Antioxidant effect of homogenetisic acid on hydrogen peroxide induced oxidative stress in human lung fibroblast cells

Pre-exposure to Fe2O3 or TiO2 Nanoparticles Inhibits Subsequent Biological Uptake of 55Fe-Labeled Fe2O3 Nanoparticles

Aquatic organisms are frequently exposed to various nanoparticles (NPs) in the natural environment. Thus, studies of NP bioaccumulation should include organisms that have been previously exposed to NPs. Our study investigated the effects of pre-exposure of Tetrahymena thermophila (T. thermophila) to Fe₂O₃ or TiO₂ NPs on the protozoan's subsequent uptake of ⁵⁵Fe-labeled Fe₂O₃ (⁵⁵Fe₂O₃) NPs. Molecular mechanisms underlying the pre-exposure effects were explored in transcriptomic and metabolomic experiments. Pre-exposure to either NPs inhibited the subsequent uptake of ⁵⁵Fe₂O₃ NPs. The results of the transcriptomic experiment indicated that NP pre-exposure influenced the expression of genes related to phagosomes and lysosomes and physiological processes such as glutathione and lipid metabolism, which are closely associated with the endocytosis of ⁵⁵Fe₂O₃ NPs. The differentially expressed metabolites obtained from the metabolomic experiments showed an enrichment of energy metabolism and antioxidation pathways in T. thermophila pre-exposed to NPs. Together, these results demonstrate that the pre-exposure of T. thermophila to Fe₂O₃ or TiO₂ NPs inhibited the protozoan's subsequent uptake of ⁵⁵Fe₂O₃ NPs, possibly by mechanisms involving the alteration of endocytosis-related organelles, the induction of oxidative stress, and a lowering of the intracellular energy supply. Thus, NP pre-exposure represents a scenario which can inform increasingly realistic estimates of NP bioaccumulation.

Cytotoxic activity of strawberry tree (Arbutus unedo L.) honey, its extract, and homogentisic acid on CAL 27, HepG2, and Caco-2 cell lines

Strawberry tree (Arbutus unedo L.) honey (STH), also known as “bitter honey”, is a traditional medicine widely used in the Mediterranean area. Regardless of geographical origin, it usually has a very high content of phenolic compounds and strong antioxidant capacity. Yet, little is still known about the effects of STH, its phenolic extract (STHE), and its main bioactive compound – homogentisic acid (HGA) – at the cell level. The aim of this study was to estimate total phenolic content, DPPH radical scavenging activity, and ferric reducing antioxidant power of STH made in Croatia and investigate cytotoxic and pro-oxidative effects of STH, STHE and HGA on three human cell lines: tongue squamous cell carcinoma (CAL 27), hepatocellular carcinoma (HepG2), and epithelial colorectal adenocarcinoma cells (Caco-2) cells. These substances were tested at four concentrations (0.5–5× average human daily intake of STH) and over 30 min and 1 and 2 h. Croatian STH had a total phenolic content of 1.67 g gallic acid equivalents (GAE) per kg of honey, DPPH radical scavenging activity of 2.96 mmol Trolox equivalents (TE) per kg of honey, and ferric reducing antioxidant power (FRAP) of 13.5 mmol Fe²⁺ per kg of honey. Our results show no clear and consistent time- or concentration-dependent cytotoxicity in any of the cell lines. ROS levels in all the three cell types at almost all exposure times were not significantly higher than control. The most important observation is that the tested substances have low cytotoxicity and high biocompatibility, regardless of concentration, which is a good starting point for further research of their biological effects in other models.

Opioids and Vitamin C: Known Interactions and Potential for Redox-Signaling Crosstalk

Opioids are among the most widely used classes of pharmacologically active compounds both clinically and recreationally. Beyond their analgesic efficacy via μ opioid receptor (MOR) agonism, a prominent side effect is central respiratory depression, leading to systemic hypoxia and free radical generation. Vitamin C (ascorbic acid; AA) is an essential antioxidant vitamin and is involved in the recycling of redox cofactors associated with inflammation. While AA has been shown to reduce some of the negative side effects of opioids, the underlying mechanisms have not been explored. The present review seeks to provide a signaling framework under which MOR activation and AA may interact. AA can directly quench reactive oxygen and nitrogen species induced by opioids, yet this activity alone does not sufficiently describe observations. Downstream of MOR activation, confounding effects from AA with STAT3, HIF1α, and NF-κB have the potential to block production of antioxidant proteins such as nitric oxide synthase and superoxide dismutase. Further mechanistic research is necessary to understand the underlying signaling crosstalk of MOR activation and AA in the amelioration of the negative, potentially fatal side effects of opioids.

