Sustained hypoglycemia affects glucose transporter expression of human blood leukocytes

The scarce data available on leukocyte glucose transporter expression are contradictory and nothing is known about its regulation by glycemic state. Therefore, cytospin preparations of blood leukocytes were searched immunocytochemically for the high-affinity glucose transporters GLUT1, 3, and 4. Hypoglycemia-associated quantitative changes in transporter expression were assessed by flow cytometry. Granulocytes and monocytes stained for GLUT1, 3, and 4. Granulocyte GLUT4 levels were increased by 73% (P < 0.05) under hypoglycemic conditions, which was paralleled by a reduction in GLUT1 and a rise in GLUT3. In monocytes, GLUT3 was elevated by 134% (P < 0.05), whereas GLUT1 and GLUT4 remained unaffected upon hypoglycemia. Apart from a minor subpopulation, lymphocytes were negative for these carriers. In conclusion, GLUT1, 3, and 4 are abundantly expressed in granulocytes and monocytes. The differential response of individual isoforms to hypoglycemia may represent a mechanism to protect the cells from the stress of glucose deprivation.

Hyperglycaemia in vitro alters the proliferation and mitochondrial activity of the choriocarcinoma cell lines BeWo, JAR and JEG-3 as models for human first-trimester trophoblast

AIMS/HYPOTHESIS

Early intrauterine growth delay in diabetes could be caused by a reduced growth of the placenta. Our study investigates whether hyperglycaemia in vitro reduces trophoblast proliferation.

METHODS

First-trimester trophoblast cell models (BeWo, JAR and JEG-3 choriocarcinoma cells) were cultured for 24 and 48 h with 5.5 mmol/l D-glucose, 25 mmol/1 D-glucose (hyperglycaemia) and with an osmotic control. Cell number, total protein and nucleic acid content and mitochondrial activity (tetrazolium salt assay) were measured, the cell cycle analysed (FACS, cyclin B1 levels) and apoptosis (Annexin-V) measured.

RESULTS

In BeWo cells hyperglycaemia reduced cell number, protein, nucleic acid and cyclin B1 levels. The reduced G2/M and increased G0/G1 population after 24 h reflects growth arrest at G0/G1. In JAR cells after 24 h the population was arrested in G0/G1, whereas after 48 h the G0/G1 block was abrogated and the cells were arrested at G2/M. The net effect was an unchanged cell number. In JEG-3 cells hyperglycaemia resulted in fewer cells after 24 h but not after 48 h indicating some adaptation. Mitochondrial activity was either stimulated (BeWo) or reduced (JAR, JEG-3) under hyperglycaemia. Some of these effects were also induced by hyperosmolarity alone.

CONCLUSION/INTERPRETATION

Hyperglycaemia has the potential to inhibit the proliferation of first-trimester trophoblast cell models. The mechanisms leading to growth arrest and to changes in mitochondrial activity are complex and depend on differentiation. We hypothesise a hyperglycaemia-induced impairment of placental growth in the first trimester of a poorly controlled diabetic pregnancy.

Endothelin-1 stimulates the proliferation and invasion of first trimester trophoblastic cells in vitro--a possible role in the etiology of pre-eclampsia?

BACKGROUND

Endothelin-1 is a potent mitogen and stimulates cell chemokinesis, but these properties have not been investigated in the placenta. Trophoblastic cells from pre-eclamptic pregnancies have a reduced invasive potency and secrete less endothelin-1 than those from normal pregnancies. The present study tested the hypothesis that endothelin-1 affects trophoblast proliferation and invasion.

METHODS

Trophoblastic cells were isolated from 37 placentae of normal human pregnancies at week 12 by dispastrypsin digestion and subsequently immunopurified to remove nontrophoblastic components. The effects of 5, 10, and 20 nmol/mL endothelin-1 on proliferation and invasion were determined after 24 and 72 hours, respectively, by fluorescence-activated pulse cytometry (FACS) analysis, by measuring DNA synthesis using two different methods and by a Matrigel invasion assay.

RESULTS

All cell preparations uniformly responded to 10 nmol/mL by increased proliferation, owing to a greater proportion of cells in the S-phase of their cell cycle, and invasion. The effects were more pronounced after 24 hours than after 72 hours, by which time cell viability, as measured by the secretion of human chorionic gonadotropin (hCG-beta), had deteriorated. The nonselective receptor antagonist PD 142893 inhibited both endothelin-1 effects.

CONCLUSION

Endothelin-1 is a mitogenic stimulus for first trimester trophoblastic cells in vitro. The stimulation of cellular invasion represents a novel effect of endothelin-1. We suggest the implication of endothelin-1 in proliferation and invasion of trophoblast and tumour cells and hypothesize a possible role in the etiology of pre-eclampsia.

Mutant p53 expression and DNA analysis in human breast cancer comparison with conventional clinicopathological parameters

Scientific research evaluates the prognostic importance of 53 expression and DNA flow cytometry controversially. To evaluate the prognostic relevance of mutant p53 protein overexpression and DNA flow cytometry in primary breast cancer we correlated these factors with the common prognostic parameters such as tumor size, lymph node status, grading, menopausal status and receptor status. Human breast cancer specimens from 180 previously untreated patients were collected and deep frozen. On each specimen DNA-analysis by Geohde's technique (Partec PAS II) and immunohistochemical evaluation of mutant p53 protein (PAb 1801 and 240, Novocastra Lab., Great Britain) were performed. Besides TNM- and histological classification, estrogen (ER)- and progesterone (PgR) receptor content was recorded. Overexpression of mutant p53 protein was found in 34 (19%) of all specimens. All these 34 tumors were aneuploid (p = 0.007), 86% of them were receptor negative (p 0.0001), 79% had a high tumor grade (p 0.0001), 73% a high S-phase-fraction (SPF) (p = 0.045) and 53% were premenopausal (p 0.0001). Tumor size and node status did not correlate significantly with p53 expression. 27 (15%) out of 180 carcinomas were diploid. There was a significant correlation between ploidy and the tumor grade (p = 0.003) and SPF (p 0.0001), but not correlation between ploidy and tumor size (p = 0.21), node status (p = 0.33) or receptor status (p = 0.18). A low SPF was predominantly found in tumors less than 2 cm in diameter (p 0.0001); no significant correlation was found between SPF, receptor status, tumor grade, node and menopausal status. Mutant p53 protein expression and DNA analysis in combination with common prognostic parameters might help to detect prognostically unfavourable subgroups of breast cancer patients.

Preventive action of phentolamine on adrenaline induced blood glucose elevation in humans

A comparison of the action of adrenaline infusion and a combined adrenaline + alpha blocker (phentolamine, Regitine) infusion on blood glucose (BG), plasma immunoreactive insulin (IRI), BG/IRI ratio, C-peptide, and plasma cortisol levels was made in healthy young human subjects. The purpose of the experiment was to check, whether alpha block could abolish adrenaline-induced enhancement of blood glucose levels. The results show that during enhanced adrenaline levels, the use of regitine could indeed normalize blood glucose levels, not so much by increasing the IRI secretion, but by diminishing adrenaline-induced liver glycogenolysis via alpha receptors. This could be a model to prevent stress (adrenaline) induced metabolic deviations in diabetics, especially before and during predictable stress situations, e.g. examinations or surgery.