Suppression of intestinal ischemia-reperfusion injury by a specific peroxisome proliferator-activated receptor-gamma ligand, pioglitazone, in rats

Systemic and Lung Inflammation and Oxidative Stress Associated With Behavioral Changes Induced by Inhaled Paraquat Are Ameliorated by Carvacrol

Paraquat (PQ) is an herbicide toxin that induces injury in different organs. The anti-inflammatory and antioxidant effects of carvacrol were reported previously. The effects of carvacrol and pioglitazone (Pio) alone and their combination on inhaled PQ-induced systemic and lung oxidative stress and inflammation as well as behavioral changes were examined in rats. In this study, animals were exposed to saline (control [Ctrl]) or PQ (PQ groups) aerosols. PQ-exposed animals were treated with 0.03 mg/kg/day dexamethasone (Dexa), 20 and 80 mg/kg/day carvacrol (C-L and C-H), 5 mg/kg/day Pio, and Pio+C-L for 16 days. Inhaled PQ markedly enhanced total and differential white blood cell (WBC) counts, nitric oxide (NO), and malondialdehyde (MDA) levels but decreased catalase (CAT) and superoxide dismutase (SOD) activities and thiol levels both in the bronchoalveolar lavage fluid (BALF) and blood and increased interferon-gamma (INF-γ) and interleukin-10 (IL-10) levels in the BALF (p < 0.001 for all cases) except lymphocyte count in blood which was not significantly changed. The escape latency and traveled distance were increased in the PQ group. However, the time spent in the target quadrant in the Morris water maze (MWM) test and the duration of time latency in the dark room in the shuttle box test were reduced after receiving an electrical shock (p < 0.05-p < 0.001). Inhaled PQ-induced changes were significantly improved in carvacrol, Pio, Dexa, and especially in the combination of the Pio+C-L treated groups (p < 0.05-p < 0.001). Carvacrol and Pio improved PQ-induced changes similar to Dexa, but ameliorative effects produced by combination treatments of Pio+C-L were more prominent than Pio and C-L alone, suggesting a potentiating effect for the combination of the two agents.

Cilostazol mitigates mesenteric ischemia/reperfusion-induced lung lesion: Contribution of PPAR-γ, NF-κB, and STAT3 crosstalk

AIMS

Cilostazol (Cilo), a phosphodiesterase-III inhibitor, has signified its efficacy against different ischemia/reperfusion (IS/RE) models. Nevertheless, it has not fully illuminated its potential effect against intestinal IS/RE-induced lung injury. Consequently, the study was fashioned to evaluate the feasible mechanism of action of Cilo against intestinal IS/RE-induced lung injury.

MAIN METHODS

Wistar rats were treated with Cilo (0.1 g/kg, p.o.) or with a vehicle for 14 days prior to IS/RE, induced by clamping of the superior mesenteric artery for 30 min with subsequent clamp removal for 2 h.

KEY FINDINGS

The mechanistic study disclosed that Cilo protected the two studied organs, viz., lung, and intestine partially by intensifying the expression/content of PPAR-γ accompanied by reducing the expression/content of NF-қB-p65 and STAT3. In addition to normalizing MDA, iNOS, and NOx, the Cilo antioxidant power was confirmed by intensifying tissues content of the total antioxidant capacity. With regard to the anti-inflammatory effect, Cilo reduced the effects of TNF-α, IL-6, and ICAM-1, which were reflected in MPO activity. Furthermore, Cilo had an anti-apoptotic attribute demonstrated by enhancing Bcl-2 content and lessening caspase-3 level.

SIGNIFICANCE

Cilo provided conceivable protective mechanisms to modulate events concomitant with mesenteric IS/RE partly by modulating oxidative stress, inflammation, and apoptosis feasibly via the participation of PPAR-γ, STAT3, and NF-κB p65 signaling pathways.

Remote ischemic conditioning: A potential therapeutic strategy of type 2 diabetes

Type 2 diabetes (T2D) is one of the major public diseases which is characterized by peripheral insulin resistance (IR) and progressive pancreatic β-cell failure. While in the past few years, some new factors, such as inflammation, oxidative stress, immune responses and other potential pathways, have been identified to play critical roles in T2D, and thereby provide novel promising targets for the treatment of T2D. Remote ischemic conditioning (RIC) is a non-invasive and convenient operation performed by transient, repeated ischemia in distant place. Nowadays, RIC has been established as a potentially powerful therapeutic tool for many diseases, especially in I/R injuries. Through activating a series of neural, humoral and immune pathways, it can release multiple protective signals, which then regulating inflammation, oxidative stress, immune response and so on. Interestingly, several recent studies have discovered that the beneficial effects of RIC on I/R injuries might be abolished by T2D, wherein the higher basal levels of inflammation and oxidative stress, dysregulation of immune system and some potential pathways secondary to hyperglycemia may play critical roles. In contrast, a higher intensity of conditioning could restore the protective effects. Based on the overlapped mechanisms RIC and T2D performs, we provide a hypothesis that RIC may also play a protective role in T2D via targeting these signaling pathways.

Eicosanoid production varies by sex in mesenteric ischemia reperfusion injury

Intestinal ischemia/reperfusion (I/R)-induced injury is an inflammatory response with significant morbidity and mortality. The early inflammatory response includes neutrophil infiltration. However, the majority of rodent studies utilize male mice despite a sexual dimorphism in intestinal I/R-related diseases. We hypothesized that sex may alter inflammation by changing neutrophil infiltration and eicosanoid production. To test this hypothesis, male and female C57Bl/6 mice were subjected to sham treatment or 30 min intestinal ischemia followed by a time course of reperfusion. We demonstrate that compared to male mice, females sustain significantly less intestinal I/R-induced tissue damage and produced significant LTB₄ concentrations. Male mice release PGE₂. Finally, treatment with a COX-2 specific inhibitor, NS-398, attenuated I/R-induced injury, total peroxidase level, and PGE₂ production in males, but not in similarly treated female mice. Thus, I/R-induced eicosanoid production and neutrophil infiltration varies between sexes suggesting that distinct therapeutic intervention may be needed in clinical ischemic diseases.

Sevoflurane exerts brain-protective effects against sepsis-associated encephalopathy and memory impairment through caspase 3/9 and Bax/Bcl signaling pathway in a rat model of sepsis

Objective We compared the effects of sevoflurane and isoflurane on systemic inflammation, sepsis-associated encephalopathy, and memory impairment in a rat sepsis model of cecal ligation and puncture (CLP)-induced polymicrobial peritonitis. Methods Twenty-four rats were assigned to sham, CLP, CLP + sevoflurane, and CLP + isoflurane groups. At 72 hours after CLP, the rats underwent behavior tests. Serum cytokines were evaluated. Brain tissue samples were collected for determination of glutathione peroxidase (GPX), superoxide dismutase (SOD), and catalase; the wet/dry weight ratio; myeloperoxidase (MPO) and malondialdehyde (MDA); apoptotic gene release; and histologic examinations. Results The MPO level, wet/dry weight ratio, and histopathology scores were lower and the Bcl2a1 and Bcl2l2 expressions were upregulated in both the CLP + sevoflurane and CLP + isoflurane groups compared with the CLP group. The interleukin-6, interleukin-1β, MDA, and caspase 3, 8, and 9 levels were lower; the GPX, SOD, Bax, Bcl2, and Bclx levels were higher; and non-associative and aversive memory were improved in the CLP + sevoflurane group compared with the CLP + isoflurane group. Conclusion Sevoflurane decreased apoptosis and oxidative injury and improved memory in this experimental rat model of CLP. Sevoflurane sedation may protect against brain injury and memory impairment in septic patients.

