Metformin inhibits paclitaxel-induced mechanical allodynia by activating opioidergic pathways and reducing cytokines production in the dorsal root ganglia and thalamus.

It has been shown that AMP-activated protein kinase (AMPK) is involved in the nociceptive processing. This observation has prompted us to investigate the effects of the AMPK activator metformin on the paclitaxel-induced mechanical allodynia, a well-established model of neuropathic pain. Mechanical allodynia was induced by four intraperitoneal (i.p) injections of paclitaxel (2 mg/kg.day) in mice. Metformin was administered per os (p.o.). Naltrexoneandglibenclamide were used to investigate mechanisms mediating metformin activity. Concentrations of cytokines in the dorsal root ganglia (DRG) and thalamus were determined. After a single p.o. administration, the two highest doses of metformin (500 and 1000 mg/kg) attenuated the mechanical allodynia. This response was attenuated by all doses of metformin (250, 500 and 1000 mg/kg) when two administrations, 2 h apart, were carried out. Naltrexone (5 and 10 mg/kg, i.p.), but not glibenclamide (20 and 40 mg/kg, p.o.), attenuated metformin activity. Concentrations of tumor necrosis factor (TNF)-α, interleukin (IL)-1ß and CXCL-1 in the DRG were increased after administration of paclitaxel. Metformin (1000 mg/kg) reduced concentrations of TNF-α, IL-1ß and CXCL-1 in the DRG. Concentration of IL-6, but not TNF-α, in the thalamus was increased after administration of paclitaxel. Metformin (1000 mg/kg) reduced concentration of IL-6 in the thalamus. In summary, metformin exhibits activity in the model of neuropathic pain induced by paclitaxel. This activity may be mediated by activation of opioidergic pathways and reduced production of TNF-α, IL-1ß and CXCL-1 in the DRG and IL-6 in the thalamus.

RI75, a curcumin analogue, inhibits tumor necrosis factor-α and interleukin-6 production and exhibits antiallodynic and antiedematogenic activities in mice.

Curcumin and its analogues exhibited anti-inflammatory activity in different experimental models. Recently, we synthesized (2E,3E)-3-buten-2-one-4-(4-hydroxy-3-methoxyphenyl)-2-(4-(4-methoxyphenyl)-2-thiazolyl)hydrazone (RI75), a curcumin analogue with a thiazolyl hydrazone moiety. In the present study, we investigated the effects induced by RI75 in different models of inflammation and pain in mice, as well as some underlying mechanisms. Pre-treatment with RI75 (40 mg/kg, intraperitoneal; i.p.) or curcumin (40 mg/kg, i.p.) reduced the mechanical allodynia and paw edema induced by intraplantar (i.pl) injection of carrageenan. RI75 antiallodynic activity was reduced by pre-treatment with naltrexone (5 and 10 mg/kg, i.p.) and cyproheptadine (10 mg/kg, i.p.), but not glibenclamide (20 and 40 mg/kg, i.p.). In a model of neuropathic pain, a single i.p. administration of RI75 (40 mg/kg) or curcumin (40 mg/kg) attenuated the ongoing mechanical allodynia induced by repeated administrations of paclitaxel. Pre-treatment with RI75 (40 mg/kg, i.p.) or curcumin (40 mg/kg, i.p.) also reduced tumor necrosis factor-α and interleukin-6 production and myeloperoxidase activity induced by carrageenan. The results of the present study demonstrate that RI75, a synthetic curcumin analogue, exhibits antiallodynic and antiedematogenic activities. Activation of opioidergic and serotonergic mechanisms and reduced production of inflammatory mediators and neutrophil recruitment may underlie RI75 activities.

Metformin effect in models of inflammation is associated with activation of ATP-dependent potassium channels and inhibition of tumor necrosis factor-α production.

Metformin is an oral hypoglycemic drug widely used in the management of type 2 diabetes mellitus. We have recently demonstrated that metformin exhibits activity in models of nociceptive and neuropathic pain. However, little is known about its effects in experimental models of inflammation and inflammatory pain. Thus, the present study aimed to evaluate the activity of metformin in experimental models of inflammation and inflammatory pain in mice, as well as the underlying mechanisms. Previous (1 h) per os (p.o.) administration of metformin (250, 500 or 1000 mg/kg) inhibited the mechanical allodynia and paw edema induced by intraplantar (i.pl.) injection of carrageenan (600 µg) and also the pleurisy induced by this stimulus (200 µg, intrapleural). In the model of mechanical allodynia and paw edema induced by carrageenan, metformin also exhibited activity when administered after (1 h) the inflammatory stimulus. Metformin (1000 mg/kg) reduced the production of tumor necrosis factor-α induced by i.pl. injection of carrageenan. Metformin antiallodynic effect was not affected by previous administration of naltrexone (5 or 10 mg/kg, intraperitoneal) or cyproheptadine (5 or 10 mg/kg, p.o). However, this effect was abolished by previous administration of glibenclamide (20 or 40 mg/kg, p.o). In conclusion, the results demonstrate the activity of metformin in models of inflammation and inflammatory pain. In addition, the results indicate that the activity of metformin may be mediated by activation of ATP-sensitive potassium channels and reduction of production of inflammatory mediators. Altogether, these results stimulate the conduction of studies aiming to evaluate whether metformin may be repositioned in the treatment of patients with painful and inflammatory disorders.

