MYOCARDIAL ISCHEMIA/REPERFUSION-INDUCED OXIDATIVE RENAL DAMAGE IN RATS: PROTECTION BY CAFFEIC ACID PHENETHYL ESTER (CAPE)

Effects of apocynin on sciatic nerve injury in rabbits

We investigated the effects of apocynin (APO) on experimental sciatic nerve compression injury in rabbits. We used 21 male rabbits divided randomly into three groups of seven. The control group was subjected to sciatic nerve compression with no further intervention. The APO treated group was subjected to compression injury and 20 mg/kg APO was administered daily for 21 days by intraperitoneal injection beginning the day after the injury. The sham group was treated with APO without injury. The control group exhibited shrinkage of axons, disruption of myelin sheaths and loss of nerve fibers. The damage for the control group was significantly greater than for the sham group. The severity of histopathology was decreased in the APO treated group compared to the control group, as was the oxidative stress index. Our findings suggest that APO treatment may contribute to healing of sciatic nerve damage.

Recent progresses in the pharmacological activities of caffeic acid phenethyl ester

The past decades have seen a growing interest in natural products. Caffeic acid phenethyl ester (CAPE), a flavonoid isolated from honeybee propolis, has shown multiple pharmacological potentials, including anti-cancer, anti-inflammatory, antioxidant, antibacterial, antifungal, and protective effects on nervous systems and multiple organs, since it was found as a potent nuclear factor κB (NF-κB) inhibitor. This review summarizes the advances in these beneficial effects of CAPE, as well as the underlying mechanisms, and proposes that CAPE offers an opportunity for developing therapeutics in multiple diseases. However, clinical trials on CAPE are necessary and encouraged to obtain certain clinically relevant conclusions.

Cardiovascular Effects of Caffeic Acid and Its Derivatives: A Comprehensive Review

Caffeic acid (CA) and its phenethyl ester (CAPE) are naturally occurring hydroxycinnamic acids with an interesting array of biological activities; e.g., antioxidant, anti-inflammatory, antimicrobial and cytostatic. More recently, several synthetic analogs have also shown similar properties, and some with the advantage of added stability. The actions of these compounds on the cardiovascular system have not been thoroughly explored despite presenting an interesting potential. Indeed the mechanisms underlying the vascular effects of these compounds particularly need clarifying. The aim of this paper is to provide a comprehensive and up-to-date review on current knowledge about CA and its derivatives in the cardiovascular system. Caffeic acid, CAPE and the synthetic caffeic acid phenethyl amide (CAPA) exhibit vasorelaxant activity by acting on the endothelial and vascular smooth muscle cells. Vasorelaxant mechanisms include the increased endothelial NO secretion, modulation of calcium and potassium channels, and modulation of adrenergic receptors. Together with a negative chronotropic effect, vasorelaxant activity contributes to lower blood pressure, as several preclinical studies show. Their antioxidant, anti-inflammatory and anti-angiogenic properties contribute to an important anti-atherosclerotic effect, and protect tissues against ischemia/reperfusion injuries and the cellular dysfunction caused by different physico-chemical agents. There is an obvious shortage of in vivo studies to further explore these compounds' potential in vascular physiology. Nevertheless, their favorable pharmacokinetic profile and overall lack of toxicity make these compounds suitable for clinical studies.

Caffeic Acid Phenethyl Ester Decreases Oxidative Stress Index in Blunt Spinal Cord Injury in Rats

Objective

The aim of this study was to investigate the total oxidant status and total antioxidant status of caffeic acid phenethyl ester and methylprednisolone in blunt spinal cord injury in rats.

Methods

Twenty-four adult Wistar albino rats were randomised into three groups. Spinal cord injury was performed by the weight-drop model. Group 1 underwent laminectomy followed by spinal cord injury and received no medication (control group). Group 2 underwent laminectomy followed by spinal cord injury and received caffeic acid phenethyl ester (10 µmol/kg) by intraperitoneal injection. Group 3 underwent laminectomy followed by spinal cord injury and received methylprednisolone (30 mg/kg) by intraperitoneal injection. Twenty-four hours later, all rats were sacrified and after that total oxidant status, total antioxidant status and oxidative stress index levels were determined in spinal cord tissues and the obtained results were compared.

