Phosphodiesterase Inhibitor Pentoxifylline Research Articles

Inflammation in Diabetic Kidney Disease: Focus on New Therapeutic Considerations

Diabetic kidney disease (DKD) is the most common cause of end-stage renal disease (ESRD) in the U.S. and worldwide. A role of chronic low-grade inflammation in the microvascular complications in diabetic patients has now been widely accepted, and anti-inflammatory therapies for DKD are being actively pursued. Such therapies may be especially useful in the treatment of patients with chronic kidney disease (CKD) with normal to only moderately increased albuminuria, a DKD phenotype which is becoming more frequent. Current pharmacologic treatment for DKD includes inhibitors of the renin-angiotensin-aldosterone system (RAAS) and the sodium-glucose co-transporter 2 (SGLT2) in the proximal tubule. Both classes of agents are known to reduce blood pressure but also are thought to have anti-inflammatory, antioxidant, and anti-fibrotic effects independent of their hemodynamic actions. Large clinical trials with experimental agents such as bardoxolone and selonsertib that target inflammation and oxidative stress in DKD have been carried out or are in progress. The non-specific phosphodiesterase inhibitor pentoxifylline (PTX) is also being studied in a large US trial to see if this FDA-approved drug may be able to be repurposed to treat DKD. Other agents have also shown promising effects in small clinical trials but require further large-scale investigation.

Discovery of Novel Pain Therapies Without Side‐effects by Combining Targeted Mutagenesis and Phenotype‐based Drug Screening in Larval Zebrafish

IntroductionOpioid drugs provide effective pain relief but come with considerable side‐effects including addiction and respiratory depression which can be lethal with overdose. During the COVID19 pandemic, the opioid epidemic reached almost 100,000 deaths in the United States, highlighting the urgent need to identify pain killers with reduced liability so they can be safely prescribed. One approach to develop safe pain killers is to combine existing opioid analgesics with drugs reducing respiratory depression. Using our novel biotechnology platforms in larval zebrafish, we propose to identify new molecular targets and drugs with potent analgesic properties, reduced respiratory liability, and without addictive properties.MethodsCombining targeted mutagenesis and phenotype‐based drug screening approaches in larval zebrafish in vivo,we can quickly and effectively identify new molecular targets and screen new drug compounds to either target respiratory depression, analgesia (Zaig and Montandon, 2021, eLife), as well as addiction. We first screened customized drug libraries targeting voltage‐gated calcium channels and the adenylyl cyclase pathway, two molecular pathways involved in pain. We are also creating mutants using CRISPR‐cas9 in first generation zebrafish embryos to identify new molecular targets. Using our new models, we quantified respiratory depression by fentanyl in day post‐fertilization 7 larvae, as well as the nociceptive response to formalin.ResultsTo determine the role of calcium channels opioid‐mediated effects, we combined fentanyl and the calcium channel activators nefiracetam (1µM) or FLP‐64176 (1µM). Both nefiractem and FLP‐64176 prevented respiratory depression by fentanyl (1µM). To target the adenylyl cyclase pathway, we combined fentanyl and the phosphodiesterase inhibitors pentoxifylline (50µM), roflumilast (1µM), or dipyridamole (100µM). Pentaxifylline prevented respiratory depression by fentanyl but not roflumilast and dipyridamole. To perform targeted mutagenesis, we injected 4 single guide RNAs targeting the orpm1 gene, i.e. the gene coding for µ‐opioid receptors. Six days later, we measured respiratory depression by fentanyl in knockout larvae or controls. In oprm1‐/‐ knockout larvae, respiratory depression by fentanyl was substantially reduced compared to controls, therefore confirming the validity of our targeted mutagenesis approach. We are currently targeting the genes coding for calcium channels and phosphodiesterases to determine whether they can be molecular targets for respiratory depression and/or analgesia.DiscussionThe successful identification of new drug combinations to prevent respiratory depression while preserving analgesia suggests that our drug discovery platform in larval zebrafish will substantially accelerate the identification of new opioid drugs with reduced morbidity and mortality. Our platform is also being leveraged to discover non‐opioid pain killers with reduced side‐effects.

