International Immunopharmacology 9 (2009) 1394–1400
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International Immunopharmacology j o u r n a l h o m e p a g e : w w w. e l s ev i e r. c o m / l o c a t e / i n t i m p
Evidence of anti-inflammatory effects of Pioglitazone in the murine pleurisy model induced by carrageenan Tânia Silvia Fröde a,⁎, Ziliani da Silva Buss a, Gustavo Oliveira dos Reis a, Yara Santos Medeiros b a b
Departamento de Análises Clínicas, Centro de Ciências da Saúde, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil Departmento de Farmacologia, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil
a r t i c l e
i n f o
Article history: Received 26 February 2009 Received in revised form 7 August 2009 Accepted 19 August 2009 Keywords: Pioglitazone PPAR Pleurisy TNF-α IL-1β Proinflammatory effect
a b s t r a c t Several studies have shown that the anti-inflammatory effect of Pioglitazone extends beyond the cardiovascular system. This study examines the anti-inflammatory effect of Pioglitazone in comparison to reference drugs (Dexamethasone and Indomethacin) in the mouse model of pleurisy induced by carrageenan which is characterized by two distinct phases (4 and 48 h) of inflammation. Pioglitazone (20 and 50 mg/kg, i.p., 0.5 h before pleurisy) inhibited both neutrophil (4 h) and mononuclears (48 h) influxes (P < 0.01), but not exudation (P > 0.05). While one dose of Pioglitazone was effective in inhibiting inflammation at 4 h, additional doses (10 or 20 mg/kg, i.p., 0.5 h before pleurisy induction followed by either a second dose at 24 h after the first one or two further doses at 12 h of time interval after the first one) were necessary to elicit inhibition of the second (48 h) inflammation phase. These effects were associated with a marked decrease in adenosine-deaminase (ADA) activity, tumor necrosis factor-alpha (TNF-α) and interleukin 1-beta (IL-1β) levels (P < 0.01). Myeloperoxidade (MPO) activity was inhibited only at 4 h (P < 0.05). By contrast, reference drugs were able to inhibit all the studied inflammatory parameters (P < 0.05). These results demonstrated an interesting anti-inflammatory property of this thiazolidinedione class and strengthen prior evidence that PPAR pathways constitute another important route of inflammatory process inhibition of this pleurisy model. © 2009 Elsevier B.V. All rights reserved.
1. Introduction Peroxisome proliferator-activated receptors (PPARs), namely PPARα and PPAR-γ, are nuclear transcription factors originally described as important regulators in both glucose and lipid metabolisms [1,2,3]. Subsequently, PPARs have been shown to regulate the genes expression involved in other biological processes, including inflammation in both acute and chronic experimental conditions [4,5,6,7]. These effects are linked to a reduced expression of proinflammatory mediators such as cytokines and chemokines, among others. The molecular pathways of these effects involve an interaction with proinflammatory transcription factors such as STAT 1, AP-1 and NF-κB [8,9]. The thiazolidinediones class clinically employed as antidiabetic drugs such as Pioglitazone and Rosiglitazone, which are synthetic agonists of PPAR-α and PPAR-γ have been useful tools to evaluate the role of these agents in the inflammatory response modulation, besides their effects upon atherosclerosis and insulin resistance. However, PPAR expression has been described in endothelial cells, macrophages, leukocytes, and alveolar cells [9]. Thus, motivated by the fact that PPAR
⁎ Corresponding author. Universidade Federal de Santa Catarina (UFSC), Centro de Ciências da Saúde (CCS), Departamento de Análises Clínicas (ACL), Campus Universitário-Trindade, 88040-970, Florianópolis, SC, Brazil. Fax: +55 48 3244 09 36. E-mail address:
[email protected] (T.S. Fröde). 1567-5769/$ – see front matter © 2009 Elsevier B.V. All rights reserved. doi:10.1016/j.intimp.2009.08.011
activation can promote anti-inflammatory effects, and in the face of the few evidence about the anti-inflammatory activity of Pioglitazone in in vivo models [9,10,11,12], the present study investigated its effects in a mouse inflammation bimodal model and compare it with conventional anti-inflammatory drugs (Dexamethasone and Indomethacin). These latter drugs act via well known mechanism of actions [13,14], whereas it is suggested that activated PPAR-γ regulates the synthesis of proinflammatory cytokines by negatively interacting with proinflammatory transcription factors [15]. This mouse model of pleurisy induced by carrageenan is characterized by two phases (4 and 48 h), of inflammatory reaction, with different mediators involved in these two phases [16,17,18,19]. The parameters examined were: leukocytes, exudation, myeloperoxidase (MPO) and adenosine-deaminase (ADA) activities, tumor necrosis factor-alpha (TNF-α) and interleukin-1 beta (IL-1β) levels. 2. Material and methods 2.1. Animals Swiss mice, weighing 18–25 g, were housed under standardized conditions (room at constant temperature of 22 ± 2 °C with alternating 12 h periods of light and darkness and 50–60% humidity) and were fed on a standard mouse diet with water ad libitum before used.
