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.

Antinociceptive and antiedematogenic activities of fenofibrate, an agonist of PPAR alpha, and pioglitazone, an agonist of PPAR gamma.

Peroxisome proliferator activated receptors (PPAR) are ligand-regulated transcription factors that control the expression of many genes. The antiinflammatory activity of fibrates, PPARalpha agonists, and thiazolidinediones, PPARgamma agonists, has been demonstrated in many in vitro and a few in vivo studies. In the present study, we evaluated the effect of acute (100 or 300 mg/kg, p.o.) or prolonged (100 or 300 mg/kg day, 7 days, p.o.) treatment with fenofibrate and acute treatment with pioglitazone (doses ranging from 1 to 50 mg/kg, i.p.), PPARalpha and PPARgamma agonists, respectively, on experimental models of nociception and edema, in order to expand the knowledge of their potential antiinflammatory activities. Fenofibrate and pioglitazone did not inhibit the nociceptive response in the hot-plate model and the first phase of formaldehyde induced nociceptive response in mice. However, treatment with pioglitazone and prolonged treatment with fenofibrate inhibited the second phase of this response. Mechanical allodynia induced by carrageenan in rats was inhibited by prolonged treatment with fenofibrate, but not by acute treatment with pioglitazone or fenofibrate. Both drugs inhibited paw edema induced by carrageenan in rats. Fenofibrate did not inhibit mechanical allodynia or paw edema induced by phorbol-12,13-didecanoate (PDD), a protein kinase C activator, in rats. Pioglitazone inhibited paw edema, but not mechanical allodynia, induced by PDD. The results represent the first demonstration of the antinociceptive and antiedematogenic activities of fenofibrate and pioglitazone and give further support to the potential use of PPAR agonists in the treatment of different inflammatory diseases.

Thiamine and riboflavin inhibit production of cytokines and increase the anti-inflammatory activity of a corticosteroid in a chronic model of inflammation induced by complete Freund's adjuvant.

BACKGROUND: The effects induced by thiamine and riboflavin, isolated or in association with corticosteroids, in models of chronic inflammation are not known. Thus, we evaluated the effect induced by these B vitamins, isolated or in association with dexamethasone, on the mechanical allodynia, paw edema and cytokine production induced by complete Freund's adjuvant (CFA) in rats. METHODS: Chronic inflammation was induced by two injections of CFA. Nociceptive threshold, paw volume and body temperature were evaluated for 21days. Tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) contents were determined in paw tissue. Riboflavin (125, 250 or 500mg/kg) or thiamine (150, 300 or 600mg/kg) were administered per os (po), twice daily. Dexamethasone (0.5mg/kgday, po) was administered every three days. RESULTS: CFA induced long lasting mechanical allodynia and paw edema. Elevation of body temperature was observed for a short period. Riboflavin reduced neither paw edema nor mechanical allodynia. Thiamine did not change paw edema, but partially inhibited mechanical allodynia. Riboflavin (500mg/kg) and thiamine (600mg/kg) exacerbated the anti-inflammatory activity of dexamethasone. Riboflavin, thiamine and dexamethasone reduced TNF-α and IL-6 production. The association of dexamethasone with thiamine induced greater inhibition of IL-6 production when compared with that induced by dexamethasone. CONCLUSIONS: Riboflavin and thiamine exacerbate the anti-inflammatory activity of dexamethasone and reduce production of TNF-α and IL-6.

Characterization of the antinociceptive and anti-inflammatory activities of riboflavin in different experimental models.