Thiamine, riboflavin, and nicotinamide inhibit paclitaxel-induced allodynia by reducing TNF-α and CXCL-1 in dorsal root ganglia and thalamus and activating ATP-sensitive potassium channels.

Some B vitamins exhibit activities in models of nociceptive pain, inflammatory pain, and neuropathic pain induced by nerve lesions and also in certain painful conditions in humans. In the present study, we investigated the effects of thiamine, riboflavin, and nicotinamide in a neuropathic pain model induced by the chemotherapeutic paclitaxel in mice. Four intraperitoneal (i.p.) administrations of paclitaxel (2 mg/kg day, cumulative dose 8 mg/kg) induced a long-lasting mechanical allodynia. Per os (p.o.) administration of two doses of thiamine (150, 300 and 600 mg/kg), nicotinamide (250, 500 and 1000 mg/kg) or riboflavin (125, 250 and 500 mg/kg), on the seventh day after the first administration of paclitaxel, the mechanical allodynia was attenuated. The antinociceptive activity of all B vitamins was attenuated by glibenclamide (20 and 10 mg/kg, p.o.). Naltrexone (5 and 10 mg/kg, i.p.) attenuated the antinociceptive activity of thiamine. Thiamine, riboflavin, and nicotinamide also reduced the concentrations of tumor necrosis factor-α (TNF-α) and CXCL-1 in dorsal root ganglia (DRG) and thalamus. In conclusion, thiamine, riboflavin, and nicotinamide exhibit antinociceptive activity in the neuropathic pain model induced by paclitaxel. Inhibition of TNF-α and CXCL-1 production in DRG and thalamus, as well as activation of ATP-sensitive potassium channels, underly their antinociceptive activity.

Clindamycin inhibits nociceptive response by reducing tumor necrosis factor-α and CXCL-1 production and activating opioidergic mechanisms.

Clindamycin, a bacteriostatic semisynthetic lincosamide, is useful in the management of infections caused by aerobic and anaerobic Gram-positive cocci, including bacteremic pneumonia, streptococcal toxic shock syndrome and sepsis. It has been recently demonstrated that clindamycin inhibits in vitro and in vivo inflammatory cytokine production. In the present study, we investigated the effects of clindamycin in acute and chronic models of pain and inflammation in mice and the underlying mechanisms. Intraperitoneal (i.p.) administration of clindamycin (400 mg/kg) increased the animal's latency to exhibit the nociceptive behavior induced by noxious heat (hot plate model). Intrathecal injection of clindamycin (2, 10 and 50 µg) also increased the animals' latency to exhibit the nociceptive behavior. Tactile hypersensitivity and paw edema induced by intraplantar (i.pl.) injection of carrageenan were attenuated by previous administration of clindamycin (200 and 400 mg/kg, i.p.). Clindamycin (100, 200 and 400 mg/kg, i.p.) also attenuated ongoing tactile hypersensitivity and paw edema induced by i.pl. injection of complete Freund's adjuvant (CFA). The antinociceptive activity of clindamycin (400 mg/kg, i.p.) in the hot plate model was attenuated by previous administration of naltrexone (5 and 10 mg/kg, i.p.), but not glibenclamide or AM251. CFA-induced production of TNF-α and CXCL-1 was reduced by clindamycin (400 mg/kg, i.p.). Concluding, clindamycin exhibits activities in acute and chronic models of pain and inflammation. These effects are associated with reduced production of TNF-α and CXCL-1 and activation of opioidergic mechanisms. Altogether, these results indicate that the clindamycin's immunomodulatory effects may contribute to a pharmacological potential beyond its antibiotic property.

Antifungal and antioxidant activity of fatty acid methyl esters from vegetable oils.

