Alterations in behavior, steroid hormones and natural killer cell activity in male transgenic TGF alpha mice

ErbB receptor signaling in astrocytes: a mediator of neuron-glia communication in the mature central nervous system

Astrocytes are now recognized as active players in the developing and mature central nervous system. Each astrocyte contacts vascular structures and thousands of synapses within discrete territories. These cells receive a myriad of inputs and generate appropriate responses to regulate the function of brain microdomains. Emerging evidence has implicated receptors of the ErbB tyrosine kinase family in the integration and processing of neuronal inputs by astrocytes: ErbB receptors can be activated by a wide range of neuronal stimuli; they control critical steps of glutamate-glutamine metabolism; and they regulate the biosynthesis and release of various glial-derived neurotrophic factors, gliomediators and gliotransmitters. These key properties of astrocytic ErbB signaling in neuron-glia interactions have significance for the physiology of the mature central nervous system, as exemplified by the central control of reproduction within the hypothalamus, and are also likely to contribute to pathological situations, since both dysregulation of ErbB signaling and glial dysfunction occur in many neurological disorders.

Stress-related endocrinological and psychopathological effects of short- and long-term 50Hz electromagnetic field exposure in rats

It is believed that different electromagnetic fields do have beneficial and harmful biological effects. The aim of the present work was to study the long-term consequences of 50 Hz electromagnetic field (ELF-EMF) exposure with special focus on the development of chronic stress and stress-induced psychopathology. Adult male Sprague-Dawley rats were exposed to ELF-EMF (50 Hz, 0.5 mT) for 5 days, 8h daily (short) or for 4-6 weeks, 24h daily (long). Anxiety was studied in elevated plus maze test, whereas depression-like behavior of the long-treated group was examined in the forced swim test. Some days after behavioral examination, the animals were decapitated among resting conditions and organ weights, blood hormone levels as well as proopiomelanocortin mRNA level from the anterior lobe of the pituitary gland were measured. Both treatments were ineffective on somatic parameters, namely none of the changes characteristic to chronic stress (body weight reduction, thymus involution and adrenal gland hypertrophy) were present. An enhanced blood glucose level was found after prolonged ELF-EMF exposure (p=0.013). The hormonal stress reaction was similar in control and short-term exposed rats, but significant proopiomelanocortin elevation (p<0.000) and depressive-like behavior (enhanced floating time; p=0.006) were found following long-term ELF-EMF exposure. Taken together, long and continuous exposure to relatively high intensity electromagnetic field may count as a mild stress situation and could be a factor in the development of depressive state or metabolic disturbances. Although we should stress that the average intensity of the human exposure is normally much smaller than in the present experiment.

Gene x environment effects: stress and memory dysfunctions caused by stress and gonadal factor irregularities during puberty in control and TGF-alpha hypomorphic mice

The maturation of many neural functions occurs during puberty. An abnormal development of these processes, in the context of genetic vulnerability, may result in sex- and age-dependent penetrance of neuropsychiatric disorders. Reduced transforming growth factors-alpha (TGF-alpha) expression in Waved-1 (Wa-1) mice impairs the stress response and fear memory in adult males, but are absent or far less prominent in adult females and in pubertal males. Gonadectomy around the onset of puberty, when the mutant anatomical and behavioral phenotypes are undetectable, results in significant gene x environment effects. Adult control males show reduced physiological stress response as a result of gonadectomy, but not adult Wa-1 males. In females, pubertal gonadectomy elevates specific anxiety parameters only in adult control mice. There also are general sex-specific effects of pubertal gonadectomy on adult stress and fear memory. Surgical stress alone also induces sex- and genotype-dependent effects, albeit in different behavioral parameters than those affected by gonadectomy. We conclude that normal development of stress and memory processes is reliant on the levels of stress and gonadal factors during puberty, the effects of which are modulated by genetic factors and sex.

Transforming growth factor-α induces sex-specific neurochemical imbalance in the stress- and memory-associated brain structures

