Protective effects of pentoxifylline in retinal ischemia/reperfusion injury

Different Sources of Dietary Magnesium Supplementation Reduces Oxidative Stress by Regulation Nrf2 and NF-κB Signaling Pathways in High-Fat Diet Rats

Magnesium (Mg) is an essential mineral required for many physiological processes, including ionic balances in ocular tissues. We compared the effects of different Mg-chelates (Mg oxide, MgO vs. Mg picolinate, MgPic) on retinal function in a high-fat diet (HFD) rats. Forty-two rats were divided into six groups and treated orally for 8 weeks as follows: Control, MgO, MgPic, HFD, HFD + MgO, and HFD + MgPic. Mg was administered at 500 mg of elemental Mg/kg of diet. HFD intake increased the levels of retinal MDA and NF-κB, INOS, ICAM, and VEGF but downregulated Nrf2. However, in rats supplemented with MgO and MgPic, the retinal MDA level was decreased, compared with the control and HFD rats. Activities of antioxidant enzymes (SOD, CAT, and GPx) were increased in HFD animals given Mg-chelates (p < 0.001), MgPic being the most effective. Mg supplementation significantly decreased the expression levels of NF-κB, INOS, ICAM, and VEGF in HFD rats while increasing the level of Nrf2 (p < 0.001). Mg supplementation significantly decreased the levels of NF-κB, INOS, ICAM, and VEGF and increased Nrf2 level in HFD rats (p < 0.001), with stronger effects seen from MgPic. Mg attenuated retinal oxidative stress and neuronal inflammation and could be considered as an effective treatment for ocular diseases.

Protective effects of pentoxifylline in small intestine after ischemia-reperfusion

Objective

This study was performed to determine the healing effects of pentoxifylline on molecular responses and protection against severe ischemic damage in the small intestine.

Methods

Thirty-six Wistar albino rats were divided into six groups. The superior mesenteric artery was clamped for 120 minutes, and reperfusion was performed for 60 minutes. Saline (0.4 mL), pentoxifylline (1 mg/kg), and pentoxifylline (10 mg/kg) were intraperitoneally administered to the rats in the C₁, P₁, and P₃ groups, respectively, 60 minutes before ischemia and to the rats in the C₂, P₂, and P₄ groups, respectively, during reperfusion onset. Malondialdehyde, myeloperoxidase, tumor necrosis factor alpha, interleukin-1 beta, and interleukin-6 in serum and tissue were measured by enzyme-linked immunosorbent assay. Intestinal ischemic injury was histopathologically evaluated by the Chiu score and immunohistochemical staining.

Results

All serum and tissue molecular responses were significantly blunted in the pentoxifylline-treated groups compared with the controls. Significant improvement in ischemic damage was demonstrated in the pentoxifylline-treated groups by histological grading and immunohistochemical scoring.

Conclusions

The protective effects of pentoxifylline were confirmed by molecular responses and histopathological examination.

Efficacy of pentoxifylline and tadalafil in rat model of ischemic colitis

OBJECTIVE

The aim of this study is to investigate the efficacy of tadalafil against pentoxifylline in rat model of ischemic colitis (IC).

MATERIAL-METHODS

Thirty-two Wistar albino rats were subjected to laparotomy and left colon devascularization to create an IC model and then randomly placed into four groups. Group-1 (sham group) was administered 0.9% NaCl following laparotomy, group 2 (control group) was administered 0.9% NaCl following induced IC, group 3 was given pentoxifylline (n = 8), and group 4 was given tadalafil. On the third day; macroscopic findings, Gomella's ischemic area and Wallace scoring, histopathological analysis, and Chiu scoring were performed, and malondialdehyde (MDA) measurement in ischemic colon tissue was carried out through chemical analysis.

RESULTS

Significant differences were observed in acidic fluid, bowel dilatation, and serosal change (p < .05). The ischemic area measured 63.3 mm(2) in the control group, 2.8 mm(2) in the pentoxifylline group (p = .0001), and 2.4 mm(2) (p = .0001) in the tadalafil group. A significant difference was seen between the sham group and the control and pentoxifylline groups (p < .01), in terms of Wallace score and Chiu classification. Similarly, a significant difference was determined between the control group and pentoxifylline and tadalafil groups (p < .01), but no significant difference was established between the pentoxifylline group and tadalafil group (p = .33). MDA measurement was found on an average to be 63.7 in the control group, 22.7 in group 3 and 22.8 in group 4 (p = 001).

CONCLUSION

Although tadalafil is superior to pentoxifylline, both drugs are considered to have positive effects.

