Administration of pigment epithelium-derived factor prolongs bleeding time by suppressing plasminogen activator inhibitor-1 activity and platelet aggregation in rats

Therapeutic Potential of Pigment Epithelium-derived Factor in Cancer

Pigment epithelium-derived factor (PEDF) is one of the serine protease inhibitors with multifunctional properties, which is produced by various types of organs and tissues. There is an accumulating body of evidence that PEDF plays an important role in the maintenance of tissue homeostasis. Indeed, PEDF not only works as an endogenous inhibitor of angiogenesis, but also suppresses oxidative stress, inflammatory and thrombotic reactions in cell culture systems, animal models, and humans. Furthermore, we, along with others, have found that PEDF inhibits proliferation of, and induces apoptotic cell death in, numerous kinds of tumors. In addition, circulating as well as tumor expression levels of PEDF have been inversely associated with tumor growth and metastasis. These observations suggest that supplementation of PEDF proteins and/or enhancement of endogenous PEDF expression could be a novel therapeutic strategy for the treatment of cancer. Therefore, in this paper, we review the effects of PEDF on diverse types of cancer, and discuss its therapeutic perspectives.

Association of Pigment Epithelium Derived Factor With von Willebrand Factor and Plasminogen Activator Inhibitor 1 in Patients With Type 2 Diabetes

To compare circulating pigment epithelium derived factor (PEDF) levels in type 2 diabetes patients (T2D) with and without metabolic syndrome (MetS+/-) to healthy controls and assess PEDF association with plasminogen activator inhibitor-1 (PAI-1) and von Willebrand factor (vWF) as markers of endothelial dysfunction. Fifty T2D individuals and forty healthy controls were included. PEDF, PAI-1, vWF, anthropological parameters, lipids, and markers of insulin resistance were investigated in all subjects. Compared to controls only MetS+ diabetics had higher PEDF levels [14.2 (10.2-16.0) mg/l vs. 11.1 (8.6-14.4) mg/l; p<0.05]. PEDF significantly correlated: positively with body mass index (ρ=0.25), smoking (ρ=0.21), C-reactive protein (ρ=0.22), triglycerides (ρ=0.38), non-HDL-cholesterol (ρ=0.39), apolipoprotein B (ρ=0.38), fasting glucose (ρ=0.22), glycated hemoglobin (ρ=0.24), C-peptide (ρ=0.28), insulin (ρ=0.26); and negatively with HDL-cholesterol (ρ=-0.42) and apolipoprotein A1 (ρ=-0.27). Independent association of PEDF with vWF in T2DMetS- subjects was found. Significantly elevated PEDF in T2DMet+ patients and its association with adverse metabolic profile confirmed PEDF as a marker of insulin resistance. Negative independent association of PEDF with vWF in T2DMetS- patients may reveal its angio-protective role.

Anti-platelet effects of anti-glaucomatous eye drops: an in vitro study on human platelets

PURPOSE

Altered platelet aggregability has been implicated in the pathogenesis of glaucoma. This study aims to investigate the anti-platelet potential of intraocular pressure lowering drops, with the possibility of establishing it as an additional mechanism of anti-glaucomatous action.

MATERIALS AND METHODS

The anti-aggregating effects of a series of anti-glaucomatous eye drops were determined on human platelets in the platelet aggregation model, using four known aggregating factors (platelet activating factor [PAF], adenosine diphosphate [ADP], thrombin receptor-activating peptide [TRAP], and arachidonic acid [AA]).

RESULTS

Almost all of the tested samples inhibited platelet aggregation induced by PAF, ADP, TRAP, and AA, except for Alphagan, which did not demonstrate inhibition of ADP- and TRAP-induced aggregation at a wide range of concentrations. Trusopt, Betoptic, and Azarga eye drops were the most potent inhibitors of all four aggregating factors, while Alphagan was the least potent (P<0.05).

CONCLUSION

This study shows that anti-glaucomatous eye drops possess anti-platelet effects, and this was shown for the first time by experimenting on human platelets.

PEDF and its roles in physiological and pathological conditions: implication in diabetic and hypoxia-induced angiogenic diseases

Pigment epithelium-derived factor (PEDF) is a broadly expressed multifunctional member of the serine proteinase inhibitor (serpin) family. This widely studied protein plays critical roles in many physiological and pathophysiological processes, including neuroprotection, angiogenesis, fibrogenesis and inflammation. The present review summarizes the temporal and spatial distribution patterns of PEDF in a variety of developing and adult organs, and discusses its functions in maintaining physiological homoeostasis. The major focus of the present review is to discuss the implication of PEDF in diabetic and hypoxia-induced angiogenesis, and the pathways mediating PEDF's effects under these conditions. Furthermore, the regulatory mechanisms of PEDF expression, function and degradation are also reviewed. Finally, the therapeutic potential of PEDF as an anti-angiogenic drug is briefly summarized.

