The neuroprotective action of dexmedetomidine on apoptosis, calcium entry and oxidative stress in cerebral ischemia-induced rats: Contribution of TRPM2 and TRPV1 channels

From oxidative stress to metabolic dysfunction: The role of TRPM2

Metabolic syndromes including atherosclerosis, diabetes, obesity, and hypertension are increasingly prevalent worldwide. The disorders are the primary attributes of oxidative stress and inflammation. The transient receptor potential M2 (TRPM2) channel is a pivotal mediator linking oxidative stress to metabolic dysfunction. TRPM2, a non-selective cation channel activated by reactive oxygen species (ROS) and adenosine diphosphate ribose (ADPR), regulates calcium influx, inflammation, and cell death across various tissues. This review explores the structural and activation mechanisms of TRPM2, emphasizing its significance in metabolic diseases. Elevated levels of TRPM2 play a vital role in the disease progression by influencing physiological and cellular processes such as endothelial dysfunction, immune cell activation, and mitochondrial impairment. In conditions such as atherosclerosis, ischemic stroke, diabetes, obesity, and hypertension; TRPM2 exacerbates oxidative damage, amplifies inflammatory responses, and disrupts metabolic homeostasis. Recent research highlights the potential of TRPM2 as a therapeutic target, developing specified inhibitors. This review underscores the multifaceted role of TRPM2 in metabolic disorders and its promise as a target for therapeutic interventions.

Potential of Natural Products in the Treatment of Glioma: Focus on Molecular Mechanisms

Despite the waning of traditional treatments for glioma due to possible long-term issues, the healing possibilities of substances derived from nature have been reignited in the scientific community. These natural substances, commonly found in fruits and vegetables, are considered potential alternatives to pharmaceuticals, as they have been shown in prior research to impact pathways surrounding cancer progression, metastases, invasion, and resistance. This review will explore the supposed molecular mechanisms of different natural components, such as berberine, curcumin, coffee, resveratrol, epigallocatechin-3-gallate, quercetin, tanshinone, silymarin, coumarin, and lycopene, concerning glioma treatment. While the benefits of a balanced diet containing these compounds are widely recognized, there is considerable scope for investigating the efficacy of these natural products in treating glioma.

Anesthetics in pathological cerebrovascular conditions

The increasing prevalence of pathological cerebrovascular conditions, including stroke, hypertensive encephalopathy, and chronic disorders, underscores the importance of anesthetic considerations for affected patients. Preserving cerebral oxygenation and blood flow during anesthesia is paramount to prevent neurological deterioration. Furthermore, protecting vulnerable neurons from damage is crucial for optimal outcomes. Recent research suggests that anesthetic agents may provide a potentially therapeutic approach for managing pathological cerebrovascular conditions. Anesthetics target neural mechanisms underlying cerebrovascular dysfunction, thereby modulating neuroinflammation, protecting neurons against ischemic injury, and improving cerebral hemodynamics. However, optimal strategies regarding mechanisms, dosage, and indications remain uncertain. This review aims to clarify the physiological effects, mechanisms of action, and reported neuroprotective benefits of anesthetics in patients with various pathological cerebrovascular conditions. Investigating anesthetic effects in cerebrovascular disease holds promise for developing novel therapeutic strategies.

TLR4 induced TRPM2 mediated neuropathic pain

Ion channels play an important role in mediating pain through signal transduction, regulation, and control of responses, particularly in neuropathic pain. Transient receptor potential channel superfamily plays an important role in cation permeability and cellular signaling. Transient receptor potential channel Melastatin 2 (TRPM2) subfamily regulates Ca2+ concentration in response to various chemicals and signals from the surrounding environment. TRPM2 has a role in several physiological functions such as cellular osmosis, temperature sensing, cellular proliferation, as well as the manifestation of many disease processes such as pain process, cancer, apoptosis, endothelial dysfunction, angiogenesis, renal and lung fibrosis, and cerebral ischemic stroke. Toll-like Receptor 4 (TLR4) is a critical initiator of the immune response to inflammatory stimuli, particularly those triggered by Lipopolysaccharide (LPS). It activates downstream pathways leading to the production of oxidative molecules and inflammatory cytokines, which are modulated by basal and store-operated calcium ion signaling. The cytokine production and release cause an imbalance of antioxidant enzymes and redox potential in the Endoplasmic Reticulum and mitochondria due to oxidative stress, which results from TLR-4 activation and consequently induces the production of inflammatory cytokines in neuronal cells, exacerbating the pain process. Very few studies have reported the role of TRPM2 and its association with Toll-like receptors in the context of neuropathic pain. However, the molecular mechanism underlying the interaction between TRPM2 and TLR-4 and the quantum of impact in acute and chronic neuropathic pain remains unclear. Understanding the link between TLR-4 and TRPM2 will provide more insights into pain regulation mechanisms for the development of new therapeutic molecules to address neuropathic pain.

Dexmedetomidine Alleviates Brain Ischemia/Reperfusion Injury by Regulating Metastasis-associated Lung Adenocarcinoma Transcript 1/MicroRNA-140-5p/ Nuclear Factor Erythroid-derived 2-like 2 Axis

BACKGROUND

Dexmedetomidine (Dex) is widely used in perioperative anesthesia, and recent studies have reported that it protects organs from ischemia/reperfusion (I/R) injury.

OBJECTIVES

This study was performed to investigate the role of Dex in alleviating cerebral I/R injury and its regulatory effects on metastasis-associated lung adenocarcinoma transcript 1 (MALAT1)/microRNA-140-5p (miR-140-5p)/nuclear factor erythroid-derived 2-like 2 (Nrf2) axis.

METHODS

In vivo rat middle cerebral artery occlusion (MCAO) model and in vitro oxygen-glucose deprivation/re-oxygenation (OGD/R)-induced neuronal injury model were constructed. Dex was injected into the animals or used to culture HT22 cells to observe the pharmacological effects. The neurological defect, brain water content, infarct volume of the rats, and neuron viability were evaluated. The levels of reactive oxygen species (ROS), malondialdehyde (MDA), superoxide dismutase (SOD), and catalase (CAT) were detected. Besides, the regulatory effects of Dex on MALAT1, miR-140-5p, and Nrf2 expression levels and regulatory relationships among them were evaluated by quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and dual- luciferase reporter assay.

RESULTS

Dex significantly alleviated the neurological injury of rats with MCAO and promoted the viability of neurons. Dex treatment suppressed miR-140-5p expression, but elevated MALAT1 and Nrf2 expressions. MALAT1 knockdown down-regulated Nrf2 expression and promoted oxidative stress in neurons. Additionally, miR-140-5p directly targeted Nrf2, and it also functioned as a downstream target miRNA of MALAT1.

CONCLUSION

Dex, via regulating MALAT1/miR-140-5p/Nrf2 axis, plays a neuroprotective role against I/R-induced brain injury.

Cornerstone Cellular Pathways for Metabolic Disorders and Diabetes Mellitus: Non-Coding RNAs, Wnt Signaling, and AMPK

Metabolic disorders and diabetes (DM) impact more than five hundred million individuals throughout the world and are insidious in onset, chronic in nature, and yield significant disability and death. Current therapies that address nutritional status, weight management, and pharmacological options may delay disability but cannot alter disease course or functional organ loss, such as dementia and degeneration of systemic bodily functions. Underlying these challenges are the onset of aging disorders associated with increased lifespan, telomere dysfunction, and oxidative stress generation that lead to multi-system dysfunction. These significant hurdles point to the urgent need to address underlying disease mechanisms with innovative applications. New treatment strategies involve non-coding RNA pathways with microRNAs (miRNAs) and circular ribonucleic acids (circRNAs), Wnt signaling, and Wnt1 inducible signaling pathway protein 1 (WISP1) that are dependent upon programmed cell death pathways, cellular metabolic pathways with AMP-activated protein kinase (AMPK) and nicotinamide, and growth factor applications. Non-coding RNAs, Wnt signaling, and AMPK are cornerstone mechanisms for overseeing complex metabolic pathways that offer innovative treatment avenues for metabolic disease and DM but will necessitate continued appreciation of the ability of each of these cellular mechanisms to independently and in unison influence clinical outcome.

Sedation Therapy in Intensive Care Units: Harnessing the Power of Antioxidants to Combat Oxidative Stress

In critically ill patients requiring intensive care, increased oxidative stress plays an important role in pathogenesis. Sedatives are widely used for sedation in many of these patients. Some sedatives are known antioxidants. However, no studies have evaluated the direct scavenging activity of various sedative agents on different free radicals. This study aimed to determine whether common sedatives (propofol, thiopental, and dexmedetomidine (DEX)) have direct free radical scavenging activity against various free radicals using in vitro electron spin resonance. Superoxide, hydroxyl radical, singlet oxygen, and nitric oxide (NO) direct scavenging activities were measured. All sedatives scavenged different types of free radicals. DEX, a new sedative, also scavenged hydroxyl radicals. Thiopental scavenged all types of free radicals, including NO, whereas propofol did not scavenge superoxide radicals. In this retrospective analysis, we observed changes in oxidative antioxidant markers following the administration of thiopental in patients with severe head trauma. We identified the direct radical-scavenging activity of various sedatives used in clinical settings. Furthermore, we reported a representative case of traumatic brain injury wherein thiopental administration dramatically affected oxidative-stress-related biomarkers. This study suggests that, in the future, sedatives containing thiopental may be redeveloped as an antioxidant therapy through further clinical research.

Dexmedetomidine, an α2 agonist, increases the morphine analgesic effect and decreases morphine tolerance development by suppressing oxidative stress and TNF/IL-1 signalling pathway in rats

BACKGROUND

The aim of the present study is to examine the possible effect de dexmedetomidine on the development of morphine tolerance in rats including nociception, morphine analgesia, apoptosis, oxidative stress, and tumour necrosis factor (TNF)/ interleukin-1 (IL-1) pathways.

MATERIALS AND METHODS

In this study, 36 Wistar Albino (225-245 g) rats were used. Animals were divided into 6 groups: saline (S), 20 mcg/kg dexmedetomidine (D), 5 mg/kg morphine (M), M + D, morphine tolerance (MT), and MT + D. The analgesic effect was measured with hot plate and tail-flick analgesia tests. After the analgesia tests, the dorsal root ganglia (DRG) tissues were excised. Oxidative stress parameters [total antioxidant status (TAS), total oxidant status (TOS)], TNF, IL-1 and apoptosis enzymes (Caspase-3, Caspase-9), were measured in DRG tissues.