Results

The highest total antioxidant status level was observed in the caffeic acid phenethyl ester group and the highest total oxidant status level was observed in the control group. Oxidative stress index levels in the control group were statistically higher than the caffeic acid phenethyl ester and methylprednisolone groups (p<0.01).

Conclusion

Based on our results, it is concluded that caffeic acid phenethyl ester might be a promising neuroprotective agent after spinal cord injury via its antioxidant effects.

Mechanism of myocardial ischemia/reperfusion-induced acute kidney injury through DJ-1/Nrf2 pathway in diabetic rats

The objective of the present study was to investigate acute kidney injury (AKI) induced by myocardial ischemia/reperfusion (MIR) in diabetic rats and elucidate its underlying mechanism. A rat model of MIR was established by left anterior descending coronary artery occlusion for 30 min, followed by reperfusion for 2 h. Rats were randomly divided into four groups: i) Sham group, ii) sham + MIR group, iii) diabetic group and iv) diabetes + MIR group. Myocardial injury was detected by plasma creatine kinase isoenzyme MB and lactate dehydrogenase assays. AKI induced by MIR in diabetic rats was characterized by increases in cystatin C and β2-microglobulin levels. Oxidative stress injury was accompanied by an increase of malondialdehyde levels and a decrease of total antioxidative capacity in the renal tissues. Immunohistochemistry and western blot analysis demonstrated that the expression of DJ-1 and nuclear factor erythroid 2-related factor 2 (Nrf2) were significantly increased in the diabetes + MIR group compared with that in the sham + MIR and diabetic groups. Taken together, these results suggested that AKI induced by MIR in diabetic rats may be associated with activation of the DJ-1/Nrf2 pathway.

Caffeic Acid Phenethyl Ester Regulates PPAR's Levels in Stem Cells-Derived Adipocytes

Hypertrophic obesity inhibits activation of peroxisome proliferators-activated receptor gamma (PPARγ), considered the key mediator of the fully differentiated and insulin sensitive adipocyte phenotype. We examined the effects of Caffeic Acid Phenethyl Ester (Cape), isolated from propolis, a honeybee hive product, on Adipose Stem Cells (ASCs) differentiation to the adipocyte lineage. Finally we tested the effects of Cape on insulin-resistant adipocytes. Quantification of Oil Red O-stained cells showed that lipid droplets decreased following Cape treatment as well as radical oxygen species formation. Additionally, exposure of ASC to high glucose levels decreased adiponectin and increased proinflammatory cytokines mRNA levels, which were reversed by Cape-mediated increase of insulin sensitivity. Cape treatment resulted in decreased triglycerides synthesis and increased beta-oxidation. Exposure of ASCs to Lipopolysaccharide (LPS) induced a reduction of PPARγ, an increase of IL-6 levels associated with a well-known stimulation of lipolysis; Cape partially attenuated the LPS-mediated effects. These observations reveal the main role of PPARγ in the adipocyte function and during ASC differentiation. As there is now substantial interest in functional food and nutraceutical products, the observed therapeutic value of Cape in insulin-resistance related diseases should be taken into consideration.

The role of CAPE in PI3K/AKT/mTOR activation and oxidative stress on testis torsion

Ischemia reperfusion injury arises from testicular torsion resulting in a loss of spermatogenesis and significant germ cell apoptosis. This study evaluates the prooxidant/antioxidant effects of caffeic acid phenethyl ester (CAPE) through PI3K/AKT/mTOR signal pathways on testis torsion. A total of (28) male Wistar rats were divided randomly into 4 groups (n=7 for each group):group A (sham) group,group B torsion/detorsion group, group C (saturation group, during four days of CAPE, one dose (10 μmol/kg, i.p)) and group D (a single dose of CAPE 2h after torsion and before detorsion). At the end of the study, unilateral orchiectomies were performed for measurements of MDA and 8OHdG levels, histopathologic and immunohistochemical and TUNEL apoptotic cell examination. Testicular torsion-detorsion led to a significant decrease in the mean values of the Johnsen's scores and a significant increase in the apoptotic cell values of group B. There were no significant differences between group D and group A. In addition, the MDA and 8OHdG levels increased significantly in group B. The MDA and 8OHdG values were lower in group D. However, the 8OHdG levels were higher in group C than the groups A and D. On the other hand, CAPE suppresses mTOR activation and reduces the apoptosis on ischemia/reperfusion damage in rat testis. These results demonstrate that CAPE suppresses mTOR activation and reduces the apoptosis on ischemia/reperfusion damage in rat testis.

