UVB-induced DNA damage, generation of reactive oxygen species, and inflammation are effectively attenuated by the flavonoid luteolin in vitro and in vivo

Ocimum sanctum L (Holy Basil or Tulsi) and its phytochemicals in the prevention and treatment of cancer

Ocimum sanctum L. or Ocimum tenuiflorum L, commonly known as the Holy Basil in English or Tulsi in the various Indian languages, is a important medicinal plant in the various traditional and folk systems of medicine in Southeast Asia. Scientific studies have shown it to possess antiinflammatory, analgesic, antipyretic, antidiabetic, hepatoprotective, hypolipidemic, antistress, and immunomodulatory activities. Preclinical studies have also shown that Tulsi and some of its phytochemicals eugenol, rosmarinic acid, apigenin, myretenal, luteolin, β-sitosterol, and carnosic acid prevented chemical-induced skin, liver, oral, and lung cancers and to mediate these effects by increasing the antioxidant activity, altering the gene expressions, inducing apoptosis, and inhibiting angiogenesis and metastasis. The aqueous extract of Tulsi and its flavanoids, orintin, and vicenin are shown to protect mice against γ-radiation-induced sickness and mortality and to selectively protect the normal tissues against the tumoricidal effects of radiation. The other important phytochemicals like eugenol, rosmarinic acid, apigenin, and carnosic acid are also shown to prevent radiation-induced DNA damage. This review summarizes the results related to the chemopreventive and radioprotective properties of Tulsi and also emphasizes aspects that warrant future research to establish its activity and utility in cancer prevention and treatment.

Ultraviolet B (UVB) irradiation-induced apoptosis in various cell lineages in vitro

Ultraviolet B (UVB) radiation acts as a strong apoptotic trigger in many cell types, in tumor and normal cells. Several studies have demonstrated that UVB-induced cell death occurs through the generation of reactive oxygen species. The consequent oxidative stress includes the impairment of cellular antioxidants, the induction of DNA damage and the occurrence of apoptosis. In this review, we investigated UVB apoptotic action in various cell models by using ultrastructural, molecular and cytofluorimetric techniques. Myeloid leukemia HL-60, T-lymphoblastoid Molt-4 and myelomonocytic U937 human cells, generally affected by apoptotic stimuli, were studied. Human chondrocytes and C2C12 skeletal muscle cells, known to be more resistant to damage, were also considered. All of them, when exposed to UVB radiation, revealed a number of characteristic apoptotic markers. Membrane blebbing, cytoplasm shrinkage and chromatin condensation were detected by means of electron microscopy. DNA cleavage, investigated by using agarose gel electrophoresis and TUNEL reaction, was observed in suspended cells. Differently, in chondrocytes and in skeletal muscle cells, oligonucleosomic DNA fragmentation did not appear, even if a certain TUNEL positivity was detected. These findings demonstrate that UVB radiation appears to be an ideal tool to study the apoptotic behavior.

Luteolin prevents solar radiation-induced matrix metalloproteinase-1 activation in human fibroblasts: a role for p38 mitogen-activated protein kinase and interleukin-20 released from keratinocytes

Human skin is continuously exposed to solar radiation, which can result in photoaging, a process involving both dermal and, to a lesser extent, epidermal structures. Previously, we have shown that the flavonoid luteolin protects the epidermis from ultraviolet (UV)-induced damage by a combination of UV-absorbing, antioxidant, and antiinflammatory properties. The aim of the present study was to determine direct and indirect effects of luteolin on dermal fibroblasts as major targets of photoaging. Stimulation of fibroblasts with UVA light or the proinflammatory cytokine interleukin-20 (IL-20) is associated with wrinkled skin, increased IL-6 secretion, matrix metalloproteinase (MMP-1) expression, and hyaluronidase activity. All of these targets were inhibited by luteolin via interference with the p38 mitogen-activated protein kinase (MAPK) pathway. Next, we assessed the role of conditioned supernatants from keratinocytes irradiated with solar-simulated radiation (SSR) on nonirradiated dermal fibroblasts. In keratinocytes, luteolin inhibited SSR-induced production of IL-20, also via interference with the p38 MAPK pathway. Similarly, keratinocyte supernatant-induced IL-6 and MMP-1 expression in fibroblasts was reduced by pretreatment of keratinocytes with luteolin. Finally, these results were confirmed ex vivo on skin explants treated with luteolin before UV irradiation. Our results suggest that SSR-mediated production of soluble factors in keratinocytes is modulated by luteolin and may attenuate photoaging in dermal fibroblasts.