Pentoxifylline Enhances Antioxidative Capability and Promotes Mitochondrial Biogenesis in D-Galactose-Induced Aging Mice by Increasing Nrf2 and PGC-1α through the cAMP-CREB Pathway

Aging is a complex phenomenon associated with oxidative stress and mitochondrial dysfunction. The objective of this study was to investigate the potential ameliorative effects of the phosphodiesterase inhibitor pentoxifylline (PTX) on the aging process and its underlying mechanisms. We treated D-galactose- (D-gal-) induced aging mice with PTX and measured the changes in behavior, degree of oxidative damage, and mitochondrial ultrastructure and content as well as the expression of nuclear factor erythroid 2-related factor 2- (Nrf2-) mediated antioxidant genes and peroxisome proliferator-activated receptor-gamma coactivator 1-alpha- (PGC-1α-) dependent mitochondrial biogenesis genes. The results demonstrated that PTX improved cognitive deficits, reduced oxidative damage, ameliorated abnormal mitochondrial ultrastructure, increased mitochondrial content and Nrf2 activation, and upregulated antioxidant and mitochondrial biogenesis gene expression in the hippocampus of wild-type aging mice. However, the above antiaging effects of PTX were obviously decreased in the brains of Nrf2-deficient D-gal-induced aging mice. Moreover, in hydrogen peroxide-treated SH-SY5Y cells, we found that cyclic adenosine monophosphate (cAMP) response element-binding protein (CREB) and Nrf2/PGC-1α act in a linear way by CREB siRNA transfection. Thus, PTX administration improved the aging-related decline in brain function by enhancing antioxidative capability and promoting mitochondrial biogenesis, which might depend on increasing Nrf2 and PGC-1α by activating the cAMP-CREB pathway.

Pentoxifylline or theophylline use in hospitalized COVID-19 patients requiring oxygen support.

IntroductionThe phosphodiesterase inhibitors theophylline and pentoxifylline have anti‐inflammatory properties that may make them useful in COVID‐19 pneumonia. We conducted a retrospective review of hospitalized COVID‐19 patients requiring oxygen who received these drugs.ObjectivesTo examine the potential efficacy and safety of theophylline and pentoxifylline in COVID‐19 pneumonia patients.MethodsAdults with a positive test for SARS‐COV2 and were hospitalized due to pneumonia requiring either high flow nasal cannula or mechanical ventilation were included. Patients with a history of asthma or chronic obstructive pulmonary disease were preferentially given theophylline. All other patients received pentoxifylline 400 mg orally TID. A group of hospitalized COVID‐19 patients receiving standard of care acted as a comparison group. The coprimary outcomes were a change in C‐reactive protein (CRP) and ROX score between groups from day 1 to day 4 of therapy.ResultsTwo hundred and nine inpatients were reviewed. Fifty‐eight patients received pentoxifylline/theophylline, with 151 patients serving as the comparison group. Active therapy was associated with an increase in the ROX score (mean: 2.9 (95% CI: 0.6, 5.1)) and decrease in CRP (mean: −0.7 (95% CI: −4.7, 3.2). Mortality rates were theophylline/pentoxifylline 24% and comparison group had a 26%, respectively.ConclusionIn this retrospective study, theophylline and pentoxifylline were associated with an increase in ROX score and nominal decreases in CRP and mortality. Treatment was safe with few adverse reactions documented. We believe that this study could the basis for randomized‐controlled trials to further explore these drugs’ role in COVID‐19.

Enzymatic Activity of CD73 Modulates Invasion of Gliomas via Epithelial-Mesenchymal Transition-Like Reprogramming.

Glioblastoma (GBM) is the most aggressive malignant primary brain tumour in adulthood. Despite strong research efforts current treatment options have a limited impact on glioma stem-like cells (GSCs) which contribute to GBM formation, progression and chemoresistance. Invasive growth of GSCs is in part associated with epithelial–mesenchymal-like transition (EMT), a mechanism associated with CD73 in several cancers. Here, we show that CD73 regulates the EMT activator SNAIL1 and further investigate the role of enzymatic and non-enzymatic CD73 activity in GBM progression. Reduction of CD73 protein resulted in significant suppression of GSC viability, proliferation and clonogenicity, whereas CD73 enzymatic activity exhibited negative effects only on GSC invasion involving impaired downstream adenosine (ADO) signalling. Furthermore, application of phosphodiesterase inhibitor pentoxifylline, a potent immunomodulator, effectively inhibited ZEB1 and CD73 expression and significantly decreased viability, clonogenicity, and invasion of GSC in vitro cultures. Given the involvement of adenosine and A3 adenosine receptor in GSC invasion, we investigated the effect of the pharmacological inhibition of A3AR on GSC maintenance. Direct A3AR inhibition promoted apoptotic cell death and impaired the clonogenicity of GSC cultures. Taken together, our data indicate that CD73 is an exciting novel target in GBM therapy. Moreover, pharmacological interference, resulting in disturbed ADO signalling, provides new opportunities to innovate GBM therapy.