Riboflavin, similar to other vitamins of the B complex, presents anti-inflammatory activity but its full characterization has not yet been carried out. Therefore, we aimed to investigate the effect of this vitamin in different models of nociception, edema, fever and formation of fibrovascular tissue. Riboflavin (25, 50 or 100 mg/kg, i.p.) did not alter the motor activity of mice in the rota-rod or the open field models. The second phase of the nociceptive response induced by formalin in mice was inhibited by riboflavin (50 or 100 mg/kg). The first phase of this response and the nociceptive behavior in the hot-plate model were inhibited only by the highest dose of this vitamin. Riboflavin (25, 50 or 100 mg/kg, i.p.), administered immediately and 2 h after the injection of carrageenan, induced antiedema and antinociceptive effects. The antinociceptive effect was not inhibited by the pretreatment with cadmium sulfate (1 mg/kg), an inhibitor of flavokinase. Riboflavin (50 or 100 mg/kg, i.p., 0 and 2 h) also inhibited the fever induced by lipopolysaccharide (LPS) in rats. Moreover, the formation of fibrovascular tissue induced by s.c. implant of a cotton pellet was inhibited by riboflavin (50 or 100 mg/kg, i.p., twice a day for one week). Riboflavin (10 or 25 mg/kg, i.p.) also exacerbated the effect of morphine (2, 4 or 8 mg/kg, i.p.) in the mouse formalin test. In conclusion, the study demonstrates the antinociceptive and anti-inflammatory activities of riboflavin in different experimental models. These results, associated with the fact that riboflavin is a safe drug, is approved for clinical use and exacerbates the antinociceptive effect of morphine, may warrant clinical trials to assess its potential in the treatment of different painful or inflammatory conditions.

Antinociceptive, antiedematogenic and antiangiogenic effects of benzaldehyde semicarbazone.

Semicarbazones induce an anticonvulsant effect in different experimental models. As some anticonvulsant drugs also have anti-inflammatory activity, the effects of benzaldehyde semicarbazone (BS) on models of nociception, edema and angiogenesis were investigated. BS (10, 25 or 50 mg/kg, i.p.) markedly inhibited the second phase of nociceptive response induced by formaldehyde (0.34%, 20 microl) in mice, but only the highest dose inhibited the first phase of this response. The thermal hyperalgesia and mechanical allodynia induced by carrageenan (1%, 50 microl, i.pl.) in rats were also inhibited by BS (50 mg/kg, i.p.). However, treatment of mice with BS did not induce an antinociceptive effect in the hot-plate model. The paw edema induced by carrageenan (1%, 50 microl, i.pl.) in rats was inhibited by BS (25 or 50 mg/kg, i.p.). Treatment of mice with BS (0.25, 0.5 or 2.5 mg/kg/day, i.p., 7 days) also inhibited angiogenesis induced by subcutaneous implantation of a sponge disc. It is unlikely that the antinociceptive effect induced by BS results from motor incoordination or a muscle relaxing effect, as the mice treated with this drug displayed no behavioral impairment in the rotarod apparatus. In conclusion, we demonstrated that BS presents antinociceptive, antiedematogenic and antiangiogenic activities. An extensive investigation of the pharmacological actions of BS and its derivatives is justified and may lead to the development of new clinically useful drugs.

Pharmacological investigation of the nociceptive response and edema induced by venom of the scorpion Tityus serrulatus.

In this study we characterized the nociceptive response and edema induced by the venom of the scorpion Tityus serrulatus in rats and mice and carried out a preliminary pharmacological investigation of the mechanisms involved in these responses. Intraplantar injection of the venom (1 or 10mug) induced edema and a marked ipsilateral nociceptive response, characterized by thermal and mechanical allodynia and paw licking behaviour. The nociceptive response was inhibited by previous intraperitoneal administration of indomethacin (4mg/kg), dipyrone (200mg/kg), cyproheptadine (10mg/kg) or morphine (5 or 10mg/kg), but not by dexamethasone (1 or 4mg/kg) or promethazine (1 or 5mg/kg). The edema was inhibited by previous treatment with promethazine (5 or 10mg/kg) or cyproheptadine (5 or 10mg/kg), but not by indomethacin (2 or 4mg/kg), dexamethasone (1 or 4mg/kg) or cromolyn (40 or 80mg/kg). Some bioactive amines, including histamine and 5-hydroxytryptamine, were found in the venom in low concentrations. In conclusion, the nociceptive response and edema induced by the venom of T. serrulatus may result from the action of multiple mediators including eicosanoids, histamine and 5-hydroxytryptamine. These results may lead to a better understanding of the host response to potent animal toxins and also give insights into a more rational pharmacological approach to alleviate the intense pain associated with the scorpion envenomation.

