Does gestational diabetes mellitus increase the risk of cardiovascular disease? A Mendelian randomization study

PURPOSE

In recent years, epidemiological studies have revealed the relationship between gestational diabetes mellitus (GDM) and cardiovascular disease (CVD). In this study, we utilized Mendelian randomization (MR) to investigate the potential causal impact of GDM on cardiovascular disease for the first time.

METHODS

 We retrieved summary statistics from published genome-wide association studies. MR was first performed using significant SNPs extracted from the eighth data release of the FinnGen study. Next, a replication analysis for coronary artery disease (CAD) was conducted in another European ancestry population to validate our findings. Finally, mediation analysis was carried out to assess potential mediation effects.

RESULTS

Our data analysis revealed that genetically predicted GDM was significantly associated with increased CAD risk (OR 1.10, 95% CI 1.02-1.18, p 0.006). Replication analysis confirmed a significant genetic association between GDM and CAD (OR 1.07, 95% CI 1.02-1.12, p 0.003) in another European ancestry population. Mediation analysis indicated no significant mediation effect by type 2 diabetes mellitus (T2DM) on the GDM-CAD relationship (mediation effect β [95% CI]: 0.005 [-0.003, -0.017]).

CONCLUSION

Women with a prior history of GDM face an elevated risk of future CAD. This increased risk of CAD cannot be solely attributed to the subsequent onset of diabetes. Regular CAD risk assessment and primary prevention strategies are of paramount importance for women with a history of GDM.

[The expression and function of PD-L1 in CD133(+) human liver cancer stem-like cells]

Objective: To investigate the expression of programmed death protein-ligand 1 (PD-L1) in liver cancer stem-like cells (LCSLC) and its effect on the characteristics of tumor stem cells and tumor biological function, to explore the upstream signaling pathway regulating PD-L1 expression in LCSLC and the downstream molecular mechanism of PD-L1 regulating stem cell characteristics, also tumor biological functions. Methods: HepG2 was cultured by sphere-formating method to obtain LCSLC. The expressions of CD133 and other stemness markers were detected by flow cytometry, western blot and real-time quantitative polymerase chain reaction (RT-qPCR) were used to detect the expressions of stemness markers and PD-L1. The biological functions of the LCSLC were tested by cell function assays, to confirm that the LCSLC has the characteristics of tumor stem cells. LCSLC was treated with cell signaling pathway inhibitors to identify relevant upstream signaling pathways mediating PD-L1 expression changes. The expression of PD-L1 in LCSLC was down regulated by small interfering RNA (siRNA), the expression of stem cell markers, tumor biological functions of LCSLC, and the changes of cell signaling pathways were detected. Results: Compared with HepG2 cells, the expression rate of CD133 in LCSLC was upregulated [(92.78±6.91)% and (1.40±1.77)%, P<0.001], the expressions of CD133, Nanog, Oct4A and Snail in LCSLC were also higher than those in HepG2 cells (P<0.05), the number of sphere-formating cells increased on day 7 [(395.30±54.05) and (124.70±19.30), P=0.001], cell migration rate increased [(35.41±6.78)% and (10.89±4.34)%, P=0.006], the number of transmembrane cells increased [(75.77±10.85) and (20.00±7.94), P=0.002], the number of cloned cells increased [(120.00±29.51) and (62.67±16.77), P=0.043]. Cell cycle experiments showed that LCSLC had significantly more cells in the G(0)/G(1) phase than those in HepG2 [(54.89±3.27) and (32.36±1.50), P<0.001]. The tumor formation experiment of mice showed that the weight of transplanted tumor in LCSLC group was (1.32±0.17)g, the volume is (1 779.0±200.2) mm(3), were higher than those of HepG2 cell [(0.31±0.06)g and (645.6±154.9)mm(3), P<0.001]. The expression level of PD-L1 protein in LCSLC was 1.88±0.52 and mRNA expression level was 2.53±0.62, both of which were higher than those of HepG2 cells (P<0.05). The expression levels of phosphorylation signal transduction and transcription activation factor 3 (p-STAT3) and p-Akt in LCSLC were higher than those in HepG2 cells (P<0.05). After the expression of p-STAT3 and p-Akt was down-regulated by inhibitor treatment, the expression of PD-L1 was also down-regulated (P<0.05). In contrast, the expression level of phosphorylated extracellular signal-regulated protein kinase 1/2 (p-ERK1/2) in LCSLC was lower than that in HepG2 cells (P<0.01), there was no significant change in PD-L1 expression after down-regulated by inhibitor treatment (P>0.05). After the expression of PD-L1 was knockdown by siRNA, the expressions of CD133, Nanog, Oct4A and Snail in LCSLC were decreased compared with those of siRNA-negative control (NC) group (P<0.05). The number of sphere-formating cells decreased [(45.33±12.01) and (282.00±29.21), P<0.001], the cell migration rate was lower than that in siRNA-NC group [(20.86±2.74)% and (46.73±15.43)%, P=0.046], the number of transmembrane cells decreased [(39.67±1.53) and (102.70±11.59), P=0.001], the number of cloned cells decreased [(57.67±14.57) and (120.70±15.04), P=0.007], the number of cells in G(0)/G(1) phase decreased [(37.68±2.51) and (57.27±0.92), P<0.001], the number of cells in S phase was more than that in siRNA-NC group [(30.78±0.52) and (15.52±0.83), P<0.001]. Tumor formation in mice showed that the tumor weight of shRNA-PD-L1 group was (0.47±0.12)g, the volume is (761.3±221.4)mm(3), were lower than those of shRNA-NC group [(1.57±0.45)g and (1 829.0±218.3)mm(3), P<0.001]. Meanwhile, the expression levels of p-STAT3 and p-Akt in siRNA-PD-L1 group were decreased (P<0.05), while the expression levels of p-ERK1/2 and β-catenin did not change significantly (P>0.05). Conclusion: Elevated PD-L1 expression in CD133(+) LCSLC is crucial to maintain stemness and promotes the tumor biological function of LCSLC.

[Preliminary clinical effect evaluation of digital head and neck radiotherapy oral positioning stents]

Objective: To develop a designing software of digital oral positioning stent for radiotherapy of head and neck, and to compare its clinical effect with traditional oral positioning stents made by lost wax process. Methods: Thirty patients with nasopharyngeal cancer who received oral examination before radiotherapy in the prosthodontics department from July to December, 2021, were selected and divided into three groups according to the patients' wishes, 10 per group: one group without radiotherapy oral positioning stents, one group with traditional oral positioning stents (traditional stents group), and the third group with digital oral positioning stents (digital stents group). Patients' ages range from 20 years old to 71 years old. There were 15 males and 15 females involved in this study. The manufacturing time and comfort of the two positioning stents were evaluated, and the radiation doses of the radiotherapy target areas and surrounding healthy tissues were statistically analyzed at the end of radiotherapy. Results: The manufacturing time of digital stents group [(209±7) min] was much less than that of traditional stents group [(490±10) min] (t=69.85, P<0.001). The comfort of patients' wearing of digital stents [first wearing: 5 (3, 6) score; at the end of radiotherapy: 4 (3, 5) score] was better than that of traditional ones [first wearing: 7 (3, 7) score; at the end of radiotherapy: 7 (3, 7) score] (U=22.00, P=0.033; U=20.50, P=0.023). There was no significant differences in the target radiation doses among the three groups, and the radiation doses of tongue [traditional stents group: (36.74±5.45) Gy; digital stents group: (35.96±4.98) Gy] and mandible [traditional stents group: (35.46±4.19) Gy; digital stents group: (35.34±3.98) Gy] were significantly lower in the patients wearing oral positioning stents than in the patients without oral positioning stents [tongue: (41.49±4.46) Gy; madible: (39.32±3.52) Gy] (P<0.05). Conclusions: Oral positioning stents for nasopharyngeal carcinoma radiotherapy could greatly reduce the exposure doses of tongue and madible of patients. Digital oral positioning stents designed and manufactured by independently developed software had higher production efficiency than the traditional method, and patients' evaluation of comfort was better.

