Effect of pentoxifylline on endothelaemia and hypothalamic-pituitary-adrenocortical axis activation in female rats under stress exposure

Endothelial dysfunction may belong to negative consequences of stress exposure accompanied by activation of several stress systems including the hypothalamic-pituitary-adrenocortical (HPA) axis. The present experiments were aimed at testing the hypotheses that i) immobilization (IMO) stress results in sustained increase in endothelaemia for 24 h and that ii) pentoxifylline, a drug with endothelium protective properties, attenuates the rise in endothelaemia and HPA axis activation in female rats as shown previously in males. Circulating endothelial cells increased immediately after the IMO for 2 h, returned back to control levels at 12 h and increased again at 24 h. Stress-induced rise in adrenocorticotropic hormone (ACTH) and corticosterone levels was particularly high immediately after the IMO. Pretreatment with pentoxifylline (20 mg/kg subcutaneously for 7 days) attenuated the rise in endothelaemia and adrenal corticosterone measured at 24 h following IMO. Plasma levels of ACTH and proopiomelanocortin gene expression in the anterior pituitary were not affected by pentoxifylline treatment. The present results indicate that IMO stress in female rats induces a biphasic rise in endothelaemia early at the time of stress exposure and than 24 h thereafter. Based on these data and our previous study we can conclude that intensive stress has a negative influence on endothelial cells in both sexes and no gender differences seem to be present in the protective action of pentoxifylline.     

下丘脑-垂体-肾上腺皮质轴应激反应的中枢控制

应激反应是所有生物对紧张性事件的适应性反应,对生物的存活具有十分重要的意义。应激反应的主要特征是下丘脑－垂体－肾上腺皮质（ＨＰＡ）轴激活。ＨＰＨ轴激活的呆区控制十分复杂。海马参与整合感知的信息、解释环境信息的意义及定调行为反应和神经内分泌反应。杏仁核是应激性行为反应以及自主神经和神经内分泌反应的行旅地部位。下丘脑室６ 有直接激活ＨＰＡ轴的作用。负反馈机制、下丘脑局部回路和细胞因子也可能参与了调节Ｈ     

Stress-induced rise in endothelaemia, von Willebrand factor and hypothalamic-pituitary-adrenocortical axis activation is reduced by pretreatment with pentoxifylline.

Stress is considered to be a risk factor of several diseases. The following hypotheses were tested: (1) single exposure to an intensive stressor is followed by endothelial stimulation and/or damage to endothelial cells, (2) potential stress-induced endothelial cell damage is reduced by repeated pretreatment with pentoxifylline and (3) pentoxifylline treatment modifies neuroendocrine activation during stress reflected by changes in hypothalamic-pituitary-adrenocortical (HPA) axis function. Rats were treated with saline or pentoxifylline (20 mg/kg, s.c.) once daily for 7 days and then exposed to single immobilization stress for 20 or 120 min. In saline pretreated rats, stress exposure was followed by a rise in endothelaemia, von Willebrand factor concentrations, adrenocorticotropic hormone (ACTH) and corticosterone release, as well as by enhanced gene expression of hypothalamic corticotropin releasing factor (CRH). Stress-induced changes were reduced by pretreatment with pentoxifylline. Significant inhibition was observed in endothelaemia, plasma ACTH and corticosterone concentration in the adrenals. Thus, signs of endothelial injury as well as stress-induced hormone levels were reduced by pretreatment with pentoxifylline, although there is no evidence for a causal relationship. This protective action of pentoxifylline might be of benefit in the prevention and therapy of some stress-related disorders.     

Repeated citalopram treatment but not stress exposure attenuates hypothalamic-pituitary-adrenocortical axis response to acute citalopram injection

