The prostacyclin analogue iloprost increases circulating endothelial progenitor cells in patients with critical limb ischemia

Patients with critical limb ischemia (CLI) have low levels of endothelial progenitor cells (EPC). Iloprost has been demonstrated to stimulate vascular endothelial growth factor (VEGF) and promote angiogenesis. We investigated the effects of iloprost on EPC levels in vivo in CLI patients. Twenty-three patients with stage III and IV CLI were treated with iloprost for four weeks, improving clinical and instrumental parameters. Mononuclear cells isolated from peripheral blood were cultured to obtain “early” EPC, evaluated counting adherent cells with double positivity for acetylated low-density lipoprotein uptake and Ulex Europaeus lectin at flow cytometry. These cells also co-expressed the monocyte markers CD14 and CD45.Iloprost increased EPC number in the whole patient population: pre-treatment median: 13,812/ml; range: 1,263–83,648/ml; post-treatment median: 23,739/ml; range: 3,385–99,251/ml; p=0.035, irrespective of age, sex, disease stage or atherosclerosis risk factors. In conclusion, iloprost increases EPC number in peripheral blood in vivo. Such an effect may have therapeutic relevance.

Acetyl-l-carnitine prevents serotonin-induced behavioural sensitization and dishabituation in Hirudo medicinalis

Several studies suggest that acetyl-l-carnitine (ALC) might influence learning processes. Along this line of investigation, we have previously shown that ALC impaired sensitization and dishabituation induced by nociceptive stimulation of the dorsal skin of the leech Hirudo medicinalis, in the behavioural paradigm of the swim induction (SI). In previous works we showed that 5HT was involved in both sensitization and dishabituation of SI acting through the second messenger cAMP. In this work, we have reported that for given doses and temporal ranges ALC was able to block sensitization and to impair dishabituation mimicked by the injection of 5-HT or 8Br-cAMP, a membrane permeable analogue of cAMP. Our results show that a single treatment with 2mM ALC was the most effective concentration to block the onset of sensitization induced by 5-HT injection and its major effects occurred 11 days after ALC treatment. 2mM ALC also blocked sensitization induced by 8Br-cAMP injection, whereas, ALC did not completely abolish dishabituation induced by 5-HT or 8Br-cAMP injection at the tested concentrations and at every time point.

Antiangiogenic effects of β2 -adrenergic receptor blockade in a mouse model of oxygen-induced retinopathy

Oxygen-induced retinopathy (OIR) is a model for human retinopathy of prematurity. In mice with OIR, beta-adrenergic receptor (β-AR) blockade with propranolol has been shown to ameliorate different aspects of retinal dysfunction in response to hypoxia. In the present study, we used the OIR model to investigate the role of distinct β-ARs on retinal proangiogenic factors, pathogenic neovascularization and electroretinographic responses. Our results demonstrate that β(2) -AR blockade with ICI 118,551 decreases retinal levels of proangiogenic factors and reduces pathogenic neovascularization, whereas β(1) - and β(3) -AR antagonists do not. Determination of retinal protein kinase A activity is indicative of the fact that β-AR blockers are indeed effective at the receptor level. In addition, the specificity of ICI 118,551 on retinal angiogenesis has been demonstrated by the finding that in mouse retinal explants, β(2) -AR silencing prevents ICI 118,551 effects on hypoxia-induced vascular endothelial growth factor accumulation. In OIR mice, ICI 118,551 is effective in increasing electroretinographic responses suggesting that activation of β(2) -ARs constitutes an important part of the retinal response to hypoxia. Lastly, immunohistochemical studies demonstrate that β(2) -ARs are localized to several retinal cells, particularly to Müller cells suggesting the possibility that β(2) -ARs play a role in regulating vascular endothelial growth factor production by these cells. The present results suggest that pathogenic angiogenesis, a key change in many hypoxic/ischemic vision-threatening retinal diseases, depends at least in part on β(2) -AR activity and indicate that β(2) -AR blockade can be effective against retinal angiogenesis.

Role of the adrenergic system in a mouse model of oxygen-induced retinopathy: antiangiogenic effects of beta-adrenoreceptor blockade

PURPOSE

Oxygen-induced retinopathy (OIR) is a model for human retinopathy of prematurity (ROP). In OIR mice, this study determined whether blockade of β-adrenergic receptors (β-ARs) with propranolol influences retinal levels of proangiogenic factors, retinal vascularization, and blood-retinal barrier (BRB) breakdown.

