Characterization of the antinociceptive and anti-inflammatory activities of doxycycline and minocycline in different experimental models

Development of a rapid antigen-based lateral flow assay for tick-borne spotted fever rickettsioses

Tick-borne spotted fever rickettsioses (SFRs) continue to cause severe illness and death in otherwise-healthy individuals due to lack of a timely and reliable diagnostic laboratory test. We recently identified a diagnostic biomarker for SFRs, the putative N-acetylmuramoyl-l-alanine amidase RC0497. Here, we developed a prototype laboratory test that targets RC0497 for diagnosis of SFRs. The concentrations of RC0497 in sera of Rickettsia rickettsii-infected guinea pigs and R. conorii-infected mice were determined by stable isotope dilution-parallel reaction monitoring mass spectrometry (SID-PRM-MS), ranging from 0.1 to 1.1 ng/ml. Using europium chelate nanoparticle reporters, we developed a lateral flow assay (LFA) and evaluated the test with a panel of serum samples of mock and experimentally infected animals. Interestingly, 21 of 22 (95.5%) serum samples from R. rickettsii-infected guinea pigs and R. conorii-infected mice yielded positive results with a ratio of test line / control line greater than the cutoff value determined for non-infected animals. All uninfected samples were in agreement with the intended results, suggesting that the initially assessed specificity of the test is 100%, among these samples. Mice infected with a lethal dose of R. conorii and treated with doxycycline on day 3 post-infection (p.i.), upon RC0497 detection by LFA, displayed significantly decreased rickettsial loads, comparable to the sublethal infection group on day 5 p.i.. A panel of human serum samples spiked with various concentrations of recombinant RC0497 were analyzed by LFA, suggesting that the limit of detection of the LFA was 0.64 ng/mL. These findings suggest that the timely detection of RC0497 by a europium LFA offers guidance for treatment, leading to a significant improvement in infection outcomes. This work, for the first time, shows significant promise for a rapid and easy-to-use platform offering a timely diagnostic assay for severe SFRs.

Anti-nociceptive effects of non-antibiotic derivatives of demeclocycline and doxycycline against formalin-induced pain stimulation

In previous studies, some tetracycline (TC) antibiotics showed potential as analgesic. We investigated here the analgesic activity of new non-antibiotic TC derivatives using the formalin-induced nociceptive pain model in adult C57BL/6 mice. Specifically, we tested the effects of i.p. injections of DDMC (5, 10, 20 mg kg-1) and DDOX (10, 20, 40 mg kg-1), which are non-antibiotic derivatives of demeclocycline and doxycycline, respectively. Repeated treatments with DDMC remarkably reduced nociceptive pain in both phases of the test, at 10 mg kg-1 its efficacy was comparable to that of 10 mg kg-1 of morphine. DDOX was also effective in this paradigm but intrinsically less potent than DDMC, exerting analgesic effects between 20 and 40 mg kg-1. Interestingly, a single injection of DDMC (10 mg kg-1) was sufficient to produce a robust anti-nociceptive effect similar to that of morphine. A single injection of DDOX (40 mg kg-1) also produced anti-nociceptive effects but only in the second phase of the test. Noticeably, male mice exhibited a better analgesic response to DDMC (10 mg kg-1) than females. A single injection of DDMC (10 mg kg-1) and morphine but not of DDOX (40 mg kg-1), powerfully inhibited formalin-induced spinal cord c-Fos expression whereas both TC derivatives restrained the activation of Iba-1-immunoreactive cells, indicating a potential indirect effect on inflamed microglial cells. In summary, the non-antibiotic TCs, DDMC and DDOX, demonstrated notable analgesic efficacy against formalin-induced pain, suggesting their potential as alternatives for analgesic treatment.

The anti-inflammatory effects of minocycline on lipopolysaccharide-induced paw oedema in rats: a histopathological and molecular study

Minocycline is a semi-synthetic antimicrobial agent with claimed anti-inflammatory properties reported from different experimental models. This study was aimed to evaluate the anti-inflammatory effects of minocycline, compared to the actions of two common anti-inflammatory agents, on lipopolysaccharide (LPS)-induced paw oedema through some clinical, histopathological, haematological and molecular analyses. Forty-eight rats were divided into eight groups (n = 6). In control group (Ctrl), each animal was injected with normal saline into its sub-plantar region of hind paw. In groups 2-7, hind paw oedema was induced by injection of LPS. One hour before injections, groups 1 (Ctrl) and 2 (LPS) were treated orally with distilled water, 3 and 4 with methylprednisolone (Pred) and meloxicam (Melo) and 5-7 with minocycline in doses of 50, 150 and 450 mg/kg (M50, M150 and M450, respectively). The 8th group (MC) was given minocycline (150 mg/kg) orally and normal saline was injected into sub-plantar region. Paw swelling and body temperature were assessed at 0, 2, 4, 6 and 24 h post-injections. At 24 h, samples of blood and liver, kidney, spleen and hind paw tissues were taken for haematological and histopathological examinations. Some samples of the paw were also obtained for molecular analysis of some inflammatory-related cytokines at mRNA level. Paw swelling and body temperature increased in all LPS-injected groups 2 h post-injection. In LPS group, they remained significantly increased up to 24 h; however, these parameters decreased to normal in Pred, Melo and all minocycline groups. The histological findings showed mild-to-moderate signs of inflammation in tissue samples of groups 2-6, but not in group M450. Additionally, gene expression of pro-inflammatory cytokines (IL-1β and IL-6) increased significantly in LPS group compared to other groups. In conclusion, this study supports the role of minocycline as an anti-inflammatory agent with effects comparable to those of meloxicam and methylprednisolone.

Anti-inflammatory and antinociceptive effects of a pectinolide-enriched fraction from Mesosphaerum pectinatum (L.) Kuntze

ETHNOPHARMACOLOGICAL RELEVANCE

Mesosphaerum pectinatum (L.) Kuntze (Lamiaceae), also known as sambacaitá, is a medicinal plant widely used in northeastern Brazil for the treatment of inflammatory and painful conditions, bacterial infections and cancer. Hence, the medicinal use of this species is quite meaningful to the search for bioactive compounds.

AIM OF THE STUDY

To evaluate the antinociceptive and anti-inflammatory activities of the pectinolide-enriched fraction of Mesosphaerum pectinatum (PEF) in animal models.

MATERIALS AND METHODS

The PEF was analyzed with HPLC-DAD and ¹H and ¹³C NMR. After the analysis, compounds of the pectinolide class were detected as major constituents in this fraction. The PEF (50, 100 and 200 mg/kg, p.o.) and the reference drugs - morphine (3.0 mg/kg, p.o.) and dexamethasone (2.0 mg/kg, p.o.) - were evaluated using models for nociception (hot plate, formalin-induced licking response) or inflammation (carrageenan-induced peritonitis and ear edema model).

RESULTS

The PEF significantly decreased the licking time of the animals treated when compared to the control group (second phase). In the carrageenan-induced peritonitis model, PEF (100 and 200 mg/kg) significantly decreased total and differential leukocyte counts. The PEF (0.3, 1.0 and 3.0 mg/ear) significantly reduced mice ear edema at the same extent and like the results obtained with the standard drug (dexamethasone). The MPO activity was reduced in mice ear at doses of 1 and 3 mg/ear. Antinociceptive effect on the hot plate test was not observed, demonstrating that there is no analgesic activity.

CONCLUSION

Our results suggest that the pectinolide-enriched fraction exhibits anti-inflammatory effects and that it is involved with inhibiting the release of the inflammatory mediators.

Antinociceptive, anti-inflammatory and antioxidant activities of the crude ethanolic extract and alkaloid fraction of Waltheria viscosissima A. St. - Hil. (Malvaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

The Waltheria viscosissima A. St.- Hil (Malvaceae) is also known as 'Malva branca', has been reported as ethnopharmacologically useful plant containing antinociceptive and anti-inflammatory properties, but scientific evidence is absent.

AIM OF THE STUDY

Elucidate the antinociceptive, anti-inflammatory and antioxidant activity of the crude ethanol extract (EEBWa.v) and alkaloid fraction (FAWa.v) of aerial parts of the W. viscosissima in healthy mice with induced inflammation.