Value of caffeic acid phenethyl ester pretreatment in experimental sepsis model in rats

Background and Aim. The aim of this study was to determine the actions of caffeic acid phenethyl ester (CAPE) on the changes of endothelin-1 (ET-1) level, tumor necrosis factor- (TNF-) alpha, and oxidative stress parameters such as superoxide dismutase (SOD) activities and malondialdehyde (MDA) levels in experimental sepsis model in rats. Materials and Methods. Twenty-four rats were randomly divided into three experimental groups: sham (group 1), sepsis (group 2), and sepsis + CAPE (group 3), n = 8 each. CAPE was administered (10 µmol/kg) intraperitoneally to group 3 before sepsis induction. Serum ET-1, serum TNF-alpha, tissue SOD activity, and tissue MDA levels were measured in all groups. Results. Pretreatment with CAPE decreased ET-1, TNF-alpha, and MDA levels in sepsis induced rats. Additionally SOD activities were higher in rats pretreated with CAPE after sepsis induction. Conclusion. Our results demonstrate that CAPE may have a beneficial effect on ET and TNF-alpha levels and oxidative stress parameters induced by sepsis in experimental rat models. Therefore treatment with CAPE can be used to avoid devastating effects of sepsis.

Protective Effect and Mechanism of Total Flavones from Rhododendron simsii Planch Flower on Cultured Rat Cardiomyocytes with Anoxia and Reoxygenation

Many flavonoids have cardioprotection against myocardial ischemia/reperfusion (I/R) injury. Total flavones from Rhododendron simsii Planch flower (TFR) can protect myocardial ischemic injuries. However, its protective mechanism is still unknown. The present study was designed to investigate the mechanism of TFR on myocardial I/R and anoxia/reoxygenation (A/R) injuries. Rat model of myocardial I/R injury was made, and myocardial infarction was determined. A/R injury was induced in cultured rat cardiomyocytes; cellular damage was evaluated by measuring cell viability, LDH and cTnT releases, and MDA content. Expressions of ROCK₁ and ROCK₂ protein were examined by Western blot analysis, and K⁺ currents were recorded by using whole-cell patch clamp technique. TFR 20~80 mg/kg markedly reduced I/R-induced myocardial infarction. TFR 3.7~300 mg/L significantly inhibited A/R-induced reduction of cell viability, LDH and cTnT releases, and MDA production. Exposure to A/R significantly increased ROCK₁ and ROCK₂ expressions in rat cardiomyocytes, but TFR 33.3~300 mg/L obviously inhibited this increase. 300 mg/L TFR significantly augmented inward rectifier K⁺ current and other K⁺ currents in rat cardiomyocytes. These results indicate that TFR has a protective effect on rat cardiomyocytes A/R damage, and the protective mechanism may be engaged with the inhibition of ROCK₁ and ROCK₂ and activation of K⁺ channels.

Caffeic acid phenethyl ester (CAPE): scavenger of peroxynitrite in vitro and in sepsis models