Microbiome and intestinal ischemia/reperfusion injury

Intestinal ischemia/reperfusion injury is a severe disease associated with a high mortality. The mechanisms that cause ischemia/reperfusion injury are complex and many factors are involved in the injury formation process; however, the only available treatment is surgical intervention. Recent studies demonstrated that the intestinal microbiome plays a key role in intestinal ischemia/reperfusion injury and there are many factors associated with intestinal bacteria during the formation of the intestinal ischemia/reperfusion injury. Among the Toll-like receptors (TLR), TLR2, TLR4, and their adaptor protein, myeloid differentiation primary-response 88 (MyD88), have been reported to be involved in intestinal ischemia/reperfusion injury. Oxidative stress and nitric oxide are also associated with intestinal bacteria during the formation of the intestinal ischemia/reperfusion injury. This review focuses on our current understanding of the impact of the microbiome, including the roles of the TLRs, oxidative stress, and nitric oxide, on intestinal ischemia/reperfusion injury.

Gastrin attenuates ischemia-reperfusion-induced intestinal injury in rats

Intestinal ischemia-reperfusion (I/R) injury is a devastating complication when the blood supply is reflowed in ischemic organs. Gastrin has critical function in regulating acid secretion, proliferation, and differentiation in the gastric mucosa. We aimed to determine whether gastrin has an effect on intestinal I/R damage. Intestinal I/R injury was induced by 60-min occlusion of the superior mesenteric artery followed by 60-min reperfusion, and the rats were induced to be hypergastrinemic by pretreated with omeprazole or directly injected with gastrin. Some hypergastrinemic rats were injected with cholecystokinin-2 (CCK-2) receptor antagonist prior to I/R operation. After the animal surgery, the intestine was collected for histological analysis. Isolated intestinal epithelial cells or crypts were harvested for RNA and protein analysis. CCK-2 receptor expression, intestinal mucosal damage, cell apoptosis, and apoptotic protein caspase-3 activity were measured. We found that high gastrin in serum significantly reduced intestinal hemorrhage, alleviated extensive epithelial disruption, decreased disintegration of lamina propria, downregulated myeloperoxidase activity, tumor necrosis factor-α, and caspase-3 activity, and lead to low mortality in response to I/R injury. On the contrary, CCK-2 receptor antagonist L365260 could markedly impair intestinal protection by gastrin on intestinal I/R. Severe edema of mucosal villi with severe intestinal crypt injury and numerous intestinal villi disintegrated were observed again in the hypergastrinemic rats with L365260. The survival in the hypergastrinemic rats after intestinal I/R injury was shortened by L365260. Finally, gastrin could remarkably upregulated intestinal CCK-2 receptor expression. Our data suggest that gastrin by omeprazole remarkably attenuated I/R induced intestinal injury by enhancing CCK-2 receptor expression and gastrin could be a potential mitigator for intestinal I/R damage in the clinical setting.

Local and Remote Postconditioning Decrease Intestinal Injury in a Rabbit Ischemia/Reperfusion Model

Intestinal ischemia/reperfusion (I/R) injury is a significant problem that is associated with high morbidity and mortality in critical settings. This injury may be ameliorated using postconditioning protocol. In our study, we created a rabbit intestinal I/R injury model to analyze the effects of local ischemia postconditioning (LIPo) and remote ischemia postconditioning (RIPo) on intestinal I/R injury. We concluded that LIPo affords protection in intestinal I/R injury in a comparable fashion with RIPo by decreasing oxidative stress, neutrophil activation, and apoptosis.

The Effect of Perioperative Ischemia and Reperfusion on Multiorgan Dysfunction following Abdominal Aortic Aneurysm Repair

Abdominal aortic aneurysms (AAAs) are relatively common and are potentially life-threatening medical problems. The aim of this review is to provide an overview of the effect of I/R injury on multiorgan failure following AAA repair. The PubMed, CINAHL, EMBASE, Medline, Cochrane Review, and Scopus databases were comprehensively searched for articles concerning the pathophysiology of I/R and its systemic effects. Cross-referencing was performed using the bibliographies from the articles obtained. Articles retrieved were restricted to those published in English. One of the most prominent characteristics of AAA open repair is the double physiological phenomenon of ischemia-reperfusion (I/R) that happens either at the time of clamping or following the aortic clamp removal. Ischemia-reperfusion injury causes significant pathophysiological disturbances to distant organs, increasing the possibility for postoperative multiorgan failure. Although tissue injury is mediated by diverse mechanisms, microvascular dysfunction seems to be the final outcome of I/R.

Higenamine regulates Nrf2-HO-1-Hmgb1 axis and attenuates intestinal ischemia-reperfusion injury in mice

INTRODUCTION

Intestinal ischemia and reperfusion (IR) syndrome is a life-threatening dilemma caused by diverse events. Higenamine (HG), an active ingredient of Aconiti Lateralis Radix Praeparata, has been traditionally used as a heart stimulant and anti-inflammatory agent in oriental countries. But the function of HG on intestine IR injury has never been investigated.

MATERIALS AND METHODS

Mice underwent a 2 cm midline laparotomy, and the superior mesenteric artery (SMA) was obstructed by micro-vascular clamp to induce intestinal ischemia.

RESULTS

In our current study, HG increases mouse intestinal epithelial (IEC-6) cell viability through induced heme oxygenase-1 (HO-1) production in vitro. In our in vivo murine intestinal IR injury model, the increased HO-1 protein level and activity, decreased intestinal injury score, Myeloperoxidase (MPO) activity, and inflammatory cytokine expression induced by HG were all abolished with additional treatment of HO-1 inhibitor zinc protoporphyrin IX (ZnPPIX). Furthermore, HG reduced high mobility group box-1 (Hmgb1) expression in IR injury-performed intestine which was inhibited by additional administration of ZnPPIX. And HG treatment significantly decreased HO-1 expression in nuclear factor erythroid 2-related factor (Nrf-2) SiRNA-transfected cells but not in control SiRNA-transfected cells.

CONCLUSION

Our study provides evidence HG regulates Nrf2-HO-1-Hmgb1 axis and attenuates intestinal IR injury in mice.

Guanylyl cyclase-G modulates jejunal apoptosis and inflammation in mice with intestinal ischemia and reperfusion

Background

Membrane bound guanylyl cyclase-G (mGC-G), a novel form of GC mediates ischemia and reperfusion (IR)-induced renal injury. We investigated the roles of mGC-G in intestinal IR-induced jejunal damage, inflammation, and apoptosis.

Materials and methods

Male C57BL/6 wild-type (WT) and mGC-G gene knockout (KO) mice were treated with a sham operation or 45 min of superior mesenteric arterial obstruction followed by 3, 6, 12, or 24 h of reperfusion.

Results

Sham-operated KO mice had significantly lower plasma nitrate and nitrite (NOx) levels and jejunal villus height, crypt depth, and protein expression of phosphorylated-nuclear factor-kappa-B (NF-κB), phosphorylated-c-Jun N-terminal kinases (JNK) 2/3, phosphorylated-p38, and B-cell lymphoma-2 (Bcl-2). They had significantly greater jejunal interleukin-6 mRNA, cytochrome c protein, and apoptotic index compared with sham-operated WT mice. Intestinal IR significantly decreased plasma NOx in WT mice and increased plasma NOx in KO mice. The jejunal apoptotic index and caspase 3 activities were significantly increased, and nuclear phosphorylated-NF-κB and phosphorylated-p38 protein were significantly decreased in WT, but not KO mice with intestinal IR. After reperfusion, KO mice had an earlier decrease in jejunal cyclic GMP, and WT mice had an earlier increase in jejunal proliferation and a later increase in cytosol inhibitor of kappa-B-alpha. Intestinal IR induced greater increases in plasma and jejunal interleukin-6 protein in WT mice and a greater increase in jejunal interleukin-6 mRNA in KO mice.