MATERIALS AND METHODS

EEBWa.v and FAWa.v (50, 100 and 200 mg/kg) and morphine (10 mg/kg) were used in vivo tests of chemical nociception induced by acetic acid (0.6%; 10 mg/kg) and formalin (2.5%) in Swiss male mice. Acute inflammation was induced by carrageenan (1%) in vivo tests and there were several groups tested. The control (inflammation induced without treatment) and the groups treated with EEBWa.v (100 mg/kg), FAWa.v (100 mg/kg) and dexamethasone (2 mg/kg). After this procedure, the animals were euthanized and the peritoneal fluid was collected to evaluate cell migration and redox balance (malondialdehyde - MDA and Total Antioxidant Capacity - TAC).

RESULTS

The morphine, EEBWa.v (50 and 100 mg/kg) and FAWa.v (100 mg/kg) significantly reduced the number of abdominal writhes compared to the control group. FAWa.v (100 mg/kg) was superior to FAWa.v (200 mg/kg). In the formalin-induced nociception model (neurogenic phase) EEBWa.v (50 and 200 mg/kg) significantly reduced the number of paw licks. In the inflammatory phase with peripheral action, FAWa.v (100 mg/kg) was superior to EEBWa.v (200 mg/kg). EEBWa.v and FAWa.v (100 mg/kg) proved to be significant for the next experiments. Both samples showed reduction in cell migration, as well as those treated with dexamethasone, in animals with inflammation induced by carrageenan, compared to the untreated group. The redox balance (TAC and MDA) revealed that only EEBWa.v (100 mg/kg) had higher antioxidant potential than the untreated group and the dexamethasone group, p < 0.005 and p < 0.001, respectively. FAWa.v (100 mg/kg) did not show antioxidant activity superior to EEBWa.v. It was also detected that EEBWa.v and FAWa.v (100 mg/kg) failed to inhibit lipid peroxidation.

CONCLUSIONS

The W. viscosissima stimulates pain control, which can be mediated by both central and peripheral action. These bioactive compounds showed promising and potential to replace standard medicines. This bioactive effect is statistically similar to morphine and dexamethasone, standard medicines on the market, but with the advantage of antioxidant activity.

Myrtenol Reduces Orofacial Nociception and Inflammation in Mice Through p38-MAPK and Cytokine Inhibition

Orofacial pain is one of the commonest and most complex complaints in dentistry, greatly impairing life quality. Preclinical studies using monoterpenes have shown pharmacological potential to treat painful conditions, but the reports of the effects of myrtenol on orofacial pain and inflammation are scarce. The aim of this study was to evaluate the effect of myrtenol in experimental models of orofacial pain and inflammation. Orofacial nociceptive behavior and the immunoreactivity of the phosphorylated p38 (P-p38)-MAPK in trigeminal ganglia (TG) and spinal trigeminal subnucleus caudalis (STSC) were determined after the injection of formalin in the upper lip of male Swiss mice pretreated with myrtenol (12.5 and 25 mg/kg, i.p.) or vehicle. Orofacial inflammation was induced by the injection of carrageenan (CGN) in the masseter muscle of mice pretreated with myrtenol (25 and 50 mg/kg, i.p.) or its vehicle (0.02% Tween 80 in saline). Myeloperoxidase (MPO) activity and histopathological changes in the masseter muscle and interleukin (IL)-1β levels in the TG and STSC were measured. The increase in face-rubbing behavior time induced by formalin and P-p38-MAPK immunostaining in trigeminal ganglia were significantly reduced by myrtenol treatment (12.5 and 25 mg/kg). Likewise, increased MPO activity and inflammatory histological scores in masseter muscle, as well as augmented levels of IL-1β in the TG AND STSC, observed after CGN injection, were significantly decreased by myrtenol (25 and 50 mg/kg). Myrtenol has potential to treat orofacial inflammation and pain, which is partially related to IL-1β levels in the trigeminal pathway and p38-MAPK modulation in trigeminal ganglia.

The Microglial Activation Inhibitor Minocycline, Used Alone and in Combination with Duloxetine, Attenuates Pain Caused by Oxaliplatin in Mice

The antitumor drug, oxaliplatin, induces neuropathic pain, which is resistant to available analgesics, and novel mechanism-based therapies are being evaluated for this debilitating condition. Since activated microglia, impaired serotonergic and noradrenergic neurotransmission and overexpressed sodium channels are implicated in oxaliplatin-induced pain, this in vivo study assessed the effect of minocycline, a microglial activation inhibitor used alone or in combination with ambroxol, a sodium channel blocker, or duloxetine, a serotonin and noradrenaline reuptake inhibitor, on oxaliplatin-induced tactile allodynia and cold hyperalgesia. To induce neuropathic pain, a single dose (10 mg/kg) of intraperitoneal oxaliplatin was used. The mechanical and cold pain thresholds were assessed using mouse von Frey and cold plate tests, respectively. On the day of oxaliplatin administration, only duloxetine (30 mg/kg) and minocycline (100 mg/kg) used alone attenuated both tactile allodynia and cold hyperalgesia 1 h and 6 h after administration. Minocycline (50 mg/kg), duloxetine (10 mg/kg) and combined minocycline + duloxetine influenced only tactile allodynia. Seven days after oxaliplatin, tactile allodynia (but not cold hyperalgesia) was attenuated by minocycline (100 mg/kg), duloxetine (30 mg/kg) and combined minocycline and duloxetine. These results indicate a potential usefulness of minocycline used alone or combination with duloxetine in the treatment of oxaliplatin-induced pain.

Antinociceptive and anti-inflammatory activities of Hymenaea martiana Hayne (Fabaceae) in mice

Hymenaea martiana is a species popularly known in Northeastern Brazil as "jatobá" and used in folk medicine to treat pain and inflammation. The aim of this work was to evaluate the antinociceptive and anti-inflammatory activity of H. martiana. In the present study, we carried out an investigation about the effects of the crude ethanolic extract (Hm-EtOH) and the ethyl acetate fraction (Hm-AcOEt) in models of nociception and inflammation in mice. Chemical (acetic acid-induced writhing and formalin) and thermal stimuli (hot plate) were used for the evaluation of antinociceptive activity, while for the anti-inflammatory profile paw edema induced by carrageenan was used, along with leukocyte migration to the peritoneal cavity. The presence of the flavonoid astilbin in the samples was characterized through HPLC-DAD-MS analysis. Hm-EtOH and Hm-AcOEt (100, 200 and 400 mg.kg-1, i.p.) significantly reduced the number of abdominal contortions and decreased the paw licking time in the formalin test. In the hot plate, the extract increased the latency time of animals. Hm-EtOH and Hm-AcOEt inhibited significantly the increase in the edema after the administration of carrageenan. Hm-EtOH and Hm-AcOEt inhibited leukocyte migration in the peritonitis test. HPLC-DAD-MS analysis of Hm-EtOH and Hm-AcOEt revealed the presence of the flavonoid astilbin in the samples. According to the results of this study, both Hm-EtOH and Hm-AcOEt have antinociceptive and anti-inflammatory activities, which could be related with the presence of flavonoid in the extracts. The results reinforce the popular use of this plant.

Antibacterial Mechanisms and Efficacy of Sarecycline in Animal Models of Infection and Inflammation

Prolonged broad-spectrum antibiotic use is more likely to induce bacterial resistance and dysbiosis of skin and gut microflora. First and second-generation tetracycline-class antibiotics have similar broad-spectrum antibacterial activity. Targeted tetracycline-class antibiotics are needed to limit antimicrobial resistance and improve patient outcomes. Sarecycline is a narrow-spectrum, third-generation tetracycline-class antibiotic Food and Drug Administration (FDA)-approved for treating moderate-to-severe acne. In vitro studies demonstrated activity against clinically relevant Gram-positive bacteria but reduced activity against Gram-negative bacteria. Recent studies have provided insight into how the structure of sarecycline, with a unique C7 moiety, interacts with bacterial ribosomes to block translation and prevent antibiotic resistance. Sarecycline reduces Staphylococcus aureus DNA and protein synthesis with limited effects on RNA, lipid, and bacterial wall synthesis. In agreement with in vitro data, sarecycline demonstrated narrower-spectrum in vivo activity in murine models of infection, exhibiting activity against S. aureus, but reduced efficacy against Escherichia coli compared to doxycycline and minocycline. In a murine neutropenic thigh wound infection model, sarecycline was as effective as doxycycline against S. aureus. The anti-inflammatory activity of sarecycline was comparable to doxycycline and minocycline in a rat paw edema model. Here, we review the antibacterial mechanisms of sarecycline and report results of in vivo studies of infection and inflammation.

