Effect of lignin-derived lignophenols on vascular oxidative stress and inflammation in streptozotocin-induced diabetic rats.

Lignophenols (LP) are the derivatives of native lignin, which is an abundant organic polymer in the plant kingdom. This study investigated whether LP can attenuate vascular oxidative stress and inflammation in streptozotocin (STZ)-induced diabetic rats. The diabetic rats induced by a single intravenous injection of STZ were randomly divided into two groups fed either 0 or 1.0% LP-containing diet. After 5 weeks of treatment, the superoxide (O(2)(-)) production, mRNA expression levels of nicotinamide adenine dinucleotide (phosphate) (NAD(P)H) oxidase subunits, monocyte chemoattractant protein-1 (MCP-1) and its receptor C-C chemokine receptor 2 (CCR2), and protein expression level of inducible nitric oxide synthase (iNOS) were examined in the aorta of vehicle-injected control and diabetic rats treated with or without LP. The increased O(2)(-) production and mRNA expression levels of NAD(P)H oxidase subunits Nox4 and p47phox were found to be significantly reduced in the aorta of diabetic rats treated with LP. The mRNA expression of MCP-1 and CCR2, and the protein expression of iNOS were found to be increased in the aorta of untreated diabetic rats, whereas these levels were significantly lower in the LP-treated group. These findings suggest that LP could attenuate vascular oxidative stress and/or inflammation via inhibition of NAD(P)H oxidase. This may lead to an improvement in the vascular impairment of diabetes.

Protective effect of lignophenol derivative from beech (Fagus crenata Blume) on copper- and zinc-mediated cell death in PC12 cells.

Lignophenol, prepared using a phase-separation system, is a derivative of lignin, which is one of the components in the plant cell wall, and possesses high phenolic function, high stability and antioxidant properties. However, little is known about the beneficial effect of lignophenol. In this study, we investigated the protective effect of lignophenol from the beech tree (Fagus crenata Blume) on copper- and zinc-mediated apoptosis in PC12 cells by using DNA fragmentation and TUNEL assays. In DNA fragmentation assays, the DNA ladder patterns in the PC12 cells treated with 200 microM Cu and 200 microM Zn were enhanced, whereas the DNA ladder pattern was hardly observed in these cells treated with 20 mM lignophenol. In the TUNEL assay, TUNEL signals increased significantly in the untreated PC12 cells exposed to 200 microM Cu compared with the control. In contrast, the degree of apoptosis in the 20 mM lignophenol-treated cells was significantly lower than in the untreated cells, indicating that lignophenol inhibited Cu-induced apoptotic cell death in PC 12 cells. In the 200 microM Zn-exposed group, the degree of apoptosis in the 20 mM lignophenol-treated cells was also low compared with the untreated cells. In conclusion, these results suggest that lignophenol plays a role in protecting against Cu- and Zn-mediated PC12 apoptotic cell death.

Behavior of lignin-binding cellulase in the presence of fresh cellulosic substrate.

A model lignin-binding cellulase was prepared from Trichoderma reesei cellulase and lignocresol, which was synthesized from softwood or hardwood lignin. Filter paper was incubated with the lignocresol-cellulase complex, and it was observed that only a limited amount of cellulase migrated to the filter paper. The cellulase adsorption isotherms for the lignocresols and filter paper were fitted to a Langmuir absorption model, and the determined Langmuir constants were as follows: softwood lignocresol>hardwood lignocresol>>filter paper. The calculations demonstrated that lignin-binding cellulase can potentially be recovered by the addition of a sufficient quantity of cellulosic substrate. As a result, the lignocresol-binding cellulase is highly stable and lignocresol can potentially be used for immobilizing cellulase in the active state.

Lignin isolated from steam-exploded eucalyptus wood chips by phase separation and its affinity to Trichoderma reesei cellulase.

Steam-exploded eucalyptus wood chips were treated with p-cresol and 72% sulfuric acid at ambient temperature. Steam-exploded lignin was isolated as acetone-soluble and diethyl ether-insoluble compounds from the cresol layer. The lignin extraction yield was only 47%, and the amount of cresol grafted to lignin was much less than that in the case of eucalyptus lignin without steam explosion. Clearly, the steam explosion process depolymerized native lignin, and simultaneously, promoted polymerization via labile benzyl positions. The steam-exploded eucalyptus lignin adsorbed more Trichoderma reesei cellulase; however, its enzymatic activity was less than that of eucalyptus lignin that did not undergo steam explosion. It is evident that pretreatment potentially affects the affinity between lignin and cellulase and the resultant saccharification efficiency.

Separation of lignocresol from eucalyptus lignocresol-cellulase complex using organic solvents.

