Activation of chick tendon lysyl oxidase in response to dietary copper

Lysyl Oxidase and the Tumor Microenvironment

The lysyl oxidase (LOX) family of oxidases contains a group of extracellular copper-dependent enzymes that catalyze the cross-linking of collagen and elastin by oxidation, thus maintaining the rigidity and structural stability of the extracellular matrix (ECM). Aberrant expression or activation of LOX alters the cellular microenvironment, leading to many diseases, including atherosclerosis, tissue fibrosis, and cancer. Recently, a number of studies have shown that LOX is overexpressed in most cancers and that it is involved in the regulation of tumor progression and metastasis. In contrast, a few reports have also indicated the tumor-suppressing role of LOX. In this short review, we discuss recent research on the correlations between LOX and cancer. Further, the role of LOX in tumor microenvironment remodeling, tumorigenesis, and metastasis and the underlying mechanisms have also been elucidated.

Effect of copper on antioxidant ability and nutrient metabolism in broiler chickens stimulated by lipopolysaccharides

The aim of the experiment was to investigate the interaction between Cu intake, inflammatory challenge and oxidative stress in broiler chickens. Furthermore, it was tested whether plasma ceruloplasmin (Cp) could be a sensible parameter for dietary Cu. One hundred forty-four day old chickens were raised on a basal control diet without added copper (Group Cu-6.5, basal Cu content 6.5 mg/kg diet) or a diet supplemented with Cu at 8 or 50 mg/kg (Groups Cu-14.5 and Cu-56.5, respectively) with four replicates of 12 animals for each treatment. Starting on day 21, chickens were injected intraperitoneally with lipopolysaccharides (LPS) once a day for 3 days. Before this challenge, Group Cu-14.5 had the lowest gain and the feed to gain ratio was the highest. After injection of LPS, however, chickens of Group Cu-14.5 had the best zoo-technical performance. For chickens of Group Cu-6.5, LPS injection resulted in elevated rectal temperature, and lower erythrocyte superoxide dismutase (CuZn-SOD) activity, compared with the other groups. LPS injection increased plasma uric acid in Group Cu-6.5 significantly, but was without influence in Group Cu-56.5. At all Cu-levels, LPS injection increased erythrocyte CuZn-SOD activity and decreased thiobarbituric acid reacting substances. No significant difference in plasma Cp was found in chickens fed different dietary Cu. LPS injection significantly increased plasma Cp in Group Cu-56.5. The results suggest that varying dietary Cu levels seem to modulate the parameters involved in immunological responses and oxidant stress and that plasma Cp is not a reliable parameter for dietary Cu.

Molecular and histologic evaluation of idiopathic hyperextension of the metacarpophalangeal and metatarsophalangeal joints in adult llamas

OBJECTIVE

To determine the molecular and histologic characteristics of hyperextension of the metacarpophalangeal and metatarsophalangeal joints in adult llamas.

ANIMALS

12 adult llamas (6 with bilateral hyperextension of the metacarpophalangeal or metatarsophalangeal joints [affected] and 6 age- and sex-matched clinically normal control llamas).

PROCEDURES

Llamas were euthanized, and specimens of superficial digital flexor tendon, deep digital flexor tendon, and suspensory ligament were obtained from 4 areas and snap frozen in liquid nitrogen or suspended in neutral-buffered 10% formalin. Histologic evaluation of collagen fiber orientation, elastin content, and proteoglycan content was performed by use of Masson trichrome, picrosirius red, Verhoeff, and Alcian blue stains. Total RNA was isolated from frozen suspensory ligament specimens. Gene expression of collagen types I and III, lysyl oxidase, and matrix metalloproteinase-13 was evaluated with a real-time quantitative reverse transcriptase PCR assay.

RESULTS

Gene expression of collagen types I and III, lysyl oxidase, and matrix metalloproteinase-13 in suspensory ligaments was similar between affected and control llamas. Collagen orientation and elastin content of the flexor tendons and suspensory ligaments were also similar between the groups. Proteoglycan content was low in most specimens but was focally increased in discrete lesions of suspensory ligaments in 2 affected and 2 control llamas.