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Animals were weighed before Pioglitazone treatment and immediately before being sacrificed. Each studied group consisted of six animals, unless otherwise stated. The number of animals used was the minimum necessary to demonstrate the drug treatment consistent effects. This study was approved by the Committee of Ethics in Animal Research at University (Protocol number — PP00181), and experiments were performed in accordance with the norms of Brazilian College of Animal Experimentation (COBEA). 2.2. Induction and analysis of pleurisy Pleurisy was induced by a single intrapleural (i.pl.) injection of 0.1 mL of sterile saline (NaCl 0.95%) plus carrageenan (1%) [16]. After pleurisy induction (4 and 48 h), animals were killed with an overdose of ether, the thorax was opened, and the pleural cavity was washed with 1.0 mL of sterile phosphate buffered saline (PBS) (pH 7.6), composition: NaCl (130 mmol), Na2HPO4 (5 mmol), KH2PO4 (1 mmol) and distillated water (1000 ml) containing heparin (20 IU/mL). Several fluid leakage samples were collected for further determinations of total and differential leukocytes, exudation, MPO and ADA activities, and TNF-α and IL-1β levels. 2.2.1. Experimental protocols and Pioglitazone, Indomethacin and Dexamethasone doses 2.2.1.1. First (4 h) inflammation phase induced by carrageenan. Initially, a set of experiments was done to determine the dose–response curve to Pioglitazone and its effects on total and differential cell contents at 4 h after pleurisy induction. Thus, different groups of animals were treated with different doses of Pioglitazone (5, 10, 20 and 50 mg/kg) administered by intraperitoneal (i.p.) route (Fig. 1A). Based on the results of this protocol, one dose of Pioglitazone was chosen to determine the time course profile of this drug, as well as other inflammatory parameters (cited below) in the first (4 h) phase of this inflammatory reaction. 2.2.1.2. Second (48 h) inflammation phase induced by carrageenan. For the analysis of Pioglitazone in the second (48 h) inflammatory response phase, 3 groups of animals were evaluated: 1) animals treated with different doses of Pioglitazone (10, 20 and 50 mg/kg, i.p.) administered 0.5 h before pleurisy induction (Fig. 1B), 2) animals treated with different doses of Pioglitazone (10 or 20 mg/kg, i.p.) administered 0.5 h before pleurisy induction followed by 2 doses of either 10 or 20 mg/kg, administered at 12 h of time interval after the first one (Fig. 1C), and 3)
Fig. 1. Schematic diagram of the experimental protocol with Pioglitazone. (A) Treatment with 5–50 mg/kg, i.p., 0.5 h before carrageenan administration and pleurisy analyzed after 4 h. (B) Treatment with 10–50 mg/kg, i.p., 0.5 h before carrageenan administration. The pleurisy was analyzed after 48 h. (C) Treatment with 10 or 20 mg/kg, i.p., 0.5 h before carrageenan administration followed by another two doses at 12 h of time interval after the first one. The pleurisy was analyzed after 48 h. (D) Treatment with 10 or 20 mg/kg, i.p., 0.5 h before carrageenan administration followed by another second dose at 24 h of interval time after the first one. The pleurisy was analyzed after 48 h. (↓) indicates the Pioglitazone treatment and (▲) the time points of pleurisy induction (0) and analysis of the inflammatory parameters (4 and 48 h).
