The role of polyphenols in the prevention of degenerative diseases is emerging in the last years. In this report, we will investigate
Research on the effects of dietary polyphenols on human health has developed considerably in the past ten years. It strongly supports a role for polyphenols in the prevention of degenerative diseases, particularly cardiovascular diseases and cancers [
Resveratrol is a nonflavonoid polyphenolic compound found in a large number of plant species (at least 72), a number of which are components of the human diet, including mulberries, peanuts, grapes, and red wines. Resveratrol exists as cis- and trans-isomeric forms, with trans to cis isomerization facilitated by UV exposure. Two phenol rings are linked by a styrene double bond to generate 3,4′,5-trihydroxystilbene (Figure
Resveratrol (trans-3,5,4′-trihydroxystilbene).
Some of the effects are due to the widely studied antioxidant properties of polyphenols, even if recent studies have shown that the mechanisms of action of polyphenols go beyond the modulation of oxidative stress. Important biological activities involve downregulation of the inflammatory response through inhibition of synthesis and release of proinflammatory mediators, modification of eicosanoid synthesis, inhibition of activated immune cells, or inhibiting, such as iNOS and COX-2, via its inhibitory effects on NF-kB or the AP-1 [
Further studies have shown the beneficial effect of resveratrol in the AD. Some studies have shown that resveratrol markedly lowers the levels of secreted and intracellular amyloid-
Elastin is the extracellular protein responsible for elasticity in vertebrates. Its production occurs during the early neonatal period and then drops dramatically and is nearly completely repressed at maturity [
In this report, we will investigate the inhibitory effect of resveratrol on the elastin amyloidogenesis. The effect of resveratrol on molecular structure was investigated by circular dichroism (CD) spectroscopy, while the inhibitory effect on self-assembly was evaluated by turbidimetry as a function of temperature and by atomic force microscopy (AFM).
The S4 peptide was synthesized by solid-phase methodology and purified by RP-HPLC as previously described [
CD spectra of S4 peptide (0.1 mg/mL) were acquired at different temperatures with a Jasco J-815 Spectropolarimeter equipped with a HAAKE thermostat as temperature controller by using 0.1 cm path length quartz cell. Samples were equilibrated at the temperature for 5 min before acquisition. Spectra were acquired by taking points every 0.1 nm, with 100 nm/min scan rate, 16 scans, an integration time of 2 s, and a 1 nm bandwidth. The data are expressed in terms of [
1.5 mL of 2 mM solutions of the S4 peptide in 15% ethanol (EtOH) in TBS buffer [Tris (50 mM), NaCl (1.5 M), and CaCl2 (1.0 mM) (pH 7.0)] was analyzed by turbidimetry at 440 nm as function of temperature on a Cary 50 UV spectrophotometer equipped with a Peltier temperature controller using quartz cells of 1 cm path length and reported as TAA (turbidimetry on apparent absorbance). The solution temperature was increased from 10 to 90°C with 5°C every 5 minutes and then decreased back to 10°C, monitoring the absorbance under stirring after 5 minutes to reach the equilibrium temperature. Resveratrol (1 mM) was added to the peptide solution. The effect of resveratrol was evaluated in the same experimental conditions.
After turbidimetry experiments, 10
The propensity of S4 peptide to self-assemble in aggregates was monitored by turbidimetry (Figure
Turbidimetry as a function of temperature. Aggregation studies by turbidimetry of S4 peptide in 15% EtOH in TBS showing the warming cycle (■) and cooling (▲) cycle. The warming cycle of S4 peptide in 15% EtOH in TBS in the presence of resveratrol is shown (●).
AFM images of S4 peptide deposited on Si (100) wafers after turbidimetry in the absence (a) and presence (b) of resveratrol.
Previous studies have investigated the capacity of resveratrol to recognize and remodel different conformers (monomers, soluble oligomers, nontoxic oligomers, fibrillar intermediates, and amyloid fibrils) of the A
To define the effect of the Res on the conformation of the peptide, CD spectra were recorded. CD spectroscopy is a useful tool able to define the peptide secondary structures, as well as the effect of ligands on the conformation of the peptide/protein. The conformational analysis of S4 peptides was previously performed and revealed the presence of significant amount of PPII conformation, whose content is reduced on increasing the temperature favoring the
CD spectra of S4 peptide recorded in 15% EtOH in TBS at different temperatures in the absence (a) and presence (b) of 1 mM resveratrol.
Recently, great effort was made in defining the protective properties of polyphenols, such as resveratrol. Many different effects were discovered that are working at various levels. In this work, we have shown a possible inhibitory effect of resveratrol on elastin amyloid deposition acting at molecular levels, which could be added among others to the possible mechanisms involved in the beneficial effects of resveratrol.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The financial support from Italian Ministry of University and Research (MIUR) (PRIN 2010-Project 2010L (SH3K) is gratefully acknowledged. Thanks are due to Dr. M. A. Crudele for technical assistance and to Dr. Neluta Ibris for AFM images (CIGAS, University of Basilicata).