AMPK activation attenuates cancer-induced bone pain by reducing mitochondrial dysfunction-mediated neuroinflammation.

Bone metastasis of cancer cells leads to severe pain by disrupting bone structure and inducing central sensitization. Neuroinflammation in the spinal cord plays a decisive role in the maintenance and development of pain. In the current study, male Sprague-Dawley (SD) rats are used to establish a cancer-induced bone pain (CIBP) model by intratibial injection of MRMT-1 rat breast carcinoma cells. Morphological and behavioral analyses verify the establishment of the CIBP model, which represents bone destruction, spontaneous pain and mechanical hyperalgesia in CIBP rats. Activation of astrocytes marked by upregulated glial fibrillary acidic protein (GFAP) and enhanced production of the proinflammatory cytokine interleukin-1ß (IL-1ß) are accompanied by increased inflammatory infiltration in the spinal cord of CIBP rats. Furthermore, activation of the NOD-like receptor pyrin domain-containing protein 3 (NLRP3) inflammasome is consistent with increased neuroinflammation. Adenosine monophosphate-activated protein kinase (AMPK) activation is involved in attenuating inflammatory pain and neuropathic pain. Intrathecal injection of the AMPK activator AICAR in the lumbar spinal cord reduces dynamin-related protein 1 (Drp1) GTPase activity and suppresses NLRP3 inflammasome activation. This effect consequently alleviates pain behaviors in CIBP rats. Cell research on C6 rat glioma cells indicates that AICAR treatment restores IL-1ß-induced impairment of mitochondrial membrane potential and elevation of mitochondrial reactive oxygen species (ROS). In summary, our findings indicate that AMPK activation attenuates cancer-induced bone pain by reducing mitochondrial dysfunction-mediated neuroinflammation in the spinal cord.

[Retracted] HCV­E2 inhibits hepatocellular carcinoma metastasis by stimulating mast cells to secrete exosomal shuttle microRNAs.

[This retracts the article DOI: 10.3892/ol.2017.6433.].

Emodin inhibits HDAC6 mediated NLRP3 signaling and relieves chronic inflammatory pain in mice.

Chronic pain reduces the quality of life and ability to function of individuals suffering from it, making it a common public health problem. Neuroinflammation which is mediated by the Nod-like receptor family pyrin domain-containing 3 (NLRP3) inflammasome activation in the spinal cord participates and modulates chronic pain. A chronic inflammatory pain mouse model was created in the current study by intraplantar injection of complete Freund's adjuvant (CFA) into C57BL/6J left foot of mice. Following CFA injection, the mice had enhanced pain sensitivities, decreased motor function, increased spinal inflammation and activated spinal astrocytes. Emodin (10 mg/kg) was administered intraperitoneally into the mice for 3 days. As a result, there were fewer spontaneous flinches, higher mechanical threshold values and greater latency to fall. Additionally, in the spinal cord, emodin administration reduced leukocyte infiltration level, downregulated protein level of IL-1ß, lowered histone deacetylase (HDAC)6 and NLRP3 inflammasome activity and suppressed astrocytic activation. Emodin also binds to HDAC6 via four electrovalent bonds. In summary, emodin treatment blocked the HDAC6/NLRP3 inflammasome signaling, suppresses spinal inflammation and alleviates chronic inflammatory pain.

LY294002 alleviates bone cancer pain by reducing mitochondrial dysfunction and the inflammatory response.

Bone cancer pain (BCP) is mainly caused by bone metastasis and markedly impairs the functional capacity and daily functions of patients. Neuroinflammation plays a pivotal role in the pathogenesis and maintenance of chronic pain. Oxidative stress in the mitochondria is a key contributor to neuroinflammation and neuropathic pain. Herein, a rat model of BCP was established which was characterized by bone destruction, pain hypersensitivity and motor disability. In the spinal cord, phosphatidylinositol 3­kinase (PI3K)/protein kinase B (Akt) signaling was activated, and the inflammatory response and mitochondrial dysfunction were also observed. The intrathecal injection of LY294002, a selective inhibitor of PI3K/Akt signaling, decreased mechanical pain sensitivity, suppressed spontaneous pain and recovered the motor coordination of rats with BCP. Second, LY294002 treatment blocked spinal inflammation by reducing astrocytic activation and downregulating the expression levels of inflammatory factors, such as NF­κB, IL­1ß and TNF­α. Moreover, LY294002 treatment recovered mitochondrial function by activating the manganese superoxide dismutase enzyme, increasing NADH:ubiquinone oxidoreductase subunit B11 expression, and decreasing BAX and dihydroorotate dehydrogenase expression. LY294002 treatment also increased the mitochondrial membrane potential and decreased the mitochondrial reactive oxygen species levels in C6 cells. On the whole, the results of the present study suggest that the inhibition of PI3K/Akt signaling by LY294002 restores mitochondrial function, suppresses spinal inflammation and alleviates BCP.