[Treatment outcome of 100 patients with hepatoblastoma based on a new risk stratification]

Objective: To provide the risk stratification method of hepatoblastoma (HB) suitable for implementation in China and explore the new treatment method for high-risk HB patients. Methods: A total of 100 cases of children and adolescents under 18 years old with newly diagnosed HB in Sun Yat-sen University Cancer Center and Sun Yat-sen University First Affiliated Hospital from September 2014 to September 2018 were included. According to the clinical stage, AFP level, pathological subtype and other factors, patients were stratified into four groups: extremely low-, low-, intermediate- and high-risk. The patients at very low risk were treated with surgery only and followed-up. The patients at very low risk were treated with C5V(Cisplatin+ 5-Fluroracil+ Vincristine) regimen for 4 courses. The patients at intermediate risk were treated with C5VD(Cisplatin+ 5-Fluroracil+ Vincristine+ Doxorubicin)regimen before and after surgery for 6-8 courses. The patients at high risk were treated with C5VD and IIV (ifoshamide+ irinotecan+ vincristine) alternately before and after surgery for 8 courses. Results: One hundred patients were stratified into extremely low-risk, low-risk, medium-risk and high-risk groups for 2, 10, 51 and 37 cases, respectively. Eighty three cases had evaluable lesions before chemotherapy. Among them, 65 patients achieved partial remission, stable disease and progressive disease were observed in 10, and 8 cases, respectively, with a response rate of 78.3%. During a median follow-up of 20 months, 30 patients experienced tumor relapse or progression, and 27 of them died. The 2-years progression-free survival (PFS) and overall survival (OS) rates were 69.2% and 72.0%, respectively. The 2-years PFS rates of patients with extremely low risk, low risk, medium risk and high risk were 100%, 88.9%, 75.3% and 43.2%, respectively. The 2-years OS rates were 100%, 100%, 81.0% and 44.8%, respectively. Conclusions: The novel HB risk classification is simple and feasible. With active comprehensive treatment, patients at extremely low-, low- and medium-risk have excellent outcomes. The survival rate of high-risk HB patients remains to be improved, and new treatment strategies need to be explored.

[A single-center retrospective analysis of 85 children and adolescents with limited-stage Hodgkin lymphoma]

Objective: To summarize the efficiency and long-term outcomes of limited-stage Hodgkin lymphoma in children and adolescents with ABVD therapy and determined whether omitting radiotherapy for a low-risk patient enabled the achievement of complete response (CR) after chemotherapy. Methods: We retrospectively analyzed data from 13 y (2004-2016) from patients aged ≤18 y with limited-stage HL admitted to the Sun Yat-sen University Cancer Center. Patients received treatment with ABVD chemotherapy alone or ABVD chemotherapy followed by low-dose involved field radiotherapy. Results: Total 85 subjects were eligible for study inclusion; the median age was 12 (3-18) y; 66 (77.6%) were men, 80 (94.1%) had stage-II disease, 56 (65.9%) were at low-risk, and the median follow-up duration was 72 (8-196) months; 12 relapsed, 2 had secondary neoplasm, and 2 died. The 5-year event free survival (EFS) was (85.6±3.8) %, and the overall survival (OS) was 100%. The 5-year EFS and OS was (89.1±4.2) % and 100%, respectively, for the low-risk cohort and (79.3±7.5) % and 100%, respectively for the intermediate-risk cohort. Among the 39 low-risk patients who achieved CR after chemotherapy, 15 received treatment with chemotherapy followed by LD-IFRT. In the exploratory subset analysis, the low-risk cohort who achieved CR after chemotherapy, the 5-year EFS for comparing ABVD alone with chemotherapy followed by LD-IFRT was (87.0±7.0) % versus 100% (P=0.506) , and the OS was 100% for both the groups. Conclusions: Our retrospective analysis showed excellent survival of limited-stage HL patients with ABVD therapy. For patients who achieving CR after chemotherapy with low-risk HL, received chemotherapy followed by LD-IFRT does not improve 5-year OS and EFS. The use of risk- and response-based stratification may facilitate the development of effective and less toxic protocols.

[Efficacy of minimally invasive pulmonary surfactant administration in preterm infants with neonatal respiratory distress syndrome: a multicenter clinical trial]

Objective: To explore the feasibility and safety of minimally invasive surfactant administration (MISA) in preterm neonates with respiratory distress syndrome (NRDS). Methods: In this multicenter prospective randomized controlled trial, 92 preterm infants with gestation age ≤30 weeks and diagnosed with NRDS were enrolled in 8 level Ⅲ neonatal intensive care units (NICU) in Beijing-Tianjin-Hebei Region from 1(st) July 2017 to 31(st) December 2018. They were randomly assigned to minimally invasive surfactant administration (MISA) group or endotracheal intubation surfactant administration (EISA) group according to random number generated by computer. Infants in both groups received calf pulmonary surfactant preparation at a dose of 70-100 mg/kg. The data of demography, perinatal situation, medication administration, complications, clinical outcomes in the two groups were compared with Chi-square test, Student's t-test, Mann-Whitney U test or Fisher's exact test. Results: Among the 92 preterm infants, 53 were males, 39 were females; 47 were in the MISA group (25 males), and 45 were in the EISA group (28 males). The gestational age and birth weight were (29.5±1.2) weeks and (1 271±242) g in all patients, (29.5±1.4) weeks and (1 285±256) g in the MISA group, and (29.6±0.9) weeks and (1 255±227) g in the EISA group. The duration of surfactant infusion and the length of whole procedure in the MISA group were significantly longer than that in the EISA group (60 (18, 270) s vs. 50 (30, 60) s, Z=3.009, P=0.003; 90 (60, 300) s vs. 60 (44, 270) s, Z=3.365, P=0.001). For the outcomes, the incidence of hemodynamically significant patent ductus arteriosus (hsPDA) and bronchopulmonary dysplasia (BPD) were lower in the MISA group than in the EISA group (36% (17/47) vs. 67% (30/45), χ(2)=8.556, P=0.003; 26% (12/47) vs. 47% (21/45), χ(2)=4.464, P=0.035). Conclusions: Minimally invasive surfactant administration is applicable in preterm infants ≤30 weeks gestational age with NRDS. Although the length of whole procedure is longer than route endotracheal administration, the benefit of decreasing the incidences of hsPDA and BPD outweighs this demerit.

[Impact of intensified maintenance therapy on the prognosis of children and adolescents with advanced lymphoblastic lymphoma]

目的

探讨增加维持治疗强度对Ⅲ期和Ⅳ期儿童青少年淋巴母细胞淋巴瘤（Lymphoblastic lymphoma, LBL）患者预后的影响。

方法

回顾性分析接受BFM-NHL-90/-95方案治疗且未做纵隔和中枢预防性放疗的Ⅲ期和Ⅳ期儿童青少年LBL患者的治疗结果。研究分组：1998年至2005年收治的患者于维持治疗阶段，在口服巯基嘌呤和甲氨蝶呤的基础上，定期采用“足叶乙甙+阿糖胞苷”和大剂量甲氨蝶呤交替进行化疗，为强化维持治疗组；其余为非强化维持治疗组。

结果

187例LBL患者纳入研究，其中强化维持治疗组52例，非强化维持治疗组135例，两组患者的性别、年龄、免疫分型、临床分期、危险度分层、受累部位的差异均无统计学意义（P值均>0.05）；中位随访48（0.5～221）个月，两组患者的5年无事件生存（EFS）率分别为（76.9±5.8）%和（77.9±4.3）%（χ²＝0.249，P＝0.617），5年总生存（OS）率分别为（78.8±5.7）%和（79.8±4.1）%（χ²＝0.353，P＝0.552），差异均无统计学意义；亚组分析结果显示，两组患者在不同临床分期（Ⅲ/Ⅳ期）、免疫分型（T/B-LBL）和危险分层（中/高危）中的EFS、OS率差异均无统计学意义（P值均>0.05）。维持治疗期间，强化维持治疗组和非强化维持治疗组患者Ⅲ、Ⅳ级骨髓抑制发生率分别为55.8%和18.5%（χ²＝25.363，P<0.05）。

结论

提高维持治疗强度并未提高Ⅲ期和Ⅳ期儿童青少年LBL患者的长期生存且可增加骨髓抑制等治疗相关不良反应。

Effects of Three Feeding Systems on Production Performance, Rumen Fermentation and Rumen Digesta Particle Structure of Beef Cattle

The effects of three different feeding systems on beef cattle production performance, rumen fermentation, and rumen digesta particle structure were investigated by using 18 Limousin (steers) with a similar body weight (575±10 kg) in a 80-d experiment. The animals were equally and randomly divided into three treatment groups, namely, total mixed ration group (cattle fed TMR), SI1 group (cattle fed concentrate firstly then roughage), and SI2 group (cattle fed roughage firstly then concentrate). The results showed that the average daily gain was significantly higher in cattle receiving TMR than in those receiving SI1 and SI2 (p<0.05). Consumption per kg weight gain of concentrate, silage, and combined net energy (NEmf) were significantly decreased when cattle received TMR, unlike when they received SI1 and SI2 (p<0.05), indicating that the feed efficiency of TMR was the highest. Blood urea nitrogen (BUN) was significantly decreased when cattle received TMR compared with that in cattle receiving SI1 (p<0.05), whereas there was no difference compared with that in cattle receiving SI2. Ammonia nitrogen concentration was significantly lower in cattle receiving TMR than in those receiving SI1 and SI2 (p<0.05). The rumen area of cattle that received TMR was significantly larger than that of cattle receiving SI1 (p<0.05), but there was no difference compared with that of cattle receiving SI2. Although there was no significant difference among the three feeding systems in rumen digesta particle distribution, the TMR group trended to have fewer large- and medium-sized particles and more small-sized particles than those in the SI1 and SI2 groups. In conclusion, cattle with dietary TMR showed increased weight gain and ruminal development and decreased BUN. This indicated that TMR feeding was more conducive toward improving the production performance and rumen fermentation of beef cattle.

