Hydroxytyrosol Treatment Research Articles

Hydroxytyrosol supplementation inhibits oxidative DNA damage, suppresses protein-lipid oxidation and modulates antioxidant enzymes in human peripheral blood lymphocytes

We investigated the oxidative modifications of DNA, proteins and antioxidants enzymes activities, in peripheral blood lymphocytes (PBL) treated with H2O2 in the presence or absence of hydroxytyrosol. Interestingly, we found a potential protection of DNA from fragmentation after hydroxytyrosol supplementation. In addition, this study showed a prospective protective action of hydroxytyrosol of PBL from the attack of reactive oxygen species. In fact, a considerable increase of superoxide dismutase and catalase activities by 76.92 and 21.67%, respectively was showed after 20 µg/ml hydroxytyrosol treatment. Moreover, 20 µg/ml of hydroxytyrosol significantly decreased the lipid peroxidation and protein oxidation rates by 97.89 and 18.5% respectively. In conclusion, the present study reveals the efficacy of hydroxytyrosol in the protection of PBL of DNA fragmentation and oxidative stress induced by H2O2 treatment, which may be attributed to its anti-oxidant potential. Key words: Hydroxytyrosol, thiol, lymphocytes, conjugated dienes, malondialdehyde, superoxide dismutase, catalase.

Hydroxytyrosol Induces Vascular Smooth Muscle Cells Apoptosis through NO Production and PP2A Activation with Subsequent Inactivation of Akt

Olive oil has been shown to exhibit beneficial effects in the prevention of cardiovascular diseases although its molecular mechanism still remains unclear. In the present study, we investigated the effect of hydroxytyrosol (HT), a major phenolic component in olive oil and leaves from OLEA EUROPAEA L. (Oleaceae family), on vascular smooth muscle cells (VSMCs) survival, migration, and apoptosis. HT treatment resulted in a dose-dependent decrease of cell survival and migration in the presence or absence of platelet-derived growth factor (PDGF) by inducing apoptosis of VSMCs. HT enhanced nitric oxide (NO) production in a dose-dependent manner, and the NO synthase inhibitor L-NMMA blocked HT-mediated effects on VSMCs survival. HT as well as the NO donor SNAP reduced the phosphorylation levels of Akt, suggesting that HT inactivates Akt via NO production with subsequent apoptosis of VSMCs. Moreover, HT-dependent apoptosis and reduction in the phosphorylation level of Akt were suppressed by okadaic acid, an inhibitor of protein phosphatase 2A (PP2A) that dephosphorylates Akt. In contrast, the phosphorylation of phosphoinositide-dependent protein kinase 1 (PDK1), an upstream activator of Akt, was not affected by HT. Together, these findings indicate that HT could induce VSMCs apoptosis through NO production and PP2A activation followed by inactivation of Akt signaling pathway.

Mitochondrial dynamic remodeling in strenuous exercise-induced muscle and mitochondrial dysfunction: Regulatory effects of hydroxytyrosol

Physical exercise is considered to exert a positive effect on health, whereas strenuous or excessive exercise (Exe) causes fatigue and damage to muscle and immune functions. The underlying molecular mechanisms are still unclear. We designed a protocol to mimic Exe and explore the ensuing cellular damage and involvement of mitochondrial dynamics. We found that Exe was prone to decrease endurance capacity and induce damage to renal function and the immune system. Muscle atrophy markers atrogin-1 and MuRF1 mRNA were increased by Exe, accompanied by increased autophagy and mitochondrial fission in skeletal muscle. Exe caused a decrease in PGC-1α and complex I expression; it also activated JNK and Erk1/2 pathways and consequently induced p53, p21, and MnSOD expression in skeletal muscle. The involvement of oxidant-induced autophagy and mitochondrial dysfunction was confirmed in C2C12 myoblasts. Hydroxytyrosol (HT), a natural olive polyphenol, efficiently enhanced endurance capacity and prevented Exe-induced renal and immune system damage. Also, HT treatment inhibited both the Exe-induced increase in autophagy and mitochondrial fission and the decrease in PGC-1α expression. In addition, HT enhanced mitochondrial fusion and mitochondrial complex I and II activities in muscle of Exe rats. These results demonstrate that Exe-induced fatigue and damage to muscle and immune functions may be mediated via the regulation of mitochondrial dynamic remodeling, including the downregulation of mitochondrial biogenesis and upregulation of autophagy. HT supplementation may regulate mitochondrial dynamic remodeling and enhance antioxidant defenses and thus improve exercise capacity under Exe conditions.

