Caveolae/caveolin-1/ERK1/2信号通路在降钙素基因相关肽抑制血管平滑肌细胞增殖中的作用

业已证明,Caveolae及其蛋白caveolin-1参与了细胞膜的胆固醇转运和细胞膜的信号转导．我们前期工作发现降钙素基因相关肽(CGRP)抑制血管平滑肌细胞(VSMC)增殖的信号通路与抑制ERK_1/2活性和上调caveolin-1表达有关．本文研究Caveolae及caveolin-1在CGRP抑制VSMC增殖中的作用,进一步研究caveolin-1表达增加是否有直接抑制ERK_1/2信号激酶活性的作用．采用大鼠主动脉贴块法培养VSMC,取3～10代VSMC用于实验,10%小牛血清(FBS)用于刺激VSMC增殖,用β-环糊精(cyclodextrin)或菲律宾菌素(filipin)剥夺胆固醇破坏Caveolae结构;MTT法和流式细胞仪用于检测细胞增殖;蛋白质印迹和免疫共沉淀法分别用于检测目的蛋白的表达或蛋白质间相互作用．结果显示,CGRP呈时间和浓度依赖性显著抑制10% FBS诱导的VSMC增殖．细胞Caveolae结构的破坏能降低CGRP抑制VSMC增殖作用,同时也增加了ERK_1/2的磷酸化;β-环糊精孵育细胞能降低 caveolin-1的表达．免疫共沉淀发现10% FBS和/或CGRP共同孵育细胞对非磷酸化ERK_1/2与caveolin-1的结合无差别,但10% FBS 能降低磷酸化ERK_1/2与caveolin-1的结合,CGRP预孵育细胞能增加这两者的相互作用．结果揭示,Caveolae及caveolin-1可以正调控CGRP抑制VSMC增殖作用,其机制可能与CGRP增加caveolin-1与p-ERK_1/2在Caveolae的结合,并抑制p-ERK_1/2核转位作用有关．     

Territorial behaviour of the red-backed salamander: Expulsion of intruders

Red-backed salamanders, Plethodon cinereus, were paired in laboratory chambers where they defended areas against each other by threat display and biting. Difference in sizes of paired individuals was not correlated with which one would enter the other's area or be more aggressive after an intrusion. We also found no sexual differences in agonistic behaviour. Both defenders and intruders assumed a threat posture for about 50% of the invasion periods, but defenders exhibited a higher rate of biting. Defenders expelled intruders in 74% of all encounters, while intruders expelled defenders in 18%, with 8% of the encounters a draw. Intruders frequently left the contested area even in the absence of biting or threat display by the defender, apparently in response to the defender's pheromones or to the high potential cost of an escalated aggressive contest (damage to the chemosensory structures). These data provide behavioural evidence that a salamander can evict intruders from a defended area and thus support the hypothesis of territoriality among terrestrial salamanders.     

A comparative climate analysis of heat-related emergency 911 dispatches: Chicago, Illinois and Phoenix, Arizona USA 2003 to 2006

Research into the health impacts of heat has proliferated since 2000. Temperature increases could exacerbate the increased heat already experienced by urban populations due to urbanization. Heat-related mortality studies have found that hot southern cities in North America have not experienced the summer increases in mortality found in their more northern counterparts. Heat-related morbidity studies have not assessed this possible regional difference. This comparison study uses data from emergency 911 dispatches [referred to as heat-related dispatches (HRD)] identified by responders as heat-related for two United States cities located in different regions with very different climates: Chicago, Illinois in the upper midwest and Phoenix, Arizona in the southwest. Phoenix’s climate is hot and arid. Chicago’s climate is more temperate, but can also experience days with unusually high temperatures combined with high humidity. This study examines the relationships between rising HRD and daily temperatures: maximum (Tmax); apparent (ATmax): minimum (Tmin) and two energy balance indices (PET and UTCI). Phoenix had more HRD cumulatively, over a longer warm weather season, but did not experience the large spikes in HRD that occurred in Chicago, even though it was routinely subjected to much hotter weather conditions. Statistical analyses showed the strongest relationships to daily ATmax for both cities. Phoenix’s lack of HRD spikes, similar to the summer mortality patterns for southern cities, suggests an avenue for future research to better understand the dynamics of possible physiological or behavioral adaption that seems to reduce residents’ vulnerability to heat.     

A syndecan-4 binding peptide derived from laminin 5 uses a novel PKCε pathway to induce cross-linked actin network (CLAN) formation in human trabecular meshwork (HTM) cells

In this study, we examined the role(s) of syndecan-4 in regulating the formation of an actin geodesic dome structure called a cross-linked actin network (CLAN) in which syndecan-4 has previously been localized. CLANs have been described in several different cell types, but they have been most widely studied in human trabecular meshwork (HTM) cells where they may play a key role in controlling intraocular pressure by regulating aqueous humor outflow from the eye. In this study we show that a loss of cell surface synedcan-4 significantly reduces CLAN formation in HTM cells. Analysis of HTM cultures treated with or without dexamethasone shows that laminin 5 deposition within the extracellular matrix is increased by glucocorticoid treatment and that a laminin 5-derived, syndecan-4-binding peptide (PEP75), induces CLAN formation in TM cells. This PEP75-induced CLAN formation was inhibited by heparin and the broad spectrum PKC inhibitor Ro-31–7549. In contrast, the more specific PKCα inhibitor Gö 6976 had no effect, thus excluding PKCα as a downstream effector of syndecan-4 signaling. Analysis of PKC isozyme expression showed that HTM cells also expressed both PKCγ and PKCε. Cells treated with a PKCε agonist formed CLANs while a PKCα?γ agonist had no effect. These data suggest that syndecan-4 is essential for CLAN formation in HTM cells and that a novel PKCε-mediated signaling pathway can regulate formation of this unique actin structure.