METHODS

Propranolol was administered subcutaneously and picropodophyllin (PPP) intraperitoneally. Intravitreal injections of vascular endothelial growth factor (VEGF) were performed. Messengers of β-ARs, VEGF, its receptors, IGF-1 and IGF-1R were measured with quantitative RT-PCR. VEGF content was determined with ELISA. β-ARs, hypoxia-inducible factor (HIF)-1α, occludin, and albumin were measured with Western blot. Retinal localization of β3-ARs was determined by immunohistochemistry. Retinopathy was assessed by scoring fluorescein-perfused retinas, and plasma extravasation was visualized by Evans blue dye.

RESULTS

Hypoxia did not influence β-AR expression, except that it increased β3-AR protein with dense β3-AR immunoreactivity localized to engorged retinal tufts. Hypoxia upregulated VEGF, IGF-1, their receptors, and HIF-1α. Propranolol dose-dependently reduced upregulated VEGF and decreased hypoxic levels of IGF-1 mRNA and HIF-1α. Blockade of IGF-1R activity with PPP did not influence propranolol's effects on VEGF. Retinal VEGF in normoxic mice or VEGF in brain, lungs, and heart of the OIR mice were unaffected by propranolol. Propranolol ameliorated the retinopathy score, restored occludin and albumin, and reduced hypoxia-induced plasma extravasation without influencing the vascular permeability induced by intravitreal VEGF.

CONCLUSIONS

This is the first demonstration that β-AR blockade is protective against retinal angiogenesis and ameliorates BRB dysfunction in OIR. Although the relevance of these results to infant ROP is uncertain, the findings may help to establish potential pharmacologic targets based on β3-AR pharmacology.

Study protocol: safety and efficacy of propranolol in newborns with Retinopathy of Prematurity (PROP-ROP): ISRCTN18523491

Background

Despite new therapeutic approaches have improved the prognosis of newborns with retinopathy of prematurity (ROP), an unfavourable structural and functional outcome still remains high. There is high pressure to develop new drugs to prevent and treat ROP. There is increasing enthusiasm for anti-VEGF drugs, but angiogenic inhibitors selective for abnormal blood vessels would be considered as an optimal treatment.

In an animal experimental model of proliferative retinopathy, we have recently demonstrated that the pharmacological blockade of beta-adrenoreceptors improves retinal neovascularization and blood retinal barrier breakdown consequent to hypoxia. The purpose of this study is to evaluate the propranolol administration in preterm newborns suffering from a precocious phase of ROP in terms of safety and efficacy in counteracting the progression of retinopathy.

Methods/Design

Preterm newborns (gestational age at birth lower than 32 weeks) with stage 2 ROP (zone II-III without plus) will be randomized, according to their gestational age, to receive propranolol added to standard treatment (treatment adopted by the ETROP Cooperative Group) or standard treatment alone. Propranolol will be administered until retinal vascularization will be completely developed, but not more than 90 days. Forty-four participants will be recruited into the study. To evaluate the safety of propranolol administration, cardiac and respiratory parameters will be continuously monitored. Blood samplings will be performed to check renal, liver and metabolic balance. To evaluate the efficacy of propranolol, the progression of the disease, the number of laser treatments or vitrectomies, the incidence of retinal detachment or blindness, will be evaluated by serial ophthalmologic examinations. Visual function will be evaluated by means of behavioural standardized tests.

Discussion

This pilot study is the first research that explores the possible therapeutic role of beta blockers in ROP. The objective of this research is highly ambitious: to find a treatment simple, inexpensive, well tolerated and with few adverse effects, able to counteract one of the major complications of the prematurity. Any favourable results of this research could open new perspectives and original scenarios about the treatment or the prevention of this and other proliferative retinopathies.

Trial Registration

Current Controlled Trials ISRCTN18523491; ClinicalTrials.gov Identifier NCT01079715; EudraCT Number 2010-018737-21

Tissue response to poly(ether)urethane-polydimethylsiloxane-fibrin composite scaffolds for controlled delivery of pro-angiogenic growth factors