Conclusions

mGC-G is involved in the maintenance of jejunal integrity and intestinal IR-induced inflammation and apoptosis. These results suggest that targeting cGMP pathway might be a potential strategy to alleviate IR-induced jejunal damages.

Effects of sulfasalazine on lipid peroxidation and histologic liver damage in a rat model of obstructive jaundice and obstructive jaundice with lipopolysaccharide-induced sepsis

BACKGROUND

Sulfasalazine, an inhibitor of cyclooxygenase, 5-lipoxygenase, and nuclear factor κB (NF-κB), has been found to alleviate oxidative damage, proinflammatory cytokine production, bile-duct proliferation, neutrophil infiltration, and fibrosis. Therefore, it may have a potential effect in attenuating lipid peroxidation and histologic liver damage in patients with biliary obstruction and biliary obstruction with sepsis.

OBJECTIVE

The aim of this study was to investigate the effect of sulfasalazine on lipid peroxidation and histologic liver damage due to obstructive jaundice (OJ) and to OJ with lipopolysaccharide (LPS)-induced sepsis in an experimental model.

METHODS

Male Wistar rats, weighing 150 to 220 g, were randomized into 6 groups: OJ; OJ + LPS; OJ + sulfasalazine; OJ + sulfasalazine + LPS (sulfasalazine administered before sepsis); OJ + LPS + sulfasalazine (sulfasalazine administered after sepsis); and sham. Liver malondialdehyde (MDA) and myeloperoxidase (MPO) activities were assessed to monitor lipid peroxidation and neutrophil infiltration in liver tissue. Histologic liver damage was evaluated with hematoxylin-eosin stained slides. Liver tissue NF-κB and caspase-3 expression were studied immunohistopathologically to evaluate lipid peroxidation, liver damage, and hepatocyte apoptosis.

RESULTS

Forty-eight rats were evenly randomized into 6 groups of 8. MDA (P = 0.001), MPO (P = 0.001), NF-κB (P = 0.003), caspase-3 expression (P = 0.002), and liver injury scores (P = 0.002) increased significantly in the OJ group compared with the sham group. Compared with the OJ group, MDA (P = 0.030) and MPO levels (P = 0.001), and liver injury scores (P = 0.033) were decreased significantly in the OJ + sulfasalazine group. In the OJ + sulfasalazine + LPS and OJ + LPS + sulfasalazine groups, MDA (P = 0.008 and P = 0.023, respectively) and MPO (both, P = 0.001) were significantly decreased; however, liver NF-κB, caspase-3 expression, and liver injury scores were not significantly different compared with the OJ + LPS group. There was no significant difference between the OJ + LPS + sulfasalazine and OJ + sulfasalazine + LPS groups in regard to all end points when comparing the effects of sulfasalazine administered before or after sepsis.

CONCLUSIONS

Sulfasalazine was associated with decreased neutrophil accumulation and lipid peroxidation in these rats with OJ. Administration of sulfasalazine before or after LPS-induced sepsis was associated with a reduction in lipid peroxidation and neutrophil accumulation; however, it did not attenuate histologic liver damage. There was no difference between the findings when sulfasalazine was administered before or after sepsis in OJ.

Ischemic postconditioning during reperfusion attenuates intestinal injury and mucosal cell apoptosis by inhibiting JAK/STAT signaling activation

The present study attempts to evaluate the role of Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling in intestinal ischemia/reperfusion (I/R)-induced intestinal injury and whether immediate ischemic postconditioning ameliorates intestinal injury via attenuation of intestinal mucosal apoptosis subsequent to inhibiting JAK/STAT signaling activation. Anesthetized adult male Sprague-Dawley rats were subjected to superior mesenteric artery occlusion consisting of 60 min of ischemia and 2 h of reperfusion; sham laparotomy served as controls. Animals received either subcutaneous administration of JAK2 inhibitor (AG490, 8 mg/kg) or STAT inhibitor (rapamycin, 0.4 mg/kg) 30 min before ischemia. Ischemic postconditioning was performed by three cycles of 30-s reperfusion and 30-s ischemia initiated immediately upon reperfusion. It was found that intestinal I/R resulted in conspicuous intestinal injury evidenced by significant increases in Chiu's score, lactic acid, and diamine oxidase activity, accompanied with increases in plasma levels of 15-F2t-isoprostane, endothelin 1, and thromboxane B2, as well as increase in the intestinal tissue myeloperoxidase activity. Meanwhile, the apoptotic index and cleaved caspase 3, phosphorylated JAK2, phosphorylated STAT1, and phosphorylated STAT3 expression were significantly enhanced versus sham control. Both ischemic postconditioning and pretreatment with AG490 or rapamycin significantly attenuated all the above changes. These results indicate that JAK/STAT pathway activation plays a critical role in I/R-induced intestinal injury, which is associated with increased oxidative stress, neutrophil accumulation, intestinal mucosal apoptosis, and microcirculation disturbance. Ischemic postconditioning mediates attenuation of intestinal I/R injury, and cell apoptosis may be attributable to the JAK/STAT signaling inhibition.

The effects of PPAR-γ agonist pioglitazone on renal ischemia/reperfusion injury in rats

BACKGROUND

Acute renal failure due to renal ischemia/reperfusion (IR) injury is a significant clinical problem in cardiovascular surgery. Reactive oxygen species and inflammation play essential roles in the pathophysiology of IR injury. Matrix metalloproteinases (MMPs) are enzymes that play important roles in inflammation and mediate extracellular matrix degradation. It is known that peroxisome proliferator-activated receptor-γ agonists have antiinflammatory and antioxidant effects. In the present study, we aimed to investigate the effects of pioglitazone, a synthetic peroxisome proliferator-activated receptor-γ agonist, on MMPs and oxidative stress in a renal IR injury model in rats.

MATERIALS AND METHODS

Male Wistar albino rats were divided into three groups: control (n = 7), placebo (n = 7; saline/p.o.), and pioglitazone (n = 7; 5 mg/kg/day/p.o.). In the control group, a right nephrectomy was conducted without left renal IR injury. In the placebo and pioglitazone groups, pretreatments were started 3 d before operation. In both groups, left renal pedicles were clamped for 60 min and then reperfused for 60 min. Paraffinized renal sections were evaluated histopathologically. Furthermore, expressions of MMP-2, MMP-9, tissue inhibitor of metalloproteinase (TIMP)-2, superoxide dismutase 1 (SOD1), and p47-phox/p67-phox subunits of NADPH oxidase were determined by immunostaining and scoring.

RESULTS

In the placebo group, renal IR injury induced diffuse tubular necrosis and intense acute inflammation, but pioglitazone inhibited these effects. MMP-2, MMP-9, and TIMP-2 expression increased in the placebo group. However, while MMP-2 and -9 expression decreased, TIMP-2 expression did not change in the pioglitazone group. p47-phox/p67-phox expression increased in the placebo group, but SOD1 expression did not change. Pioglitazone diminished p47-phox/p67-phox expression, whereas it enhanced SOD1 expression.

