Microglial TLR4-induced TAK1 phosphorylation and NLRP3 activation mediates neuroinflammation and contributes to chronic morphine-induced antinociceptive tolerance.

BACKGROUND AND PURPOSE: The aim of this work was to investigate the role and signal transduction of toll-like receptor 4 (TLR4), TGF-ß-activated kinase 1 (TAK1) and nod-like receptor protein 3 (NLRP3) in microglial in the development of morphine-induced antinociceptive tolerance. METHODS: TLR4 and NLRP3 knockout mice and 5Z-7-oxozeaeno (a selective inhibitor against TAK1 activity) were used to observe their effect on the development of morphine tolerance. Intrathecal injections of morphine (0.75 mg/kg once daily for 7 days) were used to establish anti-nociceptive tolerance, which was measured by the tail-flick test. Spinal TLR4, TAK1, and NLRP3 expression levels and phosphorylation of TAK1 were evaluated by Western blotting and immunofluorescence. RESULTS: Repeated treatment with morphine increased total expression of spinal TLR4, TAK1, and NLRP3 and phosphorylation of TAK1 in wild-type mice. TLR4 knockout attenuated morphine-induced tolerance and inhibited the chronic morphine-induced increase in NLRP3 and phosphorylation of TAK1. Compared with controls, mice that received 5Z-7-oxozeaenol showed decreased development of morphine tolerance and inhibition on repeated morphine-induced increase of NLRP3 but not TLR4. NLRP3 knockout mice showed resistance to morphine-induced analgesic tolerance with no effect on chronic morphine-induced expression of TLR4 and TAK1. TLR4, TAK1, and NLRP3 were collectively co-localized together and with the microglia marker Iba1. CONCLUSIONS: Microglial TLR4 regulates TAK1 expression and phosphorylation and results in NLRP3 activation contributes to the development of morphine tolerance through regulating neuroinflammation. Targeting TLR4-TAK1-NLRP3 signaling to regulate neuro-inflammation will be alternative therapeutics and strategies for chronic morphine-induced antinociceptive tolerance.

Neutrophil-mimicking therapeutic nanoparticles for targeted chemotherapy of pancreatic carcinoma.

Due to the critical correlation between inflammation and carcinogenesis, a therapeutic candidate with anti-inflammatory activity may find application in cancer therapy. Here, we report the therapeutic efficacy of celastrol as a promising candidate compound for treatment of pancreatic carcinoma via naïve neutrophil membrane-coated poly(ethylene glycol) methyl ether-block-poly(lactic-co-glycolic acid) (PEG-PLGA) nanoparticles. Neutrophil membrane-coated nanoparticles (NNPs) are well demonstrated to overcome the blood pancreas barrier to achieve pancreas-specific drug delivery in vivo. Using tumor-bearing mice xenograft model, NNPs showed selective accumulations at the tumor site following systemic administration as compared to nanoparticles without neutrophil membrane coating. In both orthotopic and ectopic tumor models, celastrol-loaded NNPs demonstrated greatly enhanced tumor inhibition which significantly prolonged the survival of tumor bearing mice and minimizing liver metastases. Overall, these results suggest that celastrol-loaded NNPs represent a viable and effective treatment option for pancreatic carcinoma.