Association of HMGBP1 expression with clinical periimplant parameters among smokers and never-smokers with and without peri-implantitis.

OBJECTIVE: With our study we aimed at investigating the levels of high mobility group box chromosomal protein-1 (HMGB-1), tumor necrosis factor-alpha (TNF-α) and interleukin (IL)-1ß in periimplant crevicular fluid (PICF) of smokers and never-smokers, with and without periimplantitis, and correlate these levels with the clinical and radiographic periimplant parameters. SUBJECTS AND METHODS: Sixty participants (n=15/group) were recruited and divided into 4 groups: cigarette smokers with periimplantitis (CSPI); cigarette smokers without periimplantitis (CSNPI); never-smokers with periimplantitis (NSPI); and never-smokers without periimplantitis (NSNPI). Clinical and radiographic periimplant parameters, including plaque scores (PS), bleeding on probing (BOP), probing depth (PD) and crestal bone level (CBL), were assessed. Crevicular levels of HMGB-1, TNF-α, and IL-1ß were quantified using human enzyme linked immunosorbent assay. p-values were generated using Kruskal-Wallis' test for comparison between the study groups, while correlations between HMGB-1, TNF-α, IL-1ß levels and clinical variables were analyzed using Spearman rank correlation coefficient analysis. RESULTS: Bleeding on probing was least in NSNPI and CSNPI followed by CSPI and NSPI (p<0.05). The highest PD and CBL was recorded for CSPI and NSPI groups, while the least PD and CBL were recorded among non-periimplantitis groups. HMGB-1 and IL-1ß were found to be significantly highest in CSPI groups followed by NSPI and CSNPI groups with no statistically significant difference between CSPI and NSPI groups (p<0.05). CSPI groups reported the highest TNF-α levels in the PICF in comparison to other groups (p<0.05). A significant negative correlation was observed between plaque scores (p=0.0187) and CBL (p=0.0049) in NSNPI and CSPI groups with HMGB-1, respectively. A significant positive correlation was seen for HMGB-1 in groups CSPI (p=0.0023) and NSPI (p=0.0018) for BOP. In CSPI group, a significant positive correlation was observed between TNF-α and PD (p=0.0443). On correlating IL-1ß, a significant positive correlation was observed for CBL in CSPI (p=0.0006) and NSPI (p=0.0275) groups, respectively. CONCLUSIONS: HMGB-1 could play a significant role in periimplant inflammatory response and inflammation. Higher crevicular fluid HMGB-1 levels are indicative of a possible surrogate biomarker for peri-implantitis.

Drug metabolizing enzyme activities and superoxide formation in primary and immortalized rat brain endothelial cells.

The activities of several enzymes involved in drug metabolism, NADPH-cytochrome P450 reductase, cytochrome P450 isoforms CYP1A and CYP2B, and uridine diphosphate glucuronosyltransferase (UGT) have been measured in primary cultures of rat cerebrovascular endothelial cells and in the immortalized rat brain endothelial cell line RBE4. These drug metabolizing activities were similar in the microsomes prepared from both cell types, even after 20 passages for RBE4 cells. These results were confirmed by Western immunoblotting analysis, using polyclonal antibodies raised against rat liver enzymes. The superoxide production observed during NADPH-cytochrome P450 reductase-dependent monoelectronic reduction of four xenobiotics, menadione, anthraquinone, nitrofurazone and diquat, was also investigated in these cultured cells at confluence. The rates of radical production were concentration-dependent. The superoxide formation induced by quinone metabolism was comparable in both cell cultures, and high amounts of superoxide radicals were produced even after 20 passages of RBE4 cells. On the other hand, nitrofurazone and diquat metabolism produced weak amounts of superoxide radicals in both cell types. Taken together, these results suggest that RBE4 cell line seems to constitute a valuable in vitro model for studies on the activity of some enzymatic systems involved in drug metabolism at the blood-brain barrier and the functional consequences of their activity.

Localization of drug-metabolizing enzyme activities to blood-brain interfaces and circumventricular organs.

The brain, with the exception of the choroid plexuses and circumventricular organs, is partially protected from the invasion of blood-borne chemicals by the specific morphological properties of the cerebral micro-vessels, namely, the tight junctions of the blood-brain barrier. Recently, several enzymes that are primarily involved in hepatic drug metabolism have been shown to exist in the brain, albeit at relatively low specific activities. In the present study, the hypothesis that these enzymes are located primarily at blood-brain interfaces, where they form an "enzymatic barrier," is tested. By using microdissection techniques or a gradient-centrifugation isolation procedure, the activities of seven drug-metabolizing enzymes in isolated microvessels, choroid plexuses, meningeal membranes, and tissue from three circumventricular organs (the neural lobe of the hypophysis, pineal gland, and median eminence) were assayed. With two exceptions, the activities of these enzymes were higher in the three circumventricular organs and cerebral microvessel than in the cortex. Very high membrane-bound epoxide hydrolase and UDP-glucuronosyltransferase activities (approaching those in liver) and somewhat high 7-benzoxyresorufin-O-dealkylase and NADPH-cytochrome P-450 reductase activities were determined in the choroid plexuses. The pia-arachnoid membranes, but not the dura matter, displayed drug-metabolizing enzyme activities, notably that of epoxide hydrolase. The drug-metabolizing enzymes located at these nonparenchymal sites may function to protect brain tissue from harmful compounds.