Ehrlich tumor induces TRPV1-dependent evoked and non-evoked pain-like behavior in mice

We standardized a model by injecting Ehrlich tumor cells into the paw to evaluate cancer pain mechanisms and pharmacological treatments. Opioid treatment, but not cyclooxygenase inhibitor or tricyclic antidepressant treatments reduces Ehrlich tumor pain. To best use this model for drug screening it is essential to understand its pathophysiological mechanisms. Herein, we investigated the contribution of the transient receptor potential cation channel subfamily V member 1 (TRPV1) in the Ehrlich tumor-induced pain model. Dorsal root ganglia (DRG) neurons from the Ehrlich tumor mice presented higher activity (calcium levels using fluo-4 fluorescent probe) and an increased response to capsaicin (TRPV1 agonist) than the saline-injected animals

Lipopolysaccharide induces inflammatory hyperalgesia triggering a TLR4/MyD88-dependent cytokine cascade in the mice paw.

Inflammatory pain can be triggered by different stimuli, such as trauma, radiation, antigen and infection. In a model of inflammatory pain caused by infection, injection in the mice paw of lipopolysaccharide (LPS), a Toll-like receptor 4 (TLR4) agonist, produces mechanical hyperalgesia. We identify here the TLR4 linked signaling pathways that elicit this response. Firstly, LPS paw injection in wild type (WT) mice produced mechanical hyperalgesia that was not altered in TRIF-/- mice. On the other hand, this response was absent in TLR4 mutant and MyD88 null mice and reduced in TNFR1 null mice. Either an IL-1 receptor antagonist, anti-KC/CXCL1 antibody, indomethacin or guanethidine injection also lessened this response. Moreover, LPS-induced time dependent increases in TNF-α, KC/CXCL1 and IL-1β expression in the mice paw, which were absent in TLR4 mutant and MyD88 null mice. Furthermore, in TNFR1 deficient mice, the LPS-induced rises in KC/CXCL1 and IL-1β release were less than in their wild type counterpart. LPS also induced increase of myeloperoxidase activity in the paw skin, which was inhibited in TLR4 mutant and MyD88 null mice, and not altered in TRIF-/- mice. These results suggest that LPS-induced inflammatory pain in mice is solely dependent on the TLR4/MyD88 rather than the TLR4/TRIF signaling pathway. This pathway triggers pronociceptive cytokine TNF-α release that in turn mediates rises in KC/CXCL1 and IL-1β expression. Finally, these cytokines might be involved in stimulating production of directly-acting hyperalgesic mediators such as prostaglandins and sympathomimetic amine

Antinociceptive Effect of Tephrosia sinapou Extract in the Acetic Acid, Phenyl-p-benzoquinone, Formalin, and Complete Freund’s Adjuvant Models of Overt Pain-Like Behavior in Mice

Tephrosia toxicaria, which is currently known as Tephrosia sinapou (Buc’hoz) A. Chev. (Fabaceae), is a source of compounds such as flavonoids. T. sinapou has been used in Amazonian countries traditional medicine to alleviate pain and inflammation. The purpose of this study was to evaluate the analgesic effects of T. sinapou ethyl acetate extract in overt pain-like behavior models in mice by using writhing response and flinching/licking tests. We demonstrated in this study that T. sinapou extract inhibited, in a dose (1–100 mg/kg) dependent manner, acetic acid- and phenyl-p-benzoquinone- (PBQ-) induced writhing response. Furthermore, it was active via intraperitoneal, subcutaneous, and peroral routes of administration. T. sinapou extract also inhibited formalin- and complete Freund’s adjuvant- (CFA-) induced flinching/licking at 100 mg/kg dose. In conclusion, these findings demonstrate that T. sinapou ethyl acetate extract reduces inflammatory pain in the acetic acid, PBQ, formalin, and CFA models of overt pain-like behavior. Therefore, the potential of analgesic activity of T. sinapou indicates that it deserves further investigation

Vinpocetine reduces carrageenan-induced inflammatory hyperalgesia in mice by inhibiting oxidative stress, cytokine production and NF-κB activation in the paw and spinal cord.

Vinpocetine is a safe nootropic agent used for neurological and cerebrovascular diseases. The anti-inflammatory activity of vinpocetine has been shown in cell based assays and animal models, leading to suggestions as to its utility in analgesia. However, the mechanisms regarding its efficacy in inflammatory pain treatment are still not completely understood. Herein, the analgesic effect of vinpocetine and its anti-inflammatory and antioxidant mechanisms were addressed in murine inflammatory pain models. Firstly, we investigated the protective effects of vinpocetine in overt pain-like behavior induced by acetic acid, phenyl-p-benzoquinone (PBQ) and formalin. The intraplantar injection of carrageenan was then used to induce inflammatory hyperalgesia. Mechanical and thermal hyperalgesia were evaluated using the electronic von Frey and the hot plate tests, respectively, with neutrophil recruitment to the paw assessed by a myeloperoxidase activity assay. A number of factors were assessed, both peripherally and in the spinal cord, including: antioxidant capacity, reduced glutathione (GSH) levels, superoxide anion, tumor necrosis factor alpha (TNF-α) and interleukin 1 beta (IL-1β) levels, as well as nuclear factor kappa B (NF-κB) activation. Vinpocetine inhibited the overt pain-like behavior induced by acetic acid, PBQ and formalin (at both phases), as well as the carrageenan-induced mechanical and thermal hyperalgesia and associated neutrophil recruitment. Both peripherally and in the spinal cord, vinpocetine also inhibited: antioxidant capacity and GSH depletion; increased superoxide anion; IL-1β and TNF-α levels; and NF-κB activation. As such, vinpocetine significantly reduces inflammatory pain by targeting oxidative stress, cytokine production and NF-κB activation at both peripheral and spinal cord levels

