The Effects of Brazilian Green Propolis against Excessive Light-Induced Cell Damage in Retina and Fibroblast Cells

In-vitro and in-vivo evaluations of tocotrienol-rich nanoemulsified system on skin wound healing

Proper wound healing is vital for the survival of higher organisms. Responses to skin injury can lead to complications such as scar formation that can affect the quality of life. In this study, keratinocytes migration (scratch assay) and zebrafish tail regeneration experiments were used to evaluate the wound healing effect of a tocotrienol-based nanoemulsified (NE) system against ascorbic acid and phosphate-buffered saline (PBS) as positive and negative controls, respectively. MTT assay provided a concentration range of 0.35–8.75 μg/ml of nanoemulsion that produced cell viability more than 100%. After 24 hours of treatment, the wound closure of keratinocytes were found to be significantly faster by 73.76%, 63.37% and 35.56%, respectively when treated with 3.50 μg/ml and 1.75 μg/ml of NE compared to the blank. The lethal concentration at 50% (LC₅₀ value) obtained from acute and prolonged toxicity was almost similar, which was 4.6 mg/ml and 5.0 mg/ml, respectively. Growth of zebrafish tail regeneration treated with NE at a concentration of 2.5 mg/ml was significantly faster than the untreated zebrafish, which regenerated to 40% on the fifth day, more than 60% on the tenth day of treatment and fully recovered at the twentieth day. In conclusion, these results showed the potential of the tocotrienols-based nanoemulsified system in enhancing wound healing through accelerated wound closure.

Flavonoids Present in Propolis in the Battle against Photoaging and Psoriasis

The skin is the main external organ. It protects against different types of potentially harmful agents, such as pathogens, or physical factors, such as radiation. Skin disorders are very diverse, and some of them lack adequate and accessible treatment. The photoaging of the skin is a problem of great relevance since it is related to the development of cancer, while psoriasis is a chronic inflammatory disease that causes scaly skin lesions and deterioration of the lifestyle of people affected. These diseases affect the patient's health and quality of life, so alternatives have been sought that improve the treatment for these diseases. This review focuses on describing the properties and benefits of flavonoids from propolis against these diseases. The information collected shows that the antioxidant and anti-inflammatory properties of flavonoids play a crucial role in the control and regulation of the cellular and biochemical alterations caused by these diseases; moreover, flavones, flavonols, flavanones, flavan-3-ols, and isoflavones contained in different worldwide propolis samples are the types of flavonoids usually evaluated in both diseases. Therefore, the research carried out in the area of dermatology with bioactive compounds of different origins is of great relevance to developing preventive and therapeutic approaches.

Ethanol Extract of Chinese Propolis Attenuates Early Diabetic Retinopathy by Protecting the Blood-Retinal Barrier in Streptozotocin-Induced Diabetic Rats

Propolis has been shown to reduce the level of blood glucose and suppress the histopathological changes in diabetics. However, it still remains unknown if propolis has a similar effect on diabetic retinopathy (DR). Our study aimed to evaluate the effect of the ethanol extract of Chinese propolis (EECP) on early DR in streptozotocin (STZ)-induced diabetic rats. EECP was given to diabetic rats by oral intubation for 12 weeks. The concentrations of fasting blood glucose (FBG), glycated hemoglobin (HbA1c), malondialdehyde (MDA), reactive oxygen species (ROS), and reactive nitrogen species (RNS) were measured. Pathological examinations, including hematoxylin and eosin (HE) staining, transmission electron microscopy (TEM), and immunofluorescence, were also conducted to provide further evidence of EECP's effect on early DR. EECP was able to attenuate diabetes via directly decreasing the levels of FBG and HbA1c, which also resulted in the reduction of MDA, ROS, and RNS. Furthermore, EECP could protect against the damages of photoreceptor cells, as well as retinal thickening. And the inhibition of blood-retinal barrier (BRB) leakage was also observed in EECP-treated diabetic rats, along with the inhibition the loss of tight junction proteins (occludin, ZO-1). These results suggest that EECP has an ameliorating effect on early DR by inhibition of blood-retinal barrier breakdown. PRACTICAL APPLICATION: This study sheds light on the protective effect of the ethanol extract of Chinese propolis on early diabetic retinopathy and the molecular actions underlying the inhibition of blood-retinal barrier breakdown. Our study suggests that ethanol extract of Chinese propolis can be considered as a potential therapeutic agent in the treatment of early diabetic retinopathy.