Transforming growth factor-alpha (TGFalpha) is a well-known regulator of many developmental processes. However, its role in adult nervous system is yet unclear. Studies have shown that TGFalpha can regulate stress and memory behavior in adult mice. When TGFalpha is reduced in Waved-1 (Wa-1) mutant mice, the stress response and memory are impaired predominantly in males and only after puberty. To determine the neurochemical changes resulting from the reduced TGFalpha levels that could explain the reported behavioral outcomes, biogenic amine and amino acid levels were determined in the brain regions associated with stress and memory. Interestingly, sex-specific alterations in neurochemical levels were detected, including elevated noradrenaline and reduced glutamate levels in striatum of Wa-1 males, increased noradrenaline and reduced serotonin metabolite levels in hippocampus of Wa-1 females, reduced serotonin metabolite levels in cortex and amygdala of Wa-1 females, and reduced noradrenaline, dopamine, serotonin, glutamate and glycine levels in hypothalamus of Wa-1 females compared to their respective controls. Increased dopamine turnover in cortex and reduced dopamine and serotonin turnover in amygdala were observed in both male and female Wa-1 mice. The data indicate sex-specific alterations of specific neurochemicals as a result of reduced TGFalpha expression, which may underlie sex-dependent stress response and memory impairment in Wa-1 mice.

Postpubertal sex differentiation of forebrain structures and functions depend on transforming growth factor-alpha

Sex- and age-associated deficits in brain structure and behavior are reported in a number of neuropsychiatric disorders. Although genetic and environmental factors are thought to contribute to the pathogenesis, there are only few examples in clinical or experimental systems that have identified specific causes. Here, we report that transforming growth factor-alpha (TGFalpha) may regulate sex- and age-dependent development of forebrain structures and associated neural functions after puberty. Waved-1 (Wa-1) mice inherit an autosomal recessive, spontaneous mutation that results in a postnatal reduction in TGFalpha gene expression. The assessment of forebrain structures using a three-dimensional magnetic resonance microscopy indicated ventricular enlargement and striatal reduction in both male and female Wa-1 adult mice, with Wa-1 males exhibiting a more severe phenotype. In contrast, the hippocampal volume was reduced only in adult Wa-1 males. Similarly, behavioral analyses showed impaired auditory and contextual fear learning in adult Wa-1 males only, whereas abnormal stress response was expressed by both male and female adult Wa-1 mice. Interestingly, all behavioral deficits were absent before full sexual maturation, despite some slight forebrain structural abnormalities. These results suggest that TGFalpha may regulate postpubertal, sex differentiation in ventricular and periventricular anatomy and associated behavior, affecting predominantly males. In particular, the adult male-specific reduction in hippocampal volume may reflect an age- and sex-specific regulation of stress homeostasis and fear learning. Furthermore, a lack of a behavioral phenotype, despite anatomical alterations in peripubertal Wa-1 mice, suggests that analysis of certain neuroanatomical features at puberty may predict neurobehavioral deficits in adulthood.

Stressors affect the response of male and female rats to clomipramine in a model of behavioral despair (forced swim test)

Aim of the present study was to evaluate the effects of physical stressors (electric foot-shocks) on effect of the antidepressant drug, clomipramine and plasma corticosterone levels in male and female rats tested in a model of behavioral despair (forced swim test,). Male and female rats of the Wistar strain were injected with clomipramine (50 mg/kg, i.p.) or saline. A group of animals also received electric shocks of different intensity and duration of 24, 5 and 1 h before being subjected to forced swim test. At the end of behavioral procedures, vaginal smears were assessed in all female animals and data on immobility time were plotted according to the ovarian cycle phase. After decapitation, corticosterone plasma levels were measured by radioimmunoassay in both male and female rats. Application of mild shocks (5 ms, 0.1 mA) significantly reduced immobility time in forced swim test of untreated male rats and augmented clomipramine effect on this parameter. Moderate shocks of higher intensity or duration (5 ms, 1.0 mA) also resulted in decreased immobility time of untreated male rats, but in reduced effect of clomipramine treatment. Furthermore, application of severe shocks (10 ms, 1.0 mA) increased the immobility time in untreated animals and totally abolished clomipramine effect in forced swim test. Untreated non-shocked female rats in proestrous and estrous phases exhibited a longer immobility time as compared to diestrous animals. Immobility time appeared to be generally higher when mild, moderate or severe shocks were applied prior to behavioral testing in proestrous and estrous animals, while the behavioral response of diestrous and metestrous animals did not differ from that of controls. Clomipramine effect on immobility time was generally reduced by application of shocks of every strengths. Stress-induced plasma corticosterone levels surge correlated with intensity and duration of shocks in both male and female rats, but clomipramine treatment generally blunted the hormonal response. However, severe shocks were followed by a surge of plasma corticosterone levels in both male and female clomipramine-treated rats. These results demonstrate that duration and intensity of stressful stimuli may deeply affect the behavioral response of rats in forced swim test and influence clomipramine effect in this behavioral model depending on gender-based variables, probably of the hormonal type. Plasma corticosterone levels correlate with the behavioral response to clomipramine treatment suggesting that reactivity of hypothalamus-pituitary-adrenal axis to stress may be involved in the antidepressant effect of this drug.