Granulocyte-Colony Stimulating Factor (G-CSF) induces mechanical hyperalgesia via spinal activation of MAP kinases and PI(3)K in mice

Granulocyte-colony stimulating factor (G-CSF) is a current pharmacological approach to increase peripheral neutrophil counts after anti-tumor therapies. Pain is most relevant side effect of G-CSF in healthy volunteers and cancer patients. Therefore, the mechanisms of G-CSF-induced hyperalgesia were investigated focusing on the role of spinal mitogen-activated protein (MAP) kinases ERK (extracellular signal-regulated kinase). JNK (Jun N-terminal Kinase) and p38, and PI(3)K (phosphatidylinositol 3-kinase). G-CSF induced dose (30-300 ng/paw)-dependent mechanical hyperalgesia, which was inhibited by local post-treatment with morphine. This effect of morphine was reversed by naloxone (opioid receptor antagonist). Furthermore, G-CSF-induced hyperalgesia was inhibited in a dose-dependent manner by intrathecal pre-treatment with ERK (PD98059), JNK (SB600125), p38 (SB202190) or PI(3)K (wortmanin) inhibitors. The co-treatment with MAP kinase and PI(3)K inhibitors, at doses that were ineffective as single treatment, significantly inhibited G-CSF-induced hyperalgesia. Concluding, in addition to systemic opioids, peripheral opioids as well as spinal treatment with MAP kinases and PI(3)K inhibitors also reduce G-CSF-induced pain. (C) 2011 Elsevier Inc. All rights reserved.Fundo de Apoio ao Ensino Pesquisa e Extensao/Universidade Estadual de Londrina[FAEPE/UEL 01/2009]Fundacao AraucariaConselho Nacional de Pesquisa (CNPq)Coordenadoria de aperfeicoamento de Pessoal de Nivel Superior (CAPES), Brazi

Cytokines- and direct acting mediators-induced mechanical hyperalgesia in HePas and Hej mice.

<p>HePas and Hej mice received i.pl. injection of saline (20 µl), TNF-α (100 pg/paw), CXCL1 (20 ng/paw), IL-1β (1 ng/paw), PGE₂ (100 ng/paw) or dopamine (10 µg/paw). Mechanical hyperalgesia was evaluated 3 h after i.pl. injection of hyperalgesic mediators. *<i>P</i><0.05 compared with saline control. One-way ANOVA followed by Tukey's t test.</p

LPS-induced mechanical inflammatory hyperalgesia depends on cytokines, prostaglandins and sympathomimetic amines.

<p>(<b>A</b>) LPS (100 ng/paw) was injected in TNFR1^+/+ (C57BL/6 background) or TNFR1^-/- (C57BL/6 background) mice. (<b>B</b>) C57BL/6 wild type mice were treated with anti-CXCL1 antibody (500 ng/paw, 5 min before LPS injection), or (<b>C</b>) IL-1ra (500 ng/paw, 5 min before LPS injection), or (<b>D</b>) indomethacin, (5 mg/kg, i.p. 30 min before LPS injection), guanethidine (30 mg/kg, s.c. 60 min before LPS injection) or indomethacin plus guanethidine (same doses). Mechanical hyperalgesia was evaluated 3 h after LPS injection. *<i>P</i><0.05 compared with saline control, #<i>P</i><0.05 compared with LPS control group; **<i>P</i><0.05 compared with indomethacin or guanethidine treated group. One-way ANOVA followed by Tukey's t test.</p

LPS induces a TNFR1-dependent production of CXCL1/KC and IL-1β.

<p>Saline (20 µl/paw) or LPS (100 ng/paw) was injected into the TNFR1^+/+ (C57BL/6 background) or TNFR1^-/- (C57BL/6 background) mice hindpaw. At 3 h after LPS injection, the subcutaneous tissue samples were collected for (<b>A</b>) CXCL1/KC, (<b>B</b>) or (<b>C</b>) IL-1β determination by ELISA. *<i>P</i><0.05 compared with saline control, #<i>P</i><0.05 compared with TNFR1^+/+ mice injected with LPS. One-way ANOVA followed by Tukey's t test.</p

Role of TLR4, MyD88 and TRIF signalling pathways in LPS-induced increase of myeloperoxidase activity in the mice paw skin.

<p><b>(A)</b> HePas and Hej mice received i.pl. injection of LPS (100 ng/paw) or saline (20 µl/paw). <b>(B)</b> MyD88^+/+ (C57BL/6 background) and MyD88^-/- (C57BL/6 background) mice received i.pl. injection of LPS or saline. <b>(C)</b> TRIF^+/+ (129Sv background) and TRIF^-/- (129Sv background) mice received i.pl. injection of LPS or saline. Myeloperoxidase activity was evaluated 5 h after LPS injection. *<i>P</i><0.05 compared with saline control, #<i>P</i><0.05 compared with HePas, MyD88^+/+ or TRIF^+/+ mice injected with LPS. One-way ANOVA followed by Tukey's t test.</p