Nitrogen-corrected True Metabolizable Energy and Amino Acid Digestibility of Chinese Corn Distillers Dried Grains with Solubles in Adult Cecectomized Roosters

This study was conducted to evaluate chemical composition, nitrogen-corrected true metabolizable energy (TMEn) and true amino acids digestibility of corn distillers dried grains with solubles (DDGS) produced in China. Twenty five sources of corn DDGS was collected from 8 provinces of China. A precision-fed rooster assay was used to determine TMEn and amino acids digestibility with 35 adult cecectomized roosters, in which each DDGS sample was tube fed (30 g). The average content of ash, crude protein, total amino acid, ether extract, crude fiber and neutral detergent fiber were 4.81, 27.91, 22.51, 15.22, 6.35 and 37.58%, respectively. TMEn of DDGS ranged from 1,779 to 3,071 kcal/kg and averaged 2,517 kcal/kg. Coefficient of variation for non-amino acid crude protein, ether extract, crude fiber and TMEn were 55.0, 15.7, 15.9 and 17.1%, respectively. The average true amino acid digestibility was 77.32%. Stepwise regression analysis obtained the following equation: TMEn, kcal/kg = -2,995.6+0.88×gross energy+49.63×a* (BIC = 248.8; RMSE = 190.8; p<0.01). Removing gross energy from the model obtained the following equation: TMEn, kcal/kg = 57.88×ether extracts+87.62×a* (BIC = 254.3, RMSE = 223.5; p<0.01). No correlation was found between color scores and lysine true digestibility (p>0.05). These results suggest that corn DDGS produced in China has a large variation in chemical composition, and gross energy and a* value can be used to generate TMEn predict equation.

Reduced lesions in chickens with Clostridium perfringens-induced necrotic enteritis by Lactobacillus fermentum 1.20291

Previous studies have demonstrated that Lactobacillus has anti-inflammatory properties, but the protective functions of Lactobacillus and mechanisms of inhibition of necrotic enteritis (NE) in the intestines of chickens have not been fully clarified. In the present study, we selected a probiotic strain, Lactobacillus fermentum 1.2029, which has good adhesive ability and a high survival rate in low pH and bile salts. The objective of this study was to examine the anti-inflammatory properties of L. fermentum 1.2029 against NE in chickens. Two hundred forty 1-d-old male Arbor Acres broilers were blocked into 3 experimental groups as follows: (I) nonchallenge control group, (II) Clostridium perfringens challenge group, and (III) C. perfringens challenge + L. fermentum 1.2029 group. Lactobacillus fermentum 1.2029 (1.0 mL/d, 10(8) cfu/mL) was orally administered daily to group III during the course of the experiment, and all uninfected control chickens were inoculated accordingly with the same volume of PBS. Clostridium perfringens (0.5 mL on d 1 and 1.0 mL on d 14 to 21, 10(8) cfu/mL) was administered to chickens in group II. At 28 d, scoring of gross NE lesions was performed. Ileal segments of approximately 2 cm from 24 chickens in each experimental group were collected and fixed in 4% (wt/vol) neutral-buffered formalin solution for histological scoring. Ileal mucosa samples were also collected for mRNA analysis by real-time PCR. The results showed that L. fermentum 1.2029 reduced the severity of NE lesions in chickens. Histological scores revealed that L. fermentum 1.2029 also reduced the inflammation damage of NE in chickens. Changes in cytokines and Toll-like receptors (TLR) were determined, and L. fermentum 1.2029 was found to increase interleukin-10 levels and reduce interferon-γ and TLR2 levels in NE-infected chickens. The results showed that L. fermentum 1.2029 was able to regulate the intestinal mucosal immune response and ameliorate inflammation by changing expression levels of cytokines and TLR.

Colon epithelial cell death in 2,4,6-trinitrobenzenesulfonic acid-induced colitis is associated with increased inducible nitric-oxide synthase expression and peroxynitrite production

Peroxynitrite, derived from the reaction of nitric oxide (NO(.)) with superoxide (O(2)), is a potent nitrating and oxidizing agent that can induce apoptosis in a variety of different cell types. In the present study, we investigated the possible role of peroxynitrite as a mediator of colon epithelial cell death in rat colitis. Rat colon inflammation was induced by intracolonic administration of 2,4,6-trinitrobenzenesulfonic acid (TNBS) and rats were sacrificed 24 h after TNBS administration. Expression of inducible nitric-oxide synthase (iNOS) was detected by reverse transcription-polymerase chain reaction and immunohistochemistry. The enzymatic activities of Ca(2+)-independent iNOS and Ca(2+)-dependent constitutive nitric-oxide synthase were determined biochemically. Evidence of peroxynitrite-mediated cell injury was detected by immunostaining of nitrotyrosine. Apoptosis was examined by in situ terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) assay and DNA gel electrophoresis. To evaluate the specific contribution of peroxynitrite to the observed cell injury, a selective iNOS inhibitor, L-N(G)-[1-iminoethyl]lysine (L-NIL), was administered after TNBS induction. Morphological examination and analysis of TUNEL/cytokeratin double immunofluorescence revealed significant apoptosis in mucosal epithelial cells. Nitrotyrosine was colocalized with TUNEL, strongly demonstrating the association of peroxynitrite with the apoptotic death of colon epithelial cells. The administration of L-NIL reduced iNOS activity in 24-h lesions by 92% and also significantly attenuated both nitrotyrosine staining and apoptotic cell counts in the colon epithelium. These results strongly suggest that local elevated level of peroxynitrite produced from increased iNOS expression and activity is a major contributor to colon epithelial apoptosis during colon inflammation.

Pattern of cytokine and adhesion molecule mRNA in hapten-induced relapsing colon inflammation in the rat

We examined the mRNA expression of cytokines, chemokines, integrins, and selectins in colon lesions of rat colitis with a semi-quantitative RT-PCR assay. Rat colitis was induced by trinitrobenzene sulfonic acid (TNBS) in 50% ethanol. Within 24 h, an acute inflammation occurred with hyperemia, edema, necrosis and an intense infiltration of granulocytes in the mucosa. The lesion proceeded into a T-lymphocyte/monocyte-driven chronic inflammation for two weeks and healed in 6 weeks. An acute inflammation recurred at the same site when the recovered animals were systemically injected with TNBS. We isolated RNA from colon tissue at 24 h, 1, 2, 4, 6 weeks after TNBS treatment and from the relapsed animals. The mRNA for cytokines IL-1beta, IL-6, IL-10 and the chemokines CINC, MIP-1alpha, MCP-1 were significantly (P < 0.05) elevated and persisted for 2 weeks, decreased in 6 weeks and increased again during relapse. IFN-gamma mRNA stayed at control levels initially, but increased dramatically in the second weeks of chronic inflammation as well as in relapse. The mRNA levels of adhesion molecules, ICAM-1, VCAM-1, the mucosal homing integrin beta7 as well as P- and E-selectin were greatly enhanced between 1 and 3 weeks. The data showed that the chronically inflamed tissue expresses a time-dependent changing pattern of TH1 cytokines and adhesion molecules that maintain the infiltration and activation of inflammatory cells and tissue injury.

NO modulates P-selectin and ICAM-1 mRNA expression and hemodynamic alterations in hepatic I/R

The anti-inflammatory role of nitric oxide (NO) was studied in a model of hepatic ischemia-reperfusion (I/R) in rats. Male Fischer rats were subjected to 30 min of no-flow ischemia of the left and median lobes of the liver, and animals were examined for a 4-h period of reperfusion. The animals were divided into the following groups: control-vehicle; I/R-vehicle; I/R-Nomega-nitro-L-arginine methyl ester (L-NAME, 10 mg/kg iv, 10 min before reperfusion); sham control-L-NAME, and I/R-S-nitroso-N-acetyl-penicillamine (SNAP, 25 micromol/kg iv, 10 min before reperfusion, followed by 20 micromol. kg-1. h-1 in 1.0 ml saline infused for 4 h). Results showed that mean arterial blood pressure was significantly increased in the sham control-L-NAME or I/R-L-NAME groups compared with either the I/R-vehicle or I/R-SNAP groups. However, cardiac index (CI) and stroke volume index (SVI) were markedly decreased, and systemic vascular resistance index (SVRI) was dramatically increased. Interestingly, the CI and SVI in rats treated with SNAP were markedly improved over that of the I/R group. Plasma nitrate and nitrite levels were significantly decreased in the I/R-L-NAME group; however, superoxide generation in the ischemic lobes and plasma alanine aminotransferase activity were higher compared with I/R-SNAP rats. The L-NAME-induced enhancement of hepatic injury in rats with I/R may be due in part to neutrophil infiltration, which was significantly increased compared with animals subjected to I/R or I/R-SNAP. The mechanism of L-NAME-enhanced neutrophil infiltration may be due to the fact that the ratios of P-selectin and intercellular adhesion molecule 1 (ICAM-1) mRNA to glyceraldehyde-3-phosphate dehydrogenase mRNA extracted from the ischemic lobes of I/R-L-NAME rats were significantly increased when compared with the I/R-SNAP group. These results suggest that 1) endogenous NO reduces the SVRI and permits an increased CI and SVI; 2) exogenous NO further improves CI and SVI; and 3) endogenous, but not exogenous, NO decreases P-selectin and ICAM-1 mRNA expression, thereby reducing polymorphonuclear neutrophil-dependent reperfusion tissue injury.