CONCLUSION

Our results suggest that pioglitazone might be helpful to reduce renal IR injury because of its antiinflammatory and antioxidant effects.

Thoracic epidural bupivacaine attenuates inflammatory response, intestinal lipid peroxidation, oxidative injury, and mucosal apoptosis induced by mesenteric ischemia/reperfusion

BACKGROUND

We conducted this study to evaluate the effects of thoracic epidural anesthesia (TEA) on inflammatory response, lipid peroxidation, and oxidative stress in a rat model of mesenteric ischemia/reperfusion (I/R).

METHOD

Rats were divided into 4 groups: sham group (n=6; sham laparotomy), control group (n=6; I/R), bupivacaine group (n=6; mesenteric I/R and 20 μL/h 0.5% bupivacaine), and saline group (n=6, mesenteric I/R and 20 μL/h 0.9% saline). I/R injury was established by occluding the superior mesenteric artery for 1 hour followed by 12 hours reperfusion. Blood gas, tumor necrosis factor-α, interleukin-6, interleukin-1β, glutathione peroxidise, superoxide dismutase, catalese, myeloperoxidase concentrations, immunohistochemical examinations (intracellular adhesion molecule-1), apoptosis determination, and wet/dry ratio of intestinal edema were determined.

RESULTS

Bupivacaine significantly decreased the cytokine, malondialdehyde, and myeloperoxidase levels and increased the antioxidant enzyme levels. Wet/dry ratio comparison showed a significant decrease in the bupivacaine (2.88±0.17) group in comparison with control (5.45±0.67) and saline (5.87±0.17) groups. The intestinal injury score was significantly decreased in rats in the epidural bupivacaine (2 [1-2]) infusion group in comparison with rats in the control (3 [2-3]) and saline (3 [2-4]) groups. Bupivacaine (63%) caused a significant decrease in the percentage of apoptotic cells in comparison with control (85%) only. ICAM-1 levels in the bupivacaine (27.4±7.1) group decreased in comparison with control (12.3±7.4) and saline (24.9±3.2) groups.

CONCLUSION

This study demonstrated that epidural bupivacaine attenuates the mesenteric I/R-related inflammatory response and intestinal damage.

Proteomic analysis of intestinal ischemia/reperfusion injury and ischemic preconditioning in rats reveals the protective role of aldose reductase

Intestinal ischemia/reperfusion (I/R) injury is a critical condition associated with high morbidity and mortality. Studies show that ischemic preconditioning (IPC) can protect the intestine from I/R injury. However, the underlying molecular mechanisms of this event have not been fully elucidated. In the present study, 2-DE combined with MALDI-MS was employed to analyze intestinal mucosa proteomes of rat subjected to I/R injury in the absence or presence of IPC pretreatment. The protein content of 16 proteins in the intestinal mucosa changed more than 1.5-fold following intestinal I/R. These proteins were, respectively, involved in the cellular processes of energy metabolism, anti-oxidation and anti-apoptosis. One of these proteins, aldose reductase (AR), removes reactive oxygen species. In support of the 2-DE results, the mRNA and protein expressions of AR were significantly downregulated upon I/R injury and enhanced by IPC as confirmed by RT-PCR and western blot analysis. Further study showed that AR-selective inhibitor epalrestat totally turned over the protective effect of IPC, indicating that IPC confers protection against intestinal I/R injury primarily by increasing intestinal AR expression. The finding that AR may play a key in intestinal ischemic protection might offer evidences to foster the development of new therapies against intestinal I/R injury.

Gastrointestinal Cytoprotection by PPARγ Ligands

Peroxisome proliferator-activated receptor γ (PPARγ) is a nuclear receptor that is known to play a central role in lipid metabolism and insulin sensitivity as well as inflammation and cell proliferation. According to the results obtained from studies on several animal models of gastrointestinal inflammation, PPARγ has been implicated in the regulation of the immune response, particularly inflammation control, and has gained importance as a potential therapeutic target in the management of gastrointestinal inflammation. In the present paper, we present the current knowledge on the role of PPARγ ligands in the gastrointestinal tract.

The protective effects of resveratrol and L-NAME on visceral organs following aortic clamping

BACKGROUND

This study investigated the effect of temporary occlusion of the aorta on the development of ischemia-reperfusion (I/R) injury of the visceral organs, the optimal timing of administration of resveratrol, and its mechanism of protection via inhibiting nitric oxide (NO) release with an NO synthase inhibitor.

METHODS

Rabbits were divided into seven groups according to the administration period of resveratrol and/or N(G)-nitro-L-arginine methyl ester (L-NAME): control group; group 1, resveratrol during ischemic period; group 2, resveratrol during reperfusion period; group 3, L-NAME during ischemic period; group 4, L-NAME during reperfusion period; group 5, resveratrol during ischemic period and L-NAME during reperfusion period; group 6, L-NAME during ischemic period and resveratrol during reperfusion period. The infrarenal aorta was clamped for 30 min. Blood samples were taken for the biochemical assessment, and organ specimens were taken for pathological assessment at 24hr of reperfusion.

RESULTS

In groups 5 and 6, the renal I/R injury was comparatively milder (I/R injury score 1.04+/-0.29 in control group, 0.25+/-0.17 in group 5, and 0.33+/-0.13 in group 6 [p<0.05]). The I/R injury of bowel was milder in group 5 (I/R injury score 1.8+/-0.80 in control group vs. 0.0+/-0.0 in group 5 [p<0.05]).

CONCLUSION

The protective effects of resveratrol on organs that have high metabolic rate like kidney and bowel was proven histopathologically. It may be beneficial to use different pharmacological medications in different periods of the I/R damage as they represent different characteristics with and without oxygen. The combination of resveratrol and L-NAME against I/R injury appears to be an effective option in the near future.

Immediate postconditioning during reperfusion attenuates intestinal injury

OBJECTIVE

To test the hypothesis that immediate but not delayed ischemic postconditioning (IPo) during reperfusion attenuates intestinal injury, and that ischemic preconditioning (IPC) and IPo may confer synergy in intestinal protection.

DESIGN AND SETTING

Prospective laboratory animal study with concurrent control.

SUBJECTS

Adult Sprague-Dawley rats.

INTERVENTIONS

Intestinal ischemia/reperfusion (II/R) injury in rats was produced by clamping superior mesenteric artery for 60 min followed by 60 min reperfusion; IPC was elicited by 10 min ischemia and 10 min reperfusion before index ischemia; IPo was performed by three cycles of 30 s reperfusion and 30 s ischemia initiated either immediately at the onset of reperfusion (IPo) or after reperfusion for 3 min (delayed-IPo). Combination of IPC and IPo was performed by combining both protocols.

MEASUREMENTS AND MAIN RESULTS

Intestinal ischemia/reperfusion resulted in significant intestinal injury evidenced as significant increase in Chiu's scores and wet-to-dry intestine weight ratio accompanied with increases in plasma levels of tumor necrosis factor-alpha and interleukin-6, as well as increases in the intestinal tissue lipid peroxidation product malonediadehyde and myeloperoxidase activity as compared to control animals (all P < 0.05). All these changes were significantly attenuated either by IPC or IPo or their combination (P < 0.05), and not by delayed-IPo (P > 0.05). IPC and IPo showed synergistic protection compared with either protocol alone.

CONCLUSION

Ischemic postconditioning reduces intestinal injury, in part, by inhibiting oxidative injury, neutrophils filtration and proinflammatory response. The early period of reperfusion is critical to intestinal protection by IPo, and intestinal protection with IPo can be enhanced by IPC.

