Chronic caffeine intake increases androgenic stimuli,epithelial cell proliferation and hyperplasia in rat ventral prostate

Coffee intake has been associated with a low risk of developing cancer, including prostate cancer, which is one of the most commonly diagnosed cancer in men. However, few studies have evaluated the chronic effects of caffeine, which is the most abundant methylxanthine in coffee, on prostate morphology and physiology. In the present study, we investigated the effects of chronic, low‐dose caffeine intake on rat prostate morphology from puberty to adulthood. Five‐week‐old male Wistar rats were randomized into two experimental groups: caffeine‐treated (20 ppm in drinking water, n = 12) and control (n = 12). The ventral and dorsolateral prostates were dissected, weighted and submitted to morphological, morphometrical and immunohistochemical analysis of cellular proliferation, apoptosis and androgen receptor (AR) tissue expression. The testosterone (T) and dihydrotestosterone (DHT) concentrations were measured in the plasma. Our results show that caffeine intake increased the concentrations of T and DHT, organ weight, epithelial cell proliferation and AR tissue expression in the ventral prostatic lobe. All the ventral prostates from the caffeine‐treated animals presented various degrees of epithelial and stromal hyperplasia. Our results suggest that chronic caffeine intake from puberty increases androgenic signalling and cell proliferation in the rat prostate gland and can be related to the development of benign prostatic hyperplasia.     

Chronic treatment with simvastatin upregulates muscarinic M1/4 receptor binding in the rat brain

Statins are increasingly being used for the treatment of a variety of conditions beyond their original indication for cholesterol lowering. We previously reported that simvastatin affected the dopaminergic system in the rat brain. This study aims to investigate regional changes of muscarinic M1/4 receptors in the rat brain after 4-week administration of simvastatin (1 or 10 mg/kg/day). M1/4 receptor distribution and alterations in the post-mortem rat brain were detected by [(3)H]pirenzepine binding autoradiography. Simvastatin (1 mg/kg/day) increased [(3)H]pirenzepine binding, predominantly in the prefrontal cortex (171%, P<0.001), primary motor cortex (153%, P=0.001), cingulate cortex (109%, P<0.001), hippocampus (138%, P<0.001), caudate putamen (122%, P=0.002) and nucleus accumbens (170%, P<0.001) compared with controls; while lower but still significant increases of [(3)H]pirenzepine binding were observed in the examined regions following simvastatin (10 mg/kg/day) treatment. Our results also provide strong evidence that chronic simvastatin administration, especially at a low dosage, up-regulates M1/4 receptor binding, which is likely to be independent of its muscarinic agonist-like effect. Alterations in [(3)H]pirenzepine binding in the examined brain areas may represent the specific regions that mediate the clinical effects of simvastatin treatment on cognition and memory via the muscarinic cholinergic system. These findings contribute to a better understanding of the critical roles of simvastatin in treating neurodegenerative disorders, via muscarinic receptors.     

Alpha- and beta-adrenergic receptor function in the brain during senescence

Alpha- and beta-adrenergic receptors and their second messengers play an important role in brain neurotransmission. Changes in receptor function with age may be involved in the age-related changes in arousal, mood and memory. The predominance of data indicates there is decreased beta-adrenergic receptors in all areas of the brain with the exception of the cortex. Evidence suggests a decreased rate of receptor synthesis may be contributing to this loss of receptors with age. Alpha-adrenergic receptor synthesis is also diminished with age. The modulation of receptor concentrations by hormonal factors is impaired with age, especially the time to recover from receptor down-regulation.     

Effects of caffeine and theophylline on adenosine and benzodiazepine receptors in human brain

The binding of various adenosine receptor ligands and of [3H]diazepam, as well as their inhibition of methylxanthines, have been studied in human brain cerebral cortex membranes. Caffeine and theophylline competitively inhibit binding of [3H]cyclohexyladenosine, [3H]diethylphenylxanthine, [3H]phenylisopropyladenosine and [3H]diazepam. Both caffeine and theophylline are more potent as inhibitors of adenosine receptor ligand binding compared to [3H]diazepam binding. Theophylline was more potent than caffeine in its ability to compete with adenosine receptor ligand binding while the reverse was true for [3H]diazepam binding. The meaning of these results for the mode of action of methylxantine is discussed.     

