Inhibiting NLRP3 inflammasome with MCC950 ameliorates perioperative neurocognitive disorders, suppressing neuroinflammation in the hippocampus in aged mice.

Perioperative neurocognitive disorders (PND) are characterized by deficits in cognitive functions in the elderly following anesthesia and surgery. Effective clinical interventions for preventing this disease are limited. Growing evidence demonstrates that activation of NOD-like receptor protein3 (NLRP3) inflammasome is involved in neurodegenerative diseases. We therefore hypothesized that activation of NLRP3 inflammasome is linked to neuroinflammation and the subsequent cognitive impairments that occurred in an animal model of PND. In this study, 18-month-old C57BL/6 mice were subjected to an exploratory laparotomy under isoflurane anesthesia to mimic clinical human abdominal surgery. For interventional studies, mice received NLRP3 specific inhibitor MCC950 (10 mg/kg) or the vehicle only intraperitoneally. Behavioral studies were performed at 6 and 7 d after surgery using open field and fear conditioning tests, respectively. Interleukin-1ß (IL-1ß), interleukin-18 (IL-18), tumor necrosis factor-α (TNF-α), ionized calcium-binding adaptor molecule-1 (IBA1) positive cells, glial fibrillary acidic protein (GFAP) positive cells, NLRP3, apoptosis-associated speck-like protein containing a CARD (ASC), and cleaved caspase-1 were measured at 3 days post-surgery. Brain-derived neurotrophic factor (BDNF) and postsynaptic density protein 95 (PSD95) were measured at 7 days post-surgery. Our data indicates that surgery-induced cognitive impairments were associated with significant increases in IL-1ß, IL-18, TNF-α, NLRP3, ASC, cleaved caspase-1, IBA1-positive cells and GFAP-positive cells, and decreases in BDNF and PSD95 expression in the hippocampus. Notably, administration with MCC950 attenuated inflammatory changes and rescued surgery-induced cognitive impairments. Our study suggests that surgery induces neuroinflammation and cognitive deficits that are partly attributed to the activation of NLRP3 inflammasome in the hippocampus of aged mice.

NLRP3/Caspase-1 Pathway-Induced Pyroptosis Mediated Cognitive Deficits in a Mouse Model of Sepsis-Associated Encephalopathy.

Sepsis-associated encephalopathy (SAE) is a common complication that leads to long-term cognitive impairments and increased mortality in sepsis survivors. The mechanisms underlying this complication remain unclear and an effective intervention is lacking. Accumulating evidence suggests the nucleotide-binding domain-like receptor protein3 (NLRP3)/caspase-1 pathway is involved in several neurodegenerative diseases. Thus, we hypothesized that the NLRP3/caspase-1 pathway is involved in NLRP3-mediated pyroptosis, maturation and release of inflammatory cytokines, and cognitive deficits in SAE. We used the NLRP3 inhibitor MCC950 and the caspase-1 inhibitor Ac-YVAD-CMK to study the role of the NLRP3/caspase-1 pathway in pyroptosis and cognitive deficits in a mouse model of SAE. Mice were randomly assigned to one of six groups: sham+saline, sham+MCC950, sham+Ac-YVAD-CMK, cecal ligation and puncture (CLP)+saline, CLP+MCC950, and CLP+Ac-YVAD-CMK. Surviving mice underwent behavioral tests or had hippocampal tissues collected for histochemical analysis and biochemical assays. Our results show that CLP-induced hippocampus-dependent memory deficits are accompanied by increased NLRP3 and caspase-1 positive cells, and augmented protein levels of NLRP3, caspase-1, gasdermin-D, and pro-inflammatory cytokines in the hippocampus. In addition, administration of MCC950 or Ac-YVAD-CMK rescues cognitive deficits and ameliorates increased hippocampal NLRP3-mediated neuronal pyroptosis and pro-inflammatory cytokines. Our results suggest that the NLRP3/caspase-1 pathway-induced pyroptosis mediates cognitive deficits in a mouse model of SAE.

Inhibition of spinal MAPKs by scorpion venom peptide BmK AGAP produces a sensory-specific analgesic effect.

Background Several studies have shown that scorpion venom peptide BmK AGAP has an analgesic activity. Our previous study also demonstrated that intraplantar injection of BmK AGAP ameliorates formalin-induced spontaneous nociceptive behavior. However, the effect of intrathecal injection of BmK AGAP on nociceptive processing is poorly understood. Methods We investigated the effects of intrathecal injection of BmK AGAP on spinal nociceptive processing induced by chronic constrictive injury or formalin. Thermal hyperalgesia and mechanical allodynia were measured using radiant heat and the von Frey filaments test. Formalin-induced spontaneous nociceptive behavior was also investigated. C-Fos expression was assessed by immunohistochemistry. Phosphorylated mitogen-activated protein kinase (p-MAPK) expression was monitored by Western blot assay. Results Intrathecal injection of BmK AGAP reduced chronic constrictive injury-induced neuropathic pain behavior and pain from formalin-induced inflammation, accompanied by decreased expression of spinal p-MAPKs and c-Fos protein. The results of combining low doses of different MAPK inhibitor (U0126, SP600125, or SB203580; 0.1 µg for each inhibitor) with a low dose of BmK AGAP (0.2 µg) suggested that BmK AGAP could potentiate the effects of MAPK inhibitors on inflammation-associated pain. Conclusion Our results demonstrate that intrathecal injection of BmK AGAP produces a sensory-specific analgesic effect via a p-MAPK-dependent mechanism.

Antinociceptive effects of analgesic-antitumor peptide (AGAP), a neurotoxin from the scorpion Buthus martensii Karsch, on formalin-induced inflammatory pain through a mitogen-activated protein kinases-dependent mechanism in mice.

In the present study, we investigated the anti-nociceptive effect and the underlying mechanism of the analgesic-antitumor peptide (AGAP), a neurotoxin from the scorpion Buthus martensii Karsch. AGAP in doses of 0.2, 1 and 5 µg was injected intraplantarly (i.pl.) before formalin injection 10 min at the same site. The suppression by intraplantar injection of AGAP on formalin-induced spontaneous nociceptive behaviors was investigated. The results show that AGAP could dose-dependently inhibit formalin-induced two-phase spontaneous flinching response. To investigate the mechanism of action of treatment with AGAP in inflammatory pain, the expressions of peripheral and spinal phosphorylated mitogen-activated protein kinases (phospho-MAPKs) including p-p38, p-ERK and p-JNK were examined. We found that formalin increased the expressions of peripheral and spinal MAPKs, which were prevented by pre-intraplantar injection of AGAP in inflammation pain model in mice. AGAP could also decrease the expression of spinal Fos induced by formalin. Furthermore, combinations the lower doses of the inhibitors of MAPKs (U0126, SP600125, or SB203580 0.1 µg) with the lower dose of AGAP (0.2 µg), the results suggested that AGAP could potentiate the effects of the inhibitors of MAPKs on the inflammatory pain. The present results indicate that pre-intraplantar injection of AGAP prevents the inflammatory pain induced by formalin through a MAPKs-mediated mechanism in mice.