Mechanism of the beneficial effects of pentoxifylline during sepsis: maintenance of adrenomedullin responsiveness and downregulation of proinflammatory cytokines

Apoptosis and Bcl-2 Expression in Irradiated Lungs and the Effect of Pentoxifylline

We measured number of bcl-2, apoptotic, neutrophil, and surfactant apoprotein D (SP-D) positive cells in irradiated rat lungs during different time points after the sublethal whole-thorax irradiation of rats. We also investigated the influence of pentoxifylline (PTX) therapy on these markers. Wistar rats were given 15 Gy thoracic irradiation and PTX (35 mg/kg) twice a week. Animals were examined histologically and imunohistochemically at intervals from 1-12 weeks. In non-treated rats compared with treated rats, bcl-2 expression was significantly inhibited from 4 weeks after irradiation. A higher apoptosis presence in non-treated rats from 4 weeks was found and apoptosis development in PTX-treated animals was delayed and started 8 weeks after irradiation. Similar differences were measured during neutrophil granulocytes examination. Neutrophil penetration in non-treated rats was found 5 weeks after irradiation in contrast to the RP onset of PTX-treated animals 8 weeks after irradiation. The number of SP-D positive cells in non-treated rats observed until 5 weeks after irradiation was higher than in the control group. PTX-treated animals expressed higher number of SP-D positive cells during the whole experiment than the control group. We suggest that apoptosis is linked to neutrophil granulocyte actions during the RP onset and that PTX-therapy causes diminished inflammation development.

The effect of PrP(Sc) accumulation on inflammatory gene expression within sheep peripheral lymphoid tissue

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Arrays quantified gene expression in peripheral LNs during sheep scrapie.

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Disease progression associated with alterations of inflammatory gene expression.

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Lymph node response contrasts with response of CNS.

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Step changes to gene expression after the detection of PrP^Sc in peripheral LNs.

Accumulation of the misfolded prion protein, PrP^Sc in the central nervous system (CNS) is strongly linked to progressive neurodegenerative disease. For many transmissible spongiform encephalopathies (TSEs), peripheral lymphoid tissue is an important site of PrP^Sc amplification but without gross immunological consequence. Susceptible VRQ homozygous New Zealand Cheviot sheep were infected with SSBP/1 scrapie by inoculation in the drainage area of the prescapular lymph nodes. The earliest time that PrP^Sc was consistently detected by immunohistology in these nodes was D50 post infection. This transcriptomic study of lymph node taken before (D10) and after (D50) the detection of PrP^Sc, aimed to identify the genes and physiological pathways affected by disease progression within the nodes as assessed by PrP^Sc detection. Affymetrix Ovine Gene arrays identified 75 and 80 genes as differentially-expressed at D10 and D50, respectively, in comparison with control sheep inoculated with uninfected brain homogenate. Approximately 70% of these were repressed at each time point. RT-qPCR analysis of seven genes showed statistically significant correlation with the array data, although the results for IL1RN and TGIF were different between the two technologies. The ingenuity pathway analysis (IPA) and general low level of repression of gene expression in lymphoid tissue, including many inflammatory genes, contrasts with the pro-inflammatory and pro-apoptotic events that occur within the CNS at equivalent stages of disease progression as assessed by PrP^Sc accumulation.

Adrenomedullin reduces expression of adhesion molecules on lymphatic endothelial cells

Adrenomedullin (AM) is a novel vasoactive peptide which regulates vascular tone and vascular endothelial cell growth. We recently reported that lymphatic endothelial cells (LECs) are also an attractive target of AM and concluded that AM is a potent mediator of lympangiogenesis. In the present study, we conducted a genome-wide analysis of genes that are regulated by AM in LECs. AM profoundly suppressed gene expression of cell adhesion receptors and inflammatory factors in LECs, such as intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), endothelial adhesion molecule-1 (E-selectin), interleukin-8, and chemokines, QRT-PCR and flow cytometry analysis showed that AM dose-dependently suppressed the TNF-a-induced mRNA and protein expression of ICAM-1 and VCAM-l. Treatment of LECs with a cell permeable cyclic adenosine monophosphate (cAMP) analog, 8-Br-cAMP, mimicked the suppressive effect of AM on the expression of adhesion molecules. Moreover, both AM and 8-Br-cAMP suppressed TNF-α-induced NF-κB activation in LECs, indicating that AM reduces expression of adhesion molecules in LECs via a cAMP/NF-kB dependent pathway. These results suggest that AM may have an important role in the regulation of the expression of adhesion molecules in lymphatic endothelium, which is critical in the control of immune and inflammatory responses.

