Extracellular matrix determinants and the regulation of cancer cell invasion stratagems

During development, wound repair and disease-related processes, such as cancer, normal, or neoplastic cell types traffic through the extracellular matrix (ECM), the complex composite of collagens, elastin, glycoproteins, proteoglycans, and glycosaminoglycans that dictate tissue architecture. Current evidence suggests that tissue-invasive processes may proceed by protease-dependent or protease-independent strategies whose selection is not only governed by the characteristics of the motile cell population, but also by the structural properties of the intervening ECM. Herein, we review the mechanisms by which ECM dimensionality, elasticity, crosslinking, and pore size impact patterns of cell invasion. This summary should prove useful when designing new experimental approaches for interrogating invasion programs as well as identifying potential cellular targets for next-generation therapeutics.

Enhanced expression of neutrophil NADPH oxidase components in intestine of rats after burn injury

We have evaluated the accumulation of neutrophils in the gut and their infiltration into the intestinal extravascular spaces in rats subjected to a 25% total body surface area scald burn. The accumulation of neutrophils was assessed via measurements of myeloperoxidase (MPO) activity in the intestinal homogenates, and the immunohistochemical localization of neutrophil NADPH oxidase component proteins (p47phox and p67phox) within the intestinal extravascular spaces determined neutrophil tissue infiltration. MPO measurements demonstrated a 12- and 21-fold increase above the control value in the intestinal tissue at day 1 and day 3 post-burn, respectively, suggesting that a substantial total tissue accumulation of neutrophils occurs in the gut after burn injury. The immunohistochemical staining procedures showed both a definitive presence of the neutrophil in the intestinal extravascular spaces and an enhanced immunoreactivity in neutrophils accumulating in intestine after burn injury. There was no evidence of either the presence of neutrophils in the extravascular regions or any significant neutrophil immunoreactivity to NADPH oxidase component proteins in the intestines of sham control rats. These findings indicate that burn injury causes an enhanced migration of circulating neutrophils into the intestinal interstitial spaces and an upregulation of NADPH oxidase activity in the infiltrating neutrophils.

Signaling mechanisms of elevated neutrophil O2- generation after burn injury

A full skin thickness burn injury was produced in anesthetized rats by exposing 25% of total body surface area to 98 degrees C water for 10 s. Sham (exposed to 37 degrees C water) and burn rats were killed 1, 3, 7, or 10 days later. The role of Ca2+ signaling and Ca(2+)-related protein kinase C (PKC) activation in neutrophil O2- generation was ascertained by evaluating the effect of treatment of the rats with the Ca2+ entry blocker, diltiazem. There was an overt enhancement of O2- generation by polymorphonuclear leukocytes from burn rats on days 1, 3, and 7 postburn, with the peak release occurring on day 3 postburn. O2- generation comparable to the sham was noted on day 10 after the burn. O2- releases on days 1, 3, and 7 postburn were accompanied by marked elevation of Cai2+ and PKC responses. Like the O2- release, intracellular Ca2+ concentration ([Ca2+]i) response on day 10 after burn was suppressed to levels found in the sham group. The treatment of burn rats with diltiazem prevented the upregulation of both [Ca2+]i and PKC responses as well as O2- generation in neutrophils in rats on days 1, 3, and 7 after the burn. Because previous studies have shown that increases in [Ca2+]i precede O2- generation and degranulation, our results suggest that neutrophil O2- release enhancement in the early stages after burn injury (e.g., days 1-7 postburn) results from an overactivation of the Cai2+ and PKC signaling pathways. The heightened O2- generation during the early burn injury phase might play a role in tissue damage in one or more of host organs.

Elevated expression of p47phox and p67phox proteins in neutrophils from burned rats

The molecular control of neutrophil respiratory burst in burn injury was investigated through quantitation of protein factors, p47phox and p67phox, which are required for the activation of the phagocyte plasma membrane NADPH-oxidase. Circulating neutrophils were isolated from rats with 30% body surface area covered with full thickness burns. Neutrophil O2- generation, and p47phox and p67phox expressions, respectively, were determined using spectrophotometric and immunoblot techniques. Formylmethionyl-leucyl-phenylalanine stimulated superoxide anion generation was approximately 50% higher in neutrophils from rats 24 and 72 h after burns compared with that in sham control rats. The level of superoxide production was .47 +/- .05 nanomoles per minute per 10(6) cells (mean +/- SE, n = 6) at 24 h and .45 +/- .05 (n = 6) at 72 h postburn, whereas in sham control animals it was .32 +/- .02 (n = 8). Compared with the sham group p47phox levels, p47phox expression was 5.7-fold, 4.4-fold, and 4.5-fold higher, respectively, at 24, 36 and 72 h postburn. The levels of p67phox in burned animals were 2-fold higher than in the sham group, (p < .05) at 24 h postburn, and approximately 50% higher than sham at 36 h after the burn. The p67phox levels in rats 72 h after the burn were not significantly different from the sham values. These data support the occurrence of an up-regulation of p47phox and p67phox expressions accompanying the enhanced neutrophil respiratory burst activity during the early stages of burn injury. The up-regulation of p47phox and p67phox could be responsible for the priming of neutrophil O2- production leading to host tissue injury.