Beneficial effects of minocycline on the ovary of polycystic ovary syndrome mouse model: Molecular docking analysis and evaluation of TNF-α, TNFR2, TLR-4 gene expression

Polycystic ovary syndrome (PCOS) is the most common cause of ovulatory infertility. Inflammation may be involved in the pathogenesis and development of PCOS. We investigated the anti-inflammatory effect of minocycline on TNF-α, TNFR2, and TLR4 expression levels and the key features of PCOS in a mouse model. Molecular docking was performed by Molecular Operating Environment software. PCOS was induced by estradiol valerate injection (EV) (2 mg/kg/day) in 40 mice. After 28 days, the mice were divided into five groups, including control, PCOS, minocycline control, minocycline PCOS model (50 mg/kg), and letrozole PCOS (0.5 mg/kg). The Levels of FSH, LH, E2, and testosterone were determined by ELISA. H&E staining was used for histological analysis in the ovarian tissues. Docking scores were -10.35, -10.57, and -12.45 kcal/mol for TNFα, TLR-4, and TNFR2, respectively. The expression levels of TNF-α, TNFR2, and TLR4 were detected by Real-Time PCR. PCOS models exhibited acyclicity, a significant increase in E2 levels (P < 0.01), and no difference in FSH, LH, and testosterone. The expression levels of TNF-α, TNFR2, and TLR-4 significantly increased in PCOS (2.70, 7.90, and 14.83-fold, respectively). EV treatment significantly increased graafian follicles (P < 0.001) and decreased corpus luteum (CL) (P < 0.01). Minocycline treatment in PCOS led to a significant decrease in E2 (P < 0.01) and graafian follicles (P < 0.001) and a significant increase in the CL numbers (P < 0.05). Our findings showed the positive effects of minocycline on estradiol level, CL and graafian follicles counts, suggesting that minocycline might inhibit these proteins and improve ovulation in our mouse model of PCOS.

Influence of doxycycline administration on rat embryonic development during organogenesis

This experiment was performed to evaluate the possible embryotoxic and teratogenic effects of doxycycline during rat development. Twenty-one female rats were used and distributed into three groups equally (seven animals/group). The low dose group received doxycycline at a dose of 5 mg/kg bw/day orally from the 6th to 14th day of gestation. The high dose group received 10 mg/kg bw/day orally for the same period, the Control group received 1 mL distilled water orally for the same period. The dams were dissected on the 20th day of gestation and their fetuses were subjected to morphological, skeletal, and histological examination. Moreover, DNA damage analysis of liver cells of pregnant rats and their fetuses or fetal skull was assessed by Comet assay. The obtained results showed a significant decrease in fetal body weight, several morphological anomalies, and severe lack of ossification on the skull bones, phalanges, and sternum bone as well as shortness in the ulna and radius bones. Histological studies of pregnant rats revealed congestion and dilatation of the central vein of the liver lobules and fatty degeneration of the hepatocytes. In addition, 20 day-fetuses showed a marked increase of necrotic hepatocytes associated with an increased average of megakaryocytes and periportal leukocytic infiltration. Moreover, doxycycline induced a significant increase in the percentage of DNA damage and tail length of examined samples. Conclusively, doxycycline caused certain fetal abnormalities, so it is advisable to avoid using this drug during pregnancy.

Minocycline microspheres did not significantly improve outcomes after collagenase injection of tendon

BACKGROUND

Tetracycline antibiotics inhibit matrix metalloproteinases and pro-inflammatory cytokines implicated in the pathogenesis of tendinopathy, while microsphere formulations allow sustained release of drug contents. The purpose of this study was to evaluate the ability of a local minocycline microsphere injection to restore normal tendon properties in a rat model of collagenase-induced patellar tendinopathy.

METHODS

A total of 22 rats were randomly assigned to the control (n = 11) or minocycline (n = 11) group and received bilateral patellar tendon injections of collagenase. After 7 days, the minocycline group received the minocycline microsphere treatment and the control group received phosphate buffered solution. Pain was assessed via activity monitors and Von Frey filament testing. At 4 weeks post-collagenase injections, animals were euthanized.

RESULTS

Cage crossings significantly decreased among all rats 2-3 days following each injection period, however, tactile allodynia measures did not reflect this injury response. Biomechanical properties, interleukin-1 beta levels, and glycosaminoglycan content did not differ between groups. While not statistically significant, levels of leukotriene B4 were lower in the minocycline group compared to controls (p = 0.061), suggesting a trend.

CONCLUSIONS

Our study further characterizes the collagenase model of tendinopathy by demonstrating no evidence of central sensitization with collagenase-induced injury. We found no adverse effect of intratendinous injections of minocycline-loaded poly-lactic-co-glycolic acid microspheres, although no therapeutic effect was observed. Future studies involving a more substantial tendon injury with a greater inflammatory component may be necessary to more thoroughly evaluate the effects of minocycline on tendon pathology.

In vivo tissue response and antibacterial efficacy of minocycline delivery system based on polymethylmethacrylate bone cement

This study aims the in vivo biological characterization of an innovative minocycline delivery system, based on polymethylmethacrylate bone cement. Bone cements containing 1% or 2.5% (w/w) minocycline were formulated and evaluated through solid-state characterization. Biological evaluation was conducted in vivo, within a rat model, following the subcutaneous and bone tissue implantation, and tissue implantation associated with Staphylococcus aureus is challenging. The assessment of the tissue/biomaterial interaction was conducted by histologic, histomorphometric and microtomographic techniques. Minocycline addition to the composition of the polymethylmethacrylate bone cement did not modify significantly the cement properties. Drug release profile was marked by an initial burst release followed by a low-dosage sustained release. Following the subcutaneous tissue implantation, a reduced immune-inflammatory reaction was verified, with diminished cell recruitment and a thinner fibro-connective capsule formation. Minocycline-releasing cements were found to enhance the bone-to-implant contact and bone tissue formation, following the tibial implantation. Lastly, an effective antibacterial activity was mediated by the implanted cement following the tissue challenging with S. aureus. Kinetic minocycline release profile, attained with the developed polymethylmethacrylate system, modulated adequately the in vivo biological response, lessening the immune-inflammatory activation and enhancing bone tissue formation. Also, an effective in vivo antibacterial activity was established. These findings highlight the adequacy and putative application of the developed system for orthopedic applications.

Evaluation of the Protective Effects of Doxycycline on Acetaminophen-Induced Hepatotoxicity in Mice

Acetaminophen (APAP) toxicity threatens human health due to increased mortality associated with its overdose. Doxycycline (DC) because of its properties such as antioxidant and anti-inflammatory can be a good therapeutic strategy to treat the acute toxicity induced by APAP. Male mice were divided into six groups in two periods of 3 h and 24 h as normal saline, APAP 400 mg/kg, DC 100 mg/kg and groups treated by 25, 50 and 100 mg/kg DC just before APAP, respectively. At the end of the 3 h and 24 h periods, the hepatic index, biochemical parameters including serum aspartate transaminase (AST) and alanine transaminase (ALT) activity and hepatic catalase activity, glutathione (GSH) and malondialdehyde (MDA) levels in liver and histopathological changes were evaluated. The results indicated that DC had no apparent effect on the hepatic index but significantly normalized the level of biochemical parameters and reduced APAP induced liver damage. Overall, it could be concluded that DC can inhibit or resolve harmful effects of APAP through antioxidant and anti-inflammatory properties. However, more studies are needed to understand exact mechanism of DC and its application for clinical use.