Nitric oxide donor exisulind is an effective inhibitor of murine photocarcinogenesis

NO-releasing nonsteroidal anti-inflammatory drugs (NO-NSAIDs) have been shown to have anti-inflammatory, antiproliferative and apoptosis-inducing effects in tumor cells. Herein, we have investigated the effects of NO-exisulind on the growth of UVB-induced skin tumor development in a murine model. We found that the topical treatment with NO-exisulind significantly reduced UVB-induced tumors in SKH-1 hairless mice. The tumors/tumor bearing mouse, the number of tumors/mouse and tumor volume/mouse decreased significantly (P < 0.05) as compared with vehicle-treated and UVB-irradiated positive controls. Consistently, NO-exisulind-treated animals showed reduced expression of proliferation markers, such as PCNA and cyclin D1. These mice also manifested increased expression of proapoptotic Bax and decreased expression of antiapoptotic Bcl2 with an increase in the number of TUNEL-positive cells in tumors. We also investigated whether NO-exisulind-treated tumors are less invasive and progress less efficiently from benign to malignant carcinomas. For this, tumors were stained for various epithelial-mesenchymal transition (EMT) markers. NO-exisulind decreased the expression of mesenchymal markers, such as Fibronectin, N-cadherin, SNAI, Slug and Twist and enhanced the epithelial marker E-cadherin. Similarly, UVB-induced phosphorylation of Erk1/2 and p38 was decreased in NO-exisulind-treated animals. These data suggest that NO-exisulind reduces tumor growth and inhibits tumor progression by blocking proliferation, inducing apoptosis and reducing EMT.

Contact sensitizers induce skin inflammation via ROS production and hyaluronic acid degradation

BACKGROUND

Allergic contact dermatitis (ACD) represents a severe health problem with increasing worldwide prevalence. It is a T cell-mediated skin disease induced by protein-reactive organic and inorganic chemicals. A key feature of contact allergens is their ability to trigger an innate immune response that leads to skin inflammation. Previous evidence from the mouse contact hypersensitivity (CHS) model suggests a role for endogenous activators of innate immune signaling. Here, we analyzed the role of contact sensitizer induced ROS production and concomitant changes in hyaluronic acid metabolism on CHS responses.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed in vitro and in vivo ROS production using fluorescent ROS detection reagents. HA fragmentation was determined by gel electrophoresis. The influence of blocking ROS production and HA degradation by antioxidants, hyaluronidase-inhibitor or p38 MAPK inhibitor was analyzed in the murine CHS model. Here, we demonstrate that organic contact sensitizers induce production of reactive oxygen species (ROS) and a concomitant breakdown of the extracellular matrix (ECM) component hyaluronic acid (HA) to pro-inflammatory low molecular weight fragments in the skin. Importantly, inhibition of either ROS-mediated or enzymatic HA breakdown prevents sensitization as well as elicitation of CHS.

CONCLUSIONS/SIGNIFICANCE

These data identify an indirect mechanism of contact sensitizer induced innate inflammatory signaling involving the breakdown of the ECM and generation of endogenous danger signals. Our findings suggest a beneficial role for anti-oxidants and hyaluronidase inhibitors in prevention and treatment of ACD.