In vivo evidence for a role of protein kinase C in peripheral nociceptive processing.

1. The present study was designed to characterize the nociceptive response induced by protein kinase C (PKC) peripheral activation and to investigate if this biochemical event is important for the nociceptive response induced by formaldehyde, and bradykinin (BK). 2. Intraplantar injection of phorbol-12,13-didecanoate (PDD; 0.01, 0.1 or 1 microg), a PKC activator, but not of 4 alpha-PDD (inactive analogue), dose-dependently induced thermal hyperalgesia in rats. This response was not observed at the contralateral hindpaw. Intraplantar injection of PDD (0.01, 0.1 or 1 microg) also induced mechanical allodynia. In mice, injection of PDD (0.1 or 1 microg) into the dorsum of the hindpaw induced a spontaneous licking behaviour. 3. Intraplantar co-injection of chelerythrine (10 or 50 microg), a PKC inhibitor, attenuated the thermal hyperalgesia induced by PDD (0.1 microg) in rats. 4. The second phase of the nociceptive response induced by the injection of formaldehyde (0.92%, 20 microl) into the dorsum of mice hindpaws was inhibited by ipsi-, but not contralateral, pre-treatment with chelerythrine (1 microg). 5. Intraplantar injection of BK (10 microg) induced mechanical allodynia in rats. Ipsi- but not contralateral injection of bisindolylmaleimide I (10 microg), a PKC inhibitor, inhibited BK-induced mechanical allodynia. 6. In conclusion, this study demonstrates that PKC activation at peripheral tissues leads to the development of spontaneous nociceptive response, thermal hyperalgesia and mechanical allodynia. Most importantly, it also gives in vivo evidence that peripheral PKC activation is essential for the full establishment of the nociceptive response induced by two different inflammatory stimuli.

Synthesis of novel 2,3,4-trisubstituted-oxazolidine derivatives and in vitro cytotoxic evaluation.

We have previously reported the discovery of cytotoxic and pro-apoptotic hit compound 1,1-dimethylethyl (S)- 2,2-dimethyl-4-[(3-nitrophenoxy)methyl]-3-oxazolidinecarboxylate 1 against leukemia cells. In the present work we describe the synthesis of 25 derivatives of this hit varying the substituent at ring or stereochemistry of the oxazolidine ring and evaluated them against human cancer cells lines. Six compounds exerted significant activity against HL60 promyelocytic leukemia cells with IC50 in low micromolar range (4-18 µM) and three compounds displayed activity against MDA-MB231 breast cancer cells (25-37 µM). In vitro cytotoxicity on normal cells PBMC (human peripheral blood mononuclear cells) was also evaluated. Compounds 7e (p-NO2, S) and 7m (p-COOCH3, S) showed good antiproliferative activity against HL60 (4 and 5 µM) and MDA-MB231 (37 and 25 µM) without affecting lymphocyte proliferation in PBMC, indicating low toxicity to normal cells. Besides, compound 7e induced DNA fragmentation on about 100% of HL60 cells at 50 µM. In this case, it was more potent than 7m and lead 1. This indicated that compound 7e has a great pro-apoptotic potential.

Anti-allergic potential of herbs and herbal natural products - activities and patents.

