Reversing Postcardiopulmonary Bypass Associated Cognitive Dysfunction Using k-Opioid Receptor Agonists to Regulate Microglial Polarization via the NLRP3/Caspase-1 Pathway

Cardiopulmonary bypass (CPB) is mainly used during cardiac surgeries that treat ischemic, valvular, or congenital heart disease and aortic dissections. The disorders of central nervous system (CNS) that occur after cardiopulmonary bypass are attracting considerable interest. Postoperative neurocognitive disorders (PND) have been reported as the leading cause of patients' disability and death following CPB. The k-opioid receptor (KOR) agonists (U50488H) have been suggested to be vital in the treatment of surgically induced CNS neuroinflammatory responses. In this article, the transitions between the M1 and M2 microglial polarization state phenotypes were hypothesized to significantly affect the regulatory mechanisms of KOR agonists on postcardiopulmonary bypass (post-CPB) neuroinflammation. We investigated the effects of U50488H on neuroinflammation and microglia polarization in rats exposed to CPB and explored the method of the NLRP3/caspase-1 pathway. Thirty SD rats were randomly divided into three groups: sham operation group, cardiopulmonary bypass model group, and CPB+ k-opioid receptor agonist (U50488H) group, with ten rats in each group. The Morris water maze was used to evaluate the changes in the cognitive function of CPB rats. Hematoxylin and eosin (HE) staining and TUNEL were performed to assess the rats' hippocampal damage. Enzyme-Linked Immunosorbent Assay (ELISA) was used to detect changes in brain injury markers and inflammatory factors. Furthermore, immunofluorescence was used to observe the expression of microglia polarization and NLRP3 followed by Western blots to detect the expression of the NLRP3/caspase-1 pathway and microglia polarization-related proteins. Rat microglia were cultured in vitro, with LPS stimulation, and treated with U50488H and a caspase-1 antagonist to evaluate the effects and mechanism of action of U50488H. KORs alleviated hippocampal damage caused by CPB and improved PND. CPB activated the NLRP3 inflammasome and upregulated pro-caspase-1 expression which promoted the expression of pro-IL-lβ and pro-IL-18 and resulted in increased inflammation. However, KORs also inhibited NLRP3 and transformed microglia from the M1 to the M2 state. Caspase-1 inhibitor treatment reduced the microglial polarization induced by KORs. The κ-opioid receptor agonists inhibited the inflammation mediated by microglia and improved PND through the NLRP3/caspase-1 signaling pathway.

Dexmedetomidine ameliorates high-fat diet-induced nonalcoholic fatty liver disease by targeting SCD1 in obesity mice

Fatty liver disease is one of the main hepatic complications associated with obesity. To date, there are no therapeutic drugs approved for this pathology. Insulin resistance (IR) is implicated both in pathogenesis of nonalcoholic fatty liver disease (NAFLD) and in disease progression from steatosis to nonalcoholic steatohepatitis. In this study, we have characterized effects of an α2 -adrenoceptor agonist, dexmedetomidine (DEX), which can alleviate IR in hepatocytes in high-fat diet (HFD)-induced NAFLD mice. The NAFLD mice received a daily intraperitoneal administration of DEX (100 μg·kg-1 ) after 16 days exhibited lower body weight, fewer and smaller fat droplets in the liver, markedly reduced the plasma triglyceride levels, accompanied by improvement of liver damage. This inhibition of lipid accumulation activity in obese mice was associated with a robust reduction in the mRNA and protein expression of the lipogenic enzyme stearyl-coenzyme A desaturase 1 (SCD1), which was probably mediated by the inhibition of C/EBP β, PPAR γ and C/EBP α through suppressing α2A -adrenoceptor (α2A -AR) via negative feedback. Additionally, DEX can also improve IR and inflammation by inhibiting the mitogen-activated protein kinases (MAPK) and nuclear factor kappa beta (NFκB) signaling pathway in vivo. Our findings implicate that DEX may act as a potential anti-steatotic drug which ameliorates obesity-associated fatty liver and improves IR and inflammation, probably by suppressing the expression of SCD1 and the inhibition of MAPK/NFκB pathway and suggest the potential adjuvant use for the treatment of NAFLD.