The effect of two phosphodiesterase inhibitors on bone healing in mandibular fractures (animal study in rats).

ObjectivesDespite advances in maxillofacial surgery, impaired bone healing remains a concern for surgical teams. Many studies have evaluated the effects of sildenafil and pentoxifylline on bone healing. However, their effects on healing of bone fractures have not been well investigated. This study aimed to assess the effects of the phosphodiesterase inhibitors sildenafil and pentoxifylline on healing of mandibular fractures in rats.Materials and MethodsA total of 60 rats were randomly divided into six groups of 10. Mandibular fracture was induced in all rats. After the surgical procedure, group C1 received saline, group S1 received 10 mg/kg sildenafil and group P1 received 50 mg/kg pentoxifylline. The rats were sacrificed after 1 week. Groups C4, S4, and P4 received pharmaceutical therapy as in groups C1, S1, and P1 but were sacrificed after 4 weeks. The samples then underwent histological analysis.ResultsThe mean rate of bone healing of mandibular fractures in groups S1 and P1 was significantly higher than in group C1 at 1 week (P<0.001). The mean rate of bone healing of mandibular fractures in group P1 was higher than in group S1 at 1 week (P=0.04). The mean rate of bone healing of mandibular fractures in groups S4 (P=0.001) and P4 (P=0.004) was significantly higher than in group C4 at 4 weeks, but no significant difference was noted in the rate of healing between groups P4 and S4 (P=0.53).ConclusionSildenafil and pentoxifylline can be used as adjuncts to enhance bone healing in rats.

Targeting Inflammation in Diabetic Kidney Disease: Is There a Role for Pentoxifylline?

Diabetic kidney disease (DKD) is the most common cause of ESKD in the United States and worldwide. Current treatment for DKD includes strict glycemic control and normalization of BP with renin-angiotensin-aldosterone system (RAAS) blockade. Although RAAS blockers slow progression of disease, they do not generally prevent ESKD and none of the studies with these agents in DKD included patients who were nonproteinuric, which make up an increasingly large percentage of patients with diabetes now seen in clinical practice. Recent studies with glucagon-like peptide-1 receptor agonists and sodium-glucose cotransporter-2 (SGLT2) inhibitors have shown beneficial renal effects, and the benefits of SGLT2 inhibitors likely extend to patients who are nonproteinuric. However, there remains a need to develop new therapies for DKD, particularly in those patients with advanced disease. A role of chronic low-grade inflammation in microvascular complications in patients with diabetes has now been widely accepted. Large clinical trials are being carried out with experimental agents such as bardoxolone and selonsertib that target inflammation and oxidative stress. The Food and Drug Administration-approved, nonspecific phosphodiesterase inhibitor pentoxifylline (PTX) has been shown to have anti-inflammatory effects in both animal and human studies by inhibiting the production of proinflammatory cytokines. Small randomized clinical trials and meta-analyses indicate that PTX may have therapeutic benefits in DKD, raising the possibility that a clinically available drug may be able to be repurposed to treat this disease. A large, multicenter, randomized clinical trial to determine whether this agent can decrease time to ESKD or death is currently being conducted, but results will not be available for several years. At this time, the combination of RAAS blockade plus SGLT2 inhibition is considered standard of care for DKD, but it may be reasonable for clinicians to consider addition of PTX in patients whose disease continues to progress despite optimization of current standard-of-care therapies.

Oral dosing of pentoxifylline, a pan-phosphodiesterase inhibitor restores bone mass and quality in osteopenic rabbits by an osteogenic mechanism: A comparative study with human parathyroid hormone.