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animals treated with different doses of Pioglitazone (10 or 20 mg/kg, i.p.) administered 0.5 h before pleurisy followed by a second dose (either 10 or 20 mg/kg, i.p.) administered at 24 h of time interval after the first one (Fig. 1D). The inflammatory parameters: leukocytes and exudation were evaluated 48 h after pleurisy induction. According to this data, one protocol and one Pioglitazone dose were chosen to analyze the other inflammatory parameters (cited below) in the second (48 h) inflammation phase caused by carrageenan. Dexamethasone (Dex) and Indomethacin (Indo) were used as reference drugs. Thus, parallel groups of animals were pre-treated (0.5 h before pleurisy induction) with either Dex (0.5 mg/kg, i.p.) or Indo (5.0 mg/kg, i.p.) in experiments to evaluate the first (4 h) and second (48 h) inflammation phases caused by carrageenan. The same inflammatory parameters were evaluated at these time points. In all experiments, a group of animals received only 0.1 mL of carrageenan (1%, i.pl.). This group was considered the positive controlgroup. At the same time, another group of animals received 0.1 mL of sterile saline (i.pl.) or the same vehicle volume by i.p. route. This group was considered as a negative control-group and it was considered an indicator that the process was conducted under aseptic conditions. Positive, negative or treated-groups were administered the same volumes (0.1 mL) via i.pl. and i.p. routes. 2.3. Cell influx and exudation quantification After killing the animals (4 and 48 h after pleurisy), the pleural cavity fluid samples were collected to determine the total and differential leukocyte contents, and exudation. Total leukocytes were determined in a Newbauer chamber diluting the exudates in Türk solution (1:20), and cytospin preparations of exudates were stained with May–Grünwald– Giemsa for the differential count, which was performed under an oil immersion objective. The degree of exudation was determined by the amount measurement of Evans blue dye extravasation in the exudates, as previously described [16]. Thus, in each experimental group, a separated group of animals was previously challenged (1 h) before carrageenan injection with a solution of Evans blue dye (25 mg/kg) administered by intravenous route (i.v.) in order to evaluate the exudation degree into the pleural cavity. On the day of the experiments, the dye amount of pleural wash aliquot was estimated by colorimetric method using an ELISA plate reader (Organon Teknika, Roseland, NJ, USA) at 600 nm, and interpolation from a standard curve of Evans blue dye in the range of 0.01 to 50.0 µg/mL. 2.4. Quantification of MPO and ADA activities and IL-1β and TNF-α levels In-house assays of both MPO and ADA activities were employed according to the methods described in the literature [20,21]. For cytokine analysis, the fluid leakage samples were collected and immediately prepared to quantify cytokine levels. In this protocol, commercially available kits were used with monoclonal specific antibodies for each cytokine. The cytokine levels were measured by enzyme-linked immunosorbent assay (ELISA), using the kits according to the manufacturer's instructions. The values ranges detected by these assays were: IL-1β = 100–6400 pg/mL and TNF-α = 5–2000 pg/mL. The intra- and inter-assay variation coefficients (CV) for IL-1β and TNF-α were intra CV: IL-1β = 6.2 ± 0.4% and TNF-α = 7.8 ± 0.9%; and inter CV: IL-1β = 5.1± 0.6% and TNF-α = 9.6 ± 2.1%, with sensitivity values of IL1β = 1.7 pg/mL and TNF-α = 5.0 pg/mL. All cytokine levels were estimated by means of colorimetric measurements at 450 nm on an ELISA plate reader (Organon Teknika, Roseland, NJ, USA) by interpolation from a standard curve. 2.5. Drugs and reagents The following drugs and reagents were used: Pioglitazone (Actos, Abbott, São Paulo, SP, Brazil), carrageenan (degree IV), human neutrophil myeloperoxidase, Indomethacin (Sigma Chemical Co., St.
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3. Results
time (0.5–2.0 h) before pleurisy induction to determine the best time course profile of this drug. The results of this set of experiments indicated that this drug was able to cause significant inhibition of leukocyte migration only when it was given 0.5 h before carrageenan injection (results not shown). Pioglitazone (20 mg/kg, i.p., 0.5 h before pleurisy) inhibited both MPO and ADA activities (% of inhibition: 66.95 ± 6.12 and 57.35 ± 10.60, respectively) in comparison to the positive control-group (P < 0.01) (Fig. 2A and B). The inhibition degree of the leukocyte enzymes, however, did not differ in comparison to the reference drugs (P > 0.05). Pioglitazone (20 mg/kg, i.p., 0.5 h before pleurisy) also significantly decreased TNF-α and IL-1β (% of inhibition: 60.42 ± 3.87 and 13.51 ± 0.32, respectively) in comparison to the positive controlgroup (P < 0.05) (Fig. 3A and B). In comparison to the reference drugs, Pioglitazone showed a different inhibitory effect. Whereas, this drug was more potent than Dex in inhibiting TNF-α (P < 0.01), this latter drug was more effective in inhibiting IL-1β (P < 0.01) (Fig. 3A and B). The inhibition degree of Pioglitazone in these experiments did not differ in comparison to Indomethacin (P > 0.05).
