Hormonal changes and their impact on cognition and mental health of ageing men

Demographic changes resulting in ageing of the world's population have major implications for health. As men grow older, circulating levels of the principal androgen or male sex hormone testosterone (T) decline, while the prevalence of ill-health increases. Observational studies in middle-aged and older men have shown associations between lower levels of T and poorer mental health in older men, including worse cognitive performance, dementia and presence of depressive symptoms. The role of T metabolites, the more potent androgen dihydrotestosterone (DHT) and the oestrogen receptor ligand estradiol (E2) in the pathophysiology of cognitive decline are unclear. Studies of men undergoing androgen deprivation therapy in the setting of prostate cancer have shown subtle detrimental effects of reduced T levels on cognitive performance. Randomised trials of T supplementation in older men have been limited in size and produced variable results, with some studies showing improvement in specific tests of cognitive function. Interventional data from trials of T therapy in men with dementia are limited. Lower levels of T have also been associated with depressive symptoms in older men. Some studies have reported an effect of T therapy to improve mood and depressive symptoms in men with low or low-normal T levels. T supplementation should be considered in men with a diagnosis of androgen deficiency. Beyond this clinical indication, further research is needed to establish the benefits of T supplementation in older men at risk of deteriorating cognition and mental health.     

Glutamate in cancers: from metabolism to signaling

Glutamine and glutamate are major bioenergy substrates for normal and cancer cell growth. Cancer cells need more biofuel than normal tissues for energy supply, anti-oxidation activity and biomass production. Genes related to metabolic chains in many cancers are somehow mutated, which makes cancer cells more glutamate dependent. Meanwhile, glutamate is an excitatory neurotransmitter for conducting signals through binding with different types of receptors in central neuron system. Interestingly, increasing evidences have shown involvement of glutamate signaling, guided through their receptors, in human malignancy. Dysregulation of glutamate transporters, such as excitatory amino acid transporter and cystine/glutamate antiporter system, also generates excessive extracellular glutamate, which in turn, activates glutamate receptors on cancer cells and results in malignant growth. These features make glutamate an attractive target for anti-cancer drug development with some glutamate targeted but blood brain barrier impermeable anti-psychosis drugs under consideration. We discussed the relevant progressions and drawbacks in this field herein.     

The Claustrum in the Squirrel Monkey

The claustrum (CLA) is a subcortical structure that is reciprocally and topographically connected with the cerebral cortex. The complexity of the cerebral cortex varies dramatically across mammals, raising the question of whether there might also be differences in CLA organization, circuitry, and function. Species variations in the shape of the CLA are well documented. Studies in multiple species have identified subsets of neurochemically distinct interneurons; some data suggest species variations in the nature, distribution, and numbers of different neurochemically identified neuronal types. We have studied the CLA in a smooth-brained primate, the squirrel monkey, using Nissl-stained sections and immunohistochemistry. We found that the shape of the CLA is different from that in other primates. We found several different neurochemically defined populations of neurons equally distributed throughout the CLA. Immunoreactivity to GAD_65/67 and GABA_A receptors suggest that GABAergic interneurons provide widespread inhibitory input to CLA neurons. Immunoreactivity to glutamate transporters suggests widespread and overlapping excitatory input from cortical and possibly subcortical sources. Comparison of CLA organization in different species suggests that there may be major species differences both in the organization and in the functions of the CLA. Anat Rec, 303:1439–1454, 2020. © 2019 American Association for Anatomy     

