomidine administration reduced the expression of JAK2 and STAT3 mRNA (P<0.05); pJAK2 and pSTAT3 (P<0.05) protein levels were also reduced as assessed by western blotting and immunohistochemistry (P<0.05).

Conclusions

Dexmedetomidine treatment reduced CPB-related myocardial injury by inhibiting inflammatory reactions and myocardial apoptosis, and can be a potential therapy in CPB-related surgery.

Dexmedetomidine protects against lidocaine-induced neurotoxicity through SIRT1 downregulation-mediated activation of FOXO3a

Lidocaine, a typical local anesthetic, has been shown to directly induce neurotoxicity in clinical settings. Dexmedetomidine (DEX) is an alpha-2-adrenoreceptor agonist that has been used as anxiolytic, sedative, and analgesic agent which has recently found to protect against lidocaine-induced neurotoxicity. Nicotinamide adenine dinucleotide-dependent deacetylase sirtuin-1 (SIRT1)/forkhead box O3 (FOXO3a) signaling is critical for maintaining neuronal function and regulation of the apoptotic pathway. In the present study, we designed in vitro and in vivo models to investigate the potential effects of lidocaine and DEX on SIRT1 and FOXO3a and to verify whether SIRT1/FOXO3a-mediated regulation of apoptosis is involved in DEX-induced neuroprotective effects against lidocaine. We found that in both PC12 cells and brains of mice, lidocaine decreased SIRT1 level through promoting the degradation of SIRT1 protein. Lidocaine also increased FOXO3a protein level and increased the acetylation of SIRT1 through inhibiting SIRT1. Upregulation of SIRT1 or downregulation of FOXO3a significantly inhibited lidocaine-induced changes in both cell viability and apoptosis. DEX significantly inhibited the lidocaine-induced decrease of SIRT1 protein level and increase of FOXO3a protein level and acetylation of FOXO3a. Downregulation of SIRT1 or upregulation of FOXO3a suppressed DEX-induced neuroprotective effects against lidocaine. The data suggest that SIRT1/FOXO3a is a potential novel target for alleviating lidocaine-induced neurotoxicity and provide more theoretical support for the use of DEX as an effective adjunct to alleviate chronic neurotoxicity induced by lidocaine.

Dexmedetomidine protects PC12 cells from lidocaine-induced cytotoxicity via downregulation of Stathmin 1

Background: Understanding of lidocaine-induced neurotoxicity is not complete, resulting in the unsuccessful treatment in some clinical settings. Dexmedetomidine (DEX) has been shown to alleviate lidocaine-induced neurotoxicity in our previous cell model. However, the rationale for DEX combined with lidocaine to reduce lidocaine-induced neurotoxicity in the clinical setting remains to be further clarified in the detailed molecular mechanism. Methods: In this study, we established a cellular injury model by lidocaine preconditioning. Cell Counting Kit-8 (CCK-8) and 5-ethynyl-2'-deoxyuridine (EdU) proliferation assay kit were used to analyze cell proliferation. Cell apoptosis was measured by flow cytometry and Hoechst 33342 staining. Cell cycle progression was detected by flow cytometry. The protein expression levels were detected by Western blotting and immunofluorescence staining. Results: Our results showed that DEX dose-dependently restored impaired proliferation of PC12 cells induced by lidocaine，as reflected by the increased cell viability and EdU positive cells, which were consistent with the decreased expression of tumor suppressor protein p21 and increased expression of cell cycle-related cyclin D1 and CDK1. In addition, DEX dose-dependently reduced apoptotic PC12 cells induced by lidocaine，as reflected by the decreased expression of apoptosis-related Bax, caspase-3 and caspase-9 and increased expression of anti-apoptotic Bcl-2 compared to the cells only treated with lidocaine. Mechanistically, with gain-or-loss-of-function of STMN1, we showed that DEX-mediated neuroprotection by lidocaine-induced damage is associated with downregulation of STMN1 which might be an upstream molecule involved in regulation of mitochondria death pathway. Conclusion: Our results reveal that DEX is likely to be an effective adjunct to alleviate chronic neurotoxicity induced by lidocaine.