Transplanted olfactory ensheathing cells restore retinal function in a rat model of light-induced retinal damage by inhibiting oxidative stress

There is still not an effective treatment for continuous retinal light exposure and subsequent photoreceptor degeneration. Olfactory ensheathing cell (OEC) transplantation has been shown to be neuroprotective in spinal cord, and optic nerve injury and retinitis pigmentosa. However, whether OECs protect rat photoreceptors against light-induced damage and how this may work is unclear. Thus, to elucidate this mechanism, purified rat OECs were grafted into the subretinal space of a Long-Evans rat model with light-induced photoreceptor damage. Light exposure decreased a- and b- wave amplitudes and outer nuclear layer (ONL) thickness, whereas the ONL of rats exposed to light for 24 h after having received OEC transplants in their subretinal space was thicker than the PBS control and untreated groups. A- and b- wave amplitudes from electroretinogram of OEC-transplanted rats were maintained until 8 weeks post OEC transplantation. Also, transplanted OECs inhibited formation of reactive oxygen species in retinas exposed to light. In vitro experiments showed that OECs had more total antioxidant capacity in a co-cultured 661W photoreceptor cell line, and cells were protected from damage induced by hydrogen-peroxide. Thus, transplanted OECs preserved retinal structure and function in a rat model of light-induced degeneration by suppressing retinal oxidative stress reactions.

Mechanisms underlying the wound healing potential of propolis based on its in vitro antioxidant activity

BACKGROUND

Propolis is a resinous substance collected by honeybees, Apis mellifera, from various plant sources. Having various pharmacological and biological activities, it has been used in folk medicine and complementary therapies since ancient times.

PURPOSE

To evaluate the effects and underlying mechanism of the protective effects of the ethanol extract of Chinese propolis (EECP) on L929 cells injured by hydrogen peroxide (H₂O₂).

STUDY DESIGN

The wound healing activities of EECP in L929 cells with H₂O₂-induced damage were investigated.

METHODS

The main components of EECP were analyzed by RP-HPLC, and the free radical scavenging capacity and reducing power were also measured. The effects of EECP on the expression of antioxidant-related genes in fibroblast L929 cells were determined using qRT-PCR and western blotting.

RESULTS

EECP had significant protective effects against cell death induced by H₂O₂ and significantly inhibited the decline of collagen mRNA expression caused by H₂O₂ in L929 cells.

CONCLUSION

EECP induced the expression of antioxidant-related genes, such as HO-1, GCLM, and GCLC, which has great implications for the potential of propolis to alleviate oxidative stress in wound tissues. The protective effects of propolis have great implications for using propolis as a wound healing regent.

Anti-photoaging potential of propolis extract in UVB-irradiated human dermal fibroblasts through increasing the expression of FOXO3A and NGF genes

Propolis is a resinous compound that has been widely used in folk medicine. Different biological activities and therapeutic applications of propolis have been studied before. However, the effects of propolis on longevity-associated genes expression in the prevention of skin photoaging still remained unclear. Therefore in this study the protective effects of propolis on the expressions of two longevity-associated genes, FOXO3A and NGF genes, against UVB-induced photoaging in human dermal fibroblasts (HDF) were investigated. Propolis extract demonstrated a concentration-dependent free radical scavenging activity that was determined by 2, 2-diphenyl-1-picrylhydrazyl (DPPH) assay. Also, Folin-Ciocalteu method was used to measure the total phenolic content of the extract. The viability of HDF cells was decreased gradually with increasing UVB radiation doses and 248mJ/cm² was selected as the sub-cytotoxic dose. Pre-treatment with propolis extract increased the viability of UVB-irradiated human dermal fibroblasts and decreased the number of β-galactosidase positive cells as senescent cells among them. It also increased the expression of FOXO3A and NGF genes in irradiated and non-irradiated cells. Consequently, these findings suggest that propolis extract has anti-photoaging potential and this property, in addition to its strong antioxidant activity, may be due to its effects on upregulation of longevity-associated genes.

