Controlling N-methyl-D-aspartate receptor subunit 1 with calcitonin gene related peptide after cerebral ischemic injury

BACKGROUND: Activation of N-methyl-D-aspartate receptor (NMDAR) is a key link of exitotoxicity at the phase of cerebral ischemic injury. Because NMDAR is a main way to mediate internal flow of Ca2+ among glutamic acid receptors, over-excitation can cause neuronal apoptosis. Calcitonin gene related peptide has a strongly biological activity. On one hand, it can protect ischemic neurons through inhibiting the expression of NMDAR1 mRNA; on the other hand, it can play the protective effect through down-regulating the expression of NMDAR1 mRNA by exogenous calcitonin gene related peptide. OBJECTIVE: To observe the expression of NMDAR1 and the regulatory effect of calcitonin gene related peptide on the expression of NMDAR1 mRNA and protein in the cerebral cortex of rats with focal cerebral ischemia/reperfusion (I/R). DESIGN: Randomized controlled animal study. SETTING: China Medical University. MATERIALS: A total of 216 healthy male Wistar rats, general grade, weighing 250-280 g, were selected in this study. Twelve rats were randomly selected to regard as control group; meanwhile, other 204 rats were used to establish middle cerebral artery occlusion/reperfusion (MACO) models. The main reagents were detailed as follows: calcitonin gene related peptide (Sigma Company); calcitonin gene related peptide kit (Boster Company); antibody Ⅰ, Ⅱ and antibody β-actin Ⅰ, Ⅱ of NMDAR1 mRNA and chemiluminescence reagent (Santa Cruz Company, USA). METHODS: The experiment was carried out in the Laboratory of Neurobiology of China Medical University from August 2005 to June 2006. ① Right MCAO models of rats were established to cause focal ischemia and scored based on Zea Longa five-grade scale. If the scores were 1, 2 and 3 after wakefulness, the MACO models were established successfully and involved in the experiment. A total of 120 rats with successful modeling were randomly divided into I/R group and administration group with 60 in each group. All rats in the both groups were observed at five time points, including 6, 12, 24, 48 and 72 hours after reperfusion and after 2-hour ischemia, with 12 experimental animals at each time point. Six rats were prepared for detection of hybridization in situ, and the other 6 were used for Western blotting histochemical detection. Rats in the control group were opened their skin to separate common carotid artery and not treated with line and drugs. In addition, rats in the I/R group were treated with 1 mL saline at 2 hours after focal cerebral ischemia, and then, rats in the administration group were treated with 1 mL (1 g/L) calcitonin gene related peptide at 2 hours after focal cerebral ischemia. ② The expression of NMDAR1 mRNA was detected with hybridization in situ at various time points; moreover, the expression of NMDAR1 protein was measured with Western blotting method at various time points. The results were analyzed with Metamoph imaging analytical system. MAIN OUTCOME MEASURES: The expression of NMDAR1 mRNA and its protein in cortical neurons of rats at various time points. RESULTS: A total of 84 rats were excluded because of non-symptoms, exanimation or death; and then, 132 rats were involved in the final analysis. The expression of NMDAR1 mRNA and its protein in cortical neurons of rats in the control group was 0.205±0.001 and 0.184±0.001, respectively; after I/R, expression of NMDAR1 mRNA and its protein was up-regulated, especially, expression of mRNA at 6, 12, 24, 48 and 72 hours was 0.245±0.003, 0.287±0.004, 0.354±0.008, 0.284±0.002 and 0.217±0.006, respectively; moreover, expression of protein at 6, 12, 24, 48 and 72 hours was 0.222±0.003, 0.261±0.028, 0.311±0.004, 0.259±0.013 and 0.210±0.008, respectively. There was significant difference between the two groups (0.205±0.001, P < 0.01). The expression was up-related in the former 24 hours, reached peak at 24 hours, down-regulated, and decreased to the level of control group at 72 hours. Except 72 hours, the expression of NMDAR1 mRNA and its protein was lower in administration group than that in I/R group at other four time points. In addition, the expression of mRNA at 6, 12, 24, 48 and 72 hours was 0.223±0.005, 0.243±0.001, 0.292±0.002, 0.250±0.003 and 0.213±0.003, respectively; moreover, the expression of protein at 6, 12, 24, 48 and 72 hours was 0.216±0.006, 0.245±0.025, 0.276±0.003, 0.241±0.045 and 0.202±0.013, respectively. There was significant difference at various time points (P < 0.05). CONCLUSION: The expressions of NMDAR1 mRNA and its protein of peripheral cortical neurons are up-related in ischemic area after focal cerebral I/R. Meanwhile, exogenous calcitonin gene related peptide can protect cortical neurons through inhibiting expression of NMDAR1 mRNA and its protein after focal cerebral I/R.