Dexmedetomidine: present and future directions

Dexmedetomidine is a potent, highly selective α-2 adrenoceptor agonist, with sedative, analgesic, anxiolytic, sympatholytic, and opioid-sparing properties. Dexmedetomidine induces a unique sedative response, which shows an easy transition from sleep to wakefulness, thus allowing a patient to be cooperative and communicative when stimulated. Dexmedetomidine may produce less delirium than other sedatives or even prevent delirium. The analgesic effect of dexmedetomidine is not strong; however, it can be administered as a useful analgesic adjuvant. As an anesthetic adjuvant, dexmedetomidine decreases the need for opioids, inhalational anesthetics, and intravenous anesthetics. The sympatholytic effect of dexmedetomidine may provide stable hemodynamics during the perioperative period. Dexmedetomidine-induced cooperative sedation with minimal respiratory depression provides safe and acceptable conditions during neurosurgical procedures in awake patients and awake fiberoptic intubation. Despite the lack of pediatric labelling, dexmedetomidine has been widely studied for pediatric use in various applications. Most adverse events associated with dexmedetomidine occur during or shortly after a loading infusion. There are some case reports of dexmedetomidine-related cardiac arrest following severe bradycardia. Some extended applications of dexmedetomidine discussed in this review are promising, but still limited, and further research is required. The pharmacological properties and possible adverse effects of dexmedetomidine should be well understood by the anesthesiologist prior to use. Moreover, it is necessary to select patients carefully and to determine the appropriate dosage of dexmedetomidine to ensure patient safety.

Dexmedetomidine protects the developing rat brain against the neurotoxicity wrought by sevoflurane: role of autophagy and Drp1-Bax signaling

BACKGROUND

The effect of sevoflurane on the nervous system is controversial. As an adjuvant anesthetic, dexmedetomidine has a protective role in various nerve-injury diseases. We investigated the effect of dexmedetomidine on injury to the developing brain induced by sevoflurane anesthesia, and if autophagy and mitochondrial damage are involved in the neuroprotective effects of dexmedetomidine.

METHODS

Pregnant rats on gestational day 20 were exposed to 3% sevoflurane for 4 hours. Saline and dexmedetomidine were injected intraperitoneally 15 minutes before exposure to sevoflurane or control gas. Bilateral hippocampi were harvested on postnatal day 1. Hippocampal morphology was observed by Nissl staining and expression of the microtubule-related protein LC3I/II, p62, Drp1, Bax, and Bcl2 were evaluated by Western blotting and immunohistochemistry.

RESULTS

Nissl staining showed that sevoflurane anesthesia during the third trimester caused neuronal damage to the hippocampi of rat pups. Western blotting and immunohistochemistry showed that pregnant rats exposed to sevoflurane during the third trimester led to pups having increased expression of LC3 and p62, suggesting that sevoflurane blocked autophagic flow in the hippocampus. Expression of Drp1 and Bax was increased after sevoflurane exposure, whereas Bcl2 expression was downregulated. All these effects were alleviated by pretreatment with dexmedetomidine.

CONCLUSION

Sevoflurane exposure during the third trimester caused neurological injury to rat pups. Autophagy and abnormalities in mitochondrial dynamics were involved in this neurotoxic process and were antagonized by dexmedetomidine.