Elevated serum cytokines correlated with altered behavior, serum cortisol rhythm, and dampened 24-hour rest-activity patterns in patients with metastatic colorectal cancer

PURPOSE

Incapacitating symptom burden in cancer patients contributes to poor quality of life (QOL) and can influence treatment outcomes because of poor tolerance to therapy. In this study, the role of circulating cytokines in the production symptoms in cancer patients is evaluated.

EXPERIMENTAL DESIGN

Eighty patients with metastatic colorectal cancer with either normal (group I, n = 40) or dampened (group II, n = 40) 24-hour rest/activity patterns measured by actigraphy were identified. Actigraphy patterns were correlated with QOL indices, serum cortisol obtained at 8:00 a.m. and 4:00 p.m. and with serum levels of transforming growth factor-alpha, tumor necrosis factor-alpha, and interleukin 6 (IL-6) obtained at 8:00 a.m. and analyzed in duplicate by ELISA. Cytokine levels and survival were also correlated.

RESULTS

Group II patients had significantly higher pre treatment levels of all three cytokines, displayed significantly poorer emotional and social functioning, had higher fatigue, more appetite loss, and poorer performance status compared with group I patients. Transforming growth factor-alpha (TGF-alpha) and IL-6 were significantly increased in the patients with WHO performance status >1 and in those with appetite loss. Fatigue was significantly associated with elevated TGF-alpha only. IL-6 was increased in those patients with extensive liver involvement and multiple organ replacement, and it was significantly correlated with dampened cortisol rhythm. In a multivariate analysis, IL-6 was correlated with poor treatment outcome.

CONCLUSIONS

Significant correlations were found between serum levels of TGF-alpha and IL-6, circadian patterns in wrist activity and serum cortisol and tumor-related symptoms in patients with metastatic colorectal cancer. These data support the hypothesis that some cancer patient's symptoms of fatigue, poor QOL, and treatment outcome are related to tumor or host generated cytokines and could reflect cytokine effects on the circadian timing system. This interplay between cytokine signaling pathways, the hypothalamic-pituitary-adrenal axis, the autonomic nervous system, and efferent pathways of the suprachiasmatic nucleus that control circadian physiology, opens the way to new rational interventions for symptom management in cancer patients.

Sex differences in expression of transforming growth factor-α and epidermal growth factor receptor mRNA in waved-1 and C57Bl6 mice

A reduction of transforming growth factor-alpha (TGFalpha) expression in the spontaneous Waved-1 (Wa-1) mutant mouse causes specific behavioral and anatomical changes, including reduced fear learning and stress response and enlarged lateral ventricles. These alterations are observed predominantly in male Wa-1 mice after puberty. We hypothesized that regional differences in the expression of TGFalpha and its receptor, epidermal growth factor receptor (EGFR), may regulate the sexual dimorphism of the brain structures and functions during postnatal development. In general, fear learning-associated structures, including hippocampus and amygdala, showed maximum expression before puberty, regardless of genotype. In contrast, an overall temporal delay in the rise of both transcript levels, which peaked around or after puberty onset, was observed for the major stress regulatory hypothalamo-pituitary-adrenal axis. This pattern of expression was reversed for amygdala EGFR and hypothalamus TGFalpha and EGFR transcripts in males. When regional TGFalpha expression was compared between control and Wa-1 mice, far more complex patterns than expected were observed that revealed sex- and structure-dependent differences. In fact, the amygdala, hypothalamus, and pituitary TGFalpha expression pattern in Wa-1 exhibited a clear sex dependency across various age groups. Surprisingly, there was no compensatory up-regulation of the EGFR transcript in Wa-1 mice. The observed expression patterns of the TGFalpha signaling system during normal development and in the Wa-1 mutant mouse suggest complex sex- and age-dependent transcription regulatory mechanisms.

Endocrine and lymphoproliferative response changes produced by social stress in mice

Daily dyadic resident-intruder encounters and uninterrupted cohabitation in pairs were used to assess the impact of different durations (5 and 15 days) of dominance and subordination experiences on splenic lymphoproliferative responses in male OF1 strain mice. HPA axis activity was assessed by measuring serum corticosterone levels, whereas splenic norepinephrine (NE) content provided a sympathetic activity index. Corticosterone levels in subordinate subjects were generally higher than in their control or dominant counterparts in both treatment paradigms. Corticosterone levels in dominant subjects were lower than in their control counterparts in both. Increasing the duration of treatments generally decreased such titers, especially so in subordinate subjects. No differences were detected in splenic NE content. Animals subjected to social interaction generally showed greater proliferation than their control counterparts. This effect was more pronounced in subordinates than dominants and after longer- rather than short-duration treatments. There was no inverse relation between proliferative responses and the subject's corticosterone levels. While corticosterone may have a general immunomodulating effect, other mediators apparently account for the effects produced by these social stress paradigms on splenic proliferative response.