RESULTS

Dexmedetomidine showed an antinociceptive effect when given alone (p < 0.05 to p < 0.001). In addition, dexmedetomidine increased the analgesic effect of morphine (p < 0.001), and also decreased the tolerance to morphine at a significant level (p < 0.01 to p < 0.001). Moreover, it decreased oxidative stress (p < 0.001) and TNF/IL-1 levels when given as an additional drug of single-dose morphine and morphine tolerance group (p < 0.001). Furthermore, dexmedetomidine decreased Caspase-3 and Caspase-9 levels after tolerance development (p < 0.001).

CONCLUSION

Dexmedetomidine has antinociceptive properties, and it increases the analgesic effect of morphine and also prevents tolerance development. These effects probably occur by the modulation of oxidative stress, inflammation and apoptosis.

A-80426 suppresses CFA-induced inflammatory pain by suppressing TRPV1 activity via NFκB and PI3K pathways in mice

OBJECTIVES

Pain is associated with many circumstances, including inflammatory reactions, which arise from modification of the features of signaling pathways. α2-adrenergic receptor antagonists are widely utilized in narcosis. Here, the authors focused on the narcotic effect of A-80426 (A8) on Complete Freund's Adjuvant (CFA) injections-triggered chronic inflammation pain in WT and TRPV1-/- mice and explored whether its antinociceptive impact was modulated via Transient Receptor Potential Vanilloid 1 (TRPV1).

METHOD

CFA with or without A8 was co-administered to the mice, which were categorized randomly into four groups: CFA, A8, control, and vehicle. Pain behaviors underwent evaluation through mechanical withdrawal threshold, abdominal withdrawal reflex, and thermal withdrawal latency of WT animals.

RESULTS

Quantitative polymerase chain reaction revealed that inflammation-promoting cytokines (IL-1β, IL-6, and TNF-α) were upregulated in Dorsal Root Ganglion (DRG) and Spinal Cord Dorsal Horn (SCDH) tissues of WT animals. A8 administration reduced the pain behaviors and production of pro-inflammatory cytokines; however, this effect was significantly reduced in TRPV1-/- mice. Further analysis showed that CFA treatment reduced the TRPV1 expression in WT mice and A8 administration increased its expression and activity. The co-administration of SB-705498, a TRPV1 blocker, did not influence the pain behaviors and inflammation cytokines in CFA WT mice; however, SB-705498 the effect of A8 in WT mice. In addition, the TRPV1 block decreased the NFκB and PI3K activation in the Dorsal Root Ganglia (DRG) and Spinal Cord Dorsal Horn (SCDH) tissues of WT mice.

CONCLUSIONS

Together, A8 exerted a narcotic impact on CFA-supplemented mice via the TRPV1-modulated NFκB and PI3K pathway.

NMDA Receptor Activation Stimulates Hypoxia-Induced TRPM2 Channel Activation, Mitochondrial Oxidative Stress, and Apoptosis in Neuronal Cell Line: Modular Role of Memantine

TRPM2 channel is activated by the increase of hypoxia (HYP)-mediated excessive mitochondrial (mROS) and cytosolic (cROS) free reactive oxygen species generation and intracellular free Ca²⁺ ([Ca²⁺]_i) influx. The stimulations of the N-methyl-d-aspartate(NMDA) receptor and TRPM2 channel induce mROS and apoptosis in the neurons, although their inhibitions via the treatments of memantine (MEM) and MK-801 decrease mROS and apoptosis. However, the molecular mechanisms underlying MEM treatment and NMDA inhibition' neuroprotection via TRPM2 inhibition in the HYP remain elusive. We investigated the modulator role of MEM and NMDA via the modulation of TRPM2 on oxidative neurodegeneration and apoptosis in SH-SY5Y neuronal cells. Six groups were induced in the SH-SY5Y and HEK293 cells as follows: Control, MEM, NMDA blocker (MK-801), HYP (CoCl₂), HYP + MEM, and HYP + MK-801. The HYP caused to the increases of TRPM2 and PARP-1 expressions, and TRPM2 agonist (H₂O₂ and ADP-ribose)-induced TRPM2 current density and [Ca²⁺]_i concentration via the upregulation of mitochondrial membrane potential, cROS, and mROS generations. The alterations were not observed in the absence of TRPM2 in the HEK293 cells. The increase of cROS, mROS, lipid peroxidation, cell death (propidium iodide/Hoechst) rate, apoptosis, caspase -3, caspase -8, and caspase -9 were restored via upregulation of glutathione and glutathione peroxidase by the treatments of TRPM2 antagonists (ACA or 2-APB), MEM, and MK-801. In conclusion, the inhibition of NMDA receptor via MEM treatment modulated HYP-mediated mROS, apoptosis, and TRPM2-induced excessive [Ca²⁺]_i and may provide an avenue for protecting HYP-mediated neurodegenerative diseases associated with the increase of mROS, [Ca²⁺]_i, and apoptosis.

Dexmedetomidine alleviates myocardial ischemia-reperfusion injury by down-regulating miR-34b-3p to activate the Jagged1/Notch signaling pathway

BACKGROUND

Myocardial ischemia/reperfusion (I/R) injury is a fatal event that usually occurs after reperfusion therapy for myocardial infarction. Dexmedetomidine (Dex) has been shown to be beneficial in the treatment of myocardial infarction, however, its underlying mechanism for regulating I/R injury is unclear.

METHODS

H9c2 cell and rat models of I/R injury were established via oxygen-glucose deprivation reoxygenation (OGD/R) and occlusion of the left anterior descending branch of coronary artery, respectively. Flow cytometry, MTT, or DHE assay detected cell activity, ROS, or apoptosis, respectively. The expression levels of miR-34b-3p and related mRNAs were determined using qRT-PCR. Related protein expression levels were detected by Western blotting and ELISA test. The interaction between miR-34b-3p and Jagged1 was assessed by dual luciferase reporter and RIP assays. The morphology of cardiac tissue was examined by TTC, HE, and TUNEL labeling.

RESULTS

Dex markedly inhibited the inflammatory damage and apoptosis caused by OGD/R in H9c2 cells. MiR-34b-3p and Jagged1 levels were increased and decreased in myocardial I/R injury model, respectively, while Dex reversed this effect. Moreover, miR-34b-3p was firstly reported to directly bind and decrease Jagged1 expression, thereby inhibiting Notch signaling pathway. Transfection of agomiR-34b-3p or Jagged1 silencing eliminated Dex's defensive impact on OGD/R-induced cardiomyocytes damage. Dex relieved the myocardial I/R injury of rats via inhibiting miR-34b-3p and further activating Notch signaling pathway.

CONCLUSION

Dex protected myocardium from I/R injury via suppressing miR-34b-3p to activate Jagged1-mediated Notch signaling pathway. Our findings revealed a novel mechanism underlying of Dex on myocardial I/R injury.

Transient receptor potential ion channels and cerebral stroke

METHODS

The databases Pubmed, and the National Library of Medicine were searched for literature. All papers on celebral stroke and transient receptor potential ion channels were considered.

RESULTS

Stroke is the second leading cause of death and disability, with an increasing incidence in developing countries. About 75 per cent of strokes are caused by occlusion of cerebral arteries, and substantial advances have been made in elucidating mechanisms how stroke affects the brain. Transient receptor potential (TRP) ion channels are calcium-permeable channels highly expressed in brain that drives Ca²⁺ entry into multiple cellular compartments. TRPC1/3/4/6, TRPV1/2/4, and TRPM2/4/7 channels have been implicated in stroke pathophysiology.

CONCLUSIONS

Although the precise mechanism of transient receptor potential ion channels in cerebral stroke is still unclear, it has the potential to be a therapeutic target for patients with stroke if developed appropriately. Hence, more research is needed to prove its efficacy in this context.

Dexmedetomidine Attenuates Apoptosis and Neurological Deficits by Modulating Neuronal NADPH Oxidase 2-Derived Oxidative Stress in Neonates Following Hypoxic Brain Injury

Hypoxic-ischemic brain injury is an important cause of neonatal neurological deficits. Our previous study demonstrated that dexmedetomidine (Dex) provided neuroprotection against neonatal hypoxic brain injury; however, the underlying mechanisms remain incompletely elucidated. Overactivation of NADPH oxidase 2 (NOX2) can cause neuronal apoptosis and neurological deficits. Hence, we aimed to investigate the role of neuronal NOX2 in Dex-mediated neuroprotection and to explore its potential mechanisms. Hypoxic injury was modeled in neonatal rodents in vivo and in cultured hippocampal neurons in vitro. Our results showed that pre- or post-treatment with Dex improved the neurological deficits and alleviated the hippocampal neuronal damage and apoptosis caused by neonatal hypoxia. In addition, Dex treatment significantly suppressed hypoxia-induced neuronal NOX2 activation; it also reduced oxidative stress, as evidenced by decreases in intracellular reactive oxygen species (ROS) production, malondialdehyde, and 8-hydroxy-2-deoxyguanosine, as well as increases in the antioxidant enzymatic activity of superoxide dismutase and glutathione peroxidase in neonatal rat hippocampi and in hippocampal neurons. Lastly, the posthypoxicneuroprotective action of Dex was almost completely abolished in NOX2-deficient neonatal mice and NOX2-knockdown neurons. In conclusion, our data demonstrated that neuronal NOX2-mediated oxidative stress is involved in the neuroprotection that Dex provides against apoptosis and neurological deficits in neonates following hypoxia.