Dexmedetomidine Protects Against Chemical Hypoxia-Induced Neurotoxicity in Differentiated PC12 Cells Via Inhibition of NADPH Oxidase 2-Mediated Oxidative Stress

Dexmedetomidine (Dex) is a widely used sedative in anesthesia and critical care units, and it exhibits neuroprotective activity. However, the precise mechanism of Dex-exerted neuroprotection is not clear. Increased neuronal NADPH oxidase 2 (NOX2) contributes to oxidative stress and neuronal damage in various hypoxia-related neurodegenerative disorders. The present study investigated whether Dex regulated neuronal NOX2 to exert its protective effects under hypoxic conditions. Well-differentiated PC12 cells were exposed to cobalt chloride (CoCl₂) to mimic a neuronal model of chemical hypoxia-mediated neurotoxicity. The data showed that Dex pretreatment of PC12 cells significantly suppressed CoCl₂-induced neurotoxicity, as evidenced by the enhanced cell viability, restoration of cellular morphology, and reduction in apoptotic cells. Dex improved mitochondrial function and inhibited CoCl₂-induced mitochondrial apoptotic pathways. We further demonstrated that Dex attenuated oxidative stress, downregulated NOX2 protein expression and activity, and inhibited intracellular calcium ([Ca²⁺]i) overload in CoCl₂-treated PC12 cells. Moreover, knockdown of the NOX2 gene markedly improved mitochondrial function and attenuated apoptosis under hypoxic conditions. These results demonstrated that the protective effects of Dex against hypoxia-induced neurotoxicity in neural cells were mediated, at least partially, via inhibition of NOX2-mediated oxidative stress.

Influence of sedation on onset and quality of euthanasia in sheep

The purpose of this study was to determine if dexmedetomidine administered IV prior to euthanasia in sheep affected the speed or quality of euthanasia. Twenty clinically healthy Dorset-cross adult ewes between 1 and 3years of age were enrolled in a randomized blinded experimental trial. The subjects were randomly assigned to receive dexmedetomidine 5μg/kg IV or an equivalent volume of saline. Five minutes later, euthanasia was accomplished with a pentobarbital/phenytoin overdose given IV. The time to apnea, asystole, cessation of audible heartbeat, and absence of corneal reflex were recorded by two blinded investigators. If any muscle spasms, contractions, vocalization, and/or dysrhythmias were noted, the time was recorded and type of ECG abnormality was described. An overall score of the euthanasia event was assigned using a numeric rating scale (NRS) after the animal was declared dead. The time to loss of corneal reflex was significantly longer in sheep given dexmedetomidine compared with those who received saline (P=0.03). Although vocalization was observed only in some animals premedicated with dexmedetomidine, no significance was found for this event and no other significant differences between groups were noted. Dexmedetomidine at 5μg/kg IV 5min prior to injection of pentobarbital/phenytoin for euthanasia did not substantially affect the progress of euthanasia. Dexmedetomidine may be given to sedate sheep prior to euthanasia without concern for it adversely affecting the progress of euthanasia, however vocalization may occur.

Dexmedetomidine reduces the neuronal apoptosis related to cardiopulmonary bypass by inhibiting activation of the JAK2-STAT3 pathway

Cardiopulmonary bypass (CPB) constitutes one of the primary methodologies pertaining to cardiac surgery. However, this form of surgery can cause damage to the body. Many studies have reported that dexmedetomidine confers cerebral protection. In this study, we aimed to investigate the effect and mechanism of dexmedetomidine on neuronal apoptosis caused by CPB. Here, rats were treated with different doses of dexmedetomidine by intravenous infusion 2 hours after CPB. We observed that dexmedetomidine treatment to rats reduces the S100β, NSE levels in plasma, and neuronal apoptosis following CPB in a dose-dependent manner. Furthermore, we observed that the beneficial effect of dexmedetomidine treatment following CPB was associated with a reduction in IL6, an inflammatory cytokine in plasma and cortex. Our results suggest that dexmedetomidine provides neuroprotective effects by inhibiting inflammation and reducing neuronal apoptosis. There was a correlation between the protective effect on the brain and the dose of dexmedetomidine. In addition, dexmedetomidine administration inhibits phosphorylation of JAK2 and STAT3 proteins in the hippocampus of rats 2 hours after CPB. Therefore, we speculate that the JAK2–STAT3 pathway plays an important role in the neuroprotective effects of dexmedetomidine following brain injury induced by CPB.