The non-selective phosphodiesterase inhibitor pentoxifylline (PTX) is used for the treatment of intermittent claudication due to artery occlusion. Previous studies in rodents have reported salutary effects of the intraperitoneal administration of PTX in segmental bone defect and fracture healing, as well as stimulation of bone formation. We determined the effect of orally dosed PTX in skeletally mature ovariectomized (OVX) rabbits with osteopenia. The half-maximal effective concentration (EC50) of PTX in rabbit bone marrow stromal cells was 3.07 ± 1.37 nM. The plasma PTX level was 2.05 ± 0.522 nM after a single oral dose of 12.5mg/kg, which was one-sixth of the adult human dose of PTX. Four months of daily oral dosing of PTX at 12.5 mg/kg to osteopenic rabbits completely restored bone mineral density, bone mineral content (BMC), microarchitecture and bone strength to the level of the sham-operated (ovary intact) group. The bone strength to BMC relationship between PTX and sham was similar. The bone restorative effect of PTX was observed in both axial and appendicular bones. In osteopenic rabbits, PTX increased serum amino-terminal propeptide, mineralized nodule formation by stromal cells and osteogenic gene expression in bone. PTX reversed decreased calcium weight percentage and poor crystal packing found in osteopenic rabbits. Furthermore, similar to parathyroid hormone (PTH), PTX had no effect on bone resorption. Taken together, our data show that PTX completely restored bone mass, bone strength and bone mineral properties by an anabolic mechanism. PTX has the potential to become an oral osteogenic drug for the treatment of post-menopausal osteoporosis.

The Phosphodiesterase Inhibitor Pentoxifylline as a Novel Adjunct to Antidepressants in Major Depressive Disorder Patients: A Proof-of-Concept, Randomized, Double-Blind, Placebo-Controlled Trial

Background: There is evidence for an association between major depressive disorder (MDD) and both inflammatory and phosphodiesterase (PDE) pathways. This study aimed to evaluate the adjunct role of the PDE inhibitor pentoxifylline (PTX), a compound with anti-inflammatory properties, in the treatment of adult patients with MDD. Methods: This was a prospective, 12-week, double-blind study of parallel groups. Eighty adult outpatients who met the DSM-IV criteria for MDD participated in the trial. Patients were required to have a baseline Hamilton Rating Scale for Depression (HAM-D) score of at least 18. Patients were allocated randomly: 40 received escitalopram 20 mg/day plus placebo while the other 40 received escitalopram 20 mg/day plus PTX (400 mg b.i.d.). Patients were assessed by a psychiatrist at baseline, and 4, 8, and 12 weeks after the medication had been started. The serum levels of TNF-α, IL-6, IL-10, BDNF, 8-OHdG, and serotonin were measured at baseline and after therapy. Results: After 8 and 12 weeks, the PTX group showed a statistically significantly greater improvement in HAM-D score compared to the control group (least squares mean difference [LSMD] –3.29, p = 0.000 and LSMD –3.49, p = 0.000, respectively). Moreover, the PTX group showed a statistically significantly greater reduction in the serum levels of TNF-α, IL-6, IL-10, and 8-OHdG along with a statistically significant increase in the levels of BDNF and serotonin in comparison with the control group after the treatment. Conclusion: The findings of this study suggest that PTX could be a promising adjunct to antidepressants in the treatment of MDD patients.

Pentoxifylline attenuates the local andsystemic inflammatory response afterinfrarenal abdominal aortic ischemia-reperfusion.