Silencing TRPM2 enhanced erastin- and RSL3-induced ferroptosis in gastric cancer cells through destabilizing HIF-1α and Nrf2 proteins

Ferroptosis is a regulated form of cell death driven by small molecules or conditions that induce lipid-based reactive oxygen species (ROS) accumulation. Cation channel transient receptor potential melastatin-2 (TRPM2) is crucial for cancer cell survival. Our bioinformatic analysis revealed that TRPM2 is associated with cellular responses to chemical stimulus and oxidative stress, implying the potential role of TRPM2 in ferroptosis. Gastric cancer cells were treated with the ferroptosis-inducer, Erastin and RSL3. siRNA transfection was used to silence TRPM2. The levels of GSH, Fe2+, ROS and lipid peroxidation, and the activity of GPx activity were evaluated by flow cytometry and spectrophotometer. The effect of TRPM2 on ubiquitination of HIF-1α and Nrf2 were evaluated by co-immunoprecipitation. Erastin and RSL3 induced the up-regulation of TRPM2 in gastric cancer cell lines, especially in SGC7901 and MGC803. These two cells also showed stronger resistance to Erastin and RSL3 than the other cell lines. TRPM2 knockdown reduced the concentration of GSH and GPx activity, but enhanced the concentration of Fe2+, ROS and lipid peroxidation, which are significant indicators of ferroptosis. Importantly, silencing TRPM2 enhanced the inhibitory effects of Erastin and RSL3 on gastric cancer cell viability, migration, and invasion. TRPM2 stabilized and finally elevated the abundance of HIF-1α and Nrf2 in SGC7901 and MGC803 cells upon Erastin and RSL3. Activation of HIF-1α impaired Erastin- and RSL3-induced ferroptosis after TRPM2 knockdown. Collectively, silencing TRPM2 enhanced Erastin- and RSL3-induced ferroptosis in gastric cancer cells through destabilizing HIF-1α and Nrf2 proteins.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10616-022-00545-z.

TRPV1 stimulation increased oxidative neurotoxicity and apoptosis in the glia cell membrane but not in the perinuclear area: An evidence of TRPV1 subtype

Glia are essential neurons of the immune system in the central nervous system. The effective mission of glia depends on their activation, release of cytokines, and oxidative cleaning of debris material from neuronal cells. Accumulating evidence indicates that microglia activation-induced oxidative stress via the activation Ca2+ permeable TRPV1 channel has an essential role in the pathophysiology of neurodegenerative diseases. However, there is scarce information on the cytosolic localization of TRPV1 and the induction of oxidative cytotoxicity in the glia. Hence, we investigated the interactions between cytosolic TRPV1 expression levels and oxidative neurotoxicity in the BV2, C8-D1A, N9 glia, and DBTRG glioblastoma cells. We observed TRPV1 expression in the perinuclear area but not in the cell membrane in the BV2, C8-D1A, and N9 cells. Hence, we observed no activation of TRPV1 on the increase of mitochondrial free reactive oxygen species (mROS) and apoptosis in the cells after the capsaicin stimulation. However, we observed TRPV1 channel expression in the positive control (DBTRG) cell membranes. Hence, the Ca2+ influx, TRPV1 current density, apoptosis, and mROS levels were increased in the DBTRG cells after the capsaicin stimulation, although their levels were diminished by the treatment of the TRPV1 blocker (capsazepine). In conclusion, the presence of TRPV1 in the cell membrane of DBTRG cells induced excessive generation of mROS and apoptosis actions, although the presence of TRPV1 in the perinuclear area did not cause the actions. It seems that there is a subtype of TRPV1 in the perinuclear area, and it is not activated by the capsaicin.

Dexmedetomidine Alleviates Neuropathic Pain via the TRPC6-p38 MAPK Pathway in the Dorsal Root Ganglia of Rats

Purpose

Neuropathic pain is a chronic intractable disease characterized by allodynia and hyperalgesia. Effective treatments are unavailable because of the complicated mechanisms of neuropathic pain. Transient receptor potential canonical 6 (TRPC6) is a nonselective calcium (Ca2+)-channel protein related to hyperalgesia. Dexmedetomidine (Dex) is an alpha-2 (α2) adrenoreceptor agonist that mediates intracellular Ca2+ levels to alleviate pain. However, the relationship between TRPC6 and Dex is currently unclear. We speculated that the α2 receptor agonist would be closely linked to the TRPC6 channel. We aimed to investigate whether Dex relieves neuropathic pain by the TRPC6 pathway in the dorsal root ganglia (DRG).

Methods

The chronic constriction injury (CCI) model was established in male rats, and we evaluated the mechanical withdrawal threshold (MWT) and thermal withdrawal latency (TWL). The expression of TRPC6 and Iba-1 in the DRG were analyzed using quantitative real-time polymerase chain reaction, Western blot, and immunofluorescence assay. The levels of inflammatory cytokines were measured using an enzyme-linked immunosorbent assay.

Results

Compared with the CCI normal saline group, both the MWT and TWL were significantly improved after 7 days of Dex administration. Results demonstrated that TRPC6 expression was increased in the DRG following CCI but was suppressed by Dex. In addition, multiple administrations of Dex inhibited the phosphorylation level of p38 mitogen-activated protein kinase and the upregulation of neuroinflammatory factors.

Conclusion

The results of this study demonstrated that Dex exhibits anti-nociceptive and anti-inflammatory properties in a neuropathic pain model. Moreover, our findings of the CCI model suggested that Dex has an inhibitory effect on TRPC6 expression in the DRG by decreasing the phosphorylation level of p38 in the DRG.

Low-dose dexamethasone in combination with luteolin improves myocardial infarction recovery by activating the antioxidative response

This study aimed to explore the effects of dexamethasone (DEX) and its combination with luteolin (LUT) on cardiac function during myocardial infarction (MI) in a mouse model. We evaluated whether the Keap1/Nrf2 pathway mediates the cardioprotective function of DEX both in vivo and in vitro. The MI mouse model was established by ligation of the left anterior descending coronary artery of wild-type (WT) and Nrf2 knockout mice. After recovery for 21 days, DEX or its combination with LUT was intraperitoneally administered at different doses to WT or Nrf2 knockout mice daily for 7 consecutive days. Mice treated with DEX at a low dose (50 μg/kg/day) showed better cardiac function, fewer cardiac lesions, and smaller infarct sizes compared with MI model mice. DEX (50 μg/kg/day) administration also significantly decreased the production of reactive oxygen species (ROS) and pro-inflammatory cytokines, increased the expression of antioxidative enzymes, and activated the Keap1/Nrf2/HO-1 pathway. However, in Nrf2 knockout mice, DEX treatment did not influence cardiac function, inflammation, the oxidative response, or Keap1/Nrf2/HO-1 activation. In the MI cell model, low concentrations of DEX attenuated the H₂O₂-induced decreases in cell viability and antioxidative enzyme levels and activated the Keap1/Nrf2/HO-1 pathway. Low doses of DEX exerted protective effects in MIR mice and MI cell models by improving cardiac function, eliminating ROS, inhibiting inflammatory responses, and activating antioxidative responses. The protective effects of DEX on myocardial tissues were mediated by the Keap1/Nrf2/HO-1 pathway.

Umbilical cord-derived mesenchymal stem cell conditioned medium reverses neuronal oxidative injury by inhibition of TRPM2 activation and the JNK signaling pathway

Background

The mechanism by which MSC-CM protects neuronal cells against ischemic injury remains to be elucidated. In this study, we aimed to clarify the protective effect of umbilical cord-derived mesenchymal stem cell conditioned medium (UC-MSC-CM) on neuronal oxidative injury and its potential mechanism.

Methods and Results

Neuronal oxidative damage was mimicked by H2O2 treatment of the HT22 cell line. The numbers of cleaved-Caspase-3-positive cells and protein expression of Caspase-9 induced by H2O2 treatment were decreased by UC-MSC-CM treatment. Furthermore, SOD protein expression was increased in the MSC-CM group compared with that in the H2O2 group. The H2O2-induced TRPM2-like currents in HT22 cells were attenuated by MSC-CM treatment. In addition, H2O2 treatment downregulated the expression of p-JNK protein in HT22 cells, and this the downward trend was reversed by incubation with MSC-CM.

Conclusions

UC-MSC-CM protects neurons against oxidative injury, possibly by inhibiting activation of TRPM2 and the JNK signaling pathway.

A novel antagonist of TRPM2 and TRPV4 channels: Carvacrol

The overload cytosolic free Ca²⁺ (cCa²⁺) influx-mediated excessive generation of oxidative stress in the pathophysiological conditions induces neuronal and cellular injury via the activation of cation channels. TRPM2 and TRPV4 channels are activated by oxidative stress, and their specific antagonists have not been discovered yet. The antioxidant and anti-Covid-19 properties of carvacrol (CARV) were recently reported. Hence, I suspected possible antagonist properties of CARV against oxidative stress (OS)/ADP-ribose (ADPR)-induced TRPM2 and GSK1016790A (GSK)-mediated TRPV4 activations in neuronal and kidney cells. I investigated the antagonist role of CARV on the activations of TRPM2 and TRPV4 in SH-SY5Y neuronal, BV-2 microglial, and HEK293 cells. The OS/ADPR and GSK in the cells caused to increase of TRPM2/TRPV4 current densities and overload cytosolic free Ca²⁺ (cCa²⁺) influx with an increase of mitochondrial membrane potential, cytosolic (cROS), and mitochondrial (mROS) ROS. The changes were not observed in the absence of TRPM2 and TRPV4 or the presence of Ca²⁺ free extracellular buffer and PARP-1 inhibitors (PJ34 and DPQ). When OS-induced TRPM2 and GSK-induced TRPV4 activations were inhibited by the treatment of CARV, the increase of cROS, mROS, lipid peroxidation, apoptosis, cell death, cCa²⁺ concentration, caspase -3, and caspase -9 levels were restored via upregulation of glutathione and glutathione peroxidase. In conclusion, the treatment of CARV modulated the TRPM2 and TRPV4-mediated overload Ca²⁺ influx and may provide an avenue for protecting TRPM2 and TRPV4-mediated neurodegenerative diseases associated with the increase of mROS and cCa²⁺. The possible TRPM2 and TRPV4 blocker action of carvacrol (CARV) via the modulation oxidative stress and apoptosis in the SH-SY5Y neuronal cells. TRPM2 is activated by DNA damage-induced (via PARP-1 activation) ADP-ribose (ADPR) and reactive oxygen species (ROS) (H₂O₂), although it is inhibited by nonspecific inhibitors (ACA and 2-APB). TRPV4 is activated by the treatments of GSK1016790A (GSK), although it is inhibited by a nonspecific inhibitor (ruthenium red, RuRe). The treatment of GSK induces excessive generation of ROS. The accumulation of free cytosolic Ca²⁺ (cCa²⁺) via the activations of TRPM2 and TRPV4 in the mitochondria causes the increase of mitochondrial membrane depolarization (ΔΨm). In turn, the increase of ΔΨm causes the excessive generation of ROS. The TRPM2 and TRPV4-induced the excessive generations of ROS result in the increase of apoptosis and cell death via the activations of caspase -3 (Casp-3) and caspase -9 (Casp-9) in the neuronal cells, although their oxidant actions decrease the glutathione (GSH) and glutathione peroxidase (GSHPx) levels. The oxidant and apoptotic adverse actions of TRPM2 and TRPV4 are modulated by the treatment of CARV.