Antioxidant activities and molecular mechanisms of the ethanol extracts of Baccharis propolis and Eucalyptus propolis in RAW64.7 cells

Context Numerous studies have reported that propolis possesses strong antioxidant activities. However, their antioxidant molecular mechanisms are unclear. Objective We utilize ethanol extracts of Chinese propolis (EECP) as a reference to compare ethanol extracts of Eucalyptus propolis (EEEP) with ethanol extracts of Baccharis propolis (EEBGP) based on their antioxidant capacities and underlying molecular mechanisms. Materials and methods HPLC and chemical analysis are utilized to evaluate compositions and antioxidant activities. ROS-eliminating effects of EEBGP (20-75 μg/mL), EEEP (1.25-3.75 μg/mL) and EECP (1.25-5 μg/mL) are also determined by flow cytometry analysis. Moreover, we compared antioxidant capacities by determining their effects on expressions of antioxidant genes in RAW264.7 cells with qRT-PCR, western blot and confocal microscopy analysis. Results EEBGP mainly contains chlorogenic acid (8.98 ± 0.86 mg/g), kaempferide (11.18 ± 8.31 mg/g) and artepillin C (107.70 ± 10.86 mg/g), but EEEP contains 10 compositions, whereas EECP contains 17 compositions. Meantime, although EEEP shows DPPH (IC50 19.55 ± 1.28), ABTS (IC50 20.0 ± 0.31) and reducing power (2.70 ± 0.08 mmol TE/g) better than EEBGP's DPPH (IC50 43.85 ± 0.54), ABTS (IC50 38.2 ± 0.33) and reducing power (1.53 ± 0.05 mmol TE/g), EEBGP exerts much higher ROS inhibition rate (40%) than EEEP (under 20%). Moreover, EEBGP strengthen antioxidant system by activating p38/p-p38 and Erk/p-Erk kinase via accelerating nucleus translocation of Nrf2. EEEP and EECP improve antioxidant gene expression only via Erk/p-Erk kinase-Nrf2 signalling pathway. Discussion and conclusion EEBGP and EEEP exert antioxidant activities via different molecular mechanisms, which may depend on chemical compositions.

Polyphenol-Rich Propolis Extracts Strengthen Intestinal Barrier Function by Activating AMPK and ERK Signaling

Propolis has abundant polyphenolic constituents and is used widely as a health/functional food. Here, we investigated the effects of polyphenol-rich propolis extracts (PPE) on intestinal barrier function in human intestinal epithelial Caco-2 cells, as well as in rats. In Caco-2 cells, PPE increased transepithelial electrical resistance and decreased lucifer yellow flux. PPE-treated cells showed increased expression of the tight junction (TJ) loci occludin and zona occludens (ZO)-1. Confocal microscopy showed organized expressions in proteins related to TJ assembly, i.e., occludin and ZO-1, in response to PPE. Furthermore, PPE led to the activation of AMPK, ERK1/2, p38, and Akt. Using selective inhibitors, we found that the positive effects of PPE on barrier function were abolished in cells in which AMPK and ERK1/2 signaling were inhibited. Moreover, rats fed a diet supplemented with PPE (0.3% in the diet) exhibited increased colonic epithelium ZO-1 expression. Overall, these data suggest that PPE strengthens intestinal barrier function by activating AMPK and ERK signaling and provide novel insights into the potential application of propolis for human gut health.

Brazilian green propolis water extract up-regulates the early expression level of HO-1 and accelerates Nrf2 after UVA irradiation

Background

Exposure to ultraviolet A (UVA) irradiation is the major cause of human skin aging. Suppression of UVA irradiation-induced skin fibroblast cell damage protects the skin against aging. An oxidative stress response transcription factor nuclear factor-(erythroid-derived 2)-related factor 2 (Nrf2) has an important role as a cytoprotective system against oxidative stress in the human skin and other organs. Propolis has been commonly used as a traditional medicine since ancient times. The water extract of propolis (WEP) mainly contains caffeoylquinic acids. In our previous study, we reported that WEP and its major constituents protected immortalized human skin fibroblast cells (NB1-RGB) against UVA irradiation-induced cell death. In this study, we examined the mechanism of WEP-mediated skin protection and the possible involvement of Nrf2/antioxidant response element (ARE) pathways.