PPARs Mediate Lipid Signaling in Inflammation and Cancer

Lipid mediators can trigger physiological responses by activating nuclear hormone receptors, such as the peroxisome proliferator-activated receptors (PPARs). PPARs, in turn, control the expression of networks of genes encoding proteins involved in all aspects of lipid metabolism. In addition, PPARs are tumor growth modifiers, via the regulation of cancer cell apoptosis, proliferation, and differentiation, and through their action on the tumor cell environment, namely, angiogenesis, inflammation, and immune cell functions. Epidemiological studies have established that tumor progression may be exacerbated by chronic inflammation. Here, we describe the production of the lipids that act as activators of PPARs, and we review the roles of these receptors in inflammation and cancer. Finally, we consider emerging strategies for therapeutic intervention.

Plant histaminase as an investigational drug in splanchnic artery occlusion and reperfusion

BACKGROUND

Amine oxidases are ubiquitous enzymes involved in the metabolism of biogenic amines. Copper amine oxidases catalyze the oxidative deamination of primary amine groups of several biogenic amines, such as putrescine, cadaverine and histamine.

OBJECTIVE

In the present review the effects of a plant amine oxidase (histaminase, EC1.4.3.6), purified from pea seedlings, in the prevention of splanchnic postischemic reperfusion damage are reported.

CONCLUSION

Various studies have clearly indicated that the use of histaminase will offer a good perspective for a novel therapeutic approach in the medical treatment of intestinal ischemia.

Time-dependent alterations in serum NO concentration after oral administration of L-arginine, L-NAME, and allopurinol in intestinal ischemia/reperfusion

Objective

To study the effect of oral administration of a nitric oxide (NO) donor l-arginine (l-Arg), a NO synthase inhibitor N^G-nitro-l-arginine methyl ester (l-NAME) and an inhibitor of xanthine oxidase, allopurinol (Allo), on serum NO concentration and catalase activity after intestinal ischemia/reperfusion (I/R) in rats.

Methods

Male Wistar rats received per osl-Arg (800 mg/kg) or l-NAME (50 mg/kg) or Allo (100 mg/kg) 24 hrs, 12 hrs and 1 hr before underwent 1 hr occlusion of superior mesenteric artery followed by 1 hr of reperfusion (l-Arg(IR1), l-NAME(IR1) and Allo(IR1) respectively) or 1 hr occlusion followed by 8 hrs of reperfusion (l-Arg(IR8), l-NAME(IR8) and Allo(IR8) respectively). There was one group underwent 1 hr occlusion (I), a group underwent 1 hr occlusion followed by 1 hr reperfusion (IR1), a group subjected to 1 hr occlusion followed by 8 hrs of reperfusion (IR8) and a last group that served as control (C). Serum NO concentration and catalase activity were measured.

Results

After 1 hr of reperfusion serum NO concentration was elevated in IR1 and l-Arg(IR1) groups compared with group C but not in l-NAME(IR1) and Allo(IR1) group. Catalase activity was enhanced in l-NAME(IR1) group. Interestingly, serum NO concentration was increased after 8 hrs of reperfusion in all groups (IR8, l-Arg(IR8), l-NAME(IR8) and Allo(IR8)) compared with control while catalase activity did not show significant difference in any group.

Conclusions

The results of the present study show that NO concentration is elevated in serum after intestinal I/R and the elevation sustained after administration of l-Arg but not after administration of l-NAME or Allo after 1 hr reperfusion. However, after 8 hrs of reperfusion NO concentration was increased in all groups studied, focusing attention on its possible important role in a complicated situation such as intestinal I/R that involves intestine and other organs. Serum catalase activity does not seem to be affected by per os supplementation of l-Arg or Allo in intestinal I/R.

Sepsis-induced inhibition of neutrophil chemotaxis is mediated by activation of peroxisome proliferator-activated receptor-{gamma}

Neutrophils (polymorphonuclear leukocytes [PMNs]) are critical to the immune response, including clearance of infectious pathogens. Sepsis is associated with impaired PMN function, including chemotaxis. PMNs express peroxisome proliferator-activated receptor-gamma (PPAR-gamma), a ligand-activated nuclear transcription factor involved in immune and inflammatory regulation. The role of PPAR-gamma in PMN responses, however, is not well characterized. We report that freshly isolated human PMNs constitutively express PPAR-gamma, which is up-regulated by the sepsis-induced cytokines TNF-alpha and IL-4. PMN chemotactic responses to formylmethionyl-leucyl-phenylalanine (fMLP) and IL-8 were dose-dependently inhibited by treatment with the PPAR-gamma ligands troglitazone and 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)) and by transfection of PMN-like HL-60 cells with a constitutively active PPAR-gamma construct. Inhibition of chemotaxis by PPAR-gamma ligands correlated with decreases in extracellular signal-regulated kinase-1 and -2 activation, actin polymerization, and adherence to a fibrinogen substrate. Furthermore, PMN expression of PPAR-gamma was increased in sepsis patients and mice with either of 2 models of sepsis. Finally, treatment with the PPAR-gamma antagonist GW9662 significantly reversed the inhibition of PMN chemotaxis and increased peritoneal PMN recruitment in murine sepsis. This study indicates that PPAR-gamma activation is involved in PMN chemotactic responses in vitro and may play a role in the migration of these cells in vivo.

Novel pharmacological approaches to the treatment of renal ischemia-reperfusion injury: a comprehensive review

Renal ischemia-reperfusion (I-R) contributes to the development of ischemic acute renal failure (ARF). Multi-factorial processes are involved in the development and progression of renal I-R injury with the generation of reactive oxygen species, nitric oxide and peroxynitrite, and the decline of antioxidant protection playing major roles, leading to dysfunction, injury, and death of the cells of the kidney. Renal inflammation, involving cytokine/adhesion molecule cascades with recruitment, activation, and diapedesis of circulating leukocytes is also implicated. Clinically, renal I-R occurs in a variety of medical and surgical settings and is responsible for the development of acute tubular necrosis (a characteristic feature of ischemic ARF), e.g., in renal transplantation where I-R of the kidney directly influences graft and patient survival. The cellular mechanisms involved in the development of renal I-R injury have been targeted by several pharmacological interventions. However, although showing promise in experimental models of renal I-R injury and ischemic ARF, they have not proved successful in the clinical setting (e.g., atrial natriuretic peptide, low-dose dopamine). This review highlights recent pharmacological developments, which have shown particular promise against experimental renal I-R injury and ischemic ARF, including novel antioxidants and antioxidant enzyme mimetics, nitric oxide and nitric oxide synthase inhibitors, erythropoietin, peroxisome-proliferator-activated receptor agonists, inhibitors of poly(ADP-ribose) polymerase, carbon monoxide-releasing molecules, statins, and adenosine. Novel approaches such as recent research involving combination therapies and the potential of non-pharmacological strategies are also considered.

Peroxisome proliferator-activated receptors ligands and ischemia-reperfusion injury

Peroxisome proliferator-activated receptors (PPARs) belong to a subfamily of transcription nuclear factors. Three isoforms of PPARs have been identified: alpha, beta/delta and gamma, encoded by different genes and distributed in various tissues. They play important roles in metabolic processes like regulation of glucose and lipid redistribution. They also have anti-atherogenic, anti-inflammatory as well as antihypertensive functions. There is good evidence that ligands of PPARs reduce tissue injury associated with ischemia and reperfusion. The potential utility of PPAR ligands in ischemia and reperfusion will be discussed in this review.