Interaction between leukocytes and erythrocytes in the human retina: effects of pentoxifylline on hyperoxia-induced vasoconstriction during increased neutrophil counts

PURPOSE

Pentoxifylline, a nonselective phosphodiesterase inhibitor, shows vasodilator effects in certain vascular beds and reduces blood viscosity. We have previously shown that under states of vasoconstriction an interaction between circulating erythrocytes and leukocytes may play a role in the control of blood flow. The reason for this observation is not entirely clear but may be related to a mechanical interaction between red and white blood cells. In the present study we hypothesized that pentoxifylline may alter this interaction during oxygen-induced vasoconstriction.

METHODS

24 healthy male subjects participated in this double masked, randomized, placebo-controlled 2 way cross over trial. In order to increase white blood cell count (WBC) count, 300 μg of G-CSF was administered intravenously. Vasoconstriction of retinal vessels was induced by oxygen inhalation. 400mg of pentoxifylline or placebo was infused at two different study days. White blood cell flux was assessed with the blue-field entoptic technique. Vessel calibers were measured with a dynamic vessel analyzer (DVA) and red blood cell velocity (RBCV) was determined with laser Doppler velocimetry (LDV). Retinal blood flow was calculated based on retinal vessel diameters and RBCV.

RESULTS

Administration of G-CSF induced a significant increase in WBC, both in the placebo and the pentoxifylline group (p<0.01 for both groups). Retinal vessel diameter, RBCV, calculated retinal blood flow and white blood cell flow were not altered by administration of pentoxifylline. Hyperoxia induced a pronounced decrease in retinal blood flow parameters. No difference was observed between groups during oxygen breathing in vessel diameters (p=0.54), RBCV (p=0.34), calculated retinal blood flow (p=0.3) and white blood cell flow (p=0.26).

CONCLUSION

Our data indicate that short time administration of pentoxifylline does not alter the oxygen-induced effect on ocular blood flow parameters during leukocytosis. Whether long-term treatment could improve retinal blood flow under states of vasoconstriction remains to be investigated.

Effects of intravenous administration of pentoxifylline in pancreatic ischaemia-reperfusion injury

BACKGROUND

Therapeutic strategies to reduce the occurrence of pancreatic ischaemia-reperfusion (I-R) injury might improve outcomes in human pancreas and kidney transplantation. In addition to its haemorrheologic effects, pentoxifylline has an anti-inflammatory effect by inhibiting NF-κB activation. This group has previously demonstrated that pentoxifylline induces an anti-inflammatory response in acute pancreatitis and liver I-R models. This led to the hypothesis that pentoxifylline might reduce pancreatic and renal lesions and the systemic inflammatory response in pancreatic I-R injury. The aim of this experimental study was to evaluate the effect of pentoxifylline administration in a rat model of pancreatic I-R injury.

METHODS

Pancreatic I-R was performed in Wistar rats over 1 h by clamping the splenic vessels. The animals submitted to I-R were divided into two groups: Group 1 (n = 20, control) rats received saline solution administered i.v. at 45 min after ischaemia, and Group 2 (n = 20) rats received pentoxifylline (25 mg/kg) administered i.v. at 45 min after ischaemia. Blood samples were collected to enable the determination of amylase, creatinine, tumour necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-10. Pancreatic malondialdehyde (MDA) content, pancreas histology and pulmonary myeloperoxidase (MPO) were also assessed.

RESULTS

Significant reductions in serum TNF-α, IL-6 and IL-10 were observed in Group 2 compared with Group 1 (P < 0.05). No differences in pancreatic MDA content or serum amylase levels were observed between the two groups. The histologic score was significantly lower in pentoxifylline-treated animals, denoting less severe pancreatic histologic damage.

CONCLUSIONS

Pentoxifylline administration reduced the systemic inflammatory response, the pancreatic histological lesion and renal dysfunction in pancreatic I-R injury and may be a useful tool in pancreas and kidney transplantation.

Diosmin protects rat retina from ischemia/reperfusion injury

OBJECTIVE

Diosmin, a natural flavone glycoside, possesses antioxidant activity and has been used to alleviate ischemia/reperfusion (I/R) injury. The aim of this study was to clarify whether the administration of diosmin has a protective effect against I/R injury induced using the high intraocular pressure (IOP) model in rat retina, and to determine the possible antioxidant mechanisms involved.

