Luteolin relieves lung cancer-induced bone pain by inhibiting NLRP3 inflammasomes and glial activation in the spinal dorsal horn in mice.

BACKGROUND: Bone cancer pain (BCP) is one of the most severe complications in cancer patients. However, the pharmacological therapeutic approaches are limited. Luteolin, a major component of flavones, is widely distributed in plants and plays a critical role in the antinociceptive effects, but whether luteolin could alleviate cancer pain and its underlying mechanisms are not known. HYPOTHESIS/PURPOSE: This study investigated the molecular mechanisms by which luteolin reduced BCP. METHODS: Behavioral, pharmacological, immunohistochemical, and biochemical approaches were used to investigate the effect of luteolin on BCP. RESULTS: Luteolin treatment ameliorated Lewis lung cancer (LLC)-induced bone pain in mice in a dose-dependent manner. Luteolin treatment could inhibit the activation of neurons, glial cells, and NOD-like receptor protein 3 (NLRP3) inflammasomes in the dorsal spinal cord in the BCP mouse model. Furthermore, phosphorylated p-38 mitogen-activated protein kinase (MAPK) in the spinal dorsal horn (SDH) was suppressed by luteolin treatment that could influence the analgesic and glial inhibition effects of luteolin. CONCLUSION: Our results demonstrated that luteolin inhibited neuroinflammation by obstructing glial cell and NLRP3 inflammasome activation via modulating p38 MAPK activity in SDH, ultimately improving LLC-induced BCP.

Endocannabinoid signaling in hypothalamic circuits regulates arousal from general anesthesia in mice.

Consciousness can be defined by two major attributes: awareness of environment and self, and arousal, which reflects the level of awareness. The return of arousal after general anesthesia presents an experimental tool for probing the neural mechanisms that control consciousness. Here we have identified that systemic or intracerebral injection of the cannabinoid CB1 receptor (CB1R) antagonist AM281 into the dorsomedial nucleus of the hypothalamus (DMH) - but not the adjacent perifornical area (Pef) or the ventrolateral preoptic nucleus of the hypothalamus (VLPO) - accelerates arousal in mice recovering from general anesthesia. Anesthetics selectively activated endocannabinoid (eCB) signaling at DMH glutamatergic but not GABAergic synapses, leading to suppression of both glutamatergic DMH-Pef and GABAergic DMH-VLPO projections. Deletion of CB1R from widespread cerebral cortical or prefrontal cortical (PFC) glutamatergic neurons, including those innervating the DMH, mimicked the arousal-accelerating effects of AM281. In contrast, CB1R deletion from brain GABAergic neurons or hypothalamic glutamatergic neurons did not affect recovery time from anesthesia. Inactivation of PFC-DMH, DMH-VLPO, or DMH-Pef projections blocked AM281-accelerated arousal, whereas activation of these projections mimicked the effects of AM281. We propose that decreased eCB signaling at glutamatergic terminals of the PFC-DMH projection accelerates arousal from general anesthesia through enhancement of the excitatory DMH-Pef projection, the inhibitory DMH-VLPO projection, or both.

Gastrodin protects against chronic inflammatory pain by inhibiting spinal synaptic potentiation.

Tissue injury is known to produce inflammation and pain. Synaptic potentiation between peripheral nociceptors and spinal lamina I neurons has been proposed to serve as a trigger for chronic inflammatory pain. Gastrodin is a main bioactive constituent of the traditional Chinese herbal medicine Gastrodia elata Blume, which has been widely used as an analgesic since ancient times. However, its underlying cellular mechanisms have remained elusive. The present study demonstrated for the first time that gastrodin exhibits an analgesic effect at the spinal level on spontaneous pain, mechanical and thermal pain hypersensitivity induced by peripheral inflammation, which is not dependent on opioid receptors and without tolerance. This analgesia by gastrodin is at least in part mediated by depressing spinal synaptic potentiation via blockade of acid-sensing ion channels. Further studies with miniature EPSCs and paired-pulse ratio analysis revealed the presynaptic origin of the action of gastrodin, which involves a decrease in transmitter release probability. In contrast, neither basal nociception nor basal synaptic transmission was altered. This study revealed a dramatic analgesic action of gastrodin on inflammatory pain and uncovered a novel spinal mechanism that could underlie the analgesia by gastrodin, pointing the way to a new analgesic for treating chronic inflammatory pain.