孕期雌鼠摄入超量咖啡因对胎鼠软骨内骨化的影响及其机制

目的 探讨孕期雌鼠摄入超量咖啡因对胎鼠软骨内骨化的影响及其分子机制.方法 在孕第9～20天,咖啡因暴露组Wistar孕鼠每天灌胃120 mg/kg咖啡因,对照组灌胃相同体积的蒸馏水.将孕20 d的孕鼠脱颈处死,取出胎鼠,测量两组胎鼠体长;分离胎鼠股骨远端,测量股骨远端软骨长度,并制备原代软骨细胞,分别用咖啡因(0.1、...     

RNA synthesis in the rat brain during changes in CNS function

RNA synthesis in the phenolic fractions of nuclei and cytoplasm from higher structures of the rat brain under normal conditions, during training in defensive movements in a maze, and in an active control (irregular presentation of stimuli evoking defensive movements) was investigated by electrophoresis in polyacrylamide gel. Behavioral stimulation and irregular presentation of the same stimuli to the animals as during training, but not leading to the formation of defensive skills, activates synthesis of 18S, 28S, and higher forms of RNA in the phenolic extracts of the nuclei. An increase in the incorporation of labeled precursor in the 18S region was found for cytoplasmic RNA.     

Maternal glutamate intake during gestation and lactation regulates adenosine A1 and A2A receptors in rat brain from mothers and neonates

Pregnant rats were treated daily with 1 g/L of l-glutamate in their drinking water during pregnancy and/or lactation. The effect on adenosine A₁ receptor (A₁R) and A_2A receptor (A_2AR) in brains from both mothers and 15-day-old neonates was assayed using radioligand binding and real time PCR assays. Mothers receiving l-glutamate during gestation, lactation, and throughout gestation and lactation showed a significant decrease in total A₁R number (water+water, 302±49 fmol/mg; l-glutamate+water, 109±11 fmol/mg, P<0.01; water+l-glutamate, 52±13 fmol/mg, P<0.01; l-glutamate+l-glutamate, 128±33 fmol/mg, P<0.05). No variations were detected in the Kd parameter. Concerning adenosine A_2AR, radioligand binding assays revealed that Bmax parameter remains unaltered in maternal brain in response to glutamate exposure. However, Kd parameter was significantly decreased in all l-glutamate-treated groups (water+water, 5.3±1.3 nM; l-glutamate±water, 0.5±0.1 nM; water+l-glutamate, 0.9±0.1 nM; l-glutamate±l-glutamate, 0.7±0.1 nM, P<0.01 in all cases). In both male and female neonates, A₁R was also decreased after long-term glutamate exposure during gestation, lactation, and gestation plus lactation (male neonates: water+water, 564±68 fmol/mg; l-glutamate+water, 61±8 fmol/mg; water+l-glutamate, 95±20 fmol/mg; l-glutamate+l-glutamate, 111±15 fmol/mg; P<0.01 in all cases; female neonates: water+water, 216±35 fmol/mg; l-glutamate+water, 59±9 fmol/mg; water+l-glutamate, 139±16 fmol/mg; l-glutamate+l-glutamate, 97±14 fmol/mg; P<0.01 in all cases). No variations were found in mRNA level coding adenosine A₁R in maternal or neonatal brain. Concerning adenosine A_2AR, radioligand binding assays revealed that Bmax parameter was significantly increased in male and female neonates exposed to l-glutamate during lactation (male neonates: water+water, 214±23 fmol/mg; water+l-glutamate, 581±49 fmol/mg; P<0.01; female neonates: water+water, 51±10 fmol/mg; water+l-glutamate, 282±52 fmol/mg; P<0.05). No variations were found in mRNA level coding adenosine A_2AR in maternal or neonatal brain. In summary, long-term l-glutamate treatment during gestation and lactation promotes a significant down-regulation of A₁R in whole brain from both mother and neonates and a significant up-regulation of A_2AR in neonates exposed to l-glutamate during lactation.     