Peroxynitrite induces apoptosis of HL-60 cells by activation of a caspase-3 family protease

Apoptosis is an active process critical for the homeostasis of organisms. Enzymes of the caspase family are responsible for executing this process. We have previously shown that peroxynitrite (ONOO-), a biological product generated from the interaction of nitric oxide and superoxide, induces apoptosis of HL-60 cells. The aim of this study was to elucidate the mechanisms involved in the execution process of peroxynitrite-induced apoptosis. Proteolytic cleavage of poly(ADP-ribose) polymerase, an indication of caspase-3 family protease activation and an early biochemical event accompanying apoptosis, was observed in a time-dependent manner during peroxynitrite-induced apoptosis of HL-60 cells. Activation of caspase-3 during peroxynitrite-induced apoptosis was substantiated by monitoring proteolysis of the caspase-3 proenzyme and by measuring caspase-3 activity with a fluorogenic substrate. Furthermore, pretreatment of HL-60 cells with N-acetyl-Asp-Glu-Val-Asp-aldehyde, a specific inhibitor of caspase-3, but not N-acetyl-Tyr-Val-Ala-Asp-aldehyde, a specific inhibitor of caspase-1, decreased peroxynitrite-induced apoptosis. These results suggest that the activation of a caspase-3 family protease is essential for initiating the execution process of peroxynitrite-induced apoptosis of HL-60 cells.

Roles of adhesion molecules ICAM-1 and alpha4 integrin in antigen-induced changes in microvascular permeability associated with lung inflammation in sensitized brown Norway rats

Increased microvascular permeability and mucosal edema are pathological features of airway inflammation in asthma. In this study, we investigated the characteristics of the edema response occurring in a model of antigen-induced lung inflammation in sensitized brown Norway rats and examined the effects of monoclonal antibodies (mAbs) to adhesion molecules on this response. Ovalbumin (OA) challenge-induced increases in lung permeability were determined by the leakage of 125I-labeled bovine serum albumin (BSA) into the extravascular tissues of the lungs 24 h after challenge in animals intravenously injected (prechallenge) with this tracer. Inflammatory cell infiltration into the alveolar space was determined by bronchoalveolar lavage (BAL). Mean extravascular plasma volume in the lung increased 233% as compared with control (P < 0.005) at 24 h and increased to 517% by 72 h. The 24-h edema response was completely inhibited by two oral doses (0.1 mg/kg) of dexamethasone 1 h before, and 7 h after, challenge. Intraperitoneal administration of the anti-rat ICAM-1 mAb 1A29, or anti-rat alpha4 integrin mAb TA-2 (2 mg/kg at 12 and 1 h before, and 7 h after, antigen challenge), significantly suppressed eosinophil infiltration into the alveolar space without inhibiting the enhanced microvascular leakage and lung edema. Determination of plasma antibody concentrations by ELISA of mouse IgG1 indicated that sufficient concentrations of the appropriate mAb were present to block alpha4- or ICAM-1-dependent adhesion. The results suggest that increases in microvascular permeability and plasma leakage occurred independently of eosinophil accumulation.

Reactive oxygen species participate in peroxynitrite-induced apoptosis in HL-60 cells

Peroxynitrite (ONOO-) is a physiological product generated by the interaction of superoxide (O2.-) and nitric oxide (.NO). We have previously shown that peroxynitrite induces apoptosis in HL-60 cells. In the present study, we demonstrated that peroxynitrite generates reactive oxygen species (ROS) in HL-60 cells. Brief exposure of HL-60 cells to ONOO- induced elevation of lucigenin chemiluminescence, indicating generation of superoxide anion. Exogenous superoxide dismutase (SOD), a scavenger of O2.-, fully abolished the chemiluminescence response, further supporting this notion. Following O2.- generation, the accumulation of hydrogen peroxide (H2O2) was observed. The addition of SOD exacerbated but that of catalase attenuated peroxynitrite-induced DNA fragmentation, suggesting that this H2O2 production contributes to the apoptotic process. In addition, pre-treatment of HL-60 cells with N-acetyl-L-cysteine (15 mM), a ROS scavenger, fully scavenged peroxynitrite-elicited ROS generation and effectively inhibited (ONOO-)-induced apoptosis, further enforcing this hypothesis. In summary, our results suggest that (ONOO-)-stimulated ROS formation may serve as a mechanism for the propagation of peroxynitrite-mediated apoptotic cell death in an intact cell system.

Phenotypic analysis of airway eosinophils and lymphocytes in a Th-2-driven murine model of pulmonary inflammation

In order to investigate whether the pulmonary response to helminth antigens mimics that seen in allergic inflammation of the airways, we have examined the phenotypic characteristics of lymphocytes and eosinophils recruited to the airways following Nippostrongylus brasiliensis (N.b.) infection. Specifically, the cellular response was divided into an early and a late phase. During the early response there was a small but significant increase in neutrophil numbers recovered by bronchoalveolar lavage (BAL). Phenotypic analysis of BAL leukocytes revealed an early rise in the percentage of BAL lymphocytes expressing the naive T cell markers CD45RB and L-selectin, and the activation marker IL-2R. In addition, during the early response, there was an increased percentage of lymphocytes expressing the gamma delta TCR, but not the alpha beta TCR. In contrast, the late response was marked by a much larger accumulation, in the lungs and BAL, of memory CD4+ T lymphocytes and an influx of small, hypodense eosinophils which produced LTB4 and LTC4 on stimulation with calcium ionophore. At this time there was a substantial increase in the number of T lymphocytes and eosinophils expressing ICAM-1 and the integrins VLA-4 and LFA-1, implicating these adhesion molecules in inflammatory cell recruitment to the airways. We conclude that the pattern and phenotypic characteristics of the cellular recruitment seen following N.b. infection resemble those seen in early- and late-phase allergic inflammation of the airways in asthma, and therefore N.b. may be used to model these aspects of the disease.

Changes in membrane properties during energy depletion-induced cell injury studied with fluorescence microscopy

The changes in membrane structural properties occurring during the process of ATP depletion-induced cell injury in adherent human astrocytoma cells (UC-11 MG) were studied with two epifluorescence techniques: 1) steady-state fluorescence anisotropy (r) to examine microstructural changes in the membrane phospholipids and 2) fluorescence redistribution after photobleaching (FRAP) to examine membrane fluidity changes. A new method for r measurement was established that provides the unique advantage of simultaneously monitoring both vertical and horizontal polarized fluorescence emissions needed for the calculation of r. In this study, r in the astrocytoma cells labeled with 1-(4-trimethylammonium phenyl)-6-phenyl-1,3,5-hexatriene p-toluenesulfonate was shown to remain stable for up to 90 min. However, when the cells were treated with 75 microM iodoacetic acid (IAA), a metabolic inhibitor that induces rapid depletion of cellular ATP, r continually decreased, indicating a decrease in membrane lipid order and perturbation of the bilayer structure. This decrease in r could be prevented by the pretreatment of cells with lipophilic antioxidants such as tirilazad or gossypol. Tirilazad itself caused a significant increase in r, suggesting that tirilazad intercalates into the membrane bilayer and profoundly increases the lipid order in uninjured cells. Gossypol, however, did not exhibit this property. Further investigations into these phenomena with FRAP confirmed the r results and indicated that membrane fluidity increased while its structure became less rigid during the process of ATP-induced cell injury. In addition, lipophilic antioxidants prevented the membrane structural aberrations induced by IAA. Experimental results suggest that different mechanisms of cytoprotective action may exist for tirilazad and the antioxidant gossypol. Gossypol appears to prevent or delay the observed cell injury entirely because of its antioxidant action, whereas tirilazad's protection is mediated not only via its antioxidant activity, but also by its ability to increase cell membrane lipid order.