Methods

Brazilian green propolis was used in the present study (Minas Gerais State, Brazil), Baccharis dracunculifolia is its main source. The Baccharis propolis was extracted with water at 50 °C to yield water extract. The NB1-RGB cell cultures were incubated for 23 h. After replenishing the medium, WEP or its constituents were added to the cell cultures. After 1 h, the cells were exposed to 10 J/cm² of UVA light (365 nm UVA light source, CL-1000 L UV Closslinkers, Ultraviolet Products Ltd., Cambridge, UK). Heme oxygenase-1 (HO-1) expression levels in NB1-RGB cells were evaluated using western blotting. Nrf2 nuclear translocation changes in NB1-RGB cells were indicated using immunostaining.

Results

We demonstrated that WEP pretreatment up-regulated HO-1 expression level after UVA irradiation at earlier time points than vehicle pretreatment did, and three main constituents of WEP showed similar effects. Furthermore, WEP pretreatment also accelerated Nrf2 nuclear translocation after UVA irradiation.

Conclusions

Our findings indicated that WEP acts as an early inducer of HO-1 and rapid activator of Nrf2 to protect against UVA-induced oxidative stress.

Down-regulation of let-7 microRNA increased K-ras expression in lung damage induced by radon

Radon has long been recognized as a human carcinogen leading to lung cancer, but the underlying mechanisms remain obscure. Recent studies have shown that the let-7 microRNA and K-ras play an important role in the development of various cancers. However, the exact role between let-7 and K-ras in radon induced lung damage has not been explored so far. In the present study, wistar rats and human bronchial epithelial (HBE) cells were long-term exposed to radon, and then alterations in histological pathology of rat lung tissue, ROS, antioxidant enzymes activities and clonogenic formation in HBE cells, as well as changes in let-7 and K-ras expression were determined to observe the adverse effects induced by radon. The results showed that long-term exposure to radon produced severe lung damage in rats, significantly increased ROS production and clonogenic formation ratios and decreased SOD activities in HBE cells. In addition, an obvious down-regulation of let-7 and up-regulation of K-ras were also revealed both in mRNA and in protein level in lung tissue of rats and HBE cells exposed to radon. Furthermore, a significant down-regulation of K-ras was then confirmed in both let-7b-3p and let-7a-2-3p transfected HBE cells. Taken together, the present results propose an involvement of let-7 microRNA and K-ras in radon induced lung damage both in vivo and in vitro, which may thus be of potential value in early diagnosis and therapy of radon-induced lung tumorgenesis.

Dopamine D2 receptor blocker thioridazine induces cell death in human uterine cervical carcinoma cell line SiHa

AIM

The aim of this study was to explore the correlation of dopamine D2 receptor (DRD2) and the development of uterine cervical cancer, and the effect of thioridazine (an antagonist of DRD2) on the SiHa cell line.

MATERIAL AND METHODS

The expression of DRD2 in tissues was detected with immunohistochemistry. SiHa cells were exposed to different concentrations of thioridazine for 24 h, and then cell viability was determined. After 20-μM thioridazine treatment for 24 h, the protein level of DRD2 in SiHa cells was analyzed by Western blots, apoptosis was detected with the phosphatidylserine externalization and comet assay, and necrosis was detected by measuring high-mobility group box 1 protein (HMGB1).

RESULTS

The expression of DRD2 gradually increased from normal to cancer tissues (P < 0.01). In vitro, DRD2 blocker thioridazine treatment resulted in death of SiHa cells with the expression of DRD2 significantly regulated down (P < 0.05), and thioridazine significantly induced SiHa apoptosis (P = 0.016) and necrosis (P < 0.01).

CONCLUSION

Higher DRD2 expression is closely associated with cervical cancer progression. After blocking DRD2, SiHa cell growth is significantly suppressed, indicating that DRD2 may function as a novel tumor marker and a potential therapeutic target for cervical cancer.