Effects of chronic mild stress on lymphocyte proliferative response. Participation of serum thyroid hormones and corticosterone

There is increasing evidence that stress produces changes in various immune processes. Some of these changes may be due to neurochemical and hormonal alterations including thyroid hormones levels. This work was carried out to study the impact of chronic mild stress (CMS) exposure on proliferative responses and its correlation with serum thyroid hormone levels. In addition, the influence of serum corticosterone levels on these responses was also studied. For this purpose, mice were submitted from1 to 6 weeks to a CMS model. After undergoing the stress schedule for 4 weeks, an alteration in the proliferative response was observed. Lymphocytes from exposed animals showed a decrease in T-cell response to concanavalin-A (Con A) and phytohemagglutinin (PHA) and an increase in B-cell proliferation to lipopolysaccharides (LPS). In parallel, a reduction in T3 and T4 serum levels was observed. On the contrary, serum corticosterone levels increased in animals exposed to CMS for 1 or 2 weeks and then return to normal values. Lowering serum thyroid hormone levels by propylthiouracil (PTU) treatment negatively modulates T-cell response without affecting B-cell response. On the other hand, the substitutive T4 treatment in stressed animals improved significantly the proliferative T-cell response. Non-significative changes in CD4/CD8 ratio were observed neither in stressed, PTU- or T4-treated animals. Taken together, our results suggest an impact of chronic stress on thyroid function that in turn alters T-cell response. These findings may help to elucidate the physiological mechanisms through which stress plays a roll in the etiology of many diseases.

Genetic basis of anxiety-like behaviour: a critical review

The way genetic and/or environmental factors influence psychiatric disorders is an enduring question in the field of human psychiatric diseases. Anxiety-related disorders provide a relevant example of how such an interaction is involved in the aetiology of a psychiatric disease. In this paper we review the literature on that subject, reporting data derived from human and rodent studies. We present in a critical way the animal models used in the studies aimed at investigating the genetic basis of anxiety, including inbred mice, selected lines, multiple marker strains, or knockout mice and review data reporting environmental components influencing anxiety-related behaviours. We conclude that anxiety is a complex behaviour, underlined not only by genetic or environmental factors but also by multiple interactions between these two factors.

Molecular basis of aggression

Recent pharmacological and genetic studies have dramatically expanded the list of neurotransmitters, hormones, cytokines, enzymes, growth factors, and signaling molecules that influence aggression. In spite of this expansion, serotonin (5-HT) remains the primary molecular determinant of inter-male aggression, whereas other molecules appear to act indirectly through 5-HT signaling. We review evidence of interactions among these molecules and aggressive behavior. Slight modulations in 5-HT levels, turnover, and metabolism, or in receptor subtype activation, density, and binding affinity affect aggression. Activation of specific 5-HT receptors evokes distinct, but highly interacting, second messenger systems and multiple effectors. Understanding the interactions between 5-HT receptor subtypes should lead to novel insights into the molecular mechanisms of aggression.

Ethylnitrosourea-induced mutation and molecular analysis of transgenic mice containing the gpt shuttle vector

