生命科学与人类疾病研究的重要模型——果蝇

黑腹果蝇(Drosophilamelanogaster)是生物学研究中最重要的模式生物之一,它在遗传的染色体理论建立中起到非常重要的作用。由于果蝇自身独特的优势,20世纪70年代以来,它又在发育生物学、神经科学、人类疾病研究等领域得到广泛应用,作出许多新的重要贡献。果蝇在神经退行性疾病研究中是非常有用的模型。可以预期,随着研究手段的丰富及科学的发展,果蝇将作为一种理想的模式生物在生物医学中发挥更大的作用。     

Computational modeling of blood component transport related to coronary artery thrombosis in Kawasaki disease

Coronary artery thrombosis is the major risk associated with Kawasaki disease (KD). Long-term management of KD patients with persistent aneurysms requires a thrombotic risk assessment and clinical decisions regarding the administration of anticoagulation therapy. Computational fluid dynamics has demonstrated that abnormal KD coronary artery hemodynamics can be associated with thrombosis. However, the underlying mechanisms of clot formation are not yet fully understood. Here we present a new model incorporating data from patient-specific simulated velocity fields to track platelet activation and accumulation. We use a system of Reaction-Advection-Diffusion equations solved with a stabilized finite element method to describe the evolution of non-activated platelets and activated platelet concentrations [AP], local concentrations of adenosine diphosphate (ADP) and poly-phosphate (PolyP). The activation of platelets is modeled as a function of shear-rate exposure and local concentration of agonists. We compared the distribution of activated platelets in a healthy coronary case and six cases with coronary artery aneurysms caused by KD, including three with confirmed thrombosis. Results show spatial correlation between regions of higher concentration of activated platelets and the reported location of the clot, suggesting predictive capabilities of this model towards identifying regions at high risk for thrombosis. Also, the concentration levels of ADP and PolyP in cases with confirmed thrombosis are higher than the reported critical values associated with platelet aggregation (ADP) and activation of the intrinsic coagulation pathway (PolyP). These findings suggest the potential initiation of a coagulation pathway even in the absence of an extrinsic factor. Finally, computational simulations show that in regions of flow stagnation, biochemical activation, as a result of local agonist concentration, is dominant. Identifying the leading factors to a pro-coagulant environment in each case—mechanical or biochemical—could help define improved strategies for thrombosis prevention tailored for each patient.     

Plasma PAF-acetylhydrolase in patients with coronary artery disease: results of a cross-sectional analysis

Inflammation underlies both onset and perpetuation of atherosclerosis. Plasma lipoproteins transport the platelet-activating factor-acetylhydrolase (PAF-AH) with potentially anti-inflammatory activities. Our aim was to determine whether PAF-AH activity was associated with inflammatory markers and with coronary artery disease (CAD). PAF-AH activity and a panel of inflammatory mediators were measured in plasma of 496 patients with CAD and in 477 controls; 276 patients presented with stable angina pectoris and 220 with acute coronary syndrome (ACS). Individuals within the highest quartile of PAF-AH activity had an 1.8-fold increase in CAD risk [95% confidence interval (CI), 1.01 to 3.2; P = 0.048] compared with those in the first quartile (adjusted for clinical and metabolic factors). When excluding individuals receiving statin and angiotensin-converting enzyme-inhibitor medication, individuals within the highest quartile of PAF-AH activity revealed a 3.9-fold increase in CAD risk (95% CI, 2.0 to 7.7; P < 0.0001). In these subjects, the plasma PAF-AH activity increased gradually in stable angina and in ACS both in men (P < 0.0001) and in women (P < 0.001), as compared with controls.No correlation was found between PAF-AH levels and those of common markers of inflammation. This study and the previous ones raise the important issue of whether PAF-AH is simply a marker of risk or directly promotes atherosclerosis.     

Connective tissue responses in blacks in relation to disease: further observations

Additional information is presented in support of the hypothesis (Polednak: Am. J. Phys. Anthropol. 41:49-58, 1974) that in some black populations certain connective-tissue responses, which are involved in protection against infection and repair after injury, also may predispose to specific chronic diseases. These diseases include some autoimmune disorders (i.e., systemic lupus erythematosus, sarcoidosis, and scleroderma) and various benign and malignant tumors involving connective-tissue cells. Complex interactions between genetic factors (HLA and non-HLA loci) and environmental agents may be involved both in the etiology of these autoimmune diseases and in population differences in the incidence of these diseases. A framework is reviewed whereby cellular responses to infectious agents, involving chiefly immunoglobulin-producing cells and macrophages, may have consequences in terms of pathogenesis of specific chronic diseases more common in some black populations. The possible role of natural selection in maintaining some of these diseases is also considered, along with the need for involvement of biomedical anthropologists in their investigation.     