Peroxisome proliferator-activated receptor-gamma antagonists GW9662 and T0070907 reduce the protective effects of lipopolysaccharide preconditioning against organ failure caused by endotoxemia

OBJECTIVE

There is evidence that a) ligands of the nuclear receptor peroxisome proliferator-activated receptor (PPAR)-gamma and b) lipopolysaccharide preconditioning protect the organs against the multiple organ injury and dysfunction caused by endotoxemia. Here we investigate the hypothesis that the protective effects of lipopolysaccharide preconditioning are due to an enhanced formation of endogenous ligands of PPAR-gamma.

DESIGN

Prospective, randomized study.

SETTING

University-based research laboratory.

SUBJECTS

Ninety-nine anesthetized male Wistar rats.

INTERVENTIONS

Rats were pretreated with low-dose lipopolysaccharide (1 mg/kg intraperitoneally, 24 hrs before induction of endotoxemia) in the absence or presence of the selective PPAR-gamma antagonists GW9662 (1 mg/kg intraperitoneally) or T0070907 (1 mg/kg intraperitoneally) or the selective cyclooxygenase-2 inhibitor parecoxib (20 mg/kg intraperitoneally). At 24 hrs after preconditioning with low-dose lipopolysaccharide, the rats were subjected to acute severe endotoxemia (lipopolysaccharide 6 mg/kg intravenously).

MEASUREMENTS AND MAIN RESULTS

Lipopolysaccharide preconditioning significantly attenuated the development of renal dysfunction (serum creatinine), hepatocellular injury (serum alanine aminotransferase and aspartate aminotransferase), and circulatory failure (hypotension) as well as the increase in the plasma levels of interleukin-1beta caused by severe endotoxemia. All of these beneficial effects afforded by preconditioning with lipopolysaccharide were attenuated by the specific PPAR-gamma antagonists used. In contrast, the cyclooxygenase-2 inhibitor parecoxib did not affect the beneficial effects afforded by preconditioning with lipopolysaccharide.

CONCLUSIONS

We propose that endogenous ligands of PPAR-gamma contribute to the protection afforded by lipopolysaccharide preconditioning against the organ injury and dysfunction associated with severe endotoxemia in the rat.

Rosuvastatin reduces rat intestinal ischemia-reperfusion injury associated with the preservation of endothelial nitric oxide synthase protein

AIM: To investigate the protective effect of rosuvastatin on ischemia-reperfusion (I-R)-induced small intestinal injury and inflammation in rats, and to determine the effect of this agent on the expression of endothelial nitric oxide synthase (eNOS) protein.

METHODS: Intestinal damage was induced in male Sprague-Dawley rats by clamping both the superior mesenteric artery and the celiac trunk for 30 min, followed by reperfusion for 60 min. Rosuvastatin dissolved in physiological saline was administered intraperitoneally 60 min before ischemia. The severity of the intestinal mucosal injury and inflammation were evaluated by several biochemical markers, as well as by histological findings. The protein levels of eNOS were determined by Western blot.

RESULTS: The levels of both intraluminal hemoglobin and protein, as indices of mucosal damage, were significantly increased in the I-R group compared with those in the sham-operated group. These increases, however, were significantly inhibited by treatment with rosuvastatin in a dose-dependent manner. The protective effects of rosuvastatin were also confirmed by histological findings. Exposure of the small intestine to I-R resulted in mucosal inflammation characterized by significant increases in thiobarbituric acid-reactive substances, tissue-associated myeloperoxidase activity, and the mucosal contents of rat cytokine-induced neutrophil chemoattractant-1 (CINC-1) and tumor necrosis factor-α (TNF-α). These increases in inflammatory parameters after I-R were significantly inhibited by pretreatment with rosuvastatin at a dose of 10 mg/kg. Furthermore, mRNA expression of CINC-1 and TNF-α was increased after I-R, and this increase was also inhibited by rosuvastatin. The mucosal protein levels of eNOS decreased during I-R, but were preserved in rats treated with rosuvastatin.

CONCLUSION: Rosuvastatin inhibits rat intestinal injury and inflammation induced by I-R, and its protection is associated with the preservation of eNOS protein.

Involvement of PPAR nuclear receptors in tissue injury and wound repair

Tissue damage resulting from chemical, mechanical, and biological injury, or from interrupted blood flow and reperfusion, is often life threatening. The subsequent tissue response involves an intricate series of events including inflammation, oxidative stress, immune cell recruitment, and cell survival, proliferation, migration, and differentiation. In addition, fibrotic repair characterized by myofibroblast transdifferentiation and the deposition of ECM proteins is activated. Failure to initiate, maintain, or stop this repair program has dramatic consequences, such as cell death and associated tissue necrosis or carcinogenesis. In this sense, inflammation and oxidative stress, which are beneficial defense processes, can become harmful if they do not resolve in time. This repair program is largely based on rapid and specific changes in gene expression controlled by transcription factors that sense injury. PPARs are such factors and are activated by lipid mediators produced after wounding. Here we highlight advances in our understanding of PPAR action during tissue repair and discuss the potential for these nuclear receptors as therapeutic targets for tissue injury.

Protective effect of peroxisome proliferator activated receptor gamma agonists on diabetic and non-diabetic renal diseases

Peroxisome proliferator activated receptor gamma (PPARgamma) agonist has not only antidiabetic effect but also a protective effect against various types of injury of the kidney. The protective effects of PPARgamma agonists are observed in diabetic nephropathy and non-diabetic renal diseases such as 5/6 ablation model of renal failure, experimental glomerulonephritis, ischemia-reperfusion injury, hypertensive nephropathy and cyclosporin-induced renal injury. The mechanism of renoprotection by PPARgamma agonist is multifactorial. Anti-fibrotic and anti-inflammatory effects, suppression of renin-angiotensin system, vascular protective effect and antiapoptotic effect were proposed.

Modulation of the oxidative stress and inflammatory response by PPAR-γ agonists in the hippocampus of rats exposed to cerebral ischemia/reperfusion

Agonists of the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) exert protective effects in several models of ischemia/reperfusion injury, but their role in stroke is less clear. The study investigates the effects of two PPAR-gamma agonists, rosiglitazone and pioglitazone, on oxidative stress and inflammatory response induced by ischemia/reperfusion in the rat hippocampus. Common carotid artery occlusion for 30 min followed by 1 h reperfusion resulted in a significant increase in the generation of reactive oxygen species, nitric oxide and the end products of lipid peroxidation as well as markedly reduced endogenous antioxidant glutathione levels and up-regulated superoxide dismutase activity. Western blot analysis showed that ischemia/reperfusion lead to an increase in cyclooxygenase-2 (COX-2) expression, as well activating p38 and p42/44 mitogen-activated protein kinases (MAPKs) and nuclear factor-kappaB (NF-kappaB). Pre-treatment with either rosiglitazone or pioglitazone significantly reduced oxidative stress, COX-2 protein expression and activation of MAPKs and NF-kappaB. Taken together, the results provide convincing evidence that PPAR-gamma agonists exert protective effects in a rat model of mild forebrain ischemia/reperfusion injury by inhibiting oxidative stress and excessive inflammatory response.

The selective PPARγ antagonist GW9662 reverses the protection of LPS in a model of renal ischemia-reperfusion

BACKGROUND

We have recently reported that pretreatment of rats with endotoxin (lipopolysaccharide, LPS) and selective agonists of the nuclear receptor peroxisome proliferator-activated receptor-gamma (PPARgamma) protect the kidney against ischemia/reperfusion (I/R) injury. Here we investigate the hypothesis that the renoprotective effects of LPS may be due to an enhanced formation of endogenous ligands of PPARgamma, rather than an up-regulation of PPARgamma expression.