We studied the new anti-inflammatory effects of non-specific phosphodiesterase (PDE) inhibitor pentoxifylline (PTX) on ischaemia-reperfusion injury and postconditioning of the lower extremities. We aimed to examine the oxidative stress parameters (OSP), the inflammatory response and the changes in structure of skeletal muscle after revascularization surgery. 50 Wistar rats in five groups underwent a 60 min infrarenal aortic cross clamping. After the ischaemia in IR+PC group ischemic postconditioning was performed, intermittent 15 seconds reperfusion, 15 seconds ischaemic periods were applied four times. The ischemic phase was followed by a 120 min of reperfusion. In IR+PTX group the animals were treated with PTX. In IR+PC+PTX group both ischemic postconditioning and PTX treatment were performed. Blood samples and biopsy from quadriceps muscle were collected. Plasma malondialdehyde, reduced glutathione, -SH-groups, TNF-alpha, IL-6 concentrations and superoxide dismutase enzyme activity were measured. The levels of OSP and the inflammatory proteins were significantly higher in the IR group. PTX treatment and PC could significantly decrease the levels of OSP and inflammatory proteins. When the animals were co-treated with PTX and PC the results were even better. Inhibition of PDE by PTX could markedly decrease the inflammatory response and moderate the ischaemia-reperfusion damages after lower limb ischemia and reperfusion. Administration of PTX could potentiate the beneficial effects of PC.

Reduction of chlorpyrifos-induced toxicity in human lymphocytes by selected phosphodiesterase inhibitors

One of the most famous and commonly used compounds from organophosphate (OP) family is chlorpyrifos (CP) which is widespreadly used as a powerful insecticide. Previous studies have shown that OPs induce oxidative stress, inflammation and apoptosis by generating the free radicals. The protective effects of three members of phosphodiesterase inhibitor (PDEI) family, including rolipram (RLP), milrinon (MLR) and pentoxifylline (PTX) were evaluated in the human lymphocytes against CP's toxicity. In this case, the level of oxidative stress biomarkers, the viability of the cells and the rate of apoptosis by flow cytometry were investigated. The results of this study revealed that CP makes a significant increase in the level of inflammatory and oxidative stress markers such as meyloperoxidase (MPO), lipid peroxidation (LPO), total thiol molecules (TTM) and total antioxidant potential (TAP), and also makes an enhancement in the rate of apoptosis process. On the other hand, PDEIs and specifically the combination of them restored the negative effects of CP and significantly prevented the apoptosis and oxidative stress imbalance. It is concluded that these PDEIs have positive effects in attenuation, recovery, and protection of CP-induced toxicity in the human lymphocytes.

The role of estrogen in atrazine-mediated inhibition of CD4+ T cell function and induction of CD4+CD25+Foxp3+ regulatory T cells (IRC4P.479)

Abstract The herbicide Atrazine (ATR) is the most common drinking water contaminant in the US. Biochemically, ATR is a phosphodiesterase (PDE) inhibitor and also elevates estrogen via induction of aromatase. Based upon these biochemical activities and several previous studies, ATR is considered potentially immunotoxic. We have previously shown that when activated in the presence of ATR CD4+ T cell proliferation and expression of CD25 and CD69 are significantly reduced. This is accompanied by a 2-5 fold increase in the frequency of Foxp3+ CD25+ Treg. While this phenotype is partially mimicked by treatment with the PDE inhibitor pentoxifylline, the ATR phenotype is more pronounced in cells derived from male mice. This suggests the possibility that estrogen is playing an important role in the observed CD4+ T cell phenotype. To examine the potential role of estrogen in the ATR-associated phenotype, we have investigated the role of the G-protein coupled estrogen receptor, GPER1/GPR-30, in the ATR-mediated inhibition of CD4+ T cell activation and induction of Treg. Treatment with estrogen and the GPER1 agonist G1 mimic the effects of low ATR concentrations. Studies to further define the role of estrogen and GPER1 in the ATR inhibition of T cell activation and iTreg conversion are currently underway.

Rolipram Attenuates Bile Duct Ligation–Induced Liver Injury in Rats: A Potential Pathogenic Role of PDE4