3.1. Effects of Pioglitazone on the first (4 h) phase inflammation induced by carrageenan
3.2. Effects of Pioglitazone on the second (48 h) inflammation phase induced by carrageenan
Table 1 shows that only the doses of 20 and 50 mg/kg, i.p. of Pioglitazone, 0.5 h before pleurisy induction, were effective in inhibiting leukocyte influx into the pleural cavity in comparison to the positive control-group (P < 0.01). This inhibition was associated with a marked decrease in neutrophil migration (P < 0.01) (Table 1). As expected, Dex and Indo also significantly inhibited both inflammatory parameters (P < 0.01). The inhibition degree caused by Pioglitazone (20 and 50 mg/kg, i.p.) did not differ in comparison to Indo (P > 0.05), whereas Dex was more potent in inhibiting these parameters (P < 0.05) (Table 1). Regarding mononuclears, an enhancement was observed when low doses of Pioglitazone (5 and 10 mg/kg, i.p.) were employed in comparison to the positive control-group (P < 0.01) (Table 1). The same event was observed in relation to the group pre-treated with Indo (P < 0.01). However, the doses of Pioglitazone (20 and 50 mg/kg, i.p.) and Dex did not modify intrapleural mononuclears after carrageenan injection (P > 0.05), but Indo treatment was associated with the highest mononuclears levels in relation to the positive control-group (P < 0.01) (Table 1). Pioglitazone did not affect exudation levels (P > 0.05) (results not shown), whereas both reference drugs also inhibited exudation: (% of inhibition: Dex 44.01 ± 3.51, Indo 49.87 ± 8.12) (P < 0.01) (results not shown). According to the results above, the dose of 20 mg/kg, i.p. of Pioglitazone was chosen to be administered at different periods of
Table 2 shows the results of the different experimental protocols upon leukocyte migration into the pleural cavity. As it is shown, only the dose of 20 mg/kg, i.p. of Pioglitazone was effective in inhibiting leukocyte migration when it was administered (0.5 h) before and after pleurisy induction either at 12 or 24 h of time interval (see experimental protocol: Fig. 1C and D) in comparison to the positive control-group (P < 0.01). This inhibition was related to a significant mononuclear influx reduction (P < 0.01) (Table 2). However, no
Louis, MO, USA), Dexamethasone (Ache Pharmaceutical Laboratories S.A., São Paulo, SP, Brazil), NaH2PO4.H20 and Na2HPO4.H2O (Vetec, Rio de Janeiro, RJ, Brazil), NH3SO4 (Labsynth, São Paulo, SP, Brazil), adenosine (Fluka, Ronkonkoma, NY, USA), phenol (Reagen, Rio de Janeiro, RJ, Brazil), nitroprussiate (Nuclear, São Paulo, SP, Brazil), enzyme-linked immunosorbent assay (ELISA) for mouse quantitative determination TNF-α (BD — Biosciences Pharmingen, San Diego, CA, USA) and mouse IL-1β (IBL-Immuno Biological Laboratories Co. Ltd., Fujioka, Gunma, Japan). Other reagents used were also of analytical grade and were obtained from different commercial sources. 2.6. Statistical analysis Data is reported as mean ± S.E.M. Statistical differences between groups (raw data) were determined by two-way variance analysis (ANOVA) complemented with Dunnett's and/or Student's “T” tests, when necessary. P < 0.05 was considered as indicative of significance.
