[Introduction to Guidelines for public health protection against high temperature and heatwaves].

In recent years, the high temperature and heatwaves have seriously affected the health of Chinese residents, and there is an important need for public health protection guidelines for high temperature and heatwaves in China. The National Bureau of Disease Control and Prevention has organized experts to fully investigate the evidence from epidemiological research on the health of populations in high temperature and heatwaves globally and in China, analyze the health hazards and protection needs of different populations, and put forward practical and effective individual protection measures and health recommendations. For this reason, the "Guideline for Public Health Protection against High Temperature and Heatwaves" (referred to as the "Guideline") was officially issued in June 2023. This article interprets the background and significance of the Guideline, the principles of compilation, the main considerations, the main contents, the implementations and promotions and other aspects, to improve the understanding of the content of the Guideline and strengthen the publicity and implementations.

Stochastic simulation of hydrogen-oxygen auto-ignition at the microscale.

A hybrid stochastic simulation method is developed to study H2-O2 auto-ignition at the microscale. Simulation results show that the discrete and stochastic characteristics of reaction collisions have notable impacts on the ignition process, particularly in the early stages when only a few radicals exist. The statistical properties of ignition delay time, which reflect the accumulated stochasticity during ignition, are obtained and analyzed for different initial temperatures and total molecular numbers. It is found that the average and standard deviation of ignition delay time increase as the total molecular number decreases, with this phenomenon being particularly pronounced near the crossover temperature. When the total molecular number is sufficiently small, the chain initiation reaction becomes crucial to the stochastic properties, as its average firing time exhibits an inverse proportionality to the total molecular number. As the total molecular number increases, the influence of other chain reactions intensifies, causing the power law relation between standard deviation and total molecular number to shift from -1 power to -0.5 power. Owing to different chain reaction paths for high- and low-temperature auto-ignition, the strongest relative fluctuation occurs near the crossover temperature. A theoretical equation for the standard deviation of ignition delay time is obtained based on dimensional analysis, giving excellent agreement with the simulation results in both high- and low-temperature modes.

[Study on formulation of standard limits for trichloroethylene and tetrachloroethylene in "Standards for indoor air quality（GB/T 18883-2022）" in China].

There are clear indoor air pollution sources of trichloroethylene and tetrachloroethylene. A large number of epidemiological evidence has confirmed their carcinogenic toxicity and non-carcinogenic toxicity. Several countries and international organizations have paid attention to indoor air trichloroethylene and tetrachloroethylene. It has been also assessed that there should be certain potential health risk of indoor air trichloroethylene and tetrachloroethylene in China. Based on the latest research results of health risk assessment of indoor air trichloroethylene and tetrachloroethylene, the "Standards for indoor air quality (GB/T 18883-2022)" added trichloroethylene and tetrachloroethylene as indicators. The index limit of trichloroethylene is 6 µg/m3 for an 8-hour average concentration. The index limit of tetrachloroethylene is 120 µg/m3 for an 8-hour average concentration. The technical contents related to the determination of the standard limits of trichloroethylene and tetrachloroethylene in indoor air were analyzed and discussed, including the sources, the exposure, the health effects, the determination of the limit values, and the recommendations for standard implementation. It also proposed recommendations for the implementation of"Standards for indoor air quality (GB/T 18883-2022)".

[The North-South difference of the relationship between cold spells and mortality risk of cardiovascular diseases in China].

Objective: To analyze the North-South difference of the relationship between cold spells and mortality risk of cardiovascular diseases in China. Methods: The time series analysis method was used to collect the daily counts of cardiovascular mortality data, meteorological data and PM2.5 concentration in the cold season (November to March of the following year) from January 1, 2013 to December 31, 2018 in 280 districts and counties in China. The non-constrained distributed lag linear model was used to analyze the relationship between cold spells and mortality risk of cardiovascular diseases and its North-South difference in China. Results: From 2013 to 2018, the mean of daily average temperature of the cold season in 280 districts and counties was 5.4 ℃. The mean of daily average relative humidity was 64.4%, and the mean of daily average PM2.5 concentration was 73.7 µg/m3. The average cold spell days in each county was 11.7 days per year,the mean of daily average temperature on cold spell days was (-2.4±6.7) ℃, and M (Q1, Q3) was -1.5 (-5.1, 1.1) ℃. The average of daily number of cardiovascular disease deaths in each county/district was (6±5) cases, and M (Q1, Q3) was 5 (2, 8) cases. The percentage change (95%CI) in the South was 4.94% (3.69%, 6.20%) (lag 0 d), higher than that in the North [the percentage change (95%CI) was 1.49% (1.14%-1.84%) (lag 0-7 d)]. In the North, the mortality risk of ≥75 years old was relatively low among three age groups, with a percentage change (95%CI) about 1.63% (1.33%-1.93%) (lag 0-21 d). In the South, the mortality risk of ≥ 75 years old was relatively high among three age groups, with a percentage change (95%CI) about 5.18% (3.78%-6.59%) (lag 0 d). Conclusion: The mortality risk of cardiovascular diseases caused by cold spells in the South is higher than that in the North of China, and the risk peak occurs earlier in the South.

