Ammoxetine attenuates diabetic neuropathic pain through inhibiting microglial activation and neuroinflammation in the spinal cord.

BACKGROUND: Diabetic neuropathic pain (DNP) is a common and distressing complication in patients with diabetes, and the underlying mechanism remains unclear. Tricyclic antidepressants (TCAs) and serotonin and norepinephrine reuptake inhibitors (SNRIs) are recommended as first-line drugs for DNP. Ammoxetine is a novel and potent SNRI that exhibited a strong analgesic effect on models of neuropathic pain, fibromyalgia-related pain, and inflammatory pain in our primary study. The present study was undertaken to investigate the chronic treatment properties of ammoxetine on DNP and the underlying mechanisms for its effects. METHODS: The rat model of DNP was established by a single streptozocin (STZ) injection (60 mg/kg). Two weeks after STZ injection, the DNP rats were treated with ammoxetine (2.5, 5, and 10 mg/kg/day) for 4 weeks. The mechanical allodynia and locomotor activity were assayed to evaluate the therapeutic effect of ammoxetine. In mechanism study, the activation of microglia, astrocytes, the protein levels of pro-inflammatory cytokines, the mitogen-activated protein kinases (MAPK), and NF-κB were evaluated. Also, microglia culture was used to assess the direct effects of ammoxetine on microglial activation and the signal transduction mechanism. RESULTS: Treatment with ammoxetine for 4 weeks significantly relieved the mechanical allodynia and ameliorated depressive-like behavior in DNP rats. In addition, DNP rats displayed increased activation of microglia in the spinal cord, but not astrocytes. Ammoxetine reduced the microglial activation, accumulation of pro-inflammatory cytokines, and activation of p38 and c-Jun N-terminal kinase (JNK) in the spinal cord of DNP rats. Furthermore, ammoxetine displayed anti-inflammatory effects upon challenge with LPS in BV-2 microglia cells. CONCLUSION: Our results suggest that ammoxetine may be an effective treatment for relieving DNP symptoms. Moreover, a reduction in microglial activation and pro-inflammatory release by inhibiting the p-p38 and p-JNK pathways is involved in the mechanism.

Evaluation of the analgesic effects of ammoxetine, a novel potent serotonin and norepinephrine reuptake inhibitor.

AIM: The selective serotonin (5-HT) and norepinephrine (NE) reuptake inhibitors (SNRIs) are commonly used for the treatment of neuropathic pain and fibromyalgia. Ammoxetine ((±)-3-(benzo[d] [1,3]dioxol-4-yloxy)-N-methyl-3-(thiophen-2-yl)propan-1-amine) has been identified as a novel potent SNRI. In this study, we evaluated the acute analgesic properties of ammoxetine in different animal models of pain, and examined the involvement of monoamines in its analgesic actions. METHODS: The analgesic effects of ammoxetine were assayed using models of acetic acid- and formalin-induced pain in mice, neuropathic pain induced by sciatic nerve injury (SNI), chronic constriction injury (CCI) and reserpine-induced fibromyalgia pain in rats. The contents of 5-HT and NE in brain regions of fibromyalgia rats were measured using HPLC-ECD. In all the experiments, duloxetine was used as a positive control drug. RESULTS: Oral administration of ammoxetine (0.625-10 mg/kg) or duloxetine (2.5-40 mg/kg) dose-dependently decreased the number of acetic acid-induced writhing and formalin-induced first phase and second phase paw licking time in mice. Oral administration of ammoxetine (2.5-10 mg/kg) or duloxetine (10 mg/kg) alleviated mechanical allodynia in SNI and CCI rats and thermal hyperalgesia in CCI rats. The antiallodynic effect of ammoxetine in CCI rats was abolished by pretreatment with para-chlorophenylalanine methyl ester hydrochloride (PCPA, a 5-HT synthesis inhibitor) or α-methyl-para-tyrosine methylester (AMPT, a catecholamine synthesis inhibitor). Oral administration of ammoxetine (30 mg/kg) or duloxetine (50 mg/kg) significantly attenuated tactile allodynia in rats with reserpine-induced fibromyalgia. In the fibromyalgia rats, administration of ammoxetine (10, 30 mg/kg) or duloxetine (30, 50 mg/kg) dose-dependently increased the levels of 5-HT and NE, and decreased the metabolite ratio of 5-HT (5-HIAA/5-HT) in the spinal cord, hypothalamus, thalamus and prefrontal cortex. CONCLUSION: Ammoxetine effectively alleviates inflammatory, continuous, neuropathic and fibromyalgia-related pain in animal models, which can be attributed to enhanced neurotransmission of 5-HT and NE in the descending inhibitory systems.