Coronary artery bypass grafting is associated with immunoparalysis of monocytes and dendritic cells

Coronary artery bypass grafting (CABG) triggers a systemic inflammatory response that may contribute to adverse outcomes. Dendritic cells (DC) and monocytes are immunoregulatory cells potentially affected by CABG, contributing to an altered immune state. This study investigated changes in DC and monocyte responses in CABG patients at 5 time-points: admission, peri-operative, ICU, day 3 and day 5. Whole blood from 49 CABG patients was used in an ex vivo whole blood culture model to prospectively assess DC and monocyte responses. Lipopolysaccharide (LPS) was added in parallel to model responses to an infectious complication. Co-stimulatory and adhesion molecule expression and intracellular mediator production was measured by flow cytometry. CABG modulated monocyte and DC responses. In addition, DC and monocytes were immunoparalysed, evidenced by failure of co-stimulatory and adhesion molecules (eg HLA-DR), and intracellular mediators (eg IL-6) to respond to LPS stimulation. DC and monocyte modulation was associated with prolonged ICU length of stay and post-operative atrial fibrillation. DC and monocyte cytokine production did not recover by day 5 post-surgery. This study provides evidence that CABG modulates DC and monocyte responses. Using an ex vivo model to assess immune competency of CABG patients may help identify biomarkers to predict adverse outcomes.

Risk factors of sepsis after open congenital cardiac surgery in infants: a pilot study

Background: Postsurgical sepsis is one of the main causes of the high mortality and morbidity after open congenital heart surgery in infants.  This study aimed to evaluate the role of cardiopulmonary bypass duration, thymectomy, surgical complexity, and nutritional status on postsurgical sepsis after open congenital cardiac surgery in infants.Methods: A total of 40 patients <1 year of age with congenital heart disease, Aristotle Basic Score (ABS) ≥6 were followed for clinical and laboratory data before and after surgery until the occurrence of signs or symptoms of sepsis or until a maximum of 7 days after surgery. Bivariate analyses were performed. Variables with p≤0.200 were then included for logistic regression.Results: Duration of cardiopulmonary bypass ≥90 minutes was associated with 5.538 increased risk of postsurgical sepsis in comparison to those ≤90 minutes (80% vs 25%, RR=5.538, p=0.006). No association was observed between the incidence of postsurgical sepsis with poor nutritional status (86% vs 84%, RR=1.059, p=1.000), thymectomy (and 50% vs 76%, RR=0.481, p=0.157), and Aristotle Basic Score (p=0.870).Conclusion: Cardiopulmonary bypass time influences the incidence of sepsis infants undergoing open congenital cardiac surgery. Further studies are needed to elaborate a number of risk factors associated with the incidence of sepsis in this population.

Effect of perioperative dexmedetomidine on the endocrine modulators of stress response: a meta-analysis

This study examined the effects of perioperative dexmedetomidine treatment on physiological modulators of surgical stress response. The quality of the included studies was assessed prior to performing meta-analyses of the weighted mean differences in the changes from baseline of stress hormones and interpreted in the light of statistical heterogeneity between the studies. Nineteen studies (844 surgical subjects) data were used for this meta-analysis. Dexmedetomidine administration significantly decreased blood cortisol levels (μg/dL) postoperatively (mean difference with 95% confidence interval (CI) from controls: -18.78 (-28.45, -9.10); P < 0.05). In the subgroup analysis, the mean difference between dexmedetomidine-treated and saline-treated subjects in the changes from baseline of the cortisol levels was -20.10 (-30.96, -9.25; P < 0.05) but, between dexmedetomidine- and comparator-treated subjects, it was not statistically significantly different (-15.13 (-49.78, 19.52); P < 0.05). Compared with controls, dexmedetomidine treatment also decreased adrenaline and noradrenaline levels significantly (mean difference in the percent changes from baseline: -90.41 (-145.79, -35.03)%; P < 0.05 and -62.82 (-85.47, -0.40.17)%; P < 0.05, respectively). Dexmedetomidine also decreased prolactin levels with a mean difference of -19.42 (-39.37, 0.52) μg/L (P = 0.06). In conclusion, perioperative use of dexmedetomidine reduces serum catecholamine and cortisol levels but the decrease in cortisol levels was not statistically different from the comparator anaesthetics. More data will be required to assess the effects of dexmedetomidine on corticotropin, prolactin, and growth hormone.