Karin Wertz

Lycopene and vitamin E interfere with autocrine/paracrine loops in the dunning prostate cancer model

Epidemiological studies have consistently associated high intakes of lycopene or vitamin E with a reduced prostate cancer risk. Both compounds were tested in the MatLyLu Dunning prostate cancer model to gain insight into the in vivo action of lycopene and vitamin E. Supplementation for 4 weeks with 200 ppm lycopene, 540 ppm vitamin E, or both led to plasma levels comparable with those in humans. Both compounds also accumulated in tumor tissue. Macroscopic evaluation of the tumors by magnetic resonance imaging showed a significant increase in necrotic area in the vitamin E and the lycopene treatment groups. Microarray analysis of tumor tissues revealed that both compounds regulated local gene expression. Vitamin E reduced androgen signaling without affecting androgen metabolism. Lycopene interfered with local testosterone activation by down‐regulating 5‐α‐reductase and consequently reduced steroid target genes expression (cystatin‐related protein 1 and 2, prostatic spermine binding protein, prostatic steroid binding protein C1, C2 and C3 chain, probasin). In addition, lycopene down‐ regulated prostatic IGF‐I and IL‐6 expression. Based on these findings, we suggest that lycopene and vitamin E contribute to the reduction of prostate cancer by interfering with internal autocrine or paracrine loops of sex steroid hormone and growth factor activation/synthesis and signaling in the prostate.

Lycopene reduced gene expression of steroid targets and inflammatory markers in normal rat prostate

Epidemiological evidence links consumption of lycopene, the red carotenoid of tomato, to reduced prostate cancer risk. We investigated the effect of lycopene in normal prostate tissue to gain insight into the mechanisms, by which lycopene can contribute to primary prostate cancer prevention. We supplemented young rats with 200 ppm lycopene for up to 8 wk, measured the uptake into individual prostate lobes, and analyzed lycopene‐induced gene regulations in dorsal and lateral lobes after 8 wk of supplementation. Lycopene accumulated in all four prostate lobes over time, with all‐trans lycopene being the predominant isoform. The lateral lobe showed a significantly higher total lycopene content than the other prostate lobes. Transcriptomics analysis revealed that lycopene treatment mildly but significantly reduced gene expression of androgen‐metabolizing enzymes and androgen targets. Moreover, local expression of IGF‐I was decreased in the lateral lobe. Lycopene also consistently reduced transcript levels of proinflammatory cytokines, immunoglobulins, and immunoglobulin receptors in the lateral lobe. This indicates that lycopene reduced inflammatory signals in the lateral prostate lobe. In summary, we show for the first time that lycopene reduced local prostatic androgen signaling, IGF‐I expression, and basal inflammatory signals in normal prostate tissue. All of these mechanisms can contribute to the epidemiologically observed prostate cancer risk reduction by lycopene.

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.

Targeting mitochondrial biogenesis for preventing and treating insulin resistance in diabetes and obesity: Hope from natural mitochondrial nutrients☆

Insulin resistance is an important feature of type 2 diabetes and obesity. The underlying mechanisms of insulin resistance are still unclear and may involve pathological changes in multiple tissues. Mitochondrial dysfunction, including mitochondrial loss and over-production of oxidants, has been suggested to be involved in the development of insulin resistance. Increasing evidence suggests that targeting mitochondria to protect mitochondrial function as a unique measure, i.e. mitochondrial medicine, could prevent and ameliorate various diseases associated with mitochondrial dysfunction. In this review, we have summarized recent progress in pharmaceutical and nutritional studies of drugs and nutrients to targeting mitochondria by stimulating mitochondrial metabolism (biogenesis and degradation) to improve mitochondrial function and decrease oxidative stress for preventing and ameliorating insulin resistance. We have focused on nutrients from natural sources to stimulating mitochondrial biogenesis in cellular systems and in animal models. The in vitro and in vivo studies, especially our own work on the effects and mechanisms of mitochondrial targeting nutrients or their combinations, may help us to understand the importance and mechanisms of mitochondrial biogenesis in insulin resistance, and provide hope for developing mitochondria-targeting agents for preventing and treating insulin resistance in type 2 diabetes and obesity.