Effects of maternal hypoxia or nutrient restriction during pregnancy on endothelial function in adult male rat offspring

Compromised fetal growth impairs vascular function; however, it is unclear whether chronic hypoxia in utero affects adult endothelial function. We hypothesized that maternal hypoxia (H, 12% O₂, n = 9) or nutrient restriction (NR, 40% of control, n = 7) imposed from day 15–21 pregnancy in rats would impair endothelial function in adult male offspring (relative to control, C, n = 10). Using a wire myograph, endothelium-dependent relaxation in response to methacholine was assessed in small mesenteric arteries from 4- and 7-month-old (mo) male offspring. Nitric oxide (NO) mediation of endothelium-dependent relaxation was evaluated using N ^ω-nitro- l -arginine methyl ester ( l -NAME; NO synthase inhibitor). Observed differences in the NO pathway at 7 months were investigated using exogenous superoxide dismutase (SOD) to reduce NO scavenging, and sodium nitroprusside (SNP; NO donor) to assess smooth muscle sensitivity to NO. Sensitivity to methacholine-induced endothelium-dependent relaxation was reduced in H offspring at 4 months ( P < 0.05), but was not different among groups at 7 months. l -NAME reduced methacholine sensitivity in C ( P < 0.01), H ( P < 0.01) and NR ( P < 0.05) offspring at 4 months, but at 7 months l -NAME reduced sensitivity in C ( P < 0.05), tended to in NR ( P = 0.055) but had no effect in H offspring. SOD did not alter sensitivity to methacholine in C, but increased sensitivity in H offspring ( P < 0.01). SNP responses did not differ among groups. In summary, prenatal hypoxia, but not nutrient restriction impaired endothelium-dependent relaxation at 4 months, and reduced NO mediation of endothelial function at 7 months, in part through reduced NO bio-availability. Distinct effects following reduced maternal oxygen versus nutrition suggest that decreased oxygen supply during fetal life may specifically impact adult vascular function.     

Thiopental inhibits glycine receptor function in acutely dissociated rat spinal dorsal horn neurons

Whole-cell patch-clamp was used to assess the modulatory effect of thiopental (Thio) on glycine (Gly) receptor in mechanically dissociated rat spinal dorsal horn neurons. It was found that Thio inhibited the amplitude, accelerated the desensitization and prolonged the deactivation of Gly-induced currents (I_Gly) in a concentration-dependent manner. In addition, a rebound current occurred after washout of the co-application of Gly and Thio in most neurons tested. Moreover, the inhibitory effect of Thio was not the result of cross-inhibition between Gly and GABA_A receptors. Furthermore, taurine-induced currents, a low-affinity agonist for Gly receptors, were also markedly inhibited by Thio in a similar way to I_Gly. These results indicate that Thio suppresses Gly receptor function and suggest that Thio anesthetic actions might not be mediated by Gly receptors. We speculate that the weak muscle relaxation and the limited analgesic effects observed during Thio anesthesia may attribute to its inhibitory effects on Gly receptors.     

Cyclosporine A inhibits acetylcholinesterase activity in selected parts of the rat brain

Cyclosporine A (CsA) is the major immunosuppressive drug used for organ and neural transplantation and the therapy of selected autoimmune diseases. We investigated the effect of CsA on the activity of acetylcholinesterase (AChE) in the frontal cortex, hippocampus, septum, and basal ganglia. AChE was determined spectrophotometrically with acetylthiocholine as substrate and 5,5-bis-2-nitrobenzoic acid as chromogen. CsA was administered in single doses of 20 or 45 mg/kg perorally; in the case of the higher dose we also performed a repeated administration of CsA in three consecutive doses separated by 24 h intervals. Both lower and higher doses of CsA decreased AChE activity in the frontal cortex and hippocampus to practically the same extent. On the contrary, AChE activity was more diminished in the case of the higher dose of CsA used in the septum and basal ganglia. Repeated administration of the higher dose of CsA did not lead, with the exception of the hippocampus, to a further decrease in AChE activity in the brain structures observed. These findings contribute to rare evidence concerning the interaction of CsA and the cholinergic system in the brain.     