[Associations between personal fine particulate matter and blood lipid profiles: A panel study in Chinese people aged 60-69 years].

Objective: To explore the association between short-term exposures to fine particulate matter (PM2.5) on blood lipids in the elderly. Methods: In this panel study, five repeated measurements were performed on 76 people aged 60-69 in Jinan city. Each participant had a PM2.5 monitor for 72 hours before each health examination, including a questionnaire survey, physical examination, and biological sample collection. Serum triglycerides (TG), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), and low-density lipoprotein cholesterol (LDL-C) were examined, and non-HDL-C concentrations were calculated by subtracting HDL-C from TC. The generalized linear mixed-effects model was used to quantify the association of personal PM2.5 exposure at different lag with blood lipids and dyslipidemia. Results: The age of 70 participants was (65.0±2.8) years, of which 48.6% (34/70) were males. The BMI of participants was (25.0±2.5) kg/m2. Their TC, TG, LDL-C, HDL-C, and non-HDL-C concentrations were (5.75±1.32), (1.55±0.53), (3.27±0.94), (1.78±0.52), and (3.97±1.06) mmol/L, respectively. Generalized linear mixed-effects model showed that after adjusting for confounding factors, at lag 72 hours, each 10 µg/m3 increase in PM2.5 was associated with the percentage change in TC, LDL-C, HDL-C and non-HDL-C about 1.77% (95%CI: 1.22%-2.32%), 1.90% (95%CI: 1.18%-2.63%), 1.99% (95%CI: 1.37%-2.60%) and 1.74% (95%CI: 1.11%-2.37%), and the OR values (95%CI) of hypercholesterolemia, hypertriglyceridemia and hyperbetalipoproteinemia were 1.11 (1.01-1.22), 1.33 (1.03-1.71) and 1.15 (1.01-1.31), respectively. Conclusion: There is a significant association of short-term PM2.5 exposure with the concentration of blood lipids and the risk of dyslipidemia in the elderly.

[Evaluation of the fresh air purification system in the classroom under heavy pollution weather].

Evaluate the effect of the fresh air purification system on the improvement of indoor PM2.5 levels in a primary school classroom in Jinan City, Shandong Province. Our purpose is to explore the optimal operating time of the fresh air system and the main factors that affect the fresh air purification system to improve indoor air quality. From December 9, 2019 to December 10, 2019, two classrooms of the same area on the third floor of a primary school building in Jinan City, Shandong Province were selected as monitoring points. During the operation of the fresh air purification system, the PM2.5 concentration in the classroom is reduced by an average of 48.1%-61.5% compared to the outdoor PM2.5 concentration. After running for about 2 hours, the indoor PM2.5 concentration decreased to a relatively stable concentration level. The operating time of the fresh air purification system, student activities between classes, indoor temperature, indoor relative humidity, and outdoor PM2.5 concentration are important factors that affect the indoor particulate removal rate. In the case of a certain amount of fresh air and indoor area, closing doors and windows and appropriately extending the operation time of the fresh air purification system can improve the air quality in the classroom to a certain extent and protect the health of students.

[The impact of persistent high ambient fine particulate matters exposures on mortality in the 40 districts/counties of China, 2013-2015].

