Dexmedetomidine alleviates blunt chest trauma and hemorrhagic shock‑resuscitation‑induced acute lung injury through inhibiting the NLRP3 inflammasome

HEMORRHAGIC SHOCK ASSESSED BY TISSUE MICROCIRCULATORY MONITORING: A NARRATIVE REVIEW

ABSTRACT

Hemorrhagic shock (HS) is a common complication after traumatic injury. Early identification of HS can reduce patients' risk of death. Currently, the identification of HS relies on macrocirculation indicators such as systolic blood pressure and heart rate, which are easily affected by the body's compensatory functions. Recently, the independence of the body's overall macrocirculation from microcirculation has been demonstrated, and microcirculation indicators have been widely used in the evaluation of HS. In this study, we reviewed the progress of research in the literature on the use of microcirculation metrics to monitor shock. We analyzed the strengths and weaknesses of each metric and found that microcirculation monitoring could not only indicate changes in tissue perfusion before changes in macrocirculation occurred but also correct tissue perfusion and cell oxygenation after the macrocirculation index returned to normal following fluid resuscitation, which is conducive to the early prediction and prognosis of HS. However, microcirculation monitoring is greatly affected by individual differences and environmental factors. Therefore, the current limitations of microcirculation assessments mean that they should be incorporated as part of an overall assessment of HS patients. Future research should explore how to better combine microcirculation and macrocirculation monitoring for the early identification and prognosis of HS patients.

Dexmedetomidine compared to low-dose ketamine better protected not only the brain but also the lungs in acute ischemic stroke

BACKGROUND

Dexmedetomidine (DEX) and low-dose ketamine (KET) present neuroprotective effects in acute ischemic stroke (AIS); however, to date, no studies have evaluated which has better protective effects not only on the brain but also lungs in AIS.

METHODS

AIS-induced Wistar rats (390 ± 30 g) were randomized after 24-h, receiving dexmedetomidine (STROKE-DEX, n = 10) or low-dose S(+)-ketamine (STROKE-KET, n = 10). After 1-h protective ventilation, perilesional brain tissue and lungs were removed for histologic and molecular biology analysis. STROKE animals (n = 5), receiving sodium thiopental but not ventilated, had brain and lungs removed for molecular biology analysis. Effects of DEX and KET mean plasma concentrations on alveolar macrophages, neutrophils, and lung endothelial cells, extracted primarily 24-h after AIS, were evaluated.

RESULTS

In perilesional brain tissue, apoptosis did not differ between groups. In STROKE-DEX, compared to STROKE-KET, tumor necrosis factor (TNF)-α and vascular cell adhesion molecule-1 (VCAM-1) expressions were reduced, but no changes in nuclear factor erythroid 2-related factor-2 (Nrf2) and super oxide dismutase (SOD)-1 were observed. In lungs, TNF-α and VCAM-1 were reduced, whereas Nrf2 and SOD-1 were increased in STROKE-DEX. In alveolar macrophages, TNF-α and inducible nitric oxide synthase (M1 macrophage phenotype) were lower and arginase and transforming growth factor-β (M2 macrophage phenotype) higher in STROKE-DEX. In lung neutrophils, CXC chemokine receptors (CXCR2 and CXCR4) were higher in STROKE-DEX. In lung endothelial cells, E-selectin and VCAM-1 were lower in STROKE-DEX.

CONCLUSIONS

In the current AIS model, dexmedetomidine compared to low-dose ketamine reduced inflammation and endothelial cell damage in both brain and lung, suggesting greater protection.

Neuroprotective Effect of Dexmedetomidine against Postoperative Cognitive Decline via NLRP3 Inflammasome Signaling Pathway

Dexmedetomidine (Dex), widely used as a sedative in surgical procedures and intensive care units, induces sympatholytic, anxiolytic, analgesic, and sedative effects. Postoperative cognitive dysfunction (POCD) is routinely observed in postoperative care following surgery and general anesthesia. The NLRP3 inflammasome complex plays a critical role in innate immune response by detecting pathogenic microorganisms and activating pro-inflammatory cytokines. Although there are numerous protective effects of Dex among the neurological diseases, specific mechanisms including NLRP3 inflammasome-mediated neuroinflammation via oxidative stress response in a POCD model are not fully understood. Here, we investigated whether Dex exhibits neurocognitive effects through the NLRP3 inflammasome signaling in a POCD mouse model using a neurobehavioral test and ELISA analysis. We also confirmed the level of oxidative stress-related response in the in vitro system in the POCD model. Furthermore, we evaluated the NLRP3 inflammasome complex by immunoprecipitation analysis. In summary, the results of the present study indicated that Dex showed a neuroprotective effect in the POCD model by reducing oxidative stress response through NLRP3 inflammasome-mediated neuroinflammation.