Chronic lithium chloride injection increases glucocorticoid receptor but not mineralocorticoid receptor mRNA expression in rat brain

Lithium has been used clinically for the treatment of bipolar disorders. However, the brain mechanisms, by which lithium acts, are still unclear. An impaired hypothalamic-pituitary-adrenal (HPA) axis has been implicated in the pathogenesis of mood disorders. In this study, we investigated the effects of chronic lithium on the corticosteroid receptors in the brain. Male Wistar rats were injected with LiCl (1.5 mEq/kg) or saline intraperitoneally (i.p.) once a day for 14 days. Twenty-four hours after the last injection, the expressions of mRNA for glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) in the brain were determined by non-radioactive in situ hybridization. Chronic administration of LiCl increased the expression of GR mRNA in the hippocampus and paraventricular nucleus of the hypothalamus (PVN). However, no significant changes were observed in the expression of either MR mRNA in the hippocampus or GR mRNA in the locus ceruleus. Since the hippocampus and PVN mediate negative feedback regulation of the HPA axis, an increased expression of GR mRNA in these regions may normalize HPA axis activity in mood disorders. Thus, the effect of chronic lithium on GR function may be involved in its antimanic and/or prophylactic activity in bipolar disorders.     

Caffeine intake and CYP1A2 variants associated with high caffeine intake protect non-smokers from hypertension

The 15q24.1 locus, including CYP1A2, is associated with blood pressure (BP). The CYP1A2 rs762551 C allele is associated with lower CYP1A2 enzyme activity. CYP1A2 metabolizes caffeine and is induced by smoking. The association of caffeine consumption with hypertension remains controversial. We explored the effects of CYP1A2 variants and CYP1A2 enzyme activity on BP, focusing on caffeine as the potential mediator of CYP1A2 effects. Four observational (n = 16 719) and one quasi-experimental studies (n = 106) including European adults were conducted. Outcome measures were BP, caffeine intake, CYP1A2 activity and polymorphisms rs762551, rs1133323 and rs1378942. CYP1A2 variants were associated with hypertension in non-smokers, but not in smokers (CYP1A2-smoking interaction P = 0.01). Odds ratios (95% CIs) for hypertension for rs762551 CC, CA and AA genotypes were 1 (reference), 0.78 (0.59-1.02) and 0.66 (0.50-0.86), respectively, P = 0.004. Results were similar for the other variants. Higher CYP1A2 activity was linearly associated with lower BP after quitting smoking (P = 0.049 and P = 0.02 for systolic and diastolic BP, respectively), but not while smoking. In non-smokers, the CYP1A2 variants were associated with higher reported caffeine intake, which in turn was associated with lower odds of hypertension and lower BP (P = 0.01). In Mendelian randomization analyses using rs1133323 as instrument, each cup of caffeinated beverage was negatively associated with systolic BP [-9.57 (-16.22, -2.91) mmHg]. The associations of CYP1A2 variants with BP were modified by reported caffeine intake. These observational and quasi-experimental results strongly support a causal role of CYP1A2 in BP control via caffeine intake.     

IL-1 activity is expressed differently during pregnancy in the rat uterine artery than in aortic or uterine tissues