Nonopioid Analgesics for the Perioperative Geriatric Patient: A Narrative Review

Management of acute perioperative pain in the geriatric patient can be challenging as the physiologic and pharmacokinetic changes associated with aging may predispose older patients to opioid-related side effects. Furthermore, elderly adults are more susceptible to postoperative delirium and postoperative cognitive dysfunction, which may be exacerbated by both poorly controlled postoperative pain and commonly used pain medications. This narrative review summarizes the literature published in the past 10 years for several nonopioid analgesics commonly prescribed to the geriatric patient in the perioperative period. Nonopioid analgesics are broken down as follows: medications prescribed throughout the perioperative period (acetaminophen and nonsteroidal anti-inflammatory drugs), medications limited to the acute perioperative setting (N-methyl-D-aspartate receptor antagonists, dexmedetomidine, dexamethasone, and local anesthetics), and medications to be used with caution in the geriatric patient population (gabapentinoids and muscle relaxants). Our search identified 1757 citations, but only 33 specifically focused on geriatric analgesia. Of these, only 21 were randomized clinical trials' and 1 was a systematic review. While guidance in tailoring pain regimens that focus on the use of nonopioid medications in the geriatric patient is lacking, we summarize the current literature and highlight that some nonopioid medications may extend benefits to the geriatric patient beyond analgesia.

Sufentanil alleviates cerebral ischemia-reperfusion injury by inhibiting inflammation and protecting the blood-brain barrier in rats

Stroke is a brain system disease with a high fatality rate and disability rate. About 80% of strokes are ischemic strokes. Cerebral ischemia-reperfusion injury (CIRI) caused by ischemic stroke seriously affects the prognosis of stroke patients. The purpose of this study is to investigate the effect of sufentanil (SUF) on CIRI model rats. We used middle cerebral artery occlusion (MCAO) to make the CIRI model in rats and monitored region cerebral blood flow (rCBF) to ensure that blood flow was blocked and recanalized. We used ELISA and RT-PCR to detect the expression of inflammatory factors in rat serum and brain tissue. In addition, we detected the expression of metalloproteinase (MMP) 2, MMP9 and collagen IV in brain tissues and performed Evans blue (EB) assay to determine the permeability of the blood-brain barrier (BBB). Finally, we clarified the apoptosis of brain tissue through the TUNEL staining and the detection of caspase3, Bcl2 and Bax. Various concentrations of SUF, especially 5, 10 and 25 μg/kg of SUF, all alleviated the infarct size, neurological function and brain edema of MCAO rats. SUF pretreatment also effectively reduced the expression of inflammatory cytokines in MCAO rats, including interleukin (IL)-1β, IL-4, IL-6, IL-8, IL-10 and tumor necrosis factor (TNF)-α. In addition, SUF also inhibited MMP2 and MMP9 and promoted the expression of collagen IV, indicating that SUF attenuated the destruction of the BBB. SUF also inhibited caspase3 and Bax rats and promoted Bcl2 in MCAO rats, thus inhibiting cell apoptosis. SUF pretreatment effectively improved the neurological function and cerebral infarction of MCAO rats, inhibited excessive inflammation in rats, protected the BBB, and inhibited cell apoptosis in brain tissue.

Electroacupuncture Pretreatment Attenuates Cerebral Ischemia-Reperfusion Injury in Rats Through Transient Receptor Potential Vanilloid 1-Mediated Anti-apoptosis via Inhibiting NF-κB Signaling Pathway

Our previous study showed that electroacupuncture (EA) pretreatment elicited protective effect on cerebral ischemia-reperfusion injury (CIRI) in rats, at least partly, which was associated with transient receptor potential vanilloid 1 (TRPV1)-regulated anti-oxidant stress and anti-inflammation. In this study, we further investigated the possible contribution of TRPV1-mediated anti-apoptosis in EA pretreatment-evoked neuroprotection in CIRI. After EA pretreatment at Baihui (GV20), bilateral Shenshu (BL23) and Sanyinjiao (SP6) acupoints, transient focal cerebral ischemia was induced by middle cerebral artery occlusion (MCAO) for 2 h followed by reperfusion for 6 h in rats. Then, infarct volume, nerve cell injury, neuronal apoptosis, NF-κB signaling activation, and expression of TRPV1 were evaluated by TTC staining, Hematoxylin-Eosin staining, transmission electron microscopy, immunochemistry, immunofluorescence, and Western blot, respectively. The presented data showed that EA pretreatment significantly reduced infarct volume, relieved nerve cell injury, decreased the expression of pro-apoptotic proteins Bax and cleaved caspase-3, increased the level of anti-apoptotic protein Bcl-2, inhibited NF-κB (p65) transcriptional activity, and curbed TRPV1 expression in MCAO rats. By contrast, enhancement of TRPV1 expression accompanying capsaicin application, the specific TRPV1 agonists, markedly accelerated nerve cell damage, aggravated neuronal apoptosis, prompted nuclear translocation of NF-κB (p65), resulting in the reversion of EA pretreatment-evoked neuroprotective effect in MCAO rats. Thus, we conclude that EA pretreatment-induced downregulation of neuronal TRPV1 expression plays an anti-apoptosis role through inhibiting NF-κB signaling pathway, thereby protecting MCAO rats from cerebral ischemia-reperfusion injury.

TRPM2 in ischemic stroke: Structure, molecular mechanisms, and drug intervention

Ischemic stroke has a high lethality rate worldwide, and novel treatments are limited. Calcium overload is considered to be one of the mechanisms of cerebral ischemia. Transient receptor potential melastatin 2 (TRPM2) is a reactive oxygen species (ROS)-sensitive calcium channel. Cerebral ischemia-induced TRPM2 activation triggers abnormal intracellular Ca2+ accumulation and cell death, which in turn causes irreversible brain damage. Thus, TRPM2 has emerged as a new therapeutic target for ischemic stroke. This review provides data on the expression, structure, and function of TRPM2 and illustrates its cellular and molecular mechanisms in ischemic stroke. Natural and synthetic TRPM2 inhibitors (both specific and nonspecific) are also summarized. The three-dimensional protein structure of TRPM2 has been identified, and we speculate that molecular simulation techniques will be essential for developing new drugs that block TRPM2 channels. These insights about TRPM2 may be the key to find potent therapeutic approaches for the treatment of ischemic stroke.

Hydroxychloroquine Attenuates Acute Inflammation (LPS)-Induced Apoptosis via Inhibiting TRPV1 Channel/ROS Signaling Pathways in Human Monocytes

Simple Summary

LPS is a well-known agent in cell line models, including U937 monocytes, for inducing acute inflammation (INF). It is not known whether antioxidant HCQ, through the inhibition of TRPV1 in U937, can decrease oxidative monocyte toxicity and cell death. We investigated the modulator action of HCQ treatment through the modulation of TRPV1 on the levels of mROS, INF, and apoptosis in an LPS-stimulated U937 monocyte model. Acute INF activates apoptotic, inflammatory, and oxidant action through acute INF-dependent excessive cROS, MDA, cytokine generation, and Ca²⁺ influx in U937 human monocyte cells. Furthermore, treatment with acute INF increases TRPV1 and apoptotic marker (CAS3, CAS9, Bax, and Bcl-2) concentrations via downregulation of glutathione level and glutathione peroxidase activity in U937 monocytes. The acute INF-caused U937 oxidative stress and cytotoxicity is diminished by the treatment of HCQ and TRPV1 inhibitor (CPZ). In summary, treatment with HCQ and CPZ induced anti-inflammatory, anti-apoptotic, and antioxidant action via the inhibition of cROS, cytokine generation, and caspase activation.

Abstract

Acute inflammation (INF) and apoptosis are induced in monocytes by the generation of several factors, including the products of cytosolic oxygen free radicals (cROS) and the excessive influx of Ca²⁺ via the stimulation of TRPV1. These are main factors in the etiology of monocyte activation-induced inflammatory and neurodegenerative diseases. Importantly, the protective action of hydroxychloroquine (HCQ) treatment via the inhibition of TRPV1 on the levels of inflammatory factors, cROS, and apoptosis in acute INF (lipopolysaccharide, LPS)-exposed neuronal cells was recently reported. However, the relationships between acute INF via TRPV1 activation and HCQ in monocytes have not been fully clarified yet. The cell membrane of U937 human monocytes contains natural TRPV1. In the study plan, we used U937 cells in four main groups, namely control, HCQ (60 μM for 48 h), INF (1 μg/mL LPS for 16 h), and HCQ + INF. The current data indicate that LPS-induced acute INF caused the upregulation of excessive cytosolic Ca²⁺ accumulation via the stimulation of TRPV1 in the cells. The treatment of INF additionally upregulated the levels of apoptosis and cytokines (IL6, IL1β, and TNFα), due to upregulated cROS and lipid peroxidation levels as well as upregulated generation of caspase -3 (CAS3) and -9 (CAS9) but a decrease in glutathione and glutathione peroxidase. The expression levels of TRPV1, Bax, CAS3, and CAS9 were also upregulated by the treatment of LPS. However, treatment with HCQ and TRPV1 blocker (capsazepine) modulated the levels of cytokines, caspases, cROS, Ca²⁺ influx, and apoptosis through the modulation of TRPV1 in the U937 that were stimulated with LPS. In summary, the present data suggest TRPV1 activation through the acute INF (LPS)-induced inflammatory, oxidant, and apoptotic adverse actions in monocyte cells, whereas HCQ prevented adverse actions via the modulation of TRPV1. The results may be significant in the modulation of monocyte activation-caused inflammatory and neurodegenerative diseases.