Antioxidant therapy for pain relief in patients with chronic pancreatitis: systematic review and meta-analysis.

BACKGROUND: Currently, there is no specific therapy for chronic pancreatitis (CP). The treatment of micronutrient antioxidant therapy for painful CP has been sporadically used for more than 30 years, however, its efficacy are still poorly understood. OBJECTIVE: The purpose of this meta-analysis is to investigate the safety and efficacy of antioxidant therapy for pain relief in patients with CP. SETTING: University Hospital in China STUDY DESIGN: Systematic review and meta-analysis METHODS: Two authors independently reviewed the search results and extracted data and disagreements were resolved by discussion. Effects were summarized using standardized mean differences (SMDs), weighted mean differences, or odds ratio (OR) according to the suitable effect model. MEDLINE, PsycINFO, Scopus, EMBASE, and the Cochrane Central Register of Controlled Trials  were searched from 1980 through December 2012. Randomized controlled trials (RCTs) that studied antioxidant supplementation for pain relief in patients with CP were analyzed. RESULTS: Nine randomized controlled trials (RCTs) involving 390 patients were included. Overall, there was no association of antioxidant therapy with pain reduction in CP patients (SMD, -0.55; 95% CI, -1.22 to 0.12; P = 0.67). However, antioxidant therapy significantly increased blood levels of antioxidants in CP patients versus the placebo group (SMD, 1.08; 95% CI, 0.74 to 1.43; P < 0.00001). Interestingly, combined antioxidant (selenium, ß-carotene, vitamin C, vitamin E, methionine) therapy was found to be associated with pain relief (SMD, -0.93; 95% CI, -1.72 to -0.14; P = 0.02), while the trials in which a single antioxidant was used revealed no significant pain relief (SMD, -0.12; 95% CI, -1.23 to 0.99; P = 0.83) in CP patients. Strong evidence was obtained that the antioxidants increased adverse effects (OR, 6.09; 95% CI, 2.29 to 16.17, P < 0.01); nevertheless, none was serious. LIMITATIONS: Because of the small sample, a consolidated conclusion cannot be reached based on current RCTs. Large-sample RCTs are needed to clarify the analgesic effect of antioxidants in CP patients. CONCLUSIONS: Combined antioxidant therapy seems to be a safe and effective therapy for pain relief in CP patients. Measures of total antioxidant status may not help to monitor the efficacy of antioxidant therapy for patients with CP.

Triptolide prevents and attenuates neuropathic pain via inhibiting central immune response.

BACKGROUND: Current treatments for neuropathic pain are far from satisfactory. Considering the essential contribution of central immune factors to the pathogenesis of neuropathic pain, targeting inflammatory response is well accepted as an effective strategy for treating neuropathic pain. Triptolide has a long history in traditional Chinese medicine for treating inflammatory diseases and has been proven to inhibit cytokines released from glial cells. OBJECTIVE: In the present study, we tested whether systemic treatment with triptolide could prevent or attenuate nocifensive behaviors associated with neuropathic pain. We further tried to explore the underlying mechanism of the potential anti-allodynia effect of triptolide. STUDY DESIGN: A randomized, double blind, controlled animal trial. METHODS: Triptolide was administered systemically in a rat model of neuropathic pain induced by spinal nerve ligation (SNL) in the single bolus and repeated treatment manners. In the single bolus treatment experiment, triptolide (30 ug/kg, 100 ug/kg, 300 ug/kg) or vehicle was given to SNL and sham-operated rats once on day 1 or on day 10 after surgery (n = 6 each). In the repeated treatment study, prophylactic treatment with triptolide (30 ug/kg, 100 ug/kg, 300 ug/kg) was given to rats during the period of day -3 (3 days prior to SNL) to day 7 (7 days post-SNL) inclusively (n = 6 each). Another set of SNL and sham rats on postoperative day 10 received treatment with triptolide (30 ug/kg, 100 ug/kg, 300 ug/kg) or vehicle during the period of days 11-20 inclusively (n = 6 each), to assess potential reversal of established pain behavior. Mechanical allodynia of the rats was tested with von Frey filaments. Astrocytic and microglial activation in the spinal dorsal horn was evaluated with immunofluorescent histochemistry. Phosphorylation of mitogen-activated protein kinases (MAPKs), and expression of inflammatory cytokines (interleukin-6, interleukin-1beta, monocyte chemotactic protein-1, and tumor necrosis factor-alpha) were examined with Western blot analysis and real-time reverse transcription polymerase chain reaction study. RESULTS: A single bolus treatment with triptolide could neither prevent the induction nor reverse the maintenance of SNL-induced mechanical allodynia. However, repeated administration of triptolide dose-dependently inhibited neuropathic pain behavior in both preventative and interventional paradigms. Triptolide hampered SNL-induced activation of glial cells (astrocytes and microglia) in the spinal dorsal horn without influencing neurons. In addition, SNL-induced phosphorylation of MAPKs could be inhibited by triptolide. Furthermore, up-regulated expression of inflammatory cytokines in neuropathic pain states could be remarkably blocked by triptolide. LIMITATIONS: The direct target site (such as a specific receptor) of triptolide is still to be determined. In addition, triptolide could not completely block the SNL-induced mechanical allodynia. CONCLUSIONS: Our data suggest that triptolide may be a potential novel treatment for neuropathic pain through modulating immune response in the spinal dorsal horn.

