Biomedical subjects

Magdalena Karolczak

Publications and source records attributed to Magdalena Karolczak.

10 recordsLinked to original sources

PubMed2005

Diurnal variation in CREB phosphorylation and PER1 protein levels in lactotroph cells of melatonin-proficient C3H and melatonin-deficient C57BL mice: similarities and differences.

The pineal hormone melatonin plays an important role in the maintenance of rhythmic functions of the hypophyseal pars tuberalis, which controls the lactotroph cells of the pars distalis. To analyze the effects of melatonin deficiency on the activity state of these cells, we have investigated the levels of Ser133-phosphorylated (p)CREB and PER1 protein in immunocytochemically identified lactotroph cells of melatonin-proficient C3H and melatonin-deficient C57BL mice at four different time points of a 12/12 LD cycle. At night, the percentage of lactotroph cells showing a positive nuclear pCREB and PER1 immunoreaction is significantly smaller in C57BL than in C3H mice. In both mouse strains, the percentage of pCREB-immunoreactive cells is minimal in the early morning and gradually increases to reach a maximum in the late night. PER1 levels show a parallel temporal variation in C3H, but in C57BL, they are drastically reduced in the early afternoon. The observation that, during darkness, the percentage of lactotroph cells with nuclear pCREB immunoreaction is significantly higher in C3H than in C57BL mice suggests the existence of a distinct cell population that is under the control of melatonin-dependent intrapituitary signaling. Interestingly, the percentage of pCREB- and PER1-immunoreactive lactotroph cells reaches minimal and maximal values at the same time points. This suggests that the correlation between CREB phosphorylation and PER1 induction differs between these cells and other neuroendocrine centers, e.g., the pineal organ and suprachiasmatic nucleus, displaying a temporal gap between CREB phosphorylation and PER1 induction.

Animals↗

PubMed2005

Estrogen receptor-alpha is associated with the plasma membrane of astrocytes and coupled to the MAP/Src-kinase pathway.

Estrogens influence CNS development and a broad spectrum of neural functions. Several lines of evidence also suggest a neuroprotective role for estrogen. Different modes of estrogen action have been described at the cellular level involving classical nuclear estrogen receptor (ER)-dependent and nonclassical membrane ER-mediated rapid signaling. We have previously shown that nonclassical estrogen signaling is implicated in the control of dopamine cell function and protection. Since nonclassical interactions between estrogens and glia may contribute to these effects, our aim was to demonstrate the presence of membrane-associated ERs and their putative coupling to intracellular signaling pathways in astrocytes. Confocal image analysis and fluorescence-activated cell sorting (FACS) studies indicated the attachment of ER-alpha but not ER-beta to the plasma membrane of astrocytes. ERs were located in the cell soma region and glial processes. FACS analysis revealed that only a subpopulation of midbrain astrocytes possesses membrane ER-alpha. In FACS studies on ER-alpha knockout astrocytes, only a few membrane ER-positive cells were detected. The activation of membrane ERs appears to be coupled to the MAP-kinase/Src signaling pathway as shown by Western blotting. In conclusion, our data provide good evidence that nonclassical estrogen action in astrocytes is mediated by membrane ER-alpha. The physiological consequence of this phenomenon is not yet understood, but it might have a pivotal role in estrogen-mediated protective effects on midbrain dopamine neurons.

Animals↗

PubMed2005

The rhythm and blues of gene expression in the rodent pineal gland.

In all vertebrates, melatonin is rhythmically synthesized in the pineal gland and functions as a hormonal message, encoding for the duration of night. In rodents, the nocturnal rise and fall of the arylalkylamine N-ace-tyltransferase (AA-NAT) activity controls the rhythmic synthesis of melatonin. This rhythm is centered around the transcriptional regulation of the AA-NAT by two norepinephrine-inducible transcription factors, the activator CREB (Ca2+/cAMP-response element binding protein) and the inhibitor ICER (inducible cAMP early repressor). CREB is activated by phosphorylation, which is one of the fastest responses in pinealocytes upon adrenergic stimulation, occurring within minutes. ICER in turn accumulates only after several hours, a time gap resulting from the required de novo protein synthesis upon adrenergic stimulation. However, these molecular components of neuroendocrine signaling in the rodent pineal gland are supplemented by the impact of a variety of neurotransmitters and neuromodulators, and by translational and post-translational mechanisms. By molecular crosstalk, those different inputs on pinealocytes seem to fine-tune the shape of the melatonin signal, by interacting at various levels with the NE/cAMP/pCREB/ICER pathway. In addition, these alternate signaling routes may be important in acute "emergency" situations. Together, concerted signaling events in the rodent pineal gland help to generate a stable and reliable hormonal message of darkness for the body, that, however, can be altered rapidly upon sudden and unexpected "error" signals.