Anti-inflammatory and antifibrotic effects of the broad spectrum phosphodiesterase (PDE) inhibitor pentoxifylline have suggested an important role for cyclic nucleotides in the pathogenesis of hepatic fibrosis; however, studies examining the role of specific PDEs are lacking. Endotoxemia and Toll-like receptor 4 (TLR4)-mediated inflammatory and profibrotic signaling play a major role in the development of hepatic fibrosis. Because cAMP-specific PDE4 critically regulates lipopolysaccharide (LPS)-TLR4-induced inflammatory cytokine expression, its pathogenic role in bile duct ligation-induced hepatic injury and fibrogenesis in Sprague-Dawley rats was examined. Initiation of cholestatic liver injury and fibrosis was accompanied by a significant induction of PDE4A, B, and D expression and activity. Treatment with the PDE4-specific inhibitor rolipram significantly decreased liver PDE4 activity, hepatic inflammatory and profibrotic cytokine expression, injury, and fibrosis. At the cellular level, in relevance to endotoxemia and inflammatory cytokine production, PDE4B was observed to play a major regulatory role in the LPS-inducible tumor necrosis factor (TNF) production by isolated Kupffer cells. Moreover, PDE4 expression was also involved in the in vitro activation and transdifferentiation of isolated hepatic stellate cells (HSCs). Particularly, PDE4A, B, and D upregulation preceded induction of the HSC activation marker α-smooth muscle actin (α-SMA). In vitro treatment of HSCs with rolipram effectively attenuated α-SMA, collagen expression, and accompanying morphologic changes. Overall, these data strongly suggest that upregulation of PDE4 expression during cholestatic liver injury plays a potential pathogenic role in the development of inflammation, injury, and fibrosis.

A Review on the Role of Oxidative Stress and Inflammation in Necrotizing Enterocolitis and Benefits of the Phosphodiesterase Inhibitor Pentoxifylline

A Review on the Role of Oxidative Stress and Inflammation in Necrotizing Enterocolitis and Benefits of the Phosphodiesterase Inhibitor Pentoxifylline

Pentoxifylline and prevention of hyperoxia-induced lung ­injury in neonatal rats

Oxygen exposure plays an important role in the pathogenesis of bronchopulmonary dysplasia (BPD). The phosphodiesterase inhibitor pentoxifylline (PTX) has anti-inflammatory and antifibrotic effects in multiple organs. It was hypothesized that PTX would have a protective effect on hyperoxia-induced lung injury (HILI). Newborn Sprague-Dawley rats were exposed to >95% oxygen (O(2)) and injected subcutaneously with normal saline (NS) or PTX (75 mg/kg) twice a day for 9 d. NS-injected, room air-exposed pups were controls. At days 4 and 9, lung tissue was collected to assess edema, antioxidant enzyme (AOE) activities, and vascular endothelial growth factor (VEGF) expression. At day 9, pulmonary macrophage infiltration, vascularization, and alveolarization were also examined. At day 9, treatment with PTX significantly increased survival from 54% to 88% during hyperoxia. Treatment with PTX significantly decreased lung edema and macrophage infiltration. PTX treatment increased lung AOE activities including those of superoxide dismutase (SOD), catalase (CAT), and glutathione peroxidase (GPX). Furthermore, PTX treatment also increased the gene expression of VEGF189 and VEGF165, increased VEGF protein expression, and improved pulmonary vascularization. These data indicate that the reduced lung edema and inflammation, increased AOE activities, and improved vascularization may be responsible for the improved survival with PTX during hyperoxia. PTX may be a potential therapy in reducing some of the features of BPD in preterm newborns.

Impact of Pentoxifylline on Platelet Function Profiles in Patients With Type 2 Diabetes Mellitus and Coronary Artery Disease on Dual Antiplatelet Therapy With Aspirin and Clopidogrel

The aim of this study was to evaluate the impact of the phosphodiesterase (PDE) inhibitor pentoxifylline on platelet function profiles in patients receiving dual antiplatelet therapy (DAPT). Previous studies have shown that, in patients receiving DAPT, the adjunctive use of a PDE inhibitor enhances platelet inhibition, particularly in those presenting with diabetes mellitus (DM). However, the pharmacodynamic (PD) effects of the PDE inhibitor pentoxifylline on platelet function profiles in DM patients receiving DAPT are unknown. This was a prospective, randomized, double-blind, parallel design study conducted in DM patients with stable coronary artery disease receiving DAPT. Patients were randomly assigned to either pentoxifylline 400 mg or placebo 3 times daily for 14 days. The PD effects were assessed by vasodilator-stimulated phosphoprotein phosphorylation assay, light transmittance aggregometry, VerifyNow P2Y12 assay (Accumetric, Inc., San Diego, California), and multiple electrode aggregometry at baseline and 14 days. The PD effects were also assessed according the presence or absence of high on-treatment platelet reactivity status. A total of 40 patients were available for analysis. At 14 days, there were no differences in the P2Y(12) reactivity index as assessed by vasodilator-stimulated phosphoprotein phosphorylation between treatment groups (primary endpoint; p = 0.93). Intra-group comparisons also failed to show any differences between baseline and 14-day P2Y(12) reactivity index assessment in the placebo and pentoxifylline arms (p = 0.61). There were no significant inter- and intra-group differences in all other PD measures. The PD effects did not vary according the presence or absence of high on-treatment platelet reactivity. Adjunctive treatment with pentoxifylline is not associated with increased platelet inhibitory effects in DM patients with coronary artery disease receiving DAPT.