A functional lignin-based material, lignocresol, was synthesized from eucalyptus wood meal by using phase separation treatment with p-cresol and 72% sulfuric acid. Lignocresol physically adsorbs Trichoderma reesei cellulase and functions as an immobilized cellulase. Lignocresol-immobilized cellulase was treated with acetone or ethanol to separate the enzyme and its support. Most lignocresol was dissolved in organic solvents and then precipitated in diethyl ether. The recovery yield of lignocresol using acetone was 85% and that using ethanol was 72%, with very low or negligible residual cellulase. Lignocresol is an innovative recyclable enzyme support that can be easily separated using only organic solvents after deactivation of the immobilized enzyme.

Effect of lignin-derived lignophenols on hepatic lipid metabolism in rats fed a high-fat diet.

The effect of lignin-derived lignophenols on lipid metabolism in the livers of rats fed a high-fat diet was investigated. Rats fed a diet providing 45% of energy from fat were divided into 2 groups, namely 0% and 0.5% lignophenols-containing diets. The controls were fed a diet providing 10% of energy from fat. Plasma blood parameters, protein expression of acetyl-CoA carboxylase (ACC) and sterol regulatory element-binding protein (SREBP)-1, and SREBP-1c mRNA expression in the livers were examined. The plasma triglyceride levels in the rats fed lignophenols-containing diets were decreased. SREBP-1c mRNA expression in the rats fed lignophenols-containing diets was significantly reduced compared with the rats fed high-fat diets, and phosphorylated ACC protein in the rats fed lignophenols-containing diets was significantly increased. Our results suggested that lignophenols suppress the expression of SREBP-1c mRNA and the phosphorylation of ACC in the liver, and may lead to a decrease in plasma triglyceride levels.

Lignophenols decrease oleate-induced apolipoprotein-B secretion in HepG2 cells.

Lignin is one of the components in the plant cell wall, after cellulose, making up 20-30% of the global plant biomass. Lignophenols (LPs) are derivatives of lignin with high phenolic function and antioxidant properties. However, their medicinal property is not well characterised. Apolipoprotein-B (apo-B) is an essential component in very low-density lipoprotein, and high levels of serum apolipoprotein-B (apo-B) are a major factor for coronary heart disease. In this study, we examined the effect of lignophenols on apo-B secretion in HepG2 cells. HepG2 cells were treated with varying concentrations of LPs and 0.8 mm sodium oleate. LPs decreased oleate-induced apo-B secretion in a dose-dependent manner. LPs also decreased oleate-induced microsomal triglyceride transfer protein (MTTP) mRNA expression and cellular total cholesterol, suggesting that lipid bioavailability and lipidation of lipoprotein are likely involved in the decreased secretion of apo-B. Furthermore, LPs decreased oleate-induced mature sterol regulatory element binding protein 2 (SREBP-2), a transcription factor that activates cholesterol biosynthesis. This is the first study to show that LPs can decrease oleate-induced apo-B secretion in HepG2 cells. The modulations of MTTP mRNA expression, cellular total cholesterol metabolism and mature SREBP-2 expression may be important factors in the regulation of apo-B secretion by LPs.

Lignin-derived lignophenols attenuate oxidative and inflammatory damage to the kidney in streptozotocin-induced diabetic rats.

This study investigated the effects of lignin-derived lignophenols (LPs) on the oxidative stress and infiltration of macrophages in the kidney of streptozotocin (STZ)-induced diabetic rats. The diabetic rats were divided into four groups with 0%, 0.11%, 0.33% and 1.0% LP diets. The vehicle-injected controls were given a commercial diet. At 5 weeks, superoxide (O(2)(-)) production, macrophage kinetics, the degree of fibrosis in glomeruli and mRNA expression for monocyte chemoattractant protein-1 (MCP-1) were examined. The NADPH-stimulated O(2)(-) levels in the kidney of the diabetic rats treated with 1.0% LP were significantly lower than those in untreated diabetic rats. The number of macrophages, levels of MCP-1 mRNA expression and degree of glomerular fibrosis increased in untreated LP and these levels were significantly lower in 1.0%LP-treated rats. The results suggested that LPs suppress the excess oxidative stress, the infiltration and activation of macrophages and the glomerular expansion in STZ-induced diabetic kidneys.

Enzymatic synthesis of polyphenols from highly phenolic lignin-based polymers (lignophenols).

Peroxidase-catalyzed polymerization of lignin-based macromonomers (lignophenols), lignocatechol and lignocresol, prepared by phenolation of lignin with catechol or p-cresol, was carried out in aqueous organic solvent mixtures. The two lignophenols were polymerized to give cross-linked polymers. The highest yield of polymerization (83%, w/w) was obtained with lignocatechol, and the maximum yield for the polymerization of lignocresol was 55% (w/w). Pyrolysis GC-MS analysis of polymers indicated that the polymerization of lignophenols involved the oxidative coupling of the introduced phenol derivatives.