Prostaglandin D2 pathway and peroxisome proliferator-activated receptor gamma-1 expression are induced by mechanical loading in an osteoblastic cell line.

OBJECTIVE: The hypothesis underlying the current study was that the arachidonic acid cascade, specifically activation of the prostaglandin (PG) D(2) pathway in osteoblasts, is an anabolic signal induced by mechanical loading. BACKGROUND: Previous studies have shown that mechanical loading of osteoblasts triggers cyclooxygenase (COX)-2, PGE(2) and prostacyclin (PGI(2)) synthesis. Since modest mechanical loading of osteoblasts promotes bone formation, we sought to determine whether mechanical stress activates the osteoblastic PGD(2) pathway resulting in the synthesis of osteogenic cyclopentenones, including Delta(12)PGJ(2). METHODS: Osteoblast monolayers were stretched using a Bioflex apparatus at a frequency of 1 Hz with 1% elongation. Cells and cell media were collected at various time points: 5, 10, 15, 30 min; and 1, 4, 16, 24 h. RNA was extracted for quantitative reverse transcriptase-polymerase chain reaction (RT-PCR). In certain experiments, cells were pre-labeled with (14)C arachidonic acid prior to stretching. Radiolabeled metabolites in cell media were identified by reverse-phase high performance liquid chromatography (RP-HPLC). Osteoblasts were evaluated for an induction in bone nodule formation by stretching. RESULTS: Mechanical strain significantly increased mRNA expression of COX-1, COX-2, PGD(2) synthase and peroxisome proliferator-activated receptor (PPAR) gamma-1, but not of PPARgamma-2 as compared to control unstretched cells (p < 0.05). Mechanical loading stimulated the release of PGE(2), PGD(2) and the PGD(2) metabolite Delta(12)PGJ(2). Mechanical strain resulted in the induction of bone nodules. CONCLUSIONS: This report indicates that mechanical loading of osteoblasts results in activation of PGD(2) and the concomitant expression of transcription factor PPARgamma-1 mRNA. The coordinated synthesis of Delta(12)PGJ(2), a natural ligand for PPARgamma-1, with the increased expression of PPARgamma-1, suggests that biomechanical transduction pathways that initially involve the activation of cyclooxygenases may also involve the activation of the Delta(12)PGJ(2)-PPAR pathway.

Campylobacter rectus mediates growth restriction in pregnant mice.

BACKGROUND: Recent studies have suggested that subclinical infection may be an important cause of low birth weight. Campylobacters are important human pathogens, causing septicemia and occasionally abortion, premature labor, or severe perinatal infection. The potential role of oral species of Campylobacter in mediating adverse pregnancy outcomes in animal models has not yet been determined. Our objective was to determine the effects of Campylobacter rectus (C. rectus) infection on pregnancy outcomes in a mouse model. METHODS: On embryonic day (E) 7.5, pregnant mice received a subcutaneous, intra-chamber challenge with live C. rectus at concentrations of 0, 10(7) or 10(9) colony forming units (CFU)/ml. They were sacrificed on E 16.5 and fetuses were evaluated for stage of development, weight, and crown-rump length. RESULTS: Dams receiving C. rectus had more fetal resorptions after challenge with 10(7) or 10(9) CFU/ml (24.1% and 30.1%, respectively) than controls (9%). Higher numbers of growth-restricted fetuses were also observed in the C. rectus challenged groups (21%) as compared to controls (2.3%). Fetuses from dams challenged with 10(9) CFU/ml weighed less (0.49 +/- 0.05 g) and had shorter crown-rump lengths (14.69 +/- 0.56 mm) than controls (0.53 +/- 0.04 g; 15.54 +/- 0.63 mm). C. rectus was detected by polymerase chain reaction (PCR) in the placentas from both treated groups and in maternal liver tissues from the 10(9) CFU/ml challenged group. CONCLUSIONS: Remote subcutaneous maternal C. rectus infection increases fetal resorptions and fetal growth restriction in a mouse model. The effects of an oral C. rectus infection on pregnancy remain to be determined.

Novel long-circulating liposomes containing peptide library-lipid conjugates: synthesis and in vivo behavior.

Rapid uptake of intravenously injected liposomes by the mononuclear phagocyte system has limited their use as drug delivery vehicles. Recently, various long-circulating liposomes have been prepared by incorporating glycolipids or other amphiphilic molecules into the lipid bilayer of conventional liposomes. The purpose of the present study was to design a new class of biodegradable membrane modifiers that would increase the half-life of liposomes in vivo. Using solid-phase peptide synthesis, synthesized were 30-residue random libraries consisting of a random sequence of glycine, beta-alanine and gamma-aminobutyric acid. The libraries were coupled to stearic acid (SA) or phosphatidylethanolamine (PE). The resulting amphiphilic conjugates were mixed with egg phosphatidylcholine (PC) and cholesterol (Chol) in a 6:47:47 ratio, and unilamellar liposomes were prepared. For comparison, plain PC/Chol (50:50) liposomes, as well as liposomes containing polyethylene glycol (PEG)-SA/PC/Chol (6:47:47) and PEG-PE/PC/Chol (6:47:47) were also prepared. Calcein was entrapped in the liposomes, which were given intravenously to rats at a dose of 9.2 mumol lipid/kg, and the amount of intact liposomes present in serum was followed with time. While the conventional liposomes had a short elimination half-life (28 min), the liposomes modified with library-PE had a much longer half-life (170 min), while library-SA provided no improvement of the liposome pharmacokinetics. PEG-PE greatly improved the half-life of the liposomes (400 min) while PEG-SA only provided a marginal improvement. All liposome preparations were cleared in a biphasic fashion. In conclusion, a novel biodegradable lipopeptide conjugate was designed that endows liposomes with a prolonged circulation time in vivo. The pharmacokinetic profile of these modified liposomes was drastically improved over that of conventional liposomes. Since the library is prepared by solid-phase synthesis, length and/or composition could easily be modified in order to modulate the clearance profile of the liposomes. Tailoring of the pharmacokinetic profile of the liposomes depending on their intended application may allow for a greater flexibility of use than PEG-PE.