Excessive free radical production by immune cells has been linked to cell death and tissue injury during sepsis. Peroxynitrite is a short-lived oxidant and a potent inducer of cell death that has been identified in several pathological conditions. Caffeic acid phenethyl ester (CAPE) is an active component of honeybee products and exhibits antioxidant, anti-inflammatory, and immunomodulatory activities. The present study examined the ability of CAPE to scavenge peroxynitrite in RAW 264.7 murine macrophages stimulated with lipopolysaccharide/interferon-γ that was used as an in vitro model. Conversion of 123-dihydrorhodamine to its oxidation product 123-rhodamine was used to measure peroxynitrite production. Two mouse models of sepsis (endotoxemia and cecal ligation and puncture) were used as in vivo models. The level of serum 3-nitrotyrosine was used as an in vivo marker of peroxynitrite. The results demonstrated that CAPE significantly improved the viability of lipopolysaccharide/interferon-γ-treated RAW 264.7 cells and significantly inhibited nitric oxide production, with effects similar to those observed with an inhibitor of inducible nitric oxide synthase (1400W). In addition, CAPE exclusively inhibited the synthesis of peroxynitrite from the artificial substrate SIN-1 and directly prevented the peroxynitrite-mediated conversion of dihydrorhodamine-123 to its fluorescent oxidation product rhodamine-123. In both sepsis models, CAPE inhibited cellular peroxynitrite synthesis, as evidenced by the absence of serum 3-nitrotyrosine, an in vivo marker of peroxynitrite. Thus, CAPE attenuates the inflammatory responses that lead to cell damage and, potentially, cell death through suppression of the production of cytotoxic molecules such as nitric oxide and peroxynitrite. These observations provide evidence of the therapeutic potential of CAPE treatment for a wide range of inflammatory disorders.

Caffeic acid phenethyl amide ameliorates ischemia/reperfusion injury and cardiac dysfunction in streptozotocin-induced diabetic rats

BACKGROUND

Caffeic acid phenethyl ester (CAPE) has been shown to protect the heart against ischemia/reperfusion (I/R) injury by various mechanisms including its antioxidant effect. In this study, we evaluated the protective effects of a CAPE analog with more structural stability in plasma, caffeic acid phenethyl amide (CAPA), on I/R injury in streptozotocin (STZ)-induced type 1 diabetic rats.

METHODS

Type 1 diabetes mellitus was induced in Sprague-Dawley rats by a single intravenous injection of 60 mg/kg STZ. To produce the I/R injury, the left anterior descending coronary artery was occluded for 45 minutes, followed by 2 hours of reperfusion. CAPA was pretreated intraperitoneally 30 minutes before reperfusion. An analog devoid of the antioxidant property of CAPA, dimethoxyl CAPA (dmCAPA), and a nitric oxide synthase (NOS) inhibitor (Nω-nitro-l-arginine methyl ester [l-NAME]) were used to evaluate the mechanism involved in the reduction of the infarct size following CAPA-treatment. Finally, the cardioprotective effect of chronic treatment of CAPA was analyzed in diabetic rats.

RESULTS

Compared to the control group, CAPA administration (3 and 15 mg/kg) significantly reduced the myocardial infarct size after I/R, while dmCAPA (15 mg/kg) had no cardioprotective effect. Interestingly, pretreatment with a NOS inhibitor, (L-NAME, 3 mg/kg) eliminated the effect of CAPA on myocardial infarction. Additionally, a 4-week CAPA treatment (1 mg/kg, orally, once daily) started 4 weeks after STZ-induction could effectively decrease the infarct size and ameliorate the cardiac dysfunction by pressure-volume loop analysis in STZ-induced diabetic animals.

CONCLUSIONS

CAPA, which is structurally similar to CAPE, exerts cardioprotective activity in I/R injury through its antioxidant property and by preserving nitric oxide levels. On the other hand, chronic CAPA treatment could also ameliorate cardiac dysfunction in diabetic animals.

Caffeic acid phenethyl ester as a protective agent against nephrotoxicity and/or oxidative kidney damage: a detailed systematic review

Caffeic acid phenethyl ester (CAPE), an active component of propolis, has been attracting the attention of different medical and pharmaceutical disciplines in recent years because of its antioxidant, anti-inflammatory, antiproliferative, cytotoxic, antiviral, antifungal, and antineoplastic properties. One of the most studied organs for the effects of CAPE is the kidney, particularly in the capacity of this ester to decrease the nephrotoxicity induced by several drugs and the oxidative injury after ischemia/reperfusion (I/R). In this review, we summarized and critically evaluated the current knowledge regarding the protective effect of CAPE in nephrotoxicity induced by several special medicines such as cisplatin, doxorubicin, cyclosporine, gentamycin, methotrexate, and other causes leading to oxidative renal injury, namely, I/R models and senility.