Many experimental, clinical and epidemiological studies have shown a direct connection between exposure to stress or adverse life events and disease, but little is known about the effect of stress on the action of drugs. The aim of this study was to test the hypothesis that previous exposure to stress changes the action of the antidepressant drug citalopram (10 mg/kg, i.p.) on hypothalamic-pituitary-adrenocortical (HPA) axis function, gene expression of selected neuropeptides and serotonin reuptake. Three different stress models were used, which included immobilization, restraint and unpredictable stress stimuli. Samples of plasma for hormone measurement were taken from conscious cannulated animals. Changes in corticotropin-releasing hormone (CRH) and proopiomelanocortin (POMC) gene expression in the paraventricular nucleus of the hypothalamus and the anterior pituitary, respectively, and the ability of citalopram to inhibit serotonin reuptake were investigated. The exposure to three different stress models did not influence citalopram action on individual parameters of HPA axis and on serotonin reuptake. On the other hand, repeated administration of the drug led to significant attenuation of ACTH and CRH mRNA responses. The present results allow to suggest that the stressors used did not influence serotonergic neurotransmission to the extent that would modify HPA axis response to citalopram challenge. Activation of HPA axis by acute citalopram treatment was found to be accompanied by increased CRH gene expression in the hypothalamus. Repeated administration of the drug led to the development of tolerance to activation of central and peripheral components of HPA axis, but not to serotonin reuptake inhibition.     

Genetic variation in the hypothalamic-pituitary-adrenocortical axis regulatory factor, T-box 19, and the angry/hostility personality trait

Neurotic personality traits are important factors in several psychiatric disorders and suicidal behavior. Here, we have investigated the existence of potential relationships between neurotic personality traits and genetic variation. Non-suicidal parents derived from trios (suicide attempter and both parents) and non-suicidal volunteers, examined by the Neuroticism, Extraversion and Openness (NEO) Personality Inventory - Revised (NEO PI-R), were divided into screening and replication samples. The screening sample (n= 127) was used to select potential relationships between neurotic personality traits and genetic variation among 130 single nucleotide polymorphisms (SNPs). Screening (analysis of variance) with regard to the personality dimension neuroticism indicated potential relationships at three different loci. More detailed analysis of these three SNPs at NEO PI-R facet level indicated four potential relationships. T-test analysis in the replication sample (n= 617) was used to retest the relationships indicated during screening. One of those relationships was confirmed in the replication sample (P= 0.0052; Bonferroni correction), indicating that genetic variation at the human T-box 19 (TBX19) locus is related to the personality trait angry/hostility. Furthermore, using analysis of haplotypes among trios by transmission disequilibrium test and its extension, the family-based association test, overtransmission of a haplotype GAC at the TBX19 locus was associated with increased angry/hostility scores among suicide attempters (P= 0.009; Bonferroni correction). This is to our knowledge the first report on the association of the angry hostility personality trait with genetic variation at the TBX19 locus, an important regulator of the hypothalamic-pituitary-adrenocortical axis.     

Cocaine-mediated microglial activation involves the ER stress-autophagy axis

Cocaine abuse leads to neuroinflammation, which, in turn, contributes to the pathogenesis of neurodegeneration associated with advanced HIV-1 infection. Autophagy plays important roles in both innate and adaptive immune responses. However, the possible functional link between cocaine and autophagy has not been explored before. Herein, we demonstrate that cocaine exposure induced autophagy in both BV-2 and primary rat microglial cells as demonstrated by a dose- and time-dependent induction of autophagy-signature proteins such as BECN1/Beclin 1, ATG5, and MAP1LC3B. These findings were validated wherein cocaine treatment of BV-2 cells resulted in increased formation of puncta in cells expressing either endogenous MAP1LC3B or overexpressing GFP-MAP1LC3B. Specificity of cocaine-induced autophagy was confirmed by treating cells with inhibitors of autophagy (3-MA and wortmannin). Intriguingly, cocaine-mediated induction of autophagy involved upstream activation of 2 ER stress pathways (EIF2AK3- and ERN1-dependent), as evidenced by the ability of the ER stress inhibitor salubrinal to ameliorate cocaine-induced autophagy. In vivo validation of these findings demonstrated increased expression of BECN1, ATG5, and MAP1LC3B-II proteins in cocaine-treated mouse brains compared to untreated animals. Increased autophagy contributes to cocaine-mediated activation of microglia since pretreatment of cells with wortmannin resulted in decreased expression and release of inflammatory factors (TNF, IL1B, IL6, and CCL2) in microglial cells. Taken together, our findings suggest that cocaine exposure results in induction of autophagy that is closely linked with neuroinflammation. Targeting autophagic proteins could thus be considered as a therapeutic strategy for the treatment of cocaine-related neuroinflammation diseases.     

Catecholaminergic regulation of the hypothalamic-pituitary-adrenocortical activity.