CONCLUSIONS AND CLINICAL RELEVANCE

Hyperextension of the metacarpophalangeal or metatarsophalangeal joints in llamas did not appear to be caused by degeneration or inflammation of the suspensory ligament. Although focal proteoglycan accumulation existed in the suspensory ligaments of 2 affected llamas, widespread abnormal connective tissue proteoglycan accumulation was not found.

Morphologic and biochemical characterization of hyperextension of the metacarpophalangeal and metatarsophalangeal joints in llamas

OBJECTIVE

To determine the morphologic and biochemical characteristics of hyperextension of the metacarpophalangeal and metatarsophalangeal joints in llamas.

ANIMALS

12 adult llamas (6 with bilateral hyperextension of the metacarpophalangeal or metatarsophalangeal joints and 6 age- and sex-matched control llamas).

PROCEDURES

Llamas were evaluated by use of lameness examination, ultrasonography, and radiography. A CBC, serum biochemical analysis, and determination of concentrations of trace minerals in serum and liver samples were performed. Llamas were euthanized, and samples of the superficial digital flexor tendon, deep digital flexor tendon, and suspensory ligament were obtained from 4 areas and snap-frozen in liquid nitrogen or suspended in neutral-buffered 10% formalin. Immunohistochemical evaluation of collagen types I and III and assays for measurement of lysyl oxidase activity were performed.

RESULTS

2 affected llamas had a visible gait deficit associated with metacarpophalangeal joint hyperextension. Radiographic evidence of osteoarthritis was detected in 1 severely affected llama, and ultrasonographic changes of soft tissue mineralization and suspensory desmitis were observed in 2 llamas. Liver concentrations of copper were lower and serum concentrations of zinc higher in affected llamas, compared with values in control llamas. Lysyl oxidase activity and collagen distribution did not differ significantly between groups.

CONCLUSIONS AND CLINICAL RELEVANCE

Hyperextension of the metacarpophalangeal or metatarsophalangeal joints in llamas does not appear to be the result of injury or degeneration of the suspensory ligament or flexor tendons. Lower copper concentrations coupled with higher zinc concentrations in affected llamas may be indicative of secondary copper deficiency.

How reliable and robust are current biomarkers for copper status?

Cu is an essential nutrient for man, but can be toxic if intakes are too high. In sensitive populations, marginal over- or under-exposure can have detrimental effects. Malnourished children, the elderly, and pregnant or lactating females may be susceptible for Cu deficiency. Cu status and exposure in the population can currently not be easily measured, as neither plasma Cu nor plasma cuproenzymes reflect Cu status precisely. Some blood markers (such as ceruloplasmin) indicate severe Cu depletion, but do not inversely respond to Cu excess, and are not suitable to indicate marginal states. A biomarker of Cu is needed that is sensitive to small changes in Cu status, and that responds to Cu excess as well as deficiency. Such a marker will aid in monitoring Cu status in large populations, and will help to avoid chronic health effects (for example, liver damage in chronic toxicity, osteoporosis, loss of collagen stability, or increased susceptibility to infections in deficiency). The advent of high-throughput technologies has enabled us to screen for potential biomarkers in the whole proteome of a cell, not excluding markers that have no direct link to Cu. Further, this screening allows us to search for a whole group of proteins that, in combination, reflect Cu status. The present review emphasises the need to find sensitive biomarkers for Cu, examines potential markers of Cu status already available, and discusses methods to identify a novel suite of biomarkers.

Abnormal deposition of collagen around hepatocytes in Wilson's disease is associated with hepatocyte specific expression of lysyl oxidase and lysyl oxidase like protein-2

BACKGROUND/AIMS

Lysyl-oxidases catalyze the oxidation of lysine residues in collagen and elastin thereby promoting their polymerization. We have studied here the expression of four lysyl-oxidases in normal and diseased human liver.

METHODS

The expression of the different lysyl-oxidases in paraffin embedded liver sections was studied using in-situ hybridization and immunohistochemistry. The enzymatic activity of lysyl-oxidase like protein-2 (Loxl2 or LOR-1) using a previously described lysyl-oxidase assay.