Adrenomedullin and adrenomedullin binding protein-1 protect endothelium-dependent vascular relaxation in sepsis

Downregulation of vascular endothelial constitutive nitric oxide synthase (ecNOS) contributes to the vascular hyporesponsiveness in sepsis. Although coadministration of the potent vasodilatory peptide adrenomedulin (AM) and the newly discovered AM binding protein (AMBP-1) maintains cardiovascular stability and reduces mortality in sepsis, it remains unknown whether AM/AMBP-1 prevents endothelial cell dysfunction. To investigate this possibility, we subjected adult male rats to sepsis by cecal ligation and puncture (CLP), with or without subsequent intravenous administration of the combination of AM (12 microg/kg) and AMBP-1 (40 microg/kg). Thoracic aortae were harvested 20 h after CLP (i.e., the late stage of sepsis) and endothelium-dependent vascular relaxation was determined by the addition of acetylcholine (ACh) in an organ bath system. In addition, ecNOS gene and protein expression was assessed by RT-PCR and immunohistochemistry, respectively. The results indicate that ACh-induced (i.e., endothelium-dependent) vascular relaxation was significantly reduced 20 h after CLP. Administration of AM/AMBP-1 prevented the reduction of vascular relaxation. In addition, ecNOS gene expression in aortic and pulmonary tissues was downregulated 20 h after CLP and AM/AMBP-1 attenuated such a reduction. Moreover, the decreased ecNOS staining in thoracic aortae of septic animals was prevented by the treatment with AM/AMBP-1. These results, taken together, indicate that AM/AMBP-1 preserves ecNOS and prevents reduced endothelium-dependent vascular relaxation (i.e., endothelial cell dysfunction) in sepsis. In light of our recent finding that AM/AMBP-1 improves organ function and reduces mortality in sepsis, it is most likely that the protective effect of these compounds on ecNOS is a mechanism responsible for the salutary effect of AM/AMBP-1 in sepsis.

Effect of pentoxifylline on lung inflammation and gas exchange in a sepsis-induced acute lung injury model

Experimental models of sepsis-induced pulmonary alterations are important for the study of pathogenesis and for potential intervention therapies. The objective of the present study was to characterize lung dysfunction (low PaO2 and high PaCO2, and increased cellular infiltration, protein extravasation, and malondialdehyde (MDA) production assessed in bronchoalveolar lavage) in a sepsis model consisting of intraperitoneal (ip) injection of Escherichia coli and the protective effects of pentoxifylline (PTX). Male Wistar rats (weighing between 270 and 350 g) were injected ip with 10(7) or 10(9) CFU/100 g body weight or saline and samples were collected 2, 6, 12, and 24 h later (N = 5 each group). PaO2, PaCO2 and pH were measured in blood, and cellular influx, protein extravasation and MDA concentration were measured in bronchoalveolar lavage. In a second set of experiments either PTX or saline was administered 1 h prior to E. coli ip injection (N = 5 each group) and the animals were observed for 6 h. Injection of 10(7) or 10(9) CFU/100 g body weight of E. coli induced acidosis, hypoxemia, and hypercapnia. An increased (P < 0.05) cell influx was observed in bronchoalveolar lavage, with a predominance of neutrophils. Total protein and MDA concentrations were also higher (P < 0.05) in the septic groups compared to control. A higher tumor necrosis factor-alpha (P < 0.05) concentration was also found in these animals. Changes in all parameters were more pronounced with the higher bacterial inoculum. PTX administered prior to sepsis reduced (P < 0.05) most functional alterations. These data show that an E. coli ip inoculum is a good model for the induction of lung dysfunction in sepsis, and suitable for studies of therapeutic interventions.

Cyclic adenosine monophosphate-phosphodiesterase inhibitors reduce skeletal muscle protein catabolism in septic rats

We have previously shown that catecholamines exert an inhibitory effect on muscle protein degradation through a pathway involving the cyclic adenosine monophosphate (cAMP) cascade in normal rats. In the present work, we investigated in vivo and in vitro effects of cAMP-phosphodiesterase inhibitors on protein metabolism in skeletal muscle from rats submitted to a model of acute sepsis. The in vivo muscle protein metabolism was evaluated indirectly by measurements of the tyrosine interstitial concentration using microdialysis. Muscle blood flow (MBF) was monitored by ethanol perfusion technique. Sepsis was induced by cecal ligation and puncture and resulted in lactate acidosis, hypotension, and reduction in MBF (-30%; P < 0.05). Three-hour septic rats showed an increase in muscle interstitial tyrosine concentration (approximately 150%), in arterial plasma tyrosine levels (approximately 50%), and in interstitial-arterial tyrosine concentration difference (approximately 200%; P < 0.05). Pentoxifylline (50 mg/kg of body weight, i.v.) infusion during 1 h after cecal ligation and puncture prevented the tumor necrosis factor alpha increase and significantly reduced by 50% (P < 0.05) the interstitial-arterial tyrosine difference concentration. In situ perfusion with isobutylmethylxanthine (IBMX; 10(-3) M) reduced by 40% (P < 0.05) the muscle interstitial tyrosine in both sham-operated and septic rats. Neither pentoxifylline nor IBMX altered MBF. The addition of IBMX (10(-3) M) to the incubation medium increased (P < 0.05) muscle cAMP levels and reduced proteolysis in both groups. The in vitro addition of H89, a protein kinase A inhibitor, completely blocked the antiproteolytic effect of IBMX. The data show that activation of cAMP-dependent pathways and protein kinase A reduces muscle protein catabolism during basal and septic state.

