Analysis of apoptosis in the human adrenal appears to be of eminent importance in the understanding of adrenal structure, zonation, and function. In this study we investigated the programmed cell ...death of normal adrenal tissues on the basis of apoptotic index by the nonradioactive in situ end labeling of DNA fragments, proliferating cell nuclear antigen, (PCNA), CD95 (cluster of differentiation), major histocompatibility complex class II immunohistochemistry, and ultrastructural analysis. The highest apoptotic index was detected in the outermost zones of the adrenal cortex, mainly in the zona glomerulosa. A labeling index of 50.46 +/- 5.22% (mean +/- SEM) for zona glomerulosa, 9.36 +/- 1.68% for zona fasciculata, 3.90 +/- 0.78% for zona reticularis, and 7.37 +/- 1.62% for the zona medullaris was found. Immunohistochemistry was used to distinguish between apoptotic and S phase cells. Positive anti-PCNA staining occurred in the inner cortical zones, whereas anti-CD95 signals appeared throughout the whole cortex, albeit at a much weaker level. MHC class II expression, which is known to be associated with programmed cell death, was demonstrated in the inner cortical zone. The data showed that mechanisms of cell death other than necrosis occur in the adrenal. In conclusion, we found a differential regulation of cell death for each zone of the adrenal cortex; the old theories of adrenal zonation (migrational vs. zonal or transformation theory) may, in fact, correlate with each other.
The hypothalamic-pituitary-adrenal axis and the immune system interact in a bidirectional manner providing the basis for the regulation of the immune response due to a pathogenic stimulus. This ...interplay is commonly believed to be based on the action of hormones or cytokines, respectively. Since it has been detected that adrenocortical cells offer immunological properties such as expression of MHC class II antigens and/or CD95 (Fas antigen) and its ligand, the question has to be raised whether direct intercellular communication between immune cells and 'immunocompetent' endocrine cells contributes to the complexity of immunoregulation. Here we discuss the possible reciprocal relevance of physiological and pathological adrenal changes, as well as T-cell-mediated immune response for immune and/or adrenal pathology during disease.
Adrenal androgen production was reduced by 80% in patients receiving T
lymphocyte-suppressive medications compared to that in age-matched
controls. In vitro, however, neither tacrolimus nor
...cyclosporin A reduced dehydroepiandrosterone (DHEA)
release by adrenocortical cells. Therefore, we examined the potential
role of lymphocytes in adrenal androgen production, using cocultures of
human T lymphocytes and adrenocortical primary or transformed cells.
Cocultures led to a 4-fold elevation of DHEA levels
(490.4 ± 94.8% over basal), which was greater than the increase
observed after the addition of maximal concentrations of ACTH
(117.4 ± 14.8%). Separation of cells by semipermeable membranes
abolished this effect, and transfer of leukocyte-conditioned medium had
little androgen-stimulating effect. These data suggested that the
observed stimulation of androgen secretion required cell contact rather
than soluble paracrine factor(s). Furthermore, we examined human
adrenal glands for the presence of T lymphocytes and contact between
these cells and steroid-secreting cells of the zona reticularis.
Indeed, T lymphocytes expressing CD4 and CD8 antigens were present
within human adrenal zona reticularis by immunohistochemical subtyping.
Electron microscopic analyses demonstrated direct cell-cell contact
between T lymphocytes and adrenocortical cells in situ.
This study provides evidence for a novel mechanism of immune-endocrine
interactions of direct T lymphocyte-adrenocortical cell
contact-mediated stimulation of adrenal androgen secretion.
Major histocompatibility complex (MHC) class II antigens are
expressed on adrenocortical cells of the zona reticularis and have been
shown to be a marker of dignity. This suggests a correlation to ...the
zellular differentiation of the adrenal cortex. Therefore, we
immunohistochemically investigated the MHC class II expression in the
context of the ontogenesis of the zonal and cellular differentiation in
fetal, postnatal, childhood, and adult adrenals. Cell types and cell
turnover were studied using specific immune markers (including
expression of CD95/Fas), in situ end labeling of
apoptosis, and electron microscopy. We show that prenatal (fetal and
definitive) steroid cells, as well as postnatal adrenals, reveal no
expression of MHC class II. In childhood, these antigens first appear
by the fourth year, in parallel with the differentiation of reticularis
cells. The expression index in childhood was 7.43% ± 2.78 (mean±
sem), in adult adrenals 18.63% ± 3.14 (third decade),
and 15.15% ± 1.26 (fourth through sixth decade). In conclusion, MHC
class II expression and the development of the functional maturation of
the adult adrenal cortex occur simultaneously. The expression of MHC
class II on steroid cells may thus be involved in potential
immune-adrenal interactions.
The migration and proliferation of adrenocortical cells is accompanied by mechanisms of cellular knock-out. We compared the programmed cell death of normal and malignant adrenocortical tissues on the ...basis of apoptotic rates by the nonradioactive in situ end-labelling of DNA-fragments, immunohistochemistry against PCNA, CD95 and ultrastructural analysis. The highest labelling index (LI) was detectable in the outermost zones of the adrenal cortex of normal adrenals. Average LI in normal adrenal cortex was 20% whereas only 2% was detectable in adrenocortical neoplasms. MHC class II, which was previously shown to be involved in programmed cell death in lymphocyte populations (1), was detectable in normal and benign but not in malignant adrenocortical neoplastic cells. In conclusion, the analysis of apoptosis provides new aspects of normal adrenal zonation and allows the differentiation between normal and neoplastic adrenal cortex although the differentiation between malignant and benign neoplasms requires further markers.
Immunologic escape includes the loss of Fas-receptor and the gain of Fas-ligand expression. Normal adrenal glands express the Fas-receptor and MHC class II molecules in inner cortical zones. A ...distinctive feature of adrenocortical tumors is the loss of MHC class II expression.
Here we demonstrate loss of Fas and gain of Fas-ligand expression in the adrenocortical carcinoma cell line NCI-H295 by immunohistochemistry and RT-PCR. In a co-culture system of turnor cells and HLA-matched leukocytes, CD 8-positive or CD 4-positive lymphocytes, we examined the immunologic escape and the ability to induce apoptosis in the immune cells. The direct co-culture with either leukocytes, CD 8-positive or CD 4-positive lymphocytes reduced spontaneous apoptosis in immunecells from 49.9% to 13.0%, 8.6% and 15.3%, respectively, as determined by FACS analysis of Annexin V binding and LDH release in the medium. In co-culture, cortisol secretion increased up to 200%.
Cellular communication does not induce apoptosis in immune cells, but promotes their survival. This may be due to partial HLA class I mismatches contributing to immunologic activity. The viability of the tumor cells was not affected, and these cells were stimulated to secrete cortisol. In summary, immune escape of adrenocortical carcinomas may occur because of altered Fas/Fas-L system expression and loss of MHC class H expression.
PDF