Pentoxifylline Enhances the Radioprotective Properties of γ-Tocotrienol: Differential Effects on the Hematopoietic, Gastrointestinal and Vascular Systems

The vitamin E analog γ-tocotrienol (GT3) is a potent radioprotector and mitigator. This study was performed to (a) determine whether the efficacy of GT3 can be enhanced by the addition of the phosphodiesterase inhibitor pentoxifylline (PTX) and (b) to obtain information about the mechanism of action. Mice were injected subcutaneously with vehicle, GT3 [400 mg/kg 24 h before total-body irradiation (TBI)], PTX (200 mg/kg 30 min before TBI), or GT3+PTX before being exposed to 8.5-13 Gy TBI. Overall lethality, survival time and intestinal, hematopoietic and vascular injury were assessed. Cytokine levels in the bone marrow microenvironment were measured, and the requirement for endothelial nitric oxide synthase (eNOS) was studied in eNOS-deficient mice. GT3+PTX significantly improved survival compared to GT3 alone and provided full protection against lethality even after exposure to 12.5 Gy. GT3+PTX improved bone marrow CFUs, spleen colony counts and platelet recovery compared to GT3 alone. GT3 and GT3+PTX increased bone marrow plasma G-CSF levels as well as the availability of IL-1α, IL-6 and IL-9 in the early postirradiation phase. GT3 and GT3+PTX were equally effective in ameliorating intestinal injury and vascular peroxynitrite production. Survival studies in eNOS-deficient mice and appropriate controls revealed that eNOS was not required for protection against lethality after TBI. Combined treatment with GT3 and PTX increased postirradiation survival over that with GT3 alone by a mechanism that may depend on induction of hematopoietic stimuli. GT3+PTX did not reduce GI toxicity or vascular oxidative stress compared to GT3 alone. The radioprotective effect of either drug alone or both drugs in combination does not require the presence of eNOS.

IMMUNOMODULATORY PROPERTIES OF PENTOXIFYLLINE ARE MEDIATED VIA ADENOSINE-DEPENDENT PATHWAYS

The phosphodiesterase inhibitor pentoxifylline (PTX) exerts multiple beneficial immunomodulatory effects in states of hyperinflammation. However, the exact mechanism of action still remains elusive, and the clinical effects of PTX cannot be reliably predicted. In immune cells, the G protein-coupled adenosine A2A receptor (A2AR) exerts strong anti-inflammatory effects. As PTX amplifies signaling pathways downstream of Gs protein-coupled receptors, the A2AR-signaling pathway might be involved in the mediation of immune-suppressive effects of PTX. Here, we investigated this assumption in LPS-stimulated human polymorphonuclear (PMN) leukocytes and in anti-CD3/CD28-stimulated human T cells. In stimulated PMN leukocytes, PTX treatment led to a 4.5-fold decrease of the 50% inhibitory concentrations of adenosine on the H2O2 production; i.e., for adenosine plus PTX (in clinically relevant concentrations), an overadditive increase of inhibitory effects from less than 20% (estimated for each) to 56% (+/-5%) was found. In T cells, adenosine plus PTX revealed similar synergistic inhibitory effects on proinflammatory cytokine production. Inhibition of interferon gamma and TNF-alpha production increased from 7% (+/-1%) and 31% (+/-6%) (PTX alone) to 49% (+/-2%) and 69% (+/-6%), respectively. In T cells and PMN leukocytes, mRNA transcription of the A2AR was significantly increased upon stimulation, which was not influenced by PTX. In human PMN leukocytes and T cells, clinically relevant anti-inflammatory effects of PTX can be achieved only in the presence of sufficient adenosine concentrations. Sufficient adenosine levels might be a prerequisite for the accessibility of sepsis patients to treatment with PTX.