The mechanism of cytoprotective action of lazaroids I: Inhibition of reactive oxygen species formation and lethal cell injury during periods of energy depletion

Tirilazad mesylate and related compounds, known as lazaroids, are recognized as inhibitors of membrane lipid peroxidation that also act as free radical scavengers. These compounds have demonstrated protective activity in animal models of traumatic head injury and cerebral ischemia. In this study we used an in vitro cell model to investigate the mechanism by which tirilazed mesylate and related antioxidants delay or prevent the lethal cell injury provoked by chemically induced energy depletion. When the cultured human astrocytoma cell line UC-11MG was treated with the metabolic inhibitor sodium iodoacetate for 4 hr, the cells exhibited signs of irreversible cell injury, including alterations in plasma membrane morphology, the breakdown of membrane phospholipids (release of arachidonic acid into the extracellular medium) and the loss of viability as indicated by the leakage of cytoplasmic components. A large quantity of reactive oxygen species (ROS) was detected in the injured cells by a dichlorofluorescin assay. Increases in early lipid peroxidation products were detected as elevated hydroxyeicosatetraenoic acids in the membrane phospholipds, which indicated that the membrane lipids were oxidatively damaged. The addition of tirilazad mesylate, a troloxamine derivative or the common phenolic antioxidant nordihydroguaiaretic acid effectively prevented the increases in ROS, attenuated the elevation of hydroxyeicosatetraenoic acids, and delayed irreversible cell injury. We propose that the destruction of crucial cell constituents in the lipophilic compartments by ROS is one of the major causes of lethal cell injury. The cyytoprotective action of the lazaroids in related, as least in part, to their ability to block the formation of ROS and to arrest the secondary cell injury.

Alterations in reactive oxygen, pH, and calcium in astrocytoma cells during lethal injury

Exposure of cultured human astrocytoma cells to iodoacetic acid results in rapid depletion of cellular ATP and cell death. Pathophysiological changes in the injured cells, including formation of reactive oxygen species (ROS), cell viability, glutathione, pH, and cytosolic calcium, were characterized at the cellular level via fluorescence microscopy. After iodoacetic acid treatment, cellular ATP and intracellular glutathione fell sharply to undetectable levels within 2 h. ROS, as detected by the oxidation of dichlorofluorescein, appeared in 20 min and reached a maximum before the loss of membrane integrity. Cells became acidotic within 10 min. Cytosolic free calcium concentration exhibited a slow increase and then a sharp influx shortly before the rupture of the cell membrane. The addition of lipophilic antioxidants, nordihydroguaiaretic acid or the troloxamine U-78517F, eliminated the accumulation of ROS and delayed the onset of cell death without affecting other parameters observed in the early phase of the injury. We conclude that ROS is formed and may play important roles during lethal cell injury caused by energy depletion.

The 21-aminosteroid tirilazad mesylate can ameliorate inflammatory bowel disease in rats

The 21-aminosteroid tirilazad mesylate (U74006F) is a lipophilic antioxidant and free radical scavenger that has been reported to attenuate brain or spinal cord injury caused by trauma, stroke, ischemia and reperfusion injury. In this study, we have examined the effect of U74006F in reducing the inflammatory parameters of trinitrobenzene sulfonic acid (TNBS)-induced inflammatory bowel disease (IBD) in rats. To induce IBD, rats were given ethanolic TNBS intracolonically. Rats received either 1) TNBS and U74006F 2) TNBS and vehicle or 3) saline and vehicle. Rats were sacrificed 1, 2 and 3 weeks after IBD induction. Colon to body weight ratio (an index of tissue edema) was markedly increased in the vehicle-treated IBD rats after 1 week of administration of TNBS. The ratio was significantly lower after U74006F treatment and the trend remained even after 3 weeks of chronic inflammation. Myeloperoxidase (MPO) activity in vehicle-treated IBD rats was substantially increased compared with controls during the entire 3 weeks of the experiment. U74006F-treated animals had significantly reduced MPO activity (60% lower) when compared with vehicle-treated animals at the end of the second and third weeks. These observations were confirmed by histopathology studies showing reduced granulocyte infiltration after drug treatment. U74006F treatment decreased basal (by 70%) and fMLP stimulated (by 75%) superoxide generation from colonic tissue from IBD rats compared with vehicle treatment after 2 weeks, but there was no apparent difference in superoxide generation among all three groups after 3 weeks. The results of this study suggested that administration of U74006F effectively reduces the inflammatory parameters in this chronic rat model of IBD. As such, U74006F may be therapeutically beneficial for the treatment of IBD in humans.

Antibodies to intercellular adhesion molecule-1 ameliorate the inflammatory response in acetic acid-induced inflammatory bowel disease

The transendothelial migration of leukocytes in many inflammatory responses is now believed to be dependent on the interaction of leukocyte and endothelial cell-derived adhesion molecules. To examine the role of intercellular adhesion molecule-1 (ICAM-1) in the development of inflammation in a rat model of colitis, we investigated the effects of antibodies to rat ICAM-1 given 24 hrs after inflammation was induced by acetic acid. Antibodies to rat ICAM-1 substantially ameliorated the inflammatory response as indicated by a reduction in gross inflammatory characteristics, tissue/body weight ratio, myeloperoxidase activity and superoxide levels. The results demonstrate that ICAM-1 plays an important role in the development of inflammatory bowel disease in rats. The use of antibodies to ICAM-1 to inhibit the adherence of leukocytes to endothelium, may be of potential therapeutic value in the treatment of inflammatory bowel disease in man.

Lack of effect of postinjury treatment with methylprednisolone or tirilazad mesylate on the increase in eicosanoid levels in the acutely injured cat spinal cord

Methylprednisolone (MP) improves motor recovery in spinal cord-injured patients when administered in a 24 h intensive high dose regimen beginning within 8 h after spinal cord injury (SCI). The rationale for this regimen has been based upon the need for high doses (i.e., 30 mg/kg initial IV dose) to inhibit posttraumatic lipid peroxidation (LP) in the injured spinal segment. However, injury also triggers the immediate calcium-mediated activation of phospholipase A2 (PLA2), the release of arachidonic acid, and the enzymatic formation of potentially deleterious prostaglandins (PGE2 alpha, PGE2), thromboxane A2 (TXA2), and leukotrienes (LTs). Thus, in view of the glucocorticoid receptor-mediated inhibition of PLA2 that underlies much of MP's antiinflammatory actions, an additional neuroprotective mechanism may relate to an inhibition of eicosanoid formation. Using the cat spinal cord compression model (180g x 5 min at L3; Na pentobarbitol anesthesia), we examined whether 30 min postinjury dosing with MP (30 mg/kg IV) could attenuate spinal tissue eicosanoid levels measured by enzyme immunoassay at 1 h (Experiment 1). Pial blood flow was measured over the dorsal columns at the injury site using laser doppler flowmetry to monitor posttraumatic hyperperfusion as an index of the microvascular pathophysiology of acute SCI. In vehicle treated animals at 1 h postinjury, there was a significant increase in the tissue levels of PGF2 alpha (+290%), PGE2 (+260%), TXB2 (stable analog of TXA2, +126%), and LTB4 (+73%) in comparison to sham, uninjured animals. However, 6-keto-PGF1 alpha (stable analog of prostacyclin or PGI2) and LTC4 did not increase. Methylprednisolone did not reduce the increase in eicosanoid production. In the case of LTB4 and LTC4, MP actually increased the levels further. In addition, we examined the effects of a double dose MP regimen (30 mg/kg IV at 30 min plus 15 mg/kg IV at 2.5 h postinjury) on spinal cord eicosanoid levels at 4 h postinjury (Experiment 2). At 4 h postinjury, significant increases in PGF2 alpha, PGE2, TXB2, and 6-keto-PGF1 alpha were observed, and with the exception of PGE2, no MP attenuation of the increased eicosanoids was seen. These results fail to provide evidence that postinjury administration of high dose MP exerts a significant anti-PLA2 action. On the other hand, MP effectively inhibited secondary spinal cord pial hyperperfusion, which is believed to be largely mediated by free radical-lipid peroxidative mechanisms. Thus, it seems likely that the protective action of MP on the acute microvascular pathophysiology of SCI is mediated by its well-documented effects on posttraumatic LP.(ABSTRACT TRUNCATED AT 400 WORDS)

Effects of the lipid peroxidation inhibitor tirilazad mesylate (U-74006F) on gerbil brain eicosanoid levels following ischemia and reperfusion

The present study measured the production of eicosanoids in the gerbil brain during early reperfusion after either a 3-h unilateral carotid occlusion (UCO, model of focal ischemia) or a 10-min bilateral carotid occlusion (BCO, model of global ischemia). Arachidonic acid (AA) metabolites were examined to determine if pretreatment with the 21-aminosteroid lipid peroxidation inhibitor U-74006F (tirilazad mesylate) could influence postreperfusion synthesis of brain eicosanoids. In the 3-h UCO focal ischemia model, there was an early (5-min) postreperfusion elevation in brain levels of PGF2 alpha, TXB2 and LTC4 (P < 0.05 vs. sham for all three eicosanoids). LTB4 also rose but not significantly. On the other hand, PGE2 and 6-keto-PGF1 alpha tended to decrease during ischemia and at 5-min postreperfusion (P < 0.05 vs. sham for PGE2). Pretreatment with known neuroprotective doses of U-74006F in this model (10 mg/kg i.p. 10 min before and again immediately upon reperfusion) did not affect the increase in PGF2 alpha or TXB2 but significantly blunted the elevations in LTC4 and LTB4. The postreperfusion decrease in PGE2 was also attenuated. In the 10-min BCO global ischemia model, there was also an increase in each of the measured eicosanoids, except LTB4, at 5 min after reperfusion. Pretreatment with U-74006F (10 mg/kg i.p. 10 min before ischemia) selectively decreased the rise in LTC4 but did not significantly affect the other eicosanoids. In contrast, the antioxidant actually caused a significant enhancement of the postreperfusion increase in PGE2 vs. vehicle-treated animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Metabolism of leukotriene B4 by guinea pig eosinophils