Origins of endomorphin-2 immunopositive fibers and terminals in the rat medullary dorsal horn.

Endomorphin-2-immunoreactive (EM2-IR) fibers and terminals are densely present in the medullary dorsal horn (MDH) and are key factors in regulating central nociceptive processing. However, the origins of these EM2-IR fibers and terminals remain elusive. It was hypothesized that there were at least three possible origins of the EM2-IR fibers and terminals in the MDH: intrinsic dorsal horn neurons, primary afferent fibers, and projection fibers from higher parts of the brain. Different kinds of measures were employed in the current study to elucidate this hypothesis. After intracerebral ventricle administration of colchicine, no EM2-IR neuronal cell bodies were detected in the MDH, suggesting that there was no intrinsic EM2-IR dorsal horn neuron. Disruption of bilateral primary afferents (exposed to the primary afferent neurotoxin, capsaicin) decreased bilateral EM2 expression but did not eliminate it. Transection of the trigeminal nerve sensory root significantly decreased EM2 expression on the ipsilateral but not on the contralateral MDH. After injecting FluoroGold (FG) into the MDH, FG retrogradely labeled some EM2-IR neurons in the bilateral hypothalamus and nucleus tractus solitarii (NTS), and some of the FG retrogradely labeled neurons in the ipsilateral trigeminal ganglion also showed EM2-immunoreactivities. These results indicate that EM2-IR fibers and terminals in the MDH come not only from ipsilateral primary trigeminal afferents but also from bilateral fibers from the hypothalamus and NTS.

The multifaceted mechanisms for coffee's anti-tumorigenic effect on liver.

Epidemiological studies have found an inverse association between coffee consumption and the risk of liver cancer. Animal data support such a chemopreventive effect of coffee. Substantial research has been devoted to the identification of coffee components that may be responsible for these beneficial effects. Based on the current available literature, three major components, i.e. coffee diterpenes cafestol and kahweol (C+K), caffeine and chlorogenic acid contribute to the beneficial effects. These components induce phase II detoxifying and antioxidant enzymes as well as inhibit the expression or decrease the activity of phase I activating enzymes thus prevent carcinogenesis. These components target different stages of a common pathway, Kelch-like ECH-associated protein 1 (Keap1)--NF-E2-related factor-2 (Nrf2)--antioxidant-responsive-element (ARE) signal pathway thus alter the ARE-dependent expression of genes needed in the anti-tumorigenic effects.

Method for single-cell microarray analysis and application to gene-expression profiling of GABAergic neuron progenitors.

The mammalian central nervous system is populated with various types of neurons and glia. To investigate the functions and development of individual cells requires gene-expression analysis at the single-cell level. Here, we developed a microarray-based method for the gene-expression profiling of single cells and tested it for GABAergic neuron progenitors. Single GABAergic neuron progenitors were collected from the neocortex of GAD67-GFP knock-in mice by dissociation followed by the aspiration of GFP-positive cells. Complementary DNA from the single cells was amplified by a method in which Super SMART PCR and T7 RNA polymerase amplification were combined at a optimized condition. The cRNA was subjected to microarray hybridization and analysis, which yielded reliable and reproducible results.