Animals↗

PubMed2004

Clock gene mRNA and protein rhythms in the pineal gland of mice.

In vertebrates, the rhythmic transcription of clock genes, regulated by their own gene products, provides the basis for self-sustaining circadian clockworks. These endogenous clocks are lost in most mammalian tissues, but not in the central pacemaker of the hypothalamic suprachiasmatic nucleus (SCN). An interesting model system to understand this phylogenetic shift in function of clock gene products is the rodent pineal gland, as its intrinsic clockwork was replaced during evolution by an input-dependent oscillator. By means of immunohistochemistry, immunoblotting and real time PCR, we investigated the day/night expression profiles of all major clock genes and their products in the pineal gland of one melatonin-proficient and one melatonin-deficient mouse strain. All clockwork elements known to be indispensable for a sustained rhythm generation in the SCN were also found in the pineal organ of both mouse strains. Only mPer1 mRNA and PER1 protein accumulation coincides with timecourses of many other pineal genes and their products, which are cyclicAMP inducible. Here, presented data together with the known mechanisms for regulation of the mPer1 gene in the rodent pineal gland forward the idea that in this tissue PER1 may have a trigger function for initiating the cycles of the clockwork's transcriptional/translational feedback loops.

Animals↗

PubMed2003

Membrane receptors for oestrogen in the brain.

Oestrogen is important for the development of neuroendocrine centres and other neural networks including limbic and motor systems. Later in adulthood, oestrogen regulates the functional performance of different neural systems and is presumably implicated in the modulation of cognitive efficiency. Although still a matter of controversial discussion, clinical and experimental studies point at a potential neuroprotective role of oestrogen. Concerning the concept of cellular oestrogen action, it is undisputed that it comprises the binding and activation of nuclear receptors. The last decades have, however, immensely broadened the spectrum of steroid signalling within a cell. Novel steroid-activated intracellular signalling mechanisms were described which are usually termed 'non-classical' or 'non-genomic'. The brain appears to be a rich source of this new mode of oestrogen action. Studies from the past years have pinpointed non-classical oestrogen effects in many CNS regions. All available data support the view that non-classical oestrogen action requires interactions with putative membrane binding sites/receptors. In this article, we aim at compiling the most recent findings on the nature and identity of membrane oestrogen receptors with respect to the brain. We also attempt to turn readers attention to the coupling of these 'novel' receptors to distinct intracellular signalling pathways.

Animals↗

PubMed2003

Ontogenetic expression of estrogen and progesterone receptors in the mouse lung.

In the mammalian lung, estrogen and progesterone seem to be import for the morphological and functional maturation. Despite this, only sparse information is available on the onset and ontogenic expression of estrogen receptors (ER) and progesterone receptors (PR) in the perinatal lung. The expression patterns of the two known nuclear isoforms ER-alpha and ER-beta and the PR were analyzed in the pre- and postnatal lungs of BALB/c mice. Steroid receptor mRNA expression of all three receptors were highest in the prenatal lung and declined thereafter to significantly lower levels in the postnatal and adult lung. The ontogenetic pattern of ER and PR expression supports the view that both gonadal steroids are pivotal for prenatal lung maturation and development.

Aging↗

PubMed2003

Regulation of gene expression in the developing midbrain by estrogen: implication of classical and nonclassical steroid signaling.

Estrogen plays an important role during midbrain development. This is indicated by the presence of nuclear estrogen receptors and the transient expression of the estrogen-forming enzyme aromatase. A number of recent studies have shown that estrogen promotes the differentiation and survival, as well as physiological performance, of midbrain dopaminergic cells. In addition, we have reported that both ways of cellular estrogen signaling (classical and nonclassical) as well as interactions with nonneuronal target cells are involved in the transmission of intra- and intercellular estrogen effects in this brain region. This study provides additional evidence that (i) estrogen is capable of regulating gene expression in cultured embryonic neurons and astrocytes differently and (ii) both signaling mechanisms, i.e., classically through nuclear receptors and nonclassically through the stimulation of membrane-estrogen receptors, which are coupled to distinct intracellular signal transduction cascades, contribute diversely to gene regulation. These data reveal a high degree of complexity of estrogen action at the genomic level in the developing brain. Further studies are warranted to unravel the exact contribution of the differently regulated genes for developmental estrogen action.