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.

[Role of adrenomedullin in the pathogenesis and treatment of cardiovascular dysfunctions and sepsis]

Adrenomedullin (AM) is an endogenous vasodilatory peptide hormone, which plays a key role in the regulation and preservation of cardiovascular and pulmonary functions. Clinical and experimental studies have demonstrated that AM represents an alternative therapeutic option in the treatment of pulmonary hypertension. In addition, AM proved to be useful in the treatment of cardiovascular dysfunctions, such as arterial hypertension and congestive heart failure following myocardial infarction. Recent research has also shown that AM plays a pivotal role in the development of sepsis-associated hemodynamic and microcirculatory disorders. Experimental studies also suggest that infusion of exogenous AM might be a rational approach to prevent and treat hypodynamic septic shock. The objectives of this review article are to characterize the regulative properties of AM and to discuss clinical and experimental studies which allow to judge the role of AM in the setting of cardiovascular dysfunction and sepsis.

Hypernociceptive role of cytokines and chemokines: targets for analgesic drug development?

Pain is one of the classical signs of the inflammatory process in which sensitization of the nociceptors is the common denominator. This sensitization causes hyperalgesia or allodynia in humans, phenomena that involve pain perception (emotional component+nociceptive sensation). As this review focuses mainly on animal models, which don't allow discrimination of the emotional component, the terms nociception and hypernociception are used to describe overt behavior induced by mechanical stimulation and increase of nociceptor sensitivity, respectively. Pro- and anti-inflammatory cytokines and chemokines are endogenous small protein mediators released by local or migrating cells whose balance modulates the intensity of inflammatory response. The inflammatory stimuli or tissue injuries stimulate the release of characteristic cytokine cascades, which ultimately trigger the release of final mediators responsible for inflammatory pain. These final mediators, such as prostanoids or sympathetic amines, act directly on the nociceptors to cause hypernociception, which results from the lowering of threshold due to modulation of specific voltage-dependent sodium channels. Furthermore, a direct effect of cytokines on nociceptors is also described. On the other hand, there are also anti-inflammatory cytokines, such as interleukin (IL)-10, IL-4 and IL-13, and IL-1 receptor antagonists (IL-1ra), which inhibit the production of hypernociceptive cytokines and/or the final hypernociceptive mediators, preventing the installation of or the increase in the hypernociception. This review highlights the importance of the direct and indirect actions of cytokines and chemokines in inflammatory and neuropathic hypernociception, emphasizing the evidence suggesting these molecules are potential targets to develop novel drugs and therapies for the treatment of pain.

Differential induction of adrenomedullin, interleukins and tumour necrosis factor-alpha by lipopolysaccharide in rat tissues in vivo

The aim of the present study was to determine the temporal changes in tissue adrenomedullin (AM) and cytokine contents and cytokine and preproAM mRNA levels in the kidney, liver, adrenal gland and spleen of lipopolysaccharide (LPS)-treated rats. Rats were injected with LPS (10 mg/kg, i.p.). Radioimmunoassay and solution hybridization-RNase protection assays were used to follow the changes in AM and its mRNA levels, respectively; ELISA and reverse transcription-polymerase chain reaction were used to follow the changes in cytokines and their mRNA levels, respectively. In the kidney, the preproAM mRNA levels were increased 1 and 3 h after LPS treatment, whereas AM levels were decreased at 3 h. Interleukin (IL)-6 and IL-1beta levels were increased at 3 and 6 h, respectively. The preproAM mRNA levels were elevated in the liver 3 h after LPS injection. Concentrations of tumour necrosis factor (TNF)-alpha and IL-1beta were increased at l and 6 h, respectively. There were no changes in the levels of either preproAM mRNA or AM in the adrenal gland and the spleen. In the spleen, TNF-alpha levels were elevated at 1 and 3 h after LPS injection and IL-1beta was elevated at 1 and 6 h after LPS injection, whereas in the adrenal gland IL-1beta was elevated at 6 h after injection. The mRNA levels of the three cytokines were elevated at all three time intervals examined in the kidney, liver, adrenal gland and spleen, with the exception that TNF-alpha mRNA was not elevated in the adrenal gland at 6 h after LPS injection and IL-1beta mRNA was not elevated in the spleen at 3 and 6 h. The plasma concentrations of TNF-alpha were increased at 1 and 3 h after LPS injection, whereas plasma concentration of IL-1beta and IL-6 were elevated at 3 and 6 h for both. The present results suggest that the biosynthesis and secretion of AM may be differentially regulated in various tissues of rats injected with LPS and that AM may interact with cytokines during inflammation.

