Anti-angiogenic activities of chitooligosaccharides

Advances in the preparation and assessment of the biological activities of chitosan oligosaccharides with different structural characteristics

Chitosan oligosaccharides (COSs) are widely used biopolymers that have been studied in relation to a variety of abnormal biological activities in the food and biomedical fields. Since different COS preparation technologies produce COS compounds with different structural characteristics, it has not yet been possible to determine whether one or more chito-oligomers are primarily responsible for the bioactivity of COSs. The inherent biocompatibility, mucosal adhesion and nontoxic nature of COSs are well documented, as is the fact that they are readily absorbed from the intestinal tract, but their structure-activity relationship requires further investigation. This review summarizes the methods used for COS preparation, and the research findings with regard to the antioxidant, anti-inflammatory, anti-obesity, bacteriostatic and antitumour activity of COSs with different structural characteristics. The correlation between the molecular structure and bioactivities of COSs is described, and new insights into their structure-activity relationship are provided.

Enzymatic Modification of Native Chitin and Conversion to Specialty Chemical Products

Chitin is one of the most abundant biomolecules on earth, occurring in crustacean shells and cell walls of fungi. While the polysaccharide is threatening to pollute coastal ecosystems in the form of accumulating shell-waste, it has the potential to be converted into highly profitable derivatives with applications in medicine, biotechnology, and wastewater treatment, among others. Traditionally this is still mostly done by the employment of aggressive chemicals, yielding low quality while producing toxic by-products. In the last decades, the enzymatic conversion of chitin has been on the rise, albeit still not on the same level of cost-effectiveness compared to the traditional methods due to its multi-step character. Another severe drawback of the biotechnological approach is the highly ordered structure of chitin, which renders it nigh impossible for most glycosidic hydrolases to act upon. So far, only the Auxiliary Activity 10 family (AA10), including lytic polysaccharide monooxygenases (LPMOs), is known to hydrolyse native recalcitrant chitin, which spares the expensive first step of chemical or mechanical pre-treatment to enlarge the substrate surface. The main advantages of enzymatic conversion of chitin over conventional chemical methods are the biocompability and, more strikingly, the higher product specificity, product quality, and yield of the process. Products with a higher M_w due to no unspecific depolymerisation besides an exactly defined degree and pattern of acetylation can be yielded. This provides a new toolset of thousands of new chitin and chitosan derivatives, as the physio-chemical properties can be modified according to the desired application. This review aims to provide an overview of the biotechnological tools currently at hand, as well as challenges and crucial steps to achieve the long-term goal of enzymatic conversion of native chitin into specialty chemical products.

Validated HPAEC-PAD Method for the Determination of Fully Deacetylated Chitooligosaccharides

An efficient and sensitive analytical method based on high-performance anion exchange chromatography with pulsed amperometric detection (HPAEC-PAD) was established for the simultaneous separation and determination of glucosamine (GlcN)₁ and chitooligosaccharides (COS) ranging from (GlcN)₂ to (GlcN)₆ without prior derivatization. Detection limits were 0.003 to 0.016 mg/L (corresponding to 0.4-0.6 pmol), and the linear range was 0.2 to 10 mg/L. The optimized analysis was carried out on a CarboPac-PA100 analytical column (4 × 250 mm) using isocratic elution with 0.2 M aqueous sodium hydroxide-water mixture (10:90, v/v) as the mobile phase at a 0.4 mL/min flow rate. Regression equations revealed a good linear relationship (R² = 0.9979-0.9995, n = 7) within the test ranges. Quality parameters, including precision and accuracy, were fully validated and found to be satisfactory. The fully validated HPAEC-PAD method was readily applied for the quantification of (GlcN)_1-6 in a commercial COS technical concentrate. The established method was also used to monitor the acid hydrolysis of a COS technical concentrate to ensure optimization of reaction conditions and minimization of (GlcN)₁ degradation.

Chitosan aerosol inhalation alleviates lipopolysaccharide- induced pulmonary fibrosis in rats

PURPOSE

Pulmonary fibrosis (PF) is an insidiously progressive scarring disorder of the alveoli and is associated with high mortality. Currently, therapies available are associated with restricted efficacy and side effects. This study aimed to investigate the effect of chitosan aerosol inhalation on lipopolysaccharide (LPS)-induced pulmonary remodeling and fibrosis in rats.

METHODS

A rat model of PF was established by intratracheal injection of LPS (5 mg/kg). Chitosan was nebulized to rats from day 4 to 28 after LPS injection. We analyzed the effect of chitosan on LPS-induced pulmonary remodeling and fibrosis by hematoxylin-eosin staining (HE), Masson staining, and the determination of the hydroxyproline content. The expression intensities of matrix metalloproteinase-3 (MMP-3) and tissue inhibitor of metalloproteinase-1 (TIMP-1) were analyzed by western blots.