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 does not compromise neuronal viability, synaptic connectivity, learning and memory in a rodent model

Recent animal studies have drawn concerns regarding most commonly used anesthetics and their long-term cytotoxic effects, specifically on the nervous tissue. It is therefore imperative that the search continues for agents that are non-toxic at both the cellular and behavioural level. One such agent appears to be dexmedetomidine (DEX) which has not only been found to be less neurotoxic but has also been shown to protect neurons from cytotoxicity induced by other anesthetic agents. However, DEX's effects on the growth and synaptic connectivity at the individual neuronal level, and the underlying mechanisms have not yet been fully resolved. Here, we tested DEX for its impact on neuronal growth, synapse formation (in vitro) and learning and memory in a rodent model. Rat cortical neurons were exposed to a range of clinically relevant DEX concentrations (0.05-10 µM) and cellular viability, neurite outgrowth, synaptic assembly and mitochondrial morphology were assessed. We discovered that DEX did not affect neuronal viability when used below 10 µM, whereas significant cell death was noted at higher concentrations. Interestingly, in the presence of DEX, neurons exhibited more neurite branching, albeit with no differences in corresponding synaptic puncta formation. When rat pups were injected subcutaneously with DEX 25 µg/kg on postnatal day 7 and again on postnatal day 8, we discovered that this agent did not affect hippocampal-dependent memory in freely behaving animals. Our data demonstrates, for the first time, the non-neurotoxic nature of DEX both in vitro and in vivo in an animal model providing support for its utility as a safer anesthetic agent. Moreover, this study provides the first direct evidence that although DEX is growth permissive, causes mitochondrial fusion and reduces oxygen reactive species production, it does not affect the total number of synaptic connections between the cortical neurons in vitro.

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.

Dexmedetomidine attenuates myocardial ischemia-reperfusion injury in vitro by inhibiting NLRP3 Inflammasome activation

Background

Myocardial ischemia-reperfusion injury (MIRI) is the most common cause of death worldwide. The NOD-, LRR- and pyrin domain-containing protein 3 (NLRP3) inflammasome plays an important role in the inflammatory response to MIRI. Dexmedetomidine (DEX), a specific agonist of α2-adrenergic receptor, is commonly used for sedation and analgesia in anesthesia and critically ill patients. Several studies have shown that dexmedetomidine has a strong anti-inflammatory effect in many diseases. Here, we investigated whether dexmedetomidine protects against MIRI by inhibiting the activation of the NLRP3 inflammasome in vitro.

Methods

We established an MIRI model in cardiomyocytes (CMs) alone and in coculture with cardiac fibroblasts (CFs) by hypoxia/reoxygenation (H/R) in vitro. The cells were treated with dexmedetomidine with or without MCC950 (a potent selective NLRP3 inhibitor). The beating rate and cell viability of cardiomyocytes, NLRP3 localization, the expression of inflammatory cytokines and NLRP3 inflammasome-related proteins, and the expression of apoptosis-related proteins, including Bcl2 and BAX, were determined.

Results

Dexmedetomidine treatment increased the beating rates and viability of cardiomyocytes cocultured with cardiac fibroblasts. The expression of the NLRP3 protein was significantly upregulated in cardiac fibroblasts but not in cardiomyocytes after H/R and was significantly attenuated by dexmedetomidine treatment. Expression of the inflammatory cytokines IL-1β, IL-18 and TNF-α was significantly increased in cardiac fibroblasts after H/R and was attenuated by dexmedetomidine treatment. NLRP3 inflammasome activation induced the increased expression of cleaved caspase1, mature IL-1β and IL-18, while dexmedetomidine suppressed H/R-induced NLRP3 inflammasome activation in cardiac fibroblasts. In addition, dexmedetomidine reduced the expression of Bcl2 and BAX in cocultured cardiomyocytes by suppressing H/R-induced NLRP3 inflammasome activation in cardiac fibroblasts.

Conclusion

Dexmedetomidine treatment can suppress H/R-induced NLRP3 inflammasome activation in cardiac fibroblasts, thereby alleviating MIRI by inhibiting the inflammatory response.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12871-021-01334-5.

Selenium and Neurological Diseases: Focus on Peripheral Pain and TRP Channels

Pain is a complex physiological process that includes many components. Growing evidence supports the idea that oxidative stress and Ca2+ signaling pathways participate in pain detection by neurons. The main source of endogenous reactive oxygen species (ROS) is mitochondrial dysfunction induced by membrane depolarization, which is in turn caused by Ca2+ influx into the cytosol of neurons. ROS are controlled by antioxidants, including selenium. Selenium plays an important role in the nervous system, including the brain, where it acts as a cofactor for glutathione peroxidase and is incorporated into selenoproteins involved in antioxidant defenses. It has neuroprotective effects through modulation of excessive ROS production, inflammation, and Ca2+ overload in several diseases, including inflammatory pain, hypersensitivity, allodynia, diabetic neuropathic pain, and nociceptive pain. Ca2+ entry across membranes is mediated by different channels, including transient receptor potential (TRP) channels, some of which (e.g., TRPA1, TRPM2, TRPV1, and TRPV4) can be activated by oxidative stress and have a role in the induction of peripheral pain. The results of recent studies indicate the modulator roles of selenium in peripheral pain through inhibition of TRP channels in the dorsal root ganglia of experimental animals. This review summarizes the protective role of selenium in TRP channel regulation, Ca2+ signaling, apoptosis, and mitochondrial oxidative stress in peripheral pain induction.

Dexmedetomidine Alleviates Hypoxia-Induced Synaptic Loss and Cognitive Impairment via Inhibition of Microglial NOX2 Activation in the Hippocampus of Neonatal Rats

BACKGROUND

Perinatal hypoxia is a universal cause of death and neurological deficits in neonates worldwide. Activation of microglial NADPH oxidase 2 (NOX2) leads to oxidative stress and neuroinflammation, which may contribute to hypoxic damage in the developing brain. Dexmedetomidine has been reported to exert potent neuroprotection in several neurological diseases, but the mechanism remains unclear. We investigated whether dexmedetomidine acts through microglial NOX2 to reduce neonatal hypoxic brain damage.

METHODS

The potential role of microglial NOX2 in dexmedetomidine-mediated alleviation of hypoxic damage was evaluated in cultured BV2 microglia and neonatal rats subjected to hypoxia. In vivo, neonatal rats received dexmedetomidine (25 μg/kg, i.p.) 30 min before or immediately after hypoxia (5% O2, 2 h). Apocynin-mediated NOX inhibition and lentivirus-mediated NOX2 overexpression were applied to further assess the involvement of microglial NOX2 activation.

RESULTS

Pre- or posttreatment with dexmedetomidine alleviated hypoxia-induced cognitive impairment, restored damaged synapses, and increased postsynaptic density-95 and synaptophysin protein expression following neonatal hypoxia. Importantly, dexmedetomidine treatment suppressed hypoxia-induced microglial NOX2 activation and subsequent oxidative stress and the neuroinflammatory response, as reflected by reduced 4-hydroxynonenal and ROS accumulation, and decreased nuclear NF-κB p65 and proinflammatory cytokine levels in cultured BV2 microglia and the developing hippocampus. In addition, treating primary hippocampal neurons with conditioned medium (CM) from hypoxia-activated BV2 microglia resulted in neuronal damage, which was alleviated by CM from dexmedetomidine-treated microglia. Moreover, the neuroprotective effect of dexmedetomidine was reversed in NOX2-overexpressing BV2 microglia and diminished in apocynin-pretreated neonatal rats.

CONCLUSION

Dexmedetomidine targets microglial NOX2 to reduce oxidative stress and neuroinflammation and subsequently protects against hippocampal synaptic loss following neonatal hypoxia.

The decrease in hippocampal transient receptor potential M2 (TRPM2) channel and muscarinic acetylcholine receptor 1 (CHRM1) is associated with memory loss in a surgical menopause rat model

INTRODUCTION

The aim of the study was to investigate the association of transient receptor potential M2 (TRPM2) channel and muscarinic acetylcholine receptor 1 (CHRM1) activity with the memorial functions that are deteriorated in surgical menopause.

MATERIAL AND METHODS

A total of 14 female rats were randomly divided into 2 groups: group (G)1: sham group; group (G)2: surgical menopause group, the group in which bilateral ovariectomy was performed. Fourteen days after the surgical procedure, learning and memorial tests were performed in G1 and G2 for a totally 13 days. The time required for the rats to find the cheese in the labyrinth was recorded and statistical evaluation of it was performed between groups. On the 14^th day of the memory test, the rats were decapitated and the brain tissues were fixed in 10% formalin. Hippocampal TRPM2 and CHRM1 gene expression was evaluated with RNA isolation, complementary DNA (cDNA) synthesis and quantitative real-time PCR (qRT-PCR) analysis. TRPM2 and CHRM1 immunoreactivity was evaluated in hippocampal tissue with the immunohistochemical method. Histo-score was calculated regarding the diffuseness of and severity of the staining; and statistical analyses were performed.

RESULTS

In the ovariectomized group, the mean time required for the rats to find the cheese was statistically significantly elongated (39.29 ±4.0 s vs. 29.86 ±2.6 s). When the hippocampal TRPM2 and CHRM1 gene expression and immunoreactivity were compared with the sham group, there was a statistically significant decrease in the surgical menopause group (p < 0.05).

CONCLUSIONS

In surgical menopause, in deterioration of memorial functions, hippocampal TRPM2 channel and CHRM1 activity plays an important role.

Supplementation with γ-glutamylcysteine (γ-GC) lessens oxidative stress, brain inflammation and amyloid pathology and improves spatial memory in a murine model of AD

INTRODUCTION

The accumulation of oxidative stress, neuroinflammation and abnormal aggregation of amyloid β-peptide (Aβ) have been shown to induce synaptic dysfunction and memory deficits in Alzheimer's disease (AD). Cellular depletion of the major endogenous antioxidant Glutathione (GSH) has been linked to cognitive decline and the development of AD pathology. Supplementation with γ-glutamylcysteine (γ-GC), the immediate precursor and the limiting substrate for GSH biosynthesis, can transiently augment cellular GSH levels by bypassing the regulation of GSH homeostasis.