Table 1 Effects of Pioglitazone upon: leukocytes on the first (4 h) inflammation phase induced by carrageenan. Groups/doses
Leukocytes (×106)
Neutrophils (×106)
Mononuclears (×106)
Cga Pio (5 mg/kg)b Pio (10 mg/kg)b Pio (20 mg/kg)b Pio (50 mg/kg)b Dex (0.5 mg/kg)b Indo (5 mg/kg)b
5.35 ± 0.30 5.40 ± 0.21 5.43 ± 0.22 3.21 ± 0.34⁎⁎# 3.15 ± 0.22⁎⁎## 1.68 ± 0.20⁎⁎ 3.17 ± 0.30⁎⁎#
4.60 ± 0.33 3.90 ± 0.19 5.10 ± 0.35 2.50 ± 0.29⁎⁎# 2.60 ± 0.19⁎⁎# 0.93 ± 0.20⁎⁎ 1.95 ± 0.20⁎⁎#
0.75 ± 0.13 1.50 ± 0.23⁎⁎ 1.33 ± 0.09⁎⁎ 0.71 ± 0.08+ 0.55 ± 0.06++ 0.75 ± 0.20 1.22 ± 0.16⁎
Cg = positive control-group, Pio = treated (0.5 h before) with one dose of Pioglitazone. Dex = treated (0.5 h before) with Dexamethasone, Indo = treated (0.5 h before) with Indomethacin. Each group represents the mean ± S.E.M. of 6 animals. ⁎⁎P < 0.01: Cg vs Pio (5 to 50 mg/kg) and Cg vs reference drugs, #P < 0.05 and ##P < 0.01: Dex vs Pio (20 and 50 mg/kg) and Dex vs Indo, +P < 0.05 and ++P < 0.01: Indo vs Pio. a = i.pl. route, b = i.p. route.
Fig. 2. Effects of Pioglitazone (Pio: 20 mg/kg, i.p., o.5 h before) upon (A) MPO and (B) ADA activities on the first (4 h) pleurisy phase induced by carrageenan. Cg = positive controlgroup, Dex = treated with dexamethasone (0.5 mg/kg, i.p., 0.5 h before), Indo = treated with indometacin (5 mg/kg, i.p., 0.5 h before). Bars indicate the mean± S.E.M. of 6 mice per group. ⁎⁎P < 0.01: Cg vs Pio and Cg vs reference drugs.
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Fig. 3. Effects of Pioglitazone (Pio: 20 mg/kg, i.p., 0.5 h before) upon TNF-α (A) and IL-1β (B) levels on the first (4 h) pleurisy phase induced by carrageenan. Cg = positive controlgroup, Dex = treated with dexamethasone (0.5 mg/kg, i.p., 0.5 h before), Indo = treated with indometacin (5 mg/kg, i.p., 0.5 h before). Bars indicate the mean ± S.E.M. of 6 mice per group. ⁎P < 0.05 and ⁎⁎P < 0.01: Cg vs Pio and Cg vs reference drugs, ##P < 0.01: Dex vs Pio.
significant statistical difference was observed between experimental protocols (P > 0.05). Under the same experimental conditions, no change in neutrophil content (Table 2) neither in the exudation levels (results not shown) into the pleural cavity was detected in comparison to the findings in the positive control-group (P > 0.05). In relation to the reference drugs studied, both Dex and Indo significantly decreased leukocyte, neutrophil and mononuclear migrations in comparison to the positive control-group (P < 0.01) (Table 2). Furthermore, these drugs also significantly inhibited exudation (% of inhibition: Dex 22.69 ± 5.43, Indo 26.11 ± 7.37) (P < 0.05) (results not shown). According to this data, Pioglitazone (20 mg/kg, i.p.) administered 0.5 h before pleurisy followed by a second dose at 24 h after the first dose was selected as the dose to be used to evaluate the other inflammatory parameters studied.
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Fig. 4. Effects of Pioglitazone (Pio: 20 mg/kg, i.p., 0.5 h before pleurisy and followed by another dose administered at 24 h of time interval after the first one) on the second (48 h) pleurisy phase induced by carrageenan upon: (A) MPO and (B) ADA activities. Cg = positive control-group, Dex = treated with dexamethasone (0.5 mg/kg, i.p., 0.5 h before), Indo = treated with indomethacin (5 mg/kg, i.p., 0.5 h before). Bars indicate the mean ± S.E.M. of 6 mice per group. ⁎P < 0.05 and⁎⁎P < 0.01: Cg vs Pio and Cg vs reference drugs, ##P < 0.01: Dex vs Pio, ++P < 0.01: Indo vs Pio.
