Timed feeding of mice modulates light-entrained circadian rhythms of reticulated platelet abundance and plasma thrombopoietin and affects gene expression in megakaryocytes

Circadian ( c . 24 h) rhythms of physiology are entrained to either the environmental light-dark cycle or the timing of food intake. In the current work the hypothesis that rhythms of platelet turnover in mammals are circadian and entrained by food intake was explored in mice. Mice were entrained to 12 h light-dark cycles and given either ad libitum (AL) or restricted access (RF) to food during the light phase. Blood and megakaryocytes were then collected from mice every 4 h for 24 h. It was found that total and reticulated platelet numbers, plasma thrombopoietin (TPO) concentration and the mean size of mature megakaryocytes were circadian but not entrained by food intake. In contrast, a circadian rhythm in the expression of Arnt1 in megakaryocytes was entrained by food. Although not circadian, the expression in megakaryocytes of Nfe2 , Gata1 , Itga2b and Tubb1 expression was downregulated by RF, whereas Ccnd1 was not significantly affected by the feeding protocol. It is concluded that circadian rhythms of total platelet number, reticulated platelet number and plasma TPO concentration are entrained by the light-dark cycle rather than the timing of food intake. These findings imply that circadian clock gene expression regulates platelet turnover in mammals.     

骨髓内皮细胞条件培养液中TGF-β1对CFU-Meg生成的影响

【目的】探讨骨髓内皮细胞条件培养液（E—CM）中转化生长因子-β（TGF-β1）对巨核细胞集落形成单位（CFU—Meg）生成的影响。【方法】将含不同浓度TGF-β1的培养体系体外半固体培养巨核系细胞，观察它们对CFU—Meg生成的影响。将〉10kDE—CM用抗TGF-β1抗体中和后，加入CFU—Meg培养体系中，观察〉10kDE—CM对CFU—Meg生成的影响的变化。【结果】在0．5～10ng／ml体系的浓度范围内，TGF-β1。对CFU—Meg的生成有抑制作用；〉10kDE-CM对CFU—Meg生成有促进作用；用抗TGF-β1，抗体中和〉10kDE-CM中的TGF-β1，后，〉10kDE—CM促CFU-Meg生成的作用明显增强。【结论】rmTGF-β1，和内皮细胞条件培养液中的TGF-β1对CFU—Meg的生成有明显的抑制作用。     

Megakaryocytic emperipolesis and platelet function abnormalities in five patients with gray platelet syndrome

The gray platelet syndrome (GPS) is a rare congenital platelet disorder characterized by mild to moderate bleeding diathesis, macrothrombocytopenia and lack of azurophilic α-granules in platelets. Some platelet and megakaryocyte (MK) abnormalities have been described, but confirmative studies of the defects in larger patient cohorts have not been undertaken. We studied platelet function and bone marrow (BM) features in five GPS patients with NBEAL2 autosomal recessive mutations from four unrelated families. In 3/3 patients, we observed a defect in platelet responses to protease-activated receptor (PAR)1-activating peptide as the most consistent finding, either isolated or combined to defective responses to other agonists. A reduction of PAR1 receptors with normal expression of major glycoproteins on the platelet surface was also found. Thrombin-induced fibrinogen binding to platelets was severely impaired in 2/2 patients. In 4/4 patients, the BM biopsy showed fibrosis (grade 2–3) and extensive emperipolesis, with many (36–65%) MKs containing 2–4 leukocytes engulfed within the cytoplasm. Reduced immunolabeling for platelet factor 4 together with normal immunolabeling for CD63 in MKs of two patients demonstrated that GPS MKs display an alpha granule-specific defect. Increased immunolabeling for P-selectin and decreased immunolabeling for PAR1, PAR4 and c-MPL were also observed in MKs of two patients. Marked emperipolesis, specific defect of MK alpha-granule content and defect of PAR1-mediated platelet responses are present in all GPS patients that we could study in detail. These results help to further characterize the disease.     

Exploring the cause of the most ancient clinical sign of medicine: finger clubbing

OBJECTIVE: Digital clubbing is regarded as the oldest clinical sign of medicine. The cause of this unique finger deformity has remained elusive throughout the centuries. For 3 decades our group has studied the etiology of this acropachy. This article reviews the current knowledge on the cause of digital clubbing. METHODS: PubMed database (www.pubmed.gov) was accessed. In clinical queries/clinical study service we entered "clubbing" or "hypertrophic osteoarthropathy," choosing the "etiology" category with a "broad sensitive" search scope. The time span was from January 1975 to August 2006. Additionally, this article narrates the chronology of our research on the pathogenesis of clubbing. RESULTS: The many dreadful internal illnesses associated with digital clubbing have in common enhanced platelet/endothelial cell activation. Emerging evidence suggests that, in hypoxic conditions with extrapulmonary shunting of blood, large megakaryocyte fragments fail to enter the pulmonary circulation. Instead they gain access to the systemic circulation impacting at the most distal sites, there releasing growth factors and thus inducing clubbing. In cases of lung cancer, the purported growth factor could gain direct entrance to the systemic circulation. Vascular endothelial growth factor (VEGF) may play a central role in the development of digital clubbing. It is a platelet-derived factor induced by hypoxia, and it is also abnormally produced by diverse malignant tumors fostering their uncontrolled growth. On the other hand VEGF produces vascular hyperplasia, edema, and fibroblast/osteoblast proliferation. Such are clubbing histologic characteristics. Enhanced VEGF expression has been reported in practically all internal illnesses associated with this type of finger deformity. Recent studies have demonstrated high circulating levels as well as increased local expression of VEGF in different groups of patients with digital clubbing. CONCLUSION: Abnormal expression of VEGF may be the cause of digital clubbing.     

人巨细胞病毒体外感染巨核系细胞加重凋亡

为了研究人巨细胞病毒 (HCMV)感染对巨核系细胞加快凋亡的作用机制及HCMV感染引起血小板减少症的机制 ,采用巨核细胞株CHRF 2 88 11和HCMVAD16 9株共同培养 ,用PCR检测HCMVIEA ,用形态学观察、DNALadder形成及AnnexinV/PI流式细胞仪检测分析细胞凋亡情况。结果显示 :HCMVAD16 9株的不同浓度病毒组(10 -3 ,10 -2 ,10 -1)均能显著抑制CHRF细胞的生长。在感染 7天后 ,3组细胞的活率水平分别是 77% ,73%和 6 8% ,而对照组为 98%。用流式细胞仪检测AnnexinV/PI,在感染 7天后 ,10 -3 ,10 -2 和 10 -1病毒组凋亡细胞的百分数是(2 1.3± 2 .4 9) % ,(2 5 .8± 3.6 5 ) %和 (31.4± 3.91) % ,对照组则为 (3.6 8± 1.4 7) %。凋亡率随培养液中病毒浓度的加大和感染后时间的延长而增高 ,二者呈依赖关系。形态学观察和DNALadder的形成进一步证实了凋亡细胞的存在 ,用PCR确定了在CHRF细胞内有HCMVIEA的表达。结论 :HCMV可直接感染巨核系细胞并加重它的凋亡。