The metabolism of leukotriene B4 (5(S),12(R)-dihydroxy-6-cis-8,10-trans-14-cis-eicosatetraenoic acid) by isolated guinea pig eosinophils was investigated. Incubation of guinea pig eosinophils with [3H]-leukotriene B4 resulted in the rapid conversion of leukotriene B4 to several more polar metabolites. Two of these metabolites were identified by ultraviolet spectroscopy and gas chromatography-mass spectrometry as the omega oxidation products 5(S),12(R),20-trihydroxy-6,8,10,14-eicosatetraenoic acid (20-hydroxy-leukotriene B4) and 5(S),12(R),19-trihydroxy-6,8,10,14- eicosatetraenoic acid (19-hydroxy-leukotriene B4). Two novel metabolites, 5(S),12(R),18,19-tetrahydroxy-6,8,10,14 eicosatetraenoic acid (18,19-dihydroxy-leukotriene B4) and 5(S),12(R)-dihydroxy-1,18-dicarboxylic-6,8,10,14,16-octadecapentaenoi c acid (delta 16,17-18-carboxy-19,20-dinor-leukotriene B4) were tentatively identified. The identification of these compounds indicates that guinea pig eosinophils are capable of metabolizing leukotriene B4 by both omega and beta oxidation. This catabolic activity may play a role in modulating inflammatory reactions by removing the chemoattractant leukotriene B4 from inflammatory sites.

Degradation of membrane phospholipids in the cultured human astroglial cell line UC-11MG during ATP depletion

The exposure of brain cells to adverse conditions, such as ATP depletion, induces the degradation of membrane phospholipids and the accumulation of free fatty acids. We have investigated the mechanism of membrane breakdown in an in vitro cell injury model. Confluent cells from the human astroglial cell line UC-11MG were treated with sodium iodoacetate to deplete their intracellular ATP. Large amounts of saturated (palmitic acid) and unsaturated (oleic, linoleic and arachidonic acid) free fatty acids as well as diacylglycerols containing prelabeled fatty acids were released from the cells prior to the loss of plasma membrane integrity. The capacity of the cells to reincorporate free fatty acid into membrane phospholipids decreased in parallel with the loss of intracellular ATP, indicating the failure of the acyltransferase pathway. The addition of the phospholipase A2 inhibitors manoalide, mepacrine, or U-26384, or the phospholipase C inhibitor U-73122, reduced the severity of cell injury, but did not maintain cell viability. The addition of a battery of protease inhibitors with or without the phospholipase inhibitors had no protective effect. These results suggest that the activation of phospholipases A2 and C coupled with the loss of the reacylation process lead to the breakdown of membrane components during lethal cell injury.

Pituitary oncocytoma: three cases report

Three out of 102 pituitary adenoma patients, including 2 males and one female, had their pituitary tumors diagnosed as "oncocytomas" and underwent transsphenoidal adenomectomy. The tumors were confirmed as "pituitary oncocytomas" by both immunohistochemical staining and electron microscopy. They had poorly developed subcellular organelles and were markedly hyperplastic and pleomorphic, with swollen mitochondria in the cytoplasm and scattered secretory granules along the cell membranes. Postoperative follow-up revealed that visual acuity gradually improved in all the patients, and no tumor recurrence was found. The accurate preoperative diagnosis of pituitary oncocytomas relies on endocrinological, neuroradiological clinical evaluation, and the management of this disease must be surgery with postoperative radiotherapy.

Functional properties of guinea pig eosinophil leukotriene B4 receptor

It is currently thought that pulmonary eosinophils play a proinflammatory role in bronchial asthma. Leukotriene B4 (LTB4) is being considered as an important mediator in regulating eosinophil function because of its potent activities in inducing leukocyte chemotaxis, chemokinesis, degranulation, and aggregation. Because the LTB4 receptor has not been characterized in eosinophils, we report in this study the presence of a functional high affinity receptor for LTB4 on guinea pig (GP) eosinophils. Scatchard analysis of saturation binding studies yielded a Kd of 1.4 +/- 0.2 nM (mean +/- SEM, n = 3) and a Bmax of 1.6 +/- 0.4 pmol/mg of protein for LTB4 in GP eosinophil membranes. A linear Scatchard plot was obtained, suggesting that GP eosinophil membranes expressed only a single high affinity LTB4 receptor population. Saturation binding studies in whole cells also yielded a linear Scatchard plot, with a Kd of 2.8 +/- 0.96 nM (mean +/- SEM, n = 4) and a Bmax of 4 x 10(4) +/- 6 x 10(3) receptors/cell. Competitive binding studies using several compounds with structures similar to that of LTB4 showed that these agents bound to the receptor in the following descending order of affinity (Ki, nM): LTB4 (0.96) less than TB3 (1.0) greater than 20-hydroxy-LTB4 (3.5) greater than 12(R)-hydroxy-5,8,14-cis,10-trans-eicosatetraenoic acid (20) greater than 12(S)-hydroxy-5,8,14-cis,10-trans-eicosatetraenoic acid (231) greater than 20-carboxy-LTB4 (350) greater than 5(S),12(S)-dihydroxy-6,10-trans,8,14-cis-eicosatetraenoic acid (541). This rank order of potency in binding affinity correlates closely with the ability of these compounds to induce both chemotaxis and superoxide anion generation. Analysis of the structure-activity relationship suggests that the 12R-hydroxyl group and a cis double bond at the C-6 position are important for optimal agonist binding to the LTB4 receptor present in GP eosinophil membranes. The results suggest that LTB4 may be an important chemoattractant for eosinophils in GP and may induce the release of reactive oxygen species from this cell.

Functional properties of guinea pig eosinophil leukotriene B4 receptor

It is currently thought that pulmonary eosinophils play a proinflammatory role in bronchial asthma. Leukotriene B4 (LTB4) is being considered as an important mediator in regulating eosinophil function because of its potent activities in inducing leukocyte chemotaxis, chemokinesis, degranulation, and aggregation. Because the LTB4 receptor has not been characterized in eosinophils, we report in this study the presence of a functional high affinity receptor for LTB4 on guinea pig (GP) eosinophils. Scatchard analysis of saturation binding studies yielded a Kd of 1.4 +/- 0.2 nM (mean +/- SEM, n = 3) and a Bmax of 1.6 +/- 0.4 pmol/mg of protein for LTB4 in GP eosinophil membranes. A linear Scatchard plot was obtained, suggesting that GP eosinophil membranes expressed only a single high affinity LTB4 receptor population. Saturation binding studies in whole cells also yielded a linear Scatchard plot, with a Kd of 2.8 +/- 0.96 nM (mean +/- SEM, n = 4) and a Bmax of 4 x 10(4) +/- 6 x 10(3) receptors/cell. Competitive binding studies using several compounds with structures similar to that of LTB4 showed that these agents bound to the receptor in the following descending order of affinity (Ki, nM): LTB4 (0.96) less than TB3 (1.0) greater than 20-hydroxy-LTB4 (3.5) greater than 12(R)-hydroxy-5,8,14-cis,10-trans-eicosatetraenoic acid (20) greater than 12(S)-hydroxy-5,8,14-cis,10-trans-eicosatetraenoic acid (231) greater than 20-carboxy-LTB4 (350) greater than 5(S),12(S)-dihydroxy-6,10-trans,8,14-cis-eicosatetraenoic acid (541). This rank order of potency in binding affinity correlates closely with the ability of these compounds to induce both chemotaxis and superoxide anion generation. Analysis of the structure-activity relationship suggests that the 12R-hydroxyl group and a cis double bond at the C-6 position are important for optimal agonist binding to the LTB4 receptor present in GP eosinophil membranes. The results suggest that LTB4 may be an important chemoattractant for eosinophils in GP and may induce the release of reactive oxygen species from this cell.

