Scavenging effect of benzophenones on the oxidative stress of skeletal muscle cells

Exploration of Ligand-receptor Binding and Mechanisms for Alginate Reduction and Phenotype Reversion by Mucoid Pseudomonas aeruginosa

Bacteria in general can develop a wide range of phenotypes under different conditions and external stresses. The phenotypes that reside in biofilms, overproduce exopolymers, and show increased motility often exhibit drug tolerance and drug persistence. In this work, we describe a class of small molecules that delay and inhibit the overproduction of alginate by a non-swarming mucoid Pseudomonas aeruginosa. Among these molecules, selected benzophenone-derived alkyl disaccharides cause the mucoid bacteria to swarm on hydrated soft agar gel and revert the mucoid to a nonmucoid phenotype. The sessile (biofilm) and motile (swarming) phenotypes are controlled by opposing signaling pathways with high and low intracellular levels of bis-(3',5')-cyclic diguanosine monophosphate (cdG), respectively. As our molecules control several of these phenotypes, we explored a protein receptor, pilin of the pili appendages, that is consistent with controlling these bioactivities and signaling pathways. To test this binding hypothesis, we developed a bacterial motility-enabled binding assay that uses the interfacial properties of hydrated gels and bacterial motility to conduct label-free ligand-receptor binding studies. The structure-activity correlation and receptor identification reveal a plausible mechanism for reverting mucoid to nonmucoid phenotypes by binding pili appendages with ligands capable of sequestering and neutralizing reactive oxygen species.

Protective effect of maghemite nanoparticles on ultraviolet-induced photo-damage in human skin fibroblasts

This study examined the optical properties of an oxidized form of maghemite (γ-Fe(2)O(3)) nanoparticles and their protective effects against the photoaging of human skin fibroblasts irradiated with ultraviolet (UV) light. Nanoparticles with diameters ranging from 8.7 to 12 nm were prepared using a chemical co-precipitation method. The nanoparticles were coated with two surfactants to obtain a water-based product. The onset of the absorption of the γ-Fe(2)O(3) nanoparticles in the UV-visible absorption spectra increased with increasing particle size. The γ-Fe(2)O(3) nanoparticles significantly inhibited the production of matrix metalloproteinase-1 in human skin fibroblast HS 68 cells by 60% compared with the UV-irradiated control. These results suggest that γ-Fe(2)O(3) nanoparticles have photoprotective properties, and have potential use as an agent against photoaging.

Iron load and redox stress in skeletal muscle of aged rats

Loss of skeletal muscle mass (sarcopenia) is a major contributor to disability in old age. We used two-dimensional gel electrophoresis and mass spectrometry to screen for changes in proteins, and cDNA profiling to assess transcriptional regulations in the gastrocnemius muscle of adult (4 months) and aged (30 months) male Sprague-Dawley rats. Thirty-five proteins were differentially expressed in aged muscle. Proteins and mRNA transcripts involved in redox homeostasis and iron load were increased, representing novel components that were previously not associated with sarcopenia. Tissue iron levels were elevated in senescence, paralleling an increase in transferrin. Proteins involved in redox homeostasis showed a complex pattern of changes with increased SOD1 and decreased SOD2. These results suggest that an elevated iron load is a significant component of sarcopenia with the potential to be exploited clinically, and that mitochondria of aged striated muscle may be more vulnerable to radicals produced in cell respiration.

Troglitazone administration limits infarct size by reduced phosphorylation of canine myocardial connexin43 proteins

Troglitazone, an antidiabetic thiazolidinedione, has been shown to have a scavenging effect on reactive oxygen species, which can modulate expression of connexin43. The study purpose was to evaluate whether troglitazone provides cardioprotection and to assess whether the cardioprotection is associated with an attenuated expression of connexin43 at the border of infarction in a canine model of acute myocardial infarction. Vehicle or troglitazone (1, 5, and 50 mg/kg; n = 14 for each group) was given intravenously 15 min before the coronary artery occlusion. Among the survivors, infarct size was significantly larger in the control than in the supplemented groups. There was a significantly lower infarct size in the high-dose group compared with that in the low-dose group (15 +/- 7% vs. 23 +/- 10% of the risk region in the low-dose group, P = 0.04). Reperfusion caused a significant elevation in superoxide anions as measured by lucigenin-derived chemiluminescence, which was significantly inhibited in animals treated with troglitazone. Connexin43 underwent dephosphorylation in response to ischemia-reperfusion measured by Western blot in control hearts at the border zone; these changes were significantly enhanced by troglitazone administration. Confocal microscopy confirmed the changes of junctional complexes. The magnitude of infarct size positively correlated with the magnitude of phosphorylated connexin43 expression assessed by Western blot analysis (r = 0.73, P < 0.0001). This result demonstrated that the cardioprotective effect of troglitazone as an antioxidant may be associated with reduced phosphorylation of myocardial connexin43 protein.