The effects of pentoxifylline on diabetic renal changes in streptozotocin-induced diabetes mellitus

The aim of the study was to investigate the effects of pentoxifylline on the renal growth, the epidermal growth factor receptor expression, and renal total nitric oxide content in streptozotocin-induced diabetic rats. Adult male Wistar albino rats were randomly divided into three groups: normal control (the N group), diabetic nephropathy (the DN group), and diabetic nephropathy treated with pentoxifylline at the dosage of 20 mg x kg(-1) x d(-1), intraperitoneally (the group DNP). Diabetes was induced by injection of streptozotocin intraperitoneally. The kidney wet weight (KWW) and dry weight (KDW), fractional kidney weight (FKW), glomerular volume (VG), renal tissue protein (RTP) contents, and renal tissue total nitric oxide (NO) production were determined after the rats were sacrificed on 10th day. There was a significant increase in KWW and KWD in the DNP and DN groups when compared to the N group (p=0.000 for the DNP group, p = 0.000 and p < 0.01 for the DN group). In the DN group, FKW was increased for both wet and dry kidney weight (p<0.05 and p=0.001, respectively) while in the DNP group there was increase in FKW only for dry kidney weight. VG was increased in both two diabetic groups (p<0.05), but this increase was less prominent in the rats treated with pentoxifylline. RTP was significantly decreased in the DNP group when compared with the values in the DN group (p < 0.05). Immunohistochemically epidermal growth factor receptor expression was increased in diabetic rats, and it was not affected by pentoxifylline treatment. In diabetic rats renal content of total NO was decreased (p<0.05 for the DNP group, p<0.01 for the DN group). In conclusion, the results provide that pentoxifylline may have some beneficial effects on renal changes in streptozotocin-induced diabetic rats.

Pentoxifylline does not improve outcome in a murine model for the multiple-organ dysfunction syndrome

OBJECTIVE

To investigate the effects of pentoxifylline (PTX) administration in a murine model for the multiple-organ dysfunction syndrome (MODS).

DESIGN AND SETTING

Prospective double-blind randomized animal study in a university research laboratory.

INTERVENTIONS AND MEASUREMENTS

Sixty C57BL/6 mice were given an aseptic intraperitoneal injection of lipopolysaccharide followed after 6 days by zymosan (day 0) at a dose of either 0.9 or 1.0 mg/g body weight. Starting on day 0 mice were administered PTX at a dose of 80 mg/kg body weight or saline per os every 8 h. On day 17 surviving animals were killed, and their liver, lungs, spleen, and kidneys were collected.

RESULTS

Mortality, course of body temperature, body weight, and macroscopic lung damage were similar between zymosan-treated groups. Administration of PTX did not significantly alter survival, body temperature, body weight, or macroscopic lung damage. In addition, there were no significant differences in organ weights between mice that received PTX and mice that received PBS. Although PTX inhibited the lipopolysaccharide-induced increase in tumor necrosis factor alpha and interleukin 6 expression (but not interleukin 1beta expression) at both mRNA and protein level in a murine macrophage cell line, tumor necrosis factor alpha mRNA expression in the livers of PTX-treated mice was not significantly inhibited.

CONCLUSIONS

The results reported here do not support the hypothesis that PTX improves outcome in zymosan-induced multiple-organ dysfunction in mice.

Preincisional intravenous pentoxifylline attenuating perioperative cytokine response, reducing morphine consumption, and improving recovery of bowel function in patients undergoing colorectal cancer surgery

Cytokine release during surgery can produce a long-lasting hyperalgesia. Thus, preoperatively-administered cytokine inhibitors might reduce the production of cytokines, decreasing central nervous system sensitization and improving the quality of postoperative pain relief. We investigated the hypothesis that preincisional IV pentoxifylline (PTX) treatment could attenuate the release of proinflammatory (tumor necrosis factor, interleukin (IL)-1beta, IL-6, and IL-8) and antiinflammatory (IL-1 receptor antagonist) cytokines in patients who underwent elective colorectal cancer surgery. Forty patients were randomly assigned to 1 of 2 groups of 20 each: the PTX group received a PTX 5 mg/kg IV infusion before the induction of anesthesia, whereas the control group received an equal volume of normal saline. Venous blood samples were obtained at frequent intervals. After surgery, all patients received patient-controlled analgesia (PCA) morphine for postoperative pain relief. Patients in the PTX group exhibited longer PCA trigger times, less morphine consumption, and a faster return of bowel function compared with patients in the control group. Moreover, the plasma levels of IL-6, IL-8, and IL-1 receptor antagonist were less in the treatment group, and there was no significant difference in wound infections, tumor recurrence, or metastatic rates between groups during a 2-yr follow-up.

