No abstract

Pigment epithelium-derived factor (PEDF), a neuritepromoting factor, has an amino acid primary structure that is related to members of the serine protease inhibitor (serpin) family. Controlled proteolysis of native PEDF (50 kDa) with either trypsin, chymotrypsin, elastase, or subtilisin yields in each case one major limited product of 46 kDa as analyzed by SDS-polyacrylamide gel electrophoresis. N-terminal sequence analysis of the isolated 46-kDa products indicates a favored cleavage region located toward the C-terminal end of PEDF. A proteolyzed PEDF protein reaction mixture reveals two overlapping sequences: that of the N terminus of intact PEDF and that of an internal region, consistent with cleavage of PEDF about position 382. These data indicate that PEDF protein has a globular conformation with one protease-sensitive exposed loop that contains the homologous serpin-reactive site. Cleavage within the reactive-site loop of PEDF does not cause a conformational change in the molecules (the stressed (S) 3 relaxed (R) transition) and results in heat denaturation identical to its native counterpart. This lack of conformational change is also seen upon cleavage within the reactive-site loop of the noninhibitory serpin ovalbumin. Furthermore, the PEDF neurite-promoting function is not lost with cleavage of the exposed loop. Recombinant PEDF polypeptide fragments with larger truncations from the C-terminal end show neurotrophic activity. Our results clearly indicate that integrity of the PEDF homologous serpin reactive center is dispensable for neurotrophic activity. Thus, the PEDF induction of neurites must be mediated by a mechanism other than serine protease inhibition. Altogether our data indicate that PEDF belongs to the subgroup of noninhibitory serpins and that its N-terminal region confers a neuritepromoting activity to the protein. The neurotrophic active site of PEDF is separated from the serpin reactivesite loop, not only in the primary structure, but also in the folded protein structure. PEDF1 was first described as a neurite-promoting factor that is released by human fetal retinal pigment epithelial (RPE) cells. It was reported that PEDF isolated from medium conditioned by human fetal RPE primary cultures promotes neurite outgrowth in cultured human retinoblastoma Y-79 cells (1). Information about the PEDF peptide sequence has permitted the isolation and cloning of a human PEDF cDNA (2). From cDNA clones, expression vectors were constructed (3, 4) and, in turn, specific antisera to PEDF were developed from the recombinant PEDF proteins (4, 5). Antiserum Ab-rPEDF has been instrumental in the identification of PEDF protein in physiological sources. PEDF is present in bovine eyes in the interphotoreceptor matrix (IPM), i.e. the extracellular matrix located between RPE and the neural retina, and is the sole IPM component responsible for the IPM neurite-promoting activity (5). In addition to the effect on retinoblastoma cells, PEDF has the capacity of promoting neuronal survival of primary cerebellar granule...

Polyphenols have been extensively investigated with regard to their antioxidant, anti-inflammatory, and immunomodulant properties in many inflammatory chronic conditions. The aim of this review is to summarise how these compounds can modulate the inflammatory pathways which characterise the most prevalent arthropathies including osteoarthritis, rheumatoid arthritis and crystal-induced arthritis. Among polyphenols, epigallocatechin gallate, carnosol, hydroxytyrosol, curcumin, resveratrol, kaempferol and genistein have been the most widely investigated in arthritis. The most important results of the studies outlined in this article show how polyphenolic compounds are able to inhibit the expression and the release of a number of pro-inflammatory mediators and proteolytic enzymes, the activity of different transcriptional factors and the production of reactive oxygen species in vitro. Studies on animal models of rheumatoid arthritis, osteoarthritis and gout show interesting results in terms of reduced tissue damage, restored cartilage homeostasis, and decreased levels of uric acid, respectively. Despite the multiple protective effects of polyphenols, there are no dietary recommendations for patients affected by rheumatic diseases. Future studies, including intervention trials, should be conducted to determine the relevance of polyphenols consumption or supplementation in arthritis. © 2017 Society of Chemical Industry.