A Novel Fluid Resuscitation Strategy Modulates Pulmonary Transcription Factor Activation in a Murine Model of Hemorrhagic Shock

INTRODUCTION:Combining the hemodynamic and immune benefits of hypertonic saline with the anti-inflammatory effects of the phosphodiesterase inhibitor pentoxifylline (HSPTX) as a hemorrhagic shock resuscitation strategy reduces lung injury when compared with the effects of Ringer’s lactate (RL). We hypothesized that HSPTX exerts its anti-inflammatory effects by interfering with nuclear factor kappa B/cAMP response element-binding protein (NF-κB-CREB) competition for the coactivator CREB-binding protein (CBP) in lung tissue, thus affecting pro-inflammatory mediator production.METHODS:Male Sprague-Dawley rats underwent 60 minutes of hemorrhagic shock to reach a mean arterial blood pressure of 35 mmHg followed by resuscitation with either RL or HSPTX (7.5% HS + 25 mg/kg PTX). After four hours, lung samples were collected. NF-κB activation was assessed by measuring the levels of phosphorylated cytoplasmic inhibitor of kappa B (I-κB) and nuclear NF-κB p65 by western blot. NF-κB and CREB DNA-binding activity were measured by electrophoretic mobility shift assay (EMSA). Competition between NF-κB and CREB for the coactivator CBP was determined by immunoprecipitation. Interleukin-8 (IL-8) levels in the lung were measured by ELISA.RESULTS:RL resuscitation produced significantly higher levels of lung IL-8 levels, I-κB phosphorylation, p65 phosphorylation, and NF-κB DNA binding compared with HSPTX. NF-κB-CBP-binding activity was similar in both groups, whereas CREB-CBP-binding activity was significantly increased with HSPTX. CREB-DNA binding-activity increased to a greater level with HSPTX compared with RL.DISCUSSION:HSPTX decreases lung inflammation following hemorrhagic shock compared with conventional resuscitation using RL through attenuation of NF-κB signaling and increased CREB-DNA binding activity. HSPTX may have therapeutic potential in the attenuation of ischemia-reperfusion injury observed after severe hemorrhagic shock.

TNF-α modulates iNOS expression in an experimental rat model of indomethacin-induced jejunoileitis

Multiple mucosal immune factors, such as TNF-alpha and IL-1beta, are thought to be key mediators involved in inflammatory bowel disease. We evaluated the role of the pro-inflammatory cytokine TNF-alpha on nitric oxide synthase (NOS) expression in indomethacin-induced jejunoileitis in rats. Jejunoileitis was induced in rats with subcutaneous injections of indomethacin (7.5 mg/kg) 24 h apart for two consecutive days, and animals were randomized into four groups. Group 1 received only indomethacin. Group 2 was treated with a daily dose of phosphodiesterase (PDE) inhibitor (theophylline or pentoxifylline) by oral gavage for 2 days before and 4 days after indomethacin. Group 3 received a single dose of anti-TNF-alpha monoclonal antibody (TNF-Ab, IP) 30 min before indomethacin. Group 4 was treated with 1 h hyperbaric oxygenation (HBO(2)) for 5 days after indomethacin. Rats were sacrificed at 12 h or 4 days after final indomethacin injection. PDE inhibitor, TNF-Ab, or HBO(2) treatment significantly decreased indomethacin-induced ulceration, myeloperoxidase activity, and disease activity index. Although indomethacin significantly increased serum TNF-alpha and nitrate/nitrite (NOx) concentrations above control values at 12 h, inducible NOS (iNOS) expression was detected only at day 4. Serum IL-1beta levels did not change at 12 h but increased 4-fold after 4 days. Indomethacin had no effect on constitutive NOS. Treatment with PDE inhibitor, TNF-Ab, or HBO(2) significantly reduced serum/tissue TNF-alpha, IL-1beta, NOx, and iNOS expression. Our data show TNF-alpha plays an early pro-inflammatory role in indomethacin-induced jejunoileitis. Additionally, down-regulation of NOx by PDE inhibitors, TNF-Ab, or HBO(2) suggests that TNF-alpha modulates iNOS expression.