Upregulation of cardiovascular ghrelin receptor occurs in the hyperdynamic phase of sepsis

Ghrelin, a newly identified endogenous ligand for growth hormone secretagogue receptor 1a (GHSR-1a, i.e., ghrelin receptor), was recently demonstrated to be a potent vasoactive peptide. Although sepsis is characterized by an early, hyperdynamic phase, it remains unknown whether ghrelin or GHSR-1a plays a role in the cardiovascular response to sepsis. To determine this, polymicrobial sepsis was induced by cecal ligation and puncture in male adult rats. At 5 h (i.e., early sepsis) or 20 h (i.e., late sepsis) after cecal ligation and puncture, blood and tissue samples were collected. Ghrelin levels and ghrelin and GHSR-1a mRNA expression were assessed by RIA and RT-PCR, respectively. In addition, GHSR-1a protein levels in aorta, heart, and small intestine were determined by Western blotting. The vascular response to ghrelin was determined by using an isolated gut preparation. A primary rat aortic smooth muscle cell culture was used to determine the effects of LPS on GHSR-1a expression. The results indicate that although ghrelin levels decreased at early and late sepsis, its receptor was markedly elevated in early sepsis. Moreover, ghrelin-induced relaxation in resistance blood vessels of the isolated small intestine increased significantly during early sepsis but was not altered in late sepsis. Furthermore, GHSR-1a expression in smooth muscle cells was significantly increased at mRNA and protein levels with stimulation by LPS at 10 ng/ml. These results demonstrate that GHSR-1a expression is upregulated and vascular sensitivity to ghrelin stimulation is increased in the hyperdynamic phase of sepsis.

Pentoxifylline reduces acute lung injury in chronic endotoxemia

BACKGROUND

Pentoxifylline (PTX) attenuates end-organ injury in models of sepsis and hemorrhage. PTX is thought to act by inhibiting phosphodiesterase, thus increasing cAMP and decreasing tumor necrosis factor-alpha (TNF-alpha) synthesis. The effects of PTX on neutrophil and endothelial cell adhesion molecules and, ultimately, organ injury in a chronic endotoxemia model have not been studied. We hypothesized that continuous infusion of PTX reduces acute lung injury (ALI) caused by chronic lipopolysaccharide (LPS) exposure.

MATERIALS AND METHODS

Male Sprague-Dawley rats were given continuous infusion of LPS, PTX + LPS combined, or saline (sham) by implantable pumps. Neutrophil CD11b expression, lung histopathology, lung intercellular adhesion molecule-1 (ICAM-1) expression assessed by immune staining, serum TNF-alpha, serum interleukin-6 (IL-6), and bronchoalveolar lavage (BAL) IL-8 were evaluated at different time points. Lung injury was graded in a blinded fashion from 0 (normal) to 4 (severe) for interstitial inflammation, neutrophil infiltration, congestion, and edema. Total lung injury score (TLIS) was calculated by adding listed categories. White cell count in the peripheral blood and in the BAL was also performed.

RESULTS

Animals treated with PTX + LPS showed a significant reduction in lung injury score, a marked decrease in ICAM-1 expression, and a significant decrease in IL-8 levels in the BAL and serum IL-6 levels when compared with LPS-treated animals.

CONCLUSIONS

Continuous infusion of PTX reduces ALI caused by chronic endotoxemia. The effect seems to be a result of decreased expression of endothelial and epithelial ICAM-1 and modulation of proinflammatory cytokine synthesis.

Protective effects of pentoxifylline in retinal ischemia/reperfusion injury

We studied the effect of pentoxifylline on retinal lipid peroxidation and histopathologic changes due to ischemia/reperfusion (I/R). A total of 15 pigmented male guinea pigs were divided into 3 equal groups as control, sham and treatment groups. After application of high intraocular pressure for 90 min for the induction of retinal ischemia, 24-hour reperfusion was established in the sham and treatment groups. In the treatment and sham groups, either 45 mg/kg of pentoxifylline or saline was given 3 times at 8-hour intervals. Biochemical assay and histopathologic evaluation were performed on one randomly selected eye of each animal which was enucleated at the end of the reperfusion period, and retinal malondialdehyde (MDA) levels and thickness of the retinal tissue were determined for each group. The mean MDA level of the sham group was significantly higher versus the control and treatment groups (p < 0.001). When compared with the control group, the mean MDA level of the treatment group was slightly higher, but the difference was not statistically significant (p > 0.05). In comparison with the control group there was a significant increase in the thickness of the retina in the sham group (p < 0.0001), and no significant difference was found in the retinal thickness of the treatment group (p > 0.05). Pentoxifylline might have a preventive effect on the I/R injury of the retina.