Pioglitazone (20 mg/kg, i.p., 0.5 h before pleurisy followed by a second dose administered 24 h of time interval after the first one) did not affect MPO activity (P > 0.05) (Fig. 4A), but inhibited ADA activity by 32.55 ± 3.35% in comparison to positive control-group (P < 0.01) (Fig. 4B). At this time, Dex and Indo inhibited both enzymatic activities (% of inhibition: MPO: 44.31 ± 7.50 and 24.65 ± 4.30; ADA: 75.61 ± 6.20 and 70.38 ± 8.80, respectively) (P < 0.05) (Fig. 4A and B). Regarding ADA inhibition, Dex was more potent than Pioglitazone (P < 0.01). Under the same experimental protocol, Pioglitazone inhibited the levels of TNF-α by 56.99 ± 12.15% and IL-1β by 49.85 ± 4.42% (P < 0.01) (Fig. 5A and B). Similar effects were observed in relation
Table 2 Effects of Pioglitazone upon: leukocytes on the second (48 h) inflammation phase induced by carrageenan. Groups/doses
Leukocytes (×106)
Neutrophils (×106)
Mononuclears (×106)
Cga Pio (10 mg/kg)b (0.5 h) Pio (20 mg/kg)b (0.5 h) Pio (50 mg/kg)b (0.5 h) Pio (10 mg/kg)b (0.5 and Pio (20 mg/kg)b (0.5 and Pio (10 mg/kg)b (0.5 and Pio (20 mg/kg)b (0.5 and Dex (0.5 mg/kg)b (0.5 h) Indo (5 mg/kg)b (0.5 h)
11.12 ± 0.60 9.93 ± 0.97 9.20 ± 0.13 9.14 ± 0.59 8.69 ± 1.54⁎#++ 4.84 ± 0.51⁎⁎ 9.46 ± 0.26##++ 4.22 ± 0.47⁎⁎ 4.15 ± 0.25⁎⁎ 4.76 ± 0.91⁎⁎
1.65 ± 0.19 2.33 ± 0.38 1.39 ± 0.19 2.34 ± 0.43 2.11 ± 0.28## 1.41 ± 0.19## 1.98 ± 0.30## 1.92 ± 0.31## 0.18 ± 0.04⁎⁎ 1.00 ± 0.22⁎⁎##
9.47 ± 0.56 7.60 ± 0.90 7.80 ± 0.09 6.79 ± 0.47⁎ 6.58 ± 1.33⁎ 3.43 ± 0.39⁎⁎ 7.48 ± 0.52⁎##++ 2.30 ± 0.29⁎⁎##+ 3.97 ± 0.28⁎⁎ 3.76 ± 0.59⁎⁎
12 h, twice) 12 h, twice) 24 h) 24 h)
Cg = positive control-group, Pio = treated with Pioglitazone (0.5 h before), Dex = treated with Dexamethasone (0.5 h before), Indo = treated with Indomethacin (0.5 h before). Each group represents the mean ± S.E.M. of 6 animals. ⁎P < 0.05 and ⁎⁎P < 0.01: Cg vs Pio and Cg vs reference drugs; #P < 0.05 and ##P < 0.01: Dex vs Pio (20 mg/kg) and Dex vs Indo, +P < 0.05 and ++P < 0.01: Indo vs Pio. a = i.pl. route, b = i.p. route.
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Fig. 5. Effects of Pioglitazone (Pio: 20 mg/kg, i.p., 0.5 h before) followed by another dose administered at 24 h of time interval after the first one) on the second (48 h) pleurisy phase induced by carrageenan upon TNF-α (A) and IL-1β (B) levels. Cg = positive controlgroup, Dex = treated with dexamethasone (0.5 mg/kg, i.p., 0.5 h before), Indo = treated with indomethacin (5 mg/kg, i.p., 0.5 h before). Bars indicate the mean± S.E.M. of 6 mice per group. **P < 0.01: Cg vs Pio and Cg vs reference drugs.