GSK-3ß inhibition alleviates arthritis pain via reducing spinal mitochondrial reactive oxygen species level and inflammation.

Pain is the main symptom of osteoarthritis, which severely reduces the patients' quality of life. Stimulated neuroinflammation and elevated mitochondrial oxidative stress are associated arthritis pain. In the present study, arthritis model was established by intra-articular injection of complete Freund's adjuvant (CFA) on mice. Knee swelling, pain hypersensitivity and motor disability were observed in CFA-induced mice. In spinal cord, neuroinflammation was triggered and presented as severe infiltration of inflammatory cells and up-regulated expressions of glial fibrillary acidic protein (GFAP), nuclear factor-kappaB (NF-κB), PYD domains-containing protein 3 (NLRP3), cysteinyl aspartate specific proteinase (caspase-1) and interleukin-1 beta (IL-1ß). Mitochondrial function was disrupted and characterized as elevated expressions of B-cell lymphoma 2 (Bcl-2)-associated X protein (Bax), dihydroorotate dehydrogenase (DHODH) and cytochrome C (Cyto C), and reduced expressions of Bcl-2 and Mn-superoxide dismutase (Mn-SOD) activity. Meanwhile, as a potential target for pain management, glycogen synthase kinase-3 beta (GSK-3ß) activity was up-regulated in CFA induced mice. To explore potential therapeutic options for arthritis pain, GSK-3ß inhibitor TDZD-8 was intraperitoneally injected for three days on CFA mice. Animal behavioral tests found that TDZD-8 treatment elevated mechanical pain sensitivity, suppressed spontaneous pain and recovered motor coordination. Morphological and protein expression analysis indicated that TDZD-8 treatment decreased spinal inflammation score and inflammatory related protein levels, recovered mitochondrial related protein levels, and increased Mn-SOD activity. In summary, TDZD-8 treatment inhibits GSK-3ß activity, reduces mitochondrial mediated oxidative stress, suppresses spinal inflammasome response, and alleviates arthritis pain.

Ultrasound-guided paravertebral nerve block anesthesia on the stress response and hemodynamics among lung cancer patients.

BACKGROUND: Thoracic surgery for radical resection of lung tumor requires deep anesthesia which can lead to an adverse inflammatory response, loss of hemodynamic stability, and decreased immune function. Herein, we evaluated the feasibility and benefits of ultrasound-guided paravertebral nerve block anesthesia, in combination with general anesthesia, for thoracic surgery for lung cancer. The block was performed by diffusion of anesthetic drugs along the paravertebral space to achieve unilateral multi-segment intercostal nerve and dorsal branch nerve block. AIM: To evaluate the application of ultrasound-guided paravertebral nerve block anesthesia for lung cancer surgery to inform practice. METHODS: The analysis was based on 140 patients who underwent thoracic surgery for lung cancer at our hospital between January 2018 and May 2020. Patients were randomly allocated to the peripheral + general anesthesia (observation) group (n = 74) or to the general anesthesia (control) group (n = 66). Patients in the observation group received ultrasound-guided paravertebral nerve block anesthesia combined with general anesthesia, with those in the control group receiving an epidural block combined with general anesthesia. Measured outcomes included the operative and anesthesia times, as well as the mean arterial pressure (MAP), heart rate (HR), and blood oxygen saturation (SpO2) measured before surgery, 15 min after anesthesia (T1), after intubation, 5 min after skin incision, and before extubation (T4). RESULTS: The dose of intra-operative use of remifentanil and propofol and the postoperative use of sufentanil was lower in the observation group (1.48 ± 0.43 mg, 760.50 ± 92.28 mg, and 72.50 ± 16.62 mg, respectively) than control group (P < 0.05). At the four time points of measurement (T1 through T4), MAP and HR values were higher in the observation than control group (MAP, 90.20 ± 9.15 mmHg, 85.50 ± 7.22 mmHg, 88.59 ± 8.15 mmHg, and 90.02 ± 10.02 mmHg, respectively; and HR, 72.39 ± 8.22 beats/min, 69.03 ± 9.03 beats/min, 70.12 ± 8.11 beats/min, and 71.24 ± 9.01 beats/min, respectively; P < 0.05). There was no difference in SpO2 between the two groups (P > 0.05). Postoperative levels of epinephrine, norepinephrine, and dopamine used were significantly lower in the observation than control group (210.20 ± 40.41 pg/mL, 230.30 ± 65.58 pg/mL, and 54.49 ± 13.32 pg/mL, respectively; P < 0.05). Similarly, the postoperative tumor necrosis factor-α and interleukin-6 levels were lower in the observation (2.43 ± 0.44 pg/mL and 170.03 ± 35.54 pg/mL, respectively) than control group (P < 0.05). There was no significant difference in the incidence of adverse reactions between the two groups (P > 0.05). CONCLUSION: Ultrasound-guided paravertebral nerve block anesthesia improved the stress and hemodynamic response in patients undergoing thoracic surgery for lung cancer, with no increase in the rate of adverse events.