Adrenomedullin and adrenomedullin binding protein-1: their role in the septic response

Adrenomedullin (AM) is a recently discovered, potent vasodilatory peptide with activities including maintenance of cardiovascular and renal homeostasis. Studies have indicated that AM is important in initiating the hyperdynamic response during the early stage of sepsis, and reduction of the vascular effects of AM marks the transition from the initial hyperdynamic phase to the late hypodynamic phase in experimental sepsis. The decreased AM responsiveness in late sepsis may be related to alterations in the AM receptor binding characteristics and/or signaling pathways. Genetic experiments have provided useful information by enhancing AM gene expression. Moreover, a plasma protein which binds AM, adrenomedullin binding protein-1 (AMBP-1), was reported very recently and is just beginning to be investigated as an important modulator in the biphasic septic response. In this regard, our recent results have demonstrated that AMBP-1 synergistically enhanced AM-induced vascular relaxation in both sham and septic animals. It appears that decreased levels of AMBP-1 play a critical role in producing vascular AM hyporesponsiveness during the late stage of sepsis. Furthermore, administration of AM and AMBP-1 in combination prevented the transition from the hyperdynamic to hypodynamic response during the progression of polymicrobial sepsis. Thus, modulation of vascular responsiveness to AM by AMBP-1 may provide a novel approach for the management of sepsis.

Adrenomedullin binding protein-1 modulates vascular responsiveness to adrenomedullin in late sepsis

Adrenomedullin (AM), a potent vasodilatory peptide, plays an important role in initiating the hyperdynamic response during the early stage of sepsis. Moreover, the reduced vascular responsiveness to AM appears to be responsible for the transition from the early, hyperdynamic to the late, hypodynamic phase of sepsis. Although the novel specific AM binding protein-1 (AMBP-1) enhances AM-mediated action in a cultured cell line, it remains to be determined whether AMBP-1 plays any role in modulating vascular responsiveness to AM during sepsis. To study this, adult male rats were subjected to sepsis by cecal ligation and puncture (CLP). The thoracic aorta was harvested for determination of AM-induced vascular relaxation. Aortic levels of AMBP-1 were determined by Western blot analysis, and AM receptor gene expression in the aortic tissue was assessed by RT-PCR. The results indicate that AMBP-1 significantly enhanced AM-induced vascular relaxation in aortic rings from sham-operated animals. Although vascular responsiveness to AM decreased at 20 h after CLP (i.e., the late, hypodynamic stage of sepsis), addition of AMBP-1 in vitro restored the vascular relaxation induced by AM. Moreover, the aortic level of AMBP-1 decreased significantly at 20 h after CLP. In contrast, AM receptor gene expression was not altered under such conditions. These results, taken together, suggest that AMBP-1 plays an important role in modulating vascular responsiveness to AM, and the reduced AMBP-1 appears to be responsible for the vascular AM hyporesponsiveness observed during the hypodynamic phase of sepsis.

Adrenomedullin has multiple roles in disease stress: development and remission of the inflammatory response

The upregulation of adrenomedullin (AM) gene expression and increases in systemic circulatory as well as localized tissue AM concentrations is well coordinated with the onset and progression of trauma, infection, and sepsis. As such, the coordinated change in AM suggests a key role for this peptide in the inflammatory response. By clinical definition, the process of inflammation constitutes an orchestrated cascade of localized tissue and systemic responses to immunological challenges. Classical responses to the onset of disease stresses are manifested in the timely elaboration of humoral, blood-borne signal effectors (such as adrenocortical and locally produced tissue hormones, immune cytokines, and inorganic signals such as nitric oxide) as well as patterned migration and infiltration of circulating bone marrow-derived cells (mononuclear cells such as monocyte-macrophages and polymorphonuclear cells like neutrophils) largely associated with or delivered through the vascular system. The body's attempts to combat acute infection to restore homeostatic equilibrium are further compromised by underlying disease situations. Atherosclerosis, diabetes, and cardiovascular disease, as well as nutritional metabolic derangements and persistent subclinical infection perturb the regulatory feedback loops necessary for proper control of response effectors like hormones and cytokines. When imbalances occur, tissue necrosis can ensue as driven by free radical damage to cell components. A true appreciation of the inflammatory response can only be grasped through an integrative approach in which the relationship between the different physiological systems is viewed in terms of a changing, dynamic interaction. In essence, the inflammatory response can be thought of in three phases: a period of severity assessment, a period of remediation, and a period of homeostatic restoration. Indeed, AM has differential effects on cellular metabolism, immune function, endocrine function, and cardiovascular function. This peptide appears to play a pivotal role in both reprioritizing the biological needs of tissues and organs during the three phases of inflammatory response as well as a role in restoring homeostatic equilibrium to the body.

Andrenomedullin and cardiovascular responses in sepsis

The typical cardiovascular response to polymicrobial sepsis is characterized by an early, hyperdynamic phase followed by a late, hypodynamic phase. Although the factors and/or mediators responsible for producing the transition from the hyperdynamic to the hypodynamic stage are not fully understood, recent studies have suggested that adrenomedullin (AM), a potent vasodilatory peptide, appears to play an important role in initiating the hyperdynamic response following the onset of sepsis. In addition, the reduced vascular responsiveness to AM may result in the transition from the early, hyperdynamic phase to the late, hypodynamic phase of sepsis. It is possible that changes in newly reported AM receptors calcitonin receptor-like receptor (CRLR) and receptor activity modifying protein-2 or -3 (RAMP2, RAMP3) as well as AM binding protein-1 (AMBP-1) may also play distinct roles in the biphasic cardiovascular response observed during sepsis. Although it remains unknown whether AM gene delivery or a chronic increase in vascular AM production in transgenic animals attenuates the development of hypodynamic sepsis and septic shock, it has been shown that modulation of AM vascular responsiveness with pharmacologic agents reduces sepsis-induced mortality. It has been recently demonstrated that AMBP-1 enhances AM's physiologic effects and plasma levels of AMBP-1 decrease following infections. We therefore propose that downregulation of AMBP-1 and the reduced AM receptor responsiveness are crucial factors responsible for the transition from the hyperdynamic phase to the hypodynamic phase of sepsis.