to Dex and Indo which also inhibited the levels of TNF-α by 82.12 ± 2.36% and 65.45 ± 7.49%, respectively and IL-1β by 58.53 ± 3.25% and 55.72 ± 10.01%, respectively (P < 0.01) (Fig. 5A and B). In these experiments the inhibition pattern of Pioglitazone did not differ from Indo and Dex (P > 0.05). No weight differences were observed between animals treated with Pioglitazone and positive control-group (results not shown). 4. Discussion Data from our study indicate that Pioglitazone was able to inhibit the two pools of leukocytes that peak at 4 and 48 h after carrageenan administration in the murine pleurisy model. This profile of action presented by Pioglitazone was similar to that elicited by Indomethacin, albeit the inhibition pattern induced by Dexamethasone upon the same parameters was more potent. In addition, Pioglitazone did not modify exudation, but decreased TNF-α, IL-1β levels and ADA activity at both inflammatory peaks (4 and 48 h). Altogether, these results demonstrated an interesting anti-inflammatory property of this thiazolidinedione and strengthen prior evidence that PPAR pathways constitute another important route of inflammatory process inhibition in this pleurisy model. In our study, the first (4 h) inflammation phase, the doses of 20 and 50 mg/kg of Pioglitazone were effective in inhibiting leukocyte influx by selectively decreasing neutrophil content when it was administered 0.5 h before pleurisy induction. It is interesting to note that this inhibition pattern was similar to that present in Indomethacin. Several studies have demonstrated the participation of COX-2 products [22], besides an enhancement of cytokines and leukocyte enzymes (MPO and ADA) in the pleural exudate in this murine pleurisy phase [18,19]. At present, although the classical effects of non-steroidal anti-inflammatory drugs like Indomethacin upon inflammation are linked to COX-2 pathways blockage, more recently
several hypothesis were raised regarding also the role of these compounds upon PPAR activation [23]. In this aspect, the relationships among PPAR ligands like Pioglitazone and non-steroidal antiinflammatory drugs have been explored. PPAR-γ has been associated with inflammation control by inhibiting cytokine stimulation of COX2 and inducible nitric oxide synthase (iNOS) expression in different cell types [22,24]. Another evidence of the anti-inflammatory effects induced by Pioglitazone (20 mg/kg) is based on the results that the myeloperoxidase activity inhibition, an activated neutrophil indicator at the inflammation site, did not differ in comparison to both Dexamethasone and Indomethacin. Furthermore, both Pioglitazone and Indomethacin also did not differ in their inhibition degree of both TNF-α and IL-1β levels, whereas Dexamethasone inhibition presents the highest inhibition profile. At this time, ADA activity was also inhibited, but no significant statistical difference was detected among Pioglitazone and reference drugs. The most probable source of increased ADA activity at this time is certainly from activated mononuclears (includes both monocytes and macrophages). Whether these results reflect differences in the doses of the studied drugs it is not possible to discard; however, a role of Pioglitazone in preventing inflammation at this peak-time of neutrophils in the murine pleurisy model caused by carrageenan is remarkable. Another possibility is that the anti-inflammatory mechanism of this thiazolidinedione is mediated via interaction with proinflammatory transcription factors such as activator protein 1 that mediated transcriptional activation of COX-2 [25] and other transcription factors that consequently cause the proinflammatory mediators inhibition such as cytokines [26,27]. Furthermore, it is described that neutrophils may express PPAR-γ which suggests that this receptor may play the inflammatory process role, whereas other studies have shown that PPAR-γ ligands could modulate leukocyte–endothelial interactions during inflammation showing that the administration of PPAR-γ ligand (15-deoxyDelta12,14-prostaglandin J2: 15d-PGJ2) inhibited neutrophil influx in a murine peritonitis model induced by carrageenan by decreasing leukocyte rolling and adhesion to the inflamed mesenteric tissues by a mechanism dependent on nitric oxide [23,28]. Pioglitazone (20 mg/kg) given before and after pleurisy induction was also effective in inhibiting mononuclear influx that occurs 48 h after pleurisy induction by carrageenan. At this time, the main population of mononuclears is constituted by macrophages [15]. At the tested administration doses and time-intervals, Pioglitazone inhibited ADA activity, although Dexamethasone and Indomethacin were more potent. However, the inhibition degree of both TNF-α and IL-1β levels did not vary among Pioglitazone and reference drugs. Since it is well known that PPAR-α and PPAR-γ are expressed in macrophages [9,29], altogether these results are in accordance with data reported in the literature [24]. PPAR ligands inhibit the inducible nitric oxide synthase induction (iNOS) and the cytokine production like TNF-α and IL-1β in macrophages. Moreover, PPAR activation induces apoptosis in macrophages which could have a role in the inflammatory site [30,31]. Based on this data, it is not possible to discard that these effects may contribute to the inhibition of the second (48 h) inflammation phase in the murine pleurisy model. This murine pleurisy model induced by carrageenan constitute a unique opportunity to evaluate neutrophil and mononuclear peaks at different time points, which permit to evaluate the participation of different mediators and the effects caused by putative anti-inflammatory drugs. Previous studies from our laboratory have also shown that some potent immunosuppressive drugs also presented similar acute anti-inflammatory profiles, but did not inhibit exudation. Although, the results were not similar, both cyclosporine A [32] and methotrexate [33] in the same murine pleurisy model did not inhibit exudation 4 h after pleurisy. Reasons for these discrepancies are not known, but one cannot exclude the possibility that these drugs and Pioglitazone are more potent in inhibiting cell influx and synthesis of cell mediators than exudation in this model.