Biological activity of leukotriene B4 analogs: inhibition of guinea pig eosinophil migration in vitro by the 2,6-disubstituted pyridine analogs U-75,302 and U-75,485

A "late phase" antigen-induced bronchoalveolar eosinophilia has been demonstrated in ovalbumin sensitized guinea pigs (1,2). This in vivo response to antigen inhalation can be inhibited by a 2,6-disubstituted pyridine analog of LTB4, U-75,302(2) (3). In the present study, the mechanism of the drug action was studied by assessing the activity of U-75,302 and a second analog, U-75,485 to displace [3H]-leukotriene B4 binding at the guinea pig eosinophil membrane, as well as their action as chemoattractants or inhibitors of the directional migration of guinea pig eosinophils in vitro. Radioligand competition experiments demonstrated that both analogs interacted strongly with the high affinity LTB4 binding sites on guinea pig eosinophil membrane. Both analogs are powerful chemoattractants for guinea pig eosinophils since they induced directional migration of guinea pig eosinophils when administered alone. In addition, when the cells were treated with either analog and their chemotaxis response was measured in response to a natural chemoattractant, both U-75,302 and U-75,485 at concentrations of 0.1 to 100 microM dose dependently inhibited the LTB4 induced chemotaxis response. The EC50s obtained for U-75,302 and U-75,485 as inhibitors of LTB4 induced guinea pig eosinophil chemotaxis were estimated to be 11.5 +/- 5.5 microM and 5.4 +/- 2.5 microM respectively. Under the same conditions, they had no significant effect upon eosinophil migration induced by zymosan activated plasma at concentrations below 100 microM. We suggest that the inhibition of antigen-induced eosinophil infiltration in guinea pig airway in vivo by U-75,302 or U-75,485 may be a result of partial antagonism or desensitization at the LTB4 receptor level of guinea pig eosinophils.

Biochemical and functional differences between eosinophils from animal species and man

Eosinophils were isolated from peritoneal lavages of repeated horse serum-injected guinea pigs or rhesus monkeys and from peripheral blood of normal human donors. Eicosanoid metabolism and chemotaxis by these cells were studied by in vitro techniques. Upon calcium ionophore stimulation guinea pig eosinophils released thromboxane B2 (TXB2) and leukotriene B4 (LTB4) while monkey and human cells produced LTC4, LTB4, and 5-HETE. Guinea pig cells do not synthesize sulfidopeptide LTs, because they lack the specific LTA4 glutathione S-transferase. Guinea pig eosinophils exhibit maximal chemotactic responses to LTB4, zymosan activated plasma, and human recombinant C5a, while producing only a negligible response to platelet activating factor (PAF). Monkey and human cells responded maximally to PAF, but exhibit only a weak response to LTB4. These results suggest that the guinea pig eosinophils differ from monkey and human eosinophils in both the synthetic capacity and functional chemotaxis responses to lipid mediators.

Contribution of leukotriene B4 to airway inflammation and the effect of antagonists

Inhalation of aerosols of ovalbumin in sensitized guinea pigs produced a marked, bronchoalveolar eosinophilia 24 hr after challenge. The lung eosinophilia was not prevented by the cyclooxygenase inhibitors, indomethacin or PAF antagonists (WEB-2086 and L-652731) but was inhibited by methylprednisolone, the 5-LO inhibitor, U-66858 and a series of structural analogs of LTB4, U-75302, U-77692, U-75485 and U-78489. The effectiveness of LTB4 antagonists but not PAF antagonists in vivo was consistent with in vitro studies in which LTB4 was shown to be far more chemotactic than PAF for guinea pig eosinophils. LTB4 elicited maximal directional migration of guinea pig eosinophils at concentrations from 10(-7) M to 10(-9) M while PAF showed no effect over the same concentration range. The structural analogs of LTB4 were shown to inhibit LTB4 induced chemotaxis of guinea pig eosinophils and produced a dose-related inhibition of binding of LTB4 to guinea pig eosinophil membranes. To add further proof to the hypothesis that LTB4 contributed to the antigen-induced lung eosinophilia we attempted to measure LTB4 release into BAL fluid immediately after and at various time points up to 24 hr after antigen inhalation. However, using a sensitive radioimmunoassay (detection limit 10 pg/ml) very low levels of LTB4 (24.9-67.9 pg/ml) or its metabolite, 20-OH LTB4 (24.9-98.2 pg/ml) were detected in BAL fluid and these levels did not increase significantly following antigen provocation. Inhalation of LTB4 aerosols in unsensitized Brown-Norway rats or inhalation of aerosols of ovalbumin in sensitized Brown-Norway rats also produced a marked "late-phase" eosinophil-rich influx of inflammatory cells into the lungs. The lung eosinophilia in the rat was prevented by two structurally unrelated leukotriene B4 (LTB4) antagonists, U-75302 and Ly255283. These data implicate LTB4 as a mediator of allergen-induced bronchopulmonary eosinophilia. Leukotriene B4 antagonists may provide leads for the development of compounds which inhibit the chronic airway inflammation associated with asthma in man.

Purification, cloning, expression and biological characterization of an interleukin-1 receptor antagonist protein

A human myelomonocytic cell line, U937, produced an interleukin-1 (IL-1) receptor antagonist protein (IRAP) which was purified and partially sequenced. A complementary DNA coding for IRAP was cloned and sequenced. The mature translation product of the cDNA has been expressed in Escherichia coli and was an active competitive inhibitor of the binding of IL-1 to the T-cell/fibroblast form of the IL-1 receptor. Recombinant IRAP specifically inhibited IL-1 bioactivity on T cells and endothelial cells in vitro and was a potent inhibitor of IL-1 induced corticosterone production in vivo.

Arachidonic acid metabolism in guinea pig eosinophils: synthesis of thromboxane B2 and leukotriene B4 in response to soluble or particulate activators

The arachidonic acid metabolism of guinea pig eosinophils isolated from either peritoneal cavity or bronchoalveolar lavages was studied by reverse-phase high-performance liquid chromatography. The purified eosinophils (95-100%) from either source released thromboxane B2 (TxB2), luekotriene B4 (LTB4) and 5-hydroxy eicosatetraenoic acid (5-HETE) following calcium ionophore A23187 stimulation. Quantification by radioimmunoassay indicated that maximal mediator output from the stimulated peritoneal cells was reached at 3 min after stimulation. The increase in production of TxB2 and LTB4 was correlated to increasing calcium ionophore A23187 concentration up to 1.0 micrograms/ml. In addition to calcium ionophore, the guinea pig peritoneal cells were also activated by f-met-leu-phe, phorbol 12-myristate, 13-acetate (PMA), and to lesser extent platelet-activating factor (PAF) to produce TxB2. LTB4 synthesis was stimulated by calcium ionophore, by f-met-leu-phe, as well as by unopsonized glucan, a particulate phagocytotic stimulus. The guinea pig eosinophils do not synthesize sulfidopeptide leukotrienes because of the absence of the specific LTA4 glutathione S-transferase. These results suggest that the guinea pig eosinophils differ from the human circulating eosinophils in the synthetic capacity of lipid mediators derived from arachidonic acid metabolism. This difference may be important in the understanding of the role of the eosinophils in inflammatory reactions such as that which occurs in the bronchial tissues of asthmatics.

Binding of leukotriene C4 by glutathione transferase: a reassessment of biochemical and functional criteria for leukotriene receptors

Studies of the molecular structures and biological activities of leukotrienes (LTs) provided evidence for the presence of multiple, subclass-specific receptors on the surface of responding tissues. Distinct receptors for LTC4 and LTD4 have been defined based on functional and metabolic criteria. However, radioligand-binding studies of LTC4-binding sites revealed anomalous results that failed to demonstrate a parallel relationship between binding affinity and functional activity for a number of agonists. In this study, we identified a high-affinity binding unit for LTC4 as the Ya subunit containing glutathione transferases (EC 2.5.1.18) that is present in both the cytosolic and the membrane fractions of rat liver homogenate. This enzyme accounted for a substantial portion of the LTC4-binding activity in rat liver cytosol as well as in mitochondrial and microsomal fractions. We suggest that the LTC4-binding sites in tissues are heterogeneous and that some binding units may have functions other than transduction of a signal across the cell membrane.

Identification of a high affinity leukotriene C4-binding protein in rat liver cytosol as glutathione S-transferase

A soluble high affinity binding unit for leukotriene (LT) C4 in the high speed supernatant of rat liver homogenate was characterized at 4 degrees C as having a single type of saturable affinity site with a dissociation constant of 0.77 +/- 0.27 nM (mean +/- S.E., n = 5). The binding activity was identified as the liver cytosolic subunit 1 (Ya) of glutathione S-transferase, commonly known as ligandin, by co-purification with the catalytic activity during DEAE-cellulose column chromatography and 11,12,14,15-tetrahydro-LTC4 (LTC2)-affinity gel column chromatography; resolution into two major bands by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of Mr 23,000 and 25,000, of which only the smaller protein was labeled with [3H]LTC4 coupled via a photoaffinity cross-linking reagent; and immunodiffusion analysis with rabbit antiserum to glutathione S-transferase which showed a line of identity between the purified LTC4-binding protein and rat liver glutathione S-transferase. The affinity-purified binding protein bound 800 pmol of [3H] LTC4/mg of protein and possessed 12 mumol/min/mg of glutathione transferase activity as assayed with 1-chloro-2,4-dinitrobenzene as substrate. The enzyme activity of the cytosolic LTC4-binding protein was inhibited by submicromolar quantities of unlabeled LTC4, and the binding activity for [3H]LTC4 was blocked by the ligandin substrates, hematin and bilirubin. The high affinity interaction between LTC4 and glutathione S-transferase suggests that glutathione S-transferase may have a role in LTC4 disposition and that previous studies of LTC4 binding to putative receptors in nonresponsive tissues may require redefinition of the binding unit.