Novel transgenic mice were developed in order to study the in vivo mutagenesis. The transgenic mice carried pCGK shuttle vector, which contained the Escherichia coli gpt gene as a mutational target, the kanamycin-resistant gene (Kanr) and cos region derived from bacteriophage lambda. The shuttle vector can be recovered from the transgenic mouse genome into the gpt-deficient E. coli by an in vitro packaging method and is selectable as a Kanr phenotype. Mutations induced at the gpt gene can be easily detected with a selective agent, 6-thioguanine (6-TG). In the previous study, the pCGK shuttle vector was incorporated into Chinese hamster CHL/IU cells and the resultant transgenic cell line was shown to be a useful system to study in vitro mutagenesis at the gpt gene. Therefore, an advantage of the shuttle vector is that in vivo mutational data obtained from the transgenic mouse can be compared with those of transgenic cell line in vitro. A transgenic CD-1 mouse line, designated as #128, that carried approximately 50 copies of pCGK shuttle vectors, was selected among 4 transgenic mouse lines. To investigate the sensitivity of the #128 line, the transgenic mice were treated with a single intraperitoneal injection of 250 mg/kg of N-ethyl-N-nitrosourea (ENU) or with 50 mg kg-1 day-1 of ENU for 5 consecutive days, and bone marrow, spleen and liver were dissected to investigate their mutational responses. The background mutant frequency was between 18x10(-6) and 75x10(-6) among all tissues tested. ENU induced significant increases in the mutant frequency above the background level in all three tissues at 14 days after single or 5-day treatment with the chemical. The increases in the mutant frequencies in bone marrow, spleen and liver were 6.4- to 6.8-fold, 3.0- to 5.6-fold and 3.0- to 3.3-fold, respectively. The shuttle vector DNA was recovered from the bone marrow of both spontaneous and ENU-treated mice and the gpt gene was amplified by polymerase chain reaction. The amplified DNA was subject to DNA sequence analysis. Out of 79 spontaneous and 52 ENU-induced mutants, the gpt gene could be amplified from 28 spontaneous and 46 ENU-induced mutants. DNA sequence analysis showed that predominant mutations were identified as A:T to T:A transversions (22 out of 46 sequenced mutants) and G:C to A:T transitions (9/46) in ENU-induced mutants, whereas G:C to T:A transversions (7 out of 28 sequenced mutants) were predominant in spontaneous mutants. These results demonstrate that this transgenic mouse, in combination with the transgenic CHL/IU cell line, is a useful system to study in vivo and in vitro mutational events at the same target gene.

Effects of chronic mild stress (CMS) and imipramine administration, on spleen mononuclear cell proliferative response, serum corticosterone level and brain norepinephrine content in male mice

There is increasing evidence that stress and emotional reactions produce changes in various immune processes. These changes may be due to alterations of the stress responses endocrine and for autonomic mediating mechanisms. In order to study such effects, the impact of chronic mild stress (CMS) application, and of subsequent imipramine administration were studied on the spleen mononuclear cell proliferative response period. OFI strain male mice were subjected to 4 or 7 weeks of CMS. The effects of these treatments on serum corticosterone levels and hypothalamic and hippocampal norepinephrine (NE) contents were also assessed. Subjects submitted to CMS had a higher spleen mononuclear cell proliferative response after either treatment duration. Imipramine treatment diminished this response enhancement in CMS exposed animals, but did not alter the proliferative responses of control subjects. Serum corticosterone levels, as well as hypothalamic and hippocampal nonrepinephrine contents did not significantly vary between groups. Taken together, these results suggest that CMSs effects on immune reactivity are not related to serum glucocorticoids or NE changes in these locations associated with the hypothalamic-pituitary- adrenocortical (HPA) axis.

Serum estradiol levels and ethanol-induced aggression

The biological mechanisms behind ethanol-induced aggression are not known. Because gonadal hormones are linked both to aggression and ethanol, the present study examined relationships among the levels of serum estradiol (E2), testosterone (T), and aggressive behavior in ethanol-treated male mice. We found that among group-housed male mice, serum E2 levels were significantly elevated 30 min after a single injection of 0.6 g/kg ethanol. Serum T levels showed a nonsignificant decrease by ethanol. The E2/T ratio, an index of aromatization of T to E2, was significantly higher in the ethanol-treated animals when compared with the vehicle-treated animals. We also determined aggressive behavior in the resident-intruder test among isolated male mice at baseline (after a vehicle), and after an injection of 0.6 g/kg ethanol. The mice were grouped accordingly to those that increased, decreased, or remained nonaggressive in response to ethanol administration. We found that at baseline, neither serum T or E2 levels, nor E2/T ratio differed significantly between the increased or reduced aggressor mice. In contrast to the increase in serum E2 levels seen in the nonaggressive mice, ethanol significantly reduced circulating E2 levels, but did not affect aromatization of E2 from T in the mice that became aggressive following an ethanol injection. These data suggest that mice who exhibit a paradoxical decrease in serum E2 levels by ethanol may be particularly prone to ethanol-induced aggression.

Mechanisms by which high maternal fat intake during pregnancy increases breast cancer risk in female rodent offspring

Emerging evidence indicates that a high in utero estrogenic environment increases breast cancer risk in women. We have proposed that a maternal intake of a high-fat diet is a source for high pregnancy estrogen levels and increases breast cancer risk among female offspring. In this review, the role of dietary fat in breast cancer, particularly during fetal life, is discussed. In addition, we provide possible mechanisms of action of the effects of a high-fat diet on the breast. These mechanisms include protein kinase C, estrogens and estrogen receptor, and alterations in mammary parenchymal structures.