METHODS

In the present study, we investigated the effect of dietary supplementation of γ-GC on oxidative stress and Aβ pathology in the brains of APP/PS1 mice. The APP/PS1 mice were fed γ-GC from 3 months of age with biomarkers of apoptosis and cell death, oxidative stress, neuroinflammation and Aβ load being assessed at 6 months of age.

RESULTS

Our data showed that supplementation with γ-GC lowered the levels of brain lipid peroxidation, protein carbonyls and apoptosis, increased both total GSH and the glutathione/glutathione disulphide (GSH/GSSG) ratio and replenished ATP and the activities of the antioxidant enzymes (superoxide dismutase (SOD), catalase, glutamine synthetase and glutathione peroxidase (GPX)), the latter being a key regulator of ferroptosis. Brain Aβ load was lower and acetylcholinesterase (AChE) activity was markedly improved compared to APP/PS1 mice fed a standard chow diet. Alteration in brain cytokine levels and matrix metalloproteinase enzymes MMP-2 and MMP-9 suggested that γ-GC may lower inflammation and enhance Aβ plaque clearance in vivo. Spatial memory was also improved by γ-GC as determined using the Morris water maze.

CONCLUSION

Our data collectively suggested that supplementation with γ-GC may represent a novel strategy for the treatment and/or prevention of cognitive impairment and neurodegeneration.

Up-regulation of miRNA-151-3p enhanced the neuroprotective effect of dexmedetomidine against β-amyloid by targeting DAPK-1 and TP53

Alzheimer's disease (AD) is the most common cause of dementia and is the leading lethal disease among the elderly. Dexmedetomidine (Dex) has been reported to have multiple neuroprotective effects, but its effect against beta-amyloid (Aβ) has not been completely determined and understood. Dex can activate both α2 adrenoceptor/cAMP/PKA and imidazoline I receptors/ERK1/2 signals. To determine which signal is critical for the effect of Dex on Aβ toxicity, we treated SH-SY5Y and PC12 cells with inhibitors of α2 adrenoceptor and ERK1/2. Dex suppressed the apoptosis of neuronal cells and production of reactive oxygen species induced by Aβ. These suppressive effects were attenuated by both inhibitors. As indicated by western blot, Dex stimulates both pro-apoptosis (activating death-associated protein kinase 1 [DAPK-1] and p53) and anti-apoptotic (up-regulating bcl-2 and bcl-xL) signals in Aβ-treated neuronal cells. This effect is likely associated with ERK1/2 signaling because ERK1/2 inhibitor disrupts the effect of Dex on these signals. To eliminate the pro-apoptotic effect of Dex while retaining its anti-apoptosis action, we screened miRNA-151-3p to target DAPK-1 and p53. Transfection with miRNA-151-3p mimics suppressed DAPK-1 and TP53 expression induced by Dex and increased Nrf-2 and SOD expression. More importantly, increasing miRNA-151-3p enhanced the anti-apoptotic and antioxidative effects of Dex in Aβ-treated neuronal cells. Overall, this study revealed that Dex additionally stimulated pro-apoptosis signaling, although it suppressed Aβ-induced apoptosis of neuronal cells. miRNA-151-3p enhanced the neuroprotective effect of Dex against Aβ by targeting DAPK-1 and TP53.

Dexmedetomidine Protects against Myocardial Ischemia/Reperfusion Injury by Ameliorating Oxidative Stress and Cell Apoptosis through the Trx1-Dependent Akt Pathway

Dexmedetomidine (Dex) was reported to reduce oxidative stress and protect against myocardial Ischemia/Reperfusion (I/R) injury. However, the molecular mechanism involved in its antioxidant property is not fully elucidated. The present study was aimed at investigating whether the Trx1/Akt pathway participated in the cardioprotective effect of Dex. In the present study, I/R-induced myocardial injury in isolated rat hearts and OGD/R-induced injury in H9c2 cardiomyocytes were established. Our findings suggested that Dex ameliorated myocardial I/R injury by improving cardiac function, reducing myocardial apoptosis and oxidative stress, which was manifested by increased GSH and SOD contents, decreased ROS level, and MDA generation in both the isolated rat hearts and OGD/R-treated H9C2 cells. More importantly, it was found that the level of Trx1 was preserved, and Akt phosphorylation was significantly upregulated by Dex treatment. However, these effects of Dex were abolished by PX-12 (a specific Trx1 inhibitor) administration. Taken together, this study suggests that Dex plays a protective role in myocardial I/R injury, improves cardiac function, and relieves oxidative stress and cell apoptosis. Furthermore, our results present a novel signaling mechanism that the cardioprotective effect of Dex is at least partly achieved through the Trx1-dependent Akt pathway.

Resveratrol diminishes bisphenol A-induced oxidative stress through TRPM2 channel in the mouse kidney cortical collecting duct cells

Bisphenol A (BisPH-A) is a latent danger that threatens our health, which we frequently exposure in our modern life (e.g. the widespread use of drinking water in plastic pet bottles). But the BisPH-A induced transient receptor potential melastatin 2 (TRPM2)-mediated oxidative stress and apoptosis in these cells has not been studied yet. Calcium (Ca²⁺) plays an important role in a versatile intracellular signal transduction that works over a wide range to regulate oxidative stress processes. TRPM2 is activated by oxidative stress and it has emerged as an important Ca²⁺ signaling mechanism in a variety of cells, contributing many cellular functions including cell death. Resveratrol (RESV), which belongs to the polyphenol group, acts as an antioxidant, eliminating cellular oxidative stress and increasing the body's resistance to diseases. The current study aimed to elucidate the effect of antioxidant resveratrol on TRPM2-mediated oxidative stress induced by BisPH-A exposure in the mouse kidney cortical collecting duct cells (mpkCCD_cl4). The cells were divided into four groups as control, resveratrol (50 µM for 24 h), BisPH-A (100 µM for 24 h) and BisPH-A + RESV. Intracellular free Ca²⁺ concentrations and TRPM2 channel currents were high in BisPH-A treated cells, but decreased with resveratrol treatment. In addition, BisPH-A induced mitochondrial membrane depolarization, reactive oxygen species (ROS), caspase 3, caspase 9 and apoptosis values were decreased by the resveratrol treatment. In conclusion, resveratrol protected cells from BisPH-A induced oxidative damage. In this study, we showed that TRPM2 channel mediates this protective effect of resveratrol.

[Role of mitochondrial fusion and fission in protective effects of dexmedetomidine against cerebral ischemia/reperfusion injury in mice]

OBJECTIVE

To investigate the protective effects of dexmedetomidine (DEX) against cerebral ischemia/reperfusion (I/R) injury in mice and its relation with mitochondrial fusion and fission.

METHODS

Male ICR mice were randomly divided into sham-operated group, I/R group, I/R+DEX group and I/R+DEX+dorsomorphin group. Mouse models of cerebral I/R injury were established by modified thread occlusion of the middle cerebral artery. DEX (50 μg/kg) was injected intraperitoneally at 30 min before cerebral ischemia, which lasted for 1 h followed by reperfusion for 24 h. The neurobehavioral deficits of the mice were evaluated based on Longa's scores. The volume of cerebral infarction was detected by TTC staining. The changes in mitochondrial morphology of the brain cells were observed with transmission electron microscopy. Western blotting was performed to detect the expressions of phosphorylated AMP-activated protein kinase (p-AMPK), mitochondrial fusion protein (Mfn2) and mitochondrial fission protein (p-Drp1) in the brain tissues.

RESULTS

DEX pretreatment significantly reduced the neurobehavioral score and the percent volume of cerebral infarction in mice with cerebral I/R injury. Treatment with dorsomorphin (an AMPK inhibitor) in addition to DEX significantly increased the neurobehavioral score and the percent volume of cerebral infarction in the mouse models. Transmission electron microscopy showed that DEX obviously reduced mitochondrial damage caused by cerebral I/R injury and restored mitochondrial morphology of the brain cells, and such effects were abolished by dorsomorphin treatment. Western blotting showed that DEX pretreatment significantly increased the expressions of p-AMPK and Mfn2 protein and decreased the expression of p-Drp1 protein in the brain tissue of the mice, and these changes were also reversed by dorsomorphin treatment.

CONCLUSIONS

Preconditioning with DEX produces protective effects against cerebral I/R injury in mice possibly by activating AMPK signaling to regulate mitochondrial fusion and fission in the brain cells.

TRPV1 Contributes to the Neuroprotective Effect of Dexmedetomidine in Pilocarpine-Induced Status Epilepticus Juvenile Rats

To investigate the antiepileptic and neuroprotective effects of dexmedetomidine (Dex) in pilocarpine- (Pilo-) induced status epilepticus (SE) juvenile rats, rats were randomly assigned to the following six groups (n = 20): normal, normal+Dex, SE, SE+Cap, SE+Dex, and SE+Dex+Cap. The rats were treated with either diazepam (i.p., an antiepileptic drug) or Dex after the onset of SE. The Morris water maze was used to assess rat cognitive behavior. Flow cytometry was used to detect the concentrations of Ca²⁺, mitochondrial membrane potential, and reactive oxygen species. Transmission electron microscopy was performed to evaluate specimens of brain tissue. The levels of caspase 3 and TRPV1 were examined by western blot and immunohistochemistry (IHC). Treatment with Dex significantly decreased the escape latency of the SE rats (P < 0.05). Capsaicin, a TRPV1 agonist, delivery aggravated the performance of SE rats. Pathological changes in SE rat were attenuated by Dex and deteriorated by capsaicin. Swollen mitochondria and abnormal endoplasmic reticulum were found in SE rats and were then aggravated by capsaicin and reversed by Dex. Moreover, our data showed that Dex significantly restrained calcium overload, ROS production, and mitochondrial membrane potential loss, all of which were induced by Pilo and capsaicin (P < 0.05). Dex decreased the apoptotic rate in the Model SE group (P < 0.05) and TRPV1 and caspase 3 expression in the Dex treatment group (P < 0.05). Interestingly, all these effects of Dex were partially counteracted by the TRPV1 agonist, capsaicin (P < 0.05). Our study showed that Dex exerted a neuroprotective effect in Pilo-induced SE rats by inhibiting TRPV1 expression and provided information for therapy to SE patients.