Homogentisic acid, a main phenolic constituent of strawberry tree honey, protects human peripheral blood lymphocytes against irinotecan-induced cytogenetic damage in vitro

Homogentisic acid (HGA) is the most abundant phenolic compound in strawberry tree (Arbutus unedo L.) honey and an intermediate in the metabolism of phenylalanine and tyrosine. Since HGA exerts its dual nature (pro-oxidant and antioxidant), which depends on the concentration and cell type, the aim of study was to determine whether HGA possess cytoprotective effects and could counteract the cyto- and genotoxic effects of the antineoplastic drug irinotecan (IRI). Tested concentrations corresponded to HGA content in average daily dose of strawberry tree honey as well as five- and ten-fold higher concentrations. Cyto- and genoprotective effects were tested on human peripheral blood lymphocytes using chromosomal aberrations assay and cytokinesis-block micronucleus cytome assay. HGA, even at concentrations 10-fold higher than the one present in the daily amount of consumed strawberry tree honey, posed a non-significant cytotoxic threat to lymphocytes, had a negligible potential for causing cytogenetic damage in treated cells, and did not significantly impair their proliferation. Results of the chromosomal aberration assay and CBMN Cyt assay also showed that HGA efficiently counteracted the detrimental cytogenetic effects of IRI in vitro. The finding on cyto- and genoprotective effects of HGA merits further research in order to better explain the safety profile of this compound and to assess its potency for the development of novel nutraceutical products.

Arbutus species (Ericaceae) as source of valuable bioactive products

In addition to nutrients, plant foods contain compounds that may provide additional health benefits improving the quality of life. Species from Arbutus genus (Ericaceae) represent a promising source of healthy phytochemicals. Bioactive compounds including such as anthocyanins, iridoids, phenols, triterpenes, sterols, and fatty acids are reported from Arbutus species. Some Arbutus species revealed promising biological activities including antioxidant, anti-inflammatory, anti-proliferative, anti-diabetic, and antimicrobial activities, and deserve for that reason further consideration for new drug discovery. However, only few species are investigated scientifically for their chemical profile and biological activities. The aim of this article is to summarize the current knowledge of the components and biological properties of Arbutus species common in Mediterranean area, as well as the future prospects on their applications as potentially valuable products.

Multi-elemental composition and antioxidant properties of strawberry tree (Arbutus unedo L.) honey from the coastal region of Croatia: Risk-benefit analysis

The concentration of 23 major and trace elements, total phenolic content (TPC) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity were determined in nine samples of strawberry tree honey and compared to other types of unifloral honeys. The most abundant elements in strawberry tree honey were potassium, calcium, magnesium and sodium, ranging between 1276 and 2367, 95.2-154, 14.4-74.4 and 13.4-64.3mg/kg, respectively. Strawberry tree honey had generally higher TPC (range: 0.314-0.522g GA/kg) and DPPH (1.94-4.45mM TE/kg) compared to other analysed unifloral honeys. A strong positive relationship was found between TPC and DPPH, TPC and concentration of homogentisic acid (HGA), chemical marker of strawberry tree honey, and between DPPH and HGA. Regarding daily intake of essential elements, strawberry tree honey can be considered nutritionally richer than the majority of unifloral honeys available in Croatia, while contribution to tolerable intake set for potentially toxic elements was very low, corresponding to pristine areas.

Conversion of Squid Pen to Homogentisic Acid via Paenibacillus sp. TKU036 and the Antioxidant and Anti-Inflammatory Activities of Homogentisic Acid

The culture supernatant of Paenibacillus sp. TKU036, a bacterium isolated from Taiwanese soils, showed high antioxidant activity (85%) when cultured in a squid pen powder (SPP)-containing medium at 37 °C for three days. Homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA) was isolated and found to be the major antioxidant in the culture supernatant of the SPP-containing medium fermented by Paenibacillus sp. TKU036. Tryptophan was also present in the culture supernatant. The results of high-performance liquid chromatography (HPLC) fingerprinting showed that HGA and tryptophan were produced via fermentation but did not pre-exist in the unfermented SPP-containing medium. Neither HGA nor tryptophan was found in the culture supernatants obtained from the fermentation of nutrient broth or other chitinous material, i.e., medium containing shrimp head powder, by Paenibacillus sp. TKU036. The production of HGA via microorganisms has rarely been reported. In this study, we found that squid pen was a potential carbon and nitrogen source for Paenibacillus sp. Tryptophan (105 mg/L) and HGA (60 mg/L) were recovered from the culture supernatant. The isolated HGA was found to have higher antioxidant activity (IC50 = 6.9 μg/mL) than α-tocopherol (IC50 = 17.6 μg/mL). The anti-inflammatory activity of the isolated HGA (IC50 = 10.14 μg/mL) was lower than that of quercetin (IC50 = 1.14 μg/mL). As a result, squid pen, a fishery processing byproduct, is a valuable material for the production of tryptophan and the antioxidant and anti-inflammatory HGA via microbial conversion.