Isozymes of superoxide dismutase from Aloe vera

Extracts from the parenchymatous leaf gel and the rind of the Aloe vera plant (Aloe barbadensis Miller) were shown to contain seven electrophoretically-identifiable superoxide dismutases (SODs). The chromatographic elution profiles and the migration of these bands on native polyacrylamide gel electrophoresis (PAGE), for both the gel and rind, are quite similar. Two of these seven activities are insensitive to cyanide treatment, suggesting that they are mangano-SODs. The other five activities are sensitive to cyanide treatment, but insensitive to azide treatment and are presumed to be cupro-zinc SODs. All of the seven proteins appear to be homodimers with apparent native molecular masses centered at approximately 32 and 42 kD as indicated by SDS-PAGE and gel-filtration (FPLC) chromatography. The specific activities of SODs in the A. vera rind and gel are comparable to those of spinach leaves and of rabbit liver.

Skin burn injury and oxidative stress in liver and lung tissues of rabbit models

The effects of burn injury (30% of total body surface area) on the levels of oxidized and reduced glutathione, malondialdehyde, and on the activities of certain glutathione-dependent enzymes, have been determined in tissues of rabbit models. Thus, the malondialdehyde, glutathione (GSH), glutathione disulfide (GSSG) concentrations and the specific activities of glutathione peroxidase, glutathione S-transferase, and glutathione reductase were measured in liver and lung of 24-h burn rabbit models and compared to the corresponding values in 24-h sham burn (medicated, anesthetic/analgesic) rabbit models. It was found that the concentrations of malondialdehyde in liver and lung of burn models were increased by 17% and 29% respectively. Glutathione concentrations were decreased by 29% in liver and 13% in lung, and glutathione disulfide concentrations were increased by 35% in liver and 33% in lung, in burn versus sham burn models. It was also found that the specific activities of glutathione peroxidase decreased significantly, resultant to burn injury, by an average of 35% and 27% in liver and lung, respectively. Burn injury also decreased glutathione S-transferase specific activities by 14% in liver and 23% in lung tissues. In contrast, glutathione reductase specific activity was increased in liver tissues (22%), but was decreased (19%), as with the other enzymes studied, in lung tissues of burn models. Control model studies (no medication, no sham burn) show that these effects of burn injury are additional to effects elicited by medication associated with sham burn models. The data of this study are indicative of a major oxidative stress in liver and lung tissues due to burn injury at a remote site.

Dipeptidyl peptidase IV and aminopeptidase in burn wound exudates: implications for wound healing

Two catalytically active proteases, dipeptidyl peptidase IV (DP IV) and aminopeptidase (AP), not previously reported as present in burn wound exudates, have been identified by substrate specificity and susceptibility to known enzyme inhibitors. The ratio of the two enzymes in exudates is significantly different from the ratio in plasma collected from the same patient during the same time interval, suggesting that measurement of exudate components may be more significant than plasma activities in evaluating local conditions in the wound. A number of biologically significant substances are DP IV substrates, and the list can be considerably extended by the sequential action of AP and DP IV. Some polypeptides are converted to their biologically active form by DP IV action, while others are degraded to inactive forms. Either action generates X-Pro dipeptides, which have a demonstrably beneficial effect on wound healing. Although not resolved by molecular sizing or anion exchange chromatography, DP IV and AP in a burn wound exudate were purified by affinity chromatography.

Purification and characterization of a glutathione peroxidase from the Aloe vera plant

Extracts from the parenchymous leaf-gel of the Aloe vera plant (Aloe barbadensis Miller) were shown to contain glutathione peroxidase (GSHPx) activity. The activity was purified to homogeneity by ion exchange and gel filtration (FPLC) chromatography in the presence of 0.5 mM glutathione. The native enzyme has an apparent molecular weight of 62 kD as determined by gel filtration. In the presence of sodium dodecylsulfate (SDS), the molecular weight was estimated to be about 16 kD as determined by polyacrylamide-gel electrophoresis (SDS-PAGE). The native enzyme is proposed to be constituted of four identical subunits; it also contains one atom of selenium per subunit, as found with most glutathione peroxidases from animal sources. The Km values were determined to be 3.2 mM for glutathione and 0.26 mM for the hydroperoxide substrate, cumene hydroperoxide. The enzyme is competitively inhibited by N, S, bis-FMOC glutathione (Ki = 0.32 mM), a potent inhibitor of glyoxalase II. Inhibitors of glyoxalase I (e.g. S-octylglutathione) have no effect on the peroxidase activity.