Understanding the neural repair-promoting properties of olfactory ensheathing cells

Olfactory ensheathing glial cells (OECs) are a specialized type of glia that form a continuously aligned cellular pathway that actively supports unprecedented regeneration of primary olfactory axons from the periphery into the central nervous system. Implantation of OECs stimulates neural repair in experimental models of spinal cord, brain and peripheral nerve injury and delays disease progression in animal models for neurodegenerative diseases like amyotrophic lateral sclerosis. OECs implanted in the injured spinal cord display a plethora of pro-regenerative effects; they promote axonal regeneration, reorganize the glial scar, remyelinate axons, stimulate blood vessel formation, have phagocytic properties and modulate the immune response. Recently genome wide transcriptional profiling and proteomics analysis combined with classical or larger scale "medium-throughput" bioassays have provided novel insights into the molecular mechanism that endow OECs with their pro-regenerative properties. Here we review these studies and show that the gaps that existed in our understanding of the molecular basis of the reparative properties of OECs are narrowing. OECs express functionally connected sets of genes that can be linked to at least 10 distinct processes directly relevant to neural repair. The data indicate that OECs exhibit a range of synergistic cellular activities, including active and passive stimulation of axon regeneration (by secretion of growth factors, axon guidance molecules and basement membrane components) and critical aspects of tissue repair (by structural remodeling and support, modulation of the immune system, enhancement of neurotrophic and antigenic stimuli and by metabolizing toxic macromolecules). Future experimentation will have to further explore the newly acquired knowledge to enhance the therapeutic potential of OECs.

A multilevel screening strategy defines a molecular fingerprint of proregenerative olfactory ensheathing cells and identifies SCARB2, a protein that improves regenerative sprouting of injured sensory spinal axons

Olfactory ensheathing cells (OECs) have neuro-restorative properties in animal models for spinal cord injury, stroke, and amyotrophic lateral sclerosis. Here we used a multistep screening approach to discover genes specifically contributing to the regeneration-promoting properties of OECs. Microarray screening of the injured olfactory pathway and of cultured OECs identified 102 genes that were subsequently functionally characterized in cocultures of OECs and primary dorsal root ganglion (DRG) neurons. Selective siRNA-mediated knockdown of 16 genes in OECs (ADAMTS1, BM385941, FZD1, GFRA1, LEPRE1, NCAM1, NID2, NRP1, MSLN, RND1, S100A9, SCARB2, SERPINI1, SERPINF1, TGFB2, and VAV1) significantly reduced outgrowth of cocultured DRG neurons, indicating that endogenous expression of these genes in OECs supports neurite extension of DRG neurons. In a gain-of-function screen for 18 genes, six (CX3CL1, FZD1, LEPRE1, S100A9, SCARB2, and SERPINI1) enhanced and one (TIMP2) inhibited neurite growth. The most potent hit in both the loss- and gain-of-function screens was SCARB2, a protein that promotes cholesterol secretion. Transplants of fibroblasts that were genetically modified to overexpress SCARB2 significantly increased the number of regenerating DRG axons that grew toward the center of a spinal cord lesion in rats. We conclude that expression of SCARB2 enhances regenerative sprouting and that SCARB2 contributes to OEC-mediated neuronal repair.

Administration of pigment epithelium-derived factor inhibits left ventricular remodeling and improves cardiac function in rats with acute myocardial infarction

Oxidative stress and inflammation are involved in cardiac remodeling after acute myocardial infarction (AMI). We have found that pigment epithelium-derived factor (PEDF) inhibits vascular inflammation through its anti-oxidative properties. However, effects of PEDF on cardiac remodeling after AMI remain unknown. We investigated whether PEDF could inhibit left ventricular remodeling and improve cardiac function in rats with AMI. AMI was induced in 8-week-old Sprague-Dawley rats by ligation of the left ascending coronary artery. Rats were treated intravenously with vehicle or 10 μg PEDF/100 g b.wt. every day for up to 2 weeks after AMI. Each rat was followed until 16 weeks of age. PEDF levels in infarcted areas and serum were significantly decreased at 1 week after AMI and remained low during the observational periods. PEDF administration inhibited apoptotic cell death and oxidative stress generation around the infarcted areas at 2 and 8 weeks after AMI. Further, PEDF injection suppressed cardiac fibrosis by reducing transforming growth factor-β and type III collagen expression, improved left ventricular ejection fraction, ameliorated diastolic dysfunction, and inhibited the increase in left ventricular mass index at 8 weeks after AMI. The present study demonstrated that PEDF could inhibit tissue remodeling and improve cardiac function in AMI rats. Substitution of PEDF may be a novel therapeutic strategy for cardiac remodeling after AMI.

Pigment epithelium-derived factor (PEDF) as a therapeutic target in cardiovascular disease

In this review we discuss the role of pigment epithelium-derived factor (PEDF) as a possible new target molecule to therapeutically influence cardiovascular disease. PEDF is a multifunctional, pleiotropic protein with antiangiogenic, antitumorigenic, antioxidant, anti-inflammatory, antithrombotic, neurotrophic and neuroprotective properties. First identified in retinal pigment epithelium cells, it is expressed in various tissues throughout the body such as the eye, liver and adipose tissue. Recently PEDF has also been characterized in the heart. PEDF has been suggested to have a protective role in atherosclerosis, the main cause of coronary heart disease, myocardial infarction and heart failure due to its anti-inflammatory, antioxidant and antithrombotic effects in the vessel wall and platelets. Additionally PEDF has strong antiangiogenic effects by inducing apoptosis in endothelial cells and by regulating the expression of other angiogenic factors. Therefore blocking of PEDF locally for example in ischemic tissue in the heart might favour angiogenesis, induce neovascularization and lead to increased perfusion of the injured tissue. On the other hand, local overexpression of PEDF restricted to atherosclerotic lesions might block angiogenesis, inflammation and thrombosis at these sites and thus counteract destabilization and rupture of the lesion otherwise caused by inflammatory activation and excessive angiogenesis and inhibit subsequent thrombus formation.