The significance and site of adrenergic receptors involved in the control of the hypothalamic-pituitary-adrenal axis (HPA) activity was assessed indirectly by estimation of serum corticosterone levels 1 h after drug administration to conscious rats. Adrenergic drugs were given intracerebroventricularly (icv) and intraperitoneally (ip), the antagonists 15 min prior to the agonists. Noradrenaline, adrenalin and isoproterenol given by either route increased dose-dependently the serum corticosterone levels. The corticosterone response to icv noradrenaline was almost abolished by icv pretreatment with propranolol, a beta-adrenergic antagonist, and yohimbine, and alpha 2-receptor blocker, and was also considerably reduced by prazosin, an alpha 1-adrenergic antagonist. When given ip, these antagonists did not significantly influence the noradrenaline induced corticosterone response, which suggests a suprapituitary site of action of noradrenaline in stimulation of the HPA. The corticosterone response to icv adrenalin was suppressed by prazosin given by either route. The corticosterone response to ip adrenalin was almost abolished by pretreatment with yohimbine, and also significantly diminished by propranolol given by the same route. The increase in corticosterone secretion, induced by isoproterenol given by either route, was abolished by ip injection of propranolol. These results indicate that noradrenaline stimulates the HPA via alpha- and beta-adrenergic receptors, mainly at the suprapituitary level. Adrenalin increases that activity both via central and pituitary alpha- and beta-adrenoceptors. Isoproterenol activates the HPA by stimulation of pituitary beta-receptors.     

Time-dependent mediators of HPA axis activation following live Escherichia coli

The hypothalamus-pituitary-adrenal (HPA) axis is activated during an immune challenge to liberate energy and modulate immune responses via feedback and regulatory mechanisms. Inflammatory cytokines and prostaglandins are known contributors to HPA activation; however, most previous studies only looked at specific time points following LPS administration. Since whole bacteria have different immune stimulatory properties compared with LPS, the aim of the present studies was to determine whether different immune products contribute to HPA activation at different times following live Escherichia coli challenge. Sprague-Dawley rats were injected intraperitoneally with E. coli (2.5 × 10(7) CFU) and a time course of circulating corticosterone, ACTH, inflammatory cytokines, and PGE(2) was developed. Plasma corticosterone peaked 0.5 h after E. coli and steadily returned to baseline by 4 h. Plasma PGE(2) correlated with the early rise in plasma corticosterone, whereas inflammatory cytokines were not detected until 2 h. Pretreatment with indomethacin, a nonselective cyclooxygenase inhibitor, completely blocked the early rise in plasma corticosterone, but not at 2 h, whereas pretreatment with IL-6 antibodies had no effect on the early rise in corticosterone but attenuated corticosterone at 2 h. Interestingly, indomethacin pretreatment did not completely block the early rise in corticosterone following a higher concentration of E. coli (2.5 × 10(8) CFU). Further studies revealed that only animals receiving indomethacin prior to E. coli displayed elevated plasma and liver cytokines at early time points (0.5 and 1 h), suggesting prostaglandins suppress early inflammatory cytokine production. Overall, these data indicate prostaglandins largely mediate the early rise in plasma corticosterone, while inflammatory cytokines contribute to maintaining levels of corticosterone at later time points.     

Contribution of RAGE axis activation to the association between metabolic syndrome and cancer

Molecular and Cellular Biochemistry - Far beyond the compelling proofs supporting that the metabolic syndrome represents a risk factor for diabetes and cardiovascular diseases, a growing body of...     

Inhomogeneous hippocampal activation along the rostrocaudal axis in mice after exploration of novel environment

Levels of the c-Fos protein expression in neurons were used as an index of neural activation in the hippocampus of C57BL/6 mice after their exploration of novel environments. C-Fos expression was measured at 8 levels along the rostrocaudal axis of the hippocampus. In Experiment 1, C57BL/6 mice were trained in a modified 8-arm radial maze to find the entry to a home cage through a target arm (1 day, 6 trials). Animals of control group were trained to enter the home cage through an isolated arm. In mice trained in 8-arm maze, functional rostrocaudal inhomogeneity of hippocampus was found. C-Fos expression was increased, mainly, in the caudal parts of CA1, CA3 and dentate gyrus as compared to the control group. In Experiment 2, C57BL/6 mice were tested (1 day, 6 trials) in a novel open-field arena. In this case, c-Fos activity was increased in CA1 (to a greater extent in the caudal than in rostral parts) and CA3 and dentate gyrus (equally in rostrocaudal direction). Significant positive correlations between the exploration activity and density of c-Fos positive cells were found in both experiments. The findings suggest that exploration in novel environment differentially affects the hippocampal subfields along the hippocampal rostrocaudal axis.     