The development of a scaffold able to mimic the mechanical properties of elastic tissues and to induce local angiogenesis by controlled release of angiogenic growth factors could be applied in the treatment of several ischemic diseases. For this purpose a composite scaffold made of a poly(ether)urethane-polydimethylsiloxane (PEtU-PDMS) semi-interpenetrating polymeric network (semi-IPN) and fibrin loaded growth factors (GFs), such as VEGF and bFGF, was manufactured using spray, phase-inversion technique. To evaluate the contribution of each scaffold component with respect to tissue response and in particular to blood vessel formation, three different scaffold formulations were developed as follows: 1) bare PEtU-PDMS; 2) PEtU-PDMS/Fibrin; and 3) PEtU-PDMS/Fibrin + GFs. Scaffolds were characterized in vitro respect to their morphology, VEGF and bFGF release kinetics and bioactivity. The induction of in vivo angiogenesis after subcutaneous and ischemic hind limb scaffold implantation in adult Wistar rats was evaluated at 7 and 14 days by immunohistological analysis (IHA), while Laser Doppler Perfusion Imaging (LDPI) was performed in the hind limbs at 0, 3, 7, 10 and 14 days. IHA of subcutaneously implanted samples showed that at 7 and 14 days the PEtU-PDMS/Fibrin + GFs scaffold induced a statistically significant increase in number of capillaries compared to bare PEtU-PDMS scaffold. IHA of ischemic hind limb showed that at 14 days the capillary number induced by PEtU-PDMS/Fibrin + GFs scaffolds was higher than that of PEtU-PDMS/Fibrin scaffolds. Moreover, at both time-points PEtU-PDMS/Fibrin scaffolds induced a significant increase in number of capillaries compared to bare PEtU-PDMS scaffolds. LDPI showed that at 10 and 14 days the ischemic/non-ischemic blood perfusion ratio was significantly greater in the PEtU-PDMS/Fibrin + GFs than in the other scaffolds. In conclusion, this study showed that the semi-IPN composite scaffold acting as a pro-angiogenic GFs delivery system has therapeutic potential for the local treatment of ischemic tissue and wound healing.

Action mechanisms of the secondary metabolite euplotin C: signaling and functional role in Euplotes

Among secondary metabolites, the acetylated hemiacetal sesquiterpene euplotin C has been isolated from the marine, ciliated protist Euplotes crassus, and provides an effective mechanism for reducing populations of potential competitors through its cytotoxic properties. However, intracellular signaling mechanisms and their functional correlates mediating the ecological role of euplotin C are largely unknown. We report here that, in E. vannus (an Euplotes morphospecies that does not produce euplotin C and shares with E. crasssus the same interstitial habitat), euplotin C rapidly increases the intracellular concentration of both Ca(2+) and Na(+), suggesting a generalized effect of this metabolite on cation transport systems. In addition, euplotin C does not induce oxidative stress, but modulates the electrical properties of E. vannus through an increase of the amplitude of graded action potentials. These events parallel the disassembling of the ciliary structures, the inhibition of cell motility, the occurrence of aberrant cytoplasmic vacuoles, and the rapid inhibition of phagocytic activity. Euplotin C also increases lysosomal pH and decreases lysosomal membrane stability of E. vannus. These results suggest that euplotin C exerts a marked disruption of those homeostatic mechanisms whose efficiency represents the essential prerequisite to face the challenges of the interstitial environment.

The prostacyclin analogue iloprost increases circulating endothelial progenitor cells in patients with critical limb ischemia

Patients with critical limb ischemia (CLI) have low levels of endothelial progenitor cells (EPC). Iloprost has been demonstrated to stimulate vascular endothelial growth factor (VEGF) and promote angiogenesis. We investigated the effects of iloprost on EPC levels in vivo in CLI patients. Twenty-three patients with stage III and IV CLI were treated with iloprost for four weeks, improving clinical and instrumental parameters. Mononuclear cells isolated from peripheral blood were cultured to obtain "early" EPC, evaluated counting adherent cells with double positivity for acetylated low-density lipoprotein uptake and Ulex Europaeus lectin at flow cytometry. These cells also co-expressed the monocyte markers CD14 and CD45. Iloprost increased EPC number in the whole patient population: pre-treatment median: 13,812/ml; range: 1,263-83,648/ml; post-treatment median: 23,739/ml; range: 3,385-99,251/ml; p = 0.035, irrespective of age, sex, disease stage or atherosclerosis risk factors. In conclusion, iloprost increases EPC number in peripheral blood in vivo. Such an effect may have therapeutic relevance.

Modulation of the neuronal response to ischaemia by somatostatin analogues in wild-type and knock-out mouse retinas

Somatostatin acts at five G protein-coupled receptors, sst(1)-sst(5). In mouse ischaemic retinas, the over-expression of sst(2) (as in sst(1) knock-out mice) results in the reduction of cell death and glutamate release. In this study, we reported that, in wild-type retinas, somatostatin, the multireceptor ligand pasireotide and the sst(2) agonist octreotide decreased ischaemia-induced cell death and that octreotide also decreased glutamate release. In contrast, cell death was increased by blocking sst(2) with cyanamide. In sst(2) over-expressing ischaemic retinas, somatostatin analogues increased cell death, and octreotide also increased glutamate release. To explain this reversal of the anti-ischaemic effect of somatostatin agonists in the presence of sst(2) over-expression, we tested sst(2) desensitisation because of internalisation or altered receptor function. We observed that (i) sst(2) was not internalised, (ii) among G protein-coupled receptor kinases (GRKs) and regulators of G protein signalling (RGSs), GRK1 and RGS1 expression increased following ischaemia, (iii) both GRK1 and RGS1 were down-regulated by octreotide in wild-type ischaemic retinas, (iv) octreotide down-regulated GRK1 but not RGS1 in sst(2) over-expressing ischaemic retinas. These results demonstrate that sst(2) activation protects against retinal ischaemia. However, in the presence of sst(2) over-expression sst(2) is functionally desensitised by agonists, possibly because of sustained RGS1 levels.