RESULTS

Histological assessments showed that chitosan aerosol inhalation attenuated the fibrotic changes in LPS-induced PF in rats. Compared with the LPS group, the fibrosis parameters were significantly improved in the LPS + chitosan group (LCh group), although not as good as those of the control group. The expressions of MMP-3 and TIMP-1 in the LCh group were markedly less than that of the LPS group on the 28th day.

CONCLUSIONS

Our findings show that chitosan aerosol inhalation inhibits the expression of MMP-3 and TIMP-1, and ameliorates LPS-induced pulmonary remodeling and fibrosis in rats.

Chitooligosaccharide ameliorates diet-induced obesity in mice and affects adipose gene expression involved in adipogenesis and inflammation

Chitooligosaccharide (CO) has been reported to have potential antiobestic effects in a few studies, but the antiobesity properties of CO and its related mechanisms in models of dietary obesity remain unclear. We investigated the effect of CO on body weight gain, size of adipocytes, adipokines, and lipid profiles in high-fat (HF) diet-induced obese mice and on the gene expression in adipose tissue using a complementary DNA microarray approach to test the hypothesis that CO supplementation would alleviate HF diet-induced obesity by the alteration of adipose tissue-specific gene expression. Male C57BL/6N mice were fed a normal diet (control), HF diet, or CO-supplemented HF diet (1% or 3%) for 5 months. Compared with the HF diet mice, mice fed the 3% CO-supplemented diet gained 15% less weight but did not display any change in food and energy intake. Chitooligosaccharide supplementation markedly improved serum and hepatic lipid profiles. Histologic examination showed that epididymal adipocyte size was smaller in mice fed the HF + 3% CO. Microarray analysis showed that dietary CO supplementation modulated adipogenesis-related genes such as matrix metallopeptidases 3, 12, 13, and 14; tissue inhibitor of metalloproteinase 1; and cathepsin k in the adipose tissues. Twenty-five percent of the CO-responsive genes identified are involved in immune responses including the inflammatory response and cytokine production. These results suggest that CO supplementation may help ameliorate HF diet-induced weight gain and improve serum and liver lipid profile abnormalities, which are associated, at least in part, with altered adipose tissue gene expression involved in adipogenesis and inflammation.

Inhibition of angiogenesis by chitooligosaccharides with specific degrees of acetylation and polymerization

Chitooligosaccharides (CHOS) inhibit angiogenesis and may be used in the treatment of cancer tumors. We have studied the effect of the fraction of acetylation (FA) and the degree of polymerization (DP) on CHOS anti-angiogenic activity. We tested enzymatically produced CHOS-mixtures with FA0.15, FA0.3 and FA0.6, and DP≤12 in initial experiments with chorioallantoic membranes. All of the samples reduced the formation of new blood vessels, CHOS with FA0.3 giving the best effect. Single-DP fractions from the FA0.3 sample purified by size-exclusion chromatography (DP3-DP12) were then tested for inhibition of migration of human endothelial cells, which is an important element of the angiogenesis process. All of the fractions inhibited migration, meaning that, within the DP area tested in this study, FA is more important than DP for the effect. Generally, the results reveal that DP3-DP12 CHOS have considerable potential as anti-angiogenic compounds.

Production of chitooligosaccharides and their potential applications in medicine

Chitooligosaccharides (CHOS) are homo- or heterooligomers of N-acetylglucosamine and D-glucosamine. CHOS can be produced using chitin or chitosan as a starting material, using enzymatic conversions, chemical methods or combinations thereof. Production of well-defined CHOS-mixtures, or even pure CHOS, is of great interest since these oligosaccharides are thought to have several interesting bioactivities. Understanding the mechanisms underlying these bioactivities is of major importance. However, so far in-depth knowledge on the mode-of-action of CHOS is scarce, one major reason being that most published studies are done with badly characterized heterogeneous mixtures of CHOS. Production of CHOS that are well-defined in terms of length, degree of N-acetylation, and sequence is not straightforward. Here we provide an overview of techniques that may be used to produce and characterize reasonably well-defined CHOS fractions. We also present possible medical applications of CHOS, including tumor growth inhibition and inhibition of T(H)2-induced inflammation in asthma, as well as use as a bone-strengthener in osteoporosis, a vector for gene delivery, an antibacterial agent, an antifungal agent, an anti-malaria agent, or a hemostatic agent in wound-dressings. By using well-defined CHOS-mixtures it will become possible to obtain a better understanding of the mechanisms underlying these bioactivities.