JNK inhibition alleviates delayed neurocognitive recovery after surgery by limiting microglia pyroptosis.

Delayed neurocognitive recovery (dNCR) is a prevalent complication after surgery in older adults. Neuroinflammation plays a pivotal role in the pathogenesis of dNCR. Recently,compelling evidence suggests that theinvolvement of microglia pyroptosis in the regulation of neuroinflammation in neurologicaldiseases. Nevertheless, the exact role of microglia pyroptosis in dNCR remains elusive. In the study, in vitro and in vivo models of dNCR were used to examine the potential effects of the mitogen­activated protein kinase signaling pathway on Nod-like receptor protein 3 (NLRP3) inflammasome-mediated microglia pyroptosis and cognitive deficits following surgery. In vivo, we observed surgery-induced upregulation of phosphorylated (p)-c-Jun N-terminal kinases (JNK) in microglia and subsequently NLRP3 inflammasome activation, pyroptosis, and inflammatory cytokines release in mice hippocampus. Interestingly, JNK inhibitor SP600125 significantly attenuated surgery-induced cognitive impairments through inhibiting pyroptosis, inflammatory responses, and reducing immunoreactivity of NLRP3 and gasdermin D N terminus (GSDMD-N) in hippocampal microglia. In vitro, NLRP3 inflammasome- and pyroptosis-associated proteins and immunoreactivity of NLRP3, GSDMD-N, and interleukin-1ß were activated in BV2 microglial cells following lipopolysaccharide (LPS) stimulation. These effects were significantly suppressed in BV2 cells by SP600125 treatment. Furthermore, treatment with NLRP3 specific inhibitor, MCC950, attenuated microglia pyroptosis induced by LPS, but did not rescue LPS-induced increased expression of p-JNK. These results indicate that the JNK pathway is largely upstream of the NLRP3 inflammasome, which exerts a crucial regulatory impact on microglia pyroptosis and inflammatory responses, thus providing a promising avenue to prevent dNCR.

The Non-peptide Angiotensin-(1-7) Mimic AVE 0991 Attenuates Delayed Neurocognitive Recovery After Laparotomy by Reducing Neuroinflammation and Restoring Blood-Brain Barrier Integrity in Aged Rats.

Delayed neurocognitive recovery (dNCR) after surgery is a common postoperative complication in older adult patients. Our previous studies have demonstrated that cognitive impairment after surgery involves an increase in the brain renin-angiotensin system (RAS) activity, including overactivation of the angiotensin 2/angiotensin receptor-1 (Ang II/AT1) axis, which provokes the disruption of the hippocampal blood-brain barrier (BBB). Nevertheless, the potential role of the counter-regulatory RAS axis, the Ang-(1-7)/Mas pathway, in dNCR remains unknown. Using an aged rat model of dNCR, we dynamically investigated the activity of both axes of the RAS following laparotomy. AVE 0991, a nonpeptide analog of Ang-(1-7), was administered intranasally immediately after laparotomy. We found that the elevation of Ang II, induced by surgery was accompanied by a decrease of Ang-(1-7) in the hippocampus, but not in the circulation. Surgery also significantly downregulated hippocampal Mas receptor expression at 24 h postsurgery. Mas activation with intranasal AVE 0991 treatment significantly improved hippocampus-dependent learning and memory deficits induced by surgery. Furthermore, it attenuated hippocampal neuroinflammation, as shown by the decreased level of the microglial activation marker cluster of differentiation 11b (CD11b) and the decreased production of several inflammatory molecules. Along with these beneficial effects, the AVE 0991 treatment also alleviated the imbalance between matrix metalloproteinase-9 (MMP-9) and tissue inhibitor of matrix metalloproteinase-3 (TIMP-3), modulated the expression of occludin, and alleviated the IgG extravasation, thereby restoring the integrity of the BBB. In conclusion, these data indicate that activation of Mas by AVE 0991 attenuates dNCR after surgery by reducing neuroinflammation and restoring BBB integrity. Our findings suggest that the Ang-(1-7)/Mas pathway may be a novel therapeutic target for treating dNCR after surgery in older adult patients.

[Composition and changes of intestinal flora in septic mouse model].