RESULTS

We have found that the four lysyl-oxidases which we examined are not significantly expressed in the normal liver. By contrast, Wilson's disease and primary biliary cirrhosis (PBC) patients express lysyl-oxidase (Lox) and lysyl-oxidase like protein-2 (Loxl2 or LOR-1) in hepatocytes, and the expression is accompanied by collagen deposition around the hepatocytes. Lysyl-oxidases are also expressed in additional fibrotic liver diseases such as hepatitis B and C but in these diseases the expression is confined to the fibrotic lesions and collagen does not accumulate around hepatocytes. We have found that Loxl2 is able to oxidize lysine residues of collagen, and behaves in that respect similarly to Lox. The copper chelator D-penicillamine inhibits Loxl2 induced oxidation of collagen but the Lox inhibitor beta-aminopropionitrile did not inhibit the oxidation using a BAPN concentration at which Lox activity was completely inhibited. Loxl2 also catalyzed the oxidation of cell surface proteins on HepG2 hepatoblastoma cells and inhibited their proliferation.

CONCLUSIONS

Upregulation of Lox and Loxl2 in hepatocytes of Wilson's disease and PBC patients may contribute to liver damage by various mechanisms. The upregulation of Lox and Loxl2 in Wilson's disease could perhaps be utilized for diagnostic purposes since their expression is up-regulated in hepatocytes even before the onset of fibrosis.

Metavanadate causes cellular accumulation of copper and decreased lysyl oxidase activity

Selected indices of copper metabolism in weanling rats and fibroblast cultures were progressively altered in response to increased levels of sodium metavanadate. In diets, vanadium was added in amounts ranging from 0 to 80 microg V/g of diet, that is, 0-1.6 micromol V/g of diet. In fibroblast cultures, vanadium ranged from 0 to 400 nmol V/ml. The inhibition of P-ATPase-7A activity by metavanadate, important to copper egress from cells, was a primary focus. In skin, and tendon, the copper concentration was increased in response to increased dietary levels of metavanadate, whereas lysyl oxidase activity, a secreted cuproprotein, was reduced. The reduction in lysyl oxidase activity was also accompanied by reduced redox cycling potential of isolated fractions of lysyl oxidase, presumably due to reduced lysyltyrosyl quinone (LTQ) formation at the active site of lysyl oxidase. In contrast, liver copper concentrations and plasma ceruloplasmin activity were not affected by metavanadate exposure. However, semicarbazide-sensitive benzylamine oxidase (SCBO) activity, which was taken as an indirect measure of vascular adhesive protein-1 (VAP-1), was increased. In cultured fibroblasts, cellular copper was also increased and lysyl oxidase decreased in response to metavanadate. Moreover, the steady-state levels of atp7a and lysyl oxidase mRNAs were not affected by addition of metavanadate to culture medium up to 200 nmol/ml. Taken together, these data suggest that pathways involving copper egress and lysyl oxidase activation are particularly sensitive to metavanadate exposure through processes that are predominately posttranslational.

Lysyl oxidase and P-ATPase-7A expression during embryonic development in the rat

Lysyl oxidase activity is critical for the assembly and cross-linking of extracellular matrix proteins, such as collagen and elastin. Moreover, lysyl oxidase activity is sensitive to changes in copper status and genetic perturbations in copper transport, e.g., mutations in the P-type ATPase gene, ATP7A, associated with cellular copper transport. Lysyl oxidase may also serve as a vehicle for copper transport from extracellular matrix cells. Herein, we demonstrate that sufficient lysyl oxidase functional activity is present in the rat embryo at gestation day (GD) 9 to be detected in conventional enzyme assays. Estimation of embryonic lysyl oxidase functional activity, however, required partial purification in order to remove inhibitors. From GD 9 to GD 15, lysyl oxidase activity was relatively constant when expressed per unit of protein or DNA. In contrast, the steady-state levels of lysyl oxidase and ATP7A mRNA, measured by RT-PCR and expressed relative to total RNA and cyclophilin mRNA, increased approximately fourfold from GD 9 to 15. The pattern of temporal expression for ATP7A was consistent with its possible role in copper delivery to lysyl oxidase.