Function of hypothalamic-pituitary-adrenocortical system in hypertensive rats of ISIAH strain

Functional activity of hypothalamic-pituitary-adrenocortical axis has been studied under control and restraint stress conditions in rats with inherited stress-sensitive arterial hypertension (ISIAH strain) and in normotensive WAG (Wistar Albino Glaxo) strain. The levels of hypothalamic CRH-mRNA (in control and 2 hrs stress), pituitary and plasma ACTH and plasma corticosterone (in control and after 5, 15 or 30 min of restraint stress), were evaluated. Hypothalamic CRH-mRNA level was found to be approximately the same in the control rats of both strains. In control conditions, the pituitary and plasma ACTH content in ISIAH rats was significantly lower whereas the corticosterone level in the plasma differed from each other in both strain. The restraint stress resulted in a statistically significant increase of the CRH-mRNA in ISIAH rats and not in the WAG rats. Moreover, in spite of the lower ACTH level in stressed ISIAH rats, the corticosterone blood plasma concentration in hypetensive rats was significantly higher. The data obtained confirm the idea that the stress-dependent hypertension might be related to an enhanced sensitivity of the main endocrine links involved in the stress response organization.     

Short ACTH test in assessing hypothalamic-pituitary-adrenocortical function.

The adrenocortical response to the simple 30-minute ACTH stimulation test was compared with the hypothalamic-pituitary-adrenocortical (HPA) response to insulin-induced hypoglycaemia in 25 patients with various degrees of hypothalamic-pituitary malfunction. The correlations between the increase in plasma cortisol during insulin hypoglycaemia and that during ACTH stimulation (r = 0-66) and between peak plasma cortisol levels during the two tests (r = 0-90) were highly significant. Peak plasma cortisol levels in individual patients were similar on both tests, no patient showing any major discrepancy between the two test results. Thus the simple 30-minute ACTH stimulation test seems to be reliable in detecting imparied HPA function.     

A novel beta-catenin-binding protein inhibits beta-catenin-dependent Tcf activation and axis formation

beta-Catenin is efficiently phosphorylated by glycogen synthase kinase-3beta in the Axin complex in the cytoplasm, resulting in the down-regulation. In response to Wnt, beta-catenin is stabilized and translocated into the nucleus where it stimulates gene expression through Tcf/Lef. Here we report a novel protein, designated Duplin (for axis duplication inhibitor), which negatively regulates the function of beta-catenin in the nucleus. Duplin was located in the nucleus. Duplin bound directly to the Armadillo repeats of beta-catenin, thereby inhibiting the binding of Tcf to beta-catenin. It did not affect the stability of beta-catenin but inhibited Wnt- or beta-catenin-dependent Tcf activation. Furthermore, expression of Duplin in Xenopus embryos inhibited the axis formation and beta-catenin-dependent axis duplication, and prevented the beta-catenin's ability to rescue ventralizing phenotypes induced by ultraviolet light irradiation. Thus, Duplin is a nuclear protein that inhibits beta-catenin signaling.     

Assessing behavioural effects of chronic HPA axis activation using conditional CRH-overexpressing mice

The corticotropin-releasing hormone (CRH) and its cognate receptors have been implicated in the pathophysiology of stress-related disorders. Hypersecretion of central CRH and elevated glucocorticoid levels, as a consequence of impaired feedback control, have been shown to accompany mood and anxiety disorders. However, a clear discrimination of direct effects of centrally hypersecreted CRH from those resulting from HPA axis activation has been difficult. Applying a conditional strategy, we have generated two conditional CRH-overexpressing mouse lines: CRH-COE ( Del ) mice overexpress CRH throughout the body, while CRH-COE ( APit ) mice selectively overexpress CRH in the anterior and intermediate lobe of the pituitary. Both mouse lines show increased basal plasma corticosterone levels and consequently develop signs of Cushing's syndrome. However, while mice ubiquitously overexpressing CRH exhibited increased anxiety-related behaviour, overexpression of CRH in the pituitary did not produce alterations in emotional behaviour. These results suggest that chronic hypercorticosteroidism alone is not sufficient to alter anxiety-related behaviour but rather that central CRH hyperdrive on its own or in combination with elevated glucocorticoids is responsible for the increase in anxiety-related behaviour. In conclusion, the generated mouse lines represent valuable animal models to study the consequences of chronic CRH overproduction and HPA axis activation.     