Neuroprotection of dexmedetomidine against propofol-induced neuroapoptosis partly mediated by PI3K/Akt pathway in hippocampal neurons of fetal rat*

The aim was to investigate how the PI3K/Akt pathway is involved in the protection of dexmedetomidine against propofol. The hippocampal neurons from fetal rats were separated and cultured in a neurobasal medium. Cell viability was assayed by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay. Then neurons were pretreated with different concentrations of dexmedetomidine before 100 μmol/L propofol was added. Akt, phospho-Akt (p-Akt), Bad, phospho-Bad (p-Bad), and Bcl-xL were detected by Western blot. Also, neurons were pretreated with dexmedetomidine alone or given the inhibitor LY294002 before dexmedetomidine pretreatment, and then propofol was added for 3 h. The results demonstrated that propofol decreased the cell viability and the expression of p-Akt and p-Bad proteins, increased the level of Bad, and reduced the ratio of Bcl-xL/Bad. Dexmedetomidine pretreatment could reverse these effects. The enhancement of p-Akt and p-Bad induced by dexmedetomidine was prevented by LY294002. These results showed that dexmedetomidine potently protected the developing neuron and this protection may be partly mediated by the PI3K/Akt pathway.

Dexmedetomidine sedation combined with caudal anesthesia for lower abdominal and extremity surgery in ex-preterm and full-term infants

BACKGROUND

Awake caudal anesthesia is a potentially attractive option, because the administration of general anesthesia is associated with a high rate of respiratory complications and hemodynamic disturbances and potential neurotoxic effects. To facilitate the caudal puncture and subsequent surgical intervention, additional sedatives are commonly administered.

AIM

We aimed to establish a new, safe, and effective anesthetic procedure for very young children with comorbidities.

METHODS

We retrospectively analyzed 23 children who underwent lower abdominal or lower extremity surgery with dexmedetomidine sedation and caudal anesthesia from January 2015 to August 2015. Dexmedetomidine was initiated with a total bolus infusion of 0.7-1.1 μg·kg^-1 followed by a continuous infusion of 1 μg·kg^-1 ·h^-1 . Bupivacaine (2.5 mg·kg^-1 ) was supplemented with 5-10 μg·kg^-1 epinephrine to strengthen and prolong motor block. According to maturity at birth, two groups were defined: ex-preterm and full-term infants.

RESULTS

There were 12 ex-preterm and 10 full-term infants available for analysis. The median postmenstrual age was 44 (38-52) weeks in ex-preterm and 46.5 (40-72) weeks in full-term infants. Without any additional intervention, surgery was successfully accomplished in 82% of all cases. While respiratory complications were not a problem, hemodynamic disturbances commonly occurred. Maximum decreases in heart rate (HR) of 30% were accompanied by maximum decreases in mean arterial pressure (MAP) of 38%. No infant had a heart rate below 100 bpm. MAP declined in one ex-preterm infant to a minimum value of 32 mmHg.

CONCLUSION

Caudal anesthesia combined with dexmedetomidine sedation is an effective anesthetic technique for lower abdominal and extremity surgery in ex-preterm and full-term infants with severe comorbidities.

Toll-like receptor 4 mediates vascular remodeling in hyperhomocysteinemia

Although hyperhomocysteinemia (HHcy) is known to promote downstream pro-inflammatory cytokine elevation, the precise mechanism is still unknown. One of the possible receptors that could have significant attention in the field of hypertension is toll-like receptor 4 (TLR-4). TLR-4 is a cellular membrane protein that is ubiquitously expressed in all cell types of the vasculature. Its mutation can attenuate the effects of HHcy-mediated vascular inflammation and mitochondria- dependent cell death that suppresses hypertension. In this review, we observed that HHcy induces vascular remodeling through immunological adaptation, promoting inflammatory cytokine up-regulation (IL-1β, IL-6, TNF-α) and initiation of mitochondrial dysfunction leading to cell death and chronic vascular inflammation. The literature suggests that HHcy promotes TLR-4-driven chronic vascular inflammation and mitochondria-mediated cell death inducing peripheral vascular remodeling. In the previous studies, we have characterized the role of TLR-4 mutation in attenuating vascular remodeling in hyperhomocysteinemia. This review includes, but is not limited to, the physiological synergistic aspects of the downstream elevation of cytokines found within the vascular inflammatory cascade. These events subsequently induce mitochondrial dysfunction defined by excessive mitochondrial fission and mitochondrial apoptosis contributing to vascular remodeling followed by hypertension.