METHODS

Retinal I/R injury was induced in the rats by elevating the IOP to 110 mmHg for 60 min. Diosmin (100 mg/kg) or vehicle solution was administered intragastrically 30 min before the onset of ischemia and then daily after I/R injury until the animals were sacrificed. The levels of malondialdehyde (MDA) and the activities of total-superoxide dismutase (T-SOD), glutathione peroxidase (GSH-Px), and catalase (CAT) in the retinal tissues were determined 24 h after I/R injury. At 7 days post-I/R injury, electroretinograms (ERGs) were recorded, and the density of surviving retinal ganglion cells (RGCs) was estimated by counting retrograde tracer-labeled cells in whole-mounted retinas. Retinal histological changes were also examined and quantified using light microscopy.

RESULTS

Diosmin significantly decreased the MDA levels and increased the activities of T-SOD, GSH-Px, and CAT in the retina of rats compared with the ischemia group (P<0.05), and 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, inner plexiform layer, and outer retinal layer and the number of cells in the ganglion cell layer were significantly less after I/R injury (P<0.05), and diosmin remarkably ameliorated these changes on retinal morphology. Diosmin also attenuated the I/R-induced loss of RGCs of the rat retina (P<0.05).

CONCLUSION

Diosmin protected the retina from I/R injury, possibly via a mechanism involving the regulation of oxidative parameters.

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.

Effect of oral pentoxifylline on cystoid macular edema associated with central retinal vein occlusion

PURPOSE

To determine whether oral pentoxifylline, a xanthine-derived hemorheologic agent, decreases cystoid macular edema (CME) and improves visual acuity in eyes with a perfused central retinal vein occlusion (CRVO).

METHODS

Retrospective chart review of consecutive patients on pentoxifylline (400 mg po TID) for CRVO was performed. Inclusion criteria included CME, pentoxifylline use for at least 1 month, and a follow-up period of at least 4 months. Exclusion criteria included nonperfused or indeterminate CRVO, the presence of neovascularization, and previous or concurrent laser therapy or any other treatment for CRVO. Statistical analysis of collected data was performed.

RESULTS

Eleven patients were identified. All patients had a perfused CRVO. The mean best-corrected Early Treatment Diabetic Retinopathy Study visual acuity was 60 letters (Snellen equivalent 20/128) before the initiation of oral pentoxifylline. The mean time from onset of CRVO to start of pentoxifylline therapy was 5 months (range, 1-12 months). The mean duration of pentoxifylline use was 5.3 months (range, 2.5-10.2 months). The mean follow-up period was 8 months (range, 2.7-16.5 months). Cystoid macular edema had improved in 64% (7/11) of eyes at last follow-up as measured by biomicroscopy and optical coherence tomography. The visual acuity was not significantly changed at 62 letters (20/128 +2) (Student t-test, P = 0.7) at last follow-up. There were no significant side effects from pentoxifylline. One patient had mild gastrointestinal disturbance.

CONCLUSION

Pentoxifylline has a favorable adverse effect profile, and can reduce CME in eyes with CRVO. Visual acuity does not appear to change significantly. A larger, randomized, multiarmed clinical trial evaluating the effects of pentoxifylline as an adjunctive treatment modality may be of benefit since even a small positive effect in altering the natural history of CME related to CRVO may be of value for these patients.

Effects of Vitamin E, Pentoxifylline and Aprotinin on Light-Induced Retinal Injury

PURPOSE

A considerable amount of clinical and experimental evidence exists suggesting the involvement of reactive oxygen species (ROS) in the etiology of light-induced retinal injury. The aim of this study was to investigate the protective role of vitamin E, pentoxifylline (PTX) and aprotinin against light-induced retinal injury in guinea pigs.

METHODS

Thirty adult male guinea pigs were divided into 5 groups of 6 animals each. The first group was used as control. The guinea pigs were kept in cyclic light for 2 weeks before the experiments. The animals were maintained in 12-hour light-dark cycles, before and after exposure to intense white fluorescent light, for as long as 12 h and then returned to cyclic light. Groups 3-5 received intraperitoneal injections of vitamin E, PTX and aprotinin, respectively. One eye of each animal was selected for histopathological evaluation and the other for biochemical assay. Retinal malondialdehyde (MDA) levels and the thickness of the outer nuclear layers were measured.

RESULTS

The compounds had the following relationships: vitamin E more than PTX more than aprotinin in preventing light-induced retinal damage. All 3 gave significant protection against the formation of MDA. Retinas of all 3 treatment groups had been protected from light-induced injury.

CONCLUSION

The intraperitoneal vitamin E, PTX and aprotinin supplementations may strengthen the antioxidant defense system because of decreased ROS, and these agents may play a role in treating light-induced retinal injury.

Pentoxifylline decreases up-regulated nuclear factor kappa B activation and cytokine production in the rat retina following transient ischemia

AIM

To investigate whether pentoxifylline (PTX) could influence the increased cytokine gene expression in the retina flowing transient ischemia, and if so, whether it acts through the modulation of nuclear factor kappa B (NF-kappaB) activation.