Objective: To investigate the impact of persistent high ambient fine particulate matters (PM(2.5)) exposures on mortality in the polluted areas of 40 districts/counties in China. Methods: Using a convenient sampling method, we selected 40 districts/counties as research sites from the Beijing-Tianjin-Hebei Metropolitan Region, the Yangtze River Delta, the Pearl River Delta, and Heilongjiang, Shanxi, and Sichuan province. The daily concentrations of PM(2.5), meteorological data and population death data from January 1, 2013 to December 31, 2015 were collected. The six persistent PM(2).5 pollution episode scenarios were defined by the average daily concentration of PM(2.5) (75 µg/m(3), P(75) and P(90) of the average daily concentration of each district/county respectively) and the duration (≥2 days or 3 days). Generalized linear models and meta analyses were used to explore the impact of PM(2.5) pollution episodes on mortality in 40 districts/counties. Results: The mean±SD and P(50) (P(25), P(75)) of average daily temperature, relative humidity and PM(2.5) were (15.26±10.48) ℃, 17.20 (7.50, 23.70) ℃, (67.31±19.26)%, 72.00% (57.00%, 81.00%), (72.81±60.93) µg/m(3) and 55.38 (33.77, 91.45) µg/m(3), respectively in 40 districts/counties during 2013-2015. The average number of non-accidental, cardiovascular and cerebrovascular diseases deaths per day were (12±7), (5±4) and (2±2) in each district/county, respectively. When the daily concentrations of PM(2.5) were ≥75 µg/m(3) (≥2 days), ≥P(75) (≥2 days), ≥P(90) (≥2 days), ≥75 µg/m(3) (≥3 days), and ≥P(75) (≥3 days), the excess risk (95%CI) of the total non-accidental deaths and cardiovascular diseases deaths were 1.77% (0.89%,2.66%), 2.69% (1.06%,4.35%), 1.67% (0.59%,2.76%), 2.31% (0.67%, 3.97%), 0.71% (-0.75%, 2.20%), 1.95% (0.08%, 3.86%), 1.15% (0.12%, 2.18%), 1.85% (0.25%, 3.47%), 1.39% (0.15%, 2.64%), 2.29% (0.39%, 4.23%), respectively. Conclusion: Persistently high PM(2.5) exposures were associated with total non-accidental deaths and cardiovascular disease deaths.

[Estimating and projecting the acute effect of cold spells on excess mortality under climate change in Guangzhou].

Objective: To estimate future excess mortality attributable to cold spells in Guangzhou, China. Methods: We collected the mortality data and metrological data from 2009-2013 of Guangzhou to calculated the association between cold spell days and non-accidental mortality with GLM model. Then we projected future daily average temperatures (2020-2039 (2020s) , 2050-2069 (2050s) , 2080-2099 (2080s) ) with 5 GCMs models and 2 RCPs (RCP4.5 and RCP8.5) to identify cold spell days. The baseline period was the 1980s (1980-1999). Finally, calculated the yearly cold spells related excess death of 1980s, 2020s, 2050s, and 2080s with average daily death count of non-cold spell days, exposure-response relationship, and yearly number of cold spell days. Results: The average of daily non-accidental mortality in Guangzhou from 2009 to 2013 was 96, and the average of daily average was 22.0 ℃. Cold spell days were associated with 3.3% (95%CI: 0.4%-6.2%) increase in non-accidental mortality. In 1980s, yearly cold spells related deaths were 34 (95%CI: 4-64). In 2020s, the number will increase by 0-10; in 2050s, the number will increase by 1-9; and in 2080s, will increase by 1-9 under the RCP4.5 scenario. In 2020s, the number will increase by 0-9; in 2050s, the number will increase by 1-6; and in 2080s, will increase by 0-11 under the RCP8.5 scenario. Conclusion: The cold spells related non-accidental deaths in Guangzhou will increase in future under climate change.

[Related factors analysis for lymph node metastasis in papillary thyroid carcinoma: a series of 2 073 patients].