Alpha-tocopherol ameliorates oxidative renal insult associated with spinal cord reperfusion injury

Ischemic-reperfusion procedures targeting a specific organ often results in remote multiple organ injuries mediated possibly by heightened oxidative stress levels. As the kidney is one of the most vulnerable organs for ischemic oxidative stress, the aim of the present study was to confirm the occurrence of renal complication secondary to spinal cord ischemic-reperfusion injury (SC-IRI) induced by aortic clamping. The study also investigated the possible prophylactic effect of long-term administration of α-tocopherol (α-TOL) against high level of renal oxidative stress and inflammatory processes induced by SC-IRI. In this study, a total of 60 male Sprague-Dawley rats were randomly divided into five equal groups: C group underwent no surgery; CE group received α-TOL 600 mg/kg intramuscular twice weekly for 6 weeks; S group were subjected to laparotomy without clamping of the aorta; SE group were handled as S group and treated with α-TOL as group CE; SC-IRI group were subjected to laparotomy with clamping of the aorta just above the bifurcation of the aorta for 45 min, then the clamp was released for 48 h for reperfusion. SC-IRIE group was subjected to IRI as in group SC-IRI and was injected with α-TOL in the same dose and route as α-TOL-treated control group. SC-IRI resulted in increases in serum creatinine, blood urea nitrogen, plasma nitrite/nitrate level, serum tumor necrosis factor alpha, renal tissue homogenate level for malondialdehyde, superoxide dismutase and prostaglandin E2. Long-term prophylactic treatment with α-TOL resulted in amelioration of the renal functional disturbances and all measured parameters of oxidative stress and inflammation. Ischemic reperfusion injury of the spinal cord induced some remote renal functional disturbances although some of the observed changes may have resulted from decreased renal blood flow due to the hypotension induced during the procedure. Prophylactic long-term α-TOL administration guards against the renal function disturbances an effect that can be attributed, at least partially, to improvement of the renal pro-oxidant/antioxidant balance and inhibition of the inflammatory processes.

Caffeic acid phenethyl ester effects in the kidney during ischemia and reperfusion in rats anesthetized with isoflurane

BACKGROUND

The purpose of this investigation was to examine the effect of caffeic acid phenethyl ester (CAPE) in renal ischemia/reperfusion injury in rats anesthetized with isoflurane (iso).

METHODS

We randomly assigned 26 male Wistar rats anesthetized with isoflurane, intubated and mechanically ventilated to 3 groups: G1 (controls; n = 8), G2 (CAPE; n = 10), and G3 (ethanol; n = 8). Mean arterial pressure was monitored for anesthetic control. Intraperitoneal CAPE (G2) or ethanol (G3) injections were administered 40 minutes before left renal ischemia. All animals underwent right nephrectomy and the left kidney was submitted to ischemia for 25 minutes. Serum creatinine (cr) values were determined at the beginning (M1), end (M2), and 24 hours after the experiment (M3) upon intracardiac blood samples. The left kidney was removed for histologic analysis, using a scale for tubular necrosis (0-5, injury maximum). Statistical analysis was applied to serum creatinine and histological score injury considering statistical differences to be significant when P < .05.

RESULTS

The cr values in the CAPE were significantly higher at M2 (0.8 mg/mL; P = .0012) and M3 (3.7 mg/mL; P = .0014) than the control (0.5 and 0.9 mg/mL) or G3 (0.6 and 1.0 mg/mL), respectively. Histologic examination showed the CAPE group to display more pericapsular tubular necrosis (3.0 [2.0; 3.0]) than the G1 group (2.0 [1.0; 2.0]) or G3 group (1.5 [1.0; 2.0]; P < .001). The CAPE group displayed more medullary tubular necrosis (2.0 [2.0; 3.0] than G1 (2.0 [1.0; 2.0] or G3 (1.0 [0.0; 2.0]; P < .001).

CONCLUSION

CAPE promoted greater functional and anatomic renal injury when rats were anesthetized with iso than control or ethanol groups, as demonstrated by histologic analysis and serum values.