Indomethacin plus minocycline coadministration relieves chemotherapy and antiretroviral drug-induced neuropathic pain in a cannabinoid receptors-dependent manner

Neuropathic pain sometimes occurs during chemotherapy with paclitaxel or HIV/AIDS antiretroviral therapy with nucleoside reverse transcriptase inhibitors (NRTIs). We previously reported that coadministration of indomethacin plus minocycline (IPM) was antihyperalgesic in a cannabinoid type 1 (CB1) receptor-dependent manner in a mouse model of paclitaxel-induced neuropathic pain. We evaluated if IPM combination has antihyperalgesic and antiallodynic activities in animal models of paclitaxel or NRTI (ddC, zalcitabine)-induced neuropathic pain, and whether antagonists of CB1, CB2 receptors or G protein-coupled receptor 55 (GPR55) can inhibit these activities of IPM. IPM produced antihyperalgesic and antiallodynic effects against paclitaxel and ddC-induced thermal hyperalgesia and mechanical allodynia. WIN 55,212-2, a cannabinoid receptor agonist, also had antihyperalgesic activity. The antihyperalgesic and antiallodynic activities of IPM were antagonized by a CB1 receptor antagonist AM251 and a CB2 receptor antagonist AM630, but not a GPR55 antagonist ML193. IPM had no effects on the mean time spent on the rotarod, whereas WIN 55,212-2 reduced it in a dose-dependent manner. These results show that IPM at a fixed ratio produces antihyperalgesic and antiallodynic effects in mice models of both paclitaxel and NRTI-induced neuropathic pain which is dependent on both CB1 and CB2 receptors, without causing the typical cannabinoid receptor agonist-induced motor impairment.

iNKT Cell Activation Exacerbates the Development of Huntington's Disease in R6/2 Transgenic Mice

Huntington's disease (HD) is an inherited neurodegenerative disorder which is caused by a mutation of the huntingtin (HTT) gene. Although the pathogenesis of HD has been associated with inflammatory responses, if and how the immune system contributes to the onset of HD is largely unknown. Invariant natural killer T (iNKT) cells are a group of innate-like regulatory T lymphocytes that can rapidly produce various cytokines such as IFNγ and IL4 upon stimulation with the glycolipid α-galactosylceramide (α-GalCer). By employing both R6/2 Tg mice (murine HD model) and Jα18 KO mice (deficient in iNKT cells), we investigated whether alterations of iNKT cells affect the development of HD in R6/2 Tg mice. We found that Jα18 KO R6/2 Tg mice showed disease progression comparable to R6/2 Tg mice, indicating that the absence of iNKT cells did not have any significant effects on HD development. However, repeated activation of iNKT cells with α-GalCer facilitated HD progression in R6/2 Tg mice, and this was associated with increased infiltration of iNKT cells in the brain. Taken together, our results demonstrate that repeated α-GalCer treatment of R6/2 Tg mice accelerates HD progression, suggesting that immune activation can affect the severity of HD pathogenesis.

Repeated immune activation with low-dose lipopolysaccharide attenuates the severity of Huntington's disease in R6/2 transgenic mice

Huntington's disease (HD) is a neurodegenerative disorder caused by a mutation in the huntingtin gene. Previously, therapeutic approaches using anti-inflammatory agents were reportedly not effective for preventing HD progression. Since whether immune responses contribute to the onset of HD is not entirely understood, we herein investigated the role of immune activation in HD using the R6/2 transgenic (Tg) HD model mouse. IL12 production and the expression of costimulatory molecules (e.g. CD86 and CD40) on innate immune cells (DCs and macrophages) were diminished in the disease stage of R6/2 Tg mice. Moreover, the number of adaptive T cells (CD4⁺ and CD8⁺ T cells) and the frequency of effector memory phenotype CD4⁺ T cells were decreased in these mice. These results suggest that the severity of HD is closely related to an impaired immune system and might be reversed by activation of the immune system. Since lipopolysaccharide (LPS), a potent TLR4 agonist, activates immune cells, we evaluated the effect of immune activation on the pathogenesis of HD using LPS. The repeated immune activation with low-dose LPS significantly recovered the impaired immune status back to normal levels and attenuated both severe weight loss and the increased clasping phenotype found in the disease stage of R6/2 Tg mice, consequently resulting in prolonged survival. Taken together, these results strongly indicate that immune activation has beneficial influences on alleviating HD pathology and could provide new therapeutic strategies for HD.

Neuroinflammatory reactions in sickness behavior induced by bacterial infection: Protective effect of minocycline

The neurological changes elicited by bacterial infection are called sickness behavior. Minocycline (MIN) is neuroprotective with a remarkable brain tissue penetration. MIN was orally administered at a dose 90 mg/kg for 3 days, whereas Escherichia coli was given as a single intraperitoneal injection (0.2 mL of 24 h growth) on the third day. After 24 h of bacterial infection, behavioral tests namely open field and forced swimming were carried out, then animals were decapitated. Rats infected with E. coli displayed reduced struggling time in forced swimming test, as well as, exploration and locomotion in open field test with reduction in neurotransmitters (norepinephrine, dopamine, and serotonin) versus elevation in the inflammatory (tumor necrosis factor-alpha, interferon-gamma) and oxidative stress (thiobarbituric acid reactive substance, reduced glutathione) biomarkers. Inflammatory infiltrates of nuclear cells were observed in brains of infected rats. MIN administration prevented the deleterious effects of E. coli infection, thus protects against sickness behavior possibly via defending from neuroinflammation.

Sex-Dependent Glial Signaling in Pathological Pain: Distinct Roles of Spinal Microglia and Astrocytes

Increasing evidence suggests that spinal microglia regulate pathological pain in males. In this study, we investigated the effects of several microglial and astroglial modulators on inflammatory and neuropathic pain following intrathecal injection in male and female mice. These modulators were the microglial inhibitors minocycline and ZVEID (a caspase-6 inhibitor) and the astroglial inhibitors L-α-aminoadipate (L-AA, an astroglial toxin) and carbenoxolone (a connexin 43 inhibitor), as well as U0126 (an ERK kinase inhibitor) and D-JNKI-1 (a c-Jun N-terminal kinase inhibitor). We found that spinal administration of minocycline or ZVEID, or Caspase6 deletion, reduced formalin-induced inflammatory and nerve injury-induced neuropathic pain primarily in male mice. In contrast, intrathecal L-AA reduced neuropathic pain but not inflammatory pain in both sexes. Intrathecal U0126 and D-JNKI-1 reduced neuropathic pain in both sexes. Nerve injury caused spinal upregulation of the astroglial markers GFAP and Connexin 43 in both sexes. Collectively, our data confirmed male-dominant microglial signaling but also revealed sex-independent astroglial signaling in the spinal cord in inflammatory and neuropathic pain.

Minocycline enhances inhibitory transmission to substantia gelatinosa neurons of the rat spinal dorsal horn

Minocycline, a second-generation tetracycline, is well known for its antibiotic, anti-inflammatory, and antinociceptive effects. Modulation of synaptic transmission is one of the analgesic mechanisms of minocycline. Although it has been reported that minocycline may suppress excitatory glutamatergic synaptic transmission, it remains unclear whether it could affect inhibitory synaptic transmission, which also plays a key role in modulating pain signaling. To examine the effect of minocycline on synaptic transmission in rat spinal substantia gelatinosa (SG) neurons, we recorded spontaneous inhibitory postsynaptic currents (sIPSCs) using whole-cell patch-clamp recording at a holding potential of 0 mV. Bath application of minocycline significantly increased the frequency but not the amplitude of sIPSCs in a reversible and concentration-dependent manner with an EC50 of 85. The enhancement of inhibitory synaptic transmission produced by minocycline was not affected by the glutamate receptor antagonists CNQX and D-APV or by the voltage-gated sodium channel blocker tetrodotoxin (TTX). Moreover, the potency of minocycline for facilitating sIPSC frequency was the same in both glycinergic and GABAergic sIPSCs without changing their decay phases. However, the facilitatory effect of minocycline on sIPSCs was eliminated in a Ca(2+)-free Krebs solution or by co-administration with calcium channel blockers. In summary, our data demonstrate that baseline inhibitory synaptic transmission in SG neurons is markedly enhanced by minocycline. This may function to decrease the excitability of SG neurons, thus leading to a modulation of nociceptive transmission.

Targeting p38 Mitogen-activated Protein Kinase to Reduce the Impact of Neonatal Microglial Priming on Incision-induced Hyperalgesia in the Adult Rat

BACKGROUND

Neonatal surgical injury triggers developmentally regulated long-term changes that include enhanced hyperalgesia and spinal microglial reactivity after reinjury. To further evaluate priming of response by neonatal hindpaw incision, the authors investigated the functional role of spinal microglial p38 mitogen-activated protein kinase after reincision in adult rodents.

METHODS

Plantar hindpaw incision was performed in anesthetized adult rats, with or without previous incision on postnatal day 3. Numbers and distribution of phosphorylated-p38 (1, 3, 24 h) and phosphorylated extracellular signal-regulated kinase (15 min, 24 h) immunoreactive cells in the lumbar dorsal horn were compared after adult or neonatal plus adult incision. Withdrawal thresholds evaluated reversal of incision-induced hyperalgesia by p38 inhibition with intrathecal SB203850.