Therapeutic Effect of Carboxyamidotriazole on Adjuvant Arthritis in Rats.

OBJECTIVE: To study the effect of carboxyamidotriazole (CAI) on adjuvant arthritis (AA) in rats. METHODS: The rats were randomly divided into normal group,two vehicle groups (polyethylene glycol 400 control and normal sodium control group), CAI-treated groups (10, 20, and 40 mg/kg) and positive control dexamethasone group. Freund's completed adjuvant was used to induce AA in rats. The arthritis index (AI) was scored, and X-ray check of the hind limbs and histopathological examination were performed. The levels of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß, and IL-6 in the inflamed paw tissues were measured. RESULTS: The administration of CAI significantly decreased the AI, restored the body weights, and ameliorated the radiological and histopathological features of joint destruction in AA rats (P<0.05, P<0.01). In addition, CAI reduced the TNF-α, IL-1ß, and IL-6 levels in the inflamed paw tissues (P<0.05, P<0.01). CONCLUSION: CAI has therapeutic effect on AA rats, which may be achieved by decreasing the pro-inflammatory cytokines at the site of inflammation.

[Anti-inflammatory and analgesic potency of carboxyamidotriazole, a tumoristatic agent].

OBJECTIVE: To explore the potential anti-inflammatory and analgesic activities of carboxyamidotriazole (CAI). METHODS: A variety of animal models, including the croton oil-induced ear edema, the cotton-induced granuloma, the rat adjuvant-induced arthritis, were used to evaluate anti-inflammatory effect of CAI. Vascular endothelial growth factor (VEGF)--or histamine-stimulated local vascular permeability in mouse modulated by CAI was also determined. In addition, we assessed the effect of CAI on the levels of proinflammatory cytokines tumor necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-beta) at the site of inflammation and in sera. Moreover, antinociceptive effect of CAI on inflammatory pain was assessed using acetic acid-induced writhing model and the formalin test. RESULTS: CAI significantly inhibited acute and chronic phases of inflammation, reduced VEGF or histamine-induced vascular permeability, and showed marked inhibition of proinflammatory cytokines such as TNF-alpha and IL-1 beta. CAI also showed potential therapeutic effect on peripheral inflammatory pain. CONCLUSION: CAI is a promising anti-inflammatory and analgesic agent.

Carboxyamidotriazole alleviates muscle atrophy in tumor-bearing mice by inhibiting NF-κB and activating SIRT1.

Cancer cachexia is a complex disorder characterized by inflammatory responses, and it is associated with poor performance status and high mortality rate of cancer patients. Carboxyamidotriazole (CAI), a noncytotoxic chemotherapy agent, shows anti-inflammatory features in the treatment of many diseases. Here, we investigated the preventive and therapeutic effects of CAI on muscle loss that occurred in mice with advanced Lewis lung carcinoma (LLC). The carcass weights of CAI-treated mice were significantly higher than that of mice in the vehicle group from Day 19 to the end of the study. The gastrocnemius and epididymal adipose tissue weights were also increased by CAI treatment. The protective mechanisms might be attributed to the following points: CAI treatment inhibited the proteolysis in muscles by decreasing expressions of muscle-specific FoxO3 transcription factor and ubiquitin E3 ligases (MuRF1 and atrogin1). Moreover, CAI restricted the NF-κB signaling, downregulated the level of TNF-α in muscle and both TNF-α and IL-6 levels in serum, directly stimulated SIRT1 activity in vitro, and increased SIRT1 content in muscle. These results indicate that CAI can alleviate muscle wasting and is a promising drug against lung cancer cachexia.

Carboxyamido-triazole inhibits proliferation of human breast cancer cells via G(2)/M cell cycle arrest and apoptosis.

Carboxyamido-triazole (CAI), a voltage-independent calcium channel inhibitor, has been shown to be able to induce growth inhibition and apoptosis in cancer cells. In the present study, we demonstrate that CAI significantly inhibits proliferation of cultured MCF-7 human breast cancer cells in a dose-dependent manner with an IC(50) of approximately 26 microM. Reduced proliferation of MCF-7 cells in the presence of CAI correlated with accumulation of cells in G(2)/M phase and induction of apoptosis. A treatment of MCF-7 cells with 30 microM CAI caused a time-dependent decrease in the levels of proteins that regulate G(2)/M progression, including Cdk1, Cyclin B1, and Cdc25C. A simultaneous increase in the expression of p21 protein was observed. We also demonstrated a concurrent decrease of the mitochondrial membrane potential (DeltaPsi(m)), and down-regulation of anti-apoptotic protein Bcl-2. In conclusion, it seems reasonable to hypothesize that the antitumor effect of CAI in MCF-7 cells is based on G(2)/M cell cycle arrest and inducing apoptosis.