Long Chain Fatty Acid Esters of Quercetin-3-O-glucoside Attenuate H₂O₂-induced Acute Cytotoxicity in Human Lung Fibroblasts and Primary Hepatocytes

Cellular oxidative stress causes detrimental effects to macromolecules, such as lipids, nucleic acids and proteins, leading to many pathological conditions. Quercetin-3-O-glucoside (Q3G), a glycosylated derivative of quercetin (Q), is a natural polyphenolic compound known to possess antioxidant activity. The hydrophilic/lipophilic nature of an antioxidant molecule is considered as an important factor governing the accessibility to the active sites of oxidative damages in vivo. Six long chain fatty acid esters of Q3G were evaluated with comparison to Q and Q3G, for their cytoprotective activity under H₂O₂-induced oxidative stress using cell culture model systems through cell viability, lipid peroxidation and fluorescence microscopy studies. Pre-incubation of α-linolenic acid (ALA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) esters of Q3G exhibited significantly (p ≤ 0.05) greater cell viability in both human lung fibroblast (WI-38) and human primary hepatocytes upon exposure to H₂O₂ insult when compared to the control. Cytoprotection due to oleic acid and linoleic acid esters of Q3G was observed only in human primary hepatocytes. All the derivatives, Q3G and quercetin showed ability to significantly (p ≤ 0.05) lower production of lipid hydroperoxides under induced oxidative stress, compared to the control. However, ALA and DHA esters of Q3G resulted in significantly lower lipid hydroperoxidation than Q and Q3G. Based on fluorescence microscopy study, H₂O₂-induced apoptosis was attenuated by the fatty acid derivatives of Q3G. The fatty acid derivatives of Q3G possess better cytoprotective effect than Q3G against H₂O₂-induced cytotoxicity in vitro and the concentration should be selected to avoid cytotoxicity.

Accelerated bone ingrowth by local delivery of Zinc from bioactive glass: oxidative stress status, mechanical property, and microarchitectural characterization in an ovariectomized rat model

BACKGROUND

Synthetic bone graft substitutes such as bioactive glass (BG) material are developed in order to achieve successful bone regeneration. Zn plays an important role in the proper bone growth, development, and maintenance of healthy bones.

AIMS

This study aims to evaluate in vivo the performance therapy of zinc-doped bioactive glass (BG-Zn) and its applications in biomedicine.

METHODS

Female Wistar rats were ovariectomized. BG and BG-Zn were implanted in the femoral condyles of Wistar rats and compared to that of control group. Grafted bone tissues were carefully removed to evaluate the oxidative stress status, histomorphometric profile, mechanical property, and mineral bone distribution by using inductively coupled plasma optical emission spectrometry.

RESULTS

A significant decrease of thiobarbituric acid-reactive substances was observed after BG-Zn implantation. Superoxide dismutase, catalase (CAT), and glutathione peroxidase (GPx) activities significantly increased in ovariectomized group implanted with Zinc-doped bioactive glass (OVX-BG-Zn) as compared to ovariectomized group implanted with bioactive glass (OVX-BG). An improved mechanical property was noticed in contact of OVX-BG-Zn (39±6 HV) when compared with that of OVX-BG group (26±9 HV). After 90 days of implantation, the histomorphometric analysis showed that trabecular thickness (Tb.Th) and trabecular number (Tb.N) were significantly increased with 28 and 24%, respectively, in treated rats of OVX-BG-Zn group as compared to those of OVX-BG groups. Trabecular separation (Tb.Sp) and trabecular bone pattern factor (TBPf) were significantly decreased in OVX-BG-Zn group with 29.5 and 54% when compared with those of OVX-BG rat groups. On the other hand, a rise in Ca and P ion concentrations in the implanted microenvironment was shown and lead to the formation/deposition of Ca-P phases. The ratio of pyridinoline [Pyr] to dihydroxylysinonorleucine [DHLNL] cross-links was normalized to the control level.

CONCLUSION

Our findings suggested that BG-Zn might have promising potential applications for osteoporosis therapy.

Antioxidant profile of strawberry tree honey and its marker homogentisic acid in several models of oxidative stress

The antioxidant activity of several honeys was evaluated considering the different contribution of entire samples. The strawberry tree honey emerged as the richest in total phenols and the most active honey in the DPPH and FRAP tests, and could protect cholesterol against oxidative degradation (140°C). Homogentisic acid (2,5-dihydroxyphenylacetic acid, HGA), the main phenolic compound from strawberry tree honey, showed interesting antioxidant and antiradical activities, and protective effect against thermal-cholesterol degradation, comparable to those of well known antioxidants. Moreover, the pre-treatment with HGA significantly preserved liposomes and LDL from Cu(2+)-induced oxidative damage at 37°C for 2h, inhibiting the reduction of polyunsaturated fatty acids and cholesterol and the increase of their oxidative products. This phenol had no toxic effect in human intestinal epithelial Caco-2 cells within the concentration range tested (5-1000μM). HGA was able to pass through the Caco-2 monolayers, the apparent permeability coefficients (Papp) in the apical-to-basolateral and basolateral-to-apical direction were 3.48±1.22×10(-6) and 2.18±0.34×10(-6)cm/s, respectively, suggesting a passive diffusion pathway as the dominating process. The results of the work qualify HGA as natural antioxidant, able to exert a significant in vitro protective effect and to contribute to the strawberry tree honey antioxidant activity.