The role of N-acetylcysteine in protecting synovial fluid biomolecules against radiolytically-mediated oxidative damage: a high field proton NMR study

In vivo H1 MR spectroscopy using 3 Tesla to investigate the metabolic profiles of joint fluids in different types of knee diseases

In vivo proton (H1) magnetic resonance spectroscopy (MRS) has not yet been systematically used to study joint fluids in human knees. The objective of this study, therefore, was to assess the ability of proton MRS to identify the apparent heterogeneous characteristics of metabolic spectra in the joint fluid regions in human knees using a high‐field MRI system. Eighty‐four patients with effusion lesions who were referred for routine knee MR imaging underwent proton MRS with point‐resolved, single‐voxel MR spectroscopy using a clinical 3.0 Tesla MRI system. Thirty‐eight patients were confirmed to have the following: degenerative osteoarthritis, 21 patients (Group 1); traumatic diseases, 12 patients (Group 2); infectious diseases, 4 patients and an inflammatory disease, 1 patient (Group 3). Spectroscopy data were analyzed using the public jMRUI freeware software to obtain lipid metabolites. Nonparametric statistical comparisons were performed to investigate any differences in metabolites among the three disease groups. The major metabolites were vinylic CH=CH lipids around 5.1−5.5 ppm, CH2 lipids around 1.1−1.5 ppm, and CH3 lipids around 0.7−1.0 ppm. Each patient had either a CH=CH lipid peak, CH2 and CH3 lipid peaks, or all three peaks. There were no significant differences among the three groups for the CH3 (p=0.9019), CH2 (p=0.6406), and CH=CH lipids (p=0.5467) and water (p=0.2853); none of the metabolites could differentiate between any of the three types of diseases. The CH2 lipids in the 38 patients who had confirmed fluid characteristics were significantly correlated with CH3 lipids (rho=0.835, p<0.0001). The ratio of CH3 to CH2 was highest in the degenerative disease. In both the degenerative and traumatic diseases, metabolite peaks of the vinylic CH=CH lipids around 5.1−5.5 ppm and of the sum of the CH2 and CH3 lipids around 0.7−1.5 ppm were observed, but in the infectious disease, only a metabolite peak of the sum of the CH2 and CH3 lipids was detected. Although none of the metabolites could statistically significantly differentiate between the three types of diseases, the different lipid metabolite peaks and their ratios in the three disease groups may give us a hint at the different mechanisms of joint fluids in the infectious, degenerative, and traumatic diseases.

PACS number(s): 87.61.Ff, 33.25.+k, 87.14.Cc

Oxidative damage to extracellular matrix and its role in human pathologies

The extracellular compartments of most biological tissues are significantly less well protected against oxidative damage than intracellular sites and there is considerable evidence for such compartments being subject to a greater oxidative stress and an altered redox balance. However, with some notable exceptions (e.g., plasma and lung lining fluid) oxidative damage within these compartments has been relatively neglected and is poorly understood. In particular information on the nature and consequences of damage to extracellular matrix is lacking despite the growing realization that changes in matrix structure can play a key role in the regulation of cellular adhesion, proliferation, migration, and cell signaling. Furthermore, the extracellular matrix is widely recognized as being a key site of cytokine and growth factor binding, and modification of matrix structure might be expected to alter such behavior. In this paper we review the potential sources of oxidative matrix damage, the changes that occur in matrix structure, and how this may affect cellular behavior. The role of such damage in the development and progression of inflammatory diseases is discussed.

Antioxidant N-acetylcysteine attenuates the acute liver injury caused by X-ray in mice

The aim of this study was to evaluate the protective effects of different doses and administration modes of N-acetylcysteine (NAC) against X-ray -induced liver damage in mice. Kun-Ming mice were divided into four groups, each composed of six animals: two control groups and two NAC-treated groups. An acute study was carried out to determine alterations in lipid peroxidation (determined by measuring malondiadehyde (MDA) level), glutathione (GSH) content and superoxide dismutase (SOD) activity (assayed by colorimetric method), and DNA damage (characterized by DNA-single strand break using with comet assay) as well as cell apoptosis (measured by flow cytometry) at 12 h after irradiation. The results showed that there were dose-related decreases in MDA level, DNA damage and cell apoptosis, and dose-dependent increases in GSH content and SOD activity in all NAC-treated groups compared to control groups, indicating that pre-treatment or post-treatment with NAC significantly attenuates the acute liver damage caused by X-ray. In addition, significant positive correlations were observed between MDA level and DNA damage or cell apoptosis, implying that lipid peroxidation plays a major role in X-ray-induced liver injury. The data suggest that NAC exerts its radioprotective effect by counteracting accumulated reactive oxygen species in the liver through its properties as a direct antioxidant and a GSH precursor, when administered before or after X-ray irradiation.

The effects of antioxidants on radiation-induced apoptosis pathways in TK6 cells

This study was designed to determine if radiation-mediated activation of the apoptotic pathways would be influenced by antioxidants and if a correlation would be found between radioprotection and changes in transduction pathways. Human lymphoblastoid TK6 cells, known to undergo apoptosis as a result of radiation, were irradiated (6 Gy) with and without antioxidants, and then whole-cell lysates were collected. Parallel studies were conducted to assess the survival (clonogenic assay) and apoptotic index. The impacts of two nitroxide antioxidants, tempol and CAT-1, differing in cell permeability, as well as the sulfhydryl antioxidant N-acetyl-L-cysteine (L-NAC), were estimated. Changes in apoptotic pathway proteins and p53 were assessed by Western blotting. Fraction of apoptotic cells was determined by flow cytometry. Tempol (10 mM), which readily enters cells, partially radioprotected TK6 cells against clonogenic killing, but had no effect on radiation-induced apoptotic parameters such as cleaved caspase 3 or cleaved PARP. Tempol alone did not induce cytotoxicity, yet did increase cleaved PARP levels. The radiation-induced increase in p53 protein was partly inhibited by tempol, but was unaffected by CAT-1 and L-NAC. Both CAT-1 (10 mM), which does not enter cells, and L-NAC (10 mM) had no radioprotective effect on cell survival. Although L-NAC did not protect against radiation-induced cytotoxicity, it completely inhibited radiation-induced increase in cleaved caspase 3 and cleaved PARP. Collectively, the results question the validity of using selected apoptosis pathway members as sole indicators of cytotoxicity.

Characterization of enzymatically digested hyaluronic acid using NMR, Raman, IR, and UV-Vis spectroscopies

Hyaluronic acid (HA) is a linear polysaccharide formed from disaccharide units containing N-acetylglucosamine and glucuronic acid. When HA was digested with the enzyme hyaluronidase, a double bond is formed. It is known that this double bond forms a complex (radical scavenger) with the radicals (ROO, HO) during UV irradiation, and reduced the toxicity of the radicals before they are absorbed in the human skin. Therefore, the characterization of the double bond formed after the enzymatic digestion of HA is very important. In this study, 1H NMR, 13C NMR, Raman, infrared (IR), and UV-Vis spectroscopies were used for characterization of the double bond of HA after enzymatic digestion. HA derivatives in shape of films were tested using Raman and infrared (IR) spectroscopies and the wavenumber of the double bond and some other assignment were determined. The 1H and 13C NMR spectra were measured for HA derivatives in D(2)O solutions. The chemical shifts and coupling constant of 1H and 13C were assigned to the CH=C fragment. The relative amount of olefinic proportion in the mixture was obtained from 1H and 13C NMR spectra. The spectroscopy measurement showed an increase in the double bond amount with increasing enzymatic digestion time.