RESULTS

Neonatal injury significantly increased phosphorylated-p38 expression 3 h after adult incision (55 ± 4 vs. 35 ± 4 cells per section, mean ± SEM, n = 6 to 7, P < 0.01). Increased expression was restricted to microglia, maintained across lumbar segments, and also apparent at 1 and 24 h. Preincision intrathecal SB203850 prevented the enhanced mechanical hyperalgesia in adults with previous neonatal injury and was effective at a lower dose (0.2 vs. 1 mg/kg, n = 8, P < 0.05) and for a longer duration (10 vs. 3 days). Lumbar neuronal phosphorylated extracellular signal-regulated kinase expression reflected the distribution of hindpaw primary afferents, but was not significantly altered by previous incision.

CONCLUSIONS

Neonatal incision primes spinal neuroglial signaling, and reincision in adult rats unmasks centrally mediated increases in functional microglial reactivity and persistent hyperalgesia. After early life injury, p38 inhibitors may have specific benefit as part of multimodal analgesic regimes to reduce the risk of persistent postsurgical pain.

Antinociceptive and anti-inflammatory activities of the ethanolic extract of Annona vepretorum Mart. (Annonaceae) in rodents

Background

Annona vepretorum Mart. (Annonaceae) is a native tree from Caatinga (Brazilian Northeastern savanna biome), popularly known as “araticum” and “pinha da Caatinga”. In this study, we investigated the effects of the crude ethanolic extract (Av-EtOH) in models of pain and inflammation in rodents.

Methods

The evaluation of antinociceptive activity was carried out by the acetic acid-induced writhing, formalin, hot plate and tail flick tests, while paw edema induced by carrageenan or histamine, and leukocyte migration to the peritoneal cavity were used for anti-inflammatory profile. Histological analyses also were carried out.

Results

Av-EtOH (25, 50 and 100 mg/kg, p.o) significantly reduced the number of writhing (P < 0.01) and decreased (P < 0.01) the paw licking time in both phases of the formalin test. In the hot plate and tail flick tests, this extract increased the reaction time, consequently reduced painful behavior. The effects in the formalin and hot plate tests were antagonized by naloxone. Av-EtOH inhibited significantly (P < 0.01) the increase in the edema volume after administration of carrageenan and histamine. In the peritonitis test, acute pre-treatment with Av-EtOH inhibited leukocyte migration. Histological analysis showed less inflammation in the groups treated with the extract when the inflammation was induced by carrageenan or histamine.

Conclusion

Thus, Av-EtOH has significant antinociceptive and anti-inflammatory properties, which are related probably with the activation of opioid receptors and inhibition of release of mediators of the inflammatory process. This specie is a potential target for drug discovery.

The benefit of minocycline on negative symptoms in early-phase psychosis in addition to standard care - extent and mechanism (BeneMin): study protocol for a randomised controlled trial

BACKGROUND

Negative symptoms of psychosis do not respond to the traditional therapy with first- or second-generation antipsychotics and are among main causes of a decrease in quality of life observed in individuals suffering from the disorder. Minocycline, a broad-spectrum tetracyclic antibiotic displaying neuroprotective properties has been suggested as a new potential therapy for negative symptoms. In the two previous clinical trials comparing minocycline and placebo, both added to the standard care, patients receiving minocycline showed increased reduction in negative symptoms. Three routes to neuroprotection by minocycline have been identified: neuroprotection against grey matter loss, anti-inflammatory action and stabilisation of glutamate receptors. However, it is not yet certain what the extent of the benefit of minocycline in psychosis is and what its mechanism is. We present a protocol for a multi-centre double-blind randomised placebo-controlled clinical trial entitled The Benefit of Minocycline on Negative Symptoms of Psychosis: Extent and Mechanism (BeneMin).

METHODS

After providing informed consent, 226 participants in the early phase of psychosis will be randomised to receive either 100 mg modified-release capsules of minocycline or similar capsules with placebo for 12 months in addition to standard care. The participants will be tested for outcome variables before and after the intervention period. The extent of benefit will be tested via clinical outcome measures, namely the Positive and Negative Syndrome Scale score, social and cognitive functioning scores, antipsychotic medication dose equivalent and level of weight gain. The mechanism of action of minocycline will be tested via blood screening for circulating cytokines and magnetic resonance imaging with three-dimensional T1-weighted rapid gradient-echo, proton density T2-weighted dual echo and T2*-weighted gradient echo planar imaging with N-back task and resting state. Eight research centres in UK and 15 National Health Service Trusts and Health Boards will be involved in recruiting participants, performing the study and analysing the data.

DISCUSSION

The BeneMin trial can inform as to whether in minocycline we have found a new and effective therapy against negative symptoms of psychosis. The European Union Clinical Trial Register: EudraCT 2010-022463-35 with the registration finalised in July 2011. The recruitment in the trial started in January 2013 with the first patient recruited in March 2013.

Nonneuronal central mechanisms of pain: glia and immune response

The role of central glial cells in the mechanisms underlying pain has been intensively studied in the last two decades. Most studies on glia and pain focused on the potential detrimental role of glial cells following noxious stimulus/insults manifested as an "activation" or a "reactive" state (increase in glial marker expression and production of proinflammatory/nociceptive molecules). Therefore, "activated" or "reactive" glial cells became a target for the future generation of drugs to treat chronic pain. Several glial modulators that reduce the activation of glial cells have shown great efficacy in multiple animal (rodents mostly) models of pain (acute, subacute, chronic, inflammatory, neuropathic, surgical, etc.). These encouraging findings inspired clinical trials that have been completed in the last 5 years. Unfortunately, all clinical trials with these glial modulators have failed to demonstrate efficacy for the treatment of pain. New lines of investigation and elegant experimental designs are shedding light on alternative glial functions, which demonstrate that "glial reactivity" is not necessarily deleterious in some pathological conditions. New strategies to validate findings through our current animal models are necessary to enhance the translational value of our preclinical studies. Also, more studies using human subjects would enhance our understanding of glial cells in the context of pain. This chapter explores the available literature to objectively ponder the potential role of glial cells in human pain conditions.

Minocycline encapsulated chitosan nanoparticles for central antinociceptive activity

The purpose of the study is to explore the central anti-nociceptive activity of brain targeted nanoparticles (NP) of minocycline hydrochloride (MH). The NP were formulated using the modified ionotropic gelation method (MHNP) and were coated with Tween 80 (T80) to target them to brain (cMHNP). The formulated nanoparticles have already been characterized for particle size, zeta potential, drug entrapment efficiency and in vitro drug release. The nanoparticles were then evaluated for pharmacodynamic activity using thermal methods. The pure drug and the formulation, MHNP were not able to show a statistically significant central analgesic activity. cMHNP on the other hand evidenced a significant central analgesic activity. Animal models evidenced that brain targeted nanoparticles may be utilized for effective delivery of central anti-nociceptive effect of MH. Further clinical studies are required to explore the activity for mankind.

Evaluation of the anti-inflammatory and antinociceptive effects of the essential oil from leaves of Xylopia laevigata in experimental models

Xylopia laevigata (Annonaceae) is a medicinal plant used in folk medicine to treat pain and inflammation. Thus, we investigated the possible antioxidant, antinociceptive, and anti-inflammatory effects of X. laevigata leaf essential oil (EOX) in animal models. Our EOX sample showed the presence of γ-muurolene (17.78%), δ-cadinene (12.23%), bicyclogermacrene (7.77%), and α-copaene (7.17%) as main compounds. EOX presented a strong antioxidant potential according to the DPPH, TBARS, and nitrite production tests. Additionally, pretreatment with EOX, in mice, also significantly produced (P < 0.05 or P < 0.001) antinociceptive effect by reduction of nociceptive behavior (in formalin and writhing tests). The EOX showed c-Fos label in the olfactory bulb, piriform cortex, and periaqueductal gray. Acute administration of EOX exhibited a significant (P < 0.01 or P < 0.001) anti-inflammatory profile in the carrageenan-induced peritonitis and by the carrageenan-induced hindpaw edema tests in mice. Our results provide evidence for the use of X. laevigata by traditional medicine practitioners in the management of pain and inflammatory disorders.