Dexmedetomidine alleviates inflammation in neuropathic pain by suppressing NLRP3 via Nrf2 activation

The aim of the present study was to investigate the mechanism by which dexmedetomidine (DEX) alleviates neuropathic pain in a chronic constriction injury (CCI) model in rats. A CCI rat model was established through sciatic nerve ligation. CCI rats were treated with DEX, the nuclear factor erythroid 2-related factor 2 (Nrf2) inhibitor ML385, the NLR family pyrin domain containing 3 (NLRP3) antagonist MCC950 and/or the NLRP3 activator nigericin. The mechanical withdrawal threshold (MWT) was measured to assess the pain sensitivity of CCI rats. Hematoxylin and eosin staining and TUNEL staining were used to examine spinal injury and apoptosis, respectively. ELISA was used to quantify the levels of inflammatory factors. The expression levels of Nrf2 and NLRP3 were also examined. The results indicated that a decrease in MWT and increases in spinal cord injury, apoptosis and inflammatory factors were detected in CCI rats compared with control rats. Spinal inflammation was abrogated in DEX-treated CCI rats. Compared with the model group, an increase in MWT and decreases in spinal cord injury, apoptosis and inflammatory factors were detected in rats treated with MCC950, while the opposite effects were observed in rats treated with nigericin. The opposite effects on these indicators were observed in the DEX + ML385 and MCC950 + ML385 groups compared with the DEX and MCC950 groups, respectively. MWT was increased, while spinal cord injury, apoptosis and inflammation decreased in the nigericin + DEX group compared with the nigericin group. In summary, the results of the present study indicated that DEX reduced neuropathic pain in CCI rats by suppressing NLRP3 through Nrf2 activation.

Dexmedetomidine alleviates pulmonary edema through the epithelial sodium channel (ENaC) via the PI3K/Akt/Nedd4-2 pathway in LPS-induced acute lung injury

Dexmedetomidine (Dex), a highly selective α2-adrenergic receptor (α2AR) agonist, has an anti-inflammatory property and can alleviate pulmonary edema in lipopolysaccharide (LPS)-induced acute lung injury (ALI), but the mechanism is still unclear. In this study, we attempted to investigate the effect of Dex on alveolar epithelial sodium channel (ENaC) in the modulation of alveolar fluid clearance (AFC) and the underlying mechanism. Lipopolysaccharide (LPS) was used to induce acute lung injury (ALI) in rats and alveolar epithelial cell injury in A549 cells. In vivo, Dex markedly reduced pulmonary edema induced by LPS through promoting AFC, prevented LPS-induced downregulation of α-, β-, and γ-ENaC expression, attenuated inflammatory cell infiltration in lung tissue, reduced the concentrations of TNF-α, IL-1β, and IL-6, and increased concentrations of IL-10 in bronchoalveolar lavage fluid (BALF). In A549 cells stimulated with LPS, Dex attenuated LPS-mediated cell injury and the downregulation of α-, β-, and γ-ENaC expression. However, all of these effects were blocked by the PI3K inhibitor LY294002, suggesting that the protective role of Dex is PI3K-dependent. Additionally, Dex increased the expression of phosphorylated Akt and reduced the expression of Nedd4-2, while LY294002 reversed the effect of Dex in vivo and in vitro. Furthermore, insulin-like growth factor (IGF)-1, a PI3K agonists, promoted the expression of phosphorylated Akt and reduced the expression of Nedd4-2 in LPS-stimulated A549 cells, indicating that Dex worked through PI3K, and Akt and Nedd4-2 are downstream of PI3K. In conclusion, Dex alleviates pulmonary edema by suppressing inflammatory response in LPS-induced ALI, and the mechanism is partly related to the upregulation of ENaC expression via the PI3K/Akt/Nedd4-2 signaling pathway.