Estrogen-regulated non-reproductive behaviors and breast cancer risk: animal models and human studies

The possible role of personality patterns and psychosocial factors in breast cancer has been studied extensively, through both human and animal experiments. The data are conflicting, and the conclusions controversial. This review will serve two purposes. First, we present evidence that behavioral patterns most commonly linked to breast cancer risk are at least partly regulated by estrogens. This section will suggest that some estrogen-regulated behaviors may be markers of increased breast cancer risk. Second, we will briefly review recent findings in animals connecting psychosocial factors to cancer. We also will address the plausible biological mechanisms. The literature suggests that estrogens, particularly when exposure occurs during the critical developmental periods, such as in utero, puberty, pregnancy, and menopause, influence affective behaviors and increase breast cancer risk. The affective behaviors include depression, aggression, and alcohol intake. Thus, psychosocial and personality factors do not necessarily have a direct impact on breast cancer risk; instead, estrogens have a dual effect on behavior and on the breast.

Early postnatal treatment with transforming growth factor alpha does not alter nonreproductive behavior

Estrogen acting during the critical developmental period has been postulated to defeminize and possibly masculinize male sexual behavior. Transforming growth factor alpha (TGF alpha) also may be involved, because this growth factor, at least partly, mediates the mitotic effects of estrogen on target tissues. Male transgenic mice overexpressing TGF alpha have elevated serum estradiol (E2) levels and they exhibit feminization of many nonreproductive actions, suggesting that either TGF alpha and/or E2, or both, participate in the control of some nonreproductive behavior. Male and female CD-1 mice were treated with 4 microg of recombinant human TGF alpha or 2-4 microg E2 during the first 3 days of life. Although early TGF alpha treatment accelerates physical development and influences the growth of the uterus and mammary gland, it failed to have any effect on behavior, either in male or female mice. Early E2 treatment significantly lengthened immobility time in the swim test and reduced voluntary alcohol intake among the male mice. No changes in locomotor activity or aggressive behavior were noted. The expression of TGF alpha mRNA in the brainstem of adult male mice was not altered following neonatal TGF alpha or E2 treatment. However, neonatal exposure to TGF alpha caused a moderate elevation in TGF alpha mRNA expression in the female brainstem. Our results indicate that in male, but not in female mice, an excess of E2 during early life affects some nonreproductive behavior. Furthermore, early treatment with recombinant human TGF alpha does not alter nonreproductive behavior in mice.

Use of transgenics, null mutants, and antisense approaches to study ethanol's actions

Behavioral and biochemical responses mediating ethanol's actions have been difficult to study in humans and animals because of their complex polygenic nature. Recent progress in the creation of new animal models using recombinant DNA technology has provided a set of genetic tools by which the role of specific candidate genes in ethanol's actions can be examined. These techniques include the creation of transgenic and null mutant mice, as well as manipulation of protein synthesis with antisense treatments. These techniques are reviewed, and their potential applications to alcohol research are discussed.

Gonadal hormones and aggression-maintaining effect of alcohol in male transgenic transforming growth factor-alpha mice

We have characterized a new transgenic mouse model that offers the unique opportunity to study the biological mechanisms linking aggression to alcohol. In contrast to all other aggressive animal models, the male transgenic mice that overexpress transforming growth factor-alpha (TGF-alpha) maintain their highly elevated aggressive behavior following an alcohol administration. The transgenic mice also exhibit elevated plasma levels of 17 beta-estradiol (E2). Animal data support the role of E2 in aggression and alcohol intake in males. Further, type 2 alcoholism is male-limited, suggesting that gonadal hormones are important. We examined whether gonadal hormones play a role in the resistance to respond to alcohol in the resident-intruder test of aggression among the male transgenic TGF-alpha mice. As previously reported, alcohol had a biphasic effect on sham-operated, nontransgenic controls: 0.6 g/kg increased and 2.0 g/kg inhibited their aggressiveness. Alcohol did not significantly reduce the high levels of aggression in the sham-operated TGF-alpha mice. Castration abolished the difference in aggressive behavior between the transgenic and nontransgenic male mice by reducing aggression. Alcohol did not increase aggressive behavior in these mice. Treatment with pellets releasing 0.25 mg E2 over a 60-day period increased aggression in the castrated male TGF-alpha mice and nontransgenic controls to the levels seen in intact male transgenic mice. Alcohol did not significantly alter aggressive behavior in the E2-treated castrated mice.(ABSTRACT TRUNCATED AT 250 WORDS)

