The Molecular Signatures of Acute-immobilization-induced Antinociception and Chronic-immobilization-induced Antinociceptive Tolerance

Aging-Dependent Downregulation of SUV39H1 Histone Methyltransferase Increases Susceptibility to Stress-Induced Depressive Behavior

Aging induces cellular and molecular changes including gene expression alteration in the brain, which might be associated with aging-induced decrease in stress coping ability. In the present study, we investigate how aging changes the ability to cope with stress and increases sensitivity to stress. Aged mice show decreased expression of SUV39H1 histone methyltransferase and increased expression of Mkp-1 in the hippocampus. The siRNA-mediated knockdown of SUV39H1 increases Mkp-1 expression and suppresses p-CREB and Bdnf expression in HT22 cells and in the hippocampus of mice. Chromatin immunoprecipitation assays indicate that the levels of SUV39H1 and methylated histone-H3 bound to the promoter of the Mkp-1 in the hippocampus are reduced in aged mice. Aged mice exhibit depression-like behavior following weak stress that does not induce depressive behavior in young mice. Rosmarinic acid, a phenolic compound that increases SUV39H1 expression, reverses stress-induced changes of SUV39H1, Mkp-1, and Bdnf expression in the hippocampus via an overlapping but distinct mechanism from those of fluoxetine and imipramine and produces anti-depressive effects. These results suggest that aging increases susceptibility to stress via downregulation of SUV39H1 and resulting changes in SUV39H1-regulated signaling pathways in the hippocampus.

Endogenous opiates and behavior: 2019

This paper is the forty-second consecutive installment of the annual anthological review of research concerning the endogenous opioid system, summarizing articles published during 2019 that studied the behavioral effects of molecular, pharmacological and genetic manipulation of opioid peptides and receptors as well as effects of opioid/opiate agonists and antagonists. The review is subdivided into the following specific topics: molecular-biochemical effects and neurochemical localization studies of endogenous opioids and their receptors (1), the roles of these opioid peptides and receptors in pain and analgesia in animals (2) and humans (3), opioid-sensitive and opioid-insensitive effects of nonopioid analgesics (4), opioid peptide and receptor involvement in tolerance and dependence (5), stress and social status (6), learning and memory (7), eating and drinking (8), drug abuse and alcohol (9), sexual activity and hormones, pregnancy, development and endocrinology (10), mental illness and mood (11), seizures and neurologic disorders (12), electrical-related activity and neurophysiology (13), general activity and locomotion (14), gastrointestinal, renal and hepatic functions (15), cardiovascular responses (16), respiration and thermoregulation (17), and immunological responses (18).

The changes of nociception and the signal molecules expression in the dorsal root ganglia and the spinal cord after cold water swimming stress in mice

Several studies have previously reported that exposure to stress provokes behavioral changes, including antinociception, in rodents. In the present study, we studied the effect of acute cold-water (4°C) swimming stress (CWSS) on nociception and the possible changes in several signal molecules in male ICR mice. Here, we show that 3 min of CWSS was sufficient to produce antinociception in tail-flick, hot-plate, von-Frey, writhing, and formalin-induced pain models. Significantly, CWSS strongly reduced nociceptive behavior in the first phase, but not in the second phase, of the formalin-induced pain model. We further examined some signal molecules' expressions in the dorsal root ganglia (DRG) and spinal cord to delineate the possible molecular mechanism involved in the antinociceptive effect under CWSS. CWSS reduced p-ERK, p-AMPKα1, p-AMPKα2, p-Tyk2, and p-STAT3 expression both in the spinal cord and DRG. However, the phosphorylation of mTOR was activated after CWSS in the spinal cord and DRG. Moreover, p-JNK and p-CREB activation were significantly increased by CWSS in the spinal cord, whereas CWSS alleviated JNK and CREB phosphorylation levels in DRG. Our results suggest that the antinociception induced by CWSS may be mediated by several molecules, such as ERK, JNK, CREB, AMPKα1, AMPKα2, mTOR, Tyk2, and STAT3 located in the spinal cord and DRG.

NLRP3 inflammasome inhibitor MCC950 attenuates primary dysmenorrhea in mice via the NF-κB/COX-2/PG pathway

Background

Primary dysmenorrhea (PD) constitutes a common gynecological disease among young women. The NLRP3 inflammasome may be activated and expressed in PD, but the mechanistic link between NLRP3 inflammasome activation and PD is still unclear.

Methods

To investigate the potential role of NLRP3 inflammasome activation in the pathogenesis of PD, 30 female Kunming mice without pregnancy were used for experiments. The PD mouse model was constructed by 11 days of successive co-treatment with estradiol and oxytocin. MCC950, a potent and specific small-molecule inhibitor of the NLRP3 inflammasome, was used to treat PD mice. The disease level was assessed by the writhing response and hot water tail-flick test. The levels of prostaglandin E₂ (PGE₂) and prostaglandin F₂ alpha (PGF_2α) in the uterine tissues of mice were detected by ELISA. The expression levels of protein and cytokines, including NLRP3, cysteine aspartic acid-specific protease 1 (caspase-1), interleukin (IL)-1β, IL-18, nuclear factor kappa B (NF-κB) p65, phospho-NF-κB p65, and cyclooxygenase-2 (COX-2) were revealed by western blot analysis.

Results

MCC950 greatly ameliorated the writhing response induced by the combination of oxytocin and estradiol, with an increasing length of tail-flick latency. MCC950 also significantly decreased the levels of PGF_2α and PGE₂, and the expressions of NLRP3, caspase-1, IL-1β, IL-18, phospho-NF-κB p65, NF-κB p65, and COX-2 in the uterus.

Conclusions

MCC950 markedly alleviated the pain and pathological damage in PD mice by inhibiting NLRP3 activation. The underlying mechanism may be related to hypoactive uterine inflammation via suppression of NLRP3 activation and the NF-κB/COX-2/PG pathway in uteruses of PD mice.

Antinociceptive Effects of Shenling Baizhu through PI3K-Akt-mTOR Signaling Pathway in a Mouse Model of Bone Metastasis with Small-Cell Lung Cancer

Shenling Baizhu additive powder (SLBZ-AP), a formulation of a variety of natural medicinal plants, has clinical efficacy in treating cancers in previous studies. We explored the effect of SLBZ-AP in bone metastasis of lung cancer (BMLC) mice, and the possible mechanism involved was further investigated in the present study. Mice model of BMLC was made and treated with SLBZ-AP. Pain behavioral tests were performed to explore the effect on BMLC-induced pain in mice. TUNEL staining was used to investigate apoptosis. The mRNA expression of markers in the PI3K/Akt/mTOR pathway was measured by qPCR, and protein expression was detected by western blotting and immunohistochemistry analysis. SLBZ-AP relieved BMLC-induced pain and prolonged animals' survival, promoted cell apoptosis in the marrow from the tibia of BMLC mice, and inhibited mRNA and protein expression of AKT, mTOR, P70S6, and VEGF, as well as protein expression of p-AKT, p-mTOR, p-P70S6, and VEGF upregulation in the marrow of tibia induced by BMLC, an effect which was similar to rapamycin. Our results suggested that SLBZ-AP may have antinociceptive effect and prolong survival of BMLC mice at least partially by inhibiting cell proliferation and promoting apoptosis through the PI3K/Akt/mTOR signaling pathway. SLBZ-AP may be a potential candidate for BMLC therapy.