Effects of olive oil polyphenols on fatty acid synthase gene expression and activity in human colorectal cancer cells

Oleuropein (OL) and hydroxytyrosol (HT), the main olive oil polyphenols, possess anti-proliferative effects in vitro. Fatty acid synthase, a key anabolic enzyme of biosynthesis of fatty acids, plays an important role in colon carcinoma development. Our aim was to investigate whether gene expression of FAS, as well as its enzymatic activity, is regulated by HT and OL in two human colon cancer cell lines, as HT-29 and SW620. In addition, we investigated the effects of these polyphenols on growth and apoptosis in these cells. FAS gene expression and activity in treated HT-29 and SW620 cells were evaluated by real-time PCR and radiochemical assay, respectively. Cell growth and apoptosis, after polyphenols treatment, were measured by MTT test and flow cytometry, respectively. The inhibition of proliferation, detected after HT treatment, was mediated by an inhibition of FAS expression and its enzymatic activity in SW620 cells, while the anti-proliferative effect in HT-29 cells seems to be independent from FAS. OL exerted an anti-proliferative effect only on SW620 cells with a mechanism which excluded FAS. Olive oil polyphenols used were able to induce apoptosis in both cell lines studied. The increase of apoptosis in these cells was accompanied by the block of cell cycle in the S phase. This study demonstrates that HT and OL may induce anti-proliferative and pro-apoptotic effects only in certain human colorectal cancer cell types. These effects are FAS mediated only in SW620 cells after treatment with HT.

Hydroxytyrosol protects against oxidative damage by simultaneous activation of mitochondrial biogenesis and phase II detoxifying enzyme systems in retinal pigment epithelial cells

Studies in this laboratory have previously shown that hydroxytyrosol, the major antioxidant polyphenol in olives, protects ARPE-19 human retinal pigment epithelial cells from oxidative damage induced by acrolein, an environmental toxin and endogenous end product of lipid oxidation, that occurs at increased levels in age-related macular degeneration lesions. A proposed mechanism for this is that protection by hydroxytyrosol against oxidative stress is conferred by the simultaneous activation of two critically important pathways, viz., induction of phase II detoxifying enzymes and stimulation of mitochondrial biogenesis. Cultured ARPE-19 cells were pretreated with hydroxytyrosol and challenged with acrolein. The protective effects of hydroxytyrosol on key factors of mitochondrial biogenesis and phase II detoxifying enzyme systems were examined. Hydroxytyrosol treatment simultaneously protected against acrolein-induced inhibition of nuclear factor-E2-related factor 2 (Nrf2) and peroxisome proliferator-activated receptor coactivator 1 alpha (PPARGC1α) in ARPE-19 cells. The activation of Nrf2 led to activation of phase II detoxifying enzymes, including γ-glutamyl-cysteinyl-ligase, NADPH (nicotinamide adenine dinucleotide phosphate)-quinone-oxidoreductase 1, heme-oxygenase-1, superoxide dismutase, peroxiredoxin and thioredoxin as well as other antioxidant enzymes, while the activation of PPARGC1α led to increased protein expression of mitochondrial transcription factor A, uncoupling protein 2 and mitochondrial complexes. These results suggest that hydroxytyrosol is a potent inducer of phase II detoxifying enzymes and an enhancer of mitochondrial biogenesis. Dietary supplementation of hydroxytyrosol may contribute to eye health by preventing the degeneration of retinal pigment epithelial cells induced by oxidative stress.

Hydroxytyrosol promotes mitochondrial biogenesis and mitochondrial function in 3T3-L1 adipocytes

Hydroxytyrosol (HT) in extra-virgin olive oil is considered one of the most important polyphenolic compounds responsible for the health benefits of the Mediterranean diet for lowering incidence of cardiovascular disease, the most common and most serious complication of diabetes. We propose that HT may prevent these diseases by a stimulation of mitochondrial biogenesis that leads to enhancement of mitochondrial function and cellular defense systems. In the present study, we investigated effects of HT that stimulate mitochondrial biogenesis and promote mitochondrial function in 3T3-L1 adipocytes. HT over the concentration range of 0.1–10 μmol/L stimulated the promoter transcriptional activation and protein expression of peroxisome proliferator-activated receptor (PPAR) coactivator 1 alpha (PPARGC1α, the central factor for mitochondrial biogenesis) and its downstream targets; these included nuclear respiration factors 1 and 2 and mitochondrial transcription factor A, which leads to an increase in mitochondrial DNA (mtDNA) and in the number of mitochondria. Knockdown of Ppargc1α by siRNA blocked HT's stimulating effect on Complex I expression and mtDNA copy number. The HT treatment resulted in an enhancement of mitochondrial function, including an increase in activity and protein expression of Mitochondrial Complexes I, II, III and V; increased oxygen consumption; and a decrease in free fatty acid contents in the adipocytes. The mechanistic study of the PPARGC1α activation signaling pathway demonstrated that HT is an activator of 5′AMP-activated protein kinase and also up-regulates gene expression of PPARα, CPT-1 and PPARγ. These data suggest that HT is able to promote mitochondrial function by stimulating mitochondrial biogenesis.