Drug repositioning: playing dirty to kill pain

The number of approved new molecular entity drugs has been decreasing as the pharmaceutical company investment in research and development is increasing. As we face this painful crisis, called an innovation gap, there is increasing awareness that development of new uses of existing drugs may be a powerful tool to help overcome this obstacle because it takes too long, costs too much and can be risky to release drugs developed de novo. Consequently, drug repositioning is emerging in different therapeutic areas, including the pain research area. Worldwide, pain is the main reason for seeking healthcare, and pain relief represents an unmet global clinical need. Therefore, development of analgesics with better efficacy, safety and cost effectiveness is of paramount importance. Despite the remarkable advancement in research on cellular and molecular mechanisms underlying pain pathophysiology over the past three decades, target-based therapeutic opportunities have not been pursued to the same extent. Phenotypic screening remains a more powerful tool for drug development than target-based screening so far. It sounds somewhat heretical, but some multi-action drugs, rather than very selective ones, have been developed intentionally. In the present review, we first critically discuss the utility of drug repositioning for analgesic drug development and then show examples of 'old' drugs that have been successfully repositioned or that are under investigation for their analgesic actions. We conclude that drug repositioning should be more strongly encouraged to help build a bridge between basic research and pain relief worldwide.

Prolonged minocycline treatment impairs motor neuronal survival and glial function in organotypic rat spinal cord cultures

Background

Minocycline, a second-generation tetracycline antibiotic, exhibits anti-inflammatory and neuroprotective effects in various experimental models of neurological diseases, such as stroke, Alzheimer’s disease, amyotrophic lateral sclerosis and spinal cord injury. However, conflicting results have prompted a debate regarding the beneficial effects of minocycline.

Methods

In this study, we analyzed minocycline treatment in organotypic spinal cord cultures of neonatal rats as a model of motor neuron survival and regeneration after injury. Minocycline was administered in 2 different concentrations (10 and 100 µM) at various time points in culture and fixed after 1 week.

Results

Prolonged minocycline administration decreased the survival of motor neurons in the organotypic cultures. This effect was strongly enhanced with higher concentrations of minocycline. High concentrations of minocycline reduced the number of DAPI-positive cell nuclei in organotypic cultures and simultaneously inhibited microglial activation. Astrocytes, which covered the surface of the control organotypic cultures, revealed a peripheral distribution after early minocycline treatment. Thus, we further analyzed the effects of 100 µM minocycline on the viability and migration ability of dispersed primary glial cell cultures. We found that minocycline reduced cell viability, delayed wound closure in a scratch migration assay and increased connexin 43 protein levels in these cultures.

Conclusions

The administration of high doses of minocycline was deleterious for motor neuron survival. In addition, it inhibited microglial activation and impaired glial viability and migration. These data suggest that especially high doses of minocycline might have undesired affects in treatment of spinal cord injury. Further experiments are required to determine the conditions for the safe clinical administration of minocycline in spinal cord injured patients.

Bioassay-guided evaluation of Dioscorea villosa - an acute and subchronic toxicity, antinociceptive and anti-inflammatory approach

BACKGROUND

Dioscorea villosa (DV) has been used in Brazil as an alternative medicine to attenuate menopause symptoms, as well as for the treatment of joint pain and rheumatoid arthritis. In spite of the popular use of DV for the treatment of various disorders, there are limited scientific data regarding safety aspects of this herb. In this regard, we carried out to evaluated both antinociceptive and anti-inflammatory activities in experimental models and assess the toxic effects of the acute (single dose) and subchronic (30 days) oral administration of dry extract of Dioscorea villosa in rodents.

METHODS

The LC analyses were performed to assess the presence of the diosgenin in samples of DV. The antinociceptive study of DV was performed using models of acetic acid-induced writhing and formalin-induced pain in mice. The anti-inflammatory study was accomplished by leukocyte migration to the peritoneal cavity. A dry extract of DV was tested at doses of 100, 200 and 400 mg/kg (per os or p.o.). The toxicological properties of the dry extract were evaluated by toxicity assays of acute (5 g/kg, single dose) and subchronic (1 g/kg/day, 30 days) treatment. Haematological, biochemical, and histopathological parameters were studied. The results are expressed as mean ± S.D., and statistical analysis of the data were performed with the Student's t-test or one-way analysis of variance (ANOVA) followed by Tukey's test. In all cases differences were considered significant if p < 0.05.

RESULTS

HPLC-DAD analysis of the extract from DV revealed the presence of diosgenin as the major compound. Doses of 200 and 400 mg⁄kg significantly reduced the amount of acetic acid-induced writhing in relation to the vehicle (p < 0.0001). In the first phase, using the formalin-induced neurogenic pain test, only the 400 mg/kg dose of DV showed significant inhibition of neurogenic pain (p < 0.001). In the second phase, 200 and 400 mg/kg of DV showed significant inhibition of inflammatory pain (p < 0.0001). Significant inhibition of leukocyte migration was observed with doses of 100 (p < 0.001), 200 (p < 0.01) and 400 mg/kg (p < 0.01). Haematological, biochemical and histopathological data obtained in both acute and subchronic toxicological assays revealed only unremarkable changes, which are unlikely to indicate DV toxicity with oral administration.

CONCLUSION

We found that DV possesses antinociceptive and anti-inflammatory properties in rodent models. In addition, no acute or subchronic toxicity was evident when the herbal extract was administered orally. These results supporting the folkloric usage of the plant to treat various inflammatory diseases.

Borneol, a bicyclic monoterpene alcohol, reduces nociceptive behavior and inflammatory response in mice

Borneol, a bicyclic monoterpene, has been evaluated for antinociceptive and anti-inflammatory activities. Antinociceptive and anti-inflammatory activities were studied by measuring nociception by acetic acid, formalin, hot plate, and grip strength tests, while inflammation was prompted by carrageenan-induced peritonitis. The rotarod test was used to evaluate motor coordination. Borneol produced a significant (P < 0.01) reduction of the nociceptive behavior at the early and late phases of paw licking and reduced the writhing reflex in mice (formalin and writhing tests, resp.). When the hot plate test was conducted, borneol (in higher dose) produced an inhibition (P < 0.05) of the nociceptive behavior. Such results were unlikely to be provoked by motor abnormality. Additionally, borneol-treated mice reduced the carrageenan-induced leukocytes migration to the peritoneal cavity. Together, our results suggest that borneol possess significant central and peripheral antinociceptive activity; it has also anti-inflammatory activity. In addition, borneol did not impair motor coordination.

The efficacy of a glial inhibitor, minocycline, for preventing persistent pain after lumbar discectomy: a randomized, double-blind, controlled study

Minocycline strongly inhibits microglial activation, which contributes to central sensitization, a major mechanism underlying chronic pain development. We hypothesized that the perioperative administration of minocycline might decrease persistent pain after lumbar discectomy. We randomly assigned 100 patients undergoing scheduled lumbar discectomy to placebo and minocycline groups. The minocycline group received 100mg minocycline orally, twice daily, beginning the evening before surgery and continuing for 8 days. The primary outcome was the change in lower limb pain intensity at rest between baseline and 3 months. Secondary outcomes were pain intensity on movement, the incidence of persistent pain and chronic neuropathic pain, back pain intensity at rest and on movement, and changes in Neuropathic Pain Symptom Inventory, Brief Pain Inventory, and Roland-Morris scores at 3 months. An intention-to-treat analysis was performed for patients assessed from the day before surgery to 3 months. The decrease in lower limb pain intensity was similar in the placebo and minocycline groups, both at rest -1.7 ± 1.6 vs -2.3 ± 2.4 and on movement -2.5 ± 2.1 vs -3.4 ± 2.9. The incidence and intensity of neuropathic pain and functional scores did not differ between the minocycline and placebo groups. Exploratory analysis suggested that minocycline might be effective in a subgroup of patients with predominantly deep spontaneous pain at baseline. Perioperative minocycline administration for 8 days does not improve persistent pain after lumbar discectomy.