Objective: To investigate the related factors for lymph node metastasis (LNM), especially for high volume LNM (>5 metastatic lymph nodes) in papillary thyroid carcinoma (PTC). Methods: The medical records of 2 073 consecutive PTC patients who underwent lobectomy, near-total thyroidectomy or total thyroidectomy with ipsilateral or bilateral central lymph node dissection in Department of General Surgery, Peking Union Medical College Hospital from November 2013 to October 2014 were reviewed. Clinical and pathological features were collected. Univariate and multivariate analysis were performed to identify the related factors for LNM/high volume LNM. Results: In all 2 073 patients, LNM and high volume LNM were confirmed in 936 (45.15%) cases and 254 (12.25%) cases respectively. In univariate analysis, large tumor size, young patients (<40 years), male were associated with both LNM and high volume LNM. In multivariate analysis, tumor size >2.0 cm, young patients (<40 years), male were independent related factors of LNM (OR=5.262, 95% CI: 3.468 to 7.986; OR=2.447, 95% CI: 2.000 to 2.995; OR=1.988, 95% CI: 1.593 to 2.480, respectively, all P=0.000) and high volume LNM (OR=6.687, 95% CI: 4.477 to 9.986; OR=2.975, 95% CI: 2.224 to 3.980; OR=2.354, 95% CI: 1.737 to 3.191, respectively, all P=0.000). In 1 414 PTMC patients, a similar result was also demonstrated.Compared with young patients (<40 years), old patients (≥60 years) had lower incidence of LNM (25.47% vs. 52.24%, χ(2)=62.903, P=0.000) and high volume LNM (1.89% vs. 13.18%, χ(2)=37.341, P=0.000). Additionally, old patients also had lower risk of both LNM (OR=0.316, 95% CI: 0.194 to 0.517, P=0.000) and high volume LNM (OR=0.142, 95% CI: 0.034 to 0.599, P=0.000). Conclusions: The tumor size was the main related factor for both LNM and high volume LNM in PTC. The treatment should be more active in patients with tumor size >2 cm with consideration of higher incidence and risk for LNM and high volume LNM. Young patient was another important related factor for LNM and high volume LNM. In PTMC, old patients had lower incidence and risk for both LNM and high volume LNM. Dynamic observation or less surgical extent could be an option for these patients.

Association between the C804A polymorphism in the TGF-ß gene and the risk of myocardial infarction: a meta-analysis.

Tumor necrosis factor-ß (TNF-ß) is an important mediator of inflammation and may play a role in the pathogenesis of myocardial infarction (MI). While several published studies have investigated the association between the C804A polymorphism in the TNF-ß gene and MI risk, their results are controversial and ambiguous. In this study, we evaluated the contribution of the TNF-ß C804A polymorphism to MI risk. A literature search was conducted in the PubMed, Embase, Web of Science, Cochrane Library, and Google Scholar databases to identify eligible studies published before November 1, 2013. We performed a meta-analysis of 9 case-control studies, which included a total of 19,404 MI patients and 13,684 healthy controls. Overall analysis suggested that the TNF-ß C804A polymorphism was associated with a significantly increased risk of MI. Stratified analysis based on ethnicity revealed a significant association in Asian populations, but not in Caucasian populations. In conclusion, this meta-analysis revealed that the TNF-ß C804A polymorphism may be associated with an increased risk of MI only in Asian populations. However, additional studies should be conducted to further confirm the association between TNF-ß C804A and MI risk.

Genetic variation of Sargassum horneri populations detected by inter-simple sequence repeats.

The seaweed Sargassum horneri is an important brown alga in the marine environment, and it is an important raw material in the alginate industry. Unfortunately, the fixed resource that was originally reported is now reduced or disappeared, and increased floating populations have been reported in recent years. We sampled a floating population and 4 fixed cultivated populations of S. horneri along the coast of Zhejiang, China. Inter-simple sequence repeat (ISSR) markers were applied in this research to analyze the genetic variation between floating populations and fixed cultivated populations of S. horneri. In total, 220 loci were amplified with 23 ISSR primers. The percentage of polymorphic loci within each population ranged from 53.64 to 95.45%. The highest diversity was observed in population 3, which was the local species that was suspension cultured in the lab and then fixed cultivated in the Nanji Islands before sampling. The lowest diversity was obtained in the floating population 4. The genetic distances among the 5 S. horneri populations ranged from 0.0819 to 0.2889, and the distance tendency confirmed the genetic diversity. The results suggest that the floating population had the lowest genetic diversity and could not be joined into the cluster branch of the fixed cultivated populations.

Risk factors for oxaliplatin-induced peripheral neuropathy: a systematic review and meta-analysis.