Pentoxifylline influences the autocrine function of organ cultured donor corneas and enhances endothelial cell survival

BACKGROUND/AIMS

Scientific interest in pentoxifylline has been reawakened owing to the recognised effects of this drug on immune functions, particularly its influence on cytokine production. In a previous study, the authors demonstrated that spiking of organ culture media with endotoxin elicited a marked enhancement in the release of IL-6 and IL-8 from corneal tissue and that these events coincided with degenerative changes in endothelial cells and a higher incidence of actual loss among this population. Since traces of donor derived endotoxin can be detected in up to 50% of corneal organ cultures, this substance may have a direct influence on graft viability or trigger inflammatory responses in the host. They, therefore, wished to ascertain whether supplementation of media with pentoxifylline improved endothelial cell survival in organ cultured donor corneas.

METHODS

12 fellow pairs of donor corneas were cultured for 20 days, with a change of medium on day 10: One of each pair was incubated in the absence, and the other in the presence, of pentoxifylline (25 microg/ml). Samples of medium were withdrawn at regular intervals during the course of incubation and screened for cytokines IL-6, IL-8, and prostaglandin E2 by ELISA. Endothelial cell morphology and numerical density were assessed on days 0, 10 and 20.

RESULTS

Addition of pentoxifylline to organ culture media led to a significant improvement in endothelial cell survival. This drug also elicited a significant increase in the level of IL-6 and marginally suppressed that of IL-8 during the initial 10 day phase of incubation. During the second 10-20 day phase, the level of both IL-6 and IL-8 decreased significantly in the presence of pentoxifylline, the relation between these two cytokines being the inverse of that observed in the absence of the drug. No significant changes in the level of prostaglandin E2 were apparent.

CONCLUSION

The addition of pentoxifylline to organ culture media leads, ultimately, to a suppression of IL-6 and IL-8 secretion by corneal tissue. The potentially damaging effects of these cytokines are thereby quelled, as evidenced by the improvement in endothelial cell survival.

The small intestine is an important source of adrenomedullin release during polymicrobial sepsis

Adrenomedullin (AM), a potent vasodilatory peptide, has recently been reported to be involved in the altered cardiovascular responses under various pathophysiological conditions. Although the increase in plasma AM levels is associated with upregulation of AM gene expression in various tissues, it remains unknown whether the gut is an important source of AM release under such conditions. To determine this, adult male rats were subjected to sepsis by cecal ligation and puncture (CLP) followed by fluid resuscitation. Systemic and portal blood samples were collected simultaneously at 10 and 20 h after CLP or sham operation. A portion of the jejunum was also harvested. Plasma and tissue levels of AM were then determined by RIA. The localization of AM in the intestinal tissue was examined using immunohistochemistry. In an additional group of normal rats, synthetic rat AM (8.5 microg/kg body wt) was infused for 15 min at a constant rate via the portal vein (which produces a similar level of AM as observed during sepsis). Cardiac output, stroke volume, total peripheral resistance, and microvascular blood flow in various organs were determined before and 30 min after AM administration. The results indicate that AM levels in portal blood were significantly higher than in systemic blood at 10 and 20 h after CLP. Intestinal AM was also markedly elevated. Immunohistochemical visualization shows that AM immunostainings were localized in the mucosa, submucosa, and intestinal nerve fibers, and they were increased at 10-20 h post-CLP. Because AM-immunopositive nerve fibers increase in the gut during sepsis, a nerve pathway may be involved in the regulation of vascular reactivity by this peptide. Moreover, intraportal administration of AM increased cardiac output, stroke volume, and microvascular blood flow in the liver, kidney, small intestine, and spleen. In contrast, total peripheral resistance was significantly reduced. Thus the gut plays an important role in increasing the levels of circulating AM during the progression of sepsis. Gut-derived AM appears to be a major factor in initiating the hyperdynamic response after the onset of sepsis.