[Binding characteristics of new synthesized opioid receptor ligands to cloned mu opioid receptors stably expressed in CHO cell].

OBJECTIVE: To determine the affinity of new opioid receptor ligands to cloned mu opioid receptors stably expressed in CHO cell. METHODS: The binding characteristics of the opioid ligand [3H] diprenorphine (3H-dip) were studied by cellular biological techniques and radioligands binding in cloned mu opioid receptors stably expressed in CHO cells in saturation binding experiments, and were followed by competition binding experiments with a variety of new synthesized opioid receptor ligands. RESULTS: The Kd and Bmax of [3H] diprenorphine bound to mu receptors were 1.06 nmol/L and 930 fmol/mg protein, respectively. Competition binding experiments revealed that ligand 3# and 12# displayed much higher affinity than DAMGO and Morphine for the cloned mu opioid receptor. However, the affinities of ligands 2#, 6#, 8# and 9# were lower than DAMGO and Morphine. CONCLUSION: The present results suggest that the new ligands 3# and 12# have higher affinity to mu opioid receptors. However, ligands 2#, 6#, 8# and 9# have lower affinity to mu opioid receptors.

[Dual regulation by delta opioid receptor agonists on the delayed rectified potassium channels in NG108-15 cells].

OBJECTIVE: To investigate the dual effects by the delta opioid receptor agonists DPDPE on the delayed rectified potassium channels in NG108-15 cells. METHODS: A series of outward currents were evoked in NG108-15 cells by depolarizing voltage from -50 mV to +80 mV at holding potential of -90 mV. These currents were delayed rectified potassium currents. Relatively selected delta opioid receptor agonists DPDPE of higher and lower concentrations were used to modulate the delayed rectified K+ current in NG108-15 cells. Opioid receptor antagonist Naloxone (NAL) and relatively selected delta opioid receptor antagonist Naltrindole (NTI) were used in the present experiments for the characterization of the actions of opioid receptors. RESULTS: The relatively higher concentrations of delta opioid receptor agonist DPDPE (> or = 10(-6) mol/L) significantly increased the amplitude of the delayed rectified K+ current. On the contrary, the relatively lower concentrations of DPDPE (< or = 10(-12) mol/L) decreased the amplitude of the delayed rectified K+ current (P < 0.05). Furthermore both the increase and decrease were time-dependent. CONCLUSIONS: delta opioid receptor agonist has dual regulatory effects on the delayed rectified potassium channels in NG108-15 cells.

[Effect of G protein in the dual regulation of opioid receptor agonist on the delayed rectified potassium channels].

OBJECTIVE: To observe the role of G protein in the dual regulation of opioid receptor agonist on the delayed rectified potassium channels. METHODS: Using whole-cell patch-clamp techniques applied to NG108-15 cells, investigate the effect of opioid receptor agonist on the delayed rectified potassium channels by administration of Guanosine-5'-0'-2-thiociphosphate (GDP beta S), Pertusis Toxin (PTX), Tetroacetic acid nueleoside diphosphate kinase (NDPK) and Adenosine-3' 5' cyclic monophosphate cAMP in the pipette solution. RESULTS: (1) GDP beta S could block the changes induced by both high and low concentration of (D-Pen2.5)-enkephalin (DPDPE) (P < 0.05). (2) PTX could inhibit the excitative regulation on K+ channel by high concentration of DPDPE (P < 0.05). But CTX had no effect on K+ channel caused by DPDPE. (3) UDP could block the excitative effect of K+ channel by high concentration of NDPK, while have no changes on the inhibitory effect caused by low concentration of opioid agonists. (4) cAMP took part in the regulation in high concentration of agonist administration (P < 0.05), while no changes for low concentration of agonists. CONCLUSIONS: Dual changes were observed on delayed rectifier potassium channel by agonist treatment on NG108-15 cells. The excitative effect was Gi/o coupled in high concentration of agonist incubation, related to cAMP. While the inhibitory effect was possibly induced by G protein beta gamma subunit directly.