OBJECTIVE: Oxaliplatin-induced neuropathy is a significant complication of cancer therapy. We aimed at investigating the risk factors of oxaliplatin-induced neuropathy (OIPN) and providing evidence to enhance its prevention. MATERIALS AND METHODS: PubMed, Medline, Web of Science, Embase, China Knowledge Resource Integrated Database, and the Wanfang Database were searched comprehensively for observational studies investigating the prevalence and risk factors of OIPN from inception to November 30, 2021. The Newcastle-Ottawa Scale was used by two independent reviewers to assess methodological quality. When applicable, we used meta-analysis to determine mean differences and odds ratios for continuous and nominal scaled data. RESULTS: We included 20 studies involving 10,900 participants for analysis. Factors associated with OIPN risk identified by meta-analysis were age, gender, diabetes, anemia, hypomagnesaemia, alcohol consumption, body mass index, body surface area, cumulative oxaliplatin dose and the number of chemotherapy cycles. Factors not associated with OIPN risk included smoking history and chemotherapy regimen. CONCLUSIONS: This meta-analysis identified multiple variables associated with OIPN. The recognition of modifiable risk factors is an urgent priority to improve prevention and treatment outcomes.

Differential gene expression profiles of normal human parotid and submandibular glands.

BACKGROUND: Parotid and submandibular glands have different properties including characteristics of the secreted saliva and tumor incidences. The differences in properties of parotid and submandibular glands are not clear from a genetic viewpoint. OBJECTIVE: To study differential gene expression profiles between normal human parotid and submandibular glands. MATERIALS AND METHODS: Three pairs of normal parotid and submandibular glands were obtained. RNA was extracted from these samples. After reverse transcription, the cDNA was in vitro-transcribed to produce biotin-labeled cRNA. The purified biotin-labeled cRNA samples were hybridized to microarray chips. RESULTS: Among the 54 675 tested transcripts, 47 transcripts were upregulated at least twofold in the parotid gland compared with the submandibular gland, including tumor-associated genes (pleiotrophin, WNT5A, ABCC1) and transport-associated genes (SLCO1A2, SLC13A5, KCNJ15). Ninety-eight transcripts were upregulated at least twofold in the submandibular gland compared with the parotid gland, including the chloride channel CFTR and mucin-associated genes that belong to the starch and sucrose metabolism pathway (GalNAc-T4, GalNAc-T7 and GalNAc-T13). Quantitative real-time reverse transcriptase-polymerase chain reaction (RT-PCR) analysis of nine differentially expressed genes confirmed the microarray results. CONCLUSION: This study revealed the different gene expression profiles of normal human parotid and submandibular glands, providing a genetic basis for their differing properties.

[Simulation study of air quality health index in 5 cities in China: 2013-2015].

Objective: To construct the air quality health index (AQHI) by inclusion of air pollutants PM(2.5) and O(3) in Guangzhou, Shanghai, Xi' an, Beijing, Shenyang, and explore scientificity and feasibility of its application in China. Methods: The daily average concentrations of PM(2.5) and O(3) in air, and daily average mortality from 2013 to 2015 in the 5 cities in China, the exposure-response coefficients of PM(2.5) and O(3) and total mortality from Meta studies in China were used to construct local AQHI. The health risk levels of air pollution in the 5 cities were calculated and compared with the characteristics of single pollutant concentrationof PM(2.5) or O(3). Results: In the 5 cities, the average concentration of PM(2.5) was highest in Beijing (82 µg/m(3)) and lowest in Guangzhou (46 µg/m(3)). And the average concentration of O(3) was highest in Shanghai (72 µg/m(3)) and lowest in Xi' an (45 µg/m(3)). In all the cities, the average concentration of PM(2.5) was highest in winter and lowest in summer. In summer, the average concentration of O(3) was lowest. But the health risk level of AQHI showed that the 5 cities had higher frequency of low or medium risk averagely. And Beijing had the highest frequency of high risk in summer (5.69%). Xi' an had the highest frequency of extremely high risk in winter (1.63%). Conclusions: In this study, AQHI could be constructed by using air PM(2.5) and O(3) concentration data which can be obtained in many areas in China. The application of this index is scientific and feasible in China.

Gene transfer into fetal baboon hematopoietic progenitor cells.