PROBLEM: Uterine artery was shown to be unique in its capacity to change in size and function during pregnancy. As interleukin-1 (IL-1) was shown to be involved in reproduction processes, the aim of this study was to determine the levels of IL-1 activity of the uterine artery tissue in pregnant rat. METHOD OF STUDY: Nine virgins and nine midpregnant rats were selected. Both uterine arteries were obtained, together with reference tissues from aorta and uterus. The levels of IL-I were examined in the above tissues after culturing with media alone (control; CT), and media that contained stimulants like tumor necrosis factor-alpha (TNF-a) or lipopolysaccharide (LPS). IL-1-like activity was evaluated by its capacity to promote the culture growth of 1A-5 and cytotoxic T lymphocyte derived (CTLD) cell lines. This activity was expressed as optical density (OD)/mg protein of the examined organ. RESULTS: Uterine artery tissue, of pregnant rats, cultured in medium alone produced significantly higher levels of IL-1 than uterine artery of virgin animals under the same conditions (16.2 S.E. 1.3 versus 0.6 S.E. 0.05 OD/mg protein, respectively; P < 0.02). Stimulation of uterine artery in vitro by LPS and TNF increased their capacity to secrete IL-1. In comparison with uterine artery, aorta produced higher levels of IL-1 in virgin rats compared with pregnant rats (13.6 S.E. 1.2 versus 1.6 S.E. 0.1; P < 0.02). Stimulation of aorta tissues (from both virgin and pregnant rats) with LPS, in vitro, significantly decreased their capacity to secrete IL-1 (P < 0.04). Stimulation of aorta tissues from virgin rats with TNF-alpha, in vitro, did not change their capacity to secrete IL-1 activity. However, stimulation of aorta tissues from pregnant rats with TNF-alpha decreased the secretion of bioactive IL-1. The levels of IL-1 produced by uterine tissues from virgin and pregnant rats were similar, and stimulation with either LPS or TNF-alpha significantly decreased their capacity to secrete IL-1 (P < 0.04). CONCLUSIONS: The high level of IL-1 activity detected during pregnancy in the uterine artery may suggest its unique involvement in the changes occurring throughout pregnancy in those blood vessels.     

核受体相关因子1在大鼠脑发育过程中的表达研究

目的 观察孤儿核受体相关因子1( Nurr1)在大鼠脑发育过程中蛋白表达的动态变化及其与增殖细胞核抗原(PCNA)的相关关系,探讨 Nurr1表达在神经细胞分化迁移中的意义. 方法 采用石蜡包埋组织切片,免疫组织化学染色及免疫组织化学双重染色. 结果 Nurr1从胚胎12d开始在侧脑室周围出现少量表达,随着发育阳性细胞数目明显增多,而且呈现向脑室远侧分化、迁移的趋势;生后侧脑室周围的阳性细胞明显减少,高量表达出现在生后1～5d的大脑皮层,随着细胞的分化成熟阳性表达又明显减少,成熟的大脑皮层仅见少量阳性表达,与PCNA的对比观察表明,两者表达在不同的部位和不同的细胞中,Nurr1 主要表达在分化、迁移的幼稚神经细胞中,在增殖细胞中不表达. 结论 Nurr1 可能在大鼠脑神经细胞从幼稚到成熟的分化、迁移过程中有调控作用.     

On the mechanism by which theophylline inhibits histamine release from rat mast cells

Theophylline (2.5 mM) did not influence the spontaneous release of histamine but inhibited histamine release induced by antigen, compound 48/80 or phosphatidylserine. The effect on 48/80-induced histamine release could not be reversed by increasing extracellular Ca2+. Exogenous adenosine (10(-8) to 10(-4) M) did not influence spontaneous histamine release or 48/80-induced release but potentiated antigen-induced release. The adenosine potentiation was competitively inhibited by theophylline in concentrations (10(-5) to 10(-4) M) lower than those required to inhibit antigen-induced histamine release in the absence of adenosine. In order to see if endogenous adenosine levels are high enough to potentiate an anaphylactic histamine release in vivo, adenosine was determined in mast cell incubates and in plasma from 4 different strains of rat. The levels were 0.18 to 0.99 microM in plasma, which is sufficient to cause significant potentiation of histamine release, but only 3 x 10(-8) M in mast cell incubates. Theophylline (2.5 mM) increased cAMP levels about 100%, whereas adenosine (10(-5) M) had little effect on cAMP and cGMP levels. However, when incubated together, adenosine could inhibit the theophylline-induced increase in cAMP levels but not the inhibition of histamine release. It is concluded that the effect of low concentrations of theophylline could be due partly to antagonism of adenosine effects. In addition, in higher doses, theophylline appears to exert an inhibitory action that is unrelated to cyclic nucleotides, extracellular calcium and adenosine.     