METHODS

Sprague-Dawley rats were randomly divided into three equal groups: control group, saline-treated group, and PTX-treated group. Increased intraocular pressure was applied for 90 min to induce retinal ischemia, and reperfusion was established by lowering the bottle to eye level. The reperfusion period lasted for 48 h. In the PTX-treated group, an initial dose of 20 mg PTX was injected via tail vein at the beginning of reperfusion. Then the rat received infusion of PTX at a rate of 6 mg/kg/h throughout the entire reperfusion period. The retinal tissues were collected at the end of 1, 6, 12, 24, and 48 h of reperfusion, respectively, for biochemical analysis. Histological examination was done on the tissues collected at the end of 48 h after reperfusion.

RESULTS

Histological examination revealed reduction of overall retinal thickness and thinning of the inner retinal layer in saline-treated rats after 48-hour reperfusion. However, PTX treatment significantly reduced the loss of overall retinal thickness and thinning of inner retinal layers. Dramatic increase in NF-kappaB activation, tumor necrosis factor-alpha (TNF-alpha) and interleukin-1beta (IL-1beta) production and mRNA expression were observed in the saline-treated group after reperfusion, with the peak reached around 12 h. In the PTX-treated group, NF-kappaB activation, TNF-alpha and IL-1beta production and mRNA expression were significantly reduced at each corresponding time point compared to the saline-treated group.

CONCLUSION

PTX decreased the up-regulated activation of NF-kappaB and the expression of proinflammatory cytokines, TNF-alpha and IL-1beta in rat retinas following ischemia/reperfusion. This may contribute to significantly reduce the loss of overall retinal thickness and thinning of inner retinal layers.

A taurine-supplemented vegan diet may blunt the contribution of neutrophil activation to acute coronary events

Neutrophils are activated in the coronary circulation during acute coronary events (unstable angina and myocardial infarction), often prior to the onset of ischemic damage. Moreover, neutrophils infiltrate coronary plaque in these circumstances, and may contribute to the rupture or erosion of this plaque, triggering thrombosis. Activated neutrophils secrete proteolytic enzymes in latent forms which are activated by the hypochlorous acid (HOCl) generated by myeloperoxidase. These phenomena may help to explain why an elevated white cell count has been found to be an independent coronary risk factor. Low-fat vegan diets can decrease circulating leukocytes--neutrophils and monocytes--possibly owing to down-regulation of systemic IGF-I activity. Thus, a relative neutropenia may contribute to the coronary protection afforded by such diets. However, vegetarian diets are devoid of taurine - the physiological antagonist of HOCl--and tissue levels of this nutrient are relatively low in vegetarians. Taurine has anti-atherosclerotic activity in animal models, possibly reflecting a role for macrophage-derived myeloperoxidase in the atherogenic process. Taurine also has platelet-stabilizing and anti-hypertensive effects that presumably could reduce coronary risk. Thus, it is proposed that a taurine-supplemented low-fat vegan diet represents a rational strategy for diminishing the contribution of activated neutrophils to acute coronary events; moreover, such a regimen would work in a number of other complementary ways to promote cardiovascular health. Moderate alcohol consumption, the well-tolerated drug pentoxifylline, and 5-lipoxygenase inhibitors--zileuton, boswellic acids, fish oil--may also have potential in this regard.

Retinal ischemia: mechanisms of damage and potential therapeutic strategies

Retinal ischemia is a common cause of visual impairment and blindness. At the cellular level, ischemic retinal injury consists of a self-reinforcing destructive cascade involving neuronal depolarisation, calcium influx and oxidative stress initiated by energy failure and increased glutamatergic stimulation. There is a cell-specific sensitivity to ischemic injury which may reflect variability in the balance of excitatory and inhibitory neurotransmitter receptors on a given cell. A number of animal models and analytical techniques have been used to study retinal ischemia, and an increasing number of treatments have been shown to interrupt the "ischemic cascade" and attenuate the detrimental effects of retinal ischemia. Thus far, however, success in the laboratory has not been translated to the clinic. Difficulties with the route of administration, dosage, and adverse effects may render certain experimental treatments clinically unusable. Furthermore, neuroprotection-based treatment strategies for stroke have so far been disappointing. However, compared to the brain, the retina exhibits a remarkable natural resistance to ischemic injury, which may reflect its peculiar metabolism and unique environment. Given the increasing understanding of the events involved in ischemic neuronal injury it is hoped that clinically effective treatments for retinal ischemia will soon be available.