The increase of allergic diseases has accompanied the global population growth and the major challenge is to reduce morbidity. The currently available treatments present limitations regarding efficacy and safety. Hence, patients with chronic allergic conditions seek alternatives to achieve better control of symptoms. Many natural products have been identified as potential anti-allergic agents. In addition, plant formulations have demonstrated, in general, to be safe in clinical trials and demonstrate additional effects along with Western medicines such as synergism and modulation of the immune system. It is known that plants represent a source of new therapeutic agents and some of them have shown mechanisms of action similar to synthetic agents. However, in general, herbs and their combination are patented mainly by Asian countries to be used in food and drinks or cosmetics and dietary supplements and the anti-allergic mechanisms of action are not yet fully elucidated. In this review, we highlight relevant patent and studies with cultivated plants, plant formulations, and secondary metabolites that have been evaluated with respect to its anti-allergic potential.

Implication of eIF2α kinase GCN2 in induction of apoptosis and endoplasmic reticulum stress-responsive genes by sodium salicylate.

OBJECTIVES: Sodium salicylate (NaSal) can disturb cell viability by affecting the activity of multiple cellular molecules. In this work, we investigated the involvement of stress-responsive kinase GCN2 in regulating cell death and expression of stress genes in mouse embryonic fibroblasts (MEFs) upon exposure to NaSal. METHODS: Cell viability was assayed using the 3-(4,5-dimethylthiazol-2yl)-2,5-diphenyltetrazolium bromide (MTT) method, and apoptosis was evaluated by annexin V and propidium iodide staining. A polymerase chain reaction (PCR) array approach was used to analyse differential expression of a panel of 84 endoplasmic reticulum (ER) stress-associated genes. Gene reporter assays were carried out to determine activity of ER stress element (ERSE), and the protein levels of activating transcription factor 6 (ATF6) and C/EBP homologous protein (CHOP) were determined by western blot. KEY FINDINGS: NaSal treatment resulted in reduction of cellular viability and induction of apoptosis in wild-type but not Gcn2(-/-) cells. Many genes with important functions in protein synthesis/degradation, transcriptional regulation and apoptosis were induced by NaSal and most of these were dependent on GCN2. The activation of ERSE within Ddit3 and the production of CHOP and ATF6 induced by NaSal required GCN2. CONCLUSIONS: Our data provide evidence for the involvement of GCN2 in apoptosis and gene expression triggered by NaSal, and contributes to the understanding of molecular events occurring in NaSal-treated cells.

Osteogenic differentiation of bone marrow mesenchymal stem cells of ovariectomized and non-ovariectomized female rats with thyroid dysfunction.

The objective of this study was to verify the osteogenic potential of the bone marrow mesenchymal stem cells (MSCs) of ovariectomized and non-ovariectomized female rats with hypo- and hyperthyroidism. Sixty two-month-old female rats were assigned to the following groups: (1) control (sham-operated), (2) ovariectomized (OVX'd), (3) hypothyroid sham-operated (Hypo-), (4) hypothyroid OVX'd, (5) hyperthyroid sham-operated (Hyper-) and (6) hyperthyroid OVX'd. After 135 days of treatment, the female rats were euthanized. We collected plasma to measure the levels of free T4, and the femur for extraction of MSCs. At 7 and 21 days of osteogenic differentiation of MSCs, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) conversion, alkaline phosphatase activity, mineralized nodule number and gene expression for collagen I, osteocalcin, bone sialoprotein and osteopontin were analyzed. The hypothyroid group presented a significant reduction in the osteogenic differentiation of MSCs. The hyperthyroid group did not present changes in the synthesis of mineralized nodules for MSCs at day 21 of differentiation. However, in ovariectomized rats, hyperthyroidism increased the osteogenic differentiation of MSCs characterized by the increase of the alkaline phosphatase activity, the number of mineralized nodules and the expression of osteocalcin, sialoprotein and osteopontin. Our results demonstrated that the hypothyroidism reduces the osteogenic differentiation of MSCs only in non-ovariectomized rats and that the hyperthyroidism increases the osteogenic differentiation of MSCs only in ovariectomized rats.