Alterations in brain monoamines and GABAA receptors in transgenic mice overexpressing TGF alpha

This study investigated the possibility that overexpression of transforming growth factor alpha (TGF alpha) changes those neurotransmitter systems that have been associated with behaviors found to be altered in the transgenic TGF alpha CD-1 mice. The female TGF alpha mice showed elevated levels of norepinephrine (NE) in the hypothalamus and serotonin (5-HT) in the cortex and brain stem when compared with nontransgenic CD-1 females. The concentrations of monoamines were not altered in the male transgenic brain. The 5-hydroxyindoleacitic acid (5-HIAA)/5-HT ratio was significantly reduced in the brain stem of the male TGF alpha mice and frontal cortex in the female transgenics. The binding of the [3H]GBR 12935-labeled DA transporter was lower in the frontal cortex in the transgenic male TGF alpha mice than in the female TGF alpha mice. No gender difference in dopamine (DA) transporter binding was noted between the nontransgenic male and female mice. Serotonin and GABAA receptors were measured only in males. No differences in the number of 5-HT1A and 5-HT2 receptors were found in the cortex or hippocampus. Maximal GABA stimulation of [3H]flunitrazepam binding in the forebrain hemispheres and cerebellar binding of an imidazobenzodiazepine, [3H]Ro 15-4513, were not different between transgenic and nontransgenic male mice. However, forebrain [35S]TBPS binding in male TGF alpha mice was less affected by the blockade of the GABA agonist sites by the specific GABAA antagonists SR 95531 and bicuculline than the binding of the controls, suggesting either altered endogenous GABA concentrations or a change in receptor populations.(ABSTRACT TRUNCATED AT 250 WORDS)

Stress influence on development of hepatocellular tumors in transgenic mice overexpressing TGF alpha

We investigated whether stress increases tumorigenesis in male transgenic mice that overexpress the gene encoding human transforming growth factor alpha (TGF alpha). At the age of 10-15 months, these mice begin to develop spontaneous hepatocellular carcinomas at high incidence. The male TGF alpha mice were housed with their siblings (non-stressful environment), housed in social isolation, or housed with aggressive non-siblings (stressful environment). Some animals in each group were exposed once a week to a second stressor (swim stress), beginning at the age of 7 months. Housing with aggressive non-siblings increased neoplastic growth in the male TGF alpha mice: the incidence and multiplicity of liver tumors, and tumor burden were higher in these animals than in the sibling-housed mice. Among the isolated TGF alpha mice, only the tumor burden was increased, when compared with the sibling-housed TGF alpha mice. Swim stress significantly increased the incidence of liver tumors and tumor burden in the sibling-housed TGF alpha mice. Plasma levels of 17 beta-estradiol (E2) that are elevated in the TGF alpha mice, were modestly but significantly higher in the non-sibling housed transgenic mice than in the sibling-housed. Natural killer (NK) cell activity, reduced in these mice, was not affected by housing environment. These data suggest that stress promotes the growth of hepatocellular tumors in the male TGF alpha mice. Whether estrogens are involved in mediating this association remains to be determined.

Psychosocial factors in the development and progression of breast cancer

The factors responsible for the genesis of breast cancer remain unclear. Emerging, although controversial, evidence suggests that factors related to life-style, such as dietary fat or alcohol intake, or exposure to various forms of stressors, are associated with mammary tumorigenesis. The possible role of life-style factors in breast cancer is important in light of the fact that mortality to this disease is increasing in most countries and that development of curative therapies for breast cancer has not been forthcoming. Thus, determining the role of life-style factors in the onset and progression of breast cancer, particularly among individuals genetically vulnerable to breast cancer or women with breast cancer in remission, is critical to prevent this disease. We will review the three main hypotheses which have been suggested to link psychosocial factors to the etiology of cancer, emphasizing data obtained through animal models. Interpretation of the existing data suggests that the number of stressful life-events does not predict vulnerability to develop breast cancer or survival from it; a certain level of stress appears to protect from malignancies. The crucial factor affecting tumor growth is the interaction among stress, an individual's personality, and available psychosocial support, and the effect of this interaction on an individual's ability to cope with stress. In addition, other risk factors for breast cancer known to be closely associated with psychosocial factors, namely dietary fat and alcohol consumption, may interact with the effects of psychosocial factors on breast cancer.