Clinical trials and basic research: defining mechanisms and improving treatment in connective tissue disease

Despite advances in elucidating the pathogenic factors responsible for its development, systemic sclerosis remains complex and poorly understood, and treatment options are limited. Multidisciplinary collaborative efforts are needed to better characterize clinical and prognostic parameters and to design and implement large-scale clinical trials in well defined populations with therapies that target potential disease modulators.     

Fibroblast growth factor receptor 4 polymorphisms and susceptibility to coronary artery disease

Fibroblast growth factors (FGFs) and their receptors (FGFRs) play crucial roles in vascular smooth muscle cell proliferation and atherosclerosis and, therefore, may potentially affect the development of coronary artery disease (CAD). FGFR4 rs351855 (Gly388Arg) polymorphism has shown to be a risk factor for many diseases. The aim of this study was to investigate the association between FGFR4 polymorphisms and the susceptibility to CAD in the Chinese population. Two polymorphisms, rs351855 (Gly388Arg) and rs641101, were detected by polymerase chain reaction-restriction fragment length polymorphism and direct sequencing in 687 CAD cases and 732 age-matched controls. Data were analyzed using the chi-square test. Results showed that frequencies of GA genotype, AA genotype, and A allele in rs351855 (Gly388Arg) polymorphism were significantly lower in CAD patients than in controls (odds ratio (OR)=0.78, 95% confidence intervals (CIs): 0.62-0.98, p=0.034; OR=0.58, 95% CI: 0.42-0.80, p=0.001; and OR=0.77, 95% CI: 0.66-0.90, p=0.001, respectively). The rs641101 polymorphism did not show any correlation with CAD. Haplotype analysis revealed that rs351855 and rs641101 AG haplotype also had lower frequency in CAD patients (OR=0.79, 95% CI: 0.67-0.92, p=0.002). Our data suggested that the FGFR4 rs351855 (Gly388Arg) polymorphism and AG haplotype (rs351855 and rs641101) could act as protective factors against CAD in the Chinese population and indicated that a single gene polymorphism could have diverse functions in different diseases.     

Plasma distribution of apoA-IV in patients with coronary artery disease and healthy controls

Recent studies showed lower apolipoprotein A-IV (apoA-IV) plasma concentrations in patients with coronary artery disease (CAD). The actual distribution of the antiatherogenic apoA-IV in human plasma, however, is discussed controversially and it was never investigated in CAD patients. We therefore developed a gentle technique to separate the various apoA-IV-containing plasma fractions. Using a combination of precipitation of all lipoproteins with 40% phosphotungstic acid and 4 M MgCl2, as well as immunoprecipitation of all apoA-I-containing particles with an anti-apoA-I antibody, we obtained three fractions of apoA-IV: lipid-free apoA-IV (about 4% of total apoA-IV), apoA-IV associated with apoA-I (LpA-I:A-IV, 12%), and apoA-I-unbound but lipoprotein-containing apoA-IV (LpA-IV, 84%). We compared these three apoA-IV fractions between 52 patients with a history of CAD and 52 age- and sex-matched healthy controls. Patients had significantly lower apoA-IV levels when compared to controls (10.28 +/- 3.67 mg/dl vs. 11.85 +/- 2.82 mg/dl, P = 0.029), but no major differences for the three plasma apoA-IV fractions. We conclude that our gentle separation method reveals a different distribution of apoA-IV than in many earlier studies. No major differences exist in the apoA-IV plasma distribution pattern between CAD patients and controls. Therefore, the antiatherogenic effect of apoA-IV has to be explained by other functional properties of apoA-IV (e.g., the antioxidative characteristics).     

Exaggerated responsiveness to thyrotrophin releasing hormone: a risk factor in women with coronary artery disease.

Thyroid function tests were performed and thyroid antibodies and serum cholesterol concentrations measured in 12 women aged 60 years or under with severe coronary artery disease proved by coronary angiography. This group was compared with 11 women with normal coronary angiography. Ten out of the 12 women with coronary artery disease had an exaggerated response of thyroid stimulating hormone to thyrotrophin releasing hormone compared with two out of 11 controls (p less than 0.008). The mean serum cholesterol concentration was significantly higher in those with coronary artery disease than in the controls. Thyroid antibodies were present in four of those with coronary artery disease and one of the controls. There was no difference in the risk factors for coronary artery disease between the two groups except for cigarette smoking. Eleven out of 12 in the coronary artery disease group smoked cigarettes compared with four out of 11 in the control group (p less than 0.01). Minimal impairment of thyroid function is an important risk factor for coronary artery disease in women.     