Inhibition of Na+/K+ ATPase potentiates synaptic transmission in tactile sensory neurons of the leech

Increasing evidence indicates that modulation of Na(+)/K(+) ATPase activity is involved in forms of neuronal and synaptic plasticity. In tactile (T) neurons of the leech Hirudo medicinalis, Na(+)/K(+) ATPase is the main determinant of the afterhyperpolarization (AHP), which characterizes the firing of these mechanosensory neurons. Previously, it has been reported that cAMP (3',5'-cyclic adenosine monophosphate), which mediates the effects of serotonin (5HT) in some forms of learning in the leech, negatively modulates Na(+)/K(+) ATPase activity, thereby reducing the AHP amplitude in T neurons. Here, we show that a transient inhibition of Na(+)/K(+) ATPase can affect the synaptic connection between two ipsilateral T neurons. Bath application of 10 nm dihydroouabain (DHO), an ouabain analogue, causes an increase in the amplitude of the synaptic potential (SP) recorded in the postsynaptic element when a test stimulus is applied in the presynaptic neuron. Iontophoretic injection of cAMP into the presynaptic T neuron also produces an increase of SP. Simulations carried out by using a computational model of the T neuron suggest that a reduction of the pump rate and a consequent depression of the AHP might facilitate the conduction of action potentials to the synaptic terminals. Moreover, nearly intact leeches injected with 10 nm DHO respond with a swimming episode more quickly to an electrical stimulation, which selectively activates T neurons exhibiting sensitization of swimming induction. Collectively, our results show that inhibition of Na(+)/K(+) ATPase is critical for short-term plasticity.

Acetyl-l-carnitine affects nonassociative learning processes in the leech Hirudo medicinalis

Acetyl-L-carnitine is a natural molecule widely distributed in vertebrate and invertebrate nervous system. It is known to have significant effects on neuronal activity playing a role as neuroprotective and anti-nociceptive agent, as well as neuromodulatory factor. About its capability of affecting learning processes the available data are controversial. In the present study, we utilized the simplified model system of the leech Hirudo medicinalis to analyze the effects of acetyl-L-carnitine, assessing whether and how it might affect elementary forms of nonassociative learning processes. In leeches with the head ganglion disconnected from the first segmental ganglion, repetitive application of weak electrical shocks onto the caudal portion of the body wall induces habituation of swim induction whereas brush strokes on the dorsal skin produces sensitization or dishabituation when the nociceptive stimulus is delivered on previously habituated animals. Herein, the effects of different concentrations of acetyl-L-carnitine (2 mM - 0.05 mM) have been tested at different times on both sensitization and dishabituation. The results show that a single treatment of acetyl-L-carnitine blocked the onset of sensitization in a dose- and time-dependent manner. In fact, the most effective concentration able to block this process was 2 mM, which induced its major effects 11 days after the treatment, whereas 0.05 mM was unable to affect the sensitization process at all considered time points. On the contrary, acetyl-L-carnitine did not completely abolish dishabituation at the tested concentrations and at every time point. Finally, acetyl-L-carnitine also impaired the habituation of swim induction, but only 11 days after treatment.

A comparative study of protein immobilization techniques for optical immunosensors

This paper presents the results of a study of a number of antibody immobilization techniques for application to optical immunosensors. In particular, well-known methods such as covalent binding and physical adsorption have been extended to the Langmiur-Blodgett method in an attempt to improve the density and possibly the uniformity of orientation of monoclonal antibodies on an optical surface. The surface density of active immobilized antibodies was determined from enzyme immunoassay and their thickness and refractive index were deduced from ellipsometry. It is shown that, although high surface densities (500 ng/cm2) of antibody can be obtained, the major obstacle to the detection of low concentrations of antigens or haptens is the non-specific binding of foreign molecules to the sensing surface.

Vi serology in detection of chronic Salmonella typhi carriers in an endemic area

A passive haemagglutination assay measuring antibody to highly purified Vi antigen, known to be sensitive and specific for the detection of chronic Salmonella typhi carriers in a non-endemic area, was assessed in an endemic area. A reciprocal serum Vi antibody titre of 160 was found to have a sensitivity of 75%, specificity of 92%, and a high predictive value in screening for chronic S typhi carriers in high-risk population group (eg, women over 40 years). This simple assay can screen for chronic S typhi carriers even in areas where typhoid fever is highly endemic.