Studies on the involvement of histamine in the hypothalamic-pituitary-adrenal axis activation induced by nerve growth factor

Nerve growth factor (NGF) has been shown to stimulate the hypothalamic-pituitary-adrenocortical (HPA) axis. Since NGF induces the release of histamine from mast cells and in consideration of the fact that histamine is an HPA axis activator, we investigated whether NGF adrenocortical stimulation is mediated by histamine. To accomplish with it, the H1 histamine antagonist promethazine and the H2 antagonists metiamide and zolantidine were used in freely-moving cannulated rats. The increase in plasma corticosterone concentration induced by histamine administration was prevented completely by promethazine pretreatment but was unaffected by the H2 antagonists. Neither H1 nor H2 antagonists affected the adrenocortical stimulation induced by NGF administration. Moreover, since mast cells are reportedly present in the rat adrenal gland and the locally released histamine mediates the release of adrenaline which, in turn, stimulates glucocorticoid synthesis and secretion, we studied the effect of NGF on basal and ACTH-stimulated corticosterone release from in vitro isolated quartered adrenal glands and collagenase-dispersed adrenal cells. The results from these in vitro experiments have indicated that NGF modified neither spontaneous nor stimulated corticosterone release. Altogether these observations suggest that endogenous histamine is unlikely to be involved in HPA axis stimulation by NGF and reinforce the previously proposed concept of an active participation of NGF in the control of adrenocortical activity.     

Activation of hypothalamic-pituitary-adrenocortical system as important gastroprotective component of stress reaction

The review is focused on the action of glucocorticoids released during activation of hypothalamic-pituitary-adrenocortical axis, on the susceptibility of gastric mucosa to injury. The data support the idea that glucocorticoids produced in response to acute stress or other ulcerogenic stimuli have a gastroprotective action but not ulcerogenic one as it has generally been considered for some decades. It has been shown that gastroprotective action of glucocorticoids may be mediated by multiple actions, including maintenance of glucose homeostasis, gastric mucosal blood flow, mucus production and attenuation of enhanced gastric motility and microvascular permeability. For maintenance of gastric mucosal integrity glucocorticoids may cooperate with other gastroprotective factors. Glucocorticoid hormones exert a pivotal role in the maintenance of gastric mucosal integrity in the case of impaired gastroprotective mechanisms provided by prostaglandins, nitric oxide and capsaicin-sensitive sensory neurons. These findings indicate that activation of hypothalamic-pituitary-adrenocortical system could be considered as a significant hormonal gastroprotective component of stress reaction and therefore glucocorticoid hormones are natural gastroprotective factors.     

Vasopressin pressor receptor-mediated activation of HPA axis by acute ethanol stress in rats

The plasma arginine vasopressin (AVP), ACTH, and corticosterone levels and the hypothalamic corticotropin-releasing hormone (CRH) content were measured after oral administration of 1 ml of 75% ethanol to rats, a model known to induce acute gastric erosions and stress. Elevated plasma AVP, ACTH, and corticosterone levels were detected 1 h after ethanol administration. Treatment with the vasopressin pressor (V(1)) receptor antagonist [d(CH(2))(5)Tyr(Me)-AVP] before ethanol administration significantly reduced the ACTH and corticosterone level increases. A higher hypothalamic CRH content was measured at 30 or 60 min after ethanol administration. V(1) receptor antagonist injection, 5 min before ethanol administration, inhibited the rise in hypothalamic CRH content. The protein synthesis blocker cycloheximide prevented the hypothalamic CRH content elevation after stress. The AVP-, CRH-, and AVP + CRH-induced in vitro ACTH release in normal anterior pituitary tissue cultures was also prevented by pretreatment with the V(1) receptor antagonist. The results support the hypothesis that stress-induced AVP may not only act directly on the ACTH producing anterior pituitary cells but also indirectly at the hypothalamic level via the synthesis and release of CRH.