Fatty acid methyl esters (FAMEs) were obtained from vegetable oils of soybean, corn and sunflower. The current study was focused on evaluating the antifungal activity of FAMEs mainly against Paracoccidioides spp., as well as testing the interaction of these compounds with commercial antifungal drugs and also their antioxidant potential. FAMEs presented small IC50 values (1.86-9.42 µg/mL). All three FAMEs tested showed antifungal activity against isolates of Paracoccidioides spp. with MIC values ranging from 15.6-500 µg/mL. Sunflower FAMEs exhibited antifungal activity that extended also to other genera, with an MIC of 15.6 µg/mL against Candida glabrata and C. krusei and 31.2 µg/mL against C. parapsilosis. FAMEs exhibited a synergetic effect with itraconazole. The antifungal activity of the FAMEs against isolates of Paracoccidioides spp. is likely due to the presence of methyl linoleate, the major compound present in all three FAMEs. The results obtained indicate the potential of FAMEs as sources for antifungal and antioxidant activity.

Nicorandil antiallodynic activity in a model of neuropathic pain is associated with the activation of ATP-dependent potassium channels and opioidergic pathways, and reduced production of cytokines and neutrophils recruitment in paw, sciatic nerve, and dorsal root ganglia.

BACKGROUND: Recently, we demonstrated that nicorandil inhibits mechanical allodynia induced by paclitaxel. In the present study, we evaluated the effect induced by nicorandil in a model of neuropathic pain induced by chronic constriction injury (CCI) in mice. We also investigated putative mechanisms underlying such an effect. METHODS: CCI was induced by three ligatures of the left sciatic nerve. Mechanical allodynia was evaluated by measuring the paw withdrawal threshold with an electronic von Frey apparatus. Concentrations of cytokines and myeloperoxidase activity were determined in the paw tissue, sciatic nerve, and dorsal root ganglia (DRG). RESULTS: Oral administration of two doses of nicorandil (150 mg/kg po), but not equimolar doses of nicotinamide or nicotinic acid, attenuated mechanical allodynia induced by CCI. Nicorandil activity was reduced by previous administration of glibenclamide (40 mg/kg) or naltrexone (5 mg/kg or 10 mg/kg). Two doses of nicorandil (150 mg/kg, po) reduced tumor necrosis factor-α, interleukin-1ß and interleukin-6, but not CXCL-1, concentrations in the paw tissue of CCI mice. Two doses of nicorandil (150 mg/kg, po) reduced concentrations of all these mediators in the sciatic nerve and DRG. Two doses of nicorandil (150 mg/kg, po) also reduced the myeloperoxidase activity in the paw tissue, sciatic nerve, and DRG. CONCLUSIONS: Nicorandil exhibits antiallodynic activity in a model of neuropathic pain induced by CCI. Inhibition of cytokines production and reduction of neutrophils recruitment in paw tissue, sciatic nerve, and DRG as well as activation of ATP-dependent potassium channels and opioidergic pathways, underlie nicorandil antiallodynic activity.

A clindamycin acetylated derivative with reduced antibacterial activity inhibits articular hyperalgesia and edema by attenuating neutrophil recruitment, NF-κB activation and tumor necrosis factor-α production.

We recently demonstrated that clindamycin exhibits activities in acute and chronic models of pain and inflammation. In the present study, we investigated the effects of clindamycin and a clindamycin acetylated derivative (CAD) in models of acute joint inflammation and in a microbiological assay. Joint inflammation was induced in mice by intraarticular (i.a.) injection of zymosan or lipopolysaccharide (LPS). Clindamycin or CAD were administered via the intraperitoneal route 1 h before zymosan or LPS. Paw withdrawal threshold, joint diameter, histological changes, neutrophil recruitment, tumor necrosis factor-α (TNF-α) production and phosphorylation of the IκBα and NF-κB/p65 were evaluated. In vitro assays were used to measure the antibacterial activity of clindamycin and CAD and also their effects on zymosan-induced TNF-α production by RAW264.7 macrophages. Clindamycin exhibited activity against Staphylococcus aureus and Salmonella Typhimurium ATCC® strains at much lower concentrations than CAD. Intraarticular injection of zymosan or LPS induced articular hyperalgesia, edema and neutrophil infiltration in the joints. Zymosan also induced histological changes, NF-κB activation and TNF-α production. Responses induced by zymosan and LPS were inhibited by clindamycin (200 and 400 mg/kg) or CAD (436 mg/kg). Both clindamycin and CAD inhibited in vitro TNF-α production by macrophages. In summary, we provided additional insights of the clindamycin immunomodulatory effects, whose mechanism was associated with NF-κB inhibition and reduced TNF-α production. Such effects were extended to a clindamycin derivative with reduced antibacterial activity, indicating that clindamycin derivatives should be investigated as candidates to drugs that could be useful in the management of inflammatory and painful conditions.