We studied hematopoietic progenitors from fetal baboon blood, marrow, and liver at four time points (125, 140, 160, and 175 days) during the third trimester (gestation approximately 180 days) to determine if fetal baboons might be an appropriate model for in utero gene therapy of hematopoietic stem cells (HSCs). Cells were studied for expression of CD34, CD33, CD38, and HLA-DR, for progenitor content in colony-forming cell assays, and for susceptibility of CD34+ progenitors to retrovirus-mediated gene transfer. Throughout the third trimester, the frequency of CD34+ progenitors in blood and marrow appears to remain unchanged at approximately 0.6 and 5.0%, respectively. In liver, progenitors progressively decrease to undetectable levels by day 175. The proportion of fetal baboon bone marrow and liver CD34+ cells expressing CD38 and HLA-DR appears to increase with increasing fetal age, similar to changes reported for human cord blood CD34+ cells. In fetal baboon blood the proportion of CD34+ cells expressing CD33 appears to decrease with increasing gestational age, also similar to changes reported for human cord blood cells. Progenitors from human cord blood and baboon fetal tissues were similarly susceptible to transduction by the gibbon ape leukemia pseudotyped retroviral vector LAPSN(PG13) containing the genes for human placental alkaline phosphatase (AP) and the bacterial neomycin phosphotransferase (neo). Fetal baboon and human hematopoietic progenitor cells undergo similar phenotypic changes during the third trimester of fetal development and are similarly susceptible to retrovirus-mediated gene transfer. The fetal baboon may be a model in which approaches to mobilization and gene transfer into fetal HSCs can be studied.

Platelet endothelial cell adhesion molecule-1 (PECAM-1) is a target glycoprotein in drug-induced thrombocytopenia.

Drug-induced immune thrombocytopenia (DITP) is a serious complication of drug treatment. Previous studies demonstrated that most drug-dependent antibodies (DDAbs) react with the platelet membrane glycoprotein (GP) complexes IIb/IIIa and Ib/IX/V. We analyzed the sera from 5 patients who presented with DITP after intake of carbimazole. Notably, thrombocytopenia induced by carbimazole was relatively mild in comparison to patients with DITP induced by quinidine. The sera reacted with platelets in an immunoassay on addition of the drug. In immunoprecipitation experiments with biotin-labeled platelets and endothelial cells, reactivity with the platelet endothelial cell adhesion molecule-1 (PECAM-1, CD31) could be demonstrated, whereas neither GPIIb/IIIa nor GPIb/IX was precipitated in the presence of the drug. These results could be confirmed by GP-specific immunoassay (MAIPA) using monoclonal antibodies (mabs) against PECAM-1. In addition, the binding of DDAbs could be abolished by preincubation with soluble recombinant PECAM-1. Carbimazole-dependent antibodies showed similar reactivity with platelets carrying the Leu(125) and Val(125) PECAM-1 isoforms, indicating that this polymorphic structure, which is located in the first extracellular domain, is not responsible for the epitope formation. Binding studies with biotin-labeled mutants of PECAM-1 and analysis of sera with mabs against different epitopes on PECAM-1 in MAIPA assay suggested that carbimazole-dependent antibodies prominently bound to the second immunoglobulin homology domain of the molecule. Analysis of 20 sera from patients with quinidine-induced thrombocytopenia by MAIPA assay revealed evidence that DDAbs against PECAM-1 are involved in addition to anti-GPIb/IX and anti-GPIIb/IIIa. We conclude that PECAM-1 is an important target GP in DITP. (Blood. 2000;96:1409-1414)

Individually distinct Ig homology domains in PECAM-1 regulate homophilic binding and modulate receptor affinity.