The immunoregulatory effects of caffeic acid phenethyl ester on the cytokine secretion of peripheral blood mononuclear cells from asthmatic children

BACKGROUND

Asthma is a chronic inflammatory disease of the airways for which current treatments are mainly based on pharmacological interventions, such as glucocorticoid therapy. Our objective was to study the immunoregulatory effects of caffeic acid phenethyl ester (CAPE, a phytochemical synthesized from propolis) on cytokine secretion of peripheral blood mononuclear cells (PBMCs) from asthmatic children.

METHODS

PBMCs from asthmatic children (5.5 ± 3.3 years old, n=28) and healthy children (5.6 ± 2.8 years old, n=23) were co-cultured with CAPE in vitro with and without phorbol-12-myristate-13-acetate-ionomycin.

RESULTS

Our results show that predominant interleukin 4 (IL-4) and interferon-gamma secretion of cultured supernatant were detected in healthy donors compared with asthmatics. In the presence of phorbol-12-myristate-13-acetate-ionomycin, with or without CAPE treatment, the asthmatic children showed significantly decreased levels of IL-10 secretion compared with the healthy controls. However, CAPE significantly decreased IL-10 and interferon-gamma in healthy donors. There was a slight but not statistically significant reduction of IL-4 secretion in CAPE-treated PBMCs compared with untreated control PBMCs from the healthy children. Our data also shows that CAPE significantly enhanced transforming growth factor-beta 1 production from PBMCs from asthmatic children.

CONCLUSION

The immunoregulatory effects of CAPE on human PBMCs may be through the induction of regulatory T cells, as evidenced by the enhanced transforming growth factor-beta 1 production from PBMCs from asthmatic children in our study.

Protective effects of caffeic acid phenethyl ester on retinal ischemia/reperfusion injury in rats

PURPOSE

To investigate whether caffeic acid phenethyl ester (CAPE) has a protective effect on retinal ischemia/reperfusion (I/R) injury in rats, and to determine the possible antioxidant mechanisms.

METHODS

Seventy-six female Wistar rats were randomized evenly into Sham, I/R injury model (M group), model plus vehicle (MV), and model plus CAPE (MC) groups. Retinal ischemia/reperfusion injury was induced by increasing the intraocular pressure to 110 mmHg for 60 min. Rats in the MV and MC groups were injected with vehicle and CAPE (10 µmol/kg i.p.), respectively, before reperfusion and once a day for one or seven days after I/R. The levels of malondialdehyde (MDA), superoxide dismutase (SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the retinal tissues were determined 24 hr after I/R. Retinal cells apoptosis was detected 24 hr after I/R injury by terminal deoxynucleotidyl transferase-mediated digoxigenin-dUTP nick-end labeling staining. On day 7 after reperfusion, the electroretinogram (ERG) was recorded, and the retinal histology was examined and quantified using light microscopy.

RESULTS

CAPE significantly decreased the MDA levels and increased the activities of SOD, GSH-Px, and CAT in the retina compared with the ischemia group (p< 0.05). CAPE attenuated the I/R-induced apoptosis of retinal cells in the inner nuclear and ganglion cells of the rat retina. CAPE also suppressed the I/R-induced reduction in the a- and b-wave amplitudes of the ERG (p<0.05). The thickness of the entire retina, inner nuclear layer, and inner plexiform layer and the number of cells in the ganglion cell layer in the MC group were significantly greater than those in the M group (p<0.05).

CONCLUSIONS

CAPE can protect the rat retina from I/R injury by enhancing the antioxidation ability and inhibiting the apoptosis of retinal cells, which suggests that CAPE is potentially useful for treating I/R-induced eye disorders.

Structure-activity relationships in the cytoprotective effect of caffeic acid phenethyl ester (CAPE) and fluorinated derivatives: effects on heme oxygenase-1 induction and antioxidant activities