A minocycline derivative reduces nerve injury-induced allodynia, LPS-induced prostaglandin E2 microglial production and signaling via toll-like receptors 2 and 4

Many studies have shown that minocycline, an antibacterial tetracycline, suppresses experimental pain. While minocycline's positive effects on pain resolution suggest that clinical use of such drugs may prove beneficial, minocycline's antibiotic actions and divalent cation (Ca(2+); Mg(2+)) chelating effects detract from its potential utility. Thus, we tested the antiallodynic effect induced by a non-antibacterial, non-chelating minocycline derivative in a model of neuropathic pain and performed an initial investigation of its anti-inflammatory effects in vitro. Intraperitoneal minocycline (100mg/kg) and 12S-hydroxy-1,12-pyrazolinominocycline (PMIN; 23.75 mg/kg, 47.50mg/kg or 95.00 mg/kg) reduce the mechanical allodynia induced by chronic constriction injury of mouse sciatic nerve. PMIN reduces the LPS-induced production of PGE2 by primary microglial cell cultures. Human embryonic kidney cells were transfected to express human toll-like receptors 2 and 4, and the signaling via both receptors stimulated with PAM3CSK4 or LPS (respectively) was affected either by minocycline or PMIN. Importantly, these treatments did not affect the cell viability, as assessed by MTT test. Altogether, these results reinforce the evidence that the anti-inflammatory and experimental pain suppressive effects induced by tetracyclines are neither necessarily linked to antibacterial nor to Ca(2+) chelating activities. This study supports the evaluation of the potential usefulness of PMIN in the management of neuropathic pain, as its lack of antibacterial and Ca(2+) chelating activities might confer greater safety over conventional tetracyclines.

Antinociceptive, anti-inflammatory and antioxidant activities of aqueous extract from Remirea maritima (Cyperaceae)

ETHNOPHARMACOLOGICAL RELEVANCE

Remirea maritima Aubl., popularly known as "capim-da-praia", is popularly employed in the treatment of diarrhea, kidney disease, fever, and for analgesic and anti-inflammatory purposes through the preparation of teas. Few studies have focused on the chemical composition and its biological properties.

AIM OF THE STUDY

This work evaluated the antinocipetive, anti-inflammatory and antioxidant activities of the aqueous extract from Remirea maritima Aubl. as well as the isolation and identification of the chemical compounds.

MATERIALS AND METHODS

Compounds were isolated from aqueous extract of Remirea maritima through preparative HPLC and the structures were identified by means of NMR and MS analysis. The tests for antinociceptive, anti-inflammatory, and antioxidant activities, along with motor coordination test (Rota rod), were performed over the aqueous extract.

RESULTS

The phytochemical investigation of aqueous extract of Remirea maritima resulted in the isolation of three flavone glycosides. The structures of these compounds were determined by means of MS and 1D and 2D NMR data as vitexin-2″-O-β-D-glucopyranoside, isovitexin-2″-O-β-D-glucopyranoside, and luteolin-7-O-glucuronide. Acute pretreatment with aqueous extract (100, 200 or 400mg/kg, i.p.) caused a significant decrease (p<0.001) in the number of abdominal writhes. In the formalin test, higher doses significantly inhibited the late (inflammatory pain) phase of formalin-induced licking (p<0.05 or 0.001). In the hot plate test, there was no significant difference in nociceptive behavior, discarding the possible central effect of the aqueous extract. In the rota rod test, it was verified that the aqueous extract in all concentration evaluated does not alter the motor coordination of mice, such antinociceptive results were unlikely to be caused by motor abnormality. In the peritonitis test, induced by carrageenan, the treatment with aqueous extract produced a significant reduction in leukocyte migration in all concentration evaluated. Additionally, a significant reduction of lipoperoxidation (TBARS test) and in nitric oxide formation (.NO Scavenging assay) was observed in antioxidant activity assay.

CONCLUSION

The biological and phytochemical investigations of the aqueous extract of Remirea maritima resulted in the identification of three flavone glycosides that have been described here for the first time in Remirea and effective analgesic activity in various pain models, probably mediated via the inhibition of peripheral mediators which could be related to its strong antioxidant effect observed in vitro.

Minocycline markedly reduces acute visceral nociception via inhibiting neuronal ERK phosphorylation

Background

Minocycline prevents the development of neuropathic and inflammatory pain by inhibiting microglial activation and postsynaptic currents. But, how minocycline obviates acute visceral pain is unclear. The present study investigated whether minocycline had an any antinociceptive effect on acetic acid-induced acute abdominal pain after intraperitoneal (i.p.) administration of saline or minocycline 1 hour before acetic acid injection (1.0%, 250 μl, i.p.).

Results

Minocycline (4, 10, or 40 mg/kg) significantly decreased acetic acid-induced nociception (0-60 minutes post-injection) and the enhancement in the number of c-Fos positive cells in the T5-L2 spinal cord induced by acetic acid injection. Also, the expression of spinal phosphorylated extracellular signal-regulated kinase (p-ERK) induced by acetic acid was reduced by minocycline pre-administration. Interestingly, intrathecal introduction of PD98059, an ERK upstream kinase inhibitor, markedly blocked the acetic acid-stimulated pain responses.

Conclusions

These results demonstrate that minocycline effectively inhibits acetic acid-induced acute abdominal nociception via the inhibition of neuronal p-ERK expression in the spinal cord, and that minocycline may have therapeutic potential in suppressing acute abdominal pain.

Tetracyclines and pain

Tetracyclines are natural or semi-synthetic bacteriostatic agents which have been used since late 1940s against a wide range of gram-positive and gram-negative bacteria and atypical organisms such as chlamydia, mycoplasmas, rickettsia, and protozoan parasites. After the discovery of the first tetracyclines, a second generation of compounds was sought in order to improve water solubility for parenteral administration or to enhance bioavailability after oral administration. This approach resulted in the development of doxycycline and minocycline in the 1970s. Doxycycline was included in the World Health Organization Model List of Essential Medicines either as antibacterial or to prevent malaria or to treat patients with this disease. Additional development led to the third generation of tetracyclines, being tigecycline the only medicine of this class to date. Besides antibacterial activities, the anti-inflammatory, antihypernociceptive and neuroprotective activities of tetracyclines began to be widely studied in the late 1990s. Indeed, there has been an increasing interest in investigating the effects induced by minocycline as this liposoluble derivative is known to cross the blood-brain barrier to the greatest extent. Minocycline induces antihypernociceptive effects in a wide range of animal models of nociceptive, inflammatory and neuropathic pain. In this study, we discuss the antihypernociceptive activity of tetracyclines and summarise its underlying cellular and molecular mechanisms.

Anti-inflammatory and toxicity studies of atranorin extracted from Cladina kalbii Ahti in rodents

Atranorin (ATR) is the main compound from the lichen Cladina kalbii Ahti, which grows in the arid regions of northeastern Brazil. This study was conducted to evaluate the anti-inflammatory and toxicological properties of ATR. To evaluate anti-inflammatory properties, paw edema was induced by injecting 0.1 mL of carrageenan into the subplantar region of the right hind paw of rats, and leukocyte migration was induced by injection of 500 µL of carrageenan into the peritoneal cavity of mice. In addition, we determined ATR cytotoxicity in L929 cells by MTT assay and acute (5 g/kg-single dose) and subchronic (50 mg/kg-30 days) toxicity tests in Wistar rats. The results showed that ATR (100 mg/kg and 200 mg/kg) exhibited significant anti-inflammatory activity (paw edema and leukocyte migration). In the acute toxicity test, the animals showed hypoactivity and lethargy during the initial period (first 6 hours) and increase in total protein, total and indirect bilirubin, and alkaline phosphatase after 14 days in ATR-treated male rats. The subchronic toxicity test revealed increases in total protein, globulin, gamma-glutamyl transferase, alkaline phosphatase, and total and direct bilirubin in ATR-treated female rats. Histological analysis revealed no changes in the architecture and morphology of the organs. These results suggest that ATR has significant anti-inflammatory activity, with no significant acute and subchronic toxicity or cytotoxicity.

Priming of adult pain responses by neonatal pain experience: maintenance by central neuroimmune activity

Adult brain connectivity is shaped by the balance of sensory inputs in early life. In the case of pain pathways, it is less clear whether nociceptive inputs in infancy can have a lasting influence upon central pain processing and adult pain sensitivity. Here, we show that adult pain responses in the rat are 'primed' by tissue injury in the neonatal period. Rats that experience hind-paw incision injury at 3 days of age, display an increased magnitude and duration of hyperalgesia following incision in adulthood when compared with those with no early life pain experience. This priming of spinal reflex sensitivity was measured by both reductions in behavioural withdrawal thresholds and increased flexor muscle electromyographic responses to graded suprathreshold hind-paw stimuli in the 4 weeks following adult incision. Prior neonatal injury also 'primed' the spinal microglial response to adult injury, resulting in an increased intensity, spatial distribution and duration of ionized calcium-binding adaptor molecule-1-positive microglial reactivity in the dorsal horn. Intrathecal minocycline at the time of adult injury selectively prevented both the hyperalgesia and early microglial reactivity associated with prior neonatal injury. The enhanced neuroimmune response seen in neonatally primed animals could also be demonstrated in the absence of peripheral tissue injury by direct electrical stimulation of tibial nerve fibres, confirming that centrally mediated mechanisms contribute to these long-term effects. These data suggest that early life injury may predispose individuals to enhanced sensitivity to painful events.