Oral pentoxifylline inhibits release of tumor necrosis factor-alpha from human peripheral blood monocytes : a potential treatment for aseptic loosening of total joint components

BACKGROUND

Pentoxifylline (Trental) is a methylxanthine-derivative drug that has been used for more than twenty years in the treatment of peripheral vascular disease. Pentoxifylline is also a potent inhibitor of tumor necrosis factor-alpha (TNF-alpha) secretion, both in vitro and in vivo, and has demonstrated efficacy in the treatment of certain animal and human inflammatory diseases. Pentoxifylline has a potential therapeutic role in the treatment of aseptic loosening of total joint replacement components because it inhibits TNF-alpha secretion by particle-stimulated human peripheral blood monocytes. The purpose of our study was to determine whether the particle-stimulated secretion of TNF-alpha by peripheral blood monocytes was inhibited in volunteers who had received pentoxifylline orally.

METHODS

Human peripheral blood monocytes were harvested from eight healthy volunteers and were exposed to three different concentrations of titanium particles or to 500 ng/mL of lipopolysaccharide as a positive control. The same volunteers were then given pentoxifylline (400 mg, five times per day) for seven days. Their peripheral blood monocytes were again isolated and exposed to experimental conditions, and the TNF-alpha levels were measured.

RESULTS

The peripheral blood monocytes from all eight volunteers showed a significant reduction in TNF-alpha release following oral treatment with pentoxifylline. This reduction was observed at exposures of 10(7) and 10(6) titanium particles/mL and in the lipopolysaccharide-treated group, but not at 10(5) particles/mL.

CONCLUSIONS

To our knowledge, this is the first study to demonstrate the ability of an oral drug to decrease the release of TNF-alpha from human peripheral blood monocytes exposed ex vivo to particle debris. TNF-alpha is involved in the pathogenesis of osteolysis and subsequent loosening of total joint arthroplasty components. The ability to suppress the release of TNF-alpha in patients with a total joint replacement may help to control osteolysis and to reduce the development of aseptic loosening. This effect could increase implant longevity and decrease the need for revision arthroplasty.

Effect of pentoxifylline on nitrogen balance and 3-methylhistidine excretion in parenterally fed endotoxemic rats

Pentoxifylline interrupts early gene activation for tumor necrosis factor, interleukin-1, and interleukin-6 production and improves survival from experimental sepsis. These effects can alter nitrogen loss during critical illness. To determine the dose-dependent influence of pentoxifylline on nitrogen loss, 44 male Sprague-Dawley rats (220 to 265 g) were randomized to receive parenteral nutrition only (PN), PN plus continuous infusion of Escherichia coli 026:B6 lipopolysaccharide (LPS) at 9 mg x kg(-1) x d(-1), or PN plus LPS plus a continuous infusion of pentoxifylline at either 25 (PEN25) or 100 mg x kg(-1) x d(-1) (PEN100) for 48 h. Before randomization, all animals underwent intravenous cannulation and 40 h of PN adaptation. All animals received isocaloric, isonitrogenous PN (160 kcal x kg(-1) x d(-1) and 1.0 gN x kg(-1) x d(-1)) and were kept nil per os except for water ad libitum. Administration of LPS significantly worsened nitrogen balance for all three groups compared with PN control; however, pentoxifylline only modestly improved nitrogen balance compared with LPS (206 +/- 255, -497 +/- 331, -332 +/- 329, and -310 +/- 383 mg/48hr for the PN, LPS, PEN25, and PEN100 groups, respectively; P < 0.001). Pentoxifylline did not significantly change 3-methylhistidine urinary excretion compared with LPS (573 +/- 180, 705 +/- 156, 780 +/- 326, and 683 +/- 266 microg/48 h for the PN, LPS, PEN25, and PEN100 groups, respectively, P not significant). Pentoxifylline, given in therapeutic doses after an endotoxin challenge, modestly, but not significantly, improved nitrogen balance. Urinary 3-methylhistidine excretion was not influenced by pentoxifylline. A dose-dependent effect by pentoxifylline on these markers was not evident.

The role of adrenomedullin in producing differential hemodynamic responses during sepsis

Although the hemodynamic response to polymicrobial sepsis is characterized by an early, hyperdynamic phase followed by a late, hypodynamic phase, the factors responsible for producing the transition from the hyperdynamic to the hypodynamic stage are not fully understood. The failure to recognize or prevent this transition may lead to progressive deteriorations in cell and organ functions and ultimately result in multiple organ failure. Despite the fact that several vasoactive mediators (i.e., nitric oxide, prostacyclin, calcitonin gene-related peptide) have been implicated in producing cardiovascular alterations during sepsis, recent studies have indicated that adrenomedullin (AM), a novel vasodilatory peptide, plays an important role in initiating the hyperdynamic response during the early stage of polymicrobial sepsis. In addition, the reduced vascular responsiveness appears to be responsible for producing the transition from the early, hyperdynamic phase to the late, hypodynamic phase of sepsis. Moreover, modulation of AM vascular responsiveness reduces sepsis-induced mortality. In this review the physiological effects of AM, mechanisms of its action, and regulation of its production under various pathophysiological conditions will be discussed. Furthermore, the role of AM in producing the biphasic hemodynamic responses observed during polymicrobial sepsis and approaches for pharmacologically modulating vascular responsiveness and hemodynamic stability under such conditions will be described.