Perinatal factors increase breast cancer risk

Emerging evidence suggests that breast cancer may originate during early life. In particular, offspring of mothers who during pregnancy exhibited behaviors that are associated with increased incidence of breast cancer, may be at risk. These behaviors include intake of high fat diet or alcohol, or stressful life style. We have found that neonatal exposure to handling that leads to improved ability to cope with stress, reduces 7,12-dimethylbenz(a)anthracene (DMBA)-induced mammary tumors in rats. Further, our results indicate that maternal exposure to high fat diet increases the incidence of DMBA-induced mammary tumors in female offspring. High fat diet also increases serum 17 beta-estradiol (E2) levels in pregnant animals. These results support the hypothesis that in utero concentrations of estrogens play a critical role in the vulnerability to develop breast cancer. The mechanism of estrogen action might be related to its effect on the induction of epithelial hyperplasia and altered breast differentiation. These events then increase the rate of genetic/epigenetic changes that increase the possibility of neoplastic transformation. Increased pregnancy estrogens may also lead to behavioral alterations in the offspring. This could explain the proposed association between certain behavioral patterns and increased tumorigenity. Our results in transgenic mice overexpressing transforming growth factor alpha (TGF alpha) are in accordance with this interpretation. The male TGF alpha mice exhibit elevated serum E2 levels, impaired ability to cope with stress, increased voluntary alcohol intake and high incidence of spontaneous hepatocellular tumors. These findings indicate that animal models offer a unique opportunity to investigate the role of timing of risk behaviors on breast cancer. They are also useful in the attempts to understand the mechanism of early estrogen action on mammary tumorigenesis.

Effects of tryptophan and serotonin uptake inhibitors on behavior in male transgenic transforming growth factor alpha mice

Our findings have implicated that transgenic male mice overexpressing human growth factor alpha (TGF alpha) exhibit lengthened immobility in the swim test and elevated levels of aggression in the resident-intruder test. Further, these animals have a reduced ratio between the metabolite of serotonin (5-HT), and 5-HT in the brain. The present study investigated whether pharmacological manipulations of serotonergic transmission affect the altered behavioral patterns of the male TGF alpha mice. For that purpose, we used tryptophan (0, 50 or 100 mg/kg), a precursor substance to 5-HT, and 5-HT uptake inhibitors, zimelidine (0, 12.5 or 25 mg/kg) and clomipramine (0, 10 or 20 mg/kg). Administration of tryptophan or zimelidine significantly shortened immobility in the swim test in the TGF alpha male mice. Tryptophan or clomipramine did not influence the male non-transgenic CD-1 mice, and zimelidine significantly lengthened their immobility. High levels of aggression were completely reversed by zimelidine or clomipramine in the transgenic male mice. Neither of these compounds altered behavior of the control mice in the resident-intruder test. Tryptophan failed to affect aggressive behavior in the TGF alpha or control male mice. These results suggest that TGF alpha may influence behavior by affecting the uptake of 5-HT in neurons.

Opposing behavioural alterations in male and female transgenic TGF alpha mice: association with tumour susceptibility

Psychosocial factors are thought to influence risk and survival from cancer. We have previously studied specific behaviours in transgenic male CD-1 MT42 mice, which overexpress the gene encoding human transforming growth factor alpha (TGF alpha) in multiple tissues, and which develop a high incidence of spontaneous hepatocellular carcinoma. The male TGF alpha mice spent a lengthened time immobile in the swim test, were highly aggressive, had increased plasma levels of 17 beta-estradiol (E2), and reduced natural killer (NK) cell activity. The female transgenic MT42 TGF alpha mice do not develop an increased rate of tumours at any site. We hypothesised that if the alterations in male TGF alpha mice are associated with their development of hepatocellular carcinomas, female TGF alpha should not show these alterations. The data in the present study indicate that female TGF alpha mice display shortened immobility in the swim test, suggesting an improved ability to cope with stress, and appear less aggressive in the resident-intruder test than non-transgenic female CD-1 mice. The female TGF alpha mice also exhibit a 3-fold increase in the plasma levels of E2, and a 3-fold increase in NK cell activity. These findings suggest that the elevated expression of TGF alpha in the transgenic mice is associated with gender-specific behavioural alterations, and the development of spontaneous hepatocellular tumours in the males. Furthermore, TGF alpha alters hormonal and immune parameters similarly in both sexes. It remains to be determined whether the development of hepatocarcinoma in the male TGF alpha animals is associated with an impaired ability to cope with stress and elevated aggressive tendencies and/or whether manipulations leading to an impaired ability to cope with stress will promote tumourigenesis in female TGF alpha mice.