Antioxidative and hypolipidemic effects of barley leaf essence in a rabbit model of atherosclerosis

The antioxidative and hypolipidemic effects of barley leaf essence (BL) were investigated in a rabbit model of atherosclerosis. Twenty-four New Zealand White male rabbits were assigned randomly into four dietary groups. The normal group was fed regular rabbit chow and the control group was fed a chow containing 0.5% cholesterol and 10% corn oil. The BL group and the probucol group were fed the same diet as the control group plus 1% (w/w) BL or 1% (w/w) probucol, respectively. The plasma levels of total cholesterol, triacylglycerol, lucigenin-chemiluminescence (CL) and luminol-CL were increased in the control group compared to the normal group; and they were decreased in the BL group and the probucol group compared to the control group. The value of T50 of red blood cell hemolysis and the lag phase of low-density lipoprotein oxidation increased in the BL group and in the probucol group compared to the controls. Ninety percent of the intimal surface of the thoracic aorta was covered with atherosclerotic lesions in the control group, but only 60% of the surface was covered in the BL group. This 30% inhibition of hyperlipidemic atherosclerosis by BL was associated with a decrease in plasma lipids and an increase in antioxidative abilities (as measured by T50, lag phase and CL). These results suggest that the antioxidant and hypolipidemic effects of BL could be useful in the prevention of cardiovascular disease in which atherosclerosis is important.

The relationship between UVB screening and cytoprotection by microcorpuscular ZnO or ascorbate against DNA photodamage and membrane injuries in keratinocytes by oxidative stress

Decreased cell viability and increased formation of cyclobutane-type pyrimidine dimers (CPDs) in DNA of UVB-irradiated keratinocytes were shown to be appreciably restored by the addition of w/o emulsion of microcorpuscular zinc oxide (mcZnO) with a corpuscle diameter of 0.15 microm. The cytoprotection was exerted only by 20 wt/wt% mcZnO at levels equivalent to 40- to 100-microm-thick emulsion layers, which screened 90-92% of the incident UVB. However, protection was not seen by mcZnO below 20-microm thickness, which, unexpectedly, screened 79% of the incident radiation. This suggests that thorough UVB screening is necessary for cytoprotection. This may be attributable to involvement of intracellular reactive oxygen species (ROS) secondarily generated from UVB-irradiated mcZnO. Intracellular ROS was increased in mcZnO-added cells in a time-dependent manner even after UVB irradiation, contrasting with reduction of intracellular ROS in ascorbic acid-added cells. UVB-induced disruption of cell membrane integrity was reduced by mcZnO at 100-microm thickness, equivalent to the addition of ascorbic acid of 50 microM. Thus, mcZnO was thought to be cytoprotective through reductions of intracellular ROS generation, CPD formation and cell membrane disintegration when added so abundantly so as to achieve UVB-screening more than 90%.

Photosensitization of the sunscreen octyl p-dimethylaminobenzoate by UVA in human melanocytes but not in keratinocytes

Sunscreens penetrate human epidermis and modify the biology of proliferating cells. This study addressed the question whether the UV response of cultured human cells is affected by direct treatment with nontoxic levels of sunscreens. Cell survival following exposure to UVC or unfiltered UBV was not altered by preincubation with 25 micrograms/mL of octyl p-dimethylaminobenzoate (o-PABA), 2-ethylhexyl p-methoxycinnamate (EHMC) or oxybenzone. However, UVA or UVB filtered to reproduce the solar UV spectrum penetrating to the basal layer of the epidermis, highly sensitized cells to killing by o-PABA but not by its hydrolysis product, 4-dimethylaminobenzoic acid. Sensitization was found in all cell types tested, except normal keratinocytes, and could be prevented by certain antioxidants particularly pyruvate and the hydroxyl radical scavenger mannitol. o-PABA and EHMC applied without UV reduced the adherence of cells. The results indicate that sunscreens may increase cell mobility and the combination of o-PABA with solar UV may selectively damage melanocytes in the skin.