PECAM-1 (CD31) is a 130-kDa member of the immunoglobulin (Ig) gene superfamily that is constitutively expressed at high concentration at endothelial cell intercellular junctions and at moderate density on the surface of circulating leukocytes and platelets. Recent in vitro and in vivo studies have shown the PECAM-1 plays a central role in mediating the extravasation of leukocytes from the vessel wall in response to inflammatory mediators. To study the binding characteristics of PECAM-1, phospholipid vesicles were prepared and examined by flow cytometry and immunofluorescence microscopy for their ability to associate with each other and with cells. Proteoliposomes containing high concentrations of PECAM-1 interacted homophilically with each other, forming large self-aggregates. PECAM-1 proteoliposomes, as well as soluble bivalent PECAM-1 in the form of a PECAM-1/IgG immunoadhesin, associated homophilically with cells expressing human, but not murine, PECAM-1. This binding could be completely inhibited by monoclonal antibody Fab fragments specific for Ig homology Domain 1 or Domains 1 + 2. Binding studies using cells expressing human PECAM-1 deletion mutants and murine/human chimeras confirmed that both Ig Domains 1 and 2 were both necessary and sufficient for homophilic binding. In contrast, engagement of membrane-proximal Domain 6 with monoclonal antibody Fab fragments had the opposite effect and augmented the binding of PECAM-1 proteoliposomes to cells. Thus, PECAM-1, like certain integrins, appears to be capable of antibody-induced conformational changes that alter affinity for its ligand. Similar changes induced by physiologic stimuli could be important in regulating the function of PECAM-1 in vascular cells.

Cell surface glycosaminoglycans do not serve as ligands for PECAM-1. PECAM-1 is not a heparin-binding protein.

Previous studies have suggested that PECAM-1 mediates cellular interactions via both homophilic and heterophilic adhesive mechanisms. Cell surface glycoaminoglycans have been implicated as one of the heterophilic ligands for PECAM-1. To determine whether PECAM-1 is capable of interacting directly with glycosaminoglycans, we examined the adhesive properties of multiple monovalent and multivalent forms of this adhesion molecule. We found that the binding of a bivalent PECAM-1/IgG chimeric protein or multivalent PECAM-1-containing proteoliposomes to multiple different cell lines was 1) strictly dependent upon cell surface expression of PECAM-1 and 2) unaffected by the presence of excess heparin or heparan sulfate. The extracellular domain of PECAM-1 failed to interact specifically with heparin-Sepharose, 3H-labeled heparin, or a heparin-bovine serum albumin conjugate. In addition, an amino acid sequence motif inadvertently created by the juxtaposition of PECAM-1 and IgG sequences within the hinge region of certain PECAM-1/IgG chimeric constructs was found to confer glycosaminoglycan binding properties not normally present within the extracellular domain of the native molecule. Together, these data suggest that the mechanism by which heparin is able to affect PECAM-1-dependent cell-cell adhesion is indirect and occurs via inhibition of events that occur downstream from PECAM-1 engagement.

A point mutation in the cysteine-rich domain of glycoprotein (GP) IIIa results in the expression of a GPIIb-IIIa (alphaIIbbeta3) integrin receptor locked in a high-affinity state and a Glanzmann thrombasthenia-like phenotype.

This article reports a Glanzmann thrombasthenia (GT) patient, N.M., with a point mutation in the third cysteine-rich repeat of beta3-integrin or platelet glycoprotein (GP) IIIa, leading to the expression of a constitutively activated fibrinogen receptor. The diagnosis of GT was based on a severely reduced platelet-aggregation response to a series of agonists and approximately 20% of surface-expressed GPIIb-IIIa. The patient's GPIIb-IIIa constitutively expressed epitopes recognized by antibodies to ligand-induced binding sites (LIBS) and also spontaneously bound the fibrinogen-mimetic antibody, PAC-1. Furthermore, significant amounts of bound fibrinogen were detected on his platelets ex vivo. No signs of platelet activation were observed on sections of unstimulated platelets from N.M. by electron microscopy. Immunogold labeling highlighted the presence of surface-bound fibrinogen but revealed platelet heterogeneity with regard to the surface density. When the patient's platelets were stimulated by thrombin-receptor activating peptide, amounts of surface-expressed GPIIb-IIIa increased and the aggregation response improved, although it failed to normalize. Platelets from N.M. were able to adhere and spread on immobilized fibrinogen. Sequence analysis of genomic DNA from N.M. revealed a homozygous g1776T>C mutation in GPIIIa, leading to a Cys560Arg amino acid substitution. A stable Chinese hamster ovary (CHO) cell line was prepared expressing surface GPIIb-Arg560IIIa. Like platelets from the patient, GPIIb-Arg560IIIa-transfected CHO cells constitutively bound LIBS antibodies and PAC-1. They also showed an enhanced ability to adhere on surface-bound fibrinogen. Overall, these data demonstrate that a gain-of-function mutation can still be associated with a thrombasthenic phenotype even though platelets show spontaneous fibrinogen binding.