ABCA1基因多态性与冠心病易感性的关联研究

目的探讨三磷酸腺苷结合盒转运子A1（ATP binding cassette transporter1,ABCA1）基因R219K及M883I单核苷酸多态性（SNP）位点与脂代谢和冠心病（coronary heart disease,CHD）易感性的关系。方法以医院为基础的病例-对照研究。经冠状动脉造影确诊的冠心病病例224例,同一地区正常对照248例。分别以PCR-RFLP和PIRA-PCR对ABCA1第219密码子G→A（Arg219Lys）和第883G→A（Met883Ile）密码子多态进行检测,比较不同基因型与个体血脂水平和冠心病患病风险的关系。结果吸烟、高血压和高血糖是冠心病的独立危险因素。与携带219RR基因型者比较,携带至少1个219K等位基因者（即RK和KK基因型）冠心病患病风险显著降低59％（OR = 0．41,95％ CI = 0．27～0．61）。而在883位点,II基因型携带者患冠心病率较低（OR = 0．54,95％ CI = 0．26～1．11）。而两位点联合作用分析发现与携带219RR,883MM或883MI基因型者相比较,携带其他组合基因型的个体冠心病患病风险降低61％（OR = 0．39,95％ CI = 0．26～0．60）。另外,对照组中携带219K等位基因者血清HDL-C水平显著高于219K非携带者（P = 0．037）,提示Arg219Lys位点的多态改变主要通过改变HDL-C水平影响个体冠心病的患病风险。结论ABCA1 R219K可能与中国汉族人群冠心病遗传易感性有关,血清高密度脂蛋白可能是其作用靶点。     

Quantification of biliary excretion and sinusoidal excretion of 5(6)-carboxy-2′,7′-dichlorofluorescein (CDF) in cultured hepatocytes isolated from Sprague Dawley,Wistar and Mrp2-deficient Wistar (TR−) rats

Hepatic efflux of drug candidates is an important issue in pre-clinical drug development. Here we utilise a method which quantifies and distinguishes efflux of drugs at the canalicular and sinusoidal membranes in rat hepatocyte cultures. Bi-phasic kinetics of transport of 5(6)-carboxydichlorofluorescein (CDF) at the canalicular membrane was demonstrated in Sprague Dawley (SD) and Wistar (W) rat hepatocytes. The high affinity component (Km = 3.2 ± 0.8 μM (SD), 9.0 ± 3.1 μM (W)) was attributed to Mrp2-mediated transport, the low affinity component (Km = 192.1 ± 291.5 μM (SD), 69.2 ± 36.2 μM (W)) may be attributed to transport involving a separate Mrp2 binding site. Data from membranes (Hill coefficient (h) = 2.0 ± 0.5) and vesicles (h = 1.6 ± 0.2) expressing Mrp2 and from SD (h = 1.6 ± 0.4) and Wistar (h = 4.0 ± 0.6) hepatocytes suggests transport involves more than one binding site. In TR⁻ hepatocytes, CDF efflux was predominantly over the sinusoidal membrane (Km = 100.7 ± 36.0 μM), consistent with low abcc2 (Mrp2) expression and compensatory increase in abcc3 (Mrp3) expression. This report shows the potential of using this in vitro method to model changes in biliary excretion due to alterations in transporter expression.     

Digoxin net secretory transport in bronchial epithelial cell layers is not exclusively mediated by P-glycoprotein/MDR1

The impact of P-glycoprotein (MDR1, ABCB1) on drug disposition in the lungs as well as its presence and activity in in vitro respiratory drug absorption models remain controversial to date. Hence, we characterised MDR1 expression and the bidirectional transport of the common MDR1 probe ³H-digoxin in air–liquid interfaced (ALI) layers of normal human bronchial epithelial (NHBE) cells and of the Calu-3 bronchial epithelial cell line at different passage numbers. Madin–Darby Canine Kidney (MDCKII) cells transfected with the human MDR1 were used as positive controls. ³H-digoxin efflux ratio (ER) was low and highly variable in NHBE layers. In contrast, ER = 11.4 or 3.0 were measured in Calu-3 layers at a low or high passage number, respectively. These were, however, in contradiction with increased MDR1 protein levels observed upon passaging. Furthermore, ATP depletion and the two MDR1 inhibitory antibodies MRK16 and UIC2 had no or only a marginal impact on ³H-digoxin net secretory transport in the cell line. Our data do not support an exclusive role of MDR1 in ³H-digoxin apparent efflux in ALI Calu-3 layers and suggest the participation of an ATP-independent carrier. Identification of this transporter might provide a better understanding of drug distribution in the lungs.     