Stimulation of GSH synthesis to prevent oxidative stress-induced apoptosis by hydroxytyrosol in human retinal pigment epithelial cells: activation of Nrf2 and JNK-p62/SQSTM1 pathways

The Nrf2-Keap1 pathway is believed to be a critical regulator of the phase II defense system against oxidative stress. By activation of Nrf2, cytoprotective genes such as heme oxygenase-1 (HO-1), NAD(P)H:quinone oxidoreductase (NQO-1) and γ-glutamyl-cysteine ligase (GCL) are induced. GCL-induced glutathione (GSH) production is believed to affect redox signaling, cell proliferation and death. We here report that tert-butyl hydroperoxide (t-BHP)-induced GSH reduction led to mitochondrial membrane potential loss and apoptosis in cultured human retinal pigment epithelial cells from the ARPE-19 cell line. Hydroxytyrosol (HT), a natural phytochemical from olive leaves and oil, was found to induce phase II enzymes and GSH, thus protect t-BHP-induced mitochondrial dysfunction and apoptosis. Depletion of GSH by buthionine-[S,R]-sulfoximine enhanced t-BHP toxicity and abolished HT protection. Overexpression of Nrf2 increased GSH content and efficiently protected t-BHP-induced mitochondrial membrane potential loss. Meanwhile, HT-induced GSH enhancement and induction of Nrf2 target gene (GCLc, GCLm, HO-1, NQO-1) messenger RNA (mRNA) were inhibited by Nrf2 knockdown, suggesting that HT increases GSH through Nrf2 activation. In addition, we found that HT was able to activate the PI3/Akt and mTOR/p70S6-kinase pathways, both of which contribute to survival signaling in stressed cells. However, the effect of HT was not inhibited by the PI3K inhibitor LY294002. Rather, c-Jun N-terminal kinase (JNK) activation was found to induce p62/SQSTM1 expression, which is involved in Nrf2 activation. Our study demonstrates that Nrf2 activation induced by the JNK pathway plays an essential role in the mechanism behind HTs strengthening of the antiapoptotic actions of the endogenous antioxidant system.

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.

Enhanced autophagy plays a cardinal role in mitochondrial dysfunction in type 2 diabetic Goto–Kakizaki (GK) rats: ameliorating effects of (−)-epigallocatechin-3-gallate

Oxidative stress and mitochondrial dysfunction are known to play important roles in type 2 diabetes mellitus (T2DM) and insulin resistance. However, the pathology of T2DM remains complicated; in particular, the mechanisms of mitochondrial dysfunction in skeletal muscle and other insulin-sensitive tissues are as yet unclear. In the present study, we investigated the underlying mechanisms of oxidative stress and mitochondrial dysfunction by focusing on mitochondrial dynamics, including mitochondrial biogenesis and autophagy, in skeletal muscle of a nonobese diabetic animal model--the Goto-Kakizaki (GK) rat. The results showed that GK rats exhibited impaired glucose metabolism, increased oxidative stress and decreased mitochondrial function. These dysfunctions were found to be associated with induction of LC3B, Beclin1 and DRP1 (key molecules mediating the autophagy pathway), while they appeared not to affect the mitochondrial biogenesis pathway. In addition, (-)-epigallocatechin-3-gallate (EGCG) was tested as a potential autophagy-targeting nutrient, and we found that EGCG treatment improved glucose tolerance and glucose homeostasis in GK rats, and reduced oxidative stress and mitochondrial dysfunction in skeletal muscle. Amelioration of excessive muscle autophagy in GK rats through the down-regulation of the ROS-ERK/JNK-p53 pathway leads to improvement of glucose metabolism, reduction of oxidative stress and inhibition of mitochondrial loss and dysfunction. These results suggest (a) that hyperglycemia-associated oxidative stress may induce autophagy through up-regulation of the ROS-ERK/JNK-p53 pathway, which may contribute to mitochondrial loss in soleus muscle of diabetic GK rats, and (b) that EGCG may be a potential autophagy regulator useful in treatment of insulin resistance.