OBJECTIVE: To investigate the dynamic changes of intestinal flora in septic model mice. METHODS: Forty-two male SPF C57BL/6 mice were selected, the sepsis model was reproduced by cecal ligation and puncture (CLP), and the experimental mice were divided into CLP 6-12 hours group (n = 9) and 1, 2, 3 days group (all n = 10) and Sham group (n = 3) according to the time points after modeling. Intestinal flora 16S rRNA sequencing was carried out within feces from the colonic lumen of mice, and the effective sequences were clustered to obtain an operational classification unit (OTU) for statistical analysis of biological information, including Alpha diversity analysis, species composition analysis, principal coordinate analysis (PCoA analysis) and species difference analysis (LEfSe analysis), the dynamic changes of intestinal flora after CLP modeling were analyzed. RESULTS: Compared with Sham group, with the prolongation of modeling time, the Alpha diversity of intestinal flora decreased, showing a decrease in community richness index (3 days after CLP: Chao index 1 was 367.9±162.6 vs. 508.3±105.9, Ace index was 372.5±151.9 vs. 498.8±104.2), Shannon index decreased in community diversity index (3 days after CLP: 2.57±1.06 vs. 4.30±0.57, Simpson index increased (3 days after CLP: 0.26±0.19 vs. 0.04±0.03), suggesting that with the progress of CLP modeling time, the richness and diversity of intestinal flora decreased. According to species composition analysis, in OTU level, OTU 633 accounted for the highest proportion in CLP 1 day group (24.79%), OTU 1016 was dominant in CLP 2 days and 3 days groups, and the highest proportion was 61.75% in CLP 3 days group; in genus level, the abundance of norank_f_Muribaculaceae showed a slight increase and then a significant decrease with time, the abundance of Escherichia-Shigella increased significantly in CLP 2 days and 3 days groups, the abundance of Lactobacillus increased first and then decreased with time, the abundance of Bacteroides showed a trend of gradual increase with time. PCoA analysis suggested that CLP 6-12 hours group had a higher structural similarity with Sham group. The flora structure changed gradually with the time after modeling, and the change was significant after 3 days of CLP. LEfSe analysis indicated that the main components that caused the differences among the groups were g_norank_f_Muribaculaceae, g_Prevotellaceae_UCG-001, s_uncultured_Bacteroidales_bacterium_g_norank_f_Muribaculaceae, g_Parabacteroides, Escherichia-Shigella and OTU 1016. The differences in abundance of Escherichia-Shigella and OTU 016 among the five groups ranked first in the genus level and OTU level respectively; the abundance of Escherichia-Shigella gradually increased from 0.01% (0%, 0.02%) in 6-12 hours after CLP to 44.79% (3.71%, 53.75%) in 3 days with time, and the abundance of OTU 1016 increased from 0.01% (0%, 0.02%) in 6-12 hours after CLP to 44.69% (3.66%, 53.64%) in 3 days with time. CONCLUSIONS: Intestinal dysbiosis occurred in all CLP model groups, the diversity of the flora gradually decreased with the progress of modeling time, Escherichia-Shigella gradually became the dominant bacteria.

Baicalin Ameliorates Cognitive Impairment and Protects Microglia from LPS-Induced Neuroinflammation via the SIRT1/HMGB1 Pathway.

Systemic inflammation often induces neuroinflammation and disrupts neural functions, ultimately causing cognitive impairment. Furthermore, neuronal inflammation is the key cause of many neurological conditions. It is particularly important to develop effective neuroprotectants to prevent and control inflammatory brain diseases. Baicalin (BAI) has a wide variety of potent neuroprotective and cognitive enhancement properties in various models of neuronal injury through antioxidation, anti-inflammation, anti-apoptosis, and stimulating neurogenesis. Nevertheless, it remains unclear whether BAI can resolve neuroinflammation and cognitive decline triggered by systemic or distant inflammatory processes. In the present study, intraperitoneal lipopolysaccharide (LPS) administration was used to establish neuroinflammation to evaluate the potential neuroprotective and anti-inflammatory effects of BAI. Here, we report that BAI activated silent information regulator 1 (SIRT1) to deacetylate high-mobility group box 1 (HMGB1) protein in response to acute LPS-induced neuroinflammation and cognitive deficits. Furthermore, we demonstrated the anti-inflammatory and cognitive enhancement effects and the underlying molecular mechanisms of BAI in modulating microglial activation and systemic cytokine production, including tumor necrosis factor- (TNF-) α and interleukin- (IL-) 1ß, after LPS exposure in mice and in the microglial cell line, BV2. In the hippocampus, BAI not only reduced reactive microglia and inflammatory cytokine production but also modulated SIRT1/HMGB1 signaling in microglia. Interestingly, pretreatment with SIRT1 inhibitor EX-527 abolished the beneficial effects of BAI against LPS exposure. Specifically, BAI treatment inhibited HMGB1 release via the SIRT1/HMGB1 pathway and reduced the nuclear translocation of HMGB1 in LPS-induced BV2 cells. These effects were reversed in BV2 cells by silencing endogenous SIRT1. Taken together, these findings indicated that BAI reduced microglia-associated neuroinflammation and improved acute neurocognitive deficits in LPS-induced mice via SIRT1-dependent downregulation of HMGB1, suggesting a possible novel protection against acute neurobehavioral deficits, such as delayed neurocognitive recovery after anesthesia and surgery challenges.

Autophagy prevents hippocampal α-synuclein oligomerization and early cognitive dysfunction after anesthesia/surgery in aged rats.

Stress-induced α-synuclein aggregation, especially the most toxic species (oligomers), may precede synaptic and cognitive dysfunction. Under pathological conditions, α-synuclein is degraded primarily through the autophagic/lysosomal pathway. We assessed the involvement of autophagy in α-synuclein aggregation and cognitive impairment following general anesthesia and surgical stress. Autophagy was found to be suppressed in the aged rat hippocampus after either 4-h propofol anesthesia alone or 2-h propofol anesthesia during a laparotomy surgery. This inhibition of autophagy was accompanied by profound α-synuclein oligomer aggregation and neurotransmitter imbalances in the hippocampus, along with hippocampus-dependent cognitive deficits. These events were not observed 18 weeks after propofol exposure with or without surgical stress. The pharmacological induction of autophagy using rapamycin markedly suppressed α-synuclein oligomerization, restored neurotransmitter equilibrium, and improved cognitive behavior after prolonged anesthesia or anesthesia combined with surgery. Thus, both prolonged propofol anesthesia alone and propofol anesthesia during surgery impaired autophagy, which may have induced abnormal hippocampal α-synuclein aggregation and neurobehavioral deficits in aged rats. These findings suggest that the activation of autophagy and the clearance of pathological α-synuclein oligomers may be novel strategies to ameliorate the common occurrence of postoperative cognitive dysfunction.