Protective effects of collagen polypeptide from tilapia skin against injuries to the liver and kidneys of mice induced by d-galactose.

We wished to investigate the role of a tilapia skin collagen polypeptide (TSCP; molecular weight <3 kDa) in alleviating liver and kidney injuries in aging mice induced by d-galactose (d-gal) and its underlying mechanism of action. First, we characterized TSCP. TSCP was passed through a 3-kDa ultrafiltration membrane, desalted in water by a solid-phase extraction column, purified further by reverse phase-high performance liquid chromatography, and analyzed by electrospray ionization mass spectrometry and tandem mass spectrometry. TSCP contained 17 types of amino acids (AAs) and 41 peptide chains of length 7 AAs to 22 AAs. The content of free AAs and total AAs of TSCP was 13.5% and 93.79%, respectively. Next, we undertook animal experiments. Mice were injected once-daily with D-gal (300 mg/kg body weight, s.c.) for 8 weeks, and TSCP was administered simultaneously once-daily by intragastric gavage. TSCP could visibly improve the decreased body weight, depressed appetite, and mental deterioration of mice triggered by d-gal. TSCP could also alleviate d-gal-induced damage to the liver and kidneys according to histopathology (especially high-dose TSCP). Consistent with these macroscopic and pathologic changes, TSCP could also prevent d-gal-induced increases in serum levels of alanine aminotransferase, aspartate transaminase, alkaline phosphatase, lipid peroxidation, creatinine and uric acid, as well as decreases in serum levels of immunoglobulin (Ig)G and IgM. Moreover, TSCP improved the activities of superoxide dismutase, catalase, and glutathione peroxidase, but also inhibited the increases in the levels of malondialdehyde and inducible nitric oxide synthase expression in the liver and kidneys of d-gal-treated mice. These results suggest that TSCP can alleviate the injuries to the liver and kidneys in aging mice induced by d-gal, and that its mechanism of action might be, at least partially, associated with attenuation of oxidative stress and enhancement of immune function.

Anti-Aging Effect of Chitosan Oligosaccharide on d-Galactose-Induced Subacute Aging in Mice.

Chitosan oligosaccharide (COS), a natural polysaccharide with good antioxidant and anti-inflammatory properties, is the depolymerized product of chitosan possessing various biological activities. The present study was designed to investigate the possible anti-aging effect of COS on the aging model mouse induced by d-galactose (d-gal) and explore the underlying mechanism. In the experiment, 48 male Kunming mice (KM mice) were randomly divided into the normal group, model group, positive group, and low-medium-high dose polysaccharide groups (300, 600, 1200 mg/kg/day). The results showed that COS, by intragastric gavage after subcutaneous injection of d-gal (250 mg/kg/day) into the neck of mice consecutively for eight weeks, gradually recovered the body weight, the activity of daily living, and organ indices of mice, as well as effectively ameliorated the histological deterioration of the liver and kidney in mice triggered by d-gal. To be specific, COS obviously improved the activities of antioxidant enzymes in liver and kidney of KM mice, including catalase (CAT), glutathione peroxidase (GSH-Px), and superoxide dismutase (SOD), as well as decreased malondialdehyde (MDA) levels when compared with those in model group mice. Furthermore, COS not only elevated the diminished levels of serum immunoglobulin G (IgG) and IgM induced by d-gal, but also significantly inhibited the d-gal-caused upregulation of serum alanine aminotransferase (ALT), aspartate transaminase (AST), alkaline phosphatase (ALP), uric acid (UA) and creatinine (CREA) levels as compared with those of mice in the model group. These results demonstrate that COS has an obvious anti-aging activity in d-gal-induced subacute aging mice, the mechanism of which, to some extent, is associated with enhancing the antioxidant defenses, reducing oxidative stress, and improving the immune function of aging model mice.

Branched Peptide, B2088, Disrupts the Supramolecular Organization of Lipopolysaccharides and Sensitizes the Gram-negative Bacteria.

Dissecting the complexities of branched peptide-lipopolysaccharides (LPS) interactions provide rationale for the development of non-cytotoxic antibiotic adjuvants. Using various biophysical methods, we show that the branched peptide, B2088, binds to lipid A and disrupts the supramolecular organization of LPS. The disruption of outer membrane in an intact bacterium was demonstrated by fluorescence spectroscopy and checkerboard assays, the latter confirming strong to moderate synergism between B2088 and various classes of antibiotics. The potency of synergistic combinations of B2088 and antibiotics was further established by time-kill kinetics, mammalian cell culture infections model and in vivo model of bacterial keratitis. Importantly, B2088 did not show any cytotoxicity to corneal epithelial cells for at least 96 h continuous exposure or hemolytic activity even at 20 mg/ml. Peptide congeners containing norvaline, phenylalanine and tyrosine (instead of valine in B2088) displayed better synergism compared to other substitutions. We propose that high affinity and subsequent disruption of the supramolecular assembly of LPS by the branched peptides are vital for the development of non-cytotoxic antibiotic adjuvants that can enhance the accessibility of conventional antibiotics to the intracellular targets, decrease the antibiotic consumption and holds promise in averting antibiotic resistance.