Oxidized phospholipids are ligands for LRP6

Low-density lipoprotein receptor–related protein 6(LRP6) is a co-receptor for Wnt signaling and can be recruited by multiple growth factors/hormones to their receptors facilitating intracellular signaling activation. The ligands that bind directly to LRP6 have not been identified. Here, we report that bioactive oxidized phospholipids(oxPLs) are native ligands of LRP6, but not the closely related LRP5. oxPLs are products of lipid oxidation involving in pathological conditions such as hyperlipidemia, atherosclerosis, and inflammation. We found that cell surface LRP6 in bone marrow mesenchymal stromal cells(MSCs) decreased rapidly in response to increased oxPLs in marrow microenvironment. LRP6 directly bound and mediated the uptake of oxPLs by MSCs. oxPL-LRP6 binding induced LRP6 endocytosis through a clathrin-mediated pathway, decreasing responses of MSCs to osteogenic factors and diminishing osteoblast differentiation ability. Thus, LRP6 functions as a receptor and molecular target of oxPLs for their adverse effect on MSCs, revealing a potential mechanism underlying atherosclerosis-associated bone loss.

Therapeutic potential of brain-derived neurotrophic factor(BDNF)and a small molecular mimics of BDNF for traumatic brain injury

Traumatic brain injury（TBI） is a major health problem worldwide.Following primary mechanical insults,a cascade of secondary injuries often leads to further neural tissue loss.Thus far there is no cure to rescue the damaged neural tissue.Current therapeutic strategies primarily target the secondary injuries focusing on neuroprotection and neuroregeneration.The neurotrophin brain-derived neurotrophic factor（BDNF） has significant effect in both aspects,promoting neuronal survival,synaptic plasticity and neurogenesis.Recently,the flavonoid 7,8-dihydroxyflavone（7,8-DHF）,a small Trk B agonist that mimics BDNF function,has shown similar effects as BDNF in promoting neuronal survival and regeneration following TBI.Compared to BDNF,7,8-DHF has a longer half-life and much smaller molecular size,capable of penetrating the blood-brain barrier,which makes it possible for non-invasive clinical application.In this review,we summarize functions of the BDNF/Trk B signaling pathway and studies examining the potential of BDNF and 7,8-DHF as a therapy for TBI.

Protective Effect of Norcantharidin on Collagen-Induced Arthritis Rats

Objective： To observe the effect of norcantharidin（NCTD） on collagen-induced arthritis（CIA） rats. Methods： Sixty Sprague-Dawley（SD） rats were randomly divided into 6 groups（n=10）： normal group, CIA model group（model group）, NCTD low-dose group [1.35 mg/（kg·d）], NCTD middle-dose group [2.7 mg/（kg·d）], NCTD high-dose group [5.4 mg/（kg·d）] and methotrexate（MTX） group [1.8 mg/（kg/w）]. Anesthetized rats were sacrificed by luxation of cervical vertebra after 4 weeks of administration. The arthritis scores were evaluated twice a week. The pathological changes in the ankle joints of rats were observed by hematoxylin-eosin（H＆E） staining. The serum levels of interleukin（IL） 1β, IL-6, tumor necrosis factor（TNF）-α, vascular endothelial growth factor（VEGF）, IL-17 and transform growth factor（TGF） β were detected by enzyme linked immunosorbent assay（ELISA）. The mRNA expression of retinoid-related orphan nuclear receptor γ t（ROR γ t） and forkhead box P3（Foxp3） in peripheral blood lymphocytes were confirmed by real-time polymerase chain reaction. Results： MTX and high-dose NCTD not only decreased the arthritis scores but also alleviated the pathological changes in CIA rats＇ ankle joints compared with the model group（P〈0.05 or P〈0.01）. All doses of NCTD significantly inhibited the serum levels of IL-6, IL-17 and TNF-α in CIA rats（P〈0.05）. Only middle-and high-dose of NCTD prominently decreased serum IL-1β and TGF-β levels of CIA rats（P〈0.05）. However, NCTD has no effect on vascular endothelial growth factor（VEGF） level in CIA rats. The Foxp3 mRNA expression in all NCTD groups were increased significantly than in the model group（P〈0.05）. The mRNA expression of RORγt in NCTD high-dose group was decreased apparently in comparison with the model group（P〈0.05）. Conclusion： NCTD showed therapeutic effect on CIA rats by inhibition of cytokines and regulation of Th17/Treg cells.

Association of common polymorphisms in the LRP6 gene with sporadic coronary artery disease in a Chinese population

Background Genetic factors contribute to the development of coronary artery disease （CAD）.Recently,a missense mutation in the low density lipoprotein receptor related protein 6 （LRP6） gene,encoding low density lipoprotein receptor related protein 6,has been implicated in an autosomal dominant form of early-onset CAD.The aim of this study was to determine whether the common variants in LRP6 are associated with sporadic CAD in Chinese.Methods A total of 766 CAD patients and 806 healthy controls were included in this study.The presence of angiographic CAD was determined by coronary angiographic analysis.Six signal nucleotide polymorphisms （SNPs） were genotyped using the polymerase chain reaction-restriction fragment length polymorphism （PCR-RFLP） technique.Results A significant association was detected between rs11054731 in LRP6 intron 2 and CAD in our cohort （P=0.001）.The CC genotype and C allele frequency in the case group were 52% and 72%.Using a dominant model of inheritance,the C allele of rs11054731 was shown to be an independent risk factor for CAD with an OR of 1.45 （95% CI：1.19-1.77,P=0.0002）.With the stratification according to the number of affected coronary arteries,an association was observed between rs11054731 and CAD （P=0.0002）.No significant association was observed between any other SNPs and the risk of CAD.Conclusion The C allele of the rs11054731 within the LRP6 gene was associated with increased risk and extent of CAD in Chinese.