Hydroxytyrosol Is the Major Anti-Inflammatory Compound in Aqueous Olive Extracts and Impairs Cytokine and Chemokine Production in Macrophages

Substances in olive products contribute to improved health as suggested by epidemiological data. In this study we assessed the effects of hydroxytyrosol (HT) on inflammatory mediators, cytokines and chemokines, and identified anti-inflammatory constituents of aqueous olive extracts, I.E., olive vegetation water (OVW). Murine macrophages (RAW264.7 cells) were stimulated with lipopolysaccharide (LPS) in the absence or presence of substances; inflammatory mediators [nitric oxide (NO), prostaglandin E₂ (PGE₂), cytokines, interleukins, chemokines] were determined by the Griess reaction, EIA, or multiplex ELISA (Luminex technology). Expression of inflammatory genes was determined by RT-PCR. Aqueous olive extracts were fractionated by preparative HPLC and the fractions investigated for their effects on NO and PGE₂ production. Results were further analyzed by principal component analysis. HT inhibited production of NO and PGE₂ with an IC₅₀ of 11.4 and 19.5 µM, respectively, reflecting strong anti-inflammatory activity. HT and OVW diminished secretion of cytokines (IL-1 α, IL-1 β, IL-6, IL-12, TNF- α), and chemokines (CXCL10/IP-10, CCL2/MCP-1). HT and OVW concentration-dependently reduced the expression of genes of inducible nitric oxide synthase (iNOS), IL-1 α, CXCL10/IP-10, MIP-1 β, matrix metalloproteinase-9, and prostaglandin E₂ synthase (PGES). The effects of HT were partly mediated VIA the NF- κB pathway, as shown by RT-PCR analysis. HT was identified as the main bioactive compound of OVW. The data provide a molecular basis for elucidating the effects of HT on inflammatory processes. The effects of HT on NO and chemokine production point to their impact on chronic inflammatory processes in endothelium or arthritis.

Lycopene in the prevention of renal cell cancer in the TSC2 mutant Eker rat model

Renal cell carcinoma (RCC) is the most frequent upper urinary tract cancer in humans and accounts for 80-85% of malignant renal tumors. Eker rat represents a unique animal model to study RCC since these rats develop spontaneous renal tumors and leiomyoma, which may be due to tuberous sclerosis 2 (TSC2) mutation resulting in the activation of the mammalian target of rapamycin (mTOR) pathway. This study examines the role of a lycopene-rich diet in the development of RCC in the TSC2 mutant Eker rat model. Ten-week old female Eker rats (n=90) were assigned in equal numbers to receive 0, 100 or 200mg/kg of lycopene as part of their daily diet. After 18 months the rats were sacrificed and the kidneys were removed. Immunohistochemical staining with antibodies against mTOR, phospho-S6 and EGFR were performed, as well as hematoxylin-eosin staining for histologic examination of the tumors. Tumors were counted and measured in individual kidneys. Presence of tumor decreased from 94% in control animals to 65% in the experimental group, but the difference was not statistically significant (P<0.12). However, mean numbers of renal carcinomas were statistically significantly decreased in the lycopene-treated rats (P<0.008) when compared to untreated controls. In the lycopene group, tumor numbers decreased (P<0.002) and the numbers tended to decrease linearly (P<0.003) as supplemental lycopene increased from 0 to 200. Control rats fed only basal diet had a greater length of tumors (23.98 mm) than rats fed lycopene supplement groups (12.90 mm and 11.07 mm) (P<0.05). Moreover tumor length decreased (P<0.02) and tumor length tended to decrease linearly (P<0.03) as supplemental lycopene increased from 0 to 200mg/kg. All tumors showed strong staining with antibodies against mTOR, phospho-S6 and EGFR. In conclusion, dietary supplementation with lycopene attenuates the development of renal cell cancers in the predisposed TSC2 mutant Eker rat model. These results suggest that lycopene may play a role in the prevention of RCC.

Skin Photoprotection by Carotenoids

In Western populations, a lifestyle favouring tanned skin leads to increased exposure to natural and artificial sources of UV-radiation (UVR). To keep the adverse effects of this exposure, such as sunburn, immunosuppression, photoaging and photocarcinogenesis, to a minimum, nutritional manipulation of the basic endogenous protective properties of skin is an attractive target. In this respect, considerable interest has been directed for many years towards the dietary carotenoids, because of their radical scavenging and singlet oxygen quenching properties and thus their putative role in photochemistry, photobiology and photomedicine.