One Single Nucleotide Polymorphism of the TRPM2 Channel Gene Identified as a Risk Factor in Bipolar Disorder Associates with Autism Spectrum Disorder in a Japanese Population

The transient receptor potential melastatin 2 (TRPM2) is a non-specific cation channel, resulting in Ca²⁺ influx at warm temperatures from 34 °C to 47 °C, thus including the body temperature range in mammals. TRPM2 channels are activated by β-NAD⁺, ADP-ribose (ADPR), cyclic ADPR, and 2′-deoxyadenosine 5′-diphosphoribose. It has been shown that TRPM2 cation channels and CD38, a type II or type III transmembrane protein with ADP-ribosyl cyclase activity, simultaneously play a role in heat-sensitive and NAD⁺ metabolite-dependent intracellular free Ca²⁺ concentration increases in hypothalamic oxytocinergic neurons. Subsequently, oxytocin (OT) is released to the brain. Impairment of OT release may induce social amnesia, one of the core symptoms of autism spectrum disorder (ASD). The risk of single nucleotide polymorphisms (SNPs) and variants of TRPM2 have been reported in bipolar disorder, but not in ASD. Therefore, it is reasonable to examine whether SNPs or haplotypes in TRPM2 are associated with ASD. Here, we report a case-control study with 147 ASD patients and 150 unselected volunteers at Kanazawa University Hospital in Japan. The sequence-specific primer-polymerase chain reaction method together with fluorescence correlation spectroscopy was applied. Of 14 SNPs examined, one SNP (rs933151) displayed a significant p-value (OR = 0.1798, 95% CI = 0.039, 0.83; Fisher’s exact test; p = 0.0196). The present research data suggest that rs93315, identified as a risk factor for bipolar disorder, is a possible association factor for ASD.

Curcumin diminishes cisplatin-induced apoptosis and mitochondrial oxidative stress through inhibition of TRPM2 channel signaling pathway in mouse optic nerve

Background: Cisplatin (CiSP), a chemotherapeutic agent, is widely used to treat several types of cancers. However, its clinical use is limited due to adverse side effects caused by excessive production of reactive oxygen species (ROS) and death of neurons. The transient receptor potential (TRP) melastatin 2 (TRPM2) cation channel is activated by ADP-ribose (ADPR) and ROS. The protective effect of curcumin (CURCU) against CiSP-induced apoptosis and mitochondrial ROS through inhibition of TRP channels in several types of neuron except optic nerve, was recently reported. The aim of the current study is to clarify the protective effect of CURCU on CiSP-induced mitochondrial oxidative injury and TRPM2 activation in the mice optic nerve and SH-SY5Y human derived neuronal cells.Material and methods: The SH-SY5Y cells and mice were divided into four groups: Control, CURCU, CiSP, and CURCU + CiSP. The mice were treated for 14 days and the cells were incubated with CiSP and CURCU for 24 h.Results: CURCU and PARP-1 inhibitor (PJ34) treatments ameliorated CiSP-induced mitochondrial membrane depolarization, mitochondrial and cytosolic ROS levels and neuronal death in the optic nerve. In the patch-clamp of SH-SY5Y cells and laser confocal microscopy experiments of optic nerve, CURCU and TRPM2 blocker treatments also decreased ADPR-induced TRPM2 currents and cytosolic free calcium ion (Ca²⁺) concentration, suggesting a suppression of Ca²⁺ influx and neuronal death.Conclusion: CURCU prevents CiSP-induced optic nerve oxidative injury and cell death by suppressing mitochondrial ROS production via regulating TRPM2 signaling pathways. CURCU may serve as a potential therapeutic target against CiSP-induced toxicity in the optic nerve of CiSP-treated patients.

Knocking down TRPM2 expression reduces cell injury and NLRP3 inflammasome activation in PC12 cells subjected to oxygen-glucose deprivation

Transient receptor potential melastatin 2 (TRPM2) is an important ion channel that represents a potential target for treating injury caused by cerebral ischemia. However, it is unclear whether reducing TRPM2 expression can help repair cerebral injury, and if so what the mechanism underlying this process involves. This study investigated the protective effect of reducing TRPM2 expression on pheochromocytoma (PC12) cells injured by oxygen-glucose deprivation (OGD). PC12 cells were transfected with plasmid encoding TRPM2 shRNAS, then subjected to OGD by incubation in glucose-free medium under hypoxic conditions for 8 hours, after which the cells were allowed to reoxygenate for 24 hours. Apoptotic cells, mitochondrial membrane potentials, reactive oxygen species levels, and cellular calcium levels were detected using flow cytometry. The relative expression of C-X-C motif chemokine ligand 2 (CXCL2), NACHT, LRR, and PYD domain-containing protein 3 (NALP3), and caspase-1 were detected using fluorescence-based quantitative reverse transcription-polymerase chain reaction and western blotting. The rates of apoptosis, mitochondrial membrane potentials, reactive oxygen species levels, and cellular calcium levels in the TRPM2-shRNA + OGD group were lower than those observed in the OGD group. Taken together, these results suggest that TRPM2 knockdown reduces OGD-induced neuronal injury, potentially by inhibiting apoptosis and reducing oxidative stress levels, mitochondrial membrane potentials, intracellular calcium concentrations, and NLRP3 inflammasome activation.

Sedation with midazolam worsens the diaphragm function than dexmedetomidine and propofol during mechanical ventilation in rats

BACKGROUND

Mechanical ventilation (MV) is identified as an independent contributor to diaphragmatic atrophy and contractile dysfunction. Appropriate sedation is also essential during MV, and anesthetics may have direct adverse effects on the diaphragm. However, there is a lack of research into the effects of different anesthetics on diaphragm function during MV.

OBJECTIVES

In the present study, we aim to examine the effect of midazolam, dexmedetomidine, and propofol on diaphragm function during MV.

DESIGN

Animal study.

SETTING

University research laboratory.

SUBJECTS

Male Wistar rats.

INTERVENTIONS

Animals were experienced 12 h of MV or spontaneous breathing (SB) with continuous anesthetics infusion. Diaphragm contractile properties, cross-sectional areas, microcirculation, oxidative stress, and proteolysis were examined.

MEASUREMENTS AND MAIN RESULTS

Diaphragmatic specific force was markedly reduced in the midazolam group compared with the dexmedetomidine (-60.4 ± 3.01%, p < 0.001) and propofol group (-58.3 ± 2.60%, p < 0.001) after MV. MV sedated with midazolam induced more atrophy of type II fibers compared with dexmedetomidine (-21.8 ± 2.11%, p = 0.0001) and propofol (-8.2 ± 1.53%, p = 0.003). No significant differences of these indices were found in the midazolam, dexmedetomidine, and propofol groups under SB condition (all p > 0.05, respectively). Twelve hours of MV resulted in a time dependent reduction in diaphragmatic functional capillary density (PB -25.1%, p = 0.0001; MZ -21.6%, p = 0.0003; DD -15.2%, p = 0.022; PP -24.8%, p = 0.0001, respectively), which did not occur in the gastrocnemius muscle. The diaphragmatic lipid peroxidation adducts 4-HNE and HIF-1α levels were significantly lower in dexmedetomidine group and propofol group compared to midazolam group (p < 0.05, respectively). Meanwhile, the catalase and SOD levels were also relatively lower (p < 0.05, respectively) in midazolam group compared to dexmedetomidine group and propofol group.

CONCLUSIONS

Twelve hours of mechanical ventilation during midazolam sedation led to a more severe diaphragm dysfunction than dexmedetomidine and propofol, possibly caused by its relative weaker antioxidant capacity.

Dexmedetomidine inhibits neuronal apoptosis by inducing Sigma-1 receptor signaling in cerebral ischemia-reperfusion injury

Dexmedetomidine is known to alleviate cerebral ischemia-reperfusion injury (CIRI). We established a rat model of CIRI, which exhibited higher neurological deficit scores and a greater number of apoptotic cells in the cerebral ischemic penumbra than controls. Dexmedetomidine reversed the neuronal apoptosis and improved neurological function in this model. We then examined Sigma-1 receptor (Sig-1R) expression on the endoplasmic reticulum (ER) in brain tissues at different reperfusion time points. Sig-1R expression increased with CIRI and decreased with increasing reperfusion times. After 24 hours of reperfusion, dexmedetomidine upregulated Sig-1R expression, and ER stress proteins (GRP78, CHOP, JNK and Caspase-3) were detected in brain tissues with Western blotting. Moreover, GRP78 expression followed a pattern similar to Sig-1R. Dexmedetomidine induced GRP78 expression but inhibited CHOP, Caspase-3 and phosphorylated-JNK expression in brain tissues. A Sig-1R-specific inhibitor reduced GRP78 expression and partially inhibited the upregulation of GRP78 by dexmedetomidine. The inhibitor also increased CHOP and Caspase-3 expression and partially reversed the inhibitory effects of dexmedetomidine on these pro-apoptotic ER stress proteins. These results suggest that dexmedetomidine at least partially inhibits ER stress-induced apoptosis by activating Sig-1R, thereby attenuating brain damage after 24 hours of ischemia-reperfusion.

High‑fat treatment prevents postoperative cognitive dysfunction in a hyperlipidemia model by protecting the blood‑brain barrier via Mfsd2a‑related signaling

Damage to the blood-brain barrier (BBB) resulting from systemic inflammation caused by surgical trauma is associated with cognitive dysfunction, and individuals with hyperlipidemia are more sensitive to such impairment. The present study was designed to ascertain whether dexmedetomidine (Dex) treatment could reduce the incidence of cognitive dysfunction following surgery in a hyperlipidemia model. Hyperlipidemia was induced in Sprague-Dawley rats (male, 6–7 months old) by consuming a high-fat diet, and rats were divided into three groups (n=10 each) and underwent: exploratory laparotomy to introduce surgical trauma (surgery group), laparotomy and Dex treatment (surgery+Dex group), or sham surgery (sham group). Learning, memory and exploration behavior were assessed using the Morris water maze. Concentrations of tumor necrosis factor (TNF)-α and interleukin (IL)-1β, were determined by enzyme-linked immunosorbent assay. BBB permeability was assessed by Evans blue staining. Relative major facilitator superfamily domain-containing protein 2 (Mfsd2a) mRNA expression was determined by quantitative PCR. In the Morris water maze test, the time and distance ratio for the surgery group was significantly lower than those of the sham and surgery+Dex groups (P<0.05). In addition, the TNF-α concentrations in the sham and surgery+Dex groups were lower than that in the surgery group (P<0.05 on days 1 and 3). Evans Blue staining was increased in the surgery group on day 1 (P<0.01). Mfsd2a mRNA expression was higher in the sham and surgery+Dex groups compared with that noted in the surgery group (P<0.05). In conclusion, Dex treatment decreased the incidence of cognitive dysfunction following surgical trauma in a hyperlipidemia rat model. We demonstrated that Dex stabilized BBB integrity through increased Mfsd2a gene expression.

