No abstract

Induction of apoptosis of mononucleated cells is a physiological process for regulating the intensity of the immune response. The female steroid hormones estrogen (E2) and progesterone (Prog) are known to modulate the reactivity of the immune system; recently it has been demonstrated that they can regulate induction of apoptosis of endothelial cells and osteoblasts. TNF-alpha-mediated induction of apoptosis has been well characterized in myeloid cells. We investigated whether E2 and Prog could interfere with TNF-alpha-induced apoptosis of the monoblastoid U937 cell line. Treatment with E2 or Prog increased survival and prevented apoptosis induced by TNF-alpha in both undifferentiated and macrophage-like PMA-differentiated U937 cells, as assessed by trypan blue exclusion cell counting, thymidine incorporation, AnnexinV labeling, followed by flow cytometry and DNA fragmentation studies. This effect can be associated with the activation of specific hormone receptors, since we observed the expression of the estrogen receptor alpha (ER-alpha), ER-beta, and progesterone receptor (PR) mRNAs; the ER-alpha protein expression was confirmed by immunocytochemical analysis. In addition, hormone-mediated survival against apoptosis was concentration dependent, reaching the half-maximal effect at 10 nM and blocked by the ER antagonist ICI 182,780 in undifferentiated cells, further supporting a receptor-mediated mechanism of cell survival. Other steroid receptor drugs such as Raloxifene, RU486, or the ICI 182,780 in PMA-differentiated cells displayed agonist activity by preventing TNF-alpha-induced apoptosis as efficiently as the hormones alone, providing further evidence to the notion that steroid receptor drugs may manifest agonist or antagonist activities depending on the cellular context in which they are studied. Treatment with E2 was also associated with a time-dependent decrease in the mRNA level of the proapoptotic Nip-2 protein, supporting the hypothesis that hormone responsiveness of U937 cells is mediated by target gene transcription. Together, these results demonstrate that ER and PR can be activated by endogenous or exogenous ligands to induce a genetic response that impairs TNF-alpha-induced apoptosis in U937 cells. The data presented here suggest that the female steroid receptors play a role in regulation of the immune response by preventing apoptosis of monoblastoid cells; this effect might have important consequences in the clinical use of steroid receptor drugs. --Vegeto, E., Pollio, G., Pellicciari, C., Maggi, A. Estrogen and progesterone induction of survival of monoblastoid cells undergoing TNF-alpha-inuced apoptosis.

The aim of this paper is to review the data in the literature concerning ribonucleoprotein components during apoptosis, where a major rearrangement of RNPs takes place. In parallel with chromatin changes, the nucleoplasmic constituents (perichromatin fibrils; perichromatin granules; interchromatin granules and nuclear bodies) as well as the nucleoli aggregate into heterogeneous clusters called HERDS, in the interchromatin space. Later, these RNP-containing structures are extruded from the nucleus and leave the cell within cytoplasmic blebs. We propose also a role for HERDS as markers of irreversible transcriptional arrest. © 2004 Elsevier SAS. All rights reserved.Keywords: Electron microscopy; HERDS; Immunocytochemistry; Nuclear ribonucleoproteins; Transcription The cell nucleus during apoptosis: an introductionThe basic functions of the nucleus such as replication, transcription, DNA repair and their timing, as well as the correct sorting of information need an architectural support; this support, however, needs not to be a stable structural one only, but preferably derived from the dynamic interaction of many different components to be -at the same time-flexible and stable enough for these processes to proceed (Marshall, 2002;Stein et al., 2003).The nucleus is compartmentalized, both structurally and functionally and, in fact, may be considered as composed of at least two largely interacting parts: chromatin and the ribonucleoprotein (RNP)-containing structures. Already during the sixties of the last century, Bernhard and co-workers (Bernhard, 1969;Monneron and Bernhard, 1969; Bernhard, 1971,1973) showed that, thanks to a rather simple ultrastructural technique based on treatment with EDTA, condensed chromatin may be quite efficiently bleached whereas the interchromatin space becomes more contrasted. Under these conditions, it was possible -for the very first time-to detect and describe in detail some RNP-based structures. Those pioneering papers have then been followed by a plethora of articles aimed at elucidating the organization, chemical composition and functional significance of nuclear RNPs (for a recent review, see Fakan, 2004, and Table 1). One specific region (or domain), perichromatin compartment, is of particular interest since it is the place where most of the functions related to transcription, splicing and gene silencing are located (Cmarko et al., 2003).It is now widely accepted that, in eukaryotic cells, nuclear RNPs are part of the transcription and splicing machinery, and are always organized as morphologically recognizable structures (as schematically reported in Fig. 1a); at the electron microscope, these structures have been described as perichromatin fibrils (PF), perichromatin granules (PG), and interchromatin granules (IG) (Fakan, 1994;Spector, 1996), and nucleolus (Raška et al., 2004, in this issue). These structures are characterized by the presence of some marker proteins, such as hnRNP core proteins in PF (Martin and Okamura, 1981;Fakan et al., 1984), SC-35, Sm and PANA ...

Advancing adult age is associated with a progressive decrease in skeletal muscle mass, strength and quality known as sarcopenia. The mechanisms underlying age-related skeletal muscle wasting and weakness are manifold and still remain to be fully elucidated. Despite the increasing evidence that the progress of muscle diseases leading to muscle atrophy/dystrophy may be related to defective RNA processing, no data on the morpho-functional features of skeletal muscle nuclei in sarcopenia are available at present. In this view, we have investigated, by combining morphometry and immunocytochemistry at light and electron microscopy, the fine structure of myonuclei as well as the distribution and amount of RNA processing factors in skeletal myofibres of biceps brachii and quadriceps femoris from adult and old rats. Results demonstrate that the myonuclei of aged type II fibres show an increased amount of condensed chromatin and lower amounts of phosphorylated polymerase II and DNA/RNA hybrid molecules, clearly indicating a decrease in pre-mRNA transcription rate compared to adult animals. In addition, myonuclei of aged fibres show decreased amounts of nucleoplasmic splicing factors and an accumulation of cleavage factors, polyadenilated RNA and perichromatin granules, suggesting a reduction in the processing and transport rate of pre-mRNA. During ageing, it seems therefore that in rat myonuclei the entire production chain of mRNA, from synthesis to cytoplasmic export, is less efficient. This failure likely contributes to the reduced responsiveness of muscle cells to anabolic stimuli in the elderly.