Relationship between periodontal disease and C-reactive protein among adults in the Atherosclerosis Risk in Communities study.

BACKGROUND: Moderately elevated serum C-reactive protein (CRP) concentration is a systemic marker of inflammation and a documented risk factor for cardiovascular disease in otherwise healthy persons. Unrecognized infections, such as periodontal disease, may induce an acute-phase response, elevating CRP levels. We evaluated the association between periodontal disease and CRP levels in adults in the Atherosclerosis Risk in Communities study. METHODS: Oral examinations were conducted between January 1, 1996, and December 31, 1998, on 5552 ARIC participants (aged 52-74 years) from 4 US communities. Periodontal disease was quantified as the percentage of periodontal sites with pocket depth of 4 mm or more. Serum CRP concentration was quantified in milligrams per liter using an enzyme-linked immunosorbent assay. RESULTS: Mean (SE) CRP level was 7.6 (0.6) mg/L among people with extensive periodontal pockets (>30% of sites with pocket depth > or =4 mm), approximately one-third greater than that for people with less extensive periodontal pockets (5.7 [0.1] mg/L). In a multivariable linear regression model that controlled for age, sex, diabetes mellitus, cigarette use, and nonsteroidal anti-inflammatory drug use, the association of extensive periodontal pockets with CRP concentration was modified by body mass index (BMI; calculated as weight in kilograms divided by the square of height in meters). For people with a BMI of 20, the model predicted a 2-fold difference in mean CRP concentration between periodontal pocket groups (7.5 vs 3.6 mg/L), but the difference decreased with increasing BMI and was negligible when BMI equaled 35. CONCLUSIONS: Extensive periodontal disease and BMI are jointly associated with increased CRP levels in otherwise healthy, middle-aged adults, suggesting the need for medical and dental diagnoses when evaluating sources of acute-phase response in some patients.

Transcellular biosynthesis contributes to the production of leukotrienes during inflammatory responses in vivo.

Leukotrienes are lipid mediators that evoke primarily proinflammatory responses by activating receptors present on virtually all cells. The production of leukotrienes is tightly regulated, and expression of 5-lipoxygenase, the enzyme required for the first step in leukotriene synthesis, is generally restricted to leukocytes. Arachidonic acid released from the cell membrane of activated leukocytes is rapidly converted to LTA(4) by 5-lipoxygenase. LTA(4) is further metabolized to either LTC(4) or LTB(4) by the enzyme LTC(4) synthase or LTA(4) hydrolase, respectively. Unlike 5-lipoxygenase, these enzymes are expressed in most tissues. This observation previously has led to the suggestion that LTA(4) produced by leukocytes may, in some cases, be delivered to other cell types before being converted into LTC(4) or LTB(4). While in vitro studies indicate that this process, termed transcellular biosynthesis, can lead to the production of leukotrienes, it has not been possible to determine the significance of this pathway in vivo. Using a series of bone marrow chimeras generated from 5-lipoxygenase- and LTA(4) hydrolase-deficient mice, we show here that transcellular biosynthesis contributes to the production of leukotrienes in vivo and that leukotrienes produced by this pathway are sufficient to contribute significantly to the physiological changes that characterize an ongoing inflammatory response.

Periodontal disease increases the risk of preterm delivery among preeclamptic women.

BACKGROUND: Preterm births are a major cause of neonatal morbidity and mortality, and represent an important public health issue. About 30% of preterm births are due to medical conditions of the mother or the fetus, among "which preeclampsia plays a major role. We have previously reported that maternal periodontal disease enhances the risk for preterm delivery and preeclampsia. Our current objective was to determine whether maternal periodontal disease increases the risk for preterm delivery among preeclamptic women. METHODS: Women were enrolled prior to their twenty-sixth week of gestation. Periodontal status was assessed at baseline and defined as healthy, mild, or moderate/severe. Repeat examinations were performed at delivery to assess changes in periodontal status. RESULTS: A cohort of 1,020 women was studied, 47 of whom had preeclampsia. A strong association between periodontal disease status at enrollment and rate of premature delivery was observed among preeclamptic women after adjusting for the major risk factors for preterm delivery, including maternal race; age; marital status; WIC (women, infants, children program) or food stamps; insurance; previous preterm delivery; and chorioamnionitis. Among preeclamptic women, 49.3% with mild periodontal disease and 82.6% with moderate to severe disease delivered preterm (hazard ratios [HR] 4.11 and 11.0, respectively). Periodontal disease worsening during pregnancy in preeclamptic women was also associated with an increased risk of preterm births (HR 8.44). CONCLUSION: These results suggest that mothers with preeclampsia may be at greater risk for preterm delivery if periodontal disease is present early in pregnancy or progresses during pregnancy.