Proteomic analysis of spinal cord tissue in a rat model of cancer-induced bone pain.

Background: Cancer-induced bone pain (CIBP) is a moderate to severe pain and seriously affects patients' quality of life. Spinal cord plays critical roles in pain generation and maintenance. Identifying differentially expressed proteins (DEPs) in spinal cord is essential to elucidate the mechanisms of cancer pain. Methods: CIBP rat model was established by the intratibial inoculation of MRMT-1 cells. Positron emission tomography (PET) scan and transmission electron microscopy (TEM) were used to measure the stats of spinal cord in rats. Label free Liquid Chromatography with tandem mass spectrometry (LC-MS-MS) were used to analyze the whole proteins from the lumbar spinal cord. Differentially expressed proteins (DEPs) were performed using Gene Ontology (GO) and Kyoto encyclopedia of genes and genomes (KEGG) enrichment analysis, and verified using Western blot and immunofluorescence assay. Results: In the current study, CIBP rats exhibited bone damage, spontaneous pain, mechanical hyperalgesia, and impaired motor ability. In spinal cord, an hypermetabolism and functional abnormality were revealed on CIBP rats. An increase of synaptic vesicles density in active zone and a disruption of mitochondrial structure in spinal cord of CIBP rats were observed. Meanwhile, 422 DEPs, consisting of 167 up-regulated and 255 down-regulated proteins, were identified among total 1539 proteins. GO enrichment analysis indicated that the DEPs were mainly involved in catabolic process, synaptic function, and enzymic activity. KEGG pathway enrichment analysis indicated a series of pathways, including nervous system disease, hormonal signaling pathways and amino acid metabolism, were involved. Expression change of synaptic and mitochondrial related protein, such as complexin 1 (CPLX1), synaptosomal-associated protein 25 (SNAP25), synaptotagmin 1 (SYT1), aldehyde dehydrogenase isoform 1B1 (ALDH1B1), Glycine amidinotransferase (GATM) and NADH:ubiquinone oxidoreductase subunit A11 (NDUFA11), were further validated using immunofluorescence and Western blot analysis. Conclusion: This study provides valuable information for understanding the mechanisms of CIBP, and supplies potential therapeutic targets for cancer pain.

HCV-E2 inhibits hepatocellular carcinoma metastasis by stimulating mast cells to secrete exosomal shuttle microRNAs.

Exosomal miRNAs are emerging as mediators of the interaction between mast cells (MCs) and tumor cells. The exosomal miRNAs can be internalized by liver cancer cells to inhibit cell metastasis. We explored the interaction between MCs and hepatocellular carcinoma (HCC) cells. We used hepatitis C virus E2 envelope glycoprotein (HCV-E2) to stimulate MCs and harvest MCs-derived exosomes to detect the miRNAs and changes of exosomal miRNAs before and after stimulation. Through miRNA microarray analysis, we identified 19 differentially expressed miRNAs in exosomes derived from MCs with or without HCV-E2 treatment. HCV-E2 not only increased the level of miRNA-490 in MCs and their secreted exosomes but also increased the levels of miRNA-490 in recipient HepG2 cells, which ultimately inhibited the ERK1/2 pathway. The transfection of antagomiR-490 significantly decreased the levels of miR-490 in MCs, MCs-derived exosomes, and recipient HepG2 cells and increased migration of HepG2, indicating that miR-490 is involved in the regulation of HepG2 cell migration. The present study suggests that MCs can inhibit HCC cell metastasis by inhibiting the ERK1/2 pathway by transferring the exosomal shuttle microRNAs into HCC cells, which provides new insights for the biological therapy of HCC induced by hepatitis C.