Matrix Metalloproteinase-2 and Tissue Inhibitor of Metalloproteinase-1 in the Retinal Pigment Epithelium and Interphotoreceptor Matrix: Vectorial Secretion and Regulation

Matrix metalloproteinases (MMPs) and the tissue inhibitors of metalloproteinases (TIMPs) play an essential role in both normal and pathological extracellular matrix degradation, and a TIMP has been associated with at least one type of retinal degeneration. We have studied expression of MMP-2 and TIMP-1 by zymography, immunocytochemistry, and immunoblotting in the retinal pigment epithelium (RPE) from normal, aged and diseased retinas. MMPs and TIMPs were found in the rat RPE, interphotoreceptor matrix (IPM), and in media conditioned by human and rat RPE in culture. In other polarized cells, MMPs and TIMP-2 are secreted vectorially towards the basal lamina. In the RPE, however, MMP-2 and TIMP-1 were secreted preferentially from the apical surface, the surface bordering the IPM. These findings provide new evidence that MMPs and TIMPs could play a role in the turnover of IPM components.Cell homogenates and conditioned media from RPE isolated from mutant Royal College of Surgeons (RCS) rats with inherited retinal dystrophy had similar amounts of MMP-2 and TIMP-1 as those from congenic control rats. The secretion of MMP-2 and TIMP-1 from RPE cell cultures isolated from young and aged human donors varied widely. However, with increasing cell passage number, secretion of MMPs and TIMPs from human RPE increased dramatically. Also, growing human RPE on bovine corneal endothelial cell-generated extracellular matrix instead of plastic reduced the secretion of both MMPs and TIMPs. These data suggest that the integrity of Bruch's membrane may serve to regulate RPE functions in MMP and TIMP secretion and that extracellular matrices contain signals that regulate MMP and TIMP synthesis and/or secretion by the RPE.     

Effect of maternal age on autosomal trisomies

The effect of maternal age on the genesis of trisomy was studied by comparing data from 362 trisomic and 790 chromosomally normal spontaneous abortions. As a group the trisomies were associated with a substantial increase in maternal age but there were considerable differences in the magnitude of the effect for different trisomies. The effect of increasing maternal age was most pronounced for trisomies involving the small chromosomes, both acrocentric and non-acrocentric. However, trisomy 16 was conspicuously different from trisomies for all the other small chromosomes, both in the reduced importance of increased maternal age and in the high frequency with which it occurred. The effect of increasing maternal age on trisomies for chromosomes in groups A, B and C was less clear than that for the small chromosomes. However, the evidence suggested that trisomy for these chromosomes was associated with a moderate increase in maternal age.
It was suggested that the maternal age-dependent trisomies might result from precocious disjunction of the bivalents and random segregation of the resulting univalents, a process which would affect chromosomes with the fewest number of chiasmata and which might be more prevalent in oocytes of older women. It was further suggested that true non-disjunction, that is, the failure of bivalents to separate at anaphase, might also result in the production of trisomies. This process might be independent of, or only slightly influenced by, increasing maternal age but be affected by the presence of large blocks of heterochromatin.     

Modelling crack cocaine use trends over 10 years in a Canadian setting

Introduction and Aims. Crack cocaine use among illicit drug users is associated with a range of health and community harms. However, long‐term epidemiological data documenting patterns and risk factors for crack use initiation remain limited especially among injection drug users. We investigated longitudinal patterns of crack cocaine use among polydrug users in Vancouver, Canada. Design and Methods. We examined the rate of crack use among injection drug users enrolled in a prospective cohort study in Vancouver, Canada between 1996 and 2005. We also used a Cox proportional hazards regression analysis to identify independent predictors of crack use initiation among this population. Results. In total, 1603 injection drug users were recruited between May 1996 and December 2005. At baseline, 7.4% of participants reported ever using crack and this rate increased to 42.6% by the end of the study period (Mantel trend test P < 0.001). Independent predictors of crack use initiation during the study period included frequent cocaine injection, crystal methamphetamine injection, residency in the city's drug using epicenter and involvement in the sex trade (all P < 0.05). Discussion and Conclusions. These findings demonstrate a massive increase in crack use among injection drug users in a Canadian setting. Our findings also highlight the complex interactions that contribute to the initiation of crack use among injection drug users and suggest that evidence‐based interventions are urgently needed to address crack use initiation and to address harms associated with its ongoing use.[Werb D, DeBeck K, Kerr T, Li K, Montaner J, Wood E. Modelling crack cocaine use trends over 10 years in a Canadian setting. Drug Alcohol Rev 2010]     

1,2-二氯乙烷吸入染毒对SD大鼠肝脏遗传损伤效应及代谢酶表达的影响

目的研究1,2-二氯乙烷(1,2-DCE)吸入染毒对SD大鼠肝脏的遗传损伤作用及代谢酶表达的影响。方法SPF级健康成年SD雄性大鼠30只,按体重随机分为对照组(n=8)、低剂量组(n=11)和高剂量组(n=11)。采用口鼻式动式吸入染毒法,低、高剂量组分别给予质量浓度为600和1 800 mg/m~3的1,2-DCE染毒8h/d,连续7d;对照组采取相同处理方式吸入正常空气。实验结束后,利用实时荧光定量PCR技术检测代谢酶及遗传损伤相关指标p53的m RNA表达改变。结果实时荧光定量PCR结果显示,1,2-DCE染毒后高剂量组大鼠肝脏中Ⅰ相代谢酶细胞色素P4502E1(CYP2E1)、乙醇脱氢酶1(ADH1)、乙醛脱氢酶3α1(ALDH3α1)、Ⅱ相代谢酶谷胱甘肽S-转移酶A1(GSTA1)、谷胱甘肽S-转移酶M1(GSTM1)、谷胱甘肽S-转移酶A3(GSTA3)以及遗传损伤相关基因p53 m RNA表达均被诱导升高,差异有统计学意义(P0.05)。结论CYP2E1、ADH1、ALDH3α1、GSTA1、GSTM1和GSTA3是1,2-DCE的主要代谢酶,其表达量可以被1,2-DCE染毒诱导而发生改变,p53信号通路所介导的遗传损伤应激可能参与了1,2-DCE诱导大鼠肝细胞坏死或凋亡的过程。