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In the different animal inflammation models where thiazolidinediones (Pioglitazone and Rosiglitazone) were tested, it is important to mention that distinct doses, administration routes (oral route (p.o.) or i.p.), and treatment length were employed. These differences were, in part, related to whether the treatment protocol was acute or chronic. In relation to the acute treatment, Akahori et al. [34] observed that Pioglitazone (20 mg/kg, p.o.) protected the liver against acute injury and improved survival in mice. In our study, an acute dose of 20 mg/kg, i.p. was effective in reducing cell (neutrophil) influx in the first (4 h) inflammation phase. However, repeated doses of this drug were necessary to inhibit the second (48 h) peak of cell (mononuclear) migration. In addition, Koufany et al. [35] demonstrated that chronic treatments with higher doses of this thiazolidinedione were required for the treatment of chronic arthritis than for the restoration of insulin sensitivity. Thus, it is possible that the anti-inflammatory doses of Pioglitazone are related to the inflammation model type rather than to the treatment duration. This hypothesis needs to be evaluated with further studies. Although, differences between species limit comparisons among the models, it is not possible to exclude that these distinct biological effects may be linked to differences between the chemical structures within the same class of drugs. The various thiazolidinediones have differential effects on PPAR-γ and PPAR-α. Whereas Rosiglitazone is classified as a PPAR-γ agonist, Pioglitazone also exerts dual effects upon both PPAR-α and PPAR-γ [36]. This may account for the different effects that Pioglitazone and Rosiglitazone have on inflammatory models. In the pleurisy induced by carrageenan in rats which is characterized by only one peak of cell (neutrophil) infiltration, Cuzzocrea et al. [37] showed that Rosiglitazone, a more selective PPAR-γ agonist, elicits its antiinflammatory effect also by inhibiting both exudation and cell influx. These effects were associated with significant reductions in lung MPO activity, and TNF-α, IL-1β, prostaglandin E2 (PGE2) and nitrite–nitrate levels in the pleural exudates and a decreased expression of adhesion molecules (ICAM-1 and P-selectin) (COX-2). In addition, Oliveira et al., [38] showed that Rosiglitazone presented antioedematogenic effects when tested in the rat paw oedema model induced by carrageenan. On the other hand, Pioglitazone was shown to be effective in experimental arthritis models [35], inflammatory bowel disease [39], myocarditis [40], autoimmune encephalomyelitis [41], and atherosclerosis [42]. Whether these results reflect differences in animal species, inflammation models or even in the chemical molecule structure of this class of drug is not yet clear [43]. In this context, Orasanu et al. [43] showed that the inhibition induced by Pioglitazone in a murine peritonitis model occurs via PPAR-α activation. In summary, this study provides evidence that Pioglitazone exhibits an anti-inflammatory profile by inhibiting both neutrophil and mononuclear influxes, but not exudation in a bimodal model of inflammation. This effect is linked to inhibition of TNF-α and IL-1β levels but with distinct effects upon MPO and ADA activities. Whether this effect is related to transcriptional regulation of both PPAR-γ and PPAR-α activations needs further investigations. References [1] Bishop-Bailey D, Warner TD. PPARγ ligands induce prostaglandin production in vascular smooth muscle cells: indomethacin acts as a peroxisome proliferatoractivated receptor-γ antagonist. FASEB J 2003;1:1–15. [2] Chinetti G, Fruchart JC, Staels B. Peroxisome proliferators activated receptors and inflammation: from basic science to clinical applications. Int J Obes Relat Metab Disord 2003;27:S41–5. [3] Buckingham RE. Thiazolidinediones: pleiotropic drugs with potent anti-inflammatory properties for tissue protection. Hepatol Res 2005;33:167–70. [4] Li AC, Glass CK. PPAR- and LXR-dependent pathways controlling lipid metabolism and the development of atherosclerosis. J Lipid Res 2004;45:2161–73. [5] Lehrke M, Lazar AM. The many faces of PPAR. Cell 2005;123:993–9. [6] Belvisi MG, Hele DJ, Birrel MA. Peroxisome proliferator-activated receptor gamma agonists as therapy for chronic airway inflammation. Eur J Pharmacol 2006;533:101–9. [7] Széles L, Töröcsik D, Nagy L. PPARγ in immunity and inflammation: cell types and diseases. Biochim Biophys Acta 2007;1771:1014–30.
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