Neuroprotective effects of dexmedetomidine against hyperoxia-induced injury in the developing rat brain

Dexmedetomidine (DEX) is a highly selective agonist of α2-receptors with sedative, anxiolytic, and analgesic properties. Neuroprotective effects of dexmedetomidine have been reported in various brain injury models. In the present study, we investigated the effects of dexmedetomidine on hippocampal neurogenesis, specifically the proliferation capacity and maturation of neurons and neuronal plasticity following the induction of hyperoxia in neonatal rats. Six-day old sex-matched Wistar rats were exposed to 80% oxygen or room air for 24 h and treated with 1, 5 or 10 μg/kg of dexmedetomidine or normal saline. A single pretreatment with DEX attenuated the hyperoxia-induced injury in terms of neurogenesis and plasticity. In detail, both the proliferation capacity (PCNA+ cells) as well as the expression of neuronal markers (Nestin+, PSA-NCAM+, NeuN+ cells) and transcription factors (SOX2, Tbr1/2, Prox1) were significantly reduced under hyperoxia compared to control. Furthermore, regulators of neuronal plasticity (Nrp1, Nrg1, Syp, and Sema3a/f) were also drastically decreased. A single administration of dexmedetomidine prior to oxygen exposure resulted in a significant up-regulation of expression-profiles compared to hyperoxia. Our results suggest that dexmedetomidine may have neuroprotective effects in an acute hyperoxic model of the neonatal rat.

Toll-like receptor 4 mutation suppresses hyperhomocysteinemia-induced hypertension

Hyperhomocysteinemia (HHcy) has been observed to promote hypertension, but the mechanisms are unclear. Toll-like receptor 4 (TLR-4) is a cellular membrane protein that is ubiquitously expressed in all cell types of the vasculature. TLR-4 activation has been known to promote inflammation that has been associated with the pathogenesis of hypertension. In this study we hypothesize that HHcy induces hypertension by TLR-4 activation, which promotes inflammatory cytokine (IL-1β, IL-6, and TNF-α) upregulation and initiation of mitochondria-dependent apoptosis, leading to cell death and chronic vascular inflammation. To test this hypothesis, we used C57BL/6J (WT) mice, cystathionine β-synthase (CBS)-deficient (CBS^+/-) mice with genetic mild HHcy, C3H/HeJ (C3H) mice with TLR-4 mutation, and mice with combined genetic HHcy and TLR-4 mutation (CBS^+/-/C3H). Ultrasonography of the superior mesenteric artery (SMA) detected an increase in wall-to-lumen ratio, resistive index (RI), and pulsatility index (PI). Tail cuff blood pressure (BP) measurement revealed elevated BP in CBS^+/- mice. RI, PI, and wall-to-lumen ratio of the SMA in CBS^+/-/C3H mice were similar to the control group, and BP was significantly alleviated. TLR-4, IL-1β, IL-6, and TNF-α expression were upregulated in the SMA of CBS^+/- mice and reduced in the SMA of CBS^+/-/C3H mice. Molecules involved in the mitochondria-mediated cell death pathway (BAX, caspase-9, and caspase-3) were upregulated in CBS^+/- mice and attenuated in CBS^+/-/C3H mice. We conclude that HHcy promotes TLR-4-driven chronic vascular inflammation and mitochondria-mediated cell death, inducing hypertension. TLR-4 mutation attenuates vascular inflammation and cell death, which suppress hypertension.