Plasma levels of plant sterols and the risk of coronary artery disease: the prospective EPIC-Norfolk Population Study

Some studies have suggested that a modest increase of plant sterol levels is a risk factor for coronary artery disease (CAD). We studied the relationship between plant sterol levels and CAD risk in a prospective nested case-control study consisting of 373 cases and 758 controls. Sitosterol and campesterol concentrations did not differ between cases and controls [sitosterol, 0.21 vs. 0.21 mg/dl (P = 0.1); campesterol, 0.31 vs. 0.32 mg/dl (P = 0.5)]. The sitosterol-to-cholesterol ratio was significantly lower in cases than in controls (1.19 vs. 1.29 microg/mg; P = 0.008), whereas the campesterol-to-cholesterol ratio did not differ significantly (1.78 vs. 1.88 microg/mg; P = 0.1). Plant sterol concentrations correlated positively with cholesterol levels and inversely with body mass index and triglyceride and lathosterol concentrations. Among individuals in the highest tertile of the sitosterol concentration, the unadjusted odds ratio (OR) for future CAD was 0.75 [95% confidence interval (CI) = 0.56-1.01]. After adjustment for traditional risk factors, the OR was 0.79 (95% CI = 0.56-1.13). For the campesterol concentration, the unadjusted OR was 0.95 (95% CI = 0.71-1.29) and the adjusted OR was 0.97 (95% CI = 0.68-1.39). In this large prospective study, higher levels of plant sterols, at least in the physiological range, do not appear to be adversely related to CAD in apparently healthy individuals.     

Thermolabile methylenetetrahydrofolate reductase: an inherited risk factor for coronary artery disease.

Severe methylenetetrahydrofolate reductase (MTHFR) deficiency with less than 2% of normal enzyme activity is characterized by neurological abnormalities, atherosclerotic changes, and thromboembolism. We have discovered a "new" variant of MTHFR deficiency which is characterized by the absence of neurological abnormalities, an enzyme activity of about 50% of the normal value, and distinctive thermolability under specific conditions of heat inactivation. In this study, lymphocyte MTHFR specific activities in the thermolabile variant and control groups were 5.58 +/- 0.91 and 10.33 +/- 2.89 nmol formaldehyde formed/mg protein/h, respectively. The difference was significant (P less than .01). However, there was overlap among the individual values from the two groups. On the other hand, residual MTHFR activity after heat inactivation was 11.2 +/- 1.43% in the thermolabile variant and 36.3 +/- 5.18% in the controls. There was no overlap. Enzyme studies in 10 subjects with thermolabile MTHFR and their family members support the hypothesis that thermolabile MTHFR is inherited as an autosomal recessive trait. To elucidate the association of thermolabile MTHFR with the development of coronary artery disease, we determined the thermostability of lymphocyte MTHFR in 212 patients with proven coronary artery disease and in 202 controls without clinical evidence of atherosclerotic vascular disease. Thermolabile MTHFR was found in 36 (17.0%) cardiac patients and 10 (5.0%) controls. The difference in incidence between the two groups was statistically significant (P less than .01). The average age at onset of clinical coronary artery disease in 36 patients with thermolabile MTHFR was 57.3 +/- 7.6 years (35-72 years). The mean total plasma homocysteine concentration in patients with thermolabile MTHFR was 13.19 +/- 5.32 nmol/ml and was significantly different from the normal mean of 8.50 +/- 2.80 nmol/ml (P less than .05). There was no association between thermolabile MTHFR and other major risk factors. We conclude that thermolabile MTHFR is a variant(s) of MTHFR deficiency which is inherited as an autosomal recessive trait. In addition, it is positively associated with the development of coronary artery disease. Determination of in vitro thermostability of lymphocyte MTHFR is a reliable method for identifying subjects with this abnormality.     

Plasma kinetics of a cholesterol-rich emulsion in subjects with or without coronary artery disease

A cholesterol-rich emulsion (LDE) that resembles the LDL lipidic structure is taken-up by LDL receptors after intravenous injection by means of apolipoprotein E it acquires in the circulation and can be used to probe LDL metabolism. In this study, LDE was labeled with [14C]cholesteryl oleate and [3H]cholesterol and injected into 19 patients with coronary artery disease (CAD) and into 14 subjects without CAD to verify whether the kinetic behavior of the radioactive lipids is different in CAD. Blood was sampled over 24 h for radioactivity measurement after lipid extraction and separation by thin-layer chromatography. Fractional clearance rate (FCR, in h-1) of [14C]cholesteryl ester was not different in CAD and nonCAD expressed as median (25%; 75%): 0.08 (0.062; 0.134) h-1 versus 0.06 (0.04; 0.083) h-1, P = 0.167. However, [3H]cholesterol FCR was greater in CAD than in nonCAD (mean +/- SEM): 0.163 +/- 0.016 h-1 versus 0.077 +/- 0.014 h-1, P < 0.001. Esterification of the LDE [3H]cholesterol was also greater in CAD subjects than nonCAD at 10 h and 24 h after emulsion injection (P = 0.029 and 0.024 respectively). In conclusion, both removal from the plasma and esterification of the LDE-cholesterol were increased in CAD. These findings may contribute for unraveling pro-atherogenic mechanisms and the establishment of novel CAD markers.     