Production of prostaglandin D2 by murine macrophage cell lines

Several tumor-derived murine macrophage cell lines were evaluated in vitro as cloned prototypes of tissue macrophages for their ability to metabolize arachidonic acid. Unexpectedly, two cell lines, J774A.1 and WR19M.1, rapidly converted exogenous 14C-arachidonic acid (AA) to a single major prostaglandin metabolite. The compound, PGD2, was positively identified by TLC, HPLC, and GC-MS. The enzymatic formation of the PGD2 was shown by inhibition of its formation by indomethacin and reduced formation of 14C-PGD2 from 14C-PGH2 in boiled cells. When J774A.1 cells were prelabeled with 3H-AA, cultured for 24 hours, and stimulated with lipopolysaccharide (LPS), PGD2 was again the predominant product. No other tumor derived cell lines, including several other murine macrophage lines, produced significant amounts of PGD2. Elicited and activated murine peritoneal macrophages produced only small amounts of PGD2, but resident peritoneal macrophages produced modest amounts of PGD2. Exaggerated formation of PGD2 by J774A.1 and WR19M.1 cells may be a consequence of neoplastic transformation or the clonal expansion of a minor subpopulation of normal tissue macrophages.

Disappearance and metabolism of leukotriene B4 during carrageenan-induced pleurisy

Leukotriene B4 (LTB4) has been implicated as a mediator in the inflammatory process by virtue of its potent chemotactic activity. At present, very little is known of the stability of this compound in vivo; therefore, the present study was designed to determine the half-life and metabolic fate of radiolabeled LTB4 during a 2-hr intrapleural incubation in rats with acute carrageenan pleurisy. After injection of 0.2 ml of 1% sodium carrageenan (Viscarin), inflammation was allowed to develop for 4 hr. A small polyethylene cannula was then inserted into the chest, and 0.1 microCi of [14C]LTB4 was injected into the chest. Samples for radioactivity determination were taken at 0, 1, 2, 3, 4, 5, 7, 10, 15, 20, 30, 45, 60, 90 and 120 min via the cannula, and at 120 min the entire content of the chest was collected. The half-life for the disappearance of radioactivity from the chest was 45.8 +/- 3.5 min. The 120-min samples were treated with acetone to precipitate protein and extracted with Sep-Paks. The extracts were analyzed by reversed phase high performance liquid chromatography using an ultraviolet detector set at 269 nm and a radioactivity detector. An additional experiment was run using multi-[3H]LTB4, and the only major metabolites detected were omega-hydroxylated compounds. It can be concluded from these results that LTB4 is relatively stable in vivo and could be present for long enough at the inflammatory site to have an influence upon inflammatory cell migration.

Epoxidation of prostacyclin in the rabbit kidney

In the isolated Tyrode's perfused rabbit kidney, metabolism of [9-3H]prostacyclin was examined. In addition to 7,9-dihydroxy-4,13-diketo-dinor-prostanoic acid, dinor-6-keto-prostaglandin F1 alpha, and pentanorprostaglandin (PG)F1 alpha gamma-lactone, a new, previously unreported, metabolite was isolated and identified by radio-gas chromatography and gas chromatography-mass spectrometry as 5-hydroxy-6-keto-PGF1 alpha. The structure of this metabolite was further confirmed by comparison of the mass spectra to that of the synthetic standard. The formation of 5-hydroxy-6-keto-PGF1 alpha in the kidney suggested epoxidation of prostacyclin via the renal epoxygenase pathway.

The biosynthesis of leukotriene B4, the predominant lipoxygenase product in rabbit alveolar macrophages, is enhanced during immune activation

Rabbit alveolar macrophages synthesize prostaglandins in response to various stimuli. We have previously shown that prostaglandin production was decreased in immunologically activated (live Bacillus Calmette-Guérin (BCG)-injected) animals. (Hsueh, W., Lamb, R. and Gonzalez-Crussi, F. (1982) Biochim. Biophys. Acta 710, 406-414). In the present study, we examined the lipoxygenase products of alveolar macrophages from normal and immunologically activated rabbits injected intravenously with live BCG or complete Freund's adjuvant. We found: unstimulated lung macrophages produced no detectable leukotrienes; the predominant lipoxygenase product upon stimulation was leukotriene B4; alveolar macrophages did not significantly degrade leukotriene B4 into its 20-hydroxy derivative, and the total degradation of leukotriene B4 during 90 min of incubation was minimal; the production of leukotriene B4 reached the peak at 30 min after A23187 stimulation, while zymosan caused a much slower and smaller release; following stimulation, immunologically activated lung macrophages produced more leukotriene B4 than resident macrophages. It is possible that the increased leukotriene B4 production in immunologically activated lung macrophages was related to the immunoregulatory function of this substance, such as enhancing cytotoxicity, interferon production and proliferation of suppressor-cytotoxic T cells.

15-Hydroxyeicosatetraenoic acid is a potent inflammatory mediator and agonist of canine tracheal mucus secretion

It was shown that 15-hydroxyeicosatetraenoic acid (15-HETE) but not 15-H(P)ETE or 5-HETE is a potent agonist for secretion of glycoprotein-containing mucus from the in vivo canine trachea. Given by aerosol into the lungs or by intra-arterial injection into the trachea, 15 HETE also caused the chemotaxis of inflammatory cells into the lumen of the airways. Accompanying this inflammatory cell infiltrate was an increase (183%, p less than 0.05) of expiration of fluid in the partially saturated air coming from the lung. The levels of 15-HETE extracted from tracheal mucus correlated well with hillocks and weight of secreted mucus found in the mucus after hypoxia or after arachidonic acid loading. Indomethacin and atropine blocked the mucus secretagogue effect of 15-HETE in the trachea. Indomethacin and U-52, 412 (a 15-lipoxygenase inhibitor) pretreatment abolished a portion of the 15-HETE-induced enhancement of mucus weight and 15-HETE level in the secretion.

Oxidation of prostacyclin and its analogs by three 15-hydroxyprostaglandin dehydrogenases

A study of the oxidation of prostacyclin and some of its analogs by three 15-hydroxyprostaglandin dehydrogenases was undertaken to determine the structural features of these compounds which might influence their rate of enzymatic inactivation. The effect of some structural changes seemed to be determined by the substrate specificity of individual enzymes. Other changes influenced the rate of oxidation by all three enzymes similarily. Among this latter group it was noted that a 15S hydroxyl group is necessary for oxidation to occur and that steric changes in the carboxy side chain and structural changes in the epoxy ring have a greater effect on the affinity of the substrate for the enzyme than on its maximum rate of oxidation. Certain analogs of prostacyclin are not substrates for one or more of the enzymes tested. Of these, (5S)-9-deoxy-5,9 alpha-epoxy-PGF1 and its methyl ester are potent inhibitors of only the placental enzyme---an interesting case of apparent selective metabolic regulation.

Metabolism of arachidonic acid by human neutrophils. Characterization of the enzymatic reactions that lead to the synthesis of leukotriene B4

Human neutrophils stimulated with calcium ionophore A23187 synthesized 5-hydroxyeicosatetraenoic acid (5-HETE) and leukotriene B4. Time-course studies showed that the concentrations of both products reached a maximum after 2 min after which the products were rapidly removed. In longer incubations, 5-HETE was esterified into membrane lipids, and leukotriene B4 was converted to 20- hydroxyleukotriene B4 and/or 20- carboxyleukotriene B4. The reaction is apparently self-limiting. After the maximum was reached, addition of fresh ionophore, Ca2+ or oxygen had little effect. Fresh arachidonic acid increases the yields of 5-HETE and delta 6-trans-leukotriene B4 but not additional leukotriene B4. Only the addition of fresh neutrophils gave additional leukotriene B4. This finding suggests that leukotriene B4 synthesis is limited by both substrate availability and enzyme inhibition by hydroperoxide intermediate. Exogenous arachidonic acid added with ionophore had different effects on the syntheses of leukotriene B4, delta 6-trans-leukotriene B4, and 5-HETE. As the arachidonic acid concentration increases, product formation increases in the following order: 5-HETE greater than delta 6-trans-leukotriene B4 greater than leukotriene B4. At a high concentration (more than 10 microM) of arachidonic acid, the synthesis of delta 6-trans-leukotriene B4 was greater than leukotriene B4 itself. Since delta 6-trans-leukotriene B4 represents the nonenzymatic decomposition of leukotriene A4, we suggest that one of the rate-limiting steps in the synthesis of leukotriene B4 is the leukotriene A4 hydrolase. Our data suggest the synthesis of leukotriene B4 is under the control of three factors: (1) substrate availability; (2) limited capacity of the leukotriene A4 hydrolase, and (3) enzyme inactivators generated during the reaction, such as hydroperoxide intermediate. The tightly controlled system assures only a finite amount of this powerful bioactive substance will be produced under most conditions.