METHODS

Rats were pretreated with LPS (1 mg/kg, IP, 24 hours prior to ischemia) in the absence (control) or presence of the selective PPARgamma antagonist GW9662 (1 mg/kg, IP, 24 and 12 hours prior to ischemia). Twenty-four hours after injection of LPS, rats were subjected to 60 minutes of bilateral renal ischemia, followed by 6 hours of reperfusion. Serum and urinary indicators of renal injury and dysfunction were measured, specifically serum creatinine, aspartate aminotransferase, and gamma-glutamyl-transferase, creatinine clearance, urine flow, and fractional excretion of sodium. Kidney PPARgamma1 mRNA levels were determined by reverse transcriptase-polymerase chain reaction.

RESULTS

Pretreatment with LPS significantly attenuated all markers of renal injury and dysfunction caused by I/R. Most notably, GW9662 abolished the protective effects of LPS. Additionally, I/R caused an up-regulation of kidney PPARgamma1 mRNA levels compared to sham animals, which were unchanged in rats pretreated with LPS.

CONCLUSION

We document here for the first time that endogenous ligands of PPARgamma may contribute to the protection against renal I/R injury afforded by LPS pretreatment in the rat.

A PPAR-gamma ligand, 15-deoxy-Delta12,14-prostaglandin J(2), inhibited gastric mucosal injury induced by ischemia-reperfusion in rats

INTRODUCTION

Recent studies have demonstrated the anti-inflammatory action of 15-deoxy-Delta12,14-prostaglandin J(2) (15d-PGJ(2)), a derivative of the PGD(2) metabolic pathway. Acute inflammation, including neutrophil activation, plays a critical role in the pathogenesis of ischemia-reperfusion (I/R). The aim of the present study was to determine the effect of 15d-PGJ(2) on I/R-induced gastric mucosal injury in rats.

METHODS

Gastric mucosal damage was induced in male Wistar rats by clamping the celiac artery for 30 min followed by reperfusion. 15d-PGJ(2) (0.01-1.0 mg/kg) was given to the rats intraperitoneally 1 h before the vascular clamping. The area of gastric mucosal erosions (erosion index) was measured. Thiobarbituric acid reactive substances (TBARS) and tissue-associated myeloperoxidase (MPO) activity were measured in the gastric mucosa as indices of lipid peroxidation and neutrophil infiltration. The expression of tumor necrosis factor-alpha (TNF-alpha) in gastric mucosa was measured by ELISA. In addition, to elucidate whether the protective effects of 15d-PGJ(2) are related to the activation of the PPAR-gamma receptor, we also investigated the effects of a PPAR-gamma antagonist, GW9662.

RESULTS

After 60 min of reperfusion, the area of gastric erosion index had significantly increased from the mean basal levels. The increase in the erosion index was significantly inhibited by pretreatment with 15d-PGJ(2) in a dose-dependent manner. On the other hand, GW9662 reversed the protective effect of 15d-PGJ(2). The concentration of TBARS and MPO activity in the gastric mucosa were both significantly increased after I/R, and pretreatment with 15d-PGJ(2) significantly reduced these increases. The TNF-alpha content was significantly higher in the I/R group than in the sham-operated group. However, the increase in TNF-alpha was significantly inhibited by pretreatment with 15d-PGJ(2).

CONCLUSIONS

15d-PGJ(2) significantly inhibited the severity of acute gastric mucosal injury induced by I/R in rats through PPAR-gamma-dependent mechanisms. This effect may be due, in part, to a reduction in the infiltration of neutrophils into the gastric mucosa, possibly via the inhibition of inflammatory cytokine.

Pathophysiology of mesenteric ischemia/reperfusion: a review

During ischemia, the cell structures are progressively damaged, but restoration of the blood flow, paradoxically, intensifies the lesions caused by the ischemia. The mechanisms of ischemia injury and reperfusion (I/R) have not been completely defined and many studies have been realized in an attempt to find an ideal therapy for mesenteric I/R. The occlusion and reperfusion of the splanchnic arteries provokes local and systemic alterations principally derived from the release of cytotoxic substances and the interaction between neutrophils and endothelial cells. Substances involved in the process are discussed in the present review, like oxygen-derived free radicals, nitric oxide, transcription factors, complement system, serotonin and pancreatic proteases. The mechanisms of apoptosis, alterations in other organs, therapeutic and evaluation methods are also discussed.

Peroxisome proliferator-activated receptors gamma ligands and ischemia and reperfusion injury

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid and thyroid hormone receptors. The PPAR subfamily comprises of three members, PPAR-alpha, PPAR-beta and PPAR-gamma. PPAR-gamma has recently been implicated as a regulator of cellular proliferation and inflammatory responses. There is good evidence that ligands of PPAR-gamma, including certain thiazolinediones, reduce tissue injury associated with ischemia and reperfusion. The potential utility of PPAR-gamma ligands in ischemia and reperfusion will be discussed in this review.

Expression of Peroxisome Proliferator-Activated Receptor-γ in Renal Ischemia-Reperfusion Injury

The pathogenesis of ischemia-reperfusion injury is known to involve cytokines and particularly surface adhesion molecules, the expression of which initiates the attachment of inflammatory cells. Peroxisome proliferator-activated receptor (PPAR)-gamma is considered an important immunomodulatory factor as well as a fatty acid regulator. In this study, we researched the expression of PPAR-gamma in renal ischemia-reperfusion injury of the rat. The right kidney was harvested and left renal artery and vein were clamped under laparotomy. The kidney was reperfused after 90 minutes of ischemia, and rats were sacrificed at 0, 1.5, 3, 5, 12, and 24 hours after reperfusion. PPAR-gamma expression was analyzed by immunohistochemical staining using monoclonal antibody. In normal kidney, PPAR-gamma staining was weak on endothelial cells, including mesangial cells. On the other hand, PPAR-gamma staining was weak on interstitial cells and strong on collecting ducts of medulla. From 1.5 to 5 hours after reperfusion, PPAR-gamma staining was strong on endothelial cells, moderate on interstitial cells, and strong on collecting ducts. Twelve hours after reperfusion, PPAR-gamma staining was weak on endothelial cells, moderate on interstitial cells, and strong on collecting ducts. PPAR-gamma is induced on collecting ducts, interstitial cells, and endothelial cells in a rat model having renal ischemia-reperfusion injury.

Study of peroxisome proliferator-activated receptor (PPAR)-gamma in renal ischemia-reperfusion injury

Recent studies of ischemia-reperfusion (I/R) injury have focused on the function of neutrophils, the action mechanism of inflammatory cytokines. However, few reports have addressed peroxisome proliferator-activated receptor (PPAR)-gamma. PPAR-gamma is a ligand-activated transcriptional factor belonging to the steroid receptor superfamily. It plays a role in both adipocyte differentiation and tumorigenesis. We researched the expression of PPAR-gamma in renal I/R injury of the rat. Male Lewis rats were used. The right kidney was harvested and the left renal artery and vein were clamped at 90 minutes of ischemic time. Rats were killed at 0, 1.5, 3, 5, and 12 hours after reperfusion. PPAR-gamma expression was studied by immunohistostaining. PPAR-gamma expression was observed only on mesangial and endothelial cells of normal kidney. From 1.5 to 3 hours after reperfusion, PPAR-gamma expression gradually became stronger on mesangial and endothelial cells. PPAR-gamma expression was most intense on mesangial cells and endothelial cells at 3 hours after reperfusion. Twelve hours after reperfusion, necrosis extended throughout the ischemic kidney and nearly all the tubular epithelial cells were destroyed, but 12 hours after reperfusion PPAR-gamma expression gradually became weaker on mesangial and endothelial cells. PPAR-gamma was expressed in the rat model having renal I/R injury. Several hours after maximal of PPAR-gamma expression, maximal renal I/R injury was observed. These results may indicate a relationship between PPAR-gamma expression and renal I/R injury.