Proteomics of Alzheimer's disease: understanding mechanisms and seeking biomarkers

Alzheimer's disease is the scourge of the modern, aging world: a costly, damaging disease that robs the elderly of their ability to function as well as their memories. Three decades of progress have resulted in a deep understanding of the pathological processes and a range of targets for therapy, many of which have advanced to late-stage clinical trials. Proteomics has contributed greatly to these advances and will continue to have a growing role in determining the nature of the pathological lesions in the brain. In addition, proteomics (both gel based and gel free, mass spectrometry based), is likely to play an increasing role in identifying biomarkers that may assist in early diagnosis and in monitoring progression and, most importantly, response to therapy.     

Genetic susceptibility to coronary artery disease: from promise to progress

Family history is an important independent risk factor for coronary artery disease (CAD), and identification of susceptibility genes for this common, complex disease is a vital goal. Although there has been considerable success in identifying genetic variants that influence well-known risk factors, such as cholesterol levels, progress in unearthing novel CAD genes has been slow. However, advances are now being made through the application of large-scale, systematic, genome-wide approaches. Recent findings particularly highlight the link between CAD and inflammation and immunity, and highlight the biological insights to be gained from a genetic understanding of the world's biggest killer.     

Targets of oncogenes and tumor suppressors: key for understanding basic mechanisms of carcinogenesis

Changes in expression of protooncogenes and tumor suppressor genes play a key role in oncogenesis. Dysfunction of their protein products leads to abnormal regulation of signaling pathways, which control the cell cycle, apoptosis, genetic stability, cell differentiation, and morphogenetic reactions. Changes in these important physiological processes are obviously responsible both for initial steps of neoplastic cell transformation and for determination of subsequent tumor progression resulting in the development of malignant tumors.     

The role of tissue factor in thrombosis and hemostasis

The tissue factor (TF) is one of the most important regulators of arterial thrombosis. Because arterial thrombosis is the pathophysiologic background of acute coronary syndrome, the possible impact of blocking the arterial thrombosis on its onset is a challenging problem. The investigations of TF brought a new concept of "cell-based coagulation model" which highlighted the question of blood-borne TF as a source of TF in circulating blood. In this review we summarize essential information on the pathophysiology, molecular structure, expression and distribution of TF and we propose a novel concept of blood-borne TF, suggesting the possibilities of inhibition of the coagulation cascade with newly synthetized drugs.     

Genetic contribution of the leukotriene pathway to coronary artery disease

We evaluated the genetic contribution of the leukotriene (LT) pathway to risk of coronary artery disease (CAD) in 4,512 Caucasian and African American subjects ascertained through elective cardiac evaluation. Of the three previously associated variants, the shorter "3" and "4" alleles of a promoter repeat polymorphism in ALOX5 increased risk of CAD in African Americans (OR?=?1.4, 95% CI 1.0-1.9; p?=?0.04), whereas a haplotype of LTA4H (HapK) was associated with CAD in Caucasians (OR?=?1.2, 95% CI 1.01-1.4; p?=?0.03). In Caucasians, first-stage analysis of 254 haplotype-tagging SNPs in 15 LT pathway genes with follow-up of 19 variants in stage 2 revealed an LTA4H SNP (rs2540477) that increased risk of CAD (OR?=?1.2, 95% CI 1.1-1.5; p?=?0.003) and a PLA2G4A SNP (rs12746200) that decreased risk of CAD (OR?=?0.7, 95% CI 0.6-0.9; p?=?0.0007). The PLA2G4A rs12746200 variant also decreased risk of experiencing a major adverse cardiac event (MACE?=?myocardial infarction, stroke, or death) over 3?years of follow-up (HR?=?0.7, 95% CI 0.5-0.9; p?=?0.01), consistent with its cardioprotective effect. Functional experiments demonstrated that stimulated monocytes from carriers of LTA4H variants HapK or rs2540477 had 50% (p?=?0.002) and 33% (p?=?0.03) higher LTB(4) production, respectively, compared to non-carriers. These ex vivo results are consistent with LTB(4) being the direct product of the reaction catalyzed by LTA4H and its role in promoting monocyte chemotaxis to sites of inflammation, including the artery wall of atherosclerotic lesions. Taken together, this study provides additional evidence that functional genetic variation of the LT pathway can mediate atherogenic processes and the risk of CAD in humans.