Animals↗

PubMed2002

Cell type-specificity of nonclassical estrogen signaling in the developing midbrain.

Estrogens have widespread biological functions in the CNS involving the coordination of developmental processes, the regulation of cell physiology, and the control of neuroendocrine systems. In the midbrain, estrogens promote the survival, maturation, and function of neurons and, in particular, of dopamine cells. Aside from classical signaling through nuclear estrogen receptors, we have provided evidence that cellular transmission of estrogen effects in the midbrain comprises a complex intracellular signaling scenario. The major conclusion drawn from our studies is that estrogens interact with yet unidentified membrane receptor complexes which stimulate the phospholipase C and induce the formation of inosite-tri-phosphate (IP(3)). This causes a rapid and transitory rise in intracellular free calcium. The modulation of calcium homeostasis is the primary nonclassical physiological response to estrogens in all cell types. Surprisingly, a different secondary downstream signaling cascade seems to be activated in each estrogen-responsive cell population, i.e. phosphatidylinositol-3 kinase (PI3-kinase) in GABAergic and cAMP/ protein kinase A (PKA) in dopaminergic neurons, mitogen-activated protein kinase (MAP-kinase) in astrocytes. The precise biological role of estrogens for the different cell types is still fragmentary. We assume that estrogens positively influence intracellular signaling mechanisms which are important for cell differentiation and survival. It remains to be elucidated what determines the cell type-specificity of these estrogen responses.

Animals↗

PubMed2002

Sry does not fully sex-reverse female into male behavior towards pups.

Investigations in mice suggest that the Y-chromosomal genes affect certain behaviors. Here, we studied whether a part of the Y chromosome, the Sxr locus, has an effect on induction of motivation for parental care (pup retrieval) or of parental aggression towards pups (infanticide). XX females, XX males with the Sxr locus on the X chromosome, and XY males of the C57BL/6J strain were tested. The induced pup retrieval or infanticide behaviors were genotype-dependent. XX mice always retrieved pups and never were infanticidal. On the first test, significantly more XY males (38%) than XX males (17%) were infanticidal. When the same animals were tested for a second time, all except one of the XX males retrieved pups. Overall, motivation for parental care was highest in XX females, followed by XX males, and lowest in XY mice. On the other hand, the incidence of infanticide was highest in XY males, lower in XX males, and absent in XX females. We conclude that the Sxr locus of the Y chromosome, when operating in a XX background, partially erases but does not fully defeminize motivation for pup retrieval. Further, it induces infanticide to a level higher than that of XX females but significantly lower than that of normal males (XY). Hence, we suggest that genes outside the sex-determining region of the Y chromosome and/or genes on autosomes are necessary for manifestation of full male-type parental behavior.

Animals↗

PubMed2002

Estradiol stimulates GDNF expression in developing hypothalamic neurons.

Estrogens stimulate the differentiation of neurons and neural networks in the CNS. The concordance of the cellular responses of estrogens and growth factors suggests that both factors may interact on the cellular level to ensure their developmental role. We have put forward this hypothesis and analyzed the effect of estrogens on the expression of glial cell line-derived neutrotrophic factor (GDNF) in developing hypothalamic cells. Using Western blotting and competitive RTPCR, we have demonstrated that 17beta-estradiol (E2) increases the expression of GDNF in hypothalamic cell cultures. E2-induced GDNF expression was seen in neurons but not astrocytes. GDNF induction by E2 appeared to be transmitted through nonclassical estrogen action, since the application of the nuclear estrogen receptor antagonists ICI 182, 780 did not abolish this effect. Only inhibitors of intracellular Ca(2+) and cAMP/protein kinase A signaling were effective in preventing E2 effects. We conclude that E2 is capable of influencing GDNF expression in the developing hypothalamus. Thus, it is conceivable that developmental E2 effects in the hypothalamus are partially mediated through the regulation of other important developmental signals such as growth factors.

Animals↗