Phytochemical characterization and antinociceptive effect of Lippia gracilis Schauer

Lippia gracilis Schauer is an aromatic plant widely found in Northeastern Brazil. The leaf infusions or decoctions and alcoholic macerate are used for some inflammatory diseases and headache. This paper reports the isolation of naringenin by semi-preparative liquid chromatography from the methanolic extract of L. gracilis (ELg) and the evaluation of the analgesic and anti-inflammatory activities of this extract by measuring nociception through acetic acid, formalin, and hot-plate tests in carrageenan-induced inflammation in mice. Following oral administration, ELg (100, 200, and 400 mg/kg) significantly reduced the number of writhes in the writhing test and the time of paw licks in both phases of the formalin test when compared to the control group animals. Mice treated with ELg did not exhibit any behavioral alteration during the hot plate and rota-rod tests, suggesting non-participation of the supraspinal components in the modulation of pain by ELg and no motor abnormality. The oral administration of 400 mg/kg of ELg produced an anti-inflammatory effect on peritonitis induced by carrageenan. These effects can be associated with a decrease of inflammatory mediator synthesis by compounds of ELg, such as naringenin, which has anti-inflammatory action as already described.

Spatial and temporal activation of spinal glial cells: role of gliopathy in central neuropathic pain following spinal cord injury in rats

In the spinal cord, neuron and glial cells actively interact and contribute to neurofunction. Surprisingly, both cell types have similar receptors, transporters and ion channels and also produce similar neurotransmitters and cytokines. The neuroanatomical and neurochemical similarities work synergistically to maintain physiological homeostasis in the normal spinal cord. However, in trauma or disease states, spinal glia become activated, dorsal horn neurons become hyperexcitable contributing to sensitized neuronal-glial circuits. The maladaptive spinal circuits directly affect synaptic excitability, including activation of intracellular downstream cascades that result in enhanced evoked and spontaneous activity in dorsal horn neurons with the result that abnormal pain syndromes develop. Recent literature reported that spinal cord injury produces glial activation in the dorsal horn; however, the majority of glial activation studies after SCI have focused on transient and/or acute time points, from a few hours to 1 month, and peri-lesion sites, a few millimeters rostral and caudal to the lesion site. In addition, thoracic spinal cord injury produces activation of astrocytes and microglia that contributes to dorsal horn neuronal hyperexcitability and central neuropathic pain in above-level, at-level and below-level segments remote from the lesion in the spinal cord. The cellular and molecular events of glial activation are not simple events, rather they are the consequence of a combination of several neurochemical and neurophysiological changes following SCI. The ionic imbalances, neuroinflammation and alterations of cell cycle proteins after SCI are predominant components for neuroanatomical and neurochemical changes that result in glial activation. More importantly, SCI induced release of glutamate, proinflammatory cytokines, ATP, reactive oxygen species (ROS) and neurotrophic factors trigger activation of postsynaptic neuron and glial cells via their own receptors and channels that, in turn, contribute to neuronal-neuronal and neuronal-glial interaction as well as microglia-astrocytic interactions. However, a systematic review of temporal and spatial glial activation following SCI has not been done. In this review, we describe time and regional dependence of glial activation and describe activation mechanisms in various SCI models in rats. These data are placed in the broader context of glial activation mechanisms and chronic pain states. Our work in the context of work by others in SCI models demonstrates that dysfunctional glia, a condition called "gliopathy", is a key contributor in the underlying cellular mechanisms contributing to neuropathic pain.

Efficacy of combined topical treatment of acne vulgaris with adapalene and nadifloxacin: a randomized study

Topical retinoid and antibiotic combination therapy is an integral part of acne treatment and is considered the appropriate first-line therapy according to the Japanese guideline for moderate and severe acne. In this combination, clindamycin or doxycycline are mostly used as antibiotics, but there have been no reports on the effectiveness of nadifloxacin, a widely used antibiotic in Japan and European countries for acne, in combination with topical retinoid. To confirm the efficacy and safety of adapalene gel and nadifloxacin cream in the treatment of Japanese patients with acne vulgaris, a total of 50 patients were randomized to the two groups, the combination therapy and the adapalene monotherapy, and each therapy was tested for 8 weeks. The percentage reduction in the number of inflammatory acne lesions was evaluated and the safety was monitored through adverse events. The combination of adapalene gel and nadifloxacin cream produced a significantly higher reduction in the inflammatory lesions at 2 weeks (P = 0.047) and at 8 weeks (P = 0.011) after the starting than did adapalene gel monotherapy. The combination did not elevate the side effects of erythema and scale scores, but rather significantly depressed erythema at 1 week. This study showed the efficacy and safety of the combination therapy of nadifloxacin cream with adapalene gel for the inflammatory acne.

Cryotherapy and topical minocycline as adjunctive measures to control pain after third molar surgery: an exploratory study

PURPOSE

To assess the impact of cryotherapy or topical minocycline on patients' perceptions of recovery from pain after third molar surgery in an exploratory comparative-effectiveness study.

PATIENTS AND METHODS

Subjects aged at least 14 years who were having all 4 third molars removed were enrolled in 3 separate institutional review board-approved studies. Study groups included subjects treated with a passively applied cold wrap for 24 hours postoperatively, subjects treated with topical minocycline during surgery, and subjects enrolled in a nonconcurrent comparison group who had received neither topical minocycline nor directed cryotherapy. Third molar surgery was performed in all cases by trained surgeons using the same protocol. An exact Kruskal-Wallis test was used to compare the distributions of the worst and average pain scores and a Fisher exact test to compare verbal responses from Gracely pain scales among the 3 groups for postsurgical days (PSDs) 1 to 3.

RESULTS

This study comprised 51 cryotherapy subjects (2005-2009), 63 minocycline subjects (2003-2004), and 92 comparison-group subjects (2002-2006) who were treated at academic centers and in community practices across the United States (N = 206). Demographic descriptors were similar among all groups. For PSDs 1 through 3 (unadjusted), the highest scores for worst pain (6-7 [out of 7] on Likert-type scale) were reported less frequently in each of the study groups than in subjects in the comparison group, although the numbers of subjects reporting the highest scores were few. The distribution of pain outcomes was significantly different among the 3 groups for worst pain and affective words on PSD 1 (P = .04 for both). However, the small number of subjects who reported the highest pain scores precluded adequate multivariate statistical analyses for all outcomes on PSD 1 to 3.

CONCLUSIONS

Data from this exploratory study suggest that adjunctive therapy to decrease postoperative pain-cryotherapy or topical minocycline-might be effective at moderating the patient's highest pain levels after third molar surgery. The topic should be studied further in a multicenter, prospective, randomized trial.

Antinociceptive action and redox properties of citronellal, an essential oil present in lemongrass

Citronellal (CT) is a monoterpenoid and the major constituent of the mixture of terpenoids that give the citronella oil its lemon scent. Citronella oil is widely used around the world for various purposes and is mainly obtained from plants of the Cymbopogon genus, which are known as "lemongrass." Considering these plants have been used worldwide for various medicinal purposes, the interest of researchers to understand the biological activities of monoterpenoids related to the Cymbopogon genus has been increasing. In the present work, we investigated the antinociceptive action and the redox properties of CT. Our results indicate that intraperitoneal injection of CT was effective in reducing nociceptive face-rubbing behavior in both phases of the formalin test, which was also naloxone-sensitive. CT also evoked antinociceptive response in the capsaicin and glutamate tests. The total radical-trapping antioxidant parameter and total antioxidant reactivity assays indicate that CT at doses of 0.1 and 1 mg/mL exerts a significant antioxidant activity, which is probably related to its ability to scavenge superoxide and nitric oxide, but not H(2)O(2) or hydroxyl radicals, as evaluated separately by specific in vitro tests. These results show for the first time the antinociceptive potential of CT and indicate that the antioxidant properties of this compound may rely on its mechanism of biological actions because CT-containing natural products are used to treat various diseases related to oxidative stress and reactive species.