A tamoxifen derivative,N,N-diethyl-2-[4-(phenylmethyl) phenoxy] ethanamine,selectively targets P-glycoprotein-positive multidrug resistant Chinese hamster cells

DPPE, a tamoxifen derivative with antihistamine activity, was previously shown to potentiate the toxicity of chemotherapeutic drugs. Recently, a Phase III clinical study using doxorubicin with DPPE demonstrated significant increase in the overall survival of breast cancer patients. In this study we examined the effects of DPPE alone on the growth of drug sensitive and P-gp positive CHO cell line. Our results demonstrate DPPE is selectively toxic to P-gp positive cells and the sensitivity to DPPE alone correlated with the levels of P-gp expression. Moreover, in MDR cells, DPPE-induced apoptosis was significantly reduced with Bcl2 overexpression and in the presence of P-gp ATPase inhibitor, PSC833. Furthermore, knockdown of P-gp expression in MDR cells with P-gp-siRNA reversed DPPE sensitivity and increased their sensitivity to doxorubicin and taxol but not to cisplatin. The addition of DPPE to membrane fractions led to dose-dependent increase in P-gp ATPase that was inhibited with PSC833. Moreover, incubation of P-gp positive cells with DPPE led to a significant increase in superoxide levels and a drop in cellular ATP and GSH pools that were reversible with inhibitors of P-gp ATPase. The combined presence of DPPE and the mitochondria electron transport complex III inhibitor, antimycin A, synergized in their effects on the growth of MDR cells but had no effect on the growth of parental drug sensitive cells. Collectively, the results of this study provide a possible mechanism that may be relevant to the clinical results of DPPE in breast cancer trial and demonstrates DPPE as P-gp collateral sensitivity drug.     

ABCC11/MRP8 Expression in the Gastrointestinal Tract and a Novel Role for?Pepsinogen Secretion

ATP-binding cassette (ABC) transporters are involved in chemotherapy resistance. Multidrug-resistance protein 8 (ABCC11/MRP8) is also involved in 5-fluorouracil (5-FU) metabolism. 5-FU and its derivatives are widely used in the treatment of gastrointestinal tract cancers, but little is known about the contribution of ABCC11/MRP8 to gastrointestinal tract and related cancers. Here, we report our investigation of ABCC11/MRP8 expression in normal and cancerous gastrointestinal tract tissues and reveal its novel role in the gastric mucosa. In tissue microarray and surgically resected cancer specimens, immunohistochemical (IHC) staining revealed significantly reduced expression of ABCC11/MRP8 in gastrointestinal tract cancers compared with other cancers. In contrast, strong ABCC11/MRP8 expression was observed in normal gastric mucosa. Additional immuno­fluorescence assays revealed co-localization of ABCC11/MRP8 and pepsinogen I in normal gastric chief cells. Quantitative PCR and Western blot analysis also revealed significant expression of ABCC11/MRP8 in fundic mucosa where the chief cells are mainly located. Furthermore, the ABCC11 mRNA-suppressed NCI-N87 gastric cancer cell line failed to secret pepsinogen I extracellularly. Thus, low expression of ABCC11/MRP8 is consistent with chemotherapeutic regimens using 5-FU and its derivatives in gastrointestinal tract cancers. Our results indicated a novel function of ABCC11/MRP8 in the regulation of pepsinogen I secretion in the normal gastric chief cells.     

介导肿瘤多药耐药的ATP结合盒转运体的研究进展

多药耐药（MDR）是阻碍肿瘤化疗成功的一大障碍,其机制之一就是耐药的肿瘤细胞高表达三磷酸腺苷（ATP）结合盒（ABC）转运体。依据此机制提出克服肿瘤细胞耐药的策略即开发外排转运体抑制剂,以期逆转MDR。最近的研究发现肿瘤干细胞也可能是通过表达外排转运体天然耐药,这就提供了一个新的抗癌药物作用靶点。对介导肿瘤细胞多药耐药的ABC转运体及其抑制剂的开发作一综述。