Biomarine extracts significantly protect from ultraviolet A-induced skin photoaging: an ex vivo study

We tested the activity of the marine nutraceutical CL-1222 added with a coenzyme Q10 (CoQ10)-lutein-selenium component (Celergen(®), Laboratoires-Dom, Switzerland) to protect human fibroblasts against ultraviolet A (UVA)-induced photoaging. Cells obtained from 22- to 39-year-old healthy donors were pretreated with CL-1222 before UV irradiation, as compared with same quantity of the CoQ10-lutein-selenium component. As compared to untreated control, UVA-irradiated samples exhibited a significant increase of secreted matrix metalloproteinase-1 (MMP-1) (p<0.001) with over four-fold MMP-1 upregulation (p<0.001). Samples treated with CL-1222, but not with the CoQ10-lutein-selenium component, showed a significant decrease of MMP-1 secretion (p<0.01) and expression decrease (>60%, p<0.01) with >54% elastase activity inhibition (p<0.01). This preliminary study shows that such marine nutraceuticals can significantly protect against UV-irradiation irrespective of the CoQ10-lutein-selenium component with a specific protective gene expression modulation amenable to novel clinical applications.

In vivo photoprotective and anti-inflammatory effect of hyperforin is associated with high antioxidant activity in vitro and ex vivo

Hyperforin, a major constituent of St. John's Wort (Hypericum perforatum, HP), provides anti-inflammatory, anti-tumor, and anti-bacterial properties. Previous studies have shown anti-oxidative properties of St. John's Wort extracts; however, its free radical scavenging activity in skin cells or skin has not been assessed in detail so far. Therefore, the free radical scavenging activity of hyperforin was tested in the H(2)DCFDA-assay in vitro in HaCaT keratinocytes irradiated with solar simulated radiation. Hyperforin (EC(50) 0.7 μM corresponding to 0.42 μg/ml) was much more effective compared to Trolox (EC(50) 12 μg/ml) and N-acetylcysteine (EC(50) 847 μg/ml) without showing phototoxicity. The radical protection factor of a cream containing 1.5%w/w of a hyperforin-rich HP extract was determined to be 200 × 10(14) radicals/mg, indicating a high radical scavenging activity. The cream was further applied ex vivo on porcine ear skin and significantly reduced radical formation after infrared irradiation. Finally, the UV-protective effect of the HP cream was tested on 20 volunteers in a randomized, double-blind, vehicle-controlled study. HP cream significantly reduced UVB-induced erythema as opposed to the vehicle. Occlusive application of HP cream on non-irradiated test sites did not cause any skin irritation. Taken together, these results demonstrate that hyperforin is a powerful free radical scavenger.

Contact sensitizers induce skin inflammation via ROS production and hyaluronic acid degradation

BACKGROUND

Allergic contact dermatitis (ACD) represents a severe health problem with increasing worldwide prevalence. It is a T cell-mediated skin disease induced by protein-reactive organic and inorganic chemicals. A key feature of contact allergens is their ability to trigger an innate immune response that leads to skin inflammation. Previous evidence from the mouse contact hypersensitivity (CHS) model suggests a role for endogenous activators of innate immune signaling. Here, we analyzed the role of contact sensitizer induced ROS production and concomitant changes in hyaluronic acid metabolism on CHS responses.

METHODOLOGY/PRINCIPAL FINDINGS

We analyzed in vitro and in vivo ROS production using fluorescent ROS detection reagents. HA fragmentation was determined by gel electrophoresis. The influence of blocking ROS production and HA degradation by antioxidants, hyaluronidase-inhibitor or p38 MAPK inhibitor was analyzed in the murine CHS model. Here, we demonstrate that organic contact sensitizers induce production of reactive oxygen species (ROS) and a concomitant breakdown of the extracellular matrix (ECM) component hyaluronic acid (HA) to pro-inflammatory low molecular weight fragments in the skin. Importantly, inhibition of either ROS-mediated or enzymatic HA breakdown prevents sensitization as well as elicitation of CHS.

CONCLUSIONS/SIGNIFICANCE

These data identify an indirect mechanism of contact sensitizer induced innate inflammatory signaling involving the breakdown of the ECM and generation of endogenous danger signals. Our findings suggest a beneficial role for anti-oxidants and hyaluronidase inhibitors in prevention and treatment of ACD.