Metformin antinociceptive effect in models of nociceptive and neuropathic pain is partially mediated by activation of opioidergic mechanisms.

Metformin, an AMP-activated protein kinase (AMPK) activator, is an oral hypoglycemic drug widely used to treat patients with type 2 diabetes. As AMPK plays a role in the nociceptive processing, investigating the effects induced by metformin in experimental models of pain is warranted. In the present study, we further evaluated the effects induced by metformin in models of nociceptive and neuropathic pain and investigated mechanisms that could mediate such effects. Metformin was administered per os (p.o.) in mice. Nociceptive response induced by heat (hot-plate) and mechanical allodynia induced by chronic constriction injury (CCI) were used as pain models. Naltrexone (intraperitoneal) and glibenclamide (p.o.) were used to investigate mechanisms mediating metformin effects. A single administration of metformin (500 or 1000 mg/kg) inhibited the nociceptive response in the hot-plate model. Single and repeated administration of metformin (250, 500 or 1000 mg/kg) inhibited the mechanical allodynia induced by CCI. Metformin (250, 500 or 1000 mg/kg) did not affect the time mice spent in the rota-rod apparatus. The activity of metformin (1000 mg/kg) in both pain models was attenuated by naltrexone (10 mg/kg), but not by glibenclamide. Concluding, metformin exhibited activity in models of nociceptive and neuropathic pain. In the model of neuropathic pain, preventive and therapeutic effects were observed. Activation of opioidergic pathways partially mediates metformin antinociceptive activity. Altogether, the results indicate that metformin should be further investigated aiming its repositioning in the treatment of patients with different painful conditions.

Nicorandil inhibits mechanical allodynia induced by paclitaxel by activating opioidergic and serotonergic mechanisms.

Recently, we demonstrated that nicorandil exhibits activities in models of inflammatory and nociceptive pain. In the present study, we extended this investigation by evaluating the effects of nicorandil in models of neuropathic pain induced by paclitaxel or nerve injury in mice. Four intraperitoneal (i.p.) injections of paclitaxel (2 mg/kg.day, cumulative dose 8 mg/kg) or chronic constriction injury (CCI) of the sciatic nerve induced a long lasting mechanical allodynia. Per os (p.o.) administration of two doses of nicorandil (50, 100 and 150 mg/kg) on the 14th day after the first paclitaxel injection attenuated the mechanical allodynia. Equimolar doses of nicotinamide (86.7 mg/kg, p.o.) or nicotinic acid (87.7 mg/kg, p.o.) were devoid of effect. Mechanical allodynia induced by CCI was also attenuated by p.o. administration of two doses of nicorandil (150 mg/kg) on the 14th day after nerve injury. Nicorandil (50, 100 and 150 mg/kg, p.o.) did not affect motor activity. The antinociceptive activity of nicorandil in the model of mechanical allodynia induced by paclitaxel was partially attenuated by naltrexone (5 and 10 mg/kg, i.p.) or cyproheptadine (5 and 10 mg/kg, i.p.), but not by glibenclamide (20 and 40 mg/kg, p.o.). Concluding, nicorandil exhibits activity in experimental models of neuropathic pain when mechanical allodynia is fully established. Activation of opioidergic and serotonergic pathways mediates the antinociceptive activity of nicorandil. It is unlikely that this activity requires biotransformation to nicotinamide or nicotinic acid. Nicorandil should be further evaluated aiming to identify a new alternative in the pharmacological management of neuropathic pain.

Antifungal and antioxidant activity of fatty acid methyl esters from vegetable oils

ABSTRACT Fatty acid methyl esters (FAMEs) were obtained from vegetable oils of soybean, corn and sunflower. The current study was focused on evaluating the antifungal activity of FAMEs mainly against Paracoccidioides spp., as well as testing the interaction of these compounds with commercial antifungal drugs and also their antioxidant potential. FAMEs presented small IC50 values (1.86-9.42 μg/mL). All three FAMEs tested showed antifungal activity against isolates of Paracoccidioides spp. with MIC values ranging from 15.6-500 µg/mL. Sunflower FAMEs exhibited antifungal activity that extended also to other genera, with an MIC of 15.6 μg/mL against Candida glabrata and C. krusei and 31.2 μg/mL against C. parapsilosis. FAMEs exhibited a synergetic effect with itraconazole. The antifungal activity of the FAMEs against isolates of Paracoccidioides spp. is likely due to the presence of methyl linoleate, the major compound present in all three FAMEs. The results obtained indicate the potential of FAMEs as sources for antifungal and antioxidant activity.