Dexmedetomidine protects H9c2 cardiomyocytes against oxygen-glucose deprivation/reoxygenation-induced intracellular calcium overload and apoptosis through regulating FKBP12.6/RyR2 signaling

Purpose

Intracellular calcium ([Ca²⁺]i) overload is a major cause of cell injury during myocardial ischemia/reperfusion (I/R). Dexmedetomidine (DEX) has been shown to exert anti-inflammatory and organ protective effects. This study aimed to investigate whether pretreatment with DEX could protect H9c2 cardiomyocytes against oxygen-glucose deprivation/reoxygenation (OGD/R) injury through regulating the Ca²⁺ signaling.

Methods

H9c2 cardiomyocytes were subjected to OGD for 12 h, followed by 3 h of reoxygenation. DEX was administered 1 h prior to OGD/R. Cell viability, lactate dehydrogenase (LDH) release, level of [Ca²⁺]i, cell apoptosis, and the expression of 12.6-kd FK506-binding protein/ryanodine receptor 2 (FKBP12.6/RyR2) and caspase-3 were assessed.

Results

Cells exposed to OGD/R had decreased cell viability, increased LDH release, elevated [Ca²⁺]i level and apoptosis rate, down-regulated expression of FKBP12.6, and up-regulated expression of phosphorylated-Ser2814-RyR2 and cleaved caspase-3. Pretreatment with DEX significantly blocked the above-mentioned changes, alleviating the OGD/R-induced injury in H9c2 cells. Moreover, knockdown of FKBP12.6 by small interfering RNA abolished the protective effects of DEX.

Conclusion

This study indicates that DEX pretreatment protects the cardiomyocytes against OGD/R-induced injury by inhibiting [Ca²⁺]i overload and cell apoptosis via regulating the FKBP12.6/RyR2 signaling. DEX may be used for preventing cardiac I/R injury in the clinical settings.

Dexmedetomidine Impairs Diaphragm Function and Increases Oxidative Stress but Does Not Aggravate Diaphragmatic Atrophy in Mechanically Ventilated Rats

BACKGROUND

Anesthetics in ventilated patients are critical as any cofactor hampering diaphragmatic function may have a negative impact on the weaning progress and therefore on patients' mortality. Dexmedetomidine may display antioxidant and antiproteolytic properties, but it also reduced glucose uptake by the muscle, which may impair diaphragm force production. This study tested the hypothesis that dexmedetomidine could inhibit ventilator-induced diaphragmatic dysfunction.

METHODS

Twenty-four rats were separated into three groups (n = 8/group). Two groups were mechanically ventilated during either dexmedetomidine or pentobarbital exposure for 24 h, referred to as interventional groups. A third group of directly euthanized rats served as control. Force generation, fiber dimensions, proteolysis markers, protein oxidation and lipid peroxidation, calcium homeostasis markers, and glucose transporter-4 (Glut-4) translocation were measured in the diaphragm.

RESULTS

Diaphragm force, corrected for cross-sectional area, was significantly decreased in both interventional groups compared to controls and was significantly lower with dexmedetomidine compared to pentobarbital (e.g., 100 Hz: -18%, P < 0.0001). In contrast to pentobarbital, dexmedetomidine did not lead to diaphragmatic atrophy, but it induced more protein oxidation (200% vs. 73% in pentobarbital, P = 0.0015), induced less upregulation of muscle atrophy F-box (149% vs. 374% in pentobarbital, P < 0.001) and impaired Glut-4 translocation (-73%, P < 0.0005). It activated autophagy, the calcium-dependent proteases, and caused lipid peroxidation similarly to pentobarbital.

CONCLUSIONS

Twenty-four hours of mechanical ventilation during dexmedetomidine sedation led to a worsening of ventilation-induced diaphragm dysfunction, possibly through impaired Glut-4 translocation. Although dexmedetomidine prevented diaphragmatic fiber atrophy, it did not inhibit oxidative stress and activation of the proteolytic pathways.

Mitochondrial oxidative stress-induced brain and hippocampus apoptosis decrease through modulation of caspase activity, Ca2+ influx and inflammatory cytokine molecular pathways in the docetaxel-treated mice by melatonin and selenium treatments

Docetaxel (DOCE) is widely used to treat several types of glioblastoma. Adverse effects DOCE seriously limit its clinical use in several tissues. Its side effects on brain cortex and hippocampus have not been clarified yet. Limited data indicated a protective effect of melatonin (MLT) and selenium (SELEN) on DOCE-induced apoptosis, Ca²⁺ influx and mitochondrial reactive oxygen species (ROS) in several tissues except brain and hippocampus. The purpose of this study is to discover the protective effect of MLT and SELEN on DOCE-induced brain and hippocampus oxidative toxicity in mice. MLT and SELEN pretreatments significantly ameliorated acute DOCE-induced mitochondrial ROS production in the hippocampus and brain tissues by reducing levels of lipid peroxidation, intracellular ROS production and mitochondrial membrane depolarization, while increasing levels of total antioxidant status, glutathione, glutathione peroxidase, MLT, α-tocopherol, γ-tocopherol, vitamin A, vitamin C and β-carotene in the tissues. Furthermore, MLT and SELEN pretreatments increased cell viability and TRPM2 channel activation in the hippocampus and brain followed by decreased activations of TNF-α, IL-1β, IL-6, and caspase -3 and - 9, suggesting a suppression of calcium ion influx, apoptosis and inflammation responses. However, modulator role of SELEN on the values in the tissues is more significant than in the MLT treatment. MLT and SELEN prevent DOCE-induced hippocampus and brain injury by inhibiting mitochondrial ROS and cellular apoptosis through regulating caspase -3 and - 9 activation signaling pathways. MLT and SELEN may serve as potential therapeutic targets against DOCE-induced toxicity in the hippocampus and brain.

Protective effect of dexmedetomidine against diabetic hyperglycemia-exacerbated cerebral ischemia/reperfusion injury: An in vivo and in vitro study

AIMS

Dexmedetomidine (Dex) has been noted to have neuroprotective effect against cerebral ischemia-reperfusion (I/R) injury. However, the effect of Dex in diabetic hyperglycemia-exacerbated cerebral I/R injury and its underlying mechanism remain unclear.

MAIN METHODS

The infarct volume and brain edema were evaluated by 2,3,5-triphenyltetrazolium chloride staining and standard wet-dry method. Modified neurological severity score was utilized to assess the neurological deficits. The oxidative stress and inflammation were evaluated by detecting reactive oxygen species (ROS), malondialdehyde (MDA), tumor necrosis factor (TNF)-α and interleukin (IL)-1β. Terminal deoxynucleotidyl transferase dUTP nick end labeling assay and cell count kit-8 were applied to measure cell apoptosis and viability.

KEY FINDINGS

Dex treatment reduced infarct volume, decreased brain water content and improved neurological deficit in middle cerebral artery occlusion/reperfusion (MCAO/R) mice. Dex treatment reduced the levels of ROS, MDA, TNF-α and IL-1β in the entire middle cerebral artery territory of diabetic mice subjected to MCAO/R, as well as in primary culture of mouse hippocampal neurons stimulated with 50 mM glucose and oxygen glucose deprivation/reperfusion. Dex treatment inhibited neuronal apoptosis induced by diabetic hyperglycemia-exacerbated cerebral I/R injury. Dex upregulated nuclear factor of activated T-cells 5 (NFAT5) and Sirtuin 1 (SIRT1) expression, induced NF-E2-related factor 2 (Nrf2) translocation from cytoplasm to nucleus and inhibited the acetylation of Nrf2. However, these changes triggered by Dex treatment were abrogated by NFAT5 knockdown.

SIGNIFICANCE

Dex protects against diabetic hyperglycemia-exacerbated cerebral I/R injury through attenuation of oxidative stress, inflammation and apoptosis. The underlying mechanism is at least the NFAT5/SIRT1/Nrf2 signaling pathway dependent.

Dexmedetomidine alleviates cerebral ischemia-reperfusion injury in rats via inhibition of hypoxia-inducible factor-1α

Dexmedetomidine (Dex) was reported to reduce ischemia-reperfusion (I/R) injury in kidney and brain tissues. Thus, we aimed to study the role and mechanism of Dex in cerebral I/R injury by inhibiting hypoxia-inducible factor-1α (HIF-1α) and apoptosis. First, I/R injury models were established. Six groups were assigned after different treatments: sham, I/R, I/R+Dex, I/R+2-methoxyestradiol (2ME2) (HIF-1α inhibitor), I/R+CoCl ₂ (HIF-1α activator), and I/R+Dex+CoCl ₂ groups. Neurological function, cerebral infarction volume, survival, and apoptosis of brain cells were then analyzed. Besides, immunohistochemistry and Western blot analysis were used to detect the expression of HIF-1α, BCL-2[B-cell leukemia/lymphoma 2] adenovirus E1B interacting protein 3 (BNIP3), B-cell leukemia/lymphoma 2 (BCL2), BCL2[B-cell leukemia/lymphoma 2] associated X (Bax), and cleaved-caspase3 proteins in brain tissues. I/R rats showed cerebral infarction, increased neurological function score, number of terminal-deoxynucleoitidyl transferase mediated nick end labeling (TUNEL)-positive cells and HIF-1α-positive cells as well as decreased neurons. Inhibition of HIF-1α can reduce the apoptosis induced by I/R, and overexpression of HIF-1α can aggravate apoptosis in brain tissue of I/R rats. Furthermore, activation of HIF-1α expression blocks the inhibitory effect of Dex on neuronal apoptosis in I/R rats. Dex may inhibit the neuronal apoptosis of I/R rats by inhibiting the HIF-1α pathway and then improve the cerebral I/R injury in rats.