To determine the relationship between catechol ring modifications and the activity of caffeic acid phenethyl ester (CAPE) as a cytoprotective agent, six catechol ring-fluorinated CAPE derivatives were evaluated for their cytoprotective abilities, as well as for their antioxidant and heme oxygenase-1 (HO-1) inducing capacity in a human umbilical vein endothelial cell (HUVEC) model of oxidant stress. To ascertain the involvement of HO-1 induction in the cytoprotective effects of CAPE analogues, their ability to induce HO-1 at 20microM was determined by reverse transcriptase polymerase chain reaction, western blotting and the use of HO-1 inhibitor tin protoporphyrin IX. There was significant induction of HO-1 by CAPE derivatives. Inhibition of HO-1 enzymatic activity resulted in reduced cytoprotection. Modification of the catechol ring of CAPE by introduction of fluorine at various positions resulted in dramatic changes in cytoprotective activity. The maintenance of at least one hydroxyl group on the CAPE catechol ring and the phenethyl ester portion was required for HO-1 induction. CAPE and its derivatives were screened for their ability to scavenge intracellular reactive oxygen species generated in HUVECs by measuring 5-(and-6)-chlormethyl-2', 7'-dichlorodihydrofluorescein diacetate oxidation. The maintenance of 3, 4-dihydroxyl groups on the catechol ring was required for antioxidant activity, but antioxidant activity did not guarantee cytoprotection. Methylation or replacement of one hydroxyl group on the catechol ring of CAPE, however, provided both pro-oxidant and cytoprotective activities. These results indicate that the induction of HO-1 plays a more important role in the cytoprotective activity of CAPE derivatives than their direct antioxidant activity.

Stability of caffeic acid phenethyl ester and its fluorinated derivative in rat plasma

The stability of caffeic acid phenethyl ester (CAPE) and its fluorinated derivative (FCAPE) in rat plasma and conditions preventing their degradation are reported. Reverse-phase high-pressure liquid chromatography (HPLC) using taxifolin as an internal standard was applied for the quantitative determination of CAPE and FCAPE in rat plasma extracted with ethyl acetate. The assay was validated over a linear range of 0.25-10 microg/mL plasma (r(2) > 0.9990, n = 3). No endogenous interferences were observed in the chromatographic region of interest. The limits of quantification and detection were set at 0.25 and 0.1 microg/mL, respectively. The precision ranged from 0.7 to 13.7% for CAPE, and from 0.4 to 10.4% for FCAPE. Accuracy ranged from -2.8 to 12.4% for CAPE and from -0.6 to 6.8% for FCAPE. The stability was conducted at 4, 25 and 37 degrees C. First-order kinetics was observed for the degradation of CAPE and FCAPE. The energies of activation of CAPE and FCAPE were found to be 17.9 and 20.1 kcal/mol, respectively. Addition of 0.4% of sodium chloride and pH adjustment to 6 prevented their degradation in rat plasma for 24 h and at least one month at -20 degrees C. This study provides useful information for the future pharmacokinetic study of CAPE and FCAPE in rat.

Renal damage in rats induced by myocardial ischemia/reperfusion: Role of nitric oxide

BACKGROUND

It has been demonstrated that myocardial ischemia/reperfusion (MI/R) causes renal damage. However, the mechanism underlying this damage in kidneys during revascularization of myocardium is unclear. Direct renal ischemia/reperfusion has been implicated in the induction of inducible nitric oxide synthase (iNOS) that leads to increase production of nitric oxide (NO). Recently, excessive production of NO has been found to be involved in causing renal injury by formatting peroxinitrite (ONOO(-)). The aim of this study was to investigate whether NO has a role in this damage, using aminoguanidine (AMG), a known iNOS inhibitor and an antioxidant, in rats undergoing MI/R.

METHODS

Male Wistar rats were used for the experiments (n = 7 each group). In the MI/R group, the left coronary artery was occluded for 30 min and then reperfused for 120 min; the same procedure was used for the AMG group, with the additional step of AMG (200 mg/kg) administered 10 min prior to ischemia. A control group underwent sham operation. At the end of the reperfusion period, all rats were killed and their kidneys removed for biochemical determination and histopathological analysis.

RESULTS

Myocardial ischemia/reperfusion in the rat kidney was accompanied by a significant increase in malondialdehyde and NO production, and a decrease in glutathione content. Administration of AMG reduced malondialdehyde and NO production and prevented depletion of glutathione content. These beneficial changes in the biochemical parameters were also associated with parallel changes in histopathological appearance.

CONCLUSION

These findings suggest that MI/R plays a causal role in kidney injury and AMG exerts renal-protective effects, probably by inhibiting NO production and antioxidant activities.