Neuroendocrine mechanisms of change in food intake during pregnancy: a potential role for brain oxytocin

During pregnancy body weight, and particularly adiposity, increase, due to hyperphagia rather than decreased energy metabolism. These physiological adaptations provide the growing fetus(es) with nutrition and prepare the mother for the metabolically-demanding lactation period following birth. Mechanisms underlying the hyperphagia are still poorly understood. Although the peripheral signals that drive appetite and satiety centers of the brain are increased in pregnancy, the brain may become insensitive to their effects. For example, leptin secretion increases but hypothalamic resistance to leptin actions develops. However, several adaptations in hypothalamic neuroendocrine systems may converge to increase ingestive behavior. Oxytocin is one of the anorectic hypothalamic neuropeptides. Oxytocin neurons, both centrally-projecting parvocellular oxytocin neurons and central dendritic release of oxytocin from magnocellular neurons, may play a key role in regulating energy intake. During feeding in non-pregnant rats, magnocellular oxytocin neurons, especially those in the supraoptic nucleus, become strongly activated indicating their imminent role in meal termination. However, in mid-pregnancy the excitability of these neurons is reduced, central dendritic oxytocin release is inhibited and patterns of oxytocin receptor binding in the brain alter. Our recent data suggest that lack of central oxytocin action may partly contribute to maternal hyperphagia. However, although opioid inhibition is a major factor in oxytocin neuron restraint during pregnancy and opioids enhance food intake, an increase in opioid orexigenic actions were not observed. While changes in several central input pathways to oxytocin neurons are likely to be involved, the high level of progesterone secretion during pregnancy is probably the ultimate trigger for the adaptations.     

Chronic intrahypothalamic infusions of insulin or insulin antibodies alter body weight and food intake in the rat.

In Experiment 1, one-week infusion of insulin (0.15, 1.5, or 15.0 microU/hr) into the ventromedial hypothalamus (VMH) of rats reduced body weight (BW) and nighttime food intake (FI). While 0.15 microU/h decreased daytime FI, 1.5 microU/h increased daytime FI and 15.0 microU/h left daytime FI unchanged. Total daily FI was decreased by the two highest doses. In Experiment 2, intra-VMH infusion of specific insulin antibodies (1.5 microUeq/h) increased BW and FI, while C-peptide antibodies were ineffective. In Experiment 3a, intracerebroventricular infusions of insulin failed to decrease FI and BW comparably to similar intrahypothalamic infusions. In Experiment 3b, intra-VMH insulin was infused via cannulae that bypassed the cerebral ventricles. The decrease in FI and BW was comparable to that observed when insulin was infused via cannulae that penetrated a ventricle. Histology from animals used in Experiments 1-3 indicates that optimum sites for insulin-induced changes in BW and FI in the hypothalamus lie in an area that includes portions of the paraventricular, arcuate, dorsomedial, and ventromedial nuclei.     

Changes in noradrenaline release and in beta receptor number in rat hippocampus following long-term treatment with theophylline or L-phenylisopropyladenosine

The administration of a stable adenosine analogue, L-N6-phenylisopropyladenosine (L-PIA, 0.3 mg/kg i. p.), caused a decrease in the accumulation of L-DOPA in the rat hippocampus after blockade of aromatic amino acid decarboxylase by NSD 1015 (150 mg/kg). Conversely, the adenosine receptor antagonist theophylline (15 mg/kg) increased the L-DOPA accumulation. In slices from rat hippocampus L-PIA causes an inhibition of the stimulation-evoked release of [3H]-noradrenaline (NA). The magnitude of this effect was enhanced after 1 week treatment with theophylline (15 mg/kg/day). The number of beta-adrenoceptors in the rat hippocampus, measured by binding of [3H]-dihydroalprenolol was significantly reduced after theophylline treatment, and tended to be higher after L-PIA treatment. The results show that activation of adenosine receptors in vivo causes a decreased synthesis of NA in the rat hippocampus. The reason may be a reduced firing-rate of the NA-neurons. Theophylline, by contrast, enhanced the synthesis, possibly indicating a role for endogenous adenosine in the regulation of NA-turnover. Long-term treatment with these drugs caused adaptive changes in the presynaptic adenosine receptor activity and in the number of beta-adrenoceptors.