Ligands of the peroxisome proliferator-activated receptor-gamma and heart failure

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid and thyroid hormone receptors. The PPAR subfamily comprises of three members, PPAR-alpha, PPAR-beta and PPAR-gamma. There is good evidence that ligands of PPAR-gamma, including certain thiazolinediones, reduce myocardial tissue injury and infarct size. The use of PPAR-gamma agonists in the treatment of heart failure is, however, controversial.

Peroxisome proliferator-activated receptor-γ ligands reduce inflammation and infarction size in transient focal ischemia

Newly developed insulin-sensitizing agents, which target the nuclear receptor peroxisome proliferator-activated receptor-gamma have recently been appreciated to exhibit potent anti-inflammatory actions. Since stroke is associated with an intense inflammatory response, we reasoned that these agents may ameliorate injury from stroke. We report that administration of troglitazone or pioglitazone 24 h before and at the time of cerebral infarction dramatically reduced infarction volume and improved neurological function following middle cerebral artery occlusion in rats. Furthermore, we find that delayed therapy also significantly reduced infarct volume. The brains of the drug-treated animals displayed reduced inflammation as evidenced by decreased immunoreactivity for microglial/macrophage markers and reduced protein and mRNA for interleukin-1beta, cyclooxygenase-2 and inducible nitric oxide synthase. We argue that the beneficial effects of these drugs are likely due to reduced expression of these inflammatory mediators, which are known to exacerbate ischemic injury following stroke. These results are of particular relevance to diabetic patients chronically treated with these agents who may benefit from the neuroprotective actions of these drugs.

Tumor necrosis factor-alpha-induced apoptosis of human coronary artery endothelial cells: modulation by the peroxisome proliferator-activated receptor-gamma ligand pioglitazone

The cytokine tumor necrosis factor-alpha (TNF-alpha) plays an important role in endothelial injury, which is associated with the release of reactive oxygen species and the induction of apoptosis. We report on our study of TNF-alpha-induced apoptosis in human coronary artery endothelial cells and its modulation by the peroxisome proliferator-activated receptor-gamma (PPAR-gamma) ligand pioglitazone. Treatment of cells with TNF-alpha (40 ng/mL) resulted in apoptosis as measured by DNA laddering and caspase-3 activation. TNF-alpha treatment decreased the expression of antiapoptotic protein Bcl-2 (P <.05 vs control), but not the expression of Fas or FLIP, in human coronary artery endothelial cells. Treatment of cells with TNF-alpha also enhanced lipid peroxidation (P <.01 vs control). Pretreatment of cells with the PPAR-gamma ligand pioglitazone blocked TNF-alpha-mediated apoptosis, caspase-3 activation, expression of Bcl-2, and lipid peroxidation (P <.01 vs TNF-alpha alone). These results indicate that TNF-alpha induces oxidative stress in human coronary artery endothelial cells, resulting in apoptosis through a reduction in Bcl-2 expression and the subsequent activation of caspase-3. The PPAR-gamma ligand pioglitazone modulates lipid peroxidation, alters Bcl-2 expression and caspase-3 activation, and finally reduces apoptosis. The antioxidant and antiapoptotic effects of pioglitazone may be the mechanism by which this agent reduces endothelial injury.

Mechanism of delayed resuscitation in promoting loss of intestinal mucous membrane barrier function after rats scalding

AIM: To investigate the effect of delayed resuscitation on intestinal mucous membrane barrier function and its relationship with neutrophil infiltration of local tissue after rats scalding.

METHODS: Rats with 40% full-thickness scald burn were randomly divided into two group: immediately resuscitation group (IR group) and delayed resuscitation group (DR group). The content of D-lactate, diamine oxidase (DAO) in plasma and myeloperoxidase (MPO), superoxide dismutase (SOD) and malondialdehyde (MDA) in intestinal mucous tissue were determined at different time points after burn. Apoptosis of mucous epithelial cells were identified by terminal deoxynucletidyl-transferase mediated dUTP-biotin nick end labeling (TUNEL) histochemical methods.

RESULTS: The contents of D-lactate in plasma in DR group were much higher than those of IR group (P < 0.01 or 0.05), MPO activity in intestinal mucous tissue of DR group were dramatically increased accompanying with decrease of SOD activity and increase of MDA contents. Herein, we found a close correlation between the contents of D-lactate and activity of MPO. Meanwhile, we also found an increase of the activity of DAO in plasma and number of TUNEL positive staining epithelial cells in DR group.

CONCLUSION: Delayed resuscitation promotes the loss of intestinal mucous membrane barrier function due to the increase of both cell necrosis and cell apoptosis, which may be related to increased neutrophil infiltration in local tissue.

Ligands of the peroxisome proliferator-activated receptor-gamma and heart failure

Peroxisome proliferator-activated receptors (PPARs) are members of the nuclear hormone receptor superfamily of ligand-activated transcription factors that are related to retinoid, steroid and thyroid hormone receptors. The PPAR subfamily comprises of three members, PPAR-alpha, PPAR-beta and PPAR-gamma. There is good evidence that ligands of PPAR-gamma, including certain thiazolinediones, reduce myocardial tissue injury and infarct size. The use of PPAR-gamma agonists in the treatment of heart failure is, however, controversial.

Agonists of peroxisome-proliferator activated receptor-gamma reduce renal ischemia/reperfusion injury

BACKGROUND/AIMS

Recent evidence indicates that peroxisome-proliferator activated receptor (PPAR) agonists protect against ischemia/reperfusion (I/R) injury. Here we investigate the effects of the PPAR-gamma agonists, rosiglitazone and ciglitazone, on the renal dysfunction and injury caused by I/R of the rat kidney in vivo.

METHODS

Rosiglitazone or ciglitazone were administered to male Wistar rats prior to and during reperfusion. Biochemical indicators of renal dysfunction and injury were measured and histological scoring of kidney sections was used to assess renal injury. Expression of PPAR isoforms and intercellular adhesion molecule-1 during renal I/R were assessed using RT-PCR and Northern blot, respectively. Myeloperoxidase activity and activation of poly(ADP-ribose) polymerase (PARP) were used as indicators of polymorphonuclear (PMN) cell infiltration and oxidative stress, respectively.

RESULTS

Expression of PPAR-alpha, PPAR-beta and PPAR-gamma 1 (but not PPAR-gamma 2) was observed in kidneys with down-regulation of PPAR-alpha expression during renal I/R. Rosiglitazone and ciglitazone significantly reduced biochemical and histological signs of renal dysfunction and injury. Renal expression of ICAM-1 caused by I/R was reduced by rosiglitazone and ciglitazone which was reflected by decreased PMN infiltration into reperfused renal tissues. Both rosiglitazone and ciglitazone reduced PARP activation indicating a reduction of oxidative stress.

CONCLUSION

These results suggest that the PPAR-gamma agonists rosiglitazone and ciglitazone reduce the renal dysfunction and injury associated with I/R of the kidney. We propose that one mechanism underlying the protective effects involves inhibition of the expression of ICAM-1, a reduction of PMN infiltration into renal tissues and subsequent reduction of oxidative stress.